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. 08, 2008
Filed:
Aug. 18, 2006
Izumi Watanabe, Hitachinaka, JP;
Junichi Horie, Hitachinaka, JP;
Keiichi Nakada, Hitachinaka, JP;
Kei Ueyama, Asuka, JP;
Masamichi Yamada, Hitachinaka, JP;
Izumi Watanabe, Hitachinaka, JP;
Junichi Horie, Hitachinaka, JP;
Keiichi Nakada, Hitachinaka, JP;
Kei Ueyama, Asuka, JP;
Masamichi Yamada, Hitachinaka, JP;
Hitachi, Ltd., Tokyo, JP;
Hitachi Car Engineering Co., Ltd., Hitachinaka-shi, JP;
Abstract
A flow rate sensor has a problem that a resistance value of a heat generating resistor itself varies and sensor characteristics are changed during use of the sensor for a long term. Also, the temperature of the heat generating resistor must be adjusted on a circuit substrate with a resistance constituting one side of a fixed temperature difference control circuit, and this has been one of factors pushing up the production cost. All resistances used for fixed temperature difference control are formed on the same substrate as temperature sensitive resistors of the same material. This enables all the resistances for the fixed temperature difference control to be exposed to the same environmental conditions. Hence, even when the resistances change over time, the changes over time occur substantially at the same tendency. Since the resistances for the fixed temperature difference control change over time essentially at the same rate, a resulting output error is very small.