JP4453061B2 - Control device for internal combustion engine - Google Patents

Description

上式は、なまし係数が１／４であるが、１／３、１／６、１／８等であっても良い。
【００７４】
図１１の燃料系異常診断実行ルーチンは、所定時間毎に実行される。本ルーチンが起動されると、まず、ステップ７０１で、燃料系異常診断実行条件が成立した状態が所定時間（例えば２０秒）継続したか否かを判定する。ここで、燃料系異常診断実行条件としては、エンジン始動後の経過時間が所定時間（例えば６０秒）を越えていること、空燃比フィードバック制御中であること等であり、これらの条件を全て満たしていれば、燃料系異常診断実行条件が成立する。
【００７５】
上記ステップ７０１で、燃料系異常診断実行条件が成立した状態が所定時間（例えば２０秒）継続していないと判定された場合には、以降の燃料系異常診断処理を行わずに本ルーチンを終了する。
【００７６】
その後、燃料系異常診断実行条件が成立した状態が所定時間（例えば２０秒）継続した時点で、ステップ７０１から７０２に進み、リッチスパイク制御実施中又はリッチスパイク制御終了から所定期間内であるか否かを判定する。本ルーチンは、後述するステップ７０３，７０６で、実空燃比ＡＦを用いて算出した異常診断パラメータなまし値ＤＧＤＥＬＡＦＳを用いて燃料系の異常診断を行うため、リッチスパイク制御中やリッチスパイク制御終了直後に燃料系の異常診断を行うと、リッチスパイク制御による一時的な空燃比変化の影響を受けた異常診断パラメータなまし値ＤＧＤＥＬＡＦＳに基づいて燃料系の異常の有無を診断してしまう。従って、ステップ７０２で、リッチスパイク制御実施中又はリッチスパイク制御終了から所定期間内と判定された場合は、そのまま本ルーチンを終了して、燃料系異常診断を禁止し、リッチスパイク制御の影響による燃料系異常診断精度の低下を防止する。このステップ７０２の処理が、特許請求の範囲でいう異常診断禁止手段に相当する役割を果たす。
【００７７】
一方、ステップ７０２で、リッチスパイク制御実施中でなく且つリッチスパイク制御終了から所定期間内でもないと判定された場合は、ステップ７０３に進み、異常診断パラメータなまし値ＤＧＤＥＬＡＦＳＭをリッチ側異常診断基準値ｔＤＦＡＦＲと比較し、ＤＧＤＥＬＡＦＳＭ≦ｔＤＦＡＦＲ（リッチ側の異常）であれば、ステップ７０４に進み、リッチ側の異常が所定時間（例えば２０秒）継続したか否かを判定し、所定時間継続すれば、ステップ７０５に進み、最終的に燃料供給系のリッチ側の異常と診断して、リッチ側異常診断フラグＤＧＦＵＥＬＲＮＧをリッチ側の異常を意味する「１」にセットし、次のステップ７０９で、警告ランプ（図示せず）を点灯又は点滅させて運転者に警告すると共に、ＥＣＵ２９のメモリにリッチ側の異常の情報を記憶して本プログラムを終了する。
【００７８】
上記ステップ７０４で、リッチ側の異常が所定時間（例えば２０秒）継続していない場合には、最終的な診断結果を出さずに本プログラムを終了する。
【００７９】
また、上記ステップ７０３で、ＤＧＤＥＬＡＦＳＭ＞ｔＤＦＡＦＲ（リッチ側正常）と判定された場合には、ステップ７０６に進み、異常診断パラメータなまし値ＤＧＤＥＬＡＦＳＭをリーン側異常診断基準値ｔＤＦＡＦＬと比較し、ＤＧＤＥＬＡＦＳＭ≧ｔＤＦＡＦＬ（リーン側の異常）であれば、ステップ７０７に進み、リーン側の異常が所定時間（例えば２０秒）継続したか否かを判定し、所定時間継続すれば、ステップ７０８に進み、最終的に燃料供給系のリーン側の異常と診断してリーン側異常診断フラグＤＧＦＵＥＬＬＮＧをリーン側の異常を意味する「１」にセットし、次のステップ７０９で、警告ランプを点灯又は点滅させて運転者に警告すると共に、ＥＣＵ２９のメモリにリッチ側の異常の情報を記憶して本プログラムを終了する。
【００８０】
上記ステップ７０６で、リーン側の異常が所定時間（例えば２０秒）継続していない場合には、最終的な診断結果を出さずに本プログラムを終了する。
以上説明したセンサ異常診断に関連する技術は、特開平１１−８２１１７号公報に詳細に記載されている。
【００８２】
以上説明した本実施形態によれば、リッチスパイク制御実施中及びリッチスパイク制御終了から所定期間内は、リッチスパイク制御の影響を受ける失火診断、触媒劣化診断、センサ異常診断及び燃料系異常診断を禁止するようにしたので、リッチスパイク制御による一時的な空燃比変化や回転変動の影響を受けた異常診断パラメータに基づいて異常診断を行ってしまうことを防止することができて、各異常診断の精度を向上することができ、エンジン制御システムの信頼性を向上することができる。
【００８３】
尚、上記実施形態では、リッチスパイク制御実施中及びリッチスパイク制御終了から所定期間内は、他の異常診断実行条件が成立しても異常診断が実施されない。この場合、リッチスパイク制御終了から所定期間が経過して異常診断の禁止が解除された後に、他の異常診断実行条件が成立していることを条件に、異常診断を実施するようにしても良いが、リッチスパイク制御実施中及びリッチスパイク制御終了から所定期間内に、他の異常診断実行条件が成立したときは、異常診断の実施を遅延させ、リッチスパイク制御終了から所定期間が経過した後に異常診断を実施するようにしても良い。
【００８４】
また、上記実施形態では、失火診断、触媒劣化診断、センサ異常診断及び燃料系異常診断を全て実施するシステムに本発明を適用したが、これらの異常診断のうちの１つ又は複数の異常診断を実施するシステムに本発明を適用しても良く、また、異常診断方法を適宜変更しても良い。更に、リッチスパイク制御による一時的な空燃比変化や回転変動の影響を受ける他の異常診断を実施するシステムに本発明を適用しても良い。また、本発明は、異常診断を禁止（又は遅延）する期間をリッチスパイク制御中のみに限定しても良い。
【００８５】
その他、本発明は、リーンバーンエンジン以外に、直噴エンジン等、リッチスパイク制御によって吸蔵ＮＯｘを還元浄化する必要がある触媒を備えたエンジンに適用することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示すエンジン制御システム全体の概略構成図
【図２】燃料噴射量設定ルーチンの処理の流れを示すフローチャート
【図３】目標空燃比設定ルーチンの処理の流れを示すフローチャート
【図４】リッチ運転時間ＴＲの算出マップを概念的に示す図
【図５】目標空燃比ＡＦＴＧの算出マップを概念的に示す図
【図６】空燃比と周期カウンタの挙動を示すタイムチャート
【図７】失火診断ルーチンの処理の流れを示すフローチャート
【図８】触媒劣化診断ルーチンの処理の流れを示すフローチャート
【図９】センサ異常診断ルーチンの処理の流れを示すフローチャート
【図１０】燃料系異常診断パラメータ算出ルーチンの処理の流れを示すフローチャート
【図１１】燃料系異常診断実行ルーチンの処理の流れを示すフローチャート
【符号の説明】
１１…エンジン（内燃機関）、２０…燃料噴射弁、２３…排気管、２４…ＮＯｘ触媒、２５…空燃比センサ、２６…酸素センサ（下流側センサ）、２９…ＥＣＵ（リッチスパイク制御手段，異常診断手段，異常診断禁止手段）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine that performs rich spike control that temporarily controls the air-fuel ratio to the rich side in order to reduce and purify nitrogen oxides stored in the catalyst (hereinafter referred to as “NOx”). It is.
[0002]
[Prior art]
In recent years, lean burn engines and in-cylinder injection engines that control the air-fuel ratio to be leaner than the stoichiometric air-fuel ratio have been developed for the purpose of improving fuel efficiency. Some of these engines employ a NOx occlusion reduction type catalyst (hereinafter referred to as “NOx catalyst”) in order to reduce NOx emission. This NOx catalyst has a characteristic of storing NOx in the exhaust gas when the air-fuel ratio of the exhaust gas is lean, and reducing and purifying the stored NOx when the air-fuel ratio becomes rich.
[0003]
Therefore, in order to prevent the NOx occlusion amount of the NOx catalyst from being saturated during the lean operation, as shown in JP 2000-34943 A, the lean operation time and the rich operation time are set to a predetermined ratio (for example, 50: 1). Set and repeat the process of reducing and purifying NOx stored in the NOx catalyst during lean operation by performing rich spike control that temporarily enriches the air-fuel ratio in a predetermined cycle during lean operation There is.
[0004]
In recent years, electronically controlled engine control systems improve the reliability of the engine control system by performing various types of abnormality diagnosis while the engine is running to self-diagnose the presence of abnormalities such as system failure and deterioration. I try to let them.
[0005]
[Problems to be solved by the invention]
As described above, in an engine control system that periodically performs rich spike control, the abnormality diagnosis execution timing may overlap with the rich spike control execution timing while the abnormality diagnosis is repeated during engine operation. When rich spike control is performed, the air-fuel ratio changes suddenly, and engine rotation fluctuations also occur due to the sudden change. Therefore, when abnormality diagnosis is performed at such a time, depending on the type of abnormality diagnosis, it occurred due to rich spike control. The presence / absence of abnormality is diagnosed based on the abnormality diagnosis parameter affected by the air-fuel ratio change and engine rotation fluctuation. As a result, there is a possibility that the abnormality diagnosis accuracy is lowered and the reliability of the engine control system is lowered.
[0006]
The present invention has been made in view of such circumstances, and the object of the present invention is to prevent the abnormality diagnosis based on the abnormality diagnosis parameter affected by the rich spike control. An object of the present invention is to provide a control device for an internal combustion engine capable of improving the accuracy of abnormality diagnosis.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the control apparatus for an internal combustion engine according to claim 1 of the present invention performs a predetermined abnormality diagnosis by the abnormality diagnosis prohibiting means during the execution of rich spike control and / or for a predetermined period after the end of rich spike control. Prohibited or delayed This is a first feature, and furthermore, a second feature is that the presence or absence of misfire is diagnosed based on the rotational fluctuation of the internal combustion engine. As described above, during the predetermined period during the rich spike control and / or after the end of the rich spike control, the predetermined abnormality diagnosis is prohibited or delayed. In this way, when an abnormality diagnosis is performed using an abnormality diagnosis parameter that is affected by rich spike control (that is, a parameter that is affected by air-fuel ratio change or rotation fluctuation), during rich spike control or immediately after the end of rich spike control, Even if other abnormality diagnosis execution conditions are satisfied, the abnormality diagnosis can be prevented from being performed. As a result, it is possible to prevent an abnormality diagnosis based on the abnormality diagnosis parameter temporarily changed by the rich spike control, and to accurately prevent the abnormality diagnosis parameter from being affected by the rich spike control. An abnormality diagnosis can be performed, and the abnormality diagnosis accuracy can be improved.
[0008]
The present invention Technical matter that prohibits or delays a predetermined abnormality diagnosis during the execution of rich spike control and / or for a predetermined period after the end of rich spike control Is widely applicable to a system for diagnosing an abnormality based on an abnormality diagnosis parameter that is affected by an air-fuel ratio change caused by rich spike control or an engine rotation fluctuation. 1 As described above, the present invention may be applied to a system for diagnosing the presence or absence of misfire based on the rotational fluctuation of the internal combustion engine. In other words, if the misfire diagnosis based on rotation fluctuation is prohibited or delayed during execution of rich spike control or during a predetermined period immediately after that, rotation fluctuation caused by rich spike control will occur. In Accordingly, it is possible to prevent the deterioration of misfire diagnosis accuracy.
[0009]
Claims 2 As described above, the present invention is applied to a system in which a downstream sensor for detecting the air-fuel ratio or rich / lean of exhaust gas is provided on the downstream side of the catalyst, and the presence or absence of catalyst deterioration is diagnosed based on the output of the downstream sensor. You may do it. Or claims 3 As described above, the present invention may be applied to a system for diagnosing the presence / absence of an abnormality in a sensor that detects the air-fuel ratio or rich / lean of exhaust gas. The output of the sensor for detecting the air-fuel ratio and rich / lean of the exhaust gas fluctuates due to the influence of the air-fuel ratio change caused by the rich spike control. Therefore, if the catalyst deterioration diagnosis based on the downstream sensor output or the abnormality diagnosis of the sensor itself is prohibited or delayed during the execution of the rich spike control or in a predetermined period immediately after that, the catalyst deterioration diagnosis accuracy of the rich spike control can be improved. It is possible to prevent a decrease and a decrease in sensor abnormality diagnosis accuracy.
[0010]
Claims 4 As described above, the present invention may be applied to a system for diagnosing the presence or absence of abnormality in the fuel system. The fuel system is a system to be controlled by fuel injection control (air-fuel ratio control), and the parameters used for abnormality diagnosis of the fuel system fluctuate under the influence of the air-fuel ratio change caused by rich spike control. Therefore, if the fuel system abnormality diagnosis is prohibited or delayed during execution of the rich spike control or during a predetermined period immediately after that, it is possible to prevent the deterioration of the fuel system abnormality diagnosis accuracy due to the rich spike control.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a lean burn engine will be described with reference to the drawings.
[0012]
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an intake air temperature sensor 14 that detects the intake air temperature is provided downstream of the air cleaner 13. A throttle valve 15 and a throttle opening sensor 16 for detecting the throttle opening are provided on the downstream side of the intake air temperature sensor 14.
[0013]
Further, an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided on the downstream side of the throttle valve 15, and a surge tank 18 is provided on the downstream side of the intake pipe pressure sensor 17. The surge tank 18 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. . A spark plug 21 is attached to the cylinder head of the engine 11 for each cylinder, and a high voltage generated by the ignition device 22 is applied to the spark plug 21 of each cylinder at each ignition timing.
[0014]
On the other hand, a NOx occlusion reduction catalyst (hereinafter referred to as “NOx catalyst”) 24 for purifying exhaust gas is installed in the middle of the exhaust pipe 23 of the engine 11. The NOx catalyst 24 occludes NOx in the exhaust gas during the lean operation where the oxygen concentration in the exhaust gas is high, and the rich operation in which the air-fuel ratio is switched to rich (or stoichiometric) and the oxygen concentration in the exhaust gas decreases. Inside, NOx occluded so far is reduced and purified and released.
[0015]
An air-fuel ratio sensor (linear A / F sensor) 25 that outputs a linear air-fuel ratio signal AF corresponding to the air-fuel ratio of the exhaust gas is provided upstream of the NOx catalyst 24, and downstream of the NOx catalyst 24. An oxygen sensor 26 (downstream sensor) is provided in which the output voltage VOX2 is inverted depending on whether the air-fuel ratio of the exhaust gas is rich or lean with respect to the stoichiometric air-fuel ratio. An air-fuel ratio sensor (linear A / F sensor) may be provided on the downstream side of the NOx catalyst 24 instead of the oxygen sensor 26. A water temperature sensor 27 for detecting the coolant temperature and a crank angle sensor 28 for detecting the engine rotation speed are attached to the cylinder block of the engine 11.
[0016]
The engine control circuit (hereinafter referred to as “ECU”) 29 is mainly composed of a microcomputer comprising a CPU 30, a ROM 31, a RAM 32, a backup RAM 33 backed up by a battery (not shown), an input port 34, an output port 35 and the like. Has been. The input port 34 receives the output signals of the various sensors described above. Further, the fuel injection valve 20, the ignition device 22, and the like are connected to the output port 35. The ECU 29 controls the operation of the engine 11 by executing various engine control programs stored in the ROM 31 by the CPU 30.
[0017]
The ECU 29 sets the lean operation time and the rich operation time at a predetermined ratio (for example, 50: 1) based on the engine operation state, and performs rich spike control for temporarily performing the rich operation during the lean operation. Thereby, in the NOx catalyst 24, the NOx in the exhaust gas is occluded during the lean operation, and the occluded NOx is reduced and purified by rich spike control and released.
[0018]
The ECU 29 performs various abnormality diagnoses while the engine is running to self-diagnose whether there is an abnormality such as a failure or deterioration of the system. However, if rich spike control is performed, the air-fuel ratio changes suddenly. In addition, because of this, rotation fluctuations also occur. Therefore, if abnormality diagnosis is performed at such time, depending on the type of abnormality diagnosis, abnormalities affected by air-fuel ratio changes or rotation fluctuations caused by rich spike control The presence / absence of an abnormality is diagnosed based on the diagnosis parameter, and as a result, the abnormality diagnosis accuracy may be reduced and the reliability of the engine control system may be reduced.
[0019]
Therefore, the ECU 29 uses the abnormality diagnosis parameter that is affected by the rich spike control (that is, the abnormality diagnosis parameter that is affected by the change in the air-fuel ratio or the rotational fluctuation) during the rich spike control and for a predetermined period after the end of the rich spike control. Diagnosis, for example, misfire diagnosis, catalyst deterioration diagnosis, sensor abnormality diagnosis, fuel system abnormality diagnosis, etc., which will be described later, is prohibited, and abnormality diagnosis based on abnormality diagnosis parameters affected by rich spike control is prevented in advance. .
Hereinafter, specific processing contents of each routine executed by the ECU 29 will be described.
[0021]
[Fuel injection amount setting]
The fuel injection amount setting routine of FIG. 2 is a routine for setting the fuel injection amount TAU through air-fuel ratio F / B (feedback) control, and is executed at each fuel injection timing of each cylinder. When this routine is started, first, in step 101, the engine operating state (engine rotational speed Ne, intake pressure PM, cooling water temperature Tw, etc.) is read, and in the next step 102, the basic injection stored in advance in the ROM 31 is read. By searching the amount map, the basic injection amount Tp corresponding to the current engine speed Ne and the intake pressure PM is calculated. Thereafter, the routine proceeds to step 103, where it is determined whether the air-fuel ratio F / B condition is satisfied. Here, the air-fuel ratio F / B condition is that the cooling water temperature Tw is equal to or higher than a predetermined temperature, the operation state is not a high rotation / high load region, the air-fuel ratio sensor 25 is in an active state, etc. The air-fuel ratio F / B condition is satisfied when all the conditions are satisfied.
[0022]
If it is determined in step 103 that the air-fuel ratio F / B condition is not satisfied, the process proceeds to step 107, the air-fuel ratio correction coefficient FAF is set to “1.0”, and the process proceeds to step. In this case, the air-fuel ratio is not corrected.
[0023]
On the other hand, if it is determined in step 103 that the air-fuel ratio F / B condition is satisfied, the routine proceeds to step 104 where a target air-fuel ratio setting routine shown in FIG. 3 described later is executed to set the target air-fuel ratio AFTG. In step 105, the air-fuel ratio correction coefficient FAF is calculated based on the deviation between the actual air-fuel ratio AF detected by the air-fuel ratio sensor 25 and the target air-fuel ratio AFTG.
[0024]
Thereafter, the routine proceeds to step 106, where the basic injection amount Tp, the air-fuel ratio correction coefficient FAF, other correction coefficients FALL (various correction coefficients such as cooling water temperature and air conditioner load) and learning learned by a correction coefficient learning routine (not shown) are learned. Using the correction coefficient KG, the fuel injection amount TAU is calculated by the following equation, and this routine is terminated.
