JP2011000654A - Power tool - Google Patents

Abstract

【Task】
Provided is an easy-to-use electric tool provided with a display unit for displaying a load state applied to a motor.
[Solution]
An electric tool having a circuit board on which a switching element for driving a brushless motor is mounted, wherein a grip part 2b extending from a body part (motor housing part) 2a of the housing 2 is formed, and a display showing a load state of the switching element The portion 18 is provided on the housing portion on the side opposite to the motor, that is, on the lower side than the grip portion. The display part 18 is good to display the load condition of an electric tool with the some light emitting member 21-1 to 21-3. In order to display the load status, the circuit board is provided with temperature detecting means of the switching element so that the temperatures detected as the load status are indicated at a plurality of levels.
[Selection] Figure 2

Description

  The present invention relates to an electric power tool such as an impact driver and an impact wrench, and more particularly to an electric power tool using a brushless DC motor so that an operator can easily recognize the operating state of the motor.

  In recent years, a brushless DC motor has been adopted as a drive source for electric tools. A brushless DC motor is more efficient than a commutator motor, and in an electric tool using a rechargeable battery, the working time per charge can be greatly improved. The brushless DC motor includes a magnet rotor having a permanent magnet, a stator having a multi-phase stator coil such as a three-phase winding, and a magnetic sensor for detecting the position of the rotor by detecting the magnetic force of the permanent magnet of the rotor ( Hall IC) and an inverter circuit board for switching a DC voltage using a semiconductor switching element such as an FET to convert it to a three-phase AC current and energizing a stator coil of each phase. The plurality of magnetic sensors correspond to a plurality of phase stator coils, and each magnetic sensor is configured to set the energization timing of each phase stator coil based on the rotor position detection result.

  Since an electric tool using a brushless DC motor is equipped with a control circuit for rotationally driving the motor, the motor can be controlled with high precision by electronic control. Moreover, not only the rotation control of the motor but also various controls such as the display of the operating state and the setting state of the electric tool can be realized using the control circuit.

  As a technique for displaying the operating state of the electric tool by the control circuit, for example, the technique of Patent Document 1 is known. In Patent Document 1, the motor of the power tool, and a rotation unit that performs tightening of bolts is rotated by the motor, a torque detection unit that detects a torque of the rotating unit, a control circuit for stopping the motor reaches the torque set In the electric tool having, a display lamp for informing the user that the tightening is completed with the set torque is provided. The indicator lamp is provided at the rear part of the housing of the electric tool and is realized as a planar or belt-like lamp. When the set torque is reached, the lamp is turned on, and the rotation of the motor is automatically stopped by the control circuit.

  In a power tool using a brushless DC motor, a large amount of current is passed through a semiconductor switching element such as an FET mounted on an inverter circuit board. Therefore, if the power tool is used continuously, the amount of heat generated from the semiconductor switching element. May exceed the allowable value. Therefore, if heat generation countermeasures are not sufficiently taken, the inverter circuit board, the semiconductor switching element mounted on the inverter circuit board, and other circuit elements become hot and are thermally damaged, causing deterioration or destruction. As a countermeasure against this, the temperature rise of the semiconductor switching element on the inverter circuit board is detected by a thermistor, and when the temperature rise exceeds the reference value, the brushless DC motor is stopped or controlled to reduce the rotation speed. There is also a power tool to do.

JP 2006-346771 A

  According to the technique of Patent Document 1 described above, since the indicator lamp is provided at the rear end of the motor part of the housing of the electric tool, when the electric tool main body falls with the rear part of the housing being down, the electric tool main body Since all of the weight is added to the display part at the rear of the housing, the display part may be damaged. For this reason, the inventors considered that it is necessary to take measures to prevent breakage during the fall when providing any display unit in this way.

  The present invention has been made in view of the above background, and an object thereof is to provide an easy-to-use electric tool including a display unit that displays a load state applied to a motor.

  Another object of the present invention is to provide a power tool capable of realizing a display unit for displaying a load status with a simple configuration and suppressing a cost increase for manufacturing.

  Still another object of the present invention is to provide a long-life power tool in which a display portion is not easily damaged due to dropping of the tool or the like.

  The characteristics of representative ones of the inventions disclosed in the present application will be described as follows.

