JPH08304B2 - Movable electrode drive - Google Patents

Description

Detailed Description of the Invention

[0001]

[Industrial applications]

[0002]

2. Description of the Related Art In multi-welding in which a plurality of spot welding electrodes are arranged side by side to perform spot welding at a plurality of locations at the same time, the distance between adjacent spot welding electrodes is made as short as possible, that is, each welding point is made a short distance. May be required.

For example, in a spot welding electrode of a type in which an electrode is driven by an air cylinder, as shown in FIG. 4, the bore of the cylinder is made small so that the distance between adjacent spot welding electrodes can be reduced and the movable electrode and The tandem system has been adopted in order to secure a sufficient pressing force between the fixed electrodes, but the structure of the cylinder and the piston rod is complicated as shown in the figure.

The hydraulic cylinder 302 illustrated in FIG.
In the spot welding electrode in which the movable electrode 304 is driven by the movable electrode 304 and the fixed electrode 3 even if the bore is made small.
Although it is possible to secure a sufficient pressure force between 06, the device structure is complicated because the hydraulic oil supply / discharge mechanism 310 including the hydraulic pump 308 and the like is required.

As illustrated in FIG. 5, the movable electrode 3
In order to cool 04 and the fixed electrode 306, a cooling water circulation mechanism 314 including a cooling water pump 312 and the like was mounted. Such a cooling water circulation mechanism was also installed in an air cylinder type spot welding electrode.

[0006]

SUMMARY OF THE INVENTION The present invention uses the cooling water supplied for cooling the spot welding electrodes as the drive medium for the movable electrodes, so that the distance between adjacent spot welding electrodes is the same as in the prior art. The present invention provides a movable electrode driving device for a spot welding electrode, which can be reduced in size and has a simpler structure as compared with the prior art.

[0007]

As a means for solving the above-mentioned problems, a movable electrode driving apparatus according to claim 1 is a spot welding electrode including a fixed electrode and a movable electrode which approaches and separates from the fixed electrode. A movable electrode driving device for reciprocally driving the movable electrode, comprising a cylinder arranged to face the fixed electrode and fixed in a relative position to the fixed electrode, and slidably inserted into the cylinder. A hollow cylindrical point holder having a piston portion forming a head chamber in the cylinder and an internal hole opening at the end on the head chamber side and holding the movable electrode at the other end, and the head chamber A water supply port communicating with the cylinder, a water supply pipe having one end connected to the water supply port and the other end inserted through the inner hole of the point holder, and the water supply port communicating with the head chamber. A drainage port formed in the cylinder, a cooling water pump for supplying cooling water to the water supply port via a water supply line connected to the water supply port, and a cooling connected to the drainage port and discharged from the drainage port A drain line for guiding water to a cooling water tank connected to the cooling water pump, a water supply disconnecting means for connecting and disconnecting the communication between the water supply line and the cooling water pump, and a communication between the drain line and the cooling water tank A drainage connecting / disconnecting means for connecting and disconnecting the head holder, a pressurizing means for pressurizing the head chamber through the drainage line, and a point holder returning means for driving the point holder along the direction of separating from the fixed electrode. A movable electrode drive device characterized by:

According to a second aspect of the present invention, there is provided the movable electrode drive apparatus according to the first aspect, wherein the point holder returning means is elastically deformed by moving the point holder toward the fixed electrode. It is a spring member. Next, a movable electrode driving device according to a third aspect is the movable electrode driving device according to the first aspect, wherein the point holder returning means is provided on the opposite side of the head chamber with the piston member sandwiched between the cylinders. And a pressure fluid supply mechanism for supplying a pressure fluid to the rod chamber.

[0009]

In the movable electrode driving device according to claim 1,
First, the water supply disconnecting means is operated to connect the water supply line and the cooling water pump, and the drainage connecting means is operated to connect the drain line to the cooling water tank. The cooling water supplied from the cooling water pump is discharged into the internal hole of the point holder through the water supply line, the water supply port and the water supply pipe. The cooling water discharged into the internal hole moves through the space formed between the water supply pipe and the internal hole and reaches the head chamber of the cylinder through the opening of the internal hole. The point holder and the movable electrode are cooled by the cooling water passing through the inner hole. Further, since the cooling water is discharged from the head chamber to the cooling water tank through the drain port and the drain line, the cooling water circulation from the cooling water pump to the cooling water tank is formed.

Next, after the member to be welded is inserted between the fixed electrode and the movable electrode, the water supply disconnecting means is operated to cut off the communication between the water supply line and the cooling water pump, and the drainage connecting means is operated. The communication between the drain line and the cooling water tank is cut off, and the head chamber is pressurized by the pressurizing means. Since the water supply line and the drain line leading to the head chamber are cut off, the pressure in the head chamber acts on the point holder via the piston portion and drives the point holder along the direction toward the fixed electrode. This causes the movable electrode held by the point holder to approach the fixed electrode. Due to the movement of the movable electrode, the member to be welded is sandwiched between the fixed electrode and the movable electrode and pressed. In this state, the members to be welded can be spot-welded by energizing both electrodes.

As described above, since the cooling water for cooling the electrode is used as the pressure medium for driving the point holder, a mechanism such as a hydraulic pump is not required, and a cylinder and a piston rod are specially provided unlike the tandem system. It is not necessary to have a simple structure. Therefore, the structure is simple as compared with the prior art. Moreover, since the electrodes are driven by hydraulic pressure as in the case of using a hydraulic cylinder, sufficient pressure can be secured between the movable electrode and the fixed electrode even if the bore of the cylinder is reduced, and the distance between adjacent spot welding electrodes can be increased. Can be shortened and used.

After the spot welding, the pressure of the head chamber is released by the pressing means, the point holder is driven by the point holder returning means, and the movable electrode is separated from the fixed electrode. At the same time, the next spot welding operation can be started by operating the water supply disconnecting means to connect the water supply line and the cooling water pump and operating the drainage connecting means to connect the drain line to the cooling water tank.

Next, in the movable electrode driving apparatus according to the second aspect, the spring member as the point holder returning means is elastically deformed by the approach movement of the point holder to the fixed electrode due to the pressurization of the head chamber. After the spot welding, if the pressure of the head chamber is released by the pressure applying means, the repulsive force of the spring member drives the point holder in the direction to separate from the fixed electrode. do not need.

Further, in the movable electrode driving device according to the third aspect, the pressure fluid supply mechanism supplies the pressure fluid to the rod chamber. When the head chamber is pressurized by the above-mentioned pressurizing means, the point holder moves to the fixed electrode side against the pressure of the rod chamber, and when the pressurization of the head chamber by the pressurizing means is released, the point holder is released. Is driven by the pressure of the rod chamber in the direction to separate from the fixed electrode. It is sufficient to provide a rod chamber in the cylinder and supply pressurized fluid to this rod chamber.
For example, since it is not necessary to mount parts such as spring members,
The structure near the cylinder becomes simple.

[0015]

Next, embodiments of the present invention will be described. (Embodiment 1) First, the configuration of the movable electrode driving device 10 of this embodiment will be described.

As shown in FIGS. 1 and 2, the spot welding electrode 12 is provided with a main body 22 having a structure in which a fixed member 16 on which the fixed electrode 14 is mounted and a cylinder 18 are connected by a connecting member 20. , Is fixed to a pedestal (not shown) via a connecting member 20. The fixed electrode 14 has a hollow hemispherical shape, and the inner cavity 14 a communicates with a cooling water passage 24 formed in the fixed member 16. A water supply port 26 and a drainage port 28 are provided in the cooling water passage 24,
In the water supply port 26, the water conduit 3 whose tip reaches the inner cavity 14a
0 is connected. As a result, the cooling water supplied from the water supply port 26 can be discharged to the inner cavity 14 a via the water conduit 30 and further discharged from the drain port 28.

A small-diameter hole 34 on the fixed electrode 14 side and a large-diameter hole 36 on the cylinder head 18a side are formed in the cylinder 18 facing the fixed electrode 14 substantially coaxially and in communication with each other. A ring-shaped neck portion 38 is provided between the small diameter hole 34 and the large diameter hole 36. A drainage port 40 and a water supply port 42 communicating with the large diameter hole 36 are bored in the cylinder head 18a. A water supply pipe 44 is erected on the cylinder head 18a substantially coaxially with the large diameter hole 36 and the small diameter hole 34, and the end of the water supply pipe 44 communicates with the water supply port 42.

