RU2782720C1 - Method for control of vehicle transmission and vehicle - Google Patents

Abstract

FIELD: car industry.

SUBSTANCE: invention relates to continuously variable transmissions. In a method for control of a continuously variable transmission of a vehicle, at different heights, at least one of height and atmospheric pressure is determined; a frequency of rotation of a driven pulley is determined; a position of a gas control body and a position of a throttle valve are determined. A piston is selectively activated, depending on at least one of height and atmospheric pressure. A piston force is controlled, depending on the frequency of rotation of the driven pulley and one of the position of the gas control body and the position of the throttle valve. The piston force is controlled based on the first control map corresponding to the first height and the second control map corresponding to the second height, depending on the determined one of height and atmospheric pressure.

EFFECT: control efficiency depending on the environment is increased.

14 cl, 11 dwg

Description

[0001] This application is separated from the application No. 2016134025 for the grant of a patent of the Russian Federation for an invention, filed 02/02/2015, claiming priority according to US Provisional Patent Application 61/934,498, filed January 31, 2014, the contents of which are herein fully incorporated by reference.

[0002] This application relates to International Patent Application No. PCT/US2013/062125 filed September 27, 2013, US Provisional Application 61/758,322 filed January 30, 2013, and US Provisional Application 61/768,285 filed February 22 2013, the contents of which are hereby incorporated by reference in their entirety.

The technical field to which the invention belongs

[0003] The present technology generally relates to a continuously variable transmission and to methods of driving a vehicle.

State of the art

[0004] Continuously variable transmissions (CVTs) driven by an endless belt are used in many vehicles such as snowmobiles, off-road vehicles (ATS), scooters, and the like. to obtain an unlimited number of gear ratios between the engine and the wheels of the vehicle. Typically, the control of the BST is performed mechanically using centrifugal weights (usually on the drive side), overcoming the force of the spring to obtain the required gear ratios. The characteristics of the BST, including the change in gear ratio as a function of engine speed, vehicle speed, torque, etc., can be adjusted by appropriate selection of flywheels and springs on the driving side and cams on the driven side.

[0005] Mechanically controlled BSTs have limitations in control options, since the configuration of various components cannot be changed on the fly depending on operating conditions. BST with mechanical control may have low power efficiency due to friction losses in the belt structure. In addition, when driving at constant high speeds, unwanted noise and vibrations come from the engine and other components in it operating at speeds (rpm), and also increase fuel consumption.

[0006] In some BSTs, especially in stationary installations, mechanical controls have been replaced by a pneumatic or hydraulic system that adjusts the gear ratio of the BST. Such fully controlled BSTs, in which one or both pulleys are driven, either hydraulically or pneumatically or electrically, require additional components such as pumps and tanks to be attached to the BST, adding cost and weight.

[0007] Thus, there is a need for a BST control method that would quickly and efficiently adjust the configuration of the BST depending on the driving conditions of the vehicle.

The essence of the invention

[0008] The purpose of the present technology is to eliminate at least some of the disadvantages inherent in the prior art.

[0009] In accordance with one aspect of the present technology, a method for driving a vehicle at various heights is provided. The vehicle comprises an engine, a throttle control controlled by the vehicle driver, a throttle valve that regulates the air flow to the engine, the throttle valve position being at least partially based on the position of the gas control element, and a continuously variable transmission (CVT) operatively connected to the engine. The BST contains a driving pulley, a driven pulley and a belt functionally connecting the driving pulley to the driven pulley. At least one ground contact element is operatively connected to the driven pulley and includes at least one of a wheel and a track. The piston is operatively connected to the drive pulley to apply, upon actuation to the drive pulley, a piston force to change the effective diameter of the drive pulley. The control unit controls the actuation of the piston and the force of the piston. The method includes determining at least one of altitude and atmospheric pressure, determining a driven pulley speed, and determining at least one of a throttle control position and a throttle position. The piston is selectively actuated depending on at least one of altitude and atmospheric pressure. The piston force is controlled depending on the speed of the driven pulley and at least one of the position of the gas control and the position of the throttle.

[0010] In some embodiments, piston force is controlled based on a control map.

[0011] In some embodiments, the control card includes a first control card corresponding to a first height and a second control card corresponding to a second height.

[0012] In some embodiments, one of altitude and atmospheric pressure is altitude. The piston force is set to zero in response to the determined height exceeding the upper threshold height.

[0013] In some embodiments, the vehicle also includes a mode switch for selecting one of a plurality of vehicle operating modes. The method also includes determining one operating mode that has been selected from the plurality of operating modes and controlling the piston force at least in part based on the one selected from the plurality of operating modes of the vehicle.

[0014] In some embodiments, piston force is controlled based on a control map associated with a mode selected from a plurality of vehicle operating modes.

[0015] In some embodiments, the engine speed is determined and the piston force is set to be at least equal to the minimum piston force, the minimum piston force being pre-set as a function of the determined engine speed.

[0016] In some embodiments, the vehicle also includes a plurality of centrifugal weights operatively connected to the drive pulley to control the drive pulley's effective diameter. The method also includes controlling the effective diameter of the drive pulley by centrifugal weights depending on the speed of the drive pulley.

[0017] In some embodiments, the piston is at least one of pneumatically actuated and hydraulically actuated.

[0018] In accordance with another aspect of the present technology, a method for driving a vehicle is provided. The vehicle comprises an engine, a throttle control controlled by the vehicle driver, a throttle valve that regulates the air flow to the engine, the throttle valve position being at least partially based on the position of the throttle control, a continuously variable transmission (CVT) operatively connected to the engine. The BST contains a driving pulley, a driven pulley and a belt functionally connecting the driving pulley to the driven pulley. At least one ground contact element is operatively connected to the driven pulley and includes at least one of a wheel and a track. The piston is operatively connected to the drive pulley to apply, upon actuation to the drive pulley, a piston force to change the effective diameter of the drive pulley. The control unit controls the actuation of the piston and the force of the piston. The method includes determining at least one of a throttle control position and a throttle valve position, detecting a vehicle parking/pulling off condition indicating either that the vehicle is parked or that the vehicle is pulling away, and in response to the parking/driving condition detection, actuating the piston and controlling the piston force based on at least one of the throttle position and the throttle position.

[0019] In some embodiments, the park/start condition includes the following: a vehicle speed is below a threshold park speed of the vehicle; and the engine speed is below the park engine speed threshold. The method also includes determining engine speed and vehicle speed.

[0020] In some embodiments, the threshold parking speed of the vehicle is 10 km/h.

[0021] In some embodiments, the driven pulley threshold parking speed is 1500 rpm.

[0022] In some embodiments, the vehicle also includes a brake operatively coupled to the ground contacting member, and the park/start condition also includes an unapplied brake state.

[0023] In some embodiments, the vehicle also includes an engine coolant temperature sensor that measures the temperature of the engine coolant. The method also includes determining the engine coolant temperature and controlling the piston force in response to the engine coolant temperature.

[0024] In some embodiments, the piston force is the first piston force when the engine coolant temperature is the first engine coolant temperature that is less than the engine coolant operating temperature threshold. The piston force is the second piston force when the engine coolant temperature is the second engine coolant temperature. The second engine coolant temperature is greater than the engine coolant operating temperature threshold. The second piston force is less than the first piston force.

[0025] In some embodiments, if a parking/driving condition is detected, the piston force is controlled regardless of engine speed.

[0026] In some embodiments, if the existence of a parking/starting condition is detected, then the piston force is controlled regardless of the speed of the driven pulley.

[0027] In some embodiments, the vehicle also includes a mode switch for selecting one of a plurality of vehicle operating modes. The method also includes determining one operating mode that has been selected from the plurality of operating modes and controlling the piston force at least in part based on the mode selected from the plurality of vehicle operating modes.

[0028] In some embodiments, the engine speed is determined and the piston force is set at least equal to the minimum piston force, the minimum piston force being pre-set as a function of the determined engine speed.

[0029] In some embodiments, the piston is at least one of pneumatically actuated and hydraulically actuated.

[0030] In some embodiments, a method for driving a vehicle is provided. The vehicle comprises an engine, a throttle control controlled by the driver of the vehicle, a throttle valve that regulates the air flow to the engine, the throttle valve position being at least partially dependent on the position of the throttle control, and a continuously variable transmission (CVT) operatively connected with engine. The BST contains a driving pulley, a driven pulley and a belt functionally connecting the driving pulley to the driven pulley. At least one ground contact element is operatively connected to the driven pulley and includes at least one of a wheel and a track. The piston is operatively connected to the drive pulley to apply, upon actuation to the drive pulley, a piston force to change the effective diameter of the drive pulley. The control unit controls the actuation of the piston and the force of the piston. The method includes determining the engine speed and controlling the piston force depending on the engine speed.

[0031] In some embodiments, the piston force is set at least equal to the minimum piston force, wherein the minimum piston force is pre-set as a function of a determined engine speed.

[0032] In some embodiments, at least one of a throttle position and a throttle position is determined and a negative load condition is detected indicative of a negative load on the engine. In response to detecting a negative load condition, the piston force is controlled in response to engine speed. The negative load condition includes: an engine speed exceeding a threshold engine speed for downhill driving; and at least one of the following: the throttle control position is less than a threshold for downhill throttle control position; and the throttle position is less than the threshold for downhill throttle position.

[0033] In some embodiments, if a negative load condition is detected, piston force is controlled regardless of throttle position and throttle control position.

[0034] In some embodiments, if a negative load condition is detected, then the piston force is controlled regardless of the speed of the driven pulley.

[0035] In some embodiments, the vehicle also includes an engine coolant temperature sensor that measures the temperature of the engine coolant. The method also includes determining the engine coolant temperature and controlling the piston force in response to the engine coolant temperature.

[0036] In some embodiments, the piston force is the first piston force when the engine coolant temperature is the first engine coolant temperature and the second piston force when the engine coolant temperature is the second engine coolant temperature. The first engine coolant temperature is less than a threshold engine coolant operating temperature. The second engine coolant temperature is greater than the engine coolant operating temperature threshold. The second piston force is less than the first piston force.

[0037] In some embodiments, the vehicle also includes a mode switch for selecting one of a plurality of vehicle operating modes. The method also includes determining one mode selected from the plurality of operating modes and controlling the piston force at least in part based on the mode selected from the plurality of vehicle operating modes.

[0038] In some embodiments, the piston is at least one of pneumatically actuated and hydraulically actuated.

[0039] In accordance with yet another aspect of the present technology, a method for driving a vehicle is provided. The vehicle comprises an engine, a throttle control controlled by the vehicle driver, a throttle valve that regulates air flow to the engine, the throttle valve position being at least partially based on the position of the throttle control, a continuously variable transmission (CVT) operatively connected to the engine. The BST contains a driving pulley, a driven pulley and a belt functionally connecting the driving pulley to the driven pulley. At least one ground contact element is operatively connected to the driven pulley and includes at least one of a wheel and a track. The piston is operatively connected to the drive pulley to apply, upon actuation to the drive pulley, a piston force to change the effective diameter of the drive pulley. The control unit controls the actuation of the piston and the force of the piston. The method includes detecting a shutdown condition indicating that the vehicle is stalling and, in response to detecting the shutdown condition, setting the piston force to zero.

