JP2001091324A - Heat resistor type air flowrate measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an accurate heat resistor type air flowrate measuring device superior in treatment and low in cost. SOLUTION: The heat resistor type air flowrate measuring device is provided with a main air flow path body 20 forming a main air flow path 22 where air flows and a measuring module 52 containing heating resistors 3, 4, etc. inserted in the main air flow path body for measuring air flowrate. The measuring module 52 has a heating resistor and the like inside a sub-air flow path body 10 forming an L-shape sub-air flow path 13 consisting of an inlet opening 11, a vertical path 13a, a horizontal path 13b and an outlet opening 12 opening to the parallel direction to the main flow line. The main air flow path body 20 has an orifice 21 on the periphery of the side wall inside upstream the sub-air flow path body 10. Inside a flux region D forming the air flow 23 expanding from the tip end of the orifice 21 to the parallel direction of the main flow line, both the inlet opening 11 and outlet opening 12 are arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As a conventional technique for improving the measurement accuracy under a pulsating flow of a heating resistor type air flow measuring device used in an internal combustion engine, a passage structure having an L-shaped detection tube disclosed in Japanese Patent Application Laid-Open No. 2-1518 is disclosed. Things are disclosed. That is, by providing a wall for the flow in the reverse direction, the passage structure is such that the heat flow does not directly hit the heating resistor. By adopting such a passage structure, the detection value of the heating resistor type air flow measuring device, which is generated when the pulsation amplitude becomes large even without backflow, that is, the so-called binary phenomenon is improved.

Further, as a structure having a throttle in the passage,
There is one disclosed in JP-A-1-110220. This structure is a structure in which a heating resistor is disposed immediately downstream of a throttle in a detection tube having a short distance from a straight pipe with respect to a main flow direction.

[0004]

In the above-mentioned prior art, it is impossible to measure the flow direction separately. For this reason, if the average output of the heating resistor type air flow meter is plotted by changing the boost pressure by gradually opening the throttle valve while keeping the rotation speed constant, for example, as shown in FIG. A jumping phenomenon that gradually increases with respect to the flow velocity (flow rate) and indicates a measurement error on the plus side occurs. This is because, as shown in FIG. 13, the pulsation amplitude of the heating resistor type air flow meter gradually increases, and backflow occurs after point B. When a backflow occurs, the heating resistor cannot determine the direction of the flow, so that the forward flow and the reverse flow are similarly detected, so that the average output increases. This phenomenon is particularly noticeable in engines with four cylinders or less.
It is known that this phenomenon is likely to occur in a relatively low rotation speed range of 000 to 2,000 rpm, and is unlikely to occur in an engine having more cylinders.

For this reason, by providing a wall for the reverse flow, which is one of the prior arts described above, the passage structure is such that the reverse flow does not directly hit the heating resistor, thereby reducing errors due to the reverse flow. It is possible. However, the reduction is only half. This is because when a backflow occurs, the forward flow also increases accordingly. And it is difficult to eliminate backflow in the intake pipe due to the configuration of the engine and its intake pipe. Therefore, in order to reduce the error due to the backflow, a complicated method such as a structure for subtracting the backflow from the forward flow, a structure for measuring not only the forward flow but also the backflow, and the like must be adopted.

Accordingly, an object of the present invention is to provide a simple configuration,
It is an object of the present invention to provide a heating resistor type air flow measuring device which is improved in measurement accuracy (including low variation accuracy) under a pulsating flow accompanied by a reverse flow when mounted on an actual vehicle, and which is inexpensive and excellent in handleability.

