JPH11254150A - Resistance welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistance welding equipment capable of correctly recognizing the thermal margin during the welding operation by a worker. SOLUTION: An operating means 6 operates the thermally equivalent current of a resistance welding equipment based on the elapsed time from the time point when the previous welding sequence is completed to the time point when the present welding sequence is completed and the energization time of the welding current, and the welding current detected by a current detector 11, and displays the operated value on a thermally equivalent current display means 12 to allow a worker to correctly recognize the thermal condition of the resistance welding equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resistance welding apparatus, and more particularly to a resistance welding apparatus capable of accurately recognizing a thermal margin during a welding operation.

[0002]

2. Description of the Related Art Conventionally, a resistance welding apparatus is equipped with a switching element, a welding transformer, and the like that generate heat when a welding current is applied. The switching element and the welding transformer are overheated and burned when a welding current is applied in excess of the specified usage rate. However, in order to obtain the usage rate of the resistance welding apparatus, the welding current conduction time, the conduction suspension time, and the like must be individually measured over a long period of time, and the measurement error is large. It is very difficult to determine the usage rate. Therefore, as an alternative to the usage rate, a temperature detector is attached to the switching element or welding transformer, etc., and the temperature of each part is directly detected, and if those temperatures exceed the set temperature, the welding current is stopped. I am trying to issue an alarm. The resistance welding device using the above temperature detecting means can prevent the burning of the switching element and the welding transformer, etc., but the alarm is suddenly issued during the welding work and the welding current is stopped, so that the usability is poor. There is. Also, Japanese Patent Application Laid-Open No. 8-141747 (Japanese Patent Application No.
No. 283558) discloses a means for determining the usage rate only by the time element in the "control device for electric resistance welding machine". However, since the present invention does not consider the thermal effect based on the magnitude of the welding current value, when a welding current smaller than the rated current value is applied, for example, the usage rate is sufficiently large while having sufficient thermal margin. There is a problem that an alarm is issued when exceeds a set value.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a resistance welding apparatus which enables an operator to accurately recognize a thermal margin during a welding operation.

[0004]

According to the present invention, an elapsed time from the end of the previous welding sequence to the end of the current welding sequence, and an energizing time of the welding current during the elapsed time are provided. And means for calculating a thermal equivalent current based on the magnitude of the welding current, and means for displaying the thermal equivalent current.

[0005] A second aspect of the present invention, in the first aspect of the present invention, comprises an alarming means for issuing an alarm when the thermal equivalent current exceeds a predetermined value.

According to the first aspect of the present invention, the thermal equivalent current can be obtained at the end of each welding sequence and its value can be displayed, so that the operator can control the heat of the resistance welding apparatus during the welding operation. Can be accurately recognized.

According to the second aspect of the present invention, an alarm can be issued when the thermal equivalent current exceeds a preset value, so that the operator has less thermal margin of the resistance welding apparatus. Can be surely recognized.

[0008]

Next, an embodiment of the present invention will be described. FIG. 1 is a block diagram showing the overall configuration of the resistance welding apparatus. As shown in FIG.
The switching element 2 composed of a thyristor is connected to the primary side of the welding transformer 3. A pair of electrodes 4 is connected to the secondary side of the welding transformer 3. When the electrodes 4 are pressurized by the pressurizing device 5, a welding current can be supplied to the workpiece.

The arithmetic processing means 6 forms the center of control of the resistance welding device. The arithmetic processing means 6 outputs a switching signal to the switching element 2 and outputs a pressing command signal for pressing the electrode 4 by the pressing device 5 to a pressing signal output circuit 7. . Further, a current detector 11 provided for detecting a welding current flowing on the secondary side of the welding transformer 3 outputs a welding current detection signal proportional to the welding current to the arithmetic processing means 6. still,
The arithmetic processing means 6 samples the welding current detection signal at a predetermined sampling time interval and obtains an actual welding current based on the sampled value, or calculates an actual welding current based on an effective value of the welding current detection signal. Find the welding current.

The welding condition input means 8 sets welding conditions comprising a plurality of processing steps in a welding sequence from when the pressing device 5 presses the electrode 4 to when the electrode 4 is opened. Then, the set welding conditions are transmitted to the arithmetic processing means 6. The start command input means 9 outputs a welding start command to the arithmetic processing means 6 when a start signal such as a start push button switch (not shown) is input.

The timer means 10 outputs to the arithmetic processing means 6 a timing signal for advancing the welding sequence set by the welding condition input means 8. That is, this timer means 1
0 measures each of the times T1 to T4 in the welding sequence as shown in FIG. 2 and outputs the respective timing signals to the arithmetic processing means 6. As will be described later, a pause time T5 from the end of the first welding sequence.
And outputs the measured time data to the arithmetic processing means 6. According to the first welding sequence in FIG. 2, the time during which the pressing device 5 presses the electrode 4 is (T1 + T2 + T3),
When one hour has elapsed, the welding current is supplied for T2 time, and is maintained for T3 time from the end of the application of the welding current, and then the electrode 4 is opened for T4 time. Then, when the pause time T5 has elapsed, the second welding sequence is started.

The arithmetic processing means 6 calculates a continuous elapsed time (T5 + T1 + T2 + T3 + T) from the end of the first welding sequence to the end of the second welding sequence.
4) Using the welding current conduction time T2 and the actual welding current obtained as described above, a thermal equivalent current indicating the thermal state of the resistance welding apparatus is calculated. The thermal equivalent current is obtained by the following equation. Thermal equivalent current = welding current × ΔT2 / (T5 + T1 + T2
+ T3 + T4)｝ ^{1/2 In} the above equation, {T2 / (T5 + T1 + T2 + T)
3 + T4)｝ is the usage rate described in the section of the related art.

The thermal equivalent current display means 12 shown in FIG.
Indicates the thermal equivalent current calculated by the arithmetic processing means 6. Then, the thermal equivalent current data is transmitted to the comparing and judging means 13. Further, a thermal equivalent current input means 14 for inputting thermal equivalent current data unique to the resistance welding apparatus to the comparison determination means 13 is provided. The comparing and judging means 13 compares the thermal equivalent current data from the thermal equivalent current input means 14 with the thermal equivalent current computed by the arithmetic processing means 6, and calculates the computed thermal equivalent current. When the thermal equivalent current data from the equivalent current input means 14 is exceeded, an alarm signal is output. When this warning signal is transmitted to the warning means 15, the warning means 15 warns that the thermal equivalent current of the resistance welding apparatus has exceeded the limit and the thermal margin has decreased. The alarm means 15 uses a buzzer or a lamp.
Ensure that the operator can recognize the alarm.

In the resistance welding apparatus, the switching element 2, the welding transformer 3, or a secondary cable connected to the secondary side of the welding transformer 3 is a place where the thermal equivalent current becomes a problem. However, what is particularly problematic is the switching element 2 that is easily damaged by heat. Since the switching element 2 is connected to the primary side of the welding transformer 3, the thermal equivalent current in the switching element 2 is obtained by the following equation. Welding current × Ra × ΔT2 / (T5 + T1 + T2 + T3 +
T4)｝ ^1/2 where Ra is the reciprocal of the turns ratio of the secondary winding to the primary winding of the welding transformer 3. In the above equation, the value of the welding current detected by the current detector 11 is, for example, 1000
When the current is 0 amperes and the reciprocal Ra of the winding ratio of the welding transformer 3 is 1/20, the current flowing through the switching element 2 is 500 amperes in calculation. In addition, the usage rate,
That is, when {T2 / (T5 + T1 + T2 + T3 + T4)} is 0.2 (20%), the thermal equivalent current in the switching element 2 is 10,000 × (1/2).
0) × (0.2) ^1/2 = 224 amps. Therefore, when trying to recognize the thermal situation of the resistance welding apparatus with respect to the thermal equivalent current in the switching element 2, the set value in the thermal equivalent current input means 14 is changed to the thermal equivalent current of the switching element 2. It must be a value corresponding to.

As described above, the thermal equivalent current indicating the thermal state of the resistance welding apparatus is calculated by the arithmetic processing means 6,
Since the thermal equivalent current is displayed by the thermal equivalent current display means 12, the operator can accurately recognize the thermal state of the resistance welding device. Further, when the calculated thermal equivalent current exceeds the value set by the thermal equivalent current input means 14, an alarm is issued from the alarm means 15, so that the operator has a thermal margin of the resistance welding apparatus. It is possible to reliably recognize that the number has decreased.

Although the welding current is applied once in each welding sequence shown in FIG. 2, even in the case of pulsation control in which the welding current is applied a plurality of times in one welding sequence. By applying the total value of the welding currents of the respective conduction times to the numerator of the above-mentioned equation of the usage rate, the thermal equivalent current in the pulsation control can be obtained by the aforementioned equation for obtaining the thermal equivalent current. Further, in the above embodiment, the thermal equivalent current is calculated at the time when each welding sequence is completed and is displayed on the thermal equivalent current display means 12. However, the thermal equivalent current in a plurality of welding sequences is calculated. May be calculated and displayed. Incidentally, the thermal equivalent current display means 12 may display the current thermal equivalent current and also the thermal equivalent current unique to the resistance welding apparatus set by the thermal equivalent current input means 14. . Thereby, the operator can know the thermal margin of the resistance welding apparatus more accurately.

[0017]

According to the first aspect of the present invention, the thermal equivalent current can be obtained at the end of each welding sequence and its value can be displayed, so that the operator can perform the welding operation during the welding operation. Can accurately recognize the thermal margin.

According to the second aspect of the present invention, an alarm can be issued when the thermal equivalent current exceeds a preset value, so that the operator has less thermal margin of the resistance welding apparatus. Can be surely recognized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a resistance welding apparatus according to an embodiment of the present invention.

FIG. 2 is a timing chart of a welding sequence.

[Description of Signs] 1 AC power supply 2 Switching element 3 Welding transformer 4 Electrode 5 Pressurizing device 6 Arithmetic processing means 7 Pressurizing signal output circuit 8 Welding condition input means 9 Start command input means 10 Timer means 11 Current detector 12 Heat Equivalent current display means 13 comparison determination means 14 thermal equivalent current input means 15 alarm means

Claims (2)

[Claims] 1. An elapsed time from the end of the previous welding sequence to the end of the current welding sequence, the welding current conduction time during the elapsed time, and the magnitude of the welding current. A resistance welding apparatus comprising: means for determining a thermal equivalent current; and means for displaying the thermal equivalent current. 2. An alarm means for issuing an alarm when the thermal equivalent current exceeds a preset value.
The resistance welding apparatus according to item 1.