JPH05321969A - Cylinder device - Google Patents

Abstract

PURPOSE:To prevent damage of the sliding face between a cylinder and a piston rod caused by a coil spring so as to eliminate accident of oil leakage. CONSTITUTION:A coil bearing 21 formed of a small diameter coil part 21A, a tapered coil part 21B and a large diameter coil part 21C is arranged between a spring bearing 11 and a rod guide 3 positioned around a piston rod 9. Free length size of the small diameter coil part 21A is set smaller than the non-sliding range h4 of the outer circumferential face of the piston rod 9, and the free length size of the large diameter coil part 21C is set smaller than a non-sliding range h5 of the inner circumferential face of an inner cylinder 2, and thereby contact interference of the coil spring 21 on the sliding face between the inner cylinder 2 and the piston rod 9 is prevented when it is compressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder device suitable for use in, for example, a hydraulic shock absorber or a gas spring, and more particularly to a spring device of a spring built-in type for absorbing a shock at the time of maximum extension of a piston rod. Regarding a cylinder device.

[0002]

2. Description of the Related Art FIGS. 3 and 4 show a hydraulic shock absorber as an example of a conventional cylinder device.

In the figure, reference numeral 1 denotes an outer cylinder constituting a main body of a hydraulic shock absorber, 2 denotes an inner cylinder as a cylinder coaxially arranged in the outer cylinder 1, and a lower end side of the inner cylinder 2 is an outer cylinder. It is closed together with the cylinder 1 by a bottom cap (not shown) or the like.
An annular oil chamber A is defined between the inner cylinder 2 and the outer cylinder 1, and the annular oil chamber A communicates with an oil chamber C described later on the lower end side of the inner cylinder 2. Reference numeral 3 denotes a rod guide provided on the upper end side of the inner cylinder 2 and having a guide bush 3A. Reference numeral 4 denotes a cap which covers the upper end side of the outer cylinder 1 together with the rod guide 3 and the like.

Reference numeral 5 denotes a piston slidably fitted in the inner cylinder 2, and the piston 5 defines the inside of the inner cylinder 2 into upper and lower oil chambers B and C. Further, on the upper and lower surfaces of the piston 5, there are provided damping force valves 6 and 7 on the contraction side and the extension side, respectively, which generate a predetermined damping force by the pressure oil flowing between the oil chambers B and C, respectively. A piston seal 8 made of an elastic resin material is provided on the outer peripheral side of the piston 5, and the piston seal 8 seals between the inner cylinder 2 and the piston 5.

Reference numeral 9 denotes a piston rod having a lower end fixed to the piston 5 via a nut 10 and an upper end protruding to the outside of the inner cylinder 2 via a guide bush 3A of the rod guide 3, and the protruding end of the piston rod 9 is shown. The side is attached to, for example, the vehicle body side of the vehicle, and is constantly urged in the extension direction by a suspension spring (not shown) or the like.

Reference numeral 11 denotes a spring bearing located above the piston 5 and fixed to the outer circumference of the piston rod 9. The spring bearing 11 is made of a material having a high rigidity and is formed in a stepped cylindrical shape. A collar portion 11A is provided. The spring receiver 11 supports a spring 12 described later by the collar portion 11A, and compresses and deforms the spring 12 when the piston rod 9 is greatly extended.

Reference numeral 12 denotes a spring that is located inside the inner cylinder 2 and is inserted around the piston rod 9. In the spring 12, the inner diameter of each coil portion 12A spirally wound is the outer diameter of the piston rod 9. It is composed of a larger coil spring, and its lower end side is press-fitted into the spring receiver 11. Also, the upper end of the spring 12 is a free end,
When the piston rod 9 extends in the F direction shown by the arrow, the piston rod 9 contacts the lower surface of the rod guide 3 and is elastically compressed and deformed together with the spring receiver 11. When the piston 12 is fully extended, the spring 5 causes the piston 5 to move to the rod guide 3
It is designed to prevent the collision with and to absorb the impact at this time.

