Electric working machine

Abstract

The present invention provides an electric working machine. The electric working machine is provided with a brushless motor, and when the motor rotates at a low speed, the rotation position can be detected without using a rotation sensor, and the detection can be achieved at a low cost. The electric working machine includes an inverter unit and a control unit that performs PWM control on the motor's power-on current by switching the power-on mode with the help of the inverter unit. The control unit has a plurality of switch combinations with different on / off states of a plurality of switch elements as the power-on mode switched at each commutation moment, and switches the switch combinations in sequence in synchronization with the cycle of the PWM control, and detects the rotation position of the brushless motor based on the magnitude relationship of the brushless motor inductance generated by the switching of the switch combinations, and sets the commutation moment.

Description

Technical Field

[0001] The present invention relates to an electric working machine having a brushless motor as a power source. Background Art

[0002] The brushless motor needs to switch the energization pattern of the stator coil every predetermined rotation angle of the rotor. Therefore, an electric working machine equipped with a brushless motor has a detection unit for detecting the rotation position of the brushless motor (specifically, the rotor).

[0003] As the detection unit, generally known are a rotation sensor that generates a signal according to the rotation angle of the rotor, or a sensorless detection unit that detects the rotation position based on an induced voltage generated by the rotation of the rotor.

[0004] Moreover, according to the sensorless detection unit that uses a structure that detects the rotation position of the brushless motor (in other words, the rotor) based on the induced voltage, it is only necessary to detect the voltage of each phase terminal of the brushless motor and detect the specified rotation position when the detected voltage passes through the zero crossing point.

[0005] Therefore, according to the electric working machine including the sensorless detection unit, the device configuration can be simplified compared to a case where a configuration is adopted in which a rotation sensor is used to detect the rotation position.

[0006] However, since the induced voltage is proportional to the number of revolutions of the brushless motor, when the brushless motor rotates at a low speed, the voltage may not reach a level required for detecting the rotational position, and the rotational position may not be detected.

[0007] In response to this, a sensorless detection unit that detects the rotational position of a brushless motor without using an induced voltage has been proposed that alternately generates a power-on period for generating torque on a rotor and a detection period for position detection (see, for example, Patent Document 1).

[0008] In the device of this scheme, a current for position detection is passed through the coil of the brushless motor for a sufficiently short time compared to the energization period for generating torque in the brushless motor, and the inductance of the stator coil is calculated by measuring the current value. Then, the time when the inductance reaches the maximum is detected as the specified rotation position.

[0009] Patent Literature

[0010] Patent Document 1: U.S. Patent Application Publication No. 2011 / 0279073 Summary of the invention

[0011] According to the device of the above aspect, the inductance that changes according to the rotational position of the brushless motor is obtained, and the rotational position is detected when the inductance reaches a maximum. Therefore, the rotational position can be detected even when the brushless motor rotates at a low speed.

[0012] However, in the device of the above scheme, in order to detect the rotational position, a low current for position detection that does not cause the rotor to generate torque is passed, and the inductance is calculated by detecting this current, so the inductance calculation accuracy is required.

[0013] Therefore, in the device of the above scheme, although the rotation sensor may not be used, there is a problem that an expensive arithmetic circuit with high arithmetic performance must be used as the arithmetic circuit used for position detection, which leads to an increase in cost.

[0014] In addition, in the device of the above scheme, the drive current and the position detection current for generating torque on the rotor need to be supplied alternately, so the rotor cannot generate torque during the position detection period. Therefore, there is a case where the acceleration characteristics when the rotation of the brushless motor is accelerated are reduced, and the brushless motor may stop when a load is applied to its output shaft.

[0015] One aspect of the present invention is to provide an electric working machine including a brushless motor, to detect a rotation position without using a rotation sensor when the brushless motor rotates at a low speed, and to achieve such detection at low cost.

[0016] An electric working machine according to one aspect of the present invention includes a brushless motor as a power source, and includes an inverter unit and a control unit for driving the brushless motor.

[0017] The inverter unit includes a plurality of switching elements provided on a current-carrying path between a DC power supply and a plurality of terminals of the brushless motor, and is configured to be able to control energization and energization directions of a plurality of coils of the brushless motor using the plurality of switching elements.

[0018] The control unit switches the energization pattern for energizing the plurality of coils using the inverter unit at each predetermined commutation timing of the brushless motor, turns on / off the plurality of switching elements of the inverter unit according to the energization pattern, and thereby performs PWM control on the energization current of the plurality of coils.

[0019] In addition, the control unit has a plurality of switch combinations with different on / off states of the plurality of switch elements as a power-on mode switched at each commutation moment. Furthermore, the control unit sequentially switches the switch combination for controlling the on / off state of the switch element to one of the plurality of switch combinations in synchronization with the cycle of the PWM control.

[0020] When the switch combination is switched in this way, the path of the current flowing through the brushless motor changes. Even if the rotational position is the same, the inductance generated by each current path will change due to the difference in the magnetic permeability of the magnets provided on the rotor (the so-called salient polarity of the rotor).

[0021] That is, the control unit changes the inductance of the stator coil by sequentially switching the energization mode to one of a plurality of switch combinations within the rotation angle range of the rotor from the commutation timing to the next commutation timing.

[0022] The rotation position of the brushless motor (rotor) is detected based on the magnitude relationship of the inductance generated in each current path that varies due to the switching of the switch combination, and the commutation combination is set.

[0023] Therefore, according to the electric working machine of the present invention, even when the brushless motor rotates at a low speed, the rotation position can be detected without using a rotation sensor.

[0024] Furthermore, unlike the conventional device described above, there is no need to alternately form a power-on period for generating torque on the rotor and a detection period for position detection. Instead, a current for position detection is passed during the detection period, and the inductance of the coil is accurately calculated based on the current value.

[0025] That is, in the electric working machine of the present invention, in order to detect the rotational position of the brushless motor, it is only necessary to determine the relationship between the inductances generated by different switch combinations, without having to accurately calculate the inductance based on the position detection current as in the prior art.

[0026] Therefore, according to the electric working machine of the present invention, it is not necessary to provide an expensive calculation circuit with high calculation capability as in the conventional device in the control unit for detecting the rotational position, so that the structure of the control unit can be simplified and the cost can be reduced.

[0027] Furthermore, in order to detect the rotational position, the control unit only needs to determine the magnitude relationship of the inductance generated by the different switch combinations, so there is no need to calculate the inductance based on the current flowing through the brushless motor as in the prior art.

[0028] Specifically, a current detection unit is provided to detect the current flowing through the brushless motor. Furthermore, the control unit is configured to obtain the current values ​​detected by the current detection unit when the brushless motor is powered by a plurality of switch combinations as parameters representing the inductance, and detect the rotation position based on the magnitude relationship of the obtained current values.

[0029] In this way, it is not necessary to calculate the inductance based on the current flowing through the brushless motor, and the rotation position can be detected only based on the magnitude relationship of the current value obtained by the current detection unit, so the device structure can be further simplified.

[0030] However, although the control unit forms a power path for supplying power to the brushless motor by turning on the switching elements of the inverter unit according to the switch combination, even if the switching elements are turned off to cut off the power path, circulating current or regenerative current will flow in the brushless motor.

[0031] This is because when the power supply to the brushless motor is cut off, the energy accumulated in the coil due to the power supply generates a voltage, so the inverter unit has a circulating or regenerating diode that allows the current to continue to flow through the brushless motor at this voltage.

[0032] When the on-time of the switching element in each cycle of PWM control is short (i.e., the duty cycle is small), the circulating current or regenerative current can be made zero from the time when the switching element cuts off the power path from the DC power supply to the next on-time. This is because the energy stored in the coil of the brushless motor is small when the DC power supply is turned on.

[0033] However, if the on-time of the switching element per cycle of PWM control is long (the duty cycle is large), the energy stored in the coil will increase. Therefore, the circulating current or regenerative current will continue to flow from the time when the power supply path from the DC power supply is cut off to the next on-time.

[0034] Therefore, when the switching element of the inverter unit is turned on according to the switch combination while a circulating current or a regenerative current is flowing, the circulating current or the regenerative current flows as an initial current in the power path from the DC power supply to the brushless motor, and thereafter the current flowing in the power path begins to change based on the initial current.

[0035] Therefore, when the rotation position is detected based on the magnitude relationship of the current values ​​under the use condition where the circulating current or the regenerative current cannot be reduced to zero within one cycle of the PWM control, it is preferable to configure the control unit as follows.

