192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
1998-09-14
2001-08-07
Bonck, Rodney H (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S03000R, C192S090000
Reexamination Certificate
active
06269926
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns friction clutches, notably for motor vehicles, including on the one hand a clutch engagement device comprising a diaphragm bearing on a cover, fixed to a flywheel for driving in rotation, for action on a thrust plate and clamping the friction linings of a friction disc between the thrust plate and the driving flywheel and on the other hand a linkage for acting in an opposing fashion on the internal end of the diaphragm, an actuator for controlling the said linkage, and an adjustment device, referred to as a device for taking up wear, for compensating for the wear on the friction linings, in which the actuator has manoeuvring means with an electric motor, a mechanical transmission with an input element formed by the output shaft of the electric motor, an output element for acting on the linkage, elastic assistance means acting between a fixed part and an element of the transmission in order to act in an opposing fashion with respect to the diaphragm so that the electric motor provides only a small force for disengaging the clutch.
For example (
FIG. 1
) the actuator has an electric motor
50
acting on a mechanical transmission
60
having pinions and a toothed sector to which is attached a coil spring
70
constituting the elastic assistance means.
The linkage
80
has a fork connected to the toothed sector and a clutch release bearing acting on the internal end of the fingers of the diaphragm mounted pivotally on the base of the cover
2
by means of assembly means
8
having a primary support formed by pressing in the base of the diaphragm and a spring ring forming a secondary support opposite the primary support.
The spring ring, in a known fashion, is carried by lugs formed by cutting and bending in the base of the cover, the said lugs passing through the diaphragm
3
having in a known fashion a peripheral part in the form of a Belleville washer extended radially inwards by a central part divided into radial fingers by slots. The Belleville washer constitutes the clutch engagement means, whilst the radial fingers form the clutch disengagement means.
The external periphery of the diaphragm
3
bears on the thrust plate
1
in order to clamp the friction linings of the friction disc
6
between the thrust plate
1
and the driving flywheel
102
fixed, in a manner which cannot be seen, to a driving shaft, whilst the friction disc
6
has centrally a fluted hub cooperating with the flutes on a driven shaft
101
passing through the aforementioned clutch release bearing. Thus referred to the clutch release bearing, the characteristic curves of
FIG. 2
are obtained, in which the X-axis C corresponds to the travel of the clutch release bearing in mm and the Y-axis E to forces in newtons.
The curve A corresponds to the load on the clutch release bearing, the curve B to the opposing load of the elastic assistance means and the curve D to the force developed by the electric motor.
The elastic assistance means store the energy of the diaphragm
3
during the clutch engagement operation and restores it, usually more quickly, at the time of the declutching operation.
Thus the electric motor supplies only the difference between the force of the diaphragm and the force of the elastic assistance means.
In addition, as described in the document FR-A-2 564 921, a device for taking up wear is provided, making it possible to reduce the travel of the elastic assistance means, thus affording excellent behaviour of these elastic means, which can thus be located conveniently in the actuator.
Nevertheless it may be desirable to reduce the cost of the actuator still further and to simplify the latter still further whilst having a robust and compact design.
The object of the present invention is to meet these requirements.
SUMMARY OF THE INVENTION
According to the invention a friction clutch of the above-mentioned type is characterised in that the elastic assistance means bear on a fixed part and on a part which is movable in translation and fixed in rotation forming a nut for cooperating with the output shaft of the electric motor, forming a screw, movable in rotation and fixed in translation, in that the movable part forms the output element of the mechanical transmission whilst being able to act on the linkage and in that the device for taking up wear is mounted within the declutching device.
By virtue of the invention the linkage and the actuator of the electromechanical type are simplified since the device for taking up wear is mounted within the clutch engagement device, which makes it possible to increase the service life of the said clutch, whilst having a stable and roughly constant position for the declutching means, such as a diaphragm, when the clutch is in the engaged position.
The actuator is simplified since it has no toothed sector and pinion. It is also light.
In one embodiment the elastic assistance means consist of a simple coil spring surrounding the nut, which makes it possible to reduce costs and to make the actuator compact and robust.
In another embodiment the elastic assistance means have recourse to a mounting of Belleville washers in series.
Mounting the Belleville washers in series makes it possible to easily reproduce the characteristic curve of the diaphragm in association with the driving system of the nut and screw type formed by the movable part and the output shaft of the electric motor.
In addition, during the declutching operation, it is possible to have sufficient travel because of the mounting in series of the said washers compressed when the clutch is engaged and sloping during the declutching travel of the clutch.
The actuator is thus compact and robust and of reduced cost, its mechanical transmission being simplified.
In one embodiment the actuator has a casing fixed to a plate serving as a support for the electric motor, the casing/plate assembly forms a housing mounted on a fixed part.
The threaded output shaft of the electric motor enters the said casing and the movable part, forming a nut, of the mechanical transmission. This nut can be connected with respect to rotation to a sleeve on the housing, with the possibility of axial movement for example by a connection of the mortice and tenon type. The nut carries a movable support for the coil spring or Belleville washers, whilst the plate or casing carries a fixed support for the said spring or the said Belleville washers.
Force transmission means can easily be located between the external and respectively internal peripheries of the Belleville washers. These force transmission means are guided in a simple and economical fashion respectively by the casing and the nut. The actuator is thus very inexpensive whilst being reliable, and of a simple, robust and compact form. The risks of jamming are reduced.
The nut acts either by pulling or by pushing on the linkage, which may include in a conventional fashion a release fork acting on the clutch release bearing. In a variant this linkage has a hydraulic control with a receiver whose piston acts on the clutch release bearing and a sender whose piston is controlled by the nut of the actuator. The receiver is, in this case, of the concentric type, whilst having the driven shaft passed through it centrally. The nut can act on a cable of the linkage.
As a variant the electric motor can be mounted on a plate fixed to the cover of the clutch, as described in the document FR-A-2 580 753.
In all cases the actuator forms an assembly which can be handled and transported easily and fitted easily because of its small size.
In another embodiment the output shaft of the electric motor drives a phonic wheel associated with a Hall-effect sensor for measuring the movement of the movable part. It is even possible to mount the power electronics in the casing.
REFERENCES:
patent: 4586401 (1986-05-01), Nogle
patent: 4865173 (1989-09-01), Leigh-Monstevens et al.
patent: 4878396 (1989-11-01), Grunberg
patent: 5267635 (1993-12-01), Peterson et al.
patent: 5353902 (1994-10-01), Flowtow et al.
patent: 5704460 (1998-01-01), L
Boclet Jacques
Graton Michel
Lebas Gilles
Lemoine Benoit
Randriazanamparany Veve R.
Bonck Rodney H
Liniak Berenato Longacre & White
Valeo
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