[0007]

According to a first aspect of the present invention, there is provided a heating resistor type air flow measuring device which achieves the above object, comprises a main air passage which forms a main air passage through which a fluid to be measured flows, and a main air passage inserted into the main air passage. A heating module for measuring the flow rate of the fluid to be measured, the heating module including a heating resistor and the like, wherein the measurement module includes an inlet opening that opens in a direction perpendicular to a main streamline of the fluid to be measured. A heating element and the like inside a sub air passage body forming a substantially L-shaped sub air passage including a portion and an outlet opening opening in a direction parallel to the main streamline; The passage body has a throttle around an inner side wall located on the upstream side of the sub air passage body, and a flow area of a flux region formed by the measured fluid extending from a tip of the throttle in a direction parallel to the main streamline. Inside, the entrance In which both the openings of the mouth the outlet opening is arranged.

According to the present invention, the increase in the flow velocity in the flux region formed by the throttle reduces the influence of the backflow flowing through the auxiliary air passage having both openings disposed in the flux region. Therefore, the measurement accuracy is improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a front (cross-sectional) view showing a heating resistor type air flow measuring device according to an embodiment of the present invention. FIG. 2 is a side view as viewed from the upstream side in FIG. This will be described with reference to FIGS.
The heating resistor type air flow measuring device (hereinafter, referred to as a flow measuring device) includes a measuring module 52 for measuring a flow rate and a body 53 forming the main air passage 22 (that is, the main air passage body 2).
0) and a screw 54a and a seal 54b as components for attaching the measurement module 52 to the body 53.

That is, the body 5 forming the main air passage 22
A hole 25 is formed in the wall surface of the main air passage body 20 serving as 3. The measurement module 52 (of the sub air passage body 10) is inserted into the hole 25 so that the mounting surface of the main air passage body 20 is The mounting surface of the housing 1 is fixed by screws 7 or the like so as to maintain mechanical strength. Further, a seal 54b is attached between the measurement module 52 and the body 53 (the main air passage body 20) to maintain airtightness.

On the other hand, the measuring module 52 mainly comprises a housing 1 containing a circuit board 2 on which a drive circuit described later is mounted, and a sub air passage 10 made of a non-conductive member. A heating resistor 3 for detecting an air flow rate and a temperature-sensitive resistor 4 for compensating an intake air temperature are electrically connected to the circuit board 2 via a support 5 made of a conductive member. It is arranged to be. That is, the housing 1, the circuit board 2, the heating resistor 3, the temperature-sensitive resistor 4, the sub air passage 10, etc.
It is integrated as.

The operation principle of the flow rate measurement of the flow rate measuring device will be described from the circuit configuration. FIG. 3 is a circuit configuration diagram showing the heating resistor type air flow measuring device of FIG. The drive circuit formed on the circuit board 2 of the flow measurement device is roughly composed of a bridge circuit and a feedback circuit. Heating resistor 3 (RH) for measuring intake air flow rate, temperature-sensitive resistor 4 for compensating intake air temperature
(RC), the above-mentioned bridge circuit is assembled by the resistors R10 and R11, and the heating current is supplied to the heating resistor RH so as to maintain a constant temperature difference between the heating resistor RH and the temperature-sensitive resistor RC while applying feedback using the operational amplifier OP1. Ih is flown to output an output signal V2 corresponding to the air flow rate. That is, when the flow velocity is high, a large amount of heat is taken from the heating resistor RH, so that a large amount of the heating current Ih flows. On the other hand, when the flow velocity is low, the amount of heat taken from the heating resistor Rh is small, so that the heating current can be reduced. The amount of heat deprived from the heating resistor Rh is the same regardless of the direction of the flow of air, whether it is a forward flow or a reverse flow. Therefore, the heating current Ih flows even at the time of the reverse flow, and a jumping-up phenomenon of the flow measurement device occurs.

Returning to FIG. 1 and FIG. 2, the configuration characteristic of the present invention will be described in detail. The sub air passage body 10 as “the passage structure forming the L-shaped detection tube” has a sub air passage inlet 11 that opens vertically to the main streamline of the forward air flow 23, A vertical passage 13a extending from the sub air passage inlet 11 in parallel with the main streamline;
A lateral passage 13b that is bent substantially at right angles and extends perpendicular to the main streamline, and a sub air passage outlet 12 at the end of the lateral passage 14 that opens parallel to the mainstream line. A substantially L-shaped auxiliary air passage 13 (vertical passage 13a and horizontal passage 14) is formed. In general, the heating resistors such as the heating resistor 3 and the temperature-sensitive resistor 4 are disposed inside the vertical passage 13a.

