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Title:
ELECTRIC TOOL
Document Type and Number:
WIPO Patent Application WO/2017/187890
Kind Code:
A1
Abstract:
Provided is an electric tool that comprises: a brushless motor that performs rotational drive when applied voltage is at or above induced voltage; a supply circuit that applies voltage to the brushless motor; and a control unit that controls the supply circuit. The supply circuit comprises: a rectifier circuit that rectifies and outputs alternating current voltage; a capacitor that smooths voltage that is inputted via the rectifier circuit; and a switching circuit that, by performing a switching operation, can adjust the time that drive voltage is applied. The control unit establishes a duty ratio within a prescribed range, outputs a PWM signal to the switching circuit at the established duty ratio, and can thereby control the switching operation. The control unit can also perform fixed rotational speed control that alters the duty ratio and makes the brushless motor rotate at a target rotational speed. During fixed rotational speed control, the capacitor has a capacity that keeps the smoothed voltage at or above induced voltage.

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Inventors:
KURAGANO SHINJI (JP)
KUMAKURA TAKERU (JP)
Application Number:
PCT/JP2017/013668
Publication Date:
November 02, 2017
Filing Date:
March 31, 2017
Export Citation:
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Assignee:
HITACHI KOKI KK (JP)
International Classes:
B25F5/00; B25F5/02; H02P6/06
Domestic Patent References:
WO2015129358A12015-09-03
WO2012098780A12012-07-26
Foreign References:
JPS57177292A1982-10-30
JP2012196723A2012-10-18
JPH10146064A1998-05-29
JPH07327816A1995-12-19
JP2013193133A2013-09-30
JP2015100887A2015-06-04
JP2014079873A2014-05-08
JP2010173042A2010-08-12
JPH11243668A1999-09-07
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