JPH08233003A - Wet friction plate - Google Patents

Abstract

PURPOSE: To maintain a high friction coefficient without impairing a cooling effect in a wet friction plate, which is used while a cooling fluid is supplied to the friction surface, by forming a plurality of grooves on the friction surface at a prescribed interval. CONSTITUTION: A friction plate 1 is used while it is maintained in a wet condition by the oil such as a fluid for an automatic transmission. Fine grains are sticked to the surfaces (both front and reverse sides) of a base plate 2 of the friction plate 1 through an adhesive means such as plating or brazing, so that a friction layer 3 is formed by these fine grains. Multiple stripes of oil grooves 4, which open at the front side of the friction layer 3, are formed on the friction layer 3. The pitch of these oil grooves 4 is less than 1.2mm. In addition, the width of these oil grooves is made narrower than that of a part of the friction layer 3, which is held between the oil grooves 4. With this, excessive oil, which forms a film in a sliding condition, can be eliminated by the oil grooves 4, and it can be restricted or prevented that the oil is drawn out of the oil grooves 3 to form a film on the friction surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet friction plate which is used while being kept wet by a fluid such as transmission oil.

[0002]

2. Description of the Related Art Friction plates used in brakes and clutches inevitably slip during the transitional period of engagement and disengagement, so it is necessary to prevent temperature rise and deterioration due to frictional heat. Conventionally, a wet friction plate is known which is used in a state where a fluid such as lubricating oil is supplied to the friction surface. Various materials for the friction plate have been developed according to the conditions under which they are used.For example, as a friction plate for a wet friction engagement device in a vehicle of a passenger car or less, heat is obtained by impregnating cellulose with resin. A molded product or a product obtained by mixing a resin with metal fiber or asbestos and thermoforming is used. Also, when the usage conditions are more severe, sintered metallic and cermet are used.

In these wet type friction plates, it is necessary to supply a lubricating oil for cooling, but if the lubricating oil stays on the friction surface, the cooling effect will be small and the friction coefficient will be reduced. There is also. Therefore, conventionally, an oil groove is formed on the friction surface in order to enable continuous supply of the lubricating oil to the friction surface, and an example thereof is described in Japanese Utility Model Laid-Open No. 1-135236. There is. In the friction plate described in this publication, a friction surface is formed by paper, and a grid-shaped oil groove that is not covered by the paper is formed on the friction surface. Further, the grid grooves on both front and back sides are connected by through holes. ing.

[0004]

If the oil groove is formed to promote the supply of the lubricating oil to the friction surface as much as possible, the cooling effect is improved, and the structure described in the above publication is used. If so, the drag torque can be reduced, and the purpose of forming the oil groove can be achieved. However, depending on the shape and size of the oil groove, the supply of lubricating oil to the friction surface becomes excessive, which causes a reduction in the coefficient of friction, but no attention has been paid to this point in the past, and there is no mention in the above publication. Not not.

In the friction plate as described in the above publication, in which a fiber material such as paper, cellulose or asbestos is impregnated with resin, the lubricating oil penetrates into the friction material and the friction plate itself is engaged. Even if the lubricating oil is supplied excessively to some extent, it has little effect on the reduction of the friction coefficient because the compression deformation is caused by the pressure of time. However, in a friction plate made of a hard material such as sintered metallic or cermet, if an oil film is formed on the friction surface, the oil film cannot be eliminated during frictional contact with the mating material,
This causes the friction coefficient to decrease significantly.

In a friction plate made of a sintered material, a large number of complicated holes are formed on the friction surface, and lubricating oil may enter there, but the holes do not necessarily communicate with other holes. It does not always exist, and if it is a closed hole, the lubricating oil does not enter beyond a certain level, so it does not function to eliminate the oil film. In addition, the area of the flat surface formed between the holes may be excessively large in some areas, so it is difficult to prevent the formation of an oil film in those areas.

In any case, if there is a groove for supplying a fluid for cooling, there is a possibility that the supply of the fluid becomes excessive and the coefficient of sliding friction may be reduced. No means have been developed for the recognition and resolution of social problems. In particular, regarding a friction plate made of a metal, no means has hitherto been known for achieving both cooling and maintaining the friction coefficient.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a wet friction plate capable of maintaining a high friction coefficient without impairing the cooling effect.

