JP6627278B2 - Electric tool - Google Patents

Description

  The present invention relates to a power tool driven by a motor.

  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 that rotates by a rotating shaft and holds 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

  The above-described power tool has a structure in which a power switch operated by an operator to turn on / off a motor is supported by the housing at a rear side of the housing. The switch has a structure in which the switch is connected to a control board for controlling the driving of the motor by an electric wire, and has a problem in assemblability.

  Further, since the switch is provided in the housing on the rear side of the control board, a structure in which a switch operation unit for operating the switch is provided around the motor housing cannot be adopted or the operation of the switch operation unit is not possible. The structure for turning the switch on and off in conjunction with the operation becomes complicated.

  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 having good assemblability.

  Another object of the present invention is to provide a power tool having good assemblability in a power tool having a motor housing, a rear cover for accommodating a control board, and an operation portion for operating a switch in the motor housing.

  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, a housing that houses the motor, a spindle that is rotated by the motor and to which a tip tool can be attached, a gear case that rotatably holds the spindle, and a housing An intake port and an exhaust port provided, and a fan that is rotated by the motor and generates a flow of air from the intake port to the exhaust port inside the housing.
An inverter circuit having a plurality of switching elements for performing a switching operation and controlling the driving of a motor; a control unit for controlling on / off operation of the switching elements; and an output signal to the control unit by an operation of an operator. switch and a circuit board for mounting the pre-Symbol switching element, housing the circuit board has an opening that opens in one direction, the container-shaped case for holding the circuit board inside the resin is filled switched When it has said switching element is out collision from the circuit board toward the opening, thereby allow non portions covered by the resin, arranged so as to be cooled by the flow of the previous SL air The spindle protrudes from the gear case along the one direction, and the switch is provided on the circuit board.

  According to another feature of the present invention, a motor housing accommodating a motor, an inverter circuit connected to the motor housing, having a plurality of switching elements, performing a switching operation to control the driving of the motor, and turning on or off the switching elements. A control unit for controlling an OFF operation, a circuit board on which the switching element is mounted, and a power cover having a rear cover for housing a switch for switching an output signal to the control unit, wherein the switch is provided on the circuit board; An operation unit for operating the switch is provided in the motor housing.

  According to the present invention, it is possible to provide a power tool with good assemblability.

1 is a longitudinal sectional view illustrating an entire structure of a power tool according to an embodiment of the present invention, and arrows indicate flows of cooling air generated when a motor is turned on. FIG. 2 is a bottom view of FIG. 1 showing a relationship between a motor housing and a case. It is a perspective view showing a case. FIG. 2 is a sectional view taken along line AA of FIG. 1. FIG. 2 is an enlarged partial cross-sectional view of a main part of FIG. 1 showing a rotor. FIG. 2 is a block diagram illustrating a configuration of a motor drive circuit. 5 is a flowchart illustrating motor start control.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, 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 longitudinal sectional 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 a power transmission mechanism, a motor housing 2 that houses a motor 5, and a rear cover 3 that is attached to the rear of the motor housing 2 and houses electric devices. And three main parts. 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 made of resin and has a substantially cylindrical shape having an opening on the front side. The motor housing 2 has an outer diameter slightly larger than the outer diameter of the stator 9 of the motor 5, and the outer surface side of the motor housing 2 constitutes a portion (grip portion) that is gripped by an operator with one hand. A cylindrical rear cover 3 is attached to the rear 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 7 by a rotating position detecting element 69 using 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 the rotor rotates in the space on the inner peripheral side of the stator 9, and is a so-called inner rotor type. The stator 9 is manufactured in a laminated structure in which many thin iron plates manufactured by press working are stacked in the axial direction. Six teeth are formed on the inner peripheral side of the stator 9, and resin insulators 11 and 12 are mounted in the axial front and rear direction of each tooth, and a copper wire is formed in such a manner that the teeth are sandwiched between the insulators 11 and 12. Is wound to form the coil 13. 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 9, the rotor 7 is fixed to the rotating shaft 6. The rotor 7 is formed in parallel with the axial direction on the rotor 7 in which a number of annular thin iron plates manufactured by press working are laminated in the axial direction, and the N-pole and the S-pole are formed in a slot portion having a rectangular cross section. The plate-shaped permanent magnet 8 is inserted. Balancers 6a and 6b made of a metal material are provided at the front and rear ends of the rotor 7, and the balance of the rotation of the rotor 7 can be adjusted by shaving the balancers 6a and 6b.

  The rotating shaft 6 includes a rear bearing (first bearing) 14 a held by the motor housing 2 and a front bearing (second bearing) held near a connection between the gear case 21 and the motor housing 2. 14b so as to be rotatable. 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 conjunction with the rotating shaft 6 so that the motor 5 and the control circuit and the like are arranged inside the housing in directions indicated by a plurality of arrows. A flow of cooling air (cooling air) is generated. The cooling air is sucked from the wind window 3c provided on the side surface of the rear cover 3 near the rear end of the circuit board 60, flows around the case 40 accommodating the circuit board 60 from the rear to the front, and flows through the bearing of the motor housing 2. After passing through the opening 20 a (FIG. 2) provided in the holder section 20, it 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 a gap between the outer peripheral side of the stator 9 and the motor housing 2 and a gap between the stator 9 and the rotor 7, and passes through the through hole of the fan cover 16. Through the through hole 21b of the gear case 21, or through the through hole 21c, it is discharged forward. 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 arranged from the rear (windward side) to the front as viewed on the axis of the rotating shaft 6 of the motor 5. They are arranged in series (on a straight line) in the axial direction. The wind window 3a serving as an outside air intake is disposed around the circuit board 60 and behind the elements that generate a large amount of heat, in particular, the diode bridge 71 and the switching elements Q1 to Q6 (see FIG. 2 described later). . As described above, in the present embodiment, the cooling air flows in such a manner as to be substantially in contact with the entire outer peripheral surface from the rear side to the front side of the housing when viewed in the axial direction of the rotating shaft 6 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 an axial direction (here, the front-rear direction) of the rotation shaft 6 of the motor 5, and a first bevel gear is provided on a front end portion of the rotation shaft 6. A first bevel gear 22 meshes with a second bevel gear 23 mounted on the upper end of a 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 7, and has NSNS and four poles formed in order in the circumferential direction at intervals of 90 degrees. 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 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 every predetermined angle in the rotational direction, here at every 60 °. Can be

  An arithmetic unit (control unit) 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 on one surface, and is entirely hardened by a curable resin that cures a liquid resin. Here, when the grindstone 30 of the power tool 1 is lowered (in the direction of FIG. 1), the opening of the case 40 is arranged so as to face downward, and the plurality of switching elements Q <b> 1 to Q <b> 1 included in the inverter circuit 80 are arranged. Q6 is arranged to extend downward from circuit board 60.

  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 the wind window 3a serving as the suction port, they are directly exposed to the cooling air indicated by the arrow. A power supply circuit 70 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 (diode bridge 71) for converting a commercial power supply (AC) supplied from the outside into DC. The rectifier circuit is located on the rear side of the case 40 close to the power cord 3b wired so as to extend from the rear end face of the rear cover 3 to the outside and behind the switching elements Q1 to Q6 (motor 5 on the opposite side of the motor).

  The circuit board 60 is further provided with a calculation unit for controlling the rotation of the motor 5. The arithmetic unit includes a microcomputer 100 (hereinafter, referred to as “microcomputer 100”), and controls the start and stop of the motor 5 and the rotation speed by driving the inverter circuit 80. 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 speed adjustment board 65 is mounted on the outside of the container 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 axial direction of the rotating shaft 6 of the motor 5, and the speed adjusting board 65 is arranged so as to be parallel to the axial direction of the rotating shaft 6.

  FIG. 2 is a bottom view of FIG. 1 and shows a state before the rear cover 3 is attached to the motor housing 2. 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, the circuit board 60 is immersed in a resin that hardens and hardens from a liquid. The components mounted on the circuit board 60 mainly control a power supply circuit 70 including a rectifier circuit and a smoothing circuit, an inverter circuit 80 including six switching elements Q1 to Q6, and the inverter circuit 80. An arithmetic unit including the microcomputer 100 and a constant voltage power supply circuit 90 for generating a constant voltage DC for the arithmetic unit. A power supply cord 3b 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 power cord 3b 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 (diode bridge 71) and a smoothing circuit 75, and includes a choke coil 73 and a varistor 74. The smoothing circuit 75 includes an electrolytic capacitor 76 and a resistor 78 described later. are doing.

  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. The switching elements Q1 to Q6 have three metal terminals extending from the lower side of a substantially rectangular parallelepiped ceramic or the like package, and a metal heat sink is embedded on the back side of the package. 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, a plurality of switching elements Q1 to Q3 Are provided with common metal plates 82, 83a to 83c. 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 orthogonal to the longitudinal direction (front-back direction, axial direction of the rotating shaft 6) of the circuit board 60. With this arrangement, the surfaces of the metal plates 83a to 83c on the side opposite to the switching elements are oriented parallel to the direction in which the cooling air flows (see the arrow in FIG. 1), so that the heat radiation effect can be enhanced.

  The circuit board 60 further includes a microcomputer 100 as an arithmetic unit, a constant voltage power supply circuit 90 described later, and a switch 64 that operates in conjunction with the switch bar 4a. These can be mounted in any space on the circuit board 60. In this embodiment, the microcomputer 100 is mounted behind the switch 64. 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.

  A speed adjusting board 65 on which a variable resistor 66 is mounted is provided on the rear side of the case 40. The switch board 65 is provided at a portion protruding rearward from the container-like portion of the case 40, and a speed change dial 17 that is partially exposed from the rear cover 3 is provided on a rotating shaft of the variable resistor 66. The circuit boards 60 and 55 are wired by lead wires 63.

  The case 40 has a container shape having an opening surface 40a, and is formed so as not to leak even if a liquid is put into the internal space. However, when the case 40 is disposed in the power tool 1, the normal direction of the opening surface 40a is downward. It is arranged in an inverted state to face. In other words, the case 40 is arranged so as to open downward. This is to prevent the inside of the case 40 from accumulating 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 power tool 1 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 if the switching elements Q1 to Q6 are covered only about half. It became possible. 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.

  Screw holes 42a, 42b for fixing the motor housing 2 to the motor housing 2 with screws 42c, 42d are formed at the front end of the case 40. The bearing holder 20 of the motor housing 2 is formed with a plurality of columns (not shown) extending outward from a cylindrical portion that holds the outer ring portion of the bearing 14a (see FIG. 1), and has openings 20a in places other than the columns. The cooling air flows from the space in which the case 40 is accommodated to the space in which the motor 5 is accommodated. The rear cover 3 is fixed to the motor housing 2 by being screwed to the rear end of the case 40 fixed to the motor housing 2 with a screw 42e. This eliminates the necessity of disposing parts for fixing at the connecting portion between the motor housing 2 and the rear cover 3, so that the shape can be made easy for an operator to grasp.

  An electrolytic capacitor 94 used in the constant voltage power supply circuit 90 is mounted on the circuit board 60.

  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 and the like. A smoothing circuit 75 is connected between the output side of the power supply circuit 70 and the inverter circuit 80. The inverter circuit 80 includes six switching elements Q1 to Q6, and the switching operation is controlled by gate signals H1 to H6 supplied from the operation unit (microcomputer 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 (microcomputer 100) are mounted together on the same circuit board 60.

  The power supply circuit 70 includes a rectifier circuit mainly configured by a diode bridge 71, and the input side of the rectifier circuit is connected to, for example, the commercial AC power supply 35, and the output side is connected to the smoothing circuit 75. The term “normal power supply circuit” may refer to a circuit having both a rectifier circuit and a smoothing circuit. The rectifier circuit performs full-wave rectification on the input AC and outputs the rectified AC to the smoothing circuit 75. The smoothing circuit 75 is disposed between the rectifier circuit and the inverter circuit 80, smoothes a pulsating current included in the current rectified by the rectifier circuit to a state close to a direct current, and outputs the pulsating flow to the inverter circuit 80. . The smoothing circuit 75 includes an electrolytic capacitor 76 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 commercial AC power supply 35 to the smoothing circuit 75 also increases. ing. Therefore, the electrolytic capacitor 76 provided in the smoothing circuit 75 is required to have a large capacitance.

  The inverter circuit 80 includes six switching elements Q1 to Q6 connected in a three-phase bridge format. Inside the stator 9 of the motor 5, the rotor 7 having the permanent magnet 8 rotates. A sensor magnet 18 for position detection is connected to the rotating shaft 6 of the rotor 7. The position of the sensor magnet 18 is detected by a rotation position detecting element 69 such as a Hall IC, so that the arithmetic unit (microcomputer 100) Detect the rotational position.

  The calculation unit (microcomputer 100) is a control unit for performing on / off and rotation speed control of the motor 5, and is a microcomputer (microcomputer). The arithmetic unit (microcomputer 100) is mounted on the circuit board 60, controls the rotation speed of the motor 5 based on a start signal input by operating the switch 64, and a speed signal set by the speed change dial 17, and , V, W and the drive voltage. 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 Ql 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 (microcomputer 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 (microcomputer 100) in advance. When the detected current value exceeds the threshold value, an inverter circuit 80 is provided to stop driving the motor 5. To stop the switching operation. As a result, the occurrence of burnout or the like due to the overcurrent flowing to the motor 5 is suppressed.

  The constant voltage power supply circuit 90 is a power supply circuit that is directly connected to the output side of the rectifier circuit 71 and supplies a low-voltage DC to the arithmetic unit 100. The constant voltage power circuit 90 includes a diode 96, a smoothing electrolytic capacitor 94, an IPD circuit 91, a capacitor 93, and a regulator 92. The constant voltage power supply circuit 90 is a circuit for supplying a stabilized reference voltage to an operation unit (microcomputer 100) and the like based on the output from the power supply circuit 70. Each part of the constant voltage power supply circuit 90 is mounted on the circuit board 60.

  Next, the shape of the case 40 will be described with reference to FIG. The case 40 is a non-conductive material, and is manufactured by integral molding of a synthetic resin such as plastic. FIG. 3 is a perspective view showing that the opening surface 40a is directed 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. 41e, and the other surface is an opening surface 40a. The joints between the side surfaces 41c and 41d and the bottom surface 41e are not formed at right angles, but are formed along the cylindrical inner wall shape of the rear cover 3, and are connected at a further surface formed obliquely here. 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.

  Next, the relationship between the motor housing 2 and the motor 5 will be described with reference to FIG.

  As shown in FIG. 4, the outer peripheral shape of the stator 9 has a linear shape, and has four caulking portions 9 a which are protruding portions protruding from the circumferential shape in order to caulk thin iron plates. It has a shape having a pair of plane portions 9b orthogonal to each other in the circumferential direction of the caulking portion 9a. Each of the flat portions 9b is formed to extend in a direction orthogonal to the axial direction (front-back direction) of the rotating shaft 6. In other words, one caulking part 9a has a plane part 9b extending in the left-right direction and a plane part 9b extending in the left-right direction.

  A total of eight ribs 2a are provided on the inner peripheral side of the motor housing 2 for receiving the caulked portion 9a of the stator 9 and for four pairs of ribs 2a abutting on the flat portion 9b. The rib 2 a and the caulking portion 9 a extend in the direction of the rotating shaft 6 of the motor 5 and have a shape extending at least over the range of the stator 7.

  More specifically, a pair of ribs 2a are provided so as to be orthogonal to each other and protrude toward the caulking portion 9a, and are also arranged in the circumferential direction of one caulking portion 9a (clockwise and counterclockwise in FIG. 4). The caulking portion 9a is positioned by making surface contact with the flat portion 9b provided on the (side) side. At this time, each rib 2a is provided so as to project in a direction perpendicular to the direction in which the contacting flat portion 9b extends. With such a structure, the motor 5 is held by the plurality of ribs 2a from above, below, right and left, and thus can be firmly fixed to the motor housing 2. Further, since the ribs 2a and the plane portions 9b are in contact with each other on a surface orthogonal to the axial direction of the rotating shaft 6, when the stator 9 attempts to rotate in the rotating direction of the rotating shaft 6, a load applied to the ribs 2a is reduced. By dispersing, the breakage of the rib 2a is suppressed. Specifically, since the contact surface is inclined by about 30 degrees with respect to the rotation direction, the load on the rib 2a in the rotation direction is offset, and the rib 2a can be prevented from being damaged.

  When the stator 9 is inserted into the motor housing 2, the flat portion 9b is pressed into the rib 2a. The rotation of the stator 9 is restricted by the rib 2a in the motor housing 2. Centering is performed.

  The motor housing 2 has a structure having a step portion or the like in the circumferential direction, but an outer peripheral portion provided with the rib 2a is formed thicker than other portions and has a thickness of 2.3 mm. On the other hand, the rib 2a is formed to have a thickness of 1.5 mm, which is thinner than this, and the rib 2a is configured to be thinner than the outer peripheral portion of the motor housing 2 so that the rib 2a is provided. The occurrence of sink marks on the outer peripheral portion of the housing 2 is suppressed.

  The stator 9 is supported by the ribs 2a such that a gap is formed between the outer periphery of the stator 9 and the motor housing 2 between the pair of ribs 2a and the other pair of ribs 2a. Through which cooling air passes, and a flow path through which the cooling air flows is secured. It should be noted that a switch bar 4a to be described later is arranged in one gap.

  Also, a gap is formed between the outer periphery of the caulked portion 9a and the motor housing 2 between the pair of ribs 2a, so that the outer periphery of the caulked portion 9a abuts on the motor housing 2 so that the centering is not affected. In addition to this, it also helps to secure the flow path for cooling air.

  In the disk grinder as in the present embodiment, the operator performs the work while gripping the motor housing 2, and it is desired that the diameter of the motor housing 2 be small from the viewpoint of easy gripping. With the above-described configuration, the cooling air flows without increasing the diameter of the motor housing 2 by, for example, adding a new part for regulating the rotation of the stator 9 in the motor housing 2. The motor support structure is compact and has good cooling performance without hindrance.

  As shown in FIG. 4, the rib 2a has a shape extending so as to intersect the radial direction of the rotating shaft 6, and has a structure in which the tip of the rib 2a supports the stator 7. When the generated rotational torque is received by the rib 2a, concentration of stress at the root corner of the rib 2a is suppressed, and the force can be dispersed and received in the protruding direction of the rib 2a, thereby realizing a strong support structure. be able to.

  In addition, four caulking portions 9a are provided on a diagonal line, and a total of eight ribs 2a can disperse the load in the rotation direction applied to each rib 2a, thereby making the rib 2a thinner. In addition, the outer peripheral portion of the motor housing 2 is made thinner to suppress sink marks on the outer peripheral portion of the motor housing 2.

  Further, as described above, the cooling air is sucked by the cooling fan 15 not only through the gap between the outer peripheral side of the stator 9 and the motor housing 2 but also through the gap between the stator 9 and the rotor 7. The gap between the stator 9 and the rotor 7 is about 0.5 mm in the radial direction, and iron powder may enter during the operation of the disc grinder. The iron powder that has entered during this time may adhere to the stator 7 due to the magnetic force of the permanent magnet 8 in the stator 7. The disk grinder of the present embodiment has a rotation speed of the brushless motor 5 of about 9,000 rpm when the speed dial 17 is set to the minimum speed, a rotation speed of 32,700 rpm when the speed dial 17 is set to the maximum speed, the stator 9 and the rotor. 7 is set to be about 26 m / sec, which is higher than 20 m / sec.

  When the number of revolutions of the motor 5 is set to the minimum number of revolutions, the iron powder that has entered the gap between the stator 9 and the rotor 7 continues to adhere to the stator 7, but the above-described wind speed is obtained. With this configuration, the iron powder adhered to the rotor 7 is blown off together with the cooling air at least when the maximum speed is set, and the iron powder is less likely to adhere to the rotor 7 during rotation of the motor 5.

  Next, among the balancers 6a and 6b provided before and after the rotor 7 constituting the brushless motor 5, the shape of the balancer 6a on the bearing holder 20 side will be described with reference to FIG.

  As described above, the balancers 6a and 6b are made of a metal material, and are provided so as to adjust the rotational balance of the rotor 7. The balancers 6a and 6b are configured to rotate integrally with the rotating shaft 6 and the rotor 7. Have been.

  Between the balancer 6a and the bearing 14a, a seal member 10 made of resin or the like, which is an insulating member, is mounted on the rotating shaft 6 so as to be in contact with the bearing 14a. The seal member 10 is provided to prevent dust from entering the bearing 14a. A mold 6d made of a resin, which is an insulating material, is formed on the entire outer circumference of the rotary shaft 6 from the area where the rotor 7 is provided to the inner side of the seal member 10 on the near side of the bearing 14a. A mold 6d is not provided on the outer peripheral portion of the rotating shaft 6 that is in contact with the bearing 14a, for the purpose of accurately centering the rotating shaft 6 and suppressing shaft blur.

