JP5556589B2 - Fault detection device for valve stop mechanism - Google Patents

Fault detection device for valve stop mechanism Download PDF

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JP5556589B2
JP5556589B2 JP2010240774A JP2010240774A JP5556589B2 JP 5556589 B2 JP5556589 B2 JP 5556589B2 JP 2010240774 A JP2010240774 A JP 2010240774A JP 2010240774 A JP2010240774 A JP 2010240774A JP 5556589 B2 JP5556589 B2 JP 5556589B2
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fuel ratio
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valve
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康人 今井
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Description

本発明は、要求に応じて吸排気弁の作動を停止する弁停止機構を備える内燃機関において、その弁停止機構の故障を検出する故障検出装置に関する。   The present invention relates to a failure detection device that detects a failure of a valve stop mechanism in an internal combustion engine including a valve stop mechanism that stops the operation of an intake / exhaust valve in response to a request.

多気筒内燃機関において、その一部の気筒について吸排気弁の作動を停止させることによってその運転を休止する休筒運転モードを備える内燃機関が知られている。こうした内燃機関における吸排気弁の作動状態を判定する装置として特許文献１に開示されている技術が知られている。この装置は、全筒運転から部分気筒休止運転へと移行した後における排気ガスの空燃比に基づいて、休筒運転中の気筒の弁停止機構の動作異常を検出するものである。   In a multi-cylinder internal combustion engine, an internal combustion engine having a cylinder resting operation mode in which operation of a part of the cylinders is stopped by stopping the operation of intake and exhaust valves is known. A technique disclosed in Patent Document 1 is known as a device for determining an operating state of an intake / exhaust valve in such an internal combustion engine. This device detects an abnormal operation of the valve stop mechanism of the cylinder during the idle cylinder operation based on the air-fuel ratio of the exhaust gas after the transition from the all cylinder operation to the partial cylinder idle operation.

特開２００４−１００４８６号公報JP 2004-1000048 A

一方、内燃機関の排気ガス中には、窒素酸化物（ＮＯｘ）、一酸化炭素（ＣＯ）、炭化水素（ＨＣ）などの浄化すべき物質が含まれており、これらの物質を浄化するために、排気通路に三元触媒を設けたものがある。休筒運転時に弁故障が起きると触媒へと流出する燃料ガスを含まない空気の比率が増加し、触媒に酸素過多の状態が生じる。この状態では、触媒の浄化作用が低下してしまうほか、触媒自体の劣化を招く。この触媒の劣化状態を把握するためには、触媒へと流入する排ガスの状態を知る必要がある。中でも故障した弁数を把握することが好ましい。しかしながら、特許文献１の技術においては、気筒に複数の弁が存在するような場合に故障弁の数を把握することが困難である。   On the other hand, the exhaust gas of the internal combustion engine contains substances to be purified such as nitrogen oxide (NOx), carbon monoxide (CO), hydrocarbon (HC), etc. In order to purify these substances In some cases, a three-way catalyst is provided in the exhaust passage. If a valve failure occurs during the idle cylinder operation, the ratio of air that does not contain fuel gas flowing out to the catalyst increases, resulting in an excessive oxygen state in the catalyst. In this state, the purification effect of the catalyst is lowered and the catalyst itself is deteriorated. In order to grasp the deterioration state of the catalyst, it is necessary to know the state of the exhaust gas flowing into the catalyst. In particular, it is preferable to know the number of failed valves. However, in the technique of Patent Document 1, it is difficult to grasp the number of failure valves when there are a plurality of valves in a cylinder.

そこで本発明は、弁停止機構を備える内燃機関において、弁停止要求に対して動作異常弁の個数を判別することを可能とした弁停止機構の故障検出装置を提供することを課題とする。   Accordingly, an object of the present invention is to provide a failure detection device for a valve stop mechanism that can determine the number of abnormally operated valves in response to a valve stop request in an internal combustion engine having a valve stop mechanism.

上記課題を解決するため、本発明にかかる故障検出装置は、要求に応じて吸排気弁の作動を停止させる弁停止機構を備える内燃機関における該弁停止機構の故障を検出する故障検出装置において、内燃機関が有する気筒には、複数の排気弁が存在し、排気空燃比を検出する空燃比検出手段と、弁停止要求時以降の空燃比検出手段で検出した排気空燃比の変化速度に基づいて、停止要求時に閉弁保持できない故障排気弁の数を検出する故障判定手段と、を備え、故障判定手段は、排気空燃比の変化速度が大きいほど故障排気弁の数が多いと判断することを特徴とする。 In order to solve the above problems, a failure detection device according to the present invention is a failure detection device that detects a failure of the valve stop mechanism in an internal combustion engine that includes a valve stop mechanism that stops the operation of the intake and exhaust valves as required. The cylinder of the internal combustion engine has a plurality of exhaust valves. Based on the air-fuel ratio detection means for detecting the exhaust air-fuel ratio and the change rate of the exhaust air-fuel ratio detected by the air-fuel ratio detection means after the valve stop request. Failure determination means for detecting the number of failed exhaust valves that cannot be closed when requested to stop, and the failure determination means determines that the greater the exhaust air / fuel ratio change rate, the greater the number of failed exhaust valves. Features.

この内燃機関が複数の気筒を有している場合、故障判定手段は、空燃比検出手段で検出した排気空燃比の変化速度が変化するタイミングに基づいて故障排気弁を有する気筒を判定するとよい。   When this internal combustion engine has a plurality of cylinders, the failure determination means may determine the cylinder having the failed exhaust valve based on the timing at which the change rate of the exhaust air / fuel ratio detected by the air / fuel ratio detection means changes.

ここで、排気空燃比の時間変化率は、エンジンの回転数または車速が大きいほど多くなるという関係が記憶された記憶装置を更に備え、故障判定手段は、関係と空燃比検出手段で検出された排気空燃比とを利用して故障排気弁の数を検出してもよい。また、排気空燃比の時間変化率は、エンジンの回転数または車速が大きいほど多くなるという関係が記憶された記憶装置を更に備え、故障判定手段は、関係と空燃比検出手段で検出された排気空燃比とを利用して故障排気弁を有する気筒を判定してもよい。 Here, the exhaust gas air-fuel ratio further includes a storage device storing a relationship that the time change rate of the exhaust air / fuel ratio increases as the engine speed or the vehicle speed increases, and the failure determination means is detected by the relation and the air-fuel ratio detection means. The number of faulty exhaust valves may be detected using the exhaust air / fuel ratio. Further, the exhaust air-fuel ratio further includes a storage device storing a relationship that the time change rate of the exhaust air / fuel ratio increases as the engine speed or the vehicle speed increases, and the failure determination unit includes the exhaust gas detected by the relationship and the air-fuel ratio detection unit. You may determine the cylinder which has a failure exhaust valve using an air fuel ratio .

弁停止要求中に開弁している弁数が多いほど排気側へと流出する新空気量が多くなり、排気空燃比のリーン側への移行速度が速くなる。したがって、排気空燃比のリーン側への移行速度（排気空燃比の変化速度）に基づいて閉弁保持できない故障排気弁の数を検出することができる。   As the number of valves opened during the valve stop request increases, the amount of new air flowing out to the exhaust side increases, and the transition speed of the exhaust air-fuel ratio to the lean side increases. Therefore, the number of faulty exhaust valves that cannot be closed can be detected based on the transition speed of the exhaust air / fuel ratio to the lean side (change speed of the exhaust air / fuel ratio).

弁停止機構が故障している場合には、通常時と同様のタイミングで弁が作動する。この作動タイミングに応じて排気空燃比がリーン側へと移行するので、移行タイミングから弁の作動タイミングを知ることができ、該当気筒を特定することが可能である。   When the valve stop mechanism is out of order, the valve operates at the same timing as normal. Since the exhaust air-fuel ratio shifts to the lean side according to this operation timing, the valve operation timing can be known from the transition timing, and the corresponding cylinder can be specified.

