JPH03189430A - Disc brake rotor of metallic group composite material - Google Patents

Abstract

PURPOSE:To improve the durability of a brake rotor by constituting the brake rotor with a composite metal material of 10 to 15% volume rate comprising a matrix of Al alloy and a reinforcing member of an inorganic material having a thermal expansion factor less than the Al alloy. CONSTITUTION:A disc part 14 comprises two annular plate parts 18 and 20, and a plurality of ribs 22 extended radially and positioned remotely from each other peripherally for integrally connecting the aforesaid plate parts 18 and 20. A rotor body 12 is constituted with a composite material having a matrix of Al alloy and a reinforcing member of an inorganic material, for example, SiC particles (average grain size of about 10mum) of a thermal expansion factor less than the aforesaid Al alloy. The annular plate parts 18 and 20 are covered with a friction resistance layer 24 and this layer 24 determines a surface area 26 in slidable contact with a pad.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a disc brake built into a vehicle such as an automobile, and more particularly to a brake rotor made of a metal matrix composite material.

[Prior art] As a brake rotor incorporated into a disc brake,
For example, as described in Japanese Patent Application Laid-Open No. 60-89558, the sliding surface with the pad is made of aluminum alloy.
Disc brake rotors defined by a coating layer of a metal with excellent wear resistance, such as an e-Cr-C alloy, have been known for some time, and as described, for example, in JP-A-59-173234. 2. Description of the Related Art Disc brake rotors made of a metal matrix composite material having an aluminum alloy as a matrix and ceramic fibers as a reinforcing material are conventionally known.

[Problem to be solved by the invention] However, in the former disc brake rotor mentioned above,
The coefficient of thermal expansion of the metal that makes up the coating layer is smaller than that of the aluminum alloy that makes up the brake rotor body, so when the brake rotor is subjected to a cooling/heating cycle due to disc brake operation, the brake rotor body and the coating will Due to the difference in thermal expansion between the layers, cracks may occur in the coating layer or at the interface between the coating layer and the main body, or the coating layer may peel off from the main body. Further, in the latter brake rotor mentioned above, the wear resistance of the sliding surface with the pad is insufficient, and therefore, there is a problem that the brake rotor is prone to early wear and deterioration.

SUMMARY OF THE INVENTION In view of the above-mentioned problems with conventional brake rotors, it is an object of the present invention to provide a brake rotor made of a metal matrix composite material that is more durable than conventional brake rotors.

[Means for Solving the Problems] According to the present invention, the above object is achieved by using an aluminum alloy as a matrix, an inorganic material having a smaller thermal expansion coefficient than the aluminum alloy as a reinforcing material, and a volume ratio of the reinforcing material of 10. This is achieved by a disc brake rotor made of a metal matrix composite material with a coefficient of thermal expansion of ~50%, and whose sliding surface with the pad is defined by a wear-resistant coating layer with a coefficient of thermal expansion smaller than that of the aluminum alloy.

[Operation of the Invention] According to the present invention, the strength of the brake rotor body is ensured by being made of a metal matrix composite material, and the sliding surface with the pad is defined by the wear-resistant coating layer. By doing so, the wear resistance of the sliding surface with the pad is ensured, and furthermore, the brake rotor body has an aluminum alloy as a matrix and is reinforced with an inorganic material that has a coefficient of thermal expansion smaller than that of the aluminum alloy, so that the volume ratio of the reinforcement material is reduced. It is made of a metal matrix composite material with a ratio of 10 to 50%, which reduces the difference in thermal expansion between the coating layer and the main body compared to when the main body is made of aluminum alloy. This effectively prevents cracks from occurring between the coating layer and the coating layer and the main body, and from peeling off the coating layer from the main body.

The reinforcing material used in the present invention may be any inorganic material having a coefficient of thermal expansion smaller than that of the aluminum alloy constituting the matrix, but in particular alumina (Al
), silicon carbide (S i C), silicon nitride (Si:+
It is preferable that the material has a higher volumetric specific heat than Matri-Sox, such as Na), and has excellent dispersion strengthening performance.

