Title of the invention
Clutch release bearing in contact with a plate spring
Description Field of the invention
The invention relates to a clutch release bearing in contact with a plate spring, with the clutch release bearing having at least one curved run-on face, which is spaced apart radially with respect to the rotational axis of the clutch release bearing, for the run-on of at least one end of at least one spring tongue of the plate spring.
Background of the invention
A clutch release bearing of the generic type is described in DE 37 438 53 Al. The run-on face is formed either on an inner ring or on an outer ring of the clutch release bearing. The ends of the spring tongues are in contact with the run-on face. Here, the run-on face is on the one hand an annular face which runs around the rotational axis. Alternatively, a plurality of segment-like run-on faces which are peripherally adjacent to one another are formed on the clutch release bearing. If a plurality of the segment-like run-on faces are formed on the clutch release bearing, then for example ribs are provided between the run-on faces for engagement between the spring tongues, as described in DE 37 438 53 Al.
When separating the clutch, the encircling run-on face on the bearing ring of the release bearing is pressed with force against the spring tongue(s), and the spring tongues deflect axially as a result. The contact region at which the spring tongues impinge on the contact face

moves, during the deflection and relaxation, on the run-on face radially inwards in the direction of the rotational axis of the release bearing or radially away from the rotational axis. The contact region also moves with increasing wear in the clutch.
The ends of the spring tongues which impinge on the run-on face are therefore often bent so as to be curved to such an extent that said ends are convexly arched towards the run-on face on the bearing, and that said ends, during deflection and relaxation, always run with linear contact with respect to the run-on face which is often also convexly curved in the direction of the end on the spring tongue. An example of a release bearing arrangement of said type is described in DE 37 438 53 Al.
There are however clutch or vehicle manufacturers who, for various reasons, use plate springs whose ends of the spring tongues are of straight design. A release bearing arrangement of said type is described in EP 015 383 59 Al. The ends are generally in contact with a curved run-on face. Said release bearing arrangements generally have optimum linear contact only at one operating point, which linear contact merges into two-point contact in the event of movement in one radial direction, and becomes ever smaller, and finally ends in single-point contact, in the event of movement in the other radial direction. When the clutch is actuated, the contact region will move radially outwards so as to generate single-point contact, and when returning, on account of wear, so as to generate two-point contact. Such minimizing of the contact region leads to high contact pressures and promotes impermissible wear in the contact region at the contact faces. The actions in the contact region on release bearing arrangements of the prior art are described with Figures 1 and 2.

Figure 1 schematically shows the contact region conditions during the contact of a spring tongue with respect to the release bearing arrangement as is described in EP 015 383 5A1. Considered by way of example as a curved run-on face is a part of a lateral surface of a toroidal body 1. The toroidal body 1 is illustrated in simplified form by grid lines 2 and 3. The axial arching of the run-on face is symbolized by the grid lines 2. The grid lines 2 run in planes in which the rotational axis 4 runs and which are aligned with the rotational axis 4. Peripheral curves of the run-on face in planes which are penetrated perpendicularly by the rotational axis 4 are symbolized by the grid lines 3. The contact face of the non-curved end of a spring tongue is symbolized by the face 5.
The surface line marked by 3.1 symbolizes the furthest axially projecting surface line 3.1 at the axial apex 3.1 of the run-on face. In Figure 2, a longitudinal section through the body along the rotational axis 4, the surface line 3.1 marks the turning point (apex) of a curvature which is described in longitudinal section by one of the grid lines 2.
The contact of the face 5 with the surface line 3.1 at the apex of the curvature results in an optimum linear contact region 6. The line described by the linear contact region 6 is illustrated in Figure 1 so as to be curved corresponding to the profile of the surface line 3.1. If the face 5 runs on the run-on face so as to be tilted in the direction of the arrow 7, two-point contact is finally given at the contact regions 8 and 9. If the face 5 runs on the run-on face so as to be tilted in the direction of the arrow 10, the linear contact region becomes ever smaller until the face 5 and the run-on face are finally in single-point contact at the point 11.

