JP2015120208A - Electric tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the cooling characteristics of a motor for driving a tip tool.SOLUTION: A motor 31 which drives a tip tool is covered by a resin motor case 82, and at least a part of the motor case 82 is covered by a motor housing 14c which is exposed to the exterior and made of aluminum alloy. A cooling passage 83 which guides outer air is provided between the motor case 82 and the motor housing 14c. A fan 79 is provided at an output shaft of the motor and cooling air generated by the fan 79 is guided to the cooling passage 83.

Description

  The present invention relates to an electric tool in which a tip tool is driven by an electric motor.

  Examples of the electric tool configured to drive the tip tool using an electric motor as a driving source include a hammer, a hammer drill, and a grinder. Hammers and hammer drills are also called striking tools, with a drill bit or anchor drill as the tip tool. These striking tools are used for applying an impact force to a work object by the tip tool or rotating the tip tool while applying the impact force. The grinder is a power tool for grinding a work object by rotating a grinding wheel as a tip tool, and is also called a disc grinder or disc sander. Examples of the electric tool that operates the work target by driving the tip tool include an impact driver, an impact wrench, and a cutter.

  The electric tool includes an electric motor for driving the tip tool, and a motion conversion mechanism for converting the rotational motion of the motor output shaft into the rotational motion and impact motion of the tip tool. For example, Patent Literature 1 describes an impact tool that is an electric tool in which an impact force is applied to a work target with a tip tool. A piston is reciprocally mounted in a cylinder to which the tool holder is attached, and an electric motor for driving the piston is incorporated in the housing.

JP 2007-331072 A

  In order to cool the electric motor, a fan is provided on the motor output shaft. The cooling air generated by the fan flows through the gap between the rotor and the stator of the electric motor to cool the electric motor.

  An object of the present invention is to improve the cooling characteristics of a motor for driving a tip tool.

  The electric tool of the present invention has a motor that is covered with a resin motor case and drives a tip tool, and an aluminum alloy motor housing that covers at least a part of the motor case and is exposed to the outside. A cooling passage for guiding outside air is provided between the motor case and the motor housing.

  According to the present invention, the cooling passage is provided between the motor case and the motor housing that houses the motor, and the motor housing is formed of the aluminum alloy. In addition, the motor can be efficiently cooled by the outside air guided to the cooling passage. Since the cooling characteristics of the motor are improved, the durability can be improved even if the output of the motor is increased.

(A) is a perspective view which shows the external appearance of the impact tool which is an example of an electric tool, (B) is a perspective view which shows the external appearance of the impact tool which is a modification. It is a longitudinal cross-sectional view of the impact tool shown by FIG. It is an expanded sectional view which shows the principal part of FIG. It is the sectional view on the AA line in FIG. FIG. 4 is a sectional view taken along line BB in FIG. 3. It is a block diagram which shows a motor control circuit. It is sectional drawing which shows the principal part of the impact tool which is a modification. It is CC sectional view taken on the line in FIG. It is sectional drawing which shows the principal part of the impact tool which is another modification. It is the DD sectional view taken on the line in FIG. It is sectional drawing which shows the principal part of the impact tool which is a modification. It is sectional drawing which shows the principal part of the impact tool which is a modification. It is the EE sectional view taken on the line in FIG. It is sectional drawing which shows the principal part of the impact tool which is a modification. It is the FF sectional view taken on the line in FIG. It is a longitudinal cross-sectional view of the impact tool which is a modification. It is the GG line expanded sectional view in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same code | symbol is attached | subjected to the common member.

  The power tool shown in FIGS. 1A and 2 is a striking tool 10a called a hammer drill, and a drill bit as a tip tool T is detachably attached thereto. The drill bit, that is, the tip tool T, is subjected to rotational motion and impact motion, and the impact tool 10a is used for drilling or the like using concrete or stone as a work object. . The operation mode by the impact tool 10a includes an impact mode in which an impact force is applied to the tip tool T and a rotation impact mode in which the tip tool T is rotated in addition to the impact force.

  As shown in FIG. 2, the impact tool 10 a includes a cylinder 11, and a cylindrical tool holder 12 is fixed to the tip of the cylinder 11 by a pin 13. The tool holder 12 is supported by a cylinder housing 14a via a bearing 15, and the cylinder 11 and the tool holder 12 are rotatably mounted in the cylinder housing 14a. When the cylinder 11 is rotated with the tip tool T mounted on the tool holder 12, the tip tool T is rotationally driven.