[0040] In some embodiments, the implementation of the method includes determining the speed of the driven pulley. The self-shutdown condition includes the following: the speed of the driven pulley decreases; and the rate of decrease in the frequency of rotation of the driven pulley in magnitude exceeds the threshold intensity for self-shutdown.

[0041] In some embodiments, the implementation of the threshold intensity for self-off is 150 (rpm)/s ² .

[0042] In some embodiments, the vehicle also includes a brake operatively coupled to the ground contacting member, and the self-deactivate condition also includes the applied state of the brake.

[0043] In some embodiments, the piston is at least one of pneumatically actuated and hydraulically actuated.

[0044] In accordance with yet another aspect of the present technology, a method for driving a vehicle is provided. The vehicle comprises an engine, a throttle control controlled by the driver of the vehicle, a throttle valve that regulates the air flow to the engine, the throttle valve position being at least partially based on the position of the throttle control, and a continuously variable transmission (CVT) operatively connected to the engine. The BST contains a driving pulley, a driven pulley and a belt functionally connecting the driving pulley to the driven pulley. At least one ground contact element is operatively connected to the driven pulley and includes at least one of a wheel and a track. The piston is operatively connected to the drive pulley to apply, upon actuation to the drive pulley, a piston force to change the effective diameter of the drive pulley. The control unit controls the actuation of the piston and the force of the piston. The method includes determining the speed of the driven pulley. A hill stop condition is detected indicating that the vehicle is stopping on a hill, and in response to the detection of the hill stop condition, the piston force is controlled depending on the speed of the driven pulley.

[0045] In some embodiments, the vehicle also includes a brake operatively connected to at least one ground engaging element. The hill stop condition also includes applying the brake followed by releasing and at least one of the following: a throttle control position less than a threshold for the hill stop throttle position and a throttle position less than a threshold for the hill stop throttle position;

[0046] In some embodiments, the slope of the road is measured, and the hill stop condition also includes that the measured slope is positive.

[0047] In some embodiments, controlling the piston force includes, in response to the driven pulley speed being negative, increasing the piston force until at least one of the following occurs: the driven pulley speed becomes zero; and the piston force will become equal to the maximum piston force.

[0048] In some embodiments, the piston force is increased at such an rate that the piston force is increased to the maximum piston force for a threshold uphill stop duration.

[0049] In some embodiments, the hill stop threshold duration is one second.

[0050] In some embodiments, the piston is at least one of pneumatically actuated and hydraulically actuated.

[0051] In some embodiments, the engine speed is determined and the piston force is set to a value at least equal to the minimum piston force, the minimum piston force being pre-set as a function of the determined engine speed.

[0052] In accordance with another aspect of the present technology, there is provided a vehicle comprising an engine, a throttle control operated by the driver of the vehicle, a throttle valve controlling airflow to the engine, wherein the throttle position is at least partially based on the position of the throttle control , continuously variable transmission (BST), functionally connected to the engine. The BST contains a driving pulley, a driven pulley and a belt functionally connecting the driving pulley to the driven pulley. At least one ground contact element is operatively connected to the driven pulley and includes at least one of a wheel and a track. The piston is operatively connected to the drive pulley to apply, upon actuation to the drive pulley, a piston force to change the effective diameter of the drive pulley. The control unit controls the actuation of the piston and the force of the piston. The altitude sensor measures at least one of altitude and atmospheric pressure. The control unit is configured to control the actuation of the piston and the force of the piston depending on the measured at least one of the height and atmospheric pressure.

[0053] In some embodiments, a plurality of centrifugal weights are operatively connected to the drive pulley to control the drive pulley's effective diameter.

[0054] In some embodiments, the vehicle also includes a mode switch for selecting one of the plurality of vehicle operating modes, and the control unit is configured to control the piston force, at least in part, based on the operating mode selected from the plurality of vehicle operating modes. funds.

[0055] In some embodiments, the vehicle also includes connected to the piston at least one of the hydraulic and pneumatic systems, and the control unit is connected to at least one of the hydraulic and pneumatic systems to control the force of the piston.

[0056] In accordance with another embodiment, there is provided a vehicle comprising an engine, a throttle control operated by a driver of the vehicle, a throttle valve controlling air flow to the engine, wherein the throttle position is at least partially based on the position of the throttle control, continuously variable transmission (BST) functionally connected to the engine. The BST contains a driving pulley, a driven pulley and a belt functionally connecting the driving pulley to the driven pulley. At least one ground contact element is operatively connected to the driven pulley and includes at least one of a wheel and a track. The piston is operatively connected to the drive pulley to apply, upon actuation to the drive pulley, a piston force to change the effective diameter of the drive pulley. The control unit controls the actuation of the piston and the force of the piston. The engine coolant temperature sensor measures the coolant temperature of the engine cooling system. The engine speed sensor measures the engine speed. The driven pulley speed sensor measures the speed of the driven pulley. The control unit is configured to control the actuation of the piston and the force of the piston depending on at least one of the following: an operating mode selected from a plurality of engine operating modes, a measured engine coolant temperature, a measured engine speed, and a measured driven pulley speed.

[0057] In some embodiments, a plurality of centrifugal weights are operatively connected to the drive pulley to control the drive pulley's effective diameter.

[0058] In some embodiments, the vehicle also includes connected to the piston at least one of the hydraulic and pneumatic systems, and the control unit is connected to at least one of the hydraulic and pneumatic systems to control the force of the piston.

[0059] In some embodiments, the vehicle also includes a piston force selector, which selector can be operated by the driver of the vehicle. The control unit is connected to the piston force selector to receive from said selector the driver's choice, while the control unit is configured to control the piston force, at least in part, based on the received driver's choice.

[0060] In another aspect, the method includes controlling the force of the piston, at least in part, based on the operating mode of the vehicle.

[0061] With reference to the present application, terms relating to spatial orientation in the description of the vehicle and components relative to the vehicle, such as "front", "rear", "left", "right", "top" and "bottom" follows understand from the driver's point of view when the vehicle is oriented straight ahead (i.e., not turning left or right) in a strictly upright position (i.e., not tilted).

[0062] Definitions of terms given here take precedence over terms given in any of the documents incorporated herein by reference.

[0063] Each of the implementations of the present technology has at least one of the above goals and/or aspects, but not necessarily all of them. It should be understood that some aspects of the present technology, resulting from attempts to achieve the aforementioned goal, may not satisfy this goal and/or may satisfy other goals not specifically stated here.

[0064] Additional and/or alternative features, aspects, and advantages of the present technology will become apparent from the following description, the accompanying drawings, and the appended claims.

Brief description of the drawings

[0065] For a better understanding of the present technology, as well as its other aspects and additional features, it is proposed to read the following description, which should be read in conjunction with the accompanying drawings, in which:

[0066] in FIG. 1 snowmobile is shown in the right side view;

[0067] in FIG. 2A is a front left perspective view showing the power unit of FIG. 1 snowmobile;

[0068] in FIG. 2B schematically shows the throttle control system of FIG. 1 snowmobile;

[0069] in FIG. 2C illustrates throttle response to a change in throttle position in various operating modes of FIG. 1 snowmobile;

[0070] in FIG. 3 schematically shows the elements of the electronic engine control unit shown in FIG. 1 snowmobile;

[0071] in FIG. 4A is a sectional view showing the drive pulley of the continuously variable transmission (CVT) shown in FIG. 2 power units with the drive pulley in an inactive configuration;

[0072] in FIG. 4B, the drive pulley shown in FIG. 4A is shown in sectional view and in working configuration;

[0073] in FIG. 5 schematically shows the pneumatic control system for the BST of the power unit shown in FIG. 2;

[0074] in FIG. 6 is a block diagram illustrating the method of controlling the BST at various altitudes and in various modes.

[0075] in FIG. 7 shows a piston force control map for sport mode operation at sea level;

[0076] in FIG. 8A shows a piston force control map for standard high altitude operation;

[0077] in FIG. 8B shows a piston force control map for standard mode operation at sea level;

[0078] in FIG. 9A shows a piston force control map for economy mode and high altitude operation;

[0079] in FIG. 9B shows a piston force control map for economy mode operation at sea level;

[0080] in FIG. 10 shows a map of piston force control during park/start in standard and economy modes, with piston force shown as a function of throttle position and engine temperature;

[0081] in FIG. 11A shows a minimum piston force control map for downhill travel for standard mode operation; and

[0082] in FIG. 11B shows a minimum downhill piston force control map for economy mode operation.

Detailed disclosure of the invention

[0083] The present technology will be described in relation to a snowmobile. However, it is understood that this technology can be used in other vehicles, which, among others, include a motorcycle, a three-wheeler and an all-terrain vehicle (ATS). Aspects of the technology are also applicable to motorized devices other than vehicles using a continuously variable transmission (CVT).

[0084] Shown in FIG. 1, the snowmobile 10 includes a front end 12 and a rear end 14 defined in accordance with the forward direction. The snowmobile 10 has a frame 16 including a tunnel 18, an engine subframe part 20, and a front engine mount part 22. The tunnel 18, usually bent from sheet metal into a U-shaped geometric shape, extends back along the longitudinal axis 61 of the snowmobile 10, and is attached to the front part 20 of the engine subframe. Shown schematically in FIG. 1, engine 24 is supported on engine subframe portion 20 of frame 16. Fuel tank 25, supported above tunnel 18, supplies fuel to engine 24 to operate the latter.

[0085] Two skis 26 located at the front end 12 of the snowmobile 10 are attached to the frame 16 by a front suspension assembly 28. Front suspension assembly 28 includes ski racks 30, support arms 32, and ball joints (not shown) for functional connection of respective skis 26 to steering column 34.

[0086] An endless drive track 65 is located at the rear end 14 of the snowmobile 10. The drive track 65 is located generally below the tunnel 18 and is operatively connected to the engine 24 by a continuously variable transmission system 40 (CVT) (shown schematically in dashed lines in FIG. 1) and a drive sprocket ( not shown). The operation of engine 24 and BST 40 will be discussed in more detail below. The endless drive track 65 is driven to run around the rear suspension assembly 42 to propel the snowmobile 10.

[0087] Rear suspension assembly 42 includes a pair of guide rails 44 in sliding contact with endless drive track 65. Rear suspension assembly 42 also includes one or more shock absorbers 46 and suspension arms 48 and 40 for attaching guide rails 44 to frame 16. The rear suspension assembly 42 also has one or more intermediate wheels 52.

