JP2832287B2 - AC resistance welding control device and AC resistance welding measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding control device or measuring device used in an AC resistance welding machine.

[0002]

2. Description of the Related Art An AC-type resistance welding machine supplies an AC power supply voltage of a commercial frequency (50 Hz or 60 Hz) to a primary coil of a welding transformer through a contactor composed of a pair of thyristors, and an AC power supply from the secondary coil. A welding current (secondary current) is applied to join the workpieces metallurgically.

[0003] The welding current in an AC resistance welding machine is controlled by controlling the firing angle of the thyristor.
When performing the constant current control, for example, a welding current is detected by a toroidal coil, the detected welding current value is compared with a set value, and the firing angle of the thyristor is controlled so that the comparison error becomes zero.

[0004] The firing angle is defined as the time from when the forward voltage starts to be applied to the thyristor to when the thyristor is turned on (when the current starts to flow). Therefore, in the firing angle control, the thyristor is turned on after a fixed time (firing angle) from the reference time when the forward voltage starts to be applied to the thyristor.

In the conventional AC resistance welding control apparatus, the reference point is obtained from a power supply line. In other words, after the AC power supply voltage of, for example, 200 volts applied to the thyristor is reduced to, for example, about 15 volts by a control transformer, the low-voltage AC voltage is shaped into a waveform, so that the rising edge corresponding to the voltage zero cross point A sync pulse of a commercial frequency having a falling edge and a falling edge is generated, and the rising edge or the falling edge is used as a reference timing of the firing angle control using the synchronization pulse as a clock. Further, in the conventional AC resistance welding measuring apparatus, the clock obtained in this manner is used for measuring the energizing time, measuring the power factor angle, measuring the energizing angle, and the like.

[0006]

In a factory where an AC resistance welding machine is generally installed, a large number of resistance welding machines and other devices and machines use a common factory power supply voltage or distribution voltage. The AC voltage on the line is different from a high-quality commercial voltage supplied to ordinary homes and offices, and frequently fluctuates to easily disturb the voltage waveform.

When the voltage waveform of the AC voltage on the power supply line is disturbed, the voltage zero-cross point fluctuates on the time axis, so that the rising edge or the falling edge of the clock (phase pulse) also fluctuates on the time axis. . For this reason, the conventional AC resistance welding control device has a problem that the reference timing of the firing angle control is shifted and the current control becomes unstable. Further, in the conventional AC resistance welding control device, there is a problem that an error occurs in measured values of the power factor angle and the conduction angle.

The present invention solves such a problem, and generates a stable clock that maintains a constant frequency and phase even if the AC voltage on the power supply line fluctuates and the voltage waveform is disturbed. AC resistance melting that guarantees the reliability of
It is an object to provide a contact control device and a resistance welding measuring device .

[0009]

In order to achieve the above object, an AC resistance welding control apparatus according to the present invention comprises a control line from a power supply line for supplying power to an AC resistance welding machine. ><br/> Oite the AC resistance welding control apparatus adapted to generate a lock, and the synchronizing pulse generating means for generating a sync pulse corresponding to the waveform of the AC voltage on the power line, the synchronizing pulse generating means And a PLL circuit for generating the clock in response to the synchronization pulse from the controller.

[0010] Further , the AC resistance welding measuring apparatus of the present invention.
Is a power line for supplying power to the AC resistance welding machine.
AC resistor that generates a clock for measurement from the
In the anti-welding measuring device, the AC voltage on the power line
Synchronous pulse generation that generates a synchronous pulse corresponding to the waveform of
Means for responding to a synchronization pulse from the synchronization pulse generating means.
Operable to generate the clock.
The configuration was adopted. Also, in the present invention, the fluctuation of the power supply line voltage is
In order to increase the stability of the clock with respect to
In the anti-welding control device or the measuring device, the PLL
The configuration was such that the response speed of the road was reduced.

