GB2482862A

GB2482862A - Hill hold launch assist for a motor vehicle

Info

Publication number: GB2482862A
Application number: GB201013402A
Authority: GB
Inventors: Martin Robekowski; Ian Halleron
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2010-08-10
Filing date: 2010-08-10
Publication date: 2012-02-22
Anticipated expiration: 2030-08-10
Also published as: GB2482862B; CN102372002A; GB201013402D0; DE102011080293A1; CN102372002B

Abstract

Launch assist of a vehicle is disclosed in which engagement of an electronically controlled clutch 11 is controlled by a controller 20 in response to sensed motion of an input shaft 13 to produce zero rotation of the input shaft 13 while one or more brakes 31 holding the vehicle 5 stationary are released and then engaging the clutch 13 fully to produce positive rotation of the input shaft 13 after the one or more brakes 31 are released, thus achieving synchronization of the clutch and brakes. The clutch engagement may be increased when the parking brake 31 is fully released. The parking brake 31 may be reapplied if negative rotation of the input shaft is sensed, or if positive rotation of the input shaft is not achieved a short time after initiation of the launch.

Description

A System and Method for Assisting a Motor Vehicle Launch This invention relates to motor vehicles and in particular to a system and method for assisting a driver of a motor vehicle in achieving a vehicle launch from a hill.

It is known that it is a problem when starting or launching a motor vehicle on an incline that the vehicle can roll in the opposite direction to the intended direction of travel if the driver incorrectly coordinates the release of the brakes holding the vehicle stationary on the incline with the engagement of the clutch. It is a further problem that if the clutch is engaged to a state where the vehicle is moved in the desired direction before the brakes holdinq the vehicle are released then noise can be generated from the brakes.

It is an object of this invention to provide a system and method for assisting a driver with a launch and in particular with a launch on an incline.

According to a first aspect of the invention there is provided a system for assisting with a motor vehicle launch on an incline, the system comprising a gearbox input sensor to monitor the rotation of an input shaft of a gearbox, an electronically controlled clutch to provide drive to the input shaft from an engine of the motor vehicle, at least one electronically controlled parking brake used to hold the motor vehicle in a stationary position and a controller to synchronise the engagement of the electronically controlled clutch with the release of the parking brake based upon a signal received from the gearbox input sensor wherein the controller is operable to control engagement of the clutch to produce substantially zero rotation of the input shaft during release of the parking brake.

This has the advantage that there is no roll-back or creeping of the motor vehicle while the parking brake is being released.

When the parking brake is fully released the controller may be operable to increase engagement of the clutch.

The controller may be further operable to reapply the parking brake if negative rotation of the input shaft is sensed to be occurring.

The controller may be operable to apply the parking brake and disengage the clutch if positive rotation of the input shaft has not been achieved in a short predetermined period of time following the initiation of the launch.

According to a second aspect of the invention there is provided a method for assisting with a launch of a motor vehicle on an incline wherein the method comprises controlling the engagement of a clutch during a launch based upon the motion of an input shaft to a gearbox to produce substantially zero rotation of the input shaft as a parkinq brake is released.

The method may further comprise synchronising the release of the parking brake and the engagement of the clutch to produce the desired zero rotation of the input shaft.

The method may further comprise increasing the engagement of the clutch when the parking brake has been fully released.

The method may further comprise fully engaging the parking brake and disengaging the clutch if positive rotation of the input shaft has not been achieved within a short predetermined period of time following the initiation of the launch.

The invention will now be described by way of example with reference to the accompanying drawing of which:-Fig.1 is a schematic block diagram of a motor vehicle having a launch assist system according to one aspect of the invention.

With reference to Fig.1 there is shown a motor vehicle 5 having an engine 10 driving a multi-speed gearbox 12 via an electronically controlled clutch 11.

The gearbox 12 drives two rear wheels 6L, 6R of the motor vehicle 5 via a propeller shaft 14, differential 15d and two halfshafts 15L, 15R. The motor vehicle 5 also has two non-driven front wheels 4L, 4R and each of the four wheels 4L,4R;6L, 6R has a brake 7 associated with it to effect braking of the motor vehicle 5.

The motor vehicle 5 also has an electronically controlled friction parking brake 31 the operation of which is controlled by a brake controller 30. This type of parking brake allows the braking force to be gradually reduced as it is released.

An electronic controller 20 is arranged to receive a number of inputs from various sensors located on the motor vehicle 5. The sensors include a clutch position sensor 21 used to monitor the position of a clutch pedal 16, a brake pedal sensor 22 used to monitor the position of a brake pedal 17, a demand sensor 23 used to monitor the position of an accelerator pedal 18 and a gearbox input sensor 24 used to monitor the motion of an input shaft 13 to the gearbox 12.

The electronic controller 20 is operable during normal operation of the motor vehicle 5 to control the operation of the electronically controlled clutch 11 based upon a signal received from the clutch pedal sensor 21.

