JP5434685B2 - Air-fuel ratio detection device - Google Patents

Air-fuel ratio detection device Download PDF

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JP5434685B2
JP5434685B2 JP2010048131A JP2010048131A JP5434685B2 JP 5434685 B2 JP5434685 B2 JP 5434685B2 JP 2010048131 A JP2010048131 A JP 2010048131A JP 2010048131 A JP2010048131 A JP 2010048131A JP 5434685 B2 JP5434685 B2 JP 5434685B2
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sensor
pressure
exhaust gas
air
fuel ratio
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JP2011185097A (en
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大治 長岡
輝男 中田
裕之 遊座
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Isuzu Motors Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1448—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an exhaust gas pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1448—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an exhaust gas pressure
    • F02D41/145—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an exhaust gas pressure with determination means using an estimation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0812—Particle filter loading
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
    • F02D41/029—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a particulate filter

Description

本発明は、ラムダセンサを用いた空燃比検出装置に係り、ラムダセンサが出力する空燃比の補正を新規に圧力センサを設けることなく実現できる空燃比検出装置に関する。   The present invention relates to an air-fuel ratio detection apparatus using a lambda sensor, and more particularly to an air-fuel ratio detection apparatus that can realize correction of an air-fuel ratio output from a lambda sensor without providing a new pressure sensor.

エンジンの排気ガスや大気等の対象ガスにおける空燃比を検出するために広帯域ラムダセンサ（以下、ラムダセンサという）が用いられる。空燃比とは、空気に対する燃料の重量比である。ラムダセンサは、酸化ジルコニウムで形成されるセル室を設けたものである。対象ガス中の酸素濃度が理論空燃比における酸素濃度より高い場合は、空燃比はリーン（燃料リーン）となり、セル室内に酸化イオンが流入する。対象ガス中の酸素濃度が理論空燃比における酸素濃度より低い場合は、空燃比はリッチ（燃料リッチ）となり、セル室内から酸化イオンが流出する。このように、セル室内に酸化イオンが流入するか又はセル室内から酸化イオンが流出するときのポンピング電流によって空燃比が検出される。   A broadband lambda sensor (hereinafter referred to as a lambda sensor) is used to detect an air-fuel ratio in a target gas such as engine exhaust gas or air. The air-fuel ratio is the weight ratio of fuel to air. The lambda sensor is provided with a cell chamber made of zirconium oxide. When the oxygen concentration in the target gas is higher than the oxygen concentration at the stoichiometric air-fuel ratio, the air-fuel ratio becomes lean (fuel lean), and oxide ions flow into the cell chamber. When the oxygen concentration in the target gas is lower than the oxygen concentration at the stoichiometric air-fuel ratio, the air-fuel ratio becomes rich (fuel rich), and oxide ions flow out from the cell chamber. As described above, the air-fuel ratio is detected by the pumping current when the oxide ions flow into or out of the cell chamber.

ラムダセンサの検出精度を高めることで、エンジンにおける各種の制御の精度を高めることができる。例えば、ラムダセンサで検出した空燃比を用いて燃料流量を補正する制御を行うことができる。空燃比は、空気と燃料の重量比であるので、ラムダセンサで検出した空燃比とＭＡＦセンサで検出した吸入空気量から、流れている対象ガス中の燃料重量、すなわち実燃料流量を算出することができる。この燃料重量と燃料流量指示値との乖離を求める。その乖離を小さくして実燃料流量が所望する値となるように燃料流量指示値を補正する。また、ＥＧＲと可変ノズルターボの協調制御においては、吸入空気量とＥＧＲ量と燃料量を調整してラムダセンサで検出される空燃比を最適に制御することは、スモーク、動力性能、排気ガスの最適化に寄与する。   By increasing the detection accuracy of the lambda sensor, the accuracy of various controls in the engine can be increased. For example, it is possible to perform control for correcting the fuel flow rate using the air-fuel ratio detected by the lambda sensor. Since the air-fuel ratio is the weight ratio of air to fuel, the fuel weight in the flowing target gas, that is, the actual fuel flow rate is calculated from the air-fuel ratio detected by the lambda sensor and the intake air amount detected by the MAF sensor. Can do. The difference between the fuel weight and the fuel flow rate instruction value is obtained. The fuel flow rate instruction value is corrected so that the deviation is reduced and the actual fuel flow rate becomes a desired value. In the cooperative control of EGR and variable nozzle turbo, adjusting the intake air amount, the EGR amount, and the fuel amount to optimally control the air-fuel ratio detected by the lambda sensor means that the smoke, power performance, and exhaust gas are controlled. Contributes to optimization.

