JP2002061685A - Brake disc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake disc which can increase bonding strength between an aluminum alloy base material and a hardened layer. SOLUTION: In this brake disc 4, formed with a hardened layer 14 serving as a friction surface in an outer surface of a disc main unit 10 consisting of aluminum alloy, the disc main unit 10, formed by forge molding of aluminum alloy, has a grain flow a spread radially from the center part, when the disc main unit 10, in a section traversing its grain flow a, is observed in a direction of the grain flow, irregularity is present in an interface between the disc main unit 10 and the hardened layer 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake disk in which a hardened layer is formed on the surface of a disk body made of an aluminum alloy so as to enhance abrasion resistance.

[0002]

2. Description of the Related Art As a conventional brake disk having a hardened layer formed on the surface of a disk body made of an aluminum alloy, for example, a donut-shaped disc made of an iron-based metal is joined to the surface of the disk body by an Alfin joint (Japanese Unexamined Patent Application Publication No. 5-1
No. 0667) and those joined by friction welding (see Japanese Patent Application Laid-Open No. 5-26268).

[0003]

However, since aluminum alloys have a higher coefficient of thermal expansion than ferrous metals such as cast iron,
In a structure in which a cast iron disk is joined to an aluminum alloy disk body, the brake disk may bend or bend, or the cast iron part may peel off from the disk body due to the thermal stress generated with the temperature rise during braking. there were.

[0004] In addition, a special joining device is required to join the cast iron disk to the disk body by the above-described Alfin joining or friction welding, and there has been a problem that the manufacturing cost is increased.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a brake disk capable of increasing the adhesive strength between an aluminum alloy base material and a hardened layer.

[0006]

According to a first aspect of the present invention, there is provided a brake disk in which a hardened layer serving as a friction surface is formed on an outer surface of a disk body made of an aluminum alloy, wherein the disk body is formed by forging an aluminum alloy. It has a grain flow line that spreads radially from the center,
When observed in the direction of the grain flow line in a cross section of the disk body crossing the grain flow line, irregularities are present at the interface between the disk body and the hardened layer.

According to a second aspect of the present invention, in the first aspect, the forging line is raised by selectively removing a peripheral portion of the forging line on the outer surface of the disk main body, so that the irregularities are reduced. It is characterized by being formed.

According to a third aspect of the present invention, in the second aspect, the irregularities are formed by selectively removing a portion of the outer surface of the disk body around the grain flow line by shot peening or alkali etching. It is characterized by:

According to a fourth aspect of the present invention, there is provided a brake disk in which a hardened layer serving as a friction surface is formed on an outer surface of a disk body made of an aluminum alloy.
Aluminum alloy particles are solidified and then forged, and have a forging line radially extending from a central portion, and a length in which the particles forming the disk main body that are connected to each other extend in the radial direction of the brake disk. It is characterized by a circular shape.

According to a fifth aspect of the present invention, in the fourth aspect, the particle shape factor f of the particles is f = L / W ≧ 1.5 (L: major axis of the particle, W: minor axis of the particle). It is characterized by.

According to a sixth aspect of the present invention, the disk body according to any one of the first to fifth aspects, wherein the forged material having a smaller diameter and a longer axial length than the disk body is radially compressed while being compressed in the axial direction. It is characterized by being manufactured by expanding it.

According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the disk main body is made of an Al—
It is characterized by being die-forged Fe-based aluminum alloy powder.

According to an eighth aspect of the present invention, in the first aspect, the hardened layer is formed by coating a hard component made of a metal or a non-metal having higher hardness than the disk body on the disk body by electroplating or thermal spraying. It is characterized by becoming.

According to a ninth aspect of the present invention, the aluminum alloy particles according to any one of the first to seventh aspects have an average particle size of 0.1 to 500 μm, and the average particle size of the aluminum alloy crystal grains constituting the aluminum alloy particles. The diameter is 0.005
-10 μm.

[0015]

According to the first aspect of the present invention, the disk main body has a forging line extending radially from the center, and the disk main body and the hardened layer are formed when viewed in a cross section crossing the forging line. There is unevenness at the interface of, and the unevenness increases the fixed area between the disk body and the hardened layer, and accordingly the fixing strength of the hardened layer increases.