エンジン回転数または車速に応じて排気空燃比の変化速度は異なってくるから、これと故障排気弁との関係を変化させると精度よく判定を行うことができる。   Since the rate of change of the exhaust air-fuel ratio varies depending on the engine speed or the vehicle speed, the determination can be made with high accuracy by changing the relationship between this and the faulty exhaust valve.

本発明にかかる弁停止機構検出装置を含む内燃機関の制御装置の構成を示すブロック図である。It is a block diagram which shows the structure of the control apparatus of the internal combustion engine containing the valve stop mechanism detection apparatus concerning this invention. 図１の装置における故障判定手法の一例を示すフローチャートである。It is a flowchart which shows an example of the failure determination method in the apparatus of FIG. 図２の判定時の排気空燃比の変化例を示すグラフである。3 is a graph showing an example of a change in exhaust air / fuel ratio at the time of determination in FIG. 2. 図２の判定時の排気空燃比の別の変化例を示すグラフである。6 is a graph showing another example of change in the exhaust air-fuel ratio at the time of determination in FIG. 2. 図２の判定時の排気空燃比のさらに別の変化例を示すグラフである。6 is a graph showing still another example of change in the exhaust air-fuel ratio at the time of determination in FIG. 2. エンジン回転数、車速と空気量の関係を示すグラフである。It is a graph which shows the relationship between an engine speed, a vehicle speed, and air quantity. エンジン回転数、車速と空燃比の時間変化率の関係を示すグラフである。It is a graph which shows the relationship between an engine speed, a vehicle speed, and the time change rate of an air fuel ratio. エンジン回転数の違いによる故障弁個数による排気空燃比の変化の差異を説明するグラフである。It is a graph explaining the difference of the change of the exhaust air fuel ratio by the number of failure valves by the difference in engine speed.

以下、添付図面を参照して本発明の好適な実施の形態について詳細に説明する。説明の理解を容易にするため、各図面において同一の構成要素に対しては可能な限り同一の参照番号を附し、重複する説明は省略する。   DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.

図１に、本発明に係る弁停止機構の故障診断装置のブロック図を示す。本実施形態における当該故障診断装置は、エンジン（内燃機関）の制御を行うエンジン制御ＥＣＵ（Electronic Control Unit）１の一部としてソフトウェアにより提供される。このエンジン制御ＥＣＵ１は、計算処理を行うＣＰＵ（CentralProcessing Unit）１０、記憶装置であるＲＡＭ(Randam Access Memory)１５、ＲＯＭ(Read only memory)１６から構成される。この故障診断装置をエンジン制御ＥＣＵ１から独立して設けてもよく、その他のＥＣＵと統合することも可能である。   FIG. 1 shows a block diagram of a failure diagnosis device for a valve stop mechanism according to the present invention. The failure diagnosis apparatus according to the present embodiment is provided by software as part of an engine control ECU (Electronic Control Unit) 1 that controls an engine (internal combustion engine). The engine control ECU 1 includes a CPU (Central Processing Unit) 10 that performs calculation processing, a RAM (Randam Access Memory) 15 that is a storage device, and a ROM (Read only memory) 16. This failure diagnosis device may be provided independently of the engine control ECU 1 or may be integrated with other ECUs.

ＣＰＵ１０には、フューエルカット（Fuel Cut＝ＦＣ）要求・弁停止要求処理部１１、弁故障検出処理部１２、異常検出後処理部１３、ソレノイド駆動処理部１４を備える。これらの各処理部は、例えば、ＣＰＵ１０上で作動するソフトウェアによって実現されればよく、ソフトウェアはそれぞれ独立していなくとも一部を共有していてもよく、同一のプログラム内で機能を実現してもよい。   The CPU 10 includes a fuel cut (FC) request / valve stop request processing unit 11, a valve failure detection processing unit 12, an abnormality detection post-processing unit 13, and a solenoid drive processing unit 14. Each of these processing units may be realized by, for example, software that operates on the CPU 10, and the software may not share each part but may share a part, and realize functions in the same program. Also good.

