JP6307343B2 - Motor driving device and control method of motor driving device - Google Patents

Description

  The present invention relates to a motor drive device and a control method for the motor drive device.

  Conventionally, an arc welding machine that performs arc welding using a consumable electrode has a supply device that supplies the consumable electrode to a welding target. The supply device has a rotary encoder that outputs a pulse signal corresponding to the number of rotations of the motor for feeding the consumable electrode. The control device of the arc welding machine monitors the feed amount of the consumable electrode based on the pulse signal output from the supply device, and supplies the motor of the supply device so that the amount of consumable electrode corresponding to welding is supplied to the welding object. (See, for example, Patent Document 1).

JP 2002-172464 A

  By the way, when an abnormality such as disconnection of the signal line transmitting the pulse signal or failure of the rotary encoder occurs, the motor rotates at the maximum number of rotations, so that the welding wire is supplied excessively. For this reason, the welding wire is wasted, or the welding quality is degraded.

  The present invention has been made to solve the above-described problems, and an object thereof is to reduce excessive feeding of consumable electrodes.

  A motor driving device that solves the above problem is a motor driving device that is included in a welding machine that performs welding with a consumable electrode and drives a motor that feeds the consumable electrode, and includes a feed command value and a feed feedback value. And a reference value setting circuit for outputting a feed reference value, and the control value and the feed reference value are selectively selected according to a first abnormality detection signal. A switching circuit for switching to output, a driving circuit for outputting a driving signal for driving the motor in accordance with an output value of the switching circuit, and a value obtained as a result of measuring a cycle of a pulse signal corresponding to the rotation of the motor. Comparing the output value of the period measurement circuit, the signal conversion circuit for converting the output value of the period measurement circuit into the feeding feedback value, and the output value of the period measurement circuit with the first reference determination value, and according to the comparison result An abnormality that outputs the first abnormality detection signal Having a detection circuit.

  According to this configuration, when the control value is selected, a drive signal for driving the motor according to the feed command value is generated based on the feed command value and the feed feedback value. When the feed reference value is selected, a drive signal for driving the motor is generated according to the feed reference value. When an abnormality occurs in which the pulse signal does not change in a pulse shape, the motor is driven using the feed reference value instead of the control value, so that the rotation speed corresponds to the feed reference value instead of the maximum motor speed. The motor can be rotated. Since the consumable electrode is fed by the motor, excessive feeding of the consumable electrode can be suppressed by keeping the rotation speed of the motor low.

  In the motor driving apparatus, the abnormality detection circuit compares the output value of the period measurement circuit with a second reference determination value larger than the first reference determination value, and outputs a second abnormality detection signal according to the comparison result. A start signal for instructing the start of feeding the consumable electrode, and a second switching circuit for switching the supply or stop of the start signal to the comparison operation circuit according to the second abnormality detection signal. The comparison operation circuit preferably generates the control value so as to stop the motor in response to the supply stop of the start signal.

  According to this configuration, when the state where the pulse signal does not change in a pulse shape continues to the second reference determination value, the supply of the start signal is stopped, so that the motor is stopped and the consumable electrode is supplied by the motor. It becomes possible to stop.

  In the motor drive device, the abnormality detection circuit supplies the control value from the comparison operation circuit to the drive circuit when generating the second abnormality detection signal so as to stop the supply of the start signal. Preferably, the first abnormality detection signal is generated.

  According to this configuration, the supply of the consumable electrode by the motor can be stopped by supplying the control value generated by the comparison operation circuit to the drive circuit in response to the supply stop of the activation signal. it can.

  In the above motor drive device, it is preferable that the period measurement circuit measures a half period of the pulse signal based on the rise and fall of the pulse signal and outputs a value of the measurement result.

  According to this configuration, the half cycle from the rise to the fall of the pulse signal and the half cycle from the fall to the rise are measured. Therefore, it is possible to control the motor in accordance with the abnormality that occurs after the rise and fall of the pulse signal.

  A control method for a motor drive device that solves the above-mentioned problem is a control method for a motor drive device that is included in a welding machine that performs welding with a consumable electrode and that drives a motor that feeds the consumable electrode. A control value is generated by comparing and calculating the value and the feeding feedback value, the control value and the feeding reference value are selected according to the first abnormality detection signal, and the selected control value or the feeding reference value is selected. A signal conversion circuit for generating a drive signal for driving the motor according to the rotation, measuring a cycle of the pulse signal according to the rotation of the motor, and converting the cycle of the pulse signal into the feed feedback value; and The period of the signal is compared with the first reference determination value, and the first abnormality detection signal is generated according to the comparison result.

  According to this configuration, when the control value is selected, a drive signal for driving the motor according to the feed command value is generated based on the feed command value and the feed feedback value. When the feed reference value is selected, a drive signal for driving the motor is generated according to the feed reference value. When an abnormality occurs in which the pulse signal does not change in a pulse shape, the motor is driven using the feed reference value instead of the control value, so that the rotation speed corresponds to the feed reference value instead of the maximum motor speed. The motor can be rotated. Since the consumable electrode is fed by the motor, excessive feeding of the consumable electrode can be suppressed by keeping the rotation speed of the motor low.

