JPH07104192B2 - 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 that 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, as a heat ray type sensor, a sensor for detecting a flow rate (hereinafter referred to as an air flow rate sensor) and a sensor for correcting a signal output from the sensor according to an air flow temperature (hereinafter referred to as a temperature Compensation sensor) is used.

Each of the sensors is provided in a tubular body disposed in the intake pipe, as described in JP-A-56-108911, or disclosed in JP-A-59-190623. As described above, it is provided in the straight portion of the 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.

As described above, the heat ray sensor is provided in the tubular body arranged in the intake pipe or in the straight portion of the bypass passage arranged so as to branch from the intake passage in the intake pipe.

However, in the tubular body or in the bypass passage,
When both the air flow rate sensor and the temperature compensation sensor are arranged close to each other, the heat generated by one sensor is transferred to the other sensor by radiation or convection, and the sensor detects the air flow rate or the air flow temperature. May be inaccurate.

In addition, the air flow passing through one sensor may be disturbed on the downstream side of the air flow of the sensor, and the disturbed air flow may hit the other sensor, resulting in inaccurate air flow detection or air flow temperature detection. is there.

Such concerns can be eliminated, for example, by placing the air flow sensor and the temperature compensation sensor at a distance from each other in the tubular body or in the bypass passage.

However, as is well known, the air flow is laminar as much as possible in the portions in which the sensors are arranged in the tubular body and the bypass passage so that a stable and stable air flow is applied to each sensor. Needs to be configured to
And it is practically impossible to form such a portion over a long distance because the air flow meter becomes too large.

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 provides an air flow sensor and a temperature compensation sensor that form an angle with each other when viewed from the air flow direction. , In other words, by taking a means of arranging so that the angle is set within the range of more than 0 degree and 90 degrees or less, the sensor arranged on the downstream side of the air flow is provided with the sensor on the upstream side. It is characterized in that the effect of heat caused by the arranged sensor and the effect of turbulence of the air flow passing through the sensor are not exerted so much.

(Example) Below, this invention is demonstrated in detail with reference to drawings.

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, and FIG. 3 is a book of FIG. 2 viewed from the upstream side of the air flow. Front view of the first embodiment of the invention, Fourth
FIG. 5 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. 5 is a sectional view taken along the line C-C of 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.

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 are sensing passages for detecting the amount of intake air.
Make up 21.

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 described later.

Further, the end portion of the press-fit collar 3 on the upstream side of the air flow (hereinafter, referred to as a tip portion), that is, the tip portion of the sensing passage 21 is
Although it is drawn so as to project upstream of the intake passage 1A, which will be described later, the intake passage 1A may be flush with the tip of the intake passage 1A or may be retracted downstream of the tip of the intake passage 1A. May be configured to do so.

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, a hot-wire type air flow rate sensor 7 and a temperature compensation sensor 8 are arranged.

FIG. 6 is a schematic sectional view of the air flow rate sensor 7 shown in FIGS.

In FIG. 6, a support 703 having conductivity is fixed to both ends of the bobbin 701 with an adhesive 702, and a heat ray resistance 705 is provided on the surfaces of the bobbin 701 and the support 703.
Is wound. A glass coating 706 is applied to the surface of the heat ray resistance 705.

The support 703 is fixed to the lead wire 70.

The temperature compensation sensor 8 is also manufactured similarly to the air flow rate sensor 7.

Returning to FIGS. 1 and 3 again, the air flow rate sensor 7 and the temperature compensation sensor 8 are mounted so as to intersect with each other when viewed from the direction of the air flow passing through the sensing passage 21, that is, to form an angle. There is. In this embodiment, the air flow sensor 7 and the temperature compensation sensor 8 form an angle of 90 degrees when viewed from the direction of the air flow passing through the sensing passage 21, and the air flow sensor 7 is So that it is located upstream of the temperature compensation sensor 8 in the air flow,
Installed.

The lead wires 70 of the sensors 7 and 8 are connected via the terminal holder 5 attached to the upstream body 1 with the male screw 19D,
It is drawn out of the upstream body 1.

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 70 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.