[0036] That is, the control unit is preferably configured to obtain, as a parameter representing the inductance value of the brushless motor, a difference between a energization start current at the start of energization and a energization end current at the end of energization when energizing the brushless motor using the switch combination.

[0037] In this way, when the switching elements of the inverter unit are turned on according to the switch combination, even if a circulating current or a regenerative current flows, the control unit can use the circulating current or the regenerative current as the initial power-on value, and obtain the current change from the initial power-on value to the power-on end current as the current value for position detection.

[0038] Therefore, in this case, even if, for example, the duty ratio of PWM control is large and a circulating current or a regenerative current flows when power is supplied to the brushless motor by the switch combination, the rotation position of the brushless motor can be detected without being affected by the circulating current or the regenerative current.

[0039] On the other hand, the control unit can also be configured to: after starting to power the brushless motor with a plurality of switch combinations, measure the time taken for the current value detected by the current detection unit to reach a specified threshold value, use it as a parameter representing the inductance of the brushless motor, and detect the rotation position based on the magnitude relationship of the measured time.

[0040] In this way, the rotation position of the brushless motor can be detected only by the magnitude relationship of the measured time, without calculating the inductance, and the device structure can be simplified as in the case where the rotation position is detected based on the magnitude relationship of the current value.

[0041] It should be noted that, under usage conditions where the circulating current or regenerative current cannot be reduced to zero within one cycle of PWM control, when the time taken for the current value to reach a predetermined threshold is measured as a parameter representing the inductance, the control unit is preferably configured as follows.

[0042] That is, the control unit is preferably configured to measure, when the brushless motor is energized by the switch combination, the time taken for the current value to change from the energization start current to the predetermined threshold value as a parameter representing the inductance value of the brushless motor.

[0043] In this way, even if a circulating current or a regenerative current flows when the brushless motor is energized by the switch combination, the control unit can use the circulating current or the regenerative current as the energization initial value to obtain the time taken for the current value to change by a predetermined threshold from the energization initial value.

[0044] Therefore, even if the control unit is configured in this way, the rotation position of the brushless motor can be detected without being affected by the circulating current or the regenerative current.

[0045] Furthermore, the plurality of switch combinations are respectively set so that when the on / off state of the switching element is controlled by each switch combination, the rotor of the brushless motor generates torque.

[0046] In this way, even if the switch combination is switched, the rotor can generate torque to drive the motor, thereby preventing the rotor from being unable to generate torque during position detection as in the above-mentioned conventional device.

[0047] Therefore, according to the electric working machine of the present invention, it is possible to suppress a decrease in acceleration characteristics when the rotation of the brushless motor is accelerated for position detection, or to suppress a stoppage of the brushless motor when a load is applied to its output shaft.

[0048] Furthermore, the control unit may be configured to detect the rotational position using the timing at which the plurality of switch combinations are switched so that the magnitude relationship of the inductances of the brushless motors is interchanged as the detection timing.

[0049] Specifically, the time when the magnitude relationship of the current values ​​acquired as the parameter representing the inductance is reversed, or the time when the magnitude relationship of the times acquired as the parameter representing the inductance is reversed may be detected as the predetermined rotational position of the rotor.

[0050] In this way, the predetermined rotational position can be detected only by comparing the latest value and the previous value of each parameter, so that correction calculation of each parameter is not necessary, and the rotational position can be detected more simply.

[0051] It should be noted that, considering that the size relationship of the above-mentioned parameters (i.e. inductance, current value, time, etc.) may also be interchanged due to noise, etc., it is also possible to wait for a certain period of time after the size relationship is interchanged, and then determine the rotation position after confirming that the size relationship is stable.

[0052] In addition, the current value flowing through the brushless motor is sometimes unstable just after the power-on mode is switched at the commutation moment. Therefore, the position detection action of determining the magnitude relationship of the above parameters may be performed after a specified time has passed after the commutation moment.

[0053] Furthermore, the control unit may be configured to adjust the on-time of the switching element when the brushless motor is PWM-controlled by the switch combination, according to the power supply voltage of the DC power supply.

[0054] That is, the current flowing through the brushless motor changes according to the power supply voltage. Even if the on-time of the switching element (in other words, the energization time of the stator coil) is constant, the current will also change when the power supply voltage changes.

[0055] Therefore, by adjusting the on-time of the switching element according to the power supply voltage of the DC power supply, it is possible to suppress the fluctuation of the current flowing through the brushless motor due to the fluctuation of the power supply voltage, thereby enabling stable position detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a perspective view showing the appearance of the electric working machine according to the embodiment.

[0057] Figure 2 This is a block diagram showing the electrical configuration of the electric working machine according to the first embodiment.

[0058] Figure 3 It is an explanatory diagram for explaining the motor energization pattern in the high-speed mode.

[0059] FIG. 4 is an explanatory diagram for explaining a motor energization pattern in a low speed mode.

[0060] Figure 5 This is an explanatory diagram for explaining current changes caused by switching of the switch combination in the low speed mode.

[0061] Figure 6 This is a flowchart showing the control process executed by the control unit.

[0062] Figure 7 Yes means Figure 6 Flowchart of the motor control process shown.

[0063] Figure 8 Yes means Figure 7 The flowchart of the motor stop process is shown.

[0064] Fig. 9 Yes means Figure 7 Flowchart of the motor drive process shown.

[0065] Fig.10 1 is a flowchart showing the PWM carrier interruption process at the OFF timing executed by the control unit.

[0066] Fig.11 This is a timing chart showing the position detection operation using the current value according to the first embodiment.

[0067] Fig.12 It is a timing chart for explaining the position detection operation of the first modification example.

[0068] Fig.13 This is a flowchart showing the PWM carrier interrupt processing at the ON timing according to the first modification.

[0069] Fig.14 This is a flowchart showing the PWM carrier interrupt processing at the OFF timing according to the first modification.

[0070] Fig.15 It is a block diagram showing the electrical configuration of the electric working machine according to the second embodiment.

[0071] Fig.16 This is a flowchart showing the motor stop process according to the second embodiment.

[0072] Fig.17 This is a flowchart showing the motor driving process according to the second embodiment.

[0073] Fig.18 This is a flowchart showing the current value comparison unit output signal interruption process executed by the control unit.

[0074] Fig.19 This is a flowchart showing the PWM timer overflow interrupt processing executed by the control unit.

[0075] Fig. 20 This is a timing chart for explaining the switching operation of the switch combination using the PWM timer.

[0076] Fig.21 This is a timing chart showing the position detection operation using the timer value in the second embodiment.

[0077] Fig. 22 It is a timing chart for explaining the position detection operation of the second modification example.

[0078] Fig.23 This is a flowchart showing the PWM timer overflow interrupt processing according to the second modification example.

[0079] Description of Reference Numerals

[0080] 1: Electric working machine; 3: Control unit; 4: Drive unit; 8: Operation / display unit; 10: Trigger switch; 18: Battery pack; 20: Motor; 22: Rotor; 24A~24C: Coil; 30: Control unit; 30A: Non-volatile memory; 32: Inverter unit; 34: Current detection unit; 36: Position detection unit; 38: Current value comparison unit; Q1~Q6: Switching elements. DETAILED DESCRIPTION

[0081] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0082] [First embodiment]

[0083] In the present embodiment, a lawn mower is described as an example of an electric working machine.

[0084] like Figure 1 As shown, the electric working machine 1 of this embodiment is a lawn mower including a main pipe 2, a control unit 3, a drive unit 4 and a handle 7. The main pipe 2 is formed in a long and hollow rod shape. The control unit 3 is provided at the rear end side of the main pipe 2, and the drive unit 4 is provided at the front end side of the main pipe 2.

[0085] The driving unit 4 is provided with a rotary blade 5, which can be detachably mounted and rotated. The rotary blade 5 is used to cut objects such as grass and small-diameter trees. Figure 1 The rotating knife shown is a so-called saw blade.

[0086] That is, the rotary blade 5 is made of metal and is in the shape of a disk, and has sawtooth-like teeth formed in the entire outer circumference. A hard blade head is installed at the top of each tooth.

[0087] A guard 6 is provided on the front end side of the main pipe 2. The guard 6 is provided to prevent grass cut by the rotary blade 5 from being splashed toward the operator.

[0088] The drive unit 4 contains a drive source for driving the rotary blade 5 to rotate, that is, a motor 20 (see Figure 2) and a gear mechanism for transmitting the rotation of the motor 20 to an output shaft, on which a rotating blade 5 is detachably mounted.

