Work equipment

Abstract

To provide a work machine that can reduce the number of switches while offering three or more types of wiring methods. [Solution] The switch section for delta connection (switches S1-S3) changes its on / off state before and after switching between connection methods 1 and 2 (delta connection, star connection), but does not change its on / off state before and after switching between connection methods 2 and 3 (star connection, star series connection). The switch section for star connection (switches S4, S5) changes its on / off state both before and after switching between connection methods 1 and 2, and before and after switching between connection methods 2 and 3. The switch section for star series connection (switches S6, S7) changes its on / off state before and after switching between connection methods 2 and 3, but does not change its on / off state before and after switching between connection methods 1 and 2.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a working machine that switches the winding connection method of a motor from a first connection method to a second connection method in response to an increase in the working load applied to the motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It would be convenient if many characteristics could be obtained with a single motor. However, in order to enable switching between many connection methods to obtain many characteristics, there is a problem that the number of switches for switching the connection method increases. When applied to a working machine, the enlargement of the working machine becomes a problem.

[0005] An object of the present invention is to provide a working machine capable of suppressing the number of switches while having three or more connection methods.

Means for Solving the Problems

[0006] One aspect of the present invention is a working machine capable of switching the winding connection method of a motor to at least three connection methods, a U-phase winding having a first U-phase coil, a second U-phase coil, and a U-phase midpoint connecting one end of the first U-phase coil and one end of the second U-phase coil, a V-phase winding having a first V-phase coil, a second V-phase coil, and a V-phase midpoint connecting one end of the first V-phase coil and one end of the second V-phase coil, A W-phase winding having a first W-phase coil, a second W-phase coil, and a W-phase intermediate point connecting one end of the first W-phase coil and one end of the second W-phase coil, A switch section for delta connection, A first U-phase to V-phase switch that connects or disconnects the U-phase midpoint and the other end of the first V-phase coil, A first V-phase to W-phase switch that connects or disconnects the V-phase midpoint and the other end of the first W-phase coil, A switch section for delta connection having a first W-phase-U-phase switch that connects or disconnects the W-phase midpoint and the other end of the first U-phase coil, A switch section for star connection, A second U-phase to V-phase switch that connects or disconnects the U-phase midpoint and the V-phase midpoint, A star-connection switch section having a second V-phase to W-phase switch that connects or disconnects the V-phase midpoint and the W-phase midpoint, A switch section for star series connection, A third U-phase to V-phase switch connects or disconnects the other end of the second U-phase coil and the other end of the second V-phase coil, A star series connection switch section having a third V-phase to W-phase switch that connects or disconnects the other end of the second V-phase coil and the other end of the second W-phase coil, A control unit that controls the delta connection switch section, the star connection switch section, and the star series connection switch section, Equipped with, The control unit, A delta connection mode is achieved by connecting the aforementioned delta connection switch section and disconnecting the aforementioned star connection switch section and the aforementioned star series connection switch section. A star connection mode is achieved by connecting the star connection switch section and disconnecting the delta connection switch section and the star series connection switch section. The system includes a star-series connection mode in which the star-series connection switch section is connected and the delta connection switch section and the star connection switch section are disconnected. This is a work machine characterized by the following features.

[0007] Another aspect of the present invention is, A work machine capable of switching the motor winding connection method to at least three connection methods, A U-phase winding having a first U-phase coil, a second U-phase coil, and a U-phase midpoint connecting one end of the first U-phase coil and one end of the second U-phase coil, A V-phase winding having a first V-phase coil, a second V-phase coil, and a V-phase midpoint connecting one end of the first V-phase coil and one end of the second V-phase coil, A W-phase winding having a first W-phase coil, a second W-phase coil, and a W-phase intermediate point connecting one end of the first W-phase coil and one end of the second W-phase coil, A switch section for delta connection, A first U-phase to V-phase switch that connects or disconnects the U-phase midpoint and the other end of the first V-phase coil, A first V-phase to W-phase switch that connects or disconnects the V-phase midpoint and the other end of the first W-phase coil, A switch section for delta connection having a first W-phase-U-phase switch that connects or disconnects the W-phase midpoint and the other end of the first U-phase coil, A switch section for delta series connection, A second U-phase to V-phase switch connects or disconnects the other end of the second U-phase coil and the other end of the first V-phase coil, A second V-phase to W-phase switch that connects or disconnects the other end of the second V-phase coil and the other end of the first W-phase coil, A switch unit for delta series connection having a second W-phase to U-phase switch that connects or disconnects the other end of the second W-phase coil and the other end of the first U-phase coil, A switch section for star series connection, A third U-phase to W-phase switch connects or disconnects the other end of the second U-phase coil and the other end of the second W-phase coil, A star series connection switch section having a third V-phase to W-phase switch that connects or disconnects the other end of the second V-phase coil and the other end of the second W-phase coil, A control unit that controls the aforementioned delta connection switch section, the aforementioned delta series connection switch section, and the aforementioned star series connection switch section, comprising the control unit a delta connection mode in which the delta connection switch section is connected and the delta series connection switch section and the star series connection switch section are cut off; a delta series connection mode in which the delta series connection switch section is connected and the delta connection switch section and the star series connection switch section are cut off; a star series connection mode in which the star series connection switch section is connected and the delta connection switch section and the delta series connection switch section are cut off, and a working machine characterized by this.

[0008] Another aspect of the present invention is a working machine capable of switching the wiring method of a motor to at least a first wiring method, a second wiring method, and a third wiring method, comprising a wiring switching section for switching the wiring method, the wiring switching section a first switch section having a plurality of switches whose on and off states change before and after switching between the first wiring method and the second wiring method, while the on and off states do not change before and after switching between the second wiring method and the third wiring method; a second switch section having a plurality of switches whose on and off states change before and after switching between the second wiring method and the third wiring method, while the on and off states do not change before and after switching between the first wiring method and the second wiring method; a third switch section having a plurality of switches whose on and off states change both before and after switching between the first wiring method and the second wiring method and before and after switching between the second wiring method and the third wiring method, and having a working machine characterized by this.

