JP2019203524A - Clutch piston - Google Patents

Abstract

To provide a clutch piston which enables a piston to be moved quickly when needed.SOLUTION: A clutch piston includes: a piston which reciprocates in a piston chamber into which oil flows; and a seal member which seals the oil in the piston chamber. The seal member has: a base part attached to the piston; and a seal lip which slides relative to a wall surface of the piston chamber when the piston reciprocates. The seal lip has: an oil surface which is located adjacent to the wall surface and makes surface contact with the oil; and an air surface which is located adjacent to the wall surface and contacts with air. An angle θof the oil surface relative to the wall surface is smaller than an angle θof the air surface relative to the wall surface.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a clutch piston that operates a clutch of a transmission.

  A clutch piston that operates a multi-plate clutch of a transmission used in an automobile or the like, for example, an automatic transmission (AT) or a continuously variable transmission (CVT) is known (Patent Document 1). The clutch piston has a piston that reciprocates in a piston chamber into which oil flows, and a seal member that is attached to the piston and seals the oil in the piston chamber. The piston operates a multi-plate clutch.

Japanese Patent Laid-Open No. 9-210088

  In the clutch piston, it is important to seal the oil in a predetermined chamber, but it is desirable that the piston can be quickly moved when desired, that is, the piston has high movement response.

  Therefore, the present invention provides a clutch piston that can quickly move the piston when desired.

A clutch piston according to an aspect of the present invention is a piston that reciprocates in a piston chamber into which oil flows, a seal member that seals oil in the piston chamber, a base portion attached to the piston, and the piston And a sealing member having a sealing lip that slides against the wall surface of the piston chamber when reciprocating. The seal lip has an oil surface adjacent to the wall surface and in contact with the oil, and an air surface adjacent to the wall surface and in contact with air, and an angle θ _{1 of the} oil surface with respect to the wall surface is Is smaller than the angle θ _{2 of the} air surface relative to.

In this aspect, since the angle θ ₁ of the oil surface of the seal lip is smaller than the angle θ _{2 of the} air surface, there is little oil in the gap between the tip portion of the seal lip where the oil surface intersects the air surface and the wall surface. Easy to invade. Therefore, the lubricity between the seal lip and the wall surface is improved (friction is reduced), and the piston can be moved quickly in response to a change in the oil pressure in the piston chamber. The angle theta ₁ of the oil surface of the seal lip is smaller than the angle theta ₂ of the air plane, when incorporating a clutch piston while the sealing lip is elastically deformed in the piston chamber, the sealing lip risk is reduced that turned up.

Preferably, the seal lip protrudes toward the back of the piston chamber in the moving direction of the piston from the base, and the tip end of the seal lip where the oil surface intersects the air surface is more than the base. The oil surface is arranged in the back of the piston chamber in the moving direction of the piston, and the oil surface is arranged in the back of the piston chamber in the moving direction of the piston rather than the air surface. and the base, the distance between the tip δ is, the farthest point from the base of the sealing lip in the direction of movement of the piston, is smaller than the distance L ₁ between the front end portion of the seal lip . In this case, since the seal lip protrudes from the base toward the back of the piston chamber, the seal lip receives the pressure of oil in the piston chamber. Here, since the distance δ on the air surface side is smaller than the distance L ₁ on the oil surface side, the force pressing the seal lip against the wall surface of the piston chamber due to the oil pressure in the piston chamber is small. Therefore, the frictional force between the front end portion of the seal lip where the oil surface intersects the air surface and the wall surface is small. In addition, oil easily enters the gap between the tip of the seal lip and the wall surface. Therefore, the piston can be moved more quickly in response to a change in the oil pressure in the piston chamber.

Preferably, the oil surface is disposed further to the back of the piston chamber in the moving direction of the piston than the air surface, and the root of the air surface in the moving direction of the piston, the oil surface and the air surface There is a distance [delta] ₁ between the tip of the seal lip that intersects the farthest point from the base of the sealing lip in the direction of movement of the piston, the distance between the tip of the seal lip L ₁ Smaller than. In this case, than the distance L ₁ of the oil surface side disposed towards the inner part of the piston chamber than air plane, the distance [delta] ₁ of the air side is small, the sealing lip which receives a reaction force from the wall surface elastic The amount of deformation can be suppressed.

