JPH0792398B2 - Air flow meter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air flow meter, and particularly to an air flow rate sensor which is disposed in an intake pipe of an internal combustion engine and uses a hot-wire sensor such as platinum as its sensor. It is about the total.

(Prior Art) There are various types of air flow meters arranged in an intake pipe of an internal combustion engine. Among them, a so-called hot wire type air flow meter using a hot wire such as a platinum wire as a sensor is It is widely used because of its good response and the fact that the mass of air flowing per unit time can be measured.

In such an air flow meter, the sensor is provided in a cylindrical body arranged in the intake pipe, as described in, for example, JP-A-56-108911 and JP-A-59-158030. Alternatively, as described in Japanese Patent Application Laid-Open No. 59-190623, it is provided in a straight portion of a bypass passage arranged so as to branch from the intake passage in the intake pipe.

(Problems to be Solved by the Invention) The above-described conventional technique has the following problems.

(1) In order to accurately measure the amount of intake air, it is necessary to make the air passing through the intake pipe into a laminar flow state and apply it to the sensor.

However, when the sensor is provided in the cylindrical body arranged in the intake pipe, the air flow in the cylindrical body is often disturbed, and it is often difficult to make the air flow a laminar flow state. Moreover, as a result, the cylindrical body must be necessarily elongated in the air flow passage direction.

Therefore, the air flow meter becomes large at least in the air flow direction.

Further, when backfire occurs, there is also a drawback that the sensor is easily damaged by the blast and the life of the air flow meter is shortened.

Further, even when backfire occurs, the blast air is detected as intake air, so that the amount of intake air cannot be accurately measured.

(2) When the sensor is arranged in the bypass passage, the end portion of the bypass passage on the downstream side of the air flow is opened to the inner side surface portion of the intake pipe. Are sucked in, and as a result, the air flow in the bypass passage is likely to be relatively laminar.

However, since the straight portion of the bypass passage in which the sensor is arranged is bent and connected to the rear end portion of the bypass passage opened to the inner side surface portion of the intake pipe, the air flow is likely to be disturbed at the bent portion. Therefore, the sensor needs to be arranged avoiding the air flow downstream side of the straight portion of the bypass passage.

As a result, the bypass passage must be formed to be relatively long, and the air flow meter becomes large in the air flow direction.

Furthermore, since the bypass passage is formed directly inside the intake pipe side wall or on the outside surface of the side wall, heat generated in the internal combustion engine is conducted to the wall surface forming the bypass passage.
The sensor or the air passing through the bypass passage may be heated. As a result, the measurement of the air flow rate becomes inaccurate.

The present invention has been made to solve the above problems.

(Means and Actions for Solving Problems) In order to solve the above problems, the present invention has a sensing passage provided in a heat ray sensor inside thereof, and is arranged so as to surround the sensing passage. And an intake passage, and a communication passage is provided so as to connect the sensing passage and the side surface of the intake passage.
It is characterized in that the cross-sectional area is formed so as to continuously decrease toward the intake passage.

As a result, the air flowing into the sensing passage is sucked through the communication passage so as to be radially spread by the air flow passing through the intake passage. It is possible to produce the function and effect of reliably achieving the laminar flow state without much movement in the flow passage direction.

In addition, the blast from the backfire is unlikely to flow into the sensing passage in which the sensor is arranged. Since the energy of the blast is diffused inside the communication passage, the effect of not affecting the measurement of the sensor and the intake air amount can be produced.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of FIG. 3 taken along line BB, FIG. 2 is a side view of the first embodiment of the present invention, and FIG. 3 is a book of FIG. 2 seen from the upstream side of the air flow. Front view of the first embodiment of the invention, Fourth
FIG. 2 is a rear view of the first embodiment of the present invention as viewed from the downstream side of the air flow in FIG. 2, and FIG. In FIG. 5, the cover 13 shown in FIGS. 1 to 4 and the circuit board 11 arranged in the cover 13 are shown.
(FIG. 1) and the like are omitted.

First, in FIG. 2, the air flow meter 100 is arranged in an intake pipe of an internal combustion engine mounted on a vehicle. Air flow meter 100
Are connected to joints 101 and 102 at both ends thereof, the joint 101 being on the air cleaner (not shown) side of the intake pipe, and the joint 102 being the fuel injection valve and the throttle valve of the intake pipe (both (Not shown) side, respectively.

Therefore, the air sucked from the air cleaner passes in the direction of arrow A.

Next, in FIGS. 1, 3, and 5, a large-diameter portion 1B having an inner diameter substantially the same as the inner diameter of the joint 101 is formed on the upstream body 1 at the connection portion side with the joint 101. An annular groove 1Z for arranging an O-ring and a plurality of bolt holes 1Y for connecting with the joint 101 are formed around the large diameter portion 1B.

An annular groove 1W for arranging an O-ring 15 and a plurality of internal threads 18B (Fig. 5) are formed on the side of the upstream body 1 facing the downstream body 2.

In this example, as shown in FIG. 1, a cylindrical press-fit collar 3 and a terminal collar 4 are arranged in the center of the upstream body 1. The inner walls of the press-fit collar 3 and the terminal collar 4 form a sensing passage 21 for detecting the amount of intake air.

The press-fit collar 3 and the terminal collar 4 are made of resin,
It is made of a material such as ceramic or metal.

Further, the press-fit collar 3 and the terminal collar 4 are
It may be integrally formed with the upstream body 1 and / or the terminal holder 5 and the like described later.

Although the end of the press-fitting collar 3 on the upstream side of the air flow (hereinafter referred to as the front end), that is, the front end of the sensing passage 21, is drawn so as to project to the upstream side of the air flow with respect to an intake passage 29 described later. It may be configured so as to be flush with the tip end portion of the intake passage 29, or to be retracted downstream of the tip end portion in the air flow direction.

A plurality of intake passages 1A are formed outside the press-fit collar 3 and the terminal collar 4 of the upstream body 1.

Inside the terminal collar 4, a hot-wire type air flow rate sensor 7 and a temperature compensation sensor 8 are arranged. The lead wires of the sensors 7 and 8 are drawn out of the upstream body 1 via a terminal holder 5 attached to the upstream body 1 by a male screw 19D.

The terminal holder 5 is made of a material such as resin, ceramic, metal or the like.

An intake air amount detection circuit for detecting the intake air amount using the air flow rate sensor 7 and the temperature compensation sensor 8 is formed on the circuit board 11 fixed to the outer wall of the upstream body 1. The lead wire is connected to the circuit board 11.

In addition to the intake air amount detection circuit, the circuit board 11 receives a signal output from the detection circuit in order to inject fuel from the fuel injection valve according to the intake air amount detected by the detection circuit. A control circuit that amplifies and sets the valve opening time (duty ratio) of the fuel injection valve based on the amplified signal is formed. Since the intake air amount detection circuit and the control circuit are publicly known, description thereof will be omitted.

The circuit board 11 is covered with a resinous cover 13 having a characteristic of blocking electrical disturbance. The cover 13 is attached to the upstream body 1 with a male screw 19C in a state where the gasket 14 is arranged between the cover 13 and the upstream body 1.

Reference numeral 12 is a power control resistance element.

An end portion of the sensing passage 21 on the downstream side of the air flow (hereinafter referred to as a rear end portion) has a downstream body 2 to be described later.
A rectifier 6 attached to the central part of the is arranged.

The rectifier 6 may be formed integrally with the downstream body 2.

Next, referring to FIGS. 1 and 4 and 5,
The joint 102 is connected to the joint 102 side.
A large diameter portion 2B having an inner diameter substantially the same as the inner diameter of
Further, an annular groove for arranging an O-ring is provided around the large diameter portion 2B.
2Z and a plurality of bolt holes 2Y for connecting with the joint 102 are formed.

As described above, the rectifier 6 is fixed to the downstream body 2 by the male screw 19A so as to correspond to the rear end of the sensing passage 21. The rectifier 6 constitutes the bottom of the sensing passage 21.

A plurality of intake passages 2A are formed in the downstream body 2 around the rectifier 6 so as to correspond to the intake passages 1A formed in the upstream body 1.

The downstream body 2 is placed in the annular groove 1W of the upstream body 1 at O.
It is fixed to the upstream body 1 with the ring 15 arranged. Since the fixation is formed on the upstream body 1, the screw 18
It is performed by screwing a male screw 19B (Fig. 4) into B (Fig. 5).

The intake passage 29 formed by the intake passages 1A and 2A is formed to be parallel to the sensing passage 21.

Further, in this embodiment, the intake passage 29 is formed in a venturi shape, but the present invention is not limited to this, and may be formed in a simple tubular shape. .

The upstream body 1, the terminal collar 4, and the downstream body 2 are, as shown in FIGS.
When they are joined, the sensing passage 21
The communication passage 22 is formed so as to communicate with the side wall of each intake passage 29.

The communication passage 22 is such that the cross-sectional area cut along a plane substantially perpendicular to the air flow passing through the communication passage 22 continuously decreases toward the intake passage 29, in other words, the cross-sectional area is the sensing passage. It is formed so that it increases continuously toward 21. Also, in this example,
The communication passage 22 is formed along the bottom of the sensing passage 21, that is, along the side surface of the rectifier 6.

