JPH09242802A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorber having a structure suited for miniaturization. SOLUTION: A shock absorber 1 provided with a body case 2 and a piston rod 6, absorbs shock applied to the piston rod 6 by drag brought about by a fluid. By allowing the piston rod 6 to abut against a piston valve 17, a case- inside and outside connecting path 15 is opened in the course of sinking stroke of the piston rod. When negative pressure is applied to the inside of the body case 2, the case-inside and outside connecting path 15 is opened by projecting stroke.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber that absorbs a shock of a work.

[0002]

2. Description of the Related Art Since a shock of a work is likely to be applied to the end of a movable part of industrial equipment, some kind of shock absorbing equipment is often installed at that position. As a kind of such equipment, what is called a shock absorber (or damper) has been conventionally known.

Among shock absorbers, those utilizing fluid pressure generally have a basic structure in which a piston rod is inserted in a cylinder tube so as to be retractable. The piston portion of this piston rod defines a pressure chamber in the cylinder tube, and one end of the rod portion projects outside from the cylinder tube. A fluid such as oil is contained in the pressure chamber. Therefore, when the work comes into contact with the protruding end surface of the rod portion, the piston rod retracts into the cylinder tube due to the pressing force. In this case, the oil in the pressure chamber is pressurized, and the drag force of the oil acting on the piston rod increases. As a result, the impact of the work is absorbed.

[0004]

However, when designing a conventional shock absorber using oil, it is necessary to secure a space of a certain volume in the cylinder tube. Specifically, it is a space for holding the oil in an unloaded state, a space for allowing the oil to escape when the piston rod is retracted, a space for the insertion volume of the piston rod, and the like. Therefore, it is extremely difficult in design to downsize the entire shock absorber while securing these spaces.

In addition to those using oil as described above, several shock absorbers using air have been proposed in the past (Japanese Utility Model Publication No. 5-18504, Japanese Patent Application Laid-Open No. 1-145440, Japanese Patent Application Laid-Open No. 1-145440). No. 307531). Each of the shock absorbers disclosed in these publications can take in the air outside the cylinder body into itself. The reaction force generated by compressing the taken-in air is configured to absorb the impact of the work applied to the piston rod. Therefore, each of the above-described devices that utilize a fluid outside is advantageous in that a space or the like for holding the air that is a fluid is unnecessary.

However, these conventional devices still have the following problems. Fair fair 5-18504
In the conventional device of the publication, air is supplied into the cylinder body through the fine holes of the air filter and the small holes penetrating the valve in the protruding stroke of the piston rod.
However, since the air supply speed is slow, the protrusion stroke speed becomes slow. Further, when the piston rod and the work are separated and the former does not follow the latter, air cannot be self-supplied in the cylinder body.

The conventional apparatus disclosed in Japanese Patent Laid-Open No. 1-145440 has a structure in which a perforated plate having a large number of fine holes is provided on a path for discharging air and the opening area of the fine holes is variable. However, since it was extremely difficult to form a perforated plate with this configuration, it was not suitable for miniaturization. Further, in this device, the air supply path and the air discharge path are separate and independent, and a valve is required for each. Therefore, even from this point of view, it has to be said that it is not suitable for miniaturization.

In the conventional device disclosed in JP-A-1-307531, a coil spring is provided so as to surround the outer peripheral surface of the cylinder body. This coil spring biases the piston rod in the rod protruding direction. Therefore, even if the piston rod and the work are separated, the piston rod returns by itself, and at that time, self-sufficient air is supplied.
However, this device is not suitable for miniaturization because the air supply route and the air discharge route are separate and independent. Further, in the conventional technique of this type, it is necessary to set the urging force of the spring provided at the end of the immersion stroke to a considerably large value, and this point is also unsuitable for downsizing.

The present invention has been made to solve the above problems, and an object thereof is to provide a shock absorber having a structure suitable for downsizing because it does not have the above problems.