Furthermore, the clutch piston is a further seal member that opposes the piston and defines an oil chamber between the piston and seals the oil in the oil chamber, and a base portion attached to the canceller, It may further comprise a further seal member having a further seal lip that slides against the inner wall surface forming the oil chamber of the piston when the piston reciprocates. In this case, the further seal lip has an oil surface adjacent to the inner wall surface and in surface contact with the oil, and an air surface adjacent to the inner wall surface and in contact with air, and the oil surface with respect to the inner wall surface The angle θ ₁ is smaller than the angle θ _{2 of the} air surface with respect to the inner wall surface. Gap between this case, the angle theta ₁ of the oil surface of the additional sealing lip is smaller than the angle theta ₂ of the air plane, the tip and the inner wall surface of the piston seal lip of the oil surface and the air plane intersects Oil is easy to enter slightly. Therefore, the lubricity between the seal lip and the inner wall surface is improved (friction is reduced), and the piston can be moved quickly in response to a change in the oil pressure in the piston chamber. The angle theta ₁ of the oil surface of the additional sealing lip is smaller than the angle theta ₂ of the air plane, when incorporating the canceller while deforming elastically additional sealing lip to the piston, a possibility that further sealing lip turned up is reduced.

A clutch piston according to another aspect of the present invention includes a piston that reciprocates in a piston chamber into which oil flows, a canceller that faces the piston and defines an oil chamber between the piston, and an oil in the oil chamber. A base member attached to the canceller, and a seal lip that slides against an inner wall surface that forms the oil chamber of the piston when the piston reciprocates. And a seal member. The seal lip has an oil surface adjacent to the inner wall surface and in contact with the oil, and an air surface adjacent to the inner wall surface and in contact with air, and an angle θ _{1 of the} oil surface with respect to the inner wall surface is The angle [theta] _{2 of the} air surface with respect to the inner wall surface is smaller.

In this embodiment, the angle theta ₁ of the oil surface of the sealing lip is smaller than the angle theta ₂ of the air plane, the gap between the tip and the inner wall surface of the piston seal lip of the oil surface and the air plane intersects Oil is slightly intrusive. Therefore, the lubricity between the seal lip and the inner wall surface is improved (friction is reduced), and the piston can be moved quickly in response to a change in the oil pressure in the piston chamber. The angle theta ₁ of the oil surface of the seal lip is smaller than the angle theta ₂ of the air plane, when incorporating the sealing lip on the piston a canceller while elastically deforming, the seal lip risk is reduced that turned up.

Preferably, the seal lip protrudes toward the back of the oil chamber in the movement direction of the piston from the base, and the tip of the seal lip where the oil surface intersects the air surface is more than the base. The oil surface is arranged in the back of the oil chamber in the moving direction of the piston, and the oil surface is arranged in the back of the oil chamber in the moving direction of the piston than the air surface, and in the moving direction of the piston and the base, the distance between the tip δ is, the farthest point from the base of the sealing lip in the direction of movement of the piston, is smaller than the distance L ₁ between the front end portion of the seal lip . In this case, since the seal lip protrudes from the base portion toward the back of the oil chamber, the seal lip receives the oil pressure in the oil chamber. Here, the distance of the air side δ is smaller than the distance L ₁ of the oil surface, due to the pressure of the oil chamber of the oil, the force to press the seal lip on the inner wall surface of the piston is small. Therefore, the frictional force between the front end portion of the seal lip where the oil surface intersects the air surface and the inner wall surface is small. In addition, oil easily enters the gap between the tip of the seal lip and the wall surface. Therefore, the piston can be moved more quickly in response to a change in the oil pressure in the piston chamber.

