Machine element or mechanism – Gearing – Interchangeably locked
Patent
1995-05-09
1997-03-11
Bonck, Rodney H.
Machine element or mechanism
Gearing
Interchangeably locked
192 8713, 192 8718, 192103F, F16H 6106, F16D 2510
Patent
active
056090684
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a process for controlling and regulating the load take-up in an automatic transmission.
In an automatic transmission the load take-up takes place during the gear-changing operation by mechanical or hydraulic means, such as a one-way clutch or shut-off valve. Another embodiment of the load take-up is an overlapping gear change. In such a gear change a first engaging clutch takes up the torque from a second disengaging clutch. In order that the traction is uninterrupted, the range of the pressure build-up of the first clutch and the disengaging operation of the second clutch overlap.
DE-41 14 382 has disclosed a method of clutch shifting in an automatic transmission. Here a first clutch is thrown into gear and a second clutch is released.
The problem on which the invention is based, is to make the operation of the second, disengaging clutch in an overlapping change of gear dependent on the manner in which the first, engaging clutch takes up the load to be shifted.
According to the invention, the problem is solved by the characteristic features of the first claim.
The solution according to the invention constitutes a control process. The control process offers the advantage of combining quickness and simple construction with a great measure of interference security. The control process is based on the fact that the periodic operation and pressure build-up in a first engaging clutch are known, for ex., from testing. The actual operation, the pressure build-up in the first clutch and the pressure drop in a second disengaging clutch follow the controlled standard. In order to know with certainty the load take-up point, the pressure level in the second clutch is lowered until a slight speed difference, such as <10 rpm, appears in it. Due to the pressure build-up in the first clutch, it starts transmitting a torque so that the speed difference diminishes. If said difference drops to zero, the second clutch is disengaged, since the first clutch has completely taken up the load. The load take-up point, that is, the pressure value at which the transmitted torque in the first clutch is greater than in the second clutch, remains constant.
As a result of interference levels, a temporary shifting of the take-up point can occur. Tolerances of mechanical structural parts and the temperature of the pressure medium, for ex., are interference levels. This leads to an increased friction load of the clutch discs. An improvement is obtained by superimposing a regulation on the control process.
In this regulation process, it is assumed that the periodic operation and the pressure build-up in a first clutch are unknown. A second clutch should only open completely when the first clutch can take up the load with certainty. The degree of load take-up of the first clutch is derived from a feedback value. For this purpose, during the quick loading phase of the first clutch, the pressure level in the second clutch is lowered until a constant slip value appears. At what moment and in what manner the first clutch starts transmitting a torque is detected by the change of regulating variables, clutch slippage, or speed difference. The pressure in the second clutch is lowered to the same extent as pressure builds up in the first clutch by comparing a given desired speed difference with the actual speed difference.
Combinations of both processes are advantageous. At lower temperatures of the pressure medium, the regulating process is first used. If the pressure medium has reached a higher temperature range, then a change to the control process is made. A change to the regulating process is always made when, in the control process, the speed difference increases as result of poor loading of the first clutch.
In both processes, a new signal can be generated from the value of the speed difference in the electronic transmission control. When the speed difference is zero or almost zero, said new signal can be used, for example, to change the firing angle in an electronic engine control. A change of the firing angle toward
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Danz Wolfgang
Deiss Harald
Gruhle Wolf-Dieter
Schwab Manfred
Sigg Peter
Bonck Rodney H.
ZF Friedrichshafen AB
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