Title:
SPEED CONTROLLER FOR DC MOTOR
Document Type and Number:
Japanese Patent JP3288432
Kind Code:
B2
Abstract:
PURPOSE: To enhance durability by providing a forcible ON signal generating circuit for forcibly turning a semiconductor switching element ON immediately before turn ON of a contact switch which is turned ON when an operating member is operated substantially to the maximum thereby preventing occurrence of spark in the switch.
CONSTITUTION: When the speed controller is applied to r.p.m. control of a motor tool, a semiconductor switching element Q and a contact switch SW1 being turned ON upon operation of an operating member, i.e., a trigger Tr, by minute amount are connected in series with a DC motor M and a battery B and the element Q is bypassed by a second contact switch SW2 being turned ON upon operation of the trigger Tr substantially to the maximum. A set voltage to be generated depending on the operating amount of trigger is then compared through a comparing circuit 16 with a voltage(electromotive force) to be induced in the DC motor M upon turn OFF of the element Q and a switching signal is outputted depending on the comparison result. The element Q is forcibly turned ON through a current mirror circuit 8 immediately before turn ON of the second contact switch SW2.
Inventors:
Masahiko Sakou
Application Number:
JP19349692A
Publication Date:
June 04, 2002
Filing Date:
June 26, 1992
Export Citation:
Assignee:
Makita Corporation
International Classes:
H02P7/06; H02P7/29; (IPC1-7): H02P5/17; H02P5/06
Domestic Patent References:
| JP4178192A | ||||
| JP2285996A | ||||
| JP5944101U |
Attorney, Agent or Firm:
Hidehiko Okada (2 outside)
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