WO2017082082A1

WO2017082082A1 - Electric tool

Info

Publication number: WO2017082082A1
Application number: PCT/JP2016/082058
Authority: WO
Inventors: 拓家吉成; 俊彰小泉; 一彦船橋; 祐貴武田
Original assignee: 日立工機株式会社
Priority date: 2015-11-13
Filing date: 2016-10-28
Publication date: 2017-05-18

Abstract

Provided is an electric tool for which, by devising the arrangement of circuit boards so as to be filled with resin, mounting efficiency is increased and output is increased while size reduction is achieved. A board case (40) is disposed inside a cylindrical housing (2, 3) for housing a brushless motor, and a first circuit board (50) for driving a motor (5) and a second circuit board (70) on which a control circuit is installed are housed inside the board case. The boards (50, 70) are stacked inside the board case in the direction that is perpendicular to the open face thereof and are disposed so as to extend in directions that are parallel to the open face. The boards (50, 70) are stacked so as to be parallel using a pin header and only the first circuit board (50) is screwed to the board case. Then, a curable resin that hardens from a liquid state is filled inside the board case (40) and is cured with the boards (50, 70) completely immersed therein.

Description

Electric tool

The present invention relates to a power tool driven by a motor, and more particularly to a device for mounting a control circuit and an inverter circuit.

There is known an electric tool that uses a brushless motor and performs high-precision motor rotation control by a controller such as a microcomputer. The brushless motor detects the rotational position of the rotor using a magnetic sensor, and controls the drive current supplied to the motor windings by the controller. As an example (grinder) of an electric tool using such a brushless motor, the technique of Patent Document 1 is known. In Patent Document 1, a brushless motor is accommodated coaxially with a cylindrical housing. In the motor, a stator having a coil is arranged on the outer peripheral side, and on the inner peripheral side, a rotor core that is rotated by a rotating shaft and holds a permanent magnet is provided. The rotating shaft is pivotally supported by a bearing on the front side and the rear side of the motor, and a cylindrical sensor magnet for detecting the rotational position of the rotor is provided behind the rear side bearing. Housed on the rear side of the housing are two substrates for mounting a position sensor such as a Hall IC that detects the position of the sensor magnet, an inverter circuit having a switching element, a microcomputer, a power supply circuit that controls the motor, and the like. Is done.

JP 2010-269409 A

In the technique of Patent Document 1, an inverter circuit, a microcomputer, and the like are mounted on a circuit board that extends in a direction perpendicular to the longitudinal direction of the housing, so that the size of the mounted element is limited due to the limitation of the outer shape of the housing. In recent years, power tools are required to be small but have a large output, so switching elements used for inverter circuits, capacitors for countermeasures against peak voltage, etc. become large, and the problem to be solved is that the power tools become large was there. In addition, when the output of the power tool is increased, the power supply circuit that converts AC power into DC and the switching elements such as FETs (field effect transistors) become larger, so the circuit board on which they are mounted becomes larger, This hinders the downsizing of tools.

The present invention has been made in view of the above background, and its purpose is to provide an electric tool that improves the mounting efficiency by devising the arrangement of the circuit board accommodated in the housing and suppresses the enlargement of the main body size. There is to do. Another object of the present invention is to provide an electric motor that uses a large-capacity IGBT (Insulated Gate Bipolar Transistor) as a switching element to improve the degree of freedom of the installation position while increasing the output while improving the cooling efficiency of the heating element. To provide a tool. Still another object of the present invention is to provide a circuit board on which a switching element such as an IGBT is mounted and a circuit board on which a control circuit is mounted in a board case, and these are hardened with resin, thereby improving reliability and durability. It is to provide a power tool that is greatly enhanced.

Of the inventions disclosed in the present application, typical features will be described as follows. According to one aspect of the present invention, a driving circuit for driving a brushless motor, a first circuit board on which the driving circuit is mounted, a control circuit for controlling the driving circuit, and a second circuit on which at least a part of the control circuit is mounted. In a power tool having a circuit board, a board case for housing a first circuit board and a second circuit board and having an opening surface on one side, and a housing for housing a brushless motor and the board case, the board case A first circuit board and a second circuit board were accommodated therein. In the board case, the first circuit board and the second circuit board are arranged in a direction perpendicular to the opening surface, and the first circuit board and the second circuit board extend in a direction parallel to the opening surface. did. The first circuit board is disposed on the side close to the opening surface, and the switching element included in the drive circuit is mounted on the opening surface side of the first circuit board. Further, an element (such as a microcomputer) constituting the control circuit was mounted on the surface of the second circuit board opposite to the first circuit board.

According to another aspect of the present invention, the plurality of switching elements are arranged such that the longitudinal direction thereof is orthogonal to the first circuit board, and a part of the switching elements is mounted so as to protrude from the opening surface of the board case. . The first circuit board is further mounted with a rectifier circuit for converting commercial AC power into DC, and the rectifier circuit includes a smoothing capacitor. The capacitor is mounted on the first circuit board so as to be partially exposed from the opening surface. In addition, the first circuit board and the second circuit board are immersed in the resin by allowing the curable resin to flow and harden in the substrate case. The control circuit includes a microcomputer that controls the inverter circuit by the switching element, and the microcomputer is mounted on the second circuit board. The first circuit board and the second circuit board are electrically connected by a connector (for example, a pin header).

According to still another feature of the present invention, the substrate case is narrowed so that the two parallel wall portions extending orthogonally from the opening surface and the width dimension from the parallel wall portion to the side opposite to the opening portion become smaller. It is the container shape which formed the bottom part by. The first circuit board is formed with a width smaller than that of the second circuit board and is larger than the width of the bottom portion. The second circuit board has a size smaller than the width of the first circuit board and a size larger than the width of the bottom portion.

According to still another feature of the present invention, a cylindrical motor housing that houses a brushless motor, and a cylindrical rear cover that is attached to one of the motor housings and houses a substrate case, the outer diameter of the rear cover is The outer diameter of the motor housing was made smaller than the outer diameter. In addition, an output shaft that is rotated by the rotational force of the brushless motor, a power transmission mechanism that transmits the rotational force of the brushless motor to the output shaft, and a gear case that is attached to the other of the motor housing and accommodates the power transmission mechanism, The shaft protrudes from the gear case, and the opening of the substrate case is configured to open in the same direction as the protruding direction of the output shaft from the gear case.

