JP2994515B2 - Cylinder device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder device suitably used for, for example, a hydraulic shock absorber or a gas spring, and more particularly to a cylinder device with a built-in spring in which a shock at the maximum extension of a piston rod is reduced by a spring. It relates to a cylinder device.

[0002]

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

In the drawing, 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 disposed in the outer cylinder 1, and a lower end of the inner cylinder 2 is an outer cylinder. Together with the cylinder 1, it is closed 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 below at the lower end of the inner cylinder 2. Reference numeral 3 denotes a rod guide provided on the upper end side of the inner cylinder 2 and has a guide bush 3A. Reference numeral 4 denotes a cap covering the upper end side of the outer cylinder 1 together with the rod guide 3 and the like.

[0004] Reference numeral 5 denotes a piston slidably inserted into the inner cylinder 2, and the piston 5 defines upper and lower oil chambers B and C in the inner cylinder 2. On the upper and lower surfaces of the piston 5, there are provided reduction side and extension side damping force valves 6 and 7, 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 whose lower end is fixed to the piston 5 via a nut 10 and whose upper end protrudes outside the inner cylinder 2 via a guide bush 3A of the rod guide 3. The protruding end of the piston rod 9 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 receiver which is located above the piston 5 and is fixed to the outer periphery of the piston rod 9. The spring receiver 11 is formed in a stepped cylindrical shape from a material having high rigidity. A flange 11A is provided. The spring receiver 11 supports a spring 12, which will be described later, by a flange 11A, and compresses and deforms the spring 12 when the piston rod 9 is greatly extended.

Reference numeral 12 denotes a spring located in the inner cylinder 2 and inserted around the piston rod 9. The spring 12 has an inner diameter of each coil portion 12A wound in a spiral shape and an outer diameter of the piston rod 9. The lower end of the coil spring is press-fitted into the spring receiver 11. The upper end of the spring 12 is a free end,
When the piston rod 9 extends in the direction of arrow F, it comes into contact with the lower surface of the rod guide 3 and is elastically compressed and deformed between the piston rod 9 and the spring receiver 11. When the piston 12 reaches its maximum extension position, the spring 5 moves the piston 5 into the rod guide 3.
In addition to preventing collision, the impact at this time is reduced.

In the hydraulic shock absorber constructed as described above, for example, the lower end of the outer cylinder 1 is attached to the axle side of the vehicle, the protruding end of the piston rod 9 is attached to the vehicle body, and a suspension spring for suspending the vehicle body. The piston rod 9 is constantly urged in the extending 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, and the pressure oil flows between the oil chambers B and C via the damping force valves 6 and 7. Therefore, the vibration can be buffered by the damping force generated by the damping force valves 6 and 7.

When the piston rod 9 extends greatly in the direction of arrow F, the upper end of the spring 12 abuts against the lower surface of the rod guide 3 and is elastically compressed and deformed between the spring receiver 11 and the spring. The speed in the extension direction of the piston rod 9 can be limited by the spring force of 12, and the impact when the piston rod 9 extends to near the stroke end can be reduced.

[0010]

By the way, in the above-mentioned prior art, a free length consisting of each coil portion 12A spirally wound with a spring 12 for relaxing an impact near the stroke end of the piston rod 9 is provided. h, the compression dimension when the spring 12 is compressed and deformed until the coil portions 12A adjacent to each other above and below contact (closely contact) each other. Is set to the dimension h1 as shown in FIG.

However, if the aspect ratio (free length h / coil average diameter) of the spring 12 is large, a large load acts on the piston rod 9 and when the piston rod 9 extends to the stroke end shown in FIG. 12
During the compression process, the spring 12 is buckled, and the spring 12 is over-compressed to the dimension h2 beyond the normal compression dimension h1 (close contact height). In this compression process, each coil 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, thereby damaging these surfaces. Sometimes.

For this reason, in the prior art, the separation dimension h3 between the rod guide 3 and the piston seal 8 when the piston rod 9 reaches the stroke end as shown in FIG.
If 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 scar at this time will damage the piston seal 8, and the oil chamber B, There is a problem that it becomes impossible to seal between Cs.

Further, when the spring 12 is overcompressed from the free length h to the dimension h2, if each coil portion 12A of the spring 12 comes into contact with the outer peripheral surface of the piston rod 9 and makes a scar, the scar 12 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 outside.

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

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problem, the feature of the structure adopted by the present invention is that a spring is used.
The piston side is constituted by a coil spring having a small-diameter coil section, and the rod guide side is constituted by a coil spring having a large-diameter coil section. The free length of the large-diameter coil section is such that even if the large-diameter coil section is compressed and buckled, the inner peripheral surface of the cylinder is formed. The length of the small-diameter coil portion is set so that the position where the small-diameter coil portion is in contact with the inner peripheral surface of the cylinder is in the non-slidable region when the piston rod is in maximum extension. Even when the portion is compressed and buckled, the length in which the position in 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 fully extended. It has been set to.

[0016]

According to the above construction, when the piston rod is fully extended to the stroke end and the coil spring is compressed, the large-diameter coil portion extends beyond the non-sliding region of the piston seal with respect to the inner peripheral surface of the cylinder, and the inside of the cylinder is moved. Contact interference with the peripheral surface can be prevented, and the small-diameter coil portion can be prevented from interfering 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]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the embodiment, the same components as those in the prior art shown in FIGS. 3 and 4 are denoted by the same reference numerals, and the description thereof will be omitted.

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

In the figure, reference numeral 21 denotes a coil spring as a spring for reducing the impact when the piston rod 9 extends to the vicinity of the stroke end. The coil spring 21 is substantially the same as the spring 12 described in the prior art. The free length of the coil spring 2 is set to the dimension h.
1 is a small-diameter coil portion 21A 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 diameter of the inner cylinder 2 is set. Is larger than the difference value ΔR1 (ΔR2
> ΔR1). The small-diameter coil portion 21A has a free length dimension such that the non-sliding area h4 of the guide bush 3A with respect to the outer peripheral surface of the piston rod 9 when the piston rod 9 is maximally extended (shown in FIG. (Corresponding to the dimension h2), and its lower end is press-fitted into the spring receiver 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 outer diameter of the piston rod 9 is set. Is larger than the difference value ΔR3 (ΔR4>
ΔR3). The large-diameter coil portion 21C has a free length dimension in which the piston seal 8 is in a non-slidable region h5 with respect to the inner peripheral surface of the inner cylinder 2 when the piston rod 9 is fully extended (see FIG. (Corresponding to the separation dimension h3 shown in FIG. 3).

On the other hand, the upper end of the small-diameter coil portion 21A and the lower end of the large-diameter coil portion 21C are integrally connected by a tapered coil portion 21B, and the diameter of the tapered coil portion 21B gradually increases upward. It is formed by a coil having a winding degree. Then, the piston rod 9 moves to the arrow F
When reduced 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 this embodiment has the above-described configuration, and its basic operation is not particularly different from that of the prior art.

In this embodiment, however, the coil spring 21 as a spring for alleviating the impact when the piston rod 9 is extended to the vicinity of the stroke end includes the small-diameter coil portion 21A located on the piston 5 side and the small-diameter coil portion 21A.
A is connected to the upper end side of the rod A via a tapered coil part 21B, and has a large-diameter coil part 21C whose upper end is in contact with the lower surface of the rod guide 3. The free length of the small-diameter coil part 21A is shown in FIG. The sliding area h4 is smaller than the sliding area h4, and the free length of the large diameter coil portion 21C is set to the non-sliding area h shown in FIG.
Since the value is set smaller than 5, the following operation and effect can be obtained.

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 free length dimension h shown in FIG. 1, the large-diameter coil portion 21C of the coil spring 21 is moved to the position shown in FIG. When buckling is caused by being compressed from the illustrated state, it comes into contact with and interferes with the inner peripheral surface of the inner cylinder 2. However, at this time, the free length of the large-diameter coil portion 21C is smaller than the non-sliding region h5 shown in FIG. 1 and the large-diameter coil portion 21C is lower than the non-sliding region h5 on the inner peripheral surface of the inner cylinder 2. Since the side portion does not slide, the portion of the inner peripheral surface of the inner cylinder 2, which is the sliding surface with the piston seal 8, 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 maintained in a smooth surface state.

The large-diameter coil portion 21C is set so that the difference ΔR3 between the inner diameter of the inner cylinder 2 and the difference ΔR4 between the outer diameter of the piston rod 9 and ΔR3 <ΔR4.
Since the large-diameter coil portion 21C is compressed, it does not interfere with the outer peripheral surface of the piston rod 9 because the outer peripheral surface of the piston rod 9 is large because the large-diameter coil portion 21C is compressed. Damage by the radial coil portion 21C can be prevented.

On the other hand, when the small-diameter coil portion 21A buckles when the coil spring 21 is compressed, the piston rod 9
Comes into contact with the outer peripheral surface of the device. However, at this time, the free length of the small-diameter coil portion 21A is smaller than the non-sliding region h4 shown in FIG. 1, and the small-diameter coil portion 21A slides on the outer peripheral surface of the piston rod 9 above the non-sliding region h4. 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 the sliding surface can be kept in a smooth surface state.

Further, the difference value ΔR1 of the small diameter coil portion 21A is obtained.
, ΔR2 are set to satisfy 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. 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 the present embodiment, when the piston rod 9 extends near the stroke end, the sliding surfaces of the inner cylinder 2 and the piston rod 9 can be reliably prevented from being damaged by the coil spring 21. Thus, various effects are obtained, such as damage to the piston seal 8 and the guide bush 3A can be prevented over a long period of time, and a desired damping force characteristic can be secured for a long period without oil leakage.

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

Here, the small-diameter coil portion 32 is formed with substantially the same coil diameter as the small-diameter coil portion 21A of the coil spring 21 described in the first embodiment.
Is set to be smaller than the non-sliding area h4. The large-diameter coil portion 34 has a coil diameter substantially the same as that of the large-diameter coil portion 21C of the coil spring 21 described in the first embodiment, and has a free length dimension of the non-sliding region h.
It is set smaller than 5. When the piston rod 9 contracts in the direction opposite to the direction indicated by the arrow F, the upper end of the large-diameter coil portion 34 is separated from the lower surface of the rod guide 3.

The spring support 33 is formed as an annular flat plate having a predetermined thickness from a fluorine-based resin material or the like, and the inner peripheral side thereof has an insertion hole 33A through which the piston rod 9 is inserted.
It has become. The spring receiver 33 is connected to each coil 3
A notch 33 disposed between the outer peripheral side and the outer peripheral side;
B, 33B,... Allow the pressure oil (oil liquid) in the oil chamber B to flow above and below the spring receiver 33.

Thus, in this embodiment having the above-described structure, substantially the same operation and effect as those of the first embodiment can be obtained. In particular, in this embodiment, each of the coil portions 32 and 3 is provided.
Since the spring receiver 33 made of a fluorine-based resin material is disposed between the spring members 4, the respective coil portions 32 and 34 can be independently compressed and deformed. Damage can be reliably prevented.

In the above embodiments, the small-diameter coil portion 2
Although the free length of 1A (32) is set smaller than the non-sliding area h4 and the free length of the large-diameter coil portion 21C (34) is set smaller than the non-sliding area h5,
Instead, each free length dimension is set to the non-sliding area h4.
, H5, and the free length may be set larger than the non-sliding areas h4, h5. However, when the small-diameter coil portion 21A (32) is set to be large as described above, the free length of the small-diameter coil portion 21A (32) is limited even if the small-diameter coil portion 21A (32) is compressed and buckled. The length of the large-diameter coil portion 21C (34) should be such that the position in contact with the surface is within the non-sliding region h4. Even if the buckling member is compressed and buckled, the length of the buckled portion may be set so that the position where the buckling portion contacts 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 the lower end of the 1A (32) is press-fitted into the spring receiver 11, the upper end of the large-diameter coil portion 21C (34) is brought into contact with the lower surface of the rod guide 3, but instead of this,
The upper end of the large-diameter coil portion 21C (34) is
And the lower end of the small-diameter coil portion 21A (32) may contact the spring receiver 11 (33) or the like.

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

[0037]

As described in detail above, 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 of the small diameter coil part and the large diameter coil part are set to predetermined dimensions, when the piston rod expands near the stroke end and compresses the coil spring, the sliding surfaces of the cylinder and piston rod are moved by the coil spring. Thus, the problem that the piston seal, the guide bush, and the like are damaged can be solved. Therefore, for example, an oil leak accident that easily occurs in a hydraulic shock absorber or the like can be eliminated, and the reliability of the cylinder device with a built-in spring can be improved.

[Brief description of the drawings]

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

FIG. 2 is a vertical sectional view showing a main part of a hydraulic shock absorber according to a second embodiment.

FIG. 3 is a longitudinal sectional view showing a conventional hydraulic shock absorber.

FIG. 4 is an enlarged 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 receiver 21 coil spring (spring) 21A, 32 small diameter coil part 21C, 34 large diameter coil part 31 spring h4, h5 non Sliding area

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F16F 9/00-9/58

Claims (1)

(57) [Claims] 1. A cylinder having one end closed and a rod guide provided with a guide bush at the other end, and slidably inserted into the cylinder via a piston seal. A piston defined in the chamber, a piston rod having one end fixed to the piston and the other end protruding out of the cylinder via a guide bush of the rod guide, and a piston positioned around the piston rod and in the cylinder. Wherein the piston rod is provided with a small-diameter coil portion on the piston side when the piston rod largely extends from the cylinder, and the spring is compressed and deformed between the rod guide and the piston. The guide side is constituted by a coil spring having a large-diameter coil portion, and the free length of the large-diameter coil portion is determined by the large-diameter coil portion. Even if the piston rod is compressed and buckled, a length dimension in which the position in contact with the inner peripheral surface of the cylinder 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 fully extended. 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 in contact with the outer peripheral surface of the piston rod is the outer peripheral surface of the piston rod when the piston rod is fully extended. The length of the cylinder device is set to be within the non-sliding region of the guide bush.