JPH0658350A - Disc brake pad - Google Patents

Abstract

PURPOSE:To prevent cracking in a friction material in a disc brake pad where the friction material is stuck to a back plate by reducing a difference in temperature in a plate thickness direction at the side surface of the friction material. CONSTITUTION:The side surface of a friction material 12 is coated with graphite power, and acrylic resin is coated as a binder to make it easy to transmit heat generated at the friction surface of the friction material 12 to the side surface of the friction material 12 and reduce a difference in temperature in a plate thickness direction at the side surface of the friction material 12. If the difference in temperature is reduced, the distribution of thermal stress will be made uniform to prevent cracking from being generated by uneven thermal expansion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle disc brake pad, and more particularly to a technique for preventing cracks from being generated on the side surface of a friction material of the disc brake pad.

[0002]

2. Description of the Related Art Disc brake pads are generally constructed by attaching a friction material, which is pressed against a disc rotor rotating with a wheel to suppress the rotation of the wheel, to a backing metal.

In this disc brake pad, there has been a demand for preventing cracks from being generated on the side surface of the friction material, and the present applicant has previously proposed the following technique in order to satisfy the demand. As described in Japanese Utility Model Laid-Open No. 58-45436 of the present applicant,
This is a technique of making the density of the friction material higher in the peripheral portion than in the central portion.

[0004]

After that, the present applicant conducted various studies on the cause of crack generation in the friction material, and as a result, found the following new fact.

During vehicle braking, the friction surface of the friction material is pressed against the friction surface of the disk rotor, and as a result, the temperature of the friction surface of the friction material rises due to friction. At this time, for example, as shown in the graph on the right side of FIG. 4, the temperature of the friction material locally rises on the friction surface and decreases as the distance from the friction surface increases. Further, since the side surface of the friction material is in contact with air and is more easily cooled than the center portion thereof, the temperature distribution in the plate thickness direction of the friction material is as shown in the graph in the figure, and the center portion of the side surface is It will rapidly drop from the friction surface to the back metal. Thus, there is a large temperature difference in the plate thickness direction on the side surface of the friction material.Therefore, there is a large difference in the thermal expansion amount of the friction material between the vicinity of the friction surface and the vicinity of the back metal, and a large amount of heat is generated. A stress is generated and a crack is generated on the side surface of the friction material.

In summary, the present applicant has found that not only the load repeatedly applied to the friction material but also the temperature difference on the side surface of the friction material is the cause of the cracks, and the present invention is based on such knowledge. The problem was to prevent the occurrence of cracks in the friction material.

[0007]

In order to solve this problem, the present invention provides a disc brake pad in which a friction material to be pressed against a disc rotor rotating with a wheel is fixed to a back metal. It is characterized by being coated with a material having good thermal conductivity.

[0008]

In the disc brake pad according to the present invention, the side surface of the friction material is coated with a material having better heat conductivity. Therefore, the heat generated on the friction surface of the friction material is easily transferred to the side surface of the friction material through the coating material, and as a result, for example, as shown in the graph of FIG. Is reduced.

[0009]

As described above, according to the present invention, since the temperature difference on the side surface of the friction material is reduced, the distribution of the thermal stress is made uniform, and the friction material is less likely to be cracked. To be

Particularly, when the present invention is used in combination with the technique of increasing the density of the friction material in the portion where cracks are likely to occur as compared with the other portions as described above, the effect that cracks can be more reliably prevented is produced. Is obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A disc brake pad according to an embodiment of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, this disc brake pad is constructed by attaching a friction material 12 to a back metal 10. The friction material 12 is made of non-asbestos.