According to the present invention, since a board for a drive circuit and a board for a control circuit are connected to each other by a board-to-board connector such as a pin header, a large switching element can be used by effectively utilizing space, so that a high output This makes it possible to perform stable motor control. Further, the cooling efficiency can be improved by arranging the switching element so as to be exposed to the outside from the opening. In addition, the electronic device mounted on the circuit board is covered with resin, and the circuit board is disposed separately from the cooling air flow path generated by the rotation of the cooling fan, so that moisture that has entered from the outside enters the electronic element. Adhesion can be suppressed and the life of the power tool can be extended.

It is a longitudinal cross-sectional view which shows the whole structure of the electric tool 1 which concerns on the Example of this invention, and the black arrow shows the flow of the cooling wind in the state which turned on the trigger switch. FIG. 6 is a perspective view of electronic elements mounted on a substrate case 40 before being incorporated in the motor housing 2 when viewed from the opening surface side. FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 (except for the rear cover 3). FIG. 2 is a cross-sectional perspective view taken along line AA in FIG. 1. 2 is a block diagram illustrating a circuit configuration of a drive control system of the electric tool 1. FIG. It is a perspective view which shows the single-piece | unit shape of the substrate case 40 of FIG. FIG. 5 is a view for explaining a housing state of the first circuit board 50 in the board case 40 of FIG. 1 and an arrangement state of the pin headers 56 to 58; 4 is a side view of the pin header 58. FIG.

Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, parts having the same function are denoted by the same reference numerals, and repeated description is omitted. Further, in this specification, description will be made assuming that the front, rear, left, right, and up and down directions are directions shown in the drawing.

FIG. 1 is a top view of a power tool 1 according to an embodiment of the present invention. Here, as an example of the electric power tool 1, a disc grinder is shown in which a spindle 24 that rotates in a direction orthogonal to the rotation shaft 6 of the motor 5 is provided, and a tip tool connected to the spindle 24 is a circular grindstone 30. A housing (outer frame or casing) of the electric power tool 1 is attached to the rear of the motor housing 2 and a gear case 21 that houses a power transmission mechanism, a cylindrically-shaped integrally formed motor housing 2 that houses a motor 5, and an electric tool. It is composed of three main parts of a cylindrical rear cover 3 that accommodates equipment. The method of forming the housing is arbitrary, and it may be configured by three parts in the front-rear direction as in the present embodiment, the motor housing 2 and the rear cover 3 may be configured integrally, or other divisions. It may be formed in a shape. The motor housing 2 is made of resin or metal and has a substantially cylindrical shape having an opening 2a on the front side and an opening 2b on the rear side. The inner diameter of the motor housing 2 has a diameter slightly larger than the outer diameter of the stator core 9 of the motor 5, and the outer surface side of the motor housing 2 constitutes a portion (gripping part) that the operator grips with one hand. An opening 3 a of the rear cover 3 is attached to the rear opening 2 b of the motor housing 2. The outer diameter of the rear cover 3 is substantially equal to or slightly smaller than the outer diameter of the motor housing 2.

The motor 5 has a rotation shaft 6 disposed along the central axis direction (front-rear direction) of the motor housing 2, and the calculation unit determines the rotation position of the rotor core 7 from rotation position detection elements 49a to 49c (in the drawing). 49b only), and the inverter circuit 60 composed of a plurality of switching elements Q1 to Q6 (only Q4 to Q6 is visible in the figure) is controlled to drive sequentially to a predetermined coil 12 of the motor 5. By supplying electric power, a rotating magnetic field is formed to rotate the rotor. The motor 5 is a three-phase brushless DC motor, and the rotor rotates in the inner circumferential space of the stator core 9 having a substantially cylindrical shape. The stator core 9 is manufactured by a laminated structure of annular thin iron plates. Six teeth (not shown) are formed on the inner peripheral side of the stator core 9, and resin-made

insulators

10 and 11 are mounted in the longitudinal direction of each tooth, and the teeth are sandwiched between the

insulators

10 and 11. A coil 12 is formed by winding a copper wire in an elliptical shape. In this embodiment, the coil 12 is preferably a star connection having three phases of U, V, and W phases, and three lead wires for U, V, and W phases for supplying driving power to the coil 12 are used. (Not shown) is connected to the first circuit board 50. On the inner peripheral side of the stator core 9, the rotor core 7 is fixed to the rotating shaft 6. The rotor core 7 is formed by laminating a large number of annular thin steel plates in the axial direction, and a flat permanent magnet 8 having N poles and S poles is inserted into a slot portion having a rectangular cross-sectional shape.

The rotary shaft 6 includes a rear-side bearing (first bearing) 14 a fixed to the motor housing 2 and a front-side bearing (second bearing) fixed in the vicinity of the connection portion between the gear case 21 and the motor housing 2. 14b and is held rotatably. A cooling fan 15 is provided between the bearing 14 b and the motor 5 when viewed in the axial direction of the rotary shaft 6. The cooling fan 15 is, for example, a plastic centrifugal fan. When the motor 5 rotates, the cooling fan 15 rotates in synchronization with the rotating shaft 6, so that the motor 5, the control circuit, etc. A wind flow (cooling air) for cooling the air is generated. The cooling air is sucked from

suction ports

3d and 3e provided on the upper and lower and left and right side walls of the rear cover 3 in the vicinity of the rear end of the first circuit board 50, and accommodates the first circuit board 50 and the second circuit board 70. It flows from the rear to the front side around the case 40, passes through the bearing holder portion 20 of the motor housing 2, and flows into the accommodation space of the motor 5. The bearing holder portion 20 is formed with a plurality of columns (not shown) from the cylindrical portion holding the outer ring portion of the bearing 14a (see FIG. 1) toward the outside, and is hollow at locations other than the columns. The cooling air flows from the space in which the substrate case 40 is accommodated to the space in which the motor 5 is accommodated.

Cooling air that has flowed into the housing space of the motor 5 is sucked by the cooling fan 15 through the gap between the outer periphery of the stator core 9 and the motor housing 2 (see the black arrow in the figure) and the inner space of the stator core 9. Then, the air is discharged from the through hole 21 b of the gear case 21 to the front side through the through hole of the fan cover 16 or forward from the lower hole 21 c of the fan cover 16. In this embodiment, the first circuit board 50, the sensor magnet 18, the bearing 14a, the motor 5, the cooling fan 15, and the rear circuit (windward side) to the front side as viewed on the axis of the rotating shaft 6 of the motor 5, The bearings 14b are arranged in series (on a straight line) in the axial direction. The air windows such as the

suction ports

3d and 3e for sucking outside air are arranged around the first circuit board 50 and behind the elements that generate large amounts of heat, particularly the switching elements Q1 to Q6 (see FIG. 2 described later). Is done. As described above, in this embodiment, as viewed in the direction of the rotation axis of the motor 5, the element that generates heat when the cooling air flows so as to substantially contact the entire outer peripheral surface from the rear side to the front side of the housing is effectively cooled. Can do. Here, the cooling air is configured to flow evenly so as to be substantially in contact with the entire inner peripheral surface of the housing. However, in the housing portion of the rear cover 3, the cooling air is configured to concentrate on a specific portion from the opening. The cooling air may be concentrated on the switching elements Q1 to Q6 and the diode bridge (described later in FIG. 2).

The gear case 21 is formed by integrally molding a metal such as aluminum, for example, and accommodates a power transmission mechanism including a pair of bevel gears (22, 23), and rotatably holds a spindle 24 serving as an output shaft. . The spindle 24 is disposed so as to extend in a direction substantially orthogonal to the axial direction (here, the front-rear direction) of the rotating shaft of the motor 5, and the first bevel gear 22 is disposed at the front end portion of the rotating shaft 6. The first bevel gear 22 meshes with a second bevel gear 23 attached to the upper end portion of the spindle 24, and this power transmission means acts as a speed reduction mechanism. The upper end side of the spindle 24 is rotatably supported by a gear case 21 by a cylindrical metal 25, and is supported by a bearing 26 by a ball bearing near the center. The bearing 26 is fixed to the gear case 21 via a spindle cover 27.

A mounting base 28 is provided at the tip of the spindle 24, and a tip tool such as a grindstone 30 is attached by a washer nut 31. The grindstone 30 is, for example, a resinoid flexible toy, flexible toy, resinoid toy, sanding disk, etc. having a diameter of 100 mm. Depending on the type of abrasive used, surface grinding and curved surface grinding of metals, synthetic resins, marble, concrete, etc. are possible. is there. The wheel guard 32 covers the radially outer side and upper side of the rear side of the grindstone 30. In addition, as a front-end tool with which the electric tool 1 is mounted | worn, not only the grindstone 30 but other tools, such as a bevel wire brush, a nonwoven fabric brush, and a diamond wheel, can be attached similarly.

A sensor magnet 18, which is a magnetic body having different magnetic poles in the rotation direction, is attached to the rear end of the rotation shaft 6 of the motor 5. The sensor magnet 18 is a thin cylindrical permanent magnet that is attached to detect the rotational position of the rotor core 7, and an N pole and an S pole are formed in order by 90 degrees in the circumferential direction. A substantially semicircular sensor substrate 48 arranged in a direction perpendicular to the rotation shaft 6 is provided behind the sensor magnet 18 and inside the substrate case 40, and the position of the sensor magnet 18 is set on the sensor substrate 48. Rotation position detecting elements 49a to 49b for detecting are provided. The rotational position detecting elements 49a to 49b detect the rotational position of the rotor core 7 by detecting a change in the magnetic field of the rotating sensor magnet 18, and each rotational position detecting element 49a to 49b is detected at a predetermined angle in the rotational direction. Provided.

The interior of the rear cover 3 formed in a substantially cylindrical shape is supplied by a calculation unit (described later) that controls the rotation of the motor 5, an inverter circuit 60 that is a circuit for driving the motor 5, and a power cord (not shown) from the outside. A power supply circuit 65 for converting the alternating current to direct current is accommodated. In this embodiment, these circuits are mounted on a common first circuit board 50. The first circuit board 50 is disposed so as to be parallel to the longitudinal center axis (coaxial with the rotating shaft 6 of the motor 5) of the electric power tool 1. Here, the front and back surfaces of the first circuit board 50 and the second circuit board 70 are arranged to extend in the front-rear and left-right directions. The first circuit board 50 is disposed inside a container-like substrate case 40 having an opening surface, and is entirely covered with a curable resin that is hardened by being cured from a liquid state. Here, when the grindstone 30 of the electric power tool 1 is down (in the direction of FIG. 1), the plurality of switching elements Q <b> 1 are arranged so that the opening surface of the substrate case 40 faces downward. To Q6 are arranged to extend downward from the first circuit board 50. Here, the electric power tool 1 according to an embodiment of the present invention is a tool mainly for working by grinding and grinding a workpiece by rotating a grindstone 30 attached to a spindle 24. And dust is generated. For this reason, the worker keeps the workpiece as low as possible so that dust or the like does not fall on himself / herself. Therefore, normally, the operator works with the spindle 24 not facing up, preferably with the spindle 24 facing down rather than in the left-right direction. At this time, in the electric tool 1 (grinder) to which the present invention is applied, the opening direction of the opening surface 40a of the substrate case 40 is the same as the direction of the spindle 24 (the protruding direction from the gear case 21). The opening direction of the opening surface 40a is generally directed downward, and even if dust generated during processing enters the interior of the rear cover 3 from the wind window, accumulation in the substrate case 40 is suppressed. Further, when the worker completes the work, the power tool 1 is placed on a place such as the ground, but if there are no special circumstances, the power tool 1 is placed in the direction it is held. . That is, the electric tool 1 is placed with the spindle 24 facing downward. For this reason, even if dust or the like enters the substrate case 40 due to the influence of cooling air, for example, the dust in the substrate case 40 is removed due to the influence of gravity or the like when placed.

Since the inverter circuit 60 needs to pass a large drive current through the coil 12, a large-capacity output transistor such as an FET (field effect transistor) or IGBT is used as the switching elements Q1 to Q6. Since these switching elements Q1 to Q6 generate a large amount of heat, a heat dissipating structure for improving the cooling effect is considered. In this embodiment, a cooling metal plate is further attached to the heat dissipating plates of the switching elements Q1 to Q6. Since the heat radiating plate and the metal plate are arranged on the leeward side (motor side) from the wind window (not shown) serving as the suction port, they are directly exposed to the cooling air indicated by the black arrows. A power supply circuit 65 is provided on the rear side of the switching elements Q1 to Q6. The power supply circuit 65 of the present embodiment includes a rectifier circuit that converts commercial power (AC) supplied from the outside into DC. The power supply circuit 65 is located on the rear side of the substrate case 40 so as to be close to a power cord (not shown) wired so as to extend from the rear end surface of the rear cover 3 to the outside from the efficiency of wiring, and the switching elements Q1 to Q6. It is mounted on the rear side (the non-motor side far from the motor 5).

In the space defined by the substrate case 40 (inside the container), in addition to the first circuit substrate 50, a sensor substrate 48 on which the rotational position detecting elements 49a to 49b are mounted is provided. The sensor substrate 48 is disposed so as to be orthogonal to the rotation axis direction of the motor 5. On the rear side of the substrate case 40, a power cord holding portion 43 and an abutting portion 44 that abuts against the inner wall surface of the rear cover 3 are formed.