  According to the present invention, excessive feeding of the consumable electrode can be reduced.

It is the schematic of an arc welding machine. It is an electric block diagram of a motor drive circuit. It is a wave form diagram explaining operation | movement of a motor drive circuit. It is a wave form diagram explaining operation | movement of a motor drive circuit. It is a wave form diagram explaining operation | movement of a motor drive circuit. It is a block diagram of the motor drive circuit of a comparative example. It is a wave form diagram explaining operation | movement of the motor drive circuit of a comparative example. It is a wave form diagram explaining operation | movement of the motor drive circuit of a comparative example.

Hereinafter, an embodiment will be described.
As shown in FIG. 1, the arc welder 10 includes a welding power source 11, a supply device 12, and a welding torch 13. The welding object 21 is connected to the welding power source 11.

  The welding power source 11 has a control device 14. The control device 14 controls the welding power supplied from the welding power source 11 to the welding wire 15 held by the welding torch 13. Further, the control device 14 controls the supply device 12 to supply the welding wire 15 from the supply device 12 to the welding target 21.

  The supply device 12 has a motor for feeding the welding wire 15 to the welding target and a sensor for detecting the rotation of the motor. For example, the motor is a servo motor, and the sensor is a rotary encoder attached integrally with the motor. The rotary encoder outputs a pulse signal having a cycle corresponding to the number of rotations of the motor. The control device 14 drives the motor based on the pulse signal. That is, the control device 14 performs so-called feedback control in which the drive signal for the motor is controlled by a pulse signal corresponding to the motor line.

As shown in FIG. 2, the control device 14 has a motor drive device 30 connected to the motor M1 and the rotary encoder R1 included in the supply device 12 shown in FIG.
The motor drive device 30 includes a motor control circuit 31 and a drive circuit 32. The motor control circuit 31 is, for example, a central processing unit (CPU) or a digital processing circuit included in the CPU. The motor control circuit 31 operates based on the start signal St, and outputs a control value Ea based on the feed command value Cw and the pulse signal Re from the rotary encoder R1. The drive circuit 32 converts the control value Ea into a drive signal Dr. The drive signal Dr is a signal at a level for driving the motor M1.

  In the present embodiment, the motor driving device 30 drives the motor M1 by pulse width modulation (PWM) control. The drive circuit 32 outputs a drive signal Dr having a pulse width corresponding to the control value Ea. For example, the drive circuit 32 increases the pulse width of the drive signal Dr as the control value Ea increases. The pulse width of the drive signal Dr corresponds to the time during which the drive voltage is applied to the motor M1. Therefore, increasing the pulse width of the drive signal Dr increases the force for rotating the motor M1. Further, increasing the pulse width of the drive signal Dr increases the rotational speed of the motor M1.

The motor control circuit 31 includes a comparison operation circuit 41, a period measurement circuit 42, a period conversion circuit 43, an abnormality detection circuit 44, a reference value setting circuit 45, and switches Sw1 and Sw2.
The activation signal St is supplied to the comparison operation circuit 41 via the switch Sw2. The switch Sw2 is turned on / off based on an abnormality detection signal Er2 described later.

  The start signal St is a signal for instructing to start / stop the feeding wire 15 shown in FIG. 1, that is, the supply device 12 (motor M1). For example, the H level start signal St corresponds to feeding of the welding wire 15 (start of the motor M1), and the L level start signal St corresponds to stop of feeding of the welding wire 15 (stop of the motor M1).

  The switch Sw2 is turned on / off based on the abnormality detection signal Er2 from the abnormality detection circuit 44. For example, the switch Sw2 is turned on based on the L level abnormality detection signal Er2, and is turned off based on the H level abnormality detection signal Er2. When the switch Sw2 is turned on, the activation signal St is supplied to the comparison operation circuit 41. When the switch Sw2 is turned off, the supply of the activation signal St is stopped.

The comparison operation circuit 41 is supplied with a feed command value Cw. The comparison operation circuit 41 is supplied with a feed feedback value Fw from a cycle conversion circuit 43 described later.
In response to the H level activation signal St, the comparison operation circuit 41 calculates the feed command value Cw and the feed feedback value Fw to generate the control value Ea. The comparison calculation circuit 41 generates the control value Ea so as to minimize the difference between the feed command value Cw and the feed feedback value Fw. The calculation process is, for example, a PID calculation. The proportionality coefficient is Kp, the differential coefficient is Kd, and the integration coefficient is Ki.

  The comparison operation circuit 41 is a digital processing circuit that performs an operation process every predetermined time. The comparison calculation circuit 41 has a storage circuit such as a register, and stores each value (feed command value Cw, feed feedback value Fw) for each calculation process.

  A control value Ea calculated at a predetermined time (t) is defined as Ea (t). The comparison operation circuit 41 stores the feed command value Cw (t) and the feed feedback value Fw (t) at this time (t). The comparison operation circuit 41 includes the feed command values Cw (t-1), Cw (t-2), the feed feedback value Fw (t-1) at the past times (t-1) and (t-2), Fw (t-2) is stored.

