192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2000-12-08
2002-05-28
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S090000
Reexamination Certificate
active
06394253
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to improvements in fluid-operated motors in general, and more particularly to improvements in apparatus which can be utilized in the power trains of motor vehicles to change the condition of engageable-disengageable torque transmitting devices. Still more particularly, the invention relates to improvements in apparatus which can be utilized with advantage to change the condition of friction clutches serving to establish or to interrupt a torque transmitting connection between a prime mover (such as an internal combustion engine) and a transmission or another torque-receiving unit in the power train of a motor vehicle.
In many presently utilized types of motor vehicles, the clutch actuating apparatus comprises a first hydraulic cylinder and piston unit known as slave cylinder and serving to disengage the friction clutch in response to shifting of its piston relative to its cylinder (hereinafter called housing) as a result of admission into the housing of a flow of pressurized hydraulic fluid from a second hydraulic cylinder and piston unit known as master cylinder. Reference may be had, for example, to commonly owned U.S. Pat. No. 5,632,706 granted May 27, 1997 to Kremmling et al. for “MOTOR VEHICLE WITH ELECTRONIC CLUTCH MANAGEMENT SYSTEM”. In the patented power train, the piston of the slave cylinder is arranged to pivot a lever serving to shift a release bearing which is arranged to change the conicity of a diaphragm spring forming part of the friction clutch and serving to urge a pressure plate against the friction linings of a clutch disc as long as the clutch is engaged. The diaphragm spring is free to reengage the clutch as soon as the piston of the slave cylinder is free or is caused to return to its retracted position in the housing of the slave cylinder. When the clutch is engaged, it causes or enables the output shaft (such as a crankshaft or a camshaft) of the engine to transmit torque to a change-speed transmission so that the latter can transmit torque to the front and/or rear wheels of the motor vehicle, e.g., by way of a differential.
The slave cylinder is or can be coaxial with the output shaft of the engine, and its housing can be separably mounted on the case of the transmission. The piston of the slave cylinder can constitute an annular member which is slidable in an axial bore or hole of the housing and slidably surrounds a sleeve-like guide which is sealingly and fixedly (such as non-rotatably and/or non-shiftably) affixed to the housing and/or to another stationary part, e.g., to the transmission case. The piston, the housing and the sleeve-like guide (hereinafter called guide for short) define an annular plenum chamber which can receive pressurized hydraulic fuid (such as oil) from the master cylinder. The rear end portion of the piston carries an annular sealing member which is in sealing engagement with but can slide along the internal surface of the housing as well as along the external surface of the guide. The front end portion of the piston carries or indirectly transmits motion to a release bearing which can disengage the friction clutch in response to admission of pressurized hydraulic fluid into the plenum chamber of the slave cylinder. As already mentioned above, the release bearing can be coaxial with the output shaft of the engine and with the diaphragm spring of the clutch, or it can change the conicity of the diaphragm spring by way of a lever (e.g., the so-called clutch fork).
A slave cylinder of the just outlined character is described and shown, for example, in published German patent application Ser. No. 43 13 346 A1. The guide is made in accordance with a non-cutting shaping technique (e.g., in a deep drawing machine) and one of its ends is provided with a flange adjacent the transmission case and form-lockingly connected with the housing of the slave cylinder. The flange can also serve as a boundary for one end of the annular plenum chamber of the slave cylinder. In addition, an axially projecting part of the flange can perform a centering function in that it extends into a complementary recess of the housing.
When the slave cylinder is properly assembled, the annular flange of the guide is clamped between the transmission case and a part of the clutch disengaging unit to thus hold the guide in a predetermined axial position. The means for establishing a seal between the guide and the housing of the slave cylinder comprises an annular seal which is radially offset relative to the annular plenum chamber. When such annular seal is acted upon by pressurized hydraulic fluid, it provides a relatively large effective pressurized surface extending from the external surface of the guide to the seal, i.e., radially of and well beyond the cross-sectional area of the plenum chamber. This causes the housing of the slave cylinder to undergo a pronounced stress. Therefore, the dimensions of the housing must be increased accordingly and/or the quality of the material of the housing must be selected with a view to ensure that the slave cylinder and its parts will be capable of withstanding the developing stresses (particularly deforming stresses), preferably during the entire useful life of the power train.
Other presently known types of slave cylinders for use in the power trains of motor vehicles are disclosed in pubished UK patent application Serial No. 2 259 555 of Grosspletsch et al., in published French patent application Serial No. 2 597 590, and in published European patent application Serial No. 0 168 932. The disclosure of the commonly owned German priority application Serial No. 198 25 965.4 (filed Jun. 10, 1998) as well as that of each U.S. and/or foreign patent and/or patent application identified in the specification of the present application is incorporated herein by reference.
OBJECTS OF THE INVENTION
An object of the invention is to provide a slave cylinder wherein the sealing device(s) between the constituents of the slave cylinder is or are simpler, more compact and less expensive than, but at least as reliable as, in presently known slave cylinders.
Another object of the invention is to provide a slave cylinder wherein the seal between the tubular guide and the housing is constructed, assembled and installed in such a way that these parts are not subjected to stresses which would necessitate the utilization of bulkier and/or otherwise more expensive parts.
A further object of the invention is to provide a novel housing and a novel tubular guide for use in the slave cylinder of a clutch disengaging system in the power train of a motor vehicle.
An additional object of the invention is to provide a novel and improved disengaging unit for the friction clutches of power trains in motor vehicles.
Still another object of the invention is to provide a novel and improved method of establishing one or more seals between selected constituents of the clutch actuating apparatus in the power train of a motor vehicle.
A further object of the present invention is to provide a novel and improved arrangement of confining and locating one or more sealing elements between the constituents of a slave cylinder in a clutch engaging-disengaging assembly forming part of the clutch actuating apparatus in the power train of a motor vehicle.
SUMMARY OF THE INVENTION
The invention is embodied in a fluid-operated apparatus which can be utilized as a clutch actuating apparatus in the power train of a motor vehicle, for example, in a power train wherein a shaft (such as the output shaft of an engine or another prime mover or the input shaft of a change-speed transmission or another torque-receiving unit) is rotatable about a predetermined axis. The improved actuating apparatus can constitute a slave cylinder which is actuatable to engage and/or disengage a friction clutch and comprises a support (such as the case of a change-speed transmission), a housing or cylinder which is separably or more or less permanently mounted on the support and has a cylindrical internal surface coaxial with and spacedly surrounding
Adler Dieter
Meyer Gerhard
Winkelmann Ludwig
Darby & Darby
Lorence Richard M.
LuK Lamellen und Kupplungsbau GmbH
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