JP2002219569A - Drive/control device for welding wire feed motor and inverter type arc welding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive/control device for welding wire feed motor capable of feeding a welding wide with a fixed speed to the welding head side, and small in size. SOLUTION: By using a switch regulator circuit 2 including a switching means 5 provided on a primary side winding of a transformer Ti and a second PWM control circuit 4, and a first PWM control circuit 3, the switching means is duty-pulse-controlled, thereby even if a load is applied to a DC motor M, the rotational speed of the DC motor M is maintained at the motor speed set value set by a motor rotational speed setting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding wire feed motor drive control apparatus and an inverter type arc welding machine, and more particularly to a commercial AC power supply used for supplying power suitable for a welding wire feed motor. A small welding wire feed motor drive control device using a down regulator for stepping down a power supply as a switching regulator using a high frequency switching transformer, and an inverter type arc welding machine equipped with such a welding wire feed motor drive control device About.

[0002]

2. Description of the Related Art In a conventional inverter type arc welding machine,
The power source for driving the DC motor (welding wire feed motor) for feeding the welding wire uses a down transformer to convert the frequency of the commercial power supply to a voltage suitable for the DC motor (welding wire feed motor). The motor (welding wire feed motor) is supplied.

FIG. 4 schematically shows a drive control device for a welding wire feed motor used in a conventional inverter type arc welding machine, which has already been proposed by the present applicant in Japanese Patent Application Laid-Open No. 62-217888. 3 is a circuit block diagram shown in FIG. This welding wire feed motor drive control device 101 includes:
A down transformer Tc for stepping down a commercial AC power supply is provided.

[0004] The power supply stepped down to a predetermined voltage by the down transformer Tc is supplied to a DC motor (welding wire feed motor) M via a switch means (FET) 105.

The on / off control (duty pulse control) of the switch means (FET) 105 is performed by a first PWM control circuit 103 and a second PWM control circuit 104. First PWM control circuit 10
3 is a sample hold circuit 106 and an error amplifier (E
AMP) 107 and comparator (COMP) 108
And an inverter (INV) 109.

[0006] The sample and hold circuit 106 includes switch means SW and a hold capacitor 110.

The switch means SW operates during a period during which the output signal (a predetermined frequency selected from the range of 20 kHz to 50 kHz) from the second PWM control circuit 104 is lost, that is, a DC motor (welding wire feed motor) M It turns on during the period when the voltage application to is paused,
As a result, charge is stored in the hold capacitor 110.

That is, the sample-and-hold circuit 106 turns on the switch SW while the switch 105 keeps the OFF state, and the voltage is applied to the DC motor (welding wire feed motor) M. During the pause, the back electromotive force Ea of the DC motor (welding wire feed motor) M is sampled.

The rotational speed of the DC motor (welding wire feed motor) M can be set, for example, by a motor speed setting signal Vs input from a control panel (not shown) of an inverter type arc welding machine. .

A motor speed setting signal Vs inputted from a control panel (not shown) of the inverter type arc welding machine is supplied to an error amplifier (EAMP) 107 by a DC motor (welding wire feed) detected by a sample and hold circuit 106. The voltage is compared with the back electromotive voltage Ea of the feed motor (M). The error amplifier (EAMP) 107 outputs an error signal Ve between the motor speed setting signal Vs and the back electromotive voltage Ea.

The error signal Ve is supplied to a comparator (CO
MP) 108 and the comparator (COMP) 1
At 08, the signal is compared with the reference signal Vref, and the comparator (COMP) 108 outputs the signal from the inverter (INV) 10
9 is output. Error signal Ve output from comparator (COMP) 108 to inverter (INV) 109
Is inverted by an inverter (INV) 109 and then input to the second PWM control circuit 104.

