JP5530142B2 - Piston seal structure - Google Patents

Description

  The present invention relates to an improvement in a seal structure of a piston portion.

  Conventionally, this type of piston part seal structure is embodied, for example, in a piston part of a shock absorber for a vehicle and is slidably inserted into a cylinder to divide the cylinder into two liquid chambers. And a piston ring that is attached to the outer periphery of the piston and slidably contacts the inner periphery of the cylinder to seal between the piston and the cylinder.

  And, when using an annular piston ring that does not have a joint, there is one that pressurizes and attaches a heated piston ring to the outer periphery of the piston, and in the seal structure configured in this way, Residual stress is generated and one end of the piston ring is warped toward the cylinder. Therefore, the outer peripheral edge of the one end is cut to reduce the residual stress, thereby reducing the contact surface pressure with the cylinder and reducing sliding friction. (For example, refer to Patent Document 1).

  When a piston ring having a joint is used, the piston ring is constituted by a pair of seal rings provided with a joint, and these are overlapped in the axial direction and mounted in an annular groove provided on the outer periphery of the piston. Some of the facing surfaces of these seal rings are provided with stepped portions or slopes so that the ring joints do not coincide with each other in the circumferential direction (see, for example, Patent Documents 2 and 3).

JP 2006-17233 A Japanese Utility Model Publication No. 01-75638 Japanese Utility Model Publication No. 06-47770

  The above-described piston part sealing structure disclosed in Japanese Patent Application Laid-Open No. 2006-17233 does not cause any problem in terms of function. However, although the contact surface pressure with the cylinder is reduced to reduce sliding friction, one end of the piston ring is used. When the piston is displaced with respect to the cylinder, the one end may scratch the oil film on the inner periphery of the cylinder, and further reduction of sliding friction is desired. Since one end of the piston ring is warped, the sliding friction differs in the direction of displacement of the piston with respect to the cylinder, which makes it difficult to tune the characteristics of the generated damping force of the shock absorber to which the seal structure is applied.

  Also, the piston seal structure disclosed in Japanese Utility Model Laid-Open No. 01-75638 and Japanese Utility Model Laid-Open No. 06-47770 is applied to a shock absorber interposed between a vehicle body and an axle. In this case, when the piston is displaced in a tilted state with respect to the cylinder due to lateral force acting on the shock absorber or a change in the suspension geometry, the edge of the end of the piston ring is strongly pressed against the inner periphery of the cylinder and the oil film is blocked. There is a place where it is not stable because it is scraped off and the sliding friction increases.

  Accordingly, the present invention has been developed to improve the above-described problems, and an object of the present invention is to provide a piston structure sealing structure that can stabilize sliding friction while reducing sliding friction. .

In order to solve the above-described object, the problem-solving means in the present invention includes a piston that is inserted into a cylinder and divides the inside of the cylinder into two liquid chambers, and an annular groove provided on the outer periphery of the piston. In a piston part seal structure including a piston ring that slides in contact with the periphery and seals between the piston and the cylinder, the piston ring includes a pair of seal rings arranged along the axial direction in the annular groove. Is opposed to the inner circumference of the piston and is provided with an annular bottom having a central smooth surface in surface contact with the smooth annular inner circumferential surface of the piston ring, and provided at both ends in the axial direction and away from the cylinder at the end of the piston ring. An annular relief groove that allows escape in the direction is provided.

According to the seal structure of the piston portion of the present invention, even when the piston is inclined with respect to the cylinder , the clearance grooves are provided at both ends which are the upper and lower ends of the annular groove, Since the upper end and the lower end of the other seal ring escape into the corresponding relief grooves, the end of each seal ring is strongly pressed against the cylinder, and the contact surface pressure between the piston ring and the cylinder does not become excessive. Since the piston ring does not scrape off the liquid film adhering to the inner periphery of the cylinder, it can be stabilized while reducing sliding friction.

  Therefore, by applying this seal structure to a shock absorber used for vehicle suspension applications, it is possible to improve the riding comfort in the vehicle by causing the shock absorber to exert a damping force with little influence of the sliding friction. The seal structure is suitable for a vehicle shock absorber.

  Further, in the case of the seal structure of the piston portion, since the configuration in which only one end of the piston ring is warped is not adopted, the sliding friction does not change even if the piston is displaced in any direction with respect to the cylinder.

  Even if the piston ring thermally expands due to the operation of the shock absorber or the temperature change of the atmosphere surrounding the shock absorber, the volume increase due to the expansion is released to the relief groove, thereby reducing the contact surface pressure with the cylinder. It is possible to reduce the rise.