特開２００５−５３０１５４号公報JP 2005-530154 A 特開２００６−２４２０１１号公報JP 2006-242011 A

ところで、図３に示されるように、ラムダセンサでは、対象ガスの圧力の影響を受けて出力が変動する。すなわち、対象ガスの圧力が中間的な値のときを基準にして誤差０パーセントとしたとき、対象ガスの圧力が高くなると誤差がプラス側に増加し、対象ガスの圧力が低くなると誤差がマイナス側に増加する。この結果、対象ガスの圧力が高いときにはラムダセンサの検出値が実際の空燃比より高くなり、対象ガスの圧力が低いときにはラムダセンサの検出値が実際の空燃比より低くなる。   By the way, as shown in FIG. 3, in the lambda sensor, the output fluctuates under the influence of the pressure of the target gas. In other words, when the error is 0% based on the intermediate pressure of the target gas, the error increases to the positive side when the target gas pressure increases, and the error decreases to the negative side when the target gas pressure decreases. To increase. As a result, when the target gas pressure is high, the detected value of the lambda sensor is higher than the actual air-fuel ratio, and when the target gas pressure is low, the detected value of the lambda sensor is lower than the actual air-fuel ratio.

対象ガスの圧力変動によって空燃比の検出精度が低下すると、空燃比を利用する各種の制御の精度も低下することになる。しかし、ラムダセンサの設置場所におけるガスの圧力が安定であることは期待できない。なぜなら、エンジンの場合、排気管には、排気ガスの圧力を利用して吸気を圧縮するターボチャージャ、排気ガス中の粒子状物質（Particurate Matter；以下、ＰＭという）を除去するＤＰＦ（Diesel Particulate Filter；ディーゼルパティキュレートフィルタ）、触媒を用いた浄化器、サイレンサなどが設けられる。これらの部材が抵抗となって、配管内での排気ガスの圧力は場所により異なる。また、海抜高度の差異や気候の影響により大気圧が変動すると、排気ガスの圧力も変動する。   If the detection accuracy of the air-fuel ratio decreases due to the pressure fluctuation of the target gas, the accuracy of various controls that use the air-fuel ratio also decreases. However, it cannot be expected that the gas pressure at the place where the lambda sensor is installed is stable. This is because, in the case of an engine, a turbocharger that compresses intake air using the pressure of exhaust gas, and a DPF (Diesel Particulate Filter) that removes particulate matter (hereinafter referred to as PM) in the exhaust gas. A diesel particulate filter), a purifier using a catalyst, a silencer, and the like. These members serve as resistances, and the pressure of the exhaust gas in the piping varies depending on the location. In addition, when the atmospheric pressure changes due to the difference in altitude above sea level or the influence of the climate, the exhaust gas pressure also changes.

この対策として、ラムダセンサの設置箇所に対象ガスの圧力を検出する圧力センサを設置し、ラムダセンサの出力を対象ガスの圧力で補正することはできる。しかし、車両の場合、新規に圧力センサを設置することは、コストの増加を招くので、避けたいところである。   As a countermeasure, a pressure sensor that detects the pressure of the target gas can be installed at the location where the lambda sensor is installed, and the output of the lambda sensor can be corrected by the pressure of the target gas. However, in the case of a vehicle, installing a new pressure sensor invites an increase in cost, so it is desirable to avoid it.

そこで、本発明の目的は、上記課題を解決し、ラムダセンサが出力する空燃比の補正を新規に圧力センサを設けることなく実現できる空燃比検出装置を提供することにある。   Accordingly, an object of the present invention is to provide an air-fuel ratio detection apparatus that solves the above problems and can realize correction of the air-fuel ratio output from the lambda sensor without providing a new pressure sensor.

