Electric power tool

Patent metadata

Field	Value
Publication number	US-11235445-B2
Application number	US-201716487794-A
Country	US
Kind code	B2
Filing date	Nov 30, 2017
Priority date	Feb 24, 2017
Publication date	Feb 1, 2022
Grant date	Feb 1, 2022

Abstract

An electric power tool includes: a driving shaft that is rotated by a motor; an output shaft on which a front-end tool is attachable; and a torque transmission mechanism that transmits a torque produced by the rotation of the driving shaft to the output shaft. The torque transmission mechanism includes a magnet coupling including a driving magnet member coupled to a side of the driving shaft and a driven magnet member coupled to a side of the output shaft, and the driving magnet member and the driven magnet member are provided such that respective magnetic surfaces face each other, S-poles and N-poles being alternately arranged on each of the magnetic surfaces.

First claim

The invention claimed is:

1. An electric power tool comprising:
a driving shaft that is rotated by a motor;
an output shaft on which a front-end tool is attachable; and
a torque transmission mechanism that transmits a torque produced by the rotation of the driving shaft to the output shaft, wherein:
the torque transmission mechanism includes a magnet coupling including a driving magnet member coupled to a side of the driving shaft and a driven magnet member coupled to a side of the output shaft,
the driving magnet member and the driven magnet member are provided such that respective magnetic surfaces face each other, S-poles and N-poles being alternately arranged on each of the magnetic surfaces,
the magnet coupling has a function of applying an intermittent rotary impact force to the output shaft by losing synchronization, and
the driving magnet member is coupled to the driving shaft so as to be rotatable relative to the driving shaft.

2. The electric power tool according to claim 1 , wherein
S-pole magnets and N-pole magnets are alternately arranged on the magnetic surface of each of the driving magnet member and the driven magnet member.

3. The electric power tool according to claim 1 , wherein
an electromagnet is provided on the magnetic surface of at least one of the driving magnet member and the driven magnet member.

4. The electric power tool according to claim 3 , further comprising:
a control unit that controls a current supplied to the electromagnet, wherein
the control unit causes the magnet coupling to apply an intermittent rotary impact force to the output shaft by controlling the current supplied to the electromagnet.

5. The electric power tool according to claim 4 , further comprising:
a rotational angle sensor that senses a relative angle between the magnetic surface of the driving magnet member and the magnetic surface of the driven magnet member, wherein
the control unit controls the current supplied to the electromagnet in accordance with an output of the rotational angle sensor.

6. The electric power tool according to claim 5 , wherein
the control unit supplies the current to the electromagnet when the rotational angle sensor senses that the relative angle between the two magnetic surfaces is deviated from a relative angle that occurs in a synchronous state in a range more than ½ times and less than an angle of arrangement pitch of magnetic poles on the magnetic surface of the driving magnet member.

7. The electric power tool according to claim 1 , wherein:
the driving shaft has a groove formed in a circumferential direction of the outer circumference,
the driving magnet member has a ball retention part formed in the inner circumferential surface, and
a steel ball is retained in a space formed between the groove of the driving shaft and the ball retention part of the driving magnet member.

8. The electric power tool according to claim 1 , wherein
the magnet coupling applies the intermittent rotary impact force to the output shaft by changing a magnetic force exerted between the magnetic surface of the driving magnet member and the magnetic surface of the driven magnet member.

9. The electric power tool according to claim 1 , wherein
the magnet coupling loses synchronization when a load torque beyond a predetermined value is applied to the output shaft.

10. The electric power tool according to claim 1 , wherein
an angle through which a relative rotation of the driving magnet member and the driving shaft is possible is substantially equal to an angle of arrangement pitch of magnetic poles on the magnetic surface of the driving magnet member.

11. The electric power tool according to claim 1 , wherein
an angle through which a relative rotation of the driving magnet member and the driving shaft is possible is smaller than an angle of arrangement pitch of magnetic poles on the magnetic surface of the driving magnet member.

12. The electric power tool according to claim 1 , wherein
an angle through which a relative rotation of the driving magnet member and the driving shaft is possible is larger than an angle of arrangement pitch of magnetic poles on the magnetic surface of the driving magnet member.

13. The electric power tool according to claim 1 , wherein
the driving magnet member is coupled to the driving shaft via a steel ball provided in a groove formed in the driving shaft in a circumferential direction.

14. The electric power tool according to claim 1 , further comprising:
a moving mechanism that changes relative positions of the magnetic surface of the driving magnet member and the magnetic surface of the driven magnet member in the magnet coupling.

15. The electric power tool according to claim 14 , wherein
the moving mechanism changes relative axial positions of the driving magnet member and the driven magnet member.

Assignees

• Panasonic Ip Man Co Ltd

Inventors

• Murui Itaru
• Murakami Hiroaki
• Mizuno Mitsumasa
• Honda Akiko
• Kajiyama Satoshi

Classifications

• B25D17/11

  Arrangements of noise-damping means {(noise damping in general G10K11/16)} · CPC title

• B25B21/02 Primary

  with means for imparting impact to screwdriver blade or nut socket · CPC title

• B25D17/00

  Details of, or accessories for, portable power-driven percussive tools {(details or components, e.g. casings, bodies, of portable power-driven tools not particularly related to the operation performed B25F5/00)} · CPC title

• B25D16/00 Primary

  Portable percussive machines with superimposed rotation {, the rotational movement of the output shaft of a motor being modified to generate axial impacts on the tool bit (combined percussion and rotary drilling adapted for earth drilling E21B6/00)} · CPC title

• B25B21/026 Primary

  Impact clutches · CPC title