JPH03242516A - flow measuring device - Google Patents

Abstract

PURPOSE:To remove divagation of a fluid by providing a sensor part approximately on the central axis of a flow path, and a generally cylindrical rectifying member having a through-hole extending approximately along the central axis of the flow path and the outer peripheral surface of which is streamlined approximately on the central axis at the upper position of the stream of the flow path. CONSTITUTION:A fluid running in a flow path 10 flows through a through-hole 13 of a rectifying member 14 and an interval between an outer peripheral surface of the rectifying member 14 and an inner peripheral surface of the flow path 10 to a sensor part 12. In this case, the axial component of the fluid running along the central axis of the flow path 10 passes smoothly through the through-hole 13 of the rectifying member 14 to the sensor part 12. On the other hand, the peripheral component running along the inner peripheral part of the flow path 10 flows through the interval between the outer peripheral surface of the rectifying member 14 and inner peripheral surface of the flow path 10. If the distribution of the flow velocity of the fluid is turned irregular, the flow of the fluid running through a part of the interval between the outer peripheral surface of the rectifying member 14 and the inner peripheral surface of the flow path 10 is increased, but runs mainly in the central part of the flow path 10.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a flow rate measuring device used, for example, to measure the intake air amount of an internal combustion engine, and particularly relates to a technique for improving measurement accuracy.

(Prior Art) Measuring the intake air amount of an internal combustion engine A conventional flow measuring device used is shown in FIG. 4 (see Japanese Utility Model Publication No. 6150323, etc.).

That is, in the figure, a hot film element 1 as a heat generating resistor which is interposed in an intake passage and constitutes a sensor section and a reference resistor 2 are connected in series. Further, a temperature compensation resistor 3 and a fixed resistor 4.5, which are arranged in the same atmosphere as the hot film element 1, are connected in series. These two series circuits are then connected in parallel to form a bridge circuit. The potential Us of the voltage dividing point a on the side where the real film element l and the reference resistor 2 of this bridge circuit are connected in series
(terminal voltage of reference resistor 2) and potential Us (terminal voltage of fixed resistor 5) at the voltage dividing point on the side where temperature compensation resistor 3 and fixed resistor 4.5 are connected in series. The differential amplifier 6 and transistors 7 and 8 control the current supplied to the fringe circuit.

Therefore, in a state where the bridge circuit is balanced, if the intake air flow rate increases, e.g.
is cooled further, its resistance value decreases, the bridge circuit becomes unbalanced, the terminal voltage Us of the reference resistor 2 increases,
The output of the differential amplifier 6 increases. This increases the supply current to the bridge circuit controlled by transistor 7.8, heats the hot film element 1 and increases its resistance value, restoring the equilibrium state of the bridge circuit.

Here, when the intake air temperature decreases, the hot film element 1 is cooled and its resistance value decreases, but the temperature compensation resistor 3, which is in the same atmosphere as the hot film element 1, is also cooled at the same time and its resistance value decreases. Therefore, changes in the current value supplied to the bridge circuit due to changes in intake air temperature are suppressed.

In other words, the intake air flow rate and the current supplied to the circuits correspond to zero regardless of the intake air temperature. For example,
By detecting the terminal voltage Us of the reference resistor 2, the intake air flow rate is measured.

For example, the hot film element 1 has a cylindrical structure in which a thin platinum film layer is coated on the outer peripheral surface of a ceramic tube serving as an insulating member having a predetermined area.

<Problems to be Solved by the Invention> By the way, the conventional flow rate measuring device as described above has the following problems.

That is, since the intake flow rate in a narrow range near the central axis of the intake passage is measured by the degree of cooling of the hot film element 1, the intake air flow rate flowing through the intake passage is measured.
For example, if a biased flow occurs in the intake air flowing in the intake passage due to an air cleaner placed upstream or a bend in the intake pipe, the average flow velocity of the intake air flowing in the intake passage and the sensor section may be adjusted. There is a difference in the inspiratory flow velocity in the affected area.

As a result, for example, the case where the upstream side of the sensor section 9 is a straight pipe as shown in FIG. 5(a), and the case where it is a bent pipe as shown in FIG. 5(b) are respectively indicated by AB. When the flow velocity distribution of the intake air is different, as shown in Fig. 6, there is a deviation in the relationship between the intake air flow rate Q and the output Us of the fL quantity meter, and the layout of the intake pipe that forms the intake passage is different for each car model. To do this, it is necessary to prepare a different correction coefficient map for correcting the folding ratio for each vehicle type, which causes the engine control system to become complicated.

