DE102021107993B4 - Groove pattern for friction discs - Google Patents

Abstract

Groove pattern (10) for friction discs (19), the groove pattern (10) being formed by means of first friction lining pads (11) with a first pad geometry (31) and by means of second friction lining pads (12) with a second pad geometry (32), the groove pattern ( 10) results in an annular form from an alternating sequence of first and second pad geometries (31,32), which are spaced apart from one another by segmentation grooves (15), the first pad geometry (31) being a combination of a trapezoidal geometry with two, one radially on the inside and one radially on the outside, rectangular geometries directly adjoining the trapezoid and the second pad geometry (32) is embodied as a pentagonal geometry, which is embodied as a combination of a triangular geometry with an immediately adjacent rectangular geometry, characterized in that the first friction lining pads (11) each have a Y-shaped embossed groove (14) with embossed grooves (16).

Description

The invention relates to a groove pattern for friction discs with the features according to the preamble of claim 1.

Grooves or groove patterns - also referred to as pad geometry in the context of this document - serve to cool the lamellae by means of an oil flow, even when the switching elements are closed. They cut through the oil film and thereby stabilize the coefficient of friction. This creates the desired friction behavior when shifting. The idling behavior is improved and the drag torque is reduced.

• Nasslaufende Lamellenkupplungen und -bremsen finden breite Anwendung in konventionellen lastschaltbaren Getrieben, in neuartigen Hybridmodulen in hochbeanspruchten Antriebssträngen oder in schaltbaren E-Achsen, und stellen dabei leistungsfähige, hoch beanspruchte Bauteile dar. Die Forderungen nach geringerem CO2-Ausstoß und Verbesserung des Wirkungsgrades von Antriebssträngen in Kraftfahrzeuganwendungen sind von großer Bedeutung. Neben der Reduzierung von lastunabhängigen Verlusten bei Schaltelementen sind die thermische Belastung und die ausreichende Kühlung zu beachten. Im Spannungsfeld von Reibcharakteristik, Wärmehaushalt und Effizienz nimmt das Nutmuster der Reiblamelle eine zentrale Rolle ein. (vgl. 1)

The scope of the invention:

• Wet-running multi-plate clutches and brakes are widely used in conventional power-shift transmissions, in new hybrid modules in highly stressed drive trains or in switchable electric axles, and they represent high-performance, highly stressed components. The demands for lower CO2 emissions and improved efficiency of drive trains in Automotive applications are of great importance. In addition to reducing load-independent losses in switching elements, the thermal load and adequate cooling must be taken into account. The groove pattern of the friction disc plays a central role in the area of tension between friction characteristics, heat balance and efficiency. (see. 1 )

The DE 10 2011 109 452 A1 discloses a wet-running friction lining with at least two friction lining sections, the friction surface of the first friction lining section being arranged raised relative to the friction surface of the second friction lining section, and the first friction lining section having a lower resin absorption than the second friction lining section.

WO 2008/037390 A1 and DE 10 2005 029 509 A1 disclose annular, wet-running friction linings with grooves running in a y-shape in the radial direction, which connect the inner circumference and the outer circumference.

The invention is based on the task of minimizing the drag losses in friction discs by means of a suitable groove pattern (cf. 2 ) and improve cooling performance.

The object is solved by a groove pattern with the features according to claim 1.

• erster Reibbelagpads mit einer ersten Padgeometrie und
• zweiter Reibbelagpads mit einer zweiten Padgeometrie gebildet wird und das Nutmuster sich ringförmig durch eine alternierende Abfolge erster und zweiter Padgeometrien ergibt, die jeweils durch Segmentierungsnuten voneinander beabstandet sind,
• dadurch gekennzeichnet, dass
• die erste Padgeometrie als Kombination einer trapezförmigen Geometrie mit zwei, einer radial innen und einer radial außen unmittelbar ans Trapez angrenzenden rechteckförmigen Geometrien ausgeführt ist und
• die zweite Padgeometrie als 5-Eck-förmige Geometrie ausgeführt ist, die als Kombination einer dreieckförmigen Geometrie mit einer unmittelbar angrenzenden rechteckförmigen Geometrie ausgeführt ist.

