JP2016098361A - Wet friction material and wet friction plate including wet friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet friction material that is used in a wet friction plate for a wet multi-plate clutch and has a μ-V property showing a positive gradient even when compressed under a high surface pressure.SOLUTION: In a wet friction material 12 produced by impregnating a paper substrate with a resin, the resin ratio of a friction surface 31 of the wet friction material 12 is higher than the average resin ratio of the entire wet friction material 12, and the resin ration of at least a part of the inside of the wet friction material 12 is lower than the average resin ratio.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a wet friction material used for a wet friction plate of a wet multi-plate clutch used in an automatic transmission and a wet friction plate having a wet friction material.

  Generally, a wet friction material for a friction plate used in a wet multi-plate clutch is produced by impregnating and curing a resin on a paper base material at a certain ratio.

  When the wet multi-plate clutch is used in an automatic transmission under a high surface pressure condition, the entire frictional thickness of the friction material is excessively compressed by the surface pressure, which is one of the friction plate performances. Characteristic function cannot be maintained and deteriorates.

  In order to maintain the function of the μ-V characteristic, it is necessary to ensure porosity against a compressive load such as using a porous paper base material as the material of the wet friction material or reducing the amount of resin impregnated in the paper base material. It was a general technique.

  Examples of reports effective for recent compression loads include an example in which the components of the paper base material are adjusted as described in Patent Document 1, and an example in which the composition of the resin is adjusted as described in Patent Document 2. .

  However, even with these measures, maintaining the function of the μ-V characteristic under high surface pressure conditions has not been considered. In addition, it was rarely applied to use conditions under high surface pressure and high temperature.

JP 2004-138121 A JP 2006-282972 A

  In recent years, wet multi-plate clutches for automatic transmissions have been increasingly used under high surface pressure from the viewpoint of improving torque capacity. Under high surface pressure, the wet friction material of the wet friction plate for the wet multi-plate clutch is brought into pressure contact, so that the μ-V characteristic becomes a negative gradient, and there is a problem of causing vibration, shock, etc. during shifting in the automatic transmission.

  Accordingly, an object of the present invention is to provide a wet friction material having a μ-V characteristic that has a positive gradient even when the wet friction material used in a wet friction plate for a wet multi-plate clutch is compressed under a high surface pressure. Is to provide.

In order to achieve the above object, the wet friction material of the present invention comprises:
In the wet friction material produced by impregnating the paper base material with resin,
The resin ratio of the friction surface of the wet friction material is higher than the average resin ratio of the entire wet friction material, and the resin ratio of at least a part of the inside of the wet friction material is lower than the average resin ratio. .

In order to achieve the above object, the wet friction plate of the present invention is
The wet friction material is manufactured by being fixed to an annular core plate.

According to the present invention, the following effects can be obtained.
When the paper base material is impregnated with resin during the production of the friction material, the function of the μ-V characteristic can be maintained by increasing the resin ratio of the friction material surface in the thickness direction of the friction material from the inside (positive gradient property). Can be secured).

  In particular, it is effective in maintaining the performance of the μ-V characteristic in a use environment in which the wet friction material is compressed under high surface pressure conditions.

  In the present invention described below, the mechanism for maintaining the performance of the μ-V characteristics and the effects thereof are as follows.

  (1) Normally, when the wet friction material is subjected to compressive stress, if the resin ratio is uniform, the porosity is also lowered uniformly, and the μ-V characteristic has a negative gradient.

  (2) On the other hand, if the resin ratio of the surface layer is made higher than the layer below the surface layer, when subjected to compressive stress, the surface layer is compressed in a state of maintaining porosity without being affected by the stress, and the interior under the surface layer is Since the resin ratio is low, the porosity can be secured even after being compressed.

  (3) Therefore, even after being subjected to compressive stress, it is effective in maintaining the porosity of the wet friction material, and the μ-V characteristic can maintain a positive gradient. In particular, under high surface pressure, the hardness of the surface layer disperses the compressive stress, and the interior under the surface layer relaxes the compression state, so it retains more porosity than a wet friction material with a normal resin ratio. This is effective in maintaining the function of the μ-V characteristic.

FIG. 1 is a partial axial sectional view of a wet multi-plate clutch provided with a wet friction plate of the present invention. It is a front view of the wet friction board which can apply the wet friction material of the example of the present invention. It is sectional drawing of the wet friction material which shows the Example of this invention along the AA line of FIG. It is a graph which shows the resin rate of the thickness direction of the wet friction material of the Example of this invention. It is a graph which shows the micro-V characteristic of the wet friction material of the Example of this invention. It is a graph which shows the peeling durability test result of the wet friction material of the Example of this invention, and a comparative example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the Example described below illustrates this invention, and it cannot be overemphasized that this invention is not limited to an Example.

  FIG. 1 is a partial sectional view in the axial direction of a wet multi-plate clutch 10 including a wet friction plate having a wet friction material of the present invention. The wet friction plate of the embodiment according to the present invention is applicable.

  The wet multi-plate clutch 10 includes a substantially cylindrical clutch drum 1 that is opened at one end in the axial direction, a hub 4 that is disposed on the inner periphery of the clutch drum 1 and relatively rotates on the same axis, and an inner periphery of the clutch drum 1. An annular separator plate 2 disposed on a spline 8 provided on the outer periphery of the hub 4 and an axially movable separator plate 2 disposed on the outer periphery of the hub 4 are disposed alternately with the separator plate 2 in the axial direction. It comprises an annular wet friction plate 3 having a friction surface fixed by an adhesive or the like. The separator plate 2 includes a spline portion 2 a that engages with the spline 8, and the wet friction plate 3 includes a spline portion 3 a that engages with the spline 5. A plurality of wet friction plates 3 and separator plates 2 are provided.

  The wet multi-plate clutch 10 holds the separator plate 2 and the wet friction plate 3 in a fixed state at one end in the axial direction, and the piston 6 that presses and fastens the separator plate 2 and the wet friction plate 3. A backing plate 7 provided on the inner periphery and a retaining ring 17 for holding the backing plate 7 are provided.

  As shown in FIG. 1, the piston 6 is slidably disposed in the axial direction within the closed end of the clutch drum 1. An O-ring 9 is interposed between the outer peripheral surface of the piston 6 and the inner surface of the clutch drum 1. Further, a seal member (not shown) is also interposed between the inner peripheral surface of the piston 6 and the outer peripheral surface of the inner peripheral cylindrical portion (not shown) of the clutch drum 1. Therefore, an oil tight hydraulic chamber 11 is defined between the inner surface of the closed end of the clutch drum 1 and the piston 6.

  The wet friction plate 3 held axially slidable by the hub 4 has friction material segments 12 and 13 having a predetermined friction coefficient fixed to both surfaces thereof. However, the friction material segments 12 and 13 can be provided only on one side of the wet friction plate 3. The hub 4 is provided with a lubricating oil supply port 15 penetrating in the radial direction, and the lubricating oil is supplied from the inner diameter side to the outer diameter side of the wet multi-plate clutch 10 through the lubricating oil supply port 15. .

  The wet multi-plate clutch 10 configured as described above engages (fastens) and releases the clutch as follows. The state of FIG. 1 shows the clutch release state, and the separator plate 2 and the wet friction plate 3 are separated from each other. In the released state, the piston 6 is in contact with the closed end side of the clutch drum 1 by the biasing force of a return spring (not shown).

  In order to engage the wet multi-plate clutch 10 in this state, hydraulic pressure is supplied to the hydraulic chamber 11 defined between the piston 6 and the clutch drum 1. As the hydraulic pressure rises, the piston 6 moves to the right in the axial direction in FIG. 1 against the urging force of a return spring (not shown) to bring the separator plate 2 and the wet friction plate 3 into close contact with each other. As a result, the wet multi-plate clutch 10 is engaged.

  To release the wet multi-plate clutch 10 again after the wet multi-plate clutch 10 is engaged, the hydraulic pressure in the hydraulic chamber 11 is released. When the hydraulic pressure is released, the piston 6 moves to a position where it abuts against the closed end of the clutch case 1 by the urging force of a return spring (not shown). That is, the wet multi-plate clutch 10 is released.

  FIG. 2 is a front view of a friction plate to which the friction material of each embodiment of the present invention can be applied. The wet friction plate 3 is manufactured by fixing an annular wet friction material 12 to one or both surfaces of the metal-made annular core plate 30 in the axial direction by bonding or the like. On the inner periphery of the core plate 30 is provided a spline portion 3a that fits into the spline 5 of the hub 4 shown in FIG.

  Hereinafter, wet friction materials according to examples of the present invention will be described in detail.

  FIG. 3 is a sectional view of the wet friction material showing an embodiment of the present invention along the line AA in FIG. For the sake of explanation, each part is drawn by changing the actual scale. The wet friction material 12 is bonded to the core plate 30. The wet friction material 12 is made by impregnating and curing a resin on a paper base made from a mixture of natural pulp fiber, aramid fiber, diatomaceous earth and the like. Examples of the resin to be impregnated include a phenol resin and / or a silicone resin. These are only examples, and other mixtures and other resins can be used.

  The wet friction material 12 has the friction surface 31 which rubs against the separator plate 2 (FIG. 1) at the uppermost part. The wet friction material 12 is impregnated with resin so that the surface layer including the friction surface 31 has the highest resin rate (resin content rate), and the resin rate decreases as it goes inside (closer to the core plate 30).

  In the present embodiment, the resin ratio of the surface layer including the friction surface 31 of the wet friction material 12 is made highest. The resin ratio of the friction surface 31 is set to four resin ratios that are 5%, 10%, 20%, and 25% higher than the overall average resin ratio of the wet friction material 12. By doing in this way, a surface layer is hard and becomes flexible toward the inside, and the inside under a surface layer can relieve a compression state. Compared with a wet friction material having a general resin ratio as a whole, the porosity can be maintained, which is effective in maintaining the function of the μ-V characteristic.

  FIG. 4 is a graph showing the resin ratio in the thickness direction of the wet friction material of the example of the present invention. The result of having measured the resin rate in the thickness direction (axial direction) of the produced wet friction material 12 is represented. The comparative example (conventional example) is a wet friction material having an average resin ratio in any part in the thickness direction. The wet friction material 12 was sliced in the thickness direction, and the resin ratio from the portion A including the friction surface 31 to the portion E close to the core plate 30 was measured. Parts B to E correspond to the inside of the wet friction material 12. Each portion A to E of the wet friction material 12 is divided into five layers at approximately equal intervals for the sake of convenience in order to measure the resin ratio.

  When the resin rate of the portion A is 5%, 10%, 20%, and 25% higher than the average resin rate, the innermost portion E close to the core plate 30 is 5% and 10% respectively than the average resin rate. , 20% and 25% lower. Moreover, in the part B close | similar to a surface layer, although higher than an average resin rate, the resin rate is lower than the part A. In the portion C which is substantially in the middle of the thickness direction, the resin ratio is substantially close to the average resin ratio. Further, in the portion D, the resin rate is equal to or lower than the average resin rate regardless of the set value of the resin rate of the portion A. As described above, the resin ratio of the friction surface 31 of the wet friction material 12 is higher than the average resin ratio of the entire wet friction material 12, and the resin ratio of at least a part of the wet friction material 12 is lower than the average resin ratio.

  Combinations other than the combinations shown in FIG. 4 are possible for the resin ratio at each of the friction surface 31 and the internal portion of the wet friction material 12. For example, the resin rate of the portion A which is the surface layer can be made 25% higher than the average resin rate, and the resin rate of the inner portion E can be made 5% lower than the average resin rate.

（10secで0-250rpmとし、10secで250-0rpmが１サイクルとする） (Evaluation test)
Test conditions shown in Table 1 for the wet friction material 12 produced based on the examples according to the present invention (the resin ratio of the surface layer is set 5%, 10%, 20% and 25% higher than the average resin ratio) and the comparative example An evaluation test was conducted. Specifically, a μ-V characteristic test was conducted using a slip tester under the following test conditions.

(10-sec is 0-250 rpm, 10 sec is 250-0 rpm)

(Evaluation test results)
FIG. 5 shows the performance result based on the Δμ value obtained from the μ-V characteristic test result. FIG. 5 is a graph showing the μ-V characteristics of the wet friction material 12 of the example and the comparative example.

  Δμ is μ200−μ50 (μ value difference at each rotation). According to FIG. 5, the Δμ performance of the wet friction material 12 according to the example of the present invention shows a positive gradient under conditions where the surface pressure is higher than that of the wet friction material of the comparative example (conventional example). I understand that.

  Here, the relationship between the friction coefficient μ of the wet friction material and the sliding speed of the wet friction material is as follows. In general, when μ is a positive region, function maintenance is indicated by showing a positive gradient. This is called positive gradient. On the other hand, when μ is in a negative region, a negative gradient is indicated, indicating a decline in function. This is called negative gradient.

(Peeling durability evaluation test)
Hereinafter, in order to measure the strength of the friction material according to the example of the present invention, a peel durability evaluation test was performed using a compression fatigue tester under the conditions shown in Table 2.

(Results of peel durability evaluation test)
FIG. 6 is a graph showing the peel durability test results of the wet friction materials of Examples and Comparative Examples of the present invention. As shown in FIG. 6, the wet friction material and the wet friction material of the comparative example when the resin ratio is 5%, 10%, 20%, and 25% higher than the average resin ratio, respectively, are described in FIG. It can be seen that the target peeling durability cycle TC indicated by the broken line is exceeded and sufficient strength is secured. In the graph, the reason that the peeling durability cycles of the examples up to 25% in the graph and the comparative example are all the same is because the test was stopped at the acceptable value.

  On the other hand, the wet friction material in which the resin rate is set 30% higher than the average resin rate does not reach the target peeling durability cycle TC as shown in FIG. For this reason, in order to ensure sufficient strength while ensuring the performance maintaining effect of the μ-V characteristic, it is preferable to set the resin rate to a height of 25% or less from the average resin rate.

  Further, the wet friction material 12 is not annular, and a segment-like friction material can also be annularly arranged.

  The wet friction material of the present invention can be used as an automatic transmission for automobiles and industrial machines.

2 Separator plate 3 Friction plate 12 Friction material 30 Core plate 31 Friction surface

Claims (3)

In the wet friction material produced by impregnating the paper base material with resin,
The resin ratio of the friction surface of the wet friction material is higher than the average resin ratio of the entire wet friction material, and the resin ratio of at least a part of the inside of the wet friction material is lower than the average resin ratio. Wet friction material.   The resin ratio of the friction surface of the wet friction material is 5 to 25% higher than the average resin ratio of the entire wet friction material, and the resin ratio of at least a part of the inside of the friction surface is 5 to 5% higher than the average resin ratio. The wet friction material according to claim 1, which is 25% lower.   A friction plate produced by fixing the wet friction material according to claim 1 to an annular core plate.

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