JPH08245810A - Wet friction material - Google Patents

Abstract

PURPOSE: To provide a wet friction material improved in the resistances to heat, wear and load, mechanical strength, and elastic deformation by impregnating a metal foam having a three-dimensional network structure with an org. binder, and curing the binder. CONSTITUTION: An org. material foam such as a polyurethane foam is plated, and then heat-treated to decompose and remove the org. material. The remaining metal is sintered to obtain a metal foam having a three-dimensional network structure. The metal foam is impregnated with an org. binder, and then cured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet friction material suitable for use in a wet multiple disc clutch, a lockup clutch, a limited slip differential, etc. in an automatic transmission for vehicles.

[0002]

2. Description of the Related Art As a conventional wet friction material, a paper friction material using paper as a base material is disclosed in JP-A-59-80539 and JP-A-6-1965. The paper friction material is manufactured by mixing various friction modifiers and the like into pulp, making paper, and then impregnating a binder resin such as a phenol resin and curing the paper. This paper friction material has a high friction coefficient, and the relationship between the friction coefficient and the peripheral speed (μ-V characteristic) is flat due to the property of rich elastic deformation and the porosity.

[0003]

However, since the paper friction material is a molded product having a laminated structure, the engine output has been increased in recent years, and the sliding time has been lengthened as a measure against shock torque during lockup. Under the condition that the load on the friction material is increased due to, the problems that heat resistance and wear resistance are insufficient and the laminated layers are fatigued and peeled off due to repeated compressive load. Further, since the base material of the paper friction material is an organic fiber material such as pulp, the heat resistance limit thereof is as low as 120 to 150 ° C. The present invention solves the above problems and provides a wet friction material which has sufficient heat resistance and wear resistance even under conditions of increased load and does not cause peeling.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a wet friction material obtained by impregnating a metal foam having a three-dimensional network structure with an organic binder and curing the metal foam. In the present invention, the metal foam having a three-dimensional network structure is, for example, one obtained as follows. (1) For organic foams such as polyurethane foam,
It is obtained by plating a metal such as copper, heat treating it to decompose and remove organic substances, and then sintering the remaining metal. (2) An organic foam such as polyurethane foam is impregnated with a solution of an adhesive, the solvent is removed, and then inserted into the metal powder and shaken to adhere the metal powder to the foam. It is obtained by decomposing and removing organic substances by heat treatment and then sintering the remaining metal. (3) A kneaded material in which metal powder is dispersed in a solution of an adhesive is applied to a foam of an organic material such as polyurethane foam by spraying, etc., dried, and then heat treated in the same manner as (1) below to decompose and remove the organic material. , And then sintering the remaining metal.

The metal foam having a three-dimensional network structure has open cells for impregnating the organic binder, and the bubble ratio is preferably 50% by volume or more so that the organic binder can be easily impregnated. The metal of the metal foam having a three-dimensional network structure is preferably nickel, copper or brass because it has a high heat resistance temperature and stable friction characteristics. As the organic binder to be impregnated in the metal foam having a three-dimensional network structure, a thermosetting resin such as phenol resin, melamine resin, epoxy resin or polyimide resin,
NBR and the like are preferable because of their high heat resistance temperature, and phenol resin is particularly preferable. It is possible to use a plurality of organic binders in combination. There is no limitation on the method of impregnation, and any of vacuum impregnation and dipping may be used. After the impregnation, the solvent is removed and heat treatment is performed at a temperature suitable for curing the resin or the like to obtain a wet friction material in which a metal foam having a three-dimensional network structure and the resin or the like are combined.

The wet friction material according to the present invention has a bubble ratio of 20.
If about 70% by volume, the mechanical strength is optimum,
Rich in elastic deformation, uniform contact with sliding surface, μ in oil
The -V characteristic is also flat, which is preferable. In the present invention, in addition to the above components, in order to further stabilize the frictional properties, friction modifiers such as graphite, molybdenum disulfide, antimony trisulfide, cashew resin and barium sulfate may be added to the organic binder. It may be added and impregnated to form a composite.

