JPH03207582A - Method for controlling resistance welding machine - Google Patents

Abstract

PURPOSE:To assure the quality of a weld zone by comparing the detection temperature with the reference temperature and stopping a welding current applied to materials to be welded from an electrode when the surface temperature of the materials to be welded coincides with the reference temperature. CONSTITUTION:The surface temperature of the materials 2a and 2b to be welded corresponding to the peripheral parts of welding electrodes 1a and 1b separated by the predetermined distance from the centers of the welding electrodes 1a and 1b is detected by a temperature detector 4b. The temperature detector 4b detects the temperature and transmits a detection signal by using an optical fiber 4a. The temperature detector 4b detects the temperature from the detection signal. The detection temperature is compared with the preset reference temperature by an error amplifier circuit 5. The welding current applied to the materials 2a and 2b to be welded from the welding electrodes 1a and 1b is stopped when the surface temperature of the materials 2a and 2b to be welded coincides with the reference temperature. By this method, the resistance welding machine control method by which safety, working efficiency and economical efficience are improved can be furnished.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application in Industry) The present invention relates to a control method for a resistance welding machine that automatically guarantees the quality of a welded part during resistance welding.

(Conventional technology) In conventional resistance welding machines, the welding condition of the welded material changes greatly depending on the shape of the welding electrode tip, the electrode pressure, the surface treatment state of the welded material, the processing state of the shape of the welded material, etc. . Therefore, even if the welding current, welding time, and electrode pressure are kept constant, the welding quality of the welded part cannot be made constant, and the current situation is that a sampling destructive test is performed after welding is completed.

In addition, in order to cope with such problems, various quality assurance methods such as an inter-electrode voltage method, an inter-electrode resistance method, and an ultrasonic method have been considered as methods for monitoring the quality of a welded part.

(Problems to be Solved by the Invention) However, in the above conventional control method of a resistance welding machine, in which the welding current, welding time, and electrode pressure are kept constant, the shape of the welding electrode tip and the electrode pressure are pressure,
It is difficult to maintain a constant welding quality because the surface treatment state of the welded material, the shape and processing state of the welded material, etc. change greatly. For this reason, welding is carried out by setting welding conditions more excessively than necessary; however, this method creates dents on the surface of the weld, resulting in a poor appearance of the weld.

Additionally, there are problems from a safety and economic perspective, such as generation of dust, increase in input power and welding time, and reduction in electrode life due to deformation of the tip of the welding electrode.

However, the above-mentioned monitoring method has limitations such as being unable to put it into practical use due to the shape of the welding electrode tip and the surface treatment condition of the welded material, and being applicable only after welding is completed, and cannot always guarantee the quality of the welded part. do not have. Furthermore, a method has been proposed in which the temperature of the welded part is monitored using an infrared camera, but the shape of the camera is large and interferes with welding work, making it difficult to put this method into practical use.

The present invention solves the above conventional problems, and is a practical resistance welding machine control method that can automatically control welding conditions during welding, ensure welding quality, and form just the right welding nugget. The purpose is to provide the following.

(Means for Solving the Problems) In order to achieve the above object, the present invention uses an optical fiber to measure the surface temperature of a material to be welded at a predetermined distance from the center of the welding electrode and corresponding to the surrounding area of the welding electrode. a signal transmission means for detecting temperature and transmitting a detection signal; a temperature detection means for detecting temperature from the detection signal; The quality of the welded part is guaranteed by stopping the welding current applied from the welding electrode to the workpiece when the temperature matches the reference temperature.

(Function) Figure 2 shows a typical example of the relationship between the nugget diameter formed in the weld and the welding current in spot welding, which is a method of resistance welding, and Figure 3 shows the relationship between the nugget diameter and welding current. FIG. 4 shows a typical example of the relationship between the current application time and a typical example of the relationship between the nugget diameter and the tensile shear strength of the weld.

The quality of the weld zone refers to the nucket and the tensile shear strength of the weld zone obtained by it, and ensuring the quality of the weld zone means that the diameter of the nugget formed in the weld zone is specified by the material to be welded. This means controlling the size of the object. For this purpose, the relationships shown in Figures 2 and 3 show that when the welding current is set approximately constant, controlling the welding current application time is an effective means. There is.

Therefore, according to the present invention, the size of the nugget formed in the welded material can be detected by detecting the temperature change conducted to the surface of the welded material, and a preset standard nugget diameter can be formed. Since the welding current is controlled to stop when the difference from the reference temperature corresponding to Welding quality can be guaranteed.

(Embodiment) FIG. 1 shows the configuration of a resistance welding machine control method in an embodiment of the present invention. In the construction drawing, ↓a and lb are welding electrodes which sandwich and pressurize the materials to be welded 2a and 2b, and welding current is supplied from a power supply circuit 3 of a resistance welding machine through a transformer and a semiconductor element. 4a is an infrared fiber, which detects the temperature generated in the welded materials 2a and 2b and transmits it as a detection signal; 4b is a temperature detector that converts the detection signal from the optical fiber into an electrical signal and outputs it. , 5 is an error amplification circuit, 6 is a welding condition setting circuit into which the plate thickness and material of the material to be welded, the required diameter of the nugget, etc. are inputted, and 7 is an arithmetic circuit including a microcomputer, etc., and welding condition setting circuit 6 The reference temperature data stored in the storage circuit 8 is called in accordance with the output value. 9 is a reference temperature generation circuit that outputs a reference temperature signal from reference temperature data; 0 is a current control circuit that controls the output of the power supply circuit 3 to be approximately constant based on the signal from the arithmetic circuit 7; 11 is a current that detects the welding current. The detector 12 is an amplifier circuit that amplifies the signal detected by the current detector 11 and feeds it back to the arithmetic circuit.

Next, the operation of the above embodiment will be explained. Conditions for obtaining a desired welding result are input to the welding condition setting circuit 6, and in accordance with these conditions, the arithmetic circuit 7 selects one of the reference temperature data stored in the memory circuit 8 and sets the reference temperature generation circuit. Enter 9.

The reference temperature generation circuit 9 generates a reference temperature signal and inputs it to the error amplification circuit 5. The error amplifier circuit 5 compares the signal from the temperature sensor 4b with the reference temperature signal, and inputs the error signal to the arithmetic circuit 7. If the surface temperature of the welded materials 2a, 2b is lower than the reference temperature signal, the arithmetic circuit 7 keeps the welding current flowing through the power supply circuit 3 substantially constant and outputs it via the current control circuit. When the value of the error signal becomes zero, the arithmetic circuit 7 stops the welding current flowing through the power supply circuit 3 via the current control circuit. The current detector 11 and the amplifier circuit 12 are welding current detection means that detects the welding current and feeds back the state of the welding current to the arithmetic circuit 7 to keep the welding current substantially constant.

As described above, according to the embodiment of the present invention, the materials to be welded 2a,
The nugget diameter formed in 2b is the welding electrode la, lb
Even if the conditions of the welding part, such as the welding materials 2a, 2b and the applied pressure, change, the temperature is constantly monitored by the temperature sensor 4b, and when the signal from the temperature sensor 4b reaches the reference temperature signal, the nugget 1 diameter is Since welding ends when the desired value is reached, the welding time is not set excessively and the welding current is applied for a long time, which does not affect the electrode life, and there is no dust generation, making it safe and ensuring proper welding. quality is obtained and welding quality is guaranteed.

Furthermore, since welding is automatically completed in the shortest possible time, the number of welding operations per time period increases, improving efficiency.

Furthermore, unnecessary power is not consumed, and welding costs can be reduced.

Furthermore, since the optical fiber 4a is used, the temperature measuring section can be made small and practical.

(Effects of the Invention) As is clear from the above embodiments, the present invention detects the surface temperature of the material to be welded corresponding to the surrounding area of the welding electrode, compares the detected temperature with a preset reference temperature, When the temperatures match, the welding current applied to the welding electrode is stopped, which guarantees the quality of the welded part and is a practical resistor that improves safety, work efficiency, and economy. This has the effect of providing a welding machine control method.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the structure of a resistance welding machine control method = 7 method according to an example of the present invention, and Figure 2 is the relationship between nugget diameter and welding current in spot welding, which is a type of resistance welding machine. Figure 3 is a typical example showing the relationship between the nugget diameter of the spot welding method and the welding current application time, and Figure 4 is a representative example showing the relationship between the spot welding diameter and the welding current application time.
This is a representative example showing the relationship between the tensile shear strength and the nugget diameter of one welding method. la, lb-welding electrode, 2a, 2b-material to be welded,
3...Power circuit, 4a...Optical fiber, 4
b...Temperature detector, 5...Error amplification circuit, 6
... Welding condition setting circuit, 7 ... Arithmetic circuit, 8
...Memory circuit, 9...Reference temperature generation circuit, 10
...Current control circuit, 11...Current detector, J2...
Amplification circuit/

Claims (1)

[Claims] A temperature detector is provided that is located a predetermined distance from the center of the welding electrode and detects the surface temperature of the welded material corresponding to the surrounding area of the welding electrode, and the temperature detector detects and detects the temperature using an optical fiber. It has a signal transmission means for transmitting a signal, and a temperature detection means for detecting temperature from the detection signal, and the detected temperature is compared with a preset reference temperature, and the surface temperature of the welded material is determined to be the reference temperature. A method for controlling a resistance welding machine, comprising: stopping a welding current applied from the welding electrode to the material to be welded when the temperature matches the temperature.