JP5370114B2 - Air flow measurement device - Google Patents

Air flow measurement device Download PDF

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JP5370114B2
JP5370114B2 JP2009281438A JP2009281438A JP5370114B2 JP 5370114 B2 JP5370114 B2 JP 5370114B2 JP 2009281438 A JP2009281438 A JP 2009281438A JP 2009281438 A JP2009281438 A JP 2009281438A JP 5370114 B2 JP5370114 B2 JP 5370114B2
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bypass passage
throttle
detection element
upstream
downstream
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JP2011122962A (en
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信一 神谷
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Denso Corp
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Denso Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/6842—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow with means for influencing the fluid flow

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air flow meter capable of stabilizing output characteristics by giving a drift-free stable flow velocity distribution to a detection element 14, regardless of a direction of air flowing through a bypass passage 5. <P>SOLUTION: The bypass passage 5 includes a folding-back formed halfway in a passage between the entrance and the exit, and three throttles located in the passage upstream of the folding-back. The three throttles include a main throttle 6 to be located in a part in which the detection element 14 is to be disposed, an upstream throttle 7 to be located upstream of the part in which the detection element 14 is to be disposed, and a downstream throttle 8 to be located downstream of the part in which the detection element 14 is to be disposed. A cross-sectional area of a maximum throttle to be formed in the main throttle 6 is designed smaller than that of a throttling passage to be formed in the upstream throttle 7 and the downstream throttle 8. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

本発明は、空気の流量および流れ方向（順流と逆流）を検出できる空気流量測定装置に関する。   The present invention relates to an air flow rate measuring device capable of detecting an air flow rate and a flow direction (forward flow and reverse flow).

例えば、自動車用エンジンの吸入空気量を測定する空気流量測定装置がある。
この空気流量測定装置は、ダクトの内部を流れる空気の一部を取り込むバイパス通路を有し、このバイパス通路の内部に流量測定用の検出素子を配置している。
この空気流量測定装置では、バイパス通路に流入する空気の流れに乱れ（不安定な偏った流速分布）が生じると、検出素子の検出精度が低下するため、出力特性が安定しないという問題が生じる。
そこで、特許文献１では、空気の乱れを抑制する手段として、バイパス通路に絞り部を設けている。この絞り部は、バイパス通路の入口部から検出素子が配置されている部位までの断面が三次元的に徐々に絞った形状を有している。
また、特許文献２の発明では、バイパス通路の検出素子が配置される部位より上流側（バイパス通路の入口側）に絞り部を設けることで空気の乱れを抑制している。 For example, there is an air flow rate measuring device that measures the intake air amount of an automobile engine.
This air flow rate measuring device has a bypass passage that takes in a part of the air flowing inside the duct, and a detection element for flow rate measurement is arranged inside the bypass passage.
In this air flow rate measuring device, if the flow of air flowing into the bypass passage is disturbed (unstable and uneven flow velocity distribution), the detection accuracy of the detection element is lowered, and the output characteristics are not stable.
Therefore, in Patent Document 1, a throttle portion is provided in the bypass passage as means for suppressing air turbulence. The narrowed portion has a shape in which the cross section from the inlet portion of the bypass passage to the portion where the detection element is arranged is gradually narrowed in three dimensions.
Further, in the invention of Patent Document 2, air turbulence is suppressed by providing a throttle portion on the upstream side (inlet side of the bypass passage) from the portion where the detection element of the bypass passage is disposed.

特開２００２−３５７４６５号公報JP 2002-357465 A 特開平１１−１１８５５９号公報Japanese Patent Application Laid-Open No. 11-118559

ところで、図４（ａ）に示す様に、バイパス通路１００に不安定な偏った流速分布を有する空気が流入すると、その流速分布の偏った空気が、絞り部１１０を通過する際に絞られることにより、安定した流速分布が得られる。つまり、流速部分の偏った空気が、絞り部１１０を通過することで流速分布の広がりが狭められるため、安定した流速分布が形成される。
しかし、絞り部１１０による効果、すなわち、安定した流速分布が得られるのは、絞り部１１０によってバイパス通路１００の断面積が最も狭くなっている部分（最絞り部と呼ぶ）を通過した後であり、検出素子１２０が配置される最絞り部では、最絞り部を通過した後と比較すると、安定した流速分布が得られない。
このため、特許文献１に記載されている様に、最絞り部に検出素子１２０を配置しても、その検出素子１２０に対し安定した流速分布を与えることは困難である。 By the way, as shown in FIG. 4A, when air having an unstable and uneven flow velocity distribution flows into the bypass passage 100, the air having the uneven flow velocity distribution is restricted when passing through the throttle portion 110. Thus, a stable flow velocity distribution can be obtained. That is, since the spread of the flow velocity distribution is narrowed by the air having a biased flow velocity portion passing through the throttle portion 110, a stable flow velocity distribution is formed.
However, the effect of the throttle portion 110, that is, the stable flow velocity distribution is obtained after passing through the portion (referred to as the maximum throttle portion) where the cross-sectional area of the bypass passage 100 is the narrowest by the throttle portion 110. In the most restrictive portion where the detection element 120 is disposed, a stable flow velocity distribution cannot be obtained as compared with after passing through the most restrictive portion.
For this reason, as described in Patent Document 1, it is difficult to provide a stable flow velocity distribution to the detection element 120 even if the detection element 120 is arranged at the most narrowed portion.

