Airflow meter

• US 20050241386A1
• Filed: 04/27/2005
• Published: 11/03/2005
• Est. Priority Date: 04/28/2004
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Matsuura, Hideki, Kitahara, Noboru, Goka, Yasushi
• Granted Patent: US 7,043,978 B2
• Time in Patent Office: Days
• US Class Current: 73/202.500
• CPC Class Codes: G01F 1/6842 with means for influencing the fluid flow
• CPC Class Codes: G01F 5/00 Measuring a proportion of the volume flow

Abstract

An airflow meter has a bypass passage disposed in an air passage and a sensing portion disposed in the bypass passage to detect an airflow amount. The bypass passage is provided with a restriction portion to gradually decrease a passage width of the bypass passage in an airflow direction in the bypass passage. The restriction portion includes a first restriction portion and the second restriction portion disposed at an immediately downstream side of a narrowest portion of the first restriction portion. The first restriction portion gradually decreases the passage width in the airflow direction. The second restriction portion increases the passage width than the passage width at the narrowest portion in a stepped manner. The sensing portion is located in a bound in which the restriction portion is disposed.

Claims

1. An airflow meter for detect an airflow amount flowing in an air passage comprising a bypass passage disposed in the air passage and provided with:

a first restriction portion gradually decreasing a passage width of the bypass passage in an airflow direction in the bypass passage; and

a second restriction portion disposed at an immediately downstream side of a narrowest portion of the first restriction portion and increasing the passage width than the passage width at the narrowest portion in a stepped manner to limit the passage width to a constant width over a predetermined length in the airflow direction,

and further comprising a sensing portion located in a bound in which at least one of the first restriction portion and the second restriction portion is disposed.

2. The airflow meter according to claim 1, wherein the sensing portion is located at an immediately upstream side or at an immediately downstream side of the narrowest portion.

3. The airflow meter according to claim 1, wherein a stepped portion disposed between the first restriction portion and the second restriction portion is a slant face gradually increasing the passage width from the narrowest portion of the first restriction portion to the second restriction portion.

4. The airflow meter according to claim 1, wherein a downstream end portion of the second restriction portion is a slant face inclined toward an inner face of the bypass passage.

5. The airflow meter according to claim 1, wherein the second restriction portion is disposed to extend all over a width of the bypass passage or over a part of the width of the bypass passage.