上記目的を達成するために本発明は、エンジンの排気管に設置されて排気ガス中の粒子状物質を除去するディーゼルパティキュレートフィルタと、前記ディーゼルパティキュレートフィルタの出口に設置され排気ガスにおける空燃比を検出するラムダセンサと、前記ディーゼルパティキュレートフィルタの入口出口間を繋ぐセンサ用バイパス管と、前記センサ用バイパス管に設置され上流側下流側間の差圧を検出する差圧センサと、前記センサ用バイパス管の前記差圧センサと前記ディーゼルパティキュレートフィルタの入口間に設置されて前記差圧センサの上流側を大気へ開放させるか前記ディーゼルパティキュレートフィルタの入口に連通させるか切り替え可能な三方弁と、大気圧を検出する大気圧センサと、前記三方弁により前記差圧センサの上流側が大気へ開放されているときに、前記大気圧センサが検出した大気圧と前記差圧センサが検出した差圧とから前記ラムダセンサの設置箇所である前記ディーゼルパティキュレートフィルタの出口の排気ガス圧力を推定する排気ガス圧力推定手段と、前記排気ガス圧力推定手段が推定した排気ガス圧力と前記ラムダセンサの圧力特性とにより、前記ラムダセンサが検出した空燃比を補正する空燃比補正手段とを備え、前記排気ガス圧力推定手段は、前記エンジンが定常状態のとき、一時的に前記三方弁により前記差圧センサの上流側を大気へ開放させて、前記ラムダセンサの設置箇所の排気ガス圧力を推定し、この排気ガス圧力を排気ガス圧力と大気圧と圧力ロス係数の関係式に代入して圧力ロス係数を算出し、この圧力ロス係数を記憶しておき、前記三方弁により前記差圧センサの上流側が前記ディーゼルパティキュレートフィルタの入口に連通されているときには、前記大気圧センサが検出した大気圧と記憶されている圧力ロス係数を前記関係式に代入して排気ガス圧力を推定するものである。 To accomplish the above object, a diesel particulate filter that is disposed in an exhaust pipe of the engine to remove particulate matter in the exhaust gas, it is installed in the outlet of the diesel particulate filter air in the exhaust gas A lambda sensor for detecting a fuel ratio, a sensor bypass pipe connecting between the inlet and outlet of the diesel particulate filter , a differential pressure sensor installed in the sensor bypass pipe for detecting a differential pressure between the upstream side and the downstream side; Three-way switch installed between the differential pressure sensor of the sensor bypass pipe and the inlet of the diesel particulate filter so that the upstream side of the differential pressure sensor can be opened to the atmosphere or communicated with the inlet of the diesel particulate filter Valve, an atmospheric pressure sensor for detecting atmospheric pressure, and the three-way valve When the upstream side of the capacitors is open to the atmosphere, the outlet of the diesel particulate filter is installed location of the lambda sensor and an atmospheric pressure atmospheric pressure sensor detects said difference pressure difference is pressure sensor detects Exhaust gas pressure estimating means for estimating exhaust gas pressure, and air-fuel ratio correcting means for correcting the air-fuel ratio detected by the lambda sensor based on the exhaust gas pressure estimated by the exhaust gas pressure estimating means and the pressure characteristics of the lambda sensor And the exhaust gas pressure estimating means temporarily opens the upstream side of the differential pressure sensor to the atmosphere by the three-way valve when the engine is in a steady state, and exhausts the exhaust gas at the place where the lambda sensor is installed. Estimate the pressure, calculate the pressure loss coefficient by substituting this exhaust gas pressure into the relational expression of exhaust gas pressure, atmospheric pressure, and pressure loss coefficient. When the upstream side of the differential pressure sensor communicates with the inlet of the diesel particulate filter by the three-way valve, the atmospheric pressure detected by the atmospheric pressure sensor and the stored pressure loss coefficient are The exhaust gas pressure is estimated by substituting into the relational expression .

本発明は次の如き優れた効果を発揮する。   The present invention exhibits the following excellent effects.

（１）ラムダセンサが出力する空燃比の補正を新規に圧力センサを設けることなく実現できる。   (1) Correction of the air-fuel ratio output from the lambda sensor can be realized without providing a new pressure sensor.

本発明の一実施形態を示す空燃比検出装置の構成図である。It is a block diagram of the air fuel ratio detection apparatus which shows one Embodiment of this invention. 図１の空燃比検出装置における三方弁の動作状態を示す図であり、（ａ）は遮断時の構成図、（ｂ）は開放時の構成図である。It is a figure which shows the operation state of the three-way valve in the air fuel ratio detection apparatus of FIG. 1, (a) is a block diagram at the time of interruption | blocking, (b) is a block diagram at the time of open | release. ラムダセンサの雰囲気圧力対誤差特性図である。It is an atmospheric pressure versus error characteristic diagram of a lambda sensor.

以下、本発明の一実施形態を添付図面に基づいて詳述する。   Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

