Electric work machine

Abstract

The present invention provides an electric power tool that can suppress variations in the start-up time due to differences in the inertia of the cutting tool, while also suppressing overshoot in rotational speed. [Solution] An electric work machine in one aspect of the present disclosure comprises a motor, a drive switch, and a control unit. The control unit increases the magnitude of the applied voltage applied to the motor at a first rate of increase based on the drive switch being turned on. The control unit changes the first rate of increase to a second rate of increase which is smaller than the first rate of increase based on the acquired actual rotational speed reaching a set rotational threshold.

Description

Technical Field

[0001] The present disclosure relates to a power working machine equipped with a motor.

Background Art

[0002] In the lawn mower described in Patent Document 1, a cutting blade or a nylon cord that rotates by the power of a motor is attached to its tip. When the trigger switch of the lawn mower changes from off to on, the rotation speed of the motor gradually increases to the target rotation speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The nylon cord has less inertia than the cutting blade. Suppressing an increase in the startup period at the cutting blade may cause an overshoot in the rotation speed during startup with the nylon cord. Also, suppressing an overshoot in the rotation speed during startup with the nylon cord may increase the startup period at the cutting blade.

[0005] One aspect of the present disclosure provides a power working machine capable of suppressing an overshoot in the rotation speed while suppressing variations in the startup period due to differences in the inertia of the tip tool.

Means for Solving the Problems

[0006] An electric work machine in one aspect of the present disclosure comprises a motor, a drive switch, and a control unit. The motor generates a driving force for rotating a cutting tool. The drive switch is operated by a user to drive the motor. Based on the fact that the drive switch is turned on, the control unit increases the magnitude of the applied voltage applied to the motor at a first rate of increase, obtains the actual rotational speed of the motor, and based on the fact that the obtained actual rotational speed has reached a set rotation threshold, changes the first rate of increase to a second rate of increase which is smaller than the first rate of increase, and starts constant rotation control of the motor to maintain the actual rotational speed at the target rotational speed before the actual rotational speed reaches a target rotational speed which is greater than the rotation threshold.

[0007] In one aspect of the electric work machine of this disclosure, when the actual rotational speed reaches a rotational threshold, the rate of increase in the magnitude of the applied voltage is reduced. When the inertia of the electric work machine is relatively small, the rate of increase in the magnitude of the applied voltage is reduced relatively quickly, thus suppressing overshoot of the actual rotational speed. When the inertia of the electric work machine is relatively large, the rate of increase in the magnitude of the applied voltage is reduced relatively slowly, thus suppressing an increase in the startup period. Therefore, it is possible to suppress overshoot of the actual rotational speed while suppressing variations in the startup period due to differences in the inertia of the electric work machine.

[0008] An electric work machine in another aspect of the present disclosure comprises a motor, a drive switch, and a control unit. The motor generates a driving force for rotating a cutting tool. The drive switch is operated by a user to drive the motor. Based on the fact that the drive switch is turned on, the control unit increases the magnitude of the applied voltage applied to the motor at a predetermined rate of increase, obtains the actual rotational speed of the motor, and based on the fact that the obtained actual rotational speed has reached a set rotation threshold, fixes the magnitude of the applied voltage to a predetermined value, the predetermined value being less than or equal to the magnitude of the applied voltage at the time the actual rotational speed reaches the rotation threshold, and starts constant rotation control of the motor to maintain the actual rotational speed at the target rotational speed before the actual rotational speed reaches a target rotational speed greater than the rotation threshold.

[0009] In one aspect of the electric work machine of this disclosure, when the actual rotational speed reaches a rotational threshold, the magnitude of the applied voltage is fixed to a value less than or equal to the value at that point. When the inertia of the electric work machine is relatively small, the magnitude of the applied voltage is fixed to a predetermined value relatively quickly, suppressing overshoot of the actual rotational speed. When the inertia of the electric work machine is relatively large, the magnitude of the applied voltage is fixed to a predetermined value relatively slowly, suppressing an increase in the startup period. Therefore, it is possible to suppress overshoot of the actual rotational speed while suppressing variations in the startup period due to differences in the inertia of the electric work machine. [Brief explanation of the drawing]

[0010] [Figure 1A] This figure shows an example of the appearance of an electric work machine according to the first embodiment. [Figure 1B] This figure shows another example of the appearance of an electric work machine according to the first embodiment. [Figure 2] This figure shows the operation and display unit of an electric work machine according to the first embodiment. [Figure 3] This figure shows the electrical configuration of the electric work machine according to the first embodiment. [Figure 4] This is a flowchart showing the main processing performed by the microcontroller of the electric work machine according to the first embodiment. [Figure 5] This is a flowchart showing the motor control process executed by the microcontroller of the electric work machine according to the first embodiment. [Figure 6] This is a flowchart showing the output duty cycle setting process performed by the microcontroller of the electric work machine according to the first embodiment. [Figure 7] Figures 7A and 7B are tables showing the correspondence between the drive modes of the electric work machine according to the first embodiment and various values. [Figure 8] This is a flowchart showing the process of setting the target duty cycle executed by the microcontroller of the electric work machine according to the first embodiment. [Figure 9] This is a flowchart showing the rotation threshold setting process executed by the microcontroller of the electric work machine according to the first embodiment. [Figure 10]It is a flowchart showing the fixed duty ratio control process executed by the microcomputer of the electric working machine according to the first embodiment. [Figure 11] It is a flowchart showing the constant rotation control process executed by the microcomputer of the electric working machine according to the first embodiment. <000007二>It is a flowchart showing the initial duty ratio setting process executed by the microcomputer of the electric working machine according to the first embodiment. [Figure 13] It is a flowchart showing the setting process of the target rotation speed executed by the microcomputer of the electric working machine according to the first embodiment. [Figure 14] It is a diagram showing the time change of the actual rotation speed and output duty ratio of the electric working machine with small inertia and the electric working machine with large inertia according to the first embodiment. [Figure 15] It is a diagram showing the time change of the actual rotation speed and output duty ratio of the electric working machine with small inertia and the electric working machine with large inertia according to the reference example. [Figure 16] It is a diagram showing the time change of the actual rotation speed and output duty ratio of the electric working machine with small inertia and the electric working machine with large inertia according to another reference example. [Figure 17] It is a flowchart showing the setting process of the output duty ratio executed by the microcomputer of the electric working machine according to the second embodiment. [Figure 18] It is a diagram showing the time change of the actual rotation speed and output duty ratio of the electric working machine with small inertia and the electric working machine with large inertia according to the second embodiment. [Figure 19] It is a flowchart showing the setting process of the output duty ratio executed by the microcomputer of the electric working machine according to the third embodiment. [[ID=三9]] [Figure 20] It is a flowchart showing the setting process of the fixed duty ratio executed by the microcomputer of the electric working machine according to the third embodiment. [Figure 21] It is a diagram showing the time change of the actual rotation speed and output duty ratio of the electric working machine with small inertia and the electric working machine with large inertia according to the third embodiment.

Mode for Carrying Out the Invention

[0011] [Summary of Embodiments] In one embodiment, an electric working machine may be provided that includes at least any one of the following features. · Feature 1: A motor that generates a driving force for rotating a tip tool. · Feature 2: A drive switch operated by a user to drive the motor. · Feature 3: A control unit. · Feature 4: Based on the drive switch being turned on, the control unit increases the magnitude of the applied voltage to the motor at a first rising rate. · Feature 5: The control unit acquires the actual rotational speed of the motor. · Feature 6: Based on the acquired actual rotational speed reaching a set rotation threshold value, the control unit changes the first rising rate to a second rising rate smaller than the first rising rate. · Feature 7: Before the actual rotational speed reaches a target rotational speed greater than the rotation threshold value, the control unit starts constant rotation control of the motor to maintain the actual rotational speed at the target rotational speed.

[0012] In an electric working machine having at least Features 1 to 7, when the actual rotational speed reaches the rotation threshold value, the rising rate of the magnitude of the applied voltage is decreased. When the inertia of the electric working machine is relatively small, the rising rate of the magnitude of the applied voltage is decreased relatively quickly, so overshoot of the actual rotational speed is suppressed. When the inertia of the electric working machine is relatively large, the rising rate of the magnitude of the applied voltage is decreased relatively slowly, so an increase in the startup period is suppressed. Therefore, it is possible to suppress overshoot of the actual rotational speed while suppressing variations in the startup period due to differences in the inertia of the electric working machine.

