US20190153988A1 - Method and system for starting an internal combustion engine - Google Patents
Method and system for starting an internal combustion engine Download PDFInfo
- Publication number
- US20190153988A1 US20190153988A1 US16/253,358 US201916253358A US2019153988A1 US 20190153988 A1 US20190153988 A1 US 20190153988A1 US 201916253358 A US201916253358 A US 201916253358A US 2019153988 A1 US2019153988 A1 US 2019153988A1
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- ecu
- voltage
- crankshaft
- ice
- etm
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N11/00—Starting of engines by means of electric motors
- F02N11/08—Circuits or control means specially adapted for starting of engines
- F02N11/0814—Circuits or control means specially adapted for starting of engines comprising means for controlling automatic idle-start-stop
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L50/00—Electric propulsion with power supplied within the vehicle
- B60L50/10—Electric propulsion with power supplied within the vehicle using propulsion power supplied by engine-driven generators, e.g. generators driven by combustion engines
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/04—Introducing corrections for particular operating conditions
- F02D41/06—Introducing corrections for particular operating conditions for engine starting or warming up
- F02D41/062—Introducing corrections for particular operating conditions for engine starting or warming up for starting
- F02D41/064—Introducing corrections for particular operating conditions for engine starting or warming up for starting at cold start
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N11/00—Starting of engines by means of electric motors
- F02N11/04—Starting of engines by means of electric motors the motors being associated with current generators
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N11/00—Starting of engines by means of electric motors
- F02N11/04—Starting of engines by means of electric motors the motors being associated with current generators
- F02N11/06—Starting of engines by means of electric motors the motors being associated with current generators and with ignition apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N11/00—Starting of engines by means of electric motors
- F02N11/08—Circuits or control means specially adapted for starting of engines
- F02N11/0803—Circuits or control means specially adapted for starting of engines characterised by means for initiating engine start or stop
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N11/00—Starting of engines by means of electric motors
- F02N11/08—Circuits or control means specially adapted for starting of engines
- F02N11/0862—Circuits or control means specially adapted for starting of engines characterised by the electrical power supply means, e.g. battery
- F02N11/0866—Circuits or control means specially adapted for starting of engines characterised by the electrical power supply means, e.g. battery comprising several power sources, e.g. battery and capacitor or two batteries
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N3/00—Other muscle-operated starting apparatus
- F02N3/02—Other muscle-operated starting apparatus having pull-cords
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/14—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N11/00—Starting of engines by means of electric motors
- F02N11/08—Circuits or control means specially adapted for starting of engines
- F02N2011/0881—Components of the circuit not provided for by previous groups
- F02N2011/0885—Capacitors, e.g. for additional power supply
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N11/00—Starting of engines by means of electric motors
- F02N11/08—Circuits or control means specially adapted for starting of engines
- F02N2011/0881—Components of the circuit not provided for by previous groups
- F02N2011/0888—DC/DC converters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N11/00—Starting of engines by means of electric motors
- F02N11/08—Circuits or control means specially adapted for starting of engines
- F02N2011/0881—Components of the circuit not provided for by previous groups
- F02N2011/0896—Inverters for electric machines, e.g. starter-generators
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N2200/00—Parameters used for control of starting apparatus
- F02N2200/02—Parameters used for control of starting apparatus said parameters being related to the engine
- F02N2200/022—Engine speed
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N2200/00—Parameters used for control of starting apparatus
- F02N2200/02—Parameters used for control of starting apparatus said parameters being related to the engine
- F02N2200/023—Engine temperature
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N2200/00—Parameters used for control of starting apparatus
- F02N2200/04—Parameters used for control of starting apparatus said parameters being related to the starter motor
- F02N2200/044—Starter current
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N2200/00—Parameters used for control of starting apparatus
- F02N2200/04—Parameters used for control of starting apparatus said parameters being related to the starter motor
- F02N2200/046—Energy or power necessary for starting
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N2200/00—Parameters used for control of starting apparatus
- F02N2200/06—Parameters used for control of starting apparatus said parameters being related to the power supply or driving circuits for the starter
- F02N2200/063—Battery voltage
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N2200/00—Parameters used for control of starting apparatus
- F02N2200/12—Parameters used for control of starting apparatus said parameters being related to the vehicle exterior
- F02N2200/122—Atmospheric temperature
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N3/00—Other muscle-operated starting apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N3/00—Other muscle-operated starting apparatus
- F02N3/04—Other muscle-operated starting apparatus having foot-actuated levers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Definitions
- the present technology relates to a method and system for starting an internal combustion engine.
- a recoil starter is sometimes provided.
- the user pulls on a rope of the recoil starter which causes the crankshaft of the engine to turn. If the crankshaft turns fast enough, the engine can be started. If not, the rope needs to be pulled again until the engine starts.
- an electric starting system In order to facilitate the starting of the engine, some vehicles have been provided with an electric starting system.
- This system consists of an electric motor, known as a starter, which engages and turns a ring gear connected to the crankshaft via a BendixTM mechanism, when an ignition key is turned or a start button is pushed by the user.
- the starter turns the crankshaft fast enough to permit the starting of the engine, and once the engine has started, disengages the ring gear and is turned off.
- the vehicle has a battery to supply electric current to the starter in order to turn the crankshaft.
- an electrical generator is operatively connected to the crankshaft of the engine. As the crankshaft turns the rotor of the electrical generator, the generator generates electricity.
- motor-generator units also called starter-generators, which replace the starter and the electrical generator.
- the motor-generator is operatively connected to the crankshaft in a manner similar to the aforementioned electrical generator.
- the motor-generator unit can be used as a starter or as a generator. By applying current to the motor-generator unit, the motor-generator unit operates as a starter and turns the crankshaft to enable starting of the engine. When the motor-generator is operated as a generator, the rotation of the crankshaft causes the motor-generator to generate electricity.
- the use of such systems addresses some of the deficiencies of starting systems using separate starters and electrical generators.
- the torque applied to the crankshaft to make it turn has to be sufficiently large to overcome the compression inside the engine's cylinders resulting from the pistons moving up in their respective cylinders as the crankshaft rotates.
- the motor-generator unit needs to be sufficiently large to properly operate as a starter.
- Another problem relates to the control of the motor-generator.
- the motor-generator When operating as a starter, the motor-generator generally operates at low rotational speeds, sufficient to allow the onset of ignition in the internal combustion engine. This operation requires the provision of a certain voltage to the motor-generator by the electric starting system.
- the motor-generator When operating as a generator, the motor-generator provides electric power over a wide range of rotational speeds of the internal combustion engine, oftentimes far exceeding the starting rotational speed. Without specific voltage control solutions, the motor-generator operating at high rotational speeds could generate voltages that far exceed the needs of the various components of the vehicle.
- the present technology provides a system supporting an electrical start procedure for an internal combustion engine (ICE) and a method for electrical starting the ICE that uses an electric turning machine (ETM) connected to the crankshaft to start the engine.
- the method permits an electrical start of the engine using a power source that is smaller and lighter than conventional batteries.
- electrical power is delivered from the power source to the ETM in a first control strategy to rotate the crankshaft so that fuel injection and ignition can occur.
- electrical power is delivered from the ETM to an accessory in a second control strategy.
- the accessory may consist of the power source that may be recharged in view of a future electrical start command.
- the electrical start procedure can be made to conditional to an initial voltage of the power source being equal to or above a minimum threshold.
- the first control strategy is tailored to provide sufficient torque to rotate the crankshaft without fully depleting the energy stored in the power source.
- the second control strategy is tailored so that electrical power is delivered to the accessory, for example to the power source, at a voltage that remains fairly constant for a wide range of rotational speeds of the crankshaft.
- the present technology also provides a method for starting an internal combustion engine (ICE) having a crankshaft.
- the method involves a cold start of the ICE, followed by stopping of the ICE and then by restarting of the ICE using an electric start procedure.
- the ICE is cold-started using a recoil starter.
- an electric turning machine (ETM) mounted to the crankshaft operates as a generator to charge a power source that is smaller and lighter than conventional batteries.
- ETM electric turning machine
- the electric start procedure uses the power source to deliver electrical power to the ETM, which is now operating as a starter.
- the present technology further provides a method and a system for an assisted start of the ICE.
- electric power is delivered from the power source to the ETM to assist starting of the ICE.
- the ICE is running, whether it has been started manually by pulling the rope of a recoil starter, using the assisted start procedure to facilitate the task of pulling the rope of the recoil starter, or using the electric start procedure, electrical power is also delivered from the ETM to an accessory.
- the electric start procedure and the assisted start procedure can be made conditional to an initial voltage of the power source being equal to or above a minimum threshold.
- the electric start procedure and the assisted start procedure are tailored to provide sufficient torque to rotate the crankshaft without fully depleting the energy stored in the power source.
- Some implementations may include either the electrical start procedure or the assisted start procedure.
- Other implementations may include both the electrical start procedure and the assisted start procedure.
- a method for starting an internal combustion engine (ICE) having a crankshaft comprises rotating the crankshaft using a recoil starter, and while the crankshaft is rotating, delivering electric power from a power source to an electric turning machine (ETM) co-axially mounted to the crankshaft for starting the ICE.
- ETM electric turning machine
- electric power is delivered from the power source to the ETM for starting the ICE while the crankshaft is rotating if a voltage of the power source meets or exceeds an assisted start voltage threshold.
- the method further comprises delivering electric power from the ETM to charge the power source while the ICE is operating.
- the method further comprises stopping the ICE providing a manual start indication if the voltage of the power source is below the assisted start voltage threshold, providing an assisted start indication if the voltage of the power source meets or exceeds the assisted start voltage threshold and if the voltage of the power source is below an electric start voltage threshold, and providing an electric start indication if the voltage of the power source meets or exceeds the electric start voltage threshold.
- the method further comprises using a position sensor to detect that the crankshaft is rotating before delivering electric power from the power source to the ETM.
- delivering electric power from the power source to the ETM is conditional on a value provided by a sensor and on a comparison between the value and a predetermined threshold.
- the method further comprises using an air temperature sensor to measure an air temperature, wherein delivering electric power from the power source to the ETM is conditional on a comparison between the air temperature a minimum air temperature threshold.
- the method further comprises providing a manual start indication if the air temperature is below the minimum air temperature.
- the method further comprises using a controller temperature sensor to measure a temperature of a controller for the ICE, wherein delivering electric power from the power source to the ETM is conditional on a comparison between the temperature of the controller for the ICE and a minimum temperature for the controller.
- the method further comprises providing a manual start indication if the temperature of the controller is below the minimum temperature for the controller.
- the method further comprises using a timer to measure a a time duration for the delivery of electric power to the ETM, wherein delivering electric power from the power source to the ETM is conditional on a comparison between the time duration for the delivery of electric power to the ETM and a maximum time duration for the delivery of electric power to the ETM.
- the method further comprises providing a manual start indication if the time duration for the delivery of electric power to the ETM exceeds the maximum time duration for the delivery of electric power to the ETM.
- the method further comprises delivering electric power from the ETM to the power source when a revolution speed of the crankshaft meets or exceeds a minimal revolution threshold.
- the power source is selected from a battery and a capacitance.
- the method further comprises operating the ETM as a starter and as a generator.
- the method further comprises delivering electric power from the generator to an accessory.
- the ETM is operated as a generator when a generated voltage of the ETM meets or exceeds a voltage generation threshold.
- the method further comprises converting electric power generated by the ETM from the generated voltage to an accessory voltage, and delivering electric power at the accessory voltage to an accessory.
- the generated voltage is greater than the accessory voltage.
- the method further comprises injecting fuel in a combustion chamber of the ICE as a piston of the ICE moves toward its top dead center (TDC) position and igniting the fuel in the combustion chamber of the ICE as the piston of the ICE moves beyond its TDC position.
- TDC top dead center
- a system for starting an internal combustion engine (ICE) having a crankshaft comprising an electric turning machine (ETM) adapted for being co-axially mounted to the crankshaft, a recoil starter adapted for causing a rotation of the crankshaft for starting the ICE, a power source, a position sensor adapted for detecting a rotation of the crankshaft, and an engine control unit (ECU) operatively connected to the position sensor and adapted for controlling a delivery of electric power from the power source to the ETM for starting the ICE when the position sensor indicates that the crankshaft is rotating.
- ETM electric turning machine
- recoil starter adapted for causing a rotation of the crankshaft for starting the ICE
- a power source a position sensor adapted for detecting a rotation of the crankshaft
- an engine control unit ECU
- the ECU is adapted for controlling a delivery of electric power from the ETM for charging the power source while the ICE is operating.
- the ECU is adapted for initiating the delivery of electric power from the ETM to the power source when the position sensor indicates that a revolution speed of the crankshaft meets or exceeds a minimal revolution threshold.
- the system further comprises a voltage sensor operatively connected to the ECU and adapted for measuring of voltage of the ETM, wherein the ECU is adapted for initiating the delivery of electric power from the ETM to the power source when the voltage of the ETM meets or exceeds a voltage generation threshold.
- the system further comprises a voltage sensor operatively connected to the ECU and adapted for measuring of voltage of the power source, wherein the ECU is adapted for preventing the delivery of electric power from the power source to the ETM is the voltage of the power source is below an assisted start voltage threshold.
- the system further comprises a display, the display being operatively connected to the ECU, wherein the ECU is adapted for stopping the ICE causing the display to provide a manual start indication if the voltage of the power source is below the assisted start voltage threshold, causing the display to provide an assisted start indication if the voltage of the power source meets or exceeds the assisted start voltage threshold and if the voltage of the power source is below an electric start voltage threshold, and causing the display to provide an electric start indication if the voltage of the power source meets or exceeds the electric start voltage threshold.
- the system further comprises a sensor operatively connected to the ECU and adapted for measuring an air temperature, wherein ECU is adapted for preventing the delivery of electric power from the power source to the ETM if the air temperature is below a minimum air temperature.
- the system further comprises a sensor operatively connected to the ECU and adapted for measuring a temperature of the ECU, wherein the ECU is adapted for preventing the delivery of electric power from the power source to the ETM if the temperature of the ECU is below a minimum temperature for the ECU.
- the system further comprises a timer operatively connected to the ECU and adapted for measuring a time duration for the delivery of electric power to the ETM, wherein the ECU is adapted for terminating the delivery of electric power from the power source to the ETM after a maximum time duration for the delivery of electric power to the ETM.
- the power source is selected from a battery and a capacitance.
- the ETM is adapted for operating as a starter and as a generator.
- the ETM is adapted for delivering electric power to an accessory.
- the system further comprises a voltage converter adapted for converting a voltage generated by the generator to an accessory voltage.
- the ECU is implemented on a single processor.
- the ECU is implemented on a single module, the module comprising a first processor adapted for controlling a delivery of electric power from the ETM to the power source and for controlling the delivery of electric power from the power source to the ETM, and a second processor adapted for controlling a fuel injection function and an ignition function of the ICE.
- an internal combustion engine comprising the system for starting the ICE, the ICE further comprising the crankshaft, a cylinder, a cylinder head connected to the cylinder, and a piston operatively connected to the crankshaft and disposed in the cylinder, the cylinder, the cylinder head and the piston defining a variable volume combustion chamber therebetween.
- the ICE further comprises a fuel injector operatively connected to the ECU, and an ignition system operatively connected to the ECU, wherein the ECU is adapted for causing the fuel injector to inject fuel in the combustion chamber as the piston moves toward its top dead center (TDC) position and for causing the ignition system to ignite the fuel in the combustion chamber as the piston moves beyond from its TDC position.
- TDC top dead center
- FIG. 1 is a right side perspective view of a snowmobile
- FIG. 2 is a perspective view taken from a front, left side of the internal combustion engine of the snowmobile of FIG. 1 ;
- FIG. 3 is a rear elevation view of the engine of FIG. 2 ;
- FIG. 4 is a cross-sectional view of the engine of FIG. 2 taken through line 4 - 4 of FIG. 3 ;
- FIG. 5 is a cross-sectional view of the engine of FIG. 2 taken through line 5 - 5 of FIG. 4 with a drive pulley of a CVT mounted on a crankshaft of the engine;
- FIG. 6 is a schematic diagram of components of a control system of the engine of FIG. 2 ;
- FIG. 7 is a block diagram of a dual-strategy control system for delivery of electric power between the capacitance and the electric turning machine (ETM) of FIG. 6 ;
- FIG. 8 is a block diagram of an energy management circuit for the capacitance of FIG. 6 ;
- FIG. 9 is a logic diagram of a method for starting the engine of FIG. 2 according to an implementation
- FIG. 10 is a timing diagram showing an example of variations of an engine resistive torque as a function of time along with corresponding engine rotational speed variations
- FIG. 11 is a logic diagram of a method for starting the engine of FIG. 2 according to another implementation
- FIG. 12 is a circuit diagram showing connections between the inverter, the capacitance and the motor-generator of FIG. 6 ;
- FIG. 13 is a block diagram of a typical implementation of a vector control drive
- FIG. 14 is a block diagram of an electric system according to an implementation of the present technology.
- FIG. 15 is a timing diagram showing an example of a sequence for changing the control strategy for the delivery of electric power between the capacitance and the electric turning machine (ETM) along with corresponding engine rotational speed variations; and
- FIG. 16 is another timing diagram showing an example of an impact of the control strategies on a current exchanged between the capacitance and the ETM and on a system voltage.
- the method and system for starting an internal combustion engine (ICE) and the method and system for an assisted start of the ICE will be described with respect to a snowmobile 10 .
- the method and system could be used in other vehicles, such as, but not limited to, on-road vehicles, off-road vehicles, a motorcycle, a scooter, a three-wheel road vehicle, a boat powered by an outboard engine or an inboard engine, and an all-terrain vehicle (ATV).
- ATV all-terrain vehicle
- the method and system could be used in devices other than vehicles that have an internal combustion engine such as a generator.
- the method and system will also be described with respect to a two-stroke, inline, two-cylinder internal combustion engine (ICE) 24 .
- the method and system could be used with an internal combustion engine having one or more cylinders and, in the case of multi-cylinder engines, having an inline or other configuration, such as a V-type engine as well as 4-stroke engines.
- a snowmobile 10 includes a forward end 12 and a rearward end 14 that are defined consistently with a forward travel direction of the snowmobile 10 .
- the snowmobile 10 includes a frame 16 that has a tunnel 18 , an engine cradle portion 20 and a front suspension assembly portion 22 .
- the tunnel 18 consists of one or more pieces of sheet metal arranged to form an inverted U-shape that is connected at the front to the engine cradle portion 20 and extends rearward therefrom along the longitudinal axis 23 .
- An ICE 24 (schematically illustrated in FIG. 1 ) is carried by the engine cradle portion 20 of the frame 16 . The ICE 24 is described in greater detail below.
- Two skis 26 are positioned at the forward end 12 of the snowmobile 10 and are attached to the front suspension assembly portion 22 of the frame 16 through a front suspension assembly 28 .
- the front suspension assembly 28 includes shock absorber assemblies 29 , ski legs 30 , and supporting arms 32 .
- Ball joints and steering rods (not shown) operatively connect the skis 26 to a steering column 34 .
- a steering device in the form of handlebar 36 is attached to the upper end of the steering column 34 to allow a driver to rotate the ski legs 30 and thus the skis 26 , in order to steer the snowmobile 10 .
- An endless drive track 38 is disposed generally under the tunnel 18 and is operatively connected to the ICE 24 through a CVT 40 (schematically illustrated by broken lines in FIG. 1 ) which will be described in greater detail below.
- the endless drive track 38 is driven to run about a rear suspension assembly 42 for propulsion of the snowmobile 10 .
- the rear suspension assembly 42 includes a pair of slide rails 44 in sliding contact with the endless drive track 38 .
- the rear suspension assembly 42 also includes a plurality of shock absorbers 46 which may further include coil springs (not shown) surrounding one or more of the shock absorbers 46 .
- Suspension arms 48 and 50 are provided to attach the slide rails 44 to the frame 16 .
- a plurality of idler wheels 52 are also provided in the rear suspension assembly 42 .
- Other types and geometries of rear suspension assemblies are also contemplated.
- fairings 54 enclose the ICE 24 and the CVT 40 , thereby providing an external shell that protects the ICE 24 and the CVT 40 .
- the fairings 54 include a hood and one or more side panels that can be opened to allow access to the ICE 24 and the CVT 40 when this is required, for example, for inspection or maintenance of the ICE 24 and/or the CVT 40 .
- a windshield 56 is connected to the fairings 54 near the forward end 12 of the snowmobile 10 . Alternatively the windshield 56 could be connected directly to the handlebar 36 .
- the windshield 56 acts as a wind screen to lessen the force of the air on the driver while the snowmobile 10 is moving forward.
- a straddle-type seat 58 is positioned over the tunnel 18 .
- Two footrests 60 are positioned on opposite sides of the snowmobile 10 below the seat 58 to accommodate the driver's feet.
- the ICE 24 operates on the two-stroke principle.
- the ICE 24 has a crankshaft 100 that rotates about a horizontally disposed axis that extends generally transversely to the longitudinal axis 23 of the snowmobile 10 .
- the crankshaft drives the CVT 40 for transmitting torque to the endless drive track 38 for propulsion of the snowmobile 10 .
- the CVT 40 includes a drive pulley 62 coupled to the crankshaft 100 to rotate with the crankshaft 100 and a driven pulley (not shown) coupled to one end of a transversely mounted jackshaft (not shown) that is supported on the frame 16 through bearings.
- the opposite end of the transversely mounted jackshaft is connected to the input member of a reduction drive (not shown) and the output member of the reduction drive is connected to a drive axle (not shown) carrying sprocket wheels (not shown) that form a driving connection with the drive track 38 .
- the drive pulley 62 of the CVT 40 includes a pair of opposed frustoconical belt drive sheaves 64 and 66 between which a drive belt (not shown) is located.
- the drive belt is made of rubber, but it is contemplated that it could be made of metal linkages or of a polymer.
- the drive pulley 62 will be described in greater detail below.
- the driven pulley includes a pair of frustoconical belt drive sheaves between which the drive belt is located.
- the drive belt is looped around both the drive pulley 62 and the driven pulley. The torque being transmitted to the driven pulley provides the necessary clamping force on the drive belt through its torque sensitive mechanical device in order to efficiently transfer torque to the other powertrain components.
- the drive pulley 62 includes a pair of opposed frustoconical belt drive sheaves 64 and 66 as can be seen in FIG. 5 . Both sheaves 64 and 66 rotate together with the crankshaft 100 .
- the sheave 64 is fixed in an axial direction relative to the crankshaft 100 , and is therefore referred to as the fixed sheave 64 .
- the fixed sheave 64 is also rotationally fixed relative to the crankshaft 100 .
- the sheave 66 can move toward or away from the fixed sheave 64 in the axial direction of the crankshaft 100 in order to change the drive ratio of the CVT 40 , and is therefore referred to as the movable sheave 66 .
- the fixed sheave 64 is disposed between the movable sheave 66 and the ICE 24 .
- the fixed sheave 64 is mounted on a fixed sheave shaft 68 .
- the fixed sheave 64 is press-fitted on the fixed sheave shaft 68 such that the fixed sheave 64 rotates with the fixed sheave shaft 68 .
- the fixed sheave 64 could be connected to the fixed sheave shaft 68 in other known manners to make the fixed sheave 64 rotationally and axially fixed relative to the fixed sheave shaft 68 .
- the fixed sheave shaft 68 is hollow and has a tapered hollow portion. The tapered hollow portion receives the end of the crankshaft 100 therein to transmit torque from the ICE 24 to the drive pulley 62 .
- a fastener 70 is inserted in the outer end (i.e. the left side with respect to FIG. 5 ) of the drive pulley 62 , inside the fixed sheave shaft 68 , and screwed into the end of the crankshaft 100 to prevent axial displacement of the fixed sheave shaft 68 relative to the crankshaft 100 .
- the fixed sheave shaft 68 could be connected to the crankshaft 100 in other known manners to make the fixed sheave shaft 68 rotationally and axially fixed relative to the crankshaft 100 .
- the crankshaft 100 could be the fixed sheave shaft 68 .
- a cap 72 is taper-fitted in the outer end of the fixed sheave shaft 68 .
- the fastener 70 is also inserted through the cap 72 to connect the cap 72 to the fixed sheave shaft 68 . It is contemplated that the cap 72 could be connected to the fixed sheave shaft 68 by other means.
- the radially outer portion of the cap 72 forms a ring 74 .
- An annular rubber damper 76 is connected to the ring 74 .
- Another ring 78 is connected to the rubber damper 76 such that the rubber damper 76 is disposed between the rings 74 , 78 .
