DE102021116936B3 - Friction plate with a surface design applied in two stages - Google Patents

Abstract

The friction plates 10 described here are characterized by two helical grooves 11, 17 which are introduced into a plate body 23 stamped from sheet steel. This significantly improves the judder behavior in interaction with a friction partner in a friction clutch. At the same time, a corresponding friction plate 10 can be easily produced by two consecutive embossing processes.

Description

The present invention relates to a friction plate, in particular for use in a friction clutch, and a method for producing such a friction plate.

Friction plates are used in particular in friction clutches for the frictional transmission of torque, for example as pressure plates, disks or counter-pressure plates. From the DE 10 2018 100 803 A1 a friction plate is known which is produced from a cast material and then provided with a defined friction surface by turning. This is complex, so that the corresponding friction plates have a disadvantage in terms of manufacturing costs.

From the U.S. 5,232,076 A a friction plate of a clutch is also known, in which two spiral grooves running in opposite directions are made in the friction surface.

From the DE 10 2006 017 207 A1 is a friction plate designed as a brake disk with radially separate sections with spiral grooves running in opposite directions in the friction surface.

The object of the present invention is to at least partially overcome the problems known from the prior art.

This object is solved with the features of the independent claims. Further advantageous refinements of the invention are specified in the dependently formulated claims. The features listed individually in the dependent claims can be combined with one another in a technologically meaningful manner and can define further refinements of the invention. In addition, the features specified in the claims are specified and explained in more detail in the description, with further preferred configurations of the invention being presented.

The friction plate according to the invention, in particular a pressure plate and/or counter-plate and/or intermediate plate and/or plate of a clutch, for transmitting a friction torque to a friction partner, with a plate body made from sheet steel, with at least one friction side, with a first spiral groove with a second first groove depth and a second spiral groove with a second groove depth are stamped, the second groove depth being greater than the second first groove depth.

The friction plate has an axis of rotation, it is designed to rotate about this axis of rotation. The terms used in this document, such as radial and radial direction, axial and axial direction and circumferential direction, are each related to this axis of rotation.

In particular, the plate body is manufactured from the steel sheet by stamping. The spirals on which the first and second grooves run are planar spirals around the axis of rotation. Depending on the angle w, the respective radius r of the spiral can be described as the product of the angle w with a constant a. The winding distance between two adjacent windings in the radial direction is preferably constant and can be calculated as the product of the constant a and twice the circuit number.

The formation of two spiral-shaped grooves or grooves by embossing creates rounded valleys in the grooves, which are separated by almost pointed ridges between the grooves. By designing the grooves as spiral grooves, the formation of circumferential grooves in the friction surface of the adjacent friction partner can be avoided. This improves the behavior of the friction clutch with regard to juddering. The grooves are introduced in particular by a two-stage embossing process, in particular with an identical embossing tool which is used offset by (preferably) 180° in the second embossing process. In this way, a configuration of the friction surface can be achieved in a simple manner, in which the second groove is formed exactly between the first groove. This means that in a radial section through the friction plate, one turn of the first groove follows one turn of the second and these are preferably equidistant in the radial direction.

The plastic deformation when embossing the grooves creates a friction surface, even when using a single embossing tool, in which the second grooves, ie the grooves newly embossed in the second embossing step, are deeper than the first grooves. In particular, the first grooves are reduced in their groove depth by the plastic deformation during the second embossing step and at the same time an essentially flat plateau between adjacent turns of the first groove is broken up, in which the second groove is formed in the plateau. As a result, the plateau between two radially adjacent turns of the first groove is reshaped into two almost pointed elevations or ridges. This improves the transmission of torque in the engaged state or in a state in which there is frictional engagement with another partner, and the effect of resonant effects when engaging and disengaging the clutch, i.e. when adjusting the rotational speed of the friction partners, is reduced.

A ratio of the second groove depth to the second first groove depth in the range from 1.5 to 3.5, preferably in the range from 1.75 to 2.3, is preferred. The preferred ratio between the first groove depth and the second first groove depth is on the one hand in an area that can be easily produced using an embossing tool and on the other hand allows foreign particles to be accommodated, for example due to abrasion from the friction partner or particles penetrating from outside, such as grains of sand, in the second groove, without disturbing the frictional connection between the friction plate and the friction partner. This improves transmission behavior and reduces wear caused by foreign particles.

The friction plate according to the invention, whose friction surface has two helical grooves, exhibits advantageous behavior in relation to interference phenomena that are dependent on the rotational frequency, such as juddering. At the same time, the friction plate can be produced inexpensively, since both the punching process and the necessary embossing processes can be carried out quickly and inexpensively. A friction plate is thus obtained which can also be used in cost-sensitive applications without there being any loss of comfort or safety.

