Rotary impact tool and method for controlling the same

Patent metadata

Field	Value
Publication number	US-10427282-B2
Application number	US-201615236718-A
Country	US
Kind code	B2
Filing date	Aug 15, 2016
Priority date	Aug 24, 2015
Publication date	Oct 1, 2019
Grant date	Oct 1, 2019

Abstract

In a rotary impact tool according to an aspect of the present disclosure, an impact mechanism rotates an output shaft by a rotational force of a motor and, when a torque equal to or greater than a given value is externally applied to the output shaft in a direction opposite a rotational direction of the output shaft, the impact mechanism intermittently applies an impact force as a momentary torque to the output shaft in the rotational direction of the output shaft. A protection unit stops the motor or reduces a rotational speed of the motor on condition that an abnormal impact detection unit detects the abnormal impact. A control unit controls activation of the protection unit differently when the rotational direction of the motor is set to a reverse rotational direction in comparison with when the rotational direction of the motor is set to a forward rotational direction.

First claim

What is claimed is:

1. A rotary impact tool comprising:
a motor;
an impact mechanism including an output shaft for attachment thereto of a tool element, the impact mechanism being configured to rotate the output shaft by a rotational force of the motor and, when a torque equal to or greater than a given value is externally applied to the output shaft in a direction opposite a rotational direction of the output shaft, to intermittently apply an impact force as a momentary torque to the output shaft in the rotational direction of the output shaft;
a rotational direction setting unit configured to be operated by a user of the rotary impact tool to set a rotational direction of the motor either to a forward rotational direction as a direction of tightening an object using the tool element or to a reverse rotational direction as a direction of loosening the tightened object;
an abnormal impact detection unit configured to detect an abnormal impact, the abnormal impact being a state in which a reaction force from the output shaft against the impact mechanism is greater than a specified value when the impact mechanism produces the impact force;
a protection unit configured to stop the motor or reduce a rotational speed of the motor on a condition that the abnormal impact detection unit detects the abnormal impact;
a control unit configured to control activation of the protection unit differently when the rotational direction of the motor is set to the reverse rotational direction by the rotational direction setting unit in comparison with when the rotational direction of the motor is set to the forward rotational direction by the rotational direction setting unit; and
a count value determination unit configured to determine whether a count value corresponding to the number of abnormal impacts detected by the abnormal impact detection unit has reached a specified value,
the protection unit being configured to be activated on a condition that the count value determination unit determines that the count value has reached the specified value, and
the control unit being configured to set the specified value to a larger value when the rotational direction of the motor is set to the reverse rotational direction in comparison with when the rotational direction of the motor is set to the forward rotational direction.

2. The rotary impact tool according to claim 1 , further comprising a time determination unit configured to determine whether a specified time period has elapsed since the count value determination unit has determined that the count value has reached the specified value,
wherein the protection unit is configured to be activated on a condition that the time determination unit determines that the specified time period has elapsed, and
wherein the control unit is configured to set also the specified time period to a larger value when the rotational direction of the motor is set to the reverse rotational direction in comparison with when the rotational direction of the motor is set to the forward rotational direction.

3. The rotary impact tool according to claim 1 , further comprising an after-detection time determination unit configured to determine whether a specified time period has elapsed since the abnormal impact detection unit has detected the abnormal impact,
wherein the protection unit is configured to be activated on a condition that the after-detection time determination unit determines that the specified time period has elapsed, and
wherein the control unit is configured to set the specified time period to a larger value when the rotational direction of the motor is set to the reverse rotational direction in comparison with when the rotational direction of the motor is set to the forward rotational direction.

4. The rotary impact tool according to claim 1 , wherein the control unit is configured to control the activation of the protection unit by prohibiting the activation of the protection unit when the rotational direction of the motor is set to the reverse rotational direction.

5. The rotary impact tool according to claim 4 , wherein the control unit is configured to prohibit activation of the abnormal impact detection unit when the rotational direction of the motor is set to the reverse rotational direction.

6. A method for controlling a rotary impact tool according to claim 1 , the method comprising:
performing a protective operation that stops the motor or reduces a rotational speed of the motor on a condition that an abnormal impact is detected, the abnormal impact being a state in which a reaction force from the output shaft against the impact mechanism is greater than a specified value when the impact mechanism produces the impact force; and
controlling the protective operation differently when the rotational speed of the motor is set to the reverse rotational direction by the rotational direction setting unit in comparison with when the rotational speed of the motor is set to the forward rotational direction by the rotational direction setting unit.

7. A rotary impact tool comprising:
a motor;
a tool holder that engages and retains a tool element;
a gear mechanism that converts output of the motor to a driving force on the tool holder;
a control circuit that controls the motor; and
a forward/reverse changeover switch configured to send a signal to the control circuit to have the motor driven in a forward direction or a reverse direction, wherein:
the control circuit is configured to perform a protection execution condition determination process to protect the rotary impact tool and a motor control process for the motor;
the protection execution condition determination process including:
determining whether a rotational direction is set to forward; and
performing one of a first setting process when the rotational direction is set to forward and a second setting process when the rotational direction is set to reverse;

the first setting process including:
setting a specified value to a first value (N 1 ); and
setting a specified time period to a first time period (T 1 );

the second setting process including:
setting the specified value to a second value (N 2 ); and
setting the specified time period to a second time period (T 2 );

N 2 being greater than N 1 , and T 2 being greater than T 1 ;
the result of the protection execution condition determination process is the setting of values and times for determining when a motor stop process should be initiated due to certain conditions; and
the motor control process is conducted based on the result of the protection execution condition determination process.

8. The rotary impact tool according to claim 7 ,
wherein the protection execution condition determination process further includes:
determining that an abnormal impact determination flag is not set;
determining that a time count start flag is not set;
performing an abnormal impact determination process;
determining that an abnormal impact counter is equal to or greater than the specified value; and
setting the time count start flag.

9. The rotary impact tool according to claim 7 ,
wherein the protection execution condition determination process further includes:
determining that an abnormal impact determination flag is not set;
determining that a time count start flag is set;
incrementing a time counter;
determining that an elapsed time period is equal to or greater than the specified time period; and
setting an abnormal impact determination flag.

10. The rotary impact tool according to claim 9 ,
wherein the motor control process includes:
determining that the abnormal impact determination flag is set; and
performing a motor stop pro

Assignees

• Makita Corp

Inventors

• Ishikawa Goshi
• Ito Yoshihiro
• Takada Toshihisa

Classifications

• B25B21/02 Primary

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

• B25B23/1475 Primary

  for impact wrenches or screwdrivers · CPC title

• B25F5/006

  Vibration damping means · CPC title