Electric working machine

Abstract

An electric working machine according to one embodiment of the present invention is provided with a motor, a drive switch, and a control unit. The control unit increases the magnitude of the applied voltage applied to the motor on the basis of the driving switch being turned on. The control unit suppresses an increase in the magnitude of the applied voltage on the basis of the actual rotation speed of the motor having reached the set rotation threshold value.

Description

Technical Field

[0001] This invention relates to an electric work machine equipped with a motor. Background Technology

[0002] The lawnmower described in Japanese Patent Application Publication No. 2018-57327 has a blade or nylon rope mounted at its front end that rotates using the power of a motor. When the trigger switch changes from off to on, the actual rotational speed of the lawnmower's motor gradually increases to the target rotational speed. Summary of the Invention

[0003] The inertia of a lawnmower equipped with a nylon rope is less than that of a lawnmower equipped with a blade. Therefore, if the increase in motor start-up time is prevented when a blade is attached to the lawnmower, an overshoot in rotational speed may occur during motor start-up when the nylon rope is attached. Conversely, if the overshoot in rotational speed during motor start-up is prevented when the nylon rope is attached, the start-up time of the motor may increase when the blade is attached.

[0004] One aspect of the present invention aims to suppress the deviation during motor startup caused by the inertia difference of the front tool, while also suppressing the overshoot of the motor's rotational speed.

[0005] One embodiment of the electric work machine of the present invention includes: a motor, a drive switch, and a control unit. The motor generates a driving force for rotating a front-end tool. The drive switch is operated by a user to drive the motor. The control unit increases the applied voltage to the motor based on the drive switch being turned on, suppresses the increase in applied voltage based on the actual rotational speed of the motor reaching a set rotational threshold, and begins constant rotational 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 rotational threshold.

[0006] According to the above-described electric work machine, when the actual rotational speed has reached the rotational threshold, the rate of increase of the applied voltage decreases. When the electric work machine has relatively low inertia, the overshoot of the actual rotational speed is suppressed earlier because the increase of the applied voltage is suppressed earlier. When the electric work machine has relatively high inertia, the increase during startup is suppressed later because the increase during startup is suppressed later. Therefore, it is possible to suppress deviations during startup caused by differences in the inertia of the electric work machine, and also to suppress overshoot of the actual rotational speed.

[0007] Regarding another aspect of the present invention, a method for controlling the motor of an electric work machine involves increasing the applied voltage to the motor based on the fact that the drive switch of the electric work machine has been turned on, suppressing the increase in the applied voltage based on the fact that the actual rotational speed of the motor has reached a set rotational threshold, initiating constant rotational control of the motor before the actual rotational speed reaches a target rotational speed greater than the rotational threshold, and maintaining the actual rotational speed at the target rotational speed.

[0008] The above method can achieve the same effect as the electric work machine mentioned above. Attached Figure Description

[0009] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0010] Figure 1A This is a diagram showing an example of the appearance of the electric work machine according to the first embodiment.

[0011] Figure 1B This is another example of the appearance of the electric work machine according to the first embodiment.

[0012] Figure 2 This is a diagram showing the operation / display unit of the electric work machine according to the first embodiment.

[0013] Figure 3 This is a diagram showing the electrical configuration of the electric work machine according to the first embodiment.

[0014] Figure 4 This is a flowchart illustrating the main processing performed by the control circuit of the electric work machine according to the first embodiment.

[0015] Figure 5 This is a flowchart illustrating the motor control processing performed by the control circuit of the electric work machine according to the first embodiment.

[0016] Figure 6 This is a flowchart illustrating the output duty cycle setting process performed by the control circuit of the electric work machine according to the first embodiment.

[0017] Figure 7A It is a graph showing the correspondence between the drive mode of the electric work machine of the first embodiment and the value related to the rotation speed.

[0018] Figure 7B It is a graph showing the correspondence between the drive mode of the electric work machine in the first embodiment and the value related to the duty cycle.

[0019] Figure 8 This is a flowchart illustrating the target duty cycle setting process performed by the control circuit of the electric work machine in the first embodiment.

[0020] Figure 9 This is a flowchart illustrating the rotation threshold setting process performed by the control circuit of the electric work machine according to the first embodiment.

[0021] Figure 10 This is a flowchart illustrating the constant duty cycle control process performed by the control circuit of the electric work machine according to the first embodiment.

[0022] Figure 11 This is a flowchart illustrating the constant rotation control process performed by the control circuit of the electric work machine according to the first embodiment.

[0023] Figure 12 This is a flowchart illustrating the initial duty cycle setting process performed by the control circuit of the electric work machine according to the first embodiment.

[0024] Figure 13 This is a flowchart illustrating the target rotation speed setting process performed by the control circuit of the electric work machine according to the first embodiment.

[0025] Figure 14 This is a graph showing the actual rotational speed and output duty cycle of the electric work machine as a function of time when the inertia is small / large in the first embodiment.

[0026] Figure 15 This is a graph showing the actual rotational speed and output duty cycle of the electric work machine as a function of time when the inertia of the reference example is small / large.

[0027] Figure 16 This is a graph showing the actual rotational speed and output duty cycle of the electric work machine as a function of time when the inertia is smaller / larger in another reference example.

[0028] Figure 17 This is a flowchart illustrating the output duty cycle setting process performed by the control circuit of the electric work machine in the second embodiment.

[0029] Figure 18 This is a graph showing the actual rotational speed and output duty cycle of the electric work machine as a function of time when the inertia is small / large in the second embodiment.

[0030] Figure 19 This is a flowchart illustrating the output duty cycle setting process performed by the control circuit of the electric work machine in the third embodiment.

[0031] Figure 20 This is a flowchart illustrating the fixed duty cycle setting process performed by the control circuit of the electric work machine in the third embodiment.

[0032] Figure 21This is a graph showing the actual rotational speed and output duty cycle of the electric work machine as a function of time when the inertia is small / large in the third embodiment. Detailed Implementation

[0033] [1. Overview of the implementation methods]

[0034] One embodiment may provide an electric work machine having at least one of the following features.

[0035] • Feature 1: A motor that generates the driving force to rotate the front tool.

[0036] • Feature 2: A drive switch that is operated by the user to drive the motor.

[0037] • Feature 3: Control unit.

[0038] • Feature 4: The control unit increases the applied voltage to the motor based on the fact that the drive switch has been turned on.

[0039] • Feature 5: The control unit suppresses the increase in the applied voltage based on the fact that the actual rotational speed of the motor has reached the set rotational threshold.

[0040] • Feature 6: The control unit begins constant rotation control of the motor before the actual rotation speed reaches the target rotation speed, thereby maintaining the actual rotation speed at the target rotation speed.

[0041] • Feature 7: The target rotation speed is greater than the rotation threshold.

[0042] In an electric workpiece possessing at least features 1 to 7, the increase in the magnitude of the applied voltage is suppressed when the actual rotational speed has reached the rotational threshold. When the electric workpiece has relatively low inertia, the increase in the magnitude of the applied voltage is suppressed earlier, thus suppressing overshoot of the actual rotational speed. When the electric workpiece has relatively high inertia, the increase in the magnitude of the applied voltage is suppressed later, thus suppressing the increase during startup. Therefore, deviations during startup caused by differences in the inertia of the electric workpiece can be suppressed, while also suppressing overshoot of the actual rotational speed.

[0043] In addition to having at least one of the features 1 to 7 described above, a certain embodiment may also have at least one of the following features.

[0044] • Feature 8: The control unit increases the applied voltage at the first rate of increase based on the fact that the drive switch has been turned on.

[0045] • Feature 9: The control unit replaces the first rate of increase with the second rate of increase based on the actual rotational speed reaching the rotational threshold.

[0046] • Feature 10: The second rate of increase is less than the first rate of increase.

[0047] In electric work machines possessing at least features 1 to 10, when the inertia of the electric work machine is relatively small, the rise in the magnitude of the applied voltage can be suppressed earlier. Conversely, when the inertia of the electric work machine is relatively large, the rise in the magnitude of the applied voltage can be suppressed later.

[0048] In addition to having at least one of the features 1 to 7 described above, a certain embodiment may also have at least one of the following features.

[0049] • Feature 11: The control unit increases the applied voltage to the motor at a predetermined rate of increase based on the fact that the drive switch has been turned on.

[0050] • Feature 12: The control unit fixes the applied voltage to a specified value based on the actual rotation speed having reached the rotation threshold.

[0051] • Feature 13: The specified value is below the magnitude of the applied voltage at the point when the actual rotation speed has reached the rotation threshold.

[0052] In electric work machines possessing at least features 1 to 7 and 11 to 13, when the inertia of the electric work machine is relatively small, the rise in the magnitude of the applied voltage can be suppressed earlier. Furthermore, when the inertia of the electric work machine is relatively large, the rise in the magnitude of the applied voltage can be suppressed later.

[0053] In addition to having at least one of the features 1 to 10 described above, or alternatively, a certain embodiment may also have the following features.

[0054] • Feature 14: The second rate of increase is zero.

[0055] • Feature 15: During the period from when the actual rotational speed reaches the rotational threshold until constant rotational control begins, the control unit fixes the applied voltage to a predetermined value.

[0056] • Feature 16: The specified value is the magnitude of the applied voltage at the point in time when the actual rotational speed has reached the rotational threshold.

[0057] In electric work machines possessing at least features 1 to 10 and 14 to 16, the applied voltage is fixed at the point in time when the actual rotational speed has reached a rotational threshold. Accordingly, the rate of increase of the actual rotational speed is slow, thereby suppressing overshoot.

[0058] In addition to having at least one of the features 1 to 16 described above, a certain embodiment may also have at least one of the following features.

[0059] • Feature 17: It is configured as a drive circuit to drive a motor.

[0060] • Feature 18: The control unit changes the magnitude of the applied voltage based on the output duty cycle of the pulse width modulation signal output to the drive circuit.

[0061] • Feature 19: During the period from when the drive switch is turned on to when constant rotation control begins, the control unit controls the output duty cycle to be below the set target duty cycle.

[0062] In electric work machines possessing at least features 1 to 7 and features 17 to 19, the output duty cycle is controlled below the target duty cycle before constant rotation control begins. Accordingly, during startup, a sharp increase in the actual rotational speed can be suppressed.

[0063] In addition to having at least one of the features 1 to 19 described above, a certain embodiment may also have at least one of the following features.

[0064] • Feature 20: The control unit begins constant rotation control based on the fact that the actual rotation speed has reached the starting rotation speed.

[0065] • Feature 21: The initial rotation speed is greater than the rotation threshold but less than the target rotation speed.

[0066] In an electric work machine that possesses at least features 1 to 7 and features 20 to 21, the control unit begins constant rotation control before the actual rotational speed reaches the target rotational speed. This suppresses overshoot of the actual rotational speed.

[0067] In addition to having at least one of the features 1 to 21 described above, a certain embodiment may also have at least one of the following features.

[0068] • Feature 22: The motor's drive modes include Mode 1 and Mode 2.

[0069] • Feature 23: A selection switch operated by the user to select the first mode or the second mode.

[0070] • Feature 24: The control unit sets the first threshold to the rotation threshold based on selecting the first mode by means of a selection switch.

[0071] • Feature 25: The control unit sets a second threshold, which is different from the first threshold, as a rotation threshold based on selecting the second mode by means of a selection switch.

[0072] In electric work machines that possess at least features 1 to 7 and features 22 to 25, the control unit changes the rotation threshold according to the drive mode. This suppresses deviations during startup caused by differences in the drive mode, and also suppresses overshoot of the actual rotational speed.

[0073] In addition to having at least one of the features 1 to 25 described above, a certain embodiment may also have at least one of the following features.

[0074] • Feature 26: The control unit sets the first duty cycle to the target duty cycle based on selecting the first mode by means of a selection switch.

[0075] • Feature 27: The control unit sets the second duty cycle, which is different from the first duty cycle, as the target duty cycle based on the selection of the second mode by means of the selection switch.

[0076] In electric work machines that possess at least features 1-7, features 17-19, 22-23, and 26-27, the control unit changes the target duty cycle according to the drive mode. This suppresses deviations during startup caused by differences in drive mode, and also suppresses overshoot of the actual rotational speed.

[0077] In addition to having at least one of the features 1 to 27 described above, a certain embodiment may also have at least one of the following features.

[0078] • Feature 28: The control unit sets the third threshold as the rotation threshold based on the motor rotating in the positive direction.

[0079] • Feature 29: The control unit sets a fourth threshold, which is different from the third threshold, as the rotation threshold based on the motor rotating in the opposite direction to the positive direction.

[0080] In an electric work machine having at least features 1 to 7 and features 28 to 29, the control unit changes the rotation threshold according to the rotation direction of the motor. This suppresses deviations during startup caused by differences in rotation direction, and also suppresses overshoot of the actual rotational speed.

[0081] In addition to having at least one of the features 1 to 29 described above, a certain embodiment may also have at least one of the following features.

[0082] • Feature 30: The control unit sets the third duty cycle as the target duty cycle based on the motor rotating in the positive direction.

[0083] • Feature 31: The control unit sets a fourth duty cycle, which is different from the third duty cycle, as the target duty cycle based on the motor rotating in the opposite direction to the positive direction.

[0084] In electric work machines that possess at least features 1 to 7, features 17 to 19, and features 30 to 31, the control unit changes the target duty cycle according to the rotation direction of the motor. This suppresses deviations during startup caused by differences in rotation direction, and also suppresses overshoot of the actual rotational speed.

[0085] In one embodiment, a method for controlling the motor of an electric work machine that has at least one of the following features may also be provided.

[0086] • Feature 32: Based on the fact that the drive switch of the electric work machine has been turned on, the magnitude of the applied voltage to the motor increases.

[0087] • Feature 33: Based on the fact that the actual rotational speed of the motor has reached the set rotational threshold, the increase in the applied voltage is suppressed.

[0088] • Feature 34: Before the actual rotational speed reaches the target rotational speed which is greater than the rotational threshold, constant rotational control of the motor is initiated, thereby maintaining the actual rotational speed at the target rotational speed.

[0089] The method having at least features 32 to 34 can achieve the same effect as an electric work machine having at least features 1 to 7.

[0090] Examples of the aforementioned power work machines include various equipment configured for use in construction, manufacturing, horticulture, and civil engineering work sites. Specifically, these include power tools for stonemasonry, metalworking, woodworking, horticulture, and site preparation. In particular, examples of the aforementioned power work machines include power tools for stonemasonry, metalworking, woodworking, and horticulture that can be equipped with multiple front-end tools or attachments. Examples of such power tools include lawnmowers capable of mounting multiple front-end tools, detachable lawnmowers capable of mounting multiple attachments on the pole, and electric hammers, electric drills, electric screwdrivers, and electric impact screwdrivers capable of mounting multiple front-end tools.

[0091] In one embodiment, features 1 to 34 described above can also be any combination.

[0092] In one embodiment, any one of the features 1 to 34 described above may be excluded.

[0093] (First Embodiment)

[0094] <1-1. Composition>

[0095] <1-1-1. Overall Composition>

[0096] Reference Figure 1A And 1B, to explain the electric work machine 1 according to this embodiment. The electric work machine 1 according to this embodiment is, for example, a lawnmower. The electric work machine 1 includes a main pipe 2. The main pipe 2 has a first end and a second end, and is formed into a long and hollow rod shape.

[0097] The electric cutting machine 1 includes a drive unit 3. The drive unit 3 is mounted at the first end of the main pipe 2. The drive unit 3 houses a motor 20, which will be described later. The drive unit 3 has a reduction gear mechanism at the front end of the rotating shaft of the motor 20. A rotary blade 4 is detachably mounted to the output shaft of the gear mechanism. The rotary blade 4 is an example of a front-end tool. When the motor 20 rotates, the output shaft of the gear mechanism rotates integrally with the rotary blade 4. The rotary blade 4 is formed as a metal disc. The rotary blade 4 has multiple serrated teeth formed along the outer circumference of the disc. The rotary blade 4 rotates under the driving force of the motor 20, thereby cutting grass and branches.

[0098] like Figure 1B As shown, the nylon rope cutter 160 can also be detachably mounted to the output shaft of the gear mechanism, replacing the rotary blade 4. The nylon rope cutter 160 is another example of a front-end tool. The nylon rope cutter 160 includes a cylindrical reel 16 and a nylon rope 56 housed in the reel 16. Two holes are formed on the side of the reel 16, through which the nylon rope 56 is pulled out. The reel 16 is rotated by the driving force of the motor 20, thereby causing the nylon rope 56 pulled out from the two holes to come into contact with grass or the like, thus cutting the grass or the like.

[0099] The nylon rope cutter 160 is lighter than the rotary blade 4. Therefore, the inertia of the electric work machine 1 equipped with the nylon rope cutter 160 is less than that of the electric work machine 1 equipped with the rotary blade 4. That is, the inertia of the electric work machine 1 varies depending on the type of tool mounted on the front end of the electric work machine 1.

[0100] The electric work machine 1 includes a cover 5. The cover 5 is mounted on the first end of the main pipe 2. The cover 5 is mounted at a position closer to the second end than the rotary blade 4 or the nylon rope cutter 160. The cover 5 is used to prevent grass or other materials cut by the rotary blade 4 or the nylon rope cutter 160 from flying towards the user.

[0101] The electric work machine 1 includes a control unit 6. The control unit 6 is connected to the main pipe 2 near the middle position along its length. The control unit 6 is U-shaped, with handles mounted at both ends of the U. The user holds the two handles to operate the electric work machine 1.

[0102] The electric work machine 1 includes an operation / display unit 7. The operation / display unit 7 is located on one of the two handles of the control unit 6. The operation / 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 / display unit 7 includes a trigger switch 12 and a lockout switch 13.

[0103] To drive the motor 20, the user operates the trigger switch 12. Specifically, when the main power is turned on, the user pulls the trigger switch 12 to drive the motor 20, and releases the trigger switch 12 to stop the motor 20. During the period the trigger switch 12 is pulled, it outputs an "on" signal to the control circuit 33 (described later), and during the period it is released, it outputs an "off" signal to the control circuit 33. In this embodiment, the trigger switch 12 is an example of the drive switch of the present invention.

[0104] The lock / unlock switch 13 is operated by the user, becoming either locked or unlocked. When the lock / unlock switch 13 is locked, the user cannot pull the trigger switch 12. When the lock / unlock switch 13 is unlocked, the user can pull the trigger switch 12.

[0105] The electric work machine 1 includes a control unit 9. The control unit 9 is installed at the second end of the main pipe 2. The control unit 9 houses a controller 30, which will be described later. The controller 30 is connected to the motor 20 via a wiring harness passing through the main pipe 2. Additionally, the controller 30 is connected to the operation / display unit 7 via a wiring harness passing through the main pipe 2. Furthermore, a battery pack 8 is removably mounted in the control unit 9. The battery pack 8 comprises multiple 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 battery pack 8 via the controller 30.

[0106] <1-1-2. Operation / Display Unit>

[0107] Reference Figure 2This section describes the display unit 11 and the operation unit 15 of the electric work machine 1. The operation unit 15 is operated by the user to activate the electric work machine 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 touch switch, operated by the user to turn the main power on / off or to select the normal mode. When the user presses and holds the main power / mode selection switch 151, the main power changes from off to on or from on to off. A long press is equivalent to continuously pressing for a specified time or more. When the user briefly presses the main power / mode selection switch 151, the normal mode changes. A brief press is equivalent to releasing the switch after pressing and before a specified time has elapsed. The main power / mode selection switch 151 outputs an on signal to the control circuit 33 during the pressing period and an off signal to the control circuit 33 during the releasing period.

[0108] In this embodiment, the driving modes of motor 20 include a normal mode and a reverse mode described later. The normal mode includes a low-speed mode and a high-speed mode. In the normal mode, motor 20 rotates in the forward direction. Whenever the user briefly presses the main power / mode selection switch 151, the driving mode changes in the order of low-speed mode → high-speed mode → low-speed mode. The target rotational speed ωt in the low-speed mode is less than the target rotational speed ωt in the high-speed mode. The target rotational speed ωt is the target value of the rotational speed of motor 20. In this embodiment, the main power / mode selection switch 151 corresponds to an example of the selection switch of the present invention, and the high-speed mode and low-speed mode correspond to examples of the first mode and the second mode of the present invention.

[0109] The reverse switch 152 is a touch switch operated by the user to select the reverse mode. In reverse mode, the motor 20 rotates in the opposite direction to the forward direction. When grass or other materials are entangled in the rotating blade 4 or the nylon rope cutter 160, the grass will be removed from the rotating blade 4 or the nylon rope cutter 160 by driving the motor 20 in reverse mode.

[0110] When the user presses the reverse switch 152, the drive mode changes from the normal mode to the reverse mode. In the reverse mode, the drive mode changes from the reverse mode to the normal mode as soon as the user presses the reverse switch 152. Furthermore, after the motor 20 starts driving in the reverse mode, it automatically stops after a certain period of time (e.g., a few seconds). The drive mode then automatically changes from the reverse mode to the normal mode. Therefore, after the motor 20 automatically stops, when the user pulls the trigger switch 12, the motor 20 rotates in the forward direction. The reverse switch 152 outputs an ON signal to the control circuit 33 while being pressed and an OFF signal to the control circuit 33 while being released.

[0111] In addition, in other implementations, the driving mode may include other modes besides low-speed mode, high-speed mode, and reverse mode.

[0112] The display unit 11 notifies the user of the set drive mode and abnormal status. 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 (LEDs) corresponding to low-speed and high-speed modes. In low-speed mode, one of the two LEDs is lit; in high-speed mode, the other LED is lit. In reverse mode, both LEDs flash. The abnormality display unit 113 includes one LED. When an abnormal status is detected during the operation of the electric work machine 1, the LED flashes or lights up to notify the user of the abnormal status.

[0113] <1-1-3. Electrical Configuration>

[0114] Reference Figure 3 The electrical configuration of the electric work machine 1 is described below. The electric work machine 1 includes a motor 20. The motor 20 is a three-phase brushless motor. The motor 20 includes: a three-phase winding (i.e., a stator) 22 and a rotor 21. The motor 20 is a sensorless motor. In other embodiments, the motor 20 is not limited to a three-phase motor; it may also be a single-phase motor, a two-phase motor, or a multi-phase motor with four or more phases. Alternatively, the motor 20 may also be a brushed motor.

[0115] The electric work machine 1 is equipped with a controller 30. The controller 30 includes: a power control circuit 31, a regulator 32, a control circuit 33, a gate circuit 34, a drive circuit 35, a current detection circuit 36, a rotor position detection unit 37, a power cord 38, and a cut-off switch 39.

[0116] When the main power supply is on, the power control circuit 31 drives the regulator 32 to generate a power supply voltage Vcc. The regulator 32 then supplies the generated power supply voltage Vcc to the control circuit 33 and other components.

[0117] Power line 38 connects the positive terminal of battery pack 8 to drive circuit 35. A disconnect switch 39 is located on power line 38. When disconnect switch 39 is in the ON state, power line 38 is conductive, supplying power from battery pack 8 to drive circuit 35. When disconnect switch 39 is in the OFF state, power line 38 is disconnected, and power is not supplied from battery pack 8 to drive circuit 35.

[0118] The drive circuit 35 is a three-phase full-bridge circuit comprising three high-side switching elements and three low-side switching elements. The six switching elements are, for example, Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs). The switching on / off state of the six switching elements is controlled by the control circuit 33 via gate circuit 34. The drive circuit 35 is controlled by the control circuit 33, thereby applying a pulse-width modulated voltage to the winding 22 of the motor 20. In other embodiments, the six switching elements can be other FETs, Insulated Gate Bipolar Transistors (IGBTs), Silicon Controlled Rectifiers (SCRs), etc.

[0119] Gate circuit 34 is connected to power line 38 and, based on the control signal output from control circuit 33, turns on or off the six switching elements of drive circuit 35. The control signal is a pulse width modulation (PWM) signal with a set output duty cycle. Additionally, gate circuit 34 turns on or off cut-off switch 39 based on the command signal output from control circuit 33. Specifically, gate circuit 34 turns on cut-off switch 39 when control circuit 33 allows motor 20 to drive, and turns off cut-off switch 39 when control circuit 33 disables motor 20 to drive.

[0120] The current detection circuit 36 ​​detects the magnitude of the current flowing into the winding 22 of the motor 20 and outputs the current detection value corresponding to the magnitude of the current to the control circuit 33.

[0121] The rotor position detection unit 37 detects the zero-crossing point of the induced voltage generated by each winding 22 and outputs the detection signal of each phase to the control circuit 33.

[0122] The control circuit 33 includes a CPU 331 and a memory 332. Based on the detection signals of each phase input from the rotor position detection unit 37, the control circuit 33 calculates the rotational position of the rotor 21. Furthermore, the control circuit 33 calculates the actual rotational speed of the motor 20.

[0123] In addition, the control circuit 33 generates a control signal based on various input information and outputs the generated control signal to the gate circuit 34. Specifically, the control circuit 33 generates the control signal based on (i) the on or off signals input from the trigger switch 12, the main power / mode selection switch 151, and the inverting switch 152, (ii) the current detection value input from the current detection circuit 36, and (iii) the calculated rotational speed.

[0124] Furthermore, the control circuit 33 illuminates, flashes, or turns off each LED of the display unit 11 based on the on / off signals input from the trigger switch 12, the main power / mode selection switch 151, and the inverting switch 152. In this embodiment, the control circuit 33 is an example of the control unit of the present invention.

[0125] In other embodiments, at least one of the following components may be excluded from the controller 30: power control circuit 31, regulator 32, control circuit 33, gate circuit 34, drive circuit 35, current detection circuit 36, rotor position detection unit 37, power line 38, and cut-off switch 39.

[0126] <1-2. Treatment>

[0127] <1-2-1. Main Processor>

[0128] Reference Figure 4 The flowchart illustrates the main process executed by control circuit 33. Control circuit 33 begins this process when the main power supply changes from off to on, and repeats this process at a predetermined cycle.

[0129] In S10, the control circuit 33 performs switch operation detection processing. Specifically, the control circuit 33 obtains an on or off signal from the trigger switch 12, the main power / mode selection switch 151, and the reverse switch 152, respectively.

[0130] Next, in S20, the control circuit 33 performs motor control processing to control the drive of the motor 20. Details of the motor control processing will be described later.

[0131] <1-2-2. Motor Control Processing>

[0132] Reference Figure 5 The flowchart illustrates the motor control processing performed by the control circuit 33 in the main processing step S20.

[0133] In S100, the control circuit 33 obtains the detection signals of each phase from the rotor position detection unit 37 and calculates the actual rotational speed of the motor 20.

[0134] Next, in S110, the control circuit 33 sets the drive mode based on the on or off signals obtained from the main power / mode selection switch 151 and the reverse switch 152. Specifically, the control circuit 33 sets any one of the low-speed mode, high-speed mode, and reverse mode as the drive mode.

[0135] Next, in S120, the control circuit 33 sets the drive permission or enables the braking action. Specifically, the control circuit 33 sets the drive permission when the trigger switch 12 changes from off to on. Additionally, the control circuit 33 enables the braking action when the trigger switch 12 changes from on to off, or when an abnormality is detected.

[0136] Next, in S130, the control circuit 33 performs an output duty cycle setting process to set the output duty cycle of the PWM signal output to the gate circuit 34. That is, the control circuit 33 sets the duty cycle of the voltage applied to the winding 22 of the motor 20. Details of the output duty cycle setting process will be described later.

[0137] <1-2-3. Output Duty Cycle Setting Processing>

[0138] Reference Figure 6 The flowchart illustrates the output duty cycle setting process performed by the control circuit 33 in S130 of the motor control process.

[0139] In S200, it is determined whether the set drive mode has changed from the drive mode in the previous processing cycle. If the control circuit 33 determines that the drive mode has changed (S200: YES), it proceeds to the processing in S210. If the control circuit 33 determines that the drive mode has not changed (S200: NO), it proceeds to the processing in S230.

[0140] In S210, the control circuit 33 performs the setting process for the target duty cycle α, setting 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 start-up period of the motor 20. During the start-up period, within a range below the target duty cycle α, the control circuit 33 gradually increases the output duty cycle. After the start-up period, the control circuit 33 performs constant rotation control. The start-up period is the period from the start time of the motor 20's drive to the arrival time. The start time of the motor 20's drive corresponds to the time when the trigger switch 12 changes from off to on. The arrival time corresponds to the time when the actual rotational speed reaches the starting rotational speed ωc. The starting rotational speed ωc is the speed at the start of constant rotation control, and is less than the target rotational speed ωt. Further details regarding the setting process of the target duty cycle α will be described later.

[0141] Next, in S220, the control circuit 33 performs the setting process of the rotation threshold ω0, setting the rotation threshold ω0 according to the drive mode. The rotation threshold ω0 is a value less than the starting rotation speed ωc. The rotation threshold ω0 is a threshold used to change the rate of increase of the output duty cycle during startup. The inertia of the electric work machine 1 varies depending on the type of front-end tool. When the inertia of the electric work machine 1 is relatively small, if the output duty cycle is continuously increased at a constant rate of increase until the actual rotation speed reaches the starting rotation speed ωc, the actual rotation speed may overshoot. When the rate of increase of the output duty cycle is suppressed, the overshoot of the actual rotation speed is suppressed. However, when the inertia of the electric work machine 1 is relatively large, when the rate of increase of the output duty cycle is suppressed, the startup period may increase. Consequently, the user experience may deteriorate.

[0142] Therefore, in this embodiment, during startup, the control circuit 33 reduces the rate of increase of the output duty cycle at the point when the actual rotational speed reaches the rotational threshold ω0. When the inertia of the electric machine 1 is relatively small, the actual rotational speed reaches the rotational threshold ω0 earlier. Therefore, the rate of increase of the output duty cycle decreases earlier, and overshoot of the actual rotational speed is suppressed. When the inertia of the electric machine 1 is relatively large, the actual rotational speed reaches the rotational threshold ω0 later. Therefore, the rate of increase of the output duty cycle decreases later, and the increase during startup is suppressed. Furthermore, the details of the rotational threshold ω0 setting process will be described later.

[0143] In S230, control circuit 33 determines whether the condition for constant rotation control is met. The condition for constant rotation control is based on the fact that the actual rotational speed has exceeded the initial rotational speed ωc. For example... Figure 7A As shown, regardless of the drive mode, the initial rotational speed ωc is set to a constant value. For example, the initial rotational speed ωc is 2500 rpm. When constant rotational control begins after the actual rotational speed reaches the target rotational speed ωt, the actual rotational speed may exceed the target rotational speed ωt. Therefore, the control circuit 33 begins constant rotational control before the actual rotational speed reaches the target rotational speed ωt.

[0144] On the other hand, high-precision actual rotation speed is required for high-precision constant rotation control. As described above, the rotational position of the rotor 21 is calculated based on the zero-crossing of the induced voltage generated by the winding 22 in a sensorless motor. The induced voltage is proportional to the actual rotational speed of the motor 20. Therefore, when the actual rotational speed of the motor 20 is low, the zero-crossing detection accuracy decreases. Consequently, the calculation accuracy of the rotor 21's rotational position decreases, and the calculation accuracy of the actual rotational speed also decreases. Therefore, it is preferable that the control circuit 33 starts constant rotation control after the actual rotational speed rises to a level where the zero-crossing detection accuracy stabilizes.

[0145] Furthermore, even when motor 20 is a sensor-equipped motor, control circuit 33 can begin constant rotation control once the actual rotational speed has risen to a level where the detection accuracy for zero crossing stabilizes. When the rotational position of rotor 21 is detected using a three-phase Hall sensor, the time interval between signals output from the Hall sensor becomes longer when the rotational speed is too low. Consequently, the frequency at which control circuit 33 calculates the actual rotational speed decreases, potentially reducing the accuracy of constant rotation control.

[0146] If the condition for constant rotation control is met (S230: YES), control circuit 33 proceeds to process S270. If the condition for constant rotation control is not met (S230: NO), control circuit 33 proceeds to process S240.

[0147] In S240, the control circuit 33 determines whether the actual rotational speed is less than the rotational threshold ω0 set in S220. If the control circuit 33 determines that the actual rotational speed is less than the rotational threshold ω0 (S240: YES), it proceeds to the process in S250. If the control circuit 33 determines that the actual rotational speed is greater than or equal to the rotational threshold ω0 (S240: NO), it proceeds to the process in S260.

[0148] In S250, control circuit 33 performs constant duty cycle control processing, increasing the output duty cycle by the first rate of increase. Constant duty cycle control is feedback-free control. Furthermore, control circuit 33 terminates this process. Details of the constant duty cycle control processing will be described later.

[0149] In S260, the control circuit 33 sets the output duty cycle to a fixed value, with the rate of increase of the output duty cycle to zero. The fixed value is the output duty cycle at the point when the actual rotational speed reaches the rotational threshold ω0, which is below the target duty cycle α. The control circuit 33 outputs a PWM signal with a fixed value to the gate circuit 34. That is, the control circuit 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 rotational speed reaches the rotational threshold ω0. Furthermore, the control circuit 33 terminates this process.

[0150] In S270, control circuit 33 performs constant rotation control, maintaining the actual rotation speed at the target rotation speed ωt. Then, control circuit 33 terminates this process. Further details of constant rotation control will be described later.

[0151] <1-2-4. Setting and processing of target duty cycle>

[0152] Reference Figure 8 The flowchart illustrates the target duty cycle α setting process performed by the control circuit 33 in the output duty cycle setting process S210.

[0153] In step S300, the control circuit 33 determines whether the drive mode has been set to reverse mode. If the control circuit 33 determines that the drive mode has been set to reverse mode (S300: YES), it proceeds to step S310. If the control circuit 33 determines that the drive mode has not been set to reverse mode (S300: NO), it proceeds to step S320.

[0154] In S310, the control circuit 33 sets the first target value corresponding to the inversion mode as the target duty cycle α. For example... Figure 7B As shown, the target duty cycle α is set according to the drive mode. The first target value is, for example, 20%. Furthermore, the control circuit 33 terminates this process.

[0155] In S320, the control circuit 33 determines whether the drive mode has been set to high-speed mode. If the control circuit 33 determines that it has been set to high-speed mode (S320: YES), it proceeds to the process in S330. If the control circuit 33 determines that it has not been set to high-speed mode (S320: NO), it proceeds to the process in S340.

[0156] In step S330, control circuit 33 sets the second target value corresponding to the high-speed mode as the target duty cycle α and ends the process. 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 can be suppressed. Therefore, control circuit 33 sets a value larger than the target duty cycle α in reverse mode and low-speed mode as the target duty cycle α in high-speed mode.

[0157] In step S340, control circuit 33 sets the third target value corresponding to the low-speed mode as the target duty cycle α and ends the process. The third target value is, for example, 25%. The third target value is less than the second target value and greater than the first target value.

[0158] <1-2-5. Rotation Threshold Setting Process>

[0159] Reference Figure 9 The flowchart illustrates the setting process of the rotation threshold ω0 performed by the control circuit 33 in the output duty cycle setting process S220.

[0160] In step S400, control circuit 33 determines whether the drive mode has been set to reverse mode. If control circuit 33 determines that it has been set to reverse mode (S400: YES), it proceeds to step S410. If control circuit 33 determines that it has not been set to reverse mode (S400: NO), it proceeds to step S420.

[0161] In S410, the control circuit 33 sets the first threshold corresponding to the reversal mode as the rotation threshold ω0. For example... Figure 7A As shown, the rotation threshold ω0 is set according to the driving mode. The first threshold is, for example, 600 / min.

[0162] In S420, the control circuit 33 determines whether the drive mode has been set to high-speed mode. If the control circuit 33 determines that it has been set to high-speed mode (S420: YES), it proceeds to the process in S430. If the control circuit 33 determines that it has not been set to high-speed mode (S420: NO), it proceeds to the process in S440.

[0163] In step S430, the control circuit 33 sets the second threshold corresponding to the high-speed mode as the rotation threshold ω0 and ends the process. The second threshold is, for example, 2000 / min. When the target rotation speed ωt is large, even if the rotation threshold ω0 is increased, the overshoot of the actual rotation speed can be suppressed. Therefore, the control circuit 33 sets a value larger than the rotation threshold ω0 in the reverse mode and the low-speed mode as the rotation threshold ω0 in the high-speed mode.

[0164] In step S440, the control circuit 33 sets the third threshold corresponding to the low-speed mode as the rotation threshold ω0 and ends the process. The third threshold is, for example, 1000 / min. The third threshold is less than the second threshold and greater than the first threshold. In this embodiment, the rotation threshold ω0 is set to one-fifth of the target rotation speed ωt in all drive modes. That is, the ratio of the rotation threshold ω0 to the target rotation speed ωt is equal in all drive modes. In other embodiments, the ratio of the rotation threshold ω0 to the target rotation speed ωt may differ depending on the drive mode.

[0165] <1-2-6. Constant Duty Cycle Control Process>

[0166] Reference Figure 10 The flowchart illustrates the constant duty cycle control process performed by control circuit 33 in S250 of the output duty cycle setting process.

[0167] In S500, the control circuit 33 determines whether it is before outputting a PWM signal with an output duty cycle. If the control circuit 33 determines that it is before outputting a PWM signal (S500: YES), it proceeds to the process in S510. If the control circuit 33 determines that it is after outputting a PWM signal (S500: NO), it proceeds to the process in S550.

[0168] In S510, the control circuit 33 determines whether the set drive mode has changed from the drive mode in the previous processing cycle. If the control circuit 33 determines that the drive mode has changed (S510: YES), it proceeds to the processing in S520. If the control circuit 33 determines that the drive mode has not changed (S510: NO), it proceeds to the processing in S530.

[0169] In S520, control circuit 33 performs initial duty cycle setting processing, setting the initial duty cycle β as the initial value of the output duty cycle. Then, control circuit 33 proceeds to processing in S530. Details of the initial duty cycle setting processing will be described later.

[0170] In S530, control circuit 33 determines whether the output condition of the PWM signal is met. If drive permission is set, control circuit 33 determines that the output condition is met (S530: YES) and proceeds to process S540. If drive permission is not set, control circuit 33 determines that the output condition is not met (S530: NO) and ends this process.

[0171] In S540, the control circuit 33 begins to output a PWM signal with the set output duty cycle to the gate circuit 34. Furthermore, the control circuit 33 terminates this process.

[0172] In S550, control circuit 33 determines whether the set output duty cycle is less than the target duty cycle α. If control circuit 33 determines that the output duty cycle is less than the target duty cycle α (S550: YES), it proceeds to process S560. If control circuit 33 determines that the output duty cycle is greater than or equal to the target duty cycle α (S550: NO), it terminates this process.

[0173] In S560, the control circuit 33 increases the output duty cycle, ending the process. For example, the control circuit 33 updates the output duty cycle by adding a preset constant increment value to the output duty cycle. The increment value is positive. Accordingly, the output duty cycle gradually increases at a first rate of increase. Furthermore, the magnitude of the applied voltage to the motor 20 gradually increases at a first rate of increase.

[0174] <1-2-7. Constant Rotation Control Process>

[0175] Reference Figure 11 The flowchart illustrates the constant rotation control process performed by the control circuit 33 in the output duty cycle setting process S270.

[0176] In S600, the control circuit 33 performs a target rotation speed setting process, setting the target rotation speed ωt in constant rotation control. In constant rotation control, the control circuit 33 maintains the actual rotation speed at the target rotation speed ωt. Further details of the target rotation speed setting process will be described later.

[0177] Next, in S610, the control circuit 33 determines whether the set target rotational speed ωt is greater than the actual rotational speed calculated in S100. If the control circuit 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 the control circuit 33 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.

[0178] In S620, the control circuit 33 increases the output duty cycle to increase the actual rotational speed in order to make the actual rotational speed closer to the target rotational speed ωt. For example, the control circuit 33 updates the output duty cycle by adding a constant increment to the output duty cycle. The increment in S620 can be the same as or different from the increment in S560. Then, the control circuit 33 terminates this process.

[0179] In S630, control circuit 33 determines whether the actual rotational speed is greater than the target rotational speed ωt. If control circuit 33 determines that the actual rotational speed is greater than the target rotational speed ωt (S630: YES), it proceeds to process S640. If control circuit 33 determines that the actual rotational speed is equal to the target rotational speed ωt (S630: NO), it terminates this process.

[0180] In S640, the control circuit 33 reduces the actual rotational speed by decreasing the output duty cycle in order to make the actual rotational speed closer to the target rotational speed ωt. For example, the control circuit 33 updates the output duty cycle by subtracting a preset constant subtraction value from the output duty cycle. The subtraction value is positive. Furthermore, the control circuit 33 terminates this process.

[0181] <1-2-8. Initial Duty Cycle Setting Processing>

[0182] Reference Figure 12 The flowchart illustrates the initial duty cycle β setting process performed by control circuit 33 in S520 of constant duty cycle setting process.

[0183] In S700, the control circuit 33 determines whether the drive mode has been set to reverse mode. If the control circuit 33 determines that the reverse mode has been set (S700: YES), it proceeds to the process in S710. If the control circuit 33 determines that the reverse mode has not been set (S700: NO), it proceeds to the process in S720.

[0184] In S710, control circuit 33 sets the first initial value corresponding to the inversion mode to the initial duty cycle β, and ends the process. For example... Figure 7B As shown, the initial duty cycle β is set according to the drive mode. The first initial value is, for example, 3%. When the initial duty cycle β is set to 0%, the time required until the motor 20 starts rotating will increase. Therefore, the control circuit 33 sets the initial duty cycle β to a value greater than 0%.

[0185] In S720, the control circuit 33 determines whether the drive mode has been set to high-speed mode. If the control circuit 33 determines that it has been set to high-speed mode (S720: YES), it proceeds to the process in S730. If the control circuit 33 determines that it has not been set to high-speed mode (S720: NO), it proceeds to the process in S740.

[0186] In S730, the control circuit 33 sets the second initial value corresponding to the high-speed mode as the initial duty cycle β and ends the process. The second initial value is, for example, 10%. When the target rotational speed ωt is large, even if the initial duty cycle β is increased, the overshoot of the actual rotational speed can be suppressed. Therefore, the control circuit 33 sets the initial duty cycle β in the high-speed mode to a value larger than that in the reverse mode and the low-speed mode.

[0187] In S740, control circuit 33 sets the third initial value corresponding to the low-speed mode as the initial duty cycle β, and ends the process. The third initial value is, for example, 5%. The third initial value is less than the second initial value and greater than the first initial value.

[0188] <1-2-9. Setting and processing of target rotation speed>

[0189] Reference Figure 13 The flowchart illustrates the target rotation speed setting process performed by the control circuit 33 in the constant rotation speed processing S600.

[0190] In S800, the control circuit 33 determines whether the drive mode has been set to reverse mode. If the control circuit 33 determines that the reverse mode has been set (S800: YES), it proceeds to the process in S810. If the control circuit 33 determines that the reverse mode has not been set (S800: NO), it proceeds to the process in S820.

[0191] In S810, the control circuit 33 sets the first target speed corresponding to the reversal mode to the target rotation speed ωt, and ends the process. For example... Figure 7A As shown, the target rotation speed ωt is set according to the drive mode. The first target speed is, for example, 3000 / min.

[0192] In S820, the control circuit 33 determines whether the drive mode has been set to high-speed mode. If the control circuit 33 determines that it has been set to high-speed mode (S820: YES), it proceeds to the process in S830. If the control circuit 33 determines that it has not been set to high-speed mode (S820: NO), it proceeds to the process in S840.

[0193] In S830, the control circuit 33 sets the second target speed corresponding to the high-speed mode to the target rotation speed ωt, and ends the process. The second target speed is, for example, 10000 / min.

[0194] In S840, control circuit 33 sets the third target speed corresponding to the low-speed mode as the target rotational speed ωt and ends the process. The third target speed is, for example, 5000 / min. The third target speed is less than the second target speed but greater than the first target speed.

[0195] <1-3. Actions>

[0196] Figure 14 The following is shown: the actual rotational speed and output duty cycle of the electric work machine 1 with low inertia and high inertia, respectively, as a function of the output duty cycle setting process according to the first embodiment, are shown. The electric work machines 1 with low inertia and high inertia are set with the same drive mode. Hereinafter, the electric work machine 1 with low inertia will be referred to as the first electric work machine 1, and the electric work machine 1 with high inertia will be referred to as the second electric work machine 1.

[0197] The output duty cycle of the first electric work machine 1 increases at a first rate of increase. Furthermore, at time point t1, the actual rotational speed of the first electric work machine 1 reaches the rotation threshold ω0, and the output duty cycle of the first electric work machine 1 is fixed at the value at time point t1. Additionally, at time point t2, the actual rotational speed of the first electric work machine 1 reaches the starting rotational speed ωc, and constant rotation control of the first electric work machine 1 begins. Because the output duty cycle of the first electric work machine 1 is fixed at the value at time point t1, the rate of increase of the actual rotational speed of the first electric work machine 1 during the period from time point t1 to t2 decreases. Moreover, after time point t2, the actual rotational speed of the first electric work machine 1 does not exceed the target rotational speed ωt and is maintained at the target rotational speed ωt.

[0198] After increasing at the first rate of increase, the output duty cycle of the second electric machine 1 becomes constant at the target duty cycle α. Furthermore, at time point t3, the actual rotational speed of the second electric machine 1 reaches the rotation threshold ω0, and the output duty cycle of the second electric machine 1 is fixed at the value at time point t3, i.e., the target duty cycle α. Additionally, at time point t4, the actual rotational speed of the second electric machine 1 reaches the starting rotational speed ωc, and constant rotational control of the second electric machine 1 begins. After time point t4, the actual rotational speed of the second electric machine 1 does not exceed the target rotational speed ωt and is maintained at the target rotational speed ωt.

[0199] Even for either the first or second electric working machine 1, overshoot in actual rotational speed can be suppressed. Furthermore, the difference t4-t2 between the start-up periods of the first and second electric working machines 1 is small. That is, deviations in the start-up period due to differences in inertia are also suppressed.

[0200] Figure 15The following diagram shows the changes in the actual rotational speed and output duty cycle over time for the electric work machine with low inertia and the electric work machine with high inertia involved in the first reference example. Hereinafter, the electric work machine with low inertia involved in the first reference example will be referred to as the third electric work machine, and the electric work machine with high inertia involved in the first reference example will be referred to as the fourth electric work machine. The third and fourth electric work machines are configured with the same drive mode. In the first reference example, the output duty cycle of the third and fourth electric work machines increases at a first rate of increase until the actual rotational speed of the third and fourth electric work machines reaches the initial rotational speed ωc.

[0201] The output duty cycle of the third electric work machine increases at the first rate of increase. Furthermore, at time point t11, the actual rotational speed of the third electric work machine reaches the initial rotational speed ωc, and constant rotation control of the third electric work machine begins. After time point t11, the actual rotational speed of the third electric work machine is temporarily greater than the target rotational speed ωt, and thereafter is maintained at the target rotational speed ωt.

[0202] The output duty cycle of the fourth electric work machine increases at the first rate of increase. Furthermore, at time point t12, the actual rotational speed of the fourth electric work machine reaches the initial rotational speed ωc, and constant rotation control of the fourth electric work machine begins. After time point t12, the actual rotational speed of the fourth electric work machine does not exceed the target rotational speed ωt and is maintained at the target rotational speed ωt.

[0203] In the first reference example, the difference t12-t11 between the start-up period of the third electric work machine and the start-up period of the fourth electric work machine is relatively large. That is, in the first reference example, compared with this embodiment, the deviation in start-up period due to the difference in inertia is increased. In the first reference example, the rate of increase of the output duty cycle of the third electric work machine is not reduced before the actual rotational speed of the third electric work machine reaches the starting rotational speed ωc. As a result, the third electric work machine can accelerate earlier than the first electric work machine 1 according to this embodiment because the difference in start-up time due to the difference in inertia is larger. In addition, the actual rotational speed of the third electric work machine exhibits overshoot.

[0204] Figure 16The following diagram illustrates the time-varying actual rotational speed and output duty cycle of the electric work machine with low inertia and the electric work machine with high inertia involved in the second reference example. Hereinafter, the electric work machine with low inertia involved in the second reference example will be referred to as the fifth electric work machine, and the electric work machine with high inertia involved in the second reference example will be referred to as the sixth electric work machine. The fifth and sixth electric work machines are configured with the same drive mode. In the second reference example, until the actual rotational speed of the fifth and sixth electric work machines reaches the initial rotational speed ωc, the output duty cycle of the fifth and sixth electric work machines increases at a second rate of increase. The second rate of increase is less than the first rate of increase.

[0205] The output duty cycle of the fifth electric work machine increases at the second rate of increase. Furthermore, at time point t21, the actual rotational speed of the fifth electric work machine reaches the rotational threshold ω0, and the output duty cycle of the fifth electric work machine continues to increase at the second rate of increase. Additionally, at time point t23, the actual rotational speed of the fifth electric work machine reaches the initial rotational speed ωc, and constant rotational control of the fifth electric work machine begins. After time point t23, the actual rotational speed of the fifth electric work machine does not exceed the target rotational speed ωt and remains at the target rotational speed ωt.

[0206] The output duty cycle of the sixth electric work machine increases at the second rate of increase. Furthermore, at time point t22, the actual rotational speed of the sixth electric work machine reaches the rotational threshold ω0, and the output duty cycle of the sixth electric work machine continues to increase at the second rate of increase. Additionally, at time point t24, the actual rotational speed of the sixth electric work machine reaches the initial rotational speed ωc, and constant rotational control of the sixth electric work machine begins. After time point t24, the actual rotational speed of the sixth electric work machine does not exceed the target rotational speed ωt and remains at the target rotational speed ωt.

[0207] In the second reference example, even in the case of either the fifth or sixth electric workpiece, overshoot of the actual rotational speed can be suppressed. However, the start-up period of the fifth and sixth electric workpieces becomes longer. Therefore, the user experience may deteriorate.

[0208] <1-4. Effects>

[0209] According to the first embodiment described in detail above, the following effects can be achieved.

[0210] (1) When the actual rotational speed has reached the rotational threshold ω0, the rate of increase of the output duty cycle is set to zero. When the inertia of the electric machine 1 is relatively small, a relatively small fixed value is set for the output duty cycle, and the overshoot of the actual rotational speed is suppressed. When the inertia of the electric machine 1 is relatively large, a relatively large fixed value is set for the output duty cycle, and therefore, the increase during startup is suppressed. Therefore, it is possible to suppress the deviation during startup caused by the difference in inertia of the electric machine 1, and at the same time, it is also possible to suppress the overshoot of the actual rotational speed.

[0211] (2) Before constant rotation control begins, the output duty cycle is controlled below the target duty cycle α. This helps to suppress the sharp increase in actual rotational speed during startup.

[0212] (3) The control circuit 33 starts constant rotation control before the actual rotation speed reaches the target rotation speed ωt. Accordingly, it can suppress the overshoot of the actual rotation speed.

[0213] (4) By changing the rotation threshold ω0 according to whether the driving mode is high speed mode or low speed mode, the deviation during startup caused by the difference in driving mode can be suppressed, and the overshoot of the actual rotation speed can also be suppressed.

[0214] (5) By changing the target duty cycle α according to whether the drive mode is high speed mode or low speed mode, the deviation during startup caused by the difference in drive mode can be suppressed, and the overshoot of the actual rotation speed can also be suppressed.

[0215] (6) By changing the rotation threshold ω0 according to the rotation direction of the motor 20, the deviation during startup caused by the difference in rotation direction can be suppressed, and the overshoot of the actual rotation speed can also be suppressed.

[0216] (7) By changing the target duty cycle α according to the rotation direction of the motor 20, the deviation during startup caused by the difference in rotation direction can be suppressed, and the overshoot of the actual rotation speed can also be suppressed.

[0217] (2. Second implementation method)

[0218] <2-1. Differences from the first embodiment>

[0219] Since the basic structure of the second embodiment is the same as that of the first embodiment, only the differences will be described below. Furthermore, the same reference numerals as in the first embodiment indicate the same structure; therefore, please refer to the preceding description.

[0220] In the first embodiment described above, the control circuit 33 fixes the output duty cycle when the actual rotational speed during startup is above the rotational threshold ω0. The difference between the second and first embodiments is that, when the actual rotational speed during startup is above the rotational threshold ω0, the control circuit 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.

[0221] <2-2. Output Duty Cycle Setting Processing>

[0222] Reference Figure 17 The flowchart illustrates the output duty cycle setting process performed by the control circuit 33 in S130 of the motor control process.

[0223] In S900 to S940, the control circuit 33 performs the same processing as in S200 to S240.

[0224] If, in S940, the control circuit 33 determines that the actual rotational speed is less than the rotational threshold ω0 (S940: YES), it proceeds to process S950. In S950, the control circuit 33 sets a first increment value as the increment value in the constant duty cycle control process S560. The first increment value is equal to the increment value in S560 of the first embodiment and corresponds to the first rate of increase. After processing in S950, the control circuit 33 proceeds to process S970.

[0225] If, in S940, the control circuit 33 determines that the actual rotational speed is above the rotational threshold ω0 (S940: NO), it proceeds to process S960. In S960, the control circuit 33 sets a second increment value as the increment value in the constant duty cycle control process of S560. The second increment value is less than the first increment value, corresponding to the second rate of increase. After processing in S960, the control circuit 33 proceeds to processing in S970.

[0226] In S970, the control circuit 33 performs the constant duty cycle control processes of S500 to S560, and ends the current process.

[0227] If the condition for constant rotation control is met in S930 (S930: YES), the control circuit 33 proceeds to the process in S980. In S980, the control circuit 33 performs the same process as in S270 and ends the current process.

[0228] <2-3. Actions>

[0229] Figure 18The following is shown: the actual rotational speed and output duty cycle of the first and second electric work machines 1 over time when the output duty cycle setting process according to the second embodiment is performed. The first and second electric work machines 1 are set with the same drive mode.

[0230] The output duty cycle of the first electric work machine 1 increases at a first rate of increase. Furthermore, at time point t31, the actual rotational speed of the first electric work machine 1 reaches the rotational threshold ω0, and the rate of increase of the output duty cycle of the first electric work machine 1 changes from the first rate of increase to the second rate of increase. Additionally, at time point t32, the actual rotational speed of the first electric work machine 1 reaches the starting rotational speed ωc, and constant rotational control of the first electric work machine 1 begins. After time point t32, the actual rotational speed of the first electric work machine 1 is temporarily greater than the target rotational speed ωt, and thereafter is maintained at the target rotational speed ωt.

[0231] After the output duty cycle of the second electric work machine 1 increases at the first rate of increase, it becomes a constant target duty cycle α. Furthermore, at time point t33, the actual rotational speed of the second electric work machine 1 reaches the rotation threshold ω0, and the output duty cycle of the second electric work machine 1 remains fixed at the target duty cycle α. Additionally, at time point t34, the actual rotational speed of the second electric work machine 1 reaches the starting rotational speed ωc, and constant rotational control of the second electric work machine 1 begins. After time point t34, the actual rotational speed of the second electric work machine 1 does not exceed the target rotational speed ωt and is maintained at the target rotational speed ωt.

[0232] According to the first electric machine 1, after the actual rotational speed has reached the rotational threshold ω0, the overshoot of the actual rotational speed is suppressed because the rate of increase of the output duty cycle decreases. Compared with the first reference example mentioned above, the overshoot of the actual rotational speed can be suppressed. In addition, the difference t34-t32 between the start-up period of the first electric machine 1 and the start-up period of the second electric machine 1 is smaller. That is, the deviation during the start-up period due to the difference in inertia is also suppressed.

[0233] <2-3. Effects>

[0234] According to the second embodiment described in detail above, the effects of the first embodiment (2) to (7) described above can be achieved, and in addition, the following effects can also be achieved.

[0235] (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 machine 1 is relatively small, the rate of increase of the output duty cycle is reduced earlier, thus suppressing the overshoot of the actual rotational speed. When the inertia of the electric machine 1 is relatively large, the rate of increase of the output duty cycle is reduced later, thus suppressing the increase during startup. Therefore, it is possible to suppress the deviation during startup caused by the difference in inertia of the electric machine 1, and at the same time, it is possible to suppress the overshoot of the actual rotational speed.

[0236] (3. Third implementation method)

[0237] <3-1. Differences from the first embodiment>

[0238] Since the basic structure of the third embodiment is the same as that of the first embodiment, only the differences will be described below. Furthermore, the same reference numerals as in the first embodiment indicate the same structure; therefore, please refer to the preceding description.

[0239] In the first embodiment described above, when the actual rotational speed during startup is above the rotational threshold ω0, the control circuit 33 sets a fixed value as the output duty cycle regardless of the drive mode. In contrast, in the third embodiment, when the actual rotational speed during startup is above the rotational threshold ω0, the control circuit 33 sets a fixed duty cycle γ corresponding to the drive mode as the output duty cycle. This differs from the first embodiment. The fixed duty cycle γ is a fixed value or less. Therefore, in the third embodiment, the output duty cycle may be discontinuous before and after the actual rotational speed reaches the rotational threshold ω0.

[0240] <3-2. Treatment>

[0241] <3-2-1. Output Duty Cycle Setting Processing>

[0242] Reference Figure 19 The flowchart illustrates the output duty cycle setting process performed by the control circuit 33 in S130 of the motor control process.

[0243] In S1000 to S1020, the control circuit 33 performs the same processing as in S200 to S220.

[0244] Next, in S1030, the control circuit 33 performs a fixed duty cycle γ setting process to set the fixed duty cycle γ. Details of the fixed duty cycle γ setting process will be described later.

[0245] Next, in S1040 to S1060, control circuit 33 performs the same process as in S230 to S250.

[0246] If the control circuit 33 determines in S1050 that the actual rotational speed is above the rotational threshold ω0 (S1050: NO), it proceeds to process S1070. In S1070, the control circuit 33 outputs a PWM signal with a fixed duty cycle γ set in S1030 to the gate circuit 34, ending this process. That is, the control circuit 33 fixes the magnitude of the voltage applied to the winding 22 to be below the value of the applied voltage at the time when the actual rotational speed reaches the rotational threshold ω0.

[0247] If the condition for constant rotation control is met in S1040 (S1040: YES), the control circuit 33 proceeds to the process in S1080. In S1080, the control circuit 33 performs the same process as in S270 and ends the current process.

[0248] <3-2-2. Fixed Duty Cycle Setting Process>

[0249] Reference Figure 20 The flowchart illustrates the fixed duty cycle γ setting process performed by the control circuit 33 in the output duty cycle setting process S1030.

[0250] In S1100, the control circuit 33 determines whether the drive mode has been set to reverse mode. If the control circuit 33 determines that the reverse mode has been set (S1100: YES), it proceeds to the process in S1110. If the control circuit 33 determines that the reverse mode has not been set (S1100: NO), it proceeds to the process in S1120.

[0251] In S1110, the control circuit 33 sets the first fixed value corresponding to the inversion mode to a fixed duty cycle γ, and ends the process. For example... Figure 7B As shown, the fixed duty cycle γ is set according to the drive mode. The first fixed value is, for example, 6%.

[0252] In S1120, the control circuit 33 determines whether the drive mode has been set to high-speed mode. If the control circuit 33 determines that the high-speed mode has been set (S1120: YES), it proceeds to the process in S1130. If the control circuit 33 determines that the high-speed mode has not been set (S1120: NO), it proceeds to the process in S1140.

[0253] In S1130, the control circuit 33 sets the second fixed value corresponding to the high-speed mode to a fixed duty cycle γ, and ends the process. The second fixed value is, for example, 20%. The rotation threshold ω0 in the high-speed mode is set to a value larger than the rotation threshold ω0 in the reverse mode and the low-speed mode. Therefore, the control circuit 33 sets a value larger than the fixed duty cycle γ in the reverse mode and the low-speed mode as the fixed duty cycle γ in the high-speed mode.

[0254] In S1140, the control circuit 33 sets the third fixed value corresponding to the low-speed mode to a fixed duty cycle γ, and ends the process. The third fixed value is, for example, 10%. The third fixed value is less than the second fixed value and greater than the first fixed value.

[0255] <3-3. Actions>

[0256] Figure 21 The following is shown: the actual rotational speed and output duty cycle of the first and second electric work machines 1 over time when the output duty cycle setting process according to the third embodiment is performed. The first and second electric work machines 1 are set with the same drive mode.

[0257] The output duty cycle of the first electric work machine 1 increases at a first rate of increase. Furthermore, at time point t41, the actual rotational speed of the first electric work machine 1 reaches the rotational threshold ω0, and the fixed duty cycle γ is set as the output duty cycle of the first electric work machine 1. Additionally, at time point t42, the actual rotational speed of the first electric work machine 1 reaches the starting rotational speed ωc, and constant rotational control of the first electric work machine 1 begins. After time point t42, the actual rotational speed of the first electric work machine 1 does not exceed the target rotational speed ωt and is maintained at the target rotational speed ωt.

[0258] After the output duty cycle of the second electric machine 1 increases at the first rate of increase, it becomes a constant target duty cycle α. Furthermore, at time point t43, the actual rotational speed of the second electric machine 1 reaches the rotation threshold ω0, and the output duty cycle of the second electric machine 1 is fixed at a fixed duty cycle γ, which is smaller than the target duty cycle α. Additionally, at time point t44, the actual rotational speed of the second electric machine 1 reaches the starting rotational speed ωc, and constant rotational control of the second electric machine 1 begins. After time point t44, the actual rotational speed of the second electric machine 1 does not exceed the target rotational speed ωt and is maintained at the target rotational speed ωt.

[0259] In this embodiment, at the point when the actual rotational speed reaches the rotational threshold ω0, a fixed duty cycle γ, independent of inertia differences, is set as the output duty cycle. Therefore, the difference t44-t42 between the start-up period of the first electric machine 1 and the second electric machine 1 is slightly larger than in the first embodiment. Consequently, the deviation in the start-up period due to inertia differences is greater than in the first embodiment. However, compared to the second reference example described above, the start-up period is shortened. Furthermore, even in the case of either the first electric machine 1 or the second electric machine 1, overshoot of the actual rotational speed can be suppressed.

[0260] <3-4. Effects>

[0261] According to the third embodiment described in detail above, the effects of the first embodiment (2) to (7) can be achieved, and the following effects can also be achieved.

[0262] (9) When the actual rotational speed reaches the rotational threshold ω0, the fixed duty cycle γ is set as the output duty cycle. When the inertia of the electric machine 1 is relatively small, the output duty cycle is fixed to γ ​​earlier, and the overshoot of the actual rotational speed is suppressed. When the inertia of the electric machine 1 is relatively large, the output duty cycle is fixed to γ ​​later, and therefore, the increase during startup is suppressed. Therefore, it is possible to suppress the deviation during startup caused by the difference in inertia of the electric machine 1, and at the same time, it is also possible to suppress the overshoot of the actual rotational speed.

[0263] (4. Other implementation methods)

[0264] The above describes the embodiments of the present invention, but the present invention is not limited to the embodiments described above and can be implemented in various ways.

[0265] (a) In the above embodiment, although the electric work machine 1 does not have a position sensor for detecting the position of the rotor 21, the electric work machine 1 may also have a position sensor for detecting the position of the rotor 21. The control circuit 33 may also calculate the actual rotational speed of the motor 20 based on the position signal detected by the position sensor.

[0266] (b) In the above embodiments, the controller 30 has a control circuit 33, but the controller 30 may replace the control circuit 33, or have a combination of various separate electronic devices in addition to the control circuit 33. It may have an Application Specified Integrated Circuit (ASIC), or an Application Specific Standard Product (ASSP), such as a programmable logic device such as an FPGA (Field Programmable Gate Array), or a combination thereof.

Claims

1. An electric work machine, characterized in that, The electric work machine has the following features: A motor, configured to generate driving force for rotating a front-end tool; A drive switch configured to be operated by a user to drive the motor; and The control unit is configured to increase the applied voltage to the motor when the drive switch is turned on, suppress the increase of the applied voltage when the actual rotational speed of the motor has reached a set rotational threshold, and start constant rotational control of the motor before the actual rotational speed reaches the target rotational speed, thereby maintaining the actual rotational speed at the target rotational speed. The target rotation speed is greater than the rotation threshold.

2. The electric work machine according to claim 1, characterized in that, The control unit is configured to: increase the applied voltage at a first rate of increase based on the fact that the drive switch has been turned on; and replace the first rate of increase with a second rate of increase based on the fact that the actual rotational speed has reached the rotational threshold. The second rate of increase is less than the first rate of increase.

3. The electric work machine according to claim 1, characterized in that, The control unit is configured to: increase the applied voltage at a predetermined rate of increase based on the fact that the drive switch has been turned on; and fix the applied voltage at a predetermined value based on the fact that the actual rotational speed has reached the rotational threshold. The specified value is below the magnitude of the applied voltage at the time point when the actual rotation speed has reached the rotation threshold.

4. The electric work machine according to claim 2, characterized in that, The second rate of increase is zero. The control unit is configured to fix the applied voltage to a predetermined value during the period from when the actual rotational speed reaches the rotational threshold until the constant rotational control begins. The specified value is the magnitude of the applied voltage at the time point when the actual rotation speed has reached the rotation threshold.

5. The electric work machine according to any one of claims 1 to 4, characterized in that, The electric work machine also includes a drive circuit configured to drive the motor. The control unit is configured to change the magnitude of the applied voltage based on the output duty cycle of the pulse width modulation signal output to the drive circuit, and to control the output duty cycle to be below a set target duty cycle during the period from when the drive switch is turned on until the constant rotation control begins.

6. The electric work machine according to any one of claims 1 to 5, characterized in that, The control unit is configured to initiate constant rotation control based on the fact that the actual rotation speed has reached the starting rotation speed. The initial rotation speed is greater than the rotation threshold but less than the target rotation speed.

7. The electric work machine according to any one of claims 1 to 6, characterized in that, The motor's drive modes include mode 1 and mode 2. The electric work machine also includes a selection switch configured to be operated by the user to select the first mode or the second mode. The control unit is configured to: set a first threshold as the rotation threshold based on selecting the first mode by means of the selection switch, and set a second threshold, which is different from the first threshold, as the rotation threshold based on selecting the second mode by means of the selection switch.

8. The electric work machine according to claim 5, characterized in that, The motor's drive modes include mode 1 and mode 2. The electric work machine also includes a selection switch configured to be operated by the user to select the first mode or the second mode. The control unit is configured to: set a first duty cycle as the target duty cycle based on selecting the first mode by means of the selection switch, and set a second duty cycle, which is different from the first duty cycle, as the target duty cycle based on selecting the second mode by means of the selection switch.

9. The electric work machine according to any one of claims 1 to 8, characterized in that, The control unit is configured to: set a third threshold as the rotation threshold based on the motor rotating in the positive direction, and set a fourth threshold, which is different from the third threshold, as the rotation threshold based on the motor rotating in the opposite direction to the positive direction.

10. The electric work machine according to claim 5 or 8, characterized in that, The control unit is configured to set a third duty cycle as the target duty cycle based on the motor rotating in the positive direction, and to set a fourth duty cycle, which is different from the third duty cycle, as the target duty cycle based on the motor rotating in the opposite direction to the positive direction.

11. A method for controlling the motor of an electric work machine, characterized in that, Since the drive switch of the electric work machine has been turned on, the applied voltage to the motor increases. Based on the fact that the actual rotational speed of the motor has reached the set rotational threshold, the increase in the applied voltage is suppressed. Before the actual rotational speed reaches the target rotational speed which is greater than the rotational threshold, constant rotational control of the motor is initiated, thereby maintaining the actual rotational speed at the target rotational speed.

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