JPH0719271A - Wet type friction material - Google Patents

Abstract

PURPOSE:To provide a wet friction material which is prepared to have heat resistance, sufficient porosity, and impact resistance by a method wherein a paper-making substance containing a fiber base material of ceramic fibers and an inorganic filler is heated and sintered. CONSTITUTION:A paper-making substance containing ceramic fibers, such as alumina fibers, or an inorganic filler, such as ceramic fibers and calcium carbonate, is prepared by paper-making by means of a long net type paper making machine. After the paper-made paper-making substance is dried, it is formed in a given shape by a means, such as blanking. The paper-making substance is heated and sintered at temperature lower than the melt point of ceramic fibers. This way produces a porous wet friction material with which ceramic fibers are formed integrally by sintering. Thus, heat resistance is provided, resulting in prevention of the occurrence of thermal deterioration even when it is used on a high load condition and provision of excellent wear resistance and durability. Further, sufficient porosity necessary to form an oil film on a friction surface is provided.

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 used in a fluid automatic transmission of an automobile, and more particularly to a wet friction material composed of an inorganic porous material having excellent heat resistance.

[0002]

2. Description of the Related Art Conventionally, in automatic transmissions for automobiles, a friction mating member composed of a plurality of disk plates having a wet friction material adhered to the surface of a substrate which is usually made of metal and a single plate such as a metal plate. Alternately arranged with a plurality of separate plates, and in the ATF (Automatic Transmission Fluid) used as lubricating oil, press the wet friction material that is stopped against the rotating mating material to stop the rotation. The driving force of the prime mover is transmitted or cut off by pressing the rotating wet friction material against the stationary counterpart material to rotate the counterpart friction material and the wet friction material at the same time. Further, in order to smoothly transmit the driving force of the prime mover, it is also possible to generate the differential rotation between the wet friction material and the mating material while transmitting the driving force in the same state as the half clutch.

Wet friction materials used in such oils are
It is formed as a porous body because it needs to be sufficiently impregnated with oil, and since it is cheaper and lighter than before, it is impregnated with a thermosetting resin in a paper body of a fiber base material and heat-cured. Things are common. Wood pulp is generally used as the fiber base material, and a filler such as a friction modifier and a solid lubricant is appropriately added to the paper body. Regarding this type of wet friction material, for example, JP-A-1-1691
34, Japanese Patent Application Laid-Open No. 1-288639, Japanese Patent Publication No. 2
Various improved techniques are disclosed in, for example, Japanese Patent Publication No. 616161.

[0004]

However, with respect to such a wet friction material as well, the demand for its performance is becoming more and more severe due to the recent increase in the output of automobile engines and the downsizing of transmissions. In particular, one of them is heat resistance. For example, when the shift point of the automatic transmission is improved to improve the acceleration performance of the vehicle, the engagement rotational speed of the friction material is increased, and the friction engagement surface is instantaneously increased to 400%. It can reach as high as ℃. Therefore, in the conventional wet friction material using wood pulp as a fiber base material, it is not possible to obtain a stable friction coefficient due to heat deterioration, and it becomes impossible to sufficiently satisfy wear resistance and durability. ing.

On the other hand, it has long been known that the wet friction material is composed of an inorganic porous material such as a heat-resistant sintered alloy. Further, for example, JP-A-59-83980 proposes a wet friction material formed by sintering ceramic powder into a sheet shape.

However, although these metal or ceramic powders have heat resistance, it is difficult to secure a sufficient porosity necessary to form an oil film on the friction surface, and There was a problem in that it was vulnerable to shock.

Therefore, the present invention has heat resistance and
It is an object of the present invention to provide a wet friction material having sufficient porosity and excellent impact resistance.

[0008]

The wet friction material according to the invention of claim 1 is obtained by heating and sintering a papermaking body containing a fiber base material composed of ceramic fibers.

A wet friction material according to a second aspect of the present invention is obtained by heating and sintering a papermaking body containing a fiber base material made of ceramic fibers and an inorganic filler.

[0010]

In the first aspect of the invention, the wet friction material is composed of a sintered body of ceramic fibers, and therefore has heat resistance. Further, since the fiber base material composed of ceramic fibers is sintered in the state of being made into a papermaking body, it has sufficient porosity, and since the ceramics is in the form of fibers, it has toughness and Excellent impact resistance.

Further, in the second aspect of the invention, since the inorganic filler is further included, the friction performance is improved and the strength of the friction material is further increased.

Here, as the ceramic fibers, alumina fibers, silica fibers, alumina-silica fibers, potassium titanate fibers, carbide fibers such as silicon carbide and the like can be used, and whiskers can also be used. it can. These fibers can be used alone or in combination, and their average fiber length is 0.5.
~ 5 mm (preferably 1-2 mm), fiber diameter 0.1 ~ 6μ
m (preferably 1.5 to 2.0 μm) is generally used.

As the filler, an inorganic filler which has been conventionally used in wet friction materials and which does not undergo thermal decomposition or strength deterioration during heating and sintering can be used as it is. , Barium sulfate, graphite, molybdenum disulfide, iron oxide, silicon oxide, magnesium oxide, wollastonite, diatomaceous earth and the like can be used alone or in combination of two or more. And
These fillers are fixed between the fibers by sintering the ceramic fibers, but it is more preferable that the filler is sintered and integrated with the ceramic fibers at the time of heat sintering. From this point as well, among these fillers, diatomaceous earth which is also porous is particularly suitable, and particles having a particle diameter of 2 to 20 μm, preferably 4 to 6 μm can be used.
The inorganic filler may not be used in particular, but when it is used, it is generally 5 to 5 with respect to the entire friction material.
It is used in a proportion of 0% by weight, preferably 5 to 30% by weight.

