Electric power tool

• US 9,579,776 B2
• Filed: 03/10/2014
• Issued: 02/28/2017
• Est. Priority Date: 03/13/2013
• Status: Expired due to Fees

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: Inagaki, Kenichirou, Arimura, Tadashi, Ohashi, Toshiharu, Kaizo, Hiroyuki, Sekino, Fumiaki
• Primary Examiner(s): Smith, Scott A.
• Application Number:
  US14/202,107
• Publication Number:
  US 20140262390A1
• Time in Patent Office: 1,086 Days
• Field of Search: 173/2, 173/176, 173/178, 173/128, 173/181, 173/183, 173/93, 173/93.6, 173/217, 318/430, 318/434, 318/12, 318/139, 320/114, 320/132
• US Class Current: 1/1
• CPC Class Codes: B25B 21/02 with means for imparting impact to screwdriver blade or nut socket
• CPC Class Codes: B25B 21/026 Impact clutches
• CPC Class Codes: B25B 23/1405 for impact wrenches or screwdrivers
• CPC Class Codes: B25B 23/147 specially adapted for electrically operated wrenches or screwdrivers
• CPC Class Codes: B25B 23/1475 for impact wrenches or screwdrivers
• CPC Class Codes: H02P 2201/09 Boost converter, i.e. DC-DC step up converter increasing the voltage between the supply and the inverter driving the motor
• CPC Class Codes: H02P 7/295 of the kind having one thyristor or the like in series with the power supply and the motor

Abstract

An electric power tool includes a voltage step-up condition setting operation unit that serves as a human machine interface and a voltage converter capable of performing a voltage step-up operation to raise a voltage supplied from a power supply and supply a raised voltage to a motor. The voltage converter is further capable of changing a voltage step-up level in the voltage step-up operation in accordance with the operation of the voltage step-up condition setting operation unit. A driving state detection unit generates a driving state signal corresponding to a driving state of the electric power tool. A control unit controls a stop timing of the motor in accordance with the driving state signal.

Claims

1. An electric power tool comprising:

a power supply;

a motor including a drive shaft;

a trigger switch to adjust an output of the motor;

a tool output shaft configured to be driven based on a torque of the drive shaft of the motor;

a voltage step-up condition setting operation unit that serves as a human machine interface;

a voltage converter capable of performing a voltage step-up operation to raise a voltage supplied from the power supply and supply a raised voltage to the motor, the voltage converter being capable of changing a voltage step-up level in the voltage step-up operation in accordance with the operation of the voltage step-up condition setting operation unit;

a driving state detection unit configured to generate a driving state signal corresponding to a driving state of the electric power tool; and

a control unit configured to determine whether or not a load torque acting on the tool output shaft is greater than or equal to a prescribed torque in accordance with the driving state signal and stop the driving of the motor when the load torque is the prescribed torque or more, wherein

the control unit is configured to perform a starting voltage step-up control, and

the voltage converter is configured to, in the starting voltage step-up control, increase the voltage step-up level over time after the operation of the trigger switch.

2. The electric power tool according to claim 1, further comprising:

a power conversion unit configured to change the magnitude of the torque of the drive shaft transmitted to the tool output shaft,

wherein the control unit is configured to calculate a rotation amount of the drive shaft, the tool output shaft, or the power conversion unit in accordance with the driving state signal.

3. The electric power tool according to claim 1, further comprising:

a power conversion unit configured to convert the torque of the drive shaft into an impact load and hit the tool output shaft based on the impact load,

wherein the control unit is configured to calculate the number of times the power conversion unit hits the tool output shaft in accordance with the driving state signal.

4. The electric power tool according to claim 1, further comprising:

a power conversion unit configured to convert the torque of the drive shaft into an impact load and hit the tool output shaft based on the impact load,

wherein the control unit is configured to calculate a rotation amount of one of the drive shaft, the tool output shaft, and the power conversion unit in accordance with the driving state signal wherein the control unit calculates the rotation amount generated by one hitting of the power conversion unit.

5. The electric power tool according to claim 4, wherein the control unit is configured to calculate the number of times the power conversion unit hits the tool output shaft in accordance with the driving state signal when the rotation amount is less than a reference rotation amount.

6. The electric power tool according to claim 1, wherein the driving state detection unit is configured to generate a driving time signal, which indicates driving time of the motor, as the driving state signal.

7. The electric power tool according to claim 1, wherein the driving state detection unit is configured to generate an output current signal, which indicates a current flowing through the motor, as the driving state signal.

8. The electric power tool according to claim 1, wherein the voltage converter is further capable of performing a voltage step-down operation to lower the voltage supplied from the power supply and supply a lowered voltage to the motor.

9. The electric power tool according to claim 1, wherein the voltage converter is configured to continue to increase the voltage step-up level after the operation of the trigger switch until the raised voltage reaches at a reference output voltage.

10. The electric power tool according to claim 1, wherein the voltage converter is configured to increase the voltage step-up level in steps up to a maximum step-up level after the operation of the trigger switch.