JPH0221458B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dry clutch facing (hereinafter simply referred to as a friction material) for use in a vehicle. Conventionally, this type of friction material has been manufactured using asbestos fiber as a base material through various predetermined processes. However, since this friction material is based on asbestos, which is harmful to the human body, it has the disadvantage of deteriorating the working environment and having an adverse effect on the human body of the worker.
Therefore, in recent years, the development of asbestos-free friction materials has begun to be actively promoted in this industry, and several types of friction materials have been provided. A typical example is a friction material based on steel fibers, but steel generally has a high specific gravity,
This has the drawback that it increases the weight of the friction material and, as a result, it is not possible to obtain the required moment of inertia. or,
It also has the disadvantage of causing rust and sticking to the mating material, impairing the functions of clutches, etc. On the other hand, natural organic fibers and general organic synthetic fibers, which do not have the drawbacks of steel fibers, have been investigated as friction material base materials to replace asbestos fibers, but they both have low heat resistance and low strength. However, it was not possible to provide a good friction material. In addition, highly heat-resistant glass fibers, phenol fibers, carbon fibers, etc. have been provided as friction material base materials, but the surfaces of these fibers are uneven and have poor adhesion with binders, making it impossible to obtain the desired strength. . Therefore, the present inventors have provided a friction material that eliminates all of the above-mentioned drawbacks by subjecting the glass fibers, phenol fibers, and carbon fibers to bulk processing and using these fibers as the base material of the friction material. did. However, although this type of friction material is a practically useful friction material, it has some drawbacks in its judder properties and also in that it sometimes causes poor clutch disengagement. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a friction material which is extremely useful in practical use and has excellent jerk characteristics and does not cause poor clutch disengagement. First, in order to improve the jamder characteristics and poor clutch disengagement, we will first try to find out the causes of these defects. First, the phenomenon of poor disengagement occurs when the clutch pedal is depressed to remove the load on the pressure plate, but negative pressure is generated on the friction surface between the flywheel and the clutch disk, causing the clutch disk to rotate with the flywheel and the clutch not disengaging. . That is, a phenomenon occurs in which the shift cannot be performed. Therefore, a disk spring is usually disposed in the center of the clutch disk, and this spring biases the clutch disk toward the pressure plate to cope with the negative pressure. This biasing force works well on the outer circumferential surface of the clutch disk and is difficult to act on the inner circumferential surface. However, at this time, if the hardness of the clutch disc is low, poor cutting will inevitably occur.
If the hardness is high, jitter is likely to occur, and it is technically difficult to satisfy both. Therefore, the inventors of the present invention increased the hardness of only the inner circumferential surface of the friction material, that is, increased the rigidity to improve the cutting defects on the inner circumferential surface where the disc spring does not work properly, and by keeping the hardness of the outer circumferential surface low, the clutch disengagement defects and We have now completed a friction material that satisfies both of the jamder properties. Next, a method for manufacturing this friction material will be described. A semi-finished product wound into a loop shape using the well-known semi-molding method or spiral woven method is placed in a mold shown in the first figure and subjected to pressure and heat molding. Thereafter, a friction material is obtained by subjecting it to heat treatment, finishing processing, etc. according to conventional methods. The semi-finished product obtained by this pressurized and heated molding has a shape as shown in the second figure. As is clear from the figure, the inner peripheral side b of the friction material is molded with a higher surface pressure than the outer peripheral side _l1 , so that it is molded with high hardness. Dimensions a and b shown in the second figure are important factors for improving the jamder characteristics and clutch disengagement defects, so dimension a should be 10% or less of the thickness t of the molded product.
That is, a/t=0.1 or less. Also, b should be 35% or less of the width 1 of the molded product, that is, b/l = 0.35 or less. A semi-finished product wound into a loop with approximately average thickness is molded into a convex shape as shown in the mold 2 shown in the first diagram, and only the inner circumferential side 3 of the semi-finished product is placed on the outer circumference of the friction material by a dimension a on one side. Compared to this, it is made smaller in size,
These two convex-shaped protrusions should be determined in consideration of the molding dimensions. The molding conditions of the compression molding machine used during this pressurization and heating are well-known conditions and there are no particular restrictions, but the molding temperature is 160-170℃, the surface pressure is 90-110℃
Kg/cm ^2nd place is preferred. Next, as shown in the first figure, the molded product that has been pressurized and heated has a dimension of A on one side and a step on the outer circumference, but in order to obtain a friction material, at least one side of the outer circumference should be A.
The thickness of the friction material must be made uniform by sanding the dimensions. Next, the fiber group serving as the base material of this invention refers to a fiber group having heat resistance at 300°C, and specifically includes glass fiber, phenol fiber, carbon fiber, etc. The term heat resistance means that the fiber is stable to heat at 300°C without any loss of fiber or shrinkage phenomenon. Further, the single fibers of the above fiber group are preferably 12 μm or less, and when used, it is most preferable to bundle several hundred of these single fibers, perform necessary fiber processing such as a strand, and then process the fibers to make them bulky. (Example) After converging E-glass single fibers having a fiber size of 6 μm and processing various fibers such as strands, the fibers were subjected to bulk processing. After impregnating this fiber with a phenolic resin solution prepared with methanol at a fixed content of 15%, it was dried at 120°C for about 1 hour until the methanol was sufficiently volatilized. Zinc white and
Carbon black, calcium carbonate, barium sulfate, diatomaceous earth, and copper powder are kneaded with a rubber roller, and the rubber content is dissolved in toluene, and the viscosity is adjusted to 10,000-20,000 C.PS.The mixture is impregnated into a coating tank, and the rubber is impregnated. coat. At the same time, a brass wire is wound around the fiber. After that, it was thoroughly air-dried and wound into a loop using a winder, and then heated at 165℃ and 100℃.
Pressure and heat mold for 3 minutes using a compression molding machine set at kg/cm ² . At this time, remove the glass several times at first. The obtained molded product has t=4.7mm as shown in the second diagram.
a=0.5mm. This molded product is heated to 150℃ in a heating furnace.
The material was heated continuously for 6 hours at 200°C, 3 hours at 250°C, and 3 hours at 250°C, and both the front and back of the friction surface were polished to obtain a friction material with a uniform thickness (t) of 3.5 mm. (Comparative example) In the pressure and heating process, the friction material was pressurized and heated to a uniform thickness of 3.7 mm, and both sides of the friction surface of this molded product were polished to obtain a friction material with a uniform thickness of 3.5 mm. A friction material was obtained in the same manner as in the example. As described above, the hardness of the outer circumferential side, central part, and inner circumferential side of the friction materials obtained in the Examples and Comparative Examples and the drag torque (T _L ) at low surface pressure were measured. The results are shown in Table 1 below.

[Table] What is the above drag torque? The clutch disk is rotated by a motor and pressed against a fixed flywheel with a low load (2 kg), and the drag torque at that time is measured. The larger this torque is, the more likely cutting defects will occur. As is clear from Table 1 above, the product of the present invention (Example) has less torque and has significantly improved cutting defects compared to the conventional product (Comparative example).
Further, since the friction material has a high hardness only on the inner circumferential side, a friction material with significantly improved jadder characteristics is provided. In addition, in actual vehicle tests, the product of the present invention had excellent jerk characteristics, no clutch disengagement problems, and good friction characteristics.

[Brief explanation of drawings]

The first illustration is a partial sectional view of a mold, and the second illustration is a partial sectional view of a friction material showing an embodiment of the present invention.

Claims (1)

[Claims] 1. Using at least one or two or more types of fibers selected from the group consisting of glass fibers, phenolic fibers, and carbon fibers that have been subjected to bulk processing as a base material, this is impregnated with a phenolic resin liquid, dried, and further made into rubber. 1. A ring-shaped dry clutch facing obtained by coating a dry clutch facing with a binder, characterized in that the hardness of the inner circumferential side of the dry clutch facing is higher than the hardness of the outer circumferential side.