- the rubber damper 76 is vulcanized to the rings 74 , 78 , but it is contemplated that they could be connected to each other by other means such as by using an adhesive for example. It is also contemplated that the damper 76 could be made of a material other than rubber.
- a spider 80 is disposed around the fixed sheave shaft 68 and axially between the ring 78 and the movable sheave 66 .
- the spider 80 is axially fixed relative to the fixed sheave 64 .
- Apertures (not shown) are formed in the ring 74 , the damper 76 , and the ring 78 .
- Fasteners (not shown) are inserted through the apertures in the ring 74 , the damper 76 , the ring 78 and the spider 80 to fasten the ring 78 to the spider 80 .
- torque is transferred between the fixed sheave shaft 68 and the spider 80 via the cap 72 , the rubber damper 76 and the ring 78 .
- the damper 76 dampens the torque variations from the fixed sheave shaft 68 resulting from the combustion events in the ICE 24 .
- the spider 80 therefore rotates with the fixed sheave shaft 68 .
- a movable sheave shaft 82 is disposed around the fixed sheave shaft 68 .
- the movable sheave 66 is press-fitted on the movable sheave shaft 82 such that the movable sheave 66 rotates and moves axially with the movable sheave shaft 82 .
- the movable sheave 66 could be connected to the movable sheave shaft 82 in other known manners to make the movable sheave 66 rotationally and axially fixed relative to the shaft 82 .
- the movable sheave 66 and the movable sheave shaft 82 could be integrally formed.
- a torque transfer assembly consisting of three roller assemblies 84 connected to the movable sheave 66 is provided.
- the roller assemblies 84 engage the spider 80 so as to permit low friction axial displacement of the movable sheave 66 relative to the spider 80 and to eliminate, or at least minimize, rotation of the movable sheave 66 relative to the spider 80 .
- torque is transferred from the fixed sheave 64 to the spider 80 via the damper 76 .
- the spider 80 engages the roller assemblies 84 which transfer the torque to the movable sheave 66 with no, or very little, backlash. As such, the spider 80 is considered to be rotationally fixed relative to the movable sheave 66 . It is contemplated that in some implementations, the torque transfer assembly could have more or less than three roller assemblies 84 .
- a biasing member in the form of a coil spring 86 is disposed inside a cavity 88 defined radially between the movable sheave shaft 82 and the spider 80 .
- the spring 86 gets compressed.
- the spring 86 biases the movable sheave 66 and the movable sheave shaft 82 away from the fixed sheave 64 toward their position shown in FIG. 5 . It is contemplated that, in some implementations, the movable sheave 66 could be biased away from the fixed sheave 64 by mechanisms other than the spring 86 .
- the spider 80 has three arms 90 disposed at 120 degrees from each other.
- Three rollers 92 are rotatably connected to the three arms 90 of the spider 80 .
- Three centrifugal actuators 94 are pivotally connected to three brackets (not shown) formed by the movable sheave 66 .
- Each roller 92 is aligned with a corresponding one of the centrifugal actuators 94 . Since the spider 80 and the movable sheave 66 are rotationally fixed relative to each other, the rollers 92 remain aligned with their corresponding centrifugal actuators 94 when the shafts 68 , 82 rotate.
- the centrifugal actuators 94 are disposed at 120 degrees from each other.
- the centrifugal actuators 94 and the roller assemblies 84 are arranged in an alternating arrangement and are disposed at 60 degrees from each other. It is contemplated that the rollers 92 could be pivotally connected to the brackets of the movable sheave 66 and that the centrifugal actuators 94 could be connected to the arms 90 of the spider 80 . It is also contemplated that there could be more or less than three centrifugal actuators 94 , in which case there would be a corresponding number of arms 90 , rollers 92 and brackets of the movable sheave. It is also contemplated that the rollers 92 could be omitted and replaced with surfaces against which the centrifugal actuators 94 can slide as they pivot.
- each centrifugal actuator 94 includes an arm 96 that pivots about an axle 98 connected to its respective bracket of the movable sheave 66 .
- the position of the arms 96 relative to their axles 98 can be adjusted. It is contemplated that the position of the arms 96 relative to their axles 98 could not be adjustable. Additional detail regarding centrifugal actuators of the type of the centrifugal actuator 94 can be found in International Patent Publication No. WO2013/032463 A2, published Mar. 7, 2013, the entirety of which is incorporated herein by reference.
- drive pulley 62 corresponds to one contemplated implementation of a drive pulley that can be used with the ICE 24 . Additional detail regarding drive pulleys of the type of the drive pulley 62 can be found in International Patent Publication No. WO 2015/151032 A1, published on Oct. 8, 2015, the entirety of which is incorporated herein by reference. It is contemplated that other types of drive pulleys could be used.
- the ICE 24 has a crankcase 102 housing a portion of the crankshaft 100 .
- the crankshaft 100 protrudes from the crankcase 102 .
- the crankshaft 100 could drive an output shaft connected directly to the end of the crankshaft 100 or offset from the crankshaft 100 and driven by driving means such as gears in order to drive the drive pulley 62 .
- the crankshaft 100 could drive, using gears for example, a counterbalance shaft housed in part in the crankcase 102 and that the drive pulley 62 could be connected to the counterbalance shaft, in which case, the crankshaft 100 does not have to protrude from the crankcase 102 for this purpose.
- a cylinder block 104 is disposed on top of and connected to the crankcase 102 .
- the cylinder block 104 as shown defines two cylinders 106 A, 106 B ( FIG. 5 ).
- a cylinder head 108 is disposed on top of and is connected to the cylinder block 104 .
- crankshaft 100 is supported in the crankcase 102 by bearings 110 .
- the crankshaft 100 has two crank pins 112 A, 112 B.
- the crank pins 112 A, 112 B are provided at 180 degrees from each other. It is contemplated that the crank pins 112 A, 112 B could be provided at other angles from each other to account for other cylinder arrangements, such as in a V-type engine.
- a connecting rod 114 A is connected to the crank pin 112 A at one end and to a piston 116 A via a piston pin 118 A at the other end.
- the piston 116 A is disposed in the cylinder 106 A.
- a connecting rod 114 B is connected to the crank pin 112 B at one end and to a piston 116 B via a piston pin 118 B at the other end.
- the piston 116 B is disposed in the cylinder 106 B.
- Rotation of the crankshaft 100 causes the pistons 116 A, 116 B to reciprocate inside their respective cylinders 106 A, 106 B.
- the cylinder head 108 , the cylinder 106 A and the piston 116 A define a variable volume combustion chamber 120 A therebetween.
- the cylinder head 108 , the cylinder 106 B and the piston 116 B define a variable volume combustion chamber 120 B therebetween.
- the cylinder block 104 could define more than two cylinders 106 , in which case the ICE 24 would be provided with a corresponding number of pistons 116 and connecting rods 114 .
- Air is supplied to the crankcase 102 via a pair of air intake ports 122 (only one of which is shown in FIG. 4 ) formed in the back of the cylinder block 104 .
- a pair of throttle bodies 124 is connected to the pair of air intake ports 122 .
- Each throttle body 124 has a throttle plate 126 that can be rotated to control the air flow to the ICE 24 .
- Motors (not shown) are used to change the position of the throttle plates 126 , but it is contemplated that throttle cables connected to a throttle lever could be used. It is also contemplated that a single motor could be used to change the position of both throttle plates 126 .
- a pair of reed valves 128 ( FIG. 4 ) are provided in each intake port 122 . The reed valves 128 allow air to enter the crankcase 102 , but prevent air from flowing out of the crankcase 102 via the air intake ports 122 .
- Fuel is injected in the combustion chambers 120 A, 120 B by fuel injectors 132 a , 132 b respectively.
- the fuel injectors 132 a , 132 b are mounted to the cylinder head 108 .
- the fuel injectors 132 a , 132 b are connected by fuel lines and/or rails (not shown) to one or more fuel pumps (not shown) that pump fuel from a fuel tank 133 ( FIG. 1 ) of the snowmobile 10 .
- the fuel injectors 132 a , 132 b are E-TECTM direct fuel injectors, however other types of injectors are contemplated.
- the fuel-air mixture in the combustion chamber 120 A, 120 B is ignited by spark plugs 134 a , 134 b respectively (not shown in FIGS. 2 to 5 , but schematically illustrated in FIG. 6 ).
- the spark plugs 134 a , 134 b are mounted to the cylinder head 108 .
- each cylinder 116 A, 116 B defines one main exhaust port 136 A, 136 B respectively and two auxiliary exhaust ports 138 A, 138 B respectively. It is contemplated that each cylinder 116 A, 116 B could have only one, two or more than three exhaust ports.
- the exhaust ports 136 A, 136 B ( FIG. 4 ), 138 A, 138 B are connected to an exhaust manifold 140 .
- the exhaust manifold is connected to the front of the cylinder block 104 .
- Exhaust valves 142 A, 142 B mounted to the cylinder block 104 , control a degree of opening of the exhaust ports 136 A, 136 B, 138 A, 138 B.
- the exhaust valves 142 A, 142 B are R.A.V.E.TM exhaust valves, but other types of valves are contemplated. It is also contemplated that the exhaust valves 142 A, 142 B could be omitted.
- ETM electric turning machine
- the ETM is a motor-generator 144 ( FIG. 5 ), and more specifically a three-phase alternating current motor-generator 144 , such as a permanent magnet motor for example.
- the motor-generator may include a number of pole pairs, generating electric power cycling at a rate that is a multiple of the rotational speed of the crankshaft 100 .
- other types of motor-generators could be used, including for example multi-phase motor-generators or poly-phase motor-generators.
- the motor-generator 144 could be connected to another shaft operatively connected to the crankshaft 100 , by gears or belts for example.
- the motor-generator 144 can act as a motor or as a generator and can be switched between either functions. Under certain conditions as described hereinbelow, the motor-generator 144 is operated in motor operating mode, being powered either by a small battery (not shown) or by a capacitance 145 (shown on FIG. 6 ).
- a battery that is smaller and lighter than one conventionally used for cold starting of the ICE 24 may be used for an electric start procedure and/or for an assisted start procedure that will be described hereinbelow.
- the electric start procedure and/or the assisted start procedure may rely on the use of a capacitance 145 .
- capacitances include a high-capacity capacitor, an ultracapacitor (U-CAP), an electric double layer capacitor and a supercapacitor Either the small battery or the capacitance 145 supplies electric power to the motor-generator 144 for turning the crankshaft 100 .
- the capacitance 145 can accumulate relatively large amounts of energy.
- the capacitance 145 comprises a plurality of capacitors assembled in series, each capacitor of the series possibly including several capacitors mounted in parallel so that the capacitance 145 can withstand voltages generally within an operating voltage range of direct fuel injectors.
- references are made to the capacitance 145 as a single unit. Without limitation and for brevity, implementations in which the electric start procedure or the assisted start procedure, or both, are implemented using the capacitance 145 along with the motor-generator 144 will be described hereinbelow.
- the motor-generator 144 When operating as a generator, the motor-generator 144 is turned by the crankshaft 100 and generates electricity that is supplied to the capacitance 145 and to other electrical components of the ICE 24 and the snowmobile 10 . Electric power is exchanged between the capacitance 145 and the motor-generator 144 through an electrical converter.
- the electrical converter is a three-phase inverter 146 .
- Use of multi-phase or poly-phase invertors in cooperation with a multi-phase or a poly-phase motor-generator is also contemplated. Control strategies of the motor-generator 144 applicable to its motoring and generating functions and the impact of these strategies on the capacitance 145 and on the inverter 146 are described hereinbelow.
- the motor-generator 144 has a stator 148 and a rotor 150 .
- the stator 148 is disposed around the crankshaft 100 outside of the crankcase 102 and is fastened to the crankcase 102 .
- the rotor 150 is connected by splines to the end of the crankshaft 100 and partially houses the stator 148 .
- a housing 152 is disposed over the motor-generator 144 and is connected to the crankcase 102 .
- a cover 154 is connected to the end of the housing 152 .
- a first procedure comprises a manual start procedure that relies on the use of a recoil starter 156 .
- a second starting procedure comprises an electric start procedure.
- a third starting procedure comprises an assisted start procedure.
- One or both of the electric and assisted start procedures may be present in any implementation of the snowmobile 10 .
- the second and third starting procedures will be describer further below.
- the recoil starter 156 is disposed inside the space defined by the housing 152 and the cover 154 , between the cover 154 and the motor-generator 144 .
- the recoil starter 156 has a rope 158 wound around a reel 160 .
- a ratcheting mechanism 162 selectively connects the reel 160 to the rotor 150 .
- a user pulls on a handle 163 ( FIG. 3 ) connected to the end of the rope 158 .
- This turns the reel 160 in a direction that causes the ratcheting mechanism 162 to lock, thereby turning the rotor 150 and the crankshaft 100 .
- the rotation of the crankshaft 100 causes the pistons 116 A, 116 B to reciprocate which permits fuel injection and ignition to occur, thereby starting the ICE 24 .
- the drive pulley 62 and the motor-generator 144 are both mounted to the crankshaft 100 . It is contemplated that the drive pulley 62 and the motor-generator 144 could both be mounted to a shaft other than the crankshaft 100 , such as a counterbalance shaft for example. In the present implementation, the drive pulley 62 , the motor-generator 144 and the recoil starter 56 are all coaxial with and rotate about the axis of rotation of the crankshaft 100 .
- the drive pulley 62 , the motor-generator 144 and the recoil starter 56 could all be coaxial with and rotate about the axis of rotation of a shaft other than the crankshaft 100 , such as a counterbalance shaft for example. It is also contemplated that at least one of the drive pulley 62 , the motor-generator 144 and the recoil starter 56 could rotate about a different axis. In the present implementation, the drive pulley 62 is disposed on one side of the ICE 24 and the motor-generator 144 and the recoil starter 56 are both disposed on the other side of the ICE 24 . It is contemplated the motor generator and/or the recoil starter 56 could be disposed on the same side of the ICE 24 as the drive pulley 62 .
- FIG. 6 is a schematic diagram of components of a control system of the engine of FIG. 2 .
- the control of the components used to start the ICE 24 in the electric start procedure and in the assisted start procedure is done by an engine control unit (ECU) 164 as will be explained below.
- the ECU 164 is also used to control the operation of the ICE 24 after it has started.
- the ECU 164 is illustrated as a single physical module (later shown in FIG. 14 ) comprising a single processor (also in FIG. 14 ), for example a single microcontroller. Other configurations are within the scope of the present disclosure.
- the ECU 164 may be implemented using a plurality of co-processors, for example two or more microcontrollers. It is also contemplated that the various tasks of the ECU 164 could be split between two or more microprocessors integrated in a single electronic module or two or more microprocessors distributed among various electronic modules.
- the single electronic module may comprise a first processor adapted for controlling a delivery of electric power from the motor-generator 144 to the capacitance 145 and to control the delivery of electric power from the capacitance 145 to the motor-generator 144 , and a second processor adapted for controlling a fuel injection function and an ignition function of the ICE.
- the ECU 164 receives inputs from the components disposed to the left of the ECU 164 in FIG. 6 , some of which are optional and not present in all implementations, as will be described below. Using these inputs, the ECU 164 obtains information from control maps 166 as to how the components disposed to the right of the ECU 164 in FIG. 6 should be controlled in order to start the ICE 24 .
- the control maps 166 are stored in an electronic data storage device, such as a static random access memory (SRAM), an electrically-erasable programmable read-only memory (EEPROM) or a flash drive.
- the ECU 164 could use control algorithms to control the components disposed to the right of the ECU 164 in FIG. 6 .
- the ECU 164 is connected with the various components illustrated in FIG. 6 via wired connections; however it is contemplated that it could be connected to one or more of these components wirelessly.
- a user actionable electric start switch 168 provided on the snowmobile 10 , for example a push button mounted on or near the handlebar 36 , sends a signal to the ECU 164 that the user desires the ICE 24 to start when it is actuated.
- the electric start switch 168 can also be a switch actuated by a key, a sensor, or any other type of device through which the user can provide an input to the ECU 164 that the ICE 24 is to be started.
- the electric start switch 168 may be a sensor operably connected to the rope 158 of the recoil starter 156 and to the ECU 164 . Some traction, for example a simple tugging on the rope 158 by an operator, may be detected by this sensor, resulting in the initiation of the electric start procedure of the ICE 24 , provided that all conditions for the electric start procedure are present.
- a crankshaft position sensor 170 is disposed in the vicinity of the crankshaft 100 in order to sense the position of the crankshaft 100 .
- the crankshaft position sensor 170 sends a signal representative of the position of the crankshaft 100 to the ECU 164 .
- the crankshaft position sensor 170 is an absolute position sensor, such as a sin/cos Hall Effect encoder for example. Based on the change in the signal received from the crankshaft position sensor 170 , the ECU 164 is also able to determine an angular position of the crankshaft 100 .
- crankshaft position sensor 170 could alternatively sense the position of an element other than the crankshaft 100 that turns with the crankshaft 100 , such as the rotor 150 of the motor-generator 144 for example, and be able to determine the position of the crankshaft 100 from the position of this element.
- Use of a relative position sensor to sense the position of the crankshaft 170 is also contemplated as expressed hereinbelow.
- the assisted start procedure may be initiated, provided that conditions are met as described hereinbelow, when a rotation of the crankshaft 100 is initiated by the user pulling on the rope 158 of the recoil starter 156 .
- the crankshaft position sensor 170 informs the ECU 170 of the rotation of the crankshaft 100 .
- a voltage sensor 167 for example a voltmeter, provides a measurement of a voltage of the capacitance 145 to the ECU 164 . As explained in more details hereinbelow, the ECU 164 uses this voltage measurement to determine whether an energy reserve of the capacitance 145 is sufficient to start the ICE 24 using the electric start procedure or to provide assist using the assisted start procedure.
- sensors can be used to determine whether or not the engine can be started using the electric start procedure or the assisted start procedure as expressed hereinbelow.
- sensors include for example an engine temperature sensor 172 , an air temperature sensor 174 , an atmospheric air pressure sensor 176 , an exhaust temperature sensor 178 , a timer 180 and an ECU temperature sensor 182 .
- the engine temperature sensor 172 is mounted to the ICE 24 to sense the temperature of one or more of the crankcase 102 , the cylinder block 104 , the cylinder head 108 and engine coolant temperature.
- the engine temperature sensor 172 sends a signal representative of the sensed temperature to the ECU 164 .
- the air temperature sensor 174 is mounted to the snowmobile 10 , in the air intake system for example, to sense the temperature of the air to be supplied to the ICE 24 .
- the air temperature sensor 174 sends a signal representative of the air temperature to the ECU 164 .
- the atmospheric air pressure sensor 176 is mounted to the snowmobile 10 , in the air intake system for example, to sense the atmospheric air pressure.
- the atmospheric air pressure sensor 176 sends a signal representative of the atmospheric air pressure to the ECU 164 .
- the exhaust temperature sensor 178 is mounted to the exhaust manifold 140 or another portion of an exhaust system of the snowmobile 10 to sense the temperature of the exhaust gases.
- the exhaust temperature sensor 178 sends a signal representative of the temperature of the exhaust gases to the ECU 164 .
- the timer 180 is connected to the ECU 164 to provide information to the ECU 164 regarding the amount of time elapsed since the ICE 24 has stopped.
- the timer 180 can be an actual timer which starts when the ICE 24 stops.
- the function of the timer 180 can be obtained from a calendar and clock function of the ECU 164 or another electronic component.
- the ECU 164 logs the time and date when the ICE 24 is stopped and looks up this data to determine how much time has elapsed since the ICE 24 has stopped when the ECU 164 receives a signal from the electric start switch 168 that the user desires the ICE 24 to be started.
- the ECU temperature sensor 182 is mounted to a physical module (not shown) that includes one or more processors (not shown) configured to execute the functions of the ECU 164 .
- the ECU temperature sensor 182 sends a signal representative of the temperature of that module to the ECU 164 .
- one or more of the sensors 172 , 174 , 176 , 178 , 182 and the timer 180 could be omitted. It is also contemplated that one or more of the sensors 172 , 174 , 176 , 178 , 180 , 182 and the timer 180 could be used only under certain conditions. For example, the exhaust temperature and pressure sensors 178 , 180 may only be used if the ICE 24 has been recently stopped, in which case some exhaust gases would still be present in the exhaust system, or following the first combustion of a fuel-air mixture in one of the combustion chambers 120 A, 120 B.
- the ECU 164 uses the inputs received from at least some of the electric start switch 168 , the sensors 167 , 170 , 172 , 174 , 176 , 178 , 182 and the timer 180 to retrieve one or more corresponding control maps 166 and to control the motor-generator 144 , the fuel injectors 132 a , 132 b , and the spark plugs 134 a , 134 b using these inputs and/or the control maps 166 to start the ICE 24 , as the case may be.
- the inputs and control maps 166 are also used to control the operation of the ICE 24 once it has started.
- the ECU 164 is also connected to a display 186 provided on the snowmobile 10 near the handlebar 36 to provide information to the user of the snowmobile 10 , such as engine speed, vehicle speed, oil temperature, and fuel level, for example.
- FIG. 7 is a block diagram of a dual-strategy control system for delivery of electric power between the capacitance and the ETM of FIG. 6 . Some components introduced in the foregoing description of FIG. 6 are reproduced in FIG. 7 in order to provide more details on their operation.
- Electric power is delivered between the capacitance 145 and the motor-generator 144 through the inverter 146 .
- the ECU 164 includes, or is otherwise operatively connected to, a strategy switch 184 that is operative to change the control strategy for the delivery of electric power between the capacitance 145 and the motor-generator 144 between at least two (2) distinct control strategies.
- the ECU 164 controls the inverter 146 through the strategy switch 184 .
- the user of the snowmobile 10 enters an input on the electric start switch 168 , for example by depressing a push button.
- the ECU 164 is informed of this command.
- the ECU 164 may control a delivery of electric power from the capacitance 145 to the motor-generator 144 based on a pre-determined amount of torque, or torque request, sufficient to cause rotation of the crankshaft 100 for starting the ICE 24 .
- the ECU 164 may determine the torque request.
- the determination of the torque request is made considering that ICE 24 is expected to have a highly irregular resistive torque; alternatively, instead of determining the torque request, the ECU 164 may determine a speed request applicable to the crankshaft 100 to control an amount of power that that the motor-generator 144 should apply to the crankshaft 100 for starting the ICE 24 .
- a voltage of the capacitance 145 is sensed by the voltage sensor 167 and provided to the ECU 164 . If this voltage is below an electric start voltage threshold V MinE , which is a minimum voltage of the capacitance 145 for the electric start procedure, the ECU 164 determines that the capacitance 145 does not hold sufficient energy to provide the torque request, or the speed request, sufficient to start the ICE 24 using the electric start procedure.
- the ECU 164 does not allow starting the ICE 24 using the electric start procedure and causes the display 186 to show a “manual start” indication or an “assisted start” indication, in implementations where this option is available.
- the electric start voltage threshold V MinE is based on a determination of a sufficient charge of the capacitance 145 allowing a successful electric start procedure in most operating conditions. If this minimum voltage threshold for the electric start procedure is met, the ECU 164 causes delivery of electric power from the capacitance 145 to the motor-generator 144 , via the inverter 146 , in a first control strategy, initiating a rotation of the crankshaft 100 .
- the ECU 164 also causes the fuel injectors 132 a and 132 b to inject fuel in the combustion chambers 120 A, 120 B and causes the spark plugs 134 a and 134 b to ignite the fuel in the combustion chambers 120 A, 120 B.
- the ICE 24 may comprise one or more cylinders and the mention of two (2) combustion chambers 120 A and 120 B is for explanation purposes only. If these operations are successful, the rotation of the crankshaft 100 reaches a minimum revolution threshold corresponding to a successful start of the ICE 24 .
- the ECU 164 controls the delivery of electric power from the motor-generator 144 to the capacitance 145 , still via the inverter 146 , to cause charging of the capacitance 145 .
- the delivery of electric power from the motor-generator 144 to the capacitance 145 generally occurs in a second control strategy distinct from the first control strategy.
- a variant in which the delivery of electric power from the motor-generator 144 to the capacitance 145 occurs in the first control strategy at low revolution speeds of the crankshaft 100 , or under low throttle demands, and in the second control strategy at high revolution speeds of the crankshaft 100 is also contemplated.
- a current sensor 188 may be used to optimize the capacitance 145 current consumption and optimize its energy usage.
- the current sensor 188 provides to the ECU 164 an indication of the energy from the capacitance 145 being consumed during the electric start procedure.
- the current sensor 188 comprises a combination of phase current sensors (not explicitly shown) provided on two (2) phases of the motor-generator 144 . Encoding of measurements from these two (2) phase current sensors provide a good estimation of a current flowing between the capacitance 145 and the motor-generator 144 . As shown on FIG. 13 , current measurements may be obtained on all three (3) phases of the motor-generator 144 .
