JP2013204792A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylindrical shock absorber with a simple structure which smoothly discharges air entrained in a cylinder while securing the sealing performance under high pressure of a seal part of a piston rod.SOLUTION: A seal groove 40 is formed around a rod guide 8 for guiding a piston rod 6. An elastic seal ring 41 is provided in the seal groove 40 and closely stuck to the piston rod 6 so as to form a gap C1 against an inner surface of the seal groove 40. The seal ring 41 is pressed to an end of the seal groove 40 by a spring force of a wave spring 42, and a venting channel 43 is formed on the end of the seal groove 40. Usually, sealing performance is secured by closing the venting channel 43 by pressing the seal ring 41 to the end of the seal groove 40 by cylinder internal pressure and a spring force of the wave spring 42. When the cylinder internal pressure is low just after a piston rod has shifted from an elongation stroke to a contraction stroke, the seal ring 41 is moved by being dragged by the piston rod 6 and the venting channel 43 is opened, so that the air entrained in the cylinder is discharged together with a small amount of oil.

Description

  The present invention relates to a shock absorber attached to a suspension device of an automobile, a railway vehicle or the like.

  In general, a cylindrical shock absorber mounted on a suspension device of a vehicle such as an automobile or a railway vehicle generally allows a piston connected to a piston rod to slide in a cylinder filled with an oil liquid as a working fluid. It is inserted and has a structure in which a damping force generating mechanism including an orifice and a disk valve is provided in the piston portion. As a result, the piston in the cylinder slides with respect to the stroke of the piston rod, and the resulting fluid flow is controlled by the orifice and the disk valve to generate a damping force.

  In such a shock absorber, when air is mixed into the cylinder, the damping force becomes unstable due to fluctuations in the flow resistance caused by the damping force generation mechanism and air compression and expansion. Accordingly, the seal portion of the piston rod of the shock absorber is required to have a function of discharging air mixed in the cylinder while ensuring the sealing performance against the oil and the lubricity of the piston rod.

  Conventionally, in the hydraulic shock absorber described in Patent Document 1, for example, a check valve that allows a small amount of oil to flow from the inside of the cylinder to the reservoir is provided in the seal portion of the piston rod, so that air mixed in the cylinder can be obtained. Is discharged together with a small amount of oil into the reservoir.

JP 2003-14029 A

  In recent years, there has been a demand for stabilizing damping force characteristics and increasing the pressure of oil liquid in a cylinder. For this reason, the seal part of the piston rod is required to have a function of smoothly discharging air while ensuring a sealing property against high pressure, and an improvement in productivity by simplifying the structure is desired.

  An object of the present invention is to provide a shock absorber that has a simple structure and can smoothly discharge air mixed in a cylinder while ensuring the sealing performance against the high pressure of the seal portion of the piston rod.

In order to solve the above-described problems, the present invention provides a cylinder in which oil is sealed, a piston that is slidably inserted into the cylinder, and a piston that is connected to the piston and extends outside the cylinder. A rod, a rod guide that is attached to the end of the cylinder and guides the piston rod, and is attached to the outside of the rod guide at the end of the cylinder and seals between the piston rod and the rod In a shock absorber provided with an oil seal that forms an oil sump chamber with the guide,
An annular seal member that forms an annular seal groove on the inner peripheral surface of the rod guide, adheres closely to the outer peripheral surface of the piston rod in the seal groove, and forms a gap between the inner peripheral surface of the seal groove A ventilation groove is formed at an end of the seal groove that contacts the seal member or an end of the seal member that contacts the end of the seal groove, and the inside of the cylinder is interposed through the ventilation groove. And a front oil sump chamber, spring means for pressing the seal member against the end of the seal groove is provided in the seal groove, and the air flow is achieved by pressing the seal member against the end of the seal groove. The groove can be cut off.