[0089] The motor 20 is an IPM (Interior Permanent Magnet) type three-phase brushless motor having a magnet embedded in a rotor 22, and is controlled by a control unit 30 (see Figure 2 ) drives and controls the motor 20.

[0090] The handle 7 is connected to the main pipe 2 near the middle of the main pipe 2 in the longitudinal direction. The handle 7 is used for the operator to hold the electric working machine 1 when performing a grass cutting operation. In the present embodiment, the handle 7 is a so-called U-shaped handle with grips at both ends. It should be noted that the handle 7 may also be other handles such as a ring handle.

[0091] An operation / display unit 8 is provided at a grip portion of the handle 7 . The operation / display unit 8 is used for an operator to operate with fingers and can allow the operator to confirm an operation status.

[0092] The operation / display unit 8 is provided with a trigger switch 10 , an unlock switch 12 , and a display panel 14 .

[0093] The display panel 14 is used to display the rotation state of the motor 20, the remaining power of the battery pack 18 (the remaining power of the battery in the battery pack 18), etc. In addition, the display panel 14 is also provided with an operating switch for the operator to set the rotation direction of the motor 20 (in other words, the rotary blade 5), etc.

[0094] It should be noted that if Figure 1 As shown, the battery pack 18 is detachably mounted on the rear end side of the control unit 3 and is used to supply direct current to the control unit 3 .

[0095] The trigger switch 10 is an operation switch for inputting a drive command for the motor 20 , and the unlock switch 12 is a switch that is pressed by an operator to enable the trigger switch 10 to be operated.

[0096] The trigger switch 10 and the display panel 14 are connected to the control unit 30 in the control unit 3 via the cable 19. The control unit 30 monitors the operation status of the trigger switch 10 and the display panel 14, and drives the motor 20, switches the rotation direction, or displays on the display panel 14.

[0097] like Figure 2 As shown, the control unit 3 is provided with an inverter unit 32 in addition to the control unit 30 , and the inverter unit 32 supplies power to the motor 20 to rotate it.

[0098] The inverter unit 32 is constituted by a three-phase full-bridge circuit, and receives power supply from the battery pack 18 (specifically, the batteries in the battery pack 18 ) to pass current through the coils 24A, 24B, and 24C wound on the stators of the respective phases of the motor 20 .

[0099] That is, the inverter unit 32 is formed of six switching elements Q1 to Q6 constituted by MOSFETs (Metal Oxide Field Effect Transistors).

[0100] In the inverter unit 32 , three switching elements Q1 to Q3 are provided as so-called high-side switches between three terminals of the motor 20 , namely, the U-phase, V-phase, and W-phase, and a power supply line connected to the positive electrode side of the battery pack 18 .

[0101] Furthermore, the remaining three switching elements Q4 to Q6 are provided as so-called low-side switches between the respective terminals of the motor 20 and a ground line connected to the negative electrode side of the battery pack 18 .

[0102] A current detection unit 34 for detecting a current flowing through the motor 20 is provided on a current conduction path from the inverter unit 32 to the negative electrode side of the battery pack 18 of the motor 20 , and a current detection signal is input from the current detection unit 34 to the control unit 30 .

[0103] Furthermore, the control unit 3 is provided with a position detection unit 36 ​​for detecting the rotation position of the motor 20 (specifically, the rotor) based on the terminal voltages of the phases U, V, and W of the motor 20 when the motor 20 is driven in the high speed mode.

[0104] The position detector 36 obtains an induced voltage from the terminals of each phase U, V, W of the motor 20 , compares the induced voltage with a reference voltage generated from a power supply voltage, and detects a predetermined rotational position of the motor 20 when the induced voltage exceeds the reference voltage.

[0105] That is, in high-speed mode, if Figure 3 As shown, one of the high-side switches Q1 to Q3 and one of the low-side switches Q4 to Q6 in the inverter unit 32 are sequentially selected for energization, and the energization and energization direction of each phase coil of the motor 20 are switched.

[0106] Therefore, each time the switching is performed, one of the three terminals of the motor 20 becomes open, and an induced voltage is generated at the terminal along with the rotation of the motor 20. The induced voltage changes from the positive side to the negative side of the inverter unit 32, or changes from the negative side to the positive side, and the rotation position of the motor 20 can be determined by detecting the center of the change.

[0107] Therefore, in the position detection unit 36, the power supply voltage is divided into 1 / 2 to generate the center of variation of the induced voltage, that is, the reference voltage, and the reference voltage is compared with the terminal voltages Vu, Vv, and Vw of each phase U, V, and W of the motor 20 by a comparator.

[0108] Therefore, in the position detection unit 36, when the output of the comparator that compares the induced voltage obtained from the terminal in the open state with the reference voltage is inverted, it can be determined that the induced voltage has exceeded the reference voltage.

[0109] Then, the position detection unit 36 ​​detects the time when the induced voltage passes through the reference voltage as a zero-crossing point, and the control unit 30 specifies the rotational position of the motor 20 based on the zero-crossing point.

[0110] It should be noted that, in this embodiment, Figure 3 As shown, when a positive or negative voltage is applied to the terminals of each phase U, V, W of the motor 20 to drive the motor 20, the current supplied to the motor 20 is controlled by PWM control of the applied voltage in the second half of the voltage application period of each terminal. Hereinafter, this driving method is referred to as the second half PWM drive.

[0111] Furthermore, the control unit 30 is constituted by a microcomputer (microcomputer) including a CPU, a ROM, a RAM, and the like.

[0112] When the trigger switch 10 is operated to input a driving command for the motor 20, the control unit 30 energizes the motor 20 in a predetermined energization pattern to initially drive the motor 20. Then, after the initial drive, the rotation position and number of revolutions (specifically, the number of revolutions per unit time, i.e., the rotation speed) of the motor 20 are obtained based on the detection signal from the position detection unit 36, and the motor 20 is then continuously driven.

[0113] However, the position detection unit 36 ​​detects the rotational position of the motor 20 based on the induced voltage obtained from the terminals of each phase U, V, and W of the motor 20. Therefore, when the motor 20 rotates at a low speed, the induced voltage decreases and the rotational position may not be accurately detected.

[0114] Therefore, the control unit 30 drives the motor 20 in the low speed mode after the initial driving of the motor 20 until the number of revolutions of the motor 20 reaches the reference number of revolutions Nth, and drives the motor 20 in the high speed mode when the number of revolutions of the motor 20 reaches or exceeds the reference number of revolutions Nth.

[0115] That is, the control unit 30 drives the motor 20 by the second half PWM drive in the high speed mode and drives the motor 20 by the second half PWM drive in the low speed mode. Figure 4B The switching elements Q1 to Q6 of the inverter unit 32 are driven by the switch combination shown, thereby driving the motor 20 while detecting the rotational position.

[0116] Figure 4B The switch combination shown is stored in the non-volatile memory 30A in the control unit 30. Figure 4A As shown, the rotation range of the rotor 22 in one revolution is divided into 60-degree spans, and the switching elements Q1 to Q6 to be turned on in the inverter section 32 are defined for each rotation range.

[0117] The switch combination is set according to the positive (+) and negative (-) rotation directions of the motor 20 , and two combinations that can cause the rotor 22 of the motor 20 to generate torque are set as the switch combination according to each rotation range and each rotation direction.

[0118] Then, the control unit 30 switches the switch combination alternately to one of two combinations (combination 1 and combination 2) in synchronization with the control cycle of PWM control of the motor 20, and turns on the switching elements Q1 to Q6 of the inverter unit 32.

[0119] As a result, the terminals of each phase U, V, W of the motor 20 specified by the switch combination become positive (UH, VH, WH) or negative (UL, VL, WL) potential, so that current flows through the coils 24A~24C between the terminals and the rotor 22 generates torque.

[0120] It should be noted that the energization period (on time) of the motor 20 in each cycle of PWM control is set according to, for example, the target rotation speed of the motor 20 , and the lower the rotation speed of the motor 20 , the shorter the energization time.

[0121] Furthermore, since the switch combination is alternately switched to combination 1 or combination 2 in synchronization with the PWM control period, the current detected by the current detection unit 34 changes according to the rotational position of the motor 20 .

[0122] Therefore, the control unit 30 detects the rotational position of the motor 20 (rotor 22 ) based on the current change caused by the switching of the switch combination, and determines the commutation timing for switching the switch combination for each rotation range.