On the other hand, main air passage 2 as body 53
0 has a throttle 21 formed around the inner side wall of the main air passage body 20 on the upstream side of the inserted sub air passage body 10, and serves as an inlet opening (surface) of the above-described sub air passage body 10. The opening (surface) of the sub air passage inlet 11 and the sub air passage outlet 12 as the outlet opening (surface) is formed so that the forward air flow 23 as the fluid to be measured flows from the tip of the throttle 21 to the main streamline. A flux region D formed by extending in a direction parallel to the main surface (an inner region surrounded by streamlines G1 and G2 extending in a direction parallel to the main streamline from the tip of the throttle 21 as shown in FIG. 1). For example, if the main air passage body 20 is a circular pipe as shown in FIG. 2, the main air passage body 20 is disposed so as to enter the inside of a flux region corresponding to the inner diameter D).

That is, as shown in FIG.
The shape of the main air passage body 20 into which 0 is inserted is substantially cylindrical.
(Circular pipe), and the effective cross-sectional area formed by the flux of the air flow as the fluid to be measured flowing through the main air passage 22 formed by the main air passage body 10 is determined by the inlet / outlet opening (as the inlet / outlet opening of the sub air passage body 10). The sub air passage inlet 11 and the sub air passage outlet 12) are included.

In other words, a throttle 21 is formed around the inner side wall of the main air passage body 20 located upstream of the sub air passage body 10.
Is provided. The cross-sectional shape of the throttle 21 is the same as that of the main air passage 22.
And a venturi-shaped cross section having substantially the same central axis as that of the diaphragm 21. The upstream side of the diaphragm 21 has a substantially arc shape.
Is substantially perpendicular to the forward airflow 23. Further, as shown in FIG. 2, when the throttle 21 and the sub air passage inlet 11 and the sub air passage outlet 12 of the sub air passage body 10 are viewed from the upstream side, the arrangement of the throttle 21 and the inner diameter D (shown in FIG. Both the sub air passage inlet 11 and the sub air passage outlet 12 are arranged inside the flux region D). The auxiliary air passage inlet 11 is located at a position near the passage wall near the inside of the stream line G1 shown in FIG. 1, and the auxiliary air passage outlet 12 is located near the passage wall near the inside of the stream line G2 shown in FIG. It is desirable to be arranged at the position.

The upstream half of the throttle 21 is formed in an arc shape.
(Bellmouth shape) in order not to disturb the air flow near the center of the passage downstream of the throttle 21.
As shown in FIG. 5 described below, the downstream half of the throttle 1 is shaped substantially perpendicular to the main streamline direction of the air flow.
This is because the separation in the forward air flow 23 is likely to occur on the downstream side of the air flow. This makes it possible to increase the forward flow velocity during pulsation without disturbing the flow downstream of the inside of the throttle diameter.

That is, the features of the heating resistor type air flow measuring device according to the present invention are that a main air passage forming a main air passage through which the fluid to be measured flows, In a heating resistor type air flow measurement device including a measurement module including a heating resistor for measuring a flow rate, the measurement module includes an inlet opening that opens in a direction perpendicular to a main streamline of the fluid to be measured, A vertical passage extending from the inlet opening in parallel with the main streamline, a horizontal passage communicating with the vertical passage, bending at a substantially right angle and extending perpendicular to the main streamline, and a main streamline at an end of the horizontal passage. A sub-air passage body that forms a substantially L-shaped sub-air passage composed of an outlet opening portion opened in a direction parallel to the sub-air passage body, and holding the heating resistor and the like inside the sub-air passage body; The main air passage body Having a throttle around the inner side wall located on the upstream side of the sub air passage body, inside a flux region formed by the fluid to be measured extending from the tip of the throttle in a direction parallel to the main streamline, It can be said that both the opening of the inlet and the opening of the outlet are provided.