In the radial direction, a distance between a winding of the first groove and an adjacent winding of the second groove is preferably constant over the radius, preferably within the scope of manufacturing tolerances. The second groove is therefore preferably designed in such a way that it lies exactly in the area which lies between adjacent turns of the first groove. This facilitates the construction and manufacture of the friction plate.

The first groove is preferably separated from the second groove by two ramparts. A wall is understood here in particular to mean that the upper side of the wall does not form a plateau, that is to say does not have a constant height, but is rather pointed. This improves the friction behavior and reduces clutch judder.

The first groove and the second groove are preferably described by a spiral equation that differs only by an offset angle. This offset angle is preferably 180°. This enables the first groove and the second groove to be formed with a single tool. At the same time, an offset angle of 180° allows the second slot to be formed in the areas between adjacent turns of the first slot.

An Archimedean spiral equation is preferably given as the spiral equation, which links the radius r with the angle w and a constant a. Then the first groove can be described by the first spiral equation by the following equation: $$\text{right}\left(\text{w}\right)=\text{a*w+IR}$$

IR designates the inner radius of the friction plate, which as a rule is designed essentially in the shape of a circular ring. The second spiral equation then has the offset angle w0 compared to the first spiral equation: $$\text{right}\left(\text{w}\right)=\text{a*}\left(\text{w-w0}\right)\text{+IR}$$

Preferably, the first groove and the second groove represent an Archimedean spiral. These are given by the first and second spiral equations given above.

• - Ausstanzen des Plattenkörpers aus einem Blech, insbesondere einem Stahlblech, wobei eine ebene Oberfläche des Blechs eine Reibseite des Plattenkörpers ausbildet,
• - Prägen der Reibseite zur Erzeugung der ersten Nut mit einer ersten ersten Nuttiefe,
• - Prägen der Reibseite zur Erzeugung der zweiten Nut im Bereich zwischen benachbarten Windungen der ersten Nut mit einer zweiten Nuttiefe, wobei die Nuttiefe der ersten Nut von der ersten ersten Nuttiefe zu einer zweiten ersten Nuttiefe reduziert wird.

Furthermore, a method for producing a friction plate according to the invention is proposed, comprising the following steps:

• - Punching out the plate body from a sheet metal, in particular a steel sheet, with a flat surface of the sheet metal forming a friction side of the plate body,
• - embossing the friction side to produce the first groove with a first first groove depth,
• - Embossing the friction side to produce the second groove in the area between adjacent turns of the first groove with a second groove depth, the groove depth of the first groove being reduced from the first first groove depth to a second first groove depth.

This enables the friction plate to be manufactured easily and inexpensively using a two-stage embossing process in which the groove depth of the first groove is reduced by the second embossing process and at the same time a plateau between adjacent turns of the first groove, which is produced in the first embossing process, is broken up. This avoids the friction plate having relatively large raised areas of constant height, which are problematic for speed-dependent resonance phenomena.

The friction plate preferably has an axis of rotation and the embossing processes are carried out with an identical embossing tool, which is rotated by 180° around the axis of rotation when embossing the second groove compared to embossing the first groove. In a simple manner, this causes the helical second groove to extend precisely between the regions of adjacent turns of the first helical groove. At the same time, production with a single embossing tool is reduced compared to training with two separate embossing tools gene further simplified and the manufacturing costs are further reduced.

As a precaution, it should be noted that the numerals used here (“first”, “second”,...) primarily (only) serve to distinguish between several similar objects, sizes or processes, i.e. in particular no dependency and/or sequence of these objects, sizes or make processes mandatory for each other. Should a dependency and/or order be necessary, this is explicitly stated here or it is obvious to the person skilled in the art when studying the specifically described embodiment.

• 1: ein Beispiel einer Doppelkupplung im Querschnitt;
• 2: ein Beispiel einer Reibplatte in Herstellung nach einem ersten Bearbeitungsschritt in Draufsicht;
• 3: einen Ausschnitt einer Oberflächenkontur der Reibplatte nach 2;
• 4: das Beispiel einer Reibplatte in Herstellung nach einem zweiten Bearbeitungsschritt in Draufsicht;
• 5: einen Ausschnitt einer Oberflächenkontur der Reibplatte nach 4; und
• 6: ein Prägewerkzeug.

The invention and the technical environment are explained in more detail below with reference to the figures. It should be pointed out that the invention should not be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description and/or figures. In particular, it should be pointed out that the figures and in particular the proportions shown are only schematic. The same reference symbols designate the same objects, so that explanations from other figures can be used as a supplement if necessary. Show it:

• 1 : an example of a double clutch in cross section;
• 2 : an example of a friction plate in production after a first machining step in plan view;
• 3 : a section of a surface contour of the friction plate 2 ;
• 4 : the example of a friction plate in production after a second machining step in plan view;
• 5 : a section of a surface contour of the friction plate 4 ; and
• 6 : an embossing tool.

