JPS63273574A - Resistance welding control device - Google Patents

Abstract

PURPOSE:To perform stabilized welding by selecting the current pattern stored in a welding current pattern storing means qualified by a welding current pattern qualifying means in advance and controlling by using a control means according to this pattern. CONSTITUTION:The pattern of a welding current specially coped with the requirement for the body to be welded is set in advance by a welding current pattern setting circuit 2 and stored in a memory circuit 3. In welding, the specified pattern is called to execute the phase control of a current 7 via a phase control circuit 1. With the device of this composition, stabilized welding is performed and stabilized welding strength is obtainable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement of a welding current control device for a resistance spot welder.

(Prior art) In a resistance spot welding machine, the electrode generally wears out as the number of welds accumulates, and as the contact area increases, the current value per unit area of the nugget decreases, making it impossible to obtain the initial welding strength. It disappears. Therefore, in the conventional technology, the nugget's lt! is simply increased by increasing the current value. The density is kept constant and the specified welding strength is achieved.

(Problem to be solved by the invention) However, on the other hand, increasing the current makes it easier to generate dust, and the welding strength decreases accordingly. There are certain limitations in maintaining a specified welding quality including welding strength, and a solution using new technology has been expected. Therefore, it is an object of the present invention to provide a resistance welding control and device that can flow a current to the nugget that satisfies the final chain of welding quality while constantly minimizing the generation of dust in the continuous resistance spot welding work process. This is a technical issue.

(Means for Solving the Problem) The technical means for solving the above problem is to provide a resistance welding control device with a phase control means or an inverter type control means capable of controlling 11 flows in each cycle, and a a welding current pattern setting means for setting an arbitrary current pattern in one welding cycle using a current controlled for each cycle; a welding current pattern storage means for storing the welding current pattern; and a welding current pattern storage means for storing the welding current pattern; According to the cumulative value of heat input recognized as the product, another welding current pattern previously set by the welding current pattern setting means and stored in the welding current pattern storage means is selected, and the welding 1tBi! and a main controller that controls the phase 111111 means or the inverter type control means according to the pattern.

(Function) Next, the function of the above configuration will be described. The phase control means or inverter type control means controls the control signal from the welding current pattern setting means for each cycle. 111)
T11) 40DtlLAT1014) Pulse width modulation,
Alternatively, by frequency modulation, the current value is increased or decreased to form a predetermined current pattern for the period of one welding cycle, and a welding current according to the current pattern is applied to perform resistance spot welding. The welding current pattern setting means is optimal for resistance spot welding of the workpiece based on the heat input for one welding cycle, which is determined from specification conditions such as the welding strength of the workpiece, the shape of the gun used for resistance spot welding, etc. Design and program the welding current pattern. The welding current pattern storage means stores the programmed welding current pattern. Resistance spot welding work is then carried out for a certain work unit of the object to be welded, but as the work progresses, the shape of the gun becomes deformed due to wear. Therefore, the number of welding times or heat input counter cumulatively counts the number of welding times or the amount of heat input expressed as the product of welding current and welding time. When the cumulative value of the counter reaches a preset value, the main control unit controls the welding current pattern storage means to select the next welding current -
Call a pattern and phase according to that pattern! 1J
111 means or an inverter-type control means to perform resistance spot welding on the object to be welded using a predetermined welding current pattern.

(Embodiment) The configuration of an embodiment of the present invention will be explained below using a block die frame shown in FIG. The resistance welding control device includes a phase control circuit 1, a welding current pattern setting circuit 2, a welding current pattern storage circuit 3, a welding port number or heat input counter circuit 4, a main IIJiIII device 5, and a current sensor 6.
It is combined with a welding machine body consisting of an AC power source 7, a welding transformer 8, and a gun 9. A workpiece 10 to be welded is set in a gun 9.

Next, the operation of the above configuration will be described. The AC power source 7 is phase-controlled by the phase control circuit 1 for each cycle, and supplies a primary current to the primary coil of the welding transformer 8 in accordance with a welding current pattern set for one welding process. A secondary current is induced in the secondary coil of the welding transformer 8 and output as a welding current, and the gun 9 performs resistance spot welding on the workpiece.

The above is the function of the resistance spot welding machine, but in the present invention, the welding current pattern in one welding cycle is determined in advance according to the welding strength required for the workpiece, the shape of the gun used, etc., for example, as shown in Figure 2. As shown in FIG. 2, the welding current pattern setting circuit 2 sets the current to a small value at the beginning of welding and then increases it rapidly, and the welding current pattern storage circuit 3 stores the current. Then, assuming deformation due to wear of the gun when the main welding operation continues, for example, 500 times or at 8000 amperes, the same procedure as above is performed to obtain a welding current pattern different from the initial welding current pattern as shown in Fig. 3. In this way, multiple types of welding current patterns can be prepared according to the number of lots of workpieces to be welded, by setting and memorizing the current pattern.
Current sensor 6 installed in the main circuit through which welding current directly flows
The welding current is detected by the counter circuit 4, and the count is accumulated as the number of welding times or the product of the welding current and the welding time, and when this reaches a predetermined value, the main controller @5 stores it in the welding current pattern storage circuit 3. The next scheduled welding current pattern is called and replaced. The main controller 5 outputs a control signal to the phase control circuit 1 according to the new welding current pattern, and the phase control circuit 1 controls the phase of the AC power source 7 according to this control signal to form a welding current waveform corresponding to the planned welding current pattern. is formed and output to the welding transformer 8.

FIG. 4 is a flowchart illustrating the above IIIll system. Starting from step 101 step 1
If it is determined in step 02 whether or not to weld, the process ends in step 106, and if YES, in step 103, the number of times of welding or the product of welding current and welding time is counted and registered. When the set value is reached, the process moves to step 104 and a new welding current pattern is taken out. Next, in step 105, current control using a new welding current pattern is commanded, and the flow ends in step 1.6. FIG. 5 does not show the welding current pattern according to the prior art, but shows that the current value is simply increased in response to wear and deformation of the gun.

(Effect of the invention) As the number of welds increases during welding with a resistance spot welder, the tip of the gun wears out and the contact area with the workpiece increases, and the welding current must be increased accordingly to maintain a constant current density. Therefore, a method of increasing the welding current is generally adopted since it is not possible to obtain a predetermined welding strength. However, as the welding current increases, dust tends to occur, which may actually reduce the welding strength. The present invention produces less dust in one process of resistance spot welding, that is, in the very early stages of the resistance spot welding process, the welding current value is kept low to reduce the generation of dust, and the welding current pattern gradually increases. is set, the welding current is controlled, and the wear of the gun is followed to perform welding 1! By changing the fft pattern and controlling the welding current, the welding conditions of the welding surface of the workpiece are always kept constant, the generation of dust is suppressed, and spot welding with stable welding strength can be performed.

[Brief explanation of the drawing]

Figure 1 is a block diagram of this resistance welding control device.
Figure 2 shows an example of the first welding current pattern for spot welding, and the third
The figure shows an example of the second welding current pattern (thick solid line), the third (dotted line), the fourth (dashed line), and the fifth (double-dashed line). FIG. 4 is a flowchart of the control system, and FIG. 5 is a diagram showing a welding current pattern according to the prior art. 1... Phase control circuit 2... Welding current pattern setting circuit 3... Welding-current pattern memory circuit 4... Counter 5... Main controller 6... Current sensor applicant Nagoya Den Co., Ltd. Former company agent Patent attorney Hidehiko Okada (3 others) Figure 1 Figure 4

Claims (1)

[Claims] a phase control means or an inverter-type control means capable of controlling the current for each cycle; a welding current pattern setting means for setting an arbitrary current pattern in one welding cycle by the current controlled for each cycle by the control means; a welding current pattern storage means for storing a current pattern; an accumulation means for an amount of heat input recognized as the number of times of welding or a product of a welding current and a welding time; and a main controller for selecting another welding current pattern set by the setting means and stored in the welding current pattern storage means and controlling the phase control means or the inverter type control means in accordance with the welding current pattern. Characteristic resistance welding control device.