  A tip end portion of the hammer member 16 is incorporated in the base end portion of the tool holder 12 so as to be capable of reciprocating in the axial direction, and the base end portion of the hammer member 16 projects into the cylinder 11. A striking element 17 for applying an impact force to the hammer member 16 is mounted in the cylinder 11 so as to be reciprocally movable in the axial direction, and a piston 18 is reciprocally movable in the axial direction in the rear end portion of the cylinder 11. It is installed. An air chamber 19 is provided between the striker 17 and the piston 18, and when the piston 18 is driven forward, the air in the air chamber 19 is compressed and the striker 17 is driven in the forward direction. Thereby, the striker 17 collides with the hammer member 16, and the impact force of the striker 17 is applied to the tip tool T via the hammer member 16.

  A tip cover 21 is attached to the cylinder housing 14a and constitutes a part of the cylinder housing 14a. A rubber tip cap 22 is attached to the tip of the tool holder 12. A detachable sleeve 23 is mounted on the outside of the tip cap 22 so as to be reciprocally movable in the axial direction. A spring force in a direction away from the cylinder housing 14 a, that is, a forward direction is urged by the coil spring 24. . The tool holder 12 is fitted with an engagement roller that engages a groove provided in the tip tool T, that is, an engagement member 25 movably in the radial direction. The detachable sleeve 23 is provided with a fastening ring 26. As shown in FIG. 2, when the fastening ring 26 projects the engaging member 25 radially inward, the tip tool T is fastened to the tool holder 12. The On the other hand, when the detachable sleeve 23 is moved backward against the spring force, the engagement between the fastening ring 26 and the engaging member 25 is released. Under this state, when the tip tool T is pulled, the engaging member 25 is retracted radially outward, and the tip tool T can be removed. On the other hand, when the tip tool T is inserted into the tip of the tool holder 12 and the tool holder 12 is moved forward by a spring force with the detachable sleeve 23 moved backward, the tip tool T is held by the tool. It is attached to the tool 12 and fastened by the engaging member 25.

  A gear housing 14b is provided at the rear end of the cylinder housing 14a, and a motor housing 14c is provided in the gear housing 14b. The motor housing 14c is oriented substantially perpendicular to the cylinder housing 14a, and the housing 14 of the impact tool 10a is formed by these housings 14a to 14c. An operation handle 28 is provided at the rear portion of the housing 14 so as to protrude rearward. The handle 28 has a main body portion 28a extending in a direction substantially perpendicular to the cylinder 11, and two leg portions 28b, 28c provided at both ends thereof, and the upper end portion of the main body portion 28a, that is, a gear housing. The upper leg portion 28b is integrated with the side, and the lower leg portion 28c is integrated with the lower end portion of the main body portion 28a, that is, the motor housing side. Further, both the leg portions 28 b and 28 c are integrally connected by a connecting wall 28 d, and the connecting wall 28 d forms the housing 14. The respective leg portions 28 b and 28 c are attached to the back surface of the housing 14, and a grip space 29 is provided between the main body portion 28 a and the housing 14. When the operator grips the main body 28 a of the handle 28 and performs an operation such as drilling a work target with the impact tool 10 a, the operator enters his / her hand into the gripping space 29. The connecting wall 28 d forms the rear wall of the housing 14 and faces the main body 28 a of the handle 28, and the inner surface of the main body 28 a faces the rear side of the housing 14.

  When an operator works with the impact tool 10a, the operator usually handles the handle so that the upper leg portion 28b is on the upper side, that is, the cylinder housing 14a is on the upper side of the motor housing 14c. 28 is held, that is, held in the hand. The vertical relationship between the two legs 28b and 28c of the handle 28 and the vertical relationship between the cylinder housing 14a and the motor housing 14c indicate the posture in which the impact tool 10a is normally used, as shown in FIG. The cylinder housing 14a and the motor housing 14c are assembled via a gear housing 14b, and the gear housing 14b is formed by an upper portion 30a on the cylinder housing 14a side and a lower portion 30b on the motor housing 14c side.

  A brushless motor 31 is accommodated in the motor housing 14c. The brushless motor 31 has a cylindrical stator 32 around which a coil is wound, and a rotor 33 incorporated therein. An output shaft 34 is attached to the rotor 33, and the output shaft 34 faces in a direction orthogonal to the reciprocating direction of the cylinder 11 and outputs the rotational driving force of the motor 31. A base end portion of the output shaft 34 is rotatably supported by a bearing 35, and an output end portion of the output shaft 34 is rotatably supported by a bearing 36. The bearing 35 is integrated into a retainer 38 that forms a part of the motor housing 14 c integrally with the bottom wall portion of the motor housing 14 c, and the retainer 38 is covered with a bottom cover 37 that is attached to the housing 14. The bearing 36 is attached to the lower side portion 30b of the gear housing 14b. An upper cover 39 is attached to the upper surface of the rear side of the housing 14. The top cover 39 and the bottom cover 37 each constitute a part of the housing 14.