In the first embodiment of the present invention having the above configuration, when the operation of the internal combustion engine equipped with the air flow meter 100 is started, air is sucked from the air cleaner arranged at the tip of the intake pipe of the internal combustion engine. , Passes through the air flow meter 100 in the direction of arrow A (Figs. 1 and 2). As described above, the sensing passage 21 is open to the side wall of each intake passage 29 through the communication passage 22, so that the air that has flowed into the sensing passage 21 from the communication passage 22 inside each of the intake passages 29. Is sucked into.

Here, as described above, each of the intake passages 29 has the same shape, and as shown in FIGS. 3 to 5, the adjacent ones thereof have the same distance from each other, and It is formed so that the distance from the center of the sensing passage 21 is equal. Further, the shapes of the communication passages 22 are also the same.

As a result, the air flowing into the sensing passage 21 uniformly flows out from the center of the rear end portion of the sensing passage 21 so as to spread radially, so that the air flow passing through the sensing passage 21 is equal to that of the air flow. A laminar flow state can be achieved without much movement in the passing direction. Therefore, the amount of intake air can be accurately detected without forming the sensing passage 21, and thus the air flow meter 100, too long in the air flow passage direction.

Further, the communication passage 22 becomes closer to the intake passage 29,
Since the cross-sectional area is formed so as to continuously decrease, in other words, the shape of the flow passage is smoothly changed in order to eliminate a sudden change in flow passage resistance, so that the air flow is less likely to be disturbed. Moreover, even if the backfire occurs, the blast does not easily flow into the sensing passage 21 through the communication passage 22. Even if the blast flows into the communication passage 22, the communication passage 22 is formed so that its cross-sectional area increases toward the sensing passage 21,
The energy of the blast is the sensing passage 21 of the communication passage 22.
It is diffused at the end portion on the side and does not shorten the life of the air flow rate sensor 7 and the temperature compensation sensor 8 or detect the blast as intake air.

FIG. 6 is a sectional view of the second embodiment of the present invention, which is similar to FIG. In FIG. 6, the same reference numerals as those in FIG. 1 represent the same or equivalent portions, and thus the description thereof will be omitted.

In FIG. 6, the rectifier as applied to the first embodiment is not arranged at the bottom of the sensing passage 21 formed at the center of the air flow meter 200. Then, the downstream body 202, which constitutes the bottom portion of the sensing passage 21,
The surface on the upstream body 1 side is formed in a planar shape.

Communication passage that connects the sensing passage 21 and each intake passage 29
Like the first embodiment, the 222 is arranged so that its cross-sectional area decreases toward the intake passage 29 side, and in this example, it follows the bottom of the sensing passage 21 that is configured to be flat. Has been formed.

The sensing passage 21 inner wall surface (indicated by reference numeral 21A) adjacent to the communication passage 222 in the inner circumferential direction of the sensing passage 21 is
The terminal collar 4 is formed to have the same inner diameter as that of the terminal collar 4, and in this embodiment, it is formed integrally with the downstream body 202.

Also in this example, the air flow passing through each intake passage 29 uniformly sucks the air passing through the sensing passage 21 through the communication passage 222 so as to radially spread, and the air flow inside the sensing passage 21 is increased. Becomes a laminar flow.

Even if a backfire occurs, the blast of
Difficult to flow into the sensing passage 21 via 2.

FIG. 7 is a cross-sectional view of the third embodiment of the present invention.
It is a figure similar to a figure. In FIG. 7, the same reference numerals as those in FIGS. 1 and 6 represent the same or equivalent portions,
The description is omitted.

In FIG. 7, the first end is provided at the rear end of the sensing passage 21.
There is no rectifier as shown. A concave buffer chamber 31 is formed in a portion of the downstream body 302 corresponding to the rear end portion.

The communication passage 322 is similar to the first and second embodiments,
It is formed so that its cross-sectional area decreases toward the intake passage 29.

Also in the air flow meter 300 having this configuration, the air flowing through the respective intake passages 29 uniformly sucks the air passing through the sensing passages 21 through the communicating passages 322 so as to radially spread, and the sensing is performed. The air flow in the passage 21 becomes a laminar flow.

Even if a backfire occurs, the blast of the blast 32
Difficult to flow into the sensing passage 21 via 2.

Further, since the buffer chamber 31 is formed at the rear end of the sensing passage 21, the air flow pulsation passing through the inside of the sensing passage 21 is mitigated by the air damper effect of the air flowing into the buffer chamber 31.

In the above description, only one communication passage is provided for each intake passage, but the present invention is not limited to this, and two or more communication passages may be provided. Good.

Further, around the sensing passage 21, the intake passages 29, which have a circular shape when viewed from the air flow passage direction and have the same size, are arranged such that the distances between adjacent ones are equal to each other, and So that the distance from the center is equal,
Although four pieces are formed, the present invention is not particularly limited to this.

In other words, the intake passage 29 is for making the air flow in the sensing passage 21 laminar by sucking the air flow in the sensing passage 21 through the communication passage, and the optimum The shape, the number, and the arrangement vary depending on various factors such as the sectional shape, size, and length of the sensing passage 21 or the communication passage, the displacement of the inner surface engine, the number of cylinders, the intake pipe shape, the intake pipe length, or the like. .

Therefore, it is desirable that the shape, the number, and the arrangement of the intake passages 29 be modified according to the various factors.

Further, although it has been described that the plurality of the intake passages 29 are provided around the sensing passage 21 and one communicating passage is formed in each of the sensing passages 21, only one is provided in the C-shape so as to surround the sensing passage 21. An intake passage is provided, and a plurality of communication passages are provided in the intake passage, or C is provided along the intake passage.
You may make it form one V-shaped communicating path.

Furthermore, when the intake passage 29 has a venturi shape, the intake passage 29 is formed so that the communication passage opens at the narrowest part of the venturi in FIGS. However, the present invention is not particularly limited to this, and the communication passage may be formed so as to open at a position deviated from the narrowest part of the venturi to the upstream or downstream side of the air flow.

Furthermore, it goes without saying that the shape of the sensing passage 21 may be set to any shape depending on various factors such as the number of cylinders of the internal combustion engine and the length of the intake pipe.

(Effects of the Invention) As is clear from the above description, according to the present invention, around the sensing passage provided with the heat ray type sensor therein,
In addition to providing the intake passage, a communication passage that connects the sensing passage and the side surface of the intake passage is provided, and further, the communication passage is formed so that its cross-sectional area decreases continuously toward the intake passage. The following effects are achieved.

(1) The sensing passage communicates with a side surface of the intake passage through the communication passage, and the communication passage is formed so that its cross-sectional area continuously decreases toward the intake passage. Since there is no abrupt change in resistance, the air flow is less likely to be disturbed, and even if backfire occurs, the blast will be less likely to flow into the sensing passage via the communication passage.

Even if the blast flows into the communication passage, the communication passage is formed so that its cross-sectional area increases toward the sensing passage, so that the energy of the blast is diffused.

Therefore, the life of the sensor is not shortened or deteriorated by the backfire.

Further, since the blast caused by the backfire is no longer measured as the intake air amount, it is possible to always measure the accurate intake air amount.

(2) The air flowing through the intake passage radially sucks the air flowing into the sensing passage from the bottom side thereof, so that the air does not move much in the air flow passage direction and the laminar flow is ensured. It becomes a state.

Therefore, the laminar airflow can be applied to the hot wire type sensor without forming the airflow meter to be so large in the airflow passage direction, and the intake air amount can be reliably and accurately measured by the sensor. be able to.

(3) Since the sensing passage is arranged substantially on the central axis of the intake pipe, it is unlikely to be affected by the heat generated in the internal combustion engine.
Therefore, the air flow in the sensing passage is not heated, and the air flow rate can be accurately measured.

[Brief description of drawings]

FIG. 1 is a sectional view of FIG. 3 taken along the line BB. FIG. 2 is a side view of the first embodiment of the present invention. FIG. 3 is a front view of the first embodiment of the present invention seen from the upstream side of the air flow in FIG. FIG. 4 is a rear view of the first embodiment of the present invention in which FIG. 2 is viewed from the downstream side of the air flow. FIG. 5 is a sectional view of FIG. 1 taken along the line C-C. FIG. 6 is a sectional view of the second embodiment of the present invention. FIG. 7 is a sectional view of the third embodiment of the present invention. 1 …… Upstream body, 1A, 2A, 29 …… Intake passage, 2,202,30
2 …… Downstream body, 3 …… Press-fit collar, 4 …… Terminal collar, 5 …… Terminal holder, 6 …… Rectifier,
7 ... Air flow rate sensor, 8 ... Temperature compensation sensor, 11 ...
Circuit board, 21 …… Sensing passage, 22,222,322 …… Communication passage, 31 …… Buffer chamber, 100,200,300 …… Air flow meter

Claims (2)

[Claims] 1. An air flow meter provided in an intake pipe of an internal combustion engine for measuring an intake air amount, comprising: a sensing passage arranged substantially on a central axis of the intake pipe; and an outer circumference of the sensing passage. A flow meter main body having at least one intake passage arranged in parallel with the sensing passage, and a communication passage communicating the sensing passage with a side surface of the intake passage; and a hot wire type arranged in the sensing passage. A sensor, wherein the communication passage is closer to a side surface of the intake passage,
An air flow meter, characterized in that its cross-sectional area is formed so as to decrease continuously. 2. The air flow meter according to claim 1, wherein the sensing passage has a bottom portion on the downstream side of the air flow.