JPH0440323A - Hot-wire type air flowmeter - Google Patents

Abstract

PURPOSE:To reduce an output noise by forming the minor axis side opening internal wall surface of a subordinate flow passage whose intake opening part is elliptic in parallel with the axial direction of the main flow passage and slanting the major axis side opening internal wall surface at an angle of <=90 deg. to the center axis. CONSTITUTION:The subordinate flow passage 12 which is formed integrally with a flowmeter main body while crossing the main flow passage 11 is provided in the main flow passage 11 of the flowmeter 1. The entrance 121 of the subordinate flow passage is formed elliptically and the center part 123 of the subordinate flow passage is formed circularly; and an internal wall whose minor axis direction is parallel to the main flow passage 11 and an internal wall 122 which has the opposite slanting surface whose major axis direction is at 45 deg. to the center axis of the circle 123 are formed between the elliptic part 121 and circular part 123. Further, a sensor circuit unit 2 consists of a hot-wire element 23 and a temperature sensing element 24 which are welded to a lead terminal 22 incorporated in a plastic molding 21 and loaded in the unit insertion opening 3 of the flowmeter 1. Then air 4 flowing in the flowmeter 1 passes through the main flow passage 11, part of it is guided to the subordinate flow passage 12 and reaches the subordinate flow passage 123 provided with the internal wall 122 having the slanting surface, and the air 4 is guided to the hot-wire element 23 without being disordered.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hot-wire air flow meter, particularly for configuring the intake system of an automobile engine, detecting the amount of intake air, and controlling the amount of fuel injection. This invention relates to a hot wire air flow meter for internal combustion engines suitable for use in internal combustion engines.

[Conventional technology]

Conventional hot-wire air flowmeters for internal combustion engines have a concave and elliptical shape for the sub-channel opening near the top of the recess in order to stabilize the flow rate distribution in the sub-channel against variations in the flow just before the flow meter inlet. It has a structure that equalizes the pressure.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into account flow disturbances caused by the shape of the inlet recess in the structure of the sub-channel, and therefore the hot wire element provided in the sub-channel does not detect the disturbance. , there was a problem with large output noise. When the output noise becomes large, the control to ensure that the engine is operated at optimum air/fuel efficiency becomes incomplete, and the exhaust gas from the engine is not cleaned.

This was an obstacle to improving fuel efficiency.

An object of the present invention is to provide an inlet shape of a sub-channel that can reduce output noise.

[Means to solve the problem]

The hot wire air flow meter of the present invention for achieving the above object has the following features:
The inlet opening of the sub-channel has a structure in which both long-diameter opening walls of a recess formed in the inflow portion face each other at an inclination angle of 90° or less with respect to the central axis.

[Effect]

With this configuration, there is no part at the entrance of the sub-channel that blocks the flow in a direction perpendicular to the main channel and causes stagnation, and the flow can be smoothly guided into the sub-channel. Therefore, it is possible to eliminate the flow turbulence that occurs due to damming up a portion of the inflowing air, and it is possible to reduce the output noise of the hot wire air flowmeter.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Diagrams showing one embodiment of the present invention will be described below.

FIG. 1 is a top view of a hot-wire air flow meter for an internal combustion engine according to the present invention, and FIG. 2 is a sectional view taken along the line II in FIG.

The flowmeter 1 is provided with a sub-flow path 12 in the main flow path 11, which is integrally formed with the flow meter main body and extends across the main flow path. The sub-channel inlet 121 has an elliptical shape, and the sub-channel center portion 123 has a circular shape. Between the elliptical shape 121 and the circular shape 123, there is an inner wall 12 whose minor diameter direction is parallel to the main flow path, and whose major diameter direction has an inclined surface facing the center axis of the circular shape 123 at 45 degrees.
It is connected by 2.

The sensor circuit unit 2 is formed of a hot wire element 23 and a temperature sensing element 24 welded to a lead terminal 22 built into a cylindrical plastic mold 21. The sensor circuit unit 2 is attached to the unit insertion port 3 provided in the flow meter 1, and the hot wire element 23 and the temperature sensing element 24 are arranged at the center of the sub-flow path.

The inflow air 4 that has entered the flow meter 1 passes through the main flow path, and a portion of it is guided to the sub flow path. The inner wall of the subchannel inlet has a slope of 12
2 is provided, and the air reaching the sub-flow path 123 is guided to the hot wire element 23 without being disturbed.

Figure 3 shows the maximum noise output, which shows the detection error of the sensor output with respect to the air flow rate, in terms of air flow rate, between a conventional sub-flow path with a concave inlet shape and a flow meter with a sub-flow path according to the present invention. Data showing the relationship between fluctuation widths is shown.

FIG. 3 shows that according to the present invention, the maximum noise output variation range is reduced by up to 1/3 depending on the flow point.

〔Effect of the invention〕

According to the present invention, it is possible to reduce air turbulence generated at the inlet of the sub-channel of the flowmeter, so the maximum output of the sensor output obtained by being detected by the hot wire element arranged in the sub-channel and amplified by the circuit unit. This has the effect of reducing the width of noise fluctuation9.Therefore, it has the effect of improving the control accuracy of the internal combustion engine, purifying the exhaust gas of the engine, and improving fuel efficiency.

[Brief explanation of drawings]

FIG. 1 is a top view of an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line 1-1 in FIG. 1, and FIG. 3 is a diagram showing the relationship between the maximum noise output fluctuation range and the air flow rate. 1...ff1l meter, 2...sensor circuit unit, 3...
・Unit insertion port, 4... Incoming air, 11... Main channel, 12... Sub-channel, 21... Plastic mold,
22... Lead terminal, 23... Hot wire element, 24...
・Temperature sensing element, 121... Sub-channel entrance. Figure: Funeral map. 50 IO2 9 Air flow rate Q (':/Ar')

Claims (1)

[Claims] 1. A main flow path constituting an intake air flow path of an internal combustion engine, a hot wire element for measuring the amount of intake air, and the hot wire element inside;
In the hot-wire air flowmeter, the sub-flow meter includes a sub-flow path provided in the main flow path, and the sub-flow path includes a flow path formed in the axial direction of the main flow path and a flow path formed in the radial direction of the main flow path. , the inlet opening has an elliptical or oval shape, the inner wall surface of the opening on the shorter diameter side is parallel to the axial direction of the main flow path, and the inner wall surfaces of both openings on the longer diameter side are at an angle of 90 degrees or less with respect to the central axis. A hot wire air flow meter characterized by having structures facing each other at an inclination angle of . 2. The hot-wire air flowmeter according to claim 1, wherein the sub-flow path formed in the axial direction of the main flow path is provided near the center of the main flow path. 3. In claim 1, the sub-channel is formed inside a bridge member that is integral with the body constituting the main channel and crosses the main channel through the center and bisects the main channel. A hot-wire air flowmeter characterized by: 4. The hot-wire air flow meter according to claim 1, wherein the inner wall surface of the opening on the major axis side of the elliptical inlet portion of the sub-channel is bellmouth-shaped. 5. In claim 1, the sub-channel formed in the axial direction of the main channel is eccentric to one side from the center of the main channel, and has an elliptical shape including the center of the main channel. A hot-wire air flowmeter characterized by: