AIR FLOW MEASURING DEVICE

• US 20170074703A1
• Filed: 09/01/2016
• Published: 03/16/2017
• Est. Priority Date: 09/11/2015
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: TSUCHIYA, Takuma
• Granted Patent: US 10,641,631 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01F 1/6842 with means for influencing the fluid flow
• CPC Class Codes: G01F 1/72 Devices for measuring pulsing fluid flows
• CPC Class Codes: G01F 5/00 Measuring a proportion of the volume flow

Abstract

The cross-sectional area of a reduced passage increases at a constant ratio from a maximum reduction part where a cross-sectional area of the reduced passage becomes the smallest toward a downstream side. The cross-sectional area of the reduced passage is equal to the cross-sectional area of a bypass passage at a downstream end of a cross-sectional area increasing region intersecting with a wall surface of the bypass passage. (Cross-sectional area increase ratio)=(B−A)/X is satisfied. A [mm²] is the cross-sectional area of the reduced passage at an upstream end of the increasing region. B [mm²] is the cross-sectional area of the reduced passage at the downstream end of the increasing region. X [mm] is a distance from the upstream end to the downstream end of the increasing region along an air flow direction through the reduced passage. The ratio is 1.5 [mm²/mm] or smaller.

Claims

1. An air flow measuring device comprising:

a bypass passage that takes in a part of air flowing through an air passage;

a flow rate detecting element that measures a flow rate of air flowing through the bypass passage; and

a reduced part that reduces a cross-sectional area of the bypass passage in a predetermined range in a flow direction of the air flowing through the bypass passage, wherein;

when a region of the bypass passage, in which the reduced part is provided, is referred to as a reduced passage, the flow rate detecting element is disposed in the reduced passage;

the cross-sectional area of the reduced passage increases at a constant ratio from a maximum reduction part of the reduced part, at which a cross-sectional area of the reduced passage becomes the smallest, toward a downstream side in the flow direction of the air;

the reduced part includes a cross-sectional area increasing region;

the cross-sectional area of the reduced passage is formed to be equal to the cross-sectional area of the bypass passage at a downstream end of the cross-sectional area increasing region, which intersects with a wall surface of the bypass passage;

an equation;

(cross-sectional area increase ratio)=(B−

A)/X 

 

(1)

is satisfied, where;

A [mm²] is the cross-sectional area of the reduced passage at an upstream end of the cross-sectional area increasing region;

B [mm²] is the cross-sectional area of the reduced passage at the downstream end of the cross-sectional area increasing region; and

X [mm] is a distance from the upstream end of the cross-sectional area increasing region to the downstream end of the cross-sectional area increasing region along a flow direction of air flowing through the reduced passage; and

the cross-sectional area increase ratio defined by the above equation (1) is set to be equal to or smaller than 1.5 [mm²/mm].

2. The air flow measuring device according to claim 1, wherein the flow rate detecting element is disposed at the maximum reduction part in the reduced passage.