JPH04258533A - Disc brake rotor - Google Patents

Abstract

PURPOSE:To provide a disc rotor of improved coefficient of friction and corrosion resistance as maintaining coolness. CONSTITUTION:As a flame layer M, massive particles (SUS440C Wire Rod Massive Particles) of average particle diameter not more than 100mum and compression not more than 70% with a hardness harder than a matrix is dispersed in a matrix composed of a copper material (Cu Wire Rod Massive Particles) and a stainless steel material (SUS420 J2 Wire Rod Massive Particles) without permitting existance of an oxide film in-between.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in disc brake rotors (hereinafter referred to as disc rotors) used in disc brakes.

0002

[Prior Art] In a disc brake, a disc rotor rotates together with the vehicle's wheels, and when braking the vehicle, the disc brake pad is pressed by a disc brake caliper, and the disc rotor and the lining of the disc brake pad are pressed against each other. Friction causes the vehicle to brake. Such a disc rotor is required to have (1) a high coefficient of friction with the lining of the disc brake pad in order to obtain a large resistance, and (2) the organic components of the lining melt at high temperatures and cause the disc rotor to In order to prevent a film from decreasing the above-mentioned coefficient of friction by forming a film on the surface of the
3) Corrosion resistance is also required to improve durability.

[0003] Conventionally, as such a disc rotor, there has been known a disc rotor in which a sprayed layer that comes into contact with a disc brake pad is formed, as disclosed in, for example, Japanese Unexamined Patent Publication No. 111331/1983. This sprayed layer is made by spraying a soft copper material with excellent thermal conductivity and a hard stainless steel material in a predetermined ratio. This thermal spray layer can be formed either by using an arc spray gun to spray two types of materials under uniform conditions in an oxidizing atmosphere, or by using plasma spraying, where particles fly at a high speed, to spray two types of materials in an oxidizing atmosphere. It was mainly formed by. In this disc rotor, a hard stainless steel material is combined with a soft copper material in the thermal spray layer to maintain a suitable coefficient of friction, while the copper material with excellent thermal conductivity provides suitable cooling performance. and suitable corrosion resistance due to the adhesion between the particles of the copper-based material and the particles of the stainless-steel material.

0004

[Problems to be Solved by the Invention] However, in the above-mentioned conventional disc rotor, as shown in FIG. If it is not present in this state, the sprayed layer becomes porous and the adhesion between both particles is inhibited, making it impossible to ensure sufficient corrosion resistance, which limits the improvement of the coefficient of friction.

[0005] Furthermore, in the conventional disc rotor, the sprayed layer was formed in an oxidizing atmosphere by the method described above, so that the stainless steel material was decarburized and oxidized, and particles of the stainless steel material having the desired hardness were sprayed. It is difficult to exist in the layer. In addition, in this case, since both particles are present in the sprayed layer via an oxide film, hair cracks are likely to propagate due to the brittle oxide due to thermal stress, and particles of the stainless steel material may fall off during friction with the lining. It is easy to cause scratches and wear on the surface. Therefore, corrosion resistance was also impaired in these respects.

The present invention has been made in view of the above-mentioned conventional limitations, and it is an object of the present invention to provide a disc rotor that has an improved coefficient of friction and corrosion resistance while ensuring cooling performance.

[0007]

[Means for Solving the Problems] A disc rotor of the present invention is provided with a thermally sprayed layer that comes into contact with a disc brake pad, and the thermally sprayed layer includes a matrix containing a copper-based material and an oxidized layer in the matrix. It is characterized by being dispersed without any intervening film, having an average particle diameter of 100 μm or less, and an oblateness ratio of 70% or less, and consisting of bulk particles that are harder than the matrix.

[0008] The sprayed layer consists of a matrix and massive particles dispersed in the matrix without an intervening oxide film. The matrix includes a copper-based material. Stainless steel materials can also be included in this matrix. When the matrix is composed of a copper-based material and a stainless-steel material, it is preferable that no oxide film is interposed between the particles of the copper-based material and the particles of the stainless-steel material. In this case, a method can be adopted in which particles of a copper-based material and particles of a stainless-steel material are thermally sprayed in an inert gas atmosphere.

[0009] The bulk particles have an average particle diameter of 100 μm or less and an oblateness of 70% or less. The average particle size of lump particles is 100μm
If it exceeds this, the area ratio of the lump particles in the matrix becomes too large, the polishing effect of the lump particles will not be sufficiently exhibited, and the coefficient of friction will not be improved sufficiently. Furthermore, if the flatness of the lumpy particles exceeds 70%, the polishing effect of the lumpy particles will be difficult to exhibit, and the improvement in the coefficient of friction will still not be sufficient. In order to disperse the lumpy particles in the matrix in this way, when thermal spraying is carried out using an arc spray gun, the pressure of the compressed gas can be lowered to reduce the flight speed of the particles, thereby reducing the collision energy. Moreover, the particle size of the lump particles may be adjusted by the feed rate of the wire rod when thermal spraying is performed with an arc thermal spray gun. That is, the smaller the feeding amount of the wire rod is, the smaller the particle size of the lump particles can be made.

[0010] Also, the bulk particles are harder than the matrix. When the matrix contains a stainless steel material, the bulk particles are preferably harder than the stainless material. Unless the agglomerated particles are harder than the matrix, the abrasive effect of the agglomerated particles will not be exhibited. In order to disperse the massive particles in the matrix without intervening an oxide film, a method of spraying the massive particles under an inert gas atmosphere can be adopted. When the matrix contains a stainless steel material, in order to disperse the bulk particles in the matrix without intervening an oxide film, the matrix is formed with a predetermined ratio of copper material and stainless steel material using one arc spray gun. At the same time, it is possible to adopt a method in which the bulk particles are sprayed in an inert gas atmosphere using another arc spray gun.

[0011]

[Function] In the sprayed layer of the disc rotor of the present invention, the bulk particles dispersed without an oxide film maintain the desired hardness before spraying in the sprayed layer, and the bulk particles contain a soft copper-based material. By dispersing the particles in the matrix with an average particle size of 100 μm or less and an aspect ratio of 70% or less, the abrasive effect of the lump particles is exhibited and a high coefficient of friction is obtained. When a stainless steel material is included in the matrix, a suitable coefficient of friction is maintained to some extent by the matrix which is a composite of a hard stainless steel material in a soft copper material, and furthermore, the above-mentioned lump particles are contained in this matrix. By being dispersed, the abrasive effect of the lump particles is exhibited, and an even higher coefficient of friction can be obtained.

[0012] Also, since the lump particles do not have an oxide film intervening in the sprayed layer, they do not cause hair cracks due to thermal stress, and if the average particle size and aspect ratio are within the above range, they will not cause any hair cracks during friction with the lining. Agglomerated particles are difficult to fall off. In addition, these lumpy particles have good wettability because they are dispersed in the matrix without an oxide film intervening, and if the average particle size and oblateness are within the above range, they will adhere well to the matrix and, on the contrary, will be absorbed into the matrix. Acts as an aggregate to increase mechanical strength. Therefore, the sprayed layer ensures suitable corrosion resistance. Even if the matrix contains a stainless steel material, if the particles of the copper material and the particles of the stainless steel material exist in a flat state in the matrix, the sprayed layer will not become porous and both particles will be in close contact with each other. Here, the lumpy particles do not impede the adhesion between the two, but rather increase the mechanical strength and ensure even more suitable corrosion resistance.

Furthermore, this sprayed layer is made of a copper-based material with excellent thermal conductivity to ensure suitable cooling performance as in the past.

[0014]

[Example] Hereinafter, thermal sprayed layers 1, 2, 5, and 6 in disc rotors of examples embodying the present invention will be explained together with thermal sprayed layers 3, 4, 7 to 12 in disc rotors of comparative examples with reference to the drawings. do. First, as shown in Fig. 1, a sprayed surface 1 that comes into contact with a disc brake pad (not shown)
A disc rotor main body 1 having a shape was prepared. In addition, two arc spray guns 2 and 3 are prepared, Cu wire 4 is used as the copper material, and SUS42 is used as the stainless steel material.
A 0J2 wire 5 and a SUS440C wire 6 were prepared as the bulk particle material. Note that SUS440C is SUS420
It has a higher C content and is harder than J2. In other words, SUS
440C is 560Hv (100g), SUS420J2
is 430Hv (100g).

[0015] Next, one arc spraying gun 2 is equipped with Cu
A wire rod 4 and a SUS420J2 wire rod 5 were equipped, and the other arc spray gun 3 was equipped with SUS440C wire rods 6 and 6. Then, one arc spray gun 2 sprays Cu wire 4 and SUS420J2 wire 5 on the sprayed surface 1a under predetermined conditions using compressed air, and at the same time, the other arc spray gun 3 sprays Ar gas. The SUS440 wire rods 6, 6 were thermally sprayed on the surface 1a to be thermally sprayed under the predetermined conditions used. Note that the conditions of the arc spray gun 3 are, for example,
The average particle diameter of the lump particles is 100 (μm), and the oblateness ratio is 70 (%).
In the case of: Current: 100A Voltage: 30V Ar gas compression pressure (primary): 5kgf/cm2 Ar gas compression pressure (secondary): 0kgf/cm2. In this way, a disc rotor having sprayed layers M (1 to 12) was obtained.

At this time, the particles of the Cu wire 4 and the SUS4
The volume ratio, each average particle diameter, and each oblateness (%) of the particles of the 20J2 wire 5 were adjusted by the feed rate of each wire 4, 5, etc., and were kept constant under the following conditions. In addition, the aspect ratio was expressed as {(ab)/a}×100, where the length (longitudinal direction) is a and the thickness is b in the cross section of each particle. Also,
Each average particle size cannot be displayed because the oblateness is high.

