JP2982513B2 - Manufacturing method of metallic friction material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a friction material used for a brake of an automobile, and more particularly to a method for producing a metallic friction material whose matrix is made of metal.

[0002]

2. Description of the Related Art The performance required of a friction material includes excellent wear resistance, a high friction coefficient, and a stable friction coefficient. It is difficult to satisfy these performances with a single material, and the friction material is composed of a composite material in which many materials are mixed.

[0003] Such friction materials can be roughly classified as follows. (1) Cork, Cellulose: There are simple substances, but most are impregnated with resin and thermoformed. (2) Woven: String impregnated with glass, brass wire and made of asbestos, organic fiber, etc. with resin (3) Semi-mold: impregnated with resin, filled with rubber material, and thermoformed (4) Resin mold: Asbestos, glass fiber, etc. as base material, phenol (5) Rubber mold: A resin using rubber instead of resin in resin mold (6) Semi-metallic: Among resin molds, the base material is metal fiber ( 7) Metallic: Sintered metal powder (8) Cermet: Sintered ceramic powder and metal powder For automobiles, semi-mold and resin mold Friction materials have been widely used conventionally. However, with the recent improvement in engine output and the like, friction materials are required to have higher speed and higher load performance, and the use of metallic friction materials is also being studied. Metallic friction materials are also widely used for transportation machines, machine tools, or industrial vehicles.

[0004] This metallic friction material is also called a sintered metallic friction material, and a base metal powder such as a copper-based metal serving as a matrix, a lubricant powder such as graphite, and a friction component such as silica sand, mullite and short metal fibers. It is manufactured by mixing powder and molding and sintering it. However,
For example, in a brake device made of a metallic friction material containing short metal fibers, the short metal fibers fall out of the matrix and exist between the friction material and the disk rotor, etc., and are crushed at the time of braking, so that “brake squeal” occurs. It became clear.

Therefore, Japanese Patent Laid-Open Publication No. 3-79733 discloses that
A friction material using a metal short fiber bent and / or curved at at least one position in a longitudinal direction is disclosed. According to this friction material, the short metal fibers are prevented from dropping out of the matrix due to the entanglement of the short metal fibers, so that the squeal can be prevented.

[0006]

Graphite widely used as a lubricant in a metallic friction material, for example, when used in a friction material having a copper-based metal as a matrix, has no binding force between copper and graphite. Therefore, there was a problem that graphite was easily dropped during friction sliding. The present invention has been made in view of such circumstances, and has as its object to provide a metallic friction material in which graphite is prevented from falling off.

[0007]

According to the present invention, there is provided a method of manufacturing a metallic friction material, comprising: a first mixing step of mixing a substantially spiral metal fiber and graphite powder; and a first mixing step. A second mixing step of further mixing the base metal powder constituting the friction material matrix with the mixed powder thus obtained;
The method is characterized by comprising a forming step of forming a friction material shaped body from the mixed powder formed in the second mixing step, and a sintering step of sintering the formed body.

[0008]

In the production method of the present invention, first, a first mixing step of mixing a substantially spiral metal fiber and graphite powder is performed, and then a base metal powder is further mixed in a second mixing step. Thus, the graphite powder is effectively held in the substantially spiral metal fiber, and is prevented from being independently present in the base metal powder.

[0009] In the metallic friction material molded and sintered from such a mixed powder, the substantially spiral metal fibers are sintered integrally with the base metal constituting the matrix, and the graphite is contained in the matrix. It is prevented from existing in a lump, and is present in the matrix while being held in the substantially spiral metal fiber. Therefore, even if there is no binding force between the graphite and the base metal, the graphite is prevented from falling off during friction sliding with the counterpart material. Since graphite is gradually supplied to the sliding surface from the gap between the spiral metal fibers during frictional sliding, the graphite exhibits a lubricating action for a long period of time and is excellent in wear resistance and the like.

[0010] In order to ensure the retention of graphite, the spiral pitch of the spiral metal fibers is preferably smaller than the diameter of the graphite powder.