[0088] At the front end 12 of the snowmobile 10, the fairings 54 enclose the engine 24 and the BST 40, thereby providing an outer shell that protects the engine 24 and the BST 40. The fairings 54 include a cowl (not shown) and one or more side panels that can be opened to provide access to the engine 24 and BST 40 when required, for example, for inspection or maintenance of the engine 24 and/or BST 40. Attached to the fairings 54 windshield 56 near the front end 12 of the snowmobile 10 serves as protection against wind, dampening the effect of the wind on the rider while the snowmobile is in motion 10.

[0089] A saddle-type seat 58 is located on top of the fuel tank 25, extending rearward from the fairings 54, and is designed to accommodate the driver of the snowmobile 10. The rear of the seat 58 may include a storage compartment, or may be used to accommodate a passenger seat (not shown). ). On each side of the snowmobile there is a footrest 60 located under the seat 58 and designed so that the driver can put his feet on it.

[0090] The upper end of the steering column 34 is attached to a steering device, such as a steering wheel 36, located in front of the seat 58. The steering wheel 36 is used to turn the racks 30 of the skis, and, accordingly, the skis 26 themselves, to change the direction of the vehicle 10.

[0091] A throttle control 37 shaped as a finger-operated pinky to index throttle 37 is mounted adjacent to the right handlebar 36. It is contemplated that other types of throttle controls may be provided, such as a thumb-operated throttle. gas and rotary knob. The throttle lever 37 is normally biased, usually by a spring, to a position where it is furthest from the steering wheel 36. This position of the throttle lever 37 indicates that the driver wishes the engine 24 to "idle" as it would disclosed below. Throttle lever 37 may be pushed toward handlebar 36 to increase the air supply to engine 24, thereby increasing the power output of engine 24 via an electronic control (EC) system. In U.S. Provisional Application No. 61/666,443, filed June 29, 2012, the contents of which are incorporated herein by reference in their entirety, discloses additional details of electronic throttle control systems in vehicles. The PP position of the throttle control is defined as a fraction of its fully activated position (when the throttle lever 37 is closest to the handlebar 36), that is, the PP value changes from 0% (inactive or idle position) to 100% (fully activated position or position when the throttle lever 37 is as close as possible to the steering wheel 36). It is understood that the snowmobile may not have a power steering system.

[0092] The brake control 38, in the form of a finger-operated brake from the little finger to the index lever 38, is installed near the right handlebar 36. The brake lever 38 is connected to a brake disc (not shown) connected to the sprocket to brake the sprocket and , therefore, the endless track 65 as well as known to those skilled in the art.

[0093] An instrument panel 64 (FIG. 3) is provided in front of the handlebar 36 for displaying information addressed to the driver of the snowmobile 10, such as vehicle speed, engine speed, vehicle operating conditions, temperature, and the like. The instrument panel 64 may include one or more instruments, display screens, indicator lights, and audio devices such as speakers, horns, and the like.

[0094] A mode switch 62 is provided at or near the steering wheel 62 (see FIG. 3). The mode switch 62 is in the form of a toggle switch, but is intended to be a user control in the form of a push button switch, mushroom, lever, or other element installed in the dashboard 64 or in appliances. The mode switch 62 has positions corresponding to ECO mode, STD mode and SPORT mode, as will be detailed below. Switch 62 can be latched progressively between ECO mode, Standard mode and Sport mode. The snowmobile operator 10 expresses a desire to change the operating mode from the current mode CM to the desired snowmobile operating mode DM by moving the mode switch 62 to the position corresponding to the desired mode DM. It is envisaged that modes of operation of the vehicle may be associated with authorization or identification of the driver, for example, information about which may be encoded in the key used to start the vehicle 10. For example, different keys may be associated with different modes, or each of the keys may give authorization to drive the vehicle in one or more modes. It is envisaged that the number and names of operating modes may differ from those described here.

[0095] Engine 24 is an internal combustion engine. The internal structure of engine 24 may be of any known type and may operate in a two-stroke or four-stroke cycle. Engine 24 drives a crankshaft 57 (FIG. 4A) to rotate about a horizontal axle 85 (FIG. 4A) extending generally transverse to the longitudinal axis 61 of the snowmobile 10. Crankshaft 57 drives a BST 40, as detailed below, in order to transmit torque to the endless drive track 65 to advance the snowmobile 10.

[0096] FIG. 2A schematically shows the power unit 75 of the snowmobile 10. The power unit 75 includes a motor 24, a BST 40, and a fixed ratio gear drive 78. BST 40 includes a drive pulley 80 associated for rotation directly with the crankshaft 57 of the engine, and a driven pulley 88 associated with one end of the intermediate shaft 92, located transversely and supported in the bearings of the frame 16. As shown, the intermediate shaft 92 is transversely located crosses the width of the engine 24. The opposite end of the lateral layshaft 92 is connected to the gear drive input 78, and the gear drive output 78 is connected to a drive axle 90 carrying gears (not shown) forming a drive connection to the drive track 65. Typically, the gear drive input element 78 consists of a small sprocket connected to a transverse countershaft 92 and coupled for driving to an output element consisting of a larger sprocket connected to the drive shaft 90 via a drive chain, all contained within the gear drive housing 78.

[0097] In this particular example, the drive pulley 80 rotates at the same frequency ES as the crankshaft 57 of the engine 24, while the rotational speed of the transverse intermediate shaft 92 is determined in accordance with the instantaneous value of the gear ratio BST 40. Drive axle 90 rotates at a speed lower than the speed of the transverse countershaft 92 as a result of the action of the gear drive 78. It is provided that the drive pulley 80 may be connected to an engine shaft other than the crankshaft 57, for example, to the output shaft, balance shaft or take-off shaft power driven by the engine 24 and departing from it. Similarly, it is contemplated that the driven pulley 88 may be coupled to a shaft other than the transverse countershaft 92, such as directly to the drive axle 90 or any other shaft operatively coupled to the snowmobile's ground contact element (i.e., the drive track 65). in the case of a snowmobile 10).

[0098] The drive pulley 80 of the BST 40 includes a pair of opposing and frustoconical disks 82 and 84 between which the endless belt element 86 is held. The drive pulley 80 will be detailed below. driven pulley 88 BST 40 includes a pair of opposing and frustoconical disks 87 and 89 holding the endless belt element 86.

[0099] The gear ratio of the BST 40 is given as the ratio of the effective diameter D2 of the driven pulley 88 to the effective diameter D1 of the driving pulley 80. The effective diameters D1 and D2 of the pulleys 80, 88 are determined by the radial position of the belt 86 held between two pairs of disks - 82, 84 and 87 , 89 of the respective pulleys 80, 88. The radial position of the belt 86 held between the two disks 82 and 84 and 87 and 89 varies with the distance between the disks 82 and 84 and 87 and 89. Since the length of the belt 86 remains constant, the effective diameters D1, D2 of the driving and driven pulleys 80 and 88 are inversely proportional to each other. When the belt 86 is displaced radially outward on the drive pulley 80 (i.e., when the drive sheave discs 82 and 84 converge with each other), thereby increasing the effective diameter D1 of the drive sheave 80, then the belt 86 is forced to be displaced radially inward on the driven sheave 88 (then there are discs 87 and 89 of the driven pulley diverge from each other), thereby reducing the effective diameter D2 of the driven pulley 88 and changing the gear ratio of the BST.

[00100] Drive pulley disks 82, 84 are spaced apart such that when they are not rotating, drive pulley disks 82, 84 are spaced apart and belt 86 is disengaged from drive pulley 80. The movable disk moves in response to change the engine speed ES. The effective diameters D1, D2 of the pulleys 80, 88 are inversely proportional to each other. As the crankshaft 57 and the drive pulley discs 82, 84 begin to rotate at an increasing rotational speed ES, the discs 82, 84 converge towards each other due to the action of a set of centrifugal weights that pushes the movable disc towards the stationary disc. At a certain engine speed ES, the drive pulley disks 82, 84 engage the belt 86, which in turn starts to rotate the driven pulley disks 87, 89. The rotational speed ES (of the crankshaft 57 and the drive pulley discs 82, 84) at which the drive pulley discs 82, 84 engage the belt 86 is called the _engagement revolutions ES.

[ ₀₀₁₀₁ ] At speeds ES greater than clutch engagement ES, engine 24 is operatively coupled via BST 40 to track 65. At speeds ES _below clutch engagement ES, BST 40 is disengaged, i.e., power unit 75 cannot transmit torque and power from engine 24 to track 65. That is, snowmobile 10 is not driven by engine 24, and at speeds lower than ES _engage engine 24 is idling. The idle operation of engine 24 allows power to be provided to vehicle systems such as displays 64, electronic control unit (ECU) 200, and the like. The engine 24 can be set to idle by releasing the throttle lever 37 without shutting off the engine 24. Turning the engine 24 on and off is typically accomplished by inserting a key (mechanical and/or electronic) into the key box or operating a switch.

[00102] The engine 24 through the crankshaft 57 transmits torque to the drive pulley 80 to rotate the latter. The distance between the drive pulley discs 82 and 85 and the effective diameter of the drive pulley 80 are controlled by an adjustment mechanism, which will be detailed below. The belt 86 is engaged by the drive pulley disks 82, 84 as described above. The belt in turn engages the driven pulley 88 by rotating the discs 87 and 89 and changing the distance between them and the effective diameter D2 of the driven pulley 88 as described above. Thus, the torque from the motor 24 is transmitted to the drive pulley 80, the belt 86, the driven pulley 88 and finally to the drive axle 90.

[00103] In a high LST (low gear) ratio, the drive pulley 80 makes several revolutions per revolution of the driven pulley 88. This configuration is required in certain situations, such as when accelerating the snowmobile 10, when it is required to transfer a large amount of torque to the drive pulley 88 and , respectively, the drive axle 90.

[00104] At low gear ratio BST (upshift), for one revolution of the drive pulley 80, the driven pulley 88 makes one revolution. This configuration is required in certain situations, such as when driving a snowmobile at constant and high speeds.

[00105] Engine 24 is an in-line, two-cylinder, four-stroke internal combustion engine. However, it is contemplated that the design of the engine 24 may be of any known type. Engine 24 receives fuel from fuel tank 25 via fuel injection system 76 (FIG. 3). Engine 24 receives air from intake system 66 (FIG. 2B) through throttle body 68. The ignition of the air-fuel mixture in the engine 24 is carried out by the ignition system 74. Engine power output P, torque τ, and engine speed ES are partly determined by the quality of the air-fuel mixture in the engine and the ignition timing setting IT. In order to cool the engine 24 during operation, it is in fluid communication with the cooling system 284. An electronic control unit (ECU) 200 is operatively connected to the engine 24 to control the operation of the engine 24 as described below.