Preferably, the oil surface is disposed further to the back of the oil chamber in the moving direction of the piston than the air surface, and the root of the air surface in the moving direction of the piston, the oil surface and the air surface There is a distance [delta] ₁ between the tip of the seal lip that intersects the farthest point from the base of the sealing lip in the direction of movement of the piston, the distance between the tip of the seal lip L ₁ Smaller than. Seal this case, than the distance L ₁ of the oil surface side disposed towards the back of the oil chamber than the air side, the distance [delta] ₁ of the air side is small, that receives a reaction force from the inner wall surface of the piston The amount of elastic deformation of the lip can be suppressed.

It is sectional drawing which shows the clutch piston which concerns on embodiment of this invention. It is sectional drawing which expands and shows each seal member of a clutch piston. It is sectional drawing which expands and shows the sealing member of a comparative example. It is a figure which shows the disadvantage of the sealing member of FIG. It is sectional drawing which expands and shows the sealing member of another comparative example. It is a figure which shows the disadvantage of the sealing member of FIG. It is sectional drawing which expands and shows the sealing member of the clutch piston which concerns on a modification.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. In the drawings, the scale does not necessarily accurately represent the product of the embodiment, and some dimensions may be exaggerated.

  As shown in FIG. 1, the clutch piston 1 according to the embodiment is used for operating a multi-plate clutch 6 disposed in a clutch chamber 4 of a clutch housing 2 of an automobile. The multi-plate clutch 6 is provided, for example, in an automatic transmission (AT) or a continuously variable transmission (CVT). A part of the clutch chamber 4 is used as a piston chamber 8 in which the clutch piston 1 is disposed. An oil supply path 9 formed in the clutch housing 2 is connected to the piston chamber 8, and the pressure in the piston chamber 8 can be changed by the oil supplied from the oil supply path 9.

  The clutch piston 1 according to the embodiment includes a piston 10, a canceller 12, and a return spring 18.

  The piston 10 is formed by bending a sheet metal by, for example, pressing. The piston 10 reciprocates in the piston chamber 8 in accordance with a change in the pressure of oil in the piston chamber 8 supplied from the oil supply path 9.

  The canceller 12 is also formed by bending a sheet metal by, for example, pressing. The canceller 12 faces the piston 10, and an oil chamber 14 is defined between the canceller 12 and the piston 10. An oil supply path 15 formed in the clutch housing 2 is connected to the oil chamber 14, and oil is supplied from the oil supply path 15.

  The canceller 12 is supported by a seal washer 16 fixed to the clutch housing 2, and the movement of the canceller 12 downward in FIG. 1 is restricted by the seal washer 16.

  The return spring 18 is a spring (for example, a coil spring) disposed inside the oil chamber 14, and is supported by the canceller 12 to always apply a force to push the piston 10 back toward the back of the piston chamber 8 (upward in FIG. 1). It is given to the piston 10. When the oil pressure in the piston chamber 8 increases due to the adjustment of the oil supply passage 9, the piston 10 moves downward in FIG. 1 against the force of the return spring 18, and the multi-plate clutch 6 is fastened. The plate clutch 6 makes it possible to transmit the power of the automobile. When the oil pressure in the piston chamber 8 decreases due to the adjustment of the oil supply path 9, the piston 10 is pushed back into the piston chamber 8 by the force of the return spring 18, thereby releasing the engagement of the multi-plate clutch 6. The power is not transmitted. Thus, the piston 10 reciprocates relative to the clutch housing 2 and the canceller 12.

  1, a common axis C of the clutch housing 2, the multi-plate clutch 6, the piston 10 and the canceller 12 is shown. FIG. 1 shows only the left part of the clutch housing 2, the multi-plate clutch 6, the piston 10 and the canceller 12, which have a rotationally symmetric structure. Therefore, the piston 10 and the canceller 12 are annular.