- the capacitance 145 energy usage can alternatively be optimized without current sensors, for example, an open loop approach having a predetermined torque request pattern being applied by the ECU 164 to drive all cranking sequences can be used. It is also possible to optimize the energy usage of the capacitance 145 based on a speed request with well-tuned regulators or based on a predetermined pattern of multistep speed requests.
- Electric start of the ICE 24 may fail although initial conditions for the electric start procedure were initially present. This may occur for instance if, while electric power is being delivered from the capacitance 145 to the motor-generator 144 , the voltage sensor 167 detects that the voltage of the capacitance 145 falls below a residual voltage threshold V MinR , lower than the electric start voltage threshold V MinE , before the rotational speed of the crankshaft 100 reaches the minimum revolution threshold corresponding to the successful start of the ICE 24 . Under such conditions, the ECU 164 ceases the delivery of power from the capacitance 145 to the motor-generator 144 and causes the display 186 to provide a manual start indication or an assisted start indication, in implementations where this option is available.
- the residual voltage threshold V MinR corresponds to a minimum charge of the capacitance 145 that is expected to suffice in allowing the injection and ignition of fuel injection in the combustion chambers 120 A, 120 B while continuing the rotation of the crankshaft 100 .
- the user of the snowmobile 10 pulls on the rope 158 of the recoil starter 156 , initiating a rotation of the crankshaft 100 .
- the crankshaft position sensor 170 informs the ECU 170 of the rotation of the crankshaft 100 .
- the ECU 164 may control a delivery of electric power from the capacitance 145 to the motor-generator 144 to assist the rotation of the crankshaft 100 for starting the ICE 24 .
- a voltage of the capacitance 145 is sensed by the voltage sensor 167 and provided to the ECU 164 .
- assisted start voltage threshold V MinA which is a minimum voltage of the capacitance 145 for the assisted start procedure
- the ECU 164 determines that the capacitance 145 does not hold sufficient energy to assist starting the ICE 24 and the ECU 164 does not allow starting the ICE 24 using the assisted start procedure, instead causing the display 186 to show a “manual start” indication.
- the assisted start voltage threshold V MinA is based on a determination of a sufficient charge of the capacitance 145 allowing a successful assisted start procedure in predetermined operating conditions. In implementations where both electric and assisted start procedures are present, the assisted start voltage threshold V MinA is lower than the electrical start voltage threshold V MinE .
- the ECU 164 causes delivery of electric power from the capacitance 145 to the motor-generator 144 , via the inverter 146 , in the first control strategy, assisting the rotation of the crankshaft 100 .
- the ECU 164 also causes the fuel injectors 132 a and 132 b to inject fuel in the combustion chambers 120 A, 120 B and causes the spark plugs 134 a and 134 b to ignite the fuel in the combustion chambers 120 A, 120 B.
- the ICE 24 may comprise one or more cylinders and the mention of two (2) combustion chambers 120 A and 120 B is for explanation purposes only. If these operations are successful, the rotation of the crankshaft 100 reaches a minimum revolution threshold corresponding to a successful start of the ICE 24 . Thereafter, operation of the ICE 24 is as expressed in the foregoing description to the electrical start procedure.
- FIG. 8 is a block diagram of an energy management circuit for the capacitance 145 of FIG. 6 .
- a circuit 200 shows how, in an implementation, the ECU 164 and the capacitance 145 are electrically connected using the electric start switch 168 , which is shown as a pushbutton.
- the capacitance 145 is illustrated as a sum of smaller capacitors 202 connected in series. As mentioned earlier, each of these smaller capacitors 202 may actually consist of a plurality of capacitors connected in parallel. Each of the smaller capacitors 202 can withstand a relatively low voltage applied thereon.
- the capacitance 145 formed by the sum of the smaller capacitors 202 in series can withstand the nominal voltage of the circuit 200 , which is also the nominal voltage of the electrical systems of the snowmobile 10 , with the addition of a safety margin for occasional overvoltage.
- the voltage present on the capacitance 145 is defined between terminals 204 and 206 that are electrically connected to the voltage sensor 167 shown on earlier Figures.
- the circuit 200 provides an output voltage between a lead 208 and a ground reference 210 when the circuit 200 is active.
- MOSFET metal-oxide semiconductor field effect transistor
- the capacitance 145 is disconnected from the ground reference 210 by a metal-oxide semiconductor field effect transistor (MOSFET) Q 1 which is, at the time, turned off and therefore open circuit.
- MOSFET metal-oxide semiconductor field effect transistor
- Substituting a bipolar transistor, for example an insulated gate bipolar transistor (IGBT), for the MOSFET Q 1 is also contemplated.
- a capacitor C 1 is present between the lead 208 and the ground reference 210 .
- the role of the capacitor C 1 is to filter voltage variations at the output 204 for the benefit of the various electrical components of the snowmobile 10 , including for example the fuel injectors 132 a and 132 b , headlights, and the like.
- the voltage between the lead 208 and the ground reference 210 which is a system voltage for the snowmobile 10 , is essentially the same as the nominal voltage of the capacitance 145 , although operating voltages between different system states may not be constant at all times.
- the voltage on the capacitance 145 falls below the electric start voltage threshold V MinE and below the assisted start voltage threshold V MinA , and the circuit 200 is not energized. Resorting to the manual start procedure is therefore required for starting the ICE 24 .
- the voltage on the capacitance 145 may be equal to or above the electric start voltage threshold V MinE , in which case the electric start procedure is available. If the voltage of the capacitance 145 is lower than the electric start voltage threshold V MinE while at least equal to or greater than the assisted start voltage threshold V MinA , the assisted start procedure may be available.
- the assisted start procedure is described in more details hereinbelow.
- the user may depress the electric start switch 168 (pushbutton) to invoke the electric start procedure.
- This user action is sensed by a button state detector 212 of the ECU 164 .
- the button state detector 212 being referenced to the terminal 206 , it becomes placed in parallel with the capacitance 145 when the start switch 168 is depressed.
- electrical power is provided from the capacitance 145 to the ECU 164 , waking up the ECU 164 .
- the button state detector 212 may accept a simple brief electrical contact provided by the electric start switch 168 to initiate the electric start procedure.
- the button state detector 212 may alternatively require the electric start switch 168 to be depressed for a few seconds. A variant in which the button state detector 212 is not present, in which the electric start switch 168 needs to be depressed until the ICE 24 is actually started is also contemplated. After sensing the electric start command, the button state detector 212 sends a signal to a wake up circuit 214 of the ECU 164 .
- the wake up circuit 214 controls the following operations.
- the wake up circuit 214 applies a signal to a driver 216 of the transistor Q 1 .
- the transistor Q 1 turns on, effectively placing the capacitance 145 in parallel with the capacitor C 1 .
- the wake up circuit 214 can control the driver 216 to turn on and off the transistor Q 1 at a high frequency in order to prevent excessive current flowing from the capacitance 145 to the capacitor C 1 .
- Electrical conduction through the transistor Q 1 may be controlled in a small duty cycle at first, the duty cycle increasing as a voltage difference between the capacitor C 1 and the capacitance 145 decreases. Regardless, the capacitor C 1 rapidly charges to reach the voltage of the capacitance 145 .
- the capacitance 145 voltage may reduce slightly, but this effect is limited by the fact that the capacitor C 1 is much smaller than the capacitance 145 .
- the electric start continues with the ECU 164 controlling the delivery of power from the capacitance 145 to the motor-generator 144 via the lead 208 , which is connected to the inverter 146 .
- the motor-generator 144 may initially have a limited power generating capacity.
- Accessories of the snowmobile 10 including for example the fuel injectors 132 a and 132 b and headlights, require a certain amount of power. It is more critical to the operation of the vehicle to power these accessories than recharging the capacitance 145 .
- the ECU 164 may optionally control the driver 216 to turn off the transistor Q 1 until the crankshaft 100 rotates at more than a predetermined revolution threshold.
- the ECU 164 may again control the driver 216 and the transistor Q 1 to place the capacitance 145 in parallel with the capacitor C 1 .
- the transistor Q 1 may be turned on and off at a small duty cycle at first, the duty cycle increasing as a voltage difference between the capacitor C 1 and the capacitance 145 decreases. The transistor Q 1 may therefore be controlled in order to regulate the charging rate of capacitance 145 while respecting the electrical power availability at any speed of the ICE 24 .
- the ECU 164 may optionally integrate an automatic shutdown circuit that may terminate all electrical functions of the snowmobile 10 in case of system failure.
- Table I provides a sequence of events including a manual start procedure of the ICE 24 , followed by an electric start procedure command received after a waiting time that does not exceed the capabilities of the electric start system.
- PWM pulse width modulation
- both minimum voltage thresholds V MinE and V MinR may be defined within an operating voltage range of the direct fuel injectors so that, if the voltage of the capacitance 145 is not sufficient for the direct fuel injectors to inject fuel in the cylinders 106 A, 106 B, the electric start procedure is not attempted, or terminated if unsuccessful.
- FIG. 9 is a logic diagram of a method for starting the engine of FIG. 2 according to an implementation.
- a sequence shown in FIG. 9 comprises a plurality of operations, some of which may be executed in variable order, some of the operations possibly being executed concurrently, and some of the operations being optional.
- the method begins at operation 300 when the ICE 24 of the snowmobile 10 is stopped.
- a voltage of the capacitance 145 is measured by the voltage sensor 167 at operation 302 .
- the display 186 may provide an “automatic start” indication if the voltage meets or exceeds the electric start voltage threshold V MinE and if other conditions described hereinbelow for the electric start procedure are met.
- the user actuates the electric start switch 168 , this being detected by the button state detector 212 at operation 304 .
- a comparison is made by the ECU 164 , at operation 306 , between the voltage of the capacitance 145 and the electric start voltage threshold V MinE to determine whether it is possible to initiate the electric start procedure for the ICE 24 . If it is determined that the voltage of the capacitance 145 is below the electric start voltage threshold V MinE , the electric start procedure is prevented. Otherwise, verification is made at operation 308 that the engine temperature measured by the engine temperature sensor 172 meets or exceeds an engine temperature threshold T 0 . The electric start procedure is prevented in this threshold for the engine temperature is not met.
- the ECU temperature sensor 182 provides a reading of the temperature of the ECU 164 that meets or exceeds an ECU temperature threshold T 1 .
- the electric start procedure is prevented if this threshold for the ECU temperature is not met. Additional operations related to use of measurements obtained from other sensors introduced in the foregoing description of FIG. 6 may take place. These measurements may be provided to the ECU 164 by the air temperature sensor 174 , the atmospheric temperature sensor 176 , or the timer 180 . Additional tests based on those measurements may be executed by the ECU 164 to determine whether or not the electric start procedure is likely to succeed or to determine a torque value sufficient to cause the rotation of the crankshaft 100 .
- the electric start procedure may be made conditional, in the ECU 164 , on the timer 180 informing the ECU 164 that a period of time since the ICE 24 has been stopped is below a predetermined time value when the user actuates the electric start switch 168 at operation 304 .
- the electric start voltage threshold V MinE knowing a maximum charge voltage of the capacitance 145 from a previous running sequence of the ICE 24 , and based on a typical energy leakage of the capacitance 145 .
- the method proceeds to operation 312 .
- the ECU 164 causes the display 186 to display “Manual Start” or some other message indicating to the user of the snowmobile 10 that the snowmobile 10 will need to be started manually using the recoil starter 156 (i.e. by pulling on the handle 163 ).
- the display 186 may instead display “Assisted Start” or some other equivalent message, provided that current conditions allow using this procedure.
- Displaying the manual start indication or the assisted start indication at operation 312 may follow any decision taken by the ECU 164 to not proceed with the electric start procedure. It is contemplated that instead of providing a message on the display 186 , that the ECU 164 could cause a sound to be heard or provide some other type of feedback to the user of the snowmobile 10 , indicating that the snowmobile 10 will need to be started manually using the recoil starter 156 .
- a manual start procedure or an assisted start procedure may be initiated when the user pulls on the rope 158 of the recoil starter 156 . If conditions for the assisted start procedure are met, this procedure may be initiated as described hereinbelow.
- the manual start procedure may be initiated at operation 314 when, in response to sensing the operation of the recoil starter 156 by the user of the snowmobile 10 , the ECU 164 initiates an engine control procedure associated with the use of the recoil starter 156 in order to start the ICE 24 using the recoil starter 156 . Then at operation 316 , the ECU 164 determines if the ICE 24 has been successfully started using the recoil starter 156 . If not, then operation 314 is repeated. It is also contemplated that if at operation 316 it is determined that the ICE 24 has not been successfully started, that the method could return to operation 312 to display the message again.
- the method proceeds to operations 318 and 320 , these last two (2) operations being operated concurrently.
- the ECU 164 operates the ICE 24 according to the control strategy or strategies to be used once the ICE 24 has started.
- the ECU 164 controls the inverter 146 to cause power to be delivered from the motor-generator 144 to the capacitance 145 , charging the capacitance 145 using the second control strategy at a voltage that remains fairly constant for a wide range of rotational speeds of the crankshaft 100 .
- the ECU 164 may linearly regulate the voltage generated by the motor-generator 144 may be using a series regulation mode or a shunt mode.
- the maximum voltage threshold may for example be equal or slightly superior to the nominal voltage of the circuit 200 .
- the method continues at operation 322 where the ECU 164 controls the driver 216 of the transistor Q 1 to place the capacitance 145 in parallel with the capacitor C 1 to equalize their voltages. Then at operation 324 , the ECU 164 obtains a value of the angular position of the crankshaft 100 from the crankshaft position sensor 170 . This operation 324 may continue on an ongoing fashion during the complete electric start procedure so that the following operations may be optimized according to the varying angular position of the crankshaft 100 .
- operations 322 and 324 may be omitted or substituted with other actions.
- the electric start procedure may be rendered independent from the angular position of the crankshaft 100 by providing a capacitance 145 , the battery, or other power source having sufficient energy storage capability to rotate the crankshaft 100 with no concern for its actual angular position.
- the electric start procedure proceeds with operation 326 and continues through operations 328 , 330 and, if required, operation 332 . These operations are initiated in the sequence as shown on FIG. 9 , but are then executed concurrently until the electric start procedure is found successful or until it needs to be terminated.
- the ECU 164 determines the torque value sufficient to cause the rotation of the crankshaft 100 and initiates delivery of power from the capacitance 145 to the motor-generator 144 , through the inverter 146 , via the first control strategy which adapts the delivery of power in view of the determined torque value. This transfer of power causes a rotation of the crankshaft 100 .
- the ECU 164 may determine the torque value in sub-steps, in which a first sub-step comprises delivering electric power from the capacitance 145 to the three-phase motor-generator 144 according to a first torque value to cause slow turning of the crankshaft at a first rotational speed until the piston is brought beyond its top dead center (TDC), based on information provided by the crankshaft position sensor 170 and based on the contents of the control maps 166 , a second sub-step comprising delivering electric power from the capacitance 145 to the three-phase motor-generator 144 according to a second torque value, greater than the first torque value to cause turning of the crankshaft at a second rotational speed, the second rotational speed being greater than the first rotational speed.
- a first sub-step comprises delivering electric power from the capacitance 145 to the three-phase motor-generator 144 according to a first torque value to cause slow turning of the crankshaft at a first rotational speed until the piston is brought beyond its top dead center (
- operation 326 is ongoing, particularly while the second sub-step is ongoing if operation 326 comprises two sub-steps, the method proceeds to operation 328 in which the ECU 164 causes the fuel injectors 132 a , 132 b to inject fuel in the combustion chambers 132 a , 132 b and causes the spark plugs 134 a , 134 b to ignite the fuel in the combustion chambers 134 a , 134 b , thereby accelerating the rotation of the crankshaft 100 .
- the angular position of the crankshaft 100 170 may be used by the ECU 164 to properly time the fuel injection and the ignition.
- the position sensor 170 is an absolute position sensor that can determine the position of the crankshaft 100 while it is stationary, prior to starting of the ICE 140 .
- This technique provides precise fuel injection and ignition timing at a very low rotational speed of the ICE 24 , such as when the ICE 24 is starting.
- This technique decreases the chances of a failed start-up procedure due to an insufficient combustion within the combustion chambers 102 A, 120 B, this insufficient combustion resulting from imprecise fuel injection quantities or ignition timing calculated from an imprecise crankshaft position.
- This technique further promotes faster synchronization between all components of the ICE 24 that rely on the position of the crankshaft 100 when compared to the use of position sensors that require the crankshaft 100 to be rotating to determine its position.
- a quantity of fuel to be injected and the ignition timing as applied by the ECU 164 at operation 328 may be evaluated using any known method, optionally depending on one or more of an engine temperature, an air temperature, an atmospheric pressure, and an exhaust temperature, these values being provided to the ECU 164 by the various sensors shown on FIG. 6 .
- operation 330 the ECU 164 compares a rotational speed of the crankshaft 100 to a minimum revolution threshold to determine if the ICE 24 has been successfully started using the electric start procedure. If the rotational speed of the crankshaft 100 is equal to or above the minimum revolution threshold, the ICE 24 has been successfully started, the electric start procedure ends and the method proceeds to operations 318 and 320 , which are described hereinabove.
- the method continues at operation 332 where the ECU 164 monitors again the voltage of the capacitance 145 . It is expected that this voltage will be reduced somewhat as energy previously stored in the capacitance 145 has been spent during operations 326 and 328 . However, if a remaining voltage of the capacitance 145 is equal to or above the residual voltage threshold V MinR , the electric start procedure returns to operations 326 and 328 , which are still ongoing, and then at operation 330 .
- the method proceeds to operation 334 where the ECU 164 ceases the delivery of power from the capacitance 145 to the motor-generator 144 and terminates operations 326 and 328 .
- the method then moves from operation 334 to operation 312 , which is described hereinabove, in which the ECU 164 causes the display 186 to display a manual start indication, or an assisted start indication in implementations where this option is available, operation 312 being followed by operations 314 , 316 , 318 and 320 in the case of a manual start.
- FIG. 10 is a timing diagram showing an example of variations of an engine resistive torque as a function of time along with corresponding engine rotational speed variations.
- a graph 400 shows a variation of the resistive torque of the ICE 24 , in Newton-Meters (Nm) as a function of time, in seconds. The graph 400 was obtained from a SimulinkTM model.
- a graph 402 shows a corresponding variation of a rotational speed of the crankshaft 100 over the same time scale.
- the two-cylinder ICE 24 is firing when a piston first reaches near TDC. After less than 0.1 seconds, the resistive torque becomes negative because the piston has passed beyond its TDC. Compression present in the combustion chamber pushes on the piston and accelerates the rotation of the crankshaft 100 .
- the ECU 164 controls the torque applied to the crankshaft 100 by the motor-generator 144 , accelerating the rotation of the crankshaft 100 .
- the rotational speed of the crankshaft 100 reaches a plateau at about 0.17 seconds because the piston is now compressing gases present in the combustion chamber.
- the rotational speed decreases as the piston arrives near its TDC. TDC is reached at about 0.32 seconds.
- Successful ignition takes place, whereafter the rotational speed of the crankshaft 100 increases rapidly while the resistive torque on the motor-generator 144 becomes essentially negative, following a toothed saw wave shape as the piston cycles up and down in its cylinder.
- FIG. 11 is a logic diagram of a method for starting the engine of FIG. 2 according to another implementation.
- a sequence shown in FIG. 11 comprises a plurality of operations, some of which may be executed in variable order, some of the operations possibly being executed concurrently, and some of the operations being optional.
- the method begins at operation 600 when the ICE 24 of the snowmobile 10 is stopped.
- a voltage of the capacitance 145 is measured by the voltage sensor 167 at operation 602 .
- the display 186 may provide an “assisted start” indication if the voltage meets or exceeds the assisted start voltage threshold V MinA and if other conditions described hereinbelow for the assisted start procedure are met.
- the user initiates a rotation of the crankshaft 100 by pulling on the rope 158 of the recoil starter 156 .
- the crankshaft position sensor 170 detects an initial rotation of the crankshaft 100 and informs the ECU 164 of the rotation. Detecting the initial rotation of the crankshaft 100 may be conditional to the crankshaft position sensor 170 detecting that a revolution speed of the crankshaft 100 meets or exceeds a minimal revolution threshold.
- a comparison is made by the ECU 164 at operation 608 between the voltage of the capacitance 145 and the assisted start voltage threshold V MinA to determine whether it is possible to initiate the assisted start procedure for the ICE 24 .
- the assisted start procedure is prevented. Otherwise, verification is made at operation 610 that the engine temperature measured by the engine temperature sensor 172 meets or exceeds an engine temperature threshold T 0 . The assisted start procedure is prevented in this threshold for the engine temperature is not met. Otherwise, verification is made at operation 612 that the ECU temperature sensor 182 provides a reading of the temperature of the ECU 164 that meets or exceeds an ECU temperature threshold T 1 . The assisted start procedure is prevented if this threshold for the ECU temperature is not met. Additional operations related to the use of measurements obtained from other sensors introduced in the foregoing description of FIG. 6 may take place.
- These measurements may be provided to the ECU 164 by the air temperature sensor 174 , the atmospheric temperature sensor 176 , or the timer 180 . Additional tests based on those measurements may be executed by the ECU 164 to determine whether or not the assisted start procedure is likely to succeed.
- the assisted start procedure may be made conditional, in the ECU 164 , on the timer 180 informing the ECU 164 that a period of time since the ICE 24 has been stopped is below a predetermined time value when the user pulls on the rope 158 of the recoil starter 156 at operation 604 , On the basis of the period of time since the ICE 24 has been stopped, it is possible to estimate whether the voltage of the capacitance 145 will have fallen below the assisted start voltage threshold V MinA knowing a maximum charge voltage of the capacitance 145 from a previous running sequence of the ICE 24 , and based on a typical energy leakage of the capacitance 145 .
- Displaying the manual start indication at operation 614 may follow any decision taken by the ECU 164 to not proceed with the assisted start procedure. Whether the assisted start procedure is prevented because the voltage of the capacitance 145 is insufficient (operation 608 ), because the engine temperature is too low (operation 610 ), because the ECU temperature is too low (operation 612 ) or for any other reason, the method proceeds to operation 614 .
- the display 186 may display “Manual Start”.
- the user may continue pulling on the rope 158 of the recoil starter 156 at operation 616 . Operation 616 may continue until it is detected at operation 618 that the ICE 24 is properly started.
- Control of ICE 24 and delivery of electric power from the motor-generator 145 to the capacitance 144 follow at 620 and 622 , which are the same or equivalent as operations 318 and 320 of FIG. 9 including, in an implementation, controlling the ICE 24 using the above described control strategies.
- the ECU 164 determines that the capacitance voltage is equal to or above the assisted start voltage threshold V MinA and that the temperature conditions and any further condition are also met, the method continues at operation 624 where the ECU 164 controls the driver 216 of the transistor Q 1 to place the capacitance 145 in parallel with the capacitor C 1 to equalize their voltages.
- the assisted start procedure proceeds with operation 626 and continues through operations 628 , 630 and, if required, operation 632 . These operations are initiated in the sequence as shown on FIG. 11 , but are then executed concurrently until the assisted start procedure is found successful or until it needs to be terminated.
- the ECU 164 initiates delivery of power from the capacitance 145 to the motor-generator 144 , through the inverter 146 . This transfer of power accelerates the rotation of the crankshaft 100 and reduces the amount of effort that needs to be exerted by the user pulling on the rope 158 of the recoil starter 156 .
- the ECU 164 may optionally determine a torque value in the same manner as described in the foregoing description of operation 326 ( FIG. 9 ).
- operation 626 the method proceeds to operation 628 in which the ECU 164 causes the fuel injectors 132 a , 132 b to inject fuel in the combustion chambers 132 a , 132 b and causes the spark plugs 134 a , 134 b to ignite the fuel in the combustion chambers 134 a , 134 b , thereby accelerating further the rotation of the crankshaft 100 .
- the angular position of the crankshaft 100 may be used by the ECU 164 to properly time the fuel injection and the ignition.
- Use of mechanical actuators (not shown) operably connected to the crankshaft 100 to control injection and ignition timings is also contemplated.
- a quantity of fuel to be injected and the ignition timing as applied by the ECU 164 at operation 628 may depend on one or more of an engine temperature, an air temperature, an atmospheric pressure, and an exhaust temperature, these values being provided to the ECU 164 by the various sensors shown on FIG. 6 .
- the method proceeds to operation 630 , in which the ECU 164 compares a rotational speed of the crankshaft 100 to a minimum revolution threshold to determine if the ICE 24 has been successfully started using the assisted start procedure. If the rotational speed of the crankshaft 100 is equal to or above the minimum revolution threshold, the ICE 24 has been successfully started, the assisted start procedure ends and the method proceeds to 620 and 622 , which are described hereinabove.
- the method continues at operation 632 where the ECU 164 monitors again the voltage of the capacitance 145 . It is expected that this voltage will be reduced somewhat as energy previously stored in the capacitance 145 has been spent during 626 and 628 . However, if a remaining voltage of the capacitance 145 is equal to or above a residual voltage threshold, the assisted start procedure returns to operations 626 and 628 , which are still ongoing, and then at operation 630 .
- the residual voltage threshold applicable to the assisted start procedure may be the same value V MinR as in the case of the electric start procedure.
- a different residual voltage threshold may be used given that the amount of power delivered to the motor-generator 144 by the capacitance 145 complements the effort of the user pulling on the rope 158 of the recoil starter 156 . If however the ECU 164 determines at operation 632 that the capacitance voltage has fallen below the residual voltage threshold V MinR , the method proceeds to operation 634 where the ECU 164 ceases the delivery of power from the capacitance 145 to the motor-generator 144 and terminates operations 626 and 628 .
- the method then moves from operation 634 to operation 614 , which is described hereinabove, in which the ECU 164 causes the display 186 to display a manual start indication, operation 614 being followed by operations 616 , 618 , 620 and 622 .
- the snowmobile 10 may be configured to support any one of the manual, electric and assisted start procedures.
- operation 312 FIG. 9
- operation 312 may provide a manual start or an assisted start indication, depending on the voltage of the capacitance 145 . If the voltage of the capacitance is below the electric start voltage threshold V MinE while meeting or exceeding the assisted start voltage threshold V MinA , operation 312 of FIG. 9 may provide the assisted start indication and may be followed by operation 604 of FIG. 11 if the user pulls on the rope 158 of the recoil starter 156 .
- the ICE 24 after having started the ICE 24 using the assisted start procedure, the ICE 24 may be stopped and the display 186 may provide an indication of the available start procedure depending on current conditions reported to the ECU 164 by the various sensors.
- FIG. 12 is a circuit diagram showing connections of the inverter 146 , the capacitance 145 and the motor-generator 144 of FIG. 6 . As shown on FIG. 12 , the inverter 146 has three phases, each phase being electrically connected to a corresponding phase of the three-phase motor-generator 144 .
- the inverter 146 is formed of three (3) switching legs, each switching leg including a pair of MOSFETs T 1 , T 2 , T 3 , T 4 , T 5 and T 6 matched with corresponding freewheel diodes D 2 , D 1 , D 3 , D 2 , D 6 and D 5 .
- a first leg forming a first phase includes a top transistor T 1 matched with a freewheel diode D 2 and a bottom transistor T 2 matched with a freewheel diode D 1 .
- a second leg forming a second phase includes transistors T 3 and T 4 matched with diodes D 4 and D 3 respectively while a third leg forming a third phase includes transistors T 5 and T 6 matched with diodes D 6 and D 5 respectively.
- MOSFETs bipolar transistors, for example IGBTs, or any other power electronic switches are also contemplated.
- Each transistor T 1 -T 6 has a corresponding gate G 1 -G 6 through which a signal, or control pulse, can be applied under the control of the ECU 164 via the strategy switch 184 , either directly or through a gate driver (not shown), to turn-on (short-circuit) or turn-off (open circuit) the corresponding transistors T 1 -T 6 .
- the freewheel diodes D 1 -D 6 are used to attenuate transient overvoltage that occurs upon switching on and off of the transistors T 1 -T 6 .
- a first control pulse is applied at the gate G 1 to short-circuit the transistor T 1 .
- Current flows from a positive tab of the capacitance 145 through the transistor T 1 and reaches a phase of the motor-generator 144 defined between an input A and a neutral connection between the phases of the motor-generator 144 , hereinafter “Phase A”.
- Phase A a phase of the motor-generator 144 defined between an input A and a neutral connection between the phases of the motor-generator 144 .
- the first control pulse is removed from the gate G 1 so the transistor T 1 becomes an open-circuit.
- a second control pulse is applied on the gate G 2 , causing the transistor T 2 to turn-on.
- Phase A of the motor-generator 144 needs to exit through one or both of the other phases of the motor-generator 144 .
- Phase B is defined between an input B and the neutral connection.
- Phase C is defined between an input C and the neutral connection.
- the current flows from Phase A through Phase B, or Phase C, or both Phases B and C, depending on whether one or both of transistors T 4 or T 6 is turned on by control pulses applied on their respective gates G 4 or G 6 when the transistor T 1 is also turned on.
- the current exiting the motor-generator 144 via one or both of Phases B and/or C returns to a negative tab of the capacitance 145 through one or both of the transistors T 4 and/or T 6 .
- the freewheel diodes D 1 -D 6 assist in supporting phase inductance currents during freewheel periods.
- Examples of parameters that may be considered by programming of the ECU 164 to control the delivery of electric power in both control strategies include, without limitation, current and voltage of each phase voltages and currents in each of the Phases A, B and C of the motor-generator 144 , the angular position and rotational speed of the crankshaft 100 .
- the ECU 164 uses these values to determine an electromagnetic torque of the motor-generator 144 , this torque having positive value when the motor-generator 144 is used during the electric start procedure or the assisted start procedure and a negative value when used in generator operating mode.
- the first control strategy uses a technique called vector control or field-oriented control (FOC).
- FOC field-oriented control
- the first control strategy is used mainly to control the delivery of electric power from the capacitance 145 to the motor-generator 144 to cause or assist a rotation of the crankshaft 100 in the electric start procedure or in the assisted start procedure of the ICE 24 .
- ECU 164 determines a torque request sufficient to cause the rotation of the crankshaft 100 .
- the ECU 164 determines a speed request applicable to the crankshaft 100 , sufficient to cause ignition and start of the ICE 24 . This determination of the speed request or torque request may be made by the ECU 164 applying a predetermined speed or torque request value or pattern based on the contents of the control maps 166 .
- the ECU 164 may increment the torque request if a first torque application causes no rotation of the crankshaft 100 .
- the ECU 164 may increment the speed request if a rotation of the crankshaft 100 is not sufficient to allow ignition and start of the ICE 24 .
- the ECU 164 may calculate the speed or torque request based on a combination of parameters, including in a non-limitative example a mathematical representation of internal components of the ICE 24 and on the angular position of the crankshaft 100 .
- the ECU 164 controls the delivery of electric power from the capacitance 145 to the motor-generator 144 , based on the determined speed request or torque request, through the generation of control pulses applied to selected ones of the transistors T 1 -T 6 .
- the ECU 164 calculates a number, timing, and width of the various control pulses so that the amount of electric power flowing from the capacitance 145 through the inverter 146 and to the motor-generator 144 fulfills the determined speed or torque request.
- This manner of controlling the transistors T 1 -T 6 by applying timed pulses to their gates G 1 -G 6 , each pulse having a calculated width, is known as pulse width modulation (PWM).
- PWM pulse width modulation
- FIG. 13 is a block diagram of a typical implementation of a vector control drive.
- a vector control drive 500 of FIG. 13 may be implemented at least in part in the ECU 164 .
- An input to the vector control drive includes a set point 504 for a required speed (the speed request) that is determined as sufficient for starting the ICE 24 . This set point 504 is applied to a slow speed control loop 506 .
- Other inputs to the vector control drive 500 include current measurements 508 a , 508 b and 508 c for the three phases of the motor-generator 144 and a voltage measurement 510 obtained from the inverter 146 and/or from the motor-generator 144 . These current and voltage measurements are applied to an analog to digital converter (ADC) 512 .
- ADC analog to digital converter
- Crankshaft angular position measurements (encoder signals u A , u S ) 514 are applied to a quadrature timer 516 .
- the quadrature timer 516 calculates an actual position of the crankshaft 100 .
- the ADC 512 calculates a digitized voltage value 518 and digitized current values 520 a , 520 b and 520 c for the three phases of the motor-generator 144 . These digitized values and an actual position 522 of the crankshaft 100 calculated by the quadrature timer 516 are provided to a fast current control loop 524 .
- the actual position 522 of the crankshaft 100 is converted to an actual (measured) speed 526 by a speed calculator 528 of the slow speed control loop 506 .
- a difference 528 between the measured speed 526 and the required speed set point 504 is applied to a first proportional-integral (PI) controller 530 that in turn yields a current-image 532 of a torque request that is applied as a set point (Isq_req) to the fast current control loop 524 .
- PI proportional-integral
- an optional field weakening module 534 having an internal map attenuates values of its output based on the measured speed 526 of the crankshaft 100 to provide a current-image 536 of a magnetic field of the motor-generator 144 as an additional set point (Isd_req) applied to the fast current control loop 524 .
- a Clark Transform 538 converts the three-phase current measurements 520 a , 520 b and 520 c into a two-phase model 540 .
- a Park Transform 542 fed with sine and cosine values 523 of the actual position 522 of the crankshaft 100 , calculated by a sin/cos converter 525 , converts further this model 540 to provide a stationary current-image 544 of the actual torque on the motor-generator 144 (Isq) and a stationary current-image 546 of the actual magnetic field of the motor-generator (Isd).
- Outputs 544 and 546 of this model are respectively compared to the Isq_req set point 532 and to the Isd_req set point 536 (if used), and their differences are respectively applied to second and third PI controllers 548 , 550 .
- An Inverse Park Transform 552 is applied to stationary voltage requests Uq 554 and Ud 556 produced by the second and third PI controllers 548 , 550 , the Inverse Park Transform 552 using the sine and cosine values 523 of the actual position 522 of the crankshaft 100 to produce outputs 558 , 560 of the Inverse Park Transform 552 that are applied to a space vector modulation-pulse width modulation (SV-PWM) transform 562 .
- the SV-PWM transform 562 provides three-phase control 564 to a PWM module 566 that generates pulses 502 that the ECU 164 provides for application to the gates G 1 -G 6 of the inverter 146 .
- the ECU 164 may control a delivery of electric power from the capacitance 145 to the motor-generator 144 based on a pre-determined amount of torque, or torque request, sufficient to cause rotation of the crankshaft 100 for starting the ICE 24 .
- a pre-determined amount of torque, or torque request sufficient to cause rotation of the crankshaft 100 for starting the ICE 24 .
- the amount of torque required to rotate the crankshaft 100 before ignition of the cylinder (or cylinders) varies based on the angular position of the crankshaft 100 in relation to the top dead center (TDC) position of each piston
- TDC top dead center
- the angular position of the crankshaft 100 is provided by the crankshaft position sensor 170 or, alternatively, by a relative position sensor.
- the ECU 164 magnetizes two out of the three phases of the alternating current motor-generator 144 , moving and then locking the rotor of the motor-generator 144 and thereby locking the crankshaft 100 , which is attached thereto, in a known repetitive electric angle. From there, rotating positions of the crankshaft 100 are calculated continuously from a counter of pulses received from the relative position sensor. An absolute position of the crankshaft 100 is calculated and an electric angle is derived from that calculation to perform vector control. In a particular implementation, an incremental encoder providing 1024 pulses per revolution of the crankshaft 100 is contemplated.
- the ECU 164 calculates or otherwise determines the torque request based on an angular position of the crankshaft 100 provided by the crankshaft position sensor 170 , values of the torque request being updated at various points of the rotation of the crankshaft 100 .
- the torque request can be optimized so that it is sufficient to rotate the crankshaft 100 as it reaches various angular positions while using as little as possible of the energy stored in the capacitance 145 .
- the ECU 164 controls the amount of torque applied on the motor-generator 144 so that it turns at a very low speed until a given piston 116 A, 116 B passes its TDC for a first time. During this brief period of time, gas is slowly expelled from the combustion chamber 120 A, 120 B in which this given piston 116 A, 116 B is located. Very little energy is drawn from the capacitance 145 in this operation. Once the piston 116 A, 116 B has moved beyond its TDC, the crankshaft 100 has acquired at least some momentum.
- the ECU 164 then raises the torque request applied to the motor-generator 144 so that the crankshaft 100 rotates at a speed sufficient to allow injection of fuel in the combustion chamber 120 A, 120 B as the piston 116 A, 116 B moves towards its TDC, ignition taking place in the combustion chamber 120 A, 120 B as soon as the piston moves beyond its TDC.
- This increase of the torque request may be linear until a predetermined torque set-point is reached, so that the rotational speed of the crankshaft 100 increases smoothly.
- the crankshaft 100 drives the motor-generator 144 at a variable rotational speed, most of the time significantly exceeding a rotational speed used in the course of any of the start procedures.
- operation of the motor-generator 144 switches to generator operating mode.
- the ECU 164 may determine a revolution speed of the crankshaft 100 based on successive readings provided by the crankshaft position sensor 170 and cause the motor-generator 144 to start delivering electric power to the capacitance 145 when the revolution speed of the crankshaft meets or exceeds a minimal revolution threshold.
- the ECU 164 starts controlling the strategy switch 184 and the inverter 146 using the second control strategy.
- the first control strategy may be used in generator operating mode until the voltage measurement provided by the voltage sensor 167 meets or exceeds a voltage generation threshold.
- the voltage generation threshold can be set slightly lower than a nominal voltage of the capacitance 145 , for example.
- the second control strategy uses a “shunt” technique.
- the output of the motor-generator 144 now generating, is used to charge the capacitance 145 , to supply electrical power to the injectors 132 a , 132 b , to spark the spark plugs 134 a , 134 b , and, generally, to supply electrical power to electrical accessories of the snowmobile 10 .
- the ECU 164 alters a position of the strategy switch 184 so that electrical power now flows from the motor-generator 144 to the capacitance 145 , still through the inverter 146 .
- the ECU 164 monitors the voltage of the capacitance 145 through measurements obtained from the voltage sensor 167 .
- the ECU 164 Based on these voltage measurements, the ECU 164 generates control pulses that are applied, via the strategy switch 184 , to the gates G 1 -G 6 of the transistors T 1 -T 6 in the inverter 146 . PWM is still applied by the ECU 164 to the gates G 1 -G 6 , but this time according to the second control strategy.
- the inverter 146 is controlled by the ECU 164 to reduce the voltage at which electrical power is delivered from the motor-generator 144 to the capacitance 145 .
- the ECU 164 may generate control pulses applied to various gates G 2 , G 4 and G 6 to effectively bypass, or “shunt”, one or more of the phases of the motor-generator 144 , at the same time applying no control pulse to the gates G 1 , G 3 and G 5 in order to cause the transistors T 1 , T 3 and T 5 to remain non-conductive (open circuit).
- applying pulses to the gates G 2 and G 6 causes the transistors T 2 and T 6 to turn on and become conductive. As a result, a closed loop is formed between Phases A and C of the motor-generator 144 along with the transistors T 2 and T 6 . Under this condition, no electrical power is delivered from two (2) of the phases of the motor-generator 144 to the capacitance 145 .
- a duration (width) and timing of the pulses applied to the gates G 2 and G 6 impacts a duration of time when Phases A and C are shunted, in turn impacting the charging voltage applied at the capacitance 145 .
- PWM can be applied to any pair of the bottom transistors T 2 , T 4 and T 6 , so that they can be shorted at a desired time to shunt a pair of phases of the motor-generator 144 .
- the ECU 164 may actually modify, over time, a determination of which pair of transistors is made part of a shunt in order to avoid their overheating due to conduction losses in the inverter 146 .
- voltage regulation in shunt mode involves successively activating the transistors T 2 , T 4 and T 6 .
- the delivery of electric power from the motor-generator 144 to the capacitance 145 can be made at a desired voltage over a broad range of the rotational speed of the crankshaft 100 .
- a series voltage regulation mode is also contemplated, in which the freewheel diodes D 1 , D 3 and D 5 may optionally be replaced by additional transistors (not shown) mounted in reverse-parallel with the transistors T 1 , T 3 and T 5 , these additional transistors being turned on and off as required to allow current from the motor-generator 144 to recharge the capacitance 145 while not exceeding the nominal voltage value.
- voltage regulation in shunt mode may benefit from the measurements provided by the position sensor 170 .
- the position sensor 170 allows the ECU 164 to determine a mechanical position of the crankshaft 100 .
- the ECU 164 calculates an equivalent electrical angle by multiplying the mechanical position of the crankshaft 100 by a known number of pole pairs of the motor-generator 144 . If the output voltage of the motor-generator 144 is above a predetermined value, starting from a voltage rise of any one of the phases A, B or C, all three (3) phases are consecutively shunted once, in synchrony with the operation of the motor-generator 144 . This shunting sequence may be repeated when the output voltage of the motor-generator 144 rises again above the predetermined value.
- the inverter 146 is controlled by the ECU 164 to deliver electrical power available from the motor-generator 144 to the capacitance 145 without shunting any of the Phases A, B or C. Under this condition, which may for example occur for a brief duration after the start of the ICE 24 , the control of the power delivery could be construed as a neutral control mode distinct from the first and second control strategies. In the neutral control mode, the inverter 146 acts as a three-phase full-wave diode bridge rectifier, providing no voltage or current regulation.
- FIG. 14 is a block diagram of an electric system according to an implementation of the present technology.
- a circuit 700 includes variants of elements introduced in the foregoing description of the various drawings, these elements being grouped into subsystems.
- the motor-generator 144 is one such subsystem.
- Another subsystem is in the form of a control module 702 that, in an implementation, comprises a single physical module including a processor 703 programmed to execute the functions of the ECU 164 , the inverter 146 , the ECU temperature sensor 182 and further includes a DC-DC converter 704 .
- the ECU 164 includes connections for the electric start switch 168 , for the measurements provided by the various sensors 170 , 172 , 174 , 176 and 182 , and connections to the gates G 1 -G 6 of the inverter 146 .
- the voltage sensor 167 is implemented as a DC voltage sensor 167 DC that measures a voltage of the capacitance 145 and as an AC voltage sensor 167 AC that measures a voltage on one phase of the motor-generator 144 , these two components of the voltage sensor 167 being integrated within the ECU 164 .
- Use of external voltage sensors operatively connected to the ECU 164 is also contemplated.
- a third subsystem 706 includes the capacitance 145 , as well as a charging circuit 705 and a discharging circuit 707 that use the driver 216 and the transistor Q 1 of FIG. 8 to control charging and discharging of the capacitance 145 .
- the circuit 700 operates at a nominal system voltage, which is typically the voltage of the capacitance 145 when fully charged.
- a fourth subsystem 708 includes components of the snowmobile 10 that operate at the system voltage. These components may include the fuel injectors 132 a , 132 b , an electric oil pump 710 , ignition coils 712 for the spark plugs 134 a , 134 b and a fuel pump 714 .
- a fifth subsystem 716 includes accessories of the snowmobile 10 that operate at an accessory voltage. These accessories may include a multi-port fuel injector (MPH) 718 , lighting 720 , an instrument cluster 722 including the display 186 , heated grips 724 mounted on the handlebar 36 and an exhaust valve 726 .
- the DC-DC convertor 704 converts the system voltage to the accessory voltage and thus provides electric power to the accessories.
- the circuit 700 normally operates at a system voltage of 55 volts and some accessories of the snowmobile normally operate at an accessory voltage of 12 volts.
- the DC-DC converter 704 is a 55V-12V converter. These values for the system voltage and for the accessory voltage are nominal for this implementation and may vary according to the actual operating conditions of the snowmobile 10 .
- FIG. 15 is a timing diagram showing an example of a sequence for changing the control strategy for the delivery of electric power between the capacitance 145 and the motor-generator 144 along with corresponding engine rotational speed variations.
- a graph 410 shows a variation of electrical power delivery control strategies applied by the ECU 164 , as a function of time, in seconds.
- “Strategy 1” indicates the application of the first control strategy, specifically using a vector control
- “Strategy 2” indicates the application of the second control strategy, which uses shunting of phases of the motor-generator 144 to control the voltage applied to charge the capacitance 145
- “Neutral” indicates the application of the neutral control mode.
- the voltage generated by the motor-generator 144 may simply be converted to direct current and applied to charge the capacitance 145 , provided that a peak back electromotive force voltage of the motor-generator 144 is higher than the nominal voltage of the circuit 200 , a condition that is usually met when the ICE 24 reaches a sufficient revolution speed.
- a graph 412 shows a corresponding variation of a rotational speed of the crankshaft 100 over a same time scale. In a first half-second of operation following the user command for the electric start procedure for the ICE 24 , no power is delivered between the capacitance 145 and the motor-generator 144 . This period is used to equalize the voltages of the capacitance 145 and of the capacitor C 1 .
- the actual duration of this period may vary considerably as a function of the value of the capacitor C 1 .
- a period ranging from 0.5 to about 1.1 seconds corresponds essentially to the period covered between 0 and 0.4 seconds on the graphs 400 and 402 .
- the ECU 164 uses the first control strategy (Strategy 1) to control delivery of electric power from the capacitance 145 to the motor-generator 144 until the ICE 24 is actually started. Then, between 1.1 and 1.3 seconds, as the ICE 24 accelerates, electric power is delivered from the motor-generator 144 to the capacitance 145 in the neutral control mode.
- Strategy 1 the first control strategy
- the motor-generator 144 starts generating power at a voltage that tends to exceed the nominal voltage of the capacitance 145 .
- This is when the ECU 164 starts using the second control strategy (Strategy 2) to control delivery of electrical power from the motor-generator 144 to the capacitance 145 .
- the neutral control mode is not implemented is also contemplated, in which the ECU 164 starts using the second control strategy as soon as the ICE 24 is successfully started.
- FIG. 16 is another timing diagram showing an example of an impact of the control strategies on a current exchanged between the capacitance and the ETM and on a system voltage.
- a graph 420 shows a voltage of one of the Phases A, B or C of the motor-generator 144 as a function of time, in seconds, and as a function of the control strategies.
- the ECU 164 controls the application of voltage pulses to the motor-generator 144 in pulse width modulation (PWM) mode, at a very rapid rate typically expressed in kilohertz.
- PWM pulse width modulation
- a graph 422 shows a variation of a current flowing between the capacitance 145 and the motor-generator 144 as the ECU 164 changes from the first control strategy to the neutral control mode to the second control strategy.
- a three-phase current flows from the capacitance 145 toward the motor-generator 144 , through the inverter 146 .
- all transistors T 1 -T 6 of the inverter are open and no current flows between the capacitance 145 and the motor-generator 144 .
- Significant current is generated by each phase of the motor-generator 144 after the start of the ICE 24 .
- the ECU 164 applies shunting of the phases of the motor-generator 144 for preventing excess voltage at its output, as illustrated by the strong variations of the current in the right-hand part of graph 422 .
- the graph 424 shows an actual voltage measured on the capacitance 145 as the ECU 164 changes from the first control strategy to the neutral control mode to the second control strategy.
- the voltage of the capacitance 145 initially decreases while electric power is delivered to the motor-generator 145 .
- the ECU 164 places the system in neutral control mode.
- a discharge of the freewheel diodes D 1 -D 6 causes a modest increase of the voltage of the capacitance 145 .
- Opening of the transistor Q 1 at the beginning of the operation in the second control strategy temporary isolates the capacitance 145 from the motor-generator so that electric power produced by the motor-generator is mainly available for other needs of the system, such as injection, ignition, control, and the like. Closing again of the transistor Q 1 allows charging of the capacitance 145 , with a voltage that oscillates near the nominal system voltage according to the shunting of the motor-generator 144 .
- timing values, rotational speed values, and torque values illustrated in the various graphs 400 , 402 , 410 , 412 , 420 , 422 and 424 are provided for illustration and do not limit the present disclosure. Actual values may depend greatly on the construction of the ICE 24 , of the motor-generator 144 , of the capacitance 145 and on the operation strategy of the ECU 164 .
- the ICE 24 could be provided with a decompression system.
- the decompression system can release pressure in the combustion chambers 120 A, 120 B, thereby reducing compression forces that need to be overcome by the motor-generator 144 at operations 326 and 626 described above. Therefore, by providing a decompression system, it is contemplated that the motor-generator 144 could be even smaller and lighter, a size and a weight of the capacitance 145 being reduced accordingly.
- the foregoing description is intended to be exemplary rather than limiting. The scope of the present technology is therefore intended to be limited solely by the scope of the appended claims.
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Abstract
Description
- The present application is a continuation of U.S. patent application Ser. No. 15/775,616 filed on May 11, 2018, which is a National Stage of International Patent Application No. PCT/IB16/56824 filed on Nov. 11, 2016, which claims priority to U.S. Provisional Patent Application No. 62/254,421, filed Nov. 12, 2015, the entirety of each of which is incorporated herein by reference.
- The present technology relates to a method and system for starting an internal combustion engine.