It is sectional drawing in the piston part which embodied the seal structure of the piston part in one Embodiment. It is a partial expanded sectional view of the piston part which embodied the seal structure of the piston part in one embodiment. It is a perspective view of the piston ring which embodied the seal structure of the piston part in one embodiment.

  Hereinafter, the seal structure of the piston portion of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, the seal structure of the piston part in one embodiment is embodied in the piston part 1 of the shock absorber. Specifically, in this example, the piston part is inserted into the cylinder 6. The piston 2 that divides the inside of the cylinder 6 into two liquid chambers R1 and R2 and the annular groove 2b provided on the outer periphery of the piston 2 are slidably contacted with the inner periphery of the cylinder 6 and between the piston 2 and the cylinder 6 It is embodied in a piston part 1 with a piston ring 3 for sealing.

Hereinafter, each part of the seal structure of the piston part 1 will be described. First, as shown in FIGS. 1 and 2, the piston 2 includes a disc-shaped piston body 2a, an annular groove 2b provided on the outer periphery of the piston body 2a, and annular rings provided at both ends of the annular groove 2b in the axial direction. The relief grooves 21b and 21c are provided. Specifically, the annular groove 2b is formed with an annular bottom 21a having a smooth surface facing the inner periphery of the cylinder 6 and depths at both ends of the upper and lower ends of the annular groove 2b in FIG. 2 deeper than the bottom 21a. The escape grooves 21b and 21c, the side wall 21d formed by a step between the upper end of the escape groove 21b in FIG. 2 and the outer periphery of the piston body 2a, and the lower end of the escape groove 21c in FIG. 2 and the outer periphery of the piston body 2a. And a side wall 21e formed of a stepped portion therebetween. The escape grooves 21b and 21c gradually increase in depth from the bottom 21a on the center side of the annular groove 2b, and are provided with tapered surfaces 21f and 21g on the bottom 21a side.

  In the case of this embodiment, the piston 2 has ports 2c and 2d that penetrate the piston body 2a and communicate the two liquid chambers R1 and R2 in addition to the above-described configuration. 1, leaf valves 4 and 5 stacked on the upper and lower ends can generate a damping force by giving resistance to the flow of liquid passing through the ports 2c and 2d.

  On the other hand, a shock absorber to which the piston portion 1 embodying the seal structure is applied is well known and will not be described in detail, but specifically, for example, the cylinder 6 and the upper end of the cylinder 6 are sealed. A head member (not shown), a piston rod 7 slidably passing through the head member (not shown), a piston 2 fixed to the tip of the piston rod 7, and a piston 2 in the cylinder 6 1, the upper liquid chamber R1 and the lower liquid chamber R2, a sealing member (not shown) for sealing the lower end of the cylinder 6, and a cylinder corresponding to the volume of the piston rod 7 protruding and retracting from the cylinder 6. A reservoir or an air chamber (not shown) that compensates for changes in the internal volume is provided, and the cylinder 6 is filled with a working liquid, specifically, for example, working oil.

  In the shock absorber, when the piston 2 moves up and down in FIG. 1 with respect to the cylinder 6, the hydraulic oil flows between the liquid chamber R1 and the liquid chamber R2 via the ports 2c and 2d. The hydraulic oil flow is given resistance by the leaf valves 4 and 5 corresponding to the ports 2c and 2d to generate a predetermined pressure loss, thereby generating a damping force.

  In this embodiment, the piston ring 3 includes a pair of seal rings 8 and 9 each having a joint 8a and 9a. When the seal rings 8 and 9 are mounted in the annular groove 2b of the piston 2 by the joints 8a and 9a, the seal rings 8 and 9 can be mounted while expanding their diameters. It can be attached to 2b. The seal rings 8 and 9 can be made of a material such as resin or synthetic resin, for example.

  In addition, although this seal ring 8 and 9 is provided with the joints 8a and 9a along an axial direction, you may provide the joints 8a and 9a inclining with respect to an axial direction, and the middle of the joints 8a and 9a. A stepped portion may be provided. Further, when the piston ring 3 is an annular ring having no joint, the piston main body 2a is a piece having an upper side wall 21b and a piece having a lower side wall 21c of the annular groove 2b in FIG. It can also be set as the structure divided | segmented into two upper and lower sides, and can also be set as the structure which pinches the piston ring 3 with these pieces.