In the hydraulic shock absorber thus constructed, for example, the lower end side of the outer cylinder 1 is attached to the axle side of the vehicle, the projecting end side of the piston rod 9 is attached to the vehicle body side, and a suspension spring for suspending the vehicle body side is used. The piston rod 9 is constantly urged in the extension direction. Then, when vibration is applied to the vehicle due to unevenness of the road surface, the piston rod 9 expands and contracts from the outer cylinder 1 so that the pressure oil flows between the oil chambers B and C via the damping force valves 6 and 7. Therefore, the vibration can be damped by the damping force generated by the damping force valves 6 and 7.

When the piston rod 9 extends greatly in the direction of the arrow F, the upper end of the spring 12 contacts the lower surface of the rod guide 3 and is elastically compressed and deformed between it and the spring receiver 11. The spring force of 12 can limit the speed of the piston rod 9 in the extension direction, and the impact when the piston rod 9 extends to the vicinity of the stroke end can be alleviated.

[0010]

By the way, in the above-mentioned prior art, a free length consisting of each coil portion 12A in which a spring 12 for mitigating impact near the stroke end of the piston rod 9 is spirally wound. 3 is a coil spring of h, and the contact height of the spring 12, that is, the compression dimension when the spring 12 is compressed and deformed until the adjacent upper and lower coil portions 12A contact (contact) with each other is shown in FIG. The dimension is set to h1 as shown in.

However, if the aspect ratio (free length h / coil average diameter) of the spring 12 is large, when a large load acts on the piston rod 9 and the piston rod 9 extends to the stroke end shown in FIG. 12
During the compression process, the spring 12 is in a buckled state, and the spring 12 is overcompressed to the size h2 beyond the normal compression size h1 (contact height). In this compression process, each coiled portion 12A of the buckled spring 12 moves while contacting and interfering with the inner peripheral surface of the inner cylinder 2 and the outer peripheral surface of the piston rod 9, thus scratching these surfaces. It may happen.

Therefore, in the prior art, the distance h3 between the rod guide 3 and the piston seal 8 when the piston rod 9 reaches the stroke end as shown in FIG.
When the inner peripheral surface of the inner cylinder 2 is scratched within the range of the free length h (h> h3) of the spring 12, the piston seal 8 is damaged by the scratch at this time, and the piston seal 8 causes the oil chamber B, There is a problem that it becomes impossible to seal between C.

When the spring 12 is overcompressed from the free length h to the dimension h2, each coil portion 12A of the spring 12 comes into contact with and interferes with the outer peripheral surface of the piston rod 9 to make a scar. There is a problem that the guide bush 3A of the rod guide 3 is damaged and, for example, the pressure oil (oil liquid) in the oil chamber B leaks to the outside.

The present invention has been made in view of the above problems of the prior art. The present invention prevents the sliding surfaces of the cylinder and the piston rod from being damaged by the spring when the piston rod extends to the vicinity of the stroke end. It is an object of the present invention to provide a cylinder device that is capable of preventing oil leakage and the like.

[0015]

The features of the structure adopted by the present invention to solve the above-mentioned problems are as follows.
It is composed of a coil spring in which the piston side is a small diameter coil part and the rod guide side is a large diameter coil part. The free length of the large diameter coil part is the inner peripheral surface of the cylinder even when the large diameter coil part is compressed and buckled. Is set to a length dimension such that the position of contact with the piston rod is within the non-sliding region of the piston seal with respect to the inner peripheral surface of the cylinder when the piston rod is maximally extended. Length dimension such that the position of contact with the outer peripheral surface of the piston rod is within the non-sliding region of the guide bush with respect to the outer peripheral surface of the piston rod when the piston rod is maximally extended even if the portion is compressed and buckled. Has been set to.

[0016]

With the above construction, when the piston rod is maximally extended to the stroke end and the coil spring is compressed, the large-diameter coil portion exceeds the non-sliding area of the piston seal with respect to the inner peripheral surface of the cylinder, and It is possible to prevent contact interference with the peripheral surface, and prevent the small-diameter coil portion from contacting interference with the outer peripheral surface of the piston rod beyond the non-sliding region of the guide bush with respect to the outer peripheral surface of the piston rod.

[0017]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. In the embodiment, the same components as those of the prior art shown in FIGS. 3 and 4 described above are designated by the same reference numerals, and the description thereof will be omitted.

First, FIG. 1 shows a first embodiment of the present invention.

In the figure, reference numeral 21 denotes a coil spring as a spring that absorbs an impact when the piston rod 9 extends near the stroke end. The coil spring 21 is almost the same as the spring 12 described in the prior art. Although the free length of the coil spring is set to the dimension h, the coil spring 2
1 is a small-diameter coil portion 21A that is spirally wound,
It is composed of a tapered coil portion 21B and a large-diameter coil portion 21C.

Here, in the small-diameter coil portion 21A, the difference value ΔR1 between the coil inner diameter and the outer diameter of the piston rod 9 is set to, for example, about 1 to 3 mm, and the difference value ΔR2 between the coil outer diameter and the inner cylinder 2 is set. Is larger than the difference value ΔR1 (ΔR2
> ΔR1). The free length dimension of the small-diameter coil portion 21A is such that when the piston rod 9 is fully extended, the non-sliding region h4 of the guide bush 3A with respect to the outer peripheral surface of the piston rod 9 (shown in FIG. 4 described in the prior art). (Corresponding to the dimension h2), and its lower end side is press-fitted to the spring bearing 11.

In the large-diameter coil portion 21C, the difference value ΔR3 between the coil outer diameter and the inner diameter of the inner cylinder 2 is set to, for example, about 1 to 3 mm, and the difference value ΔR4 between the coil inner diameter and the piston rod 9 outer diameter. Is larger than the difference value ΔR3 (ΔR4>
ΔR3). The free length dimension of the large-diameter coil portion 21C is such that when the piston rod 9 is fully extended, the non-sliding region h5 of the piston seal 8 with respect to the inner peripheral surface of the inner cylinder 2 (see FIG. (Corresponding to the separation dimension h3 shown in 1)).

On the other hand, the upper end side of the small-diameter coil portion 21A and the lower end side of the large-diameter coil portion 21C are integrally connected by a tapered coil portion 21B, and the tapered coil portion 21B gradually expands upward, for example, 3 It is formed by a coil having a winding degree. Then, the piston rod 9 is indicated by an arrow F.
When contracted in the opposite direction, the large-diameter coil portion 21
The upper end side of C is separated from the lower surface of the rod guide 3.

The hydraulic shock absorber according to the present embodiment has the above-described structure, and its basic operation is not different from that of the prior art.

In the present embodiment, however, the coil spring 21 as a spring that absorbs the impact when the piston rod 9 extends near the stroke end is provided with the small-diameter coil portion 21A located on the piston 5 side and the small-diameter coil portion 21.
A large diameter coil portion 21C connected to the upper end side of A via a tapered coil portion 21B and the upper end side of which contacts the lower surface of the rod guide 3, and the free length dimension of the small diameter coil portion 21A is shown in FIG. It is made smaller than the sliding area h4, and the free length dimension of the large-diameter coil portion 21C is shown in FIG.
Since it is set smaller than 5, the following operational effects are achieved.

That is, when the piston rod 9 extends to the vicinity of the stroke end and the entire coil spring 21 is compressed from the dimension h of the free length shown in FIG. 1, the large-diameter coil portion 21C of the coil spring 21 becomes as shown in FIG. When it is compressed and buckled from the illustrated state, it comes into contact interference with the inner peripheral surface of the inner cylinder 2. However, at this time, the free length dimension of the large-diameter coil portion 21C is smaller than the non-sliding area h5 shown in FIG. 1, and the large-diameter coil portion 21C is below the non-sliding area h5 of the inner peripheral surface of the inner cylinder 2. Since it does not slide on the side portion, a portion of the inner peripheral surface of the inner cylinder 2 which is a sliding surface with the piston seal 8 and which is below the non-sliding region h5 is damaged by the large-diameter coil portion 21C. The sliding surface below the non-sliding area h5 can be kept in a smooth surface state.

Further, the large-diameter coil portion 21C is set such that the difference value ΔR3 from the inner diameter of the inner cylinder 2 is ΔR3 <ΔR4 with respect to the difference value ΔR4 from the outer diameter of the piston rod 9.
Since it is largely separated from the outer circumference of the piston rod 9 in the radial direction, there is no contact interference with the outer circumference of the piston rod 9 when the large-diameter coil portion 21C is compressed, and the outer circumference of the piston rod 9 is large. The diameter coil portion 21C can be prevented from being damaged.

On the other hand, if the small-diameter coil portion 21A buckles when the coil spring 21 is compressed, the piston rod 9
It comes into contact with the outer peripheral surface of the. However, at this time, the free length dimension of the small-diameter coil portion 21A is smaller than the non-sliding area h4 shown in FIG. 1, and the small-diameter coil portion 21A slides above the non-sliding area h4 on the outer peripheral surface of the piston rod 9. Since it does not move, the sliding surface of the piston rod 9 can be prevented from being damaged by the small-diameter coil portion 21A, and this sliding surface can be maintained in a smooth surface state.

Further, the difference value ΔR1 of the small diameter coil portion 21A
, ΔR2 are set to have a relationship of ΔR1 <ΔR2, and the small-diameter coil portion 21A is largely separated from the inner peripheral surface of the inner cylinder 2 in the radial direction, so that the small-diameter coil portion 21A is arranged on the inner peripheral surface of the inner cylinder 2. Contact interference can be reliably prevented, and the inner peripheral surface of the inner cylinder 2 can be prevented from being damaged by the small-diameter coil portion 21A.

Therefore, according to this embodiment, when the piston rod 9 extends near the stroke end, it is possible to reliably prevent the sliding surfaces of the inner cylinder 2 and the piston rod 9 from being damaged by the coil spring 21. It is possible to prevent damage to the piston seal 8 and the guide bush 3A for a long period of time, to prevent oil leakage, and to secure desired damping force characteristics for a long period of time.

Next, FIG. 2 shows a second embodiment of the present invention. The feature of this embodiment is that a spring 31 for cushioning the impact when the piston rod 9 extends near the stroke end, and a spring at the lower end side is a spring. A small-diameter coil portion 32 that is press-fitted into the receiver 11 and wound in a spiral shape, and is disposed on the upper end side of the small-diameter coil portion 32 via another spring receiver 33, and is wound in a spiral shape. And a large-diameter coil portion 34.

Here, the small-diameter coil portion 32 is formed to have a coil diameter substantially similar to that of the small-diameter coil portion 21A of the coil spring 21 described in the first embodiment.
The free length dimension of is set smaller than the non-sliding area h4. Further, the large-diameter coil portion 34 is formed with a coil diameter substantially similar to the large-diameter coil portion 21C of the coil spring 21 described in the first embodiment, and its free length dimension is the non-sliding region h.
It is set smaller than 5. The upper end of the large-diameter coil portion 34 separates from the lower surface of the rod guide 3 when the piston rod 9 contracts in the direction opposite to the arrow F direction.

Further, the spring receiver 33 is formed as an annular flat plate having a predetermined plate thickness by a fluorine resin material or the like, and the inner peripheral side thereof is an insertion hole 33A through which the piston rod 9 is inserted.
Has become. Then, the spring receiver 33 is provided in each coil portion 3.
A notch 33 formed on the outer peripheral side and disposed between the two
B, 33B, ... Allows the pressure oil (oil liquid) in the oil chamber B to flow above and below the spring bearing 33.

Thus, in this embodiment having such a structure, it is possible to obtain substantially the same operational effects as in the first embodiment, but particularly in this embodiment, the coil portions 32, 3 are formed.
Since the spring bearings 33 made of a fluorine-based resin material are arranged between the coil portions 4 and 4, the coil portions 32 and 34 can be independently compressed and deformed, and the sliding surface of the inner cylinder 2 and the piston rod 9 has the spring bearings 33. Can be surely prevented from being damaged.

In each of the above embodiments, the small diameter coil portion 2
The free length dimension of 1A (32) is set smaller than the non-sliding area h4, and the free length dimension of the large-diameter coil portion 21C (34) is set smaller than the non-sliding area h5.
In place of this, each free length dimension is set to the non-sliding area h4.
, H5, and the length of each free length may be set larger than the non-sliding regions h4, h5. However, in such a large setting, the free length dimension of the small-diameter coil portion 21A (32) is such that, even if the small-diameter coil portion 21A (32) is compressed and buckled, the outer circumference of the piston rod 9 at this buckling portion. The length dimension may be such that the position in contact with the surface is within the non-sliding region h4, and the free length dimension of the large diameter coil portion 21C (34) is the large diameter coil portion 21C (34). Even if it is compressed and buckled, the length dimension may be such that the position of this buckling portion in contact with the inner peripheral surface of the inner cylinder 2 is within the non-sliding region h5.

In each of the above embodiments, the small diameter coil portion 2
Although it has been described that the lower end side of 1A (32) is press-fitted into the spring receiver 11 and the upper end side of the large-diameter coil portion 21C (34) is brought into contact with the lower surface of the rod guide 3, instead of this,
The upper end of the large-diameter coil portion 21C (34) is attached to the rod guide 3
The lower end side of the small-diameter coil portion 21A (32) may be brought into contact with the spring receiver 11 (33) or the like.

Further, in each of the above-mentioned embodiments, the hydraulic shock absorber has been described as an example, but the present invention is not limited to this, and can be applied to a cylinder device such as a gas spring, a hydraulic cylinder, a pneumatic cylinder or the like.

[0037]

As described above in detail, according to the present invention, a spring is constituted by a coil spring having a small diameter coil portion on the piston side and a large diameter coil portion on the rod guide side,
Since the free length dimensions of the small-diameter coil portion and the large-diameter coil portion are set to the specified dimensions, when the piston rod extends near the stroke end and compresses the coil spring, the sliding surface of the cylinder and piston rod is Therefore, it is possible to prevent the damage from being caused, and it is possible to solve the problem that the piston seal, the guide bush and the like are damaged. Therefore, it is possible to eliminate an oil leak accident that is likely to occur in, for example, a hydraulic shock absorber, and to improve the reliability of the cylinder device with a built-in spring.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing a hydraulic shock absorber according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of an essential part showing a hydraulic shock absorber according to a second embodiment.

FIG. 3 is a vertical sectional view showing a hydraulic shock absorber according to a conventional technique.

FIG. 4 is an enlarged cross-sectional view of a main part in FIG. 3 showing a state where a spring is overcompressed.

[Explanation of symbols]

 2 Inner cylinder (cylinder) 3 Rod guide 3A Guide bush 5 Piston 8 Piston seal 9 Piston rod 11, 33 Spring bearing 21 Coil spring (spring) 21A, 32 Small diameter coil portion 21C, 34 Large diameter coil portion 31 Spring h4, h5 Non Sliding area

Claims (1)

[Claims] 1. A cylinder having one end closed and a rod guide provided with a guide bush at the other end, and a cylinder that is slidably inserted into the cylinder via a piston seal to form a cylinder inside the cylinder. A piston defined in the chamber, a piston rod having one end fixed to the piston and the other end protruding outside the cylinder via a guide bush of the rod guide, and a piston rod located around the piston rod and inside the cylinder. In the cylinder device, which is provided and includes a spring that is compressed and deformed between the rod guide and the piston when the piston rod greatly extends from the cylinder, in the spring, the piston side is a small diameter coil portion, The guide side is a coil spring having a large-diameter coil portion, and the free length of the large-diameter coil portion is the large-diameter coil portion. A length dimension such that the position of contact with the inner peripheral surface of the cylinder is within the non-sliding area of the piston seal with respect to the inner peripheral surface of the cylinder when the piston rod is maximally extended even if it is compressed and buckled. The free length of the small-diameter coil portion is such that, even when the small-diameter coil portion is compressed and buckled, the position where the small-diameter coil portion contacts the outer peripheral surface of the piston rod is the outer peripheral surface of the piston rod when the piston rod is maximally extended. The length of the guide bush is set so as to be within the non-sliding area of the guide bush.