  According to one feature of the present invention, mounted with brushless motor, a power transmission unit for rotating the tool bit by transmitting a rotational force of the brushless motor, a housing that accommodates these, a switching element for driving the brushless motor In the electric tool having a circuit board, a grip portion extending from a motor housing portion of the housing is formed, and a display portion indicating a load state of the switching element is provided in the housing portion on the side opposite to the motor from the grip portion. The display unit may display the load state of the electric tool with a plurality of light emitting members. In order to display the load status, the circuit board is provided with temperature detecting means for the switching element, and the load status indicates the detected temperature at a plurality of levels.

 According to another feature of the present invention, the circuit board is installed inside the grip part or inside the housing on the side opposite to the motor, and the light emitting member is mounted on the circuit board for display in the display part. The display unit can be configured to include a window unit and a light guide unit that is attached to the window unit and guides light of the light emitting member to the window unit. The circuit board was provided with a wall that partitions the light emitting member and the switching element, and the switching element was configured such that its outer surface was coated with a heat resistant resin.

 According to still another feature of the present invention, the display unit can be provided between a strap unit formed on the housing and a grip unit of the housing. Alternatively, the display unit can be provided side by side with an operation unit provided on the non-motor side of the housing. The display part is formed in a curved surface shape, and the housing is formed with a notch for sandwiching the display part.

  According to the first aspect of the present invention, since the display portion indicating the load state of the switching element is provided in the housing portion on the side opposite to the motor from the grip portion, the operator can immediately recognize the load state of the switching element. it can. In particular, since the temperature display is displayed step by step, it is possible to predict the time until the motor stops, and it is easier to avoid sudden motor stop due to temperature rise depending on how the operator uses it. It is possible to provide an electric tool that can be used easily.

  According to the second aspect of the present invention, the display unit is configured to include the light emitting member that indicates the load state of the electric tool in a plurality of stages. Therefore, the display unit can be realized with a simple structure and at a relatively low cost.

  According to the invention of claim 3, the temperature detection means of the switching element provided on the circuit board, load status, since indicating the detected temperature at multiple levels understand harsh usage of the power tool at a glance, a user-friendly electric A tool can be provided.

  According to the invention of claim 4, the circuit board is installed inside the grip part or inside the housing on the side opposite to the motor, and the light emitting member is mounted on the circuit board for display in the display part. The overall length of the main body can be shortened.

  According to the invention of claim 5, the display section includes the window section and a light guide means attached to the window section for guiding the light of the light emitting member to the window section. Since it can be mounted on the side, it is possible to effectively prevent damage to the light emitting element due to impact or dropping.

  According to the invention of claim 6, the circuit board has a wall that partitions the light emitting member and the switching element, and the switching element is coated with a heat resistant resin. It can be prevented from being exposed.

  According to the seventh aspect of the present invention, since the display unit is provided between the strap unit formed on the housing and the grip unit of the housing, the display is displayed regardless of the direction in which the electric tool falls on the ground surface or the like. Damage to the part can be prevented.

  According to the eighth aspect of the present invention, the display unit is provided side by side with the operation unit provided on the side opposite to the motor of the housing. Therefore, the present invention can be realized without changing the conventional housing structure.

  According to the invention of claim 9, since the display part is formed in a curved surface shape and the notch part for sandwiching the display part is formed in the housing, the display part has a simple structure without impairing the outer shape of the housing. Can be attached.

  According to the invention of claim 10, the housing has a body part that accommodates the brushless motor and a grip part that extends downward from the body part, and the grip part is provided with a display part that indicates a load state of the switching element. Therefore, the operator can immediately recognize the load condition of the switching element.

  According to the eleventh aspect of the present invention, the housing has a battery attachment portion to which the battery pack can be attached below the grip portion. Therefore, when the electric tool is placed on the floor or dropped, the housing is damaged. A display portion can be provided at a position that is difficult to receive.

  According to the twelfth aspect of the present invention, since the display unit is provided on the rear side of the grip unit, the operator can easily check the display status of the display unit even during work.