  The clutch housing 2, the piston 10 and the canceller 12 rotate about the common axis C. A centrifugal force is applied to the oil in the piston chamber 8 as the clutch housing 2 and the piston 10 rotate. The canceller 12 defines an oil chamber 14 on the side opposite to the piston chamber 8 for the piston 10, and is provided to generate a centrifugal force in the oil in the oil chamber 14 that cancels out the centrifugal force of the oil in the piston chamber 8. ing. By canceling out the centrifugal force, the response of the piston 10 to the oil pressure change in the piston chamber 8 (and hence the response of the multi-plate clutch 6) is improved.

  The canceller is also called a balancer. A clutch piston having such a canceller is called a bonded piston seal or a seal bonded piston.

  In order to seal the oil in the piston chamber 8, the clutch piston 1 further includes an outer piston seal member 20 and an inner piston seal member 22. The outer piston seal member 20 is fixed to the outer wall of the piston 10 and slidably contacts the outer wall surface of the piston chamber 8. The inner piston seal member 22 is fixed to the inner end edge of the piston 10 and slidably contacts the inner wall surface of the piston chamber 8.

  In order to seal the oil in the oil chamber 14, the clutch piston 1 further includes a canceller seal member 24. The canceller seal member 24 is fixed to the outer edge of the canceller 12 and slidably contacts the outer wall surface of the oil chamber 14 (that is, the inner wall surface of the piston 10).

  A gap between the inner end edge of the canceller 12 and the clutch housing 2 is sealed with an annular seal washer 16. A stopper 26 is disposed around the seal washer 16 in order to restrict the expansion of the diameter due to the centrifugal force of the seal washer 16. In place of the annular seal washer 16, a C-shaped seal washer having a discontinuous portion in the circumferential direction may be used to allow a small amount of oil to flow out of the oil chamber 14 through the discontinuous portion. Good.

  Each of the seal members 20, 22, 24 has a base portion 30 attached to the piston 10 or the canceller 12, and a seal lip 32 protruding from the base portion 30. Each seal lip 32 projects toward the back of the piston chamber 8 (upward in FIG. 1) in the moving direction of the piston 10 from the base.

  Other portions differ depending on the seal members 20, 22, and 24. Specifically, as shown in FIG. 1, the outer piston seal member 20 has an extension portion 20 a that extends from the base portion 30 thereof and covers a part of the outer peripheral surface of the piston 10. The inner piston seal member 22 includes an extension 22a that extends from the base 30 thereof and covers a part of the inner peripheral surface of the piston 10, and an extension that extends from the base 30 and covers a part of the surface of the piston 10 on the canceller 12 side. 22b. The canceller seal member 24 has an extension 24a that extends from the base 30 thereof and covers a part of the surface of the canceller 12 on the multi-plate clutch 6 side.

  Each seal member is formed from an elastomer. For example, the seal member may be formed by placing the piston 10 or the canceller 12 and an elastomer material, which is a material of the seal member, in the mold, and pressing. Alternatively, the seal member may be formed by injection molding.

  FIG. 2 shows an enlarged view of the base 30 and the seal lip 32 of each seal member. In FIG. 2 and subsequent drawings, hatching is omitted. The base 30 is fixed to the corner portion 34 of the piston 10 or the canceller 12. The base 30 of the piston seal member 20 or 22 is fixed to the corner portion 34 of the piston 10. The base portion 30 of the canceller seal member 24 is fixed to the corner portion 34 of the canceller 12.

  The seal lip 32 of the piston seal member 20 or 22 protrudes from the base 30 toward the back of the piston chamber 8 in the moving direction of the piston 10. The seal lip 32 of the canceller seal member 24 protrudes from the base 30 toward the back of the oil chamber 14 in the moving direction of the piston 10.

  When the piston 10 reciprocates, each seal lip 32 slides with respect to the wall surface 36. The tip portion 38 of the seal lip 32 of the piston seal member 20 or 22 is brought into contact with the wall surface of the piston chamber 8 (that is, the wall surface of the clutch housing 2). It slides with respect to the wall surface 36. The tip end portion 38 of the seal lip 32 of the canceller seal member 24 is brought into contact with the inner wall surface forming the oil chamber 14 of the piston 10, and when the piston 10 reciprocates, the tip end portion 38 contacts the wall surface 36 of the oil chamber 14. Slide against.

  Each seal lip 32 has an oil surface 40 adjacent to the wall surface 36 and in surface contact with oil, and an air surface 42 adjacent to the wall surface 36 and in surface contact with air. A portion where the oil surface 40 and the air surface 42 intersect is a tip portion 38. The oil surface 40 of the seal lip 32 of the piston seal member 20 or 22 is disposed in the back of the piston chamber 8 in the moving direction of the piston 10 relative to the air surface 42, and is in surface contact with the oil in the piston chamber 8, The air surface 42 of the seal lip 32 is in surface contact with the air on the multi-plate clutch 6 side in the piston chamber 8. The oil surface 40 of the seal lip 32 of the canceller seal member 24 is disposed in the back of the oil chamber 14 in the moving direction of the piston 10 relative to the air surface 42, and is in surface contact with the oil in the oil chamber 14, and the seal lip The 32 air surfaces 42 are in surface contact with the air on the multi-plate clutch 6 side in the piston chamber 8.

As shown in FIG. 2, the angle θ ₁ of the oil surface 40 with respect to the wall surface 36 is smaller than the angle θ ₂ of the air surface 42 with respect to the wall surface 36. As a result, the oil slightly enters the gap between the front end portion 38 of the seal lip 32 and the wall surface 36 where the oil surface 40 and the air surface 42 intersect. Therefore, the lubricity between the seal lip 32 and the wall surface 36 is improved (friction is reduced), and the piston 10 can be moved quickly in response to the change in the oil pressure in the piston chamber 8. That is, the movement responsiveness of the piston 10 is high. Further, since the lubricity between the seal lip 32 and the wall surface 36 is improved, even if the wall surface 36 and the seal lip 32 move relative to each other, the possibility that the seal lip 32 is turned up is reduced. These effects can be applied to the piston seal members 20 and 22 that move while being fixed to the piston 10 and the canceller seal member 24 that is fixed to the canceller 12 and does not move. In the piston seal member 20 or 22, oil enters from the piston chamber 8 into the gap between the tip portion 38 and the wall surface 36, and in the canceller seal member 24, oil flows from the oil chamber 14 between the tip portion 38 and the wall surface 36. Break into the gap. Therefore, in the embodiment, each seal lip 32 does not need to completely seal the oil inside the piston chamber 8 or the oil chamber 14, and a small amount of oil can be allowed to flow out from the piston chamber 8 or the oil chamber 14. The

As shown in FIG. 2, the distal end portion 38 of the seal lip 32 is disposed behind the piston chamber 8 or the oil chamber 14 in the movement direction of the piston 10 than the base portion 30 of the seal member. The distance between the base 30 of the seal member and the tip 38 of the seal lip 32 in the moving direction of the piston 10 is δ, and the point 44 farthest from the base 30 of the seal lip 32 and the tip in the moving direction of the piston 10 Let L ₁ be the distance to 38. In embodiments, the distance δ is smaller than the distance L _1.

Since the seal lip 32 protrudes from the base 30 toward the back of the piston chamber 8, the seal lip 32 receives the pressure P of the oil in the piston chamber 8 or the oil chamber 14. Specifically, the oil surface 40 of the seal lip 32 receives a pressure P in a direction to pull the seal lip 32 away from the wall surface 36, and the back surface 46 opposite to the oil surface 40 presses the seal lip 32 against the wall surface 36. The pressure P is received in the direction to be attempted. In general, the force F _{1 for} pulling the seal lip 32 away from the wall surface 36 can be considered as L · X ₀ · P · cos θ ₁ , and the force F ₂ for pressing the seal lip 32 against the wall surface 36 is , L · X ₂ · P · cos θ ₃ . Here, L is the peripheral length of the seal lip 32 although not shown. X ₀ is the length of the oil surface 40, and X ₂ is the length of the back surface 46. θ ₃ is an inclination angle of the back surface 46 and X ₂ · cos θ ₃ ≈L ₂ . L ₂ is a distance between the base 44 and the point 44 farthest from the base 30 of the seal lip 32 in the moving direction of the piston 10. As a result, the force F for pressing the seal lip 32 against the wall surface 36 is given by the following equation.
F = F ₂ −F ₁
≒ L ・ X ₂・ P ・ cos θ ₃ −L ・ X ₀・ P ・ cos θ ₁ Formula (1)
From FIG. 2, the relationship X ₀ · cos θ ₁ ≈X ₁ · cos θ ₃ ≈L ₁ is established. Here, X ₁ is the length from the point 44 farthest from the base 30 of the seal lip 32 to the portion corresponding to the tip portion 38 in the back surface 46, and X ₂ = X ₁ + Δ. Δ is the length of the back surface 46 to the portion corresponding to the base 30 and the tip 38, and Δcos θ ₃ ≈δ.

