Heat generation type flow sensor

Abstract

A heat generation type flow sensor of an enhanced output sensitivity which is destined for use, for example, as an air flow sensor employed in an engine control system of a motor vehicle. The heat generation type flow sensor includes a silicon substrate (20), a diaphragm (10) disposed on the silicon substrate (20) and having a cavity (11a) formed in a surface thereof, a flow rate detecting element (1) provided on the diaphragm (10) and including a heat generating resistor (2) for outputting an electric signal indicative of a heating current flowing through the heat generating resistor (2), a supporting member (13) for supporting the flow rate detecting element (1) on the diaphragm (10) in such a deposition that one surface of the diaphragm (10) is exposed to a fluid for measurement while the fluid for measurement is difficult to flow into the cavity (11a) formed in the other surface of the diaphragm (10), and a control unit for performing such control that temperature of the heat generating resistor (2) is sustained higher by a predetermined temperature than that of the fluid for measurement, wherein the heat generating resistor (2) and the diaphragm (10) are so dimensioned that ratio of a width of the heat generating resistor (2) to that of the diaphragm (10) is in a range from 0.4 to 0.6 inclusive and that ratio of a length (Yh) in a longitudinal direction of the heat generating resistor (2) to that (Yd) of the diaphragm (10) is in a range from 0.4 to 0.6 inclusive.

Dependencies are inferred from the claim text.