The groove pattern according to the invention for friction discs therefore provides that the groove pattern by means

• first friction pads with a first pad geometry and
• second friction lining pads are formed with a second pad geometry and the annular groove pattern results from an alternating sequence of first and second pad geometries, which are spaced apart from one another by segmentation grooves,
• characterized in that
• the first pad geometry is designed as a combination of a trapezoidal geometry with two rectangular geometries directly adjoining the trapezoid radially on the inside and radially on the outside, and
• the second pad geometry is designed as a pentagon-shaped geometry, which is designed as a combination of a triangular geometry with an immediately adjacent rectangular geometry.

The first friction lining pads each have a Y-shaped embossed groove.

The first and the second friction lining pads are attached to a carrier plate, for example a carrier plate. The carrier lamella essentially has the shape of a circular ring disk. Gearing is provided radially on the inside or radially on the outside of the carrier plate, which serves to create a non-rotatable connection with a plate carrier. Advantageously, an edge on the carrier disk remains free of the friction lining pads radially on the inside and radially on the outside. In this way, tolerances in the size and/or shape of the friction lining pads can be compensated for when they are fastened to the carrier plate. In addition, the first and the second friction lining pads are advantageously spaced apart from one another in a circumferential direction, repeating in pairs. The segmentation grooves between the friction lining pads result from the distances between the friction lining pads. The pad geometries of the friction lining pads are advantageously chosen such that the segmentation grooves between two first friction lining pads together with a second friction lining pad result in a Y-shaped groove pattern.

A preferred exemplary embodiment of the groove pattern is characterized in that a groove width or a groove cross section of the segmenting grooves opens radially outwards between the first and the second friction lining pads. The groove width or the groove cross section of the segmentation grooves is advantageously designed in such a way that a diffuser effect results when oil flows through the segmentation grooves from radially inside to radially outside.

According to the invention, the groove pattern provides that the first friction lining pads each have a Y-shaped embossed groove with embossed grooves. The Y-shaped embossed groove with the embossed grooves results in three almost identical unembossed pad surfaces in the first friction lining pad due to the first pad geometry. In the first pad geometry, the unembossed pad surfaces are delimited by the embossed grooves and each have the shape of triangles, which are each combined with a rectangle. The apex of a triangle arranged radially on the outside is directed radially inwards. The vertices of two radially inner triangles point radially outward. The Y-shaped stamped groove with the stamped grooves can advantageously further reduce the drag torque and optimize the cooling.

A further preferred exemplary embodiment of the groove pattern is characterized in that the embossed grooves of the Y embossing have a greater groove width than the segmentation grooves. The width of the segmentation grooves is defined by the distance between the friction lining pads relative to one another. The smaller groove width of the embossed grooves is particularly advantageous because the embossed grooves preferably have a smaller groove depth than the segmentation grooves.

A further preferred exemplary embodiment of the groove pattern is characterized in that the embossed grooves of the Y embossing have the same groove angle as the segmentation grooves. This means that the arrangement of the segmentation grooves between the first and second friction lining pads essentially corresponds to the arrangement of the embossed grooves in the Y embossing.

Another preferred embodiment of the groove pattern is characterized in that the groove angles are between ninety and one hundred degrees. The groove angles of the coined grooves and the segmentation grooves are preferably 96.7 degrees.

Another preferred exemplary embodiment of the groove pattern is characterized in that the segmentation grooves include inner webs and outer webs that occupy at least ten percent, preferably between fifteen and twenty-five percent, of a radial extension of the first friction lining pads radially inside and radially outside between the friction lining pads. This has proven to be particularly effective in terms of reducing drag torque. The inner webs and the outer webs preferably run in radial directions. Due to the alternating pairs of first and second friction lining pads, there is an offset between the inner webs and the outer webs in the circumferential direction.

Another preferred embodiment of the groove pattern is characterized in that pad interior angles in pad corners of the first friction lining pads are between eighty-five and two hundred and thirty degrees, wherein pad interior angles in pad corners of the second friction lining pads are between ninety and one hundred and eighty-five degrees. Included in each pad corner is a pad interior angle. Due to the first pad geometry, which is composed of a trapezoidal geometry and two rectangular geometries, the result is that the first friction lining pads include eight inner angles. Due to their pentagonal second pad geometry, which is composed of a triangular geometry and a rectangular geometry, the second friction lining pads comprise five pad interior angles.