- In order to start the internal combustion engine of small vehicles, such as a snowmobile, a recoil starter is sometimes provided. To start the engine, the user pulls on a rope of the recoil starter which causes the crankshaft of the engine to turn. If the crankshaft turns fast enough, the engine can be started. If not, the rope needs to be pulled again until the engine starts.
- In order to facilitate the starting of the engine, some vehicles have been provided with an electric starting system. This system consists of an electric motor, known as a starter, which engages and turns a ring gear connected to the crankshaft via a Bendix™ mechanism, when an ignition key is turned or a start button is pushed by the user. The starter turns the crankshaft fast enough to permit the starting of the engine, and once the engine has started, disengages the ring gear and is turned off. The vehicle has a battery to supply electric current to the starter in order to turn the crankshaft.
- Although it is very convenient for the user, electric starting systems of the type described above have some drawbacks. The battery, the starter and their associated components add weight to the vehicle. As would be understood, additional weight reduces the fuel efficiency of the vehicle and can affect handling of the vehicle. In the case of snowmobiles, this weight also makes it more difficult for the snowmobile to ride on top of snow. These electric starting systems also require additional assembly steps when manufacturing the vehicle and take up room inside the vehicle.
- To recharge the battery and to provide the electric current necessary to operate the various components of the vehicle once the engine has started, an electrical generator is operatively connected to the crankshaft of the engine. As the crankshaft turns the rotor of the electrical generator, the generator generates electricity.
- In recent years, some vehicles have been provided with motor-generator units, also called starter-generators, which replace the starter and the electrical generator. The motor-generator is operatively connected to the crankshaft in a manner similar to the aforementioned electrical generator. The motor-generator unit can be used as a starter or as a generator. By applying current to the motor-generator unit, the motor-generator unit operates as a starter and turns the crankshaft to enable starting of the engine. When the motor-generator is operated as a generator, the rotation of the crankshaft causes the motor-generator to generate electricity. As would be understood, the use of such systems addresses some of the deficiencies of starting systems using separate starters and electrical generators.
- In order to start the engine, the torque applied to the crankshaft to make it turn has to be sufficiently large to overcome the compression inside the engine's cylinders resulting from the pistons moving up in their respective cylinders as the crankshaft rotates. In order to provide this amount of torque, the motor-generator unit needs to be sufficiently large to properly operate as a starter.
- Another problem relates to the control of the motor-generator. When operating as a starter, the motor-generator generally operates at low rotational speeds, sufficient to allow the onset of ignition in the internal combustion engine. This operation requires the provision of a certain voltage to the motor-generator by the electric starting system. When operating as a generator, the motor-generator provides electric power over a wide range of rotational speeds of the internal combustion engine, oftentimes far exceeding the starting rotational speed. Without specific voltage control solutions, the motor-generator operating at high rotational speeds could generate voltages that far exceed the needs of the various components of the vehicle.
- There is therefore a need for a method and system for starting an internal combustion engine that address at least some of the above inconveniences.
- It is an object of the present technology to ameliorate at least some of the inconveniences present in the prior art.
- The present technology provides a system supporting an electrical start procedure for an internal combustion engine (ICE) and a method for electrical starting the ICE that uses an electric turning machine (ETM) connected to the crankshaft to start the engine. The method permits an electrical start of the engine using a power source that is smaller and lighter than conventional batteries. In order to start the engine, electrical power is delivered from the power source to the ETM in a first control strategy to rotate the crankshaft so that fuel injection and ignition can occur. Once the engine is running, whether it has been started manually by pulling the rope of a recoil starter or using the electrical start procedure, electrical power is delivered from the ETM to an accessory in a second control strategy. For example, the accessory may consist of the power source that may be recharged in view of a future electrical start command. The electrical start procedure can be made to conditional to an initial voltage of the power source being equal to or above a minimum threshold. The first control strategy is tailored to provide sufficient torque to rotate the crankshaft without fully depleting the energy stored in the power source. The second control strategy is tailored so that electrical power is delivered to the accessory, for example to the power source, at a voltage that remains fairly constant for a wide range of rotational speeds of the crankshaft.
- The present technology also provides a method for starting an internal combustion engine (ICE) having a crankshaft. The method involves a cold start of the ICE, followed by stopping of the ICE and then by restarting of the ICE using an electric start procedure. The ICE is cold-started using a recoil starter. While the ICE is running, an electric turning machine (ETM) mounted to the crankshaft operates as a generator to charge a power source that is smaller and lighter than conventional batteries. After stopping the ICE, the electric start procedure uses the power source to deliver electrical power to the ETM, which is now operating as a starter.
- The present technology further provides a method and a system for an assisted start of the ICE. When the crankshaft is rotated by use of the recoil starter, electric power is delivered from the power source to the ETM to assist starting of the ICE. While the ICE is running, whether it has been started manually by pulling the rope of a recoil starter, using the assisted start procedure to facilitate the task of pulling the rope of the recoil starter, or using the electric start procedure, electrical power is also delivered from the ETM to an accessory. The electric start procedure and the assisted start procedure can be made conditional to an initial voltage of the power source being equal to or above a minimum threshold. The electric start procedure and the assisted start procedure are tailored to provide sufficient torque to rotate the crankshaft without fully depleting the energy stored in the power source. Some implementations may include either the electrical start procedure or the assisted start procedure. Other implementations may include both the electrical start procedure and the assisted start procedure.
- According to a first aspect of the present technology, there is provided a method for starting an internal combustion engine (ICE) having a crankshaft. The method comprises rotating the crankshaft using a recoil starter, and while the crankshaft is rotating, delivering electric power from a power source to an electric turning machine (ETM) co-axially mounted to the crankshaft for starting the ICE.
- In some implementations of the present technology, electric power is delivered from the power source to the ETM for starting the ICE while the crankshaft is rotating if a voltage of the power source meets or exceeds an assisted start voltage threshold.
- In some implementations of the present technology, the method further comprises delivering electric power from the ETM to charge the power source while the ICE is operating.
- In some implementations of the present technology, the method further comprises stopping the ICE providing a manual start indication if the voltage of the power source is below the assisted start voltage threshold, providing an assisted start indication if the voltage of the power source meets or exceeds the assisted start voltage threshold and if the voltage of the power source is below an electric start voltage threshold, and providing an electric start indication if the voltage of the power source meets or exceeds the electric start voltage threshold.
- In some implementations of the present technology, the method further comprises using a position sensor to detect that the crankshaft is rotating before delivering electric power from the power source to the ETM.
- In some implementations of the present technology, delivering electric power from the power source to the ETM is conditional on a value provided by a sensor and on a comparison between the value and a predetermined threshold.
- In some implementations of the present technology, the method further comprises using an air temperature sensor to measure an air temperature, wherein delivering electric power from the power source to the ETM is conditional on a comparison between the air temperature a minimum air temperature threshold.
- In some implementations of the present technology, the method further comprises providing a manual start indication if the air temperature is below the minimum air temperature.
- In some implementations of the present technology, the method further comprises using a controller temperature sensor to measure a temperature of a controller for the ICE, wherein delivering electric power from the power source to the ETM is conditional on a comparison between the temperature of the controller for the ICE and a minimum temperature for the controller.
- In some implementations of the present technology, the method further comprises providing a manual start indication if the temperature of the controller is below the minimum temperature for the controller.
- In some implementations of the present technology, the method further comprises using a timer to measure a a time duration for the delivery of electric power to the ETM, wherein delivering electric power from the power source to the ETM is conditional on a comparison between the time duration for the delivery of electric power to the ETM and a maximum time duration for the delivery of electric power to the ETM.
- In some implementations of the present technology, the method further comprises providing a manual start indication if the time duration for the delivery of electric power to the ETM exceeds the maximum time duration for the delivery of electric power to the ETM.
- In some implementations of the present technology, the method further comprises delivering electric power from the ETM to the power source when a revolution speed of the crankshaft meets or exceeds a minimal revolution threshold.
- In some implementations of the present technology, the power source is selected from a battery and a capacitance.
- In some implementations of the present technology, the method further comprises operating the ETM as a starter and as a generator.
- In some implementations of the present technology, the method further comprises delivering electric power from the generator to an accessory.
- In some implementations of the present technology, the ETM is operated as a generator when a generated voltage of the ETM meets or exceeds a voltage generation threshold.
- In some implementations of the present technology, the method further comprises converting electric power generated by the ETM from the generated voltage to an accessory voltage, and delivering electric power at the accessory voltage to an accessory.
- In some implementations of the present technology, the generated voltage is greater than the accessory voltage.
- In some implementations of the present technology, the method further comprises injecting fuel in a combustion chamber of the ICE as a piston of the ICE moves toward its top dead center (TDC) position and igniting the fuel in the combustion chamber of the ICE as the piston of the ICE moves beyond its TDC position.
- According to a second aspect of the present technology, there is provided a system for starting an internal combustion engine (ICE) having a crankshaft. The system comprises an electric turning machine (ETM) adapted for being co-axially mounted to the crankshaft, a recoil starter adapted for causing a rotation of the crankshaft for starting the ICE, a power source, a position sensor adapted for detecting a rotation of the crankshaft, and an engine control unit (ECU) operatively connected to the position sensor and adapted for controlling a delivery of electric power from the power source to the ETM for starting the ICE when the position sensor indicates that the crankshaft is rotating.
- In some implementations of the present technology, the ECU is adapted for controlling a delivery of electric power from the ETM for charging the power source while the ICE is operating.
- In some implementations of the present technology, the ECU is adapted for initiating the delivery of electric power from the ETM to the power source when the position sensor indicates that a revolution speed of the crankshaft meets or exceeds a minimal revolution threshold.
- In some implementations of the present technology, the system further comprises a voltage sensor operatively connected to the ECU and adapted for measuring of voltage of the ETM, wherein the ECU is adapted for initiating the delivery of electric power from the ETM to the power source when the voltage of the ETM meets or exceeds a voltage generation threshold.
- In some implementations of the present technology, the system further comprises a voltage sensor operatively connected to the ECU and adapted for measuring of voltage of the power source, wherein the ECU is adapted for preventing the delivery of electric power from the power source to the ETM is the voltage of the power source is below an assisted start voltage threshold.
- In some implementations of the present technology, the system further comprises a display, the display being operatively connected to the ECU, wherein the ECU is adapted for stopping the ICE causing the display to provide a manual start indication if the voltage of the power source is below the assisted start voltage threshold, causing the display to provide an assisted start indication if the voltage of the power source meets or exceeds the assisted start voltage threshold and if the voltage of the power source is below an electric start voltage threshold, and causing the display to provide an electric start indication if the voltage of the power source meets or exceeds the electric start voltage threshold.
- In some implementations of the present technology, the system further comprises a sensor operatively connected to the ECU and adapted for measuring an air temperature, wherein ECU is adapted for preventing the delivery of electric power from the power source to the ETM if the air temperature is below a minimum air temperature.
- In some implementations of the present technology, the system further comprises a sensor operatively connected to the ECU and adapted for measuring a temperature of the ECU, wherein the ECU is adapted for preventing the delivery of electric power from the power source to the ETM if the temperature of the ECU is below a minimum temperature for the ECU.
- In some implementations of the present technology, the system further comprises a timer operatively connected to the ECU and adapted for measuring a time duration for the delivery of electric power to the ETM, wherein the ECU is adapted for terminating the delivery of electric power from the power source to the ETM after a maximum time duration for the delivery of electric power to the ETM.
- In some implementations of the present technology, the power source is selected from a battery and a capacitance.
- In some implementations of the present technology, the ETM is adapted for operating as a starter and as a generator.
- In some implementations of the present technology, the ETM is adapted for delivering electric power to an accessory.
- In some implementations of the present technology, the system further comprises a voltage converter adapted for converting a voltage generated by the generator to an accessory voltage.
- In some implementations of the present technology, the ECU is implemented on a single processor.
- In some implementations of the present technology, the ECU is implemented on a single module, the module comprising a first processor adapted for controlling a delivery of electric power from the ETM to the power source and for controlling the delivery of electric power from the power source to the ETM, and a second processor adapted for controlling a fuel injection function and an ignition function of the ICE.
- According to a third aspect of the present technology, there is provided an internal combustion engine (ICE) comprising the system for starting the ICE, the ICE further comprising the crankshaft, a cylinder, a cylinder head connected to the cylinder, and a piston operatively connected to the crankshaft and disposed in the cylinder, the cylinder, the cylinder head and the piston defining a variable volume combustion chamber therebetween.
- In some implementations of the present technology, the ICE further comprises a fuel injector operatively connected to the ECU, and an ignition system operatively connected to the ECU, wherein the ECU is adapted for causing the fuel injector to inject fuel in the combustion chamber as the piston moves toward its top dead center (TDC) position and for causing the ignition system to ignite the fuel in the combustion chamber as the piston moves beyond from its TDC position.
- Additional and/or alternative features, aspects and advantages of implementations of the present technology will become apparent from the following description, the accompanying drawings and the appended claims.
- For a better understanding of the present technology, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:
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FIG. 1 is a right side perspective view of a snowmobile; -
FIG. 2 is a perspective view taken from a front, left side of the internal combustion engine of the snowmobile ofFIG. 1 ; -
FIG. 3 is a rear elevation view of the engine ofFIG. 2 ; -
FIG. 4 is a cross-sectional view of the engine ofFIG. 2 taken through line 4-4 ofFIG. 3 ; -
FIG. 5 is a cross-sectional view of the engine ofFIG. 2 taken through line 5-5 ofFIG. 4 with a drive pulley of a CVT mounted on a crankshaft of the engine; -
FIG. 6 is a schematic diagram of components of a control system of the engine ofFIG. 2 ; -
FIG. 7 is a block diagram of a dual-strategy control system for delivery of electric power between the capacitance and the electric turning machine (ETM) ofFIG. 6 ; -
FIG. 8 is a block diagram of an energy management circuit for the capacitance ofFIG. 6 ; -
FIG. 9 is a logic diagram of a method for starting the engine ofFIG. 2 according to an implementation; -
FIG. 10 is a timing diagram showing an example of variations of an engine resistive torque as a function of time along with corresponding engine rotational speed variations; -
FIG. 11 is a logic diagram of a method for starting the engine ofFIG. 2 according to another implementation; -
FIG. 12 is a circuit diagram showing connections between the inverter, the capacitance and the motor-generator ofFIG. 6 ; -
FIG. 13 is a block diagram of a typical implementation of a vector control drive; -
FIG. 14 is a block diagram of an electric system according to an implementation of the present technology; -
FIG. 15 is a timing diagram showing an example of a sequence for changing the control strategy for the delivery of electric power between the capacitance and the electric turning machine (ETM) along with corresponding engine rotational speed variations; and -
FIG. 16 is another timing diagram showing an example of an impact of the control strategies on a current exchanged between the capacitance and the ETM and on a system voltage. - The method and system for starting an internal combustion engine (ICE) and the method and system for an assisted start of the ICE will be described with respect to a
snowmobile 10. However, it is contemplated that the method and system could be used in other vehicles, such as, but not limited to, on-road vehicles, off-road vehicles, a motorcycle, a scooter, a three-wheel road vehicle, a boat powered by an outboard engine or an inboard engine, and an all-terrain vehicle (ATV). It is also contemplated that the method and system could be used in devices other than vehicles that have an internal combustion engine such as a generator. The method and system will also be described with respect to a two-stroke, inline, two-cylinder internal combustion engine (ICE) 24. However, it is contemplated that the method and system could be used with an internal combustion engine having one or more cylinders and, in the case of multi-cylinder engines, having an inline or other configuration, such as a V-type engine as well as 4-stroke engines. - Turning now to
FIG. 1 , asnowmobile 10 includes aforward end 12 and arearward end 14 that are defined consistently with a forward travel direction of thesnowmobile 10. Thesnowmobile 10 includes aframe 16 that has atunnel 18, anengine cradle portion 20 and a frontsuspension assembly portion 22. Thetunnel 18 consists of one or more pieces of sheet metal arranged to form an inverted U-shape that is connected at the front to theengine cradle portion 20 and extends rearward therefrom along thelongitudinal axis 23. An ICE 24 (schematically illustrated inFIG. 1 ) is carried by theengine cradle portion 20 of theframe 16. TheICE 24 is described in greater detail below. Twoskis 26 are positioned at theforward end 12 of thesnowmobile 10 and are attached to the frontsuspension assembly portion 22 of theframe 16 through afront suspension assembly 28. Thefront suspension assembly 28 includesshock absorber assemblies 29,ski legs 30, and supportingarms 32. Ball joints and steering rods (not shown) operatively connect theskis 26 to asteering column 34. A steering device in the form ofhandlebar 36 is attached to the upper end of thesteering column 34 to allow a driver to rotate theski legs 30 and thus theskis 26, in order to steer thesnowmobile 10. - An
endless drive track 38 is disposed generally under thetunnel 18 and is operatively connected to theICE 24 through a CVT 40 (schematically illustrated by broken lines inFIG. 1 ) which will be described in greater detail below. Theendless drive track 38 is driven to run about arear suspension assembly 42 for propulsion of thesnowmobile 10. Therear suspension assembly 42 includes a pair of slide rails 44 in sliding contact with theendless drive track 38. Therear suspension assembly 42 also includes a plurality ofshock absorbers 46 which may further include coil springs (not shown) surrounding one or more of theshock absorbers 46.Suspension arms frame 16. A plurality ofidler wheels 52 are also provided in therear suspension assembly 42. Other types and geometries of rear suspension assemblies are also contemplated. - At the
forward end 12 of thesnowmobile 10,fairings 54 enclose theICE 24 and theCVT 40, thereby providing an external shell that protects theICE 24 and theCVT 40. Thefairings 54 include a hood and one or more side panels that can be opened to allow access to theICE 24 and theCVT 40 when this is required, for example, for inspection or maintenance of theICE 24 and/or theCVT 40. Awindshield 56 is connected to thefairings 54 near theforward end 12 of thesnowmobile 10. Alternatively thewindshield 56 could be connected directly to thehandlebar 36. Thewindshield 56 acts as a wind screen to lessen the force of the air on the driver while thesnowmobile 10 is moving forward. - A straddle-
type seat 58 is positioned over thetunnel 18. Twofootrests 60 are positioned on opposite sides of thesnowmobile 10 below theseat 58 to accommodate the driver's feet. - Turning now to
FIGS. 2 to 5 , theICE 24 and theCVT 40 will be described. TheICE 24 operates on the two-stroke principle. TheICE 24 has acrankshaft 100 that rotates about a horizontally disposed axis that extends generally transversely to thelongitudinal axis 23 of thesnowmobile 10. The crankshaft drives theCVT 40 for transmitting torque to theendless drive track 38 for propulsion of thesnowmobile 10. - The
CVT 40 includes adrive pulley 62 coupled to thecrankshaft 100 to rotate with thecrankshaft 100 and a driven pulley (not shown) coupled to one end of a transversely mounted jackshaft (not shown) that is supported on theframe 16 through bearings. The opposite end of the transversely mounted jackshaft is connected to the input member of a reduction drive (not shown) and the output member of the reduction drive is connected to a drive axle (not shown) carrying sprocket wheels (not shown) that form a driving connection with thedrive track 38. - The
drive pulley 62 of theCVT 40 includes a pair of opposed frustoconical belt drive sheaves 64 and 66 between which a drive belt (not shown) is located. The drive belt is made of rubber, but it is contemplated that it could be made of metal linkages or of a polymer. Thedrive pulley 62 will be described in greater detail below. The driven pulley includes a pair of frustoconical belt drive sheaves between which the drive belt is located. The drive belt is looped around both thedrive pulley 62 and the driven pulley. The torque being transmitted to the driven pulley provides the necessary clamping force on the drive belt through its torque sensitive mechanical device in order to efficiently transfer torque to the other powertrain components. - As discussed above, the
drive pulley 62 includes a pair of opposed frustoconical belt drive sheaves 64 and 66 as can be seen inFIG. 5 . Both sheaves 64 and 66 rotate together with thecrankshaft 100. Thesheave 64 is fixed in an axial direction relative to thecrankshaft 100, and is therefore referred to as the fixedsheave 64. The fixedsheave 64 is also rotationally fixed relative to thecrankshaft 100. Thesheave 66 can move toward or away from the fixedsheave 64 in the axial direction of thecrankshaft 100 in order to change the drive ratio of theCVT 40, and is therefore referred to as themovable sheave 66. As can be seen inFIG. 5 , the fixedsheave 64 is disposed between themovable sheave 66 and theICE 24. - The fixed
sheave 64 is mounted on a fixedsheave shaft 68. The fixedsheave 64 is press-fitted on the fixedsheave shaft 68 such that the fixedsheave 64 rotates with the fixedsheave shaft 68. It is contemplated that the fixedsheave 64 could be connected to the fixedsheave shaft 68 in other known manners to make the fixedsheave 64 rotationally and axially fixed relative to the fixedsheave shaft 68. As can be seen inFIG. 5 , the fixedsheave shaft 68 is hollow and has a tapered hollow portion. The tapered hollow portion receives the end of thecrankshaft 100 therein to transmit torque from theICE 24 to the drivepulley 62. Afastener 70 is inserted in the outer end (i.e. the left side with respect toFIG. 5 ) of thedrive pulley 62, inside the fixedsheave shaft 68, and screwed into the end of thecrankshaft 100 to prevent axial displacement of the fixedsheave shaft 68 relative to thecrankshaft 100. It is contemplated that the fixedsheave shaft 68 could be connected to thecrankshaft 100 in other known manners to make the fixedsheave shaft 68 rotationally and axially fixed relative to thecrankshaft 100. It is also contemplated that thecrankshaft 100 could be the fixedsheave shaft 68. - A
cap 72 is taper-fitted in the outer end of the fixedsheave shaft 68. Thefastener 70 is also inserted through thecap 72 to connect thecap 72 to the fixedsheave shaft 68. It is contemplated that thecap 72 could be connected to the fixedsheave shaft 68 by other means. The radially outer portion of thecap 72 forms aring 74. Anannular rubber damper 76 is connected to thering 74. Anotherring 78 is connected to therubber damper 76 such that therubber damper 76 is disposed between therings rubber damper 76 is vulcanized to therings damper 76 could be made of a material other than rubber. - A
spider 80 is disposed around the fixedsheave shaft 68 and axially between thering 78 and themovable sheave 66. Thespider 80 is axially fixed relative to the fixedsheave 64. Apertures (not shown) are formed in thering 74, thedamper 76, and thering 78. Fasteners (not shown) are inserted through the apertures in thering 74, thedamper 76, thering 78 and thespider 80 to fasten thering 78 to thespider 80. As a result, torque is transferred between the fixedsheave shaft 68 and thespider 80 via thecap 72, therubber damper 76 and thering 78. Thedamper 76 dampens the torque variations from the fixedsheave shaft 68 resulting from the combustion events in theICE 24. Thespider 80 therefore rotates with the fixedsheave shaft 68. - A
movable sheave shaft 82 is disposed around the fixedsheave shaft 68. Themovable sheave 66 is press-fitted on themovable sheave shaft 82 such that themovable sheave 66 rotates and moves axially with themovable sheave shaft 82. It is contemplated that themovable sheave 66 could be connected to themovable sheave shaft 82 in other known manners to make themovable sheave 66 rotationally and axially fixed relative to theshaft 82. It is also contemplated that themovable sheave 66 and themovable sheave shaft 82 could be integrally formed. - To transmit torque from the