[0011]

[Action] While the AC voltage on the power supply line is in a normal state, P
An output signal (clock) is locked to an input signal (synchronization pulse) of the LL circuit, and a clock having the same frequency and phase as the synchronization pulse is output from the PLL circuit.

When the AC voltage on the power supply line fluctuates and its voltage waveform is disturbed, the voltage zero cross point fluctuates on the time axis, and the rising edge and the falling edge of the synchronization pulse corresponding to each voltage zero cross point also fluctuate on the time axis. I do. Then, the PLL circuit operates to cause the clock to follow such a change in the synchronization pulse. However, in general, the change in the power supply line voltage is instantaneous (temporary) and returns to a normal state immediately. Is not significantly disturbed from the normal state.

In particular, when the response speed of the PLL circuit is reduced by increasing the damping factor of the low-pass filter in the PLL circuit, the output signal (clock) of the PLL immediately follows the fluctuation of the synchronization pulse. Therefore, the same phase and cycle as before (normal) are maintained for a while. While doing so, the power supply line voltage returns to the normal state, and the phase and cycle of the synchronization pulse and the clock again coincide.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a circuit configuration of a single-phase AC resistance welding control device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a circuit configuration of a PLL circuit in the embodiment, and FIG. 3 is included in the PLL circuit. FIG. 4 is a diagram showing a step response characteristic of the low-pass filter, and FIG. 4 is a timing chart for explaining the operation of the embodiment.

In FIG. 1, for example, an AC power supply voltage E0 of a commercial frequency is input to the present single-phase AC resistance welding machine via a power supply line 10 from a main power supply in a factory. The AC power supply voltage E0 is supplied to the primary coil of the welding transformer 16 via a contactor composed of a pair of thyristors 12 and 14, and the secondary voltage obtained at the secondary coil of the welding transformer 16 is applied to the pair of welding electrodes 18 and 20. Material to be welded 22,
The welding current (secondary current) Iw flows to the secondary circuit by being applied to the secondary circuit 24, and the workpieces 22, 24 are metallurgically joined by Joule heat.

In this resistance welding machine, the welding current Iw is
The constant current control method is used to control the current to a constant value throughout the energization time. For the constant current control, a toroidal coil 26, a current waveform restoration circuit 28, a current effective value calculation circuit 30, a welding current setting circuit 32, and a welding current control unit 34 are provided.

When the welding current Iw flows, the toroidal coil 26 wound around the conductor of the secondary circuit outputs a voltage Dw representing a differential waveform thereof. The current waveform restoring circuit 28 integrates the detected voltage Dw from the toroidal coil 26 with time to obtain a voltage signal S corresponding to the waveform of the welding current Iw.
Generate w. The effective current value calculation circuit 30 calculates the effective value of the welding current based on the voltage signal Sw from the current waveform restoration circuit 28, and supplies the calculated value (measured value) <Iw> to the welding current control unit 34. The welding current control unit 34 compares the measured welding current value <Iw> with the welding current setting value <I0> from the welding current setting circuit 32, and fires a firing control signal SR which makes the comparison error close to zero. It is sent to the pulse generation circuit 36. The firing pulse generating circuit 36 supplies a firing pulse to both thyristors 12 and 14 at a timing according to the firing control signal SR. In this manner, constant current control is performed such that the welding current Iw is maintained at the set value <I0>.

In such a constant current control circuit, the current effective value calculation circuit 30 performs calculation (measurement section) for calculating the effective value.
, The welding current control unit 34 needs a clock in order to obtain the reference timing of ignition.

The sequence control unit 38 controls the entire welding sequence, and the welding current control unit 34
, An instruction to start and stop energization, an instruction to start and release pressurization to a pressurizing mechanism (not shown), and a communication with an external device are performed. Requires a clock to take. Further, the measuring unit 40 that measures the power factor angle, the conduction angle, and the like based on the welding current detection signal Sw from the voltage waveform restoration circuit 28 also needs a clock to know the measurement calculation section.