[00106] As shown in FIG. 2B, throttle body 68 includes a throttle valve 70 that controls the amount of air flowing through throttle body 68 and entering engine 24. Throttle valve 70 is a butterfly valve having a circular disc mounted within tubular body 68 that rotates on a rod extending diametrically across the disk. The disk rotating on the rod prevents the passage of air through the tubular body 68 of the throttle valve to a variable degree. The throttle valve 70 is in its fully open position (minimum obstruction of air flow) when the circular surface of the disc is at a minimum angle to the central axis of the tubular body 68, and is in its fully closed position (maximum obstruction of air flow) when the circular surface disk is at a maximum angle to the central axis of the tubular body 68 of the throttle valve. Throttle valve actuator 72, in the form of an electric motor, is operatively connected to the disc to change the position of the latter, thereby controlling the opening degree of throttle valve 70. Throttle valve position TVP can be set in terms of throttle valve opening degree 70. Throttle valve position TVP is defined as a fraction of its fully open position, and therefore TVP can vary from 0% (fully closed position) to 100% (fully open position). A throttle sensor 206 is connected to the throttle valve 70 and measures its TVP position. The throttle actuator 72 positions the throttle valve 70 depending in part on the position of the snowmobile throttle lever 37 PP. As noted above, the snowmobile 10 is equipped with an electronic control (EC) system in which the control of the throttle 70 is performed electronically, instead of having mechanical wiring between the throttle lever 37 and the throttle valve 70. The position of the PP of the throttle lever 37 is monitored by a sensor 204 gas control position. Actuator 72 is controlled in part based on signals received from ECU 200 as described below.

[00107] As shown in FIG. 2B and FIG. 3, ECU 200 communicates electronically with various sensors from which it receives signals. These signals are used by ECU 200 to control throttle actuator 72, ignition system 74, and fuel injection system 76 in the case of a fuel injected engine, in order to control the operation of engine 24. The methods by which ECU 200 controls engine 24 are detailed below. .

[00108] Those skilled in the art will appreciate that not all of the FIGS. 3 sensors or components are required to achieve aspects of the present invention. Those skilled in the art should also understand that, depending on the particular aspect of the invention, some sensors and components may not be available, some sensors and components may be replaced by other types of sensors and components, and two or more sensors may be combined in one sensor. , which can be used to perform many functions within the scope of the present technology.

[00109] The throttle position sensor 204 measures the position of the PP of the throttle control 37 (in the illustrated embodiment of the snowmobile 10, the throttle lever 37 actuated by index finger to pinky finger or thumb) and sends a signal to ECU 200 containing the information on the position of the RR of the gas control. Depending on the type of throttle control, the throttle position sensor 204 is typically located near the throttle control 37 and measures the movement of the throttle control 37 or the linear displacement of a cable connected to the throttle control 37.

[00110] ECU 200 sends a signal to throttle actuator 72 to control the position of TVP, that is, the opening degree of throttle valve 70 inside throttle body 68. The throttle valve position TVP is adjusted in part depending on the position of the throttle control PP, but also depending on other factors such as ignition timing setting IT, desired output power and torque τ, current operating mode CM, and the like.

[00111] Throttle position sensor 206 measures the position (i.e., degree of opening) of throttle valve 70 and sends a signal containing information about the TVP position of throttle valve 70 to ECU 200. Throttle position sensor 206 acts as a feedback source for ECU 200 because the ECU 200 uses the signal received from the throttle position sensor 206 to determine whether the actuator 214 has moved the throttle valve 37 to the desired position and make appropriate adjustments. Throttle position sensor 206 may be any type of sensor, such as rheostatic, Hall effect, potentiometric, and the like. Depending on the type of throttle actuator 72 used, a separate throttle position sensor 206 may not be required. For example, a separate throttle position sensor 206 may not be needed if the throttle actuator 72 is a servomotor, since the servomotors have their own feedback circuit that corrects the position of the motor and has a built-in throttle position sensor 206 for this.

[00112] The engine speed sensor 208 measures the engine 24 speed ES and sends a signal containing the engine 24 speed ES information to the ECU 200. The engine speed sensor 208 is a Hall sensor associated with a trigger wheel on the engine output shaft. It is contemplated that the engine speed sensor 208 may be coupled to any rotating engine shaft, such as a crankshaft. The rotational speed ES of the engine 24 may be used by the ECU 200 to calculate the engine torque τ and the engine 24 output power P.

[00113] The mode switch sensor 210 senses the position or movement of the mode switch 62 and sends to the ECU 200 a signal containing information about the required DM operating mode (also referred to here as the selected vehicle operating mode). In some embodiments, mode switch sensor 210 is configured to measure the position of mode switch 62, and ECU 200 determines the appropriate desired operating mode from the signal received from mode switch 210. In some embodiments, the mode switch sensor 210 is configured to measure the movement of the mode switch 62, including the number of steps of movement (one or two steps in the illustrated embodiment) and direction of movement (up or down). The mode switch sensor 210 sends to the ECU 200 a signal containing information about the specified movement, and the ECU 200 determines the desired operation mode DM from the current operation mode CM and from the received information about the movement of the mode switch 62.

[00114] The vehicle speed sensor 202 measures the speed VS of the snowmobile 10 and sends a signal containing the speed information VS of the snowmobile 10 to the dashboard 64. It is contemplated that the vehicle speed sensor 202 may also send a signal containing the speed information VS of the snowmobile to ECU 200. The vehicle speed sensor 202 is a Hall sensor associated with a trigger wheel on a drive shaft, such as a drive axle 90, so as to measure the speed of the latter. It is envisaged that in order to determine the speed of the snowmobile 10, the vehicle speed sensor 202 may measure the speed of any shaft driven by the driven pulley 88 (i.e., any shaft connected between the driven pulley 88 and the track 65), including the shafts within the reduction drive 78. Any suitable type of vehicle speed sensor 202 is contemplated. Alternatively, the vehicle speed sensor 202 may include a GPS global positioning system module. Using information from the GPS module, the speed of the vehicle 10 can be determined by calculating the change in location of the vehicle 10 over a period of time, which is typically a function of the GPS module.

[00115] The driven pulley speed sensor 203 measures the frequency N _{2 of} the driven pulley 88 and sends a signal containing the frequency N ₂ information to the ECU 200. The driven pulley speed sensor 203 is a Hall sensor coupled to the intermediate shaft 92 so as to measure rotation frequency of the latter.

[00116] The height sensor 205 provided with the vehicle 10 detects the height at which the vehicle 10 is operating and sends a signal to the ECU. The height sensor in the illustrated embodiment is an air pressure sensor (or barometer) that measures the atmospheric pressure in the vicinity of the vehicle 10 and determines the altitude based on the measured atmospheric pressure. The sensor 205 is provided to be an altimeter. It is contemplated that the height sensor 205 may be part of the GPS module mentioned above.

[00117] The slope sensor 280, which is equipped with the vehicle 10, is designed to measure the slope of the road on which the vehicle is operating. It is contemplated that the slope sensor 280 may be part of the GPS module mentioned above.

[00118] ECU 200 is coupled to ignition system 74 in order to control ignition of the air-fuel mixture in engine 24 combustion chamber. and/or engine speed ES. The ECU 200 is also connected to the fuel injection system 76 in order to control the injection of fuel into the engine 24. The ECU is connected to the engine coolant temperature sensor 288 to monitor the temperature of the engine coolant flowing through the engine cooling system 284 to thereby monitor the engine operating temperature T _E 24.

[00119] the ECU 200 is connected to the dashboard 64 to control the visualization of information on it. ECU 200 sends signals to dashboard 64 to display information about engine speed and vehicle speed, as well as the selected operating mode.

[00120] It is contemplated that ECU 200 may be divided into a plurality of units, each of which is provided with one or more of the functions discussed above or below.

[00121] ECU 200 controls the operation of engine 24 based at least in part on signals received from sensors 202, 203, 204, 205, 206, 208, 210, and depending on the particular circuit or control map used by ECU 200 Control cards provide information related to a variety of parameters (eg, throttle position TVP, throttle control PP position, fuel injection, ignition timing IT setting, engine torque, power output, etc.) needed to operate an engine 24 For example, the control map may provide information about the required change in throttle position and engine speed to achieve a particular engine power output or torque. ECU 200 may also use algorithms in addition to control maps to determine some of the parameters.

[00122] The snowmobile 10, as mentioned above, can be operated in different operating modes (in the illustrated embodiments, these are the following modes: sport, standard and economy). Some of the control maps used by ECU 200 are specific to each operating mode and indicate the variations in engine parameters required to operate in that mode.

[00123] As seen in FIG. 2C, for different operating modes, the throttle response (ie, throttle position TVP versus throttle position PP) is different for different operating modes. As mentioned above, the throttle position TVP is defined as a fraction of its fully open position, and therefore TVP can vary from 0% (fully closed position) to 100% (fully open position). The PP position of the throttle control is also defined as a fraction of its fully activated position and varies accordingly from 0% (idle or idle position) to 100% (fully activated position).

[00124] As the throttle position PP value increases from 0% to 100%, the corresponding throttle position TVP value in each mode increases from the mode's minimum value to the mode's maximum value. For all modes, the minimum throttle position TVP corresponding to 0% throttle position PP is a value greater than zero. The minimum throttle position TVP corresponds to the idle throttle position ITVP and is set to a value greater than zero to allow idle operation in this mode.

[00125] It can be seen that for any particular throttle position PP, the corresponding throttle position TVP in economy mode is less than the corresponding throttle positions TVP in sport and standard modes. Also, for any particular throttle position PP other than 100%, the throttle position TVP in sport mode is greater than the corresponding throttle position TVP in standard mode. With throttle PP set to 100%, the TVP throttle positions in Sport and Standard modes are the same.

[00126] In the illustrated embodiment, the maximum throttle position TVP in sport and standard modes is set to the fully open position (i.e., 100%), while in economy mode the maximum throttle position TVP is limited to 50% of the fully open position. . It is envisaged that the maximum throttle position TVP in standard mode may be less than that in sport mode so that each of the three modes will have its own maximum throttle position TVP. It is also contemplated that the maximum throttle position TVP in standard mode may be the same as in economy mode. In the illustrated embodiment, for each of the three modes, the maximum throttle position TVP is reached when the accelerator pedal 37 is at its maximum 100% throttle position PP. It is envisaged that the maximum value of the TVP position can be reached when the value of the position PP of the throttle control is less than 100%.

[00127] The engine 24 of the snowmobile 10 is capable of producing a certain maximum power output determined by its displacement, as will be appreciated by one of ordinary skill in the art. The power P produced by the engine at any given time is a function of several parameters, among which are the throttle position TVP, ignition timing IT and fuel injection. The ECU 200 controls the operation of the engine 24 in such a way that the power output P generated by the engine 24 also depends on the current operating mode of the CM. For example, in economy mode, the power output P produced by engine 24 is limited to a maximum value of approximately 50% of the maximum power output available from engine 24.

[00128] It is also provided that the vehicle speed be limited in one of the modes, for example, to improve fuel efficiency, the vehicle speed can be limited in the economy mode.

[00129] Next, with reference to figa and 4B is considered in detail the drive pulley 80.