[0007]

EXAMPLES Examples of the present invention will be described below. Example 1 A polyurethane foam having a three-dimensional network structure (manufactured by Bridgestone Corporation, trade name Everlite SF) is a dispersion of colloidal graphite (manufactured by Hitachi Powdered Metals Co., Ltd., trade name Hitasol AF-).
After immersion in 3) for 15 minutes to deposit graphite in the cells of the polyurethane foam to impart conductivity, nickel was electrodeposited in the cells by electroplating. Then 500
After decomposing and removing the polyurethane foam of the base material by keeping it in the air at 10 ° C for 10 minutes, it was treated at 1200 ° C for 20 minutes in a reducing atmosphere in which hydrogen gas was flown to sinter the nickel. 95% by volume of three-dimensional network structure, 2
A metal foam having a 50 mm square and a thickness of 1 mm was obtained. Next, this metal foam was mixed with 30 wt% ME of novolac type phenol resin (Hitachi Chemical Co., Ltd., trade name HP491UP).
After soaking in K (methyl ethyl ketone) solution for 5 minutes, 8
Remove solvent by heating at 0 ° C for 1 hour, then 200 ° C
The resin was hardened by heating for 2 hours to obtain a wet friction material having a resin adhesion rate of 20% by weight and a bubble rate of 50% by volume.

Example 2 The polyurethane foam used in Example 1 was immersed in a 5% by weight MEK solution of an acrylic pressure-sensitive adhesive (Hitachi Chemical Co., Ltd., trade name AS-406) for 2 minutes and then at 100 ° C. 1
Dry for 0 minutes, and then carbonyl nickel powder (US International Nickel Co., Sharp 123)
It was inserted into the inside and rocked, and nickel powder was made to adhere in the bubbles. Next, the polyurethane foam was removed and nickel was sintered through the same steps as in Example 1 to obtain a metal foam having a three-dimensional network structure with a porosity of 95% by volume. Then, a phenolic resin was impregnated and cured through the same steps as in Example 1 to obtain a wet friction material having a square of 250 mm and a thickness of 1 mm.

The wet friction materials obtained in Examples 1 and 2 and the paper friction material generally used as a comparative example were machined to prepare test pieces having an outer diameter of 133 mm, an inner diameter of 113 mm and a thickness of 1 mm. Using this, an SAE (American Society of Automotive Engineers) # 2 friction tester was used to perform a test. The items of the tests carried out are: (A) dynamic friction coefficient after 1000 cycles, (B) dynamic friction coefficient after 10,000 cycles,
(C) is μ ₀ / μ ₆₀₀ (μ ₀ is the friction coefficient at the time of stopping, μ ₆₀₀
Is the friction coefficient at a rotation speed of 600 rpm, and (D) is the wear amount (μm). The oil used in the # 2 friction tester was Nissanmatic Fluid D (Nissan Motor Co., Ltd.)
(Pure automatic oil manufactured by K.K.), test conditions are oil temperature: 120 ° C, inertia: 0.203 kg. m ² , surface pressure; 1108 KPa, pressurizing time; 2 seconds, motor rotation speed;
The rotation speed was 3000 revolutions / minute, the interval was 30 seconds / time, and the durability was 10,000 cycles. Table 1 shows the test results.

[0010]

[Table 1]

It can be seen from Table 1 that both Examples 1 and 2 have a good friction coefficient, and the value of μ ₀ / μ ₆₀₀ shows that the μ-V characteristic is flat. The amount of wear is also better than that of the paper friction material of the comparative example.

[0012]

The wet friction material according to the first aspect of the present invention has high heat resistance, wear resistance, and load bearing characteristics, and is sufficiently durable for future use under further high load conditions. Further, since it is not a laminated material such as a paper friction material but an integrated molded body, peeling does not occur even when a load is repeatedly applied. The wet friction material according to the second aspect exhibits the effect of the wet friction material according to the first aspect, and further has a high heat resistant temperature and stable friction characteristics. The wet friction material according to claim 3 has the effect of the wet friction material according to claim 1, and is further excellent in heat resistance.

Claims (3)

[Claims] 1. A wet friction material obtained by impregnating a metal foam having a three-dimensional network structure with an organic binder and curing the same. 2. The wet friction material according to claim 1, wherein the metal of the metal foam is nickel, copper or brass. 3. The wet friction material according to claim 1, wherein the organic binder is a phenol resin.