Work machine

Abstract

Provided is a work machine capable of controlling a connection switching unit at an appropriate timing. A computing unit 50 is capable of performing connection switching control for switching the coil connection scheme of a motor 340 from a delta connection to a star connection. The computing unit 50 is configured to start the connection switching control in a state where the motor rotational speed is higher than the idling rotational speed (star connection idling rotational speed) of the motor 340 during the star connection, and complete the same while the motor rotational speed is equal to or lower than the star connection idling rotational speed. The computing unit 50 is configured so as to, when an inverter circuit 64 is in a drive stop state during the connection switching control, switch from a state in which a delta connection relay element 32 is ON and a star connection relay element 33 is OFF to a state in which both the delta connection relay element 32 and the star connection relay element 33 are OFF (connection terminated state), and switch from the connection terminated state to a state in which the delta connection relay element 32 is OFF and the star connection relay element 33 is ON.

Description

Work equipment

[0001] The present invention relates to a work machine.

[0002] 2. Description of the Related Art There is known a technology (motor connection switching technology) that enables driving suited to a task by changing the connection method of the motor coils.

[0003] Patent Document 1 describes an electric power tool as a work machine in which the wiring method of the motor coil can be switched depending on the type of power source (power source voltage) to be connected.

[0004] Patent Document 2 describes an electric power tool as a work machine in which the motor windings are star-connected (Y-connected) and the number of series or parallel connections of the coils in the star connection can be changed depending on the workload applied to the motor. It also describes that when switching the winding connections, a period is set during which the connection changes are repeated, thereby suppressing sudden changes in torque and rotation speed.

[0005] Patent Document 3 describes a motor control for an automobile that can switch between star connection and delta connection.

[0006] JP 2017-121158 A JP 2013-111734 A JP 5-003694 A

[0007] The present inventors have recognized that there are the following issues to be resolved when introducing motor connection switching technology into a work machine. Issue 1: To provide a work machine that has a high working speed while using motor connection switching technology. Issue 2: To provide a work machine that has high reliability against failures while using motor connection switching technology. Issue 3: To provide a work machine that has high durability against overloads while using motor connection switching technology. Issue 4: To provide a work machine that can apply an electric brake to the motor while using motor connection switching technology.

[0008] The present invention aims to solve at least one of the above problems 1 to 4.

[0009] One aspect of the present invention is a work machine including a motor having multiple windings, a drive unit that drives the motor, a connection switching unit configured to switch between a high rotation speed connection state in which the multiple windings are connected to each other to provide high rotation speed characteristics and a high torque connection state in which the multiple windings are connected to each other to provide high torque characteristics, an operation unit that operates to start and stop the motor, and a control unit that controls the drive unit and the connection switching unit, wherein the control unit is capable of executing connection switching control to switch from the high rotation speed connection state to the high torque connection state, and is configured to start the connection switching control when the motor rotation speed is higher than the no-load rotation speed of the high torque connection state.

[0010] Another aspect of the present invention is a work machine including a motor having a plurality of windings, a drive unit that drives the motor, a connection switching unit configured to switch between a high rotation speed connection state in which the plurality of windings are connected to each other to achieve high rotation speed characteristics and a high torque connection state in which the plurality of windings are connected to each other to achieve high torque characteristics, an operation unit that operates to start and stop the motor, and a control unit that controls the drive unit and the connection switching unit, wherein the control unit is capable of executing connection switching control to switch from the one connection state to the other connection state, and is configured to switch the drive unit to a drive-stop state in which supply of drive power to the motor is stopped, and to switch the connection switching unit from the one connection state to a connection-disconnected state in which the plurality of windings are disconnected from each other.

[0011] Another aspect of the present invention is a work machine including a motor having a rotor and a stator with a plurality of windings, a connection switching unit capable of switching a connection type of the plurality of windings between a first connection type for high rotation and a second connection type for high torque, a drive unit having a plurality of switching elements for driving the motor, and a control unit for controlling the drive unit and the connection switching unit, wherein the control unit is configured to execute connection switching control in a first mode for switching the connection type from the first connection type to the second connection type in response to an increase in workload on the motor, and to execute overload protection control for stopping the motor when the workload satisfies an overload protection condition only after the connection switching control, but not before the connection switching control.

[0012] Another aspect of the present invention is a work machine including a motor having a rotor and a stator with a plurality of windings, a connection switching unit capable of switching a connection type of the plurality of windings between a first connection type for high rotation and a second connection type for high torque, a drive unit having a plurality of switching elements for driving the motor, a control unit for controlling the drive unit and the connection switching unit, and a mode selection unit operable by an operator, wherein the control unit is configured to select, in response to operation of the mode selection unit by an operator, either a first mode in which connection switching control is configured to switch the wiring type from the first connection type to the second connection type in response to an increase in workload on the motor, or a second mode in which the wiring type is maintained at the second wiring type.

[0013] Another aspect of the present invention is a work machine including: a motor having multiple windings driven by power supplied from a power source; a connection switching unit that can switch the connection type of the motor's multiple windings between a first connection type for high rotation and a second connection type for high torque; a control unit that controls the motor and the connection switching unit; a housing that accommodates the motor, the connection switching unit, and the control unit; and a detection unit that detects a physical quantity that changes when the motor is driven or the type of power source, wherein the control unit is configured to execute connection switching control to switch the connection type from the first connection type to the second connection type when a predetermined winding switching condition is satisfied, the detected value including a workload applied to the motor, and the winding switching condition including a duration of any workload equal to or greater than a load threshold being equal to or greater than a time threshold that varies depending on the magnitude of the workload.

[0014] Another aspect of the present invention is a work machine including a motor having a rotor and a stator with a plurality of windings, a connection switching unit that switches the connection of the plurality of windings, a drive unit having a plurality of switching elements and driving the motor, a control unit that controls the drive unit and the connection switching unit, and a switch that instructs starting and stopping of the motor, wherein the control unit is configured to control the connection switching unit to switch the connection from a high rotation mode to a high torque mode when a load applied to the motor increases, and the control unit is configured to switch the mode to the high torque mode and apply an electric brake to the motor when the switch is turned off in the high rotation mode.

[0015] Another aspect of the present invention is a work machine including a motor having a rotor and a stator with a plurality of windings, a connection switching unit that switches the connection of the plurality of windings, a drive unit having a plurality of switching elements that drives the motor, a control unit that controls the drive unit and the connection switching unit, and a switch that instructs starting and stopping of the motor, wherein the control unit is configured to control the connection switching unit to switch the connection to switch the motor from a high rotation mode to a high torque mode when a load applied to the motor increases, and the control unit is configured to apply an electric brake to the motor while the motor is in the high rotation mode to stop the motor when the switch is turned off in the high rotation mode.

[0016] The present invention may be expressed as an "electric working machine," "electric tool," "electrical equipment," etc., and such expressions are also valid as aspects of the present invention.

[0017] According to the present invention, at least one of the above problems 1 to 4 can be solved.

[0018] 1 is a perspective view of a working machine 1 according to a first embodiment of the present invention, as seen from above. A perspective view of the working machine 1, as seen from below. A front view of the working machine 1. A cross-sectional view taken along the line CC of FIG. 3. A cross-sectional view showing a state in which the left opening of the intermediate housing 324 in FIG. 4 is covered with a cover member 328. A cross-sectional view of a motor 340 of the working machine 1. An external view of an operation panel 316 of the working machine 1. A circuit block diagram of the working machine 1. A simplified graph showing the relationship between the torque and rotation speed of the motor 340 when the motor 340 is of low rotation specification. A simplified graph showing the relationship between the effective current value and torque of the motor 340 when the motor 340 is of low rotation specification. A simplified graph showing the relationship between the torque and rotation speed of the motor 340 when the motor 340 is of high rotation specification. A simplified graph showing the relationship between the effective current value and torque of the motor 340 when the motor 340 is of high rotation specification. A simplified graph showing the relationship between the effective current value and torque of the motor 340 when the motor 340 is of high rotation specification. A graph showing the relationship between the product torque of the working machine 1 and the saw blade rotation speed. 14A is a graph showing an example of the change over time in current flowing through the battery pack 307 of the work machine 1 when a first control is performed to complete the switch from the delta connection to the star connection when the rotation speed of the motor 340 is higher than the no-load rotation speed in the star connection. (B) is a graph showing an example of the change over time in the saw blade rotation speed of the work machine 1 when the first control is performed. (C) is a graph showing an example of the change over time in voltage between the input terminals of the inverter circuit 64 of the work machine 1 when the first control is performed. (A) to (C) are enlarged graphs of the vicinity of the timing of the connection switch in FIGS. 14A to 14C, respectively. (D) is a graph showing the on / off of the inverter circuit 64 on the same time scale as FIGS. 15A to 15C. (A) is a graph showing an example of the change over time in current flowing through the battery pack 307 of the work machine 1 when a second control is performed to complete the switch from the delta connection to the star connection after the rotation speed of the motor 340 falls below the no-load rotation speed in the star connection. 16A to 16C are enlarged graphs showing the vicinity of the timing of switching the wiring connections in FIGS. 16A to 16C, respectively. 17D is a graph showing the on / off of the inverter circuit 64 on the same time scale as FIGS. 17A to 17C. 17C is a graph showing the on / off of the inverter circuit 64 on the same time scale as FIGS. 17A to 17C ...1 is a diagram showing the on / off changes over time of the delta connection relay element 32 and the star connection relay element 33 when a command to turn off the delta connection relay element 32 and a command to turn on the star connection relay element 33 are simultaneously issued in the connection switching control. FIG. 1 is a diagram showing the on / off changes over time of the delta connection relay element 32 and the star connection relay element 33 when a command to turn on the star connection relay element 33 is issued after a wait time has elapsed since a command to turn off the delta connection relay element 32 is issued in the connection switching control. A simplified graph showing an example of the expected change over time in the rotation speed of the motor 340 when third control is performed to complete the connection switching control at the timing when the rotation speed of the motor 340 has decreased to the expected rotation speed for the star connection. A simplified graph showing an example of the change over time in the actual rotation speed of the motor 340 when third control is performed. A simplified graph showing an example of the change over time in the actual rotation speed of the motor 340 when fourth control is performed to complete the connection switching control before the rotation speed of the motor 340 has decreased to the expected rotation speed for the star connection. 10 is a simplified graph showing an example of time variation in the actual rotation speed of the motor 340 when fifth control is performed, which performs constant speed control when the motor is connected in star connection, and which completes connection switching control when the rotation speed of the motor 340 has decreased to the rotation speed for constant speed control in star connection. A control flowchart for the working machine 1. A graph showing the relationship between the motor torque and motor rotation speed of the working machine 1, relating to the second embodiment of the present invention, where the pushing load of the working machine 1 against the mating material is increased in each of the automatic switching mode and the tenacity mode. A graph showing the relationship between the saw blade torque and saw blade rotation speed of the working machine 1, where the pushing load of the working machine 1 against the mating material is increased in each of the automatic switching mode and the tenacity mode. A graph showing the relationship between the saw blade torque and saw blade rotation speed of the working machine 1, where the pushing load of the working machine 1 against the mating material is increased and then decreased in the automatic switching mode. A graph showing the relationship between the effective battery current of the working machine 1 and the saw blade rotation speed, where the pushing load of the working machine 1 against the mating material is increased and then decreased in the automatic switching mode.34 is an enlarged graph showing the vicinity of the timing of switching the wiring method. 35 is a graph showing the vicinity of the timing of switching the wiring method. 36 is a graph showing the vicinity of the timing of switching the wiring method. 37 is a graph showing the vicinity of the timing of switching the wiring method. 38 is a graph showing the vicinity of the timing of switching the wiring method. 39 is a graph showing the vicinity of the timing of switching the wiring method. 40 is a graph showing the vicinity of the timing of switching the wiring method. 41 is a graph showing the vicinity of the timing of switching the wiring method. 42 is a graph showing the vicinity of the timing of switching the wiring method. 43 is a graph showing the vicinity of the timing of switching the wiring method. 44 is a graph showing the vicinity of the timing of switching the wiring method. 45 is a graph showing the vicinity of the timing of switching the wiring method. 43(A) and 43(B) are graphs showing the time changes in battery current and saw blade rotation speed in tenacity mode of the working machine 1, where the pushing load of the working machine 1 against the mating material is set to 110 N or less. 43(A) and 43(B) are graphs showing the time changes in battery current and saw blade rotation speed in tenacity mode of the working machine 1, where the pushing load of the working machine 1 against the mating material is suddenly increased to 120 N or more while operating in delta connection. 43(B) is a circuit block diagram of a working machine 2 according to a third embodiment of the present invention. 43(A) and 43(B) are graphs showing the time changes in battery current and saw blade rotation speed in automatic switching mode of the working machine 2, where the pushing load of the working machine 1 against the mating material is suddenly increased to 120 N or more while operating in delta connection. 43(B) is a circuit block diagram of a working machine 3 according to a fourth embodiment of the present invention. 43(A) and 43(B) are graphs showing the relationship between the current ranges and time thresholds shown in FIGS. 43(A) and 43(B). 43(A) is a table summarizing the winding switching conditions when the circuit of the working machine 3 is at a low temperature. 45(B) is a table summarizing winding switching conditions when the circuit temperature of the work machine 3 is high. FIG. 45(A) is a graph showing the relationship between the current range and the time threshold shown in FIG. 45(B).47A and 47B are diagrams showing the relationship between the current range and the time threshold value for each of the winding switching conditions and the overcurrent protection activation conditions for the work machine according to the fifth embodiment of the present invention. 47B is a diagram showing the relationship between the current range and the time threshold value for each of the winding switching conditions and the overcurrent protection activation conditions for the work machine according to the fifth embodiment of the present invention. 47C is a diagram showing the circuit block diagram of the work machine according to the sixth embodiment of the present invention. 47D is a diagram showing the circuit block diagram of the work machine according to the sixth embodiment of the present invention. 47E is a diagram showing the circuit block diagram of the work machine according to the sixth embodiment of the present invention. 47F ... 52(B). FIG. 52(C). A time chart of a second operation example of the work machine 4, including operations corresponding to the control of S9 to S17 in FIG. 51. A time chart of a third operation example of the work machine 4. A time chart of a fourth operation example of the work machine 4, including operations corresponding to the control of S9 to S61 in FIG. 52(B). A time chart of a fifth operation example of the work machine 4, including operations corresponding to the control of S9 and S71 in FIG. 52(C). A perspective view of a work machine 5 according to a seventh embodiment of the present invention, as seen from above. A perspective view of the work machine 5 according to a seventh embodiment of the present invention, as seen from above with a portion of the housing 1320 of the work machine 5 removed. A front view of the work machine 5. A side view of the work machine 5, as seen from the side with a portion of the housing 1320 of the work machine 5 removed. A perspective view showing a state in which the motor housing 1321 and the control board 1311 have been removed in FIG. 59.