The DC motor (welding wire feed motor) M is a motor speed setting signal input from a control panel (not shown) of the inverter type arc welding machine when no load is applied to the DC motor M. Based on Vs, the switch means (FET) 105 receives a reference signal Vref from 0 volts to a predetermined voltage value (this predetermined voltage value is input from a control panel (not shown) of an inverter type arc welding machine). Motor speed setting signal Vs
It is determined based on. ) Is turned off for a predetermined period until the reference signal Vref becomes
Switch means (FET) at a predetermined frequency (a predetermined frequency selected from 20 kHz to 50 kHz) for a predetermined period from a predetermined voltage value to a peak value (volt).
By the pulse control of turning on and off the 105,
The inverter-type arc welding machine is driven at a rotation speed corresponding to a motor speed setting signal Vs input from a control panel (not shown).

At the time of starting, the error signal Ve becomes maximum and the duty of the first PWM control circuit 103 becomes maximum. At this time, the second PWM control circuit 10
In 4, the current flowing to the DC motor (welding wire feed motor) M is controlled so as not to exceed the limit value of the switching element (FET) 105, and the switching element (FET) 105 is overloaded at the time of starting. I try not to be. The operating frequency of the first PWM control circuit 103 is 1/100 or less of the operating frequency of the second PWM control circuit 104.

When a load is applied to the DC motor (welding wire feed motor) M, the motor speed setting signal Vs and the back electromotive voltage E
An error signal Ve with respect to a is generated.

The second PWM control circuit 104 detects the current flowing through the DC motor M by the resistor Rc, compares the current thus detected with the motor current designation Ims,
Control is performed so that the current flowing through the DC motor (welding wire feed motor) M is constant. That is, the second PWM control circuit 104 uses the signal based on the output of the first PWM control circuit 103 to output the reference signal Vref of the triangular wave signal.
Turns off the switch means (FET) 105 from 0 volt until the value of the reference signal Vref of the triangular wave signal matches the value of the error signal Ve, and the reference signal Vref of the triangular wave signal changes to the value of the error signal Ve. And the switch means (FET) 1 at a predetermined frequency (a predetermined frequency selected from the range of 20 kHz to 50 kHz) until the reference signal Vref of the triangular wave signal reaches the peak value.
05 is turned on and off to perform duty pulse control.

When the operation period of the second PWM control circuit 104 is controlled by the first PWM control circuit 103, the second PWM control circuit 104 switches the switching means by the first PWM control circuit 103. While receiving a signal to turn on the operation of the (FET) 105, at a high speed (20
The switching means 105 is repeatedly turned on and off at a predetermined frequency within a range of kHz to 50 kHz).

This welding wire feed motor drive control device 1
In 01, when a load is applied to the DC motor (welding wire feed motor) M, the switch means (FET) 105
Is turned on, the rotation speed of the DC motor (welding wire feed motor) M is reduced by the speed of the motor speed setting signal Vs input from the control panel (not shown) of the inverter type arc welding machine. Is maintained.

As a result, the inverter type arc welding machine provided with the welding wire feed motor drive control device 101 has the following features.
A control panel (not shown) from a DC motor (welding wire feed motor) M to a welding wire on a welding head side.
There is an advantage that the motor can be fed by the motor speed setting signal Vs input from the controller.

[0019]

However, the inverter type arc welding machine provided with the above-described conventional welding wire feed motor drive control device 101 uses a down transformer to reduce the frequency of the commercial power supply to a DC motor (weld wire feed motor).
After the voltage is converted to a voltage suitable for the motor, the DC voltage is supplied to a DC motor (welding wire feed motor).

That is, the power supply for driving the DC motor (welding wire feed motor) M of the inverter type arc welding machine usually requires a considerably large capacity as compared with the control power supply for the arc welding machine. In order to obtain a power supply suitable for driving the motor (welding wire feed motor) M, a large down transformer (down transformer Tc shown in FIG. 6) is required.

For this reason, when attempting to develop a compact inverter-type arc welding machine, the size of the down transformer (down transformer Tc shown in FIG. 4) becomes a bottleneck even if the size can be reduced to some extent. There was a problem that downsizing of the inverter type arc welding machine had a certain limit.

In consideration of the operability of the inverter type arc welding machine, when the welding wire is fed to the welding head side, the welding wire is moved at a constant speed set by an operator or the like. It is necessary to have a function of driving a direct current motor (welding wire feed motor) so that it can be supplied to the side.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can supply a welding wire to a welding head at a constant speed, and can drive a welding wire feed motor. It is an object of the present invention to provide a welding wire feed motor drive control device capable of reducing the size of the control device itself and an inverter type arc welding machine including such a welding wire feed motor drive control device.

