JPS6363578A - Electrode force detector for resistance welding - Google Patents

Abstract

PURPOSE:To eliminate the noise of a welding current and to improve detecting accuracy of the electrode force by providing a welding current application finishing point detection means, an output detection means of an electrode force detection means and a means to store and calculate the output of the output detection means to the electrode force detection means. CONSTITUTION:The electrode force detection means 5 is a circuit to detect the quantity of strain of the electrode which corresponds to a strain gage, etc. The welding current application finishing point detection means 6 corresponds to a means to detect the flow finishing points of time l1, l2... for every half cycle of a power source cycle and is constituted of a current transformer to detect a primary current of a resistance welding machine, a zero point detection circuit, etc., connected with the current transformer. The storage and arithmetic means 7 is a microcomputer to input and process detected signals of the current application finishing points l1, l2.... The output detection means 8 of the electrode force detection mean is constituted of a sample holding circuit and an A/D converter circuit, etc., connected therewith and corrects and operates the real electrode force data in a moment when the welding current finishes flowing for every half cycle and displays the corrected and operated data on a display or the analog data are displayed on a welding force display device 9 by an O/A converter incorporated in the storage and arithmetic means 7 to detect the electrode force.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an electrode pressurizing force detection device for a resistance welding machine, particularly a spot welding machine, a seam welding machine, etc., which can detect the electrode pressurizing force while electricity is being applied. .

(Prior Art) As is well known, the electrode pressure is one of the typical welding conditions that determines the welding quality of spot welding, along with the welding current, the electric current time, etc.

Conventionally, when measuring electrode pressure, it is common to insert a flexible pressure gauge between electrode tips, apply electrode pressure, and measure the amount of deflection that occurs in the pressure gauge using a dial gauge. be.

(Problems to be Solved by the Invention) Conventional sensors have problems with monitoring accuracy due to noise that enters the detection circuit, when obtaining optimal welding quality by monitoring during energization or feedback of pressurizing force during the in-press process. It has been difficult to accurately and dynamically detect the electrode force associated with squeeze time or continuous electrode force such as seam welding.

In other words, the detection of the electrode pressing force during energization is difficult because the sensor circuit is installed directly or close to the electrode.
The induced voltage caused by the welding current was added to the tiny detector output voltage as noise, making it impossible to dynamically detect the true electrode pressure.

(Means for Solving the Problem) Therefore, in the present invention, in order to accurately detect the electrode pressurizing force during energization, a means is taken to remove the noise of the induced voltage due to the welding current. Its specific configuration includes means for detecting the electrode pressing force of the resistance welder, means for detecting the point in time when the welding current finishes flowing every half cycle of the power frequency, and the It is characterized by comprising means for detecting the output of the electrode pressurizing force detecting means, and means for storing and calculating the output of the electrode pressurizing force detecting means.

(Function) In the present invention, the noise of the induced voltage is removed from the minute electrode pressing force detection force, and the electrode pressing force can be accurately detected even when welding nuggets are generated. By hacking the electrode pressure force during monitoring and in-process, it is possible to improve the precision of pressure monitoring to obtain the optimal welding quality, and also to closely monitor the pressure force such as squeeze time in sequence control. be able to.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an example of electrode pressing force detection in a spot welding machine.

1 is a welding machine main body, 2 is a welding electrode, and 3 is an object to be welded. 4 is an electrode pressure detector such as a strain gauge.

FIG. 2 shows the relationship between the welding current, the induced voltage 3L in the welding current, and the true electrode pressure signal.

The output of the electrode pressing force detector detected here is given as the sum of a minute voltage corresponding to the true electrode pressing force and an induced voltage due to the welding current. This induced voltage is noise, which appears as a much larger noise than the output of the true electrode pressure detector.

FIG. 3 is an explanatory diagram of the configuration and operation of the present invention.

5 in the figure is a means for detecting the electrode pressing force of the resistance welding machine, and corresponds to the strain gauge in Figure 1.
This is a detection circuit that detects the amount of electrode distortion and is amplified by an operational amplifier.

6 is the time e when the flow of each half cycle of the power supply frequency ends;
, e2... corresponds to means for detecting resistance welding) 8
It consists of a current transformer to detect the primary current of the transformer and a zero point detection circuit connected to it.

As a result, the energization end point e1 for each half cycle. (・２・・
can be detected.

7 is 4g/calculating means, and the above-mentioned energization end point el+"
A microcomputer or the like is used that inputs and processes the detected symbols of 2.

8 corresponds to a means for detecting the output of the electrode pressurizing force detecting means, for example, a sample hold circuit and A connected thereto.
/D conversion circuit, etc., and based on the commands from the computer, the data for the e, e2, etc., i.e., the true electrode pressure at the moment when the welding current finishes flowing every half cycle. The data is corrected and calculated and displayed on the display, or analog data is displayed on the pressure display 9 using the D/A converter built in the memory/calculation circuit 7.

Since the electrode pressing force is detected in this way, there is no noise component due to the induced voltage due to the welding current, and the detection accuracy of the electrode pressing force can be significantly improved.

In addition, as a method for removing the induced voltage component due to the welding current, in this embodiment, the method of detecting the energization end point has been described, but it is also possible to detect the peak point f of the welding current shown in FIG. That is, since the induced voltage due to the welding current, which is a noise component, is a differential waveform of the welding current, there is no variation at the peak point f of the welding current, and the induced voltage becomes zero. The same effect can be obtained by detecting this time point f with a detection shift ζ and holding the electrode pressure at the time point A in the same manner as in step 7.

(Effects of the Invention) As described above, the present invention provides an electrode pressurizing force detection device for a resistance welding machine.
Since we have taken measures to remove the noise caused by the induced voltage of the welding current from the detection circuit, it is possible to precisely monitor the true electrode pressure even when the current is on, and the monitoring accuracy required to control optimal welding quality in-process can be improved. It can be improved significantly.

Therefore, it is possible to dynamically check the electrode force such as the squeeze time during spot welding sequence control, and to check the continuous electrode force such as seam welding while energizing, thereby controlling welding quality. can contribute to the improvement of

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of electrode pressing force detection in a spot welding machine. FIG. 2 is a waveform diagram showing the relationship between welding current, its induced voltage, and true electrode pressing force. FIG. 3 is an explanatory diagram of the configuration and operation of the present invention. [Explanation of symbols] 1... Spot welding machine 5... Electrode pressure detection means 6... Welding current energization end point detection means 7... Memory and calculation means 8... Electrode pressure detection means Output detection means 9... Pressure pressure indicator

Claims (1)

[Claims] means for detecting the electrode pressing force of the resistance welding machine; means for detecting the point in time when the welding current finishes flowing every half cycle of the power supply frequency; and means for detecting the output of the electrode pressing force detecting means with respect to the point in time; A resistance welding electrode pressurizing force detection device comprising means for storing and calculating the output of the means for detecting the electrode pressurizing force.