Further, the unevenness acts to lock the hardened layer to the disk body with respect to the braking force acting on the hardened layer, so that the fixing strength of the hardened layer also increases from this point.

According to the second aspect of the present invention, a portion of the outer surface of the disk main body around the forging wire is, for example, a third aspect.
As described above, the grain flow lines were raised by selective removal by shot peening or alkali etching, so that the above-mentioned irregularities could be easily and reliably formed, and the bonding strength between the disk body and the hardened layer was improved. Can be increased.

According to the fourth aspect of the present invention, since the particles constituting the disk main body are formed into an elliptical shape extending in the radial direction of the brake disk, the heat generated in the disk main body has good heat conduction to the center side. And deformation of the disk due to heat generation,
As a result, it is possible to avoid the problem of a decrease in the fixing strength of the cured layer due to the deformation.

That is, a part of the heat generated by the friction between the brake pad and the hardened layer during braking moves toward the center in the brake disk and is released to the atmosphere from the front wheel hub, bracket and the like. However, in the present invention, the particles constituting the disk main body have a long oval shape in the radial direction of the brake disk, so when viewed in unit length as compared to the case where the particles are spherical. The number of grain boundaries is small. These grain boundaries are covered with an oxide film having poor thermal conductivity. Therefore, as the number of grain boundaries increases, heat is less likely to be transmitted to the hub side. In the present invention, for example, as shown in the invention of claim 5,
Since the particles have an elliptical shape so that the particle shape coefficient f is 1.5 or more, the number of grain boundaries is smaller than in the case where the particles are spherical, and the thermal conductivity becomes better accordingly.

According to the invention of claim 6, the disk main body is made of an Al-Fe-based aluminum alloy powder containing no Cu, and has a small diameter and an axial length. It is manufactured by expanding a long rod-shaped pre-forging material in the radial direction while compressing it in the axial direction.In the process of forging, a forging flow line extending radially from the center of the disk is obtained, and each constituent particle is drawn in the radial direction. In this case, it is possible to realize the above-described respective effects.

According to the eighth aspect of the present invention, since the hardened layer is formed by electroplating or thermal spraying, the fixing strength of the hardened layer to the disk body can be easily increased.

According to the ninth aspect of the present invention, the aluminum alloy particles have an average particle size of 0.1 to 500 μm, and the disk body has a dense structure. The aluminum alloy crystal grains have an average particle size of 10 μm or less, and the aluminum alloy crystal grains are not broken by forging, so that sufficient strength can be secured in the disk body.

[0023]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 to 5 are views for explaining a disc brake device according to an embodiment of the present invention.
FIG. 2 is a front view, a sectional side view,
FIG. 3 is a manufacturing process diagram, and FIGS. 4 and 5 are schematic diagrams for explaining a fine structure.

In FIG. 1, reference numeral 1 denotes a disk brake device for a front wheel of a motorcycle. The boss member 2 is keyed to the hub of the front wheel, the brake disk 4 is fixed to the flange portion 2a formed integrally with the boss member 2 by caulking a rivet 3, and the brake disk 4 is sandwiched. And a caliper 5 for generating a braking force.

The caliper 5 is of the opposed two-piston type and has the following structure. Coupling bolts 6c, 6c
Inner and outer cylinders 6a, 6 integrally connected by
The pistons 7, 7 are inserted and arranged so as to be able to move forward and backward in the piston hole b. The brake pads 8, 8 are arranged so as to sandwich the brake disc 4, and the holding plates 8a, 8a to which the brake pads 8, 8 are fixed are bridged over the front and rear cylinders 6a, 6b. It is movably supported by a guide pin 8c. The front end surface of the piston is in contact with the back surface of the holding plate 8a. The bracket 6e of the outer cylinder 6b is fixed to the front fork by the mounting bolt 6d.

The hydraulic pressure is applied to the cylinder 6 via the hydraulic hose 12.
When the piston 7 is supplied to the hydraulic chamber surrounded by the piston holes a and 6b and the piston 7, the piston 7 moves forward, and the brake pads 8, 8 pinch the brake disc 4, thereby generating a braking force.

