Power tool

Patent metadata

Field	Value
Publication number	US-9731410-B2
Application number	US-201113989918-A
Country	US
Kind code	B2
Filing date	Nov 28, 2011
Priority date	Dec 2, 2010
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

To provide a hand-held power tool which is equipped with a motor and can be used in a normal driving mode for a tip end tool and also in driving modes other than the normal driving mode. A power tool in which a tip end tool is driven by a motor to thereby perform a predetermined machining process on a workpiece, wherein the motor is a dual rotor motor comprising: an inner rotor; an outer rotor; and a stator including a driving coil mechanism, with the inner rotor and the outer rotor being coaxially disposed.

First claim

The invention claimed is:

1. A power tool which performs a predetermined operation on a workpiece with a tool bit driven by a motor, wherein:
the motor comprises an inner rotor, an outer rotor and a stator having a driving coil mechanism and is configured as a dual rotor motor in which the inner rotor and the outer rotor are coaxially arranged,
the tool bit is driven by using one of the inner rotor and the outer rotor, and a rotatable fan is driven by using the other rotor, and
the inner and outer rotors both provide a drive toward the tool bit.

2. The power tool as defined in claim 1 , wherein the stator comprises a single member.

3. The power tool as defined in claim 2 , wherein the driving coil mechanism includes an inner rotor driving coil for driving the inner rotor and an outer rotor driving coil for driving the outer rotor.

4. The power tool as defined in claim 2 , wherein the driving coil mechanism comprises one driving coil for driving both the inner rotor and the outer rotor.

5. The power tool as defined in claim 1 , wherein the stator includes a first stator having an inner rotor driving coil for driving the inner rotor and a second stator having an outer rotor driving coil for driving the outer rotor.

6. The power tool as defined in claim 5 , comprising a housing for housing the dual rotor motor, wherein the inner motor includes the inner rotor and the first stator and the outer motor includes the outer rotor and the second stator, and wherein the inner motor and the outer motor are arranged in the housing at positions displaced from each other in the longitudinal direction, and a space is formed between an outer circumferential region of the inner motor and the housing.

7. The power tool as defined in claim 6 , wherein the outer circumferential region of the first stator of the inner motor is fixedly supported with respect to the housing directly or via a supporting member in the space.

8. The power tool as defined in claim 6 , wherein the first and second stators are partly aligned in contact with each other in a radial direction transverse to the longitudinal direction and connected together in the aligned region.

9. The power tool as defined in claim 8 , wherein the first and second stators are connected together by a pin in the aligned region.

10. The power tool as defined in claim 8 , wherein the first and second stators are connected together by a resin layer in the aligned region.

11. The power tool as defined in claim 6 , wherein the outer motor is configured as an axial gap motor in which the outer rotor and the second stator are opposed to each other in the longitudinal direction.

12. The power tool as defined in claim 11 , wherein the first and second stators are partly aligned in the longitudinal direction and connected together in the aligned region.

13. The power tool as defined in claim 12 , wherein the outer circumferential region of the second stator of the outer motor is fixedly supported by the housing.

14. The power tool as defined in claim 1 , wherein the tool bit is driven by using both the inner rotor and the outer rotor.

15. The power tool as defined in claim 14 , comprising a speed reducing mechanism, wherein the dual rotor motor drives the tool bit via the speed reducing mechanism, and the speed reducing mechanism has at least first and second speed reduction ratios and switches at least one of the inner and outer rotors between a driven state and a stopped state to thereby switch between the first and second speed reduction ratios.

16. The power tool as defined in claim 15 , wherein the switching between the speed reduction ratios is made according to any one of an electric current value, torque, rotation speed and temperature of the dual rotor motor.

17. The power tool as defined in claim 15 , wherein the output torque to be outputted to the tool bit is changed by the switching between the first and second speed reduction ratios.

18. The power tool as defined in claim 17 , wherein the output torque of the tool bit is intermittently changed by continuously driving one of the inner rotor and the outer rotor and intermittently driving the other rotor.

19. The power tool as defined in claim 15 , wherein the rotation speed of the tool bit is changed by the switching between the first and second speed reduction ratios.

20. The power tool as defined in claim 15 , wherein:
the speed reducing mechanism comprises a planetary gear mechanism,
the planetary gear mechanism includes a sun gear and an internal gear which are coaxially arranged and a planetary gear which engages with both the sun gear and the internal gear and revolves around the sun gear,
the internal gear is connected to the outer rotor and the sun gear is connected to the inner rotor,
a difference of relative rotation between the sun gear and the internal gear is controlled by control of drive of the outer rotor or the inner rotor, whereby the revolution speed of the planetary gear is changed to switch the speed reduction ratio.

21. The power tool as defined in claim 20 , wherein the inner rotor is constantly driven.

22. The power tool as defined in claim 20 , wherein the outer rotor is constantly driven.

23. The power tool as defined in claim 20 , comprising a clutch which is disposed between the outer rotor and the internal gear or between the inner rotor and the sun gear and transmits torque from the outer rotor and the internal gear side to the tool bit side, but not in the reverse direction, wherein the clutch locks the internal gear or the sun gear against rotation according to torque on the tool bit and independently of rotation of the outer rotor or the inner rotor.

24. The power tool as defined in claim 1 , wherein the outer rotor has an extending region formed on one end of the outer rotor in the longitudinal direction and extending forward of front ends of the stator and the inner rotor in the longitudinal direction, and wherein the fan is disposed inside of the extending region of the outer rotor.

25. The power tool as defined in claim 1 , wherein the fan is a cooling fan for cooling the dual rotor motor and is constantly driven.

26. The power tool as defined in claim 1 , wherein the fan is a cooling fan for cooling the dual rotor motor and is intermittently driven according to at least one of the temperature, rotation speed and torque of the dual rotor motor.

27. The power tool as defined in claim 1 , wherein the fan is a dust collecting fan for collecting dust generated during operation and driven upon request for dust collection.

28. A power tool which performs a predetermined operation on a workpiece with a tool bit driven by a motor, wherein:
the motor comprises an inner rotor, an outer rotor and a stator having a driving coil mechanism and is configured as a dual rotor motor in which the inner rotor and the outer rotor are coaxially arranges, and
the outer rotor has an extending region formed on one end of the outer rotor in the longitudinal direction and extending forward of front ends of the stator and the inner rotor in the longitudinal direction, and wherein a fan is disposed inside of the extending region of the outer rotor.

29. The power tool as defined in claim 28 , wherein the fan is disposed completely inside of the extending region of the outer rotor.

Assignees

• Hirabayashi Shinji
• Ota Kenichi
• Makita Corp

Inventors

• Hirabayashi Shinji
• Ota Kenichi

Classifications

• B25F5/001 Primary

  Gearings, speed selectors, clutches or the like specially adapted for rotary tools · CPC title

• B25F5/008

  Cooling means · CPC title

• B25B23/00

  Details of, or accessories for, spanners, wrenches, screwdrivers (bolt tensioners B25B29/02) · CPC title

• H02K16/00

  Machines with more than one rotor or stator {(machines for transmitting mechanical power from a driving shaft to a driven shaft and comprising structurally interrelated motor and generator parts H02K51/00; permanent magnet machines with multiple rotors or stators relatively rotated for vectorially combining the excitation fields or the armature voltages H02K21/029)} · CPC title

• B25B21/00

  Portable power-driven screw or nut setting or loosening tools; (details or components, e.g. casings, bodies, of portable power-driven tools not particularly related to the operation performed B25F5/00; {for mounting or dismounting wheels B60B29/006}); Attachments for drilling apparatus serving the same purpose (machines B23P19/06) · CPC title