JP6443655B2 - Motor drive device and electric tool - Google Patents

Description

  The present invention relates to a motor drive device and a power tool for driving a motor, and more particularly to a motor drive device and a power tool used by being connected to an AC power source.

  In a conventional motor drive device used by connecting to a commercial AC power supply, the AC power from the commercial AC power supply is full-wave rectified by a rectifier circuit and then smoothed by a smoothing capacitor having a large capacitance, and the DC power is converted into an inverter. Input to the circuit. And an inverter circuit converts direct-current power into alternating current power, and supplies drive power to a motor. Based on this drive power, the motor is driven.

  FIG. 9 is a diagram for explaining voltage and current waveforms in a conventional motor driving apparatus having a smoothing capacitor. FIG. 9A shows the time change of the input voltage Vac input from the commercial AC power source to the rectifier circuit. FIG. 9B shows the time change of the input voltage Vinv input to the inverter circuit after rectification and smoothing. FIG. 9C shows the time of the input current Ic input to the smoothing capacitor after rectification. Showing change.

  In the above-described conventional motor driving apparatus, as shown in FIG. 9C, harmonic distortion occurs in the current waveform due to the smoothing capacitor. Therefore, there is a problem that a phase shift occurs between the input voltage and the input current to the inverter circuit, and the power source power factor decreases.

  In order to solve such a problem, in recent years, a motor drive device without a smoothing capacitor has been used. An example is shown in FIG. FIG. 10 is a circuit diagram showing an electrical configuration of a conventional motor driving apparatus 100 without a smoothing capacitor. The motor driving device 100 includes a motor 101, a rectifier circuit 102, a film capacitor 103, an inverter circuit 104, a noise absorbing capacitor 105, and a backflow prevention diode 106, and is used by being connected to a commercial AC power source 200.

  In the motor drive device 100, the rectifier circuit 102 performs full-wave rectification on the AC power from the commercial AC power supply 200 and converts it to DC power. The film capacitor 103 is a capacitor having a small electrostatic capacity for absorbing high frequency noise. The inverter circuit 104 converts the DC power from the rectifier circuit 102 into AC power and supplies the AC power to the motor 101.

  The noise absorption capacitor 105 and the backflow prevention diode 106 are connected in series to each other and are connected in parallel to the inverter circuit 104. The noise absorbing capacitor 105 absorbs and accumulates regenerative power output from the inverter circuit 104, external noise superimposed from the outside, and the like. The backflow prevention diode 106 connects the cathode to the noise absorption capacitor 105 and prevents the energy stored in the noise absorption capacitor 105 from flowing into the inverter circuit 104.

  In the motor driving device 100 shown in FIG. 10, since a smoothing capacitor having a large capacitance is not provided, the power source power factor can be improved. On the other hand, the backflow prevention diode 106 is used in the discharge direction from the noise absorbing capacitor 105. Since the current is cut off, when the motor 101 is continuously driven for a long time, the amount of energy accumulated in the noise absorbing capacitor 105 is increased. For this reason, there is a problem that the voltage across the noise absorbing capacitor 105 increases and the inverter circuit 104 is damaged.

  In order to solve such a problem, the following Patent Document 1 discloses a motor driving device that reduces the rotation speed of the motor and suppresses the voltage increase of the noise absorbing capacitor when the voltage across the noise absorbing capacitor increases. ing.

JP 2008-118759 A

  However, in the motor drive device disclosed in Patent Document 1, a sufficient output cannot be obtained because the rotational speed of the motor is reduced. For example, when incorporated in a power tool, the operability and workability are impaired. was there. Further, when the driving is continued by lowering the rotation speed of the motor, the voltage of the noise absorbing capacitor continues to rise without being lowered although the rising speed is suppressed. Therefore, in order to prevent damage to the circuit, the motor has to be stopped.

  Therefore, an object of the present invention is to provide a motor drive device and a power tool that can prevent circuit breakage. Moreover, it aims at providing the motor drive device and electric tool which can suppress the fall of a power supply power factor. Furthermore, it aims at providing the motor drive device and electric tool which can drive a motor continuously with a desired rotational speed.

In order to solve the above problems, a motor drive device according to the present invention converts a motor, a first circuit for rectifying AC power from an AC power source, and power output from the first circuit to supply the motor to the motor. An inverter circuit that is connected to the inverter circuit in parallel, and is a second circuit to which the power output from the first circuit is input, the backflow prevention means and the charge connected in series downstream of the backflow prevention means A second circuit having a storage means, a discharge means for discharging the charge stored in the charge storage means, connected downstream of the backflow prevention means and upstream of the charge storage means, and controlling discharge by the discharge means A control means, a both-end voltage detection means for detecting a voltage across the charge storage means, and a power supply voltage detection means for detecting the power supply voltage of the AC power supply, and the control means when the both-end voltage reaches a predetermined upper limit voltage , Release Discharge means is started, and when the both-ends voltage reaches a predetermined lower limit voltage after the discharge means starts discharge, the discharge is stopped, and a calculation means for calculating the predetermined lower limit voltage based on the power supply voltage It is further provided with the feature.
A motor driving apparatus according to the present invention includes a motor, a first circuit that rectifies AC power from an AC power supply, an inverter circuit that converts power output from the first circuit, and supplies the power to the motor, and an inverter A second circuit connected in parallel to the circuit and to which the electric power output from the first circuit is input, the backflow prevention means, the charge storage means connected in series downstream of the backflow prevention means, and the backflow prevention A second circuit connected to the downstream of the means and the upstream of the charge storage means for discharging the charge stored in the charge storage means; a control means for controlling discharge by the discharge means; A zero cross detecting means for detecting a zero cross of the AC power input to the circuit, and a time measuring means for measuring an elapsed time since the detection of the zero cross as a discharge control time. When the reached the predetermined time, characterized in that to initiate the discharge by the discharge means.
Furthermore, a motor driving apparatus according to the present invention includes a motor, a first circuit that rectifies AC power from an AC power supply, an inverter circuit that converts power output from the first circuit, and supplies the power to the motor, and an inverter A second circuit connected in parallel to the circuit and to which the electric power output from the first circuit is input, the backflow prevention means, the charge storage means connected in series downstream of the backflow prevention means, and the backflow prevention A second circuit having a discharge means connected to the downstream of the means and upstream of the charge storage means for discharging the charge stored in the charge storage means; and a control means for controlling discharge by the discharge means. The control means starts discharging by the discharging means while the input voltage of the AC power source input to the first circuit decreases from the maximum value to 0 and increases from the minimum value to 0.
The motor driving device according to the present invention includes a motor, a first circuit that rectifies AC power from an AC power source, an inverter circuit that converts power output from the first circuit and supplies the power to the motor, A second circuit connected in parallel to the inverter circuit and to which the electric power output from the first circuit is input. The second circuit is connected in series to the backflow prevention means and the downstream side of the backflow prevention means. It has a charge storage means, and a discharge means connected to the downstream of the backflow prevention means and the upstream of the charge storage means for discharging the charge stored in the charge storage means.