また、特許文献２の発明では、バイパス通路１００の検出素子１２０が配置される部位より上流側に絞り部１１０を設けているため、例えば、吸気脈動によりダクト内に逆流が発生した場合は、絞り部１１０を設けたことによる効果を得ることが出来ない。つまり、図４（ｂ）に矢印で示す様に、バイパス通路１００に偏った流速分布を有する逆流が流れ込んだ場合、その逆流方向に対しては、絞り部１１０より検出素子１２０の方が上流側（図示上側）に位置しているため、偏った流速分布を有する逆流を検出素子１２０で検出することになり、出力変動が大きくなる。
さらに、特許文献２では、ダクト内を流れる空気の流れ方向が順流の場合でも、検出素子１２０が配置される部位に絞り部１１０を設けていない。このため、検出素子１２０の上流側に設けられた絞り部１１０によって整流された空気が絞り部１１０を通過した後に拡散すると、検出素子１２０を通過する空気の流速が低下して、検出精度にばらつきが生じる恐れがある。 Further, in the invention of Patent Document 2, since the throttle portion 110 is provided on the upstream side of the portion where the detection element 120 of the bypass passage 100 is disposed, for example, when a backflow occurs in the duct due to intake pulsation, The effect by providing the part 110 cannot be obtained. That is, as shown by the arrow in FIG. 4B, when a reverse flow having a biased flow velocity distribution flows into the bypass passage 100, the detection element 120 is upstream of the throttle unit 110 in the reverse flow direction. Since the detection element 120 detects a reverse flow having a biased flow velocity distribution, the output fluctuation increases.
Further, in Patent Document 2, even when the flow direction of the air flowing in the duct is a forward flow, the throttle portion 110 is not provided at a portion where the detection element 120 is disposed. For this reason, if the air rectified by the throttle unit 110 provided on the upstream side of the detection element 120 diffuses after passing through the throttle unit 110, the flow velocity of the air passing through the detection element 120 decreases, and the detection accuracy varies. May occur.

本発明は、上記事情に基づいて成されたもので、その目的は、バイパス通路を流れる空気の流れ方向に係わらず、つまり、順流と逆流のどちらにおいても、検出素子に対して偏流の無い安定した流速分布を与えることにより、出力特性の安定化を図ることが出来る空気流量測定装置を提供することにある。   The present invention has been made on the basis of the above circumstances, and its object is to provide a stable flow without any deviation with respect to the detection element regardless of the flow direction of the air flowing through the bypass passage, that is, in both the forward flow and the reverse flow. An object of the present invention is to provide an air flow rate measuring device capable of stabilizing output characteristics by giving a flow velocity distribution.

（請求項１に係る発明）
本発明は、ダクトの内部を流れる空気の一部を取り込むバイパス通路と、このバイパス通路に配置される流量測定用の検出素子と、この検出素子によって得られる情報を基に、バイパス通路を流れる空気の流量、及び、空気の流れ方向（順流と逆流）を検出できる空気流量測定装置であって、バイパス通路の断面積を絞る複数の絞り部を有し、複数の絞り部は、検出素子が配置される部位に設けられるメイン絞り部と、検出素子が配置される部位より上流側に設けられる上流側絞り部と、検出素子が配置される部位より下流側に設けられる下流側絞り部とを有し、上流側絞り部および下流側絞り部は、それぞれメイン絞り部との間に所定の間隔をあけて独立して設けられ、且つ、バイパス通路の断面積を所定の長さに渡って一定の割合で絞った通路状に形成されていることを特徴とする。 (Invention according to Claim 1)
The present invention relates to a bypass passage that takes in part of the air flowing inside a duct, a detection element for measuring a flow rate arranged in the bypass passage, and air flowing through the bypass passage based on information obtained by the detection element. Air flow measurement device capable of detecting the flow rate of air and the direction of air flow (forward flow and reverse flow), and having a plurality of throttle portions for reducing the cross-sectional area of the bypass passage, and a plurality of throttle portions are arranged with detection elements A main throttle portion provided at a portion where the detection element is disposed, an upstream throttle portion provided upstream from the portion where the detection element is disposed, and a downstream throttle portion provided downstream from the portion where the detection element is disposed. The upstream throttle portion and the downstream throttle portion are each independently provided with a predetermined interval from the main throttle portion, and the cross-sectional area of the bypass passage is constant over a predetermined length. Squeeze by percentage Characterized in that it is formed in the passage shape.

