JP3053311B2 - Air flow meter - Google Patents

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 a flow rate of air flowing into an internal combustion engine.

[0002]

2. Description of the Related Art As a flow rate measuring device for measuring a flow rate of air flowing into an internal combustion engine, for example, Japanese Patent Application Laid-Open No. Hei 4-1164.
There is one described in Japanese Patent Application Publication No.

This flow rate measuring device includes a plurality of detectors provided in a flow path, a plurality of detection circuits for converting outputs from the respective detectors into flow velocity values, and a flow path based on outputs from these circuits. And a fuzzy arithmetic unit for calculating the average flow velocity. In this device, first, each detection circuit converts the output from each detector into a flow velocity, determines a drift distribution from each flow velocity, and matches this drift distribution with a plurality of previously prepared drift distribution model patterns. The degree is obtained by fuzzy calculation. Next, using the empirical formula corresponding to each drift model pattern, the average flow velocity for each drift model pattern is determined, and the weighted average of the respective average flow rates for each drift model pattern is calculated using the previously determined fitness as a weight. This is determined as the average flow velocity in the pipe. The average flow velocity in the pipe is multiplied by the cross-sectional area of the pipe to obtain the air flow rate.

[0004]

The above-mentioned prior art is characterized in that an accurate average flow velocity can be obtained even if the flow velocity distribution in the intake pipe has a bias, so that the air flow rate can be obtained very accurately. Are better. However, a plurality of detection circuits are required for a plurality of detectors, a memory for storing a plurality of drift distribution model patterns and empirical formulas,
A processor unit (a memory and a processor unit are provided in the fuzzy operation unit) for executing a fuzzy operation and the like is required, and there is a problem that a circuit configuration is complicated and cost is increased. In addition, in general, in a flow path that guides air to an internal combustion engine, there is a blowback from the internal combustion engine. Therefore, there is a problem that the detector is easily stained by the blowback, and an accurate flow rate cannot be obtained. .

The present invention has been made in view of such conventional problems. The circuit configuration is simple, the manufacturing cost can be reduced. It is an object of the present invention to provide an air flow meter capable of determining the following.

[0006]

According to an air flow meter for solving the above-mentioned object, a bypass passage through which a part of air passing through an intake pipe flows is formed, and the bypass passage has an upstream portion at an upstream portion thereof. A bypass passage forming member in which an air inlet portion whose diameter is gradually increased toward, and a resistance portion that obstructs air flow from the internal combustion engine side is formed in a downstream portion thereof; A plurality of heat probes connected between the plurality of heat probes and a plurality of heat probes connected in parallel, which are provided between the air inlet portion and the resistance portion, are supplied with current from a power supply, and are connected to each other. And a calculation circuit for converting the amount of current at the connection portion into a flow rate of air flowing through the intake pipe by a predetermined conversion method.

In another air flow meter for achieving the above object, a bypass passage through which a part of the air passing through the intake pipe flows is formed, and the bypass passage is distributed in a radial direction of the intake pipe. A plurality of air inlet portions are formed, and a bypass portion forming member in which a resistance portion obstructing air flow from the internal combustion engine side is formed in a downstream portion thereof, and a plurality of the air in the bypass passage portion A plurality of heat probes provided in each inlet portion, arranged immediately downstream of the air inlet portion, supplied with a current from a power supply, and connected in parallel, and a plurality of heat probes connected in parallel, And an arithmetic circuit for converting the amount of current in the connection part to which the is connected to the flow rate of air flowing through the intake pipe by a predetermined conversion method.

[0008]

The air passing through a portion where a plurality of thermal probes are provided (hereinafter, this portion is referred to as the most divergent portion for the sake of explanation) passes through an air inlet portion that collects air from a wide area in the intake pipe. Therefore, even if there is a bias in the flow velocity distribution in the intake pipe, it can be said that the flow velocity of the air passing through the most divergent portion is representative of the average flow velocity in the intake pipe to some extent. And the influence of the change in the flow velocity is reduced.

[0009] However, even in the most divergent portion, the influence of the flow velocity distribution in the intake pipe and the change of this flow velocity distribution is slightly affected. For this reason, a plurality of heat wire probes connected in parallel are provided in this portion, and the air flow rate is determined from the amount of current at the connection between the two. This is because the current amount at the connection of the plurality of hot wire probes connected in parallel is the sum of the current amounts of the respective heat probes, so that even if the flow velocity distribution is biased to the most divergent part, this bias will not occur. This is because they are offset. Therefore, according to the present invention, it is possible to obtain the flow rate of the air flowing through the intake pipe fairly accurately even if the air flow velocity distribution is biased in the intake pipe.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the air flow meter according to the present invention will be described below. In describing various embodiments, the same portions are denoted by the same reference numerals, and redundant description will be omitted. First, an air flow meter according to a first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the air flow meter according to the present embodiment includes an insertion type hot wire air flow meter 2 inserted into an intake pipe 1 and a bypass passage forming member 5 forming a bypass passage 6; The two hot-wire probes 9a, 9b and the room-temperature probe 10 arranged in the bypass passage 6 and the circuit unit 4 for obtaining the mass air flow rate flowing through the intake pipe 1 from the current flowing through these probes 9a, 9b, 10 Have. In the air flow meter 2, the bypass passage forming member 30 is inserted into the intake pipe 1 and attached to the intake pipe 1 via the spacer 3.

An engine (not shown) is connected downstream of the intake pipe 1 and a flow control valve 19 is provided between the position where the air flow meter 2 is provided and the engine.
Is provided. The flow control valve 19 is a butterfly-type valve and includes a valve plate 20 having a diameter corresponding to the inner diameter of the intake pipe 1 and a valve shaft 21 for rotating the valve plate 20.

The bypass passage 6 has an air inlet 7 whose diameter is gradually increased toward the upstream side, and a narrowest portion 8 formed downstream of the air inlet 7 at the upstream side. And a diverter 32 diverted by a resistance plate 31 formed perpendicular to the air flow direction.
The thickness of the spacer 3 is adjusted so that the highest part 8 is located at the center of the intake pipe 1. In addition, the downstream end of the branch part 32 forms the air exhaust port 11.

As shown in FIG. 2, the enlarged diameter portion 7 extends in a direction perpendicular to the valve shaft 21 of the flow control valve 19. The hottest section 8 is provided with two hot-wire probes 9a and 9b and a normal-temperature probe 10. Two hot wire probes 9
a and 9b are supported by two stays 32a and 32b provided in the bypass passage forming member 5. The room temperature probe 10 is also supported by two stays 33a and 33b provided in the bypass passage forming member 5.

FIG. 3 shows the configuration of the circuit section 4. Power supply 17
Is connected to the collector of the transistor 12, and its emitter is connected to the hot-wire probes 9a and 9b and the room-temperature probe 10. The heating wire probes 9a and 9b are connected in parallel with each other and connected at a connection point 17. Hot wire probe 9
a, 9b, room temperature probe 10, resistor 14, resistor 13
They are connected at connection points 17 and 18 to form a bridge circuit. The connection point 17 is connected to the + input of the operational amplifier 15, and the connection point 18 is connected to the − input of the operational amplifier 15. The output of the operational amplifier 15 is the transistor 1
2 bases. The connection point 17 is the arithmetic circuit 1
6 is also connected. The arithmetic circuit 16 is provided with arithmetic means for obtaining the air flow rate from the amount of current flowing through the connection point 17.

Next, the operation of this embodiment will be described.
Generally, the flow velocity of the air flowing through the intake pipe 1 has a bias. This flow velocity distribution changes under the influence of the pipe shape, the air flow rate, the one provided at the upstream end or the downstream end of the intake pipe 1, and the like. By the way, the air passing through the most divergent portion 8 of the bypass passage 6 has passed through the air inlet portion 7 that collects the air in the intake pipe 1 from the widest possible range in the radial direction of the intake pipe 1. Even if there is a bias in the flow velocity distribution 1, the flow velocity of the air passing through the most divergent portion 8 can be said to represent the average flow velocity in the intake pipe 1 to some extent. The effect of the change is smaller. In the present embodiment, since the flow control valve 19 is provided on the downstream side of the air flow meter 2, the flow velocity at the junction between the intake pipe 1 and the valve shaft 21 is almost zero as shown in FIG. Since the flow velocity in the portion perpendicular to the valve shaft 21, that is, in the gap S between the valve plate 20 and the intake pipe 1, is maximized, it is necessary to cope with such a deviation in the flow velocity distribution. ,
The air inlet 7 extends in a direction perpendicular to the valve shaft 21.

