Heat-sensitive air flow meter

Abstract

PURPOSE:To improve responsivity to fluctuation in air flow-rates, by covering surface of coiled metallic wire of heating resistor material with glass layer. CONSTITUTION:A 20mum wide Pt wire 2 is wound up around a 0.5mm Mo core wire 18 and the coil is sintered after covering with glass material 4. This heating resistor 1 and resistor 5 for air temperature measurement are installed in a suction air bypass 102. By this arrangement, as, among the heat generated in the Pt wire 2 of the resistor 1, amount of the heat lost by the supporting body 3 is not significant, and almost all the heat is lost in the air, transient responsivity in case of sudden changes of the oil flow-rates is improved pronouncedly. The resistor 1 is controlled by a transistor to higher temperature by the specified constant value than that of the resistor 5 and suction air temperature is corrected by an infinitesimal current transmitted to the resistor 5. An equalizing feedback is So made that voltage obtained by dividing voltages on both ends of the resistor 1 by resistances 11, 12 equals that obtained by amplification 7 of voltage drop of a resistance 10 and the air flow-rate can be measured by the voltage drop of the resistor 10.

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Cited By (5)

    Publication numberPublication dateAssigneeTitle
    JP-2008107146-AMay 08, 2008Horiba Ltd, Horiba Stec Co Ltd, 株式会社堀場エステック, 株式会社堀場製作所Thermal mass flow sensor and mass flow controller
    JP-H02114126-AApril 26, 1990Hitachi Automot Eng Co Ltd, Hitachi LtdHot-wire protection of hot-wire air flowmeter and heating resistor therefor
    US-2011035959-A1February 17, 2011Maguire Products, Inc.Gas flow rate determination method and apparatus and granular material dryer and method for control thereof
    US-5020214-AJune 04, 1991Hitachi, Ltd.Method of manufacturing a hot wire air flow meter
    US-8141270-B2March 27, 2012Maguire Products, Inc.Gas flow rate determination method and apparatus and granular material dryer and method for control thereof