JPH10196609A - Fluid pressure cylinder - Google Patents

Abstract

(57) [Problem] To provide a fluid pressure cylinder capable of reliably buffering an impact applied to a piston rod over the entire stroke. SOLUTION: This fluid pressure cylinder 1 includes a piston rod 5 driven by the action of fluid pressure. The piston rod 5 includes a proximal rod portion 16 and a distal rod portion 17.
And is divided into: The two rod portions 16 and 17 are connected so as to be relatively movable along the rod axis direction. An impact buffer 23 is provided at a connection portion between the rod portions 16 and 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydraulic cylinder having a piston rod driven by the action of hydraulic pressure.

[0002]

2. Description of the Related Art Conventionally, various types of fluid pressure cylinders have been proposed in which a fluid such as air is supplied and discharged to drive a piston rod by its pressure. Such hydraulic cylinders are used, for example, in spot welders. In this case, a gun arm is attached to a tip of a piston rod protruding from a cylinder tube constituting a fluid pressure cylinder, and an electrode tip is attached to the tip. A large current is instantaneously passed through this electrode tip. Therefore, when current is applied while the electrode tip is pressed against the workpiece, the material to be welded is welded by the heat generation resistance.

[0003] By the way, during welding, an impact is repeatedly applied to the electrode tip.
Problems such as breakage, noise and vibration occur. Also, when there is a large number of welding locations in one workpiece, it is necessary to set the moving speed of the entire hydraulic cylinder and the expansion and contraction speed of the hydraulic cylinder to be high in order to improve the processing speed. However, in this case, the impact applied to the electrode tip naturally increases, so that set, breakage, noise and vibration become more remarkable.

[0004] Under the circumstances described above, in the conventional hydraulic cylinder, a shock absorber is separately installed outside the cylinder tube, or a structure is provided in which an air cushion function acts between the cylinder tube and the piston rod. To reduce the impact. Such measures are intended to prevent breakage, reduce noise and vibration, and achieve high-speed processing.

[0005]

However, in the conventional device having the air cushion mechanism, there is a problem that the shock absorbing function can be obtained only at the stroke end due to its structure. On the other hand, since the shock absorber can be installed at any position other than the end of the stroke, the shock absorber can be achieved even in the middle of the stroke in the conventional device having the shock absorber outside. But,
With such a configuration, once the installation position of the shock absorber is determined, there is a problem that the shock absorbing effect is obtained only at that position. That is, the shock cannot be buffered over the entire stroke, and it is not suitable for the spot welding machine.

Further, in the case of a conventional device having a shock absorber outside the cylinder, the structure is inevitably complicated, and a fluid pressure cylinder having a simple structure has been desired. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydraulic cylinder capable of reliably buffering an impact applied to a piston rod over the entire stroke.

[0007]

According to one aspect of the present invention, there is provided a fluid pressure cylinder having a piston rod driven by the action of fluid pressure. A fluid pressure, wherein the fluid pressure is divided into an end rod portion and a tip rod portion, the two rod portions are connected so as to be relatively movable, and an impact buffer is provided at a connection portion between the two rod portions. The cylinder is the gist.

According to the second aspect of the present invention, in the first aspect, an insertion recess for inserting the proximal end of the distal rod portion is formed at the distal end of the proximal rod portion,
A positioning portion for restricting the movement of the distal rod portion in the rod axis direction was formed in the insertion concave portion.

According to a third aspect of the present invention, in the first or second aspect, the two rod portions are connected to each other by a connecting member detachably screwed to the base rod portion. did.

According to a fourth aspect of the present invention, in the second or third aspect, the impact buffer is housed in the insertion recess. According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the impact buffer is
The elastic body has a small coefficient of restitution interposed between the surfaces where the rod portions contact each other.

According to a sixth aspect of the present invention, there is provided the spot welding machine according to any one of the first to fifth aspects, wherein the fluid pressure cylinder has an electrode tip of a spot welding machine attached to a distal end of the distal rod portion. Fluid cylinder.

The "action" of the present invention will be described below. According to the first to sixth aspects of the present invention, the distal rod portion and the proximal rod portion move relative to each other, and the impact buffering action of the impact buffer provided at the connecting portion between the two rod portions works. Thereby, the shock applied to the piston rod is reliably buffered. In addition, since the shock buffer is provided on the piston rod itself which is on the moving side instead of the fixed side, the shock is buffered not only at a specific position of the stroke but also over the entire stroke. Further, with this configuration, the structure is simplified as compared with the conventional device in which the shock absorber is installed outside the cylinder.

According to the second aspect of the present invention, the movement of the distal rod in the rod axis direction is restricted by the contact of the distal rod with the positioning portion in the insertion recess. As a result, the distal rod portion is positioned with respect to the proximal rod portion. Further, since the distal end rod portion cannot be relatively moved during the positioning, a predetermined pressing force can be obtained even when the piston rod is pressed somewhere, for example.

According to the third aspect of the present invention, since the two rod portions can be easily brought into the connected state and the non-connected state by attaching and detaching the connecting member, the assemblability is improved.

According to the fourth aspect of the present invention, since the shock absorber is built into the piston rod, the appearance is improved as compared with the case where the shock absorber is externally attached to the piston rod. In addition, it is suitable for simplifying the structure.

According to the fifth aspect of the present invention, the impact applied to the piston rod is reliably buffered by the elastic body interposed between the surfaces where both rod portions come into contact with each other. Also,
Since this elastic body has a small coefficient of restitution, it takes some time for the elastic body that has been elastically deformed to return to its original shape. As a result, bouncing of the rod portion on the distal end side during shock absorption is reliably prevented. Further, since the structure is simpler, the cost of the hydraulic cylinder can be reduced.

According to the present invention, the electrode tip can be pressed against the workpiece by driving the piston rod by supplying and discharging the fluid.
At this time, the shock applied to the piston rod is reliably buffered by the above-described shock buffering function and the like, so that damage to the electrode tip is prevented, noise and vibration are reduced, and the processing speed is increased.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A hydraulic cylinder 1 according to one embodiment of the present invention will be described below in detail with reference to FIGS.

The hydraulic cylinder 1 of the present embodiment is a hydraulic cylinder 1 used for a spot welding machine. As shown in FIG. 1, the fluid pressure cylinder 1 includes a cylinder tube 2, a rod cover 3, a head cover 4, a piston rod 5 including a rod portion P1 and a piston portion P2, and the like.

Openings at both ends of a cylinder tube 2 constituting the fluid pressure cylinder 1 are sealed by a rod cover 3 and a head cover 4, respectively. As a result, a space is formed in the cylinder tube 2. The piston rod 5 is accommodated in the space inside the cylinder tube 2 so as to be movable along the longitudinal direction of the cylinder. In addition,
The piston rod 5 divides the space in the cylinder tube 2 by 2
Is divided into two pressure action chambers R1 and R2. The first pressure action chamber R1 is located on the rod cover 3 side of the piston portion P2, and the second pressure action chamber R2 is located on the head cover 4 side of the piston portion P2.

A first port 6 is formed on the outer peripheral surface of the rod cover 3, and the port 6 communicates with the first pressure action chamber R 1 via a flow path 8. The flow path 8 has a large diameter portion and a small diameter portion, and a tapered step is formed at a boundary between the two. A sealing member 10 having a communication hole is screwed into the large-diameter portion of the flow channel 8 from the pressure action chamber R1 side. In a small space defined by the large-diameter portion of the flow path 8 and the sealing member 10, a check ball 11 and a spring 12 for constantly biasing the check ball 11 toward the tapered step portion are accommodated. Therefore, the rod cover 3 of the present embodiment has a check valve therein. This check valve only allows air to flow from the first port 6 to the first pressure action chamber R1.
From the pressure action chamber R1 to the first port 6. In addition, the first port 6 and the first pressure action chamber R1 are also communicated with each other by a sub-flow path 13 formed separately from the flow path 8. This sub flow path 13 is provided with the flow path 8
Are formed to have a smaller diameter than the small diameter portion.

That is, in the fluid pressure cylinder 1 of the present embodiment, the air cushion mechanism for buffering the impact at the stroke end by the flow path 8, the sealing member 10, the check ball 11, the spring 12, and the sub flow path 13 is used. It is configured.

On the other hand, a second port 7 is formed on the outer peripheral surface of the head cover 4, and the port 7 is connected to a second pressure action chamber R 2 via a flow path 9. As shown in FIGS. 1 and 2, a rod insertion hole 15 is formed at the center of the rod cover 3 so as to pass therethrough. The rod portion P1 of the piston rod 5 is slidably inserted into the rod insertion hole 15. Hereinafter, the configuration of the piston rod 5 will be described in detail.

The rod portion P1 of the piston rod 5 is divided into a main rod portion 16 as a proximal rod portion and a sub rod portion 17 as a distal rod portion. And these rod parts 16 and 17
It is connected so as to be relatively movable by a connecting cap 21 as a connecting member described later.

Base end of main rod portion 16 (right end in FIG. 1)
Is joined to a piston portion P2 as a partition. On the other hand, the tip of the main rod portion 16 (the left end in FIG. 1)
Project outside the cylinder tube 2 through the rod insertion hole 15.

At the left end of the main rod portion 16, an insertion recess 18 for inserting the base end (the left end in FIG. 1) of the sub rod portion 17 is formed. The insertion recess 18 has an opening on the left end face of the main rod portion 17 and extends along the longitudinal direction of the rod. The inside of the insertion recess 18
Large-diameter portion 18a and small-diameter portion 1 located deeper than it
8b. The large-diameter portion 18a accommodates the left end of the sub-rod portion 17, and the small-diameter portion 18b accommodates a part of the shock absorber. Large diameter part 18a
A positioning step portion 20 as a positioning portion is formed at the boundary between the small-diameter portion 18b. This positioning step 2
0 serves to regulate the movement of the sub rod portion 17 in the rod axis direction (here, the movement in the right direction in FIG. 1). The positioning step 20 is formed over the entire inner wall surface of the insertion recess 18.

The small-diameter portion 18 of the insertion recess 18
A shock absorber 23 is inserted in b as an impact buffer. That is, in the fluid pressure cylinder 1, the shock absorber 23 is built in the piston rod 5. The shock absorber 23 includes a cylinder tube, a piston, a rod, and the like, and is configured to absorb a shock by viscous resistance of oil filled in the cylinder tube. This shock absorber 23
Are arranged so as to protrude toward the opening side of the insertion concave portion 18.

On the outer peripheral surface at the left end of the main rod portion 16,
An external thread groove is formed. On the other hand, a female screw groove is formed on the inner peripheral surface of the connecting cap 21 as a connecting member at a pitch corresponding to the male screw groove. Therefore, the connection cap 21 can be detachably screwed to the left end side of the main rod portion 16. The connection cap 21 has a rod insertion hole 22. The rod insertion hole 22 is formed at the center of the connection cap 21. The shaft portion 17a of the sub rod portion 17 is slidably inserted into the rod insertion hole 22.

The sub-rod portion 17 of the present embodiment includes the shaft portion 1
7a and a flange portion 17b. An electrode tip 25 is attached to the tip of the shaft 17a. in this case,
The electrode tip 25 may be directly attached as shown in FIG. 2, or may be indirectly attached via a gun arm. In either case, the electrode tip 25 is energized. The flange portion 17 has a larger diameter than the shaft portion 17a, and
7a is provided on one end side.

Here, the rod insertion hole 22 and the shaft portion 17a
May have a circular shape or a non-circular shape such as a square shape or a hexagonal shape. If these are formed in a non-circular shape, the rotation of the sub rod portion 17 with respect to the main rod portion 16 can be prevented. In this case, the cross-sectional shapes of the rod insertion hole 15 and the main rod portion 16 of the rod cover 3 may be non-circular. By doing so, the rotation of the piston rod 5 itself with respect to the cylinder tube 2 can be prevented.

The flange portion 17b located on the inner end surface side of the connection cap 21 is slidably accommodated in the large-diameter portion 18a of the accommodation concave portion 18. Therefore, the flange portion 17b
Is set to be slightly smaller than the inner diameter of the large-diameter portion 18a of the accommodation recess 18. That is, there is a clearance between the flange portion 17b and the large diameter portion 18a.

A recess is formed at the center of the right end face of the flange portion 17b. The head of the rod of the shock absorber 23 is in contact with this recess. The rod urges the sub-rod portion 17 to the left in FIG. Therefore, the left end surface of the flange portion 17b is always in contact with the inner end surface of the connection cap 21. With this configuration, the sub rod portion 17 is prevented from coming off from the main rod portion 16. Therefore, the connection cap 21 serves to connect the two rod portions 16 and 17 so as to be relatively movable along the rod longitudinal direction.

The length of the flange portion 17b is
Is set to be somewhat shorter than the length (depth) of the large diameter portion 18a. The difference between the lengths corresponds to the movable distance when the rod portions 16 and 17 relatively move along the longitudinal direction of the rod.

The right end face of the flange portion 17b is in a positional relationship facing the positioning step portion 20. Therefore, when the sub-rod portion 17 moves to the right, the right end surface of the flange portion 17b contacts the positioning step portion 20. Therefore, the sub rod part 17 cannot move any more.

Next, the operation of the hydraulic cylinder 1 configured as described above will be described. This fluid pressure cylinder 1
Both ports 6 and 7 are connected to an air supply source (not shown) via an electromagnetic valve or the like.

When the pressurized air is supplied to the first port 6, the pressurized air flows into the first pressure action chamber R1 through the sub flow path 13. At this time, the check ball 11 on the flow path 8 is urged rightward in FIG. 1 by the pressure of the pressurized air. Therefore, the check ball 11 separates from the tapered step, and pressurized air flows to the first pressure action chamber R1 through the gap. That is, at this time, the pressurized air flows into the first pressure action chamber R1 via the two paths of the flow path 8 and the sub flow path 13. Then, the first pressure action chamber R1
The piston portion P2 is pressed rightward in FIG. 1 due to the rise in the air pressure inside, and the piston rod 5 starts moving in the same direction. The air in the second pressure action chamber R2 is discharged to the outside of the fluid pressure cylinder 1 through the flow path 9 and the second port 7.

When the piston rod 5 reaches the stroke end on the head side, the supply / discharge direction of the pressurized air is switched by the solenoid valve, and the pressurized air is supplied to the second port 7. Then, the pressurized air supplied to the second port 7 flows into the second pressure action chamber R2 via the flow path 9. As a result, the piston portion P2 is pressed leftward in FIG. 1 due to an increase in the air pressure in the second pressure action chamber R2, and the piston rod 5 starts moving in the same direction.

The air in the second pressure action chamber R 2 reaches the second port 7 only through the sub flow path 13 and is discharged to the outside of the fluid pressure cylinder 1. That is, at this time, the check ball 11 on the flow path 8 is urged leftward in FIG. 1 by the pressure of the pressurized air and the urging force of the spring 12. As a result, the check ball 11 is pressed against the tapered step and blocks the flow path 8.

When the piston portion P2 reaches the vicinity of the stroke end, a closed space defined by the piston portion P2, the rod cover 3, and the cylinder tube 2 appears inside the fluid pressure cylinder 1. Therefore, the cushioning effect of the air in the closed space can cushion the impact at the rod-side stroke end. After the piston rod 5 has completely reached the rod-side stroke end, the supply / discharge direction of the pressurized air is switched again by the solenoid valve, and the pressurized air is supplied to the first port 6.

Next, the operation of another shock absorbing mechanism in the fluid pressure cylinder 1 will be described. As shown in FIG. 2, the welding surface of the workpiece 24 is not flat but has a height difference. In order to press the electrode tip 25 against such a welding surface, it is necessary to move the piston rod 5 in the direction of the rod-side stroke end and extend the fluid pressure cylinder 1. However, since the welding surface has a height difference as described above, the degree of extension of the fluid pressure cylinder 1 naturally differs depending on the location. Therefore, when the electrode tip 25 collides with the welding surface, the impact applied to the electrode tip 25 and the piston rod 5 needs to be buffered not only in a specific position of the stroke but also in the entire stroke.

In the case of the fluid pressure cylinder 1, the impact that the electrode tip 25 receives at the time of collision is also transmitted to the sub rod portion 17 to which the electrode tip 25 is fixed. The direction of the impact is the rightward direction in FIGS. At this time,
The sub-rod 17 slides in the insertion recess 18 rightward, and the amount of projection of the sub-rod 17 from the main rod 16 decreases. That is, the rod portions 16 and 17 relatively slide at this time. Then, the drag of the shock absorber 23 increases accordingly, and the sub-rod portion 17 tries to be pushed back in the opposite direction. As a result, the shock applied to the piston rod 5 is reliably buffered.

When the left end surface of the sub-rod portion 17 comes into contact with the positioning step portion 20, the sub-rod portion 17 is immovable, thereby achieving positioning. Therefore, at the time of such positioning, the electrode tip 25 can be pressed against the workpiece 24 with a predetermined pressing force. And if electricity is supplied in this state, the workpiece 24 can be reliably welded.

Now, the characteristic effects of the present embodiment will be enumerated below. (A) In the fluid pressure cylinder 1 of the present embodiment, the piston rod 5 is divided into a main rod portion 16 and a sub rod portion 17, and both rod portions 16, 17 are connected so as to be relatively movable, and the connection therebetween. An impact buffer is provided at the site. Therefore, the impact applied to the piston rod 5 is reliably buffered by the relative movement of the two rod portions 16 and 17 and the impact buffering action of the shock absorber 23 serving as an impact buffer.

Further, since the shock absorber 23 is provided on the piston rod 5 itself which is on the moving side instead of the fixed side, the shock can be buffered not only at a specific position of the stroke but also over the entire stroke.

Accordingly, the fluid pressure cylinder 1 is extremely suitable as a fluid pressure cylinder for a spot welding machine. In other words, the above-described shock buffering action can prevent the electrode tip 25 from being damaged, reduce noise and reduce vibration, and can achieve higher processing speed.

(B) In this fluid pressure cylinder 1,
The shock absorber 23 serving as a shock buffer is inserted into the insertion recess 1.
8, the shock absorber 23
In other words, it is built into the piston rod 5. Therefore, the appearance is improved and the structure is simplified as compared with the conventional device in which the shock absorber is installed outside the cylinder.

(C) In the hydraulic cylinder 1, the positioning of the sub-rod 17 with respect to the main rod 16 is achieved by providing the positioning step 20. Therefore, at the time of positioning, the electrode tip 25 can be pressed against the workpiece 24 with a predetermined pressing force.
Can be reliably welded.

(D) In this fluid pressure cylinder 1, the two rod portions 16, 17 can be easily connected and disconnected by attaching and detaching the connecting cap 21 as a connecting member. Therefore, the assemblability of the fluid pressure cylinder 1 is improved. Similarly, since the disassembly can be easily performed, the maintainability is also improved. Further, even if a failure or the like occurs in the piston rod 5 or the shock absorber 23, there is an advantage that it is sufficient to replace only some of the parts.

(E) The hydraulic cylinder 1 is also provided with an air cushion mechanism for buffering an impact at the rod-side stroke end. Therefore, especially at the rod-side stroke end, an excellent shock buffering action can be obtained by the synergistic effect of the air cushion mechanism and the shock absorber 23. Second Embodiment Next, a hydraulic cylinder 31 according to a second embodiment will be described with reference to FIG. Here, differences from the fluid pressure cylinder 1 of the first embodiment will be mainly described, and other configurations will be assigned only common member numbers, and detailed description will be omitted.

The rod portion P1 of the piston rod 5 of the fluid pressure cylinder 31 is divided into a main rod portion 32 as a proximal rod portion and a sub rod portion 17 as a distal rod portion. . And these rod parts 32 and 17 are connected so as to be relatively movable by a connection cap 21 as a connection member. However,
The accommodation recess 18 of the main rod portion 32 of the present embodiment has only a portion corresponding to the large diameter portion 18a in Embodiment 1, and does not have a portion corresponding to the small diameter portion 18b.
A positioning step 33 as a positioning section is formed on the inner wall surface of the housing recess 18.

The fluid pressure cylinder 31 has a rubber cushion 34 as an impact buffer. Specifically, “Haneite” (trade name, manufactured by Towa Rubber Co., Ltd.) having a coefficient of restitution of zero is used as the rubber cushion 34. The rubber cushion 34 is an annular elastic body. The rubber cushion 34 includes two rod portions 32, 1
7 are interposed between the surfaces where they come into contact with each other, so to say, are built into the piston rod 5. Rubber cushion 3
4 contacts both the right end face of the sub-rod part 17 and the inner bottom face of the accommodation concave part 18, and presses the sub-rod part 17 leftward in FIG. In the normal state, the sub rod portion 17
Is separated from the positioning step 33 by the pressing force.

When the sub-rod portion 17 receives an impact, the sub-rod portion 17 slides in the insertion concave portion 18 to the right,
The amount of protrusion of the sub rod portion 17 from the main rod portion 32 is reduced. That is, the rod portions 32 and 17 slide relative to each other at this time. Accordingly, elastic deformation occurs, and the rubber cushion 34 is compressed in the axial direction. At this time,
The rubber cushion 34 tries to return to the original shape, and a drag is generated to push the sub rod portion 17 back in the opposite direction. As a result, the shock applied to the piston rod 5 is reliably buffered.

When the left end surface of the sub-rod portion 17 comes into contact with the positioning step portion 33, the sub-rod portion 17 is immovable and positioning is achieved. Therefore, at the time of such positioning, the electrode tip 25 can be pressed against the workpiece 24 with a necessary pressing force. And if electricity is supplied in this state, the workpiece 24 can be reliably welded.

Now, the characteristic effects of the hydraulic cylinder 31 of the present embodiment will be enumerated below. (A) This hydraulic cylinder 31 has the same basic configuration as the hydraulic cylinder 1 of the first embodiment. Therefore, it goes without saying that the effects of the items (a) to (e) listed in the first embodiment are exhibited.

(B) In addition, the fluid pressure cylinder 31 employs a configuration in which a rubber cushion 34 is interposed between the surfaces where the rod portions 32 and 17 come into contact with each other. Since the rubber cushion 34 as an elastic body has a coefficient of restitution of zero, it takes some time to return to the original shape after elastic deformation. As a result, there is an advantage that bouncing of the sub-rod portion 17 during shock buffering is reliably prevented. Further, since the rubber cushion 34 is used, the structure is further simplified as compared with the first embodiment, and the cost of the fluid pressure cylinder 31 is reduced.

It should be noted that the present invention is not limited to the first and second embodiments, but can be changed to another form as follows, for example. ◎ Like another example of the fluid pressure cylinder 41 shown in FIG.
Instead of the shock absorber 23 and the rubber cushion 34, a coil spring 42 may be used as an impact buffer. The coil spring 42 is housed in the housing recess 18. Further, one end of the coil spring 42 abuts on the main rod portion 16 side, and the other end abuts on the sub rod portion 17 side. A feature of such another example is that the structure is simpler than at least the device of the first embodiment. In addition,
Of course, urging means other than the coil spring 42, such as a leaf spring, may be used.

The number of impact buffers is not limited to one as in the first and second embodiments and the other examples in FIG. 4, but may be plural. The fluid pressure cylinder 51 of another example shown in FIG. 5 has a configuration including two types of shock absorbers, the shock absorber 23 and the rubber cushion 34. The fluid pressure cylinder 61 of another example shown in FIG. 6 has a configuration including two types of shock absorbers, a rubber cushion 34 and a coil spring 42. Of course,
The shock absorber 23 and the coil spring 42 may be combined.

◎ Another example of the hydraulic cylinder 7 shown in FIG.
In FIG. 1, the connection cap 21 as a connection member is omitted. Instead, the shaft portion 17a of the sub rod portion 17
A male screw groove 72 is formed on the outer peripheral surface of the base end. A female screw groove 73 is formed on the inner peripheral surface of the opening of the housing recess 18 of the main rod portion 16. Therefore, in the fluid pressure cylinder 71, the sub rod portion 17 can be directly screwed to the main rod portion 16 without using a connecting member. The disadvantage of such a configuration is that the production is slightly complicated, and the advantage thereof is that it is advantageous in reducing the number of parts and increasing the diameter of the sub rod portion 17.

The impact buffer does not necessarily have to be built into the piston rod 5. In another example of the hydraulic cylinder 81 shown in FIG. 8, the rod portion P1 of the piston rod 5 is divided into a main rod portion 82 and a sub rod portion 83. The sub rod portion 83 has flange portions 83b and 83c at two places separated from each other in the shaft portion 83a. The base side flange portion 83b is connected to the main rod portion 8.
It is slidably accommodated in the second accommodation recess 18. The distal flange portion 83c is located outside the main rod portion 82. The coil spring 34, which is an impact buffer, is interposed between the right side surface of the front flange portion 83c and the left end surface of the main rod portion 82. That is, the coil spring 34 has the two rod portions 82, 8
Although it is arranged at the connecting portion of No. 3, it is in a state of being externally attached, so to speak. Note that, instead of the coil spring 34, for example, an elastic body such as rubber may be used.

The air cushion mechanism for buffering the impact at the stroke end may be provided not only on the rod side but also on the head side. Of course, the air cushion mechanism may be omitted if unnecessary.

In the first and second embodiments, the connecting member such as the connecting cap 21 may be attached to the main rod portions 16 and 32 by a method other than screwing. At this time, the connecting member may be irremovably attached using, for example, an adhesive. Further, the connecting member need not be a cap.

The fluid pressure cylinders 1 and 3 of the present invention
1, 41, etc. can be used not only in the spot welding machine illustrated in the above embodiment, but also in, for example, a press machine or a press-fitting machine.

Here, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiments are listed below together with their effects. (1) In claim 3, the connecting member has a rod insertion hole for slidably inserting the distal rod portion, and can be screwed into a male screw groove on the outer peripheral surface of the proximal rod. A fluid pressure cylinder comprising a connection cap having a female thread groove. With this configuration,
Since attachment / detachment can be performed extremely easily, the assembling property is further improved.

(2) The fluid pressure cylinder according to claim 5, wherein the elastic body is a rubber cushion having a coefficient of restitution of zero. With this configuration, it is possible to more reliably prevent the distal rod portion from bouncing.

(3) In the technical idea 1, the rod insertion hole has a non-circular cross section. With this configuration, the tip-side rod portion can be prevented from rotating.

(4) The hydraulic cylinder according to any one of claims 1 to 6, wherein the hydraulic cylinder has a separate shock buffering mechanism (for example, an air cushion mechanism) for buffering a shock at a stroke end. . With this configuration, more excellent shock absorption is achieved at the stroke end due to a synergistic effect.

The technical terms used in this specification are defined as follows. "Fluids: nitrogen, oxygen, argon, carbon dioxide, hydrogen,
In addition to gas such as air which is a mixture of them,
For example, liquids such as water, alcohol, oil, and so-called critical fluids are also included. "

[0068]

As described in detail above, according to the first to sixth aspects of the present invention, it is possible to provide a fluid pressure cylinder capable of reliably cushioning the impact applied to the piston rod over the entire stroke. . Further, the structure becomes simpler than that of the conventional device in which the shock absorber is installed outside the cylinder.

According to the second aspect of the present invention, since the positioning of the distal rod portion with respect to the proximal rod portion is achieved, a structure suitable for pressing the piston rod to somewhere with a predetermined pressing force is obtained. .

According to the third aspect of the invention, the assembling property can be improved. According to the fourth aspect of the invention, the appearance can be improved and the structure can be simplified.

According to the fifth aspect of the present invention, the bouncing of the rod portion on the distal end side can be prevented, and the structure can be simplified, so that the cost of the fluid pressure cylinder can be reduced.

According to the sixth aspect of the present invention, as a result of the shock being buffered, damage to the electrode tip can be prevented, noise and vibration can be reduced, and the processing can be speeded up.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a hydraulic cylinder according to a first embodiment.

FIG. 2 is a partial sectional view of the cylinder.

FIG. 3 is a partial sectional view of a fluid pressure cylinder according to a second embodiment.

FIG. 4 is a partial cross-sectional view of another example of a hydraulic cylinder.

FIG. 5 is a partial cross-sectional view of another example of a hydraulic cylinder.

FIG. 6 is a partial cross-sectional view of another example of a hydraulic cylinder.

FIG. 7 is a partial cross-sectional view of another example of a hydraulic cylinder.

FIG. 8 is a partial cross-sectional view of another example of a hydraulic cylinder.

[Explanation of symbols]

1, 31, 41, 51, 61, 71, 81 ... fluid pressure cylinder, 5 ... piston rod, 16, 32, 82 ... main rod part as base end rod part, 17, 83 ... tip side rod part Sub rod part, 18 insertion recess, 2
Reference numerals 0, 33: positioning step portions as positioning portions, 21: connecting caps as connecting members, 23: shock absorbers as impact buffers, 34: rubber cushions (as elastic bodies) as impact buffers, 42 ... impacts Coil spring as a buffer.

Claims (6)

[Claims] In a hydraulic cylinder having a piston rod driven by the action of hydraulic pressure, the piston rod is divided into a proximal rod portion and a distal rod portion, and the two rod portions are moved relative to each other. A fluid pressure cylinder, which is movably connected and has an impact buffer at a connection portion between the two rod portions. 2. An insertion recess for inserting a proximal end of the distal rod portion at a distal end of the proximal rod portion, and movement of the distal rod portion in the rod axial direction in the insertion recess. 2. The fluid pressure cylinder according to claim 1, wherein a positioning portion for regulating pressure is formed. 3. The fluid pressure according to claim 1, wherein the two rod portions are connected to each other by a connecting member detachably screwed to the proximal rod portion. Cylinder. 4. The fluid pressure cylinder according to claim 2, wherein the impact buffer is accommodated in the insertion recess. 5. The shock-absorbing body according to claim 1, wherein the shock-absorbing body is an elastic body having a small coefficient of restitution interposed between surfaces where the two rod portions come into contact with each other. Hydraulic cylinder. 6. The fluid pressure cylinder according to claim 1, wherein the fluid pressure cylinder is a fluid pressure cylinder for a spot welding machine to which an electrode tip of a spot welding machine is attached at a tip of the rod portion on the tip side. 2. The fluid pressure cylinder according to claim 1.