JPS63210714A - Air flowmeter - Google Patents

Abstract

PURPOSE:To securely place an air flow in a laminar state and to accurately measure intake air capacity by providing an intake passage at the periphery of a sensing passage and communicating the sensing passage with the flank of the intake passage. CONSTITUTION:When an internal combustion engine begins to operate, air is sucked from an air cleaner and passes in an air flowmeter 100 as shown by an arrow A. The air flowing in the sensing passage 21 is sucked into the intake passage 29 from respective communicating passages 22. Here, the respective communicating passages 22 are in the same shape and at an equal distance to adjacent passages, and the air flowing in the sensing passage 21 flows out uniformly from the center of the rear end part of the sensing passage 21 to spread radially, but the air flow passing in the sensing passage 21 securely enters a laminar state. The intake air capacity is accurately detected by an air flow rate sensor 7 and a temperature compensating sensor 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air flow meter, and in particular to an air flow meter that is placed in the intake pipe of an internal combustion engine and uses a hot wire sensor such as platinum as the sensor. It is related to the meter.

(Prior Art) There are various types of air flow meters placed in the intake pipe of an internal combustion engine. Among them, the so-called hot wire type air flow meter that uses a hot wire such as a platinum wire as a sensor is one of the most popular types. It is widely used because of its good response and ability to measure the mass of air flowing per unit time.

In such an air flow meter, the sensor is disclosed in, for example, Japanese Unexamined Patent Publication No. 56-108911, Japanese Utility Model Application No. 59-1580.
As described in Japanese Patent Publication No. 30, etc., it is provided in a cylindrical body disposed in the intake pipe, or
As described in Japanese Patent No. 190623, etc., the bypass passage is provided in a straight portion of a bypass passage arranged to branch from an intake passage in an intake pipe.

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

(1) 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 a cylindrical body disposed in an intake pipe, the airflow within the cylindrical body is highly turbulent, making it difficult to bring the airflow into a laminar state.

Another drawback is that when a backfire occurs, the sensor is easily damaged by the blast, which shortens the life of the air flow meter.

Furthermore, even when a backfire occurs, the blast wave is detected as intake air, making it impossible to accurately measure the amount of intake air.

(2) When the sensor is disposed in the bypass passage, the end of the bypass passage on the downstream side of the air flow is open to the inner side surface of the intake pipe, so the air in the bypass passage is is drawn in, and as a result, the air flow within the bypass passage tends to be relatively laminar.

However, since the straight portion of the bypass passage in which the sensor is disposed is bent and connected to the rear end portion of the bypass passage that opens to the inner side surface of the intake pipe, airflow is likely to be disturbed at the bent portion. Therefore, the sensor needs to be placed away from the downstream side of the air flow in the straight portion of the bypass passage.

As a result, the bypass passage must be formed relatively long, making the air flow meter complicated and large.

Furthermore, since the bypass passage is formed directly inside the side wall of the intake pipe or on the outer surface of the side wall, heat generated by the internal combustion engine is conducted to the wall surface constituting the bypass passage, and passes through the sensor or the bypass passage. There is a risk of the air being heated. This results in inaccurate airflow measurements.

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

(Means and effects for solving the problems) In order to solve the above-mentioned problems, the present invention provides a sensing passage provided with a hot wire sensor therein, and an intake passage surrounding the sensing passage. and a communication passage is provided so that the sensing passage and the side surface of the intake passage communicate with each other, so that the air flowing into the sensing passage can flow into the intake passage through the communication passage. The air flow passing through the passage causes suction to spread radially, thereby ensuring that the air flow within the sensing passage becomes laminar. The feature is that the sensor does not flow into the sensing passage where the sensor is disposed.

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

Figure 1 is a cross-sectional view of Figure 3 taken along line B-B, Figure 2 is a side view of the first embodiment of the present invention, and Figure 3 is a book view of Figure 2 from the upstream side of the air flow. Front view of the first embodiment of the invention, fourth
The figure is a rear view of the first embodiment of the present invention as seen from the downstream side of the air flow in FIG.

First, in FIG. 2, an air flow meter 100 is placed in an intake pipe of an internal combustion engine mounted on a vehicle.

The air flow meter 100 has joints 101 at both ends.
and 102 are connected, the joint 101 is connected to the air cleaner (not shown) side of the intake pipe, and the joint 102 is connected to the fuel injection valve and throttle valve (both not shown) sides of the intake pipe. be done.

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

Next, in FIG. 1.3, there is a joint 101 on the side of the upstream body 1 connected to the joint 101.
A large diameter portion IB having an inner diameter substantially the same as the inner diameter of the O-ring is formed around the large diameter portion IB. A plurality of bolt holes IY for connection with the joint 101 are formed.