  According to such a configuration, since a smoothing capacitor having a large capacitance is not provided, it is possible to suppress a decrease in the power source power factor. Even when the motor is continuously driven for a long time, the charge accumulated in the charge accumulating means is discharged by the discharging means, so that an increase in voltage of the charge accumulating means can be suppressed. Therefore, the circuit can be prevented from being damaged without restricting the driving of the motor, and the motor can be continuously driven at a desired rotational speed for a long time. Moreover, when it is used by being incorporated in an electric tool, it becomes possible to work continuously at a desired output for a long time, and operability and workability are improved.

  The motor drive device described above preferably further includes control means for controlling discharge by the discharge means.

  According to such a configuration, the charge accumulated in the charge accumulating means can be discharged at an appropriate timing, so that an increase in voltage of the charge accumulating means can be suppressed and circuit damage can be prevented.

  The motor driving apparatus described above may further include a both-end voltage detection unit that detects a both-end voltage of the charge storage unit. In this case, it is preferable that the control means starts discharging by the discharging means when the both-ends voltage reaches a predetermined upper limit voltage.

  According to such a configuration, it is possible to reliably prevent the voltage across the charge accumulating means from rising above a predetermined upper limit voltage, and thus it is possible to reliably prevent damage to the circuit.

  The control means preferably stops the discharge when the both-ends voltage reaches a predetermined lower limit voltage after the discharge is started by the discharge means.

  According to this configuration, it is possible to reliably absorb noise while preventing damage to the circuit. Therefore, the motor can be driven stably even when connected to a generator and used with a long cord reel.

  The motor drive device described above preferably further includes power supply voltage detection means for detecting the power supply voltage of the AC power supply and calculation means for calculating a predetermined lower limit voltage based on the power supply voltage.

  According to this configuration, it is possible to stop the discharge of the charge storage unit at an appropriate timing, and it is possible to prevent the occurrence of an inrush current from the input of the AC power source to the charge storage unit, thereby preventing the circuit from being damaged. Therefore, the motor can be driven stably.

  The motor drive device described above may further include a zero cross detection unit that detects a zero cross of the AC power input to the first circuit, and a time measuring unit that measures an elapsed time from the detection of the zero cross as a discharge control time. . In this case, it is preferable that the control means starts discharge by the discharge means when the discharge control time reaches the first predetermined time.

  According to such a configuration, it becomes possible to control the timing of discharge by the discharge means by simple control, and it is possible to prevent the circuit from being damaged by suppressing the voltage rise of the charge storage means.

  The control means preferably stops the discharge when the discharge control time reaches the second predetermined time.

  According to this configuration, it is possible to reliably absorb noise while preventing damage to the circuit by simple control.

  In the motor drive device described above, the discharge means is preferably a switching element.

  According to such a configuration, by turning on / off the switching element, it becomes possible to control the discharge of the charge accumulated in the charge accumulating means, and it is possible to suppress the voltage rise of the charge accumulating means and prevent the circuit from being damaged.

  Moreover, it is preferable that a discharge means is a discharge resistance.

  According to such a configuration, the charge absorbed from the rectifying means side and accumulated in the charge accumulating means is converted into heat by the discharge resistance and released, so that the voltage increase of the charge accumulating means can be suppressed. Therefore, damage to the circuit can be prevented without complicated control.

  In the motor drive device described above, it is preferable that the second circuit further includes a Zener diode connected in series with the discharge resistor and connected in parallel with the charge storage unit.

  According to this configuration, since the charge is discharged when the voltage across the charge accumulating means exceeds a predetermined voltage, the circuit can be prevented from being damaged.

  A motor driving device according to the present invention includes a motor, a first circuit that rectifies AC power from an AC power supply, an inverter circuit that converts power output from the first circuit and supplies the power to the motor, A second circuit that branches from a current path that leads from one circuit to the inverter circuit, the second circuit comprising a backflow prevention element, a charge storage element connected in series downstream of the backflow prevention element, and a backflow prevention And a third circuit connected to the downstream of the device and upstream of the charge storage device for discharging the charge stored in the charge storage device.

  According to such a configuration, since a smoothing capacitor having a large capacitance is not provided, it is possible to suppress a decrease in the power source power factor. Even when the motor is continuously driven for a long time, the charge accumulated in the charge storage element is discharged by the third circuit, so that the voltage increase of the charge storage element can be suppressed. Therefore, the circuit can be prevented from being damaged without restricting the driving of the motor, and the motor can be continuously driven at a desired rotational speed for a long time.

  Moreover, the electric tool according to the present invention includes the motor driving device having the above-described configuration.

  According to such a configuration, even when the motor is continuously driven for a long time, it is possible to prevent the circuit from being damaged, so that it is possible to work continuously at a desired output for a long time. Therefore, operability and workability are improved.

  Furthermore, an electric power tool according to the present invention includes a motor, a first circuit that rectifies AC power from an AC power source, an inverter circuit that converts power output from the first circuit, and supplies the power to the motor, and an inverter circuit And a second circuit to which power output from the first circuit is input. The second circuit includes a backflow prevention element and a charge storage connected in series to the downstream side of the backflow prevention element. And a discharge means connected to the downstream of the backflow prevention element and upstream of the charge storage element for discharging the charge stored in the charge storage element.

  According to such a configuration, since a smoothing capacitor having a large capacitance is not provided, it is possible to suppress a decrease in the power source power factor. In addition, even when the motor is continuously driven for a long time, the charge accumulated in the charge storage element is discharged by the discharge means, so that the voltage increase of the charge storage element can be suppressed. Therefore, it is possible to prevent the circuit from being damaged without restricting the driving of the motor, and work can be continued for a long time with a desired output, so that operability and workability are improved.

  An electric power tool according to the present invention includes a motor, a first circuit that rectifies AC power from an AC power supply, an inverter circuit that converts power output from the first circuit and supplies the power to the motor, A second circuit branched from a current path from the circuit to the inverter circuit, the second circuit comprising: a backflow prevention element; a charge storage element connected in series downstream of the backflow prevention element; and a backflow prevention element And a third circuit connected to the downstream of the charge storage element and upstream of the charge storage element for discharging the charge stored in the charge storage element.

  According to such a configuration, since a smoothing capacitor having a large capacitance is not provided, it is possible to suppress a decrease in the power source power factor. Even when the motor is continuously driven for a long time, the charge accumulated in the charge storage element is discharged by the third circuit, so that the voltage increase of the charge storage element can be suppressed. Therefore, it is possible to prevent the circuit from being damaged without restricting the driving of the motor, and work can be continued for a long time with a desired output, so that operability and workability are improved.

  According to the motor driving device and the electric tool of the present invention, it is possible to prevent the circuit from being damaged and to continuously drive the motor at a desired rotation speed without reducing the power source power factor.