Then, the paper body containing these ceramic fibers or the ceramic fibers and the inorganic filler is processed by a Fourdrinier or cylinder type paper machine in the same manner as in the production of a usual wet friction material. Can be obtained by doing. Then, the papermaking body thus formed is dried and then formed into a predetermined shape by means such as punching. Next, the papermaking body is heated at a temperature equal to or lower than the melting point of the ceramic fiber and sintered. The filler may be contained in the papermaking body at the time of papermaking, or may be coated on the surface after forming the papermaking body. The coating can be performed by applying the dispersion liquid of the filler by means such as spraying or by passing the papermaking body through the dispersion liquid of the filler.

In this way, a porous wet friction material having ceramic fibers integrated by sintering can be obtained. The obtained wet friction material preferably has a porosity of 30 to 50%. However, a porosity outside this range is also possible. The wet friction material is used in oil by adhering it to a substrate such as a disc plate of an automatic transmission as in the case of a normal wet friction material.

[0016]

EXAMPLES Examples of the present invention will be described below.

The wet friction material of the present invention was prepared by the following formulation and manufacturing method.

Example 1 Average fiber length 1 mm, fiber diameter 2 μ
m ceramic fiber (50 wt% alumina, 50 silica)
% By weight) was dispersed in water containing PVA as a fixing agent, and was made into a sheet having a thickness of 0.5 mm by a paper machine. After drying this sheet-shaped paper body, the outer diameter is 130 mm and the inner diameter is 10
A 0 mm hollow disk was punched out to form a ring-shaped papermaking body. Next, this was placed in an electric furnace and subjected to a firing treatment at a final reached temperature of 1300 ° C. in an air atmosphere. As a result, a wet friction material composed of a porous body in which ceramic fibers were integrally sintered was obtained.

<Embodiment 2> The thickness of the film formed in Embodiment 1 is 0.
A sheet-shaped paper body made of 5 mm of ceramic fiber and having an average particle size of 4
The diatomaceous earth having a mean film thickness of 4 μm or less was dipped in a suspension prepared by dispersing diatomaceous earth in water, lifted, and dried. This was punched into a hollow disk shape having an outer diameter of 130 mm and an inner diameter of 100 mm to obtain a ring-shaped paper body, which was fired under the same conditions as in Example 1.

As a result, a wet friction material comprising a porous body in which the ceramic fiber and the diatomaceous earth were sintered and integrated was obtained.

Example 3 70 parts by weight of the ceramic fiber used in Example 1 and 30 parts by weight of diatomaceous earth having an average particle size of 4 μm were thoroughly mixed in a machine chest and dispersed in water containing PVA as a fixing agent. The paper was made into a sheet having a thickness of 0.5 mm with a paper machine. Outer diameter 130mm, inner diameter 100mm
Example 1
The firing process was performed under the same conditions as described above.

As a result, a wet friction material similar to that of Example 2 was obtained, which was a porous body in which ceramic fibers and diatomaceous earth were sintered and integrated together.

Next, with respect to the wet friction materials according to these examples, the wet friction plates were prepared by adhering the wet friction materials to a core metal and subjecting the edges to burrs and the like to machine them to prepare a wet friction plate. The abrasion resistance was evaluated.

As a comparative example, a porosity of 30 to 50 was obtained by impregnating a thermosetting resin into a papermaking body composed of pulp fibers, diatomaceous earth, organic and inorganic friction modifiers, and heat molding. The same test was performed using a conventional wet friction material of volume%.

<Abrasion resistance test> Under the conditions shown below, SA
The ENo. 2 test was carried out for 50,000 cycles.

(Test conditions) Number of sheets: 3 sheets Rotation speed: 5000 rpm Load: 8 kg / cm ² Inertia amount: 3.5 kg · cm · sec ² Oil amount: 1000 ml Temperature: 100 ° C. The results obtained by the above test are shown in the table below. Shown in 1.

[0027]

[Table 1]

From these results, it can be seen that the wet friction materials of the respective examples of the present invention are much more excellent in wear resistance than the conventional wet friction materials of the comparative examples.

In terms of friction performance, the comparative example is 100
While the friction performance reached the limit in the cycle of 0 to 20000, Example 1 did not show deterioration over time, and both of the Examples 2 and 3 showed stable friction performance up to 50,000 cycles. .

[0030]

As described above, the wet friction material according to the first aspect of the present invention is obtained by heating and sintering a paper body containing a fiber base material made of ceramic fibers. Therefore, since it is composed of sintered ceramic fibers, it has heat resistance and can generally withstand temperatures of 500 ° C. or higher. Therefore, even if it is used under a high load condition, it is not thermally deteriorated and has excellent wear resistance and durability. Further, since the ceramic fiber is sintered in the form of a papermaking body, it has sufficient porosity necessary to form an oil film on the friction surface, and is further formed as a sintered body of ceramic fiber. Therefore, it has toughness and excellent impact resistance. These enable use under high load conditions, and are suitable for use in automatic transmissions and the like.

Since the wet friction material of the second aspect of the present invention further includes an inorganic filler, the friction performance and the strength of the friction material can be further improved. Further, the strength of the friction material can be further increased by using an inorganic filler that is sintered at the same temperature as the ceramic fiber.

Claims (2)

[Claims] 1. A wet friction material characterized by comprising heating and sintering a papermaking body containing a fiber base material made of ceramic fibers. 2. A wet friction material comprising a papermaking body containing a fibrous base material made of ceramic fibers and an inorganic filler, which is heated and sintered.