WO2016098564A1

WO2016098564A1 - Electric tool

Info

Publication number: WO2016098564A1
Application number: PCT/JP2015/083427
Authority: WO
Inventors: 祥和河野; 一彦船橋; 俊彰小泉; 弘識益子
Original assignee: 日立工機株式会社
Priority date: 2014-12-18
Filing date: 2015-11-27
Publication date: 2016-06-23
Also published as: DE112015005645T5; CN107107326A; CN107107326B; JPWO2016098564A1; JP6460123B2

Abstract

In the present invention, the size of an electric tool is reduced by providing a large radiating means to a switching element and efficiently arranging the radiating means and the switching element in a grip part of a housing. An electric tool having: a brushless motor 5; a cooling fan 10; a housing 2 for accommodating the motor 5 and the cooling fan 10, the housing 2 extending in a rotational axis direction; a control board 31 arranged so as to intersect with the axial direction; and a switch 7 for switching rotation of the motor on or off; wherein a plurality of switching elements 33, 35 for controlling conduction of electricity to the motor are arranged between the switch and the control board, and a shared heat sink 40 in contact with the plurality of switching elements is provided. The heat sink is a thick plate made of a light metal and is arranged so as to extend in the rotational axis direction in a direction orthogonal to the control board, and the switching elements are fixed to one side and the other side of the heat sink.

Description

Electric tool

The present invention relates to an electric tool that adjusts the rotational speed of a motor using a switching element, and in particular, to provide an electric tool that devise the accommodation position of the switching element and improve heat dissipation.

As an example of an electric tool that adjusts the rotational speed of a motor using a switching element, a disc grinder described in Patent Document 1 is known. FIG. 10 is a longitudinal sectional view showing a conventional disc grinder 101 shown in Patent Document 1. As shown in FIG. The disc grinder 101 has a motor housing 102 that houses a motor 105 that is a drive source. A separate tail cover 104 having a plurality of intake holes 119 is provided at the rear of the motor housing 102. The tail cover 104 turns on / off the power cord 130 connected to the outside and the power of the disc grinder 101. A power switch 107 is provided. A gear case 103 is provided in front of the motor housing 102. The gear case 103 houses drive transmission means for converting the power transmission direction of the motor rotation shaft by about 90 degrees. A grindstone 70 is attached to a spindle 111 that extends vertically in the gear case 103. The rotary shaft 105 c is rotatably held by a front bearing 118 a fixed to the gear case 103 and a rear bearing 118 b fixed to the main body housing 102. A cooling fan 110 is provided between the bearing 118a of the rotating shaft 105c and the motor 105. By rotating in synchronization with the rotation of the motor 105, outside air is sucked from the intake hole 119 and flows into the main body housing 102. Thus, an air flow that passes in the vicinity of the

switching elements

133 and 136 and the motor 105 is generated, and is mainly discharged forward from the exhaust hole 103a.

There are various types of motors 105 that can be used for the disc grinder 101, but recently brushless DC motors are often used. A brushless DC motor is a DC (direct current) motor without a brush (rectifying brush), and a coil (armature winding) is provided on the stator side, and a permanent magnet is used as a field means on the rotor side, which is driven by an inverter device. The rotor is rotated by sequentially energizing the predetermined power to a predetermined coil. As the

switching elements

133 and 136 constituting the inverter device, for example, an FET (Field Effect Transistor) that is a semiconductor element is used. Since it is commercial alternating current that is supplied from the power cord 130, a rectifier circuit 139 is provided, and the rectified direct current is input to the inverter device. The switching element 133 is disposed on the front side of the inverter circuit board 132, and the switching element 136 is disposed on the rear side of the inverter circuit board 132. A position detection element 138 made of a Hall IC is further mounted on the front surface of the inverter circuit board 132.

A 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 the NSNS poles at intervals of 90 degrees in the circumferential direction. The inverter circuit board 132 is provided perpendicular to the rotating shaft 105 c so as to face the rear side of the sensor magnet 121. The position detection element 138 detects the rotational position of the rotor 105a by detecting the position of the rotating sensor magnet 121, and is disposed, for example, at every 60 ° in the rotational direction. A plurality of intake holes 119 are formed in the tail cover 104 portion in the vicinity of the

switching elements

133 and 136, and the

switching elements

133 and 136 are effectively cooled by the air sucked by the cooling fan 110 to cool the motor 105. The