In the present embodiment, a PLL, which will be described later, is applied to the current effective value calculation circuit 30, the welding current control unit 34, the sequence control unit 38, and the power factor angle / conduction angle measurement unit 40.
The circuit 50 supplies a stable clock CK synchronized with the power supply line voltage.

The clock generator in this embodiment includes a control transformer 42 having a primary coil connected to the power supply line 10.
A synchronization pulse generating circuit 44 for shaping an AC voltage obtained in a secondary coil of the control transformer 42 and outputting a synchronization pulse SP corresponding to a power line voltage waveform; and a PLL circuit using the synchronization pulse as an input signal. 50. Among them, the control transformer 42 and the synchronizing pulse generation circuit 44 are common parts to the conventional device. That is, in the conventional device, the synchronization pulse obtained from the synchronization pulse generation circuit is supplied as it is to each unit as a clock. However, as described above, since such a synchronization pulse is directly affected by the fluctuation of the power supply line voltage, a stable clock cannot be obtained. In this embodiment, the PLL
The circuit 50 obtains a stable clock which is not affected by the voltage fluctuation on the power supply line 10.

In FIG. 2, the PLL circuit 50 includes a phase comparator 52, a low-pass filter 54, and a VCO (voltage controlled oscillator) 56. The synchronization pulse SP from the synchronization pulse generation circuit 44 is input to one input terminal of the phase comparator 52, and the output signal (clock CK) of the VCO 56 is input to the other input terminal. Phase comparator 52
Compares the two input signals and generates a difference signal voltage corresponding to the phase difference and the frequency difference. The low-pass filter 54
Of the difference signal voltage from the phase comparator 52, high frequency components are removed and only low frequency components are passed. VCO56
Is controlled by the voltage from the low-pass filter 54.

The circuit configuration of the PLL circuit 50 is basically the same as that of a general PLL circuit. However, in a general PLL circuit, the input speed is increased by increasing the response speed of a phase comparator, a low-pass filter, or the like, or by inserting an amplifier circuit for increasing a loop gain between the low-pass filter and the VCO. While a contrivance has been taken to improve the followability of the output signal to the signal, the PLL according to the present embodiment
In the circuit 50, contrary to the general one, the response speed of the phase comparator 52 and the low-pass filter 54 is reduced,
Further, the followability of the output signal to the input signal is reduced without using a loop gain amplifier circuit or the like.

For this purpose, for example, the low-pass filter 5
In No. 4, a filter having a large damping factor is used as shown by a solid line SL in FIG. 3 by increasing the time constant of an internal time constant circuit. Dotted line M in FIG.
L is a step response characteristic when the damping factor is small.

Next, the operation of the clock generator of this embodiment will be described with reference to the timing chart of FIG. In this example, ta
This is a case where the AC voltage E0 on the power supply line 10 fluctuates temporarily during the period from to tb, and the voltage waveform is disturbed. In general,
The voltage fluctuation in the power supply line in the factory is thus temporary.

In this case, before time ta, the clock CK is phase-locked to the synchronization pulse SP, and the synchronization pulse SP and the clock CK rise and fall at the same timing. Therefore, each pulse width... SP1, SP2
, CK1 and CK2 are maintained at constant values. During this time, the difference signal voltage of the phase detector 52 is maintained at a substantially constant value (for example, zero volt).

However, during the time between ta and tb, the waveform of the power supply line voltage E0 is disturbed, and its zero cross point fluctuates on the time axis, and the synchronization pulse S corresponding to each voltage zero cross point is obtained.
The rising and falling edges of P also fluctuate on the time axis. Then, the phase and period (SP3 to SP8) of the synchronization pulse SP and the clock CK fluctuate,
The phase comparator 52 outputs a pulse-like difference signal voltage according to the fluctuation. This difference signal voltage is applied to the low-pass filter 54.
And a low-frequency component (DC component) is input to the VCO 56 as a control voltage to the low-pass filter 54.