[0123] It should be noted that the reason why the current changes according to the switching of the switch combination is that in the brushless motor, the magnetic permeability of the magnets provided on the rotor 22 is different, so that even if the rotation position is the same, the inductance will change (the so-called salient polarity of the rotor).

[0124] That is to say, Figure 4BIn the switch combinations shown, for example, when the rotation position (rotor position) of the motor 20 is 330 degrees, when the motor 20 is rotated in the forward direction, the coils 24B and 24C are energized in the path from the U and V phase terminals to the W phase terminal in combination 1. In addition, in combination 2, the coils 24A and 24B are energized in the path from the V phase terminal to the U and W phase terminals.

[0125] Furthermore, when the coils 24B, 24C or 24A, 24B of the motor 20 are energized according to the combination 1 or 2, Figure 5 As shown, in combination 1, the magnetic path is wide, so the magnetic permeability is large, and in combination 2, the magnetic path is narrow, so the magnetic permeability is small. As a result, for the current detected by the current detection unit 34 in this case, the current detected in combination 2 is larger than the current I1 detected in combination 1.

[0126] In addition, if the rotor 22 is rotated forward without changing the switch combination, when the rotation position is 0 degrees, the magnetic permeabilities in each combination 1 and 2 are consistent, and the currents I1 and I2 are consistent. In addition, when the rotation position is 60 degrees, the magnitude relationship of the magnetic permeabilities in each combination 1 and 2 is reversed, and the magnitude relationship of the currents I1 and I2 is also reversed.

[0127] Therefore, in the low speed mode, the currents I1 and I2 are monitored by alternately switching the switch combination when the motor 20 is PWM-driven to the combination 1 and the combination 2 every 60 degrees of the rotation range of the motor 20 .

[0128] Then, the switching timing (ie, commutation timing) of the switch combination for each rotation range is determined by taking the time when the detection currents I1 and I2 are reversed as a predetermined rotation position of the motor 20 (eg, rotor position: 0 degrees).

[0129] Below, along Figure 6 to Figure 10 The flowchart shown in FIG. 1 illustrates a control process executed by the control unit 30 to drive the motor 20 in this manner.

[0130] It should be noted that, in the following description, the driving of the motor 20 in the low speed mode is referred to as combined PWM driving. In addition, the rotation position of the motor 20 is also referred to as the rotor position.

[0131] like Figure 6 As shown, this control process is implemented by repeatedly executing the processes of S120 to S140 (S represents step) in a predetermined control cycle.

[0132] That is, the control unit 30 waits for the predetermined control cycle to pass by determining whether the base time of the control cycle has passed in S110 , and proceeds to S120 when it is determined in S110 that the base time has passed.

[0133] In S120, a drive instruction acquisition process is executed to acquire a drive instruction from the trigger switch 10 and the operation switch provided on the display panel 14. In addition, in S130, an error detection process is executed to detect abnormalities in the above-mentioned components in the operation / display unit 8, the motor 20, or the battery pack 18. Then, in the next S140, a motor control process is executed to drive the motor 20 or stop the motor 20, and then the process proceeds to S110.

[0134] Then, if Figure 7 As shown, in the motor control process of S140, first in S150, it is determined whether a drive command for the motor 20 is currently input based on the result of the drive command acquisition process of S120.

[0135] Then, when it is determined in S150 that a drive command has been input, the process proceeds to S160 , and it is determined based on the detection result in the error detection process of S130 whether any abnormality (error) has occurred currently.

[0136] If it is determined in S150 that the drive command has not been input, or if it is determined in S160 that an error has occurred, the process proceeds to S180, a motor stop process is executed to stop the motor 20, and the motor control process is terminated.

[0137] If it is determined in S160 that no error has occurred, the process proceeds to S170 to execute a motor driving process for driving the motor 20, and then the motor control process ends.

[0138] Then, if Figure 8 As shown, in the motor stop process of S180 , the output (PWM output) of the drive signal to the inverter unit 32 is stopped in S200 , thereby stopping the second half PWM drive or combined PWM drive of the motor 20 .

[0139] Then, in the following S210 and S220, the flags indicating the first current acquisition and the first low-speed drive are set to "not yet", respectively, and then the process proceeds to S230.

[0140] In S230, the rotor position is acquired from the position detection unit 36, and in S240, it is determined whether the rotor position can be detected by the position detection unit 36. That is, since the rotor position cannot be detected by the position detection unit 36 ​​when the motor 20 rotates at an extremely low speed, in S240, it is determined whether the motor 20 is substantially stopped by whether the rotor position is detected.

[0141] Then, when it is determined in S240 that the rotor position cannot be detected by the position detection unit 36, the process proceeds to S250, the operation mode of the control unit 30 is set to the initial position mode, and the motor stop process is terminated.

[0142] On the other hand, when it is determined in S240 that the rotor position can be detected by the position detector 36 , the process proceeds to S260 , and the free run rotation speed of the motor 20 is detected based on, for example, a change in the terminal voltage of the motor 20 detected by the position detector 36 .

[0143] Then, in the next S270, it is determined whether the speed detected in S260 is lower than the reference speed Nth for high-speed judgment. When the speed is lower than the reference speed Nth, the process proceeds to S280, sets the action mode to the low-speed mode, and then ends the motor stop processing.

[0144] If it is determined in S270 that the number of revolutions is equal to or greater than the reference number of revolutions Nth, the process proceeds to S290, the operation mode is set to the high-speed mode, and the motor stop process is terminated.

[0145] Then, if Fig. 9 As shown, in the motor driving process of S170, first, in S300, it is determined whether the operation mode of the control unit 30 is the initial position mode, the low speed mode, or the high speed mode.

[0146] If the operation mode is the initial position mode, the rotor position is set to a preset initial position in S310 and the process proceeds to S400. It should be noted that S310 sets the rotor position to the initial position by, for example, energizing a preset coil in the motor 20 via the inverter unit 32.

[0147] Next, when it is determined in S300 that the operation mode is the low speed mode, in order to rotate the motor 20 at a low speed by the above-mentioned combined PWM drive, the output method of the drive signal to the inverter unit 32 is set to the combined PWM output in S320, and then enters S330.

[0148] It should be noted that in S320, when the output mode of the driving signal is set to the second half PWM output for performing the second half PWM drive on the motor 20, the output mode is switched to the combined PWM output; when the output mode of the driving signal has been set to the combined PWM output, S330 is directly entered.

[0149] Next, in S330 , it is determined whether the first low-speed drive flag is set to “completed”, thereby determining whether the low-speed drive of the motor 20 has been currently performed.

[0150] Then, when the initial low-speed drive flag is set to "completed" and the low-speed drive has started, the process proceeds to S380, and when the initial low-speed drive flag is set to "not yet" and the low-speed drive has not started, the process proceeds to S340.

[0151] In S340, based on the current rotor position and the rotation direction of the motor 20, Figure 4B The switch combination shown is designated and set to select two switch combinations (combination 1 and combination 2) required for driving the motor 20 at a low speed.

[0152] Then, in the next S350, one of the two switch combinations selected in S340 (here, combination 1) is set as the combination PWM to be used for driving the motor 20 at a low speed via the inverter unit 32, and then the process proceeds to S360.

[0153] In S360, the first low-speed drive flag is set to "completed", and in the next S370, the output of the drive signal to the inverter unit 32 (combination PWM output) is started with the combination 1 set as the combination PWM in S350.

[0154] It should be noted that when the combined PWM output starts in S370, at the turn-on moment generated in each control cycle (constant time) of the subsequent PWM control, a drive signal corresponding to combination 1 is output to the inverter unit 32, so that some switches among the switching elements Q1 to Q6 are turned on.

[0155] Next, when it is determined in S300 that the operation mode is the high speed mode, the process proceeds to S420 to set the output method of the drive signal to the inverter unit 32 to the second half PWM output in order to drive the motor 20 at high speed by the second half PWM.

[0156] Then, in the following S430 and S440, the first current acquisition flag and the first low-speed drive flag used when the motor 20 is driven by the combined PWM in the low-speed mode are set to "not yet", and then the process proceeds to S450.

[0157] In S450, Figure 3 The high-speed driving (second-half PWM driving) in which the motor 20 is rotated at a high speed in the energization mode for high-speed driving shown is performed, and then the process proceeds to S380.