spider 80 to themovable sheave 104, a torque transfer assembly consisting of threeroller assemblies 84 connected to themovable sheave 66 is provided. Theroller assemblies 84 engage thespider 80 so as to permit low friction axial displacement of themovable sheave 66 relative to thespider 80 and to eliminate, or at least minimize, rotation of themovable sheave 66 relative to thespider 80. As described above, torque is transferred from the fixedsheave 64 to thespider 80 via thedamper 76. Thespider 80 engages theroller assemblies 84 which transfer the torque to themovable sheave 66 with no, or very little, backlash. As such, thespider 80 is considered to be rotationally fixed relative to themovable sheave 66. It is contemplated that in some implementations, the torque transfer assembly could have more or less than threeroller assemblies 84. - As can be seen in
FIG. 5 , a biasing member in the form of acoil spring 86 is disposed inside acavity 88 defined radially between themovable sheave shaft 82 and thespider 80. As themovable sheave 66 and themovable sheave shaft 82 move axially toward the fixedsheave 64, thespring 86 gets compressed. Thespring 86 biases themovable sheave 66 and themovable sheave shaft 82 away from the fixedsheave 64 toward their position shown inFIG. 5 . It is contemplated that, in some implementations, themovable sheave 66 could be biased away from the fixedsheave 64 by mechanisms other than thespring 86. - The
spider 80 has threearms 90 disposed at 120 degrees from each other. Threerollers 92 are rotatably connected to the threearms 90 of thespider 80. Threecentrifugal actuators 94 are pivotally connected to three brackets (not shown) formed by themovable sheave 66. Eachroller 92 is aligned with a corresponding one of thecentrifugal actuators 94. Since thespider 80 and themovable sheave 66 are rotationally fixed relative to each other, therollers 92 remain aligned with their correspondingcentrifugal actuators 94 when theshafts centrifugal actuators 94 are disposed at 120 degrees from each other. Thecentrifugal actuators 94 and theroller assemblies 84 are arranged in an alternating arrangement and are disposed at 60 degrees from each other. It is contemplated that therollers 92 could be pivotally connected to the brackets of themovable sheave 66 and that thecentrifugal actuators 94 could be connected to thearms 90 of thespider 80. It is also contemplated that there could be more or less than threecentrifugal actuators 94, in which case there would be a corresponding number ofarms 90,rollers 92 and brackets of the movable sheave. It is also contemplated that therollers 92 could be omitted and replaced with surfaces against which thecentrifugal actuators 94 can slide as they pivot. - In the present implementation, each
centrifugal actuator 94 includes anarm 96 that pivots about anaxle 98 connected to its respective bracket of themovable sheave 66. The position of thearms 96 relative to theiraxles 98 can be adjusted. It is contemplated that the position of thearms 96 relative to theiraxles 98 could not be adjustable. Additional detail regarding centrifugal actuators of the type of thecentrifugal actuator 94 can be found in International Patent Publication No. WO2013/032463 A2, published Mar. 7, 2013, the entirety of which is incorporated herein by reference. - The above description of the
drive pulley 62 corresponds to one contemplated implementation of a drive pulley that can be used with theICE 24. Additional detail regarding drive pulleys of the type of thedrive pulley 62 can be found in International Patent Publication No. WO 2015/151032 A1, published on Oct. 8, 2015, the entirety of which is incorporated herein by reference. It is contemplated that other types of drive pulleys could be used. - The
ICE 24 has acrankcase 102 housing a portion of thecrankshaft 100. As can be seen inFIGS. 2, 3 and 5 , thecrankshaft 100 protrudes from thecrankcase 102. It is contemplated that thecrankshaft 100 could drive an output shaft connected directly to the end of thecrankshaft 100 or offset from thecrankshaft 100 and driven by driving means such as gears in order to drive thedrive pulley 62. It is also contemplated that thecrankshaft 100 could drive, using gears for example, a counterbalance shaft housed in part in thecrankcase 102 and that thedrive pulley 62 could be connected to the counterbalance shaft, in which case, thecrankshaft 100 does not have to protrude from thecrankcase 102 for this purpose. Acylinder block 104 is disposed on top of and connected to thecrankcase 102. Thecylinder block 104 as shown defines twocylinders FIG. 5 ). Acylinder head 108 is disposed on top of and is connected to thecylinder block 104. - As best seen in
FIG. 5 , thecrankshaft 100 is supported in thecrankcase 102 bybearings 110. Thecrankshaft 100 has two crank pins 112A, 112B. In the illustrated implementation where the twocylinders rod 114A is connected to the crankpin 112A at one end and to apiston 116A via apiston pin 118A at the other end. As can be seen, thepiston 116A is disposed in thecylinder 106A. Similarly, a connectingrod 114B is connected to the crankpin 112B at one end and to apiston 116B via apiston pin 118B at the other end. As can be seen, thepiston 116B is disposed in thecylinder 106B. Rotation of thecrankshaft 100 causes thepistons respective cylinders cylinder head 108, thecylinder 106A and thepiston 116A define a variablevolume combustion chamber 120A therebetween. Similarly, thecylinder head 108, thecylinder 106B and thepiston 116B define a variablevolume combustion chamber 120B therebetween. It is contemplated that thecylinder block 104 could define more than two cylinders 106, in which case theICE 24 would be provided with a corresponding number of pistons 116 and connecting rods 114. - Air is supplied to the
crankcase 102 via a pair of air intake ports 122 (only one of which is shown inFIG. 4 ) formed in the back of thecylinder block 104. A pair ofthrottle bodies 124 is connected to the pair ofair intake ports 122. Eachthrottle body 124 has athrottle plate 126 that can be rotated to control the air flow to theICE 24. Motors (not shown) are used to change the position of thethrottle plates 126, but it is contemplated that throttle cables connected to a throttle lever could be used. It is also contemplated that a single motor could be used to change the position of boththrottle plates 126. A pair of reed valves 128 (FIG. 4 ) are provided in eachintake port 122. Thereed valves 128 allow air to enter thecrankcase 102, but prevent air from flowing out of thecrankcase 102 via theair intake ports 122. - As the
pistons crankcase 102 flows into thecombustion chambers scavenge ports 130. Fuel is injected in thecombustion chambers fuel injectors fuel injectors cylinder head 108. Thefuel injectors FIG. 1 ) of thesnowmobile 10. In the illustrated implementation, thefuel injectors combustion chamber spark plugs FIGS. 2 to 5 , but schematically illustrated inFIG. 6 ). The spark plugs 134 a, 134 b are mounted to thecylinder head 108. - To evacuate the exhaust gases resulting from the combustion of the fuel-air mixture in the
combustion chambers cylinder main exhaust port auxiliary exhaust ports cylinder exhaust ports FIG. 4 ), 138A, 138B are connected to anexhaust manifold 140. The exhaust manifold is connected to the front of thecylinder block 104.Exhaust valves cylinder block 104, control a degree of opening of theexhaust ports exhaust valves exhaust valves - An electric turning machine (ETM) is connected to the end of the
crankshaft 100 opposite the end of thecrankshaft 100 that is connected to the drivepulley 62. In the present implementation, the ETM is a motor-generator 144 (FIG. 5 ), and more specifically a three-phase alternating current motor-generator 144, such as a permanent magnet motor for example. It is contemplated that the motor-generator may include a number of pole pairs, generating electric power cycling at a rate that is a multiple of the rotational speed of thecrankshaft 100. It is further contemplated that other types of motor-generators could be used, including for example multi-phase motor-generators or poly-phase motor-generators. It is also contemplated that the motor-generator 144 could be connected to another shaft operatively connected to thecrankshaft 100, by gears or belts for example. The motor-generator 144, as its name suggests, can act as a motor or as a generator and can be switched between either functions. Under certain conditions as described hereinbelow, the motor-generator 144 is operated in motor operating mode, being powered either by a small battery (not shown) or by a capacitance 145 (shown onFIG. 6 ). - A battery that is smaller and lighter than one conventionally used for cold starting of the
ICE 24 may be used for an electric start procedure and/or for an assisted start procedure that will be described hereinbelow. Alternatively, the electric start procedure and/or the assisted start procedure may rely on the use of acapacitance 145. Non-limiting examples of capacitances include a high-capacity capacitor, an ultracapacitor (U-CAP), an electric double layer capacitor and a supercapacitor Either the small battery or thecapacitance 145 supplies electric power to the motor-generator 144 for turning thecrankshaft 100. Thecapacitance 145 can accumulate relatively large amounts of energy. In at least one implementation, thecapacitance 145 comprises a plurality of capacitors assembled in series, each capacitor of the series possibly including several capacitors mounted in parallel so that thecapacitance 145 can withstand voltages generally within an operating voltage range of direct fuel injectors. In the context of the present disclosure, references are made to thecapacitance 145 as a single unit. Without limitation and for brevity, implementations in which the electric start procedure or the assisted start procedure, or both, are implemented using thecapacitance 145 along with the motor-generator 144 will be described hereinbelow. - When operating as a generator, the motor-
generator 144 is turned by thecrankshaft 100 and generates electricity that is supplied to thecapacitance 145 and to other electrical components of theICE 24 and thesnowmobile 10. Electric power is exchanged between thecapacitance 145 and the motor-generator 144 through an electrical converter. In implementations in which the motor-generator 144 is a three-phase motor, the electrical converter is a three-phase inverter 146. Use of multi-phase or poly-phase invertors in cooperation with a multi-phase or a poly-phase motor-generator is also contemplated. Control strategies of the motor-generator 144 applicable to its motoring and generating functions and the impact of these strategies on thecapacitance 145 and on theinverter 146 are described hereinbelow. - As can be seen in
FIG. 5 , the motor-generator 144 has astator 148 and arotor 150. Thestator 148 is disposed around thecrankshaft 100 outside of thecrankcase 102 and is fastened to thecrankcase 102. Therotor 150 is connected by splines to the end of thecrankshaft 100 and partially houses thestator 148. Ahousing 152 is disposed over the motor-generator 144 and is connected to thecrankcase 102. Acover 154 is connected to the end of thehousing 152. - Three starting procedures of the
snowmobile 10 may be available to the user. A first procedure comprises a manual start procedure that relies on the use of arecoil starter 156. A second starting procedure comprises an electric start procedure. A third starting procedure comprises an assisted start procedure. One or both of the electric and assisted start procedures may be present in any implementation of thesnowmobile 10. The second and third starting procedures will be describer further below. As can be seen inFIG. 5 , therecoil starter 156 is disposed inside the space defined by thehousing 152 and thecover 154, between thecover 154 and the motor-generator 144. Therecoil starter 156 has arope 158 wound around areel 160. Aratcheting mechanism 162 selectively connects thereel 160 to therotor 150. To start theICE 24 using therecoil starter 156 in the manual start procedure, a user pulls on a handle 163 (FIG. 3 ) connected to the end of therope 158. This turns thereel 160 in a direction that causes theratcheting mechanism 162 to lock, thereby turning therotor 150 and thecrankshaft 100. The rotation of thecrankshaft 100 causes thepistons ICE 24. When theICE 24 starts, the rotation of thecrankshaft 100 relative to thereel 160 disengages theratcheting mechanism 162, and as such thecrankshaft 100 does not turn thereel 160. When the user releases the handle, a spring (not shown) turns thereel 160 thereby winding therope 158 around thereel 160. - In the present implementation, the
drive pulley 62 and the motor-generator 144 are both mounted to thecrankshaft 100. It is contemplated that thedrive pulley 62 and the motor-generator 144 could both be mounted to a shaft other than thecrankshaft 100, such as a counterbalance shaft for example. In the present implementation, thedrive pulley 62, the motor-generator 144 and therecoil starter 56 are all coaxial with and rotate about the axis of rotation of thecrankshaft 100. It is contemplated that thedrive pulley 62, the motor-generator 144 and therecoil starter 56 could all be coaxial with and rotate about the axis of rotation of a shaft other than thecrankshaft 100, such as a counterbalance shaft for example. It is also contemplated that at least one of thedrive pulley 62, the motor-generator 144 and therecoil starter 56 could rotate about a different axis. In the present implementation, thedrive pulley 62 is disposed on one side of theICE 24 and the motor-generator 144 and therecoil starter 56 are both disposed on the other side of theICE 24. It is contemplated the motor generator and/or therecoil starter 56 could be disposed on the same side of theICE 24 as thedrive pulley 62. - Available starting procedures of the
snowmobile 10 comprise an electric start procedure, an assisted start procedure and a manual start procedure.FIG. 6 is a schematic diagram of components of a control system of the engine ofFIG. 2 . The control of the components used to start theICE 24 in the electric start procedure and in the assisted start procedure is done by an engine control unit (ECU) 164 as will be explained below. TheECU 164 is also used to control the operation of theICE 24 after it has started. TheECU 164 is illustrated as a single physical module (later shown inFIG. 14 ) comprising a single processor (also inFIG. 14 ), for example a single microcontroller. Other configurations are within the scope of the present disclosure. For instance, it is contemplated that features of theECU 164 may be implemented using a plurality of co-processors, for example two or more microcontrollers. It is also contemplated that the various tasks of theECU 164 could be split between two or more microprocessors integrated in a single electronic module or two or more microprocessors distributed among various electronic modules. As a non-limitative example, the single electronic module may comprise a first processor adapted for controlling a delivery of electric power from the motor-generator 144 to thecapacitance 145 and to control the delivery of electric power from thecapacitance 145 to the motor-generator 144, and a second processor adapted for controlling a fuel injection function and an ignition function of the ICE. To initiate an electric start procedure or an assisted start procedure of theICE 24, theECU 164 receives inputs from the components disposed to the left of theECU 164 inFIG. 6 , some of which are optional and not present in all implementations, as will be described below. Using these inputs, theECU 164 obtains information fromcontrol maps 166 as to how the components disposed to the right of theECU 164 inFIG. 6 should be controlled in order to start theICE 24. The control maps 166 are stored in an electronic data storage device, such as a static random access memory (SRAM), an electrically-erasable programmable read-only memory (EEPROM) or a flash drive. It is contemplated that instead of or in addition to the control maps 166, theECU 164 could use control algorithms to control the components disposed to the right of theECU 164 inFIG. 6 . In the present implementation, theECU 164 is connected with the various components illustrated inFIG. 6 via wired connections; however it is contemplated that it could be connected to one or more of these components wirelessly. - A user actionable
electric start switch 168, provided on thesnowmobile 10, for example a push button mounted on or near thehandlebar 36, sends a signal to theECU 164 that the user desires theICE 24 to start when it is actuated. Theelectric start switch 168 can also be a switch actuated by a key, a sensor, or any other type of device through which the user can provide an input to theECU 164 that theICE 24 is to be started. In at least one implementation, theelectric start switch 168 may be a sensor operably connected to therope 158 of therecoil starter 156 and to theECU 164. Some traction, for example a simple tugging on therope 158 by an operator, may be detected by this sensor, resulting in the initiation of the electric start procedure of theICE 24, provided that all conditions for the electric start procedure are present. - A
crankshaft position sensor 170 is disposed in the vicinity of thecrankshaft 100 in order to sense the position of thecrankshaft 100. Thecrankshaft position sensor 170 sends a signal representative of the position of thecrankshaft 100 to theECU 164. In the present implementation, thecrankshaft position sensor 170 is an absolute position sensor, such as a sin/cos Hall Effect encoder for example. Based on the change in the signal received from thecrankshaft position sensor 170, theECU 164 is also able to determine an angular position of thecrankshaft 100. It is contemplated that thecrankshaft position sensor 170 could alternatively sense the position of an element other than thecrankshaft 100 that turns with thecrankshaft 100, such as therotor 150 of the motor-generator 144 for example, and be able to determine the position of thecrankshaft 100 from the position of this element. Use of a relative position sensor to sense the position of thecrankshaft 170 is also contemplated as expressed hereinbelow. - The assisted start procedure may be initiated, provided that conditions are met as described hereinbelow, when a rotation of the
crankshaft 100 is initiated by the user pulling on therope 158 of therecoil starter 156. Thecrankshaft position sensor 170 informs theECU 170 of the rotation of thecrankshaft 100. - A
voltage sensor 167, for example a voltmeter, provides a measurement of a voltage of thecapacitance 145 to theECU 164. As explained in more details hereinbelow, theECU 164 uses this voltage measurement to determine whether an energy reserve of thecapacitance 145 is sufficient to start theICE 24 using the electric start procedure or to provide assist using the assisted start procedure. - Optionally, other sensors can be used to determine whether or not the engine can be started using the electric start procedure or the assisted start procedure as expressed hereinbelow. These optional sensors include for example an
engine temperature sensor 172, anair temperature sensor 174, an atmosphericair pressure sensor 176, anexhaust temperature sensor 178, atimer 180 and anECU temperature sensor 182. - The
engine temperature sensor 172 is mounted to theICE 24 to sense the temperature of one or more of thecrankcase 102, thecylinder block 104, thecylinder head 108 and engine coolant temperature. Theengine temperature sensor 172 sends a signal representative of the sensed temperature to theECU 164. - The
air temperature sensor 174 is mounted to thesnowmobile 10, in the air intake system for example, to sense the temperature of the air to be supplied to theICE 24. Theair temperature sensor 174 sends a signal representative of the air temperature to theECU 164. - The atmospheric
air pressure sensor 176 is mounted to thesnowmobile 10, in the air intake system for example, to sense the atmospheric air pressure. The atmosphericair pressure sensor 176 sends a signal representative of the atmospheric air pressure to theECU 164. - The
exhaust temperature sensor 178 is mounted to theexhaust manifold 140 or another portion of an exhaust system of thesnowmobile 10 to sense the temperature of the exhaust gases. Theexhaust temperature sensor 178 sends a signal representative of the temperature of the exhaust gases to theECU 164. - The
timer 180 is connected to theECU 164 to provide information to theECU 164 regarding the amount of time elapsed since theICE 24 has stopped. Thetimer 180 can be an actual timer which starts when theICE 24 stops. Alternatively, the function of thetimer 180 can be obtained from a calendar and clock function of theECU 164 or another electronic component. In such an implementation, theECU 164 logs the time and date when theICE 24 is stopped and looks up this data to determine how much time has elapsed since theICE 24 has stopped when theECU 164 receives a signal from theelectric start switch 168 that the user desires theICE 24 to be started. - The
ECU temperature sensor 182 is mounted to a physical module (not shown) that includes one or more processors (not shown) configured to execute the functions of theECU 164. TheECU temperature sensor 182 sends a signal representative of the temperature of that module to theECU 164. - It is contemplated that one or more of the
sensors timer 180 could be omitted. It is also contemplated that one or more of thesensors timer 180 could be used only under certain conditions. For example, the exhaust temperature andpressure sensors ICE 24 has been recently stopped, in which case some exhaust gases would still be present in the exhaust system, or following the first combustion of a fuel-air mixture in one of thecombustion chambers - The
ECU 164 uses the inputs received from at least some of theelectric start switch 168, thesensors timer 180 to retrieve one or more corresponding control maps 166 and to control the motor-generator 144, thefuel injectors ICE 24, as the case may be. The inputs andcontrol maps 166 are also used to control the operation of theICE 24 once it has started. - The
ECU 164 is also connected to adisplay 186 provided on thesnowmobile 10 near thehandlebar 36 to provide information to the user of thesnowmobile 10, such as engine speed, vehicle speed, oil temperature, and fuel level, for example. - Turning now to
FIG. 7 , details of an electronic system for the electric and assisted start procedures for theICE 24 will now be described.FIG. 7 is a block diagram of a dual-strategy control system for delivery of electric power between the capacitance and the ETM ofFIG. 6 . Some components introduced in the foregoing description ofFIG. 6 are reproduced inFIG. 7 in order to provide more details on their operation. - Electric power is delivered between the
capacitance 145 and the motor-generator 144 through theinverter 146. TheECU 164 includes, or is otherwise operatively connected to, astrategy switch 184 that is operative to change the control strategy for the delivery of electric power between thecapacitance 145 and the motor-generator 144 between at least two (2) distinct control strategies. TheECU 164 controls theinverter 146 through thestrategy switch 184. - To start the
ICE 24 using the electric start procedure, the user of thesnowmobile 10 enters an input on theelectric start switch 168, for example by depressing a push button. TheECU 164 is informed of this command. In response, theECU 164 may control a delivery of electric power from thecapacitance 145 to the motor-generator 144 based on a pre-determined amount of torque, or torque request, sufficient to cause rotation of thecrankshaft 100 for starting theICE 24. In a variant, theECU 164 may determine the torque request. The determination of the torque request is made considering thatICE 24 is expected to have a highly irregular resistive torque; alternatively, instead of determining the torque request, theECU 164 may determine a speed request applicable to thecrankshaft 100 to control an amount of power that that the motor-generator 144 should apply to thecrankshaft 100 for starting theICE 24. A voltage of thecapacitance 145 is sensed by thevoltage sensor 167 and provided to theECU 164. If this voltage is below an electric start voltage threshold VMinE, which is a minimum voltage of thecapacitance 145 for the electric start procedure, theECU 164 determines that thecapacitance 145 does not hold sufficient energy to provide the torque request, or the speed request, sufficient to start theICE 24 using the electric start procedure. Consequently, theECU 164 does not allow starting theICE 24 using the electric start procedure and causes thedisplay 186 to show a “manual start” indication or an “assisted start” indication, in implementations where this option is available. Generally speaking, the electric start voltage threshold VMinE is based on a determination of a sufficient charge of thecapacitance 145 allowing a successful electric start procedure in most operating conditions. If this minimum voltage threshold for the electric start procedure is met, theECU 164 causes delivery of electric power from thecapacitance 145 to the motor-generator 144, via theinverter 146, in a first control strategy, initiating a rotation of thecrankshaft 100. TheECU 164 also causes thefuel injectors combustion chambers combustion chambers ICE 24 may comprise one or more cylinders and the mention of two (2)combustion chambers crankshaft 100 reaches a minimum revolution threshold corresponding to a successful start of theICE 24. Thereafter, when a speed of thecrankshaft 100 is equal to or above the minimum revolution threshold, theECU 164 controls the delivery of electric power from the motor-generator 144 to thecapacitance 145, still via theinverter 146, to cause charging of thecapacitance 145. The delivery of electric power from the motor-generator 144 to thecapacitance 145 generally occurs in a second control strategy distinct from the first control strategy. A variant in which the delivery of electric power from the motor-generator 144 to thecapacitance 145 occurs in the first control strategy at low revolution speeds of thecrankshaft 100, or under low throttle demands, and in the second control strategy at high revolution speeds of thecrankshaft 100 is also contemplated. - A
current sensor 188 may be used to optimize thecapacitance 145 current consumption and optimize its energy usage. Thecurrent sensor 188 provides to theECU 164 an indication of the energy from thecapacitance 145 being consumed during the electric start procedure. In an implementation, thecurrent sensor 188 comprises a combination of phase current sensors (not explicitly shown) provided on two (2) phases of the motor-generator 144. Encoding of measurements from these two (2) phase current sensors provide a good estimation of a current flowing between thecapacitance 145 and the motor-generator 144. As shown onFIG. 13 , current measurements may be obtained on all three (3) phases of the motor-generator 144. Thecapacitance 145 energy usage can alternatively be optimized without current sensors, for example, an open loop approach having a predetermined torque request pattern being applied by theECU 164 to drive all cranking sequences can be used. It is also possible to optimize the energy usage of thecapacitance 145 based on a speed request with well-tuned regulators or based on a predetermined pattern of multistep speed requests. - Electric start of the
ICE 24 may fail although initial conditions for the electric start procedure were initially present. This may occur for instance if, while electric power is being delivered from thecapacitance 145 to the motor-generator 144, thevoltage sensor 167 detects that the voltage of thecapacitance 145 falls below a residual voltage threshold VMinR, lower than the electric start voltage threshold VMinE, before the rotational speed of thecrankshaft 100 reaches the minimum revolution threshold corresponding to the successful start of theICE 24. Under such conditions, theECU 164 ceases the delivery of power from thecapacitance 145 to the motor-generator 144 and causes thedisplay 186 to provide a manual start indication or an assisted start indication, in implementations where this option is available. Generally speaking, the residual voltage threshold VMinR corresponds to a minimum charge of thecapacitance 145 that is expected to suffice in allowing the injection and ignition of fuel injection in thecombustion chambers crankshaft 100. - To start the
ICE 24 using the assisted start procedure, the user of thesnowmobile 10 pulls on therope 158 of therecoil starter 156, initiating a rotation of thecrankshaft 100. Thecrankshaft position sensor 170 informs theECU 170 of the rotation of thecrankshaft 100. In response, theECU 164 may control a delivery of electric power from thecapacitance 145 to the motor-generator 144 to assist the rotation of thecrankshaft 100 for starting theICE 24. Optionally, a voltage of thecapacitance 145 is sensed by thevoltage sensor 167 and provided to theECU 164. In this case, if this voltage is below an assisted start voltage threshold VMinA, which is a minimum voltage of thecapacitance 145 for the assisted start procedure, theECU 164 determines that thecapacitance 145 does not hold sufficient energy to assist starting theICE 24 and theECU 164 does not allow starting theICE 24 using the assisted start procedure, instead causing thedisplay 186 to show a “manual start” indication. Generally speaking, the assisted start voltage threshold VMinA is based on a determination of a sufficient charge of thecapacitance 145 allowing a successful assisted start procedure in predetermined operating conditions. In implementations where both electric and assisted start procedures are present, the assisted start voltage threshold VMinA is lower than the electrical start voltage threshold VMinE. If this minimum voltage threshold for the assisted start procedure is met, theECU 164 causes delivery of electric power from thecapacitance 145 to the motor-generator 144, via theinverter 146, in the first control strategy, assisting the rotation of thecrankshaft 100. TheECU 164 also causes thefuel injectors combustion chambers combustion chambers ICE 24 may comprise one or more cylinders and the mention of two (2)combustion chambers crankshaft 100 reaches a minimum revolution threshold corresponding to a successful start of theICE 24. Thereafter, operation of theICE 24 is as expressed in the foregoing description to the electrical start procedure. -
