JP2016056753A - Air-fuel ratio sensor diagnostic device for internal combustion engine - Google Patents

Air-fuel ratio sensor diagnostic device for internal combustion engine Download PDF

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JP2016056753A
JP2016056753A JP2014184676A JP2014184676A JP2016056753A JP 2016056753 A JP2016056753 A JP 2016056753A JP 2014184676 A JP2014184676 A JP 2014184676A JP 2014184676 A JP2014184676 A JP 2014184676A JP 2016056753 A JP2016056753 A JP 2016056753A
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fuel ratio
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catalyst
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真二郎 石田
Shinjiro Ishida
真二郎 石田
鴨志田　平吉
Heikichi Kamoshita
平吉 鴨志田
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Hitachi Astemo Ltd
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Hitachi Automotive Systems Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide an air-fuel ratio sensor diagnostic device for an internal combustion engine capable of accurately diagnosing an offset failure of the air-fuel ratio sensor irrespective of deterioration of a catalyst.SOLUTION: In-catalyst oxygen storage amount estimation part 103 estimates an in-catalyst oxygen storage amount on the basis of signals from a pre-catalyst air-fuel ratio sensor measuring part 101, an intake air amount measuring part 102, and in-catalyst central air-fuel ratio estimation part 107. An oxygen storage amount correction part 116 calculates an in-catalyst oxygen storage amount on the basis of the in-catalyst oxygen storage amount and a correction value from a catalyst deterioration index part 114. A target air-fuel ratio correction amount calculation part 108 calculates a target air-fuel ratio correction amount from the in-catalyst oxygen storage amount and an oxygen sensor signal correction value on the basis of a proportional portion correction value PB from the correction value calculation part 105, an integration portion correction value IB from the correction value calculation part 106 and an in-catalyst central air-fuel ratio CNTABF from an in-catalyst central air-fuel ratio estimation part 107. A pre-catalyst air-fuel ratio sensor offset failure first determination part 112 determines a pre-catalyst air-fuel ratio sensor offset failure on the basis of the calculated target air-fuel ratio correction amount.SELECTED DRAWING: Figure 5

Description

本発明は、内燃機関の空燃比センサ診断装置に関する。   The present invention relates to an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine.

自動車の内燃機関における有害排気ガスを減少させ、かつ燃費や運転性を向上させるための手段として、エンジン等の内燃機関の排気ガス成分に関する情報によって、空燃比を制御するフィードバック方式の空燃比制御装置が実用化されている。   As a means for reducing harmful exhaust gas in an internal combustion engine of an automobile and improving fuel efficiency and drivability, a feedback type air-fuel ratio control apparatus that controls the air-fuel ratio based on information on exhaust gas components of an internal combustion engine such as an engine Has been put to practical use.

上記の空燃比制御装置において、排気ガス成分の異常や、制御システム上での異常は、使用されるセンサ、例えば空燃比センサ（ＬＡＦセンサ）自身の故障や劣化により発生することがあり、空燃比制御を適正に行うことができない場合が生じる。   In the above air-fuel ratio control apparatus, an abnormality in the exhaust gas component or an abnormality in the control system may occur due to a failure or deterioration of a sensor used, for example, an air-fuel ratio sensor (LAF sensor) itself. There are cases where control cannot be performed properly.

特に、上記のＬＡＦセンサは、エンジンの排気を直接受ける位置に設置されるため、高温、高圧や振動の影響、粗悪燃料等の影響を受け、劣化し易い傾向がある。また、多気筒エンジンの場合、他の気筒のサイクルの影響を受けるため、極めて正確な検出精度を有している必要がある。   In particular, the LAF sensor is installed at a position that directly receives engine exhaust, and therefore tends to be easily deteriorated due to the influence of high temperature, high pressure, vibration, and bad fuel. In the case of a multi-cylinder engine, since it is affected by the cycle of other cylinders, it needs to have extremely accurate detection accuracy.

特に、北米向けの自動車は、ＯＢＤII規制（車載自己診断装置の装着を義務付けた法律）に対応する必要があり、上記ＬＡＦセンサに排気規制値の１．５倍を超えるような故障が発生した場合、速やかに運転者に異常を警告し、修理を促す必要がある。   In particular, North American automobiles must comply with the OBDII regulations (laws requiring the installation of on-board self-diagnosis devices), and the LAF sensor has a failure that exceeds 1.5 times the exhaust emission control value. It is necessary to promptly warn the driver of the abnormality and prompt repair.

したがって、ＬＡＦセンサの検出精度が何らかの原因で低下した時には、ＬＡＦセンサの交換等の適切な処置を施す必要がある。このため、ＬＡＦセンサの異常状態を判定するために、触媒の下流側に配置された酸素センサからの出力信号に基づいて、ＬＡＦセンサの異常状態判定を行う手段が知られている。   Therefore, when the detection accuracy of the LAF sensor decreases for some reason, it is necessary to take an appropriate measure such as replacement of the LAF sensor. For this reason, in order to determine the abnormal state of the LAF sensor, means for determining the abnormal state of the LAF sensor based on an output signal from an oxygen sensor arranged on the downstream side of the catalyst is known.

特許文献１には、触媒前に配置されたＬＡＦセンサの出力信号と空気流量とに基づいて触媒内の酸素蓄積量を演算し、該酸素蓄積量と触媒後に配置された酸素センサの出力信号とに基づいて、ＬＡＦセンサの故障モードであるオフセット故障を判定する診断装置が開示されている。   In Patent Document 1, an oxygen accumulation amount in the catalyst is calculated based on an output signal of an LAF sensor disposed before the catalyst and an air flow rate, and the oxygen accumulation amount and an output signal of an oxygen sensor disposed after the catalyst are calculated. Based on the above, a diagnostic device for determining an offset failure which is a failure mode of the LAF sensor is disclosed.

また、特許文献２には、燃料カットから燃料リカバまでの計測時間と燃料リカバ後の触媒後に設置された酸素センサの出力信号の上昇勾配に基づいて、ＬＡＦセンサの故障を判定する診断装置が開示されている。   Further, Patent Document 2 discloses a diagnostic device for determining a failure of a LAF sensor based on a measurement time from a fuel cut to a fuel recovery and an ascending gradient of an output signal of an oxygen sensor installed after the catalyst after the fuel recovery. Has been.

特開２０１２−２２９６５９号公報JP 2012-229659 A 特開２０１１−１２２４７０号公報JP 2011-122470 A

しかしながら、従来技術における空燃比センサ診断装置にあっては、触媒後に配置された酸素センサが触媒劣化による影響を受け、酸素センサの特性に影響を及ぼした場合には、正確にＬＡＦセンサのオフセット故障を判定することが出来ない。   However, in the conventional air-fuel ratio sensor diagnostic apparatus, when the oxygen sensor disposed after the catalyst is affected by the catalyst deterioration and affects the characteristics of the oxygen sensor, the LAF sensor offset failure is accurately detected. Cannot be determined.

本発明の目的は、触媒の劣化に関わらず、空燃比センサのオフセット故障を正確に診断可能な内燃機関の空燃比センサ診断装置を実現することである。   An object of the present invention is to realize an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine that can accurately diagnose an offset failure of an air-fuel ratio sensor regardless of catalyst deterioration.

本発明は、上記目的を達成するため、次のように構成される。   In order to achieve the above object, the present invention is configured as follows.

