Electric power tool

Patent metadata

Field	Value
Publication number	US-10549396-B2
Application number	US-201414292813-A
Country	US
Kind code	B2
Filing date	May 30, 2014
Priority date	May 31, 2013
Publication date	Feb 4, 2020
Grant date	Feb 4, 2020

Abstract

An object of the present invention is to provide an electric power tool capable of automatically changing the rotating speed of an electric motor in accordance with operation conditions. The electric power tool 11 which carries out an operation of polishing, peel-off, cutting, or the like by swinging a tip tool 13 attached to a tool retaining 31 part within the range of predetermined angles by the drive power of the electric motor 12, wherein the electric power tool has a control device configured to indirectly detect the load of the tip tool from a current value, and to control the rotating speed of the electric motor 12 to a maximum rotating speed and a minimum rotating speed on the basis of the load of the tip tool 13.

First claim

What is claimed is:

1. An electric power tool comprising:
an electric motor;
a control part configured to control a rotating speed of the electric motor; and
a rotating speed detecting circuit connected to the control part, and configured to detect a rotating speed of the electric motor, wherein
the control part has an automatic mode in which the control part controls the rotating speed of the electric motor on the basis of a load judge value and a no-load judge value,
when the control part is in the automatic mode, and the electric motor is at least in a no-load state, the control part carries out a feedback control so that the rotating speed of the electric motor approaches a no-load rotating speed, by controlling a control value that is changing a voltage supplying to the motor,
the control part is configured to set the load judge value to be smaller than the no-load judge value,
the control part controls the electric motor so that the electric motor is rotated at a no-load rotating speed when the control value of the electric motor is smaller than the no-load judge value, and the control part controls the electric motor so that the electric motor is rotated at a load rotating speed that is larger than the no-load rotating speed when the control value of the electric motor is larger than the load judge value.

2. The electric power tool according to claim 1 , further comprising a speed changing part operable by a user,
wherein the control part is configured to change the load rotating speed by operation of the speed changing part.

3. The electric power tool according to claim 2 ,
wherein the control part is configured to change the no-load rotating speed by operation of the speed changing part.

4. The electric power tool according to claim 2 , further comprising a display part configured to display at least one of the load rotating speed and the no-load rotating speed.

5. The electric power tool according to claim 2 , further comprising an operating piece which is operated to supply the current to the electric motor, wherein the speed changing part and the operating piece are operable separately.

6. The electric power tool according to claim 1 , wherein
the control part is configured to control the electric motor at the load rotating speed for a predetermined period of time when starting to rotate the electric motor.

7. The electric power tool according to claim 1 , wherein
the electric motor is configured to drive a tip tool,
the control part is configured to change the load rotating speed on the basis of the type of tip tool.

8. The electric power tool according to claim 1 , wherein
the control part is configured to turn on and off a switching element to control a voltage applied to the electric motor,
the control value corresponds to an on-time of the switching element.

9. The electric power tool according to claim 1 , wherein
the control part has a stationary mode in which the control part controls the rotating speed of the electric motor so as to hold the rotating speed constant, without being affected by a load applied to the electric motor.

10. The electric power tool according to claim 9 , further comprising a mode switch which is operated by an operator so as to switch the control part between the stationary mode and the automatic mode.

11. The electric power tool according to claim 1 ,
wherein the control part is configured to perform a conduction angle control,
wherein the control value is a conduction angle.

12. The electric power tool according to claim 1 , further comprising an inverter circuit having a plurality of switching elements,
wherein the motor is a brushless motor which is controlled by the inverter circuit,
wherein the control value is a duty ratio of the switching elements.

13. An electric power tool comprising:
an electric motor;
a control part configured to control a rotating speed of the electric motor by controlling a control value that is changing a voltage supplying to the motor; and
a rotating speed detecting circuit connected to the control part, and configured to detect a rotating speed of the electric motor, wherein
the control part has an automatic mode in which the control part changes the rotating speed of the electric motor on the basis of a load judge value and a no-load judge value,
wherein the control unit is configured to perform in the automatic mode that:
drives the electric motor so that the rotating speed of the electric motor approaches a no-load rotating speed in a no-load state by controlling the control value,
drives the electric motor so that the rotating speed of the electric motor approaches a load rotating speed that is larger than the no-load rotating speed in a load state by controlling the control value,
increasing the control value and drives the electric motor at the load rotating speed when the control value changed by the control unit in accordance with increasing in a load on the electric motor exceeds the load judge value in the no-load state,
reducing the control value and drives the electric motor at the no-load rotating speed, when the control value changed by the control unit in accordance with decreasing in the load on the electric motor becomes smaller than the no-load judge value in the no-load state, and
wherein the no-load judge value is larger than the load judge value.

Assignees

• Hitachi Koki Kk
• Koki Holdings Co Ltd

Inventors

• Matsunaga Kenichi
• Kawano Yoshikazu

Classifications

• B25F5/00 Primary

  Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for · CPC title

• B23Q15/0075 Primary

  Controlling reciprocating movement, e.g. for planing-machine · CPC title

• H02P7/245

  whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value · CPC title

• B23Q5/027

  reciprocating members · CPC title