Summary of the invention
The object of the invention is therefore that of creating a clutch release bearing with which optimum contact with respect to the spring tongues is produced in order in particular to reduce the wear in the arrangement.
Said object is achieved with a clutch release bearing according to the features of Claim 1, and is refined by means of the features of further dependent claims.
The release bearing has a plurality of peripherally successive run-on faces. The run-on faces are either directly adjacent to one another and in this case merge into one another at chamfers, or the run-on faces are separated from one another so that for example functional elements of the release bearing are arranged between the run-on faces.
For example, one embodiment of the invention provides that an axial rib-like projection is formed between at least two peripherally successive run-on faces, with the axial projection being provided for engagement into a peripheral spacing between two spring tongues which are peripherally adjacent to one another. The projection is pointed in the shape of a roof in the axial direction.
The plate springs have an arbitrary number of spring tongues which are distributed with uniform pitch with respect to one another or are distributed at the periphery with different spacings to one another. The spring tongues of a plate spring have either an identical design to one another or a different design from one another. Each of the run-on faces is/are preferably assigned one of the ends, or alternatively a

plurality of ends of a spring tongue.
Each of the run-on faces is curved in the planes which run longitudinally with the rotational axis - but not in the peripheral direction. The run-on face is described, in planes which are penetrated perpendicularly by the rotational axis, by an arbitrary number of rectilinear surface lines which are adjacent to one another and are aligned parallel to one another. Each of the surface lines runs in each case so as to be aligned tangentially and rectilinearly with respect to in each case one imaginary circle which lies in one of the planes. The rotational axis of the clutch release bearing extends perpendicularly through the circle at the circle central point.
The run-on face is convexly arched towards the end and is described by surface lines which for example correspond, through one radius, to the profile of the curve of an ellipse, or are convexly curved in any other desired way.
One embodiment of the invention provides that the run-on face is described by at least one segment of an outer lateral surface of a cylinder. The axis of symmetry of the cylinder is aligned tangentially with respect to an imaginary peripheral line which runs around the rotational axis, and runs parallel to the surface lines. The parallel spacing between the axis of symmetry and each of the surface lines of the run-on face is preferably at least 5 mm and therefore corresponds to the radius of the cylinder.
The run-on faces are fixed either to the inner ring or to the outer ring of the clutch release bearing. Here, the run-on faces are fixed either directly to the material of the respective ring or to at least one pressure piece or the like. Use is preferably made, as

materials for the inner ring, outer ring or for the annular pressure piece, of a tempering steel such as C 45; CF 53, C 75 or a tool steel, which can be deep-drawn, such as C 80 U.
The run-on piece is for example produced as a deep-drawn, embossed or extruded part and is subjected to heat treatment. The run-on faces are alternatively provided with a wear-resistant, heat-resistant surface with a low level of roughness composed of hard material coatings, which surface is composed for example of plastic, hard materials or of ceramic or nickel-aluminium alloys. Also provided are layers composed of materials with the trade name "Triondur" - coatings based on chrome or nitridic chrome layers. The layers are for example applied by plasma coating, sintering, chemical coating or by spraying in a flame spraying, arc spraying, plasma or in a high-speed spraying process, or by vapour deposition or sputtering, vacuum-or plasma-assisted processes.
The pressure piece or some other suitable component are for example composed selectively of plastic, hard metal, of hardened sheet metal or other suitable materials or of arbitrary combinations of these. The pressure pieces are selectively snapped on, adhesively bonded to, welded to, sprayed on (applied by means of spraying, extrusion coating or the like) the corresponding bearing ring, or fastened in some other suitable way in a cohesive, form-fitting or force-fitting manner to the bearing ring. Fastening possibilities are for example in a force-fitting manner by means of an interference fit, in a form-fitting manner by means of snap-action connections, and in a cohesive manner by means of soldering, ultrasound connection and hot embossing and adhesive bonding.
Alternative materials for the pressure pieces with run-

