CN107107326B - electrical tools - Google Patents

Abstract

By providing a large heat dissipation mechanism in the switching element, the grip portion of the housing is effectively disposed, and the electric power tool can be downsized. In an electric tool provided with a brushless motor (5), a cooling fan (10), a housing (2) which houses the motor and extends in the direction of a rotation axis, a control board (31) which is disposed so as to intersect the axial direction, and a switch (7) which turns the motor on or off, a plurality of switching elements (33, 35) which control the energization of the motor are disposed between the switch and the control board, and a common heat sink (40) which is in contact with the plurality of switching elements is provided. The heat sink is a thick plate made of light metal, is disposed so as to extend in a direction perpendicular to the control board and in the direction of the rotation axis, and fixes the switching element on one surface side and the other surface side.

Description

electrical tools

technical field

The present invention relates to an electric power tool that adjusts the rotational speed of a motor using a switch element, and particularly provides an electric power tool with improved heat dissipation by focusing on the accommodation position of the switch element.

Background technique

As an example of an electric power tool which adjusts the rotational speed of a motor using a switching element, the disc grinder described in patent document 1 is well known. FIG. 10 is a longitudinal cross-sectional view showing a conventional disc grinder 101 described in Patent Document 1. FIG. The disc polisher 101 includes a motor casing 102 that accommodates a motor 105 as a drive source. A split tail cover 104 with a plurality of air intake holes 119 is provided behind the motor casing 102, and a power cord 130 connected to the outside is provided on the tail cover 104 to turn on/off the power of the disc grinder 101. The power switch 107 is turned off. A gear housing 103 that accommodates a drive transmission mechanism that converts the power transmission direction of the motor rotating shaft by about 90 degrees is provided in front of the motor housing 102 . In the gear housing 103, the grindstone 70 is attached to the main shaft 111 extending in the vertical direction. The rotating shaft 105c is rotatably held by a front bearing 118a fixed to the gear housing 103 and a rear bearing 118b fixed to the main body casing 2 . The cooling fan 110 is provided between the bearing 118a of the rotating shaft 105c and the motor 105, and rotates in synchronization with the rotation of the motor 105, so that the external air is sucked from the suction hole 119 and flows into the main body casing 102, and the switching elements 133 and 136 are generated by the cooling fan 110. , The air flow near the motor 105 is mainly discharged forward from the exhaust hole 103a.

There are various types of motors 105 used in the disc grinder 101, and brushless DC motors have been widely used in recent years. A brushless DC motor is a DC (direct current) motor without a brush (brush for commutation), a coil (motor sub-coil) is provided on the stator side, a permanent magnet is used as a magnetic field mechanism on the rotor side, and the electric power driven by a transformer device is passed through. The rotor is rotated by sequentially energizing predetermined coils. As the switching elements 133 and 136 constituting the inversion device, for example, an FET (Field Effect Transistor) which is a semiconductor element is used. In order that the power supplied from the power cord 130 is a commercial AC, a rectifier circuit 139 is provided, and the rectified DC is input to the inversion device. The switching element 133 is arranged on the front side of the inverter circuit board 132 , and the switching element 136 is arranged on the rear side of the inverter circuit board 132 . On the front surface of the inversion circuit board 132, a position detection element 138 composed of a hole IC is further mounted.

The sensor magnet 121 is attached to the rear end of the rotating shaft 105c. The sensor magnet 121 is a circular magnet attached to the rear end of the rotating shaft 105c in order to detect the rotational position of the rotor 105a, and is formed in the order of NSNS poles every 90 degrees in the circumferential direction. The inversion circuit board 132 is provided perpendicular to the rotation shaft 105c so as to face the rear side of the sensing magnet 121 . The position detection elements 138 are means for detecting the rotational position of the rotor 105 a by detecting the position of the rotating sensor magnet 121 , and are arranged, for example, three at intervals of 60° in the rotational direction. A plurality of air intake holes 119 are formed in the portion of the tail cover 104 near the switching elements 133 and 136, and the switching elements 133 and 136 can be effectively cooled by the air drawn in by the cooling fan 110 in order to cool the motor 105.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2010-269409

SUMMARY OF THE INVENTION

The problem to be solved by the invention

In the technique of Patent Document 1, the front side and the rear side of an inverter circuit 132 are used by disposing switching elements 133 and 136 as switching elements for opening and closing energization to a coil wound around the stator, which are arranged behind the motor. , and forming an air intake hole 119 near the inversion circuit 132 to effectively dissipate heat from the switching elements 133 and 136 using the cooling air for cooling the motor 105 . However, when the motor 105 is rotated at a high speed, since the heat generation of the switching elements 133 and 136 increases, it is necessary to further improve the heat dissipation. Therefore, it is considered to mount a metal heat sink to each of the switching elements 133 and 136, but since the storage space required to mount the heat sink to the six switch elements increases, there is a problem that the overall length of the power tool becomes longer. On the other hand, it is considered that the switching elements 133 and 136 are arranged in the vicinity of the rear end of the tail cover 104 in terms of a spatial margin. However, in this case, the switching elements are not located in the air passage of the cooling air for the motor. The temperature rise of 133 and 136 becomes larger.

