192 clutches and power-stop control – Clutches – Operators
Patent
1990-10-19
1991-10-29
Lorence, Richard
192 clutches and power-stop control
Clutches
Operators
192 91R, 60533, F16D 2512, B60K 2302
Patent
active
050607766
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an arrangement for controlling a hydraulically operated friction disk clutch that is provided with a diaphragm spring, the control being provided through an operating unit including a hydraulic piston that acts on the diaphragm spring to release the engagement of the clutch disks. The hydraulic piston is controlled by a pressure medium which in turn is controlled by a control signal proportional to the extent of the disengagement of the clutch disks. The invention particularly relates to a spring associated with the hydraulic piston and which comes into action to control the releasing motion of the diaphragm spring as the hydraulic piston shifts.
BACKGROUND OF THE INVENTION
For operating a conventional friction clutch between an engine and a transmission box in, for example, a motor vehicle, it is already known to use hydraulic operating mechanisms with a master cylinder actuated by the clutch pedal and a slave cylinder located at the clutch. This cylinder either pulls or exerts pressure on a spring-compressed disc clutch for disengagement. A pressure clutch of this type is shown, for example, in U.S. Pat. No. 3,489,257.
However, development of clutch systems, especially for motor vehicles, is moving towards more or less automated clutch functions. In automated clutch systems an electronic control unit can regulate the entire engagement and disengagement procedure, so that the clutch at all times acquires an optimum slippage function at each speed difference which can occur between the input shaft and the output shaft of the clutch. An automated clutch can also regulate the slippage level in the clutch in order to achieve damping of torque pulses. This technique is described in, for example, U.S. Pat. Nos. 4,253,414 and 4,457,411.
A majority of motor vehicle clutches comprise a diaphragm spring pressing the friction discs together. A solution for disengaging friction disc clutches held together by a diaphragm spring is previously disclosed in GB Patent No. 2,117,076 corresponding to U.S. Pat. No. 4,878,396. In this respect use is made of an electric motor of the low output type, for example a windscreen wiper motor, which is able to disengage the friction disc clutch by means of a compensating spring arrangement acting over the entire disengagement stroke. The compensating springs provide a force counter-acting the diaphragm spring, which force follows the force and deflection characteristic of the diaphragm spring over the entire stroke. In this way the power requirement of the electric motor can be kept low, by which means it is possible, with a small and inexpensive motor, to obtain a system which is suitable for an automated clutch function. However, the compensating spring construction is relatively complicated, since the diaphragm spring does not have a linear force and deflection characteristic over the entire disengagement stroke. Moreover, the system does not have the same quick response of a hydraulic system.
The advantage of a disc clutch held together by a diaphragm spring is that the axial dimension of the clutch can be kept low. In the case of a conventional manually effected disengagement, there is also a decreased power requirement at the end of the disengagement movement. In this way the driver can hold the clutch pedal down in the bottom position for a longer period of time without becoming tired. The diaphragm springs which are present in clutches in today's cars also afford an extremely reliable and functional clutch at a reasonable cost and with an extremely long service life of the diaphragm spring itself.
SUMMARY OF THE INVENTION
The object of the present invention is to provide for an automated hydraulic operating of a friction disc clutch held together with a diaphragm spring and with a simple hydraulic piston cylinder. In order to automate a hydraulically operated diaphragm spring clutch, the system can be modified so that, at each specific operating pressure, the clutch acquires a predetermined disengagement degree. This eliminates the need for expe
REFERENCES:
patent: 2593192 (1952-04-01), Rockwell
patent: 2967396 (1961-01-01), Staadt
patent: 3709340 (1973-01-01), Murakami et al.
patent: 3752282 (1973-08-01), Espenshied
patent: 4878396 (1989-11-01), Grunberg
Abstract of EP 158 004 corresponding to DE 34 13 983.
Nordling Tommy
Skog Lars
Svenke Per-Ola
Lorence Richard
Saab Automobile Aktiebolag
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