Motor drive device and work machine

Abstract

To provide a motor drive device capable of improving the response of a brushless motor upon activation (startup) in a sensorless drive system.SOLUTION: A control unit 50 controls switching elements Q1 to Q3 into an OFF state, and continuously or intermittently controls switching elements Q4 to Q6 into an OFF state in a state where a driving switch 45 is commanding stop of a motor 6 and the motor 6 is at rest. When a rotor 6a is externally rotated, the control unit 50 performs rotor position detection control on the basis of a current that flows in each of an U-phase coil, a V-phase coil, and a W-phase coil due to the rotation of the rotor 6a . The control unit 50 performs rotor position detection control when in a state where the driving switch 45 is commanding stop of the motor 6 when the control unit 50 is activated.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a motor drive device and a working machine.

Background Art

[0002] A brushless motor is used as a drive source for a working machine (for example, a power tool). As a drive method for a brushless motor, a sensorless drive method that does not use an element for detecting the position information of a rotor is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a sensorless drive method, in order to stably start (initiate) a brushless motor, it is necessary to detect the initial position of the rotor. When detecting the initial position of the rotor after a motor drive operation on an operation unit such as a trigger switch, the response of the start of the brushless motor deteriorates by the time required for detecting the initial position.

[0005] An object of the present invention is to provide a motor drive device and a working machine capable of improving the response of starting (initiating) a brushless motor in a sensorless drive method.

Means for Solving the Problems

[0006] One aspect of the present invention is a motor drive device. This motor drive device includes a brushless motor having a rotor and a stator having a plurality of windings, An inverter circuit connected to the plurality of windings; A control unit that controls the operation of the inverter circuit; An operation unit that instructs the start and stop of the brushless motor; A motor drive device comprising: The control unit is configured to perform rotor position detection control for detecting the position of the rotor when the operation unit instructs the stop of the brushless motor when the control unit itself starts, and When the rotor is rotated from the outside, the rotor position detection control is configured to be performed based on the current flowing through the winding or the voltage generated in the winding due to the rotation of the rotor. Characterized in that. Another aspect of the present invention is a motor drive device. This motor drive device is

[0007] A brushless motor having a rotor and a stator having a plurality of windings, An inverter circuit connected to the plurality of windings, A control unit that controls the operation of the inverter circuit, An operation unit that instructs the start and stop of the brushless motor, A motor drive device comprising: The inverter circuit includes A plurality of first switching elements that are one of the upper arm side switching element and the lower arm side switching element, A plurality of second switching elements that are the other of the upper arm side switching element and the lower arm side switching element, and When the operation unit instructs the stop of the brushless motor and the brushless motor is stopped, the control unit is configured to continuously or intermittently control the plurality of first or second switching elements to be in an on state. Characterized in that. Another aspect of the present invention is a working machine. This working machine is

[0008] The motor drive device, And A power supply that supplies power to the motor drive device, It is characterized by comprising.

[0009] Another aspect of the present invention is a working machine. This working machine A brushless motor having a rotor and a stator having a plurality of windings, An inverter circuit connected to the plurality of windings, A control unit that controls the operation of the inverter circuit, An operation unit that instructs the start and stop of the brushless motor, A working machine provided with The control unit When the operation unit instructs the stop of the brushless motor when the control unit itself starts up, it is configured to perform rotor position detection control for detecting the position of the rotor, and When the rotor is rotated from the outside, it is configured to perform the rotor position detection control based on the current flowing through the winding or the voltage generated in the winding due to the rotation of the rotor. It is characterized by this.

[0010] Another aspect of the present invention is a working machine. This working machine A brushless motor having a rotor and a stator having a plurality of windings, An inverter circuit connected to the plurality of windings, A control unit that controls the operation of the inverter circuit, An operation unit that instructs the start and stop of the brushless motor, A working machine provided with The inverter circuit A plurality of first switching elements that are one of the upper arm side switching element and the lower arm side switching element, A plurality of second switching elements that are the other of the upper arm side switching element and the lower arm side switching element, and has When the control unit is in a state where the operation unit instructs the stop of the brushless motor and the brushless motor has stopped, the plurality of second switching elements are configured to be controlled to be in an on state continuously or intermittently. It is characterized by this.