さらに、エンジン制御ＥＣＵ１には、クランク角度を検出するクランク角度センサ２１、アクセルペダルの操作量を検出するアクセル開度センサ２２、排気空燃比（Ａ／Ｆ）を検出するＡ／Ｆセンサ２３の各出力が入力されている。Ａ／Ｆセンサ２３としては、例えば、Ｏ２センサを用いるとよい。一方、エンジン制御ＥＣＵ１は、各気筒の吸気弁、排気弁それぞれの作動を制御する吸気弁ソレノイド４１〜４４、排気弁ソレノイド５１〜５４と、燃料供給を行う各インジェクタ（図示せず。）に対する制御信号を出力する。 Further, the engine control ECU 1 includes a crank angle sensor 21 that detects a crank angle, an accelerator opening sensor 22 that detects an operation amount of an accelerator pedal, and an A / F sensor 23 that detects an exhaust air-fuel ratio (A / F). Output is being input. For example, an O 2 sensor may be used as the A / F sensor 23. On the other hand, the engine control ECU 1 controls the intake valve solenoids 41 to 44 and the exhaust valve solenoids 51 to 54 that control the operation of the intake valve and the exhaust valve of each cylinder, and each injector (not shown) that supplies fuel. Output a signal.

本発明にかかる故障診断装置を搭載した車両は、前述した休筒運転モードを備えている。具体的には、フューエルカット要求・弁停止要求処理部１１が、クランク角度センサ２１、アクセル開度センサ２２の出力に基づいて弁停止要求の有無を判定し、ソレノイド駆動処理部１４に指示して各吸気弁ソレノイド４１〜４４、排気弁ソレノイド５１〜５４の作動を制御することで、弁の作動を停止させる。   A vehicle equipped with the failure diagnosis apparatus according to the present invention has the above-described cylinder deactivation mode. Specifically, the fuel cut request / valve stop request processing unit 11 determines whether or not there is a valve stop request based on the outputs of the crank angle sensor 21 and the accelerator opening sensor 22 and instructs the solenoid drive processing unit 14 to instruct. By controlling the operations of the intake valve solenoids 41 to 44 and the exhaust valve solenoids 51 to 54, the operation of the valves is stopped.

吸排気弁を停止させるシステムが故障して、ＦＣ時に閉弁動作できなかった場合、触媒に低温の空気が流れ込むことによりその性能低下や触媒そのものの劣化を招くおそれがある。また燃費悪化の要因にもなる。一方、ＦＣからの復帰時に正常に弁が作動しない場合には、バックファイア等の障害を引き起こす可能性がある。そのため、弁停止機構の故障を早期にかつ確実に検出する必要がある。以下、本発明にかかる故障診断装置における弁停止機構の故障診断手法を例示する。この診断手法は、ＣＰＵ１０によって実施されるものである。   If the system that stops the intake / exhaust valve fails and the valve cannot be closed during FC, low-temperature air flows into the catalyst, which may lead to performance degradation or deterioration of the catalyst itself. It also causes a deterioration in fuel consumption. On the other hand, when the valve does not operate normally when returning from the FC, there is a possibility of causing a failure such as a backfire. Therefore, it is necessary to detect the failure of the valve stop mechanism early and reliably. Hereinafter, the failure diagnosis method of the valve stop mechanism in the failure diagnosis apparatus according to the present invention will be exemplified. This diagnostic method is performed by the CPU 10.