[0024]

According to a first aspect of the present invention, there is provided a welding wire feed motor drive control device including a switching means provided on a primary winding of a transformer and a second PWM control circuit. Circuit, a rectifier circuit provided on the secondary winding of the transformer, a dc motor connected to the rectifier circuit provided on the secondary winding of the transformer, for feeding a welding wire, and a dc motor. A rotation speed detection circuit for detecting the rotation speed of the DC motor; a motor rotation speed setting means for setting the rotation speed of the DC motor to a predetermined rotation speed; and a rotation speed of the DC motor and a motor rotation speed detected by the rotation speed detection circuit. The motor speed setting value set by the setting means is compared with the motor speed setting value, and an error signal between the rotation speed of the DC motor detected by the rotation speed detection circuit and the motor speed setting value set by the motor rotation speed setting means is calculated. And a first PWM control circuit for comparing the error signal output from the error amplifier with a reference signal having a predetermined repetition period and outputting a duty pulse signal. The control circuit performs constant current control of the current flowing in the DC motor by the switching means, the motor current command, and the current detecting means for detecting the current flowing to the primary winding of the transformer, and outputs the current from the first PWM control circuit. While the received duty pulse signal is being received, the switch means is turned on to maintain the rotation speed of the DC motor at the motor speed set value set by the motor rotation speed setting means.

Here, the "motor current command" is obtained from a motor speed setting value (voltage value) set by the motor rotation speed setting means and a current value defined by the rated resistance value of the DC motor, or from a control panel or the like. The input current value means a current value required for rotating the DC motor at a constant rotation speed at a motor speed set value set by the motor rotation speed setting means. In this welding wire feed motor drive control device, when the load of the DC motor (weld wire feed motor) fluctuates,
Duty ratio of first PWM control circuit and second PWM
When the duty ratio of the M control circuit fluctuates and the load on the DC motor (welding wire feed motor) increases, the motor current increases and the load on the DC motor (welding wire feed motor) decreases. Controls the motor current so that the DC motor (welding wire feed motor)
Is supplied with a voltage corresponding to the rotational speed set value of the DC motor (welding wire feed motor).

As a result, by using this welding wire feed motor drive control device, the welding wire can be fed to the welding head side at a constant speed.

Further, the inverter type arc welding machine according to the present invention employs a welding wire feed motor drive control device for feeding the welding wire at a constant speed to the welding head side. It can be fed to the welding head side at a constant speed.

In addition, in the welding wire feed motor drive control device according to the present invention, the duty pulse control of the DC motor (weld wire feed motor) is performed on the primary winding side of the transformer. There is no need to use a large transformer like a down transformer.

That is, in the drive control apparatus for a welding wire feed motor according to the present invention, in order to obtain a power source for a DC motor (weld wire feed motor), a down transformer conventionally used is replaced by a high frequency switching transformer. As a result, the welding wire feed motor drive control device can be downsized.

As a result, if the welding wire feed motor drive control device according to the present invention is employed in an inverter type arc welding machine, downsizing of the inverter type arc welding machine can be further promoted.

According to a second aspect of the present invention, there is provided a welding wire feed motor drive control device according to the first aspect of the present invention, wherein the welding wire feed motor drive control device comprises a first PWM control circuit and a second PWM drive.
The transmission of the duty pulse signal to the M control circuit is performed by electrically insulated means.

Here, “electrically insulated means” means that when transmitting a signal from a certain device to another certain device, a certain device converts an electric signal to be transmitted to another certain device into an electric signal. Means to replace other signals and transmit them to some other device. Specifically, such electrically insulated means includes, for example, a photocoupler.

In this welding wire feed motor drive control device, the transmission of the duty pulse signal from the first PWM control circuit to the second PWM control circuit is performed by electrically insulated means. Since the first PWM control circuit and the second PWM control circuit are always electrically insulated from each other and only necessary information is transmitted, the first PWM control circuit And the second PW
The safety is superior to that of a device in which the M control circuit is electrically connected to the M control circuit. In the inverter type arc welding machine according to the third aspect, the welding wire feed motor drive control device according to the first or second aspect is connected to a primary side of an inverter circuit that converts a commercial AC power supply to a high frequency. .

