Electric working machine

Abstract

To suppress the increase in the peak value of the current flowing through the brushless motor in an electric working machine when the rotation speed of a brushless motor drops during heavy load operation.SOLUTION: The control unit selects a pair of driven switches in accordance with the rotational position of the motor each time the rotation angle detection unit detects that the motor has rotated a reference rotation angle, and turns on the pair of driven switches in a predetermined current conduction pattern to energize and drive the motor. The control unit has a time counter that measures the time until the rotation angle detection unit detects that the motor has rotated a reference rotation angle as a current conduction control time, and when the current conduction control time reaches a time limit during measurement by the time counter, cuts off the current to the brushless motor through current conduction control.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to an electric work machine equipped with a brushless motor. [Background technology]

[0002] Patent Document 1 describes that in an electric working machine equipped with a brushless motor, both PWM control and conduction angle control are used to control the brushless motor. Of these, PWM control sets the drive duty ratio of the switching element selected for each specified rotation angle of the brushless motor so that the brushless motor reaches the target rotation speed, and turns the selected switching element on and off according to that drive duty ratio.

[0003] In addition, in conduction angle control, the on period of the switching element selected as described above is set by the rotation angle (i.e., conduction angle) of the brushless motor so that the brushless motor reaches the target rotation speed, and the switching element is turned on according to that conduction angle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-31617 Summary of the Invention [Problem to be solved by the invention]

[0005] Conduction angle control does not require switching elements to be turned on and off at a predetermined cycle, as is the case with PWM control, so the number of times the switching elements are switched can be reduced compared to PWM control. This reduces switching loss that occurs in the current path to the brushless motor, and suppresses heat generation in the motor drive system.

[0006] However, when the rotation speed of a brushless motor decreases during heavy-load operation by an electric power tool, the time required for the brushless motor to rotate a predetermined angle increases, which in turn increases the ON time of the switching elements due to conduction angle control. When the ON time of the switching elements increases, the peak value of the current flowing through the brushless motor increases, causing problems such as failure of the switching elements or demagnetization of the brushless motor's magnets.

[0007] One aspect of the present disclosure aims to suppress an increase in the peak value of current flowing through a brushless motor in an electric work machine equipped with a brushless motor when the rotation speed of the brushless motor decreases during heavy-load work. [Means for solving the problem]

[0008] An electric work machine according to one aspect of the present disclosure includes a brushless motor, a plurality of positive electrode side current paths, a plurality of negative electrode side current paths, a plurality of high-side switches, a plurality of low-side switches, a rotation angle detection unit, and a control unit.

[0009] The brushless motor has a plurality of terminals and is configured to rotate an object to be driven. The plurality of positive electrode side current paths are configured to connect the plurality of terminals of the brushless motor to the positive electrode of the DC power supply, and the plurality of negative electrode side current paths are configured to connect the plurality of terminals of the brushless motor to the negative electrode of the DC power supply.

[0010] The plurality of high-side switches are provided on the plurality of positive-side current paths, and the plurality of low-side switches are provided on the plurality of negative-side current paths, respectively. The rotation angle detector is configured to detect the rotation angle of the brushless motor.

[0011] The control unit is configured to perform the following power supply control. That is, each time the rotation angle detector detects that the brushless motor has rotated a predetermined reference rotation angle, the controller selects one of a plurality of high-side switches and one of a plurality of low-side switches, which are preset according to the rotation position of the brushless motor, as a pair of driven switches, and then turns on the pair of driven switches in a predetermined current conduction pattern to energize and drive the brushless motor.

[0012] The control unit also includes a time counter. The time counter is configured to measure, each time the rotation angle detection unit detects that the brushless motor has rotated a reference rotation angle, the time until the brushless motor subsequently rotates the reference rotation angle as a power supply control time. Then, when the power supply control time reaches a preset time limit during measurement by the time counter, the control unit cuts off power supply to the brushless motor through the power supply control.

[0013] In this way, the control unit selects a pair of driven switches that will energize the brushless motor each time the brushless motor rotates by the reference rotation angle, and energizes the brushless motor by turning on the selected pair of driven switches in a predetermined energization pattern. Therefore, if the rotation speed of the brushless motor decreases, the energization control time while the brushless motor rotates by the reference rotation angle becomes longer.

[0014] In response to this, the control unit measures the power supply control time while the brushless motor rotates a reference rotation angle using a time counter, and when the power supply control time reaches a time limit during this measurement, it cuts off the power supply to the brushless motor through the power supply control.

[0015] Therefore, with the electric power tool disclosed herein, when the rotation speed of the brushless motor decreases during heavy-load work and the energization control time becomes longer, it is possible to prevent an increase in the peak value of the current flowing through the brushless motor, thereby preventing the high-side switch and low-side switch that are turned on to energize the brushless motor from breaking down and the magnet of the brushless motor from being demagnetized during heavy-load work using the electric power tool. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a configuration diagram showing the overall configuration of a grass mower according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the circuit configuration of a controller of the brush cutter. [Figure 3] 4 is a time chart showing a control operation by the control circuit when there is no load. [Figure 4] 4 is a time chart showing a control operation by the control circuit under a heavy load. [Figure 5] 4 is a time chart showing a control operation performed by a control circuit when a motor lock is detected. [Figure 6] 4 is a flowchart showing a main loop control process executed by a control circuit. [Figure 7] 10 is a flowchart showing a main loop timer interrupt process executed by the control circuit. [Figure 8] 10 is a flowchart showing a commutation timer interrupt process executed by a control circuit. [Figure 9] 4 is a flowchart showing a Hall sensor signal detection process executed by a control circuit. [Figure 10] 4 is a flowchart showing a switch operation detection process executed by a control circuit. [Figure 11] 4 is a flowchart showing a motor lock detection process executed by a control circuit. [Figure 12] 4 is a flowchart showing a motor control process executed by a control circuit. [Figure 13] 4 is a flowchart showing a display process executed by a control circuit. [Figure 14] 6 is a time chart showing a control operation under a heavy load by the control circuit of the second embodiment. [Figure 15] 10 is a flowchart illustrating a main loop timer interrupt process according to the second embodiment. [Figure 16]10 is a time chart showing a control operation under a heavy load by the control circuit of the third embodiment. [Figure 17] 10 is a flowchart illustrating a main loop timer interrupt process according to the third embodiment. [Figure 18] 10 is a time chart showing a control operation under a heavy load by the control circuit of the fourth embodiment. [Figure 19] 10 is a flowchart illustrating a main loop timer interrupt process according to the fourth embodiment. [Figure 20] 10 is a time chart showing a control operation of the control circuit of the fifth embodiment under heavy load. DETAILED DESCRIPTION OF THE INVENTION

[0017] [Summary of the embodiment] In one embodiment, the electric operating machine may include a brushless motor having a plurality of terminals and configured to rotate a driven object.

[0018] Additionally / alternatively, the electric operating machine may include a plurality of positive-side current paths configured to connect a plurality of terminals of the brushless motor to a positive electrode of the DC power supply, and a plurality of high-side switches may be provided on each of the plurality of positive-side current paths.

[0019] Additionally / alternatively, the electric operating machine may include a plurality of negative-side current paths configured to connect a plurality of terminals of the brushless motor to a negative electrode of the DC power supply, and a plurality of low-side switches may be provided on each of the plurality of negative-side current paths.

[0020] Additionally or alternatively, the electric working machine may include a rotation angle detection unit configured to detect the rotation angle of the brushless motor. Additionally or alternatively, the electric working machine may include a control unit configured to control the energization of the brushless motor.

