192 clutches and power-stop control – Clutches – Axially engaging
Reexamination Certificate
2000-05-23
2002-01-01
Marmor, Charles A. (Department: 3681)
192 clutches and power-stop control
Clutches
Axially engaging
C192S111400
Reexamination Certificate
active
06334521
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns friction clutches, notably for motor vehicles, and relates more particularly to the unitary assembly which such a clutch has, described for example in the documents FRY-A-2 242 892 and FRY-A-2 420 690. Such a unitary assembly is referred to as a clutch mechanism.
2. Description of the Related Art
Conventionally, a friction clutch has a driving flywheel, possibly in two parts in order to form in particular a torsion damming flywheel or a flexible flywheel. The driving flywheel has a reaction plate.
The driving flywheel is fixed with respect to rotation to a first shaft, such as a driving shaft, namely the crankshaft of the internal combustion engine in the context of an application to a motor vehicle.
The reaction plate has a friction face on the back and is fixed with respect to rotation to a pressure plate able to move axially with respect to the reaction plate.
This pressure plate has on the front a friction face opposite that of the reaction plate.
The friction linings of a friction disc are interposed between the pressure and reaction plates, or more precisely between the friction faces thereof, forming friction tracks.
These linings are fixed to a support, usually elastically deformable axially in order to form a progressive friction disc affording assistance during the declutching operation. This support, possibly duplicated, is rigidly or elastically connected to a hub fixed with respect to rotation to a second shaft, such as a driven shaft, namely the input shaft of a movement transmission, for example a gearbox, in the context of an application to a motor vehicle. As a variant, the support is embedded in a friction lining. In all cases, the friction disc has at its external periphery two friction faces which wear during the service life of the clutch.
When the friction lining or linings are clamped between the pressure and reaction plates (clutch engaged), the torque is transmitted from the driving shaft to the driven shaft via the friction disc. When the friction linings are not clamped between the said plates (clutch disengaged), the driven shaft is not driven by the driving shaft. To do this, axially acting engagement means are provided and form an assembly with disengagement means designed to counteract as required the action of the engagement means bearing on a cover for action on the pressure plate, or more precisely for action on support means carried by the pressure plate fixed with respect to rotation to the cover whilst being able to move axially with respect to the latter, for example by means of a connection with axially elastic tongues or by means of a connection of the mortice and tenon type; radial lugs—forming tenons—on the pressure plate being engaged for axial sliding in grooves—forming mortices—in the cover.
This cover has at its external periphery fixing means for fixing it to the reaction plate detachably or non-detachably.
The engagement means include at least one Belleville washer and the disengagement means of the disengagement levers for action on the disengagement means. Usually these engagement and disengagement means belong to the same axially elastic piece referred to as the diaphragm. This diaphragm, frustoconical in shape in the free state, has a peripheral part in the form of a Belleville washer, extended radially towards the centre by a central part divided into radial fingers by blind slots with broadened bottoms to form broadened orifices at the internal periphery of the Belleville washer constituting the axially acting engagement means, whilst the radial fingers form disengagement levers and therefore the clutch disengagement means.
In the documents FRY-A-2 242 892 and FRY-A-2 420 690, the cover constitutes, with the pressure plate, the elastic tongues and the diaphragm, a unitary assembly called a clutch mechanism, which is attached to the reaction plate. Naturally this clutch mechanism can constitute, with the friction disc and reaction plate, a module which is attached in a unitary fashion to the crankshaft of the vehicle engine or to a flange fixed to the crankshaft, the reaction plate then being fixed to the flange, advantageously flexible.
SUMMARY OF THE INVENTION
This mechanism is advantageously equipped with a compensation device, referred to as a wear take-up device, in order to compensate for the wear on the friction lining or linings and the friction faces of the pressure and reaction plates so that the diaphragm has a substantially constant position when the clutch is engaged, and this throughout the service life of the friction clutch. The diaphragm thus exerts a substantially constant load on the pressure plate in the clutch-engaged position. The travel of the clutch release bearing, acting on the internal end of the fingers of the diaphragm, is, in a known manner, substantially constant during the disengagement operation.
This wear take-up device has ramps and counter-ramps acting between the pressure plate and the support means of the diaphragm or between the diaphragm and the cover.
A trigger, sensitive to the state of wear on the friction lining or linings, makes it possible to make the ramps turn in the event of wear so that the diaphragm always occupies the same position when the clutch is engaged under the action of the engagement means (linings clamped).
The trigger has, in one embodiment, a ratchet wheel and a worm system, forming part of a cartridge as described in the document FR-A-2 753 503.
More precisely, an elastic member is provided with a control tongue cooperating with the teeth on the ratchet wheel and a non-return catch.
In the event of wear, the control tongue is maneuvered by an actuator, in this case an appendage of the diaphragm, in order to cause the ratchet wheel to turn and compress a take-up spring allowed subsequently to expand. A non-return catch prevents the worm from turning in the opposite direction, notably when the spring expands. The worm comes into engagement with the set of teeth integral with a ring provided with ramps for cooperating with counter-ramps fixed to the pressure plate.
Thus, in the event of wear, the thickness of the pressure plate, composed of the pressure plate proper and the ring with ramps, is increased, the said ring carrying support protrusions constituting the support means for the engagement means.
The ring therefore comes into engagement directly with the worm.
Such an arrangement gives satisfaction, but nevertheless the applicant has wondered whether it is not possible to eliminate the non-return catch in order to simplify the elastic member.
According to the invention, an engagement mechanism of the above indicated type is characterised in that the set of teeth belong to an intermediate piece connected with respect to rotation to the ring with ramps by means of connecting with respect to rotation allowing an axial movement of the ring with ramps with respect to the intermediate piece.
By virtue of the invention, the non-return catch can be omitted because the set of teeth is solely coupled in rotation to the ring with ramps by the intermediate piece and because the worm can drive the set of teeth in rotation but not vice-versa, the connection being of an irreversible design. Because the set of teeth is not axially connected to the ring with ramps and is therefore not driven by the latter during engagement and disengagement operations, the connection between worm and set of teeth can be reversible. The intermediate piece is axially fixed overall and consists for example of a washer. By virtue of the invention, the presence of a ratchet wheel and control tongue is no longer obligatory. This is because the appendage on the diaphragm can enter a recess in a drum as described in the document FR-A-2 424 442.
In one embodiment, the connection is of the cooperation of shapes type with circumferential mounting clearance and the elastic tongues rotatably connecting the pressure plate to the cover are used for gripping a washer, constituting the intermediate piece, between two tongue
Blard Michel
Dalbiez Andre
de Briel Jacques Thirion
Liniak Berenato Longacre & White
Marmor Charles A.
Rodríguez Saúl
Valeo
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