JP2004332830A - High torque capacity wet paper friction material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet paper friction material provided with both of high torque capacity and excellent thermal stability. <P>SOLUTION: This wet paper friction material is manufactured by impregnating a paper material with a thermosetting resin, heating for solidification, and pressurizing for formation. A fiber basic material occupies 20-80 % of the paper material, and cellulose pulp, aramide pulp and single-polymer acrylic pulp adjusted at 120-280 ml of water filtration are contained. As the thermosetting resin, 20-40 wt.% of straight phenol resin, alkyl modified phenol resin, epoxy modified phenol resin, tung oil modified phenol resin, cashew oil modified phenol resin, tung oil/cashew oil modified phenol resin are contained to obtain high torque capacity, heat resistance and mechanical strength. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wet paper friction material used for a clutch and a brake element of an automatic transmission of a vehicle.
[0002]
[Prior art]
Wet paper friction material is made by dispersing a mixture of fiber base material such as pulp and friction modifier in water, making paper, impregnating with thermosetting resin after drying, heat curing and pressure molding. Manufactured. The function of the wet paper friction material is affected by the composition of the paper material such as the fiber base material, filler and friction modifier, which are the main components of such a paper material, and the thermosetting resin to be impregnated. The selection and blending amount have been continuously improved in accordance with the use of the wet paper friction material.
[0003]
Friction modifier plays an important role as it affects the porosity and surface shape, and the fiber component affects the porosity and flexibility of the friction material, affecting the friction characteristics, heat resistance, and mechanical strength Has been known to exert.
The phenolic resin mainly used as a binder affects not only the mechanical strength of the wet paper friction material but also the friction coefficient and the speed dependence of the friction coefficient. In particular, since the friction coefficient in the low speed region defined as "torque capacity" is greatly affected by the resin, various oil-based materials and modified materials have been studied so far.
For example, in Patent Document 1, a thermosetting resin is impregnated into a paper body in which a pulp obtained by fibrillating polyacrylonitrile-based copolymerized acrylic fibers (hereinafter referred to as “copolymerized acrylic pulp”) and a filler are blended. There is a wet friction material that has been cured.
[0004]
[Patent Document 1]
Japanese Patent Publication No. 5-45808
[Problems to be solved by the invention]
In a clutch or a brake element of an automatic transmission, transmitting the torque while stopped or slightly slipping is the most basic design function as a torque capacity. When the torque capacity is large, for example, it is possible to reduce the diameter of the clutch or to reduce the number of clutches and downsize the clutch element. On the other hand, since the friction coefficient is high, the amount of heat generated per unit area when the clutch and the brake operate is increased. Therefore, the heat resistance and mechanical strength of the friction material are often impaired, and a wet paper friction material satisfying both high torque capacity, heat resistance and mechanical strength cannot be easily produced.
[0006]
Also in the wet friction material of Patent Document 1, the copolymerized acrylic pulp has particularly low heat resistance and chemical resistance, and causes dimensional shrinkage in the processing step of the wet friction material, so that it is difficult to process with high accuracy. In addition, when the friction material is operated, there is a problem that the strength is significantly reduced due to frictional heat or chemicals in the automatic transmission fluid.
[0007]
The present invention has been made in view of the above circumstances, and has as its object to provide a wet paper friction material having both high torque capacity and good thermal stability mainly for use in clutches and brakes of automatic transmissions. Yes, of the composition of conventional wet friction materials, focusing on the fiber base material and resin in the friction modifier, which constitutes the paper, improves the friction properties, heat resistance, and mechanical strength, and limits the application. It succeeded in developing a versatile, high-torque capacity wet paper friction material that is free of friction.
[0008]
[Means for Solving the Problems]
The present invention is directed to a wet paper friction material obtained by impregnating a thermosetting resin into a paper body, heating and curing, and further press-molding, wherein the paper body comprises a fiber base material and a filler; The wet paper friction material, which comprises 20 to 80% by weight of the total weight of the papermaking body, and includes cellulose pulp, aramid pulp, and monopolymerized acrylic pulp having a freeness of 120 to 280 ml. Was solved.
[0009]
[Action]
In the present invention, the fiber base material occupies 20 to 80% by weight of the total amount of the papermaking body, and includes a cellulose pulp, an aramid pulp, and a monopolymerized acrylic pulp having a freeness of 120 to 280 ml. A wet paper friction material excellent in heat resistance and mechanical strength can be provided.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The wet paper friction material of the present invention is a wet paper friction material manufactured by impregnating a thermosetting resin in a paper body manufactured by blending a fiber base material and a filler having specified properties, heat curing, and molding. In addition, cellulose pulp, aramid pulp, monopolymerized acrylic pulp, and other fibers are used as the fiber base material in an amount of 20 to 80% by weight based on the total amount of the papermaking body, and the freeness of the single heavy acrylic pulp is adjusted to 120 to 280 ml. Further, as a thermosetting resin, a straight phenol resin, an alkyl-modified phenol resin, an epoxy-modified phenol resin, a tung oil-modified phenol resin, a cashew oil-modified phenol resin, and a tung oil / cashew oil-modified phenol resin are added in an amount of 20 to 40 to the papermaking body. By impregnating by weight%, high torque capacity, heat resistance and mechanical strength are compatible.
[0011]
The fiber base material contains cellulose pulp, aramid pulp, monopolymerized acrylic pulp, and other fibers in an amount of 20 to 80% by weight based on the total amount of the papermaking body.
Aramid pulp has good thermal stability and papermaking properties, but is more expensive than cellulose pulp and has poorer compatibility with thermosetting resins such as phenolic resins. Cellulose pulp has good compatibility with resin and is inexpensive as compared with aramid pulp, but has poor thermal stability and mechanical strength. On the other hand, monopolymerized acrylic pulp has good compatibility with thermosetting resins such as phenolic resin, and has the characteristic of not melting under heat.Therefore, when used in combination with aramid pulp or cellulose pulp, good thermal stability is achieved. And mechanical strength can be obtained relatively inexpensively. When these fiber bases are more than 80% by weight of the total papermaking body, a smooth material surface cannot be obtained, and when it is less than 20% by weight, the mechanical strength decreases.
[0012]
The freeness of the monopolymerized acrylic pulp constituting the papermaking body is adjusted to 120 to 280 ml.
The freeness is the degree of beating of the fibers, and the lower the degree of freeness, the more the fibers are beaten, and the greater the degree of branching of each fiber. As the degree of branching of the acrylic pulp increases, the entanglement between fibers increases, and sufficient mechanical strength can be obtained after impregnating and hardening the phenol resin.
[0013]
When the monopolymerized acrylic pulp constituting the papermaking body has a freeness of less than 120 ml, since the number of fibers in the branched state is too large and the pores are too small, clogging tends to occur during friction sliding, Reduces heat resistance.
If the aramid pulp constituting the papermaking body has a freeness greater than 280 ml, sufficient mechanical strength cannot be obtained because the entanglement between the fibers is reduced.
[0014]
As the thermosetting resin, a straight phenol resin, an alkyl-modified phenol resin, an epoxy-modified phenol resin, a tung oil-modified phenol resin, a cashew oil-modified phenol resin, or one or more of tung oil / cashew oil-modified phenol resins, 20 to 40% by weight of the paper is impregnated.
[0015]
Generally, tung oil-modified phenolic resin, cashew oil-modified phenolic resin, tung oil / cashew oil-modified phenolic resin, and the like are known to have an effect of increasing the friction coefficient in a low-speed region. On the other hand, when such an oily modified material is used, there is a problem that heat resistance and mechanical strength are impaired. On the other hand, although straight phenol has a small effect of raising the friction coefficient in the low-speed range, it has sufficient heat resistance and mechanical strength, so when used in combination with the above-mentioned modified material, it has a high friction coefficient, heat resistance, and mechanical strength. Can be compatible. When the impregnated amount of these resins is less than 20% by weight of the papermaking body, no mechanical strength can be obtained, and when it is more than 40% by weight, heat resistance is reduced.
[0016]
【Example】
Hereinafter, specific examples will be described.
(Example)
30% by weight of a straight phenolic resin obtained by adding an oily modification to a papermaking body containing 10% by weight of cellulose pulp, 10% by weight of aramid pulp, 30% by weight of monopolymerized acrylic pulp, and 50% by weight of a filler such as diatomaceous earth It was impregnated, heated and cured, and adhered to a core metal to produce a clutch disk.