上記の構成によれば、検出素子が配置される部位と、その検出素子が配置される部位より上流側および下流側の３個所にそれぞれ絞り部を設けているので、順流と逆流とに係わらず、検出素子に対し常に安定した流速分布を与えることが出来る。
なお、ダクトの内部を一方から他方に向かって空気が流れる時に、その空気の一部がバイパス通路の入口から流入して出口より流出する流れを順流と呼び、ダクトの内部を他方から一方に向かって空気が流れる時に、その空気の一部がバイパス通路の出口から流入して入口より流出する流れを逆流と呼ぶ。 According to the above-described configuration, the throttling portions are provided in the part where the detection element is arranged and the upstream side and the downstream side of the part where the detection element is arranged. Therefore, regardless of forward flow or reverse flow, A stable flow velocity distribution can always be given to the detection element.
When air flows inside the duct from one side to the other, a part of the air flows in from the inlet of the bypass passage and flows out of the outlet is called forward flow, and the inside of the duct is directed from the other side to the other. When the air flows, a part of the air that flows in from the outlet of the bypass passage and flows out of the inlet is called backflow.

順流の時は、バイパス通路の入口より流入した空気の乱れが上流側絞り部を通過することにより整流されて安定した流速分布を得ることができ、且つ、検出素子が配置される部位に設けられるメイン絞り部によって空気の拡散を防止できる。その結果、検出精度が向上し、出力特性の安定化を図ることが出来る。
一方、逆流の時は、バイパス通路の出口より流入した空気の乱れが下流側絞り部を通過することにより整流されて安定した流速分布を得ることができ、且つ、検出素子が配置される部位に設けられるメイン絞り部によって空気の拡散を防止できる。その結果、検出精度が向上し、出力特性の安定化を図ることが出来る。 During forward flow, the turbulence of the air flowing in from the inlet of the bypass passage is rectified by passing through the upstream restrictor, so that a stable flow velocity distribution can be obtained, and the detection element is provided at the site. Air diffusion can be prevented by the main throttle. As a result, detection accuracy can be improved and output characteristics can be stabilized.
On the other hand, at the time of reverse flow, the turbulence of the air flowing in from the outlet of the bypass passage can be rectified by passing through the downstream throttle part to obtain a stable flow velocity distribution, and at the part where the detection element is arranged. Air diffusion can be prevented by the main throttle portion provided. As a result, detection accuracy can be improved and output characteristics can be stabilized.

（請求項２に係る発明）
請求項１に記載した空気流量測定装置において、メイン絞り部は、バイバス通路の断面積が最も小さくなる最絞り部から上流側および下流側へ向かって次第にバイバス通路の断面積が大きくなる様に設けられ、検出素子は、最絞り部に配置されていることを特徴とする。
本発明の空気流量測定装置は、順流だけでなく逆流も検出するので、最絞り部（メイン絞り部によってバイパス通路の断面積が最も狭くなっている部分）に検出素子を配置することにより、順流と逆流の両方で検出精度を向上できる。 (Invention according to Claim 2)
2. The air flow rate measuring device according to claim 1, wherein the main throttle portion is provided such that the cross-sectional area of the bypass passage gradually increases from the lowest throttle portion where the cross-sectional area of the bypass passage is smallest to the upstream side and the downstream side. The detection element is arranged at the most narrowed portion.
Since the air flow rate measuring device of the present invention detects not only forward flow but also reverse flow, the forward flow can be obtained by arranging the detection element at the most restrictive portion (the portion where the cross-sectional area of the bypass passage is narrowest by the main restrictive portion). And detection accuracy can be improved by both reverse flow and reverse flow.

（請求項３に係る発明）
請求項１または２に記載した空気流量測定装置において、上流側絞り部によって絞られるバイパス通路の断面積および下流側絞り部によって絞られるバイパス通路の断面積より、メイン絞り部によって絞られるバイパス通路の断面積の方が小さいことを特徴とする。 上記の構成によれば、バイパス通路の断面積がメイン絞り部で最も小さく（狭く）設定されるので、バイパス通路を流れる空気の流量をメイン絞り部でコントロールできる。つまり、バイパス通路を流れる空気の流量をメイン絞り部に配置された検出素子により精度良く検出できる。 (Invention according to claim 3)
The air flow rate measuring device according to claim 1 or 2, wherein the bypass passage is restricted by the main restrictor from the cross-sectional area of the bypass passage restricted by the upstream restrictor and the cross-sectional area of the bypass passage restricted by the downstream restrictor. The cross-sectional area is smaller. According to the above configuration, since the cross-sectional area of the bypass passage is set to be the smallest (narrow) in the main throttle portion, the flow rate of the air flowing through the bypass passage can be controlled by the main throttle portion. That is, the flow rate of the air flowing through the bypass passage can be detected with high accuracy by the detection element disposed in the main throttle portion.