[00130] As discussed above, the drive pulley 80 includes a pair of disks 82 and 84, which both rotate with the crankshaft 57 about the axis of rotation 85 of the drive pulley 80. When applied to the drive pulley, the term "axial direction" refers to the direction parallel to the axis 85 rotation.

[00131] Both the inner and outer discs 82 and 84 have a belt contact surface 83. The belt 86 is held by the belt contact surface 83 of the drive discs 82 and 84. The inner disc 82, located between the outer disc 84 and the motor 24, is fixed in the axial direction , and is therefore called fixed disc 82. Outer disc 84 can be moved toward or away from fixed disc 82 in an axial direction to change the gear ratio of BST 40, and hence disc 84 is referred to as movable. Axial mobility is provided for both discs 82 and 84.

[00132] The disks 82, 84 of the drive pulley 80 are mounted on a drive shaft 100 rotatably connected to the crankshaft 57. A portion 101 of the drive shaft 100 is fitted with a cone fit on the end face of the crankshaft 57. At the end opposite the portion 101, into the drive shaft 100 a bolt 102 is inserted and screwed into the end of the crankshaft to secure the drive shaft 100 to the crankshaft 57. It is provided that the drive shaft 100 is rotatably coupled to the crankshaft 57 by other known methods. For example, the drive shaft 100 may be keyed to the crankshaft 57.

[00133] The stationary disk 82 is installed with an interference fit on the inner end of the drive shaft 100 to rotate with it and be stationary in the axial direction.

[00134] The movable disk 84 is mounted on the drive shaft 100 axially outside the stationary disk 82. The movable disk 84 is mounted on the drive shaft 100 on support sleeves 104 to be able to slide in the axial direction.

[00135] An annular spring chamber 110 coaxial with the drive shaft 100 is formed between the movable disc 84 and the drive shaft 100. Within the spring chamber 110 is a helical pressure spring 116 coaxial with the drive shaft 100. A collar 112 extending radially outward from the outer surface of the drive shaft 100 into the spring chamber 110 forms a spring stopper. The spring 116 is held in the spring chamber 110 between the axially fixed spring retainer 112 and the axially movable outer wall 114 formed by a portion of the movable disc 84. In this configuration, the spring 116 moves the movable disc 84 away from the fixed disc 82.

[00136] Spring 116 is provided to be held between a portion of the fixed disc 82 and a portion of the movable disc 84, or an element fixedly connected to the sliding movable disc 84. It is also provided that the spring 116 may be held between the portion of the movable disc 84 and the axially stationary portion of the driving pulley. , other than bead 112, if the axially fixed part is located axially inside the part of the movable disk 84.

[00137] A plurality of centrifugal weights 120 are mounted on the outer surface of the movable disk 84. In the illustrated embodiment, the centrifugal weights are in the form of flywheels or levers 120, in which one end 121 is attached to the outer surface of the movable disk 84, and the other end 122 can freely hinge deviate from the movable disc 84. When the movable disc 84 is at rest, the free end 122 of the centrifugal arms 120 rests on its outer surface. As the rotational speed of the movable disk 84 increases, the free end 122 pivots away from the movable disk 84 radially outward relative to the drive shaft 100.

[00138] A spider 90 and a cover 92 are mounted on the drive shaft 100 axially outside the movable disk 84 to rotate with the drive shaft 100. The cover 92 is attracted to the drive shaft 100 by a bolt 102 that fastens the drive shaft 100 to the crankshaft 57. The spider 90 is attached to cover 92 with bolts inserted into holes 126 at the outer edge. Cross 90 and cover 92 thus rotate with drive shaft 100.

[00139] The spider 90 has a cylindrical hub 124 extending coaxially around and separated from the drive shaft 100. Cross 90 has six pairs of ribs 128 extending inwardly towards the movable disk 84. Six pairs of ribs 128 are distributed radially along the outer edge. Each pair of collars 128 has a roller 130 rotatably mounted between their ends. Each of the rollers 130 is in contact with one respective centrifugal arm 120 of the movable disk 84. shaft 100 around the axis 85. Each response bead 129 of the movable disk 84 is received in the space between adjacent pairs of bead 128 of the cross 90.

[00140] The spider 90 is made of aluminum. It is envisaged that the cross 90 is made of other suitable materials. The spider 90 has a plurality of apertures 140 formed radially outward from the hub 124 and between the pairs of collars 128. The presence of the apertures 140 aids in weight reduction. It is envisaged that the apertures 140 are omitted.

[00141] Cover 92 is made of aluminum. Cover 92 is contemplated to be made from other suitable materials. A number of cavities 138 are formed in the surface of the cover 92 facing away from the movable disk 84. The cavities 138 are formed to reduce weight. It is provided that the cavities 138 are absent.

[00142] At a low operating speed (rpm) of the engine, the fixed disk 82 and the movable disk 84 of the drive pulley 80 are positioned as shown in FIG. 4A. At high engine speeds, discs 82 and 84 are positioned as shown in FIG. 4B. Centrifugal weights 120, with which you can change the configuration, are part of the adjustment mechanism for adjusting the gear ratio of the BST.

[00143] As shown in FIG. 4A, when the drive shaft 100, that is, both the movable disk 84 and the spider 90 are at rest, the movable disk 84 is on the drive shaft 100 in its maximum outward position and at the maximum distance from the fixed disk 82. In this configuration, the rollers 130 of the spider 90 are in contact with the levers 120 near the non-free end 121 attached to the movable disk 184.

[00144] As the speed of the movable disc 84 increases, the free end 122 of the levers 120 moves outwards, pushing the rollers 130 and pushing the movable disc 84 away from the spider 90 towards the fixed disc 82. The contact point of the lever 120 with the roller 130 moves from the non-free end 121, attached to the movable disk 84 towards the free end 122 of the arm 120.

[00145] As shown in FIG. 4B, when the movable disk 84 is on the drive shaft 100 in its most inboard position, and in its position closest to the fixed disk 82, the free ends 122 of the arms 120 are in contact with the rollers 130 of the spider 90. This configuration of the drive pulley 80 is achieved at high frequency of rotation of the drive shaft 100.

[00146] It is contemplated that the centrifugal weights 120 may be attached to the spider 90 so as to be in contact with the movable disc 90 and push the movable disc 84 away from the spider 90 as the frequency of rotation of the spider 90 increases. It is also possible that the centrifugal weights could be in the form of roller weights, with an increase in the speed of the drive pulley 80 rolling radially outward. In such an embodiment, the surfaces in contact with the roller weights are inclined so that the roller weights can push the movable disk away from the spider 90.

[00147] When the movable disc 84 is pushed against the fixed disc 82, the compressed spring 116 exerts a force on the movable disc 84 to move it away from the fixed disc 82, that is, in a direction opposite to the direction of the force applied to the movable disc 84 by centrifugal weights 120. The balance of these opposing forces determines, in part, the axial position of the movable disk 84. Thus, the centrifugal weights 120 are the mechanical part of the gear ratio adjustment mechanism of the BST.

[00148] The piston 94 is slidably mounted on the drive shaft 100, axially internal to the cover 92 and inside the cylindrical hub 124 of the spider 90. The piston 94 is isolated from the outer surface of the drive shaft 100 by a seal 131 received in a groove formed in the inner cylindrical surface of the piston 94 The piston is isolated from the inner surface of the cylindrical hub 124 by a seal 133 received in a groove formed in the outer cylindrical surface of the piston 94. Thus, the cylindrical hub 124 forms a cylinder for the piston 94. For simplicity, the cylindrical hub 124 will hereinafter be referred to as the cylinder 124 Piston 94 is moved away from cap 92 by filling the space between piston 94 and cap 92 with pressurized air, as will be discussed below.

[00149] In this embodiment, the stationary movable disc 84 (i.e., the movable disc 84 at its maximum outward axial position) abuts against the piston 94 when the latter is not actuated, as shown in the configuration shown in FIG. 4A. It is possible for the immobilized movable disk 84 to be at a distance from the piston 94 that is not actuated. It is also contemplated that the piston may be attached to the movable disc 84 to slide and rotate with the movable disc 84. It is envisaged that the piston may be located in a cylinder that is not part of the spider 90. It is also envisaged that the piston 94 may be geometrically shaped, different from the one shown here. It is contemplated that a plurality of pistons with a corresponding number of cylinders can be provided to apply force to the movable disk.

[00150] A connector 96 mounted on cover 92 connects air duct 98 to the interior of cylinder 124 through air passages 93 formed in cover 92. Connector 96 rotates with cover 92, and air duct 98 is stationary. Bearings 137 are inserted between the fixed duct 98 and the connector 96. The connector 96 is rotatably isolated from the fixed duct 98 by lip seals 132. When pressurized air is supplied through the duct 98 to the cylinder 124, the piston 94 slides away from the cover 92, pushing the movable disk 84 to the stationary disk 82 and increasing the effective diameter of the drive pulley 80. That is, the force applied to the movable disk 84 by the piston 94 acts in the same direction as the force applied to the movable disk 84 by the centrifugal weight mechanism.

[00151] As explained above, in general, a higher engine speed causes the drive pulley 80 to rotate faster, increasing the force applied to the movable disk 84 by centrifugal weights 120, resulting in an increase in the effective diameter of the drive pulley 80 (i.e., reduction of the effective diameter of the driven pulley 88) and to a decrease in the gear ratio of the BST 40. That is, the gear ratio of the BST is determined by the operating speed of the engine 24.

[00152] The pneumatically actuated piston 94 changes the characteristic curve of the drive pulley 80. The drive pulley 80, at the same engine speed, achieves a larger effective diameter when the action of the centrifugal weight mechanism is supported by the action of the pneumatic piston 94 than when the pneumatic piston are not put into action. The pneumatic piston 94 effectively shifts the snowmobile 10 into a higher gear at a lower engine speed than would be the case if the BST 40 were controlled purely mechanically (ie, centrifugal weights 120). When the pressure is released so that the piston 94 is no longer actuated, the spring 116 returns the movable disk 84 to its original position, so that the BST 40 returns to a purely mechanical setting of the effective diameter of the drive pulley, that is, and the gear ratio of the BST, exclusively by centrifugal weights. 120.

[00153] That is, the BST 40 is fully operational both with and without actuation of the piston 94. Pneumatic piston 94 allows you to control the gear ratio of the BST, regardless of the engine speed. For example, the gear ratio of the BST can be adjusted based on factors such as the torque required on the drive axle 90, fuel consumption, driver comfort, and so on. The air pressure driving the piston 94 can also be adjusted to obtain the desired characteristic curve. For example, the BST 40 can be configured to maximize fuel economy or throttle response, or to optimize both. Pneumatic piston 94 can also be used to simulate the response of a multi-stage transmission. Further, several methods of pneumatic control of the BST 40 are considered in detail.