図２は、故障診断実施例を示すフローチャートである。最初に、弁故障検出処理部１２は、Ａ／Ｆセンサ２３の出力から排気Ａ／Ｆ値を検出する（ステップＳ１）。次に、弁停止要求中か否かを判定する（ステップＳ２）。弁停止要求中でない場合には、その後の処理を行うことなく処理を終了する。一方、弁停止要求中である場合には、ステップＳ３へと移行し、弁停止要求からの経過時間ｔｘを算出する。次に、検出した排気Ａ／Ｆ値がストイキ値より一定程度以上空気（酸素）が多いリーン状態であるか否かを判定する（ステップＳ４）。リーン状態でない、具体的には、ストイキ状態のときには、ステップＳ６へと移行して排気弁故障なしと判定する。一方、リーン状態である場合には、ステップＳ５へと移行して、Ａ／Ｆの変化状況を予めＲＯＭ１５等に格納しているマップと比較することにより、故障している排気弁を特定し、処理を終了する。   FIG. 2 is a flowchart showing a failure diagnosis embodiment. First, the valve failure detection processing unit 12 detects the exhaust A / F value from the output of the A / F sensor 23 (step S1). Next, it is determined whether or not a valve stop request is being made (step S2). If the valve stop request is not being requested, the process is terminated without performing the subsequent process. On the other hand, when the valve stop request is being made, the process proceeds to step S3, and an elapsed time tx from the valve stop request is calculated. Next, it is determined whether or not the detected exhaust A / F value is in a lean state where there is more air (oxygen) than the stoichiometric value by a certain degree or more (step S4). When the engine is not in the lean state, specifically, in the stoichiometric state, the process proceeds to step S6 and it is determined that there is no exhaust valve failure. On the other hand, if the engine is in the lean state, the process proceeds to step S5, and the faulty exhaust valve is identified by comparing the change state of the A / F with a map stored in advance in the ROM 15 or the like. The process ends.

具体的な排気弁の特定手法について述べる。図３は、異なる気筒の排気弁が故障している場合における排気Ａ／Ｆの変化を示したものである。ここでは、４気筒式であって、通常時に第１気筒、第２気筒、第３気筒、第４気筒、第１気筒の順に排気弁が開弁する場合を例に説明する。なお、いずれもいずれか一つの気筒の排気弁１つが故障している場合を例に説明する。   A specific method for specifying the exhaust valve will be described. FIG. 3 shows changes in exhaust A / F when exhaust valves of different cylinders are malfunctioning. Here, an example will be described in which the exhaust valve is opened in the order of the first cylinder, the second cylinder, the third cylinder, the fourth cylinder, and the first cylinder in the normal mode. In any case, the case where one of the exhaust valves of any one cylinder is broken will be described as an example.

第１気筒の弁停止機構が故障した場合には、第１気筒の通常時の排気弁開弁タイミングｔ１から速やかに排気Ａ／Ｆはリーン側へと移行する図中ａで示される推移を描く。一方、第２気筒の弁停止機構が故障した場合には、これよりリーン側への移行は遅れ、通常時の第２気筒の排気弁開弁タイミングｔ２から排気Ａ／Ｆがリーン側へと移行する図中ｂで示される推移を描くことになる。第３気筒の弁停止機構が故障した場合には、さらに、リーン側への移行は遅れ、通常時の第３気筒の排気弁開弁タイミングｔ３から排気Ａ／Ｆがリーン側へと移行する図中ｃで示される推移を描くことになる。したがって、排気Ａ／Ｆがリーン側へと移行するタイミングを通常の開弁タイミングと比較することで、どの気筒の排気弁が故障しているか否かを判定することができる。 When the first cylinder of the valve stop mechanism fails, the transition quickly exhaust A / F from the exhaust valve opening timing t 1 of the normal of the first cylinder is shown in the figure shifts to the lean side a Draw. On the other hand, when the second cylinder of the valve stop mechanism has failed, than this transition to the lean side delay, exhaust A / F from the exhaust valve opening timing t 2 of the second cylinder at the normal time to lean side The transition indicated by b in the figure to be transferred is drawn. When the third cylinder valve stop mechanism has failed, further transition to the lean side delay, exhaust A / F from the exhaust valve opening timing t 3 of the third cylinder in the normal transitions to the lean side The transition indicated by c in the figure is drawn. Therefore, by comparing the timing at which the exhaust A / F shifts to the lean side with the normal valve opening timing, it is possible to determine which cylinder has an exhaust valve malfunctioning.

次に一つの気筒に複数の排気弁が存在している場合を考える。図４は、同一気筒において異なる個数の弁が故障した場合における排気Ａ／Ｆの変化を示したものである。ここでは、第１気筒に３つの排気弁がある場合を考える。図中Ａ線は、全ての弁が正常に動作している場合のＡ／Ｆ遷移であり、ストイキ状態で維持される。図中Ｂ線、Ｃ線、Ｄ線はそれぞれ故障排気弁数が１個、２個、３個の場合を示しているが、図から明らかなように、故障排気弁数が多くなるにしたがって、排気Ａ／Ｆがリーン側へと移行するのが速くなる。言い換えると、空燃比の変化速度は故障排気弁数が多いほど大きくなる。Ｂ線、Ｃ線、Ｄ線のそれぞれにおいて、所定のリーン状態αに達した時点をｔｂ、ｔｃ、ｔｄとすると、ｔｄが最も早く到来し、ｔｃ、ｔｂの順になる。したがって、空燃比の変化速度に基づいて故障排気弁数を判定することができる。 Next, consider a case where a plurality of exhaust valves exist in one cylinder. FIG. 4 shows changes in exhaust A / F when different numbers of valves fail in the same cylinder. Here, a case where there are three exhaust valves in the first cylinder is considered. The A line in the figure is an A / F transition when all the valves are operating normally, and is maintained in a stoichiometric state. The B line, C line, and D line in the figure show cases where the number of failed exhaust valves is 1, 2, and 3, respectively. As is apparent from the figure, as the number of failed exhaust valves increases, The exhaust A / F moves faster to the lean side. In other words, the rate of change of the air-fuel ratio increases as the number of failed exhaust valves increases. B-line, C-line, in each of the D-line, when the time of reaching a predetermined lean state α and t b, t c, t d , t d is reached earliest, t c, becomes in the order of t b. Therefore, the number of failed exhaust valves can be determined based on the change rate of the air-fuel ratio.

次に、複数の気筒の排気弁が同時に故障した場合の挙動を説明する。図５は、複数の気筒が同時に故障した場合の排気Ａ／Ｆの変化を示している。ここでは、それぞれ１個の排気弁を有する４気筒式の内燃機関において、１つないし４つの気筒で排気弁が同時に故障した場合を示す。図中Ａ線は、全ての弁が正常に動作している場合のＡ／Ｆ遷移であり、ストイキ状態で維持される。図中Ｂ線、Ｃ線、Ｄ線、Ｅ線はそれぞれ故障排気弁のある気筒が第１気筒のみ、第１気筒と第２気筒、第１気筒から第３気筒、４気筒全ての場合を示している。図から明らかなように、第１気筒の通常の開弁タイミング（ｔ１）から第２気筒の通常の開弁タイミング（ｔ２）までの挙動はＢ線〜Ｅ線のいずれも一致している。しかし、ｔ２段階で、Ｃ線〜Ｅ線の場合は、Ｂ線に比べて排気Ａ／Ｆがリーン側へと移行するのが速くなる。その後、各開弁タイミングごとに当該開弁タイミングの気筒が故障排気弁のある気筒である場合には、それ以前に比べて排気Ａ／Ｆがリーン側へと移行する速度が速くなる。したがって、各タイミングにおける空燃比の変化速度に基づいて複数の気筒で故障が起こっている場合であっても故障している気筒、弁数を判定することができる。 Next, the behavior when the exhaust valves of a plurality of cylinders fail simultaneously will be described. FIG. 5 shows changes in exhaust A / F when a plurality of cylinders fail simultaneously. Here, in a four-cylinder internal combustion engine having one exhaust valve each, the case where one to four cylinders have failed at the same time is shown. The A line in the figure is an A / F transition when all the valves are operating normally, and is maintained in a stoichiometric state. B line, C line, D line, and E line in the figure show the case where the cylinder with the failed exhaust valve is only the first cylinder, the first cylinder and the second cylinder, and the first to third cylinders and all the four cylinders. ing. As is apparent from the figure, the behavior from the normal opening timing (t 1 ) of the first cylinder to the normal opening timing (t 2 ) of the second cylinder is the same for all the B-line and E-line. . However, at t 2 stages, in the case of C-line ~E line, the exhaust A / F is that shifts to the lean side is faster than the B line. Thereafter, when the cylinder at the valve opening timing is a cylinder having a faulty exhaust valve at each valve opening timing, the speed at which the exhaust A / F shifts to the lean side becomes faster than before. Therefore, even if a failure occurs in a plurality of cylinders based on the change rate of the air-fuel ratio at each timing, the failed cylinder and the number of valves can be determined.

ここで、図６に示されるように、排気空気量は、エンジン回転数または車速が大きいほど多くなる。また、故障している排気弁が同一の場合であっても、図７に示されるように、排気Ａ／Ｆの時間変化率（ｄＮＴ／ｄｔ）は、エンジン回転数または車速が大きいほど多くなる。そこで、正常作動時、各種弁故障時のこれらの関係を予めＲＯＭ１５等に記憶しておいて、実際の変化率をこれと比較することで、故障した弁の個数等を判定するとよい。 Here, as shown in FIG. 6, the amount of exhaust air increases as the engine speed or the vehicle speed increases. Even when the exhaust valves having the same failure are the same, as shown in FIG. 7, the time change rate (dN T / dt) of the exhaust A / F increases as the engine speed or the vehicle speed increases. Become. Therefore, it is preferable to store the relationship between the normal operation and various valve failures in the ROM 15 or the like in advance and compare the actual change rate with this to determine the number of failed valves.

図８は、エンジン回転数の違いによる排気弁正常時または故障時の排気Ａ／Ｆの推移を比較して示す図である。ここでは、同一気筒における排気弁の故障数が０（正常の場合）をＡ線、１個、２個、３個の場合をそれぞれＢ線、Ｃ線、Ｄ線で示す。図８（ａ）は、エンジン回転数が低い場合、図８（ｂ）は、エンジン回転数がこれより高い場合を示している。エンジン回転数が高いほど単位時間あたりの排気量が多くなるため、リーン側への移行が早くなる。いずれの場合においても故障している弁が多いほど移行が早くなる点は共通している。図に示される傾向に基づいて故障している弁の個数、該当気筒を精度よく検出することが可能である。   FIG. 8 is a diagram showing a comparison of the transition of the exhaust A / F when the exhaust valve is normal or failed due to a difference in engine speed. Here, when the number of failure of the exhaust valve in the same cylinder is 0 (normal), the cases of A line, 1, 2, 3 are shown by B line, C line, and D line, respectively. FIG. 8A shows a case where the engine speed is low, and FIG. 8B shows a case where the engine speed is higher. The higher the engine speed, the greater the displacement per unit time, and the faster the shift to the lean side. In any case, the more the number of failed valves, the faster the transition. Based on the tendency shown in the figure, it is possible to detect the number of failed valves and the corresponding cylinder with high accuracy.

以上、述べたように、本発明にかかる故障診断装置によれば、弁停止要求時以降の排気Ａ／Ｆの推移（変化速度）に基づいて故障した弁停止機構、特に、閉弁保持できない故障排気弁を特定することができる。このため、異常検出後処理部１３において、休筒運転を行う気筒を切り換える対処が容易である。   As described above, according to the failure diagnosis apparatus according to the present invention, the valve stop mechanism that has failed based on the transition (change speed) of the exhaust A / F after the valve stop request, particularly the failure that cannot hold the valve closed. An exhaust valve can be identified. For this reason, in the abnormality detection post-processing unit 13, it is easy to cope with switching the cylinder that performs the cylinder deactivation operation.

１…エンジン制御ＥＣＵ、１０…ＣＰＵ、１１…フューエルカット要求・弁停止要求処理部、１２…弁故障検出処理部、１３…異常検出後処理部、１４…ソレノイド駆動処理部、１５…ＲＯＭ、１６…ＲＡＭ、２１…クランク角度センサ、２２…アクセル開度センサ、２３…Ａ／Ｆセンサ、４１〜４４…吸気弁ソレノイド、５１〜５４…排気弁ソレノイド。   DESCRIPTION OF SYMBOLS 1 ... Engine control ECU, 10 ... CPU, 11 ... Fuel cut request | requirement valve stop request | requirement process part, 12 ... Valve failure detection process part, 13 ... Abnormality detection post-processing part, 14 ... Solenoid drive process part, 15 ... ROM, 16 ... RAM, 21 ... Crank angle sensor, 22 ... Accelerator opening sensor, 23 ... A / F sensor, 41-44 ... Intake valve solenoid, 51-54 ... Exhaust valve solenoid.

Claims (4)

要求に応じて吸排気弁の作動を停止させる弁停止機構を備える内燃機関における該弁停止機構の故障を検出する故障検出装置において、
前記内燃機関が有する気筒には、複数の排気弁が存在し、
排気空燃比を検出する空燃比検出手段と、
弁停止要求時以降の前記空燃比検出手段で検出した排気空燃比の変化速度に基づいて、停止要求時に閉弁保持できない故障排気弁の数を検出する故障判定手段と、
を備え、
前記故障判定手段は、前記排気空燃比の変化速度が大きいほど前記故障排気弁の数が多いと判断することを特徴とする故障検出装置。 In a failure detection device that detects a failure of the valve stop mechanism in an internal combustion engine provided with a valve stop mechanism that stops the operation of the intake and exhaust valves as required.
The cylinder of the internal combustion engine has a plurality of exhaust valves,
Air-fuel ratio detecting means for detecting the exhaust air-fuel ratio;
Failure determination means for detecting the number of failed exhaust valves that cannot be kept closed at the time of a stop request based on the change rate of the exhaust air / fuel ratio detected by the air / fuel ratio detection means after the valve stop request time;
Equipped with a,
The failure detection device determines that the number of the failure exhaust valves is larger as the change rate of the exhaust air-fuel ratio is larger . 前記内燃機関は、複数の前記気筒を有しており、前記故障判定手段は、前記空燃比検出手段で検出した排気空燃比の変化速度が変化するタイミングに基づいて故障排気弁を有する気筒を判定することを特徴とする請求項１記載の故障検出装置。 The internal combustion engine has a plurality of said cylinders, said fault determining means determines a cylinder having a fault exhaust valve on the basis of the timing at which the change rate of the exhaust air-fuel ratio detected by the air-fuel ratio detecting means is changed The failure detection apparatus according to claim 1. 前記排気空燃比の時間変化率は、エンジンの回転数または車速が大きいほど多くなるという関係が記憶された記憶装置を更に備え、
前記故障判定手段は、前記関係と前記空燃比検出手段で検出された前記排気空燃比とを利用して故障排気弁の数を検出することを特徴とする請求項１に記載の故障検出装置。 The exhaust air-fuel ratio time change rate further includes a storage device storing a relationship that increases as the engine speed or vehicle speed increases,
2. The failure detection apparatus according to claim 1, wherein the failure determination means detects the number of failure exhaust valves using the relationship and the exhaust air / fuel ratio detected by the air / fuel ratio detection means . 前記排気空燃比の時間変化率は、エンジンの回転数または車速が大きいほど多くなるという関係が記憶された記憶装置を更に備え、
前記故障判定手段は、前記関係と前記空燃比検出手段で検出された前記排気空燃比とを利用して故障排気弁を有する気筒を判定することを特徴とする請求項２に記載の故障検出装置。 The exhaust air-fuel ratio time change rate further includes a storage device storing a relationship that increases as the engine speed or vehicle speed increases,
The failure detection device according to claim 2, wherein the failure determination unit determines a cylinder having a failure exhaust valve by using the relationship and the exhaust air / fuel ratio detected by the air / fuel ratio detection unit. .
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