内燃機関の空燃比センサ診断装置において、内燃機関の排気系に設けられた触媒と、触媒の上流側に配置された空燃比センサから出力される空燃比を検出する触媒前空燃比計測部と、上記触媒の下流側に配置され触媒からの排気の酸素濃度を検出する触媒後酸素計測部と、上記内燃機関の吸入空気量を計測する吸入空気量計測部と、上記触媒内の中心空燃比を推定する触媒内中心空燃比推定部と、上記触媒前空燃比計測部により計測された空燃比、上記吸入空気量計測部により計測された吸入空気量、及び上記触媒内中心空燃比推定部により推定された触媒内の中心空燃比に基づいて触媒内酸素蓄積量を推定する触媒内酸素蓄積量推定部と、上記内燃機関の燃料カット時間と燃料リカバ時の空燃比リッチ時間と上記触媒後酸素信号計測部が計測した空燃比とに基づいて触媒劣化指標を算出する触媒劣化指標部と、上記触媒劣化指標部が算出した触媒劣化指標に基づいて触媒後酸素計測部が計測した酸素濃度信号を補正する酸素濃度信号補正部と、上記触媒劣化指標部が算出した触媒劣化指標に基づいて上記触媒の酸素貯積量を補正する酸素貯積量補正部と、上記酸素貯積量補正部が補正した触媒の酸素貯積量及び上記酸素濃度信号補正部が補正した酸素濃度信号に基づいて、比例分補正値及び積分分補正値を演算し、演算した比例分補正値及び積分分補正値と、上記触媒内中心空燃比推定部が推定した触媒内中心空燃比とに基づいて目標空燃比補正量を演算する空燃比補正部と、上記触媒内中心空燃比推定部が推定した触媒内中心空燃比に基づいて、空燃比の上下限を演算する上下限判定値演算部と、上記空燃比補正部が演算した目標空燃比補正量及び上記上下限判定値演算部が演算した上下限に基づいて上記空燃比センサのオフセット故障を判定する第１判定部と、を備える。   In the air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, a catalyst provided in an exhaust system of the internal combustion engine, a pre-catalyst air-fuel ratio measurement unit that detects an air-fuel ratio output from an air-fuel ratio sensor disposed upstream of the catalyst, A post-catalyst oxygen measurement unit that is disposed downstream of the catalyst and detects the oxygen concentration of exhaust gas from the catalyst, an intake air amount measurement unit that measures the intake air amount of the internal combustion engine, and a central air-fuel ratio in the catalyst Estimated by the in-catalyst center air-fuel ratio estimating unit, the air-fuel ratio measured by the pre-catalyst air-fuel ratio measuring unit, the intake air amount measured by the intake air amount measuring unit, and the in-catalyst center air-fuel ratio estimating unit An in-catalyst oxygen accumulation amount estimation unit for estimating the oxygen accumulation amount in the catalyst based on the central air-fuel ratio in the catalyst, the fuel cut time of the internal combustion engine, the air-fuel ratio rich time during fuel recovery, and the post-catalyst oxygen signal The measuring unit measures A catalyst deterioration index unit that calculates a catalyst deterioration index based on the air-fuel ratio, and an oxygen concentration signal that corrects the oxygen concentration signal measured by the post-catalyst oxygen measurement unit based on the catalyst deterioration index calculated by the catalyst deterioration index unit A correction unit, an oxygen storage amount correction unit for correcting the oxygen storage amount of the catalyst based on the catalyst deterioration index calculated by the catalyst deterioration index unit, and an oxygen storage amount of the catalyst corrected by the oxygen storage amount correction unit. Based on the product amount and the oxygen concentration signal corrected by the oxygen concentration signal correction unit, a proportional correction value and an integral correction value are calculated, and the calculated proportional correction value and integral correction value are calculated. An air-fuel ratio correction unit that calculates a target air-fuel ratio correction amount based on the in-catalyst center air-fuel ratio estimated by the fuel ratio estimation unit, and an in-catalyst center air-fuel ratio estimation unit that estimates the air-fuel ratio correction amount. Up and down to calculate the upper and lower limits of the fuel ratio A determination value calculation unit; a first determination unit that determines an offset failure of the air-fuel ratio sensor based on a target air-fuel ratio correction amount calculated by the air-fuel ratio correction unit and an upper / lower limit calculated by the upper / lower limit determination value calculation unit; .

触媒の劣化に関わらず、空燃比センサのオフセット故障を正確に診断可能な内燃機関の空燃比センサ診断装置を実現することができる。   An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine that can accurately diagnose an offset failure of an air-fuel ratio sensor regardless of catalyst deterioration can be realized.

本発明が適用される内燃機関システムの概略構成図である。1 is a schematic configuration diagram of an internal combustion engine system to which the present invention is applied. 本発明の実施例１を含めた空燃比フィードバック制御のブロック図である。It is a block diagram of air-fuel ratio feedback control including Example 1 of the present invention. ＬＡＦセンサのオフセットずれの吸収動作を示す図である。It is a figure which shows the absorption operation | movement of the offset shift | offset | difference of a LAF sensor. 触媒劣化時のＬＡＦセンサオフセット故障の動作を示す図である。It is a figure which shows the operation | movement of the LAF sensor offset failure at the time of catalyst deterioration. 本発明の実施例１におけるＬＡＦセンサ診断部１００の内部ブロック図である。It is an internal block diagram of the LAF sensor diagnostic part 100 in Example 1 of this invention. 本発明の実施例１における動作フローチャートである。It is an operation | movement flowchart in Example 1 of this invention. 本発明の実施例２におけるＬＡＦセンサ診断部の内部ブロック図である。It is an internal block diagram of the LAF sensor diagnostic part in Example 2 of this invention.

以下、添付図面を参照して、本発明に実施形態による内燃機関の空燃比センサ診断装置を説明する。   Hereinafter, an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to an embodiment of the present invention will be described with reference to the accompanying drawings.

（実施例１）
図１は、本発明が適用される内燃機関システムの概略構成図である。図１において、内燃機関システムは、内燃機関と、吸気系と、排気系とを備える。内燃機関には点火装置３０１、燃料噴射装置３０２および回転数検出装置３０３が取り付けられている。 (Example 1)
FIG. 1 is a schematic configuration diagram of an internal combustion engine system to which the present invention is applied. In FIG. 1, the internal combustion engine system includes an internal combustion engine, an intake system, and an exhaust system. An ignition device 301, a fuel injection device 302, and a rotation speed detection device 303 are attached to the internal combustion engine.

エアークリーナ３００から流入される空気は、スロットルバルブ３１３で流量を調節された後、流量検出手段３０４で流量が計測され、燃料噴射装置３０２から所定の角度で噴射される燃料と混合されて各気筒３１４に供給される。   The air flowing in from the air cleaner 300 is adjusted in flow rate by the throttle valve 313, then the flow rate is measured by the flow rate detecting means 304, and mixed with the fuel injected at a predetermined angle from the fuel injection device 302, and then in each cylinder. 314 is supplied.

また、排気系には、空燃比センサ３０５、三元触媒３０６が取り付けられており、排気ガスは三元触媒３０６で浄化された後に、大気に排出される。空燃比センサ３０５は三元触媒３０６の上流側（排気ガスの流れ方向上流）に配置されている。   In addition, an air-fuel ratio sensor 305 and a three-way catalyst 306 are attached to the exhaust system, and the exhaust gas is purified by the three-way catalyst 306 and then discharged to the atmosphere. The air-fuel ratio sensor 305 is disposed upstream of the three-way catalyst 306 (upstream in the exhaust gas flow direction).

内燃機関制御装置３０７は、流量検出手段３０４の出力信号Ｑａと、回転数検出手段３０３によってリングギアまたはプレート３０８の回転数Ｎｅとを取り込み、燃料噴射量Ｔｉを計算し、燃料噴射装置の噴射量を制御する。   The internal combustion engine control device 307 takes in the output signal Qa of the flow rate detection means 304 and the rotation speed Ne of the ring gear or the plate 308 by the rotation speed detection means 303, calculates the fuel injection amount Ti, and calculates the injection amount of the fuel injection device. To control.

また、内燃機関制御装置３０７は、内燃機関内の空燃比を空燃比センサ３０５から検出し、内燃機関内の空燃比を理論空燃比になるように燃料噴射量Ｔｉを補正する空燃比フィードバック制御を行う。また、触媒後の空燃比を酸素センサ３１５で検出する。   Further, the internal combustion engine control device 307 detects air / fuel ratio in the internal combustion engine from the air / fuel ratio sensor 305, and performs air / fuel ratio feedback control for correcting the fuel injection amount Ti so that the air / fuel ratio in the internal combustion engine becomes the stoichiometric air / fuel ratio. Do. Further, the air / fuel ratio after the catalyst is detected by the oxygen sensor 315.

一方、燃料タンク３０９内の燃料は、燃料ポンプ３１０によって、吸引・加圧された後、プレッシャーレギュレータ３１１を備えた燃料管３１２を通って燃料噴射装置３０２の燃料入口に導かれ、余分な燃料は、燃料タンク３０９に戻される。   On the other hand, the fuel in the fuel tank 309 is sucked and pressurized by the fuel pump 310, and then led to the fuel inlet of the fuel injection device 302 through the fuel pipe 312 having the pressure regulator 311. And returned to the fuel tank 309.

以上が、本発明が適用される内燃機関システムである。   The above is the internal combustion engine system to which the present invention is applied.

図２は、本発明の実施例１を含めた空燃比フィードバック制御のブロック図である。図２において、通常、三元触媒３０６による排気浄化システムでは、触媒３０６の前、つまり上流側に配置されたＬＡＦセンサ３０５の信号を用いて、ＰＩ制御等を行うＬＡＦセンサ制御部３０７２の制御動作により、触媒３０６前の空燃比を目標空燃比（理論空燃比ｅｔｃ）に制御している。その際、触媒３０６の後、つまり下流側に配置されたＯ２センサ３１５の信号により、目標空燃比を補正することによって、ＬＡＦセンサ３０５の検出ずれを吸収する。また、目標空燃比演算部３０７３が触媒３０６の要求する空燃比（触媒内中心空燃比）に目標空燃比を合わせることにより、より的確な空燃比フィードバック制御を実現する。そして、燃料噴射制御部３０７１がエンジン４００における燃料噴射量を制御する。 FIG. 2 is a block diagram of air-fuel ratio feedback control including the first embodiment of the present invention. In FIG. 2, normally, in the exhaust purification system using the three-way catalyst 306, the control operation of the LAF sensor control unit 3072 that performs PI control or the like using the signal of the LAF sensor 305 disposed before the catalyst 306, that is, upstream. Thus, the air-fuel ratio before the catalyst 306 is controlled to the target air-fuel ratio (theoretical air-fuel ratio etc). At this time, the detection deviation of the LAF sensor 305 is absorbed by correcting the target air-fuel ratio by the signal of the O 2 sensor 315 disposed after the catalyst 306, that is, downstream. Further, the target air-fuel ratio calculation unit 3073 matches the target air-fuel ratio to the air-fuel ratio required by the catalyst 306 (in-catalyst center air-fuel ratio), thereby realizing more accurate air-fuel ratio feedback control. Then, the fuel injection control unit 3071 controls the fuel injection amount in the engine 400.

