Highly heat dissipative and abrasion resistant brake disk for bicycles

Abstract

The present invention provides a highly heat dissipative and abrasion resistant bicycle brake disk. The brake disk is of a metal-based composite material, wherein the metal-based composite material includes a metal-containing material and 5% to 40% by volume of ceramic particles.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a bicycle brake disk, and more particularly to a bicycle brake disk made of a metal-based composite material.

[0003] 2. Description of the Prior Art

[0004] Stainless steel has high abrasion resistance therefore, bicycle brake disks are generally made of stainless steel. However, stainless steel disks' adherence is reduced when wet. This causes slippage in the interface between the brake disk and brake block in wet or rainy conditions, which in turn results in decreased braking force In addition, stainless steel has inferior heat dissipation. Thus, after several successive brakings, the temperature of stainless steel brake disks becomes relatively high. For mechanical braking, this high temperature causes the brake disk to become pliable and deformed, also resulting in inadequate braking force. For fluid pressure (fluid hydraulic) braking, this high temperature causes the braking fluid to expand and degrade, which also results in inadequate braking force

SUMMARY OF THE INVENTION

[0005] Therefore, the object of the present invention is to solve the above-mentioned problems and to provide a bicycle brake disk with high heat dissipation and good abrasion resistance.

[0006] To achieve the above object, the highly heat dissipative and abrasion resistant bicycle brake disk of the present invention is made of a metal-based composite material, wherein the metal-based composite material includes a metal-containing material and 5% to 40% by volume of ceramic particles.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 shows a perspective view of a bicycle brake disk of a metal-based composite material according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0008] The feature of the present invention is to use a metal-based composite material to manufacture a bicycle brake disk different from a conventional brake disk made of stainless steel.

[0009] Refer to FIG. 1, showing a perspective view of a bicycle brake disk of a metal-based composite material according to the present invention, The metal-based composite material includes a metal containing material and 5% to 40%, preferably 5% to 15% by volume, of ceramic particles. Suitable ceramic particles can be particles of SiC, Al2O3, TiB, or B4C, preferably SiC particles or Al2O3 particles. Preferably, the ceramic particles have a particle size of 5 to 100 &mgr;m.

[0010] The metal-containing material suitable for use in the present invention can be aluminium, aluminium alloy, magnesium, magnesium alloy, titanium, or titanium alloy, preferably aluminum or aluminum alloy. Representative examples of the aluminum alloy include AlSi, AlSiCu, AlSiZn, AlSiMg, AlSiCuZn, AlZn, AlZnMg, AlGe, AlGeSi, AlCu, AlMn, AlMg, AlLi, AlSn, and AlPb, preferably AlMgSi.

[0011] In the present invention, using the metal-based composite material to manufacture a bicycle brake disk has the following advantages: light weight, good heat dissipation, and good abrasion resistance, explained below.

[0012] The metal-containing material used in the present invention is preferably a metal or its alloy having a specific gravity of 1.7 to 4.6 g/cm3. Thus, the brake disk thus manufactured is lightweight. For example, when the metal-containing material is aluminum or aluminum alloy, the specific gravity of the composite of aluminum or aluminum alloy combined with ceramic particles is approximately 2.8 g/cm3. The specific gravity of stainless steel is approximately 7.8 g/cm3. Thus, the bicycle brake disk made of the aluminum-based composite material of the present invention is approximately one third the weight of the conventional one of stainless steel.

[0013] The thermal conductivity of ceramic particles is about 100 cal/cm·s·° C., about 1000 times the thermal conductivity of stainless steel (0.145 cal/cm·s·° C.). Therefore, the metal-based composite material combined with ceramic particles of the present invention has a much higher thermal conductivity than stainless steel. Consequently, after several successive brakings, the bicycle brake disk of the aluminum-based composite material of the present invention has a temperature that is not too high For mechanical braking the brake disk better resists becoming pliable and deformed. For fluid pressure braking, the brake disk better resists exceeding an acceptable working temperature. After several successive brakings, the brake disk still provides a good braking effect.