本発明に係る絞り部を設けたバイパス通路の一部断面図である。It is a partial cross section figure of the bypass passage which provided the restricting part concerning the present invention. エアフロメータを吸気ダクトに取り付けた断面図である。It is sectional drawing which attached the air flow meter to the intake duct. （ａ）センサ部による流量計測の原理を説明する温度分布図、（ｂ）センサ部に使用される検出素子の断面図である。(A) Temperature distribution diagram illustrating the principle of flow rate measurement by the sensor unit, (b) a cross-sectional view of a detection element used in the sensor unit. （ａ）特許文献１の従来技術を示すバイパス通路の一部断面図、（ｂ）特許文献２の従来技術を示すバイパス通路の一部断面図である。(A) Partial cross-sectional view of the bypass passage showing the prior art of Patent Document 1, (b) Partial cross-sectional view of the bypass passage showing the prior art of Patent Document 2.

本発明を実施するための最良の形態を以下の実施例により詳細に説明する。   The best mode for carrying out the present invention will be described in detail with reference to the following examples.

（実施例１）
この実施例１は、例えば、自動車用エンジンの吸入空気量を測定するエアフロメータ１に本発明の空気流量測定装置を適用した一例である。
エアフロメータ１は、図２に示す様に、吸気ダクト２に取り付けられるセンサボディ３と、このセンサボディ３の内部に組み込まれるセンサ部４とを有する。
吸気ダクト２は、エンジンの吸気ポート（図示せず）に接続される吸気通路の一部を形成するもので、例えば、吸気通路の最上流に配置されるエアクリーナの出口パイプ、あるいは、この出口パイプの下流側に接続される吸気管等である。 Example 1
The first embodiment is an example in which the air flow measuring device of the present invention is applied to an air flow meter 1 that measures the intake air amount of an automobile engine, for example.
As shown in FIG. 2, the air flow meter 1 includes a sensor body 3 attached to the intake duct 2 and a sensor unit 4 incorporated in the sensor body 3.
The intake duct 2 forms part of an intake passage connected to an intake port (not shown) of the engine. For example, an outlet pipe of an air cleaner arranged at the uppermost stream of the intake passage, or the outlet pipe An intake pipe or the like connected to the downstream side.

センサボディ３は、吸気ダクト２に空けられた取付け孔より吸気ダクト２の内部に着脱可能に挿入され、図示しないコネクタと一体に設けられたフランジ部３ａを介して吸気ダクト２に固定されている。
このセンサボディ３の内部には、吸気ダクト２の内部を図２の右側（エアクリーナ側）から左側（エンジン側）に向かって流れる空気、つまり、エンジンに吸入される空気の一部を取り込むバイパス通路５が形成されている。
バイパス通路５は、吸気ダクト２の上流側に向かって開口する入口５ａと、吸気ダクト２の下流側に向かって開口する出口５ｂとを有し、入口５ａと出口５ｂとの間の通路途中に、通路方向が１８０度反転する折り返し部が形成されている。また、折り返し部より上流側のバイパス通路５には、後述する３つの絞り部６、７、８（図１参照）が設けられている。 The sensor body 3 is detachably inserted into the intake duct 2 through a mounting hole formed in the intake duct 2, and is fixed to the intake duct 2 via a flange portion 3a provided integrally with a connector (not shown). .
Inside the sensor body 3, a bypass passage that takes in a portion of the air that flows from the right side (air cleaner side) to the left side (engine side) of FIG. 5 is formed.
The bypass passage 5 has an inlet 5a that opens toward the upstream side of the intake duct 2 and an outlet 5b that opens toward the downstream side of the intake duct 2, and is in the middle of the passage between the inlet 5a and the outlet 5b. A folded portion is formed in which the passage direction is reversed by 180 degrees. Further, in the bypass passage 5 on the upstream side from the folded portion, three throttle portions 6, 7, and 8 (see FIG. 1) described later are provided.

センサ部４は、図３（ｂ）に示す様に、例えば、シリコン製のセンサ基板９に設けられるダイヤフラム１０の表面上に薄膜抵抗体（発熱抵抗体１１と側温抵抗体１２、１３）を形成した検出素子１４と、発熱抵抗体１１の発熱温度を制御すると共に、側温抵抗体１２、１３の抵抗値を基に、空気の流量と流れ方向（順流と逆流）に応じたセンサ信号を出力する制御回路部（図示せず）とを有し、図１に示す様に、検出素子１４がバイパス通路５の折り返し部より上流側に配置されている。
発熱抵抗体１１は、バイパス通路５を流れる空気の温度よりも一定温度高い基準温度に通電制御される。
側温抵抗体１２、１３は、発熱抵抗体１１の上流側に近接して配置される側温抵抗体（以下、上流側温抵抗体１２と呼ぶ）と、発熱抵抗体１１の下流側に近接して配置される側温抵抗体（以下、下流側温抵抗体１３と呼ぶ）とで構成される。 As shown in FIG. 3B, the sensor unit 4 includes, for example, a thin film resistor (a heating resistor 11 and side temperature resistors 12, 13) on the surface of a diaphragm 10 provided on a sensor substrate 9 made of silicon. While controlling the heat generation temperature of the formed detection element 14 and the heat generating resistor 11, a sensor signal corresponding to the air flow rate and the flow direction (forward flow and reverse flow) is generated based on the resistance values of the side temperature resistors 12, 13. And a control circuit section (not shown) for outputting. As shown in FIG. 1, the detection element 14 is arranged upstream of the folded portion of the bypass passage 5.
The heating resistor 11 is energized and controlled to a reference temperature that is higher than the temperature of the air flowing through the bypass passage 5 by a certain temperature.
The side temperature resistors 12 and 13 are located close to the upstream side of the heating resistor 11 (hereinafter, referred to as the upstream temperature resistor 12) and close to the downstream side of the heating resistor 11. And a side temperature resistor (hereinafter referred to as downstream temperature resistor 13).

上記のセンサ部４による空気流量の計測原理について説明する。
発熱抵抗体１１が基準温度に通電制御されると、発熱抵抗体１１の発熱による温度分布が生じる。ここで、バイパス通路５に空気の流れが発生していない時は、図３（ａ）に破線グラフで示す様に、発熱抵抗体１１の位置を中心として上流側と下流側とで温度分布が左右対称となるため、上流側温抵抗体１２で検出される温度と、下流側温抵抗体１３で検出される温度とが等しくなる。
これに対し、例えば、バイパス通路５に順流が生じると、図３（ａ）に実線グラフで示す様に、発熱抵抗体１１の下流側（図示右側）へ偏った温度分布が生じるため、上流側温抵抗体１２の検出温度より、下流側温抵抗体１３の検出温度の方が高くなる。 The measurement principle of the air flow rate by the sensor unit 4 will be described.
When the heating resistor 11 is energized and controlled to the reference temperature, a temperature distribution due to heat generated by the heating resistor 11 occurs. Here, when there is no air flow in the bypass passage 5, as shown by the broken line graph in FIG. 3A, the temperature distribution between the upstream side and the downstream side centered on the position of the heating resistor 11. Since the left and right are symmetrical, the temperature detected by the upstream temperature resistor 12 is equal to the temperature detected by the downstream temperature resistor 13.
On the other hand, for example, when a forward flow occurs in the bypass passage 5, a temperature distribution biased toward the downstream side (right side in the figure) of the heating resistor 11 occurs as shown by the solid line graph in FIG. The detected temperature of the downstream temperature resistor 13 is higher than the detected temperature of the temperature resistor 12.

一方、バイパス通路５に逆流が生じると、発熱抵抗体１１の上流側（図示左側）へ偏った温度分布が生じるため、下流側温抵抗体１３の検出温度より、上流側温抵抗体１２の検出温度の方が高くなる。
これにより、上流側温抵抗体１２の検出温度と下流側温抵抗体１３の検出温度との間に温度差ＤＴｈが生じるため、この温度差ＤＴｈに応じて、上流側温抵抗体１２と下流側温抵抗体１３の抵抗値がそれぞれ変化し、この抵抗値の変化により生じる電位差が増幅されて、センサ信号（例えばアナログ電圧）として、コネクタに接続される外部のＥＣＵ（図示せず）へ出力される。なお、センサ信号は、アナログ電圧を周波数値に変換して出力することも出来る。 On the other hand, when a reverse flow occurs in the bypass passage 5, a temperature distribution that is biased toward the upstream side (the left side in the drawing) of the heating resistor 11 occurs, and therefore, the detection of the upstream temperature resistor 12 from the detection temperature of the downstream temperature resistor 13. The temperature is higher.
As a result, a temperature difference DTh occurs between the detected temperature of the upstream temperature resistor 12 and the detected temperature of the downstream temperature resistor 13, so that the upstream temperature resistor 12 and the downstream side are in accordance with this temperature difference DTh. The resistance value of the temperature resistor 13 changes, and the potential difference caused by the change in resistance value is amplified and output as a sensor signal (for example, analog voltage) to an external ECU (not shown) connected to the connector. The The sensor signal can also be output by converting an analog voltage into a frequency value.

次に、本発明に係る３つの絞り部６〜８について説明する。
３つの絞り部６〜８は、図１に示す様に、検出素子１４が配置される部位に設けられるメイン絞り部６と、検出素子１４が配置される部位より上流側（バイパス通路５の入口５ａ側：図１の下側）に設けられる上流側絞り部７と、検出素子１４が配置される部位より下流側（バイパス通路５の出口５ｂ側）に設けられる下流側絞り部８とを有する。
メイン絞り部６は、バイパス通路５の断面積を最も小さくする最絞り部から上流側および下流側へ向かって次第にバイパス通路５の断面積が大きくなる様に設けられ、且つ、最絞り部より上流側と下流側の絞り形状が対称に設けられている。 Next, the three apertures 6 to 8 according to the present invention will be described.
As shown in FIG. 1, the three throttle portions 6 to 8 include a main throttle portion 6 provided at a portion where the detection element 14 is disposed, and an upstream side (an inlet of the bypass passage 5) from the portion where the detection element 14 is disposed. 5a (lower side in FIG. 1) and an upstream throttle 7 provided on the downstream side (the outlet 5b side of the bypass passage 5) from the part where the detection element 14 is disposed. .
The main throttle portion 6 is provided so that the cross-sectional area of the bypass passage 5 gradually increases from the maximum throttle portion that minimizes the cross-sectional area of the bypass passage 5 toward the upstream side and the downstream side, and upstream of the maximum throttle portion. The throttle shapes on the side and the downstream side are provided symmetrically.

上流側絞り部７と下流側絞り部８は、同一の絞り形状を有し、且つ、メイン絞り部６から、それぞれ略等距離の位置に設けられている。
この上流側絞り部７および下流側絞り部８は、例えば、バイパス通路５の断面積を所定の長さに渡って一定の割合で絞った絞り通路部と、この絞り通路部の入口側と出口側とに設けられ、それぞれ絞り通路部よりバイパス通路５の断面積が漸増するテーパ部とを有している。
なお、メイン絞り部６に形成される最絞り部の断面積は、上流側絞り部７および下流側絞り部８に形成される絞り通路部の断面積より小さく設定されている。 The upstream throttle unit 7 and the downstream throttle unit 8 have the same throttle shape and are provided at substantially equal distances from the main throttle unit 6.
The upstream throttle portion 7 and the downstream throttle portion 8 are, for example, a throttle passage portion in which the cross-sectional area of the bypass passage 5 is throttled at a constant ratio over a predetermined length, and an inlet side and an outlet of the throttle passage portion. And a tapered portion in which the cross-sectional area of the bypass passage 5 gradually increases from the throttle passage portion.
The cross-sectional area of the most restrictive portion formed in the main restricting portion 6 is set smaller than the cross-sectional areas of the restricting passage portions formed in the upstream restricting portion 7 and the downstream restricting portion 8.

（実施例１の作用および効果）
本実施例のエアフロメータ１は、図２に示す様に、バイパス通路５の通路方向が吸気ダクト２の通路方向と略直交して形成されている。つまり、バイパス通路５の折り返し部より上流側の通路と下流側の通路は、その通路方向が図２に示す上下方向に延びて形成されており、吸気ダクト２の通路方向（図示左右方向）と略直交している。
この場合、例えば、エンジンが空気を吸引する順流の時は、吸気ダクト２を流れる空気の一部がバイパス通路５の入口５ａからバイパス通路５へ流入した後、流れ方向が大きく（略直角に）変化する。このため、バイパス通路５の入口５ａ付近では、図１に示す様に、流速の最大値が図示左側に偏った不安定な流速分布が形成される。 (Operation and Effect of Example 1)
As shown in FIG. 2, the air flow meter 1 of the present embodiment is formed such that the passage direction of the bypass passage 5 is substantially orthogonal to the passage direction of the intake duct 2. That is, the passage on the upstream side and the passage on the downstream side of the folded portion of the bypass passage 5 are formed so that the passage directions extend in the vertical direction shown in FIG. It is almost orthogonal.
In this case, for example, when the engine is in a forward flow for sucking air, a part of the air flowing through the intake duct 2 flows into the bypass passage 5 from the inlet 5a of the bypass passage 5, and then the flow direction is large (substantially at right angles). Change. For this reason, in the vicinity of the inlet 5a of the bypass passage 5, as shown in FIG. 1, an unstable flow velocity distribution in which the maximum value of the flow velocity is biased to the left side in the drawing is formed.

これに対し、本実施例では、バイパス通路５に３つの絞り部（メイン絞り部６、上流側絞り部７、下流側絞り部８）を設け、メイン絞り部６に形成される最絞り部に検出素子１４を配置しているので、順流と逆流とに係わらず、検出素子１４に対し常に安定した流速分布を与えることが出来る。
例えば、吸気ダクト２を流れる空気の流れ方向が順流の時は、図１に示す様に、バイパス通路５に流入した空気に不安定な偏った流速分布が生じても、その偏った流速分布を有する空気の流れが検出素子１４に到達する前に、上流側絞り部７を通過することで流速分布の偏りが抑制される。その後、メイン絞り部６を通過する際に、上流側絞り部７を通過した後に拡散した流速分布が絞られる（流速分布の拡散が抑えられる）ため、安定した流速分布が形成される。これにより、検出素子１４を通過する空気の流速が安定するため、検出精度のばらつきが抑制され、安定した出力特性を得ることが出来る。 On the other hand, in this embodiment, the throttling portion (the main throttling portion 6, the upstream throttling portion 7, and the downstream throttling portion 8) is provided in the bypass passage 5, and the most throttling portion formed in the main throttling portion 6 is provided. Since the detection element 14 is arranged, a stable flow velocity distribution can be always given to the detection element 14 regardless of forward flow or reverse flow.
For example, when the flow direction of the air flowing through the intake duct 2 is forward, as shown in FIG. 1, even if an unstable and uneven flow velocity distribution occurs in the air flowing into the bypass passage 5, the uneven flow velocity distribution is The flow velocity distribution is suppressed by passing through the upstream restricting portion 7 before the air flow has reached the detection element 14. Thereafter, when passing through the main restricting portion 6, the flow velocity distribution diffused after passing through the upstream restricting portion 7 is restricted (diffusion of the flow velocity distribution is suppressed), so that a stable flow velocity distribution is formed. Thereby, since the flow velocity of the air passing through the detection element 14 is stabilized, variation in detection accuracy is suppressed, and stable output characteristics can be obtained.

また、逆流の時でも、順流の時と同様に、偏った流速分布を有する空気の流れが検出素子１４に到達する前に、下流側絞り部８を通過することで流速分布の偏りが抑制され、その後、メイン絞り部６を通過する際に、下流側絞り部８を通過した後に拡散した流速分布が絞られることにより、検出素子１４を通過する空気の流速が安定する。その結果、検出精度のばらつきが抑制されて、安定した出力特性を得ることが出来る。
さらに、３つの絞り部６〜８は、メイン絞り部６に形成される最絞り部の断面積が、上流側絞り部７および下流側絞り部８に形成される絞り通路部の断面積より小さく設定されている。その結果、バイパス通路５を流れる空気の流量をメイン絞り部６でコントロールできるので、メイン絞り部６に配置された検出素子１４により空気の流量を精度良く検出できる。 Further, even in the case of the reverse flow, as in the case of the forward flow, the deviation of the flow velocity distribution is suppressed by passing through the downstream restrictor 8 before the air flow having the uneven flow velocity distribution reaches the detection element 14. Thereafter, when passing through the main restrictor 6, the flow velocity distribution diffused after passing through the downstream restrictor 8 is restricted, so that the flow velocity of the air passing through the detection element 14 is stabilized. As a result, variations in detection accuracy are suppressed, and stable output characteristics can be obtained.
Further, the three throttle parts 6 to 8 are such that the cross-sectional area of the maximum throttle part formed in the main throttle part 6 is smaller than the cross-sectional areas of the throttle passage parts formed in the upstream side throttle part 7 and the downstream side throttle part 8. Is set. As a result, the flow rate of air flowing through the bypass passage 5 can be controlled by the main throttle portion 6, so that the air flow rate can be accurately detected by the detection element 14 disposed in the main throttle portion 6.

（変形例）
実施例１の説明では、バイパス通路５の折り返し部より上流側（入口５ａ側）に３つの絞り部（メイン絞り部６、上流側絞り部７、下流側絞り部８）を全て設けているため、メイン絞り部６と上流側絞り部７および下流側絞り部８との間隔が小さく（狭く）なっているが、メイン絞り部６と上流側絞り部７および下流側絞り部８との間隔を大きく（広く）しても良い。例えば、メイン絞り部６をバイパス通路５の折り返し部に設けて、その最絞り部に検出素子１４を配置し、且つ、上流側絞り部７をバイパス通路５の入口５ａ付近、下流側絞り部８をバイパス通路５の出口５ｂ付近に設けることも出来る。 (Modification)
In the description of the first embodiment, all three throttle parts (main throttle part 6, upstream throttle part 7, and downstream throttle part 8) are provided on the upstream side (inlet 5a side) from the folded part of the bypass passage 5. The intervals between the main throttle unit 6 and the upstream throttle unit 7 and the downstream throttle unit 8 are small (narrow), but the intervals between the main throttle unit 6 and the upstream throttle unit 7 and the downstream throttle unit 8 are reduced. It may be large (wide). For example, the main throttle portion 6 is provided in the folded portion of the bypass passage 5, the detection element 14 is disposed at the most restrictive portion, and the upstream throttle portion 7 is located near the inlet 5 a of the bypass passage 5, the downstream throttle portion 8. Can also be provided in the vicinity of the outlet 5b of the bypass passage 5.

本発明に係る３つの絞り部（メイン絞り部６、上流側絞り部７、下流側絞り部８）は、バイパス通路５を二次元的に絞った形状でも良いし、三次元的に絞った形状でも良い。
また、実施例１に記載したメイン絞り部６は、最絞り部より上流側と下流側の絞り形状を対称に設けているが、必ずしも対称形状である必要はなく、最絞り部に検出素子１４が配置されていれば良い。 The three throttle parts according to the present invention (the main throttle part 6, the upstream throttle part 7, and the downstream throttle part 8) may have a shape in which the bypass passage 5 is two-dimensionally narrowed or a three-dimensionally narrowed shape. But it ’s okay.
In addition, the main diaphragm portion 6 described in the first embodiment is provided with the upstream and downstream diaphragm shapes symmetrically with respect to the most restrictive portion, but it is not always necessary to have a symmetrical shape. Should just be arranged.

１ エアフロメータ（空気流量測定装置）
２ 吸気ダクト
５ バイパス通路
６ メイン絞り部
７ 上流側絞り部
８ 下流側絞り部
１４ 検出素子 1 Air flow meter (air flow measuring device)
2 Intake duct 5 Bypass passage 6 Main restrictor 7 Upstream restrictor 8 Downstream restrictor 14 Detection element

Claims (3)

ダクトの内部を流れる空気の一部を取り込むバイパス通路と、
このバイパス通路に配置される流量測定用の検出素子と、
この検出素子によって得られる情報を基に、前記バイパス通路を流れる空気の流量、及び、空気の流れ方向（順流と逆流）を検出できる空気流量測定装置であって、
前記バイパス通路の断面積を絞る複数の絞り部を有し、
前記複数の絞り部は、
前記検出素子が配置される部位に設けられるメイン絞り部と、
前記検出素子が配置される部位より上流側に設けられる上流側絞り部と、
前記検出素子が配置される部位より下流側に設けられる下流側絞り部とを有し、
前記上流側絞り部および前記下流側絞り部は、それぞれ前記メイン絞り部との間に所定の間隔をあけて独立して設けられ、且つ、前記バイパス通路の断面積を所定の長さに渡って一定の割合で絞った通路状に形成されていることを特徴とする空気流量測定装置。 A bypass passage for taking in part of the air flowing inside the duct;
A detection element for measuring a flow rate disposed in the bypass passage;
On the basis of information obtained by the detection element, an air flow rate measuring device capable of detecting a flow rate of air flowing through the bypass passage and a flow direction of air (forward flow and reverse flow),
Having a plurality of throttle portions for reducing the cross-sectional area of the bypass passage;
The plurality of apertures are
A main diaphragm provided in a portion where the detection element is disposed;
An upstream throttle portion provided upstream of the portion where the detection element is disposed;
Possess a downstream throttle portion provided downstream from the site where the detecting element is disposed,
The upstream throttle part and the downstream throttle part are each independently provided with a predetermined interval from the main throttle part, and the cross-sectional area of the bypass passage extends over a predetermined length. An air flow rate measuring device characterized in that it is formed in the shape of a passage narrowed at a certain rate. 請求項１に記載した空気流量測定装置において、
前記メイン絞り部は、前記バイバス通路の断面積が最も小さくなる最絞り部から上流側および下流側へ向かって次第に前記バイバス通路の断面積が大きくなる様に設けられ、
前記検出素子は、前記最絞り部に配置されていることを特徴とする空気流量測定装置。 In the air flow rate measuring device according to claim 1,
The main throttle portion is provided such that the cross-sectional area of the bypass passage gradually increases from the most narrowed portion where the cross-sectional area of the bypass passage becomes the smallest toward the upstream side and the downstream side,
The air flow rate measuring device according to claim 1, wherein the detection element is disposed in the most restrictive portion. 請求項１または２に記載した空気流量測定装置において、
前記上流側絞り部によって絞られる前記バイパス通路の断面積および前記下流側絞り部によって絞られる前記バイパス通路の断面積より、前記メイン絞り部によって絞られる前記バイパス通路の断面積の方が小さいことを特徴とする空気流量測定装置。 In the air flow rate measuring device according to claim 1 or 2,
The cross-sectional area of the bypass passage restricted by the main restrictor is smaller than the cross-sectional area of the bypass passage restricted by the upstream restrictor and the cross-sectional area of the bypass passage restricted by the downstream restrictor. A characteristic air flow rate measuring device.
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