  According to the shock absorber of the present invention, air mixed in the cylinder can be smoothly discharged with a simple structure while ensuring the sealing performance against the high pressure of the seal portion of the piston rod.

It is a longitudinal section showing a shock absorber concerning one embodiment of the present invention partially fractured. It is a longitudinal cross-sectional view which expands and shows the seal part of the piston rod which is the principal part of the shock absorber of FIG. It is a longitudinal cross-sectional view which expands further and shows the seal part of the piston rod shown in FIG.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the shock absorber 1 according to the present embodiment is a cylindrical damping force adjustment type hydraulic shock absorber, and has a multi-cylinder structure in which an outer cylinder 3 is provided outside a cylinder 2. An annular reservoir 4 is formed between the outer cylinder 3 and the outer cylinder 3. A piston 5 is slidably inserted into the cylinder 2. The piston 5 defines the inside of the cylinder 2 as two chambers, a cylinder upper chamber 2A (rod side chamber) and a cylinder lower chamber 2B (bottom side chamber). Yes. One end of a piston rod 6 is connected to the piston 5 by a nut 7, and the other end side of the piston rod 6 passes through the cylinder upper chamber 2 </ b> A and is a rod guide attached to the upper ends of the cylinder 2 and the outer cylinder 3. 8 and the oil seal 9 are extended to the outside of the cylinder 2. A base valve 10 that partitions the cylinder lower chamber 2 </ b> B and the reservoir 4 is provided at the lower end of the cylinder 2.

  The piston 5 is provided with passages 11 and 12 for communicating between the cylinder upper and lower chambers 2A and 2B. The passage 11 is provided with a check valve (not shown) that allows only fluid to flow from the cylinder lower chamber 2B side to the cylinder upper chamber 2A side. A disk valve 14 is provided that opens when the fluid pressure reaches a predetermined pressure and relieves the fluid to the cylinder lower chamber 2B side.

  The base valve 10 is provided with passages 15 and 16 that allow the cylinder lower chamber 2B and the reservoir 4 to communicate with each other. The passage 15 is provided with a check valve 17 that allows only fluid to flow from the reservoir 4 side to the cylinder lower chamber 2B side. In the passage 16, the pressure of the fluid on the cylinder lower chamber 2B side is provided. A disk valve 18 is provided that opens when a predetermined pressure is reached and relieves it to the reservoir 4 side. An oil liquid is sealed in the cylinder 2 as a working fluid, and an oil liquid and a gas are sealed in the reservoir 4.

  A separator tube 20 is externally fitted to the cylinder 2 via seal members 19 at both upper and lower ends, and an annular passage is formed between the side wall of the cylinder 2 and the cylindrical side wall of the separator tube 20 provided on the outer periphery thereof. 21 is formed. The annular passage 21 is communicated with the cylinder upper chamber 2 </ b> A by a passage 22 provided in a side wall near the upper end portion of the cylinder 2. The lower end of the annular passage 21 is connected to a damping force generation mechanism 25 attached to the lower part of the side wall of the outer cylinder 3.

  The damping force generation mechanism 25 is disposed on the downstream side of the pilot valve, which is a pilot-type (back pressure type) main valve, a solenoid-operated pressure control valve that controls the valve opening pressure of the main valve, and at the time of failure And a fail valve that operates. The oil introduced from the annular passage 21 is circulated to the reservoir through the main valve, the pilot valve, and the fail valve to generate a damping force. Further, the damping force is adjusted by energizing the solenoid through the lead wire 26 to adjust the control pressure of the pilot valve and the valve opening pressure of the main valve.