[00154] Compressed air to actuate piston 94 is provided by an electric compressor 320 (FIG. 5) located elsewhere on the snowmobile. The compressor 320 includes an air/water separator designed to prevent or minimize moisture content within the BST 40. It is envisaged that a mechanical compressor is used instead of an electric compressor. Compressor 320 is contemplated to be any compressor capable of generating the pressure required to actuate piston 94. Compressor 320 is also contemplated to be driven by an engine other than engine 24, a motor or a battery, depending on the particular requirements.

[00155] The pneumatic pressure applied to the piston 94 and the resulting piston force to completely bring the movable and fixed discs 82 and 84 together is much less for the BST 40 embodiment shown in FIG. 4A and 4B than for the BST, in which the gear ratio is controlled purely pneumatically. The size of the pump or compressor 320 required to generate a given piston force is significantly smaller than that required for a purely pneumatically controlled BST, thus achieving energy and space savings for the snowmobile 10.

[00156] Installed between pump 220 and cylinder 124 is an accumulator 322 (FIG. 5) to act as a reservoir of compressed air to ensure rapid actuation of piston 94 under all operating conditions and to limit pressure fluctuations.

[00157] It is also envisaged that compressed gas cylinders are used instead of compressor 320 and accumulator 322 to provide compressed air to drive piston 94.

[00158] The actuation control of the piston 94 is automatically controlled depending on parameters such as vehicle speed, engine speed (rpm), required torque, remaining fuel, and the like. The various ways to control the BST 40 are described below.

[00159] It is envisaged that the snowmobile operator may additionally manually control the actuation of the piston 94. For example, a switch, such as a push button switch, may be provided to enable and disable the actuation of the piston. Alternatively, an infinitely variable knob could be provided with which the snowmobile rider could set the amount of force applied by the piston 94.

[00160] Next, with reference to FIG. 5 details the pneumatic system 300 for supplying compressed air to the piston 94, as well as the pneumatic control unit (PCU) 310 for automatically controlling the pneumatic actuator of the piston 94.

[00161] The pneumatic system 300 includes a compressor 320, an electric motor 340, an accumulator 322, a pressure control unit 328 containing an air inlet valve 324, an air outlet valve 326, a cylinder pressure sensor 330, and an accumulator pressure sensor 332.

[00162] MODU 310 controls the compressed air pressure supplied to piston 94 for selective and controlled actuation of piston 94.

[00163] As discussed above, cylinder 124 is connected to a compressor 320 to provide compressed air. Compressor 320 is operatively connected to PMU 310. PMU 310 sends electronic signals to compressor 320 to actuate it. It is envisaged that the PMU 310 is also configured to receive signals from the compressor 320.

[00164] As also discussed above, accumulator 322, in fluid communication with compressor 320 (and connected downstream of the compressor), stores compressed air to actuate piston 94 and helps reduce the inertia of actuating piston 94. That is, compressor 320 is connected to cylinder 124 via accumulator 322. Compressed air flows from compressor 320 to accumulator 322 and from accumulator 322 to cylinder 124. It is envisaged that an additional flow of compressed air flowing from compressor 320 to cylinder 124 is provided. without passing through the battery 322. The absence of the battery 322 is also provided.

[00165] Air inlet valve 324 connected between accumulator 322 and cylinder 124 allows air to flow from accumulator 322 to cylinder 124. Air inlet valve 324 is opened if the pressure inside cylinder 124 (detected by cylinder pressure sensor 330) is less than desired, and if accumulator 322 may supply pressurized air at a pressure (detected by accumulator pressure sensor 332) in excess of the pressure in cylinder 124.

[00166] Connected to the cylinder 124, the air outlet valve 124 allows compressed air in the cylinder 124 to be vented to the atmosphere. The air outlet valve 326 is opened if the pressure in the cylinder 124 exceeds the desired pressure.

[00167] Air inlet valve 324 and air outlet valve 326 are operatively connected to PMU 310. Valves 324, 326 may each be configured to open at certain pressure settings. The pressure setpoints for valves 324, 326 can be electronically assigned or mechanically adjusted. PBU 310 sends control signals to valves 324, 326 to initiate their opening and closing. The PMU 310 is also configured to receive signals from the valves 324, 326. It is envisaged that the air inlet valve 324 and the air outlet valve 326 are replaced by a single proportional relay valve.

[00168] The battery pressure sensor 322 is connected to the battery 322 to measure the air pressure in the battery 322. In the illustrated embodiment, the battery pressure sensor 332 is connected downstream of the battery 322, between the battery 322 and the air intake valve 324. However, less provided that the battery pressure sensor 322 is connected anywhere in the battery 322.

[00169] Cylinder air pressure sensor 330 measures air pressure in cylinder 124. Cylinder pressure sensor 330 is shown connected between air intake valve 324 and cylinder 124.

[00170] Each of the sensors 330, 332 is communicatively connected to the PMU 310. The PMU 310 is configured to receive data and/or signals from the pressure sensors 330, 332 containing information about the air pressure measured by the pressure sensors 330, 332. It is envisaged that the PBU 310 could also be configured to send control signals or data signals to the pressure sensors 330, 332. PBU 310 is also configured to send control signals to air inlet valve 324, air outlet valve 326, and compressor 320, these control signals being based in part on signals received from pressure sensors 330, 332.

[00171] As mentioned above, it is provided that a compressed gas cylinder is used instead of the compressor 320 and accumulator 322. In such an embodiment, the PMU 310 will be operatively connected to the compressed air cylinder and will be configured to provide control signals or data signals to it, which signals will be based on signals received from other sensors, such as the cylinder pressure sensor 330.

[00172] PMU 310 communicates with ECU 200 to control the operation of piston 94. It is envisaged that some or all of the functions of PMU 310 are integrated into ECU 200.

[00173] In the illustrated embodiment of snowmobile 10, a piston force selector 380 is also provided. The piston force selector 380 is operated by the driver of the snowmobile 10 to actuate the piston and/or select the desired piston force Pf. The PMU 310 communicates with the piston force selector 380 to optionally control the piston force Pf in part depending on the selected piston force value. The piston force selector 380 may be in the form of a push button, switch, mushroom, lever, or the like, which can be moved within a plurality of piston force selection positions, such as between the "0" position, the "low force" position, and the " high effort.

[00174] With reference to FIG. 6 - fig. 10 further discusses several ways of pneumatic control of the BST 40.

[00175] In the illustrated embodiment of the BST 40 control method, the centrifugal weights 120 of the BST 40 are optimized for operation in the SPORT mode and at high altitude (set, in this embodiment of the vehicle 10, to 2000 meters above sea level and above). At the same time, in the SPORT mode and at high altitude, the force Pf applied by the piston 94 to the movable disk 84 is equal to zero. The drive pulley diameter D1 is determined depending on the engine speed ES, which is in turn controlled by the ECU 200 based on the sport mode engine speed control map (not shown).

[00176] In the absence of any force Pf applied by piston 94, the engine speed ES obtained for a particular throttle position TVP and ignition timing setting IT is greater at low altitudes than at high altitudes due to the fact that at low altitudes, atmospheric pressure is higher. The higher atmospheric pressure at low altitudes causes more air to be sucked through the throttle body into the combustion chamber for the same throttle valve opening degree TVP. In order to maintain a stoichiometric air-fuel ratio, more fuel is injected into the engine 24 at low altitudes than at high altitudes, and more power is generated to rotate the crankshaft at a higher engine speed ES for the same throttle opening degree TVP.

[00177] The pneumatic piston 94 enables the engine speed ES to be controlled regardless of the throttle position TVP. The pneumatic piston may be actuated to reduce the engine speed ES to thereby counteract the increase in engine speed ES due to the height of the vehicle.

[00178] With reference to FIG. 6 further details a method 400 for controlling the BST 400 to compensate for the effect of height.

[00179] The method starts at step 410, where BSP 310 determines the height based on the signal received from the height sensor.

[00180] Next, at step 420, BSP 310 determines the operating mode based on the signal received from the mode switch 62 or based on which key is in the key receiver.

[00181] The method 400 then proceeds to step 430 where, based on the signals received by the ECU 200 from the mode switch sensor 210 and the height sensor 205, it is determined whether the operating mode is the SPORT mode and whether the height is at least equal to the upper threshold height A _NT (that is, high altitude). In the illustrated embodiment, the upper threshold height A _HT is set to 2000 meters, but the upper threshold height A _HT is provided to be other than 2000 meters. If it is determined in step 430 that the operating mode is SPORT and the altitude is high, then method 400 proceeds to step 435 where the piston force Pf is set to zero for all values of throttle position PP and driven pulley speed N ₂ . If it is determined in step 430 that the operating mode is not a SPORT mode (i.e., is a standard STD mode or an ECO mode), or if it is determined that the altitude is 2000 meters or less (i.e., is a low altitude), then the method 400 proceeds to step 440.

[00182] In step 440, BCM 310 determines the position of the throttle control PP based on the signal from the throttle position sensor 204, and then proceeds to step 450, where BCM 310 determines the driven pulley frequency N ₂ based on the signal received from the sensor 203 speed of the driven pulley. The method then proceeds to step 460.

[00183] In step 460, BSP 310 finds the required piston force value Pf in the corresponding piston force control map for the particular mode and altitude. If the operating mode is the SPORT mode and the altitude is low, then the PMU 310 finds the piston force Pf from the SPORT MODE - LOW ALTITUDE control map (FIG. 7). If the operating mode is standard mode STD and the height is low, then FCU 310 finds the piston force Pf from the control map STANDARD MODE - LOW ALTITUDE (FIG. 8B). If the operating mode is standard mode STD and the height is high, then the PMU 310 finds the piston force Pf from the control map STANDARD MODE - HIGH ALTITUDE (FIG. 8A). For ECO operating mode and low altitude, FCU 310 finds the piston force Pf from the ECO MODE - LOW ALTITUDE control map (Fig. 9B), and for ECO operating mode and high altitude, FMU 310 finds the piston force Pf from the ECO MODE - HIGH control map HEIGHT (FIG. 9A).

[00184] Finally, at step 470, the PMU 310 adjusts the pneumatic pressure P in the cylinder 144 depending on the required piston force Pf found at step 470 in the corresponding control map. PBU 310 receives signals from pressure sensors 330, 332 and provides signals to compressor 340 and valves 324, 326 in order to adjust the pneumatic pressure to the desired value.

[00185] In the illustrated control method 400, BSP 310 uses a HIGH ALTITUDE control map for any altitude not less than the upper altitude threshold A _HT , and a SEA LEVEL control map for altitudes less than the upper altitude threshold A _HT . It is envisaged that for intermediate heights between the upper threshold height A _HT and sea level, the FPU 310 can interpolate between the HIGH ALTITUDE and SEA LEVEL control maps for a particular operating mode. More than two steering maps are contemplated to compensate for the effect of altitude, for example, an additional steering map can be provided for intermediate altitudes between upper threshold height A _HT and sea level. It is provided that a lower threshold height A _LT be set, that up to the lower threshold height A _LT a LOW ALTITUDE control card is used, and that for heights from the lower threshold height A _LT to the upper threshold height A _LT can use the INTERMEDIATE HEIGHT control card. It is envisaged that a management map would also be provided for altitudes below sea level.