[0014] The hardness of ceramic particles is Hv 2550, higher than that of stainless steel (Hv 400) by six times. When the bicycle brake disk made of the aluminum-based composite material of the present invention is rubbed against a braking block, the harder ceramic particles are exposed to the surface, providing the brake disk of the invention with enhanced abrasion resistance.

[0015] The following examples are intended to illustrate the process and the advantages of the present invention more fully without limiting its scope, since numerous modifications and variations will be apparent to those skilled in the art.

EXAMPLES

[0016] The following tests were taken according to DIN 79100 Part II 5.6.4 “Breaking performance test”.

[0017] The brake disk of the present invention and a conventional bicycle brake disk were subjected to separate testing. The tested brake disk of the present invention was made of aluminum-based composite material (the aluminum alloy AlMgSi, and ceramic particles SiC). The conventional brake disk was made of stainless steel. The brake disk was rubbed against a bicycle braking block to generate a braking force. Testing methods included: (1) brake performance testing, (2) heat resistance testing, and (3) mechanical endurance testing.

EXAMPLE 1

[0018] Brake Performance Testing

[0019] (1) Test Content:

[0020] The testing speed (V) in dry conditions was 12.5 km/hr.

[0021] Before any measurements were taken, 10 trials were performed in order to break in the brake blocks.

[0022] The force applied on the brake lever was not larger than 180 N. The running wheels were not allowed to lock up.

[0023] The average braking force (F) is the average value of the braking forces determined. The average braking deceleration (a) is calculated according to the formula: a=F/m.

[0024] The mass (m) is 100 kg for calculation.

[0025] (2) Test Requirement:

[0026] DIN 79100 Part II 5.6.4 requires that the braking deceleration in dry conditions not be less than 3.4 m/s2, and in wet conditions, not be less than 2.2 m/s2.

[0027] (3) Test Results:

[0028] The test results are shown in Tables 1 and 2.

[0029] For the braking test in dry conditions, the abrasion resistance of the stainless steel brake disk is provided by its hardness. As to the aluminum-based composite brake disk, although the aluminum matrix is soft, once the ceramic particles are exposed to the surface, these ceramic particles can effectively withstand abrasion. Thus, the measured abrasion resistance of the brake disc of either the aluminum-based composite or stainless steel is very close.

[0030] For braking testing in wet conditions, the stainless brake disc exhibits slippage in its interface with the braking block during braking. Thus, the braking force is low. The ceramic particles in the aluminum-based composite brake disc are much more easily exposed during the wet braking test. Thus, the aluminum-based composite brake disk exhibits higher braking force than a conventional stainless steel brake disk when the same force is applied to the brake lever. 1 TABLE 1 Force Abrasion applied to Braking condition of the brake deceleration the brake disc Brake disk type lever (N) (m/s2) after test Al-based 80 3.59 no abrasion composite material Stainless steel 80 3.62 no abrasion

[0031] 2 TABLE 2 Force Abrasion Applied to Braking condition of the brake deceleration the brake disc Brake disk type lever (N) (m/s2) after test Al-based 60 2.59 no abrasion composite material Stainless steel 60 2.23 no abrasion

EXAMPLE 2

[0032] Heat Resistance Testing

[0033] (1) Test content:

[0034] Braking power =225 W.

[0035] The test period was 2 runs of 15 minutes.

[0036] 10 releases of the brake were allowed during each run, and the time of each release was not longer than 2 seconds.

[0037] Temperatures were determined during a total determination period of 30 minutes, and the average temperature was calculated.

[0038] (2) Test Requirement:

[0039] The temperature of the clamp was not allowed to exceed 100° C. during the heat resistance test.

[0040] (3) Test Results:

[0041] The results are shown in Table 3.