It is sectional drawing of the impact driver which concerns on embodiment of this invention. It is a circuit diagram which shows the electric constitution of the motor drive device which concerns on the 1st Embodiment and 2nd Embodiment of this invention. It is a flowchart which shows the on / off control operation | movement of the switching element in the motor drive device which concerns on the 1st Embodiment of this invention. It is a figure explaining the waveform of the voltage in the motor drive device which concerns on the 1st Embodiment of this invention, an electric current, and a signal. It is a flowchart which shows the on / off control operation | movement of the switching element in the motor drive device which concerns on the 2nd Embodiment of this invention. It is a figure explaining the waveform of the voltage in the motor drive device which concerns on the 2nd Embodiment of this invention, a timer count value, and a signal. It is a circuit diagram which shows the electric constitution of the motor drive device which concerns on the 3rd Embodiment of this invention. It is a circuit diagram which shows the electric constitution of the motor drive device which concerns on the 4th Embodiment of this invention. It is a figure explaining the waveform of the voltage and electric current in the conventional motor drive device which has a smoothing capacitor. It is a circuit diagram which shows the electrical constitution of the conventional motor drive device which does not provide a smoothing capacitor.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, the case where the present invention is applied to an impact driver will be described as an example.

  FIG. 1 is a cross-sectional view of an impact driver according to an embodiment of the present invention. The impact driver 50 corresponds to the electric tool of the present invention. As shown in FIG. 1, the impact driver 50 mainly includes a housing 52, a motor 11, a gear mechanism 54, a hammer 55, an anvil portion 56, an inverter circuit portion 14, and a power cord 58. Composed.

  The housing 52 is made of resin and forms an outer shell of the impact driver 50, and is mainly composed of a substantially cylindrical body portion 52a and a handle portion 52b extending from the body portion 53a. As shown in FIG. 1, the motor 11 is disposed in the body portion 52 a so that the axial direction thereof coincides with the longitudinal direction of the body portion 52 a, and the gear mechanism 54, the hammer 55, and the anvil portion 56 are The motor 11 is arranged side by side toward one end in the axial direction.

  A metal hammer case 68 in which the hammer 55 and the anvil part 56 are housed is disposed at the front side position in the body part 52a. The hammer case 68 has a substantially funnel shape whose diameter gradually decreases toward the front, and an opening 68a is formed at the front end portion, and a tip portion of a tip tool holding portion 66 described later is exposed from the opening 68a. An opening 55a is formed at the tip. In addition, an air inlet and an air outlet (not shown) are formed in the body 52a for sucking and discharging outside air into the body 52a by a cooling fan 64 described later. The motor 11 and the inverter circuit unit 14 are cooled by the outside air.

  The handle portion 52b extends downward from a substantially central position in the front-rear direction of the body portion 52a, and is configured integrally with the body portion 52a. A switch mechanism 59 is built in the handle portion 52b, and a power cord 58 that can be connected to a commercial AC power source extends at a distal end position in the extending direction. In the handle portion 52b, a trigger 60, which is an electronic switch, is provided at the base portion from the body portion 52a and at the front side position as an operation location of the operator. The trigger 60 is connected to the switch mechanism 59 and is used for switching between supply and interruption of drive power to the motor 11. A forward / reverse changeover switch 61 for switching the rotation direction of the motor 11 is provided at a connection portion between the handle portion 52b and the body portion 52a and immediately above the trigger 60.

  The motor 11 is a brushless motor, and as shown in FIG. 1, a rotor 11b including an output shaft 11e and a plurality of permanent magnets 11d, and a stator 11a including a plurality of coils 11c arranged at positions facing the rotor 11b. And mainly consists of The output shaft 11e is disposed in the body portion 52a so that the axial direction coincides with the front-rear direction, protrudes forward and backward from the rotor 11b, and is rotatably supported by the body portion 52a by a bearing at the protruding portion. . In the output shaft 11e, a cooling fan 64 that rotates coaxially with the output shaft 11e is provided at a portion protruding forward.

  The gear mechanism 54 is disposed in front of the motor 11. The gear mechanism 54 is a speed reduction mechanism configured by a planetary gear mechanism having a plurality of gears, and reduces the rotation of the output shaft 11 e and transmits it to the hammer 55. The hammer 55 includes a pair of collision portions 65 at the front end. Further, the hammer 55 is biased forward by a spring 55a, and is configured to be able to move backward against the biasing force.

  The anvil part 56 is disposed in front of the hammer 55 and is mainly composed of a tip tool holding part 66 and an anvil 67. The anvil 67 has a pair of impacted portions 67 a that are integrally formed with the tip tool holding portion 66 and are disposed opposite to the rotation center of the tip tool holding portion 66 behind the tip tool holding portion 66. When the hammer 55 rotates, one collision part 65 and one collided part 67a collide with each other, and the other colliding part 65 and the other collided part 67a collide with each other. 67 and the anvil 67 is hit. In addition, after the collision between the collision part 65 and the collided part 67a, the hammer 55 moves backward while rotating against the urging force of the spring 55a. When the collision part 65 gets over the collision part 67a, the elastic energy stored in the spring 55a is released, the hammer 55 moves forward, and the collision part 65 and the collision part 67a collide again. Become. The tip tool is detachably held in the opening 55a formed at the tip of the tip tool holding portion 66.

The inverter circuit section 14, a circular plate-shaped circuit board, MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or IGBT (Insulated Gate Bipolar Transistor) switching elements 14a is formed is provided, such as. The power cord 58 supplies power to each unit by connecting to a commercial AC power source.

  Next, the motor drive device according to the first embodiment of the present invention will be described with reference to FIGS.

  FIG. 2 is a circuit diagram showing an electrical configuration of the motor driving apparatus 10 according to the first embodiment of the present invention. The motor drive device 10 is incorporated in the impact driver 50 shown in FIG. 1, and as shown in FIG. 2, the motor 11, the rectifier circuit unit 12, the capacitor 13, the inverter circuit unit 14, the capacitor 15, the diode 16, and the switching element. 17, a power supply voltage detection circuit unit 18, a capacitor voltage detection circuit unit 19, a calculation unit 20, and a gate driver unit 21.

  In this embodiment, the motor 11 is composed of a three-phase brushless motor, and includes a rotor 11b (FIG. 1) and a stator 11a. The stator 11a has a cylindrical outer shape and includes three-phase stator windings U, V, and W that are star-connected.

  The rectifier circuit unit 12 is configured by bridge-connecting four diodes (not shown), and full-wave rectifies the AC voltage input from the commercial AC power supply 1. The rectifier circuit unit 12 corresponds to the first circuit of the present invention. In the present embodiment, the capacitor 13 is a film capacitor having a small capacitance, and absorbs high frequency noise.

  The inverter circuit unit 14 is configured by mounting six switching elements Q1 to Q6 connected in a three-phase bridge form on a substrate. The inverter circuit unit 14 receives the voltage that has been full-wave rectified by the rectifier circuit unit 12. The inverter circuit unit 14 converts this input voltage into an AC voltage and supplies it to the motor 11.

  As shown in FIG. 2, the capacitor 15, the diode 16, and the switching element 17 connect the capacitor 15 in series to the downstream side of the diode 16, and connect the switching element 17 downstream of the diode 16 and upstream of the capacitor 15. Thus, on the output side of the rectifier circuit unit 12, the current is connected from the rectifier circuit unit 12 to the inverter circuit unit 14 and is connected in parallel to the inverter circuit unit 14. The capacitor 15, the diode 16, and the switching element 17 constitute a second circuit of the present invention.

  The capacitor 15 is a noise absorbing capacitor provided to absorb regenerative power output from the inverter circuit unit 14 and external noise superimposed from the outside. In this embodiment, the capacitor 15 is a capacitor having a large capacitance, and can absorb both high-frequency noise and low-frequency noise. Here, the external noise is often generated, for example, when the motor driving device 10 is connected to a generator, used, when the commercial AC power supply 1 is in a bad state, or driven using a long cord reel. Noise. The capacitor 15 absorbs and accumulates such external noise and the like. The capacitor 15 corresponds to the charge storage means and the charge storage element of the present invention.

  The diode 16 is a backflow prevention diode, and has a cathode connected to the capacitor 15 and an anode connected to the inverter circuit unit 14. The diode 16 allows a current from the inverter circuit unit 14 to the capacitor 15, while blocking a current from the capacitor 15 to the inverter circuit unit 14. The diode 16 corresponds to the backflow prevention means and backflow prevention element of the present invention.

  The switching element 17 is, for example, a MOSFET, and its source is connected between the capacitor 15 and the cathode of the diode 16, and its drain is connected between the anode of the diode 16 and the inverter circuit unit 14. The gate of the switching element 17 is connected to the calculation unit 20. Switching element 17 cuts off current between capacitor 15 and inverter circuit section 14 together with diode 16 in the off state, and allows current from capacitor 15 to inverter circuit section 14 in the on state. The switching element 17 corresponds to the discharging means and the third circuit of the present invention.

  The power supply voltage detection circuit unit 18 is a circuit for detecting the input voltage Vac from the commercial AC power supply 1, and includes a diode 18a, a diode 18b, a resistor 18c, and a resistor 18d as shown in FIG. The anodes of the diode 18a and the diode 18b are connected to lines connecting the commercial AC power supply 1 and the rectifier circuit unit 12, respectively. The cathodes of the diode 18a and the diode 18b are connected to GND through the resistor 18c and the resistor 18d. The power supply voltage detection circuit unit 18 outputs the divided voltage of the resistor 18 c and the resistor 18 d to the calculation unit 20. The power supply voltage detection circuit unit 18 corresponds to the power supply voltage detection means of the present invention.

  The capacitor voltage detection circuit unit 19 is a circuit for detecting the voltage Vc across the capacitor 15, and includes a resistor 19a and a resistor 19b as shown in FIG. The resistor 19a and the resistor 19b are connected to each other in series, one end of which is connected between the capacitor 15 and the diode 16, and the other end is connected to GND. The capacitor voltage detection circuit unit 19 outputs the divided voltage of the resistor 19a and the resistor 19b to the calculation unit 20. The capacitor voltage detection circuit unit 19 corresponds to the both-end voltage detection means of the present invention.

  The arithmetic unit 20 is, for example, a microcomputer, and has a function of generating a drive signal based on a processing program and data, a function of storing information necessary for the processing program and various controls, a function of measuring time, and the like.

  The arithmetic unit 20 controls the energization direction and energization time of the stator windings U, V, and W so as to control the rotation direction and the rotation speed of the motor 11. The arithmetic unit 20 generates drive signals H1 to H6 for turning on / off the six switching elements Q1 to Q6 mounted on the inverter circuit unit 14.

  The arithmetic unit 20 is connected to the gate of the switching element 17 and controls the on / off of the switching element 17. The arithmetic unit 20 generates a control signal Vs for turning on the switching element 17 and supplies the generated control signal Vs to the gate of the switching element 17 at a predetermined timing. In addition, the arithmetic unit 20 stops supplying the control signal Vs to the gate of the switching element 17 at a predetermined timing. The computing unit 20 corresponds to the control means of the present invention.

  As shown in FIG. 2, the gate driver unit 21 is connected to the gates of the six switching elements Q1 to Q6 mounted on the inverter circuit unit 14. The gate driver unit 21 supplies the drive signals H1 to H6 generated by the calculation unit 20 to the gates of the switching elements Q1 to Q6.

  Here, each of the six switching elements Q1 to Q6 of the inverter circuit section 14 is connected to the gate driver section 21 and each drain or each source is connected to the stator windings U, V, and W of the motor 11. The The switching elements Q1 to Q6 perform a switching operation based on the drive signals H1 to H6 input from the gate driver unit 21, and supply the voltage supplied from the commercial AC power supply 1 via the rectifier circuit unit 12 to three phases (U phase). , V phase, W phase) The drive power is supplied to the stator windings U, V, W of the motor 11 as the voltages Vu, Vv, Vw.

  Next, the motor drive device 10 according to the first embodiment will be described in detail. In the present embodiment, the motor drive device 10 controls on / off of the switching element 17 based on the voltage across the capacitor 15.

  The calculation unit 20 is connected to the capacitor voltage detection circuit unit 19 as shown in FIG. The calculation unit 20 acquires the voltage Vc across the capacitor 15 based on the input from the capacitor voltage detection circuit unit 19 and monitors the voltage Vc across the capacitor 15.

  In addition, the calculation unit 20 stores a predetermined upper limit voltage Vmax in advance. When the voltage Vc across the capacitor 15 increases and reaches the upper limit voltage Vmax, the arithmetic unit 20 generates the control signal Vs and supplies the control signal Vs to the gate of the switching element 17. Thereby, the switching element 17 is turned on, and a current from the capacitor 15 to the inverter circuit unit 14 is allowed. That is, the capacitor 15 can be discharged.

  Here, the upper limit voltage Vmax stored by the calculation unit 20 is a numerical value set in advance based on, for example, the absolute rating values (breakdown voltage) of the switching elements Q1 to Q6 mounted on the inverter circuit unit 14. When switching elements Q1-Q6 are IGBTs and their absolute rating value is 600V, upper limit voltage Vmax is set to a value smaller than the absolute rating value of IGBT, for example, 480V corresponding to 80% of the absolute rating value.

The computing unit 20 also calculates a predetermined lower limit voltage Vmin based on the power supply voltage of the commercial AC power supply 1. The calculation unit 20 is connected to the power supply voltage detection circuit unit 18 as shown in FIG. The arithmetic unit 20 acquires the input voltage Vac from the commercial AC power source 1 based on the input from the power source voltage detection circuit unit 18, and acquires the power source voltage effective value Ve of the commercial AC power source 1 based on this. And the calculating part 20 calculates the minimum voltage Vmin based on following Numerical formula (1). The calculation unit 20 corresponds to the calculation means of the present invention.

  The arithmetic unit 20 stops the supply of the control signal Vs when the voltage Vc across the capacitor 15 decreases during the supply of the control signal Vs to the switching element 17 and reaches the lower limit voltage Vmin. As a result, the switching element 17 is turned off, and the current from the capacitor 15 is cut off. That is, the discharge from the capacitor 15 is stopped. Here, when the power supply voltage effective value Ve of the commercial AC power supply 1 is 100 V, for example, the lower limit voltage Vmin is set to about 141 V.

  The set value of the lower limit voltage Vmin of the capacitor 15 corresponds to the maximum value of the input voltage Vac from the commercial AC power supply 1. If the voltage Vc across the capacitor 15 is lowered to the input voltage Vac or less from the commercial AC power supply 1, a voltage is applied from the input voltage Vac to the capacitor 15 and an inrush current may flow. Therefore, the lower limit voltage Vmin is set so that the voltage Vc across the capacitor 15 does not drop below the input voltage Vac from the commercial AC power supply 1.

  Next, the operation of turning on / off the switching element 17 in the motor driving apparatus 10 according to the first embodiment will be described with reference to the flowchart shown in FIG. FIG. 3 is a flowchart showing an on / off control operation of the switching element 17 in the motor driving apparatus 10 according to the first embodiment of the present invention.

  When the motor driving device 10 is connected to the commercial AC power source 1 and power feeding from the commercial AC power source 1 is started, the input voltage Vac from the commercial AC power source 1 is input from the power source voltage detection circuit unit 18 to the arithmetic unit 20. The Based on this input, the arithmetic unit 20 acquires the power supply voltage effective value Ve of the commercial AC power supply 1 (step S101).

  Subsequently, the calculation unit 20 calculates the lower limit voltage Vmin based on the power supply voltage effective value Ve. The computing unit 20 calculates and stores the lower limit voltage Vmin based on the formula (1) (step S102).

  Next, the computing unit 20 determines whether the switching element 17 is in an on state or an off state (step S103). When power supply from the commercial AC power supply 1 is started, no control signal is input to the gate of the switching element 17, and the switching element 17 is in an off state (step S103: YES). In the OFF state of the switching element 17, the arithmetic unit 20 acquires the voltage Vc across the capacitor 15 based on the input from the capacitor voltage detection circuit unit 19, and compares the voltage Vc across the capacitor 15 with the upper limit voltage Vmax (step). S104). When the both-ends voltage Vc is less than the upper limit voltage Vmax (step S104: NO), the calculation unit 20 does not generate and supply the control signal, and the switching element 17 continues to be in the off state (step S106). The motor drive apparatus 10 returns to the process of step S103 after step S106. The calculation unit 20 continues to monitor the both-end voltage Vc until the both-end voltage Vc reaches the upper limit voltage Vmax in the off state of the switching element 17 (steps S103 to S104, S106).

  In step S104, when the both-ends voltage Vc is equal to or higher than the upper limit voltage Vmax (step S104: YES), the arithmetic unit 20 generates the control signal Vs and supplies it to the gate of the switching element 17. As a result, the switching element 17 is turned on (step S105), and discharging from the capacitor 15 is started. The motor drive apparatus 10 returns to the process of step S103 after step S105.

  Even after the switching element 17 is turned on, the arithmetic unit 20 continues to monitor the voltage Vc across the capacitor 15. The arithmetic unit 20 compares the both-ends voltage Vc and the lower limit voltage Vmin while the control signal Vs is being supplied to the switching element 17, that is, when the switching element 17 is on (step S103: NO) (step S107). When both-ends voltage Vc is larger than lower limit voltage Vmin (Step S107: NO), operation part 20 continues supply of control signal Vs, and switching element 17 continues an ON state (Step S109). The motor drive apparatus 10 returns to the process of step S103 after step S109. The calculation unit 20 continues to monitor the both-ends voltage Vc until the both-ends voltage Vc reaches the lower limit voltage Vmin in the ON state of the switching element 17 (steps S103, S107, S109).

  When the both-ends voltage Vc falls and becomes equal to or lower than the lower limit voltage Vmin (step S107: YES), the calculation unit 20 stops supplying the control signal Vs to the switching element 17. Thereby, the switching element 17 is turned off (step S108), and the discharge from the capacitor 15 is stopped. The motor drive apparatus 10 returns to the process of step S103 after step S108. The arithmetic unit 20 continues to monitor the voltage Vc at both ends.

  As described above, when the voltage Vc across the capacitor 15 rises and reaches the upper limit voltage Vmax, the switching element 17 is turned on and the charge accumulated in the capacitor 15 is discharged. Further, when the voltage Vc across the capacitor 15 decreases and reaches the lower limit voltage Vmin, the switching element 17 is turned off and the discharge from the capacitor 15 is stopped.

  FIG. 4 is a diagram for explaining voltage, current, and signal waveforms in the motor drive device 10 according to the first embodiment of the present invention. FIG. 4A shows the change over time of the input voltage Vac input from the commercial AC power supply 1 to the rectifier circuit unit 12. FIG. 4B shows the time change of the input voltage Vinv input to the inverter circuit unit 14, and FIG. 4C shows the time change of the input current Iinv input to the inverter circuit unit 14. 4D shows the time change of the voltage Vc across the capacitor 15, and FIG. 4E shows the time change of the control signal Vs output from the arithmetic unit 20. Here, FIG. 4A to FIG. 4E are waveform diagrams after a certain period of time has elapsed from the start of power supply from the commercial AC power supply 1 to the motor drive device 10.

  The voltage Vc across the capacitor 15 rises by absorbing regenerative power, external noise, and the like from the inverter circuit unit 14. When the both-end voltage Vc reaches the upper limit voltage Vmax, as shown in FIGS. 4D and 4E, the control signal Vs is output from the arithmetic unit 20, and the switching element 17 is turned on. As a result, the capacitor 15 can be discharged, and the voltage Vc across the capacitor 15 drops.

  When the voltage Vc across the capacitor 15 reaches the lower limit voltage Vmin, as shown in FIGS. 4D and 4E, the output of the control signal Vs is stopped and the switching element 17 is turned off. As a result, the discharge from the capacitor 15 is stopped, and the voltage Vc across the capacitor 15 rises again.

  The waveform of the input voltage Vinv to the inverter circuit unit 14 (FIG. 4B) is a waveform obtained by full-wave rectifying the input voltage Vac (FIG. 4A) from the commercial AC power supply 1 and the output period of the control signal Vs. Except for (FIG. 4 (e)), it is substantially similar. This is because the input voltage Vinv is not smoothed by disabling discharge from the capacitor 15. In the output period of the control signal Vs, the voltage value of the input voltage Vinv of the inverter circuit unit 14 increases compared to the case where the input voltage Vac becomes similar to the waveform obtained by full-wave rectification due to the discharge from the capacitor 15. Will be. This means that the energy stored in the capacitor 15 is applied to the inverter circuit unit 14, that is, the use efficiency of energy is improved.

  Further, the waveform of the input voltage Vinv and the waveform of the input current Iinv of the inverter circuit section 14 are substantially similar as shown in FIGS. 4B and 4C. This is because harmonic distortion does not occur in the input current Iinv by connecting the diode 16 in series with the capacitor 15, and the phases of the input voltage Vinv and the input current Iinv substantially match. Therefore, the power factor is greatly improved as compared with the case where a smoothing capacitor having a large capacity is provided.

  As described above, according to the motor drive device 10 of the present embodiment, the diode 16 and the switching element 17 are connected to the capacitor 15 for absorbing regenerative power, external noise, and the like from the inverter circuit unit 14. Until the voltage Vc at both ends of 15 reaches the upper limit voltage Vmax, the input current to the capacitor 15 is allowed, but the discharge from the capacitor 15 is disabled. Therefore, the occurrence of harmonic distortion in the current after rectification can be suppressed, and a reduction in power factor can be suppressed as compared with the case where a large-capacity smoothing capacitor is provided.

  Further, when the both-ends voltage Vc of the capacitor 15 reaches the upper limit voltage Vmax, the switching element 17 is turned on and discharge from the capacitor 15 is enabled, so that an excessive voltage increase of the capacitor 15 can be prevented. Therefore, it is possible to prevent the circuit from being damaged without restricting the driving of the motor 11, and the motor 11 can be continuously driven for a long time. At this time, the energy released from the capacitor 15 is applied to the motor 11 via the inverter circuit unit 14, so that the energy use efficiency is improved and the driving performance of the motor 11 can be improved. Further, since the rise of the voltage Vc across the capacitor 15 can be suppressed, the switching elements Q1 to Q6 of the inverter circuit unit 14 have high absolute rating values (withstand voltage) by appropriately setting the upper limit voltage Vmax ( For example, it is not necessary to use 600V), and an inexpensive switching element can be used.

  Further, after the discharge from the capacitor 15 is started, when the both-end voltage Vc decreases to the lower limit voltage Vmin, the switching element 17 is turned off, and the discharge from the capacitor 15 is disabled again. The motor 11 can be driven stably.

  Further, when the motor drive device 10 is used by being incorporated in an electric tool, it is possible to work continuously for a long time with a desired output, and operability and workability are improved.

  Next, a motor drive device according to a second embodiment will be described with reference to FIG. 2, FIG. 5, and FIG. The motor drive device according to the second embodiment has the same configuration as the motor drive device 10 according to the first embodiment shown in FIG. 2, and in this embodiment, the elapsed time from the zero cross described later. Based on the above, on / off of the switching element 17 is controlled.

  In the present embodiment, the power supply voltage detection circuit unit 18 detects a zero cross where the input voltage Vac from the commercial AC power supply 1 becomes zero. The power supply voltage detection circuit unit 18 corresponds to zero cross detection means of the present invention.

  In the present embodiment, the arithmetic unit 20 has a discharge start timer and a discharge stop timer (not shown), and counts down to the discharge start time and the discharge stop time. The computing unit 20 corresponds to the time measuring means of the present invention.

  The calculation unit 20 stores a predetermined time T1 in advance. The discharge start timer counts down the count value t1 using the predetermined time T1 as an initial value. Based on the input from the power supply voltage detection circuit unit 18, the calculation unit 20 starts the countdown of t1 by the discharge start timer at each zero cross detection time. When the count value t1 becomes 0, that is, when the elapsed time from the zero cross reaches a predetermined time T1, the calculation unit 20 detects that the discharge start time has been reached, and starts discharging from the capacitor 15. Therefore, the control signal Vs is generated and supplied to the gate of the switching element 17. Thereby, the switching element 17 is turned on, and the capacitor 15 can be discharged. Here, the elapsed time from the zero cross corresponds to the discharge control time of the present invention.

  Moreover, the calculating part 20 has memorize | stored predetermined time T2 previously. The discharge stop timer counts down the count value t2 using the predetermined time T2 as an initial value. When the count value t1 of the discharge start timer becomes 0 and the discharge start time is reached, the arithmetic unit 20 starts to count down the count value t2 by the discharge stop timer. When the count value t2 of the discharge stop timer becomes 0, that is, when the elapsed time from the discharge start time reaches a predetermined time T2, the arithmetic unit 20 detects that the discharge stop time has been reached, and the capacitor 15 The supply of the control signal Vs to the switching element 17 is stopped in order to stop the discharge from. Thereby, the switching element 17 is turned off, and the discharge from the capacitor 15 is cut off.

  Here, the predetermined time T1 is set to a value that is shorter than the half cycle T / 2 of the input voltage Vac from the commercial AC power supply 1. The predetermined time T2 is set to be a value obtained by subtracting twice the predetermined time T1 from the period T of the input voltage Vac from the commercial AC power supply 1. That is, in the present embodiment, the predetermined times T1 and T2 are set so that the relational expression 2 × T1 + T2 = T is established. The predetermined time T1 corresponds to the first predetermined time of the present invention. The sum of the predetermined time T1 and the predetermined time T2, that is, T1 + T2, corresponds to the second predetermined time of the present invention.

  Next, the operation of turning on / off the switching element 17 in the motor drive device 10 according to the second embodiment will be described with reference to the flowchart shown in FIG. FIG. 5 is a flowchart showing an on / off control operation of the switching element 17 in the motor driving apparatus 10 according to the second embodiment of the present invention.

  When the motor drive device 10 is connected to the commercial AC power source 1 and power feeding from the commercial AC power source 1 is started, the input voltage Vac of the commercial AC power source 1 is input from the power source voltage detection circuit unit 18 to the arithmetic unit 20. . Based on this input, the arithmetic unit 20 detects a zero cross where the input voltage Vac becomes 0 (step S201: YES). When calculating zero cross, calculation unit 20 turns on the discharge start timer (step S202). The discharge start timer starts counting down from the count value t1 = T1.

  Next, the computing unit 20 determines whether the switching element 17 is in an on state or an off state (step S203). When power supply from the commercial AC power supply 1 is started, no control signal is input to the gate of the switching element 17, and the switching element 17 is in an off state (step S203: YES). In the OFF state of the switching element 17, the arithmetic unit 20 monitors the count value by the discharge start timer. When the discharge start timer is not underflow, that is, when the count value has not reached 0 (step S204: NO), the arithmetic unit 20 does not generate and supply the control signal, and the switching element 17 continues to be in the off state. (Step S207). The motor drive apparatus 10 returns to the process of step S201 after step S207. The arithmetic unit 20 continues to monitor the count value t1 until the count value t1 of the discharge start timer reaches 0 in the OFF state of the switching element 17 (steps S201 to S204, S207).

  In step S204, when the discharge start timer is underflow, that is, the count value t1 is 0 or less (step S204: YES), the arithmetic unit 20 generates the control signal Vs and supplies it to the gate of the switching element 17. . As a result, the switching element 17 is turned on (step S205), and discharging from the capacitor 15 is started. Moreover, the calculating part 20 turns ON a discharge stop timer (step S206). The discharge stop timer starts counting down from the count value t2 = T2. The motor drive apparatus 10 returns to the process of step S201 after step S206.

  Even after the switching element 17 is turned on, the arithmetic unit 20 detects zero crossing. In step S201, when the zero cross is not detected (step S201: NO), the arithmetic unit 20 determines whether the switching element 17 is in the on state or the off state (step S203). When the switching element 17 is in the on state (step S203: NO), the arithmetic unit 20 monitors the count value t2 of the discharge stop timer that has started counting down after the switching element 17 is turned on. When the discharge stop timer is not underflow, that is, the count value t2 has not reached 0 (step S208: NO), the arithmetic unit 20 continues to supply the control signal Vs, and the switching element 17 continues to be in the ON state. (Step S210). The motor drive apparatus 10 returns to the process of step S201 after step S210. The arithmetic unit 20 continues to detect the zero cross and monitor the count value t2 of the discharge stop timer in the ON state of the switching element 17 (steps S201 to S203, S208, and S210).

  When the calculation unit 20 detects the next zero cross in the ON state of the switching element 17 (step S201: YES), the calculation unit 20 turns on the discharge start timer (step S202). The discharge start timer starts counting down from the count value t1 = T1. At this time, the discharge start timer and the discharge stop timer are both in the on state, and count down t1 and t2, respectively.

  If the arithmetic unit 20 determines that the switching element 17 is in the on state (step S203: NO), the arithmetic unit 20 monitors the count value t2 of the discharge stop timer. When the discharge stop timer is underflow, that is, when the count value t2 is 0 or less (step S208: YES), the arithmetic unit 20 stops supplying the control signal Vs to the switching element 17. As a result, the switching element 17 is turned off (step S209), and the discharge from the capacitor 15 is stopped. The motor drive apparatus 10 returns to the process of step S201 after step S210. The computing unit 20 monitors the count value t1 of the discharge start timer (steps S201 to S204, S207).

  As described above, when a predetermined time T1 has elapsed since the detection of the zero cross, the switching element 17 is turned on and the electric charge accumulated in the capacitor 15 is discharged. When a predetermined time T2 elapses after the switching element 17 is turned on, the switching element 17 is turned off and the discharge from the capacitor 15 is stopped.

  FIG. 6 is a diagram for explaining a voltage, a timer count value, and a signal waveform in the motor driving apparatus 10 according to the second embodiment of the present invention. 6A shows the change over time of the input voltage Vac input from the commercial AC power supply 1 to the rectifier circuit unit 12, and FIG. 6B shows the change over time of the input voltage Vinv input to the inverter circuit unit 14. Indicates. FIG. 6C shows a time change of the count value t1 of the discharge start timer, and FIG. 6D shows a time change of the count value t2 of the discharge stop timer. FIG. 6E shows the time change of the voltage Vc across the capacitor 15, and FIG. 6F shows the time change of the control signal Vs output from the calculation unit 20. Here, FIG. 6A to FIG. 6F are waveform diagrams after a certain time has elapsed from the start of power supply from the commercial AC power supply 1 to the motor drive device 10.

  When the zero cross where the input voltage Vac from the commercial AC power supply 1 becomes 0 is detected, as shown in FIGS. 6A and 6C, the discharge start timer is turned on, and the count down of the count value t1 is performed. Be started. When t1 = 0, as shown in FIGS. 6C and 6F, the control signal Vs is output from the arithmetic unit 20, and the switching element 17 is turned on. As a result, the capacitor 15 can be discharged, and the voltage Vc across the capacitor 15 drops as shown in FIG. 6 (e). Further, as shown in FIG. 6D, the discharge stop timer is turned on, and the countdown of the count value t2 is started.

  When the next zero cross is detected during the output of the control signal Vs, the discharge start timer is turned on again and the count down of the count value t1 is started as shown in FIGS. 6 (a) and 6 (c). The

  When t2 = 0, as shown in FIG. 6D and FIG. 6F, the output of the control signal Vs is stopped, and the switching element 17 is turned off. As a result, the discharge from the capacitor 15 is stopped, and the voltage Vc across the capacitor 15 rises again as shown in FIG. 6 (e).

  The waveform of the input voltage Vinv to the inverter circuit unit 14 (FIG. 6B) is the full-wave rectification of the input voltage Vac (FIG. 6A) from the commercial AC power supply 1 as in the first embodiment. Except for the waveform and the output period of the control signal Vs (FIG. 6 (f)), they are substantially similar. During the output period of the control signal Vs, the energy stored in the capacitor 15 is applied to the inverter circuit unit 14 by the discharge of the capacitor 15 and the voltage value of the input voltage Vinv of the inverter circuit unit 14 increases. Here, since the initial values T1 and T2 of the discharge start timer and the discharge stop timer are set to be 2 × T1 + T2 = T with respect to the cycle T of the commercial AC power supply 1, the output period of the control signal Vs is the commercial AC This is a period before and after the zero crossing of the input voltage Vac of the power source 1. Therefore, the energy is applied from the capacitor 15 to the inverter circuit unit 14 during a period when the value of the input voltage Vinv to the inverter circuit unit 14 is small. By discharging the capacitor 15 during this period, the input voltage Vinv to the inverter circuit unit 14 is prevented from being excessively increased and damage to the circuit is reliably prevented, and the operation efficiency is improved by applying energy to the motor 11. It becomes possible to improve.

  As described above, according to the motor drive device 10 of the present embodiment, the elapsed time from the zero cross of the commercial AC power supply 1 is counted, and when the predetermined time has elapsed, the switching element 17 is turned on and the capacitor 15 It is possible to discharge from. Therefore, the discharge timing can be controlled by simple control, and an excessive voltage rise of the capacitor 15 can be prevented to prevent circuit damage. Further, since the capacitor 15 is discharged before and after the zero crossing, the voltage Vc across the capacitor 15 and the input voltage Vinv of the inverter circuit unit 14 can be prevented from excessively rising, and circuit damage can be reliably prevented. In addition, the energy utilization efficiency and the driving performance of the motor 11 can be improved.

  In the present embodiment, the time from the detection of the zero cross is measured by the discharge start timer and the time from the discharge start time is measured by the discharge stop timer. However, the present invention is not limited to this. For example, when the next zero cross is detected after the discharge start time, the time is measured by the discharge stop timer, and the switching element 17 is stopped to stop the discharge after a predetermined time, that is, the second predetermined time of the present invention has elapsed. It is also possible to stop the supply of the control signal Vs.

  Next, a motor driving device 30 according to a third embodiment will be described with reference to FIG. FIG. 7 is a circuit diagram showing an electrical configuration of the motor drive device 30 according to the third embodiment of the present invention. The motor drive device 30 according to the third embodiment is different from the motor drive device 10 (FIG. 2) according to the first and second embodiments in that a discharge resistor 31 is provided instead of the switching element 17. Different. Hereinafter, the same components as those of the motor driving apparatus 10 according to the first and second embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

  In the motor drive device 30 of the present embodiment, the capacitor 15, the diode 16, and the discharge resistor 31 connect the capacitor 15 in series to the downstream side of the diode 16, as shown in FIG. A discharge resistor 31 is connected upstream of the capacitor 15, and is branched from a current path connected from the rectifier circuit unit 12 to the inverter circuit unit 14 on the output side of the rectifier circuit unit 12, and connected in parallel to the inverter circuit unit 14. The The capacitor 15, the diode 16, and the discharge resistor 31 constitute a second circuit of the present invention.

  The discharge resistor 31 has one end connected between the capacitor 15 and the cathode of the diode 16, and the other end connected between the anode of the diode 16 and the inverter circuit unit 14. The discharge resistor 31 corresponds to the discharge means and the third circuit of the present invention.

  The calculation unit 32 controls the energization direction to the stator windings U, V, and W so as to control the rotation direction and the rotation speed of the motor 11.

  As described above, the parallel circuit of the diode 16 and the discharge resistor 31 is connected to the capacitor 15 in series. However, since the impedance of the diode 16 is lower than that of the discharge resistor 31, the capacitor 15 is connected from the diode 16 side. Energy such as noise is absorbed. The absorbed energy is converted into heat by the discharge resistor 31 and released.

  By configuring the motor drive device 30 as described above, it is possible to suppress an increase in the voltage across the capacitor 15 without performing the on / off control of the switching element by the calculation unit 32.

  As described above, in the motor drive device 30 according to the present embodiment, the discharge resistor 31 is provided instead of the switching element, and the charge accumulated in the capacitor 15 is converted into heat by the discharge resistor 31 and released. Thus, the voltage rise of the capacitor 15 can be suppressed. Therefore, the circuit can be prevented from being damaged without complicated control.

  Next, a motor driving device 40 according to a fourth embodiment will be described with reference to FIG. FIG. 8 is a circuit diagram showing an electrical configuration of a motor drive device 40 according to the fourth embodiment of the present invention. The motor drive device 40 according to the fourth embodiment differs from the motor drive device 30 (FIG. 7) according to the third embodiment in that a Zener diode 41 is further provided in addition to the discharge resistor 31. Hereinafter, the same components as those of the motor drive device 30 according to the third embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

  In the motor drive device 40 of the present embodiment, the capacitor 15, the diode 16, the discharge resistor 31, and the Zener diode 41 are connected to the capacitor 15 in series downstream of the diode 16 as shown in FIG. A discharge resistor 31 is connected downstream of 16 and upstream of the capacitor 15, and a Zener diode 41 is further connected in series with the discharge resistor 31 and in parallel with the capacitor 15. From the rectifier circuit unit 12, It branches from the current path connected to the inverter circuit unit 14 and is connected to the inverter circuit unit 14 in parallel. The capacitor 15, the diode 16, the discharge resistor 31, and the Zener diode 41 constitute a second circuit of the present invention. Further, the discharge resistor 31 and the Zener diode 41 constitute a third circuit of the present invention.

  The Zener diode 41 has a cathode connected to the connection portion of the discharge resistor 31, the diode 16 and the capacitor 15, and an anode connected between the capacitor 15 and the inverter circuit portion 14.

  As described above, by configuring the motor drive device 40, it is possible to reliably prevent the voltage across the capacitor 15 from rising beyond a predetermined upper limit voltage.

  As described above, in the motor drive device 30 according to the present embodiment, the discharge resistor 31 is provided instead of the switching element, and the Zener diode 41 is further provided in parallel with the capacitor 15, so that the voltage of the capacitor 15 is set to a predetermined value. Can be maintained at a voltage of. Therefore, the circuit can be prevented from being damaged without complicated control.

DESCRIPTION OF SYMBOLS 1 Commercial AC power supply 10, 30, 40 Motor drive device 11 Motor 12 Rectifier circuit part 13 Capacitor 14 Inverter circuit part 15 Capacitor 16 Diode 17 Switching element 18 Power supply voltage detection circuit part 19 Capacitor voltage detection circuit part 20, 32 Operation part 31 Discharge Resistor 41 Zener diode 50 Impact driver

Claims (6)

A motor,
A first circuit for rectifying AC power from an AC power source;
An inverter circuit that converts electric power output from the first circuit and supplies the converted electric power to the motor;
A second circuit connected in parallel to the inverter circuit and to which the electric power output from the first circuit is input, the backflow prevention means, and a charge storage connected in series downstream of the backflow prevention means And a second circuit having a discharge means for discharging the charge accumulated in the charge accumulation means, connected to the downstream of the backflow prevention means and upstream of the charge accumulation means,
Control means for controlling discharge by the discharge means;
Both-end voltage detection means for detecting the both-end voltage of the charge storage means;
Power supply voltage detection means for detecting the power supply voltage of the AC power supply,
The control means starts discharge by the discharge means when the both-end voltage reaches a predetermined upper limit voltage, and after the start of the discharge by the discharge means, when the both-end voltage reaches a predetermined lower limit voltage, the discharge means Is configured to stop
The motor drive device further comprising a calculating means for calculating the predetermined lower limit voltage based on the power supply voltage. A motor,
A first circuit for rectifying AC power from an AC power source;
An inverter circuit that converts electric power output from the first circuit and supplies the converted electric power to the motor;
A second circuit connected in parallel to the inverter circuit and to which the electric power output from the first circuit is input, the backflow prevention means, and a charge storage connected in series downstream of the backflow prevention means And a second circuit having a discharge means for discharging the charge accumulated in the charge accumulation means, connected to the downstream of the backflow prevention means and upstream of the charge accumulation means,
Control means for controlling discharge by the discharge means;
Zero-cross detection means for detecting a zero-cross of the AC power input to the first circuit;
Time measuring means for measuring the elapsed time from the detection of the zero cross as a discharge control time,
The motor drive device according to claim 1, wherein the control means starts discharge by the discharge means when the discharge control time reaches a first predetermined time.   3. The motor drive device according to claim 2, wherein the control unit stops the discharge when the discharge control time reaches a second predetermined time. 4.   The motor driving apparatus according to claim 1, wherein the discharging unit is a switching element.   The motor driving apparatus according to claim 1, wherein the discharging unit is a discharging resistor.   6. The motor driving apparatus according to claim 5, wherein the second circuit further includes a Zener diode connected in series to the discharge resistor and connected in parallel to the charge storage unit.

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