FIG. 8 is a block diagram of an energy management circuit for thecapacitance 145 ofFIG. 6 . Acircuit 200 shows how, in an implementation, theECU 164 and thecapacitance 145 are electrically connected using theelectric start switch 168, which is shown as a pushbutton. Thecapacitance 145 is illustrated as a sum ofsmaller capacitors 202 connected in series. As mentioned earlier, each of thesesmaller capacitors 202 may actually consist of a plurality of capacitors connected in parallel. Each of thesmaller capacitors 202 can withstand a relatively low voltage applied thereon. Thecapacitance 145 formed by the sum of thesmaller capacitors 202 in series can withstand the nominal voltage of thecircuit 200, which is also the nominal voltage of the electrical systems of thesnowmobile 10, with the addition of a safety margin for occasional overvoltage. The voltage present on thecapacitance 145 is defined betweenterminals voltage sensor 167 shown on earlier Figures. - The
circuit 200 provides an output voltage between a lead 208 and aground reference 210 when thecircuit 200 is active. When thecircuit 200 is inactive, thecapacitance 145 is disconnected from theground reference 210 by a metal-oxide semiconductor field effect transistor (MOSFET) Q1 which is, at the time, turned off and therefore open circuit. Substituting a bipolar transistor, for example an insulated gate bipolar transistor (IGBT), for the MOSFET Q1 is also contemplated. - A capacitor C1 is present between the lead 208 and the
ground reference 210. The role of the capacitor C1 is to filter voltage variations at theoutput 204 for the benefit of the various electrical components of thesnowmobile 10, including for example thefuel injectors ground reference 210, which is a system voltage for thesnowmobile 10, is essentially the same as the nominal voltage of thecapacitance 145, although operating voltages between different system states may not be constant at all times. - When the
ICE 24 has been stopped for a long time, more than a few hours for example, the voltage on thecapacitance 145 falls below the electric start voltage threshold VMinE and below the assisted start voltage threshold VMinA, and thecircuit 200 is not energized. Resorting to the manual start procedure is therefore required for starting theICE 24. When theICE 24 has been stopped for a relatively short time, a duration of which depends in large part on the energy storage capacity of thecapacitance 145, the voltage on thecapacitance 145 may be equal to or above the electric start voltage threshold VMinE, in which case the electric start procedure is available. If the voltage of thecapacitance 145 is lower than the electric start voltage threshold VMinE while at least equal to or greater than the assisted start voltage threshold VMinA, the assisted start procedure may be available. The assisted start procedure is described in more details hereinbelow. - When the voltage of the
capacitance 145 is at least equal or greater than the electric start voltage threshold VMinE, the user may depress the electric start switch 168 (pushbutton) to invoke the electric start procedure. This user action is sensed by abutton state detector 212 of theECU 164. Thebutton state detector 212 being referenced to the terminal 206, it becomes placed in parallel with thecapacitance 145 when thestart switch 168 is depressed. At the same time, electrical power is provided from thecapacitance 145 to theECU 164, waking up theECU 164. Depending on specific implementations, thebutton state detector 212 may accept a simple brief electrical contact provided by theelectric start switch 168 to initiate the electric start procedure. Thebutton state detector 212 may alternatively require theelectric start switch 168 to be depressed for a few seconds. A variant in which thebutton state detector 212 is not present, in which theelectric start switch 168 needs to be depressed until theICE 24 is actually started is also contemplated. After sensing the electric start command, thebutton state detector 212 sends a signal to a wake upcircuit 214 of theECU 164. The wake upcircuit 214 controls the following operations. - Initially, the wake up
circuit 214 applies a signal to adriver 216 of the transistor Q1. The transistor Q1 turns on, effectively placing thecapacitance 145 in parallel with the capacitor C1. The wake upcircuit 214 can control thedriver 216 to turn on and off the transistor Q1 at a high frequency in order to prevent excessive current flowing from thecapacitance 145 to the capacitor C1. Electrical conduction through the transistor Q1 may be controlled in a small duty cycle at first, the duty cycle increasing as a voltage difference between the capacitor C1 and thecapacitance 145 decreases. Regardless, the capacitor C1 rapidly charges to reach the voltage of thecapacitance 145. Thecapacitance 145 voltage may reduce slightly, but this effect is limited by the fact that the capacitor C1 is much smaller than thecapacitance 145. After the capacitor C1 has been charged, the electric start continues with theECU 164 controlling the delivery of power from thecapacitance 145 to the motor-generator 144 via thelead 208, which is connected to theinverter 146. - Once the electric start procedure has been successfully executed, as engine is running at idle, the motor-
generator 144 may initially have a limited power generating capacity. Accessories of thesnowmobile 10, including for example thefuel injectors capacitance 145. To avoid an excessive drop of the voltage of the capacitor C1, at thelead 208, while theICE 24 is idling, theECU 164 may optionally control thedriver 216 to turn off the transistor Q1 until thecrankshaft 100 rotates at more than a predetermined revolution threshold. Once theICE 24 has acquired a sufficient speed, the voltage at thelead 208 being now sufficient, theECU 164 may again control thedriver 216 and the transistor Q1 to place thecapacitance 145 in parallel with the capacitor C1. Once again, in order to avoid excessive current flowing from the capacitor C1 to thecapacitance 145 and to avoid an excessive voltage drop at thelead 208, the transistor Q1 may be turned on and off at a small duty cycle at first, the duty cycle increasing as a voltage difference between the capacitor C1 and thecapacitance 145 decreases. The transistor Q1 may therefore be controlled in order to regulate the charging rate ofcapacitance 145 while respecting the electrical power availability at any speed of theICE 24. - The
ECU 164 may optionally integrate an automatic shutdown circuit that may terminate all electrical functions of thesnowmobile 10 in case of system failure. - Table I provides a sequence of events including a manual start procedure of the
ICE 24, followed by an electric start procedure command received after a waiting time that does not exceed the capabilities of the electric start system. In Table I, mentions of “PWM” refer to “pulse width modulation”, a technique used in the first and second control strategies as expressed hereinbelow. -
TABLE I Motor- ECU 164Capacitance Driver 216 generator TYPE Event state C1 voltage 145 voltage duty cycle 144 MANUAL Initial OFF 0 volt 0 volt 0% Stopped conditions Pulling Wake- Up Rising 0 volt 0% Rising the rope speed (1st time) Pulling Firing Rising to 0 volt 0% Rising to the rope nominal idle speed (2nd time) voltage Releasing Ignition/ Nominal Rising, but less Partial to Idle speed the rope PWM voltage than nominal allow voltage charging of the capacitance Ready to Ignition/ Nominal Rising, but less Partial to Slow apply PWM voltage than nominal allow charging throttle voltage charging of the capacitance Partial or Ignition/ Nominal Nominal 100% Charging full PWM voltage voltage throttle — Stop Turning Falling Nominal 0% Falling OFF voltage speed Waiting OFF Close to 0 Less than 0% Stopped time volt nominal voltage, but equal to or above VMinE ELECTRIC Electric Wake-Up Close to 0 Less than 0% Stopped start volt nominal command voltage, but equal to or above VMinE — Ignition/ Equalizing to Reducing Partial to Stopped PWM the slightly allow voltage capacitance equalization voltage — Cranking Equal to the Reducing, but 100% Rising capacitance still equal to or speed voltage above VMinR — Firing Rising Rising 100% Rising to idle speed Ready to Ignition/ Nominal Nominal 100% Idle speed apply PWM voltage voltage throttle - In at least one implementation in which the
fuel injectors capacitance 145 is not sufficient for the direct fuel injectors to inject fuel in thecylinders -
FIG. 9 is a logic diagram of a method for starting the engine ofFIG. 2 according to an implementation. A sequence shown inFIG. 9 comprises a plurality of operations, some of which may be executed in variable order, some of the operations possibly being executed concurrently, and some of the operations being optional. The method begins atoperation 300 when theICE 24 of thesnowmobile 10 is stopped. A voltage of thecapacitance 145 is measured by thevoltage sensor 167 atoperation 302. In thesame operation 302, thedisplay 186 may provide an “automatic start” indication if the voltage meets or exceeds the electric start voltage threshold VMinE and if other conditions described hereinbelow for the electric start procedure are met. The user actuates theelectric start switch 168, this being detected by thebutton state detector 212 atoperation 304. A comparison is made by theECU 164, atoperation 306, between the voltage of thecapacitance 145 and the electric start voltage threshold VMinE to determine whether it is possible to initiate the electric start procedure for theICE 24. If it is determined that the voltage of thecapacitance 145 is below the electric start voltage threshold VMinE, the electric start procedure is prevented. Otherwise, verification is made atoperation 308 that the engine temperature measured by theengine temperature sensor 172 meets or exceeds an engine temperature threshold T0. The electric start procedure is prevented in this threshold for the engine temperature is not met. Otherwise, verification is made atoperation 310 that theECU temperature sensor 182 provides a reading of the temperature of theECU 164 that meets or exceeds an ECU temperature threshold T1. The electric start procedure is prevented if this threshold for the ECU temperature is not met. Additional operations related to use of measurements obtained from other sensors introduced in the foregoing description ofFIG. 6 may take place. These measurements may be provided to theECU 164 by theair temperature sensor 174, theatmospheric temperature sensor 176, or thetimer 180. Additional tests based on those measurements may be executed by theECU 164 to determine whether or not the electric start procedure is likely to succeed or to determine a torque value sufficient to cause the rotation of thecrankshaft 100. For example, the electric start procedure may be made conditional, in theECU 164, on thetimer 180 informing theECU 164 that a period of time since theICE 24 has been stopped is below a predetermined time value when the user actuates theelectric start switch 168 atoperation 304. On the basis of the period of time since theICE 24 has been stopped, it is possible to estimate whether the voltage of thecapacitance 145 will have fallen below the electric start voltage threshold VMinE knowing a maximum charge voltage of thecapacitance 145 from a previous running sequence of theICE 24, and based on a typical energy leakage of thecapacitance 145. - Whether the electric start procedure is prevented because the voltage of the
capacitance 145 is insufficient (operation 306), because the engine temperature is too low (operation 308), because the ECU temperature is too low (operation 310), or for any other reason, the method proceeds tooperation 312. Atoperation 312, theECU 164 causes thedisplay 186 to display “Manual Start” or some other message indicating to the user of thesnowmobile 10 that thesnowmobile 10 will need to be started manually using the recoil starter 156 (i.e. by pulling on the handle 163). In implementations where the assisted start procedure is available, thedisplay 186 may instead display “Assisted Start” or some other equivalent message, provided that current conditions allow using this procedure. Displaying the manual start indication or the assisted start indication atoperation 312 may follow any decision taken by theECU 164 to not proceed with the electric start procedure. It is contemplated that instead of providing a message on thedisplay 186, that theECU 164 could cause a sound to be heard or provide some other type of feedback to the user of thesnowmobile 10, indicating that thesnowmobile 10 will need to be started manually using therecoil starter 156. A manual start procedure or an assisted start procedure may be initiated when the user pulls on therope 158 of therecoil starter 156. If conditions for the assisted start procedure are met, this procedure may be initiated as described hereinbelow. Otherwise, when the conditions for the assisted start procedure are not met, the manual start procedure may be initiated atoperation 314 when, in response to sensing the operation of therecoil starter 156 by the user of thesnowmobile 10, theECU 164 initiates an engine control procedure associated with the use of therecoil starter 156 in order to start theICE 24 using therecoil starter 156. Then atoperation 316, theECU 164 determines if theICE 24 has been successfully started using therecoil starter 156. If not, thenoperation 314 is repeated. It is also contemplated that if atoperation 316 it is determined that theICE 24 has not been successfully started, that the method could return tooperation 312 to display the message again. If atoperation 316 it is determined that theICE 24 has been successfully started, then the method proceeds tooperations operation 318, theECU 164 operates theICE 24 according to the control strategy or strategies to be used once theICE 24 has started. Atoperation 320, theECU 164 controls theinverter 146 to cause power to be delivered from the motor-generator 144 to thecapacitance 145, charging thecapacitance 145 using the second control strategy at a voltage that remains fairly constant for a wide range of rotational speeds of thecrankshaft 100. This may be achieved by theECU 164 shunting one or more of the Phases A, B and C of the motor-generator 144 if, in the second control strategy, the motor-generator 144 generates a voltage that exceeds a maximum voltage threshold. TheECU 164 may linearly regulate the voltage generated by the motor-generator 144 may be using a series regulation mode or a shunt mode. The maximum voltage threshold may for example be equal or slightly superior to the nominal voltage of thecircuit 200. - If at
operations ECU 164 determines that the capacitance voltage is equal to or above the electric start voltage threshold VMinE and that the temperature conditions and any other condition are also met, the method continues atoperation 322 where theECU 164 controls thedriver 216 of the transistor Q1 to place thecapacitance 145 in parallel with the capacitor C1 to equalize their voltages. Then atoperation 324, theECU 164 obtains a value of the angular position of thecrankshaft 100 from thecrankshaft position sensor 170. Thisoperation 324 may continue on an ongoing fashion during the complete electric start procedure so that the following operations may be optimized according to the varying angular position of thecrankshaft 100. It is contemplated thatoperations crankshaft 100 by providing acapacitance 145, the battery, or other power source having sufficient energy storage capability to rotate thecrankshaft 100 with no concern for its actual angular position. - The electric start procedure proceeds with
operation 326 and continues throughoperations operation 332. These operations are initiated in the sequence as shown onFIG. 9 , but are then executed concurrently until the electric start procedure is found successful or until it needs to be terminated. - At
operation 326, theECU 164 determines the torque value sufficient to cause the rotation of thecrankshaft 100 and initiates delivery of power from thecapacitance 145 to the motor-generator 144, through theinverter 146, via the first control strategy which adapts the delivery of power in view of the determined torque value. This transfer of power causes a rotation of thecrankshaft 100. Optionally, theECU 164 may determine the torque value in sub-steps, in which a first sub-step comprises delivering electric power from thecapacitance 145 to the three-phase motor-generator 144 according to a first torque value to cause slow turning of the crankshaft at a first rotational speed until the piston is brought beyond its top dead center (TDC), based on information provided by thecrankshaft position sensor 170 and based on the contents of the control maps 166, a second sub-step comprising delivering electric power from thecapacitance 145 to the three-phase motor-generator 144 according to a second torque value, greater than the first torque value to cause turning of the crankshaft at a second rotational speed, the second rotational speed being greater than the first rotational speed. - While
operation 326 is ongoing, particularly while the second sub-step is ongoing ifoperation 326 comprises two sub-steps, the method proceeds tooperation 328 in which theECU 164 causes thefuel injectors combustion chambers combustion chambers crankshaft 100. The angular position of thecrankshaft 100 170 may be used by theECU 164 to properly time the fuel injection and the ignition. In a particular implementation, theposition sensor 170 is an absolute position sensor that can determine the position of thecrankshaft 100 while it is stationary, prior to starting of theICE 140. This technique provides precise fuel injection and ignition timing at a very low rotational speed of theICE 24, such as when theICE 24 is starting. This technique decreases the chances of a failed start-up procedure due to an insufficient combustion within thecombustion chambers 102A, 120B, this insufficient combustion resulting from imprecise fuel injection quantities or ignition timing calculated from an imprecise crankshaft position. This technique further promotes faster synchronization between all components of theICE 24 that rely on the position of thecrankshaft 100 when compared to the use of position sensors that require thecrankshaft 100 to be rotating to determine its position. Use of mechanical actuators (not shown) operably connected to thecrankshaft 100 to control injection and ignition timings is also contemplated. It is further contemplated that a quantity of fuel to be injected and the ignition timing as applied by theECU 164 atoperation 328 may be evaluated using any known method, optionally depending on one or more of an engine temperature, an air temperature, an atmospheric pressure, and an exhaust temperature, these values being provided to theECU 164 by the various sensors shown onFIG. 6 . - While
operations operation 330, in which theECU 164 compares a rotational speed of thecrankshaft 100 to a minimum revolution threshold to determine if theICE 24 has been successfully started using the electric start procedure. If the rotational speed of thecrankshaft 100 is equal to or above the minimum revolution threshold, theICE 24 has been successfully started, the electric start procedure ends and the method proceeds tooperations - If, at
operation 330, theECU 164 determines that theICE 24 has not yet been started, the rotational speed of thecrankshaft 100 being below the minimum revolution threshold, the method continues atoperation 332 where theECU 164 monitors again the voltage of thecapacitance 145. It is expected that this voltage will be reduced somewhat as energy previously stored in thecapacitance 145 has been spent duringoperations capacitance 145 is equal to or above the residual voltage threshold VMinR, the electric start procedure returns tooperations operation 330. If however theECU 164 determines atoperation 332 that the capacitance voltage has fallen below the residual voltage threshold VMinR, the method proceeds tooperation 334 where theECU 164 ceases the delivery of power from thecapacitance 145 to the motor-generator 144 and terminatesoperations operation 334 tooperation 312, which is described hereinabove, in which theECU 164 causes thedisplay 186 to display a manual start indication, or an assisted start indication in implementations where this option is available,operation 312 being followed byoperations -
FIG. 10 is a timing diagram showing an example of variations of an engine resistive torque as a function of time along with corresponding engine rotational speed variations. Agraph 400 shows a variation of the resistive torque of theICE 24, in Newton-Meters (Nm) as a function of time, in seconds. Thegraph 400 was obtained from a Simulink™ model. Agraph 402 shows a corresponding variation of a rotational speed of thecrankshaft 100 over the same time scale. In the simulation, the two-cylinder ICE 24 is firing when a piston first reaches near TDC. After less than 0.1 seconds, the resistive torque becomes negative because the piston has passed beyond its TDC. Compression present in the combustion chamber pushes on the piston and accelerates the rotation of thecrankshaft 100. At about 0.12 seconds, theECU 164 controls the torque applied to thecrankshaft 100 by the motor-generator 144, accelerating the rotation of thecrankshaft 100. The rotational speed of thecrankshaft 100 reaches a plateau at about 0.17 seconds because the piston is now compressing gases present in the combustion chamber. The rotational speed decreases as the piston arrives near its TDC. TDC is reached at about 0.32 seconds. Successful ignition takes place, whereafter the rotational speed of thecrankshaft 100 increases rapidly while the resistive torque on the motor-generator 144 becomes essentially negative, following a toothed saw wave shape as the piston cycles up and down in its cylinder. -
FIG. 11 is a logic diagram of a method for starting the engine ofFIG. 2 according to another implementation. A sequence shown inFIG. 11 comprises a plurality of operations, some of which may be executed in variable order, some of the operations possibly being executed concurrently, and some of the operations being optional. The method begins atoperation 600 when theICE 24 of thesnowmobile 10 is stopped. A voltage of thecapacitance 145 is measured by thevoltage sensor 167 atoperation 602. In thesame operation 602, thedisplay 186 may provide an “assisted start” indication if the voltage meets or exceeds the assisted start voltage threshold VMinA and if other conditions described hereinbelow for the assisted start procedure are met. Atoperation 604, the user initiates a rotation of thecrankshaft 100 by pulling on therope 158 of therecoil starter 156. Atoperation 606, thecrankshaft position sensor 170 detects an initial rotation of thecrankshaft 100 and informs theECU 164 of the rotation. Detecting the initial rotation of thecrankshaft 100 may be conditional to thecrankshaft position sensor 170 detecting that a revolution speed of thecrankshaft 100 meets or exceeds a minimal revolution threshold. A comparison is made by theECU 164 atoperation 608 between the voltage of thecapacitance 145 and the assisted start voltage threshold VMinA to determine whether it is possible to initiate the assisted start procedure for theICE 24. If it is determined that the voltage of thecapacitance 145 is below the assisted start voltage threshold VMinA, the assisted start procedure is prevented. Otherwise, verification is made atoperation 610 that the engine temperature measured by theengine temperature sensor 172 meets or exceeds an engine temperature threshold T0. The assisted start procedure is prevented in this threshold for the engine temperature is not met. Otherwise, verification is made atoperation 612 that theECU temperature sensor 182 provides a reading of the temperature of theECU 164 that meets or exceeds an ECU temperature threshold T1. The assisted start procedure is prevented if this threshold for the ECU temperature is not met. Additional operations related to the use of measurements obtained from other sensors introduced in the foregoing description ofFIG. 6 may take place. These measurements may be provided to theECU 164 by theair temperature sensor 174, theatmospheric temperature sensor 176, or thetimer 180. Additional tests based on those measurements may be executed by theECU 164 to determine whether or not the assisted start procedure is likely to succeed. For example, the assisted start procedure may be made conditional, in theECU 164, on thetimer 180 informing theECU 164 that a period of time since theICE 24 has been stopped is below a predetermined time value when the user pulls on therope 158 of therecoil starter 156 atoperation 604, On the basis of the period of time since theICE 24 has been stopped, it is possible to estimate whether the voltage of thecapacitance 145 will have fallen below the assisted start voltage threshold VMinA knowing a maximum charge voltage of thecapacitance 145 from a previous running sequence of theICE 24, and based on a typical energy leakage of thecapacitance 145. - Displaying the manual start indication at
operation 614 may follow any decision taken by theECU 164 to not proceed with the assisted start procedure. Whether the assisted start procedure is prevented because the voltage of thecapacitance 145 is insufficient (operation 608), because the engine temperature is too low (operation 610), because the ECU temperature is too low (operation 612) or for any other reason, the method proceeds tooperation 614. Atoperation 614, thedisplay 186 may display “Manual Start”. Followingoperation 614, the user may continue pulling on therope 158 of therecoil starter 156 atoperation 616.Operation 616 may continue until it is detected atoperation 618 that theICE 24 is properly started. Control ofICE 24 and delivery of electric power from the motor-generator 145 to thecapacitance 144 follow at 620 and 622, which are the same or equivalent asoperations FIG. 9 including, in an implementation, controlling theICE 24 using the above described control strategies. - If at
operations ECU 164 determines that the capacitance voltage is equal to or above the assisted start voltage threshold VMinA and that the temperature conditions and any further condition are also met, the method continues atoperation 624 where theECU 164 controls thedriver 216 of the transistor Q1 to place thecapacitance 145 in parallel with the capacitor C1 to equalize their voltages. - The assisted start procedure proceeds with
operation 626 and continues throughoperations operation 632. These operations are initiated in the sequence as shown onFIG. 11 , but are then executed concurrently until the assisted start procedure is found successful or until it needs to be terminated. - At
operation 626, theECU 164 initiates delivery of power from thecapacitance 145 to the motor-generator 144, through theinverter 146. This transfer of power accelerates the rotation of thecrankshaft 100 and reduces the amount of effort that needs to be exerted by the user pulling on therope 158 of therecoil starter 156. TheECU 164 may optionally determine a torque value in the same manner as described in the foregoing description of operation 326 (FIG. 9 ). - While
operation 626 is ongoing, the method proceeds tooperation 628 in which theECU 164 causes thefuel injectors combustion chambers combustion chambers crankshaft 100. The angular position of thecrankshaft 100 may be used by theECU 164 to properly time the fuel injection and the ignition. Use of mechanical actuators (not shown) operably connected to thecrankshaft 100 to control injection and ignition timings is also contemplated. It is further contemplated that a quantity of fuel to be injected and the ignition timing as applied by theECU 164 atoperation 628 may depend on one or more of an engine temperature, an air temperature, an atmospheric pressure, and an exhaust temperature, these values being provided to theECU 164 by the various sensors shown onFIG. 6 . - While 626 and 628 are ongoing, the method proceeds to
operation 630, in which theECU 164 compares a rotational speed of thecrankshaft 100 to a minimum revolution threshold to determine if theICE 24 has been successfully started using the assisted start procedure. If the rotational speed of thecrankshaft 100 is equal to or above the minimum revolution threshold, theICE 24 has been successfully started, the assisted start procedure ends and the method proceeds to 620 and 622, which are described hereinabove. - If, at
operation 630, theECU 164 determines that theICE 24 has not yet been started, the rotational speed of thecrankshaft 100 being below the minimum revolution threshold, the method continues atoperation 632 where theECU 164 monitors again the voltage of thecapacitance 145. It is expected that this voltage will be reduced somewhat as energy previously stored in thecapacitance 145 has been spent during 626 and 628. However, if a remaining voltage of thecapacitance 145 is equal to or above a residual voltage threshold, the assisted start procedure returns tooperations operation 630. In one variant, the residual voltage threshold applicable to the assisted start procedure may be the same value VMinR as in the case of the electric start procedure. In another variant, a different residual voltage threshold may be used given that the amount of power delivered to the motor-generator 144 by thecapacitance 145 complements the effort of the user pulling on therope 158 of therecoil starter 156. If however theECU 164 determines atoperation 632 that the capacitance voltage has fallen below the residual voltage threshold VMinR, the method proceeds tooperation 634 where theECU 164 ceases the delivery of power from thecapacitance 145 to the motor-generator 144 and terminatesoperations operation 634 tooperation 614, which is described hereinabove, in which theECU 164 causes thedisplay 186 to display a manual start indication,operation 614 being followed byoperations - In an implementation, the
