JPH10153201A - Hydraulic cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic cylinder capable of changing thrust at the specific portion of a stroke even with a simple structure at a low cost. SOLUTION: This hydraulic cylinder 3 is designed to drive a piston rod 32 as a moving member housed in a cylinder body 21 under the action of fluid pressure and has a pressure bearing area changing mechanism. This mechanism divides pressure working chambers R1 and R2 formed with the cylinder body 21 and the piston rod 32 into a plurality of small spaces r1 and r2 to the specific position of a stroke so that a pressure bearing area is changed by block members 38 and 39 for maintaining non-pressure bearing areas on the end faces of the piston rod 32 for a prescribed period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cylinder, and more particularly, to a hydraulic cylinder whose thrust changes during a stroke.

[0002]

2. Description of the Related Art Conventionally, a cylinder system using a fluid pressure cylinder has been used as an actuator in a spot welding device or a clamping device. In this type of device, there is a case where a user wants a usage method in which low thrust operation is performed up to a certain distance from the beginning of the stroke, and high thrust operation is performed near the end of the stroke. Less than,
Some examples of such conventional cylinder systems are given below.
These will be briefly described individually.

A first conventional cylinder system 111 shown in FIG. 17 uses two systems of pressure.
The cylinder system 111 includes a hydraulic cylinder 11
2, 2-position 5-way switching valve 113, 2-position 3-way switching valve 11
4. It is composed of a low pressure reducing valve 115, a high pressure reducing valve 116 and the like. In this system 111, fluid is supplied to the cylinder 72 via the low-pressure reducing valve 115 and the switching valves 113 and 112 before the piston rod 117 reaches near the end of the stroke. Therefore, at this time, the cylinder 112 performs a low thrust operation. After the piston rod 117 reaches near the end of the stroke, fluid is supplied to the cylinder 112 via the high-pressure reducing valve 116 and the switching valves 113 and 112. Therefore, at this time, the cylinder 112 performs a high thrust operation. In addition,
The fluid pressure cylinder 112 is provided with a position sensor 118 for detecting a stroke position. The switching from the low thrust operation to the high thrust operation is performed by driving the switching valve 113 based on the output signal from the sensor 118.

A second conventional cylinder system 121 shown in FIG. 18 utilizes a differential pressure due to fluid leakage. The cylinder system 121 includes a fluid pressure cylinder 112, a two-position five-way switching valve 113, a two-position two-way switching valve 122, a plurality of speed adjusting valves 123 and 124, and the like. The two-position two-way switching valve 122 is connected to the cylinder 112 in parallel. This switching valve 1
22 leaks a part of the fluid supplied to one port side to the other port side after the piston rod 117 reaches near the end of the stroke. The adjustment of the leak amount at that time is performed by the two-position two-way switching valve 122 and the fluid pressure cylinder 11.
Speed regulating valve 123 interposed between the two ports.
Done by The fluid pressure cylinder 112 is also provided with the position sensor 118 as described above.
Then, by switching the switching valve 122 based on the output signal from the sensor 118, switching from the low thrust operation to the high thrust operation is performed.

A third conventional cylinder system 131 shown in FIG. 19 has two cylinders 13 having different sizes.
Tandem cylinder 134 which is a combination of 2,133
Is used. The system 131 includes a tandem cylinder 134, a two-position five-way switching valve 113, and a three-position five
It is constituted by a one-way switching valve 135 and the like. The tandem cylinder 134 includes a large-diameter cylinder 132 having a large piston rod 136 and a small piston rod 13.
7 and a small-diameter cylinder 133 having the same. Since the piston rods 136 and 137 are connected, they move integrally.

In this system 131, fluid is supplied only to the small diameter cylinder 133 before the piston rods 136, 137 reach the vicinity of the end of the stroke. Therefore, at this time, the tandem cylinder 134 performs a low thrust operation. Then, after the piston rods 136 and 137 reach the vicinity of the end of the stroke, the fluid is also supplied to the large-diameter cylinder 132. Therefore, at this time, the tandem cylinder 134 performs a high thrust operation. The tandem cylinder 134 is also provided with the position sensor 118 as described above. Then, by switching the switching valve 135 based on the output signal from the sensor 118, switching from the low thrust operation to the high thrust operation is performed.

Further, these cylinder systems 111,
121 and 131, for example, JP-A-8-61308
Is disclosed in Japanese Patent Application Laid-Open Publication No. HEI 9-203 (1995). This publication discloses a fluid pressure cylinder in which a small-diameter cylinder having a small-diameter piston and a large-diameter cylinder having a large-diameter piston are connected in the axial direction (fourth conventional example). Until the small-diameter piston reaches the vicinity of the end of the stroke, the small-diameter piston and the large-diameter piston are not connected, and only the small-diameter piston is driven. At this time, the fluid pressure cylinder performs a low thrust operation. Then, after reaching near the end of the stroke, the small-diameter piston comes into contact with the large-diameter piston, so that both move integrally. As a result, the hydraulic cylinder switches from low thrust operation to high thrust operation.

[0008]

SUMMARY OF THE INVENTION
The fourth conventional example has the following problems. That is, in the first to third conventional examples, it is necessary to sense the positions of the piston rods 117, 136, and 137 by the position sensor 118. Therefore, the need for control means such as a computer (not shown) complicates the electric circuit, and the cost of the systems 111, 121, and 131 tends to increase accordingly. Further, since it is necessary to use some cylinder-related equipment such as the pressure reducing valves 115 and 116 and the speed adjusting valves 123 and 124, the pneumatic circuit is inevitably complicated. This has also led to higher costs. Therefore, in order to achieve cost reduction, there has been a demand for a fluid pressure cylinder that requires a small number of cylinder auxiliary equipment.

The fourth conventional example is superior to the other examples in that the configuration of the electric circuit is not complicated because the position sensor 118 is not required. However, since the configuration of the fluid pressure cylinder itself is complicated, there is a problem that the cost cannot be avoided. The third conventional example has the same problem.

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 changing the thrust at a specific position of a stroke despite its simple structure and low cost. Is to provide.

It is a second object of the present invention to provide a compact hydraulic cylinder having the above excellent characteristics. Further, a third object of the present invention is to provide a hydraulic cylinder which is hardly affected by a change in stroke length.

[0012]

According to a first aspect of the present invention, there is provided a fluid pressure cylinder for driving a moving body accommodated in a cylinder body by the action of fluid pressure. The pressure receiving area is changed by a partition that secures a non-pressure receiving area on the end surface of the moving body for a certain period by dividing a pressure action chamber formed by the body and the moving body into a plurality of small spaces up to the specific position of the stroke. The gist of the present invention is a fluid pressure cylinder provided with a pressure receiving area changing mechanism.

According to a second aspect of the present invention, in the first aspect, the cylinder body allows a fluid to flow into a small space to which the non-pressure receiving region belongs and prevents a fluid from flowing out from the small space. A check valve was provided.

According to a third aspect of the present invention, in the first or second aspect, the partition body is provided on a first fitting portion provided on the moving body and on an inner end surface of the cylinder body, and A second fitting portion capable of fitting to the first fitting portion, and the two fitting portions are configured to be in a non-fitting state at a specific position of the stroke.

According to a fourth aspect of the present invention, in the third aspect, the first fitting portion is a rod fitting hole opened at one end surface of the moving body, and the second fitting portion is a rod fitting hole. The guide rod protrudes from the inner end surface of the cylinder body and can be fitted into the rod fitting hole.

According to a fifth aspect of the present invention, in the fourth aspect, the moving body is a piston rod, and the rod fitting hole is formed in a rod portion therein. According to a sixth aspect of the present invention, in the first aspect, when one of the stroke end positions moves, a specific position transition mechanism that changes a specific position of the stroke by a corresponding amount in accordance with the movement is provided. did.

In the invention described in claim 7, in claim 6, the partition body is provided on a first fitting portion provided on the moving body and on an inner end face of the cylinder body, and the first body is provided on the first end portion of the cylinder body. It is configured to include a second fitting portion fitted to the fitting portion and a sealing member for sealing between the two fitting portions for a certain period.

According to an eighth aspect of the present invention, in the seventh aspect, the specific position transition mechanism is configured to allow the second fitting portion to move only in one direction along the longitudinal direction of the cylinder. It is assumed that the locking means and the biasing means for biasing the second fitting portion in a direction opposite to the direction in which the second fitting portion can move are configured.

Hereinafter, the "action" of the present invention will be described. According to the first to eighth aspects of the present invention, since the partition of the pressure receiving area changing mechanism partitions the pressure action chamber into a plurality of small spaces up to a specific position of the stroke, a non-pressure receiving area is secured on the end surface of the moving body for a certain period. Is done. As a result, the pressure receiving area of the moving body is changed at a specific position of the stroke, and the action of the fluid pressure applied to the moving body changes accordingly. For example, if the fluid is supplied / discharged to a small space to which a non-pressure receiving area does not belong among a plurality of small spaces before the moving body reaches a specific position of a stroke, fluid pressure acts on the entire end surface on one side of the moving body. Disappears. Therefore, the moving body can be operated with low thrust. After the moving body reaches the specific position of the stroke, the non-pressure receiving region disappears, so that the fluid pressure acts on the entire end surface on one side of the moving body. Therefore, the moving body can be operated with high thrust.

That is, according to the pressure receiving area changing mechanism, the thrust can be switched without changing the flow rate of the fluid supplied to and discharged from the cylinder. Therefore, unlike the conventional apparatus which requires fluid flow control, there is no need for ancillary equipment for the cylinder (that is, the above-described pressure reducing valve, speed control valve, and the like), thereby achieving cost reduction. In addition, if the position where the partition functions is set in advance, the position detecting means is not required. This also contributes to cost reduction.

According to the second aspect of the present invention, when the fluid can flow into the small space to which the non-pressure receiving area belongs, the moving space does not become negative pressure when the moving body moves, and the movement of the moving body does not occur. Becomes smoother.

According to the third aspect of the present invention, before the moving body reaches the specific position of the stroke, the first fitting portion and the second fitting portion are fitted to each other, so that the inside of the cylinder is formed. Is partitioned into the plurality of small spaces. After the moving body reaches the specific position of the stroke, the small spaces disappear as a result of the two fitting portions being in a non-fitting state. Therefore, the fluid pressure acts on the entire end surface on one side of the moving body.

According to the fourth aspect of the present invention, before the moving body reaches the specific position of the stroke, the guide rod is fitted into the rod fitting hole, so that the pressure action chamber in the cylinder is formed. It is divided into a plurality of small spaces. After the movable body reaches the specific position of the stroke, the small space disappears due to the guide rod coming off the rod fitting hole, and the fluid pressure acts on the entire one-side end surface of the movable body. Also,
With such a fitting portion, the mechanical structure becomes relatively simple, which contributes to cost reduction. If the length of the guide rod and the depth of the rod fitting hole are changed, the position at which the thrust switches can be set in advance, so that the position detecting means becomes unnecessary.

According to the fifth aspect of the present invention, since the rod portion of the piston rod usually has such a length that a deep hole can be formed, the piston of the piston rod needs to have a space for drilling. It is not necessary to form the part thick. Therefore, the fluid pressure cylinder can be made compact. In addition, with such a configuration, since the load is not biased, the operability of the piston rod is also improved.

According to the sixth aspect of the present invention, according to the specific position transition mechanism, even if one of the stroke end positions moves, the specific position of the stroke can be shifted by a corresponding amount following the movement. it can. Therefore,
It is less susceptible to changes in stroke length.

According to the seventh aspect of the present invention, before the moving body reaches the specific position of the stroke, the pressure action chamber in the cylinder is partitioned into the plurality of small spaces. After the moving body reaches the specific position of the stroke, the non-pressure receiving region disappears due to the disappearance of the small space, and as a result, the fluid pressure acts on the entire one-side end surface of the moving body.

According to the present invention, when a force greater than the urging force of the urging means is applied to the second fitting portion, the second fitting portion is moved in one direction along the longitudinal direction of the cylinder. To a predetermined amount. Then, the second fitting portion is held at the moved position by the action of the one-way locking means. Therefore, a new stroke end position and a new specific position can be reliably set.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A first embodiment in which the present invention is embodied in a spot welding apparatus using a fluid pressure cylinder will be described in detail with reference to FIGS.

FIGS. 6A to 6C schematically show a spot welding apparatus 1. FIG. Spot welding equipment 1
Is an apparatus for performing spot welding, which is one type of resistance welding. The main body 2 of the spot welding apparatus 1 accommodates a fluid pressure cylinder 3 whose thrust changes during a stroke and a two-position five-way switching valve as an electromagnetic valve 4. A bent upper gun arm 5 is fixed downward to the tip of a piston rod 32 as a moving body in the fluid pressure cylinder 3. An electrode tip 6 is attached to the tip of the upper gun arm 5. Immediately below the upper gun arm 5, a lower gun arm 7 is arranged upward with a predetermined distance therebetween. An electrode tip 8 is similarly attached to the tip of the lower gun arm 7. The space between the two electrode tips 6 and 8 facing each other has a material 9 to be welded.
Are arranged in a superimposed state. The material 9 to be welded is pressed and clamped from both sides by the chips 6 and 8 during welding. Then, in this state, both electrode tips 6, 8
When a large current is applied for a short period of time, the material to be welded 9 is melted in a spot due to heat generated by resistance, and the materials to be welded 9 are joined to each other.