空燃比フィードバック制御を実現する手段として、Ｏ２センサ３１５を用いた制御であるリアＯ２センサ制御がある。これは、本発明に係るＬＡＦセンサ診断部１００によって実行される。したがって、まず、前提となるリアＯ２センサ制御について説明する。 As means for realizing air-fuel ratio feedback control, there is rear O 2 sensor control which is control using an O 2 sensor 315. This is executed by the LAF sensor diagnostic unit 100 according to the present invention. Therefore, the rear O 2 sensor control as a premise will be described first.

リアＯ２センサ制御の目的の一つとして、ＬＡＦセンサ３０５のオフセットずれの吸収がある。 One of the purposes of rear O 2 sensor control is to absorb offset deviation of the LAF sensor 305.

図３は、ＬＡＦセンサ３０５のオフセットずれの吸収動作を示す図であり、縦軸は検出空燃比を示し、横軸は実空燃比を示す。   FIG. 3 is a diagram illustrating an offset shift absorption operation of the LAF sensor 305, in which the vertical axis indicates the detected air-fuel ratio and the horizontal axis indicates the actual air-fuel ratio.

図３において、正規の特性（実線で示す）に、オフセットずれが発生すると、仮に実空燃比が１４．７の場合、動作点がａ点に移動し、ＬＡＦセンサ制御で、ｂ点になるように制御される（破線図示）。しかし、実空燃比はｃ点（実線上）の値であるため、このｃ点の空燃比が、リアＯ２センサの信号に現れてくる。 In FIG. 3, if an offset deviation occurs in the normal characteristic (shown by a solid line), if the actual air-fuel ratio is 14.7, the operating point moves to point a, and the LAF sensor control is set to point b. (The broken line is shown). However, since the actual air-fuel ratio is a value at point c (on the solid line), the air-fuel ratio at point c appears in the signal of the rear O 2 sensor.

本発明においては、このリアＯ２センサ信号を活用し、目標空燃比を補正することで、オフセットずれを吸収し、あたかもオフセットずれが無いセンサを使用しているような制御を行う。 In the present invention, this rear O 2 sensor signal is utilized to correct the target air-fuel ratio, thereby performing control such that an offset deviation is absorbed and a sensor having no offset deviation is used.

リアＯ２センサ制御のもう一つの目的は、触媒３０６の状況に応じて、目標空燃比を補正することにある。その方法として、リアＯ２センサの制御動作において、触媒内酸素蓄積量を推定し、その結果から、触媒内中心空燃比を演算する。通常の三元触媒の場合、空燃比を理論空燃比１４．７に制御することが望ましいが、運転領域や、触媒の劣化、活性状態により、必ずしも、空燃比を１４．７に制御することが良いとは限らない。 Another purpose of the rear O 2 sensor control is to correct the target air-fuel ratio in accordance with the state of the catalyst 306. As the method, in the control operation of the rear O 2 sensor, the oxygen accumulation amount in the catalyst is estimated, and the central air-fuel ratio in the catalyst is calculated from the result. In the case of an ordinary three-way catalyst, it is desirable to control the air-fuel ratio to the stoichiometric air-fuel ratio of 14.7. However, the air-fuel ratio may not necessarily be controlled to 14.7 depending on the operation region, catalyst deterioration, and active state. Not necessarily good.

そこで、リアＯ２センサの制御動作内で、触媒３０６内の酸素蓄積量を推定し、触媒３０６の状況に応じて、最も排気浄化率が高い空燃比（触媒内中心空燃比）を演算し、目標空燃比を補正することで、最良の空燃比フィードバック制御を実現する。 Therefore, within the control operation of the rear O 2 sensor, the amount of oxygen accumulated in the catalyst 306 is estimated, and the air-fuel ratio (in-catalyst center air-fuel ratio) with the highest exhaust purification rate is calculated according to the state of the catalyst 306, The best air-fuel ratio feedback control is realized by correcting the target air-fuel ratio.

次に、上記制御を前提として、本発明の実施例１についてのさらなる説明を行う。   Next, further description will be given of the first embodiment of the present invention based on the above control.

図２に戻るが、ＬＡＦセンサ３０５のオフセット故障は、オフセットずれの過度の状態であり、前述したように、リアＯ２センサ制御の動作自体に、オフセットずれを吸収する機能が備わっているため、リアＯ２センサ制御動作内のパラメータをモニタすることで、オフセット故障を検出することができる。そこで、次に、触媒３０６の劣化により触媒後酸素センサ３１５が影響を受けた場合においても、オフセット故障を正確に検知可能であることについて説明する。 Returning to FIG. 2, the offset failure of the LAF sensor 305 is an excessive state of offset deviation, and as described above, the operation of the rear O 2 sensor control itself has a function of absorbing the offset deviation. An offset failure can be detected by monitoring the parameters in the rear O 2 sensor control operation. Therefore, next, it will be described that the offset failure can be accurately detected even when the post-catalyst oxygen sensor 315 is affected by the deterioration of the catalyst 306.

図４は、触媒劣化時のＬＡＦセンサオフセット故障の動作を示す図である。   FIG. 4 is a diagram illustrating the operation of the LAF sensor offset failure during catalyst deterioration.

図４において、ＬＡＦセンサオフセット故障時は、触媒を介して、リア酸素センサ信号ＶＯ２Ｒに、その影響が出やすくなり、比例分補正値ＰＢ、積分分補正値ＩＢが変化し、結果として、リアＯ２センサ制御の出力値である目標空燃比補正量ＴＡＢＦＲＯ２が変化する。 In FIG. 4, when the LAF sensor offset failure occurs, the rear oxygen sensor signal VO2R is easily influenced through the catalyst, and the proportional correction value PB and the integral correction value IB change. The target air-fuel ratio correction amount TABFRO2 that is the output value of the two- sensor control changes.

したがって、目標空燃比演算において目標空燃比が補正され、ＬＡＦセンサ制御により、ＬＡＦセンサ信号ＲＡＢＦが実空燃比に制御される。つまり、ＬＡＦセンサ信号ＲＡＢＦのオフセット故障分が、ＴＡＢＦＲＯ２に反映される。よって、目標空燃比補正量ＴＡＢＦＲＯ２をモニタすることでＬＡＦセンサオフセット故障の診断を行うことができる。   Therefore, the target air-fuel ratio is corrected in the target air-fuel ratio calculation, and the LAF sensor signal RABF is controlled to the actual air-fuel ratio by LAF sensor control. That is, the offset failure of the LAF sensor signal RABF is reflected in TABFRO2. Therefore, the LAF sensor offset failure can be diagnosed by monitoring the target air-fuel ratio correction amount TABFRO2.

触媒劣化時は、リアＯ２センサ信号ＶＯ２Ｒの特性が変化するため、燃料カット時にリアＯ２センサ信号ＶＯ２Ｒの出力がリーン出力となった後、燃料リカバ時に目標空燃比をリッチ側となるように制御し、リアＯ２センサ信号計測手段の出力がリッチに反転するまでの時間に応じた補正値を算出し、リアＯ２センサ信号ＶＯ２Ｒの補正を行い、目標空燃比補正量ＴＡＢＦＲＯ２をモニタすることで診断を行うことができる。 Since the characteristic of the rear O 2 sensor signal VO2R changes when the catalyst is deteriorated, the target air-fuel ratio is set to the rich side during fuel recovery after the output of the rear O 2 sensor signal VO2R becomes a lean output when the fuel is cut. Controlling, calculating a correction value according to the time until the output of the rear O 2 sensor signal measuring means is richly inverted, correcting the rear O 2 sensor signal VO2R, and monitoring the target air-fuel ratio correction amount TABFRO2. Diagnosis can be made with

図５は、本発明の実施例１におけるＬＡＦセンサ診断部１００の内部ブロック図である。   FIG. 5 is an internal block diagram of the LAF sensor diagnostic unit 100 according to the first embodiment of the present invention.

図５において、触媒前空燃比センサ信号計測部１０１は、触媒前ＬＡＦセンサ３０５からの出力信号ＲＡＢＦに基づいて触媒前空燃比を計測する。また、吸入空気量計測部１０２は、内燃機関に吸入される空気量ＱＡＲを計測する。   In FIG. 5, the pre-catalyst air-fuel ratio sensor signal measuring unit 101 measures the pre-catalyst air-fuel ratio based on the output signal RABF from the pre-catalyst LAF sensor 305. The intake air amount measuring unit 102 measures an air amount QAR taken into the internal combustion engine.

