JP2010019325A - Sealing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep a fictional resistance to the minimum by decreasing a contact area of a lip while securing a surficial pressure of a lip of a sealing member for contacting an outer peripheral surface of a rod. <P>SOLUTION: In a cross-sectional shape along an axis line of the lip 28c of the sealing member 28, an axial length of the shape increases from an apical end A of an inside of a radial direction to two basal portions B, C of an outside of the radial direction. Hence, a compressed amount of the lip 28c in contact with the rod is secured to hold a surficial pressure of a contact surface at a high level while certainly preventing a liquid from leaking from a liquid chamber, an increase in contact surface area is minimized to permit a frictional force of the lip 28c to be reduced. Additionally, in the lip 28c, a space 30 is formed which is depressed more to the outside of the radial direction than to an inner circumferential surface of a guide hole 20a. Therefore, when a crosswise force is applied to the rod to excessively compress the lip 28c, a portion of the lip 28c is allowed to escape to the space 30 to prevent the surficial pressure of the lip 28c from excessively increasing, thus permitting the frictional force of the rod to be kept low. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  According to the present invention, a rod is slidably fitted into a guide hole formed in a rod guide, and an annular seal member lip mounted in a seal groove formed in the inner peripheral surface of the guide hole is formed on the outer peripheral surface of the rod. The present invention relates to a sealing device that seals a liquid chamber partitioned on one end side in the axial direction of the sealing member by sliding contact.

Patent Document 1 below describes a variable damping force damper for a vehicle using a magnetorheological fluid whose viscosity changes due to magnetic action. This variable damping force damper allows a piston rod connected to a piston fitted to a cylinder filled with magnetorheological fluid to slidably pass through a rod guide that closes the end of the cylinder, and to the inner peripheral surface of the rod guide. The provided seal member is brought into sliding contact with the outer peripheral surface of the piston rod to prevent leakage of the magnetorheological fluid.
US Pat. No. 6,883,649

  By the way, a high contact surface pressure is required for a sealing member that suppresses leakage of a magnetorheological fluid or magnetic fluid sealed in a high pressure state in a liquid chamber in order to ensure sealing performance. It is necessary to reduce the frictional force by making the contact area with the sliding counterpart member as small as possible.

  The present invention has been made in view of the above-mentioned circumstances, and while ensuring the surface pressure of the lip of the sealing member that contacts and seals the outer peripheral surface of the rod, the frictional resistance is minimized by reducing the contact area of the lip. The purpose is to suppress.

  In order to achieve the above object, according to the first aspect of the present invention, the seal groove is formed on the inner peripheral surface of the guide hole by slidably fitting the rod into the guide hole formed in the rod guide. In a sealing device that seals the liquid chamber partitioned on one end side in the axial direction of the seal member by sliding the lip of the annular seal member attached to the outer peripheral surface of the rod along the axis of the lip of the seal member The cross-sectional shape in the direction increases in the axial length from the radially inner tip to the two radially outer bases, and is adjacent to the base of the two bases opposite to the liquid chamber. Thus, a sealing device is proposed in which a space is formed that is recessed radially outward from the inner peripheral surface of the guide hole.

  According to the invention described in claim 2, in addition to the configuration of claim 1, the sectional shape in the direction along the axis of the lip of the seal member is such that the tip portion and the two base portions form a substantially triangular shape. A sealing device is proposed which is characterized by:

  According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, a sealing device is proposed in which the space is formed in an annular shape so as to surround the axis. .

  According to the invention described in claim 4, in addition to the configuration of any one of claims 1 to 4, the seal member is radially inward on the opposite side of the lip across the space. There is proposed a sealing device including an annular protrusion protruding in a direction, and the radially inner end of the annular protrusion is located radially outside the tip end of the lip.

  According to the invention described in claim 5, in addition to the configuration of any one of claims 1 to 4, the seal member is provided between the space and the step portion of the seal groove. There is proposed a sealing device that includes a backup ring that is harder than the seal member, and that the radially inner end of the backup ring is located radially outside the tip of the lip.

  According to the invention described in claim 6, in addition to the configuration of any one of claims 1 to 5, the liquid chamber is filled with a magnetorheological fluid or magnetic fluid containing metal fine particles. There is proposed a sealing device characterized in that.

  The piston rod 13 of the embodiment corresponds to the rod of the present invention, the second liquid chamber 16 of the embodiment corresponds to the liquid chamber of the present invention, and the piston rod guide 20 of the embodiment corresponds to the rod of the present invention. Corresponds to the guide.

