FR2814515A1 - ANNULAR PRESSURE PLATE FOR A FRICTION CLUTCH AND CLUTCH PROVIDED WITH SUCH A PRESSURE PLATE - Google Patents

Abstract

Pressure plate for a friction clutch, characterized in that the plate (30) is essentially annular.The external radial zone (38) of the plate (30) has a rigidity different from its internal radial zone (37), and the ratio between the rigidities of the external radial zone (38) and of the internal radial zone (37) is adjusted according to the outline and / or the material of the external radial zone (38) and the internal radial zone (37).

Description

The present invention relates to a pressure plate for a clutch with

  friction, this essentially annular pressure plate being subdivided into several segments which follow each other in the peripheral direction and which can at least partially move relative to one another, these segments being joined by an assembly device. The invention also relates to a friction clutch.

equipped with such a tray.

  The friction clutch pressure plates are used to pinch the friction linings of the clutch disc against the flywheel. Under these conditions, when the clutch is closed, it is in a torque transmission state. For this, the pressure plates are stressed by a force accumulator, for example a diaphragm, and are prestressed in the direction of the friction linings, that is to say of the flywheel. During clutch and disengage operations, the different surface areas of the friction linings and the pressure plate or flywheel rub against each other, which

gives off heat.

  In particular if the friction clutch is used in a vehicle, the pressure plate unilaterally receives heat at its friction surface during the start-up phase. The wheel

  engine is also heated unilaterally, which causes ef-

  effects, disadvantages and consequences described below for the flywheel.

  One-sided heating creates a temperature difference from the face of the pressure plate without the surface

  friction. This temperature difference first of all produces a deformation

  elastic mation of the pressure plate, so that the outer radial zone

  pressure plate moves away from the friction surface and decreases

  thus the mean friction radius. This deformation is called "warping".

  By this deformation effect, the pressure plate deforms to the ma-

  of a veiled wheel, so that its inner radial area presses towards the flywheel. This means that it can be protruding

  in the radial direction with respect to the outer radial area of the plate

pressure plate.

  But this decreases the transmission security of

  the clutch, because it slips awkwardly. In addition, when re-

  subsequent cooling, there may be a permanent deformation of the outer radial zone of the pressure plate, so that the friction linings will wear in a conical shape (usually, wear will

  more important radially outside than radially inside).

  Up to now, this difficulty has been avoided by a plateau of

  pressure as thick as possible. But that weighs on the press

  unjustified price. In addition, it is bulky. It has also been proposed to give the pressure plate

  a concave shape when cold. But this solution presents a certain

  many disadvantages. We will thus have an irregular reach when cold.

  It has also been proposed to cool the pressure plate by a ventilation system. But this solution has the disadvantage that the pressure plate is usually made of gray cast iron, and that this

  has poor thermal conductivity compared to air. Another in-

  serious downside is that cooling is relatively late for

avoid warping.

  A larger diameter clutch has also been proposed. However, this solution has the disadvantage of resulting in a heavier, more expensive and large-size clutch. In addition, this enlarged clutch has a greater moment of inertia, which is bad for

engine acceleration.

  To avoid the induced negative effects of the increase in temperature in the friction range, it is also known according to document DE 198 48 583, a pressure plate for a friction clutch which is produced essentially in the annular form and has at least one slot. This allows the material of the pressure plate to escape into the slot under the effect of thermal expansion, so that

  the pressure plate does not deform relative to its initial shape.

  According to another solution proposed in this document DE 198 48 583, the pressure plate is subdivided into several segments which follow one another in the peripheral direction and which are at least partly movable with respect to one another. The different segments making up the pressure plate are connected by an assembly device. Thanks to

  this realization separate from the different segments, in case of contribution of each

  their, there will be no common deformation movement. On the contrary, the different segments making up the pressure plate each take a position in which they rest fully against the linings

friction.

  The object of the present invention is to develop a pressure plate for a friction clutch and a clutch thus equipped, which makes it possible to avoid any thermal deformation in a simple and reliable manner.

annoying pressure plate.

  The invention relates to a pressure plate for a

  friction clutch characterized by an essentially annular shape, the radial outer zone of the plate having a rigidity different from the internal radial zone of the plate and the ratio of rigidities between the external radial zone and the internal radial zone being adjusted according to the contour

  and / or the material of the outer radial area and the inner radial area

  pool. This pressure plate makes it possible to avoid any annoying veiling,

  not wanted by a unilateral thermal contribution in the pressure plate.

  The simple geometrical shaping or the appropriate choice of materials makes it possible to design the buckling behavior of the pressure plate so that the deformation depending on the temperature gradient does not cause

  not a change in the friction radius.

  A different radial thickness can be provided for the

  outer radial area and inner radial area. The outer radial zone

  may have an axial length different from the internal radial zone

  pool. It is also possible to envisage an external radial zone and / or

  inner radial with one or more cutouts. In the same con-

  editions, it is possible to make the outer radial area of a material other than the inner radial area. These different possibilities can

  be used separately or in any combination.

  Advantageously, the outer radial zone is more

  gide in bending and / or torsion than the inner radial area.

  The present invention further relates to a pressure plate assembly in particular for a vehicle friction clutch

  automobile fitted with at least one pressure plate as described above

  above. The present invention will be described below using a

  exemplary embodiment shown in the accompanying drawings, in the-

what:

  - Figure 1 is a simplified partial longitudinal section of an em-

  motor vehicle friction clutch, 3s - FIGS. 2a, 2b are a sectional view of a model of pressure plate,

  - Figures 3a, 3b are a sectional view of a mechanical model equi-

apply to that of FIGS. 2a, 2b.

