WO2018077882A1

WO2018077882A1 - A brake pad

Info

Publication number: WO2018077882A1
Application number: PCT/EP2017/077176
Authority: WO
Inventors: Marc-Gregory Elstorpff; Bernhard Haemmerl; Christoph Siegl; Marco Langwadt
Original assignee: Knorr-Bremse Systeme für Schienenfahrzeuge GmbH
Priority date: 2016-10-27
Filing date: 2017-10-24
Publication date: 2018-05-03
Also published as: CN107989931A

Abstract

A brake pad for a railway vehicle with a brake disc, the brake pad comprising at least one friction element (100) non-rigidly attached to a pad carrier. The friction element (100) comprises a friction surface (105) being in contact, during braking, with the brake disc to provide a friction force acting along friction lanes (110) on the friction surface The friction element (100) comprises at least one groove (130) extending along the friction surface non-parallel to a friction force acting during braking of the railway vehicle, wherein the at least one groove (130) is arranged symmetrically or asymmetrically in respect to a geometric center of the friction surface (105).

Description

DESCRIPTION

A Brake Pad The present invention relates to a brake pad and, in particular, to a brake pad for a railway vehicle with sintered friction elements with at least one groove.

Each brake pad for railway vehicles may have one or more friction elements which are held by a pad carrier. During a braking action all friction elements shall get into touch with a brake disc, ideally with their complete friction surface. The friction elements can be attached to the pad carrier in a rigid way or flexible to ensure equal distributed load to the brake disc.

When a friction element comes into contact with a metal brake disc, so-called metal pickups (abrasion material from the brake disc) may be produced and lower the braking efficiency of conventional friction elements and may also damage the brake disc.

Likewise, water or moisture on the brake disc may lower the friction between the friction elements and the brake disc. There is no solution available for these problems and the detrimental effect of the abrasion material becomes increasingly relevant in view of the increasing requirements in braking systems of modern railway vehicles. Therefore, there is an ongoing demand of improving the friction performance of friction elements. At least some of the above-mentioned problems are solved by a brake pad according to claim 1 and a railway vehicle according to claim 10. The dependent claims relate to further specifically advantageous realizations.

The present invention relates to a brake pad for a railway vehicle with a brake disc. The brake pad comprises at least one friction element non-rigidly attached to a pad carrier, the friction element comprises a friction surface being in contact, during braking, with the brake disc to provide a friction force acting along friction lanes on the friction surface. The friction element comprises at least one groove extending along the friction surface in a non-parallel way to a friction force acting during braking of the railway vehicle. The at least one groove is arranged symmetrically or asymmetrically in respect to a geometric center of the friction surface. Optionally, the at least one groove is configured, during braking, to collect and convey material along the friction lanes.

Hence, according to the present invention, the friction element comprises a groove extending on the friction surface to pick-up material along the friction lanes, or multiple grooves extending along the friction surface. Even if there is only a single groove, this groove may be arranged symmetrically or asymmetrically, for example, with respect to the geometric center of the friction surface.

It is understood that the term "an element" does not mean that only one element is present, but covers any number of elements. Hence, the term "a groove" limits the number of grooves only in so far that at least one groove is present. Furthermore, the term "non-rigidly" shall be construed broadly in that it covers any relative movement (e.g. tilting, pivoting, rotating) between the friction element and the pad carrier, at least up to a certain degree.

It is understood that the friction lanes occur when the friction element is attached to a pad carrier and the pad carrier together with the friction element(s) is pressed on the brake disc. The resulting friction will act along the friction lanes, which thus may become visible. For example, a non-parallel alignment between the groove and the friction lanes may provide the effect that material between the friction element and the brake disc can be effectively collected and conveyed. This material can be any material which lowers the friction force, for example, metal pickups from the brake disc or other abrasion material, but also water, moisture, dust, etc. It is further understood that the desired effect can be realized in many different ways. For example, the friction element may be configured to be attached to the pad carrier in a predetermined way such that the groove will always be non-parallel to the friction lanes. It may also be possible that rotations of the friction elements are prevented by the arrangements of other friction elements. For example, they may abut each other thereby preventing a relative rotation which ensures a desired alignment of the groove. Another possibility is that the shape of the groove is adapted (e.g. non-uniform) so that the circular friction lanes have to pass the groove. Yet another possibility would be to arrange multiple grooves or a pattern of grooves ensuring the desired effect - independently of the rotational position of the friction element on the pad carrier.

Optionally, a recess may extend as a hole through the friction element accommodating at least partly attachment means for attaching the friction element to the pad carrier. Optionally, the attachments means are configured to attach the friction element to the pad carrier such that the groove extends in the non-parallel direction to the friction lanes. It is understood that the attachment means can be any means which are suitable to attach the friction element to the pad carrier and include, for example, screw connection, bolt connection with a fixing spring or any other connection which is sufficiently strong to withhold forces, which occur during a brake action.

Optionally, the attachment means are configured to rotationally fix the friction element on the pad carrier or to allow maximal rotations, for example, of 50° or 30° about a rotation axis extending perpendicular to the pad carrier.

Optionally, the attachment means are configured to flexibly attach the friction element on the pad carrier enabling the friction surface to come into contact with the brake disc with a maximum surface area to provide an equally distributed pressing force to the brake disc to avoid local disc overload.

The pad carrier may be configured to hold a plurality of friction elements at

predetermined positions. In this case, the friction element may have a shape so that, upon rotation, the friction element abuts another friction element of the plurality of friction elements, thereby enabling rotations of the friction elements on the pad carrier only up to a maximal rotation angle (e.g. 10° or 5°). For example, the shape of the friction element may represent a polygon (e.g. triangle, rectangle, pentagon, hexagon, octagon, etc.) or a circle or an ellipse. Multiple friction elements may be positioned such that they prevent rotations of the single friction elements. Optionally, the groove crosses the optional recess and comprises a width within the range between 3 and 15 mm, or between 4 and 10 mm. The width of the groove can be adapted in order to collect or pick-up effectively the abrasion material (e.g. metal pickups) or water, moisture, or other materials and to transport this material to an edge portion of the friction element.

Optionally, an angle between the direction of the groove and the friction lanes is in an angular range between 40° to 140°. The angle can be adjusted to promote an efficient transport of collected material to an edge part of the friction element.

The friction elements may be made of sinter material adapted to provide a high level of friction when getting into touch with the brake disc. The brake disc may comprise a metal and may or may not be part of a railway wheel.

The present invention relates further to a railway vehicle with a brake system including the brake pad and a brake disc to brake the railway vehicle by pressing the friction elements with their frictional surfaces on the brake disc while the groove(s) extend(s) non-parallel to the brake force exerted between the friction elements and the brake disc.

Some examples of the friction element and/or brake pad will be described in the following by way of examples only, and with respect to the accompanying figures, in which: Fig. 1 depicts a friction element according to an embodiment of the present

invention;

Fig. 2 depicts a brake pad with a plurality of friction elements according to an embodiment;

Fig. 3 depicts a partial view of the brake pad of Fig. 2;

Fig. 4 depicts an enlarged view of a friction element;

Figs. 5A,B show a cross-sectional views through the friction elements with a

symmetric and an asymmetric groove according to embodiments; and Figs. 6A,B depict embodiments with multiple grooves arranged along the friction surface.

Fig. 7 depicts an embodiment for the brake pad.

Fig. 8 depicts another embodiment for the brake pad.

Fig. 1 shows a rectangular friction element 100 according to an embodiment of the present invention. The friction element 100 is suitable for a railway vehicle with a pad carrier and a brake disc (not shown in Fig. 1 ). The friction element 100 is attachable to the pad carrier and comprises a friction surface 105 being in contact, during braking, with the brake disc to provide a friction force acting along friction lanes 1 10 on the friction surface 105 of the friction element 100. The friction element 100 comprises a recess 120 in the friction surface 105 for attaching the friction element 100 to the pad carrier, and a groove 130 extending in a direction along the friction surface that is non- parallel to the friction lanes 1 10.

As indicated in Fig. 1 the friction lanes 1 10 extend along the friction surface 105 to form an angle a between the direction of the groove 130 and the friction lanes. The angle a can be within the range of 40° to 140°. In particular, the angle a can be selected such that the friction lanes 1 10 are perpendicular (90°) to the direction of groove 130. The optional recess 120 may be a through hole (e.g. with a diameter between 10 and 25 mm or about 16 mm) and may accommodate at least part of attachment means (not shown in Fig. 1 ) to attach the friction element 100 to the pad carrier. The angle a can be ensured by an appropriate attachment of the friction element on the pad carrier, for example, by preventing a free rotation of the friction element on the pad carrier.