In this inverter type arc welding machine, since the welding wire feed motor drive control device according to claim 1 or 2 is used, the inverter type arc welding machine can be downsized.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a welding wire feed motor drive control apparatus and an inverter type arc welding machine according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a circuit block diagram schematically showing an example of a drive control device for a welding wire feed motor according to the present invention. The welding wire feed motor drive control device 1 includes a switching regulator circuit 2 and a first PWM control circuit 3.

The switching regulator circuit 2 includes a switching means 5 provided on the primary winding side of the transformer Ti.
And a second PWM control circuit 4.

This welding wire feed motor drive control device 1
Is driven as a single unit using a commercial AC power supply, the bridge circuit 12 and the capacitance means (capacitor) 1
3, the commercial AC power supply is converted to a DC power supply, and the DC power supply obtained in this way is connected to the connection terminal P.
1. Connect P2.

The rated voltage of the DC motor M is usually several tens of volts (generally, about 18 V to 24 V in an actual circuit).
It is. By the way, a commercial AC power supply is connected to a power supply circuit 11 having a bridge circuit 12 and a capacitance means (capacitor) 13.
, The voltage of the DC power supply becomes 300 V DC or more. Therefore, in the welding wire feed motor drive control device 1, the winding ratio between the primary winding N1 and the secondary winding N2 of the transformer Ti is expressed as N1: N2 =
The voltage between terminal P1 and terminal P2 (V (P1-P
2)): The design is such that the relationship is about the rated voltage of the DC motor M × 2 times. That is, in the welding wire feed motor drive control device 1, the voltage on the secondary side of the transformer Ti is set by the transformer Ti to a voltage that can supply power to the DC motor M against the back electromotive force of the DC motor M. are doing. That is, the welding wire feed motor drive control device 1
Then, power is supplied to the DC motor M by the transformer Ti.
The dangerous high voltage supplied to the primary side of the transformer Ti is converted into a safe voltage, and then the DC motor M is supplied with power.

In FIG. 1, D1 and D2 each represent a diode, L represents an induction coil,
A rectifier circuit is constituted by the diodes D1 and D2 and the induction coil L.

In this example, a field effect transistor (FET) is used as the switching means 5.

In this example, the switch means 5 is 20 KH
A device capable of performing a switching operation at a high frequency of not less than z and not more than 50 KHz is used. This welding wire feed motor drive control device 1 is particularly characterized in that the on / off control (duty pulse control) of the switch means 5 is performed on the primary side of the transformer Ti.

On / off control (duty pulse control) of the switch means (FET) 5 is performed by the switching regulator circuit 2 and the first PWM control circuit 3. The first PWM control circuit 3 includes a sample hold circuit 6 and an error amplifier (EAMP) 7.
And a comparator (COMP) 8.

The sample and hold circuit 6 includes a switch SW and a hold capacitor 10.

The switch means SW operates during a period during which the output signal (predetermined frequency selected from the range of 20 kHz to 50 kHz) from the second PWM control circuit 4 disappears, that is, a DC motor (welding wire feed motor) M The switch is turned on during a period in which the application of a voltage to the capacitor is stopped, so that charges are stored in the hold capacitor 10.

That is, the sample-and-hold circuit 6 turns on the switch SW while the switch 5 is kept in the OFF state, so that the voltage is applied to the DC motor (welding wire feed motor) M. During the pause, the back electromotive force Ea of the DC motor (welding wire feed motor) M is sampled.

In FIG. 1, reference numeral 9 denotes a photocoupler for transmitting a signal output from the comparator (COMP) 8 of the first PWM control circuit 3 to the second PWM control circuit 4. ing.

The photocoupler 9 electrically insulates the first PWM control circuit 3 and the second PWM control circuit 4 from each other, and converts only the signal output from the first PWM control circuit 3 to the first PWM control circuit 3. 2 is provided for transmission to the PWM control circuit 4. Further, the first PWM control circuit 3 and the second P
If the potential of the WM control circuit 4 is different from that of the WM control circuit 4, the first PWM control circuit 3 and the second PWM control circuit 4
And a signal for controlling the switch means 5 to be turned on and off cannot be transferred. Therefore, this photocoupler 9
It is used for adjusting the potentials of the first PWM control circuit 3 and the second PWM control circuit 4.

The rotation speed of the DC motor (welding wire feed motor) M can be set, for example, by a motor speed setting signal Vs input from a control panel (not shown) of the inverter type arc welding machine. .

The motor speed setting signal Vs input from the control panel (not shown) of the inverter type arc welding machine receives the DC motor (welding wire feed) detected by the sample and hold circuit 6 in the error amplifier (EAMP) 7. The voltage is compared with the back electromotive voltage Ea of the feed motor M. The error amplifier (EAMP) 7 outputs an error signal Ve between the motor speed setting signal Vs and the back electromotive voltage Ea.

The error signal Ve is supplied to a comparator (CO
MP) 8 and is compared with a reference signal Vref in a comparator (COMP) 8 to be compared with a comparator (C
An on / off control signal for the switch means (FET) 5 is output from the OMP 8 to the second PWM control circuit 4. In this example, the comparator (COM
P) The electric signal outputted from the second PWM control circuit 4 to the second PWM control circuit 4 is once converted into an optical signal by the photocoupler 9 and is again converted into an electric signal, and then the second comparator (COMP) 8 to the second PWM control circuit 4.

Next, the operation of the welding wire feed motor drive control device 1 will be described.

FIG. 2 is a time chart for explaining the operation of the welding wire feed motor drive control device of the inverter type arc welding machine according to the present invention.

More specifically, FIG. 2A schematically illustrates the operation of the first PWM control circuit 3.
FIG. 2B schematically illustrates the on / off operation of the switch means SW of the sample hold circuit 6.
2C schematically illustrates the output of the sample and hold circuit 6, and FIG. 2D illustrates the output of the second PWM control circuit 4.
FIG. 2 (e) shows a switch connected to the primary side of the transformer Ti based on a signal output from the second PWM control circuit 4. By means of duty pulse control of the means 5, the primary current value input to the primary winding side of the transformer Ti is schematically shown. FIG. 2 (f) shows a DC motor (welding wire feed). 2 schematically shows the motor current supplied to the supply motor (M).

DC motor (welding wire feed motor) M
In a state where no load is applied to the DC motor M, the switch means (FET) 5 is set to a reference signal based on a motor speed setting signal Vs input from a control panel (not shown) of the inverter type arc welding machine. Vref
Is a predetermined voltage value from 0 volt (the predetermined voltage value is
It is determined based on a motor speed setting signal Vs input from a control panel (not shown) of the inverter type arc welding machine. ) For a predetermined period until the reference signal Vref changes from a predetermined voltage value to a peak value (volts) for a predetermined period,
By a pulse control of turning on and off the switch means (FET) 5 at a predetermined frequency (a predetermined frequency selected from 20 kHz to 50 kHz), an input is made from a control panel (not shown) of the inverter type arc welding machine. The motor is driven at a rotation speed corresponding to the motor speed setting signal Vs.

At the time of starting, the error signal Ve becomes the largest, and the duty of the first PWM control circuit 3 becomes
Will be the largest. At this time, in the second PWM control circuit 4, the current flowing to the DC motor M is switched by the switching element (F
ET) Because it is controlled not to exceed the limit value of 5,
At the time of starting, an overload is not applied to the switching element (FET) 5 (see a period t1 from the time of starting to the time of rated starting in FIG. 2). First PWM
The operating frequency of the control circuit 3 is 1/100 or less of the operating frequency of the second PWM control circuit 4.

When a load is applied to the DC motor M, an error signal Ve between the motor speed setting signal Vs and the back electromotive voltage Ea is generated.

The second PWM control circuit 4 includes a DC motor M
Is detected by the resistance Ri, and this current is compared with the motor current designation Ims, and the current flowing through the DC motor M is controlled to be constant. That is, the second PW
The M control circuit 4 uses the signal based on the output of the first PWM control circuit 3 to change the reference signal Vref of the triangular wave signal to 0.
During the period from volts until the value of the reference signal Vref of the triangular wave signal matches the value of the error signal Ve, the switch means (FE
T) 5 is turned off, and the reference signal Vre of the triangular wave signal is set.
During a period from when f matches the value of the error signal Ve to when the reference signal Vref of the triangular wave signal reaches a peak value, the switching means (a predetermined frequency selected from 20 kHz to 50 kHz) is used. FET) 5 is turned on / off to perform duty pulse control.

Then, by the first PWM control circuit 3,
When the operation period of the second PWM control circuit 4 is controlled, the second PWM control circuit 4 uses the first PWM control circuit 3 while receiving a signal for turning on the switch means (FET) 5. The switching of the switch means 5 is repeated at a high speed (a predetermined frequency within a range of 20 kHz to 50 kHz) (see FIG. 2E).

Therefore, in the welding wire feed motor drive control device 1, the DC motor (weld wire feed motor) M
When a load is applied to the switch, the switch means (FET) 5
Is turned on, the rotation speed of the DC motor (welding wire feed motor) M is maintained at the motor speed setting signal Vs input from the control panel (not shown) of the inverter type arc welding machine. (See period t2 during which a load is applied to DC motor (welding wire feed motor) M in FIG. 2).

To describe this in another expression, when a load is applied to the DC motor (welding wire feed motor) M,
As a result, the period during which the switch means (FET) 5 is turned on becomes longer, so that the DC motor (welding wire feed motor)
As a result of the current flowing through M being kept substantially constant, the motor speed setting signal Vs input from the control panel (not shown) of the inverter type arc welding machine is maintained. That is, when the load of the DC motor (welding wire feeding motor) M changes, the duty ratio of the first PWM control circuit 3 and the duty ratio of the second PWM control circuit 4 change, and the DC motor (welding wire feeding motor) changes. The motor is controlled so that the motor current increases when the load on the motor (M) increases, and the motor current decreases when the load on the DC motor (welding wire feed motor) decreases. The motor (welding wire feeding motor) M is supplied with a voltage corresponding to the rotation speed set value of the DC motor (welding wire feeding motor).

As a result, if the welding wire feed motor drive control device 1 is used, the welding wire can be fed to the welding head side (not shown) at a constant speed.

Therefore, in the inverter type arc welding machine provided with the welding wire feed motor drive control device 1, the welding wire is fed from the DC motor (welding wire feed motor) M to the welding head side, and a control panel (not shown). ) Has the advantage that the motor can be fed by the motor speed setting signal Vs input from (1).

Not only that, the conventional welding wire feed motor drive control device 101 uses the down-transformer (down-transformer Tc shown in FIG. 4) to switch the commercial AC power supply to a voltage suitable for driving the DC motor M. While the duty control is performed after the voltage is reduced to a value, in the welding wire feed motor drive control device 1, the duty control is performed on the primary winding side of the transformer Ti. The down transformer is unnecessary, and as a result, the welding wire feed motor drive control device 1 can be downsized. For this reason, by employing this welding wire feed motor drive control device 1 in an inverter type arc welding machine,
The downsizing of the inverter type arc welding machine can be further promoted.

In the welding wire feed motor drive control device 1, as described above, the first PWM control circuit 3
And the second PWM control circuit 4 are electrically insulated from each other.
The signal output from the comparator (COMP) 8 of the WM control circuit 3 is once converted into an optical signal,
Since the signal is transmitted to the WM control circuit 4, safety is superior to a circuit in which the first PWM control circuit 3 and the second PWM control circuit 4 are directly connected by electric wiring.

In the welding wire feed motor drive control device 1 shown in the embodiment of the present invention, the transformer Ti, the switching means 5, the second PWM control circuit 4, and the secondary winding side of the transformer Ti Provided diodes D1, D
2 shows an example in which a rectifier circuit configured by the inductor 2 and the induction coil L forms a forward converter.
The rectifier circuit provided on the transformer Ti, the switching means 5, the second PWM control circuit 4, and the secondary winding side of the transformer Ti is not limited to such a forward converter.
A flyback converter, a bridge converter, or another type of switching regulator may be used. Such a circuit may be suitably selected according to the rating of the DC motor.

Further, in the embodiment of the present invention, as the welding wire feed motor drive control device, the transmission of the duty pulse signal between the first PWM control circuit 3 and the second PWM control circuit 4 is performed electrically. Although the device 1 is described as being performed by means (e.g., the photocoupler 9 in the embodiment of the present invention) insulated from the first PWM control circuit 3 and the second PWM control circuit 3, PW
A signal line may be connected to the M control circuit 4 to electrically transmit the duty pulse signal. FIG. 3 exemplarily shows a circuit block diagram of an inverter type arc welding machine having the welding wire feeding motor drive control device 1.

This inverter type arc welding machine A converts a commercial AC power supply (three-phase AC power supplies U, V, W) into a high-frequency power supply by using an inverter circuit 21, and uses an inverter welding power supply transformer Tp to To obtain a suitable welding power output. The welding wire feed motor drive control device 1 according to the present invention is connected to the primary side of an inverter circuit 21 of an inverter type arc welding machine that converts a commercial AC power into a high frequency in order to obtain a required welding power output.

More specifically, the connection terminals P1 and P2 shown in FIG. 1 are connected to the connection terminals Q1 and Q2 provided at the subsequent stage of the rectifier circuit of the inverter circuit in FIG.

As described above, when the connection terminals P1 and P2 of the welding wire feed motor drive control device 1 according to the present invention are connected to the connection terminals Q1 and Q2 provided at the subsequent stage of the rectifier circuit 22 of the inverter circuit 21, Each of the rectifier circuit 22 and the capacitance means (condenser) 23 constituting the welding power supply inverter circuit 21 is provided with a rectifier circuit of a power supply circuit for taking a DC power supply of the welding wire feed motor drive control device 1 (FIG. 1) and capacity means (capacitor) (capacity means (capacitor) 13 shown in FIG. 1)
The rectifier circuit (the bridge circuit 12 shown in FIG. 1) and the capacitance means (the capacitor) (the capacitor shown in FIG. 1) for configuring the power supply circuit for the welding wire feed motor drive control device 1 Means (condenser) 13)
Becomes unnecessary.

In FIG. 3, G1, G2, G3, G4, E
1, E2, E3, and E4 indicate inverter switching signals.

As described in detail above, claim 1 is as follows.
In the welding wire feed motor drive control device described in the above, when the load of the DC motor (weld wire feed motor) fluctuates,
Duty ratio of first PWM control circuit and second PWM
When the duty ratio of the M control circuit fluctuates and the load on the DC motor (welding wire feed motor) increases, the motor current increases and the load on the DC motor (welding wire feed motor) decreases. Controls the motor current so that the DC motor (welding wire feed motor)
Is supplied with a voltage corresponding to the rotational speed set value of the DC motor (welding wire feed motor).

As a result, by using the welding wire feed motor drive control device, the welding wire can be fed to the welding head side at a constant speed.

Further, in the inverter type arc welding machine according to the present invention, the welding wire feed motor drive control device for feeding the welding wire to the welding head side at a constant speed is employed. It can be fed to the welding head side at a constant speed.

In addition, in the welding wire feeding motor drive control device according to the present invention, the duty pulse control of the DC motor (welding wire feeding motor) is performed on the primary winding side of the transformer, and as a result, the conventional motor is controlled. There is no need to use a large transformer like a down transformer.

That is, in the welding wire feed motor drive control device according to the present invention, a down transformer conventionally used is replaced with a high frequency switching transformer in order to obtain a power source for a DC motor (weld wire feed motor). As a result, the welding wire feed motor drive control device can be downsized.

As a result, if the welding wire feed motor drive control device according to the present invention is employed in an inverter type arc welding machine, downsizing of the inverter type arc welding machine can be further promoted.