snowmobile 10 may be configured to support any one of the manual, electric and assisted start procedures. In such implementation, operation 312 (FIG. 9 ) may provide a manual start or an assisted start indication, depending on the voltage of thecapacitance 145. If the voltage of the capacitance is below the electric start voltage threshold VMinE while meeting or exceeding the assisted start voltage threshold VMinA,operation 312 ofFIG. 9 may provide the assisted start indication and may be followed byoperation 604 ofFIG. 11 if the user pulls on therope 158 of therecoil starter 156. Also in this implementation, after having started theICE 24 using the assisted start procedure, theICE 24 may be stopped and thedisplay 186 may provide an indication of the available start procedure depending on current conditions reported to theECU 164 by the various sensors. - As expressed hereinabove, the
ECU 164 controls theinverter 146 through thestrategy switch 184. To this end, theECU 164 generates control pulses that are applied to thestrategy switch 184. These control pulses are generated differently in the two (2) control strategies. In at least one implementation, the effect of these control pulses depends on the internal structure of theinverter 144.FIG. 12 is a circuit diagram showing connections of theinverter 146, thecapacitance 145 and the motor-generator 144 ofFIG. 6 . As shown onFIG. 12 , theinverter 146 has three phases, each phase being electrically connected to a corresponding phase of the three-phase motor-generator 144. In more details, theinverter 146 is formed of three (3) switching legs, each switching leg including a pair of MOSFETs T1, T2, T3, T4, T5 and T6 matched with corresponding freewheel diodes D2, D1, D3, D2, D6 and D5. For instance, a first leg forming a first phase includes a top transistor T1 matched with a freewheel diode D2 and a bottom transistor T2 matched with a freewheel diode D1. A second leg forming a second phase includes transistors T3 and T4 matched with diodes D4 and D3 respectively while a third leg forming a third phase includes transistors T5 and T6 matched with diodes D6 and D5 respectively. As substitutes to MOSFETs, bipolar transistors, for example IGBTs, or any other power electronic switches are also contemplated. Each transistor T1-T6 has a corresponding gate G1-G6 through which a signal, or control pulse, can be applied under the control of theECU 164 via thestrategy switch 184, either directly or through a gate driver (not shown), to turn-on (short-circuit) or turn-off (open circuit) the corresponding transistors T1-T6. The freewheel diodes D1-D6 are used to attenuate transient overvoltage that occurs upon switching on and off of the transistors T1-T6. - For example, when the motor-
generator 144 is in motor operating mode, being used as a starter for theICE 24, a first control pulse is applied at the gate G1 to short-circuit the transistor T1. Current flows from a positive tab of thecapacitance 145 through the transistor T1 and reaches a phase of the motor-generator 144 defined between an input A and a neutral connection between the phases of the motor-generator 144, hereinafter “Phase A”. Thereafter, the first control pulse is removed from the gate G1 so the transistor T1 becomes an open-circuit. At the same time, a second control pulse is applied on the gate G2, causing the transistor T2 to turn-on. Current now flows in the opposite direction in Phase A of the motor-generator 144, returning to a negative tab of thecapacitance 145 via the transistor T2. As a result of this sequence of turning on and off the transistors T1 and T2, an alternating current flows in the Phase A of the motor-generator 144. - The current flowing into Phase A of the motor-
generator 144 needs to exit through one or both of the other phases of the motor-generator 144. “Phase B” is defined between an input B and the neutral connection. “Phase C” is defined between an input C and the neutral connection. The current flows from Phase A through Phase B, or Phase C, or both Phases B and C, depending on whether one or both of transistors T4 or T6 is turned on by control pulses applied on their respective gates G4 or G6 when the transistor T1 is also turned on. The current exiting the motor-generator 144 via one or both of Phases B and/or C returns to a negative tab of thecapacitance 145 through one or both of the transistors T4 and/or T6. The freewheel diodes D1-D6 assist in supporting phase inductance currents during freewheel periods. - To operate the motor-
generator 144 as a conventional three-phase motor, current would flow concurrently in all three (3) Phases A, B and C, a timing control of the various transistors T1-T6 being separated by 120 degrees. Other operating modes of the motor-generator 144 in which current does not concurrently flow in all three (3) Phases A, B and C are however contemplated. - Examples of parameters that may be considered by programming of the
ECU 164 to control the delivery of electric power in both control strategies include, without limitation, current and voltage of each phase voltages and currents in each of the Phases A, B and C of the motor-generator 144, the angular position and rotational speed of thecrankshaft 100. TheECU 164 uses these values to determine an electromagnetic torque of the motor-generator 144, this torque having positive value when the motor-generator 144 is used during the electric start procedure or the assisted start procedure and a negative value when used in generator operating mode. - The first control strategy uses a technique called vector control or field-oriented control (FOC). The first control strategy is used mainly to control the delivery of electric power from the
capacitance 145 to the motor-generator 144 to cause or assist a rotation of thecrankshaft 100 in the electric start procedure or in the assisted start procedure of theICE 24. In one implementation,ECU 164 determines a torque request sufficient to cause the rotation of thecrankshaft 100. In another implementation, theECU 164 determines a speed request applicable to thecrankshaft 100, sufficient to cause ignition and start of theICE 24. This determination of the speed request or torque request may be made by theECU 164 applying a predetermined speed or torque request value or pattern based on the contents of the control maps 166. TheECU 164 may increment the torque request if a first torque application causes no rotation of thecrankshaft 100. TheECU 164 may increment the speed request if a rotation of thecrankshaft 100 is not sufficient to allow ignition and start of theICE 24. Alternatively, theECU 164 may calculate the speed or torque request based on a combination of parameters, including in a non-limitative example a mathematical representation of internal components of theICE 24 and on the angular position of thecrankshaft 100. TheECU 164 controls the delivery of electric power from thecapacitance 145 to the motor-generator 144, based on the determined speed request or torque request, through the generation of control pulses applied to selected ones of the transistors T1-T6. Using vector control, theECU 164 calculates a number, timing, and width of the various control pulses so that the amount of electric power flowing from thecapacitance 145 through theinverter 146 and to the motor-generator 144 fulfills the determined speed or torque request. This manner of controlling the transistors T1-T6 by applying timed pulses to their gates G1-G6, each pulse having a calculated width, is known as pulse width modulation (PWM). -
FIG. 13 is a block diagram of a typical implementation of a vector control drive. A vector control drive 500 ofFIG. 13 may be implemented at least in part in theECU 164. An input to the vector control drive includes aset point 504 for a required speed (the speed request) that is determined as sufficient for starting theICE 24. Thisset point 504 is applied to a slowspeed control loop 506. Other inputs to the vector control drive 500 include current measurements 508 a, 508 b and 508 c for the three phases of the motor-generator 144 and avoltage measurement 510 obtained from theinverter 146 and/or from the motor-generator 144. These current and voltage measurements are applied to an analog to digital converter (ADC) 512. Crankshaft angular position measurements (encoder signals uA, uS) 514 are applied to aquadrature timer 516. Thequadrature timer 516 calculates an actual position of thecrankshaft 100. TheADC 512 calculates a digitizedvoltage value 518 and digitized current values 520 a, 520 b and 520 c for the three phases of the motor-generator 144. These digitized values and anactual position 522 of thecrankshaft 100 calculated by thequadrature timer 516 are provided to a fastcurrent control loop 524. Theactual position 522 of thecrankshaft 100 is converted to an actual (measured)speed 526 by aspeed calculator 528 of the slowspeed control loop 506. Adifference 528 between the measuredspeed 526 and the required speed setpoint 504 is applied to a first proportional-integral (PI)controller 530 that in turn yields a current-image 532 of a torque request that is applied as a set point (Isq_req) to the fastcurrent control loop 524. - As expressed hereinabove, in some variants, it may be desired to operate the motor-
generator 144 so that it delivers electric power to thecapacitance 145 in the first control strategy, at least at low revolution speeds of thecrankshaft 100. To this end, an optionalfield weakening module 534 having an internal map attenuates values of its output based on the measuredspeed 526 of thecrankshaft 100 to provide a current-image 536 of a magnetic field of the motor-generator 144 as an additional set point (Isd_req) applied to the fastcurrent control loop 524. - In the fast
current control loop 524, aClark Transform 538 converts the three-phase current measurements 520 a, 520 b and 520 c into a two-phase model 540. APark Transform 542 fed with sine andcosine values 523 of theactual position 522 of thecrankshaft 100, calculated by a sin/cos converter 525, converts further thismodel 540 to provide a stationary current-image 544 of the actual torque on the motor-generator 144 (Isq) and a stationary current-image 546 of the actual magnetic field of the motor-generator (Isd).Outputs Isq_req set point 532 and to the Isd_req set point 536 (if used), and their differences are respectively applied to second andthird PI controllers Inverse Park Transform 552 is applied to stationaryvoltage requests Uq 554 andUd 556 produced by the second andthird PI controllers Inverse Park Transform 552 using the sine andcosine values 523 of theactual position 522 of thecrankshaft 100 to produceoutputs Inverse Park Transform 552 that are applied to a space vector modulation-pulse width modulation (SV-PWM) transform 562. In turn, the SV-PWM transform 562 provides three-phase control 564 to aPWM module 566 that generatespulses 502 that theECU 164 provides for application to the gates G1-G6 of theinverter 146. - The
ECU 164 may control a delivery of electric power from thecapacitance 145 to the motor-generator 144 based on a pre-determined amount of torque, or torque request, sufficient to cause rotation of thecrankshaft 100 for starting theICE 24. However, considering that the amount of torque required to rotate thecrankshaft 100 before ignition of the cylinder (or cylinders) varies based on the angular position of thecrankshaft 100 in relation to the top dead center (TDC) position of each piston, calculation of a variable torque request is also contemplated. In a variant, the angular position of thecrankshaft 100 is provided by thecrankshaft position sensor 170 or, alternatively, by a relative position sensor. When using the relative position sensor, at each operational sequence of theECU 164, prior to initiating rotation of thecrankshaft 100, theECU 164 magnetizes two out of the three phases of the alternating current motor-generator 144, moving and then locking the rotor of the motor-generator 144 and thereby locking thecrankshaft 100, which is attached thereto, in a known repetitive electric angle. From there, rotating positions of thecrankshaft 100 are calculated continuously from a counter of pulses received from the relative position sensor. An absolute position of thecrankshaft 100 is calculated and an electric angle is derived from that calculation to perform vector control. In a particular implementation, an incremental encoder providing 1024 pulses per revolution of thecrankshaft 100 is contemplated. Sensorless control of the crankshaft position is also possible, though with this solution, producing high torque at very low angular velocity of thecrankshaft 100 may be rather challenging. Regardless, in a variant introduced in the foregoing description of operation 326 (FIG. 9 ), theECU 164 calculates or otherwise determines the torque request based on an angular position of thecrankshaft 100 provided by thecrankshaft position sensor 170, values of the torque request being updated at various points of the rotation of thecrankshaft 100. As a result, the torque request can be optimized so that it is sufficient to rotate thecrankshaft 100 as it reaches various angular positions while using as little as possible of the energy stored in thecapacitance 145. In a particular variant, theECU 164 controls the amount of torque applied on the motor-generator 144 so that it turns at a very low speed until a givenpiston combustion chamber piston capacitance 145 in this operation. Once thepiston crankshaft 100 has acquired at least some momentum. TheECU 164 then raises the torque request applied to the motor-generator 144 so that thecrankshaft 100 rotates at a speed sufficient to allow injection of fuel in thecombustion chamber piston combustion chamber crankshaft 100 increases smoothly. - Following starting of the
ICE 24, irrespective of whether theICE 24 was started using the manual start procedure, the assisted start procedure or the electric start procedure, thecrankshaft 100 drives the motor-generator 144 at a variable rotational speed, most of the time significantly exceeding a rotational speed used in the course of any of the start procedures. Once theICE 24 is started, operation of the motor-generator 144 switches to generator operating mode. In an implementation, theECU 164 may determine a revolution speed of thecrankshaft 100 based on successive readings provided by thecrankshaft position sensor 170 and cause the motor-generator 144 to start delivering electric power to thecapacitance 145 when the revolution speed of the crankshaft meets or exceeds a minimal revolution threshold. At this point or soon thereafter, theECU 164 starts controlling thestrategy switch 184 and theinverter 146 using the second control strategy. Optionally, the first control strategy may be used in generator operating mode until the voltage measurement provided by thevoltage sensor 167 meets or exceeds a voltage generation threshold. The voltage generation threshold can be set slightly lower than a nominal voltage of thecapacitance 145, for example. - The second control strategy uses a “shunt” technique. The output of the motor-
generator 144, now generating, is used to charge thecapacitance 145, to supply electrical power to theinjectors snowmobile 10. To this end, theECU 164 alters a position of thestrategy switch 184 so that electrical power now flows from the motor-generator 144 to thecapacitance 145, still through theinverter 146. TheECU 164 monitors the voltage of thecapacitance 145 through measurements obtained from thevoltage sensor 167. Based on these voltage measurements, theECU 164 generates control pulses that are applied, via thestrategy switch 184, to the gates G1-G6 of the transistors T1-T6 in theinverter 146. PWM is still applied by theECU 164 to the gates G1-G6, but this time according to the second control strategy. - If an output voltage of the motor-
generator 144 is above its nominal value, or above its nominal value plus a predetermined tolerance factor, theinverter 146 is controlled by theECU 164 to reduce the voltage at which electrical power is delivered from the motor-generator 144 to thecapacitance 145. To this end, in one operating dissipative voltage regulation mode, theECU 164 may generate control pulses applied to various gates G2, G4 and G6 to effectively bypass, or “shunt”, one or more of the phases of the motor-generator 144, at the same time applying no control pulse to the gates G1, G3 and G5 in order to cause the transistors T1, T3 and T5 to remain non-conductive (open circuit). For example, applying pulses to the gates G2 and G6 causes the transistors T2 and T6 to turn on and become conductive. As a result, a closed loop is formed between Phases A and C of the motor-generator 144 along with the transistors T2 and T6. Under this condition, no electrical power is delivered from two (2) of the phases of the motor-generator 144 to thecapacitance 145. A duration (width) and timing of the pulses applied to the gates G2 and G6 impacts a duration of time when Phases A and C are shunted, in turn impacting the charging voltage applied at thecapacitance 145. PWM can be applied to any pair of the bottom transistors T2, T4 and T6, so that they can be shorted at a desired time to shunt a pair of phases of the motor-generator 144. TheECU 164 may actually modify, over time, a determination of which pair of transistors is made part of a shunt in order to avoid their overheating due to conduction losses in theinverter 146. To this end, voltage regulation in shunt mode involves successively activating the transistors T2, T4 and T6. As a result, the delivery of electric power from the motor-generator 144 to thecapacitance 145 can be made at a desired voltage over a broad range of the rotational speed of thecrankshaft 100. A series voltage regulation mode is also contemplated, in which the freewheel diodes D1, D3 and D5 may optionally be replaced by additional transistors (not shown) mounted in reverse-parallel with the transistors T1, T3 and T5, these additional transistors being turned on and off as required to allow current from the motor-generator 144 to recharge thecapacitance 145 while not exceeding the nominal voltage value. - In a particular implementation, voltage regulation in shunt mode may benefit from the measurements provided by the
position sensor 170. In this implementation, theposition sensor 170 allows theECU 164 to determine a mechanical position of thecrankshaft 100. TheECU 164 calculates an equivalent electrical angle by multiplying the mechanical position of thecrankshaft 100 by a known number of pole pairs of the motor-generator 144. If the output voltage of the motor-generator 144 is above a predetermined value, starting from a voltage rise of any one of the phases A, B or C, all three (3) phases are consecutively shunted once, in synchrony with the operation of the motor-generator 144. This shunting sequence may be repeated when the output voltage of the motor-generator 144 rises again above the predetermined value. - If the voltage of the
capacitance 145 is at or below its nominal value, theinverter 146 is controlled by theECU 164 to deliver electrical power available from the motor-generator 144 to thecapacitance 145 without shunting any of the Phases A, B or C. Under this condition, which may for example occur for a brief duration after the start of theICE 24, the control of the power delivery could be construed as a neutral control mode distinct from the first and second control strategies. In the neutral control mode, theinverter 146 acts as a three-phase full-wave diode bridge rectifier, providing no voltage or current regulation. -
FIG. 14 is a block diagram of an electric system according to an implementation of the present technology. Acircuit 700 includes variants of elements introduced in the foregoing description of the various drawings, these elements being grouped into subsystems. The motor-generator 144 is one such subsystem. Another subsystem is in the form of acontrol module 702 that, in an implementation, comprises a single physical module including a processor 703 programmed to execute the functions of theECU 164, theinverter 146, theECU temperature sensor 182 and further includes a DC-DC converter 704. As shown, theECU 164 includes connections for theelectric start switch 168, for the measurements provided by thevarious sensors inverter 146. In the illustrated example, thevoltage sensor 167 is implemented as aDC voltage sensor 167 DC that measures a voltage of thecapacitance 145 and as anAC voltage sensor 167 AC that measures a voltage on one phase of the motor-generator 144, these two components of thevoltage sensor 167 being integrated within theECU 164. Use of external voltage sensors operatively connected to theECU 164 is also contemplated. Athird subsystem 706 includes thecapacitance 145, as well as a chargingcircuit 705 and a dischargingcircuit 707 that use thedriver 216 and the transistor Q1 ofFIG. 8 to control charging and discharging of thecapacitance 145. - The
circuit 700 operates at a nominal system voltage, which is typically the voltage of thecapacitance 145 when fully charged. Afourth subsystem 708 includes components of thesnowmobile 10 that operate at the system voltage. These components may include thefuel injectors electric oil pump 710, ignition coils 712 for the spark plugs 134 a, 134 b and afuel pump 714. Afifth subsystem 716 includes accessories of thesnowmobile 10 that operate at an accessory voltage. These accessories may include a multi-port fuel injector (MPH) 718,lighting 720, an instrument cluster 722 including thedisplay 186,heated grips 724 mounted on thehandlebar 36 and an exhaust valve 726. The DC-DC convertor 704 converts the system voltage to the accessory voltage and thus provides electric power to the accessories. - In an implementation, the
circuit 700 normally operates at a system voltage of 55 volts and some accessories of the snowmobile normally operate at an accessory voltage of 12 volts. In this implementation, the DC-DC converter 704 is a 55V-12V converter. These values for the system voltage and for the accessory voltage are nominal for this implementation and may vary according to the actual operating conditions of thesnowmobile 10. -
FIG. 15 is a timing diagram showing an example of a sequence for changing the control strategy for the delivery of electric power between thecapacitance 145 and the motor-generator 144 along with corresponding engine rotational speed variations. A graph 410 shows a variation of electrical power delivery control strategies applied by theECU 164, as a function of time, in seconds. In this graph 410, “Strategy 1” indicates the application of the first control strategy, specifically using a vector control, “Strategy 2” indicates the application of the second control strategy, which uses shunting of phases of the motor-generator 144 to control the voltage applied to charge thecapacitance 145, and “Neutral” indicates the application of the neutral control mode. In the neutral control mode, the voltage generated by the motor-generator 144 may simply be converted to direct current and applied to charge thecapacitance 145, provided that a peak back electromotive force voltage of the motor-generator 144 is higher than the nominal voltage of thecircuit 200, a condition that is usually met when theICE 24 reaches a sufficient revolution speed. A graph 412 shows a corresponding variation of a rotational speed of thecrankshaft 100 over a same time scale. In a first half-second of operation following the user command for the electric start procedure for theICE 24, no power is delivered between thecapacitance 145 and the motor-generator 144. This period is used to equalize the voltages of thecapacitance 145 and of the capacitor C1. The actual duration of this period may vary considerably as a function of the value of the capacitor C1. A period ranging from 0.5 to about 1.1 seconds corresponds essentially to the period covered between 0 and 0.4 seconds on thegraphs ECU 164 uses the first control strategy (Strategy 1) to control delivery of electric power from thecapacitance 145 to the motor-generator 144 until theICE 24 is actually started. Then, between 1.1 and 1.3 seconds, as theICE 24 accelerates, electric power is delivered from the motor-generator 144 to thecapacitance 145 in the neutral control mode. When thecrankshaft 100 reaches a sufficient rotational speed, at about 1.3 seconds, the motor-generator 144 starts generating power at a voltage that tends to exceed the nominal voltage of thecapacitance 145. This is when theECU 164 starts using the second control strategy (Strategy 2) to control delivery of electrical power from the motor-generator 144 to thecapacitance 145. A variant in which the neutral control mode is not implemented is also contemplated, in which theECU 164 starts using the second control strategy as soon as theICE 24 is successfully started. -
FIG. 16 is another timing diagram showing an example of an impact of the control strategies on a current exchanged between the capacitance and the ETM and on a system voltage. Agraph 420 shows a voltage of one of the Phases A, B or C of the motor-generator 144 as a function of time, in seconds, and as a function of the control strategies. In the first control strategy, theECU 164 controls the application of voltage pulses to the motor-generator 144 in pulse width modulation (PWM) mode, at a very rapid rate typically expressed in kilohertz. Then, as ignition of theICE 24 beings, in the neutral control mode, the motor-generator 144 starts generating voltage on its own, this voltage increasing until the mode changes to the second control strategy, the voltage cycling at a rate that follows the rotation of thecrankshaft 100. It may be observed that because of the configuration of theinverter 146, the voltage on each phase of the motor-generator alternates between zero (0) volt and the nominal system voltage without cycling through negative values. Agraph 422 shows a variation of a current flowing between thecapacitance 145 and the motor-generator 144 as theECU 164 changes from the first control strategy to the neutral control mode to the second control strategy. Initially, in the first control strategy, a three-phase current flows from thecapacitance 145 toward the motor-generator 144, through theinverter 146. For most of the neutral control strategy, all transistors T1-T6 of the inverter are open and no current flows between thecapacitance 145 and the motor-generator 144. Significant current is generated by each phase of the motor-generator 144 after the start of theICE 24. TheECU 164 applies shunting of the phases of the motor-generator 144 for preventing excess voltage at its output, as illustrated by the strong variations of the current in the right-hand part ofgraph 422. Thegraph 424 shows an actual voltage measured on thecapacitance 145 as theECU 164 changes from the first control strategy to the neutral control mode to the second control strategy. The voltage of thecapacitance 145 initially decreases while electric power is delivered to the motor-generator 145. Following ignition of theICE 24, theECU 164 places the system in neutral control mode. A discharge of the freewheel diodes D1-D6 causes a modest increase of the voltage of thecapacitance 145. Opening of the transistor Q1 at the beginning of the operation in the second control strategy temporary isolates thecapacitance 145 from the motor-generator so that electric power produced by the motor-generator is mainly available for other needs of the system, such as injection, ignition, control, and the like. Closing again of the transistor Q1 allows charging of thecapacitance 145, with a voltage that oscillates near the nominal system voltage according to the shunting of the motor-generator 144. - The timing values, rotational speed values, and torque values illustrated in the
various graphs ICE 24, of the motor-generator 144, of thecapacitance 145 and on the operation strategy of theECU 164. - Modifications and improvements to the above-described implementations of the present technology may become apparent to those skilled in the art. For example, it is contemplated that the
ICE 24 could be provided with a decompression system. The decompression system can release pressure in thecombustion chambers generator 144 atoperations generator 144 could be even smaller and lighter, a size and a weight of thecapacitance 145 being reduced accordingly. The foregoing description is intended to be exemplary rather than limiting. The scope of the present technology is therefore intended to be limited solely by the scope of the appended claims.
Claims (17)
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Also Published As
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WO2017081664A2 (en) | 2017-05-18 |
US20180347534A1 (en) | 2018-12-06 |
US11415096B2 (en) | 2022-08-16 |
US10859052B2 (en) | 2020-12-08 |
RU2018121135A3 (en) | 2019-12-16 |
WO2017081664A3 (en) | 2017-06-29 |
US10883467B2 (en) | 2021-01-05 |
RU2726148C2 (en) | 2020-07-09 |
CA3005153A1 (en) | 2017-05-18 |
US20210062774A1 (en) | 2021-03-04 |
RU2018121135A (en) | 2019-12-16 |
US20190153990A1 (en) | 2019-05-23 |
CA3197928A1 (en) | 2017-05-18 |
US20190153989A1 (en) | 2019-05-23 |
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