Next, a cylinder system including the fluid pressure cylinder 3 and the switching valve 4 will be described. The switching valve 4 used in the present embodiment is a two-position switching type as described above. The P port 11 of the switching valve 4 is connected to a fluid supply source 16. From this fluid supply source, pressurized air as a pressurized fluid for driving the hydraulic cylinder 3 is sent under pressure. Further, the switching valve 4 includes a spring 14 and a solenoid 15 as valve body return means. FIG. 1 and the like show a first switching state, and FIG. 2 and the like show a second switching state. In the first switching state, the P port 11 and the A port 12 communicate with each other, and the P port 11 and the B port 13 do not communicate with each other. Therefore, at this time, pressurized air is supplied to the A port 12. In the second switching state, the P port 11 and the B port 13 are in communication, and the P port 11 and the A port 12 are not in communication. Therefore, pressurized air is supplied to the B port 13 at this time.

Next, the structure of the hydraulic cylinder 3 will be described. As shown in FIG. 1 and the like, a cylinder body 21 constituting the fluid pressure cylinder 3 of the present embodiment includes a cylindrical cylinder tube 22, and a rod cover 23 and a head cover 24 for closing both end surfaces thereof. Each member 2
An annular gasket 25 is interposed between the joints 2, 23, and 24 to improve the sealing performance. An internal space is formed by these members 22, 23, and 24.

A first port 26 is provided at the end of the cylinder tube 22 on the side closed by the rod cover 23. This port 26 is connected to a pipe 27
And is connected to the A port 12 of the switching valve 4 via the. The head cover 24 is provided with a second port 28. The second opening on the side surface of the head cover 24
Port 28 is connected to the B port 13 of the switching valve 4 via a pipe 29. The second port 28 communicates with the internal space via a communication passage 31. A boundary portion between the second port 28 and the communication passage 31 has a taper narrowing toward the inside of the cylinder, and a check ball 30 is accommodated in the tapered portion. Therefore, only the outflow of air from the inside of the cylinder 3 to the outside is permitted, and the inflow of air from the outside of the cylinder 3 to the inside is prevented. That is, the second port 28 has a function as a check valve.

In the internal space of the cylinder body 21, a piston rod 32 as a moving body is reciprocally housed. The piston rod 32 includes a disk-shaped piston portion 33 and a cylindrical rod portion 34 protruding from the center of one end surface of the piston portion 33. The piston section 33 roughly divides the internal space into a rod-side pressure action chamber R1 and a head-side pressure action chamber R2. The free end of the rod portion 34 penetrates a rod insertion hole 35 provided in the center of the rod cover 23 and projects outside the cylinder 3. The base end of the upper gun arm 5 is fixed to the protruding free end. Therefore, the piston rod 32 and the upper gun arm 5 move integrally. Note that annular packings 36 and 37 are interposed between the rod portion 34 and the rod insertion hole 35 and between the piston portion 33 and the inner wall surface of the cylinder tube 22, respectively.

A pressure receiving area changing mechanism for changing the pressure receiving area of the piston rod 32 at a specific stroke position is provided inside the cylinder body 21 of the fluid pressure cylinder 3. Hereinafter, this mechanism will be described in detail.

As shown in FIG. 1 and the like, a rod fitting hole 38 having a circular cross section as a first fitting portion is formed in the rod portion 34 of the piston rod 32 along the cylinder axis direction. . This rod fitting hole 38 is
No. 3 is open at the center of the head-side end face. On the other hand, a guide rod 39 having a circular cross section as a second fitting portion is provided at the center of the inner end surface of the head cover 24 so as to protrude along the cylinder axis direction. This guide rod 39
Has a slightly smaller outer diameter than the inner diameter of the rod fitting hole 38. Therefore, the guide rod 39 can be fitted into the rod fitting hole 38. Further, the guide rod 39 is hollow, and the hollow portion is the third
A communication path 39a for communicating the port 40 of the head with the head side pressure action chamber R2. The third port 40 formed at the center of the head cover 24 is connected to a pipe 29 a branched from the pipe 29. Therefore, pressurized air is supplied to the port 40 from the switching valve 4, and the pressurized air is introduced into the head side pressure action chamber R2 via the communication passage 39a. Further, the tip of the guide rod 39 is tapered to facilitate the fitting. A Y-packing 41 as an annular seal member is provided in a concave portion formed on the inner peripheral surface near the opening of the rod fitting hole 38. With the Y packing 41, the space between the guide rod 39 and the rod fitting hole 38 is sealed. In this embodiment, the guide rod 39 and the rod fitting hole 38 form a partition.

Here, the length of the guide rod 39 is set to be somewhat shorter than the movement amount of the piston portion 33 of the piston rod 32, that is, the stroke length. Therefore, when the piston rod 32 moves to the rod side (left side),
From the right stroke end to the specific position near the left stroke end, the two 38 and 39 maintain the fitted state (see FIGS. 2 and 3). Then, from the specific position to the left stroke end, the two 38 and 39 are in a non-fitting state (see FIG. 4). The same can be said for the stroke in the opposite direction. In the present embodiment, the stroke length is set to 90 mm. The length from the specific position to the left stroke end, in other words, the length for performing the high thrust operation is set to 5 mm. Therefore, the length for performing the low thrust operation is 85 mm.

By the way, when the guide rod 39 is fitted in the rod fitting hole 38, the head side pressure action chamber R2 is partitioned into two small spaces r1, r2. First small space r
Reference numeral 1 designates an outer peripheral surface of the guide rod 39 and an inner peripheral surface of the rod fitting hole 38. Pressurized air is supplied to the small space r1 communicating with the third port 40, and the pressurized air acts on the inner bottom surface of the rod fitting hole 38. That is, in the present embodiment, the inner bottom surface of the rod fitting hole 38 is a pressure receiving area of the piston rod 32 at the time of fitting. On the other hand, the second small space r2 includes the inner peripheral surface of the cylinder tube 22, the head-side end surface of the piston 33, and the head cover 24.
And the outer peripheral surface of the guide rod 39. However, no pressurized air is supplied to this small space r2 at the time of fitting. For this reason, the end face on the head side of the piston portion 33 belonging to the small space r2 is a non-pressure receiving area. The area S2 of the non-pressure receiving area is substantially equal to the axial projection area S1 of the piston portion 33 minus the axial projection area of the guide rod 39 (that is, the area of the pressure receiving area) S1. The ratio of S1: S1 + S2 is equivalent to the ratio of the thrust at the time of the low thrust operation to the thrust at the time of the high thrust operation.

The head cover 24 is provided with a check valve 42 having a check ball 30. The check valve 42 has a function of permitting only air to flow into the second small space r2 and preventing air from flowing out of the second small space r2. Therefore, when the piston rod 32 moves to the left, outside air is taken in, so that the second small space r2 does not become negative pressure.

Next, the operation of the thus configured cylinder system will be described. FIG. 1 shows a state in which the stroke in the rightward direction has been completed. After reaching this state,
The switching valve 4 is switched to the second switching state (see FIG. 2).
Then, when the B port 13 of the switching valve 4 communicates with the fluid supply source 16, pressurized air is supplied to the second port 28 via the pipe 29 and to the third port 40 via the pipe 29 a. Pressurized air is supplied. However, the pressurized air does not flow from the second port 28 having the check valve function, and the pressurized air flows only from the third port 40.

