JP2002257178A - Cylinder unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent leakage of oil from a piston rod portion in a cylinder unit in spite of a stroke direction of the piston rod. SOLUTION: A piston connected with the piston rod is slidably fitted in the cylinder enclosing oil, and the piston rod 5 is also extended to the outside by penetrating through a rod guide 6 installed in en end portion of the cylinder. A circular seal member 13 inserting through the piston rod 5 is inserted in a circular groove 11 formed in an inner peripheral surface of the rod guide 6. A wave washer 22 is inserted in clearance between an end portion of the inside of the circular groove 11 and the seal member 13, and the seal member 13 is pressed onto a seal surface 11a of the circular groove 11 by spring force of the wave washer. As the seal member 13 is maintained in the seal surface 11a in a regularly pressed state in spite of a stroke direction of the piston rod 5, a stable sealing property can be obtained, and leakage of oil is also surely prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a cylinder device such as a hydraulic shock absorber mounted on a suspension system of a vehicle.

[0002]

2. Description of the Related Art A conventional seal structure for a piston rod in a hydraulic shock absorber will be described with reference to FIGS. As shown in FIG. 4, the hydraulic shock absorber 1
The outer cylinder 3 is provided with an outer cylinder 3, and a reservoir 4 is formed between the cylinder 2 and the outer cylinder 3. Cylinder 2
Has a piston connected to a piston rod 5 (not shown)
Is slidably fitted, and the piston defines the inside of the cylinder 2 into a cylinder upper chamber 2a on the piston rod 5 side and a cylinder lower chamber (not shown) on the opposite side.

A stepped cylindrical rod guide 6 is attached to the upper ends of the cylinder 2 and the outer cylinder 3, and a piston rod 5 is inserted through the rod guide 6 and extends to the outside. The rod guide 6 has a small diameter portion 7 and a large diameter portion 8 fitted in the cylinder 2 and the outer cylinder 3, respectively.
An annular retainer 9 is superimposed on the end of the large-diameter portion 8, and the opening of the outer cylinder 3 is fixed by caulking at several places. In addition, outer cylinder 3
The cap 10 is press-fitted to the outside of the opening.

As shown in FIG. 5, an annular groove 11 is formed in the inner peripheral portion of the rod guide 6, and an enlarged diameter portion having a diameter slightly larger than that of the annular groove 11 is formed in the annular groove 11 on the cylinder upper chamber 2a side. 12 are formed. The annular groove 11 has a rectangular cross-section sealing member 1 for sealing between the rod guide 6 and the piston rod 5.
A bush 14 made of a cylindrical metal for slidingly guiding the piston rod 5 is inserted into the enlarged diameter portion 12.
Is press-fitted. The inner surface of the bush 14 is coated with a fluororesin to make the piston rod 5 slide smoothly. A groove 11b having a small cross-sectional area for removing only gas such as air generated in the cylinder is provided on the upper end surface of the annular groove 11. Actually, a small amount of the oil liquid flows out from the groove 11b, but the amount does not affect the damping characteristics and the like.

A recess 15 is formed around the opening on the large diameter portion 8 side of the rod guide 6, and a spring-containing oil seal for sealing between the retainer 9 and the piston rod 5 is provided on the inner periphery of the retainer 9. An oil chamber 17 is formed in the recess 15. The rod guide 6 is provided with an oil passage 18 that allows the oil chamber 17 and the reservoir 4 to communicate with each other. The oil seal 16 includes an oil lip 19 disposed inside the retainer 9 and slidably in contact with the piston rod 5, and a dust seal 20 disposed outside the retainer 9 and slidably in contact with the piston rod 5.
The oil chamber of the oil passage 18
A check valve 21 that allows only the flow of the oil liquid from the 17 side to the reservoir 4 side is provided.

The piston is provided with an oil passage communicating between the upper and lower chambers of the cylinder and a damping force generating mechanism (orifice, disk valve, etc.) for controlling the flow of the oil in the oil passage to generate a damping force. . At the lower end of the cylinder, there are provided an oil path for communicating the lower chamber of the cylinder and the reservoir 4, and a damping force generating mechanism (orifice, disk valve, etc.) for controlling the flow of the oil in the oil path. An oil liquid is sealed in the cylinder 2, and an oil liquid and a gas are sealed in the reservoir 4.

