192 clutches and power-stop control – Clutches – Operators
Patent
1990-03-08
1991-11-05
Herrmann, Allan D.
192 clutches and power-stop control
Clutches
Operators
192 85CA, F16D 2500
Patent
active
050625152
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a hydraulic control device for a clutch, comprising a clutch release bearing acting on the rotary parts of the clutch and a piston acting on the ring of the clutch bearing.
Most vehicles sold throughout the world are equipped with a clutch having one or, where appropriate, more friction discs. The friction disc is mounted on the driven shaft which transmits the engine power to the wheels. The shaft is splined at the location where the disc is mounted, so as to allow this disc to slide axially along the shaft. The engine flywheel fixed to the crankshaft has a surface which corresponds to that of the disc and against which the disc is to be laid by sliding along the splines of the shaft. To ensure that the disc is laid against the flywheel, a pressure plate integral in terms of rotation with the flywheel, but axially moveable in the same way as the disc is arranged on the other side of the disc. Springs usually of the diaphragm type press this plate against the disc and lay the latter against the flywheel. In this position, the disc is clamped between the flywheel and the plate, and the mechanism is in the engaged position. Release is obtained by pulling the pressure plate rearwards. Conventionally, this movement is controlled by levers which are arranged round the plate and which are actuated as a result of the axial thrust of the clutch bearing, itself controlled by the clutch fork (in modern devices with a diaphragm spring, the bearing acts directly on that part of the diaphragm spring performing the function of a lever). In turn, the clutch fork which is a lever is usually actuated by a hydraulic piston which acts under the pressure of a fluid delivered by way of a pipe by a master cylinder itself actuated by the clutch pedal.
This mechanism of universal use has the advantage of being widely tried and tested. However, it has a size disadvantage: the assembly formed by the bearing, fork and release cylinder comprises numerous components which result in a relatively high price and which cause many maladjustments; these maladjustments give rise to various noises and require resetting, thereby incurring expense.
To overcome these disadvantages, various mechanisms have been provided, all based on the same principle: instead of the convention bearing actuated by a fork, there is arranged around the tube surrounding the driveshaft a cylinder which is concentric relative to this tube and in which or round which slides a piston likewise concentric relative to the tube, the piston or cylinder acting on the levers which control the movement of the plate. The relative movement of the piston and of the cylinder is controlled directly as a result of the introduction of fluid under pressure coming from the hydraulic master cylinder actuated by the clutch pedal.
Of the various solutions of this type, the patent application Nos. PCT/US87/02641 (publication WO 88/03235), European Patent Application Nos. 0,119,784 and 0,092,823, French Patent Application No. FR 7,630 128 and French Patent Nos. FR 7,226,979, FR 7,227,714, FR 1,521,148, FR 1,551,796 and FR 1,556,578 may be mentioned.
As a general rule, these devices are of somewhat complex construction. Thus, most have flexible skirts or diaphragms ensuring sealing between the cylinder and the piston or relative to the outside. At all events, they require an adaptation of at least one part of the clutch for which they are intended. For example, the device described in the application No. PCT/US87/02641 has to be fastened to the clutch housing or to a fixed tube surrounding the driveshaft, these two components having to be modified.
There is no doubt that the reason why the above-mentioned devices have never been mounted on mass-produced vehicles is that it is necessary to modify components produced in large series, this modification involving considerable investment.
The use of diaphragms or membranes to ensure sealing between the cylinder and the piston is another cause of an increase in cost of the construction which has certai
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Herrmann Allan D.
Schneider Walter H.
Whitelaw Nicholas
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