JP3904252B2 - Friction material manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a wet friction plate used for a clutch, a brake, and the like in a friction engagement device.
[0002]
[Prior art]
An example of the basic configuration of the wet friction engagement device is shown in FIG. 3. The drive plate 2 fitted to the spline part 51 of the hub 5 fitted to the input shaft 6 and the spline part 41 of the retainer 4 are fitted. Torque is transmitted by contact of the passive plates 1 to be joined. In the figure, 3 is a pressure plate and 7 is a pressing piston.
[0003]
4 is a perspective view of the passive plate and the drive plate, and FIG. 5 is a side sectional view of the combined state. The passive plate 1 includes a steel plate portion 11 and a spline projection 12, and the drive plate 2 includes a steel plate portion 21 and a spline projection 22. And a wet friction material 23 bonded to both sides of the steel plate portion 21.
[0004]
Due to current energy and environmental problems, the friction engagement device is small and light, has a high torque capacity, and at the same time, it has a small operating shock and no self-excited vibration such as judder. Is required. In addition, it is necessary to cope with high energy accompanying the high rotation and high output of the automobile engine, and the demand is extremely high. In the conventional friction engagement device, in order to reduce fuel consumption and operating shock, the continuous slipping state of the clutch during driving is expanded, the clutch efficiency is changed, and the engine is controlled and input when the clutch is engaged. Many advanced controls are being adopted, such as lowering the torque / clutch capacity ratio.
[0005]
Wet friction materials contain fiber base materials such as natural pulp fibers and organic synthetic fibers, and fillers such as diatomaceous earth and cashew resin, friction modifiers, and binders such as thermosetting resins. The binder formed an impregnated layer (a strong binder layer) having a high concentration on the surface layer and the back layer (that is, the surfaces on both sides). As an example of a binder, a thermosetting resin is generally a material constituting a wet friction material (composite fiber paper). Examples of this type of resin include phenol resin, epoxy resin, urea resin, melamine resin, and silicone resin. Applicable. In addition, a papermaking type is known as the above-mentioned wet friction material, and the friction material is made of natural pulp fiber, organic synthetic fiber, etc. as a fiber base material, mixed with a filler and a friction modifier, and made by papermaking. A friction material is manufactured by making paper, impregnating the raw paper with a diluted thermosetting resin solution, volatilizing the diluting solvent in the drying step, and then heat-curing the resin.
[0006]
The drying process from the impregnation of the binder will be further explained. First, the binder is diluted with an organic solvent when impregnated into the raw paper. After the raw paper is sufficiently impregnated with the diluted binder, the organic solvent is volatilized in the drying step. However, due to surface tension, an excess binder film and a layer with high binder concentration are formed on the extreme surface layer (about 100 μm) of the friction material surface due to surface tension, and the binder distribution in the thickness direction of the friction material is concentrated on the extreme surfaces of the surface layer and the back layer. It was inevitable that a high binder layer was formed. Here, the back surface or the back layer is not a friction surface but a surface to be bonded to a steel plate opposite to the friction surface.
[0007]
Thus, it has been found that the influence of the excessive binder film formed on the extreme surface layer of the friction material surface and the layer having a high binder concentration causes the following various problems due to the physical properties (surface tension) of the binder. Yes. (1) The binder film coated on the fiber substrate of the extreme surface layer in the initial state is hard, lacks flexibility, and forms microprotrusions. The contact with the sliding surface) forms the sliding surface only by the protruding portion of the binder. For this reason, the contact portion is small, and the friction coefficient between the binder and the passive plate is originally low, so that the initial friction coefficient is lowered.
[0008]
By repeatedly sliding, the binder wears, and the flexible fiber base material appears on the sliding surface. Therefore, the contact portion becomes large and smooth, and the fiber base material having a high friction coefficient is formed on the surface. By appearing, the friction coefficient increases. This is a factor of initial conformability indicating a change in the friction coefficient.
(2) Since the surface layer has many binders and lacks flexibility and smoothness, the contact with the passive plate becomes non-uniform, and the wedge effect of the oil film occurs microscopically, deteriorating the operating shock and judder properties. It is a factor.
[0009]
(3) The binder concentration in the surface layer is high, and this is a factor that easily causes plasticization of the friction material that occurs due to a rapid temperature rise. This conformability is regarded as a major quality problem because the initial torque capacity changes in a short time, particularly from the time of a new article.
[0010]
The problem with the product is that if the capacity of the clutch is designed with a low friction coefficient of the new friction material, the high torque capacity after familiarization due to the time-series change of the friction coefficient will cause the operating shock. It will be. High-priced luxury cars sometimes added extra learning functions to the control. Also, when the new product has a low coefficient of friction under severe driving conditions, the surface temperature rises due to frictional heat accompanying the extension of the sliding time, and the surface layer has a large amount of binder. The surface binder re-hardens or carbonizes due to frictional heat, causing the friction surface to become a mirror surface), which causes the occurrence of a fade phenomenon and a further decrease in the friction coefficient, resulting in a problem of heat durability. Become. As another event, the additive inside the lubricating oil decomposes and precipitates due to frictional heat and adheres to the friction material surface and the mating sliding surface, clogging the friction material surface, the original performance is not demonstrated, A similar decrease in the coefficient of friction may occur.
[0011]
These measures include increasing the operating push force and shortening the sliding time, but lowering the peel life due to repeated compression fatigue due to high surface pressure, and the friction surface of the other party due to an increase in the heat generation rate per unit time ( Many problems occur, such as heat spot generation in the passive plate), thermal deformation, an increase in the size of the hydraulic pump for generating high hydraulic pressure, and problems with durability such as leakage of hydraulic oil.
[0012]
In addition, when the amount of binder impregnation (concentration) is increased to improve the peel life of the friction material and the strength of the friction material is improved, the friction characteristics (operation shock, judder performance) deteriorate due to the lack of flexibility of the friction material. Lubricant deterioration due to the influence of the binder on the surface of the friction material, deterioration of the conformability that shows the change in coefficient of friction after engagement and after the engagement experience, and lubrication that adsorbs to the mating sliding surface due to the structure between the fibers on the surface being strengthened by the binder Many problems such as transfer of the additive to the friction material due to the removal of the oil additive and a reduction in the friction coefficient associated therewith have occurred. Many of these problems are caused by the excessive binder film and the binder-rich (high concentration) layer formed on the extreme surface layer of the friction material as described above at the time of a new article, causing various problems as described above. It is.
[0013]
As measures for these problems, the conventional method has been to slide for a certain period of time to reduce the surplus binder film on the surface of the friction material or to cut the surface of a new friction material (JP-A-5-99297) to remove the surplus binder film. In addition, the durability life is significantly reduced due to strength reduction due to fiber cutting or the like. Also, a method of smoothing the hot plate (Japanese Utility Model Publication No. 62-149629) to carbonize the friction material surface or forcibly smoothing the surface is employed, but the former is for reducing strength due to carbonization of the fiber. The service life will be reduced and the latter will be smooth, but it will not be connected with the removal of excess binder film, it will not be a drastic measure against the fade phenomenon and judder performance, and it will be free from the problem of increasing the product price. There wasn't. Therefore, as a method of preventing excess binder formed on the surface layer due to surface tension, two friction materials of the same material (different materials and thicknesses may be different) are overlapped, fully impregnated with diluted binder, and then dried. After the process, heat is applied while the two sheets are superposed in the curing process. After completion of the curing process, the two friction materials are pulled apart. When the friction materials are in close contact with each other, the surface tension does not move on the inner surface, so an excess binder layer cannot be formed as in the conventional surface. In addition, it is possible to obtain a friction material that prevents formation of a layer having a high binder concentration. Also, in the curing process, the closely contacted inner surface is more flexible than the surface directly subjected to heat, and flexibility is achieved by simultaneously forming and bonding the friction material with pressure and heating with a hot plate or the like. It is possible to obtain a friction material that promotes the smoothness of the surface with a good smooth surface.
[0014]
[Problems to be solved by the invention]
When impregnation and drying / curing are performed by superimposing two friction materials as described above, if they are not fixed, peeling or misalignment will occur due to floating, warping, etc. of the two-layer structure in the impregnation, drying and curing processes. A surplus binder film due to the surface tension of the binder and a layer with high binder concentration are formed, and in the curing process, it receives direct heat, so it loses flexibility and does not form a good smooth surface, achieving the desired action and effect I cannot escape the shortcoming of not being done.
[0015]
[Means for Solving the Problems]
In order to eliminate the above-mentioned drawbacks, the present invention provides a method for producing a friction material, characterized in that the edges of two friction materials that are overlapped are fixed by pressing with a compression press. By this fixing means, the friction material, which has a two-layer structure formed by superimposing two sheets, floats in the impregnation, drying, and curing processes, does not peel off due to warpage, etc., and does not cause deviation, achieving the intended function and effect. can do.
[0016]
【Example】
FIG. 1 shows that the friction materials 60A and 60B are fixed at the edge 67 by pressure bonding using a compression press. FIG. 2 shows a state during pressing, in which the edge 67 of the friction material 60A, 60B is pressure-bonded by the upper die 71 and the lower die 72 of the press.
[0017]
【The invention's effect】
The present invention is configured as described above, and the two-layer structure of the friction material that is superposed on the two sheets does not cause peeling or slippage due to floating or warping during the manufacturing process. The formation of a friction material and the production of a friction material having a good smoothness with a surface layer rich in flexibility is achieved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of fixing by pressure bonding.
FIG. 2 is a diagram showing a state during pressure bonding by a press.
FIG. 3 is a side sectional view of an example of a wet friction engagement device.
FIG. 4 is a perspective view of a passive plate and a drive plate.
FIG. 5 is a side sectional view showing a state in which a friction plate is assembled.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Passive plate 11 Steel plate part 12 Spline protrusion 2 Drive plate 21 Steel plate part 22 Spline protrusion 23 Friction material 3 Pressure plate 4 Retainer 41 Spline part 5 Hub 51 Spline part 6 Input shaft 7 Pressing piston 60A Friction material 60B Friction material 67 Crimp part 71 Press upper die 72 Press lower die

Claims (1)

Impregnation and drying of binders when manufacturing friction materials including fiber base materials such as natural pulp fibers and organic synthetic fibers, fillers such as diatomaceous earth and cashew resins, and binders such as friction modifiers and thermosetting resins In order to prevent excessive binder from adhering to the surface of the friction material during the curing process and to obtain a smooth and flexible friction material surface, the two friction materials are overlapped, In the manufacturing method of the friction material which was made to separate after performing the steps of impregnation, drying and curing,
In the process of impregnating, drying and curing the binder, the edges of the two superimposed friction materials are pressed and fixed with a compression press so that the two superimposed friction materials do not peel off or shift. A method for manufacturing a friction material.

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