Here, the brake pad 8 is made of a material having a lower hardness than a metal or ceramic constituting the hardened layer 14 of the disk body 10 described later, or a material in which ceramic is dispersed in metal, for example, A synthetic resin-based material, a sintered material containing copper, or the like is used. By setting the hardness of the brake pad 8 relatively low as described above, it is possible to prevent the hardened layer 14 from being worn by friction during braking.

The disk plate 4 is of a floating type, and has an annular base plate 9 fixed to the flange portion 2a of the boss 2 made of an aluminum alloy casting, and surrounds the base plate 9 and forms the same plane. The structure is such that the annular disk main body 10 arranged as described above is connected by six connecting pins 11.

A slight gap is provided between the outer periphery of the base plate 9 and the inner periphery of the disk body 10,
In addition, the connecting pin 11 is inserted into the connecting hole formed at the boundary.
Is inserted and arranged. The connecting pin 11 has a locking flange 11a at one end, and is prevented from falling off by a retaining ring 11c with a washer 11b interposed at the other end. In this manner, the disk main body 10 can be slightly moved relative to the base plate 9 in the circumferential direction and the axial direction. Thus, even when the disk body 9 is deformed due to heat or the like, the caliper 5 can reliably press the disk body 9 to generate a braking force.

Here, the base plate 9 and the disk body 10 are formed by forging aluminum alloy powder. The disk main body 10 is manufactured in detail through the following steps. The base plate 9 is manufactured in the same process as that of the disk body 10, but no hardened layer is formed on the base plate 9.

An aluminum alloy ingot having the components shown in Tables 1 (a), (b) and (c) was melted, and the molten aluminum alloy was spray-formed from the molten aluminum alloy.
A cylindrical mass w1 is created (see FIG. 3A).

[0033]

[Table 1]

In a molten aluminum alloy, hard component powder containing at least 10% by weight of any one of silicon carbide, aluminum oxide and aluminum nitride having an average particle diameter of 0.1 to 50 μm or a combination of a plurality thereof is contained in an amount of 10% by weight or less. You may make it do. By adjusting the dispersion content of the hard component powder, the rigidity, strength, and toughness of the disk body 10 formed through a post-process can be improved. In this case, the average particle diameter of the aluminum alloy particles formed in the subsequent step is set to be larger than the average particle diameter of the hard component particles.

More specifically, in the spray forming method, the molten aluminum alloy is sprayed from a nozzle toward a target having a predetermined radius in a nitrogen gas atmosphere.
A method in which the formed aluminum alloy spray droplets are cooled in the middle by passing them through cold air or room temperature nitrogen gas to be in a semi-solid state, and the semi-solid aluminum alloy spray droplets are stacked into a substantially cylindrical shape having a predetermined diameter. It is.

The atmosphere in the space for spraying and the space for cooling and solidifying the spray droplets may be room temperature air, cooling air, or argon gas.
Further, the atmosphere of the space for jetting and the atmosphere of the space for cooling and coagulating the spray droplets are changed, and for example, after jetting into a nitrogen gas or an argon gas, the gas is cooled by passing through an atmosphere having a large proportion of air. good. The size of the spray droplets can be changed depending on the spray pressure, spray nozzle diameter, molten metal temperature, etc., so that the average particle size of the aluminum alloy particles formed by solidification of the spray droplets is 0.1 to 500 μm. . Also, by changing the temperature of the molten metal, the atmosphere of the space in which the spray droplets are cooled and solidified, particularly the temperature, and the flight distance of the spray droplets, the average particle size of the aluminum alloy crystal grains in the aluminum alloy particles is 0.005 to 10 μm. So that

The bulk material w1 is transferred to a cylindrical mold 13
a in a state where the piston 13 is cooled or heated at a desired temperature at which the aluminum alloy does not melt again.
A rod-shaped material w2 is prepared by extrusion molding extruded at b, and the rod-shaped material w2 is cut into a length corresponding to the disk body 10 to prepare a forged material w3.
(See (b) and (c)). The pre-forging material w3 has a rod shape having a smaller diameter and a longer length in the axial direction than the disk body 10 described above.

