Power tool

Abstract

To provide a power unit which is connected with an electric tool body with a brushless DC motor of which the miniaturization or weight reduction and cost reduction can be contrived.SOLUTION: In an electric tool 1, a power unit to be connected with an electric tool body 2 with a brushless DC motor 21 comprises: at least one of an inverter 35 which drives the brushless DC motor and a control circuit 34 which controls the inverter; and a power supply part 33 which supplies power to the inverter.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to power tools. [Background technology]

[0002] Patent Document 1 describes a technique relating to an electric power tool. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-103318 A Summary of the Invention

[0004] A power supply device and a power tool are disclosed. In one embodiment, the power supply device is connected to a power tool body including a brushless DC motor and a step-down circuit that steps down an input voltage. The power supply device includes an inverter that drives the brushless DC motor, and a power supply unit that supplies power to the inverter and supplies the input voltage to the step-down circuit.

[0005] In one embodiment, a power tool includes the power supply device and a power tool body to which the power supply device is connected. The power tool body includes a sensor that detects the rotational position of the brushless DC motor. The step-down circuit generates power for the sensor. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of an electric power tool. [Diagram 2] FIG. 2 is a diagram mainly showing an example of a circuit configuration of a power tool. [Diagram 3] FIG. 1 is a diagram illustrating an example of a configuration of an electric power tool. [Figure 4] FIG. 1 is a diagram illustrating an example of a configuration of an electric power tool. [Diagram 5] FIG. 2 is a diagram mainly showing an example of a circuit configuration of a power tool. [Figure 6] FIG. 1 is a diagram illustrating an example of a configuration of an electric power tool. [Figure 7] FIG. 2 is a diagram mainly showing an example of a circuit configuration of a power tool. [Figure 8] FIG. 1 is a diagram illustrating an example of a configuration of an electric power tool. [Figure 9] FIG. 1 is a diagram illustrating an example of a configuration of an electric power tool. [Figure 10] FIG. 1 is a diagram illustrating an example of a configuration of an electric power tool. [Figure 11] FIG. 1 is a diagram illustrating an example of a configuration of an electric power tool. [Figure 12] FIG. 1 is a diagram illustrating an example of a configuration of an electric power tool. [Figure 13] FIG. 2 is a diagram illustrating an example of the configuration of a power supply unit. [Figure 14] FIG. 2 is a diagram illustrating an example of the configuration of a power supply unit. [Figure 15] FIG. 2 is a diagram illustrating an example of the configuration of a power supply unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] FIG. 1 is a diagram showing a schematic configuration example of a power tool 1. As shown in FIG. 1, the power tool 1 includes a power tool main body 2, a power supply device 3, a connection cable 4, and a connection cable 5. The power tool 1 shown in FIG. 1 is, for example, a handheld disc grinder. The power tool 1 may be a handheld power tool other than a disc grinder. For example, the power tool 1 may be an impact driver, a driver drill, a circular saw, a reciprocating saw, or a polisher. Hereinafter, the power tool main body 2 may be simply referred to as the main body 2.

[0009] The main body 2 includes a housing 20 that contains a plurality of components and is held by a user. The housing 20 contains a brushless DC motor 21, a sensor board 22, a cooling fan 23, a connector 24, and the like.

[0010] The main body 2 also includes a drive unit driven by the brushless DC motor 21. The drive unit includes, for example, a gear unit accommodated in the housing 20 and a disk-shaped grinding wheel 25 exposed from the housing 20. The gear unit transmits the rotation of the brushless DC motor 21 to the grinding wheel 25 by reducing the rotation speed. The brushless DC motor 21 can rotate the grinding wheel 25 via the gear unit. The power tool 1 can perform grinding, cutting, polishing, and the like by rotating the grinding wheel 25. The brushless DC motor 21 is driven by the power supply device 3.

[0011] The sensor board 22 can detect the rotational position of the brushless DC motor 21. More specifically, the sensor board 22 can detect the rotational position of a rotor included in the brushless DC motor 21. The cooling fan 23 is connected to the rotating shaft 210 of the brushless DC motor 21. The cooling fan 23 rotates as the rotating shaft 210 rotates. When the cooling fan 23 rotates, air is taken into the housing 20 from an intake port provided at the rear of the housing 20. The air taken in from the intake port cools the brushless DC motor 21 and the like in the housing 20, and is then discharged to the outside of the housing 20 from an exhaust port provided at the front of the housing 20. The connector 24 is partially exposed from the housing 20, and the connection cable 4 is connected to the connector 24. It can be said that the connector 24 is a connection point to which the connection cable 4 is connected. Hereinafter, the brushless DC motor 21 may be simply referred to as the motor 21.

[0012] The power supply device 3 is a separate device from the main body 2, and includes a housing 30 that houses a plurality of components. The housing 30 houses a circuit board 31, a connector 37, and a connector .

[0013] The circuit board 31 includes a board 32, and a power supply unit 33, a control circuit 34, and an inverter 35 mounted on the board 32. The power supply unit 33 is capable of supplying power to the inverter 35. The power supply unit 33 converts, for example, an AC voltage supplied from a commercial power source into a DC voltage, and supplies the generated DC voltage to the inverter 35. The power supply unit 33 can also be called a power supply circuit. The inverter 35 is capable of driving the motor 21 provided in the main body 2. The control circuit 34 is capable of controlling the inverter 35.

[0014] The connector 37 is partially exposed from the housing 30. The connection cable 4 is connected to the connector 37. The connector 37 can be said to be a connection point where the connection cable 4 is connected. The connection cable 4 extends from the housing 30 of the power supply device 3 to the housing 20 of the main body 2. The length of the connection cable 4 is, for example, several tens of centimeters to several meters. The length of the connection cable 4 is not limited to this.

[0015] The connector 38 is partially exposed from the housing 30. The connection cable 5 is connected to the connector 38. The connector 38 can be said to be a connection point where the connection cable 5 is connected.

[0016] One end of the connection cable 4 is provided with a connector 41 that is connected to the connector 24 of the main body 2. The other end of the connection cable 4 is provided with a connector 42 that is connected to the connector 37 of the power supply device 3. One end of the connection cable 5 is provided with a connector 51 that is connected to the connector 38 of the power supply device 3. The other end of the connection cable 5 is provided with a connector 52 that is connected to an outlet that supplies AC voltage from a commercial power source. Connector 52 is sometimes called a power plug.

[0017] In this example, one end of the connection cable 4 is detachable from the main body 2. Specifically, the connector 41 of the connection cable 4 is detachable from the connector 24 of the main body 2. In addition, the other end of the connection cable 4 is detachable from the power supply device 3. Specifically, the connector 42 of the connection cable 4 is detachable from the connector 37 in the housing 30.

[0018] In this example, one end of the connection cable 5 is detachable from the power supply device 3. Specifically, the connector 51 of the connection cable 5 is detachable from the connector 38 in the housing 30. Furthermore, the connector 52 of the connection cable 5 is detachable from the outlet. It can be said that the power tool 1 includes a cable-attached power supply device 300 that includes the power supply device 3 and the connection cables 4 and 5.

[0019] Fig. 2 is a diagram mainly showing an example of a circuit configuration of the power tool 1. As shown in Fig. 2, a single-phase AC voltage from a commercial power source is supplied to the connector 52 of the connection cable 5. The AC voltage is supplied to the connector 38 of the power supply device 3 through the connection cable 5. The connection cable 5 has two signal lines 50a. An AC voltage with an effective value of 100V, for example, is supplied to the connector 38.

[0020] The AC voltage supplied to the connector 38 is supplied to the power supply unit 33. The power supply unit 33 includes an AC-DC converter 330. The AC-DC converter 330 converts the AC voltage into a DC voltage and outputs it. The AC-DC converter 330 is configured with, for example, a rectifier circuit, and has a diode and a capacitor. The AC-DC converter 330 outputs a DC voltage of, for example, about 140 V. The DC voltage output by the AC-DC converter 330 is supplied to the control circuit 34. In addition, the DC voltage output by the AC-DC converter 330 is supplied to the inverter 35 as a power source.

[0021] The inverter 35 includes, for example, six switching elements 350. The switching elements 350 are, for example, FETs (Field effect transistors). The switching elements 350 may be IGBTs (Insulated Gate Bipolar Transistors) or other elements. In the inverter 35, three switching circuits, each of which is made up of two switching elements 350 connected in series, are connected in parallel. In each switching circuit, the voltage at the connection point of the two switching elements is supplied to the motor 21 as a drive signal 351.

[0022] The three drive signals 351 generated by the inverter 35 are supplied to the motor 21 through the connector 37 of the power supply device 3, the connection cable 4, and the connector 24 of the main body 2. The connection cable 4 includes three signal lines 40a that transmit the three drive signals 351 from the power supply device 3 to the main body 2, respectively. The motor 21 is, for example, a three-phase motor, and includes a U-phase coil 21a, a V-phase coil 21b, and a W-phase coil 21c. The three drive signals 351 are supplied to the U-phase coil 21a, the V-phase coil 21b, and the W-phase coil 21c, respectively.

[0023] The sensor board 22 of the main body 2 includes, for example, three sensors 220. Each sensor 220 detects the rotational position of the motor 21. The three sensors 220 are arranged, for example, at intervals of 120 degrees along the rotational direction of the motor 21. An output signal (in other words, a position detection signal) 230 of each sensor 220 is supplied to the connector 24. The three output signals 230 supplied to the connector 24 are supplied to the control circuit 34 through the connection cable 4 and the connector 37 of the power supply device 3. The connection cable 4 includes three signal lines 40d that transmit the output signals 230 of the three sensors 220 from the main body 2 to the power supply device 3, respectively. Hereinafter, the output signals 230 of the sensors 220 may be referred to as sensor signals 230.

[0024] The control circuit 34 includes, for example, a microcomputer 341 and a DC-DC converter 340. The DC-DC converter 340 steps down the DC voltage supplied from the AC-DC converter 330 and outputs it. The DC-DC converter 340 can be said to be a step-down circuit. The DC-DC converter 340 generates power for the microcomputer 341. The DC-DC converter 340 also generates power for the sensor 220 of the sensor board 22. The power for the sensor 220 generated by the DC-DC converter 340 is supplied to each sensor 220 through the connector 37, the connection cable 4, and the connector 24. The connection cable 4 includes a signal line 40b that transmits a positive power supply for the sensor 220 from the power supply device 3 to the main body 2, and a signal line 40c that transmits a negative power supply for the sensor 220 from the power supply device 3 to the main body 2. In this example, the connection cable 4 includes eight signal lines.

[0025] The microcomputer 341 controls the inverter 35 based on the three sensor signals 230 from the sensor board 22, thereby controlling the rotation of the motor 21. Specifically, the microcomputer 341 controls the voltage of the control terminal of each switching element 350 of the inverter 35 based on the three sensor signals 230, thereby controlling the on / off state of each switching element 350. As a result, the inverter 35 supplies appropriate drive signals 351 to each of the U-phase coil 21a, the V-phase coil 21b, and the W-phase coil 21c of the motor 21, thereby controlling the rotation of the motor 21. The microcomputer 341 generates six control signals 342 and supplies the six generated control signals 342 to the control terminals of the six switching elements 350, respectively. Note that the control circuit 34 may include a hardware circuit that does not require software to realize its function, instead of the microcomputer 341 that requires software to realize its function.

[0026] As described above, in the electric power tool 1 according to the present embodiment, the power supply device 3 including the inverter 35, the control circuit 34, and the power supply unit 33 is provided in addition to the main body 2. This allows the power supply device 3 to be shared among a plurality of main bodies 2. For example, the power supply device 3 can be shared among the main bodies 2 of a plurality of disc grinders. Also, the power supply device 3 can be shared among the main bodies 2 of a plurality of types of electric power tools 1. For example, the power supply device 3 can be shared among the main bodies 2 of a disc grinder, an impact driver, a drill driver, a circular saw, a reciprocating saw, and a polisher. In this case, the power supply device 3 can be connected to each of the main bodies 2 of the disc grinder, the impact driver, the drill driver, the circular saw, the reciprocating saw, and the polisher. Therefore, since it is not necessary to provide the inverter 35, the control circuit 34, and the power supply unit 33 individually for each electric power tool 1, the cost of the electric power tool 1 can be reduced.

[0027] Furthermore, since the inverter 35, the control circuit 34, and the power supply unit 33 are provided separately from the main body 2, the size of the main body 2 can be reduced. Alternatively, the weight of the main body 2 can be reduced. This makes it easier for the user to hold the main body 2 and perform work.

[0028] 3 is a diagram showing a schematic configuration example of a power tool 100 including a main body 2 having an inverter 35, a control circuit 34, and a power supply unit 33. In the example of FIG. 3, a circuit board 31 is accommodated in a housing 20 of the main body 2. Furthermore, the housing 20 is not provided with a connector 24, and two signal lines 50a of the connection cable 5 are directly connected to the board 32. Comparing the power tool 100 in FIG. 3 with the power tool 1 in FIG. 1, the length of the housing 20 held by the user is shorter in the power tool 1 than in the power tool 100. Furthermore, the main body 2 of the power tool 1 is lighter than the main body 2 of the power tool 100.

[0029] In the case where the connection cable 5 is detachable from the power supply device 3 as in this example, the connection cable 5 can be easily replaced. In addition, by preparing a plurality of types of connection cables 5 with different lengths, the length of the connection cable 5 can be easily changed. In addition, since the power tool 1 can be stored in the case with the connection cable 5 detached from the power supply device 3, the user can easily carry the power tool 1.

[0030] Furthermore, in the case where the connection cable 4 is detachable from the main body 2 and the power supply device 3 as in this example, the connection cable 4 can be easily replaced. Furthermore, by preparing a plurality of types of connection cables 4 with different lengths, the length of the connection cable 4 can be easily changed. Furthermore, since the power tool 1 can be stored in the case with the connection cable 4 detached from the main body 2 and the power supply device 3, the user can easily carry the power tool 1.

[0031] In the above example, the power supply unit 33, the control circuit 34, and the inverter 35 are mounted on one board 32, but at least two of the power supply unit 33, the control circuit 34, and the inverter 35 may be mounted on different boards.

[0032] In the above example, the inverter 35 is provided in the power supply device 3, but may be provided in the main body 2. Fig. 4 is a diagram showing an example of the configuration of the power tool 1 including the main body 2 having the inverter 35. Fig. 5 is a diagram mainly showing an example of the circuit configuration of the power tool 1 including the main body 2 having the inverter 35. INV shown in Fig. 4 means inverter. The power tool 1 including the main body 2 having the inverter 35 may be particularly referred to as power tool 1A.

[0033] 5, in the power tool 1A, a DC voltage generated by the AC-DC converter 330 is supplied to a connector 37. In addition, six control signals 342 generated by the control circuit 34 are supplied to the connector 37.

[0034] The connection cable 4 of the power tool 1A includes thirteen signal lines, specifically, the signal lines 40b and 40c, the three signal lines 40d, the signal lines 40e and 40f, and six signal lines 40g.

[0035] The signal line 40e transmits the positive potential of the DC voltage generated by the AC-DC converter 330 from the power supply device 3 to the main body 2. The positive potential transmitted by the signal line 40e is supplied to the inverter 35 as a positive power source through the connector 24 of the main body 2. The signal line 40f transmits the ground potential of the DC voltage generated by the AC-DC converter 330 from the power supply device 3 to the main body 2. The ground potential transmitted by the signal line 40f is supplied to the inverter 35 as a negative power source through the connector 24. The six signal lines 40g transmit six control signals 342 generated by the control circuit 34 from the power supply device 3 to the main body 2. The control signals transmitted by the signal line 40g are supplied to the control terminals of the switching elements 350 of the inverter 35 through the connector 24. The on / off state of the switching elements 350 is controlled by the control signals.

[0036] Comparing the power tool 100 in Fig. 3 with the power tool 1A in Fig. 4, the length of the housing 20 held by the user is shorter in the power tool 1A than in the power tool 100. In addition, the main body 2 of the power tool 1A is lighter than the main body 2 of the power tool 100. This makes it easier for the user to hold the main body 2 of the power tool 1A in his or her hand and perform work.

[0037] The control circuit 34 may be provided in the main body 2 instead of in the power supply device 3. Fig. 6 is a diagram showing an example of the configuration of a power tool 1 including a main body 2 having a control circuit 34. Fig. 7 is a diagram mainly showing an example of the circuit configuration of a power tool 1 including a main body 2 having a control circuit 34. Hereinafter, the power tool 1 including a main body 2 having a control circuit 34 may be referred to as a power tool 1B.

[0038] 7, the connection cable 4 of the power tool 1B includes eleven signal lines. Specifically, the connection cable 4 includes the above-mentioned three signal lines 40a, the above-mentioned signal lines 40e and 40f, and six signal lines 40h. The DC voltages (in other words, the positive potential and the ground potential) transmitted by the signal lines 40e and 40f are supplied to the DC-DC converter 340 of the control circuit 34 through the connector 24. The six control signals 342 output by the control circuit 34 are supplied to the connector 24. The six signal lines 40h transmit the six control signals 342 supplied to the connector 24 from the main body 2 to the power supply device 3, respectively.

[0039] Comparing the power tool 100 in Fig. 3 with the power tool 1B in Fig. 6, the length of the housing 20 held by the user is shorter in the power tool 1B than in the power tool 100. In addition, the main body 2 of the power tool 1B is lighter than the main body 2 of the power tool 100. This makes it easier for the user to hold the main body 2 of the power tool 1B in his or her hand and perform work.

[0040] Comparing the power tools 1, 1A, and 1B, the power tool 1 has the fewest number of signal lines in the connection cable 4, followed by the power tool 1B, and then the power tool 1A has the most. Therefore, among the connection cables 4 provided in the power tools 1, 1A, and 1B, the connection cable 4 provided in the power tool 1 has the lowest possibility of being broken.

[0041] In the above example, the connection cable 5 of the cable-equipped power supply device 300 is detachable from the power supply device 3, but it may be fixed undetachably to the power supply device 3. In this case, the two signal lines 50a of the connection cable 5 may be directly connected to the board 32 without providing the connectors 38 and 51 on the power supply device 3 and the connection cable 5, respectively.

[0042] In addition, in the cable-equipped power supply device 300, the connection cable 4 may be fixed undetachably to the power supply device 3. In this case, each signal line of the connection cable 4 may be directly connected to the board 32 without providing the connectors 37 and 42 on the power supply device 3 and the connection cable 4, respectively.

[0043] In addition, in the cable-attached power supply device 300, the connection cable 4 may be fixed undetachably to the main body 2. In this case, each signal line of the connection cable 4 may be drawn into the housing 20 of the main body 2 without providing the connectors 24 and 41 on the main body 2 and the connection cable 4, respectively.

[0044] In addition, since the inverter 35 easily generates heat, the power supply device 3 including the inverter 35 may be provided with a cooling fan for cooling the inverter 35. When the main body 2 includes the inverter 35, the inverter 35 can be cooled by the cooling fan 23 of the main body 2.

[0045] In the above example, the main body 2 includes the sensor board 22, but the main body 2 may not include the sensor board 22. In this case, the control circuit 34 may, for example, detect the current flowing through the motor 21 and determine the rotational position of the motor 21 based on the detection result. The control circuit 34 may, for example, detect the induced voltage generated in the motor 21 and determine the rotational position of the motor 21 based on the detection result. When the main body 2 does not include the sensor board 22, the connection cable 4 may be configured without the signal lines 40b and 40c for transmitting the power supply for the sensor 220 from the power supply device 3 to the main body 2 and the three signal lines 40d for transmitting the output signal 230 of the sensor 220 from the main body 2 to the power supply device 3. As a result, the number of necessary signal lines is reduced, and the cost of the power tool 1 can be reduced.

[0046] In the above example, the main body 2 and the power supply device 3 are connected by the connection cable 4, but the power supply device 3 may be directly detachable from the main body 2. Fig. 8 is a diagram showing an example of the configuration of the electric tool 1 in which the power supply device 3 is detachable from the main body 2. In Fig. 8, some of the configuration inside the housings 20 and 30 is omitted.

[0047] In the example of FIG. 8, the housing 30 of the power supply device 3 is detachable from the housing 20 of the main body 2. In the housing 30, instead of the connector 37, a connection terminal group 39 consisting of a plurality of connection terminals is provided. Each connection terminal of the connection terminal group 39 is exposed from the housing 30. In the housing 20, instead of the connector 24, a connection terminal group 27 consisting of a plurality of connection terminals is provided. Each connection terminal of the connection terminal group 27 is exposed from the housing 20. When the housing 30 is attached to the housing 20, the plurality of connection terminals of the connection terminal group 39 are in contact with the plurality of connection terminals of the connection terminal group 27, respectively. In the power tool 1 in which the power supply device 3 includes the power supply unit 33, the control circuit 34, and the inverter 35, when the housing 30 is attached to the housing 20, the control circuit 34 is electrically connected to the sensor board 22, and the inverter 35 is electrically connected to the motor 21, as in the above-mentioned FIG. 2. 5, the control circuit 34 of the power supply device 3 is electrically connected to the inverter 35 and the sensor board 22 of the main body 2, and the DC voltage output from the AC-DC converter 330 of the power supply device 3 is supplied to the inverter 35 of the main body 2. In the power tool 1B, when the housing 30 is attached to the housing 20, the inverter 35 of the power supply device 3 is electrically connected to the motor 21 and the control circuit 34 of the main body 2, and the DC voltage output from the AC-DC converter 330 of the power supply device 3 is supplied to the control circuit 34 of the main body 2, as in FIG.

[0048] In this way, even if the housing 30 of the power supply unit 3 is detachable from the housing 20 of the main body 2, the power supply unit 3 can be shared among multiple main bodies 2, thereby reducing the cost of the power tool 1.

[0049] In the above example, the power supply unit 33 of the power supply device 3 includes the AC-DC converter 330, but a battery may be provided instead of the AC-DC converter 330. FIG. 9 is a diagram showing a configuration example of the power tool 1 in which the power supply unit 33 includes the battery 335. In FIG. 9, all components in the housing 20 are omitted, and some components in the housing 30 are omitted. When the power supply unit 33 includes the battery 335, the connection cable 5 is not required. The battery 335 may be rechargeable by a charger separate from the power tool 1. In this case, a charging terminal for charging the battery 335 is provided in the housing 30 of the power supply device 3 so as to be exposed from the housing 30. A charging voltage from the charger is supplied to the charging terminal, and the battery 335 is charged. The DC voltage output from the battery 335 is supplied to the inverter 35 and the DC-DC converter 340 of the control circuit 34 instead of the DC voltage generated by the AC-DC converter 330.

[0050] In this way, even if the power supply unit 33 includes the battery 335, the power supply device 3 can be shared among a plurality of main bodies 2, which reduces the cost of the power tool 1. In addition, the main body 2 can be made smaller and lighter.

[0051] In the example of Fig. 9, the main body 2 and the power supply device 3 are connected by the connection cable 4, but as shown in Fig. 10, the power supply unit 33 of the power tool 1 in which the housing 30 is detachable from the housing 20 may include a battery 335. In Fig. 10, the illustration of some of the configuration inside the housings 20 and 30 is omitted.

[0052] Also, the main body 2 may be provided with a connector 24 and a group of connection terminals 27, and the power supply device 3 may be provided with a connector 37 and a group of connection terminals 39, so that the main body 2 and the power supply device 3 can be connected with the connection cable 4, and the housing 30 of the power supply device 3 may be detachably attached to the housing 20 of the main body 2. Figs. 11 and 12 are diagrams showing an example of the configuration of the power tool 1 in this case. Fig. 11 shows the power tool 1 in which the main body 2 and the power supply device 3 are connected with the connection cable 4. Fig. 12 shows the power tool 1 in which the housing 30 of the power supply device 3 is attached to the housing 20 of the main body 2. Figs. 11 and 12 omit the illustration of a part of the configuration inside the housings 20 and 30. Figs. 11 and 12 show the power tool 1 without the connection cable 5, but in the power tool 1 with the connection cable 5, the main body 2 may be provided with a connector 24 and a group of connection terminals 27, and the power supply device 3 may be provided with a connector 37 and a group of connection terminals 39, so that the main body 2 and the power supply device 3 can be connected with the connection cable 4, and the housing 30 may be detachably attached to the housing 20.

[0053] Furthermore, the power supply unit 33 of the power supply device 3 may include a boost circuit. Fig. 13 is a diagram mainly showing a configuration example of the power supply unit 33 including an AC-DC converter 330 and a boost circuit 336. In the example of Fig. 13, the boost circuit 336 boosts and outputs the DC voltage output from the AC-DC converter 330. The boost circuit 336 boosts the DC voltage output from the AC-DC converter 330, for example, by several times. The DC voltage output from the boost circuit 336 is supplied to the inverter 35 and the DC-DC converter 340 of the control circuit 34.

[0054] 14 is a diagram mainly showing another configuration example of the power supply unit 33 including an AC-DC converter 330 and a boost circuit 336. In the example of FIG. 14, the boost circuit 336 boosts and outputs the AC voltage supplied to the connector 52. The AC voltage output from the boost circuit 336 is then converted to a DC voltage by the AC-DC converter 330. The DC voltage generated by the AC-DC converter 330 is supplied to the inverter 35 and the DC-DC converter 340 of the control circuit 34.

[0055] In this way, since the power supply unit 33 includes the boost circuit 336, a high voltage can be supplied to the inverter 35. This allows a high voltage to be supplied to the motor 21. This makes it possible to reduce the current flowing through the inverter 35 and the motor 21. As a result, heat generation by the inverter 35 and the motor 21 can be suppressed.

[0056] 15, the power supply unit 33 may include a battery 335 and a boost circuit 336. In this case, the boost circuit 336 boosts and outputs the output voltage of the battery 335. The DC voltage output from the boost circuit 336 is supplied to the inverter 35 and a DC-DC converter 340 of the control circuit 34.

[0057] Although the power tool has been described in detail as above, the above description is merely illustrative in all respects, and this disclosure is not limited thereto. In addition, the above-described various examples can be combined and applied as long as they are not mutually inconsistent. It is understood that countless examples not illustrated can be envisioned without departing from the scope of this disclosure. [Explanation of symbols]

[0058] 1,1A,1B Power tools 2 Power tool body 3 Power supply 4 Connection cable 20. Housing 21 Brushless DC motor 30 Housing 33 Power supply section 34 Control circuit 35 Inverter 220 Sensors 300 Power Supply with Cable 330 AC-DC Converter 335 Battery 338 Boost Circuit

Claims

1. A power supply device, An electric tool body, a connection cable for connecting the power supply device and the power tool body; Equipped with The electric power tool body includes: A brushless DC motor; a step-down circuit for stepping down an input voltage; a first housing that accommodates the brushless DC motor and the step-down circuit; having The power supply device is an inverter that drives the brushless DC motor; a power supply unit that supplies power to the inverter and supplies the input voltage to the step-down circuit; a second housing that accommodates the inverter and the power supply unit; having The power tool, wherein the connection cable is detachable from at least one of the first housing and the second housing.

2. The power tool according to claim 1, The step-down circuit is a DC-DC converter.

3. The power tool according to claim 1 or 2, The power supply unit includes an AC-DC converter that converts an AC voltage as the input voltage into a DC voltage and outputs the DC voltage.

4. The power tool according to any one of claims 1 to 3, The power tool body includes a sensor for detecting a rotational position of the brushless DC motor, The step-down circuit generates a power supply for the sensor.

5. The power tool according to claim 4, The power tool body includes a microcomputer. The step-down circuit generates power for the microcomputer.

6. The power tool according to any one of claims 1 to 5, The step-down circuit steps down the input voltage supplied to the power tool body through the connection cable.

7. The power tool according to claim 6, The power tool body includes a signal line extending from the connection cable to the step-down circuit.

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