In addition, the form of the reinforcing material may be fibers (including whiskers) or particles, and when it is a fiber, the average fiber diameter is 0.1 to 10 μm, especially 0.1 to 5 μm, and the average fiber length is 10 μm to It is preferably 10 mm, especially 20 μω to 5 mm, and in the case of particles, the average particle size is 0.1 to 500 μ
It is particularly preferable that m1 is 3 to 100 μm.

As described below, as the volume fraction of the reinforcing material increases, the thermal expansion coefficient of the composite material decreases, and when the volume fraction of the reinforcing material is less than 10', c+, the occurrence of cracks can be sufficiently prevented. On the other hand, if the volume fraction of the reinforcing material exceeds 50%, the reinforcing material molded body becomes brittle, making it difficult to process the molded body into the shape of the rotor body, and making it difficult to finish the rotor body after casting. Tool wear and deterioration becomes more severe. Therefore, the volume fraction of the reinforcing material is preferably 10 to 50%, particularly 20 to 40%.

Further, the material constituting the wear-resistant coating layer used in the present invention may be any material that has a coefficient of thermal expansion smaller than that of the aluminum alloy and can ensure the wear resistance of the sliding surface with the pad. For example, Fe-Cr alloy, Fe-Cr-C alloy, F
It may be an e-Cr-C-Cu alloy or a composite material in which hard particles are dispersed therein.

Further, in the present invention, the difference in thermal expansion coefficient (linear expansion coefficient) between the metal matrix composite material constituting the main body of the brake rotor and the material constituting the coating layer is 7.0XIO-6/℃ or less, particularly 4
．． It is preferable that OX 10''-6/'C or less.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

Embodiment 1 FIG. 1 is an illustrative sectional view showing a disc brake rotor according to the present invention cut along a plane passing through its axis.

In the figure, reference numeral 10 indicates a brake rotor as a whole, and the rotor includes a rotor body 12 consisting of a disk portion 14 and a lug portion 16. The day space portion 14 includes two annular plate portions 18 and 20, and a plurality of rib portions 22 extending in the radial direction and spaced apart from each other in the circumferential direction and integrally connecting the plate portions 18 and 20 to each other. It's getting better. In the illustrated embodiment, the rotor body 12 is made of aluminum alloy (JI
It is composed of a composite material with a matrix of S standard 6061) and a reinforcing material of SiC particles (average particle size 10 μIm) with a volume fraction of 20%, and its thermal expansion coefficient is 17.5
10-6/°C.

The plates 18 and 20 are covered with a wear-resistant coating 24, which defines a sliding surface 26 with a pad (not shown). In the illustrated embodiment, 3
0wt%Cr, 50wt%Cu.

It is made of a Fe-Cr-Cu alloy with a composition of minute amounts of N1, SiSC, Mn5S, and the balance Fe, and its thickness is 300 μm, and its coefficient of thermal expansion is 14 x 1.
It is 0-6/'C.

The brake rotor of this example was formed as follows. First, SiC particles are poured into molten aluminum alloy in a vacuum, stirred and kneaded using a specially shaped propeller, cast into a predetermined shape by low pressure casting, and then machined to form the rotor body. did. Next, a Fe-Cr-Cu alloy was sprayed onto the plate-shaped portion of the rotor body under the following conditions: current: 2 o A, voltage: 30 V, compressed air pressure: 80 psi (5.6 kg/cd), spraying distance: 150 cm. The surface of the sprayed layer was finished by grinding. The outer diameter of the rotor was 24011 m, and the thickness of the disk portion was 22 mm.

For comparison purposes, the entire brake rotor has a thermal expansion coefficient of 23.
6 x 10-”/”C aluminum alloy (JIs
A brake rotor of the same shape and size was formed according to the standard 6061).

Next, using a brake dynamo tester, these brake rotors were tested to have an inertial mass of 4 kg f・m's.
Effective radius of tire 0.287m, JASO-C406-
A durability evaluation test was conducted using the first fade recovery test and the second fade recovery test of 82.