The present invention was made in view of the above-mentioned background, and an object of the present invention is to provide an electric power tool in which a large-scale heat dissipation mechanism is mounted on a switch element, and these are efficiently arranged inside a casing to shorten the overall length. Another object of the present invention is to provide an electric power tool that uses a thick plate-shaped radiator as a heat dissipation mechanism for a plurality of switching elements, and which improves heat dissipation and assembly by fixing a plurality of switching elements to the radiator sex.

methods for solving problems

Among the inventions shown in the present application, representative features are described below. According to one feature of the present invention, there is provided a motor having a rotating shaft, a cooling fan that rotates by the rotation of the rotating shaft, a casing that accommodates the motor and the cooling fan and extends in the direction of the rotating shaft of the motor, is housed in the casing and A control board arranged to intersect the rotation axis, a switch provided in the casing between the motor and the control board to turn the motor on or off, and a plurality of switching elements provided on the control board and controlling energization to the motor In the electric power tool of , a plurality of heat sinks are provided in contact with the switching elements, and the heat sinks are arranged so as to extend perpendicularly to the control board, that is, in the direction of the rotation axis. The heat sink is a thick metal plate, a part of the plurality of switching elements is fixed to one surface side of the heat sink, and the remaining switching elements are fixed to the other surface side of the heat sink.

According to another feature of the present invention, the power tool further includes a battery pack attachable to and detachable from the casing, and the control board is disposed so as to be sandwiched between the motor and the battery pack when viewed in the rotation axis direction. The housing includes a portion for accommodating the motor and an enlarged diameter portion for mounting the battery pack, and the control board is accommodated in the enlarged diameter portion, and is configured such that the longitudinal dimension of the control board is larger than the diameter dimension of the motor. The switching element is in surface contact with the heat sink in a direction parallel to the rotation axis, and the size of the heat sink in the rotation axis direction is larger than that of the switching element.

According to another feature of the present invention, the motor is a brushless DC motor, and the switching elements are arranged such that three are arranged on one side of the heat sink and three are arranged on the other side opposite to the one side. The switching element is fixed in direct surface contact with the heat sink or indirect surface contact through a thermally conductive member. Here, the lateral dimension of the arrangement of the switching elements of the heat sink may be larger than the height dimension of the casing perpendicular to the lateral direction.

According to another feature of the present invention, the casing is provided with an air intake hole through which cooling air flows into the casing when the cooling fan rotates, an exhaust hole through which cooling air is discharged from the casing, and the flow of the cooling air in the casing by the radiator The middle is located on the upstream side compared to the motor. In addition, a rotation speed adjustment mechanism which is electrically connected to the control board and can adjust or switch the rotation speed of the motor is provided, and the rotation speed adjustment mechanism and the heat sink are arranged so as to overlap in the rotation axis direction.

Invention effect

According to the present invention, since the switching element and the circuit board are housed in the rear end portion (diameter-enlarged portion) of the casing, only the brushless motor can be housed in the grip portion, and the grip portion can be reduced in diameter. In addition, since a control circuit including an inverter circuit, a microcomputer, etc. is mounted on the control board, it is possible to realize a small-diameter grip portion and efficiently arrange the electronic device on the rear end portion of the casing. Furthermore, since the switching element constituting the inverter circuit is fixed to the metal thick plate-shaped heat sink, heat dissipation can be improved, and the temperature rise of the switching element can be suppressed.

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

Description of drawings

FIG. 1 is a perspective view showing the overall shape of a disc grinder 1 according to an embodiment of the present invention.

FIG. 2 is a partial perspective view showing the vicinity of the rear end bottom surface of the disc grinder 1 according to the embodiment of the present invention.

FIG. 3 is a longitudinal cross-sectional view of the disc polisher 1 related to the embodiment of the present invention.

FIG. 4 is a block diagram showing a circuit configuration of a drive control system of the motor 5 .

FIG. 5 is an arrow view viewed from the direction of arrow A in FIG. 3 , and is a diagram showing a part of it in a perspective view.

FIG. 6 is a diagram showing a state in which the control board 31 is viewed from the front side in the rotation axis direction of the motor.

FIG. 7 is a cross-sectional view of a portion B-B in FIG. 6 .

FIG. 8 is a perspective view showing a single shape of the heat sink 40 .

FIG. 9 is a diagram for explaining the arrangement relationship between the dial 9 and the heat sink 40 .

FIG. 10 is a longitudinal cross-sectional view showing the overall structure of a conventional disc polisher 101 .

