JPH018755Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a cylindrical shock absorber, and particularly to a double-tube shock absorber suitable for being incorporated into a vehicle suspension system.

(Prior art) As shown in, for example, Japanese Utility Model Application Publication No. 55-73641, a double-tube shock absorber has an inner cylinder that defines a cylinder chamber that slidably accommodates a piston, and can communicate with the cylinder chamber. an outer cylinder for defining a reservoir chamber surrounding the inner cylinder, and an open end of the outer cylinder is provided with a sealing mechanism for sealing the open end to allow sliding of the piston rod. It is being

The sealing mechanism includes an annular sealing member having a support portion held by the outer cylinder, and a lip portion continuous with the support portion and extending downward in contact with the piston rod. The pressure of a gas such as air or nitrogen gas sealed above the hydraulic fluid reserved in the reservoir chamber acts on the back surface. The gas pressure acting on the rear surface of the lip portion usually acts to press the lip portion against the piston rod, thereby enhancing the sealing effect of the sealing mechanism.

However, when the gas pressure increases, for example due to the contraction operation of the shock absorber, the tip of the lip portion is excessively pressed against the piston rod by the gas pressure, and the piston rod is temporarily locked. Therefore, the smooth operation of the piston rod is prevented, and as a result,
This may lead to a decrease in the vibration damping characteristics of the shock absorber. Further, excessive pressure of the tip of the lip portion on the piston rod causes premature wear of the seal member.

Furthermore, in the shock absorber used in a vehicle suspension system, when the pressure of the gas enclosed in the gas is increased in order to improve damping force characteristics, the frictional force between the seal member and the piston rod increases in proportion to this. As the frictional force increases, the smooth operation of the piston rod is hindered, and the riding comfort of the vehicle is deteriorated. Therefore, it was not possible to sufficiently suppress the occurrence of calibration of the hydraulic fluid.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a double-tube shock absorber that has excellent durability and vibration damping characteristics without causing premature wear of the sealing member.

(Means for Solving the Problem) The present invention provides a restraining member for restricting movement of the tip end portion of the lip portion toward the piston rod when the gas pressure in the upper portion of the reservoir chamber increases. It is characterized in that it is arranged so as to be able to engage with the tip end of the lip portion.

(Function) When the gas pressure in the upper part of the reservoir chamber increases due to, for example, a contraction operation of the shock absorber, the restraining member engages with the tip portion of the lip portion and causes the tip portion to move toward the piston rod. By restricting the movement of the piston rod, the pressing force of the lip portion against the piston rod is substantially reduced.

(Effect of the invention) Therefore, even if the gas pressure in the reservoir chamber increases, the tip end of the lip portion will not be excessively pressed against the piston rod with a strong force as in the conventional case, so that the piston rod will not be pressed against the piston rod temporarily. Furthermore, even if the pressure of the gas filled in the gas is increased to prevent the occurrence of calibration, smooth operation of the piston rod can be ensured. It is possible to improve the vibration damping characteristics of. Also,
Since the tip end portion of the lip portion is not pressed excessively against the piston rod, the degree of wear of the lip portion can be substantially reduced compared to the conventional one, and the durability of the seal member can be increased. , it is possible to improve the durability of the buffer.

(Embodiments) The features of the present invention will become clearer from the following description of the illustrated embodiments.

As shown in FIG. 1, the shock absorber 10 according to the present invention includes an inner cylinder 16 that defines a cylinder chamber 14 that slidably accommodates a piston 12, and a reservoir chamber 18 that can communicate with the cylinder chamber 14. and an outer cylinder 20 that defines the outer cylinder 20. In the illustrated example, the buffer 10 is
It is incorporated into a vehicle suspension system, and a knuckle spindle 22 serving as an axle is fixed to the lower part of the outer cylinder 20. Further, the upper end of the piston rod 24 connected to the piston 12 is supported by the vehicle body via a conventionally well-known elastic support device, although not shown.

The piston 12 is provided with a port 26 that allows the flow of pressurized fluid within the cylinder chamber 14 and a conventionally well-known valve mechanism 28 for controlling the opening and closing of the port. The damping force is primarily generated by the piston 12 with the mechanism 28 . A conventionally well-known base valve assembly 30 is provided at the lower end of the cylinder chamber 14 for generating damping force mainly during the contraction operation of the shock absorber 10.
4 and the hydraulic fluid in the reservoir chamber 18 can flow with each other via the base valve assembly 30.

A piston rod 2 is attached to the upper end of the inner cylinder 16.
Guide member 3 for guiding 4 in its axial direction
2 is provided, and the guide member connects the piston rod 24 through a bush 34 made of a low friction material.
is slidably accepted. The guide member 32 is provided with a gasket 36 for sealing the space between the guide member and the outer cylinder 20, and a gasket 36 is provided on the guide member 32 to seal the space between the guide member and the outer cylinder 20. A return port 38 is formed for returning upwardly leaked hydraulic oil to the reservoir chamber 18. A stopper 40 that can come into contact with the lower surface of the guide member 32 is held on the piston rod via a retainer 42 to restrict the extension movement of the piston rod 24.

A ring nut 44 is provided at the upper end, which is the open end, of the outer cylinder 20, and is arranged around the piston rod 24 and is screwed into the open end.
A cap 48 consisting of a top plate 46 fixed to the top surface of the ring nut 44 is disposed so as to surround the piston rod 24, and the guide member 32 is fixed by tightening the cap. The ring nut is provided with a well-known air vent hole 50. Further, the open end of the outer cylinder 20 is provided with air or nitrogen gas to prevent the hydraulic oil in the cylinder chamber 14 and the reservoir chamber 18 from leaking to the outside of the shock absorber 10, and to store air or nitrogen gas in the upper part of the reservoir chamber 18. A sealing mechanism 52 is provided for sealing in a gas such as, in the illustrated example, the sealing mechanism is provided in association with the ring nut 44.

The sealing mechanism 52 is disposed around the piston rod 24, as clearly shown in FIG.
a generally annular sealing member 54 supported on the
and an annular restraint member 56 provided in association with the seal member.

The sealing member 54 is inserted into an annular groove 58 formed on the inner peripheral surface of the ring nut 44 at an upper edge 58 of the groove.
A cylindrical support part 5 that is press-fitted with its upper end in contact with a.
4a, an annular flange portion 54b extending radially inward from the upper end of the support portion, and an annular upper lip portion 54c extending upwardly and downwardly from the inner edge of the flange portion so as to be able to abut the piston rod 24. and an annular lower lip portion 54d.

The upper lip portion 54c extending upward along the piston rod 24 is an auxiliary lip portion provided for the purpose of preventing dust from entering, and can be made unnecessary.

The lower lip portion 54d extends downward along the piston rod 24, that is, toward the piston 12.
A main lip part for sealing is formed, and a tapered surface 60 is formed at the tip end of the lip part, the diameter of which gradually increases toward the tip end. An annular reinforcing member 62 is embedded within the seal member 54 and extends from the support portion 54a to the flange portion 54b. Further, well-known annular garter springs 64 are mounted on the upper and lower lip portions 54c and 54d, respectively, for pressing the respective lip portions against the piston rod 24.

The annular restraint member 56 has a central opening 56a.
The outer edge portion is press-fitted into the support portion 54a of the seal member 54 so as to allow the piston rod 24 to penetrate therethrough, and
Thereby, it is elastically supported by the support portion.
The restraining member 56 can be fixedly supported on the outer cylinder 20 via the ring nut 44. An annular groove 66 is formed on the upper surface of the restraining member 56 to receive the tip of the lower lip portion 54d, and a groove surface 66a of the annular groove is formed on the upper surface of the upper lip portion 54.
Leave a space from the tip of d. Further, the restraining member 56 is provided with an orifice 68 consisting of a through hole for applying the gas pressure above the reservoir chamber 18 to the back surface of the lower lip portion 54d.
The restraining member 56 can be made of a material with relatively low elasticity, such as a synthetic resin plate, a steel plate, or an aluminum plate.

During the contraction operation of the double-tube shock absorber, the hydraulic oil in the cylinder chamber flows into the reservoir chamber 18 via the base valve assembly 30 as the piston rod 24 enters the cylinder chamber 14.
As the hydraulic fluid in the reservoir chamber 18 increases, the pressure of the gas sealed in the upper part of the reservoir chamber increases. However, in the normal operating state of the shock absorber, in which the lower lip portion 54d is not subjected to gas pressure strong enough to elastically deform the tapered surface 60 at its tip toward the piston rod 24, the lower lip portion 54d As shown in FIG. 2, the tapered surface 60 of the tip portion is spaced apart from the groove surface 66a of the annular groove 66 formed in the restraint member 56, so that the lip portion 54d
The movement of the piston rod 24 toward the piston rod 24 is not restricted by the restraining member 56. Therefore, the lower lip portion 54d is moved by the piston rod 2 due to the garter spring 64 and the gas pressure acting on the back surface of the lower lip portion 54d.
4 is properly pressed. Therefore, leakage of the hydraulic oil and sealing gas can be reliably prevented without causing significant wear on the lower lip portion 54d and without interfering with the smooth movement of the piston rod 24.

On the other hand, the gas pressure increases due to the large contraction operation of the shock absorber 10, and the pressure on the back side of the lower lip portion 54d increases due to the increase in gas pressure, causing the lower lip portion to collapse at its tip. When the tapered surface 60 of the lip portion 54d is to be elastically deformed in order to press it toward the piston rod 24, the tapered surface 60 of the lip portion 54d will deform as shown in FIG. Groove 6
6, the lip portion 5
The movement of the distal end portion of the piston rod 4d toward the piston rod 24 is restricted by a restraining member 56 that engages with the distal end portion. Therefore, the strong pressure gas directed toward the piston rod 24 acts on the back surface of the lower lip portion 54d, including the tip portion, but the restraining member prevents the tip portion of the lower lip portion 54d from moving. Since movement toward the piston rod is restricted, the pressing force exerted by the high pressure gas on the lower lip portion 54d is substantially reduced.

Therefore, even if the gas pressure in the reservoir chamber 18 increases, the tip portion of the lower lip portion 54d
Since the piston rod 24 is not pressed excessively by a strong force as in the conventional shock absorber, the piston rod 24 is not temporarily locked, and the piston rod 2
The smooth movement of the shock absorber 10 improves the vibration damping characteristics of the shock absorber 10, thereby improving the ride comfort of the vehicle.

Furthermore, since the tip of the lip portion 54d, which is most likely to wear, is not pressed excessively against the piston rod 24, the lip portion 54d
The durability of the sealing member 54 can be increased by substantially reducing the degree of wear d compared to the conventional one, thereby improving the durability of the shock absorber.

FIG. 4 shows a comparison between the shock absorber according to the present invention and the conventional shock absorber, which shows the relationship between the pressure of the gas sealed in the reservoir chamber and the frictional force that the piston rod receives from the seal mechanism. This is a graph showing the above-mentioned sealed gas pressure (PKg/cm ² ) on the X axis.
, and the Y axis represents the frictional force (FKgf). The characteristic line of the buffer 10 according to the present invention is shown by a solid line, and the characteristic line of the conventional buffer is shown by a broken line.

As is clear from this graph, in the conventional shock absorber, the frictional force increases in direct proportion to the increase in the sealed gas pressure. Therefore, when the pressure of the filled gas is increased in order to effectively suppress the occurrence of calibration of the hydraulic fluid, the frictional force increases in proportion to the increase in the pressure of the filled gas, which facilitates smooth movement of the piston rod. is inhibited, and because of this,
The damping force characteristics of the shock absorber deteriorate, and the ride comfort of the vehicle deteriorates.

On the other hand, according to the present invention, even if the sealed gas pressure exceeds, for example, about 4 kg/cm ² , the frictional force can be maintained at a low, almost constant value of, for example, about 7 kgf. Therefore, even if the pressure of the sealed gas is increased in order to effectively suppress the occurrence of the above-mentioned calibration, smooth movement of the piston rod can be ensured without causing a decrease in the damping force characteristics. The ride comfort of the vehicle can be improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view partially showing the dual-tube shock absorber according to the present invention, and FIG. 2 is a vertical cross-sectional view showing the sealing mechanism shown in FIG. FIG. 3 is a drawing similar to FIG. 2 showing the sealing mechanism shown in FIG. 1 in a restrained state in an enlarged manner, and FIG. It is a graph showing a comparison between the shock absorber according to the present invention and a conventional shock absorber in terms of the relationship with force. 10: shock absorber, 12: piston, 14: cylinder chamber, 16: inner cylinder, 18: reservoir chamber, 20: outer cylinder, 24: piston rod, 52: seal mechanism,
54: Seal member, 54a: Support portion, 54d: Lip portion, 56: Restraint member.

Claims (1)

[Scope of utility model registration request] The piston is located at an open end of an outer cylinder that is disposed over an inner cylinder that defines a cylinder chamber that slidably accommodates the piston, and that defines a reservoir chamber outside the cylinder chamber that can communicate with the cylinder chamber. a sealing mechanism for sealing the open end of the barrel to permit sliding of a piston rod extending outwardly through the open end of the barrel, the sealing mechanism being retained in the barrel; a generally annular sealing member comprising a support portion connected to the support portion and a lip portion extending toward the piston side by contacting the piston rod; and a sealing member disposed so as to be engageable with a distal end portion of the lip portion; and a restraining member for engaging the tip end of the lip portion and restricting the movement of the tip portion toward the piston rod when the gas pressure in the upper part of the reservoir chamber increases. Type buffer.