Planetary gear transmission systems or components – Condition responsive control – Stepped – torque responsive ratio change
Patent
1998-02-23
2000-12-05
Marmor, Charles A
Planetary gear transmission systems or components
Condition responsive control
Stepped, torque responsive ratio change
475116, 475267, 477175, F16H 374
Patent
active
061559520
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of controlling a change of ratio in a transmission device, in particular an automatic multiple-ratio transmission device.
The present invention also relates to a transmission device implementing such a method.
From WO-A-9207206 there is known an automatic transmission in which a clutch selectively connects two rotary members of a differential gearing, such as an epicyclic train, according to whether one or the other of two antagonistic forces dominates. The first force is for example a gearing reaction, more particularly an axial thrust produced by a pinion with helical teeth mounted in an axially mobile manner, tending to disengage the clutch. The second force, tending to engage the clutch, can be produced by springs and/or by a centrifugal tachometric means. When the clutch is disengaged, it is necessary to prevent the rotation of a third rotary member of the differential gearing, and this can be ensured by a free wheel preventing this third member from rotating in the reverse direction.
This type of transmission is very advantageous as its basic functioning requires neither an external power source, nor sensors, nor a control circuit. It is the transmission device itself which produces the forces which will control it and these forces are at the same time a measurement of the parameters necessary for the control.
For modern transmissions having to provide a high level of comfort and of optimisation of the operation, the previously mentioned forces are advantageously completed by additional forces, for example produced by hydraulic actuators. The additional forces can be used to modify at will the speed and torque conditions under which the transmission changes ratio, or for locking the transmission in a given ratio when this is required (PCT/FR 94/00 176).
From another aspect, it has been observed, according to the invention, that the change of ratio under the action of forces such as a centrifugal force or a gearing reaction could exhibit certain defects, such as excessive slowness.
Furthermore, when the transmission offers a number of transmission ratios which is high in comparison with the number of gear trains used, there is in general at least one ratio change process which necessitates releasing one coupling and activating another, whilst synchronising these two operations perfectly. Any imperfection in this synchronization makes the change of ratio uncomfortable for the occupants of the vehicle and introduces stresses and/or shocks, which generate wear, in the transmission.
According to U.S. Ser. No. 4,713,984, the coupling which must be activated receives an engaging force which is at first small and then increases progressively up to the maximum value, whilst the engaging force of the other coupling is progressively released. The hydraulic means for implementing this solution are complex, expensive and difficult to perfect.
The DE-A-41 19 078 teaches to adjust the hydraulic pressure which is used for performing a ratio change in an automatic transmission, this adjustment being made as a function of the position of the gas throttle of the engine. The DE-A-41 19 078 furthermore teaches to modify the hydraulic pressure only after a certain delay in case of a variation of the position of the gas throttle, thereby to take into account the delay of variation of the engine torque as a result of the new position of the throttle. The tuning of such a system to every possible practical situation is extremely complicated, and abrupt shocks or on the contrary excessive slippings cannot be avoided with certainty. The tuning of the system depends upon the correct operation of the engine and regresses as the engine and the transmission device wear.
The purpose of the present invention is to provide better control of the ratio change process involving the actuating of at least one selective coupling means.
According to the invention, the method for controlling progressive change from an old transmission ratio to a new transmission ratio in a transmission device offerin
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Anthonov Automotive Technologies B.V.
Ho Ha
Marmor Charles A
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