Detailed ways

Example 1

Hereinafter, embodiments of the present invention will be described based on the drawings. In addition, in the following figures, the same code|symbol is attached|subjected to the part which has the same function, and the repeated description is abbreviate|omitted. In addition, in this specification, the front-back, left-right, and up-down directions are described as the directions shown in the drawings.

FIG. 1 is a perspective view showing the overall shape of a disc grinder 1 as an example of an electric power tool according to an embodiment of the present invention. The casing (casing) of the disc grinder 1 is constituted by a main body casing 2 which accommodates a motor as a drive source therein, and a gear casing 3 which is attached to the front of the main body casing 2 . The main body casing 2 has a substantially cylindrical shape whose central axis extends in the front-rear direction, and the outer diameter (height and The grip portion (small-diameter portion) 2b having a smaller diameter and/or width) is configured so that the operator can easily grip. A switch lever 8 of a switch for turning on or off the rotation of the motor is provided on the side (left side) near the front end of the main body casing 2 . The gear case 3 is fixed on the front side of the main body casing 2 by four bolts 16 inserted from the front to the rear with the fan cover 17 interposed therebetween. The gear housing 3 is a member that fixes a main shaft (output shaft) in which a grindstone 70 is mounted, and the grindstone 70 passes through a rotation transmission mechanism (not shown) housed in the gear housing 3 in conjunction with the rotation of the motor. rotate.

The grindstone 70 is, for example, a resin flexible grindstone, flexible grindstone, resin grindstone, sandpaper grindstone, etc. with a diameter of 100 mm, and can be used for surface grinding of metal, synthetic resin, marble, concrete, etc., by selecting the type of abrasive particles used. Surface grinding. The rotational speed of the grindstone 70 can be adjusted to an arbitrary number of revolutions such as 1000 to 5000 rpm. A wheel protector 20 is provided around the rear side of the grindstone 70 for protecting the operator from the splashing of parts to be ground, broken abrasive grains, and the like. A removable lateral handle 4 is provided on one side (here, the right side) of the gear housing 3 . Intake holes 19b for sucking in external air by a cooling fan described later are formed on the front side surface of the main body casing 2 and on both side surfaces near the rear end of the main body casing 2, and the gear casing 3 is provided with a The exhaust hole 3a from which the sucked air is discharged.

FIG. 2 is a partial perspective view showing the vicinity of the rear end bottom surface of the disc grinder 1 according to the embodiment of the present invention. A dial 9 for adjusting the rotational speed of the motor is provided on the rear side of the main body casing 2 and in the vicinity of the connection portion between the grip portion 2b and the enlarged diameter portion 2c. The dial 9 is of a rotary type, and numbers indicating speed levels are marked on the dial. Furthermore, the rotation speed adjustment mechanism of the motor 5 is not only a dial-type adjustment mechanism, but can be set by a switch for switching high and low, or an electronic switch. A cover portion 2d that holds the battery pack 60 and closes air holes formed in the battery pack 60 is provided behind and on the lower side of the enlarged diameter portion 2c. A display panel 25 is provided on the cover portion 2d, and an AUTO button 26 and a remaining battery level check button 27 are provided. These can consist of contact switches. The AUTO button 26 is a button for setting the control method to the automatic shifting mode. When the automatic shifting mode is set, the number of revolutions of the motor 5 is reduced when there is no load, and when a load is detected, it is switched to normal (select with the dial). ) for this control of the number of revolutions. When the battery remaining amount check button 27 is pressed, the battery remaining amount display lamp 28 lights up according to the remaining battery amount. Here, the remaining battery level indicator 28 is formed of a plurality of LEDs. For example, when the remaining battery level is high, all the LEDs are turned on, and the number of LEDs that are turned on decreases as the remaining battery level decreases. When the battery assembly 60 is removed, the elastic keys 61 provided on both sides of the battery assembly are pressed and moved in the direction of removal indicated by the arrow in the figure.

FIG. 3 is a longitudinal cross-sectional view showing the internal structure of the disc polisher 1 according to the embodiment of the present invention. The motor 5 has an elongated shape in the axial direction (front-rear direction), and a three-phase brushless DC motor is used here as the motor 5 . The motor 5 includes a stator 5b having a substantially cylindrical outer shape, and a rotor 5a provided concentrically in an inner peripheral portion of the stator 5b, and is accommodated in a substantially cylinder manufactured by molding a polymer resin such as polycarbonate. The front side of the inside of the main body casing 2 in the shape of a The stator 5b of the motor 5 is fixed inside the main body casing 2, the front side of the rotating shaft 5c is supported by a bearing 18a fixed to the fan cover 17 sandwiched between the gear casing 3 and the main body casing 2, and the rear side is supported. The sides are pivotally supported by a bearing 18b fixed to the vicinity of the center of the main body casing 2 . A coil (electrical sub-coil) composed of three-phase coils U, V, W is wound around the stator 5b. The rotor is composed of a metal rotor core attached to the outer peripheral side of the rotating shaft 5c, and a cylindrical magnet (permanent magnet) having an N pole and an S pole. As the magnet, the diameter of the rotor can be reduced by using, for example, a cylindrical rubidium sintered magnet. A detection substrate 21 on which three position detection elements are mounted is provided between the stator 5b and the bearing 18b. The detection substrate 21 may be an annular or semicircular substrate having a through hole through which the rotation shaft 5c passes, and the position detection elements 22 , 23 , and 24 (see FIG. 4 ) are provided on the detection substrate 21 . The position detection elements 22 , 23 , and 24 are elements that detect the rotational position of the rotor 5 a by detecting the position of the magnet of the rotating rotor 5 a , and for example, Hall ICs are used, and three are arranged every 60° in the rotational direction.