[0011]

The present invention will be specifically described below with reference to examples. (Example) <First mixing step> Average outer diameter 1.0 mm, average length 3.0
helical copper fiber having an average wire diameter of 0.1 mm and graphite powder having an average particle diameter of 0.3 mm, by weight ratio of copper fiber: graphite = 4:
The mixture was charged into a V-type mixer so that the mixture became 8, and mixed for 1 hour. <Second mixing step> Copper powder and tin powder as base metal powder and SiO ₂ powder as friction component powder were further charged into the V-type mixer so as to have the composition shown in Table 1,
Mix for 30 minutes.

[0012]

[Table 1] In addition, as the base metal, in addition to the above, copper, a copper-based metal such as a copper-tin-zinc alloy, an iron-based metal mainly containing iron, to which copper, nickel, cobalt, or the like is added, can be used. . As the friction component, mullite, silica sand, or the like can be used. Further, in addition to graphite, a lead compound such as lead sulfide or lead sulfate, MoS ₂ or the like can be used as a lubricant. <Molding Step> The obtained mixed powder was placed in a mold and compression-molded to form a disk pad-shaped molded body. <Sintering Step> The obtained compact was placed on the surface of the copper-plated back metal, pressed at 800 ° C. for 2 hours, sintered, and then machined to obtain a disk pad. <Test> Set this disc pad on the caliper,
A wear test was performed using the cast iron rotor as a mating material under the conditions shown in Table 2 to measure the wear rate. The results are shown in FIG. In addition,
An insulating plate was installed between the disk pad and the piston to prevent vapor lock.

[0013]

[Table 2] (Comparative Example) 4 staple copper fibers instead of spiral copper fibers
A disk pad of a comparative example was formed in the same manner as in the example except that the first mixing step was not performed and the whole was mixed at once in the second mixing step. And the wear rate was measured similarly, and the result is shown in FIG. (Evaluation) FIG. 3 shows that the disk pad obtained by the manufacturing method of the example has a smaller wear rate in the wear test and is superior in wear resistance to the disk pad obtained by the manufacturing method of the comparative example. Recognize.

In the disk pad obtained by the manufacturing method of the embodiment, as shown in FIG. 1, the helical copper fiber 1 and the SiO ₂ particles are uniformly dispersed in the copper matrix 4 and are integrally held. Since the graphite 2 is held in the copper fiber 1, the graphite 2 is prevented from falling off from the copper matrix 4 during frictional sliding. And graphite 2 is spiral copper fiber 1
This is due to the fact that the lubricating action of the graphite 2 is maintained for a long period of time.

On the other hand, in the disk pad obtained by the manufacturing method of the comparative example, as shown in FIG. 2, the graphite 2 becomes a lump having an average particle size of 0.1 to 0.4 mm, and the SiO ₂ particles 3 and the copper It is uniformly dispersed in the matrix 4 together with the fibers 5, and the bonding force between the graphite 2 and the copper matrix 4 is extremely weak. Therefore, the graphite 2 easily falls off from the copper matrix 4 during frictional sliding, and the lubricating action of the graphite 2 gradually decreases, so that the wear rate in the wear test increases.

[0016]

According to the metallic friction material obtained by the production method of the present invention, graphite is prevented from falling off during frictional sliding, and the lubricating effect of graphite acts for a long period of time, resulting in excellent wear resistance. ing. According to the production method of the present invention, such a metallic friction material can be produced easily, stably and reliably.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a metallic friction material obtained by a production method of the present invention.

FIG. 2 is a schematic sectional view of a metallic friction material obtained by a conventional manufacturing method.

FIG. 3 is a bar graph illustrating a degree of a wear rate.

[Explanation of symbols]

1: spiral copper fiber 2: graphite
3: SiO ₂ particles 4: Copper matrix 5: Copper short fiber

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16D 69/02 B22F 5/00 G

Claims (1)

(57) [Claims] 1. A first mixing step of mixing a substantially spiral metal fiber and graphite powder, and a base metal powder constituting a friction material matrix is further added to the mixed powder formed in the first mixing step. Second to mix
A metallic friction comprising: a mixing step; a forming step of forming a friction material shaped compact from the mixed powder formed in the second mixing step; and a sintering step of sintering the compact. The method of manufacturing the material.