[0010]

In order to solve the above-mentioned problems, according to the invention as set forth in claim 1, the impact of the work which comes into contact with and separates from the piston rod provided in the main body case so as to be retractable is After absorbing by the drag force generated by the compression of the fluid in the pressure chamber defined in the main body case,
A shock absorber that discharges the fluid out of the main body case and further supplies the fluid outside the main body case into the pressure chamber by itself is slidably accommodated in the main body case and contacts the piston rod. A piston valve that is pressed in the rod retraction direction by contact, a first pressure chamber that is defined between the piston rod and the piston valve, and an opposite surface side of the first pressure chamber via the piston valve. A second pressure chamber, a pressure chamber communication passage that communicates the pressure chambers with each other, a case inner / outer communication passage that communicates the inside and outside of the main body case, and the piston rod is biased in the rod protruding direction. Piston rod urging means for closing the inner and outer communication passages of the case by urging the piston valve in the rod protruding direction. And a piston valve urging means for holding the piston rod, and the piston rod comes into contact with the piston valve to open the case inner / outer communication path in the middle of the retraction stroke, and to make the main body case negative pressure. A gist of the shock absorber is characterized in that the communication path between the inside and outside of the case is opened by a protruding stroke.

According to a second aspect of the present invention, the gist of the first aspect is that the case inner / outer communication passage communicates the second pressure chamber with an outer region of the main body case.

A third aspect of the present invention is summarized in that, in the first or second aspect, the outer opening of the case inner / outer communication passage is arranged in a recess in the outer peripheral surface of the main body case.

Hereinafter, the "action" of the present invention will be described. The operation of the invention described in claim 1 will be described. Since the piston rod is biased by the piston rod biasing means, when the work is not in contact, the piston rod is in a completely projected state. In such an unloaded state, the piston valve is held at a position that closes the case inner / outer communication passage. Therefore, the fluid does not move in and out of the main body case.

When a work comes into contact with the piston rod, the piston rod is pressed by the work to start an immersion stroke. Then, the pressure of the fluid in the pressure chamber gradually increases, and the drag force on the piston rod gradually increases accordingly. Therefore, at this time, the kinetic energy of the work is reduced, and the shock absorption is achieved. The urging force of the piston rod urging means also contributes to the shock absorption.

When the piston rod moves to the predetermined position of the retracting stroke, the piston rod contacts the piston valve and presses the piston valve in the rod retracting direction. Then, the case inside / outside communication passage closed by the piston valve is opened, and the fluid compressed in the pressure chamber is discharged to the outside of the main body case. Therefore, the internal pressure of the body case is rapidly reduced, and the drag force on the piston rod is also rapidly reduced. After this, the pressure difference between the inside and outside of the main body case becomes extremely small.

When the work starts to move in the opposite direction, the piston rod starts to move in the rod projecting direction in order to return to the original position mainly by the urging force of the piston rod urging means. When the immersing stroke is switched to the projecting stroke in this way, both pressure chambers become negative pressure as the volume of both pressure chambers increases. As a result of the pressure difference between the inside and outside of the main body case, the communication passage inside and outside the case is opened. Therefore, the fluid in the outer region of the main body case flows into the main body case through the case internal / external communication passages. Therefore, the fluid is supplied by itself, and finally the original unloaded state is restored.

Therefore, according to the invention of claim 1,
Since the fluid can be self-supplied from the outside of the case body, a space or the like for retaining the fluid is unnecessary. Therefore, the structure is suitable for miniaturization. Moreover, the supply and discharge of the fluid are performed not by the separate and independent means but by the case inner / outer communication passage and the piston valve. Such common use surely contributes to downsizing. Furthermore, with this configuration, the fluid will flow in smoothly,
The speed of the projecting stroke does not slow down.

According to the second aspect of the present invention, the first pressure chamber is communicated with the outer region of the main body case via the second pressure chamber and the communication passage between the pressure chambers, whereby the fluid is supplied and discharged. Done. Therefore, as compared with the case where the fluid is directly supplied to and discharged from the first pressure chamber, the risk of dust and the like entering is reduced. Therefore, it is possible to prevent the slidability of the piston rod from decreasing.

According to the third aspect of the present invention, even if there is an obstacle on the outer peripheral surface of the main body case, the outer opening of the case internal / external communication passage is not blocked by the obstacle. Therefore, even in such a case, it is possible to reliably supply and discharge the fluid.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION One embodiment of a shock absorber 1 embodying the present invention will be described in detail below with reference to FIGS.

As shown in FIG. 1 and the like, a main body case 2 constituting the shock absorber 1 is a cylindrical member, and a screw groove for fixing itself to another member is provided on the outer peripheral surface thereof. (Not shown) is formed. A disk-shaped head cover 3 is attached to one end surface of the body case 2. A packing 4 is fitted in an annular mounting groove on the outer peripheral surface of the head cover 3. The packing 4 seals the gap between the inner wall surface of the main body case 2 and the outer peripheral surface of the head cover 3.

