JPH11344006A - Pinch pressure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pinch pressure device incorporating an improved mechanism which allows conducting spot welding, etc., even for an object to be pinched having a low rigidity by performing the pinch pressure holding without causing deformation of the object with only a rough locational accuracy. SOLUTION: As the first pressure chambers 26 on the side of approaching a pair of electrodes 24 are in communication with each other through a first communication passage 38, one electrode 24 abuts first to an object to be welded (to be held by pinch pressure) 22 when the two electrodes 24 are approaching each other, and if farther movement is hindered, the other electrode 24 is solely moved approaching farther to cause the object 22 to be pinched, and thereby certain holding by pinch pressure can be established even if the relative positioning of the object 22 is made rough. Further even if the electrode 24 abuts to the object 22, its deformation can be avoided despite a low rigidity eventually because the deflecting load applied to the object 22 is nullified substantially as long as the moving resistances of the two electrodes 24 in approaching remain the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pinching device, and more particularly to a pinching device capable of pinching even rough positioning accuracy without deforming a pinched object.

[0002]

2. Description of the Related Art A squeezing device for squeezing an object to be squeezed between a pair of squeezing heads arranged so as to face each other on a straight line is a device for holding various types of robots, a temporary fixing device, and a spot welding device. It is frequently used as such. 62-1
The spot welding apparatus described in Japanese Patent Application Laid-Open No. 09883 is an example of such a spot welding apparatus that performs spot welding by clamping an object to be welded (an object to be clamped) between a pair of fixed electrodes and a movable electrode that is a clamping head. The movable electrode is attached to the piston rod of the air cylinder, and the movable electrode is moved with a low load based on the differential pressure of the pressure air supplied to the pair of pressure chambers of the air cylinder. After the workpiece is temporarily clamped between these steps, a high load is applied to strongly clamp the workpiece. Further, as another spot welding device, a pair of electrodes (pressing heads) is provided on the housing and the piston rod of the air cylinder, and the housing itself is slidably provided, and the housing itself is slid according to the position of the workpiece. There is a floating type in which a workpiece can be always reliably pressed by a pair of electrodes by moving a housing.

[0003]

However, in the former spot welding apparatus for welding with a fixed electrode and a movable electrode, for example, when the welding operation is performed while moving the apparatus with respect to an object to be welded, slight displacement occurs. If a gap or the like occurs between the workpiece and the fixed electrode, the workpiece may be deformed when the movable electrode clamps. In addition, even if a plurality of pairs of electrodes are arranged and spot welding is performed at a plurality of locations at the same time, it is difficult to prevent displacement at all welding positions, and welding is performed one location at a time. In addition to the necessity, it is necessary to position each welding position with high accuracy, and there is a problem that the working efficiency is poor.

On the other hand, in the latter spot welding apparatus of the floating type, a high positioning accuracy is not necessarily required because the pinching position of the pair of electrodes changes according to the position of the work to be welded. In some cases, the reaction force (unbalanced load) corresponding to the movement resistance acts on the workpiece and may be deformed depending on the rigidity of the workpiece.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to pinch an object to be pressed without deforming it with rough positioning accuracy even when the rigidity of the object to be pressed is low. An object of the present invention is to provide a clamping mechanism having a new mechanism capable of performing spot welding or the like by pressing.

[0006]

According to a first aspect of the present invention, a pair of pressure-pressing heads disposed so as to face each other on a straight line are brought closer to each other to pinch a pressure-pressed object. (A) one of a housing and a piston rod is fixed to a frame, and the other is provided with the pair of clamping heads, and supplied to a pair of pressure chambers on both sides of the piston. A pair of cylinders that reciprocate their clamping heads in a straight line reciprocating along the straight line, respectively, by projecting the piston rod relative to the housing in accordance with the pressure of the pressure fluid and driving the piston rod in and out; A first communication passage for communicating the first pressure chambers of the pair of cylinder pressure chambers on the side of bringing the pair of pressure-pressing heads closer to each other by supplying a pressure fluid; (C) first pressure adjusting means for adjusting the pressure of the pressure fluid supplied to the first communication path; and (d) the pressure chamber of the pair of cylinders is supplied with the pressure fluid to thereby form the pair of cylinders. And a second pressure adjusting means for adjusting the pressure of the pressure fluid supplied to the second pressure chamber on the side that separates the clamping heads from each other.

According to a second aspect of the present invention, in the pressure device according to the first aspect, the first pressure adjusting means and the second pressure adjusting means adjust the pressure fluid supplied to the first communication passage and the second pressure chamber. By controlling the differential pressure, the piston rods of the pair of cylinders are relatively moved with respect to the housing with a low load, respectively, so that the pair of the clamping heads approach each other, and the object to be clamped is clamped with a low load. After that, there is provided a clamping control means for increasing the load acting in the clamping direction to clamp the object to be clamped with a high load.