A point holder 48 having a hollow hemispherical movable electrode 46 fixed to the tip thereof is inserted into the cylinder 18 so as to be capable of reciprocating along the axial direction. The point holder 48 has an internal hole 50 communicating with the inner cavity 46a of the movable electrode 46 and having an opening 50a on the cylinder head 18a side. The water supply pipe 44 is inserted into the internal hole 50. A portion of the point holder 48 on the side of the movable electrode 46 is a sliding portion 52 that can slide in the small diameter hole 34 of the cylinder 18. Further, on the cylinder head 18a side, a small diameter portion 54, which is connected to the sliding portion 52 and has a diameter smaller than the inner diameter of the neck portion 38, is provided, and a step 56 is provided between the sliding portion 52 and the small diameter portion 54. Are formed. Further, the small diameter portion 5 is provided at the end of the point holder 48 on the cylinder head 18a side.
4 is provided with a flange portion 58 connected to the cylinder 4, and a compression coil spring 60 is interposed between the flange portion 58 and the neck portion 38 of the cylinder 18. The biasing force of the compression coil spring 60 is adjusted to slightly exceed the total weight of the point holder 48 (including the movable electrode 46) when the internal hole 50 is filled with water. Therefore, the point holder 48 is biased toward the cylinder head 18a by the compression coil spring 60, and is held in a state where the flange portion 58 is brought close to the cylinder head 18a in the state where no external force acts (see FIG. 1). But,
When an external force is applied in the direction of separating the flange portion 58 from the cylinder head 18a, the movable electrode 46 can move in the direction of approaching the fixed electrode 14 against the biasing force of the compression coil spring 60.

Although illustration and description are omitted, electric wires from a welding power source are connected to the fixed electrode 14 and the movable electrode 46, and a welding current can be supplied. Water supply port 26 of fixed member 16 and cylinder head 1
A water supply line 62 is connected to the water supply port 42 of 8a, and a drainage line 64 is connected to the drainage port 28 and the drainage port 40. The water supply line 62 is connected to the water discharge port 68 of the water pressure booster 66, and the drainage line 64
Is connected to the return port 70 of the hydraulic booster 66.

The water pressure booster 66 includes a small diameter water pressure portion 72 having a water discharge port 68 and a return port 70 and a large diameter air pressure portion 74 connected to the water pressure portion 72. A hydraulic cylinder chamber 76 is formed inside the hydraulic portion 72 so as to communicate with the return port 70. Hydraulic cylinder chamber 7
6, a constricted portion 78 having a slightly smaller diameter is formed coaxially with the hydraulic cylinder chamber 76, and a packing 80 having an inner diameter that matches the constricted portion 78 is mounted between the hydraulic cylinder chamber 76 and the constricted portion 78. Has been done. Further, the drainage chamber 8 communicating with the constricted portion 78 and having substantially the same diameter and coaxial with the hydraulic cylinder chamber 76 is provided.
2 is drilled. A discharge port 84 that communicates with the drain chamber 82 and opens to the outside is provided, and the discharge port 84 is connected to a cooling water tank 88 via a drain conduit 86. Further, the constricted portion 78 communicates with the drainage chamber 82.
A sliding chamber 90 having substantially the same diameter as that of the coaxial chamber is bored. The sliding chamber 90 communicates with the above-mentioned water outlet port 68, and also communicates with a water receiving port 92 paired with the water outlet port 68. The water receiving port 92 is connected to the discharge side of the cooling water pump 96 via a water supply conduit 94. On the other hand, the suction side of the cooling water pump 96 is connected to the cooling water tank 88. Although not shown, the water supply conduit 94 is provided with a pressure reducing valve with a relief, and the cooling water discharged from the relief port of the pressure reducing valve is returned to the cooling water tank 88.

One end of the sliding chamber 90 is connected to a pneumatic cylinder chamber 98 which is bored inside the air pressure portion 74 substantially coaxially with the sliding chamber 90. A piston 100 is slidably accommodated in the pneumatic cylinder chamber 98. Piston 10
At 0, the head 102 capable of sliding in the constricted portion 78 and the sliding chamber 90, the small diameter shaft portion 104 having a smaller diameter than the head 102, and the sliding chamber 90 having substantially the same diameter as the head 102 can slide. The base end portion 106 of the sliding rod 108 including the base end portion 106 is fixed. The sliding rod 108 can reciprocate between the pneumatic cylinder chamber 98 and the hydraulic cylinder chamber 76 according to the reciprocal sliding movement of the piston 100.

