192 clutches and power-stop control – Clutches
Reexamination Certificate
1999-07-19
2001-03-27
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
C192S070180, C116S208000
Reexamination Certificate
active
06206158
ABSTRACT:
SUMMARY OF THE INVENTION
1. Field of the Invention
The invention is directed to a device for a clutch which is subject to wear brought about by friction, especially for motor vehicles, for signaling that a wear limit has been reached. The clutch has a pressure plate which is connected, via tangential leaf springs, with a clutch housing so as to be fixed with respect to rotation relative to the clutch housing, but so as to be axially displaceable, and by means of which pressure plate a clutch disk provided with friction linings can be pressed against a flywheel of an internal combustion engine or the like.
2. Discussion of the Prior Art
German reference DE 26 40 088 A1 discloses a device for determining abrasion in a clutch disk lining in which the axial position of the thrust plate is detected by a sensor. For this purpose, there is affixed to the thrust plate a marking which is formed of two marks adjoining one another in the circumferential direction of the thrust plate and extending in the axial direction of the clutch and a third mark connecting the front end of one mark with the rear end of the other mark so that the marking has a Z-shape. An inductive sensor is inserted into an opening of the clutch housing. The sensor and the marking are oriented relative to one another in such a way that the effective direction of the sensor covers a center line of the Z-shaped marking when the clutch is engaged and the friction lining is new. An evaluating unit having a display unit is connected with the sensor. The wear of the friction linings is determined in a continuous manner with this complex device.
German reference DE 29 16 807 A1 discloses a distance sensing device for a friction clutch in which pins supported against a pressure spring are inserted in the flywheel of the internal combustion engine. The movement of a pin is transmitted, via a lever, to a ring which is movable in the axial direction and which cooperates with a proximity switch arranged in a stationary manner in the clutch housing. When the clutch is closed, the pins are pressed by the clutch disk into the flywheel against the force of the pressure spring. This distance sensing device is used, especially in trucks, for detecting the exact cutoff point or action point when closing the clutch in order to reduce the shifting times of the pneumatically actuated clutch, because the clutch can be further actuated quickly initially and then slowly after contact for engagement of the clutch. Wear of the friction lining of the clutch disk can only be taken into account by these sensors during engagement of the clutch but cannot be determined.
It is also known to take a reading of lining wear by means of marks on the actuating system. A path measurement is also carried out by means of a moving coil at the concentric slave cylinder.
In view of the extended warranty periods aimed for by vehicle manufacturers, it is desirable to have a device for determining lining wear in a clutch so that the clutch disk can be exchanged in a timely manner without the need for periodic visual inspection. In this way, friction lining wear can be continuously determined, monitored and displayed. It is also possible to detect only the limit of maximum permissible lining wear, which limit, when reached, is displayed via a signal device.
Realization of systems in which wear of the friction linings is continuously determined and displayed is very costly. In order to prevent errors, a complicated electronic circuit is needed. Such devices are not only expensive, but also prone to malfunction.
The path or distance marks on the actuating system are read at intervals during maintenance. The path of an actuating element is indicated. Tolerances and play between the worn lining and this actuating element or the indicator cannot be eliminated and consequently undermine the results, which in the worst possible case can lead to the mark remaining in the positive range when the maximum permissible wear has already occurred or is immediately impending.
The path of the clutch release bearing or throwout bearing, and not the lining wear directly, is determined by the moving coil at the concentric slave cylinder. However, the path of the throwout bearing is influenced by temperature variations. Consequently, the measurements are not exact. Moreover, the axial play as well as the wobble impact of the flywheel falsify measurement.
SUMMARY OF THE INVENTION
Proceeding from this statement of the problem, it is an object of the present invention to provide a device which can signal that a maximum permissible wear limit of the friction linings has been reached without the disadvantages of the known devices mentioned above.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a device of the type mentioned above having two structural component parts which can be braced or clamped against one another, one of which structural component parts is arranged so as to be movable in the radial direction and the clamping can be canceled when a wear limit is reached. Preferably, the clamping can be cancelled through force acting on one of the structural component parts which springs the movable structural component part into another radial position and the movable structural component remains there.
As a result of this construction, when the wear limit is reached, the movable structural component part occupies a different radial position which can be detected. Detection can be carried out optically or electrically via a sensor. It is also possible that the structural component part swings away, severs a thread, wire or the like and triggers a signal to the driver of the vehicle which indicates that the wear limit has been reached.
Due to the fact that only a few structural component parts are needed which are not exposed to wear for the life of the clutch since a relative movement is only possible when the friction linings are worn, the device according to the invention is very simple and accordingly inexpensive to build. Further, due to the fact that the clamping must be disengaged mechanically, the functioning of this device is extremely dependable.
With the device according to the invention, axial and radial play and wobbling of a flywheel have no effect on the releasing of the movable structural component part. Also, due to the purely mechanical construction without the intermediary of additional structural component parts, temperature is not expected to influence signaling. No adjustment is necessary when assembling. The lining wear is measured directly. Furthermore, the device requires no maintenance and displays only two states (good or bad).
The structural component parts which can be clamped against one another can be fastened to a pressure plate or to a clutch housing.
One structural component part is preferably a spring clip with a finger which projects in the direction of the flywheel and which has a projection or a flag extending essentially vertical to the finger. When the wear limit is reached, the finger runs against the flywheel so that the clamping relative to the other structural component part is canceled, the clip springs back and the resulting changed radial position of the flag can be detected. The cancellation of the clamping need not be carried out in a sudden manner, but can be introduced gradually by a (radial) displacing movement of the finger.
The two structural component parts can be connected with the pressure plate or with the housing via a fastening rivet for the tangential leaf springs.
In another embodiment, it is also possible for one structural component part to be a spring clip with a free end in the direction of the pressure plate, this free end being clamped against the other structural component part. The spring clip has a flag and the pressure plate is provided with an axial projection which stops against the free end and, when the wear limit is reached, the clamping relative to the other structural component part is canceled, the clip springs back and the resulting cha
Greubel Marco
Hirschmann Frank
Muller Roland
Ziegler Erwin
Cohen & Pontani, Lieberman & Pavane
Lorence Richard M.
Mannesmann Sachs AG
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