A METHOD FOR FORMING A FRICTION MEMBER AND A FRICTION MEMBER

Abstract

A method of forming a friction surface of a friction member with an increased friction coefficient on the friction surface is described. The method includes forming the friction member including a matrix composite of a first material and reinforcing particles of a second material embedded in the first material, wherein the first material has a lower melting temperature than the second material, and forming the friction surface by melting a surface layer of the first material of the friction member to expose a part of the reinforcing particles and thereby to enable an increase of the friction coefficient of the friction surface of the friction member.

Claims

1. A method of forming a friction surface of a friction member, the method comprising: forming the friction member including comprising a matrix composite of a first material and reinforcing particles of a second material embedded in the first material, wherein said first material has a lower melting temperature than said second material, and forming said friction surface by melting a surface layer of the first material of the friction member to expose a part of the reinforcing particles and thereby to enable an increase of the friction coefficient of the friction surface of the friction member.

2. The method according to claim 1, wherein said melting the surface layer of the first material includes generating a beam directed towards a surface of the friction member to melt said surface layer of the first material.

3. The method according to claim 2, wherein said beam is a laser beam.

4. The method according to claim 2, wherein said beam is an electron beam.

5. The method according to claim 2, comprising generating a relative movement between the friction member and the beam during said melting of said surface layer.

6. The method according to claim 1, comprising generating a relative movement between the friction member and a melting device arranged to melt said surface layer of the first material.

7. The method according to claim 5, wherein said relative movement comprises rotation of the friction member.

8. The method according to claim 1, wherein said melting of the surface layer of the first material includes creating a surface structure pattern on said friction surface.

9. The method according to claim 1, wherein said first material comprises one or more of aluminium and alloying elements.

10. The method according to claim 1, wherein said second material comprises a ceramic material.

11. The method according to claim 10, wherein said ceramic material comprises at least one of SiC, Al2O3, WC and other carbides.

12. The method according to claim 1, wherein said reinforcing particles form at least 10% of the volume of the matrix composite, preferably said reinforcing particles form at least 20% of the volume of the matrix composite and more preferably said reinforcing particles form at least 30% of the volume of the matrix composite.

13. The method according to claim 1, wherein said reinforcing particles form at the most 70% of the volume of the matrix composite, preferably said reinforcing particles form at the most 60% of the volume of the matrix composite and more preferably said reinforcing particles form at the most 50% of the volume of the matrix composite.

14. The method according to claim 1, wherein said reinforcing particles are uniformly distributed in the first material.

15. The method according to claim 1, wherein said friction member is formed to a brake disc, a brake drum or to a clutch plate.

16. A friction member comprising a matrix composite of a first material and reinforcing particles of a second material embedded in the first material, wherein said first material has a lower melting temperature than said second material, characterized in that the fiction member has a friction surface formed by melting a surface layer of the first material of the friction member to expose a part of the reinforcing particles and thereby to enable an increase of the friction coefficient of the friction surface of the friction member.

17. The friction member according to claim 16, wherein said surface layer is melted by means of a beam directed towards a surface of the friction member.

18. The friction member according to claim 16, wherein said friction surface comprises a surface structure pattern on said friction surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In the following preferred embodiments of the invention are described with reference to the attached drawings, on which:

[0056] FIG. 1a is a cut view of a part of a friction member before a treatment in accordance with the method according to present invention,

[0057] FIG. 1b is a cut view of the part of a friction member illustrated in FIG. 1a after a treatment in accordance with the method according the present invention,

[0058] FIG. 2 is a perspective view, showing, in a schematic way, an apparatus adapted to perform a method in accordance with the present invention and

[0059] FIG. 3 is a side view illustrating the friction surface in FIG. 1b with a surface structure pattern on the friction surface according to an embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0060] FIG. 1a is a cut view of a part of a friction member 1 comprising a matrix composite comprising a first material 2 and reinforcing particles 3 of a second material embedded in the first material 2. The first material 2 may comprise aluminium and possibly alloying elements. The second material may comprise a ceramic material such as at least one of silicon carbide (SiC), aluminium oxide (Al.sub.2O.sub.3), tungsten carbide (WC) and other carbides.

[0061] The first material has a lower melting temperature than the second material. The melting temperature of aluminium is approximately 670° C., the melting temperature of the SiC particles is approximately 2730° C., the melting temperature of Al.sub.2O.sub.3 is approximately 2072° C. and the melting temperature of WC is approximately 2870° C. As a result of this melting temperature difference, a layer of the first material can be selectively removed by applying energy at a certain level, while the reinforcing particles of the second material can remain unchanged and in a solid form during and after the removal of the layer of the first material.