  In order to convert the rotational movement of the output shaft 34 of the motor 31 into the reciprocating motion of the piston 18, a crankshaft 41 is rotatably mounted on the gear housing 14b. The crankshaft 41 is arranged on the tool holder side in parallel with the output shaft 34, and a large-diameter pinion gear 42 provided on the crankshaft 41 meshes with a gear portion provided at the tip of the output shaft 34. ing. An eccentric member 43 having a function as a crank weight is attached to the tip of the crankshaft 41, and a crankpin 44 is attached to the eccentric member 43 at a position eccentric from the rotation center of the crankshaft 41. One end of a connecting rod 45 is rotatably fitted to the crank pin 44 and the other end is fitted to a piston pin 46 attached to the piston 18 so as to be swingable. Thereby, the rotational motion of the crankshaft 41 driven by the output shaft 34 is converted into the reciprocating motion of the piston 18 in the direction orthogonal to the output shaft 34 by the motion conversion mechanism 47 including the eccentric member 43 and the connecting rod 45. The The eccentric member 43, the crank pin 44, and the like are covered with an upper cover 39.

  In order to transmit the rotational motion of the output shaft 34 to the rotational motion of the cylinder 11, a rotation transmission shaft 51 is rotatably supported in the gear housing 14 b, and the rotation transmission shaft 51 is provided on the crankshaft 41. A large-diameter pinion gear 53 that meshes with the small-diameter pinion gear 52 is provided. The rotational force of the output shaft 34 is transmitted to the rotation transmission shaft 51 by the motion conversion mechanism having such a gear. A driven sleeve 54 is fitted to the outside of the cylinder 11 so as to be movable in the axial direction. A drive-side bevel gear 55 provided at the distal end of the rotation transmission shaft 51 is provided at the base end of the driven sleeve 54. A meshing driven bevel gear 56 is provided. A key member (not shown) is provided between the driven sleeve 54 and the cylinder 11. When the driven sleeve 54 is moved backward to a position where the driven bevel gear 56 meshes with the driving bevel gear 55, the driven sleeve 54 is engaged with the cylinder 11 by the key member as shown in FIG. Thereby, the rotational motion of the output shaft 34 is transmitted to the rotational motion of the cylinder 11, and the impact tool 10a is in the rotational impact mode. On the other hand, when the driven sleeve 54 is moved forward, the engagement between the driven sleeve 54 and the cylinder 11 is released, the rotational force is not transmitted to the cylinder 11, and the impact tool 10a enters the impact mode.

  A coil spring 57 is mounted in the cylinder housing 14a in order to bias the spring force in the backward direction against the driven sleeve 54. A mode switching lever (not shown) is provided in the housing 14 in order to operate to a position where the driven sleeve 54 meshes with the drive-side bevel gear 55 and a position where the meshing state is released. Thus, when the operator operates the lever, the mode is switched between an impact mode in which an impact force is applied to the tip tool T and a rotation impact mode in which the tip tool T is rotated in addition to the impact force.

  The brushless motor 31 uses a commercial power source as a power source, and a power supply cable 58 is attached to the handle 28. In FIG. 2, only a part of the power supply cable 58 is shown, and an outlet (not shown) is provided at the tip of the power supply cable 58. In order to switch between a state in which the motor 31 is driven and a state in which the motor 31 is stopped, a trigger switch, that is, an operation switch 59 is provided on the main body 28a of the handle 28 as shown in FIG.

  The housing 14 is provided with an energizing lamp (not shown) as an informing means, and this energizing lamp is lit when the outlet is inserted into the plug of the commercial power source. A speed setting dial 62 as speed setting means for inputting the rotation speed of the motor 31 is disposed on the rear side surface of the housing 14 as shown in FIG. By operating the speed setting dial 62, the rotational speed of the motor 31 is input. In order to display the rotation speed of the motor 31, a speed display unit (not shown) is arranged on the housing 14 as a notification unit. The speed setting means includes not only a dial type but also a button type, and a button type may be used instead of the dial type. Furthermore, an abnormal state display lamp that is turned on when the load applied to the tip tool T becomes a predetermined value or more may be provided in the housing 14 as a notification means.

  FIG. 6 is a block diagram showing a motor control circuit for controlling the rotation speed of the brushless motor 31. As shown in FIG. 6, the stator, that is, the stator 32 of the brushless motor 31 is provided with U-phase, V-phase, and W-phase windings, and the rotor, that is, the rotor 33 is spaced apart in the circumferential direction. There are four permanent magnets. In order to detect the rotational position of the rotor 33, the motor control circuit has three Hall elements S1 to S3 corresponding to the three-phase windings as the rotational position detection sensor. Each Hall element is provided on the sensor substrate 64 shown in FIG. Each of the Hall elements S1 to S3 is a magnetic field detection element that outputs a detection signal when the polarity of the magnetic pole portion of the rotor 33 becomes the neutral point of the N pole and the S pole by detecting the magnetic flux. The position of the rotor 33 is detected based on the detection signals from the elements S1 to S3, and a commutation operation for each winding, that is, an energization switching operation for the winding is performed. The rotational position detection sensor is not limited to the Hall element, but an electronic circuit having a comparator function and a Hall IC in which the Hall element is integrated into one chip may be used.

  The motor control circuit has an inverter circuit 65 for controlling drive currents for the U-phase, V-phase, and W-phase windings. The inverter circuit 65 includes a rectifier circuit 67 for rectifying the alternating current of the commercial power supply 66 into a direct current, and a power factor correction circuit (PFC) 68 for boosting the rectified direct current voltage and supplying it to the inverter circuit 65. Electric power is supplied through. The power factor correction circuit 68 includes an IC 69 that outputs a PWM control signal to the transistor Tr made of a MOSFET, and suppresses the harmonic current generated in the switching element of the inverter circuit 65 to a limit value or less. A noise countermeasure circuit 70 is provided between the power supply 66 and the rectifier circuit 67 in order to prevent noise generated in the inverter circuit 65 and the like from being transmitted to the power supply side.

  The inverter circuit 65 is a three-phase full-bridge inverter circuit, and includes two switching elements Tr1, Tr2 connected in series, two switching elements Tr3, Tr4, and two switching elements Tr5, Tr6, Each is connected to the positive and negative output terminals of the power factor correction circuit 68. Three switching elements Tr1, Tr3, Tr5 connected to the positive electrode side are on the high side, and three switching elements Tr2, Tr4, Tr6 connected to the negative electrode side are on the low side. One connection terminal of the U-phase winding is connected between the two switching elements Tr1 and Tr2. One connection terminal of the V-phase winding is connected between the two switching elements Tr3 and Tr4. One connection terminal of the W-phase winding is connected between the two switching elements Tr5 and Tr6. The other connection terminals of the U-phase, V-phase, and W-phase windings are connected to each other, and each winding is star-connected. In addition, as a connection system, it is good also as a delta connection. MOSFETs are used as the switching elements Tr1 to Tr6. For example, when a control signal is applied to the gates of the high-side switching element Tr1 and the low-side switching element Tr4, current is supplied to the U-phase and V-phase windings. The commutation operation for each winding is controlled by adjusting the timing of the control signal supplied to each switching element.

  The motor control unit 71 that calculates and outputs a control signal to the inverter circuit 65 has a controller 72. A control signal is sent from the controller 72 to the inverter circuit 65 via the control signal output circuit 73. Detection signals from the Hall elements S1 to S3 as the rotational position detection sensors are sent to the rotor position detection circuit 74. The rotor position detection circuit 74 sends a signal to the motor rotation number detection circuit 75, and the motor rotation number detection circuit 75 outputs a signal corresponding to the motor rotation number to the controller 72. A detection signal corresponding to the motor current is sent from the motor current detection circuit 76 for detecting the current flowing through the motor 31 to the controller 72. The controller 72 includes a microprocessor that calculates control signals, and a memory that stores control programs, arithmetic expressions, data, and the like.

  When the operation switch 59 shown in FIG. 2 is input by an operator, an on / off detection signal is sent to the controller 72 via the operation switch detection circuit 77. An energizing lamp 61 is connected to the controller 72, and a lighting signal is sent to the energizing lamp 61 when the outlet of the power feeding cable 58 is inserted into a plug of a commercial power source. A speed setting dial 62 is connected to the controller 72, and the motor 31 is driven to rotate at a rotational speed set by operating the speed setting dial 62. The motor rotation speed, that is, the rotation speed is controlled by adjusting the voltage supplied to each winding. The voltage control for the winding is performed by adjusting the duty ratio of the ON signal applied to the gates of the switching elements Tr1 to Tr6 of the inverter circuit 65 by PWM controlling the switching elements. For example, when the duty ratio is set to 20%, a voltage of 20% of the output voltage from the power factor correction circuit 68 is supplied to each winding, and when the duty ratio is set to 100%, the motor rotation speed becomes the maximum rotation speed. . In order to display the set rotational speed, a speed display unit 63 is connected to the controller 72. The inverter circuit 65, rectifier circuit 67, power factor correction circuit 68, motor control unit 71, and the like are provided on a control board 78 shown in FIG.

  A fan 79 for generating cooling air is provided at the tip of the output shaft 34 of the motor 31, and the outer periphery of the fan 79 is covered with a cylindrical fan case 81. The fan 79 is an axial fan, but a centrifugal fan may be used. As shown in FIGS. 3 to 5, the motor 31 has a resin motor case 82, and the cylindrical stator 32 is covered with the motor case 82. The motor 31 is press-fitted and incorporated in a motor housing 14c made of aluminum alloy, and cooling air can pass between the motor case 82 and the motor housing 14c as shown in FIGS. A cooling passage 83 is provided. The cooling passage 83 is formed between a plurality of grooves formed along the axial direction on the outer peripheral surface of the motor case 82 and the motor housing 14c. On the other hand, a plurality of grooves may be formed on the inner surface of the motor housing 14c without providing grooves on the outer peripheral surface of the motor case 82, and the cooling passage 83 may be formed by the grooves of the motor housing 14c. The cooling air generated by driving the fan 79 flows through the gap between the stator 32 and the rotor 33 and also flows through the cooling passage 83 to cool the brushless motor 31. Further, a cooling passage 83 may be formed by providing grooves on both the outer peripheral surface of the motor case 82 and the inner peripheral surface of the motor housing 14c, and a groove is formed in at least one of the motor case 82 and the motor housing 14c. As a result, a cooling passage 83 is formed. In FIG. 4, the interior of the motor case 82 is not shown.

  Thus, the motor housing 14c is made of an aluminum alloy and exposed to the outside, so that the rigidity of the housing 14 is increased and the durability of the electric tool is improved. Since the heat conductivity of the motor housing 14 c is higher than that of the resin motor case 82, the effect that the motor 31 can be cooled via the motor case 82 is obtained. In particular, the motor 31 can be cooled even when the fan 79 is not rotating.

  Since the motor 31 is covered with a resin motor case 82, the motor 31 has an insulating structure that suppresses transmission of electric power and magnetic force acting on the motor 31 to the operator. That is, this electric tool is obtained by interposing a resin motor case 82 between the motor housing 14c and the motor 31 while obtaining the rigidity of the motor housing 14c by exposing the aluminum motor housing 14c to the outside. The power applied to the motor 31 is not transmitted to the worker.

  As described above, the motor case 82 is molded from a resin, and the motor housing 14c is molded from a material having a higher thermal conductivity than a resin, such as an aluminum alloy. As the structure of the motor housing 14c, a form in which the motor housing 14c is entirely made of an aluminum alloy, and a part exposed to the outside of the motor housing 14c, that is, only a part covering the tool holder 12 side is made of an aluminum alloy, and other parts There is a form of a composite structure made of resin. In any form, since at least a part of the motor housing 14c is made of an aluminum alloy, it is possible to improve the heat radiation of the cooling air that flows through the cooling passage 83 and cools the brushless motor 31. Further, when the motor housing 14c is formed of an aluminum alloy, the strength of the motor housing can be increased as compared with the case where the motor housing 14c is made of resin.

  As shown in FIG. 3, the bottom cover 37 is provided with a vent hole 84a, and the bottom wall of the motor housing 14c provided with the retainer 38 is provided with a vent hole 38a. As shown in FIG. Ventilation holes 84b and 84c are provided at both front and rear ends of the upper cover 39 at the upper portion of 14. Further, a vent hole (not shown) is also provided on the side surface of the housing 14. When the output shaft 34 is driven, outside air is taken in from the vent 84a to generate cooling air, and the generated cooling air is discharged from the upper vents such as the vents 84b and 84c. Accordingly, in the housing 14, as indicated by the broken line arrow C in FIG. 3, the air vent 84 a is used as a cooling air intake, and after passing through the air vent 38 a described above, the air vents 84 b and 84 c are used as discharge ports. A cold air flow path is formed.

  Thus, by adopting a configuration in which an air passage is formed between the motor case 82 and the motor housing 14c, a clearance between the stator 32 and the rotor 33, and a cooling passage between the motor case 82 and the motor housing 14c. 83, and the outside of the motor housing 14c can flow cooling air, so that the motor 31 can be cooled by fan air from the inside and outside, and the heat generation of the motor housing 14c itself can be suppressed, and the motor housing 14c. Can be easily gripped by hand. Further, even when the fan 79 is not rotating, the motor housing 14c is easily cooled by the cooling passage 83 between the motor case 82 and the motor housing 14c. Further, the retainer 38 constituting a part of the motor housing 14c is also an aluminum alloy, and the heat generated by the bearing 35 can be cooled by the motor housing 14c exposed to the outside through the retainer 38.

  As shown in FIGS. 3 and 5, the control board 78 is accommodated in the base plate 85. The control board 78 is arranged adjacent to the motor housing 14c, that is, adjacent to the motor housing 14c, and is fixed inside the housing 14 along the axial direction on the outer peripheral surface of the motor housing 14c. The control board 78 is disposed between the bottom cover 37 covering the end face of the brushless motor 31 and the brushless motor 31, and is adjacent to the motor housing 14c. Therefore, the control board 78 is disposed in the cold air flow path generated by the fan 79. Is done. Thereby, the cooling characteristic of the control board 78 can be improved.

  The control board 78 is provided with six switching elements Tr1 to Tr6 constituting the inverter circuit 65. FETs are used as the switching elements, and the switching elements are shown as FETs in FIG. The control board 78 is provided with the inverter circuit 65, the power factor correction circuit 68, the motor control unit 71 and the like shown in FIG. 6, but only the switching element FET is shown in FIG. The illustration is omitted.

