Automatic clutch with emergency strategy for speed sensor failur

Details Automatic clutch with emergency strategy for speed sensor failur Automatic clutch with emergency strategy for speed sensor failur

1999-03-25

2000-05-09

Marmor, Charles A.

Machine element or mechanism

Gearing

Interchangeably locked

477906, 701 63, F16H 5900

Patent

active

06058792&

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION

The invention concerns an automatic clutch arranged between the engine and the drive train of a motor vehicle, having a transmission which is arranged on the output side of the clutch. An adjusting unit serves for releasing and engaging the clutch and is controlled by a system of sensors taking predetermined parameters into account. The system of sensors has signalling devices for the state of the transmission as well as signalling devices arranged on the input side and output side of the clutch for sensing rotational speed and controlling the engagement of the clutch as a function of differences in speed between the input and output of the clutch. A substitute signal is generated if a speed signal fails to be obtained on the output side.
Such an automatic clutch is the subject of European Patent document EP 0 241 216 A2. According to this document, the automatic clutch is combined with an automatic transmission, so that the clutch is released only when a manually actuated operating element for the transmission is brought into an idling position or the idling position is passed through when switching over between forward and reverse travel of the vehicle. To be able to synchronize the clutch during subsequent engaging, i.e. when selecting a drive position, the speed on the output side of the transmission must be known, among other things. Should the corresponding signal fail, a substitute signal can be generated by assuming that no appreciable changes have occurred since the time at which the clutch was released. Consequently, the speed on the output side can be determined from the state of the transmission, i.e. the transmission ratio, determined before release of the clutch, together with the engine speed.
If required in the case where a service brake is actuated continuously before and after the last release of the clutch, the amount of the drop in speed before releasing the clutch can be registered and the assumption subsequently made that the effect of the service brake remained essentially the same. As a result, an analogous drop in speed on the output side of the transmission with the clutch released is then assumed in calculation.
Wherever vehicles have a transmission switched manually between various transmission stages, during the change of transmission stages the power flow between the engine and the drive wheels regularly has to be interrupted by releasing a clutch.
It is known in principle to use an automatic clutch for this purpose, i.e. the clutch is automatically released when changing the transmission stage or gear and is subsequently re-engaged. With a view to increased comfort, differences in speed existing between the clutch input and clutch output may be taken into account when engaging the clutch. There is consequently the possibility, for example, of engaging the clutch with a longer slipping phase in the event of a greater difference in speed. Moreover, the difference in speed may be taken into account in an automatic engine control, if provided, in such a way that the engine speed, and consequently the speed of the input of the clutch, are made to match the speed of the output of the clutch.
German Patent document DE 40 12 595 A1 discloses a corresponding automatic clutch. According to this document, a device for detecting intended shifting is provided such that, during manual changing of the transmission stages, a signal representing the new transmission stage is generated before this transmission stage has been fully activated. In connection with the signals of a sensor sensing the speed of the transmission input, and consequently of the clutch output, the speed of the transmission input or clutch output to be expected when the new transmission stage is fully activated is then calculated. It is assumed that the vehicle does not change its travelling speed, or that it changes only insignificantly, during the change of transmission stages.
According to German Patent document DE 28 33 961 C2, it is envisaged to control an automatic clutch dur

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patent: 5983740 (1999-11-01), Salecker et al.
patent: 5992255 (1999-11-01), Fujita et al.

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