According to a third aspect of the present invention, in the clamping device according to the second aspect, (a) the second pressure chambers of the pair of cylinders are connected to each other by a second communication passage, and the second pressure adjusting means is Adjusting the pressure of the pressurized fluid supplied to the second communication path, and (b) the second pressure adjusting means comprises:
(b-1) a second pressure regulating valve for regulating the pressure of the pressure fluid supplied from the fluid supply source to a preset second pressure; and (b-2) the second pressure regulating valve and the second communication passage. Between the second pressure regulating valve and the second communication passage, the communication state between the second pressure regulating valve and the second communication passage, and the communication between the second pressure regulating valve and the second communication passage. A second switching valve that switches between two states, that is, a shut-off state that allows the fluid to flow out, and (c) the first pressure adjusting means includes (c-1)
The pressure of the pressurized fluid supplied from the fluid supply source to the second
A first pressure set in advance so that the pair of squeezing heads can be brought closer to each other by being supplied to the first communication path while the pressure fluid of the second pressure is being supplied to the communication path. (C-2) a communication device disposed between the first pressure control valve and the first communication passage for communicating the first pressure control valve with the first communication passage; A first switching valve that switches between two states, a first state and a first state in which the first pressure regulating valve and the first communication path are shut off and the pressure fluid is allowed to flow out of the first communication path. (D) the squeezing pressure control means includes: (d-1) an opening means for separating the pair of squeezing heads from each other by setting the second switching valve in a communication state and setting the first switching valve in a shut-off state. (D-2) The first switching valve is switched to the communicating state while the second switching valve is kept in the communicating state. Instead, the piston rods of the pair of cylinders are relatively moved with respect to the housing with a low load to bring the pair of clamping heads closer to each other, and the pressure to be clamped disposed between the pair of clamping heads is adjusted. And (d-3) switching the second switching valve to the shut-off state while keeping the first switching valve in the communicating state, and interposing the pressure between the pair of clamping heads. And a main pressing means for pressing the object to be pressed with a high load.

According to a fourth aspect of the present invention, in the pinching device according to any one of the first to third aspects, (a) the pair of cylinders has a housing attached to the frame such that the piston rods face each other on the straight line. The piston is fixed, and the pressure head is attached to the tip of the piston rod. (B) Between the first pressure adjusting means and the first communication passage, the first pressure adjusting means A check valve for preventing the flow of the pressure fluid to the first communication passage and permitting the flow in the opposite direction, and a flow control for restricting the flow of the pressure fluid flowing from the first pressure adjusting means to the first communication passage; The valve is provided in parallel.

According to a fifth aspect of the present invention, in the pinching device according to any one of the first to fourth aspects, a plurality of pairs of pressing heads are arranged so as to face each other on different straight lines. A plurality of pairs of cylinders are provided corresponding to the pair of clamping heads, and the first communication passage, the first pressure adjustment unit, and the second pressure adjustment unit are independently provided for each pair of cylinders. It is characterized by.

[0011]

In such a pressure device, the first communication passage and the second pressure passage are arranged such that the pair of pressure heads disposed opposite to each other are moved by the cylinder in the direction approaching each other. By adjusting the differential pressure of the pressure fluid supplied to the chamber by the first pressure adjusting means and the second pressure adjusting means, it is possible to squeeze the object to be squeezed disposed between the squeezing heads. In this case, since the first pressure chambers on the side where the pair of pressing heads approach each other are communicated with each other by the first communication passage, the pair of pressing heads are connected to each other as in a conventional floating type welding device. When moving in the approaching direction, if one of the pressure heads comes into contact with the pressure object first and further movement is prevented,
Only the other pressing head is further moved closer to press the pressed object. Therefore, even if the relative positioning accuracy with respect to the pressure object is rough, the pressure object can be reliably pressed. Moreover, in the present invention, even if one of the clamping heads comes into contact with the object to be clamped, a reaction force corresponding to the movement resistance of the cylinder housing acts on the object to be clamped as in a conventional floating type welding apparatus. If the movement resistance (such as the relative movement resistance between the housing and the piston rod) when the two pressure heads approach each other is the same, the unbalanced load acting on the object to be pressed becomes substantially zero. Even when the rigidity of the object is low or the object to be clamped is lightweight, it is possible to avoid deformation or displacement of the object to be clamped as much as possible.

