JP4407392B2 - Impact tools - Google Patents

Description

  The present invention relates to an impact tool using a motor as a power source.

  In a power tool that uses a motor as a power source, when controlling the rotation speed of the motor, a rotation speed sensor that detects the rotation speed of the motor is provided, and as this rotation speed sensor, the rotation axis of the motor is arranged radially. A so-called frequency generator is used in which a magnet is provided and two yokes and coils are arranged on the outer periphery of the magnet with claw-shaped protrusions corresponding to the number of poles of the magnet.

  However, in such a rotational speed sensor, in an impact tool in which the rotational shaft of the motor itself vibrates in the axial direction, the magnet attached to the rotational shaft may be damaged by interference with the yoke.

In addition, the number of parts of the sensing side members such as yokes and coils is large, and it is difficult to reduce the size and weight.

  The present invention has been invented in view of the above-described conventional problems, and is capable of reliably detecting the rotational speed without being affected by the axial vibration of the rotating shaft of the motor, and is advantageous in reducing the size and weight. It is an object to provide a simple impact tool.

In order to solve the above-described problems, an impact tool according to the present invention includes a motor and an impact mechanism that generates impact impact from the rotation of the motor, and also includes a rotation speed sensor for detecting the motor rotation speed. in things, a magnet attached to a rotating shaft of the motor speed sensor is magnetized radially, Ri Do and a magnetically sensitive element disposed on the outer periphery of the magnet, the magnetic circuit of the magnet and the motor It is characterized in that a magnetic bearing for receiving the rotation shaft of the motor is located between them. The rotation axis itself of the motor is vibrated in the axial direction, Ru der that there is no such thing as a magnet and a magnetic sensitive element is interference. And since the magnetic bearing that receives the rotation axis of the motor is located between the magnet and the magnetic circuit part of the motor, the rotational speed can be detected without being influenced by the magnetic circuit part. The

  The magnetic sensitive element is sandwiched and fixed in a direction intersecting the axial direction of the motor rotation shaft by a housing that houses the motor, to prevent a decrease in rotational speed detection accuracy due to positional deviation or vibration of the magnetic sensitive element. Is preferable.

  The present invention does not cause interference between the magnet and the magnetically sensitive element even when the rotation shaft of the motor itself vibrates in the axial direction. For this reason, the present invention has high stability with respect to rotation speed detection and has a high frequency. Compared to the generator, the number of parts is small, which is advantageous for reducing the size and weight.

  Hereinafter, the present invention will be described based on embodiments shown in the accompanying drawings. The impact tool of the illustrated example has a motor 3 as a drive source, a speed reducer 4 for decelerating its output, and an impact mechanism section 5 in a main body 1 in which a battery pack 2 is detachably attached to the lower end of a grip section 10. A switch 12 having a trigger lever 11 is built in the base of the grip portion 10. In the figure, 6 is an output shaft, 13 is a display setting section for displaying the setting state and changing the rotation speed setting value, and 14 is a control circuit section.

  The motor 3 is of a built-in type having the housing of the main body 1 as a motor case, and one end side of the rotating shaft 31 is connected to the speed reducer 4, but the other end is radially formed as shown in FIG. A magnetized magnet 70 is attached. Further, a magnetic sensitive element 71 sandwiched and fixed by a housing that is divided into two parts of the main body 1 is disposed at the outer peripheral position of the magnet 70, and the rotational speed sensor 7 is constituted by the magnet 70 and the magnetic sensitive element 71. Has been.

  The switching of the magnetic field of the magnet 70 when the motor 3 rotates is output as a square wave from the magnetic sensing element 71, and the control circuit unit 14 calculates the rotation speed of the motor 3 by calculating the period of the square wave signal. Based on the detection result, the rotational speed of the motor 3 is controlled by, for example, PWM control driving of the switching element 15 to adjust the impact striking force. Reference numeral 72 in FIG. 3 denotes a lead wire that is led out from the magnetic detection element 71 (in the illustrated example, a Hall element) and connected to the control circuit unit 14.

  The magnetic sensitive element 71 is arranged on the outer periphery of the magnet 70, and even if the rotating shaft 31 itself of the motor 3 vibrates in the axial direction, the magnet 70 and the magnetic sensitive element 71 do not interfere with each other. Even if the position of 70 changes in the axial direction, the rotation speed detection is performed based on the switching of the magnetic field due to the rotation of the radially magnetized magnets 70, so that the rotation speed detection is not hindered. Further, since the magnetic sensitive element 71 is sandwiched in the direction intersecting the rotating shaft 31 by the housing of the main body 1 that is divided into two on the left and right, the magnetic sensitive element 71 may move in the horizontal direction due to the influence of vibration. For this reason, high rotational speed detection accuracy can be obtained.

  Here, the magnet 70 is attached to the end of the rotating shaft 31 of the motor 3 so that the bearing 30 is positioned between the magnetic circuit portion and the magnet 70 in the motor 3, as shown in FIG. This is because the lines of magnetic force of the magnetic circuit section pass through the bearing 30 made of a magnetic material so as not to affect the rotation speed sensor 7 side.

Of course, the rotational speed sensor 7 may be provided for any purpose. For example, impact impact may be detected by a change in the rotational speed, and the impact tightening force may be controlled by cutting off the power to the motor 3 when the number of impacts is counted a predetermined number of times and reaches a predetermined number. It may be provided only for displaying the number of rotations of 3.

It is a longitudinal cross-sectional view of an example of embodiment of this invention. It is a partial expanded longitudinal cross-sectional view same as the above. It is a cross-sectional view same as the above. It is a schematic diagram same as the above. It is a block diagram same as the above. It is explanatory drawing about the magnetic force line of a motor same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main body 3 Motor 5 Impact mechanism part 7 Rotation speed sensor 31 Rotating shaft 70 Magnet 71 Magnetic sensitive element

Claims (2)

In an impact tool that includes a motor and an impact mechanism that generates impact impact from the rotation of the motor and includes a rotation speed sensor for detecting the rotation speed of the motor, the rotation speed sensor is radially magnetized. a magnet attached to a rotating shaft of the motor, Ri Do and a magnetically sensitive element disposed on the outer periphery of the magnet, the magnetic body made of a bearing for receiving the rotary shaft of the motor between the magnetic circuit of the magnet and the motor Impact tool characterized in that is located . The magnetic sensitive element Impact Engineering tool according to claim 1, characterized in that it is clamped fixed in the direction orthogonal to the axial direction of the rotating shaft of the motor by a housing that contains the motor.

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