A switch 7 for rotating the motor 5 is provided behind the bearing 18b and in the vicinity of the approximate center of the main body casing 2 . The switch 7 is a device that instructs the rotation of the motor 5 to turn on or off by operating in conjunction with the switch lever 8 (see FIG. 1 ), and is switched on (connected state) or off by moving the push button 7 a (off state) 1 circuit 1 contact switch. The push switch 7 a is operated by a link structure (not shown) that moves in conjunction with the movement of the switch lever 8 . In addition, there are various mechanical mechanisms for moving the push switch 7a in conjunction with the movement of the switch lever 8, and since those are well known, the description here is omitted.

The cooling fan 10 is provided between the bearing 18a on the front side and the rotor 5a and the stator 5b. The cooling fan 10 is an air blowing mechanism that is rotated by the rotation of the rotating shaft 5c to generate an air flow from the air intake hole 19b (refer to FIG. 2 ) on the rear side to the exhaust hole 3a on the front side. The air flow sucked in from the outside of the main body casing 2 cools the switching elements 33 and 36 and the like by passing through the vicinity of the radiator 40 as indicated by the black arrows in the figure, and then passes around the switch 7 to reach the motor 5 . In the vicinity of the motor 5, the cooling air reaches the cooling fan 10 through the gaps between the outer periphery of the stator 5b and the inner wall surface of the main body casing 2 and between the stator 5b and the rotor 5a, and then is mainly discharged from the exhaust hole 3a in the forward direction to the cooling fan 10. outside of the enclosure.

A detachable battery pack 60 is attached to the end on the rear side of the main body casing 2 . The battery pack 60 is a rechargeable rechargeable battery, such as a nickel-cadmium battery, a nickel-metal hydride battery, or a lithium battery, etc. can be used. In this embodiment, the battery assembly 60 is slidably installed from the upper direction to the lower direction, and is fixed by the elastic key 61 . The dimension H _B in the height direction of the battery pack 60 is much larger than the diameter d _m of the housing portion of the motor 5 of the main body casing 2 . In order to hold the battery pack 60 having such a height dimension larger than the diameter of the main body casing 2 , the enlarged diameter portion 2 c is formed in the mounting portion of the battery pack 60 of the main body casing 2 . The enlarged diameter portion 2c is a portion formed larger in the height direction and the width direction (left-right direction) of the main body casing 2 than the diameter of the housing portion of the motor 5 of the main body casing 2, and the control board 31 is arranged in the enlarged internal space. The control board 31 is housed inside the board case 32 , and the surface of the control board 31 is arranged so that the surface of the control board 31 is perpendicular to the direction of the rotation axis of the motor 5 (the longitudinal direction of the main body casing 2 ), and is parallel to the sliding surface of the battery pack 60 . way to configure. Six switching elements ( 33 , 36 , etc.) and a microcomputer (not shown) constituting a control mechanism are mounted on the control board 31 , and the switching elements having a relatively large installation space extend from the control board 31 toward the motor 5 . way to configure. A large heat sink 40 is provided on the six switching elements (33, 36, etc.) for their cooling. The heat sink 40 is composed of a thick metal plate, and the switching elements 33 and 36 and the like are fixed to one surface (upper surface) and the other surface (lower surface) of the thick plate, respectively.

A dial 9 for setting the rotational speed of the motor 5 is provided on the front side of the enlarged diameter portion 2 c of the main body casing 2 . The dial 9 is rotatable about a rotating shaft 9 a which is arranged parallel to the direction of the rotating shaft of the motor 5 , and most of the dial 9 is accommodated in the main body casing 2 except for a part of the outer peripheral portion. . The dial 9 is a variable resistor and is connected to the control circuit. Since the wiring with the control board 31 is shortened by providing the dial 9 in the front part of the enlarged diameter part 2c in this way, it can mount efficiently. The main body casing 2 of the present embodiment has a split structure that is divided left and right from a vertical plane through which the rotating shaft of the motor 5 passes. The holding portion (mounting rib) on the inner wall of the side portion is sandwiched and fixed.

