BRAKE DISC FOR A DISC BRAKE

Abstract

A brake disc, also referred to as a rotor, for a disc brake has the function of interacting with a brake lining as a friction partner in the disc brake. The brake disc is formed at least in part of a material having a molybdenum content of ?50 wt. %.

Claims

1-14. (canceled)

15. A brake disk for a disk brake, the brake disk comprising: at least partly of a material having a molybdenum content of ?50 wt. %.

16. The brake disk according to claim 15, further comprising a circumferential friction section, wherein said circumferential friction section containing at least partly of a material having a molybdenum content of ?50 wt. %.

17. The brake disk according to claim 15, wherein said material with said molybdenum content of ?50 wt. % takes a form of a composite material or of a material composite.

18. The brake disk according to claim 15, wherein said material with said molybdenum content of ?50 wt. % at least partly takes a form of a coating.

19. The brake disk according to claim 15, wherein the brake disk is formed entirely from said material having said molybdenum content of ?50 wt. %.

20. The brake disk according to claim 15, wherein said material having said molybdenum content of ?80 wt. %.

21. The brake disk according to claim 15, wherein said material having said molybdenum content of ?95 wt. %.

22. The brake disk according to claim 15, wherein said material having said molybdenum content of ?50 wt. % is formed by a molybdenum alloy having a molybdenum content of ?99.93 wt. %, a boron content of ?3 ppmw and a carbon content of ?3 ppmw.

23. The brake disk according to claim 15, wherein the brake disk has been produced by powder metallurgy.

24. The brake disk according to claim 23, wherein the brake disk has been produced by pressing and sintering.

25. A method of using a brake disk, which comprises the steps of: providing a bicycle; and installing the brake disk according to claim 15 on the bicycle.

26. A brake disk, comprising: at least one brake caliper; at least one brake lining; and a brake disk containing at least partly of a material having a molybdenum content of ?50 wt. %.

27. A disk brake, comprising: at least one brake caliper; a brake disk; and a brake lining containing at least partly of a material having a molybdenum content of ?10 wt. %.

28. A method of producing a brake disk, which comprises the steps of: providing a powder mixture having a molybdenum content of ?50 wt. %; performing either of: i) pressing and sintering the powder mixture to give a sintered body, forming the sintered body to give a semifinished product, and cutting out the brake disk; or ii) pressing the powder mixture to near a net shape, followed by sintering.

29. The method according to claim 28, which further comprises additionally performing step ii) by processing the net shape to create the brake disk.

Description

[0096] Further advantages and benefits of the invention are apparent from the description of working examples that follows, with reference to the appended figures.

[0097] The figures show:

[0098] FIG. 1: a brake disk in a working example

[0099] FIG. 2a, 2b: schematic cross sections of further working examples

[0100] FIG. 3 a working example of an assembled brake disk

[0101] FIG. 4 a schematic diagram of a disk brake

[0102] FIG. 5 a schematic diagram of a brake lining

[0103] FIG. 6 a vehicle with a disk brake

[0104] FIG. 7a, 7b a diagram of individual braking operations

[0105] FIG. 8 a diagram of a series of 100 brake tests

[0106] FIG. 9 a diagram of a series of 500 brake tests

[0107] FIG. 1 shows a perspective view of a brake disk 1 in a working example. What is shown is a typical brake disk for disk brakes on bicycles. This type of brake disk features a slim design. A material thicknesssis typically between 1.5 mm and 2.5 mm. A diameterDis typically between 140 mm and 210 mm.

[0108] The brake disk 1 has a circumferential friction section 2, which is in a friction pairing in a braking operation. Frequently, the friction section 2 has holes 21 for improved removal of heat. In general, a brake disk 1 has distinct material cutouts.

[0109] By means of a securing section 4, the brake disk 1 can be secured to a hub or the like for transmission of a braking torque. The securing section 4 is configured here as a 6-hole receiver.

[0110] There is a carrier section 3 between securing section 4 and friction section 2. Frequently, the carrier section 3 is not filled with material, but has distinct material cutouts 31, such that the carrier section 3 consists essentially of arms 32.

[0111] Dimensions of the arms 32 follow mechanical requirements. It is also possible for a heat budget of the brake disk 1 to influence the configuration of the carrier section 3.