[0019] 1 to 24 relate to a work machine 1 according to a first embodiment of the present invention. Figures 3 and 4 define the mutually orthogonal front-to-rear, up-down, and left-to-right directions of the work machine 1. The left-to-right direction is a direction parallel to the axial direction of a motor shaft 341 of the work machine 1. The work machine 1 is a portable circular saw. The work machine 1 includes a housing 320.

[0020] The housing 320 is, for example, a resin molded body, and includes a motor housing 321 that houses the motor 340 and the like, a handle housing 322 that is gripped by the operator, a battery attachment portion 323, and an intermediate housing 324.

[0021] The motor housing 321 is a cylindrical part whose central axis is approximately parallel to the left-right direction. The handle housing 322 extends obliquely in the front-to-back and up-down directions above the right part of the motor housing 321. A trigger switch 306 is provided at the upper end of the handle housing 322 as an operation part that allows the user to start and stop the motor 340.

[0022] A metal gear case (saw cover) 325 is connected to the left side of the handle housing 322. The gear case 325 houses a reduction mechanism (not shown) and covers the upper half of the saw blade 309 as the tool tip.

[0023] The battery attachment section 323 extends leftward from the rear end of the handle housing 322, and allows the battery pack 307 to be detachably attached. The work machine 1 is powered by the battery pack 307 and operates on the power of the battery pack 307. The work machine 1 has an operation panel 316 on the top surface of the battery attachment section 323. The user can switch the operation mode of the work machine 1 using the operation panel 316.

[0024] The intermediate housing 324 is located behind the motor housing 321 , to the side (right side) of the battery mounting portion 323 , and below the handle housing 322 .

[0025] The work machine 1 has a motor 340 inside a motor housing 321. The rotation of the motor 340 is reduced in speed by a reduction mechanism inside a gear case 325 and transmitted to the saw blade 309.

[0026] 6 , the motor 340 is an inner rotor brushless motor and includes a motor shaft 341 (output shaft), a rotor core 342, a rotor magnet 343 (permanent magnet), a stator core 344, and a stator coil 345.

[0027] The rotor core 342 is provided around the motor shaft 341 and rotates integrally with the motor shaft 341 relative to the stator core 344. There are four rotor magnets 343, which are inserted and held at 90-degree intervals in the circumferential direction in the rotor core 342. The rotor cores 342 and the rotor magnets 343 constitute the rotor of the motor 340.

[0028] The stator core 344 is arranged to surround the outer periphery of the rotor core 342. The stator core 344 includes a cylindrical (annular) yoke portion 346 and six teeth 347 (teeth portions) that protrude radially inward from the yoke portion 346. A stator coil 345 is provided on each tooth 347. Each tooth 347 forms a winding slot. The stator core 344 and the stator coil 345 form a stator of the motor 340. The stator coil 345 forms multiple windings of the motor 340.

[0029] The work machine 1 has a control board 311 (FIG. 5) and a plurality of battery connection terminals 327 (FIG. 2) inside the battery mounting section 323. The plurality of battery connection terminals 327 face downward from the battery mounting section 323. The plurality of battery connection terminals 327 come into contact with terminals of the battery pack 307 mounted in the battery mounting section 323 and are electrically connected thereto.

[0030] As shown in FIG. 4 , the work machine 1 has a relay board 30 inside the intermediate housing 324. The relay board 30 is mounted with a plurality of relay elements 31. The plurality of relay elements 31 constitute a relay unit. The plurality of relay elements 31 are an example of a connection switching unit that can switch the wiring method of the stator coil 345 (hereinafter referred to as the "coil wiring method") between a first wiring method for high rotation and a second wiring method for high torque, that is, a connection switching unit configured to be able to switch between a high rotation speed connection state in which the plurality of windings are connected to each other so as to have a high rotation speed characteristic, which is a characteristic that the rotation speed is higher than other characteristics, and a high torque connection state in which the plurality of windings are connected to each other so as to have a high torque characteristic, which is a characteristic that the torque is higher than other characteristics.

[0031] The relay board 30 is attached to the intermediate housing 324 with screws or the like. The intermediate housing 324 has an opening on the left side. This opening is covered by the battery pack 307 attached to the battery attachment section 323. As shown in Fig. 5, a cover member 328 is attached to this opening with screws or latches, and covering the opening with the cover member 328 prevents the relay board 30 from falling off and provides waterproofing and dust protection.

[0032] As shown in FIG. 7, the operation panel 316 is provided with an operation mode changeover switch 312, an operation mode display LED 313, a light mode changeover switch 314, and light mode display LEDs 315 and 317.

[0033] The operation mode changeover switch 312 is an operation mode changeover unit (mode selection unit) that allows the operator to change the operation mode of the work machine 1 between an automatic changeover mode (first mode) and a tenacious mode (second mode). The operation mode display LED 313 is an operation mode display unit that displays the current operation mode, and is turned off in the automatic changeover mode and turned on in the tenacious mode, for example.

[0034] The light mode selector switch 314 is a light mode switching unit that allows the operator to switch the light mode of the work machine 1. The light modes include, for example, a constant light mode and a trigger operation light mode in which the light is turned on only when the trigger switch 306 is pulled. The light mode display LED 315 is turned on in the trigger operation light mode and is turned off in the constant light mode. The light mode display LED 317 is turned on in the constant light mode and is turned off in the trigger operation light mode.

[0035] FIG. 8 is a circuit block diagram of the work machine 1.

[0036] The battery pack 307 includes a battery cell 67 and a protection IC 68. The protection IC 68 functions as a battery-side control unit, and outputs a discharge stop signal (LD signal) when the discharge current from the battery cell 67 exceeds a battery-side overcurrent protection threshold.

[0037] The inverter circuit 64 is a drive unit that is made up of six switching elements connected in a three-phase bridge and drives the motor 340. Each switching element of the inverter circuit 64 is an example of a heat-generating element that constitutes the work machine 1. The inverter circuit 64 is provided between the output terminals of the battery pack 307. The detection resistor 65 is provided in the path of the current (hereinafter referred to as "motor current") that flows through the stator coil 345. The inverter circuit 64 is mounted on the control board 311.

[0038] The control power supply circuit 51 converts the output voltage of the battery pack 307 into a power supply voltage for the calculation unit 50 and other components, and supplies it to the calculation unit 50 and other components. The current detection circuit 52 detects the motor current from the voltage across the detection resistor 65 and sends it to the calculation unit 50, which serves as a control unit. The switch operation detection circuit 53 detects the operation of the trigger switch 306 and sends it to the calculation unit 50. The battery type detection circuit 54 detects the type of battery pack 307 (rated voltage, rated capacity, etc.) from the voltage of an identification terminal (not shown) of the battery pack 307 and sends it to the calculation unit 50. The battery type detection circuit 54 constitutes a detection unit that detects the capacity of the power supply. The voltage detection circuit 55 detects the output voltage of the battery pack 307 (hereinafter referred to as "battery voltage") and sends it to the calculation unit 50.

[0039] The LD detection circuit 66 detects a discharge stop signal (LD signal) from the battery pack 307 and transmits it to the calculation unit 50. The calculation unit 50 and each circuit such as the control power supply circuit 51 are mounted on a control board 311.

[0040] The control signal circuit 56 outputs control signals that control the on / off of each switching element of the inverter circuit 64 under the control of the calculation unit 50. The rotational position detection circuit 57 detects the rotational position of the motor 340 based on the output signal of a Hall IC (magnetic sensor) 63 provided near the rotor magnet 343 and transmits the detected signal to the calculation unit 50. The rotation speed detection circuit 58 detects the rotation speed of the motor 340 (hereinafter referred to as "motor rotation speed") based on the output signal of the rotational position detection circuit 57 and transmits the detected signal to the calculation unit 50. In this specification, "rotation speed" refers to the number of rotations per unit time and represents the rotation speed. The operation mode detection circuit 59 detects the operation mode (operation mode) in response to the user's operation of the operation mode switch 312 and transmits the detected signal to the calculation unit 50. The illumination LED drive circuit 61 drives the illumination LED 62 under the control of the calculation unit 50.

[0041] The calculation unit 50 is a control unit that includes a microcontroller or the like and controls the overall operation of the work machine 1. The calculation unit 50 controls the drive of the inverter circuit 64 via the control signal circuit 56 (for example, PWM control of each switching element of the inverter circuit 64) and controls the drive current supplied to the stator coil 345. The calculation unit 50 can detect the torque of the motor 340 (hereinafter "motor torque"), i.e., the load applied to the motor 340 (hereinafter "work load"), from the motor current.

[0042] The calculation unit 50 controls the relay element 31 to switch the coil connection method (coil connection) between a delta connection for high rotation speeds and a star connection (Y connection) for high torque. The delta connection state of the coil connection method corresponds to a high rotation speed connection state, and the star connection state of the coil connection method corresponds to a high torque connection state. The calculation unit 50 can execute connection switching control to switch the coil connection method from the delta connection to the star connection, that is, connection switching control to switch from a high rotation speed connection state to a high torque connection state.

[0043] The plurality of relay elements 31 include three delta connection relay elements 32 as a first relay unit and three star connection relay elements 33 as a second relay unit. The calculation unit 50 sets the coil connection method to delta connection by turning on the delta connection relay elements 32 and turning off the star connection relay elements 33, and sets the coil connection method to star connection by turning on the star connection relay elements 33 and turning off the delta connection relay elements 32. Note that the number of star connection relay elements 33 may be two. In other words, one of the three star connection relay elements 33 may be replaced with a short circuit.

[0044] The operation modes (control modes by the calculation unit 50) of the work machine 1 include an automatic switching mode (first mode) and a tenacious mode (second mode). As described above, the operator can select the operation mode using the operation mode changeover switch 312.

[0045] In the automatic switching mode (first mode), the calculation unit 50 switches the coil connection method from a delta connection (first connection method) for high rotation to a star connection (second connection method) for high torque in response to an increase in the workload. That is, in the automatic switching mode, the calculation unit 50 is configured to control the multiple relay elements 31 so that the coil connection method is switched from the high rotation mode to the high torque mode when the workload increases.

[0046] In the tenacity mode (second mode), the calculation unit 50 does not switch the coil wiring method from a high-speed connection to a high-torque connection, regardless of an increase in the workload. Specifically, in the tenacity mode, the calculation unit 50 fixes the coil wiring method to a star connection, which is for high torque, and does not switch the coil wiring method regardless of the workload. The workload is the load applied to the motor 340 by work, i.e., the load applied to the motor 340 when the rotating saw blade 309 is pressed against the mating material, and does not include a temporary high load associated with starting the motor 340. That is, in the tenacity mode, the calculation unit 50 maintains the wiring method as the second wiring method.

[0047] In the present embodiment, the automatic switching mode will be described below.

[0048] Figure 9 is a graph showing the relationship between motor torque and motor rotation speed, with the horizontal axis representing motor torque and the vertical axis representing motor rotation speed, when the motor 340 is a low-speed specification. Figure 10 is a graph showing the relationship between motor torque and motor rotation speed, with the horizontal axis representing the effective value of motor current and the vertical axis representing motor torque. When the motor 340 is a low-speed specification, the delta connection is switched to the star connection at the intersection of the delta connection characteristic line and the star connection characteristic line (the winding switching point in Figure 9). Because the effective value of the motor current at the torque at the intersection is smaller than the overcurrent protection threshold, the overcurrent protection will not be activated before the connection is switched. However, there is an issue that the low motor rotation speed results in slow operating speed.

[0049] 11 and 12 show the relationship between motor torque and motor speed, and the relationship between the effective value of motor current and motor torque, respectively, when the motor 340 is configured for high-speed rotation, which is suitable for high rotation. The motor 340 can be configured for high rotation by, for example, reducing the number of turns of the stator coil 345, thereby improving operating speed. On the other hand, with a high-speed rotation specification, the motor current increases significantly compared to a low-speed rotation specification for the same torque. The effective value of the motor current at the intersection of the delta-connection characteristic line and the star-connection characteristic line exceeds the overcurrent protection threshold. For this reason, with a high-speed rotation specification, it is difficult to switch from a delta connection to a star connection at the intersection of the delta-connection characteristic line and the star-connection characteristic line (switching point 2 in FIG. 11 ). Therefore, with a high-speed rotation specification, the delta-connection to the star-connection is switched at switching point 1, where the torque is lower than at the intersection of the delta-connection characteristic line and the star-connection characteristic line. The time from the start to the completion of the wiring changeover is very short, for example, 100 ms or less, and it is important from the viewpoint of the working feeling to appropriately switch on and off the relay element 31 and the inverter circuit 64 during this time. This point will be described later.

[0050] FIG. 13 is a graph showing the relationship between the product torque (torque of the saw blade 309) of the work machine 1 and the rotational speed of the saw blade 309 (saw blade rotation speed) on the horizontal axis. Note that FIG. 13 illustrates an example in which the motor 340 is controlled at a constant speed in the low torque range, and the saw blade rotation speed is constant in the low torque range. A graph showing the relationship between torque and rotation speed of the tool bit can be obtained by the following experiment. A load device is connected to the output shaft holding the tool bit, and the rotational speed and torque of the output shaft are measured while the load torque generated by the load device is gradually increased from zero. The results are output as a graph with the torque of the output shaft on the horizontal axis and the rotational speed of the output shaft on the vertical axis. In many work machines, the motor and the output shaft holding the tool bit are connected via a reduction gear mechanism, so the torque and rotational speed of the motor can be calculated from the torque and rotational speed of the output shaft holding the tool bit and the reduction ratio of the reduction gear mechanism. Therefore, a graph showing the relationship between motor torque and rotational speed can also be obtained by an experiment similar to the above.