When the piston 100 is in the retracted position, which is located on the head 98a side of the pneumatic cylinder chamber 98, the tip of the head 102 of the sliding rod 108 is located in the drainage chamber 82, and the small diameter shaft The portion 104 is located at a position corresponding to the water outlet port 68 and the water receiving port 92 (see FIG. 1). Therefore, at this time, the water discharge port 68 and the water reception port 92 are
The sliding chamber 90 is in a communication state through a space formed around the small diameter shaft portion 104. On the other hand, the piston 100
When is moved in a direction of separating from the head 98a of the pneumatic cylinder chamber 98, the head 102 of the sliding rod 108 can slide through the constricted portion 78 and project into the hydraulic cylinder chamber 76. Further, at this time, the water outlet port 68 of the sliding chamber 90
And the base end portion 106 at a position corresponding to the water receiving port 92.
, The communication between the water outlet port 68 and the water receiving port 92 is blocked (see FIG. 2).

Further, in the air pressure portion 74, the head 98a of the air pressure cylinder chamber 98 and the cover portion 98b facing the head 98a are respectively connected to the first air port 110 and the second air port 112 which communicate with the air pressure cylinder chamber 98. Has been drilled. The first air port 110 and the second air port 112 are connected to an air source 116 via a 2-position 3-port solenoid valve 114. As a result, the solenoid valve 1
By switching the position of 14, the pressurized air is supplied to the second air port 112 and the first air port 110
Backward operation (see FIG. 1) for discharging the air from the side and retreating the piston 100 and forward moving the piston 100 forward by supplying pressurized air to the first air port 110 and discharging the air from the second air port 112 side. Operation (see FIG. 2) is possible.

Next, the operation of the movable electrode driving device 10 having the above structure will be described. First, the cooling water pump 96
The solenoid valve 114 is moved to the position shown in FIG.
Is the position shown in FIG. As a result, the water receiving port 92 and the water outlet port 68 are brought into communication with each other, so that the cooling water discharged from the cooling water pump 96 flows around the small diameter shaft portion 104 of the water supply conduit 94 → the water receiving port 92 → the sliding rod 108. It flows into the water supply port 26 of the fixed-side member 16 and the water supply port 42 of the cylinder head 18 a through the space → the water supply port 68 → the water supply line 62. The cooling water that has flowed into the water supply port 26 flows into the inner cavity 14a of the fixed electrode 14 via the water conduit 30, further passes through the cooling water passage 24, and then flows out from the drain port 28 to the drain line 64. On the other hand, the water supply port 42
The cooling water that has flowed into the movable electrode 4 passes through the water supply pipe 44.
6 into the inner cavity 46a. The cooling water then passes through the space between the water supply pipe 44 and the internal hole 50, enters the large diameter hole 36 from the opening 50a of the internal hole 50, and further passes through the drain port 40 to the drain line 64. leak. The cooling water flowing into the drain line 64 flows into the hydraulic cylinder chamber 76 from the return port 70, passes through the constricted portion 78, the drain chamber 82 and the drain port 84, and returns from the drain conduit 86 to the cooling water tank 88. In this way, the cooling water tank 88
-Fixed electrode 14 and movable electrode 46-Cooling water tank 88
The cooling water circulation is realized, and the fixed electrode 14 and the movable electrode 46 are cooled.

After a member to be welded (not shown) is inserted between the fixed electrode 14 and the movable electrode 46 in the state shown in FIG. 1, the solenoid valve 114 is switched to the position shown in FIG. By this switching operation of the electromagnetic valve 114, pressurized air is supplied to the first air port 110 of the pneumatic cylinder chamber 98 and air is discharged from the second air port 112 side, so that the piston 100 is advanced. When the sliding rod 108 advances due to the advance of the piston 100, the sliding chamber 90
Since the base end portion 106 enters into the portions corresponding to the water receiving port 92 and the water outlet port 68, the communication between the water receiving port 92 and the water outlet port 68 is blocked, and the cooling water to the fixed electrode 14 and the movable electrode 46 sides is cut off. Supply is stopped. together,
Since the head 102 of the sliding rod 108 penetrates the constricted portion 78 to block the communication between the hydraulic cylinder chamber 76 and the drainage chamber 82, the cooling water flow path from the drainage line 64 to the cooling water tank 88 is also blocked. To be done. That is, both the inflow side and the outflow side of the cooling water path of the water supply line 62 to the fixed electrode 14 and the movable electrode 46 to the drain line 64 are closed, and this path is in a sealed state. Further, when the piston 100 moves forward and the head 102 of the sliding rod 108 enters the hydraulic cylinder chamber 76, the cooling water in the hydraulic cylinder chamber 76 is cooled by the head 102.
It is moved to the drain line 64 side by pressing. Along with this, the cooling water flows backward from the drain line 64 to the large diameter hole 36 side and is pressed by the cooling water that has moved to the large diameter hole 36 side,
The driven point holder 48 moves toward the fixed electrode 14 side against the biasing force of the compression coil spring 60. The movable electrode 46 approaches the fixed electrode 14 by the movement of the point holder 48, and the member to be welded is sandwiched between the movable electrode 46 and the fixed electrode 14.