[0112] Friction section 2, carrier section 3 and securing section 4 are not physically separated here. Instead, in the present working example, the brake disk 1 consists of one piece of a material having a molybdenum content of ?50 wt. %. Production can especially be effected via laser cutting of sheet metal material.

[0113] As an alternative to the one-piece execution, friction section 2, carrier section 3 and securing section 4 may be manufactured separately and bonded to one another.

[0114] FIGS. 2a and 2b show, in schematic form and by way of example, cross sections of possible further forms of a material having a molybdenum content of ?50 wt. %, of which the inventive brake disk 1 consists at least partly. The cross sections may be taken, for example, from a section in a cutting planeSfrom FIG. 1.

[0115] FIG. 2a shows a composite material composed of a framework of molybdenum (Mo) and a second material (X), which second material infiltrates the molybdenum framework.

[0116] Using the example of copper as second material, it is possible to achieve a particularly high thermal conductivity coupled with good mechanical indices. One example is a composite material with up to 30 percent by weight of copper. This composite combines the high thermal conductivity of copper and the low thermal expansion of molybdenum.

[0117] Using the example of aluminum as second material, it is possible to achieve high thermal conductivity coupled with very good mechanical indices and low weight.

[0118] FIG. 2b shows a schematic of a further alternative form of a material for an inventive brake disk 1. The material with a molybdenum content of ?50 wt. % is present here as composite material of layers of molybdenum with at least one second material (X). For example, it may be the case that the laminas that form one surface of a brake disk 1 consist of molybdenum with a copper core laminated thereto.

[0119] Using the example of aluminum as second material, it is possible to achieve a high thermal conductivity coupled with very good mechanical indices and low weight.

[0120] There may also certainly be several layers and/or different material combinations. In particular, it is also conceivable to coat a carrier material, for example steel, with molybdenum. In particular, molybdenum may take the form of a layer applied by thermal spraying or one applied via cold gas spraying.

[0121] FIGS. 2a and 2b thus illustrate, by way of example and merely by way of extracts, possible forms of the molybdenum-based material.

[0122] It is conceivable to create the entire brake disk 1 from molybdenum-based composite materials or from material composites comprising molybdenum. However, it may be more economically viable to create merely the friction section 2 from a molybdenum-based composite material or material composite.

[0123] It is certainly the simplest case that the molybdenum-based material consists of pure molybdenum or of a molybdenum alloy.

[0124] FIG. 3 shows a brake disk 1 in a further working example. The circumferential friction section 2 therein is designed as a separate component connected to the carrier section 3. What is not shown here, but is additionally conceivable, is a physically separate design and subsequent bonding of carrier section 3 and securing section 4.

[0125] The circumferential friction section 2 is preferably formed from a molybdenum-based material. Carrier section 3 and securing section 4 may consist, for example, of steel.

[0126] The bonding of friction section 2 and carrier section 3 is implemented here via rivets as bonding means. Alternatively or additionally, other bonds or bonding techniques such as form-fitting, welding, soldering, adhesive bonding etc. are also conceivable.

[0127] The design shown here with a separately executed friction section 2 is of particular interest when the friction section 2 consists, for example, of a molybdenum-based composite material or material composite. In such a case, it is then possible for carrier section 3 and securing section 4 to be designed essentially with regard to mechanical criteria, while the friction section 2 may be designed predominantly with regard to its friction properties and/or heat management. In other words, this design enables decoupling of the design criteria of friction section 2, carrier section 3 and securing section 4.

[0128] It is also possible in a particularly simple manner by the design to achieve different material thicknesses in friction section 2, carrier section 3 and securing section 4.

[0129] It is certainly also conceivable to form a brake disk 1 according to the principle of construction detailed here even completely from a molybdenum-based material.

[0130] FIG. 4 shows a schematic of a disk brake 5 for a bicycle. The disk brake 5 comprises a brake disk 1, a brake caliper 6 and brake linings 7.

[0131] On actuation of the disk brake 5, the brake linings 7 are pressed against the brake disk 1 and create a braking effect by friction.

[0132] FIG. 5 shows a schematic of a brake lining 7. The brake lining 7 refers here to the actual friction lining fixed on a carrier plate.

