JPH01118378A - Controller for resistance welding machine - Google Patents

Abstract

PURPOSE:To always perform welding at the activity ratio less than the allowable activity ratio by calculating the weld prohibitive time from the allowable activity ratio of an electric current and the weld time set respectively to apply a welding current intermittently. CONSTITUTION:When an electrification permission signal (d) is produced after a starting and holding signal (c) is produced, the current value data (i) and the weld time data (t) are generated on a current setter 1 and a time setter 2 by an inner starting signal. The current value data (i) are added to a current control circuit 5 and the weld time data (t) are converted into the weld time (e) with the weld time width and added to the current control circuit 5. As a result, the welding current with a current value set by the current setter 1 is carried to an electrode chip 8. When the electrification is finished, an electrification prohibitive control circuit 13 is operated and after the weld prohibitive time at the allowable activity ratio calculated from the data (i) and (t) by an arithmetic circuit 12, the circuit 13 outputs the electrification permission signal (d). When the starting and holding signal (c) is produced at this point of time, the welding current again starts to flow to a next welding point.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention automatically maintains the usage rate of rectifier diodes, current control transistors, thyristors, etc. that are inserted in the welding current circuit within an allowable range. The present invention relates to a control device for a resistance welding machine that performs welding to protect diodes, transistors, etc.

(Prior art) Conventionally, in response to a start signal from a robot controller that occurs intermittently, a welding current of a current value and energization time set by a current setting device and a time setting device is intermittently applied to a welding current circuit. When automatically welding multiple welding points in sequence using a resistance welding machine control device that is energized,
In order to prevent damage to rectifier diodes, current control transistors, or thyristors that are inserted into the welding current circuit, the operator must ensure that the usage rate of transistors, etc. for the set values of welding current and energization time is below the allowable usage rate. For example, the interval between activation signals generated from the robot controller was set.

(Problem to be solved by the invention) The above-mentioned work requires skill, and if the usage rate is mistakenly set to an excessive value, it may cause the inconvenience of burning out the diode, transistor, or thyristor. .

It is an object of the present invention to solve these conventional disadvantages.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a current setting device and a time setting device that are set by a current setting device and a time setting device in response to a start signal from a robot controller etc. that is generated at intervals. In a control device for a resistance welding machine in which a welding current of a current value and a welding time is intermittently applied to a welding circuit, an allowable usage rate at the current value is calculated from the current value set by the current setting device. and calculation means for calculating the energization prohibition time from the allowable usage rate and the energization time set by the time setting device;
energization prohibition time control means that starts from the end of energization of the welding current and outputs an energization permission signal after the lapse of the energization prohibition time calculated by the /7A calculation means, and the energization permission signal output from the control means and the activation. The present invention is characterized in that the welding current is applied to the welding circuit in response to both signals.

(Function) The calculation means calculates the current value set by the current setting device from the allowable usage rate characteristic for the current value as shown in FIG.
The allowable usage rate S1 is determined, and the energization prohibition time is calculated from this allowable usage rate S1 and the energization time set by the time setting device. In this way, after the welding current of the current value set by the current setting device is energized for the time set by the time setting device, the next welding current will not be energized even if a start signal is input until the energization prohibition time has elapsed. . Therefore, welding is always performed intermittently below the allowable usage rate.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of one embodiment of the invention.

In the figure, 1 is a current setting device that sets the welding current value of a plurality of welding points, 2 is a time setting device that sets the energization time, and the current setting device 1 and time setting device 2 are internally activated. Digital signals of current value data i and energization time data t respectively set by signal a are output, and the internal start signal a is a start holding signal that holds a start signal output from, for example, a robot controller. circuit 3
It is generated when the activation holding signal C and the energization permission signal d are input to the AND gate 4.

Reference numeral 5 denotes a current control circuit, which is interposed between a direct current (not shown) and a control pole of a current control element 6, which is a transistor or a cyrisk, and the current control element 6, which is connected to an AC power source (not shown), is a transformer. The welding current flowing through the electrode tip 8 is detected by a current transformer 9 and input to the current control circuit 5, and these circuits are particularly different from conventional ones. It won't happen.

Reference numeral 10 denotes an energization time control circuit, which is composed of, for example, a preset counter, and is preset with a digital signal of energization time data t set by the time setting device 2, and then presets a clock pulse to be output from the reference clock generator 11. It outputs a continuous time signal e until it counts up to the current value, that is, the set energization time, and the energization time data t signal is combined with the current value data i set by the current setting device 1. It is input to the current control circuit 5 and becomes its set value.

Reference numeral 12 denotes an arithmetic circuit, which includes a memory (not shown) storing allowable usage rate characteristics for current values as shown in FIG. Then, the current value data i, for example, the allowable usage rate S1 in 1 is read out from the memory, and this and the input energization time data of the time setting device 2, for example, tl, are used to calculate the regular time data ts. There is.

Reference numeral 13 denotes an energization prohibition time control circuit consisting of, for example, a preset counter, which is preset with the energization inhibition time data ts. Counting of clock pulses is started from the end of the welding current application, and an energization permission signal is output after the calculated energization prohibition time has elapsed.

Note that the startup holding circuit 3 is reset at the start of the energization time signal e.

Next, the operation of this embodiment will be explained based on the time chart shown in the second figure.

When a start signal C is input from a robot controller or the like to the start hold circuit 3, the start hold signal C is output from the circuit 3.

The current setting device 1 and the time setting device 2 output an internal activation signal a when the energization permission signal d is generated after the activation holding signal C is generated.
Current value data i and energization time data t are generated by
The current value data i is applied to the current control circuit 5, and the energization time data t is converted into an energization time signal e having the energization time width and is applied to the current control circuit 5. Thus, a welding current, for example 11, having a current value set by the current setting device 1 flows through the electrode tip 8. When the energization of this welding current 1 is completed, the energization prohibition control circuit 13 starts operating, and after the energization prohibition time ts at the allowable usage rate calculated by the arithmetic circuit 12, the circuit 1
3 outputs the energization permission signal d, so if the startup holding signal C is generated at this point, the welding current I2 starts flowing again to the next welding point. If the activation hold signal C has not yet been output at this point, it starts flowing after time t2 upon its generation. If the energization permission signal d has not yet been generated at the time when the startup hold signal is generated, the welding current begins to flow after the generation of the energization permission signal d.

In the above embodiment, the energization time control circuit 10, the reference clock generator 11. Although the arithmetic circuit 12 and the energization prohibition time control circuit 13 are used, they can be replaced by a computer.

(Effects of the Invention) As is clear from the above configuration, according to the present invention, when sequentially welding a plurality of welding points, an operator does not have to strictly consider the usage rate of diodes, transistors, etc. The welding current can be sequentially passed through the welding points at a rate below the allowable usage rate, and has the effect of preventing burnout of diodes and transistors.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a time chart of a plurality of signals, etc. to explain its operation, and Fig. 3 is a diagram showing current vs. allowable usage rate characteristics of diodes, etc. It is.

Claims (1)

[Claims] Resistance welding in which the welding current is intermittently energized to the welding circuit at the current value and energization time set by the current setting device and time setting device in response to start signals from a robot controller etc. that are generated at intervals. In the control device of the machine, the allowable usage rate at the current value is calculated from the current value set by the current setting device, and the energization prohibition time is calculated from the allowable usage rate and the energization time set by the time setting device. and an energization prohibition time control means that starts from the end of energization of the welding current and outputs an energization permission signal after the lapse of the energization prohibition time calculated by the calculation means, and the energization permission signal is output from the control means. A control device for a resistance welding machine, characterized in that the welding current is applied to the welding circuit in response to both the start signal and the start signal.