GB2455507A - Electric motor vehicle emergency braking system - Google Patents

Electric motor vehicle emergency braking system Download PDF

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Publication number
GB2455507A
GB2455507A GB0724071A GB0724071A GB2455507A GB 2455507 A GB2455507 A GB 2455507A GB 0724071 A GB0724071 A GB 0724071A GB 0724071 A GB0724071 A GB 0724071A GB 2455507 A GB2455507 A GB 2455507A
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United Kingdom
Prior art keywords
epb
vehicle
ecu
control switch
apply
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
GB0724071A
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GB0724071D0 (en
Inventor
David Robert Cox
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Ford Global Technologies LLC
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Ford Global Technologies LLC
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Publication date
Application filed by Ford Global Technologies LLC filed Critical Ford Global Technologies LLC
Priority to GB0724071A priority Critical patent/GB2455507A/en
Publication of GB0724071D0 publication Critical patent/GB0724071D0/en
Publication of GB2455507A publication Critical patent/GB2455507A/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
    • B60W30/18—Propelling the vehicle
    • B60W30/18009—Propelling the vehicle related to particular drive situations
    • B60W30/18109—Braking
    • B60W30/18127—Regenerative braking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L7/00—Electrodynamic brake systems for vehicles in general
    • B60L7/10—Dynamic electric regenerative braking
    • B60L7/18—Controlling the braking effect
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K6/00—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00
    • B60K6/20—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00 the prime-movers consisting of electric motors and internal combustion engines, e.g. HEVs
    • B60K6/50—Architecture of the driveline characterised by arrangement or kind of transmission units
    • B60K6/52—Driving a plurality of drive axles, e.g. four-wheel drive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L3/00—Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption
    • B60L3/12—Recording operating variables ; Monitoring of operating variables
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L7/00—Electrodynamic brake systems for vehicles in general
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L7/00—Electrodynamic brake systems for vehicles in general
    • B60L7/24—Electrodynamic brake systems for vehicles in general with additional mechanical or electromagnetic braking
    • B60L7/26—Controlling the braking effect
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T1/00—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles
    • B60T1/02—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles acting by retarding wheels
    • B60T1/10—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles acting by retarding wheels by utilising wheel movement for accumulating energy, e.g. driving air compressors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/74—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive
    • B60T13/746—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive and mechanical transmission of the braking action
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W10/00—Conjoint control of vehicle sub-units of different type or different function
    • B60W10/04—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units
    • B60W10/08—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units including control of electric propulsion units, e.g. motors or generators
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W10/00—Conjoint control of vehicle sub-units of different type or different function
    • B60W10/18—Conjoint control of vehicle sub-units of different type or different function including control of braking systems
    • B60W10/184—Conjoint control of vehicle sub-units of different type or different function including control of braking systems with wheel brakes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
    • B60W30/18—Propelling the vehicle
    • B60W30/18009—Propelling the vehicle related to particular drive situations
    • B60W30/18109—Braking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/10—Vehicle control parameters
    • B60L2240/12—Speed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/10—Vehicle control parameters
    • B60L2240/30—Parking brake position
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2510/00—Input parameters relating to a particular sub-units
    • B60W2510/18—Braking system
    • B60W2510/186—Status of parking brakes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2520/00—Input parameters relating to overall vehicle dynamics
    • B60W2520/10—Longitudinal speed
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/62—Hybrid vehicles

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Power Engineering (AREA)
  • Electromagnetism (AREA)
  • Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Electric Propulsion And Braking For Vehicles (AREA)

Abstract

An electric motor vehicle (hybrid) 11 comprises wheels 15, a traction motor / generator 35 arranged to drive at least one of said wheels, a traction battery 61, an ECU 51, and an electrically operated park brake (EPB) 57, 58 operable on said wheels, and a driver-operable control switch 45 to control operation of the EPB, wherein the ECU is arranged such that the motor / generator provides regenerative braking when the vehicle is travelling above a predetermined speed and when the control switch is operated to apply the electric parking brake. In other words, when the service brakes fail, the driver would be able to initiate emergency braking by actuating the parking brake, which would result in regenerative braking occurring until the speed reduces below a preset velocity, before the electric parking (friction) brake engages. The ECU may inhibit or enable application of the parking brake above said predetermined speed depending on whether sufficient retardation is provided.

