JP7194903B2 - Electric tool - Google Patents

Description

The present invention relates to an electric power tool having a rotation detector that detects the rotation angle of a motor.

2. Description of the Related Art Hand-held electric power tools used for drilling and fastening screws often use built-in motors in order to reduce the size and weight (for example, Patent Documents 1 to 3). A built-in type motor is constructed by directly assembling components of the motor to rib members projecting from the inner peripheral surface of a housing.

JP 2007-136607 A Japanese Unexamined Patent Application Publication No. 2006-972 JP 2012-71360 A

Electric power tools such as impact rotary tools are controlled to estimate tightening torque from the rotation angle of the motor. In order to increase the accuracy of tightening torque estimation, it is necessary to equip the power tool with a rotation detector that detects the rotation angle of the motor with high accuracy. Therefore, there is a great demand for miniaturization of the rotation detector.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technology that contributes to miniaturization of a rotation detector that detects the rotation angle of a motor.

In order to solve the above problems, an electric power tool according to one aspect of the present invention includes a motor, a transmission mechanism for transmitting rotational output of the motor to a tip tool, a magnetic rotation detector for detecting the rotation angle of the motor, wherein the rotation detector has a rotor having a magnet attached to the motor shaft of the motor, and a position detector that outputs a rotational position signal corresponding to the rotational position of the rotor. At least one of the rotating body and the position detection section has a back yoke structure.

ADVANTAGE OF THE INVENTION According to this invention, the technique which contributes to size reduction of the rotation detection part which detects the rotation angle of a motor can be provided.

1 is a schematic diagram of a partial cross section of an electric power tool according to an embodiment; FIG. It is a figure which shows the cross section of a rotating body and a motor shaft.

FIG. 1 shows a partial cross-sectional schematic diagram of an electric power tool according to an embodiment of the present invention. The power tool 1 has a housing 2 in which a motor unit 4 is installed. The motor unit 4 is configured as a built-in motor that functions by assembling a stator and a rotor that is integrated with the motor shaft 9 into the housing 2, and contributes to miniaturization and weight reduction of the power tool 1 by not having a motor case. do. Hereinafter, the motor shaft 9 on the front side of the motor unit 4 will be called "motor shaft 9a", and the motor shaft 9 on the rear side will be called "motor shaft 9b". A cooling fan 3, which is a centrifugal fan, is fixed to the motor shaft 9a.

The drive block 5 has a transmission mechanism that transmits the rotational output of the motor to the tip tool. Specifically, the drive block 5 has a power transmission mechanism that transmits the rotational output of the motor shaft 9a to the output shaft 6, and the power transmission mechanism has a planetary gear reduction mechanism that meshes with a pinion gear attached to the motor shaft 9a. good. When the power tool 1 is an impact rotary tool, the power transmission mechanism includes an impact mechanism that intermittently generates an impact force of rotation on the output shaft 6 . A chuck mechanism 7 is connected to the output shaft 6 so that a tip tool such as a drill or a driver can be attached and detached. A grip portion of the housing 2 is provided with an operation switch 8 operated by an operator. When the operator pulls the operation switch 8, the rotor in the motor unit 4 rotates and the output shaft 6 drives the tool bit.

The motor unit 4 is an inner rotor type brushless motor, and a rotor having a plurality of permanent magnets rotates inside a stator. A rotor and a stator, which are components of the motor unit 4, are fixed to the housing 2 independently of each other. The housing 2 is composed of a pair of (left and right) half-split housing members that are bisected by a vertical plane crossing the center of the rotation axis of the power tool 1 . The motor unit 4 is assembled to the housing 2 by incorporating the first bearing 10a and the second bearing 10b of the stator and the motor shaft 9 into one housing member, overlapping the other housing member, and screwing the pair of housing members together. It is done by joining with tightening or the like.

A magnetic rotation detector 12 is provided behind the motor unit 4 to detect the rotation angle of the motor. The rotation detector 12 has a rotor 20 attached to the motor shaft 9 b and a position detector 30 that outputs a rotational position signal corresponding to the rotational position of the rotor 20 . The rotor 20 has magnets 26 .

The rotation detector 12 is configured as a magnetic encoder, and the rotating body 20 includes a fixing bush 27 for fixing the magnet 26 . The position detection unit 30 is provided on the sensor substrate and includes a magnetic sensor that detects changes in magnetic force. The fixing bush 27 holds the magnet 26 so as to face the position detection section 30 . In order to increase the detection accuracy of the motor rotation angle, the gap between the rotor 20 and the position detector 30 is set narrow, for example, about 2 mm. The position detection unit 30 outputs a rotational position signal corresponding to the rotational position of the rotor 20 to a control unit (not shown) that controls motor rotation.

The position detector 30 is fixed to the stator side of the motor unit 4 by the support member 14 . By fixing the rotating body 20 to the motor shaft 9b and fixing the position detecting section 30 to the motor unit 4, the assembly accuracy of the rotating body 20 and the position detecting section 30 can be improved. The interval of the portion 30 can be set to a predetermined value with high accuracy. Moreover, compared with the case where the position detection section 30 is fixed to the housing 2 , by fixing the position detection section 30 to the motor unit 4 , the deformation of the housing 2 is affected by the relative positions of the rotor 20 and the position detection section 30 . It is possible to realize the highly reliable rotation detection unit 12 that is not easily affected by .

In the power tool 1 of the embodiment, at least one of the rotating body 20 and the position detection section 30 has a back yoke structure. Since the rotation detector 12 has the back yoke structure, the magnetic force between the rotor 20 and the position detector 30 can be increased, and the size of the magnet 26 can be reduced.

In order to provide the position detection section 30 with a back yoke structure, a magnetic body 31 as a back yoke is arranged on the back side of the surface of the position detection section 30 facing the rotor 20 . By arranging the magnetic body 31 on the back surface of the position detection section 30, the magnetic force between the rotating body 20 and the position detection section 30 can be increased, and the size of the magnet 26 can be reduced.

FIG. 2 shows a section of the rotating body 20 and the motor shaft 9b. The rotating body 20 has an opening 21 , and the motor shaft 9 b of the embodiment is press-fitted into the opening 21 of the rotating body 20 . The motor shaft 9b and the rotating body 20 may be fixed by screwing.

The magnet fixing surface of the fixing bushing 27 is formed with a recess into which one end face side of the magnet 26 is fitted, and the magnet 26 is fitted into and fixed to the recess. It is preferable that the magnet 26 has a shape that fits into the concave portion of the fixing bush 27 so as to be non-rotatable relative to the concave portion. A magnet 26 is fixed in the recess with an adhesive.

In order to provide the rotating body 20 with a back yoke structure, the fixing bush 27 may be made of a magnetic material and function as a back yoke. Alternatively, the motor shaft 9b, which is a magnetic body, may be brought into contact with the magnet 26 so that the motor shaft 9b functions as a back yoke. In the rotor 20, either one of the fixing bush 27 and the motor shaft 9b may function as the back yoke, or both may function as the back yoke. Thereby, miniaturization of the magnet 26 can be realized.

The rotation detector 12 may be surrounded by a magnetic shield made of a magnetic material. As a result, the rotation detector 12 is less likely to be affected by an external magnetic field, and the detection accuracy of the motor rotation angle can be improved. As shown in FIG. 1, the position detection section 30 is fixed to the stator side of the motor unit 4 by the support member 14. The support member 14 is made of a magnetic material so as to surround the rotation detection section 12. , the support member 14 surrounding the rotation detector 12 can function as a magnetic shield. The magnetic shield surrounding the rotation detector 12 may be formed by rib members projecting from the housing 2 .

The present invention has been described above based on the embodiments. It should be understood by those skilled in the art that this embodiment is an example, and that various modifications can be made to the combination of each component or each treatment process, and such modifications are also within the scope of the present invention. .

A summary of aspects of the invention follows.
An electric power tool (1) according to one aspect of the present invention comprises a motor (4), a transmission mechanism (5) for transmitting rotational output of the motor to a tip tool, and a rotation detector (12) for detecting the rotation angle of the motor. Prepare. The rotation detector (12) includes a rotating body (20) having a magnet (26) attached to the motor shaft (9b) of the motor, and a position detecting section (which outputs a rotational position signal corresponding to the rotational position of the rotating body). 30). At least one of the rotor (20) and the position detector (30) preferably has a back yoke structure.

The rotating body (20) has a fixing bush (27) for fixing the magnet (26), and the fixing bush is preferably made of a magnetic material. A magnetic body (31), which is a back yoke, is preferably arranged on the back side of the surface of the position detection section (30) facing the rotating body (20). A magnet (26) of the rotating body (20) may contact the motor shaft (9b). The rotation detector (30) is preferably surrounded by a magnetic shield made of a magnetic material. The position detector (30) may be fixed relative to the motor (4).

DESCRIPTION OF SYMBOLS 1... Electric tool, 2... Housing, 4... Motor unit, 5... Drive block, 6... Output shaft, 9a, 9b... Motor shaft, 10a... First bearing , 10b... second bearing, 12... rotation detector, 20... rotor, 26... magnet, 27... fixing bush, 30... position detector, 31... magnetic material.

Claims (5)

a motor unit configured as a built-in motor that functions by assembling a stator and a rotor integrated with a motor shaft into a housing ;
a transmission mechanism for transmitting the rotational output of the motor unit to the tip tool;
and a magnetic rotation detector that detects the rotation angle of the motor unit ,
The rotation detection section has a rotating body having a magnet attached to a motor shaft on the rear side of the motor unit , and a position detecting section that outputs a rotational position signal corresponding to the rotational position of the rotating body,
The rotating body has a fixing bush for fixing the magnet. The fixing bush is made of a magnetic material and attached to the motor shaft . It has a back yoke structure that makes the bush function as a back yoke,
The position detection unit is fixed to the stator side of the motor unit by a support member extending from the motor unit without interposing the housing.
A power tool characterized by: The position detection unit is provided at a position facing the magnet of the rotating body in the axial direction,
the magnet of the rotating body abuts the end of the motor shaft;
The power tool according to claim 1, characterized in that: A magnetic body functioning as a back yoke is arranged on the back side of the surface of the position detection unit facing the rotating body.
The power tool according to claim 1 or 2 , characterized in that: the rotation detection unit is surrounded by a magnetic shield made of a magnetic material;
The power tool according to any one of claims 1 to 3 , characterized in that: the magnet contacts the motor shaft positioned in front of the magnet;
The power tool according to any one of claims 1 to 4, characterized in that:

Images