Since the piston 100 is biased in the forward direction, the sliding rod 108 is also continuously biased in the forward direction. Therefore, the cooling water in the hydraulic cylinder chamber 76 is applied with a pressure obtained by increasing the pressure of the air acting on the piston 100 in accordance with the ratio of the pressure receiving area of the piston 100 and the pressure receiving area of the head 102. become. Large diameter hole 36 and small diameter hole 34 of hydraulic cylinder chamber 76 and cylinder 18
Are communicated with each other, the point holder 48 receives a pressure corresponding to the hydraulic pressure of the hydraulic cylinder chamber 76, and presses the member to be welded with a force corresponding to this pressure. If a current for welding is supplied to the fixed electrode 14 and the movable electrode 46 together with this pressurization, the member to be welded is spot-welded.

After that, the position of the solenoid valve 114 is changed to that shown in FIG.
When the state is switched to the state shown in (4), the sliding rod 108 moves backward together with the piston 100, and the circulation of the cooling water is restarted. Along with this, the pressure exerted on the cooling water in the hydraulic cylinder chamber 76 via the sliding rod 108 is also released, and the water pressure for urging the point holder 48 is also released. The urging force of the spring 60 causes the spring 60 to move along the direction in which it is separated from the fixed electrode 14, and reaches the position shown in FIG. Here, the member to be welded is taken out from between the fixed electrode 14 and the movable electrode 46.

Further, if a new member to be welded is inserted and the position of the solenoid valve 114 is switched, the member to be welded can be sandwiched and pressed between the fixed electrode 14 and the movable electrode 46 in the same manner as described above. Spot welding can be performed by supplying the current of.
As described above, in the movable electrode driving device 10 of the present embodiment, the fixed electrode 14 of the movable electrode 46 is used by using the cooling water path.
Since it can be moved and pressurized to the side, for example, no hydraulic system is required, and the structure is simple as compared with the prior art. Moreover, since liquid (cooling water) is used as the pressurizing medium,
It is possible to reduce the bore of the cylinder 18 as in the conventional hydraulic cylinder system. Further, unlike the air cylinder system, it is not necessary to use the tandem system to reduce the bore of the cylinder.

Therefore, the movable electrode driving device 10
Has a simpler structure as compared with the prior art, but the distance between adjacent spot welding electrodes can be reduced as in the prior art. (Second Embodiment) This second embodiment differs from the first embodiment in that the driving of the point holder in the returning direction after spot welding is performed by fluid pressure.

First, the structure of the movable electrode driving device 210 of this embodiment will be described. As shown in FIG. 3, the spot welding electrode 212 includes a main body 222 having a structure in which a fixed member 216 on which the fixed electrode 214 is mounted and a cylinder 218 are connected by a connecting member 220.
It is fixed to a mount (not shown) via. Although illustration and description are omitted, electric wires from a welding power source are connected to the fixed electrode 214 and the movable electrode 246, and a welding current can be supplied.

The fixed electrode 214 is a hollow hemisphere and has a lumen 2
14a communicates with a cooling water passage 224 formed in the fixed member 216. The cooling water passage 224 is provided with a water supply port 226 and a drainage port 228, and the water supply port 226 is connected with a water guide pipe 230 whose tip reaches the inner cavity 214a. As a result, the water supply port 22
The cooling water supplied from 6 passes through the water conduit 230, and the lumen 21
4a, and can be further discharged from the drain port 228.

