Interrelated power delivery controls – including engine control – Transmission control – With clutch control
Patent
1999-03-24
2000-06-20
Bonck, Rodney H.
Interrelated power delivery controls, including engine control
Transmission control
With clutch control
192 363, B60K 4128, B60K 4102
Patent
active
060771895
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns an automatic control of a clutch in the drive train of a motor vehicle, having a transmission shifted by the driver between different transmission stages or gears and an engine controlled by the driver by means of a control element, for example a gas pedal. The clutch is automatically set by a motorized adjusting unit, actuated by the control, to a creeping torque at low travelling speed or when the vehicle is stationary and the transmission stage has been selected, the brake is unactuated and the control element is not actuated.
In motor vehicles with customary internal combustion engines, a transmission must be arranged in the drive train to allow the transmission ratio between the speed of the vehicle engine and the speed of the drive wheels to be changed according to the respective travelling speed and loading of the vehicle. In customary manually shifted transmissions, during the change of a transmission stage the power flow between engine and drive wheels has to be interrupted by releasing the clutch.
When starting the vehicle, the clutch must operate with slip, since the aforementioned transmission is not able to operate steplessly and conventional vehicle engines, in particular internal combustion engines, can only operate and deliver adequate power above a minimum speed.
It is known in principle to use automatic clutches for this purpose so that a clutch is automatically released when changing a transmission stage and is subsequently re-engaged. In starting situations, the clutch initially transmits only a limited torque, i.e. the creeping torque, which is adequate for making the vehicle start to slowly creep forward under normal driving conditions. If the vehicle is then accelerated by corresponding actuation of the gas pedal, the torque which can be transmitted by the clutch increases, so that, depending on the respective operating parameters, at a varying level of engine speed the clutch can transmit a torque which is above the engine torque.
It is known from EP 03 75 162 B1 to allow the automatic control of the clutch also to operate in dependence on the brake actuation in a creeping phase of the vehicle.
SUMMARY OF THE INVENTION
The object of the invention is thus to optimize the control of the clutch in the creeping phase.
This object is achieved according to the invention by initially setting a high creeping torque, at low travelling speed or when the vehicle is stationary, the transmission stage has been selected, the brake is unactuated and the control element is not actuated. The high creeping torque is automatically reduced after a predetermined time period if the brake continues to be unactuated and the gas pedal is not actuated.
In particular, the relatively high creeping torque can be initially set during starting, even after ending a brake actuation.
The invention is based on the general idea of controlling the clutch at the beginning of a starting situation, i.e. after selecting a transmission stage and ending a brake actuation and with the gas pedal not actuated, initially to deliver a relatively high creeping torque, in order to ensure that the vehicle can start reliably and comparatively rapidly. Should the gas pedal continue to remain unactuated within the predetermined time period, this is an indication that this is not a "normal" starting situation and the torque effective for driving the vehicle should be reduced. This at the same time protects the clutch against excessive wear. This applies in particular if the driver should hold a stationary or virtually stationary vehicle on an incline just by using the creeping torque of the clutch.
According to a preferred embodiment of the invention, the reduction in the creeping torque may be relinquished if a threshhold value for the travelling speed has been exceeded. This is because a higher travelling speed often indicates that a starting phase is unlikely to be terminated by the driver. Furthermore, it is ensured on inclines that the engine can, if required, have a br
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Grass Thomas
Kosik Franz
Bonck Rodney H.
Daimler-Chrysler AG
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