Further, the upper and lower ends of the piston ring 3, in this case, the upper end 8 b of the seal ring 8 and the lower end 9 b of the seal ring 9 are in contact with the seal rings 8, 9, respectively, and the side walls 21 d of the annular grooves 2 b facing each other. It is good to contact 21e. By doing so, it is possible to prevent the seal rings 8 and 9 from playing in the axial direction in the annular groove 2b and generating sound. As a reference example, when the piston ring 3 is a single annular piston ring, both ends of the piston ring 3 may be brought into contact with the side walls 21d and 21e.

The seal rings 8 and 9 are arranged in the axial direction as shown in FIGS. 1 to 3 and the joints 8a and 9a are shifted in the circumferential direction. In a state shifted 180 degrees in the circumferential direction, the piston 2 is mounted in the annular groove 2b , and the annular smooth inner peripheral surface is brought into surface contact with the bottom 21a of the annular groove 2b . The piston 2 and the cylinder 6 are sealed in sliding contact with the circumference.

  When the piston ring 3 is mounted in the annular groove 2b of the piston 2 as described above, the inner periphery of the upper end 8b of the seal ring 8 disposed on the upper side in FIG. 1, which is the upper end of the piston ring 3, faces the escape groove 21b. The inner periphery of the lower end 9b of the seal ring 9 disposed on the lower side in FIG. 1, which is the lower end of the piston ring 3, faces the escape groove 21c.

  In the piston portion 1 configured as described above, the piston ring 3 mounted in the annular groove 2 b provided on the outer periphery of the piston 2 is in sliding contact with the inner periphery of the cylinder 6. And the fluid chambers R1 and R2 are prevented from communicating with each other through the piston 2 and the cylinder 6.

  Further, since the seal rings 8 and 9 constituting the piston ring 3 are mounted in the annular groove 2b of the piston 2 in a state where the joints 8a and 9a are shifted in the circumferential direction, the liquid chambers R1 and R1 are interposed through the joints 8a and 9a. Communication with R2 is also prevented.

  In order to reliably prevent the joints 8a and 9a from matching, for example, the side walls 21d and 21e or the bottom 21a of the annular groove 2b of the piston 2 enter the joints 8a and 9a to the piston 2 of the seal rings 8 and 9 with respect to the piston 2. Protrusions that prevent circumferential rotation may be provided and used as blocking means for blocking the coincidence of the joints 8a and 9a. Also, the seal rings 8 and 9 are prevented from moving relative to each other in the circumferential direction. A recessed portion in which an inclined surface is provided at an end portion of the facing surfaces of 8 and 9 facing each other, or a protruding portion that protrudes toward one of the opposite ends of the seal rings 8 and 9 is provided, and the protruding portion enters the other These may be used as blocking means for reliably blocking the coincidence of the joints 8a and 9a.

  When the blocking means is provided in this way, the matching of the joints 8a and 9a in the circumferential direction can be prevented, so that the piston ring 3 is used as the seal rings 8 and 9 having the pair of joints 8a and 9a, and the annular groove 2b of the piston 2 is used. The liquid chambers R1 and R2 can be prevented from communicating with each other and can be sealed tightly while being easily mounted.

  When the piston 2 is displaced in the vertical direction in FIG. 1 with respect to the cylinder 6, a bending moment is applied to the shock absorber by a lateral force (lateral force), or the geometry changes in the suspension in which the shock absorber is incorporated. Even if the piston 2 is inclined with respect to the cylinder 6, relief grooves 21b and 21c are provided at both ends of the upper and lower ends of the annular groove 2b, which are indicated by broken lines in FIG. Thus, since the upper end 8b of the seal ring 8 and the lower end 9b of the seal ring 9 escape into the corresponding relief grooves 21b and 21c, the end portions 8b and 9b of the seal rings 8 and 9 are strongly pressed against the cylinder 6 The contact surface pressure with 6 does not become excessive.

  At the time of the relief deformation of the seal rings 8 and 9, the seal rings 8 and 9 are deformed with the edge of the boundary between the relief grooves 21b and 21c and the bottom 21a as a fulcrum, but both the relief grooves 21b and 21c are annular grooves. Since the taper surfaces 21f and 21g are provided on the center side of 2b, the edge at the deformation fulcrum of the seal rings 8 and 9 becomes an obtuse angle, and an unreasonable load is applied to the back surface that becomes the side surface of the bottom 21a of the seal rings 8 and 9, This prevents the seal rings 8 and 9 from deteriorating. If the edge is rounded, the seal rings 8 and 9 can be further prevented from deteriorating.