As a result, in the brake rotor of the comparative example, many fine cracks were generated on the sliding surface with the pad, whereas in the brake rotor of the example, no cracks were observed at all. The maximum temperature of the rotor in this test was 570'C.

Example 2 SiC whiskers with a volume fraction of 40% (average fiber diameter 0.5 μm 1 average fiber length 35 μm) were used as reinforcing material, and the thermal expansion coefficient of the composite material constituting the rotor body was 16.
10=/°C, and the materials constituting the wear-resistant coating layer are 40vt%Cr, 30wt0ciCu, and trace amounts of Ni, Si, C, and Mn.

A brake rotor was manufactured in the same manner and under the same conditions as in Example 1, except that a Fe-Cr-Cu alloy having a composition of N1 and balance Fe was used, and its coefficient of thermal expansion was set at 12X10-6/°C. A durability test was conducted on the brake rotor in the same manner and under the same conditions as in Example 1.

As a result, no cracks were observed in this example either.

Although the present invention has been described above in detail with reference to two embodiments, the present invention is not limited to these embodiments, and various other embodiments are possible within the scope of the present invention. This will be obvious to those skilled in the art.

For example, Figure 2 shows an aluminum alloy (JIS ffl rating 60).
The relationship between the volume fraction of the reinforcing material and the coefficient of thermal expansion of the composite material is shown for a composite material having 61) as a matrix and various substances as reinforcing materials. Intrinsically, SiC means that the reinforcing material is SiC particles with an average particle size of 10 μm,
For Al, 03, the reinforcing material has an average fiber diameter of 3 μm and a fiber length of 0.5
~3rarA alumina fiber, Si
In 3N4, the reinforcing material has a fiber diameter of 0.1 to 1.6 μm and a fiber length of 5.
It shows that it is a ~200 μm Si3N4 whisker. Additionally, the coefficient of thermal expansion of the alloy used as the material constituting the wear-resistant coating layer is generally 10XIO-6 to 15X
Since it is about 10-6/'C, the difference between the coefficient of thermal expansion of the alloy used for the wear-resistant coating layer and the coefficient of thermal expansion of the composite material is 7xlO-6/'C or less, preferably 4x10-6/'C. 6/℃
The type of reinforcing material and its volume fraction may be appropriately set so as to be as follows.

[Effects of the Invention] As is clear from the above description, according to the present invention, the brake rotor main body is made of a metal matrix composite material, thereby ensuring the strength of the main body and improving the sliding surface with the pad. The abrasion resistance of the sliding surface with the pad is ensured by the abrasion-resistant coating layer, and the brake rotor body is made of an inorganic material with an aluminum alloy matrix and a coefficient of thermal expansion smaller than that of the aluminum alloy. The reinforcing material is made of a metal matrix composite material with a volume fraction of the reinforcing material set to 10 to 50%, and as a result, the distance between the coating layer and the main body is reduced compared to when the main body is made of aluminum alloy. The difference in the amount of thermal expansion is reduced, which effectively prevents the occurrence of cracks between the coating layer and the coating layer and the main body, and the separation of the coating layer from the main body, compared to conventional products. This can improve the durability of the brake rotor.

[Brief explanation of drawings]

FIG. 1 is an illustrative sectional view showing an embodiment of a disc brake rotor according to the present invention taken along a plane passing through its axis, and FIG. 2 shows the volume fraction of the reinforcing material and the thermal expansion of the composite material. It is a graph showing the relationship between 10... Brake rotor, 12... Rotor body, 1
4...Disc part, 16...Hub part, 18.20.
... Plate-shaped part, 22 ... Rib part, 24 ... Wear-resistant coating layer, 26 ... Sliding surface with pad

Claims (1)

[Claims] It is made of a metal matrix composite material in which an aluminum alloy is used as a matrix, an inorganic material having a coefficient of thermal expansion smaller than that of the aluminum alloy is used as a reinforcing material, and the volume percentage of the reinforcing material is 10 to 50%, and the sliding surface with the pad is made of the aluminum alloy. Disc brake rotor defined by a wear-resistant coating layer with a lower coefficient of thermal expansion than alloy.