  Since the balancer 6a is made of a metal member and is electrically connected to the rotor 7, the balancer 6a is connected to the balancer 6a in order to prevent a current flowing through the motor 5 through the bearing 14a made of a conductive member from flowing through the motor housing 2. It is necessary to secure a distance between the balancer 6a and the end face of the mold 6d located between the bearing 14a.

  If the configuration is such that the distance between the balancer 6a and the bearing 14a is largely separated, it is possible to easily secure the distance for preventing the above-mentioned energization, but in this case, it is possible to increase the size of the entire grinder, The distance between the balancer 6a and the seal member 10 increases, and dust easily enters the bearing 14a through this distance.

  In the present embodiment, the configuration in which the balancer 6a has the concave portion 6c in the inner peripheral portion is adopted, so that the distance between the end face of the mold 6d and the balancer 6a in the axial direction of the rotating shaft 6 is secured, and the balancer 6a and the seal are formed. Dust does not easily enter between the member 10.

  Further, the outer peripheral side surface of the concave portion 6c has a shape inclined toward the radially outer side toward the bearing 14a side (rearward). Thus, the shape is such that the spatial distance between the rear end portion of the mold 6d and the balancer 6a can be kept large, and the area of the outer peripheral side surface of the balancer 6a is ensured large to balance the rotation of the rotor 7. Therefore, it has a shape that can be easily cut.

  In addition, in order to further suppress intrusion of dust into the bearing 14a, the structure in which the seal member 10 is provided is adopted. However, even if the seal member 10 is not provided, the balancer 6a is provided with the concave portion 6c. Thus, the distance between the bearing 14a and the outer peripheral end face of the balancer 6a can be reduced, so that a configuration in which dust does not easily enter the bearing 14a can be realized while having a compact structure in which current leakage is suppressed. .

  Next, the configuration of the switch operation unit 4 and the switch 64 and the startup control when the switch 64 operates will be described.

  As described above, the switch 64 is mounted on the circuit board 60. The switch 64 is a micro switch and has a plunger 64a which is always biased in a protruding direction. When the plunger 64a is in a protruding state, the switch 64 transmits an OFF signal to the microcomputer 100, and the plunger 64a is in a non-protruding state. In such a case, an ON signal is transmitted to the microcomputer 100.

  The switch 64 has a leaf spring 64b that contacts the plunger 64a.

  The motor housing 2 is provided with a switch operation unit 4 that is exposed to the outer periphery of the motor housing 2 and is operable by an operator and is movable in the axial direction of the rotation shaft 6. The switch bar 4 a is connected to the switch bar 4 a extending in the axial direction of the rotary shaft 6. The switch bar 4 a is slidable in the axial direction of the rotary shaft 6 together with the switch operation unit 4.

  A biasing force of a spring 4c provided between the motor housing 2 and the switch bar 4a always acts on the switch bar 4a, and the plunger 64a of the switch 64 and the leaf spring 64b are provided on the switch bar 4a on the rear side. An abutting portion 4b is provided to abut via the contact portion.

  In the initial state, the switch operation unit 4 and the switch bar 4a are positioned rearward as shown in FIGS. 1 and 2 by the urging force of the spring 4c. When the switch bar 4a is located on the rear side in this way, the contact portion 4b is not in contact with the leaf spring 64b, the plunger 64a is in the protruding state, and the switch 64 outputs an OFF signal to the microcomputer 100. .

  When the operator operates the switch operation unit 4 from the state shown in FIG. 2 and slides the switch operation unit 4 and the switch bar 4a forward, the contact unit 4b contacts the plunger 64a via the leaf spring 64b, Move to a non-projecting position. As a result, the switch 64 outputs an ON signal to the microcomputer 100, and the microcomputer 100 starts the brushless motor 5.

  As shown in FIG. 2, the motor housing 2 is provided with an engaging portion 2b for engaging with the switch operating portion 4 to maintain a state where the switch operating portion 4 is moved to the front side. That is, a configuration is provided in which a so-called on-lock mechanism is provided, which maintains the activated state of the motor 5 by setting the switch operation unit 4 to the state of being engaged with the engagement unit 2b.

  The microcomputer 100 controls the start-up of the motor 5 by receiving a signal from the switch 64. However, since the microcomputer 100 has the above-described on-lock mechanism, the microcomputer 100 is in the on-lock state, and after the power failure is restored after the power failure occurs. When the power cord 3b is connected in the on-lock state or when the power cord 3b is connected, the motor 5 is not started and the 0V release control is provided.

  Specifically, the microcomputer 100 performs the startup control shown in FIG.

  When the power cord 3b is connected or recovers from the power failure, the microcomputer 100 starts up as shown in S1. Thereafter, the microcomputer 100 determines whether or not an OFF signal has been received from the switch 64. If an OFF signal is received in S2, it is determined whether or not an ON signal is received in S3, and if an ON signal is received, the process proceeds to S4 and the motor 5 is started.

  That is, when the microcomputer 100 starts up, if the ON signal is received from the switch 64, the motor 5 is not started up without proceeding to S3. This prevents the motor 5 from suddenly starting up when the power cord 3b is connected or when returning from a power failure, and prevents the work material or the like from being damaged by the grindstone 30.

  After the motor 5 is started, the power supply to the motor 5 is maintained until the OFF signal is received in S5, and the power supply to the motor 5 is stopped in S6 when the ON signal is received.

  In this embodiment, since the switch 64 is directly mounted on the circuit board 60, electrical connection between the switch 64 and the circuit board 60 can be easily performed, and assemblability can be improved. Although the circuit board 60 can be divided, it is effective to mount the circuit board 60 on the same circuit board 60 as the microcomputer 100 and the inverter circuit 80 as a control unit in consideration of electrical connection. In addition, it is desirable to mount the switch 64 on the same circuit board 60 as the inverter circuit 80, considering that the power supply circuit 70 requiring the most cooling needs to be arranged on the upstream side of the cooling air.

  The switch 64 is disposed on the motor 5 side of the circuit board 60 so that other electric components such as the inverter circuit 80 and the power supply circuit 70 do not block the contact of the switch bar 4a with the switch 64, thereby preventing the switch 64 from coming into contact with the switch 64. The switch 64 can be changed between the ON state and the OFF state without adding another component different from the bar 4a.

  In addition, since the leaf spring 64b is interposed between the plunger 64a and the contact portion 4b of the switch bar 4a, the operating direction of the plunger 64a is orthogonal to the operating direction of the contact portion 4b. This also enables the plunger 64a to operate smoothly by the operation of the contact portion 4b. Note that the switch operation unit 4 may directly contact the plunger 64a without providing the switch bar 4a. Even in this case, the operation direction of the switch operation unit 4 and the operation direction of the plunger 64a are orthogonal to each other. It is desirable to interpose a leaf spring 64b.

  Further, in the disk grinder as in the present embodiment, although there is a possibility that iron powder may enter the inside of the housing, the switch 64 is constituted by a microswitch whose output signal is switched when the plunger 64a is in a protruding or non-protruding state. Even if the iron powder enters near 64, occurrence of malfunction due to the iron powder is suppressed.

  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, a description has been given using a grinder as an example of the power tool 1. However, the present invention is not limited to the grinder, and can be similarly applied to other power tools. For example, in a saver saw, a multi-cutter, a driver, an impact driver, and the like. Can be similarly applied.

DESCRIPTION OF SYMBOLS 1 Power tool, 2 motor housing, 2a rib, 2b bearing holder part, 3 rear cover, 3a wind window, 3b power cord, 4 switch operation part, 4a switch bar, 4b contact part, 5 motor, 6 rotating shaft, 6a, 6b Balancer, 7 rotor, 8 permanent magnet, 9 stator, 10 sealing member, 11, 12 insulator, 13 coil, 14a, 14b bearing, 15 cooling fan, 16 fan cover, 17 speed change dial, 18 sensor magnet, 20 bearing holder, 20a Opening, 21 gear case, 21b through hole, 21c through hole, 22, 23 bevel gear, 24 spindle, 25 metal, 26 bearing, 27 spindle cover, 28 mounting base, 30 grinding stone, 31 washer nut, 32 wheel guard, 35 commercial AC Power supply, 40 cases, 4 a Opening surface, 41a front surface, 41b rear surface, 41c, 41d side surface, 41e bottom surface, 42 cylinder portion, 42a, 42b screw hole, 42c, 42d, 42e screw, 43 power cord holding portion, 44 switch board holding portion, 45a, 45b Step, 46a screw boss, 47 guide rail, 60 circuit board, 64 switch, 64a plunger, 64b leaf spring, 65 speed adjustment board, 66 variable resistor, 68 sensor board, 69 rotation position detecting element, 70 power supply circuit, 71 diode Bridge, 72 choke coil, 73 varistor, 75 smoothing circuit, 76 electrolytic capacitor, 78 resistor, 80 inverter circuit, 90 constant voltage power supply circuit, 91 IPD circuit, 92 regulator, 93 capacitor, 94 electrolytic capacitor, 96 diode, 100 arithmetic unit (My C), 102 current detection resistor, Q1-Q6 switching element

Claims (10)

Motor and
A housing for housing the motor;
A spindle rotated by the motor and capable of attaching a tip tool;
A gear case for rotatably holding the spindle,
An intake port and an exhaust port provided in the housing;
A fan that is rotated by the motor and generates an air flow from the intake port to the exhaust port inside the housing;

An inverter circuit having a plurality of switching elements and performing a switching operation to control driving of the motor;
A control unit for controlling the on or off operation of the switching element,
A switch for switching an output signal to the control unit by an operation of an operator,
A circuit board on which the switching element is mounted,
A container-shaped case that accommodates the circuit board, has an opening that opens in one direction, and is filled with a resin therein and holds the circuit board ,
The switching device issues impact from the circuit board toward the opening, thereby allow non portions covered by the resin, is arranged to be cooled by the flow of the previous SL air,
The spindle projects from the gear case along the one direction,
An electric tool, wherein the switch is provided on the circuit board. The power tool according to claim 1, wherein the switch has a plunger that switches between a protruding state and a non-protruding state, and is a microswitch that switches an output signal according to a position of the plunger. It has a switch operation unit that can be operated by workers,
The power tool according to claim 2, wherein the state of the plunger is switched in conjunction with the operation of the switch operation unit. 4. The electric motor according to claim 3, wherein an operation direction of the switch operation unit is orthogonal to an operation direction of the plunger, and a leaf spring is provided between the switch operation unit and the plunger. tool. The housing has a motor housing that houses the motor, and a rear cover that houses the circuit board,
The power tool according to claim 3, wherein the switch operation unit is provided on the motor housing. The power tool according to claim 5, wherein an operation direction of the switch operation unit is a direction parallel to a rotation axis of the motor. The power tool according to claim 5, wherein a control circuit, a rectifier circuit, and a smoothing circuit are mounted on the circuit board, and the switch is located on the motor side of the circuit board. The power tool according to any one of claims 5 to 7, wherein a cooling fan that flows on the circuit board and generates cooling air that flows into the motor housing when the motor is rotated is attached to the motor. . The said control part does not start the said motor, even if it receives the output signal which shows starting the said motor from the said switch at the time of the start of the said control part, The said motor is not started. The described power tool. A motor housing containing a motor and a fan;
A gear cover that is connected to the motor housing and that supports a spindle that is rotated by the motor and detachable with a tool bit;
An inverter circuit that is connected to the motor housing, has a plurality of switching elements, performs a switching operation and controls driving of the motor, a control unit that controls on or off operation of the switching elements, a circuit board on which the switching elements are mounted, A rear cover that houses a switch that switches an output signal to the control unit;
An operation unit provided on an outer surface of the motor housing and capable of being operated by an operator in an axial direction of the motor;
A transmitting member that receives an operating force to the operating unit and operates in the motor axis direction to transmit the operating force to the switch;
An intake port provided in the rear cover,
An exhaust port provided in the gear cover,
A fan that is rotated by the motor and generates a flow of air from the intake port to the exhaust port;
A container-shaped case that houses the circuit board, has an opening that opens in one direction, and has a container-shaped case that is filled with resin and holds the circuit board ,
The switching device issues impact from the circuit board toward the opening, thereby allow non portions covered by the resin, is arranged to be cooled by the flow of the previous SL air,
Said spindle, said formic Yakaba or al protrudes along the one direction,
The said switch, with a plunger for switching the output signal by pressing are provided, the protruding direction of the plunger so as to be along the one direction provided the switch on the circuit board,
The transmission member is provided with a contact portion protruding so as to approach the switch,
A power tool is provided between the contact part and the switch, and a transmission part that converts the movement of the contact part that operates in the motor axis direction into the one direction and transmits the one direction to the switch is provided.