JP 2010-269409 A

In the technique of Patent Document 1, switching

elements

133 and 136 that are switching elements for turning on and off energization of a coil wound around a stator are arranged on the front side and the rear side of the inverter circuit board 132 behind the motor. At the same time, a method of effectively dissipating the

switching elements

133 and 136 using cooling air for cooling the motor 105 is formed by forming the intake holes 119 in the vicinity of the inverter circuit board 132. However, when the speed of the motor 105 is rotated at a high speed, the heat generation of the

switching elements

133 and 136 becomes large, so that it is necessary to further improve the heat dissipation. For this reason, it is conceivable to attach a metal heat sink to each of the

switching elements

133, 136. However, if the heat sink is attached to six switching elements, the necessary accommodation space becomes large, so that the overall length of the entire power tool is reduced. There is a problem of becoming longer. On the other hand, it is conceivable to arrange the

switching elements

133 and 136 near the rear end of the tail cover 104, for example, where there is room in space. The temperature rise of the

switching elements

133 and 136 will increase.

The present invention has been made in view of the above background, and an object of the present invention is to provide an electric tool having a short overall length by attaching large heat dissipating means to a switching element and efficiently disposing them in the housing. is there. Another object of the present invention is to provide an electric tool that uses one thick plate heat sink as a heat radiating means for a plurality of switching elements, and has a plurality of switching elements fixed to the heat sink to improve heat dissipation and assembly. It is to provide.

Of the inventions disclosed in the present application, typical features will be described as follows. According to one aspect of the present invention, a motor having a rotation shaft, a cooling fan that rotates by rotation of the rotation shaft, a motor and a cooling fan are accommodated, and a housing that extends in the direction of the rotation axis of the motor is accommodated in the housing. A control board disposed so as to intersect the rotation axis, a switch provided between the motor and the control board in the housing, for turning on / off the rotation of the motor, and provided on the control board. In an electric tool having a plurality of switching elements for controlling energization, a heat sink that contacts the plurality of switching elements is provided, and the heat sink is disposed so as to extend in a direction perpendicular to the control board and in the rotation axis direction. 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.

According to another aspect of the present invention, the electric tool further includes a battery pack that can be attached to and detached from the housing, and the control board is disposed so as to be sandwiched between the motor and the battery pack in the direction of the rotation axis. The housing has a motor accommodating portion and a diameter-enlarged portion for attaching the battery pack, the control board is accommodated in the enlarged-diameter portion, and the longitudinal dimension of the control board is larger than the diameter dimension of the motor. It was configured as follows. The switching element is configured to be in surface contact with the heat sink in a direction parallel to the rotation axis, and the dimension of the heat sink in the rotation axis direction is larger than the dimension of the switching element.

According to another feature of the invention, the motor is a brushless DC motor, and three switching elements are arranged side by side on one side of the heat sink and three on the other side opposite to the one side. The switching element is fixed so as to be in direct surface contact with the heat sink or indirectly in contact with the heat sink. Here, the horizontal dimension in which the switching elements of the heat sink are arranged is preferably larger than the height dimension of the housing orthogonal to the horizontal dimension.

According to still another aspect of the present invention, the housing has an intake hole that allows cooling air to flow into the housing as the cooling fan rotates, and an exhaust hole that discharges cooling air from the housing. In the flow of the cooling air in the housing, it is positioned upstream of the motor. Further, a rotational speed adjusting means that is electrically connected to the control board and can adjust or switch the rotational speed of the motor is provided, and the rotational speed adjusting means is arranged so as to overlap with the heat sink in the rotational axis direction.

According to the present invention, since the switching element and the circuit board are accommodated in the rear end portion (expanded diameter portion) of the housing, only the brushless motor needs to be accommodated in the grip portion, and the grip portion is reduced in diameter. it can. In addition, since the control circuit including the inverter circuit and the microcomputer is mounted on the control board, the electronic device can be effectively arranged at the rear end portion of the housing while realizing a grip portion having a small diameter. Furthermore, since the switching element constituting the inverter circuit is fixed to a metal thick plate heat sink, the 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 become apparent from the following description and drawings.