Since the positioning accuracy may be rough as described above, a plurality of pairs of pressing heads are provided as in the fifth invention, and a plurality of pressing heads are provided corresponding to the plurality of pairs of pressing heads. Even when a pair of cylinders are provided and the first communication passage, the first pressure adjusting means, and the second pressure adjusting means are independently provided for each of the pair of cylinders, even when the clamping pressure is performed at a plurality of locations in parallel, It is possible to clamp the object to be clamped reliably at the pressure portion. For example, the work efficiency of spot welding and the like is improved compared to the case where spot welding is performed while moving the clamping position one by one with high positioning accuracy. Significantly improved. In this case, the clamping conditions (clamping load, clamping timing, etc.) at each clamping portion can be set independently,
It is also possible to simultaneously squeeze a plurality of types of objects to be squeezed or squeezed portions having different squeezing conditions.

[0013] In the squeezing device of the second invention having the squeezing pressure control means, the piston rods of the pair of cylinders are respectively controlled by controlling the differential pressure of the pressure fluid supplied to the first communication passage and the second pressure chamber. After the object to be pressed is squeezed with a low load by a pair of squeezing heads by moving the object relatively to the housing with a low load, the load acting in the squeezing direction is increased and the object to be squeezed with a high load is increased. Because it is designed to squeeze, it is possible to securely squeeze with a large load without deforming the object to be squeezed or causing displacement.
For example, in the case of spot welding, resistance welding can be appropriately performed by squeezing a workpiece with an appropriate squeezing load.

In the third aspect of the present invention, the first switching valve and the second switching valve are appropriately switched by the pinching pressure control means, and the supply state of the pressurized fluid to the first communication passage and the second communication passage is changed. The pair of pressure heads that are separated from each other are pressed close to each other with a low load and press against the object to be pressed, and then press with a high load, so that feedback control is performed while detecting the pressure of the pressurized fluid. Compared to a case where the change is made in a plurality of stages, the apparatus can be configured simply and inexpensively and the cycle time can be shortened.

In the fourth invention, a pair of cylinders are arranged such that the piston rods face each other on a straight line,
Since the clamping head is attached to the tip of the piston rod, compared to the conventional floating type welding device, it can efficiently clamp the object to be clamped without causing twisting, and the device is compact. Be composed. In particular, in a device in which a plurality of pairs of cylinders are provided and a plurality of locations can be simultaneously pressed as in the fifth invention, a pair of cylinders can be provided relatively close to each other, so that a pressing portion is provided. , The spot welding can be performed by pressing simultaneously.

Further, since the pressure head is attached to the piston rod, its inertia is relatively small, and the flow rate of the pressurized fluid flowing from the first pressure adjusting means to the first communication passage is restricted by the flow control valve. Since the moving speed of the pressing head when pressing the object to be pressed by approaching the pair of pressing heads is suppressed, the impact when the pressing head comes into contact with the object to be pressed is small, The deformation and displacement of the pressure object can be more effectively prevented. Further, since a check valve that allows a flow in the opposite direction is provided in parallel with the flow control valve, the moving speed when separating the pair of squeezing heads is not limited, and the cycle time of a series of operations is reduced. Can be shortened.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In a pinching device according to the present invention, a pair of electrodes (pressing heads) arranged so as to be opposed to each other on a straight line are brought close to each other to form an object to be welded (pressing object). It is suitably applied to a spot welding apparatus for spot welding the workpiece by applying a welding current between the electrodes while pinching, but is preferably applied to a pair of clamping heads such as a gripping apparatus for clamping a workpiece or the like. Thus, the present invention can be applied to various devices for clamping an object to be clamped.

A pair of cylinders for linearly reciprocating the pair of clamping heads respectively has a housing fixed to the frame such that the piston rods face each other on a straight line as in the fourth invention, and the pair of cylinders are clamped at the tip of the piston rod. It is desirable to have a pressure head attached,
The cylinder may be provided at a position separated from the straight line where the pressure head is located, or the pressure head may be attached to the housing with the piston rod fixed to the frame. As the pair of cylinders, an air cylinder operated by pressurized air is preferably used, but it is also possible to employ a cylinder operated by another pressure fluid such as hydraulic oil.

In the second invention, the squeezing pressure is automatically changed in two stages by the squeezing pressure control means. May be brought close to each other to squeeze the object to be squeezed, or the squeezing load may be changed in three or more stages. Further, in some cases, the operator may manually operate the first pressure adjusting unit or the second pressure adjusting unit to control the differential pressure.