図１に示されるように、本発明に係る空燃比検出装置１は、エンジン２の排気管３に設置されて排気ガス中の粒子状物質を除去するディーゼルパティキュレートフィルタ（以下、ＤＰＦ）４と、ＤＰＦ４の出口に設置され排気ガスにおける空燃比を検出するラムダセンサ５と、ＤＰＦ４の入口出口間を繋ぐセンサ用バイパス管６と、センサ用バイパス管６に設置され上流側下流側間の差圧を検出する差圧センサ７と、センサ用バイパス管６の差圧センサ７とＤＰＦ４の入口間に設置されて差圧センサ７の上流側を大気へ開放させるかＤＰＦ４の入口に連通させるか切り替え可能な三方弁８と、大気圧を検出する大気圧センサ９と、三方弁８により差圧センサ７の上流側が大気へ開放されているときに、大気圧センサ９が検出した大気圧と差圧センサ７が検出した差圧とからラムダセンサ５の設置箇所であるＤＰＦ４の出口の排気ガス圧力を推定する排気ガス圧力推定手段１０と、排気ガス圧力推定手段１０が推定した排気ガス圧力とラムダセンサ５の圧力特性とにより、ラムダセンサ５が検出した空燃比を補正する空燃比補正手段１１とを備えたものである。   As shown in FIG. 1, an air-fuel ratio detection apparatus 1 according to the present invention includes a diesel particulate filter (hereinafter referred to as DPF) 4 that is installed in an exhaust pipe 3 of an engine 2 and removes particulate matter in exhaust gas. The lambda sensor 5 installed at the outlet of the DPF 4 detects the air-fuel ratio in the exhaust gas, the sensor bypass pipe 6 connecting the inlet and outlet of the DPF 4, and the differential pressure between the upstream and downstream sides installed in the sensor bypass pipe 6 Can be switched between the differential pressure sensor 7 for detecting the pressure difference and the differential pressure sensor 7 of the sensor bypass pipe 6 and the inlet of the DPF 4 to open the upstream side of the differential pressure sensor 7 to the atmosphere or to communicate with the inlet of the DPF 4 The three-way valve 8, the atmospheric pressure sensor 9 for detecting atmospheric pressure, and the atmospheric pressure and the differential pressure detected by the atmospheric pressure sensor 9 when the upstream side of the differential pressure sensor 7 is opened to the atmosphere by the three-way valve 8. The exhaust gas pressure estimating means 10 for estimating the exhaust gas pressure at the outlet of the DPF 4 where the lambda sensor 5 is installed from the differential pressure detected by the sensor 7, the exhaust gas pressure and the lambda sensor estimated by the exhaust gas pressure estimating means 10 5 is provided with air-fuel ratio correction means 11 for correcting the air-fuel ratio detected by the lambda sensor 5 based on the pressure characteristic of 5.

エンジン２は、例えば、ディーゼルエンジンであり、ここではターボチャージャ１２を具備している。ターボチャージャ１２は、排気マニホールド１３から排気管３に流れる排気ガスでタービンを駆動して吸気管１４から取り入れられる空気をコンプレッサで圧縮して吸気マニホールド１５へと供給するものである。吸気管１４には、空気流量センサ（以下、ＭＡＦ）１６が設けられる。   The engine 2 is a diesel engine, for example, and includes a turbocharger 12 here. The turbocharger 12 drives the turbine with exhaust gas flowing from the exhaust manifold 13 to the exhaust pipe 3, compresses air taken from the intake pipe 14 with a compressor, and supplies the compressed air to the intake manifold 15. The intake pipe 14 is provided with an air flow rate sensor (hereinafter MAF) 16.

ＤＰＦ４は、ＰＭを除去して排気ガスを浄化するためのものである。ＤＰＦ４は、酸化触媒部材（Diesel Oxidation Catalyst；以下、ＤＯＣという）とキャタライズド・スート・フィルタ（Catalyzed Soot Filter）とから構成される。   The DPF 4 is for purifying exhaust gas by removing PM. The DPF 4 includes an oxidation catalyst member (Diesel Oxidation Catalyst; hereinafter referred to as DOC) and a catalyzed soot filter.

ラムダセンサ５は、すでに述べたように、セル室に対する酸化イオンの流入・流出におけるポンピング電流によって空燃比を検出するものであるが、対象ガスの圧力の影響を受けて出力が変動する。なお、図１には示さなかったが、排気管３にはラムダセンサ５よりも下流に、触媒を用いた浄化器、サイレンサなどの部材が設置される。   As described above, the lambda sensor 5 detects the air-fuel ratio by the pumping current in the inflow / outflow of the oxide ions to / from the cell chamber, but the output fluctuates due to the influence of the pressure of the target gas. Although not shown in FIG. 1, members such as a purifier using a catalyst and a silencer are installed in the exhaust pipe 3 downstream of the lambda sensor 5.