Description

Braking of Electric Vehicles The invention relates to the braking of electric vehicles, including hybrid electric motor vehicles powered by an engine and an electric motor as well as those which are powered by electricity alone. Particularly it relates to problems which can arise when such a vehicle includes an electric park brake.
Electric park brakes are required to not only hold the vehicle securely braked when parked but also to provide an emergency brake when the vehicle is being driven if the main braking system should fail. However, while such brakes function well when used for parking, when used for braking a moving vehicle it can be difficult to control the degree of retardation without the use of sophisticated and expensive controls.
According to one aspect of the invention there is provided an electric motor vehicle having at least one front wheel and one rear wheel, a traction motor/generator arranged to drive at least one of said wheels, a traction battery arranged to receive current from and supply current to the motor/generator under the control of an electronic control unit (ECU), an electrically actuated park brake (EPB) operable on at least one of said wheels and a driver-operable control switch to control operation of the EPB, wherein the ECU is arranged so that the traction motor/generator provides regenerative braking when the vehicle is travelling at more than a predetermined road speed and the control switch is operated to apply the EPB.
Preferably, the ECU is arranged to inhibit the application of the EPB if the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed, in which case the ECU may monitor the regenerative braking and operate to apply the EPB if regenerative braking cannot provide sufficient retardation when the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed.
The invention also provides, according to another aspect thereof, a method of controlling an electnc motor vehicle having at least one front wheel and one rear wheel, a traction motor/generator arranged to drive at least one of said wheels, a traction battery arranged to receive current from and supply current to the motor/generator under the control of an electronic control unit (ECU), an electrically actuated park brake (EPB) operable on at least one of said wheels and a driver-operable control switch to control operation of the EPB, the ECU controlling the traction motor/generator to provide regenerative braking when the vehicle is travelling at more than a predetermined road speed and the control switch is operated to apply the EPB.
The invention will now be described by way of example and with reference to the accompanying drawings, in which:-Fig.1 is a schematic diagram of a vehicle according to the invention; and Fig.2 is a schematic diagram of a final drive unit shown in Fig. 1.
Referring to Figs. I and 2, a hybrid electric motor vehicle 11 has an transverse mounted IC engine 12 which is connected to a pair of front wheels 15 and to a pair of rear wheels 21 by a mechanical driveline including a transmission 13 which in turn drives a front final drive unit 14 connected to the front wheels 15 by front dnveshafts 16. The front final drive unit 14 also drives a rear drive take-off unit 17 which is connected to a rear final drive unit 18 by a longitudinal propshaft 19. The rear final drive unit 18 is connected to the rear wheels 21 by rear dnveshafts 22.
The rear final drive unit 18 has a casing 23 which comprises a rear casing part 24 and a front casing part 25, the casing parts being connected at a flange face 26. The rear casing part 24 carries the inboard ends of the rear driveshafts 22 and a crownwheel 27 which drives the rear dnveshafts 22 through a differential 28. The front casing part 25 carries a pinion 31 which meshes with the crownwheel 27 and is part of a pinion shaft 32 which is joumalled in the front casing part 25. The rear end of the propshaft 19 is also joumalled in the front casing part 25 and carries a control clutch 33 which controllably couples the propshaft 19 to the pinion shaft 32. The front casing part 25 also houses the stator 34 of a traction motor/generator 35 whose rotor 36 is rotatable on the pinion shaft 32, the rotor 36 being fast with a sun gear 37 which meshes with planet gears 38 of an epicyclic reduction gear 39. The planet gears 38 are each rotatable on a carrier 41 which is rotatable on the pinion shaft 32 and is coupled to the pinion shaft 32. The planet gears 38 also mesh with a ring gear 43 fast with the front casing part 25. The epicyclic reduction gear 39 provides a reduction gear ratio between the rotor 36 and the pinion shaft 32.
The traction motor/generator 35 is controlled by an electronic control unit (ECU) 51 which also controls the transmission 13 according to the usual parameters of engine load and speed, road speed, etc and an input from a transmission selector 46 having a selector lever 47 under the control of the driver. The ECU 51 also has an input from a driver-controlled park brake control switch 45. Another motor/generator, conveniently referred to as the engine starter generator or, more conventionally, the integrated starter generator (ISG) 29, is driven by the engine 12. Both the traction motor/generator 35 and the ISG 29 draw current from or supply current to a traction battery 61 and to an auxiliaries battery 62.
The traction battery 61 would ordinarily be a high voltage unit while the auxiliaries battery 62 would be I 2V for the supply & control of the normal vehicle electrical systems. The park brake control switch 45 cooperates with a park brake controller 55 and a park brake actuator 56 to apply park brakes 57 on each rear wheel 21 through cables 58. The park brake actuator 56, cables 58 and park brakes 57 are together conveniently referred to as the electric park brake (EPB). In some vehicle installations there may be a separate park brake actuator for each park brake which may be integrated with the park brake itself.