TAU = Tp × FAF × FALL × KG
[0025]
[Target air-fuel ratio setting]
Next, the processing contents of the target air-fuel ratio setting routine of FIG. 3 executed in step 104 of FIG. 2 will be described. This routine sets the time ratio between the lean operation time and the rich operation time so that the rich spike control is performed at a predetermined cycle during the lean operation (see FIG. 6), and the target for the lean operation and the rich operation This routine sets the air-fuel ratio AFTG, and plays a role corresponding to the rich spike control means in the claims.
[0026]
When this routine is started, first, at step 201, it is determined whether or not the value of the period counter for counting the lean operation time after the end of the previous rich spike control is “0” (that is, at the time of rich spike control end). If the cycle counter = 0, the routine proceeds to step 202, where the lean operation time TL and the rich operation time TR are set based on the engine speed Ne and the intake pressure PM. Here, the lean operation time TL and the rich operation time TR correspond to the number of fuel injections at the lean air-fuel ratio and the number of fuel injections at the rich air-fuel ratio, respectively. As the intake pressure PM is higher or the intake pressure PM is higher, the lean operation time TL and the rich operation time TR are set to larger values. In the present embodiment, the map of the rich operation time TR shown in FIG. 4 is searched, the rich operation time TR corresponding to the current engine speed Ne and the intake pressure PM is calculated, and a predetermined coefficient α is added to the rich operation time TR. To calculate the lean operation time TL.
TL = TR × α
[0027]
Here, the coefficient α may be a fixed value (for example, 50) in order to simplify the arithmetic processing, but may be varied according to the engine operating state (engine rotational speed Ne, intake pressure PM, etc.). After setting the lean operation time TL and the rich operation time TR in this way, the process proceeds to step 203.
[0028]
If the period counter has been incremented in the process up to the previous time (during lean operation), it is determined in step 201 that the period counter ≠ 0, the process of step 202 is skipped, and the process proceeds to step 203.
[0029]
During the lean operation, in step 203, the cycle counter is incremented by "1" to count the lean operation time, and in the next step 204, the value of the cycle counter corresponds to the lean operation time TL set in step 202 above. Determine if the value has been reached. If the value of the cycle counter has not reached the set lean operation time TL, the routine proceeds to step 205, where a map of the target air-fuel ratio AFTG shown in FIG. 5 is searched and the current engine speed Ne and intake pressure PM are determined. The target air-fuel ratio AFTG is calculated, and this routine is terminated. In this case, the target air-fuel ratio AFTG is set to a lean control value (for example, a value corresponding to air-fuel ratio = 20 to 23), and the lean operation is continued. However, the target air-fuel ratio AFTG is set to a value in the vicinity of stoichiometry when the conditions for performing lean operation are not satisfied, such as during transient operation.
[0030]
Thereafter, when the value of the cycle counter reaches the set lean operation time TL, the routine proceeds from step 204 to step 206, where the target air-fuel ratio AFTG is set to the rich control value. In this case, the target air-fuel ratio AFTG may be a fixed value for simplification of the arithmetic processing, but the target air-fuel ratio AFTG may be set by searching a map that uses the engine speed Ne and the intake pressure PM as parameters. good. When performing a map search, it is preferable to set the target air-fuel ratio AFTG so that the rich degree becomes stronger as the engine rotational speed Ne is higher or the intake pressure PM is higher.
[0031]
After setting the target air-fuel ratio AFTG, the routine proceeds to step 207, where the rich spike control flag XRS is set to “1” meaning execution of rich spike control, and then proceeds to step 208, where the value of the cycle counter is set to the lean operation time TL. It is determined whether or not the value corresponding to the total time “TL + TR” of the rich operation time TR has been reached. During the period counter <TL + TR (during rich spike control), this routine is terminated as it is, and then the period counter When it is determined that ≧ TL + TR (that is, when rich spike control is terminated), the process proceeds from step 208 to step 209, the cycle counter is cleared to “0”, and the rich spike control flag XRS is released. Is reset to “0”, meaning that the routine is terminated.
[0032]
As a result, as shown in FIG. 6, during the period of cycle counter = 0 to TL (period of time t1 to t2), the lean operation for lean control of the air-fuel ratio is performed to convert NOx in the exhaust gas to the NOx catalyst 24. Occlude. Then, during the period of period counter = TL to TL + TR (period of time t2 to t3), rich spike control for controlling the air-fuel ratio to rich is performed, and the NOx catalyst 24 is produced by rich components (HC, CO) in the exhaust gas. NOx is reduced and released.
[0033]
[Misfire diagnosis]
The misfire diagnosis routine of FIG. 7 is a routine for diagnosing the presence or absence of misfire of the engine 11 by comparing the crank angular speed fluctuation amount Δω with the misfire determination value, and corresponds to the abnormality diagnosis means described in claim 2 of the claims. To play a role. Hereinafter, the case of a 6-cylinder engine will be described.
[0034]
This routine is started by interruption processing every crank angle 60 ° C. When this routine is started, first, at step 301, a time T120 (i) required for the crankshaft to rotate at 120 ° C. is calculated as follows. The time from the previous interrupt time of this routine to the current interrupt time is calculated as the time T60 (i) required for the crankshaft to rotate at 60 ° C., and every time the interrupt timing of this routine reaches ATDC 60 ° C. T120 (i) is calculated by integrating the past two data of T60 (that is, every rotation of 120 ° C. A).
[0035]
After calculating T120 (i), the routine proceeds to step 302, where the current crank angular velocity ω (n) is calculated by the following equation.
ω (n) = (KDSOMG−ΔθnL) / T120 (i)
In the above equation, KDSOMG is a conversion coefficient for converting the rotation time into an angular velocity, and ΔθnL is a learned value learned by an inter-cylinder crank angular velocity deviation learning routine (not shown).
[0037]
Thereafter, the routine proceeds to step 303, where the crank angular speed fluctuation amount Δω (nA-1) is calculated by the following equation.
Δω (nA-1) = {ω (nA-2) −ω (nA-1)} − {ω (n−1) −ω (n)}
Here, A is set in the range of 0 to 5 (in the case of a 6-cylinder engine) so that the rotational fluctuation due to misfire appears largely in the crank angular speed fluctuation amount Δω (nA-1).
[0039]
Thereafter, the process proceeds to step 304, and it is determined whether or not the rich spike control is being performed or within a predetermined period from the end of the rich spike control. Here, whether or not the rich spike control is being performed is determined by whether or not the rich spike control flag XRS is set to “1”, and whether or not the rich spike control is within a predetermined period from the end of the rich spike control is determined. The determination may be made based on whether or not the control flag XRS is within a predetermined period after switching from “1” to “0”.
[0040]
Since this routine makes a misfire diagnosis using the crank angular speed fluctuation amount Δω (nA-1) in the next step 305, if a misfire diagnosis is made during rich spike control or immediately after the end of rich spike control, temporary rotation by rich spike control is performed. The presence or absence of misfire is diagnosed based on the crank angle speed fluctuation amount Δω (nA-1) affected by the fluctuation. Therefore, if it is determined in step 304 that the rich spike control is being performed or within the predetermined period from the end of the rich spike control, the process proceeds to step 307 without performing the subsequent misfire diagnosis processing. This prohibits misfire diagnosis and prevents the deterioration of misfire diagnosis accuracy due to the effect of rich spike control. The processing of step 304 plays a role corresponding to the abnormality diagnosis prohibiting means in the claims.
[0041]
If it is determined in step 304 that the rich spike control is not being performed and the rich spike control is not completed within the predetermined period, the process proceeds to a misfire diagnosis process in step 305, where the crank angular speed fluctuation amount Δω (nA-1) is It is determined whether or not it is larger than a predetermined misfire determination value REF1. If it is determined that the crank angular speed fluctuation amount Δω (nA-1) is larger than the misfire determination value REF1, it is determined that a misfire has occurred, and the routine proceeds to step 306, where the misfire counter CMIS (nA-1) is determined. Then, the process proceeds to step 307. If the count value of the misfire counter CMIS (nA-1) reaches a predetermined value, the catalyst 24 may be damaged due to misfire. Therefore, the misfire information is stored in the memory of the ECU 29 and a warning lamp (FIG. (Not shown) is lit or flashing to alert the driver.
[0042]
On the other hand, if it is determined that the crank angular speed fluctuation amount Δω (nA−1) is equal to or less than the misfire determination value REF1, it is determined that no misfire has occurred, and the process of step 306 is skipped and the process proceeds to step 307.
[0043]
In this step 307, crank angular velocity data ω (n-5), ω (n-4), ω (n-3), ω (n-2), ω (n-1) stored in the RAM 32 are The routine is completed after updating with ω (n-4), ω (n-3), ω (n-2), ω (n-1), and ω (n), respectively.
The technique related to the misfire diagnosis described above is described in detail in Japanese Patent Laid-Open No. 9-166042.
[0045]
[Catalyst deterioration diagnosis]
The catalyst deterioration diagnosis routine of FIG. 8 integrates the change width of the output voltage VOX2 of the oxygen sensor 26 on the downstream side of the catalyst 24, so that the diagnosis data ΣV (the oxygen sensor 26 of the oxygen sensor 26 reflects the amount of the purified gas component in the catalyst 24). This is a routine for determining the presence or absence of deterioration of the catalyst 24 by comparing the diagnosis data ΣV with a predetermined deterioration determination value and determining the presence or absence of deterioration of the catalyst 24. It plays a role corresponding to the means.
[0046]
This routine is executed every predetermined time (for example, every 64 ms). When this routine is started, first, at step 401, it is determined whether or not the catalyst temperature TCAT exceeds a deterioration diagnosis start temperature (for example, 150 ° C.). If not, the subsequent catalyst deterioration diagnosis process is performed. This routine is terminated. This is because when the catalyst temperature TCAT has not reached the deterioration diagnosis start temperature, the temperature of the oxygen sensor 26 is low and the sensor output VOX2 is not stable. This prevents a decrease in diagnostic accuracy.
[0047]
Then, when the catalyst temperature TCAT exceeds the deterioration diagnosis start temperature (for example, 150 ° C.), the routine proceeds to step 402, where it is determined whether or not the rich spike control is being performed or within the predetermined period from the end of the rich spike control. In this routine, in step 408 described later, since the catalyst deterioration diagnosis is performed using the diagnosis data ΣV calculated using the output voltage VOX2 of the oxygen sensor 26, the catalyst deterioration diagnosis is performed during the rich spike control or immediately after the end of the rich spike control. The presence or absence of deterioration of the catalyst 24 is diagnosed based on the diagnosis data ΣV affected by the temporary air-fuel ratio change (the output fluctuation of the oxygen sensor 26) by the rich spike control. Therefore, if it is determined in step 402 that the rich spike control is being performed or within the predetermined period from the end of the rich spike control, this routine is terminated as it is, the catalyst deterioration diagnosis is prohibited, and the catalyst deterioration due to the effect of the rich spike control is prohibited. Prevent degradation of diagnostic accuracy. The process of step 402 plays a role corresponding to the abnormality diagnosis prohibiting means in the claims.
[0048]
On the other hand, if it is determined in step 402 that the rich spike control is not being performed and the rich spike control is not completed within a predetermined period, the process proceeds to step 403, where diagnostic data ΣV1 (oxygen sensor 26 reflecting the amount of the purified gas component is reflected. Of the output voltage fluctuation) is calculated by the following equation.
ΣV1 (n) = ΣV1 (n-1) + | VOX2 (i) −VOX2 (i-1) |
[0049]
Here, VOX2 (i) is the output voltage of the oxygen sensor 26 during the current process, and VOX2 (i-1) is the output voltage of the oxygen sensor 26 during the previous process. The above equation calculates the locus length of the output voltage fluctuation of the oxygen sensor 26 by integrating the change width of the output voltage VOX2 of the oxygen sensor 26 downstream of the catalyst 24 at a predetermined sampling period (for example, 64 ms). The amount of the purified gas component is evaluated.
[0050]
Further, in this step 403, data ΣΔA / F · Q1 obtained by quantifying the catalyst inflow gas component fluctuation is calculated by the following equation.
ΣΔAF · Q1 (n) = ΣΔAF · Q1 (n-1) + Q × | AFTG-AF |
[0051]
Here, Q is an intake air flow rate, and is used as data substituting the exhaust gas flow rate. The above equation is expressed by the deviation | AFTG-AF | from the target air-fuel ratio AFTG of the air-fuel ratio AF detected by the air-fuel ratio sensor 25 upstream of the catalyst 24 in a predetermined sampling period (for example, 64 ms) and the exhaust gas flow rate (= intake air flow rate). Q) is multiplied and the multiplied values are integrated to obtain the data ΣΔAF · Q1 of the catalyst inflow gas component fluctuation.
[0052]
Thereafter, in step 404, it is determined whether or not a predetermined time (for example, 10 seconds) has elapsed from the start of calculation of the diagnostic data ΣV1 and ΣΔAF · Q1, and when ΣV1 and ΣΔAF · Q1 within the predetermined time are calculated, Proceeding to 405, the current ΣV1 is integrated with the previous ΣV1 integrated value ΣV to update ΣV, and the previous ΣΔAF · Q1 integrated value ΣΔAF · Q is integrated with the current ΣΔAF · Q1 to obtain ΣΔAF · Q. After updating, the process proceeds to step 406 and both ΣV1 and ΣΔAF · Q1 are cleared.
[0053]
Thereafter, the routine proceeds to step 407, where it is determined whether or not the catalyst temperature TCAT has exceeded a predetermined temperature (for example, 550 ° C.). If not, the routine is terminated without diagnosing the deterioration of the catalyst 24. When the catalyst temperature TCAT exceeds the predetermined temperature, the process proceeds to step 408, where diagnostic data ΣV (the locus length of the output voltage fluctuation of the oxygen sensor 26 on the downstream side of the catalyst 24) reflecting the amount of the purified gas component accumulated so far is obtained. ) Is larger than the deterioration determination value. This deterioration determination value is set according to ΣΔAF · Q using a data table stored in the ROM 31. If the diagnosis data ΣV is larger than the deterioration determination value, it is determined that the catalyst 24 has deteriorated (step 409), information on catalyst deterioration is stored in the memory of the ECU 29, and a warning lamp (not shown) is turned on or blinked. Warning the driver. On the other hand, when the diagnosis data ΣV is equal to or less than the deterioration determination value, it is determined as normal (step 410).
[0054]
The technology related to the catalyst deterioration diagnosis described above is described in detail in Japanese Patent Application Laid-Open No. 9-310612.
[0055]
In the catalyst deterioration diagnosis routine of FIG. 8 described above, the locus length of the output fluctuation of the oxygen sensor 26 on the downstream side thereof becomes longer with the deterioration of the catalyst 24 (the amplitude and frequency of the output fluctuation of the oxygen sensor 26 increase). Although the catalyst deterioration diagnosis is performed using the characteristics, other catalyst deterioration diagnosis methods include, for example, the following (1) to (4).
[0056]
(1) Method using area of sensor output (integrated value of difference between sensor output and target value)
When the amplitude and frequency of the output of the oxygen sensor 26 increase due to the deterioration of the catalyst 24, the catalyst 24 is utilized by utilizing the characteristic that the output area of the oxygen sensor 26 (the integrated value of the difference between the sensor output and the target value) increases. The presence or absence of deterioration is determined.
[0057]
(2) Method of using sensor output rich / lean reversal count (frequency, period)
When the catalyst 24 deteriorates, the frequency of the output of the oxygen sensor 26 (the number of rich / lean reversals) increases, and the presence or absence of deterioration of the catalyst 24 is determined using the characteristic that the cycle is shortened.
[0058]
(3) Method using amplitude of sensor output
When the catalyst 24 deteriorates, the presence or absence of deterioration of the catalyst 24 is determined using the characteristic that the amplitude of the output of the oxygen sensor 26 increases.
[0059]
(4) Method using sensor response delay time
When the catalyst 24 deteriorates, the storage amount (saturated adsorption amount of exhaust gas components) of the catalyst 24 decreases, and the exhaust gas components that pass through without being purified by the catalyst 24 increase. In this relationship, the response delay time from when the rich / lean of the target air-fuel ratio λTG is inverted to when the output of the oxygen sensor 26 is inverted becomes shorter as the catalyst 24 deteriorates. Therefore, the presence or absence of deterioration of the catalyst 24 can be determined based on whether or not the response delay time of the oxygen sensor 26 is equal to or less than a predetermined determination value.
[0060]
In the case of a system in which an air-fuel ratio sensor (linear A / F sensor) is provided downstream of the catalyst 24 instead of the oxygen sensor 26, catalyst deterioration diagnosis is performed based on the output of the air-fuel ratio sensor downstream of the catalyst 24. You can go. Further, in a system in which another catalyst is installed on the downstream side (or upstream side) of the NOx catalyst 24, deterioration diagnosis of the catalyst is performed based on the output of a sensor (air-fuel ratio sensor, oxygen sensor, etc.) on the downstream side of the catalyst. You may make it do.
[0061]
[Sensor abnormality diagnosis]
The sensor abnormality diagnosis routine of FIG. 9 obtains the change rate ΔI of the output of the air-fuel ratio sensor 25 after returning from the fuel cut (after restarting fuel injection) performed at the time of deceleration or the like, and uses the change rate ΔI as an abnormality determination value. It is a routine for diagnosing the presence or absence of abnormality of the air-fuel ratio sensor 25 as compared with Ifc, and plays a role corresponding to the abnormality diagnosis means described in claim 4 of the claims.
[0062]
This routine is executed every predetermined time or every predetermined crank angle. When this routine is started, first, at step 501, it is determined whether or not the fuel cut has been returned (fuel injection resumed). If the fuel cut has not been returned, the routine ends without performing the subsequent sensor abnormality diagnosis process. To do.
[0063]
Thereafter, when the fuel cut return is performed, the routine proceeds to step 502 where the output (hereinafter referred to as “sensor output”) I1 of the air-fuel ratio sensor 25 at the time of the fuel cut return is read and stored, and the timer is operated to operate the fuel. The elapsed time after cut recovery is counted.
[0064]
Thereafter, the process proceeds to step 503, and it is determined whether or not the rich spike control is being performed or within a predetermined period from the end of the rich spike control. In this routine, since sensor abnormality diagnosis is performed using the sensor output change rate ΔI in step 507 described later, if the sensor abnormality diagnosis is performed during rich spike control or immediately after the end of rich spike control, a temporary air-fuel ratio by rich spike control The presence or absence of abnormality of the air-fuel ratio sensor 25 is diagnosed based on the sensor output change rate ΔI affected by the change (the output fluctuation of the air-fuel ratio sensor 25). Therefore, if it is determined in step 503 that the rich spike control is being performed or within the predetermined period from the end of the rich spike control, this routine is ended as it is, the sensor abnormality diagnosis is prohibited, and the sensor abnormality due to the effect of the rich spike control is prohibited. Prevent degradation of diagnostic accuracy. The processing in step 503 plays a role corresponding to the abnormality diagnosis prohibiting means in the claims.
[0065]
On the other hand, if it is determined in step 503 that the rich spike control is not being performed and the rich spike control is not completed within the predetermined period, the process proceeds to step 504 to determine whether the sensor output has decreased to I2, When the sensor output has decreased to I2, the process proceeds to step 505, and after reading and storing the time T from the return of fuel cut until the sensor output decreases to I2, the process proceeds to step 506. The sensor output change rate ΔI is calculated by the following equation.
ΔI = (I2 -I1) / T
[0066]
Thereafter, the process proceeds to step 507, where the change rate ΔI of the sensor output calculated by the above equation is compared with the abnormality determination value Ifr. If the change rate ΔI of the sensor output is equal to or less than the abnormality determination value Ifr (| ΔI in the absolute value comparison) In the case of | ≧ | Ifr |), the response of the air-fuel ratio sensor 25 has not deteriorated and the sensor output is normal, and thus this routine ends. However, since the absolute value of the sensor output change rate ΔI decreases as the responsiveness of the air-fuel ratio sensor 25 deteriorates, the sensor output change rate ΔI becomes larger than the abnormality determination value Ifr (compare absolute values). If | ΔI | <| Ifr |), it is determined that the air-fuel ratio sensor 25 is abnormal (deteriorated). In this case, the process proceeds to step 508, where sensor abnormality information is stored in the memory of the ECU 29, and a warning lamp (not shown) is lit or blinked to warn the driver.
[0067]
The technology related to the sensor abnormality diagnosis described above is described in detail in Japanese Patent Application Laid-Open No. 8-177575.
The sensor to be subjected to abnormality diagnosis is not limited to the air-fuel ratio sensor 25 on the upstream side of the catalyst 24, but other sensors for detecting the air-fuel ratio or rich / lean of exhaust gas, such as the oxygen sensor 26 on the downstream side of the catalyst 24. You may make it perform abnormality diagnosis of.
[0069]
[Fuel system abnormality diagnosis]
The fuel system abnormality diagnosis parameter calculation routine of FIG. 10 obtains the abnormality diagnosis parameter DGDELAF based on the difference between the actual air-fuel ratio AF and the target air-fuel ratio AFTG, the air-fuel ratio correction coefficient FAF, and the learning correction coefficient KG, and smoothes this 11 is a routine for calculating the abnormality diagnosis parameter smoothed value DGDELAFSM. The fuel system abnormality diagnosis execution routine of FIG. 11 compares the abnormality diagnosis parameter smoothed value DGDELAFSM with the abnormality diagnosis reference value to determine whether there is an abnormality in the fuel system. A routine to diagnose. The fuel system abnormality diagnosis parameter calculation routine of FIG. 10 and the fuel system abnormality diagnosis execution routine of FIG. 11 play a role corresponding to the abnormality diagnosis means described in claim 5 of the claims.
[0070]
The fuel system abnormality diagnosis parameter calculation routine of FIG. 10 is executed at every predetermined crank angle. When this routine is started, first, at step 601, it is determined whether the air-fuel ratio feedback control is being performed (when the air-fuel ratio feedback condition is satisfied at step 103 in FIG. 2), and the air-fuel ratio feedback control is performed. If not, the process proceeds to Steps 604 and 605, where the abnormality diagnosis parameter DGDELAF and the abnormality diagnosis parameter smoothed value DGDELAFSM are both set to “1.0” meaning no abnormality, and this routine is terminated.
[0071]
On the other hand, when the air-fuel ratio feedback control is being performed, the routine proceeds to step 602, where (1) the difference between the actual air-fuel ratio AF detected by the air-fuel ratio sensor 25 and the target air-fuel ratio AFTG, and (2) the air-fuel ratio correction coefficient FAF are (3) The learning correction coefficient KG is summed to obtain the abnormality diagnosis parameter DGDELAF.
DGDELAF = (AF−AFTG) + FAF + KG
[0072]
Thereafter, the process proceeds to step 603, where the abnormality diagnosis parameter DGDELAF is subjected to a smoothing process according to the following equation to calculate an abnormality diagnosis parameter smoothed value DGDELAFSM.

In the above equation, the smoothing coefficient is 1/4, but may be 1/3, 1/6, 1/8, or the like.
[0074]
The fuel system abnormality diagnosis execution routine of FIG. 11 is executed every predetermined time. When this routine is started, first, in step 701, it is determined whether or not the state where the fuel system abnormality diagnosis execution condition is satisfied continues for a predetermined time (for example, 20 seconds). Here, the fuel system abnormality diagnosis execution condition is that the elapsed time after engine start exceeds a predetermined time (for example, 60 seconds), the air-fuel ratio feedback control is being performed, etc., and all these conditions are satisfied. If so, the fuel system abnormality diagnosis execution condition is satisfied.
[0075]
If it is determined in step 701 that the condition for executing the fuel system abnormality diagnosis has not been satisfied for a predetermined time (for example, 20 seconds), this routine is terminated without performing subsequent fuel system abnormality diagnosis processing. To do.
[0076]
Thereafter, when the fuel system abnormality diagnosis execution condition is satisfied for a predetermined time (for example, 20 seconds), the process proceeds from step 701 to step 702 to determine whether the rich spike control is being performed or within the predetermined period from the end of the rich spike control. Determine whether. In this routine, in step 703 and 706, which will be described later, the abnormality diagnosis of the fuel system is performed using the abnormality diagnosis parameter smoothed value DGDELAFS calculated using the actual air-fuel ratio AF. Therefore, during the rich spike control or immediately after the end of the rich spike control. If the abnormality diagnosis of the fuel system is performed, the presence or absence of abnormality of the fuel system is diagnosed based on the abnormality diagnosis parameter smoothed value DGDELAFS affected by the temporary air-fuel ratio change by the rich spike control. Therefore, if it is determined in step 702 that the rich spike control is being performed or within the predetermined period from the end of the rich spike control, this routine is ended as it is, the fuel system abnormality diagnosis is prohibited, and the fuel due to the influence of the rich spike control is determined. Prevents deterioration of system abnormality diagnosis accuracy. The processing in step 702 plays a role corresponding to the abnormality diagnosis prohibiting means in the claims.
[0077]
On the other hand, if it is determined in step 702 that the rich spike control is not being performed and the rich spike control is not completed within the predetermined period, the process proceeds to step 703 where the abnormality diagnosis parameter smoothed value DGDELAFSM is set to the rich abnormality diagnosis reference value. If DGDELAFSM ≦ tDFAFR (rich side abnormality) compared to tDFAFR, the process proceeds to step 704, where it is determined whether or not the rich side abnormality has continued for a predetermined time (for example, 20 seconds). Proceeding to step 705, the rich side abnormality of the fuel supply system is finally diagnosed, the rich side abnormality diagnosis flag DGFULRNG is set to “1” meaning the rich side abnormality, and in the next step 709, a warning lamp (Not shown) is lit or flashed to warn the driver and the ECU 29 memory is rich And stores the abnormality of information by terminating the program.
[0078]
If the rich-side abnormality does not continue for a predetermined time (for example, 20 seconds) in step 704, the present program is terminated without producing a final diagnosis result.
[0079]
If it is determined in step 703 that DGDELAFSM> tDFAFR (rich side normal), the process proceeds to step 706, where the abnormality diagnosis parameter smoothed value DGDELAFSM is compared with the lean side abnormality diagnosis reference value tDFAFL, and DGDELAFSM ≧ tDFAFL If (lean side abnormality), the process proceeds to step 707, where it is determined whether the lean side abnormality has continued for a predetermined time (for example, 20 seconds), and if the predetermined time continues, the process proceeds to step 708, and finally The lean side abnormality diagnosis flag DGFULLNG is set to “1” which means the lean side abnormality in the fuel supply system, and in the next step 709, the warning lamp is lit or blinked to inform the driver. A warning is made and information on the rich side abnormality is stored in the memory of the ECU 29, and this program is executed. To completion.
[0080]
In step 706, if the lean-side abnormality does not continue for a predetermined time (for example, 20 seconds), this program is terminated without giving a final diagnosis result.
The technology related to the sensor abnormality diagnosis described above is described in detail in Japanese Patent Application Laid-Open No. 11-82117.
[0082]
According to this embodiment described above, misfire diagnosis, catalyst deterioration diagnosis, sensor abnormality diagnosis, and fuel system abnormality diagnosis that are affected by rich spike control are prohibited during rich spike control execution and within a predetermined period from the end of rich spike control. Therefore, it is possible to prevent abnormality diagnosis based on abnormality diagnosis parameters affected by temporary air-fuel ratio change and rotation fluctuation by rich spike control, and the accuracy of each abnormality diagnosis And the reliability of the engine control system can be improved.
[0083]
In the above-described embodiment, abnormality diagnosis is not performed even if other abnormality diagnosis execution conditions are satisfied during execution of rich spike control and within a predetermined period from the end of rich spike control. In this case, the abnormality diagnosis may be performed on the condition that another abnormality diagnosis execution condition is satisfied after the prohibition of the abnormality diagnosis is canceled after a lapse of a predetermined period from the end of the rich spike control. However, when other abnormality diagnosis execution conditions are satisfied during execution of rich spike control and within a predetermined period from the end of rich spike control, the execution of abnormality diagnosis is delayed, and an abnormality occurs after the predetermined period has elapsed from the end of rich spike control. Diagnosis may be performed.
[0084]
In the above embodiment, the present invention is applied to a system that performs all of misfire diagnosis, catalyst deterioration diagnosis, sensor abnormality diagnosis, and fuel system abnormality diagnosis. However, one or more abnormality diagnosis among these abnormality diagnosis is performed. The present invention may be applied to a system to be implemented, and the abnormality diagnosis method may be appropriately changed. Furthermore, the present invention may be applied to a system that performs another abnormality diagnosis that is affected by a temporary air-fuel ratio change or rotation fluctuation by rich spike control. Further, the present invention may limit the period during which abnormality diagnosis is prohibited (or delayed) only during rich spike control.
[0085]
In addition to the lean burn engine, the present invention can be applied to an engine equipped with a catalyst that needs to reduce and purify stored NOx by rich spike control, such as a direct injection engine.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment of the present invention.
FIG. 2 is a flowchart showing a flow of processing of a fuel injection amount setting routine.
FIG. 3 is a flowchart showing a process flow of a target air-fuel ratio setting routine.
FIG. 4 is a diagram conceptually showing a calculation map of rich operation time TR.
FIG. 5 is a diagram conceptually showing a calculation map of a target air-fuel ratio AFTG.
FIG. 6 is a time chart showing air-fuel ratio and cycle counter behavior.
FIG. 7 is a flowchart showing the flow of processing of a misfire diagnosis routine.
FIG. 8 is a flowchart showing a flow of processing of a catalyst deterioration diagnosis routine.
FIG. 9 is a flowchart showing a process flow of a sensor abnormality diagnosis routine.
FIG. 10 is a flowchart showing the flow of processing of a fuel system abnormality diagnosis parameter calculation routine.
FIG. 11 is a flowchart showing a flow of processing of a fuel system abnormality diagnosis execution routine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 20 ... Fuel injection valve, 23 ... Exhaust pipe, 24 ... NOx catalyst, 25 ... Air-fuel ratio sensor, 26 ... Oxygen sensor (downstream sensor), 29 ... ECU (rich spike control means, abnormality) Diagnosis means, abnormality diagnosis prohibition means).

Claims (4)

Rich spike control means for performing rich spike control for temporarily controlling the air-fuel ratio to the rich side during lean operation of the internal combustion engine in order to reduce and purify nitrogen oxides stored in the catalyst provided in the exhaust passage of the internal combustion engine; ,
An abnormality diagnosis means for diagnosing the presence or absence of an abnormality in the engine control system;
An abnormality diagnosis prohibiting unit that prohibits or delays a predetermined abnormality diagnosis by the abnormality diagnosis unit during the rich spike control and / or during a predetermined period after the rich spike control ends , and
The control apparatus for an internal combustion engine, wherein the abnormality diagnosis means diagnoses the presence or absence of misfire based on a rotational fluctuation of the internal combustion engine. Rich spike control means for performing rich spike control for temporarily controlling the air-fuel ratio to the rich side during lean operation of the internal combustion engine in order to reduce and purify nitrogen oxides stored in the catalyst provided in the exhaust passage of the internal combustion engine; ,
An abnormality diagnosis means for diagnosing the presence or absence of an abnormality in the engine control system;
An abnormality diagnosis prohibiting means for prohibiting or delaying a predetermined abnormality diagnosis by the abnormality diagnosis means during the rich spike control and / or during a predetermined period after the rich spike control ends;
A downstream sensor for detecting the air-fuel ratio or rich / lean of the exhaust gas downstream of the catalyst ;
With
The abnormality diagnosis means, the control device of the internal combustion engine you wherein diagnosing the presence or absence of deterioration of the catalyst based on the output of the downstream sensor. The control apparatus for an internal combustion engine according to claim 1 or 2 , wherein the abnormality diagnosis means diagnoses the presence or absence of abnormality of a sensor that detects an air-fuel ratio or rich / lean of exhaust gas of the internal combustion engine. The abnormality diagnosis means, the control device for an internal combustion engine according to any of claims 1 to 3, characterized in that detects the presence of a failure in the fuel system.

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