In FIG. 3, the aluminum alloy powder having an average particle diameter of 0.1 to 500 μm is completely solidified by an atomizing method without being piled up in a substantially solid state in a semi-solid state, and this powder is used as it is or A thin wall made of pure aluminum or an aluminum alloy containing a hard component powder having a mean particle diameter of 0.1 to 50 μm and containing 10% by weight or less of a hard component powder alone or in combination of any one of aluminum oxide and aluminum nitride. A cylindrical container may be filled in place of the columnar bulk material w1. Using the thin-walled cylindrical container filled with the aluminum alloy powder, the extrusion molding shown in FIG. 3B is performed to form a rod-shaped material w2.

The outer diameter is gradually increased while compressing the forged material w3 in the axial direction by forging, and the forged product w4 having a required thickness and diameter corresponding to the disk body 10 is formed.
Is manufactured (see FIG. 3D). And this forged product w4
The disk body 10 or the base plate 9 is finished by performing required finishing machining (FIG. 3 (e)).
reference).

The disk main body 10 and the base plate 9 manufactured through the above-described steps have countless flowing lines a radially extending radially from the center to the outer peripheral side. this is,
In the above forging process, the forged product w4 is produced by compressing the small-diameter pre-forging material w3 in the axial direction and expanding the material in the radial direction. And this forged product w
When the outer surface of the forged product w4 is microscopically observed, each particle p constituting the forged product w4 has an oval shape extending radially from the center of the forged product w4 toward the outer peripheral side, and has an oval shape. Many particles p constitute a single line, and the line connecting the particles p is the above-mentioned grain flow line a.

Here, it is desirable that the particle shape coefficient f of each of the particles p is f = L / W ≧ 1.5 (L: major axis of particle p, W: minor axis of particle p). The average particle diameter D of the particles p is 0.1 to 500.
If the particle shape after forging becomes an ellipsoid, the particle volume hardly changes by casting, so the particle volume before forging = (π / 6) × D ³ = particle volume after forging = (π / 6) × L × W ² holds. When the particle coefficient is 1.5, since L = 1.31D, the major axis L
= 0.13-655 μm, minor axis W = 0.087-43
It is about 7 μm. Also, by changing the temperature of the molten metal, the atmosphere of the space in which the spray droplets are cooled and solidified, particularly the temperature, and the flight distance of the spray droplets, the average particle size of the aluminum alloy crystal grains in the aluminum alloy particles is 0.005 to 10
μm.

On the outer surface of the disk body 10, an annular hardened layer 14 serving as a friction surface for generating a braking force by pressing the brake pad 8 is formed by electroplating or thermal spraying. In forming the hardened layer 14, first, shot peening or alkali etching is performed on the outer surface of the finished disk body 10 (see FIGS. 5A and 5B). As a result, the relatively low hardness part b around the high hardness flow line a is selectively removed, and the flow line a is raised.

Thereafter, the cured layer 14 is formed by thermal spraying or plating.
Is formed (see FIG. 5C). As a result, the cured layer 14
In the boundary between the disk surface and the disk body 10, irregularities are formed due to the presence of the embossed flow line a on the outer surface and the surrounding part b, and the hardened layer 14 is engaged with the irregularities. ing.

Here, the electroplating treatment is performed in the following manner. First, degreasing, pickling, alkali etching,
General pretreatment including acid activation, zinc substitution, nitric acid immersion, etc. is performed, and electroplating is performed. This electroplating is performed by immersing the disk body 10 together with the anode in a plating solution together with the anode, and supplying DC power to these. Fe ions, as ions to be contained in the plating solution,
The hardened layer 14 can be made of Fe, Fe-
It can be formed of a metal having high wear resistance, such as a Cr alloy, Cr, Ni, etc., and is adjusted to approximately 20 by adjusting the amount of current.
It is formed to a thickness of μm or more.

In the plating solution, fine silicon carbide,
A hard component powder of aluminum oxide or aluminum nitride alone or in combination of two or more may be dispersed to form a dispersion plating. Thereby, the surface hardness of the hardened layer 14 can be further increased.

