Method for producing a brake disc, brake disc and motor vehicle

Abstract

The invention relates to a method for producing a brake disc (10), in which a main body (12) for the brake disc (10) is coated (V1) with a coating (14) composed of a hard material and a roughness of the coating (14) is reduced (V2) by a non-abrasive, compression-forming process, wherein during this process at least one depression (24) is introduced into the coating (14), wherein the depression (24) serves as an indicator for wear of the coating (14) of the brake disc (10).

Description

[0001] Method for producing a brake disc, brake disc and motor vehicle

[0002] The invention relates to a method for producing a brake disc, a brake disc and a motor vehicle with a brake disc.

[0003] EP 2 105 628 B1 discloses a brake disc with a device for monitoring the wear condition of the brake disc. The device comprises at least one load indicator connected to the brake disc by a connecting element. Upon reaching a predetermined wear condition, the connecting element releases the load indicator or displaces the load indicator by a predetermined displacement distance.

[0004] Furthermore, US Pat. No. 6,457,566 B1 discloses a brake rotor for a vehicle braking system comprising a radially extending annular disc having inner and outer planar brake contact surfaces. At least one optical wear indicator is formed as a recess in at least one of the inner and outer brake contact surfaces. The optical wear indicator comprises a recessed surface substantially parallel to the brake contact surface at a depth such that the thickness of the annular disc below the recessed surface corresponds to or is greater than a predetermined minimum usable thickness of the annular disc.

[0005] Furthermore, WO 2011 / 124312 A2 discloses a friction disc with a wear protection layer and integrated wear indicator. The friction disc has a friction surface, and the wear protection layer completely covers the friction surface. Between the wear protection layer and the friction disc, at least one indicator surface element is provided, which occupies part of the friction surface and differs from at least one of the friction surface and wear protection layer components of the friction disc by at least one of the features of color and structure.

[0006] The object of the present invention is to provide a solution which enables a particularly rapid production of a coated brake disc with a predetermined surface quality, wherein the brake disc has a wear indicator.

[0007] This object is achieved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the subclaims, the description, and the figures. Features, advantages, and possible embodiments presented in the description for one of the subject matter of the independent claims are to be regarded at least analogously as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

[0008] The invention relates to a method for producing a brake disc, in particular for a motor vehicle, in particular a motor vehicle, in particular a passenger car. The brake disc is the wheel-side part of a disc brake, on which brake pads attached to the brake caliper act in order to decelerate a rotational movement of a wheel of the motor vehicle assigned to this brake disc. A brake disc is usually designed point-symmetrically to an axle center, usually circular, and has an axle fastening via which the brake disc can be fastened to the wheel of the motor vehicle to be decelerated by means of the brake disc. The method provides for a base body for the brake disc to be coated with a hard material. In this case, the base body of the brake disc can in particular be coated with a carbide as the hard material.

[0009] The method provides for at least one depression to be subsequently created in the coating in a non-abrasive, pressure-forming process, wherein the depression serves as an indicator of wear of the coating of the brake disc. After the brake disc has been put into operation, the extent to which the coating of the brake disc has been worn can be determined based on the remaining depth of the depression. The smaller the remaining depth of the depression, the more worn the brake disc, in particular the coating of the brake disc, is. When braking using the brake disc, material can be removed from the surface of the coating, whereby the thickness of the coating is reduced. As a result, the depth of the depression decreases as the coating wears away.For example, it may be specified that as soon as the bottom of the recess is flush with the remaining outer surface of the coating, the brake disc can no longer be used and must therefore be replaced, as the brake disc's service life has been reached, as determined by the depth of the recess. Using the non-abrasive, pressure-forming process, the at least one recess can be particularly easily incorporated into the coating as an indicator of wear.

[0010] In a possible development of the invention, it is provided that, in addition to creating the recess in the coating, the roughness of the coating is reduced by the non-abrasive, pressure-forming process. During pressure forming, a workpiece is plastically deformed using compressive forces. Forming, to which pressure forming belongs as a subgroup, is one of the six main groups of manufacturing processes. During forming, blanks made of plastic materials, in this case the coating, are deliberately shaped into a different form without removing material from the blanks. The material thus retains its mass and cohesion. During the pressure-forming process, roughness peaks on a surface of the coating are deformed, thereby reducing the roughness of the coating surface.This allows a specific roughness for the coating surface to be precisely adjusted with particularly minimal material loss. Thus, during the readjustment of the brake disc, which reduces the roughness of the coating surface, at least one recess is simultaneously embossed into the coating using the non-abrasive, pressure-forming process. The brake disc can thus be manufactured particularly easily, in a particularly short time, with a particularly small number of manufacturing steps, and with particularly low material consumption for coating the base body.

[0011] In a further possible development of the invention, the coating is applied to the base body using a cold gas spraying process and / or a laser deposition welding process. Cold gas spraying is a coating process in which a coating material in powder form is applied to the carrier material, in this case the base body, at very high speed. For this purpose, a process gas heated to a few hundred degrees Celsius, in particular nitrogen, argon, helium, or other noble gases, is accelerated to supersonic speed by expansion in a Laval nozzle, and the powder particles of the coating material are then injected into the gas jet.These injected so-called spray particles are accelerated to such a high speed that, in contrast to other thermal spraying processes, they form a dense and firmly adhering layer upon impact with the carrier material, even without prior melting or melting.

[0012] Laser material deposition is a type of cladding in which a surface is deposited onto a workpiece, in this case the base body, by means of melting and simultaneous application. This can particularly be done in powder form. In laser material deposition, a high-power laser serves as the heat source. In laser material deposition with powder, the laser heats the workpiece, in this case the base body, usually in a defocused manner, and melts it locally. At the same time, an inert gas mixed with a fine coating material is applied. The active area is supplied with the powder / gas mixture via trailing or coaxial nozzles. The powder melts at the heated point and bonds with the material of the base body. Using laser material deposition with powder, the base body can be coated particularly easily and fully automatically.Cold gas spraying and laser cladding enable particularly simple and even coating of the base body with the coating.

[0013] In a further possible embodiment of the invention, it is provided that an averaged roughness depth Rz of the coating is reduced from a predetermined initial value to a predetermined final value. The averaged roughness depth Rz is the mean value of individual roughness depths from five consecutive individual measuring sections in the roughness profile. The extreme values ​​in each measuring section are added together and the range is divided by the number of measuring sections. Roughness data is usually given in micrometers. Within the scope of the method, it is thus possible to reduce the determined roughness depth Rz of the coating particularly significantly, whereby a particularly high surface quality can be achieved. At the same time, the wear indicator is introduced into the coating along with the reduction in the roughness of the surface of the coating.In a further possible embodiment of the invention, it is provided that the at least one indentation is introduced into the coating by means of a press in a pressing process. In particular, the roughness of the coating can be reduced by means of the press in the pressing process and at the same time the at least one indentation can be introduced into the coating by means of the press. The pressing process is therefore the non-abrasive, pressure-forming process in the context of which the at least one indentation is introduced into the coating. Here, the indentation can be embossed into the surface by means of a punch during pressing. Presses are forming machines with rectilinear relative movement of the tools. By means of the press, the brake disc can be pressed together at least in some regions in the axial direction of the brake disc, whereby a force is applied to the surface of the coating.As a result of the force applied to the coating surface, material can be shifted from roughness peaks on the coating surface into respective valleys on the coating surface. As a result, the roughness of the coating is reduced. Because at least one depression is created in the coating simultaneously with the surface leveling using the stamp, the brake disc can be manufactured particularly quickly with a particularly short cycle time.

[0014] In a further possible embodiment of the invention, it is provided that the at least one depression is introduced into the coating by means of at least one roller in a rolling process. In particular, the roughness of the coating can be reduced by means of at least one roller in a rolling process and at the same time the at least one depression can be introduced into the coating by means of the roller. In order to introduce the at least one depression into the coating, the roller can have an elevation on its surface which is assigned to the depression to be created. The elevation thereby forms a negative shape of the depression to be created. Rolling is a manufacturing process from the group of pressure forming in which the material, in this case the brake disc, is formed between two or more rotating rolling tools and its cross-section is reduced in the process. In terms of material deformation, rolling is a bulk forming process.Rolling allows the roughness of the coating surface to be reduced particularly easily and evenly. Furthermore, the depression in the coating can be pressed into the coating at the same time as the roughness of the coating surface is reduced. As a result, the brake disc can be manufactured particularly easily and quickly.

[0015] In this context, it can be provided, in particular, that the coated brake disc is placed in a rolling tool, at least two rollers of the rolling tool are placed against the coating from axially opposite sides of the brake disc, and by pressing the rollers against the brake disc, the coating is subjected to pressure. At least one of the rollers has an elevation which is assigned to the depression to be created. The elevation, with its outer contour, forms a negative image of the outer contour of the depression to be created. As a result of the application of pressure to the coating, the at least one depression is introduced into the coating.During the rolling process, the brake disc is pressed between rollers placed against the brake disc from opposite sides in the axial direction, whereby the rollers apply pressure to the surface of the coating on the axially opposite sides of the brake disc. In this context, it can be provided, in particular, that the rollers roll over the surface of the coating while the brake disc rotates around its axially extending central axis relative to the rollers.

[0016] In a possible further development of the invention, several depressions are introduced into the coating, each of which can have a different distance from an axial center axis of the brake disc. This allows the remaining depth of the different depressions to be used to determine whether the coating, and thus the brake disc, is suffering from oblique wear when the brake disc becomes worn.

[0017] The invention further relates to a brake disc, in particular for a motor vehicle, having a base body provided with a coating made of a hard material, in particular a carbide. In particular, the coating is applied at least to outer sides of the base body that are opposite one another in the axial direction, wherein the coating provides a braking surface for each outer side of the base body for decelerating a wheel of the motor vehicle with the brake disc assigned to that wheel. At least one recess is introduced into the coating as an indicator of coating wear in a non-abrasive, pressure-forming process. The brake disc is produced in particular using a method as already described in connection with the method according to the invention.Based on the structure of the coating, it can be determined whether the at least one depression was treated using an abrasive process during the production of the coating for the brake disc or whether the coating was subjected to a forming process. During the forming process using the non-abrasive, pressure-forming process, material is merely displaced and not removed. This can be detected if necessary during an examination of the coating, whereby it can be proven that the brake disc was produced using the described process. By providing at least one depression in the coating, the wear of the brake disc, in particular of the coating, can be detected particularly well. In this case, the wear of the coating can be determined in particular based on the remaining depth of the depression.The smaller the remaining depth of the depression in the coating, the greater the coating wear. Using the depression, brake disc wear can be determined particularly easily, without the use of tools, and reliably. Furthermore, the depression can be easily incorporated into the brake disc as an indicator of coating wear.

[0018] In a further development of the invention, it can be provided that a plurality of depressions are introduced into the coating, each having a different distance from an axial center axis of the brake disc. As a result, when the brake disc wears, oblique wear of the coating can be determined based on the depressions. In particular, this oblique wear of the coating is determined when the respective remaining depths of the depressions also increase or decrease with an increase in the radial distance of the respective depression from the center axis. Based on the remaining depths of the depressions, the oblique wear of the brake disc coating can be determined particularly easily and reliably.For example, at least three recesses can be provided, wherein one recess is arranged on each of the braking surfaces in relation to a radial distance from the central axis, one of the recesses is arranged in the middle and one of the recesses is arranged on the outside of the braking surface.

[0019] The invention further relates to a motor vehicle with a brake disc, as already described in connection with the brake disc according to the invention. This brake disc is part of a disc brake and is assigned to at least one wheel of the motor vehicle. In particular, the brake disc is connected in a rotationally fixed manner to the at least one wheel to be decelerated by this brake disc. The use of the described brake disc in the motor vehicle makes it particularly easy to determine and analyze wear of the brake disc due to use in the motor vehicle.

[0020] Further features of the invention may emerge from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures alone, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0021] The drawing shows:

[0022] Fig. 1 is a process diagram for a method for producing a brake disc;

[0023] Fig. 2 is a schematic sectional view of a section of a coating of the brake disc before forming the coating and after forming the coating;

[0024] Fig. 3 is a schematic plan view of the brake disc, wherein several recesses are introduced into the coating of the brake disc;

[0025] Fig. 4 is a schematic sectional view of the brake disc inserted into a press; and

[0026] Fig. 5 is a schematic sectional view of the brake disc inserted into a rolling tool.

[0027] In the figures, identical and functionally equivalent elements are provided with the same reference numerals. Fig. 1 shows a process diagram for a method for producing a brake disc 10. The brake disc 10 is part of a disc brake of a motor vehicle. The method comprises a first method step V1 and a second method step V2 which follows the first method step V1. In the first method step V1 of the method, a coating 14 made of a hard material, in this case a carbide, is applied to a base body 12 of the brake disc 10. The coating 14 can be applied to the base body 12 using a cold gas spraying process and / or a laser deposition welding process. For example, after being applied to the base body 12, the coating 14 has an average roughness depth Rz of approximately 25 micrometers as an initial value.In order to reduce this average roughness depth Rz of the coating 14 from 25 micrometers, for example, to a maximum of ten micrometers as a specified final value, in particular to a maximum of 6.3 micrometers, it is provided that in the second method step V2, the roughness of the coating 14 is reduced by a non-abrasive, pressure-forming process. The roughness of the coating 14 can be reduced in a pressing process shown in Fig. 4 or in a rolling process shown in Fig. 5.

[0028] Fig. 2 shows a cross-section of the coating 14 before the non-abrasive pressure forming process and after the non-abrasive pressure forming process. It can be seen that respective roughness peaks 18 on the surface 20 of the coating 14 are reshaped to reduce the roughness of the surface 20 of the coating 14. During the forming process, material is shifted from the roughness peaks 18 into respective roughness valleys 22 of the surface 20 of the coating 14. As a result, the average roughness depth Rz of the coating 14 is reduced during the non-abrasive pressure forming process.

[0029] In order to be able to detect wear of the brake disc 10, in particular of the coating 14, particularly well when the brake disc 10 is used, it is provided that in the second method step V2, at least one depression 24 is introduced into the coating 14 as part of the non-abrasive, pressure-forming process.

[0030] Fig. 3 shows a schematic plan view of the brake disc 10, in which a plurality of depressions 24 are introduced into the coating 14. The depressions 24 are each created by embossing into the surface 20 of the coating 14. The wear and tear of the coating 14 can be determined via a respective remaining depth of the depressions 24. In the embodiment of the brake disc 10 shown in Fig. 3, three depressions 24 are introduced into the coating 14, each of the depressions 24 having a different radial distance from a central axis 26 of the brake disc 10. A first of the depressions 24 is thus arranged on the inside with respect to a braking surface 28 provided by the coating 14, the second depression 24 is arranged in the middle, and the third depression 24 is arranged on the outside.Because the recesses 24 have different radial distances from the center axis 26, it can be determined on the basis of the respective remaining depths of the recesses 24 whether the coating 14 is worn away evenly as a result of the use of the brake disc 10 or is worn away at an angle and thus the brake disc 10 wears at an angle.

[0031] Fig. 4 shows the brake disc 10 during the second method step V2, wherein the brake disc 10 is processed in the non-abrasive, pressure-forming process by means of a press 30. The press 30 comprises a counterpart tool 32 which has a holder 34. The brake disc 10 is inserted into the holder 34 of the counterpart tool 32 for processing. Subsequently, at least one punch 36 of the press 30 is moved along a travel path which runs in the axial direction A of the brake disc 10. The axial direction A runs parallel to a longitudinal direction of the central axis 26. By moving the at least one punch 36 along the travel direction 38 towards the brake disc 10, the punch 36 and the counterpart tool 32 are applied to the brake disc 10 and thereby to the surface 20 of the coating 14 from sides opposite one another in the axial direction A.The brake disc 10 is then subjected to a force 40 in the axial direction A by the punch 36, as a result of which the brake disc 10 is partially pressed together between the at least one punch 36 and the counterpart tool 32. As a result, the surface 20 of the coating 14 is reshaped, as a result of which the roughness of the surface 20 of the coating 14 is reduced. The punch 36 and / or the counterpart tool 32 can have a projection associated with the recess 24 for creating the recess 24 in the coating 14, which projection forms a negative image of the shape of the recess 24 created. By pressing the brake disc 10 together between the at least one punch 36 and the counterpart tool 32, a recess 24 associated with each projection is created in the coating 14. The at least one recess 24 is thus embossed into the coating 14 by means of the at least one punch 36.

[0032] Fig. 5 shows a schematic sectional view of the brake disc 10 during the second method step V2, wherein the brake disc 10 is machined in the second method step V2 using a rolling tool 42. The rolling tool 42 has a counterpart tool 32 which provides a receptacle 34 for the brake disc 10. The brake disc 10 can be inserted into this receptacle 34 when the brake disc 10 is machined using the rolling tool 42. In the present case, the rolling tool 42 comprises two rollers 44, of which only one is shown in Fig. 5. The rollers 44 are each configured to be rotated about axes of rotation 46 assigned to the respective rollers 44 and running centrally to the respective rollers 44. As a result of the rotation, the respective rollers 44 can roll over the surface 20 of the coating 14 and in doing so can apply the force 40 to the surface 20 of the coating 14.The rollers 44 of the rolling tool 42 are designed to be applied to the brake disc 10 from opposite sides in the axial direction A. In the present case, the roller 44, not explicitly shown in Fig. 5, is integrated into the counterpart tool 32. Thus, the rollers 44 are applied to the coating 14 of the brake disc 10 from above and below along the axial direction A, whereby the brake disc 10 is pressed together between the rollers 44 with a force 40. During the rolling of the brake disc 10, the brake disc 10 rotates about the central axis 26 in the holder 34. The brake disc 10 is driven along a wheel bolt bore 48 of the brake disc 10.

[0033] At least one of the rollers 44 can have a raised portion on its outer surface provided for introducing a respective depression 24 into the coating 14, which elevation, with its outer contour, forms a negative image of the inner contour of the depression 24 to be created. If multiple depressions 24 are to be introduced into the coating 14, then at least one of the rollers 44 has at least one raised portion provided for introducing at least one depression 24 into the coating 14. It is possible for multiple depressions 24 to be introduced into the coating 14 using the raised portion of a single roller 44 by rolling the roller 44 over the coating 14 with multiple revolutions.The described method makes it possible for at least one embossing to be introduced simultaneously at least one location, in particular several embossings at different locations of the coating 14 in the form of the depression 24, in particular by means of the at least one stamp 36 or by means of the roller 44, during the working step of non-abrasive pressure forming of the surface 20 of the coating 14.

[0034] The pressing process or the rolling process makes it possible to compensate for distortions from upstream processes, such as laser cladding.

[0035] Overall, the invention shows how a wear indicator, in this case the recess 24 as a wear indicator, can be introduced into the hard-coated brake disc 10.

[0036] List of reference symbols

[0037] 10 brake disc

[0038] 12 basic bodies

[0039] 14 Coating

[0040] 18 Roughness peak

[0041] 20 Surface

[0042] 22 Rauigkeitstal

[0043] 24 Deepening

[0044] 26 Central axis

[0045] 28 braking surface

[0046] 30 Press

[0047] 32 Counterpiece tool

[0048] 34 recording

[0049] 36 stamps

[0050] 38 Travel direction

[0051] 40 power

[0052] 42 rolling tool

[0053] 44 roller

[0054] 46 Rotation axis

[0055] 48 wheel bolt hole

[0056] A axial direction

[0057] V1 to V2 respective process steps

Claims

Patent claims 1. Method for producing a brake disc (10), in which a base body (12) for the brake disc (10) is coated with a coating (14) made of a hard material (V1) and then at least one depression (24) is introduced into the coating (14) in a non-abrasive, pressure-forming process (V2), wherein the depression (24) serves as an indicator of wear of the coating (14) of the brake disc (10).

2. Method according to claim 1, characterized in that in addition to the introduction of the recess (24) into the coating (14), a roughness of the coating (14) is reduced by the non-abrasive, pressure-forming process (V2).

3. Method according to claim 1 or 2, characterized in that the coating (14) is applied to the base body (12) in a cold gas spraying process and / or in a laser deposition welding process.

4. Method according to claim 2 or according to claim 3 with reference to claim 2, characterized in that an average roughness depth Rz of the coating (14) is reduced from a predetermined initial value to a predetermined value.

5. Method according to one of the preceding claims, characterized in that the at least one recess (24) is introduced into the coating (14) by means of a press (30) in a pressing process.

6. Method according to one of the preceding claims, characterized in that the at least one depression (24) is introduced into the coating (14) by means of at least one roller (44) in a rolling process.

7. Method according to claim 6, characterized in that the coated brake disc (10) is placed in a rolling tool (42), two rollers (44) of the rolling tool (42) are applied to the coating (14) from axially opposite sides of the brake disc (10), at least one of which rollers has a projection associated with the depression (24) to be created, which projection forms a negative image of the depression (24) to be formed, and by pressing the rollers (44) onto the brake disc (10), the coating (14) is subjected to pressure, whereby the at least one depression (24) is introduced into the coating (14).

8. Method according to one of the preceding claims, characterized in that a plurality of depressions (24) are introduced into the coating (14), each of which has a different distance from an axial center axis (26) of the brake disc (10), whereby in the event of wear of the brake disc (10), an oblique wear of the coating (14) can be determined based on the depressions (24).

9. Brake disc (10) having a base body (12) provided with a coating (14) made of a hard material, wherein at least one depression (24) is introduced into the coating (14) in a non-abrasive, pressure-forming process as an indicator of wear of the coating (14).

10. Motor vehicle with a brake disc (10) according to claim 9.

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