JP5545343B2 - Charging tool - Google Patents

Description

  The present invention relates to a DC brushless motor used for a charging tool such as an impact driver, and more particularly to a DC brushless motor with an improved cooling mechanism for cooling a switching element and a coil, and a charging tool equipped with the DC brushless motor.

  Recently, DC brushless motors are used for charging tools such as impact drivers in place of conventional brush motors. The DC brushless motor is configured such that a plurality of switching elements (FETs) sequentially distribute and energize windings corresponding to each switching element, thereby continuously generating a magnetic field and rotating the rotor core.

  By the way, the weak point of a DC brushless motor is that a switching element and a winding coil generate heat. Therefore, many charging tools equipped with a DC brushless motor are provided with a cooling fan for cooling the switching element and the winding coil.

  For example, it is known that a cooling fan is provided on the front side (output side) of the motor housing and a switching element is provided on the rear side (opposite side) (Patent Document 1). By rotating the cooling fan, the cooling air taken from the rear of the motor housing is brought into contact with the switching element and a part of the winding protruding from the rear of the core, and then passes between the core and the motor housing. In this structure, the coil is brought into contact with the winding protruding from the front of the core, cooled, and discharged to the outside of the motor housing.

JP 2008-279564 A

  However, the above structure has the following problems.

  First, since the cooling fan is arranged on the front side of the motor housing, the axial dimension of the motor increases, and the overall length of the tool becomes long. Next, since the switching element is located at the rear part of the tool, there is a possibility that the switching element may be damaged or damaged due to an impact at the time of dropping, such as when the tool is dropped with the rear part down. Considering this point, some switching elements are provided in other parts such as the grip of the tool, but it is not enough to suppress the temperature rise of the switching elements, and precise switching control cannot be performed. There is a problem that the performance of numerical control is impaired.

  The present invention solves the above-mentioned problems, can minimize the increase of the total length, and further effectively cools the switching element and can protect the battery from an impact when dropped. The problem is to provide a tool.

In order to solve the above-mentioned problem, an invention according to claim 1 is directed to a rotating shaft provided rotatably on a motor housing via a bearing, a rotor core having a magnet fixed to the rotating shaft, and around the rotor core. A stator core having a plurality of windings, and a DC brushless for rotating the rotor core by sequentially forming a magnetic field by distributing a direct current to the windings of the rotating stator core by a plurality of switching elements mounted on the substrate A charging tool in which a motor unit provided with a motor and a power transmission unit using the rotational force of the motor unit as a drive source are arranged in series from the rear to the front, respectively, and a cooling fan provided on the rotary shaft was placed at the end portion, the substrate so as to face the DC brushless motor disposed on the sides of the motor housing, of the substrate An air hole provided in a position facing the surface, so that the cooling air taken in through the air hole from the outside of the motor housing to cool the DC brushless motor after flowing along the substrate by the cooling fan Further, a cooling air passage is formed.

  According to a second aspect of the present invention, in the first aspect, the substrate and the switching element are dust-proof and waterproof-coated with a coating material.

  The invention according to claim 3 is characterized in that, in claim 2, the coating material has a thermal conductivity of 0.5 W / m · k or more.

  According to the first aspect of the present invention, since the substrate on which the switching element is mounted is disposed so as to face the DC brushless motor and the cooling fan is disposed at the rearmost part, the rear part of the tool is dropped down. Even when the switching element is not directly impacted, it is unlikely to be damaged or damaged by a shock when dropped, and even in such a case, the motor speed control performance is ensured. Precise switching control can be maintained.

  In terms of design, the rear part has a cooling fan with a relatively small outer diameter, so the rear part of the motor housing can be narrowed down, the entire tool can be made compact, and visually. It can be configured to look small.

  In addition, since the cooling air passage is formed so that the cooling air taken in from the outside of the motor housing by the cooling fan flows along the substrate, the fresh air just taken in from the outside contacts the switching element. The cooling effect is high.

  According to the second aspect of the present invention, since the substrate and the switching element are dust-proof and waterproof-coated with the coating material, the conductive portion can be protected from corrosion and short circuit due to intrusion of dust and water.

  According to the invention of claim 3, by using a coating material having a good thermal conductivity of 0.5 W / m · k or more, the switching element of the heat source and the cooling air can efficiently exchange heat, and the cooling effect Can be high.

The perspective view which showed a part of impact driver which is embodiment of this invention in the cross section Cross section showing a part of the motor in an enlarged manner Perspective view of motor section Longitudinal section of DC brushless motor only

  FIG. 1 is a sectional view of a part of an impact driver on which a DC brushless motor according to the present invention is mounted. In FIG. A grip 2 is formed in the lower portion of the driver body 1, and a trigger switch 3 is disposed on the grip 2. A battery pack 4 is detachably provided below the grip 2.

  The driver main body 1 is formed in a cylindrical shape and includes a rear motor portion 1a and a front power transmission portion 1b.

  The motor unit 1a is provided with a DC brushless motor 5 that supplies a rotational force as a power source of the power transmission unit 1b. The DC brushless motor 5 will be described in detail later.

  Inside the power transmission unit 1b, a planetary gear mechanism 7, a spindle 8, a striking mechanism 9, and an anvil 10 are provided in series in order from the rear side on the same axis as the rotating shaft 6 of the DC brushless motor 5. A driver bit (not shown) can be attached to the tip of the anvil 10. As a result, the rotation of the DC brushless motor 5 is decelerated and transmitted to the spindle 8 by the planetary gear mechanism 7, and the rotation of the spindle 8 is constituted by the hammer 11, the compression spring 12, etc. and generates an impact force. Is converted into a rotary impact force, and this rotary impact force is transmitted to the anvil 10 rotatably supported by the housing. The structure of the power transmission unit 1b is known.

  Next, as shown in FIGS. 2 and 3, the DC brushless motor 5 provided in the motor unit 1a is rotatably provided in a motor housing 13 forming a part of the driver body 1 via bearings 20 and 21. A rotor core 15 having a magnet 14 fixed to the rotary shaft 6, a stator core 17 having a plurality of windings 16 around the rotor core 15, and an end face on the output side of the stator core 17. The substrate 18 is provided.

  One bearing 20, 21 is arranged before and after the rotating shaft 6, and is pressed into the rotating shaft 6 and fixed. Inside the housing 22, there is disposed a component in which a first cylindrical fixing portion 24 for fitting and fixing to the bearing 23 of the planetary gear mechanism 7 of the power transmission portion 1b is formed, and the first cylindrical fixing portion A second cylindrical fixing portion 25 is formed at the rear of 24 so as to extend. The front bearing 20 is fitted and fixed to the second cylindrical fixing portion 25. The rear bearing 21 is fitted and fixed in a recess 26 at the center of the rear wall 13a of the motor housing 13.

  The rotor core 15 is fixed to the rotary shaft 6, the outer periphery thereof is formed in a circular shape in cross section, and a space having a rectangular cross section is formed in the inner periphery, and a cubic magnet 14 is disposed in this space.

  The stator core 17 is formed in a ring shape having a square cross section, and is fixed inside the motor housing 13. Inside the stator core 17, a plurality of iron cores are provided radially toward the center of the stator core 17, and windings 16 are wound around each iron core via an insulating material.

  Next, the board | substrate 18 is arrange | positioned at the front side (power transmission part 1b side) of the motor part 1a. As shown in FIG. 3, a circular opening 28 larger than the front bearing 20 is formed through the substrate 18 around the rotation shaft 6. Further, a magnetic sensor (not shown) may be attached to the rear side (magnet 14 side) of the substrate 18. The magnetic sensor detects the position of the magnetic pole of the rotor core 15 and rotates the rotor core 15 by causing a motor drive circuit (not shown) to flow current sequentially through the windings 16 to form a magnetic field. Reference numeral 18 denotes an electric circuit board of the DC brushless motor 5.

  By the way, it is performed by six switching elements (FET: Field Effect Transistor) 27 that sequentially distribute the current to each winding 16. The switching elements 27 are arranged at intervals in the front part of the substrate 18, around the opening 28, that is, at a position far from the rotating shaft 6.

  Further, the switching element 27 is disposed so as to overlap the front bearing 20 of the rotating shaft 6 in a direction orthogonal to the rotating shaft 6. In other words, when the front bearing 20 is extended to the outer peripheral side, the switching element 27 is disposed so as to interfere by the width W. However, the switching element 27 and the front bearing 20 are not completely overlapped, but are arranged so as to be slightly shifted and overlapped. Therefore, a sufficient space is formed between the opening portion 28 of the substrate 18 and the second cylindrical fixing portion 25 to which the front bearing 20 is fixed so that the cooling air can pass. Of course, the opening 28 may be enlarged so that the switching element 27 and the front bearing 20 are completely overlapped.

  Next, a cooling fan 30 is provided on the rear portion of the stator core 17 opposite to the substrate 18. The cooling fan 30 is fixed between the rotor core 15 of the rotating shaft 6 and the rear bearing 21. Since the rear bearing 21 is fixed to the rear wall 13a of the motor housing 13, the cooling fan 30 is disposed at the rearmost part.

  Air holes 31 and 32 are formed in the motor housing 13 at positions corresponding to the substrate 18 and the cooling fan 30, respectively. As a result, as indicated by arrows in FIG. 2, the air flows from the air hole 31 of the motor housing 13 along both the front and back surfaces of the substrate 18, and further passes through the inside of the stator core 17 from the opening 28 to the air hole of the motor housing 13. A passage for cooling air blown out from 32 is formed.

  Therefore, when the cooling fan 30 rotates together with the rotating shaft 6, the cooling air is taken into the inside from the air hole 31 of the motor housing 13. The cooling air strikes the end surface of the substrate 18 and is divided into front and back surfaces, and flows along both the front and back surfaces to cool the switching element 27 and the winding 16. After that, both flows come together at the opening 28 of the substrate 18, and further pass between the stator core 17 and the rotor core 15 toward the air hole 32 of the motor housing 13. The air is discharged from the air hole 32 to the outside. Thus, fresh air just taken in from the outside comes into contact with the switching element 27, and its cooling effect is high. At this time, the portion of the winding 16 of the stator core 17 exposed to the substrate 18 is also cooled in the same manner. Further, the portion of the winding 16 exposed on the side opposite to the substrate 18 also comes into contact with the cooling air having passed through the inside of the stator core 17 and whose flow velocity has increased again, so that the winding 16 is effectively cooled.

  Moreover, according to the said structure, since the cooling fan 30 is arrange | positioned, the dimension of the axial direction of the DC brushless motor 5 is bulky, and the full length of an impact driver must be lengthened. However, the switching element 27 is disposed so as to overlap the front bearing 20 of the rotating shaft 6 in a direction orthogonal to the rotating shaft 6. Therefore, since the axial dimension of the DC brushless motor 5 is shorter than that in which the switching element 27 and the front bearing 20 are arranged in series, the increase in the overall length of the impact driver can be minimized. .

  Further, since the switching element 27 is disposed at the front of the impact driver, that is, between the motor unit 1a and the power transmission unit 1b, even when the impact driver is dropped with the rear part down, the switching element 27 is Since it is not directly impacted, it is unlikely to be damaged or damaged by a shock at the time of dropping. Even in such a case, the motor speed control performance is ensured and precise switching control is performed. Can be maintained.

  Furthermore, from a design point of view, as shown in FIG. 1, since the cooling fan 30 having a relatively small outer diameter is provided at the rear part, the rear part of the motor housing 13 can be narrowed down, and the whole is compact. And can be configured to look small visually.

In the present embodiment, the substrate 18 and the switching element 27 described above are protected from dust by a coating material having a thermal conductivity of 0.5 W / m · k or higher (for example, a special polymer adhesive containing a high thermal conductivity silyl group). Waterproof coating. For this reason, an electroconductive part can be protected from the corrosion and short circuit by infiltration of dust or water.
In addition, by using a coating material with good thermal conductivity, the switching element of the heat source and the cooling air can efficiently exchange heat, and the cooling effect is enhanced. In other words, if a coating material with a thermal conductivity of less than 0.5 W / m · k is used, heat exchange with the cooling air cannot be performed efficiently, and the switching element gets hot and may be damaged in some cases. However, such a problem can be prevented by using a coating material having good thermal conductivity.

DESCRIPTION OF SYMBOLS 1a Motor part 1b Power transmission part 13 Motor housing 14 Magnet 15 Rotor core 16 Winding 17 Stator core 18 Substrate 20 Front bearing 27 Switching element 28 Opening 30 Cooling fan 31, 32 Air hole

Claims (3)

A rotating shaft provided rotatably on a motor housing via a bearing, a rotor core having a magnet fixed to the rotating shaft, and a stator core having a plurality of windings around the rotor core, and on a substrate A motor unit provided with a DC brushless motor that rotates the rotor core by sequentially forming a magnetic field by distributing direct current to the windings of the rotating stator core by a plurality of attached switching elements, and the rotational force of the motor unit It is a charging tool in which a power transmission part as a drive source is arranged in series from the rear part to the front part,
The cooling fan provided on the rotating shaft is disposed at the rearmost part, the substrate is disposed to face the DC brushless motor, and an air hole is provided on the side surface of the motor housing at a position facing the end surface of the substrate. A cooling air passage is formed to cool the DC brushless motor after cooling air taken in through the air holes from the outside of the motor housing by the cooling fan flows along the substrate. The charging tool characterized by being.   2. The charging tool according to claim 1, wherein the substrate and the switching element are dustproof and waterproof coated with a coating material.   The charging tool according to claim 2, wherein the coating material has a thermal conductivity of 0.5 W / m · k or more.

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