ELECTRIC ROTATING TOOL, CONTROL METHOD, AND PROGRAM

• US 20110000688A1
• Filed: 02/16/2009
• Published: 01/06/2011
• Est. Priority Date: 02/29/2008
• Status: Abandoned Application

• Current Assignee: Hitachi KOKI Company Limited (Koki Holdings Co., Ltd.)
• Original Assignee: Hitachi KOKI Company Limited (Koki Holdings Co., Ltd.)
• Inventors: Iwata, Kazutaka
• Application Number:
  US12/919,952
• Publication Number:
  US 20110000688A1
• Time in Patent Office: Days
• US Class Current: 173/1
• CPC Class Codes: B25B 21/00 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 Class Codes: B25B 23/147 specially adapted for electrically operated wrenches or screwdrivers
• CPC Class Codes: H02P 29/032 Preventing damage to the motor, e.g. setting individual current limits for different drive conditions

Abstract

Tightening torque is appropriately managed by a simple means. An electric rotating tool (40) has a brushless DC motor (2), an inverter circuit part (3), and a control circuit part (4). The control circuit part (4) has a current detecting circuit (18), which detects a motor current I, a rotation number detecting circuit (17), which detects the number of rotations of the motor (N), and a computing part (19), which calculates first tightening torque (T1) based on the detection information of the motor current (I) and calculates second tightening torque (T2) based on the number of rotations of the motor (N). The computing part (19) estimates tightening torque Tave based on the estimate value of the first tightening torque (T1) or the second tightening torque (T2). The computing part (19) stops driving the motor (2) when the estimated tightening torque Tave exceeds a set value Tset.

Claims

1. An electric rotating tool comprising:

an operating part;

a power source part;

a motor having a rotor and a stator coil;

an inverter circuit part which has a semiconductor switching element inserted between the power source part and the stator coil;

a current detection part which detects a drive current, which flows through the stator coil, and outputs a signal corresponding to a result of the detection;

a rotation number detection part which detects the number of rotations of the rotor and outputs a signal corresponding to a result of the detection;

a torque setting part which sets a target value of tightening torque;

a control part which generates and outputs a PWM signal for driving the semiconductor switching element of the inverter circuit part based on an operated degree of the operating part, the detection signal of the current detection part, and the detection signal of the rotation number detection part; and

a torque estimating part which estimates tightening torque based on at least either one of the drive current, which is detected by the current detection part, and the number of rotations, which is detected by the rotation number detection part;

wherein

the control part stops driving the motor when the estimated tightening torque exceeds the target value.

2. The electric rotating tool according to claim 1, characterized in that

the torque estimating part calculates first tightening torque based on the detected drive current,

calculates second tightening torque based on the detected number of rotations, and

calculates an estimate value of the tightening torque based on the first tightening torque and the second tightening torque.

3. The electric rotating tool according to claim 2, characterized in that

the torque estimating part calculates an average value of the first tightening torque and the second tightening torque as the estimate value of the tightening torque.

4. The electric rotating tool according to claim 1, characterized in that

the control part adjusts the current, which flows through the stator coil, and the rotation of the rotor by adjusting the PWM duty of the PWM signal.

5. The electric rotating tool according to claim 4, characterized in that

the control part adjusts the PWM duty while comparing the PWM duty with a set value of the PWM duty of the PWM signal corresponding to the target value of the tightening torque, which is set by the torque setting part.

6. The electric rotating tool according to claim 4, characterized in that

the control part controls the tightening torque by changing the magnitude of the PWM duty while comparing the PWM duty with a set value of the PWM duty corresponding to the target value of the tightening torque, which is set by the torque setting part.

7. The electric rotating tool according to claim 4, characterized in that

the control part changes the PWM duty of the PWM signal in accordance with an operated degree of the operating part.

8. The electric rotating tool according to claim 1, characterized in that

the electric rotating tool is a driver drill, a drill, an impact driver, a driver, or a disk grinder.

9. The electric rotating tool according to claim 1, characterized in that the battery pack has a secondary battery.

10. The electric rotating tool according to claim 1, characterized in that the battery pack has a lithium ion secondary battery.

11. A control method of an electric rotating tool comprising:

an operating part;

a power source part;

a motor having a rotor and a stator coil;

an inverter circuit part which has a semiconductor switching element inserted between the power source part and the stator coil; and

a control part which generates and outputs a PWM signal for driving the semiconductor switching element of the inverter circuit part;

the control method including;

a first step of setting a target value of tightening torque;

a second step of detecting a drive current which flows through the stator coil;

a third step of detecting the number of rotations of the rotor;

a fourth step of estimating tightening torque based on at least either one of the detected drive current and the detected number of rotations; and

a fifth step of causing the control part to stop driving the motor when the estimated tightening torque exceeds the target value.

12. A program which causes a computer to control an electric rotating tool comprising:

an operating part;

a power source part;

a motor having a rotor and a stator coil;

an inverter circuit part which has a semiconductor switching element inserted between the power source part and the stator coil; and

a control part which generates and outputs a PWM signal for driving the semiconductor switching element of the inverter circuit part;

wherein the program causes the computer to execute

a first procedure of setting a target value of tightening torque;

a second procedure of detecting the drive current which flows through the stator coil;

a third procedure of detecting the number of rotations of the rotor;

a fourth procedure of estimating tightening torque based on at least either one of the detected drive current and the detected number of rotations; and

a fifth procedure of causing the control part to stop driving the motor when the estimated tightening torque exceeds the target value.