In normal on-road use of the vehicle lithe engine 12 can drive the front wheels 15 through the transmission 13, the front final drive unit 14 and the front driveshafts 16 while also driving the rear wheels 21 through the rear take-off unit 17, the propshaft 19, the rear final drive unit 18 and the rear dnveshafts 22. The rear take-off unit 17 is driven in a direct ratio of the drive to the front wheels 15, the control clutch 33 allowing drive torque to the rear wheels 21 as required to maintain an appropriate torque split between the front and rear wheels. Under gentle low speed driving conditions, the traction motor/generator 35 can be used to drive the vehicle with the engine 12 stopped, in which case the control clutch 33 would disconnect and drive would be to the rear wheels 21 only through the epicyclic reduction gear 39. For higher road speeds, particularly out of town driving, the engine 12 would drive as described above with the ISG 29 and, where needed, the traction motor/generator 35 supplying current to the batteries 61 and 62.
The driver can operate the park brake control switch 45 to apply and release the park brakes 57. During normal operation of the vehicle 11, the park brake control switch 45 is only used when the vehicle is stationary, either to secure the vehicle when it is left unattended or to hold it during starting from rest, particularly on a hill. In both circumstances, application and release of the park brakes 57 may be automatic as is established practice. However, in the unlikely event that the main service brakes on the vehicle fail (or are perceived to have failed), it is desirable or legally necessary to provide an emergency means of braking and the park brake control switch 45 would then be used to apply the park brakes in such circumstances. Unfortunately, the design of the park brakes 57 and the operation of the control, including the actuator 56 and cables 58, are such that the degree of control of the braking is relatively coarse. Moreover, the park brakes 57 are themselves frequently of a design where rapid wear or fade may occur if they are used to more than a limited extent. To overcome these disadvantages, the ECU 51 is programmed to apply regenerative braking using the motor/generator 35 if the vehicle is travelling at more than a predetermined road speed, e.g. about 8 kph. Preferably, the operation of the park brakes 57 is inhibited if the vehicle is travelling at more than a predetermined road speed. This predetermined road speed may be the same as or greater than that which determines when regenerative braking is applied. In both cases, there is preferably a hysteresis so that re-application of the park brake occurs at a lower speed.
The ECU 51 monitors the regenerative braking and will operates to apply the EPB if regenerative braking cannot provide sufficient retardation when the control switch 45 is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed. In particular, this might occur if the traction battery 61 is fully charged. in some vehicles, the current from the motor/generator 35 might be diverted to a braking rheostat or other resistor or reactance to provide braking by the motor/generator if the battery is unable to take the current and the term regenerative braking is intended to include such alternatives.
While the motor/generator 35 and park brake controller 55 are shown and described as separate units which communicate with each other, e.g. via a CAN bus, they may be combined in a single ECU which may also control other vehicle functions. While a hybrid electric motor vehicle has been described by way of example, the invention may be applied to other electrically powered vehicles, e.g. battery/electric vehicles or ones using fuel cells for electricity generation. Braking of Electric Vehicles The invention relates to the braking of electric vehicles, including hybrid electric motor vehicles powered by an engine and an electric motor as well as those which are powered by electricity alone. Particularly it relates to problems which can arise when such a vehicle includes an electric park brake.
Electric park brakes are required to not only hold the vehicle securely braked when parked but also to provide an emergency brake when the vehicle is being driven if the main braking system should fail. However, while such brakes function well when used for parking, when used for braking a moving vehicle it can be difficult to control the degree of retardation without the use of sophisticated and expensive controls.
According to one aspect of the invention there is provided an electric motor vehicle having at least one front wheel and one rear wheel, a traction motor/generator arranged to drive at least one of said wheels, a traction battery arranged to receive current from and supply current to the motor/generator under the control of an electronic control unit (ECU), an electrically actuated park brake (EPB) operable on at least one of said wheels and a driver-operable control switch to control operation of the EPB, wherein the ECU is arranged so that the traction motor/generator provides regenerative braking when the vehicle is travelling at more than a predetermined road speed and the control switch is operated to apply the EPB.
Preferably, the ECU is arranged to inhibit the application of the EPB if the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed, in which case the ECU may monitor the regenerative braking and operate to apply the EPB if regenerative braking cannot provide sufficient retardation when the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed.
The invention also provides, according to another aspect thereof, a method of controlling an electnc motor vehicle having at least one front wheel and one rear wheel, a traction motor/generator arranged to drive at least one of said wheels, a traction battery arranged to receive current from and supply current to the motor/generator under the control of an electronic control unit (ECU), an electrically actuated park brake (EPB) operable on at least one of said wheels and a driver-operable control switch to control operation of the EPB, the ECU controlling the traction motor/generator to provide regenerative braking when the vehicle is travelling at more than a predetermined road speed and the control switch is operated to apply the EPB.
The invention will now be described by way of example and with reference to the accompanying drawings, in which:-Fig.1 is a schematic diagram of a vehicle according to the invention; and Fig.2 is a schematic diagram of a final drive unit shown in Fig. 1.
Referring to Figs. I and 2, a hybrid electric motor vehicle 11 has an transverse mounted IC engine 12 which is connected to a pair of front wheels 15 and to a pair of rear wheels 21 by a mechanical driveline including a transmission 13 which in turn drives a front final drive unit 14 connected to the front wheels 15 by front dnveshafts 16. The front final drive unit 14 also drives a rear drive take-off unit 17 which is connected to a rear final drive unit 18 by a longitudinal propshaft 19. The rear final drive unit 18 is connected to the rear wheels 21 by rear dnveshafts 22.