In order to solve these problems, it has been known in the past to arrange a restrictor, a rectifier grid, and a rectifier plate in the intake passage, or these members reduce pressure loss (dynamic pressure damping effect).
Since this is intended to average out the deviation in the intake velocity distribution, this configuration sacrifices pressure loss.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide a flow rate measuring device that prevents the influence of uneven flow of fluid without sacrificing pressure loss.

<Means for Solving the Problems> For this reason, the flow rate measuring device of the present invention is equipped with a sensor section made of a hot body in the fluid passageway 2, and measures the fluid flow rate passing through the fluid passageway according to the fluid flow rate G. The second flow rate measuring device is equipped with a flow meter that detects based on a change in resistance of a heating resistor that changes in temperature, and the sensor section is disposed approximately on the central axis of the fluid passage, and the sensor part of the fluid passage is arranged approximately on the central axis of the fluid passage. A substantially cylindrical rectifying member having a through hole extending substantially along the central axis of the fluid passage and having a streamlined outer peripheral surface is disposed approximately on the central axis at an upstream position of the fluid passage.

<Operation> In this configuration, the fluid flowing through the fluid passage passes through the through hole of the rectifying member and between the outer circumferential surface of the rectifying member and the inner circumferential surface of the fluid passage, and flows in the direction in which the sensor section is located.

In this case, the axial component of the fluid flowing along the central axis of the fluid passage flows smoothly through the through hole of the rectifying member,
Leading to the sensor section.

On the other hand, the passage circumferential component flowing along the inner circumferential portion of the fluid passage passes between the outer circumferential surface of the rectifying member and the inner circumferential surface of the fluid passage.

For example, if a bias occurs in the fluid flow velocity distribution,
Although the flow of fluid that passes through a portion between the outer circumferential surface of the rectifying member and the inner circumferential surface of the fluid passage increases, this fluid flow is concentrated in the center of the passage.

That is, as a result of the increase in the flow of passing fluid as described above, the pressure increases, while in other parts the flow of passing fluid decreases, resulting in lower pressure.

As a result, the fluid that passes through one part flows smoothly along the streamlined shape of the rectifying member toward the other part where the pressure is lower, and since there is fluid flowing in the other part, it merges with this fluid flow. As a result, the fluid flows in a concentrated manner in the center of the passage, and the unbalanced flow of the fluid is eliminated.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, an intake pipe 10 constituting an intake passage on the downstream side of an air cleaner in an internal combustion engine has a larger diameter on the upstream side.
The downstream side is formed to have a small diameter, and the large diameter portion and the small diameter portion are smoothly connected by a substantially conical tapered portion, and a Hentury passage portion 11 is formed in this connected portion.

A sensor section 12 made of a hot film element or the like as a heating resistor in a flow meter is disposed on the central axis of the passage in the small diameter portion of the intake pipe 10.

This flowmeter is similar to the conventional one in that it detects the flow rate of fluid flowing through a fluid passage based on a change in resistance of a hot film element or the like whose temperature changes in accordance with the fluid flow rate.

At a position upstream of the sensor portion 12 of the passage in the intake pipe 10, that is, approximately on the central axis of the passage in the large diameter portion, there is a through hole 13 extending approximately along the central axis of the passage, and the outer circumferential surface is A substantially cylindrical flow regulating member 14 formed in a streamlined shape is provided.

Here, FIG. 2 is Q ~ a - b - c in FIG. 1 (a).
This is a diagram showing how the cross-sectional area of the passage changes according to O-a-b in this figure, and the streamlined shape of the outer circumferential surface of the flow regulating member 14 is set so that the cross-sectional area of the passage changes as shown by O-a-b in this figure.

The flow regulating member 14 is a mounting leg 15 whose one end is connected to the outer circumferential surface of the flow regulating member 14 and whose other end is connected to the inner circumferential surface of the intake pipe 10. It is held within the intake pipe 10 by four mounting feet 15 spaced apart at 90 degrees.

In addition, in the figure, 16 is a control circuit.

By providing the rectifying member as described above, the following actions and effects are achieved.

