JPH0644534Y2 - Pressure controller for resistance spot welder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention controls the pressurized air sent to the pressurizing cylinder by an electropneumatic proportional valve that adjusts the supply pressure according to the drive current, and the welding electrode. The present invention relates to a welding force control device for a resistance spot welding machine that controls the welding pressure force of the welding electrode to an optimum value, and particularly relates to a welding force control device for a resistance spot welding machine that keeps the welding electrode pressure force at a set value regardless of disturbance. .

[Conventional technology]

In the conventional resistance spot welding machine, the control of the welding electrode pressure using the electropneumatic proportional valve has been performed as shown in FIG.

That is, the pressure of the welding electrode 51 is the material of the member 52 to be welded,
Pressurization force setter that sets the optimum value according to the plate thickness and other conditions
A drive current is output from the power amplifier 54 to the electropneumatic proportional valve 55 in accordance with the pressure signal of 53, and the electropneumatic proportional valve 55 supplies the pressurized air from the pressurized air source 56 to the pressurized cylinder 57. By adjusting the pressure proportional to the drive current, the pressure applied to the welding electrode 51 by the pressure cylinder 57 is controlled to an optimum value suitable for the member 52 to be welded.

As a means for controlling the pressure applied to the welding electrode in this manner, for example, JP-A-57-165189 and JP-A-58-1385 are known.
There is a pressure control device in a resistance welding machine described in Japanese Patent Publication No. 82 etc.

[Problems to be solved by the invention]

However, in the conventional resistance spot welder, the pressure cylinder
If the welding electrode 51 is pulled due to the malfunction of 57 or the tension of the secondary cable for power supply connected to the welding electrode 51 is too strong, even if the electropneumatic proportional valve 55 is operating normally, There is a problem that the welding electrode 51 has a pressing force lower than the set value and the welding force is insufficient, resulting in poor welding of the member 52 to be welded or welding of the welding electrode 51 to the member 52 to be welded.

When welding of the welding electrode 51 occurs, there is a problem that the cooling water leaks from the welding machine and the working environment is deteriorated, or the productivity is lowered due to repair.

Therefore, the object of the present invention is to always keep the welding electrode pressure at the set value regardless of the disturbance, and to give an alarm when an abnormality occurs that cannot keep the welding pressure at the set value. It is to prevent the abnormal state from continuing as much as possible.

[Means for solving problems]

Therefore, in the present invention, the welding electrode pressure is detected and the feedback current of the drive current of the electropneumatic proportional valve is controlled so that the welding electrode pressure is maintained at the set pressure. When an abnormal value is shown, an alarm is issued, and the alarm is generated only when the pressing force is stable.

Specifically, an electropneumatic proportional valve that controls the pressure value proportional to the drive current is used to adjust the pressure of the pressurized air supplied to the pressure cylinder to control the welding electrode pressure to the set pressure. In the pressure control device for resistance spot welding machine,
A differential amplifier circuit is connected between a pressing force setting device for setting a pressing force and a drive circuit for driving the electropneumatic proportional valve, and the pressing force of the welding electrode is detected by a pressing force detection sensor, Input to the differential amplifier circuit to perform feedback control of the drive current to keep the welding electrode pressure at the set pressure.
Further, the difference between the drive signal and the set pressurization signal is compared with the comparison reference value by the comparison circuit. If the difference is larger than the comparison reference value, the pressing force cannot be controlled. It is characterized in that an alarm signal is sent to an alarm circuit through an opening gate circuit to generate an alarm.

[Action]

According to the configuration of the present invention, the welding electrode pressure is detected,
Since the drive current of the electropneumatic proportional valve is feedback-controlled, the welding electrode pressure is always maintained even if a factor that reduces the pressure force occurs due to malfunction of the pressure cylinder or pulling of the secondary cable. It can be maintained at the set pressure.
Further, when the pressing force cannot be maintained at the set pressing force by the above-mentioned feedback control, if the gate circuit is opened, the comparator circuit outputs an abnormal signal to the alarm circuit and an alarm is issued. Therefore, the abnormal situation is immediately known,
The abnormal situation is prevented from continuing.

〔Example〕

Next, a pressure control device for a resistance spot welding machine according to an embodiment of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 1 is a member to be welded, reference numerals 2A and 2B are upper electrodes and lower electrodes which are welding electrodes for energizing and welding to the member 1 to be welded, and a lower electrode 2B is a resistance spot welding machine. It is fixed to the body side.