In the case of thermal spraying, after shot peening or alkali etching is performed as shown in FIG. 5B, Fe, Cr, Ni
Is supplied to the nozzle part by itself or a mixture containing a plurality of these, and is melted at a very high temperature of 15,000 ° C. by an electric current, and sprayed from the nozzle at a high speed with a working gas composed of argon and helium to form liquid fine particles. Is sprayed on the surface of the disk body 14 to solidify and solidify the liquid fine particles in the state of flat particles to form a film-like cured layer 14. Since the melting temperature is extremely high, a mixture of a metal powder and a hard component powder obtained by combining one or more of silicon carbide, aluminum oxide, and aluminum nitride, or only the hard component powder may be supplied to the nozzle portion. .

As described above, in the present embodiment, since the forging line a is raised, the fixed area of the hardened layer 14 is increased, and the fixed strength of the hardened layer 14 is improved accordingly. In addition, since the raised flow line a extends in a direction orthogonal to the braking force f acting on the hardened layer 14 in the circumferential direction, the flow line a
Functions as a locking member for the hardened layer 14, which also increases the fixing force of the hardened layer 14, and as a result, problems such as peeling of the hardened layer can be prevented.

Since the heat transfer area between the hardened layer 14 and the disk body increases, even if the surface of the hardened layer 14 is heated by frictional heat generated during braking, the amount of heat radiation to the disk body 14 increases. As a result, the temperature difference between the hardened layer 14 and the disk body 14 is reduced, and the difference in the amount of thermal expansion is also reduced. This also contributes to preventing the hardened layer 14 from peeling off.

During braking, heat is generated due to friction between the brake pad 8 and the hardened layer 14. Part of this heat moves toward the center in the brake disc 4 and is released to the atmosphere from the hub or bracket of the front wheels. In the brake disc 4 of the present embodiment, the particles p constituting the brake disc 4 Since the brake disk has an oval shape that is long in the radial direction, heat can be efficiently transferred to the hub side.

That is, since the particles p of the present embodiment have an elliptical shape, the number of grain boundaries s as viewed in unit length t is smaller than that of the spherical particles p as shown in FIG. 'Is 5 for the oval particle p, whereas it is 5 for the oval particle p. The grain boundaries s are covered with the oxide film _po having poor thermal conductivity. Therefore, as the number of grain boundaries s increases, heat is less likely to be transmitted to the hub side. In the present embodiment, the number of grain boundaries s is smaller than in the case of the spherical particles p ', so that the thermal conductivity becomes better.

The frictional heat generated during braking is applied to the hardened layer 1.
If the heat is not radiated from the disk body 14 to the hub or the like even though the heat is radiated from the disk body 4 to the disk body 14, the temperature of the disk body 14 increases, the strength decreases, and the hardened layer 14
There is a possibility that the support portion of the hardened layer 14 of the disk body 14 is broken or plastically deformed by the braking force from However, in this embodiment, since the heat radiation from the disk body 14 to the hub or the like can be sufficient, a stable braking force can be secured. Furthermore, even if the heat capacity of the brake disc is reduced, the temperature does not easily rise, so that the thickness of the brake disc can be reduced to reduce the weight.

In the extrusion or forging step, the lump material w1 or the forged material w3 is maintained at a temperature slightly higher than the maximum temperature of the disk body at the time of braking, specifically, for example, at 500 ° C. or more. It is desirable to carry out extrusion molding or forging.

Thus, blistering (bulging) of the hardened layer 14 due to H ₂ dissolved in the aluminum alloy can be prevented, and peeling of the hardened layer can be prevented. That is, the aluminum alloy has a property of easily absorbing water vapor in the air in a molten state, and the absorbed water is H ₂ and O _2.
This H ₂ enters between atoms of the aluminum alloy and is fixed at room temperature. However, the blister is discharged to the outside due to a rise in temperature during braking, causing so-called blisters to expand the hardened layer 14 from the inside, thereby causing peeling of the hardened layer.