触媒内酸素蓄積量推定部１０３は、触媒前空燃比センサ信号計測部１０１から供給される触媒前空燃比と、吸入空気量計測部１０２からの供給される吸入空気量と、触媒内中心空燃比推定部１０７から供給される触媒内中心空燃比とから、触媒内酸素蓄積量を推定する。   The in-catalyst oxygen accumulation amount estimation unit 103 includes a pre-catalyst air-fuel ratio supplied from the pre-catalyst air-fuel ratio sensor signal measurement unit 101, an intake air amount supplied from the intake air amount measurement unit 102, and an in-catalyst center air-fuel ratio. From the in-catalyst center air-fuel ratio supplied from the estimation unit 107, the in-catalyst oxygen accumulation amount is estimated.

触媒後酸素センサ信号計測部１０４は、触媒後酸素センサ３１５から供給される信号ＶＯ２Ｒから触媒後の酸素濃度を計測する。また、触媒劣化指標部１１４は、触媒後酸素センサ信号計測部１０４の結果（リッチ応答時間）から、酸素センサ信号補正値を演算する。   The post-catalyst oxygen sensor signal measurement unit 104 measures the post-catalyst oxygen concentration from the signal VO2R supplied from the post-catalyst oxygen sensor 315. Further, the catalyst deterioration indicator 114 calculates an oxygen sensor signal correction value from the result (rich response time) of the post-catalyst oxygen sensor signal measurement unit 104.

酸素センサ信号補正部１１５は、触媒劣化指標部１１４からの酸素センサ信号補正値と、触媒後酸素センサ信号計測部１０４からの酸素濃度とから、酸素センサ信号の補正後の出力値を演算する。酸素貯積量補正部１１６は、触媒劣化指標部１１４からの補正値と、触媒内酸素蓄積量推定部１０３からの触媒内酸素蓄積量とから酸素貯積量補正後の出力値を演算する。触媒劣化指標部１１４は、内燃機関の燃料カット時に触媒後酸素計測部１０２の出力がリーン出力となった後、燃料リカバ時に目標空燃比がリッチ側になるように触媒劣化指標を演算し、触媒後酸素計測部１０２の出力がリッチ側に反転するまでの時間を算出する。   The oxygen sensor signal correction unit 115 calculates the corrected output value of the oxygen sensor signal from the oxygen sensor signal correction value from the catalyst deterioration index unit 114 and the oxygen concentration from the post-catalyst oxygen sensor signal measurement unit 104. The oxygen storage amount correction unit 116 calculates an output value after the oxygen storage amount correction from the correction value from the catalyst deterioration indicator unit 114 and the in-catalyst oxygen storage amount estimation unit 103. The catalyst deterioration index unit 114 calculates the catalyst deterioration index so that the target air-fuel ratio becomes rich during fuel recovery after the output of the post-catalyst oxygen measurement unit 102 becomes lean output when the fuel of the internal combustion engine is cut. The time until the output of the post oxygen measuring unit 102 is reversed to the rich side is calculated.

比例分補正値演算部１０５は、酸素蓄積量補正部１１６から供給される触媒内酸素蓄積量と、酸素センサ信号補正部１１５から供給される触媒後酸素濃度とから、比例分補正値を演算する。   The proportional correction value calculation unit 105 calculates a proportional correction value from the in-catalyst oxygen accumulation amount supplied from the oxygen accumulation amount correction unit 116 and the post-catalyst oxygen concentration supplied from the oxygen sensor signal correction unit 115. .

また、積分分補正値演算部１０６は、酸素蓄積量補正部１１６から供給される触媒内酸素蓄積量と、酸素センサ信号補正部１１５から供給される触媒後酸素濃度とから積分分補正値を演算する。また、触媒内中心空燃比推定部１０７は、酸素蓄積量補正部１１６から供給される触媒内酸素蓄積量（酸素貯積量）と、酸素センサ信号補正部１１５から供給される触媒後酸素濃度とから、触媒内中心空燃比の推定値を演算する。   The integral correction value calculation unit 106 calculates an integral correction value from the in-catalyst oxygen accumulation amount supplied from the oxygen accumulation amount correction unit 116 and the post-catalyst oxygen concentration supplied from the oxygen sensor signal correction unit 115. To do. Further, the in-catalyst center air-fuel ratio estimation unit 107 includes the in-catalyst oxygen accumulation amount (oxygen storage amount) supplied from the oxygen accumulation amount correction unit 116 and the post-catalyst oxygen concentration supplied from the oxygen sensor signal correction unit 115. From this, the estimated value of the center air-fuel ratio in the catalyst is calculated.

また、目標空燃比補正量演算部１０８は、比例分補正値演算部１０５からの比例分補正値と、積分分補正値演算部１０６からの積分分補正値と、触媒内中心空燃比推定部１０７からの触媒内中心空燃比と、から目標空燃比補正量を演算する。   Further, the target air-fuel ratio correction amount calculation unit 108 includes a proportional correction value from the proportional correction value calculation unit 105, an integral correction value from the integral correction value calculation unit 106, and an in-catalyst center air-fuel ratio estimation unit 107. The target air-fuel ratio correction amount is calculated from the in-catalyst center air-fuel ratio.

なお、比例分補正値演算部１０５と、積分分補正値演算部１０６と、目標空燃比補正量演算部１０８とにより空燃比補正部１２０が形成される。   The proportional correction value calculation unit 105, the integral correction value calculation unit 106, and the target air / fuel ratio correction amount calculation unit 108 form an air / fuel ratio correction unit 120.

上限判定値演算部１０９は、触媒内中心空燃比推定部１０７から供給される触媒内中心空燃比から、上限判定値を演算する。また、下限判定値演算部１１０は、触媒内中心空燃比推定部１０７から供給される触媒内中心空燃比から、空燃比の下限判定値を演算する。上限判定値演算部１０９及び下限判定値演算部１１０により上下限判定値演算部が形成される。   The upper limit determination value calculation unit 109 calculates an upper limit determination value from the in-catalyst center air-fuel ratio estimation unit 107 supplied from the in-catalyst center air-fuel ratio estimation unit 107. The lower limit determination value calculation unit 110 calculates the lower limit determination value of the air-fuel ratio from the in-catalyst center air-fuel ratio supplied from the in-catalyst center air-fuel ratio estimation unit 107. The upper limit determination value calculation unit 109 and the lower limit determination value calculation unit 110 form an upper and lower limit determination value calculation unit.

診断領域判定部１１１は、空燃比センサの診断を実行すべき領域であるか否か（水温、エンジン回転数が診断を実行するのに適切な領域であるか否か）を判断し、その判断信号を触媒前空燃比センサオフセット故障第１判定部１１２及び触媒前空燃比センサオフセット故障第２判定部１１３に供給する。   The diagnosis area determination unit 111 determines whether or not the air-fuel ratio sensor should be diagnosed (whether the water temperature and the engine speed are appropriate areas for executing the diagnosis), and the determination. The signal is supplied to the pre-catalyst air / fuel ratio sensor offset failure first determination unit 112 and the pre-catalyst air / fuel ratio sensor offset failure second determination unit 113.

触媒前空燃比センサオフセット故障第１判定部１１２は、上限判定値演算部１０９から供給される上限判定値と、下限判定値演算部１１０から供給される下限判定値と、診断領域判定部１１１から供給される診断実行判定結果と、目標空燃比補正量補正量演算部１０８から供給される目標空燃比補正量とから、触媒前空燃比センサのオフセット故障を判定する。   The pre-catalyst air-fuel ratio sensor offset failure first determination unit 112 receives an upper limit determination value supplied from the upper limit determination value calculation unit 109, a lower limit determination value supplied from the lower limit determination value calculation unit 110, and a diagnosis region determination unit 111. An offset failure of the pre-catalyst air-fuel ratio sensor is determined from the diagnosis execution determination result supplied and the target air-fuel ratio correction amount supplied from the target air-fuel ratio correction amount correction unit 108.

また、触媒前空燃比センサオフセット故障第２判定部１１３でも、診断領域判定部１１１から供給される診断実行判定結果と、触媒内中心空燃比推定部１０７から供給される触媒内中心空燃比とから、触媒前空燃比センサ３０５のオフセット故障を判定する。   The pre-catalyst air / fuel ratio sensor offset failure second determination unit 113 also uses the diagnosis execution determination result supplied from the diagnosis region determination unit 111 and the in-catalyst center air / fuel ratio supplied from the in-catalyst center air / fuel ratio estimation unit 107. The offset failure of the pre-catalyst air-fuel ratio sensor 305 is determined.

なお、図５に示した、触媒前空燃比センサ信号計測部１０１、吸入空気量計測部１０２、触媒内酸素蓄積量推定部１０３、触媒後酸素センサ信号計測部１０４、比例分補正値演算部１０５、積分分補正値演算部１０６、触媒内中心空燃比推定部１０７、目標空燃比補正量演算部１０８は、図２に示したリアＯ２制御部に対応する。 Note that the pre-catalyst air-fuel ratio sensor signal measuring unit 101, the intake air amount measuring unit 102, the in-catalyst oxygen accumulation amount estimating unit 103, the post-catalyst oxygen sensor signal measuring unit 104, and the proportional correction value calculating unit 105 shown in FIG. The integral correction value calculation unit 106, the in-catalyst center air-fuel ratio estimation unit 107, and the target air-fuel ratio correction amount calculation unit 108 correspond to the rear O 2 control unit shown in FIG.

また、図５に示した、上限判定値演算部１０９、下限判定値演算部１１０、断領域判定部１１１、触媒前空燃比センサオフセット故障第１判定部１１２、触媒前空燃比センサオフセット故障第２判定部１１３、触媒劣化指標部１１４、酸素センサ信号補正部１１５、酸素貯積量補正部１１６は、図２に示した触媒前ＬＡＦセンサオフセット故障診断部に対応する。   Further, the upper limit determination value calculation unit 109, the lower limit determination value calculation unit 110, the disconnection region determination unit 111, the pre-catalyst air-fuel ratio sensor offset failure first determination unit 112, the pre-catalyst air-fuel ratio sensor offset failure second shown in FIG. The determination unit 113, the catalyst deterioration indicator unit 114, the oxygen sensor signal correction unit 115, and the oxygen storage amount correction unit 116 correspond to the pre-catalyst LAF sensor offset failure diagnosis unit shown in FIG.

図６は、本発明の実施例１における動作フローチャートである。   FIG. 6 is an operation flowchart according to the first embodiment of the present invention.

図６のステップ７０１で、触媒前ＬＡＦセンサ信号計測部１０１が触媒前ＬＡＦセンサ信号ＲＡＢＦを計測する。次に、ステップ７０２で、吸入空気量計測部１０２が吸入空気量ＱＡＲを計測する。そして、ステップ７０３で、触媒内酸素蓄積量推定部１０３が、触媒前空燃比センサ信号ＲＡＢＦF、触媒内中心空燃比推定値ＣＮＴＡＢＦ、吸入空気量ＱＡＲから、触媒内酸素蓄積量ＯＳＥＳＴを演算する。   In step 701 in FIG. 6, the pre-catalyst LAF sensor signal measurement unit 101 measures the pre-catalyst LAF sensor signal RABF. Next, in step 702, the intake air amount measuring unit 102 measures the intake air amount QAR. In step 703, the in-catalyst oxygen accumulation amount estimation unit 103 calculates the in-catalyst oxygen accumulation amount OSEST from the pre-catalyst air / fuel ratio sensor signal RABFF, the in-catalyst center air / fuel ratio estimated value CNTABF, and the intake air amount QAR.

算出式は（ＯＳＥＳＴ＝ＯＳＥＳＴold＋（ＲＡＢＦ−ＣＮＴＡＢＦold）×ＱＡＲ）である。ただし、ＯＳＥＳＴold、ＣＮＴＡＢＦoldは、前回おけるＯＳＥＳＴ、ＣＮＴＡＢＦそれぞれの値である。   The calculation formula is (OEST = OESTold + (RABF−CNTABold) × QAR). However, OSESTold and CNTABFold are the values of OSEST and CNTABF in the previous time, respectively.

続いて、ステップ７０４で、触媒後酸素センサ信号計測部１０４が触媒後酸素センサ信号ＶＯ２Ｒを計測する。そして、ステップ７０５で、触媒劣化指標部１１４が、燃料カットから燃料リカバ時における触媒後酸素センサ信号ＶＯ２Ｒの応答時間から触媒劣化指標値ＣＡＴＶＡを演算する。ステップ７０５においては、リッチ応答時間に対する触媒劣化指標値ＣＡＴＶＡのテーブルがある。   Subsequently, in step 704, the post-catalyst oxygen sensor signal measurement unit 104 measures the post-catalyst oxygen sensor signal VO2R. In step 705, the catalyst deterioration index unit 114 calculates a catalyst deterioration index value CATVA from the response time of the post-catalyst oxygen sensor signal VO2R during the fuel recovery from the fuel cut. In step 705, there is a table of the catalyst deterioration index value CATVA for the rich response time.

次に、ステップ７０６で、酸素蓄積量補正部１１６が、触媒劣化指標値ＣＡＴＶＡと触媒内酸素蓄積量ＯＳＥＳＴとから酸素貯積量補正値ＯＳＥＳＴＮを演算する（ＯＳＥＳＴＮ＝ＯＳＥＳＴ＊ＣＡＴＶＡ）。そして、ステップ７０７で、酸素センサ信号補正部１１５は、触媒劣化指標値ＣＡＴＶＡと触媒後酸素センサ信号ＶＯ２Ｒとから酸素センサ信号補正値ＶＯ２ＲＮを演算する（ＶＯ２ＲＮ＝ＶＯ２Ｒ＊ＣＡＴＶＡ）。   Next, in step 706, the oxygen accumulation amount correction unit 116 calculates an oxygen storage amount correction value OSESTN from the catalyst deterioration index value CATVA and the in-catalyst oxygen accumulation amount OSEST (OSESTN = OSEST * CATVA). In step 707, the oxygen sensor signal correction unit 115 calculates an oxygen sensor signal correction value VO2RN from the catalyst deterioration index value CATVA and the post-catalyst oxygen sensor signal VO2R (VO2RN = VO2R * CATVA).

次に、ステップ７０８で、比例分補正値演算部１０５が、酸素貯積量補正値ＯＳＥＳＴＮと、酸素センサ信号補正値ＶＯ２ＲＮとから、比例分補正値ＰＢを演算する。そして、ステップ７０９で、積分分補正値演算部１０６が、酸素貯積量補正値ＯＳＥＳＴＮと、酸素センサ信号補正値ＶＯ２ＲＮとから、積分分補正値ＩＢを演算する。   Next, in step 708, the proportional correction value calculator 105 calculates the proportional correction value PB from the oxygen storage amount correction value OSESTN and the oxygen sensor signal correction value VO2RN. In step 709, the integral correction value calculator 106 calculates an integral correction value IB from the oxygen storage amount correction value OSESTN and the oxygen sensor signal correction value VO2RN.

次に、ステップ７１０で、触媒内中心空燃比推定部１０７が、酸素貯積量補正値ＯＳＥＳＴＮと、酸素センサ信号補正値ＶＯ２ＲＮとから、触媒内中心空燃比ＣＮＴＡＢＦを演算する。そして、ステップ７１１で、目標空燃比補正量演算部１０８が、比例分補正値ＰＢと、積分分補正値ＩＢと、触媒内中心空燃比ＣＮＴＡＢＦとを加算し、目標空燃比補正量ＴＡＢＦＲＯ２を演算する。   Next, in step 710, the in-catalyst center air-fuel ratio estimation unit 107 calculates the in-catalyst center air-fuel ratio CNTABF from the oxygen storage amount correction value OSESTN and the oxygen sensor signal correction value VO2RN. In step 711, the target air-fuel ratio correction amount calculation unit 108 adds the proportional correction value PB, the integral correction value IB, and the in-catalyst center air-fuel ratio CNTABF, and calculates the target air-fuel ratio correction amount TABFRO2. .

次に、ステップ７１２で、積分分補正値ＩＢ、触媒内中心空燃比ＣＮＴＡＢＦ、酸素貯積量補正値ＯＳＥＳＴＮの前回値を、それぞれ、ＩＢold、ＣＮＴＡＢＦold、ＯＳＥＳＴＮoldとする。そして、ステップ７１３で、触媒内中心空燃比ＣＮＴＡＢＦの加重平均値または学習値をＣＮＴＡＢＦＬＴとする。ステップ７１２、７１３における演算は、必要なパラメータを入力可能とすれば、目標空燃比補正量演算部１０８にて実行可能である。   Next, in step 712, the previous values of the integral correction value IB, the in-catalyst center air-fuel ratio CNTABF, and the oxygen storage amount correction value OSESTN are set to IBold, CNTABFold, and OSESTNold, respectively. In step 713, the weighted average value or learned value of the catalyst center air-fuel ratio CNTABF is set to CNTABFLT. The calculation in steps 712 and 713 can be executed by the target air-fuel ratio correction amount calculation unit 108 if necessary parameters can be input.

次に、ステップ７１４で、上限判定値演算部１０９が、上限判定値を加重平均値または学習値ＣＮＴＡＢＦＬＴから演算する。ＣＮＴＡＢＦＬＴは目標空燃比補正量演算部１０８から上限判定値演算部１０９に供給可能である。次に、ステップ７１５で、下限判定値演算部１１０が、下限判定値を加重平均値または学習値ＣＮＴＡＢＦＬＴから演算する。ＣＮＴＡＢＦＬＴは目標空燃比補正量演算部１０８から下限判定値演算部１１０に供給可能である。   Next, in step 714, the upper limit determination value calculation unit 109 calculates the upper limit determination value from the weighted average value or the learned value CNTABFLT. CNTABFLT can be supplied from the target air-fuel ratio correction amount calculation unit 108 to the upper limit determination value calculation unit 109. Next, in step 715, the lower limit determination value calculation unit 110 calculates the lower limit determination value from the weighted average value or the learned value CNTABFLT. CNTABFLT can be supplied from the target air-fuel ratio correction amount calculation unit 108 to the lower limit determination value calculation unit 110.

次に、ステップ７１６で、診断領域判定部１１１は、ＬＡＦセンサ３０５を診断すべき診断領域か否かをチェックする。診断領域であれば、ステップ７１７に進む。ステップ７１６で診断領域外であれば、診断は実行しない。   Next, in step 716, the diagnosis area determination unit 111 checks whether the LAF sensor 305 is a diagnosis area to be diagnosed. If it is a diagnostic region, the process proceeds to step 717. If it is outside the diagnosis area in step 716, the diagnosis is not executed.

ステップ７１７において、触媒前空燃比センサオフセット故障第１判定部１１２は、上限判定値演算部１０９が演算した上限判定値より目標空燃比補正量ＴＡＢＦＲＯ２が大か否かを判断する。また、ステップ７１７においては、触媒前空燃比センサオフセット故障第１判定部１１２は、下限判定値演算部１１０が演算した下限判定値より目標空燃比補正量ＴＡＢＦＲＯ２が小か否かを判断する。   In step 717, the pre-catalyst air-fuel ratio sensor offset failure first determination unit 112 determines whether or not the target air-fuel ratio correction amount TABFRO2 is larger than the upper limit determination value calculated by the upper limit determination value calculation unit 109. In step 717, the pre-catalyst air-fuel ratio sensor offset failure first determination unit 112 determines whether or not the target air-fuel ratio correction amount TABFRO2 is smaller than the lower limit determination value calculated by the lower limit determination value calculation unit 110.

ステップ７１７の条件が成立（ＴＡＢＦＯ２が上限判定値より大 またはＴＡＢＦＯ２が下限判定値より小）するとき、ステップ７１９に進み、触媒前空燃比センサオフセット故障第１判定部１１２はオフセット故障と判定する。   When the condition of step 717 is satisfied (TABFO2 is larger than the upper limit determination value or TABFO2 is smaller than the lower limit determination value), the process proceeds to step 719, and the pre-catalyst air / fuel ratio sensor offset failure first determination unit 112 determines that the offset is faulty.

ステップ７１７の条件が不成立のときは、ステップ７１８に進み、触媒前空燃比センサオフセット故障第２判定部１１３は、触媒内中心空燃比ＣＮＴＡＢＦが定数１より小か否か、または定数２より大か否かをチェックする。ステップ７１８の条件が成立（ＣＮＴＡＢＦが定数２より大 または、ＣＮＴＡＢＦが定数１より小）のとき、ステップ７１９で、オフセット故障と判定する。ステップ７１８の条件が不成立の時は、ステップ７２０で、ＯＫと判定する。   When the condition of step 717 is not satisfied, the routine proceeds to step 718, where the pre-catalyst air-fuel ratio sensor offset failure second determination unit 113 determines whether the in-catalyst center air-fuel ratio CNTABF is smaller than the constant 1 or larger than the constant 2. Check whether or not. When the condition in step 718 is satisfied (CNTABF is greater than constant 2 or CNTABF is less than constant 1), it is determined in step 719 that an offset failure has occurred. When the condition of step 718 is not satisfied, it is determined as OK at step 720.

ステップ７１８における定数１、定数２は、触媒内中心空燃比が一定の範囲内であるか否かを判定するための数値であって、任意に設定可能である。   The constants 1 and 2 in step 718 are numerical values for determining whether or not the in-catalyst center air-fuel ratio is within a certain range, and can be arbitrarily set.

また、ステップ７１９において、オフセット故障と判定したときは、エンジンチェックランプを点灯させる等のアラームを出力させることが可能である。   If it is determined in step 719 that an offset failure has occurred, an alarm such as turning on the engine check lamp can be output.

以上のように、本発明の実施例１においては、触媒後の酸素センサ３１５からの信号と、触媒内酸素蓄積量とに基づいて、触媒前空燃比センサ３０５のオフセット故障を判断し、空燃比センサ３０５がオフセット故障を発生したと判断したときは、酸素センサ３１５からの信号に基づいて、空燃比センサ３０５の補正値を算出して、空燃比センサ３０５の信号を補正し、空燃比を制御するように構成されている。   As described above, in the first embodiment of the present invention, the offset failure of the pre-catalyst air-fuel ratio sensor 305 is determined based on the signal from the post-catalyst oxygen sensor 315 and the amount of oxygen accumulated in the catalyst, and the air-fuel ratio is determined. When the sensor 305 determines that an offset failure has occurred, the correction value of the air-fuel ratio sensor 305 is calculated based on the signal from the oxygen sensor 315, the signal of the air-fuel ratio sensor 305 is corrected, and the air-fuel ratio is controlled. Is configured to do.

触媒の劣化に関わらず、空燃比センサのオフセット故障を正確に診断可能な内燃機関の空燃比センサ診断装置を実現することができる。   An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine that can accurately diagnose an offset failure of an air-fuel ratio sensor regardless of catalyst deterioration can be realized.

また、空燃比センサのオフセット故障が発生した場合であっても、実際の空燃比を演算して、演算した空燃比で内燃機関を制御することが可能であり、燃費や運転性を向上することが可能である。   In addition, even when an offset failure of the air-fuel ratio sensor occurs, it is possible to calculate the actual air-fuel ratio and control the internal combustion engine with the calculated air-fuel ratio, improving fuel efficiency and drivability Is possible.

（実施例２）
次に、本発明の実施例２について説明する。 (Example 2)
Next, a second embodiment of the present invention will be described.

図７は、本発明の実施例２におけるＬＡＦセンサ診断部１００の内部ブロック図である。図５に示した本発明の実施例１におけるＬＡＦセンサ診断部１００の内部ブロック図と、図７に示した内部ブロック図との相違点は、図５に示されていた酸素センサ信号補正部１１５及び酸素貯積量補正部１１６は、図７のブロック図では省略されている。そして、図５には示されていない目標空燃比補正量マップ補正部１１７が図７に示すブロック図に追加されている。他の構成部分は図５と図７とは共通する。   FIG. 7 is an internal block diagram of the LAF sensor diagnostic unit 100 according to the second embodiment of the present invention. The difference between the internal block diagram of the LAF sensor diagnosis unit 100 in the first embodiment of the present invention shown in FIG. 5 and the internal block diagram shown in FIG. 7 is that the oxygen sensor signal correction unit 115 shown in FIG. The oxygen storage amount correction unit 116 is omitted in the block diagram of FIG. A target air-fuel ratio correction amount map correction unit 117 not shown in FIG. 5 is added to the block diagram shown in FIG. Other components are the same as those in FIGS.

図７において、目標空燃比補正量マップ補正部１１７は、触媒劣化指標部１１４からの酸素センサ信号補正値に基づいてマップ補正値を演算する。   In FIG. 7, the target air-fuel ratio correction amount map correction unit 117 calculates a map correction value based on the oxygen sensor signal correction value from the catalyst deterioration index unit 114.

比例分補正値演算部１０５は、触媒内酸素蓄積量推定部１０３からの触媒内酸素蓄積量と、触媒後酸素センサ信号計測部１０２からの触媒後酸素濃度と、目標空燃比補正量マップ補正部１１７からのマップ補正信号とから、比例分補正値を演算する。   The proportional correction value calculation unit 105 includes an in-catalyst oxygen accumulation amount from the in-catalyst oxygen accumulation amount estimation unit 103, a post-catalyst oxygen concentration from the post-catalyst oxygen sensor signal measurement unit 102, and a target air-fuel ratio correction amount map correction unit. From the map correction signal from 117, a proportional correction value is calculated.

積分分補正値演算部１０６は、触媒内酸素蓄積量推定部１０３からの触媒内酸素蓄積量と、触媒後酸素センサ信号計測部１０２からの触媒後酸素濃度と、目標空燃比補正量マップ補正部１１７からのマップ補正信号とから、積分分補正値を演算する。   The integral correction value calculation unit 106 includes an in-catalyst oxygen accumulation amount from the in-catalyst oxygen accumulation amount estimation unit 103, a post-catalyst oxygen concentration from the post-catalyst oxygen sensor signal measurement unit 102, and a target air-fuel ratio correction amount map correction unit. An integral correction value is calculated from the map correction signal from 117.

触媒内中心空燃比推定部１０７は、触媒内酸素蓄積量推定部１０３からの触媒内酸素蓄積量と、触媒後酸素センサ信号計測部１０２からの触媒後酸素濃度と、目標空燃比補正量マップ補正部１１７からのマップ補正信号とから、触媒内中心空燃比を演算する。   The in-catalyst center air-fuel ratio estimation unit 107 includes the in-catalyst oxygen accumulation amount from the in-catalyst oxygen accumulation amount estimation unit 103, the after-catalyst oxygen concentration from the after-catalyst oxygen sensor signal measurement unit 102, and the target air-fuel ratio correction amount map correction. From the map correction signal from the unit 117, the center air-fuel ratio in the catalyst is calculated.

図７に示した他の構成部分は、図５に示した構成部分と同等であるので、詳細な説明は省略する。   The other components shown in FIG. 7 are the same as the components shown in FIG.