Next, referring to FIGS. 4 and 5, a description will be given of a mechanism for reducing a jump error and a binary phenomenon caused by a backflow by the characteristic structure of the present invention having a restriction on the upstream side of the L-shaped auxiliary air passage body. A description will be given based on a comparison of the presence or absence of a diaphragm using the above. FIG. 4 is a diagram showing a mechanism for reducing a jump error by the diaphragm according to the present embodiment. FIG. 5 is a diagram illustrating a mechanism of reducing the binary phenomenon by the diaphragm according to the present embodiment.

First, FIGS. 4 (a) and 4 (b) show flow velocity waveforms compared with and without the restriction. If there is no conventional aperture,
Even if a reverse flow like the flow velocity waveform shown in FIG. 4 (a) occurs in the main air passage, the flow direction cannot be detected by the heating resistor alone, so that the flow velocity shown in FIG. The waveform is folded near zero. Also, as shown in the waveform of the sub air passage effect shown in FIG. 4 (a), by adopting the L-shaped sub air passage described above, it is possible to prevent the backflow from entering the sub air passage.

If there is a flow velocity amplitude that occurs up to the reverse flow at the average flow velocity U1 when there is no throttle, the reverse flow will not enter the sub air passage due to the effect of the sub air passage, but the response delay of the heating resistor will be reduced. Since the average value of the considered waveform does not deduct the portion where the backflow has occurred, the forward flow increases by that amount, and ΔU1 increases. This ΔU1 becomes a detection error due to the backflow.

On the other hand, if the throttle is arranged upstream of the L-shaped auxiliary air passage, a separation vortex is generated downstream of the throttle, so that the effective cross-sectional area of the main air passage is reduced at the auxiliary air passage arrangement portion. The average flow velocity U2 is faster than U1, and the pulsation amplitude also increases. However, for backflow, there is no means to reduce the effective cross-sectional area of the passage in the sub air passage arrangement part, that is, the restriction on the upstream side of the sub air passage is irrelevant to backflow. ΔU1 as an effect of flow rate)
And ΔU2 show almost the same value. That is, by arranging the throttle upstream of the sub air passage, only the average flow velocity can be increased without changing the reverse flow rate.

Therefore, the measurement error (bounce error) due to the backflow of the flow measuring device is the above-mentioned relationship, that is,
From U1 <U2, ΔU1 = ΔU2, (ΔU1 / U
1)> (ΔU2 / U2) holds, and the measurement error due to the backflow can be reduced when a throttle is provided upstream of the sub air passage.

On the other hand, as an effect of providing a throttle upstream of the auxiliary air passage, there is a reduction in the detection value of the flow rate measuring device, which is caused when the pulsation amplitude increases even without backflow, that is, an improvement in the so-called binary phenomenon. Can be As shown in FIG. 13, the binary phenomenon is a decrease in output that occurs when the throttle valve is gradually opened while the rotation speed is kept constant to change the suction negative pressure. This occurs because the output characteristics of the heating resistor with respect to the air flow rate (flow velocity) have a non-linear relationship.

When such a phenomenon occurs, two different operating conditions exist for the same flow rate instruction value, so that the engine control system cannot perform accurate fuel control. As described in the prior art, this phenomenon can be avoided to some extent by arranging the heating resistor in the L-shaped auxiliary air passage having a bend without restriction. However, in order to improve the binary phenomenon for all engines, it is necessary to optimize the shape of the L-shaped auxiliary air passage for each engine. On the other hand, the restriction on the upstream side of the sub air passage provided in the heating resistor type air flow measuring device according to the present invention is effective for improving the binary phenomenon in all engines. This will be described with reference to FIGS. 5A and 5B showing flow velocity distributions compared with and without the restriction.