  A heat radiating plate, that is, a heat sink 87 is fixed to the switching element FET by a screw member 86 and a nut 86a, and the heat sink 87 abuts against a plurality of protrusions 88 provided to protrude toward the control board 78 on the motor housing 14c. Being touched. Thus, since the control board 78 is mounted on the motor housing 14 c via the protrusions 88, the cooling air can pass between the outer peripheral surface of the motor housing 14 c and the heat sink 87 by the respective protrusions 88. A heat radiating space 89 is partitioned. The heat sink 87 is formed of a member having a higher thermal conductivity than that of resin, iron, or the like, such as an aluminum alloy or a copper alloy. By attaching the heat sink 87 to the switching element, a cooling passage inside the motor housing 14c. The control board 78 and the cooling air flowing between the heat sink 87 and the control board 78 and the cooling air flowing between the heat sink 87 and the control board 78 are provided on the control board 78. The cooling characteristics of the switching element can be improved.

  As shown in FIG. 3, the bottom wall of the fan case 81 is provided with an opening 81a through which cooling air enters. A large-diameter portion 14d that covers the outside of the fan case 81 is provided at the upper end portion of the motor housing 14c. The large-diameter portion 14d includes cooling air that flows outside the motor housing 14c, a heat sink 87, and a control board 78. A communication hole 81 b is provided for guiding the cooling air flowing between them into the fan case 81.

  Thus, by arranging the control board 78 in the cold air flow path C indicated by the broken-line arrow, the motor cooling air is also used as the cooling air for cooling the brushless motor 31, like the inverter circuit 65. In addition, the electronic device that generates heat can be cooled. Of the electronic devices provided on the control board 78, the switching elements constituting the inverter circuit 65 for performing commutation control and speed control on the windings generate a large amount of heat, but the control board 78 is disposed in the cold air flow path C. As a result, the inverter circuit 65 is cooled by the motor cooling air, the switching element is prevented from being overheated, and the durability of the control board 78 including the switching element can be improved. The generated heat is not transmitted to the housing 14, and the workability of the impact tool 10a can be improved.

  FIG. 7 is a cross-sectional view showing a main part of a hitting tool 10b which is a modified example, and FIG. 8 is a cross-sectional view taken along the line CC in FIG. In the impact tool 10b, the protrusion 88 shown in FIG. 5 is not provided in the motor housing 14c. The heat sink 87 is separated from the surface of the motor housing 14c, but is disposed close to it. A heat radiation space 89 is formed between the heat sink 87 and the outer peripheral surface of the motor housing 14c. The heat sink 87 is attached to the switching element FET by a screw member 86, and the base plate 85 provided with the control board 78 is fixed to the housing 14 by the screw member 90.

  As an arrangement form of the heat sink 87, there are a form in which the heat sink 87 is brought into contact with the motor housing 14c as shown in FIG. 5, and a form in which the heat sink 87 is brought close to the motor housing 14c as shown in FIG. Also in the embodiment, the control board 78 is disposed adjacent to the motor housing 14 c, and the cooling performance of the switching element can be improved via the heat sink 87.

  FIG. 9 is a cross-sectional view showing a main part of an impact tool 10c which is another modification, and FIG. 10 is a cross-sectional view taken along the line DD in FIG. In this striking tool 10 c, the motor housing 14 c is provided with a projection 88 as in the embodiment shown in FIG. 5, and the base plate 85 is fixed to the projection 88 by a screw member 90. That is, the control board 78 is attached to the motor housing 14c in a posture in which the front and back are reversed with respect to the above-described form. As shown in FIG. 10, the heat sink 87 has a quadrilateral cross section, the abutting wall 87a is abutted against the base plate 85, and the switching element FET is perpendicular to the abutting wall 87a. It is attached to the attachment wall 87b by a screw member 86. The nut 86a screwed to the screw member 86 is disposed in a space surrounded by the heat sink 87, and cooling air flows through the space.

  As shown in FIGS. 9 and 10, the housing 14 has a vent hole 84 d that faces the control board 78. Therefore, in the impact tool 10c shown in FIGS. 9 and 10, when the fan 79 is driven, the surface of the control board 78 is added to the vent hole 84a formed in the bottom cover 37 so as to face the end of the motor 31. In addition, cooling air is blown from the vent 84d.

  FIG. 11 is a cross-sectional view showing a main part of an impact tool 10d which is another modified example, and the same part as the part shown in FIG. 3 of the impact tool 10d is shown. While the speed setting dial 62 shown in FIG. 3 is exposed on the side surface of the housing 14 and provided on the control board 78, in the impact tool 10d, the speed setting dial 62 is provided on the main body 28a of the handle 28. It has been. As shown in FIG. 1B, the speed setting dial 62 is exposed on the side surface of the main body 28a.

  FIG. 12 is a cross-sectional view showing a main part of a striking tool 10e as a modification, and FIG. 13 is a cross-sectional view taken along the line EE in FIG. In the impact tool 10e, a control board 78 is disposed on a bottom cover 37 that constitutes a part of the housing 14. A speed setting dial 62 is provided on the control board 78, and the speed setting dial 62 is exposed on the side surface of the bottom cover 37. A switching element FET is attached to the heat sink 87. The heat sink 87 has two parallel wall portions 87c that are parallel to each other, and a connecting wall portion 87d that connects the ends of both parallel wall portions 87c to each other, and the cross-sectional shape is a U-shape. It has become. Each parallel wall portion 87 c is in contact with a retainer 38 into which the bearing 35 is incorporated, and the connecting wall portion 87 d forms a gap with the retainer 38. The retainer 38 is formed of an aluminum alloy having a high thermal conductivity, and heat of the switching element FET is transmitted to the heat sink 87 and the retainer 38. Since the heat sink 87 has a surface extending in the axial direction, the cooling air guided to the motor 31 flows along the heat sink 87, and the cooling performance of the switching element FET is enhanced.

  FIG. 14 is a cross-sectional view showing a main part of an impact tool 10f which is another modification, and FIG. 15 is a cross-sectional view taken along the line FF in FIG. In the impact tool 10 f, the control board 78 is disposed on the inner surface of the bottom cover 37, and the speed setting dial 62 is provided on the control board 78 in the same manner as the impact tool 10 e shown in FIGS. 12 and 13. In this impact tool 10f, a hall element S as a detecting means for detecting the rotational position of the rotor 33 is attached to the control board 78, and the hall element S is provided at the proximal end portion of the output shaft 34. In response to the sensor-driving permanent magnet M, an output signal is output to the rotor position detection circuit 74 shown in FIG. Each of the permanent magnets M is provided with the same phase in the rotational direction so as to correspond to the four permanent magnets provided on the rotor 33. 14 and 15, only two of the four magnets and the three Hall elements S are shown. The heat sink 87 of the impact tool 10f has the same structure as that shown in FIG.

  As shown in FIGS. 12 to 15, even in the form in which the control board 78 is disposed inside the bottom cover 37, the cooling air flowing through the cooling passage 83 inside the motor housing 14 c and the cooling flowing through the outer periphery of the motor housing 14 c are used. Wind and cooling air flowing along the surface of the control board 78 are formed in the housing 14. Further, as shown in FIGS. 12 to 15, at least a part of the heat sink 87 is in contact with the retainer 38 made of aluminum alloy, and the heat sink 87 is close to the retainer 38. Then, the control board 78 can be cooled by the motor housing 14c.

  FIG. 16 is a longitudinal sectional view showing an impact tool 10g which is still another modified example, and FIG. 17 is an enlarged sectional view taken along the line GG in FIG. In this impact tool 10g, the flow direction of the cooling air is different from the impact tool described above. In the hitting tool 10a and the like described above, the vent hole 84a provided in the bottom cover 37 is used as an air intake port, and the vent holes 84b and 84c provided in the upper portion of the housing 14 are used as discharge ports. 84a is a discharge port, and vents 84b and 84c are air intake ports. That is, the cold air flow path C is made to flow in the opposite direction to that described above. Thus, the form of the cold air flow path C includes a form that flows from the proximal end side of the motor 31 to the distal end side and a form that flows from the distal end side of the motor 31 toward the proximal end side. In this impact tool 10g, a base plate 85 provided with a control board 78 is abutted against and in contact with the outer surface of the motor housing 14c.

  In addition to the vent 84c, if a vent as an air intake is provided on the back side of the housing 14, the cooling air of the fan 79 is supplied from the gripping space 29 side of the handle 28 on the opposite side to the tip tool T. It becomes the form to inhale and the effect that dust is difficult to enter inside is acquired.

  Further, in the impact tool 10g, as shown in FIG. 17, a connecting fitting 91 is attached to the rear end portion of the housing 14, and a receiving fitting having a U-shaped cross section is formed inside the leg portion 28b of the handle 28. 92 is attached by a screw member 93. The metal fitting 92 has a bottom wall portion 92a and side wall portions 92b integrated with both side portions thereof. The connecting fitting 91 is provided with a long hole 94 having a long diameter in the axial direction of the cylinder 11, that is, the striking axis direction. The long hole 94 is opened to the receiving fitting 92 by a constricted portion 94a. The receiving bracket 92 is provided with a cylindrical portion 95 that is movable in the elongated hole 94. The cylindrical portion 95 has a bottom wall of the receiving bracket 92 by a connecting wall 96 having a width dimension smaller than the outer diameter. It is integral with the part 92a. A plurality of concave surfaces 97 a are provided on both sides of the coupling metal 91, and a concave surface 97 b is provided on the inner surface of the side wall portion 92 b of the receiving metal 92 so as to face the respective concave surfaces 97 a. A rubber elastic body 98 for absorbing vibration is incorporated between the concave surfaces facing each other, and a vibration isolating mechanism including the elastic body 98 is incorporated in the leg portion 28b.

  A similar metal fitting 92 is attached to the inside of the leg portion 28 c of the handle 28, and a connecting metal fitting 91 that is inserted into the metal fitting 92 is attached to the rear end portion of the housing 14. Thus, both the leg portions 28b and 28c are connected to the housing 14 via the vibration isolation mechanism shown in FIG. Thereby, the vibration transmitted from the housing 14 to the handle 28 is absorbed by the elastic body 98, and the workability of the impact tool 10g can be improved.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, although the illustrated electric power tool has a form in which a commercial power source is used as a power source, the present invention can also be applied to a battery-type electric power tool that uses a battery case of a secondary battery in the housing 14 as a power source. The present invention can be applied not only to hammer drills and grinders but also to other power tools as long as the power tool is driven by a brushless motor. Furthermore, in the illustrated embodiment, the brushless motor 31 is used as a motor, but a motor with a brush having a commutator and a brush may be used.

10a-10g Impact tool 10h Grinder 11 Cylinder 12 Tool holder 14 Housing 14a Cylinder housing 14b Gear housing 14c Motor housing 14e Base housing 16 Hammer member 28 Handle 28a Main body 28b, 28c Leg 31 Brushless motor 34 Output shaft 37 Bottom cover 41 Crankshaft 47 Motion conversion mechanism 51 Rotation transmission shaft 65 Inverter circuit 71 Motor control unit 78 Control board 79 Fan 82 Motor case 83 Cooling passages 84a to 84f Vent 87 Heat sink 88 Protrusion 89 Heat radiation space

Claims (14)

A motor that is covered by a resin motor case and drives the tip tool;
An aluminum alloy motor housing that covers at least a portion of the motor case and is exposed to the outside;
The electric tool which provided the cooling channel | path which guides external air between the said motor case and the said motor housing. A fan that is rotationally driven by the output shaft of the motor;
The power tool according to claim 1, wherein the cooling air generated by the fan is guided to the cooling passage.   The electric tool according to claim 1 or 2, wherein the cooling passage is formed by a groove formed along an axial direction on at least one of an outer peripheral surface of the motor case and an inner peripheral surface of the motor housing.   The electric tool according to any one of claims 1 to 3, wherein the motor case is press-fitted into the motor housing to incorporate the motor into the motor housing.   A control board provided with a control circuit for controlling the rotation of the motor; the control board is disposed in a cool air flow path generated by the fan; and the motor and the control board are cooled by cooling air. The electric tool according to any one of claims 2 to 4, which is configured as described above.   The electric tool according to claim 5, wherein the control board is disposed outside the motor housing adjacent to an outer periphery of the motor housing.   The power tool according to claim 5, further comprising a bottom cover that covers an end surface of the motor, wherein the control board is disposed between the bottom cover and the end surface of the motor.   The power tool according to claim 7, wherein detection means for detecting a rotational position of the motor is provided on the control board.   The electric tool according to claim 7, further comprising speed setting means that is operated by an operator to set a rotation speed of the motor, and the speed setting means is provided on the control board. A tool holder for holding the tip tool;
A motion conversion mechanism that converts a rotational motion of the output shaft of the motor into a reciprocating motion of the tool holder in a direction orthogonal to the output shaft;
A handle provided on the base end side of the tool holder;
The power tool according to claim 1, further comprising: a crankshaft that transmits a rotational force of the output shaft to the motion conversion mechanism. A power tool housing comprising a gear housing provided with the motion conversion mechanism and the crankshaft, and the motor housing;
The motor is arranged such that the output shaft is orthogonal to the reciprocating direction of the tool holder,
The handle has two legs attached to the rear end of the housing spaced apart from each other at the main body and both ends of the main body,
The electric tool according to claim 10, wherein one of the leg portions is disposed on the gear housing side, and the other leg portion is disposed on the motor housing side.   The power tool according to claim 11, wherein a vibration isolation mechanism is provided between the leg portion and the housing.   The electric tool according to claim 11 or 12, wherein the control board is disposed between the other leg portion and the motor. A rotation transmission shaft on which the tip tool is mounted, and a tool head mounted on the tip of the motor housing;
A motion conversion mechanism that converts the rotational motion of the output shaft of the motor into the rotational motion of the rotation transmission shaft in a direction orthogonal to the output shaft;
A base housing which is attached to a rear end portion of the motor housing and has a cold air flow path toward the motor;
The electric tool according to any one of claims 1 to 4, wherein a control board provided with a control circuit for controlling rotation of the motor is disposed in the base housing.

Images