Rotary impact tool

Patent metadata

Field	Value
Publication number	US-2018297179-A1
Application number	US-201815948003-A
Country	US
Kind code	A1
Filing date	Apr 9, 2018
Priority date	Apr 17, 2017
Publication date	Oct 18, 2018
Grant date	—

Abstract

A rotary impact tool in one aspect of the present disclosure includes a motor, an impact mechanism, an impact detector, and a controller. The controller executes constant duty ratio control from when the motor is started until an impact is detected by the impact detector. The controller executes constant rotation speed control in response to detection of an impact by the impact detector.

First claim

What is claimed is:

1 . A rotary impact tool comprising:
a motor; an impact mechanism including:
a hammer configured to rotate by a rotational force of the motor;
an anvil configured to rotate by receiving a rotational force of the hammer; and
a mounting portion configured to attach a tool bit to the anvil,
the impact mechanism being configured such that, in response to application of a torque equal to or greater than a specified value to the anvil, the hammer is detached from the anvil to rotate idle and to then apply an impact to the anvil in a rotational direction of the hammer;
an impact detector configured to detect the impact applied to the anvil by the hammer; a controller configured to execute drive control of the motor that includes constant duty ratio control and constant rotation speed control, the controller being configured to execute the constant duty ratio control from the start of the motor until detection of the impact by the impact detector, the controller further being configured to execute the constant rotation speed control in response to detection of the impact by the impact detector, the constant duty ratio control being a control method in which a conduction current to the motor is controlled at a constant duty ratio, and the constant rotation speed control being a control method in which the conduction current is controlled so that a rotational speed of the motor approaches a constant rotational speed.

2 . The rotary impact tool according to claim 1 , wherein
the controller is configured to continue the constant rotation speed control until a driving stop condition of the motor is satisfied after the start of the constant rotation speed control, the driving stop condition being a condition in which the motor should be stopped.

3 . The rotary impact tool according to claim 1 , wherein
the controller is configured to return the drive control of the motor, in response to no detection of the impact by the impact detector after the start of the constant rotation speed control, from the constant rotation speed control to the constant duty ratio control.

4 . The rotary impact tool according to claim 1 , wherein
the controller includes a determiner configured to determine whether the rotational speed of the motor can be maintained at the constant rotational speed by the constant rotation speed control during execution of the constant rotation speed control.

5 . The rotary impact tool according to claim 4 , wherein
the controller is configured to perform notification operation and/or stop operation, in response to determination by the determiner that the rotational speed of the motor cannot be maintained at the constant rotational speed, the controller is configured to notify a user of the rotary impact tool in the notification operation that the rotational speed of the motor cannot be maintained at the constant rotational speed, and the controller is configured to stop the motor in the stop operation.

6 . The rotary impact tool according to claim 5 , wherein
the controller is configured to set a variable duty ratio for controlling the conduction current so as to maintain the rotational speed of the motor at the constant rotational speed in the constant rotation speed control.

7 . The rotary impact tool according to claim 6 , wherein
the determiner is configured to determine that the rotational speed of the motor cannot be maintained at the constant rotational speed when the variable duty ratio is equal to or greater than a preset set value.

8 . The rotary impact tool according to claim 1 , further comprising:
a setting portion configured to switchably set a rotation speed mode of the motor to one of rotation speed modes including high speed mode and low speed mode.

9 . The rotary impact tool according to claim 8 , wherein
the controller is configured to set the constant duty ratio in accordance with the rotation speed mode that is set via the setting portion.

10 . The rotary impact tool according to claim 9 , wherein
the controller is configured to execute the constant rotation speed control, without executing the constant duty ratio control, in response to a value of the constant duty ratio equal to or lower than a preset threshold being set.

11 . A method for controlling a rotary impact tool, comprising:
detecting an impact to an anvil by a hammer, the anvil and the hammer being included in the rotary impact tool; executing constant duty ratio control in which a conduction current to a motor is controlled at a constant duty ratio until detection of the impact, the motor being included in the rotary impact tool, and the motor being configured to rotationally drive the hammer; and executing constant rotation speed control in which the conduction current is controlled so that a rotational speed of the motor approaches a constant rotational speed in response detection of the impact.

Assignees

• Makita Corp

Inventors

• Osada Takaaki
• Yamamoto Hirokatsu
• Ishikawa Goshi
• Shima Kunihisa

Classifications

• B25F5/001

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

• B25B21/008 Primary

  with automatic change-over from high speed-low torque mode to low speed-high torque mode · CPC title

• B25B21/023

  for imparting an axial impact, e.g. for self-tapping screws · CPC title

• B25B21/026

  Impact clutches · CPC title

• B25B21/02 Primary

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