The friction material 12 is manufactured as follows.
That is, as shown in FIG. 2, first, in the mixing step A, plural kinds of raw materials having a predetermined composition are mixed, and then in the preforming step B, the mixed powder is put into the preforming die. At a constant pressure (eg 600
The pressure is applied at a pressure of kg / cm ² for a fixed time (for example, 30 seconds). Then, in the thermoforming step C, with the preformed friction material 12 in close contact with the back metal 10, a constant temperature (for example, 160 ° C.) and a constant pressure (for example, 400 k)
The friction material 12 is fixed to the back metal 10 by heat molding at a rate of g / cm ² for a certain time (for example, 10 minutes). Then, in the heat treatment step D, the friction material 12
And the back metal 10 are heated at a constant temperature (for example, 250 ° C.) for a predetermined time (for example, 3 hours).

The above steps are the same as in the case of the conventional disc brake pad, but in the disc brake pad of this embodiment, the coating step E is subsequently performed, in which the side surface of the friction material 12 is coated. An acrylic resin in which graphite powder (this is an example of “a material having better thermal conductivity than a friction material” in the present invention) is melted with thinner and applied. The side surface of the friction material 12 is coated with graphite powder and acrylic resin as a binder.

Thereafter, as in the case of the conventional disc brake pad, the coating material is applied to the back metal 10 in the coating step F, and finally, in the polishing step G, the friction material 1 is applied.
The two friction surfaces are finished flat.

The Applicant conducted the following test in order to confirm the performance of the disc brake pad manufactured as described above.

That is, this disc brake pad was attached to a brake dynamometer, and four cycles of a test for reproducing rapid braking to the extent that heat fade occurred were conducted. Here, "1 cycle test" means a vehicle speed of 100k.
It rapidly decreases from m / h to 0.45G and reaches 0km /
The test of h is performed 10 times, the temperature of the friction material 12 is set to 65 ° C. prior to the first test, and each test after the second test is performed after 35 seconds have passed from the end of the previous test. Start. After this test, the disc brake pad did not crack at all.

In addition to this test, Applicants also performed a similar test on uncoated disc brake pads. Regarding this ordinary disc brake pad, cracks have already occurred as shown in Fig. 3 (a) after the test of 3 cycles, and as shown in Fig. 3 (b) after the test of 4 cycles. In addition, the cracks that had been generated after the 3-cycle fade test further grew, and new cracks were also generated.

As described above, it was confirmed that the crack resistance was improved when the coating was performed than when it was not coated.

In this embodiment, the coating material is graphite powder and the binder for adhering it to the friction material 12 is acrylic resin. However, various other coating materials and binders are used. can do. For example, aluminum flakes, copper powder or the like can be used as the coating material, and epoxy resin, phenol resin, melamine resin or the like can be used as the binder.

Further, in this embodiment, since the pores existing on the side surface of the friction material 12 are sealed by the coating and the moisture is prevented from entering the friction material 12 from the side surface, the morning sickness It is possible to obtain a unique effect that both the occurrence of the heat and the occurrence of the water fade are suppressed. Further, if the supply of water from the inside of the friction material 12 to the friction surface is prevented, the occurrence of a situation in which the friction material 12 and the disc rotor are fixed due to rust in a state where the vehicle is left alone is suppressed. The effect of is also obtained.

While one embodiment of the present invention has been described in detail with reference to the drawings, various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the scope of the claims. The present invention can be implemented in such a manner.

[Brief description of drawings]

FIG. 1 is a perspective view showing a disc brake pad according to an embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the disc brake pad.

FIG. 3 is a perspective view showing a test result of a conventional disc brake pad.

FIG. 4 is a diagram for explaining a cause of crack generation in a conventional disc brake pad.

FIG. 5 is a view for explaining a crack generation preventing mechanism in the disc brake pad according to the present invention.

[Explanation of symbols]

 10 Back metal 12 Friction material

Claims (1)

[Claims] 1. A disc brake pad comprising a backing metal and a friction material which is pressed against a disc rotor rotating together with a wheel to suppress the rotation of the wheel, and a side surface of the friction material has a better thermal conductivity than that of the friction material. Disc brake pads characterized by being coated with.