JPH08118036A - Spot welding equipment - Google Patents

Abstract

PURPOSE: To provide a spot welding equipment effectively applicable to plural welding methods without changing a welding gun. CONSTITUTION: In executing hemming welding, an indirect energizing circuit is formed as a closed circuit consisting of a welding current line 45, upper electrode 14, hemming part 25, inner panel 27, earth electrode 33, welding current line 46 and welding transformer 21. The welding current at this time is set by a control panel 18, the result is inputted into the welding transformer 21 through a welding controller 20 so that the optimum current at hemming welding is caused to flow. Successively, the control panel executes lap resistance welding. A welding circuit is formed as a closed circuit consisting of a welding transformer 21, welding current line 45, upper electrode 14, lapped part 26 of a work, lower electrode 15, welding current line 47, switching device 42, welding current line 48 and welding transformer 21, and direct energizing is executed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a spot welding apparatus.

[0002]

2. Description of the Related Art Welding of panels is indispensable when manufacturing a car body or its components. The welding of this panel is usually by automatic spot welding using a welding robot. As a form of welded joint of panels, for example, so-called hemming welding in which an outer panel such as used in a peripheral part of a door is folded back while wrapping a front end of an inner panel at a tip portion and welded to an inner panel inside the folded portion Are known. In this hemming welding, the folded portion and the inner panel are welded to each other without welding the outer surface of the outer panel constituting the outer appearance portion so that the heat-affected zone due to welding cannot be seen from the outside. In addition to the above, lap welding is known in which panels are overlapped with each other, and a welding current is passed through the overlapped portions to weld the panels of the overlapped portions. Conventionally, hemming welding and lap welding are performed using different types of guns.

When performing lap welding, a welding device having a C-shaped arm is used, one side of the overlapping portion of the panel is brought into contact with an electrode tip (for example, +), and the other side surface at the opposite position is contacted with the other. The electrode chips (for example,-) are brought into contact with each other to sandwich the work, and the two electrodes are energized, that is, direct energization is performed to perform welding. When welding the hemming portion of the work, a welding device having one electrode tip is used, and the electrode is brought into contact with the surface of the portion where the hemming welding is to be performed, and the earth electrode is connected to an appropriate place on the work to conduct electricity. The so-called indirect energization is performed. A welding device having a C-shaped arm is usually used for direct welding, but an example of applying it to indirect energization is disclosed in JP-A-3-66.
No. 480 gazette. According to this, a backing material, which is an insulator, is inserted between the welding tip on the lower side of the C-shaped arm and the portion to be welded so as to carry out indirect energization.

[0004]

[Problems to be solved] When performing spot welding,
When different welding methods are required for one work in different places, the following problems occur. For example, when welding a panel of a lift gate attached to the rear portion of a vehicle, it is necessary to perform both hemming welding on the peripheral portion and lap welding on the window opening. In such a case, since the welding method is different, a plurality of welding devices having different types of welding guns are installed, or the welding guns are changed according to hemming welding or lap welding. It was However, installing a plurality of welding devices has a problem in that the cost is increased together with a problem in space, and if the welding gun is changed, the number of steps is increased and the work efficiency is decreased. It is an object of the present invention to provide a spot welding apparatus which is configured in view of the above circumstances of the present invention and which can be effectively applied to a plurality of welding methods with a single welding apparatus and without replacing a welding gun.

[0005]

To achieve the above object, the present invention is configured as follows. That is, the spot welding apparatus according to the present invention can directly energize a welding apparatus having a C-shaped arm, an indirect energizing circuit means for enabling indirect energization of the welding circuit of the welding apparatus, and a welding circuit of the welding apparatus. Direct energizing circuit means and switching means for switching between the indirect energizing circuit means and the direct energizing circuit means. The switching means enables indirect energization of the welding circuit when welding the hemming portion of the workpiece. The switching operation is performed so that direct energization can be performed when welding the overlapping portions of the workpieces. In a preferred mode, the switching means switches other welding conditions at the same time in response to the switching operation of the welding circuit. In this case, the other welding conditions include the welding current value, the pressurizing condition of the welding device, and the like.