[0011] The working machine of the present invention may be expressed as "electric working machine", "electric tool", "electrical equipment", etc., and those expressed in this way are also effective as aspects of the present invention.

Effect of the Invention

[0012] According to the present invention, it is possible to provide a motor drive device and a working machine capable of improving the response of starting (starting) of a brushless motor in a sensorless drive method.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0014] This embodiment relates to the motor drive device 20 and the working machine 1. Fig. 1 is a block diagram of the working machine 1. The type of the working machine 1 is not particularly limited.

[0015] The working machine 1 includes a load unit 10 and a motor drive device 20. The load unit 10 varies depending on the type of the working machine 1. The load unit 10 is, for example, a tip tool holding unit that holds a tip tool such as a bit, a saw blade, or a grindstone, or a fan that generates an air flow for suction or blowing. The motor drive device 20 drives the motor 6 with the power of the power source 60. The power source 60 is, for example, a battery pack that is detachably attached to the working machine 1 or a battery pack that is built into the working machine 1.

[0016] The motor drive device 20 includes a motor 6, an inverter circuit 41, a control power supply circuit 43, a voltage detection circuit 44, a drive switch 45, a mode switch 46, OR gates 47, 48, a current detection circuit 49, and a control unit 50.

[0017] The motor 6 is, for example, an inner rotor type brushless motor and includes a rotor 6a and a stator 6b. The stator 6b includes a U-phase stator coil (hereinafter referred to as "U-phase coil"), a V-phase stator coil (hereinafter referred to as "V-phase coil"), and a W-phase stator coil (hereinafter referred to as "W-phase coil"). The U-phase coil, V-phase coil, and W-phase coil are composed of a plurality of windings. In the illustrated example, the U-phase coil, V-phase coil, and W-phase coil are Y-connected, but the U-phase coil, V-phase coil, and W-phase coil may be delta-connected.

[0018] The inverter circuit 41 converts the DC power supplied from the power source 60 into AC power and supplies it to the motor 6. The inverter circuit 41 includes switching elements Q1 to Q6 connected in a three-phase bridge. The switching elements Q1 to Q3 are upper-arm side switching elements, and the switching elements Q4 to Q6 are lower-arm side switching elements. The switching elements Q1 and Q4 are connected to one end of the U-phase coil. The switching elements Q2 and Q5 are connected to one end of the V-phase coil. The switching elements Q3 and Q6 are connected to one end of the W-phase coil.

[0019] The inverter circuit 41 includes shunt resistors Ru, Rv, and Rw connected to the sources of the switching elements Q4 to Q6, respectively. The shunt resistors Ru, Rv, and Rw are current detection units (current-voltage conversion means) that convert the current flowing through the switching elements Q4 to Q6 into voltage, respectively.

[0020] The current detection circuit 49 detects the current flowing through each of the switching elements Q4 to Q6, that is, the current flowing through each of the U-phase coil, V-phase coil, and W-phase coil (the current of each phase), based on the voltage of each of the shunt resistors Ru, Rv, and Rw, and transmits it to the control unit 50.

[0021] The control power supply circuit 43 converts the output voltage of the power source 60 into a power supply voltage (for example, 5V) for the control unit 50 and supplies it to the control unit 50 and the like. Further, the control power supply circuit 43 converts the output voltage of the power source 60 into a gate drive voltage Vgate (FIGS. 2(B) and (C)) described later and outputs it. The voltage detection circuit 44 detects the output voltage of the power source 60 and the output voltage of the control power supply circuit 43 and transmits them to the control unit 50.

[0022] The drive switch 45 is, for example, a trigger switch and is a motor drive operation unit for the user to instruct the start and stop of the motor 6. When the drive switch 45 is operated, a drive signal is transmitted to the control unit 50. The mode switch 46 is, for example, a tactile switch and is a mode switching operation unit for the user to switch the drive mode of the motor 6 or the lighting on mode (not shown). When the mode switch 46 is operated, a mode switching signal is transmitted to the control unit 50.

[0023] The OR gates 47 and 48 are circuits that transmit a power-on signal to the control power circuit 43 according to the operation of the drive switch 45 or the mode switch 46, or the power holding signal from the control unit 50. The output terminals of the drive switch 45 and the mode switch 46 are respectively connected to the input terminals of the OR gate 47. The output terminal of the OR gate 47 and the power holding signal output terminal of the control unit 50 are respectively connected to the input terminals of the OR gate 48. The output terminal of the OR gate 48 is connected to the power-on signal input terminal of the control power circuit 43.

[0024] When the drive switch 45 or the mode switch 46 is operated in a state where the control unit 50 is not activated, a power-on signal is input to the control power circuit 43 via the OR gates 47 and 48, and the control power circuit 43 is activated. The control unit 50 is activated by receiving the supply of the power voltage from the control power circuit 43 and outputs a power holding signal. The control unit 50 maintains the output of the power holding signal until the state where there is no operation on the drive switch 45 and the mode switch 46 continues for a predetermined time. By the power holding signal being input to the control power circuit 43 via the OR gate 48, even when neither the drive switch 45 nor the mode switch 46 is operated, the activated state of the control power circuit 43 is maintained and the activated state of the control unit 50 is maintained.

[0025] The control unit 50 includes a microcontroller or the like and controls the overall operation of the motor drive device 20. The control unit 50 controls the driving of the motor 6 in response to an operation of the drive switch 45 by the user, that is, controls the on / off of the switching elements Q1 to Q6 through the control of the inverter circuit 41 (application of a gate signal to the inverter circuit 41). The control unit 50 detects the position (rotation position) of the rotor 6a and the angular velocity of the rotor 6a (hereinafter referred to as "rotor angular velocity") in a sensorless manner based on the current of each phase. The control unit 50 can detect the rotation speed of the motor 6 based on the rotor angular velocity.

[0026] The drive control of the motor 6 by the control unit 50 is, for example, vector control. Vector control is also called space vector pulse width modulation (SVPWM). The details of vector control are as disclosed in, for example, Patent Document 2, and the description thereof is omitted here.

[0027] The motor drive device 20 is characterized by position detection control (hereinafter referred to as "rotor position detection control") for detecting the position of the rotor 6a (hereinafter referred to as "rotor position"), particularly the rotor position detection control in a state where the drive switch 45 instructs the stop of the motor 6 (a state where the drive switch 45 is not operated).

[0028] When the drive switch 45 instructs the stop of the motor 6 when the control unit 50 starts up (for example, when starting up by operating the mode switch 46), the control unit 50 performs rotor position detection control. A method for detecting the rotor position without rotating the rotor 6a is well-known and not particularly limited, but the control unit 50 turns on the switching elements Q1 to Q6 in a predetermined pattern for a short time such that the rotor 6a does not rotate, and detects the rotor position based on the current of each phase flowing accordingly. Note that the control unit 50 also performs rotor position detection control in the case where the drive switch 45 instructs the driving of the motor 6 when the control unit 50 starts up (when starting up by operating the drive switch 45).

[0029] When the drive switch 45 indicates the stop of the motor 6 and the motor 6 is stopped, the control unit 50 controls the switching elements Q1 to Q3 to be in the off state and controls the switching elements Q4 to Q6 to be continuously or intermittently in the on state. When the rotor 6a is rotated from the outside, the control unit 50 performs rotor position detection control based on the current flowing through each of the U-phase coil, V-phase coil, and W-phase coil (voltage across the shunt resistors Ru, Rv, and Rw) due to the rotation of the rotor 6a. For example, due to the replacement of the tip tool or vibration, the rotor 6a may be rotated from the outside while in the stopped state. In FIG. 2(A), an example of the current flow in each phase when the rotor 6a is rotated from the outside with the switching elements Q1 to Q3 off and the switching elements Q4 to Q6 on is indicated by arrows.

[0030] When the drive switch 45 indicates the stop of the motor 6 and the motor 6 is rotating, the control unit 50 performs brake control. The brake control is, for example, a control in which the switching elements Q1 to Q3 are controlled to be in the off state and the switching elements Q4 to Q6 are continuously or intermittently controlled to be in the on state to apply a short-circuit brake. Alternatively, control (regenerative operation) such as reducing the output torque so that the rotation of the motor 6 stops or generating a braking torque is also conceivable. While performing the brake control, the control unit 50 performs rotor position detection control based on the current flowing through each of the U-phase coil, V-phase coil, and W-phase coil (voltage across the shunt resistors Ru, Rv, and Rw).

[0031] When the voltage applied to the inverter circuit 41 (output voltage of the power supply 60) is equal to or lower than the low voltage threshold, and when the current detected by the current detection circuit 49 is equal to or higher than the overcurrent threshold when the rotor 6a is rotated from the outside, the control unit 50 controls the switching elements Q4 to Q6 to be in the off state. Thereby, over-discharge of the power supply 60 and overcurrent to the switching elements Q4 to Q6 are suppressed.

[0032] Figures 2(B) and (C) are circuit diagrams showing the configuration related to the gate drive of the switching element Q1. Figure 2(B) shows the state in which the switching element Q1 is turned off, and Figure 2(C) shows the state in which the switching element Q1 is turned on. In Figures 2(B) and (C), Vcc is the output voltage of the power supply 60, for example, 18V or 36V. Vgate is the gate drive voltage output by the control power supply circuit 43, for example, 15V. The high-side signal and the low-side signal are gate signals applied from the control unit 50.

[0033] The circuits shown in Figures 2(B) and (C) are called bootstrap circuits. Since the configuration itself is well-known, a simple explanation will be given here. As shown in Figure 2(B), during the period when the switching element Q1 is off and the switching element Q4 is on, the capacitor C1 is charged via the diode D1. As a result, the voltage of the capacitor C1 coincides with Vgate (the forward voltage of the diode D1 is ignored). As shown in Figure 2(C), during the period when the switching element 1 is on and the switching element Q4 is off, the voltage of the capacitor C1 is applied to the gate of the switching element Q1. As a result, the gate voltage of the switching element Q1 becomes a voltage that is Vgate higher than the source of the switching element Q1, and the switching element Q1 turns on.

[0034] Although not shown in the figure, the configuration related to the gate drive of the switching elements Q2 and Q3 is the same as the configuration related to the gate drive of the switching element Q1.

[0035] Figure 3(A) is a control flowchart of the motor drive device 20. When there is no power supply from the control power supply circuit 43 (NO in S1), the control unit 50 continues the stop state (S3). When there is a power supply from the control power supply circuit 43 (YES in S1), the control unit 50 starts up, and after performing processes such as program start and initialization (S5), it executes initial position estimation control (S7). The initial position estimation control is a subordinate concept of the rotor position detection control and is the rotor position detection control performed by the control unit 50 immediately after startup.

[0036] When the motor drive command is off (NO in S9), that is, when the drive switch 45 is not operated, the control unit 50 waits in a state where the switching elements Q1 to Q3 are off and the switching elements Q4 to Q6 are on (S11). In this state, when the control unit 50 detects that a current has flowed through at least one of the U-phase coil, V-phase coil, and W-phase coil (that the rotor 6a has been rotated from the outside) (YES in S13), it performs rotor position detection control based on the current in each phase (S15) and returns to S9. When no current flows through any of the U-phase coil, V-phase coil, and W-phase coil (NO in S13), the control unit 50 returns to S9 without performing rotor position detection control.

[0037] When the motor drive command is on (YES in S9), that is, when the drive switch 45 is operated, the control unit 50 performs drive control of the motor 6 (S17). The control unit 50 continues the drive control of the motor 6 until the motor drive command is turned off, that is, until the operation of the drive switch 45 is released (NO in S19, S17). When the motor drive command is turned off (YES in S19), the control unit 50 performs stop control of the motor 6 (S21). The stop control is, for example, the above-described brake control. When the motor 6 stops, the control unit 50 stores the rotor position (S23) and proceeds to S11.

[0038] As the rotor position at the start of the drive control of the motor 6 in S17 (hereinafter referred to as the "starting rotor position"), the control unit 50 uses the rotor position detected in S7 or S15, or the rotor position stored in S23. Specifically, when the control unit 50 proceeds to S17 without the rotor 6a being rotated from the outside (without proceeding to S15) after the initial position estimation control in S7, the rotor position detected in S7 is set as the starting rotor position. Similarly, when the control unit 50 proceeds to S17 without the rotor 6a being rotated from the outside (without proceeding to S15) after storing the rotor position in S23, the rotor position stored in S23 is set as the starting rotor position. When the rotor 6a is rotated from the outside (when proceeding to S15) after the initial position estimation control in S7 or after storing the rotor position in S23, the rotor position detected in S15 is set as the starting rotor position.

[0039] As described above, in the drive control of the motor 6 in S17, since the rotor position at startup is known, the rotor position detection control can be omitted, and the response of the startup of the motor 6 to the operation of the drive switch 45 is improved. However, only when the control power supply circuit 43 is started by the operation of the drive switch 45 and the control unit 50 is started, the initial position estimation control (S7) is performed after the operation of the drive switch 45, so the response is delayed by the time required for the initial position estimation control (S7). However, once the control unit 50 is started, it maintains the startup state for a predetermined time even if the operation of the drive switch 45 is released. Therefore, in most of the on-site work, the control unit 50 is in the startup state when the drive switch 45 is operated, and the effect of response improvement can be obtained.

[0040] FIG. 3(B) is a waveform diagram showing an example of each current of the U-phase, V-phase, and W-phase that occurs when the rotor 6a is rotated from the outside. FIGS. 3(C) and (D) are schematic cross-sectional views showing the rotor positions at times A and B in FIG. 3(B), respectively. The control unit 50 can detect the rotor position from the combination of the current values of each phase at any time.

[0041] FIG. 4(A) is a time chart showing an example of the state transition of the motor drive device 20 when the control shown in FIG. 3(A) is performed.

[0042] At time t0, the control power supply circuit 43 is started and the control unit 50 is started. At the time point of time t0, the motor 6 is stopped and the rotor position is unknown. The control unit 50 immediately performs the initial position estimation control (S7 in FIG. 3(A)) when it starts. The rotor position is detected at time t1. Thereafter, until time t2 when the drive switch 45 is operated, the rotor position is known (the rotor position detected in S7 or S15 in FIG. 3(A)).

[0043] When the drive switch 45 is operated at time t2, the control unit 50 immediately starts driving the motor 6 without performing rotor position detection control. During the driving of the motor 6, the control unit 50 detects the rotor position. The detection of the rotor position during the driving of the motor 6 is well-known. For example, a harmonic can be superimposed on the control command voltage, and the rotor position can be detected from the current response.

[0044] When the operation of the drive switch 45 is released at time t5, the control unit 50 stops the motor 6. Thereafter, until time t6 when the drive switch 45 is operated again, the rotor position is known (the rotor position stored at S23 in Fig. 3(A) or the rotor position detected at S15). After time t6, the same operation as from time t2 to t6 is repeated.

[0045] Fig. 4(B) is a time chart showing an example of the state transition of the motor drive device 20 when control is performed in a comparative example where rotor position detection control is not performed even when the rotor 6a is rotated from the outside and rotor position detection control is performed each time the motor drive command becomes on. Hereinafter, the description will focus on the differences from Fig. 4(A).

[0046] Even when the control unit 50 starts at time t10, since it does not perform rotor position detection control until the drive switch 45 is operated, the rotor position is unknown even at the time t12 when the drive switch 45 is operated. When the drive switch 45 is operated at time t12, the control unit 50 starts driving the motor 6 after performing rotor position detection control. The rotor position is detected at time t13 by the rotor position detection control, and the drive control of the motor 6 is started at time t14. The period from time t12 to t14 is the response delay period.

[0047] When the control unit 50 stops the motor 6 by releasing the operation of the drive switch 45 at time t15, it does not store the rotor position. Therefore, the rotor position is unknown even at the time t16 when the drive switch 45 is operated again. After time t16, the same operation as from time t12 to t16 is repeated.

[0048] This embodiment has the following operational effects.

[0049] (1) When the rotor 6a is rotated externally, the control unit 50 performs rotor position detection control based on the currents flowing through the U-phase coil, V-phase coil, and W-phase coil (voltages across the shunt resistors Ru, Rv, and Rw) due to the rotation of the rotor 6a. Therefore, even if the rotor 6a is rotated externally from a stopped state due to the replacement of the tip tool or vibration, etc., the rotor position is updated at any time, and when the drive switch 45 is operated, the rotor position is known. Thus, when starting the motor 6 by operating the drive switch 45, it is not necessary to perform rotor position detection control, and the response of the motor 6 to the operation of the drive switch 45 (starting) is improved. Also, different from the control of continuously detecting the rotor position by turning on the switching elements Q1 to Q6 in a predetermined pattern for only a short time when the rotor 6a does not rotate during the stop period of the motor 6, since it is possible to perform rotor position detection control when the rotor 6a is rotated without supplying high-frequency power from the power source 60 to the motor 6, power consumption and noise of the power source 60 during the stop period of the motor 6 are suppressed.

[0050] (2) When the control unit 50 starts up and the drive switch 45 instructs the stop of the motor 6 (for example, when starting up by operating the mode switch 46), the control unit 50 performs rotor position detection control. Also, the control unit 50 stores the rotor position when the motor 6 stops while the drive switch 45 is in the state of instructing the stop of the motor 6. Therefore, the rotor position becomes known before the drive switch 45 is operated. Thus, if the rotor 6a is not rotated externally, the rotor position detected by the rotor position detection control immediately after the start-up of the control unit 50, or the rotor position stored when the motor 6 stops, can be used as the start-up rotor position. Therefore, when starting the motor 6 by operating the drive switch 45, it is not necessary to perform rotor position detection control, and the response of the motor 6 to the operation of the drive switch 45 (starting) is improved.

[0051] (3) When the drive switch 45 indicates the stop of the motor 6 and the motor 6 is stopped, the control unit 50 controls the switching elements Q1 to Q3 to be in the off state, and controls the switching elements Q4 to Q6 to be in the on state continuously or intermittently. Thereby, when the rotor 6a is rotated from the outside, the current due to the induced voltage generated in each of the U-phase coil, V-phase coil, and W-phase coil can be suitably passed through the shunt resistors Ru, Rv, and Rw. Further, since the capacitor C1 of the boost circuit is charged as shown in FIG. 2(B) during the period when the switching elements Q4 to Q6 are on, it is not necessary to wait for the charging of the capacitor C1 when the drive switch 45 is operated to start the motor 6, and the response of the start (starting) of the motor 6 to the operation of the drive switch 45 is improved.

[0052] (Embodiment 2) FIG. 5 is a block diagram of a motor drive device according to Embodiment 2 of the present invention. Hereinafter, the description will focus on the differences from Embodiment 1.

[0053] The motor drive device shown in FIG. 5 is obtained by replacing the inverter circuit 41 of the motor drive device 20 shown in FIG. 1 with an inverter circuit 41a and replacing the current detection circuit 49 with a voltage detection circuit 49a. The inverter circuit 41a is obtained by removing the shunt resistors Ru, Rv, and Rw from the inverter circuit 41 of FIG. 1 and short-circuiting them. The voltage detection circuit 49a detects the voltages of the U-phase, V-phase, and W-phase and transmits them to the control unit 50.

[0054] The control unit 50 detects the rotor position and the rotor angular velocity sensorlessly based on the voltage of each phase. When the drive switch 45 indicates the stop of the motor 6 when the control unit 50 starts up, for example, the control unit 50 turns on the switching elements Q1 to Q6 in a predetermined pattern for a short time such that the rotor 6a does not rotate, and detects the rotor position based on the voltage of each phase generated accordingly.

[0055] When the drive switch 45 indicates the stop of the motor 6 and the motor 6 has stopped, the control unit 50 controls the switching elements Q1 to Q3 to be in the off state and controls the switching elements Q4 to Q6 to be in the off state continuously or intermittently. When the rotor 6a is rotated from the outside, the control unit 50 performs rotor position detection control based on the induced voltages generated in each of the U-phase coil, V-phase coil, and W-phase coil due to the rotation of the rotor 6a.

[0056] Other aspects of this embodiment are the same as those of Embodiment 1. This embodiment also has the same operational effects as Embodiment 1.

[0057] As described above, the present invention has been described by taking the embodiments as examples, but the present invention is not limited to the embodiments. Various modifications can be made to each matter specifically described in the embodiments within the scope described in the claims.

[0058] One of the shunt resistors Ru, Rv, and Rw may be omitted. In this case, the current for one phase cannot be detected, but the rotor position can be detected from the currents for two detectable phases.

[0059] The positions of the shunt resistors Ru, Rv, and Rw are not limited to the low potential side of the current path for each phase and may be on the high potential side. That is, the shunt resistors Ru, Rv, and Rw may be connected to the drains of the switching elements Q1 to Q3 respectively. In this case, when the drive switch 45 indicates the stop of the motor 6 and the motor 6 has stopped, the control unit 50 controls the switching elements Q4 to Q6 to be in the off state and controls the switching elements Q1 to Q3 to be in the on state continuously or intermittently.

[0060] The circuit that generates the gate voltages of the switching elements Q1 to Q3 is not limited to a bootstrap circuit and may be, for example, a charge pump circuit.

[0061] The number of poles of the rotor 6a and the number of slots of the stator 6b are arbitrary. That is, the motor 6 is not limited to a 2-pole 3-slot configuration and may be, for example, a 4-pole 6-slot configuration.

[0062] The working machine of the present invention may be a corded type that operates with power supplied from an external AC power source. The working machine of the present invention may be other types of cutting working machines such as a portable circular saw, a bench circular saw, a rotary band saw, a jigsaw, a saber saw (reciprocating saw), a brush cutter, etc. Further, the working machine of the present invention may be a grinding working machine having a grinding tip tool such as a grinder, a polishing working machine having a polishing tip tool such as a sander or a polisher, a cutting working machine having a cutting tip tool such as a saw, a trimmer, or a router, a drilling working machine having a drilling tip tool such as a drill, a hammer, or an earth auger, a fastening working machine having a fastening tip tool such as an impact driver, an impact wrench, a driver drill, a socket wrench, a riveter, or a wire tying machine, a crimping working machine having a crimping tip tool such as a crimping machine, a bending working machine having a bending tip tool such as a rebar bender, or a driving working machine having a driving tip tool such as a nail gun or a tacker.

[0063] The output voltage of the power supply 60, the gate drive voltage, the power supply voltage of the control unit 50, etc., exemplified as specific numerical values in the embodiments, do not limit the scope of the invention in any way and can be arbitrarily changed according to the required specifications.

Explanation of Reference Numerals

[0064] 6... motor, 6a... rotor, 6b... stator, 10... load unit, 20... motor drive device, 41... inverter circuit, 43... control power supply circuit, 44... voltage detection circuit, 45... drive switch, 46... mode switch, 47, 48... OR gate, 49... current detection circuit, 50... control unit, 60... power supply.

Claims

1. A brushless motor having a rotor and a stator having a plurality of windings, an inverter circuit connected to the plurality of windings, a control unit that controls the operation of the inverter circuit, and an operation unit that instructs start and stop of the brushless motor, wherein the control unit is configured to perform rotor position detection control for detecting the position of the rotor when the operation unit instructs stop of the brushless motor in a state where the control unit itself has started, and when the rotor is rotated from the outside, the rotor position detection control is configured to be performed based on a current flowing through the winding or a voltage generated in the winding due to the rotation of the rotor. A motor drive device characterized by the above.

2. The motor drive device according to claim 1, wherein the inverter circuit includes a plurality of first switching elements which are one of an upper arm side switching element and a lower arm side switching element, and a plurality of second switching elements which are the other of the upper arm side switching element and the lower arm side switching element, and when the operation unit instructs stop of the brushless motor and the brushless motor is stopped, the control unit is configured to continuously or intermittently control the plurality of first or second switching elements to be in an on state. A motor drive device characterized by the above.

3. A brushless motor having a rotor and a stator having a plurality of windings, an inverter circuit connected to the plurality of windings, a control unit that controls the operation of the inverter circuit, and an operation unit that instructs start and stop of the brushless motor, wherein the inverter circuit includes a plurality of first switching elements which are one of an upper arm side switching element and a lower arm side switching element, and a plurality of second switching elements which are the other of the upper arm side switching element and the lower arm side switching element, and when the operation unit instructs stop of the brushless motor and the brushless motor is stopped, the control unit is configured to continuously or intermittently control the plurality of first or second switching elements to be in an on state. A motor drive device characterized by the above.

4. The motor drive device according to claim 2 or 3, ​ ​ ​ The inverter circuit has a current detection unit that detects the current flowing through at least two of the plurality of first or second switching elements respectively. A motor drive device characterized by this.

5. A motor drive device according to claim 4, The control unit is configured to perform rotor position detection control for detecting the position of the rotor based on the current detected by the current detection unit when the rotor is rotated from the outside. A motor drive device characterized by this.

6. A motor drive device according to any one of claims 1 to 3, The control unit is configured to be able to start the brushless motor without performing the rotor position detection control when the operation unit is in a state of instructing the start of the brushless motor. A motor drive device characterized by this.

7. A motor drive device according to any one of claims 1 to 3, It includes a power supply unit that supplies the drive voltage of the control unit, The power supply unit maintains the supply of the power supply voltage to the control unit for a predetermined time after the operation unit is in a state of instructing the stop of the brushless motor. A motor drive device characterized by this.

8. A motor drive device according to any one of claims 1 to 3, The control unit is configured to store the position of the rotor when the brushless motor stops after the operation unit is in a state of instructing the stop of the brushless motor. A motor drive device characterized by this.

9. A motor drive device according to claim 2 or 3, When the voltage applied to the inverter circuit is below the low voltage threshold, and when the current detected by the current detection unit is equal to or higher than the overcurrent threshold when the rotor is rotated from the outside, the control unit is configured to control the plurality of first or second switching elements to be in an off state. A motor drive device characterized by this.

10. A motor drive device according to any one of claims 1 to 3, and A load unit driven by the motor drive device, A working machine characterized by comprising this.

11. A brushless motor having a rotor and a stator having a plurality of windings, An inverter circuit connected to the plurality of windings, A control unit that controls the operation of the inverter circuit, An operation unit that instructs the start and stop of the brushless motor, A working machine provided with this, The control unit is When the operation unit instructs the stop of the brushless motor when the device starts up by itself, it is configured to perform rotor position detection control for detecting the position of the rotor, and when the rotor is rotated from the outside, it is configured to perform the rotor position detection control based on the current flowing through the winding or the voltage generated in the winding due to the rotation of the rotor. The working machine is characterized by this.

12. A brushless motor having a rotor and a stator having a plurality of windings, an inverter circuit connected to the plurality of windings, a control unit for controlling the operation of the inverter circuit, and an operation unit for instructing the start and stop of the brushless motor. A working machine comprising: The inverter circuit has a plurality of first switching elements which are one of the upper arm side switching elements and the lower arm side switching elements, and a plurality of second switching elements which are the other of the upper arm side switching elements and the lower arm side switching elements. When the operation unit instructs the stop of the brushless motor and the brushless motor has stopped, the control unit is configured to continuously or intermittently control the plurality of second switching elements to be in an on state. The working machine is characterized by this.

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