As shown in FIGS. 5 (a) and 5 (b), the flow velocity distribution of the air flow in the pipeline generally shows a nearly parabolic distribution in a steady state. However, under the pulsating flow, when the flow velocity amplitude gradually increases, the distribution shape becomes a flow velocity distribution that approaches a flat shape from a parabolic shape. When this is compared with the presence or absence of the aperture, in the case of no aperture, FIG.
As shown in FIG. 5B, when there is a stop, the state becomes as shown in FIG.

In FIG. 5B, if there is a throttle 21, the vicinity of the wall surface of the main air passage 22 becomes a shadow of the throttle 21, so that it becomes difficult for air to flow. Therefore, the flow rate of the air flow becomes extremely high in other portions, that is, in the downstream portion of the region D of the throttle 21 (for example, the inner diameter D of the circular pipe). Furthermore, the increase in the flow velocity at a position on the side of the passage wall deviated from the center is larger than that of the center of the passage downstream of the inner diameter of the throttle 21 shown in the drawing. At this point, the sub air passage inlet 11 described above is disposed at the position near the passage wall near the inside of the flow line G1, and the sub air passage outlet 12 is disposed at the position near the passage wall near the inside of the flow line G2. There is a reason.

As described above, the flow velocity increase ΔU1 'at the position on the side of the passage wall shown in FIG.
The flow velocity increase ΔU2 ′ at the position on the side of the passage wall shown in FIG.
Therefore, if the inlet and outlet of the sub air passage are arranged downstream of the region D, the flow velocity flowing in the sub air passage increases with the increase of the pulsation amplitude. I do. Therefore, even if the output of the heating resistor decreases due to the non-linearity, the increase in the flow velocity that increases the flow velocity flowing through the auxiliary air passage can cancel the decrease. However, if the throttle size (inner diameter D) is too small, the increase in the flow velocity becomes too large, and a phenomenon occurs in which the output of the heating resistor increases despite the occurrence of no backflow. For this reason, in consideration of the reduction of the backflow effect and the reduction of the binary phenomenon, the ratio of the effective area A1 of the main air passage 20 to the effective area A2 of the throttle 21 (effective area of the region D) will be described later. Must be set to the optimal value.

Since the effect of increasing the flow velocity described above is greater at a position where the flow velocity is high, the inlet / outlet of the auxiliary air passage is disposed inside the downstream portion of the area D of the throttle 21 (for example, the inner diameter D of a circular pipe). It is important to be. In other words, the sub air passage inlet 11, which opens substantially perpendicular to the main stream line direction of the air flow, must have an arrangement structure in which the dynamic pressure of the flow is directly applied, The auxiliary air passage outlet 12 which is opened in parallel needs to have an arrangement structure that applies a dynamic pressure upstream of the outlet and generates a separation vortex to enhance the suction effect of the outlet. Further, since the auxiliary air passage outlet 12 is opened substantially parallel to the main streamline direction, the loss due to collision between the wall surface of the main air passage body 20 and the air flow must be suppressed. , The auxiliary air passage outlet 12 must be properly spaced from the wall.

Next, the results of experimentally studying the dimensions of the above-described aperture using an actual vehicle are shown in FIGS.
This will be described with reference to FIG. FIG. 6 is a diagram showing the relationship between the size of the stop and the jump error. FIG. 7 is a diagram illustrating a relationship between the entrance / exit relative position of the aperture and the output noise. As the contents of the experiment, as shown in FIG.
Open the throttle gradually while keeping the rotation speed constant,
This is a plot of the detection error indicated by the heating resistor when the throttle is fully opened, with the aperture size (inner diameter D) changed. According to the experiment, as shown in FIGS. 5B and 6, the size of the throttle is determined by the effective sectional area A1 of the main air passage in which the sub air passage is arranged and the effective sectional area A2 of the throttle inner diameter D. Aperture ratio R (A2 /
In the range of A1) ≧ 70 (%), the effect of reducing the jump error due to the backflow was obtained.