[0009]

In order to achieve the above-mentioned object, the present invention is a wet type friction plate which is used in a state where a cooling fluid is supplied to the friction surface.
A plurality of grooves are formed at intervals of mm or less.

[0010]

The friction plate of the present invention is used in a state where the cooling fluid is supplied to the friction surface, and the fluid is supplied and discharged through the groove, so that the cooling can be performed sufficiently and sufficiently. When the friction plate is pressed against the mating material, the gap between the grooves is narrow, so that excess fluid that causes a liquid film is removed into the grooves. As a result, it is possible to prevent the fluid from forming a film on the friction surface and lowering the friction coefficient, and the friction coefficient in the slipping state can be maintained at a high value.

[0011]

EXAMPLES The present invention will now be described in detail based on examples. The friction plate of the present invention is a friction plate that is used while being kept in a wet state by oil (fluid) such as fluid for an automatic transmission. For example, a friction surface is formed on the surface of a disk-shaped substrate, A large number of oil grooves for circulating oil are formed on the friction surface.

FIGS. 1 and 2 show a part of the friction plate 1, in which a friction layer 3 has a predetermined thickness on the surface (both front and back sides) of a substrate 2 which is a metal plate such as a thin steel plate or an aluminum alloy plate. Has been formed. The friction layer 3 is formed with a large number of oil grooves 4 open to the surface side thereof, and the interval p between them is
It is 1.2 mm or less. The width of the oil grooves 4 is set to be narrower than the width of the friction layer 3 in the portion sandwiched by the oil grooves 4. Specifically, the interval p is 1.
In the case of 2 mm, the width is set to 0.3 mm, when the interval p is 140 μm, the width is set to 6 μm, and in other cases, the width is set to be proportional to the interval p.

The structure of the friction layer 3 which can be used in the present invention will now be described. In FIG. 3, the fine particles 5 are adhered to the surface of the substrate 2 by an adhesive means 6 such as plating or brazing. The friction layer 3 is formed by. A plane defined by connecting the outermost surface portions of the fine particles 5 is a friction surface, and the fine particles 5 are attached to the substrate 2 so that the friction surface thus determined is flat.

The fine particles 5 are made of a metal such as bronze, and the shape of these particles is the outer diameter D1.
Is approximately spherical with a diameter of 30 to 300 μm. These fine particles 5 have a protrusion height h from the adhesion means 6 of 20 to
Since the particles are randomly arranged so as to have a size of about 150 μm, there are particles that are in contact with each other and particles that are separated from each other. Even if the adjacent fine particles 5 are in contact with each other, they are spherical. Therefore, a minute recess 7 is formed between them. The entire recesses 7 communicate with each other to form an oil escape portion.

FIG. 4 shows an example in which the outer surface portion of the fine particles 5 forming the friction surface as described above is polished (ground) to bring the surface roughness Rz of the friction surface within the allowable value.

FIG. 5 shows an example in which cylindrical or prismatic fine particles 5a having an outer diameter D2 or a thickness of about 30 to 300 μm are used as the fine particles. The fine particles 5a are also made of a metal such as bronze as described above, and the tips (top surfaces) thereof are arranged with the heights h so as to form a flat surface as a whole, or It is polished and ground. Further, these fine particles 5a are separated from each other at a substantially constant interval, and as a result, a recess 7 is formed between the respective fine particles 5a, which communicates with each other and functions as an escape portion for oil.

FIG. 6 shows fine particles 5 and 5 having the same shape as described above.
Instead of a, square block-shaped fine particles 5b having a square cross section are dispersed and attached to the surface of the substrate 2 by a predetermined adhesion means 6, and the protruding ends of the fine particles 5b are polished / ground to obtain a flat surface as a whole. It is finished on the surface. Since the fine particles 5b are not oriented in the same direction, the recesses 7 are formed between the respective fine particles 5b, which are in communication with each other and serve as oil escape portions. Further, since the positions and amounts of the fine particles 5b that have been polished and ground are different, the areas of the top surfaces formed by the fine particles 5b are different from each other, but the size of each fine particle 5b is, for example, about 30 to 300 μm. Therefore, the difference in the area of the top surface is not particularly large in practical use.

