JP5332163B2 - Electric tool - Google Patents

Description

  The present invention relates to an electric tool that uses a brushless motor, and more particularly, to a highly reliable motor structure with no rotation failure with respect to a brushless motor housed in a motor housing portion.

  In general, a brushless motor (DC motor) can be miniaturized, and electrical connection using a brush and a commutator is not necessary for a rotor attached to a rotating shaft, so that a long life is possible.

  The brushless motor is necessary for the output transistor constituting the switching element of the inverter circuit board (motor drive circuit board) to supply a large current drive signal to the stator coil.

  Therefore, it is considered that the brushless motor is suitable as a drive source for a portable electric tool using a DC power source. In general, in an electric power tool used in an air working environment in which wood powder or metal powder is mixed, such as an impact driver, metal powder such as iron powder may adhere to the Hall IC on the inverter circuit board.

JP 2006-297532 A

  If metal powder such as iron powder adheres to the Hall IC on the inverter circuit board, the position of the magnet provided on the rotor core cannot be detected, causing the motor to malfunction.

  As a simple structure for preventing foreign matter from entering the motor, it is conceivable that the entire motor housing is sealed. However, simply having the entire motor in a sealed structure results in a structure in which cooling air does not necessarily flow. Accordingly, the cooling effect is impaired, and the temperature of the windings abnormally rises even during normal operation, causing a problem that causes failure such as coil burnout.

  In order to make the electric tool compact, it is necessary to bring the stator coil and the drive circuit board as close as possible. However, if the stator coil and the drive circuit board are too close, the stator coil and the electronic components on the drive circuit board may come into contact due to manufacturing variations. In that case, the stator coil is damaged by the electronic component on the drive circuit board, and the stator coil and the electronic component are short-circuited to cause a rotation failure.

  In order to eliminate manufacturing variations, it is necessary to accurately suppress the position of the stator coil, but the cost is inevitably increased.

The object of the present invention is to provide an electric tool that is compact and excellent in workability, and is inexpensive by preventing metal powder such as iron powder from adhering to the Hall IC on the inverter circuit board at low cost. It is to provide a highly reliable electric tool.

In order to solve the above-mentioned problem , a stator in which a stator coil is wound in a slot in which a first insulating material is mounted, and a permanent magnet embedded with a rotating shaft that is rotatably supported inside the stator. A brushless motor having a rotor, and a switching element that is fixed to the first insulating material so as to face the end of the brushless motor substantially orthogonal to the rotation axis, and that controls driving of the brushless motor is provided on the side opposite to the brushless motor. A circuit board provided on the surface of the circuit board and a housing for housing the brushless motor, and a hall element for detecting the position of the rotor is provided on the surface of the circuit board facing the brushless motor and the hall element. The 2nd insulating material which coat | covers was provided.

ADVANTAGE OF THE INVENTION According to this invention, it can prevent that foreign materials, such as metal powder, adhere to an electronic component. Therefore, it is possible to prevent the motor from causing a rotation failure. Therefore, an inexpensive and highly reliable power tool can be provided.

Moreover, according to this invention, it can prevent that the electronic component on a stator coil and a circuit board contacts. Therefore, it is possible to prevent the stator coil and the electronic components on the circuit board from being short-circuited to cause a rotation failure of the motor. Therefore, a highly reliable electric tool can be provided.

Further, according to the present invention, it is possible to make it difficult for foreign matters such as metal powder to adhere to the circuit board. Therefore, it is possible to prevent the motor from causing a rotation failure. Therefore, a highly reliable electric tool can be provided.

Moreover, according to this invention, it can prevent that the leg of a switching element damages a coil.

Further, according to the present invention , the Hall element can accurately detect the position of the rotor.

In addition, according to the present invention, it is possible to reliably cover the foot and the Hall element, since the insulating material is not easily broken.

  An embodiment of the present invention will be described in detail with reference to FIGS. In the embodiment of the present invention, a cordless impact driver is used as the power tool.

  1 is an overall sectional view according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, FIG. 3 is a sectional view taken along line AA in FIG. 2, and FIG. 5 is a cross-sectional view taken along the line CC of FIG. 2, and FIG. 6 is a partial view according to the embodiment of the present invention.

  The configuration of the entire tool will be described with reference to FIG. The impact driver 50 according to the first embodiment of the present invention extends from one end (the left end in the drawing) to the other end (the right end in the drawing) along the same direction as the rotation shaft 11 of the brushless motor 3 to be described later. It is extended. The impact driver 50 includes a motor housing portion 50A made of a synthetic resin material that houses the brushless motor 3, and a power transmission housing portion 50B that houses the power transmission mechanism portion 4 formed continuously at the other end of the motor housing portion 50A. And a handle housing portion 50C depending from the motor housing portion 50A and the power transmission housing portion 50B. The end of the power transmission housing 50B 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. A bolt tightening bit can also be attached to the anvil square hole portion 10A as another tip tool.

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

  A power transmission mechanism portion 4 for transmitting the rotational force of the 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. The power transmission mechanism unit 4 includes a speed reduction mechanism unit including a planetary gear 6 and a ring gear 7, and a spindle 8 and 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 that is provided with a rotating impact force by the hammer 9 and can hold a tip tool (not shown) 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 50C at the lower end portion of the handle housing portion 50C. The battery pack case 1 accommodates a battery pack body made of a lithium ion battery, a nickel / cadmium battery or the like (not shown). Most of the battery pack main body is inserted and accommodated in the handle housing portion 50C. Alternatively, it is slidably attached to the handle housing portion 50C.

  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, and has a function of rotating the rotor 13 of the motor 3 to be a brushless motor. 3 includes an inverter circuit (not shown) including a known bridge circuit for supplying a drive current to the three stator coils 12A, a control circuit (not shown) including a CPU for controlling the inverter circuit, and the like. In particular, the inverter circuit must use a large capacity output transistor such as an IGBT (insulated gate bipolar transistor) that operates as a switching element because a large drive current needs to be applied to the stator coil 12A. For this reason, the power loss of the output transistor increases, and heat generation becomes a problem. Therefore, it is necessary to arrange the inverter circuit in consideration of the cooling effect. However, other control circuits such as a control circuit that do not generate heat that may cause a problem may be arranged in another place, and the motor drive The circuit device 2 is not arranged on one circuit board, but is arranged on several boards.

  According to the impact driver 50 configured as described above, when 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.

  During the screw tightening operation, the rotational force of the motor 3 transmitted from the rotary 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 mounting structure of the brushless motor 3 to the motor housing 50A according to the present invention will be described with reference to FIGS.

The brushless motor 3 includes a stator 12 having a cylindrical outer shape, and a rotor 13 disposed in an inner peripheral portion 12B of the stator 12 and embedded with four permanent magnet members 13A in the rotation axis direction. A slot 12D extending in the rotation axis direction is provided between the inner peripheral portion 12B and the outer peripheral portion 12C of the stator 12, and the insulating material 14 electrically insulated from the stator core rotates along the shape of the slot 12D. The stator 12 is mounted from both axial ends. A stator coil 12A is wound in a slot 12D in which the insulating material 14 is mounted. The stator coil 12A forms a star-connected three-phase coil, and its coil terminal is soldered to a wiring hole 2B provided on a drive control circuit board 2A which is one of a plurality of motor drive circuit devices 2 configured. Connected by. One side of the drive control circuit board 2A in the direction of the rotation axis 11 is attached in close contact with the outer diameter wall 14A of the insulating material 14, and the outer diameter wall 14A is used as a guide for positioning the drive control circuit board 2A. It is fixed to the insulating material 14 with screws 15. The Hall element 16 and other electronic components for detecting the position of the rotor 13 are provided on the rotor 13 side of the drive control circuit board 2A, and the upper part thereof is about 0.2MM so as to cover the Hall element 16 and other electronic components. Insulating material A18 is affixed with a double-sided tape. On the side opposite to the rotor 13 of the drive control circuit board 2A, six FETs 17 serving as switching elements for turning on and off the current flowing through the stator coil 12A are provided. A wiring pattern provided on the drive control circuit board 2A is provided. And electrically connected to the stator coil 12A. As the stator coil 12A is star-connected, the coil terminal for the neutral point of each of the three-phase coils of the stator 12 is electrically connected via the wiring pattern of the drive control circuit board 2A to form a neutral point. ing.
Next, the operation will be described. Since the six FETs 17 provided on the drive circuit board 2A are soldered to wiring holes provided on the drive circuit board 2A, the legs of the FETs 17 come out on the rotor 13 side of the drive circuit board 2A. The legs of the FET 17 become sharp because they are cut off with a nipper or the like, and protrude from the drive circuit board 2A. Since the insulating material A18 of about 0.2 MM is affixed with double-sided tape so as to cover the electronic parts such as the legs of the FET 17, the stator coil 12A is not damaged.

  In the present invention, a cloth material of about 0.2 MM is selected as the insulating material A because it is necessary to shorten the overall length of the electric tool as much as possible and to be a member that does not lose to the sharp protrusions. As the cloth material, for example, acetate cloth is suitable.

  By sticking the insulating material A18 on the drive circuit board 2A, it is possible to prevent foreign matters such as metal powder entering from the wind window from adhering to the electronic component. Therefore, the position of the magnet provided in the rotor core cannot be detected, and the motor can be prevented from causing a rotation failure. Therefore, an inexpensive and highly reliable power tool can be provided.

  By providing the insulating material A18 between the stator coil 12A and the drive circuit board 2A, the electronic components of the stator coil 12A and the drive circuit board 2A can be prevented from contacting each other. Therefore, it is possible to prevent the stator coil 12A and the electronic components on the drive circuit board 2A from being short-circuited to cause a rotation failure of the motor. Therefore, a highly reliable electric tool can be provided.

  The drive circuit board 2 </ b> A and the insulating material A <b> 18 are provided perpendicular to the axis of the rotor 13. The screw tightening operation is often performed with a tip tool such as a bit facing sideways or downward, and has a structure in which foreign matter such as iron powder is difficult to adhere to the drive circuit board 2A. Even if foreign matter such as iron powder adheres, the foreign matter is shaken off from the drive circuit board 2A by vibration during the operation of the electric power tool. In rare cases, even when working with a tip tool such as a bit facing upward, when the power tool is not used, the body is not placed upward, and the body is often placed upright as shown in FIG. The foreign matter falls down from the drive circuit board 2A. Therefore, it is possible to prevent the motor from causing a rotation failure. Therefore, a highly reliable electric tool can be provided.

  In the embodiment of the present invention, the cordless type impact driver is used as the power tool. However, the present invention can be similarly applied to other power tools.

The whole sectional view concerning the embodiment of the present invention. The partially expanded view of FIG. Sectional drawing which follows the AA line of the enlarged view shown in FIG. Sectional drawing which follows the BB line of the enlarged view shown in FIG. Sectional drawing which follows the CC line of the enlarged view shown in FIG. The fragmentary figure which concerns on embodiment of this invention.

Explanation of symbols

1 is a battery pack case, 2 is a motor drive circuit device, 2A is a drive control circuit board, 2B is a hole for wiring, 3 is a brushless motor, 4 is a power transmission mechanism, 5 is a spring, 6 is a planetary gear, 7 is a ring gear , 8 is a spindle, 9 is a hammer, 10 is an anvil, 10A is an anvil square hole,
10B is a tip tool mounting member, 11 is a rotating shaft, 12 is a stator, 12A is a stator coil, 12B is an inner periphery of the stator, 12C is an outer periphery of the stator, 12D is a stator slot, 13 is a rotor, and 13A is a permanent magnet. Members, 14 is an insulating material, 14A is an outer peripheral wall portion of the insulating material, 15 is a screw, 16 is a hall element, 17 is an FET, 18 is an insulating material A, 50 is an electric tool (impact driver), 50A is a motor housing portion, 50B is a power transmission housing part, 50C is a handle housing part, and 50D is a trigger switch.

Claims (2)

A brushless motor having a stator in which a stator coil is wound in a slot in which a first insulating material is mounted, a rotor having a rotating shaft and rotatably supported inside the stator and embedded with permanent magnets;
A circuit board having a switching element fixed to the first insulating material so as to be substantially orthogonal to the rotation shaft and opposed to the end of the brushless motor, and provided with a switching element on the anti-brushless motor side for driving and controlling the brushless motor When,
A housing for housing the brushless motor;
Have
A power tool characterized in that a Hall element for detecting the position of the rotor is provided on a surface of the circuit board facing the brushless motor and a second insulating material for covering the Hall element is provided. The circuit board has a switching element provided so that the legs penetrate from the opposite surface side of the brushless motor toward the opposite surface side,
The power tool of claim 1, wherein said second insulating material, characterized in that coating the foot exposed to the facing surface.

Images