[0062] As illustrated in FIG. 1a, the particles 3 are embedded in the first material 2. Thus, the reinforcing particles 3 are distributed within the first material 2. The reinforcing particles 3 may be mixed with the first material 2 during a mixing process in connection with the forming of the matrix composite and the friction member 1.

[0063] Thus, thanks to the reinforcing particles 3 embedded in the first material 2 the strength of the matrix composite is increased comparing to a pure first material 2.

[0064] The reinforcing particles 3 may form at least 10% of the volume of the matrix composite. Preferably the reinforcing particles 3 form at least 20% of the volume of the matrix composite, and more preferably the reinforcing particles 3 form at least 30% of the volume of the matrix composite.

[0065] Further, the reinforcing particles 3 may form at the most 70% of the volume of the matrix composite. Preferably the reinforcing particles 3 form at the most 60% of the volume of the matrix composite, and more preferably the reinforcing particles 3 form at the most 50% of the volume of the matrix composite.

[0066] The volume percentage of the reinforcing particles 3 in the matrix composite has, inter alia, an effect on the maximum operating temperature of a friction member 1 made of the matrix composite. Thus, by deciding the volume percentage of the reinforcing particles 3, the friction member 1 may be adapted to different purposes with respect to the maximum operating temperature of the friction member 1.

[0067] Further, the reinforcing particles 3 may be uniformly distributed in the first material 2. Thus, the reinforcing particles 3 embedded in the first material 2 may be distributed within the first material in a regular manner, which means that distances d, schematically illustrated in FIG. 1a, between the reinforcing particles 3 may be substantially equal.

[0068] The size of the particles 3 may be approximately between 1 to 500 μm, for instance 5-50 μm and the distance d may for example be between 1 to 500 μm, for instance 10-30 μm.

[0069] For simplicity reasons only the distances d between four particles 3 have been illustrated and only in the plane of the sheet of the FIG. 1a. However, the distance d may be valid in three dimensions of the matrix material of the friction member 1. Thereby, a uniform matrix composite is provided, by which the characteristics of a friction member 1 made of the matrix composite may be improved with respect to, inter alia, strength of the friction member 1. Thus, an improved matrix composite may be provided and by this also an improved friction member 1 made of the matrix composite may be achieved thanks to the reinforcing particles 3 uniformly distributed within the first material 2.

[0070] FIG. 1b is a cut view of the part of a friction member 1 illustrated in FIG. 1a after a treatment in accordance with the method according to the present invention. In FIG. 1b, the part of the friction member 1 is illustrated after melting of a surface layer s with thickness t by being exposed to a heat energy, wherein parts of the reinforcing particles 3 are exposed. The reinforcing particles 3 have been exposed because the melted first material 2 has be relocated within the melted surface layer s of the friction member 1. The melted first material 2 can be relocated within the surface layer s of the friction member 1 due to the change of the state of the surface layer s from solid to liquid state and due to forces acting on the surface layer s of the friction member 1 during the melting process. The forces are associated with heating of the surface layer s of the friction member 1 and may, for example, be a pressure forces.

[0071] The thickness t of the surface layer s may be controlled by varying the temperature and the energy amount applied to a surface 4 of the friction member 1. By controlling the amount of energy applied to the surface 4, or into the surface layer s, the thickness t of the surface layer s to be melted in order to expose the part of the reinforcing particles 3 may be controlled. The thickness t of the surface layer s, to be melted, may be controlled depending on the size of reinforcing particles 3, such that the thickness t of the surface layer t is less than the size of the reinforcing particles 3. Thereby, after the melting of the first material of the surface layer s at least a portion of each of the part of the reinforcing particles 3 protrude from the friction surface 5. The melting of the first material may comprise a removal of a portion of the surface layer, e.g. by evaporation of the first material.

[0072] As can be seen, the surface layer s of the first material 2 has been removed and by this some of the reinforcing particles 3 have been exposed. The exposed reinforcing particles 3 protrude from the friction surface 5 formed by removing of the surface layer s of the first material 2. The part of the reinforcing particles 3 protruding from the friction surface 5 of the friction member 1 contribute to an increase of the friction coefficient of the friction surface 5 of the friction member 1 during use of the friction member 1 because of friction forces generated by the protruding portions of the reinforcing particles 3.

[0073] FIG. 2 illustrates, in a schematic way, an apparatus 6 adapted to perform a method in accordance with the present invention. The apparatus 6 comprises a beam source 7, for example a laser beam source. The laser beam may for example be generated by a semi-conductor laser diode or may be another suitable kind of laser beam.

[0074] Further, the apparatus 6 comprises a lens 8 and a mirror 9 arranged to direct beam 10 into the surface 4 of the friction member 1 in order to form a friction surface 5 of the friction member 1. The beam source 7, the lens 8 and the mirror 9 are comprised by a melting device 11. The beam 10 may be laser beam, or the beam 10 may be electron beam. The laser beam may be a pulsed laser beam.

[0075] The apparatus 6 may comprise a holding device 12 arranged for holding of the friction member 1 before and during the forming of the friction surface 5 of the friction member 1. The holding device 12 may, for example be formed as a disc of a metallic material or of any other suitable materials.

[0076] As illustrated in FIG. 2, the friction member 1 may be formed to a brake disc. The brake disc may be suitable for a vehicle, such as a car or the brake disc may be formed to be used in, for example, a wind power plant. The friction member may also be formed to a clutch plate. The clutch plate may be used for transferring of kinetic energy from an engine, for example from a combustion engine or from an electric engine. The engine may be arranged in a vehicle.

[0077] According to an embodiment, the apparatus 6 may be arranged to enable rotation of the friction member 1 around a first axis a1 in a direction of rotation R. The direction of rotation R around the first axis a1 may be clockwise or counterclockwise direction of rotation. The rotation of the friction member 1 may be achieved by rotating the holding device 12, wherein rotational movement of the holding device 12 may be transferred to the friction member 1 held by the holding device 12.

[0078] The apparatus 6 may be arranged to enable simultaneous movement, in the same or opposite direction, of the melting device 11 and the friction member 1. The melting device 11 and the friction member 1 may rotate around the first axis a1. The first axis a1 may be a common and the same axis of rotation for both the friction member 1 and the melting device 11.

[0079] Further, according to an embodiment the friction member 1 may be fixed and the melting device 11 may move, for example rotate, in relation to the fixed friction member 1.

[0080] The rotation of the friction member 1 may, be achieved, for example, by an electric motor 13 arranged to rotate the holding device 12 and thereby also to rotate the friction member 1 around the first axis a1. In a similar way, the rotation of the melting device 11 may be achieved by an additional electric motor or by the electric motor 13 that may be arranged to rotate the holding device 12 and the friction member 1. Thus, both the friction member 1 and the melting device 11 may be rotated by the same electric motor.

[0081] According to an embodiment the relative movement between the friction member 1 and the beam 10 during the step of melting of the surface layer of the friction member 1 may also comprise a reciprocating movement of the mirror 9. The mirror 9 has a function of directing the beam 10, arriving from the beam source 7, towards the surface 4 of the friction member 1. The beam 10 is directed towards the surface 4 of the friction member 1, such that the beam 10 creates a substantially right angle with the surface 4 of the friction member 1, which means that the beam 10 is substantially perpendicular to the surface 4 of the friction member 1. Thus, the relative movement between the friction member 1 and the beam 10 may be achieved by moving the mirror 9.

[0082] The mirror 9, may be controlled such that the reciprocating movement of the mirror is achieved. The mirror 9 may by controlled to rotate around a second axis a2 in a reciprocating manner, i.e. back and forth around the second axis a2 in clockwise and counterclockwise directions as illustrated in FIG. 2. As an alternative the mirror 9 may be controlled to achieve a linear movement of the mirror 9 in order to direct the beam 10 towards the surface 4 of the friction member 1. Thus, the movement of the beam 10 along the surface 4 of the friction member 1 may be achieved by the movement of the mirror 9. The movement of the mirror 9 can cause the beam 10 to move in a back and forth, reciprocating manner, and hit the surface 4 of the friction member 1 back and forth along the surface 4 of the friction member 1.

[0083] Further, the step of melting of the surface layer of the first material may comprise creating a surface structure pattern on the friction surface 5. The surface structure pattern can be achieved by controlling the mirror 9 in order to cause the beam 10 to hit the surface 4 according to a predefined pattern intended to be formed on the friction surface 5 of the friction member 1. Further, also the movement of the friction member 1 may contribute to forming of the surface structure pattern on the friction surface 5. Different surface structure patterns on the friction surface 5 may be created, as for example lines circles, crosses or other forms. The surface structure patterns are described in conjunction to FIG. 3 below.

[0084] FIG. 3 is a cut side view illustrating the friction surface 5 in FIG. 1b with a surface structure pattern on the friction surface 5 according to an embodiment. As can be seen in FIG. 3, the surface structure pattern may be formed by depressions 14 and protrusions 15 formed by the beam 10 described in conjunction to FIG. 2. The depressions 14 and the protrusions 15 may be arranged as elongated and parallel lines forming a surface structure pattern of parallel and elongated lines. According to some embodiments, the surface structure pattern may have a form of, for example, circles, crosses or other forms. The surface structure pattern on the friction surface 5 may be a combination of circles, crosses or other forms.

[0085] The invention is not restricted to the described embodiment but may be varied freely at the scope of the claims.