Therefore, the equation (1) is modified as follows.
F≈L · X ₂ · P · cos θ ₃ −L · X ₁ · P · cos θ ₁
≒ L ・ P ・ ((X ₂ −X ₁ ) cos θ ₃ )
= L · P · Δcosθ ₃
≒ L ・ P ・ δ Formula (2)

In the embodiment, since the tip end portion 38 of the seal lip 32 is disposed behind the piston chamber 8 or the oil chamber 14 in the moving direction of the piston 10 than the base portion 30 of the seal member, the seal lip 32 is pressed against the wall surface 36. The force F is greater than zero. Therefore, the state where the seal lip 32 is in contact with the wall surface 36 can be maintained. However, the distance of the air surface 42 side δ is smaller than the distance L ₁ of the oil surface 40 side, due to the pressure of the oil, the force F that presses the sealing lip 32 on the wall 36 is small. Therefore, oil easily enters the gap between the front end portion 38 of the seal lip 32 and the wall surface 36.

On the other hand, FIG. 3 is an enlarged sectional view showing a sealing member of a comparative example. In this comparative example, contrary to the embodiment, the angle θ ₁ of the oil surface 40 with respect to the wall surface 36 is larger than the angle θ ₂ of the air surface 42 with respect to the wall surface 36. The distance δ is greater than the distance L _1. In this comparative example, since the angle θ ₁ of the oil surface 40 is larger than the angle θ ₂ of the air surface 42, the oil hardly enters the gap between the front end portion 38 of the seal lip 32 and the wall surface 36, and the seal lip Although the sealing performance of the seal 32 is high, the friction between the seal lip 32 and the wall surface 36 is large, so that the piston 10 cannot be moved quickly in response to the change in the oil pressure in the piston chamber 8. There is. Further, since the distance δ is greater than the distance L _1, due to the pressure of the oil, (see equation (2)) the force pressing the sealing lip 32 on the wall 36 F is larger than the embodiment. This also makes it difficult for oil to enter the gap between the tip portion 38 of the seal lip 32 and the wall surface 36, and increases the friction between the seal lip 32 and the wall surface 36.

FIG. 4 shows another disadvantage of the sealing member of the comparative example of FIG. In front of the wall surface 36 of the piston chamber 8, there is an inclined surface 37 that continues to the wall surface 36. A curved surface or an inclined surface 37 connected to the wall surface 36 also exists in front of the wall surface 36 of the oil chamber 14 (see FIG. 1). As indicated by the arrow, when the clutch piston 1 is assembled into the piston chamber 8, the tip end portion 38 of the seal lip 32 of the piston seal member 20 or 22 is slid on the inclined surface 37 and then the wall surface 36 is slid. Be moved. Since the piston seal member 20 or 22 is made of an elastomer, the piston seal member 20 or 22 is elastically deformed and pushed forward toward the back of the piston chamber 8. When the canceller 12 is incorporated into the piston 10, the tip end portion 38 of the seal lip 32 of the piston seal member 24 is slid on the inclined surface 37 and then slid on the wall surface 36. Since the piston seal member 24 is made of an elastomer, it is elastically deformed and pushed forward toward the back of the oil chamber 14. In the comparative example, since the angle θ ₁ of the oil surface 40 is larger than the angle θ ₂ of the air surface 42, the seal lip 32 is easily turned by receiving a reaction force from the inclined surface 37 as shown in FIG. . This turning-up may remain even if the tip portion 38 of the seal lip 32 contacts the wall surface 36 after passing through the inclined surface 37. Turning over of the seal lip 32 can cause unexpected wear of the seal lip 32 and unexpected oil spillage.