In this example, the rectifier 6 is formed so that the central portion thereof projects toward the upstream of the air flow, but the present invention is not limited to this in particular,
It may be formed to have a flat plate shape or to have a concave portion on the downstream side of the air flow.

A plurality of intake passages 2A are formed around the rectified product 6 in the downstream body 2 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. In this embodiment, the communication passage 22 is formed along the bottom of the sensing passage 21, that is, 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, since the sensing passage 21 is open to the side wall of each intake passage 29,
The air flowing into the sensing passage 21 is sucked into the intake passages 29 from the communication passage 22.

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. The shape of each of the communication passages 22 is also the same.

As a result, the air that has flowed into the sensing passage 21 uniformly flows out from the center of the rear end of the sensing passage 21 so as to spread radially, so the air that passes through the sensing passage 21 has its air flow passage direction. A laminar flow state can be reliably achieved without much movement.

Further, since the sensing passage is open to the side surface of the intake passage, in other words, since the sensing passage has a bottom portion, even if backfire occurs, the sensor arranged in the sensing passage is exposed to a blast. Less likely to be exposed.

As a result, backfire does not reduce the life of the sensor or degrade it.

Further, since the blast caused by the backfire is less likely to be measured as the intake air amount, it is possible to always measure the accurate intake air amount.

Further, the air flow rate sensor 7 and the temperature compensation sensor 8 are
The angle is 90 degrees when viewed from the direction of the air flow, and the angle is 90 degrees, that is, the overlapping part (hereinafter referred to as the lap) when viewed from the direction of the air flow is the most. Since the sensors are arranged so as to be small, the sensor arranged on the downstream side of the airflow passing through the sensing passage 21 is arranged on the upstream side as well as the influence of heat by the sensor arranged on the upstream side. It is less likely to be affected by the turbulence of the air flow due to passing through the sensor.

In this way, the air flow rate sensor 7 and the temperature compensation sensor 8
Are arranged so as to form an angle, and their overlaps are made small, the intake air amount can be accurately detected by the air flow rate sensor 7 and the temperature compensation sensor 8.

Furthermore, generally, the signal output from the air flow rate sensor 7 should be output more accurately than the signal output from the temperature compensation sensor 8, and as in this embodiment,
By arranging the air flow sensor 7 on the upstream side of the temperature compensation sensor 8 in the air flow, it is possible to reliably apply the laminar air flow to the air flow sensor 7. Therefore, the air flow rate can be detected more accurately by the air flow meter 100.

When the air flow rate sensor 7 and the temperature compensation sensor 8 are arranged so as to form an angle with each other as described above, the air flow rate sensor 7 may be arranged downstream of the temperature compensation sensor 8. . That is, in this case, the turbulent air flow after passing through the temperature compensation sensor 8 may hit the air flow rate sensor 7, or the heat generated by the compensation sensor 8 may be transferred to the air flow rate sensor 7. However, as described above, since the air flow rate sensor 7 and the temperature compensation sensor 8 are arranged so that the overlap margin is small, the influence of the disturbed air flow or heat on the air flow rate sensor 7 is minimized. Can be suppressed.

FIG. 7 is a sectional view of the second embodiment of the present invention, and FIG. 8 is a front view of the second embodiment of the present invention. FIGS. 7 and 8 are the same as FIGS. 1 and 3 described above, and the same reference numerals represent the same or equivalent portions, and thus the description thereof will be omitted.

In FIGS. 7 and 8, the air flow sensor 7 and the temperature compensation sensor 20 arranged in the sensing passage 21 of the air flow meter 200.
Similar to the first embodiment, 8 are arranged so that they form an angle when viewed from the direction of the air flow passing through the inside of the sensing passage 21, but the angle is more than 0 degree and 90 degrees. It is set to be less than degrees.

When the air flow rate sensor 7 and the temperature compensation sensor 208 are arranged in this way, the wrapping margin between them is larger than when they are arranged so that the angle formed by each sensor is 90 degrees, but at least each sensor is parallel. In comparison with the case where the angle is zero, the thermal effect of the sensor arranged on the upstream side of the air flow with respect to the sensor arranged on the downstream side of the air flow and the turbulence of the air flow passing through the sensor. Since it is possible to suppress the influence due to, it is possible to accurately measure the intake air amount.

In the above description, the communication passage 22 is described as being formed along the surface of the rectifier 6 formed so that the central portion thereof projects toward the upstream side of the air flow. Is not particularly limited to this.

That is, the communication passage 22 sucks the air passing through the sensing passage 21 by the flow of the air passing through the intake passage 29 to make the air passing through the sensing passage 21 into a laminar flow state. The optimum shape for that purpose depends on various factors such as the shape, size, and length of the sensing passage 21 or the intake passage 29, the displacement of the internal combustion engine, the number of cylinders, the intake pipe shape, the intake pipe length, or the like. Change. Therefore, it is desirable that the communication passage 22 be formed in a shape corresponding to each of the above factors.

Further, two or more communication passages 22 may be provided for one intake passage 29.

Further, around the sensing passage 21, the intake passages 29 having a circular shape as viewed from the air flow passage direction and having the same size are arranged so 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.

That is, 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 are such that the sensing passage 21 or the communication passage 22 has a sectional shape, size, length,
Alternatively, it changes depending on various factors such as the displacement of the internal combustion engine, the number of cylinders, the intake pipe shape, the intake pipe length, and 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 a plurality of intake passages are provided around the sensing passage 21 and one communicating passage is formed in each of the sensing passages 21, only one intake passage surrounds the sensing passage 21, that is, in the C-shape. A passage may be provided, and a plurality of communication passages may be formed in the intake passage, or one C-shaped communication passage may be formed along the intake passage.

Furthermore, when the intake passage has a venturi shape, the intake passage is formed so that the communication passage opens at the narrowest part of the venturi in FIGS. 1 and 7.
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 may be set to any shape according to various factors such as the number of cylinders of the internal combustion engine and the intake pipe length.

Further, in the above description, according to the present invention, a hot wire sensor is arranged, a sensing passage having a bottom portion, at least one intake passage arranged so as to surround the sensing passage, and a side surface of the intake passage. Although described as being applied to an air flow meter having a communication passage that communicates with the sensing passage, the present invention is not particularly limited to this, a bypass passage conventionally proposed,
Alternatively, it goes without saying that it may be applied to an air flow meter provided with a sensing passage such as a tubular body having no bottom.

(Effects of the Invention) As is apparent from the above description, according to the present invention, the air flow rate sensor and the temperature compensation sensor are arranged so as to form an angle, so that the following effects are achieved.

That is, for the sensor arranged on the downstream side of the air flow,
Since the thermal effect of the sensor arranged on the upstream side of the air flow and the effect of the turbulence of the air flow passing through the sensor can be minimized, it is possible to accurately measure the intake air amount by the air flow meter. it can.

[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 in which 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 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 schematic sectional view of the air flow sensor shown in FIG. FIG. 7 is a sectional view of the second embodiment of the present invention. FIG. 8 is a front view of the second embodiment of the present invention. 1 …… Upstream body, 1A, 2A, 29 …… Intake passage, 2 …… Downstream body, 3 …… Press-fit collar, 4 …… Terminal collar, 5 …… Terminal holder, 6 …… Rectifier, 7 …… Air flow sensor, 8,208 ... Temperature compensation sensor, 11 ... Circuit board, 21 ... Sensing passage, 22 ... Communication passage, 70 ... Lead wire, 100,200 ... Air flow meter

Claims (3)

[Claims] 1. An air flow meter for interposing an intake pipe of an internal combustion engine for measuring an intake air flow rate, comprising: a flow meter main body having a sensing passage arranged in the intake pipe; A hot wire type air flow rate sensor and a temperature compensation sensor are provided, wherein the air flow rate sensor and the temperature compensation sensor each have an elongated shape, pass through the center of each sensing passage, and at a right angle to the advancing direction of the fluid. An air flow meter, which is arranged so as to form an angle with each other when viewed from the upstream side of the fluid. 2. The air flowmeter according to claim 1, wherein the angle is 90 degrees. 3. The air flow rate according to claim 1, wherein the air flow rate sensor is arranged on the upstream side of the air flow with respect to the temperature compensation sensor. Total.