An arithmetic expression in the PID calculation is, for example, the following expression (1).
Ea (t) = Kp × (e (t) −e (t−1)) + Ki × e (t)
+ Kd × ((e (t) −e (t−1)) − (e (t−1) −e (t−2))) (1)
e (t) = Cw (t) -Fw (t)
e (t-1) = Cw (t-1) -Fw (t-1)
e (t-2) = Cw (t-2) -Fw (t-2)
The comparison operation circuit 41 reads each value from the memory and calculates the value of the control value Ea (t) according to the above equation (1). Then, the comparison operation circuit 41 outputs the calculated control value Ea. The control value Ea is supplied to the switch Sw1.

  The switch Sw1 has switching terminals Ta and Tb and a common terminal Tc. The control value Ea from the comparison operation circuit 41 is supplied to the switching terminal Ta, and the feed reference value Ms from the reference value setting circuit 45 is supplied to the switching terminal Tb. The common terminal Tc is connected to the drive circuit 32. The switch Sw1 switches and connects the common terminal Tc to the switching terminal Ta and the switching terminal Tb based on the abnormality detection signal Er1 from the abnormality detection circuit 44. For example, the switch Sw1 connects the common terminal Tc to the switching terminal Ta based on the L level abnormality detection signal Er1. As a result, the control value Ea from the comparison operation circuit 41 is supplied to the drive circuit 32. The switch Sw1 connects the common terminal Tc to the switching terminal Tb based on the H level abnormality detection signal Er1. As a result, the feed reference value Ms from the reference value setting circuit 45 is supplied to the drive circuit 32.

  The drive circuit 32 outputs a drive signal Dr with a pulse corresponding to the control value Ea or the feed reference value Ms supplied via the switch Sw1. The motor M1 is rotated by the drive signal Dr. The rotary encoder R1 outputs a pulse signal Re having a period corresponding to the rotation speed of the motor M1.

  The period measurement circuit 42 measures the pulse period of the pulse signal Re from the rotary encoder R1, and outputs a pulse period value Ps (hereinafter, pulse period Ps), which is the measurement result. In the present embodiment, the period measurement circuit 42 measures a half period of the pulse signal Re.

  For example, the period measuring circuit 42 includes a timer circuit, and outputs the time (count value) counted by the timer circuit as the pulse period Ps. The period measurement circuit 42 generates an interrupt at each rising edge and falling edge of the pulse signal Re. The period measurement circuit 42 holds (holds) the count value of the timer circuit based on the interrupt, outputs the held count value as the pulse period Ps, and resets the count value (= 0). Note that the period measurement circuit 42 resets the count value of the timer circuit (= 0) at the time of activation (for example, based on the activation signal St) and starts counting.

  Therefore, the pulse period Ps alternately indicates the interval between interrupts generated by the rise and fall of the pulse signal Re, that is, the H level period and the L level period of the pulse signal Re.

  On the other hand, when the pulse signal Re is at a constant level (for example, L level), the value of the pulse period Ps continues to increase. Therefore, when the pulse signal Re is at a constant level, the pulse period Ps indicates a period during which the pulse signal Re is at a constant level.

The cycle conversion circuit 43 converts the pulse cycle Ps from the cycle measurement circuit 42 into a feed feedback value Fw corresponding to the feed command value Cw. In the present embodiment, the feed command value Cw is a target rotation speed of the motor M1. Therefore, the cycle conversion circuit 43 converts the pulse cycle Ps into a feed feedback value Fw that is the rotational speed of the motor M1. For example, the cycle conversion circuit 43 converts the pulse cycle Ps into the feed feedback value Fw according to the following equation (2).
Fw = 1 / (Px × (2 × Ps)) (2)
Note that Px in the above equation (2) is the number of pulses of the pulse signal Re output by the rotary encoder R1 by rotating the motor M1 once.

  The abnormality detection circuit 44 has a storage circuit such as a register, and stores two abnormality detection set times Et1 and Et2 in this storage circuit. The abnormality detection set time Et1 is set to a value (Et1 <Et2) smaller than the abnormality detection set time Et2. For example, the abnormality detection set time Et1 is set to 100 to 150 milliseconds (ms), and the abnormality detection set time Et2 is set to 500 to 700 milliseconds (ms).

  The abnormality detection circuit 44 compares the pulse period Ps from the period measurement circuit 42 with the abnormality detection set time Et2, and outputs an abnormality detection signal Er2 corresponding to the comparison result. The abnormality detection circuit 44 compares the pulse period Ps from the period measurement circuit 42 with the abnormality detection set time Et1, and outputs an abnormality detection signal Er1 corresponding to the comparison result.