The electronic controller 20 is also connected to the brake controller 30 and provides a control signal to the brake controller 30. It will be appreciated that the controller 20 and brake controller 30 could be formed as part of a single controller or could be separate controllers as shown in Fig.1.

During a launch from rest the normal procedure followed by a driver is to depress the clutch pedal 16 so as to disengaged the clutch 11, engage a desired gear in the gearbox 12, depress the accelerator pedal 18 and release the parking brake 31 while engaging the clutch 11. In many cases this will result in perfectly acceptable launch with no undesirable effects. However, if the launch is to be conducted on an incline then the synchronisation of the engagement of the clutch 11 with the releasing of the parking brake 31 is more difficult and less competent or less experienced drivers sometimes find such a launch difficult to execute without the vehicle rolling initially down the incline (roll-back) or dragging the brakes.

Therefore during launch conditions where the initial vehicle speed is zero the controller 20 is operable to assist the driver by controlling the engagement of the clutch 11 and the release of the parking brake 31 as described below.

During a launch the input shaft 13 is initially stationary and with a correctly executed launch the input shaft 13 will rotate in only one direction namely the direction required to move the vehicle 5 in the desired direction. For the purpose of illustration the required or positive direction is clockwise as viewed from the clutch 11.

With an incorrectly performed launch in which roll-back occurs the input shaft 13 will rotate in an incorrect or negative direction namely anti-clockwise. It will be appreciated that these directions are the same whether the vehicle 5 is attempting to drive forwardly up an incline or reverse up an incline.

Therefore by using the gearbox input sensor 24 to determine the direction of rotation of the input shaft 13 the controller 20 is able to increase engagement of the clutch 11 if any incorrect anti-clockwise rotation of the input shaft 13 is detected as the parking brake 31 is released.

During a release phase of the parking brake 31 the aim is to produce zero rotational movement of the input shaft 13 and thereafter increase engagement to effect positive rotation of the input shaft 13. If the increased engagement of the clutch 11 fails to produce the desired zero or clockwise rotation of the input shaft 13 the controller 20 is operable to send a signal to the brake controller 30 to reapply or fully engage the parking brake 31 SO as to prevent roll-back or clutch burn-out. This reapplication of the parking brake 31 occurs after a predetermined amount of time has elapsed from the time the launch sequence commenced. The short predetermined period of time may be in the order of a few seconds.

Alternatively, the controller 20 may be operable to increase a power demand from the engine 10 independently from the accelerator pedal demand if the speed of the engine is falling rapidly and the engagement of the clutch 11 is failing to produce the desired clockwise rotation of the input shaft 13 before re-applying the parking brake 31.

Once again, the parking brake 31 is reapplied after a short period of time has elapsed from the time the launch sequence commenced.

Although in the preferred embodiment described above the rotation of the input shaft is sensed, it is possible to produce a similar result with the use of a rotational speed sensor. In this case during the release phase of the parking brake 31 the controller 20 is operable to try and produce a zero rotational speed of the input shaft 13 but because the direction of rotation is not known this is less accurate and the clutch may have to be cycled between increased and decreased engagement positions to achieve the zero rotational speed.

During the take-off stage following the release of the parking brake 31, the clutch 11 is gradually engaged by the controller 11 to its fully engaged position it being assumed that the desired rotation of the input shaft 13 has been achieved. During this stage, the rotation speed of the engine 10 is monitored to make sure that it does not fall below a predetermined level and if it does the parking brake 31 is reapplied and the clutch 13 is fully disengaged.

In more detail, from an initially stationary position when the driver of the motor vehicle 5 depresses the accelerator pedal 18 and releases the clutch pedal 16 the controller 20 monitors the rotation of the input shaft 13 based upon the signal received from the gearbox input sensor 24. Initially, a small clockwise rotation of the input shaft 13 will occur due to any backlash in the gearbox 12 being absorbed (if the parking brake 31 were to be formed as part of the rear wheel brake assemblies 7 then backlash in the differential would also be absorbed), the rotation will then tend to zero because motion of the vehicle 5 is being prevented by the action of the parking brake 31. The controller 20 then sends a signal to the brake controller 30 requesting the parking brake 31 be released. As the parking brake 31 is released by the brake controller 30 the controller 20 monitors the motion of the input shaft 13 and controls engagement of the clutch 11 so that there is no anticlockwise rotation of the input shaft 13 and no clockwise rotation of the input shaft 13. In practice a very small amount of clockwise rotation may occur due to the difficulty is obtaining perfect zero rotation and the need to prevent negative rotation.

This state of zero rotation is known as the bite condition' and is maintained until the parking brake has being fully released at which point the controller 20 begins the take-off phase and further engages the clutch 11 to try and produce clockwise rotation of the input shaft 13 and will persist with this action until the clutch 11 is fully engaged and forward motion of the vehicle is occurring or until the short predetermined period of time has elapsed.

If the clutch 13 has reached full engagement and the vehicle is moving in the desired direction then the control of clutch engagement reverts to normal clutch pedal control and the controller 20 engages and disengages the clutch 11 based upon the signal received from the clutch pedal sensor 21.

If during an assisted launch the driver of the motor vehicle 5 fully depresses the clutch pedal 16 then the controller 20 takes this as an abandon launch signal and will immediately re-apply the parking brake 31 and fully disengage the clutch 11.

It will be appreciated that if the demand requested by the driver via the accelerator pedal 18 is insufficient to produce a successful launch and the driver does not respond to a rapidly falling engine speed then action must be taken to prevent the vehicle 5 rolling back or the engine stalling.

One way of dealing with this situation is for the controller 20 to re-apply the parking brake 31 and disengaqe the clutch 11 when the clutch 11 has been engaged almost fully but no clockwise rotation of the input shaft 13 has occurred or the bite condition' of zero input shaft rotation has not been achieved. This reapplication of the parking brake 31 occurs after the short predetermined period of time has elapsed.

A second method for dealing with such a situation is to provide temporary control of engine demand to the controller 20. In such a case, when the clutch 11 has been engaged a predetermined amount (such as 60%) and clockwise rotation of the input shaft 13 is not occurring or the bite condition' cannot be achieved then the demand from the engine 10 is gradually increased by the controller 20 independently of accelerator pedal position, if this fails to produce the required zero or clockwise rotation within the short predetermined period of time then the controller 20 is operable to re-apply the parking brake, disengage the clutch and revert to accelerator pedal control of engine demand in order to prevent clutch burn-out.

It will be appreciated that increasing the demand from the engine 10 will not always be successful in producing a launch if, for example, the wrong gear has been selected by the driver and a launch from such an incline is not possible in the selected gear.

Although the invention has been described with respect to its use on a full manual transmission motor vehicle having a driver operated clutch pedal it will be appreciated that it could also be applied to an automated manual gearbox arrangement in which there is no driver operable clutch pedal but the input drive to the gearbox is via a clutch.

In such arrangements the clutch is normally electronically controlled and so by adapting the controller used to control normal clutch operation to also operate the parking brake the same functionality can be achieved.

It will be appreciated that the invention is not limited to use with a rear wheel drive vehicle.

It will also be appreciated that the parking brake 31 could be incorporated into one or more of the brake assemblies 7 and need not be a friction transmission brake as shown on Fig.1 Therefore in summary the invention provides a system and method for assisting with a launch of a motor vehicle on an incline by monitoring the rotation of an input shaft and controlling a clutch of the motor vehicle to obtain zero rotation of the input shaft during a brake release phase of the launch and positive rotation during a take-off phase of the launch.

It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that one or more modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention as set out in the appended claims.

Claims

-10 -Claims 1. A system for assisting with a motor vehicle launch on an incline, the system comprising a gearbox input sensor to monitor the rotation of an input shaft of a gearbox, an electronically controlled clutch to provide drive to the input shaft from an engine of the motor vehicle, at least one electronically controlled parking brake used to hold the motor vehicle in a stationary position and a controller to synchronise the engagement of the electronically controlled clutch with the release of the parking brake based upon a signal received from the gearbox input sensor wherein the controller is operable to control engagement of the clutch to produce substantially zero rotation of the input shaft during release of the parking brake.
2. A system as claimed in claim 1 wherein when the parking brake is fully released the controller is operable to increase engagement of the clutch.
3. A system as claimed in claim 1 or in claim 2 wherein the controller is further operable to reapply the parking brake if negative rotation of the input shaft is sensed to be occurring.
4. A system as claimed in any of claims 1 to 3 wherein the controller is operable to apply the parking brake and disengage the clutch if positive rotation of the input shaft has not been achieved in a short predetermined period of time following the initiation of the launch.
5. A method for assisting with a launch of a motor vehicle on an incline wherein the method comprises controlling the engagement of a clutch during a launch based upon the motion of an input shaft to a gearbox to produce substantially zero rotation of the input shaft as a parkinq brake is released.

-11 -
6. A method as claimed in claim 5 wherein the method further comprises synchronising the release of the parking brake and the engagement of the clutch to produce the desired zero rotation of the input shaft.
7. A method as claimed in claim 5 or in claim 6 wherein the method further comprises increasing the engagement of the clutch when the parking brake has been fully released.
8. A method as claimed in any of claims 5 to 7 wherein the method further comprises fully engaging the parking brake and disengaging the clutch if positive rotation of the input shaft has not been achieved within a short predetermined period of time following the initiation of the launch.
9. A motor vehicle having a system for assisting with launch of the motor vehicle on an incline as claimed in any of claims 1 to4.
10. A system for assisting with a motor vehicle launch on an incline substantially as described herein with reference to the accompanying drawing.
11. A method for assisting with a launch of a motor vehicle on an incline substantially as described herein with reference to the accompanying drawing.
12. A motor vehicle substantially as described herein with reference to the accompanying drawing.