[0021] The control unit may be configured to select, in the energization control, one of a plurality of high-side switches and one of a plurality of low-side switches preset in accordance with the rotation angle of the brushless motor as a pair of driven switches each time the rotation angle detection unit detects that the brushless motor has rotated a predetermined reference rotation angle.

[0022] Furthermore, the control unit may be configured to energize the brushless motor by turning on the pair of driven switches in a predetermined energization pattern in the energization control, thereby energizing the brushless motor and driving the brushless motor.

[0023] Additionally / alternatively, the control unit may include a time counter configured to measure, each time the rotation angle detection unit detects that the brushless motor has rotated a reference rotation angle, the time until the brushless motor subsequently rotates the reference rotation angle as the power supply control time.

[0024] The control unit may be configured to cut off the power supply to the brushless motor through the power supply control when the power supply control time reaches a preset time limit during measurement by the time counter.

[0025] In one embodiment, if an electric work machine includes the above-mentioned brushless motor, multiple positive electrode side current paths, multiple negative electrode side current paths, multiple high side switches, multiple low side switches, a rotation angle detection unit, and a control unit, such an electric work machine can suppress an increase in the peak value of the current flowing through the brushless motor when the rotation speed of the brushless motor decreases during heavy load work and the current control time becomes longer.

[0026] Therefore, with such an electric work machine, it is possible to prevent the high-side switch and low-side switch, which are turned on to supply power to the brushless motor, from failing during heavy-load work, and to prevent the magnets of the brushless motor from being demagnetized.

[0027] Additionally / alternatively, the control unit may be configured to resume power supply control when the rotation angle detection unit detects that the brushless motor has rotated a reference rotation angle after the power supply control time reaches the time limit and power supply to the brushless motor is cut off.

[0028] With an electric work machine having a control unit configured in this manner, even if the power supply to the brushless motor is cut off by the power supply control during heavy load work by the electric work machine before the brushless motor rotates by the reference rotation angle and switches the power supply path, the power supply control can be resumed at the next reference rotation angle.

[0029] Therefore, it is possible to suppress an increase in the peak value of the current flowing through the brushless motor when the electric work machine is performing heavy load work, while continuously controlling the supply of current to the brushless motor, thereby driving the brushless motor.

[0030] Additionally / alternatively, the control unit may be configured to resume power supply control when a preset waiting time has elapsed after the power supply control time has reached the limit time and power supply to the brushless motor has been cut off.

[0031] With an electric work machine having a control unit configured in this manner, even if the power supply to the brushless motor is cut off by the power supply control during heavy load work by the electric work machine before the brushless motor rotates by the reference rotation angle and switches the power supply path, the power supply control will resume once the standby time has elapsed.

[0032] Therefore, it is possible to suppress an increase in the peak value of the current flowing through the brushless motor when the electric work machine is performing heavy load work, while continuously controlling the supply of current to the brushless motor, thereby driving the brushless motor.

[0033] Additionally / alternatively, the control unit may be configured to perform current cut-off control in which, after the current control time reaches the time limit and current to the brushless motor is cut off, the multiple high-side switches and the multiple low-side switches are kept in an off state until current control is resumed.

[0034] In an electric work machine with a controller configured in this way, when the current control time for each reference rotation angle of the brushless motor reaches the time limit, the current flowing to the brushless motor is cut off by the current cut-off control, which more reliably prevents the high-side switch and low-side switch from breaking down or the magnet of the brushless motor from being demagnetized due to the current flowing through the brushless motor.

[0035] Additionally / alternatively, the control unit may be configured to perform low-output control in which, after the current supply to the brushless motor is cut off when the current supply control time reaches the limit time, the pair of driven switches are periodically turned on and off in a second current supply pattern different from the current supply control until the current supply control is resumed, thereby causing a smaller current to flow to the brushless motor than during the current supply control.

[0036] In an electric work machine with a control unit configured in this way, when the energization control time for each reference rotation angle of the brushless motor reaches the time limit, low-output control is used to allow a smaller current to flow through the brushless motor than during energization control. This not only prevents the high-side switch or low-side switch from breaking down or the magnet of the brushless motor from being demagnetized due to the current flowing through the brushless motor, but also prevents the brushless motor from stopping rotation before normal energization control is resumed.

[0037] Additionally / alternatively, the second current conduction pattern for low output control may be set so that the amount of heat generated in the drive system of the brushless motor, which includes multiple high-side switches and multiple low-side switches, is less than the amount of heat generated during current conduction control.

[0038] With an electric work machine having a control unit configured in this way, when a pair of driven switches are turned on and off using low-output control, the amount of heat generated in the drive system of the brushless motor increases, preventing the drive system from breaking down.

[0039] Additionally / alternatively, the control unit may be configured to, after the power supply control time reaches the time limit and power supply to the brushless motor is cut off, notify of an abnormality in power supply to the brushless motor until power supply control is resumed.

[0040] With an electric work machine having such a control unit, when the power supply control time reaches the time limit and the power supply to the brushless motor is cut off, the user can be notified of a power supply abnormality. This power supply abnormality notification allows the user to know that the peak value of the current flowing when the brushless motor is driven has increased and that the protection function of the electric work machine is operating.

[0041] Additionally / alternatively, when a second current supply abnormality different from the first current supply abnormality in which the current supply control time reaches the time limit occurs during current supply control, the control unit may be configured to cut off current supply to the brushless motor and notify the power supply abnormality to the brushless motor in a different notification format from that used when the first current supply abnormality occurs.

[0042] An electric work machine with a control unit configured in this way can notify the user of an abnormality in a different manner from the first energization abnormality, for example, when the driven object hits an obstacle and the brushless motor stops rotating, resulting in a motor lock. This allows the user to not only detect an abnormality in the energization of the brushless motor, but also to understand the cause of the abnormality.

[0043] Additionally / alternatively, the control unit may be configured to perform conduction angle control as the conduction control, in which the conduction angle at which a pair of driven switches are simultaneously turned on within a reference rotation angle is controlled so that the rotation speed of the brushless motor becomes a predetermined target rotation speed.

[0044] Additionally / alternatively, the control unit may be configured to perform PWM control as the power supply control, in which at least one of the pair of driven switches is periodically turned on and off in accordance with a drive duty ratio that is set so that the rotation speed of the brushless motor becomes a predetermined target rotation speed.

[0045] In this way, whether the control unit of the electric work machine performs conduction angle control or the control unit of the electric work machine performs PWM control, the above-mentioned effects can be obtained by cutting off the conduction through the conduction control when the conduction control time for each reference rotation angle becomes long.

[0046] Specific Exemplary Embodiments Exemplary embodiments of the present disclosure will be described below in conjunction with the drawings. [First embodiment] [composition] In this embodiment, a grass cutter will be used as an example of an electric work machine.

[0047] As shown in Fig. 1, the electric working machine 1 of this embodiment is a brush cutter that includes a main pipe 2, a control unit 3, a drive unit 4, and a handle 7. The main pipe 2 is formed in the shape of a long, hollow rod. The control unit 3 is provided at the rear end of the main pipe 2, and the drive unit 4 is provided at the front end of the main pipe 2.

[0048] A rotary blade 5 is detachably and rotatably attached to the drive unit 4. The rotary blade 5 is used to cut objects to be cut, such as grass and small trees, and the one shown in Figure 1 is a so-called chip saw.

[0049] That is, the rotary blade 5 is made of metal, has a disk shape, and has saw-tooth teeth formed all around the periphery, with a hard tip attached to the tip of each tooth. A cover 6 is provided on the front end side of the main pipe 2. This cover 6 is provided to prevent grass cut by the rotary blade 5 from flying towards the worker.

[0050] The drive unit 4 houses a motor 30 (see Figure 2), which is a drive source for rotating the rotary blade 5, and a gear mechanism that transmits the rotation of the motor 30 to an output shaft, and the rotary blade 5 is detachably attached to the output shaft.

[0051] The motor 30 is an IPM (Interior Permanent Magnet) type three-phase brushless motor with a magnet embedded in the rotor, and is drive-controlled by a controller 40 in the control unit 3 (see FIG. 2).

[0052] The handle 7 is connected to the main pipe 2 near the midpoint in the longitudinal direction of the main pipe 2. The handle 7 is for an operator to hold when mowing using the electric work machine 1, and in this embodiment is configured as a so-called U-handle with grips on both ends. The handle 7 may also be a loop handle or other type of handle.

[0053] An operation and display unit 8 is provided on one grip portion of the handle 7 so that the operator can operate it with his or her fingers and check the operating state. The operation and display unit 8 is provided with a trigger switch 10, a lock-off switch 12, and a display panel 14.

[0054] The display panel 14 is used to display the rotation state of the motor 30 and the remaining capacity of the battery pack 18 (the amount of power remaining in the battery in the battery pack 18), etc. The display panel 14 is also provided with operation switches that allow the operator to set the rotation direction of the motor 30 (in other words, the rotary blade 5), etc.

[0055] The battery pack 18 is detachably attached to the rear end of the control unit 3 and serves to supply DC power to the control unit 3. The trigger switch 10 is an operation switch for inputting a drive command for the motor 30, and the lock-off switch 12 is a switch that allows an operator to operate the trigger switch 10 by pressing it.

[0056] The trigger switch 10 and the display panel 14 are connected to a controller 40 in the control unit 3 via a cable 19. The controller 40 monitors the operating states of the trigger switch 10 and the display panel 14, and drives the motor 30, switches the rotation direction, or displays information on the display panel 14.

[0057] The control unit 3 is provided with a main power switch 20 (see FIG. 2) for issuing commands to start and stop the controller 40. The display panel 14 is also provided with LEDs for displaying various states, such as a main power indicator LED that is lit (turned on) when the main power switch 20 is on and the controller 40 is operating.

[0058] The status display LEDs include an error detection notification LED 15 that lights up (turns on) when an abnormality such as a motor lock is detected, and a current restriction notification LED 16 that lights up (turns on) when the power supply to the motor 30 is restricted by the control circuit 50 described below (see Figure 2).

[0059] The controller 40 is configured to receive power from the battery pack 18 and drive and control the motor 30. That is, as shown in FIG. 2, the controller 40 includes a bridge circuit 42, a gate circuit 44, a regulator 46, a power supply control circuit 48, and a control circuit 50.

[0060] The bridge circuit 42 receives power from the battery pack 18 and supplies current to each phase winding of the motor 30. In this embodiment, the bridge circuit 42 is in the form of a three-phase full-bridge circuit including first to sixth switching elements Q1 to Q6.

[0061] In the bridge circuit 42, the first to third switching elements Q1 to Q3 are provided as so-called high-side switches on positive-side current paths L1, L2, and L3 between the first terminal U, second terminal V, and third terminal W of the motor 30 and a power supply line connected to the positive side of the battery pack 18. The first terminal U, second terminal V, and third terminal W correspond to the U-phase, V-phase, and W-phase of the motor 30, respectively.

[0062] In addition, the fourth to sixth switching elements Q4 to Q6 are provided as so-called low-side switches on the negative-side current paths L4, L5, and L6 between the first terminal U, second terminal V, and third terminal W of the motor 30 and the ground line connected to the negative side of the battery pack 18.

[0063] In this embodiment, the first to sixth switching elements Q1 to Q6 are in the form of n-channel metal oxide semiconductor field effect transistors (MOSFETs). Therefore, first to sixth diodes D1 to D6 (so-called parasitic diodes) are connected in parallel between the drain and source of each of the first to sixth switching elements Q1 to Q6, respectively, with the forward direction from the source to the drain.

[0064] Therefore, when the corresponding one of the first to sixth switching elements Q1 to Q6 is in the off state, each of the first to sixth diodes D1 to D6 can pass a current in the direction opposite to the forward direction from the positive electrode side to the negative electrode side of the battery pack 18.

[0065] The gate circuit 44 individually turns on / off the first to sixth switching elements Q1 to Q6 in the bridge circuit 42 in accordance with a control signal output from the control circuit 50, thereby passing current through each phase winding of the motor 30 and rotating the motor 30.

[0066] 2 represent control signals for the first to third switching elements Q1 to Q3, which are high-side switches for the U, V, and W phases of the motor 30. Control signals UL, VL, and WL represent control signals for the fourth to sixth switching elements Q4 to Q6, which are low-side switches for the U, V, and W phases of the motor 30.

[0067] The regulator 46 receives power from the battery pack 18 via a power supply control circuit 48 and generates a power supply voltage (constant DC voltage) Vcc for operating each part in the controller 40. The control circuit 50 and each part in the controller 40 operate using the power supply voltage Vcc from the regulator 46 as a power source.

[0068] When main power switch 20 is in the on state, power supply control circuit 48 opens the power supply path from battery pack 18 to regulator 46, causing regulator 46 to generate power supply voltage Vcc. Furthermore, when a power cutoff signal is input from battery pack 18 or control circuit 50, power supply control circuit 48 cuts off the power supply path from battery pack 18 to regulator 46, causing regulator 46 to stop generating power supply voltage Vcc. The power cutoff signal is output when some abnormality, such as a drop in battery voltage, is detected in battery pack 18 or control circuit 50.

[0069] The control circuit 50 drives and controls the motor 30 via the gate circuit 44, and corresponds to the control unit of the present disclosure. The control circuit 50 in this embodiment is in the form of an MCU (Micro Control Unit) including a CPU, ROM, and RAM. The control circuit 50 in this embodiment is provided with a non-volatile memory 51 for storing the states of the motor 30 and the controller 40 to be controlled.

[0070] In other embodiments, instead of or in addition to an MCU, control circuitry 50 may comprise a combination of electronic components, such as, for example, discrete elements, an application specific integrated circuit (ASIC), an application specific general purpose product (ASSP), a programmable logic device, such as, for example, a field programmable gate array (FPGA), or any combination thereof.

[0071] The control circuit 50 is connected to the trigger switch 10, the display panel 14, and the main power switch 20. The control circuit 50 is also connected to a voltage detection unit 52, a current detection unit 54, a rotation angle detection unit 56, and a temperature detection unit 58.

[0072] The voltage detection unit 52 is a circuit that detects the battery voltage input from the battery pack 18 to the controller 40. The current detection unit 54 is a circuit that is provided on the current path to the motor 30 that runs from the bridge circuit 42 to the ground line, and detects the power supply current ibat that is supplied from the battery pack 18 to the motor 30. Note that this power supply current ibat corresponds to the motor currents iu, iv, and iw that flow through the windings of the U, V, and W phases of the motor 30.

[0073] The rotation angle detection unit 56 shapes the waveform of the detection signal from the rotation sensor 32 to generate pulsed Hall sensor signals shown in Figures 3 to 5, which are inverted every time the rotor rotates by 180 electrical degrees for each of the U, V, and W phases of the motor 30 and have a phase shift of 60 electrical degrees.