In the third invention, the first pressure adjusting means has a first pressure regulating valve and a first switching valve, and the second pressure adjusting means has a second pressure regulating valve and a second switching valve. And
The squeezing load is changed in two stages by switching the first switching valve and the second switching valve by means of the squeezing pressure control means. By using a pressure control servo valve or a linear solenoid valve capable of continuously changing the pressure of the pressure fluid as a pressure adjusting means, or by switching a fluid circuit with a switching valve or the like, one of the pressure fluids is changed. The squeezing load may be changed by changing the pressure halfway. It is desirable that the first pressure regulating valve and the second pressure regulating valve allow the pressure fluid to flow out when the pressure on the pressure reducing side, that is, the cylinder side, exceeds a set value. However, when the air cylinder is used, it is impossible to discharge the pressure fluid. May be. Also, the first
The pressure adjusting means and the second pressure adjusting means may control the pressure of the pressure fluid independently of each other.
The pressure of the pressure fluid adjusted by the pressure adjusting means may be further reduced by a predetermined pressure by the second pressure adjusting means and supplied to the second communication path. It should be noted that the first pressure regulated by the first pressure regulating valve and the second pressure regulated by the second pressure regulating valve satisfy the relation of first pressure> second pressure if the pressure receiving area of the piston is the same. Usually, since the pressure receiving area differs depending on the presence of the piston rod, the pressure receiving area is appropriately set in consideration of the pressure receiving area difference.
It may be pressure.

In the pressing device according to the fifth aspect of the present invention, in which a plurality of pairs of pressing heads are arranged on different straight lines, the object to be pressed can be pressed by a plurality of pairs of pressing heads simultaneously. For example, the pressure may be shifted one pair at a time. The directions of the straight lines in which the plurality of pairs of the pressing heads are moved can be arbitrarily set, but are determined to be parallel to each other, for example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a front view of a spot welding apparatus 10 according to one embodiment of the present invention. Spot welding equipment 1
Reference numeral 0 denotes a U-shaped frame 14 attached to the robot arm 12, and three pairs of cylinders 16a, 16b, and 17a which are provided at the tip of the frame 14 so as to face each other on different straight lines parallel to each other. And 17b, 19a and 19b (hereinafter, simply referred to as cylinders 16, 17, and 19 unless otherwise specified). Each of the cylinders 16, 17, and 19 includes a cylindrical housing 18 fixed to the frame 14, a piston rod 20 protruding forward from the housing 18,
An electrode 24 is provided at the tip of the piston rod 20 to clamp the workpiece 22. Workpiece 2
Reference numeral 2 denotes, for example, two plate members partially overlapped with each other, and has a plurality of (three in the figure) welded portions 22a, 22b, and 22c displaced in the plate thickness direction by bending or the like. In addition, the spot welding device 10 corresponds to a clamping device, the workpiece 22 corresponds to a clamping object,
The electrode 24 corresponds to the clamping head.

FIGS. 2 to 4 are views for explaining an air circuit of the spot welding apparatus 10, and show a pair of cylinders 16a and 1a.
Although the air circuit for the cylinder 6b is shown, the same circuit is provided in the branch pipes 70 and 72 so that the cylinder 17a and 17b, 19a and 19b are supplied with pressurized air. In the drawing, the cylinder 16a and 16b are supplied with a first pressure chamber 26 on the side where the air as a pressure fluid makes the pair of electrodes 24 approach each other, and the pair of electrodes 24 are supplied with the air. A second pressure chamber 28 is provided on the side that separates the piston rod 20 from the housing 18 in accordance with the pressure of air supplied to the first pressure chamber 26 and the second pressure chamber 28. And a pair of electrodes 24 are linearly reciprocated on a common straight line.

The second pressure chamber 28 is provided with a second communication passage 30.
It has been communicated with each other by and between the second communication passage 30 and the fluid supply source 32, a second for pressurizing the second pressure P ₂ two tone preset the pressure of air supplied from the fluid supply source 32 A pressure regulating valve 34 is provided. Fluid supply 32
Is for pumping air at a predetermined flow rate and includes, for example, an air pump. The second pressure regulating valve 34 is
Even if the pressure in the communication passage 30 side of the air exceeds the second pressure P ₂ by volume change, in which pressure regulating so that the second pressure P ₂ by relief air of the second communication passage 30 side . A communication state between the second pressure regulating valve 34 and the second communication passage 30 for communicating the second pressure regulating valve 34 with the second communication passage 30 is provided between the second pressure regulating valve 34 and the second communication passage 30. And a second switching valve 36 for switching between two states, that is, a state of shutting off the air and allowing the air to flow out from the second communication passage 30. The second switching valve 36 is an electromagnetic switching valve. When the solenoid SOL2 is not energized (OFF), the second switching valve 36 is in the communication state shown in FIGS. 2 and 3, and when the solenoid SOL2 is energized (ON), the shutoff shown in FIG. State. In the shut-off state, the outflow of the air supplied from the second pressure regulating valve 34 is prevented. The second pressure regulating valve 34 and the second switching valve 36 correspond to a second pressure adjusting unit.

The first pressure chamber 26 has a first communication passage 38.
The first pressure regulating valve 40 is disposed between the first communication passage 38 and the fluid supply source 32. The first pressure regulating valve 40 supplies the pressure of the air supplied from the fluid supply source 32 to the first communication passage 38 in a state where the air at the second pressure P ₂ is supplied to the _second communication passage 30. the pressure first pressure P ₁ two tone preset so as to be able to approach each other the pair of electrodes 24.
Between the first pressure regulating valve 40 and the first communication passage 38, there is a communication state in which the first pressure regulating valve 40 communicates with the first communication passage 38, and the first pressure regulating valve 40 and the first communication passage 38 And a first switching valve 42 for switching between two states, that is, a state in which the first communication path 38 allows air to flow out of the first communication path 38 and a state in which the air is allowed to flow out. The first switching valve 42 is an electromagnetic switching valve. When the solenoid SOL1 is not energized (OFF), the first switching valve 42 is turned off as shown in FIG. 2, and when the solenoid SOL1 is energized (ON), the communication shown in FIGS. State. In the shutoff state, the outflow of the air supplied from the first pressure regulating valve 40 is prevented. Note that the first pressure regulating valve 40 and the first switching valve 42 correspond to first pressure adjusting means.

In addition, between the first communication passage 38 and the first switching valve 42, a reverse flow for preventing the flow of air from the first switching valve 42 to the first communication passage 38 and allowing the flow in the reverse direction. A stop valve 44 and a flow control valve 46 for limiting the flow rate of air flowing from the first switching valve 42 to the first communication passage 38 are provided in parallel.

FIG. 5 is a view showing a controller 50 for controlling the spot welding apparatus 10. The controller 50 includes a microcomputer having a CPU, a RAM, a ROM, and the like, and performs signal processing in accordance with a program pre-stored in the ROM while using a temporary storage function of the RAM.
Necessary information is exchanged with a robot 54 that moves the robot, and control signals are respectively transmitted to the welding power source 52, the solenoid SOL1 of the first switching valve 42, and the solenoid SOL2 of the second switching valve 36. Output. The robot 54 sequentially moves the robot arm 12 according to a preset movement path, and the spot welding apparatus 10 performs welding work at a plurality of locations. In FIG. 5,
Although only the first switching valve 42 and the second switching valve 36 for the pair of cylinders 16a and 16b are shown,
Twin cylinders 17a and 17b, 19a and 19b
The first switching valve and the second switching valve are also controlled by the common controller 50. The switching control of the first switching valve and the second switching valve is performed by three pairs of cylinders 1
The switching timing may be shifted every 6, 17, or 19.
The timing and the current value of the welding current supplied to the electrode 24 from the welding power source 52 and the pressure control of the air by the pressure regulating valves 34 and 40 are also used for the three pairs of cylinders 16, 17 and 1.
It is possible to set different energization timings, current values, and pressure values for every nine. However, three pairs of cylinders 16, 17, 1
The welding operation may be performed under the same conditions without distinguishing the welding operations. The controller 50 corresponds to a pinching pressure control unit.

FIG. 6 is a flowchart illustrating the control operation of the spot welding apparatus 10. In this control operation, step SA2 corresponds to the clamping pressure control unit and the temporary clamping unit, step SA3 corresponds to the clamping pressure control unit and the main clamping unit, and step SA5 corresponds to the clamping pressure control unit and the release. Means corresponding to each controller 5
Performed by 0.

As shown in FIG. 2, in step SA1, when the solenoids SOL1 and SOL2 of the first switching valve 42 and the second switching valve 36 are both OFF as shown in FIG. 2, the three pairs of electrodes 24 as shown in FIG. The robot arm 12 is moved so that the workpiece 22 is positioned therebetween. Step S
At A2, as shown in FIG. 3, the solenoid SOL1 of the first switching valve 42 is turned on while the solenoid SOL2 of the second switching valve 36 is turned off,
Based on the pressure difference (P ₁ −P ₂ ) between the first pressure P ₁ and the second pressure P ₂ and the pressure receiving area difference between the pistons, the piston rods 20 of the three pairs of cylinders 16, 17, 19 each have a low load. The three pairs of electrodes 24 protrude from the housing 18 and approach each other, so that the welded portions 22a, 22b, and 22c of the workpiece 22 are each pressed with a low load.

Here, a pair of cylinders 16, 17,
19, the first pressure chamber 26 and the second pressure chamber 28 are communicated by the first communication passage 38 and the second communication passage 30, respectively, so that when the pair of electrodes 24 move in the direction approaching each other. When one of the electrodes 24 comes into contact with the workpiece 22 first to prevent further movement, only the other electrode 24 is further moved closer to press the workpiece 22. Therefore, in the moving direction of the electrodes 24, that is, in the straight line direction, the workpiece 22 and the cylinders 16, 17, 19
Even if there is a displacement between the two, the workpiece 22 can be reliably pressed by the pair of electrodes 24. Further, even if the three welding portions 22a, 22b, and 22c are different from each other in the plate thickness direction, that is, in the moving direction of the electrode 24, as shown in FIG. The three pairs of cylinders 16, 17, and 19 provided can reliably clamp the welded portions 22a, 22b, and 22c, respectively.

In step SA3, as shown in FIG. 4, the solenoid SOL2 of the second switching valve 36 is turned on while the solenoid SOL1 of the first switching valve 42 is kept on.
By being a, the air pressure in the second pressure chamber 28 becomes atmospheric pressure, welding site 22a of the first pressure P ₁ Based on three pairs of electrodes 24 between the above weld object 22, 22b, 22c is high, respectively It is clamped by the load.

At step SA4, a welding current is supplied to the three pairs of electrodes 24 from the welding power source 52, and the three welding portions 22a, 22b, 22c of the workpiece 22 are spot-welded simultaneously or at a predetermined timing. . Next, in step SA5, as shown in FIG. 2, the solenoid SOL1 of the first switching valve 42 and the solenoid SOL2 of the second switching valve 36 are both turned off, so that the second
Three pairs of electrodes 24 are respectively moved away from each other on the basis of the pressure P _2.

At step SA6, it is determined whether or not all the welding operations on the workpiece 22 have been completed. If this determination is denied, steps SA1 to SA6 are repeatedly executed. If this determination is affirmed, in step SA7, the robot arm 12 is returned to the original position.

As described above, according to the spot welding apparatus 10 of the present embodiment, the three pairs of electrodes 24 disposed opposite to each other are moved in the direction approaching each other by the pair of cylinders 16, 17, and 19, respectively. The pressure difference between the air supplied to the first communication passage 38 and the second communication passage 30 is regulated by the first pressure regulating valve 40 and the second pressure regulating valve 34 so as to be located between the electrodes 24. Workpiece 22
Can be welded by pinching the welding portions 22a, 22b, 22c. In this case, since the first pressure chambers 26 on the side where the pair of electrodes 24 approach each other are connected to each other by the first communication passage 38, the pair of electrodes 24 are connected to each other as in a conventional floating type welding device. When moving in the approaching direction, one electrode 24 first
, And the further movement is prevented, only the other electrode 24 is further moved closer to pinch the workpiece 22. Therefore, even if the relative positioning accuracy with respect to the workpiece 22 is rough, the workpiece 22 can be reliably pressed.

In this embodiment, even if one of the electrodes 24 abuts on the workpiece 22, a reaction force corresponding to the movement resistance of the cylinder housing is generated as in the conventional floating type welding apparatus. If the movement resistance when the two electrodes 24 approach each other (such as the relative movement resistance between the housing 18 and the piston rod 20) is the same, the unbalanced load acting on the workpiece 22 becomes substantially zero. Therefore, even when the rigidity of the workpiece 22 is low or when the workpiece 22 is lightweight, the deformation or displacement of the workpiece 22 can be avoided as much as possible. As shown in FIG. 1, when welding is performed in a posture in which the cylinders 16, 17, and 19 are substantially horizontal, the movement resistance when projecting the electrodes 24 on both sides is substantially equal, so that one of the electrodes 24 is first covered. Even when the workpiece 22 comes into contact with the workpiece 22, the unbalanced load acting on the workpiece 22 is substantially zero.

Since the positioning accuracy may be rough as described above, three pairs of electrodes 24 are provided, and three pairs of cylinders 1 corresponding to the three pairs of electrodes 24 are provided.
6, 17, and 19, and a pair of cylinders 16, 1
By providing the first communication passage 38, the first pressure regulating valve 40, the first switching valve 42, the second communication passage 30, the second pressure regulating valve 34, and the second switching valve 36 independently for each of the positions 7 and 19,
The three welding portions 22a, 22b, and 22c can be reliably clamped, and the work efficiency of spot welding can be improved compared to, for example, performing spot welding while moving the clamping position one by one with high positioning accuracy. Is greatly improved. In this case, the clamping conditions (clamping load, clamping timing, and the like) at each of the welding portions 22a, 22b, and 22c can be set independently of each other. It is also possible to pinch.