A piston rod 6 is provided in the main body case 2 so as to be retractable. The piston rod 6 is
It is divided into a piston portion 7 and a rod portion 8. Rod part 8
Protrudes from one side surface of the piston portion 7, and a cap 9 is fitted on the tip thereof. A packing 10 is fitted in an annular mounting groove on the peripheral surface of the piston portion 7. The packing 10 seals the gap between the inner wall surface of the main body case 2 and the outer peripheral surface of the piston portion 7. The piston portion 7 includes the first protruding portion 2 on the inner wall surface of the body case 2.
It is housed so as to slide with respect to a. A housing space is formed in the main body case 2 by the piston portion 7, the main body case 2, and the head cover 3.

The free end of the rod portion 8 penetrates the bearing 11 attached to one end surface of the body case 2 and projects to the outside of the body case 2. In this way, the side (or direction) of the shock absorber 1 where the rod portion 8 projects is referred to as the rod projecting side (or direction) for convenience. On the contrary, the opposite side (or direction) will be referred to as the rod retracting side (or direction). 1 to 4, the former is on the upper side and the latter is on the lower side.

One end of a coil spring 12 as a piston rod urging means is supported in a recess provided on the rod protruding side surface of the bearing 11. Meanwhile, the cap 7
The other end of the coil spring 12 is supported in the concave portion provided on the rod recessed side surface. Therefore, the coil spring 12 plays a role of urging the piston rod 6 in the rod protruding direction. The coil spring 12 is thicker than the rod portion 8 and is
Is thinner than.

A second projecting portion 2b exists at a position closer to the rod than the first projecting portion 2a. A case inside / outside communication passage 15 for communicating the inside and outside of the main body case 2 is transparently provided in the second projecting portion 2b. The outer opening 15 a of the case inner / outer communication passage 15 is located on the bottom surface of the annular groove 16 as a recess formed in the outer peripheral surface of the main body case 1. On the other hand, the inner opening 15b of the case inner / outer communication passage 15
Is located on the surface of the second protrusion on the rod retraction side. The diameter of the case inner / outer communication passage 15 is set to about several hundreds of μm.

In the body case 2, the piston portion 7
A piston valve 17 is slidably accommodated on the rod retractable side. And this piston valve 17
Thus, the accommodation space inside the main body case 2 is divided into a first pressure chamber S1 and a second pressure chamber S2. The first pressure chamber S1 exists between the rod retracting side surface of the piston portion 7 and the rod protruding side surface of the piston valve 17. Second
The pressure chamber S2 exists between the rod retracting side surface of the piston valve 17 and the rod protruding side surface of the head cover 3.
A through hole extending in the axial direction is formed at the center of the piston valve 17. The through hole serves as an inter-pressure-chamber communication passage 14 that connects the pressure chambers S1 and S2 to each other. Further, both end surfaces of the piston valve 17 are pressure acting surfaces. The rod retraction side end surface in the second pressure chamber S2 has a larger area than the rod protruding side end surface in the first pressure chamber S1. Therefore, when positive pressure of the same magnitude acts on both pressure chambers S1 and S2, a thrust force is applied in the rod protruding direction due to the differential pressure. On the contrary, when a negative pressure of the same magnitude acts, a thrust force is applied in the rod retraction direction due to the differential pressure.

The piston portion 7 contacts the end surface of the piston valve 17 on the rod protruding side. Therefore, the piston valve 17 is pressed toward the rod retracting side during the retracting stroke.

The outer peripheral portion of the piston valve 17 has a first small diameter portion 17a, a first large diameter portion 17b, and a first large diameter portion 17b in this order from the rod protruding side.
It is divided into a second small diameter portion 17c and a second large diameter portion 17d. The packing 18 is fitted in the annular mounting groove in the first small diameter portion 17a. This packing 18 is
The outer peripheral surface of the small diameter portion 17a and the first protruding portion 2a of the main body case 2
The gap between and is sealed.

A packing 19 is fitted in the annular mounting groove in the first large diameter portion 17b. The packing 19 seals the gap between the groove portion between the first protruding portion 2a and the second protruding portion 2b and the outer peripheral surface of the first large diameter portion 17b. The width of the groove portion of the main body case 2 is equal to that of the first large diameter portion 1
It is slightly larger than the width of 7b. Therefore, this difference in size is the stroke length of the piston valve 17. That is, the movement of the piston valve 17 along the axial direction is restricted by the first large diameter portion 17b coming into contact with the side surfaces of the first protruding portion 2a and the second protruding portion 2b. A donut-shaped rubber seal member 20 is attached to the rod protruding side surface of the second large diameter portion 17d.