Next, the operation of the hydraulic shock absorber 1 will be described. The flow of the oil liquid generated by the sliding of the piston in the cylinder 2 due to the expansion and contraction of the piston rod 5 is controlled by the damping force generating mechanism provided on the piston and the damping force generating mechanism provided on the lower end of the cylinder to control the damping force Generate. At this time, the volume change in the cylinder 2 due to the penetration and retreat of the piston rod 5 is absorbed by the compression and expansion of the gas in the reservoir 4.

The seal member 13 mounted on the rod guide 6 receives the pressure of the oil liquid in the cylinder 2 and allows a small amount of oil to pass therethrough to form an appropriate oil film on the sliding surface of the piston rod 5. In addition, the sliding resistance of the piston rod 5 is reduced. Then, the oil film formed on the sliding surface of the piston rod 5 is scraped off by the oil lip 19 of the oil seal 16 to prevent leakage of the oil liquid to the outside,
In addition, the foreign matter adhering to the piston rod 5 is wiped off with the dust seal 20, thereby preventing the foreign matter from entering the oil chamber 17. After passing through the seal member 13, the oil seal 16
The oil liquid scraped off by the oil lip 19 and stored in the oil chamber 17 opens the check valve 21 and is collected into the reservoir 4 through the oil passage 18.

[0009]

However, the conventional hydraulic shock absorber has the following problems. As shown in FIG. 5, the annular groove 11 of the rod guide 6 absorbs a change in volume due to thermal expansion or the like of the seal member 13, so that its axial and radial dimensions are usually about 0.5 mm larger than the seal member 13. It is set, and the seal member 13 is assembled to the piston rod 5 with a predetermined interference in order to ensure sealing performance. For this reason, the sealing member
13, the piston rod 5 moves in the annular groove 11 together with the piston rod 5 due to the sliding resistance with the piston rod 5 when the piston rod 5 strokes.

At this time, during the extension stroke of the piston rod 5, as shown in FIG. 5, the sealing member 13 moves upward and comes into contact with the sealing surface 11a at the end of the annular groove 11 of the rod guide 6. The space between the piston rod 5 and the rod guide 6 can be reliably sealed. On the other hand, during the contraction stroke of the piston rod 5, the sealing member 13 may move downward and separate from the sealing surface 11a of the annular groove 11, and in this case, the sealing performance is reduced, and the leakage of the oil liquid is reduced. Increase. Also, as shown in FIG.
Even when the end portion of the bush 14 is in contact with the end portion, the end face of the bush 14 is not flattened, so that the sealing performance is reduced and the leakage of the oil liquid may change. When the amount of leakage of the oil liquid changes in this manner, there is a problem that the damping characteristics become unstable.

The present invention has been made in view of the above points, and provides a cylinder device such as a hydraulic shock absorber capable of obtaining a stable seal regardless of the stroke direction and speed of a piston rod. With the goal.

[0012]

In order to solve the above-mentioned problems, the invention according to claim 1 slidably fits a piston connected to a piston rod into a cylinder filled with an oil liquid. Then, the piston rod is inserted into a rod guide attached to the end of the cylinder and extended to the outside,
In a cylinder device in which a space between the rod guide and the piston rod is sealed by sealing means, the sealing means includes an annular seal for inserting the piston rod into an annular groove formed in an inner peripheral surface of the rod guide. An annular wave-type washer for inserting a member and for urging the seal member into the gap between one end in the annular groove and the seal member and pressing the seal member against the other end of the annular groove. It is characterized in that the force means is inserted. With this configuration, the sealing member is held in a state where it is pressed against the end of the annular groove by the biasing means regardless of the stroke direction of the piston rod. Further, according to the invention of claim 2, a piston to which a piston rod is connected is slidably fitted in a cylinder filled with an oil liquid, and the piston rod is attached to an end of the cylinder. An oil seal that is inserted into the rod guide and extends to the outside, and that separates the inside and outside of the cylinder device from the piston rod projecting end side of the rod guide. In a cylinder device provided with sealing means for sealing between a piston rod, the sealing means includes an annular sealing member for inserting the piston rod into an annular groove formed on an inner peripheral surface of the rod guide. An annular bias for inserting and urging the seal member into a gap between one end in the annular groove and the seal member and pressing the seal member against the other end of the annular groove Characterized by comprising inserting a stage. With this configuration, the sealing member is held in a state where it is pressed against the end of the annular groove by the biasing means regardless of the stroke direction of the piston rod. According to a third aspect of the present invention, in the second aspect of the present invention, the urging means comprises a wave-type washer. With such a configuration, the sealing member is held in a state where it is pressed substantially uniformly in the radial direction by the biasing means against the end of the annular groove regardless of the stroke direction of the piston rod. In the invention of claim 4, in the invention of claim 1 or 3, the difference between the outer diameter of the washer and the inner diameter of the annular groove is the difference between the inner diameter and the outer diameter of the piston rod. It is characterized by being smaller. Thereby, the piston rod and the washer do not come into contact with each other. According to a fifth aspect of the present invention, in the first or third aspect of the invention, the shape of the washer is such that convex portions and concave portions are provided alternately in the circumferential direction, and the number of convex portions is three or more and adjacent to each other. The distance between the projection and the projection is 10 mm or more. Thereby, the seal member can be urged stably.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. Note that the present embodiment has a generally similar configuration to the above-described conventional example except that the structure of the sealing means between the rod guide and the piston rod is different. The same reference numerals are given and only different portions will be described in detail.

In the hydraulic shock absorber according to the present embodiment, as shown in FIG. 1, an annular groove 11 is formed in the inner peripheral portion of the rod guide 6, and an annular groove is formed in the annular groove 11 on the side of the cylinder upper chamber 2a. An enlarged diameter portion 12 slightly larger in diameter than 11 is formed. The annular groove 11 is provided with a resin seal member 13 (seal means) having a rectangular cross section for sealing between the rod guide 6 and the piston rod 5.
A bush 14 made of a cylindrical metal for slidingly guiding the piston rod 5 is press-fitted into the enlarged diameter portion 12. The inner surface of the bush 14 is coated with a fluororesin to make the piston rod 5 slide smoothly.

A wave washer 22 (biasing means) is inserted into a gap between the upper end of the bush 14 and the lower end of the seal member 13. As shown in FIGS. 2 and 3, the wave washer 22 is an unbroken washer formed by forming an annular metal into a corrugated shape and having elasticity as a whole. And presses against the sealing surface 11a at the end of the annular groove 11.

The wave washer 22 has eight wavy portions which alternately rise and fall in the circumferential direction. The corrugated portion includes four convex portions 22A and four concave portions 22B, and the convex portions 22A and the concave portions 22B are alternately arranged along the circumferential direction. An initial load is applied to the wave washer 22 in the assembled state, and the sealing member 13
And the contact area of each of the four convex portions 22 </ b> A is relatively large.

When the resin sealing member 13 is urged as in this embodiment, the sealing member 13 and the wave washer
The number of the protruding portions 22 </ b> A in contact with the
When the distance from the contact point 2A is reduced, the contact area at one contact point is reduced, and the seal member 13 may be dented or damaged. Therefore, it is desirable that at least the interval (inner circumferential length) between the adjacent convex portions 22A is 10 mm or more, and the number of the convex portions 22A is desirably three or more in consideration of prevention of inclination of the seal member.

The outer diameter of the wave washer 22 is substantially the same as the inner diameter of the annular groove 11.
And the outer peripheral portion 22A of the wave washer 22 is positioned by contact. The inner diameter of the wave washer 22 is larger than the outer diameter of the piston rod 5. This prevents the inner diameter portion 22B of the wave washer 22 from coming into contact with the piston rod 5.

In the above description, the outer diameter of the wave washer 22 is substantially the same as the inner diameter of the annular groove 11, but is not limited to this, and the difference between the outer diameter of the wave washer 22 and the inner diameter of the annular groove 11 ( If the gap is smaller than the difference (gap) between the inner diameter of the wave washer 22 and the outer diameter of the piston rod 5, contact with the piston rod 5 can be prevented.

The initial load of the spring force of the wave washer 22 is set larger than the coupling force generated by the interference of the seal member 13 with the piston rod 5, that is, the static friction force generated as sliding resistance. Even if the rod 5 strokes in the shortening direction, the sealing member 1
3 is held in a state pressed against the sealing surface 11a with a sufficient force.

The operation of the embodiment having the above-described structure will be described below. Even during the compression stroke of the piston rod 5, the sealing member 13 is always pressed and held by the sealing surface 11a of the annular groove 11 by overcoming the sliding resistance with the piston rod 5 by the spring force of the wave washer 22. Therefore, stable sealing properties can be obtained, and leakage of the oil liquid can be reliably prevented regardless of the stroke direction of the piston rod 5. Further, the sealing member 13
Does not move in the annular groove 11 together with the piston rod 5, so that wear and the like can be reduced and durability can be improved.

Further, since the wave washer 22 forms a plurality of gaps between the wave washer 22 and the seal member 13, a change in volume of the seal member 13 due to thermal expansion or the like is absorbed by its elasticity. Therefore, it is possible to prevent the sliding resistance from increasing due to the thermal expansion of the seal member 13 and the like, and to ensure a stable sliding property of the piston rod 5.

In the above embodiment, as an example, the case where the wave washer 22 is used as the urging means has been described. However, the present invention is not limited to this, and the seal member may be used.
As long as the spring 13 can be urged in the axial direction and can be constantly pressed against the sealing surface 11a of the annular groove 11, a washer, a coil spring, a rubber O-ring, or the like having another shape is used as the urging means. Can also. However, if the side of the cross section of the seal member 13 is as small as about 2 to 3 mm, it is substantially difficult to insert a coil spring or an O-ring, whereas the wave washer 22 is installed. Is easy.

When a coil spring is used,
Since the upper end of the coil spring makes line contact with the lower surface of the seal member 13 in the circumferential direction, the coil spring and the seal member 1
3 may be shifted in the radial direction (that is, the coil spring and the seal member 13 may contact eccentrically). Then, the coil spring generates a force for inclining the seal member 13 with respect to the axis of the piston rod 5, and the upper or lower part of the seal member 13 comes into strong contact with the piston rod 5, and a stable sealing property is obtained. I can't. But wave washer 22
When is used, a substantially uniform force acts on the seal member in the radial direction, so that a force for inclining the seal member 13 is not easily applied, and stable sealing performance can be secured.

Further, when a coil spring is used, the upper end of the coil spring may be displaced in the radial direction and come into contact with the piston rod 5. If an O-ring is used, the O-ring may be crushed and come into contact with the piston rod 5. As described above, when a coil spring or an O-ring is used, it is necessary to prevent the piston rod 5 from coming into contact with the piston rod 5 even in the case of a maximum displacement in the radial direction during the design. There is a problem that the degree of freedom is reduced. However, when the wave washer 22 is used, the difference (gap) between the inner diameter of the wave washer 22 and the outer diameter of the piston rod 5 is determined from the difference (gap) between the outer diameter of the wave washer 22 and the inner diameter of the annular groove 11 described above. If the condition of being large is satisfied, it does not come into contact with the piston rod 5, so that the design is easy.

Further, in the above-described embodiment, as an example, the case where the present invention is applied to a double-cylinder type hydraulic shock absorber has been described. It can be widely used for various cylinder devices such as cylinder devices for active suspension and active suspension.

[0027]

