JP5190774B2 - Electric tool - Google Patents

Description

  The present invention relates to an electric tool having a compact overall length while using a brushless DC motor as a drive source.

  In recent years, brushless DC motors have come to be used in electric tools that perform a required work by rotationally driving a tip tool such as a drill or a driver with a motor. The brushless DC motor is a DC (direct current) motor without a brush (rectifying brush), and uses a coil (winding) on the stator side and a permanent magnet on the rotor side, and the electric power driven by the inverter is predetermined. The rotor is rotated by sequentially energizing the coils. As an example of a brushless DC motor, for example, one described in Patent Document 1 is known. In this Patent Document 1, a switching element for turning on and off energization of a coil wound around a stator is arranged on a circular circuit board attached to the rear end side (opposite side of the output shaft) of the motor. . The switching elements are all mounted on one surface (rear surface) of the circuit board, and are arranged in contact with a heat dissipating member fixed to the stator core separately from the circuit board for dissipating the heat generated.

JP 2004-357371 A

  In the method of mounting all the switching elements on the rear surface of the circuit board, the switching elements are arranged so that the height direction of the switching elements is parallel to the rotation axis of the motor because of the relationship between the cooling surface and the mounting space. However, with such an arrangement, good performance can be achieved in terms of cooling, but space for the height of the circuit board and the switching element is required on the rear side in the axial direction of the motor. When applied, the length in the front-rear direction of the housing becomes long.

  On the other hand, in order to prevent the length of the housing in the front-rear direction from being increased, it is conceivable that the circuit board is provided at a different position than the rear side of the motor. However, since a large current flows through the switching element, it needs to be cooled. Usually, the switching element is cooled by a cooling fan rotated by a motor. However, if the mounting board of the switching element is arranged at another position, there arises a problem of how cooling is performed.

  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 that can be configured compactly by shortening the front-rear direction of the housing.

  Another object of the present invention is to provide an electric tool that realizes a good cooling structure while mounting a switching element at a position away from a motor.

  Still another object of the present invention is to provide an electric tool that can satisfactorily cool a switching element regardless of the rotation state of the motor.

  Of the inventions disclosed in the present application, typical features will be described as follows.

According to one feature of the present invention, a motor of a brushless DC type, the power tool includes a fan that is attached taken the output shaft of the motor, a driving circuit for supplying driving power to the motor, to rotate or drive the tool bit The drive circuit includes a plurality of switching elements, is disposed on a grip part of the housing or on a substrate provided below the housing, and is provided with an electric fan in the vicinity of the switching element , and a first air passage through which air flows by the fan, A second air passage through which air flows was formed by a fan . With this configuration, the motor is cooled by a fan attached to the output shaft, and the switching element is cooled by an electric fan. Below the grip part of the housing, an intake port for sucking outside air by an electric fan and an exhaust port for discharging air blown to the switching element are provided. The intake port and the exhaust port are provided on the side surface of the housing. The suction port is provided on the rear side surface of the housing, and the exhaust port is provided on the front side surface of the housing.

  According to another feature of the invention, a temperature sensor is provided for measuring the temperature of the mounting portion of the switching element. As a control method using the temperature sensor, the electric fan can be driven when the temperature exceeds a predetermined value, and the electric fan can be stopped when the temperature falls below the predetermined temperature. As another control method, when the motor starts driving, the electric fan is rotated at the same time. Even if the motor stops rotating, the electric fan is not stopped in conjunction with it, and the temperature falls below a predetermined value. The electric fan can be stopped.

  According to still another feature of the present invention, the housing is provided with display means for indicating that the electric fan is rotating, so that the operator is informed that the electric fan is rotating. Furthermore, the electric tool has a detachable battery for supplying electric power, and the substrate on which the switching element is mounted is provided between the battery and the grip portion. And the switching element was arrange | positioned on the board | substrate so that the height direction might extend in a perpendicular direction from a board | substrate.

According to the first aspect of the present invention, the drive circuit having the switching element is disposed on the grip portion of the housing or the substrate provided below the housing, and the electric fan is provided in the vicinity of the switching element to cool the switching element. In addition, an extra space is not required on the rear side of the motor in the housing body, and an electric tool with a compact longitudinal length can be realized. In addition, since the electric fan is provided for cooling the switching element, effective cooling of the switching element can be realized.
According to the second aspect of the present invention, independent air passages are formed for the motor and the switching element and are cooled, so that both the motor and the switching element can be efficiently cooled.

According to the invention of claim 3 , the housing is provided with an intake port for sucking outside air by the electric fan and an exhaust port for discharging the air blown to the switching element below the grip portion of the housing. Even if a switching element that generates a large amount of heat is mounted in the narrow space inside, it can be cooled effectively.

According to the invention of claim 4 , since the intake port and the exhaust port are provided on the side surface of the housing below the grip portion, there is no fear that the intake port and the exhaust port are blocked by the hand of the operator, and the cooling performance is improved. It can be maintained well.

According to the invention of claim 5 , since the suction port is provided on the rear side surface of the housing and the exhaust port is provided on the front side surface of the housing, the exhaust discharged from the inside of the housing does not hit the operator, The worker can work comfortably. Further, since the intake port is on the rear side, that is, on the worker side, it is difficult for dust to enter from the intake port even in an environment where dust is generated during cutting work or the like.

According to the invention of claim 6 , the temperature sensor for measuring the temperature of the mounting portion of the switching element is provided, and the electric fan is driven only when the temperature exceeds a predetermined value, so a rechargeable battery is used. In some cases, battery consumption by the electric fan can be reduced.

According to the seventh aspect of the invention, the temperature sensor for measuring the temperature of the mounting portion of the switching element is provided, and the electric fan is rotated when the driving of the motor is started. When the temperature falls below a predetermined value, the electric fan is turned on. Since the motor is stopped, the switching element can be reliably cooled without being affected by the stop even if the rotation of the motor such as a driver drill or a disk grinder is often stopped.

According to the eighth aspect of the present invention, since the display means indicating that the electric fan is rotating is provided in the housing, the operator can check the rotation state of the electric fan even after the motor is stopped. It is possible to prevent the battery from being removed while the electric fan is rotating.

According to the ninth aspect of the present invention, the battery has a detachable battery for supplying power to the drive circuit, and the board is provided between the battery and the grip portion, so that the wiring distance from the battery to the board can be shortened. .

According to the invention of claim 10 , since the switching element is arranged on the substrate so that the height direction of the switching element extends in the vertical direction from the substrate, the switching element is also arranged inside the grip portion whose thickness is limited. be able to.

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

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. In the following description, the vertical and forward / backward directions will be described as the directions shown in FIG. FIG. 1 is a view showing an internal structure of an impact driver 1 as an embodiment of an electric power tool according to the present invention. The impact driver 1 uses a rechargeable battery 2 as a power source, drives a rotary impact mechanism 4 using a motor 3 as a drive source, and applies rotation and impact to an anvil 5 that is an output shaft, thereby providing a tip tool (not shown) such as a driver bit. Rotating impact force is intermittently transmitted to the screw to perform operations such as screw tightening and bolt tightening.

  The motor 3 is a brushless DC motor, and is accommodated in a cylindrical body portion 6a of a housing 6 having a substantially T shape in a side view. The rotation shaft 19 of the motor 3 is rotatably held by a bearing 17a on the rear end side of the body portion 6a and a bearing 17b provided in the vicinity of the center portion. A fan 18 that rotates synchronously is provided. The fan 18 sucks air from the air intake port 53 behind the body portion 6a, and the air is discharged to the outside by a plurality of slits (not shown) arranged around the fan 18. Behind the motor 3 is disposed a substrate 7 on which a position detection element 42 is mounted for connection to the drive coil of the motor 3 and for detecting the rotational position of the rotor 3b.

  A trigger switch 8 is disposed in the upper part of the grip part 6b that extends integrally at a substantially right angle from the body part 6a of the housing 6, and the trigger switch 8 is urged by a spring (not shown) to project from the grip part 6b. A portion 8c is provided. A control circuit board 9 having a function of controlling the speed of the motor 3 by the pulling operation of the trigger operation portion 8c is accommodated below the grip portion 6b. Six more switching elements 21 are mounted on the control circuit board 9, and the motor 3 is rotated by performing inverter control with these switching elements 21. A small electric fan 22 is attached above the switching element 21. The details of the drive circuit board 7, the switching element 21, and the electric fan 22 will be described later. A battery 2 such as nickel metal hydride or lithium ion is detachably attached to the battery holding portion 6c below the grip portion 6b.

  The rotary striking mechanism 4 includes a planetary gear speed reduction mechanism 10, a spindle 11, and a hammer 12. When the trigger operation portion 8c of the trigger switch 8 is pulled and the motor 3 is activated, the rotation of the motor 3 is caused by the planetary gear speed reduction mechanism 10. And is transmitted to the spindle 11, and the spindle 11 is rotationally driven at a predetermined speed. Here, the spindle 11 and the hammer 12 are connected by a cam mechanism, and this cam mechanism is formed on the V-shaped spindle cam groove 11 a formed on the outer peripheral surface of the spindle 11 and on the inner peripheral surface of the hammer 12. The hammer cam groove 12a and the balls 13 engaged with the cam grooves 11a and 12a are configured.

  The hammer 12 is always urged forward by a spring 14, and when stationary, the hammer 13 is in a position spaced from the end face of the anvil 5 by the engagement of the ball 13 and the cam grooves 11a and 12a. And the convex part which is not illustrated is symmetrically formed in two places on the rotation plane which the hammer 12 and the anvil 5 mutually oppose.

  When the spindle 11 is driven to rotate, the rotation is transmitted to the hammer 12 via the cam mechanism, and the convex portion of the hammer 12 engages with the convex portion of the anvil 5 before the hammer 12 rotates halfway. When the relative reaction occurs between the spindle 11 and the hammer 12 due to the reaction force at that time, the hammer 12 compresses the spring 14 along the spindle cam groove 11a of the cam mechanism and moves toward the motor 3 side. And start retreating.

  When the protrusion of the hammer 12 moves over the protrusion of the anvil 5 by the backward movement of the hammer 12 and the engagement between the two is released, the hammer 12 is accumulated in the spring 14 in addition to the rotational force of the spindle 11. While being accelerated rapidly in the rotational direction and forward by the action of the elastic energy and the cam mechanism, the spring 14 is moved forward by the urging force of the spring 14, and the convex portion is reengaged with the convex portion of the anvil 5 to rotate integrally. start. At this time, since a strong rotational impact force is applied to the anvil 5, the rotational impact force is transmitted to the screw via a tip tool (not shown) attached to the anvil 5.

  Thereafter, the same operation is repeated, and the rotational impact force is intermittently repeatedly transmitted from the tip tool to the screw. For example, the screw is screwed into a material to be fastened such as wood.

  FIG. 2 is an enlarged cross-sectional view of the vicinity of the attachment portion of the control circuit board 9 of FIG. A small electric fan 22 is provided above the switching element 21 mounted on the control circuit board 9. When the electric fan 22 rotates, the electric fan 22 rotates and the intake port 25 formed in the battery holding portion 6 c of the housing 6 is rotated. Outside air is introduced in the direction of the arrow 30a, and then a strong air flow is blown to the switching element 21 by the electric fan 22 through the path of the arrow 30b. In general, the switching element 21 such as a power FET often has a heat sink on the back surface. In this embodiment, an air flow is positively applied to the heat radiating plate. Further, another heat sink made of aluminum may be attached to the heat radiating plate of the switching element 21 so that air is also applied to the heat radiating device.

  The air warmed by the heat of the switching element 21 passes through the exhaust port 26 formed on the front side of the battery holding portion 6c of the housing 6 from the direction of the arrow 30c and is discharged in the direction of the arrow 30d.

  Here, the intake port 25 is disposed on the rear side of the impact driver 1 and the exhaust port 26 is disposed on the front side. This is because the front side of the impact driver 1 has a relatively large amount of dust compared to the rear side, such as generation of cutting waste, so that the dust can be prevented from entering the inside. Further, when the exhaust port 26 is on the rear side, the exhaust air hits the worker. In this embodiment, the exhaust port 26 is arranged on the front side. Note that the intake port 25 and the exhaust port 26 may be simple holes, but a net or a filter may be attached in order to prevent entry of dust and dirt.

  What is characteristic in the present invention is that not only the rotation of the electric fan 22 is interlocked with the pulling of the trigger 8c but also the rotation of the electric fan 22 according to the temperature of the switching element 21 after the trigger 8c is released. It is to control to keep it. In the conventional electric power tool, the switching element 21 is cooled by using the air flow generated by the fan 18 configured coaxially with the motor 3. Therefore, the trigger 8 c is separated regardless of the temperature of the switching element 21. When the rotation of the motor 3 stopped, the fan 18 also stopped. For this reason, the temperature of the switching element 21 becomes higher than expected, and the life of the switching element 21 may be shortened. In particular, in a product in which the rotation of the rotor 3b may be locked, such as a driver drill or a disk grinder as an electric tool, the fan 18 attached to the rotating shaft 19 does not rotate when the rotor 3b is locked. There was a fear that it could not be cooled sufficiently.

  3 is a side view of the control circuit board 9 shown in FIG. 1 seen from the side, and FIG. 4 is a top view of the control circuit board 9 seen from above. Six switching elements 21 are mounted on the control circuit board 9 in a vertical direction with respect to the control circuit board 9, that is, the height direction of the switching elements 21 is arranged vertically. Since the mounting efficiency on the substrate is improved by arranging the switching element 21 in this way, it is suitable when the switching element 21 is arranged in the grip portion 6b in which the diameter is limited. is there. A temperature sensor 52 is provided at the center of the six switching elements 21, and the temperature around the switching element 21 is detected and monitored by a temperature rise measuring circuit 45 described later.

  The control circuit board 9 has a shape that conforms to the shape of the upper surface of the battery 2, and a control panel 27 that is exposed on the upper surface of the battery holding portion 6c is attached to the front side of the upper surface. Various operation buttons and display lamps are mounted on the control panel 27. The light button 34 is a light touch switch, and the white LED light attached to the impact driver 1 can be turned ON / OFF by pressing this button. The battery remaining amount button 35 is a light touch switch. When this button is pressed, the battery remaining amount display lamp 36 showing a battery mark indicates that the remaining amount of the battery is “full charge (two LEDs are lit)” “about half (one LED is present). It is possible to check which of the three levels of “lighting” and “low remaining amount (both two LEDs do not light)”. The display lamp 37 is an LED that is lit while the electric fan 22 is in operation, so that an operator can know that the electric fan 22 is operating and cooling. The strength display lamp 38 is a lamp that indicates the strength of the tightening torque set by the strength changeover switch 33a, and in which of the four rotation speeds of the motor 3 (for example, 2600, 2000, 1200, 500 times / minute). Whether it is set or not is indicated by the number of LED lighting. The single / repetitive indication lamp 39 displays whether the single / repetitive mode is switched each time the single / repetitive changeover switch 33b is pressed. The single shot mode is a mode in which the trigger operation unit 8c is pulled to start hitting and then automatically stopped by several hits (1 to 4 times). In the continuous mode, when the trigger operation unit 8c is pulled to start hitting, continuous hitting is performed. This is a mode that does not stop automatically.

  As shown in FIG. 4, connectors 23 and 24 are provided on the rear side of the control circuit board 9, and a switching element drive signal from a control signal output circuit described later is input through the connector 24. Further, the control circuit board 9 is connected to the trigger switch 8 via the connector 23.

  Next, the configuration and operation of the drive control system of the motor 3 will be described with reference to FIG. FIG. 5 is a block diagram showing the configuration of the motor drive control system. In the present embodiment, the motor 3 is a three-phase brushless DC motor. This brushless DC motor is a so-called inner rotor type, and includes a rotor (rotor) 3b including a plurality of sets (two sets in this embodiment) of permanent magnets (magnets) including N poles and S poles. In order to detect the rotational position of the stator 3a composed of three-phase stator windings U, V, and W connected in a star connection, and the rotational position of the rotor 3b, they are arranged at predetermined intervals in the circumferential direction, for example, at an angle of 60 °. The three rotational position detecting elements (Hall elements) 42 are provided. Based on the position detection signals from these rotational position detection elements 42, the energization direction and time to the stator windings U, V, W are controlled, and the motor 3 rotates. The rotational position detecting element 42 is provided at a position facing the magnet of the rotor 3 b on the substrate 7.

  The electronic elements mounted on the control circuit board 9 include six switching elements Q1 to Q6 such as FETs (Field Effect Transistors) connected in a three-phase bridge format. The gates of the six switching elements Q1 to Q6 connected in a bridge are connected to a control signal output circuit 46 mounted on the control circuit board 9, and the drains or sources of the six switching elements Q1 to Q6 are It is connected to the stator windings U, V, W that are star-connected. As a result, the six switching elements Q1 to Q6 perform a switching operation by the switching element drive signals (drive signals such as H4, H5, and H6) input from the control signal output circuit 46, and are applied to the inverter circuit 47. Electric power is supplied to the stator windings U, V, and W using the DC voltage of the battery 2 as three-phase (U-phase, V-phase, and W-phase) voltages Vu, Vv, and Vw.

  Of the switching element drive signals (three-phase signals) for driving the gates of the six switching elements Q1 to Q6, the three negative power supply side switching elements Q4, Q5, Q6 are converted into pulse width modulation signals (PWM signals) H4, The pulse width (duty ratio) of the PWM signal is supplied as H5 and H6 and based on the detection signal of the operation amount (stroke) of the trigger operation unit 8a of the trigger switch 8 by the arithmetic unit 41 mounted on the control circuit board 9. The amount of electric power supplied to the motor 3 is adjusted by changing, and the start / stop of the motor 3 and the rotation speed are controlled.

  Here, the PWM signal is supplied to any one of the positive power supply side switching elements Q1 to Q3 or the negative power supply side switching elements Q4 to Q6 of the inverter circuit 47, and the switching elements Q1 to Q3 or the switching elements Q4 to Q6 are switched at high speed. As a result, the power supplied to the stator windings U, V, W from the DC voltage of the battery 2 is controlled. In this embodiment, since the PWM signal is supplied to the negative power supply side switching elements Q4 to Q6, the electric power supplied to each stator winding U, V, W is controlled by controlling the pulse width of the PWM signal. The rotational speed of the motor 3 can be controlled by adjusting.

  The impact driver 1 is provided with a forward / reverse switching lever 51 for switching the rotational direction of the motor 3, and the rotational direction setting circuit 50 switches the rotational direction of the motor each time a change in the forward / reverse switching lever 51 is detected. The control signal is transmitted to the calculation unit 41. Although not shown, the calculation unit 41 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. RAM, a timer, and the like.

  The control signal output circuit 46 forms a drive signal for alternately switching predetermined switching elements Q1 to Q6 based on the output signals of the rotation direction setting circuit 50 and the rotor position detection circuit 43, and controls the drive signal. The signal is output to the signal output circuit 46. As a result, the predetermined windings of the stator windings U, V, and W are alternately energized to rotate the rotor 3b in the set rotation direction. In this case, the drive signal applied to the negative power supply side switching elements Q4 to Q6 of the substrate 7 is output as a PWM modulation signal based on the output control signal of the applied voltage setting circuit 49. The current value supplied to the motor 3 is measured by the current detection circuit 48, and the value is fed back to the calculation unit 41 so as to be adjusted to the set driving power. The PWM signal may be applied to the positive power supply side switching elements Q1 to Q3.

  As a characteristic configuration of the present embodiment, a temperature sensor 52 for measuring the temperature of the switching element 21 is provided in the inverter circuit 47, and the temperature rise measuring circuit 45 constantly monitors the temperature of the switching element 21 or its surroundings. is there. The temperature rise measuring circuit 45 measures the temperature of the switching element 21 and outputs the value to the calculation unit 41. When it is determined that the temperature has risen above a preset reference value, the calculation unit 41 sends a signal to the fan rotation control unit 44 to rotate the electric fan 22. Similarly, the calculation unit 41 may control ON / OFF of the rotation of the electric fan 22 according to the measured temperature of the switching element 21 regardless of whether the motor 3 rotates. The speed at which the electric fan 22 is rotated may be controlled not only in one stage but also in two stages of low speed / high speed, or continuously variable. Although not shown, the electric fan 22 can use electric power supplied from the battery 2.

  FIG. 6 is a diagram showing a state in use of the impact driver 1 according to the embodiment of the present invention. FIG. 6 shows a state where the operator is holding the grip 6b of the housing 6 with the right hand. In this drawing, the trigger 8c is operated with the middle finger of the right hand, but the trigger 8c may be operated with the index finger. At this time, as can be understood from this figure, the portion of the battery holding portion 6c, that is, the side surface portion of the range W between the thick lines is a range that is not gripped by the operator's hand or is not covered by the hand. An intake port and an exhaust port may be provided at any location on the side surface side rather than the upper surface side of the holding portion 6c. In the present embodiment, the intake port 25 and the exhaust port 26 are provided on the side surface 62 on the front side and on the rear side. Even in such a case, there is little risk of the intake port and the exhaust port being blocked by the operator's hand, so that the cooling effect by the electric fan 22 can be effectively maintained. In addition, it is preferable to provide the intake port 25 and the exhaust port 26 on the opposite side surfaces instead of the same side surface because the air path can be shortened and the flow of the airflow by the electric fan 22 becomes smooth. Even if it is provided on the side surface, the effect of the present invention can be obtained.

  Further, even in the region 61 on the upper surface side of the battery holding portion 6c, if it is away from the grip portion 6b, for example, near the front side, there is little possibility of being blocked by the operator's hand, It is not excluded to provide a port or an exhaust port.

  FIG. 7 is a top view of the control circuit board 9 showing the second embodiment. Compared with the structure shown in FIG. 4, the second embodiment is provided with a radiator 53 having a size that abuts on the back surface of each switching element 21. The radiator 53 is an aluminum heat sink in which a large number of fins are formed, for example. For example, the switching element 21 is screwed to the radiator 53 by passing a screw through a hole formed in the radiator plate. Alternatively, the heat dissipation plate of the switching element 21 and the heatsink 53 may be simply brought into contact with each other. By arranging each part so that the air flow sent by the electric fan 22 directly hits the radiator 53, the switching element 21 can be efficiently cooled. Further, by attaching the temperature sensor 52 to the radiator 53, it is possible to detect the temperature rise state of the switching element 21 more precisely.

  As described above, according to the present invention, the brushless DC motor is used, and the switching element 21 is not disposed on the rear end side of the motor but is disposed in another place. Thus, an electric tool that can be configured compactly as a whole can be realized.

  In the above, the embodiment applied to the impact driver as an example of the electric tool of the present invention has been described. However, the present invention is not limited to any other electric tool that can use a brushless DC motor as a motor as a drive source. Of course, the same applies to the above. In the present embodiment, an example in which an FET is used as a switching element has been described. However, the present invention can be similarly applied to a case in which another output transistor element such as an IGBT (Insulated Gate Bipolar Transistor) is used.

It is a figure which shows the internal structure of the impact driver which concerns on embodiment of this invention. FIG. 2 is an enlarged cross-sectional view of the vicinity of a mounting portion of the control circuit board 9 of FIG. It is the side view which looked at the control circuit board 9 shown in FIG. 1 from the side. It is the top view which looked at the control circuit board 9 shown in FIG. 1 from the top. It is a block diagram which shows the structure of the drive control system of the motor 3 of FIG. It is a side view which shows the state at the time of use of the impact driver 1 which concerns on embodiment of this invention. It is a top view of the control circuit board 9 which shows the 2nd Embodiment of this application.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Impact driver 2 Battery 3 Motor 3a Motor stator 3b Motor rotor 4 Rotating impact mechanism 5 Anvil 6 Housing 6a Body part 6b (Housing) Grip part 6c (Housing) Battery holding part 7 Substrate 8 Trigger switch 8c Trigger operation unit 9 Control circuit board 10 Planetary gear speed reduction mechanism 11 Spindle 11a Spindle cam groove 12 Hammer 12a Hammer cam groove 13 Ball 14 Spring 15 Sleeve 16a Ball bearing 16b Metal bearing
17a, 17b Bearing 18 Fan 19 (Motor) Rotating shaft 21 Switching element 22 Electric fan 23, 24 Connector 25 Intake port 26 Exhaust port 27 Control panel 28 Driving power line 29 Hand strap 33a Strength switch 33b Single / repetitive switch 34 Light Button 35 Battery level button 36 Battery level indicator lamp 37 Indicator lamp
38 Intensity display lamp 39 Single / repetitive display lamp 41 Calculation section 42 Rotation position detection element 43 Rotor position detection circuit 44 Fan rotation control section 45 Temperature rise measurement circuit 46 Control signal output circuit 47 Inverter circuit 48 Current detection circuit 49 Applied voltage setting Circuit 50 Rotation direction setting circuit 51 Forward / reverse switching lever 52 Temperature sensor 53 Radiator 61 Area (of battery holding unit 6c) Side surface 62 (of battery holding unit 6c) Right hand (of operator)

Claims (10)

In an electric tool that has a brushless DC system motor, a fan attached to the output shaft of the motor, and a drive circuit that supplies driving power to the motor, and rotates or drives a tip tool.
The drive circuit includes a plurality of switching elements, and is disposed on a grip part of the housing or a substrate provided below the grip part ,
The electric fan provided in the vicinity of the front Symbol switching element,
An electric tool characterized in that a first air passage through which air flows by the fan and a second air passage through which air flows by the electric fan are formed . The electric tool according to claim 1, wherein the motor is cooled by the fan attached to the output shaft, and the switching element is cooled by the electric fan. Below the grip portion of the housing, an inlet port for sucking the outside air by the electric fan according to claim 1, characterized in that a said exhaust port for discharging the blown air to the switching element or 2. The electric tool according to 2 . The power tool according to claim 3 , wherein the intake port and the exhaust port are provided on a side surface of the housing. The power tool according to claim 4 , wherein the suction port is provided on a rear side surface of the housing, and the exhaust port is provided on a front side surface of the housing. Providing a temperature sensor for measuring the temperature of the mounting portion of the switching element;
The electric tool according to claim 3 , wherein the electric fan is driven when the temperature exceeds a predetermined value. Providing a temperature sensor for measuring the temperature of the mounting portion of the switching element;
The electric tool according to claim 3 , wherein the electric fan is rotated when driving of the motor is started, and the electric fan is stopped when the temperature falls below a predetermined value. The electric tool according to claim 6 or 7 , wherein display means for indicating that the electric fan is rotating is provided in the housing. The electric tool according to claim 3 , further comprising a detachable battery that supplies electric power to the drive circuit, wherein the substrate is provided between the battery and the grip portion. The power tool according to claim 9 , wherein the switching element is disposed on the substrate such that a height direction of the switching element extends in a vertical direction from the substrate.

Images