1 shows an example of a double clutch 1 in particular for use in the drive train of a motor vehicle in cross section. The double clutch 1 has a first partial clutch 2 and a second partial clutch 3 . With each sub-clutch 2, 3, an input damper 4, which is connected, for example, to a crankshaft and/or a flywheel of an internal combustion engine (not shown), can be connected to a shaft (not shown), for example a transmission input shaft, so that the double clutch 1 causes the input damper 4 can be connected to two shafts. Here, the rotation of the individual components of the double clutch 1 takes place about a rotation axis 21.

The partial clutches 2, 3 are friction clutches. The first partial clutch 2 has a first pressure plate 5 , a first clutch disk 6 and an intermediate plate 7 . The second partial clutch 3 has the intermediate plate 7 , a second clutch disk 8 and a second pressure plate 9 . The first pressure plate 5, the intermediate plate 7 and the second pressure plate 9 are examples of friction plates 10. A disk of a corresponding multi-plate clutch is also an example of a friction plate 10.

The frictional connection of the individual partial clutches 2, 3 is achieved by axial displacement of some of the respective friction partners (first pressure plate 5, first clutch disc 6, intermediate plate 7 for the first partial clutch 2 and intermediate plate 7, second clutch disc 8 and second pressure plate 9 for the second partial clutch 3) manufactured. For example, the first pressure plate 5 is displaced in the axial direction until it clamps the first clutch disk 6 against the intermediate plate 7 and torque can be transmitted by friction. For the first pressure plate 5, the clutch disc 6 represents the corresponding friction partner.

The surface quality of the friction partners and thus of the friction plates 10 is important both for the torque transmission in the engaged state and during the engagement and disengagement of the corresponding friction clutches. This leads to changes in the speed of one of the friction partners and thus to different rotational frequencies. Here it has been shown that the surface quality of the friction partners plays an important role, since - depending on the surface quality - resonant excitations can occur at certain rotational frequencies, which the driver of the motor vehicle finds unpleasant. These phenomena fall under the concept of “juddering” of a clutch. The design of the surface finish of the friction plate described here reduces this juddering considerably, even if the friction plate was only produced by stamping from sheet metal, in particular sheet steel, before the surface finish was introduced.

2 until 5 show an example of such a friction plate 10 after various manufacturing steps to produce an advantageous surface finish. First of all, a blank (not shown) is produced from a steel sheet by a stamping process. This blank has the contours of the later friction plate 10, but corresponds to the surface of the blank the surface of the rolled steel sheet. Essentially, the surface of this blank is smooth. This is unsuitable for friction plates, since when the frictional connection of the corresponding clutch, for example the partial clutches 2, 3, occurs in a slipping phase, vibrations occur which are referred to as clutch judder.

A surface treatment as proposed here is carried out by a two-stage embossing process. 2 and 3 show the friction plate 10 after the first embossing process. Here shows 2 a plan view of the friction plate 10 and the 3 a profile of the friction plate 10 in the radial direction.

A first embossing process produces a first groove 11 in a surface 12 of a friction side 22 of a plate body 23 of the friction plate 10 . This first groove 11 runs spirally. In the radial section ( 3 ) it can be seen that between areas of the first groove 11 that are adjacent in the radial direction relative to the axis of rotation 21, plateaus 13 are formed, which are caused by the plastic deformation during the embossing process. After the first deformation step, the first groove 11 has an average first groove depth 14 which can vary slightly over the length of the first groove 11 due to tolerances in the tool and the friction plate 10 . The first first groove depth 14 is measured between a profile minimum 15 of the first groove 11 and a plateau maximum 16 . The corresponding embossing tool has a spiral-shaped elevation that forms the first groove 11 during the embossing process by plastic deformation. The friction plate 10 is essentially in the form of a circular ring and has an inner radius 24 . The course of the first groove 11 is a flat spiral, which in particular follows the first spiral equation given above.

4 and 5 branch corresponding views of the friction plate 10 analogous to the 2 and 3 after the second embossing process. The second embossing process is preferably carried out using the same embossing tool as the first embossing process, the embossing tool being used rotated by 180°. This creates a second groove 17. Due to the rotation of the embossing tool, the second groove 17 lies in the areas of the plateau 13 after the first embossing process. As a result, the plateau 13 produced during the first embossing process is formed into two ridges 18, and at the same time the first groove 11 changes as a result of the plastic deformation, the groove depth of which differs from the first first groove depth 14 (cf. 3 ) to a second first groove depth 19 is reduced. By using the same embossing tool, a second groove depth 20 of the second groove 17 essentially corresponds to the first first groove depth 14. The ridges 18 are pointed elevations and essentially no longer have a constant plateau.