A further preferred exemplary embodiment of the groove pattern is characterized in that all of the pad corners are rounded along their peripheral contour. This has proven advantageous with regard to the flow around the friction lining pads. Radiuses of curvature in the pad corners are preferably greater than or equal to one millimeter. This has proven to be sufficient with regard to the flow around the friction lining pads.

Another preferred embodiment of the groove pattern is characterized in that the first and second friction lining pads have widths and heights that have a width-to-height ratio that is less than two. The first friction lining pads preferably have a width to height ratio of 1.6 to 1.8. The second friction lining pads preferably have a width to height ratio of 1.5 to 1.7. These width-to-height ratios are advantageous for both directions of rotation in which the friction plates can be rotated.

The invention also relates to a first friction lining pad and/or a second friction lining pad for a groove pattern as described above. The friction lining pads can be traded separately.

Further advantages and advantageous configurations of the invention are the subject matter of the following figures and their description.

• 1 Zusammenhänge: Lufteinzug und Schleppmoment
• 2 Aufgabe und Verbesserungen
• 3 erfindungsgemäßes Nutdesign
• 4 Dimensionierung Pad 1 des erfindungsgemäßen Nutdesigns
• 5 Dimensionierung Pad 1 des erfindungsgemäßen Nutdesigns
• 6 Dimensionierung Pad 1 und Pad 2 des erfindungsgemäßen Nutdesigns
• 7 Dimensionierung Pad 1 des erfindungsgemäßen Nutdesigns
• 8 Dimensionierung Pad 2 des erfindungsgemäßen Nutdesigns
• 9 Dimensionierung Pad 2 des erfindungsgemäßen Nutdesigns
• 10 Dimensionierung des erfindungsgemäßen Nutdesigns

They show in detail:

• 1 Relationships: air intake and drag torque
• 2 task and improvements
• 3 groove design according to the invention
• 4 Dimensioning Pad 1 of the groove design according to the invention
• 5 Dimensioning Pad 1 of the groove design according to the invention
• 6 Dimensioning Pad 1 and Pad 2 of the groove design according to the invention
• 7 Dimensioning Pad 1 of the groove design according to the invention
• 8th Dimensioning Pad 2 of the groove design according to the invention
• 9 Dimensioning Pad 2 of the groove design according to the invention
• 10 Dimensioning of the groove design according to the invention

• • Pad-Winkel (4 (1)) zwischen 85 und 230 Grad (Details siehe 11).
• • Pad-Außenkanten entlang des Umfangs verrundet, bevorzugt >= 1 mm (5 (2)).
• • Zweireihiges Design des Pad 1: durch mittige Y-Prägung (7) der Prägenuten ergeben sich drei nahezu identische ungeprägte Padflächen.
• • Grundgeometrie des Pad 1 ist als Kombination einer trapezförmigen Geometrie mit zwei, einer radial innen und einer radial außen unmittelbar ans Trapez angrenzenden rechteckförmigen Geometrien ausgeführt (3, 6, 3 und 9 - 11).
• • Breiten- (3) zu Höhen- (4) -Verhältnis des Pads unter 2 (vorzugsweise von 1,6 bis 1,8) (5).
• • Breite bzw. Querschnitt der Segmentierungsnuten zwischen Pad 1 und Pad 2 nach radial außen öffnend (6 (5)), sodass sich eine Diffusor Wirkung ergibt.
• • Breite der Y-Prägung (7) also der Prägenuten > Breite des Padabstands zwischen Pad 1 und Pad 2 also der Segmentierungsnuten (6 (5), 10).
• • Winkel der Y-Prägung (7 (8)) der Prägenuten = Winkel der Segmentierungsnuten (6 (7))
• • Winkel der Y-Prägung (7 (8)) der Prägenuten ist zwischen 90 und 100 Grad, vorzugsweise 96,7 Grad
• • Steg (7 (9)) radial innen und außen mindestens 10% der radialen Erstreckung des Pads 1, vorzugsweise zwischen 15 und 25%.

