JPH0526049B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a friction material suitable for use in oil, especially automatic transmission fluid (hereinafter referred to as ATF) with low friction characteristics. It is related to materials.

[Prior Art] In automobiles that use an internal combustion engine as the prime mover, a clutch is provided between the prime mover and the transmission. This clutch provides the necessary slip when starting or changing gears, and is also required to intermittent power when changing gears after shifting the gear transmission. Friction clutches are widely used to perform these functions.

Friction clutches can be divided into dry friction plates, which are used in a dry state, and wet friction plates, which are immersed in oil.

Friction materials used in wet friction plates used to be sintered alloys, but recently paper-based friction materials impregnated with thermosetting resin and hardened have become mainstream. This type of friction material is produced by wet-forming a fiber base material of organic fibers and inorganic fibers, an inorganic filler, and a friction modifier, impregnating it with a thermosetting resin such as phenolic resin, drying,
It is compression molded. (For example, JP-A-57-
(No. 85876, Japanese Unexamined Patent Publication No. 59-175639) [Problems to be solved by the invention] In order to smoothly operate the components of automatic transmissions installed in automobiles, etc., ATF is a power transmission,
It plays a role in speed change control, lubrication, and lubrication of friction materials to maintain appropriate friction characteristics. Recently, design conditions for modern vehicles have expanded, such as higher engine output, diversification of drive systems such as four-wheel drive vehicles (hereinafter referred to as 4WD), and the installation of lock-up clutches for fuel efficiency measures, and the demands on ATF have increased. The properties have been expanded as well.

In order to improve the shift feel of automatic transmissions, and with the development of 4WD automatic transmissions using wet friction materials, there is a growing demand for ATF to have low friction characteristics (hereinafter referred to as low μ).

When the ATF is lowered, the feeling during shifting improves, but the static friction coefficient decreases, resulting in a lack of static torque capacity in conventional automatic transmissions.
There is a problem in that the friction material slips, causing burnout.

Possible countermeasures to these problems include increasing the number of friction plates or increasing the clutch control oil pressure, but as the automatic transmission itself becomes larger, other solutions are desired.

[Means for Solving the Problems] An object of the present invention is to solve the above problems and provide a wet friction material that has excellent shift feeling and a large torque transmission capacity at the time of starting.

That is, the wet friction material of the present invention is a wet friction material comprising a fiber component, a thermosetting resin, and a friction modifier, in which the thermosetting resin is made of modified phenol formaldehyde obtained by reacting phenols, formaldehydes, and drying oil. The resin is characterized in that the amount of modification of the drying oil is 15 to 55% by weight based on the modified phenol formaldehyde resin.

The fiber components constituting the skeleton of the wet friction material of the present invention include organic fibers such as wood pulp, linter pulp, aromatic polyamide fibers, and novoloid fibers, and inorganic fibers such as glass fibers, potassium titanate fibers, silica fibers, and rock wool fibers. These fibers are used alone or in combination of two or more. The appropriate blending amount of fiber components is 40% of the total friction material.
~75% by weight.

Phenols used in the modified phenol-formaldehyde resin of the present invention include phenol, cresol, xylate, etc., and formaldehydes include formalin, paraformaldehyde, hexamethylenetetramine, etc. Formaldehyde/phenols molar ratio is 1.1 to 2.5
is suitable. As a drying oil as a modifier,
Fatty oils having two or more unsaturated double bonds in their fatty acids, such as linseed oil, tung oil, castor oil, and tall oil, are used, and the amount of modification of the drying oil is 15 to 55% relative to the modified phenol formaldehyde resin. % by weight is useful, preferably from 20 to 50% by weight. If the amount of modification of the drying oil is less than 15% by weight, the effect of increasing the coefficient of static friction will be small, and if it exceeds 55% by weight, the heat resistance of the friction material will decrease.

The modified phenol formaldehyde resin of the present invention is produced by condensing phenols, formaldehydes, and drying oil in the presence of an alkaline catalyst, such as an alkali metal or alkaline earth metal hydroxide, or ammonia or amines, followed by dehydration under reduced pressure. , obtained as a liquid resin by adding a solvent such as methanol.

The drying oil may be reacted simultaneously with phenols and formaldehyde, or the drying oil and phenol may be reacted in advance, and then formaldehyde may be added to cause a condensation reaction.

Examples of the friction modifier used in the present invention include aluminum powder, rubber powder, cashew dust, and graphite powder, and inorganic fillers such as barium sulfate, potassium carbonate, oxidized acid, and diatomaceous earth can also be used.

To manufacture the wet friction material of the present invention, fiber components, a friction modifier, and if necessary, an inorganic filler and a fixing agent are dispersed in water, and then paper is made using a paper machine, and after drying, it is stamped into a predetermined mold. Pull it out. Next, the punched base material is impregnated with a modified phenol formaldehyde resin, dried, and then heated and press-molded to obtain a wet friction material.

[Operations and Effects of the Invention] The wet friction material of the present invention comprises a fiber base material, a friction modifier, and a phenol formaldehyde resin modified with 15 to 55 parts by weight of drying oil.
Increases flexibility and improves compatibility with mating materials. As a result, the contact surface increases, resulting in an increase in the coefficient of static friction.

By using the wet friction material of the present invention in a low-μ ATF, the final dynamic friction coefficient, which has a large effect on the shift shock, is reduced by the action of the low-μ ATF, and the shift feeling is improved.
Furthermore, the increase in the coefficient of static friction of the friction material increases the torque transmission capacity at the time of starting, which prevents the friction material from slipping.

As mentioned above, the wet friction material of the present invention has a low μ
In combination with ATF, the shift feeling is excellent.
It is also a highly durable friction material that does not slip, which can cause burnout.

[Example] Examples of the present invention will be shown below, but the present invention is not limited thereto.

Example 1 45% by weight of linter valve, 5% by weight of glass fiber, and 10% by weight of aramid fiber were submerged in water at a mouth water level of 480.
After beating to a volume of ~520 ml, 30% by weight of cashew dust and 10% by weight of diatomaceous earth are sequentially charged, dispersed, and fixed with sulfuric acid bands. After that, paper is made to the specified basis weight and thickness using a circular mesh paper making machine. . This paper-made base material is punched into specified links and 30% by weight
Dipping method: 28 parts by weight of modified phenol formaldehyde resin modified with tung oil [specific gravity = 0.983, viscosity (at 25°C) = 0.4 poise, gel time (at 165°C) = 98 seconds] for 100 parts by weight of the above paper-made base material. After drying, the material is heated and pressed at 170°C for 2 minutes and simultaneously adhered to a disk plate made of a metal plate to obtain a wet friction material.

Example 2 Modified phenol formaldehyde resin modified with 40 wt% tung oil instead of modified phenol formaldehyde resin modified with 30 wt% tung oil [specific gravity = 0.978, viscosity (at 25°C) = 1.1 poise, gel time (at 165°C) = A wet friction material was obtained in the same manner as in Example 1 except that 86 seconds] was used.

Example 3 Modified phenol formaldehyde resin modified with 50 wt% tung oil instead of modified phenol formaldehyde resin modified with 30 wt% tung oil [specific gravity = 0.972, viscosity (at 25°C) = 1.1 poise, gel time (at 165°C) = A wet friction material was obtained in the same manner as in Example 1 except that 99 seconds] was used.

Comparative Example Instead of the modified phenol formaldehyde resin modified with 30% by weight of tung oil, unmodified phenol formaldehyde resin [specific gravity = 1.072, viscosity (at 25°C) = 0.4 poise, gel time (at 165°C) =
A wet friction material was obtained in the same manner as in Example 1, except that 55 seconds] was used.

Next, the wet friction materials obtained in Examples 1 to 3 and Comparative Example were subjected to a 2000 cycle friction test using a SAENo.2 tester.

The test conditions were inertia: 2.5Kgcm sec ² , rotation speed: 3600rpm, and load: 332Kg.

ATF: Toyota Auto Fluid Type T Oil temperature: 120°C The relationship between the number of engagement cycles and the static friction coefficient obtained with the SAENo.2 tester is shown in Figure 1, and the relationship with the final dynamic friction coefficient is shown in Figure 2.

As shown in FIG. 1 and FIG. 2, the friction materials of Examples 1 to 3 according to the present invention maintain the same final dynamic friction coefficient (0.155 to 0.165) as the comparative example.
It can be seen that the static friction coefficient is increased by 0.010 to 0.023 compared to the comparative example.

[Brief explanation of the drawing]

1 and 2 show the test results of the friction materials of Examples 1 to 3 and Comparative Example, and FIG. 1 is a graph showing the number of engagement cycles and the coefficient of static friction. FIG. 2 shows the number of engagement cycles and the final dynamic friction coefficient.

Claims (1)

[Claims] 1. In a wet friction material comprising a fiber component, a thermosetting resin, and a friction modifier, the thermosetting resin is a modified phenol-formaldehyde resin obtained by reacting phenols, formaldehydes, and drying oil, and the modified phenol A wet friction material characterized in that the modified amount of drying oil is 15 to 55% by weight based on formaldehyde resin.