[00186] When the vehicle 10 is operated in the SPORT mode at sea level, the piston 94 applies a force Fp to the movable disk 84 of the driving pulley 80, which is determined depending on the position of the throttle control PP and the speed N ₂ of rotation of the driven pulley (which is in known relationship with the speed VS of the vehicle). It is provided that the piston force Pf is determined as a function of the throttle valve position TVP and not as a function of the throttle position PP. In FIG. 7 shows a piston force control map 700 for low altitude and sport mode.

[00187] Referring to FIG. 7, piston force Pf is applied when the throttle position PP exceeds the lower threshold PP2 (about 20% in this embodiment), or when the driven pulley speed N ₂ exceeds the threshold N2a (about 5000 rpm). in this embodiment). For any particular driven pulley speed N ₂ , the piston force Pf increases to a maximum as the throttle position PP value increases (in the illustrated embodiment, the maximum piston force Fp is applied at a gas control position PP value of about 75%). Thereafter, the piston force Pf decreases as the gas control position PP increases. Piston force Pf is not applied when the driven pulley rotation speed N ₂ is zero if the gas control position PP does not exceed the threshold value PP1 (about 60% in this embodiment). In the high speed N ₂ mode of rotation of the driven pulley and in the mode of small values of the position PP of the gas control (PP<PP2, N ₂ >N2a), the PMU 310 applies a small, but, nevertheless, not zero force Pf of the piston. For positions PP of the gas control over PP2, with an increase in the frequency N ₂ of rotation of the driven pulley, the force Fp of the piston as a whole increases to a maximum value, after which it begins to decrease with an increase in the frequency N ₂ of rotation of the driven pulley.

[00188] As seen from FIG. 8A, when operating in standard STD mode at high altitude, piston 94 applies force Fp to drive pulley 84 to reduce gear ratio (D1/D2) and obtain lower engine speed ES compared to SPORT mode at the same vehicle speed VS. funds. The applied piston force Fp is non-zero only when the throttle position PP exceeds a specific minimum (20% in the illustrated embodiment) and when the driven pulley speed N ₂ is less than the maximum (8000 rpm in the illustrated embodiment). Piston force Fp is greatest at intermediate driven pulley speeds (about 5000 rpm in the illustrated embodiment).

[00189] As can be seen from the control map 800' shown in FIG. 8B, when operating in standard mode STD at sea level, for any particular combination of speed N ₂ of rotation of the driven pulley and position PP of the throttle control, the force Fp of the piston applied to the drive pulley 84 is greater than the force applied when operating in standard mode at high altitude and when operating in sport mode at sea level.

[00190] As can be seen from the control map 900 shown in FIG. 9A, when operating in ECO mode at high altitude, piston 94 generally applies a greater force Fp to drive pulley 84 than when operating in standard mode at high altitude to further reduce the gear ratio (D1/D2) relative to its value at work in standard mode at high altitude. However, the piston force Fp in economy mode at high altitude is not as large as the piston force Fp applied in standard mode at sea level (FIG. 9B). In the economy mode at sea level, the piston force Fp is non-zero for all rotational speeds N ₂ of the driven pulley. At high altitudes, the applied piston force Fp is non-zero only when the throttle position PP exceeds a specific minimum (20% in the illustrated embodiment, as for standard mode). Piston force Fp is greatest for intermediate driven shaft speeds (about 5000 rpm in the illustrated embodiment).

[00191] As can be seen from the control map 900' shown in FIG. 9B, when operating in economy mode at sea level, in view of the above, applied to the driving pulley 84, the force Fp of the piston 94 is increased compared to the piston force Fp for economy mode and high altitude, and also compared to the piston force Fp for standard mode. at sea level. The piston force Fp is increased in order to compensate for an increase in engine speed ES due to an increase in atmospheric pressure.

[00192] It is envisaged that the piston force Pf control maps 700, 800, 800', 900, 900' discussed above correspond to different air pressures, not different heights.

[00193] It is provided that, in addition to the cards 700, 800, 800', 900, 900' used in the FIG. 6 in the height effect compensation method, the PMU 310 could also be connected to the ECU 200 and/or other sensors, such as the engine speed sensor 208 in closed loop feedback control to control the piston force Pf to achieve the desired engine speed ES.

[00194] Next, with reference to FIG. 10 details the function of the control BCU 310 when the vehicle is parked or driven off.

[00195] When the vehicle 10 is started, the engine 24 needs to be cranked up to increase the engine speed ES above the _engagement speed ES, which will engage the clutch BST 40. Typically, the driver presses the throttle lever 37 to increase the throttle control position PP with a corresponding increase in the throttle opening degree TVP and an increase in engine speed ES. Spinning up the engine 24 in this way typically creates significant noise in addition to increased fuel consumption.

[00196] In the present embodiment shown in FIG. 10, the control map 1000 of the BST 40 is pneumatically controlled so that the vehicle 10 can be started more smoothly with reduced noise and reduced fuel consumption. The pneumatic control of the BST 40 is also performed when the vehicle 10 is running at low speed VS and when the engine 24 is running at low speeds ES.

[00197] When a pneumatic force P is applied to the piston 94, the movable disk 84 is pushed against the fixed disk 82 to engage with the belt 86, and the rotation frequency ES _engage becomes lower. By reducing the frequency of ES _engage clutch rotation, the BST 40 pneumatic control allows you to move off with less noise and less fuel consumption. After engaging the clutch BST 40, a further increase in the force Fp of the piston leads to an increase in the frequency N ₂ of rotation of the driven pulley and the speed VS of the vehicle. After starting the engine 24 and engaging the clutch BST 40, if the driver continues to increase the throttle position PP value, the MCU 310 will increase the piston force Fp applied to the pulley 84 so that the vehicle speed VS can increase without the need for a corresponding increase in the engine speed ES, which would otherwise be required in the absence of pneumatic system 300. The relative reduction in engine speed ES also results in reduced noise and fuel consumption.

[00198] As can be seen from FIG. 10, the piston force Pf in the parking function increases with the throttle position PP, the intensity of this increase being greater for throttle positions PP below the threshold throttle position PP9 (10% in the illustrated embodiment). Threshold position PP9 of the throttle control is usually set at a level at which the vehicle 10 starts off. In the area 1010 of the control map 1000 (PP<PP9), the vehicle 10 has not started yet, and in the area 1020 (PP>PP9), the vehicle is moving at a low speed VS and the engine 24 is running at a low speed ES. Piston force Pf in the park function is applied for throttle positions PP up to 50%, and the maximum applied piston force Pf in park function is approximately 700 N (in this embodiment, in which a total force of about 2000 N).

[00199] As can be seen from FIG. 10, the piston force Fp applied to the BST 40 also depends on the engine temperature T _E. If the engine 24 is already warm when the vehicle 10 is started, for example if the engine 24 is started shortly after it has been shut down, then the applied piston force Pf is such that the reduction in clutch speed will be slightly greater than in the case of a cold start of the engine 24. When engine 24 is cold, it is desirable to warm it up so that it can operate at slightly higher speeds. That is, the force exerted by the piston 94 is higher for higher engine temperatures T _E. The dependence of the piston force Pf on temperature is influenced by a number of parameters, among which parameters related to the pneumatic system, such as friction, thermal expansion, etc. It is also contemplated that the applied piston force Pf can be lower at higher temperatures. In the illustrated embodiments

[00200] The piston force Pf also depends on the mode of operation. In sport mode, in order to obtain increased torque and allow the vehicle 10 to accelerate faster, the BST 40 is operated purely mechanically without applying any piston force Pf. Non-zero piston force Pf is applied in standard and economy modes. In the illustrated embodiment, for a particular engine temperature and throttle position PP, the piston force Pf is the same for standard and economy modes. Shown in FIG. 10, the control card 1000 is used in both standard and economy modes. However, it is envisaged that the standard and economy modes use different piston force control maps to apply different piston forces. For example, for the same gas control position PP, the piston force Pf may be greater in economy mode than in standard mode.

[00201] PMU 310 causes the parking function piston to apply force when it determines the existence of a stop/start condition that indicates that the vehicle 10 is in the process of stopping or starting. PBU 310 determines the existence of a stop/start condition if the vehicle speed VS is below the initial parking threshold speed VS _P1 and the engine speed ES is below the park speed ES _P1 . In the illustrated embodiment, the threshold engine speed ES _P1 is set to 1500 rpm. In some embodiments, the stop/start conditions include an unapplied state of the brake 38.

[00202] When the stop/start conditions listed above are satisfied and the vehicle 10 is not in the sport mode, BCU 310 refers to the 1000000000000000000000000000000000000000000000000000000000000000004102000 310 and and the vehicle 10 to the stop/start condition shown in FIG. 10 control map for adjusting the pneumatic pressure P so as to generate the piston force Pf obtained from the parking piston force control map 1000 . If the vehicle 10 is in sport mode and if the air pressure is at a non-zero level, then the PMU 310 bleeds the air pressure to ensure that the BST is controlled solely by mechanical means. Normally, however, when the vehicle 10 is started, the pneumatic pressure P and the piston force Pf are zero. If closed-loop feedback control is used to control the piston force Pf, it is turned off when the parking function piston force is applied. It is provided that the piston force Pf can be applied even if the vehicle is running in sport mode and if parking/starting conditions are detected. Therefore, in some embodiments, a parking force management map may also be provided for the SPORT mode.

[00203] In some embodiments, the parking function piston force Pf is released if the BMU 310 determines that the vehicle has moved off (eg, if the vehicle speed rises above the vehicle's terminal park speed threshold VS _P2 ). In the illustrated embodiment, the final parking threshold speed VS _P2 is higher than the initial parking threshold speed VS _P1 . However, it is provided that the initial threshold parking speed VS _P1 of the vehicle is the same as the final threshold parking speed VS _P2 of the vehicle.

[00204] In the illustrated embodiment, the vehicle is considered to be moving, and the parking function piston force Pf is released when the vehicle speed VS becomes higher than the final threshold parking speed VS _P2 of the vehicle (which is set to 10 km/h in the illustrated embodiment), and when the engine speed ES exceeds the threshold engine park speed ES _P2 (which in the illustrated embodiment is set to 22,000 rpm for economy mode).

[00205] The threshold parking speed ES _P2 of engine rotation in the standard STD mode is higher than in the economy mode ECO. BCM 310 also terminates the parking function piston force Pf if BCM 310 determines that the engine speed ES is close to the engine _stall frequency ES, which is not the same for different operating modes and is typically below the engine idle speed ES _idle for a particular mode. Additionally, if the brake 38 is detected to be engaged, then the PCU 310 stops applying the parking function piston force Pf.

[00206] Next, with reference to FIG. 11A and FIG. 11B describes in detail the minimum force control of the BST 40.