on faces or alternatively at least for the run-on faces are thermoplastics or duroplastics. Preferred thermoplastics are for example high-temperature-resistant polyamides, polyaryletherketones (PEAK). Consideration is given, from the field of polyamides, preferably to polyamide 46 (PA 46) or partially aromatic polyamides, preferably polyphthalamide (PPA) or polyhexamethyleneterephthalamide (PA6T) or copolymers, polyhexamethyleneisophthalamide (PA6T/6I) and/or polyhexamethyleneadipinamide (PA6T/66, PA6T/61/66) or polymethylpentamethyleneterephthalamide (PA6T/MPMDT) with friction-reducing and wear-reducing and strength-increasing additives. Suitable additives are to be selected from carbon fibres and/or aramide fibres in a weight proportion of 1 to 40%, preferably carbon fibres with a weight proportion of 20 to 30%, aramide fibres with a weight proportion of 1 to 15%, and solid lubricants such as molybdenum disulphide with a weight proportion of 1 to 5%, together with or alternatively graphite in a weight proportion of 1 to 10%, together with or alternatively polytetrafluoroethylene (PTFE) in a weight proportion of 1 to 30%, preferably a PTFE proportion of 5 to 15% by weight, together with or alternatively polyphenylene sulphone (PPSo2, Ceramer) in a weight proportion of 1 to 30%, preferably 1 to 15% by weight.
In bearing rings and pressure pieces composed of sheet metal, the run-on face is formed preferably on the end side by means of shaping.
Hard metals are for example tungsten carbide or titanium-containing hard metals, which are provided with binding agent and correspondingly sintered.
Brief description of the drawings
The invention is explained in more detail below on the

basis of exemplary embodiments, in which;
Figure 1 shows the principle and the different contact conditions in the contact region of a spring tongue with a run-on face on release bearings of the prior art,
Figure 2 shows a partial section, in the same direction as the rotational axis, through the toroidal body as per Figure 1,
Figure 3 shows a description of the geometric ratios on the run-on faces of an exemplary embodiment of the invention,
Figure 4 shows a longitudinal section along the rotational axis through an exemplary embodiment of a clutch release bearing,
Figure 5 shows a partial view of an exemplary embodiment of a bearing ring in which are formed run-on faces which are peripherally directly adjacent to one another,
Figure 6 shows a frontal view of a pressure piece
having a plurality of run-on faces which are
peripherally separated from one another by
ribs,
Figure 7 shows a longitudinal section through the pressure piece as per Figure 6 along the line VII-VII,
Figure 8 shows the detail Z from Figure 7, enlarged and not to scale, with the description of the geometry of one of the run-on faces.

Figure 9 shows a sectioned partial view of a bearing ring with a pressure piece placed on,
Figure 10 shows a further partial view of a bearing ring with a pressure piece placed on, in section,
Figure 11 shows a sectioned partial view of a bearing ring with a pressure piece placed on,
Figure 12 shows a partial section longitudinally through a further exemplary embodiment of an inner ring, on which run-on faces are formed directly, and
Figure 13 shows a partial section through an inner ring, which is produced by means of cold shaping, with embossed run-on faces.
Detailed description of the drawings
The illustrations in Figures 1 and 2 are described in the section "Background of the invention".
Figure 3 shows, in a rough schematic fashion, an example of the geometric ratios of a run-on face 12. The run-on face 12 is a partial face of a cylinder 13. The axis of symmetry 18 of the cylinder 13 tangentially intersects, at the point of intersection 18a, the peripheral line 19 of a circle 14 or of a circular plane 14. The rotational axis 15 of a release bearing (not illustrated in any more detail) extends through the circular plane 14 at the central point 16 of the circle 14. The run-on face 12 is described by an arbitrary number of surface lines 17 and is curved in planes which are aligned in the same direction as the rotational axis 15. The surface lines 17 of the run-on face 12 are aligned parallel to one another and to the

axis of symmetry 18 of the cylinder 13, and therefore also in the plane of the drawing, to one another. Since the run-on face 12 is a partial face of a cylinder 13, R is the radius of the cylinder and is therefore identical as a spacing for all the surface lines 17 with respect to the axis of symmetry 18.
The spacing between the respective surface line and an imaginary axis which coincides with the axis of symmetry, as an alternative to the embodiment described above, becomes ever larger the further the respective surface line is from the apex line 20. Alternatively thereto, on run-on faces designed in the shape of cams, said spacing becomes ever smaller the further the respective surface line is from the apex line.
Figure 4 shows a clutch release bearing 21 composed of an outer ring 22, an inner ring 23, of balls 24 in a cage 25 and of a guide and centring sleeve of the release bearing housing 26. The inner ring 23 has run-on faces 28 on a rim 27 which is radially inwardly turned over by means of cold shaping. The run-on faces 28 are embossed in the rim 27. As an alternative to the variant specified directly above, corresponding run-on faces can also be formed on the guide and centring sleeve.
Figure 5 shows a bearing ring 29, either an inner ring or an outer ring, on which are embossed run-on faces 30 of the release bearing according to the invention, which run-on faces 30 are directly adjacent to one another and merge into one another at chamfers 31.
Figure 6 and Figure 7 show an annular pressure piece 32 with run-on faces 33 which are peripherally spaced apart from one another. The surface lines of the run-on faces 33 are aligned tangentially. Formed between the run-on faces 33 are axial projections 34 which are

pointed in the shape of a roof at the ends.
Figure 8 shows the curvature 35 of the run-on face 33 in a plane aligned parallel to the rotational axis 4, in this case the plane of the drawing of Figure 8. The curvature 35 is described by a radius R. The surface lines in a plane perpendicular to the plane of the drawing are aligned rectilinearly without a curvature. The pressure piece 32 is fastened on the end side to an inner or outer ring by means of adhesive bonding or welding.
Figure 9 shows an exemplary embodiment of an inner ring 36 with a pressure piece 37. The pressure piece has a plurality of run-on faces 33 and is fixedly pressed onto and/or adhesively bonded to the inner ring 36.
Figure 10 shows the contact region of an end 39 of an only partially illustrated spring tongue 40 with respect to a run-on face 33. The spring tongues 40 or their ends 39 are, in the end positions, in contact radially at the inside and radially at the outside with the run-on face 33 in the linear contact regions 41 and 42. The ends 39 are, in the end positions, deflected in each case by the angle a of any desired magnitude. The angle a is preferably 7 ° - 8 °. The pressure piece 43 with the run-on faces 33 is welded to an inner ring 44.
Figure 11 shows a detail of an inner ring 44 onto which a pressure piece 46 is snapped and held by means of at least one snap-action element 38. The snap-action element 38 is for example a snap-action rim or the snap-action elements are snap-action lugs. The pressure piece 46 is alternatively sprayed on.
Figures 12 and 13 show inner rings 47 and 48, on the material of which the run-on faces 33 are formed directly on a radial rim 49 and 50. The inner ring 47

additionally has axial projections 51, which are formed in one piece with the inner ring 47, for form-fitting engagement between the spring tongues of a plate spring. The inner ring 48 is a shaped part which is produced for example by means of combined processes of deep-drawing, pressing and/or rolling and also embossing.
List of reference symbols

1 Toroidal body
2 Grid line
3 Grid line
3a Surface line
4 Rotational axis
5 Face
6 Linear contact region
7 Arrow
8 Contact region
9 Contact region
10 Arrow
11 Point
12 Run-on face
13 Cylinder
14 Circle/circular plane
15 Rotational axis
16 Central point
17 Surface line
18 Axis of symmetry
18a Point of intersection
19 Peripheral line
20 Apex line
21 Clutch release bearing
22 Outer ring
23 Inner ring
24 Balls
2 5 Cage
26 Release bearing housing
27 Rim
28 Run-on face
29 Bearing ring
30 Run-on face
31 Chamfer
32 Pressure piece
33 Run-on face
34 Projection

3 5 Curvature
36 Inner ring
37 Pressure piece
38 Snap-action element
39 End of a spring tongue
40 Spring tongue
41 Linear contact region
42 Linear contact region
43 Pressure piece
44 Inner ring
45 Inner ring
46 Pressure piece
47 Inner ring
48 Inner ring
49 Radial rim
50 Radial rim
51 Projection

Patent claims
1. Clutch release bearing (21) in contact with a
plate spring, with the clutch release bearing (21)
having at least one curved run-on face (12, 28,
30, 33), which is spaced apart radially with
respect to the rotational axis (4) of the clutch
release bearing (21) , for the run-on of at least
one end (39) of at least one spring tongue (40) of
the plate spring, characterized in that the run-on
face (12, 28, 30, 33) is described by an arbitrary
number of rectilinear surface lines (17) which are
adjacent to one another and are aligned parallel
to one another, with each of the surface lines
(17) in each case running so as to be aligned
rectilinearly tangentially with respect to an
imaginary circle (14), and the rotational axis (4)
of the clutch release bearing (21) extending
perpendicularly through the circle (14) at the
circle central point (16).
2. Clutch release bearing according to Claim 1,
characterized in that the run-on face (12, 28, 30,
33) is convexly arched towards the end (39) of the
spring tongue (40).
3. Clutch release bearing according to Claim 1,
characterized in that the run-on face (12) is
described by at least one segment of an outer
lateral surface of a cylinder (13), with the axis
of symmetry (18) of the cylinder (13) being
aligned tangentially with respect to an imaginary
peripheral line (19) which runs around the
rotational axis (4), and with the axis of symmetry
(18) running parallel to the surface lines (17).
4. Clutch release bearing according to Claim 3,
characterized in that the parallel spacing between

the axis of symmetry (18) and each of the surface lines (17) of the run-on face (12) is at least 5 mm.
5. Clutch release bearing according to Claim 1,
characterized in that a plurality of the run-on
faces (12, 28, 30, 33) are arranged peripherally
around the rotational axis (4), with each of the
run-on faces (12, 28, 30, 33) being assigned at
least one of the ends (39).
6. Clutch release bearing according to Claim 5,
characterized in that the run-on faces (30) are
peripherally directly adjacent to one another in a
successive fashion.
7. Clutch release bearing according to Claim 5,
characterized in that the run-on faces (33) are
peripherally spaced apart in a successive fashion.
8. Clutch release bearing according to Claim 7,
characterized in that an axial projection (34, 51)
is formed between at least two peripherally
successive run-on faces (33).
9. Clutch release bearing according to Claim 8,
characterized in that the projection (34) is
pointed in the shape of a roof in the axial
direction.
10. Clutch release bearing having at least one inner
ring (23, 36, 44, 45, 48), and having at least one
row of rolling bodies which roll on the inner ring
(23, 36, 44, 45, 48), according to Claim 1,
characterized in that the run-on face (12, 28, 30,
33) is formed on an end side, which points in the
axial direction, of the inner ring (23, 36, 44,
45, 48).

11. Clutch release bearing according to Claim 10,
characterized in that the run-on face (28, 30, 33)
is formed on a radial rim (27, 50), which is
produced from sheet metal in a non-cutting process
by means of shaping, of the inner ring (23, 48).
12. Clutch release bearing according to Claim 11,
characterized in that a plurality of the run-on
faces (28, 30, 33) are formed directly on the
radial rim (27, 50).
13. Clutch release bearing according to Claim 10,
characterized in that the run-on face (33) is
formed on at least one pressure piece (32, 37, 43,
46) which is connected to the inner ring.
14. Clutch release bearing according to Claim 13,
characterized in that the annular pressure piece
(32, 37, 43, 46) is composed of plastic.
15. Clutch release bearing according to Claim 14,
characterized in that the plastic is a
thermoplastic.
16. Clutch release bearing according to Claim 13,
characterized in that the pressure piece (43) is
composed of hard metal.
17. Clutch release bearing according to Claim 11 or
13, characterized in that the run-on face (12, 28,
30, 33) is provided with a wear-resistant surface.