[0017] Volume ratio: Flat grain volume of Cu wire rod 4: S
Flat grain volume of US420J2 wire 5 = 50:50 Each flattening ratio...90% or more On the other hand, the volume ratio of the lumpy particles of SUS440 wire 6 is constant under the following conditions, average grain size (μm) and flattening ratio (%)
Various changes were made. Note that the average grain size cannot be displayed if the oblateness is high.

[0018] Volume ratio: flat grain volume of Cu wire 4 + S
Volume of flat grains of US420J2 wire 5: Volume of lumpy particles of SUS440 wire 6 = 90:10 Sprayed layers 1 to 12 with different average particle diameters and flattening ratios of lumpy particles
About, from 100km/h to 0km/h, 60k
The friction coefficient (μ) when braking was performed at a pressure of gf/cm2 was determined. The results are shown in Table 1.

[0019]

[Table 1] Note that the coefficient of friction of the sprayed layer in which no lump particles were present was 0.34. Further, FIG. 2 shows the metallographic structure of the surface of the sprayed layer 5 of the disc rotor of the example, and FIG. 3 shows the metallographic structure of a cross section. On the other hand, FIG. 4 shows the metallographic structure of the cross section of the sprayed layer 8 of the disc rotor of the comparative example.

[0020] The lumpy particles of the SUS440C wire rod 6 are Ar
Since it is thermally sprayed by the arc spraying gun 3 using gas, the oxide film is not interposed and is dispersed in the thermally sprayed layer, and the hardness before thermal spraying is maintained. Also, from Table 1, thermal sprayed layers 1, 2, 5
, 6 is excellent, it can be seen that if the bulk particles are present in the matrix with an average particle size of 100 μm or less and an aspect ratio of 70% or less, a sprayed layer with a higher coefficient of friction than the conventional one can be obtained. For this reason, the sprayed layers 1, 2, 5, 6
Now, hard SUS4 is included in the flat particles of the soft Cu wire 4.
The matrix in which the flat particles of the 20J2 wire 5 are composited maintains a suitable coefficient of friction to some extent, and furthermore, since the above-mentioned lump particles are dispersed in this matrix, the abrasive effect of the lump particles is exhibited, making it even more effective. It can be seen that a high coefficient of friction was obtained.

Furthermore, since the above-mentioned lump particles do not have an oxide film intervening in the sprayed layer, hair cracks will not occur due to thermal stress, and if the average particle size and aspect ratio are within the above-mentioned range, friction with the lining part will not occur. Sometimes lumpy particles are difficult to fall off. In addition, these lumpy particles are the flat particles of the Cu wire 4 and the S
The flat particles of the US420J2 wire 5 exist in a flat state in the matrix, and the sprayed layer does not become porous, and both particles suitably adhere to each other, and the lumpy particles are dispersed in the matrix without an oxide film intervening. If the average particle size and aspect ratio are within the above ranges, it will not impede the adhesion between the two, but will instead act as an aggregate in the matrix, increasing mechanical strength. Therefore, it can be seen that even more suitable corrosion resistance is ensured in thermal sprayed layers 1, 2, 5, and 6.

Furthermore, this sprayed layer is made of a copper-based material with excellent thermal conductivity to ensure suitable cooling performance as in the past.

[0023]

Effects of the Invention As detailed above, the disc rotor of the present invention has a thermally sprayed layer in which the above-mentioned lump particles are dispersed in a matrix containing a copper-based material. It can exhibit good friction coefficient and corrosion resistance. Therefore, if this disc rotor is used in a vehicle's disc brake, it will ensure sufficient cooling performance and
Because it can exhibit high friction coefficient and corrosion resistance,
The vehicle can be braked with greater resistance and can withstand use under harsher conditions, providing even higher safety than before.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a state during thermal spraying to obtain a disc rotor of an example.

FIG. 2 is a 50x micrograph showing the metal structure of the surface of the sprayed layer 5 of the disc rotor of the example.

FIG. 3 is a 200x micrograph showing the metal structure of a cross section of the sprayed layer 5 of the disc rotor of the example.

FIG. 4 is a 200x micrograph showing the metal structure of a cross section of a sprayed layer 8 of a disc rotor of a comparative example.

FIG. 5 is a cross-sectional view of a sprayed layer of a conventional disc rotor.

[Explanation of symbols]

1... Disc rotor body
1a...Surface to be sprayed 2, 3...Arc spray gun
4...Cu wire rod (copper-based material)

Claims (1)

[Claims] 1. A disc brake rotor in which a sprayed layer is formed that contacts a disc brake pad, wherein the sprayed layer includes a matrix containing a copper-based material, and is dispersed in the matrix without an oxide film interposed therebetween, and has an average Particle size 100
1. A disc brake rotor comprising bulk particles having a particle size of .mu.m or less and an oblateness of 70% or less, and which are harder than the matrix.