  Further, the escape deformation of the seal rings 8 and 9 in the piston ring 3 allows the liquid to enter between the cylinder 6 and the end portions 8 b and 9 b of the seal rings 8 and 9, and adheres to the inner periphery of the cylinder 6. The liquid film is not scraped off.

  Thus, in the seal structure of the piston portion 1 of the present invention, even when the piston 2 is inclined with respect to the cylinder 6, the contact surface pressure between the piston ring 3 and the cylinder 6 becomes excessive. Since the piston ring 3 does not scrape off the liquid film adhering to the inner periphery of the cylinder 6, it is possible to stabilize the sliding friction while reducing the sliding friction.

  Therefore, by applying this seal structure to a shock absorber used for vehicle suspension applications, it is possible to improve the riding comfort in the vehicle by causing the shock absorber to exert a damping force with little influence of the sliding friction. The seal structure is suitable for a vehicle shock absorber.

  Further, in the case of the seal structure of the piston portion 1, since the configuration in which only one end of the piston ring 3 is warped is not adopted, the sliding movement is not caused even if the piston 2 is displaced in any of the upper and lower directions in FIG. There is no change in dynamic friction, and the tuning of the damping characteristics is easy.

  Further, even if the piston ring 3 is thermally expanded due to the operation of the shock absorber or the temperature change of the atmosphere surrounding the shock absorber, the cylinder 6 is released by letting the volume increase due to the expansion escape to the escape grooves 21b and 21c. It is possible to reduce an increase in contact surface pressure with the. Specifically, if the piston ring 3 is set so as to be able to seal by sliding against the inner periphery of the cylinder 6 at the lower limit of the temperature at which the shock absorber to which the seal structure is applied is used, it is higher than this lower limit. At the temperature, the piston ring 3 expands more than the lower limit temperature. In this case, since the piston ring 3 is composed of the seal rings 8 and 9, each seal ring 8 and 9 expands. Can escape to the escape grooves 21b and 21c.

  Further, by selecting the piston ring 3 as the seal rings 8 and 9 having the joints 8a and 9a, the material of the seal rings 8 and 9 is selected as compared with the seal structure in which the piston ring is heated and pressurized on the outer periphery of the piston. The width can be increased and the degree of freedom in design can be improved.

  In the above description, the example in which the seal structure of the piston portion 1 is embodied in the piston portion of a shock absorber for a vehicle is described. However, the seal structure is a cylinder that functions as an actuator other than the shock absorber. It is also possible to apply to other hydraulic devices such as devices.

 This is the end of the description of the embodiment of the seal structure of the piston portion 1, but the scope of the present invention is not limited to the details shown or described.

The present invention can be used, for example, in a piston portion of a shock absorber.

DESCRIPTION OF SYMBOLS 1 Piston part 2 Piston 2a Piston main body 2b Annular groove | channel 2c, 2d Port 3 Piston ring 4,5 Leaf valve 6 Cylinder 7 Piston rod 8,9 Seal ring 8a, 9a Joint 8b in a seal ring Upper end 9b of a seal ring Lower end of a seal ring 21a Bottom portion 21b, 21c Escape groove 21d, 21e Side wall 21f, 21g Tapered surface R1, R2 Liquid chamber

Claims (4)

A piston that is inserted into the cylinder and divides the inside of the cylinder into two liquid chambers, and a piston ring that is mounted in an annular groove provided on the outer periphery of the piston and that slides on the inner periphery of the cylinder and seals between the piston and the cylinder The piston ring is provided with a pair of seal rings arranged in the axial direction in the annular groove, and the annular groove is opposed to the inner periphery of the cylinder and has a smooth annular shape inside the piston ring . An annular bottom having a central smooth surface in surface contact with the peripheral surface and an annular relief groove provided at both ends in the axial direction and allowing escape in the direction away from the cylinder at the end of the piston ring. A seal structure of the piston part characterized by this. 2. The piston part seal structure according to claim 1, wherein the escape groove has a tapered surface whose depth gradually increases from the center side of the annular groove. 3. 3. The seal structure for a piston portion according to claim 1 or 2, wherein each seal ring is provided with an abutment, and the abutment of these seal rings is shifted in the circumferential direction and mounted in an annular groove of the piston. 4. The piston part sealing structure according to claim 3, further comprising blocking means for blocking matching of the seal ring joints.

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