Patent ID: 7644614
Filing Date: 2010-01-12
Classification: G01F

Abstract:
1. A flow quantity measuring device that measures a flow quantity of air at an airflow passage, the flow quantity measuring device comprising: a dielectric film that extends along a plane, which is generally parallel to a flow direction of the air in the airflow passage; a heating resistor that is placed on a surface of the dielectric film and generates heat upon energization thereof; an upstream side sensing resistor that is placed on an upstream side of the heating resistor with respect to a flow direction of the air on the surface of the dielectric film and changes an electric resistance thereof in response to temperature; and a downstream side sensing resistor that is placed on a downstream side of the heating resistor with respect to the flow direction of the air on the surface of the dielectric film and changes an electric resistance thereof in response to temperature, wherein: the flow quantity measuring device measures the flow quantity of the air, which flows in the airflow passage, based on a measurement difference between a measurement of the upstream side sensing resistor and a measurement of the downstream side sensing resistor; the upstream side sensing resistor and the downstream side sensing resistor extend generally parallel to each other in a longitudinal direction thereof, which is generally perpendicular to the flow direction of the air and is generally parallel to the surface of the dielectric film; an area, which is held between and is defined by the upstream side sensing resistor and the downstream side sensing resistor on the surface of the dielectric film, forms a sensing area that is provided to sense the measurement difference and has first and second longitudinal end edges located on first and second sides, respectively, of the flow quantity measuring device; the heating resistor forms a heat generating area that heats the sensing area and has first and second longitudinal end edges located on the first and second sides, respectively, of the flow quantity measuring device; first and second electric potential ends of the heating resistor are placed at the first longitudinal end edge of the heat generating area; the first longitudinal end edge of the heat generating area projects from the first longitudinal end edge of the sensing area toward the first side of the flow quantity measuring device; the upstream side sensing resistor is provided with a plurality of electric potential ends; the downstream side sensing resistor is provided with a plurality of electric potential ends; one half of a total number of the plurality of electric potential ends of the upstream side sensing resistor and the plurality of electric potential ends of the downstream side sensing resistor extend out from the sensing area in a first direction; and an other one half of the total number of the plurality of electric potential ends of the upstream side sensing resistor and the plurality of electric potential ends of the downstream side sensing resistor extend out from the sensing area in a second direction, which is opposite from the first direction.