Further, in the examples shown in FIGS. 7 and 8, a large number of minute projections 5c are formed at regular intervals by engraving the grid-like grooves 7a in the friction layer 3. In this case, a friction material such as a bronze plate may be attached to the substrate 2 to form the lattice grooves 7a in the friction material, or the substrate 2 may be formed of a predetermined friction material and the lattice grooves 7a may be directly formed on the surface thereof. You may form.

These minute projections 5c are, for example, 80
It has a square shape of about μm × 80 μm, and the width of the grating groove 7b is, for example, about 60 μm. When the minute projections 5c and the lattice grooves 7a are formed in such a small size, the oil groove 4 can be formed so as to overlap these lattice grooves 7a. Further, the lattice groove 7a can be formed so as to also serve as the oil groove 4, and in that case, the minute projections 5 are formed.
By forming c into a rectangular shape having a size of about 800 μm × 800 μm and making the grid groove 7a have a width of about 400 μm, an oil groove having a pitch of 1.2 mm or less can be obtained.
The lattice grooves 7a can be formed by etching or cutting, for example.

In a friction plate using a metal as a base material, if the area of a continuous flat surface on the friction surface is large, an oil film is likely to be formed and the friction coefficient may become unstable accordingly. Although the friction surface is formed by the fine particles 5, 5a, 5b or the minute projections 5c on the above, it is possible to reduce the continuous flat surface at the time of frictional contact by using the grooves 5a, 5b or the minute projections 5c. It can also depend on the shape. FIG. 9 shows an example of the linear oil groove 4 formed on the friction plate 1 and the linear oil groove 4 on the mating member 1a along the direction intersecting the oil groove 4 at the time of frictional contact. The groove 4a is formed. Therefore, the unit plane that makes frictional contact becomes a surface surrounded by these oil grooves 4 and 4a. Therefore, by reducing the interval (pitch) between the oil grooves 4 and 4a, the area of the unit plane becomes a minute area. be able to.

Now, the test conducted for confirming the effect of the present invention will be described. FIG. 10 shows a schematic configuration of the test apparatus used, in which a spindle 11 is arranged above the rotary table 10, and a test piece 12 is attached to the tip (lower end) of the spindle 11. Shaft portion 13 is formed. Its shaft 1
An oil supply hole 14 is formed in the spindle 11 so as to open at the tip of the spindle 3. On the other hand, on the upper surface of the turntable 10, a mating material (for example, a metal plate such as a stainless plate) is provided.
15 is attached to the rotary table 10,
It is arranged inside the oil bath 16.

The test piece 12 is shown in FIGS. 11 and 12.
As shown in FIG. 3, a long hole 17 for inserting a bolt for transmitting torque is formed at an intermediate portion in the axial direction of the cylinder, and four grooves 18 along the radial direction are formed at the tip surface. , Are formed at regular intervals. The test piece 12 includes an elastic body 1 such as urethane rubber on the shaft portion 13.
After the 9 and the spacer 20 are fitted, the bolt 21 fitted to the tip side of the shaft portion 13 and attached to the shaft portion 13 in the radial direction penetrates the elongated hole 17. Then, in the friction test, while rotating the rotary table 10, the spindle 11 is pushed down by an actuator such as an air cylinder (not shown) to press the test piece 12 against the mating member 15, and further the lubricating oil (for example, an automatic transmission) is supplied from the oil supply hole 14. Supply oil).

FIGS. 13 and 14 show the test results obtained by the above-described test apparatus. The test piece 12 used here is made of bronze, and its friction surface has a grid groove 7a.
7 and FIG. 8 in which a large number of minute protrusions 5c are formed by forming The surface roughness Rz
Is adjusted to 5 μm. FIG. 13 shows the relationship between the pitch p of the grating groove 7a and the friction coefficient and the relationship between the relative sliding speed and the friction coefficient. When there is no relative sliding, that is, when the sliding speed is 0 m / sec, the grating groove is The coefficient of friction was almost constant regardless of the pitch p of 7a and the presence or absence of the grating groove 7a. On the other hand, when relative slippage occurs, the friction coefficient decreases as the pitch p of the lattice grooves 7a increases and the lattice groove 7a does not exist regardless of whether the sliding speed is 1 m / sec or 3 m / sec. Has the smallest friction coefficient. Especially when the pitch p exceeds 1.2 mm, the tendency of the friction coefficient to decrease becomes remarkable.