Pad 1 ( 3 - 7 , 11 ):

• • Pad Angle ( 4 (1) ) between 85 and 230 degrees (for details see 11 ).
• • Pad outer edges rounded along the circumference, preferably >= 1 mm ( 5 (2) ).
• • Pad 1's two-row design: with central Y embossing ( 7 ) of the embossed grooves result in three almost identical unembossed pad surfaces.
• • The basic geometry of Pad 1 is designed as a combination of a trapezoidal geometry with two rectangular geometries, one radially on the inside and one radially on the outside, directly adjoining the trapezium ( 3 , 6 , 3 and 9 - 11 ).
• • Pad width (3) to height (4) ratio less than 2 (preferably from 1.6 to 1.8) ( 5 ).
• • Width or cross-section of the segmentation grooves between pad 1 and pad 2 opening radially outwards ( 6 (5) ), resulting in a diffuser effect.
• • Width of the Y stamp ( 7 ) i.e. the embossing grooves > width of the pad spacing between pad 1 and pad 2 i.e. the segmentation grooves ( 6 (5) , 10 ).
• • Angle of Y embossing ( 7 (8) ) of the embossing grooves = angle of the segmentation grooves ( 6 (7) )
• • Angle of Y embossing ( 7 (8) ) of the embossing grooves is between 90 and 100 degrees, preferably 96.7 degrees
• • Bridge ( 7 (9) ) radially inside and outside at least 10% of the radial extension of the pad 1, preferably between 15 and 25%.

• • Pad-Winkel (8 (1)) zwischen 90 und 185 Grad (Details siehe 10)
• • Pad-Außenkanten entlang des Umfangs verrundet, bevorzugt >= 1 mm (9 (2))
• • Grundgeometrie des Pad 2 ist als eine 5-Eck-förmige Geometrie ausgeführt, das als Kombination einer dreieckförmigen Geometrie mit einer unmittelbar angrenzenden rechteckförmigen Geometrie ausgeführt (3, 6, 9 - 10).
• • Breiten- (3) zu Höhen- (4) -Verhältnis des Pads unter 2 (vorzugsweise von 1,5 bis 1,7) (9)

Pad 2 ( 3 , 6 , 3 9 - 10 ):

• • Pad Angle ( 8 (1) ) between 90 and 185 degrees (for details see 10 )
• • Pad outer edges rounded along the circumference, preferably >= 1 mm ( 9 (2) )
• • The basic geometry of Pad 2 is designed as a pentagon shaped geometry, which is designed as a combination of a triangular geometry with an immediately adjacent rectangular geometry ( 3 , 6 , 9 - 10 ).
• • Pad width (3) to height (4) ratio less than 2 (preferably from 1.5 to 1.7) ( 9 )

Improvement of the fibrousness and the edge quality and thus reduction of the drag torques in the open state of the friction system (among other things by overprinting ( 7 (6) ))

The cross-section of the segmentation grooves increases from radially inside to radially outside (diffuser effect), creates an additional pressure reduction in the groove and thus shifts the intake of air to low speeds. The drag torque can thus be reduced.

By reducing the groove cross-section (web section, radially inside) within the friction surface, the effectively effective viscosity of the oil-air mixture can be further reduced by reducing the pressure level and promoting the intake of air in the lubricating gap, and thus the drag torque can be further improved.

Improvement of the coefficient of friction through effective oil removal in the lubricating gap through optimized pad angles between 90° and 100°, preferably 96.7°, both in the segmentation (angle of the segmentation grooves ( 6 (7) )) as well as in the overstamping (angle of the Y embossing ( 7 (8) ) of the embossing grooves).

Ratio of segmentation (segmentation grooves) and overstamping (embossed grooves): groove volume of the segmentation grooves to groove volume of the embossed grooves in a ratio of at least 3:1, preferably between 3.5:1 and 4:1. In this way, an optimum between cooling and de-oiling of the friction system can be found. A coordinated embossing allows the cooling oil to be optimally guided to the surface of the counter friction disc, thus improving the convective heat transfer (cooling). At the same time, when open, the separation (by means of the lubricating oil) of the slats and the intake of air can be improved (lower drag torque).

In 1 1 shows how air is drawn in 26 by a conveyed volume flow 24 when this exceeds the supplied volume flow 25 . From this limit, the degree of gap filling 26 and the lubricating gap between the decreases Fins contain air. Above this limit, a supplied volume flow contains 25 air. In 2 below you can see that the air intake 26 occurs at a maximum drag torque 27 .

In 2 it is shown how a displacement of the air intake 28 to a low speed in a drag torque curve 30 is achieved with the claimed friction part 15 . through the in 3 shown groove pattern, the conveying effect of the cooling and / or lubricating medium can be improved.