Further, an annular groove IW for arranging the O-ring 15 is formed on the side of the upstream body 1 facing the downstream body 2.

At the center of the upstream body 1, as shown in FIG. 1, a cylindrical press-fit collar 3 and a terminal collar 4 are arranged. The inner walls of the press-fit collar 3 and the terminal collar 4 constitute 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 materials such as ceramics and metals.

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

Further, the airflow upstream end (hereinafter referred to as the tip) of the press-fit collar 3, that is, the tip of the sensing passage 21 is drawn to protrude to the airflow upstream side from the intake passage IA, which will be described later. However, it may be configured to be flush with the tip of the intake passage IA, or to be set back downstream of the tip.

The upstream body 1 has an intake passage IA in a C-shape surrounding the press-fit collar 3 and the terminal collar 4.
is drilled.

Inside the terminal collar 4, there is a hot wire air flow f.
A fi sensor 7 and a temperature compensation sensor 8 are arranged. The lead wire of the sensor 7.8 is led out of the upstream body 1 through a terminal holder 5 attached to the upstream body 1 by a male thread 19D.

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

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

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

The circuit board 11 has a characteristic of blocking electrical disturbances.
It is covered with a resin cover 13. The cover 13 is attached to the upstream body 1 with a male screw 19C, with a gasket 14 disposed between the cover 13 and the upstream body 1.

Reference numeral 12 is a resistance element for power control.

At the end of the sensing passage 21 on the downstream side of the air flow (hereinafter referred to as the rear end), there is a downstream body 2 which will be described later.
A rectifier 6 attached to the central part of the rectifier 6 is disposed.

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

Next, in FIGS. 1 and 4, the downstream body 2,
A large diameter portion 2B having an inner diameter that is approximately the same as the inner diameter of the joint 102 is formed on the connection side with the joint 102, and an annular groove 22 for arranging an O-ring is formed around the large diameter portion 2B. , and a plurality of bolt holes 2Y for connection with the joint 102 are formed.

As described above, the downstream body 2 has a male thread 19A corresponding to the rear end of the sensing passage 21.
The rectifier 6 is fixed by.

The rectifier 6 constitutes the bottom of the sensing passage 21 . Further, the rectifier 6 is formed such that its center portion protrudes toward the upstream side of the air flow.

Further, an intake passage 2A is formed in the downstream body 2 around the rectifier 6 so as to correspond to the intake passage IA formed in the upstream body 1.

The downstream body 2 is fixed to the upstream body 1 using means not shown, with the O-ring 15 disposed in the annular groove IW of the upstream body 1.

In this example, the intake passage 29 constituted by the intake passage IA and the intake passage 2A is formed so as to have a narrow shape at its center, in other words, so that its cross section has a so-called venturi shape. There is.

Further, the intake passage 29 is formed parallel to the sensing passage 21.

As shown in FIG. 1.3, the upstream body 1, the terminal collar 4, and the downstream body 2 are provided with:
A plurality of communication passages 22 are formed so that the sensing passage 21 communicates with the side wall of the intake passage 29 when they are joined.

In this embodiment, the communication passages 22 are arranged along the bottom of the sensing passage 21, that is, along the side surface of the rectifier 6, so that they have the same shape, and the intervals between adjacent passages are equal. Four of them are formed.

In the first embodiment of the present invention having the above configuration, when the internal combustion engine equipped with the air flow meter 100 starts operating, air is sucked through the air cleaner disposed at the tip of the intake pipe of the internal combustion engine. , passes through the air flow meter 100 in the six directions of arrows (FIGS. 1 and 2). As described above, since the sensing passage 21 is open to the side wall of the intake passage 29, the air flowing into the sensing passage 21 is sucked into the intake passage 29 through each communication passage 22.

Here, as described above, each of the communicating passages 22 has the same shape and is formed so that the distance between adjacent ones is equal, so that the air flowing into the sensing passage 21 is The air flows out uniformly and radially from the center of the rear end of the sensing passage 21, thereby ensuring that the air flow passing through the sensing passage 21 is in a laminar flow state.

Therefore, the air flow sensor 7 and the temperature compensation sensor 8
The amount of intake air can be detected accurately.

By the way, in this first embodiment, the communication passages 22 are arranged so that their central parts extend along the surface of the rectifier 6, which is formed to protrude toward the upstream side of the air flow, and have the same shape. In addition, it was explained that the spacing between adjacent ones is equal,
The present invention is not particularly limited to this.

In other words, the communication passage 22 sucks the air passing through the sensing passage 21 with the flow of air passing through the intake passage 29, and brings the air passing through the sensing passage 21 into a laminar flow state. Yes, the optimal shape for that,
Elements such as size and spacing between adjacent ones are determined by the shape and size of the sensing passage 21 or the intake passage 29,
It changes depending on various factors such as length, displacement of the internal combustion engine, number of cylinders, intake pipe shape, intake pipe length, etc.