The first communication passage 38 and the second communication passage 3
The piston rods 20 of the three pairs of cylinders 16, 17, and 19 are relatively moved with respect to the housing 18 with a low load by controlling the differential pressure of the air supplied to the cylinders 16, 17, and 19. After clamping the workpiece 22 with a low load, the load acting in the direction of the clamping is increased to clamp the workpiece 22 with a high load, so that the workpiece 22 is deformed or misaligned. It is possible to reliably pinch with a large load without making it work, and it is possible to pinch the workpiece 22 with an appropriate pinching load and appropriately perform resistance welding.

The solenoid SOL1 of the first switching valve 42 and the solenoid SOL2 of the second switching valve 36 are appropriately switched by the controller 50, and the state of air supply to the first communication passage 38 and the second communication passage 30 is changed. Thus, since the pair of electrodes 24 separated from each other are brought close to each other with a low load to squeeze the work piece 22 and then squeeze with a high load, the feedback is performed while detecting the air pressure. Compared to the case where the control is changed in a plurality of stages, the apparatus can be configured simply and inexpensively and the cycle time can be shortened.

Further, the piston rod 2
A pair of cylinders 16 are arranged so that 0 faces each other,
Since the electrode 24 is attached to the tip of the piston rod 20, compared with a conventional floating type welding apparatus, the work piece 22 can be welded without any prying or the like.
Can be efficiently pressed, and the device can be made compact. In particular, as in the present embodiment, three pairs of cylinders 1
When the cylinders 6, 17, and 19 are arranged in parallel with each other and three places are simultaneously pressed, the three pairs of cylinders 16, 17, and 19 can be arranged relatively close to each other.
Even when the intervals between 2a, 22b, and 22c are small, it is possible to perform spot welding by simultaneously squeezing pressure.

Since the electrode 24 is attached to the piston rod 20, the inertia thereof is relatively small, and the flow rate of air flowing from the first switching valve 42 to the first communication passage 38 is restricted by the flow control valve 46. Since the moving speed of the electrodes 24 when the pair of electrodes 24 approach each other to clamp the workpiece 22 is suppressed, the impact when the electrodes 24 come into contact with the workpiece 22 is small, and the workpiece 22 Deformation and displacement are more effectively prevented. Further, since the check valve 44 that allows the flow in the opposite direction is provided in parallel with the flow control valve 46, the moving speed at the time of separating the pair of electrodes 24 is not limited, and the cycle time of a series of operations is set. Can be shortened.

Although the embodiment of the present invention has been described in detail with reference to the drawings, this is merely an embodiment,
The present invention can be implemented in various modified and improved aspects based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a front view of a spot welding apparatus according to one embodiment of the present invention.

FIG. 2 is a view showing an air circuit of the spot welding apparatus of FIG. 1, wherein a solenoid SOL1 of a first switching valve 42 is turned off;
This shows a state in which the solenoid SOL2 of the second switching valve 36 is also OFF.

FIG. 3 is a view showing an air circuit of the spot welding apparatus of FIG. 1, wherein a solenoid SOL1 is ON and a solenoid SO
The state where L2 is OFF is shown.

FIG. 4 is a diagram showing an air circuit of the spot welding apparatus of FIG. 1, wherein a solenoid SOL1 is ON and a solenoid SO
The state where L2 is also ON is shown.

FIG. 5 is a view showing a controller for performing a control operation of the spot welding apparatus of FIG. 1;

FIG. 6 is a flowchart illustrating a main part of a control operation of the spot welding apparatus of FIG. 1;

FIG. 7 is a view showing a state in which an object to be welded is clamped by three pairs of electrodes provided in the spot welding apparatus of FIG. 1;

[Explanation of symbols]

10: spot welding device (clamping device) 14: frame 16a, 16b, 17a, 17b, 19a, 19b: cylinder 18: housing 20: piston rod 22: workpiece (clamping object) 24: electrode (clamping pressure) Head) 26: first pressure chamber 28: second pressure chamber 30: second communication passage 32: fluid supply source 34: second pressure regulating valve (second pressure adjusting means) 36: second switching valve (second pressure adjusting means) 38: First communication passage 40: First pressure regulating valve (first pressure adjusting means) 42: First switching valve (first pressure adjusting means) 44: Check valve 46: Flow control valve 50: Controller (clamping pressure control) Means) Step SA2 (clamping pressure control means, temporary clamping pressure means) Step SA3 (clamping pressure control means, main clamping pressure means) Step SA5 (clamping pressure control means, opening means)

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B23K 37/04 B23K 37/04 F (72) Inventor Kazuyuki Ogusu 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Invention Person Hirofumi Muta 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Masahiro Noguchi 2-10-10 Okano, Nishi-ku, Yokohama-shi, Kanagawa Prefecture Inoue Manufacturing Co., Ltd.

Claims (5)

[Claims] 1. A pressure device which presses an object to be pressed by bringing a pair of pressure heads disposed so as to face each other on a straight line close to each other, wherein one of a housing and a piston rod is a frame. The pair of pressure heads are disposed on the other side and the piston rod is protruded relative to the housing in accordance with the pressure of the pressure fluid supplied to the pair of pressure chambers on both sides of the piston, A pair of cylinders for linearly reciprocating the pressing heads along the straight line by driving the pull-in, and a pair of the pressure heads in the pressure chambers of the pair of cylinders when a pressure fluid is supplied. A first communication passage for communicating the first pressure chambers on the side closer to each other with each other, and a first communication passage for adjusting the pressure of the pressure fluid supplied to the first communication passage.
A pressure adjusting means for adjusting the pressure of the pressure fluid supplied to the second pressure chamber on the side of separating the pair of clamping heads from each other by supplying the pressure fluid among the pressure chambers of the pair of cylinders; 2. A pressure device comprising: a pressure adjusting means. 2. The pressure difference between pressure fluid supplied to the first communication passage and the second pressure chamber is controlled by the first pressure adjustment means and the second pressure adjustment means,
After the piston rods of the pair of cylinders are relatively moved with respect to the housing with a low load, the pair of the pressing heads are brought close to each other, and the object to be pressed is squeezed with a low load. 2. The clamping device according to claim 1, further comprising a clamping control means for increasing a load acting on the object to be clamped with a high load. 3. The second pressure chambers of the pair of cylinders are communicated with each other by a second communication passage, and the second pressure adjusting means adjusts the pressure of the pressure fluid supplied to the second communication passage. The second pressure regulating means regulates the pressure of the pressurized fluid supplied from the fluid supply source to a preset second pressure, the second pressure regulating valve, and the second pressure regulating valve. A communication state provided between the second pressure regulating valve and the second communication path, the communication state being provided between the second pressure regulating valve and the second communication path; A second switching valve for switching between two states, that is, a shutoff state that allows the pressure fluid to flow out of the passage, and the first pressure adjustment unit controls the pressure of the pressure fluid supplied from the fluid supply source. In a state where the pressure fluid of the second pressure is supplied to the second communication passage. A first pressure regulating valve for regulating the pressure to a first pressure set in advance so that the pair of clamping heads can be brought closer to each other by being supplied to the first communication path; A communication state arranged between the first communication passage and the first pressure regulating valve and the first communication passage; and a communication state between the first pressure regulating valve and the first communication passage. A first switching valve that switches between two states, that is, a blocking state that allows the pressure fluid to flow out of the communication passage, and the squeezing pressure control unit brings the second switching valve into a communicating state,
Opening means for closing the first switching valve in a shut-off state to separate the pair of clamping heads from each other; and switching the first switching valve to the communicating state while keeping the second switching valve in the communicating state, thereby forming the pair of cylinders The piston rods are relatively moved with respect to the housing with a low load, respectively, so that the pair of pressing heads approach each other, and the object to be pressed, which is disposed between the pair of pressing heads, is pressed with a low load. Temporary clamping means;
A main pressing means for pressing the object to be pressed with a high load between the pair of pressing heads by switching the second switching valve to a shut-off state while keeping the first switching valve in a communicating state; The clamping device according to claim 2, wherein: 4. The pair of cylinders have a housing fixed to the frame such that the piston rods face each other on the straight line, and the pressure head is attached to a tip of the piston rod. A check valve for preventing flow of the pressure fluid from the first pressure adjusting means to the first communication path side and allowing a flow in the reverse direction between the first pressure adjusting means and the first communication passage; The flow control valve for limiting the flow rate of the pressure fluid flowing from the first pressure adjusting means to the first communication passage side is provided in parallel with the first pressure adjusting means. The pinching device as described. 5. A plurality of pairs of pressurizing heads are provided so as to face each other on different straight lines, and a plurality of pairs of cylinders are provided corresponding to the plurality of pairs of pressurizing heads. The clamping pressure according to any one of claims 1 to 4, wherein the first communication passage, the first pressure adjusting means, and the second pressure adjusting means are independently provided for each of the pair of cylinders. apparatus.