In 3 a groove pattern 10 according to the invention is shown, which is also referred to as a groove design. The groove pattern 10 comprises first friction lining pads 11 and second friction lining pads 12. The friction lining pads 11, 12 are arranged on a carrier plate 18. The carrier plate 18 with the friction lining pads 11, 12 is referred to as the friction plate 19.

The first friction lining pads 11 have the shape of an isosceles trapezium, the long base side of which is arranged radially on the inside. A rectangle is attached to the long base of the trapezoid. A rectangle also adjoins the short base side of the trapezoid radially on the outside. The first friction loading pads 11 all have the same first pad geometry 31.

The first friction lining pads 11 are arranged alternately with the second friction lining pads 12 in the circumferential direction. The second friction lining pads 12 have a second pad geometry 32. The second pad geometry 32 is composed of an isosceles triangle, the tip of which is directed radially inwards. The triangle is supplemented radially on the outside by a rectangle. The combination of the triangle and the rectangle results in a pentagonal shape for the second friction lining pad 12.

All corners of the first friction lining pads 11 and the second friction lining pads 12 are rounded. All rounding radii are essentially the same and are advantageously greater than or equal to one millimeter.

The friction lining pads 11, 12 are arranged alternately and are spaced apart from one another in such a way that segmentation grooves 15 result between the first friction lining pads 11 and the second friction lining pads 12. Due to the pad geometries 31 and 32 and the arrangement of the friction lining pads 11, 12, the segmentation grooves 15 result in an essentially Y-shaped groove pattern with a centrally arranged second friction lining pad 12, which is arranged between two friction lining pads 11.

The first friction lining pads 11 comprise a Y-shaped embossed groove 14 with embossed grooves 16. The embossed grooves 16 of the Y-shaped embossed groove 14 produce a groove pattern that is similar to the segmentation grooves 15.

In 4 one of the first friction lining pads 11 is shown enlarged. Reference number 1 designates three pad interior angles. The size of the pad interior angles 1 can vary between eighty-five and two hundred and thirty degrees.

In 5 2 denotes all rounding radii in the corners of the friction lining 11 . A width of the friction lining pad 11 is denoted by 3 . A height of the friction lining pad 11 is denoted by 4 . A ratio of the widths 3 to the heights 4 of the first friction lining pads 11 is less than two, preferably 1.6 to 1.8.

In 6 a groove angle between two segmentation grooves, which are delimited on the inside by a second friction lining pad 12 (not designated) and on the outside by two friction lining pads 11, is denoted by a double arrow 7. The groove angle 7 between the segmentation grooves is also referred to as the segmentation angle.

By arrows 45 and 46 is in 6 Cooling oil indicated that the segmentation groove 15 flows through between the first friction lining pad 11 and the second friction lining pad 12 . The cooling oil enters radially on the inside and exits radially on the outside at 5 . A groove width or a groove cross section of the segmentation groove 15 opens radially outwards at 5 or towards 5 . This results in a desired diffuser effect for the cooling oil flowing through the segmentation groove 15 .

In 7 is shown enlarged that the segmentation groove 15 between the friction lining pads 11 and 12 comprises an inner web 13 radially on the inside and an outer web 9 radially on the outside. The webs 9 and 13 extend in the radial direction. Due to the pad geometries 31, 32 of the friction lining pads 11, 12, the webs 9, 13 are offset relative to one another in the circumferential direction.

A groove width or a groove cross section 6 of the Y-shaped embossed groove 14 of the first friction lining pad 31 is advantageously greater than the pad spacing between the friction lining pads 11 and 12, which is used to create the segmentation groove 15.

By a double arrow 8 is in 7 a groove angle of the Y-shaped stamped groove 14 is indicated. The groove angle 8 of the Y-shaped embossed groove 14 advantageously corresponds to that in 6 shown groove angle 7 of the Y-shaped groove image, which is shown with the segmentation grooves 15.

In 8th the second friction lining pad 12 with the second pad geometry 32 is shown enlarged. Reference number 1 designates three pad interior angles. The pad internal angles can vary in size from ninety to one hundred and fifty degrees.

In 9 are denoted by 2 rounding radii in the corners of the friction lining pad 12 . A width of the friction lining pad 12 is denoted by 3 . A height of the friction lining pad 12 is denoted by 4 . A ratio of the width 3 to the height 4 of the friction lining pad 12 is preferably less than two, preferably 1.5 to 1.7.

