192 clutches and power-stop control – Transmission control and clutch control – Interrelated
Patent
1994-05-17
1996-02-06
Bonck, Rodney H.
192 clutches and power-stop control
Transmission control and clutch control
Interrelated
477175, B60K 4122, F16D 4806
Patent
active
054890128
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a clutch control system for a vehicle.
Our earlier patent GB 2 088 007 describes a clutch control system in which the clutch is progressively engaged as the torque demand issued by the driver increases to temporarily limit the engine speed to a set value. This provides a smooth take up from rest. It is a disadvantage of these systems as described that if the vehicle while in gear should roll down a hill gathering speed while the engine is still idle, the clutch will not engage to provide a degree of braking, nor can the driver make it engage without speeding up the engine using the speed control means, an action that would appear to him totally unnatural in a circumstance when he wanted to cause the vehicle to be restrained. Furthermore, if the engine cannot be started due to failure or partial failure of the self-starting system, the engine cannot be started by any of the commonly accepted emergency starting means such as push starting or tow-starting. It is an object of the present invention to overcome these disadvantages.
The present invention provides a clutch control system for a vehicle having a clutch, a gearbox and an engine, the system comprising a vehicle speed sensor for generating a vehicle speed signal variable with the speed of the vehicle, a clutch engagement signal generator that produces a signal utilised for controlling a clutch actuation means that operates the clutch engagement, a filter means that receives the engagement signal and the engine speed to generate a clutch actuation means for engagement of the clutch in the event that either the vehicle speed signal and/or the engagement signal exceeds a predetermined minimum value.
Preferred embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:
FIG. 1 is a schematic of a control system according to a first embodiment of the present invention.
FIG. 2 is an analogue circuit diagram of the control system of FIG. 1;
FIG. 3 is a block diagram showing the steps used in a microprocessor in a second embodiment of the invention.
FIG. 4 is a graph of the clutch position Vs engine speed illustrating operation of the clutch stall limiter.
Referring to FIG. 1 a vehicle comprises an engine 10 and a gearbox 12 coupled through a clutch 14, via a clutch driven plate 13 and a gearbox input shaft 15. Fuel is supplied to the engine by a throttle 16 which includes a throttle valve 18 operated by accelerator pedal 19. The clutch 14 is actuated by a release fork 20 which is operated by a slave cylinder 22. The gearbox is operated by a gear lever 24.
An engine speed signal generator comprises an engine speed sensor 26 which includes a transducer. The state of the throttle valve 18 is monitored by a throttle valve position sensor 30. The state of the gearbox 12 is monitored by a gear position sensor 32. The position of the slave cylinder 22 is monitored by an actuation sensor 34. The speed of the gearbox output shaft 15 is monitored by a vehicle speed sensor 42. Since the speed of the vehicle depends on the driven plate speed and the gear engaged, the speed sensor can be used to calculate the driven plate speed. Signals from the sensors are transmitted to a control unit 36 which controls the actuation of the clutch via a hydraulic control 38.
Referring to FIG. 2, the system also includes a choke position sensor 44 and a reference signal generator 46. The throttle position sensor 30 produces a throttle signal Vt which is fed to an inverting input of a difference amplifier 50 via a limiter 48. The limiter 48 receives an input from a switching circuit 49. A reference signal Vr from the reference signal generator 46 is combined with a choke signal Vc from the choke position sensor 44 and input to the difference amplifier 50. The output Vs of the difference amplifier 50, being the sum of Vt, Vr and Vc, forms a modified reference signal which is fed to the input of a comparator 52.
The engine speed sensor 26 produces an engine speed signal Ve which is fed via the
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Buckley Stephen D.
Kennedy Ian D.
Automotive Products plc
Bonck Rodney H.
Germain Lee A.
Milliken Paul E.
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