Therefore, it is desirable that the elements be set according to each of the factors.

Modifications of the communication path will be described below with reference to FIGS. 5 to 8.

FIG. 5 is a longitudinal sectional view of the second embodiment of the present invention, and
FIG. In FIG. 5, the same reference numerals as in FIG. 1 refer to the same or equivalent parts, so a description thereof will be omitted.

In FIG. 5, the rectifier as applied to the first embodiment is not disposed at the bottom of the sensing passage 21 formed in the center of the air flow meter 200. and,
The surface of the downstream body 202 on the upstream body 1 side, which constitutes the bottom of the sensing passage 21, is formed into a planar shape.

A communication passage 222 that communicates the sensing passage 21 and the intake passage 29 is formed along the bottom of the flat sensing passage 21 and substantially perpendicular to the airflow passing through the intake passage 29. of the communication path 222,
The inner wall surface of the sensing passage 21 (indicated by reference numeral 21A) adjacent to the inner circumferential direction of the sensing passage 21 is formed to have the same inner diameter as the inner diameter of the terminal collar 4, and furthermore, in this embodiment, the inner wall surface of the sensing passage 21 (indicated by reference numeral 21A) is formed to have the same inner diameter as the inner diameter of the terminal collar 4. It is formed integrally with the body 202.

In this example as well, the air passing through the intake passage 29 uniformly sucks the air passing through the sensing passage 21 via the communication passage 222 so that it spreads radially, and the air flow within the sensing passage 21 is The flow becomes laminar.

FIG. 6 is a vertical sectional view of the third embodiment of the present invention, and
．． This is a diagram similar to Figure 5. In FIG. 6, the same reference numerals as in FIG. 1.5 refer to the same or equivalent parts, so a description thereof will be omitted.

In FIG. 6, sensing passage 2 of air flow meter 300
The surface of the upstream body 1 side of the downstream body 302 constituting the bottom of the device 1 is formed into a planar shape as in the second embodiment.

A communication passage 322 that communicates the sensing passage 21 with the side surfaces of the intake passage 29 is formed in a direction substantially perpendicular to the air flow passing through the intake passage 29, and has a flat end on the downstream side of the air flow. The sensing passage 21 is spaced a predetermined distance X from the bottom of the sensing passage 21. The inner wall surface of the sensing passage 21 of the communication passage 322 adjacent to the inner peripheral direction of the sensing passage 21 and the downstream side of the air flow (
21B) is formed to have the same inner diameter as the inner diameter of the terminal collar 4, and is further formed integrally with the downstream body 302 in this example.

In this example as well, the air passing through the intake passage 29 sucks the air passing through the sensing passage 21 through the communication passage 322 so as to spread radially, and the air flow within the sensing passage 21 becomes a laminar flow. become.

FIG. 7 is a front view of a fourth embodiment of the present invention, and is similar to FIG. 3. In FIG. 7, the same reference numerals as in FIG. 3 refer to the same or equivalent parts, so a description thereof will be omitted.

In FIG. 7, six communicating passages 22 having the same shape are formed in the air flow meter 400;
It is formed symmetrically with respect to the center line V of the air flow meter 400.

In this example, the air flow passing through the sensing passage 21 is drawn in such a way that it spreads out symmetrically about the center line V, and the air flow sensor 7 and/or temperature compensation sensor disposed within the sensing passage 21 8, an arbitrary imaginary line perpendicular to the air flow (e.g., the center line V)
Depending on the arrangement angle with respect to the air flow, the arrangement angle with respect to the air flow, etc., it is possible to apply the air flowing in a laminar flow state to at least one of the sensors.

FIG. 8 is a front view of the fifth embodiment of the present invention, and FIG.
This is a diagram similar to Figure 7. In FIG. 8, the same reference numerals as in FIG. 3.7 refer to the same or equivalent parts, so the explanation thereof will be omitted.

In FIG. 8, the air flow meter 500 is formed with two communicating passages 522A and two communicating passages 522B having the same shape and facing each other and arranged alternately. There is.

In this embodiment, as shown, the communication path 52
Since the shapes of the communication path 2A and the communication path 522B are different from each other, the amount of air sucked from the sensing path 21 through the communication path 522A and the communication path 522B is different.

However, similarly to the fourth embodiment, the sensing passage 2
Depending on the arrangement angle of the air flow rate sensor 7 and/or temperature compensation sensor 8 disposed in the air flow sensor 1 with respect to an arbitrary virtual line perpendicular to the air flow, the arrangement angle with respect to the air flow, etc., laminar flow may occur in each of the sensors. It is possible to apply flowing air to the area.

In this way, the communication passage connects the sensing passage to the intake passage 29.
It may have any shape, size, and arrangement as long as it communicates with the side surface of the wall.For example, it may have the shapes or arrangements shown in (A) to (D) below. Moreover, you may combine them.

(A) The communicating paths are formed in the same shape.

(B) The communication paths are formed so that the distance between adjacent ones is equal.

(C) As shown in FIG. 7, the communication path is formed symmetrically with respect to the center line of the sensing path.

(D) As shown in FIG. 8, the communication paths are configured so that at least one pair of communication paths have different shapes, and those having the same shape are arranged symmetrically with respect to the sensing path. .

Now, in the above description, it was assumed that a plurality of communication passages were provided, but the intake passage 29 formed in a C-shape
Only one may be provided along the same lines.

Further, the shape, number, etc. of the communication passages are set depending on various factors such as the number of cylinders of the internal combustion engine in which the air flow meter is installed, the length of the intake pipe, etc., but in the present invention, It goes without saying that the shape of the sensing passage may also be set depending on various factors such as the number of cylinders of the internal combustion engine and the length of the intake pipe.

Further, as shown in Fig. 1.5.6, the intake passage 29 is formed so that a communicating passage opens at its narrowest part, but the present invention is not limited to this. Instead, the communication passage may be formed to open at a position shifted upstream or downstream of the narrowest part of the air flow.

Furthermore, although the intake passage 29 has been described as being formed to have a narrow shape at its center, the present invention is not limited to this, and may simply be formed to have a cylindrical shape. may be done.

(Effects of the Invention) As is clear from the above description, according to the present invention, around the sensing passage provided with the hot wire sensor therein,
Since an intake passage is provided and a communication passage is provided that communicates the sensing passage with the side surface of the intake passage, the following effects can be achieved.

(1) The air flowing into the sensing passage is suctioned radially from the bottom side by the airflow passing through the intake passage, so the air does not move much in the airflow passage direction, ensuring a laminar flow. become a state.

Therefore, the intake air amount can be accurately measured by the hot wire type sensor without making the air flow meter too large in the airflow passing direction.

(2) Since the sensing passage communicates with the side surface of the intake passage, in other words, since the sensing passage has a bottom, even if a backfire occurs, the sensor placed in the sensing passage will not be affected by the blast. become less exposed to

As a result, the sensor life is less likely to be shortened or deteriorated due to backfire.

Furthermore, since the blast wave caused by the backfire is less likely to be measured as the amount of intake air, the amount of intake air can always be accurately measured.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of FIG. 3 taken along line B-B. FIG. 2 is a side view of the first embodiment of the invention. FIG. 3 is a front view of the first embodiment of the present invention when FIG. 2 is viewed from the upstream side of the air flow. FIG. 4 is a rear view of the first embodiment of the present invention when FIG. 2 is viewed from the downstream side of the air flow. FIG. 5 is a longitudinal sectional view of a second embodiment of the invention. FIG. 6 is a longitudinal sectional view of a third embodiment of the present invention. FIG. 7 is a front view of a fourth embodiment of the present invention. FIG. 8 is a front view of a fifth embodiment of the present invention. 1... Upstream body, IA, 2A, 29... Intake passage, 2,202.302... 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°322.5
22A, 522B...Communication path, 100.200,30
0,400.500... Patent attorney for air flow meter Michito Hiraki and 1 other person Figure 2 1 Figure 6

Claims (9)

[Claims] (1) An air flow meter installed in an intake pipe of an internal combustion engine to measure intake air flow rate, comprising a sensing passage arranged approximately on the central axis of the intake pipe, and surrounding the sensing passage. What is claimed is: 1. An air flow meter comprising: a flowmeter main body having an intake passage arranged parallel to the sensing passage; and a hot wire sensor arranged in the sensing passage. (2) The air flow meter according to claim 1, further comprising a communication passage communicating the sensing passage and the side surface of the intake passage. (3) The air flow meter according to claim 2, wherein the communication path is plural. (4) The air flow meter according to claim 3, wherein the communicating passages are each formed to have the same shape. (5) The communicating passages are formed so that their shapes are different for each pair, and those having the same shape are arranged symmetrically with respect to the sensing passage. Air flow meter as described in section. (6) The air flow meter according to any one of claims 3 to 5, wherein the communication passages are arranged so that the intervals between adjacent passages are equal. (7) The air flow meter according to any one of claims 2 to 6, wherein the communication passage is formed symmetrically with respect to a center line of the sensing passage. . (8) The air flow meter according to any one of claims 1 to 7, wherein the sensing passage has a bottom on the downstream side of the air flow. (9) The air flow meter according to any one of claims 1 to 8, wherein the intake passage is formed so that the central portion thereof has a narrow shape.