1 is a perspective view showing an overall shape of a disc grinder 1 according to an embodiment of the present invention. It is a fragmentary perspective view which shows the rear end bottom vicinity of the disk grinder 1 which concerns on the Example of this invention. 1 is a longitudinal sectional view of a disc grinder 1 according to an embodiment of the present invention. 3 is a block diagram showing a circuit configuration of a drive control system of a motor 5. FIG. It is the arrow view seen from the direction of the arrow A of FIG. 3, Comprising: It is the figure which showed a part with perspective drawing. It is a figure which shows the state which looked at the control board 31 from the front side of the rotating shaft direction of the motor. FIG. 7 is a cross-sectional view taken along a line BB in FIG. 6. 3 is a perspective view showing a single shape of a heat sink 40. FIG. It is a figure for demonstrating the arrangement | positioning relationship between the dial 9 and the heat sink 40. FIG. It is a longitudinal cross-sectional view which shows the whole structure of the conventional disc grinder 101. FIG.

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

FIG. 1 is a perspective view showing an overall shape of a disc grinder 1 which is an example of an electric tool according to an embodiment of the present invention. A housing (housing) of the disc grinder 1 includes a main body housing 2 that houses therein an electric motor that is a driving source, and a gear case 3 that is attached to the front of the main body housing 2. The main body housing 2 has a substantially cylindrical shape whose central axis extends in the front-rear direction. The main body housing 2 is provided between a portion for housing a motor, which will be described later, and a portion for holding the battery pack 60 (the enlarged diameter portion 2c). A grip portion (thin diameter portion) 2b with a small outer diameter (height and / or width) is formed, and is configured to be easily gripped by an operator. A switch lever 8 of a switch for turning on or off the rotation of the motor is provided on the side (left side surface) near the front end of the main body housing 2. The gear case 3 is fixed on the front side of the main body housing 2 by four screws 16 inserted from the front to the rear with the fan cover 17 interposed. The gear case 3 fixes a spindle (output shaft) to which the grindstone 70 is attached, and the grindstone 70 is connected via a rotation transmission mechanism (not shown) housed in the gear case 3 in conjunction with the rotation of the motor. Rotates.

The grindstone 70 is, for example, a resinoid flexible toy having a diameter of 100 mm, a flexible toy, a resinoid toy, and a sanding disk. Depending on the type of abrasive used, surface grinding or curved surface grinding of metals, synthetic resins, marble, concrete, etc. is possible. is there. The rotational speed of the grindstone 70 can be adjusted to an arbitrary rotational speed of, for example, 1000 to 5000 rpm. A wheel guard 20 is provided around the rear side of the grindstone 70 to protect the operator from scattering of ground members and broken abrasive grains. A detachable side handle 4 is provided on one side surface (here, the right side) of the gear case 3. An intake hole 19b for sucking outside air by a cooling fan, which will be described later, is formed on both side surfaces near the rear end of the main body housing 2 on the front side surface of the main body housing 2, and the sucked air is discharged to the gear case 3. An exhaust hole 3a is provided.

FIG. 2 is a partial perspective view showing the vicinity of the bottom surface of the rear end 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 housing 2 and in the vicinity of the connection portion between the grip portion 2b and the enlarged diameter portion 2c. The dial 9 is a rotary type, and a number for indicating the speed level is printed on the dial. The rotational speed adjusting means of the motor 5 is not limited to the dial type adjusting means, but may be constituted by a changeover switch for switching between high and low, or may be set using an electronic switch. . A cover portion 2d for holding the battery pack 60 and closing an air hole formed in the battery pack 60 is provided behind and below the enlarged diameter portion 2c. A display panel 25 is provided in the cover 2d, and an AUTO button 26 and a battery remaining amount check button 27 are provided. Both of these can be configured with tactile switches. The AUTO button 26 is a button for setting the control method to the automatic transmission mode. When the automatic transmission mode is set, the number of rotations of the motor 5 is reduced when no load is applied, and the normal (selected with the dial) is detected when the load is detected. Control to switch to the rotation speed is performed. When the remaining battery level check button 27 is pressed, the remaining battery level indicator lamp 28 is turned on in a form corresponding to the remaining battery level. Here, the remaining battery level indicator lamp 28 is formed by a plurality of LEDs. For example, when the remaining battery level is large, all the LEDs are turned on, and the number of LEDs to be lit is reduced as the remaining battery level decreases. What is necessary is just to comprise. When removing the battery pack 60, the latch 61 provided on both sides of the battery pack is pushed and moved in the removal direction indicated by the arrow in the figure.

