| 摘要 |
<p>PURPOSE:To constantly detect an intake air flow rate highly precisely by providing a circular bypass which surrounds all of independent main intake passages so that an outlet of an intake flow rate detecting passage communicates to the downstream side of the main intake passage via the bypass passage. CONSTITUTION:A thermal airflow meter comprises a flow meter body 1 having a sensing passage 2 and four intake passages around the passage 2. The intake passages 9 are placed symmetrically and in parallel with one another, while a circular bypass passage 11 surrounding their periphery is further formed. Air flowing into the sensing passage 2 as for each of the respective intake passages 9 first flows into a communication passage 10 on the sensing side, then flows into the bypass passage 11, and then is combined into the downstream side of each intake passage 9 through a communication passage 12 on the intake passage side. Therefore an air flow at a part where an intake flow rate detecting element comprising a thermal element 3 and a heat sensitive resistor 4 inside the sensing passage 2 is an average air flow rate which includes few pulses.</p> |