[0009] The present invention may be expressed as "electric working machine", "electric tool", "electrical equipment", etc., and those expressed as such are also effective as aspects of the present invention.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a working machine that can suppress the number of switches while having three or more connection methods.

Brief Description of the Drawings

[0011] [Figure 1] Side view of the working machine 1 according to Embodiment 1. [Figure 2] Circuit block diagram of the working machine 1. [Figure 3] Circuit diagram showing the connection method of the winding 25 of the motor 20 of the working machine 1. [Figure 4] Explanatory diagram of an example when the switches S1 to S7 in FIG. 3 are constituted by semiconductor switching elements. [Figure 5] (A) is a graph showing the relationship between the torque and the rotational speed of the motor 20 of the working machine 1. (B) is an external view of the operation panel 316 of the working machine 1. (C) is a table summarizing the relationship between the operation mode and the mode display of the working machine 1. [Figure 6] Control flowchart of the working machine 1. [Figure 7] Circuit diagram showing the connection method of the winding of the motor of the working machine according to Embodiment 2. [Figure 8] Control flowchart of the working machine according to Embodiment 2. [Figure 9] Table summarizing the correspondence relationship between the combination of connection methods and the required number of switches when switching three connection methods with a 6-slot motor. [Figure 10] Circuit diagram showing the connection method of the winding of the motor of the working machine according to Embodiment 3. [Figure 11] Circuit diagram showing the connection method of the winding of the motor of the working machine according to Embodiment 4. [Figure 12] Circuit diagram showing the connection method of the winding of the motor of the working machine according to Embodiment 4.

Modes for Carrying Out the Invention

[0012] (Embodiment 1) Figure 1 shows a side view of the work implement 1 according to Embodiment 1. The work implement 1 is a cordless circular saw powered by a detachably mounted battery pack 17, and can perform wood cutting and other tasks using a saw blade 19 (tip tool) that rotates in response to the operation of a trigger switch 15. The mechanical configuration of the work implement 1 is well known, so its explanation is omitted here.

[0013] Figure 2 is a circuit block diagram of the work machine 1.

[0014] The motor 20 is, for example, an inner-rotor type brushless motor, and includes a rotor 23 and windings 25 that constitute the stator. The windings 25 are provided for each of the three phases U, V, and W. The wiring of the windings 25 will be described later.

[0015] A capacitor 68 and an inverter circuit 64 are provided in parallel between the output terminals of the battery pack 17. The inverter circuit 64 consists of six switching elements Q1 to Q6 that are connected in a three-phase bridge configuration to the three-phase windings 25 of U, V, and W. A resistor 65 is provided in the path of the current flowing through the windings 25 of the motor 20 (hereinafter referred to as "motor current").

[0016] The control power supply circuit 51 converts the output voltage of the battery pack 17 into a power supply voltage for the calculation unit 70, etc., and supplies it to the calculation unit 70, etc. The current detection circuit 52 detects the motor current by the voltage across the resistor 65 and transmits it to the calculation unit 70. The switch operation detection circuit 53 detects the operation of the trigger switch 15 and transmits it to the calculation unit 70. The voltage detection circuit 55 detects the output voltage of the battery pack 17 and transmits it to the calculation unit 70. The temperature detection circuit 67 detects the temperature of the inverter circuit 64 by the output signal of a temperature sensor 66 such as a thermistor located near the inverter circuit 64 and transmits it to the calculation unit 70.

[0017] The control signal circuit 56 outputs a control signal that controls the on / off state of each switching element of the inverter circuit 64, in accordance with the control of the calculation unit 70. The rotational position detection circuit 57 detects the position of the rotor 23 (hereinafter referred to as "rotor position") by the output signals of three Hall ICs 63 (magnetic sensors) and transmits it to the calculation unit 70. The Hall IC 63 is an example of a position detection element that outputs a signal corresponding to the rotor position. In this embodiment, as an example, three Hall ICs 63 are arranged in the circumferential direction of the motor 20 at an electrical angle of 60 degrees apart.

[0018] The rotation speed detection circuit 58 detects the rotation speed of the motor 20 based on the output signal from the rotation position detection circuit 57 and transmits it to the calculation unit 70. The operation mode detection circuit 59 detects the operation of the operation mode switch 60 by the user and transmits it to the calculation unit 70. The lighting LED drive circuit 61 drives the lighting LED 62 according to the control of the calculation unit 70.

[0019] The calculation unit 70 is a control unit that includes a microcontroller and the like, and controls the overall operation of the work machine 1. When the trigger switch 15 is turned on, the calculation unit 70 drives the motor 20 through the control of the inverter circuit 64 (switching control of switching elements Q1 to Q6). The calculation unit 70 performs commutation control, which controls the inverter circuit 64 to switch the supply of power to the three phases U, V, and W according to the rotor position. The calculation unit 70 drives the motor 20 in the operating mode (operating mode) corresponding to the operation of the operating mode switch 60. The calculation unit 70 detects the motor current by the voltage across the resistor 65. The calculation unit 70 can detect the work load applied to the motor 20 by the motor current.

[0020] Figures 3(A) to 3(C) are circuit diagrams showing three different wiring methods for winding 25.

[0021] Coils U1 and U2 correspond to the first U-phase coil and the second U-phase coil, respectively. The U-phase midpoint P1 connects one end of coil U1 and one end of coil U2. The other end of coil U1 is the U-phase voltage input and is connected to the U-phase signal output terminal of the inverter circuit 64 shown in Figure 2, i.e., the interconnection point of switching elements Q1 and Q4.

