JPH0467051B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a friction material for a clutch, particularly a wet friction material suitable for use in an oil solution. [Conventional technology] For example, in automobiles, construction machinery, agricultural machinery, motorboats, etc., clutches that transmit drive from the prime mover to transmissions transmit sufficient power at all times, but when starting, they provide appropriate slippage and A function is required to cut off the power when changing gears of a transmission. Friction type clutches are widely used as clutches that satisfy this function. Friction type clutches include dry type clutches that are used in dry conditions and wet type clutches that are used in oily liquid. The latter wet clutch is often used in the form of a multi-disc clutch as a component in planetary gear type automatic transmissions. Friction type clutches generate frictional heat, so
In order for the above-mentioned functions to be stably performed, heat must be efficiently released from the frictional parts. In wet clutches, oil plays an important role as a heat transport medium. The heat generated on the friction surface is diffused and released throughout the system using oil as a medium. Therefore, if the amount of oil held in the friction material itself and the amount of oil flowing in and out are small, it will overheat, causing thermal deterioration of the friction material and oxidation and decomposition of the oil.
Its function as a friction material deteriorates. Wet friction materials are organic fibers such as cellulose,
A paper base material made by wet papermaking of inorganic fibers such as asbestos, inorganic fillers, and friction modifiers such as cashew dust is impregnated with a thermosetting resin such as phenol resin or melamine resin. It is thought that oil is retained and circulated in the pores of this paper base material. A conventional friction material is disclosed in, for example, Japanese Patent Laid-Open No. 60-23774. [Problems to be solved by the invention] In conventional wet friction materials, research has focused on the type and composition ratio of raw materials, and research on pores (areas where oil is retained) has not necessarily been conducted. It wasn't done enough. Because no particular consideration is given to the fiber diameters of various fibers, inorganic fillers, and particle sizes of friction modifiers, the structure of the paper base material from which paper is made tends to aggregate, while the individual pores tend to become larger. It was hot. If the structure of the paper base material is aggregated, friction materials impregnated with thermosetting resin will not circulate or retain oil in the aggregated areas, resulting in insufficient cooling and poor heat resistance. I get used to it. In addition, asbestos, which was once thought to be an excellent raw material for friction materials and was frequently used, has been found to be harmful to health, making it difficult to use, and the range of raw materials to choose from has narrowed. It is worshiped. Therefore, a friction material that has sufficient performance and is not harmful to health has not been obtained. The present invention has been made in view of these points, and it is an object of the present invention to provide a friction material that is excellent in heat resistance and friction performance and does not contain harmful substances at a low cost. [Means for solving the problem] The present inventors focused on the fact that the performance of wet friction materials is influenced by the retention and circulation of oil in the pores, and as a result of continuing research, The present invention has now been completed. In other words, the wet friction material of the present invention is made by impregnating a paper base material with a thermosetting resin into a paper base material made by wet papermaking of fibers, fibrid fibers, inorganic fibers, an inorganic filler, and a friction modifier that constitute at least the skeleton of the base material. with a porosity of 40 to 75%, and
The amount of pores is 70% or more due to pores of 5 μm or less. The fibers constituting the skeleton of the base material may be, for example, pulp, aromatic polyamide fibers, or kynol fibers (novoloid fibers). Thickness is 5~30μ
m, preferably 15 μm or less. The appropriate blending ratio is 5 to 30% by weight in the paper base material. Fibrillated fibers include, for example, cellulose fibers,
It is a fiber made by micronizing aramid pulp or the like to a thickness of 0.2 to 2 μm, and has the property of being fibrillated by wet papermaking. In particular, MFC (microfibrous cellulose), which is made from cellulose fibers, is easily fibrillated. The appropriate blending ratio is 10 to 50% by weight in the paper base material. Examples of inorganic fibers that can be used include glass fibers, potassium titanate fibers, rock wool, ceramic fibers, and metal fibers, but asbestos is unsuitable from the health standpoint as described above. The fiber diameter is
The thickness is preferably 0.1 to 10 μm, preferably 5 μm or less. The appropriate blending ratio is 10 to 50% by weight in the paper base material. Examples of inorganic fillers include diatomaceous earth, alumina powder,
These are barium sulfate, calcium carbonate, and silica.
The particle size is preferably 0.5 to 10 μm, preferably 3 μm or less. The appropriate blending ratio is 5 to 50% by weight in the paper base material.
It is. Examples of friction modifiers include graphite and cashew dust. The particle size is preferably 10 to 50 μm. A suitable blending ratio is 0 to 30% by weight in the paper base material. The above raw materials are mixed and dispersed in water, and paper is made into the desired paper weight (basis weight, g/m ² ) and thickness using, for example, a circular wire paper making machine or a fourdrinier paper making machine. A paper base material with a porosity of 60 to 90% is obtained. A thermosetting resin such as a phenolic resin, a melamine resin, an epoxy resin, etc. is impregnated in a weight ratio of 20 to 40% with respect to 100% of this paper base material, and the paper material is thermally cured. This is cut into a predetermined shape and then glued to the core metal. At this time, the finished product has a porosity of 40-75%, preferably 50-75%.
The paper is compression molded so that it is 65%. When each raw material limited above is used, the pore size is slightly large at the paper base stage, but the finished product is impregnated with thermosetting resin and compression molded.
This is a friction material in which more than 70% of the pores are pores of 5 μm or less. [Function] As shown in the pore distribution graph of FIG. 1, the wet friction material of the present invention has more pores with smaller diameters than the conventional wet friction material. The function of each of the above raw materials,
In particular, the pores become minute and dispersed due to the action of fibrid fibers. If the porosity is less than 40%, oil retention and circulation will be insufficient, and if the porosity is 75%, the mechanical strength of the friction material itself will be insufficient. In contrast, the friction material of the present invention has a porosity of 40 to 75%.
Moreover, the amount of pores is 70% due to pores of 5 μm or less.
Predict the above. Therefore, oil is retained and circulated in the pores, improving cooling performance and providing excellent heat resistance and friction performance. Furthermore, sufficient heat resistance and friction performance can be obtained even without containing harmful substances such as asbestos. [Examples] Examples of the present invention will be described in detail below. Each raw material shown in Table 1 (formulation table) below is weighed, mixed and dispersed in water, and paper is made to a predetermined basis weight and thickness using a circular mesh paper making machine to obtain a paper base material. This paper base material is impregnated with a phenolic resin by spraying in the weight ratio shown in the formulation table, and then heated and cured. A wet friction material is manufactured by the above process. Note that numerals 1 to 5 (examples) are examples of wet friction materials to which the present invention is applied, and 6 to 8 (comparative examples) are examples to which the present invention is not applied.

[Table] The porosity and pore diameter distribution of each wet friction material were measured using a porosimeter (porosity measuring meter manufactured by Shimadzu Corporation). The pore size distribution is measured by applying pressure to a sample (friction material) and filling it with viscous fluid. At the beginning of pressurization, large pores are filled, but as the pressure increases, smaller pores are filled, so the relationship between pressure and filling amount can be measured.
That is, since the filling amount is filled starting with the pores having a larger diameter as the pressure changes, by differentiating the relationship between the pressure and the filling amount, the pore diameter and the pore amount at that pore diameter can be determined. The results are shown in FIG. The curve ~ shows the pore size distribution of the friction materials of Examples 1 to 5, ~
shows the pore size distribution of the friction materials of Comparative Examples 6 to 8.
The friction materials of Examples 1 to 5 had a pore diameter distribution center of 3
~4 μm, and there are more pores with smaller diameters than in the friction materials of Comparative Examples 6 to 8 (the center of pore diameter distribution is about 10 μm). Examples 1 to 3 are 5μ
90% of the pores are 5 μm or less, and in Examples 4 and 5, 80% of the pores are 5 μm or less. Also, Comparative Example 6,
Sample No. 7 has 30% of pores of 5 μm or less, and Comparative Example 8 also has 25% of pores of 5 μm or less. In addition, the porosity of each example is 55 to 60%. Also, the friction coefficient (μd) for each wet friction material
and measure heat resistance. The test piece used was one in which the wet friction material of each of the above examples was cut into a predetermined size, and a metal center plate was sandwiched and pasted. To measure the friction coefficient, a load is applied to the friction material rotating inertia using an SAE #2 friction tester, and the friction coefficient is calculated from the torque. Measurement conditions Number of friction surfaces: 4, inertia: 2.5Kg・cm・
sec ² , rotation speed: 3600 rpm, load: 7.2 Kg/cm ² , in oil, oil temperature: 120°C. The results of measuring the friction coefficient for each example are shown in Figure 3. The friction coefficient (μd) shown in the same figure is 100 to 2000.
The friction coefficient is approximately stable during this cycle. The friction materials of Examples 1 to 5 and the friction materials of Comparative Examples 7 to 8 have approximately the same coefficient of friction. Measurement of heat resistance is the same as measurement of friction coefficient.
Measured using SAE #2 friction tester. Measurement conditions Number of friction surfaces: 6, inertia: 2.0Kg・cm・
sec ² , rotation speed: 3000 to 5200 rpm, load: adjusted so that the braking time is 1 sec, oil fluid: flow rate 1.0 cc/cm ² mm shaft blowout (q _s = 10 to 30 cal/cm ² ), oil temperature: The measurement results of 120°C heat resistance are shown in Table 2 below.
Heat resistance is evaluated as good until the coefficient of friction (μd) drops by 10% from the initial stable state or when peeling occurs.

〔Effect of the invention〕

As explained above, the wet friction material of the present invention has improved cooling properties, and is excellent in heat resistance and friction performance.
Even when used in conventional areas, thermal durability is improved without changing the friction coefficient level. Furthermore, it is safe because it can provide sufficient heat resistance and friction performance even without containing harmful substances such as asbestos.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are diagrams explaining the porosity distribution, and FIG. 3 is a diagram showing the results of measurement of the friction coefficient. 1-5...Examples of the present invention, 6-8...Comparative examples.

Claims (1)

[Claims] 1 A paper base material made by wet papermaking of fibers, fibrid fibers, inorganic fibers, an inorganic filler, and a friction modifier that constitute at least the skeleton of the base material is impregnated with a thermosetting resin, and has a porosity of 40 to 40. A wet friction material characterized in that the amount of pores with a pore diameter of 5 μm or less accounts for 70% or more of the total pore amount.