In this embodiment, the hydrogen is forcibly discharged to the outside by extruding or forging at a temperature higher than the temperature reached by the disk body at the time of braking and lower than the melting temperature. The amount of hydrogen in the inside can be reduced in advance, so that even when the temperature rises during braking, the phenomenon that hydrogen comes out can be prevented, and as a result, peeling of the hardened layer can be prevented. Heating the forged product or w4 to the above-mentioned temperature before the above-mentioned machining can also provide a certain degree of hydrogen discharge effect.

In the case where the brake disk 4 on which the hardened layer 14 is formed is subjected to a heat treatment in order to dissipate hydrogen dissolved therein, the hardened layer 14 is heated to a temperature slightly higher than the maximum temperature of the disk body during braking. The metal or hard component molecules such as Fe, Cr, Ni, etc.
The aluminum alloy diffuses toward the disk body side made of an aluminum alloy, and the aluminum alloy constituent elements of the disk body 10 are hardened.
Thus, the hardened layer 14 can be diffused to the side 4 and the degree of bonding between the hardened layer 14 and the disk body 10 can be increased.

[Brief description of the drawings]

FIG. 1 is a front view of a disc brake device according to an embodiment of the present invention.

FIG. 2 is a sectional side view of the brake device (II-II in FIG. 1).
FIG.

FIG. 3 is a manufacturing process diagram of the disk main body.

FIG. 4 is a schematic diagram for explaining a microscopic structure of a disk main body.

FIG. 5 is a schematic diagram for explaining a microscopic structure of a disk main body.

FIG. 6 is a schematic view for explaining a thermal spraying method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 disc brake device 4 brake disc 10 disc body 14 hardened layer a forging line b surrounding part of disc body forging line p particle w3 material before forging

Continued on the front page (72) Inventor Toshikatsu Koike 2500 Shinkai, Iwata-shi, Shizuoka Yamaha Motor F-term (reference) 3J058 AA43 AA48 AA53 AA66 AA74 AA77 AA84 AA87 BA41 BA47 CB11 EA06 EA08 EA31 EA34 EA35 EA35

Claims (9)

[Claims] 1. A brake disk in which a hardened layer serving as a friction surface is formed on an outer surface of a disk body made of an aluminum alloy, wherein the disk body is formed by forging an aluminum alloy, and radially extends from a central portion. A brake disk having a spreading flow line, wherein when viewed in the direction of the flow line in a cross section of the disk body crossing the flow line, irregularities are present at an interface between the disk body and the hardened layer. . 2. The disk drive according to claim 1, wherein the surface of the disk main body is selectively removed from the outer surface of the disk body, and the surface of the disk body is raised so that the irregularities are formed. A brake disc characterized by the following. 3. The method according to claim 2, wherein the irregularities are formed by selectively removing a portion of the outer surface of the disk body around the grain flow line by shot peening or alkali etching. brake disc. 4. A brake disk in which a hardened layer serving as a friction surface is formed on an outer surface of a disk body made of an aluminum alloy, wherein the disk body is formed by hardening aluminum alloy particles and then forging. A brake disk having a flow line extending radially from a portion, wherein the particles forming the disk main body are connected to each other to form an oblong shape extending in a radial direction of the brake disk. 5. The brake according to claim 4, wherein the particle shape factor f of the particles is f = L / W ≧ 1.5 (L: long diameter of particles, W: short diameter of particles). disk. 6. The disk body according to any one of claims 1 to 5, wherein the disk body is expanded in the radial direction while compressing a material before forging having a smaller diameter and a longer axial length than the disk body in the axial direction. A brake disc characterized by the following. 7. The brake disk according to claim 6, wherein the disk main body is formed by die-forging an Al—Fe-based aluminum alloy powder containing no Cu in its component. 8. The disk according to claim 1, wherein the hardened layer is formed by coating the disk body with a hard component made of a metal or a non-metal having a higher hardness than the disk body by electroplating or thermal spraying. Brake disc to do. 9. The aluminum alloy particle according to claim 1, wherein the aluminum alloy particle has an average particle size of 0.1 to 500 μm.
m, wherein the average particle size of aluminum alloy crystal grains constituting the aluminum alloy particles is 0.005 to 10 μm.