センサ用バイパス管６は、従来より差圧センサ７のために設けられている。差圧センサ７は、差圧センサ７の上流側下流側間の差圧を検出するものであり、センサ用バイパス管６がＤＰＦ４の入口出口間を繋ぐようにすることで、差圧センサ７によって、ＤＰＦ４の入口出口間の差圧が検出できる。ＤＰＦ４にＰＭが堆積していくと、排気ガスの流れが抵抗を受けるようになるため、ＤＰＦ４の入口の圧力に対する出口の圧力が低下する。これを解消するため、ＤＰＦ４に堆積したＰＭを燃焼させて除去することを再生と言うが、ＤＰＦ再生時期は、ＤＰＦ４の入口出口間の差圧が閾値に達したら再生を行うという方法で決定される。   The sensor bypass pipe 6 is conventionally provided for the differential pressure sensor 7. The differential pressure sensor 7 detects a differential pressure between the upstream side and the downstream side of the differential pressure sensor 7. By connecting the sensor bypass pipe 6 between the inlet and outlet of the DPF 4, the differential pressure sensor 7 The differential pressure between the inlet and outlet of the DPF 4 can be detected. As PM accumulates on the DPF 4, the flow of exhaust gas receives resistance, so the pressure at the outlet relative to the pressure at the inlet of the DPF 4 decreases. In order to solve this problem, regeneration of burning PM removed from the DPF 4 is called regeneration, but the DPF regeneration timing is determined by a method of performing regeneration when the differential pressure between the inlet and outlet of the DPF 4 reaches a threshold value. The

三方弁８は、図２（ａ）及び図２（ｂ）に示されるように、２つの入口に対し１つの出口を有し、図示しない内部の弁体を電磁力などで開閉することにより、出口に連通する入口を切り替えることができる。１つの入口をＤＰＦ４の入口側に繋ぎ、別の入口を大気に開放し、出口を差圧センサ７側に繋ぐ。これにより、三方弁８の開放時は、差圧センサ７の上流側が大気へ開放され、三方弁８の遮断時は差圧センサ７の上流側がＤＰＦ４の入口に連通される。   As shown in FIGS. 2 (a) and 2 (b), the three-way valve 8 has one outlet for two inlets, and opens and closes an internal valve body (not shown) by electromagnetic force or the like. The entrance communicating with the exit can be switched. One inlet is connected to the inlet side of the DPF 4, the other inlet is opened to the atmosphere, and the outlet is connected to the differential pressure sensor 7 side. Thus, when the three-way valve 8 is opened, the upstream side of the differential pressure sensor 7 is opened to the atmosphere, and when the three-way valve 8 is shut off, the upstream side of the differential pressure sensor 7 is communicated with the inlet of the DPF 4.

図１の大気圧センサ９は、従来より高地における諸制御量の補正用として車両に搭載されている。大気圧センサ９は、例えば、燃料噴射制御やＤＰＦ再生制御を含む車両の各部を制御する電子制御装置（Electronical Control Unit；ＥＣＵ）１７の筐体内に設置される。   The atmospheric pressure sensor 9 in FIG. 1 is mounted on a vehicle for correcting various control amounts at high altitudes. The atmospheric pressure sensor 9 is installed in a housing of an electronic control unit (ECU) 17 that controls each part of the vehicle including fuel injection control and DPF regeneration control, for example.

排気ガス圧力推定手段１０、空燃比補正手段１１は、ＥＣＵ１７にプログラムとして組み込まれる。   The exhaust gas pressure estimating means 10 and the air-fuel ratio correcting means 11 are incorporated in the ECU 17 as a program.

以下、本発明の空燃比検出装置１の動作を説明する。   Hereinafter, the operation of the air-fuel ratio detection apparatus 1 of the present invention will be described.

通常、車両の走行時は、ＤＰＦ再生制御を行う必要があるため、三方弁８は遮断されており、差圧センサ７の上流側がＤＰＦ４の入口に連通される。よって、差圧センサ７では、ＤＰＦ４の入口出口間の差圧が検出される。   Usually, since it is necessary to perform DPF regeneration control when the vehicle is traveling, the three-way valve 8 is shut off, and the upstream side of the differential pressure sensor 7 is communicated with the inlet of the DPF 4. Therefore, the differential pressure sensor 7 detects the differential pressure between the inlet and outlet of the DPF 4.

排気ガス圧力推定手段１０は、エンジン２が定常状態のとき、定期的に、一時的に三方弁８を開放することにより、差圧センサ７の上流側を大気へ開放させる。エンジン２の定常状態とは、エンジン２が安定に運転されている状態のことであり、燃料増加率、アクセル開度変化率等により判断することができる。   The exhaust gas pressure estimating means 10 opens the upstream side of the differential pressure sensor 7 to the atmosphere by periodically opening the three-way valve 8 periodically when the engine 2 is in a steady state. The steady state of the engine 2 is a state in which the engine 2 is stably operated, and can be determined based on a fuel increase rate, an accelerator opening change rate, and the like.