That is, the intake air flowing through the intake pipe 10 passes through the through hole 13 of the flow regulating member 14 and between the outer peripheral surface of the flow regulating member 14 and the inner peripheral surface of the intake pipe 10 in the direction in which the sensor section 12 is located.

In this case, the component of the intake air flowing along the central axis of the passage in the intake pipe 10, that is, the component of the intake air in the axial direction of the passage, is
It flows smoothly through the through hole 13 of No. 4 and reaches the sensor section.

On the other hand, a component of the intake air flowing along the inner circumferential portion of the passage in the intake pipe 10, that is, a component of the intake air in the circumferential direction of the passage passes between the outer circumferential surface of the rectifying member 14 and the inner circumferential surface of the intake pipe 10.

Here, for example, as shown in FIG. 3, the intake air flow velocity distribution C
If a deviation occurs in the air passage 5, the intake air flow passing through the portion D in FIG. 1 and FIG.

That is, as a result of the intake air flow passing through the above portion increasing,
While the pressure increases, on the other hand, in the portion E of FIG. 3 and FIG. 1(b), the intake air flow passing through it decreases, so the pressure decreases. As a result, in the D section, the intake air passing through E has a lower pressure.
Since there is intake air that flows smoothly along the streamlined shape of the rectifying member 14 toward the section E and flows through the section E, it merges with this intake air flow, and as a result, the intake air flows concentrated in the center of the passage. At the same time, due to the action of the venturi part 11, the intake air is concentrated in the center and flows to the sensor part 12, and the uneven flow of the intake air is eliminated.

As a result of the above, for example, the intake air flowing in the intake passage may have a biased flow caused by the air cleaner disposed upstream or the bending of the intake pipe, and the average flow velocity of the intake air flowing in the intake passage may There is no difference in intake flow velocity between the portions where the sensor section 12 is provided.

As a result, there is no difference in the relationship between the intake air flow rate and the output of the flowmeter, for example, depending on whether the upstream side of the sensor section 12 is a straight pipe or a bent pipe.

Therefore, even if the layout of the intake pipe that forms the intake passage differs depending on the car model, there is no need to prepare a different correction coefficient map for correcting the mixture ratio for each car model, and the engine control system Simplification becomes possible.

Furthermore, as is clear from the above explanation, the rectifying member 14 having such a configuration does not average out the bias in the velocity distribution of intake air due to pressure loss (dynamic pressure damping effect), but rather sacrifices the pressure loss. The advantage is that there is no

<Effects of the Invention> As described above, according to the present invention, there is provided a flow meter that detects the flow rate of fluid flowing through a fluid passage based on the resistance change of a heating resistor whose temperature changes in accordance with the fluid flow velocity. In the measuring device, since the fluid passage is provided with a substantially cylindrical rectifying member having a through hole extending approximately along the central axis of the passage and having a streamlined outer peripheral surface, the pressure can be reduced. Without sacrificing a few losses, it is possible to effectively prevent the difference between the average flow velocity of intake air and the intake flow velocity at the part where heat generating resistance is provided due to drift of intake air flow, etc., and in turn, simplify the engine control system. This is of great utility as it allows for

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a flow rate measuring device according to the present invention, in which (a) is a plan sectional view, (b) is a sectional view taken along the arrow A-A in (a), and FIG. 2 is a cross-sectional area. 3 is a schematic diagram illustrating the operation of the above embodiment; FIG. 4 is a circuit diagram illustrating the configuration of a conventional flowmeter; FIG. 5 is a schematic diagram illustrating the problems of the conventional flowmeter; FIG. 6 is a characteristic diagram showing the conventional problems. 10... Intake pipe 12... Sensor part 13...
・Through hole 14・-・Rectification member

Claims (1)

[Claims] In the flow rate measuring device, the flow rate measuring device includes a sensor section made of a heating element in a fluid passage, and a flow meter that detects a fluid flow rate flowing through the fluid passage based on a resistance change of a heating resistor whose temperature changes depending on the fluid flow velocity. A sensor portion is disposed approximately on the central axis of the fluid passage, and a through hole extending approximately along the central axis of the fluid passage is provided approximately on the central axis of the fluid passage at a position upstream of the sensor portion, and an outer peripheral surface thereof is provided. A flow rate measuring device characterized by having a substantially cylindrical rectifying member formed in a streamlined shape.