Next, the seal part of the piston rod 6 will be described with reference to FIGS.
As shown in FIG. 2, a stepped cylindrical rod guide 8 having a small diameter portion 8 </ b> A and a large diameter portion 8 </ b> B is attached to the upper end portions of the cylinder 2 and the outer cylinder 3. The large-diameter portion 8B is fitted into the outer cylinder 3. A guide bush 29 is press-fitted into a guide bore 28 formed on the small diameter portion 8A side of the rod guide 8, and the piston rod 6 is inserted into the guide bush 29 so as to be slidably guided. A predetermined gap is provided between the guide bush 29 and the piston rod 6 so that a small amount of oil can be circulated. A large diameter bore 30 larger than the guide bore 28 is formed on the large diameter portion 8 </ b> B side of the rod guide 7. An annular contact portion 31 protrudes from the end surface of the large diameter portion 8B of the rod guide 8. A reflux passage 32 extends through the large diameter portion 8B of the rod guide 8 along the axial direction.

  An oil seal 9 that is in contact with the contact portion 31 of the rod guide 8 and through which the piston rod 6 is inserted is attached to the upper end portion of the outer cylinder 3. The oil seal 9 holds an oil reservoir in the large-diameter bore 30. A chamber 33 is formed. The oil sump chamber 33 is connected to the reservoir 4 via the reflux passage 32. The oil seal 9 has a structure in which a main seal 35, a dust seal 36 and a seal lip 37 are integrally formed on the inner peripheral portion of a metal annular holding member 34 and vulcanized and bonded. The oil seal 9 is fixed by crimping the end of the outer cylinder 3 in a state where the holding member 34 is fitted in the outer cylinder 3 and is in contact with the contact portion 31 of the rod guide 8.

  The main seal 35 is disposed inside the holding member 34 and is in close contact with the piston rod 6 to seal the oil. The dust seal 36 is disposed on the outside of the holding member 34, closely contacts the piston rod 6, prevents foreign matter from entering the oil sump chamber 33, and scrapes off the oil adhering to the surface of the piston rod 6. Further, the seal lip 37 is elastically adhered to the step portion of the rod guide 7 and functions as a check valve that allows only the flow of the oil from the oil reservoir chamber 33 to the reservoir 4. The large diameter portion 8B of the rod guide 8 and the holding member 34 of the oil seal 9 and the outer cylinder 3 are sealed by a seal member 38. A cap 39 is further fitted on the end of the outer cylinder 3 to protect the oil seal 9.

  As shown in FIG. 3, the guide bush 29 is press-fitted with an axial gap between the guide bore 28 and the end of the guide bore 28, and the gap is formed on the inner peripheral surface of the guide rod 8 through which the piston rod 6 is inserted. An annular seal groove 40 is formed. In the seal groove 40, a seal ring 41 which is an annular seal member made of an elastic body is inserted. The seal ring 41 has an inner peripheral portion that is in close contact with the outer peripheral surface of the piston rod 6, an outer diameter that is smaller than the inner diameter of the guide bore 28, and a gap C <b> 1 is formed between the outer peripheral portion and the inner peripheral surface of the guide bore 28. ing. The seal ring 41 has an axial dimension smaller than that of the seal groove 40, and an annular wave spring 42 as a spring means is inserted between the end of the seal ring 41 and the end of the seal groove 40 on the guide bush 29 side. Has been. The seal ring 41 is pressed against the end of the seal groove 40 on the oil sump chamber 33 side by the spring force of the wave spring 42. A vent groove 43 is formed along the radial direction at an end portion of the seal groove 40 that contacts the seal ring 41, that is, an end portion on the oil sump chamber 33 side. One or a plurality of ventilation grooves 43 can be arranged along the circumferential direction. When the seal ring 41 comes into contact with the end of the seal groove 40, the inside of the seal groove 40 and the oil sump chamber 33 are formed between the ventilation groove 43 and the gap between the inner peripheral surface of the rod guide 8 and the piston rod 6. Connected via C2. In addition, the seal ring 41 is pressed against the end of the seal groove 40 by the spring force of the wave spring 42 and the pressure of the oil in the cylinder upper chamber 2A, and is elastically deformed so as to be in close contact with the air groove 43. 43 can be cut off.

