JPH08240461A - Air flow measuring device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object of the present invention to provide an exothermic resistor type air flow rate measuring device with improved output noise characteristics and excellent handleability. [Structure] The inner wall of the main air passage near the outlet of the sub air passage of the heating resistor type air flow rate measuring device is made flat so that the air flows in the main air passage and the sub air passage are smoothly joined. [Effect] By providing a flat portion on the inner wall of the main air passage near the outlet of the sub air passage, the air flows in the sub air passage and the main air passage can be smoothly merged, and stable output noise characteristics are provided. It is possible to provide a heating resistor type air flow rate measuring device having excellent handleability.

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 the intake air flow rate of an internal combustion engine, and more particularly to a heat generation resistance type air flow meter suitable for measuring the air flow rate of air taken into an automobile engine.

[0002]

2. Description of the Related Art As a problem of a heating resistor type air flow measuring device, improvement of measurement accuracy under pulsating flow when mounted on an actual vehicle can be raised. This is a phenomenon in which the heating resistor detects not only the forward flow but also the backward flow due to the backflow that occurs near the full opening of the throttle valve, and as a result, the output of the heating resistor type air flow rate measuring device increases. Unless this phenomenon is avoided, the heating resistor type air flow measuring device cannot be said to have sufficient functions. For this reason, in the past, JP-A-2-23 has been used.
A heating resistor is arranged in the L-shaped sub air passage as shown in 2524, and the wall of the sub passage makes it difficult to detect the backflow.

However, in the structure shown in JP-A-2-232524, in the body forming the main air passage, a part of the sub passage is closed by a cover made of a plate material or the like to form the sub passage. It was Therefore, it is necessary to divide the mold in the main air passage and the sub passage, and as a result, the mold dividing surface appears near the outlet of the sub passage.

[0004]

Since the heating resistor directly detects the flow of air, if the flow of air is disturbed, the output noise characteristic of the heating resistor type air flow rate measuring device deteriorates.

With the above-described structure, a convex portion of the mold dividing surface is formed near the outlet of the sub passage, so that the air near the wall surface in the main air passage is disturbed. For this reason, the air flow at the outlet of the sub air passage near the wall surface in the main air passage is also disturbed, so that the output noise characteristic of the heating resistor in the sub air passage deteriorates.

An object of the present invention is to improve the output noise characteristics of the heating resistor type air flow rate measuring device having the above-mentioned structure and to provide a heating resistor type air flow rate measuring device excellent in handleability.

[0007]

In order to improve the output noise characteristic of the heating resistor type air flow rate measuring device, the wall surface of the main air passage near the outlet of the sub air passage is made flat.

[0008]

In the vicinity of the outlet of the sub air passage, the air flows of the main air passage and the air of the sub air passage merge, and the air flow is likely to be disturbed.
Further, if there is a mold dividing surface in the vicinity of this, a step or burr generated at the time of dividing becomes a protrusion and further disturbs the air flow.

As a countermeasure against these problems, the inner wall of the main air passage near the outlet of the sub air passage is made flat. As a result, it is possible to prevent air turbulence due to steps or burrs due to mold division, and to smoothly combine the air flows in the main air passage and the sub air passage. Is also stable, and it is possible to improve the output noise characteristics of the heating resistor type air flow rate measuring device. These measures are the body which constitutes the main air passage of the heating resistor type air flow measuring device,
Alternatively, the effect is the same even if it is provided in a part of the intake pipe line.

Further, by making the opening surface of the sub air passage outlet and the flat portion of the inner wall of the main air passage parallel to each other, the flow at the outlet portion is made uniform, so that the merging can be performed more smoothly.

[0011]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a cross section of a heating resistor type air flow rate measuring apparatus showing an embodiment of the present invention, and FIG. 2 is an external view as seen from the upstream side (left side) thereof. FIG. 3 is a view showing a cross section of a conventional heating resistor type air flow rate measuring device having a passage structure.

In the body 3 forming the passage of the heating resistor type air flow rate measuring device, the heating resistor 7 for detecting the air flow rate and the intake air temperature are provided in the sub air passage constituting member 2 which crosses the main air passage 5 in a bridge shape. A sub air passage 4 including a temperature-sensitive resistor 8 for detecting is arranged. The heating resistor 7 and the temperature-sensitive resistor 8 have a support member 10 made of a conductive member,
Electrically connected to the module 9 containing the drive circuit,
The signal obtained from the heating resistor 7 is used as the air flow rate signal,
It has the function of sending to the control unit via the connector 16.

The sub air passage 4 is opened substantially parallel to the air flow in the main air passage 5 and the first passage having an inlet opening surface 4a which is opened substantially perpendicular to the air flow in the main air passage 5. Communicates with the second passage having the outlet opening surface 4b L
The character-shaped sub air passage 4 is configured. The reason why the sub air passage 4 has the L shape is to improve the measurement accuracy under the pulsating flow when the actual vehicle is mounted. This is a phenomenon in which the output of the heating resistor type air flow rate measuring device increases because the backflow generated near the full opening of the throttle valve is detected. Unless this phenomenon is avoided, the heating resistor type air flow measuring device cannot be said to have sufficient functions. For this reason, the heating resistor is arranged in the L-shaped sub air passage, and the wall of the sub passage makes it difficult to detect the backflow.

The second passage has a structure in which a U-shaped groove is punched from the body 3 and then the cover 6 is fixed by adhesion or the like. This is because the sub air passage 4 is integrally formed with the body 3 forming the main air passage 5, and therefore it is impossible to die-cut the second passage at a time. The application cover 6 is attached to form the sub air passage 4. The problem here is that the mold dividing point is that a step is formed or burr is generated due to the matching of the molds. In the conventional passage structure shown in FIG. 3, since the parting line for mold separation is arranged immediately upstream of the sub passage outlet 4b, the sub passage outlet 4b is affected by the separation vortex generated at the step on the downstream 14 of the parting line. I will receive it. Therefore, the flow state of the sub passage outlet 4b becomes unstable, and as a result, the flow at the location detected by the heating resistor 7 arranged in the sub air passage becomes unstable, and the output noise of the heating resistor type air flow rate measuring device becomes unstable. Cause increase.

As a countermeasure against this, a flat surface 1 is formed on the body 3 in the vicinity of the sub air passage outlet 4b of the lateral passage shown in FIG. The flat surface prevents separation in the vicinity of the sub air passage outlet 4b, which is the confluence of the flow of air in the main air passage 5 and the flow of the sub air passage, and stabilizes the air in the vicinity of the sub air passage outlet. The turbulence of the air flowing through the passage is prevented. This makes it possible to prevent an increase in output noise of the heating resistor type air flow measuring device.

FIG. 4 is a cross section of a heating resistor type air flow rate measuring device in which the body 3 and the sub air passage member 2 are separate members, and FIG. 5 is an external view seen from the upstream side (left side). is there.

The body 3 constituting the main air passage 5 is substantially cylindrical and has a through hole 11 penetrating from the outer wall to the inner wall.
Is open. The heating resistor type air flow rate measuring device module 9 is integrated with an L-shaped sub air passage 4 having a heating resistor 7 and a temperature sensitive resistor 8 therein, and the sub air passage 4 is inserted from the through hole 11. Functioning as a heating resistor type air flow rate measuring device. Also in this embodiment, the flat surface 1 is formed on the body 3 near the side of the sub air passage outlet 4b to stabilize the air near the sub air passage outlet and prevent the turbulence of the air flowing through the sub air passage 4. There is. Further, FIG. 6 is a view showing an embodiment in which the basic structure is the same as that of FIG. 4, but when it is used as an intake pipe 15 such as a duct used in an internal combustion engine as a member constituting the main air passage 5. 3 is a diagram showing a structure having a flat portion 1 in a part of an intake pipe 15. FIG. As shown in FIGS. 4 to 6, the flat portion 1 provided in the vicinity of the sub air passage outlet 4b is not a material that does not necessarily have to be provided in the heating resistor type air flow rate measuring device itself, and is another member in the vicinity of the sub air passage outlet 4b. Need only have a structure having the flat portion 1.

The structure shown in FIG. 7 is a view showing a further embodiment of the present invention, and FIG. 8 is a view seen from the upstream (left) side thereof. The body 3 forming the main air passage has a parting line 13 by mold division. The parting line 13 causes an increase in output noise of the heating resistor type air flow rate measuring device as described above. Up to FIG. 6, the flat portion 1 is provided on the wall surface of the main air passage, but in FIG. 7, the auxiliary air passage constituting member 2 and the flat portion 1 are integrated. By integrating the flat portion 1, the sub air passage constituting member 2, and the circuit module 9, the module of the heating resistor type air flow rate measuring device can be handled as one product.
As a result, a company that integrates internal combustion engines, for example, a car maker, can obtain a heating resistor type air flow measuring device that suppresses an increase in output noise without worrying about a slight step difference in the intake type. It is possible to perform a free layout of the system.

FIG. 9 shows an embodiment in which the product of the present invention is applied to an electronic fuel injection type internal combustion engine.

The intake air 101 sucked from the air cleaner 100 is the body 1 of the heating resistor type air flow measuring device.
02, an intake duct 103, a throttle body 104, and a manifold 106 equipped with an injector 105 to which fuel is supplied, and then is sucked into an engine cylinder 107. On the other hand, the gas 108 generated in the engine cylinder is discharged through the exhaust manifold 109.

An air flow rate signal output from the circuit module 110 of the heating resistor type air flow rate measuring device, a throttle valve opening signal output from the throttle angle sensor 111, and an oxygen concentration meter 112 provided in the exhaust manifold 109. The control unit 114, which receives the oxygen concentration signal and the rotation speed signal output from the engine tachometer 113, calculates these signals to obtain the optimum fuel injection amount and the idle air control valve opening, The injector 105 and the idle air control valve 115 are controlled.

Finally, FIG. 10 shows the output noise characteristics of the heating resistor type air flow rate measuring device of the present invention shown in FIG. 1 and the conventional product shown in FIG. 3 measured by the writer. The output noise characteristic of the product of the present invention can be reduced to about 3/4 that of the conventional product.

[0024]

According to the present invention, by providing a flat portion on the inner wall of the main air passage near the outlet of the sub air passage, it is possible to smoothly join the air flows of the sub air passage and the main air passage. It is possible to provide a heating resistor type air flow rate measuring device having stable output noise characteristics and excellent handleability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an air flow rate measuring device that is an embodiment of the present invention and has a flat surface on a body.

FIG. 2 is an external view seen from the upstream of FIG.

FIG. 3 is a cross section of a conventional air flow rate measuring device.

FIG. 4 is a cross-sectional view of an air flow measuring device according to an embodiment of the present invention, which has a flat surface on a body.

5 is an external view seen from the upstream of FIG.

FIG. 6 is a cross-sectional view of an air flow measuring device having a flat surface in an intake duct according to an embodiment of the present invention.

FIG. 7 is a cross-sectional view of an air flow rate measuring device according to an embodiment of the present invention in which a flat surface is provided in a sub air passage member.

FIG. 8 is an external view as seen from the upstream side of FIG.

FIG. 9 is a control system diagram of an internal combustion engine using the present invention.

FIG. 10 is a characteristic diagram showing output noise characteristics of the heating resistor type air flow rate measuring device of the present invention product and the conventional product.

[Explanation of symbols]

1 ... Flat surface, 2 ... Sub air passage constituent member, 3 ... Body, 4
... Sub air passage 5 ... Main air passage, 6 ... Cover, 7 ... Heating resistor, 8 ... Temperature sensitive resistor 9 ... Circuit module, 10 ... Support member, 11 ... Through hole,
12 ... rectifying grid, 13 ... parting line, 14 ... parting line downstream, 15 ... intake duct 16 ... connector, 100 ... air cleaner, 101 ... intake air, 102 ... body 103 ... intake duct, 104 ... throttle body, 10
5 ... Injector 106 ... Manifold, 107 ... Engine cylinder, 1
08 ... Gas 109 ... Exhaust manifold, 110 ... Circuit module 111 ... Throttle angle sensor, 112 ... Oxygen concentration meter 113 ... Engine tachometer, 114 ... Control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinya Igarashi 2471, Kashima Yatsu, Hitachi, Hitachinaka City, Ibaraki Prefecture 3 Hitachi Hitachi Engineering Co., Ltd. (72) Chihiro Kobayashi, 2520, Takaba, Hitachinaka City, Ibaraki Prefecture Stock Company Hitachi Automotive Systems Division (72) Inventor Takayuki Saito 2477 Kashima Yatsu Kashima Yatsu, Hitachinaka City, Ibaraki Prefecture 3 Hitachi Automotive Engineering Co., Ltd.

Claims (7)

[Claims] 1. A first air passage substantially parallel to the main air passage and a first air passage communicating with the main air passage for introducing air,
In an air flow rate measuring device having a detector in a sub air passage formed by a second air passage substantially perpendicular to the main air passage, the main air passage inner wall facing the sub air passage outlet opening surface has a substantially flat surface. Characteristic air flow rate measuring device. 2. An air flow rate measuring device according to claim 1, wherein the heating resistor type air flow rate measuring device is used for an internal combustion engine and has a heat generating resistor in the sub air passage. And a flat portion provided on the wall surface of the main air passage are substantially parallel to each other, and at least the upstream side of the flat portion has a smooth tapered surface, and a heating resistor type air flow rate measuring device. 3. The sub air passage outlet flat portion according to claim 1 or 2, wherein the main air passage and the sub air passage are integrally formed, and the sub air passage is partially separated. A heating resistor type air flow rate measuring device characterized in that it is constituted by covering with a cover made of a member. 4. An insert provided in the body, which has the sub air passage outlet flat portion according to claim 1 or 2, wherein the body forming the main air passage and the sub air passage are formed as separate members. A heating resistor type air flow rate measuring device characterized in that a passage is formed by inserting a sub air passage into the hole. 5. A member which has the flat portion of the sub air passage outlet according to claim 1 or 2 and which constitutes the main air passage uses a part of an intake pipe used for an internal combustion engine, and the intake pipe is A heating resistor type air flow rate measuring device, characterized in that a sub air passage is inserted into an insertion hole provided to form the passage. 6. A first air passage which is substantially parallel to the main air passage and communicates with the first air passage in the main air passage for introducing air.
In an air flow rate measuring device having a detection body in a sub air passage formed by a second air passage substantially perpendicular to the main air passage, a member having a flat surface facing the opening of the sub air passage outlet is provided in the sub air passage. A heating resistor type air flow rate measuring device characterized by being provided integrally with a member forming a passage. 7. An internal combustion engine control system, wherein an internal combustion engine is controlled using the heating resistance type air flow rate measuring device according to any one of claims 1 to 6.