JPS5947634B2 - spot welding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spot welding device, particularly to an improvement of a spot welding device with low current loss.

Spot welding provides an efficient processing method in mass production processing, which is widely used as a means of connecting metals, especially thin steel plates. A typical spot welding device welds metal plates by applying a predetermined pressure to electrodes or tips provided on both sides of a workpiece and instantaneously supplying a large current. In this way, spot welding uses a large current, large force, and force, so it is necessary to reduce the impedance in the spot welding circuit. That is, it is known that if the inductance or resistance of the welding circuit is large, a large power loss occurs in the device itself, and the energy loss of the entire device increases. Energy loss not only increases processing costs, but also poses secondary problems such as an increase in the temperature of welding equipment, and there has been a strong demand for improvement. In conventional spot welding equipment, a tip that comes into contact with the workpiece is provided at the tip of a gun cylinder that applies pressurizing force to the workpiece, and power from a welding transformer is supplied to this tip.

In this conventional device, the welding transformer and the chip have separate structures, and the connection between them is made by a secondary cable. Of course, the transformer is placed near the chip, and its impedance is set to a low value. However, in this conventional device, a certain amount of impedance is observed in the secondary cable itself and in the connection between the cable, the transformer, and the welding tip, and this impedance causes a non-negligible power loss. In particular, since the output power of the transformer is extremely large, it is known that large losses do not occur due to the inductance of the secondary cable. The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an improved spot welding device with less power loss. In order to achieve the above object, the present invention includes a pressure base to which a plurality of welding electrodes are fixed, and a single pressure cylinder that moves the pressure base and presses the welding electrodes to a workpiece at a predetermined position. , a hinge mechanism rotatably supporting a pressure base with respect to a pressure cylinder;
A welding transformer for supplying spot current to the workpiece, a lower electrode directly connected to the terminal of the welding transformer,
The welding transformer is configured to include a frame that holds the welding transformer and receives the pressing force applied to the lower electrode. Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a front view of a comparative example of a spot welding apparatus according to the present invention, and FIG. 2 shows a sectional view thereof.

Two electrodes 12 and 14 are fixed to the electrode base 10, forming a lower electrode.

In the illustrated comparative example, a two-point welding device is shown, and the electrode 12,
A workpiece 16 placed on top of the workpiece 14 is welded at both electrode positions. Although not shown, the pressurizing rod 18 is provided with a pressurizing cylinder above it, and the pressurizing rod 18 is pressurized in the direction of arrow A by the pressurizing cylinder. A hinge 24 to which a hinge pin 22 is pivotally attached is fixed to a receiving plate 20 fixed to the pressure rod 18, and a frame 26 is rotatably supported by the hinge pin 22. A welding transformer 28 is fixed to the frame 26. In addition, the welding transformer 28-2
The bent portions of the terminals 30 and 32 are in contact with one end of the frame 26, respectively. Although not shown, primary power is supplied to the welding transformer 28 from a well-known power supply device via a lead wire. The welding power transformed by the welding transformer 28 is guided to terminals 30 and 32. Welding electrodes 34 and 36 forming welding tips are directly connected and fixed to the terminals 30 and 32, respectively. Each welding electrode 34, 36 is connected to the lower electrode 12, 1 described above.
It is set at a position corresponding to 4. Springs 38 and 40 are provided between the substrate 20 and the frame 26 to constantly apply repulsive force between the receiving plate 20 and the frame 26.

Further, adjustment bolts 41 and 42 are provided on both ends of the receiving plate 20, and either one of the adjustment bolts 41 or 42 is connected to the frame 2.
By contacting and rotating the welding electrodes 34 and 6 with respect to the workpiece 16, the initial positions of the welding electrodes 34 and 36 relative to the workpiece 16 can be set correctly. Figure 3 shows a transformer terminal 30 and a welding electrode 34.
The fixed state with the transterminal 30 is shown in detail.
Direct connection can be easily achieved by press-fitting the tapered end 34a of the welding electrode 34 into one of the three tapered holes 30a130b130c provided in the welding electrode 34.

In the illustrated comparative example, the welding electrode 34 is coupled to the tapered hole 30a of the terminal 30. terminal 3
0 is preferably made of a low resistance metal such as copper, and the welding electrode 34 is also preferably made of a copper alloy such as chromium copper. FIG. 4 shows another preferred configuration example of the terminal 130 and the welding electrode 134, and in this configuration example, three protrusions 130a1 provided on the terminal 130
The recess 13 of the electrode 134 is located on either side of 130b1130c.
4a is press-fitted.

Incidentally, it is also preferable to configure the electrodes with eccentric electrodes in order to finely adjust the distance between the two electrodes. A comparative example of the present invention has the above structure, and its operation will be explained next.

With the pressurizing rod 18 and the pressurizing cylinder pulling up the frame 26, welding transformer 28, and welding electrodes 34, 36, the workpiece 16 is forcefully or manually installed at a predetermined position on the lower electrodes 12, 14. .

Next, the pressure cylinder is lowered, and the electrodes 34 and 36 are connected to the workpiece 1.
Contact 6. At this time, the pressurizing force is applied from the pressurizing cylinder to the pressurizing rod 18, the receiving plate 20, the frame 26, and the terminal 3.
0 and 32 between the welding electrodes 34 and 36 and the workpiece 16. Since the terminals 30 and 32 are in contact with the frame 26, most of the pressurizing force is received by the frame 26 and no pressurizing force is applied to the welding transformer 28. Therefore, the welding transformer 28, which is made of windings and other components with relatively low rigidity, is not subjected to impact force or other external forces, and the device can have sufficient durability. In this state, a primary welding current is supplied to the welding transformer 28, a large current is generated in the terminals 30 and 32, and this large power is transmitted from one terminal 32 to the electrode 34, the workpiece 16, and the electrode 1.
2. It flows through the electrode base 10, the electrode 14, the workpiece 16, and the electrode 36 to the other terminal 30.

Therefore, the current path of this secondary power is extremely short,
Furthermore, since there is little inductance in the current path, the power loss is extremely small. The supply of current is completed in a short time, and the workpiece 16 is welded by this welding current, after which the rod 18 is raised by the pressure cylinder and the welding work is completed.

As described above, the loss of power supplied from the welding transformer 28 to the workpiece 16 is extremely small, and as a result, processing costs are reduced, and the cooling device for the terminal, workpiece, or electrode can be simplified. .

FIG. 5 shows an embodiment of the invention.

This embodiment is characterized in that the welding transformer 28 is of a fixed type and constitutes a lower electrode. In the example, the same members as those in the comparative example are given the same reference numerals, and the description thereof will be omitted. This embodiment has electrodes 34 fixed to terminals 30, 32.
, 36, the workpiece 16 is placed on them. A pressure base 50 is rotatably connected to the pressure rod 18 which is moved up and down by a pressure cylinder via a hinge pin 22.
Chip electrodes 52 and 54 fixed to the lower electrodes 34 and 3
6, the workpiece 16 is brought into contact with the workpiece 16. In the embodiment shown in FIG. 5, the welding transformer 28 is fixed, so the stability of the device itself is further improved than in the comparative example. According to this embodiment, electrodes 34 are also provided at the terminals 30 and 32 of the welding transformer 28.
, 36 are directly connected and fixed, their impedance is extremely small and power loss is greatly improved. Further, as shown in the embodiment of FIG. 5, the pressure base 50 and the tip electrodes 52, 54 are constructed symmetrically with respect to a vertical line passing through the hinge pin 22. Therefore, in the case of the illustrated workpiece 16 made of a flat plate, when the rod 18 is lowered in the direction of arrow A by the pressurizing cylinder, the tip electrodes 52 and 54 are lowered with their tips kept in a horizontal state, and are properly pressed against the surface of the workpiece 16. be done. The pressurizing force of the pressurizing cylinder is applied evenly to the workpiece 16 by the tip electrodes 52 and 54. This uniform pressing force is obtained by the hinge mechanism of the present invention, and when the pressing force of both chip electrodes 52, 54 is about to change, the pressing base 50 tilts to either side about the hinge pin 22, and the pressing force equalizes. As explained above, according to the present invention, the secondary current impedance is very small, there is little power loss, the transformer itself can be made smaller, and since the secondary cable is not required, the welding equipment itself can be The cooling structure is simplified, the transformer is located at the bottom, which improves stability, and the hinge mechanism equalizes the pressure force.

[Brief explanation of drawings]

Fig. 1 is a front view showing a comparative example of a spot welding device according to the present invention, Fig. 2 is a cross-sectional view taken from Fig. 1, and Fig. 3 is an enlarged view showing the fixing structure of the terminal and welding electrode in Fig. 1. Figure, 4th
The figure is another enlarged view showing the fixing structure between the terminal and the electrode.
FIG. 5 is a front view showing an embodiment of the present invention. 16...Work, 26...Frame,
28...Welding transformer, 30, 32...
・Terminal, 34, 36...Welding electrode.

Claims (1)

[Claims] 1. A pressure base to which a plurality of welding electrodes are fixed, a single pressure cylinder that moves the pressure base to press the welding electrodes to the workpiece at a predetermined position, and a pressure base for the pressure cylinder. a hinge mechanism that rotatably supports the pressure base;
A spot welding device that includes a welding transformer for supplying a spot current to a workpiece, a lower electrode directly connected to a terminal of the welding transformer, and a frame that holds the welding transformer and receives pressing force applied to the lower electrode. .