Portable drilling device

• US 7,936,142 B2
• Filed: 12/13/2006
• Issued: 05/03/2011
• Est. Priority Date: 12/26/2005
• Status: Active Grant

• Current Assignee: Nitto Kohki Company Limited
• Original Assignee: Nitto Kohki Company Limited
• Inventors: Otsuka, Kenji, Asano, Osamu
• Primary Examiner(s): Duda; Rina I
• Application Number:
  US12/159,174
• Publication Number:
  US 20090196696A1
• Time in Patent Office: 1,602 Days
• Field of Search: 388/937, 388/800, 388/804, 388/806, 388/811, 388/815, 388/819, 318/432, 318/811, 318/599, 318/461, 173/5, 173/7, 173/180, 173/181, 173/176, 173/179
• US Class Current: 318/599
• CPC Class Codes: B23B 2260/062 Electric motors
• CPC Class Codes: B23B 2260/122 Safety devices
• CPC Class Codes: B23B 2270/32 Use of electronics
• CPC Class Codes: B23B 45/02 driven by electric power
• CPC Class Codes: B25H 1/0071 by magnetic means
• CPC Class Codes: G05B 19/4062 Monitoring servoloop, e.g. overload of servomotor, loss of feedback or reference
• CPC Class Codes: G05B 2219/37285 Load, current taken by motor
• CPC Class Codes: G05B 2219/37342 Overload of motor, tool
• CPC Class Codes: G05B 2219/42286 Speed, ramp controlled slow down of motor
• CPC Class Codes: G05B 2219/42289 Avoid overload servo motor, actuator limit servo torque
• CPC Class Codes: G05B 2219/45127 Portable, hand drill
• CPC Class Codes: Y10S 388/937 Hand tool
• CPC Class Codes: Y10T 408/14 Responsive to condition of Tool or tool-drive

Abstract

A drilling device prevents recurrence of an overload condition after occurrence of the overload condition, thereby improving operability and safety in the drilling device. A motor for rotating a drill is connected to an AC power source through a motor control unit, a current detector, and a power switch. A magnet is also connected to the AC power source through the power switch and a full-wave rectifier. The motor control unit rotationally drives the motor on the basis of a signal sent from a main control unit according to a state in which a motor start switch is on. The main control unit controls the motor control unit to gradually reduce a supply voltage to the motor when the motor becomes overloaded, to gradually increase the voltage to the normal power supply condition when the overload condition is vanished, and to stop power supply to the motor if the overload condition continues for a predetermined period.

Claims

1. A portable drilling device comprising:

a drilling device body including a motor for rotating a cutting tool;

a fixing unit for fixing the drilling device body;

a motor control unit for rotationally driving the motor according to an on state of a motor start switch; and

a main control unit for controlling the motor control unit, the main control unit comprising

a first control unit for controlling the motor control unit so as to reduce power supply to the motor when the motor becomes overloaded,

a second control unit for controlling the motor control unit so as to resume normal power supply to the motor when the overload condition is removed, and

a fourth control unit for maintaining a motor drive state for a predetermined period with the supply voltage to the motor being at a predetermined value when a load current of the motor is not less than a predetermined reference value and the supply voltage to the motor becomes the predetermined value according to operation of the first control unit.

2. The portable drilling device according to claim 1, wherein the first control unit gradually reduces a supply voltage to the motor when the motor becomes overloaded.

3. The portable drilling device according to claim 1, wherein the second control unit gradually increases the supply voltage to the motor in order to resume the normal power supply when the overload condition is removed.

4. The portable drilling device according to claim 1, wherein the main control unit includes a third control unit for controlling the motor control unit so as to stop power supply to the motor if the overload condition is not removed and continues for a predetermined period.

5. The portable drilling device according to claim 4, wherein the main control unit controls the motor control unit so as to start power supply to the motor when the motor start switch is turned on in a state in which the third control unit is in operation.

6. The portable drilling device according to claim 4, wherein when the first, the second, and the third control units are operated, the main control unit executes display control such that a light-emitting element is turned on in respective different colors and/or different ways according to respective control states of the first, the second, and the third control units.