  For example, the abnormality detection circuit 44 outputs L level abnormality detection signals Er1 and Er2 by initialization. The switch Sw2 is turned on in response to the L level abnormality detection signal Er2. The activation signal St is supplied to the comparison operation circuit 41 through the switch Sw2 that is turned on. The switch Sw1 connects the common terminal Tc to the switching terminal Ta in response to the L level abnormality detection signal Er1. As a result, the control value Ea from the comparison operation circuit 41 is supplied to the drive circuit 32 via the switch Sw1. The drive circuit 32 outputs a drive signal Dr corresponding to the control value Ea. The motor M1 rotates according to the drive signal Dr.

  The abnormality detection circuit 44 outputs an abnormality detection signal Er1 of H level when the pulse period Ps is greater than the abnormality detection set time Et1 and less than or equal to the abnormality detection set time Et2 (Et1 <Ps ≦ Et2). At this time, the abnormality detection circuit 44 outputs an L level abnormality detection signal Er2.

  The switch Sw2 is kept on by the abnormality detection signal Er2 of L level. The switch Sw1 connects the common terminal Tc to the switching terminal Tb by an H level abnormality detection signal Er1. As a result, the feed reference value Ms from the reference value setting circuit 45 is supplied to the drive circuit 32 via the switch Sw1. The drive circuit 32 outputs a drive signal Dr corresponding to the feeding reference value Ms. The motor M1 rotates according to the drive signal Dr.

  The abnormality detection circuit 44 outputs, for example, an H level abnormality detection signal Er2 and an L level abnormality detection signal Er1 when the pulse period Ps is longer than the abnormality detection set time Et2 (Et2 <Ps). The switch Sw2 is turned off in response to the H level abnormality detection signal Er2. As a result, the supply of the activation signal St to the comparison operation circuit 41 is stopped. The switch Sw1 connects the common terminal Tc to the switching terminal Ta in response to the L level abnormality detection signal Er1. As a result, the control value Ea from the comparison operation circuit 41 is supplied to the drive circuit 32 via the switch Sw1.

  Since the start signal St is not supplied to the comparison operation circuit 41 when the switch Sw2 is turned off, the comparison operation circuit 41 generates the control value Ea so as to stop the motor M1. The switch Sw1 connects the common terminal Tc to the switching terminal Ta based on the L level abnormality detection signal Er1. Thereby, the control value Ea is supplied to the drive circuit 32, and the motor M1 is stopped. Therefore, when the no-pulse state in which the pulse signal Re does not change in a pulse shape exceeds the abnormality detection set time Et2, the motor M1 is stopped. Thereby, supply of the welding wire 15 is stopped.

  The abnormality detection set time Et2 is a time set for detecting an encoder abnormality and stopping the feeding of the welding wire 15. The abnormality detection setting time Et1 smaller than the abnormality detection setting time Et2 is a time set to limit feeding of the welding wire when there is a possibility of encoder abnormality or encoder abnormality.

  The encoder abnormality includes abnormality relating to the rotary encoder R1, for example, failure of the rotary encoder R1, disconnection (wiring between the rotary encoder R1 or the motor M1 and the motor driving device 30, etc.). As described above, the pulse cycle Ps indicates a half cycle of the pulse signal Re when the pulse signal Re changes in a pulse shape, and when the pulse signal Re is at a constant level more than the assumed cycle (half cycle). Shows the period (elapsed time since the last reset).

  When no encoder abnormality has occurred, the pulse signal Re changes in a pulse shape according to the rotation of the motor M1. Therefore, the feeding feedback value Fw calculated by the above equation (2) changes according to the rotation speed of the motor M1. Then, based on the control value Ea calculated according to the feeding feedback value Fw, the rotation of the motor M1 is controlled so that the feeding feedback value Fw matches the feeding command value Cw.

  On the other hand, when the encoder abnormality occurs, the pulse signal Re becomes a constant level. In the case of the pulse signal Re at a constant level, the feed feedback value Fw generated by the cycle conversion circuit 43 is substantially “0”. The comparison operation circuit 41 calculates the control value Ea based on the feeding feedback value Fw whose value is substantially “0”. Based on this control value Ea, the motor M1 is driven at the maximum rotational speed, and the welding wire 15 is fed. Accordingly, when an encoder abnormality occurs, excessive welding wire 15 is fed. Such excessive supply of the welding wire 15 causes unnecessary consumption of the welding wire and deterioration of the welding quality.

The abnormality detection circuit 44 outputs an abnormality detection signal Er1 of H level when the pulse period Ps becomes longer than the abnormality detection set time Et1.
The switch Sw1 connects the common terminal Tc to the switching terminal Tb in response to the H level abnormality detection signal Er1. As a result, the feed reference value Ms output from the reference value setting circuit 45 is supplied to the drive circuit 32 via the switch Sw1. Based on the feed reference value Ms, the drive circuit 32 outputs a drive signal Dr having a pulse width corresponding to the feed reference value Ms. Therefore, the rotation speed of the motor M1 becomes a value according to the feeding reference value Ms. The welding wire 15 is fed by the rotation of the motor M1.

  When the feed command value Cw is a relatively large value, the feed reference value Ms of the reference value setting circuit 45 is set according to the feed command value Cw, for example. When the encoder abnormality occurs as described above, the motor M1 rotates at the maximum number of rotations. This maximum rotational speed is larger than the feed command value Cw. Then, the motor M1 rotates at the maximum rotational speed until the abnormality detection circuit 44 outputs the H level abnormality detection signal Er1. Therefore, the feed reference value Ms is set so that the motor M1 rotates at a rotational speed corresponding to the feed command value Cw. Thereby, the feeding amount of the welding wire 15 after the abnormality detection set time Et1 becomes approximately the same as when no encoder abnormality occurs. Further, by setting the abnormality detection set time Et1 to a small value, the period during which the motor M1 rotates at the maximum rotation speed is shortened, and the feeding amount of the welding wire 15 is reduced.

  When the feed command value Cw is a relatively small value, the feed reference value Ms is set assuming a high load for feeding the welding wire 15. When the feed command value Cw is a relatively small value, if the feed reference value Ms is set according to the feed command value Cw, the feed reference value Ms is also reduced. With the feed reference value Ms set in this way, the motor M1 does not rotate (for example, in the case of a high load), and thus a pulse signal Re that changes in a pulse shape cannot be obtained. For this reason, the feeding feedback value Fw is almost “0”, and it is determined that the encoder is abnormal.

  For example, the supply device 12 shown in FIG. 1 is connected to the welding torch 13 via a one-wire power cable. For example, the one-line power cable is provided with a coil liner for guiding the welding wire 15 at the center, and a hose for flowing gas on the outer periphery thereof. And the outer periphery of this hose is coat | covered with the conductive wire for supplying welding electric power, and the outermost periphery is insulation-coated.

  Therefore, the welding wire 15 is sent from the supply device 12 to the welding torch 13 while being in sliding contact with the inner periphery of the one-wire power cable. For this reason, the resistance (load) with respect to feeding of the welding wire 15 arises, for example, by the debris of the welding wire 15 scraped off by the power cable. Further, resistance (load) is generated when the welding wire 15 is fed depending on the bending rate of the power cable and the material and thickness of the welding wire 15.

  Such a load is a factor that hinders the rotation of the motor M1. When the load is high, the motor M1 is difficult to rotate. If the motor M1 does not rotate, the pulse signal Re that changes in a pulse shape cannot be obtained, and the feed feedback value Fw is substantially “0”. In this case, it is determined that the encoder is abnormal. That is, even if there is no failure in the signal line or the like, the no-pulse state continues for the abnormality detection set time Et2 or longer, and it is erroneously determined as an encoder abnormality.

  In such a state, the motor M1 can be rotated by supplying a drive signal Dr with a wide pulse width from the drive circuit 32. Even at such a high load, the feed reference value Ms is set so that the motor M1 is rotated. Thus, the abnormality detection set time Et2 is set so that the rotation of the motor M1 can be confirmed by the feed reference value Ms at a high load. In other words, the feed reference value Ms is set so that the motor M1 is rotated by the abnormality detection set time Et2 even when the load is high.

Next, the operation (action) of the motor drive device 30 will be described.
First, normal operation will be described.
As shown in FIG. 3, a feed command value Cw is set. The motor drive device 30 shown in FIG. 2 outputs a drive signal Dr based on the feed command value Cw and the feed feedback value Fw. The drive signal Dr rotates the motor M1, and a pulsed pulse signal Re is generated. The motor drive device 30 converts the cycle of the pulse signal Re into a feed feedback value Fw.

  Immediately after the feed command value Cw is given stepwise, the feed feedback value Fw is “0”. The feed feedback value Fw increases as the motor M1 rotates. Then, the motor drive device 30 controls the drive signal Dr so that the feed feedback value Fw matches the feed command value Cw. The welding wire 15 is fed by the motor M1 that is rotated by the drive signal Dr.

Next, a case where the encoder is abnormal will be described.
As an example, a case where the encoder is abnormal when the arc welder 10 is started will be described. In this case, the pulse period Ps indicates the elapsed time from the start of the arc welding machine 10.

As shown in FIG. 4, a feed command value Cw is set. The motor drive device 30 shown in FIG. 2 outputs a drive signal Dr based on the feed command value Cw and the feed feedback value Fw.
When the encoder is abnormal, the pulse signal Re at the input terminal of the period measuring circuit 42 shown in FIG. 2 is at a constant level. Therefore, as shown in FIG. 4, the feeding feedback value Fw remains “0”. The motor drive device 30 increases the control value Ea so that the feed feedback value Fw matches the feed command value Cw. As a result, the motor M1 has the maximum rotation speed. The welding wire 15 is fed at a speed Ws corresponding to the rotation of the motor M1. Note that the solid line Wc shown in the lower part of FIG. 4 indicates the feeding speed of the welding wire 15 when the motor M1 is rotated at the feeding command value Cw.

  When the pulse period Ps reaches or exceeds the abnormality detection set time Et1 (time T1), the motor driving device 30 shown in FIG. 2 generates an H level abnormality detection signal Er1 and controls the switch Sw1 to control the reference value setting circuit 45. Is supplied to the drive circuit 32. The drive circuit 32 generates a drive signal Dr corresponding to the feeding reference value Ms. The feeding reference value Ms is set according to the feeding command value Cw. Thereby, the feeding speed Ws of the welding wire 15 becomes low.

