JPH0693355A - Production of metallic friction material - Google Patents

Abstract

PURPOSE:To prevent the falling of graphite at the time of friction and sliding by forming a green compact having the shape of a friction material from special mixed powder and sintering this green compact. CONSTITUTION:In a primary mixing stage, metallic fiber having an approximately spiral shape and graphite powder 2 are mixed. In a secondary mixing stage, the mixed powder formed in the primary mixing stage is furthermore added with the powder of metal in a substrate constituting the matrix 4 of the friction material. A green compact having the shape of the friction material is formed from the mixed powder formed in the secondary mixing stage. This green compact is sintered. Thus, the metallic friction material is produced. In this way, the metallic friction material excellent in wear resistance can stably and surely be produced in an easy manner.

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 automobile brakes, 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, high friction coefficient, and stable friction coefficient. A single material is difficult to satisfy these performances, and the friction material is composed of a composite material in which many materials are mixed.

Such friction materials can be roughly classified as follows. (1) Cork, cellulose: There is also a simple substance, but most of them are thermoformed by impregnating resin (2) Wooven: Glass fiber, brass wire as core, asbestos, organic fiber impregnated with resin And then thermoformed after winding the string (3) Semi-molded: a string impregnated with resin and filled with a rubber material and thermoformed (4) Resin mold: Asbestos, glass fiber etc. as a base material, phenol (5) Rubber mold: one in which rubber is used instead of resin in resin mold (6) Semi-metallic: resin mold whose base material is metal fiber ( 7) Metallic: Sintered metal powder (8) Cermet: Sintered ceramic powder and metal powder Friction materials have been widely used conventionally. However, due to recent improvements in engine output and the like, friction materials are required to have high-speed and high-load performance, and the use of metallic friction materials is also being considered. In addition, metallic friction materials are often used for transportation machines, machine tools, and industrial vehicles.

This metallic friction material is also referred to as a sintered metallic friction material, and is a matrix metal powder such as a copper-based metal serving as a matrix, a lubricant powder such as graphite, and friction components 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 braking device made of metallic friction material containing short metal fibers, short metal fibers fall out of the matrix and exist between the friction material and the disk rotor, etc., and crushing during braking causes "brake squeal". It became clear.

Therefore, Japanese Patent Application Laid-Open No. 3-79733 discloses that
A friction material using short metal fibers bent and / or curved at at least one position in the longitudinal direction is disclosed. According to this friction material, since the short metal fibers are prevented from falling out of the matrix due to the entanglement of the short metal fibers, it is possible to prevent squeaking.

[0006]

By the way, graphite, which is widely used as a lubricant in metallic friction materials, has no bonding force between copper and graphite when it is used in a friction material containing a copper-based metal as a matrix, for example. Therefore, there is a problem that graphite easily comes off during friction sliding. The present invention has been made in view of such circumstances, and an object thereof is to provide a metallic friction material in which falling of graphite is prevented.

[0007]

A method for producing a metallic friction material of the present invention which solves the above-mentioned problems is formed by a first mixing step of mixing substantially spiral metal fibers and graphite powder, and a first mixing step. A second mixing step of further mixing the powder of the base metal forming the matrix of the friction material with the mixed powder thus obtained;
It is characterized by comprising a forming step of forming a friction material-shaped formed body from the mixed powder formed in the second mixing step and a sintering step of sintering the formed body.

[0008]

In the manufacturing method of the present invention, the first mixing step of mixing the substantially spiral metal fibers and the graphite powder is first performed, and then the base metal powder is further mixed in the second mixing step. As a result, the graphite powder is effectively retained in the substantially spiral metal fiber and is prevented from independently existing in the base metal powder.

In the metallic friction material formed and sintered from such mixed powder, the substantially spiral metal fiber is integrally sintered with the matrix metal constituting the matrix, and graphite is contained in the matrix. It is prevented from existing in the form of lumps, and is present in the matrix in a state of being retained in the substantially helical metal fibers. 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 mating material. Since graphite is gradually supplied to the sliding surface from the gap between the spiral metal fibers during friction sliding, it exhibits a lubricating action for a long period of time and is excellent in wear resistance and the like.

In order to ensure the retention of graphite, it is preferable that the spiral pitch of the spiral metal fibers be smaller than the diameter of the graphite powder.

[0011]

EXAMPLES 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
mm, an average wire diameter of 0.1 mm, and a helical copper fiber and an average particle diameter of 0.3 mm of graphite powder were used in a weight ratio of copper fiber: graphite = 4:
The mixture was put 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 the base metal powder and SiO ₂ powder as the 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 to the above, as the base metal, copper, a copper-based metal such as a copper-tin-zinc alloy, iron as a main component, and an iron-based metal in 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 or MoS ₂ may be used as a lubricant. <Molding Step> The obtained mixed powder was put into a mold and compression-molded to form a disk pad-shaped molded body. <Sintering Step> The obtained molded body was placed on the surface of a copper-plated backing metal, pressed and held at 800 ° C. for 2 hours for sintering, and then machined into a disk pad. <Test> Set this disc pad on the caliper,
A wear test was performed under the conditions shown in Table 2 using a cast iron rotor as a mating material, and the wear rate was measured. The results are shown in Fig. 3. In addition,
An insulating plate was installed between the disc pad and the piston to prevent vapor lock.

[0013]

[Table 2] (Comparative Example) 4 short copper fibers were used instead of the spiral copper fiber.
A disk pad of a comparative example was formed in the same manner as in the example except that the mixture was used in an amount of 1 wt% and the first mixing step was not performed and the whole was mixed in the second mixing step at once. Then, the wear rate was similarly measured, and the results are shown in FIG. (Evaluation) From FIG. 3, it is found that the disc pad obtained by the manufacturing method of the example has a smaller wear rate in the abrasion test and is excellent in wear resistance than the disc 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 spiral copper fiber 1 and the SiO ₂ particles are uniformly dispersed and integrally held in the copper matrix 4 to form a spiral shape. 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 friction sliding. And graphite 2 is spiral copper fiber 1
This is because the lubricating action of the graphite 2 is maintained for a long period of time because the graphite 2 is gradually supplied to the sliding surface.

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 is in the form of lumps having an average particle diameter of 0.1 to 0.4 mm, and the SiO ₂ particles 3 and copper short particles are formed. The fibers 5 and the matrix 4 are uniformly dispersed in the matrix 4, and the bonding force between the graphite 2 and the copper matrix 4 is extremely weak. Therefore, the graphite 2 is easily dropped from the copper matrix 4 during frictional sliding, and the lubricating action of the graphite 2 is gradually reduced, so that the wear rate in the wear test is increased.

[0016]

[Effects of the Invention] That is, according to the metallic friction material obtained by the manufacturing method of the present invention, the falling of graphite during friction sliding is prevented, and the lubricating action of graphite acts for a long time, so that it has excellent wear resistance. ing. According to the manufacturing method of the present invention, such a metallic friction material can be manufactured easily, stably and surely.

[Brief description of drawings]

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

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

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

[Explanation of symbols]

1: Spiral copper fiber 2: Graphite
3: SiO ₂ particles 4: copper matrix 5: copper short fiber

Claims (1)

[Claims] 1. A first mixing step of mixing substantially spiral metal fibers and graphite powder, and a powder of a base metal forming a matrix of a friction material in the mixed powder formed in the first mixing step. Second to mix
Metallic friction comprising a mixing step, a molding step of forming a friction material-shaped molded body from the mixed powder formed in the second mixing step, and a sintering step of sintering the molded body. Method of manufacturing wood.