本発明の実施例２における動作フローは、図６に示したステップ７０６及び７０７が不要となり、これらに代えて、目標空燃比補正量マップ補正部１１７の動作を行うステップを加入したフローとなる。   The operation flow in the second embodiment of the present invention does not require the steps 706 and 707 shown in FIG. 6, and instead includes a flow in which a step of operating the target air-fuel ratio correction amount map correction unit 117 is added.

本発明の実施例２においては、酸素センサ信号補正値と目標空燃比補正量との関係を予め定めたマップにより、触媒劣化指標部１１４からの酸素センサ信号補正値に基づいて目標空燃比補正量を算出する構成となっている。   In Embodiment 2 of the present invention, the target air-fuel ratio correction amount is determined based on the oxygen sensor signal correction value from the catalyst deterioration indicator 114 by using a map in which the relationship between the oxygen sensor signal correction value and the target air-fuel ratio correction amount is determined in advance. Is calculated.

本発明の実施例２においても、実施例１と同様な効果を得ることができる。   In the second embodiment of the present invention, the same effect as in the first embodiment can be obtained.

１００：ＬＡＦセンサ診断部、１０１：触媒前酸素センサ信号計測部、１０２：触媒後酸素センサ信号計測部、１０３：触媒内酸素蓄積量推定部、１０４：触媒後酸素センサ信号計測部、１０５：比例分補正値演算部、１０６：積分分補正値演算部、１０７：触媒内中心空燃比推定部、１０８：目標空燃比補正量演算部、１０９：上限判定値演算部、１１０：下限判定値演算部、１１１：診断領域判定部、１１２：触媒前空燃比センサオフセット故障第１判定部、１１３：触媒前空燃比センサオフセット故障第２判定部、１１４：触媒劣化指標部、１１５：酸素センサ信号補正部、１１６：酸素貯積量補正部、１１７：マップ補正部、１２０：空燃比補正部、３００：エアークリーナ、３０１：点火装置、３０２：燃料噴射装置、３０３：回転数検出装置、３０４：流量検出装置、３０５：触媒前酸素センサ、３０６：触媒、３０７：内燃機関制御装置、３０８：プレートまたはリングギア、３０９：燃料タンク、３１０：燃料ポンプ、３１１：プレッシャーレギュレータ、３１２：燃料管、３１３：スロットルバルブ、３１４：気筒、３１５：触媒後酸素センサ、４００：エンジン、３０７１：燃料噴射制御部、３０７２：ＬＡＦセンサ制御部、３０７３：目標空燃比演算部   100: LAF sensor diagnosis unit, 101: Pre-catalyst oxygen sensor signal measurement unit, 102: Post-catalyst oxygen sensor signal measurement unit, 103: In-catalyst oxygen accumulation amount estimation unit, 104: Post-catalyst oxygen sensor signal measurement unit, 105: Proportional Minute correction value calculation unit, 106: integral correction value calculation unit, 107: central air-fuel ratio estimation unit in catalyst, 108: target air-fuel ratio correction amount calculation unit, 109: upper limit determination value calculation unit, 110: lower limit determination value calculation unit 111: Diagnostic region determination unit 112: Pre-catalyst air / fuel ratio sensor offset failure first determination unit 113: Pre-catalyst air / fuel ratio sensor offset failure second determination unit 114: Catalyst deterioration indicator unit 115: Oxygen sensor signal correction unit 116: oxygen storage amount correction unit, 117: map correction unit, 120: air-fuel ratio correction unit, 300: air cleaner, 301: ignition device, 302: fuel injection device, 303: times Number detection device, 304: Flow rate detection device, 305: Pre-catalyst oxygen sensor, 306: Catalyst, 307: Internal combustion engine control device, 308: Plate or ring gear, 309: Fuel tank, 310: Fuel pump, 311: Pressure regulator, 312: Fuel pipe, 313: Throttle valve, 314: Cylinder, 315: Oxygen sensor after catalyst, 400: Engine, 3071: Fuel injection control unit, 3072: LAF sensor control unit, 3073: Target air-fuel ratio calculation unit

Claims (10)

