JP2011148069A - Power tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power tool in which both a power supply for driving a motor and a power supply for a control circuit with an on-board microcomputer are compactly housed in a housing. <P>SOLUTION: The power tool (1) includes the motor 3 housed in the housing 2, and the control circuit controlling the rotation of the motor 3. The housing 2 is formed with a handle 2b held by an operator. A switching power supply circuit 15 connected to the control circuit is housed in the handle 2b. The handle 2b extends substantially vertically from the body 2a. An expanded diameter portion 2c is formed near the end of the handle 2b on the side away from the body 2a. The expanded diameter portion 2c is housed with the control circuit (8) and a full-wave rectification circuit 14 converting the alternate current fed from a power supply cord 11a to the direct current for driving the motor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric tool for driving a motor using commercial AC power as a power source, and more particularly to an electric tool whose rotation is electronically controlled by a control circuit.

  In recent years, power tools that electronically control the rotation of a motor have come to be widely used in power tools that perform a required work by rotating a tip tool such as a drill or a driver with a motor. We also sell electric tools that do not have brushless motors, which are electronically controlled to allow the motor to perform a predetermined operation, to perform a clutch operation, or to count the number of screw tightenings. Has been. When electronically controlling in this way, a control circuit is required. For example, a brushless DC motor is widely used as an electronically controlled motor. A brushless DC motor is, for example, a DC (direct current) motor without a brush (rectifying brush), using a coil (winding) on the stator (stator) side and a permanent magnet on the rotor (rotor) side. The rotor is rotated by sequentially energizing the driven power to a predetermined coil. In a brushless DC motor, a switching element such as a field effect transistor (FET) for turning on and off the current supplied to a coil wound around the stator is disposed on a circuit board in the vicinity of the motor. For example, in Patent Document 1, the switching element is arranged on a substantially circular circuit board attached to the rear side of the motor (the side opposite to the tip tool).

  Here, the configuration of a conventional electric power tool will be described with reference to FIGS. FIG. 4 is a cross-sectional view showing an internal structure of a conventional power tool. The impact driver 101 uses the rechargeable battery pack 109 as a power source, drives the rotary impact mechanism 121 using the motor 103 as a drive source, applies rotational force and impact force to the anvil 130 that is the output shaft, and is positioned inside the sleeve 131. The rotary impact force is intermittently transmitted to a tip tool (not shown) such as a driver bit held in the mounting hole 130a to perform operations such as screw tightening and bolt tightening.

  The brushless DC motor 103 is accommodated in a cylindrical body portion 102a of a housing 102 having a substantially T-shape when viewed from the side. A rotary striking mechanism 121 is connected to the rotating shaft of the motor 103. A trigger switch 106 is disposed in an upper portion of a handle portion 102 b that integrally extends from the body portion 102 a of the housing 102 at a substantially right angle, and a switch circuit board 107 is provided below the trigger switch 106. A control circuit board 108 on which a control circuit for controlling the speed of the motor 103 by pulling operation of the trigger switch 106 is housed in the lower part in the handle portion 102b. The electric power tool shown in FIG. 4 is a so-called cordless type, and a battery pack 109 serving as a power source is attached to the enlarged diameter portion 102 c of the housing 102.

  FIG. 5 is a circuit block diagram of a conventional electric power tool. The DC power supplied from the battery pack 109 is input to the inverter circuit board 104. In the inverter circuit 104a mounted on the inverter circuit board 104, the drive signal (gate voltage) 137 is adjusted by the control circuit 108a, and the rotation of the motor 103 is controlled. The rotation of the motor 103 is detected by a plurality of Hall ICs 135 provided at positions facing the rotor, and input to the control circuit 108a as an output signal (position signal) 136. The control circuit 108 a detects that the trigger switch 106 has been pulled, and the control circuit 108 a drives and controls the inverter circuit 104 a via the signal line 137. The control circuit 108 a also detects the battery voltage of the battery pack 109 and monitors the amount of current flowing through the motor 103.

Various electronic circuits such as a microcomputer are mounted on the control circuit 108a, and a battery pack 109 is used as a driving power source. This connection state is shown in the circuit diagram of FIG. In FIG. 6, the electric power of the battery pack 109 is sent to the inverter circuit board 104 and simultaneously to the control circuit board 108. Therefore, the voltage at the power input section of the control circuit board 108 and the voltage at the input section of the inverter circuit board 104 are equal to + V _dc . The voltage + V _dc is, for example, about 12V to 36V.

JP 2009-72880 A

  In the cordless brushless DC motor-driven electric tool, since the voltage of the battery pack 109 as a power source is as low as about 12 to 18 V, for example, the inverter circuit 104a and the control circuit 108a can be operated with a common power source. That is, a dedicated power source for the control circuit 108a is not necessary. However, in order to drive the electric tool with a commercial power source such as AC 100V instead of operating it with the battery pack 109, it is necessary to connect a power cable to the electric tool and generate a direct current connected to the inverter circuit. Therefore, it is necessary to incorporate a rectifier circuit in order to create a DC voltage from a commercial voltage. However, if a DC voltage is created from AC 100V, a direct current of about 141V is obtained, and this DC power is connected to the inverter circuit. It will be. In addition, since the voltage is too high at the direct current 141V for the control circuit for controlling the inverter circuit 4a, the direct current 141V cannot be supplied to the control circuit as it is. Therefore, a switching power supply circuit that supplies a DC voltage of about 18 V is required as the operating voltage for the control circuit.

  The conventional cordless type power tool does not require a switching power circuit because the power for the inverter circuit and the power for the control circuit are supplied directly from the battery, but a brushless DC motor-driven power tool with a power cord is realized. Therefore, unless these two power supplies are efficiently stored in the housing, the housing becomes large and becomes an electric tool that is difficult to use.

  The present invention has been made in view of the above background, and an object thereof is to provide an electric tool in which a motor driving power source and a motor control circuit power source are efficiently stored in a housing. is there.

  Another object of the present invention is to provide a power tool that is compactly configured by preventing the housing from becoming large by devising the arrangement of the power source for driving the motor and the power source for the control circuit in the housing. There is.

  Still another object of the present invention is to accurately control the rotation of a motor using a microcomputer in an electric tool driven by a commercial power source.

  The characteristics of representative ones of the inventions disclosed in the present application will be described as follows.

  According to one aspect of the present invention, a motor, a housing that houses the motor, a handle portion that extends from a body portion of the housing and is gripped by an operator, and a power cord that extends from the housing and can be connected to a commercial AC power source And a control circuit for controlling the rotation of the motor, provided with a full-wave rectifier circuit capable of converting the alternating current of the commercial AC power source to the first direct current, and the handle portion from the first direct current In addition, a switching power supply circuit that can be converted into a second direct current having a low voltage is accommodated.

  According to another feature of the present invention, the housing has a body portion that accommodates the motor, and the handle portion extends in a direction intersecting the body portion, and the handle portion is located near an end portion of the handle portion on the side away from the body portion. An enlarged diameter portion having a diameter larger than the outer diameter of the power supply circuit was formed, and a power supply circuit for converting alternating current supplied from the control circuit and the power cord into direct current for driving the motor was accommodated in the enlarged diameter portion. The power supply circuit has a diode bridge and a capacitor. The switching power supply circuit generates low-voltage direct current used in the control circuit from the output of the power supply circuit, and is accommodated in the handle portion. It is preferable that the body portion, the handle portion, and the enlarged diameter portion of the housing are formed by integral molding of resin.

  According to still another feature of the present invention, the motor is a brushless DC motor, and a circuit board having an inverter circuit and a position detection element is provided in the housing. The control circuit includes a microcomputer that controls the inverter circuit, and is disposed between the switching power supply circuit and the power supply circuit in the housing. The housing can be divided into two parts including the extending direction in which the handle portion extends and the rotation axis direction of the motor, and the substrate on which the control circuit is mounted is arranged to extend substantially at right angles to the dividing surface and is divided into two parts. Sandwiched by the housing.

  According to still another aspect of the present invention, the power tool includes a power cord that can be connected to a commercial AC power source, and a full wave that is connected to the commercial AC power source and can convert the AC of the commercial AC power source into a first DC. A rectifier circuit, a switching power supply circuit connected to the full-wave rectifier circuit and capable of being converted to a second direct current whose voltage is lower than the first direct current, a control circuit connected to the switching power supply circuit, and a full-wave rectifier circuit And a power cord protruding from one end and having a full-wave rectifier circuit, a switching power supply circuit, a control circuit, and a housing for housing the motor.

  According to the first aspect of the present invention, in the power tool, the housing is formed with a handle portion that is gripped by an operator, and the handle portion is capable of switching to the second direct current whose voltage is lower than the first direct current. Since the power supply circuit is accommodated, it is not necessary to newly provide a space for the switching power supply circuit for the control circuit. Therefore, it is possible to realize a small-sized electric tool having a power supply cord and a control circuit.

  According to the second aspect of the present invention, the enlarged diameter portion having a diameter larger than the outer diameter of the handle portion is formed in the vicinity of the end portion of the handle portion on the side away from the body portion. Since the power supply circuit for converting the alternating current supplied from the cord into the direct current for driving the motor is accommodated, a sufficient space for the power supply circuit for driving the motor can be secured. Further, since the substrate for the control circuit can be disposed adjacent to the power supply circuit, a sufficient space for the substrate can be ensured.

  According to the invention of claim 3, since the power supply circuit includes the diode bridge and the capacitor, it is possible to realize a power supply circuit with high efficiency and a small ripple content rate (ratio of effective value of ripple voltage included in DC voltage). In addition, since the ripple content can be reduced, the motor 3 can be operated with high accuracy because the voltage fluctuation is small.

  According to the invention of claim 4, the switching power supply circuit generates low voltage direct current used in the control circuit from the output of the power supply circuit, and is housed in the handle portion, so that the switching power supply circuit for the control circuit is used. Therefore, a small brushless DC motor-driven electric tool with a power cord can be realized.

  According to the fifth aspect of the present invention, since the body portion, the handle portion, and the enlarged diameter portion of the housing are formed by integral molding of resin, a highly rigid housing can be realized. Moreover, since it is manufactured by integral molding, a lightweight and high-strength housing can be realized.

  According to the invention of claim 6, since the motor is a brushless DC motor and the circuit board having the inverter circuit and the position detecting element is provided in the housing, the drive circuit for driving the motor can be accommodated in the vicinity of the motor. it can. Further, since the motor and the inverter can be arranged adjacent to each other, the inverter circuit can also be cooled using a cooling fan for the motor.

  According to the invention of claim 7, the control circuit includes a microcomputer for controlling the inverter circuit, and is disposed between the switching power supply circuit and the power supply circuit in the housing, so that the control circuit is disposed in the vicinity of the switching power supply circuit disposed in the handle portion. A control circuit can be provided and wiring efficiency is improved.

  According to the eighth aspect of the present invention, the board on which the control circuit is mounted is disposed so as to extend substantially at right angles to the dividing surface of the housing, and is sandwiched between the two divided housings. In addition to ensuring a large amount, the assemblability is improved.

  According to the ninth aspect of the present invention, the full-wave rectifier circuit, the switching power supply circuit, the control circuit, and the motor are housed in the housing of the electric tool driven by the commercial AC power supply, so that a compact and easy-to-use electric tool can be provided. .

  The above and other objects and novel features of the present invention will become apparent from the following description and drawings.

It is sectional drawing which shows the internal structure of the impact driver 1 which concerns on the Example of this invention. 1 is a circuit block diagram of an impact driver 1 according to an embodiment of the present invention. It is a power supply wiring block diagram of the impact driver 1 which concerns on the Example of this invention. It is sectional drawing which shows the internal structure of the electric tool by a prior art. It is a circuit block diagram of the electric tool by a prior art. It is a power supply wiring block diagram of the electric tool by a prior art.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the vertical and forward / backward directions will be described as the directions shown in FIG. FIG. 1 is a view showing an internal structure of an impact driver 1 as an embodiment of an electric power tool according to the present invention. The impact driver 1 drives the rotary impact mechanism 21 using the motor 3 as a drive source, applies rotational force and impact force to the anvil 30 as an output shaft, and applies to a tip tool (not shown) such as a driver bit held in the mounting hole 30a. Rotating impact force is transmitted intermittently to perform operations such as screw tightening and bolt tightening.

  The motor 3 is accommodated in a cylindrical body portion 2a of the housing 2 having a substantially T-shape when viewed from the side. In this embodiment, the motor 3 is a brushless DC motor. The coil 3d is used on the stator 3c side, the permanent magnet 3b is used on the rotor 3a side, and the electric power driven by the inverter is sequentially energized to the predetermined coil 3d. Rotate. The motor 3 is accommodated in the housing 2 by holding the outer peripheral portion of the stator 3c by the inner wall of the body portion 2a. The rotation shaft 3e of the motor 3 is rotatably held by a bearing 19a provided near the center of the body 2a of the housing 2 and a bearing 19b on the rear end side, and coaxially with the rotation shaft 3e in front of the motor 3. A rotor fan 13 that is attached and rotates in synchronization with the motor 3 is provided, and an inverter circuit board 4 for driving the motor 3 is disposed behind the motor 3. The air flow generated by the rotor fan 13 is taken into the body portion 2a from the air intake hole 17a, flows so as to pass mainly between the rotor 3a and the stator 3c, and is sucked from the rear of the rotor fan 13. It flows in the radial direction of the rotor fan 13 and is discharged from the housing portion (not shown) around the rotor fan 13 to the outside of the housing 2. The inverter circuit board 4 is a substantially circular double-sided board that is substantially the same as the outer shape of the motor 3, and a plurality of switching elements 5 such as MOSFETs (Metal Oxide Field Field Transistors) and a permanent magnet 3 b of the rotor 3 a are provided on this board. A position detecting element 35 such as a Hall IC for detecting the rotational position of the rotor 3a by detecting the magnetic force is mounted.

  The body portion 2a, the handle portion 2b, and the enlarged diameter portion 2c of the housing 2 are configured by a left-right split type housing that is divided in the front-rear direction and the up-down direction. Each of the left and right sides of the left and right divided housing 2 is formed by integral molding of resin. A trigger switch 6 is disposed in an upper portion of the handle portion 2b integrally extending in a substantially right angle direction (downward) from the body portion 2a of the housing 2, and a switch circuit board 7 is provided below the trigger switch 6. A control circuit board 8 having a function of controlling the speed of the motor 3 by the pulling operation of the trigger switch 6 is accommodated in the lower part in the handle portion 2b. The control circuit board 8 is connected to the inverter circuit board 4 via a signal line. An enlarged-diameter portion 2c having an increased outer diameter is formed below the housing 2, that is, at an end portion in the extending direction. The power cord 11a is attached to the lower portion of the enlarged diameter portion 2c, and the full-wave rectifier circuit 14 is disposed in the enlarged diameter portion 2c. The output of the full wave rectifier circuit 14 is connected to a terminal of the switch circuit board 7. The control circuit board 8 on which the microcomputer is mounted is disposed above the full-wave rectifier circuit 14.

  The full-wave rectifier circuit 14 has a substantially rectangular shape when viewed in a cross section constituted by a front-rear direction and a vertical direction. The long side 14a of this rectangle was arrange | positioned in the direction extended in the front-back direction, and the short side 14b was arrange | positioned in the direction extended in an up-down direction. Since the full-wave rectifier circuit 14 is arranged in the enlarged diameter portion 2c expanded in the front-rear direction in this way, the enlarged diameter portion 2c can be configured compactly in the axial direction (vertical direction). Further, the switching power supply circuit 15 has a substantially rectangular shape when viewed in a cross section constituted by a front-rear direction and a vertical direction. The long side 15a of the rectangle was arranged in the vertical direction (direction in which the handle extends), and the short side 15b was arranged in the front-rear direction (direction perpendicular to the direction in which the handle extends). With this configuration, the switching power supply circuit 15 is disposed inside the handle portion 2b that extends in the vertical direction, so that the handle portion 2b can be configured compactly in the front-rear direction.

  Since the control circuit board 8 cannot be driven by a high output voltage (for example, DC 141 V) of the full-wave rectifier circuit 14, a low DC voltage is generated from the output of the full-wave rectifier circuit 14, and about 18 V is applied to the control circuit board 8. A switching power supply circuit 15 for supplying a direct current is provided. The switching power supply circuit 15 is disposed inside the handle portion 2 b between the switch circuit board 7 and the control circuit board 8. By adopting a configuration in which the switching power supply circuit 15 is arranged in the handle portion 2b in this way, the switching power supply circuit 15 can be efficiently and compactly accommodated in the housing, and a small brushless DC motor drive type electric motor with a power cord is provided. A tool can be realized.

  The rotary striking mechanism 21 includes a planetary gear reduction mechanism 22, a spindle 27, and a hammer 24, and a rear end is held by a bearing 20 and a front end is held by a metal 29. The planetary gear speed reduction mechanism 22 is connected to the rotation shaft of the motor 3 via a gear pinion or the like. When the trigger switch 6 is pulled and the motor 3 is started, the motor 3 starts to rotate in the set direction, and the rotational force is decelerated by the planetary gear reduction mechanism 22 and transmitted to the spindle 27. It is rotationally driven at a speed of Here, the spindle 27 and the hammer 24 are connected by a cam mechanism. The cam mechanism includes a V-shaped cam groove 25 formed on the outer peripheral surface of the spindle 27 and a hammer cam formed on the inner peripheral surface of the hammer 24. A groove 28 and a ball 26 engaged with the cam grooves 25 and 28 are formed.

  The convex portion of the hammer 24 is always urged forward by the spring 23, and is located at a position spaced apart from the convex portion of the anvil 30 by the engagement between the ball 26 and the cam grooves 25 and 28 when stationary. And the convex part which is not shown in figure is formed symmetrically at two places on the rotation plane where the hammer 24 and the anvil 30 face each other.

  When the spindle 27 is driven to rotate, the rotation is transmitted to the hammer 24 via the cam mechanism, and the convex portion of the hammer 24 engages with the convex portion of the anvil 30 before the hammer 24 rotates halfway. When the relative reaction occurs between the spindle 27 and the hammer 24 by the engagement reaction force at that time, the hammer 24 compresses the spring 23 along the cam groove 25 of the cam mechanism and moves toward the motor 3 side. Start retreating.

  When the protrusion of the hammer 24 moves over the protrusion of the anvil 30 due to the backward movement of the hammer 24 and the engagement between the two is released, the hammer 24 is accumulated in the spring 23 in addition to the rotational force of the spindle 27. While being accelerated rapidly in the rotational direction and forward by the action of the elastic energy and the cam mechanism, the spring 23 is moved forward by the urging force of the spring 23, and the convex portion is reengaged with the convex portion of the anvil 30 to rotate integrally. start. At this time, since a strong rotational impact force is applied to the anvil 30, the rotational impact force is transmitted to the screw via a tip tool (not shown) attached to the mounting hole 30a of the anvil 30. Thereafter, the same operation is repeated, and the rotational impact force is intermittently repeatedly transmitted from the tip tool to the screw. For example, a fastening member such as a screw or a bolt is screwed into the material to be fastened.

  FIG. 2 is a circuit block diagram of the impact driver 1 according to the present embodiment. As shown in FIG. 2, in the full-wave rectifier circuit 14, the input AC 11 serving as a commercial power supply is full-wave rectified by a diode bridge 33, and a film capacitor provided on the output side (DC side) of the diode bridge 33. Is supplied to the switching power supply circuit 15 and the inverter circuit board 4. A capacitor 32 for preventing electromagnetic interference is provided on the input side (AC side) of the diode bridge 33. If the capacitance of the nonpolar capacitor 34 provided on the output side (DC side) of the diode bridge 33 is set to be, for example, 22 μF or less, the size of the nonpolar capacitor 34 can be suppressed to be small. The size of the enlarged diameter portion 2c of the housing 2 near the power cord 11a can be made compact.

  Although not shown, the inverter circuit board 4 is provided with an inverter circuit 4a composed of six switching elements 5. The motor 3 is provided with a position detection element 35 such as a Hall IC that is provided at a position facing the permanent magnet 3b (see FIG. 1) provided on the rotor 3a and detects the rotational position of the rotor 3a. The position detection element 35 outputs a high or low signal 36 to the control circuit 8a corresponding to the polarity of the permanent magnet 3b of the opposing rotor 3a, and is provided in three positions, for example, 60 degrees apart.

Since the inverter circuit board 4 and the switching power supply circuit 15 are connected to the output side of the diode bridge 33, the voltage supplied to each of them is a predetermined DC voltage (+ VH _dc ). This + VH _dc (corresponding to the first direct current of claim 1) is about 141V when the alternating current 11 is 100V. Since the control circuit 8a cannot be driven with the high DC voltage + VH _dc , the switching power supply circuit 15 generates a low DC voltage + VL _dc (corresponding to the second DC of claim 1) from the DC voltage + VH _dc. Then, it is supplied to the control circuit board 8. The switching power supply circuit 15 is a power supply device using a semiconductor switching element for converting and adjusting electric power, and can be configured by a known DC-DC converter. The switching power supply circuit 15 of the present embodiment generates, for example, direct current 18V from direct current 141V. When the trigger switch 6 is pressed, the control circuit 8a generates a PWM (Pulse Width Modulation) control drive signal 37 for driving the switching element of the inverter circuit board 4, and outputs the drive signal 37 to the inverter circuit 4a.

Next, a power supply wiring block diagram of the impact driver 1 according to the present embodiment will be described with reference to FIG. As shown in FIG. 3, the DC voltage + VH _dc is directly applied to the inverter circuit board 4 from the full-wave rectifier circuit 14. On the other hand, since + VH _dc cannot be directly applied to the control circuit board 8 on which the microcomputer is mounted, the switching power supply circuit 15 is provided in this embodiment. The switching power supply circuit 15 is configured to generate + VL _dc of about 18 V from + VH _dc and supply it to the control circuit board 8. As described above, since a dedicated low-voltage direct current for the control circuit board 8 is supplied, an electronic element including a microcomputer or the like can be mounted on the control circuit board 8, thereby controlling the rotation of the motor 3. Fine control by electronic control can be realized.

  As described above, in this embodiment, the switching power supply circuit is provided as the power supply for the control circuit. Further, since the switching power supply circuit is housed in the handle of the housing, a small power tool with a power cord can be realized without increasing the size of the conventional power tool.

  As mentioned above, although this invention was demonstrated based on the Example, this invention is not limited to the above-mentioned Example, A various change is possible within the range which does not deviate from the meaning. For example, in the above-described embodiment, the impact driver is used as an example of the power tool. However, the power tool is not limited to the impact driver. An electric tool may be used.

  Moreover, in the Example of this invention, it was set as the structure which arrange | positions an inverter circuit board and a switching element inside a fuselage | body part. However, the arrangement of the inverter circuit board and the switching element is not limited to the inside of the body portion. For example, the inverter circuit board and the switching element may be accommodated in the handle portion. Moreover, you may accommodate an inverter circuit board and a switching element in the enlarged diameter part of a housing. Thus, even if the inverter circuit board and the switching element are arranged, the effect of the present invention can be obtained.

DESCRIPTION OF SYMBOLS 1 Impact driver 2 Housing 2a Body part 2b Handle part 2c Large diameter part 3 Motor 3a Rotor 3b Permanent magnet 3c Stator 3d Coil 3e Rotating shaft 4 Inverter circuit board 4a Inverter circuit 5 Switching element 6 Trigger switch 7 Switch circuit board 8 Control circuit board 11 AC (commercial power supply) 11a Power cord 13 Rotor fan 14 Full wave rectification circuit 15 Switching power supply circuit 17a Air intake holes 19a, 19b, 20 Bearing 21 Rotating impact mechanism 22 Planetary gear reduction mechanism 23 Spring 24 Hammer 25 Cam groove 26 Ball 27 Spindle 28 Hammer cam groove 29 Metal 30 Anvil 30a Mounting hole 31 Sleeve 32 Capacitor 33 Diode bridge 34 Nonpolar capacitor 35 Position detecting element 36 Signal 37 Drive signal 101 A Compact driver 102 Housing 102a Body portion 102b Handle portion 102c Expanded diameter portion 103 Motor 104 Inverter circuit board
104a Inverter circuit 106 Trigger switch 107 Switch circuit board 108 Control circuit board 108a Control circuit 109 Battery pack 121 Rotating impact mechanism 130 Anvil 130a Mounting hole 131 Sleeve 135 Hall IC
136 signal 137 drive signal

Claims (9)

A motor,
A housing for housing the motor;
A handle portion extending from a body portion of the housing and gripped by an operator;
A power cord extending from the housing and connectable to a commercial AC power source;
A control circuit for controlling the rotation of the motor,
A full-wave rectifier circuit capable of converting the AC of the commercial AC power source into a first DC,
A power tool characterized in that a switching power supply circuit capable of being converted into a second direct current having a voltage lower than that of the first direct current is accommodated in the handle portion. The housing has a body portion that houses the motor,
The handle portion extends in a direction intersecting with the body portion,
An enlarged diameter portion having a diameter larger than the outer diameter of the handle portion is formed near an end portion of the handle portion on the side away from the body portion,
2. The power tool according to claim 1, wherein a power circuit that converts the control circuit and an alternating current supplied from the power cord into a direct current for driving the motor is accommodated in the enlarged diameter portion.   The power tool according to claim 2, wherein the power supply circuit includes a diode bridge and a capacitor.   4. The electric motor according to claim 2, wherein the switching power supply circuit generates low-voltage direct current used in the control circuit from an output of the power supply circuit, and is housed in the handle portion. 5. tool.   The electric tool according to any one of claims 1 to 4, wherein the body portion, the handle portion, and the enlarged diameter portion of the housing are formed by integral molding of resin. The motor is a brushless DC motor;
The power tool according to any one of claims 1 to 4, wherein a circuit board having an inverter circuit and a position detection element is provided in a body portion of the housing.   The power tool according to claim 6, wherein the control circuit includes a microcomputer that controls the inverter circuit, and is disposed between the switching power supply circuit and the power supply circuit in the enlarged diameter portion of the housing. The housing is configured to be split into two in a plane including an extending direction in which the handle portion extends and a rotation axis direction of the motor,
The substrate on which the control circuit is mounted is disposed so as to extend substantially at right angles to the dividing surface,
The power tool according to claim 7, wherein the power tool is clamped by the housing divided into two parts. A power cord that can be connected to a commercial AC power source;
A full-wave rectifier circuit connected to the commercial AC power source and capable of converting AC of the commercial AC power source into a first DC;
A switching power supply circuit connected to the full-wave rectifier circuit and capable of being converted to a second direct current having a voltage lower than that of the first direct current;
A control circuit connected to the switching power supply circuit;
A motor connected to the full-wave rectifier circuit;
The power tool, wherein the power cord protrudes from one end, and includes a full-wave rectifier circuit, the switching power supply circuit, the control circuit, and a housing that houses the motor.

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