JPH0259036B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a projection welding machine, and more particularly to a projection welding machine suitable for welding a nut to a panel without a nut pilot hole.

[Background of the invention]

Conventionally, as a projection welding machine for welding a nut onto a panel, the one disclosed in Japanese Utility Model Application Publication No. 56-6580 is known. This is done by installing magnetic adsorption means on the upper electrode that moves up and down, and lowering the upper electrode while adsorbing the nut to a desired position on the panel installed on the lower electrode side, thereby simultaneously positioning and welding the nut. It is something.

However, in the conventional welding machine, the nut and the upper electrode tend to be attracted to each other, and the nut and the upper electrode tend to deviate from each other, making it impossible to accurately align the nut to the panel on the lower electrode, resulting in poor welding positioning accuracy. In this regard, it is conceivable to provide a guide means for positioning the nut on the nut suction side electrode, but this causes a problem in that the welding current is shunted through the guide means etc. during welding, resulting in a reduction in welding quality.

[Purpose of the invention]

An object of the present invention is to provide a projection welding machine that can perform projection welding with high nut welding positioning accuracy and excellent welding quality.

[Summary of the invention]

In order to achieve the above object, a projection welding machine according to the present invention includes an electrode that attracts a nut to be welded to the tip, a supply head body equipped with the electrode, and a supply head body provided within the supply head body. a cylinder, a piston that fits into the cylinder, a guide pin that is connected to the piston, passes through a hole provided in the electrode, and extends into a screw hole of a nut to be welded that is attracted to the electrode; The guide pin is provided with a control means for operating the piston to move in and out of the threaded hole of the nut, and the guide pin is configured to form a tapered surface portion that comes into contact with the opening edge of the threaded hole of the nut.

With this configuration, even if a pilot hole for the nut is not formed in the panel, the guide pin can accurately position the nut and the electrode that attracts it, and the guide pin can be used to prevent welding current from being diverted during welding. Since the retracting operation can be performed, it is possible to improve welding accuracy and welding quality.

[Embodiments of the invention]

Embodiments of the projection welding machine according to the present invention will be described in detail below with reference to the drawings.

Figure 1 shows a cross-sectional view of the upper electrode structure of a projection welding machine, Figure 2 is a perspective view of the entire welding machine including the nut supply device, and Figure 3 shows the relationship between the upper electrode, nut catch mechanism, and lower electrode. FIG. As shown in the figure, this welding machine has a welding machine main body 1.
The main body 1 has a supply head rod 3 which is held in place and pushed vertically downward by a pressure cylinder 2 provided at the top of the main body 1. An upper electrode 4 is attached to the lower part of the supply head rod 3 so as to be inserted into and enclose the lower part. Upper electrode 4
A cable terminal 5 is attached at an upper position, and a welding cable 6 is connected to this terminal 5 to supply welding current. The tip of the upper electrode 4 is a truncated cone,
The nut 7 to be welded is attracted to the tip surface and transferred to the lower electrode 8. The suction action of the nut 7 is performed by energizing and excitation of a suction coil 9 attached to the supply head rod 3.

Further, the supply head rod 3 and the upper electrode 4 are integrated to constitute a supply head body, and a guide pin 10 that can be moved in and out from the tip end face of the upper electrode 4 is arranged in the head body. This guide pin 10 is composed of a piston part 11 and a pin rod part 12 having a smaller diameter cross section.
is made to penetrate through the tip of the upper electrode 4 and protrude from the end surface. For this reason, cylinder chamber 1
The piston part 11 is reciprocated in the air cylinder mechanism 3, and the cylinder chambers at both ends sandwiching the piston part 11 are pneumatic chambers, and the supply head rod 3 is connected to the upper and lower pneumatic chambers so as to communicate with each other. Air supply and exhaust ports 14A and 14 are connected to the upper electrode 4 and the upper electrode 4.
It forms B. Here, the guide pin 10
The pin rod part 12 is inserted into the screw hole 7A of the supplied nut 7 during the protrusion operation, and performs centering of the upper electrode 4 and the nut 7. In particular, in order to perform centering accurately, A tapered surface 12A is formed in the middle, and the tapered surface 12A is inserted into the screw hole 7.
Accurate positioning is achieved by making contact at the opening edge of A.

Next, the nut 7 to be welded is continuously fed to the tip of the upper electrode 4 by a nut feeding device 15 as shown in FIG. Mechanism 1
6 is provided in the welding machine main body 1. This nut catcher mechanism 16 has a catch arm 18 attached to a support shaft 17 at both sides of the upper electrode 4, and has an inclined or straight nut feeding guide 19 and a nut receiver 20 at the tip of the arm 18. I'm trying to form it. Therefore, a half body of a guide 19 and a receiving part 20 are integrally provided at the tip of each arm 18, and when both arms 18 are closed by the action of a spring 21, the nut 7 is connected to the upper electrode 4.
The upper electrode 4 is guided to travel to the position of the distal end surface of the upper electrode 4, so that the downward movement of the upper electrode 4 is not obstructed by the arm opening operation. In order to perform the leg opening operation, as shown in FIG. 3 in particular, a cam plate 22 is attached to the supply head rod 3, and as it moves downward, the spring 21 is expanded to rotate both arms 18 in the leg opening direction. It is said that Note that the nut feeding guide 19 has a chute 2 of the nut feeding device 15.
3 in a row, making it a nut passage.

On the other hand, a lower electrode 8 facing the upper electrode 4 is fixedly arranged at the lower part of the welding machine main body 1, and a panel 24 to be welded to the nut 7 is arranged thereon.

Next, the drive mechanism of the above device is shown in FIG. The drive mechanism has an air circuit 25 that moves the guide pin 10 in and out, and pressurizes (advances) and releases (retracts) the upper electrode 4. This air circuit 25 can move the guide pin 10 in and out by switching the electromagnetic switching valves 26 and 27. A time chart for operating each driving device is constructed as shown in FIG. 5, and a sequence control circuit for implementing this is shown in FIG. In particular, in this control means, the operation of moving the guide pin 10 in and out of the upper electrode 4 is performed when the welding current is applied, and the guide pin 10 is controlled to be retracted during welding, and made to protrude after the welding current has ended. ing. This is achieved by applying a switching signal to the electromagnetic switching valve 26 which communicates with the pneumatic chambers at both ends of the guide pin 10. Specifically, when it is detected that the panel 24 has been placed on the lower electrode 8, a start command is given, the nut is fed, and the a contact CR5 of the energizing circuit of the adsorption coil 9 is activated to transfer the power to the upper electrode 4. Adsorb nut 7. When the nut is attracted, the guide pin 10 is in a state of protruding from the upper electrode 4, so the pin 10 is inserted into the screw hole 7A,
The upper electrode 4 and the nut 7 are accurately positioned by the action of the tapered surface 12A. At the same time, the upper electrode 4
Since the a contact CR5 of the drive circuit that lowers the nut is also activated, the electromagnetic switching valve 27 is switched to the pressurizing side, and the upper electrode 4 is lowered toward the panel 24 set on the lower electrode 8 with the nut attracted. . When the lowering end is reached, the limit switch LS-2 set at that position is turned on, thereby cutting off the power to the adsorption coil 9 and turning on the b contact of the circuit that operates the electromagnetic switching valve 27 for driving the guide pin 10. , and switches the valve 27 to the pin retraction side.
At the same time, the timer TR1 is activated, and the timer switch TR1 in the welding current energization circuit is activated to energize for a set time to perform welding. Then, at the same time as the application of the welding current ends, the guide pin 10 is returned to its original state, that is, the electromagnetic switch 6 is returned to the pin protruding state, and the next preparation is started.

According to the projection welding machine having the above-described configuration, the nut 7 is attached to the upper electrode 4 by an excitation action.
During suction, it is possible to insert the guide pin 10 into the screw hole 7A and perform centering using the tapered surface 12A provided on the pin, so that the nut 7 can be accurately positioned on the upper electrode 4. be able to. This means that welding to the panel 24 set on the lower electrode 8 can be accurately positioned. Therefore, some process equipment for alignment with the nut, such as providing a pilot hole in the panel 24, becomes unnecessary. Further, since the guide pin 10 is pulled into the upper electrode 4 by the control means when welding the nut 7 and the panel 24, the welding current is not shunted through the guide pin 10. Therefore, it is possible to ensure that electricity is applied only through projection, thereby improving welding quality.

In the above embodiment, the guide pin 10 is attached to the upper electrode 4, but the guide pin 10 may be arranged on the lower electrode 8 side on the fixed side.Also, the control circuit using the sequence circuit can be processed by a microcomputer. You can do it like this.

〔Effect of the invention〕

As described above, according to the projection welding machine according to the present invention, improvements in welding positioning accuracy and welding quality can be achieved with a simple configuration.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the upper electrode portion of a projection welding machine according to an embodiment, Fig. 2 is an overall perspective view of the same welding machine including the nut supply device, Fig. 3 is a side view of the upper and lower electrode parts, and Fig. 4 The figure is an air circuit diagram, FIG. 5 is a time chart, and FIG. 6 is a sequence circuit diagram. 4... Upper electrode, 7... Nut, 8... Lower electrode, 10... Guide pin, 16... Nut catch mechanism, 24... Panel, 25... Air circuit.

Claims (1)

[Claims] 1 An electrode that attracts the nut to be welded to the tip,
A supply head body equipped with the electrode, a cylinder provided in the supply head body, a piston that fits into the cylinder, and a cylinder connected to the piston, passing through a hole provided in the electrode, and connecting to the electrode. comprising a guide pin extending into the screw hole of the nut to be welded, and a control means for operating the piston to move the guide pin into and out of the screw hole,
A projection welding machine characterized in that the guide pin is formed with a tapered surface portion that comes into contact with the opening edge of the screw hole of the nut.