[0133] For brake disks 1 made of a material having a molybdenum content of

?50 wt. %, it is possible to use conventional, commercially available brake linings 7.

[0134] In a further aspect of the disclosure, it may be the case that brake linings 7 consist of a material having a molybdenum content of ?10 wt. %. It is preferably the case that the material has a molybdenum content of ?20 wt. %, further preferably of ?30 wt. %, especially preferably of ?40 wt. % and further ?50 wt. %. Benefits of molybdenum are also beneficial for use in a brake lining, especially the increase in wear resistance.

[0135] In such an arrangement, the brake disk could be in conventional physical form, for example consist of steel.

[0136] It is certainly possible, in the case of brake linings 7 made of a molybdenum-base material, for the brake disk 1 also to be formed from a molybdenum-base material.

[0137] FIG. 6 shows a schematic of a vehicle, in the present example a bicycle, equipped with disk brakes 5 having inventive brake disks 1. The inventive brake disks 1 are particularly suitable for two-wheel vehicles, especially for bicycles.

[0138] FIGS. 7a and 7b show diagrams of individual braking operations according to the test setup described further up.

[0139] An individual braking operation is divided in each case into a phase of about 2.5 seconds for buildup of a braking force, followed by a stationary phase of constant braking force of around five seconds. After about 7.5 seconds, the braking force is released again. For later discussion of steady-state braking characteristics, only the steady-state region between 2.5 seconds and 7.5 seconds of an individual braking operation is considered, and values from this range are used for averaging.

[0140] FIG. 7a shows the progression of the braking torque in [Nm] (newton meters) on the ordinate against time in seconds [s] for a braking operation on a steel brake disk (St). FIG. 7b, analogously, shows a braking operation on a molybdenum brake disk (Mo). The comparison of the two curves shows that the fluctuation in braking torque in the case of the steel brake disk is greater than in the case of the molybdenum brake disk. In the case of the molybdenum brake disk, a scatter of the braking torque in the steady-state region in a test selected as example was about 0.3 Nm about a mean of 11.6 Nm. In the case of steel, in a comparable data range, braking torque scatter in the steady-state region was around 0.5 Nm about a mean of 12.6 Nm. In practice, this means gentler braking characteristics within a braking operation with the molybdenum brake disk.

[0141] The mean braking torque on steel here is somewhat higher than in the case of molybdenum. One reason for this could be that the brake linings used are optimized for pairing with steel.

[0142] FIG. 8 shows a diagram of mean braking torque values of above-addressed steady-state regions of individual braking operations. Plotted in the diagram are mean braking torque values on the ordinate in [Nm] for the molybdenum brake disk (Mo-thick line) and the steel brake disk (St-thin dashed-and-dotted line) against the numbernof braking cycles on the abscissa. A numbernis dimensionless, i.e. [-]. 100 braking cycles were effected, and the plot corresponds to the chronological sequence of the individual braking operations.

[0143] What is striking is the significant scatter in the steady-state braking torques on the steel brake disk compared to a smooth progression with low scatter on the molybdenum brake disk. In practice, this means particularly uniform and repeatable braking characteristics with the molybdenum brake disk.

[0144] Also observed is a faster rise in the average braking torque in the case of molybdenum to a plateau after about three to five braking cycles, whereas, in the case of steel, a plateau was reached only after about 20 braking cycles. Without committing to any physical theory, the faster rise in the case of molybdenum could be attributable to the lower heat capacity and hence faster heating thereof. In practice, this means rapid attainment of an operating temperature with essentially the same friction characteristics.

[0145] FIG. 9 shows a summary of five test series, each of 100 braking cycles. What are again shown are the averaged braking torques from the steady-state regions of the individual braking operations. The braking torques are plotted on the ordinate in [Nm] against the numbern[-] of braking cycles on the abscissa. The results were plotted in their chronological sequence. The results of the test series were added together for the diagram.

[0146] It can be seen that, in the case of the molybdenum brake disk (Mothick line), the overall impression from 500 braking operations is a braking torque of very good reproducibility. The variances within each of the five test series are smaller than in the case of the steel brake disk (Stthin line).

[0147] In addition, the scatter of the braking torque between the test series is smaller for molybdenum than for steel.