Fig. 2 shows a brake pad according to an embodiment with a pad carrier 20 on which a plurality of friction elements 100 are attached. Each of the friction elementsl OO comprises the optional recess 120 arranged in the middle of the friction element 100 representing a through-hole in order to attach the friction element 100 to the pad carrier 20. In this embodiment the friction elements 100 comprise a shape of a polygon (a hexagon in the depicted embodiment). The position of attachment and the shape of the friction elements ensure that the friction elements 100 cannot be rotated relative to each other, or can be rotated only within a particular angular range (for example between ± 10°) about a rotation axis, which may be placed on the geometric center of the friction surface 105.

The depicted brake pad has the form of a circular ring adapted to get in contact to a circular brake disc. The brake pad further comprises a first attachment portion 21 on the left-hand side and a second attachment portion 22 on the right-hand side, both attachment portions 21 , 22 are configured to secure or guide the brake pad to enable brake actuators of the brake system of the exemplary railway vehicle to actuate the brake pad. The friction lanes thus extend as circular portions between the first attachment portion 21 and the second attachment portion 22. Therefore, the shape and the positions of the friction elements 100 on the pad carrier 20 ensure that the grooves 130 in each of the friction elements 100 are approximately perpendicular to the friction lanes. In addition, a circular brake disc provides centrifugal forces which will convey the collected metal/water pick-up outside the friction surface. As a result, the friction is increased.

Fig. 3 shows a partial overview of the brake pad as depicted in Fig. 2. Again, the plurality of friction elements 100 is shown to be attached to the pad carrier 20, wherein the optional recesses 120 are formed as through-holes which are used for the attachment of the friction elements 100 to the pad carrier 20. As it is apparent from Fig. 3, the grooves 130 do not need to be aligned along the same direction, but there can be a certain range of possible angular directions along which the grooves 130 may extend. In order to provide the desired effect, it is, however, of advantage when the angle between the grooves 130 and the friction lanes 1 10 is such that the length of the friction lanes 1 10 along the friction surface 105 of each of the friction elements 100 is sufficiently short. These shortened friction lanes 1 10 enable the reduction of the exemplary metal pickups (or moisture) between the friction elements 100 and the brake disc. Fig. 4 depicts an enlarged view of a friction element 100 surrounded by multiple further friction elements 101 , 102, 103. The friction element 100 comprise sinter material 140 und attachment means 125. The attachment means 125 are arranged on the backside of the sinter material 140 (opposite to the friction surface 105), can be accessed via the through-hole 120 in the middle of the friction element 100, and provide an attachment to the pad carrier 20.

Fig. 5A shows a cross-sectional view through the friction element 100 along the cross- sectional line A-A of Fig. 4, wherein the groove 130 is arranged symmetrically with respect to the rotation axis R of the friction element 100. The rotation axis R goes through a bolt/calotte element 127 as part of the attachment means 125 and is arranged in the middle position of the groove 130. Fig. 5B shows a similar friction element 100. However, in this embodiment the groove 130 is arranged asymmetrically with respect to the rotation axis R. When viewed in the direction of the groove 130, there is an offset between the rotation axis R and the position of the groove 130. In both embodiments the friction surface 105 is depicted on the bottom of the sinter material 140 and the attachment means 125 is depicted on the top. The cross section goes through the recess 120 arranged approximately in the middle of the frictional element 100 surrounded by the sinter material 140 extending radially outward. The groove 130 with a width W is shown within the recess 120 and extends along a direction perpendicular to the drawing plane. The attachment means 125 is thus arranged on a side opposite to the friction surface 105 of the sinter material 140. The attachment means 125 comprises as, an example, a backside plate 126 and the bolt or calotte element 127, wherein the bolt/calotte element 127 may provide a joint holding the plate 126 on the pad carrier 20 (e.g. pivotable, rotatable, or rigidly). Optionally, the sinter material 140 may directly be (rigidly) fixed/sintered on the pad carrier 20 or on the backside plate 126.

It is understood that the arrangement of the groove 130 is independent of the number of friction elements 100 arranged on the pad carrier 20. Hence, even if the brake pad has only a single friction element 100, this single friction element 100 may be formed as shown in Fig. 5A or in Fig. 5B. It is further understood that the desired effect of collecting and conveying pick-up material can also be achieved if not a single, straight groove 130 is formed, but multiple grooves or a pattern of grooves are formed on the friction surface 105 ensuring that at least one groove is non-parallel to the friction lanes 1 10. Multiple grooves can be positioned symmetrically or asymmetrically to the rotational point in direction of the friction lanes. For an asymmetrically arrangement the angle could be limited to 1 -10°.