[0006]

According to the present invention, there is provided a welding device having a C-shaped arm, and the welding device is provided with a switching means for switching the welding circuit to indirect energization or direct energization. The switching means is characterized by performing a switching operation so that the welding circuit can be directly energized when welding the hemming portion of the work and the direct energization can be performed when welding the overlapping portion of the work. Since the welding conditions of the hemming welding and the welding conditions of the lap welding are different, the switching means corresponds to the switching operation of the welding circuit, and other welding conditions such as the welding current value and the pressurizing condition of the welding device are simultaneously applied. Switch. So, for example,
When it is necessary to perform both hemming welding such as a lift gate and lap welding, perform indirect energization to perform hemming welding to the hemming portion, then switch the circuit to direct energization, and Perform lap welding at the opening. That is, according to the present invention, it is possible to appropriately deal with a single welding device by switching the circuit for the work.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an overall system diagram of a device configuration of a spot welding device 1 according to an embodiment of the present invention. The spot welding apparatus 1 of this example includes a welding robot 3 installed at a predetermined position on the floor surface 2. The welding robot 3 has a base portion 4 fixed to the floor 2, intermediate arms 6 and 7 extending from the base portion 4 via a joint 5, and rotation of the intermediate arms 6 and 7 via joints 8 and 9. A main body arm 10 that can be freely attached is provided.
At the tip of the main body arm 10, an extendable and retractable hand 12, which is rotatably provided via a joint 11 and is supported by the main body arm 10 in a telescopic manner, is attached. A welding gun 13 having a C-shaped arm is attached to the hand 12. The welding gun 13 is provided with upper and lower electrode tips 14 and 15 extending from the upper and lower sides in opposite directions to each other. The welding gun 13 supports the electrode tips 14 and 15 to extend in a C shape and is supported by the hand 12. The upper electrode tip 14 is a positive electrode, and the gun 13 thereof is provided with a cylinder device 16 for controlling the distance between the upper electrode tip 14 and the lower electrode tip 15. The lower electrode tip 15, that is, the negative electrode, is fixed to the tip of the arm 17.

The spot welding apparatus 1 of the present invention further includes a robot control panel 18 for controlling the operation of the robot 3. The control panel 18 is connected to a power source 19 for operating the robot so as to be supplied with electric power. Further, the apparatus of this example is connected to the welding power source 20a and controls the welding conditions. The welding controller 20 is connected to the welding controller 20 and the welding voltage and current are changed and controlled according to the signal from the control panel 18. Transformer 21
It has. Further, welding jigs 23, 24 for supporting the work 22 are installed on the floor 2, and these support the portions to be joined by welding such as the hemming portion 25 or the overlapping portion 26 from below at appropriate positions. are doing. The work 22 of this example has a panel structure of a lift gate attached to the rear part of the automobile.
7 and the outer panel 28 form a closed cross section. The lift gate of this example has two window openings 29 and 3.
0, and the outer panel 28 is folded back so as to wrap around the tip of the inner panel 27 in the peripheral portion to form the hemming portion 25.
The inner ends of the reference numerals 9 and 30 are superposed on each other without bending to form a superposed section 26. Therefore, the work 22 of this example is subjected to hemming welding in the peripheral portion thereof, and is subjected to lap welding at the joint portion 26 involved in superimposing the window openings to form a joint surface panel structure.

For this purpose, the jigs 23, 24 support an insulating material 31 interposed between the lower electrode tip 15 and the outer panel 28 to support the work when hemming welding is performed. And an arm portion 34 that supports a portion of the workpiece 22 that is connected to the ground electrode 33 when hemming welding is performed. In this case, the ground electrode 33 is applied to the portion of the work 22 where the window openings 29 and 30 are to be welded by superposition, and the arm portion 34 is positioned on the opposite side of the work 22 to sandwich the work 22. It is designed to connect to. For this purpose, the ground electrode 33 is connected to the arm portions 32, 3 of the jigs 23, 24.
4 is provided with a cylinder device 35 for controlling the pinching operation. The cylinder device 35 is the jig 2 described above.
And the base portion 36 attached to 3, 24 and the base portion 3
6, a cylinder outer cylinder 38 pivotally supported on the tip of one arm 37, a ground electrode support 40 rotatably attached to another arm 39 of the base 36, and the cylinder outer cylinder. 38 and a piston 41 that reciprocates in 38. The tip of the piston 41 is connected to one end of the earth electrode support portion 40, whereby the earth electrode 33 is rotated around the support portion 40 in response to the reciprocating movement of the piston 41, and the overlapping portion 26 of the work 22. The jigs 23 and 2
4 and the arm portions 32 and 34 of No. 4 are pressed and released.