In 10 are indicated by double arrows 51-54; 61-63 angles designated. The angles 51 to 54 are drawn on the first friction lining pad 11 and can also be referred to as the inner pad angle. The angles 61 to 63 are drawn on the second friction lining pad 12 and can also be referred to as the pad inner angle.

The different sized angle specifications result from the fact that both friction lining pads 11 and 12 in 10 have a rectangular geometry at the top. In the case of the second friction lining pad 12, the rectangular geometry is combined with a triangular geometry. In the case of the first friction lining pad 11, a trapezoidal geometry is provided between the upper rectangular geometry and a lower rectangular geometry.

Angle 51 refers to a top left corner of the top rectangle geometry. Angle 52 refers to a lower left corner of the lower rectangle geometry. Angle 53 extends from a left side of the upper rectangle geometry to a left leg of the trapezoidal geometry. Angle 54 extends from a right leg of the trapezoidal geometry to a right side of the lower rectangular geometry.

Angle 61 extends between a left side of the top rectangular geometry and a left leg of the triangular geometry. Angle 62 extends between the two legs of the triangular geometry. Angle 63 refers to an upper right corner of the upper rectangle geometry. The degrees of the interior angles are given near the double arrows.

Reference List

1

Pad Inner Angle

2

curve radii

3

latitudes

4

heights

5

groove cross-section opening outwards

6

Groove width/groove cross-section

7

groove angle

8th

groove angle

9

outer bar

10

groove pattern

11

first friction lining pads

12

second friction lining pads

13

inner bar

14

Y-shaped embossed groove

15

segmentation grooves

16

embossed grooves

18

carrier lamella

19

friction disc

20

X axis

21

y-axis

22

y-axis

23

y-axis

24

conveyed volume flow

25

supplied flow rate

26

air intake

27

drag torque

28

air intake

30

drag torque curve

31

first pad geometry

32

second pad geometry

45

Arrow

46

Arrow

51

Pad Inner Angle

52

Pad Inner Angle

53

Pad Inner Angle

54

Pad Inner Angle

61

Pad Inner Angle

62

Pad Inner Angle

63

Pad Inner Angle

Claims (9)

Groove pattern (10) for friction discs (19), the groove pattern (10) by means of first friction lining pads (11) with a first pad geometry (31) and by means of second friction lining pads (12) with a second pad geometry (32), the groove pattern (10) being formed annularly by an alternating sequence of first and second pad geometries (31,32), which are spaced apart from one another by segmentation grooves (15), the first pad geometry (31) being a combination a trapezoidal geometry with two rectangular geometries, one radially on the inside and one radially on the outside, directly adjoining the trapezoid, and the second pad geometry (32) is embodied as a pentagonal geometry, which is embodied as a combination of a triangular geometry with an immediately adjacent rectangular geometry, characterized characterized in that the first friction lining pads (11) each have a Y-shaped embossed groove (14) with embossed grooves (16). groove pattern claim 1 , characterized in that a groove width or a groove cross section (5) of the segmentation grooves (15) opens radially outwards between the first and the second friction lining pads (11, 12). groove pattern claim 1 or 2 , characterized in that the embossed grooves (16) of the Y embossing (14) have a greater groove width (6) than the segmentation grooves (15). Groove pattern according to one of Claims 1 , 2 or 3 , characterized in that the embossed grooves (16) of the Y embossing (14) have the same groove angle (8) as the segmentation grooves (15). groove pattern claim 4 , characterized in that the slot angles (7,8) have between ninety and one hundred degrees. Groove pattern according to one of the preceding claims, characterized in that the segmentation grooves (15) include inner ridges (13) and outer ridges (9) that extend radially inside and radially outside between the friction lining pads (11,12) at least ten percent, preferably between fifteen and twenty-five Percentage of a radial extent of the first friction lining pads (11). Groove pattern according to one of the preceding claims, characterized in that pad inner angles (1) in pad corners of the first friction lining pads (11) have between eighty-five and two hundred and thirty degrees, pad inner angles (1) in pad corners of the second friction lining pads (12 ) between ninety and one hundred and eighty five degrees. Groove pattern according to one of the preceding claims, characterized in that all pad corners are rounded along their peripheral contour. A groove pattern as claimed in any preceding claim characterized in that the first and second friction lining pads (11,12) have widths (3) and heights (4) which have a width (3) to height (4) ratio less than two is.

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