差圧センサ７の上流側が大気へ開放されたことにより、差圧センサ７には大気圧Ｐ2とＤＰＦ４の出口圧力Ｐ1との差圧が検出される。排気ガス圧力推定手段１０は、差圧センサ７が検出する差圧と大気圧センサ９が検出する大気圧Ｐ2とから、ＤＰＦ４の出口圧力Ｐ1、すなわちラムダセンサ５の設置箇所の排気ガス圧力を推定することができる。排気ガス圧力推定手段１０は、推定した排気ガス圧力Ｐ1を図示しないメモリに記憶する。このとき同時に、排気ガス圧力推定手段１０は、ＭＡＦ１６で検出される空気流量、図示しない温度センサで検出される排気ガス温度、ラムダセンサ５で検出される空燃比、大気圧センサ９で検出される大気圧Ｐ2などを記録する。 Since the upstream side of the differential pressure sensor 7 is opened to the atmosphere, the differential pressure sensor 7 detects the differential pressure between the atmospheric pressure P 2 and the outlet pressure P 1 of the DPF 4. The exhaust gas pressure estimating means 10 calculates the outlet pressure P 1 of the DPF 4 , that is, the exhaust gas pressure at the place where the lambda sensor 5 is installed, from the differential pressure detected by the differential pressure sensor 7 and the atmospheric pressure P 2 detected by the atmospheric pressure sensor 9. Can be estimated. The exhaust gas pressure estimating means 10 stores the estimated exhaust gas pressure P 1 in a memory (not shown). At the same time, the exhaust gas pressure estimating means 10 detects the air flow rate detected by the MAF 16, the exhaust gas temperature detected by a temperature sensor (not shown), the air-fuel ratio detected by the lambda sensor 5, and the atmospheric pressure sensor 9. Record atmospheric pressure P 2 etc.

さらに、排気ガス圧力推定手段１０は、この推定した排気ガス圧力Ｐ1を関係式（１）に代入する。 Further, the exhaust gas pressure estimating means 10 substitutes the estimated exhaust gas pressure P 1 into the relational expression (1).

Figure 0005434685
Figure 0005434685

関係式（１）は、ラムダセンサ５の設置箇所の排気ガス圧力Ｐ1と、大気圧Ｐ2と、大気に対するラムダセンサ５の設置箇所における圧力ロス係数ｋとの関係式である。ラムダセンサ５の設置箇所の排気ガス流量Ｗ12は、ＭＡＦ１６で検出される空気流量と燃料噴射制御により与えられた燃料流量とから算出される。ラムダセンサ５の設置箇所の気体密度ρ1は、図示しない温度センサが検出する排気ガス温度と、排気ガス圧力Ｐ1とから求めることができる。 The relational expression (1) is a relational expression between the exhaust gas pressure P 1 at the place where the lambda sensor 5 is installed, the atmospheric pressure P 2, and the pressure loss coefficient k at the place where the lambda sensor 5 is installed relative to the atmosphere. The exhaust gas flow rate W 12 at the place where the lambda sensor 5 is installed is calculated from the air flow rate detected by the MAF 16 and the fuel flow rate given by the fuel injection control. The gas density ρ 1 at the place where the lambda sensor 5 is installed can be obtained from the exhaust gas temperature detected by a temperature sensor (not shown) and the exhaust gas pressure P 1 .

排気ガス圧力推定手段１０は、関係式（１）により圧力ロス係数ｋを算出する。排気ガス圧力推定手段１０は、この圧力ロス係数ｋを、学習値として図示しないメモリに記憶しておく。その後、排気ガス圧力推定手段１０は、三方弁８を遮断する。   The exhaust gas pressure estimating means 10 calculates the pressure loss coefficient k from the relational expression (1). The exhaust gas pressure estimating means 10 stores this pressure loss coefficient k as a learning value in a memory (not shown). Thereafter, the exhaust gas pressure estimating means 10 shuts off the three-way valve 8.

三方弁８が遮断されたことにより、差圧センサ７の上流側がＤＰＦ４の入口に連通され、差圧センサ７でＤＰＦ４の入口出口間の差圧が検出されるようになり、ＤＰＦ再生制御への利用が再開される。   Since the three-way valve 8 is shut off, the upstream side of the differential pressure sensor 7 is communicated with the inlet of the DPF 4 so that the differential pressure between the inlet and outlet of the DPF 4 is detected by the differential pressure sensor 7. Use is resumed.

一方、このときには差圧センサ７の出力から直接、排気ガス圧力Ｐ1を推定できないので、排気ガス圧力推定手段１０は、逐次、大気圧センサ９が検出した大気圧Ｐ2と、記憶されている圧力ロス係数ｋを関係式（１）に代入して排気ガス圧力Ｐ1を推定する。 On the other hand, since the exhaust gas pressure P 1 cannot be estimated directly from the output of the differential pressure sensor 7 at this time, the exhaust gas pressure estimation means 10 stores the atmospheric pressure P 2 detected by the atmospheric pressure sensor 9 sequentially. The exhaust gas pressure P 1 is estimated by substituting the pressure loss coefficient k into the relational expression (1).

次に、空燃比補正手段１１は、排気ガス圧力推定手段１０が推定した排気ガス圧力Ｐ1をラムダセンサ５が検出した空燃比の補正に使用する。具体的には、図３の特性に基づいて、排気ガス圧力Ｐ1に対する補正値のマップを作成しておき、排気ガス圧力推定手段１０が推定した排気ガス圧力Ｐ1でマップを参照して補正値を引き当てる。 Next, the air-fuel ratio correcting means 11 uses the exhaust gas pressure P 1 estimated by the exhaust gas pressure estimating means 10 for correcting the air-fuel ratio detected by the lambda sensor 5. Specifically, based on the characteristics of Figure 3, advance to create a map of correction value for the exhaust gas pressure P 1, the correction by referring to a map in the exhaust gas pressure P 1 of the exhaust gas pressure estimating means 10 is estimated Assign a value.

補正された空燃比を使用し、その空燃比と空気流量から実燃料流量を算出することができる。実燃料流量と指示燃料流量とから、燃料流量補正係数Ｋｆが得られるので、その後は、
燃料流量補正係数Ｋｆ×指示燃料流量＝補正後燃料流量
を算出して、指示燃料流量を更新することができる。その結果、例えば、ＥＧＲと可変ノズルターボの協調制御において、吸入空気量とＥＧＲ量と燃料量を調整してラムダセンサ５で検出される空燃比を最適に制御することができるようになり、スモーク、動力性能、排気ガスの最適化に寄与する。 Using the corrected air-fuel ratio, the actual fuel flow rate can be calculated from the air-fuel ratio and the air flow rate. Since the fuel flow rate correction coefficient Kf is obtained from the actual fuel flow rate and the indicated fuel flow rate,
The fuel flow correction coefficient Kf × the indicated fuel flow rate = the corrected fuel flow rate can be calculated to update the indicated fuel flow rate. As a result, for example, in the cooperative control of EGR and variable nozzle turbo, the air-fuel ratio detected by the lambda sensor 5 can be optimally controlled by adjusting the intake air amount, the EGR amount, and the fuel amount. Contributes to optimization of power performance and exhaust gas.

以上説明したように、本発明の空燃比検出装置１によれば、三方弁８によって差圧センサ７の上流を大気開放とすることで、差圧センサ７の出力からラムダセンサ５の設置箇所の排気ガス圧力が推定できることになる。三方弁８を設置することは、ラムダセンサ５の設置箇所に対象ガスの圧力を検出する圧力センサを設置することよりも、低コストで可能である。よって、ラムダセンサ５が出力する空燃比の補正が低コストで可能となる。   As described above, according to the air-fuel ratio detection device 1 of the present invention, the upstream of the differential pressure sensor 7 is opened to the atmosphere by the three-way valve 8, so that the location of the lambda sensor 5 can be detected from the output of the differential pressure sensor 7. The exhaust gas pressure can be estimated. Installing the three-way valve 8 can be performed at a lower cost than installing a pressure sensor that detects the pressure of the target gas at the location where the lambda sensor 5 is installed. Therefore, the air-fuel ratio output from the lambda sensor 5 can be corrected at a low cost.

また、本発明の空燃比検出装置１によれば、差圧センサ７の上流が大気開放時に得ておいた圧力ロス係数ｋを学習値として記憶するようにしたので、差圧センサ７の出力が利用できない通常走行時でも、圧力ロス係数ｋを関係式（１）に代入して排気ガス圧力Ｐ1を推定することができる。よって、差圧センサ７の上流を大気開放する回数や時間を少なく限定でき、差圧センサ７の本来の利用目的であるＤＰＦ再生時期の検出には、支障を及ぼすことがない。 Moreover, according to the air-fuel ratio detection apparatus 1 of the present invention, the pressure loss coefficient k obtained when the upstream of the differential pressure sensor 7 is released to the atmosphere is stored as a learned value, so that the output of the differential pressure sensor 7 is Even during normal travel that cannot be used, the exhaust gas pressure P 1 can be estimated by substituting the pressure loss coefficient k into the relational expression (1). Therefore, it is possible to limit the number of times and time for opening the upstream of the differential pressure sensor 7 to the atmosphere, and there is no hindrance to the detection of the DPF regeneration timing which is the original purpose of use of the differential pressure sensor 7.

１ 空燃比検出装置
２ エンジン
３ 排気管
４ ＤＰＦ（ディーゼルパティキュレートフィルタ）
５ ラムダセンサ
６ センサ用バイパス管
７ 差圧センサ
８ 三方弁
９ 大気圧センサ
１０ 排気ガス圧力推定手段
１１ 空燃比補正手段 DESCRIPTION OF SYMBOLS 1 Air-fuel ratio detection apparatus 2 Engine 3 Exhaust pipe 4 DPF (diesel particulate filter)
5 Lambda sensor 6 Sensor bypass pipe 7 Differential pressure sensor 8 Three-way valve 9 Atmospheric pressure sensor 10 Exhaust gas pressure estimation means 11 Air-fuel ratio correction means

Claims (1)

エンジンの排気管に設置されて排気ガス中の粒子状物質を除去するディーゼルパティキュレートフィルタと、
前記ディーゼルパティキュレートフィルタの出口に設置され排気ガスにおける空燃比を検出するラムダセンサと、
前記ディーゼルパティキュレートフィルタの入口出口間を繋ぐセンサ用バイパス管と、 前記センサ用バイパス管に設置され上流側下流側間の差圧を検出する差圧センサと、
前記センサ用バイパス管の前記差圧センサと前記ディーゼルパティキュレートフィルタの入口間に設置されて前記差圧センサの上流側を大気へ開放させるか前記ディーゼルパティキュレートフィルタの入口に連通させるか切り替え可能な三方弁と、
大気圧を検出する大気圧センサと、
前記三方弁により前記差圧センサの上流側が大気へ開放されているときに、前記大気圧センサが検出した大気圧と前記差圧センサが検出した差圧とから前記ラムダセンサの設置箇所である前記ディーゼルパティキュレートフィルタの出口の排気ガス圧力を推定する排気ガス圧力推定手段と、
前記排気ガス圧力推定手段が推定した排気ガス圧力と前記ラムダセンサの圧力特性とにより、前記ラムダセンサが検出した空燃比を補正する空燃比補正手段とを備え、
前記排気ガス圧力推定手段は、
前記エンジンが定常状態のとき、一時的に前記三方弁により前記差圧センサの上流側を大気へ開放させて、前記ラムダセンサの設置箇所の排気ガス圧力を推定し、
この排気ガス圧力を排気ガス圧力と大気圧と圧力ロス係数の関係式に代入して圧力ロス係数を算出し、この圧力ロス係数を記憶しておき、
前記三方弁により前記差圧センサの上流側が前記ディーゼルパティキュレートフィルタの入口に連通されているときには、前記大気圧センサが検出した大気圧と記憶されている圧力ロス係数を前記関係式に代入して排気ガス圧力を推定する
ことを特徴とする空燃比検出装置。 A diesel particulate filter to remove particulate matter in the exhaust gas is installed in an exhaust pipe of an engine,
A lambda sensor installed at the outlet of the diesel particulate filter for detecting an air-fuel ratio in the exhaust gas;
A sensor bypass pipe connecting between the inlet and outlet of the diesel particulate filter ; a differential pressure sensor that is installed in the sensor bypass pipe and detects a differential pressure between the upstream and downstream sides;
Capable either switched to communicate with the inlet of said diesel particulate filter or the said differential pressure sensor of the sensor bypass pipe installed between the inlet of the diesel particulate filter to open the upstream side of the differential pressure sensor to the atmosphere A three-way valve,
An atmospheric pressure sensor for detecting atmospheric pressure;
When the upstream side of the differential pressure sensor is opened to the atmosphere by the three-way valve, the lambda sensor is installed from the atmospheric pressure detected by the atmospheric pressure sensor and the differential pressure detected by the differential pressure sensor. Exhaust gas pressure estimating means for estimating the exhaust gas pressure at the outlet of the diesel particulate filter ;
Air-fuel ratio correction means for correcting the air-fuel ratio detected by the lambda sensor based on the exhaust gas pressure estimated by the exhaust gas pressure estimation means and the pressure characteristics of the lambda sensor ;
The exhaust gas pressure estimating means includes
When the engine is in a steady state, the upstream side of the differential pressure sensor is temporarily opened to the atmosphere by the three-way valve, and the exhaust gas pressure at the location where the lambda sensor is installed is estimated.
Substituting this exhaust gas pressure into the relational expression of exhaust gas pressure, atmospheric pressure, and pressure loss coefficient, calculating the pressure loss coefficient, storing this pressure loss coefficient,
When the upstream side of the differential pressure sensor communicates with the inlet of the diesel particulate filter by the three-way valve, the atmospheric pressure detected by the atmospheric pressure sensor and the stored pressure loss coefficient are substituted into the relational expression. Estimate exhaust gas pressure
An air-fuel ratio detection apparatus characterized by the above.
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