[0022] The V1 and V2 coils correspond to the first V-phase coil and the second V-phase coil, respectively. The V-phase midpoint P2 connects one end of the V1 coil to one end of the V2 coil. The other end of the V1 coil is the V-phase voltage input and is connected to the V-phase signal output terminal of the inverter circuit 64 shown in Figure 2, i.e., the interconnection point of the switching elements Q2 and Q5.

[0023] The W1 and W2 coils correspond to the first W-phase coil and the second W-phase coil, respectively. The W-phase midpoint P3 connects one end of the W1 coil to one end of the W2 coil. The other end of the W1 coil is the W-phase voltage input and is connected to the W-phase signal output terminal of the inverter circuit 64 shown in Figure 2, i.e., the interconnection point of the switching elements Q3 and Q6.

[0024] Switch S1 is a first U-phase to V-phase switch that connects or disconnects the U-phase midpoint P1 to the other end of the V1 coil. Switch S2 is a first V-phase to W-phase switch that connects or disconnects the V-phase midpoint P2 to the other end of the W1 coil. Switch S3 is a first W-phase to U-phase switch that connects or disconnects the W-phase midpoint P3 to the other end of the U1 coil. Switches S1 to S3 constitute the switch section for delta connection.

[0025] Switch S4 is a second U-phase to V-phase switch that connects or disconnects the U-phase midpoint P1 and the V-phase midpoint P2. Switch S5 is a second V-phase to W-phase switch that connects or disconnects the V-phase midpoint P2 and the W-phase midpoint P3. Switches S4 and S5 constitute the switch section for star connection.

[0026] Switch S6 is a third U-phase to V-phase switch that connects or disconnects the other end of the U2 coil and the other end of the V2 coil. Switch S7 is a third V-phase to W-phase switch that connects or disconnects the other end of the V2 coil and the other end of the W2 coil. Switches S6 and S7 constitute the switch section for star series connection.

[0027] The calculation unit 70 shown in Figure 2 switches the winding configuration of the winding 25 by controlling the delta connection switch section, the star connection switch section, and the star series connection switch section, that is, by controlling the on / off state of switches S1 to S7. The calculation unit 70 has a delta connection mode, a star connection mode, and a star series connection mode.

[0028] In delta connection mode, the calculation unit 70 connects the delta connection switch section (switches S1 to S3) and disconnects the star connection switch section (switches S4 and S5) and the star series connection switch section (switches S6 and S7), as shown in Figure 3(A). As a result, one end of the U1 coil is connected to the other end of the V1 coil, one end of the V1 coil is connected to the other end of the W1 coil, and one end of the W1 coil is connected to the other end of the U1 coil, resulting in a delta connection using the U1, V1, and W1 coils. The delta connection using the U1, V1, and W1 coils corresponds to a partially driven state of the delta connection. The partially driven state is a state in which only a portion of the windings of each phase are used.

[0029] In star connection mode, the calculation unit 70 connects the star connection switch section (switches S4, S5) and disconnects the delta connection switch section (switches S1~S3) and the star series connection switch section (switches S6, S7), as shown in Figure 3(B). As a result, one end of the U1 coil, V1 coil, and W1 coil are connected to each other at the neutral point (points P1~P3), and the connection method becomes a star connection with the U1 coil, V1 coil, and W1 coil. The star connection with the U1 coil, V1 coil, and W1 coil corresponds to a partial drive state of the star connection.

[0030] In star series connection mode, the calculation unit 70 connects the star series connection switch section (switches S6, S7) and disconnects the delta connection switch section (switches S1~S3) and the star connection switch section (switches S4, S5), as shown in Figure 3(C). As a result, the other ends of the U2 coil, V2 coil, and W2 coil are connected to each other at the neutral point P5, and the connection method becomes a star series connection of the U1 coil, U2 coil, V1 coil, V2 coil, W1 coil, and W2 coil, i.e., a fully series driven star connection. The fully series driven state is a state in which all windings of each phase are connected in series with each other and used.

[0031] The switch section for delta connection (switches S1 to S3) constitutes a first switch section in which the on and off states change before and after switching between connection method 1 (delta connection) and connection method 2 (star connection), while the on and off states do not change before and after switching between connection method 2 (star connection) and connection method 3 (star series connection).

[0032] The star connection switch section (switches S4, S5) constitutes a third switch section (common switch section) whose on and off states change both before and after switching between connection method 1 (delta connection) and connection method 2 (star connection), and before and after switching between connection method 2 (star connection) and connection method 3 (star series connection).

[0033] The star series connection switch section (switches S6, S7) constitutes a second switch section in which the on and off states change before and after switching between connection method 2 (star connection) and connection method 3 (star series connection), while the on and off states do not change before and after switching between connection method 1 (delta connection) and connection method 2 (star connection).

[0034] Switches S1 to S7 are connection switching sections for switching the connection method of the winding 25. They are composed of relays, for example, but may also be composed of semiconductor switching elements. This point will be explained below.

[0035] Figure 4 is an explanatory diagram illustrating an example where switches S1 to S7 in Figure 3 are composed of semiconductor switching elements.

[0036] Switch S3 can be composed of, for example, N-channel FETs Q11 and Q12 with their sources connected to each other. Switches S1 and S2 can be composed in the same way as switch S3. Switches S4 and S5 can be composed of, for example, N-channel FETs Q13 to Q15 with their sources connected to each other. Switches S6 and S7 can be composed of, for example, N-channel FETs Q16 to Q18 with their sources connected to each other. In this way, by connecting two or three semiconductor switching elements with different polarities of body diodes, it is possible to connect and disconnect the current path in the same way as a relay. In this embodiment, switches S1 to S7 can be composed of 12 semiconductor switching elements.

[0037] Figure 5(A) is a graph showing the relationship between the torque and rotational speed of the motor 20 of the work machine 1.

[0038] The high-speed, low-torque mode corresponds to wiring configuration 1 (delta connection) in Figure 3(A). The medium-speed, medium-torque mode corresponds to wiring configuration 2 (star connection) in Figure 3(B). The low-speed, high-torque mode corresponds to wiring configuration 3 (star series connection) in Figure 3(C).

[0039] The characteristic curve shown as a solid line in Figure 5(A) corresponds to the automatic switching mode in which the calculation unit 70 automatically switches the wiring method according to the workload, i.e., the torque of the motor 20 (hereinafter referred to as "motor torque"). In automatic switching mode, the calculation unit 70 switches the operating mode (wiring method) in the following order in response to an increase in motor torque: high-speed / low-torque mode, medium-speed / medium-torque mode, and low-speed / high-torque mode. In automatic switching mode, the calculation unit 70 switches the operating mode (wiring method) in the following order in response to a decrease in motor torque: low-speed / high-torque mode, medium-speed / medium-torque mode, and high-speed / low-torque mode.

[0040] In automatic switching mode, the switch between high-speed / low-torque mode and medium-speed / medium-torque mode occurs when the motor torque is lower than the intersection of the characteristic curves for high-speed / low-torque mode and medium-speed / medium-torque mode in order to suppress the activation of overcurrent protection. For the same reason, the switch between medium-speed / medium-torque mode and low-speed / high-torque mode occurs when the motor torque is lower than the intersection of the characteristic curves for medium-speed / medium-torque mode and low-speed / high-torque mode. Whether or not overcurrent protection activates at the intersection of the characteristic curves depends on the specifications of the motor 20. If the specifications do not allow overcurrent protection to activate at the intersection of the characteristic curves, the operating mode may be switched at the intersection of the characteristic curves.

[0041] Figure 5(B) is an external view of the control panel 316 of the work implement 1. Figure 5(C) is a table summarizing the relationship between the operating modes of the work implement 1 and the mode display.

[0042] The control panel 316 includes an operating mode selection switch 312, an operating mode indicator LED 313, a light mode switching switch 314, and light mode indicator LEDs 315 and 317.

[0043] The operating mode selection switch 312 is a mode selection unit for the operator to select the operating mode of the work machine 1. In addition to the automatic switching mode described above, the operating modes include, for example, a high-speed / low-torque fixed mode that fixes the motor to a high-speed / low-torque mode regardless of the motor torque, a medium-speed / medium-torque fixed mode that fixes the motor to a medium-speed / medium-torque mode regardless of the motor torque, and a low-speed / high-torque fixed mode that fixes the motor to a low-speed / high-torque mode regardless of the motor torque.

[0044] The operating mode indicator LED 313 is a mode indicator that displays the current operating mode according to the control of the calculation unit 70. As shown in Figure 5(C), for example, it is off in automatic switching mode, lit in high-speed / low-torque fixed mode, blinks slowly in medium-speed / medium-torque fixed mode, and blinks quickly in low-speed / high-torque fixed mode. Alternatively, an LED may be provided for each operating mode, and the LED corresponding to the current operating mode may be selectively lit.

[0045] The light mode selector switch 314 is a light mode selector that allows the operator to switch the light mode of the work machine 1. The light modes include, for example, a constant illumination mode and a trigger operation illumination mode in which the light illuminates only when the trigger switch 15 is pulled. The light mode indicator LED 315 lights up in the trigger operation illumination mode and turns off in the constant illumination mode. The light mode indicator LED 317 lights up in the constant illumination mode and turns off in the trigger operation illumination mode.

[0046] Figure 6 is a control flowchart of the work machine 1.

[0047] When the trigger switch 15 is turned on (S101), the calculation unit 70 enters high-speed, low-torque mode and sets the winding 25 connection method to connection method 1 (delta connection) as shown in Figure 3(A) (S103). The calculation unit 70 starts driving the inverter circuit 64 (S105) and sets the electrical advance angle of the voltage applied to the winding 25 (hereinafter referred to as "winding applied voltage") to 40 degrees and the energizing angle to 120 degrees (S107). The calculation unit 70 performs soft-start control by increasing the duty cycle of the winding applied voltage (hereinafter referred to as "duty cycle") from 0% to +7% / 10ms (S109), and switches to constant speed control when the motor speed reaches the target speed (S111). If the workload does not exceed threshold A (No. in S113), the calculation unit 70 continues constant speed control with delta connection. Furthermore, in constant speed control, after the duty cycle reaches 100% due to an increase in workload, the motor speed decreases in accordance with the high-speed / low-torque mode characteristic curve shown in Figure 5(A) as the workload increases.

[0048] When the workload exceeds threshold A (Yes in S113), the calculation unit 70 stops driving the inverter circuit 64 (S115), enters medium speed / medium torque mode, and sets the winding 25 connection method to connection method 2 (star connection) as shown in Figure 3(B) (S117). The calculation unit 70 starts driving the inverter circuit 64 (S119) and immediately sets the duty cycle to 100% (S121). The settings for the electrical advance angle and energization angle are the same as in S107 (not shown).

[0049] When the workload exceeds threshold B (Yes in S123), the calculation unit 70 stops driving the inverter circuit 64 (S125), enters low-speed / high-torque mode, and sets the winding 25 connection method to connection method 3 (star series connection) as shown in Figure 3(C) (S127). The calculation unit 70 starts driving the inverter circuit 64 (S129) and immediately sets the duty cycle to 100% (S131). The settings for the electrical advance angle and energization angle are the same as in S107 (not shown).

[0050] When the trigger switch 15 is turned off (S133), the calculation unit 70 stops driving the inverter circuit 64 (S135).

[0051] Although not shown in the diagram, in low-speed / high-torque mode, when the workload falls below threshold B', the calculation unit 70 stops driving the inverter circuit 64, switches to medium-speed / medium-torque mode, sets the winding 25 connection method to connection method 2 (star connection) as shown in Figure 3(B), and restarts driving the inverter circuit 64 with a duty cycle of 100%. Also, in medium-speed / medium-torque mode, when the workload falls below threshold A', the calculation unit 70 stops driving the inverter circuit 64, switches to high-speed / low-torque mode, sets the winding 25 connection method to connection method 1 (delta connection) as shown in Figure 3(A), and restarts driving the inverter circuit 64 with a duty cycle of 100%. From the viewpoint of suppressing frequent switching of the connection method, thresholds A' and B' are preferably set to values ​​lower than thresholds A and B, respectively.

[0052] This embodiment provides the following effects and advantages.

[0053] (1) The star connection switch section (switches S4, S5) constitutes a third switch section (common switch section) whose on and off states change both before and after switching between connection method 1 (delta connection) and connection method 2 (star connection), and before and after switching between connection method 2 (star connection) and connection method 3 (star series connection). Therefore, compared to a configuration without a common switch section, the number of switches required to switch between the three types of connection methods can be reduced, thereby suppressing the increase in product size. Specifically, in a configuration with two coils per phase, switching between connection method 1 (delta connection), connection method 2 (star connection), and connection method 3 (star series connection) is possible with a reduced number of switches: 7 for relays and 12 for semiconductor switching elements.

[0054] (2) Switch S4 (second U-phase to V-phase switch) is provided at a position to connect or disconnect the U-phase midpoint P1 and the V-phase midpoint P2, and switch S5 (second V-phase to W-phase switch) is provided at a position to connect or disconnect the V-phase midpoint P2 and the W-phase midpoint P3. Therefore, switches S4 and S5 can be used as a common switch section, and the increase in the number of switches can be suppressed.

[0055] (Embodiment 2) Figures 7(A) to 7(C) are circuit diagrams showing three types of wiring methods for the motor windings of the work machine according to Embodiment 2. The following explanation will focus on the differences from Embodiment 1.

[0056] The U-phase midpoint P11 connects one end of coil U1 to one end of coil U2. The V-phase midpoint P12 connects one end of coil V1 to one end of coil V2. The W-phase midpoint P13 connects one end of coil W1 to one end of coil W2.

[0057] Switch S11 is a first U-phase to V-phase switch that connects or disconnects the U-phase midpoint P11 to the other end of the V1 coil. Switch S13 is a first V-phase to W-phase switch that connects or disconnects the V-phase midpoint P12 to the other end of the W1 coil. Switch S15 is a first W-phase to U-phase switch that connects or disconnects the W-phase midpoint P13 to the other end of the U1 coil. Switches S11, S13, and S15 constitute the switch section for delta connection.

[0058] Switch S12 is a second U-phase to V-phase switch that connects or disconnects the other end of the U2 coil to the other end of the V1 coil. Switch S14 is a second V-phase to W-phase switch that connects or disconnects the other end of the V2 coil to the other end of the W1 coil. Switch S16 is a second W-phase to U-phase switch that connects or disconnects the other end of the W2 coil to the other end of the U1 coil. Switches S12, S14, and S16 constitute the switch section for delta series connection.

[0059] Switch S17 is a third U-phase to W-phase switch that connects or disconnects the other end of the U2 coil and the other end of the W2 coil. Switch S18 is a third V-phase to W-phase switch that connects or disconnects the other end of the V2 coil and the other end of the W2 coil. Switches S17 and S18 constitute the switch section for star series connection.

[0060] The calculation unit 70 shown in Figure 2 switches the winding configuration of the winding 25 by controlling the delta connection switch unit, the delta series connection switch unit, and the star series connection switch unit, that is, by controlling the on / off state of switches S11 to S18. The calculation unit 70 has a delta connection mode, a delta series connection mode, and a star series connection mode.

[0061] In delta connection mode, the calculation unit 70 connects the delta connection switch section (switches S11, S13, S15) and disconnects the delta series connection switch section (switches S12, S14, S16) and the star series connection switch section (switches S17, S18), as shown in Figure 7(A). As a result, one end of the U1 coil is connected to the other end of the V1 coil, one end of the V1 coil is connected to the other end of the W1 coil, and one end of the W1 coil is connected to the other end of the U1 coil, resulting in a delta connection using the U1, V1, and W1 coils, i.e., a partially driven delta connection.

[0062] In delta series connection mode, the calculation unit 70 connects the delta series connection switch section (switches S12, S14, S16) and disconnects the delta connection switch section (switches S11, S13, S15) and the star series connection switch section (switches S17, S18), as shown in Figure 7(B). As a result, the other end of coil U2 is connected to the other end of coil V1, the other end of coil V2 is connected to the other end of coil W1, and the other end of coil W2 is connected to the other end of coil U1. The connection method is a delta series connection of coils U1, U2, V1, V2, W1, and W2, i.e., a fully series-driven delta connection.

[0063] In star series connection mode, the calculation unit 70 connects the star series connection switch section (switches S17, S18) and disconnects the delta connection switch section (switches S11, S13, S15) and the delta series connection switch section (switches S12, S14, S16), as shown in Figure 7(C). As a result, the other ends of the U2 coil, V2 coil, and W2 coil are connected to each other at the neutral point P15, and the connection method becomes a star series connection with the U1 coil, U2 coil, V1 coil, V2 coil, W1 coil, and W2 coil, i.e., a fully series-driven star connection.

[0064] The switch section for delta connection (switches S11, S13, S15) constitutes a first switch section in which the on and off states change before and after switching between connection method 1 (delta connection) and connection method 2 (delta series connection), while the on and off states do not change before and after switching between connection method 2 (delta series connection) and connection method 3 (star series connection).

[0065] The switch section for delta series connection (switches S12, S14, S16) constitutes a third switch section (common switch section) whose on and off states change both before and after switching between connection method 1 (delta connection) and connection method 2 (delta series connection), and before and after switching between connection method 2 (delta series connection) and connection method 3 (star series connection).

[0066] The star series connection switch section (switches S17, S18) constitutes a second switch section in which the on and off states change before and after switching between connection method 2 (delta series connection) and connection method 3 (star series connection), while the on and off states do not change before and after switching between connection method 1 (delta connection) and connection method 2 (delta series connection).

[0067] Switches S11 to S18 are connection switching sections for switching the winding connection method, and are composed of relays, for example, but may also be composed of semiconductor switching elements. In this case, switches S11 to S16 can be composed of two FETs Q11 and Q12, respectively, similar to switch S3 shown in Figure 4. Switches S17 and S18 can be composed of three FETs Q16 to Q18, similar to switches S6 and S7 shown in Figure 4. In this embodiment, switches S11 to S18 can be composed of 15 semiconductor switching elements.

[0068] Figure 8 is a control flowchart of the work machine according to Embodiment 2. This flowchart differs from the flowchart of Embodiment 1 shown in Figure 6 in that S117 (star connection, 3 coils used) is replaced with S117a (delta connection, 6 coils used), but otherwise they are the same. The explanation of Figure 6 in this specification will be explained by replacing "Figure 3" with "Figure 7" and "Connection Method 2 (star connection)" with "Connection Method 2 (delta series connection)" to explain Figure 8.

[0069] According to this embodiment, switch S12 (second U-phase to V-phase switch) is provided at a position to connect or disconnect the other end of the U2 coil and the other end of the V1 coil, switch S14 (second V-phase to W-phase switch) is provided at a position to connect or disconnect the other end of the V2 coil and the other end of the W1 coil, and switch S16 (second W-phase to U-phase switch) is provided at a position to connect or disconnect the other end of the W2 coil and the other end of the U1 coil. Therefore, switches S12, S14, and S16 can be used as a common switch section, and the increase in the number of switches can be suppressed. Specifically, in a configuration with two coils per phase, it is possible to switch between connection method 1 (delta connection), connection method 2 (delta series connection), and connection method 3 (star series connection) with a suppressed number of switches of 8 in the case of relays and 15 in the case of semiconductor switching elements. In relation to Embodiment 1, although the number of switches increases, the wiring method 2 changes from a star connection to a delta series connection, which increases the number of coils used in wiring method 2 and improves the output of wiring method 2.

[0070] (Further explanation of Embodiments 1 and 2) Figure 9 is a table summarizing the relationship between the combination of wiring methods and the number of switches required when switching between three wiring methods with a 6-slot motor.

[0071] For a 6-slot motor, there are six different wiring methods as follows: • Delta parallel connection of 6 coils (2 per phase) (Connection #1) • Delta connection of 3 coils (connection #2) • Star-parallel connection of 6 coils (2 per phase) (Connection #3) • Star connection of 3 coils (connection #4) • Delta series connection of 6 coils (2 per phase) (Connection #5) • Star series connection of 6 coils (2 per phase) (Connection #6)

[0072] Switching from connection #6 to connection #5 increases the motor speed under no-load conditions (hereinafter referred to as "no-load speed") by 1.7 times. Switching from connection #5 to connection #3 or #4 increases the no-load speed by 1.16 times. Switching between connection #3 and #4 does not change the no-load speed. Switching from connection #3 to connection #1 or #2 increases the no-load speed by 1.7 times. Switching between connection #1 and #2 does not change the no-load speed.

[0073] Therefore, switching between connections #1 and #2, or between connections #3 and #4, does not produce any difference in operating modes. Also, switching from connection #5 to connections #3 and #4 only increases the no-load rotation speed by 1.16 times, so switching between connections #3 to #5 does not produce a significant difference in operating modes. Therefore, the inventor considered combinations of connection methods consisting of one of connections #1 and #2, one of connections #3 to #5, and connection #6. The combinations corresponding to this are combinations A, B, E, F, H, and I in the table in Figure 9.

[0074] Of combinations A, B, E, F, H, and I, combinations B and F are the only ones in which the number of switches can be reduced by providing a common switch section. Combination B corresponds to Embodiment 2, and combination F corresponds to Embodiment 1.

[0075] (Embodiment 3) Figures 10(A) to (D) are circuit diagrams showing four types of wiring methods for the motor windings of the work machine according to Embodiment 3. The following explanation will focus on the differences from Embodiment 1. The circuit shown in Figure 10 is the same as the circuit of Embodiment 1 shown in Figure 3, with the addition of coils U3, V3, W3, and switches S8 and S9.

[0076] One end of coil U3 is connected to the other end of coil U2. One end of coil V3 is connected to the other end of coil V2. One end of coil W3 is connected to the other end of coil W2. Switch S8 connects or disconnects the other end of coil U3 and the other end of coil V3. Switch S9 connects or disconnects the other end of coil V3 and the other end of coil W3.

[0077] The on / off states of switches S1 to S7 in Figures 10(A) to (C) are the same as those of switches S1 to S7 in Figures 3(A) to (C). Switches S8 and S9 are off in Figures 10(A) to (C).

[0078] In ultra-low speed / ultra-high torque mode, the calculation unit 70 connects switches S8 and S9 and disconnects switches S1 to S7, as shown in connection method 4 in Figure 10(D). This results in a star series connection with 9 coils (3 coils per phase), i.e., a fully series-driven star connection. Note that connection method 1 shown in Figure 10(A) is a delta connection with 3 coils (1 coil per phase), i.e., a single-drive delta connection. Connection method 2 shown in Figure 10(B) is a star connection with 3 coils (1 coil per phase), i.e., a single-drive star connection. Connection method 3 shown in Figure 10(C) is a star series connection with 6 coils (2 coils per phase), i.e., a partially series-driven star connection.

[0079] In this embodiment, switches S4 and S5 constitute a common switch section whose on and off states change both before and after switching between wiring methods 1 and 2, and before and after switching between wiring methods 2 and 3. Switches S6 and S7 constitute a common switch section whose on and off states change both before and after switching between wiring methods 2 and 3, and before and after switching between wiring methods 3 and 4.

[0080] According to this embodiment, the number of switches required to enable switching between four types of wiring methods can be reduced, thereby preventing the product from becoming larger.

[0081] (Embodiment 4) Figures 11(A), (B) and 12(A), (B) are circuit diagrams showing the winding connection method of the motor of the work machine according to Embodiment 4. The following explanation will focus on the differences from Embodiment 2. The circuits shown in Figures 11 and 12 are the same as the circuits of Embodiment 2 shown in Figure 7, with the addition of coils U3, V3, W3, and switches S21 to S23.

[0082] One end of coil U3 is connected to the other end of coil U2. One end of coil V3 is connected to the other end of coil V2. One end of coil W3 is connected to the other end of coil W2. Switch S12 connects or disconnects the other end of coil U3 to the other end of coil V1. Switch S14 connects or disconnects the other end of coil V3 to the other end of coil W1. Switch S16 connects or disconnects the other end of coil W3 to the other end of coil U1.

[0083] Switch S21 connects or disconnects the interconnection point P21 of coils U2 and U3 from the other end of coil V1. Switch S22 connects or disconnects the interconnection point P22 of coils V2 and V3 from the other end of coil W1. Switch S23 connects or disconnects the interconnection point P23 of coils W2 and W3 from the other end of coil U1.

[0084] The on / off states of switches S11-S18 in Figures 11(A) and 12(A) and (B) are the same as those of switches S11-S18 in Figures 7(A) and (C). Switches S21-S23 are off in Figures 11(A) and 12(A) and (B).

[0085] In the medium speed / medium torque mode, the calculation unit 70 connects switches S21 to S23 and disconnects switches S11 to S18, as shown in connection method 2 in Figure 11(B). This results in a delta series connection with 6 coils (2 coils per phase), i.e., a partially series-driven delta connection. Note that connection method 1 shown in Figure 11(A) is a delta connection with 3 coils (1 coil per phase), i.e., a single-drive delta connection. Connection method 3 shown in Figure 12(A) is a delta series connection with 9 coils (3 coils per phase), i.e., a fully series-driven delta connection. Connection method 4 shown in Figure 12(B) is a star series connection with 9 coils (3 coils per phase), i.e., a fully series-driven star connection.

[0086] In this embodiment, switches S21 to S23 constitute a common switch section whose on and off states change both before and after switching between wiring methods 1 and 2, and before and after switching between wiring methods 2 and 3. Switches S12, S14, and S16 constitute a common switch section whose on and off states change both before and after switching between wiring methods 2 and 3, and before and after switching between wiring methods 3 and 4.

[0087] According to this embodiment, the number of switches required to enable switching between four types of wiring methods can be reduced, thereby preventing the product from becoming larger.

[0088] Although the present invention has been described above using embodiments as examples, the present invention is not limited to these embodiments. Various modifications are possible to each of the matters specifically described in the embodiments within the scope of the claims.

[0089] The work machine of the present invention is not limited to the circular saw exemplified in the embodiments, but may be other types such as a table saw or a grinder.

[0090] By similarly repeating the modifications made in Embodiments 3 and 4 compared to Embodiments 1 and 2, it is possible to further increase the number of wiring configurations while suppressing an increase in the number of switches. In general, it becomes possible to switch between n+1 types of wiring configurations with n coils per phase using a reduced number of switches.

[0091] The names U-phase, V-phase, and W-phase are merely for convenience to distinguish between the three different phases and do not need to correspond to the actual U-phase, V-phase, and W-phase in the product. Furthermore, the names U-phase, V-phase, and W-phase do not need to be used in the actual product. [Explanation of Symbols]

[0092] 1...Work implement, 15...Trigger switch, 17...Battery pack, 19...Saw blade (cutting tool), 20...Motor, 23...Rotor, 25...Winding, 51...Control power supply circuit, 52...Current detection circuit, 53...Switch operation detection circuit, 55...Voltage detection circuit, 56...Control signal circuit, 57...Rotation position detection circuit, 58...Rotation speed detection circuit, 59...Operation mode detection circuit, 60...Operation mode switch, 61...Illumination LED drive circuit, 62...Illumination LED, 63...Hall IC (position detection element), 64...Inverter circuit, 65...Resistor, 66...Temperature sensor, 67...Temperature detection circuit, 68...Capacitor, 70...Calculation unit (control unit), 312...Operation mode selection switch, 313...Operation mode indicator LED, 314...Light mode switching switch, 315...Light mode indicator LED, 316...Operation panel, 317...Light mode indicator LED.

Claims

1. A work machine capable of switching the motor winding connection method to at least three connection methods, A U-phase winding having a first U-phase coil, a second U-phase coil, and a U-phase intermediate point connecting one end of the first U-phase coil and one end of the second U-phase coil, A V-phase winding having a first V-phase coil, a second V-phase coil, and a V-phase midpoint connecting one end of the first V-phase coil and one end of the second V-phase coil, A W-phase winding having a first W-phase coil, a second W-phase coil, and a W-phase intermediate point connecting one end of the first W-phase coil and one end of the second W-phase coil, A switch section for delta connection, A first U-phase-V-phase switch that connects or disconnects the U-phase midpoint and the other end of the first V-phase coil, A first V-phase to W-phase switch that connects or disconnects the V-phase midpoint and the other end of the first W-phase coil, A switch section for delta connection having a first W-phase-U-phase switch that connects or disconnects the W-phase midpoint and the other end of the first U-phase coil, A switch section for star connection, A second U-phase to V-phase switch that connects or disconnects the U-phase midpoint and the V-phase midpoint, A star-connection switch section having a second V-phase to W-phase switch that connects or disconnects the V-phase midpoint and the W-phase midpoint, A switch section for star series connection, A third U-phase to V-phase switch connects or disconnects the other end of the second U-phase coil and the other end of the second V-phase coil, A star series connection switch section having a third V-phase-W-phase switch that connects or disconnects the other end of the second V-phase coil and the other end of the second W-phase coil, A control unit that controls the delta connection switch section, the star connection switch section, and the star series connection switch section, Equipped with, The control unit, A delta connection mode is achieved by connecting the aforementioned delta connection switch section and disconnecting the aforementioned star connection switch section and the aforementioned star series connection switch section. A star connection mode is achieved by connecting the star connection switch section and disconnecting the delta connection switch section and the star series connection switch section. The system includes a star-series connection mode in which the star-series connection switch section is connected and the delta connection switch section and the star connection switch section are disconnected. A work machine characterized by the following features.

2. A work machine capable of switching the motor winding connection method to at least three connection methods, A U-phase winding having a first U-phase coil, a second U-phase coil, and a U-phase intermediate point connecting one end of the first U-phase coil and one end of the second U-phase coil, A V-phase winding having a first V-phase coil, a second V-phase coil, and a V-phase midpoint connecting one end of the first V-phase coil and one end of the second V-phase coil, A W-phase winding having a first W-phase coil, a second W-phase coil, and a W-phase intermediate point connecting one end of the first W-phase coil and one end of the second W-phase coil, A switch section for delta connection, A first U-phase-V-phase switch that connects or disconnects the U-phase midpoint and the other end of the first V-phase coil, A first V-phase to W-phase switch that connects or disconnects the V-phase midpoint and the other end of the first W-phase coil, A switch section for delta connection having a first W-phase-U-phase switch that connects or disconnects the W-phase midpoint and the other end of the first U-phase coil, A switch section for delta series connection, A second U-phase to V-phase switch connects or disconnects the other end of the second U-phase coil and the other end of the first V-phase coil, A second V-phase to W-phase switch connects or disconnects the other end of the second V-phase coil and the other end of the first W-phase coil, A switch unit for delta series connection having a second W-phase to U-phase switch that connects or disconnects the other end of the second W-phase coil and the other end of the first U-phase coil, A switch section for star series connection, A third U-phase to W-phase switch connects or disconnects the other end of the second U-phase coil and the other end of the second W-phase coil, A star series connection switch section having a third V-phase-W-phase switch that connects or disconnects the other end of the second V-phase coil and the other end of the second W-phase coil, A control unit that controls the aforementioned delta connection switch section, the aforementioned delta series connection switch section, and the aforementioned star series connection switch section, Equipped with, The control unit, A delta connection mode is achieved by connecting the aforementioned delta connection switch section and disconnecting the aforementioned delta series connection switch section and the aforementioned star series connection switch section. A delta-series connection mode is achieved by connecting the aforementioned delta-series connection switch section and disconnecting the aforementioned delta-series connection switch section and the aforementioned star-series connection switch section. The system includes a star-series connection mode in which the star-series connection switch section is connected and the delta connection switch section and the delta-series connection switch section are disconnected. A work machine characterized by the following features.

3. A work machine capable of switching the motor connection method to at least a first connection method, a second connection method, and a third connection method, The system includes a wiring switching unit for switching the aforementioned wiring method, The aforementioned wiring switching unit is A first switch unit having multiple switches whose on and off states change before and after switching between the first and second wiring methods, while whose on and off states do not change before and after switching between the second and third wiring methods, A second switch unit having multiple switches whose on and off states change before and after switching between the second and third wiring methods, while whose on and off states do not change before and after switching between the first and second wiring methods, A third switch unit having multiple switches whose on and off states change both before and after switching between the first wiring method and the second wiring method, and before and after switching between the second wiring method and the third wiring method, Having, A work machine characterized by the following features.

4. A work machine according to claim 3, The motor has two or more windings for each of the U-phase, V-phase, and W-phase. It is configured to be switchable between a fully series drive state in which all windings of each phase are connected in series and used, and a partially drive state in which only some of the windings of each phase are used. A work machine characterized by the following features.

5. A work machine according to claim 4, The first wiring configuration is the partial drive state of the delta connection, The second wiring configuration is the partially driven state of the star connection, The third connection method is the star connection with all components driven in series. A work machine characterized by the following features.

6. A work machine according to claim 5, The first switch unit connects or disconnects the midpoint of the winding of each phase to the voltage input of the other phases. The third switch unit connects or disconnects the intermediate points of each phase. A work machine characterized by the following features.

7. A work machine according to claim 4, The first wiring configuration is the partial drive state of the delta connection, The second wiring configuration is the state of all series connections in the delta connection, The third wiring configuration is the star connection with all connections in series. A work machine characterized by the following features.

8. A work machine according to claim 7, The first switch unit connects or disconnects the midpoint of the winding of each phase to the voltage input of the other phases. The third switch unit connects or disconnects the end of each phase opposite to the voltage input section to the voltage input section of the other phase. A work machine characterized by the following features.

9. A work machine according to any one of claims 1 to 8, The motor is a 3-phase, 6-slot motor. A work machine characterized by the following features.

10. A work machine according to any one of claims 1 to 8, The motor is a 3-phase, 9-slot motor. A work machine characterized by the following features.

11. A work machine according to claim 4, Each of the U-phase, V-phase, and W-phase has three windings. The aforementioned wiring method can be switched to a fourth wiring method. The fourth switch section has a plurality of switches whose state changes when switching between the third wiring method and the fourth wiring method, It is possible to switch between the aforementioned fully series drive state, the aforementioned partially drive state in which two of the three windings are connected in series, and the aforementioned partially drive state in which only one winding is used. A work machine characterized by the following features.

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