[0074] That is, the rotation sensor 32 includes three Hall sensors (not shown) arranged at intervals around the rotor of the motor 30. The three Hall sensors output detection signals whose increase / decrease direction reverses every time the rotor rotates by 180 electrical degrees, and whose phases are shifted by 60 electrical degrees. For this reason, the rotation angle detection unit 56 generates the pulse-like Hall sensor signals shown in FIGS. 3 to 5 by waveform-shaping the detection signals of the U, V, and W phases.

[0075] Therefore, the control circuit 50 can detect the rotation angle of the motor 30 with a resolution of 60 electrical degrees based on the Hall sensor signal input from the rotation angle detection unit 56. Furthermore, the control circuit 50 can detect the number of rotations per unit time (in other words, the rotation speed) of the motor 30 based on the Hall sensor signal.

[0076] The temperature detection unit 58 is a temperature sensor provided in the bridge circuit 42 and detects the temperatures of the first to sixth switching elements Q1 to Q6 (in other words, the temperature of the bridge circuit 42), and is in the form of, for example, a thermistor.

[0077] [Control circuit operation] Next, the control operation of the motor 30 by the control circuit 50 will be described with reference to the time charts of FIGS.

[0078] As shown in FIG. 3, the control circuit 50 uses an electrical angle of 60 degrees, at which the Hall sensor signal input from the rotation angle detection unit 56 is updated, as the reference rotation angle, and switches the switching elements that form the current path to the motor 30 at each update timing t0, t1, t3, ....

[0079] In other words, each time the motor 30 rotates through the reference rotation angle, the control circuit 50 repeatedly switches the combination of high-side switches and low-side switches that form the current path to the motor 30, such as the first switching element Q1 and the sixth switching element Q6, the first switching element Q1 and the fifth switching element Q5, the third switching element Q3 and the fifth switching element Q5, the third switching element Q3 and the fourth switching element Q4, the second switching element Q2 and the fourth switching element Q4, and the second switching element Q2 and the sixth switching element Q6. This combination switching pattern is set in advance for each rotation direction of the motor 30.

[0080] The control circuit 50 then turns on the high-side switch and low-side switch selected in this way as a pair of driven switches, thereby passing current through the windings of each phase U, V, and W of the motor 30 and causing the motor 30 to generate rotational torque in the forward or reverse direction.

[0081] The rotational torque of the motor 30 varies depending on the motor currents iu, iv, and iw that flow through the windings of the U, V, and W phases of the motor 30. For this reason, the control circuit 50 performs conduction angle control by controlling the period during which the pair of driven switches are simultaneously turned on within each conduction control period, which is defined as the period during which the motor 30 rotates through a reference rotation angle of 60 electrical degrees.

[0082] As shown in FIG. 3, the conduction angle control is performed by turning off one of the pair of driven switches at an off timing (time tc) before the next update timing t0, t1, t3, ... at which the conduction control period ends within the conduction control period for each reference rotation angle of the motor 30.

[0083] In other words, the control circuit 50 sets the off timing (time point tc) for each power supply control period according to the rotation state of the motor 30, and controls the motor 30 to a desired rotation state by turning on and off the first to sixth switching elements Q1 to Q6 in the bridge circuit 42.

[0084] Incidentally, this conduction angle control can be carried out without any problems when the motor 30 is operating normally or under no load. However, problems can arise, for example, if grass or the like becomes tangled in the rotary blade 5, causing the motor 30 to operate under a heavy load and reducing the rotational speed of the motor 30.

[0085] That is, as shown in Figure 4, when the rotational speed of the motor 30 decreases due to heavy load operation of the electric work machine 1, the power supply control period required for the motor 30 to rotate by the reference rotation angle becomes longer, and the power supply time during which current flows to the motor 30 within the power supply control period also becomes longer.

[0086] Furthermore, if the energization time becomes longer within the energization control period, the power supply current ibat and motor currents iu, iv, and iw will rise, and the peak current values ​​will become higher, which may cause problems such as failure of the first to sixth switching elements Q1 to Q6 or demagnetization of the magnets of the motor 30.

[0087] Therefore, as shown in Figures 3 and 4, the control circuit 50 of this embodiment repeatedly measures the power supply control period from when a detection signal is input from the rotation angle detection unit 56 to when the next detection signal is input using a time counter.

[0088] Then, it is determined whether the count value of the time counter (in other words, the measured time) has reached a preset threshold value (hereinafter referred to as the limit threshold value). If the value of the time counter has not reached the limit threshold value, the current conduction limit flag is kept cleared and the conduction angle control continues (see FIG. 3).

[0089] 4, when the energization control period becomes longer and the value of the time counter reaches the limit threshold (time tc), the energization limit flag is set, turning off all of the first to sixth switching elements Q1 to Q6. As a result, increases in the power supply current ibat and the motor currents iu, iv, and iw are suppressed, and breakdowns in the first to sixth switching elements Q1 to Q6 and deterioration of the motor 30 can be suppressed.

[0090] In addition, when the value of the time counter reaches the limit threshold, the control circuit 50 sets a current flow limit flag and turns off all of the first to sixth switching elements Q1 to Q6. Then, when a detection signal is input from the rotation angle detection unit 56, the control circuit 50 clears the current flow limit flag and resumes current flow angle control.

[0091] Therefore, even if the current supply control period becomes longer and the time measured by the time counter reaches the time limit and the current path to the motor 30 is cut off, as long as the motor 30 is rotating, the detection signal is input and the conduction angle control is resumed, so that the motor 30 can continue to be driven by the conduction angle control.

[0092] Furthermore, when the current limiting flag is set, that is, when the current path to the motor 30 is cut off, the control circuit 50 lights up the current limiting notification LED 16 to notify the user that current to the motor 30 is being limited by reducing the rotation of the motor 30. Therefore, the user can detect that the electric work machine 1 is performing heavy load work, and can operate the electric work machine 1 to reduce the load.

[0093] On the other hand, if the motor 30 stops because the rotary blade 5 cannot be rotated due to, for example, tangled grass, the current limit flag is set and the current path to the motor 30 is cut off, as in the case of a heavy load shown in Figure 4, and then the current angle control cannot be resumed.

[0094] In response to this, as shown in FIG. 5, the control circuit 50 uses a motor lock detection counter to measure the elapsed time since the value of the time counter reaches the limit threshold and all of the first to sixth switching elements Q1 to Q6 are turned off.

[0095] The control circuit 50 then determines whether the count value of the motor lock detection counter (i.e., the power supply stop time) has reached a preset threshold value (hereinafter referred to as the protection detection threshold value). When the value of the motor lock detection counter reaches the protection detection threshold value (time te), the control circuit 50 determines that the motor 30 is locked and sets a motor lock detection flag.

[0096] Furthermore, when the motor lock occurs, the user must manually release the motor lock, for example by removing tangled grass, so the control circuit 50 sets the motor lock detection flag at time te and simultaneously turns on the error detection notification LED 15. As a result, the user can detect the motor lock and take action to release the motor lock.

[0097] In addition, when the control circuit 50 sets the motor lock detection flag, it clears the current limit flag and the motor lock detection counter and turns off the current limit notification LED 16 so that normal motor driving can be performed by current angle control after the motor lock is released.

[0098] [flowchart] Next, the control process executed by the control circuit 50 to drive and control the motor 30 as described above will be described with reference to FIGS.

[0099] FIG. 6 shows the main loop control process executed by the control circuit 50 when it is determined that the battery pack 18 is normal and the motor 30 can be driven by the power supplied from the battery pack 18.

[0100] As shown in Fig. 6, the control circuit 50 first determines in S10 (S represents step) whether or not the main timer flag is set. The main timer flag is set when it is determined that the main timer counter has reached a threshold value in the main loop timer interrupt process shown in Fig. 7, and is set at every predetermined control cycle.

[0101] If it is determined in S10 that the main timer flag is not set, the predetermined time determined by the control cycle has not elapsed since the last time processing from S20 onwards was started, so the determination process of S10 is executed again to wait for the predetermined time to elapse.

[0102] If it is determined in S10 that the main timer flag is set, a certain amount of time has passed since the last time processing from S20 onwards was started, so the control circuit 50 clears the main timer flag, then executes processing from S20 to S80, and proceeds to S10.

[0103] Here, in S20, it is detected that the Hall sensor signal input from the rotation angle detection unit 56 has been updated, in other words, that the motor 30 has rotated by the reference rotation angle, and an update flag is set, and a Hall sensor signal detection process is executed.

[0104] In addition, in S30, a switch operation detection process is executed to detect the operation states of various switches provided on the operation / display unit 8, such as the trigger switch 10. In addition, in S40, an A / D conversion process is executed to acquire voltage, current, temperature, etc. by taking in detection signals from the voltage detection unit 52, current detection unit 54, temperature detection unit 58, etc. and A / D converting them.

[0105] Next, in S50, the rotation state of the motor 30 obtained from the voltage, current, temperature, and Hall sensor signal acquired in the A / D conversion process in S40 is determined to be normal or not, and if an abnormality is determined, an error detection process is executed to activate a predetermined protection function. Note that this error detection process includes the motor lock detection process (see FIG. 11) described below.

[0106] In addition, in S60, the conduction angle for each conduction control period for controlling the drive of the motor 30 by conduction angle control as described above is calculated, and a control signal is output to the gate circuit 44 in accordance with the calculated conduction angle, thereby executing motor control processing to control the supply of current to the motor 30.

[0107] Next, in S70, the status of the electric operating machine 1 is displayed by turning on or off various status display LEDs provided on the display panel 14. In addition, in S80, power management processing is executed to put the control circuit 50 into a sleep state, for example, when the trigger switch 10 has not been operated for a predetermined time or longer and the conditions for transitioning to a power saving mode are met. After the processing of S80 is executed, the processing proceeds to S10, where the processing from S10 onwards described above is repeatedly executed.

[0108] Next, the main loop timer interrupt process shown in FIG. 7 is an interrupt process that is executed at regular intervals that are sufficiently shorter than the control period of the main loop. 7, in the main loop timer interrupt process, first, in S100, a main timer addition process is executed to add a value of 1 to the main timer counter. Then, in the following S110, it is determined whether the main timer counter value added in S100 is equal to or greater than a threshold value corresponding to the control period of the main loop.

[0109] If it is determined in S110 that the value of the main timer counter is equal to or greater than the threshold value, the process proceeds to S120, where the main timer flag is set, and then in S130 the main timer counter is reset, and the process proceeds to S140. However, if it is determined in S110 that the value of the main timer counter is not equal to or greater than the threshold value, the process proceeds directly to S140.

[0110] In S140, it is determined whether the motor sequence set for motor control in the motor control process (see FIG. 12), which will be described later, is set to "DRIVE." If it is determined in S140 that the motor sequence is not set to "DRIVE," there is no need to drive the motor 30, so in S150 the current limit flag is cleared, and in S160 the time counter is reset, terminating the main loop timer interrupt process.

[0111] On the other hand, if it is determined in S140 that the motor sequence is "DRIVE", it is necessary to drive the motor 30, so the flow proceeds to S170, where it is determined whether the current limit flag is cleared.

[0112] If it is determined in S170 that the current flow limit flag is not cleared (in other words, set), the process proceeds to S180. Then, in S180, an output stop process is executed to turn off all of the first to sixth switching elements Q1 to Q6 via the gate circuit 44, and the main loop timer interrupt process is ended.

[0113] If it is determined in S170 that the power supply limit flag has been cleared, the process proceeds to S190, where a time counter increment process is performed to increment the time counter by 1, and then the process proceeds to S200. Then, in S200, it is determined whether the value of the time counter is equal to or greater than the limit threshold value described above, and if the value of the time counter is less than the limit threshold value and has not yet reached the limit threshold value, the main loop timer interrupt process is terminated.

[0114] On the other hand, if it is determined in S200 that the value of the time counter is equal to or greater than the limit threshold, the current flow limit flag is set in S210. Then, in the following S220, the same output stop process as in S180 is executed, and in the following S230, the time counter is reset, and then the main loop timer interrupt process is terminated.

[0115] Next, the commutation timer interrupt process shown in FIG. 8 is an interrupt process that is executed every time one of the Hall sensor signals of the U phase, V phase, or W phase is inverted, that is, every time the motor 30 rotates by the reference rotation angle.

[0116] In this commutation timer interrupt process, first, in S410, the current limit flag is cleared, and then in S420, the time counter is reset. Finally, in S430, the motor drive commutation process is executed, in which the combination of high-side switches and low-side switches used to energize the motor 30 is switched according to a preset switching pattern.

[0117] Next, the above-described Hall sensor signal detection process is executed according to the procedure shown in FIG. That is, in the Hall sensor signal detection process, first, in S510, update information of the Hall sensor signal is obtained, for example, from the implementation status of the commutation timer interrupt process, and in S520, it is determined whether the Hall sensor signal has been updated.

[0118] If it is determined in S520 that the Hall sensor signal has been updated, the process proceeds to S530, where an update flag for the Hall sensor signal is set, and the Hall sensor signal detection process is terminated.

[0119] If it is determined in S520 that the Hall sensor signal has not been updated, the process proceeds to S540, where the Hall sensor signal update flag is cleared, and the Hall sensor signal detection process is terminated.

[0120] 10, in the switch operation detection process, the state of each switch, such as the trigger switch 10, is acquired from the input signal from each switch in S610. Then, in the following S620, the state of each switch is filtered to remove noise from the state of each switch.

[0121] In S630, a change in the state of each switch is detected from the state of each switch after filtering, and a change flag is set for the switch whose state has changed. Then, in S640, the on time or off time until the state change of each switch whose change flag has been set is measured.

[0122] The on / off time is calculated, for example, from the time difference between the time the change flag was last set and the time it is set this time. Furthermore, in S640, once the on / off time of each switch is measured, the change flag is cleared. Therefore, the switch operation detection process detects not only the operation state of each switch, but also the operation time.

[0123] Next, the motor lock detection process included in the error detection process is executed in accordance with the procedure shown in FIG. As shown in FIG. 11, in the motor lock detection process, first, in S710, it is determined whether the motor lock detection flag is currently reset and whether motor lock protection has not yet been detected.

[0124] If it is determined in S710 that motor lock protection is not currently detected, the process proceeds to S720, where it is determined whether the current limit flag is set. If the current limit flag is set, power to the motor 30 has been cut off by the output stop process of S220 described above, so the process proceeds to S730, where the motor lock detection counter is incremented by 1 to measure the output stop time.

