Work equipment

Abstract

To provide a work machine that allows for changing the motor characteristics with a simple and compact configuration. [Solution] The motor 20 has star-connected multi-phase windings 25u, 25v, and 25w. The inverter circuit 71 has three switching elements Q1 to Q3 connected to the power line and three switching elements Q4 to Q6 connected to the ground line. The half-bridge circuit 72 has a switching element Q7 connected to the power line and a switching element Q8 connected to the ground line, with a neutral point N connected to the interconnection between switching elements Q7 and Q8. It is possible to switch between a high-speed mode in which current flows through the windings 25u, 25v, and 25w via the half-bridge circuit 72 and a high-torque mode in which current flows through the windings 25u, 25v, and 25w without going through the half-bridge circuit 72.

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 connection method of the motor winding from delta connection to star connection 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] The working machine of Patent Document 1 has 5 to 6 relays for switching the connection method, so in order to suppress the increase in size, it is necessary to devise the arrangement of the relays, and there are products that are difficult to apply because they are likely to increase in size.

[0005] An object of the present invention is to provide a working machine capable of changing the characteristics of a motor with a simple and size-reduced configuration.

Means for Solving the Problems

[0006] One aspect of the present invention is a motor having a plurality of phases of windings connected in star, with one end of each phase of the winding connected to each other at the neutral point, an inverter circuit having three first upper switching elements connected to a power line and three first lower switching elements connected to a ground line, and applying a driving voltage to the other end of each phase of the winding, A half-bridge circuit comprising a second upper switching element connected to the power line and a second lower switching element connected to the ground line, wherein the neutral point is connected to the interconnection between the second upper switching element and the second lower switching element, A control unit that controls the inverter circuit and the half-bridge circuit, A work machine equipped with, The control unit has a high-speed mode in which current is supplied to the motor via the half-bridge circuit, and a high-torque mode in which current is supplied to the motor without going through the half-bridge circuit. This is a work machine characterized by the following features.

[0007] The present invention may also be described as "electric work machine," "power tool," "electric equipment," etc., and such descriptions are also valid embodiments of the present invention. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a work machine that can change the characteristics of the motor with a simple and compact configuration. [Brief explanation of the drawing]

[0009] [Figure 1] A perspective view of the work machine 1 according to this embodiment, seen from the upper right side. [Figure 2] A perspective view of the work machine 1, seen from the upper left side, with a portion of the housing 1320 removed. [Figure 3] Circuit block diagram of work machine 1. [Figure 4] Figure 3 shows the drive circuit 64 and windings 25u, 25v, and 25w extracted. [Figure 5] Time chart of commutation control in high torque mode of implement 1. [Figure 6] Time chart of commutation control in high-speed mode of implement 1. [Figure 7] Control flowchart for work machine 1. [Figure 8](A) is a diagram showing the current flow in the first state of Phase 0 in high-speed mode. (B) is a diagram showing the current flow in the second state of Phase 0 in high-speed mode. [Figure 9] (A) is a diagram showing the current flow in the third state of Phase 1 of the high-speed mode. (B) is a diagram showing the current flow in the fourth state of Phase 1 of the high-speed mode. [Figure 10] (A) is a diagram showing the current flow in the first state of Phase 2 of the high-speed mode. (B) is a diagram showing the current flow in the second state of Phase 2 of the high-speed mode. [Figure 11] (A) is a diagram showing the current flow in the third state of Phase 3 of the high-speed mode. (B) is a diagram showing the current flow in the fourth state of Phase 3 of the high-speed mode. [Figure 12] (A) is a diagram showing the current flow in the first state of Phase 4 of the high-speed mode. (B) is a diagram showing the current flow in the second state of Phase 4 of the high-speed mode. [Figure 13] (A) is a diagram showing the current flow in the third state of Phase 5 in high-speed mode. (B) is a diagram showing the current flow in the fourth state of Phase 5 in high-speed mode. [Figure 14] (A) is a diagram showing the current flow in phase 0 of the high torque mode. (B) is a diagram showing the current flow in phase 1 of the high torque mode. [Figure 15] (A) is a diagram showing the current flow in phase 2 of the high torque mode. (B) is a diagram showing the current flow in phase 3 of the high torque mode. [Figure 16] (A) is a diagram showing the current flow in phase 4 of the high torque mode. (B) is a diagram showing the current flow in phase 5 of the high torque mode. [Figure 17] (A) is a diagram showing the current flow in phase 0 of a delta connection. (B) is a diagram showing the current flow in phase 1 of a delta connection. [Figure 18](A) is a diagram showing the flow of current in phase 2 of a delta connection. (B) is a diagram showing the flow of current in phase 3 of a delta connection. [Figure 19] (A) is a diagram showing the flow of current in phase 4 of a delta connection. (B) is a diagram showing the flow of current in phase 5 of a delta connection. [Figure 20] A graph showing the relationship between the product torque of the working machine 1 and the saw blade rotation speed, together with the relationship between the product torque and the saw blade rotation speed in the case of a delta connection.

Embodiments for Carrying Out the Invention

[0010] FIG. 1 is a perspective view of the working machine 1 according to the embodiment as viewed from the upper right side. FIG. 2 is a perspective view of the working machine 1 as viewed from the upper left side with a part of the housing 1320 removed. As shown in FIG. 1, the front-rear, up-down, and left-right directions perpendicular to each other of the working machine 1 are defined. The working machine 1 is a portable circular saw. The working machine 1 includes a housing 1320.

[0011] The housing 1320 is, for example, a resin molded body, and includes a motor housing 1321 that houses the motor 20 and the like, a handle housing 1322 that a user grips, and a battery mounting portion 1323.

[0012] The motor housing 1321 is a cylindrical portion whose central axis is substantially parallel to the left-right direction. The handle housing 1322 extends obliquely in the front-rear and up-down directions above the right part of the motor housing 1321. A trigger switch 15 for a user to instruct the start and stop of the motor 20 is provided at the upper end of the handle housing 1322.

[0013] A metal gear case 1325 (saw cover) is connected to the right side of the handle housing 1322. The gear case 1325 houses a speed reduction mechanism (not shown) and covers the upper half of the saw blade 1309.

[0014] The battery mounting section 1323 extends to the left from the rear end of the handle housing 1322 and detachably mounts the battery pack 17, which provides the power supply. The work implement 1 operates on the power of the battery pack 17. The work implement 1 has an operation panel 60 above the battery mounting section 1323. The user can switch the operating mode of the work implement 1 using the operation panel 60.

[0015] A hook 1324 is attached to the front of the handle housing 1322, allowing the work implement 1 to be hooked onto the hooking part. The hook 1324 is rotatably attached to the housing 1320. A sub-handle 1326 is provided above the motor housing 1321. The sub-handle 1326 is the part that the user grips during operation.

[0016] The work machine 1 has a motor 20 inside a motor housing 1321. The rotation of the motor 20 is reduced by a reduction mechanism in a gear case 1325 and transmitted to the saw blade 1309.

[0017] The work machine 1 has a control board 1311 inside the motor housing 1321. The control board 1311 is equipped with various circuits such as the calculation unit 70 and the control power supply circuit 51 shown in Figure 3. The control board 1311 is also equipped with the drive circuit 64 shown in Figures 3 and 4.

[0018] Figure 3 is a circuit block diagram of the work machine 1. Figure 4 is a diagram showing the drive circuit 64 and windings 25u, 25v, and 25w extracted from Figure 3.

[0019] The motor 20 is, for example, an inner-rotor type brushless motor and includes a rotor 23 and three-phase (multiple-phase) windings 25u, 25v, and 25w that constitute the stator. The windings 25u, 25v, and 25w are connected in a star configuration (Y configuration), with one end connected to the other at the neutral point N. The combination of the number of poles and slots of the motor 20 is arbitrary, with 4 poles and 6 slots being one example.

[0020] A capacitor 68 and a drive circuit 64 are connected in parallel between the output terminals of the battery pack 17. As shown in Figure 4, the drive circuit 64 includes an inverter circuit 71 and a half-bridge circuit 72.

[0021] The inverter circuit 71 consists of six switching elements Q1 to Q6 connected in a three-phase bridge configuration, and applies a drive voltage to the other end of the windings 25u, 25v, and 25w. Switching elements Q1 to Q3 are first upper switching elements and are connected to a power line extending from the positive terminal of the battery pack 17. Switching elements Q4 to Q6 are first lower switching elements and are connected to a ground line extending from the negative terminal of the battery pack 17.

[0022] Switching elements Q1 and Q4 are connected in series between the power line and the ground line, and the interconnection points of switching elements Q1 and Q4 are connected to the other end of winding 25u. Switching elements Q2 and Q5 are connected in series between the power line and the ground line, and the interconnection points of switching elements Q2 and Q5 are connected to the other end of winding 25v. Switching elements Q3 and Q6 are connected in series between the power line and the ground line, and the interconnection points of switching elements Q3 and Q6 are connected to the other end of winding 25w.

[0023] The half-bridge circuit 72 includes a switching element Q7 as a second upper switching element connected to the power line and a switching element Q8 as a second lower switching element connected to the ground line, with a neutral point N connected to the interconnection between switching elements Q7 and Q8.

[0024] The control power supply circuit 51 converts the output voltage of the battery pack 17 (hereinafter referred to as "battery voltage") 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 battery current by the voltage across a resistor 65 provided in the path of the output current of the battery pack 17 (hereinafter referred to as "battery current"), and transmits it to the calculation unit 70. Note that the majority of the battery current is the current flowing through the windings 25u, 25v, and 25w of the motor 20 (hereinafter referred to as "motor current"), and the battery current is substantially equal to the motor current. The battery current is proportional to the torque applied to the motor 20 and the saw blade 1309. 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 drive circuit 64 by the output signal of a temperature sensor 66 such as a thermistor provided near the drive circuit 64, and transmits it to the calculation unit 70.

[0025] The control signal circuit 56 outputs a control signal that controls the on / off state of each switching element in the drive circuit 64, in accordance with the control of the calculation unit 70. The rotation position detection circuit 57 detects the position of the rotor 23 (hereinafter referred to as "rotor position"), i.e., the rotation position of the motor 20, based on the output signals of three Hall ICs 63 (magnetic sensors), and transmits this 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.

[0026] 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 panel operation detection circuit 59 detects user operation of the operation panel 60 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.

[0027] 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. The calculation unit 70 detects the torque applied to the motor 20 and saw blade 1309 based on the battery current. When the trigger switch 15 is turned on, the calculation unit 70 drives the motor 20 through the control of the inverter circuit 71 and the half-bridge circuit 72 (switching control of switching elements Q1 to Q8). The calculation unit 70 performs commutation control, which controls the inverter circuit 71 and the half-bridge circuit 72 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 an operating mode (operating mode) corresponding to the operation of the operation panel 60. The calculation unit 70 has a high rotation mode in which current is supplied to the motor 20 via the half-bridge circuit 72, and a high torque mode in which current is supplied to the motor 20 without going through the half-bridge circuit 72.

[0028] Figure 5 is a time chart of the commutation control (commutation control A) in the high-torque mode of the work machine 1, showing the time changes in the on / off states of switching elements Q1 to Q8. The commutation control in high-torque mode is a square wave control with an energizing angle of 120 degrees, and repeats the following six phases. The phases switch every 60 degrees in electrical angle. Note that switching elements Q7 and Q8 are always off throughout all phases. Phase 0: Switching elements Q1 and Q5 are on, and the other switching elements are off. Phase 1: Switching elements Q3 and Q5 are turned on, while the other switching elements are turned off. Phase 2: Switching elements Q3 and Q4 are turned on, while the other switching elements are turned off. Phase 3: Switching elements Q2 and Q4 are turned on, while the other switching elements are turned off. Phase 4: Switching elements Q2 and Q6 are turned on, while the other switching elements are turned off. Phase 5: Switching elements Q1 and Q6 are turned on, while the other switching elements are turned off.

[0029] Figure 6 is a time chart of the commutation control (commutation control B) in the high-speed mode of the work machine 1, showing the time changes of the on / off states of switching elements Q1 to Q8. The commutation control in high-speed mode repeats the following six phases. The phases switch every 60 degrees in electrical angle. Note that in each phase, switching elements Q7 and Q8 are driven by complementary PWM signals and are never turned on simultaneously. Phase 0: Switching elements Q1, Q5, and Q6 are on, switching element Q7 is PWM controlled with a 33% duty cycle, switching element Q8 is PWM controlled with a 67% duty cycle, and the other switching elements are off. Phase 1: Switching elements Q1, Q3, and Q5 are on, switching element Q7 is PWM controlled with a 67% duty cycle, switching element Q8 is PWM controlled with a 33% duty cycle, and the other switching elements are off. Phase 2: Switching elements Q3, Q4, and Q5 are on, switching element Q7 is PWM controlled with a 33% duty cycle, switching element Q8 is PWM controlled with a 67% duty cycle, and the other switching elements are off. Phase 3: Switching elements Q2, Q3, and Q4 are on, switching element Q7 is PWM controlled with a 67% duty cycle, switching element Q8 is PWM controlled with a 33% duty cycle, and the other switching elements are off. Phase 4: Switching elements Q2, Q4, and Q6 are on, switching element Q7 is PWM controlled with a 33% duty cycle, switching element Q8 is PWM controlled with a 67% duty cycle, and the other switching elements are off. Phase 5: Switching elements Q1, Q2, and Q6 are on, switching element Q7 is PWM controlled with a 67% duty cycle, switching element Q8 is PWM controlled with a 33% duty cycle, and the other switching elements are off.

[0030] In the high-speed mode commutation control shown in Figure 6, phases 0, 2, and 4 are first periods in which one of the switching elements Q1 to Q3 and two of the switching elements Q4 to Q6 are turned on, and phases 1, 3, and 5 are second periods in which two of the switching elements Q1 to Q3 and one of the switching elements Q4 to Q6 are turned on. The first and second periods alternate every 60 degrees in electrical angle. The calculation unit 70 alternately turns on the switching elements Q7 and Q8 at predetermined duty cycles in each of the first and second periods (performing complementary PWM control on the switching elements Q7 and Q8). A duty cycle of 33% (1 / 3) is an example of the first duty cycle. A duty cycle of 67% (2 / 3) is an example of the second duty cycle.

[0031] In both high-torque mode and high-speed mode, if the motor 20 has 4 poles and 6 slots, completing one rotation through phases 0 to 5 will cause the motor 20 to complete half a rotation in mechanical angle.

[0032] Figure 7 is a control flowchart of the work machine 1.

[0033] The calculation unit 70 starts the motor 20 when the trigger switch 15 is turned ON (S1). The calculation unit 70 initially controls the drive of the motor 20 in high-speed mode (S3). Specifically, the calculation unit 70 repeatedly performs phases 0 to 5 of the commutation control B shown in Figure 6 for switching elements Q1 to Q6, and also performs complementary PWM control shown in Figure 6 for switching elements Q7 and Q8. In the complementary PWM control, the duty cycle is 33% for switching element Q7 and 67% for switching element Q8 in phases 0, 2, and 4, and 67% for switching element Q7 and 33% for switching element Q8 in phases 1, 3, and 5. The calculation unit 70 continues the high-speed mode unless the battery current is above the high-load threshold (No. S5).

[0034] The calculation unit 70 switches to high torque mode and controls the drive of the motor 20 (S7) if the battery current is above the high load threshold in high rotation mode (Yes in S5). Specifically, the calculation unit 70 repeatedly performs phases 0 to 5 of commutation control A shown in Figure 5 for switching elements Q1 to Q6, and keeps switching elements Q7 and Q8 off at all times. Although not shown in the figure, the calculation unit 70 may also switch to high rotation mode if the battery current is below the low load threshold, which is smaller than the high load threshold, in high torque mode.

[0035] The following describes the current flow in each phase of the high-speed mode.

[0036] (High-speed mode, Phase 0) Figures 8(A) and 8(B) show the current flow in the first and second states of Phase 0 in the high-speed mode, respectively. In Phase 0, switching elements Q1, Q5, and Q6 are ON.

[0037] In the first state, switching element Q7 is ON and switching element Q8 is OFF during Phase 0. In the first state, current flows through the power line, switching element Q7, neutral point N, windings 25V and 25W, switching elements Q5 and Q6, and the ground line. Note that since point U and neutral point N are at the same potential, no current flows through winding 25u even when switching element Q1 is ON. The same applies to the following phases.

[0038] In the second state, switching element Q7 is off and switching element Q8 is on during phase 0. In the second state, current flows through the power line, switching element Q1, winding 25u, neutral point N, switching element Q8, and ground line.

[0039] The calculation unit 70 is configured to alternately switch between a first state and a second state in phase 0. The proportion of the first state in phase 0 is the duty cycle of the PWM control of switching element Q7, i.e., 33%. The proportion of the second state in phase 0 is the duty cycle of the PWM control of switching element Q8, i.e., 67%. Therefore, if the potential of the power line is V+, in phase 0 the potential of the neutral point N is effectively V+ / 3, and the potential of point U (the other end of winding 25u) is effectively 2V+ / 3. That is, in phase 0, windings 25V and 25W are driven at effectively V+ / 3, and winding 25u is driven at effectively 2V+ / 3.

[0040] (High-speed mode, Phase 1) Figures 9(A) and (B) show the current flow in the third and fourth states of Phase 1 of the high-speed mode, respectively. In Phase 1, switching elements Q1, Q3, and Q5 are ON.

[0041] The third state is when switching element Q7 is ON and switching element Q8 is OFF in Phase 1. In the third state, current flows through the power line, switching element Q7, neutral point N, winding 25V, switching element Q5, and ground line.

[0042] The fourth state is when switching element Q7 is off and switching element Q8 is on in Phase 1. In the fourth state, current flows through the power line, switching elements Q1 and Q3, windings 25u and 25w, neutral point N, switching element Q8, and ground line.

[0043] The calculation unit 70 is configured to alternately switch between the third state and the fourth state in phase 1. The proportion of the third state in phase 1 is the duty cycle of the PWM control of switching element Q7, i.e., 67%. The proportion of the fourth state in phase 1 is the duty cycle of the PWM control of switching element Q8, i.e., 33%. Therefore, if the potential of the power line is V+, in phase 1 the potential of the neutral point N is effectively 2V+ / 3, and the potentials of points U and W (the other ends of windings 25u and 25w) are effectively V+ / 3. That is, in phase 1, winding 25v is driven at effectively 2V+ / 3, and windings 25u and 25w are driven at effectively V+ / 3.

[0044] (High-speed mode, Phase 2) Figures 10(A) and (B) show the current flow in the first and second states of Phase 2 of the high-speed mode, respectively. In Phase 2, switching elements Q3, Q4, and Q5 are turned on.

[0045] The first state is when switching element Q7 is ON and switching element Q8 is OFF in Phase 2. In the first state, current flows through the following path: power line, switching element Q7, neutral point N, winding 25u, 25V, switching elements Q4 and Q5, and ground line.

[0046] The second state is when switching element Q7 is off and switching element Q8 is on in phase 2. In the second state, current flows through the power line, switching element Q3, winding 25W, neutral point N, switching element Q8, and ground line.

[0047] The calculation unit 70 is configured to alternately switch between the first state and the second state in phase 2. The proportion of the first state in phase 2 is the duty cycle of the PWM control of switching element Q7, i.e., 33%. The proportion of the second state in phase 2 is the duty cycle of the PWM control of switching element Q8, i.e., 67%. Therefore, if the potential of the power line is V+, in phase 2 the potential of the neutral point N is effectively V+ / 3, and the potential of point W (the other end of winding 25w) is effectively 2V+ / 3. That is, in phase 2, windings 25u and 25v are driven at effectively V+ / 3, and winding 25w is driven at effectively 2V+ / 3.

[0048] (High-speed mode, Phase 3) Figures 11(A) and (B) show the current flow in the third and fourth states of Phase 3 of the high-speed mode, respectively. In Phase 3, switching elements Q2, Q3, and Q4 are turned on.

[0049] The third state is when switching element Q7 is ON and switching element Q8 is OFF in Phase 3. In the third state, current flows through the power line, switching element Q7, neutral point N, winding 25u, switching element Q4, and ground line.

[0050] The fourth state is when switching element Q7 is off and switching element Q8 is on in phase 3. In the fourth state, current flows through the power line, switching elements Q2 and Q3, windings 25V and 25W, neutral point N, switching element Q8, and ground line.

[0051] The calculation unit 70 is configured to alternately switch between the third state and the fourth state in phase 3. The proportion of the third state in phase 3 is the duty cycle of the PWM control of switching element Q7, i.e., 67%. The proportion of the fourth state in phase 3 is the duty cycle of the PWM control of switching element Q8, i.e., 33%. Therefore, if the potential of the power line is V+, in phase 3 the potential of the neutral point N is effectively 2V+ / 3, and the potentials of points V and W (the other ends of windings 25V and 25W) are effectively V+ / 3. In other words, in phase 3, winding 25u is driven at effectively 2V+ / 3, and windings 25V and 25W are driven at effectively V+ / 3.

[0052] (High-speed mode, Phase 4) Figures 12(A) and (B) show the current flow in the first and second states of Phase 4 of the high-speed mode, respectively. In Phase 4, switching elements Q2, Q4, and Q6 are turned on.

[0053] The first state is when switching element Q7 is ON and switching element Q8 is OFF in Phase 4. In the first state, current flows through the following path: power line, switching element Q7, neutral point N, windings 25u and 25w, switching elements Q4 and Q6, and ground line.

[0054] The second state is when switching element Q7 is off and switching element Q8 is on in phase 4. In the second state, current flows through the power line, switching element Q2, winding 25V, neutral point N, switching element Q8, and ground line.

[0055] The calculation unit 70 is configured to alternately switch between the first state and the second state in phase 4. The proportion of the first state in phase 4 is the duty cycle of the PWM control of switching element Q7, i.e., 33%. The proportion of the second state in phase 4 is the duty cycle of the PWM control of switching element Q8, i.e., 67%. Therefore, if the potential of the power line is V+, in phase 4 the potential of the neutral point N is effectively V+ / 3, and the potential of point V (the other end of winding 25v) is effectively 2V+ / 3. That is, in phase 4, windings 25u and 25w are driven at effectively V+ / 3, and winding 25v is driven at effectively 2V+ / 3.

[0056] (High-speed mode, Phase 5) Figures 13(A) and (B) show the current flow in the third and fourth states of Phase 5 of the high-speed mode, respectively. In Phase 5, switching elements Q1, Q2, and Q6 are turned on.

[0057] The third state is when switching element Q7 is ON and switching element Q8 is OFF in phase 5. In the third state, current flows through the power line, switching element Q7, neutral point N, winding 25W, switching element Q6, and ground line.

[0058] The fourth state is when switching element Q7 is off and switching element Q8 is on in phase 5. In the fourth state, current flows through the power line, switching elements Q1 and Q2, winding 25u, 25V, neutral point N, switching element Q8, and ground line.

[0059] The calculation unit 70 is configured to alternately switch between the third state and the fourth state in phase 5. The proportion of the third state in phase 5 is the duty cycle of the PWM control of switching element Q7, i.e., 67%. The proportion of the fourth state in phase 5 is the duty cycle of the PWM control of switching element Q8, i.e., 33%. Therefore, if the potential of the power line is V+, in phase 5 the potential of the neutral point N is effectively 2V+ / 3, and the potentials of points U and V (the other ends of windings 25u and 25v) are effectively V+ / 3. That is, in phase 5, winding 25w is effectively driven at 2V+ / 3, and windings 25u and 25v are effectively driven at V+ / 3.

[0060] (High-speed mode, summary) The current flow in the first and second states of phases 0, 2, and 4 of the high-speed mode is comprehensively described as follows: In the first state, current flows through the power line, switching element Q7, neutral point N, two of the three phase windings 25u, 25v, and 25w, two of the switching elements Q4 to Q6, and the ground line. In the second state, current flows through the power line, one of the switching elements Q1 to Q3, a single phase winding of the three phase windings 25u, 25v, and 25w that is different from the winding that was energized in the first state, neutral point N, switching element Q8, and the ground line.

[0061] The current flow in the third and fourth states of phases 1, 3, and 5 of the high-speed mode is comprehensively described as follows: In the third state, current flows through the power line, switching element Q7, neutral point N, one of the three phase windings 25u, 25v, and 25w, one of the switching elements Q4 to Q6, and the ground line. In the fourth state, current flows through the power line, two of the switching elements Q1 to Q3, two of the three phase windings 25u, 25v, and 25w (different from the windings energized in the third state), neutral point N, switching element Q8, and the ground line.

[0062] (High Torque Mode) Figures 14(A), (B), 15(A), (B), and 16(A), (B) show the current flow in phases 0 to 5 of the high-torque mode, respectively.

[0063] As shown in Figure 14(A), in phase 0, switching elements Q1 and Q5 are ON, and current flows through the following path: power line, switching element Q1, winding 25u, neutral point N, winding 25v, switching element Q5, and ground line.

[0064] As shown in Figure 14(B), in Phase 1, switching elements Q3 and Q5 are ON, and current flows through the following path: power line, switching element Q3, winding 25W, neutral point N, winding 25V, switching element Q5, and ground line.

[0065] As shown in Figure 15(A), in phase 2, switching elements Q3 and Q4 are turned on, and current flows through the following path: power line, switching element Q3, winding 25w, neutral point N, winding 25u, switching element Q4, and ground line.

[0066] As shown in Figure 15(B), in phase 3, switching elements Q2 and Q4 are turned on, and current flows through the following path: power line, switching element Q2, winding 25V, neutral point N, winding 25u, switching element Q4, and ground line.

[0067] As shown in Figure 16(A), in phase 4, switching elements Q2 and Q6 are ON, and current flows through the following path: power line, switching element Q2, winding 25V, neutral point N, winding 25W, switching element Q6, and ground line.

[0068] As shown in Figure 16(B), in phase 5, switching elements Q1 and Q6 are ON, and current flows through the following path: power line, switching element Q1, winding 25u, neutral point N, winding 25w, switching element Q6, and ground line.

[0069] (Delta connection) Figures 17(A), (B), 18(A), (B), and 19(A), (B) show the current flow in phases 0 to 5 of the delta connection, respectively. Although the work machine 1 does not have a configuration in which windings 25u, 25v, and 25w are delta connected, the current flow in the delta connection is explained for comparison with the high-speed mode. In the delta connection, the combination of switching elements turned on in each phase is the same as in the high-torque mode. In the delta connection, current flows through all windings 25u, 25v, and 25w in every phase. In each phase, a voltage of V+ is applied to one phase winding, and V+ / 2 is applied to the other two phase windings. For example, in phase 0 shown in Figure 17(A), winding 25u is driven by V+, and windings 25v and 25w are driven by V+ / 2.

[0070] (Comparison of high-speed mode and delta connection) Comparing the high-speed mode phase 0 shown in Figures 8(A) and (B) with the delta-connected phase 0 shown in Figure 17(A), it can be seen that the driving voltages of windings 25u, 25v, and 25w in the high-speed mode phase 0 are 2 / 3 times the driving voltages of windings 25u, 25v, and 25w in the delta-connected phase 0. The same relationship holds for phases 1 to 5. Furthermore, the direction of the current in each phase is also the same in each phase. Therefore, the high-speed mode is substantially equivalent to the case where the battery voltage is 2 / 3 times and windings 25u, 25v, and 25w are delta-connected.

[0071] In a delta connection, the phase impedance is 1 / 3 that of a star connection, making it easier for current to flow through the 25u, 25v, and 25w windings. Therefore, the no-load rotational speed in a delta connection is √3 times that of a star connection. If we consider the high-speed mode as a delta connection with the battery voltage halved, the no-load rotational speed can be increased by approximately 15% compared to the high-torque mode (120-degree square wave control in a star connection), improving work efficiency in the low-load range. However, in the high-speed mode, as with a delta connection, the battery current increases as the load increases, making overload protection more likely to activate. Therefore, using the high-torque mode under high load conditions can provide more power and stability.

[0072] Figure 20 is a graph showing the relationship between product torque and saw blade rotation speed of the work machine 1, along with the relationship in the case of a delta connection. In both the high-speed mode and the delta connection, the system switches to a star connection when the product torque exceeds 5.5 N·m. The reason the saw blade rotation speed is flat at product torques of 1.5 N·m or less is to suppress power consumption in so-called eco mode (constant speed control). A normal mode may also be provided in which the saw blade rotation speed increases in proportion to the decrease in product torque, even at product torques of 1.5 N·m or less. As shown in Figure 20, in high-speed mode, although the saw blade rotation speed is lower than in the delta connection, it is higher than in the star connection in the low-load range, thereby improving work efficiency in the low-load range.

[0073] This embodiment provides the following effects and advantages.

[0074] (1) The calculation unit 70 has a high-speed mode in which current is supplied to the motor 20 (windings 25u, 25v, 25w) via the half-bridge circuit 72, and a high-torque mode in which current is supplied to the motor 20 (windings 25u, 25v, 25w) without going through the half-bridge circuit 72. As a result, the high-speed mode and high-torque mode can be achieved while the windings 25u, 25v, and 25w are connected in a star configuration, that is, the characteristics of the motor 20 can be changed. Therefore, 5 to 6 relays for switching the connections are not required, the product configuration can be simplified and the size can be suppressed. Furthermore, a new connection switching method can be provided that is simple in configuration and suppresses the size increase, rather than switching between star and delta connections.

[0075] (2) The calculation unit 70 is configured to drive the motor 20 in high-speed mode when the load on the motor 20 is small, and to drive the motor 20 in high-torque mode when the load is large. As a result, it is possible to work efficiently at high speed when the load is low, and also obtains tenacity when the load is high, resulting in good workability. In addition, manual mode switching is not required, which improves workability.

[0076] (3) By setting the high-speed mode as shown in Figures 6, 8(A) to 13(B), it is possible to achieve virtually equivalent characteristics to when the battery voltage is 2 / 3 times and the windings 25u, 25v, and 25w are connected in a delta configuration, even though the windings are connected in a star configuration. Therefore, the high-speed mode enables efficient work at a higher saw blade rotation speed than the star configuration (120-degree square wave control) in the low-load range.

[0077] 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.

[0078] The duty cycle, saw blade rotation speed, and other values ​​exemplified as specific numerical values ​​in the embodiments do not limit the scope of the invention in any way and can be arbitrarily changed to suit the required specifications. For example, the first duty cycle and the second duty cycle may be adjusted to any value other than 33% and 67%, respectively, as long as their sum does not exceed 100%, according to the desired characteristics. In this case, by setting the ratio of the first duty cycle to the second duty cycle to 1:2, characteristics similar to those of a delta connection can be achieved.

[0079] The work implement of the present invention may be of a type other than a portable circular saw. Since the characteristics of the motor can be changed without using 5 to 6 relays, the present invention can also be applied to small nail guns and the like. [Explanation of symbols]

[0080] 1...Work implement, 15...Trigger switch, 17...Battery pack, 20...Motor, 23...Rotor, 25u, 25v, 25w...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...Panel operation detection circuit, 60...Operation panel, 61...Illumination LED drive circuit, 62...Illumination LED, 63...Hall IC (position detection element) 64...Drive circuit, 65...Resistor, 66...Temperature sensor, 67...Temperature detection circuit, 68...Capacitor, 70...Calculation unit (control unit), 71...Inverter circuit, 72...Half-bridge circuit, 1309...Saw blade, 1311...Control board, 1320...Housing, 1321...Motor housing, 1322...Handle housing, 1323...Battery mounting section, 1324...Hook, 1325...Gear case (saw cover), 1326...Sub-handle.

Claims

1. A motor having multiple phase windings connected in a star configuration, where one end of each phase winding is connected to the others at the neutral point, An inverter circuit having three first upper switching elements connected to a power line and three first lower switching elements connected to a ground line, and applying a drive voltage to the other end of each phase winding, A half-bridge circuit comprising a second upper switching element connected to the power line and a second lower switching element connected to the ground line, wherein the neutral point is connected to the interconnection between the second upper switching element and the second lower switching element, A control unit that controls the inverter circuit and the half-bridge circuit, A work machine equipped with, The control unit has a high-speed mode in which current is supplied to the motor via the half-bridge circuit, and a high-torque mode in which current is supplied to the motor without going through the half-bridge circuit. A work machine characterized by the following features.

2. A work machine according to claim 1, The control unit is configured to drive the motor in the high-speed mode when the load on the motor is small, and to drive the motor in the high-torque mode when the load is large. A work machine characterized by the following features.

3. A work machine according to claim 1, The aforementioned high-speed mode is, A first period in which one of the three first upper switching elements and two of the three first lower switching elements are turned on, The system includes a second period in which two of the three first upper switching elements and one of the three first lower switching elements are turned on, The control unit alternately turns on the second upper switching element and the second lower switching element during each of the first and second periods. A work machine characterized by the following features.

4. A work machine according to claim 3, The control unit performs complementary PWM control on the second upper switching element and the second lower switching element in each of the first and second periods. A work machine characterized by the following features.

5. A work machine according to claim 3 or 4, The control unit, In the high-speed mode, the first period and the second period are repeated alternately while changing the combination of switching elements that are turned on. During the first period, the second upper switching element is driven with a first duty cycle, and the second lower switching element is driven with a second duty cycle. During the second period, the second upper switching element is driven with the second duty cycle, and the second lower switching element is driven with the first duty cycle. A work machine characterized by the following features.

6. A work machine according to claim 5, The second duty cycle is twice the first duty cycle. A work machine characterized by the following features.

7. A work machine according to claim 5, The first duty cycle is 1 / 3, and the second duty cycle is 2 / 3. A work machine characterized by the following features.

8. A work machine according to claim 3, In the aforementioned first period, A first state in which current flows through the second upper switching element, the neutral point, the multi-phase winding which is a part of the multi-phase winding, and the two first lower switching elements, The system is configured to alternately switch between a first upper switching element, a single phase winding among the multiple phase windings which is different from the winding energized in the first state, the neutral point, and a second state in which current flows through the second lower switching element. In the second period mentioned above, A third state in which current flows through the second upper switching element, the neutral point, the winding of one of the multiple phase windings, and one of the first lower switching elements, The system is configured to alternately switch between two first upper switching elements, a multi-phase winding which is part of the multi-phase winding and is different from the winding energized in the third state, the neutral point, and a fourth state in which current flows through the second lower switching element. A work machine characterized by the following features.

9. A work machine according to claim 3 or 4, The motor has three-phase windings, The first period and the second period appear alternately at intervals of 60 degrees in electrical angle. A work machine characterized by the following features.

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