The pressurized air that has flowed into the first small space r1 via the third port 40 and the communication passage 39a acts on the inner bottom surface of the rod fitting hole 38, which is a pressure receiving area. As a result, the piston rod 32 starts a stroke with a low thrust toward the left side. At this time, the air remaining in the rod-side pressure action chamber R1 flows to the first port 26,
It is quickly released to the atmosphere via the pipe 27 and the A port 12. And such a low thrust operation is performed by the piston portion 3
3 is maintained until it reaches a specific position near the left stroke end (see FIG. 3).

When the piston portion 33 reaches the specific position,
When the guide rod 39 comes off the rod fitting hole 39, the small spaces r1, r2 in the head side pressure action chamber R2 disappear (see FIG. 4). Therefore, the pressurized air acts on the entire end face of the piston portion 33 on the head side. As a result, it automatically switches from low thrust operation to high thrust operation,
The piston rod 32 maintains the high thrust operation until reaching the left stroke end. The head side pressure action chamber R2
At this time, the pressure inside the cylinder 3 becomes relatively higher than the external environment of the cylinder 3, so that no air leaks from the check valve 42.

When the piston section 33 reaches the left stroke end, the switching valve 4 is switched to the first switching state. Then, the A port 12 of the switching valve 4 is connected to the fluid supply source 16.
The pressurized air flows into the rod side pressure action chamber R1 via the pipe 27 and the first port 26.
The pressurized air flowing into the rod-side pressure action chamber R1 acts on the rod-side end surface of the piston portion 33. As a result, the piston rod 32 starts a stroke with a constant thrust toward the right side (see FIG. 5). At this time, the air remaining in the head side pressure action chamber R2 is mainly
Through the port 28, the pipe 29 and the B port 13 to be rapidly released to the atmosphere. Although some residual air is discharged from the third port 40, no residual air is discharged from the check valve 42. The constant thrust operation is maintained until the piston 33 reaches the right stroke end.

Hereinafter, the function and effect characteristic of the present embodiment will be listed. (A) In this cylinder system, as described above, the pressure receiving area changing mechanism having the partition body including the guide rod 39 and the rod fitting hole 38 is provided. Accordingly, the guide rod 39 and the like divide the pressure action chambers R1, R2 into a plurality of small spaces r1, r2 up to a specific position of the stroke. More specifically, the guide rod 39 and the like move the head side pressure action chamber R2 to the two small spaces r up to a specific position of the stroke.
1 and r2 to secure a non-pressure receiving area for a certain period. Therefore, before reaching the specific position of the stroke, the pressurized air does not act on the entire end surface on one side of the piston portion 33, and the piston rod 32 can be operated with low thrust. Then, since the non-pressure receiving region disappears, the pressurized air acts on the entire one-side end surface of the piston portion 33. Therefore, the piston rod 32 can be operated with high thrust.

That is, according to the pressure receiving area changing mechanism, the thrust can be switched without changing the flow rate of the pressurized air supplied to and discharged from the cylinder 3. Therefore, unlike the conventional apparatus that required the fluid flow control, there is no need for a cylinder-attached facility (that is, the above-described pressure reducing valve, speed adjusting valve, etc.) for that. Therefore, cost reduction of the cylinder system is achieved. In addition, if the position at which the partition functions is set in advance, the position detection means is not required,
This also achieves cost reduction.

(B) The hydraulic cylinder 3 of the present embodiment
A check valve 42 is provided to allow air to flow into the second small space r2 to which the non-pressure receiving region belongs and to prevent air from flowing out from the small space r2. For this reason, the piston rod 32
Is moved to the left, the second small space r2 does not become a negative pressure, and the operation of the piston rod 32 becomes smooth. That is, the operability of the cylinder 3 is improved.

(C) The cylinder 3 is provided with the partition body composed of the guide rod 39 and the rod fitting hole 38 as described above. Such a structure makes the mechanical structure relatively simple and contributes to cost reduction. If the length of the guide rod 39 and the depth of the rod fitting hole 38 are changed, the position at which the thrust switches can be set in advance, so that the position detecting means becomes unnecessary. This also contributes to cost reduction.

(D) The cylinder 3 is characterized in that the rod fitting hole 38 is formed in the rod portion 34 of the piston rod 32. Usually, such a rod portion 34 is long enough to form a deep hole. Therefore, it is not necessary to form the piston portion 33 thick in order to secure a space for drilling. For this reason, the fluid pressure cylinder 3 can be made compact. Further, with such a configuration, the load is not biased, so that the operability of the piston rod 32 is also improved.

(E) In the present embodiment, the Y-packing 41 as an annular sealing member is disposed on the inner peripheral surface of the rod fitting hole 38, so that the sealing performance between the small spaces r1, r2 is improved. be able to. Therefore, the compressed air hardly leaks from the first small space r1 to which the pressure receiving region belongs to the second small space r2 to which the non-pressure receiving region belongs. As a result, the thrust during the low thrust operation can be set accurately.

(F) In this cylinder 3, the guide rod 3
Since the tip of 9 is tapered, the guide rod 32 is easily fitted into the rod fitting hole 38. For this reason,
The operability of the piston rod 32 is improved.

(G) In the hydraulic cylinder 3 of the present embodiment, the second port 28, the third port 40, the check valve 42
And a head cover 24 having a guide rod 39 is used. Therefore, even if the guide rod 39 or the like is damaged, it is possible to repair by replacing only the head cover 24. [Second Embodiment] Next, a fluid pressure cylinder 51 used in a spot welding apparatus 1 of a second embodiment will be described with reference to FIG. Here, the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Of course, it is needless to say that the same operation and effect can be achieved with a common configuration.

In the fluid pressure cylinder 51, the structure of the head cover 52 constituting the cylinder body 54 is different from that of the first embodiment. The head cover 52 is thick and has a rod fitting hole 53 as a first fitting portion at the center of the inner end surface. On the other hand, the piston rod 55 having the rod portion 34 and the piston portion 33 further includes a sub rod portion 34A as a second fitting portion. The sub rod portion 34A is provided with the rod fitting hole 5.
3 can be fitted. Specifically, the fitting state is established until a specific position near the left stroke end is reached, and thereafter, the fitting state is not established.

(A) Even in the second embodiment,
The same operation and effect as in the first embodiment that the thrust can be changed at a specific position of the stroke even though the configuration is simple and the cost is low.

(B) Further, according to the configuration of the present embodiment,
Although the cylinder 51 is not as compact as in the first embodiment, it is not necessary to drill a hole in the thin rod portion 34. Therefore, the manufacture of the cylinder 51 becomes simpler. [Third Embodiment] Next, a fluid pressure cylinder 61 used in a spot welding apparatus 1 of a third embodiment will be described with reference to FIG. Here, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Of course, it is needless to say that the same operation and effect can be achieved with a common configuration.

In the fluid pressure cylinder 61 of this embodiment, the head cover 24 and the guide rod 62 are separate. A thread groove is formed on the outer peripheral surface of the fixed end of the guide rod 62, and this portion is screwed into a rod insertion hole 63 provided in the center of the head cover 24. A position changing nut 64 is fastened to a portion of the guide rod 62 that protrudes outside. Therefore,
By changing the amount of tightening of the nut 64, the amount of protrusion of the guide rod 62 in the cylinder 61 can be changed. Further, a third port 40 is disposed at an outer protruding end of the guide rod 62, and a communication path 62a is connected to the third port 40.

(A) Even in the third embodiment,
The same operation and effect as in the first embodiment that the thrust can be changed at a specific position of the stroke even though the configuration is simple and the cost is low.

(B) Further, according to the configuration of the present embodiment,
There is an advantage that the position where the operation is switched from the low thrust operation to the high thrust operation can be very easily changed by the nut 64. [Fourth Embodiment] Next, a fluid pressure cylinder 71 used in a spot welding apparatus 1 according to a fourth embodiment will be described with reference to FIGS. Here, the same components as those in the first embodiment are denoted by the same reference numerals, and the detailed description is omitted.

As shown in FIG. 9 and the like, a pressure receiving area changing mechanism for changing the pressure receiving area of the piston rod 32 at a specific position of the stroke is provided inside the cylinder body 21 of the fluid pressure cylinder 71. Further, the fluid pressure cylinder 71 is provided with a specific position transition mechanism that, when one stroke end position moves, changes a specific position in the stroke by a corresponding amount following the movement. Hereinafter, these mechanisms will be described in detail.

As shown in FIG. 9 and the like, a rod fitting hole 38 having a circular cross section as a first fitting portion is formed in the rod portion 34 of the piston rod 32 along the cylinder axis direction. . This rod fitting hole 38 is
No. 3 is open at the center of the head-side end face. The opening of the rod fitting hole 38 is narrower than the inside of the hole.

On the other hand, a guide rod 7 having a circular cross section as a second fitting portion is provided at the center of the inner end surface of the head cover 24.
9 is formed. A guide rod 79 is provided in the through hole 77 so as to be movable along the longitudinal direction of the cylinder. An annular packing 87 for sealing between the guide rod 79 and the head cover 24 is provided on the inner wall surface of the through hole 77.
Is installed. The packing 8 in the through hole 77
A known one-way lock mechanism 88 as one-way lock means is incorporated at a position outside the position 7. The one-way lock mechanism 88 allows the guide rod 79 to move only in one direction (here, the left direction in the drawing) along the longitudinal direction of the cylinder.

On the inner peripheral surface of the opening of the rod fitting hole 38, an annular Y packing 41 as a seal member is mounted. The Y packing 41 allows the guide rod 7
The seal between the rod 9 and the rod fitting hole 38 is provided.
In this embodiment, the guide rod 79, the rod fitting hole 38, and the Y packing 41 form a partition.

A first end of the guide rod 79 of the present embodiment (hereinafter referred to as an outer protruding end) protrudes outside the head cover 24 through the through hole 77. A large diameter portion 83 having a step-like structure is formed at the outer protruding end. The first-stage portion of the large-diameter portion 83 functions as a stopper 83a of the guide rod 79. A coil spring 89 as urging means is interposed between the second step of the large diameter portion 83 and the outer end surface of the head cover 24. The coil spring 89 urges the guide rod 79 in a direction opposite to the direction in which the guide rod 79 can move, that is, in the present embodiment, to the right. In the fluid pressure cylinder 71 of the present embodiment, the coil spring 89 and the one-way lock mechanism 88 constitute a specific position transition mechanism.

A second end of the guide rod 79 (hereinafter referred to as an inner protruding end) protrudes in the direction of the internal space of the cylinder body 21 and is fitted into the rod fitting hole 38. An engagement flange portion 84 as a stroke end position determination portion is formed on such an inner protruding end. The engagement flange portion 84 is adapted to engage with a narrow portion of the rod fitting hole 38 of the piston rod 32. As a result, the leftward movement of the piston rod 32 is restricted. That is, this position is the left stroke end.

A third port 40 is provided at the center of the end surface of the outer protruding end of the guide rod 79. This third
The port 40 is communicated with a communication hole 79a penetrated along the longitudinal direction of the guide rod 79. Also, the third
Port 40 is a pipe 29a branched from the pipe 29.
It is connected to the. Therefore, pressurized air is supplied to the port 40 from the switching valve 4, and the pressurized air is further introduced into the head side pressure action chamber R2.

An annular groove 86 is formed near the engaging flange 84 at the inner protruding end. One side surface of the annular groove 86 is a gentle tapered surface. A plurality of openings 85 of the communication passage 79a are radially formed on the bottom surface of the annular groove 86. Since the location of the annular groove 86 is smaller in diameter than the shaft 79b, the Y packing 41 and the guide rod 7 are located at the location.
There is a gap between the first and the second. With such a gap, the pressurized air can flow, so that the partition body is in an unsealed state. The length of the non-sealing state (that is, the length substantially corresponding to the length of the annular groove 86) is
This is the length L2 at which the high thrust operation is performed. Therefore, in FIG. 9 and the like, the position where the tapered surface exists is a position where the low output operation is switched to the high output operation, that is, a specific position of the stroke. Here, in the present embodiment, the stroke length L is set to 90 mm. The length from the specific position to the left stroke end (the length at which a high thrust operation is performed) L2 is set to 5 mm. Therefore, the length L1 at which the low thrust operation is performed is L-L2 = 85 mm.
Becomes

By the way, until the piston portion 33 reaches the specific position from the right stroke end, the partition body is in a sealed state, and the head side pressure action chamber R2 has two small spaces r.
1 and r2. The first small space r1 is defined by the outer peripheral surface of the guide rod 79 and the inner peripheral surface of the rod fitting hole 38. This small space r communicating with the third port 40
1 is supplied with pressurized air, and the pressurized air acts on the inner bottom surface of the rod fitting hole 38 at that time. That is, in the present embodiment, the inner bottom surface of the rod fitting hole 38 is a pressure receiving area of the piston rod 32 at the time of fitting. On the other hand, the second small space r2 is formed by the inner peripheral surface of the cylinder tube 22, the head-side end surface of the piston portion 33, the inner end surface of the head cover 24, and the outer peripheral surface of the guide rod 79. However, pressurized air is not supplied to the small space r2 in the sealed state. For this reason, the end face on the head side of the piston portion 33 belonging to the small space r2 is a non-pressure receiving area. The area S2 of the non-pressure receiving region is substantially equal to the axial projected area S of the piston portion 33-the area of the inner bottom surface of the rod fitting hole 38 (that is, the area of the pressure receiving region) S1. Here, since the area of the narrow portion of the opening of the rod fitting hole 38 is small, it is ignored in the calculation. Then, in this case, S1: S1 + S2
Is equivalent to the ratio of the thrust during the low thrust operation to the thrust during the high thrust operation.

The head cover 24 is provided with a check valve 42 having a check ball 30. The check valve 42 has a function of permitting only air to flow into the second small space r2 and preventing air from flowing out of the second small space r2. Therefore, when the piston rod 32 moves to the left, outside air is taken in, so that the second small space r2 does not become negative pressure.

Next, the operation of the thus configured cylinder system of the fourth embodiment will be described. FIG. 9 shows a state in which the stroke in the rightward direction is completed and the piston rod 32 is at the rightward stroke end. At this time, the upper gun arm 5 of the spot welding apparatus 1 is at the uppermost position, and the distance between the electrode tips 6 and 8 is equal to the stroke length L (see FIGS. 14A and 15A). At this time, the partition body maintains the sealed state.

After reaching the above state, the switching valve 4 is switched to the second switching state (see FIG. 10). Then
When the B port 13 of the switching valve 4 communicates with the fluid supply source 16, pressurized air is supplied to the second port 28 via the pipe 29 and pressurized to the third port 40 via the pipe 29 a. Air is supplied. However, the pressurized air does not flow from the second port 28 having the check valve function, and the pressurized air flows only from the third port 40.

The pressurized air that has flowed into the first small space r1 through the third port 40 and the communication passage 79a acts on the inner bottom surface of the rod fitting hole 38, which is a pressure receiving area. As a result, the piston rod 32 starts a stroke with a low thrust toward the left side. At this time, the air remaining in the rod-side pressure action chamber R1 flows to the first port 26,
It is quickly released to the atmosphere via the pipe 27 and the A port 12. And such a low thrust operation is performed by the piston portion 3
3 is maintained until it reaches a specific position near the left stroke end (see FIG. 11). At this time, as shown in FIG. 14B, the electrode tip 6 moves down to a position 5 mm from the material 9 to be welded.

When the piston portion 33 reaches the specific position,
When a gap is formed between the Y packing 41 and the outer peripheral surface of the guide rod 39, the small spaces r1, r2 in the head side pressure action chamber R2 disappear (see FIG. 12). Therefore, the pressurized air acts on the entire end face of the piston portion 33 on the head side. As a result, the operation is automatically switched from the low thrust operation to the high thrust operation, and the piston rod 32 maintains the high thrust operation until reaching the left stroke end. At this time, the electrode tip 6 of the spot welding apparatus 1 is pressed against the upper surface of the material 9 to be welded, as shown in FIG. And
By passing a large current between the two electrode tips 6 and 8 for a short time, the materials 9 to be welded are joined to each other. In this process, since the pressure in the head side pressure action chamber R2 becomes relatively higher than the external environment of the cylinder 71, air leakage from the check valve 42 does not occur.

When the piston portion 33 reaches the left stroke end, the switching valve 4 is switched to the first switching state. Then, the A port 12 of the switching valve 4 is connected to the fluid supply source 16.
The pressurized air flows into the rod side pressure action chamber R1 via the pipe 27 and the first port 26.
The pressurized air flowing into the rod-side pressure action chamber R1 acts on the rod-side end surface of the piston portion 33. As a result, the piston rod 32 starts a stroke with a constant thrust toward the right side. At this time, the head side pressure action chamber R
The air remaining in 2 is mainly due to the second port 2
8, quickly discharged to the atmosphere via the pipe 29 and the B port 13. Although some residual air is discharged from the third port 40, no residual air is discharged from the check valve 42. The constant thrust operation is performed by the piston 3
3 is maintained until the right stroke end is reached.

Here, matters that have been desired to be improved in the conventional cylinder system will be described below. Since the electrode tip attached to the tip of the gun arm gradually wears out over a long period of use, the stroke length of the cylinder becomes longer by the wear of the electrode tip. Then, the position where the low thrust operation is switched to the high thrust operation is out of the initial setting. Therefore, conventionally, the operator has to adjust the position of the position sensor, which is extremely inconvenient in use.

FIG. 13 shows a state when the electrode tip 6A is worn out in this embodiment. When the electrode tip 6A is worn, the stroke length is lengthened by the worn length L3. Then, the thrust of the piston rod 32 acts on the engagement flange portion 84, so that the guide rod 32 moves to the left against the urging force of the coil spring 89. Therefore, a new left stroke end position and a new specific position are set. FIG. 15 (b)
Indicates the movement range of the worn electrode tip 6A, assuming that there is no change in the stroke length.
On the other hand, FIG. 15C shows the movement range of the worn electrode tip 6A in the case of the present embodiment. According to FIG. 15C, even after the stroke length L is increased, the relative positional relationship between the left stroke end position and the specific position is the same as before, that is, L2 = 5 mm.
It can be seen that it is.

Hereinafter, the characteristic effects of the present embodiment will be listed. (A) The cylinder system of the spot welding apparatus 1
A pressure receiving area changing mechanism having the above-described partition is provided. Therefore, when the pressure receiving area of the piston rod 32 changes, the action of the pressurized air applied to the piston rod 32 changes accordingly. As a result, the thrust of the piston rod 32 is changed from a low thrust to a high thrust at a specific position of the leftward stroke. Further, according to the pressure receiving area changing mechanism, the thrust can be switched without changing the flow rate of the pressurized air supplied to and discharged from the cylinder 71. Therefore, unlike the conventional apparatus which requires fluid flow control, there is no need for ancillary equipment for the cylinder (that is, the above-described pressure reducing valve, speed control valve, and the like), thereby achieving cost reduction.

(B) The cylinder system of the spot welding apparatus 1 is provided with the above-described specific position transition mechanism. Therefore, even when the left stroke end position moves, the specific position of the stroke can be shifted by a corresponding amount following the movement. Therefore, even if the stroke length changes and becomes longer, the position where the low thrust operation is switched to the high thrust operation does not deviate from the initial setting. Therefore, unlike the conventional device that requires the position adjustment of the position sensor, it is not necessary to perform a troublesome adjustment operation.

(C) In the cylinder system of the present embodiment, the non-pressure receiving area is secured for a certain period by dividing the head side pressure action chamber R2 into two small spaces r1 and r2 up to a specific position of the stroke by the partitioning body. ing. Therefore, if the pressurized air is supplied to the small space r1 to which the non-pressure receiving region does not belong, the air pressure acts on not one end surface of the piston rod 32 but only one end surface thereof, and the piston rod 32 can be operated with low thrust. it can. After the piston rod 32 reaches the specific position of the stroke, the non-pressure receiving region disappears, so that the pressurized air acts on the entire end surface on one side, and the piston rod 32 can be operated with high thrust. Further, since the position where the partition functions can be set in advance, the position detecting means is not required. This also contributes to the cost reduction of the cylinder system.

(D) The specific position transition mechanism of this cylinder system is constituted by a one-way lock mechanism 88 as one-way lock means and a coil spring 89 as urging means. Therefore, when a force larger than the urging force of the coil spring 89 is applied to the guide rod 79, the guide rod 79 moves by a predetermined amount only to the left and is held at that position. Therefore, a new left stroke end position and a new specific position can be reliably set.

(E) In the present embodiment, the guide rod 79
Since the partition body is formed by using the rod fitting hole 38 and the Y packing 41, the mechanical structure is relatively simple. This certainly contributes to cost reduction. The annular groove 8 in the guide rod 79
By changing the length of 6, the position where the thrust switches can be set in advance. For this reason, as described above, the position detection means, which is conventionally essential, becomes unnecessary. In addition,
With the Y packing 41, the sealing performance between the small spaces r1 and r2 can be improved, so that the pressure is applied from the first small space r1 to which the pressure receiving region belongs to the second small space r2 to which the non-pressure receiving region belongs. Compressed air is less likely to leak. As a result, the use efficiency of the fluid is also improved.

(F) The cylinder 3 is characterized in that the rod fitting hole 38 is formed in the rod portion 34 of the piston rod 32. Usually, such a rod portion 34 is long enough to form a deep hole. Therefore, it is not necessary to form the piston portion 33 thick in order to secure a space for drilling. Therefore, the fluid pressure cylinder 71 can be made compact. Further, with such a configuration, the load is not biased, so that the operability of the piston rod 32 is also improved.

(G) In the fluid pressure cylinder 71 of this embodiment, the second port 28, the third port 40, the check valve 4
2. The guide rod 79, the one-way locking means 88 and the coil spring 89 are provided so as to concentrate on the head cover 24. Therefore, any of the above parts 2
Even in the event of damage to 8, 40, 42, etc., it is possible to repair by replacing only the head cover 24. [Fifth Embodiment] Next, a fluid pressure cylinder 91 used in a spot welding apparatus 1 according to a fifth embodiment will be described with reference to FIG. Here, the same components as those of the fourth embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Of course, it is needless to say that the same operation and effect can be achieved with a common configuration.

In the fluid pressure cylinder 91, the head cover 93 constituting the cylinder body 92 is thick. A through hole 77 is formed at the center of the head cover 93 having such a thickness, and a guide rod 101 having a second fitting portion is movably inserted into the through hole 77. A rod fitting hole 105 as a second fitting part is formed inside the shaft part 102 of the guide rod 101. An engagement stopper 106 is provided at the opening of the rod fitting hole 105, and an annular groove 107 is provided immediately inside the engagement stopper 106. The outer protruding end of the guide rod 101 is a large-diameter portion 103, and a third port 40 is formed in that portion. This third
Port 40 is connected to the rod fitting hole 1 through the communication passage 104.
It communicates with the space in 05. On the other hand, this piston rod 94 has, in addition to the rod portion 34 and the piston portion 33,
A sub rod portion 95 as a first fitting portion is provided.
The sub rod portion 95 is connected to the guide rod 6.
One rod fitting hole 38 is fitted. An engaged portion 96 that determines the left stroke end by engaging with the engagement stopper 106 is formed at the end of the sub rod portion 95.

(A) And the fifth embodiment also has
Although the configuration is simple and the cost is low, it is possible to change the thrust at a specific position of the stroke, and it is possible to obtain the same operation and effect as in the fourth embodiment, in that the thrust is hardly affected by the change in the stroke length.

The present invention can be modified, for example, as follows. (1) In the first to fifth embodiments, the second port 28, the third port 40, and the check valve 42 are connected to the cylinder tube 2
2 may be formed. In the fourth and fifth embodiments, the third port 40 may be formed in the rod cover 24.

(2) The Y-packing 41 as an annular sealing member may be provided on the outer peripheral surface of the guide rods 39 and 79. In addition to the Y packing 41,
For example, it is also possible to use packing that is not Y-shaped in cross section, such as an O-ring or so-called Dharma packing.
Further, the packing may be omitted in certain cases.

(3) In the first to fifth embodiments, the first small space r1 side is set as the non-supply side of the pressurized air, and the second small space r1 is
The second side may be the supply side of the pressurized air. That is, it is permissible to provide a non-pressure receiving area in the first small space r1.

(4) In the first to fifth embodiments, the switching valve 4
For example, a noise suppressor may be taken by connecting a muffler to the apparatus. (5) In the fourth and fifth embodiments, the urging means is not limited to the coil spring 89, and another type of spring such as a leaf spring may be used. Further, an elastic body other than a spring, for example, an elastic body such as rubber may be used as the urging means.

(6) In the fourth and fifth embodiments, the specific position shifting means is not limited to the one-way locking means and the urging means, but may be, for example, only the one-way locking means. That is, the urging means can be omitted in certain cases.

(7) The present invention is effective not only when the stroke end position is gradually increased but also when the stroke end position is gradually reduced. Here, in addition to the technical ideas described in the claims, technical ideas grasped by the above-described embodiments are listed below together with their effects.

(1) The method according to claim 1 or 2, wherein the first
Is a rod fitting hole that opens on the inner end face of the cylinder body, and the second fitting part is provided to project from one end face of the moving body and fits into the rod fitting hole. A hydraulic cylinder characterized by a possible sub-rod portion. With this configuration, the manufacture of the cylinder becomes easier.

(2) The fluid pressure cylinder according to claims 4 or 5, wherein the guide rod is screwed to the cylinder body so that the amount of protrusion can be changed. With this configuration, the position where the thrust changes can be changed very easily.

(3) In claim 8, the first fitting portion is a rod fitting hole which is opened at one end surface of the piston rod, and the second fitting portion is provided to project from an inner end surface of the head cover. A guide rod fitted in the rod fitting hole, wherein the one-way locking means only allows the guide rod to move in the direction of the inner end face of the head cover, and the urging means sets the guide rod in the head cover. A hydraulic cylinder characterized in that it is urged toward the outer end face. According to this configuration, by using the guide rod and the rod fitting hole in combination, the mechanical structure becomes relatively simple, which also contributes to cost reduction. Note that, by changing the shape and the like of the guide rod, the position at which the thrust switches can be set in advance, so that the position detecting means becomes unnecessary.

(4) In the technical idea 3, a stroke end position deciding portion for restricting the movement of the piston rod by engaging with a predetermined portion of the piston rod is provided at an inner protruding end of the guide rod. A fluid pressure cylinder, which is provided. According to this configuration,
The engagement of the stroke position determining portion of the guide rod with the piston rod restricts the movement of the piston rod, thereby determining the position of the stroke end. Also,
By the thrust of the piston rod acting on the stroke position determining section, the guide rod moves in the same direction as the piston rod against the urging force of the urging means. Therefore, a new stroke end position and a new specific position can be reliably set.

(5) The hydraulic pressure as set forth in claim 5, wherein the guide rod is hollow, and pressurized fluid is supplied into the cylinder body through the hollow portion. Cylinder. According to this configuration, the fluid is supplied to the small space defined by the outer peripheral surface of the guide rod and the inner peripheral surface of the rod fitting hole via the hollow portion of the guide rod. However, since fluid is not supplied to another small space in the pressure action chamber, the fluid pressure acts on only a part of the end surface of the piston rod in the rod fitting hole. Then, at this time, the piston rod operates with low thrust.

(6) The hydraulic cylinder according to claim 5, wherein an annular seal member is provided on an outer peripheral surface of the guide rod or an inner peripheral surface of the rod fitting hole. According to this configuration, the sealing property between the small spaces is improved by the presence of the seal member, so that the fluid does not easily leak from the small space to which the pressure receiving region belongs to the small space to which the non-pressure receiving region belongs.

(7) The hydraulic cylinder according to claim 5, wherein the tip of the guide rod is tapered. According to the ninth aspect of the present invention, if the tip of the guide rod is tapered, the guide rod can be easily fitted into the rod fitting hole.
The operability of the piston rod is improved.

(8) In the technical ideas 3 and 4, the guide rod is hollow, has a large-diameter portion serving as a stopper at an outer protruding end, and has an engaging flange portion and an annular groove portion at an inner protruding end. A fluid pressure cylinder comprising: With this configuration, the specific stroke position can be reliably set by the length of the annular groove.

The technical terms used in this specification are defined as follows. "Fluid: refers to gases such as nitrogen, oxygen, argon, carbon dioxide, hydrogen, and air such as mixtures thereof, as well as liquids such as water, alcohol, oil, and so-called critical fluids."

[0098]

According to the first to eighth aspects of the present invention, there is provided a fluid pressure cylinder capable of changing a thrust at a specific position of a stroke despite its simple structure and low cost. be able to.

According to the second aspect of the present invention, since the small space does not become negative pressure, the operation becomes smooth. According to the fourth aspect of the invention, the cost can be further reduced by eliminating the need for the position detecting means.

According to the fifth aspect of the invention, the cylinder can be made compact and the operability can be improved.
According to the sixth and seventh aspects of the present invention, it is possible to provide a fluid pressure cylinder which is hardly affected by a change in stroke length.

According to the eighth aspect of the present invention, it is possible to reliably set a new stroke end position and a new specific position.

[Brief description of the drawings]

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

FIG. 2 is a sectional view for explaining the operation of the fluid pressure cylinder.

FIG. 3 is a sectional view for explaining the operation of the fluid pressure cylinder.

FIG. 4 is a sectional view for explaining the operation of the fluid pressure cylinder.

FIG. 5 is a sectional view for explaining the operation of the fluid pressure cylinder.

FIGS. 6A to 6C are schematic diagrams showing the operation of a spot welding apparatus using the fluid pressure cylinder.

FIG. 7 is a sectional view showing a fluid pressure cylinder according to a second embodiment.

FIG. 8 is a sectional view showing a fluid pressure cylinder according to a third embodiment.

FIG. 9 is a sectional view showing a fluid pressure cylinder according to a fourth embodiment.

FIG. 10 is a sectional view for explaining the operation of the fluid pressure cylinder.

FIG. 11 is a sectional view for explaining the operation of the fluid pressure cylinder.

FIG. 12 is a sectional view for explaining the operation of the fluid pressure cylinder.

FIG. 13 is a sectional view for explaining the operation of the fluid pressure cylinder.

FIGS. 14A to 14C are schematic diagrams showing the operation of a spot welding apparatus using the same fluid pressure cylinder.

FIGS. 15A to 15C are schematic diagrams for explaining a moving range of an electrode tip of the spot welding apparatus.

FIG. 16 is a sectional view showing a fluid pressure cylinder according to a fifth embodiment.

FIG. 17 is a schematic view showing a conventional cylinder system.

FIG. 18 is a schematic view showing a conventional cylinder system.

FIG. 19 is a schematic view showing a conventional cylinder system.

[Explanation of symbols]

3, 51, 61, 71, 91 ... fluid pressure cylinder, 21,
54, 94: a cylinder body; 24, 52, 93: a head cover; 32, 55, 94: a piston rod as a moving body; 38: a rod as a first fitting portion constituting a pressure receiving area changing mechanism having a partition body. Mating holes, 39, 79 ...
A guide rod as a second fitting portion constituting a pressure receiving area changing mechanism having a partition, 34A... A sub rod portion as a second fitting portion constituting a pressure receiving area changing mechanism having a partition, 41. Y: a packing as a seal member constituting a pressure receiving area changing mechanism having: 88: a one-way locking means constituting a specific position transition mechanism; 89: a coil spring as an urging means constituting a specific position transition mechanism;
1, R2: pressure action chamber, r1, r2: small space.

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI F16J 10/02 F16J 10/02 A (72) Inventor Yoichi Shibata 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Toshio Uno 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (8)

[Claims] 1. A hydraulic cylinder for driving a moving body accommodated in a cylinder body by the action of a fluid pressure, wherein a pressure action chamber formed by the cylinder body and the moving body is provided in a plurality of small spaces up to a specific position of the stroke. A fluid pressure cylinder, wherein a pressure receiving area changing mechanism for changing a pressure receiving area is provided by a partition body which secures a non-pressure receiving area on an end face of the moving body for a certain period by partitioning the moving body into a predetermined area. 2. The cylinder body according to claim 1, further comprising a check valve for permitting fluid to flow into the small space to which the non-pressure receiving region belongs and preventing fluid from flowing out of the small space. 2. The fluid pressure cylinder according to 1. 3. The partition body has a first fitting portion provided on the moving body and a second fitting provided on an inner end surface of the cylinder body and capable of fitting with the first fitting portion. The fluid pressure cylinder according to claim 1, further comprising a mating portion, wherein the two fitting portions are configured to be in a non-fitting state at a specific position of a stroke. 4. The first fitting portion is a rod fitting hole which is opened at one end surface of the moving body, and the second fitting portion is provided to project from an inner end surface of the cylinder body and is provided with a rod. The fluid pressure cylinder according to claim 3, wherein the guide rod is a guide rod that can be fitted into the fitting hole. 5. The fluid pressure cylinder according to claim 4, wherein said moving body is a piston rod, and said rod fitting hole is formed in a rod portion therein. 6. The apparatus according to claim 1, further comprising a specific position transition mechanism that, when one of the stroke end positions moves, changes a specific position of the stroke by a corresponding amount in accordance with the movement. Fluid pressure cylinder. 7. A first fitting portion provided on the movable body and a second fitting provided on an inner end surface of the cylinder body and fitted to the first fitting portion. 7. The fluid pressure cylinder according to claim 6, wherein the fluid pressure cylinder comprises a portion and a sealing member for sealing a gap between the two fitting portions for a certain period. 8. The one-way locking means for permitting only the movement of the second fitting portion in one direction along the longitudinal direction of the cylinder, the specific position shifting mechanism comprising: The fluid pressure cylinder according to claim 7, further comprising: urging means for urging the second fitting portion in a direction opposite to a movable direction.