7. The portable drilling device according to claim 1, wherein the main control unit defines the predetermined value of the motor supply voltage to be a value at which thermal problems are not caused with regard to the motor even in a locked state.

8. The portable drilling device according to claim 7, wherein the main control unit gradually increases the supply voltage in order to resume the normal power supply via the second control unit when the load current of the motor is less than the reference value, in a case where the fourth control unit is operated.

9. The portable drilling device according to claim 1, wherein the fixing unit includes a magnet for fixing the drilling device body including the motor to a workpiece with an electromagnetic force, and wherein the main control unit rotationally drives the motor by means of the motor control unit according to a state in which the magnet is energized.

10. A portable drilling device comprising:

a drilling device body including a motor for rotating a cutting tool;

a motor control unit for rotationally driving the motor according to an on state of a motor start switch; and

a main control unit for controlling the motor control unit, the main control unit comprising

a first control unit for controlling the motor control unit so as to reduce power supply to the motor when the motor becomes overloaded,

a second control unit for controlling the motor control unit so as to resume normal power supply to the motor when the overload condition is removed,

a third control unit for controlling the motor control unit so as to stop power supply to the motor if the overload condition is not removed and continues for a predetermined period, and

a fourth control unit for maintaining a motor drive state for a predetermined period with the supply voltage to the motor being at a predetermined value when a load current of the motor is not less than a predetermined reference value and the supply voltage to the motor becomes the predetermined value according to operation of the first control unit.

11. The portable drilling device according to claim 10, further comprising a fixing unit for fixing the drilling device body to a workpiece.

12. The portable drilling device according to claim 10, wherein the first control unit gradually reduces a supply voltage to the motor when the motor becomes overloaded, and

wherein the second control unit gradually increases the supply voltage to the motor in order to resume the normal power supply when the overload condition is removed.

13. A portable drilling device comprising:

a drilling device body including a motor for rotating a cutting tool;

a motor control unit for rotationally driving the motor according to an on state of a motor start switch; and

a main control unit for controlling the motor control unit, the main control unit comprising

first control means for controlling the motor control unit so as to reduce power supply to the motor when the motor becomes overloaded,

second control means for controlling the motor control unit so as to resume normal power supply to the motor when the overload condition is removed,

third control means for controlling the motor control unit so as to stop power supply to the motor if the overload condition is not removed and continues for a predetermined period, and

fourth control means for maintaining a motor drive state for a predetermined period with the supply voltage to the motor being at a predetermined value when a load current of the motor is not less than a predetermined reference value and the supply voltage to the motor becomes the predetermined value according to operation of the first control unit.

14. The portable drilling device according to claim 13, wherein the first control means gradually reduces a supply voltage to the motor when the motor becomes overloaded.

15. The portable drilling device according to claim 13, wherein the second control means gradually increases the supply voltage to the motor in order to resume the normal power supply when the overload condition is removed.

16. The portable drilling device according to claim 13, wherein the main control unit controls the motor control unit so as to start power supply to the motor when the motor start switch is turned on in a state in which the third control means is in operation.

17. The portable drilling device according to claim 13, wherein when the first control means, the second control means, and the third control means are operated, the main control unit executes display control such that a light-emitting element is turned on in respective different colors and/or different ways according to respective control states of the first control means, the second control means, and the third control means.

18. The portable drilling device according to claim 13, wherein the main control unit defines the predetermined value of the motor supply voltage to be a value at which thermal problems are not caused with regard to the motor even in a locked state.

19. The portable drilling device according to claim 18, wherein the main control unit gradually increases the supply voltage in order to resume the normal power supply via the second control means when the load current of the motor is less than the reference value, in a case where the fourth control means is operated.

20. The portable drilling device according to claim 13, further comprising a fixing unit including a magnet for fixing the drilling device body including the motor to a workpiece with an electromagnetic force, and wherein the main control unit rotationally drives the motor by means of the motor control unit according to a state in which the magnet is energized.