Interrelated power delivery controls – including engine control – Clutch control
Patent
1995-09-29
1997-10-21
Bonck, Rodney H.
Interrelated power delivery controls, including engine control
Clutch control
477175, 477180, B60K 4102
Patent
active
056790988
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a clutch control system for the automatic control of a motor vehicle clutch which connects an engine with a gearbox under the control of a driver-operated gear ratio selector lever, the control system including an electronic control unit which controls initial clutch take-up on starting of the vehicle, clutch re-engagement following each ratio change, disengagement on movement of the gear selector lever to change the operative ratio of the gearbox, and clutch disengagement on the coming to rest of the vehicle, the level of clutch engagement being controlled in response to an engine speed error signal derived from a comparison of current engine speed and a reference speed signal generated by the control unit, said error signal being compared with a current clutch position signal to produce a clutch actuation signal. Such a clutch control system is herein after referred to as a clutch control system of the kind specified.
DESCRIPTION OF THE PRIOR ART
Examples of such systems are described in the Applicants earlier European Patents Nos. 0038113, 0043660, 0059035 and 0101220 and European Application No. 0566595.
Problems can arise with control systems of the kind specified if the operator raises the engine speed above idle and then moves the gear lever from neutral to a take-up gear. This can cause an inadvertent take-up of drive.
It is an object of the present invention to provide a control system of the kind specified which overcomes the above problem.
SUMMARY OF THE INVENTION
Thus according to the present invention there is provided a clutch control system of the kind specified characterised in that the reference signal for initial clutch take-up is derived from one of the three following references on a highest-wins basis: offset.
Thus, for example, if the operator increases the engine speed substantially above idle and then moves the gear lever to select a gear the system records a snapshot of the raised engine speed and the floating reference will thus be the largest of the three references and becomes the reference which controls clutch take-up. Thus until the operator raises the engine speed above the current floating reference value clutch engagement will not occur and hence inadvertent take-up of drive is avoided.
When the operator has raised the engine speed above the current floating reference value the clutch begins to transmit torque and the engine speed therefore falls. The engine speed is then below the no-load engine speed for the current throttle setting (i.e. the steady speed which the engine runs at for a given throttle position when under no load).
The system is arranged to ramp down the floating reference linearly as long as the engine speed is below the no-load engine speed for the current throttle setting. This promotes clutch engagement.
The system also reduces the floating reference to track any reduction in the engine speed that occurs when clutch is not transmitting torque so that the floating reference is equal to the current engine speed plus the floating reference offset.
Once the floating reference is below the throttle reference the throttle reference becomes the controlling reference on the highest-wins basis. The idle reference is determined by regularly monitoring idle speed after the system is keyed-on. The strategy for finding the lowest idle speed is to regularly check the engine speed when the throttle is closed and look for the lowest speed, subject to a lower limit.
The lowest idle speed found is modified (increased) if the idle speed is found to increase while the accelerator pedal is not pressed whilst the clutch driven plate speed is low indicating that the vehicle has stopped. Such an increase in idle speed is caused by an associated engine management system increasing the idle speed to respond to an increased engine load imposed by the switching on of accessories such as air conditioning.
The present invention also provides a clutch control system of the kind specified in which clutch take-up (ie. engagement)
REFERENCES:
patent: 4561530 (1985-12-01), Parsons et al.
patent: 4711333 (1987-12-01), Okamura
patent: 4800497 (1989-01-01), Koori et al.
patent: 4817776 (1989-04-01), Tateno et al.
patent: 4881627 (1989-11-01), Ishii
patent: 5086894 (1992-02-01), Iizuka et al.
patent: 5332073 (1994-07-01), Iizuka
patent: 5427215 (1995-06-01), Jarvis
patent: 5489012 (1996-02-01), Buckley et al.
Jones Charles John
Shepherd Paul Vincent
Automotive Products plc
Bonck Rodney H.
Germain Lee A.
Kwon Peter T.
Milliken Paul E.
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