On the contrary, in the embodiment, since the angle θ ₁ of the oil surface 40 is smaller than the angle θ ₂ of the air surface 42, the inclination is caused when the clutch piston 1 is incorporated into the piston chamber 8 while elastically deforming the seal lip 32. Even if the reaction force is received from the surface 37 or the wall surface 36, the seal lip 32 is less likely to be turned than in the comparative example.

Further, as shown in FIG. 2, the distance between the root of the air surface 42 and the front end portion 38 of the seal lip 32 in the moving direction of the piston 10 is δ ₁ . The distance δ ₁ is smaller than the distance L ₁ . When the distance δ ₁ of the air surface 42 in the moving direction of the piston 10 is large, the elastic deformation amount of the seal lip 32 that receives the reaction force from the wall surface 36 is large. For example, in the comparative example of FIG. 3, when the seal member moves downward relative to the wall surface 36 (or when the wall surface 36 moves upward relative to the seal member), the seal lip 32 receives a reaction force from the wall surface 36. Is greatly elastically deformed. When such a large elastic deformation is repeated, the seal lip 32 is fatigued.

On the other hand, in the embodiment, since the distance δ ₁ is smaller than the distance L ₁ , the elastic deformation of the seal lip 32 can be suppressed even when a reaction force is received from the wall surface 36 as compared with the comparative example.

FIG. 5 is an enlarged sectional view showing a sealing member of another comparative example. In this comparative example, the seal lip 32 has a plate shape with a uniform thickness. In this comparative example, as in the embodiment, the angle θ ₁ of the oil surface 40 with respect to the wall surface 36 is smaller than the angle θ ₂ of the air surface 42 with respect to the wall surface 36.

However, in the comparative example of FIG. 5, the distance δ ₁ is greater than the distance L ₁ . Therefore, the amount of elastic deformation of the seal lip 32 that receives the reaction force from the wall surface 36 is large. For example, in the comparative example of FIG. 5, when the seal member moves downward relative to the wall surface 36 (or when the wall surface 36 moves upward relative to the seal member), as shown in FIG. The seal lip 32 is easy to turn over under force. In this case, the angle θ ₁ of the oil surface 40 becomes larger than the angle θ ₂ of the air surface 42, and it is difficult for oil to enter the gap between the tip portion 38 of the seal lip 32 and the wall surface 36. The friction with 36 increases. Further, when such large elastic deformation is repeated, the seal lip 32 is fatigued.

On the other hand, in the embodiment, since the distance δ ₁ is smaller than the distance L ₁ , the elastic deformation of the seal lip 32 can be suppressed even when a reaction force is received from the wall surface 36 as compared with the comparative example.

Other Modifications Embodiments of the present invention have been described above. However, the above description is not intended to limit the present invention, and various modifications including deletion, addition, and replacement of components are included in the technical scope of the present invention. Examples are possible.

  For example, in the above embodiment, the same improvement is applied to the three seal members 20, 22, and 24, but the above improvement is applied to any one or two of the seal members 20, 22, and 24. It's okay.

In the above-described embodiment, as shown in FIG. 2, the distal end portion 38 of the seal lip 32 is arranged behind the piston chamber 8 or the oil chamber 14 in the moving direction of the piston 10 than the base portion 30 of the seal member. However, as shown in FIG. 7, the base portion 30 of the seal member may be disposed deeper in the piston chamber 8 or the oil chamber 14 than the distal end portion 38 of the seal lip 32. In the modification of FIG. 7, since the length of the back surface 46 of the seal lip 32 is small, the force F ₁ that tries to separate the seal lip 32 received by the oil surface 40 from the wall surface 36 causes the seal lip 32 received by the back surface 46 to move to the wall surface 36. It is larger than the force F ₂ to be pressed against.

