The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 22, 2008
Filed:
Aug. 19, 2005
Ryo Ando, Hitachinaka, JP;
Ryo Ando, Hitachinaka, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
The time it takes for a hot-wire airflow meter to begin to operate normally upon startup of an automobile is reduced. A heat-generating resistor Rh for measuring airflow rate, a temperature-compensating resistor Rc, and a resistor Rfor detecting the current through the heat-generating resistor are connected in parallel. A differential voltage between a power supply voltage Vb and the voltage across the emitter-collector junction of transistors Q, Q, or Qis applied to each of the heat-generating resistor Rh, temperature-compensating resistor Rc, and current-detecting resistor R. The transistors Q, Q, and Qform a current mirror circuit, by which the ratio of currents through the heat-generating resistor Rh, temperature-compensating resistor Rc, and current-detecting resistor Ris determined. The current ratio is maintained to be a predetermined ratio even if the heating current is controlled by an operational amplifierdue to an increase or decrease in airflow rate.