JP5333719B2 - Electric tool - Google Patents

Description

  The present invention relates to an electric tool having a compact overall length while using a brushless DC motor as a drive source.

  In recent years, brushless DC motors have come to be used in electric tools that perform a required work by rotationally driving a tip tool such as a drill or a driver with a motor. The brushless DC motor is a DC (direct current) motor without a brush (rectifying brush), and uses a coil (winding) on the stator side and a permanent magnet on the rotor side, and the electric power driven by the inverter is predetermined. The rotor is rotated by sequentially energizing the coils. As an example of a brushless DC motor, for example, one described in Patent Document 1 is known. In this Patent Document 1, a switching element for turning on and off energization of a coil wound around a stator is arranged on a circular circuit board attached to the rear end side (opposite side of the output shaft) of the motor. . The switching elements are all mounted on one surface (rear surface) of the circuit board, and are arranged in contact with a heat dissipating member fixed to the stator core separately from the circuit board for dissipating the heat generated.

JP 2004-357371 A

  In the method of mounting all the switching elements on the rear surface of the circuit board, the switching elements are arranged so that the height direction of the switching elements is parallel to the rotation axis of the motor because of the relationship between the cooling surface and the mounting space. However, with such an arrangement, good performance can be achieved in terms of cooling, but the space for the height of the circuit board and the switching element is required in the axial direction on the rear end side of the motor. When applied to a tool, the length of the housing in the front-rear direction becomes long.

  On the other hand, in order to prevent the length of the housing in the front-rear direction from being increased, it is conceivable that the circuit board is provided at a different position than the rear side of the motor. However, the wiring connecting the motor coil and the switching element is not only long, but it is difficult to dispose the substrate in another place because of the problem of heat dissipation of the switching element that easily generates heat.

  The present invention has been made in view of the above background, and an object of the present invention is to provide an electric tool that can be configured compactly by shortening the front-rear direction of the housing.

  Another object of the present invention is to provide an electric tool having a compact overall length while providing a substrate on which a switching element is mounted on the rear side of a motor.

  Still another object of the present invention is to provide an electric tool that can cool a switching element satisfactorily.

  Of the inventions disclosed in the present application, typical features will be described as follows.

According to one feature of the present invention, housing and an electric tool having a motor of a brushless DC type which is accommodated in a housing, and a drive circuit for supplying drive power to the motor, to rotate or drive the tool bit in the drive circuit includes a plurality of switching elements, at least a portion of the switching element is mounted on the substrate so as to overlap in the axial direction of the motor with respect to the scan stator. It arrange | positions in a perpendicular direction with respect to the axial direction of this motor. The overlapping switching elements are mounted on the board so as to be positioned in the left and right direction on the outer peripheral side of the motor. For this reason, the board protrudes from a circular board having the same shape as the outer diameter of the motor. The switching elements arranged in an overlapping manner are preferably fixed at the protruding portions.

  According to another feature of the invention, the housing is formed with an air inlet and an air outlet, a fan for generating an air flow from the air inlet to the air outlet is provided inside the housing, and the switching element is an air flow. An air inlet and an air outlet are formed so as to be disposed in the flow path. A plurality of ribs are formed inside the housing, and these ribs secure a gap between the housing and the motor.

  According to still another aspect of the present invention, a brushless DC system motor and a drive circuit that supplies drive power to the motor, and the power tool that rotates or drives the tip tool, the drive circuit includes a plurality of switching elements. And the drive circuit is mounted on the rear end side of the motor on a board that is provided perpendicular to the direction of the rotation axis of the motor, and the switching elements are mounted on the motor side and the non-motor side of the board. The mounted switching element was arranged so as to be horizontal with the substrate.

According to the invention of claim 1, the drive circuit includes a plurality of switching elements, and at least a part of the switching elements is mounted on the substrate so as to overlap the stator of the motor and the axial direction of the motor. In order to secure the mounting space, it is not necessary to extend the rear end of the housing, and it is possible to realize a power tool with a compact overall length (front and rear length) of the housing. Further, the housing has an air inlet and an air outlet, and a fan for generating an air flow from the air inlet to the air outlet is provided inside the housing, so that the switching element is disposed in the air passage. Since the air intake port and the air discharge port are formed, it is not necessary to separately provide a cooling device for cooling to the switching element.

  According to invention of Claim 2, since a board | substrate is arrange | positioned in the orthogonal | vertical direction with respect to the axial direction of a motor, a board | substrate can be attached in the little space of the rear-end side of a motor. Further, since the distance from the substrate to the stator winding of the motor can be short, it is useful for reducing the size and weight of the motor.

According to the invention of claim 3 , a plurality of ribs are formed inside the housing, and the gap between the housing and the motor is ensured by the ribs. Therefore, when the electric tool is dropped or bumped, the switching is performed. It is possible to prevent the element from being broken. Further, since the gap is secured by the rib, there is no possibility that the air flow path is blocked.

According to the invention of claim 4 , since the switching elements arranged in an overlapping manner are mounted on the substrate so as to be positioned on the outer peripheral side of the motor and in the left-right direction, the height of the housing in the vertical direction is increased. Without changing, it is possible to realize an electric tool with a compact overall length (front and rear length) of the housing.

According to the invention of claim 5 , the substrate has a shape having a protruding portion protruding from a circular substrate having substantially the same shape as the outer diameter of the motor, and the overlapping switching elements are fixed by the protruding portion. Therefore, the configuration of the present invention can be easily realized only by changing the shape of the substrate without changing the mounting method of the substrate fixed to the conventional motor.

According to the invention of claim 6 , in the electric tool which has a brushless direct current system motor and a drive circuit for supplying driving power to the motor, and rotates or drives the tip tool, the drive circuit includes a plurality of switching elements, The drive circuit is mounted on the back end of the motor on a board that is perpendicular to the direction of the motor's rotation axis, and the switching elements are mounted on the motor side and the non-motor side of the board. Since the switching element is mounted so as to be horizontal with the substrate, the switching element mounted on the non-motor side can prevent the front and rear length of the housing from being increased. In addition, since the switching elements are arranged on both sides of the substrate, the configuration of the present invention can be realized even in a brushless DC motor having a small diameter.

According to the seventh aspect of the invention, since the switching element mounted on the motor side is arranged so as to overlap the motor in the axial direction, it is possible to realize an electric tool having a compact overall length (front and rear length) of the housing. .

According to the invention of claim 8 , since the switching element mounted on the motor side is disposed on the outer periphery of the motor, it is not necessary to fix the substrate apart from the motor.

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

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 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 uses a rechargeable battery 2 as a power source, drives a rotary impact mechanism 4 using a motor 3 as a drive source, and applies rotation and impact to an anvil 5 as an output shaft, thereby holding a driver bit held by a sleeve 15 The rotary impact force is intermittently transmitted to a tip tool (not shown) such as screw tightening or bolt tightening.

  The motor 3 is a brushless DC motor, and is accommodated in a cylindrical body portion 6a of a housing 6 having a substantially T shape in a side view. The rotating shaft of the motor 3 is rotatably held by a bearing 17a on the rear end side of the body portion 6a and a bearing 17b provided in the vicinity of the center portion, and is attached to the rotating shaft in front of the motor 3 and is synchronized with the motor 3. A rotating fan 18 is provided, and a drive circuit board 7 for driving the motor 3 is disposed behind the motor 3. A plurality of switching elements 21a, 21b, and 21c are mounted on the drive circuit board 7, and the motor 3 is rotated by performing inverter control with these switching elements. The details of the drive circuit board 7 and the switching element will be described later.

  A trigger switch 8 is disposed in an upper portion of a handle portion 6b that integrally extends substantially perpendicularly from the body portion 6a of the housing 6, and the trigger switch 8 is biased by a spring (not shown) and protrudes from the handle portion 6b. A portion 8c is provided. A control circuit board 9 having a function of controlling the speed of the motor 3 by the pulling operation of the trigger operation part 8c is accommodated in the lower part of the handle part 6b. The control circuit board 9 includes the battery 2 and a trigger switch. 8 is electrically connected. The battery 2 is detachably attached to the battery holding portion 6c below the handle portion 6b.

  The rotary striking mechanism 4 includes a planetary gear speed reduction mechanism 10, a spindle 11, and a hammer 12. When the trigger operation portion 8c of the trigger switch 8 is pulled and the motor 3 is activated, the rotation of the motor 3 is caused by the planetary gear speed reduction mechanism 10. And is transmitted to the spindle 11, and the spindle 11 is rotationally driven at a predetermined speed. Here, the spindle 11 and the hammer 12 are connected by a cam mechanism, and this cam mechanism is formed on the V-shaped spindle cam groove 11 a formed on the outer peripheral surface of the spindle 11 and on the inner peripheral surface of the hammer 12. The hammer cam groove 12a and the balls 13 engaged with the cam grooves 11a and 12a are configured.

  The hammer 12 is always urged forward by a spring 14, and when stationary, the hammer 13 is in a position spaced from the end face of the anvil 5 by the engagement of the ball 13 and the cam grooves 11a and 12a. And the convex part which is not illustrated is symmetrically formed in two places on the rotation plane which the hammer 12 and the anvil 5 mutually oppose.

  When the spindle 11 is driven to rotate, the rotation is transmitted to the hammer 12 via the cam mechanism, and the convex portion of the hammer 12 engages with the convex portion of the anvil 5 before the hammer 12 rotates halfway. When the relative reaction between the spindle 11 and the hammer 12 occurs due to the reaction force of engagement at that time, the hammer 12 compresses the spring 14 along the spindle cam groove 11a of the cam mechanism, and the motor 3 side. Start retreating.

  When the protrusion of the hammer 12 moves over the protrusion of the anvil 5 by the backward movement of the hammer 12 and the engagement between the two is released, the hammer 12 is accumulated in the spring 14 in addition to the rotational force of the spindle 11. While being accelerated rapidly in the rotational direction and forward by the action of the elastic energy and the cam mechanism, the spring 14 is moved forward by the urging force of the spring 14, and the convex portion is reengaged with the convex portion of the anvil 5 to rotate integrally. start. At this time, since a strong rotational impact force is applied to the anvil 5, the rotational impact force is transmitted to the screw via a tip tool (not shown) attached to the anvil 5.

  Thereafter, the same operation is repeated, and the rotational impact force is intermittently repeatedly transmitted from the tip tool to the screw. For example, the screw is screwed into a material to be fastened such as wood.

  2 is a diagram showing the drive circuit board 7 shown in FIG. 1, wherein (1) is a rear view seen from the rear side, (2) is a side view seen from the side, and (3) is seen from the front side. It is a front view. Six switching elements 21a, 21b, 21c, 22a, 22b, and 22c are mounted on the drive circuit board 7. What is characteristic in the present embodiment is that, of the six switching elements, two switching elements 21c and 22c are arranged on the rear side (the side opposite to the motor 3) of the driving circuit board 7 and in parallel with the driving circuit board 7. The remaining four switching elements 21a, 21b, 22a, and 22b are arranged on the front side of the drive circuit board 7 (the same side as the motor 3), and the arrangement direction thereof is the front-rear direction (perpendicular to the drive circuit board 7). Direction).

  The drive circuit board 7 is a known board such as an epoxy board or a glass composite board, and a single-sided board or a double-sided board can be used. The shape of the drive circuit board 7 is based on a circular board having substantially the same diameter as that of the motor 3, and four protrusions 25a, 25b, 25c, and 25d for mounting the switching elements are formed on the outer periphery thereof. Between these protrusions 25a and 25b and between the protrusions 25c and 25d, a shape cut into a V shape is provided to facilitate the passage of cooling air. A hole 7 a for penetrating the rotation shaft of the motor 3 is formed at the center of the drive circuit board 7. The drive circuit board 7 is fixed to the rear of the motor 3 with screws by four screw holes 24a, 24b, 24c, and 24d.

  A connector 23 is provided below the drive circuit board 7 as shown in FIG. 2 (3), and a switching element drive signal is input from a control signal output circuit described later. Further, two lead wires for + and − are connected to the drive circuit board 7, and power from the battery 2 is supplied.

3 (1) is a cross-sectional view of the AA portion of FIG. 1 and a rear view thereof, and (2) is a cross-sectional view of the BB portion of FIG. 1 and a rear view thereof. It is a figure. The motor 3 includes a stator 3a in which a stator winding 30 is wound around a stator core 32 in which electromagnetic steel plates and the like are laminated, and a stator 3a that is rotatably attached to the inside of the stator 3a, and a two-pole magnet is fixed. It has a rotor 3b. As can be understood from these drawings, a part of the outer surface side of the stator 3a is formed with a flat part, and the four flat parts provided in the circumferential direction are formed on the inner peripheral side of the housing 6a, which will be described later. It is fixed in good contact with the flat holding part. In these figures, the upper and lower sides of the motor 3 and the left and right sides (Note: the left and right sides are based on the direction viewed from the operator holding the tool, so in this figure, the direction indicated by (1) is the left and right. ) In the vicinity of the central portion, there is a space between the motor 3 and the housing 6a. In this space, there are two ribs 38 shown in FIG. 3 (1) and four ribs shown in FIG. 3 (2). Ribs 39 are provided, and these ribs 38 and 39 are brought into contact with the outer peripheral portion of the motor 3 or adjacent to each other with a small distance.

  Since the motor 3 and the housing 6a are configured to have a predetermined gap as described above, the air generated by the fan 18 can flow into the space defined by the gap, so that the switching elements 21a, 21b, 22a, 22b Can be cooled satisfactorily. Further, since the space is prevented from being crushed by the ribs 38 and 39, an excessive load is not applied to the switching element even when the impact driver 1 is dropped or the housing 6a is hit. It is possible to provide a highly reliable power tool that can be prevented from being damaged.

  Next, the configuration and operation of the drive control system of the motor 3 will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the motor drive control system. In the present embodiment, the motor 3 is a three-phase brushless DC motor. This brushless DC motor is a so-called inner rotor type, and includes a rotor (rotor) 3b including a plurality of sets (two sets in this embodiment) of permanent magnets (magnets) including N poles and S poles. In order to detect the rotational position of the stator 3a composed of three-phase stator windings U, V, and W connected in a star connection, and the rotational position of the rotor 3b, they are arranged at predetermined intervals in the circumferential direction, for example, at an angle of 60 °. The three rotational position detecting elements (Hall elements) 42 are provided. Based on the position detection signals from these rotational position detection elements 42, the energization direction and time to the stator windings U, V, W are controlled, and the motor 3 rotates. The rotational position detection element 42 is preferably arranged on the drive circuit board 7.

  The elements mounted on the drive circuit board 7 include six switching elements Q1 to Q6 such as FETs (Field Effect Transistors) connected in a three-phase bridge format. The gates of the six switching elements Q1 to Q6 that are bridge-connected are connected to the drive circuit board 7, and the drains or sources of the six switching elements Q1 to Q6 are star-connected stator windings U. , V, W. As a result, the six switching elements Q1 to Q6 perform a switching operation by the switching element drive signals (drive signals such as H4, H5, and H6) input from the drive circuit board 7 and are applied to the drive circuit board 7. Electric power is supplied to the stator windings U, V, and W using the DC voltage of the battery 2 as three-phase (U-phase, V-phase, and W-phase) voltages Vu, Vv, and Vw.

Of the switching element drive signals (three-phase signals) for driving the gates of the six switching elements Q1 to Q6, the three negative power supply side switching elements Q4, Q5, Q6 are converted into pulse width modulation signals (PWM signals) H4, Based on the detection signal of the operation amount (stroke) L of the trigger operation unit 8c of the trigger switch 8 by the calculation unit 41 supplied as H5 and H6 and mounted on the control circuit board 9, the pulse width (duty ratio) of the PWM signal ) Is adjusted to adjust the amount of power supplied to the motor 3, and the start / stop of the motor 3 and the rotation speed are controlled.

  Here, the PWM signal is supplied to any one of the positive power supply side switching elements Q1 to Q3 or the negative power supply side switching elements Q4 to Q6 of the drive circuit board 7, and the switching elements Q1 to Q3 or the switching elements Q4 to Q6 are operated at high speed. As a result, the power supplied to the stator windings U, V, W from the DC voltage of the battery 2 is controlled by switching. In this embodiment, since the PWM signal is supplied to the negative power supply side switching elements Q4 to Q6, the electric power supplied to each stator winding U, V, W is controlled by controlling the pulse width of the PWM signal. The rotational speed of the motor 3 can be controlled by adjusting.

  The impact driver 1 is provided with a forward / reverse switching lever 51 for switching the rotational direction of the motor 3, and the rotational direction setting circuit 50 switches the rotational direction of the motor each time a change in the forward / reverse switching lever 51 is detected. The control signal is transmitted to the calculation unit 41. Although not shown, the calculation unit 41 is a central processing unit (CPU) for outputting a drive signal based on the processing program and data, a ROM for storing the processing program and control data, and for temporarily storing data. RAM, a timer, and the like.

  The control signal output circuit 46 forms a drive signal for alternately switching predetermined switching elements Q1 to Q6 based on the output signals of the rotation direction setting circuit 50 and the rotor position detection circuit 43, and controls the drive signal. The signal is output to the signal output circuit 46. As a result, the predetermined windings of the stator windings U, V, and W are alternately energized to rotate the rotor 3b in the set rotation direction. In this case, the drive signal applied to the negative power supply side switching elements Q4 to Q6 of the drive circuit board 7 is output as a PWM modulation signal based on the output control signal of the applied voltage setting circuit 49. The current value supplied to the motor 3 is measured by the current detection circuit 48, and the value is fed back to the calculation unit 41 so as to be adjusted to the set driving power. The PWM signal may be applied to the positive power supply side switching elements Q1 to Q3.

FIG. 5 is a side view showing the inner shape of the housing 6 of the impact driver 1 according to the embodiment of the present invention. An air intake port 53 that opens in the axial direction and a plurality of slits 54 that open in the circumferential direction with respect to the axial direction are provided at the rear end of the body portion 6 a of the housing 6. Furthermore, slits 55 that are a plurality of openings are formed in the vicinity of the mounting portion of the switching element that is arranged to overlap the motor 3. In the housing 6, not only slits but also ribs 38, 39, 40 for fixing the motor 3, and plane holding portions 57 for holding plane portions formed at several places on the outer peripheral portion of the motor 3 are formed. Is done. Several flat ribs are formed in the circumferential direction in the plane holding portion 57 to improve the contact property with the plane of the outer circumferential portion of the motor 3. The slit 56 is an opening formed on the outer side in the circumferential direction of the fan 18, and air inside the housing 6 is discharged to the outside through the slit 56. An attachment portion 58 for attaching the trigger switch 8 is formed in the housing 6. In FIG. 5 shows only one side of the shape of the housing 6 that is divided, is also the same shape other housing opposed thereto, the left and right housing by screwing the screws into the screw bosses 59, 60 Is fixed.

  FIG. 6 is an enlarged view of the vicinity of the rear end portion of the impact driver 1 of FIG. 1, and shows the flow of air flow for cooling. As can be understood from the drawing, the length Wm of the motor 3 in the front-rear direction (axial direction) overlaps with the length Ws required for arranging the switching elements in the front-rear direction. Therefore, the length of the body portion 6a of the housing 6 can be shortened by a length corresponding to the height of the switching elements 21a and 21b as compared with the conventional arrangement method, and a compact electric tool can be realized. In addition, with the implementation of the overlapping arrangement method, the width of the body portion 6a in the left-right direction (lateral direction) is slightly widened, but the height in the up-down direction is not different from that of a conventional electric tool. There is little need to be aware that the body 6a has become thicker.

  In FIG. 6, a part of the air sucked from the air inlet 53 and the slit 54 (FIG. 5) is sucked by the fan 18 through the upper side of the motor 3 along the path indicated by the arrow 61, and the slit 56 (FIG. 5). Is discharged to the outside. Similarly, although not shown by an arrow, a part of the air sucked from the lower air intake 53 is sucked by the fan 18 through the lower side of the motor 3 and is externally supplied from the slit 56 (FIG. 5). To be discharged.

Air sucked mainly from the slits 54 and 55 (FIG. 5) is sucked by the fan 18 through the periphery of the switching elements 21a and 21b along the path indicated by the arrow 62, and is then discharged from the slit 56 (FIG. 5) to the outside. Discharged. At this time, since the slit is formed in the vicinity of the switching element, the air sucked from the outside by the fan 18 immediately hits the switching element, so that the switching element can be effectively cooled. It is not necessary to provide a separate heat sink.
The same applies to the air flow on the switching elements 22a, 22b side. In addition, when it is desired to enhance the cooling performance, such as when used in a high temperature environment, it may be attached to another radiator on the radiator plate of the switching element.

  As described above, according to the present invention, it is possible to realize an electric tool that can be configured compactly by shortening the front-rear direction of the housing while using a brushless DC motor.

  In the above-described embodiment, the form applied to the impact driver as an example of the electric tool of the present invention has been described. However, the present invention can be applied to any other option that can use a brushless DC motor as a motor that is a drive source. Of course, the present invention can be similarly applied to the electric tool. In the above-described embodiment, an example in which an FET is used as a switching element has been described. However, the present invention can be similarly applied to a case in which another type of output transistor element such as an IGBT (Insulated Gate Bipolar Transistor) is used.

It is a figure which shows the internal structure of the impact driver which concerns on embodiment of this invention. FIGS. 2A and 2B are diagrams showing the drive circuit board 7 of FIG. 1, wherein FIG. 1A is a rear view seen from the rear side, FIG. 2B is a side view seen from the side, and FIG. (1) is a cross-sectional view of the AA portion of FIG. 1 and a rear view thereof, and (2) is a cross-sectional view of the BB portion of FIG. 1 and a rear view thereof. is there. It is a block diagram which shows the structure of the drive control system of the motor 3 of FIG. It is a side view which shows the shape inside the housing 6 of the impact driver 1 which concerns on embodiment of this invention. FIG. 2 is an enlarged view of the vicinity of a rear end portion of the impact driver 1 in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Impact driver 2 Battery 3 Motor 3a Motor stator 3b Motor rotor 4 Rotating impact mechanism 5 Anvil 6 Housing 6a Body part 6b (Housing) Handle part 6c (Housing) Battery holding part 7 Drive circuit Board 7a Hole 8 Trigger switch 8c Trigger operation part 9 Control circuit board 10 Planetary gear speed reduction mechanism 11 Spindle 11a Spindle cam groove 12 Hammer 12a Hammer cam groove 13 Ball 14 Spring 15 Sleeve 16a, 16b Bearing 17a, 17b Bearing 18 Fan 19 ) Rotating shaft 21a, 21b, 21c Switching element 22a, 22b, 22c Switching element 23 Connector 24a, 24b, 24c, 24d Screw hole 25a, 25b, 25c, 25d (Drive circuit base) Protruding portion 26 Lead wire 30 Stator winding 31 Permanent magnet 32 Stator core 38, 39, 40 Boss 41 Calculation unit 42 Rotation position detection element 43 Rotor position detection circuit 46 Control signal output circuit 48 Current detection circuit 49 Applied voltage Setting circuit 50 Rotation direction setting circuit 51 Forward / reverse switching lever 53 Air intake port 54, 55 (Intake) slit 56 (Exhaust) slit 57 Planar holding portion 58 (Trigger switch) mounting portion 59, 60 Screw boss

Claims (8)

A motor brushless DC type, a housing having a handle portion extending from the body portion and the barrel body portion that houses the motor, a driving circuit for supplying driving power to the motor, and an air inlet provided in the housing In the electric tool that has an air discharge port and a fan that is provided inside the housing and generates an air flow from the air intake port to the air discharge port , and rotates or drives the tip tool.
Wherein the drive circuit is accommodated a plurality of switching elements a Dressings containing within said body portion,
At least a part of the switching element is mounted on the substrate so as to overlap the stator of the motor in the axial direction of the motor ,
An electric tool characterized in that an air passage through which the air flow passes is formed outside the motor in the body portion, and the switching element is arranged in the air passage .   The electric power tool according to claim 1, wherein the substrate is disposed in a direction perpendicular to an axial direction of the motor. Wherein the plurality of ribs are formed inside the housing, power tool according to claim 1 or 2 gap for the air passage between the said housing motor by said ribs, characterized in that it is secured. The electric power tool according to claim 3 , wherein the switching elements arranged in an overlapping manner are mounted on the substrate so as to be positioned in a lateral direction on the outer peripheral side of the motor. The substrate has a shape having a protruding portion that protrudes from a circular substrate that is substantially the same shape as the outer diameter of the motor, and the switching elements arranged in an overlapping manner are fixed at the protruding portion. The electric tool according to claim 3 . In an electric tool that has a brushless DC system motor and a drive circuit that supplies driving power to the motor, and rotates or drives a tip tool,
The drive circuit includes a plurality of switching elements,
The drive circuit is mounted on a substrate provided perpendicularly to the rotation axis direction of the motor on the rear end side of the motor,
The switching elements are mounted in a distributed manner on the motor side and the non-motor side of the board, and the switching elements mounted on the non-motor side are arranged to be horizontal with the board. tool. The power tool according to claim 6 , wherein the switching element mounted on the motor side is disposed so as to overlap the motor in the axial direction. The power tool according to claim 7 , wherein the switching element mounted on the motor side is disposed on an outer peripheral portion of the motor.

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