FIG. 2 is a perspective view of the substrate case 40 before being assembled in the motor housing 2 as seen from the opening surface side. A power circuit 65 and an inverter circuit 60 including six switching elements Q1 to Q6 are mainly mounted on the first circuit board 50 (see FIG. 1) inside the substrate case 40. In the first circuit board 50, the power supply circuit 65 is disposed on the rear side of the first circuit board 50 in view of the wiring advantage of being close to the input and output points and the flow of the cooling air. It is arranged on the front side of the circuit board. In the present embodiment, IGBTs (insulated gate bipolar transistors) are used as the switching elements Q1 to Q6 so that a large drive current flows in order to increase the output of the motor 5. The IGBT used here is housed in a flat cubic ceramic package, and three terminals of the gate, collector, and emitter extend in parallel from one surface (bottom surface) and are adjacent to the surface from which the three terminals extend. A heat radiating plate is embedded in the back surface (one of flat and wide surfaces). A screw hole for attaching to a heat radiating means prepared separately is formed in a part of the heat radiating plate. Here, the three terminals of the switching elements Q1 to Q6 are soldered to the first circuit board 50, and the front face on which the model number and the like are printed is arranged so as to be orthogonal to the first circuit board 50.

The front and back surfaces of the switching elements Q1 to Q3 are arranged side by side so as to be parallel to one side wall surface 41c of the substrate case 40, and the front and back surfaces of the switching elements Q4 to Q6 are the other side wall surface 41d of the substrate case 40. Are arranged side by side in parallel. Between the switching elements Q4 to Q6 and the side wall surface 41d of the substrate case 40, three connectors 55a to 55c for connecting to the coil 12 of the motor 5 are provided. As can be understood from this figure, the switching elements Q1 to Q6 mounted on the first circuit board 50 are large-sized elements that occupy more than half of the internal space of the substrate case 40 when viewed in the front-rear direction. Elements constituting the power supply circuit 65 are mounted in the space behind the switching elements Q1 to Q6. Here, a diode bridge 66 is mounted at the center, a choke coil 69 and a capacitor 68a are mounted next to the diode bridge 66, and a film capacitor 67 and a capacitor 68b are mounted on the rear side thereof. At this time, the

capacitors

68a and 68b are mounted on the first circuit board 50 so as to be partially exposed from the opening surface. The choke coil 69 and the film capacitor 67 function as a noise filter that removes noise flowing from the commercial AC power supply 100 and noise of the entire circuit generated by switching control and the like.

In the switching elements Q1 to Q6, a semiconductor element is enclosed in a substantially rectangular parallelepiped package such as ceramic, and three metal terminals extend from the lower side of the package. A metal heat sink is provided on the back side of the package. Embedded. The heat radiating plate is planar, and the switching elements Q1 to Q6 are arranged so that the spreading direction of the heat radiating plate is horizontal and orthogonal to the longitudinal direction of the first circuit board 50 (the front-rear direction in FIG. 2). In addition, heat radiating metal plates 81 to 86 are fixed to the heat radiating plate on the back of the package. Normally, the collector terminal of the IGBT is electrically connected to the heat sink on the back side of the package. Therefore, when the collector terminal is commonly connected, a common metal plate is fixed to the plurality of switching elements Q1 to Q3. Also good. On the other hand, the remaining three switching elements Q4 to Q6 of the inverter circuit 60 are arranged in a line and arranged in parallel with the switching elements Q1 to Q3. The heat dissipation plate on the back of the package of switching elements Q4 to Q6 is provided with a metal plate for heat dissipation, but these collector terminals are not connected in common (between different polarities), so they must be made independent of each other. Don't be.

3 is a cross-sectional view taken along a line AA in FIG. The legs of the switching elements Q2, Q5 are fixed to the first circuit board 50 by soldering. The first circuit board 50 is a single-layer or multilayer printed board, and a multilayer glass composite board is used here. On the back side of the switching elements Q2 and Q5 (surface opposite to the print surface of the model number or the like), heat radiating

metal plates

82 and 85 are fixed by

screws

87b and 87e. The

metal plates

82 and 85 are small pieces of aluminum alloy thick plates. An electronic switch 51 that operates in conjunction with a trigger lever (not shown) is mounted between the switching element Q2 and the side wall surface 41c. The electronic switch 51 is for switching the motor 5 on and off, and is mounted on the first circuit board 50 at a position accessible from the opening surface 40a side. A metal arm 51a that can swing in a cantilever manner is provided on the top of the electronic switch 51, and is operated by a slide switch (not shown) provided so as to be partially exposed to the outside of the housing. When the slide switch moves, the plunger (not shown) of the electronic switch 51 is moved by pressing the metal arm 51a, and the switch is turned on. Connectors 55a to 55c for transmitting the outputs of the switching elements Q1 to Q6 to the coil 12 of the motor 5 are provided between the switching element Q5 and the side wall surface 41d.

On the bottom surface 41g side of the first circuit board 50, the second circuit board 70 is disposed in a state of being separated from the first circuit board 50 by a predetermined distance. The second circuit board 70 is also a single-layer or multilayer printed board, and a multilayer glass composite board is used here. In order to hold the first circuit board 50 and the second circuit board 70 at a predetermined distance and to perform necessary wiring, in this embodiment, two circuit boards are formed using

pin headers

56 and 58. Connected. In the

pin headers

56 and 58, thin members extending in the vertical direction are metal pins, and are held in a prismatic case. Here, the configuration of the pin header will be described with reference to FIG.

FIG. 8 is a side view of a plurality of connected pin headers 58. The pin header 58 is provided with a synthetic resin case 58b in the vicinity of the middle in the longitudinal direction of a thin metal pin 58a extending in the vertical direction. Each case 58b is connected by a relatively thin connecting portion 58c made of resin, and the user cuts the connecting portion 58c as necessary to adjust the number of connected pins 58a. To do. The distance P (pitch) between the pins is about 1 to 10 mm, which is 2 mm. In FIG. 8, a 6-pin header is shown as an example, but the number of connections is changed as appropriate according to the specifications of the board, and the pin header 58 of this embodiment has 13 pins (described later in FIG. 7). The pin header 56 uses the same components, and the pin header 56 has two pins (described later in FIG. 7). By selecting the axial length L of the case 58b, the distance (predetermined distance) between adjacent substrates can be arbitrarily set. Here, L = about 5 mm. Thus, if the first circuit board 50 and the second circuit board 70 are fixed using the pin headers 56 to 58, the first circuit board 50 and the second circuit board 70 are made of a conductor such as a copper foil. The circuit wiring can be electrically connected and the first circuit board 50 and the second circuit board 70 can be physically coupled. Returning again to FIG.

The first circuit board 50 is supported by stepped

portions

45a and 45c formed on the side surface inside the substrate case 40, and fixed to the circuit board with screws described later. On the other hand, the second circuit board 70 is fixed to the first circuit board 50 by pin headers 56 to 58. In other words, the first circuit board 50 and the second circuit board 70 are electrically connected by the pin headers 56 to 58 so that they cannot be moved relative to each other. Thus, in the substrate case 40 having the opening surface 40a with one surface opened, the first circuit board 50 and the second circuit board 70 are arranged so as to be overlapped in a direction perpendicular to the opening surface 40a, and the opening surface The surface of 40a, the 1st circuit board 50, and the 2nd circuit board 70 is arrange | positioned so that it may extend in a parallel direction. On the bottom surface side of the second circuit board 70, electronic elements for forming a control circuit, for example, a microcomputer, a capacitor, a resistor, and the like are mounted. Furthermore, in this embodiment, a low voltage constant voltage power supply circuit (described later) for the microcomputer is also mounted on the bottom surface side of the second circuit board 70. The electronic device arrangement space in the substrate case 40 is on the opening surface 40a side of the first circuit board 50, on the bottom surface 41g side of the second circuit board, or between the first circuit board 50 and the second circuit board 70. , Narrow in this order. Therefore, in this embodiment, an IGBT, a diode bridge 66, a noise filter film capacitor 67 and a choke coil 69, and smoothing

capacitors

68a and 68b, which are relatively large electronic elements, are arranged on the opening surface 40a side of the first circuit board 50. The arithmetic unit 71 (microcomputer), the capacitor 74, and the like, which are relatively small electronic elements, are arranged on the bottom surface 41g side of the second circuit board. Thereby, the space in the substantially cylindrical case 40 is efficiently used, and the mounting efficiency of the electronic element is increased.

The internal space of the substrate case 40 is filled with resin from the bottom surface 41 g to the position indicated by the arrow 90. The resin (not shown) is placed so that the opening surface 40a of the substrate case 40 is on the upper side, and the substrate case 40 is filled with a resin in a liquid form and then cured, and the switching elements Q1 to Q6 are liquid crystals. About half of the vertical position is immersed from the surface, and the upper portions of the

capacitors

68a and 68b and the diode bridge 66 on the rear side are exposed. Since all the parts from the bottom 41g part to the liquid level (broken line 90) are filled with the resin in the substrate case 40, the first circuit board 50 and the second circuit board 70 are firmly fixed with the resin and do not rattle. Thus, the first circuit board 50 and the second circuit board 70 are accommodated in the container-like substrate case 40, and the resin is filled therein so that the first circuit board 50 and the second circuit board 70 are completely or Since it is almost completely immersed, the waterproofness and dustproofness of the first circuit board 50 can be remarkably enhanced.

Next, a mounting structure between the housing (the motor housing 2 and the rear cover 3) and the substrate case 40 will be described with reference to FIGS. 4 is a cross-sectional perspective view taken along the line AA in FIG. 1. Here, as in FIGS. 2 and 3, the electric tool 1 is turned upside down, and the opening surface 40a of the substrate case 40 is shown in the drawing. It is shown so as to face upward. Also, illustration of the resin is omitted. In a cross-sectional shape (cross-sectional shape in FIG. 4) perpendicular to the longitudinal direction (axial direction A1), the outer shape of the substrate case 40 is substantially along the inner wall shape of the cylindrical rear cover 3, and the inner wall portion of the rear cover 3 The substrate case 40 is positioned with respect to the rear cover 3 by the edges of the opening surface 40a of the substrate case 40 coming into contact with the ribs 3c formed on both sides and continuing in the same direction as the axial direction A1. In this state, the board case 40 is fixed to the motor housing 2 by

screws

88a and 88b via

screw bosses

42a and 42b. Then, the rear cover 3 is attached to the rear of the motor housing 2 while accommodating the substrate case 40, and the rear cover 3 is fixed to the substrate case 40 with screws 39. Thus, the rear cover 3 is fixed to the motor housing 2 via the substrate case 40.

The substrate case 40 has a container shape having an opening surface 40a and is formed so as not to spill even when liquid is put into the internal space. As described above, the first circuit board 50 and the housing of the electric tool 1 are provided in the housing. When the second circuit board 70 is accommodated, mounting is performed such that the switching elements Q1 to Q6 are inverted, that is, the opening surface 40a of the board case 40 is opened downward. As a result, the normal direction of the opening surface 40a is arranged in a state in which it faces downward (the direction in which the spindle 24 protrudes from the gear case 21). Further, the switching elements Q1 to Q6 (only Q2 and Q5 are visible in the figure) have a part on the upper end side (here, about half of the length protruding from the substrate) protruding from the opening surface 40a of the substrate case 40 to the outside of the case. Therefore, it can be directly exposed to the cooling air passage. Furthermore, since the

metal plates

82 and 85 for heat dissipation are provided inside the switching elements Q2 and Q5, the cooling effect is further improved.

As described above, by placing the container-like substrate case 40 in the electric tool housing in an inverted state with the opening surface 40a facing down, the durability of the switching elements Q1 to Q6 and the like can be improved. It was. In particular, iron powder or the like accumulated between the switching elements Q1 to Q6 is likely to cause dust and water droplets to fall on the lower surface inside the rear cover 3 due to the impact when the electric tool 1 is used or placed in the direction of FIG. Become.

The metal arm 51a of the electronic switch 51 protrudes from the opening surface 40a to the outside of the case, and a contact portion (not shown) of a switch lever (not shown) contacts or separates from the protruding portion. Connectors 55a to 55c are arranged between the switching element Q5 and the side wall surface 41d of the substrate case 40, and are supplied to the U phase, V phase, and W phase of the coil 12 of the motor 5 above the connectors 55a to 55c. Lead wires 13a to 13c are arranged for this purpose. The substrate case 40 has two screw bosses on the front side, and is fixed to the motor housing 2 by

screws

88a and 88b.

Next, the circuit configuration of the drive control system of the motor 5 will be described with reference to FIG. The power supply circuit 65 includes a diode bridge 66, a choke coil 69, a film capacitor 67, an electrolytic capacitor 68a, and the like. The diode bridge 66 performs full-wave rectification on the AC input from the commercial AC power supply 100. A smoothing capacitor 68 a is connected to the output side of the power supply circuit 65 and the inverter circuit 60. The inverter circuit 60 includes six switching elements Q1 to Q6, and the switching operation is controlled by the gate signals H1 to H6 supplied from the arithmetic unit 71. When the electric power tool 1 is a disc grinder, a larger output is required as compared with other electric power tools (for example, impact driver or the like). Therefore, IGBTs are used here as the switching elements Q1 to Q6. However, the switching element is not limited to the IGBT but may be an FET (field effect transistor) or other element. The output of the inverter circuit 60 is connected to the U phase, V phase, and W phase of the coil 12 of the motor 5. A constant voltage power supply circuit 72 is connected to the output side of the power supply circuit 65. Here, the power supply circuit 65, the inverter circuit 60, and the electronic switch 51 are mounted on the opening surface 40 a side of the first circuit board 50.

Inside the stator core 9 of the motor 5, the rotor having the permanent magnet 8 rotates. A sensor magnet 18 for position detection is connected to the rotation shaft 6 of the rotor, and the calculation unit 71 detects the position of the sensor magnet 18 by rotation position detection elements 49a to 49c such as Hall ICs, whereby the calculation unit 71 rotates the rotation position of the motor 5. Can be detected.

The computing unit 71 is a control means for performing on / off and rotation control of the motor, and is mainly configured by using a microcomputer (not shown). The computing unit 71 is mainly mounted on the second circuit board 70, and the microcomputer is mounted on the side facing the bottom surface of the second circuit board 70, that is, on the side opposite to the opening surface 40a (on the side opposite to the opening). The calculation unit 71 controls the rotation of the motor 5 based on the start signal input in accordance with the operation of the electronic switch 51 and the speed set by a transmission means (not shown), and the energization time to the coils U, V, W Control drive voltage. An output signal (drive control signal) from the calculation unit 71 is connected to the gates of the six switching elements Q1 to Q6 of the inverter circuit 60, and drive signals H1 to H1 for turning on / off the switching elements Q1 to Q6. Supply H6. The collectors or emitters of the six switching elements Q1 to Q6 of the inverter circuit 60 are connected to the U phase, V phase, and W phase of the star-connected coil 12.

The switching elements Q1 to Q6 perform a switching operation based on the drive signals H1 to H6 input from the arithmetic unit 71, and the DC voltage supplied from the commercial AC power supply 100 via the power supply circuit 65 is converted into three phases (U phase, V-phase and W-phase) voltages Vu, Vv, and Vw are supplied to the motor 5. The magnitude of the current supplied to the motor 5 is detected by the computing unit 71 by detecting the voltage value across the current detecting shunt resistor 54 connected between the power supply circuit 65 and the inverter circuit 60. .

The constant voltage power supply circuit 72 is connected to the output side of the diode bridge 66 and supplies a stabilized reference voltage (low voltage) direct current to the arithmetic unit 71 configured by a microcomputer or the like. The constant voltage power circuit 72 includes a diode 52, a capacitor 68b, an IPD circuit 73, a capacitor 74, and a regulator 75. Of the constant voltage power supply circuit 72, the IPD circuit 73, the capacitor 74, and the regulator 75 are mounted on the second circuit board 70.

Next, the shape of the substrate case 40 will be described with reference to FIG. The substrate case 40 is manufactured from a non-conductive material, and is manufactured by integral molding of a synthetic resin such as plastic. FIG. 6 is a perspective view showing the opening surface 40a facing upward. The board case 40 serves as an attachment base for fixing the first circuit board 50 and the second circuit board 70 in the housing of the electric tool 1, and the board case 40 formed in a container shape has an opening surface. Adjacent to 40a, it has four walls, a front surface 41a, a rear surface 41b, and side wall surfaces 41c and 41d. The

side walls

41c and 41d and the bottom surface 41g are connected to each other by

inclined slope portions

41e and 41f formed obliquely. The bottom surface portion has a shape that is narrowed down along the shape of the rear cover 3 so that the width dimension decreases from the parallel wall portions (41c, 41d) toward the side opposite to the opening. Here, the second circuit board 70 has a shape in which a space necessary for an electronic element (such as a microcomputer) for a control circuit is secured on the back surface (side facing the bottom surface 41g), and a curved surface is formed at the center of the bottom surface 41g. The part which protrudes in the shape of the opening surface 40a side is formed. This raised portion is provided to reduce the amount of resin to be filled and reduce the weight, and to provide a space between the rear cover 3 and the substrate case 40 for allowing a screw to pass through the screw boss.

A cylindrical tube portion 42 (see FIG. 2) is formed on the outer portion of the front surface 41a. The cylindrical portion 42 is a recessed portion for accommodating the sensor magnet 18 therein, and the sensor substrate 48 is disposed on the inner side of the substrate case 40 with the front surface 41a as viewed from the sensor magnet 18. In other words, the sensor substrate 48 is disposed on the substrate case 40 so as to extend in a direction perpendicular to the opening surface 40a. The cylindrical tube portion 42 is formed with protruding portions (screw bosses 42a) protruding in the radial direction, and screw holes are respectively formed therein.

Step portions

45a and 45b for supporting and aligning the first circuit board 50 are formed on the side wall surface 41c inside the substrate case 40, and a screw boss 46a is formed. Step portions (not visible in FIG. 6) and screw bosses for aligning the first circuit board 50 are also formed on the inner wall portion of the side wall surface 41d in the same manner. On the outer side of the rear surface 41b of the substrate case 40, a power cord holding portion 43 and an abutting portion 44 for abutting and fixing to the inner wall surface of the rear cover 3 are formed.

Next, a method for assembling the substrate case 40 will be described. First, as shown in FIG. 3, necessary electronic elements are mounted on the first circuit board 50 and the second circuit board 70, and the first circuit board 50 and the second circuit board 70 are connected using the pin headers 56 to 57. Thus, an assembly in which necessary electronic elements are mounted is assumed. The mounting order of the electronic elements so far and the assembly order of the pin headers 56 to 57 are arbitrary. Next, these assemblies are accommodated in the substrate case 40 so that the second circuit board 70 faces the bottom surface 41g, and the first circuit board 50 is mounted on the board by screws 59a to 59c (see FIG. 7) described later. Screw on the case 40. At this time, the sensor board 48 (see FIG. 1) wired to the second circuit board 70 side by a lead wire (not shown) is also fitted into the guide rail portion 47 formed inside the front surface 41a of the board case 40.

Next, the resin is poured into the substrate case 40 with the opening surface 40a facing upward as shown in FIG. As the resin to be poured, a curable resin that is cured from a liquid state, for example, a urethane resin, is used, and an amount of the resin in which the fixed first circuit board 50 is completely immersed is poured. Here, it is possible to fill the resin until it is the same as the surface position of the opening surface 40a, but the weight is reduced and the cost is reduced by keeping it to the minimum necessary. In this embodiment, the liquid level of the resin is about halfway along the vertical position of the package of the switching elements Q1 to Q6 mounted on the surface of the first circuit board 50 (see the dotted line 90 in FIG. 3). Thus, the second circuit board 70 is not fixed to the board case 40 by screws or the like, but is indirectly fixed to the board case 40 so as to be fixed to the first circuit board 50. In order to realize this fixing method, the second circuit board 70 is formed to have a width smaller than that of the first circuit board 50 and larger than the width of the bottom portion (bottom surface 41g). The assembly of the first circuit board 50 and the second circuit board 70 to the board case 40 is arbitrary, and the second circuit board 70 side is screwed to the board case so that the first circuit is fixed. The substrate 50 may be completely immersed in the resin without being fixed to the substrate case 40, or the first circuit substrate 50 and the second circuit substrate 70 may be fastened together with the substrate case 40 with a common screw. It may be fixed.

Next, with reference to FIG. 7, the mounting state of the first circuit board 50 fixed to the board case 40 and the pin headers 56 to 57 will be described. FIG. 7 is a view of the substrate case 40 as viewed from the outside in the normal direction of the opening surface 40a. Only the positions of the pin headers 56 to 57 and the electronic switch 51 are shown, and the remaining elements are not shown. The shape of the first circuit board 50 accommodated in the substrate case 40 is formed with an outer contour substantially equivalent to the inner shape (width W, length L) of the substrate case 40. The second circuit board 70 (not shown) is made smaller than the width W of the first circuit board 50 and the length thereof is also shortened. A 13-pin pin header 58 and a 3-pin pin header 56 and a 3-pin pin header 57 are attached to a right side portion of the first circuit board 50 opposite to the opening surface 40a (a surface close to the bottom surface 41g), and a left side portion. Here, since the

pin headers

56 and 57 are provided on the left side at positions separated in the front-rear direction, the first circuit board 50 and the second circuit board 70 are well fixed by the three groups of pin headers 56 to 57, and the first A plurality of wirings can be connected between the one circuit board 50 and the second circuit board 70.

The first circuit board 50 is fixed by a screw 59c at one of the rear corners. On the front side, the front side of the substrate case 40 is held by fixing the fixing member 89 with

screws

59a and 59b. An arm portion extending in the left-right direction is formed at a portion of the fixing member 89 that contacts the first circuit board 50, and screw holes are formed at both ends of the arm portion. The fixing member 89 is formed with a pressing piece 89a so as to extend forward from the first circuit board 50, and the sensor board 48 is held by the pressing piece 89a so as not to drop off from the guide rail portion 47. Thus, the first circuit board 50 and the sensor board 48 are easily mounted on the board case 40 by screwing the fixing member 89 after mounting the first circuit board 50 and the sensor board 48 in the board case 40. .

As described above, according to the present embodiment, the first circuit board 50 and the second circuit board 70 are stacked and accommodated in the substrate case, and are fixed by the curable resin. The IGBT could be accommodated, and a compact electric tool could be realized with improved mounting efficiency. Moreover, the switching elements Q1 to Q6 and the heat radiating metal plate attached to the switching elements Q1 to Q6 can be directly exposed to the cooling air by arranging them on the mounting surface on the opening surface 40a side of the first circuit board. Can be increased. Further, since the resin is filled in the substrate case 40 and the switching elements Q1 to Q6 and the metal plate for heat radiation attached thereto are exposed from the resin, the electronic elements immersed in the resin are protected from dust such as iron powder. While being protected, the cooling effect with respect to a switching element can be maintained. In addition, since another circuit element such as a microcomputer is arranged on the second circuit board 70 on the side away from the first circuit board 50, it is possible to make a wasteful element arrangement that effectively uses the space in the board case 40. it can. In addition, since liquid resin is poured and cured, there is no risk of uneven coating compared to the operation of applying gel resin, and the electronic elements covered with resin are protected from dust such as iron powder. The

Further, since the rectifying diode bridge 66 and the smoothing capacitor 68a are also partially exposed from the resin and exposed to the cooling air, these elements can be efficiently cooled.

Further, since the substrate case 40 is partially formed in a substantially cylindrical shape along the inner wall of the rear cover 3, the use of the internal space of the housing efficiently suppresses the enlargement of the main body, and the compact electric tool 1 can be used. realizable.

Further, the dimension of the second circuit board 70 in the left-right direction is made smaller than that of the first circuit board 50, and the bottom of the board case 40 (the bottom surface 41g in the board case 40) is smaller than the dimension of the opening surface 40a in the left-right direction. Since the housing space of the substrate case 40 can be used efficiently, the mounting area of the electronic device can be increased.

Since the first circuit board 50 and the second circuit board are fixed by pin headers that can be fixed while being electrically connected, if one circuit board is fixed to the board case 40, the other circuit board can be fixed. It can be realized at the same time and it is easy to assemble.

In addition, a relatively large electronic element including a choke coil 69 and a film capacitor 67 serving as a noise filter is disposed on the opening surface 40a side of the first circuit board 50, and other small electronic elements are disposed on the bottom surface of the first circuit board 50. By mounting on the 41g side or the second circuit board 70, a limited electronic element mounting surface can be used efficiently.

Further, since the sensor substrate 48 is arranged inside the substrate case 40 and the electronic elements for controlling the motor 5 can be integrated into the substrate case 40, the assembly becomes easy.

Further, since the cooling air passes through the opening surface 40a side of the substrate case 40, the electronic elements exposed from the resin can be effectively cooled by being exposed to the cooling air.

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 main circuit board accommodated in the substrate case 40 is distributed and accommodated in two sheets of the first circuit board 50 and the second circuit board 70. In addition to the above, each may be accommodated in the substrate case in a state of being connected by a pin header or other connector. In the above-described embodiment, the substrate case opening direction is the same as the spindle protruding direction. However, the substrate case opening direction is directed downward when the electric tool is in a mounted state or a used state. If so, the opening direction of the opening surface may not be directly below, and the normal line direction of the opening surface 40a may be arranged obliquely downward or laterally. Furthermore, in the above-mentioned embodiment, the example of mounting the circuit board used in the grinder as an example of the electric tool 1 has been described. However, the present invention is not limited to the grinder and can be applied to other electric tools in the same manner, for example, a saver saw, a multi-cutter, The present invention can be similarly applied to mounting of a circuit board such as a hand driver or an impact driver having a cylindrical housing.

DESCRIPTION OF SYMBOLS 1 ... Electric tool, 2 ... Motor housing, 2a, 2b ... Opening, 3 ... Rear cover, 3a ... Opening, 3c ... Rib, 3d, 3e ... Inlet, 5 ... Motor, 6 ... Rotating shaft, 7 ... Rotor core, 8 ... Permanent magnet, 9 ... stator core, 10, 11 ... insulator, 12 ... coil, 13a-13c ... lead wire, 14a, 14b ... bearing, 15 ... cooling fan, 16 ... fan cover, 18 ... sensor magnet, 20 ... bearing holder part 21 ... Gear case, 21b ... Through hole, 21c ... Hole, 22, 23 ... Bevel gear, 24 ... Spindle, 25 ... Metal, 26 ... Bearing, 27 ... Spindle cover, 28 ... Mounting base, 30 ... Grinding wheel, 31 ... Washer Nut, 32 ... wheel guard, 39 ... screw, 40 ... substrate case, 40a ... opening surface, 41a ... front surface, 41b ... rear surface, 41c, 41d ... side wall surface, 41e, 1f ... slope part, 41g ... bottom face, 42 ... cylinder part, 42a, 42b ... screw boss, 43 ... power cord holding part, 44 ... abutting part, 45a to 45b ... step part, 46a ... screw boss, 47 ... guide rail part, 48 ... sensor board, 49a to 49c ... rotational position detecting element, 50 ... first circuit board, 51 ... electronic switch, 51a ... metal arm, 52 ... diode, 54 ... shunt resistor, 55a to 55c ... connector, 56 to 58 ... Pin header, 58a ... pin, 58b ... case, 58c ... connecting portion, 59a to 59c ... screw, 60 ... inverter circuit, 65 ... power supply circuit, 66 ... diode bridge, 67 ... film capacitor, 68a ... capacitor, 68b ... capacitor, 69 ... choke coil, 70 ... second circuit board, 71 ... calculation unit, 72 ... constant voltage power supply circuit, 73 ... circuit, 74 ... con Capacitors, 75 ... regulator, 81-86 ... metal plate, 87b, 87e ... screws, 88a, 88b ... screw, 89 ... fixing member, 89a ... pressing piece 90 ... resin top surface, 100 ... commercial AC power source

Claims

A brushless motor for driving a tip tool, a drive circuit for driving the brushless motor, a first circuit board on which the drive circuit is mounted, a control circuit for controlling the drive circuit, and at least a part of the control circuit A second circuit board on which the first circuit board and the second circuit board are accommodated, and a substrate case having an open surface on one side, the brushless motor, and the substrate case are accommodated. A housing, and a fan that is driven by the brushless motor and generates cooling air in the housing. In the substrate case, the first circuit board and the second circuit board are perpendicular to the opening surface. An electric power tool, wherein the electric tool is arranged so as to overlap in any direction and extends in a direction parallel to the opening surface.
The drive circuit includes a plurality of switching elements, the first circuit board is disposed on a side close to the opening surface, and the switching element is mounted on the opening surface side of the first circuit board to constitute the control circuit. The power tool according to claim 1, wherein an element to be mounted is mounted on a surface of the second circuit board opposite to the first circuit board.
The plurality of switching elements are arranged so that a longitudinal direction thereof is orthogonal to the first circuit board, and a part of the switching elements is mounted so as to protrude from the opening surface of the board case. Item 3. The electric tool according to Item 2.
The electric power tool according to any one of claims 1 to 3, wherein a rectifier circuit that converts commercial power into direct current is further mounted on the first circuit board.
5. The electric motor according to claim 4, wherein the rectifier circuit includes a smoothing capacitor, and the capacitor is mounted on the first circuit board so as to be partially exposed to the outside from the opening surface. tool.
6. The first circuit board and the second circuit board are immersed in the resin by flowing and hardening a curable resin in the substrate case. The electric tool according to one item.
The power tool according to any one of claims 1 to 6, wherein the control circuit includes a microcomputer that controls an inverter circuit using a switching element, and the microcomputer is mounted on the second circuit board.
The power tool according to any one of claims 1 to 7, wherein the first circuit board and the second circuit board are electrically connected by a connector so as not to be relatively movable.
The power tool according to claim 8, wherein the connector is a plurality of pin headers.
The substrate case has a container shape in which two parallel wall portions extending orthogonally from the opening surface and a bottom portion are formed by narrowing the width dimension from the parallel wall portion toward the opposite opening side. The power tool according to any one of claims 1 to 9, wherein the first circuit board is formed to have a width smaller than that of the second circuit board and is larger than the width of the bottom portion.
The power tool according to claim 10, wherein the second circuit board has a size smaller than a width of the first circuit board and a size larger than a width of the bottom portion.
A cylindrical motor housing that accommodates the brushless motor; and a cylindrical rear cover that is attached to one of the motor housings and that accommodates the board case. The outer diameter of the rear cover is the outer diameter of the motor housing. The power tool according to any one of claims 1 to 11, wherein the power tool has a diameter or less.
An output shaft that rotates by the rotational force of the brushless motor; a power transmission mechanism that transmits the rotational force of the brushless motor to the output shaft; and a gear case that is attached to the other of the motor housing and houses the power transmission mechanism; The output shaft projects from the gear case, and the opening of the substrate case opens in the same direction as the projecting direction of the output shaft from the gear case. Power tools.
A brushless motor for driving a tip tool, a drive circuit for driving the brushless motor, a first circuit board on which the drive circuit is mounted, a control circuit for controlling the drive circuit, and at least a part of the control circuit A second circuit board, a container-like board case that contains the first circuit board and the second circuit board, and is open on one side, and a housing that houses the brushless motor and the board case In the electric power tool, the first circuit board and the second circuit board are arranged in parallel at a predetermined distance in the board case, one circuit board is fixed to the board case, and the other circuit The board is fixed to the one circuit board through a connector, and in the fixed state, a curable resin is injected into the board case, and the first circuit board and the board The electric circuit characterized in that the two circuit boards are solidified so as to be immersed, and a part of the heating element mounted on the first circuit board is disposed so as to be exposed from the curable resin. tool.
The mounting surfaces of the first circuit board and the second circuit board are arranged so as to be parallel to the surface of the opening, and the first circuit board and the second circuit board are fixed by a plurality of pin headers. The power tool according to claim 14.
16. A grinder comprising: a spindle extending in a direction orthogonal to a rotation axis of the brushless motor; and a power transmission mechanism for transmitting a rotational force of the brushless motor to the spindle. The electric tool according to one item.