[0158] Next, the number of revolutions of the motor 20 is obtained in S380 . Specifically, in the low speed mode, the number of revolutions of the motor 20 is calculated based on the update time interval of the rotor position in the PWM carrier interruption process described later; in the high speed mode, the number of revolutions of the motor 20 is obtained from the position detector 36 .

[0159] Then, in the next S390, it is determined whether the number of revolutions obtained in S380 is lower than the reference number of revolutions Nth for high-speed judgment. When the number of revolutions is lower than the reference number of revolutions Nth, it enters S400, sets the action mode to the low-speed mode, and then ends the motor drive processing.

[0160] If it is determined in S390 that the number of revolutions is equal to or greater than the reference number of revolutions Nth, the process proceeds to S410, the operation mode is set to the high-speed mode, and the motor drive process is terminated.

[0161] Next, the PWM carrier interrupt processing is described. When the control unit 30 performs PWM control on the motor 20, the PWM carrier interrupt processing is executed once in each cycle of the PWM control in accordance with a timing signal (carrier) output from an oscillator or a timer in each cycle of the PWM control.

[0162] Specifically, the PWM carrier interruption process is not executed at the on-time when the switching element is turned on by outputting a drive signal to the inverter unit 32 through PWM control, but is executed at the off-time when the switching element is turned off after a predetermined on-time has elapsed.

[0163] This PWM carrier interrupt processing is used to update the rotor position based on the current value detected by the current detection unit 34 and switch the energization mode (commutation) of the motor 20 when the motor 20 is driven by combined PWM in the low speed mode.

[0164] like Fig.10 As shown, in the PWM carrier interrupt processing, firstly, in S500, it is determined whether the current operation mode is a low-speed mode or a high-speed mode. If it is a high-speed mode, the PWM carrier interrupt processing is terminated.

[0165] When it is determined in S500 that the operation mode is the low speed mode, the process proceeds to S510 to determine whether the current interruption is an interruption when the switch combination is set to combination 1 or an interruption when the switch combination is set to combination 2.

[0166] Then, when the switch combination is set to combination 1, the process proceeds to S520, the current value I1 detected by the current detection unit 34 when the inverter unit 32 is driven by the current combination 1 is acquired, and then the process proceeds to S530.

[0167] In S530, the switch combination of the combined PWM is changed to combination 2, and then the process proceeds to S540 to determine whether the initial current acquisition flag is "completed".

[0168] If the initial current acquisition mark is not "completed", it means that the power-on under the switch combination (combination 1) at the current rotor position (rotation range) is in the stage just after the beginning, so enter S600. If the initial current acquisition mark is "completed", enter S550.

[0169] Next, if it is determined in S510 that the current interruption is an interruption when the switch combination is set to combination 2, the process proceeds to S610. Then, in S610, the current value I2 detected by the current detection unit 34 when the inverter unit 32 is driven by the current combination 2 is acquired, and the process proceeds to S620.

[0170] In S620 , the switch combination of the combined PWM is changed to combination 1 , and then the process proceeds to S630 , the initial current acquisition flag is set to “completed”, and then the process proceeds to S550 .

[0171] Then, in S550 , the magnitude relationship between the latest current values ​​I1 and I2 acquired in S520 and S610 is determined to determine whether the magnitude relationship is reversed.

[0172] That is to say, Figure 5 As shown, the magnitude relationship between the current values ​​I1 and I2 changes according to the rotation of the rotor 22, and reverses at a predetermined rotation position (rotor position in the figure: 0 degrees).

[0173] Therefore, by determining whether the magnitude relationship between the current values ​​I1 and I2 is reversed in S550, it is determined whether the rotor 22 has passed a specified rotation position (for example, a reference angle of 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, or 300 degrees).

[0174] Then, when it is determined in S550 that the magnitude relationship between the current values ​​I1 and I2 has not reversed, the process proceeds to S600 ; when it is determined that the magnitude relationship between the current values ​​I1 and I2 has reversed, the process proceeds to S560 to update the rotor position.

[0175] It should be noted that when it is initially determined in S550 whether the magnitude relationship between the current values ​​I1 and I2 has reversed, the previous magnitude relationship is not clear. Figure 4B As shown, an initial state is set for the magnitude relationship for each rotation range and rotation direction of the motor 20 , and the initial state is stored together with the switch combination in the nonvolatile memory 30A provided in the control unit 30 .

[0176] Next, in S570, a switch combination (combination 1, combination 2) to be used for the low speed drive motor 20 is selected based on the updated rotor position.

[0177] Then, in S580, one of the selected two switch combinations (here, combination 1) is set as a combination PWM to be used for driving the motor 20 at a low speed via the inverter unit 32, and then the process proceeds to S590.

[0178] Furthermore, in S590 , in order to restart the motor driving after the rotor position is updated, the first current acquisition flag is set to “not yet”, and then the process proceeds to S600 .

[0179] Furthermore, in S600, the combined PWM output under the currently set switch combination (combination 2 or combination 1) is started, and then the PWM carrier interrupt processing is ended.

[0180] It should be noted that when combined PWM output is started in S600, as when output is started in S370, a drive signal corresponding to the current switch combination is output to the inverter unit 32 at the time of PWM control on, turning on some of the switches Q1 to Q6.

[0181] In the control unit 30, the current values ​​I1 and I2 in S520 and S610 are acquired by A / D conversion, but the timing of the A / D conversion is preferably set to the disconnection timing when the switching element of the inverter unit 32 is turned off in the PWM control. Alternatively, it can also be performed at a time before the predetermined time of the disconnection.

[0182] In this way, you can Figure 5 By obtaining the current values ​​I1 and I2 at or near the maximum value of the current flowing in combination 1 and combination 2 as shown, the difference between the current values ​​I1 and I2 when determining the magnitude relationship in S550 can be increased. As a result, the moment when the magnitude relationship between the current values ​​I1 and I2 is reversed (in other words, the rotor position) can be detected more accurately.

[0183] As described above, in the electric working machine 1 of the present embodiment, when the motor 20 rotates at a high speed equal to or higher than the reference rotation speed Nth, the control unit 30 drives and controls the motor 20 according to the rotor position detected by the position detection unit 36 ​​based on the induced voltage.

[0184] On the other hand, when the motor 20 rotates at a low speed lower than the reference rotation speed Nth, the control unit 30 sets the switch combination of combination 1 and combination 2 as the energization mode for each rotation range for switching the energization mode of the motor 20 .

[0185] In addition, if Fig.11 As shown, the driving of the motor 20 is implemented by switching the switch combination between combination 1 and combination 2 in synchronization with the cycle of the PWM control. Fig.11 In the figure, P1 represents combination 1 and P2 represents combination 2.

[0186] Furthermore, when the control unit 30 energizes the motor 20 in each combination 1 and 2, it obtains the current values ​​I1 and I2 detected by the current detection unit 34 at the time when the switch element is turned off. Then, the rotor position is detected and updated based on the magnitude relationship between the current values ​​I1 and I2 thus obtained, and the energization mode (switch combination) of the motor 20 is switched based on the updated rotor position.

[0187] Therefore, according to the electric working machine 1 of the present embodiment, even when the motor 20 rotates at a low speed and the rotor position cannot be accurately detected by the position detection unit 36 ​​, the rotor position can be accurately detected by the combined PWM drive of the motor 20 .

[0188] Therefore, the rotational position of the motor 20 can be grasped within a wide rotation range of the motor 20 from extremely low speed rotation to high speed rotation, and the energization pattern of the motor 20 can be appropriately controlled.

[0189] Furthermore, the switching combination of the switching elements that drive the inverter unit 32 in the low speed mode is set in both the combination 1 and the combination 2 so that the rotor 22 of the motor 20 generates torque.

[0190] Therefore, according to the electric working machine 1 of this embodiment, it is possible to suppress the situation in which the acceleration characteristics of the motor 20 are reduced due to a drive stop period in which the motor 20 does not generate torque in order to detect the rotor position when the motor 20 is driven at a low speed, as in the above-mentioned conventional device. In addition, when a load is applied to the output shaft of the motor 20, it is possible to suppress the motor 20 from stopping rotating.

[0191] In addition, in this embodiment, the rotor position is detected when the difference between the current values ​​I1 and I2 generated by switching the switch combination is reversed, so it is not necessary to calculate the inductance based on the current values ​​I1 and I2 as in the prior art. Therefore, it is not necessary to provide an expensive calculation circuit capable of high-speed calculation in the control unit 30 for calculating the inductance, and the device structure can be simplified and realized at a low cost.

[0192] (First Modification)

[0193] Next, a modification example (first modification example) of the first embodiment will be described.

[0194] In this embodiment, when the control unit 30 energizes the motor 20 in the low speed mode with the switch combinations 1 and 2, it obtains the current values ​​I1 and I2 at the time when the switching elements are turned off, and detects the rotor position based on the magnitude relationship thereof.

[0195] Therefore, when the switching element is turned on, when a circulating current or a regenerative current flows through the coil of the brushless motor 20, the current values ​​I1 and I2 increase accordingly with the circulating current or the regenerative current, and the rotor position cannot be accurately detected based on the magnitude relationship between the current values ​​I1 and I2.

[0196] That is, even if the current path from the battery pack 18 as the DC power source to the brushless motor 20 is cut off at the OFF timing of the PWM control, current flows through the brushless motor 20 via the known parasitic diodes included in the switching elements Q1 to Q6 .

[0197] Then, if the current (i.e., circulating current or regenerative current) does not become zero at the time of PWM control on, then Fig.12As shown, after the turn-on time ton, a circulating current or a regenerative current flows from the battery pack 18 into the power supply path of the brushless motor 20 .

[0198] As a result, the current value detected by the current detection unit 34 increases by an amount corresponding to the circulating current or the regenerative current, and the rotor position cannot be accurately detected based on the magnitude relationship between the current values ​​I1 and I2 detected at the disconnection time.

[0199] Therefore, in this variation, at the on time ton of the PWM control, the circulating current or regenerative current is detected by the current detection unit 34 as the start current value I11, I21 of power-on, and at the off time of the PWM control, the end current value I12, I22 of power-on is detected by the current detection unit 34.

[0200] Then, the energization start current values ​​I11 and I21 as deviation values ​​are subtracted from the energization end current values ​​I12 and I22 thus detected, and the differences (I12-I11, I22-I21) as the subtraction results are obtained as the current values ​​I1 and I2 for position detection, respectively.

[0201] As a result, according to this modification, even if the brushless motor 20 is driven under usage conditions where the circulating current or the regenerative current cannot be reduced to zero within one cycle of PWM control, the rotation position of the brushless motor 20 can be detected without being affected by the circulating current or the regenerative current.

[0202] It should be noted that in order to obtain the energization start current values ​​I11 and I21 as described above, Fig.13 As shown, PWM carrier interrupt processing is also executed at the turn-on timing of PWM control.

[0203] Therefore, in the PWM carrier interrupt processing, first, in S650, it is determined whether the current operation mode is the low-speed mode or the high-speed mode. If it is the high-speed mode, the PWM carrier interrupt processing is terminated.

[0204] Furthermore, when it is determined in S650 that the operation mode is the low-speed mode, the process proceeds to S660 to determine whether the current interruption is an interruption when the switch combination is set to combination 1 or an interruption when the switch combination is set to combination 2.

[0205] If it is determined in S650 that the switch combination is set to combination 1, the process proceeds to S670, and the energization start current value I11 is acquired by the current detection unit 34.

[0206] If it is determined in S650 that the switch combination is set to combination 2, the process proceeds to S680 to acquire the energization start current value I21 through the current detection unit 34. When the energization start current value I11 or I21 is acquired in this way, the PWM carrier interruption process is terminated.

[0207] On the other hand, for the PWM carrier interrupt processing executed at the disconnection time of PWM control, such as Fig.14 As shown, when it is determined in S510 that the switch combination is set to combination 1, the processing of S522 and S524 is executed instead of the processing of S520.

[0208] Furthermore, when it is determined in S510 that the switch combination is set to combination 2, the processes of S612 and S614 are executed instead of the process of S610.

[0209] Then, in S522 , the energization end current value I12 is acquired by the current detection unit 34 , and in S524 , the difference ( I12 − I11 ) between the energization end current value I12 and the energization start current value I11 is calculated as the current value I1 , and then the process proceeds to S530 .

[0210] Furthermore, in S612 , the energization end current value I22 is acquired by the current detection unit 34 , and in S614 , the difference ( I22 − I21 ) between the energization end current value I22 and the energization start current value I21 is calculated as the current value I2 , and then the process proceeds to S620 .

[0211] By executing the PWM carrier interruption process at the on time and off time of the PWM control in this way, it is possible to obtain the current values ​​I1 and I2 flowing when the switching element of the inverter unit 32 is in the on state without being affected by the circulating current or the regenerative current. As a result, according to this modification, the rotor position can be detected more accurately based on the magnitude relationship of the current values ​​I1 and I2.

[0212] It should be noted that, in the present embodiment, the switch combinations when the motor 20 is driven by the combined PWM are described as combination 1 and combination 2, but it is also possible to Figure 4B Add combination 3 to the switch combination as shown in the dotted box of .

[0213] That is to say, even if there are three or more switch combinations, as long as the combinations are switched in sequence in synchronization with the control cycle of the PWM control and the magnitude relationship of the current values ​​obtained before and after the switching is determined, the rotor position can be detected in the same way as the above embodiment.

[0214] In addition, in this embodiment, the case where the energization period (on time) of the motor 20 per cycle of PWM control is set when the inverter unit 32 is driven by combination 1 or combination 2 to drive the motor 20 at a low speed is described.

[0215] However, the current flowing through the motor 20 changes according to the power supply voltage supplied from the battery pack 18 , and if the power supply voltage fluctuates, the current values ​​I1 and I2 also fluctuate.

[0216] Therefore, the power-on period (on time) of the motor 20 in each cycle of PWM control when the motor 20 is driven at a low speed in each combination 1 or 2 can also be set according to the voltage value of the power supply voltage used to drive the motor 20, and the lower the voltage value, the longer the on time.

[0217] In this way, when the motor 20 is driven by the combined PWM, it is possible to suppress the change in the current flowing through the brushless motor due to the fluctuation of the power supply voltage, thereby improving the detection accuracy of the rotor position.

[0218] In addition, in the present embodiment, the case where the magnitude relationship of the current values ​​generated by switching the switch combination is detected by the calculation processing of the microcomputer constituting the control unit 30 is described.

[0219] For example, the current values ​​(more preferably the peak current values) detected by the current detection unit 34 under multiple switch combinations may be stored in a holding circuit outside the control unit 30, and then the current values ​​stored in each storage circuit may be compared using a comparison circuit such as a comparator. In other words, the external circuit of the control unit 30 may be used to determine the magnitude relationship of the current values ​​generated by the switching of the switch combinations.

[0220] In this way, the control unit 30 only needs to read the magnitude relationship determined by the external circuit and then determine whether the magnitude relationship is reversed, thereby reducing the processing load of the control unit 30.

[0221] [Second embodiment]

[0222] In the first embodiment, the case where the rotor position is detected based on the magnitude relationship of the current values ​​generated by switching the switch combination when the motor 20 is driven at a low speed by the combined PWM drive has been described.

[0223] However, the rotor position can be detected based on the magnitude relationship of the inductance generated by the switching of the switch combination.

[0224] Therefore, in order to detect the rotor position, it is not necessary to sequentially switch the switch combination to combination 1 and 2 to detect the current value when the motor 20 is driven at a low speed as in the first embodiment, but it is also possible to measure the time taken for the current value to reach a predetermined threshold.

[0225] Therefore, next, in the present embodiment, an electric working machine is described that measures the time taken for the current value to reach a predetermined threshold value and detects the rotor position based on the magnitude relationship of the time.

[0226] The basic structure of the electric working machine 1 of the present embodiment is the same as that of the first embodiment, and therefore the description of the common structure will be omitted and the differences will be mainly described.

[0227] like Fig.15 As shown, the control unit 3 of the present embodiment includes a current value comparison unit 38 in addition to the control unit 30 , the inverter unit 32 , the current detection unit 34 , and the position detection unit 36 ​​.

[0228] The current value comparison unit 38 is configured to compare the current value detected by the current detection unit 34 with a reference current value outputted from the control unit 30 as a threshold value, and output a signal to the control unit 30 when the current value detected by energizing the motor 20 rises and reaches the reference current value.

[0229] In addition, the control unit 30 performs the PWM carrier interrupt processing in place of the first embodiment. Fig.18 The current value comparison unit output signal interrupt processing and Fig.19 The PWM timer overflow interrupt processing shown in FIG. 1 is a timer counter that measures one cycle of PWM control.