When the hemming welding is performed as described above, the ground electrode 33 is pressed against the overlapping portion 26 of the work 22, a current is passed through the work 22 and the ground electrode 33, and when the overlap welding is performed, The cylinder device 35 operates so that the ground electrode 33 is separated from the work 22. In this case, the upper and lower electrode tips 14 and 15 of the welding device 1 having a C-shaped arm directly sandwich the overlapping portion 26 and perform direct energization. By this, welding is performed. The apparatus of this example includes a switching device 42 for switching the circuit between the above-mentioned hemming welding and lap welding. The switching device 42 includes a pair of connectors 43 and the connector 43.
A pneumatic cylinder device 44 is provided for connecting and disconnecting. Explaining the path of the welding current, the welding transformer 21 is connected to the upper electrode 14 of the welding gun 3 via the welding current line 45, and is connected to the ground electrode 33 via the welding current line 46. When performing the hemming welding, as shown in FIG. 2, a closed circuit for indirect energization in which a current flows through the welding current line 45, the upper electrode 14, the work 22, the ground electrode 33, and the welding current line 46 is formed. It Also, the welding transformer 21
Can also be connected to the lower electrode 15 via the welding current line 48, the switching device 42 and the welding current line 47.

When a closed circuit is formed by connecting the lower electrode 15 and the welding transformer 21 as described above, direct energization becomes possible as shown in FIG. 3, and the upper electrode 14 and the lower electrode are connected. The welding current will flow directly to the electrode 15. The spot welding apparatus 1 of this example includes an air pressure control system for performing the switching operation of the above switching apparatus and for controlling the pressure applied to the work 22 by the electrode. The pneumatic cylinder device 44 of the switching device 42 is connected to an air supply source 51 via an air line 50, and a switching valve 52 for switching the air pressure is provided in the middle of the air line 50. There is. Further, an air release line 53 of the cylinder device is connected to the switching valve 52. In addition, in each pressure chamber of the cylinder device 16 that controls the operation of the upper electrode 14,
A pair of pneumatic lines 54 and 55 are connected. This pneumatic line is connected to the switching valve 56. The appropriate pressure for pressing the electrode 14 against the work 22 is different between hemming welding and lap welding. In hemming welding, the inner panel 27 is welded to the inner portion of the outer panel 28 that is folded and the outer panel is welded. The pressure of the upper electrode is set so as to avoid the thermal influence of the outer portion of the electrode as much as possible. On the other hand, in the lap welding, it is desirable that the panel at the welded portion is in a close contact state as much as possible in order to effectively melt the lap welding. For this purpose, the upper electrode 14 may be strongly pressed against the lower electrode 15. From this point of view, the pressure of air on the upper electrode 14 in the hemming welding is set to be relatively low, and the pressure of air in the lap welding is set to be relatively high.

As described above, in this embodiment, the pneumatic device of the present embodiment applies the pressure supplied to the cylinder 16 of the upper electrode 14 to the hemming welding in order to provide an appropriate pressing force corresponding to each welding mode. It is changed according to lap welding. For this purpose, in this example, a pair of regulators 57 and 58 set to different pressures are provided in parallel. Then, a switching valve 59 for switching to which regulator the air pressure is introduced is provided. Therefore, when the pneumatic line 60 is selected so as to pass through the lower regulator 58 by the switching valve 59,
When the pressure becomes high, the lap welding is performed, and when the pneumatic line 61 is selected so as to pass through the upper regulator 57, the pressure becomes low and the hemming welding is performed. The pneumatic line 62 upstream of the switching valve 59 and the pneumatic line 63 upstream of the switching valve 52 are connected to the pneumatic source 51. In addition, the switching valves 52, 56, 59 described above.
Is operated by a control signal from the control board 18. In the above configuration, the work 22 is carried into the welding station and positioned by the jigs 23 and 24. Then, when hemming welding is performed, the switching device 42 is set to the state shown in FIGS. 1 and 2. That is, the welding current line 45 is connected to the ground electrode 3
3 is connected to the part of the work which is separated from the upper electrode, that is, the positive electrode. Therefore, the indirect energization circuit in the hemming welding is the welding current line 4
5, upper electrode 14, hemming portion 25, inner panel 2
7, the ground electrode 33, the welding current line 46 and the welding transformer 21 are formed as a closed circuit. The welding current at this time is set by the control panel 18, and the result is input to the welding transformer 21 via the welding controller 20 and is controlled so that the optimum current in the hemming welding flows. Also, the pressing pressure of the work piece is the switching valve 59.
The regulator 57 is selected by the operation (see FIG. 2) to suppress the work with a relatively low pressing force. The switching of the welding current by the switching device 42 and the switching of the pressing force of the work piece 22 by the cylinder device 16 of the upper electrode 14 are performed in synchronism with each other when switching from lap welding to hemming welding.

When the switching of the welding circuit and the switching of the welding conditions for the hemming welding are completed in this way, the control board 18 outputs a hemming welding execution signal to the welding robot 3. The welding robot 3 performs positioning at the hemming section 25. Hemming welding is performed under predetermined welding conditions including welding time, welding current, welding voltage, etc. which are set in advance. The hemming welding is performed at a predetermined interval, and when all the spot welding of the hemming portion around the lift gate is completed, the control board 18 outputs a switching signal for performing lap welding. This switching signal switches the switching valve that controls the introduction of air pressure to the cylinder device of the switching device that switches the welding current line for hemming welding and lap welding. Thereby, the welding circuit includes the welding transformer 21, the welding current line 45, the upper electrode 14, the work overlapping portion 26, the lower electrode 15, the welding current line 47, the switching device 42, and the welding current line 4.
8 and the welding transformer 21 form a closed circuit, which enables direct energization. At the same time, a signal for setting the clamping force of the work by the upper and lower electrodes is output to the switching valve 59 to output the regulator 5 as shown in FIG.
8 provides a relatively high pressing force. Then, the superposition portion 26 is positioned at a predetermined window opening, and is sandwiched by a predetermined pressure to perform superposition welding. in this case,
The welding robot operates so as to perform spot welding by direct energization at a predetermined interval in the overlapping portion 26 of the window opening.

[0014]

As described above, according to the present invention, it is possible to perform welding of different forms under different welding conditions with a single spot welding device without switching the welding gun, so that the efficiency of the welding operation is improved. Can be improved. Further, since it is possible to handle with a single welding device, it is advantageous in terms of space and cost.

[Brief description of drawings]

FIG. 1 is a welding current control and pneumatic pressure control system diagram of a spot welding apparatus according to an embodiment of the present invention,

FIG. 2 is an explanatory view showing a connection state of lines related to hemming welding,

FIG. 3 is an explanatory diagram showing a line connection state related to lap welding.

[Explanation of symbols]

 1 spot welding device, 3 welding robot, 13 welding gun, 14 upper electrode, 15 lower electrode, 20 welding controller, 21 welding transformer, 22 work, 25 hemming part, 26 overlapping part, 27 inner panel, 28 outer panel, 33 earth electrode, 42 switching device, 52, 56, 59 switching valve.

Claims (4)

[Claims] 1. A welding device having a C-shaped arm, indirect energizing circuit means for enabling indirect energization of a welding circuit of the welding device, and direct energizing circuit means for enabling direct energization of the welding circuit of the welding device. And a switching means for switching between the indirect energizing circuit means and the direct energizing circuit means, the switching means enabling indirect energization of the welding circuit when welding the hemming portion of the work, and the overlapping portion of the work. A spot welding device characterized by performing a switching operation so as to enable direct energization when welding. 2. The spot welding apparatus according to claim 1, wherein the switching means simultaneously switches other welding conditions in response to the switching operation of the welding circuit. 3. The spot welding apparatus according to claim 2, wherein the other welding condition is a welding current value. 4. The spot welding apparatus according to claim 2, wherein the other welding condition is a pressure condition of the welding device.