The rear final drive unit 18 has a casing 23 which comprises a rear casing part 24 and a front casing part 25, the casing parts being connected at a flange face 26. The rear casing part 24 carries the inboard ends of the rear driveshafts 22 and a crownwheel 27 which drives the rear dnveshafts 22 through a differential 28. The front casing part 25 carries a pinion 31 which meshes with the crownwheel 27 and is part of a pinion shaft 32 which is joumalled in the front casing part 25. The rear end of the propshaft 19 is also joumalled in the front casing part 25 and carries a control clutch 33 which controllably couples the propshaft 19 to the pinion shaft 32. The front casing part 25 also houses the stator 34 of a traction motor/generator 35 whose rotor 36 is rotatable on the pinion shaft 32, the rotor 36 being fast with a sun gear 37 which meshes with planet gears 38 of an epicyclic reduction gear 39. The planet gears 38 are each rotatable on a carrier 41 which is rotatable on the pinion shaft 32 and is coupled to the pinion shaft 32. The planet gears 38 also mesh with a ring gear 43 fast with the front casing part 25. The epicyclic reduction gear 39 provides a reduction gear ratio between the rotor 36 and the pinion shaft 32.
The traction motor/generator 35 is controlled by an electronic control unit (ECU) 51 which also controls the transmission 13 according to the usual parameters of engine load and speed, road speed, etc and an input from a transmission selector 46 having a selector lever 47 under the control of the driver. The ECU 51 also has an input from a driver-controlled park brake control switch 45. Another motor/generator, conveniently referred to as the engine starter generator or, more conventionally, the integrated starter generator (ISG) 29, is driven by the engine 12. Both the traction motor/generator 35 and the ISG 29 draw current from or supply current to a traction battery 61 and to an auxiliaries battery 62.
The traction battery 61 would ordinarily be a high voltage unit while the auxiliaries battery 62 would be I 2V for the supply & control of the normal vehicle electrical systems. The park brake control switch 45 cooperates with a park brake controller 55 and a park brake actuator 56 to apply park brakes 57 on each rear wheel 21 through cables 58. The park brake actuator 56, cables 58 and park brakes 57 are together conveniently referred to as the electric park brake (EPB). In some vehicle installations there may be a separate park brake actuator for each park brake which may be integrated with the park brake itself.
In normal on-road use of the vehicle lithe engine 12 can drive the front wheels 15 through the transmission 13, the front final drive unit 14 and the front driveshafts 16 while also driving the rear wheels 21 through the rear take-off unit 17, the propshaft 19, the rear final drive unit 18 and the rear dnveshafts 22. The rear take-off unit 17 is driven in a direct ratio of the drive to the front wheels 15, the control clutch 33 allowing drive torque to the rear wheels 21 as required to maintain an appropriate torque split between the front and rear wheels. Under gentle low speed driving conditions, the traction motor/generator 35 can be used to drive the vehicle with the engine 12 stopped, in which case the control clutch 33 would disconnect and drive would be to the rear wheels 21 only through the epicyclic reduction gear 39. For higher road speeds, particularly out of town driving, the engine 12 would drive as described above with the ISG 29 and, where needed, the traction motor/generator 35 supplying current to the batteries 61 and 62.
The driver can operate the park brake control switch 45 to apply and release the park brakes 57. During normal operation of the vehicle 11, the park brake control switch 45 is only used when the vehicle is stationary, either to secure the vehicle when it is left unattended or to hold it during starting from rest, particularly on a hill. In both circumstances, application and release of the park brakes 57 may be automatic as is established practice. However, in the unlikely event that the main service brakes on the vehicle fail (or are perceived to have failed), it is desirable or legally necessary to provide an emergency means of braking and the park brake control switch 45 would then be used to apply the park brakes in such circumstances. Unfortunately, the design of the park brakes 57 and the operation of the control, including the actuator 56 and cables 58, are such that the degree of control of the braking is relatively coarse. Moreover, the park brakes 57 are themselves frequently of a design where rapid wear or fade may occur if they are used to more than a limited extent. To overcome these disadvantages, the ECU 51 is programmed to apply regenerative braking using the motor/generator 35 if the vehicle is travelling at more than a predetermined road speed, e.g. about 8 kph. Preferably, the operation of the park brakes 57 is inhibited if the vehicle is travelling at more than a predetermined road speed. This predetermined road speed may be the same as or greater than that which determines when regenerative braking is applied. In both cases, there is preferably a hysteresis so that re-application of the park brake occurs at a lower speed.
The ECU 51 monitors the regenerative braking and will operates to apply the EPB if regenerative braking cannot provide sufficient retardation when the control switch 45 is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed. In particular, this might occur if the traction battery 61 is fully charged. in some vehicles, the current from the motor/generator 35 might be diverted to a braking rheostat or other resistor or reactance to provide braking by the motor/generator if the battery is unable to take the current and the term regenerative braking is intended to include such alternatives.
While the motor/generator 35 and park brake controller 55 are shown and described as separate units which communicate with each other, e.g. via a CAN bus, they may be combined in a single ECU which may also control other vehicle functions. While a hybrid electric motor vehicle has been described by way of example, the invention may be applied to other electrically powered vehicles, e.g. battery/electric vehicles or ones using fuel cells for electricity generation.

Claims (8)

  1. An electric motor vehicle having at least one front wheel and one rear wheel, a traction motor/generator arranged to drive at least one of said wheels, a traction battery arranged to receive current from and supply current to the motor/generator under the control of an electronic control unit (ECU), an electrically actuated park brake (EPB) operable on at least one of said wheels and a driver-operable control switch to control operation of the EPB, wherein the ECU is arranged so that the traction motor/generator provides regenerative braking when the vehicle is travelling at more than a predetermined road speed and the control switch is operated to apply the EPB.
  2. 2. A vehicle according to claim I wherein the ECU is arranged to inhibit the application of the EPB if the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed.
  3. 3. A vehicle according to claim 2 wherein the ECU monitors the regenerative braking and operates to apply the EPB if regenerative braking cannot provide sufficient retardation when the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed.
  4. 4. A method of controlling an electric motor vehicle having at least one front wheel and one rear wheel, a traction motor/generator arranged to drive at least one of said wheels, a traction battery arranged to receive current from and supply current to the motor/generator under the control of an electronic control unit (ECU), an electrically actuated park brake (EPB) operable on at least one of said wheels and a driver-operable control switch to control operation of the EPB, the ECU controlling the traction motor/generator to provide regenerative braking when the vehicle is travelling at more than a predetermined road speed and the control switch is operated to apply the EPB.
  5. 5. A method according to claim 4 wherein the ECU inhibits the application of the EPB if the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed..
  6. 6. A method according to claim 5 wherein the ECU monitors the regenerative braking and applies the EPB if regenerative braking cannot provide sufficient retardation when the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed.
  7. 7. An electric motor vehicle substantially as described herein with reference to the accompanying drawings.
  8. 8. A method of controlling an electric motor vehicle substantially as described herein with reference to the accompanying drawings.
    8. A method of controlling an electric motor vehicle substantially as described herein with reference to the accompanying drawings.
    An electric motor vehicle having at least one front wheel and one rear wheel, a traction motor/generator arranged to drive at least one of said wheels, a traction battery arranged to receive current from and supply current to the motor/generator under the control of an electronic control unit (ECU), an electrically actuated park brake (EPB) operable on at least one of said wheels and a driver-operable control switch to control operation of the EPB, wherein the ECU is arranged so that the traction motor/generator provides regenerative braking when the vehicle is travelling at more than a predetermined road speed and the control switch is operated to apply the EPB.
    2. A vehicle according to claim I wherein the ECU is arranged to inhibit the application of the EPB if the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed.
    3. A vehicle according to claim 2 wherein the ECU monitors the regenerative braking and operates to apply the EPB if regenerative braking cannot provide sufficient retardation when the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed.
    4. A method of controlling an electric motor vehicle having at least one front wheel and one rear wheel, a traction motor/generator arranged to drive at least one of said wheels, a traction battery arranged to receive current from and supply current to the motor/generator under the control of an electronic control unit (ECU), an electrically actuated park brake (EPB) operable on at least one of said wheels and a driver-operable control switch to control operation of the EPB, the ECU controlling the traction motor/generator to provide regenerative braking when the vehicle is travelling at more than a predetermined road speed and the control switch is operated to apply the EPB.
    5. A method according to claim 4 wherein the ECU inhibits the application of the EPB if the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed..
    6. A method according to claim 5 wherein the ECU monitors the regenerative braking and applies the EPB if regenerative braking cannot provide sufficient retardation when the control switch is operated to apply the EPB and the vehicle is travelling at more than the predetermined road speed.
    7. An electric motor vehicle substantially as described herein with reference to the accompanying drawings.
GB0724071A 2007-12-11 2007-12-11 Electric motor vehicle emergency braking system Withdrawn GB2455507A (en)

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GB2483477A (en) * 2010-09-09 2012-03-14 Lightning Car Company Ltd Control of regenerative and friction braking
CN105270405A (en) * 2014-07-25 2016-01-27 通用汽车环球科技运作有限责任公司 Method of controlling a transmission park system of a vehicle
CN105459801A (en) * 2016-01-07 2016-04-06 重庆三峡学院 Hydrogen energy-based hybrid power device for vehicle and method
FR3053298A1 (en) * 2016-07-04 2018-01-05 Renault S.A.S DEVICE FOR CONTROLLING A PARKING BRAKE OF A MOTOR VEHICLE
US11414090B2 (en) * 2017-09-29 2022-08-16 Mando Corporation Brake control apparatus and brake control method
US11981309B2 (en) 2020-09-28 2024-05-14 Ford Global Technologies, Llc Brake assist during vehicle one pedal drive

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US10821948B2 (en) * 2017-11-09 2020-11-03 Ford Global Technologies, Llc Electric parking brake with regenerative braking control system and method

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GB2417532A (en) * 2004-08-25 2006-03-01 Ford Motor Co Control system for a vehicle having regenerative braking

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US20040122579A1 (en) * 2002-12-17 2004-06-24 Nissan Motor Co., Ltd. Coordinated brake control system
JP2005297749A (en) * 2004-04-12 2005-10-27 Shin Kobe Electric Mach Co Ltd Brake control system for battery type riding golf cart
GB2417532A (en) * 2004-08-25 2006-03-01 Ford Motor Co Control system for a vehicle having regenerative braking

Cited By (11)

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Publication number Priority date Publication date Assignee Title
WO2012025823A2 (en) * 2010-08-27 2012-03-01 Eaton Corporation Electric power generating differential
WO2012025823A3 (en) * 2010-08-27 2012-04-26 Eaton Corporation Electric power generating differential
GB2483477A (en) * 2010-09-09 2012-03-14 Lightning Car Company Ltd Control of regenerative and friction braking
GB2483477B (en) * 2010-09-09 2013-07-24 Lightning Car Company Ltd Braking
CN105270405A (en) * 2014-07-25 2016-01-27 通用汽车环球科技运作有限责任公司 Method of controlling a transmission park system of a vehicle
CN105270405B (en) * 2014-07-25 2018-03-30 通用汽车环球科技运作有限责任公司 The method for controlling the speed changer parking system of vehicle
CN105459801A (en) * 2016-01-07 2016-04-06 重庆三峡学院 Hydrogen energy-based hybrid power device for vehicle and method
FR3053298A1 (en) * 2016-07-04 2018-01-05 Renault S.A.S DEVICE FOR CONTROLLING A PARKING BRAKE OF A MOTOR VEHICLE
WO2018007695A1 (en) * 2016-07-04 2018-01-11 Renault S.A.S Motor vehicle parking brake control device
US11414090B2 (en) * 2017-09-29 2022-08-16 Mando Corporation Brake control apparatus and brake control method
US11981309B2 (en) 2020-09-28 2024-05-14 Ford Global Technologies, Llc Brake assist during vehicle one pedal drive

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