Thermal type flow sensor with a constricted measuring passage
First Claim
1. A thermal type flow sensor comprising:
- a measuring passage which is disposed in a main passage;
a base portion provided along a flowing direction of a fluid passing through the measuring passage; and
a sensor element mounted on the base portion and equipped with an exothermic resistor formed on a substrate;
the thermal type flow sensor being featured in that a recessed portion is formed in the base portion, that the sensor element is fixedly fitted in the recessed portion in a manner that the surface of a detecting portion of the sensor element is positioned lower than an upper edge of the recessed portion, and that a wall portion of the measuring passage which is located to face the sensor element is constricted,wherein the constricted wall portion is configured to provide a constricted passage in the measuring passage such that a cross-sectional area of the measuring passage is gradually reduced to a narrowest portion of the constricted passage from an upstream side upper edge of the recessed portion to a downstream side thereof, and the exothermic resistor of the sensor element is mounted downstream of an upstream end of the narrowest portion of the constricted passage.
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Accused Products
Abstract
A thermal type flow sensor includes a base portion provided along the direction of a fluid flowing through a main passage, and a sensor element mounted on the base portion and having an exothermic resistor formed on a substrate for detecting the fluid flow rate. The base portion has a rectangular recessed portion in which the sensor element is fixed so that the surface of the detecting portion of the sensor element is positioned lower than an upper edge of the recessed portion. A wall portion of the measuring passage facing the sensor element is constricted. The exothermic resistor is disposed along the fluid passage and spaced away from the upstream side upper edge of the recessed portion and cannot be substantially affected by a fluid flow disturbance due to a step portion formed between the upper edge of the recessed portion and the detecting portion surface.
29 Citations
9 Claims
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1. A thermal type flow sensor comprising:
- a measuring passage which is disposed in a main passage;
a base portion provided along a flowing direction of a fluid passing through the measuring passage; and
a sensor element mounted on the base portion and equipped with an exothermic resistor formed on a substrate;the thermal type flow sensor being featured in that a recessed portion is formed in the base portion, that the sensor element is fixedly fitted in the recessed portion in a manner that the surface of a detecting portion of the sensor element is positioned lower than an upper edge of the recessed portion, and that a wall portion of the measuring passage which is located to face the sensor element is constricted, wherein the constricted wall portion is configured to provide a constricted passage in the measuring passage such that a cross-sectional area of the measuring passage is gradually reduced to a narrowest portion of the constricted passage from an upstream side upper edge of the recessed portion to a downstream side thereof, and the exothermic resistor of the sensor element is mounted downstream of an upstream end of the narrowest portion of the constricted passage. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- a measuring passage which is disposed in a main passage;
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8. A thermal type flow sensor comprising:
- a sub-passage for enabling part of a fluid to pass therethrough;
a base portion provided in the sub-passage and along a flowing direction of the fluid passing through the sub-passage; and
a sensor element mounted on the base portion and equipped with an exothermic resistor formed on a substrate;the thermal type flow sensor being featured in that a rectangular recessed portion is formed in the base portion, that the sensor element is fixedly fitted in the recessed portion in a manner that the surface of a detecting portion of the sensor element is positioned lower than an upper edge of the recessed portion, and that a wall portion of a measuring passage in the sub-passage which is located to face the sensor element is constricted, wherein the constricted wall portion is configured to provide a constricted passage in the measuring passage such that a cross-sectional area of the measuring passage is gradually reduced to a narrowest portion of the constricted passage from an upstream side upper edge of the recessed portion to a downstream side thereof, and the exothermic resistor of the sensor element is mounted downstream of an upstream end of the narrowest portion of the constricted passage. - View Dependent Claims (9)
- a sub-passage for enabling part of a fluid to pass therethrough;
Specification