However, even the most divergent portion 8 is slightly affected by the flow velocity distribution in the intake pipe 1 and a change in the flow velocity distribution. For this reason, 2
Two heat wire probes 9a and 9b are provided, and the flow rate of air flowing through the intake pipe 1 from the two heat wire probes 9a and 9b is obtained.

Here, consider the case where air having different flow rates flows through the two heating wire probes 9a and 9b. For example, it is assumed that air having a high flow rate flows through the hot wire probe 9a and air has a low flow rate flowing through the hot wire probe 9b. When air flows through the hot wire probes 9a and 9b, the heat removes the heat of the hot wire probes 9a and 9b and lowers the temperature. For this reason, the resistance of the hot wire probes 9a and 9b decreases, and the amount of current flowing therethrough increases. Therefore, the temperature of the hot wire probe 9a through which the high flow rate air flows is lower than that of the hot wire probe 9b through which the low flow rate air flows, so that more current flows. However, the amount of current flowing through the connection point 17 is the sum of the amounts of current flowing through the two hot-wire probes 9a and 9b.
Even when air having different velocities flow through the two hot-wire probes 9a and 9b, the amount of current flowing through the connection point 17 can be said to represent the average flow velocity of the most divergent portion 8 to some extent. It is hardly affected by the deviation of the flow velocity distribution or its change.

Therefore, the amount of current flowing through the connection point 17 is almost influenced by the flow velocity distribution in the intake pipe 1 and a change in the flow velocity distribution due to the effects of the air inlet 7 and the two hot-wire probes 9a and 9b. Will show no value.

When the temperature of the air flowing through the intake pipe 1 changes, the heat probes 9a, 9b
The amount of heat deprived of varies. Therefore, in order to accurately measure the air flow rate, the connection point 1 due to a change in the air temperature is required.
It is necessary to compensate for the change in the amount of current 7. When the air temperature changes, the resistance of the room temperature probe 10 changes,
The amount of current flowing here changes. The current flowing here and the current flowing through the connection unit 17 are input to the operational amplifier 15, and the current amount of the room-temperature probe 10 is subtracted from the current amount of the connection unit 17 and input to the base of the transistor 12. In the present embodiment, as described above, the room temperature probe 1
0, the operational amplifier 15 and the transistor 12 compensate for a change in the amount of current at the connection point 17 due to a change in air temperature.

The arithmetic circuit 16 converts the amount of current flowing through the connection point 17 into the flow rate of air flowing through the intake pipe 1 by a predetermined conversion formula. Here, for convenience of explanation, it has been described that the air flow rate is obtained from the amount of current flowing through the connection point 17. However, actually, the air flow rate is obtained from the voltages applied to both ends of the two hot-wire probes 9a and 9b. ing.

As described above, in the present embodiment, the connection point 17 which is hardly affected by the flow velocity distribution in the intake pipe 1 and a change in the flow velocity distribution and indicates a value representative of the average flow velocity in the intake pipe 1. Since the flow rate of the air flowing through the intake pipe 1 is obtained from the current amount of the air flow, the air flow rate can be obtained fairly accurately. Further, only one arithmetic circuit 16 is required, and
Since the content of the calculation is a simple one for converting the amount of current at the connection point 17 into an air flow rate, the manufacturing cost can be reduced.

Further, in this embodiment, each probe 9a,
Since the resistance plate 31 formed perpendicular to the air flow direction is provided on the downstream side of 9b and 10, even if there is blow-back from the engine provided downstream of the intake pipe 1, By returning, each probe 9a, 9b, 1
0 is hardly stained.

Next, a second embodiment of the air flow meter according to the present invention will be described with reference to FIGS. As shown in FIG. 4, the inner diameter of the intake pipe 1a may be smaller than the bypass passage forming member 5. In this case, an enlarged diameter portion is formed in a part of the intake pipe 1a, and the bypass passage forming member 5 is inserted therein. In the first embodiment, the thermal probes 9a and 9b are supported by two stays 32a and 32b, and the normal temperature probe 10 is also supported by two stays 33a and 33b.
In this example, four stays were used.
As shown in FIG. 5, one stay 32a is used for both a heat probe and a room temperature probe,
a, 32b, and 33a are reduced to three in total.

Next, an air flow meter according to a third embodiment of the present invention will be described with reference to FIGS. In this embodiment, a plurality of bypass passages 22a and 22b are formed in the bypass passage forming member 5a, and the hot-wire pro- ducts are formed therein.
And 9b, 9b. Hot wire probe 9a,
9b is provided immediately downstream of the air inlets of the plurality of bypass passages 22a, 22b. Bypass passage 22
a and 22b are joined at a joining portion 23 and a common exhaust port 24
Exhaust air from The room temperature probe 10 may be installed in one of the bypass passages. The bypass passage forming member 5a is also provided with a resistance plate a that impedes the flow of air from the engine. In the case of this embodiment, if the partition wall 25 is extended to the air exhaust port of the bypass passage forming member 5a to form a completely independent bypass passage, noise due to the merge of the air passing through both bypass passages can be reduced. .

Next, a fourth embodiment according to the present invention will be described with reference to FIG. In this embodiment, two completely independent bypass passages 22a and 22b are formed in the bypass passage forming member 5b, and the hot-wire probes 9a and 9b are installed in the respective bypass passages 22a and 22b. . In addition, the air exhaust ports of each of the bypass passages 22a and 22b face the inner wall side of the intake pipe 1 and face in opposite directions.

Next, a fifth embodiment according to the present invention will be described with reference to FIG. In the present embodiment, similarly to the fourth embodiment, the bypass passage 2 is formed in the bypass passage forming member 5c.
2a and 22b are formed completely independently, and hot-wire probes 9a and 9b are installed in respective bypass passages 22a and 22b. Since the air inlets 7a and 7b of the bypass passages 22a and 22b are located closer to the center of the intake pipe 1, upstream air is collected in the bypass passages 22a and 22b so that air from as wide a range as possible can be collected. The diameter is gradually increasing toward. The respective exhaust ports of the bypass passages 22a and 22b are formed at the center of the intake pipe 1.

Next, an air flow meter according to a sixth embodiment of the present invention will be described with reference to FIGS. In this embodiment, the hot-wire probes 9a and 9b are arranged closer to the circuit section 4 than the center of the intake passage. For this reason, the air inlet portion 7a is formed so as to be able to collect air from a wide range from the circuit portion 4 side as well as in the direction opposite to the circuit portion 4. In this case, the flow velocity of the most divergent portion 8a provided with the hot-wire probes 9a and 9b is:
Unlike the first embodiment, which is different from the case where the most symmetric part 8 is provided at the center of the intake pipe 1, the flow rate of the most symmetric part 8a is as follows.
Since it is still representative of the average flow velocity in the intake pipe 1, there is no problem at all.

Next, an air flow meter according to a seventh embodiment of the present invention will be described with reference to FIGS. This embodiment has basically the same configuration as the first embodiment. However, as shown in FIG. 13, the air inlet 7d of the bypass passage 6d is not only in one direction but also in this one direction. It also spreads at right angles. As described above, when the air inlet portion 7d is widened, it is possible to further reduce the influence of the flow speed of the air passing through the uppermost portion 8 on the bias of the flow velocity distribution in the intake pipe 1 and the change in the flow velocity distribution.

Next, an eighth embodiment according to the present invention will be described with reference to FIGS. In this embodiment, throttle portions 24a and 24b are added to the intake pipe 1. As shown in FIG. 15, the throttle portions 24a and 24b have parallel portions 25a and 25b (points where the interval between the throttle portions 24a and 24b is the smallest). A bypass passage forming member 5f is provided between the parallel portions 25a and 25b such that the air inlet portion 7f is provided. Since the space between the parallel portions 25a and 25b has the highest flow velocity, by taking in air from this position, the flow velocity in the bypass passage also increases, and the measurement accuracy increases. In this embodiment, the throttle portions 24a and 24b and the bypass passage forming member 5f form an integral structure, and the throttle portions 24a and 24b can be inserted into the intake pipe 1 together with the bypass passage forming member 5f. I have.

Next, a ninth embodiment according to the present invention will be described with reference to FIG. In this embodiment, the intake pipe 1b
Is formed at a part thereof, and a bypass forming member 5g is inserted into the intake pipe 1b so that the air inlet part 5 is located at the most uneven part 26. Note that, in the present embodiment, unlike the eighth embodiment, the bypass passage forming member 5g and the throttle portion 27 are not integrally formed, and the throttle portion 27 is formed only in the intake pipe 1b.

Next, a tenth embodiment according to the present invention will be described with reference to FIGS. In this embodiment,
The throttle portions 25a and 25b oppose and are formed in parallel in the intake pipe 1c, and a rectifying grid 29 is disposed above the throttle portions 25a and 25b. Thus, by arranging the rectifying member 29,
The flow velocity distribution width in the intake pipe 1c downstream of the rectifying grid 29 can be reduced, and the air flow rate can be more accurately determined. FIG. 18 shows a rectifying grid 29 from the downstream side.
Is shown.

Next, an eleventh embodiment according to the present invention will be described with reference to FIGS. As shown in FIG. 19, an element 32 is provided in an air cleaner case 31.
Is provided. In addition, an inlet portion 34 of the intake pipe 1d is inserted into the air cleaner case 31. The entrance 34 extends in a trumpet shape. The intake pipe 1d is
As in the tenth embodiment, a rectifying grid 29 inserted from the inlet 34 and a throttle 36 are provided. A slit portion 35 is formed in the throttle portion 36, from which the bypass passage forming member portion 5 is inserted.

In all of the above embodiments, the air flow meter is separate from the intake pipe, and the air flow meter is set by inserting a bypass passage forming member into the intake pipe. The invention is not limited to this.
As shown in FIG. 1, the plug-in intake pipe 1f forming a part of the intake pipe and the bypass passage forming member 5 are integrally formed, and this plug-in intake pipe 1f is connected to the intake pipe connected to the engine, so that air is removed. The flow meter 2a may be set. Although FIG. 1 is a modification of the first embodiment, the other embodiments may also be configured such that the plug-in intake pipe and the bypass passage forming member are integrated. Further, in the above embodiment, the number of thermal probes is all two, but it is needless to say that the number of thermal probes may be three or more.

[0035]

According to the present invention, since the flow rate of the air collected from a wide range in the intake pipe is detected by the plurality of thermal probes, the flow rate of the air can be measured fairly accurately. In addition, since the amount of current at the connection between the plurality of thermal probes connected in parallel determines the air flow rate, only one circuit is required for the arithmetic circuit, and the manufacturing cost can be reduced.

Further, the bypass passage forming member that collects air from a wide area in the intake pipe is provided with a resistance portion that hinders the flow of air from the internal combustion engine, so that the air is blown back from the internal combustion engine. If so, the thermal probe is almost clean.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an air flow meter according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a circuit diagram of the air flow meter according to the first embodiment of the present invention.

FIG. 4 is a sectional view of a main part of an air flow meter according to a second embodiment of the present invention.

FIG. 5 is a main part circuit diagram of an air flow meter according to a second embodiment of the present invention.

FIG. 6 is a sectional view of a main part of an air flow meter according to a third embodiment of the present invention.

FIG. 7 is a sectional view taken along line VII-VII in FIG. 6;

FIG. 8 is a sectional view of a main part of an air flow meter according to a fourth embodiment of the present invention.

FIG. 9 is a sectional view of a main part of an air flow meter according to a fifth embodiment of the present invention.

FIG. 10 is a sectional view of a main part of an air flow meter according to a sixth embodiment of the present invention.

11 is a sectional view taken along line XI-XI in FIG.

FIG. 12 is a sectional view of a main part of an air flow meter according to a seventh embodiment of the present invention.

13 is a sectional view taken along line XIII-XIII in FIG.

FIG. 14 is a sectional view of a main part of an air flow meter according to an eighth embodiment of the present invention.

15 is a sectional view taken along line XV-XV in FIG.

FIG. 16 is a sectional view of a main part of an air flow meter according to a ninth embodiment of the present invention.

FIG. 17 is a sectional view of a main part of an air flow meter according to a tenth embodiment of the present invention.

18 is a view as viewed in the direction of arrow XVIII in FIG. 17;

FIG. 19 is an explanatory diagram showing a configuration of an air flow meter of an eleventh embodiment according to the present invention.

FIG. 20 is a sectional view of an essential part of an air flow meter according to an eleventh embodiment of the present invention.

FIG. 21 is a sectional view of a main part of an air flow meter according to a twelfth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Intake pipe, 2 ... Insertion type hot wire-air flow meter, 4
... Circuit part, 5 ... Bypass passage forming member, 6 ... Bypass passage, 7 ... Air inlet part, 8 ... Shortest part, 9a, 9b ... Hot wire probe, 10 ... Normal temperature probe, 11 ... Air exhaust outlet part , 1
2 ... transistor, 15 ... operational amplifier, 16 ... arithmetic circuit, 17 ... connection part, 19 ... flow control valve, 20 ... valve plate, 2
1 ... valve shaft, 24a, 24b, 27, 25a, 25b, 3
6: throttle portion, 29: rectifying grating.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01F 1/68

Claims (7)

(57) [Claims] 1. An air flow meter for measuring an air flow rate in an intake pipe for guiding air to an internal combustion engine, wherein a bypass passage through which a part of the air passing through the intake pipe flows is formed, and the bypass passage has an upstream side. An air inlet portion is formed in the portion, the diameter of which gradually increases toward the upstream side, and a portion of the air passing through the intake pipe flows into the air inlet portion, and a resistance portion that obstructs the air flow from the internal combustion engine side is formed in the downstream portion. And a plurality of thermal probes arranged between the air inlet portion and the resistance portion in the bypass passage, supplied with a current from a power supply, and connected in parallel. An arithmetic circuit that converts a current amount at a connection portion where the plurality of thermal probes connected in parallel are connected to each other to a flow rate of air flowing through the intake pipe by a predetermined conversion method. An air flow meter characterized in that: 2. A method according to claim 1, wherein said intake pipe is provided with a butterfly valve having a valve plate having a valve plate corresponding to the inside diameter of said intake pipe and rotating around a valve shaft. The air flow meter according to claim 1, wherein the air flow meter extends at least in a radial direction and at right angles to the valve shaft. 3. An air flow meter for measuring an air flow rate in an intake pipe for guiding air to an internal combustion engine, wherein a bypass passage through which a part of the air passing through the intake pipe flows is formed, and the bypass pipe is provided in the bypass passage. A plurality of air inlets are formed, into which a part of the air that is distributed in the radial direction and flows through the intake pipe flows, and a resistance portion that obstructs the air flow from the internal combustion engine side is formed in a downstream portion thereof. A bypass passage forming member, and a plurality of air inlet portions provided in the bypass passage, arranged immediately downstream of the air inlet portion, supplied with current from a power supply, and connected in parallel. A heat probe, and a calculation circuit for converting the amount of current at a connection portion where the plurality of heat probes connected in parallel are connected to each other to a flow rate of air flowing through the intake pipe by a predetermined conversion method. Air flow meter, characterized in that it comprises, when. 4. An electric current is supplied from the power supply and arranged between the air inlet portion and the resistance portion in the bypass passage, and the amount of current flowing therethrough changes according to a temperature change of the air. A room-temperature probe that changes, and a temperature-change compensation circuit that cancels a change in current flowing through the plurality of thermal probes according to a change in the temperature of the air, based on the amount of current flowing through the room-temperature probe. The air flow meter according to claim 1, 2 or 3, wherein 5. A throttle section for narrowing a flow path diameter is formed in said intake pipe, and said air inlet section of said bypass passage forming member is located at the same position as said throttle section in said air flow direction. The air flow meter according to claim 1, 2, 3, or 4, wherein 6. The bypass passage forming member in which the plurality of thermal probes are disposed is formed separately from the intake pipe and is insertable into the intake pipe. The air flow meter according to claim 1, 2, 3, 4, or 5, wherein 7. A plug-in air intake pipe forming a part of the intake pipe, wherein the plug-in air intake pipe and the bypass flow path forming member are formed integrally. ,
The air flow meter according to 3, 4, or 5.