JPH1114421A - Heating resistor-type air-flow-rate measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heating resistor-type air-flow-rate measuring instrument in which a measuring error due to the influence of a reverse flow is reduced, in which a drop in a flow velocity inside an auxiliary air passage is prevented in a forward flow and which maintains the measuring accuracy of an air flow rate by a method wherein a hole is formed between the exit and the entrance of the auxiliary air passage so as to sandwich a heating resistor. SOLUTION: The entrance part 10 of an auxiliary air passage 2 which is bypassed nearly in a U-shape via a partition wall 9 is formed. A hole 8 by which the inside of the auxiliary air passage 2 communicates is formed in the partition wall 9 between the entrance part 10 and the upstream side of a heating resistor 4. When a reverse flow is generated, reverse flow waves come in from the exit part 11 of the auxiliary air passage 2. Then, before the reverse flow waves are transmitted to the heating resistor 4 through the inside of the auxiliary air passage 2, they flow to the upstream side of the heating resistor 4 from the hole 8. As a result, the pressure on the upstream side becomes larger than the pressure on the downstream side of the heating resistor 4, and the influence of the reverse flow is reduced. In addition, in the case of a forward flow, the hole 8 makes the dead volume of the flow of the air inside the auxiliary air passage 2 communicate with a passage part other than it. As a result, the air flows to the upstream side from the downstream side of the heating resistor 4 through the hole 8, and the flow rate of the air flowing to the heating resistor 4 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air flow measuring device for measuring an intake air flow of an internal combustion engine, and more particularly to a heating resistor type air flow measuring device for measuring an air flow taken into an automobile engine.

[0002]

2. Description of the Related Art As a prior art, there is an air flow measuring device as disclosed in Japanese Patent Application Laid-Open No. Hei 7-113672, in which a sub air passage has a passage dedicated to backflow and forward flow and a heating resistor in a passage dedicated to forward flow. . This is intended to reduce the measurement error of the heating resistor type air flow measuring device caused by the influence of the backflow.

[0003]

However, the auxiliary air passage having the above-described structure has a problem that the auxiliary air passage structure is complicated because the auxiliary air passage has a passage dedicated to the backward flow and the forward flow. Further, the flow velocity detected by the heating resistor decreases due to an increase in ventilation resistance due to a complicated passage structure, a pipe resistance due to a bent portion, and the like. In particular, there is also a problem that the flow velocity near the idle becomes slow, and the detection accuracy of the heating resistor deteriorates.

The present invention simplifies the structure of the auxiliary air passage, reduces the measurement error due to the backflow, and furthermore, when the air flows from the inlet to the outlet of the auxiliary air passage in the forward flow, the heating resistor installed in the auxiliary air passage is provided. It is an object of the present invention to prevent a decrease in the flow velocity in the section (particularly, a decrease in the flow velocity in the vicinity of the idle speed of the engine, which is a problem due to a decrease in the flow velocity in the heating resistor section), and to sufficiently maintain the measurement accuracy.

[0005]

In order to solve the above-mentioned problem, a hole is provided between the entrance and exit of the sub air passage with the heating resistor disposed in the sub air passage therebetween. The effect of backflow is reduced by allowing the backflow wave entering from the sub air passage outlet to escape to the sub air passage inlet side before being transmitted to the heating resistor by the provided hole, and the hole provided by the pressure difference at the hole at the time of forward flow More air was allowed to flow to increase the flow velocity of the heating resistor in the sub air passage.

More specifically, the hole provided in the sub air passage is provided before the backflow wave entering the heating resistor disposed in the sub air passage from the sub air passage outlet is transmitted to the heating resistor. A hole that can escape to the inlet side, in other words, a backflow wave (pressure wave transmitted from the downstream side of the heating resistor) entering from the sub air passage outlet is transmitted upstream of the heating resistor before being transmitted to the heating resistor. By transmitting the backflow wave that has entered from the auxiliary air passage outlet to the heating resistor upstream before it is transmitted to the heating resistor, by comparing the upstream and downstream pressures of the heating resistor, due to the pulsation, (Pressure downstream of the heating resistor)> (pressure upstream of the heating resistor), and the effect of the backflow can be set to (pressure downstream of the heating resistor) <(pressure upstream of the heating resistor).

[0007] In the forward flow, the pressure in the sub air passage across the heating resistor disposed in the sub air passage is expressed as (pressure downstream of the heating resistor)> (pressure upstream of the heating resistor). A hole through which the flow rate of air flows due to the pressure difference is provided between the entrance and exit of the sub air passage at the relevant location with the heating resistor interposed therebetween. In other words, a hole is formed in the auxiliary air passage so as to allow the auxiliary air passage to communicate with the separation area and the place where the dead volume of the air flow can and cannot be formed due to the structure inside the auxiliary air passage with the heating resistor interposed therebetween.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of an air flow measuring device showing one embodiment of the present invention.

A heating resistor 4 and a temperature-sensitive resistor 5 for detecting the intake air temperature are arranged in the sub air passage 2.
The heat-generating resistor and the temperature-sensitive resistor are electrically connected to a module 7 having a built-in drive circuit via a support portion 6.

The sub air passage is integrated with the circuit module of the air flow meter, and is disposed in the air flow meter body 3 forming the main air passage 1.

Further, the auxiliary air passage is formed through a partition wall 9.
A sub-air passage detouring substantially in a U-shape, and a sub-air passage partition wall between the sub-air passage inlet portion 10 and the upstream of the heating resistor,
A hole 8 connecting the sub air passages is provided.

When a backflow occurs here, before the backflow wave entering from the sub air passage outlet 11 is transmitted through the sub air passage to the heating resistor, the heat is generated by the hole 8 formed in the partition wall. Can be transmitted to the upper body.

As a result, even when a backflow occurs, a comparison of the upstream and downstream pressures of the heating resistor 4 shows that (pressure downstream of the heating resistor) <(pressure upstream of the heating resistor), and the effect of the backflow is reduced. be able to.

The hole 8 provided in the partition wall should be located at a position where (distance from the sub air passage outlet to the heating resistor)> (distance from the sub air passage to the heating resistor through the hole in the partition wall). Is desirable.

The hole 8 provided in the partition wall is provided with a hole for communicating the dead volume of the air flow in the sub air passage 2 at the time of the forward flow and the sub air passage at the other portion. Therefore, air flows through the hole from the sub-air passage downstream of the heating resistor to the sub-air passage upstream of the heating resistor due to the pressure difference generated at both ends of the hole. As a result, the flow rate of air flowing to the heating resistor can be increased.

FIG. 2 is a sectional view of an air flow measuring device showing another embodiment of the present invention. In this structure, the hole 8 provided in the partition wall 9 has an angle toward the sub air passage entrance 10.

According to this structure, when a backflow occurs, a backflow wave can be transmitted to the sub air passage inlet 10, and the backflow wave is transmitted from the sub air passage inlet to the outside of the sub air passage. Thus, the backflow wave entering from the sub air passage outlet 11 can be transmitted to the outside of the sub air passage 2 from the sub air passage entrance without being transmitted to the heating resistor 4 installed in the sub air passage. Can be reduced. Further, at the time of forward flow, the same operation and effect as those of the embodiment shown in FIG. 1 are obtained, and the flow rate of air flowing to the heating resistor can be increased.

FIG. 3 is a sectional view of an air flow measuring device showing another embodiment of the present invention. This passage structure reduces the influence of the backflow by providing a hole 8 where the same effect as that of the embodiment shown in FIG. 1 is obtained when a backflow occurs, and furthermore, by the bent portion 12 in the sub air passage during the forward flow. One opening of the hole 8 is provided in the generated peeling area, and the same operation and effect as those of the embodiment shown in FIG. 1 can be obtained. A hole is provided to connect the sub air passages to each other.

[0019]

According to the present invention, the influence of backflow when backflow occurs is reduced, and the flow velocity in the sub air passage can be increased even during forward flow. Improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an air flow measuring device according to an embodiment of the present invention.

FIG. 2 is a sectional view of an air flow measuring device according to one embodiment of the present invention.

FIG. 3 is a sectional view of an air flow measuring device according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Main air passage, 2 ... Sub air passage, 3 ... Air flow meter body, 4 ... Heating resistor, 5 ... Temperature sensitive resistor, 6 ... Support part, 7
... Module, 8 ... Hole, 9 ... Sub air passage partition wall, 10
... Sub air passage inlet, 11 ... Sub air passage outlet, 12 ... Bend in the sub air passage.

Claims (4)

[Claims] 1. An auxiliary air passage provided with a heating resistor for measuring an air flow rate based on a heat release amount to intake air in order to measure an intake air flow rate of an internal combustion engine. In the heating resistor type air flow measuring device disposed in the air passage, the sub air passage has one or more bends downstream of the heating resistor, and further includes a bend at a separation portion area in the sub air passage generated by the bend. A heating resistor type air flow measuring device, wherein a hole for connecting the auxiliary air passage is provided upstream of the heating resistor. 2. The auxiliary air passage has at least two bends that are turned back, and further has a hole connecting the auxiliary air passage before and after the bend to a dead volume region of a flow in the auxiliary air passage caused by the bend. A heating resistor type air flow measuring device provided upstream of the heating resistor. 3. A heating resistor type air flow measuring device according to claim 2, wherein a hole communicating with the auxiliary air passage is opened toward the auxiliary air passage inlet. 4. At least a heating resistor for detecting an air flow rate, a temperature-sensitive resistor for temperature compensation, a circuit for driving them, and a housing member for holding them are provided, and are integrated with a sub air passage. A heating resistor type air flow measuring device according to any one of claims 1 to 3.