Patent ID: 7287424
Filing Date: 2007-10-30
Classification: G01F

Abstract:
1. A thermal type flow measurement apparatus comprising: a heating element disposed in a fluid passage and which generates heat by a passage of a current through itself; a first thermal sensitive element disposed adjacent upstream of the heating element with respect to a forward flow in a direction of fluid flow to be measured; a second thermal sensitive element disposed adjacent downstream of the heating element with respect to the forward flow in the direction of fluid flow to be measured, the fluid passage in which the heating element, the first thermal sensitive element, and the second thermal sensitive element are disposed having an asymmetric structure with respect to the direction of fluid flow so that the forward flow is more prone to flow into the fluid passage than that of a reverse flow; means for outputting a difference of temperatures sensed by the first and the second thermal sensitive elements as a voltage to sense a flow rate of the forward flow and a flow rate of the reverse flow; and heat control means which assigns weights to respective temperatures sensed by the first and second thermal sensitive elements and controls the passage of the current through the heating element so that a sum of respective temperatures with the weights reaches a preset value; wherein a weight of temperature sensed by the second thermal sensitive element is larger than that of the first thermal sensitive element.