Next, the operation of the present embodiment configured as described above will be described.
During the extension stroke of the piston rod 6, the check valve in the passage 11 of the piston 5 is closed by the movement of the piston 5 in the cylinder 2, and the fluid on the cylinder upper chamber 2 </ b> A side is opened before the disk valve 14 in the passage 12 is opened. Is pressurized and flows through the passage 22 and the annular passage 21 to the reservoir 4 via the damping force generation mechanism 25.

  At this time, the fluid corresponding to the movement of the piston 5 opens the check valve 17 of the base valve 10 from the reservoir 4 and flows into the cylinder lower chamber 2B. When the pressure in the cylinder upper chamber 2A reaches the valve opening pressure of the disk valve 14 of the piston 5, the disk valve 14 is opened, and the pressure in the cylinder upper chamber 2A is relieved to the cylinder lower chamber 2B. Prevent excessive pressure rise of 2A.

  During the contraction stroke of the piston rod 6, the check valve in the passage 11 of the piston 5 is opened by the movement of the piston 5 in the cylinder 2, the check valve 17 in the passage 15 of the base valve 10 is closed, and the disc valve 18 is opened. Before the valve, the fluid in the piston lower chamber 2B flows into the cylinder upper chamber 2A, and the fluid that has entered the cylinder 2 through the piston rod 6 passes from the cylinder upper chamber 2A through the same path as in the extension stroke. Flow to the reservoir 4. When the pressure in the cylinder lower chamber 2B reaches the valve opening pressure of the disk valve 18 of the base valve 10, the disk valve 18 is opened, and the pressure in the cylinder lower chamber 2B is relieved to the reservoir 4, thereby Prevent excessive pressure rise of 2B.

  Thus, during the expansion / contraction stroke of the piston rod 6, the damping force generating mechanism 25 generates a damping force by the pilot valve before the main valve is opened (piston speed low speed region), and after the main valve is opened ( In the high speed region of the piston speed, a damping force is generated according to the opening. Then, the control pressure of the pilot valve is adjusted by the energization current to the solenoid. As a result, the internal pressure of the back pressure chamber changes, the valve opening pressure and the opening degree of the main valve are adjusted, and the damping force can be adjusted. In addition, when the energization to the solenoid is interrupted, by restricting the flow of the oil liquid by the fail valve, an excessive decrease in the damping force can be prevented and an appropriate damping force can be maintained.

  In the seal portion of the piston rod 6, a small amount of oil from the cylinder chamber 2 </ b> A passes through the gap between the guide bush 29 and the piston rod 6 and enters the seal groove 40, and the gap between the seal ring 41 and the inner peripheral surface of the seal groove 40. The oil flows into the oil sump chamber 33 through C1, the ventilation groove 43, and the gap C2 between the piston rod 6 and the inner peripheral surface of the rod guide 8. The oil in the oil sump chamber 33 lubricates the main seal 35 and the dust seal 36, and the excess oil is returned to the reservoir 4 through the check valve and the return passage 32 formed by the seal lip 37. Similarly, air mixed in the cylinder chamber 2 </ b> A is returned to the reservoir 4 through the oil reservoir chamber 13.

  At this time, when the inside of the cylinder chamber 2A is pressurized during the expansion and contraction strokes of the piston rod 6, the seal ring 41 is sealed by the pressure in the cylinder chamber 2A and the spring force of the wave spring 42. It is pressed against the end of the groove 40, elastically deforms and closely contacts the ventilation groove 43 to block the ventilation groove 43. Therefore, leakage of oil from the cylinder upper chamber 2A to the oil reservoir chamber 33 is suppressed, and a high pressure sealing property is achieved. Secure. Further, immediately after the piston rod 6 shifts from the expansion stroke to the contraction stroke, the piston speed is low and the pressure in the cylinder upper chamber 2A is relatively low. Therefore, the seal ring 41 contracts the piston rod 6. As a result, the cylinder moves slightly in the direction away from the ventilation groove 43 against the pressure on the cylinder upper chamber 2 </ b> A and the spring force of the wave spring 42. Thereby, the ventilation groove 43 is opened, and the air mixed in the cylinder upper chamber 2 </ b> A is discharged to the oil reservoir chamber 33 side through the ventilation groove 43. At this time, since the pressure in the cylinder upper chamber 2A is relatively low, the amount of oil that leaks through the ventilation groove 43 is minimized. In this way, the air mixed in the cylinder 2 can be smoothly discharged while ensuring the sealing performance against the high pressure of the seal portion of the piston rod 6. As a result, it is possible to reduce variations in the damping force characteristics caused by air mixed in the cylinder 2, in particular, variations that occur remarkably when the piston speed is low when the damping force characteristics are adjusted to the hard side.

  Thereafter, when the piston speed increases in the contraction stroke, the seal ring 41 is pressed against the end of the seal groove 40 by the pressure in the cylinder upper chamber 2A and the spring force of the wave spring 42, and is elastically deformed to be ventilated groove 43. The ventilation groove 43 is shut off in close contact with the air.

  As described above, in the present embodiment, the present invention is applied to a so-called one-way hydraulic shock absorber in which the cylinder upper chamber 2A (rod side chamber) is pressurized in both the expansion stroke and the contraction stroke. Since the cylinder upper chamber 2A is always pressurized and the ventilation groove 43 is shut off in the piston speed region where the occurrence of the damping force, the damping force is unlikely to vary.

  In a hydraulic shock absorber having a contraction-side damping valve in the piston portion, the rod side chamber is close to a negative pressure on the contraction side, so that the ventilation groove 43 is always in a communicating state during the contraction stroke. In this case, the damping force on the contraction side may be low, but if it is high, the damping force characteristics may vary, which is not desirable.

  In the above embodiment, other spring means may be used instead of the wave spring 42. Alternatively, the spring means may be integrated with the seal ring 41 and the seal ring 41 may be pressed against the end of the seal groove 40 by the elastic force of the seal ring 41 itself. The ventilation groove 41 may be formed on the seal ring 41 side. That is, the ventilation groove 41 can be formed at the end of the seal groove 40 with which the seal ring 41 abuts or the end of the seal ring 41 with which the end of the seal groove 40 abuts. Moreover, although the said embodiment demonstrated the case where this invention was applied to the double cylinder type shock absorber as an example, this invention is similarly applied not only to this but a single cylinder type shock absorber. be able to.

  DESCRIPTION OF SYMBOLS 1 ... Shock absorber, 2 ... Cylinder, 5 ... Piston, 6 ... Piston rod, 8 ... Rod guide, 9 ... Oil seal, 33 ... Oil sump chamber, 40 ... Seal groove, 41 ... Seal ring (seal member), 42 ... Wave spring (spring means), 43 ... ventilation groove, C1 ... gap

Claims (1)

A cylinder filled with oil, a piston slidably inserted into the cylinder, a piston rod connected to the piston and extending outside the cylinder, and attached to an end of the cylinder A rod guide that guides the piston rod and an outside of the rod guide at the end of the cylinder are sealed to seal between the piston rod and form an oil sump chamber with the rod guide. In a shock absorber with an oil seal,
An annular seal member that forms an annular seal groove on the inner peripheral surface of the rod guide, adheres closely to the outer peripheral surface of the piston rod in the seal groove, and forms a gap between the inner peripheral surface of the seal groove A ventilation groove is formed at an end of the seal groove that contacts the seal member or an end of the seal member that contacts the end of the seal groove, and the inside of the cylinder is interposed through the ventilation groove. And a front oil sump chamber, spring means for pressing the seal member against the end of the seal groove is provided in the seal groove, and the air flow is achieved by pressing the seal member against the end of the seal groove. A shock absorber characterized in that the groove can be cut off.

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