On the other hand, it has been found that when the aperture ratio R is smaller than 70%, the output starts to increase. This is because, as described above, when the amplitude increases downstream of the throttle, the detected flow velocity itself increases. For reference, the same examination results at a rotation speed at which no backflow occurs are also shown, but it was confirmed that the output sharply increased at a throttle ratio R <70%. Therefore, the sectional area A1 of the main air passage in which the sub air passage is arranged
And the ratio of the cross-sectional area A2 of the inner diameter of the throttle to R (A2 / A1)
≧ 70% is considered reasonable. However, the aperture ratio R = 1
Considering the case of no aperture of 00 (%) (equivalent to the conventional art), to reduce the jumping error, 90 ≧ R ≧ 70
It can be said that the range of (%) is desirable. In particular, if the error is halved, the range of 80 ≧ R ≧ 70 (%) is desirable.
Further, the effect of reducing the jump error is as follows: 80 ≧ R ≧ 70
If the distance L from the stop 21 to the entrance opening 11 shown in FIG. 1 is in the vicinity of the relation of L = 0.7D as shown in FIG. Have been.

Next, the relationship between the positional relationship between the throttle and the entrance and exit of the sub air passage and the output noise of the flow measuring device under a steady flow will be described with reference to FIG. 7, the vertical axis represents the value of the output noise, and the horizontal axis represents the aperture ratio R as in FIG. The drawing dimension of the sample product used in the present study was a drawing ratio R = about 60 (%). Accordingly, the fact that the throttle ratio R is within the range of 60 (%) or less means that the entrance / exit position of the sub air passage is the throttle 21
(The area on the wall side outside which is surrounded by the main streamline directions G1 and G2 shown in FIG. 1).

As shown in FIG. 7, the aperture ratio R100 to 60
In the range of (%), the output noise became smaller as the aperture ratio R became smaller. However, in the range of 60% or less, an increase in output noise was clearly observed. That is, when both positions of the entrance and exit of the sub air passage are in the area D (the area inside the main stream line direction G1 and G2 shown in FIG. 1), the output noise is reduced. Basically, it has been found that the output noise can be reduced by increasing the aperture ratio R, that is, by reducing the aperture size and increasing the flow velocity. If there is a restriction on the upstream side and separation occurs on the downstream side, in other words, if both positions of the entrance and exit of the sub air passage are in the shaded area of the restriction 21, the flow of the main air passage is disturbed and the output It turned out to increase the noise.

From the above results, since the value of the flow velocity flowing in the sub air passage is determined by the pressure difference between the entrance and the exit, it is necessary to take measures to disturb the upstream flow at both the entrance and the exit. Therefore, when a throttle or the like is arranged upstream of the sub air passage, it can be said that it is necessary to consider the relative position between the entrance and exit of the sub air passage and the size of the throttle from the viewpoint of output noise. From the results of FIGS. 6 and 7, it can be said that the range of 90 ≧ R ≧ 70 (%) is desirable in order to reduce the jump error and the output noise.

Next, another embodiment will be described with reference to FIGS.
0 will be described. FIG. 8 is a sectional view showing a heating resistor type air flow measuring device according to another embodiment of the present invention.
A cross section of a flow measuring device in which a straight pipe 41a with a throttle forming a main air passage is integrated with a part of the air cleaner clean side 41 of the air cleaner 68 is shown. In the figure, an air cleaner 68, which is one of the intake pipe constituent members forming the intake system, has an air cleaner clean side 4 integrally forming a straight pipe 41a with a throttle as the main air passage body 20.
1, an air cleaner dirty side, and an air filter element 43.

In this embodiment, a throttle 21 is provided at an intake outlet of an air cleaner clean side 41 (a duct located downstream of an air filter 43), and a straight pipe 41a with a throttle as a main air passage body 20 is provided downstream of the throttle 21. The measurement module 52 shown in FIG. 1 (the sub air passage body 10) is inserted into the hole 25 provided on the wall surface of the straight pipe 41a with the throttle. In the present embodiment, the air cleaner 68 as an existing intake pipe component is configured so that the main air passage body 20 including the throttle 21 and the hole 25 is also used. System cost can be reduced.