In the cylinder 218 arranged so as to face the fixed electrode 214, the inner chamber 2 opened to the fixed electrode 214 side.
36 is provided. Also, the cylinder head 218a
A drainage port 240 and a water supply port 242 communicating with the inner chamber 236 are bored therein, and a water supply pipe 244 is erected substantially coaxially with the inner chamber 236, and the end of the water supply pipe 244 has a water supply port 244. It is connected to 242.

In the inner chamber 236 of the cylinder 218, a point holder 248 having a hollow hemispherical movable electrode 246 fixedly attached to its tip is reciprocally inserted along the axial direction. The point holder 248 is formed with an internal hole 250 communicating with the inner cavity 246a of the movable electrode 246 and having an opening 250a on the cylinder head 218a side, and the water supply pipe 244 is inserted into the internal hole 250. A flange portion 258 is provided around the opening 250a of the point holder 248, and the flange portion 258 can slide in the inner chamber 236 of the cylinder 218. Further, the inner chamber 236 of the cylinder 218 is separated into a head chamber 236a and a rod chamber 236b by this flange portion.

Further, the rod cover 2 of the cylinder 218
A constant pressure port 260 communicating with the rod chamber 236b side of the inner chamber 236 is bored on the 18b side, and a constant pressure line 262 for supplying a constant pressure fluid is connected to the constant pressure port 260. Therefore, the constant pressure fluid from the constant pressure line 262 is supplied to the rod chamber 236b, and the head chamber 236 is
By increasing / decreasing the pressure on the a side, the point holder 248 can be reciprocated in the direction of approaching / releasing the fixed electrode 214.

A water supply line 264 is connected to the water supply port 226 of the fixed member 216 and the water supply port 242 of the cylinder head 218a, and a drainage line 266 is connected to the drainage port 228 and the drainage port 240. These water supply line 264 and drainage line 266
Is connected to a hydraulic booster (not shown) similar to that of the first embodiment, as in the first embodiment. Although not shown and described, the hydraulic booster includes a solenoid valve similar to that of the first embodiment,
The air source, the cooling water pump and the cooling water tank are the same as those in the first embodiment.
Is connected as well.

Next, the operation of the movable electrode driving device 210 having the above structure will be described. First, as described in the first embodiment, the cooling water pump is operated to adjust the position of the solenoid valve to supply the cooling water to the water supply line 264. The cooling water flows through the water supply line 264 into the water supply port 226 of the fixed-side member 216 and the water supply port 242 of the cylinder head 218a. The cooling water that has flowed into the water supply port 226 passes through the water conduit 230 and the internal cavity 21 of the fixed electrode 214.
4a, further passes through the cooling water passage 224, and flows out from the drain port 228 to the drain line 266. On the other hand,
The cooling water that has flowed into the water supply port 242 passes through the water supply pipe 244 and flows into the inner cavity 246 a side of the movable electrode 246.
The cooling water then passes through the space between the water supply pipe 244 and the internal hole 250, enters the head chamber 236a from the opening 250a of the internal hole 250, and further flows out to the drain line 266 via the drain port 240. To do. The cooling water that has flowed into the drain line 266 returns to the cooling water tank via the water pressure booster as in the first embodiment. The fixed electrode 14 and the movable electrode 46 are cooled by this circulation of the cooling water.

Along with the start of the cooling water supply, a constant pressure fluid, such as air, is supplied from the constant pressure line 262. The pressure of the constant pressure fluid is such that the point holder has a rising thrust that slightly exceeds the downward thrust acting on the point holder 248 due to the dead weight of the point holder 248 and the pressure of the cooling water on the rod chamber 236a side. Adjusted in advance. Therefore, when the cooling water and the constant pressure fluid are supplied as described above, the point holder 2
48 is at the rising end.

Next, the fixed electrode 214 and the movable electrode 24.
After the member to be welded (not shown) is inserted between 6, the position of the solenoid valve is switched as in the first embodiment. By this switching operation of the solenoid valve, the water supply line 2 from the water pressure booster
The supply of cooling water to 64 is stopped, and the flow path of cooling water from the drain line 266 to the hydraulic booster is also cut off. That is, both the inflow side and the outflow side of the cooling water path of the water supply line 264 to the fixed electrode 214 and the movable electrode 246 to the drain line 266 are closed, and this path is in a sealed state. Further, as in the first embodiment, the cooling water is made to flow backward from the water pressure booster to the drain line 266 → the head chamber 236a side, and the point holder 248 pressed and driven by the cooling water moved to the head chamber 236a side is the rod chamber. 236
It moves to the fixed electrode 214 side against the upward thrust of the constant pressure fluid of b. By the movement of the point holder 248, the movable electrode 246 approaches the fixed electrode 214, and the member to be welded is sandwiched between the movable electrode 246 and the fixed electrode 214.