[0013] One embodiment may provide an electric working machine that includes at least any one of the following features. · Feature 8: A motor that generates a driving force for rotating a tip tool. · Feature 9: A drive switch operated by a user to drive the motor. · Feature 10: A control unit. Feature 11: Based on the fact that the drive switch is turned on, the control unit increases the magnitude of the applied voltage applied to the motor at a predetermined rate of increase. Feature 12: The control unit acquires the actual rotational speed of the motor. Feature 13: The control unit fixes the magnitude of the applied voltage to a predetermined value based on the fact that the acquired actual rotational speed has reached a set rotational threshold. Feature 14: The predetermined value is less than or equal to the magnitude of the applied voltage at the point when the actual rotational speed reaches the rotation threshold. Feature 15: The control unit starts constant rotation control of the motor before the actual rotation speed reaches a target rotation speed that is greater than the rotation threshold, thereby maintaining the actual rotation speed at the target rotation speed.

[0014] In an electric work machine having at least features 8 to 15, when the actual rotational speed reaches a rotational threshold, the magnitude of the applied voltage is fixed to a value below that point. When the inertia of the electric work machine is relatively small, the magnitude of the applied voltage is fixed to a predetermined value relatively quickly, suppressing overshoot of the actual rotational speed. When the inertia of the electric work machine is relatively large, the magnitude of the applied voltage is fixed to a predetermined value relatively slowly, suppressing an increase in the startup period. Therefore, it is possible to suppress overshoot of the actual rotational speed while suppressing variations in the startup period due to differences in the inertia of the electric work machine.

[0015] In some embodiments, the following features may be included in addition to, or instead of, at least one of the above-described features 1 to 8. Feature 16: The second rate of increase is zero. Feature 17: The control unit fixes the magnitude of the applied voltage to a predetermined value from the time the acquired actual rotational speed reaches the rotation threshold until constant rotation control is started. Feature 18: The predetermined value is the magnitude of the applied voltage at the point when the actual rotational speed reaches the rotation threshold.

[0016] In electric work machines that possess at least features 1-7 and 16-18, the magnitude of the applied voltage is fixed to the value at which the actual rotational speed reaches the rotational threshold. This slows down the rate at which the actual rotational speed increases, thereby suppressing overshoot.

[0017] In some embodiments, in addition to or instead of at least one of the above-described features 1 to 18, the device may also have at least one of the following features. Feature 19: A drive circuit configured to drive a motor. Feature 20: The control unit changes the magnitude of the applied voltage based on the output duty cycle of the pulse width modulated signal output to the drive circuit. Feature 21: The control unit controls the output duty cycle to be below the set target duty cycle from the time the drive switch is turned on until constant rotation control begins.

[0018] In an electric work machine having at least features 1-7 or features 8-15 and features 19-21, the output duty cycle is controlled to be below the target duty cycle before constant rotation control is initiated. This prevents a rapid increase in the actual rotational speed during the startup period.

[0019] In some embodiments, in addition to or instead of at least one of the above-described features 1 to 21, the device may also have at least one of the following features. Feature 22: The control unit starts constant rotation control based on the fact that the acquired actual rotation speed has reached the starting speed. Feature 23: The starting speed is greater than the rotation threshold and less than the target rotation speed.

[0020] In an electric work machine having at least features 1 to 7 or features 8 to 15 and features 22 to 23, the control unit can suppress overshoot of the actual rotational speed by starting constant rotational speed control before the actual rotational speed reaches the target rotational speed.

[0021] In some embodiments, in addition to or instead of at least one of the above-described features 1 to 23, the device may also have at least one of the following features. Feature 24: A selection switch operated by the user to select either the first or second mode, which is the motor's drive mode. Feature 25: The control unit sets a first threshold for the rotation threshold when the first mode is selected via the selection switch. Feature 26: When the second mode is selected via the selection switch, the control unit sets a second rotation threshold that is different from the first threshold.

[0022] In an electric work machine equipped with at least features 1-7 or features 8-15 and features 25-26, the rotation threshold can be changed according to the drive mode, thereby suppressing variations in the startup period due to differences in drive modes while suppressing overshoot of the actual rotation speed.

[0023] In some embodiments, in addition to or instead of at least one of the above-described features 1 to 26, the device may also have at least one of the following features. Feature 27: The control unit sets the first duty cycle to the target duty cycle when the first mode is selected via the selection switch. Feature 28: When the second mode is selected via the selection switch, the control unit sets the target duty cycle to a second duty cycle that is different from the first duty cycle.

[0024] In an electric work machine having at least features 1-7 or features 8-15 and features 19-21, 24, and 27-28, the overshoot of the actual rotational speed can be suppressed while suppressing variations in the start-up period due to differences in the drive mode by changing the target duty cycle according to the drive mode.

[0025] In some embodiments, in addition to or instead of at least one of the above-described features 1 to 28, the device may also have at least one of the following features. Feature 29: The control unit sets a third threshold for the rotation threshold when the motor is rotating in the forward direction. Feature 30: The control unit sets a fourth rotation threshold, which is different from the third threshold, when the motor rotates in the forward and reverse directions.

[0026] In an electric work machine having at least features 1 to 7 or features 8 to 15 and features 29 to 30, the rotation threshold can be changed according to the rotation direction of the motor, thereby suppressing variations in the start-up period due to differences in rotation direction while suppressing overshoot of the actual rotation speed.

[0027] In some embodiments, in addition to or instead of at least one of the above-described features 1 to 30, the device may also have at least one of the following features. Feature 31: The control unit sets the third duty cycle to the target duty cycle when the motor is rotating in the forward direction. Feature 32: The control unit sets a fourth duty cycle, which is different from the third duty cycle, as the target duty cycle when the motor rotates in the forward and reverse directions.

[0028] In an electric work machine equipped with at least features 1-7 or features 8-15 and features 19-21 and 31-32, the target duty cycle can be changed according to the motor's rotation direction to suppress variations in the start-up period due to differences in rotation direction while suppressing overshoot of the actual rotation speed.

[0029] The examples of electric power tools described above include various types of equipment configured for use in construction, manufacturing, gardening, and civil engineering work sites, specifically power tools for stonework, metalwork, and woodworking, power tools for gardening, and power tools for preparing the work site environment. In particular, the examples of electric power tools described above include power tools for stonework, metalwork, and woodworking, and power tools for gardening, that can be fitted with multiple types of cutting tools or attachments. Examples of such power tools include brush cutters that can be fitted with multiple cutting tools, split brush cutters that can be fitted with multiple attachments on the shaft, electric hammers that can be fitted with multiple cutting tools, electric drills, electric screwdrivers, and electric impact drivers.

[0030] In one embodiment, features 1 to 32 may be combined in any way. In one embodiment, any of the above features 1 to 32 may be excluded.

[0031] (First Embodiment) <1-1. Structure> <1-1-1. Overall Structure> The electric work implement 1 according to this embodiment will be described with reference to Figures 1A and 1B. The electric work implement 1 according to this embodiment is, as an example, a grass trimmer. The electric work implement 1 has a main pipe 2 The main pipe 2 has a first end and a second end and is formed in the shape of a long, hollow rod.

[0032] The electric work implement 1 is equipped with a drive unit 3. The drive unit 3 is attached to the first end of the main pipe 2. The drive unit 3 incorporates a motor 20, which will be described later. The drive unit 3 is equipped with a reduction gear mechanism at the tip of the motor 20's rotating shaft. A rotating blade 4 is detachably attached to the output shaft of the gear mechanism as a cutting tool. When the motor 20 rotates, the output shaft of the gear mechanism rotates together with the rotating blade 4. The rotating blade 4 is formed in the shape of a metal disc. The rotating blade 4 has multiple saw-tooth-like teeth formed along the outer circumference of the disc. The rotating blade 4 cuts grass, branches, etc. by rotating due to the driving force of the motor 20.

[0033] As shown in Figure 1B, a nylon cord cutter 160 may be detachably mounted on the output shaft of the gear mechanism as a cutting tool instead of the rotating blade 4. The nylon cord cutter 160 comprises a cylindrical sloop 16 and a nylon cord 56 housed in the sloop 16. Two holes are formed on the side of the sloop 16, and the nylon cord 56 is pulled out from these two holes. As the sloop 16 rotates due to the driving force of the motor 20, the nylon cord 56 pulled out from the two holes strikes grass or other vegetation, cutting it.

[0034] The nylon cord cutter 160 is lighter than the rotary blade 4. Therefore, when the nylon cord cutter 160 is attached to the electric work implement 1, the inertia of the electric work implement 1 is smaller than when the rotary blade 4 is attached to the electric work implement 1. In other words, the inertia of the electric work implement 1 changes depending on the type of tip tool attached to the electric work implement 1.

[0035] The electric work implement 1 is equipped with a cover 5. The cover 5 is attached to the first end of the main pipe 2. The cover 5 is attached to the second end side of the rotating blade 4 or nylon cord cutter 160. The cover 5 prevents grass and other materials cut by the rotating blade 4 or nylon cord cutter 160 from flying towards the user.

[0036] The electric work implement 1 is equipped with a handle 6. The handle 6 is connected to the main pipe 2 near its midpoint along its length. The handle 6 is U-shaped, with grips attached to the two ends of the U-shape. The user grasps the two grips and performs work with the electric work implement 1.

[0037] The electric work implement 1 includes an operation and display unit 7. The operation and display unit 7 is located on one of the two grips of the handle 6. The operation and display unit 7 includes a display unit 11 and an operation unit 15. Details of the display unit 11 and the operation unit 15 will be described later. The operation and display unit 7 also includes a trigger switch 12 and a lock-off switch 13.

[0038] The trigger switch 12 is operated by the user to drive the motor 20. Specifically, when the main power is on, the user pulls the trigger switch 12 to drive the motor 20 and releases the trigger switch 12 to stop the motor 20. The trigger switch 12 outputs an ON signal to the microcontroller (hereinafter referred to as "microcontroller") 33, which will be described later, while it is pulled, and outputs an OFF signal to the microcontroller 33 while it is released. In this embodiment, the trigger switch 12 is an example of a drive switch of this disclosure.

[0039] The lock-off switch 13 can be operated by the user to be locked or unlocked. When the lock-off switch 13 is locked, the user cannot pull the trigger switch 12. When the lock-off switch 13 is unlocked, the user can pull the trigger switch 12.

[0040] The electric work machine 1 includes a control unit 9. The control unit 9 is attached to the second end of the main pipe 2. The control unit 9 incorporates a controller 30, which will be described later. The controller 30 is connected to the motor 20 via a harness that passes through the main pipe 2. The controller 30 is also connected to the operation / display unit 7 via a harness that passes through the main pipe 2. Furthermore, a battery pack 8 is detachably attached to the control unit 9. The battery pack 8 includes a plurality of battery cells connected in series. The battery pack 8 is a rechargeable secondary battery, such as a lithium-ion battery. The battery pack 8 supplies DC power to the controller 30. The motor 20 and the operation / display unit 7 receive DC power from the motor 20 via the controller 30.

[0041] <1-1-2. Operation and Display Unit> Referring to Figure 2, the display unit 11 and the operation unit 15 of the electric work implement 1 will be described. The operation unit 15 is operated by the user to operate the electric work implement 1. The operation unit 15 includes a main power / mode selection switch 151 and a reverse switch 152. The main power / mode selection switch 151 is a tact switch and is operated by the user to turn the main power on / off or to select the normal mode. When the user long-presses the main power / mode selection switch 151, the main power changes from off to on or from on to off. Long-pressing corresponds to holding it down for a predetermined time or longer. When the user short-presses the main power / mode selection switch 151, the normal mode changes. Short-pressing corresponds to releasing the switch before a predetermined time has elapsed after pressing it. The main power / mode selection switch 151 outputs an ON signal to the microcontroller 33 while it is pressed and an OFF signal to the microcontroller 33 while it is released.

[0042] In this embodiment, the normal mode is the mode in which the motor 20 rotates in the forward direction, and includes a low-speed mode and a high-speed mode. Each time the user briefly presses the main power / mode selection switch 151, the mode changes in the order of low-speed mode → high-speed mode → low-speed mode. The target rotational speed ωt in low-speed mode is smaller than the target rotational speed ωt in high-speed mode. The target rotational speed ωt is the target value of the rotational speed of the motor 20. In this embodiment, the main power / mode selection switch 151 corresponds to an example of the selection switch of this disclosure, and the high-speed mode and low-speed mode correspond to examples of the first mode and second mode of this disclosure.

[0043] The reverse switch 152 is a tact switch operated by the user to select the reverse mode. The reverse mode is a mode in which the motor 20 rotates in the opposite direction to the forward direction. When grass or other debris becomes entangled in the rotating blade 4 or nylon cord cutter 160, driving the motor 20 in reverse mode will release the grass from the rotating blade 4 or nylon cord cutter 160.

[0044] When the user presses the reverse switch 152, the motor switches from forward rotation mode to reverse rotation mode. If the user presses the reverse switch 152 again while in reverse rotation mode, the motor switches from reverse rotation mode back to normal rotation mode. Also, after the motor 20 starts driving in reverse rotation mode, it automatically stops after a certain period of time (for example, a few seconds). Then, it automatically switches from reverse rotation mode back to normal rotation mode. Therefore, when the user pulls the trigger switch 12 after the motor 20 has automatically stopped, the motor 20 rotates in the forward direction. The reverse switch 152 outputs an ON signal to the microcontroller 33 while it is pressed and an OFF signal to the microcontroller 33 while it is released.

[0045] In this embodiment, the low-speed mode, high-speed mode, and reverse-reverse mode are examples of the drive modes of this disclosure. In another embodiment, the drive modes may include other modes in addition to the low-speed mode, high-speed mode, and reverse-reverse mode.

[0046] The display unit 11 notifies the user of the mode set by the user. The display unit 11 includes a speed / reverse display unit 111 and an abnormality display unit 113. The speed / reverse display unit 111 includes two light-emitting diodes (hereinafter referred to as LEDs) corresponding to the low-speed mode and the high-speed mode. Of the two LEDs, the LED corresponding to the selected mode lights up. When reversing, both LEDs flash. The abnormality display unit 113 includes one LED and notifies the user by flashing or lighting the LED if an abnormal condition is detected during the operation of the electric work machine 1.

[0047] <1-1-3. Electrical Configuration> Referring to Figure 3, the electrical configuration of the electric work machine 1 will be described. The electric work machine 1 is equipped with a motor 20. The motor 20 is a three-phase brushless motor. The motor 20 comprises a three-phase winding (i.e., stator) 22 and a rotor 21. The motor 20 is a sensorless motor.

[0048] The electric work machine 1 is equipped with a controller 30. The controller 30 includes a power control circuit 31, a regulator 32, a microcontroller 33, a gate circuit 34, a drive circuit 35, a current detection circuit 36, a rotor position detection unit 37, a power line 38, and a cutoff switch 39.

[0049] The power control circuit 31 drives the regulator 32 to generate the power supply voltage Vcc when the main power supply is ON. The regulator 32 supplies the generated power supply voltage Vcc to the microcontroller 33, etc.

[0050] The power line 38 connects the positive terminal of the battery pack 8 to the drive circuit 35. The cutoff switch 39 is located on the power line 38. When the cutoff switch 39 is in the ON position, the power line 38 is conductive, and power is supplied from the battery pack 8 to the drive circuit 35. When the cutoff switch 39 is in the OFF position, the power line 38 is cut off, and no power is supplied from the battery pack 8 to the drive circuit 35.

[0051] The drive circuit 35 is a three-phase full-bridge circuit including three high-side switching elements and three low-side switching elements. The six switching elements are, for example, MOSFETs. The on / off switching of the six switching elements is controlled by the microcontroller 33 via the gate circuit 34. The drive circuit 35, controlled by the microcontroller 33, applies a pulse-width modulated voltage to the winding 22 of the motor 20.

[0052] The gate circuit 34 is connected to the power line 38 and turns on or off the six switching elements of the drive circuit 35 based on the control signal output from the microcontroller 33. The control signal is a pulse width modulation (PWM) signal with a set output duty cycle. The gate circuit 34 also turns on or off the cutoff switch 39 based on the command signal output from the microcontroller 33. Specifically, the gate circuit 34 turns on the cutoff switch 39 when the microcontroller 33 allows the motor 20 to be driven, and turns off the cutoff switch 39 when the microcontroller 33 prohibits the motor 20 from being driven.

[0053] The current detection circuit 36 ​​detects the magnitude of the current flowing through the winding 22 of the motor 20 and outputs a current detection value corresponding to the magnitude of the current to the microcontroller 33. The rotor position detection unit 37 detects the zero-crossing point of the induced voltage generated in each of the windings 22 and outputs a detection signal for each phase to the microcontroller 33.

[0054] The microcontroller 33 comprises a CPU 331 and a memory 332. The microcontroller 33 calculates the rotational position of the rotor 21 based on the detection signals of each phase input from the rotor position detection unit 37. Furthermore, the microcontroller 33 calculates the actual rotational speed of the motor 20.

[0055] Furthermore, the microcontroller 33 generates control signals based on the various input information and outputs the generated control signals to the gate circuit 34. Specifically, the microcontroller 33 generates control signals based on the on or off signals input from the trigger switch 12, the main power / mode selection switch 151, and the reverse switch 152, the current detection value input from the current detection circuit 36, and the calculated rotation speed.

[0056] Furthermore, the microcontroller 33 lights up, blinks, or turns off each LED of the display unit 11 based on the on or off signals input from the trigger switch 12, the main power / mode selection switch 151, and the reverse switch 152. In this embodiment, the microcontroller 33 is an example of the control unit of the present disclosure.

[0057] <1-2. Processing> <1-2-1. Main Processing> Referring to the flowchart in Figure 4, the main process executed by the microcontroller 33 will be explained. The microcontroller 33 starts this process when the main power is turned on from off, and repeats this process at predetermined intervals.

[0058] In S10, the microcontroller 33 performs switch operation detection processing. Specifically, the microcontroller 33 obtains an ON signal or an OFF signal from each of the trigger switch 12, the main power / mode selection switch 151, and the reverse switch 152.

[0059] Next, in S20, the microcontroller 33 executes motor control processing to control the drive of the motor 20. Details of the motor control processing will be described later. <1-2-2. Motor Control Processing> Referring to the flowchart in Figure 5, the motor control process executed by the microcontroller 33 in the main process S20 will be explained.

[0060] In S100, the microcontroller 33 acquires detection signals for each phase from the rotor position detection unit 37 and calculates the actual rotational speed of the motor 20. Next, in S110, the microcontroller 33 sets the drive mode based on the ON or OFF signal obtained from the main power / mode selection switch 151 and the reverse switch 152. Specifically, the microcontroller 33 sets one of the following drive modes: low-speed mode, high-speed mode, or reverse mode.

[0061] Next, in S120, the microcontroller 33 sets either drive permission or brake execution. Specifically, the microcontroller 33 sets drive permission when the trigger switch 12 changes from off to on. Also, the microcontroller 33 sets brake execution when the trigger switch 12 changes from on to off, or when an abnormality is detected.

[0062] Next, in S130, the microcontroller 33 performs output duty cycle setting processing and sets the output duty cycle of the PWM signal to be output to the gate circuit 34. In other words, the microcontroller 33 sets the duty cycle of the voltage applied to the winding 22 of the motor 20. Details of the output duty cycle setting processing will be described later.

[0063] <1-2-3. Output Duty Cycle Setting Process> Referring to the flowchart in Figure 6, the output duty cycle setting process performed by the microcontroller 33 in motor control process S130 will be explained.

[0064] In S200, the microcontroller 33 determines whether the set drive mode has changed since the previous processing cycle. If it determines that the drive mode has changed (S200:YES), it proceeds to the S210 process; if it determines that the drive mode has not changed (S200:NO), it proceeds to the S230 process.

[0065] In S210, the microcontroller 33 performs the process of setting the target duty cycle α and sets the target duty cycle α according to the drive mode. The target duty cycle α is the target value of the output duty cycle during the startup period of the motor 20. During the startup period, the microcontroller 33 gradually increases the output duty cycle within a range less than or equal to the target duty cycle α. After the startup period, the microcontroller 33 performs constant rotation control. The startup period is from the time when the motor 20 starts to drive until the actual rotation speed reaches the starting rotation speed ωc. The time when the motor 20 starts to drive corresponds to the time when the trigger switch 12 changes from off to on. The starting rotation speed ωc is the speed at which the constant rotation speed begins and is smaller than the target rotation speed ωt. Details of the process of setting the target duty cycle α will be described later.

[0066] Next, in S220, the microcontroller 33 performs the process of setting the rotation threshold ω0, setting the rotation threshold ω0 according to the drive mode. The rotation threshold ω0 is a value smaller than the starting rotation speed ωc. The rotation threshold ω0 is a threshold for changing the rate of increase of the output duty cycle during the startup period. The inertia of the electric work implement 1 differs depending on the type of cutting tool. If the inertia of the electric work implement 1 is relatively small, increasing the output duty cycle at a constant rate until the actual rotation speed reaches the starting rotation speed ωc may cause the actual rotation speed to overshoot. If the rate of increase of the output duty cycle is suppressed to suppress the overshoot of the actual rotation speed, the startup period may increase if the inertia of the electric work implement 1 is relatively large. Consequently, the user experience may deteriorate.

[0067] Therefore, in this embodiment, during the startup period, when the actual rotational speed reaches the rotation threshold ω0, the rate of increase of the output duty cycle is reduced. If the inertia of the electric work implement 1 is relatively small, the actual rotational speed reaches the rotation threshold ω0 relatively quickly. Therefore, the rate of increase of the output duty cycle decreases relatively quickly, and overshoot of the actual rotational speed is suppressed. If the inertia of the electric work implement 1 is relatively large, the actual rotational speed reaches the rotation threshold ω0 relatively slowly. Therefore, the rate of increase of the output duty cycle decreases relatively slowly, and an increase in the startup period is suppressed. Details of the setting process for the rotation threshold ω0 will be described later.

[0068] In S230, the microcontroller 33 determines whether the conditions for constant rotation control are met. The conditions for constant rotation control are met when the actual rotation speed exceeds the starting rotation speed ωc. As shown in Figure 7A, the starting rotation speed ωc is set to a constant value regardless of the drive mode. The starting rotation speed ωc is, for example, 2500 / min. If constant rotation control is started after the actual rotation speed reaches the target rotation speed ωt, the actual rotation speed may exceed the target rotation speed ωt. Therefore, the microcontroller 33 starts constant rotation control before the actual rotation speed reaches the target rotation speed ωt.

[0069] On the other hand, accurate constant rotation control requires a precise actual rotation speed. As mentioned above, in a sensorless motor, the rotational position of the rotor 21 is calculated based on the zero-crossing of the induced voltage generated in the winding 22. The induced voltage is proportional to the actual rotational speed of the motor 20. Therefore, if the actual rotational speed of the motor 20 is small, the detection accuracy of the zero-crossing decreases. Consequently, the calculation accuracy of the rotational position of the rotor 21 decreases, and the calculation accuracy of the actual rotational speed decreases. Therefore, it is desirable for the microcontroller 33 to start constant rotation control only after the actual rotational speed has increased to the point where the detection accuracy of the zero-crossing stabilizes.

[0070] In this embodiment, the motor 20 is a sensorless motor. However, even if the motor 20 is a motor with a sensor, the microcontroller 33 will start constant rotation control only after the actual rotation speed has increased to the point where the zero-cross detection accuracy is stable. When detecting the rotation position of the rotor 21 with a three-phase Hall sensor, if the rotation speed is too low, the interval between signals output from the Hall sensor will become longer. Consequently, the frequency with which the microcontroller 33 calculates the actual rotation speed decreases, which may reduce the accuracy of constant rotation control.

[0071] If the microcontroller 33 determines that the conditions for constant rotation control are met (S230:YES), it proceeds to process S270; if it determines that the conditions for constant rotation control are not met (S230:NO), it proceeds to process S240.

[0072] In S240, the microcontroller 33 determines whether the actual rotational speed is less than the rotation threshold ω0 set in S220. If the microcontroller 33 determines that the actual rotational speed is less than the rotation threshold ω0 (S240: YES), it proceeds to the process in S250. If it determines that the actual rotational speed is greater than or equal to the rotation threshold ω0 (S240: NO), it proceeds to the process in S260.

[0073] In the S250, the microcontroller 33 performs constant duty cycle control processing, increasing the output duty cycle at the first rate of increase. Constant duty cycle control is a control without feedback. Then, the microcontroller 33 terminates this process. Details of the constant duty cycle control processing will be described later.

[0074] In S260, the microcontroller 33 sets the rate of increase of the output duty cycle to zero and sets a fixed value for the output duty cycle. The fixed value is the output duty cycle at the point when the actual rotation speed reaches the rotation threshold ω0, and is less than or equal to the target duty cycle α. The microcontroller 33 outputs a PWM signal with the fixed value to the gate circuit 34. That is, the microcontroller 33 fixes the magnitude of the voltage applied to the winding 22 to the value of the applied voltage at the point when the actual rotation speed reaches the rotation threshold ω0. Then, the microcontroller 33 terminates this process.

[0075] In S270, the microcontroller 33 performs constant rotation control and maintains the actual rotation speed at the target rotation speed ωt. Then, the microcontroller 33 terminates this process. Details of constant rotation control will be described later.

[0076] <1-2-4. Setting the Target Duty Ratio> Referring to the flowchart in Figure 8, the process of setting the target duty cycle α, which is performed by the microcontroller 33 in S210 of the output duty cycle setting process, will be explained.

[0077] In S300, the microcontroller 33 determines whether reverse mode is set as the drive mode. If the microcontroller 33 determines that reverse mode is set (S300:YES), it proceeds to process S310; if it determines that reverse mode is not set (S300:NO), it proceeds to process S320.

[0078] In S310, the microcontroller 33 sets a first target value for the target duty cycle α that corresponds to the reverse mode. As shown in Figure 7B, a target duty cycle α is set for each drive mode. The first target value is, for example, 20%. Then, the microcontroller 33 terminates this process.

[0079] In S320, the microcontroller 33 determines whether high-speed mode is set as the drive mode. If the microcontroller 33 determines that high-speed mode is set (S320:YES), it proceeds to process S330; if it determines that high-speed mode is not set (S320:NO), it proceeds to process S340.

[0080] In S330, the microcontroller 33 sets a second target value for the target duty cycle α, corresponding to the high-speed mode. The second target value is, for example, 30%. When the target rotational speed ωt is large, even if the target duty cycle α is increased, the overshoot of the actual rotational speed is suppressed. Therefore, in high-speed mode, the microcontroller 33 sets a larger value for the target duty cycle α than in reverse mode and low-speed mode. Then, the microcontroller 33 terminates this process.

[0081] In S340, the microcontroller 33 sets a third target value for the target duty cycle α, corresponding to the low-speed mode. The third target value is, for example, 25%. The third target value is smaller than the second target value and larger than the first target value. Then, the microcontroller 33 terminates this process.

[0082] <1-2-5. Setting the rotation threshold> Referring to the flowchart in Figure 9, the process of setting the rotation threshold ω0, which is performed by the microcontroller 33 in S220 of the output duty cycle setting process, will be explained.

[0083] In S400, the microcontroller 33 determines whether reverse mode is set as the drive mode. If the microcontroller 33 determines that reverse mode is set (S400:YES), it proceeds to process S410; if it determines that reverse mode is not set (S400:NO), it proceeds to process S420.

[0084] In S410, the microcontroller 33 sets a first threshold for the rotation threshold ω0 that corresponds to the reverse mode. As shown in Figure 7B, a rotation threshold ω0 is set for each drive mode. The first threshold is, for example, 600 / min.

[0085] In S420, the microcontroller 33 determines whether high-speed mode is set as the drive mode. If the microcontroller 33 determines that high-speed mode is set (S420:YES), it proceeds to process S430; if it determines that high-speed mode is not set (S420:NO), it proceeds to process S440.

[0086] In S430, the microcontroller 33 sets a second threshold for the rotation threshold ω0, corresponding to the high-speed mode. The second threshold is, for example, 2000 / min. When the target rotational speed ωt is large, even if the rotation threshold ω0 is increased, the overshoot of the actual rotational speed is suppressed. Therefore, in high-speed mode, the microcontroller 33 sets a larger value for the rotation threshold ω0 than in reverse mode and low-speed mode. Then, the microcontroller 33 terminates this process.

[0087] In S440, the microcontroller 33 sets a third threshold for the rotation threshold ω0, corresponding to the low-speed mode. The third threshold is, for example, 1000 / min. The third threshold is smaller than the second threshold and larger than the first threshold. In this embodiment, in all drive modes, the rotation threshold ω0 is set to one-fifth of the target rotation speed ωt. That is, in all drive modes, the ratio of the rotation threshold ω0 to the target rotation speed ωt is equal. Then, the microcontroller 33 terminates this process.

[0088] <1-2-6. Constant Duty Ratio Control Process> Referring to the flowchart in Figure 10, the constant duty cycle control process executed by the microcontroller 33 in S250 of the output duty cycle setting process will be explained.

[0089] In S500, the microcontroller 33 determines whether the PWM signal with an output duty cycle has not yet been output. If the microcontroller 33 determines that the PWM signal has not yet been output (S500:YES), it proceeds to the process in S510. If it determines that the PWM signal has already been output (S500:NO), it proceeds to the process in S550.

[0090] In S510, the microcontroller 33 determines whether the set drive mode has changed since the previous processing cycle. If the microcontroller 33 determines that the drive mode has changed (S510:YES), it proceeds to process S520; if it determines that the drive mode has not changed (S510:NO), it proceeds to process S530.

[0091] In S520, the microcontroller 33 performs the initial duty cycle setting process and sets the initial duty cycle β as the initial value of the output duty cycle. Then, the microcontroller 33 proceeds to the process in S530. Details of the initial duty cycle setting process will be described later.

[0092] In S530, the microcontroller 33 determines whether the output condition for the PWM signal is met. If drive permission is set, the microcontroller 33 determines that the output condition is met; if drive permission is not set, it determines that the output condition is not met. If the microcontroller 33 determines that the output condition is met (S530:YES), it proceeds to the process in S540; if it determines that the output condition is not met (S530:NO), it terminates this process.

[0093] In S540, the microcontroller 33 outputs a PWM signal with the set output duty cycle to the gate circuit 34. Then, the microcontroller 33 terminates this process. In S550, the microcontroller 33 determines whether the set output duty cycle is smaller than the target duty cycle α. If the microcontroller 33 determines that the output duty cycle is smaller than the target duty cycle α (S550: YES), it proceeds to the process in S560. If it determines that the output duty cycle is equal to or greater than the target duty cycle α (S550: NO), it terminates this process.

[0094] In S560, the microcontroller 33 increases the output duty cycle. For example, the microcontroller 33 updates the output duty cycle by adding a predetermined fixed increment value to it. The increment value is a positive value. As a result, the output duty cycle gradually increases at a first rate of increase. Consequently, the magnitude of the voltage applied to the motor 20 gradually increases at a first rate of increase. Then, the microcontroller 33 terminates this process.

[0095] <1-2-7. Constant rotation control processing> Referring to the flowchart in Figure 11, the constant rotation control process executed by the microcontroller 33 in S270 of the output duty cycle setting process will be explained.

[0096] In the S600, the microcontroller 33 executes a target rotational speed setting process and sets the target rotational speed ωt in constant rotation control. In constant rotation control, the microcontroller 33 maintains the actual rotational speed at the target rotational speed ωt. Details of the target rotational speed setting process will be described later.

[0097] Next, in S610, the microcontroller 33 determines whether the set target rotational speed ωt is greater than the actual rotational speed calculated in S100. If the microcontroller 33 determines that the target rotational speed ωt is greater than the actual rotational speed (S610: YES), it proceeds to the process in S620. If it determines that the target rotational speed ωt is less than or equal to the actual rotational speed (S610: NO), it proceeds to the process in S630.

[0098] In S620, the microcontroller 33 increases the output duty cycle to increase the actual rotational speed and bring it closer to the target rotational speed ωt. For example, the microcontroller 33 updates the output duty cycle by adding a certain increment value. The increment value in S620 may be the same as or different from the increment value in S560. Then, the microcontroller 33 terminates this process.

[0099] In S630, the microcontroller 33 determines whether the actual rotational speed is greater than the target rotational speed ωt. If the microcontroller 33 determines that the actual rotational speed is greater than the target rotational speed ωt (S630: YES), it proceeds to the process in S640. If the microcontroller 33 determines that the actual rotational speed is equal to the target rotational speed ωt (S630: NO), it terminates this process.

[0100] In S640, the microcontroller 33 reduces the output duty cycle to decrease the actual rotational speed and bring it closer to the target rotational speed ωt. For example, the microcontroller 33 updates the output duty cycle by subtracting a predetermined fixed reduction value from the output duty cycle. The subtracted value is a positive value. Then, the microcontroller 33 terminates this process.

[0101] <1-2-8. Initial Duty Cycle Setting Process> Referring to the flowchart in Figure 12, the initial duty cycle β setting process executed by the microcontroller 33 in S520 of the constant duty cycle setting process will be explained.

[0102] In S700, the microcontroller 33 determines whether reverse mode is set as the drive mode. If the microcontroller 33 determines that reverse mode is set (S700:YES), it proceeds to process S710; if it determines that reverse mode is not set (S700:NO), it proceeds to process S720.

[0103] In S710, the microcontroller 33 sets the initial duty cycle β to a first initial value corresponding to the reverse mode. As shown in Figure 7B, the initial duty cycle β is set for each drive mode. The first initial value is, for example, 3%. If the initial duty cycle β is set to 0%, the time required for the motor 20 to start rotating increases. Therefore, the microcontroller 33 sets the initial duty cycle β to a value greater than 0%. Then, the microcontroller 33 terminates this process.

[0104] In S720, the microcontroller 33 determines whether high-speed mode is set as the drive mode. If the microcontroller 33 determines that high-speed mode is set (S720:YES), it proceeds to process S730; if it determines that high-speed mode is not set (S720:NO), it proceeds to process S740.

[0105] In S730, the microcontroller 33 sets a second initial value for the initial duty cycle β, corresponding to the high-speed mode. The second initial value is, for example, 10%. When the target rotational speed ωt is large, even if the initial duty cycle β is large, the overshoot of the actual rotational speed is suppressed. Therefore, in high-speed mode, the microcontroller 33 sets a larger value for the initial duty cycle β than in reverse mode and low-speed mode. Then, the microcontroller 33 terminates this process.

[0106] In S740, the microcontroller 33 sets a third initial value corresponding to the low-speed mode for the initial duty cycle β. The third initial value is, for example, 5%. The third initial value is smaller than the second initial value and larger than the first initial value. Then, the microcontroller 33 terminates this process.

[0107] <1-2-9. Setting the Target Rotation Speed> Referring to the flowchart in Figure 13, the target rotational speed setting process executed by the microcontroller 33 in S600 of the constant rotational speed processing will be explained.

[0108] In S800, the microcontroller 33 determines whether reverse mode is set as the drive mode. If the microcontroller 33 determines that reverse mode is set (S800:YES), it proceeds to process S810; if it determines that reverse mode is not set (S800:NO), it proceeds to process S820.

[0109] In S810, the microcontroller 33 sets the target rotational speed ωt to a first target speed corresponding to the reverse rotation mode. As shown in Figure 7A, a target rotational speed ωt is set for each drive mode. The first target speed is, for example, 3000 / min. Then, the microcontroller 33 terminates this process.

[0110] In S820, the microcontroller 33 determines whether high-speed mode is set as the drive mode. If the microcontroller 33 determines that high-speed mode is set (S820:YES), it proceeds to process S830; if it determines that high-speed mode is not set (S820:NO), it proceeds to process S840.

[0111] In S830, the microcontroller 33 sets a second target speed corresponding to the high-speed mode as the target rotational speed ωt. The second target speed is, for example, 10000 / min. Then, the microcontroller 33 terminates this process.

[0112] In S840, the microcontroller 33 sets a third target speed corresponding to the low-speed mode for the target rotational speed ωt. The third target speed is, for example, 5000 / min. The third target speed is lower than the second target speed and higher than the first target speed. Then, the microcontroller 33 terminates this process.

[0113] <1-3. Operation> Figure 14 shows the time variation of the actual rotational speed and output duty cycle of the low-inertia electric work implement 1 and the high-inertia electric work implement 1 when the output duty cycle setting process according to the first embodiment is executed. The same drive mode is set for the low-inertia electric work implement 1 and the high-inertia electric work implement 1.

[0114] In the low-inertia electric work machine 1, the output duty cycle increases at a first rate of increase, and at time t1, the actual rotational speed reaches the rotational threshold ω0. Then, the output duty cycle is fixed at the value at time t1. Furthermore, at time t2, the actual rotational speed reaches the starting rotational speed ωc, and constant rotation control is initiated. Because the output duty cycle is fixed at the value at time t1, the increase in the actual rotational speed between time t1 and t2 becomes gradual. After time t2, the actual rotational speed is maintained at the target rotational speed ωt without exceeding it.

[0115] In the highly inertial electric work machine 1, the output duty cycle increases at a first rate of increase, and then becomes constant at the target duty cycle α. Then, at time t3, the actual rotational speed reaches the rotation threshold ω0, and the output duty cycle is fixed at the value at time t3, i.e., the target duty cycle α. Furthermore, at time t4, the actual rotational speed reaches the starting rotational speed ωc, and constant rotation control is initiated. After time t4, the actual rotational speed is maintained at the target rotational speed ωt without exceeding it.

[0116] In both cases—with the low-inertia electric work implement 1 and the high-inertia electric work implement 1—overshoot of the actual rotational speed is suppressed. Furthermore, the difference t4-t2 between the startup period of the low-inertia electric work implement 1 and the startup period of the high-inertia electric work implement 1 is small, and variations in startup period due to differences in inertia are also suppressed.

[0117] Figure 15 shows the time evolution of the actual rotational speed and output duty cycle of the low-inertia and high-inertia electric work implements in the first comparative example. The same drive mode is set for both the low-inertia and high-inertia electric work implements. In the first comparative example, the output duty cycle is increased at a first rate of increase until the actual rotational speed reaches the starting rotational speed ωc.

[0118] In an electric work machine with low inertia, at time t11, the actual rotational speed reaches the starting rotational speed ωc, and constant rotation control is initiated. After time t11, the actual rotational speed temporarily exceeds the target rotational speed ωt, and is then maintained at the target rotational speed ωt.

[0119] In an electric work machine with high inertia, at time t12, the actual rotational speed reaches the starting rotational speed ωc, and constant rotation control is initiated. After time t12, the actual rotational speed is maintained at the target rotational speed ωt without exceeding it.

[0120] In the first comparative example, the difference t12-t11 between the startup period of the low-inertia electric work implement and the startup period of the high-inertia electric work implement is large, and the variation in startup period due to the difference in inertia has increased compared to this embodiment. In other words, because the rate of increase of the output duty cycle was not reduced before the actual rotational speed reached the starting rotational speed ωc, the low-inertia electric work implement accelerated faster than in this embodiment, resulting in a larger difference in startup time. Furthermore, the actual rotational speed of the low-inertia electric work implement overshoots.

[0121] Figure 16 shows the time variation of the actual rotational speed and output duty cycle of the low-inertia and high-inertia electric work implements in the second comparative example. The same drive mode is set for both the low-inertia and high-inertia electric work implements. In the second comparative example, the output duty cycle is increased at a second rate of increase, which is smaller than the first rate of increase, until the actual rotational speed reaches the starting rotational speed ωc.

[0122] In an electric work machine with low inertia, the output duty cycle increases at a second rate of increase, and at time t21, the actual rotational speed reaches the rotational threshold ω0. The output duty cycle then continues to increase at a second rate of increase, and at time t23, the actual rotational speed reaches the starting rotational speed ωc, and constant rotation control begins. After time t23, the actual rotational speed is maintained at the target rotational speed ωt without exceeding it.

[0123] In an electric work machine with high inertia, the output duty cycle increases at a second rate of increase, and at time t22, the actual rotational speed reaches the rotational threshold ω0. The output duty cycle then continues to increase at a second rate of increase, and at time t24, the actual rotational speed reaches the starting rotational speed ωc, and constant rotation control begins. After time t24, the actual rotational speed is maintained at the target rotational speed ωt without exceeding it.

[0124] In the second comparative example, overshoot of the actual rotational speed was suppressed in both the case of electric work implements with low inertia and those with high inertia. However, the overall startup time of the electric work implements became longer. Therefore, the user experience may deteriorate.

[0125] <1-4. Effects> The first embodiment described in detail above provides the following effects. (1) When the actual rotational speed reaches the rotational threshold ω0, the rate of increase of the output duty cycle is set to zero. When the inertia of the electric work implement 1 is relatively small, a relatively small fixed value is set for the output duty cycle, suppressing overshoot of the actual rotational speed. When the inertia of the electric work implement 1 is relatively large, a relatively large fixed value is set for the output duty cycle, suppressing an increase in the start-up period. Therefore, it is possible to suppress overshoot of the actual rotational speed while suppressing variations in the start-up period due to differences in the inertia of the electric work implement 1.

[0126] (2) Before starting constant rotation control, the output duty cycle is controlled to be less than or equal to the target duty cycle α. This suppresses a rapid increase in the actual rotational speed during the startup period.

[0127] (3) The microcontroller 33 starts constant rotation control before the actual rotation speed reaches the target rotation speed ωt. This suppresses overshoot of the actual rotation speed. (4) By changing the rotation threshold ω0 depending on whether high-speed mode or low-speed mode is set, it is possible to suppress variations in the startup period due to differences in drive modes while suppressing overshoot of the actual rotation speed.

[0128] (5) By changing the target duty cycle α depending on whether high-speed mode or low-speed mode is set, it is possible to suppress variations in the startup period due to differences in drive modes while suppressing overshoot of the actual rotational speed.

[0129] (6) By changing the rotation threshold ω0 according to the rotation direction of the motor 20, it is possible to suppress variations in the startup period due to differences in the rotation direction while suppressing overshoot of the actual rotation speed.

[0130] (7) By changing the target duty cycle α according to the rotation direction of the motor 20, it is possible to suppress variations in the start-up period due to differences in the rotation direction while suppressing overshoot of the actual rotation speed.

[0131] (2. Second Embodiment) <2-1. Differences from the First Embodiment> The second embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. Note that the same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0132] In the first embodiment described above, the microcontroller 33 fixed the output duty cycle when the actual rotational speed became greater than or equal to the rotation threshold ω0 during the startup period. In contrast, the second embodiment differs from the first embodiment in that, when the actual rotational speed becomes greater than or equal to the rotation threshold ω0 during the startup period, the microcontroller 33 changes the rate of increase of the output duty cycle from a first rate of increase to a second rate of increase. The second rate of increase is greater than 0 and less than the first rate of increase.

[0133] <2-2. Setting the Output Duty Cycle> Referring to the flowchart in Figure 17, the output duty cycle setting process executed by the microcontroller 33 in S130 of the motor control process will be explained.

[0134] In S900-S940, microcontroller 33 performs the same processing as in S200-S240. If the microcontroller 33 determines in S940 that the actual rotational speed is less than the rotational threshold ω0 (S940: YES), it proceeds to the process in S950. In S950, the microcontroller 33 sets a first increment value as the increment value in the process of constant duty cycle control in S560. The first increment value is equal to the increment value in S560 of the first embodiment, and increases the output duty cycle at a first rate of increase. After the process in S950, the microcontroller 33 proceeds to the process in S970.

[0135] If the microcontroller 33 determines in S9040 that the actual rotational speed is greater than or equal to the rotational threshold ω0 (S940: NO), it proceeds to the process in S960. In S960, the microcontroller 33 sets a second increment value as the increment value in the process of constant duty cycle control in S560. The second increment value is smaller than the first increment value, and the output duty cycle is increased at a second rate of increase. After the process in S960, the microcontroller 33 proceeds to the process in S970.

[0136] In S970, the microcontroller 33 executes the constant duty cycle control processes S500 to S560 and then terminates this process. If the microcontroller 33 determines in S930 that the conditions for constant rotation control are met (S930: YES), it proceeds to the process in S980. In S980, the microcontroller 33 performs the same process as in S270 and terminates this process.

[0137] <2-3. Operation> Figure 18 shows the time variation of the actual rotational speed and output duty cycle of the low-inertia electric work implement 1 and the high-inertia electric work implement 1 when the output duty cycle setting process according to the second embodiment is executed. The same drive mode is set for the low-inertia electric work implement 1 and the high-inertia electric work implement 1.

[0138] In the low-inertia electric work machine 1, the output duty cycle increases at a first rate of increase, and at time t31, the actual rotational speed reaches the rotational threshold ω0. Then, the rate of increase of the output duty cycle is changed to a second rate of increase. Furthermore, at time t32, the actual rotational speed reaches the starting rotational speed ωc, and constant rotation control is initiated. After time t32, the actual rotational speed temporarily exceeds the target rotational speed ωt, and is then maintained at the target rotational speed ωt.

[0139] In the high-inertia electric work machine 1, the output duty cycle increases at a first rate of increase, and then becomes constant at the target duty cycle α. Then, at time t33, the actual rotational speed reaches the rotation threshold ω0. The output duty cycle remains fixed at the target duty cycle α. Furthermore, at time t34, the actual rotational speed reaches the starting rotational speed ωc, and constant rotation control begins. After time t34, the actual rotational speed is maintained at the target rotational speed ωt without exceeding it.

[0140] In the case of the low-inertia electric work implement 1, the overshoot of the actual rotational speed is suppressed because the rate of increase of the output duty cycle is set to a value greater than 0 after the actual rotational speed reaches the rotational threshold ω0. However, the overshoot of the actual rotational speed is suppressed more than in the first comparative example described above. In addition, the difference t34-t32 between the startup period of the low-inertia electric work implement 1 and the startup period of the high-inertia electric work implement 1 is small, and the variation in startup period due to the difference in inertia is also suppressed.

[0141] <2-4. Effects> The second embodiment described in detail above achieves the effects (2) to (7) of the first embodiment mentioned above, and further achieves the following effects.

[0142] (8) When the actual rotational speed reaches the rotational threshold ω0, the rate of increase of the output duty cycle is reduced from the first rate of increase to the second rate of increase. When the inertia of the electric work implement 1 is relatively small, the rate of increase of the output duty cycle decreases relatively quickly, thus suppressing overshoot of the actual rotational speed. When the inertia of the electric work implement 1 is relatively large, the rate of increase of the output duty cycle decreases relatively slowly, thus suppressing an increase in the start-up period. Therefore, it is possible to suppress overshoot of the actual rotational speed while suppressing variations in the start-up period due to differences in the inertia of the electric work implement 1.

[0143] (3. Third Embodiment) <3-1. Differences from the First Embodiment> The third embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. Note that the same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0144] In the first embodiment described above, the microcontroller 33 set a fixed value for the output duty cycle when the actual rotational speed reached a rotation threshold ω0 or higher during the startup period. In contrast, the third embodiment differs from the first embodiment in that the microcontroller 33 sets a fixed duty cycle γ corresponding to the drive mode for the output duty cycle when the actual rotational speed reached a rotation threshold ω0 or higher during the startup period. The fixed duty cycle γ is less than or equal to a fixed value. Therefore, in the third embodiment, the output duty cycle may not be continuous around the time the actual rotational speed reaches the rotation threshold ω0.

[0145] <3-2. Processing> <3-2-1. Setting the Output Duty Cycle> Referring to the flowchart in Figure 19, the output duty cycle setting process performed by the microcontroller 33 in S130 of the motor control process will be explained.

[0146] In S1000-S1020, the microcontroller 33 performs the same processing as in S200-S220. Next, in S1030, the microcontroller 33 executes the process of setting the fixed duty cycle γ and sets the fixed duty cycle γ. Details of the process of setting the fixed duty cycle γ will be described later.

[0147] Next, in S1040-S1060, the microcontroller 33 performs the same processing as in S230-S250. If the microcontroller 33 determines in S1050 that the actual rotational speed is greater than or equal to the rotation threshold ω0 (S1050: YES), it proceeds to the process in S1070. In S1070, the microcontroller 33 outputs a PWM signal with a fixed duty cycle γ set in S1030 to the gate circuit 34. That is, the microcontroller 33 fixes the magnitude of the voltage applied to the winding 22 to be less than or equal to the value of the applied voltage at the time the actual rotational speed reaches the rotation threshold ω0. Then, the microcontroller 33 terminates this process.

[0148] If the microcontroller 33 determines in S1050 that the conditions for constant rotation control are met (S1040: YES), it proceeds to the process in S1080. In S1080, the microcontroller 33 performs the same process as in S270 and terminates this process.

[0149] <3-2-2. Setting the Fixed Duty Cycle> Referring to the flowchart in Figure 20, the process of setting the fixed duty cycle γ, which is performed by the microcontroller 33 in S1070 of the output duty cycle setting process, will be explained.

[0150] In S1100, the microcontroller 33 determines whether the reverse mode is set as the drive mode. If the microcontroller 33 determines that the reverse mode is set (S1100: YES), it proceeds to process S1110; if it determines that the reverse mode is not set (S1100: NO), it proceeds to process S1120.

[0151] In S1110, the microcontroller 33 sets a first fixed value for the fixed duty cycle γ that corresponds to the reverse mode. As shown in Figure 7B, a fixed duty cycle γ is set for each drive mode. The first fixed value is, for example, 6%. Then, the microcontroller 33 terminates this process.

[0152] In S1120, the microcontroller 33 determines whether high-speed mode is set as the drive mode. If the microcontroller 33 determines that high-speed mode is set (S1120: YES), it proceeds to process S1130; otherwise, it proceeds to process S1140.

[0153] In S1130, the microcontroller 33 sets a second fixed value for the fixed duty cycle γ that corresponds to the high-speed mode. The second fixed value is, for example, 20%. In high-speed mode, a larger rotation threshold ω0 is set than in reverse mode and low-speed mode, so the microcontroller 33 sets a larger value for the fixed duty cycle γ than in reverse mode and low-speed mode. Then, the microcontroller 33 terminates this process.

[0154] In S1140, the microcontroller 33 sets a third fixed value for the fixed duty cycle γ, corresponding to the low-speed mode. The third fixed value is, for example, 10%. The third fixed value is smaller than the second fixed value and larger than the first fixed value. Then, the microcontroller 33 terminates this process.

[0155] <3-3. Operation> Figure 21 shows the time variation of the actual rotational speed and output duty cycle of the low-inertia electric work implement 1 and the high-inertia electric work implement 1 when the output duty cycle setting process according to the third embodiment is executed. The same drive mode is set for the low-inertia electric work implement 1 and the high-inertia electric work implement 1.

[0156] In the low-inertia electric work machine 1, the output duty cycle increases at a first rate of increase, and at time t41, the actual rotational speed reaches the rotational threshold ω0. Then, a fixed duty cycle γ is set for the output duty cycle. Furthermore, at time t42, the actual rotational speed reaches the starting rotational speed ωc, and constant rotation control is initiated. After time t42, the actual rotational speed is maintained at the target rotational speed ωt without exceeding the target rotational speed ωt.

[0157] In the high-inertia electric work machine 1, the output duty cycle increases at a first rate of increase, and then becomes constant at the target duty cycle α. Then, at time t43, the actual rotational speed reaches the rotation threshold ω0, and a fixed duty cycle γ smaller than the target duty cycle α is fixed to the output duty cycle. Furthermore, at time t44, the actual rotational speed reaches the starting rotational speed ωc, and constant rotation control is initiated. After time t44, the actual rotational speed is maintained at the target rotational speed ωt without exceeding it.

[0158] In this embodiment, when the actual rotational speed reaches the rotation threshold ω0, a fixed duty cycle γ independent of the difference in inertia is set for the output duty cycle. Therefore, the difference t44-t42 between the startup period of the low-inertia electric work implement 1 and the high-inertia electric work implement 1 is slightly larger than in the first embodiment. Thus, the variation in startup period due to the difference in inertia is greater than in the first embodiment. However, the startup period is shorter than in the second comparative example described above. Furthermore, in both the low-inertia electric work implement 1 and the high-inertia electric work implement 1, overshoot of the actual rotational speed is suppressed.

[0159] <3-4. Effects> The third embodiment described in detail above achieves the effects (2) to (7) of the first embodiment mentioned above, and further achieves the following effects.

[0160] (9) When the actual rotational speed reaches the rotational threshold ω0, a fixed duty cycle γ is set to the output duty cycle. When the inertia of the electric work implement 1 is relatively small, the output duty cycle is fixed to γ ​​relatively quickly, suppressing overshoot of the actual rotational speed. When the inertia of the electric work implement 1 is relatively large, the output duty cycle is fixed to γ ​​relatively slowly, suppressing an increase in the startup period. Therefore, it is possible to suppress overshoot of the actual rotational speed while suppressing variations in the startup period due to differences in the inertia of the electric work implement 1.

[0161] (4. Other Embodiments) Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above and can be implemented in various modified forms.

[0162] (a) In the above embodiment, the electric work machine 1 was not equipped with a position sensor for detecting the position of the rotor 21, but the electric work machine 1 may be equipped with a position sensor for detecting the position of the rotor 21. The microcontroller 33 may calculate the actual rotational speed of the motor 20 based on the position signal detected by the position sensor.

[0163] (b) In the above embodiment, the controller 30 was equipped with a microcontroller 33, but the controller 30 may be equipped with a combination of various individual electronic components instead of the microcontroller 33, or in addition to the microcontroller 33, an Application Specified Integrated Circuit (ASIC), an Application Specific Standard Product (ASSP), a programmable logic device such as an FPGA (Field Programmable Gate Array), or a combination thereof.

[0164] (c) Multiple functions of one component in the above embodiment may be realized by multiple components, or one function of one component may be realized by multiple components. Also, 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, some of the configurations of the above embodiment may be omitted. Furthermore, at least some of the configurations of the above embodiment may be added to or replaced with the configurations of other above embodiments. [Explanation of symbols]

[0165] 1...Electric work machine, 3...Drive unit, 4...Rotating blade, 7...Operation / display unit, 8...Battery pack, 9...Control unit, 11...Display unit, 12...Trigger switch, 15...Operation unit, 20...Motor, 30...Controller, 33...Microcontroller, 34...Gate circuit, 35...Drive circuit, 37...Rotor position detection unit, 56...Nylon cord, 111...Speed ​​display unit, 113...Reverse display unit, 151...Main power / mode selection switch, 152...Reverse switch, 160...Nylon cord cutter.

Claims

1. A motor configured to generate a driving force to rotate the cutting tool, A drive switch configured to be operated by the user in order to drive the motor, A control unit, Based on the fact that the drive switch is turned on, the magnitude of the applied voltage applied to the motor is increased at a first rate of increase. The actual rotational speed of the motor is obtained, Based on the fact that the acquired actual rotational speed has reached a set rotational threshold, the first rate of increase is changed to a second rate of increase that is smaller than the first rate of increase. A control unit is configured to start constant rotation control of the motor before the actual rotation speed reaches a target rotation speed greater than the rotation threshold, thereby maintaining the actual rotation speed at the target rotation speed. An electric work machine equipped with the following features.

2. A motor configured to generate a driving force to rotate the cutting tool, A drive switch configured to be operated by the user in order to drive the motor, A control unit, Based on the fact that the drive switch is turned on, the magnitude of the applied voltage applied to the motor is increased at a predetermined rate of increase. The actual rotational speed of the motor is obtained, Based on the fact that the acquired actual rotational speed has reached a set rotation threshold, the magnitude of the applied voltage is fixed to a predetermined value, the predetermined value being less than or equal to the magnitude of the applied voltage at the time the actual rotational speed reaches the rotation threshold. A control unit is configured to start constant rotation control of the motor before the actual rotation speed reaches a target rotation speed greater than the rotation threshold, thereby maintaining the actual rotation speed at the target rotation speed. An electric work machine equipped with the following features.

3. The aforementioned second rate of increase is zero. The control unit is configured to fix the magnitude of the applied voltage to a predetermined value from the time the acquired actual rotation speed reaches the rotation threshold until the constant rotation control is started. The predetermined value is the magnitude of the applied voltage at the point when the actual rotational speed reaches the rotation threshold. The electric work machine according to claim 1.

4. The system further comprises a drive circuit configured to drive the motor, The control unit, Based on the output duty cycle of the pulse width modulated signal output to the drive circuit, the magnitude of the applied voltage is changed. The system is configured to control the output duty cycle to a set target duty cycle or less from the time the drive switch is turned on until the constant rotation control starts. An electric work machine according to any one of claims 1 to 3.

5. The control unit is configured to start the constant rotation control based on the fact that the acquired actual rotation speed has reached the starting speed. The starting speed is greater than the rotation threshold and less than the target rotation speed. An electric work machine according to any one of claims 1 to 4.

6. The system further includes a selection switch configured to be operated by the user to select a first mode or a second mode, which is the drive mode of the motor. The control unit, When the first mode is selected via the selection switch, the first threshold is set to the rotation threshold. When the second mode is selected via the selection switch, the system is configured to set a second threshold value for the rotation threshold that is different from the first threshold value. An electric work machine according to any one of claims 1 to 5.

7. The system further includes a selection switch configured to be operated by the user to select a first mode or a second mode, which is the drive mode of the motor. The control unit, When the first mode is selected via the selection switch, the first duty cycle is set as the target duty cycle. When the second mode is selected via the selection switch, the system is configured to set the target duty cycle to a second duty cycle different from the first duty cycle. The electric work machine according to claim 4.

8. The control unit, When the motor rotates in the forward direction, a third threshold is set for the rotation threshold. The system is configured such that when the motor rotates in the opposite direction to the forward direction, a fourth threshold value different from the third threshold value is set for the rotation threshold value. An electric work machine according to any one of claims 1 to 7.

9. The control unit, When the motor rotates in the forward direction, the target duty cycle is set to a third duty cycle. The system is configured such that when the motor rotates in the opposite direction to the forward direction, a fourth duty cycle different from the third duty cycle is set as the target duty cycle. The electric work machine according to claim 4 or 7.

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