  According to the configuration of the first aspect, the cross-sectional shape in the direction along the axis of the lip of the sealing member increases in the axial direction from the radially inner tip to the two radially outer bases. The lip that contacts the outer peripheral surface of the lip is secured by maintaining a high pressure on the contact surface, ensuring that the liquid does not leak from the liquid chamber, while minimizing the increase in the area of the contact surface. The frictional force can be reduced. In addition, since the lip is formed with a space that is recessed radially outward from the inner peripheral surface of the guide hole, when lateral force acts on the rod and the lip is compressed excessively, the lip flesh escapes into the space and the lip The surface pressure can be prevented from excessively increasing, and the frictional force of the lip can be kept low.

  According to the second aspect of the present invention, since the tip portion of the lip and the two base portions form a substantially triangular shape in the cross-sectional shape along the axis of the lip of the seal member, the rod increases as the amount of compression of the lip increases. The contact area with the outer peripheral surface can be gradually increased, and sudden change in frictional force can be prevented.

  According to the third aspect of the present invention, since the space of the seal member is formed in an annular shape so as to surround the axis, the surface pressure of the lip contacting the rod is made uniform over the entire area in the circumferential direction, thereby further improving the sealing performance. Can do.

  According to the fourth aspect of the present invention, the sealing member includes the annular protrusion protruding radially inward on the opposite side of the lip across the space, and the radially inner end of the annular protrusion is more than the front end of the lip. Since it is positioned radially outward, when the lip is compressed by the rod, the annular protrusion can function as a stopper to suppress excessive deformation of the lip and minimize an increase in frictional force.

  According to the fifth aspect of the present invention, the backup ring that is harder than the seal member is provided between the space of the seal member and the step portion of the seal groove, and the radially inner end of the backup ring has a diameter larger than that of the tip portion of the lip. Because it is located on the outside in the direction, the lip is prevented from being strongly compressed by bringing the inner surface of the backup ring into contact with the outer surface of the rod when a strong lateral force is applied to the rod. It is possible to prevent excessive force.

  According to the sixth aspect of the present invention, since the lip of the seal member contacts the rod with a sufficiently high surface pressure, the lip and the rod of the lip and the rod can be sealed even if a magnetorheological fluid containing metal fine particles or a magnetic fluid is sealed in the liquid chamber. It is possible to prevent the metal fine particles from entering the sliding surface and to effectively prevent the rod from being worn.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 to 9 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a variable damping force damper, FIG. 2 is an enlarged view of part 2 of FIG. 1, and FIG. 4 is an enlarged view of 4 parts of FIG. 1, FIG. 5 is a sectional view around the piston of the variable damping force damper, FIG. 6 is an explanatory view of the action when the piston is assembled, and FIG. 7 is 7 part of FIG. FIG. 8 is an enlarged view of a portion 8 in FIG. 4, and FIG. 9 is an explanatory view of the operation of the seal member.

  As shown in FIG. 1, a variable damping force damper D used in a vehicle suspension device is connected to a suspension arm (not shown) through a rubber bush joint 11 and an open cylinder 12 and a vehicle body (not shown). And a piston rod 13 fitted to the cylinder 12. A piston 14 slidably fitted to the inner peripheral surface of the cylinder 12 is fixed to the tip of the piston rod 13, and the first liquid chamber 15 and the second liquid chamber 16 are defined on both sides in the axis L direction of the piston 14. Is done. Magneto-rheological fluids (MRF: Magneto-Rheological Fluids) are sealed in the first and second liquid chambers 15 and 16. A magnetorheological fluid is a fluid in which micro-scale iron particles are mixed, and has a property that the viscosity changes when magnetism acts. A free piston 17 is slidably fitted between the first liquid chamber 15 and the closed end of the cylinder 12 via a seal member 18, and high-pressure gas flows on the side of the free piston 17 opposite to the first liquid chamber 15. The sealed gas chamber 19 is partitioned.

  The open end of the cylinder 13 on the second liquid chamber 16 side is closed by a piston rod guide 20, and the piston rod 13 is slidably fitted into a guide hole 20 a formed in the piston rod guide 20. A stopper 21 made of an elastic material is fixed to the piston rod 13 located in the second liquid chamber 16, and the stopper 21 abuts on the piston rod guide 20, thereby restricting the extension end of the piston rod 13 from the cylinder 12. Is done.