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

It is sectional drawing which shows the whole structure of the impact driver 1 which concerns on the Example of this invention. It is a rear view of the impact driver 1 which concerns on the Example of this invention. FIG. 2 is a top view of a single control circuit board 10 in FIG. 1. It is sectional drawing of the AA part of FIG. It is a figure which shows the assembly structure of the display part 18 of FIG. It is another figure which shows the assembly structure of the display part 18 of FIG. It is a block diagram which shows the structure of the drive control system of the motor 3 which concerns on the Example of this invention. It is a figure which shows the relationship between the lamp | ramp displayed on the display part of FIG. 1, and a temperature state. It is a side view which shows the positional relationship of the display part 18 at the time of placing the impact driver 1 which concerns on the Example of this invention on a floor. It is sectional drawing which shows the whole structure of the impact driver 50 which concerns on the 2nd Example of this invention. It is a figure which shows the assembly structure of the display part 58 of FIG. It is another figure which shows the assembly structure of the display part 58 of FIG. It is sectional drawing which shows the whole structure of the impact driver 80 which shows the 3rd Example of this invention. It is the figure which looked at the downward direction from the CC section of FIG. It is a side view which shows the positional relationship of the display part 86 at the time of placing the impact driver 80 which concerns on a 3rd Example on a floor.

  Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, description will be made using an impact driver as an example of an electric tool. In the following drawings, the same portions are denoted by the same reference numerals, and repeated description will be omitted. Further, in this specification, description will be made assuming that the front and rear, right and left, and up and down directions are the directions shown in FIGS.

  In FIG. 1, an impact driver 1 houses a motor 3 inside a housing 2, and a rotating shaft 3 e of the motor 3 has a speed reduction unit 5 that reduces the rotational speed of the motor, an impact mechanism unit 6 that gives a rotational impact force, An anvil 8 that transmits the rotational impact force of the impact mechanism 6 to the tip tool is connected. A tip tool (not shown) such as a driver bit is connected to the anvil 8. The housing 2 is formed not only with the body part 2a that houses the motor 3, the speed reduction part 5 and the impact mechanism part 6, but also with the grip part 2b that extends downward from the body part 2a and is held by an operator. The housing 2 is formed with a battery mounting portion 6c for holding the battery pack 9 on the opposite side of the motor, that is, on the side opposite to the side on which the motor 3 is mounted with respect to the grip portion 2b. A battery pack 9 serving as a driving power source for the motor 3 is detachably mounted on the battery mounting portion 2c.

  The motor 3 is a brushless DC motor, and is accommodated in a cylindrical body portion 2a of the housing 2 having a substantially T-shape when viewed from the side. The housing 2 is configured so as to be split into two substantially right and left members (2-1, 2-1: see FIG. 2), and these members are fixed by a plurality of screws. Therefore, a plurality of screw bosses are formed on one of the divided housings 6. The rotation shaft 3e of the motor 3 is rotatably held by a bearing 14f on the rear end side of the housing 2 and a bearing 14g provided near the center. A substantially circular motor substrate 4 on which a Hall IC (rotational position detecting element) 31 for detecting the position of the rotor 3 a is mounted is arranged behind the motor 3 so as to be perpendicular to the rotating shaft 3 e of the motor 3. The

  A trigger switch 11 and a forward / reverse switching lever 11b are provided in the upper part of the grip portion 2b of the housing 2, and the trigger switch 11 is provided with a trigger operation portion 11a that is urged by a spring (not shown) and protrudes from the grip portion 2b. . A control circuit board 10 on which an inverter circuit and a control circuit for driving the motor 3 are mounted is housed below the grip portion 2 b and above the battery pack 9. The control circuit board 10 and the motor board 4 are connected by a flat cable 7 passing through the grip portion 2b. Six semiconductor switching elements 17 are mounted on the control circuit board 10, and a thermal element, which will be described later, for measuring temperature is provided in the vicinity of the semiconductor switching elements 17.

  The battery pack 9 includes a plurality of secondary battery cells such as a nickel cadmium battery and a lithium ion battery. The battery pack 9 is electrically connected so as to supply drive power to the switch circuit board 12 and the control circuit board 10.

  A fan 13 that is attached to the rotary shaft 3e and rotates in synchronization with the motor 3 is provided in front of the motor 3. Air is sucked from the air intake 24 (see FIG. 2) on the side of the motor 3 by the fan 13, and the sucked air flows inside and on the outer peripheral side of the motor 3, near the outer peripheral side in the radial direction of the fan 13. It is discharged out of the housing 2 through a plurality of slits (not shown) formed. In FIG. 1, no air intake is formed on the rear end surface of the body portion 2a of the housing 6, but an air intake may be provided on the rear end surface.

  The speed reduction part 5 can use a known speed reduction mechanism using a planetary gear, and reduces the rotational force of the motor 3 by a predetermined number of revolutions and transmits it to the impact mechanism part 6. A known hammer mechanism can be used as the impact mechanism section 6, and a V-shaped spindle cam groove formed on the outer peripheral surface of the spindle, a hammer cam groove formed on the inner peripheral surface of the hammer, and these cam grooves And a spring that always urges the hammer forward. Due to these actions, a strong rotational striking force is generated by the elastic energy accumulated in the spring and the action of the cam mechanism.

  Near the lower end of the grip portion 2 b of the housing 2, a display portion 18 that displays the temperature rise state of the semiconductor switching element 17 is provided. The display unit 18 is provided on the rear side of the housing 2, and is provided in front of the strap screw boss 23. The display unit 18 includes a light emitting element 20, a light guide member 21 that guides light emitted from the light emitting element 20, a base 19 for holding a distal end portion (light emitting part) of the light guide member 21, a base 19, and a light guide. In order to protect the tip portion of the member 21, it is constituted by a protective sheet 22 on which characters and the like are printed.

  FIG. 2 is a rear view of the impact driver 1 according to the embodiment of the present invention. The housing 2 can be divided into right and left on a vertical plane passing through the rotation shaft of the motor, and the right housing 2-1 and the left housing 2-2 are fixed by a plurality of screws. A protective sheet 22 on which “temperature display” as character information and “low, middle, and high” characters indicating the degree of temperature are printed is attached to the display unit 18. The portion where the tip portion of the light guide member 21 is located is configured to be transparent or sufficiently transmissive to light, and when the tip portion of the light guide member 21 emits light, the operator can easily recognize lighting.

  There are various ways to turn on the light emitting element 20, and only one light emitting element 20 may be turned on or blinking corresponding to each of the low, medium and high levels. Alternatively, the low and middle two light emitting elements 20 may be lit when the temperature is medium, and all the light emitting elements 20 may be lit when the temperature is high. Note that the emission color of the light emitting element 20 is also arbitrary, and the color may be changed so that low is green, medium is orange, and high is red.

  The important point in this embodiment is that the display unit 18 is provided near the lower end of the grip unit 2b. Thereby, when the operator holds the grip portion 2b, the display portion 18 is not hidden by hand, so that the display portion 18 can be confirmed even during work. Further, since the strap screw boss 23 that protrudes greatly rearward is formed immediately below the display unit 18, the possibility of the display unit 18 being hit and damaged is extremely reduced.

  Next, a mounting structure of the light emitting element 20 for causing the display unit 18 to emit a lamp will be described with reference to FIGS. 3 and 4. FIG. 3 is a top view of the control circuit board 10 alone, and FIG. 4 is a cross-sectional view taken along line AA of FIG. On the control circuit board 10, six switching elements 17 such as FETs are arranged symmetrically with respect to a line connecting the AA portions. A thermal element 38 is provided between the two central switching elements 17. Since the switching element 17 is mounted so that the heat dissipation plate of each element is in contact with the surface of the control circuit board 10, the temperature of the switching element 17 is measured by measuring the surface temperature of the control circuit board 10 with the thermal element 38. Can be measured.

  Three light emitting elements 20 (20-1, 20-2, 20-3) are mounted on the rear side of the control circuit board 10. The light emitting element 20 is, for example, a surface mountable light emitting diode (LED). A wall 25b that divides these regions is disposed between the region where the light emitting element 20 of the control circuit board 10 is mounted and the region where the switching element 17 is mounted. The wall 25b is a rib-like member that protrudes from the inner wall of the housing 2 together with the wall 25a at the rear end. The six switching elements 17 and the thermosensitive elements 38 are preferably coated with heat resistant resin on the entire top surface.

  A control panel 26 exposed on the lower side of the grip portion 2 b of the housing 6 is attached to the front side of the upper surface of the control circuit board 10. Various operation buttons and display lamps are mounted on the control panel 26. The light button 27 is a switch for turning on / off a white LED light (not shown) attached to the impact driver 1. The battery remaining amount button 28a is a button for confirming the remaining amount of the battery. When the button is pressed, the remaining amount of the battery is displayed on the remaining battery amount display lamp 28b indicating the battery mark as “full charge (two LEDs are lit)”. "About half (one LED is lit)" and "low remaining amount (both two LEDs are not lit)" can be confirmed.

  Strength display lamp 29b is a lamp indicating the strength of the set tightening torque by intensity changeover switch 29a, the rotational speed is four steps of the motor 3 (e.g., 2600,2000,1200,500 times / min) to any of the Whether it is set or not is indicated by the number of LED lighting.

  Next, the detailed structure of the light emitting unit 18 will be described with reference to FIGS. 5 and 6. FIG. 5 (1) is a perspective view of the base 19 and the light guide member 21 (21-1, 21-2, 21-3), and shows the positional relationship viewed from the rear side of the impact driver 1. The base 19 is formed in a curved surface shape in accordance with the shape of the housing 6 near the lower end of the grip portion 2b. The housing 6 is formed with a notch corresponding to the base 19, and the base 19 is fitted to the housing 2-1, so that the convex portion 19a of the base 19 is fitted into the recess formed in the notch. Fix with 2-2. Three through holes 19c are formed on the display surface 19d of the base 19, and three light guide members 21-1, 21-2, and 21-3 are mounted from the rear. The light guide member 21 is, for example, a transparent plastic member, and light incident from the lower end surface 21a is transmitted through the light guide member 21 with low loss and is emitted from the light emitting surface 21b.

  FIG. 5B is a diagram illustrating a state after the light guide member 21 is mounted on the base 19. The display surface 19d of the base 19 and the light emitting surface of the light guide member 21 are connected to be aligned on the same surface. Although not shown, a protective sheet 22 on which characters are printed is attached to the display surface 19d of the base 19. The protective sheet 22 may have the same size as the display surface 19d, or may be configured to be larger than the display surface 19d and may be attached so as to close the gap between the base 19 and the housing 2.

  FIG. 6 is a perspective view of the base 19 and the light guide member 21 as viewed from the inside. In FIG. 6 (1), the base 19 is formed with ribs 19 b serving as separation walls for holding the light guide member 21 and preventing the influence of light leaking to the light guide member 21. The rib 19b is formed between the three through holes 19c, and plays a role of not leaking the light of the light emitting element 20 to the outside (surrounding). FIG. 6B is a diagram illustrating a state where the light guide member 21 is mounted on the base 19. The light guide member 21 has a light emitting surface 21b (see FIG. 5 (2)) whose protruding portion is fitted into the through hole 19c of the base 19, so there is no need to fix the rib 19b and the light guide member 21. However, it may be fixed with an adhesive.

  Next, the configuration and operation of the drive control system of the motor 3 will be described with reference to FIG. FIG. 7 is a block diagram showing the configuration of the motor drive control system. In this embodiment, the motor 3 is a three-phase brushless DC motor. This brushless DC motor is a so-called inner rotor type, and the rotor of the motor 3 is a three-phase winding of a rotor 3a having a permanent magnet including a pair of N poles and S poles, and a star-connected stator 3c. It consists of lines U, V, W. In order to detect the rotational position of the rotor 3a, three Hall ICs 31, 32, and 33 are arranged every 60 ° in the vicinity of the rotor, and predetermined driving is performed on the three-phase windings based on these position detection signals. Power is supplied.

  The inverter circuit 44 includes six switching elements Q1 to Q6 connected in a three-phase bridge form and a flywheel diode (not shown). The gates of the bridge-connected six switching elements Q1 to Q6 are the control signals coupled to the output circuit 34, also, the six stator windings drain or source was star-connected switching elements Q1 to Q6 U, Connected to V and W. As a result, the six switching elements Q1 to Q6 perform the switching operation by the switching drive signals H1 to H6 input from the control signal output circuit 34, and the DC voltage of the battery pack 9 applied to the inverter circuit 44 is changed to 3 Electric power is supplied to the stator windings U, V, and W as drive voltages Vu, Vv, and Vw of phases (U phase, V phase, and W phase).

  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, H5 and H6 are supplied, and the calculation unit 35 included in the control unit 45 changes the pulse width (duty ratio) of the PWM signal based on the detection signal of the operation amount (stroke) of the trigger operation unit 8a of the trigger switch 8. Thus, the power supply amount to the motor 3 is adjusted, and the start / stop of the motor 3 and the rotation speed are controlled. Although not shown, the calculation unit 35 is a central processing unit (CPU) for controlling the rotation of the motor 3 and the entire impact tool based on the processing program and data, and a ROM for storing the processing program and control data. , Including a RAM for temporarily storing data, a timer, and the like.

  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 44, 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 power supplied to each stator winding U, V, W is adjusted by controlling the pulse width of the PWM signal. Thus, the rotation speed of the motor 3 can be controlled.

  The control signal output circuit 34 forms a drive signal for alternately switching predetermined switching elements Q1 to Q6 based on the output signals of the rotation direction setting circuit 42 and the rotor position detection circuit 36, and the drive signal is converted into an inverter. Output to the circuit 44. As a result, the predetermined windings of the stator windings U, V, and W are alternately energized to rotate the rotor 3a in the set rotation direction. In this case, the drive signal applied to the negative power supply side switching elements Q4 to Q6 is output as a PWM modulation signal based on the output control signal of the applied voltage setting circuit 41. The current value supplied to the motor 3 is measured by the current detection circuit 40, and the value is fed back to the calculation unit 35, so that the set drive power is adjusted. The PWM signal may be applied to the positive power supply side switching elements Q1 to Q3.

  The temperature rise measurement circuit 39 measures the temperature from the output of the thermal element 38 (see FIG. 3) that detects the temperature rise of the semiconductor switching element 17 and outputs the temperature to the computing unit 35. Receiving the temperature data from the temperature rise circuit 39, the calculation unit 35 turns on the predetermined light emitting element 20 according to the measured temperature.

  In this embodiment, the temperature rise of the semiconductor switching element 17 is measured by the thermal element 38, and when the temperature value reaches 60 degrees, the PWM duty of the motor control is reduced to 90% and “ The light emitting element 20-1 indicating “small” is turned on. When the temperature value of the semiconductor switching element 17 reaches 100 degrees, the PWM duty of the motor control is reduced to 70% and the light emitting element 20-2 indicating “medium” in the display unit 18 is turned on. Further, when the temperature value of the semiconductor switching element 17 reaches 140 degrees, the PWM duty of the motor control is reduced to 50% and the light emitting element 20-2 indicating “high” on the display unit 18 is turned on. Finally, when the temperature value of the semiconductor switching element 17 reaches 150 degrees which is the rated temperature, the PWM duty of the motor control is reduced to 0% to stop the motor 3 and all the light emission of the display unit 18 is performed. The element is blinked to indicate that the motor 3 is abnormally stopped.

  As described above, in the present embodiment, the display unit 18 is provided in the vicinity of the lower end of the grip portion 2b, and the shape thereof is curved to match the shape of the grip portion 2b, so that the operability is not impaired. It is possible to easily recognize the load status of the power tool and to realize a user-friendly power tool.

  Moreover, according to the structure of a present Example, the time which can use an electric tool continuously can be extended by reducing PWM duty in steps with a temperature rise. In this case, since the output of the motor 2 can be confirmed by the display on the display unit 18, the power tool can be prevented from stopping suddenly, and the cause of the stop is not a failure of the power tool, but is severe in continuous work. The operator can recognize that it is in use.

  Further, the embodiment described above, on the legible display unit for displaying the operation state of the power tool, even when placed on a flat surface of the ground or the like in any direction body, since the display unit does not contact the ground directly In addition, it is possible to realize a durable electric tool that is hard to break the display unit. FIG. 9 is a diagram showing this state. As can be understood from FIG. 9, even when the impact driver 1 is placed on the floor 45 so that the back side of the impact driver 1 faces down, or when the impact driver 1 falls in this direction, the display unit 18 has a sufficient distance from the floor. Therefore, there is very little possibility that the display unit 18 is broken due to the collision.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 10 is a cross-sectional view showing the overall structure of an impact driver 50 according to the second embodiment of the present invention. In order to omit repeated description, there is a difference in configuration from the impact driver 1 described in FIG. Only the symbol is attached.

  The second embodiment is different from the first embodiment in that the light emitting element 60 is provided not near the control circuit board 51 but near the outer surface side of the housing 6. The light emitting element 60 is fixed to the base 59 via a holder 59, and the light emitting element 60 is connected to the control circuit board 51 via a lead wire 61.

  FIG. 11 is a diagram showing an assembly structure of the display unit 58 of FIG. The base 59 is formed in a curved surface shape in accordance with the shape of the housing 6 near the lower end of the grip portion 2b. The housing 6 is formed with a notch corresponding to the base 59, and the base 59 is fitted to the housing 2-1, so that the convex portion 59a of the base 59 is fitted into the recess formed in the notch. Fix with 2-2. Three through holes 59c are formed in the display surface 59d of the base 59, and three light emitting elements 60 (60-1, 60-2, 60-3) are mounted via the holder 57 from the rear. The light emitting elements 60 are mounted side by side on the substrate 62, and the substrate 62 is inserted into the slot portion 57 b of the holder 57, and the holder 57 is fixed to the back surface of the base 59. A through hole 57 a is formed in the holder 57.

  FIG. 12 is another view showing the assembly structure of the display unit 58 of FIG. On the back surface of the base 59, two ribs 59b are formed for fixing the holder 57 and guiding the light emitting elements 60 to the outside without leaking light. Although not shown in FIGS. 11 and 12, a lead wire 61 extends from the back surface of the substrate 62, and the lead wire 61 is connected to the control circuit substrate 51. On the back side of the holder 57, a notch 57c for passing the lead wire 61 is formed.

  Although not shown in FIGS. 11 and 12, a protective sheet 62 printed with characters is attached to the outer surface 59 d of the base 59. The protective sheet 62 may be the same size as the outer surface 59d, may be configured to be larger than the outer surface 59d, and may be attached so as to close the gap between the base 59 and the housing 2.

  As described above, the same effects as those of the first embodiment can be obtained in the second embodiment. In particular, since it is not necessary to mount a light emitting element on the control circuit board 50, this embodiment can be easily realized only by improving a part of the conventional housing. Further, there is an advantage that the control circuit board 50 that has been conventionally used can be used with only a few improvements.

  Next, an impact driver 80 showing a third embodiment of the present invention will be described with reference to FIG. In FIG. 13, the same parts as those of the impact driver 80 in FIG. 1 are not given the same reference numerals, and repeated description is omitted. What is characteristic of the third embodiment is that a display unit indicating the load state of the switching element is incorporated in the control panel 86. Therefore, in the cross-sectional shape shown in FIG. 8, the housing 82 does not require any processing for attaching the display unit, and the conventional housing can be used as it is.

  FIG. 14 is a view of the lower part from the CC section of FIG. The control panel 86 includes a display unit 88 that displays a load state of the switching element, for example, a measured temperature state in three stages of “low, medium, and high”, and a white LED light (not shown) attached to the impact driver 80. A switch 89 for turning on / off the motor and a strength display lamp 90 indicating the strength of the tightening torque set by a strength switching switch (not shown) are provided. It should be noted that the timing for lighting the “low, medium, high” light and the structure thereof can be realized by the same structure as the first or second, and thus the repeated description is omitted.

  According to the third embodiment, not only the operator can easily see the display unit 88 even during work, but also the impact driver 80 is faced down on a plane such as the ground as shown in FIG. even dropped (or placed), the control panel 86 with a display unit 88 does not contact the ground directly, it is possible to effectively prevent damage to the display unit 88, to improve the reliability of the power tool Can do.

  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, the arrangement position of the display unit is not limited to the two locations described above, but may be another location. For example, it may be provided on the rear side of the housing 82 and in the vicinity immediately above the grip portion 82b (in the vicinity of the arrow 91 in FIG. 13). In the above-described embodiment, the load state of the switching element displayed on the display unit is displayed based on the temperature measured by the thermal element 38. However, the current value is “small” based on the drive current flowing through the inverter circuit. You may make it display a load condition like "medium large." Furthermore, the load status may be classified by some other index and displayed on the display unit.

  In the above-described embodiment, an example in which the present invention is applied to an impact driver has been described as an example of an electric power tool. However, the present invention is not limited to an impact driver, and may be applied to any electric power tool using a semiconductor element or switching element that easily generates heat. However, the same applies. Furthermore, although the example which used the brushless DC motor as a motor was demonstrated in the Example mentioned above, it is not limited to this, Another kind of motor may be sufficient.

DESCRIPTION OF SYMBOLS 1 Impact driver 2 Housing 2a (Housing) Body part 2b (Housing) Grip part 2c (Housing) Battery mounting part 3 Motor 3a Rotor 3b Permanent magnet 3c Stator 3d Stator winding 3e Rotating shaft 4 Motor board DESCRIPTION OF SYMBOLS 5 Deceleration part 6 Impact mechanism part 7 Flat cable 8 Anvil 9 Battery pack 10 Control circuit board 11 Trigger switch 11a Trigger operation part 11b Forward / reverse switching lever 12 Switch circuit board 13 Fan 14f Bearing 14g Bearing 16 Inner cover 17 Semiconductor switching element 18 Display Part
19 base 19a (base) convex portion 19b (base) rib 19c (base) through hole 19d (base) display surface 20 light emitting element 21 light guide member 22 protective sheet 23 strap screw boss 24 air Inlet 25a, 25b Wall 26 Control panel 27 Light button 28a Battery level button 28b Battery level indicator lamp 29a Strength switch 29b Strength indicator lamp 31, 32, 33 Hall IC
34 control signal output circuit 35 arithmetic unit 36 rotor position detection circuit 37 rotation speed detection circuit 38 thermal element 39 temperature rise measurement circuit 40 current detection circuit 41 applied voltage setting circuit 42 rotation direction setting circuit 45 floor 50 impact driver 51 control circuit board
57 Holder 57a (Holder) Through-hole 57b (Holder) Slot 57c (Holder) Notch 58 Display 59 Base 59a (Base) Projection 59b (Base) Rib 59c (Base) Through hole 59d (base) display surface 60 Light emitting element 61 Lead wire 62 Protective sheet 80 Impact driver 82 Housing 82b (Housing) grip part 86 Control panel 88 Display part 89 Switch 90 Strength indicator lamp

Claims (12)

An electric tool having a brushless motor, a power transmission unit that transmits a rotational force of the brushless motor to rotate a tip tool, a housing that accommodates these, and a circuit board on which a switching element that drives the brushless motor is mounted. And
A grip portion extending from the motor housing portion of the housing is formed,
An electric tool characterized in that a display portion indicating a load state of the switching element is provided in a housing portion on the side opposite to the motor from the grip portion.   The said display part is comprised including the light emission member which shows the load condition of the said electric tool in multiple steps, The electric tool of Claim 1 characterized by the above-mentioned. Providing a temperature detecting means for the switching element on the circuit board;
The electric power tool according to claim 1, wherein the load status indicates detected temperatures at a plurality of levels. The circuit board is installed in the grip part or in the housing on the side opposite to the motor,
The power tool according to claim 3, wherein a light emitting member is mounted on the circuit board for display in the display unit.   The electric tool according to claim 4, wherein the display unit includes a window unit and a light guide unit that is attached to the window unit and guides light of the light emitting member to the window unit. The circuit board has a wall that partitions the light emitting member and the switching element,
6. The electric tool according to claim 5, wherein the switching element has an outer surface coated with a heat resistant resin.   The power tool according to claim 4, wherein the display unit is provided between a strap unit formed on the housing and a grip unit of the housing.   The electric tool according to claim 4, wherein the display unit is provided side by side with an operation unit provided on the non-motor side of the housing. The display unit is formed in a curved surface shape,
The electric tool according to claim 7, wherein the housing is formed with a notch for sandwiching the display unit. A brushless motor driven by a switching element;
A tip tool connected to and driven by the brushless motor;
A power tool having a housing for housing the brushless motor,
The housing includes a body part that houses the brushless motor, and a grip part that extends downward from the body part,
An electric power tool characterized in that a display portion indicating a load state of the switching element is provided in the grip portion.   The electric power tool according to claim 10, wherein the housing has a battery attachment portion to which a battery pack can be attached below the grip portion. The tip tool protrudes from the front of the body part,
The power tool according to claim 11, wherein the display unit is provided on a rear side of the grip unit.

Images