[0051] The no-load rotation speed of the saw blade 309 in the star connection shown in FIG. 13 is the no-load rotation speed of the saw blade 309 when it is assumed that the inverter circuit 64 is controlled at 100% duty in a no-load state and in a star connection state, and is the saw blade rotation speed (for example, about 3,000 min -1) The motor rotation speed corresponding to the no-load rotation speed of the saw blade 309 in star connection is the no-load rotation speed of the motor 340 in star connection (hereinafter referred to as the "no-load rotation speed in star connection"). In the work machine 1, the calculation unit 50 initiates connection switching control to switch the coil connection from delta connection to star connection when the coil connection is delta connection and the motor rotation speed is higher than the no-load rotation speed in star connection. Therefore, compared to when connection switching control is initiated when the motor rotation speed is lower than the no-load rotation speed in star connection, the motor 340 can be configured for higher rotation speed while preventing the motor 340 from stopping due to overcurrent protection before the start of connection switching control. Incidentally, in order to increase the work speed when the load torque is increasing, it is desirable to complete the started connection switching control as quickly as possible and resume driving the motor. Therefore, if connection switching control is initiated when the motor rotation speed is higher than the no-load rotation speed in star connection, it is natural to attempt to complete connection switching control when the motor rotation speed is higher than the no-load rotation speed in star connection, from the perspective of increasing the work speed. However, while the calculation unit 50 is executing connection switching control, the motor 340 is running idly and generates back electromotive force. Whether the motor rotation speed at the completion of connection switching control is equal to or lower than the no-load rotation speed in star connection is important from the perspective of suppressing back electromotive force in the motor 340. This point will be explained below.

[0052] Figures 14(A) to 14(C) are graphs showing an example of the changes over time in the current flowing through the battery pack 307 (hereinafter referred to as "battery current"), the saw blade rotation speed, and the voltage across the input terminals of the inverter circuit 64 (hereinafter referred to as "inverter voltage") when a first control is performed to complete the switch from the delta connection to the star connection while the motor rotation speed is higher than the no-load rotation speed in the star connection. Figures 15(A) to 15(C) are graphs that enlarge the vicinity of the timing of the connection switch in Figures 14(A) to 14(C). Figure 15(D) is a graph showing the on / off of the inverter circuit 64 on the same time scale as Figures 15(A) to 15(C).

[0053] In the case of the first control, the connection switching control is completed when the motor rotation speed is higher than the no-load rotation speed in star connection, and the star connection current path is turned on, so that at the timing of completion of the connection switching control, the inverter voltage jumps up due to the back electromotive force of the motor 340, exceeding the allowable voltage between the positive and negative electrodes of the battery pack 307 (for example, 43 V in the case of a rated voltage of 36 V) and the allowable voltage (for example, 48 V) of each switching element of the inverter circuit 64. For this reason, the first control has room for improvement in terms of suppressing the back electromotive force of the motor 340.

[0054] Figures 16(A) to 16(C) are graphs showing an example of the changes over time in battery current, saw blade rotation speed, and inverter voltage when the second control is performed to complete the switch from delta connection to star connection after the motor rotation speed falls below the no-load rotation speed in star connection. Figures 17(A) to 17(C) are graphs enlarging the vicinity of the timing of the connection switch in Figures 16(A) to 16(C). Figure 17(D) is a graph showing the on / off of the inverter circuit 64 on the same time scale as Figures 17(A) to 17(C).

[0055] In the case of the second control, the connection switching control is completed and the star-connected current path is turned on when the motor rotation speed is equal to or lower than the no-load rotation speed in star connection, so that the inverter voltage is prevented from rising due to the back electromotive force of the motor 340 at the timing when the connection switching control is completed. This reduces the risk that the inverter voltage will exceed the allowable voltage between the positive and negative electrodes of the battery pack 307 or the allowable voltage of each switching element of the inverter circuit 64.

[0056] 18A to 18C are diagrams showing the time-dependent on / off states of the delta connection relay element 32 and the star connection relay element 33 when a command to turn off the delta connection relay element 32 and a command to turn on the star connection relay element 33 are issued simultaneously during connection switching control.

[0057] If a command is issued simultaneously to turn off the delta connection relay element 32 and turn on the star connection relay element 33, a temporary short-circuit state (a state in which both the delta connection relay element 32 and the star connection relay element 33 are on) shown in FIG. 18B is likely to occur during the process of changing from the state shown in FIG. 18A (a state in which the delta connection relay element 32 is on and the star connection relay element 33 is off) to the state shown in FIG. 18C (a state in which the delta connection relay element 32 is off and the star connection relay element 33 is on).

[0058] In a short-circuited state, a brake current flows through a closed loop including the delta connection relay element 32, the star connection relay element 33, and the stator coil 345 due to the back electromotive force generated in the stator coil 345, resulting in an unnecessary drop in motor rotation speed. Also, since a brake current flows through the star connection relay element 33 the moment the star connection relay element 33 is turned on, there is a high risk of damage to the star connection relay element 33. Controls for solving these problems are shown in Figures 19(A) to 19(C).

[0059] 19A to 19C are diagrams showing the time-dependent on / off changes of the delta connection relay element 32 and the star connection relay element 33 when, during connection switching control, a command to turn off the delta connection relay element 32 is issued followed by a waiting time before a command to turn on the star connection relay element 33.

[0060] If a command to turn on the star connection relay element 33 is issued after a waiting time has elapsed since a command to turn off the delta connection relay element 32, the state changes from the state shown in Fig. 19(A) (the delta connection relay element 32 is on and the star connection relay element 33 is off) to the state shown in Fig. 19(C) (the delta connection relay element 32 is off and the star connection relay element 33 is on), temporarily resulting in the open connection state shown in Fig. 19(B) (the delta connection relay element 32 and the star connection relay element 33 are both off). The open connection state corresponds to the disconnected connection state.

[0061] In the open-circuit state, there is no closed loop through which a brake current flows due to the back electromotive force generated in the stator coil 345. This reduces the risk of a decrease in motor rotation speed and damage to the star-connection relay element 33. The open-circuit state lasts for, for example, approximately 10 ms.

[0062] Fig. 20 is a simplified graph showing an example of the expected change in motor rotation speed over time when the workload is increased, and shows an example of the expected change in motor rotation speed over time when a third control is performed to complete (terminate) the connection switching control when the motor rotation speed drops to the expected rotation speed in star connection. The expected rotation speed is, for example, 9,000 min -1 and is determined experimentally.

[0063] In FIG. 20 , the horizontal axis represents time, and the period from time (a) to time (f) represents the period from the start to the completion of the connection switching control. Time (a) is the time when the inverter circuit 64 is stopped. Stopping the inverter circuit 64 involves turning off each switching element of the inverter circuit 64 and switching the inverter circuit 64 to a stopped state in which the supply of drive power to the motor 340 is stopped. Time (b) is the time when the calculation unit 50 issues an OFF command to the delta connection relay element 32. Time (c) is the time when the delta connection relay element 32 actually turns OFF. Time (d) is the time when the calculation unit 50 issues an ON command to the star connection relay element 33. Time (e) is the time when the star connection relay element 33 actually turns ON. Time (f) is the time when the inverter circuit 64 resumes driving. The same applies to times (a) to (f) in FIGS. 21 to 23 . In addition, since the inverter circuit 64 is composed of semiconductor switching elements and responds faster to drive and stop commands from the calculation unit 50 than relay elements, the time lag from the drive and stop command to the response is ignored.

[0064] According to the assumptions in Figure 20, the motor rotation speed decreases in response to an increase in workload in the delta connection state until time (a), then the motor rotation speed drops sharply during the connection switching control period from time (a) to (f), and from time (f) onwards the motor rotation speed decreases in response to an increase in workload in the star connection state.

[0065] Figure 21 is a simplified graph showing an example of the actual change in motor rotation speed over time when the third control is performed. Unlike the assumption in Figure 20, there is a region 2 in which the motor rotation speed increases after time (f). The change in rotation speed in region 2 leads to a deterioration in the working feel. For example, if the torque-motor rotation speed characteristic line deviates upward from the expected position due to variations in the torque-motor rotation speed characteristics of the star-connected motor 340, a large increase in motor rotation speed in region 2 occurs. The variations in the torque-motor rotation speed characteristic are caused by variations in the magnetic force of the rotor magnet 343 and mechanical losses in the mechanism. Note that Figure 21 shows that when an extension line of the star-connected characteristic line is drawn, the inverter circuit 64 resumes operation at a rotation speed lower than the extension line.

[0066] 22 is a simplified graph showing an example of the change over time in the actual motor rotation speed when the fourth control is performed, which completes (ends) the connection switching control before the motor rotation speed drops to the expected rotation speed in the star connection. -1 or less (motor rotation speed is 10,000 min -1 The inverter circuit 64 is turned on when the torque vs. motor rotation speed characteristic line for the star connection of the motor 340 shifts upward from the expected position. According to the fourth control, even if the torque vs. motor rotation speed characteristic line for the star connection of the motor 340 shifts upward from the expected position, the change in rotation speed during the increase in motor rotation speed after time (f) is suppressed compared to the third control, and the deterioration of the working feeling is suppressed. Note that in Figure 23, when an extension line is drawn of the characteristic line for the star connection shown in the figure, the inverter circuit 64 resumes driving at a rotation speed higher than this characteristic line (extension line).

[0067] 23 is a simplified graph showing an example of the change in actual motor rotation speed over time when the fifth control, which performs constant speed control when the motor is connected in a star configuration, is performed, and the fifth control completes the connection switching control when the motor rotation speed drops to the rotation speed for constant speed control in the star configuration. With the fifth control, the motor rotation speed after the connection switching control is the set rotation speed for constant speed control, regardless of variations in the torque-to-motor rotation speed characteristics in the star configuration of the motor 340. Therefore, even if the torque-to-motor rotation speed characteristic line for the star configuration of the motor 340 deviates upward from the expected position, the change in rotation speed during the increase in motor rotation speed after time (f) is suppressed compared to the third control, and the deterioration of the working feel is suppressed.

[0068] 24 is a control flowchart for the work machine 1. When the trigger switch 306 is turned on (S201), the calculation unit 50 turns on the delta connection relay element 32 (S203), turns off the star connection relay element 33 (S205), starts driving the inverter circuit 64 (S207), and drives the motor 340 (operates the work machine 1) with the coil connection method set to delta connection (S209). If the workload does not exceed threshold A (No in S211), the calculation unit 50 continues driving the motor 340 in the delta connection.

[0069] When the workload exceeds threshold A (Yes in S211), the calculation unit 50 stops driving the inverter circuit 64 (S213) and sends an OFF signal to the delta connection relay element 32 (S215). This turns the delta connection relay element 32 OFF (S217). The calculation unit 50 waits until the motor rotation speed falls below the no-load speed for star connection (No in S219). When the motor rotation speed falls below the no-load speed for star connection (Yes in S219), the calculation unit 50 sends an ON signal to the star connection relay element 33 (S221). This turns the star connection relay element 33 ON (S223). The calculation unit 50 resumes driving the inverter circuit 64 (S225) and drives the motor 340 with the coil connection method set to star connection (S227). In the case of the fifth control, S227 becomes constant speed control.

[0070] This embodiment has the following advantages.

[0071] (1) The calculation unit 50 starts connection switching control, which switches the coil connection method from delta connection to star connection, when the motor rotation speed is higher than the no-load rotation speed for star connection. Therefore, compared to when connection switching control is started when the motor rotation speed is lower than the no-load rotation speed for star connection, it is possible to keep the motor 340 in a high-speed rotation specification while preventing the motor 340 from stopping due to overcurrent protection before the start of connection switching control.

[0072] (2) In the second control, the calculation unit 50 is configured to complete the connection switching control when the motor rotation speed is equal to or lower than the no-load rotation speed in star connection. Therefore, compared to when the switching from the delta connection to the star connection is completed when the motor rotation speed is higher than the no-load rotation speed in star connection, the inverter voltage is prevented from rising due to the back electromotive force of the motor 340 at the timing when the connection switching control is completed. This reduces the risk of the inverter voltage exceeding the allowable voltage between the positive and negative electrodes of the battery pack 307 or the allowable voltage of each switching element of the inverter circuit 64, causing a malfunction or damage.

[0073] (3) In the connection switching control, the calculation unit 50 switches the inverter circuit 64 to a drive stop state and switches the relay element 31 to the open connection state (connection cut state) shown in Fig. 19B. Therefore, compared to when switching from a state in which the delta connection relay element 32 is on and the star connection relay element 33 is off (a high rotation speed connection state) to a state in which the delta connection relay element 32 is off and the star connection relay element 33 is on (a high torque connection state) without an open connection state (connection cut state) in between, the risk of the connection short circuit state shown in Fig. 18B is reduced, and the risk of a decrease in motor rotation speed and damage to the star connection relay element 33 is reduced.

[0074] (4) In the connection switching control, when the inverter circuit 64 is in a drive-stop state, the calculation unit 50 is configured to switch the state from one in which the delta connection relay element 32 is on and the star connection relay element 33 is off (high rotation speed connection state) to one in which both the delta connection relay element 32 and the star connection relay element 33 are off (connection interruption state). Therefore, the delta connection relay element 32 is turned off when no current is flowing through it, which reduces the risk of damage to the delta connection relay element 32 compared to when the delta connection relay element 32 is turned off when current is flowing through it.

[0075] (5) In the connection switching control, when the inverter circuit 64 is in a drive-stop state, the calculation unit 50 is configured to switch the state in which the delta connection relay element 32 and the star connection relay element 33 are both OFF (connection interruption state) to a state in which the delta connection relay element 32 is OFF and the star connection relay element 33 is ON (high-torque connection state). Therefore, no current flows through the star connection relay element 33 at the moment the star connection relay element 33 is turned ON, thereby reducing the risk of damage to the star connection relay element 33.