The gear housing 3 is constituted by integral molding of metal such as aluminum, accommodates a power transmission mechanism using a set of bevel gear mechanisms (bevel gears 12 and 13 ), and rotatably holds a main shaft 14 serving as an output shaft. The main shaft 14 is configured to extend perpendicularly to the rotation axis 5c (horizontal direction) of the motor 5, and the grindstone 70 can be replaced by removing the fixed wheel nut 15 from the lower side of the grindstone 70 with a wrench (not shown). When the motor 5 rotates, the cooling fan generates an air flow from the rear to the front inside the main body casing 2 . A part of this air flow is indicated by arrows in FIG. 3 , and the radiator 40 is located upstream of the motor 5 and between the switch 7 and the battery pack 60 in the cooling air flow in the main body casing.

Next, the configuration of the drive control system of the motor 5 will be described based on FIG. 4 . The circuits (the control circuit mechanism and the inversion circuit mechanism) indicated by the broken lines in FIG. 4 are mounted on the control board 31 . In this embodiment, the motor 5 is constituted by a three-phase brushless DC motor. This brushless DC motor is of a so-called inner rotor type, and includes a rotor 5a including a plurality of sets (two sets in this embodiment) of permanent magnets (rubidium magnets) of N and S poles, and three star-connected magnets. The stator 5b constituted by the phase stator terminal lines U, V and W. The arithmetic unit 51 includes a central processing unit (CPU) for outputting drive signals based on a processing program and data, a ROM for storing the processing program and control data, a RAM for temporarily storing data, a timer, and the like (not shown). It is configured to control the rotational speed of the motor 5 . The rotational speed of the motor 5 can be arbitrarily set by the dial 9 , and the calculation unit 51 starts or stops the motor 5 in accordance with the operation of the switch 7 by the operator.

The inversion circuit mechanism is mainly composed of six switching elements 33 to 38 such as FETs connected in a three-phase bridge. The gates of the bridge-connected six switching elements 33 to 38 are connected to the control signal output circuit 52 , and the drains or sources of the six switching elements 33 to 38 are connected to the fixing member winding wires U, V, W. As a result, the six switching elements 33 to 38 are switched by the switching element driving signals (driving signals such as H4, H5, H6, etc.) input from the control signal output circuit 52, and the switching operation is applied to the battery pack 60 of the inverter circuit mechanism. The direct current is converted into three-phase (U-phase, V-phase, and W-phase) alternating-current voltages Vu, Vv, and Vw to supply driving power to the motor 5 to the stator windings U, V, and W.

Among the switching element drive signals (three-phase signals) for driving the gates of the six switching elements 33 to 38, the three negative power supply side switching elements 36 to 38 are supplied as pulse width modulation signals (PWM signals) H4, H5, and H6 The operation unit 51 mounted on the control board 31 starts to supply electric power to the motor 5 based on the output signals of the position detection elements 22 to 24 constituting the switching mechanism of the motor 5 . Here, the PWM signal is supplied to the negative power supply side switching elements 36 to 38 of the inverter circuit mechanism.

The operation state of the switch 7 is detected by the switch operation detection circuit 56 , and the switch operation detection circuit 56 outputs either ON (switch ON) or OFF (switch OFF) to the arithmetic unit 51 . The output of the dial 9 for adjusting the rotational speed of the motor 5 is input to the rotational speed setting circuit 57 , and the rotational speed setting circuit 57 sends a control signal corresponding to the set position of the dial 9 to the arithmetic unit 51 . The arithmetic unit 51 forms a drive signal for alternately switching the predetermined switching elements 33 to 38 based on the output signals of the switch operation detection circuit 56 and the rotation speed setting circuit 57 , and outputs the drive signal of the motor 5 to the control signal output circuit 52 . As a result, predetermined windings of the stator windings U, V, and W are alternately energized, and the rotor 5a is rotated at the set rotation speed. The rotational speed of the motor 5 is detected by the rotation number detection circuit 54 using the output of the rotor position detection circuit 53 that detects the outputs of the position detection elements 22 to 24 . The outputs of the rotor position detection circuit 53 and the rotation number detection circuit 54 are output to the calculation unit 51 together. The current value supplied to the motor 5 is measured by the current detection circuit 55 , and the value is fed back to the calculation unit 51 , and the calculation unit 51 controls the rotation of the motor 5 by adjusting the drive power to be set.

Next, the connection state of the switching elements 33 to 38 and the heat sink 40 will be described with reference to FIG. 5 . FIG. 5 is a view from the direction of arrow A in FIG. 3 , illustrating most parts in a perspective view. As can be understood here, among the plurality of switching elements, the switching elements 33 to 35 are bolted in a state in which they are arranged in a row on the front side (upper surface side) of the common heat sink 40 . At this time, it is important that the switching elements 33 to 35 are fixed so as not to contact each other and to have a predetermined interval. 5, the back side (lower side surface) of the heat sink 40 is also the same, the switching elements 36 to 38 are fixed by bolts, and the switching elements 33 to 35 and the switching elements 36 to 38 are arranged in plane-symmetrical positions. superior. There are various considerations for the shape of the heat sink 40. In this embodiment, an aluminum plate with a thickness of about 10 mm is used. The surface of the aluminum plate extends front and rear and left and right, and is arranged in a direction at right angles to the control board 31 . In other expressions, the heat sink 40 is arranged so as to extend from the control board 31 toward the motor 5 in the direction of the rotation axis.

The radiator 40 includes a sloped portion 40b formed by inclining the corner portion of the front end along the inner side wall surface of the main body casing 2 , and is chamfered to effectively utilize the space in the main body casing 2 . The terminal block 39 is provided on the rear side of the board case 32 for fixing a plurality of terminals (not shown) for contacting the connection terminals of the motor unit 60 . Air intake holes 19 a and 19 b are provided on the left and right side surfaces of the enlarged diameter portion 2 c of the main body casing 2 . In FIG. 5, in order to attach the filter device which is not shown in figure to the air intake holes 19a and 19b, it has the shape which protrudes widely to the outside. The outside air sucked into the main body casing 2 through the air intake holes 19 a and 19 b flows along the longitudinal direction of the main body casing 2 , that is, the rotation axis direction. Thereby, the cooling air flows in substantially the same direction as the extending direction of the radiator 40 , and an air flow that does not interfere with the flow can be generated in the radiator 40 . In addition, since the cooling air effectively contacts the upper, lower, left, and right side surfaces of the radiator 40, the radiator 40 and the switching elements 33 to 38 can be effectively cooled. In order to configure the heat sink 40 in this way, the gripping portion 2b having a smaller diameter than the motor housing portion 2a is provided on the rear side of the motor housing portion 2a for housing the motor 5, and the switching elements 33 to 38 can be efficiently cooled.

FIG. 6 is a diagram showing a state in which the control board 31 is viewed from the front side in the rotational axis of the motor. The control board 31 is fixed to the inside of the board case 32 made of synthetic resin. In FIG. 6 , the three switching elements 33 to 35 are in surface contact with one surface (upper surface) of a heat sink 40 made of an aluminum alloy having _a thickness Ta, and three switches are arranged on the other surface (lower surface) opposite to the one surface (upper surface). The elements 36-38 are in surface contact. At this time, the switching elements 33 to 35 and 36 to 38 may be fixed to the heat sink 40 via insulating sheets (not shown in FIG. 6 , which will be described later in FIG. 7 ). The longitudinal dimension (length Lc) of the control board 31 is much larger than the diameter of the stator 5b of the motor 5, and electronic components such as the microcomputer 51 can be mounted on the enlarged portion.

Next, the sectional view of the BB part of FIG. 6 is demonstrated using FIG. 7. FIG. The board case 32 is formed in a substantially rectangular parallelepiped container shape having an opening surface on the upper side, and accommodates the control board 31 on which the switch elements 33 to 38 are mounted therein. The heat sink 40 made of a thick metal plate is positioned slightly away from the control board 31 to have a gap 46 . Since the heat sink 40 is a conductor, the gap 46 is provided so as not to short-circuit the terminals and the like of the control board 31 . The switching elements 33 to 38 are well-known FETs (Electrical Field Effect Transistors), have three terminals 35a and 38a of a source, a drain, and a gate, and are provided with a metal material extending upward from a part of the rear surface and the rear surface of the main body. The radiator plates 35b and 38b of the screw holes. The heat sinks 35b and 38b are each screwed into the threaded holes 40a formed on the heat sink 40 by means of bolts 43, and the insulating sleeves 44 that do not conduct electricity are interposed between the heat sink 40 and the heat sinks 35b and 38b so that the heat sink 40 and the heat sinks 35b and 38b are electrically insulated. middle and fixed. At this time, the bolts 43 that fix the heat dissipation plate 35b and the bolts 43 that fix the heat dissipation plate 38b are coaxial. In addition, there is also a thermally conductive but electrically insulating resin sheet 41 between the switching elements 35 and 38 and the heat sink 40 to maintain good heat dissipation and prevent the switching elements 35 and 38 and the heat sink 40 from being electrically short-circuited. constituted in a manner. It can be understood that the dimension of the heat sink 40 in the rotational axis (front-rear direction) is much larger than the dimension F _T of the switching elements 35 and 38 . Furthermore, the switching elements 33 to 34 and 36 to 37 are also fixed to the heat sink 40 by the same method. By using such a fixing method, six switching elements 33 to 38 can be fixed to one heat sink 40 .

In this embodiment, the control board 31 including the switching elements 33 to 38 and other electronic components (not shown in FIG. 7 ) including the switching elements 33 to 38 and the microcomputer 51 (not shown in FIG. 7 ) is also filled and reinforced with a waterproof and insulating resin such as silicon. Here, the opening of the container-shaped substrate case 32 is upwardly filled with the liquid resin from the inner bottom surface to the position of the dotted line with the height H and cured. It is important that the height H is configured to be higher than the length _FB of the terminal (leg portion) 35a after the switching element 35 is mounted on the control board 31 . By making the height H of the filled resin higher than the length _FB of the terminal (leg portion) 35a in this way, breakage of the switching elements 33 to 38 due to vibration during operation of the power tool can be effectively prevented, and a long life of the power tool can be achieved. change. On the other hand, the height H is lower than the height of the main body portion (the upper end position of the ceramic package) _FT after the switching element 35 is mounted on the control board 31 . By setting in this way, the heat dissipation plate 35b extending upward from the upper end position of the ceramic package is exposed to the outside of the resin, and the heat dissipation plate 35b is exposed to the air flow generated by the cooling fan 10, thereby realizing good heat dissipation. Part of the heat sink 40 is located inside the resin, but most of it is exposed to the outside from the resin. Therefore, not only can the resin be firmly fixed without loosening, but also a good cooling effect can be obtained by the air flow generated by the cooling fan 10 .

The configuration of the present embodiment has been described above, but it is important to appropriately set the thickness and size of the radiator 40 as a thick metal plate in order to maintain the cooling effect by the radiator 40 satisfactorily. Here, when the thickness of the switching element 38 is _Tf , the thickness of the heat sink 40 corresponding thereto is configured to be equal to or greater than _2Tf . With the heat sink 40 having such a thickness, it becomes easy to fix the switching element on both surfaces using the bolts 43, and the screw hole 40a can be formed. In addition, since the heat sink 40 is made of an aluminum alloy, it is lightweight, can be manufactured at a relatively low cost, and has a sufficient heat capacity, so that good heat dissipation performance can be realized.

Next, the single body shape of the heat sink 40 will be described with reference to FIG. 8 . The shape of the heat sink 40 is considered various, and various shapes such as a complex fin shape extruded from aluminum may be used. However, in the present embodiment, six screw holes 40a are formed on both surfaces of a thick plate of a simple light metal alloy. The other screw hole 40a is arranged on the opposite surface of the screw hole 40a, and the two opposite screw holes 40a are located on the same axis. In addition, three screw holes 40a are formed on one surface, and a line connecting the three screw holes 40a extends in the left-right direction orthogonal to the rotation axis 5c. With this arrangement, the weight balance between the top, bottom, left, and right is improved. When the outer diameter of the grip portion 2b of the main body casing 2 is 46 mm, the width Wa of the heat sink 40 may be 41 mm, the plate thickness Ta may be 10 mm, and the height Ha may be about 43 mm. In addition, since the two opposing screw holes 40a may be determined relatively arbitrarily, such as coaxially coaxially or deviatingly, the arrangement is not limited to the arrangement of the present embodiment.

Next, the arrangement relationship between the dial 9 and the heat sink 40 will be described with reference to FIG. 9 . When the storage space of the control board 31 , the heat sink 40 , and the storage space of the switch 7 are viewed from the lateral direction (right or left), the portion indicated by the bold line is the L-shaped space 47 . In this embodiment, the dial 9 is provided on the portion 48 which is sandwiched in the L-shaped space 47 at a right angle. Viewed in the axial direction, the front-rear position Sa occupied by the radiator 40 and the front-rear position Sd occupied by the dial 9 have an overlapping positional relationship in the vertical direction, that is, the direction intersecting the direction along the rotation axis 5c. In this way, since the rotation speed adjustment mechanism (dial 9 etc.) is arranged so as to overlap with the radiator 40 in the rotation axis direction (the longitudinal direction of the main body casing 2), not only the radiators extending forward, backward, left and right can be mounted efficiently. 40. It is also possible to install the rotational speed adjustment mechanism in the space in the vertical direction which is not occupied by the radiator 40, and it is possible to realize the miniaturization of the electric power tool due to the efficient arrangement. In addition, the thickness Ta of the heat sink 40 (see FIG. 7 ) is smaller than the height dimension Hh of the L-shaped space 47 , and the width Wa (see FIG. 6 ) of the heat sink 40 is smaller than the height dimension Hh of the L-shaped space 47 . (the height of the inner wall portion of the main body casing 2 in the vicinity of the front and rear center of the radiator 40 ) is large. That is, the lateral dimension (width Wa) of the arrangement of the switching elements 33 to 38 of the heat sink 40 is larger than the height dimension (Hh) of the casing perpendicular to it.

As mentioned above, although the Example which showed this invention was demonstrated, this invention is not limited to the said Example, Various changes are possible in the range which does not deviate from the summary. For example, instead of detecting the position of the magnets of the rotor using a position detecting element, a so-called sensorless method is adopted, which detects the rotor position by reading the induced voltage (back electromotive force) of the coil of the stator 5b through a filter as a theoretical signal. Rotational position detection method. In addition, in this embodiment, a rechargeable battery pack is used as a power source, but an AC power source and a rectifier circuit may be used as in the conventional example. In this case, a power supply circuit board is further provided on the rear side of the control board 31, and a full-wave rectifier circuit using a diode bridge and a capacitor for converting alternating current into direct current may be mounted. Furthermore, in the above-described embodiments, the disk grinder is used as an example of the power tool, but it is not limited to the disk grinder, and can also be applied to other power tools that use an inversion circuit to drive a motor.

Symbol Description

1—Disc grinder, 2—Main body casing, 2a—Motor storage part, 2b—Grip part, 2c—Diameter expansion part, 2d—Cover part, 3—Gear housing, 3a—Exhaust hole, 4— Side handle, 5—motor, 5a—rotor, 5b—stator, 5c—rotating shaft, 7—switch, 7a—press switch, 8—switch lever, 9—dial, 9a—rotating shaft, 10—cooling fan, 12, 13—bevel gear, 14—spindle, 15—wheel nut, 16—bolt, 17—fan cover, 18a, 18b—bearing, 19a, 19b—suction hole, 20—wheel protector, 21—detection base plate, 22-24—position detection element, 25—display panel, 26—AUTO button, 27—battery remaining check button, 28—battery remaining indicator light, 31—control board, 32—board housing, 33～38—switch Components, 35a, 38a—terminals, 35b, 38b—heat sinks, 39—terminal bases, 40—heat sinks, 40a—threaded holes, 40b—slopes, 41—resin sheets, 43—bolts, 44—insulation sleeves, 46—gap, 51—operation part (microcomputer), 52—control signal output circuit, 53—rotor position detection circuit, 54—revolution detection circuit, 55—current detection circuit, 56—switch operation detection circuit, 57— Rotation speed setting circuit, 60—battery assembly, 61—spring key, 70—grinding stone, 101—disc grinder, 102—motor case, 103—gear housing, 103a—vent hole, 104—tail Cover, 105—motor, 105a—rotor, 105b—stator, 105c—rotating shaft, 107—power switch, 110—cooling fan, 111—spindle, 118a, 118b—bearing, 119—air intake hole, 120—wheel protector , 121—sensing magnet, 130—power cord, 132—inversion circuit substrate, 133, 136—switch element, 138—position detection element, 139—rectifier circuit.

Claims (9)

1. An electric tool is characterized in that the electric tool is provided with a power supply unit,

the disclosed device is provided with: a motor having a rotating shaft; a cooling fan rotated by the rotation of the rotating shaft; a motor accommodating part for accommodating the motor; a small diameter part connected to the motor accommodating part; an enlarged diameter portion connected to the small diameter portion and having a diameter larger than the small diameter portion in a radial direction of the small diameter portion; a housing which has the motor housing portion, the small diameter portion, and the diameter expanding portion, houses the cooling fan, and extends in a direction of a rotation axis of the motor; a first housing space provided in the diameter-expanding portion; a second receiving space connected to the first receiving space and provided in the small diameter portion; a control board disposed in the first housing space so as to intersect the rotation axis; a switch which is provided between the motor and the control substrate in the housing and switches on or off the rotation of the motor; a plurality of switching elements provided on the control board and controlling energization to the motor; and a heat sink in contact with the plurality of switching elements, wherein a diameter of the second housing space in a radial direction of the small diameter portion is smaller than a diameter of the first housing space, the heat sink extends in a direction intersecting the control board and a part of the heat sink is located in the second housing space,

the motor-side end portion of the heat sink is located closer to the motor than the motor-side end portion of the switching element in a direction perpendicular to the control board.

2. The power tool of claim 1,

the heat sink is a thick plate made of metal, and a part of the plurality of switching elements is fixed to one surface side of the heat sink, and the remaining switching elements are fixed to the other surface side of the heat sink.

3. The power tool of claim 1,

the control board is disposed so as to be sandwiched between the motor and the battery module when viewed in the direction of the rotation axis.

4. The power tool of claim 3,

the battery module can be attached to the enlarged diameter portion, and the control board has a dimension in the longitudinal direction larger than the diameter of the motor.

5. The electric power tool according to any one of claims 1 to 4,

the switching element is in surface contact with the heat sink in a direction parallel to the rotation axis, and a size of the heat sink in the rotation axis direction is larger than a size of the switching element.

6. The power tool of claim 5,

the motor is a brushless DC motor, and the three switching elements are arranged on one surface of the heat sink, and three switching elements are arranged on the other surface opposite to the one surface, and are in surface contact with each other.

7. The power tool of claim 6,

the dimension of the heat sink in the lateral direction in which the switching elements are arranged is larger than the height dimension of the housing perpendicular to the lateral direction.

8. The power tool of claim 1,

at least a part of the heat sink is positioned inside the grip portion.

9. The electric power tool according to any one of claims 1 to 4,

the control device includes a rotation speed adjusting mechanism electrically connected to the control board and operable by an operator to adjust a rotation speed of the motor, and an operating portion of the rotation speed adjusting mechanism is disposed so as to overlap the heat sink in the rotation axis direction.

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