Subsequently, as in the first embodiment, the head chamber 23
The movable electrode 246 fixed to the point holder 248 is pressurized by the water pressure booster on the cooling water on the 6a side.
The member to be welded is pressed with a force corresponding to the pressure on the side of the head chamber 236a. If a current for welding is supplied to the fixed electrode 214 and the movable electrode 246 together with this pressurization, the member to be welded is spot-welded.

After that, if the position of the solenoid valve is switched to the initial state, the circulation of the cooling water is restarted as in the first embodiment, and the pressure exerted from the water pressure booster to the cooling water on the head chamber 236a side is also released. Since the water pressure for urging the point holder 248 is also released, the point holder 248
Is moved along the direction of separation from the fixed electrode 214 by the upward thrust of the constant pressure fluid on the rod chamber 236b side,
Reach the rising edge. Here, the member to be welded is taken out from between the fixed electrode 214 and the movable electrode 246.

Further, if a new member to be welded is inserted and the position of the solenoid valve is switched as described above, the member to be welded can be sandwiched and pressed between the fixed electrode 214 and the movable electrode 246 in the same manner as described above. Spot welding can be performed by supplying a welding current. In this way, the movable electrode driving device 2 of this embodiment is
In FIG. 10, the movable electrode 246 using the cooling water path.
Can be moved to the fixed electrode 214 side and pressed,
For example, a hydraulic system is not required, and the structure is simple as compared with the related art. Moreover, it is a liquid (cooling water) as a pressurized medium.
Is used, it is possible to reduce the bore of the cylinder 218 as in the hydraulic cylinder system of the related art. Further, unlike the air cylinder system, it is not necessary to use the tandem system to reduce the bore of the cylinder.

Therefore, this movable electrode driving device 210
Has a simpler structure as compared with the prior art, but the distance between adjacent spot welding electrodes can be reduced as in the prior art. The movable electrode driving device 210 of the second embodiment
Is more complicated than that of the first embodiment in that a constant pressure line 262 for supplying a constant pressure fluid is required, but since it is not necessary to house the compression coil spring inside the cylinder, the structure of the cylinder itself and the point holder is the same as that of the first embodiment. Easier than that.

Although the embodiments have been described above, the present invention is not limited to such embodiments and can be variously implemented without departing from the gist of the present invention.

[0044]

As described above, in the movable electrode driving device according to the first aspect, the cooling water for cooling the electrode is used as the pressure medium for driving the point holder.
There is no need for a mechanism such as a hydraulic pump, and there is no need for a special structure for the cylinder or piston rod as in the tandem system. Therefore, the structure is simple as compared with the prior art. Moreover, since the electrodes are driven by hydraulic pressure as in the case of using a hydraulic cylinder, sufficient pressure can be secured between the movable electrode and the fixed electrode even if the bore of the cylinder is made small, and the distance between adjacent spot welding electrodes can be increased. Can be shortened and used.

Next, the movable electrode driving device according to the second aspect exhibits the same effect as the movable electrode driving device according to the first aspect. Further, since the spring member is mounted, the point holder can be reciprocally driven only by pressurizing and depressurizing the head chamber. No special mechanism is required to operate this spring member.

Further, the movable electrode driving device according to the third aspect exhibits the same effect as the movable electrode driving device according to the first aspect. Furthermore, since the point holder is driven back by the pressure fluid supplied to the rod chamber provided in the cylinder, it is not necessary to mount a component such as a spring member.
Therefore, the structure near the cylinder becomes simple.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a movable electrode driving device according to a first embodiment.

FIG. 2 is an explanatory diagram of a movable electrode driving device according to a first embodiment.

FIG. 3 is an explanatory diagram of a main part of a movable electrode driving device according to a second embodiment.

FIG. 4 is an explanatory diagram of a conventional air cylinder type movable electrode driving device.

FIG. 5 is an explanatory diagram of a conventional hydraulic cylinder type movable electrode driving device.

[Explanation of symbols]

10, 210 ... Movable electrode driving device, 12, 212 ...
..Spot welding electrodes, 14, 214 ... Fixed electrodes,
18, 218 ... Cylinder, 34 ... Small diameter hole (head chamber), 36 ... Large diameter hole (head chamber), 38 ... Neck part (head chamber), 40, 240 ... Drainage port ,
42, 242 ... Water supply port, 44, 244 ... Water supply pipe, 46, 246 ... Movable electrode, 48, 248 ...
・ Point holder, 50, 250 ... Internal hole, 50
a, 250a ... Opening, 52 ... Sliding part (piston part), 56 ... Step (piston part), 60 ... Compression coil spring (point holder returning means), 62,
264 ... Water supply line, 64, 266 ... Drain line, 66 ... Water pressure booster (water supply intermittent means, drainage intermittent means, pressurizing means), 68 ... Outflow port (water supply intermittent means), 72 ... ..Water pressure part, (water supply disconnecting means, drainage connecting means, pressurizing means) 74 ... Air pressure part (water supply disconnecting means, drainage connecting means, pressurizing means), 76 ... Hydraulic cylinder chamber (pressurizing means) , 78 ... Constricted portion (drainage intermittent means, pressurizing means), 80 ... Packing (drainage intermittent means, pressurizing means), 82 ... Drainage chamber (drainage intermittent means), 86 ...
Drainage conduit (drain line), 88 ... Cooling water tank, 9
0 ... Sliding chamber (water supply / interruption means), 92 ... Water receiving port (water supply / interruption means), 94 ... Water supply conduit (water supply line), 96 ... Cooling water pump, 98 ... Empty Pressure cylinder chamber (water supply disconnecting means, drainage connecting means, pressurizing means), 10
0 ... Piston (water supply intermittent means, drainage intermittent means, pressurizing means), 102 ... Head (drainage intermittent means, pressurizing means), 104 ... Small diameter shaft part (water supply intermittent means), 106
... Base end (water supply / interruption means), 108 ... Sliding rod (water supply / interruption means, drainage connection / disconnection means, pressurization means), 114
... Solenoid valve (water supply intermittent means, drainage intermittent means, pressurizing means), 116 ... Air source (water supply intermittent means, drainage intermittent means, pressurizing means), 236 ... Inner chamber (head chamber), 23
6a ... Head chamber, 236b ... Rod chamber, 258
... Flange (piston section), 260 ... Constant pressure port (point holder returning means), 262 ... Constant pressure line (point holder returning means, pressure fluid supply mechanism).

Claims (3)

[Claims] 1. A movable electrode driving device for reciprocatingly driving the movable electrode in a spot welding electrode comprising a fixed electrode and a movable electrode which moves toward and away from the fixed electrode, and is arranged opposite to the fixed electrode. A cylinder whose relative position to the fixed electrode is fixed, a piston portion which is slidably inserted into the cylinder to form a head chamber in the cylinder, and an internal hole which opens at the end on the head chamber side. A hollow cylindrical point holder that holds the movable electrode at the other end, a water supply port that communicates with the head chamber and is bored in the cylinder, and has one end connected to the water supply port and the other end side. Via the water supply pipe inserted into the inner hole of the point holder, the drain port communicating with the head chamber and drilled in the cylinder, and the water supply line connected to the water supply port. A cooling water pump that supplies cooling water to the water supply port, a drainage line that is connected to the drainage port and that guides the cooling water discharged from the drainage port to a cooling water tank that is connected to the cooling water pump, and the water supply Water supply disconnecting means for connecting and disconnecting the line and the cooling water pump, drainage connecting and disconnecting means for connecting and disconnecting the drain line and the cooling water tank, and pressurization for pressurizing the head chamber via the drain line A movable electrode driving device comprising: means and point holder returning means for driving the point holder along a direction of separating from the fixed electrode. 2. The movable electrode driving device according to claim 1, wherein the point holder returning means is a spring member which is elastically deformed by the approach movement of the point holder to the fixed electrode. 3. A rod chamber provided on the opposite side of the head chamber with the piston member sandwiched in the cylinder, as the point holder returning means, and a pressure fluid supply mechanism for supplying a pressure fluid to the rod chamber. The movable electrode drive device according to claim 1, further comprising: