JP6627250B2 - Electric tool - Google Patents

Description

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

  2. Description of the Related Art An electric tool that uses a brushless DC motor and controls the rotation of the motor with high accuracy by a controller such as a microcomputer is known. A brushless DC motor detects the rotational position of a rotor using a magnetic sensor, and controls a drive current supplied to a winding of the motor by a controller. As an example (grinder) of an electric tool using such a brushless DC motor, a technique disclosed in Patent Document 1 is known. In Patent Document 1, a brushless motor is housed coaxially with a cylindrical housing. The motor is provided with a stator having a coil on the outer peripheral side, and provided on the inner peripheral side with a rotor core rotating by a rotating shaft and holding a permanent magnet. The rotating shaft is supported by bearings on the front and rear sides of the motor, and a cylindrical sensor magnet for detecting the rotational position of the rotor is provided behind the rear bearing. A controller for controlling the motor and a power supply circuit are accommodated inside the rear side of the housing. Further, an inverter circuit for supplying a rotating magnetic field (three-phase alternating current) to a coil of the motor is mounted.

JP 2010-269409 A

  In the technique of Patent Literature 1, since the power supply circuit and the inverter circuit are mounted on independent circuit boards, it becomes an obstacle to further reduce the size and weight of the power tool. In particular, in recent years, a power tool having a large output has been demanded while being small, so a capacitor having a large capacity is used as a measure against the peak current. Therefore, a space for accommodating the capacitor is required, and the power tool becomes large. .

The present invention has been made in view of the above background, and an object of the present invention is to provide a power tool capable of improving the mounting efficiency by devising the arrangement of capacitors and suppressing an increase in the size of the main body.
Another object of the present invention is to provide a power tool that improves the degree of freedom of the installation position of a capacitor, fixes a circuit board using a resin, and also fixes the capacitor using a resin. .

The features of typical inventions disclosed in the present application will be described as follows.
According to one feature of the present invention, a motor for driving a tool bit, a power supply circuit for supplying electricity for driving the motor, a circuit board on which the power supply circuit is mounted, and a case for supporting the circuit board , in an electric tool with, the power supply circuit includes a capacitor, the case is a container-like housing the circuit board to fix the circuit board to the case by filling resin into the case. The capacitor is fixed to the case using this resin. The capacitor included in the power supply circuit is arranged so as to be located in the region of the circuit board when viewed from the opening of the case like a container.

According to another feature of the present invention, the capacitor included in the power supply circuit is cylindrical or rectangular parallelepiped, and the central axis of the cylindrical shape or the longitudinal centerline of the rectangular parallelepiped is substantially parallel to the circuit board. Be placed. The resin used for fixing is a curable resin that cures from a liquid state.If the resin is cured in a state where the capacitor is partially or completely immersed in the liquid state resin, the capacitor together with the substrate is also placed in the case. Can be fixed. At this time, if the capacitor and the circuit board are connected by a lead wire having a certain length, the degree of freedom of the arrangement position of the capacitor is increased and the mounting efficiency can be improved.

According to still another feature of the present invention, a part of an electronic element mounted on a circuit board is arranged so as to be sandwiched between a capacitor included in a power supply circuit and the circuit board, and the capacitor and the electronic element are insulated by a resin. Is kept to be configured. At this time, it is preferable that the resin is filled with an insulating member such as an insulating sheet interposed between the electronic element and the capacitor. A plurality of capacitors may be connected in parallel in order to secure sufficient capacitance of the capacitors. Furthermore the circuit board, to organic and inverter circuit, and a control unit for controlling the operation of the inverter circuit, a constant-voltage power supply circuit for supplying a constant voltage to the control section. The constant voltage power supply circuit has a capacitor, and the capacitor of the constant voltage power supply circuit is disposed inside the case and between the bottom surface of the case and the circuit board.

  According to the present invention, it is possible to prevent an increase in the size of a circuit board due to an increase in the size of a smoothing capacitor used as a countermeasure for a peak current in a power tool having a large output. realizable. In addition, the electronic elements mounted on the circuit board are covered with resin, and the circuit board is arranged separately from the air path of the cooling air generated by the rotation of the cooling fan. Adhesion can be suppressed, and the life of the power tool can be extended. Further, since a large smoothing capacitor can be used, it is possible to perform stable motor control while suppressing the influence of noise and voltage fluctuation.

FIG. 1 is a vertical cross-sectional view illustrating an entire structure of a power tool 1 according to an embodiment of the present invention, in which a black arrow indicates a flow of cooling air when a trigger switch is turned on. FIG. 2 is a diagram viewed from an arrow A in FIG. 1, and is a diagram illustrating a case 40 and a circuit board 60. It is sectional drawing of the BB part of FIG. FIG. 2 is a block diagram illustrating a circuit configuration of a drive control system of a motor 5 in FIG. 1. FIG. 2 is a front view of the circuit board 60 of FIG. 1 alone. FIG. 2 is a back view of the circuit board 60 of FIG. 1 alone. FIG. 2 is a perspective view illustrating shapes of a case 40 and a partition member 50 in FIG. 1. FIG. 2 is a perspective view of the case 40 of FIG. 1 as viewed from another angle. FIG. 4 is a diagram for explaining a height relationship among switching elements Q1 to Q6, a partition member 50, and a resin 48.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, portions having the same functions are denoted by the same reference numerals, and repeated description will be omitted. Further, in this specification, the front, rear, left, right, up and down directions are described as directions shown in the drawings.

  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 power tool 1, a disk grinder in which a spindle 24 that rotates in a direction orthogonal to the rotation shaft 6 of the motor 5 is provided, and a working device connected to the spindle 24 is a circular grindstone 30 is illustrated. The housing (outer frame or housing) of the power tool 1 includes a gear case 21 that houses the power transmission mechanism, a cylindrical motor housing 2 that houses the motor 5, and electric equipment mounted behind the motor housing 2. And three main parts of the rear cover 3. The housing may be formed in any manner. For example, the housing may be formed of three parts in the front-rear direction as in the present embodiment, or may be formed in another divided shape. The motor housing 2 is a resin or metal integral structure, and is formed in a substantially cylindrical shape having an opening on the front side. The inner diameter of the motor housing 2 is 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 portion) that is gripped with one hand by an operator. A rear cover 3 is attached to the rear of the motor housing 2. The rear cover 3 is configured to be dividable in the left-right direction on a vertical plane passing through a central axis in the longitudinal direction (extension line of the rotation axis of the motor), and left and right parts are not shown at positions sandwiching the rear opening of the motor housing 2. Secured by screws. 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 rotating shaft 6 arranged along the center axis direction (front-rear direction) of the motor housing 2, and a calculation unit detects a rotating position of the rotor core 7 by a rotating position detecting element 69 composed of a Hall IC. By controlling an inverter circuit 80 composed of a plurality of switching elements Q1 to Q6 (see FIG. 2 to be described later), a drive magnetic field is sequentially supplied to a predetermined coil 13 of the motor 5 to form a rotating magnetic field. To rotate. The motor 5 is a three-phase brushless DC motor in which a rotor rotates in an inner peripheral space of a stator core 9 having a substantially cylindrical shape, and is a so-called inner rotor type. The stator core 9 is manufactured in a laminated structure in which a number of annular thin iron plates manufactured by press working are stacked in the axial direction. Six teeth (not shown) are formed on the inner peripheral side of the stator core 9, and resin insulators 11 and 12 are mounted in the axial front and rear direction of each tooth, and the teeth are sandwiched between the insulators 11 and 12. The coil 13 is formed by winding a copper wire in an elliptical shape. In this embodiment, it is preferable that the coil 13 be a star connection having three phases of U, V, and W phases, and three lead wires for the U, V, and W phases for supplying drive power to the coil 13. (Not shown) are connected to the circuit board 60. 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 in parallel with the axial direction on a rotor core in which a number of annular thin iron plates manufactured by press working are laminated in the axial direction, and the cross-sectional shape thereof has an N pole and an S pole in a rectangular slot portion. A flat permanent magnet 8 is inserted.

  The rotating shaft 6 includes a rear bearing (first bearing) 14 a fixed to the motor housing 2 and a front bearing (second bearing) fixed near a connection between the gear case 21 and the motor housing 2. 14b. A cooling fan 15 is provided between the bearing 14 b and the motor 5 when viewed in the axial direction of the rotating 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. To generate a flow of air (cooling air) for cooling. Cooling air is sucked from suction ports (not shown in FIG. 1 due to the cross-sectional position) provided on the left and right sides of the rear cover 3 near the rear end of the circuit board 60, and around the case 40 that houses the circuit board 60. Flows from the rear to the front, passes through an opening (see FIG. 3 described later) provided in the bearing holder portion 20 of the motor housing 2, and flows into the housing space of the motor 5. The cooling air flowing 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 drawing) and the inner space of the stator core 9. Then, the air is discharged forward through the through hole 21b of the gear case 21 through the through hole of the fan cover 16 or forward through the lower hole 21c of the fan cover 16. In this embodiment, the circuit board 60, the sensor magnet 18, the bearing 14a, the motor 5, the cooling fan 15, and the bearing 14b are viewed from the rear side (windward side) to the front side as viewed on the axis of the rotating shaft 6 of the motor 5. Are arranged in series (on a straight line) in the axial direction. A wind window (not shown) serving as a suction port for sucking outside air is located around the circuit board 60 and behind elements that generate a large amount of heat, in particular, the diode bridge 72 and the switching elements Q1 to Q6 (see FIG. 2 described later). Placed on the side. As described above, in the present embodiment, the cooling air flows in such a manner as to substantially contact the entire outer peripheral surface from the rear side to the front side of the housing when viewed in the rotation axis direction of the motor 5.

  The gear case 21 is formed by integral molding of a metal such as aluminum, for example, and accommodates a set of bevel gear mechanisms (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 (here, up and down direction) substantially orthogonal to the axial direction (here, the front-rear direction) of the rotation shaft of the motor 5, and a first bevel gear 22 is provided on the front end portion of the rotation shaft 6. Is provided, and the first bevel gear 22 meshes with the second bevel gear 23 attached to the upper end of the spindle 24. Since the second bevel gear 23 has a large diameter and a larger number of gears than the first bevel gear 22, these power transmission means function as a reduction mechanism. The upper end of the spindle 24 is rotatably supported by the gear case 21 by a metal 25, and is supported by a ball bearing 26 near the center. The bearing 26 is fixed to the gear case 21 via the spindle cover 27.

  A mounting base 28 is provided at a tip of the spindle 24, and a tip tool such as a grindstone 30 is mounted by a washer nut 31. The grindstone 30 is, for example, a resinoid flexible tooth having a diameter of 100 mm, a flexible tooth, a resinoid tooth, a sanding disk, and the like. By selecting the type of abrasive grains to be used, metal surface, synthetic resin, marble, concrete surface and the like can be polished and curved surface polished. is there. A radially outer side and an upper side on the rear side of the grindstone 30 are covered with a wheel guard 32. The tip tool attached to the power tool 1 is not limited to the grindstone 30 but may be another tool such as a bevel wire brush, a nonwoven fabric brush, or a diamond wheel.

  At the rear end of the rotating shaft 6 of the motor 5, a sensor magnet 18, which is a magnetic material having different magnetic poles in the rotating direction, is attached. The sensor magnet 18 is a thin cylindrical permanent magnet attached for detecting the rotational position of the rotor core 7, and NSNS poles are sequentially formed at intervals of 90 degrees in the circumferential direction. On the rear side of the sensor magnet 18 and inside the case 40, there is provided a substantially semicircular sensor substrate 68 arranged in a direction perpendicular to the rotation shaft 6, and the sensor substrate 68 detects the position of the sensor magnet 18. A rotation position detecting element 69 is provided. The rotational position detecting element 69 detects the rotational position of the rotor core 7 by detecting a change in the magnetic field of the rotating sensor magnet 18, and three rotational position detecting elements 69 are provided at predetermined angles in the rotational direction, here at every 60 °. Can be

  An arithmetic unit (described later) for controlling the rotation of the motor 5, an inverter circuit 80 for driving the motor 5, and a power cord (not shown) are supplied from outside to the inside of the rear cover 3 formed in a substantially cylindrical shape. A power supply circuit 70 for converting alternating current into direct current is accommodated. In this embodiment, these circuits are mounted on a common circuit board 60, but they may be mounted on a divided circuit board. The circuit board 60 is disposed so as to be parallel to a central axis in the longitudinal direction of the electric tool 1 (coaxial with the rotation axis 6 of the motor 5). Here, the front and back surfaces of the substrate are arranged so as to extend in the front-back and left-right directions. The circuit board 60 is disposed inside a container-like case 40 having an opening 40a on one side, and is entirely hardened by a curable resin that hardens a liquid resin. Here, when the grindstone 30 of the power tool 1 is lowered (in the direction of FIG. 1), the opening 40a of the case 40 is arranged to be directed downward, and the plurality of switching elements Q1 included in the inverter circuit 80 are arranged. To Q6 are arranged to extend downward from the circuit board 60. The liquid surface of the cured resin is at the position indicated by the arrow 48, and about half of the switching elements Q1 to Q6 are located inside the resin, and about half are exposed without being covered with the resin. Here, the grinder according to the embodiment of the present invention is a tool mainly for the operation of polishing and grinding a work material by rotating a grindstone 30 attached to a spindle 24, and at the time of machining, cutting chips and dust. Occurs. Therefore, the worker positions the work material as low as possible so that dust and the like do not fall on the worker. Therefore, normally, the worker does not turn the spindle 24 upward, and preferably works with the spindle 24 facing downward rather than in the left-right direction. At this time, in the power tool 1 (grinder) to which the present invention is applied, the opening direction of the opening 40a of the case 40 is the same as the direction of the spindle 24 (the direction of projection from the gear case 21). The opening direction of the portion 40a is generally directed downward, so that even if dust generated during processing enters the inside of the rear cover 3 from the wind window, it is suppressed from accumulating in the case 40. When the worker has completed the work, he or she places the power tool 1 on a mounting location such as the ground, but places the power tool 1 in the holding direction unless there are special circumstances. . That is, the power tool 1 is placed with the spindle 24 facing downward. Therefore, for example, even if dust or the like enters the case 40 due to the influence of the cooling air, the dust in the case 40 is removed by the influence of gravity or the like at the time of mounting.

  Since the inverter circuit 80 needs to supply a large drive current to the coil 13, a large-capacity output transistor such as an FET (field effect transistor) or an IGBT (insulated gate bipolar transistor) is used as the switching elements Q1 to Q6. Used. Since the switching elements Q1 to Q6 generate a large amount of heat, a heat dissipation structure for improving the cooling effect is considered. In this embodiment, a cooling metal plate is further attached to the heat dissipation 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) of a wind window (not shown) serving as a suction port, they are directly exposed to the cooling air indicated by black arrows. A power supply circuit is provided behind the switching elements Q1 to Q6. The power supply circuit 70 of the present embodiment is configured to include a rectifier circuit that converts a commercial power supply (AC) supplied from the outside into DC. The power supply circuit 70 is located on the rear side of the case 40 close to a power supply cord (not shown) wired so as to extend from the rear end surface of the rear cover 3 to the outside, from the switching elements Q1 to Q6. Is mounted on the rear side (the side opposite to the motor 5 far from the motor 5).

  In the space defined by the case 40 (in the container), in addition to the circuit board 60, a sensor board 68 on which a rotational position detecting element 69 is mounted is provided. A switch board 65 is mounted on the outside of the case portion of the case 40 and on the rear side, and a variable resistor 66 adjusted by the speed change dial 17 is provided. The sensor board 68 is arranged so as to be orthogonal to the rotation axis direction of the motor 5, and the switch board 65 is arranged so as to be parallel to the rotation axis direction.

  FIG. 2 is a view seen from the direction of arrow A in FIG. 1, and is a diagram showing the case 40 and the circuit board 60. The shape of the circuit board 60 housed inside the case 40 is formed with an outer contour substantially equal to the inner shape of the case 40. Although not shown in the drawing, the circuit board 60 is immersed in a resin 48 that is cured from a liquid state and hardened. Mounted on the circuit board 60 are a power supply circuit 70 mainly including a rectifier circuit 71 and a smoothing circuit 75, an inverter circuit 80 including six switching elements Q1 to Q6, and an inverter circuit 80. The control unit includes a control unit including the microcomputer 101 and a constant voltage power supply circuit (not shown) for generating a constant voltage direct current for the control unit. A power supply cord (not shown) is connected to the input side of the circuit board 60 from outside the power tool 1, and a commercial AC is input to the power supply circuit 70. The capacitor 79 is for noise prevention and is connected in parallel before the rectification circuit 71. The power cord is fixed by the power cord holding unit 43. Output terminals of the circuit board 60 are terminals 84a to 84c, and three lead wires (V phase, U phase, and W phase) (not shown) connected to the coil 13 of the motor 5 are soldered.

  In the circuit board 60, the power supply circuit 70 is disposed on the rear side of the circuit board 60, and the inverter circuit 80 is located on the front side of the circuit board in view of the wiring advantage of being close to the input and output points and the point along the flow of cooling air. Placed on the side. The circuit board 60 is a single-layer or multi-layer printed board, and a multi-layer glass composite board is used here. The power supply circuit 70 includes a rectifier circuit 71 and a smoothing circuit 75. The rectifier circuit 71 includes a diode bridge 72, a choke coil 73, and a varistor 74. The smoothing circuit 75 includes an electrolytic capacitor 76a, a film, It has a capacitor 76b and a resistor 78 described later. The terminals of the electrolytic capacitor 76a and the film capacitor 76b are not directly soldered to the circuit board 60, but are wired using an extension such as a lead wire or a lead wire. It is fixed to.

  The inverter circuit 80 is arranged such that three switching elements Q1 to Q3 and Q4 to Q6 are arranged in a line in the axial direction. Each of the switching elements Q1 to Q6 has a semiconductor element sealed in a substantially rectangular parallelepiped package made of ceramic or the like, and has three metal terminals extending from the lower side of the package. A metal radiator plate is provided on the back side of the package. Embedded. The heat radiating plate has a planar shape, and the switching elements Q1 to Q6 are arranged so that the spreading direction of the surface is horizontal and orthogonal to the longitudinal direction of the circuit board 60 (the longitudinal direction in FIG. 2). Further, a metal plate 82 for heat radiation is further provided on the heat radiation plate on the back surface of the package. Normally, the collector terminal of the IGBT and the drain terminal of the FET are electrically connected to the heat sink on the back side of the package. Therefore, when the collector terminal or the drain terminal is commonly connected, the plurality of switching elements Q1 to Q3 are connected. Common metal plates 82, 83a to 83c are provided. On the other hand, the remaining three switching elements Q4 to Q6 of inverter circuit 80 are arranged so as to be aligned, and are arranged so as to be parallel to switching elements Q1 to Q3. Although a heat-dissipating metal plate is provided on the heat-dissipating plate on the back surface of the package of the switching elements Q4 to Q6, these collector terminals or drain terminals are not commonly connected, and therefore, independent metal plates 83a to 83c are provided. The surfaces of the metal plates 83a to 83c are arranged so as to be horizontal and perpendicular to the longitudinal direction of the circuit board 60 (the front-back direction, the rotation axis direction of the motor). Since the surface direction of the heat radiating plate of the switching elements Q1 to Q6 is arranged along the direction in which the cooling air flows, the surface of the metal plates 83a to 83c opposite to the switching element flows in the direction in which the cooling air flows (in FIG. 1). (See black arrow in FIG. 3), so that the heat radiation effect can be enhanced.

In further to the circuit board 60, the arithmetic unit for controlling the rotation of the motor 5 (not shown) is mounted. The arithmetic unit includes a microcomputer (hereinafter, referred to as a “microcomputer”) not shown, and controls the start and stop of the motor 5 and the rotation speed by driving the inverter circuit 80. The circuit board 60 further includes a constant voltage power supply circuit, which will be described later, and a trigger switch 64 that operates in conjunction with a trigger lever (not shown). These can be mounted in any space on the circuit board 60. In this embodiment, the microcomputer 101 is mounted near the space between the electrolytic capacitor 76a and the circuit board 60. On the front side of the circuit board 60, a sensor board 68 on which three rotational position detecting elements 69 (see FIG. 1) are mounted is arranged to be orthogonal to the circuit board 60. The circuit board 60 and the sensor board 68 are fixed by the partition member 50. The partition member 50 also serves as a fixing member for holding the circuit board 60 in the case 40 and a partition member for providing a partition plate between the switching elements Q1 to Q6 for suppressing a short circuit between the switching elements. It is made of an insulating material such as a synthetic resin, and is screwed to the case 40 by two screws 59a and 59b at both end screw boss portions extending in the left-right direction. The circuit board 60 is screwed to the case 40 with a screw hole 67 on the rear side, and is held by the case 40 by being sandwiched by the partition member 50 on the front side.

  On the rear side of the case 40, a switch board 65 on which a variable resistor 66 is mounted is provided. The switch board 65 is provided at an independent portion protruding rearward from the container-like portion of the case 40, and has a speed change mechanism in which a part of the rotation shaft of the variable resistor 66 is exposed from the opening 3 b (see FIG. 1) of the rear cover 3. A dial 17 is provided. The circuit board 60 and the switch board 65 are wired by lead wires 87.

  FIG. 3 is a sectional view taken along the line BB of FIG. Illustration of the rear cover 3 is omitted. The case 40 is in the shape of a container having an opening 40a, and is formed so as not to spill even if a liquid is put in the internal space. It is arranged in an inverted state so that the line direction faces downward (the direction in which the spindle 24 projects from the gear case 21). This is to prevent the inside of the case 40 from accumulating as much as possible when water droplets and dust enter the inside together with the cooling air. By arranging the container-like case 40 in the inverted state in the housing of the power tool in this manner, the switching elements Q1 to Q6 and the like are not completely covered with the resin, but the durability is improved even when the switching elements Q1 to Q6 are covered only about half. It became possible to increase. In particular, when the power tool 1 is placed in the direction of FIG. 1, dust and water droplets easily fall on the lower surface inside the rear cover 3 due to the impact of iron powder or the like accumulated between the switching elements Q <b> 1 to Q <b> 6.

  At the front end of the case 40, screw holes 42a and 42b for fixing the motor housing 2 with screws (not shown) are formed. The bearing holder portion 20 of the motor housing 2 has a plurality of columns 20a to 20f formed outward from a cylindrical portion that holds the outer ring portion of the bearing 14a (see FIG. 1), and is hollow at locations other than the columns. Therefore, the cooling air flows from the space in which the case 40 is housed to the space in which the motor 5 is housed. The circuit board 60 is a double-sided board, and has a diode bridge 72, a heat radiating plate 72a, a choke coil 73, and the like mounted on the front side (the lower surface in FIG. 3). The electrolytic capacitor 76a has a substantially cylindrical shape, and the film capacitor 76b has a substantially rectangular parallelepiped shape. However, the shapes of the electrolytic capacitor 76a and the film capacitor 76b are arbitrary, have a required capacity, and are arranged in a limited space. A suitable size and shape are selected.

  The electrolytic capacitor 76a and the film capacitor 76b are fixed to the surface of the circuit board 60 via an insulating sheet 98. This is fixed by a resin 48 such as urethane filled in the case 40. At this time, a plurality of electronic elements such as resistors having a relatively small size are mounted on the circuit board 60, and the electrolytic capacitor 76a and the film capacitor 76b are fixed so as to cover the plurality of electronic elements. In other words, a plurality of electronic elements are arranged on the circuit board 60 so as to be sandwiched between the electrolytic capacitor 76a and the film capacitor 76b and the circuit board 60. By arranging the circuit board 60 using the dead space in the case 40 in this manner, elements constituting the circuit can be efficiently mounted on the circuit board 60. Further, since the insulating sheet 98 is interposed between the electrolytic capacitor 76a and the film capacitor 76b and the electronic element, the electrical connection between the two can be suppressed. In the present invention, the plurality of electronic elements are configured to be sandwiched between the electrolytic capacitor 76a and the film capacitor 76b and the circuit board 60. However, it is apparent that the above-described effect is obtained if at least a part of the electronic elements is sandwiched. .

  The electrolytic capacitor 76a and the film capacitor 76b are arranged so as to fit in the inner region of the case 40 when viewed in the direction of the arrow in the normal direction of the opening 40a (when viewed as shown in FIG. 2). It is located within the dimensions of the substrate plane of substrate 60. This prevents the electrolytic capacitor 76a and the film capacitor 76b from protruding out of the case 40, and can suppress an increase in the size of the rear cover 3 accommodating the case 40. Since everything can be accommodated, the housing can be made compact, and the electric tool 1 can be prevented from becoming large. When viewed in an axial cross-sectional view of the housing as shown in FIG. 3, most of the electrolytic capacitor 76a and the film capacitor 76b are located inside the housing, and the inner wall of the housing (the inner wall of the rear cover 3) and a predetermined space are formed. They are arranged at a distance. At this time, it is preferable to arrange the electrolytic capacitor 76a and the film capacitor 76b so as not to disturb the flow of the cooling air.

  The resin 48 is placed so that the opening 40a of the case 40 is on the upper side, and is filled with a liquid resin inside the case 40 and cured. Before the curing is completed, the electrolytic capacitor 76a and the film After the capacitor 76b is partially immersed so as to be partially immersed from the liquid surface of the resin 48, the resin 48 is cured. Therefore, the entire case 40 is filled with resin from the bottom surface 41e to the liquid surface (broken line), and the resin is hardened after curing, so that the electrolytic capacitor 76a and the film capacitor 76b are stably held. You. Usually, the package of the electrolytic capacitor 76a and the film capacitor 76b is a non-insulating material, and the resin 48 itself is also a non-conductive material. However, in order to keep the insulating state more completely, an additional insulating member, here, the insulating sheet 98, is used. Interposed (may be omitted). When the electrolytic capacitor 76a and the film capacitor 76b are mounted so as to be separated from the circuit board 60 and fixed with the resin 48 in this manner, a low-height electronic element mounted on the circuit board 60, for example, an LSI It is possible to mount a film capacitor on the upper part of an element such as a microcomputer or a microcomputer.

  An electrolytic capacitor 94a used in the constant voltage power supply circuit 90 is mounted on the back surface of the circuit board 60. The electrolytic capacitor 94a is completely immersed in the resin and fixed. Although an insulating sheet 97a is interposed between the circuit board 60 and the electrolytic capacitor 94a to increase the insulating property, the insulating sheet 97a may be omitted. The shape of the bottom surface 41e of the case 40 may be substantially parallel to the bottom surface of the case 40 with a slight distance therebetween. In this embodiment, a space for accommodating the cylindrical electrolytic capacitor 94a is secured on the lower side. Although the electrolytic capacitor 94a is arranged only on the left side, a capacitor may be arranged in the space on the right side. Further, the electrolytic capacitor 76a and the film capacitor 76b arranged on the front surface (lower side) of the circuit board 60 may be arranged on the back surface of the circuit board 60. However, in this configuration, since the current output to the arithmetic unit 100 is smaller than the current flowing through the inverter circuit 80, the electrolytic capacitors 94a and 94b do not generate heat as compared with the electrolytic capacitor 76a and the film capacitor 76b, and need to be cooled. Low. For this reason, the electrolytic capacitor 76a and the film capacitor 76b to be preferentially cooled are exposed to the outside. In other words, a capacitor having a high calorific value is exposed to the outside, and a capacitor with a relatively low calorific value is completely buried in the resin 48, thereby realizing a rational arrangement of capacitors. As described above, the space between the circuit board 60 and the bottom surface 41e is a portion that is filled with the resin 48 and is hardened. Therefore, it is preferable to determine the mounting position and the mounting method in consideration of the degree of heat generation and the cooling effect. .

  Next, a circuit configuration of a drive control system of the motor 5 will be described with reference to FIG. The power supply circuit 70 includes a rectifier circuit 71 including a diode bridge 72 (see FIG. 2) and the like. A smoothing circuit 75 is connected between the output side of the power supply circuit 70 and the inverter circuit 80. Inverter circuit 80 includes six switching elements Q1 to Q6, and the switching operation is controlled by gate signals H1 to H6 supplied from operation unit 100. The output of the inverter circuit 80 is connected to the U, V, and W phases of the coil 13 of the motor 5. The constant voltage power supply circuit 90 is connected to the output side of the power supply circuit 70. Here, the power supply circuit 70, the smoothing circuit 75, the inverter circuit 80, the constant voltage power supply circuit 90, and the circuit of the arithmetic unit 100 are mounted together on the same circuit board 60.

  The power supply circuit 70 includes a rectifier circuit 71 mainly configured by a diode bridge 72 (see FIG. 2). The input side of the rectifier circuit 71 is connected to, for example, the commercial AC power supply 35, and the output side is connected to the smoothing circuit 75. The rectifier circuit 71 performs full-wave rectification on the AC input from the commercial AC power supply 35 and outputs the rectified signal to the smoothing circuit 75. The smoothing circuit 75 is disposed between the rectifier circuit 71 and the inverter circuit 80, and smoothes a pulsating flow included in the current rectified by the rectifier circuit 71 to a state close to a direct current and supplies the pulsating flow to the inverter circuit 80. Output. The smoothing circuit 75 includes an electrolytic capacitor 76a, a film capacitor 76b, and a discharging resistor 78. When the power tool 1 is a disk grinder, a large output is required as compared with other power tools (for example, an impact driver or the like), so that the voltage value input from the power supply circuit 70 to the smoothing circuit 75 also increases. I have. Therefore, the capacitors (electrolytic capacitor 76a and film capacitor 76b) provided in the smoothing circuit 75 are required to have a large capacitance. In the present embodiment, the method of fixing to the circuit board 60 is devised, so that a large electrolytic capacitor 76a and a large film capacitor 76b can be used.

  The electrolytic capacitor 76a is a polar capacitor, and the film capacitor 76b is a non-polar capacitor. By connecting these in parallel, the smoothing performance of the circuit is improved. The two capacitors are arranged between the output side of the rectifier circuit 71 and the input side of the inverter circuit 80. The inverter circuit 80 includes six switching elements Q1 to Q6 connected in a three-phase bridge format. Here, the switching elements Q1 to Q6 are MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), but IGBTs (Insulated Gate Bipolar Transistors) may be used.

  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 100 detects the rotation position of the motor 5 by detecting the position of the sensor magnet 18 with a rotation position detection element 69 such as a Hall IC. I do.

  The arithmetic unit 100 is a control unit for performing on / off and rotation control of the motor, and is mainly configured using the microcomputer 101. The arithmetic unit 100 is mounted on the circuit board 60 and controls the rotation speed of the motor 5 based on a start signal input in response to the operation of the trigger switch 64 and a signal of the variable resistor 66 set by the speed change dial 17. The power supply time to U, V, and W and the drive voltage are controlled. The arithmetic unit 100 is connected to each gate of the six switching elements Q1 to Q6 of the inverter circuit 80 and supplies drive signals H1 to H6 for turning on and off the switching elements Q1 to Q6.

  Each drain or each source of the six switching elements Q1 to Q6 of the inverter circuit 80 is connected to the U-phase, V-phase, and W-phase of the star-connected coil 13. Since the drain terminals of the switching elements Q1 to Q3 are commonly connected to the positive electrode side of the power supply circuit 70, they can be provided with a common heat-dissipating metal plate 82. On the other hand, since the drain terminals of the switching elements Q4 to Q6 are connected to the V-phase, U-phase, and W-phase terminals of the motor, the heat-dissipating metal plates 83a to 83c for the switching elements Q4 to Q6 are individually provided. .

  The switching elements Q1 to Q6 perform a switching operation based on the drive signals H1 to H6 input from the arithmetic unit 100, and convert the DC voltage supplied from the commercial AC power supply 35 through the power supply circuit 70 and the smoothing circuit 75 into three phases. (U-phase, V-phase, W-phase) Supply to the motor 5 as voltages Vu, Vv, Vw. The magnitude of the current supplied to the motor 5 is detected by the arithmetic unit 100 by detecting the voltage value at both ends of the current detection resistor 102 connected between the smoothing circuit 75 and the inverter circuit 80. A predetermined current threshold value according to the set rotation of the motor 5 is set in the arithmetic unit 100 in advance. When the detected current value exceeds the threshold value, the switching operation of the inverter circuit 80 is performed to stop the driving of the motor 5. To stop. As a result, the occurrence of burnout or the like due to the overcurrent flowing to the motor 5 is prevented.

  The constant voltage power supply circuit 90 is a power supply circuit that is directly connected to the output side of the power supply circuit 70 and supplies a stabilized reference voltage (low voltage) DC to the arithmetic unit 100 configured by a microcomputer or the like. The constant voltage power supply circuit 90 includes a diode 96, electrolytic capacitors 94a and 94b for smoothing, an IPD circuit 91, a capacitor 93, and a regulator 92. Each part of the constant voltage power supply circuit 90 is mounted on a circuit board 60, not shown in FIG. The electrolytic capacitors 94a and 94b are mounted on the back side of the circuit board 60. Note that the electrolytic capacitors 94a and 94b may be one electrolytic capacitor if capacity is possible.

  FIG. 5 is a front view of the circuit board 60 alone in FIG. 1 and is a view for explaining a wiring method of two electrolytic capacitors 76a and a film capacitor 76b. Here, two lead wires 62a and 62b are extended from the terminal 61 on the circuit board 60, and the terminals of the electrolytic capacitor 76a and the film capacitor 76b are collectively soldered 77a and 77b to the ends of the lead wires 62a and 62b. As the lead wires 62a and 62b, a vinyl wire (vinyl-coated electric wire) insulated by applying a vinyl coating to a single wire or a stranded wire is used. After the electrolytic capacitor 76a and the film capacitor 76b are connected in parallel to the lead wires 62a and 62b, the electrolytic capacitor 76a and the film capacitor 76b are free on the front side surface (the surface on which the switching elements Q1 to Q6 are arranged) of the circuit board 60. The electrolytic capacitor 76a and the film capacitor 76b are fixed in the vicinity of the space, here, in the vicinity where the microcomputer 101 is mounted.

  As described above, in the power tool 1 according to the present embodiment, the large electrolytic capacitor 76a and the film capacitor 76b are provided in the smoothing circuit 75, so that the peak current can be efficiently suppressed. Further, since the wiring is extended with the lead wire from the circuit board 60, the degree of freedom of the fixing position of the electrolytic capacitor 76a and the film capacitor 76b is increased, and the mounting efficiency of the circuit board 60 can be improved.

  FIG. 6 is a rear view of the circuit board 60 shown in FIG. 1 alone, and is a view for explaining a wiring method of the two electrolytic capacitors 94a and 94b. The terminals of the electrolytic capacitors 94a and 94b are directly soldered to the terminals 63a and 64b on the back side of the circuit board 60. At this time, the terminals of the electrolytic capacitors 94a and 94b are made longer by bending the terminals so that the cylindrical central axes of the electrolytic capacitors 94a and 94b coincide with the longitudinal direction (front-back direction) of the circuit board 60. The position of 94b is temporarily fixed. This state is a position where the electrolytic capacitors 94a and 94b are along the curved bottom surface of the case 40. By properly utilizing the space on the back side of the circuit board 60, the electrolytic capacitors 94a and 94b for the constant voltage power supply circuit 90 can be arranged. Since there is further space between the back surface of the circuit board 60 and the bottom surface 41e of the case 40, all or a part of the electrolytic capacitor 76a and the film capacitor 76b may be accommodated therein. However, since the electrolytic capacitor 76a and the film capacitor 76b have a considerable amount of heat due to the large current, if the heat dissipation is important, the electrolytic capacitor 76a and the film capacitor 76b may be partially exposed to the cooling air from the resin 48 on the surface side of the circuit board 60. Mounting is more advantageous.

  Next, the shape of the case 40 and the shape of the partition member 50 will be described with reference to FIGS. The case 40 and the partition member 50 are manufactured by a non-conductive material, and are manufactured by integral molding of a synthetic resin such as plastic. FIGS. 7 and 8 are perspective views showing an opening 40a facing upward. The case 40 serves as a mounting base used for fixing the circuit board 60 to the housing of the power tool 1. The case 40 formed in a container shape has a front surface 41a, a rear surface 41b, side surfaces 41c, 41d and a bottom surface. A bottom surface 41e having an opening 40a with the remaining surface 41e is a shape suitable for electronic elements (here, electrolytic capacitors 94a and 94b) mounted on the back surface (the side facing the bottom surface 41e) of the circuit board 60. Thus, a curved concave portion is formed. Also, the joint between the side surfaces 41c and 41d and the bottom surface 41e is not formed at a right angle, but is formed along the cylindrical inner wall shape of the rear cover 3, and is connected at a further oblique surface here. did. A cylindrical portion 42 is formed on an outer portion of the front surface 41a. The cylindrical portion 42 is a concave portion for accommodating the sensor magnet 18 therein, and the sensor substrate 68 is disposed inside the case 40 across the front surface 41a as viewed from the sensor magnet 18. A projecting portion that projects in the radial direction is formed in the cylindrical tube portion 42, and screw holes 42a and 42b are formed therein. Inside the case 40 and on the side surface 41c, step portions 45a and 45b for supporting the circuit board 60 and performing positioning are formed. Note that a step portion for positioning the circuit board 60 is similarly formed on the inner wall portion of the side surface 41d which is not visible in FIG. Outside the rear surface 41b of the case 40, a power cord holding portion 43 and a switch board holding portion 44 are formed.

  A method of attaching the circuit board 60 to the case 40 having such a shape will be described. First, as shown in FIGS. 5 and 6, necessary electronic elements are mounted on the circuit board 60 and soldered. The electrolytic capacitor 76a and the film capacitor 76b are connected by the lead wires 62a and 62b. Next, the circuit board 60 on which the electronic elements are mounted is housed in the case 40, and is screwed to the circuit board 60 using a screw hole 67 (see FIG. 2) and a screw. Although the position is not visible in FIG. 7, a screw hole is formed at a position corresponding to the screw hole 67 on the bottom surface 41e. At this time, the sensor board 68 wired by lead wires (not shown) is also fitted into the guide rail portion 47 formed inside the front surface 41a of the case 40. Similarly, the switch board 65 is attached to the switch board holding portion 44 on the rear side of the case 40. Next, the partition member 50 is attached so that the front side of the circuit board 60 is pressed down and fixed.

  The partition member 50 has a longitudinal partition plate 51 and two lateral partition plates 52 a and 52 b extending in the lateral direction from the longitudinal partition plate 51, and has a planar shape in front of the longitudinal partition plate 51. Thus, a holding plate 53 extending in a direction orthogonal to the longitudinal partition plate 51 and the circuit board 60 is formed. Arm portions 54a and 54b extending in the left-right direction are formed at portions of the holding plate 53 that are in contact with the circuit board 60, and screw holes 55a and 55b are formed at both ends of the arm portions 54a and 54b. A holding piece 56 for holding the sensor board 68 so as not to fall off from the guide rail portion 47 is provided so as to extend forward from a side of the holding plate 53 away from the circuit board 60. The circuit board 60 and the sensor board 68 are fixed to the case 40 by screwing the partition member 50 after mounting the circuit board 60 and the sensor board 68 in the case 40. After the screws are fastened, the longitudinal partition plate 51 and the lateral partition plates 52a and 52b are fixed in a non-contact state with the heat radiating plates of the switching elements Q1 to Q6 and the metal plates 82 and 83a to 83c, respectively.

  Next, in a state where the electrolytic capacitor 76a and the film capacitor 76b are temporarily placed outside the case 40, the resin 40 is placed inside the case 40 so that the opening 40a of the case 40 faces upward, that is, as shown in FIG. Pour 48. As the resin 48 to be poured, a curable resin that cures from a liquid state, for example, a urethane resin is used, and an amount of the resin 48 that completely immerses the front and back surfaces of the fixed circuit board 60 is poured. Here, it is possible to fill the resin 48 until it becomes the same as the opening surface of the opening 40a. However, the weight is reduced and the cost is reduced by minimizing the necessary amount. In the present embodiment, the liquid level of the resin 48 is set so that the liquid surface of the resin 48 is formed in the middle of the vertical position of the package of the switching elements Q1 to Q6 mounted on the surface of the circuit board 60. At this liquid level position, about half of the height of the partition member 50 (H1, H2) is about immersed in the liquid level. Next, while the resin 48 is in the liquid state, the electrolytic capacitor 76a and the film capacitor 76b are positioned at predetermined positions, and are half-submerged in the liquid resin, and the resin 48 is solidified in that state. Here, the predetermined position is located in the area of the case 40 (in the internal space) when viewed from the normal direction (the arrow A in FIG. 1) of the opening surface of the opening 40a of the container-like case 40. This means that they are preferably arranged so as to completely fit in the area of the circuit board 60.

  FIG. 8 is a perspective view of the case 40 viewed from another angle. A screw boss 46a is formed in a portion of the partition member 50 where the screw hole 55a hits. Although not visible in FIG. 8, a similar screw boss is formed in a portion of the partition member 50 that abuts on the screw hole 55b. The lower end position of the height H1 portion of the longitudinal direction partition plate 51 of the partition member 50 (see FIG. 7) fixed to the case 40 is higher than the lower surface position of the height H2 portion of the pressing plate 53. This is because the longitudinal partition plate 51 and the lateral partition plates 52a and 52b are arranged at a predetermined distance on the circuit board 60, whereas the holding plate 53 and the arm portions 54a and 54b are arranged at the front end of the circuit board 60. This is because it is placed directly on the case 40 at the portion. Therefore, the circuit board 60 is sandwiched between the holding plate 53 and the case 40. Instead of fixing the circuit board 60 by sandwiching the circuit board 60 between the partition member 50 and the case 40, the circuit board 60 may be fixed together with the partition member 50 to the case 40 with a common screw.

  Next, the relationship between the height of the switching elements Q1 to Q6 and the partition member 50 and the filling amount of the resin 48 will be described with reference to FIG. A metal plate 83a having the same height H from the surface of the circuit board 60 is screwed to the back surface of the switching element Q4. First, the metal plate 83a is fixed to the switching element Q4 using a screw (not shown), and then the three feet 81a of the switching element Q4 are passed through through holes of the circuit board 60 and then soldered. Similarly, the metal plates 83b and 83c are screwed to the switching elements Q5 and Q6, and are soldered after the three legs 81b and 81c pass through the through holes of the circuit board 60. Here, the lower ends of the metal plates 83a to 83c viewed in the height direction were separated from the circuit board by a predetermined distance S2. The partition member 50 is configured such that the height H1 of the longitudinal direction partition plate 51 and the horizontal direction partition plates 52a and 52b is smaller than the height H of the switching elements Q4 to Q6 after being mounted on the circuit board 60. You. The lower surfaces of the longitudinal partition plate 51 and the horizontal partition plates 52a and 52b in the height direction are separated from the surface of the circuit board 60 by a predetermined distance S1. This is because it is necessary to partition between the set of the switching element Q4 and the heat sink 83a, the set of the switching element Q5 and the heat sink 83b, and the set of the switching element Q6 and the heat sink 83c because of the height D filled with the resin 48. Is also the upper part in the height direction. Moreover, the height direction upper end position of the longitudinal direction partition plate 51 and the lateral direction partition plate 52a, 52b is made lower than the height of the switching elements Q4 to Q6 because heat radiation is improved by making it easier to hit the cooling wind. The reason why moisture, dust, and the like are easily deposited is that they are concentrated on the liquid surface of the resin 48. of course. The upper ends of the longitudinal direction partition plate 51 and the lateral direction partition plates 52a and 52b in the height direction may be made to coincide with the heights of the switching elements Q4 to Q6. However, when the degree of partitioning is increased, the metal plates 83a to 83c become larger. Since the effect of being exposed to the cooling air is reduced, the cooling performance is reduced. Therefore, the height H1 of the partition plate and the height H1 occupy any of the heights H in consideration of their balance. Think about it.

  In the present embodiment, while the terminal portions of the switching elements Q1 to Q6 are covered with the resin 48, about half of the metal plates 83a to 83c are exposed to the outside of the resin 48 when viewed in the height direction, and the upper end position is the partition plate. Higher than the upper end position, a good cooling effect can be obtained. Further, since the electrolytic capacitor 76a and the film capacitor 76b are also exposed to the outside of the resin at the same time, a good cooling effect can be obtained also for the electrolytic capacitor 76a and the film capacitor 76b. Further, when the circuit board 60 is accommodated in the housing of the power tool 1, the switching elements Q1 to Q6 are arranged so as to be inverted, so that the switching elements Q1 to Q6 are arranged in the compartments partitioned by the longitudinal partitioning plates 51 and the horizontal partitioning plates 52a, 52b. The possibility that dust such as moisture or iron powder accumulates is reduced, so that a power tool with high reliability and long life can be realized.

  As described above, according to the present embodiment, the circuit board 60 is accommodated in the container-like case 40, and the resin 48 is filled therein so that the circuit board 60 is completely or almost completely immersed. The waterproof and dustproof properties of the substrate 60 can be significantly improved. In addition, by arranging the capacitor on the substrate and fixing it with the curable resin 48, even a large and heavy capacitor can be stably fixed in the case 40. At this time, since a part of the capacitor is exposed from the resin 48, the capacitor can be cooled by exposing it to cooling air. In addition, since the capacitors are arranged on the substrate via the lead wires, the degree of freedom of the arrangement of the capacitors increases, and the degree of freedom of the element arrangement on the circuit board 60 increases. Further, since another circuit element such as a microcomputer is arranged between the circuit board 60 and the capacitor, the element arrangement can be made efficient by using space effectively and without waste. In addition, since the liquid resin is poured and cured, there is no possibility that uneven coating may occur as compared with the operation of applying the gel resin. Further, since the switching elements Q1 to Q6 which generate a large amount of heat are partially exposed to the outside from the resin 48, the switching elements Q1 to Q6 can be well exposed to the cooling air path, and the cooling effect can be maintained. At that time, since the insulating partition member is interposed between members that are not desirable to be short-circuited by metal powder or the like, a power tool having high durability and reliability can be realized.

  As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the terminal of the capacitor is connected to the substrate via a lead wire in order to extend the terminal. However, the terminal of the capacitor body may be extended by extending the terminal. Further, the partition plate may be interposed between at least two switching elements, and may be a single plate partitioning only between Q1 to Q3 and Q4 to Q6. This allows the cooling air to flow to the switching element more efficiently. In the above-described embodiment, the cooling air flows from the wind window (not shown) so as to substantially contact the entire inner peripheral surface of the housing. However, the cooling air flows only at the opening side in the case accommodating portion. May be configured. By doing so, the cooling air can be concentrated on the switching element. In the above-described embodiment, the opening direction of the case is set to the same direction as the projecting direction of the spindle.However, if the power tool is placed on the case, the opening direction of the case faces downward. Good. Further, in the above-described embodiment, the example of mounting the circuit board used in the grinder has been described as an example of the power tool 1. However, the same circuit board is not limited to the grinder and can be similarly applied to other power tools. The present invention can be similarly applied to a saver saw, a multi-cutter, a hand driver or an impact driver having a cylindrical housing.

DESCRIPTION OF SYMBOLS 1 Power tool 2 Motor housing 3 Rear cover 3b Opening 5 Motor 6 Rotating shaft 7 Rotor core 8 Permanent magnet 9 Stator core 11, 12 Insulator 13 Coil 14a, 14b Bearing 15 Cooling fan 16 Fan cover 17 Speed dial 18 Sensor magnet 20 Bearing holder 20a ~ 20d Prop 21 Gear case 21b Through hole (exhaust port)
21c hole (exhaust port) 22 bevel gear 23 bevel gear 24 spindle 25 metal 26 bearing 27 spindle cover 28 mounting base 30 grinding wheel 31 washer nut 32 wheel guard 35 commercial AC power supply 40 case 40a opening 41a front 41b back 41c, 41d side 41e Bottom surface 42 Tube portion 42a, 42b Screw hole 43 Power cord holding portion 44 Switch board holding portion 45a, 45b Step portion 46a Screw boss 47 Guide rail portion 48 Resin 50 Partition member 51 Longitudinal partition plate 52a, 52b Horizontal partition plate 53 Press plate 54a, 54b Arm portion 55a, 55b Screw hole 56 Pressing piece 59a, 59b Screw 60 Circuit board 61 Terminal 62a, 62b Lead wire 63a, 63b Terminal 64 Trigger switch 65 Switch board 66 Variable resistor 67 Hole 68 Sensor board 69 Rotational position detecting element 70 Power supply circuit 71 Rectifier circuit 72 Diode bridge 72a Heat sink 73 Choke coil 74 Varistor 75 Smoothing circuit 76a Electrolytic capacitor 76b Film capacitor 77a, 77b Soldering 78 Resistance 79 Capacitor 80 Inverter circuit 82 Metal plate 83a-83c Metal plate 84a-84c Terminal 87 Lead wire 90 Constant voltage power supply circuit 91 IPD circuit 92 Regulator 93 Capacitor 94a, 94b Electrolytic capacitor 95a, 95b Lead wire 96 Diode 97a, 97b, 98 Insulation sheet 99 Fuse 100 Operation unit 101 Microcomputer 102 Current detection resistors Q1 to Q6 Switching element

Claims (10)

A motor for driving the accessory tool,
A power supply circuit for supplying electricity for driving the motor,
An inverter circuit that drives the motor by a switching operation;
A control unit for controlling the operation of the inverter circuit;
A constant voltage power supply circuit connected to the power supply circuit and supplying a constant voltage to the control unit;
In a power tool including a circuit board on which the power supply circuit is mounted, and a case supporting the circuit board,
The constant voltage power supply circuit includes a capacitor,
The case is a container shape that houses the circuit board, and the circuit board is fixed to the case by filling the case with resin .
Before SL capacitor is disposed between the circuit board and the bottom surface of the case even within the casing,
An electric tool, wherein the capacitor is fixed to the case using the resin. A motor for driving the accessory tool,
A motor housing that houses the motor;
An output shaft that is rotated by the rotational force of the motor;
A power transmission mechanism for transmitting the rotational force of the motor to the output shaft;
A gear case attached to one end of the motor housing and housing the power transmission mechanism;
A power supply circuit that is connected to a power supply and supplies electricity for driving the motor;
In a power tool including a circuit board on which the power supply circuit is mounted, and a case supporting the circuit board,
It said power supply circuit includes a capacitor connected in parallel in between said power source and said motor,
The case is a container shape that houses the circuit board, and the circuit board is fixed to the case by filling the case with resin.
The output shaft projects from the gear case,
The opening of the case is opened in substantially the same direction as the direction in which the output shaft projects from the gear case,
An electric tool, wherein the capacitor is fixed to the case using the resin. The power tool according to claim 2 , wherein the capacitor is disposed in an area of the circuit board when viewed from an opening of the case. The capacitor is a cylindrical or rectangular parallelepiped shape, claim 2, characterized in that said cylindrical central axis or the cuboid longitudinal centerline are arranged in parallel the circuit board and substantially Or the power tool according to 3 . The resin is a curable resin that cures from a liquid state,
By curing the resin in the liquid state in which the resin partially or completely immersed in according to any one of claims 2 to 4, characterized in that for fixing the capacitor to the case Electric tool. The power tool according to claim 2 , wherein the capacitor is connected to the circuit board via a lead wire. A part of the electronic element mounted on the circuit board is arranged so as to be sandwiched between the capacitor and the circuit board, and the capacitor and the electronic element are kept insulated by the resin. The power tool according to claim 2 . The power tool according to claim 7 , wherein the resin is filled with an insulating member interposed between the electronic element and the capacitor. The power tool according to any one of claims 1 to 8 , wherein the capacitor includes a plurality of capacitors, which are connected in parallel. A cylindrical motor housing that houses the motor,
A cylindrical rear cover attached to one of the motor housings and housing the case,
The power tool according to claim 1, wherein an outer diameter of the rear cover is equal to or less than an outer diameter of the motor housing.

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