GB2327245A - A CVT transmission control system for a vehicle - Google Patents

A CVT transmission control system for a vehicle Download PDF

Info

Publication number
GB2327245A
GB2327245A GB9714739A GB9714739A GB2327245A GB 2327245 A GB2327245 A GB 2327245A GB 9714739 A GB9714739 A GB 9714739A GB 9714739 A GB9714739 A GB 9714739A GB 2327245 A GB2327245 A GB 2327245A
Authority
GB
United Kingdom
Prior art keywords
transmission control
vehicle
control system
speed
ground engaging
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.)
Withdrawn
Application number
GB9714739A
Other versions
GB9714739D0 (en
Inventor
Neil David Jackson
Owen Robert Treharne Davies
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MG Rover Group Ltd
Original Assignee
MG Rover Group Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by MG Rover Group Ltd filed Critical MG Rover Group Ltd
Priority to GB9714739A priority Critical patent/GB2327245A/en
Publication of GB9714739D0 publication Critical patent/GB9714739D0/en
Publication of GB2327245A publication Critical patent/GB2327245A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/66—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings
    • F16H61/662—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with endless flexible members
    • F16H61/66254—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with endless flexible members controlling of shifting being influenced by a signal derived from the engine and the main coupling
    • F16H61/66259—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with endless flexible members controlling of shifting being influenced by a signal derived from the engine and the main coupling using electrical or electronical sensing or control means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/66—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings
    • F16H2061/6604—Special control features generally applicable to continuously variable gearings
    • F16H2061/6611—Control to achieve a particular driver perception, e.g. for generating a shift shock sensation
    • F16H2061/6612—Control to achieve a particular driver perception, e.g. for generating a shift shock sensation for engine braking
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/66—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings
    • F16H2061/6604—Special control features generally applicable to continuously variable gearings
    • F16H2061/6615—Imitating a stepped transmissions

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Driving Devices And Active Controlling Of Vehicle (AREA)
  • Control Of Transmission Device (AREA)
  • Regulating Braking Force (AREA)

Abstract

A transmission control system for a vehicle 10 having a continuously variable transmission (CVT) 16 is in which a CVT controller 20 compares a wheel speed signal with a land speed signal indicative of the speed of the vehicle 10 across the surface over which it is travelling. If there is a difference between the wheel speed and the land speed, the CVT controller 20 alters the output ratio of the CVT 16 to match the wheel speed and the land speed and thereby eliminates slippage between the vehicle 10 and, for example, a steep or low friction slope.

Description

A Transmission Control Svstem for a Vehicle This invention relates to transmission control systems, and in particular to a transmission control system for a continuously variable transmission of a vehicle.
It is known to use engine braking to control the speed of a vehicle descending a slope. For example, when a four wheel drive vehicle equipped with a manual transmission is used off-road and is descending a steep slope, it is known to engage the vehicle's lowest ratio before starting the descent.
In this manner, the vehicle engine is motored through the transmission and engine braking limits the rate of hill descent so that the driver does not need to use the brakes and merely steers. It is a known problem with this technique that on an exceptionally steep incline or on a slope with a low friction surface, it is possible for the engine braking to be high enough to cause the vehicle's wheels to slip and the vehicle will then start to slide down the slope in an uncontrolled fashion. A driver experienced in off-road techniques will depress the accelerator pedal when the vehicle loses traction, thus reducing engine braking and increasing the wheel speed until it matches the new rate of descent. The wheels may then regain traction, within limits imposed by the steepness of the incline and the wheel speed available, and a controlled descent of the slope is possible.
It is an object of this invention to provide an improved transmission control system for a vehicle.
According to the invention there is provided a transmission control system for a vehicle comprising a transmission control means arranged to control the output ratio of a transmission of the vehicle, a slip detection means arranged to provide a slip signal to the transmission control means indicative of the slipping of a ground engaging member of the vehicle with respect to a surface upon which the vehicle is travelling, the transmission control means being arranged to alter said output ratio temporarily in response to said slip signal in order to reduce the slipping of said ground engaging member.
The output ratio may be altered by being increased and may be altered so as to decrease a force transmitted to the ground engaging member by the transmission. Said force may be a braking force or may be a driving force.
The slip detection means may comprise a ground engaging member speed detection means and may be arranged to use a detected member speed to detect the slipping of said ground engaging member. The slip detection means may further comprise a land speed detection means arranged to detect the land speed of the vehicle across said surface and may be arranged to use the land speed and the member speed to detect the slipping of said ground engaging member.
The alteration of the output ratio may be temporarily abandoned when a braking system of the vehicle is operated, in order to slow down the speed of said ground engaging member using said braking system.
The transmission may comprise a continuously variable transmission and may optionally be operating in substantially fixed ratios. Said alteration may be effected in a continuous manner.
The ground engaging member may comprise a wheel of said vehicle or may comprise a track of said vehicle.
The invention also provides a vehicle having a transmission control system according to the invention.
The invention will now be described by way of example with reference to the accompanying drawing, in which: Figure 1 is a schematic diagram of a vehicle having a transmission control system according to the invention.
Referring to Figure 1, a vehicle 10 has ground engaging members in the form of four wheels 12 which are driven by a driving force in the form of torque provided by an engine 14 and transmitted to the wheels 12 through a four wheel drive continuously variable transmission (CVT) 16 and a drive train 18.
The output ratio of the CVT 16 is controlled by a CVT controller 20 and the CVT 16 is operable either as a conventional CVT or in a plurality of simulated fixed ratios.
The CVT controller 20 includes a slip detector (not shown separately) which is arranged to receive a wheel speed signal from a wheel speed detection system and a land speed signal from a land speed detection system.
The wheel speed detection system comprises individual wheel speed sensor target wheels 22 which co-rotate one with each wheel 12 and associated wheel speed sensors 24 which detect the rotational speed of each target wheel 22 and each supply an individual rotational speed signal to an anti-lock braking system (ABS) 26. The ABS 26 calculates the wheel speed signal, which is indicative of the average value of the wheel speeds and which is then supplied to the CVT controller 20.
The land speed sensor 28 is arranged to detect the speed of the vehicle 10 across the surface over which it is travelling and to supply a land speed signal indicative thereof to the CVT controller 20. A suitable land speed detection system is disclosed in JP 09015332-A.
The slip detector continuously compares the wheel speed signal and the land speed signal and, if there is a difference between the wheel speed and the land speed, the CVT controller 20 alters the output ratio of the CVT 16 to match the wheel speed to the land speed.
For example, when the vehicle 10 is used off-road, the CVT 16 is optionally operated in a plurality of simulated fixed ratios. To descend a steep slope, the CVT 16 is operated in its lowest simulated fixed ratio by a vehicle user input (not shown separately) to the CVT controller 20. The rate of descent of the slope is then controlled by engine braking causing a braking force to be applied to the wheels 12 through the CVT 16.
If the slope is exceptionally steep or has a low friction surface, the vehicle 10 may lose grip and start to slide down the slope despite continued rotation of the wheels 12, which are limited in rotational speed by the engine braking. The CVT controller 20 then increases the output ratio of the CVT 16, which is effected in a continuous manner rather than in steps.
The increase in output ratio reduces the engine braking force at the wheels 12, which increases their speed of rotation in order to match the wheel speed to the land speed. When the output ratio has been raised sufficiently, traction will be regained, within limits imposed by the steepness of the incline and the wheel speed available, and the slope can then be descended in a controlled fashion.
The CVT controller 20 only increases the output ratio when it detects that slippage between the wheels 12 and the slope surface is occurring.
When the CVT controller 20 detects that slippage during the hill descent has ceased, it starts to reduce the output ratio towards the simulated fixed ratio in which the CVT 16 was originally operating. The output ratio will only be reduced from its raised level by enough to reach the original simulated fixed ratio if no further slipping is detected during the reduction.
If slipping reoccurs, the output ratio is increased again until slipping stops and the CVT controller 20 alters the output ratio under such closed loop feedback control to output the lowest ratio possible in order to provide maximum engine braking without wheel slip. The present invention operates as an aid to off-road users by removing the need for the driver to speed up the wheel rotation himself.
The present invention is also useful to regain traction when accelerating whilst operating in simulated fixed ratios. For example, if the accelerator pedal is depressed too far while accelerating on a level surface, it is possible for the wheels 12 to lose traction and to start to spin. In such circumstances, the CVT controller 20 determines that the wheel speed is greater than the land speed using the same form of comparison as described above and increases the output ratio of the CVT 16. The increase in output ratio saps power from the engine 14, which has the effect of reducing the amount of driving force transmitted to the wheels 12 and thereby reduces the amount of wheel slip. The output ratio is increased in a continuous manner, rather than in steps, until the wheel speed is brought down to the land speed and thus the CVT controller 20 achieves the maximum acceleration possible for the vehicle 10 without slippage between the wheels 12 and the surface.
The increase in output ratio is effected by temporarily abandoning the step changes in output ratio and increasing it in a continuous manner, which has the effect of regaining traction whilst the feature remains invisible to the vehicle user, to whom the CVT 16 still feels as if it is in the fixed ratio.
When the CVT controller 20 detects that slippage during acceleration has ceased, it starts to reduce the output ratio towards the simulated fixed ratio in which the CVT 16 was originally operating. The output ratio will only be reduced far enough from its raised level to reach the original simulated fixed ratio if no further slipping is detected during the reduction.
If slipping reoccurs, the output ratio is increased again until slipping stops and the CVT controller 20 alters the output ratio under this closed loop feedback control to output the lowest ratio possible to provide maximum acceleration without wheel slip.
If the driver operates the ABS 26, his use of the brakes (not shown) will cause the CVT controller 20 to temporarily abandon the alteration of the output ratio and the wheel speed will be altered in a conventional fashion by the braking system.
The ground engaging member of the present invention is not limited to a wheel and could equally be a track of a vehicle, in which case the features of the invention directed to the detection of wheel speed would be replaced by equivalent features directed to the detection of the speed of the track or of a track driving means.
In a second embodiment of the present invention, no land speed sensor is provided and the CVT controller 20 interprets the wheel speed signals from the sensors 24 to determine whether slippage is occurring or to predict that it is about to occur. For example, if the speed of the front wheels 12 of a front-wheel-drive vehicle suddenly increases while the speed of the rear wheels 12 remains substantially constant, then the CVT controller 20 will determine that the front wheels 12 have started to slip, or will predict that they are about to start slipping, and will increase the output ratio of the CVT 16 to reduce the slipping.
This example demonstrates one situation when the invention would be particularly useful to predict or detect wheel spin in a front-wheel-drive vehicle while accelerating, thus prevent slipping or regaining traction and providing maximum acceleration.

Claims (15)

1. A transmission control system for a vehicle comprising a transmission control means arranged to control the output ratio of a transmission of the vehicle, a slip detection means arranged to provide a slip signal to the transmission control means indicative of the slipping of a ground engaging member of the vehicle with respect to a surface upon which the vehicle is travelling, the transmission control means being arranged to alter said output ratio temporarily in response to said slip signal in order to reduce the slipping of said ground engaging member.
2. A transmission control system according to Claim 1, wherein the output ratio is altered by being increased.
3. A transmission control system according to Claim 1 or Claim 2, wherein the output ratio is altered so as to decrease a force transmitted to the ground engaging member by the transmission.
4. A transmission control system according to Claim 3, wherein said force is a braking force.
5. A transmission control system according to Claim 3, wherein said force is a driving force.
6. A transmission control system according to any preceding claim, the slip detection means comprising a ground engaging member speed detection means and being arranged to use a detected member speed to detect the slipping of said ground engaging member.
7. A transmission control system according to Claim 6, the slip detection means further comprising a land speed detection means arranged to detect the land speed of the vehicle across said surface and being arranged to use the land speed and the member speed to detect the slipping of said ground engaging member.
8. A transmission control system according to any preceding claim, wherein the alteration of the output ratio is temporarily abandoned when a braking system of the vehicle is operated, in order to slow down the speed of said ground engaging member using said braking system.
9. A transmission control system according to any preceding claim, the transmission comprising a continuously variable transmission.
10. A transmission control system according to Claim 9, wherein the continuously variable transmission can be operated in substantially fixed ratios.
11. A transmission control system according to Claim 9 or Claim 10, wherein said alteration is effected in a continuous manner.
12. A transmission control system according to any preceding claim, the ground engaging member comprising a wheel of said vehicle.
13. A transmission control system according to any one of Claims 1 to 11, the ground engaging member comprising a track of said vehicle.
14. A transmission control system substantially as described herein with reference to the accompanying drawing.
15. A vehicle having a transmission control system according to any preceding claim.
GB9714739A 1997-07-15 1997-07-15 A CVT transmission control system for a vehicle Withdrawn GB2327245A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9714739A GB2327245A (en) 1997-07-15 1997-07-15 A CVT transmission control system for a vehicle

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9714739A GB2327245A (en) 1997-07-15 1997-07-15 A CVT transmission control system for a vehicle

Publications (2)

Publication Number Publication Date
GB9714739D0 GB9714739D0 (en) 1997-09-17
GB2327245A true GB2327245A (en) 1999-01-20

Family

ID=10815785

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9714739A Withdrawn GB2327245A (en) 1997-07-15 1997-07-15 A CVT transmission control system for a vehicle

Country Status (1)

Country Link
GB (1) GB2327245A (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5178044A (en) * 1990-06-21 1993-01-12 Nissan Motor Co., Ltd. Traction control upon start-up of automobile with continuously variable transmission
US5262952A (en) * 1990-02-22 1993-11-16 Mazda Motor Corporation Slip control system for motor vehicle
US5383125A (en) * 1991-01-23 1995-01-17 Nissan Motor Co., Ltd. Slip control for automotive vehicle with continuously variable transmission
EP0583610B1 (en) * 1992-08-13 1995-12-06 Bayerische Motoren Werke Aktiengesellschaft, Patentabteilung AJ-3 Method for reduction of driving torque in motor vehicles when driven wheels tend to slip
GB2303184A (en) * 1993-03-31 1997-02-12 Bosch Gmbh Robert CVT operation method in which the ratio is adjusted for engine braking

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5262952A (en) * 1990-02-22 1993-11-16 Mazda Motor Corporation Slip control system for motor vehicle
US5178044A (en) * 1990-06-21 1993-01-12 Nissan Motor Co., Ltd. Traction control upon start-up of automobile with continuously variable transmission
US5383125A (en) * 1991-01-23 1995-01-17 Nissan Motor Co., Ltd. Slip control for automotive vehicle with continuously variable transmission
EP0583610B1 (en) * 1992-08-13 1995-12-06 Bayerische Motoren Werke Aktiengesellschaft, Patentabteilung AJ-3 Method for reduction of driving torque in motor vehicles when driven wheels tend to slip
GB2303184A (en) * 1993-03-31 1997-02-12 Bosch Gmbh Robert CVT operation method in which the ratio is adjusted for engine braking

Also Published As

Publication number Publication date
GB9714739D0 (en) 1997-09-17

Similar Documents

Publication Publication Date Title
CN109334656B (en) Vehicle control method and device
US6729426B2 (en) Driving force controlling apparatus and method for four-wheel drive vehicle
US6189643B1 (en) Differential limiting control apparatus for four wheel drive vehicle
US6076899A (en) Method and apparatus for controlling the brake system of electric drive vehicles
JP3675240B2 (en) Vehicle tracking control device
US20070222289A1 (en) Vehicle driving force control apparatus
GB2276683A (en) A continuously variable transmission controlled to regulate drive slip and/or engine braking
US20070299581A1 (en) Limiting Motor-Vehicle Rollback
US5107430A (en) Method and a system for controlling traction in motor vehicles with mechanical gearboxes
US6816769B2 (en) Driving performance of a motor vehicle on μ-split slopes
US6286617B1 (en) Securely stopped vehicle method and apparatus
US6896083B2 (en) Four-wheel drive control system and method
JP2003293818A (en) Device and method for controlling engine brake torque
JP3656511B2 (en) Driving force control device for four-wheel drive vehicle
US6189642B1 (en) Vehicle drive torque distribution control system
JP4496665B2 (en) Inter-vehicle distance control device
GB2327245A (en) A CVT transmission control system for a vehicle
JPH0443153A (en) Brake power controller for vehicle
GB2303184A (en) CVT operation method in which the ratio is adjusted for engine braking
JP3781011B2 (en) Travel speed control device
JPH0516686A (en) Device for judging running condition of vehicle and controller for power transmission of vehicle
EP0349254B1 (en) Method for controlling the slip of drive wheels of a vehicle
JP3561908B2 (en) Driving force distribution control device for four-wheel drive vehicle
JPH0599014A (en) Detection method for frictional factor on road surface
JP4039364B2 (en) Prior vehicle following travel control device

Legal Events

Date Code Title Description
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)