  As apparent from FIG. 2, the piston rod guide 20 is fitted to the inner peripheral surface of the open end of the cylinder 12, and the holder 22 fitted to the outer peripheral surface of the open end of the cylinder 12 is connected to the cylinder 12 and the piston rod guide. It is fixed by caulking 23 together with 20. A stopper abutting plate 24 with which the stopper 21 abuts is fixed to the end of the piston rod guide 20 facing the second liquid chamber 16. A protection plate 25 that protects the portion is fixed to the holder 22 that wraps around the end of the cylinder 12.

  A seal member 26 that seals between the inner peripheral surface of the cylinder 12 and the seal groove 20 b formed on the outer peripheral surface of the piston rod guide 20 is mounted. Further, a seal member 28 that prevents liquid leakage from the second liquid chamber 16 side is attached to a seal groove 20c that is open at one end and formed on the inner peripheral surface of the piston rod guide 20 on the second liquid chamber 16 side. A seal member 29 that prevents dust from entering the second liquid chamber 16 is attached to a seal groove 20 d that is open at one end formed on the inner peripheral surface of the guide 20 on the side opposite to the second liquid chamber 16.

  FIG. 3 shows the sectional shape of the seal member 28 mounted in the seal groove 20b on the inner peripheral surface of the piston rod guide 20 on the second liquid chamber 16 side in the free state (the axis L of the cylinder 12 and the piston rod 13 is shown). A longitudinal sectional shape cut by a plane passing through) is shown. In the drawing, the upper side is the radially outer side with respect to the axis L, and the lower side is the radially inner side with respect to the axis L.

  The seal member 28 made of nitrile rubber has an outer peripheral surface 28a that contacts the bottom portion 20e of the seal groove 20b and an end surface 28b that contacts the step portion 20f of the seal groove 20b, and is opposite to the outer peripheral surface 28a. An annular lip 28c having a triangular cross section protruding radially inward is formed, and an annular U groove 28d recessed in a U shape in the direction of the axis L is formed on the opposite side of the end face 28b. The lip 28c is provided with a tip A that protrudes most inward in the radial direction and two bases B and C on both sides in the axis L direction. The position of the base B on the end face 20b side is the guide of the piston rod guide 20 The distance d0 enters the outer side in the radial direction with respect to the hole 20a. Accordingly, an annular space 30 (a portion shown by shading) is formed in the vicinity of the base B of the lip 28c with respect to a line obtained by extending the guide hole 20a of the piston rod guide 20 in the axis L direction.

  In a state where the piston rod 13 is inserted through the guide hole 20a of the piston rod guide 20, the lip 28c of the seal member 28 is compressed radially outward and is brought into close contact with the outer peripheral surface of the piston rod 13, and as shown in FIG. Demonstrate.

  As shown in FIGS. 4 and 5, the piston 14 has a thick cylindrical piston main body 31 in which the insertion hole 31 a is fitted to the small diameter portion 13 a at the tip of the piston rod 13, and the small diameter portion 13 a of the piston rod 13. A washer 32 that contacts the stepped portion 13b, a disc-shaped first side cover 34 fixed to one end face of the piston body 31 with bolts 33, and the other end face of the washer 32 and the piston body 31. A disc-shaped second side cover 35 and an outer ring 36 fitted to the outer periphery of the piston body 31 and supported by the first and second side covers 34 and 35 at both ends in the axis L direction.

  The first side cover 34 has a plurality of (four in the embodiment) arcuate openings 34a arranged along the outer periphery thereof. The second side cover 35 has a plurality of arc-shaped (four in the embodiment) openings 35a arranged along the outer peripheral portion thereof, and a center that fits with the outer periphery of the piston rod 13 with a gap. And a hole 35b. An annular throttle 37 is formed between the outer peripheral surface of the piston body 31 and the inner peripheral surface of the outer ring 36, and one end of the annular throttle 37 passes through the opening 34 a of the first side cover 34 to form the first liquid chamber. 15, and the other end of the annular throttle 37 communicates with the second liquid chamber 16 through the openings 35 a of the second side cover 35.