FIG. 14 shows the relationship between the sliding speed and the coefficient of friction. In addition, in FIG. 14, the line described as “absent” indicates the result of the test piece in which the lattice groove is not formed, and the line described as “iron” is
The results are shown for a steel test piece having a grid groove with a pitch of 0.14 mm, and the other lines show a test made of bronze in which the pitch p of the grid groove 7a is varied in the range of 0.2 to 1.2 mm. The results for the pieces are shown. As shown in FIG. 14, in the case where the lattice groove is not formed, the friction coefficient is largely reduced as the sliding speed is increased. Shows that the friction coefficient stabilizes at a high value.

From the above results, it is possible to increase the coefficient of friction with a friction plate whose friction surface is made of metal, but it is necessary to remove the lubricant from the friction surface in view of supplying the lubricant for cooling. It was confirmed that when there is no groove that functions as, the oil film is more likely to be formed as the sliding speed increases, and the friction coefficient decreases. Even if the grooves are formed, the coefficient of friction decreases depending on the pitch, and the groove pitch is 1.
If it exceeds 2 mm, the friction coefficient is remarkably lowered, and the advantage of using the metal friction material is lost.

Here, the friction plate having a friction surface on which fine particles of bronze are dispersed and adhered, and the friction plate in which lattice grooves are formed on the bronze plate to provide minute projections on the friction surface and bronze particles are sintered. FIG. 15 shows a comparison result with the conventional product in which the friction surface is formed by the above. As is clear from this result, the coefficient of friction of any friction plate decreases as the sliding speed increases,
The friction coefficient of conventional products is markedly decreased, whereas friction plates with bronze particles dispersed and adhered and friction plates with minute protrusions formed on bronze plates have a high friction coefficient in a sliding state. .

In addition to the copper-based materials shown in the above-mentioned embodiments, other metal materials such as iron-based materials can be used in the present invention.

[0028]

As described above, according to the present invention,
In the friction plate to which the cooling fluid such as the lubricant is supplied to the friction surface, since the grooves are formed at intervals of 1.2 mm or less on the friction surface, excess fluid that forms a film in the sliding state is applied to the grooves. It can be eliminated, and the formation of a film on the friction surface due to the fluid being drawn out from the groove is suppressed or prevented, and as a result, the coefficient of friction in the sliding state is maintained at a high value, and by extension the wet friction coefficient. Increase the torque capacity of the compound device,
Alternatively, it is possible to reduce the size and weight.

[Brief description of drawings]

FIG. 1 is a partial front view schematically showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an enlarged cross-sectional view showing an example of a structure of a friction surface.

FIG. 4 is an enlarged cross-sectional view showing another example of the structure of the friction surface.

FIG. 5 is an enlarged cross-sectional view showing still another example of the structure of the friction surface.

FIG. 6 is an enlarged cross-sectional view showing another example of the structure of the friction surface.

FIG. 7 is an enlarged cross-sectional view showing another example of the structure of the friction surface.

FIG. 8 is a partial plan view showing an array state of the minute protrusions shown in FIG.

FIG. 9 is a diagram for explaining an example in which a substantially minute protrusion is formed by a groove formed in a mating member.

FIG. 10 is a schematic view showing an example of a friction test device.

FIG. 11 is a sectional view of a test piece.

FIG. 12 is a bottom view of the test piece.

FIG. 13 is a diagram showing test results obtained by measuring the relationship between groove pitch and friction coefficient.

FIG. 14 is a diagram showing test results obtained by measuring a relationship between a sliding speed and a friction coefficient.

FIG. 15 is a diagram showing a comparison of friction coefficients of a friction plate having fine particles attached thereto or formed with fine protrusions and a friction plate made of a conventional sintered material.

[Explanation of symbols] 1 friction plate 2 substrate 3 friction layer 4 groove

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoyuki Maeda 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (1)

[Claims] 1. A wet friction plate used with a cooling fluid supplied to a friction surface, wherein a plurality of grooves are formed on the friction surface at intervals of 1.2 mm or less. Wet friction plate.