内燃機関の排気系に設けられた触媒と、
上記触媒の上流側に配置された空燃比センサから出力される空燃比を検出する触媒前空燃比計測部と、
上記触媒の下流側に配置され触媒からの排気の酸素濃度を検出する触媒後酸素計測部と、
上記内燃機関の吸入空気量を計測する吸入空気量計測部と、
上記触媒内の中心空燃比を推定する触媒内中心空燃比推定部と、
上記触媒前空燃比計測部により計測された空燃比、上記吸入空気量計測部により計測された吸入空気量、及び上記触媒内中心空燃比推定部により推定された触媒内の中心空燃比に基づいて触媒内酸素蓄積量を推定する触媒内酸素蓄積量推定部と、
上記内燃機関の燃料カット時間と燃料リカバ時の空燃比リッチ時間と上記触媒後酸素信号計測部が計測した空燃比とに基づいて触媒劣化指標を算出する触媒劣化指標部と、
上記触媒劣化指標部が算出した触媒劣化指標に基づいて触媒後酸素計測部が計測した酸素濃度信号を補正する酸素濃度信号補正部と、
上記触媒劣化指標部が算出した触媒劣化指標に基づいて上記触媒の酸素貯積量を補正する酸素貯積量補正部と、
上記酸素貯積量補正部が補正した触媒の酸素貯積量及び上記酸素濃度信号補正部が補正した酸素濃度信号に基づいて、比例分補正値及び積分分補正値を演算し、演算した比例分補正値及び積分分補正値と、上記触媒内中心空燃比推定部が推定した触媒内中心空燃比とに基づいて目標空燃比補正量を演算する空燃比補正部と、
上記触媒内中心空燃比推定部が推定した触媒内中心空燃比に基づいて、空燃比の上下限を演算する上下限判定値演算部と、
上記空燃比補正部が演算した目標空燃比補正量及び上記上下限判定値演算部が演算した上下限に基づいて上記空燃比センサのオフセット故障を判定する第１判定部と、
を備えることを特徴とする内燃機関の空燃比センサ診断装置。 A catalyst provided in the exhaust system of the internal combustion engine;
A pre-catalyst air-fuel ratio measuring unit that detects an air-fuel ratio output from an air-fuel ratio sensor disposed upstream of the catalyst;
A post-catalyst oxygen measuring unit that is disposed downstream of the catalyst and detects the oxygen concentration of the exhaust gas from the catalyst;
An intake air amount measuring unit for measuring the intake air amount of the internal combustion engine;
An in-catalyst center air-fuel ratio estimating unit for estimating a center air-fuel ratio in the catalyst;
Based on the air-fuel ratio measured by the pre-catalyst air-fuel ratio measuring unit, the intake air amount measured by the intake air amount measuring unit, and the central air-fuel ratio in the catalyst estimated by the in-catalyst central air-fuel ratio estimating unit. An in-catalyst oxygen accumulation amount estimation unit for estimating the in-catalyst oxygen accumulation amount;
A catalyst deterioration index unit that calculates a catalyst deterioration index based on the fuel cut time of the internal combustion engine, the air-fuel ratio rich time during fuel recovery, and the air-fuel ratio measured by the post-catalyst oxygen signal measurement unit;
An oxygen concentration signal correction unit that corrects the oxygen concentration signal measured by the post-catalyst oxygen measurement unit based on the catalyst deterioration index calculated by the catalyst deterioration index unit;
An oxygen storage amount correction unit that corrects the oxygen storage amount of the catalyst based on the catalyst deterioration index calculated by the catalyst deterioration index unit;
Based on the oxygen storage amount of the catalyst corrected by the oxygen storage amount correction unit and the oxygen concentration signal corrected by the oxygen concentration signal correction unit, a proportional correction value and an integral correction value are calculated, and the calculated proportional component is calculated. An air-fuel ratio correction unit that calculates a target air-fuel ratio correction amount based on the correction value and the integral correction value, and the in-catalyst center air-fuel ratio estimation unit estimated by the in-catalyst center air-fuel ratio estimation unit;
An upper / lower limit determination value calculation unit that calculates upper and lower limits of the air / fuel ratio based on the central air / fuel ratio within the catalyst estimated by the in-catalyst center air / fuel ratio estimation unit;
A first determination unit for determining an offset failure of the air-fuel ratio sensor based on a target air-fuel ratio correction amount calculated by the air-fuel ratio correction unit and an upper / lower limit calculated by the upper / lower limit determination value calculation unit;
An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, comprising: 請求項１に記載の内燃機関の空燃比センサ診断装置において、
上記空燃比補正部は、上記比例分補正値を演算する比例分補正値演算部と、上記積分分補正値を演算する積分分演算部と、上記比例分補正値演算部が演算した比例分補正値、上記積分分演算部が演算した積分分補正値、及び上記触媒内中心空燃比推定部が推定した触媒内中心空燃比とに基づいて目標空燃比補正量を演算する目標空燃比補正量演算部とを有することを特徴とする内燃機関の空燃比センサ診断装置。 The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 1,
The air-fuel ratio correction unit includes a proportional correction value calculation unit that calculates the proportional correction value, an integral calculation unit that calculates the integral correction value, and a proportional correction calculated by the proportional correction value calculation unit. Target air-fuel ratio correction amount calculation for calculating the target air-fuel ratio correction amount based on the value, the integral correction value calculated by the integral calculation unit, and the catalyst center air-fuel ratio estimated by the catalyst center air-fuel ratio estimation unit And an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine. 請求項２に記載の内燃機関の空燃比センサ診断装置において、
上記上下限判定値演算部は、上記触媒内中心空燃比推定部が推定した触媒内中心空燃比に基づいて、空燃比の上限判定値を演算する上限判定値演算部と、空燃比の下限判定値を演算する下限判定値演算部とを有することを特徴とする内燃機関の空燃比センサ診断装置。 The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 2,
The upper and lower limit determination value calculation unit includes an upper limit determination value calculation unit that calculates an upper limit determination value of the air-fuel ratio based on the in-catalyst center air-fuel ratio estimated by the in-catalyst center air-fuel ratio estimation unit, and an air-fuel ratio lower limit determination An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, comprising: a lower limit determination value calculation unit that calculates a value. 請求項３に記載の内燃機関の空燃比センサ診断装置において、
上記内燃機関の空燃比センサの診断を実行すべき領域であるか否かを判定する診断領域判定部を、さらに備え、上記第１判定部は、上記診断領域判定部により空燃比センサの診断を実行すべき領域であることが判断されたときに、上記空燃比センサのオフセット故障を判定すること特徴とする内燃機関の空燃比センサ診断装置。 The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 3,
A diagnostic region determination unit that determines whether or not the air-fuel ratio sensor of the internal combustion engine is to be diagnosed; and the first determination unit diagnoses the air-fuel ratio sensor by the diagnostic region determination unit. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, wherein an offset failure of the air-fuel ratio sensor is determined when it is determined that the region is to be executed. 請求項４に記載の内燃機関の空燃比センサ診断装置において、
上記診断領域判定部により空燃比センサの診断を実行すべき領域であることが判断されたときに、上記触媒内中心空燃比推定部が推定した触媒内中心空燃比に基づいて、上記空燃比センサのオフセット故障を判定する第２判定部を備えること特徴とする内燃機関の空燃比センサ診断装置。 The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 4,
The air-fuel ratio sensor is based on the in-catalyst center air-fuel ratio estimated by the in-catalyst center air-fuel ratio estimation unit when the diagnosis region determination unit determines that the air-fuel ratio sensor should be diagnosed. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, comprising: a second determination unit that determines an offset failure of the internal combustion engine. 請求項１に記載の内燃機関の空燃比センサ診断装置において、
上記触媒劣化指標部は、内燃機関の燃料カット時に上記触媒後酸素計測部の出力がリーン出力となった後、燃料リカバ時に目標空燃比がリッチ側になるように触媒劣化指標を演算し、上記触媒後酸素計測部の出力がリッチ側に反転するまでの時間を算出することを特徴とする内燃機関の空燃比センサ診断装置。 The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 1,
The catalyst deterioration index unit calculates a catalyst deterioration index so that the target air-fuel ratio becomes rich during fuel recovery after the output of the post-catalyst oxygen measurement unit becomes a lean output at the time of fuel cut of the internal combustion engine, An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, characterized in that the time until the output of the post-catalyst oxygen measuring section is reversed to the rich side is calculated. 請求項６に記載の内燃機関の空燃比センサ診断装置において、
上記酸素濃度信号補正部は、上記触媒劣化指標部が算出した、上記触媒後酸素計測部の出力がリッチ側に反転するまでの時間に基づいて、酸素濃度信号の補正値を算出することを特徴とする内燃機関の空燃比センサ診断装置。 The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 6,
The oxygen concentration signal correction unit calculates a correction value of the oxygen concentration signal based on the time calculated by the catalyst deterioration index unit until the output of the post-catalyst oxygen measurement unit reverses to the rich side. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine. 請求項６に記載の内燃機関の空燃比センサ診断装置において、
上記酸素貯積量補正部は、上記触媒劣化指標部が算出した、上記触媒後酸素計測部の出力がリッチ側に反転するまでの時間に基づいて、上記触媒の酸素貯積量を補正することを特徴とする内燃機関の空燃比センサ診断装置。 The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 6,
The oxygen storage amount correction unit corrects the oxygen storage amount of the catalyst based on the time calculated by the catalyst deterioration index unit until the output of the post-catalyst oxygen measurement unit reverses to the rich side. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine characterized by the above. 内燃機関の排気系に設けられた触媒と、
上記触媒の上流側に配置された空燃比センサから出力される空燃比を検出する触媒前空燃比計測部と、
上記触媒の下流側に配置され触媒からの排気の酸素濃度を検出する触媒後酸素計測部と、
上記内燃機関の吸入空気量を計測する吸入空気量計測部と、
上記触媒内の中心空燃比を推定する触媒内中心空燃比推定部と、
上記触媒前空燃比計測部により計測された空燃比、上記吸入空気量計測部により計測された吸入空気量、及び上記触媒内中心空燃比推定部により推定された触媒内の中心空燃比に基づいて触媒内酸素蓄積量を推定する触媒内酸素蓄積量推定部と、
上記内燃機関の燃料カット時間と燃料リカバ時の空燃比リッチ時間と上記触媒後酸素信号計測部が計測した空燃比とに基づいて触媒劣化指標を算出する触媒劣化指標部と、
上記触媒劣化指標部が算出した触媒劣化指標に基づいて、目標空燃比の補正量を算出する目標空燃比補正量マップ補正部と、
上記触媒内酸素蓄積量推定部が推定した上記触媒内酸素蓄積量と、上記目標空燃比補正量マップ補正部が算出した目標空燃比の補正量とに基づいて、比例分補正値及び積分分補正値を演算し、演算した比例分補正値及び積分分補正値と、上記触媒内中心空燃比推定部が推定した触媒内中心空燃比とに基づいて目標空燃比補正量を演算する空燃比補正部と、
上記触媒内中心空燃比推定部が推定した触媒内中心空燃比に基づいて、空燃比の上下限を演算する上下限判定値演算部と、
上記空燃比補正部が演算した目標空燃比補正量及び上記上下限判定値演算部が演算した上下限に基づいて上記空燃比センサのオフセット故障を判定する第１判定部と、
を備えることを特徴とする内燃機関の空燃比センサ診断装置。 A catalyst provided in the exhaust system of the internal combustion engine;
A pre-catalyst air-fuel ratio measuring unit that detects an air-fuel ratio output from an air-fuel ratio sensor disposed upstream of the catalyst;
A post-catalyst oxygen measuring unit that is disposed downstream of the catalyst and detects the oxygen concentration of the exhaust gas from the catalyst;
An intake air amount measuring unit for measuring the intake air amount of the internal combustion engine;
An in-catalyst center air-fuel ratio estimating unit for estimating a center air-fuel ratio in the catalyst;
Based on the air-fuel ratio measured by the pre-catalyst air-fuel ratio measuring unit, the intake air amount measured by the intake air amount measuring unit, and the central air-fuel ratio in the catalyst estimated by the in-catalyst central air-fuel ratio estimating unit. An in-catalyst oxygen accumulation amount estimation unit for estimating the in-catalyst oxygen accumulation amount;
A catalyst deterioration index unit that calculates a catalyst deterioration index based on the fuel cut time of the internal combustion engine, the air-fuel ratio rich time during fuel recovery, and the air-fuel ratio measured by the post-catalyst oxygen signal measurement unit;
A target air-fuel ratio correction amount map correction unit that calculates a correction amount of the target air-fuel ratio based on the catalyst deterioration index calculated by the catalyst deterioration index unit;
Based on the oxygen accumulation amount in the catalyst estimated by the oxygen accumulation amount estimation unit in the catalyst and the correction amount of the target air-fuel ratio calculated by the target air-fuel ratio correction amount map correction unit, the proportional correction value and the integral correction An air-fuel ratio correction unit that calculates a target air-fuel ratio correction amount based on the calculated proportional correction value and integral correction value and the in-catalyst center air-fuel ratio estimation unit When,
An upper / lower limit determination value calculation unit that calculates upper and lower limits of the air / fuel ratio based on the central air / fuel ratio within the catalyst estimated by the in-catalyst center air / fuel ratio estimation unit;
A first determination unit for determining an offset failure of the air-fuel ratio sensor based on a target air-fuel ratio correction amount calculated by the air-fuel ratio correction unit and an upper / lower limit calculated by the upper / lower limit determination value calculation unit;
An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, comprising: 請求項９に記載の内燃機関の空燃比センサ診断装置において、
上記触媒劣化指標部は、内燃機関の燃料カット時に上記触媒後酸素計測部の出力がリーン出力となった後、燃料リカバ時に目標空燃比がリッチ側になるように触媒劣化指標を演算することを特徴とする内燃機関の空燃比センサ診断装置。 The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 9,
The catalyst deterioration index unit calculates the catalyst deterioration index so that the target air-fuel ratio becomes rich during fuel recovery after the output of the post-catalyst oxygen measurement unit becomes lean output when the fuel of the internal combustion engine is cut. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, characterized by the following.
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