[00207] When the vehicle 10 is moving downhill, the driver sometimes releases the throttle control 37, or holds the throttle control 37 at a small PP value (i.e., PP~0%) as the vehicle 10 accelerates by itself under the influence of gravity. Here, ECU 200 reduces the throttle valve position TVP in accordance with the throttle position PP. In economy ECO and standard STD modes, if the vehicle continues to move downhill, as a result of reducing the throttle position TVP, the engine speed ES can decrease to almost zero, which can cause the belt 86 to disengage from the drive pulley 82. To prevent tripping clutch BST 40 in economical ECO and standard STD modes, PBU 310 controls the piston force Pf in such a way as to keep it at the level of the minimum piston force Pf _min required to keep the BST 40 clutch engaged.

[00208] When the clutch BST 40 is engaged (by controlling the minimum force of the BST 40 piston), the vehicle speed VS and hence the driven pulley speed N ₂ is greater than the drive pulley speed N ₁ and the engine speed ES. The driven pulley 88 drives the driving pulley 80 and the output shaft 57 of the engine. Under such negative load conditions, the speed ES of the crankshaft 57 driven by the driven pulley 88 exceeds that which would be achieved if the crankshaft 57 were driven by the engine 24 at a small throttle opening degree TVP. As the vehicle 10 continues to roll downhill, and as the driven pulley 88 drives the drive pulley 80 and the engine output shaft 57, the speed of the driven pulley 88 and hence the vehicle speed VS decreases. This deceleration of the vehicle 10 is smoother than when the brakes 38 are applied.

[00209] Referring to FIG. 11A and 11B, the minimum piston force Pf _min is set as a function of engine speed ES, engine temperature T _E and operating condition, as shown in maps 1100 and 1100'. PMU 310 consults control map 1100 in standard STD mode and map 1100' in ECO mode to obtain the piston force Pf to be applied to drive pulley 80. In sport mode, PMU 310 sets piston force Pf to zero. That is, in the sport mode, the control of the BST 40 is performed exclusively by mechanical means. It is envisaged that the minimum piston force is also set for the sport mode SPORT.

[00210] In the illustrated embodiment, the minimum piston force control of the BST 40 described above with reference to FIG. 11A and FIG. 11B is activated when the BCU 310 determines that the engine speed ES exceeds the engine speed threshold ES11. The MCU 310 stops applying the force Pf obtained from the minimum downhill force control map 1100, 1100' if the engine speed ES drops below the threshold speed ES11 or if the driver switches the operating mode from standard STD and economy ECO to sport mode SPORT.

[00211] It is also provided that the minimum piston force control may be activated when a negative load condition is detected, that is, when the engine speed ES exceeds the threshold engine speed when driving downhill, and when at least one of the following is true: position PP the gas control is less than the position of the gas control, threshold for downhill movement; Throttle position TVP is less than Threshold Threshold for downhill travel.

[00212] MCU 310 also controls air piston 94 to prevent motor 24 from shutting down, as described below.

[00213] The engine 24 may self-deactivate (self-deactivate), for example, if the throttle control 37 is suddenly released and the brake 38 applied, causing the ECU 200 to close the throttle to the TVP zero position. Another example of a situation in which the engine 24 may self-shut down is when the brake 38 loses contact with the road surface of the corresponding element of the vehicle, be it the wheels or the track 65. , the FCU 310 will then cause the pneumatic valve 326 to open to relieve the piston pressure P and quickly deactivate the piston 94. When the piston 94 is deactivated, the BST 40 clutch is disengaged, which isolates the engine 24 from the unexpectedly braked wheels. The engine 24 will continue to operate at low speeds, the lower _engagement speed ES, so that when the driver releases the brake 38 and starts to actuate the throttle control 37, the engine speed ES can be rapidly increased in response to an increase in the throttle control position PP.

[00214] The shutdown protection control of the BST 40 by the BCM 310 is activated when the BCM 310 detects the existence of an engine shutdown condition. In the illustrated embodiment, the self-shutdown condition includes a high reduction rate of the speed N ₂ of rotation of the driven pulley. In the illustrated embodiment, the speed change rate of the driven pulley is considered high when the amount of change rate exceeds the self-off change rate threshold, which is set to 150 rpm/s ² . However, it is provided that the threshold rate of change during self-switching off be different from the value of 150 rpm/s ² . It is also provided that the shutdown protection control can be activated if the brake 38 is actuated at a high reduction rate of the speed N ₂ of rotation of the driven pulley.

[00215] PMU 310 controls the piston 94 in order to provide a smooth start after stopping on a hill. When the brake 38 is released after it has been applied, if the FCM 310 detects the reverse rotation of the driven pulley 88 (negative driven pulley speed N ₂ ), then the FCM 310 determines that the vehicle is located on a slope and is heading up this slope ( uphill stop condition). Alternatively, detection of the hill stop condition may also be performed depending in part on the slope of the road surface as determined by the acceleration sensor 205 or the slope sensor 280 with which the vehicle 10 is equipped.

[00216] When a hill stop condition is detected, PMU 310 increases the piston force Pf at a predetermined rate (~2000 N/s in the illustrated embodiment). The PMU 310 continues to increase the piston force Pf either until a zero driven pulley speed N ₂ is detected, or until a predetermined maximum piston force Pf (700 N in the illustrated embodiment) is reached. In the illustrated embodiment, the piston force Pf is increased at such an rate that the piston force Pf reaches its maximum value within the threshold time period for stopping on the rise. In the illustrated embodiment of the invention, the hill stop threshold duration is 1 second.

[00217] If a zero speed N ₂ rotation of the driven pulley is detected, then the force Pf of the piston is maintained at the level at which the zero speed N ₂ rotation of the driven pulley was detected. After the piston force Pf reaches a predetermined maximum level for control under hill stop conditions, the piston force Pf is continued to be maintained at that level. The pneumatic control of the BST 40 under hill stop conditions is stopped when the driver operates the throttle control 37, that is, when the throttle control position PP is non-zero, PP>0, or when the brake 38 is applied, and then the piston force Pf is returned to the default value. (that is, to a value determined based on the current operating mode, engine speed ES and other operating parameters).

[00218] The above description relates to snowmobile 10 equipped with BST 40 with pneumatic piston 94. However, it should be understood that the disclosed control methods can be applied to other vehicles and devices that use BST. It should also be understood that piston 94 may be actuated hydraulically by oil or other similar incompressible fluids rather than pneumatically compressed gas.

[00219] Those skilled in the art may appreciate the changes and improvements that can be made to the above-described embodiments of the present technology. The above description is intended to be considered as an example, but not in a limiting sense. Therefore, the scope of the present technology should be considered limited solely by the scope of the appended claims.

Claims (50)

1. A method for controlling a continuously variable transmission of a vehicle at various heights, wherein the vehicle contains: engine; a gas control controlled by the driver of the vehicle; a throttle valve that regulates the flow of air to the engine, and the position of the throttle valve is at least partially based on the position of the throttle control; a continuously variable transmission (CVT) operatively coupled to the engine and comprising a drive pulley, a driven pulley, and a belt operatively connecting the drive pulley to the driven pulley; at least one ground contact member operatively connected to the driven pulley and comprising at least one of a wheel and a track; a piston operatively connected to the drive pulley for applying, upon actuation of the drive pulley, a piston force to change the effective diameter of the drive pulley; and a control unit for controlling the actuation of the piston and the force of the piston, wherein the method comprises the following: determining at least one of altitude and atmospheric pressure; determine the frequency of rotation of the driven pulley; determining at least one of a gas control position and a throttle position; selectively actuating the piston depending on at least one of altitude and atmospheric pressure; control the piston force depending on: frequency of rotation of the driven pulley; and at least one of a throttle position and a throttle position; and the piston force is controlled based on at least the first control map corresponding to the first height and the second control map corresponding to the second height, depending on at least one of the altitude and atmospheric pressure determined. 2. The method according to claim 1, in which: one of altitude and atmospheric pressure is altitude; and the piston force is set to zero in response to the detected height exceeding the upper height threshold. 3. The method of claim 2, wherein the upper altitude threshold is 2000 m. 4. The method of claim 1, wherein the vehicle further comprises a mode switch for selecting one mode from a plurality of vehicle operating modes, wherein the method further comprises the following: determining one mode that has been selected from a plurality of operating modes; and controlling the piston force at least in part based on a mode selected from a plurality of vehicle operating modes. 5. The method according to claim 4, in which: the plurality of modes includes a first mode and a second mode; each of the first control card and the second control card is associated with the first mode; and piston force control based on a mode selected from a plurality of vehicle operating modes includes: the piston force is controlled at least in part based on one of the first control map and the second control map when the mode selected from the plurality of operating modes is the first mode; and the piston force is controlled at least in part based on a third control map corresponding to the first height and associated with the second mode when the mode selected from the plurality of operating modes is the second mode. 6. The method of claim 1, wherein the piston is at least one of a pneumatically actuated and a hydraulically actuated one. 7. The method of claim 2, wherein the piston is at least one of pneumatically actuated and hydraulically actuated. 8. The method of claim 3, wherein the piston is at least one of pneumatically actuated and hydraulically actuated. 9. The method of claim 4, wherein the piston is at least one of a pneumatically actuated and a hydraulically actuated one. 10. The method of claim 5, wherein the piston is at least one of pneumatically actuated and hydraulically actuated. 11. Vehicle containing: engine; a gas control controlled by the driver of the vehicle; a throttle valve that regulates the flow of air to the engine, and the position of the throttle valve is at least partially based on the position of the throttle control; a continuously variable transmission (CVT) operatively coupled to the engine and comprising a drive pulley, a driven pulley, and a belt operatively connecting the drive pulley to the driven pulley; at least one ground contact member operatively connected to the driven pulley and comprising at least one of a wheel and a track; a piston operatively connected to the drive pulley for applying, upon actuation of the drive pulley, a piston force to change the effective diameter of the drive pulley; and a control unit for controlling piston actuation and piston force, and an altitude sensor for measuring at least one of altitude and atmospheric pressure, wherein the control unit is configured to control the actuation of the piston and the force of the piston based on at least the first control map corresponding to the first height and the second control map corresponding to the second height, depending on the measured at least one of the height and atmospheric pressure. 12. The vehicle of claim 11, wherein the vehicle further comprises a mode switch for selecting one mode from a plurality of vehicle operating modes, wherein the control unit is further configured to control the piston force at least in part based on the selected mode. from a plurality of vehicle operating modes. 13. The vehicle according to claim. 11, in which the specified vehicle further comprises connected to the piston at least one of the hydraulic system and pneumatic system, while the control unit is connected to at least one of the hydraulic system and pneumatic system to control the force of the piston . 14. The vehicle according to claim 12, wherein said vehicle further comprises connected to the piston at least one of the hydraulic system and the pneumatic system, wherein the control unit is connected to at least one of the hydraulic system and the pneumatic system to control the force of the piston .

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