  When the pulse period Ps reaches or exceeds the abnormality detection set time Et2 (time T2), the motor drive device 30 shown in FIG. 2 generates an H level abnormality detection signal Er2 and turns off the switch Sw2. Further, the motor drive device 30 generates an L level abnormality detection signal Er1 to control the switch Sw1, and supplies the control value Ea from the comparison operation circuit 41 to the drive circuit 32. The drive circuit 32 generates a drive signal Dr corresponding to the control value Ea. At this time, the comparison operation circuit 41 generates the control value Ea so as to stop the motor M1 when the start signal St is stopped by turning off the switch Sw2. Therefore, the pulsed drive signal Dr is stopped and the motor M1 is stopped. Thereby, supply of the welding wire 15 is stopped.

  When an encoder abnormality occurs during use of the arc welder 10, the rotational speed of the motor M1 increases from the rotational speed corresponding to the feed command value Cw to the maximum rotational speed. Thereafter, when the pulse period Ps becomes equal to or longer than the abnormality detection set time Et1, the rotation speed is reduced to the number corresponding to the feed reference value Ms. The welding wire 15 is fed at a speed Ws corresponding to the rotation of the motor M1. When the pulse period Ps becomes abnormal in the abnormality detection set time Et2, the motor M1 is stopped. Thereby, the supply of the welding wire 15 is stopped.

Next, the operation when the load is high and the feed command value Cw is low will be described.
As shown in FIG. 5, a feed command value Cw is set. The motor drive device 30 shown in FIG. 2 outputs a drive signal Dr based on the feed command value Cw and the feed feedback value Fw.

  When the load is high, the motor M1 is difficult to rotate. Therefore, since the pulse-like pulse signal Re is not generated, the feeding feedback value Fw remains “0”. The motor drive device 30 increases the control value Ea so that the feed feedback value Fw matches the feed command value Cw. As a result, the pulse width of the drive signal Dr becomes wider.

  When the pulse period Ps reaches or exceeds the abnormality detection set time Et1 (time T1), the motor driving device 30 shown in FIG. 2 generates an H level abnormality detection signal Er1 and controls the switch Sw1 to control the reference value setting circuit 45. Is supplied to the drive circuit 32. The drive circuit 32 generates a drive signal Dr corresponding to the feeding reference value Ms. In this case, the feed reference value Ms is set so that the motor M1 rotates by the abnormality detection set time Et2 even when the load is high.

  When the motor M1 is rotated by the drive signal Dr, a pulsed pulse signal Re is generated. The feed feedback value Fw increases with the period of the pulse signal Re. Further, an L level abnormality detection signal Er1 is generated by the pulse period Ps, the switch Sw1 is controlled, and the control value Ea from the comparison operation circuit 41 is supplied to the drive circuit 32. Therefore, the drive signal Dr corresponding to the control value Ea is generated, and the motor M1 rotates. Therefore, at the time T2 when the elapsed time from the supply of the start signal St becomes the abnormality detection set time Et2, the pulse period Ps is not larger than the abnormality detection set time Et2, so that the rotation of the motor M1 continues without being determined as an encoder abnormality. Then, the welding wire 15 is fed.

Next, a comparative example for this embodiment will be described.
In the description of the comparative example, the same reference numerals are used for the same members as in the present embodiment.
In the motor drive device 30 of the comparative example shown in FIG. 6, the control value Ea from the comparison operation circuit 41 is directly supplied to the drive circuit 32. The abnormality detection circuit 44a compares the pulse period Ps with the abnormality detection set time Eta and outputs an abnormality detection signal Era. The abnormality detection set time Eta is equal to, for example, the abnormality detection set time Et2 of the above embodiment. The switch Swa is turned on / off based on the abnormality detection signal Era.

  As shown in FIG. 7, when an encoder abnormality occurs in the comparative example, the motor M1 is rotated at the maximum number of revolutions by the drive signal Dr until time T21 when the pulse period Ps becomes greater than the abnormality detection set time Eta. The welding wire 15 is fed at a speed Ws corresponding to the rotation of the motor M1.

  On the other hand, in the present embodiment, the abnormality detection set time Et1 smaller than the abnormality detection set time Et2 is compared with the pulse period Ps, and according to the comparison result, according to the feeding reference value Ms from the reference value setting circuit 45. A drive signal Dr is generated. Thereby, the rotation speed of the motor M1 is kept lower than the maximum rotation speed. Therefore, the period during which the welding wire 15 is fed by the motor M1 having the maximum rotation speed is shortened, and the feeding amount of the welding wire 15 is suppressed.

  In the comparative example, it is conceivable to set the abnormality detection setting time Eta small. For example, the abnormality detection set time Eta is made equal to the abnormality detection set time Et1 of the present embodiment. With this setting, it is possible to shorten the period during which the motor M1 rotates at the maximum rotation speed. However, such a setting increases false detection.

  For example, as shown in FIG. 8, in the case of a high load and a small feed command value Cw, the motor M1 is difficult to rotate. In this case, the no-pulse state of the pulse signal Re continues. Thereafter, a pulsed pulse signal Re is generated by the rotation of the motor M1, and the feed feedback value Fw increases. However, at the abnormality detection set time Eta set so as to shorten the period during which the motor M1 rotates at the maximum rotation speed, the motor M1 has not yet rotated at time T22 when the pulse period Ps becomes larger than the abnormality detection set time Eta. There is a case. In this case, in the comparative example, erroneous detection is made in which it is determined that the encoder is abnormal even though the signal line of the pulse signal Re is not abnormal. Due to this erroneous detection, the motor M1 is stopped.

  In this regard, in this embodiment, the encoder abnormality is determined by comparing the pulse period Ps with the abnormality detection set time Et2. Therefore, in the present embodiment, the erroneous detection as described above is suppressed.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The comparison calculation circuit 41 compares the feed command value Cw and the feed feedback value Fw and outputs a control value Ea. The period measurement circuit 42 measures the pulse period Ps of the pulse signal Re output from the rotary encoder R1 according to the rotation speed of the motor M1. The cycle conversion circuit 43 converts the pulse cycle Ps into a feed feedback value Fw.

  The abnormality detection circuit 44 compares the pulse period Ps with the abnormality detection set time Et1, and outputs an abnormality detection signal Er1. The switch Sw1 selectively switches between the control value Ea from the comparison operation circuit 41 and the feeding reference value Ms from the reference value setting circuit 45 based on the abnormality detection signal Er1. The drive circuit 32 outputs a drive signal Dr for rotating the motor M1 according to the control value Ea or the feed reference value Ms switched by the switch Sw1.

  When an abnormality occurs in which the pulse signal Re in the period measurement circuit 42 does not change in a pulse shape, the motor M1 is rotated by the drive signal Dr generated according to the feed reference value Ms selectively switched by the abnormality detection signal Er1. Let By setting the feed reference value Ms, the motor M1 can be rotated at a rotational speed lower than the maximum rotational speed. As a result, since the welding wire 15 is fed by the motor M1, excessive feeding of the welding wire 15 can be suppressed by suppressing the rotational speed of the motor M1.

  (2) The comparison operation circuit 41 outputs a control value Ea corresponding to the feed command value Cw and the feed feedback value Fw based on the supply of the activation signal St. Then, the comparison operation circuit 41 outputs the control value Ea so as to stop the motor M1 in response to the stop of the supply of the start signal St. By generating the drive signal Dr with this control value Ea, it becomes possible to stop the motor M1 and stop the feeding of the welding wire 15 by the motor M1.

  (3) The period measuring circuit 42 generates an interrupt at each rising edge and falling edge of the pulse signal Re, and measures the period (half period) of the pulse signal Re. That is, the period measuring circuit 42 measures the half cycle from the rising edge to the falling edge of the pulse signal Re and the half period from the falling edge to the rising edge of the pulse signal Re. Therefore, the pulse signal Re indicates the elapsed time from the rise or fall. For this reason, for example, when an encoder abnormality occurs at either the H level or the L level of the pulse signal Re, the elapsed time from the encoder abnormality can be measured. Based on the elapsed time, it is possible to reliably control the rotation speed of the motor M1 and stop the motor M1.

In addition, you may implement the said embodiment in the following aspects.
In contrast to the above-described embodiment, the abnormality detection circuit 44 outputs, for example, an H level abnormality detection signal Er2 when the pulse period Ps is equal to or longer than the abnormality detection set time Et2 (Ps ≧ Et2), and the pulse period Ps is set to be abnormal detection. For example, an L level abnormality detection signal Er2 may be output when the time is less than Et2 (Ps <Et2). Similarly, the abnormality detection circuit 44 outputs, for example, an H level abnormality detection signal Er1 when the pulse period Ps is equal to or greater than the abnormality detection set time Et1 (Ps ≧ Et1), and the pulse period Ps is smaller than the abnormality detection set time Et1. For example, the L level abnormality detection signal Er1 may be output when (Ps <Et1).

  Note that the comparison in the abnormality detection set times Et1 and Et2 with respect to the pulse period Ps may be different. For example, when the pulse period Ps is equal to or longer than the abnormality detection set time Et2 (Ps ≧ Et2), for example, an H level abnormality detection signal Er2 is output, and when the pulse period Ps is greater than the abnormality detection set time Et1 (Ps> Et1). For example, an H level abnormality detection signal Er1 may be output.

  In the above embodiment, the period measurement circuit 42 measures either the half cycle from the rising edge to the falling edge of the pulse signal Re or the half period from the falling edge to the rising edge based on the interrupt signal. Also good.

  In the above embodiment, the period measurement circuit 42 may measure one period of the pulse signal Re based on one of the interrupt corresponding to the rising edge and the interrupt corresponding to the falling edge. In this case, the cycle conversion circuit 43 shown in FIG. 2 converts the pulse cycle Ps into the feed feedback value Fw according to the measurement cycle of the cycle measurement circuit 42. Even if it does in this way, the effect similar to the said embodiment can be acquired.

  In the above embodiment, the abnormality detection set times Et1 and Et2 may be changeable. For example, an input device such as a keypad is connected to the arc welder 10 shown in FIG. 1 by wire or wirelessly, and the abnormality detection set times Et1 and Et2 are set by the input device. For example, the abnormality detection setting time Et1 is set to the minimum value (for example, “0”) in the settable range. In this case, an H level abnormality detection signal Er1 is output when the arc welder 10 is started, and the motor M1 is driven at a rotational speed corresponding to the feed reference value Ms. Therefore, the motor M1 does not rotate at the maximum rotation speed. For example, by setting the feed reference value Ms according to the feed command value Cw, the welding wire 15 can be fed at a speed according to the feed reference value Ms (= feed command value Cw). it can. Then, by setting the abnormality detection set time Et2 to the maximum value within the settable range, the arc welding process can be continued until the abnormality detection set time Et2.

  In the above embodiment, the pulse signal Re corresponding to the rotation speed of the motor M1 is generated by the rotary encoder R1 connected to the motor M1. The motor M1 feeds the welding wire 15, and the cycle of the pulse signal Re from the rotary encoder R1 corresponds to the feeding speed of the welding wire 15 fed by the motor M1. Therefore, for example, the rotary encoder R1 may be connected to a roller that guides the welding wire 15 to generate the pulse signal Re having a period corresponding to the feeding speed of the welding wire 15.

  In the above embodiment, the pulse signal Re corresponding to the rotation speed of the motor M1 is generated by the rotary encoder R1 connected to the motor M1. Instead of the rotary encoder R1, a pulse signal corresponding to the number of rotations of the motor M1 may be generated by a rotation sensor using a Hall element or the like.

DESCRIPTION OF SYMBOLS 10 Arc welding machine 11 Welding power supply 12 Supply apparatus 15 Welding wire (consumable electrode)
41 Comparison Operation Circuit 42 Period Measurement Circuit 43 Period Conversion Circuit 44 Abnormality Detection Circuit 45 Reference Value Setting Circuit M1 Motor R1 Rotary Encoder (Rotation Sensor)
Sw1, Sw2 switch (switching circuit)
Dr drive signal Ea Control value Cw Feeding command value Ms Feeding reference value Fw Feeding feedback value (feeding feedback value)
Ps Pulse period Re Pulse signal Er1 Abnormality detection signal (first abnormality detection signal)
Er2 abnormality detection signal (second abnormality detection signal)
Et1 abnormality detection set time (first abnormality judgment value)
Et2 abnormality detection set time (second abnormality determination value)

Claims (5)

A motor driving device that is included in a welding machine that performs welding with a consumable electrode and drives a motor that feeds the consumable electrode,
A comparison operation circuit that generates a control value by comparing the feed command value and the feed feedback value;
A reference value setting circuit for outputting a feeding reference value;
A switching circuit for selectively switching and outputting the control value and the feeding reference value according to a first abnormality detection signal;
A drive circuit for outputting a drive signal for driving the motor in accordance with an output value of the switching circuit;
A period measuring circuit that outputs a value of a result of measuring a period of a pulse signal according to the rotation of the motor;
A signal conversion circuit for converting the output value of the period measurement circuit into the feeding feedback value;
An abnormality detection circuit that compares an output value of the period measurement circuit with a first reference determination value and outputs the first abnormality detection signal according to a comparison result;
A motor drive device comprising: The abnormality detection circuit compares the output value of the period measurement circuit with a second reference determination value larger than the first reference determination value, and outputs a second abnormality detection signal according to the comparison result;
A start signal for instructing start of feeding of the consumable electrode is provided, and a second switching circuit for switching supply or stop of supply of the start signal to the comparison operation circuit according to the second abnormality detection signal;
The comparison arithmetic circuit generates the control value to stop the motor in response to the supply stop of the start signal;
The motor driving device according to claim 1. When the abnormality detection circuit generates the second abnormality detection signal so as to stop the supply of the start signal, the first abnormality detection signal supplies the control value from the comparison operation circuit to the drive circuit. Generating,
The motor driving device according to claim 2. The period measurement circuit measures a half period of the pulse signal based on the rise and fall of the pulse signal and outputs a value of the measurement result;
The motor drive device according to claim 1, wherein the motor drive device is a motor drive device. A control method of a motor drive device included in a welding machine that performs welding with a consumable electrode and driving a motor that feeds the consumable electrode,
A control value is generated by comparing and calculating the feed command value and the feed feedback value,
Selecting the control value and the feed reference value according to a first abnormality detection signal, and generating a drive signal for driving the motor according to the selected control value or the feed reference value;
Measure the period of the pulse signal according to the rotation of the motor,
Converting the period of the pulse signal into the feed feedback value;
Comparing the period of the pulse signal with a first reference determination value, and generating the first abnormality detection signal according to the comparison result;
A method for controlling a motor driving device.