[0125] Next, in S740, it is determined whether the value of the motor lock detection counter updated in S730 is equal to or greater than the protection detection threshold value. If the value of the motor lock detection counter is equal to or greater than the protection detection threshold value, it is determined that the motor 30 is locked, and the process proceeds to S750, where the error state is set to motor lock protection, the motor lock detection flag is set, and the motor lock detection process ends.

[0126] Also, if it is determined in S740 that the value of the motor lock detection counter has not reached the protection detection threshold value, the motor lock detection process ends immediately. If it is determined in S720 that the current limit flag is not set, the motor 30 is being driven normally by current angle control, and the flow proceeds to S770, where the motor lock detection counter is reset, and the motor lock detection process is terminated.

[0127] On the other hand, if it is determined in S710 that the motor lock protection has not been undetected, in other words, that the motor lock protection is currently in effect, the process proceeds to S760, where it is determined whether the user has performed an operation to release the motor lock, thereby enabling the protection state to be released.

[0128] In the cancellation determination process of S710, if it is determined that the protection state can be cancelled, the motor lock protection setting is cancelled, thereby putting the motor lock protection into an undetected state and clearing the motor lock detection flag.

[0129] Next, the above-mentioned motor control process is executed according to the procedure shown in FIG. As shown in FIG. 12, in the motor control process, first in S810 it is determined whether or not the main power switch 20 is in the on state, and if the main power switch 20 is in the on state, the process proceeds to S820.

[0130] In S820, it is determined whether protection of the motor 30 and the controller 40 from an error state has been detected in an error detection process such as a motor lock detection process, and if protection from an error state has not been detected, the process proceeds to S830.

[0131] Then, in S830, it is determined whether the trigger switch 10 is in the ON state, and if the trigger switch 10 is in the ON state, the process proceeds to S840, where the motor sequence is set to "DRIVE" to allow the motor 30 to be driven.

[0132] On the other hand, if it is determined in S810 that the main power switch 20 is in the OFF state, or if protection from an error state is detected in S820, or if it is determined in S830 that the trigger switch 10 is in the OFF state, the process proceeds to S870. Then, in S870, the motor sequence is set to "STOP" to prohibit driving of the motor 30.

[0133] Next, in S840, the motor sequence is set to "DRIVE", and then in the following S850, the target rotation number (in other words, the target rotation speed) of the motor 30 is set based on the operation state of the trigger switch 10 by the user and the current rotation state of the motor 30.

[0134] Then, in the next step S860, the motor output duty is calculated to control the rotation speed of the motor 30 to the target rotation speed set in step S850, and the motor control process ends. The motor output DUTY is a duty ratio that represents the time ratio of the period during which a pair of driven switches that form a current path to the motor 30 are turned on during the current control period corresponding to the reference rotation angle of the motor 30.

[0135] This motor output DUTY is used to set a conduction angle timing timer, which measures the period (i.e., the conduction angle) from the timing of updating the Hall sensor signal for each reference rotation angle of the motor 30 to the time when one of the pair of driven switches is turned off.

[0136] When the conduction angle time is measured by the conduction angle measuring timer, the control circuit 50 turns off one of the control signals output to the gate circuit 44 to turn on the pair of driven switches, thereby achieving the above-mentioned conduction angle control.

[0137] Next, if the motor sequence is set to "STOP" in S870, the motor stop process is executed in the following S880 to stop the driving of the motor 30. In this motor stopping process, the drive of the motor 30 may be stopped by cutting off the current path to the motor 30, or the windings of each phase U, V, and W of the motor 30 may be short-circuited via the bridge circuit 42 to generate a braking force in the motor 30.

[0138] Then, in the next step S890, an initialization process is performed to set the motor output duty to an initial value (for example, 0%), and the motor control process ends. Next, the above-mentioned display process is executed in accordance with the procedure shown in FIG.

[0139] That is, in the display process, first, in S910, it is determined whether or not the motor lock detection flag has been cleared. If the motor lock detection flag has been cleared, the process proceeds to S920, where the error detection notification LED 15 is turned off, and then to S940. If the motor lock detection flag has not been cleared (i.e., if it has been set), the process proceeds to S930, where the error detection notification LED 15 is turned on, and then to S940.

[0140] Next, in S940, it is determined whether the time limit flag is set. If the time limit flag is set, the process proceeds to S950, where the power limit notification LED 16 is turned on and the display process ends. If the power limit flag is not set (i.e., cleared), the power limit notification LED 16 is turned off and the display process ends.

[0141] [effect] As described above, in the electric work machine 1 of this embodiment, when the control circuit 50 drives the motor 30 by conduction angle control, if the conduction control time measured by the time counter reaches the time limit, the control circuit 50 cuts off the power to the motor 30 by performing the output stop processing of S220.

[0142] Therefore, when the load on the motor 30 increases and the rotation speed of the motor 30 decreases while the motor 30 is being driven, it is possible to prevent an increase in the peak values ​​of the power supply current ibat and the motor currents iu, iv, and iw. Therefore, the electric operating machine 1 of this embodiment can prevent an increase in the peak values ​​of the power supply current ibat and the motor currents iu, iv, and iw, which could cause the first to sixth switching elements Q1 to Q6 to break down or the magnets of the motor 30 to be demagnetized.

[0143] Furthermore, after the control circuit 50 cuts off the power supply to the motor 30 by the output stop process of S220, when the Hall sensor signal detects that the motor 30 has rotated by the reference rotation angle, the control circuit 50 resumes the power supply control of the motor 30 by power supply angle control, thereby allowing the motor 30 to continue to be driven by the power supply control.

[0144] In addition, after the power supply control time reaches the limit time and power supply to the motor 30 is cut off, the control circuit 50 notifies that a power supply abnormality (first power supply abnormality) has occurred to the motor 30 by turning on the power supply limit notification LED 16 until power supply control is resumed.

[0145] In addition, when a power supply abnormality (second power supply abnormality) occurs that requires the driving of the motor 30 to be stopped, such as the occurrence of motor lock, the control circuit 50 notifies the fact by turning on the error detection notification LED 15.

[0146] Therefore, the user can know from the lighting of the current limiting notification LED 16 that the power supply current ibat and motor currents iu, iv, and iw have increased due to an increase in the load on the motor 30, and that the protective function of the electric work machine 1 is operating. Furthermore, when an error that stops the drive of the motor 30 has occurred due to the occurrence of motor lock or the like, the user can know this from the lighting of the error detection notification LED 15.

[0147] Therefore, the user can understand that an abnormality has occurred in the power supply to the motor 30 and the details of the abnormality by the lighting of the power supply limit notification LED 16 and the error detection notification LED 15, and can then operate the electric work machine 1 so that the abnormality does not occur.

[0148] In this embodiment, two notification LEDs are used to notify each of the above-mentioned power supply abnormalities, but a common abnormality notification LED may be used to notify each of the power supply abnormalities. Furthermore, when the first power supply abnormality occurs, normal control is resumed by detecting the rotation of the motor 30, so the first power supply abnormality may not be notified.

[0149] [Second embodiment] In the first embodiment, when the current supply control time reaches the time limit and the current supply to the motor 30 is cut off, the current supply cut-off control is performed to hold all of the first to sixth switching elements Q1 to Q6 in the off state until the Hall sensor signal is updated and the current supply control is resumed.

[0150] In contrast, in this embodiment, as shown in FIG. 14, during the period from when the current conduction control time reaches the time limit until the current conduction control is started, one of the pair of driven switches is kept on and the other is periodically turned on and off, so that a smaller current flows than during the conduction angle control.

[0151] When one of the pair of driven switches is periodically turned on and off, a PWM signal having a constant pulse width and a constant cycle is output to the switching element to be turned on and off, as shown by the dotted line in Fig. 14. The duty ratio of this PWM signal is set so that the amount of heat generated by the drive system of motor 30, such as bridge circuit 42, is less than the amount of heat generated during conduction angle control.

[0152] As a result, the pair of driven switches are turned on and off in a conduction pattern different from the normal conduction angle control from the time when the power supply to the motor 30 is cut off until the power supply control is resumed. Also, similar to the first embodiment, this configuration can prevent the peak values ​​of the power supply current ibat and the motor currents iu, iv, iw from increasing, thereby preventing the first to sixth switching elements Q1 to Q6 from breaking down or the magnets of the motor 30 from being demagnetized.

[0153] In this way, in order to output a PWM signal and flow current to the motor 30 from the time when the power supply to the motor 30 is cut off until the power supply control is resumed, the control circuit 50 may execute main loop timer interrupt processing according to the procedure shown in FIG. 15.

[0154] That is, in the main loop timer interrupt process shown in Fig. 15, the processes of S225 and S185 are executed instead of the processes of S220 and S180 shown in Fig. 7. Then, in S225 and S185, PWM output process is executed to output a pulse signal having a pulse width corresponding to a preset duty ratio at a constant current supply period. Note that the duty ratio that defines the pulse width of the pulse signal may be a fixed value, or may be set according to the driving conditions of the motor 30, such as the battery voltage.

[0155] As a result, a current path to the motor 30 is formed via the pair of driven switches for a period of time corresponding to the PWM signal, and current can be continuously supplied to the motor 30. [Third embodiment] In the first embodiment, the description has been given of the case where the power supply cut-off control, in which the power supply control time reaches the time limit and the power supply to the motor 30 is cut off, is performed until the Hall sensor signal is updated.

[0156] In contrast, in this embodiment, as shown in Figure 16, when the power supply control time reaches the limit time, power supply to the motor 30 is cut off for a certain waiting time, and power supply control is resumed after the waiting time has elapsed.

[0157] In this way, as in the first embodiment, the peak values ​​of the power supply current ibat and the motor currents iu, iv, and iw increase, preventing the first to sixth switching elements Q1 to Q6 from failing or the magnets of the motor 30 from being demagnetized.

[0158] Furthermore, the power cut-off control is performed only for a certain waiting time, and the power control is resumed after the waiting time has elapsed. Therefore, even if the Hall sensor signal is not updated, the peak values ​​of the power supply current ibat and the motor currents iu, iv, and iw are limited while power is periodically supplied to the motor 30, thereby enabling the motor 30 to be driven.

[0159] In order to perform the power cutoff control for a fixed waiting time in this manner, the control circuit 50 may execute a main loop timer interrupt process in accordance with the procedure shown in FIG.

[0160] That is, in the main loop timer interrupt process shown in FIG. 17, the processes of S110 to S130 are omitted, but the processes of S110 to S130 are executed in the same manner as in the main loop timer interrupt process shown in FIG.

[0161] Then, if it is determined in S140 that the motor sequence is not "DRIVE", the processes of S150 and S160 are executed, and then in S300 the power resumption counter is reset and the main loop timer interrupt process is terminated.

[0162] This power restart counter is a counter for measuring the time elapsed since the power cutoff control was started, and is incremented by 1 in S310, which is executed when it is determined in S170 that the power limit flag has not been cleared. Therefore, when the power limit flag is set and power cutoff control is being performed, the power restart counter is repeatedly incremented in S310 to measure the duration of the power cutoff control.

[0163] Next, when the process of S310 is executed, it is determined in S320 whether the value of the power restart counter is equal to or greater than the power restart threshold value corresponding to the waiting time. If it is determined in S320 that the value of the power restart counter is not equal to or greater than the power restart threshold value, the above-mentioned output stop process is executed in S180, and the main loop timer interrupt process is terminated.

[0164] On the other hand, if it is determined in S320 that the value of the power restart counter is equal to or greater than the power restart threshold, the power limit flag is cleared in S330, the power restart counter is reset in S340, and the process proceeds to S350.

[0165] In S350, when it is determined in S200 that the value of the time counter is equal to or greater than the conduction threshold value, the switching element that was turned off in S220 is turned on, thereby executing output resumption processing to resume conduction angle control. After execution of the processing of S350, the main loop timer interrupt processing is terminated.

[0166] Therefore, when the time during which the power cutoff control is being performed by the output stop process in S220 reaches the standby time defined by the power restart threshold, the power conduction angle control is resumed. Therefore, even if the Hall sensor signal is not updated, the motor 30 can be periodically powered to drive the motor 30.

[0167] In the main loop timer interrupt processing shown in FIG. 17, when it is determined in S170 that the power supply limit flag is cleared, the processing of S190 to S230 is executed, similar to the main loop timer interrupt processing described in FIG. 7.

[0168] In addition, in this embodiment, when the implementation time of the power cut-off control reaches the standby time and the power angle control is resumed, the power limit flag is also cleared, so that the motor lock detection process of the first embodiment can no longer detect motor lock.

[0169] Therefore, in this embodiment, in the motor lock detection process shown in FIG. 11, it is determined at S720 whether the update flag for the hall sensor signal is cleared, rather than whether the power supply control flag is set.

[0170] In other words, the Hall sensor signal update flag is set when it is determined in the Hall sensor signal detection process that the Hall sensor signal has been updated, and is cleared when it is determined that the Hall sensor signal has not been updated.

[0171] Therefore, if the motor lock detection counter is incremented in S730 when it is determined in S720 that the update flag for the Hall sensor signal has been cleared, it becomes possible to measure the time that the rotation of the motor 30 is stopped. Therefore, in the motor lock detection process, it is possible to detect that the motor 30 has locked from the time that the rotation of the motor 30 is stopped.

[0172] [Fourth embodiment] In this embodiment, as shown in FIG. 18, the PWM output period of the second embodiment shown in FIG. 14 is limited to a certain waiting time, as in the third embodiment, and after the waiting time has elapsed, normal conduction angle control is resumed.

[0173] In this manner, similar to the second embodiment, after the current supply control time reaches the time limit and the current supply to the motor 30 is cut off, a PWM signal can be output to allow current to flow to the motor 30 until the current supply control is resumed. Furthermore, when the normal conduction angle control is stopped and the time during which the PWM signal is being output reaches the standby time defined by the current supply resumption threshold, the conduction angle control can be resumed, so that the motor 30 can be driven similar to the third embodiment.

[0174] In order to limit the PWM signal output period from when the energization control time reaches the time limit until the energization control is resumed to a certain waiting time, the control circuit 50 may execute a main loop timer interrupt process according to the procedure shown in FIG. 19.

[0175] The main loop timer interrupt process shown in Fig. 19 is substantially the same as the timer interrupt process of the third embodiment shown in Fig. 17, and differs from the third embodiment in that the processes of S225 and S185 are executed instead of the processes of S220 and S180 shown in Fig. 17. Then, in S225 and S185, PWM output process is executed to output a pulse signal having a pulse width corresponding to a preset duty ratio at a fixed current supply period, as in the second embodiment.

[0176] Also, in this embodiment, as in the third embodiment, in the motor lock detection process, at S720 shown in FIG. 11, it is determined whether the Hall sensor signal update flag is cleared, rather than whether the power supply control flag is set.

[0177] [Fifth embodiment] In the above first to fourth embodiments, the control circuit 50 has been described as controlling the rotation of the motor 30 by conduction angle control, which controls the conduction angle at which a pair of driven switches are simultaneously turned on within a reference rotation angle.

[0178] In contrast, the control circuit 50 of this embodiment performs PWM control, as shown in FIG. 20, by periodically turning on and off at least one of the pair of driven switches in accordance with a drive duty ratio that is set so that the rotation speed of the motor 30 becomes a predetermined target rotation speed.

[0179] In this way, even if the control circuit 50 is configured to control the current supply to the motor 30 using PWM control, the same effect as in the first embodiment can be obtained by cutting off the current supply using PWM control when the current supply control time for each reference rotation angle becomes long.

[0180] In this embodiment, the control circuit 50 may use the motor output DUTY calculated in S860 of FIG. 12 to rotate the motor 30 at the target rotation speed for PWM control.

[0181] In other words, the control circuit 50 of this embodiment may be configured to use the motor output DUTY calculated in S860 as a duty ratio that represents the time ratio of the period during which one of the pair of driven switches is turned on for each constant current-carrying period that is sufficiently shorter than the current-carrying control period.

[0182] Furthermore, when the control circuit 50 is configured to perform the energization control of the motor 30 using PWM control, the control from when the energization control time reaches the time limit until the energization control is resumed may be performed in the same manner as in any of the second to fourth embodiments.

[0183] [Variations] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modifications.

[0184] In the above embodiment, the time is measured by a time counter during the power supply control period for each rotation of the reference rotation angle of the motor 30, and when the value of the time counter reaches a limit threshold, power supply to the motor 30 is limited and the power supply limit notification LED 16 is turned on.

[0185] However, it is not necessary to provide notification by lighting the current limit notification LED 16, and the intended purpose of the present disclosure can be achieved even if no notification is provided. Notifications when current is limited or when a motor lock is detected may be provided by lighting a common notification LED. These notifications may also be provided by displaying information on the display panel 14 or by emitting a notification sound, rather than by lighting an LED.

[0186] Furthermore, in the above embodiment, a brush cutter was described as an electric work machine, but the technology disclosed herein can be applied in the same manner as in the above embodiment to any electric work machine in which the rotation speed of the motor 30 changes depending on the working condition, such as a tool bit, and similar effects can be obtained.

[0187] Furthermore, in the above embodiment, the motor 30 is described as a three-phase brushless motor equipped with a rotation sensor 32, but the motor 30 may be a brushless motor other than a three-phase motor, for example, a single-phase brushless motor, and may not be equipped with a rotation sensor 32.

[0188] If the brushless motor does not have a rotation sensor 32, for example, the rotation angle detection unit 56 may be configured to detect the rotor position (rotation angle) from the induced voltage generated in the motor coil as a so-called sensorless method.

[0189] Furthermore, in the above embodiment, the control of the current supply to the motor 30 is described as being performed by current supply angle control or PWM control, but as described in Patent Document 1, the electric work machine of the present disclosure may be configured to perform a combination of current supply angle control and PWM control.

[0190] In the above embodiments, multiple functions of one component may be realized by multiple components, or one function of one component may be realized by multiple components. Furthermore, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Furthermore, part of the configuration of the above embodiments may be omitted. Furthermore, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0191] In addition to the electric work machine, the present disclosure can also be realized in various forms, such as a system that includes an electric work machine as a component, a program for causing a computer to function as an electric work machine, a non-transient physical recording medium such as a semiconductor memory on which this program is recorded, and a control method. [Explanation of symbols]

[0192] 1...electric work machine, 30...motor, 50...control circuit, 56...rotation angle detection unit, L1 to L3...positive electrode side current path, L4 to L6...negative electrode side current path, Q1 to Q3...first to third switching elements (high side switches), Q4 to Q6...fourth to sixth switching elements (low side switches).

Claims

1. a brushless motor having a plurality of terminals and configured to rotate an object to be driven; a plurality of positive electrode side current paths configured to connect the plurality of terminals to a positive electrode of a DC power supply; a plurality of negative electrode-side current paths configured to connect the plurality of terminals and a negative electrode of the DC power supply; a plurality of high-side switches respectively provided on the plurality of positive electrode side current paths; a plurality of low-side switches respectively provided on the plurality of negative electrode side current paths; a rotation angle detection unit configured to detect a rotation angle of the brushless motor; a control unit configured to perform energization control such that, each time the rotation angle detection unit detects that the brushless motor has rotated a predetermined reference rotation angle, one of the plurality of high-side switches and one of the plurality of low-side switches, which are preset in accordance with the rotation angle of the brushless motor, are selected as a pair of driven switches, and the pair of driven switches are turned on in a predetermined energization pattern, thereby energizing the brushless motor and driving the brushless motor; Equipped with the control unit is equipped with a time counter configured to measure, each time the rotation angle detection unit detects that the brushless motor has rotated by the reference rotation angle, the time until the brushless motor subsequently rotates by the reference rotation angle as a power supply control time, and is configured to cut off power to the brushless motor by the power supply control when the power supply control time reaches a preset time limit during measurement by the time counter.

2. The electric operating machine according to claim 1, the control unit is configured to resume the energization control when the rotation angle detection unit detects that the brushless motor has rotated by the reference rotation angle after the energization control time reaches the limit time and the energization to the brushless motor is cut off.

3. The electric operating machine according to claim 1, the control unit is configured to resume the energization control when a preset waiting time has elapsed after the energization control time has reached the limit time and the energization to the brushless motor has been cut off.

4. The electric operating machine according to any one of claims 1 to 3, the control unit is configured to perform power cut-off control to hold the plurality of high-side switches and the plurality of low-side switches in an off state until the power control is resumed after the power control time reaches the limit time and power to the brushless motor is cut off.

5. The electric operating machine according to any one of claims 1 to 3, the control unit is configured to perform low-output control, after the current supply to the brushless motor has been cut off when the current supply control time has reached the limit time, by periodically turning the pair of driven switches on and off in a second current supply pattern different from the current supply control, until the current supply control is resumed, thereby passing less current through the brushless motor than during the current supply control.

6. The electric operating machine according to claim 5, the second current conduction pattern of the low output control is set so that the amount of heat generated in a drive system of the brushless motor, including the plurality of high-side switches and the plurality of low-side switches, is less than the amount of heat generated during the current conduction control.

7. An electric operating machine according to any one of claims 1 to 6, the control unit is configured to, after the power supply control time reaches the time limit and power supply to the brushless motor is cut off, notify of an abnormality in power supply to the brushless motor until the power supply control is resumed.

8. The electric operating machine according to claim 7, the control unit is configured to, when a second energization abnormality occurs during the energization control, different from a first energization abnormality in which the energization control time reaches the limit time, cut off the energization to the brushless motor and notify the energization abnormality to the brushless motor in a notification form different from that used when the first energization abnormality occurred.

9. An electric operating machine according to any one of claims 1 to 8, The control unit is configured to perform conduction angle control as the conduction control, controlling a conduction angle at which the pair of driven switches are simultaneously turned on within the reference rotation angle so that the rotation speed of the brushless motor becomes a predetermined target rotation speed.

10. An electric operating machine according to any one of claims 1 to 8, The control unit is configured to perform PWM control as the energization control, in which at least one of the pair of driven switches is periodically turned on and off in accordance with a drive duty ratio that is set so that the rotation speed of the brushless motor becomes a predetermined target rotation speed.

Images