192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2000-12-07
2002-10-29
Rodriguez, Saul (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S090000, C091S388000, C091S403000
Reexamination Certificate
active
06471025
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an actuating device for a friction clutch arranged in the drive train of a motor vehicle, in particular a commercial motor vehicle, between an internal combustion engine and a gear unit. The actuating device includes a disengagement bearing arrangement for actuating the friction clutch, and a positioning servo arrangement with a pressure-medium power cylinder arrangement which acts on the disengagement bearing arrangement and which is capable of being actuated, via a control valve connected to a pressure-medium source, as a function of a command quantity representing a desired position and of an actual quantity representing a position of the disengagement bearing arrangement. The control valve comprises a valve arrangement which is capable of being adjusted between a first control state connecting the pressure-medium power cylinder arrangement to the pressure-medium source and a second control state connecting the pressure-medium power cylinder arrangement to a first pressure compensating orifice. The valve arrangement is capable of being changed over between the two control states as a function of the actual quantity and of the command quantity, preferably as a function of a differential quantity assigned to the actual quantity and to the command quantity.
2. Description of the Prior Art
An actuating device of this type is known, for example, from German reference DE 197 16 600 A1, to which reference is made as “reference document 1” and the disclosure content of which is incorporated herein by reference. Further actuating devices of this type are known from German reference DE 197 16 641 A1 (reference is made to this as “reference document 2”), German reference DE 197 14 226 A1 which corresponds to U.S. Pat. No. 5,950,788 (reference is made to this as “reference document 3”) and German reference DE 198 00 232 A1 (reference is made to this as “reference document 4”). The disclosure of reference documents 2, 3 and 4 is likewise incorporated by reference in the disclosure of the present invention description.
Irrespective of the design of the control valve (reference documents 1 to 4 disclose various possibilities for designing the positioning servo arrangement and the control valve), it was shown that the positioning behavior of actuating devices of this type is unsatisfactory in many respects. Thus, there needs to be an improvement in the positioning accuracy and in the response behavior along the lines of a more direct response. In particular, there was shown to be a hysteresis behavior of the positioning servo arrangement in the assignment of the desired position and actual position, with so-called “play during extension” and “play during retraction” (generally a regulating travel play). The time response behavior of the known positioning servo arrangements also could not satisfy all requirements. The limitations in the performance of the known actuating device would seem to be attributable at least partially to static friction and sliding friction in the disengagement bearing arrangement and/or the pressure-medium power cylinder arrangement and/or between components, moved relative to one another, of the control valve or, in general, of the positioning servo arrangement and are also reflected in the magnitude of a minimum regulating increment which the positioning servo arrangement has and which does not satisfy all requirements.
SUMMARY OF THE INVENTION
By contrast, an object of the present invention is to provide an actuating device of the type initially mentioned, which allows improvements to the problems mentioned. In order to achieve this object, it is proposed that there be provided, in a pressure-medium subsystem comprising the pressure-medium power cylinder arrangement and the control valve, a second pressure compensating orifice which, at least when the positioning servo arrangement is in a holding state, permits a defined second pressure-medium pressure compensating flow smaller than a first pressure-medium pressure compensating flow permitted by the first pressure compensating orifice in the second control state, in order to influence at least one positioning behavior of the positioning servo arrangement.
To be precise, it was shown, surprisingly, that a measure which per se is extremely simple, namely the provision of a defined leak in said pressure-medium subsystem, for example in the pressure-medium power cylinder arrangement and/or in a pressure-medium connection connecting the control valve to the pressure-medium power cylinder arrangement and/or in a portion of the control valve located on the same side as the pressure-medium power cylinder arrangement, is sufficient to influence the positioning behavior of the positioning servo arrangement for adaption to requirements to be fulfilled. It is possible, for example, for a response behavior of the positioning servo arrangement to be improved, for example to the effect of reducing an idle time assigned to the positioning servo arrangement. Furthermore, it is possible, by means of the second pressure compensating orifice, to reduce a minimum regulating increment of the positioning servo arrangement and/or to reduce a regulating error of the positioning servo arrangement. It is particularly important, for many driving situations, that the second pressure compensating orifice can act with the effect of reducing a regulating hysteresis of the positioning servo arrangement and/or can reduce a regulating travel play of the positioning servo arrangement.
According to current knowledge, the observed modification, particularly the improvement in the response behavior of the positioning servo arrangement by means of the second pressure compensating orifice, is independent of the design of the positioning servo arrangement and especially of the control valve in particular. For example, the valve arrangement of the control valve may be capable of being adjusted as a function of the differential quantity into a third control state, in which the pressure-medium power cylinder arrangement is not connected either to the pressure-medium source or to the first pressure compensating orifice. Also, according to current knowledge, the modification or improvement in the response behavior by means of the second pressure compensating orifice is independent of the operating principle of the positioning servo arrangement and especially of the control valve.
In general, it is proposed that, in the case of a valve arrangement capable of being adjusted into the third control state, the second pressure compensating orifice permits the second pressure-medium pressure compensating flow in the third control state and preferably in the first control state and/or in the second control state, and that, in the case of a valve arrangement capable of being adjusted only between the first control state and the second control state, the second pressure compensating orifice permits the second pressure-medium pressure compensating flow at least in the first control state, preferably in the first control state and in the second control state.
The pressure medium may be a hydraulic or pneumatic pressure medium. In the case of a hydraulic pressure medium, the pressure-medium source is then in the form of a hydraulic source. In the case of a pneumatic pressure medium, the pressure-medium source is in the form of a pneumatic source. A pneumatic overpressure source is intended, in particular, here, which discharges a pressure higher than ambient pressure. However, a pneumatic underpressure source also comes under consideration, which serves for generating in the pressure-medium power cylinder arrangement an underpressure which is lower than ambient pressure.
It was possible to show the effectiveness of the idea of the invention, in terms of influencing and optimizing the positioning behavior of the positioning servo arrangement, by means of various positioning servo arrangements, especially by means of various control valves. Furthermore, it was possible to demonstrate the effect
Cohen & Pontani, Lieberman & Pavane
Mannesmann Sachs AG
Rodriguez Saul
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