A leaf spring 21 as a piston valve urging means is attached to the rod projecting side surface of the head cover 3. The leaf spring 21 biases the piston valve 17 toward the rod protruding side. Therefore, the piston valve 1
The seal member 20 of No. 7 closes / opens the inside opening 15b of the case inside / outside communication passage 15.

Next, the operation of the shock absorber 1 configured as described above will be described. Here, it is assumed that the shock absorber 1 is used in the atmosphere of normal pressure. Therefore, the shock absorber 1 uses the air A1 which is a fluid.
Surrounded by.

FIG. 1 shows the shock absorber 1 in a state where the work W is not in contact with the cap 9, that is, in the unloaded state. At this time, the piston rod 6 completely projects from the main body case 2, and the piston valve 17
Is held at a position that closes the case inside / outside communication passage 15. Therefore, the movement of the air A1 in and out of the main body case 2 does not occur at this time.

When the work W contacts the piston rod 6, the work W pushes the work rod W in the rod retraction direction. When the immersion stroke starts in this way, the volume of the first pressure chamber S1 becomes smaller, and the pressure of the air A1 in the main body case 2 gradually increases. Along with this, the drag force of the air A1 on the piston rod 6 also gradually increases. Therefore, at this time, the kinetic energy of the work W is reduced, and as a result, shock absorption is achieved. In this case, the biasing force of the coil spring 12 also contributes to the absorption of impact. The first pressure chamber S1
The air A1 therein passes through the inter-pressure-chamber communication passage 14 penetrating the piston valve 17 and flows into the second pressure chamber S2. As a result, the pressure of the air A1 in the second pressure chamber S2 becomes substantially equal to that of the first pressure chamber S1. At this time, since positive pressure acts on both end surfaces of the piston valve 17, thrust force acts on the piston valve 17 toward the rod protruding side. Therefore, the piston valve 17 is biased by this pressure difference and the biasing force of the leaf spring 21,
The case internal / external communication passage 15 is held in a closed state.

In the first half of the immersion stroke, the volume of the first pressure chamber S1 gradually decreases, and when the piston portion 7 contacts the piston valve 17, the volume becomes zero (see FIG. 2). ). After that, the pressing force of the piston portion 7 acts on the piston valve 17, and the piston valve 17 moves together with the piston rod 6 in the rod retraction direction.

Then, the case inside / outside communication passage 15 closed by the piston valve 17 is opened, and the air A1 compressed in the second pressure chamber S2 is transferred to the main body case 2
Released to the outside. Therefore, in the latter half of the immersion stroke, the internal pressure of the main body case 2 is rapidly reduced, and the drag force on the piston rod 7 is also rapidly reduced. After this, the pressure difference between the inside and outside of the main body case 2 becomes extremely small, and eventually the internal pressure becomes substantially equal to the atmospheric pressure. FIG. 3 shows a state where the piston rod 6 is completely immersed in the main body case 2.

When the work W starts moving in the opposite direction, the pressing force in the rod retracting direction is not applied to the piston rod 6, and the biasing force of the coil spring 12 exceeds it. Then, mainly the coil spring 1
The urging force of 2 causes the piston rod 6 to start moving in the rod protruding direction so as to return to the original position.

When the immersing stroke is switched to the projecting stroke in this way, as the volume of both pressure chambers S1 and S2 increases, the inside of both pressure chambers S1 and S2 has a negative pressure relative to the outer region of the main body case 2. Becomes As a result of the pressure difference between the inside and outside of the main body case 2 as described above, a thrust force for the rod immersing method acts on the piston valve 17, and the communication passage 1 inside and outside the case
5 is released. Therefore, the air A1 in the outer region of the main body case 2 flows into the main body case 2 through the case inside / outside communication passage 15. Therefore, the air A1 is supplied by itself. The self-sufficiency of the air A1 is maintained throughout the projecting stroke. Then, the shock absorber 1 finally returns to the original unloaded state as shown in FIG. 1, and the case inner / outer communication passage 15 is closed again.

Hereinafter, the function and effect characteristic of the present embodiment will be listed. (A) In this shock absorber 1, the air A1 can be self-supplied from the outside of the main body case 2. For this reason,
No space is needed to hold the air A1. Therefore, the shock absorber 1 has a structure suitable for downsizing as compared with a shock absorber 1 using oil as a fluid.

(B) Moreover, this shock absorber 1
The supply / discharge of the air A1 in (1) is performed by the case inner / outer communication passage 15 and the piston valve 17 rather than by separate means as in the prior art. That is, only one valve is required, unlike the conventional technique that requires two valves. The commonization of such a configuration surely contributes to downsizing of the shock absorber 1.

(C) Further, with this configuration, the air A1 flows into the main body case 2 through the case inside / outside communication passage 15 as described above. Therefore, as compared with the conventional technique in which the air A1 flows in through the perforated plate and the small holes, the air A1
1 smoothly flows in. Therefore, according to the shock absorber 1, the speed of the protrusion stroke does not slow down. Therefore, the shock absorber 1 is suitable for absorbing the shock of the work W moving at high speed, for example.

(D) According to this embodiment, the first pressure chamber S1 is provided via the second pressure chamber S2 and the communication passage 15 between the pressure chambers.
The inside and the outside of the body case 2 are communicated with each other, whereby the air A1 is supplied and discharged. Therefore, the first pressure chamber S
As compared with the prior art in which the air A1 is directly supplied to and discharged from the inside of 1, the risk of dust or the like entering the first pressure chamber S1 is reduced. Therefore, according to such a configuration, it is possible to prevent the slidability of the piston rod 17 from being deteriorated.

(E) According to this embodiment, the outer opening 15a of the case inner / outer communication passage 15 is arranged in the annular groove 16 on the outer peripheral surface of the main body case 2. Therefore, even if there is an obstacle on the outer peripheral surface of the main body case 2, the outer opening 15a is not blocked by the obstacle.
Therefore, even in such a case, it is possible to reliably supply and discharge the air A1.

(F) In this shock absorber 1, the coil spring 12 having a diameter smaller than that of the main body case 2 is used as the piston rod urging means. Therefore, as compared with the configuration in which the coil spring is arranged so as to surround the entire shock absorber, the size is surely reduced.

(G) The present embodiment is characterized in that the area of the pressure acting surface of the piston valve 17 is set so that the rod retraction side end surface is larger than the rod protruding side end surface. Therefore, when positive pressure of the same magnitude acts, thrust is applied in the rod protruding direction by the differential pressure, as described above. The reason why such characteristics are advantageous for the shock absorber 1 will be described below.

FIG. 5A schematically shows the essential part of the conventional damper disclosed in JP-A-1-307531. In the figure, Cs is a coil spring constituting the ventilation adjusting mechanism, P0 is an internal pressure, Sq1 is a cross-sectional area of the air passage hole, and Sq2 is a cross-sectional area of the valve shaft. Then, in order for the coil spring Cs to close the air passage hole, a load large enough to overcome the internal pressure × pressure receiving area = P0 × (Sq1 + Sq2) is required. But,
The value of the internal pressure P0 increases as the piston moves toward the retracted stroke end, and the value represented by the previous equation also increases in proportion thereto. Therefore, in the conventional device, it is necessary to use the coil spring Cs having a considerably large urging force, and it is understood that this point is structurally unsuitable for downsizing.

On the other hand, FIG. 5B schematically shows the shock absorber 1 of this embodiment. In the figure, P1 is the pressure in both pressure chambers S1 and S2, Sq3 is the area of the end face of the piston valve 17 on the rod protruding side, and Sq4
Is the area of the end face of the piston valve 17 on the rod retraction side, F3
Is a force applied to the piston valve 17 in the rod retracting direction, and F4 is a force applied to the piston valve 17 in the rod protruding direction.

In this shock absorber 1, Sq3 <Sq4 is set as described above. Therefore, as the pressure P1 increases, the degree of F3 <F4 increases, and the piston valve 17 is strongly pressed in the protruding direction. Therefore, even if the biasing force of the coil spring 12 is weak, the coil spring 12 has a structure suitable for downsizing as compared with FIG. 5A.

In addition to such effects, of course, the configuration of the present embodiment has an effect that the piston valve and the piston rod can be quickly and reliably restored during the projection stroke.

The present invention can be modified, for example, as follows. (1) Shock absorber 31 of another example 1 shown in FIG.
Then, the male screw 33 is formed on the outer peripheral surface of the head cover 32. A female screw 3 corresponding to the male screw 33 is formed on the inner wall surface of the opening of the body case 2 on the rod retracting side.
4 are formed. Therefore, such a head cover 32 is screwed to the body case 2. A recess 35 is formed at the center of the end face of the head cover 32 on the rod retraction side, into which the tip of a driver or the like can be fitted when the head cover 32 is screwed. According to such another example 1, the biasing force of the leaf spring 21, which is the piston valve biasing means, can be changed by adjusting the screwing degree of the head cover 32. Therefore, the shock absorbing capacity of the shock absorber 31 can be adjusted.

(2) The shock absorber 41 of the second example shown in FIG. 7 also has a shock absorbing ability as in the first example. In this example, the head cover 42 has a cap shape, and a female screw 44 is formed on the inner wall surface of the cap portion. A male screw 43 corresponding to the female screw 44 is formed on the outer peripheral surface of the body case 2 on the rod retracting side.
Are formed. Therefore, according to the second modification, the same effect as that of the first modification can be obtained. However, in view of the fact that the head cover 42 has a larger diameter than the main body case 2, the configuration of the other example 1 is more preferable for achieving miniaturization.

(3) In the shock absorber 51 of another example 3 shown in FIG. 8, a plurality of case inner / outer communication passages 15 for communicating the inside and the outside of the main body case 2 are provided, and each outer opening 15 a is in the annular groove 16. Are placed in multiple locations. In addition, in the annular groove 16, a metallic C having suitable elasticity is used.
The ring 52 is slidably fitted. Since the C ring 52 is partially cut out, some of the outer openings 15a can be opened and closed by changing the position of the cutout. Therefore, the C ring 52 functions as a so-called air flow rate adjusting means, and the shock absorbing ability can be adjusted.

(4) Outer opening 1 of case inner / outer communication hole 15
5a may be formed at another position, for example, the end surface of the main body case 2 or the like. (5) A biasing means other than the coil spring 12 may be used as the piston rod biasing means.

(6) As the piston valve urging means, an urging means other than the leaf spring 21, for example, a coil spring may be used. However, the configuration using the leaf spring 21 which is thin as in the above embodiment is more preferable because it can prevent the shock absorber 1 from being lengthened. Further, such a biasing means is provided in the piston valve 17
It is also permissible to provide it on the side end surface or the inner wall surface of the body case 2.

(7) It is also possible to provide the communication passage 14 between the pressure chambers at a place other than the piston valve 17, that is, at the main body case 2 side. However, the structure provided on the piston valve 17 side as in the above-described embodiment is preferable because processing is easier.

Here, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiment will be listed below. (1) After absorbing the impact of the work coming into contact with and separating from the piston rod provided in the main body case so as to be retracted, by the drag force generated by the compression of the fluid in the pressure chamber defined in the main body case, A shock absorber that discharges fluid outside the main body case and further supplies the fluid outside the main body case into the pressure chamber by itself, is slidably accommodated in the main body case, and is in contact with the piston rod. And a piston rod urging means for urging the piston rod in the rod protruding direction, and a case inner / outer communication passage. And a piston valve urging means for urging the piston valve at a position to close the A shock absorber configured such that the case inner / outer communication passage is opened by abutting the piston rod, and the case inner / outer communication passage is opened due to a pressure difference between the inside and the outside of the main body case in a projecting stroke.

(2) The shock absorber according to any one of claims 1 to 3 and technical idea 1, wherein the piston rod urging means is a coil spring installed outside the main body case.

(3) A shock absorber according to any one of claims 1 to 3 and technical idea 1, wherein the piston rod urging means is a coil spring having a diameter smaller than that of the main body case. With this configuration, the size can be further reduced.

(4) Claims 1 to 3, technical ideas 1 to 3
The shock absorber according to any one of claims 1 to 5, wherein the piston valve urging means is a leaf spring interposed between the piston valve and the head cover. With this configuration, the size can be further reduced.

(5) Claims 1 and 2, technical ideas 1 to 4
In any one of the above, the shock absorber characterized in that the outer opening of the case inner / outer communication passage is arranged in an annular groove formed on the outer peripheral surface of the main body case. With such an annular groove, processing is easy and the above C ring or the like can be slidably fitted.

(6) Claims 1 to 3, technical ideas 1 to 5
In any one of the above, the head cover having the piston valve biasing means is screwed to the main body case, and the biasing force by the piston valve biasing means can be adjusted by changing the degree of screwing. Shock absorber to do. With this configuration, the shock absorbing ability can be adjusted.

(7) Claims 1 to 3, technical ideas 1 to 6
In any one of the above, the shock absorber characterized in that the area of the pressure acting surface of the piston valve is larger on the rod retraction side end surface than on the rod protruding side end surface. With this configuration, the piston valve and the piston rod can be promptly and reliably restored during the protrusion stroke.

(8) Claims 1 to 3, technical ideas 1 to 7
In any one of the above items, the shock absorber is characterized in that the communication passage between the pressure chambers is formed so as to penetrate the piston valve.

The technical terms used in the present specification are defined as follows. "Fluid: Refers to gases such as nitrogen, oxygen, carbon dioxide, argon, and a mixture of these, such as air, as well as fluids that change in volume due to changes in pressure."

[0064]

As described in detail above, according to the first aspect of the invention, the fluid can be self-supplied from the outside of the main body case, and the fluid can be supplied and discharged through a common path. It is possible to prevent the delay of the speed of the projecting stroke. Therefore, it is possible to provide a shock absorber having a structure suitable for downsizing as compared with the related art.

According to the second aspect of the present invention, in addition to the above effects, it is possible to prevent the slidability of the piston rod from decreasing. According to the invention described in claim 3,
In addition to the above effects, fluid can be reliably supplied and discharged in any case.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a shock absorber according to an embodiment.

FIG. 2 is a sectional view of the shock absorber.

FIG. 3 is a sectional view of the shock absorber.

FIG. 4 is a sectional view of the shock absorber.

5 (a) and 5 (b) are schematic views for explaining the advantages of the shock absorber.

FIG. 6 is a cross-sectional view of a shock absorber of another example 1.

FIG. 7 is a sectional view of a shock absorber of a second example.

FIG. 8 is a sectional view of a shock absorber according to a third example.

[Explanation of symbols]

1, 31, 41, 51 ... Shock absorber, 2 ... Main body case, 6 ... Piston rod, 12 ... Coil spring as piston rod urging means, 14 ... Pressure chamber communication passage, 15 ... Case inside / outside communication passage, 15a ... Outer opening of the communication passage inside and outside the case, 16 ... Annular groove as recess, 17 ... Piston valve, 21 ... Leaf spring as urging means for piston valve, A1 ... Air as fluid, W ... Work, S1 ... First pressure Chamber, S2 ... Second pressure chamber.

Claims (3)

[Claims] 1. A pressure chamber (partitioned in the main body case (2) for impact of a work (W) coming into and out of contact with a piston rod (6) provided in the main body case (2) so as to be retractable. After being absorbed by the drag force generated by the compression of the fluid (A1) in S1, S2), the fluid is discharged to the outside of the main body case (2), and the fluid outside the main body case (2) is further transferred to the pressure chamber. In the shock absorber (1, 31, 41, 51) supplied by itself into (S1, S2), the shock absorber (1, 31, 41, 51) is slidably accommodated in the main body case (2) and abuts against the piston rod (6). A piston valve (17) which is pushed by the rod retracting direction by the piston rod (6) and the piston valve (1).
7) and a first pressure chamber (S1) defined between the first pressure chamber (S1) and a second pressure chamber defined on the opposite side of the first pressure chamber (S1) via the piston valve (17). (S2)
A pressure chamber communication passage (14) for communicating the pressure chambers (S1, S2) with each other, a case inner / outer communication passage (15) for communicating the inside and the outside of the main body case (2), and the piston rod (6). ) Urging the piston valve (17) in the rod protruding direction, and the piston valve (17) by urging the piston valve (17) in the rod protruding direction. And a piston valve urging means (21) for holding the case inside and outside the case communication path (15) in the middle of the retraction stroke by the piston rod (6) contacting the piston valve (17). ) Is opened, and a negative pressure is applied to the inside of the main body case (2), so that the communication passage (15) inside and outside the case is opened by a protruding stroke. Shock absorber to be. 2. The case internal / external communication passage (15) is provided with the second
The shock absorber according to claim 1, wherein said pressure chamber (S2) and said outer region of said body case (2) are communicated with each other. 3. The shock absorber according to claim 1, wherein an outer opening (15a) of the case inner / outer communication passage (15) is arranged in a recess (16) in an outer peripheral surface of the main body case (2).