  A coil support groove 31b is formed on the outer peripheral surface of the piston body 31 facing the inner peripheral surface of the annular throttle 37, and the resin member 39 in which the coil 38 is embedded is held so as to be fitted in the coil support groove 31b. A harness guide portion 39a extending radially inward from the resin member 39 is fitted to the tip of the piston rod 13 via a seal member 40, and a harness 41 extending from the coil 38 is connected to the inside of the harness guide portion 39a and the piston. The rod 13 is guided to the outside through the shaft hole 13c penetrating the center of the rod 13 along the axis L.

  A partial conical inclined surface 31c and a cylindrical parallel surface 31d are connected to the end of the insertion hole 31a of the piston body 31 on the second side cover 35 side, and the parallel surface 31c is the second side cover 35. Opposite the central hole 35b.

  As shown in an enlarged view in FIG. 8, an annular second annular groove 31e is formed on the inner circumferential surface of the insertion hole 31a of the piston body 31, and an annular outer circumferential surface of the piston rod 13 that faces the second annular groove 31e. The first annular groove 13d is formed. Then, an elastic C-ring 42 having a cut at one place in the circumferential direction is fitted so as to straddle the second annular groove 31e and the first annular groove 13d.

  The cross-sectional shape of the second annular groove 31e of the piston body 31 is a quadrangle with rounded bottom corners. However, as shown in FIG. 7, the cross-sectional shape of the first annular groove 13d of the piston rod 13 is the piston rod on the other end side. 13 has a first wall surface a that forms an obtuse angle α with respect to the outer peripheral surface of the piston 13, while a second wall surface b that is perpendicular to the outer peripheral surface of the piston rod 13 has one end thereof. Furthermore, a non-press-fit surface c that gradually increases in diameter and continues to the outer peripheral surface of the piston rod 13 is formed at the radially outer end of the first wall surface a of the first annular groove 13d.

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  First, an operation when the piston 14 is assembled to the piston rod 13 will be described.

  The washer 32 is fitted to the small diameter portion 13 a of the piston rod 13 and brought into contact with the stepped portion 13 b, the elastic C ring 42 is fitted to the first annular groove 13 d of the piston rod 13, and a seal member is attached to the tip of the piston rod 13. The piston rod 13 in this state is inserted into the insertion hole 31a of the piston body 31 of the piston 14 assembled in advance as a subassembly (see FIG. 6).

  Since the distal end portion of the piston rod 13, that is, the distal end portion 13d '(see FIG. 7) closer to the distal end than the first annular groove 13d has a smaller diameter than the small diameter portion 13a, the distal end portion 13d' It can be easily inserted into the insertion hole 31a of the 31 by a clearance fit. In the process, when the elastic C-ring 42 locked in the first annular groove 13d of the piston rod 13 reaches the opening end of the parallel surface 31d of the piston body 31, the elastic C-ring 42 is brought into contact with the parallel surface 31d to be reduced in diameter. It is squeezed inward in the direction and securely fits inside the parallel surface 31d. When the piston rod 13 is further inserted, the elastic C-ring 42 is guided by the inclined surface 31c connected to the parallel surface 31d and is further compressed inward in the radial direction, and is inserted into the first annular groove 13d of the piston rod 13 inside. Fully stowed. As a result, the piston rod 13 can be inserted into the insertion hole 31 a of the piston body 31 without being obstructed by the elastic C ring 42.

  Since the outer diameter of the small diameter portion 13a of the piston rod 13 is slightly larger than the inner diameter of the insertion hole 31a of the piston main body 31, the piston rod 13 is inserted into the insertion hole 31a by press fitting. At this time, the press-fitting can be performed smoothly by the action of the non-press-fitting surface c (see FIG. 7) connected to the first annular groove 13d of the piston rod 13.

  As shown in FIG. 7, if it is assumed that the inclined surface 31c of the piston body 31 extends to the end surface of the piston body 31 and there is no parallel surface 31d, the elasticity that tends to expand radially outward by its own elasticity. There is a possibility that the C-ring 42 falls out of the first annular groove 13d of the piston rod 13 and is pushed out of the piston main body 31 during the press-fitting process. However, according to the present embodiment, the elastic C ring 42 is compressed radially inward by the opening of the parallel surface 31d and held in the first annular groove 13d of the piston rod 13, so that the elastic C ring 42 is It is inserted into the insertion hole 31a of the piston body 31 without dropping from the first annular groove 13d.

  When the piston rod 13 is further press-fitted, the elastic C ring 42 expands by its own elasticity at the moment when the first annular groove 13d of the piston rod 13 coincides with the second annular groove 31e of the piston body 31, and the piston body 31 It fits in the second annular groove 31e (see FIG. 8). In this state, since the diameter of the elastic C-ring 42 is larger than the depth of the second annular groove 31e of the piston body 31, the elastic C-ring 42 has the second annular groove 31e of the piston body 31 and the first annular groove of the piston rod 13. The piston rod 13 is engaged with the piston main body 31 so that it cannot be pulled out.

  Further, in the press-fitting process of the piston rod 13, the tip end portion 13d '(see FIG. 7) of the piston rod 13 has a slightly small diameter and is fitted into the insertion hole 31a of the piston main body 31, so that the piston main body 31 is pressed by the press-fitting load. The second annular groove 31e is prevented from being deformed. Accordingly, the first annular groove 13d of the piston rod 13 and the second annular groove 31e of the piston body 31 can be opposed to each other with high accuracy, and the elastic C ring 42 can be reliably engaged therewith.

  Further, when the first annular groove 13d of the piston rod 13 faces the second annular groove 31e of the piston body 31 in the final stage of press-fitting, the piston body 31 is inserted on the rear side in the press-fitting direction of the first annular groove 13d of the piston rod 13. By providing the non-press-fit surface c smaller in diameter than the hole 31a, the outer peripheral surface of the piston rod 13 is prevented from deforming the corner on the rear side in the press-fit direction of the second annular groove 31e of the piston body 31. Can do. Accordingly, the first annular groove 13d of the piston rod 13 and the second annular groove 31e of the piston body 31 can be opposed to each other with high accuracy, and the elastic C ring 42 can be reliably engaged therewith.

  Next, the operation of the variable damping force damper D will be described.

  When the piston rod 13 is pushed into the cylinder 12 by the bumps of the suspension, the magnetoviscous fluid in the first liquid chamber 15 whose volume has been reduced becomes the opening 34a ... of the first side plate 34 of the piston 14, the annular throttle 37, and the second Through the openings 35a of the side plate 35, it flows into the second liquid chamber 16, and at that time, a damping force is generated by the flow resistance through which the magnetorheological fluid passes through the annular throttle 37. The increase in the volume of the piston rod 13 that has entered the first and second liquid chambers 15 and 16 is compensated by the decrease in the volume of the gas chamber 19 due to the advance of the free piston 17.

  When the piston rod 13 is pulled out from the inside of the cylinder 12 due to rebound of the suspension, the magneto-rheological fluid in the second liquid chamber 16 whose volume has been reduced becomes the opening 35a of the second side plate 35 of the piston 14,. Passing through the openings 34 a of the side plate 34 and flowing into the first liquid chamber 15, a damping force is generated by the flow resistance through which the magnetorheological fluid passes through the annular throttle 37. The decrease in the volume of the piston rod 13 that has escaped from the first and second liquid chambers 15 and 16 is compensated by the increase in the volume of the gas chamber 19 due to the retraction of the free piston 17.

  When the amount of energization to the coil 38 inside the piston 14 is increased when the magnetorheological fluid passes through the annular restrictor 37, the generated magnetic field becomes stronger, so that the viscosity of the magnetorheological fluid increases and passes through the annular restrictor 37. And the damping force increases. Conversely, if the amount of current supplied to the coil 38 inside the piston 14 is reduced, the generated magnetic field becomes weak, so that the viscosity of the magnetorheological fluid becomes low and easily passes through the annular throttle 37, and the damping force decreases. . Therefore, the damping force of the variable damping force damper D can be arbitrarily controlled by changing the energization amount to the coil 38.

  Next, the operation of the seal member 28 provided on the piston rod guide 20 will be described.

  In order to prevent the cavitation phenomenon from occurring in the magnetorheological fluid sealed in the first and second liquid chambers 15 and 16 when the piston 14 moves at a high speed inside the cylinder 12, high-pressure gas is introduced into the gas chamber 19. By encapsulating, high pressure is applied to the magnetorheological fluid. Therefore, the sealing member 28 provided in the piston rod guide 20 is required to have high sealing performance that prevents leakage of the magnetorheological fluid while suppressing an increase in frictional force.

  As shown in FIG. 3, the annular lip 28 c of the seal member 28 includes a distal end portion A that protrudes most inward in the radial direction and two base portions B and C on both sides in the axis L direction. An annular space 30 is formed when the position enters the radially outer side with respect to the inner peripheral surface of the piston rod guide 20 by a distance d0.