As described above in detail, according to the cylinder device of the first aspect of the present invention, the sealing means is provided with an annular groove for inserting the piston rod into an annular groove formed on the inner peripheral surface of the rod guide. An annular wave-type washer that inserts the seal member and presses the seal member into the gap between one end in the annular groove and the seal member and presses the seal member against the other end of the annular groove. By inserting the biasing means, the sealing member is held in a state of being constantly pressed against the end of the annular groove by the biasing means regardless of the stroke direction of the piston rod. And the leakage of the oil liquid can be reliably prevented regardless of the stroke direction of the piston rod. Furthermore, since a plurality of gaps are formed between the seal member and the wave member by the wave shape of the wave type washer, a volume change due to thermal expansion or the like of the seal member is absorbed by the gap between the seal member and the wave washer. You. As a result, it is possible to prevent the sliding resistance of the piston rod from increasing due to the thermal expansion or the like of the seal member, and to smoothly stroke the piston rod. According to the cylinder device of the second aspect of the present invention, the sealing means
An annular seal member for inserting the piston rod is inserted into an annular groove formed on the inner peripheral surface of the rod guide, and the seal is inserted into a gap between one end of the annular groove and the seal member. By inserting an annular urging means for urging the member and pressing the other end of the annular groove,
Regardless of the stroke direction of the piston rod, the sealing member is held in a state of being constantly pressed against the end of the annular groove by the biasing means, so that a stable sealing property can be obtained. According to the cylinder device of the third aspect of the present invention, since the urging means is formed of a wave-type washer, a plurality of gaps are formed between the urging means and the seal member depending on the wave shape thereof. A volume change due to expansion or the like is absorbed by the gap between the seal member and the washer. As a result, it is possible to prevent the sliding resistance of the piston rod from increasing due to the thermal expansion or the like of the seal member, and to smoothly stroke the piston rod. Further, according to the cylinder device of the fourth aspect, the washer is configured such that the difference between the outer diameter of the washer and the inner diameter of the annular groove is smaller than the difference between the inner diameter and the outer diameter of the piston rod. And the washer can be prevented from contacting. According to the cylinder device of the fifth aspect of the present invention, the shape of the washer is such that convex portions and concave portions are provided alternately in the circumferential direction, the number of convex portions is three or more, and By setting the interval to 10 mm or more, the seal member can be urged stably.

[Brief description of the drawings]

FIG. 1 is an enlarged longitudinal sectional view showing a seal portion of a piston rod of a hydraulic shock absorber according to one embodiment of the present invention.

FIG. 2 is a perspective view of a fragment corresponding to 45 degrees of a wave washer provided in a seal portion of FIG. 1;

FIG. 3 is a view of a wave washer provided in a seal portion of FIG. 1 as viewed from a center axis direction.

FIG. 4 is a longitudinal sectional view showing a seal portion of a piston rod in a conventional hydraulic shock absorber.

5 is an enlarged longitudinal sectional view showing a state of a seal portion during a stroke of extension of a piston rod in the hydraulic shock absorber of FIG. 4;

6 is an enlarged longitudinal sectional view showing a state of a seal portion during a contraction stroke of a piston rod in the hydraulic shock absorber of FIG. 4;

[Explanation of symbols]

 1 Hydraulic shock absorber 2 Cylinder 5 Piston rod 6 Rod guide 11 Annular groove (seal means) 13 Seal member (seal means) 22 Wave washer (urging means, seal means)

Claims (5)

[Claims] 1. A piston to which a piston rod is connected is slidably fitted in a cylinder in which an oil liquid is sealed, and the piston rod is inserted through a rod guide attached to an end of the cylinder. In a cylinder device which extends to the outside and seals between the rod guide and the piston rod by sealing means, the sealing means includes a piston rod provided in an annular groove formed on an inner peripheral surface of the rod guide. An annular seal member is inserted into the gap between one end of the annular groove and the seal member to urge the seal member and press the other end of the annular groove. A cylinder device comprising a biasing means comprising a wave-type washer provided with alternating convex portions and concave portions in a circumferential direction. 2. A piston, to which a piston rod is connected, is slidably fitted in a cylinder filled with an oil liquid, and the piston rod is inserted through a rod guide attached to an end of the cylinder. An oil seal extending to the outside and isolating the inside and outside of the cylinder device on the piston rod projecting end side of the rod guide, and a seal provided between the oil guide and the rod guide and the piston rod. A sealing device, wherein the sealing device inserts an annular sealing member through which the piston rod is inserted into an annular groove formed on the inner peripheral surface of the rod guide; An annular urging means for urging the seal member and pressing against the other end of the annular groove is inserted into a gap between one end of the seal member and the seal member. Cylinder and wherein the door. 3. The cylinder device according to claim 2, wherein said urging means comprises a wave-type washer provided with alternating convex portions and concave portions in a circumferential direction. 4. The cylinder according to claim 1, wherein a difference between an outer diameter of the washer and an inner diameter of the annular groove is smaller than a difference between the inner diameter and an outer diameter of the piston rod. apparatus. 5. The shape of the washer is such that convex portions and concave portions are provided alternately in the circumferential direction, the number of convex portions is three or more, and the interval between adjacent convex portions is 10 mm or more. The cylinder device according to claim 1 or 3, wherein