[0017]
(Comparative example)
As a comparative example, a paper material in which 30% by weight of cellulose pulp, 30% by weight of aramid pulp, 30% by weight of diatomaceous earth, and 10% by weight of a carbon-based filler were impregnated with 35% by weight of a straight phenol resin of a friction material and heat-cured. Then, a clutch disk adhered to the core was used.
[0018]
The wet friction clutch plate thus obtained was evaluated for torque capacity, heat resistance, and mechanical strength by the test methods described below.
<Torque capacity evaluation condition>
Testing machine: SAE No. 2 Conditions for obtaining friction tester performance: friction surface: 6 oil temperature: 80 ° C
Surface pressure: 0.5MPa, 1.0MPa, 2.0MPa
Rotation speed: 0.72, 1, 5, 10, 25, 50, 75, 100 rpm
As a result of the above test, the wet paper friction material of the example had a high coefficient of friction at low speed indicating the torque capacity, and also had good speed characteristics of the coefficient of friction.
[0019]
<High-speed durability evaluation conditions>
Testing machine: SAE No. 2 Conditions for obtaining friction tester performance: friction surface: 6 oil temperature: 100 ° C
Surface pressure: 0.785MPa
Rotation speed: 7100 rpm
Inertia: 0.01 kg / m ²
Lubricating oil amount: 360ml / min
As a result of the above test, as shown in FIGS. 2 and 3, the wet-type paper friction material of the example has a small decrease in the coefficient of friction indicating heat resistance, and the wear amount after the test is smaller than that of the comparative example. Met.
[0020]
<Compression strength evaluation conditions>
Testing machine: Cyclic compressive strength testing machine Evaluation condition: Friction surface: 2 oil temperature: 120 ° C
Surface pressure: 10.0 MPa
Cycle: load 2sec, unload 4sec
As a result of the above test, as shown in FIG. 4, the wet paper friction material of the example exhibited better mechanical strength than the comparative example.
[0021]
From FIG. 1 to FIG. 4, the example had a larger torque capacity and sufficient heat resistance and mechanical strength as compared with the comparative example.
From the above results, cellulose pulp, aramid pulp, monopolymerized acrylic pulp, and other fibers as the fiber base material were included in an amount of 20 to 80% by weight based on the total weight of the papermaking body, and the freeness of the single acrylic pulp was increased to 120 to 280 ml. Then, a straight phenol resin, an alkyl-modified phenol resin, an epoxy-modified phenol resin, a tung oil-modified phenol resin, a cashew oil-modified phenol resin, and a tung oil / cashew oil-modified phenol resin were added as thermosetting resins to the papermaking body. By using a friction material impregnated with 重量 40% by weight to achieve both high torque capacity, heat resistance and mechanical strength, it is expected to be applied to many wet friction applications as a high torque wet paper friction material.
[0022]
【The invention's effect】
In the present invention, the fiber base material occupies 20 to 80% by weight of the total weight of the papermaking body, and contains cellulose pulp, aramid pulp, and monopolymerized acrylic pulp having a freeness of 120 to 280 ml. The effect is that the torque capacity, heat resistance and mechanical strength of the material can be improved.
[Brief description of the drawings]
FIG. 1 is a table showing the evaluation results of torque capacity.
FIG. 2 is a chart showing durability evaluation results.
FIG. 3 is a table showing durability evaluation results.
FIG. 4 is a table showing compression strength evaluation results.

Claims (3)

In a wet paper friction material obtained by impregnating a thermosetting resin into a papermaking body, heating and curing, and then press molding,
The paper body comprises a fiber base material and a filler,
The fiber base material comprises 20 to 80% by weight of the papermaking body, and includes a cellulose pulp, an aramid pulp, and a monopolymerized acrylic pulp having a freeness of 120 to 280 ml,
Wet paper friction material. The thermosetting resin comprises one or more of a straight phenol resin, an alkyl-modified phenol resin, an epoxy-modified phenol resin, a tung oil-modified phenol resin, a cashew oil-modified phenol resin, and a tung oil / cashew oil-modified phenol resin. Item 6. A wet paper friction material according to Item 1. 3. The wet paper friction material according to claim 1, wherein the thermosetting resin accounts for 20 to 40% by weight of the friction material.

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