  9A shows a state in which the seal member 28 is in a free state, FIG. 9B shows a case in which the lip 28c of the seal member 28 is weakly pressed against the outer peripheral surface of the piston rod 13, and FIG. 28 shows a state in which the lip 28c of 28 is strongly pressed against the outer peripheral surface of the piston rod 13. As described above, when the lateral force (radial force) of the piston rod 13 increases, the amount of compression of the lip 28c of the seal member 28 gradually increases. Since the surface pressure at which the lip 28c is pressed against the outer peripheral surface of the piston rod 13 is proportional to the compression amount of the lip 28c, the surface pressure is insufficient unless the compression amount is sufficiently secured, and the magnetorheological fluid passes through the lip 28c. There is a possibility of leakage. At this time, when the contact area between the outer peripheral surface of the lip 28c and the piston rod 13 becomes excessive because the compression amount of the lip 28c is increased to increase the surface pressure, the frictional resistance increases and the piston rod 13 smoothly slides. May be hindered.

  According to the present embodiment, since the lip 28c has a triangular cross section, even if the compression amount of the lip 28c is increased to ensure a sufficient surface pressure, the contact area is prevented from becoming excessive, and the sealing property is prevented. And low friction can be achieved. If the lip of the sealing member 28 has a quadrangular cross section, the contact area becomes larger than that of the lip 28c having a triangular cross section, and the frictional force increases even if the compression amount of the lip 28c is the same.

  In order to reduce the frictional force, the width in the direction of the axis L of the lip having a quadrangular cross section may be reduced. However, in this case, the lip collapses as the piston rod 13 slides, and the sealing performance is lost. There is a problem. On the other hand, in the present embodiment, since the lip 28c has a triangular cross section, the width in the axis L direction on the bases B and C side is large even if the width in the axis L direction near the tip end A is small. Therefore, it is possible to reliably prevent the lip 28c from falling.

  As shown in FIG. 9C, when a strong lateral force acts on the piston rod 13 and the lip 28 c is greatly compressed, a space 30 is formed between the lip 28 c and the step portion 20 f of the piston rod guide 20. Therefore, the pressure of the lip 28c pressed against the outer peripheral surface of the piston rod 13 can be prevented from excessively increasing due to the meat of the lip 28c of the seal member 28 being pushed into the space 30. It is possible to suppress an increase in the frictional force of the moving part. If the space 30 does not exist, there is no escape space for the meat of the lip 28c when the seal member 28 is strongly compressed. Therefore, the surface pressure at which the lip 28c is brought into pressure contact with the outer peripheral surface of the piston rod 13 is excessively increased. The frictional force of the moving part increases rapidly.

  As described above, according to the present embodiment, by devising the shape of the lip 28c of the sealing member 28, the surface area of the contact surface can be reduced while ensuring the surface pressure of the contact surface and preventing leakage of the magnetorheological fluid. It is possible to suppress the sliding resistance of the piston rod 13 to a minimum. In particular, since the magnetorheological fluid contains iron particles, if the iron particles enter between the lip 28c and the outer peripheral surface of the piston rod 13, problems such as premature wear of the piston rod 13 occur. Since the surface pressure of the contact surface of the lip 28c can be ensured, it is possible to effectively prevent the iron particles from entering the sliding surface.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  In the second embodiment, an annular protrusion 28e extending inward in the radial direction is formed on the side of the seal member 28 that contacts the step 20f of the piston rod guide 20. The position of the inner peripheral surface of the annular protrusion 28e coincides with the guide hole 20a of the piston rod guide 20, is located radially inward from the outer peripheral surface of the space 30, and radially outward from the tip A of the lip 28c. is there.

  Accordingly, when the lip 28c of the seal member 28 is compressed by the outer peripheral surface of the piston rod 13, the annular protrusion 28e acts as a stopper to suppress the deformation of the lip 28c, so that the surface pressure of the contact surface of the lip 28c is increased. Sealing performance can be ensured.

  Next, a third embodiment of the present invention will be described with reference to FIG.

  In the third embodiment, an annular backup ring 43 made of Teflon (registered trademark) or the like that is harder than the seal member 28 and has a smaller friction coefficient between the seal member 28 and the step portion 20f of the piston rod guide 20 is used. Is the one that is attached. The position of the inner peripheral surface of the backup ring 43 is radially inward from the guide hole 20a of the piston rod guide 20, and is radially outward from the tip A of the lip 28c. The space 30 of the seal member 28 is formed between the lip 28 c and the backup ring 43.

