JP2009072867A - Power tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power tool wherein the operation of a brushless motor is stabilized by effectively cooling a switching element of a circuit board. <P>SOLUTION: An impact driver (the power tool) 50 comprises: a cylindrical motor housing part 50a for storing the brushless motor 3; and a power transmitting housing part 50b, and the brushless motor 3 is constituted of: a cylindrical stator 12; a rotor 13 arranged inside the stator 12 concentrically therewith; the circuit board 22 having the switching element 21 for controlling the rotation of the rotor 13; and a cooling fan 15 for introducing cooling air from an air inlet 17 of the motor housing part 50a into the motor housing part 50a to cool the circuit board 22 and the stator 12. Near the air inlet 17 in the inner wall of the motor housing part 50a, an air flow control rib 50g is provided extending from the inner wall for the motor housing part 50a inward in the radial direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric tool that uses a brushless motor as a drive source, and more particularly to an electric tool that enhances the cooling effect of a switching element of a brushless motor housed in a motor housing portion.

  Generally, a brushless motor (DC motor) can be reduced in size and can have a long life because an electrical connection using a brush and a commutator is not required for a rotor attached to a rotating shaft.

  However, when a brushless motor is driven, a relatively large power loss occurs as heat, and the high output of the motor and normal operation may be hindered by the influence of heat. Most of the power loss is a copper loss caused by current flowing through the stator coil and an iron loss caused in the stator core material due to a change in magnetic flux density. In particular, the iron loss in the stator portion is a large heat source. For this reason, various cooling structures for cooling the stator of the brushless motor have been proposed.

  For example, in Patent Document 1, as a stator cooling structure, an opening for sucking outside air into a motor housing and an opening for discharging cooling air inside the housing to the outside of the housing are spaced apart in the direction of the rotation axis with the stator interposed therebetween. In particular, a structure is proposed in which outside air is introduced into the housing by a cooling fan integrally attached to the rotor, and in particular, the stator coil portion is directly cooled by flowing cooling air between the stator coil and the housing. Yes.

By the way, in the brushless motor, since the output transistor that constitutes the switching element of the inverter circuit board (motor drive circuit board) supplies a large current drive signal to the stator coil, the amount of heat generation increases. Required. Regarding the cooling structure of the inverter circuit board, Patent Document 2 proposes a configuration in which the inverter circuit board is disposed together with the stator portion of the motor on the cooling gas flow path in the motor housing.
JP 2004-274800 A JP 2005-102370 A

  In a brushless motor, the output transistor that constitutes the switching element of the inverter circuit board (motor drive circuit board) supplies a large current drive signal to the stator coil, resulting in a large amount of heat generation, and cooling measures for this are required. The In a power tool using a brushless motor, when a lot of work is performed, when the cooling characteristic to the switching element is low, the switching element becomes defective due to heat, and the power tool does not operate.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electric tool that effectively cools a switching element of a circuit board and enables stable operation of a brushless motor. .

  In order to achieve the above object, the invention described in claim 1 includes a cylindrical motor housing portion that houses a brushless motor, and a power transmission housing portion that is continuously formed at one end of the motor housing portion, The brushless motor includes a cylindrical stator, a rotor arranged concentrically inside the stator, a circuit board having a switching element for controlling rotation of the rotor, and cooling for cooling the circuit board and the stator. In the electric tool comprising a cooling fan for introducing wind into the motor housing from the air inlet formed in the motor housing portion, the motor housing portion inner wall is located near the air inlet on the motor housing portion inner wall. An airflow control rib extending inward in the radial direction is provided.

  According to a second aspect of the present invention, in the first aspect of the present invention, the airflow control rib is provided on the cooling fan side of the intake port.

  A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the airflow control rib is installed in a substantially ring shape along the inner wall of the motor housing portion.

  According to the first and second aspects of the present invention, since the cooling air introduced into the motor housing portion from the air inlet by the cooling fan passes near the switching element by the air flow control rib, the wind speed near the switching element increases. The switching element is directly and efficiently cooled by the cooling air. The cooling air that has cooled the switching element cools the stator in the process of flowing through an air passage provided in the gap between the inner wall of the motor housing portion and the stator. For this reason, the cooling efficiency of the brushless motor including the switching element and the stator is increased, and the brushless motor, and thus the electric tool can be stably operated.

  According to the third aspect of the present invention, since the airflow control rib is installed in a substantially ring shape along the inner wall of the motor housing portion, the cooling air taken into the motor housing portion from the intake port efficiently cools all the switching elements. This can further improve the cooling efficiency of the switching element.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 is a cutaway side view of an impact driver as an embodiment of the electric tool according to the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, FIG. 3 is a cross-sectional view taken along line BB in FIG. It is CC sectional view taken on the line of FIG.

  The impact driver 50 according to the present embodiment is a composite that extends from one end (left end in FIG. 1) to the other end (right end in FIG. 1) along the same direction as the rotation shaft 11 of the brushless motor 3. Resin-made motor housing part 50a, power transmission housing part 50b formed continuously at the other end of motor housing part 50a, and handle housing part hanging integrally from motor housing part 50a and power transmission housing part 50b And a tool body composed of 50c.

  The brushless motor 3 is housed in the motor housing portion 50a of the tool body, the power transmission mechanism portion 4 is housed in the power transmission housing portion 50b, and the tip of the power transmission housing portion 50b is connected to the anvil 10. The end projects, and a tip tool (not shown) such as a driver bit is detachably inserted into the square hole 10a of the anvil 10 and is fixed by the mounting member 10b. It should be noted that a bolt tightening bit can be mounted in the square hole portion 10a of the anvil 10 as another tip tool.

  The motor housing portion 50a is formed in a cylindrical shape, and a brushless motor 3 as a drive source is accommodated or mounted in an 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 the power transmission housing portion 50b continuous with the motor housing portion 50a. Here, the power transmission mechanism 4 includes a speed reduction mechanism composed of a planetary gear 6 and a ring gear 7, an impact mechanism composed of a spindle 8 and a hammer 9, and an anvil 10 to which a rotational impact force is given by the hammer 9. It is configured. Here, the hammer 9 is arranged on the spindle 8 so as to be slidable back and forth, and a striking force is given by the spring 5. A tip tool (not shown) is detachably attached to the anvil 10.

  A battery pack case 1 containing a battery pack as a driving power source for the brushless motor 3 is detachably attached to the lower end portion of the handle housing portion 50c. Here, the battery pack case 1 accommodates a battery pack composed of a lithium ion secondary battery (not shown), a nickel-cadmium secondary battery or the like, and most of the battery pack is inserted and accommodated in the handle housing portion 50c. The

  The battery pack case 1 is electrically connected to the motor drive circuit device 2 via a trigger switch 50d provided in a part of the handle housing portion 50c. The motor drive circuit device 2 is connected to the stator coil 12a of the brushless motor 3. The rotor 13 of the brushless motor 3 is rotationally driven. The stator coil 12a is constituted by, for example, a star-connected three-phase coil.

  Thus, in order to electrically drive the brushless motor 3, the inverter circuit board 22 composed of a bridge circuit for energizing the drive current to the stator coil 12a of the brushless motor 3 and the inverter circuit board 22 are controlled. A motor drive circuit device 2 composed of a CPU or the like is required. In particular, the inverter circuit board 22 uses a large-capacity output transistor such as an IGBT (insulated gate bipolar transistor) that operates as the switching element 21 because a large drive current needs to be applied to the stator coil 12a. Must. For this reason, the power loss of the output transistor becomes large, and the heat generation becomes a problem.

  According to the impact driver 50 configured as described above, if the operator pulls the trigger switch 50d while holding the handle housing portion 50c, the trigger switch 50d is turned on and the operation of the impact driver 50 can be started. It becomes.

  During the screw tightening operation, the rotation of the rotary shaft 11 of the briless motor 3 is decelerated by the speed reduction mechanism portion composed of the planetary gear 6 and the ring gear 7 and transmitted to the spindle 8 and also to the anvil 10 (tip tool) during 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. As a result, the hammer 9 applies a rotational striking force to the tip tool mounted on the anvil 10 to tighten the screw.

  Next, the cooling structure of the switching element 21 constituting the gist of the present invention will be described.

  As shown in FIG. 2, the brushless motor 3 includes a cylindrical stator 12 and a rotor 13 disposed in the inner peripheral portion of the stator 12. A magnet member is embedded. A slot extending in the rotation axis direction is provided between the inner peripheral portion of the stator 12 and the outer peripheral portion thereof, and a stator coil 12a is wound around the stator core in this slot. The stator coil 12a forms a star-connected three-phase coil, and the inverter circuit board 22 constituting the motor drive circuit device 2 has six switching elements 21 (IGBTs) for supplying a large drive current to the stator coil 12a. (Output transistor)) is attached.

  As shown in FIG. 1, a cooling fan 15 and a sleeve 24 are provided on the rotating shaft 11 of the rotor 13. When the rotor 13 rotates, the cooling fan 15 and the sleeve 24 rotate simultaneously. The stator 12 is provided with an inverter circuit board 22 and a cover 25, and the rotor 13 is sealed by these.

  As shown in FIG. 2, the motor housing portion 50a is provided with a gripping member 23 for gripping the stator 12, and the gripping member 23 includes a planar gripping portion 23a and a rod-shaped gripping portion 23b. ing. Here, the rod-shaped gripping portion 23b is composed of a plurality of ribs, and an air passage 19 is formed between the ribs.

  Next, the flow of the cooling air 20 will be described with reference to FIG.

  When the brushless motor 3 is activated and its rotating shaft 11 rotates, the cooling fan 15 attached to the rotating shaft 11 is rotationally driven, and the cooling fan 15 is rotated to cause the cooling air 20 to flow from the air inlet 17 to the motor housing 50a. The switching element 21 provided on the inverter circuit board 22 is cooled. Thereafter, the cooling air 20 cools the stator 12 in the process of flowing through the air passage 19 provided in the gap between the inner wall of the motor housing portion 50 a and the stator 12, and is sucked into the cooling fan 15. The cooling air 20 flows outward in the radial direction by the centrifugal action caused by the rotation of the cooling fan 15, and is discharged into the atmosphere from the exhaust port 18 shown in FIG.

  Thus, in the present embodiment, as shown in FIGS. 3 and 4, the motor housing 50a has an inner wall near the intake port 17 (specifically, on the cooling fan 15 side of the intake port 17). Airflow control ribs 50g extending integrally from the inner wall of the housing portion 50a toward the radially inner side are provided in a ring shape along the inner wall of the motor housing portion 50a. The airflow control rib 50g causes the cooling air 20 to pass in the vicinity of the switching element 21 as shown in the inverter flow 20a, thereby increasing the wind speed in the vicinity of the switching element 21, and the switching element 21 is directly driven by the cooling air 20. It is cooled efficiently. Further, the cooling air 20 that has cooled the switching element 21 cools the stator 12 in the process of flowing through the air passage 19 provided in the gap between the inner wall of the motor housing portion 50 a and the stator 12. For this reason, the cooling efficiency of the brushless motor including the switching element 21 and the stator 12 is increased, and the brushless motor 3 and, consequently, the impact driver 50 can be stably operated.

  As shown in FIG. 4, since the airflow control rib 50g is installed in a substantially ring shape along the inner wall of the motor housing portion 50a, the cooling air 20 taken into the motor housing portion 50a from the intake port 17 is All the switching elements 21 can be efficiently cooled, and the cooling efficiency of the switching elements 21 is further enhanced.

  Although the present invention has been described with respect to an embodiment in which the present invention is applied to an impact driver, the present invention is of course applicable to any other electric tool that uses a brushless motor as a drive source. It is.

It is a fracture side view of an impact driver as one form of an electric tool concerning the present invention. It is the sectional view on the AA line of FIG. It is the BB sectional view taken on the line of FIG. It is CC sectional view taken on the line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery pack case 2 Motor drive circuit apparatus 3 Brushless motor 4 Power transmission mechanism part 5 Spring 6 Planetary gear 7 Ring gear 8 Spindle 9 Hammer 10 Anvil 10a Square hole part of anvil 10b Mounting member 11 Rotating shaft 12 Stator 12a Stator coil 13 Rotor 15 Cooling fan 17 Intake port 18 Exhaust port 19 Air passage 20 Cooling air 20a Inverter flow of cooling air 21 Switching element 22 Inverter circuit board (circuit board)
23 gripping member 23a planar gripping part of gripping member 23b stick-shaped gripping part of gripping member 24 sleeve 25 cover 50 impact driver (electric tool)
50a Motor housing part 50b Power transmission housing part 50c Handle housing part 50d Trigger switch 50e Airflow control rib

Claims (3)

A cylindrical motor housing portion that accommodates the brushless motor, and a power transmission housing portion that is continuously formed at one end of the motor housing portion. The brushless motor is disposed inside the cylindrical stator and the stator. A motor housing from a concentrically disposed rotor, a circuit board having a switching element for controlling the rotation of the rotor, and cooling air for cooling the circuit board, the stator and the like from an air inlet formed in the motor housing portion In the electric tool configured to include a cooling fan to be introduced into the inside,
An electric power tool characterized in that an airflow control rib extending radially inward from the inner wall of the motor housing portion is provided in the vicinity of the intake port of the inner wall of the motor housing portion.   The power tool according to claim 1, wherein the airflow control rib is provided on the cooling fan side of the intake port. 3. The electric tool according to claim 1, wherein the airflow control rib is installed in a substantially ring shape along the inner wall of the motor housing portion.

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