JPH0332441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cork friction material that significantly improves wear resistance and increases the amount of oil impregnated without substantially impairing the frictional properties of cork.

Conventionally, particles obtained by crushing cork, which has the excellent properties of natural products, especially its excellent coefficient of friction, have been compressed and bonded via adhesive to make friction plates, which have been used for clutches in industrial sewing machines, etc., and clutch facings for motors. It was widely used in brake shoes, etc. However, cork has low physical strength, and has disadvantages such as making noise when the clutch or brake is activated, producing a strange odor due to frictional heat, and shortening the life of the clutch due to abnormal wear caused by the clutch being partially engaged.

To solve this problem, cork particles are integrally molded with an adhesive, and the intergranular spaces of the cork friction material are impregnated with oil to improve wear resistance. Because cork particles were compressed and bonded using adhesives such as phenolic resin, urea resin, and vinyl acetate resin,
There are very few voids between cork particles and the adhesive,
Even if this is impregnated with oil by vacuum or pressure impregnation at room temperature or heating, the amount of oil impregnated is 10%.
% or less, the desired improvement in wear resistance cannot be obtained much, and most of the oil impregnation is concentrated on the surface of the friction material, and during long-term use, the oil on the surface is removed and only a small amount of oil remains. However, there was a drawback that the wear resistance was significantly reduced.

For this reason, as a method to increase the amount of oil impregnated, cork particles and oil are mixed and stirred in advance to make the oil adhere to the cork particles, and then a phenolic adhesive etc. is mixed in, stirred, and then placed in a mold and fixed. A method was devised to obtain a cork friction material in one piece. However, although the amount of oil impregnated in this material is certainly higher than that of the cork friction material mentioned above, the adhesive force is significantly reduced because the oil that prevents the adhesive from adhering is attached to the entire outer surface of the cork particles. Under harsh conditions such as clutch facing and brake shoeing, where strong forces are applied, the cork friction material is destroyed, and stirring the cork particles, oil, and adhesive takes time and makes it difficult to mix uniformly. However, there were other drawbacks such as problems with strength.

The present invention eliminates these drawbacks and provides a cork friction material that is easy to work with, has a large amount of oil impregnated, and has oil impregnated not only on the surface but also in the center.

The present invention relates to a cork friction material obtained by integrally molding cork particles having an appropriate size, substantially 10 to 80 mesh, with an adhesive, and in which oil (including but not limited to vegetable oil or mineral oil) is added. This cork friction material is impregnated with oil, and is characterized by adding a foaming agent to the adhesive and foaming it to form fine voids in the adhesive, and then impregnating the fine voids with oil. In the present invention, since voids are provided in the adhesive of the cork friction material, when the cork friction material is immersed in an oil bath or impregnated with vacuum or pressure, a large amount of oil will be absorbed into the fine gaps provided in the cork or adhesive. Cork friction impregnated with oil at a weight ratio of 25 to 30% of the cork particles is suitable for use in clutch facings, brake shoes, etc. The material can be easily obtained.

In addition, the amount of oil impregnated is suitably 15 to 50% by weight depending on the purpose and application of the cork friction material, and the optimal weight ratio is 25 to 30%, but according to the present invention, the amount of foaming can be controlled. This value can be easily obtained by doing this.

In addition, if the cork friction material is affixed to the metal substrate of clutches, brakes, etc. in advance and then impregnated with oil, it can be used as a clutch facing that has adhesive strength between the cork and the metal substrate and has excellent friction properties. It is also possible to easily obtain a brake shoe.

Furthermore, since the cork friction material of the present invention gives priority to the bonding between the cork and the adhesive, even if it is impregnated with oil, the adhesive strength will not be impaired in the slightest.

Next, the present invention will be explained with reference to Examples.

Use cork particles with a size of about 30 to 70 mesh, add an adhesive containing a foaming agent to this, stir for 5 to 10 minutes, then put the desired amount into a mold and heat compression. After the adhesive is foamed and cured, it is removed from the mold to obtain a cork friction material in the desired shape. This creates a large number of fine voids in the adhesive, resulting in a structure that allows it to be easily impregnated with oil.

The obtained cork friction material was heated under 3 mmHg for 1 hour.
By vacuum impregnating turbine oil #200, a cork friction material with a weight ratio of oil to cork particles of 32.4% by weight was obtained, and the material was impregnated with turbine oil #200 for 2 hours under 3 mmHg.
By vacuum impregnation, a cork friction material with a weight ratio of oil to cork particles of 39.2% by weight was obtained.

Therefore, the amount of foaming of the adhesive and the time of vacuum impregnation,
Adjust the pressure to adjust the oil impregnation amount to 0%, 5%, 15
%, 20%, 25%, 30%, 45%, and 60% cork friction materials were made, and the friction coefficient and amount of friction were measured, and good values were obtained as shown in the graphs in Tables 1 and 2. I got it.

Note that if the amount of oil impregnated is 65% or more, it cannot be retained in the voids of the adhesive and the oil will flow out, so it is practically impossible to manufacture.

Looking at the friction coefficient in Table 1, the decrease in the coefficient due to oil is very small, without impairing the friction characteristics, and in Table 2
As shown in the figure, the amount of wear due to the addition of oil is significantly reduced compared to the one with 15% impregnation, and its effect is clearly visible.

As described above, according to the present invention, the action of the oil impregnated into the fine pores of the adhesive significantly improves the wear characteristics without impairing the coefficient of friction, making it possible to maintain a long service life of the cork friction material. Not only that, but the distribution of oil is almost uniform, so even cork friction material obtained by machining by cutting from a block can have the same effect or excellent cork friction that cannot be obtained with conventional methods. It is a material.

Claims (1)

[Claims] 1. In a cork friction material made by integrally molding cork particles via an adhesive, a foaming agent is added to the adhesive to cause it to foam, fine voids are provided in the adhesive, and oil is filled into the fine voids. A cork friction material that is impregnated with oil and has an oil content of 15 to 50% by weight relative to the cork.