  Therefore, when the lip 28c of the seal member 28 is strongly compressed by the outer peripheral surface of the piston rod 13, the inner peripheral surface of the backup ring 43 contacts the outer peripheral surface of the piston rod 13 and prevents excessive compression of the lip 28c. Thus, it is possible to prevent a sudden increase in the frictional force between the lip 28c and the outer peripheral surface of the piston rod 13.

  Next, a fourth embodiment of the present invention will be described with reference to FIG.

  In the fourth embodiment, the first wall surface a of the first annular groove 13d of the piston rod 13 extends further to the rear than the rear end of the second annular groove 31e of the piston main body 31. The non-press-fit surface c (see FIG. 8) of the form is omitted.

  According to the shape of the first wall surface a of the fourth embodiment, the same effect as the non-press-fit surface c of the first embodiment is achieved, and the outer peripheral surface of the piston rod 13 is the first of the piston body 31. It is possible to prevent the corner portion on the rear side in the press-fitting direction of the two annular grooves 31e from being deformed.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention can perform a various design change in the range which does not deviate from the summary.

  For example, the application of the sealing device of the present invention is not limited to the variable damping force damper D of the embodiment.

  The variable damping force damper D of the embodiment uses a magnetorheological fluid, but the same effect can be obtained by using a magnetorheological fluid (a fluid mixed with nanoscale magnetic metal fine particles) instead of the magnetorheological fluid. Can be achieved.

  In the embodiment, the recess 30 of the seal member 28 is formed in an annular shape, but the recess 30 can be formed discretely in the circumferential direction.

1 is a longitudinal sectional view of a variable damping force damper according to a first embodiment. 2 enlarged view of FIG. Part 3 enlarged view of FIG. 4 enlarged view of FIG. Sectional view around the piston of the variable damping force damper Action diagram when assembling the piston 7 enlarged view of FIG. 8 enlarged view of FIG. Action diagram of the seal member The figure corresponding to the said FIG. 3 based on 2nd Embodiment. The figure corresponding to the said FIG. 3 based on 3rd Embodiment. The figure corresponding to the said FIG. 8 based on 4th Embodiment.

Explanation of symbols

13 Piston rod (rod)
16 Second liquid chamber (liquid chamber)
20 Piston rod guide (rod guide)
20a Guide hole 20c Seal groove 20f Step 28 Seal member 28c Lip 28e Annular projection 30 Space 43 Backup ring A Tip B Base C Base L Axis line

Claims (6)

A rod (13) is slidably fitted in a guide hole (20a) formed in the rod guide (20), and is attached to a seal groove (20c) formed in the inner peripheral surface of the guide hole (20a). The lip (28c) of the seal member (28) is brought into sliding contact with the outer peripheral surface of the rod (13), thereby sealing the liquid chamber (16) partitioned on one end side in the axis (L) direction of the seal member (28). In the sealing device,
The cross-sectional shape in the direction along the axis (L) of the lip (28c) of the seal member (28) is the axis from the radially inner tip (A) to the two radially outer bases (B, C). (L) The length of the rod guide (20) is increased, and the guide of the rod guide (20) is adjacent to the base (B) opposite to the liquid chamber (16) of the two bases (B, C). A sealing device characterized in that a space (30) is formed which is recessed radially outward from the inner peripheral surface of the hole (20a).   The cross-sectional shape in the direction along the axis (L) of the lip (28c) of the seal member (28) is characterized in that the tip (A) and the two bases (B, C) form a substantially triangular shape. The sealing device according to claim 1.   The sealing device according to claim 1 or 2, wherein the space (30) is formed in an annular shape so as to surround the axis (L).   The seal member (28) includes an annular protrusion (28e) projecting radially inward on the opposite side of the lip (28c) across the space (30), and the radially inner side of the annular protrusion (28e). The sealing device according to any one of claims 1 to 3, wherein the end is located radially outside the tip end (A) of the lip (28c).   The seal member (28) includes a backup ring (43) harder than the seal member (28) between the space (30) and a step portion (20f) of the seal groove (20c), The radial inner end of the backup ring (43) is located radially outside the tip end (A) of the lip (28c), according to any one of claims 1 to 4. The sealing device as described.   The sealing device according to any one of claims 1 to 5, wherein the liquid chamber (16) is filled with a magnetorheological fluid containing metal fine particles or a magnetic fluid.

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