Fig. 6A and Fig. 6B depict (from different viewing directions) embodiments for the friction element 100, where not only a single groove is arranged along the friction surface 105 of the sinter material 140, but multiple grooves 131 , 132. The depicted embodiments comprise, as an example, two grooves: a first groove 131 and a second groove 132 which extend across the sinter material 140 and which are placed on opposite sides of the rotation axis R. The embodiment of Fig. 6A shows the case, where the first groove 131 and the second groove 132 are not parallel, whereas the embodiment of Fig. 6B shows the friction element, where the first groove 131 and the second groove 132 are parallel to each other. The angle between the first groove 131 and the second groove 132 may, for example, be within a range between 0° and 10° (or at most 5° or at most 20°).

In further embodiments, more than two grooves can be arranged through the sinter material 140. An advantage of having not only a single groove but multiple non-parallel grooves is that the alignment of the friction element 100 on the pad carrier 20 can be freely chosen. In particular, if there is only a single friction element 100 on the pad carrier 20, this provided the advantage that all grooves 130 are never parallel to the friction lanes 1 10 and, hence, the desired effect is achieved.

The way of attaching the friction element 100 to the pad carrier by using a bolt/calotte element 127 together with the backside plate 126 can be the same as the one shown in Figs. 5A, 5B. In addition, as also in the previous embodiments, the grooves 131 , 132 do not go through the complete sinter material 140 (see Figs. 6A,B). It is further noted, the embodiments of Figs. 6A and 6B do not comprise any recess or through-hole. The sinter material 140 is, for example, attached to the backside plate 126 directly by the sinter process which ensures a secure attachment of the sinter material 140. The backside plate 126 may, for example, comprise a metal to ensure a secure attachment to the pad carrier 20. The holes depicted in the backside plate 126 (see Figs. 6A and 6B, the upper left drawing), can be used to fix the backside plate 126 during the sinter process, when the sinter material 140 is sintered on the backside plate 126.

The width W of the groove(s) 130, 131 , 132 may be between 4 and 10 mm or between 3 and 20 mm. This width W of the groove(s) 130, 131 , 132 can be adjusted such that the abrasion material and water can be collected by the groove(s) 130, 131 , 132 to improve the friction force. This improvement is achieved by the interrupted contact of the friction elements 100 to the brake disc as a result of the groove(s) 130, 131 , 132 - only shortened friction lanes 1 10 are possible inside the friction surface 105 of the elements 100.

Fig. 7 depicts an embodiment for the brake pad, wherein the friction elements 100 are attached directly to the pad carrier 20 using the bolt/calotte element 127. On the left- hand side, Fig. 7 shows an overview of the pad carrier 20 with one friction element 100, whereas on the right-hand side, Fig. 7 shows a cross-sectional view through the cross- section line shown on the left-hand side.

In particular, the pad carrier comprises multiple holes, through which the bolt 127 of each friction element 100 extends and is secured on the opposite side of the pad carrier 20 by a fixing spring 220. The sinter material 140 comprises the at least one groove 130 extending approximately perpendicularly to the longitudinal direction of the pad carrier 20 and thus in a nonparallel way to the acting braking force in case the brake is activated. In addition, a disc spring 210 is arranged between the pad carrier 20 and the back side plate 126 providing a preload pressure resulting in a gap between the pad carrier 20 and the back side plate 126 in case no braking force is applied. This gap enables a tilting of the friction element 100 relative to the pad carrier 20. Moreover, the backside plate 126 has a spherical part allowing the tilting of the friction element 100 relative to the pad carrier 20.

According to embodiments the friction element 100 may also be rotatable, at least to some extent, about a rotational axis passing through the bolt 127, but cannot move perpendicularly to the pad carrier 20 or in a lateral direction along the pad carrier 20.

Fig. 8 depicts another embodiment for the brake pad, wherein a rocker element 230 is arranged between the friction element 100 and the pad carrier 20, but no disc spring 210 is provided. The rocker element 230 may provide a carrier for one or more friction elements 100 attached to the pad carrier 20.

Again, the friction element(s) 100 is/are secured with a fixing spring 220 on the back side of the pad carrier 20 and a spherical calotte element 127 enables a tiltable attachment of the friction element 100 to the pad carrier 20. This tilting is made possible and limited by a gap formed between the rocker element 230 and the back side plate 126. Similarly, between the rocker element 230 and the pad carrier 20 a further gap can be formed to enable a tilting between the rocker element 230 and the pad carrier 20. Optionally, multiple friction elements 100 can be attached directly to the rocker element 230, which in turn is secured to the pad carrier 20. As a result, a group of friction elements 100 can be tilted together with respect to the pad carrier 20.

As mentioned already, the tilting of the at least one friction element 100 improves the frictional contact between the sinter element and the brake disc, thereby improving the braking effect.

Embodiments of the present invention provide the following advantages:

- The metal pickup or any other material from the brake disc is reduced, since metal pickup can only occur if the contact between the friction elements and the brake disc is not interrupted (i.e. the friction lanes are long).

- The transport of moisture or water away from the friction elements is improved, whereby the friction force during wet conditions is further improved. The description and drawings merely illustrate the principles of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise various

arrangements that, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its scope.

Furthermore, while each embodiment may stand on its own as a separate example, it is to be noted that in other embodiments the defined features can be combined differently, i.e. a particular feature descripted in one embodiment may also be realized in other embodiments. Such combinations are covered by the disclosure herein unless it is stated that a specific combination is not intended.

LIST OF REFERENCE SIGNS

20 pad carrier

100, 101 , 102, ... friction element 105 friction surface

1 10 friction lanes

120 recess or hole

125 attachment means

126 backside plate

127 bolt/calotte element

130,131 ,... groove(s)

140 sinter material

210 disc spring

220 fixing spring

230 rocker element

Claims

1 . A brake pad for a railway vehicle (10) with a brake disc, the brake pad comprising at least one friction element (100) non-rigidly attached to a pad carrier (20), the friction element (100) comprising a friction surface (105) being in contact, during braking, with the brake disc to provide a friction force acting along friction lanes (1 10) the friction surface (105)

characterized by

at least one groove (130) extending along the friction surface (105) non-parallel to the friction lanes (1 10) of the friction force acting during braking of the railway vehicle (10), wherein the at least one groove (130) is arranged symmetrically or asymmetrically in respect to a geometric center of the friction surface (105).

2. The brake pad according to claim 1 ,

characterized in that

the at least one groove (130) is configured, during braking, to collect and convey material along the friction lanes (1 10).

3. The brake pad according to claim 1 or claim 2, the friction element (100) being characterized by

- sinter material (140) providing the friction surface (105) with the groove (130) and comprising a recess (120); and

- attachment means (125) arranged on a side of the sinter material (140) which is opposite to the friction surface (105) and being accessible at least partly via the recess (120), the attachment means (125) being adapted to attach the sinter material (140) to the pad carrier (20) such that the groove (130) extends in a non- parallel direction to the friction lanes (1 10).

4. The brake pad according to claim 3,

characterized in that

the attachment means (125) are configured to rotational-fixed attach the sinter material (140) on the pad carrier (20).

5. The brake pad according to claim 3 or claim 4,

characterized in that

the attachment means (125) are configured to flexibly attach the sinter material (140) on the pad carrier (20).

6. The brake pad according to one of the preceding claims, wherein the pad carrier (20) is configured to hold a plurality of friction elements (100, 101 , 102, 103) at predetermined positions,

characterized by

comprising a shape so that, upon rotation, the friction element (100) abuts another friction element (101 , 102, 103) of the plurality of friction elements (100, 101 , 102, 103) to thereby enable rotations of the friction element (100) on the pad carrier (20) only up to a maximal rotation angle, when the plurality of friction elements (100, 101 , 102, 103) is attached to the pad carrier (20).

7. The brake pad according to claim 6,

characterized in that

the shape represents a polygon, especially a hexagon or pentagon.

8. The brake pad according to one of the claims 3 to 7,

characterized in that

the groove (130) crosses the recess (120) and comprises a width (W) within the range between 3 and 15 mm, or between 4 and 10 mm.

9. The brake pad according to one of the preceding claims,

characterized in that

an angle (a) between the direction of the groove (130) and the friction lanes (1 10) is in an angular range between 40° to 140°.

10. A railway vehicle

characterized by

- a brake pad according to one of the preceding claims; and - a brake disc to brake the railway vehicle by pressing the friction elements (100) with the friction surface (105) on the brake disc while the groove (130) extends non-parallel to the friction lanes of a friction force exerted between the friction elements (100) and the brake disc.