JP5170677B2 - Electric tool - Google Patents

Description

  The present invention relates to an electric tool that uses a brushless motor, and more particularly to a structure that shortens the overall length of the brushless motor and improves the cooling effect.

  In order to rotationally drive the brushless motor, an inverter circuit board is required. Since the switching element of the inverter circuit board generates a large amount of heat because a large current is supplied to the stator coil, and the switching element may be damaged by the heat generation, a countermeasure for cooling the switching element is required. As a cooling structure of the switching element, a structure in which the switching element is fixed to the heat radiating member and the heat radiating member is cooled has been proposed. About the electric tool which has a brushless motor, it is disclosed by patent document 1, for example.

JP 2006-297532 A

  In the above conventional example, the heat of the switching element can be effectively radiated through the heat radiating member. However, since the switching element and the heat radiating member are arranged behind the stator, there is a problem that the brushless motor becomes longer in the front-rear direction by the entire length of the switching element and the heat radiating member. Moreover, since a heat radiating member is required, the cost of a product will increase.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an electric tool that shortens the entire length of the brushless motor in the front-rear direction and improves the cooling effect of the switching element.

  In this case, the heat radiating member can be eliminated.

To achieve the above object, the present invention provides a brushless motor having a stator, a rotor rotatable inside the stator, and a motor shaft rotatable integrally with the rotor, and an inverter capable of rotating the brushless motor. A switching element for forming the switching element, a substrate on which the switching element is mounted, a housing for housing the brushless motor and the switching element, and a tip tool for performing a predetermined operation by rotation of the brushless motor. In addition, a fan driven by the rotation of the brushless motor is accommodated in the housing, and outside air taken into the housing by the fan passes between the stator and the inner periphery of the housing. a ventilation passage, air passage extending in the axial direction of the motor is set Is and the substrate, the disposed so as to extend in the axial direction of the motor, the switching element, the provided ventilation passage, is attached to the substrate so as to be positioned on the stator side with respect to the substrate It is characterized by that.

  ADVANTAGE OF THE INVENTION According to this invention, the full length of the front-back direction of a brushless motor can be shortened, and the cooling effect of a switching element can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional front view in which the electric tool of the present invention is applied to a cordless type impact driver, and FIG. 2 is a view taken along line Å-A in FIG.

  The impact driver according to the embodiment of the present invention includes a motor housing portion 50 that houses the brushless motor 3, and a power transmission housing that houses the power transmission mechanism portion 4 formed continuously at the other end of the motor housing portion 50. The tool main body comprised from the part 51 and the handle | housing housing part 52 suspended from the motor housing part 50 and the power transmission housing part 51 is included.

  The front end of the power transmission housing 51 protrudes from the end of the anvil 10, and a tool such as a driver bit (not shown) is detachably inserted into the anvil square hole 10a and can be fixed by the mounting member 10b. ing. For example, a bolt tightening bit can be attached to the anvil square hole portion 10a as another tip tool.

  The motor housing portion 50 has a cylindrical shape, and the brushless motor 3 serving as a drive source for the tip tool is accommodated in the inner peripheral portion thereof.

  A power transmission mechanism portion 4 for transmitting the rotational force of the brushless motor 3 to the anvil 10 as a rotational striking force is accommodated in a power transmission housing portion 51 that is continuous with the motor housing portion 50.

  The power transmission mechanism 4 is composed of a speed reduction mechanism composed of a planetary gear 6 and a ring gear 7, a spindle 8, a hammer 9 that is slidable back and forth on the spindle 8, and is provided with a striking force by a spring 5. And an anvil 10 which is provided with a rotating impact force by the hammer 9 and can hold the tip tool as described above.

  A battery pack case 1 serving as a driving power source for the brushless motor 3 is detachably attached to the handle housing portion 52 at the lower end portion of the handle housing portion 52. The battery pack case 1 houses a lithium ion secondary battery pack (not shown), and most of the battery pack body is inserted into the handle housing portion 52 and housed. The secondary battery pack may be a nickel / cadmium secondary battery.

  The battery pack case 1 is electrically connected to the motor drive circuit device 2 via a trigger switch 30 provided in a part of the handle housing portion 52. The motor drive circuit device 2 is electrically connected to a stator coil 12 a (for example, a star-connected three-phase coil) of the brushless motor 3 and rotationally drives the rotor 13 of the brushless motor 3.

  In order to electrically rotate the brushless motor 3, the inverter circuit board 22 including a known bridge circuit for supplying a drive current to the stator coil 12a of the brushless motor 3 or a switching element 21 provided separately from the inverter circuit board is provided. Further, in order to control these, a motor drive circuit device 2 composed of a CPU or the like is required.

  According to the impact driver configured as described above, when the operator pulls the trigger switch 30 while holding the handle housing portion 52, the trigger switch 30 is turned on, and the brushless motor 3 is driven by the secondary battery pack. Once driven, the impact driver can begin to operate.

  During the screw tightening operation, the rotational force of the motor 3 transmitted from the motor shaft 11 is decelerated by the planetary gear 6 and the ring gear 7, and the rotational force is transmitted to the spindle 8, and the anvil 10 (tip tool) during the screw tightening. When a load torque exceeding a predetermined value is applied, the hammer 9 converts the rotational force into a striking force by the action of the spring 5. Thereby, the hammer 9 can apply a rotational striking force to the tip tool mounted on the anvil 10 and tighten the screw.

  Next, the arrangement structure of the switching element 21 of the brushless motor 3 according to the present invention will be described.

  The brushless motor 3 includes a stator 12 having a cylindrical outer shape, and a rotor 13 disposed on the inner peripheral portion of the stator 12 and embedded with four permanent magnet members 14 in the motor axial direction. An insulating material 23 made of resin or the like is fixed to the stator 12, and a stator coil 12a is wound around the outside. The stator coil 12a forms a star-connected three-phase coil, and the inverter circuit board 22 is electrically connected via the board 25 with a switching element 21 for energizing the stator coil 12a with a large drive current. ing. The stator 12 is fixed by a holding portion 50 a of the motor housing 50.

  An air passage 19 is provided between the holding portion 50a and the stator 12 to allow outside air to flow. Here, the switching element 21 is disposed between the stator 12 and the handle housing portion 52 and on the cooling air passage 19. More specifically, the motor housing portion 50 has a cylindrical shape so as to extend in parallel with the motor shaft 11, and the stator 12 is also provided so as to extend in parallel with the motor shaft 11. It is formed so as to extend parallel to the motor shaft 11.

  The substrate 25 is provided to be parallel to the motor shaft 11 as shown in FIG. Further, the substrate and the switching element 21 are provided so as to be located inside the air passage 19.

  The switching element 21 is inclined with respect to the substrate 25. The inclination is along the outer periphery of the stator 12. For this reason, when the switching element is perpendicular to the substrate, the size in the vertical direction is large, but the size in the vertical direction can be reduced. Further, when the switching element is parallel to the substrate, the size in the left-right direction is large, but the size in the left-right direction can be reduced.

  Next, the flow of cooling air will be described. When the brushless motor 3 is driven to rotate, the cooling fan 15 fixed to the motor shaft 11 rotates. The cooling air 20 sucked from the air inlet 17 by the cooling fan 15 flows into the motor housing 50 and passes through an air passage provided between the inner peripheral portion of the motor housing 50 and the stator 12. At this time, the switching element 21 and the stator 12 are cooled and guided to the cooling fan 15. Thereafter, it is discharged from the discharge port 18.

  With this configuration, the distance L from the inverter circuit board 22 to the ball bearing 24 can be shortened, the overall length of the brushless motor 3 can be shortened, and the switching element 21 is directly applied to the cooling air. Can be effectively cooled.

  In the embodiment of the present invention, the impact driver is described as an example of the power tool friction, but other power tools may be used. For example, a portable electric circular saw, a portable electric driver drill, an electric hammer drill, or the like may be used.

The partial cross section front view which shows embodiment of this invention AA arrow view of FIG.

Explanation of symbols

1: Battery pack case 2: Motor drive circuit device 3: Brushless motor 4: Power transmission mechanism 5: Spring 6: Planetary gear 7: Ring gear 8: Spindle 9: Hammer 10: Anvil 10a: Anvil square hole 10b: Tip Tool mounting member 11: Motor shaft 12: Stator
12a: Stator coil 13: Rotor 14: Permanent magnet member
15: Cooling fan 17: Inlet 18: Exhaust 19: Air passage
20: Cooling air 21: Switching element 22: Inverter circuit board
23: Insulating material 24: Ball bearing 25: Substrate 30: Trigger switch 50: Motor housing part 50a: Holding part 51: Power transmission housing part 52: Handle housing part

Claims (4)

A brushless motor having a stator, a rotor rotatable inside the stator, and a motor shaft rotatable integrally with the rotor;
A switching element forming an inverter capable of rotationally driving the brushless motor;
A substrate to which the switching element is attached;
A housing that houses the brushless motor and the switching element;
A tip tool that performs a predetermined operation by rotation of the brushless motor;
An electric tool having
The housing contains a fan driven by the rotation of the brushless motor,
Wherein between the stator and the inner periphery of said housing, said a ventilation passage which ambient air passes to be incorporated into the housing by the fan, which air passage is provided extending in the axial direction of the motor,
The substrate is arranged to extend in the motor axial direction ,
The electric power tool, wherein the switching element is provided in the ventilation path and is attached to the substrate so as to be positioned on a stator side with respect to the substrate . The power tool according to claim 1, wherein the switching element is provided to be inclined with respect to the substrate. The electric tool according to claim 1, wherein the switching element is arranged along the outer periphery of the motor. The electric power tool according to any one of claims 1 to 3, wherein the substrate is fixed by being sandwiched between the housings.

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