[0042] The thermal conductivity of ceramic particles in the aluminum-based composite material-made brake disk is higher than that of stainless steel by 1000 times, allowing them to provide high heat dissipation. As shown in Table 3, during the heat resistance test period, the average temperature of the aluminum-based composite brake disk is lower than that of the stainless steel brake disk. 3 TABLE 3 Brake disk type Temperature of brake disc Al-based composite material 58° C. stainless steel 72° C.

EXAMPLE 3

[0043] Mechanical Endurance Testing

[0044] (1) Test Content:

[0045] The testing speed (V) was 12.5 km/hr. Deceleration was 2.2 m/s2.

[0046] The test braked 3000 times, and each braking lasted for 2.5 seconds.

[0047] Temperatures were regularly measured at an interval of 100 times in the entire testing period. Average temperature was calculated.

[0048] (2) Test Requirement:

[0049] DIN 79100 Part II 5.6.4 requires that a braking system should pass 3000 brakings. After the test, the rims must withstand a force of 300 N applied to the brake lever and 1.5 times the maximum tire pressure.

[0050] (3) Test Results:

[0051] The 3000 times endurance test can not only detect if the brake disk can withstand long period of abrasion, but also detect its working temperature.

[0052] As shown in Table 4, the working temperature of the aluminum-based composite brake disk is only 68° C., and the disk suffers no abrasion after testing. This is because the ceramic particles provide superior abrasion resistance and heat dissipation. The hardness of the ceramic particles provides high abrasion resistance. Moreover, the ceramic particles dissipate frictional heat through radiation, thus providing good heat dissipation.

[0053] The allowable working temperature for a fluid pressure brake disk is 130° C. When the temperature exceeds 130° C., the fluid in the brake expands and forms bubbles, compromising braking force. During the entire endurance test, the aluminum-based composite brake disk of the present invention maintains low working temperatures. Thus, it is very suitable for use as a brake disk for a fluid pressure brake, and the braking force can be maintained. 4 TABLE 4 Abrasion condition of Brake disk the brake disc after Brake disk type temperature test Al-based 68° C. no abrasion composite material stainless steel 95° C. no abrasion

[0054] The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. Obvious modifications or variations are possible in light of the above teaching. The embodiments were chosen and described to provide the best illustration of the principles of this invention and its practical application to thereby enable those skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

1. A bicycle brake disk of a metal-based composite material, wherein the metal-based composite material includes a metal-containing material and 5% to 40% by volume of ceramic particles.

2. The brake disk as claimed in claim 1, wherein the ceramic particles are particles of a material selected from the group consisting of Sic, Al2O3, TiB, and B4C.

3. The brake disk as claimed in claim 2, wherein the ceramic particles are SiC particles or Al2O3 particles.

4. The brake disk as claimed in claim 3, wherein the ceramic particles are SiC particles.

5. The brake disk as claimed in claim 1, wherein the ceramic particles have a particle size of 5 to 100 &mgr;m.

6. The brake disk as claimed in claim 1, wherein the metal-containing material has a specific gravity of 1.7 to 4.6 g/cm3.

7. The brake disk as claimed in claim 1, wherein the metal-containing material is selected from the group consisting of aluminium, aluminium alloy, magnesium, magnesium alloy, titanium, and titanium alloy.

8. The brake disk as claimed in claim 7, wherein the metal-containing material is aluminum.

9. The brake disk as claimed in claim 7, wherein the metal-containing material is aluminum alloy.

10. The brake disk as claimed in claim 9, wherein the aluminum alloy is selected from the group consisting of AlSi, AlSiCu, AlSiZn, AlSiMg, AlSiCuZn, AlZn, AlZnMg, AlGe, AlGeSi, AlCu, AlMn, AlMg, AlLi, AlSn, and AlPb.

11. The brake disk as claimed in claim 10, wherein the aluminum alloy is AlMgSi.