Reference numeral 3 denotes a pressurizing cylinder that supports the upper electrode 2A and pressurizes the member to be welded 1, and reference numeral 4 switches between supply and discharge of pressurized air to the pressurizing cylinder 3, It is a switching control valve that pressurizes and opens the upper electrode 2A.

Reference numeral 5 is a power valve for controlling the supply of a sufficient amount of pressurized air having a pressure value proportional to the indicated pressure.

Reference numeral 6 is an electropneumatic proportional valve that outputs the supplied pressurized air at a pressure proportional to the drive current, and is connected to the pressurized air source 7 together with the power valve 5.

Reference numeral 8 is a pressure control device for a resistance spot welding machine according to the present embodiment.

Reference numeral 9 is a pressurizing cylinder control circuit, which controls switching of the switching control valve 4 to control pressurization and opening of the upper electrode 2A.

Reference numeral 10 is a pressurizing force setting device that sets the pressurizing force of the upper electrode 2A by the pressurizing cylinder 3, and outputs a set pressurizing signal corresponding to the set pressurizing force.

Reference numeral 11 is a drive circuit for driving the electropneumatic proportional valve 6 with a drive current corresponding to the set pressure.

Reference numeral 12 is a pressure detection sensor such as a load cell, which detects the pressure of the upper electrode 2A and outputs a pressure signal corresponding to the pressure.

Reference numeral 13 is a comparison differential amplification integrator that is a differential amplifier circuit, and is connected between the pressing force setting device 10 and the drive circuit 11, and the set pressing signal of the pressing force setting device 10 and the The pressure signal of the pressure detection sensor 12 is compared, and the set pressure signal is increased / decreased and corrected according to a value obtained by temporally integrating the difference and output to the drive circuit 11.

Reference numeral 14 is a comparison circuit, which compares a pressurizing signal, which is a signal corresponding to the pressurizing force of the upper electrode 2A, with a set pressurizing signal output from the pressurizing setting device 10, and the difference is a reference. If it is larger than the reference voltage for abnormality determination set by the voltage generation circuit 15, an abnormality signal is output.

Reference numeral 16 is a gate circuit that passes the output signal of the comparison circuit 14 only when the gate signal is input.

Reference numeral 17 is a gate signal circuit that outputs a gate signal to the gate circuit 16, and based on the output signal of the pressurizing cylinder control circuit 9, the gate signal is output only when the pressurizing force of the pressurizing cylinder 3 is stable. To output the pressure cylinder 3
This prevents false alarms when the applied pressure is unstable at the initial stage of pressurization.

Reference numeral 18 is an alarm circuit for generating an alarm indicating an abnormality based on the abnormality signal output from the comparison circuit 14 through the gate circuit 16.

Next, the pressure control device 8 for the resistance welding machine according to the present embodiment
The action of will be described.

A drive current having a value corresponding to the set pressurization signal of the pressurizing force setter 10 is supplied from the drive circuit 11 to the electropneumatic proportional valve 6, and the electropneumatic proportional valve 6 applies a pressure value corresponding to the set pressurizing force. Pressurized air is supplied to the pressurizing cylinder 3.

By the pressurized air of the pressure value corresponding to this set pressure,
The pressurizing cylinder 3 generates a predetermined pressing force.

When the pressure applied to the pressure cylinder 3 is lowered due to the malfunction of the pressure cylinder 3 or the pulling of the secondary cable, the decrease in the pressure is caused by the pressure detection sensor 12, the comparison differential amplification integrator. It is fed back to the drive circuit 11 via 13 to increase the drive current.

Then, the pressure of the pressurized air supplied from the electropneumatic proportional valve 6 also increases, and the pressure cylinder 3 generates a predetermined set pressure.

When the degree of malfunction of the pressurizing cylinder 3 or the pulling force of the secondary cable is small and the decrease of the pressurizing force of the pressurizing cylinder 3 is small, the set pressurizing signal output from the pressurizing force setter 10 and the pressurizing force are output. Since the difference from the pressure signal output from the detection sensor 12 is small and smaller than the reference voltage indicating the abnormality set in the reference voltage generation circuit 15, the comparison circuit 14 does not output the abnormality signal.

When the wiring between the drive circuit 11 and the electropneumatic proportional valve 6 is broken or short-circuited, the drive current supplied to the electropneumatic proportional valve 6 becomes zero, and the electropneumatic proportional valve 6 and the power valve 5 are used. The pressure of the pressurized air supplied to the pressurizing cylinder 3 is reduced to almost zero, and the pressure applied to the upper electrode 2A by the pressurizing cylinder 3 is also reduced to almost zero.

Further, when the degree of malfunction of the pressurizing cylinder 3 or the pulling force of the secondary cable is large and the decrease of the pressurizing force of the pressurizing cylinder 3 is large, the pressurizing sensor 12 and the comparative differential amplification integrator are used.
Feedback is applied via 13 and the signal input to the drive circuit 11 becomes significantly larger than the set pressurization signal output from the pressurizing force setting device 10.

Then, the difference between the set pressure signal input to the comparison circuit 14 and the signal input to the drive circuit 11 becomes larger than the reference voltage, and the comparison circuit 14 outputs an abnormal signal to the gate circuit 16. It outputs to the alarm circuit 18 via this, and this alarm circuit 18 produces | generates the alarm which alert | reports the abnormality of an apparatus.

In the case of this embodiment, the pressure detection sensor 12 for detecting the pressure of the upper electrode 2A is attached to the upper electrode 2A, but this pressure sensor 12 is attached to the lower electrode 2B. Is also good.

Further, in the case of the present embodiment, since the size of the difference between the set pressurizing signal and the signal corresponding to the drive current is detected,
An abnormality around the pressurizing cylinder 3, the upper electrode 2A or an abnormality in the wiring to the electropneumatic proportional valve 6 can be promptly detected.

Further, in the case of the present embodiment, the gate signal circuit 17 and the gate circuit 16 interrupt the input of the signal to the alarm circuit 18 at the initial stage of pressurization when the pressure applied to the pressurizing cylinder 3 is in an unstable state. Therefore, the abnormality can be accurately detected without malfunction.

[Effect of device]

As described above, according to the present invention, since the pressure applied to the welding electrode is detected and the electropneumatic proportionality is feedback-controlled, the pressure applied may be reduced due to the malfunction of the pressure cylinder or the pulling of the secondary cable. Even if there is a factor that reduces the welding force, the welding electrode can always be kept at the set pressure, and it is possible to prevent defective welding. Further, according to the present invention, the alarm circuit issues an alarm when the pressurization cannot be feedback-controlled, so that even if welding failure occurs, such a situation is prevented from continuing. Furthermore, the situation where the pressure cannot be feedback-controlled is judged based on the drive signal, but the gate circuit closes and the abnormal signal is not input to the alarm circuit until the pressure is stabilized, so an erroneous alarm can be generated in advance and reliably. Can be prevented.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a pressure force control device for a resistance spot welding machine according to an embodiment of the present invention, and FIG. 2 is a block circuit diagram of a conventional pressure force control device for a resistance spot welding machine. 2A …… Upper electrode (welding electrode) 3 …… Pressure cylinder 6 …… Electropneumatic proportional valve 8 …… Pressure force controller for resistance spot welder 10 …… Pressure force setter 11 …… Drive circuit 12 …… Apply Pressure detection sensor 13 …… Comparison differential amplification integrator (differential amplification circuit) 14 …… Comparison circuit

Claims (1)

[Scope of utility model registration request] 1. A pressure applied to a welding electrode is adjusted to a set pressure by adjusting the pressure of pressurized air supplied to a pressure cylinder using an electropneumatic proportional valve that controls a pressure value proportional to a drive current. A pressure force control device for a resistance spot welding machine for controlling, comprising a pressure force setting device for outputting a set pressure signal corresponding to the set pressure force, and the drive current according to the set pressure signal for the electropneumatic A drive circuit that outputs to a proportional valve, a pressure detection sensor that detects the pressure of the welding electrode and outputs a pressure signal proportional to the value, and is connected between the drive circuit and the pressure setter. A differential amplifier circuit that corrects the set pressurizing signal according to a difference between the set pressurizing signal and the pressurizing signal and outputs the corrected pressurizing signal to the drive circuit, and a signal output from the differential amplifier circuit or Between the signal changing corresponding to the signal and the setting pressure signal From the comparison circuit that outputs an abnormal signal when is larger than a predetermined comparison reference value, and an alarm circuit that is connected to the comparison circuit via a gate circuit that closes when the applied pressure is unstable and that issues an alarm based on the abnormal signal. A pressure control device for a resistance spot welding machine, which is characterized in that