Power tool

Patent metadata

Field	Value
Publication number	US-10183384-B2
Application number	US-201414761660-A
Country	US
Kind code	B2
Filing date	Mar 18, 2014
Priority date	Mar 30, 2013
Publication date	Jan 22, 2019
Grant date	Jan 22, 2019

Abstract

The purpose of the present invention is to use a motor with as high an output as possible to complete tightening operations at a high speed while limiting continuous drive output. In a power tool having a plurality of impact operation modes, the motor thereof is controlled at a 100% duty cycle so as to rotate at a high speed in the period between pulling of a trigger and starting of an impact operation ( 71 a - 71 b ), and the duty cycle is changed to a low duty cycle matching the appropriate operation mode after an impact by an impact mechanism is started and a predetermined stroke is performed so that the motor is driven at the low duty cycle until the trigger is returned (arrow 71 c - 71 d ). The switching of the duty cycle is performed when the current flowing to the motor exceeds a threshold (I 1 ).

First claim

The invention claimed is:

1. A power tool comprising:
a motor configured to be driven by PWM controlling a semiconductor switching element;
a trigger configured to adjust startup and rotation of the motor;
an impact mechanism configured to strike or rotate an anvil by a hammer that is rotated by the motor;
a control device configured to control rotation of the motor,
wherein the power tool has a plurality of operation modes having different fastening torques,
wherein the power tool is configured to perform control at the same duty ratio, irrespective of the operation modes, in a control zone of a high duty ratio, and
wherein the power tool is configured to perform control at a duty ratio set depending on each of the operation modes, in a control zone of a low duty ratio; and
a current detection device configured to detect a current value flowing through the motor or a semiconductor switching element,
wherein when a current value, which is detected by the current detection device when the power tool is driven at the high duty ratio, exceeds a first threshold I 1 , the control device switches the duty ratio from the high duty ratio to the low duty ratio, and
wherein when a plurality of striking is continuously performed by the impact mechanism, the motor is driven at a state where a duty ratio is changed from a high value to a low value.

2. The power tool according to claim 1 , wherein the high duty ratio is 100% and the low duty ratio is 70% or lower.

3. The power tool according to claim 1 , wherein a second threshold I 2 (I 2 >I 1 ), instead of the first threshold I 1 , is used in a short specific time period after the trigger is pulled, and when the current value exceeds the second threshold I 2 , the control device switches the duty ratio from the high duty ratio to the low duty ratio.

4. A power tool comprising:
a motor configured to be driven by PWM controlling a semiconductor switching element;
a trigger configured to adjust startup and rotation of the motor;
an impact mechanism configured to strike or rotate an anvil by a hammer that is rotated by the motor;
a control device configured to control rotation of the motor; and
a current detection device configured to detect a current value flowing through the motor or semiconductor switching element,
wherein when an increase rate of a current value detected by the current detection device is continuously kept at a high state, the motor is driven at a state where a duty ratio is changed from a high value to a low value,
wherein the power tool has a plurality of operation modes having different fastening torques,
wherein the power tool is configured to perform control at the same duty ratio, irrespective of the operation modes, in a control zone of a high duty ratio, and
wherein the power tool is configured to perform control at a duty ratio set depending on each of the operation modes, in a control zone of a low duty ratio.

5. A power tool comprising:
a motor configured to be driven by PWM controlling a semiconductor switching element;
a trigger configured to adjust startup and rotation of the motor;
an impact mechanism configured to strike or rotate an anvil by a hammer that is rotated by the motor;
a control device configured to control rotation of the motor; and
a current detection device configured to detect a current value flowing through the motor or a semiconductor switching element,
wherein when a fastening member is seated by a plurality of striking by the impact mechanism, the motor is driven at a state where a duty ratio is changed from a high value to a low value,
wherein it is determined that the fastening member is seated when a current value, which is detected by the current detection device when the power tool is driven at a high duty ratio, exceeds a first threshold I 1 ,
wherein the power tool has a plurality of operation modes having different fastening torques,
wherein the power tool is configured to perform control at the same duty ratio, irrespective of the operation modes, in a control zone of the high duty ratio, and
wherein the power tool is configured to perform control at a duty ratio set depending on each of the operation modes, in a control zone of a low duty ratio.

6. The power tool according to claim 1 , wherein the control device is configured to drive the motor with PWM controlling the semiconductor switching element at a high duty ratio until striking of the anvil by the hammer is started.

7. The power tool according to claim 4 , wherein the control device is configured to drive the motor with PWM controlling the semiconductor switching element at a high duty ratio until striking of the anvil by the hammer is started.

8. The power tool according to claim 5 , wherein the control device is configured to drive the motor with PWM controlling the semiconductor switching element at a high duty ratio until striking of the anvil by the hammer is started.

Assignees

• Hitachi Koki Kk
• Koki Holdings Co Ltd

Inventors

• Takano Nobuhiro
• Iwata Kazutaka

Classifications

• B25B21/02 Primary

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

• B25F5/00 Primary

  Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for · CPC title

• B25B23/1475

  for impact wrenches or screwdrivers · CPC title