FIG. 3 is a longitudinal sectional view showing an internal configuration of the disc grinder 1 according to the embodiment of the present invention. The motor 5 has an elongated shape in the axial direction (front-rear direction). Here, a three-phase brushless DC motor is used as the motor 5. The motor 5 includes a stator 5b having a substantially cylindrical outer shape and a rotor 5a provided concentrically in the inner peripheral portion of the stator 5b. The motor 5 is manufactured by molding a polymer resin such as polycarbonate. The main body housing 2 is housed on the front side. The stator 5b of the motor 5 is fixed inside the main body housing 2, and the rotating shaft 5c is pivotally supported on the front side by a bearing 18a fixed to the fan cover 17 sandwiched between the gear case 3 and the main body housing 2. The rear side is pivotally supported by a bearing 18b fixed in the vicinity of the center of 2. A coil (armature winding) composed of three-phase windings U, V, and W is wound around the stator 5b. The rotor includes a metal rotor core attached to the outer peripheral side of the rotating shaft 5c, and a cylindrical magnet (permanent magnet) having N and S poles. As the magnet, for example, a circular neodymium sintered magnet can be used to reduce the rotor diameter. A detection substrate 21 for mounting three position detection elements 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 for allowing the rotation shaft 5c to pass therethrough, and

position detection elements

22, 23, and 24 (see FIG. 4) are provided on the detection substrate 21. Provided. The

position detection elements

22, 23, 24 detect the rotational position of the rotor 5a by detecting the position of the magnet of the rotating rotor 5a. For example, a Hall IC is used, and every 60 ° in the rotational direction. Three are arranged.

A switch 7 for rotating the motor 5 is provided behind the bearing 18 b and in the vicinity of the center of the main body housing 2. The switch 7 operates in conjunction with the switch lever 8 (see FIG. 1) to instruct turning on or off of the rotation of the motor 5. By moving the push button 7a, the switch 7 is turned on (connected state) or off ( 1-circuit 1-contact switch for switching to an intermittent state. The push button 7 a is operated by a link mechanism (not shown) that moves in conjunction with the movement of the switch lever 8. There are various mechanical mechanisms for moving the push button 7a in conjunction with the movement of the switch lever 8, and these are well-known, so the description thereof is omitted here.

A cooling fan 10 is provided between the bearing 18a on the front side, the rotor 5a, and the stator 5b. The cooling fan 10 is a blower that rotates by the rotation of the rotating shaft 5c and generates an air flow from the rear intake hole 19b (see FIG. 2) to the front exhaust hole 3a. The air flow taken in from the outside of the main body housing 2 flows in the vicinity of the heat sink 40 as shown by the black arrow in the figure to cool the switching

elements

33, 36, and then around the switch 7. Pass through and reach the motor 5. In the vicinity of the motor 5, the cooling air passes through the gap between the outer periphery of the stator 5 b and the inner wall surface of the main body housing 2 and between the stator 5 b and the rotor 5 a and reaches the cooling fan 10. It is discharged forward from 3a to the outside of the housing.

A detachable battery pack 60 is attached to the rear end of the main body housing 2. The battery pack 60 is a rechargeable secondary battery. For example, a nickel cadmium battery, a nickel metal hydride battery, a lithium ion battery, or the like can be used. In this embodiment, the battery pack 60 can be mounted so as to slide downward from the upper direction, and is fixed by the latch 61. The height dimension H _B of the battery pack 60 is sufficiently larger than the diameter d _m of the housing portion of the motor 5 of the main body housing 2. Thus, in order to hold the battery pack 60 having a height dimension larger than the diameter of the main body housing 2, an enlarged-diameter portion 2 c is formed in the mounting portion of the main body housing 2 where the battery pack 60 is mounted. The enlarged diameter portion 2c is a portion in which the height direction and the width direction (left and right direction) of the main body housing 2 are formed larger than the diameter of the accommodating portion of the motor 5 of the main body housing 2, and the expanded internal space A control board 31 is arranged. The control board 31 is accommodated in the board case 32, arranged so that the surface of the control board 31 is orthogonal to the rotation axis direction of the motor 5 (longitudinal direction of the main body housing 2), and parallel to the slide surface of the battery pack 60. It is arranged to become. The control board 31 is equipped with six switching elements (33, 36, etc.) and a microcomputer (not shown) constituting the control means, but the switching element having a relatively large mounting space is connected to the motor 5 from the control board 31. It arrange | positions so that it may extend in the direction of. The six switching elements (33, 36, etc.) are provided with a large heat sink 40 for cooling. The heat sink 40 can be composed of a thick plate made of metal, and the

switching elements

33 and 36 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 housing 2. The dial 9 is rotatable about the rotating shaft 9a. The rotating shaft 9a is arranged in parallel with the rotating shaft direction of the motor 5, and most of the dial 9 except for a part of the outer peripheral portion is the main body housing 2. Housed inside. The dial 9 is a variable resistor and is connected to a control circuit. Thus, by providing the dial 9 in the front part of the enlarged diameter portion 2c, the wiring with the control board 31 can be shortened, so that efficient mounting can be performed. The main body housing 2 of the present embodiment has a divided structure that is divided into right and left from a vertical plane passing through the rotation axis of the motor 5, and the board case 32 and the dial 9 that accommodate the control board 31 are arranged on the right side of the main body housing. It is fixed so as to be sandwiched between holding parts (attachment ribs) formed on the inner wall of the left part.

The gear case 3 is formed by integrally molding a metal such as aluminum, for example, and accommodates a power transmission mechanism using a pair of bevel gear mechanisms (bevel gears 12 and 13) and can rotate a spindle 14 serving as an output shaft. Hold. The spindle 14 extends so as to be orthogonal to the rotating shaft 5c (horizontal direction) of the motor 5, and the wheel nut 15 fixed from the lower side of the grindstone 70 with a spanner (not shown) is removed to remove the grindstone 70. Can be exchanged. When the motor 5 rotates, the cooling fan 10 generates an air flow from the rear to the front inside the main body housing 2. In FIG. 3, a part of the flow of the air flow is indicated by arrows, and the heat sink 40 is upstream of the motor 5 in the flow of the cooling air in the main body housing and the switch 7 and the battery pack 60. Located between.

Next, the configuration of the drive control system of the motor 5 will be described with reference to FIG. A circuit (control circuit means and inverter circuit means) indicated by a dotted line in FIG. In this embodiment, the motor 5 is a three-phase brushless DC motor. This brushless DC motor is a so-called inner rotor type, and is star-connected to a rotor 5a including a plurality of sets (two sets in this embodiment) of permanent magnets (magnets) including N poles and S poles. And a stator 5b composed of three-phase stator windings U, V, and W. Although not shown, the arithmetic unit 51 is a central processing unit (CPU) for outputting a drive signal based on the processing program and data, a ROM for storing the processing program and control data, and for temporarily storing data. The RAM, the timer, and the like are included, and the rotational speed of the motor 5 is controlled. The rotation speed of the motor 5 can be arbitrarily set by the dial 9, and the calculation unit 51 starts or stops the motor 5 according to the operation of the switch 7 by the operator.

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

Of 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 connected to pulse width modulation signals (PWM signals) H4, H5, The operation unit 51 supplied as H6 and mounted on the control board 31 starts power supply to the motor 5 based on the output signals of the position detection elements 22 to 24 constituting the switch means 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 means.

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 high (switch ON) or low (switch OFF) output to the calculation 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 calculation unit 51. The calculation unit 51 forms a drive signal for alternately switching 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 the drive signal of the motor 5 is used as a control signal. Output to the output circuit 52. As a result, the predetermined windings of the stator windings U, V, and W are alternately energized, and the rotor 5a is rotated at a set rotational speed. The rotation speed of the motor 5 is detected by the rotation speed 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. Both the outputs of the rotor position detection circuit 53 and the rotation speed detection circuit 54 are output to the calculation unit 51. 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, so that the calculation unit 51 adjusts the set drive power to the motor 5. Rotation control is performed.

Next, a connection state between the switching elements 33 to 38 and the heat sink 40 will be described with reference to FIG. FIG. 5 is an arrow view from the direction of the arrow A in FIG. 3 and most of the figure is a perspective view. As can be understood here, among the plurality of switching elements, the switching elements 33 to 35 are screwed in a state of being arranged in a line on the front side (upper side surface) of the common heat sink 40. At this time, it is important to fix the switching elements 33 to 35 so as to have a predetermined interval so as not to contact each other. Although not visible in FIG. 5, the switching elements 36 to 38 are similarly screwed to the back side (lower side) of the heat sink 40, and the switching elements 33 to 35 and the switching elements 36 to 38 are positioned symmetrically. Placed in. Although various shapes of the heat sink 40 can be considered, an aluminum plate having a thickness of about 10 mm is used in this embodiment. The surface of the aluminum plate extends in the front-rear direction and the left-right direction, and is disposed so as to be perpendicular to the control board 31. In other words, the heat sink 40 is disposed so as to extend in the direction of the rotation axis from the control board 31 toward the motor 5 side.

