192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2001-04-12
2003-04-01
Rodriquez, Saul (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S085060, C192S090000, C192S03000R, C192S10900B, C192S098000
Reexamination Certificate
active
06540059
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an actuation device for a friction clutch arranged in the drivetrain of a motor vehicle between a drive unit and a transmission arrangement, the actuation device having a pressure medium force cylinder arrangement for actuating the friction clutch via a release member having a release bearing arrangement, a measuring arrangement for detecting an actual release and/or instantaneous release member position, and a control/regulating valve arrangement connected with a pressure medium source, a pressure compensation opening or a pressure compensation reservoir and the pressure medium force cylinder arrangement, the control/regulating valve arrangement arranged for actuating the pressure medium force cylinder arrangement in response to the actual release or the instantaneous release member position and on a reference release which may be predetermined.
2. Description of the Related Art
An actuation device for a friction clutch including a pressure medium force cylinder arrangement for actuating the friction clutch via a release member having a release bearing arrangement and a control/regulating valve arrangement arranged for actuating the pressure medium force cylinder arrangement is known, for example, from German reference DE 197 16 600 A1, whose disclosure is incorporated in the disclosure of the present application by reference.
With regard to the service life of drivetrains, especially in utility motor vehicles, the release bearing arrangement of the actuation device for actuating the clutch is increasingly regarded as the weakest link in the drivetrain. The life of the drivetrain is an important competitive feature for automobile manufacturers and their suppliers. It would be ideal if all components would last as long as the engine, for example, 800,000 to 1 million kilometers based on conditions prevailing in Europe. With respect to conditions in the USA, a life of more than 1 million kilometers may even be assumed.
With respect to labor costs and immobilization periods of the vehicles, the mileage up to the first engine/transmission disassembly plays an important role. Until recently, clutch facings typically had to be replaced at least once during the life of the engine because of comparatively high facing wear. When the clutch facings were replaced, the relatively inexpensive release bearing was also changed as a precaution, so that it was not until recently that any attention was paid to release bearings and the release bearings were generally constructed without sealing in spite of unfavorable operating conditions (for example, temperature and dust) and release bearings generally did not require premature repair or maintenance steps. As was also the case previously, this situation still applies to distribution vehicles and construction site vehicles in which interim replacement of facings and advisably also of release bearings is still required and practiced today. However, in long-distance transport vehicles, the clutches including the clutch facings are increasingly able to last just as long as the engine. Accordingly, the life of the release bearing is now a factor. To increase the life of the release bearing, its sealing was improved and openings provided in the clutch covers were closed insofar as practicable. However, these solutions still did not produce adequate results.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the life of the release bearing for friction clutches. To meet this object, the actuation device is adjustable or displaceable in a defined manner between a non-actuation state and an actuation state according to the present invention, wherein the release bearing arrangement is decoupled from an associated release force receiving arrangement of the friction clutch in the non-actuation state and is coupled with the release force receiving arrangement in the actuation state. The release force receiving arrangement may comprise an engagement spring arrangement.
The present invention is based on the idea and insight that the friction clutches in vehicles used in long-distance transport only run about 100 to 200 hours total operating time in the fully or partially released state. It is only during this time that the release bearing transmits the release force used for clutch actuation. During the rest of the operating time, the release bearing generally rotates at the rotational speed of the crankshaft with a preloading of approximately 2 to 3% of the maximum release force.
Assuming an engine life of about 15,000 hours in engines with more than 10 liters piston capacity (in long-distance transport, this life corresponds approximately to a traveled distance of 900,000 km assuming an average speed of 60 km, while the distance is correspondingly shorter in distribution and construction site transport because of the lower average speed), the total releasing time is about 1% of the operating period. Accordingly, the release bearing idles for 99% of the operating period and transmits engine vibrations to the release system. In Class 8 vehicles in the USA, there is an even greater incongruity between clutch transmission and idle time of the release bearing because shifting occurs without clutch actuation in this class of vehicle. The clutch is needed only for startup and shifting. Therefore, a total force transmission duration of about only 50 hours may be assumed for the Class 8 vehicles.
In this connection, the construction of the actuation device according to the present invention makes an extraordinary increase in the life of the release bearing arrangement possible. For operating periods in which the clutch is not to be actuated or in which there is no pending clutch actuation, the actuation device may be adjusted to the non-actuation state in which the release bearing arrangement is decoupled from the release force receiving arrangement with a corresponding gentler treatment of the release bearing arrangement. The actuation device only needs to be moved into the actuation state for clutch actuation and possibly for expected clutch actuation to couple the release bearing arrangement with the release force receiving arrangement. In short, the construction of the actuation device according to the invention allows the release bearing arrangement to run only when it is actually used or when clutch actuation is imminent. Consequently, the release bearing arrangement is exposed to less wear and is therefore more reliable and has a longer life.
Furthermore, the increased reliability and life of the release bearing arrangement which is achieved according to the present invention allows less complicated and therefore economical release bearing components to be used.
In addition to the advantage of increased life and the resulting increased dependability of the release bearing arrangement, the direct transmission of engine vibrations to the release system is eliminated or at least greatly reduced by adjusting the actuation device to the non-actuation state. The pressure medium force cylinder arrangement may, for example, include a pneumatic force cylinder arrangement or a pneumatic ring cylinder. Micromovements of the pressure medium force cylinder induced by engine vibrations contribute to wear of the seals acting between the pressure medium piston and cylinder. Accordingly, an increased life of the seals and accordingly a prolonging of the maintenance-free operating period of the pressure medium force cylinder arrangement is achieved by reducing or eliminating micromovements of the pressure medium force cylinder arrangement deriving from microvibrations.
However, providing a non-actuation state to which the actuation device may be adjusted requires changing the typical actuation device which may forfeit some advantages of the known actuation device. For example, the adjustment of the actuation device from the non-actuation state to the actuation state requires a certain time. Accordingly, a construction of the actuation device according to the presen
Cohen & Pontani, Lieberman & Pavane
Mannesmann Sachs AG
Rodriquez Saul
LandOfFree
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