  Figure 1 shows a friction clutch 10 for a gear

  automatic vehicle. The clutch 10 includes a flywheel 1 1 of which

  the inner radial zone is connected in a manner known per se to a crankshaft

  quin 12 or other drive shaft. The expressions "radially

  "and then" radially outside "relate to the axis of rotation A. The connection between the flywheel 11 and the crankshaft 12 is made for example by screws 13. Radially outside, the flywheel 1 carries a clutch cover 14. In the clutch cover 14, there is a pressure plate 30 integral in rotation but movable axially in the direction of the axis of rotation A. The pressure plate 30 has

  a friction surface 31 and a face 32 opposite the friction surface

  tion 31. A force accumulator, for example in the form of a dia-

  phragm 16 is connected by spacing studs 15 to the clutch cover 14, and can be moved parallel to the axis of rotation A by a clutch mechanism not shown. This allows the

  pressure plate 30 relative to the flywheel 11 or to bring it closer

  expensive of it, which corresponds to a declutching operation or

  of the clutch 10.

  Friction linings 18 of a clutch disc 19 can be pinched between the friction surface 31 of the pressure plate and a corresponding friction surface 17 of the flywheel 11. The clutch disc 19 is connected to the hub 20 ( possibly via a suitable torsion damper, not shown). The hub 20 is coupled by a toothing or groove to an output shaft

  for example the input shaft 21 of the gearbox by a solid link

to rotate.

  In such clutch devices 10, the clutch and disengage operations generate relatively high temperatures at the friction surfaces 17, 31. These temperatures are generated by the slip between the friction linings 18 and the flywheel

  motor 11 or the pressure plate 30 during the ma-

  clutch work. However, these high temperatures can cause deformation of the pressure plate 30 and of the flywheel 17 again.

  called "sheer". This sheer curtain is very annoying because it considerably reduces-

  the transmission safety of the clutch device 10 in dimi-

obscuring the friction radius.

  Figure 2a shows an equivalent mechanical model. The

  friction power Q induced on one side generates in a circular washer

  cular 90 a temperature gradient represented by diagram 91.

  As this diagram indicates, this gradient extends in the thickness of the

  circular washer 90. The relation E = cx * AT (s: relative expansion; (x: coef-

  thermal expansion factor; AT: temperature difference compared to the environment), gives in the axial extent (s) different local dilations (E). These differences in expansion induce natural tensions

  and cause deformation of the entire part, that is to say the

  age of the room. This situation is shown in Figure 2b.

  Another equivalent mechanical model is shown in

  10 Figure 3a. In this case, the circular washer 90 is surrounded by a neck.

  yield 92 ideally rigid in flexion and expansion. If the washer is circulating

  the area 90 is heated, there can be no radial extension towards the outside, so that the washer 90 escapes through its interior area,

  as shown in Figure 3b.

  Figure 4a shows a mechanical model of a combination

  sound of the models of FIGS. 2a and 3a in the case of a pressure plate

  30. The pressure plate 30 is formed by a zone 38 radially outside

  thicker, rigid in bending and in torsion and with a radially inner zone 37, thinner, more elastic in bending and in torsion. Under

  the effect of thermal stress corresponding to a thermal power

  mique applied on one side (FIG. 4b), the radially outer zone 38 escapes as in conventional pressure plates, to the right

  and thus moves away from the flywheel 11 (FIG. 1). The radially inner zone

  rieure 37 bulges and deforms to move away from the flywheel due to

  the high ratio between the rigidity of the outside area and the inside area

  higher; the ideal friction radius rm remains unchanged in the ideal case.

  By modifying the radial thickness and / or the axial length and / or the material and possibly integrating cuts in the area

  indoor and / or outdoor, the ratio can be adjusted appropriately

  stiffness between the inner zone 37 and the outer zone 38 of the plate

pressure plate 30.

  Already the simple geometrical shaping of the pressure plate 30 makes it possible to adjust the buckling behavior of the plate

  pressure 30 so that its deformation depending on the temperature gradient

  erasing does not modify the friction radius rm.

NOMENCLATURE

  10. friction clutch 11. flywheel 12. crankshaft 13. screw 14. clutch cover 15. spacer stud 16. diaphragm 17. friction surface (flywheel) 18. friction lining 19. clutch disc 20. hub 21. gearbox input shaft 30. pressure plate 31. friction surface 37. radially inner zone 38. radially outer zone 90. circular washer 91. temperature gradient diagram 92. rigid surround in flexion and expansion A axis of rotation s axial extent Q friction power rm mean friction radius

Claims (5)

  1) Pressure plate for a friction clutch, characterized in that the plate (30) is essentially annular, its external radial zone (38) has a stiffness different from its internal radial zone (37), and the ratio between the rigidities of the outer radial zone (38) and of the inner radial zone (37) is adjusted according to the contour and / or the material of the   outer radial area (38) and the inner radial area (37).   2) pressure plate according to claim 1, characterized in that the outer radial zone (38) has a radial thickness different from that of the inner radial zone (37).   3) pressure plate according to one of claims 1 or 2,   characterized in that the outer radial zone (38) has an axial length different from the zone inner radial (37).   4) pressure plate according to claim 1, characterized in that   the outer radial zone (38) and / or the inner radial zone (37) comprises carry one or more cutouts.    ) Pressure plate according to claim 1, characterized in that the external radial zone (38) is more rigid in bending and / or in torsion   as the inner radial zone (37).   6) Assembly of a pressure plate, in particular for a clutch with   motor vehicle friction comprising at least one pressure plate   sion (30) according to any one of claims 1 to 5.