[0076] 1 to 8 and 25 to 41 relate to a second embodiment of the present invention. Below, descriptions of parts common to the first embodiment will be omitted as appropriate. In this embodiment, the differences between the automatic changeover mode and tenacity mode of the work machine 1 will be mainly described.

[0077] Figure 25 is a graph showing the relationship between the motor torque and motor rotation speed of the work implement 1, and is a graph showing the relationship when the pressing load of the work implement 1 against the opposing material (hereinafter referred to as the "work implement pressing force") is increased in both the automatic switching mode and the tenacity mode.

[0078] In automatic switching mode, the calculation unit 50 performs constant speed control when the motor torque is in the range of 0.4 N·m or less. Therefore, in automatic switching mode, even if the pushing force of the work implement is increased, the motor rotation speed is maintained constant as long as the motor torque is in the range of 0.4 N·m or less. When the motor torque exceeds 0.4 N·m, increasing the pushing force of the work implement increases the motor torque and decreases the motor rotation speed. Furthermore, the motor rotation speed decreases significantly before and after the coil connection method is switched from delta connection to star connection. Even in star connection, increasing the pushing force of the work implement increases the motor torque and decreases the motor rotation speed.

[0079] In the tenacity mode, there is no region of constant speed control, and when the pushing force of the work implement is increased, the motor torque increases and the motor rotation speed decreases.

[0080] 26 is a graph showing the relationship between the saw blade torque (torque of the rotating shaft of the saw blade 309) and the saw blade rotation speed (rotation speed of the saw blade 309) of the work machine 1 when the work machine pressing force is increased in both the automatic changeover mode and the tenacity mode. In this embodiment, as an example, the reduction ratio of the reduction mechanism is set to 3.88, the saw blade rotation speed is 1 / 3.88 of the motor rotation speed, and the saw blade torque is 3.88 times the motor torque.

[0081] 27 is a graph showing the relationship between the saw blade torque and saw blade rotation speed of the work machine 1, where the work machine pressing force is increased and then decreased in automatic switching mode. In automatic switching mode, the saw blade torque (4 N m or more) when the coil connection method is switched from delta connection to star connection is greater than the saw blade torque (2 N m or less) when the coil connection method is switched from star connection to delta connection. This is to prevent frequent switching between the delta connection and star connection.

[0082] 28 is a graph showing the relationship between the effective battery current value of the work implement 1 (effective value of the discharge current of the battery pack 307) and the saw blade rotation speed when the work implement pressing force is increased and then decreased in the automatic switching mode. In the automatic switching mode, when the work implement pressing force is increased and the coil connection method is switched from the delta connection to the star connection, the effective battery current value drops sharply.

[0083] FIG. 29 is a control flowchart for the automatic changeover mode of the work implement 1, and is a control flowchart for when the work implement pressing force is gradually increased after the trigger switch 306 is turned on.

[0084] When the trigger switch 306 is turned on (S1), the calculation unit 50 turns on the delta connection relay element 32 (S3), turns off the star connection relay element 33 (S5), starts driving the inverter circuit 64 (S7), and drives the motor 340 (operates the work machine 1) with the coil connection method set to delta connection (S9). If the workload does not exceed the threshold A (No in S11), the calculation unit 50 continues driving the motor 340 in the delta connection.

[0085] When the workload exceeds threshold A (Yes in S11), the calculation unit 50 stops driving the inverter circuit 64 (S13), turns off the delta connection relay element 32 (S15), turns on the star connection relay element 33 (S17), resumes driving the inverter circuit 64 (S19), and drives the motor 340 with the coil connection method set to star connection (S21). Threshold A corresponds to the first winding switching threshold. The effective value of the motor current corresponding to threshold A is, for example, 60 A. Stopping the driving of the inverter circuit 64 means turning off all six switching elements that make up the inverter circuit 64.

[0086] FIG. 30 is a control flowchart for the automatic changeover mode of the work implement 1, and is a control flowchart for when the work implement pressing force is gradually reduced during operation in star connection.

[0087] The calculation unit 50 drives the motor 340 in the star connection (S25), and if the workload is not equal to or less than the threshold B (No in S27), continues to drive the motor 340 in the star connection.

[0088] When the workload falls below threshold B (Yes in S27), the calculation unit 50 stops driving the inverter circuit 64 (S29), turns off the star connection relay element 33 (S31), turns on the delta connection relay element 32 (S33), resumes driving the inverter circuit 64 (S35), and drives the motor 340 with the coil connection method set to delta connection (S37). Threshold B corresponds to the second winding switching threshold. The aforementioned threshold A is greater than threshold B.

[0089] 31 is a control flowchart for the tenacity mode of the work machine 1. When the trigger switch 306 is turned on (S41), the calculation unit 50 turns off the delta connection relay element 32 (S43), turns on the star connection relay element 33 (S45), starts driving the inverter circuit 64 (S47), and drives the motor 340 with the coil connection method set to star connection (S49).

[0090] 32 is a flowchart of overload protection control for the work machine 1. The calculation unit 50 drives the star-connected motor 340 (S51), and if the workload does not exceed threshold C (No in S53), continues to drive the star-connected motor 340. If the workload exceeds threshold C (Yes in S53), the calculation unit 50 stops driving the inverter circuit 64 to stop the motor 340 (S55). Threshold C corresponds to the overload protection threshold. The effective value of the motor current corresponding to the overload protection threshold is, for example, 90 A. The aforementioned threshold A is equal to or less than threshold C, and is preferably equal to or greater than two-thirds of threshold C.

[0091] 33 is a flowchart of protection control in response to a discharge stop signal from the battery pack 307 of the work machine 1. The premise of this flowchart is that the battery pack 307 outputs a discharge stop signal (LD signal) when its own discharge current exceeds the battery-side overcurrent protection threshold.

[0092] The calculation unit 50 drives the motor 340 (S61), and if it does not receive a discharge stop signal from the battery pack 307 (No in S63), it continues driving the motor 340. If it receives a discharge stop signal from the battery pack 307 (Yes in S63), the calculation unit 50 stops driving the inverter circuit 64 and stops the motor 340 (S55).

[0093] As described above, the calculation unit 50 stops the motor 340 when the workload exceeds the threshold C. At this time, when the motor current exceeds the main body side overcurrent protection threshold, the calculation unit 50 determines that the workload has exceeded the threshold C. The battery side overcurrent protection threshold described above is greater than the main body side overcurrent protection threshold.

[0094] Fig. 34 is a graph showing the time variation of the battery current and the saw blade rotation speed in the automatic switching mode of the work machine 1, where the work machine pressing force is 110 N or less. A work machine pressing force of 110 N or less corresponds to the first pressing force. Fig. 35 is a graph showing an enlarged view of the vicinity of the timing (time t3) at which the wiring method is switched in Fig. 34. The rate of increase (speed of increase) of the battery current immediately before the timing of switching the wiring method in Fig. 34 corresponds to the first workload increase rate (speed of increase).

[0095] At time t1, the trigger switch 306 is turned on, and no-load operation is performed until time t2. During the period from time t1 to t2, the saw blade rotation speed increases. From time t2, the saw blade 309 is pressed against the wood (mate material) and cutting work is performed.

[0096] After time t2, the work machine pressing force increases, battery current increases, and the saw blade rotation speed decreases. At time t3, when the work machine pressing force is 110 N or less, the workload exceeds threshold A, and the coil connection method switches from delta connection to star connection. This reduces the battery current (discharge current of battery pack 307) and the saw blade rotation speed. Thereafter, the calculation unit 50 controls the motor rotation speed to increase toward the target rotation speed, thereby increasing the saw blade rotation speed. At time t4, the trigger switch 306 is turned off, and the battery current and saw blade rotation speed decrease to zero.

[0097] Fig. 36 is a graph showing the time variation of the battery current and the saw blade rotation speed in the automatic switching mode of the work machine 1, in which the work machine pressing force is suddenly increased to 120 N or more during operation in the delta connection. A work machine pressing force of 120 N or more corresponds to the second pressing force. Fig. 37 is a graph showing an enlarged view of the vicinity of the timing (time t13) at which the wiring system is switched in Fig. 36. The rate of increase (speed of increase) of the battery current immediately before the timing of the wiring system switch in Fig. 36 corresponds to the second workload increase rate (speed of increase).

[0098] At time t11, the trigger switch 306 is turned on, and no-load operation is performed until time t12. During the period from time t11 to t12, the saw blade rotation speed increases. From time t12, the saw blade 309 is pressed against the wood (mate material) and cutting work is performed.

[0099] After time t12, the work implement pressing force increases, battery current rises, and the saw blade rotation speed decreases. Before time t13, the work implement pressing force suddenly increases to 120 N or more. At time t13, the workload exceeds threshold A, and the coil connection method switches from delta connection to star connection. This causes the battery current and saw blade rotation speed to decrease. The decrease in saw blade rotation speed is greater than when the work implement pressing force is 110 N or less (Figures 34 and 35). The calculation unit 50 then attempts to start the motor 340 using star connection, but because the work implement pressing force is large, the starting current with star connection is large. As a result, the motor current exceeds the main body overcurrent protection threshold, and at time t14, immediately after switching to star connection, the motor 340 is stopped due to overload protection.

[0100] FIG. 38 is a graph showing the change over time in battery current and saw blade rotation speed in tenacity mode of the work machine 1, and is a graph when the work machine pressing force is set to 110 N or less.

[0101] At time t21, the trigger switch 306 is turned on, and no-load operation is performed until time t22. During the period from time t21 to t22, the saw blade rotation speed increases. From time t22, the saw blade 309 is pressed against the wood (mate material) and cutting work is performed.

[0102] After time t22, the pressing force of the work machine increases, the battery current increases, and the saw blade rotation speed decreases. At time t24, the trigger switch 306 turns off, and the battery current and the saw blade rotation speed decrease to zero.

[0103] FIG. 39 is a graph showing the change over time in battery current and saw blade rotation speed in tenacity mode of the work machine 1, in which the work machine pressing force is suddenly increased to 120 N or more during operation in delta connection.

[0104] At time t31, the trigger switch 306 is turned on, and no-load operation is performed until time t32. During the period from time t31 to t32, the saw blade rotation speed increases. From time t32, the saw blade 309 is pressed against the wood (mate material) and cutting work is performed.

[0105] After time t32, the pushing force of the work implement increases, the battery current rises, and the saw blade rotation speed decreases. The pushing force of the work implement increases rapidly to 120 N or more, but the overload protection function does not activate. At time t34, the trigger switch 306 turns off, and the battery current and saw blade rotation speed decrease to zero.

[0106] According to this embodiment, the following effects can be achieved.

[0107] (1) The calculation unit 50 is configured to be able to execute two modes: an automatic switching mode (first mode) in which the coil wiring method is switched from a delta connection for high rotation to a star connection (Y connection) for high torque in response to an increase in workload, and a tenacity mode (second mode) in which the coil wiring method is fixed to a star connection for high torque and the coil wiring method is not switched regardless of the workload. Therefore, unlike a mode in which the only mode is to switch the coil wiring method in response to the workload, it is possible to fix the coil wiring method regardless of the workload, which improves workability.

[0108] (2) In the automatic switching mode, when work is performed by pressing the work implement 1 against a mating material with a work implement pressing force of 110 N or less (first pressing force), the calculation unit 50 switches the coil wiring method from a delta connection for high rotation to a star connection (Y connection) for high torque in response to an increase in the workload, and when work is performed by pressing the work implement 1 against a mating material with a work implement pressing force of 120 N or more (second pressing force), the calculation unit 50 stops the motor 340 immediately after switching the coil wiring method from a delta connection for high rotation to a star connection (Y connection) for high torque in response to an increase in the workload. Therefore, by switching the coil wiring method in response to the workload, high workability can be achieved while also providing appropriate overload protection for the motor 340.

[0109] (3) In tenacity mode, the calculation unit 50 sets the coil wiring method to a star connection for high torque. By setting the coil wiring method for high torque from the beginning, unlike when switching from high rotation to high torque midway, activation of the overload protection function due to the starting current after switching to high torque can be suppressed. This prevents activation of the overload protection function even when the work implement 1 is pressed against a mating material with a work implement pressing force (second pressing force) of 120 N or more. This improves workability when performing work that requires a sudden increase in the work implement pressing force to 120 N or more (e.g., rough cutting).

[0110] (4) In the automatic switching mode, when the workload exceeds threshold A (first winding switching threshold), the calculation unit 50 switches the coil connection from a delta connection for high rotation to a star connection (Y connection) for high torque. Furthermore, when the workload exceeds threshold C (overload protection threshold), the calculation unit 50 stops the motor 340 using the overload protection function. Here, threshold A is set to a value equal to or less than threshold C. This prevents the overload protection function from operating while the motor 340 is operating in a delta connection for high rotation, thereby improving workability. Furthermore, by setting threshold A to at least two-thirds of threshold C, the range in which the motor can operate at high rotation can be expanded, thereby improving workability. This effect can be maximized by setting threshold A equal to threshold C.

[0111] (5) The work machine 1 is provided with an operation mode selector switch 312 that allows the operator to select between an automatic changeover mode (first mode) and a tenacious mode (second mode) as the operation mode of the work machine 1. This allows the operator to freely select between the automatic changeover mode and the tenacious mode depending on the type of work to be performed, resulting in good workability.

[0112] (6) When switching the coil wiring method, the calculation unit 50 provides a pause period in which all six switching elements of the inverter circuit 64 are turned off. This prevents unexpected problems from occurring due to the inverter circuit 64 being driven while the coil wiring method is being switched, thereby improving reliability.

[0113] (7) In the automatic switching mode, when the coil wiring method is a star connection (Y connection) for high torque, and the workload decreases to below threshold B (second winding switching threshold), the calculation unit 50 switches the coil wiring method to a delta connection for high rotation. Here, threshold A (first winding switching threshold) is set to be larger than threshold B. This makes it possible to prevent frequent switching of the coil wiring method between the delta connection and the star connection.

[0114] (8) When the battery pack 307's own discharge current exceeds the battery-side overcurrent protection threshold, it outputs a discharge stop signal. When the calculation unit 50 receives the discharge stop signal from the battery pack 307, it stops the motor 340. On the other hand, when the motor current exceeds the main unit-side overcurrent protection threshold, the calculation unit 50 determines that the workload has exceeded threshold C and stops the motor 340. Here, the battery-side overcurrent protection threshold is greater than the main unit-side overcurrent protection threshold. Therefore, the main unit's overload protection function basically operates before the battery pack 307's overcurrent protection function operates, thereby reducing the burden on the battery pack 307.

[0115] (9) In connection switching control for switching the coil connection method from star connection to delta connection, i.e., in connection switching control for switching from a high-torque connection state to a high-speed connection state, when the inverter circuit 64 is in a drive-stop state, the calculation unit 50 is configured to switch from a state in which the delta connection relay element 32 is off and the star connection relay element 33 is on (high-torque connection state) to a state in which both the delta connection relay element 32 and the star connection relay element 33 are off (connection interruption state). Therefore, since the star connection relay element 33 is turned off when no current is flowing through it, the risk of damage to the star connection relay element 33 is reduced compared to when the star connection relay element 33 is turned off when current is flowing through it.

[0116] (10) In the connection switching control for switching the coil connection method from star connection to delta connection, when the inverter circuit 64 is in a drive-stop state, the calculation unit 50 is configured to switch from a state in which the delta connection relay element 32 and the star connection relay element 33 are both off (connection interruption state) to a state in which the delta connection relay element 32 is on and the star connection relay element 33 is off (high rotation speed connection state). Therefore, no current flows through the delta connection relay element 32 at the moment the delta connection relay element 32 is turned on, and the risk of damage to the delta connection relay element 32 is reduced.

[0117] (Embodiment 3) Figure 40 is a circuit block diagram of a work machine 2 according to embodiment 3 of the present invention. The circuit configuration shown in Figure 40 differs from that of Figure 8 in that two battery packs 307 are provided and connected in series to each other, but is the same in other respects.

[0118] FIG. 41 is a graph showing the change over time in battery current and saw blade rotation speed in the automatic changeover mode of the work implement 2, in which the work implement pressing force is suddenly increased to 120 N or more during operation in delta connection.

[0119] At time t41, the trigger switch 306 is turned on, and no-load operation is performed until time t42. During the period from time t41 to t42, the saw blade rotation speed increases. From time t42, the saw blade 309 is pressed against the wood (mate material) and cutting work is performed.

[0120] After time t42, the work machine pressing force increases, battery current increases, and the saw blade rotation speed decreases. Before time t43, the work machine pressing force is suddenly increased to 120 N or more, and at time t43, the workload exceeds the first winding switching threshold, and the coil connection method switches from delta connection to star connection. This decreases battery current and saw blade rotation speed. Thereafter, the calculation unit 50 controls the motor rotation speed to increase toward the target rotation speed, thereby increasing the saw blade rotation speed. At time t44, the trigger switch 306 is turned off, and the battery current and saw blade rotation speed decrease to zero.

[0121] In the above-described FIG. 36 , motor 340 stops due to overload protection at time t14 immediately after switching to star connection, whereas in FIG. 41 , motor 340 does not stop due to overload protection even when switched to star connection. This is because, compared to work machine 1, work machine 2 has two battery packs 307 connected in series, doubling the output voltage and therefore halving the battery current, and the peak value of the starting current after switching to star connection is also halved.

[0122] As described above, according to this embodiment, in addition to the effects of the second embodiment, the starting current after the coil connection method is switched from the delta connection for high rotation to the star connection (Y connection) for high torque in the automatic switching mode is suppressed, thereby suppressing the activation of the overload protection function and improving workability.

[0123] In the second and third embodiments, the second mode may fix the coil connection to a delta connection for high speed rotation. In this case, workability can be improved when work at high speed is desired, even at the expense of tenacity at high torque.

[0124] Instead of or in addition to the operator selecting between the automatic switching mode and the tenacity mode using the operation mode selector switch 312, a configuration may be adopted in which a sensor such as an acceleration sensor or a current sensor detects a sudden increase in the pressing force of the work implement and automatically switches to the tenacity mode. Furthermore, the mode may be switched by operating the trigger switch 306 in a manner different from the normal operation, for example, by operating it multiple times in a short period of time, or by operating an existing switch (such as the trigger switch 306, the light mode selector switch 314, or a remaining capacity switch operated by the operator to display the remaining capacity of the battery pack) in a manner different from the normal operation. Using an existing switch reduces manufacturing costs compared to providing a dedicated switch or sensor.

[0125] As the automatic switching mode, a plurality of types of modes may be provided, each having a different threshold value for switching the coil connection method.

[0126] The second mode is a mode in which the coil wiring method is not switched from high rotation to high torque during operation after the motor 340 is started. Therefore, for example, when the motor 340 is started, i.e., when cutting operation begins before actual operation is performed, the second mode also includes control in which the load on the motor 340 is determined to be high and the coil wiring method is switched from high rotation to high torque, and actual operation is started with the coil wiring method set to high torque. Also, in a high-load state in which the overload protection function is activated immediately after switching the coil wiring method to high rotation and the motor 340 stops, control in which the coil wiring method is switched from high torque to high rotation to prevent operation from continuing is included in the second mode, because the actual operation has ended with the coil wiring method set to high torque.

[0127] 1 to 7 and 42 to 48 relate to a work machine 3 according to a fourth embodiment of the present invention. Below, descriptions of parts common to the first embodiment will be omitted as appropriate.

[0128] Figure 42 is a circuit block diagram of the work implement 3. The following description will focus on differences from Figure 8 or parts not described in Figure 8. The protection IC 68 detects the temperature of the battery cells 67 (hereinafter also referred to as "battery temperature") and outputs a battery temperature signal. The detection resistor 65 and current detection circuit 52 form a detection unit (sensor unit) that detects a physical quantity (motor current) that changes as the motor 340 is driven.

[0129] The battery temperature detection circuit 69 detects a battery temperature signal from the battery pack 307 and transmits it to the calculation unit 50. The battery temperature detection circuit 69 constitutes a detection unit that detects a physical quantity (battery temperature) that changes as the motor 340 is driven. A thermistor 70 as a temperature detection element is disposed near the inverter circuit 64 and outputs a circuit temperature signal corresponding to the temperature of each switching element of the inverter circuit 64 (hereinafter referred to as "circuit temperature"). The circuit temperature detection circuit 71 detects the circuit temperature signal from the thermistor 70 and transmits it to the calculation unit 50. The thermistor 70 and the circuit temperature detection circuit 71 constitute a detection unit (sensor unit) that detects a physical quantity (circuit temperature) that changes as the motor 340 is driven.

[0130] The calculation unit 50 has an overcurrent protection function (overload protection function) that stops the motor 340 when the overcurrent protection (overload protection) activation conditions described later in Figure 43(B) are satisfied, even if the trigger switch 306 is in the on state. The calculation unit 50 also has a temperature protection function that stops the motor 340 when the battery temperature or circuit temperature exceeds a temperature threshold, even if the trigger switch 306 is in the on state.

[0131] In the second embodiment described above, the winding switching condition is exemplified as the workload exceeding threshold A (S11 in FIG. 29 ). In the present embodiment, the winding switching condition is defined in more detail. The control flowchart of the calculation unit 50 when the work implement pressing force is increased after the trigger switch 306 is turned on in the automatic switching mode is the same as that shown in FIG. 29 , except that S11 in FIG. 29 is replaced with a branch based on whether the winding switching condition is satisfied.

[0132] (Winding Switching Conditions and Overcurrent Protection Activation Conditions) Figure 43(A) is a table summarizing the winding switching conditions in the work machine 3. Figure 43(B) is a table summarizing the overcurrent protection activation conditions in the work machine 3. Figure 44 is a graph showing the relationship between the current range and the time threshold value shown in Figures 43(A) and (B), and is a graph showing the relationship between the current range and the time threshold value under each of the winding switching conditions (solid line) and the overcurrent protection activation conditions (dotted line).

[0133] The winding switching condition and the overcurrent protection activation condition are each expressed by a combination of a motor current and its duration. Specifically, for each of the winding switching condition and the overcurrent protection activation condition, multiple ranges (hereinafter also referred to as "current ranges") are set for the motor current equal to or greater than a current threshold (here, 60 A), and a threshold value (hereinafter also referred to as "time threshold") for the duration of the motor current within that current range is set for each current range. The motor current corresponds to the workload, the current threshold corresponds to the load threshold, and the current range corresponds to the load range. Both the winding switching condition and the overcurrent protection activation condition are set so that the time threshold decreases as the current value increases within the current range.

[0134] The winding switching condition shown in Figure 43(A) can be thought of as a condition related to a time threshold set in accordance with the detected value of the motor current. That is, the calculation unit 50 identifies a current range based on the detected value of the motor current, and determines that the winding switching condition is satisfied when the duration of the motor current is equal to or longer than the time threshold corresponding to that current range. In other words, the winding switching condition is that the motor current remains in a given current range for equal to or longer than the time threshold corresponding to that current range.

[0135] The current ranges under the winding switching conditions shown in Figure 43(A) are the same as the current ranges under the overcurrent protection activation conditions shown in Figure 43(B). Meanwhile, the time thresholds corresponding to the current ranges under the winding switching conditions shown in Figure 43(A) are smaller than the time thresholds corresponding to the current ranges under the overcurrent protection activation conditions shown in Figure 43(B). In other words, the winding switching conditions are set so that the coil connection scheme is switched from the delta connection to the star connection before the overcurrent protection function is activated and the motor 340 stops. This prevents the overcurrent protection function from activating and the motor 340 from stopping before the coil connection scheme is switched from the delta connection to the star connection, improving operability.

[0136] (Winding switching conditions according to temperature) Fig. 45(A) is a table summarizing winding switching conditions when the circuit temperature of the work machine 3 is low (hereinafter also referred to as "low-temperature winding switching conditions"). Fig. 45(B) is a table summarizing winding switching conditions when the circuit temperature of the work machine 3 is high (hereinafter also referred to as "high-temperature winding switching conditions"). Fig. 46 is a graph showing the relationship between the current range and the time threshold shown in Figs. 45(A) and 45(B), and is a graph showing the relationship between the current range and the time threshold under both the low-temperature winding switching condition (solid line) and the high-temperature winding switching condition (dotted line).

[0137] The calculation unit 50 determines whether the circuit temperature is low, i.e., whether the circuit temperature is below a predetermined temperature, based on a signal from the circuit temperature detection circuit 71. A temperature below the predetermined temperature is an example of a first temperature, and a temperature above the predetermined temperature is an example of a second temperature. The table of winding switching conditions at low temperatures shown in Figure 45(A) has the same content as the table of winding switching conditions shown in Figure 43(A).

[0138] The current ranges under the high-temperature winding switching condition shown in Figure 45(B) are the same as the current ranges under the low-temperature winding switching condition shown in Figure 45(A). Meanwhile, the time thresholds corresponding to the current ranges under the high-temperature winding switching condition shown in Figure 45(B) are smaller than the time thresholds corresponding to the current ranges under the low-temperature winding switching condition shown in Figure 45(A). This prevents the motor 340 from stopping due to the temperature protection function related to the circuit temperature being activated before the coil connection method is switched from the delta connection to the star connection, improving operability.

[0139] The winding switching conditions shown in Figures 45(A) and (B) can be thought of as conditions related to time thresholds that are set according to the detected value of the motor current and the detected value of the circuit temperature. That is, the calculation unit 50 determines which of the winding switching conditions shown in Figures 45(A) and 45(B) to use based on the detected value of the circuit temperature, identifies a current range based on the detected value of the motor current, and determines that the winding switching condition is satisfied when the duration of the motor current is equal to or longer than the time threshold corresponding to that current range. In other words, the winding switching condition shown in Figures 45(A) and (B) is that the motor current remains in a given current range for a period of time equal to or longer than the time threshold corresponding to that current range and circuit temperature.

[0140] The low-temperature winding switching condition shown in Figure 45(A) may be applied as the winding switching condition when the battery temperature is low. The high-temperature winding switching condition shown in Figure 45(B) may be applied as the winding switching condition when the battery temperature is high. This prevents the temperature protection function related to the battery temperature from operating and stopping the motor 340 before the coil connection method is switched from the delta connection to the star connection. The calculation unit 50 determines whether the battery temperature is low, i.e., whether the circuit temperature is below a predetermined temperature, based on the signal from the battery temperature detection circuit 69.

[0141] (Winding switching conditions according to battery capacity) Fig. 47(A) is a table summarizing the winding switching conditions when the rated capacity of the battery pack 307 of the work machine 3 is 2.5 Ah (low capacity) (hereinafter also referred to as "winding switching conditions at low capacity"). Fig. 47(B) is a table summarizing the winding switching conditions when the rated capacity of the battery pack 307 is 4.0 Ah (high capacity) (hereinafter also referred to as "winding switching conditions at high capacity"). Fig. 48 is a graph showing the relationship between the current range and the time threshold shown in Figs. 47(A) and (B), and is a graph showing the relationship between the current range and the time threshold under the low capacity winding switching condition (solid line) and the high capacity winding switching condition (dotted line).

[0142] The calculation unit 50 determines whether the rated capacity (hereinafter also referred to as "rated capacity") of the battery pack 307 is low, i.e., whether the rated capacity is equal to or lower than a predetermined capacity, based on a signal from the battery type detection circuit 54. A rated capacity exceeding the predetermined capacity is an example of a first capacity, and a rated capacity equal to or lower than the predetermined capacity is an example of a second capacity. The table of winding switching conditions at low capacity shown in Figure 47(A) has the same content as the table of winding switching conditions shown in Figure 43(A).

[0143] The time thresholds under the high capacity winding switching condition shown in Fig. 47(B) are the same as the time thresholds under the low capacity winding switching condition shown in Fig. 47(A). Meanwhile, the current ranges corresponding to the time thresholds under the high capacity winding switching condition shown in Fig. 47(B) are larger than the current ranges corresponding to the time thresholds under the low capacity winding switching condition shown in Fig. 47(A). This allows for work with a delta connection, which is intended for high rotation speeds, up to the limit corresponding to the rated capacity, by taking advantage of the fact that a temperature rise is more gradual for the same output current when the rated capacity is large compared to when it is small, thereby improving workability.

[0144] The winding switching conditions shown in Figures 47(A) and (B) can be thought of as conditions related to time thresholds that are set according to the detected value of the motor current and the detected value of the rated capacity. That is, the calculation unit 50 determines which of the winding switching conditions shown in Figures 47(A) and 47(B) to use based on the detected value of the rated capacity, identifies a current range based on the detected value of the motor current, and determines that the winding switching condition is satisfied when the duration of the motor current is equal to or longer than the time threshold corresponding to that current range. In other words, the winding switching condition shown in Figures 47(A) and (B) is that the motor current remains in a given current range for a period of time equal to or longer than the time threshold corresponding to that current range and rated capacity.

[0145] This embodiment has the following advantages.

[0146] (1) By setting the winding switching conditions as shown in FIG. 43(A), it is possible to prevent the temperature protection function from activating and causing the motor 340 to stop before switching the coil connection method from the delta connection (first connection method) to the star connection (second connection method), thereby improving workability. Switching the coil connection method to the star connection reduces the motor current, suppressing the temperature rise of elements such as the inverter circuit 64. This prevents the temperature protection function from activating, allowing work to continue, improving workability. In a comparative example, in a configuration in which the connection method is switched when the motor current exceeds a threshold, if work is performed in which the motor current does not exceed the threshold but remains close to the threshold, the temperature protection function may be activated or elements may be damaged, making it impossible to continue work and resulting in poor workability. In the comparative example, if the threshold is set low, such as 50 A, to prevent work from being impossible to continue, the period during which work can be performed with the delta connection (first connection method) is shortened, resulting in poor workability. This embodiment effectively solves the above-mentioned problems in the comparative example.

[0147] (2) By setting the relationship between the winding switching conditions and the overcurrent protection activation conditions as shown in Figures 43(A) and 43(B), it is possible to prevent the overcurrent protection function from activating and stopping the motor 340 before the coil connection method is switched from the delta connection to the star connection, thereby improving workability. In addition, work can be performed using the delta connection (first connection method) until just before the overcurrent protection function is activated, improving workability.

[0148] (3) As shown in Figures 45(A) and 45(B), by setting different winding switching conditions for low and high circuit and battery temperatures, it is possible to prevent the temperature protection function from activating and stopping the motor 340 before the coil connection method is switched from the delta connection (first connection method) to the star connection (second connection method), thereby improving workability. Also, it becomes possible to work with the delta connection (first connection method) to the limit within the allowable range of the circuit temperature and battery temperature, improving workability.

[0149] (4) As shown in Figures 47(A) and (B), by setting different winding switching conditions depending on whether the rated capacity of the battery pack 307 is low or high, it becomes possible to work with the delta connection (first connection method) up to the limit corresponding to the rated capacity of the battery pack 307, thereby improving workability.

[0150] Fifth Embodiment Fig. 49 is a graph showing the relationship between the current range and the time threshold value under each of the winding switching condition and the overcurrent protection activation condition for a work machine according to a fifth embodiment. In the example of Fig. 44 described above, the current range is the same for the winding switching condition and the overcurrent protection activation condition, but the time threshold value corresponding to each current range is different. In contrast, in the example of Fig. 49, the time threshold value is the same for the winding switching condition and the overcurrent protection activation condition, but the current range corresponding to each time threshold value is different. The example of Fig. 49 also achieves the same effects as the example of Fig. 44. Note that both the current range and the time threshold value under the winding switching condition may be set smaller than the current range and the time threshold value under the overcurrent protection activation condition.

[0151] Although not shown in the drawings, the low-temperature winding switching condition and the high-temperature winding switching condition may be set to have the same time threshold value but different current ranges corresponding to each time threshold value (so that the current value is smaller in the current range under the high-temperature winding switching condition than in the current range under the low-temperature winding switching condition).Furthermore, both the current range and the time threshold value under the high-temperature winding switching condition may be set to be smaller than the current range and the time threshold value under the low-temperature winding switching condition.

[0152] Alternatively, the low capacity winding switching condition and the high capacity winding switching condition may be set to have the same current range but different time thresholds corresponding to each current range (so that the time threshold for the high capacity winding switching condition is larger than the time threshold for the low capacity winding switching condition). Alternatively, both the current range and the time threshold for the high capacity winding switching condition may be set to be larger than the current range and the time threshold for the low capacity winding switching condition.

[0153] In the fourth and fifth embodiments, three or more winding switching conditions may be set depending on the circuit temperature, battery temperature, and rated capacity. Furthermore, instead of switching between delta and star connections, the coil wiring method may be switched between series and parallel connections of multiple coils in a single phase. Furthermore, the thresholds of each embodiment, such as those shown in FIGS. 44 and 49, may be combined depending on the workload. For example, when the workload is light (less than 70 A), the wiring method switching and overload protection may be performed based on the threshold shown in FIG. 44, and when the load is heavy (70 A or more), the wiring method switching and overload protection may be performed based on the threshold shown in FIG. 49. Furthermore, when the workload is light (e.g., less than 70 A), the wiring method switching and overload protection may be performed based on both the load threshold and the time threshold, as shown in FIG. 44, and when the load is heavy (70 A or more), the wiring method switching and overload protection may be performed based only on the load threshold, as shown in FIG. 44, etc.

[0154] 1 to 7 and 50 to 57 relate to a work machine 4 according to a sixth embodiment of the present invention. Below, a description of parts common to the first embodiment will be omitted as appropriate.

[0155] Figure 50 is a circuit block diagram of the work machine 4. The following will mainly explain the parts that differ from Figure 8 or the parts that were not explained in Figure 8.

[0156] The six switching elements that make up the inverter circuit 64 include three upper switching elements 72 on the high potential side and three lower switching elements 73 on the low potential side.

[0157] A control circuit voltage detection circuit 74 detects the output voltage of the control circuit voltage supply circuit 51 and sends it to the calculation unit 50. A display LED drive circuit 75 drives the operation mode display LED 313 and the light mode display LEDs 315 and 317 under the control of the calculation unit 50. A winding switching operation output circuit 76 outputs control signals for controlling the on / off of the delta connection relay element 32 and the star connection relay element 33 under the control of the calculation unit 50.

[0158] The three delta connection relay elements 32 correspond to the high rotation side switching unit, and the three star connection relay elements 33 correspond to the high torque side switching unit. The delta connection is an example of a first connection through which the brake current due to the electric brake of the motor 340 flows easily. The star connection is an example of a second connection through which the brake current due to the electric brake of the motor 340 does not flow easily.

[0159] The control when the operation mode is the automatic switching mode will be described below.

[0160] 51 is a flowchart showing a first control example of the work implement 4. When the calculation unit 50 is started, it turns on the three delta connection relay elements 32 and turns off the three star connection relay elements 33 (S101).

[0161] If the trigger switch 306 is off ("Trigger OFF Maintained" in S103), the calculation unit 50 returns to S101. If the trigger switch 306 is on ("Trigger ON" in S103), the calculation unit 50 controls the inverter circuit 64 with the three delta connection relay elements 32 on (high rotation mode state) to drive the motor 340 (S105).

[0162] The calculation unit 50 checks whether or not the load is overloaded (high load) (S107). Here, the overload state is a state in which the load is equal to or greater than the overload detection threshold (first connection switching threshold).

[0163] If the calculation unit 50 does not detect an overload state ("NO" in S107), the calculation unit 50 proceeds to S109. If the trigger switch 306 is on ("TRIGGER ON KEEP" in S109), the calculation unit 50 returns to S105.

[0164] When the trigger switch 306 is off ("TRIGGER OFF" in S109), the calculation unit 50 turns off the six switching elements of the inverter circuit 64 (S111), turns off the three delta connection relay elements 32 (S113), turns on the three lower switching elements 73 of the inverter circuit 64 (S115), and turns on the three star connection relay elements 33 (S117), thereby applying the electric brake to the motor 340 in the high torque mode (star connection). One or two lower switching elements 73 may be turned on in S115. The calculation unit 50 continues the electric brake until the motor 340 stops ("NO" in S119), and when the motor 340 stops ("YES" in S119), returns to S101.

[0165] In this way, when the trigger switch 306 is turned off in the high rotation mode (delta connection), the calculation unit 50 switches to the high torque mode (star connection) and applies an electric brake to the motor 340 to stop the motor 340. At this time, after turning on the three lower switching elements 73 of the inverter circuit 64, the calculation unit 50 turns on the three star connection relay elements 33.

[0166] When the calculation unit 50 detects an overload state ("Yes" in S107), it turns off the six switching elements of the inverter circuit 64 (S121), turns off the three delta connection relay elements 32 (S123), and turns on the three star connection relay elements 33 (S125), and controls the inverter circuit 64 with the three star connection relay elements 33 on (high torque mode state) to drive the motor 340 (S127).

[0167] In this way, the calculation unit 50 is configured to switch to the high torque mode (star connection) when the workload increases in the high rotation mode (delta connection).

[0168] While the motor 340 is being driven in the high torque mode (star connection) (S127), the calculation unit 50 checks whether the motor is in a light load state (S131). The light load state is a state in which the load is equal to or less than a light load detection threshold (second connection switching threshold). The second connection switching threshold is smaller than the first connection switching threshold described above, which is used to determine whether the motor is in an overload state.

[0169] If the calculation unit 50 does not detect a light load state ("No" in S131), the calculation unit 50 proceeds to S133. If the trigger switch 306 is on ("Trigger ON Maintained" in S133), the calculation unit 50 returns to S127. If the trigger switch 306 is off ("Trigger OFF" in S133), the calculation unit 50 turns on the three lower switching elements 73 of the inverter circuit 64 (S135) and applies the electric brake to the motor 340. The calculation unit 50 continues the electric brake until the motor 340 stops ("No" in S137), and when the motor 340 stops ("Yes" in S137), the calculation unit 50 returns to S101. One or two lower switching elements 73 may be turned on in S135.

[0170] When the calculation unit 50 detects a light load state ("Yes" in S131), it turns off the six switching elements of the inverter circuit 64 (S139), turns off the three star-connection relay elements 33 (S141), and turns on the three delta-connection relay elements 32 (S143), and controls the inverter circuit 64 with the three delta-connection relay elements 32 on (high-speed mode state) to drive the motor 340 (S105).

[0171] In this way, the calculation unit 50 is configured to switch to the high rotation mode (delta connection) when the work load becomes smaller in the high torque mode (star connection).

[0172] (Second Control Example) Figure 52(A) is a flowchart showing a second control example of the work implement 4. The second control example differs from the first control example in the control when the trigger switch 306 is turned off in the high rotation mode (delta connection), but is the same in other respects. The following description will focus on the differences.

[0173] When the trigger switch 306 is off ("TRIGGER OFF" in S109), the calculation unit 50 turns off the six switching elements of the inverter circuit 64 (S144), turns off the three delta connection relay elements 32 (S145), turns on the three star connection relay elements 33 (S146), and turns on the three lower switching elements 73 of the inverter circuit 64 (S147), thereby applying the electric brake to the motor 340 in the high torque mode (star connection). One or two lower switching elements 73 may be turned on in S147. The calculation unit 50 continues the electric brake until the motor 340 stops ("NO" in S148), and when the motor 340 stops ("YES" in S148), returns to S101.

[0174] In this way, when the trigger switch 306 is turned off in the high rotation mode (delta connection), the calculation unit 50 switches to the high torque mode (star connection) and applies an electric brake to the motor 340 to stop the motor 340. At this time, after turning on the three star connection relay elements 33, the calculation unit 50 turns on the three lower switching elements 73 of the inverter circuit 64.

[0175] (Third Control Example) Figure 52(B) is a flowchart showing a third control example of the work implement 4. The third control example is different from the first control example in the control when the trigger switch 306 is turned off in the high rotation mode (delta connection), but is the same in other respects. The following description will focus on the differences.

[0176] When the trigger switch 306 is turned off in the high rotation mode (delta connection) ("TRIGGER OFF" in S109), the calculation unit 50 turns on the three lower switching elements 73 of the inverter circuit 64 (S151) and applies the electric brake to the motor 340 while the high rotation mode (delta connection) is maintained. The calculation unit 50 continues the electric brake in S151 until the motor rotation speed drops below a predetermined rotation speed ("NO" in S153). One or two lower switching elements 73 may be turned on in S151.

[0177] When the motor rotation speed drops below a predetermined rotation speed (YES in S153), the calculation unit 50 turns off the six switching elements of the inverter circuit 64 (S155), turns off the three delta connection relay elements 32 (S157), turns on the three star connection relay elements 33 (S159), and turns on the three lower switching elements 73 of the inverter circuit 64 (S161), thereby applying an electric brake to the motor 340 in the high torque mode (star connection) and stopping the motor 340 (NO in S163). One or two lower switching elements 73 may be turned on in S161.

[0178] In this way, when the trigger switch 306 is turned off in the high rotation mode (delta connection), the calculation unit 50 is configured to apply an electric brake to the motor 340 to reduce the motor rotation speed to a predetermined rotation speed or less, and then switch to the high torque mode (star connection) and apply the electric brake to the motor 340.

[0179] (Fourth Control Example) Figure 52(C) is a flowchart showing a fourth control example of the work implement 4. The fourth control example is different from the first control example in the control when the trigger switch 306 is turned off in the high rotation mode (delta connection), but is the same in other respects. The following description will focus on the differences.

[0180] When the trigger switch 306 is turned off in the high rotation speed mode (delta connection) ("TRIGGER OFF" in S109), the calculation unit 50 turns on the three lower switching elements 73 of the inverter circuit 64 (S171), applies an electric brake to the motor 340 while the motor is still in the high rotation speed mode (delta connection), and stops the motor 340 ("NO" in S173). One or two lower switching elements 73 may be turned on in S171.

[0181] (First Operation Example) Figure 53 is a time chart of a first operation example of the work machine 4, which includes an operation of switching the coil connection method from a delta connection for high rotation to a star connection for high torque in response to an increase in the work load. In this time chart, the trigger switch 306 is continuously turned on. In Figure 53, S1 indicates the overload detection threshold, and S2 indicates the light load detection threshold.

[0182] Before time T1, the load is light, and the calculation unit 50 drives the motor 340 in the high-speed mode (delta connection). That is, the calculation unit 50 performs commutation control (drive control of the motor 340) by the inverter circuit 64 with the three delta connection relay elements 32 turned on and the three star connection relay elements 33 turned off.

[0183] At time T1, the workload rises to the overload detection threshold S1, and the calculation unit 50 detects an overload state and turns off the six switching elements of the inverter circuit 64. At time T2, the calculation unit 50 outputs an OFF signal to the three delta-connection relay elements 32. At a subsequent time T2', the three delta-connection relay elements 32 are turned off. Because the relay elements are of the contact type, there is a large time lag between the signal output from the calculation unit 50 and the actual on / off switching of the relay elements compared to semiconductor switching elements.

[0184] At time T3, the calculation unit 50 outputs an ON signal to the three star connection relay elements 33. Thereafter, at time T3', the three star connection relay elements 33 are turned ON. At time T4, the calculation unit 50 resumes commutation control (drive control of the motor 340) by the inverter circuit 64.

[0185] (Second Operation Example) Figure 54 is a time chart of a second operation example of the work machine 4, and is a time chart that includes operations corresponding to the controls of S109 to S117 in Figure 51. In Figure 54, S1 is the overload detection threshold, S2 is the light load detection threshold, V1 is the battery voltage, and V2 is the rated voltage of the switching element of the inverter circuit 64.

[0186] Before time T11, the load is light, and the calculation unit 50 drives the motor 340 in the high-speed mode (delta connection). That is, the calculation unit 50 performs commutation control (drive control of the motor 340) by the inverter circuit 64 with the three delta connection relay elements 32 turned on and the three star connection relay elements 33 turned off.

[0187] At time T11, the trigger switch 306 is turned off, and the calculation unit 50 turns off the six switching elements of the inverter circuit 64. At time T12, the calculation unit 50 outputs an OFF signal to the three delta connection relay elements 32. Thereafter, at time T12′, the three delta connection relay elements 32 are turned off.

[0188] At time T13, the calculation unit 50 turns on all of the lower switching elements 73 of the inverter circuit 64. One or two of the lower switching elements 73 may be turned on. At time T14, the calculation unit 50 outputs an ON signal to the three star connection relay elements 33. Thereafter, at time T14', the three star connection relay elements 33 are turned on. From time T14', the electric brake begins to work, a brake current flows through the stator coil 345, and the rate at which the motor rotation speed decreases increases.

[0189] In the second operation example, when the three star-connection relay elements 33 are turned on at time T14', the lower switching element 73 of the inverter circuit 64 is already on, establishing a closed loop through which regenerative current flows. For this reason, even if the trigger switch 306 is turned off when the motor rotation speed is close to the no-load rotation speed, the voltage applied to the switching element of the inverter circuit 64 (inverter voltage) will not rise above the battery voltage V1.

[0190] (Third Operation Example) Figure 55 is a time chart of a third operation example of the work implement 4. In Figure 55, V1 indicates the battery voltage, and V2 indicates the rated voltage of the switching element of the inverter circuit 64.

[0191] Before time T21, the load is light, and the calculation unit 50 drives the motor 340 in the high-speed mode (delta connection). That is, the calculation unit 50 performs commutation control (drive control of the motor 340) by the inverter circuit 64 with the three delta connection relay elements 32 turned on and the three star connection relay elements 33 turned off.

[0192] At time T21, the trigger switch 306 is turned off, and the calculation unit 50 turns off the six switching elements of the inverter circuit 64. At time T22, the calculation unit 50 outputs an OFF signal to the three delta connection relay elements 32. Thereafter, at time T22′, the three delta connection relay elements 32 are turned off.

[0193] At time T23, the calculation unit 50 outputs an ON signal to the three star connection relay elements 33. Thereafter, at time T23', the three star connection relay elements 33 are turned ON. At time T24, the calculation unit 50 turns ON all of the lower switching elements 73 of the inverter circuit 64. From time T24, the electric brake begins to function, a brake current flows through the stator coil 345, and the rate at which the motor rotation speed decreases increases.

[0194] In the third operation example, when the three star-connection relay elements 33 are turned on at time T23′, all six switching elements of the inverter circuit 64 are off, and a closed loop through which regenerative current flows is not established. In the second operation example described above, the moment the three star-connection relay elements 33 are turned on and a closed loop is established, a large regenerative current flows, posing a risk of damaging the three star-connection relay elements 33. The third operation example is intended to reduce this risk of damage to the star-connection relay elements 33. Meanwhile, in the third operation example, the trigger switch 306 is turned off while the motor 340 is operating in high-speed mode (delta connection), i.e., when the motor rotation speed is high. Therefore, the voltage applied to the switching elements of the inverter circuit 64 (inverter voltage) rises above the battery voltage V1 and exceeds the rated voltage V2 of the switching elements of the inverter circuit 64, posing a risk of damaging the switching elements. The second operation example described above is intended to reduce this risk of damage to the switching elements.

[0195] (Fourth Operation Example) Figure 56 is a time chart of a fourth operation example of the work machine 4, and is a time chart that includes operations corresponding to the controls of S109 to S161 in Figure 52(B). In Figure 56, S1 indicates the overload detection threshold, and S2 indicates the light load detection threshold.

[0196] Before time T31, the load is light, and the calculation unit 50 drives the motor 340 in the high-speed mode (delta connection). That is, the calculation unit 50 performs commutation control (drive control of the motor 340) by the inverter circuit 64 with the three delta connection relay elements 32 turned on and the three star connection relay elements 33 turned off.

[0197] At time T31, the trigger switch 306 turns off, and the calculation unit 50 turns on all of the lower switching elements 73 of the inverter circuit 64. From time T31, the electric brake begins to function, a brake current flows through the stator coil 345, and the rate at which the motor rotation speed decreases increases.

[0198] At time T32, the motor rotation speed drops below a predetermined rotation speed (rotation speed threshold), and the calculation unit 50 turns off the six switching elements of the inverter circuit 64. At this point, the electric brake is temporarily stopped. Having detected that the motor rotation speed has dropped below the predetermined rotation speed, the calculation unit 50 outputs an OFF signal to the three delta connection relay elements 32 at time T33. Subsequently, at time T33', the three delta connection relay elements 32 are turned off.

[0199] At time T34, the calculation unit 50 outputs an ON signal to the three star connection relay elements 33. Thereafter, at time T34', the three star connection relay elements 33 are turned ON. At time T35, the calculation unit 50 turns ON all of the lower switching elements 73 of the inverter circuit 64. One or two of the lower switching elements 73 may be turned ON. From time T35, the electric brake begins to work again, a brake current flows through the stator coil 345, and the rate at which the motor rotation speed decreases increases.

[0200] (Fifth Operation Example) Figure 57 is a time chart of a fifth operation example of the work machine 4, and is a time chart that includes operations corresponding to the controls of S109 and S171 in Figure 52(C). In Figure 57, S1 indicates the overload detection threshold, and S2 indicates the light load detection threshold.

[0201] Before time T41, the load is light, and the calculation unit 50 drives the motor 340 in the high-speed mode (delta connection). That is, the calculation unit 50 performs commutation control (drive control of the motor 340) by the inverter circuit 64 with the three delta connection relay elements 32 turned on and the three star connection relay elements 33 turned off.

[0202] At time T41, the trigger switch 306 is turned off, and the calculation unit 50 turns on all of the lower switching elements 73 of the inverter circuit 64. One or two of the lower switching elements 73 may be turned on. From time T41, the electric brake begins to function, a brake current flows through the stator coil 345, and the rate at which the motor rotation speed decreases increases.

[0203] This embodiment has the following advantages.

[0204] (1) When the load state changes from a light load state to an overload state, the calculation unit 50 is configured to execute control in the following order: turn off the six switching elements of the inverter circuit 64, turn off the three delta connection relay elements 32, turn on the three star connection relay elements 33, and control the inverter circuit 64 to drive the motor 340. Therefore, no current flows the instant the three star connection relay elements 33 are turned on, which is advantageous in terms of durability of the three star connection relay elements 33.

[0205] (2) When the load state changes from an overload state to a light load state, the calculation unit 50 is configured to execute control in the following order: turn off the six switching elements of the inverter circuit 64, turn off the three star-connection relay elements 33, turn on the three delta-connection relay elements 32, and control the inverter circuit 64 to drive the motor 340. Therefore, no current flows the instant the three delta-connection relay elements 32 are turned on, which is advantageous in terms of durability of the three delta-connection relay elements 32.

[0206] (3) In the first control example shown in Fig. 51, when the trigger switch 306 is turned off in the high rotation mode (delta connection), the calculation unit 50 switches to the high torque mode (star connection) and applies an electric brake to the motor 340 to stop the motor 340. Therefore, compared to when the electric brake is applied in the high rotation mode (delta connection), the brake current can be suppressed and the temperature rise of the inverter circuit 64 can be suppressed. In addition, the reaction force due to the electric brake is suppressed, making it easy to use.

[0207] (4) In the first control example shown in Figure 51, when the trigger switch 306 is turned off in the high rotation speed mode (delta connection), the calculation unit 50 is configured to execute control in the following order: turn off the six switching elements of the inverter circuit 64, turn off the three delta connection relay elements 32, turn on the three lower switching elements 73 of the inverter circuit 64, and turn on the three star connection relay elements 33. Therefore, when the three star connection relay elements 33 are turned on, the lower switching element 73 of the inverter circuit 64 is already on, establishing a closed loop through which regenerative current flows. Therefore, even if the trigger switch 306 is turned off when the motor rotation speed is close to the no-load rotation speed, a voltage spike applied to the switching elements of the inverter circuit 64 is suppressed, thereby preventing damage to electronic components such as the switching elements.

[0208] (5) In the second control example shown in FIG. 52A , when the trigger switch 306 is turned off in the high-speed rotation mode (delta connection), the calculation unit 50 is configured to execute control in the following order: turn off the six switching elements of the inverter circuit 64, turn off the three delta connection relay elements 32, turn on the three star connection relay elements 33, and turn on the three lower switching elements 73 of the inverter circuit 64. Therefore, when the three star connection relay elements 33 are turned on, all six switching elements of the inverter circuit 64 are off, and a closed loop through which a regenerative current flows is not established. In the first control example described above, the moment the three star connection relay elements 33 are turned on and a closed loop is established, a large regenerative current flows, posing a risk of damaging the three star connection relay elements 33. However, the second control example can reduce the risk of damaging the star connection relay elements 33.

[0209] (6) In the third control example shown in FIG. 52(B), when the trigger switch 306 is turned off in the high-speed mode (delta connection), the calculation unit 50 applies an electric brake to the motor 340 to reduce the motor speed to a predetermined speed or less, and then switches to the high-torque mode (star connection) to apply the electric brake to the motor 340. When the electric brake is applied after the motor speed has reduced to a predetermined speed or less, the three star-connection relay elements 33 are turned on before the three lower switching elements 73 of the inverter circuit 64 are turned on. This prevents current from flowing the instant the three star-connection relay elements 33 are turned on, which is advantageous in terms of the durability of the three star-connection relay elements 33. Furthermore, because the rotational speed of the motor 340 has reduced to a predetermined speed or less, the back electromotive force generated by the motor 340 when the three star-connection relay elements 33 are turned on before the three lower switching elements 73 of the inverter circuit 64 are turned on can be suppressed. Suppressing the back electromotive force reduces the risk of damage to the switching elements 73. In particular, the risk of damage to the switching element 73 can be effectively reduced by setting the predetermined rotation speed so that the back electromotive force does not exceed the voltage of the battery pack 307. Furthermore, since no current flows through the three star connection relay elements 33 the moment the three star connection relay elements 33 are turned on, this is advantageous in terms of durability of the three star connection relay elements 33.

[0210] (7) In the fourth control example shown in Figure 52(C), when the trigger switch 306 is turned off in the high rotation mode (delta connection), the calculation unit 50 turns on the three lower switching elements 73 of the inverter circuit 64, applies an electric brake to the motor 340 while the motor is still in the high rotation mode (delta connection), and stops the motor 340. Therefore, even when the trigger switch 306 is turned off in the high rotation mode (delta connection), the three delta connection relay elements 32 and the three star connection relay elements 33 are not switched on or off, which is advantageous in terms of durability of the three delta connection relay elements 32 and the three star connection relay elements 33.

[0211] (Seventh embodiment) Figures 58 to 62 relate to a work machine 5 according to a seventh embodiment of the present invention. The work machine 5 has a partially different mechanical configuration from the work machines of the above-described embodiments. The circuit configuration and control of the work machine 5 can be applied to any of the work machines of the above-described embodiments. Figures 60 and 61 define the mutually orthogonal front-to-back, up-down, and left-to-right directions of the work machine 5. The work machine 5 is a portable circular saw. The work machine 5 includes a housing 1320.

[0212] The housing 1320 is, for example, a resin molded body, and includes a motor housing 1321 that houses the motor 340 and the like, a handle housing 1322 that is gripped by the operator, and a battery attachment section 1323 .

[0213] The motor housing 1321 is a cylindrical part whose central axis is approximately parallel to the left-right direction. The handle housing 1322 extends obliquely in the front-to-back and up-down directions above the right part of the motor housing 1321. A trigger switch 1306 is provided at the upper end of the handle housing 1322, which allows the user to start and stop the motor 340.

[0214] A metal gear case (saw cover) 1325 is connected to the left side of the handle housing 1322. The gear case 1325 houses a reduction mechanism (not shown) and covers the upper half of the saw blade 1309.

[0215] The battery attachment section 1323 extends leftward from the rear end of the handle housing 1322, and allows a battery pack 1307, which serves as a power source, to be detachably attached. The work machine 5 operates using power from the battery pack 1307. The work machine 5 has an operation panel 1316 above the battery attachment section 1323. The user can switch the operation mode of the work machine 5 using the operation panel 1316.

[0216] A hook 1324 is attached to the front of the handle housing 1322, and is configured so that the work implement 5 can be hooked onto a hooked portion. The hook 1324 is attached to the housing 1320 so as to be rotatable. In addition, a sub-handle 1326 is provided above the motor housing 1321. The sub-handle 1326 is a part that the operator grips during work.

[0217] The work machine 5 has a motor 340 inside a motor housing 1321. The rotation of the motor 340 is reduced in speed by a reduction mechanism inside a gear case 1325 and transmitted to the saw blade 1309.

[0218] The work machine 5 has a control board 1311 (FIG. 59) inside the motor housing 1321 and multiple battery connection terminals (not shown) inside the battery mounting section 1323. The control board 1311 is equipped with circuits such as the aforementioned calculation unit 50, control power supply circuit 51, and inverter circuit 64. The multiple battery connection terminals face below the battery mounting section 1323. The multiple battery connection terminals come into contact with terminals of the battery pack 1307 mounted in the battery mounting section 1323 and are electrically connected thereto.

[0219] As shown in Figure 59, the work machine 5 has a relay board 30 inside the motor housing 1321. The relay board 30 is mounted with a plurality of relay elements 31. The relay board 30 is attached to the motor 340 with screws or the like. The relay board 30 faces an air hole provided in the motor housing 1321.

[0220] Although the present invention has been described above using the embodiments as examples, the present invention is not limited to the embodiments. Various modifications can be made to the details specifically described in the embodiments within the scope of the claims.

[0221] In the first, fourth to sixth embodiments, the operation mode may be the automatic switching mode only, in which case the operation mode changeover switch 312 and the operation mode display LED 313 may be omitted.

[0222] The motor current, motor rotation speed, motor torque, battery current, saw blade rotation speed, saw blade torque, time, various voltages (inverter voltage, rated voltage, allowable voltage, etc.), rated capacity, current ranges and time thresholds for each winding switching condition and overcurrent protection activation condition, etc., which are given as specific numerical values ​​in the embodiments, do not in any way limit the scope of the invention and can be changed as desired to suit the required specifications.

[0223] The working machine of the present invention is not limited to a portable circular saw, but may be other types of cutting machines such as a bench circular saw, a rotary band saw, a jigsaw, a saber saw (reciprocating saw), a brush cutter, etc. The working machine of the present invention may also be a grinding machine having a grinding tip tool such as a grinder, a polishing machine having a polishing tip tool such as a sander or a polisher, a cutting machine having a cutting tip tool such as a plane, a trimmer or a router, a drilling machine having a drilling tip tool such as a drill, a hammer or an earth auger, a tightening machine having a tightening tip tool such as an impact driver, an impact wrench, a driver drill, a shear wrench, a riveter or a rebar tying machine, a crimping machine having a crimping tip tool such as a crimping machine, a bending machine having a bending tip tool such as a rebar bender, or a driving machine having a driving tip tool such as a nail gun or a tacker.

[0224] 1 to 5...Work machine, 50...Calculation unit (control unit), 51...Control power supply circuit (control circuit voltage supply circuit), 52...Current detection circuit (motor current detection circuit), 53...Switch operation detection circuit, 54...Battery type detection circuit, 55...Voltage detection circuit (battery voltage detection circuit), 56...Control signal circuit (control signal output circuit), 57...Rotation position detection circuit (rotor position detection circuit), 58...Rotation speed detection circuit, 59...Operation mode detection circuit, 61...Lighting LED drive circuit, 62...Lighting LED, 63...Hall IC (magnetic sensor) sensor), 64...inverter circuit, 65...detection resistor, 66...LD detection circuit, 67...battery cell, 68...protection IC (battery side control unit), 69...battery temperature detection circuit, 70...thermistor (temperature detection element), 71...circuit temperature detection circuit, 72...upper switching element, 73...lower switching element, 74...control circuit voltage detection circuit, 75...display LED drive circuit, 76...winding switching operation output circuit, 306...trigger switch, 307...battery pack, 309...saw blade, 311...control board, 312...operation Operation mode selector switch, 313...operation mode display LED, 314...light mode selector switch, 315...light mode display LED, 316...operation panel, 317...light mode display LED, 320...housing, 321...motor housing, 322...handle housing, 323...battery mounting section, 324...intermediate housing, 325...gear case (saw cover), 327...battery connection terminal, 328...cover member, 340...motor, 341...motor shaft, 342...rotor core , 343...rotor magnet (permanent magnet), 344...stator core, 345...stator coil, 346...yoke portion, 347...teeth (teeth portion), 1306...trigger switch, 1307...battery pack, 1309...saw blade, 1311...control board, 1316...operation panel, 1320...housing, 1321...motor housing, 1322...handle housing, 1323...battery mounting portion, 1324...hook, 1325...gear case (saw cover), 1326...sub-handle.

Claims

1. a motor having a plurality of windings; A drive unit that drives the motor; a connection switching unit configured to be able to switch a connection state of the plurality of windings between a high rotation speed connection state in which the plurality of windings are connected to each other so as to have a high rotation speed characteristic, and a high torque connection state in which the plurality of windings are connected to each other so as to have a high torque characteristic; An operation unit for operating start and stop of the motor; A control unit that controls the drive unit and the connection switching unit; A work machine having the control unit is capable of executing a connection switching control for switching from the high rotation speed connection state to the high torque connection state, and is configured to start the connection switching control in a state in which a rotation speed of the motor is higher than a no-load rotation speed of the high torque connection state; The control unit is configured to stop driving the motor when executing the connection switching control, and to resume driving the motor immediately after executing the connection switching control. A work machine characterized by:

2. A motor having a plurality of windings; A drive unit that drives the motor; a connection switching unit configured to be able to switch a connection state of the plurality of windings between a high rotation speed connection state in which the plurality of windings are connected to each other so as to have a high rotation speed characteristic, and a high torque connection state in which the plurality of windings are connected to each other so as to have a high torque characteristic; An operation unit for operating start and stop of the motor; A control unit that controls the drive unit and the connection switching unit; A work machine having the control unit is capable of executing a connection switching control for switching from the high rotation speed connection state to the high torque connection state, and is configured to start the connection switching control in a state in which a rotation speed of the motor is higher than a no-load rotation speed of the high torque connection state; The control unit is when a workload applied to the motor increases and reaches or exceeds a first winding switching threshold while the connection state is the high rotation speed connection state, the connection state is switched to the high torque connection state; When the work load decreases and becomes equal to or less than a second winding switching threshold while the connection state is the high torque connection state, the connection state is switched to the high rotation speed connection state, the first winding switching threshold is greater than the second winding switching threshold; A work machine characterized by:

3. A motor having a plurality of windings; A drive unit that drives the motor; a connection switching unit configured to be able to switch from one connection state to the other of a high rotation speed connection state in which the plurality of windings are connected to each other so as to have a high rotation speed characteristic and a high torque connection state in which the plurality of windings are connected to each other so as to have a high torque characteristic; An operation unit for operating start and stop of the motor; A control unit that controls the drive unit and the connection switching unit; A work machine having the control unit is capable of executing connection switching control for switching from the one connection state to the other connection state, and is configured to switch the drive unit to a drive stop state in which supply of drive power to the motor is stopped, and to switch the connection switching unit to a connection cut state in which the plurality of windings are cut off from each other, in the connection switching control; The control unit is configured to stop driving the motor when executing the connection switching control, and to resume driving the motor immediately after executing the connection switching control. A work machine characterized by:

4. A work machine according to any one of claims 1 to 3, The no-load rotation speed in the high torque connection state is the rotation speed of the motor at the intersection of an extension line of the characteristic line of the high torque connection state and a straight line with a torque of 0 in a graph showing the relationship between the rotation speed and torque of the motor as a characteristic line with the horizontal axis being torque and the vertical axis being rotation speed. A work machine characterized by:

5. A work machine according to any one of claims 1 to 3, The control unit is configured to complete the connection switching control when the rotation speed of the motor becomes equal to or lower than the no-load rotation speed of the high torque connection state. A work machine characterized by:

6. A work machine according to any one of claims 1 to 3, The control unit is configured to switch the drive unit to a drive stop state in which a supply of drive power to the motor is stopped, and to switch the connection switching unit to a connection cut-off state in which at least a part of the plurality of windings is cut off, in the connection switching control. A work machine characterized by:

7. The work machine according to claim 6, The control unit is configured to, in the connection switching control, switch the connection switching unit from the high rotation speed connection state to the connection cut-off state, or switch the connection cut-off state to the high torque connection state when the drive unit is in the drive stop state. A work machine characterized by:

8. A work machine according to any one of claims 1 to 3, the control unit is configured to be able to execute the connection switching control in response to an increase in a workload applied to the motor, and is configured to execute an overload protection control, which stops the motor when the workload satisfies an overload protection condition, only after the connection switching control and not before the connection switching control; The control unit is When the work machine is pressed against a counter member with a first pressing force or when the work machine is pressed against a counter member with a first work load increase rate, the connection switching control is executed, When the working machine is pressed against a counter material with a second pressing force larger than the first pressing force, or when the working machine is pressed against a counter material with a second workload increase rate larger than the first workload increase rate, the overload protection control is executed immediately after the connection switching control to stop the motor. A work machine characterized by:

9. A work machine according to any one of claims 1 to 3, A mode selection unit operable by an operator is provided, The control unit, in response to an operation of the mode selection unit by an operator, a first mode configured to be able to execute the connection switching control for switching the connection state from the high rotation speed connection state to the high torque connection state in response to an increase in the workload applied to the motor; a second mode configured to maintain the connection in the high torque connection state; The motor is driven in any one of the modes. A work machine characterized by:

10. A work machine according to claim 8, a first winding switching threshold, which is a threshold of the workload when the connection state is switched from the high rotation speed connection state to the high torque connection state, is equal to or greater than 2 / 3 of an overload protection threshold, which is a threshold of the workload when the motor is stopped by the overload protection control, or is equal to the overload protection threshold; A work machine characterized by:

11. The work machine according to claim 8, a battery mounting section into which a battery pack serving as a power source for the motor can be mounted, the battery pack outputting a discharge stop signal when a discharge current exceeds a battery-side overcurrent protection threshold; The control unit stops the motor when a current flowing through the motor exceeds a main body side overcurrent protection threshold, The battery-side overcurrent protection threshold is greater than the main body-side overcurrent protection threshold. A work machine characterized by:

12. a motor having a plurality of windings that is driven by power supplied from a power source; a connection switching unit that can switch a connection method of a plurality of windings of the motor between a first connection method for high rotation and a second connection method for high torque; A control unit that controls the motor and the connection switching unit; a housing that accommodates the motor, the connection switching unit, and the control unit; a detection unit that detects a physical quantity that changes due to the driving of the motor or a type of the power source; A work machine equipped with the control unit is configured to execute connection switching control for switching the connection method from the first connection method to the second connection method when a predetermined winding switching condition is satisfied, the detection value detected by the detection unit includes a workload applied to the motor, The winding switching condition includes a duration of any one of the workloads equal to or greater than a load threshold being equal to or greater than a time threshold that varies depending on the magnitude of the workload. A work machine characterized by:

13. The work machine according to claim 12, The control unit is switching the wiring method from the first wiring method to the second wiring method when a state in which a first work load is applied to the motor continues for a first time period; and switching the wiring method from the first wiring method to the second wiring method when a state in which a second workload larger than the first workload is applied to the motor continues for a second time period shorter than the first time period. A work machine characterized by:

14. The work machine according to claim 12, The detected values ​​include a workload applied to the motor and a temperature of a heating element that constitutes the working machine, the winding switching condition includes a duration of any one of the workloads equal to or greater than a load threshold being equal to or greater than a time threshold, and a combination of the workload and the time threshold varies depending on the temperature; A work machine characterized by:

15. The work machine according to claim 12, The detected values ​​include a workload applied to the motor and a rated capacity of the power source; the winding switching condition includes a duration of any one of the workloads equal to or greater than a load threshold value being equal to or greater than a time threshold value, and a combination of the workload and the time threshold value differs depending on the rated capacity; A work machine characterized by:

16. The work machine according to claim 12, the winding switching condition is set according to a detection value by the detection unit so that the connection method is switched from the first connection method to the second connection method before overload protection is activated and the motor stops, The overload protection is configured to be performed when a first workload is applied to the motor for a first period of time; the switching of the wiring method is configured to be executed when a second workload continues as the workload for a second period of time; The first workload and the second workload are substantially the same load value or load range, and the second time period is shorter than the first time period; or the first time and the second time are substantially the same time or in a range of times, and the second workload is smaller than the first workload; A work machine characterized by:

17. A work machine according to any one of claims 1 to 3, the control unit is configured to execute the connection switching control so as to switch from the high rotation speed connection state to the high torque connection state when a workload applied to the motor increases, The control unit is configured to switch to the high torque connection state and apply an electric brake to the motor when the operating unit is turned off in the high rotation speed connection state. A work machine characterized by:

18. A work machine according to claim 17, The drive unit has a plurality of switching elements, the connection switching unit has a high rotation side switching unit that is turned on when the high rotation speed connection state is reached, and a high torque side switching unit that is turned on when the high torque connection state is reached, The control unit is configured to execute any one of the following controls: A work machine characterized by: (1) When the operation unit is turned off in the high rotation speed connection state and the operation unit is switched to the high torque connection state to apply an electric brake to the motor, the plurality of switching elements and the high rotation side switching unit are turned off, the high torque side switching unit is then turned on, and then some of the plurality of switching elements are turned on. (2) When the operation unit is turned off in the high rotation speed connection state and the motor is switched to the high torque connection state to electrically brake the motor, the multiple switching elements and the high rotation side switching unit are turned off, some of the multiple switching elements are turned on, and then the high torque side switching unit is turned on. (3) When the operating unit is turned off in the high rotation speed wiring state, an electric brake is applied to the motor to reduce the rotation speed of the motor to a predetermined rotation speed or less, and then the state is switched to the high torque wiring state to apply an electric brake to the motor.

19. A work machine according to any one of claims 1 to 3, the control unit is configured to execute the connection switching control so as to switch from the high rotation speed connection state to the high torque connection state when a workload applied to the motor increases, The control unit is configured to apply an electric brake to the motor while the motor is in the high rotation speed connection state when the operation unit is turned off in the high rotation speed connection state to stop the motor. A work machine characterized by: