ELECTRIC POWER TOOL

• US 20140352995A1
• Filed: 05/30/2014
• Published: 12/04/2014
• Est. Priority Date: 05/31/2013
• Status: Active Grant

• Current Assignee: Koki Holdings Co., Ltd.
• Original Assignee: Hitachi KOKI Company Limited (Koki Holdings Co., Ltd.)
• Inventors: MATSUNAGA, Kenichi, KAWANO, Yoshikazu
• Granted Patent: US 10,549,396 B2
• Time in Patent Office: Days
• US Class Current: 173/179
• CPC Class Codes: B23Q 15/0075 Controlling reciprocating movement, e.g. for planing-machine
• CPC Class Codes: B23Q 5/027 reciprocating members
• CPC Class Codes: B25F 5/00 Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
• CPC Class Codes: H02P 7/245 whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value

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 part 31 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.

Claims

1. An electric power tool comprising:

an electric motor configured to reciprocate a tip tool within a range of a predetermined angle; and

a control part configured to detect a load of the tip tool, and to control a rotating speed of the electric motor on the basis of the detection result of the load.

2. The electric power tool according to claim 1, wherein the load of the tip tool is a current value of the electric motor.

3. The electric power tool according to claim 1, wherein the control part is configured to set a maximum rotating speed and a minimum rotating speed of the tip tool on the basis of the load of the tip tool.

4. The electric power tool according to claim 3, wherein the control part includes a control switch configured to judge whether or not to switch between the maximum rotating speed and the minimum rotating speed.

5. The electric power tool according to claim 3, wherein the control part is configured to control the electric motor at the maximum rotating speed for a predetermined period of time after the electric motor starts rotating.

6. The electric power tool according to claim 3, wherein the control part is capable to separately set the maximum rotating speed and the minimum rotating speed.

7. The electric power tool according to claim 3, comprising a display part configured to display at least one of the maximum rotating speed and the minimum rotating speed.

8. An electric power tool comprising:

an electric motor configured to drive a tip tool selected from among various tip tools and attached to a tool attaching part, the tip tool being detachable from the tool attaching part;

a switching element configured to control a voltage applied to the electric motor on the basis of a control signal;

a rotating speed detecting part configured to detect a rotating speed of the electric motor; and

a control part configured to generate the control signal so that the rotating speed of the electric motor becomes equal to a first rotating speed when a control value as the control signal is larger than a load judge reference value, and configured to generate the control signal so that the rotating speed of the electric motor becomes equal to a second rotating speed lower than the first rotating speed when the control value is smaller than a no-load judge reference value.

9. The electric power tool according to claim 8, wherein the control value as the control signal is any one or more of a conduction angle, a duty ratio of the switching element, and a current value of the electric motor.

10. An electric power tool comprising:

a switching element configured to control an alternating-current voltage applied to an electric motor by a conduction angle on the basis of a control signal;

a rotating speed detecting part configured to detect a rotating speed of the electric motor; and

a control part configured to generate the control signal on the basis of the rotating speed of the electric motor detected by the rotating speed detecting part, and to output the control signal to the switching element, wherein

when the conduction angle of the switching element is larger than a load judge reference value, the control part judges that the electric motor is in a load state, and generates the control signal so that the rotating speed of the electric motor becomes equal to a first rotating speed set by a setting signal; and

when the conduction angle of the switching element becomes smaller than a no-load judge reference value, the control part judges that the electric motor is in a no-load state, and generates the control signal so that the rotating speed of the electric motor becomes equal to a second rotating speed lower than the first rotating speed set by the setting signal.

11. The electric power tool according to claim 10, wherein the control part detects, as an initial conduction angle, the conduction angle of the switching element after the electric motor starts, sets a value obtained by adding a load judge conduction angle to the initial conduction angle as the load judge reference value, and sets a value obtained by adding a no-load judge conduction angle to the initial conduction angle as the no-load judge reference value.

12. The electric power tool according to claim 11, wherein

when the initial conduction angle of the switching element is detected, the control part controls the electric motor so that the rotating speed of the electric motor becomes equal to the second rotating speed.

13. The electric power tool according to claim 10, wherein

the control part has a memory unit which has stored therein the set load judge reference value and the no-load judge reference value as a first judge reference table, and

when the rotating speed of the electric motor set by the setting signal has a plurality of rotating speeds, the control part sets the load judge reference value and the no-load judge reference value for each of the rotating speeds of the electric motor set by the setting signal, and stores the values in the first judge reference table.

14. An electric power tool comprising:

an electric motor configured to drive a tip tool selected from among various tip tools and attached to a tool attaching part, the tip tool being detachable from the tool attaching part;

a switching element configured to control a voltage applied to the electric motor on the basis of a control signal;

a control part configured to generate and output the control signal to the switching element; and

a current detecting part configured to detect a current flowing to the electric motor, and to output a current value indicative of the detected current to the control part;

wherein

when the current value indicative of the current flowing to the electric motor is larger than a current load judge reference value, the control part judges that the electric motor is in a load state, and generates the control signal so that the rotating speed of the electric motor becomes equal to a first rotating speed set by a setting signal; and

when the current flowing to the electric motor becomes smaller than a current no-load judge reference value, the control part judges that the electric motor is in a no-load state, and generates the control signal so that the rotating speed of the electric motor becomes equal to a second rotating speed lower than the first rotating speed set by the setting signal.

15. The electric power tool according to claim 14, wherein

the control part is configured to execute a process of detecting an initial current flowing to the electric motor, and setting a value obtained by adding a load judge current value to a value indicative of the initial current as the current load judge reference value, and

a process of setting a value obtained by adding a no-load judge current value to a value indicative of the initial current as the current no-load judge reference value.

16. The electric power tool according to claim 15, wherein,

when the initial current flowing to the electric motor is detected, the control part controls so that the rotating speed of the electric motor becomes equal to the second rotating speed.

17. The electric power tool according to claim 14, wherein

the control part has a memory unit which has stored therein the set current load judge reference value and the current no-load judge reference value as a second judge reference table;

and

when the rotating speed of the electric motor set by the setting signal has a plurality of rotating speeds, the control part sets the current load judge reference value and the current no-load judge reference value for each of the rotating speeds of the electric motor set by the setting signal, and stores the set current load judge reference value and the current no-load judge reference value in the second judge reference table.

18. An electric power tool comprising:

a switching element configured to control a voltage applied to an electric motor by a conduction angle on the basis of a control signal;

a rotating speed detecting part configured to detect a rotating speed of the electric motor; and

a control part configured to generate the control signal on the basis of the rotating speed of the electric motor detected by the rotating speed detecting part, and to output the control signal to the switching element;

wherein

the control part detects an initial conduction angle of the switching element, judges that the electric motor is in a load state when the conduction angle of the switching element is increased from the initial conduction angle, and sets the rotating speed of the electric motor on the basis of the initial conduction angle and the increased conduction angle.

19. The electric power tool according to claim 18, wherein

the control part has a load rotating speed table in which the rotating speed of the electric motor is set on the basis of the initial conduction angle and the increased conduction angle;

and

when the judgment is made that the electric motor is in the load state, the control part sets the rotating speed of the electric motor with reference to the load rotating speed table.

20. The electric power tool according to claim 19, wherein,

when the initial conduction angle is detected, the control part carries out a control operation so that the rotating speed of the electric motor becomes equal to a rotating speed lower than the rotating speed set in the load rotating speed table.

21. The electric power tool according to claim 20, wherein,

when the conduction angle of the switching element becomes smaller than the no-load judge reference value, the control part judges that the electric motor is in the no-load state, and carries out a control operation so that the rotating speed of the electric motor becomes equal to the rotating speed set when the initial conduction angle is detected.

22. The electric power tool according to claim 21, wherein

the control part has a third judge reference table having the no-load judge reference value corresponding to the rotating speed of the electric motor, and judges that the electric motor is in the no-load state with reference to the third judge reference table.

23. The electric power tool according to claim 22, wherein the control part is configured to set a value obtained by adding a no-load judge conduction angle to the detected initial conduction angle in the third judge reference table as the no-load judge reference value.

24. An electric power tool comprising:

a switching element configured to control a voltage applied to an electric motor on the basis of a control signal;

a rotating speed detecting part configured to detect a rotating speed of the electric motor;

a current detecting part configured to detect a current flowing to the electric motor; and

a control part configured to generate the control signal on the basis of the rotating speed of the electric motor detected by the rotating speed detecting part, and to output the control signal to the switching element;

wherein

the control part detects an initial current flowing to the electric motor, judges that the electric motor is in a load state when the current flowing to the electric motor is increased from the initial current value, and sets the rotating speed of the electric motor on the basis of the initial current value and the increased current value.