Airflow meter

• US 6,786,089 B2
• Filed: 09/25/2002
• Issued: 09/07/2004
• Est. Priority Date: 03/28/2002
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Iwaki, Takao, Goto, Koichi, Takeuchi, Yukihiro, Goka, Yasushi
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US10/253,502
• Publication Number:
  US 20030182998A1
• Time in Patent Office: 713 Days
• Field of Search: 732/025, 731/182, 732/042.2, 732/042.6, 732/042.1
• US Class Current: 73/204.21
• CPC Class Codes: G01F 1/6842 with means for influencing the fluid flow
• CPC Class Codes: G01F 15/12 Cleaning arrangements; Filters
• CPC Class Codes: G01F 5/00 Measuring a proportion of the volume flow

Abstract

An airflow meter has a member that defines a bypass passage. The bypass passage has a sensing passage in which a sensor tip is disposed. The sensing passage is restricted in at least a lateral direction that is a direction perpendicular to both a longitudinal direction of the sensing passage and a perpendicular direction perpendicular to the surface of the sensor tip. This arrangement defines relatively wider distance in the perpendicular direction on the sensor tip.

Claims

1. An airflow meter, comprising:

a member that defines a bypass passage in which a bypass air flow comprising a part of air flowing in a main passage is introduced; and

a sensor element disposed in the bypass passage, for detecting an amount of airflow, said sensor element being disposed so that a width of the sensor element is perpendicular to a direction of bypass air flow therepast, wherein

the bypass passage has a sensing passage which restricts a cross-sectional area of the bypass passage along a longitudinal direction of the bypass passage at least before the sensor element, the sensing passage being restricted in a lateral direction that is perpendicular to said direction of bypass air flow and parallel to a width direction of the sensor element.

2. The airflow meter according to claim 1, wherein

the sensor element has a surface for detecting the amount of airflow, and the member comprises:

an outside member defining the sensing passage; and

a partition member disposed in the sensing passage for separating the sensing passage, the partition member supporting the sensor element so that the surface of the sensor element is supported in parallel to the longitudinal direction of the sensing passage, and

the lateral direction is perpendicular to both the longitudinal direction of the sensing passage and a perpendicular direction perpendicular to the surface of the sensor element.

3. The airflow meter according to claim 2, wherein the outside member defines a lateral surface that decreases the width of the sensing passage in the lateral direction, and a perpendicular surface that is perpendicular to the lateral surface and that faces the sensor element and decreases a width of the sensing passage in the perpendicular direction.

4. The airflow meter according to claim 3, wherein the sensor element is a unidirectional sensor that detects the amount of airflow in a forward direction of the longitudinal direction, and the outside member defines a means for decreasing an airflow in a reverse direction of the longitudinal direction.

5. The airflow meter according to claim 3, wherein the sensor element is a bi-directional sensor that detects the amount of airflow in both of a forward and reverse directions of the longitudinal direction, and the outside member defines curved surfaces or slopes on both ends in the longitudinal direction to introduce both the forward and the reverse airflows to the sensor element.

6. The airflow meter according to claim 5, wherein the outside member defines a plane parallel to the longitudinal direction, the plane being located on a lateral side of the sensor element.

7. The airflow meter according to claim 1, wherein the bypass passage has a largest cross-sectional area at an inlet thereof, and the sensing passage being restricted in both width in the lateral direction and width in a perpendicular direction perpendicular to the sensor element.

8. The airflow meter according to claim 7, wherein the sensing passage is gradually restricted from upstream of the sensor element to downstream of the sensor element.

9. The airflow meter according to claim 7, wherein the sensing passage is gradually restricted in width in a perpendicular direction that is perpendicular to the surface of the sensor element before the sensing passage is gradually restricted in both directions.

10. The airflow meter according to claim 7, wherein the sensing passage has a profile that decreases airflow in a reverse direction of the longitudinal direction.

11. The airflow meter according to claim 7, wherein the sensing passage has a profile that is capable of regulating airflow in both of a forward direction and a reverse direction of the longitudinal direction.

12. The airflow meter according to claim 7, wherein the sensing passage has a profile that abruptly changes restricting rate at a point close to the sensor element.

13. The airflow meter according to claim 7, wherein the sensing passage is defined by surfaces that has different heights.

14. The airflow meter according to claim 7, wherein the sensing passage defines a constant cross-sectional area or a decreasing cross-sectional area at a predetermined area downstream to the sensor element.

15. The airflow meter according to claim 7, wherein the member defines the bypass passage so as to protect the sensor element from an inlet of the bypass passage.

16. The airflow meter according to claim 1, wherein the sensing passage is restricted only in width in the lateral direction, the sensing passage being restricted by a surface that is gradually increased in height at upstream to the sensor element and is gradually decreased in height at downstream to the sensor element, and the sensing passage is defined as follows:

1.0≦

L1/H

1.0≦

L2/H

2.5≦

W/H≦

20.0

wherein H is a maximum height of the surface, L1 is a length in the longitudinal direction between a beginning point of restriction and the maximum height, L2 is a length in the longitudinal direction between the maximum height and an ending point of restriction, and W is a width of the bypass passage.

17. The airflow meter according to claim 16, wherein the sensing passage is restricted in an asymmetrical manner in the longitudinal direction with respect to the maximum height.

18. The airflow meter according to claim 16, wherein the sensing passage is restricted in a symmetrical manner in the longitudinal direction with respect to the maximum height.

19. The airflow meter according to claim 18, wherein the sensing passage is restricted by a curved surface.

20. The airflow meter according to claim 18, wherein the sensing passage is restricted by a trapezoid surface.