The formation of two spiral-shaped grooves 11, 17 with different groove depths 19, 20 creates a situation in which the deeper second grooves 17 serve to absorb abrasion, for example from the friction partner, or foreign bodies such as grains of sand, so that the Influence of abrasion or foreign bodies on the function and the characteristics of the corresponding friction clutch is significantly reduced compared to the prior art with low effort in production. As a result, post-processing, such as in particular subsequent introduction of radial grooves, for example by milling, can be omitted. This makes the production of the friction plate 10 more economical. At the same time, it has been found that the combination of the first spiral groove 11 and the second spiral groove 17 leads to a significant reduction in the aforementioned resonance phenomena, which occur in particular with stamped friction plates 10 without the processing of the surface 12 of the friction plate 10 described here.

The corresponding friction plate 10 can have corresponding grooves 11, 17 on both sides and thus two friction sides 22. The friction plate 10 can preferably be used as a pressure plate 5, 9, as a counter-pressure plate, as an intermediate plate 7 and/or as a plate of a multi-plate clutch.

In a radial direction 28 relative to the axis of rotation 21 , adjacent grooves 11 , 17 have a slightly variable spacing 27 over the radius of the friction plate 10 . This is based in particular on tolerances of the tool and local inhomogeneities in the plate body 23. In an alternative embodiment, the distance 27 is constant.

6 12 shows very schematically an embossing tool 25 with a geometrically determined cutting edge 26 which follows a spiral equation, for example the first spiral equation given above with an inner radius IR of zero. In this way, plate bodies 23 with different inner radii 24 can be embossed.

The friction plates 10 described here are characterized by two helical grooves 11, 17 which are introduced into a plate body 23 stamped from sheet steel. This significantly improves the judder behavior in interaction with a friction partner in a friction clutch. At the same time, a corresponding friction plate 10 can be easily produced by two consecutive embossing processes.

reference list

1

Double coupling

2

First partial clutch

3

Second partial clutch

4

input damper

5

First pressure plate

6

First clutch disc

7

intermediate plate

8th

Second clutch disc

9

Second pressure plate

10

friction plate

11

First groove

12

surface

13

plateau

14

First first groove depth

15

profile minimum

16

plateau maximum

17

Second groove

18

wall

19

Second first groove depth

20

Second groove depth

21

axis of rotation

22

rubbing side

23

plate body

24

inner radius

25

embossing tool

26

cutting edge

27

Distance

28

radial direction

Claims (9)

Friction plate (10), in particular pressure plate (5, 9) and/or counter plate and/or intermediate plate (7) and/or plate of a clutch, for transmitting a friction torque to a friction partner, with a plate body (23) made from sheet steel at least one friction side (22), a first helical groove (11) with a second first groove depth (19) and a second helical groove (17) with a second groove depth (20) being stamped into a surface (12) of the friction side (22). are, wherein the second groove depth (20) is greater than the second first groove depth (19). Friction plate (10) after claim 1 , In which a ratio of the second groove depth (20) to the second first groove depth (19) in the range from 2.5 to 3.5, preferably in the range from 2.75 to 3.25, particularly preferably in the range from 2.9 to 3.1 lies. A friction plate (10) according to any one of the preceding claims, in which, in the radial direction, a distance between a turn of the first groove and an adjacent turn of the second groove is constant over the radius A friction plate (10) according to any one of the preceding claims, wherein the first groove (11) is separated from the second groove (17) by two ridges (18). A friction plate (10) according to any one of the preceding claims, wherein the first groove (11) and the second groove (17) are described by a spiral equation which differs only by an offset angle. Friction plate (10) after claim 5 , where the offset angle is 180°. A friction plate (10) according to any one of the preceding claims, wherein the first groove (11) and the second groove (17) form an Archimedean spiral. A method of manufacturing a friction plate (10) according to any one of the preceding claims, comprising the following steps: - the plate body (23) is stamped out of sheet metal, in particular sheet steel, with a flat surface of the sheet metal forming a friction side (22) of the plate body (23), - Embossing the friction side (22) to produce the first groove (11) with a first first groove depth (14), - Embossing the friction side (22) to produce the second groove (17) in the area between adjacent windings of the first groove (11) with a second groove depth (20), the groove depth of the first groove (11) differing from the first first groove depth (14 ) is reduced to a second first groove depth (19). procedure after claim 8 , in which the friction plate (10) has an axis of rotation (21) and the embossing processes are carried out with an identical embossing tool (25), which is rotated by 180° around the axis of rotation (21) when embossing the second groove (17) compared to embossing the first groove (11) is used.

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