The heat sink 40 has an inclined surface portion 40b whose front end corner portion is formed obliquely along the inner wall surface of the main body housing 2 and effectively uses the space in the main body housing 2 by dropping corners. A terminal holder 39 is provided on the rear side of the substrate case 32 in order to fix a plurality of terminals (not shown) for making contact with the connection terminals of the battery pack 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 housing 2. In FIG. 5, in order to attach a filter device (not shown) to the

intake holes

19a and 19b, it has a shape that protrudes to the outside. The outside air taken into the main body housing 2 from the

intake holes

19a and 19b flows along the longitudinal direction of the main body housing 2, that is, the rotation axis direction. As a result, the cooling air flows in substantially the same direction as the direction in which the heat sink 40 extends, and an air flow that does not impede the flow of the heat sink 40 can be created. In addition, since the cooling air strikes the upper, lower, left and right side surfaces of the heat sink 40, the heat sink 40 and the switching elements 33 to 38 can be efficiently cooled. Since the heat sink 40 is configured in this way, the switching element 33 is effectively provided while the grip portion 2b having a smaller diameter than the motor housing portion 2a is provided on the rear side of the motor housing portion 2a that houses the motor 5. It became possible to cool ~ 38.

FIG. 6 is a diagram illustrating a state in which the control board 31 is viewed from the front side in the rotation axis direction of the motor. The control board 31 is fixed inside a board case 32 made of synthetic resin. In FIG. 6, three switching elements 33 to 35 are brought into surface contact with one surface (upper surface) of an aluminum alloy heat sink 40 having _a thickness Ta, and three switching elements are disposed on the other surface (lower surface) facing one surface (upper surface). 36 to 38 were brought into surface contact side by side. At this time, the switching elements 33 to 35 and 36 to 38 are preferably fixed to the heat sink 40 via an insulating sheet (not shown in FIG. 6, described later in FIG. 7). The longitudinal dimension (length Lc) of the control board 31 is sufficiently larger than the diameter of the stator 5b of the motor 5, and an electronic element such as the microcomputer 51 is preferably mounted on the enlarged portion.

Next, a cross-sectional view taken along a line BB in FIG. 6 will be described with reference to FIG. The substrate case 32 is formed in a substantially rectangular parallelepiped container shape having an opening surface on the upper side, and a control substrate 31 on which switching elements 33 to 38 are mounted is accommodated. The heat sink 40, which is a metal thick plate, is positioned so as to have a gap 46 slightly away from the control board 31. Since the heat sink 40 is a conductor, a gap 46 is provided so as not to short-circuit the terminals of the control board 31. The switching elements 33 to 38 are well-known FETs (field effect transistors), have three

terminals

35a and 38a of a source, a drain, and a gate, and are made of metal so as to extend partly from the back of the main body and upward from the back. The heat sinks 35b and 38b having the screw holes are provided. The heat sinks 35b and 38b are respectively screwed into the screw holes 40a formed in the heat sink 40 by screws 43. However, the heat sink 40 and the

heat sinks

35b and 38b are electrically insulated so that they are electrically insulated. It is fixed with a sleeve 44 interposed. At this time, the screw 43 that stops the heat sink 35b and the screw 43 that stops the heat sink 38b are located on the same axis. Further, a heat conductive but electrically insulating resin sheet 41 is interposed between the switching

elements

35, 38 and the heat sink 40, and the

switching elements

35, 38, while maintaining good heat dissipation. The heat sink 40 is configured not to be electrically short-circuited. Dimension in the rotation axis direction (longitudinal direction) of the heat sink 40 may be understood to be sufficiently larger than the size F _T of the switching

elements

35 and 38. 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, the six switching elements 33 to 38 could be fixed to one heat sink 40.

In the present embodiment, the control board 31 on which the switching elements 33 to 38 and other electronic elements including the microcomputer 51 (not shown in FIG. 7) are mounted is filled with a waterproof / insulating resin such as silicon and hardened. did. Here, the opening of the container-like substrate case 32 faces upward, and the liquid resin is filled from the inner bottom surface to the position of a one-dot chain line having a height H and solidified. The height H, it is important to be configured to be higher than the length F _B of after mounting the terminal (leg) 35a of the control board 31 of the switching element 35. By higher than the length F _B of the height H of the resin to be filled in this way the terminal (leg) 35a, it can effectively prevent damage to the switching elements 33-38 due to vibration during operation of the power tool The life of the electric tool can be extended. On the other hand, the height H was lower than F _T (upper end position of the ceramic package) the height of the main body portion after attachment to the control board 31 of the switching element 35. By setting in this way, the heat radiating plate 35b extending above the upper end position of the ceramic package is exposed to the outside of the resin, so that the heat radiating plate 35b is exposed to the air flow generated by the cooling fan 10, which is favorable. Heat dissipation can be realized. Although the heat sink 40 is partially located inside the resin, most of the heat sink 40 is exposed to the outside from the resin. Therefore, the heat sink 40 is firmly fixed so as not to be rattled by the resin. The effect of being cooled well by the flow is obtained.

Although the configuration of the present embodiment has been described above, in order to keep the cooling effect by the heat sink 40 favorable, it is important to appropriately set the thickness and size of the heat sink 40 that is a thick metal plate. Here, when the thickness of the switching element 38 is T _f, the thickness of the heat sink 40 corresponding thereto is configured to be equal to or greater than the 2T _f. With the heat sink 40 having such a thickness, it becomes easy to fix the switching elements on both surfaces using the screws 43, and the screw holes 40a can be formed. Moreover, since the heat sink 40 is aluminum, it is lightweight and can be manufactured at a relatively low cost, while having a sufficient heat capacity, it is possible to achieve good heat dissipation performance.

Next, a single shape of the heat sink 40 will be described with reference to FIG. Various shapes of the heat sink 40 are conceivable, and various shapes such as those having a complicated fin shape using aluminum extrusion molding may be used. However, in this embodiment, a simple light metal alloy thick plate is used, and six screw holes 40a are formed on both sides thereof. The screw hole 40a is arranged such that another screw hole 40a is arranged on the opposite side, and the two screw holes 40a facing each other are located on the same axis. Further, 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 shaft 5c. This arrangement improves the weight balance between the top, bottom, left and right. Further, when the outer diameter of the grip portion 2b of the main body housing 2 is 46 mm, the width Wa of the heat sink 40 may be 41 mm, the plate thickness Ta is 10 mm, and the height Ha is about 43 mm. It should be noted that the two screw holes 40a facing each other may be positioned on the same axis or shifted in a relatively arbitrary manner, and is not limited to the arrangement of the present embodiment.

Next, the positional relationship between the dial 9 and the heat sink 40 will be described with reference to FIG. Here, when the accommodation space for the control board 31 and the accommodation space for the heat sink 40 and the switch 7 are viewed from the side (right side or left side), a portion indicated by a thick line is an L-shaped space 47. In this embodiment, the dial 9 is provided in a portion 48 sandwiched at right angles in the L-shaped space 47. This relationship is a positional relationship in which the front-rear position Sa occupied by the heat sink 40 and the front-rear position Sd occupied by the dial 9 overlap in the vertical direction, that is, in a direction intersecting with the direction along the rotation shaft 5c. As described above, the rotation speed adjusting means (the dial 9 or the like) is arranged so as to overlap the heat sink 40 in the direction of the rotation axis (longitudinal direction of the main body housing 2). In addition, by mounting the rotation speed adjusting means in the vertical space that is not occupied by the heat sink 40, it is possible to reduce the size of the electric tool with a wasteful arrangement. The plate thickness Ta (see FIG. 7) of the heat sink 40 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 the height dimension of the L-shaped space 47. The relationship is larger than Hh (the height of the inner wall portion of the main body housing 2 near the front and rear center of the heat sink 40). That is, the horizontal dimension (width Wa) in which the switching elements 33 to 38 of the heat sink 40 are lined up is larger than the height dimension (Hh) of the housing orthogonal thereto.

As mentioned above, although demonstrated based on the Example which shows this invention, this invention is not limited to the above-mentioned Example, A various change is possible within the range which does not deviate from the meaning. For example, not a method of detecting the position of the rotor magnet using a position detection element, but a so-called sensorless method in which the rotor position is detected by extracting the induced voltage (back electromotive force) of the coil of the stator 5b as a logical signal through a filter. It is also possible to adopt this rotational position detection method. In this embodiment, a secondary battery pack is used as a power source. However, an AC power source and a rectifier circuit may be used as in the conventional example. In this case, a power supply circuit board may be further provided on the rear side of the control board 31, and a full-wave rectification circuit using a diode bridge and a capacitor for converting alternating current into direct current may be mounted. Furthermore, although the above embodiment has been described using the disk grinder as an example of the electric tool, the present invention is not limited to the disk grinder, and may be applied to other electric tools that drive the motor using an inverter circuit. .

DESCRIPTION OF SYMBOLS 1 ... Disc grinder, 2 ... Main body housing, 2a ... Motor accommodating part, 2b ... Holding part, 2c ... Expanding part, 2d ... Cover part, 3 ... Gear case, 3a ... Exhaust hole, 4 ... Side handle, 5 ... Motor, 5a ... rotor, 5b ... stator, 5c ... rotating shaft, 7 ... switch, 7a ... push button, 8 ... switch lever, 9 ... dial, 9a ... rotating shaft, 10 ... cooling fan, 12, 13 ... bevel gear, 14 ... Spindle, 15 ... Wheel nut, 16 ... Screw, 17 ... Fan cover, 18a, 18b ... Bearing, 19a, 19b ... Air intake hole, 20 ... Wheel guard, 21 ... Detection board, 22-24 ... Position detection element, 25 ... Display Panel, 26 ... AUTO button, 27 ... Battery level check button, 28 ... Battery level indicator lamp, 31 ... Control board, 32 ... Board case, 33-38 ... Switching Child, 35a, 38a ... Terminal, 35b, 38b ... Heat sink, 39 ... Terminal holder, 40 ... Heat sink, 40a ... Screw hole, 40b ... Slope, 41 ... Resin sheet, 43 ... Screw, 44 ... Insulating sleeve, 46 ... Clearance 51, arithmetic unit (microcomputer) 52 ... control signal output circuit 53 ... rotor position detection circuit 54 ... rotation speed detection circuit 55 ... current detection circuit 56 ... switch operation detection circuit 57 ... rotation speed setting Circuit, 60 ... Battery pack, 61 ... Latch, 70 ... Whetstone, 101 ... Disc grinder, 102 ... Motor housing, 103 ... Gear case, 103a ... Exhaust hole, 104 ... Tail cover, 105 ... Motor, 105a ... Rotor, 105b ... Stator , 105c ... rotating shaft, 107 ... power switch, 110 ... cooling fan, 111 ... spindle, 118a, 118b ... Receiving, 119 ... air intake hole, 120 ... wheel guard, 121 ... sensor magnet, 130 ... power cord, 132 ... inverter circuit board, 133, 136 ... switching device, 138 ... position detecting element, 139 ... rectifier circuit

Claims

A motor having a rotating shaft; a cooling fan that rotates by rotation of the rotating shaft; a housing that houses the motor and the cooling fan; and a housing that extends in a direction of the rotating shaft of the motor; A control board disposed so as to intersect, a switch provided between the motor and the control board in the housing to instruct on or off of rotation of the motor, provided on the control board, A plurality of switching elements that control energization to the motor; and a heat sink that contacts the plurality of switching elements, and the heat sink is disposed to extend in a direction perpendicular to the control board and in the rotation axis direction. An electric tool characterized by that.
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. The electric tool according to claim 1.
3. The battery pack according to claim 1, further comprising a battery pack detachably attached to the housing, wherein the control board is disposed so as to be sandwiched between the motor and the battery pack as viewed in the direction of the rotation axis. The electric tool described.
The housing has a portion for housing the motor and a diameter-expanded portion for attaching the battery pack, the control board is accommodated in the diameter-expanded section, and the longitudinal dimension of the control board is the diameter of the motor. The power tool according to claim 3, wherein the power tool is larger than the size.
The switching element is in surface contact with the heat sink in a direction parallel to the rotation axis, and the dimension of the heat sink in the rotation axis direction is larger than the dimension of the switching element. The power tool according to any one of the above.
6. The electric tool according to claim 5, wherein the motor is a brushless DC motor, and three of the switching elements are in surface contact with each other on one side of the heat sink and three on the other side opposite to the one side. .
The electric tool according to claim 6, wherein a horizontal dimension of the heat sink in which the switching elements are arranged is larger than a height dimension of the housing orthogonal to the switching element.
The housing has an intake hole for allowing cooling air to flow into the housing as the cooling fan rotates, and an exhaust hole, and the heat sink is less than the motor in the flow of the cooling air in the housing. The electric power tool according to any one of claims 1 to 7, wherein the power tool is located upstream.
Rotational speed adjusting means electrically connected to the control board and capable of adjusting the rotational speed of the motor, the rotational speed adjusting means being arranged to overlap the heat sink in the direction of the rotation axis. The power tool according to claim 1, wherein the power tool is provided.