  However, the state in which the seal lip 32 is in contact with the wall surface 36 is maintained by appropriately designing the elastic restoring force of the seal lip 32 by selecting the elastomer as the material of the seal member or designing the tightening allowance of the seal lip 32. be able to.

  In the above embodiment, the clutch piston 1 is a bonded piston seal having a canceller 12. However, the present invention may be applied to a clutch piston that does not have a canceller, that is, a clutch piston that is not a bonded piston seal.

1 Clutch piston 2 Clutch housing 4 Clutch chamber 6 Multi-plate clutch 8 Piston chamber 9 Oil supply path 10 Piston 12 Canceller 14 Oil chamber 15 Oil supply path 16 Seal washer 18 Return spring 26 Stopper 20 Outer piston seal member 22 Inner piston seal member 24 Canceller seal member 30 Base 32 Seal lip 20a, 22a, 22b, 24a Extension 34 Corner 36 Wall 38 Front 40 Oil surface 42 Air surface 44 Point 46 Rear surface

Claims (5)

A piston that reciprocates in a piston chamber into which oil flows;
A seal member that seals oil in the piston chamber, and has a base attached to the piston and a seal lip that slides against the wall surface of the piston chamber when the piston reciprocates. A sealing member,
The seal lip has an oil surface adjacent to the wall surface and in contact with the oil, and an air surface adjacent to the wall surface and in contact with air,
An angle θ _{1 of the} oil surface with respect to the wall surface is smaller than an angle θ _{2 of the} air surface with respect to the wall surface. The seal lip protrudes toward the back of the piston chamber in the moving direction of the piston from the base, and the tip end of the seal lip where the oil surface and the air surface intersect each other is more than the base. It is arranged at the back of the piston chamber in the moving direction,
The oil surface is arranged at the back of the piston chamber in the moving direction of the piston than the air surface,
A distance δ between the base in the moving direction of the piston and the tip is between a point farthest from the base of the seal lip in the moving direction of the piston and the tip of the seal lip. clutch piston according to claim 1, wherein less than the distance L _1. The oil surface is arranged at the back of the piston chamber in the moving direction of the piston than the air surface,
The distance δ ₁ between the root of the air surface in the moving direction of the piston and the tip of the seal lip where the oil surface intersects the air surface is the base of the seal lip in the moving direction of the piston. 3. The clutch piston according to claim 1, wherein the clutch piston is smaller than a distance L ₁ between a point farthest from the point and the tip end portion of the seal lip. A canceller facing the piston and defining an oil chamber between the piston,
A further sealing member that seals oil in the oil chamber, and slides against a base portion attached to the canceller and an inner wall surface forming the oil chamber of the piston when the piston reciprocates. A further sealing member having a further sealing lip to
The further seal lip has an oil surface adjacent to the inner wall and in surface contact with the oil, and an air surface adjacent to the inner wall and in contact with air,
Angle theta ₁ of the oil surface for the inner wall surface, a clutch piston according to any one of claims 1 to 3, characterized in that the smaller than the angle theta ₂ of the air plane with respect to the inner wall surface. A piston that reciprocates in a piston chamber into which oil flows;
A canceller facing the piston and defining an oil chamber between the piston,
A seal member for sealing oil in the oil chamber, and slides with respect to an inner wall surface forming the oil chamber of the piston when the piston reciprocates with a base portion attached to the canceller. A seal member having a seal lip;
The seal lip has an oil surface adjacent to the inner wall and in contact with the oil, and an air surface adjacent to the inner wall and in contact with air.
The clutch piston according to claim ₁ , wherein an angle θ _{1 of the} oil surface with respect to the inner wall surface is smaller than an angle θ _{2 of the} air surface with respect to the inner wall surface.

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