FIG. 9 is a sectional view showing a heating resistor type air flow measuring device according to another embodiment of the present invention. This figure shows a flow measurement device in which a throttle 21 is provided in a part of an air cleaner clean side 41 and a main air passage body 20 is further joined to the air cleaner clean side 41. FIG. 10 is a partially enlarged view showing the joint of FIG. The details of the spigot part 47 as a connecting part and the joining part 48 are shown.

This embodiment is basically the same as the embodiment shown in FIG. 8, except that the outlet opening of the air cleaner 68 as a suction outlet portion is formed as a bell mouth-shaped throttle 21.
A body 53 serving as the main air passage body 20 of the flow rate measuring device is mechanically connected downstream of the body 53 by bonding or screwing at the spigot portion 47 and the joint portion 48. That is, the throttle of the main air passage body constituting the heating resistor type air flow measurement device, which is separated from the main air passage body,
It is provided at an intake outlet portion of the intake pipe component to which the main air passage body is connected. In the present embodiment, since the throttle 21 is also used as the existing intake pipe component member, it is possible to reduce the need for a dedicated throttle, and to use the existing heating resistor type air flow measuring device without the throttle, so that the customer car manufacturer can use it. System cost can be reduced.

FIG. 11 is a diagram showing an electronic fuel injection control type internal combustion engine of one embodiment in which the flow rate measuring device of this embodiment is mounted. 1 shows an embodiment of a fuel control system for an internal combustion engine that controls a fuel supply amount using an air flow signal obtained from a heating resistor type air flow measuring device of the present embodiment. In the drawing, intake air 67 to be sucked is an air cleaner 68, a body 53 of a flow rate measuring device, a duct 55, a throttle body 58, and an injector 6 to which fuel is supplied.
The intake air is sucked into the engine cylinder 62 through an intake system formed by an intake manifold 59 having a zero. On the other hand, the exhaust gas 63 generated in the engine cylinder 62 is
The gas is exhausted through the exhaust manifold 64.

The air flow rate signal output from the measurement module 52 of the flow rate measuring device, the throttle valve angle signal output from the throttle angle sensor 57, the oxygen concentration signal output from the oximeter 65 provided in the exhaust manifold 64, The control unit 66, which inputs an engine speed signal and the like output from the engine speed meter 61, sequentially calculates these signals to obtain an optimal fuel injection amount and an idle air control valve opening, and uses the values. Thus, the injector 60 and the idle air control valve 56 control the supply amount of fuel corresponding to the intake air flow rate. Then, in the case of an electronic fuel injection type internal combustion engine employing the flow rate measuring device of the present embodiment, the intake air flow rate can be measured properly, so that the electronic fuel injection control is appropriately performed and the amount of unburned gas in the exhaust gas is controlled. Can be reduced.

[0041]

According to the present invention, the increase in the flow velocity in the flux region formed by the throttle having the simple structure can prevent the jumping error and the binary phenomenon under the pulsating flow accompanied by the reverse flow when the actual vehicle is mounted. It is effective in providing an improved, low-cost, and accurate heating resistor-type air flow measurement device. Then, appropriate flow control can be performed when the driver steps on the accelerator, which is effective, for example, in purifying exhaust gas from an electronic fuel injection type internal combustion engine.

[Brief description of the drawings]

FIG. 1 is a front (cross-sectional) view showing a heating resistor type air flow measuring device according to an embodiment of the present invention.

FIG. 2 is a side view seen from the upstream side in FIG.

FIG. 3 is a circuit configuration diagram showing the heating resistor type air flow measuring device of FIG. 1;

FIG. 4 is a diagram illustrating a mechanism for reducing a jump error by the diaphragm according to the embodiment.

FIG. 5 is a diagram showing a mechanism for reducing a binary phenomenon by the diaphragm according to the embodiment.

FIG. 6 is a diagram showing the relationship between the size of a stop and a jump error.

FIG. 7 is a diagram showing the relationship between the entrance / exit relative position of the stop and output noise.

FIG. 8 is a sectional view showing a heating resistor type air flow measuring device according to another embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a heating resistor type air flow measuring device according to another embodiment of the present invention.

FIG. 10 is a partially enlarged view showing a joint of FIG. 9;

FIG. 11 is a view showing an internal combustion engine of an electronic fuel injection control system according to an embodiment in which the flow measuring device of the embodiment is mounted.

FIG. 12 is a diagram illustrating a bouncing error under a pulsating flow of the flow measuring device.

FIG. 13 is a diagram illustrating a binary phenomenon under a pulsating flow of the flow measuring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Circuit board, 3 ... Heating resistor, 4 ...
Temperature sensing resistor, 5: support, 7: screw, 10: auxiliary air passage, 11: auxiliary air passage inlet (inlet opening), 12: auxiliary air passage outlet (outlet opening), 13a: vertical passage, 13b: lateral passage, 20: main air passage, 21: throttle, 22: main air passage, 23: forward air flow, 24: reverse air flow, 2
5 ... hole, 41 ... air cleaner clean side, 41a ...
Straight pipe with throttle, 42 ... Air cleaner dirty side, 4
3 ... air filter element, 47 ... spigot part, 48
... Junction, 52 ... Measurement module, 53 ... Body, 54
a: screw, 54b: seal, 55: duct, 56: idle air control valve, 57: throttle angle sensor, 58: throttle body, 59: intake manifold, 60: injector, 61: tachometer, 62: engine cylinder, 63 ... exhaust gas, 64 ... exhaust manifold, 65 ... oxygen concentration meter, 66 ... control unit, 67 ... intake air, 68 ... air cleaner

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G01F 1/72 F02D 35/00 366F (72) Inventor Shinya Igarashi 2477 Takaba, Hitachinaka City, Ibaraki Prefecture Hitachi Car Engineering Co., Ltd. (72) Inventor Akira Takasago 2520 Takada, Hitachinaka City, Ibaraki Pref.Hitachi, Ltd.Automotive Equipment Division

Claims (6)

[Claims] A measuring module including a main air passage that forms a main air passage through which a fluid to be measured flows, a heating resistor inserted into the main air passage to measure a flow rate of the fluid to be measured, and the like. Wherein the measurement module includes an inlet opening that opens in a direction perpendicular to a main streamline of the fluid to be measured, and an outlet opening that opens in a direction parallel to the main streamline. The heating resistor and the like are provided inside a sub air passage that forms a substantially L-shaped sub air passage, and the main air passage is around an inner side wall located upstream of the sub air passage. The inlet and the outlet are arranged inside a flux region formed by the fluid to be measured extending from the tip of the throttle in a direction parallel to the main streamline. It is characterized by being established Thermal resistor type air flow rate measuring device. 2. The throttle according to claim 1, wherein a ratio of a ratio of an effective sectional area of the throttle to an effective sectional area of the main air passage at the throttle position is in a range of 70 to 90 (%). A heating resistor type air flow measuring device, characterized in that: 3. A heating device according to claim 1, wherein the shape of the throttle is such that an upstream half of the throttle is substantially arc-shaped and a downstream half is substantially perpendicular to the main streamline direction. Resistor type air flow measurement device. 4. An air flow measuring device according to claim 1, further comprising a throttle of a main air passage body and a hole into which a measurement module is inserted, wherein said intake pipe constituting member is provided in said main air passage. An intake pipe component member, which also serves as a body. 5. The intake pipe forming member to which the main air passage is connected to a throttle which is separated from the main air passage in the heating resistor type air flow measuring device according to claim 1. An intake pipe component, which is provided at an intake outlet portion of the intake pipe. 6. A fuel control system for an internal combustion engine, wherein a fuel supply amount is controlled using an air flow signal obtained from the heating resistor type air flow measuring device according to claim 1.