In this embodiment, since the damping factor of the low-pass filter 54 is large, the difference signal voltage from the phase comparator 52 is reduced and delayed and applied to the VCO 56, so that the VCO 56 immediately outputs the synchronization pulse SP. Instead of following the fluctuation, the same phase and period (CK3 to CK8) as before (normal) are held for a while. In the meantime, at time tb, the power supply line voltage E0 returns to the normal state, the phase and frequency of the synchronization pulse SP also return to the normal state, and the phase and cycle (SP9, SP9) of the synchronization pulse SP and the clock CK again. CK9) match. Then, the pulse-like difference signal voltage is not output from the phase comparator 52.

As described above, in the resistance welding control apparatus according to the present embodiment, even if the waveform of the AC voltage E0 on the power supply line 10 is disturbed, a stable frequency and phase are maintained without being affected by the disturbance. The clock CK is obtained from the PLL circuit 50. Therefore, the current effective value calculation circuit 30, the welding current control unit 34, the sequence control unit 38, and the power factor angle / conduction angle measurement unit 40 that use the clock CK as a reference timing signal always control each current control at accurate timing. ,
Measurement operation or sequence control can be executed. Thereby, the welding quality and the accuracy of the measured values are improved.

The resistance welding control apparatus of this embodiment has a function of measuring the effective current value and the power factor angle and the conduction angle. Is applicable. Further, the present invention can be applied to an AC resistance welding control device or a measuring device other than the above-described constant current control type single-phase AC resistance welding control device.

[0031]

According to the present invention having the above-described structure, the following effects can be obtained. A synchronization pulse corresponding to the waveform of the AC voltage on the power supply line is input to the PLL circuit, and the output signal of the PLL circuit is used as a clock for control and measurement operations of each unit. Even if the waveform is disturbed, it is possible to supply a stable clock that maintains a constant frequency and phase with little fluctuation in the time axis to each unit, thereby ensuring stable welding control and welding measurement operation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an AC resistance welding control device according to an embodiment of the present invention.

FIG. 2 shows P included in the AC resistance welding control device of the embodiment.
FIG. 3 is a block diagram illustrating a circuit configuration of an LL circuit.

FIG. 3 is a characteristic diagram showing a step response characteristic of a low-pass filter of the PLL circuit according to the embodiment.

FIG. 4 is a timing chart for explaining the operation of the clock generation unit of the AC resistance welding control device according to the embodiment.

[Explanation of symbols]

 Reference Signs List 10 power supply line 12, 14 thyristor 16 welding transformer 30 current effective value calculation circuit 34 welding current control unit 36 firing pulse generation circuit 38 sequence control unit 40 power factor angle and conduction angle measurement unit 42 control transformer 44 synchronous pulse generation circuit 50 PLL circuit

Claims (4)

(57) [Claims] 1. An AC resistance welding control device configured to generate a control clock from a power supply line for supplying power to an AC resistance welding machine , wherein the AC resistance welding control device corresponds to an AC voltage waveform on the power supply line. An AC resistance welding control apparatus , comprising: a synchronization pulse generating means for generating a synchronization pulse; and a PLL circuit for generating the clock in response to a synchronization pulse from the synchronization pulse generation means . 2. The AC resistance welding control device according to claim 1, wherein the response speed of said PLL circuit is reduced. 3. To supply power to an AC resistance welding machine.
Generate a clock for measurement from the power line of
In the AC resistance welding measuring apparatus, a synchronous pulse corresponding to the AC voltage waveform on the power supply line is used.
A synchronizing pulse generating means for generating a pulse, and a synchronizing pulse from the synchronizing pulse generating means.
And a PLL circuit for generating the clock.
AC resistance welding measurement device. 4. The method according to claim 1, wherein a response speed of said PLL circuit is reduced.
The alternating-current resistance welding measuring device according to claim 3, characterized in that: