Interrelated power delivery controls – including engine control – Transmission control – Engine controlled by transmission
Patent
1993-10-14
1995-04-18
Wright, Dirk
Interrelated power delivery controls, including engine control
Transmission control
Engine controlled by transmission
477109, F16H 6108
Patent
active
054074010
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an arrangement for controlling the output torque of an automatic transmission in a motor-driven vehicle to a value pregiven by the driver. The transmission has at least two transmission stages which are alternately engageable via clutches.
BACKGROUND OF THE INVENTION
In conventional automatic transmissions, usually a drop of the output torque takes place, for example, when upshifting and this leads to a jolt which affects comfort. The engine torque can be influenced in an appropriate manner during the shifting operation in order to mitigate this jolt. This can be done, for example, by changing the ignition angle or the like in order to smooth the curve of the output torque to improve comfort and reduce the load on the transmission. A different output torque is nonetheless present before and after the shifting operation. The terms used "output moment" and "output torque" include the transmission output torque.
U.S. patent applications Ser. No. 07/923,582 and 08/050,085, filed Aug. 3, 1992 and Apr. 28, 1993, respectively, already suggest that the output torque can be held at the same level before and after the shifting operation when the driver command does not change during shifting. The output torque (torque of the transmission output) and therefore the traction force at the drive wheels is so controlled that this torque is independent within wide limits of the gear stage which has just been engaged or the state of the converter lockup clutch. This method is known to experts in the field under the name "mastershift". With the aid of this known control function, the shift points of the transmission can be placed in areas of optimal use without it being necessary to assume losses with respect to sportiness and the metering of traction force. The known control function however relates only to the control of the output torque outside of the shifting operations. A conventional engine torque curve during the shifting operation leads to an abrupt drop in the output torque during this shifting operation. It is intended to avoid this drop as possible with respect to the shifting comfort.
SUMMARY OF THE INVENTION
The arrangement according to the invention for the upshifting and downshifting affords the advantage with respect to the foregoing that the output torque remains constant even during the shifting operation so that shifting operations are achieved with optimal comfort without any jolt. Realization is possible without mechanical changes in conventional automatic transmissions when the pressure in the engaging and disengaging clutches is electronically controllable with only electronic control functions being added which lead to only a slight increase in cost.
The means of reducing the clutch-closing pressure during downshifting advantageously include a control means which affects the transition into the sliding friction of the second clutch by means of a short-term additional reduction of the engaging pressure. The transition from static friction to sliding friction is customarily associated with a hysteresis. For this reason, this transition is achieved advantageously by superposing a negative value on this engaging pressure.
In an advantageous manner, first computation means are provided in order to compute the desired value for the transmission torque in dependence upon the particular transmission stage and the clutch-engaging pressure of the corresponding clutch from the pregiven desired value for the output torque. The means for continuously time-controlling the disengagement and engagement of the clutch advantageously includes for this purpose a ramp control for the desired value of the transmission torque. A desired value for the clutch pressure required for this purpose is computed from this desired value for the transmission torque of the clutch. By means of the ramp control, the continuous disengagement and engagement of the clutch is simultaneously controlled and the desired value for the transmitting torque is computed. The desired value can s
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Bullmer Wolfgang
Schottle Richard
Streib Martin
Zhang Hong
Ottesen Walter
Robert & Bosch GmbH
Wright Dirk
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