According to a second aspect of the present invention, in the drive control device for a welding wire feed motor, the first PWM control circuit switches the second PWM control signal.
Since the transmission of the duty pulse signal to the M control circuit is performed by electrically insulated means, the connection between the first PWM control circuit and the second PWM control circuit is always electrically connected. Is in an insulated state and only necessary information is transmitted, so that it is safer than a device in which the first PWM control circuit and the second PWM control circuit are connected by electric means. Excellent in nature. The inverter type arc welding machine according to the third aspect uses the welding wire feed motor drive control device according to the first or second aspect, so that the inverter type arc welding machine can be downsized.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram schematically showing an example of a drive control device for a welding wire feed motor according to the present invention.

FIG. 2 is a time chart for explaining the operation of the drive control device for the welding wire feed motor of the inverter type arc welding machine according to the present invention. FIG. 2 (a) shows the operation of the first PWM control circuit. This is schematically described, and FIG.
FIG. 2C schematically illustrates the on / off operation of the switch means of the sample and hold circuit, FIG. 2C schematically illustrates the output of the sample and hold circuit, and FIG.
The signal input to the second PWM control circuit via the photocoupler is described. FIG. 2E shows a connection to the primary side of the transformer based on the signal output from the second PWM control circuit. FIG. 2 (f) schematically shows the primary current value input to the primary winding side of the transformer by the duty pulse control of the switch means provided.
Indicates schematically the motor current supplied to the DC motor M.

FIG. 3 is a diagram exemplarily showing a circuit block diagram of an inverter type arc welding machine including the welding wire feed motor drive control device shown in FIG. 1;

FIG. 4 is a circuit diagram schematically showing a drive control device for a welding wire feed motor used in a conventional inverter type arc welding machine, which has already been proposed by the present applicant in JP-A-62-217888. It is a block diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding wire feed motor drive control device 2 Switching regulator circuit 3 First PWM control circuit 4 Second PWM control circuit 5 Switching means 6 Revolution detection circuit 7 Error amplifier 8 Comparator 9 Photocoupler 10 Hold capacitor 11 Power supply circuit 12 Bridge Circuit 13, 23 Capacity means 21 Inverter circuit 22 Rectifier circuit A Inverter type arc welding machine M DC motor (welding wire feed motor) SW switch element Ti transformer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E082 BA01 BB02 DA01 5H571 AA14 BB03 CC05 GG02 GG04 HA02 HA03 HA04 HA09 HA16 HD02 JJ06 LL01 LL22 PP04 5H730 AS13 BB23 CC01 DD04 DD16 EE03 EE08 FD08 FG31

Claims (3)

[Claims] A switching means provided on a primary winding of a transformer; a switching regulator circuit including a second PWM control circuit; a rectifier circuit provided on a secondary winding of the transformer; A DC motor connected to a rectifier circuit provided on a secondary winding of the transformer, for feeding a welding wire to a welding head side, and a rotation speed detection circuit for detecting a rotation speed of the DC motor, Motor rotation speed setting means for setting the rotation speed of the DC motor to a predetermined rotation speed, rotation speed of the DC motor detected by the rotation speed detection circuit, and motor speed setting value set by the motor rotation speed setting means And an error for outputting an error signal between the rotation speed of the DC motor and the motor speed set value set by the motor rotation speed setting means, detected by the rotation speed detection circuit. And a first PWM control circuit for comparing the error signal output from the error amplifier with a reference signal having a predetermined repetition period and outputting a duty pulse signal, wherein the second PWM The control circuit performs a constant current control of a current flowing through the DC motor by the switching unit, a motor current command, and a current detection unit that detects a current flowing to the primary winding side of the transformer. P
While receiving the duty pulse signal output from the WM control circuit, the switch unit is turned on to maintain the rotation speed of the DC motor at the motor speed set value set by the motor rotation speed setting unit. And a welding wire feed motor drive control device. 2. A transmission of a duty pulse signal from the first PWM control circuit to the second PWM control circuit,
The welding wire feed motor drive control device according to claim 1, wherein the drive control is performed by means that is electrically insulated. 3. An inverter type arc welding machine having a welding wire feed motor drive control device according to claim 1 connected to a primary side of an inverter circuit for converting a commercial AC power supply to a high frequency.