Electric power tool

Patent metadata

Field	Value
Publication number	US-11701759-B2
Application number	US-202017026390-A
Country	US
Kind code	B2
Filing date	Sep 21, 2020
Priority date	Sep 27, 2019
Publication date	Jul 18, 2023
Grant date	Jul 18, 2023

Abstract

An electric power tool in one aspect of the present disclosure includes a motor, an impact mechanism, and a control circuit. The control circuit executes a motor control process. The motor control process includes limiting an output of the motor in response to establishment of a preset condition. The preset condition is based on a load applied to the motor.

First claim

What is claimed is:

1. An electric power tool comprising:
a motor;
an impact mechanism including a hammer and an anvil, the hammer being configured to be rotated by the motor, the anvil being configured to rotate in response to receiving a rotational force of the hammer, the anvil being configured to be attached to a tool bit, the hammer being configured to impact the anvil in a rotation direction of the hammer in response to receipt of a first torque by the anvil, and the first torque being equal to or greater than a preset magnitude;
a drive circuit configured to supply an electric power to the motor to thereby drive the motor; and
a control circuit electrically connected to the drive circuit and configured to execute a motor control process,
the motor control process including:
setting a magnitude of the electric power to a first magnitude;
switching the magnitude of the electric power from the first magnitude to a second magnitude in response to establishment of a preset condition, the second magnitude being smaller than the first magnitude and greater than zero, and the preset condition being based on a magnitude of a load applied to the motor; and
switching the magnitude of the electric power from the second magnitude to a third magnitude in response to (i) switching the magnitude of the electric power to the second magnitude and (ii) establishment of the preset condition, the third magnitude being smaller than the first magnitude and the second magnitude and greater than zero.

2. The electric power tool according to claim 1 , wherein
the preset condition is established in response to a first physical quantity reaching a threshold, the threshold being preset, the first physical quantity indicating the magnitude of the load.

3. The electric power tool according to claim 2 , wherein
the magnitude of the load corresponds to a magnitude of the torque applied to the anvil.

4. The electric power tool according to claim 2 , wherein
the magnitude of the load corresponds to a magnitude of an electric current supplied to the motor.

5. The electric power tool according to claim 2 , wherein
the magnitude of the load corresponds to a reduced amount per unit time of an actual rotational speed of the motor.

6. The electric power tool according to claim 2 , wherein
the control circuit is configured to control the magnitude of the electric power based on a pulse width modulation (PWM) signal, the PWM signal having a duty ratio, and
switching the magnitude of the electric power in response to the first physical quantity reaching the threshold includes reducing the duty ratio.

7. The electric power tool according to claim 1 , wherein
the preset condition is established in response to lock of the anvil.

8. The electric power tool according to claim 7 , wherein
the control circuit is configured to determine whether the lock has occurred, and
the preset condition is established in response to the control circuit determining that the lock has occurred.

9. The electric power tool according to claim 8 , wherein
the control circuit is configured to determine whether the lock has occurred based on the torque applied to the anvil.

10. The electric power tool according to claim 1 , wherein
the motor control process includes controlling the drive circuit so that an actual rotational speed of the motor is consistent with a target rotational speed, and
switching the magnitude of the electric power in response to establishment of the preset condition includes reducing the target rotational speed.

11. The electric power tool according to claim 1 , wherein
the motor control process further includes:
determining the first magnitude so that an actual rotational speed of the motor is consistent with a first target rotational speed, and
in response to establishment of the preset condition, (i) determining the magnitude of the electric power so that the actual rotational speed is consistent with a second target rotational speed, and (ii) reducing a determined magnitude of the electric power based on the magnitude of the load applied to the motor to thereby determine the second magnitude; and

the second target rotational speed is lower than the first target rotational speed.

12. The electric power tool according to claim 11 , further comprising:
a trigger configured to be pulled by a user of the electric power tool,
wherein the motor control process further includes obtaining the first target rotational speed corresponding to a pulling amount of the trigger pulled by the user and the second target rotational speed corresponding to the pulling amount of the trigger pulled by the user.

13. The electric power tool according to claim 1 , wherein
the control circuit is configured to output a drive signal to the drive circuit to thereby control supply of the electric power to the motor,
the drive signal is a pulse width modulation signal having a duty ratio, and
the control circuit is configured to set or vary the duty ratio based on the magnitude of the electric power.

14. An electric power tool comprising:
a motor;
an impact mechanism including a hammer and an anvil, the hammer being configured to be rotated by the motor, the anvil being configured to rotate in response to receiving a rotational force of the hammer, the anvil being configured to be attached to a tool bit, the hammer being configured to impact the anvil in a rotation direction of the hammer in response to receipt of a first torque by the anvil, and the first torque being equal to or greater than a preset magnitude;
a drive circuit configured to supply an electric power to the motor to thereby drive the motor; and
a control circuit electrically connected to the drive circuit and configured to execute a motor control process,
the motor control process including:
setting a magnitude of the electric power to a first magnitude;
switching the magnitude of the electric power from the first magnitude to a second magnitude in response to establishment of a preset condition, the second magnitude being smaller than the first magnitude and greater than zero, and the preset condition being based on a magnitude of a load applied to the motor;
switching the magnitude of the electric power from the second magnitude to a third magnitude in response to (i) switching the magnitude of the electric power to the second magnitude and (ii) establishment of the preset condition, the third magnitude being smaller than the first magnitude and the second magnitude and greater than zero; and
switching the magnitude of the electric power from the third magnitude to a fourth magnitude in response to (i) switching the magnitude of the electric power to the third magnitude and (ii) establishment of the preset condition, the fourth magnitude being smaller than the first magnitude, the second magnitude and the third magnitude and greater than zero.

Assignees

• Makita Corp

Inventors

• Kato Itsuku
• Kawai Yasuhito

Classifications

• B25B23/1475

  for impact wrenches or screwdrivers · CPC title

• B25B21/02 Primary

  with means for imparting impact to screwdriver blade or nut socket · CPC title

• B25B23/1405

  for impact wrenches or screwdrivers · CPC title

• B25D2250/221

  Sensors · CPC title

• B25F5/001

  Gearings, speed selectors, clutches or the like specially adapted for rotary tools · CPC title