[0230] In addition, if Fig.16 As shown, the control unit 30 executes the processes of S212 and S214 instead of the process of S210 of setting the first current acquisition flag to “not yet” in the motor stop process.

[0231] In addition, if Fig.17 As shown, in the motor driving process, the process of S345 is executed between S340 and S350, and the processes of S362, S364 and S375 are executed instead of the process of S370, and the process of S415 is executed before entering S420 from S300.

[0232] Here, the process of S212 executed in the motor stop process is a process for prohibiting the interrupt process based on the output signal from the current value comparison unit 38 (current value comparison unit output signal interrupt process), and the process of S214 is a process for setting the first timer value acquisition flag to "not yet".

[0233] It should be noted that the first timer value acquisition flag is a flag for determining whether a timer value has been acquired from the PWM timer after the driving of the motor 20 in combination 1 is started.

[0234] Next, the process of S345 executed in the motor driving process is a process of setting the initial state of the magnitude relationship between the timer values ​​T1 and T2 obtained from the PWM timer when the motor 20 is driven in combination 1 or combination 2.

[0235] It should be noted that the initial state of the relationship between the timer values ​​T1 and T2 is as follows: Figure 4B As shown in the right column of , like the initial state of the magnitude relationship between the current values ​​I1 and I2, it is preset according to the rotation range and rotation direction of each motor 20 and stored in the nonvolatile memory 30A together with the switch combination. Therefore, in S345, the initial state of the magnitude relationship between the current values ​​I1 and I2 is read from the nonvolatile memory 30A for setting.

[0236] In addition, in S362 executed in the motor drive process, an interrupt based on the output signal from the current value comparison unit 38 is allowed, and in S364, an initial value is set for the PWM timer. In addition, in S375, similarly to S370 of the above-mentioned embodiment, the combination 1 set as the combination PWM in S350 starts to output a drive signal to the inverter unit 32 (combination PWM output), and timing (counting operation) with the PWM timer is started.

[0237] As a result, when the drive signal is output to the inverter unit 32 in combination 1, the PWM timer starts from the initial value at the same time to count the control cycle of the PWM control. Then, when the PWM timer counts the control cycle of the PWM control, the PWM timer overflows and executes Fig.19 The PWM timer overflow interrupt processing is shown.

[0238] In the PWM timer overflow interrupt processing, if Fig.19 As shown, in S910, the counting operation of the PWM timer is stopped, and in S920, an initial value for counting the control period of the PWM control is set to the PWM timer in the same manner as in S364.

[0239] In the next S930, the drive signal is output to the inverter unit 32 (combination PWM output) using combination 1 or combination 2 currently set as combination PWM, and timing (counting operation) using the PWM timer is started. After the processing of S930 is executed, the PWM timer overflow interrupt processing is terminated.

[0240] As a result, if Fig. 20 , Fig.21 As shown, the PWM timer completes counting of the timer value, taking the time from the initial value to overflow as one cycle of PWM control.

[0241] Then, if Fig.18As shown, in the current value comparison unit output signal interrupt processing, first, in S700, the combined PWM output in the low speed mode is stopped. Then, in the next S710, it is determined whether the current interrupt is an interrupt when the switch combination is set to combination 1 or an interrupt when the switch combination is set to combination 2.

[0242] Then, when the switch combination is set to combination 1, enter S720 to obtain the current timer value T1 from the PWM timer. In the next S730, the switch combination of the combined PWM is changed to combination 2, and then enter S740 to determine whether the initial timer value acquisition flag is "completed".

[0243] If the initial timer value acquisition flag is not "completed", it means that the current operation mode is just switched to the low-speed mode, so the current value comparison unit output signal interrupt processing is terminated. If the initial timer value acquisition flag is "completed", enter S750.

[0244] Furthermore, when it is determined in S710 that the current interrupt is an interrupt when the switch combination is set to combination 2, the process proceeds to S810. Then, in S810, the current timer value T2 is acquired from the PWM timer, and the process proceeds to S820.

[0245] In S820, the switch combination of the combination PWM is changed to combination 1, and then the process proceeds to S830, the initial timer value acquisition flag is set to "completed", and then the process proceeds to S750.

[0246] Then, in S750 , the magnitude relationship between the latest timer values ​​T1 and T2 acquired in S720 and S810 is determined, and it is determined whether the magnitude relationship is reversed.

[0247] That is, the current value comparison unit 38 outputs an interrupt signal when the current value detected by the current detection unit 34 reaches the reference current value. Fig. 20 As shown, the timer values ​​T1 and T2 are values ​​indicating the time taken from the start of driving the inverter unit 32 by the combination 1 and 2 until the current value reaches the reference current value from 0.

[0248] Furthermore, the timer values ​​T1 and T2 change according to the inductance of the motor 20 and further according to the rotational position, and the magnitude relationship thereof is reversed at a predetermined rotational position, similar to the magnitude relationship between the current values ​​I1 and I2 .

[0249] Therefore, by determining in S750 whether the magnitude relationship between the timer values ​​T1 and T2 is reversed, it is determined whether the rotor 22 has passed a specified rotation position (for example, a reference angle of 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, or 300 degrees).

[0250] Then, when it is determined in S750 that the magnitude relationship between the timer values ​​T1 and T2 has not reversed, the current value comparison unit output signal interrupt processing is terminated, and when it is determined that the magnitude relationship between the timer values ​​T1 and T2 has reversed, the rotor position is updated.

[0251] It should be noted that when it is initially determined in S750 whether the magnitude relationship between the timer values ​​T1 and T2 is reversed, the initial state of the magnitude relationship of the timer values ​​stored in the nonvolatile memory 30A is used as the previous magnitude relationship.

[0252] Next, in S770, a switch combination (combination 1, combination 2) to be used for low-speed driving motor 20 is selected according to the updated rotor position.

[0253] Then, in S780, the magnitude relationship between the current timer values ​​T1 and T2 is stored in RAM or the like as an initial state for comparison with the magnitude relationship between the next timer values ​​T1 and T2, and then the process proceeds to S790.

[0254] In S790, one of the two switch combinations selected in S770 (here, combination 1) is set as a combination PWM to be used for driving the motor 20 at a low speed via the inverter unit 32, and then the process proceeds to S800.

[0255] Then, in S800 , in order to resume the motor driving after the rotor position is updated, the first timer value acquisition flag is set to “not yet”, and the current value comparison unit output signal interruption processing is terminated.

[0256] As described above, in the electric working machine 1 of the present embodiment, the switch combination is alternately switched between the combination 1 and the combination 2 in synchronization with the control cycle of the PWM control, as in the first embodiment.

[0257] Moreover, if Fig.21 As shown, the time taken for the current flowing through the motor 20 to reach the reference current value under the energization after the switching is measured using the count value of the PWM timer, and the time is used as the timer values ​​T1 and T2.

[0258] Then, each time the timer values ​​T1 and T2 are measured in this way, their size relationship with the previously measured timer values ​​T2 and T1 is detected. When the detected size relationship is reversed from the previously detected size relationship (or initial state), the rotation position of the motor 20 is detected and the power-on mode is switched.

[0259] Therefore, in this embodiment, the rotation position of the motor 20 can be grasped within a wide rotation range from extremely low speed to high speed, and the power supply mode of the motor 20 can be reasonably controlled, thereby achieving the same effect as the first embodiment.

[0260] In addition, in this embodiment, the current value detected by the current detection unit 34 is used to compare with the reference current value in the current value comparison unit 38, and there is no need to use an A / D converter to A / D convert the current value and then input it into the control unit 30 in order to detect the rotor position.

[0261] Therefore, it is not necessary to provide the control unit 30 with an A / D converter capable of performing A / D conversion of the current value at high speed, and the configuration of the control unit 30 can be simplified.

[0262] (Second Modification)

[0263] Next, a modification example (second modification example) of the second embodiment will be described.

[0264] In this embodiment, when the motor 20 is energized by the switch combinations 1 and 2 in the low speed mode, the control unit 30 measures the time taken for the current value detected by the current detection unit 34 to reach the reference current value as the timer values ​​T1 and T2.

[0265] Therefore, as described in the first modification, if a circulating current or a regenerative current flows when the switching element of the inverter unit 32 is turned on to start energizing, the rotation position of the brushless motor 20 cannot be accurately detected based on the magnitude relationship between the measured timer values ​​T1 and T2.

[0266] That is to say, Fig. 22 As shown, when the circulating current or the regenerative current cannot be reduced to zero within one cycle of the PWM control, the current value detected by the current detection unit 34 at the on time ton of the PWM control increases by an amount corresponding to the circulating current or the regenerative current.

[0267] Therefore, if the reference current value output to the current value comparison unit 38 is constant, the timer values ​​T1 and T2 are not the time required for the current value to rise to the specified threshold value, and the rotor position cannot be accurately detected based on the magnitude relationship between the timer values ​​T1 and T2.

[0268] Therefore, in this variation, at the turn-on time ton of the PWM control, the circulating current or regenerative current is detected by the current detection unit 34 as the power-on start current value Ist, and the reference current value output to the current value comparison unit 38 is set to the current value obtained by adding the specified threshold value and the power-on start current value Ist.

[0269] As a result, the timer values ​​T1 and T2 are the time required for the current flowing through the brushless motor 12 to rise to a predetermined threshold value after the current supply path from the battery pack 18 to the brushless motor 12 is opened at the OFF timing of the PWM control.

[0270] Therefore, in this variation, as in the first variation, even if the brushless motor 20 is driven under usage conditions where the circulating current or regenerative current cannot be reduced to zero within one cycle of PWM control, the rotational position of the brushless motor 20 can be detected without being affected by the circulating current or regenerative current.

[0271] It should be noted that when setting the reference current value as described above, Fig.23 As shown, in S930 of the PWM timer overflow interrupt processing, a drive signal is output to the inverter unit 32, and timing with the PWM timer is started, and then the processing of S940 and S950 is executed.

[0272] Then, in S940 , the current value detected by the current detection unit 34 at this time is acquired as the energization start current value Ist, and in S950 , the energization start current value Ist is added to a preset threshold value to set a reference current value output to the current value comparison unit 38 .

[0273] By updating the reference current value in each cycle of PWM control in this way, the time required for the current value to rise to the threshold value after power is supplied from the battery pack 18 to the brushless motor 20 can be obtained as the timer values ​​T1 and T2.

[0274] It should be noted that in this embodiment, the case where the combined PWM output is stopped when the current value reaches the reference current value is described, but the combined PWM output can also be continued after the current value reaches the reference current value, so that more current flows through the motor 20 and a greater torque is generated.

[0275] [Other embodiments]

[0276] As mentioned above, although the form for implementing this invention was described, this invention is not limited to the said embodiment and modification, It can implement|achieve various modifications.

[0277] For example, in the above embodiment, the motor 20 is described as an IPM type three-phase brushless motor in which magnets are embedded in the rotor 22 , but the motor 20 may be an SPM (Surface Permanent Magnet) type brushless motor in which magnets are attached around the rotor 22 .

[0278] That is, as long as the inductance of the stator coil changes according to the rotational position of the rotor, even if it is an SPM (Surface Permanent Magnet) type brushless motor, the present invention can be applied in the same manner as described above.

[0279] In the above embodiment, the rotor coil and each phase terminal of the brushless motor are connected in a delta configuration. However, even if the rotor coil of the brushless motor is connected in a Y configuration, the present invention can be applied in the same manner as described above.

[0280] In the above embodiment, when it is determined in the determination process of S550 or S750 that the magnitude relationship between the current values ​​I1 and I2 or the magnitude relationship between the timer values ​​T1 and T2 is reversed, the rotor position is updated in S560 or S760.

[0281] However, considering that the magnitude relationship of the inductance of the motor 20, the current value corresponding to the inductance, or the timer time may be interchanged due to noise, etc. Therefore, when the magnitude relationship is detected to be reversed in S550 or S750, the magnitude relationship may be determined multiple times thereafter, and the rotor position may be updated after confirming that the magnitude relationship is no longer reversed.

[0282] In this way, even when the inductance of the motor 20, the current value corresponding to the inductance, or the timer time are temporarily interchanged due to noise or the like, erroneous detection and erroneous updating of the rotor position can be suppressed.

[0283] In addition, in the above embodiment, when a specified rotational position (rotor position) of the motor 20 is detected, the power-on mode is changed to a switch combination (combination 1, combination 2) corresponding to the rotational position, but the current value flowing through the motor 20 is sometimes unstable just after the change.

[0284] Therefore, if Fig.11 and Fig.21 As shown, when a predetermined rotational position of the motor 20 is detected and the energization mode is switched, determination of the magnitude relationship between the current values ​​I1 and I2 or the timer values ​​T1 and T2 may be prohibited during a predetermined mask period.

[0285] In the above embodiment, the lawn mower is used as an example of the electric working machine of the present invention. However, the technology of the present invention can be applied to any electric working machine having a brushless motor as a power source, as in the above embodiment.

[0286] That is, the technology of the present invention can be applied to electric tools for masonry, metalworking, and carpentry, gardening machines, etc. More specifically, it can be applied to various electric working machines such as electric hammers, electric hammer drills, electric drills, electric screwdrivers, electric wrenches, electric grinders, electric circular saws, electric reciprocating saws, electric wire saws, electric hammers, electric cutters, electric chain saws, electric planers, electric nail guns (including riveters), electric hedge trimmers, electric lawn mowers, electric brush cutters, electric vacuum cleaners, electric hair dryers, electric sprayers, electric spreaders, and electric dust collectors.

[0287] In addition, multiple functions of one structural element in the above-mentioned embodiment can be realized by multiple structural elements, or one function of one structural element can be realized by multiple structural elements. In addition, multiple functions of multiple structural elements can be realized by one structural element, and one function realized by multiple structural elements can be realized by one structural element. In addition, part of the structure of the above-mentioned embodiment can also be omitted. In addition, at least a part of the structure of the above-mentioned embodiment can also be added to the structure of other above-mentioned embodiments or replaced. It should be noted that all methods included in the technical ideas determined by the text recorded in the claims are embodiments of the present invention.

Claims

1. An electric working machine having a brushless motor as a power source, wherein: The electric working machine comprises: an inverter unit including a plurality of switching elements respectively provided on a current-carrying path between a DC power supply and a plurality of terminals of the brushless motor, and configured to be able to control the energization and the energization direction of the plurality of coils of the brushless motor by using the plurality of switching elements; and a control unit configured to switch a power supply mode for supplying power to the plurality of coils using the inverter unit at each specified commutation time of the brushless motor, and to turn on / off the plurality of switching elements of the inverter unit according to the power supply mode, thereby performing PWM control on the current supplied to the plurality of coils, The control unit is configured as follows: as a power-on mode switched at each commutation moment, a plurality of switch combinations having different on / off states of the plurality of switch elements are provided, and the switch combination for controlling the on / off state of the switch elements is sequentially switched to one of the plurality of switch combinations in synchronization with the cycle of the PWM control; at a moment when the magnitude relationship of the inductance generated by each different current path due to the switching of the switch combination is interchanged, the rotation position of the brushless motor is detected to set the commutation moment.

2. The electric working machine according to claim 1, wherein: The electric working machine includes a current detection unit configured to detect a current flowing through the brushless motor. The control unit is configured to obtain current values ​​detected by the current detection unit when the brushless motor is energized by the plurality of switch combinations as parameters representing the inductance of the brushless motor, and detect the rotation position based on the magnitude relationship of the obtained current values.

3. The electric working machine according to claim 2, wherein: The control unit is configured to obtain, as a parameter indicating the inductance of the brushless motor, a difference between a energization start current at the start of energization and a energization end current at the end of energization when energization is applied to the brushless motor using the switch combination.

4. The electric working machine according to claim 1, wherein: The electric working machine includes a current detection unit configured to detect a current flowing through the brushless motor. The control unit is configured to measure the time taken for the current value detected by the current detection unit to reach a specified threshold value after the brushless motor starts to be energized by the multiple switch combinations, as a parameter representing the inductance of the brushless motor, and detect the rotation position based on the magnitude relationship of the measured time.

5. The electric working machine according to claim 4, wherein: The control unit is configured to measure, as a parameter indicating the inductance of the brushless motor, a time taken for the current value to change from a starting current at the start of energization to an amount equal to a predetermined threshold value when the brushless motor is energized by the switch combination.

6. The electric working machine according to any one of claims 1 to 5, wherein: The plurality of switch combinations are respectively set such that when the on / off state of the switch element is controlled by each switch combination, a rotor of the brushless motor generates torque.

7. The electric working machine according to any one of claims 1 to 5, wherein: The control unit is configured to adjust an on-time of the switching element when the brushless motor is PWM-controlled by the switch combination, according to a power supply voltage of the DC power supply.

Images