JPH0754641A - Catalyst deterioration diagnotic device for internal combustion engine - Google Patents
Catalyst deterioration diagnotic device for internal combustion engineInfo
- Publication number
- JPH0754641A JPH0754641A JP5197525A JP19752593A JPH0754641A JP H0754641 A JPH0754641 A JP H0754641A JP 5197525 A JP5197525 A JP 5197525A JP 19752593 A JP19752593 A JP 19752593A JP H0754641 A JPH0754641 A JP H0754641A
- Authority
- JP
- Japan
- Prior art keywords
- nox
- fuel ratio
- air
- lean
- catalyst
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/011—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more purifying devices arranged in parallel
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
- F01N2550/02—Catalytic activity of catalytic converters
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Exhaust Gas After Treatment (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
Abstract
Description
【0001】[0001]
【産業上の利用分野】本発明は内燃機関の触媒劣化診断
装置に関し、詳しくは、NOxを転化する排気浄化触媒
におけるNOx転化性能の低下を診断し得る装置に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst deterioration diagnosing device for an internal combustion engine, and more particularly to a device for diagnosing a decrease in NOx conversion performance of an exhaust purification catalyst that converts NOx.
【0002】[0002]
【従来の技術】従来、内燃機関の排気通路に介装される
排気浄化触媒の劣化(転化性能の低下)を診断する装置
としては、例えば特開平2−91440号公報に開示さ
れるようなものがある。前記特開平2−91440号公
報に開示される内燃機関は、排気通路に介装された三元
触媒の上流側及び下流側にそれぞれ酸素センサを備え、
これら酸素センサの出力に基づいて空燃比フィードバッ
ク制御を行う構成である。2. Description of the Related Art Conventionally, an apparatus for diagnosing deterioration (decrease in conversion performance) of an exhaust purification catalyst provided in an exhaust passage of an internal combustion engine is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-91440. There is. The internal combustion engine disclosed in Japanese Unexamined Patent Publication No. 2-91440 is provided with oxygen sensors on the upstream side and the downstream side of the three-way catalyst interposed in the exhaust passage,
The air-fuel ratio feedback control is performed based on the outputs of these oxygen sensors.
【0003】そして、かかる空燃比フィードバック制御
中における上流側の酸素センサの反転周期をfu、下流
側の酸素センサの反転周期をfdとしたときに、fd/
fu≧所定値であるときには三元触媒の転化性能は正常
であり、fd/fu<所定値であるときには三元触媒が
劣化していると診断するものである。即ち、前記診断方
法は、三元触媒における酸素ストレージ効果の度合いを
前記周期の比fd/fuで判定し、以て、触媒の劣化診
断を行わせるものである。When the inversion cycle of the oxygen sensor on the upstream side is fu and the inversion cycle of the oxygen sensor on the downstream side is fd during the air-fuel ratio feedback control, fd /
When fu ≧ a predetermined value, the conversion performance of the three-way catalyst is normal, and when fd / fu <a predetermined value, the three-way catalyst is diagnosed as being deteriorated. That is, the above-mentioned diagnosis method is to judge the degree of oxygen storage effect in the three-way catalyst by the ratio fd / fu of the above-mentioned cycle, and thereby perform the deterioration diagnosis of the catalyst.
【0004】一方、近年においては、理論空燃比よりも
大幅に希薄な空燃比域(例えば20〜22程度の空燃比)で
燃焼させる希薄燃焼機関が開発されており、かかる希薄
燃焼機関では、希薄空燃比域(空気過剰雰囲気中)でN
Oxを浄化し得る所謂リーンNOx触媒が使用されてい
る。前記リーンNOx触媒は、ゼオライトを主成分とす
るものであり、排気中のHCを一時的に吸着し、このH
CによりNOxを還元するものであると推定されてい
る。On the other hand, in recent years, a lean-burn engine has been developed which burns in an air-fuel ratio range (for example, an air-fuel ratio of about 20 to 22) that is significantly leaner than the stoichiometric air-fuel ratio. N in the air-fuel ratio range (in excess air atmosphere)
A so-called lean NOx catalyst that can purify Ox is used. The lean NOx catalyst is mainly composed of zeolite and temporarily adsorbs HC in the exhaust gas to form H
It is estimated that C reduces NOx.
【0005】[0005]
【発明が解決しようとする課題】ところで、前記従来の
診断方法は、排気中の酸素濃度が急変する境界空燃比で
ある理論空燃比を目標空燃比とする空燃比フィードバッ
ク制御が行われるときに、三元触媒の酸素ストレージ効
果により触媒下流側の酸素濃度変化に応答遅れを生じる
ことを利用して、触媒の酸素ストレージ効果の度合い、
引いては、三元触媒の転化性能の低下(劣化)を診断す
るものである。By the way, in the conventional diagnosis method, when the air-fuel ratio feedback control is performed in which the target air-fuel ratio is the theoretical air-fuel ratio which is the boundary air-fuel ratio at which the oxygen concentration in the exhaust gas suddenly changes, By utilizing the fact that the oxygen storage effect of the three-way catalyst causes a response delay in the oxygen concentration change on the downstream side of the catalyst, the degree of the oxygen storage effect of the catalyst,
Finally, the deterioration (deterioration) of the conversion performance of the three-way catalyst is diagnosed.
【0006】このため、希薄空燃比域(排気中の酸素濃
度が過剰な状態)でNOxを浄化する前記リーンNOx
触媒の診断には適用できず、リーンNOx触媒の劣化診
断が行える診断装置の提供が望まれていた。本発明は上
記問題点に鑑みなされたものであり、希薄空燃比での燃
焼状態でNOxを浄化するリーンNOx触媒のNOx転
化性能の低下(劣化)を診断できる触媒劣化診断装置を
提供することを目的とする。For this reason, the lean NOx for purifying NOx in the lean air-fuel ratio range (state where the oxygen concentration in the exhaust gas is excessive) is obtained.
It cannot be applied to the diagnosis of the catalyst, and it has been desired to provide a diagnosis device that can perform the deterioration diagnosis of the lean NOx catalyst. The present invention has been made in view of the above problems, and it is an object of the present invention to provide a catalyst deterioration diagnosis device capable of diagnosing deterioration (deterioration) of NOx conversion performance of a lean NOx catalyst that purifies NOx in a combustion state with a lean air-fuel ratio. To aim.
【0007】[0007]
【課題を解決するための手段】そのため本発明にかかる
内燃機関の触媒劣化診断装置は、少なくとも排気中のN
Oxを転化する排気浄化触媒が排気通路に介装される内
燃機関の触媒劣化診断装置であって、図1に示すように
構成される。図1において、NOxセンサは、前記排気
浄化触媒におけるNOx転化率に相関する排気中のNO
x濃度を検出するセンサである。Therefore, a catalyst deterioration diagnosing device for an internal combustion engine according to the present invention is provided with at least N in exhaust gas.
An exhaust gas purification catalyst for converting Ox is a catalyst deterioration diagnosis device for an internal combustion engine, which is provided in an exhaust passage, and is configured as shown in FIG. In FIG. 1, the NOx sensor indicates that the NO in the exhaust gas correlates with the NOx conversion rate in the exhaust purification catalyst.
It is a sensor that detects x concentration.
【0008】また、基準値設定手段は、運転条件検出手
段で検出される機関運転条件に基づいて前記NOxセン
サによる検出結果を判別するための基準値を設定する。
そして、診断手段は、前記NOxセンサによる検出結果
を前記基準値設定手段で設定された基準値に基づいて判
別して前記排気浄化触媒のNOx転化性能の低下を診断
する。The reference value setting means sets a reference value for discriminating the detection result of the NOx sensor based on the engine operating condition detected by the operating condition detecting means.
Then, the diagnosing means judges the detection result by the NOx sensor based on the reference value set by the reference value setting means, and diagnoses the deterioration of the NOx conversion performance of the exhaust purification catalyst.
【0009】ここで、前記排気浄化触媒が、酸素過剰雰
囲気でNOxを転化するリーンNOx触媒作用及び三元
触媒作用を有する触媒であって、かつ、前記内燃機関が
所定の運転領域で希薄空燃比を目標空燃比として運転さ
れる機関である場合においては、前記診断手段が前記希
薄空燃比で機関が運転されているときにNOx転化性能
の低下を診断したときに、前記希薄空燃比を目標空燃比
とする所定の運転領域における目標空燃比を強制的に理
論空燃比に切り換える空燃比切り換え制御手段を設ける
ようにすると良い。Here, the exhaust purification catalyst is a catalyst having a lean NOx catalytic action for converting NOx in an oxygen excess atmosphere and a three-way catalytic action, and the internal combustion engine has a lean air-fuel ratio in a predetermined operating region. In the case where the engine is operated with the target air-fuel ratio as the target air-fuel ratio, the diagnosis means determines the lean air-fuel ratio as the target air-fuel ratio when the deterioration of NOx conversion performance is diagnosed when the engine is operated with the lean air-fuel ratio. It is advisable to provide an air-fuel ratio switching control means for forcibly switching the target air-fuel ratio in the predetermined operating region where the fuel ratio is set to the stoichiometric air-fuel ratio.
【0010】[0010]
【作用】かかる構成の触媒劣化診断装置によると、排気
浄化触媒におけるNOx転化率に相関する排気中のNO
x濃度がNOxセンサで検出され、かかるNOxセンサ
による検出結果が、機関運転条件に応じて判別されて、
触媒におけるNOx転化性能の低下が診断される。According to the catalyst deterioration diagnosing device having such a configuration, the NO in the exhaust gas that correlates with the NOx conversion rate in the exhaust purification catalyst.
The x concentration is detected by the NOx sensor, and the detection result by the NOx sensor is determined according to the engine operating condition,
The deterioration of the NOx conversion performance of the catalyst is diagnosed.
【0011】即ち、NOxセンサを設けることで、NO
xの転化率を直接的に検知し、該検知結果と機関運転状
態に応じて期待される値との比較によって、所期のNO
x転化性能が発揮されているか否かを診断させるように
した。また、排気浄化触媒が酸素過剰雰囲気でNOxを
転化する作用を有し、これに応じて機関を希薄空燃比で
運転させる場合には、前記酸素過剰雰囲気でのNOx転
化性能が低下すると、希薄空燃比での燃焼状態でNOx
排出量が増大してしまう。そこで、希薄空燃比で運転さ
れているときに上記のようにしてNOx転化性能の低下
が診断されたときには、酸素過剰雰囲気でのNOx転化
性能の低下を示すから、目標空燃比を本来の希薄空燃比
から理論空燃比に切り換え、排気浄化触媒における三元
触媒作用でNOxを含めた排気の浄化を図れるようにし
た。That is, by providing a NOx sensor, NO
By directly detecting the conversion rate of x and comparing the detection result with a value expected according to the engine operating state, the expected NO
It was made to diagnose whether or not the x conversion performance was exhibited. Further, the exhaust purification catalyst has a function of converting NOx in an oxygen excess atmosphere, and accordingly, when the engine is operated at a lean air-fuel ratio, if the NOx conversion performance in the oxygen excess atmosphere deteriorates, the lean air-fuel ratio is reduced. NOx in the combustion state at the fuel ratio
Emissions will increase. Therefore, when the deterioration of the NOx conversion performance is diagnosed as described above during the operation at the lean air-fuel ratio, the NOx conversion performance is deteriorated in the oxygen excess atmosphere, so the target air-fuel ratio is set to the original lean air-fuel ratio. The fuel ratio is switched to the stoichiometric air-fuel ratio so that the exhaust purification catalyst can purify the exhaust gas including NOx by the three-way catalytic action.
【0012】[0012]
【実施例】以下に本発明の実施例を説明する。実施例の
システム構成を示す図2において、V型内燃機関1の各
気筒には、エアクリーナ2,スロットル弁3,吸気マニ
ホールド4を介して空気が吸引される。前記吸気マニホ
ールド4の各ブランチ部には、それぞれ電磁式の燃料噴
射弁5が設けられている。EXAMPLES Examples of the present invention will be described below. In FIG. 2 showing the system configuration of the embodiment, air is sucked into each cylinder of the V-type internal combustion engine 1 through an air cleaner 2, a throttle valve 3 and an intake manifold 4. An electromagnetic fuel injection valve 5 is provided at each branch of the intake manifold 4.
【0013】機関1からの排気は、排気マニホールド6
a,6bによって片バンク毎に集められた後、それぞれ
排気管7a,7bによってマフラ8に導かれる。前記排
気管7a,7bには、それぞれに触媒コンバータ(排気
浄化触媒)9a,9bが介装されている。前記触媒コン
バータ9a,9bは、理論空燃比付近でNOx,HC,
COを同時に高い転化率で浄化する三元触媒作用と、酸
素過剰状態(希薄空燃比燃焼状態)でNOxを還元(転
化)するリーンNOx触媒作用との両方を有するもので
ある。Exhaust gas from the engine 1 is exhausted from an exhaust manifold 6
After being collected for each bank by a and 6b, they are guided to the muffler 8 by exhaust pipes 7a and 7b, respectively. Catalytic converters (exhaust gas purification catalysts) 9a and 9b are provided in the exhaust pipes 7a and 7b, respectively. The catalytic converters 9a, 9b are configured to reduce NOx, HC, and
It has both a three-way catalytic action for simultaneously purifying CO at a high conversion rate and a lean NOx catalytic action for reducing (converting) NOx in an oxygen excess state (lean air-fuel ratio combustion state).
【0014】コントロールユニット10は、マイクロコン
ピュータを内蔵し、各種センサからの検出信号に基づい
て後述のように燃料噴射弁5による燃料噴射量Ti(噴
射パルス幅)を演算し、該燃料噴射量Tiに基づいて燃
料噴射弁5を開駆動制御することで、機関1への燃料供
給を電子制御する。尚、本実施例の機関は、所定の運転
領域においては、理論空燃比よりも大幅に希薄な空燃比
(例えば22)で燃焼させる所謂希薄燃焼機関であり、前
記希薄燃焼領域以外では、理論空燃比付近の空燃比(出
力空燃比)での燃焼を行わせ、加速性能等を確保するよ
うになっている。The control unit 10 has a built-in microcomputer, calculates the fuel injection amount Ti (injection pulse width) by the fuel injection valve 5 based on the detection signals from various sensors, and calculates the fuel injection amount Ti. The fuel supply to the engine 1 is electronically controlled by controlling the open drive of the fuel injection valve 5 based on The engine of the present embodiment is a so-called lean combustion engine that burns at an air-fuel ratio (for example, 22) that is significantly leaner than the stoichiometric air-fuel ratio in a predetermined operating region. Combustion is performed at an air-fuel ratio (output air-fuel ratio) near the fuel ratio to ensure acceleration performance and the like.
【0015】前記各種センサとしては、スロットル弁3
の上流側で機関1の吸入空気量Qaを検出するエアフロ
ーメータ11、カム軸から機関回転信号を取り出すクラン
ク角センサ12、機関1の冷却水温度Twを検出する水温
センサ13、排気マニホールド6a,6bの集合部にそれ
ぞれ設けられて各バンク毎に排気中の酸素濃度を検出す
る酸素センサ14a,14b、スロットル弁3の開度を検出
するポテンショメータ式のスロットルセンサ15が設けら
れている。The various sensors include a throttle valve 3
Upstream, the air flow meter 11 for detecting the intake air amount Qa of the engine 1, the crank angle sensor 12 for extracting the engine rotation signal from the cam shaft, the water temperature sensor 13 for detecting the cooling water temperature Tw of the engine 1, and the exhaust manifolds 6a, 6b. The oxygen sensors 14a, 14b for detecting the oxygen concentration in the exhaust gas and the potentiometer-type throttle sensor 15 for detecting the opening of the throttle valve 3 are provided for each bank.
【0016】尚、17はアイドル時の吸入空気量を調整す
るためのコントロールバルブであり、スロットル弁3を
バイパスして設けられたバイパス通路18を介して機関1
に供給される補助空気量を調整する。更に、コントロー
ルユニット10は、後述するように、前記触媒コンバータ
9a,9bにおけるNOx転化性能の低下を診断する触
媒劣化診断機能を有しており、前記診断のために、各触
媒コンバータ9a,9bにはそれぞれその上流側にNO
xセンサ16a,16bが設けられ、更に、下流側にもNO
xセンサ18a,18bが設けられている。Reference numeral 17 is a control valve for adjusting the intake air amount at the time of idling, and the engine 1 is provided through a bypass passage 18 which bypasses the throttle valve 3.
Adjust the amount of auxiliary air supplied to the. Further, as will be described later, the control unit 10 has a catalyst deterioration diagnosis function for diagnosing a decrease in NOx conversion performance of the catalytic converters 9a, 9b. NO to each upstream side
x sensors 16a and 16b are provided, and NO is also provided on the downstream side.
x sensors 18a and 18b are provided.
【0017】前記NOxセンサ16a,16b,18a,18b
は、半導体式のAg0.04V2 O5 の薄膜型センサであ
る。かかるNOxセンサは、NOxのセンサ表面への吸
着により図3に示すように抵抗値が変化する公知のセン
サである。そして、コントロールユニット10は、前記N
Oxセンサ16a,16b,18a,18bの出力に基づいて前
記触媒コンバータ9a,9bにおけるNOx転化性能の
低下を診断し、該診断の結果、前記触媒コンバータ9
a,9bのNOx転化性能が低下していると判別したと
きには、機関1が搭載された車両の運転席等に設けられ
た警告灯19(警報手段)を点灯させて、前記診断結果を
運転者に警告するようになっている。The NOx sensors 16a, 16b, 18a, 18b
Is a semiconductor type thin film sensor of Ag 0.04 V 2 O 5 . This NOx sensor is a known sensor whose resistance value changes as shown in FIG. 3 due to the adsorption of NOx on the sensor surface. Then, the control unit 10 is
Based on the outputs of the Ox sensors 16a, 16b, 18a, 18b, the deterioration of NOx conversion performance in the catalytic converters 9a, 9b is diagnosed, and as a result of the diagnosis, the catalytic converter 9 is detected.
When it is determined that the NOx conversion performances of a and 9b are deteriorated, the warning light 19 (alarm means) provided in the driver's seat of the vehicle in which the engine 1 is mounted is turned on, and the diagnosis result is output to the driver. To warn you.
【0018】即ち、触媒コンバータ9a,9bにおける
NOx転化率は、触媒上流側におけるNOx濃度と、触
媒下流側におけるNOx濃度との比で規定されるから、
上記の上流側及び下流側それぞれに設けられたNOxセ
ンサ16a,16b,18a,18bが、本実施例において、触
媒コンバータ9a,9bにおけるNOx転化率に相関す
る排気中のNOx濃度を検出するNOxセンサに相当す
る。That is, the NOx conversion rate in the catalytic converters 9a and 9b is defined by the ratio of the NOx concentration on the upstream side of the catalyst to the NOx concentration on the downstream side of the catalyst.
In the present embodiment, the NOx sensors 16a, 16b, 18a, 18b provided on the upstream side and the downstream side respectively detect the NOx concentration in the exhaust gas that correlates with the NOx conversion rate in the catalytic converters 9a, 9b. Equivalent to.
【0019】ここで、本実施例の触媒劣化診断装置の構
成を簡略化して図4のブロック図に示してある。図4に
示すように、コントロールユニット10は、クランク角セ
ンサ12及びエアフローメータ11の検出信号に基づいて基
準値を設定する基準値設定手段Aとしての機能、上流側
のNOxセンサ16a,16b及び下流側のNOxセンサ18
a,18bの検出信号に基づいて触媒コンバータ9a,9
bの上下流間におけるNOx濃度比を演算するNOx濃
度比演算手段Bとしての機能、更に、前記基準値とNO
x濃度比との比較に基づいて触媒コンバータ9a,9b
におけるNOx転化性能の低下を診断する診断手段Cと
しての機能を備えている。また、本実施例では、前記診
断手段Cにおける診断結果(診断信号)を受けて、選択
的に作動される前記警告灯19からなる警報手段Dが設け
られている。Here, the structure of the catalyst deterioration diagnosing device of this embodiment is shown in a simplified block diagram of FIG. As shown in FIG. 4, the control unit 10 functions as a reference value setting means A that sets a reference value based on the detection signals of the crank angle sensor 12 and the air flow meter 11, the upstream NOx sensors 16a, 16b, and the downstream NOx sensors 16a, 16b. Side NOx sensor 18
Catalytic converters 9a, 9 based on the detection signals of a, 18b
b, the function as the NOx concentration ratio calculating means B for calculating the NOx concentration ratio between the upstream side and the downstream side, and the reference value and NO
Based on comparison with x concentration ratio, catalytic converters 9a, 9b
It has a function as a diagnostic means C for diagnosing the deterioration of the NOx conversion performance. Further, in the present embodiment, the alarm means D including the warning light 19 which is selectively operated in response to the diagnosis result (diagnosis signal) of the diagnosis means C is provided.
【0020】ここで、前記基準値設定手段Aは、クラン
ク角センサ12及びエアフローメータ11の検出信号に基づ
いて演算される基本燃料噴射量Tpを機関負荷相当値と
し、この基本燃料噴射量Tpと機関回転数Neとに基づ
いて前記基準値RO を設定する。一方、NOx濃度比演
算手段Bは、NOxセンサの出力に基づいて触媒におけ
る転化効率を示すことになる触媒の上下流間におけるN
Ox濃度の比を演算する。そして、前記診断手段Cは、
前記基準値RO とNOx濃度比とを比較することで、N
Ox転換効率の所定以上の低下を判別し、NOx転化効
率の低下が判別されたときには、警報手段Dを作動させ
て、NOx転化性能の低下を警報する。Here, the reference value setting means A sets the basic fuel injection amount Tp calculated based on the detection signals of the crank angle sensor 12 and the air flow meter 11 as an engine load equivalent value, and the basic fuel injection amount Tp The reference value R O is set based on the engine speed Ne. On the other hand, the NOx concentration ratio calculation means B determines the conversion efficiency of the catalyst based on the output of the NOx sensor.
Calculate the ratio of Ox concentration. Then, the diagnosis means C is
By comparing the reference value R O and the NOx concentration ratio, N
When it is determined that the Ox conversion efficiency has decreased more than a predetermined value and the NOx conversion efficiency has decreased, the warning means D is activated to warn the decrease of the NOx conversion performance.
【0021】次に、図5のフローチャートに従って、前
記触媒劣化診断の様子を詳細に説明する。図5のフロー
チャートにおいて、P1では、クランク角センサ12の検
出信号に基づいて機関回転数Neを検出する。次いで、
P2では、エアフローメータ11の検出信号に基づいて機
関1の吸入空気量Qaを検出する。Next, the state of the catalyst deterioration diagnosis will be described in detail with reference to the flowchart of FIG. In the flowchart of FIG. 5, at P1, the engine speed Ne is detected based on the detection signal of the crank angle sensor 12. Then
At P2, the intake air amount Qa of the engine 1 is detected based on the detection signal of the air flow meter 11.
【0022】そして、P3では、前記機関回転数Neと
吸入空気量Qaとに基づいて前記燃料噴射弁5における
基本噴射量(基本噴射パルス幅)Tp=K×Qa/Ne
(Kは噴射弁5の流量特性に対応する比例定数であ
る。)を演算する。尚、該基本噴射量Tpは、機関負荷
を代表する値として後述する基準値の設定に用いる。ま
た、P4では、触媒コンバータ9a,9bの上流側に設
けられたNOxセンサ16a,16b(第1NOxセンサ)
の出力VRU,VLUを測定する。At P3, the basic injection amount (basic injection pulse width) Tp = K × Qa / Ne in the fuel injection valve 5 is calculated based on the engine speed Ne and the intake air amount Qa.
(K is a proportional constant corresponding to the flow rate characteristic of the injection valve 5.) is calculated. The basic injection amount Tp is used to set a reference value, which will be described later, as a value representing the engine load. Further, at P4, NOx sensors 16a and 16b (first NOx sensor) provided on the upstream side of the catalytic converters 9a and 9b.
Output V RU , V LU of
【0023】更に、P5では、触媒コンバータ9a,9
bの下流側に設けられたNOxセンサ18a,18b(第2
NOxセンサ)の出力VRD,VLDを測定する。そして、
次のP6では、前記測定された出力に基づいて触媒コン
バータ9a,9bにおけるNOx転換率を示す触媒上下
流間におけるNOx濃度比Rを以下の式に従って演算す
る。Further, in P5, the catalytic converters 9a, 9a
NOx sensors 18a, 18b (second
The outputs V RD and V LD of the NOx sensor) are measured. And
Next, at P6, the NOx concentration ratio R between the upstream and downstream of the catalyst, which indicates the NOx conversion rate in the catalytic converters 9a and 9b, is calculated based on the measured output according to the following equation.
【0024】[0024]
【数1】 [Equation 1]
【0025】尚、上記の演算式は、各バンク毎にそれぞ
れ設けられた2つの触媒コンバータ9a,9bにおける
NOx転化率を平均的に求める演算式であり、各触媒コ
ンバータ9a,9b毎にNOx濃度比を演算させるよう
にしても良い。一方、P7では、前記機関回転数Neと
基本燃料噴射量Tp(機関負荷)とをパラメータとする
マップ(図6参照)に予め記憶されている前記NOx濃
度比Rの基準値R0 の中から、現在の機関回転数Ne及
び基本燃料噴射量Tp(機関負荷)に対応するデータを
検索して読み出す。The above-mentioned arithmetic expression is an arithmetic expression for averaging the NOx conversion rates in the two catalytic converters 9a and 9b provided for each bank, and the NOx concentration for each catalytic converter 9a, 9b. You may make it calculate a ratio. On the other hand, at P7, from the reference value R 0 of the NOx concentration ratio R stored in advance in the map (see FIG. 6) using the engine speed Ne and the basic fuel injection amount Tp (engine load) as parameters. , The data corresponding to the current engine speed Ne and the basic fuel injection amount Tp (engine load) are retrieved and read.
【0026】上記のように、本実施例では、機関運転条
件としての機関回転数Neと基本燃料噴射量Tpとに基
づき基準値R0 を可変設定する構成であるから、クラン
ク角センサ12,エアフローメータ11が運転条件検出手段
に相当する。前記基準値R0 マップに記憶された基準値
R0 は、NOx濃度検出の安全率を見込んで、NOx排
出量が初期状態(劣化のない状態)に対して150 %程度
に増大した状態に対応して定められている。As described above, in this embodiment, the reference value R 0 is variably set based on the engine speed Ne and the basic fuel injection amount Tp as the engine operating conditions. Therefore, the crank angle sensor 12 and the air flow are set. The meter 11 corresponds to the operating condition detecting means. The reference value R 0 map reference value stored in R 0 is expected the safety factor of the NOx concentration detected, corresponding to a state where the NOx emission amount is increased to about 150% of the initial state (state without deterioration) Has been set.
【0027】図6に示すマップで、点線で囲まれた低負
荷・低回転運転領域は、理論空燃比よりも大幅に希薄な
空燃比で燃焼させる領域(希薄燃焼領域)であり、かか
る領域では、触媒コンバータ9a,9bにおけるリーン
NOx触媒作用の診断を行うことになる。また、前記図
6に示すマップで点線で囲まれた希薄燃焼領域以外の運
転領域は、理論空燃比付近の空燃比で燃焼させる領域
(出力空燃比領域)であり、かかる領域では、触媒コン
バータ9a,9bにおける三元触媒作用を含めたNOx
転化性能が診断されることになる。In the map shown in FIG. 6, the low load / low speed operation region surrounded by a dotted line is a region (lean combustion region) in which combustion is performed at an air-fuel ratio significantly leaner than the theoretical air-fuel ratio. , The lean NOx catalytic action in the catalytic converters 9a and 9b is diagnosed. Further, the operating region other than the lean burn region surrounded by the dotted line in the map shown in FIG. 6 is a region in which combustion is performed at an air-fuel ratio near the stoichiometric air-fuel ratio (output air-fuel ratio region), and in this region, the catalytic converter 9a , 3b NOx including three-way catalysis
The conversion performance will be diagnosed.
【0028】次いで、P8では、前記P6で演算したN
Ox濃度比Rと、前記P7で求めた基準値R0 とを比較
し、基準値R0 よりも実際のNOx濃度比Rが大きい場
合には、触媒コンバータ9a,9bにおけるNOx転化
性能が正常であると見做し、P10で警告灯19をOFFに
制御し、間接的に触媒コンバータ9a,9bが正常にN
Ox浄化を行っていることを示す。Next, at P8, the N calculated at P6 is calculated.
Compared with Ox concentration ratio R, and the reference value R 0 which has been determined by the P7, when the reference value the actual NOx concentration ratio R than R 0 is large, NOx conversion performance catalytic converters 9a, at 9b is normal Assuming that there is, the warning light 19 is controlled to be turned off at P10 and indirectly the catalytic converters 9a and 9b are normally operated.
Indicates that Ox purification is being performed.
【0029】一方、P8で、基準値R0 よりも実際のN
Ox濃度比Rが小さいと判別された場合には、触媒コン
バータ9a,9bの劣化によってNOx転化性能が低下
しているものと判断し、P9で警告灯19をONにして、
運転者等に触媒コンバータ9a,9bにおけるNOx転
化性能の低下を警告する。このように、上記実施例によ
ると、希薄空燃比燃焼状態でNOxを浄化するリーンN
Ox触媒作用の診断を行わせることが可能となり、ま
た、NOx転化性能の低下時には警告灯19を点灯させて
知らせるから、希薄燃焼状態でNOxを浄化できない状
態のまま機関が運転されることを抑止できる。On the other hand, at P8, the actual N is larger than the reference value R 0.
When it is determined that the Ox concentration ratio R is small, it is determined that the NOx conversion performance is deteriorated due to deterioration of the catalytic converters 9a and 9b, and the warning light 19 is turned on at P9,
The driver or the like is warned that the catalytic converters 9a and 9b have deteriorated NOx conversion performance. As described above, according to the above embodiment, the lean N that purifies NOx in the lean air-fuel ratio combustion state is used.
It becomes possible to diagnose the Ox catalytic action, and when the NOx conversion performance deteriorates, the warning lamp 19 is turned on to notify the operator, so that the engine is prevented from operating in the lean combustion state where NOx cannot be purified. it can.
【0030】ところで、上記のような触媒劣化診断によ
って、触媒コンバータ9a,9bにおけるリーンNOx
触媒作用の低下が診断されたときには、希薄燃焼を実行
させると、NOxが浄化されないまま排出されることに
なってしまう。そこで、希薄燃焼時のNOx濃度比の判
別に基づいてリーンNOx触媒作用の低下が診断された
ときには、希薄燃焼をキャンセルし、希薄燃焼領域とし
て初期設定されている領域での目標空燃比を強制的に理
論空燃比とし、触媒コンバータ9a,9bにおける三元
触媒作用でNOxを確実に浄化させるようにすると良
い。By the way, by the catalyst deterioration diagnosis as described above, the lean NOx in the catalytic converters 9a and 9b is obtained.
If the lean combustion is executed when it is diagnosed that the catalytic action is lowered, NOx is exhausted without being purified. Therefore, when a decrease in the lean NOx catalytic action is diagnosed based on the determination of the NOx concentration ratio during lean combustion, the lean combustion is canceled and the target air-fuel ratio in the region initially set as the lean burn region is forced. It is preferable that the theoretical air-fuel ratio is set to NOx and NOx is surely purified by the three-way catalytic action in the catalytic converters 9a and 9b.
【0031】このように、リーンNOx触媒作用の劣化
診断に基づいて、希薄燃焼領域での目標空燃比を強制的
に理論空燃比に切り換える第2実施例を以下に説明す
る。図7は、第2実施例の触媒劣化診断装置及び燃料噴
射制御装置の構成を簡略化して示すブロック図である。
この図7のブロック図においては、図4に示した構成に
加え、クランク角センサ12及びエアフローメータ11の出
力に基づいて基本燃料噴射量Tpを演算する基本燃料噴
射量演算手段E、該基本燃料噴射量演算手段Eで演算さ
れた基本燃料噴射量Tpと診断手段Cの診断結果とに基
づいて最終的な燃料噴射量Tiを演算する噴射量演算手
段F(空燃比切り換え制御手段)、該噴射量演算手段F
で演算された燃料噴射量Tiに基づいて燃料噴射弁5を
駆動制御する噴射弁駆動手段Gが、コントロールユニッ
ト10の機能として設けられている。A second embodiment for forcibly switching the target air-fuel ratio in the lean burn region to the stoichiometric air-fuel ratio based on the deterioration diagnosis of the lean NOx catalytic action will be described below. FIG. 7 is a block diagram showing a simplified configuration of the catalyst deterioration diagnosis device and the fuel injection control device of the second embodiment.
In the block diagram of FIG. 7, in addition to the configuration shown in FIG. 4, basic fuel injection amount calculation means E for calculating the basic fuel injection amount Tp based on the outputs of the crank angle sensor 12 and the air flow meter 11, and the basic fuel An injection amount calculation unit F (air-fuel ratio switching control unit) that calculates a final fuel injection amount Ti based on the basic fuel injection amount Tp calculated by the injection amount calculation unit E and the diagnosis result of the diagnosis unit C. Quantity calculation means F
An injection valve driving means G for driving and controlling the fuel injection valve 5 on the basis of the fuel injection amount Ti calculated in (3) is provided as a function of the control unit 10.
【0032】ここで、前記噴射量演算手段Fは、診断手
段Cによって触媒コンバータ9a,9bにおけるリーン
NOx触媒作用が低下していることが判別されると、希
薄空燃比に対応する噴射量の設定をキャンセルし、代わ
りに、理論空燃比に対応する噴射量の演算を行う。そし
て、かかる噴射量演算手段Fによる演算結果を受けて、
噴射弁駆動手段Gは、燃料噴射弁5に対して機関回転に
同期した所定タイミングで噴射量Ti相当のパスル幅を
有する噴射パルス信号を出力する。Here, when the diagnosis means C determines that the lean NOx catalytic action in the catalytic converters 9a, 9b is decreased, the injection amount calculation means F sets the injection amount corresponding to the lean air-fuel ratio. Is canceled, and instead, the injection amount corresponding to the theoretical air-fuel ratio is calculated. Then, receiving the calculation result by the injection amount calculation means F,
The injection valve driving means G outputs an injection pulse signal having a pulse width corresponding to the injection amount Ti to the fuel injection valve 5 at a predetermined timing synchronized with the engine rotation.
【0033】次に、図8のフローチャートに従って、上
記に概略説明したリーンNOx触媒作用の診断、及び、
該診断結果を受けた空燃比制御の様子を詳細に説明す
る。図8のフローチャートにおいて、まず、P21では、
クランク角センサ12の検出信号に基づいて機関回転数N
eを検出する。次いで、P22では、エアフローメータ11
の検出信号に基づいて機関1の吸入空気量Qaを検出す
る。Next, according to the flow chart of FIG. 8, diagnosis of the lean NOx catalytic action outlined above, and
The state of the air-fuel ratio control that has received the diagnosis result will be described in detail. In the flowchart of FIG. 8, first, in P21,
Based on the detection signal of the crank angle sensor 12, the engine speed N
e is detected. Next, at P22, the air flow meter 11
The intake air amount Qa of the engine 1 is detected based on the detection signal of.
【0034】そして、P23では、前記機関回転数Neと
吸入空気量Qaとに基づいて前記燃料噴射弁5における
基本噴射量(基本噴射パルス幅)Tp=K×Qa/Ne
(Kは噴射弁5の流量特性に対応する比例定数であ
る。)を演算する。尚、該基本噴射量Tpは、理論空燃
比相当値として演算されるようにしてある。次のP24で
は、機関回転数Ne及び基本噴射量Tpから予め設定さ
れている希薄燃焼領域であるか否かを判別を行い、希薄
燃焼領域であるときには、P25へ進む。At P23, the basic injection amount (basic injection pulse width) Tp = K × Qa / Ne in the fuel injection valve 5 is calculated based on the engine speed Ne and the intake air amount Qa.
(K is a proportional constant corresponding to the flow rate characteristic of the injection valve 5.) is calculated. The basic injection amount Tp is calculated as a theoretical air-fuel ratio equivalent value. At the next P24, it is judged from the engine speed Ne and the basic injection amount Tp whether or not it is a preset lean combustion region. If it is at the lean combustion region, the routine proceeds to P25.
【0035】P25では、前記基本噴射量Tpに基づき、
以下の式に従って噴射量Tiを演算する。 Ti=(14.6/22)×Tp+Ts 上記演算式は、理論空燃比(空燃比=14.6)相当値とし
て演算された基本噴射量Tpを、希薄燃焼領域における
目標の希薄空燃比(=22)に相当する値に変換するもの
であり、また、Tsは噴射弁5の無効噴射時間を補正す
るための値であって噴射弁5の電源であるバッテリ電圧
により決定される。At P25, based on the basic injection amount Tp,
The injection amount Ti is calculated according to the following formula. Ti = (14.6 / 22) × Tp + Ts In the above calculation formula, the basic injection amount Tp calculated as the theoretical air-fuel ratio (air-fuel ratio = 14.6) equivalent value corresponds to the target lean air-fuel ratio (= 22) in the lean combustion region. And Ts is a value for correcting the invalid injection time of the injection valve 5 and is determined by the battery voltage which is the power source of the injection valve 5.
【0036】そして、上記の希薄空燃比(=22)を目標
空燃比として演算された燃料噴射量Tiに従って噴射弁
5の噴射が制御される状態において、P26以降のNOx
転化性能の診断を行わせることで、触媒コンバータ9
a,9bにおけるリーンNOx触媒作用の劣化を診断さ
せる。P26では、触媒コンバータ9a,9bの上流側に
設けられたNOxセンサ16a,16b(第1NOxセン
サ)の出力VRU,VLUを測定する。Then, in the state where the injection of the injection valve 5 is controlled in accordance with the fuel injection amount Ti calculated with the above lean air-fuel ratio (= 22) as the target air-fuel ratio, NOx after P26.
By diagnosing the conversion performance, the catalytic converter 9
The deterioration of the lean NOx catalytic action in a and 9b is diagnosed. At P26, the outputs V RU and V LU of the NOx sensors 16a and 16b (first NOx sensor) provided on the upstream side of the catalytic converters 9a and 9b are measured.
【0037】更に、P27では、触媒コンバータ9a,9
bの下流側に設けられたNOxセンサ18a,18b(第2
NOxセンサ)の出力VRD,VLDを測定する。そして、
次のP28では、前記測定された出力に基づいて触媒コン
バータ9a,9bにおけるNOx転換率を示す触媒上下
流間におけるNOx濃度比Rを前記数1に従って演算す
る。Further, at P27, the catalytic converters 9a, 9
NOx sensors 18a, 18b (second
The outputs V RD and V LD of the NOx sensor) are measured. And
Next, at P28, the NOx concentration ratio R between the upstream and downstream of the catalyst, which indicates the NOx conversion rate in the catalytic converters 9a and 9b, is calculated based on the measured output according to the above mathematical expression 1.
【0038】一方、P29では、前記機関回転数Neと基
本燃料噴射量Tp(機関負荷)とに基づいて前記NOx
濃度比Rの判別に用いる基準値R0 を可変設定する(図
6参照)。次いで、P30では、前記P28で演算したNO
x濃度比Rと、前記P29で求めた基準値R0 とを比較
し、基準値R0 よりも実際のNOx濃度比Rが大きい場
合には、触媒コンバータ9a,9bにおけるリーンNO
x触媒作用(希薄燃焼状態でNOxを還元処理する作
用)が正常に機能しているものと判断する。そして、こ
の場合には、P31へ進み、警告灯19をOFFし、通常に
希薄燃焼領域での希薄空燃比を目標空燃比とする燃料制
御を継続させる。On the other hand, at P29, the NOx is calculated based on the engine speed Ne and the basic fuel injection amount Tp (engine load).
The reference value R 0 used to determine the density ratio R is variably set (see FIG. 6). Next, at P30, the NO calculated at P28
and x concentration ratio R, compared with a reference value R 0 which has been determined by the P29, when the reference value R 0 actual NOx concentration ratio R than is large, the catalytic converter 9a, lean in 9b NO
It is determined that the x-catalytic action (the action of reducing NOx in the lean burn state) is functioning normally. Then, in this case, the routine proceeds to P31, the warning light 19 is turned off, and the fuel control that normally makes the lean air-fuel ratio in the lean burn region the target air-fuel ratio is continued.
【0039】一方、P30で基準値R0 よりも実際のNO
x濃度比Rが小さいと判別された場合には、触媒コンバ
ータ9a,9bにおけるリーンNOx触媒作用が低下し
ているものと判断し、P32で警告灯19をONにしてNO
x転化性能の低下を知らせると共に、空燃比切り換え制
御手段としてのP33では、前記P25で演算された希薄空
燃比(=22)を目標空燃比とする燃料噴射量Tiに代え
て、理論空燃比を目標空燃比とする燃料噴射量Ti=T
p+Tsを演算させる。そして、該理論空燃比相当の噴
射量Tiに基づいて噴射弁5を駆動制御させることで、
希薄燃焼領域における目標空燃比を本来の希薄空燃比か
ら理論空燃比に切り換えて噴射弁5による燃料噴射が制
御されるようにする。On the other hand, at P30, the actual NO is lower than the reference value R 0.
If it is determined that the x concentration ratio R is small, it is determined that the lean NOx catalytic action in the catalytic converters 9a and 9b is reduced, and the warning light 19 is turned on at P32 to turn NO.
In addition to notifying the decrease in the x conversion performance, in P33 as the air-fuel ratio switching control means, the theoretical air-fuel ratio is replaced with the lean air-fuel ratio (= 22) calculated in P25 instead of the fuel injection amount Ti which is the target air-fuel ratio. Fuel injection amount Ti = T for target air-fuel ratio
Calculate p + Ts. Then, by controlling the drive of the injection valve 5 based on the injection amount Ti corresponding to the theoretical air-fuel ratio,
The target air-fuel ratio in the lean burn region is switched from the original lean air-fuel ratio to the stoichiometric air-fuel ratio so that fuel injection by the injection valve 5 is controlled.
【0040】即ち、触媒コンバータ9a,9bにおける
リーンNOx触媒作用の低下が診断されたときには、そ
のまま希薄燃焼を継続させると、NOxが浄化されない
まま排出されることになってしまうので、希薄燃焼を停
止させて理論空燃比での燃焼を本来の希薄燃焼領域にお
いても行わせ、触媒コンバータ9a,9bにおける三元
触媒作用で排気(NOx)を浄化できるようにする。That is, when a decrease in lean NOx catalytic action in the catalytic converters 9a, 9b is diagnosed, if lean combustion is continued as it is, NOx will be discharged without being purified, so lean combustion will be stopped. Then, the combustion at the stoichiometric air-fuel ratio is performed even in the original lean combustion region, and the exhaust (NOx) can be purified by the three-way catalytic action in the catalytic converters 9a and 9b.
【0041】従って、触媒コンバータ9a,9bにおけ
るリーンNOx触媒作用が低下しても、三元触媒作用が
正常であれば、希薄燃焼は行えなくなるが、少なくとも
多量のNOxが排出される不具合の発生を回避できるよ
うになる。尚、上記各実施例では、触媒コンバータ9
a,9b(排気浄化触媒)におけるNOx転化率に相関
する排気中のNOx濃度を検出するNOxセンサとし
て、各触媒コンバータ9a,9bの上流側及び下流側に
設けられたNOxセンサ16a,16b,18a,18bを示し
たが、簡易的には触媒コンバータ9a,9bそれぞれの
下流側にのみNOxセンサを設け(上記実施例のNOx
センサ18a,18b)、かかるNOxセンサで検出される
触媒による浄化後の排気中のNOx濃度と、機関運転条
件(負荷,回転)から設定される基準濃度値との比較に
基づいて、NOx転化性能の低下を診断させるようにし
ても良い。Therefore, even if the lean NOx catalytic action in the catalytic converters 9a and 9b is lowered, lean combustion cannot be performed if the three-way catalytic action is normal, but at least a large amount of NOx is discharged. You can avoid it. In each of the above embodiments, the catalytic converter 9
NOx sensors 16a, 16b, 18a provided on the upstream side and the downstream side of each of the catalytic converters 9a, 9b as NOx sensors for detecting the NOx concentration in the exhaust gas that correlates with the NOx conversion rate of a, 9b (exhaust gas purification catalyst). , 18b are shown, but for the sake of simplicity, the NOx sensor is provided only on the downstream side of each of the catalytic converters 9a, 9b (NOx of the above-described embodiment.
The sensors 18a, 18b) and the NOx conversion performance based on the comparison between the NOx concentration in the exhaust gas after purification by the catalyst detected by the NOx sensor and the reference concentration value set from the engine operating conditions (load, rotation). May be diagnosed.
【0042】[0042]
【発明の効果】以上説明したように、本発明によると、
特に、希薄空燃比での燃焼状態(空気過剰雰囲気中)で
NOxを浄化し得る所謂リーンNOx触媒作用の診断が
行えるようになり、また、かかるリーンNOx触媒作用
が触媒劣化によって低下している状態のまま希薄燃焼が
続行されて、多量のNOxが排出されることを未然に防
止することが可能になるという効果がある。As described above, according to the present invention,
In particular, it becomes possible to diagnose a so-called lean NOx catalytic action that can purify NOx in a combustion state (in an excess air atmosphere) at a lean air-fuel ratio, and a state in which the lean NOx catalytic action is deteriorated due to catalyst deterioration. There is an effect that it is possible to prevent a large amount of NOx from being discharged by continuing the lean combustion as it is.
【図1】本発明の基本構成を示すブロック図。FIG. 1 is a block diagram showing the basic configuration of the present invention.
【図2】実施例のシステム構成を示す概略図。FIG. 2 is a schematic diagram showing a system configuration of an embodiment.
【図3】NOxセンサの特性を示す線図。FIG. 3 is a diagram showing characteristics of a NOx sensor.
【図4】第1実施例の構成を示すブロック図。FIG. 4 is a block diagram showing the configuration of the first embodiment.
【図5】第1実施例の診断制御を示すフローチャート。FIG. 5 is a flowchart showing diagnostic control of the first embodiment.
【図6】NOx濃度比の基準値を記憶したマップを示す
図。FIG. 6 is a diagram showing a map storing a reference value of a NOx concentration ratio.
【図7】第2実施例の構成を示すブロック図。FIG. 7 is a block diagram showing the configuration of a second embodiment.
【図8】第2実施例の診断制御及び空燃比制御を示すフ
ローチャート。FIG. 8 is a flowchart showing diagnostic control and air-fuel ratio control of the second embodiment.
1 内燃機関 5 燃料噴射弁 9a,9b 触媒コンバータ(排気浄化触媒) 10 コントロールユニット 11 エアフローメータ 12 クランク角センサ 16a,16b,18a,18b NOxセンサ 1 Internal Combustion Engine 5 Fuel Injection Valve 9a, 9b Catalytic Converter (Exhaust Gas Purification Catalyst) 10 Control Unit 11 Air Flow Meter 12 Crank Angle Sensor 16a, 16b, 18a, 18b NOx Sensor
Claims (2)
を有した排気浄化触媒が排気通路に介装される内燃機関
の触媒劣化診断装置であって、 前記排気浄化触媒におけるNOx転化率に相関する排気
中のNOx濃度を検出するNOxセンサと、 機関運転条件を検出する運転条件検出手段と、 該運転条件検出手段で検出される機関運転条件に基づい
て前記NOxセンサによる検出結果を判別するための基
準値を設定する基準値設定手段と、 前記NOxセンサによる検出結果を前記基準値設定手段
で設定された基準値に基づいて判別して前記排気浄化触
媒のNOx転化性能の低下を診断する診断手段と、 を含んで構成されたことを特徴とする内燃機関の触媒劣
化診断装置。1. A catalyst deterioration diagnosing device for an internal combustion engine in which an exhaust purification catalyst having a function of converting at least NOx in exhaust gas is interposed in an exhaust passage, and is related to a NOx conversion rate in the exhaust purification catalyst. A NOx sensor for detecting the NOx concentration in exhaust gas, an operating condition detecting means for detecting engine operating conditions, and an operating condition detecting means for determining the detection result by the NOx sensor based on the engine operating conditions detected by the operating condition detecting means. Reference value setting means for setting a reference value and diagnostic means for diagnosing a decrease in NOx conversion performance of the exhaust purification catalyst by discriminating the detection result by the NOx sensor based on the reference value set by the reference value setting means. And a catalyst deterioration diagnosing device for an internal combustion engine, comprising:
Oxを転化するリーンNOx触媒作用及び三元触媒作用
を有する触媒であって、かつ、前記内燃機関が所定の運
転領域で希薄空燃比を目標空燃比として運転される機関
であり、前記診断手段が前記希薄空燃比で機関が運転さ
れているときにNOx転化性能の低下を診断したとき
に、前記希薄空燃比を目標空燃比とする所定の運転領域
における目標空燃比を強制的に理論空燃比に切り換える
空燃比切り換え制御手段を設けたことを特徴とする請求
項1記載の内燃機関の触媒劣化診断装置。2. The exhaust purification catalyst is N 2 in an oxygen excess atmosphere.
A catalyst having a lean NOx catalytic action for converting Ox and a three-way catalytic action, and the internal combustion engine is operated at a lean air-fuel ratio as a target air-fuel ratio in a predetermined operating region. When diagnosing a decrease in NOx conversion performance while the engine is operating at the lean air-fuel ratio, the target air-fuel ratio in a predetermined operating region where the lean air-fuel ratio is the target air-fuel ratio is forcibly set to the theoretical air-fuel ratio. 2. A catalyst deterioration diagnosing device for an internal combustion engine according to claim 1, further comprising an air-fuel ratio switching control means for switching.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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JP05197525A JP3082523B2 (en) | 1993-08-09 | 1993-08-09 | Catalyst deterioration diagnosis device for internal combustion engine |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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JP05197525A JP3082523B2 (en) | 1993-08-09 | 1993-08-09 | Catalyst deterioration diagnosis device for internal combustion engine |
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JPH0754641A true JPH0754641A (en) | 1995-02-28 |
JP3082523B2 JP3082523B2 (en) | 2000-08-28 |
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ID=16375922
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2001336415A (en) * | 2000-03-21 | 2001-12-07 | Dmc 2 Degussa Metals Catalysts Cerdec Ag | Method for inspecting operability of catalyst for exhaust gas purification |
JP2007192169A (en) * | 2006-01-20 | 2007-08-02 | Honda Motor Co Ltd | Catalyst deterioration determination device |
WO2008093616A1 (en) | 2007-02-02 | 2008-08-07 | Bosch Corporation | Breakdown diagnosing device for exhaust cleaning system, and breakdown diagnosing method for exhaust cleaning system |
US8171723B2 (en) | 2007-12-06 | 2012-05-08 | Toyota Jidosha Kabushiki Kaisha | Abnormality detection system and abnormality detection method for internal combustion engine |
-
1993
- 1993-08-09 JP JP05197525A patent/JP3082523B2/en not_active Expired - Fee Related
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2001336415A (en) * | 2000-03-21 | 2001-12-07 | Dmc 2 Degussa Metals Catalysts Cerdec Ag | Method for inspecting operability of catalyst for exhaust gas purification |
JP4625194B2 (en) * | 2000-03-21 | 2011-02-02 | ユミコア・アクチエンゲゼルシャフト・ウント・コムパニー・コマンディットゲゼルシャフト | Method for checking the working capacity of an exhaust gas purifying catalyst |
JP2007192169A (en) * | 2006-01-20 | 2007-08-02 | Honda Motor Co Ltd | Catalyst deterioration determination device |
JP4729405B2 (en) * | 2006-01-20 | 2011-07-20 | 本田技研工業株式会社 | Catalyst deterioration judgment device |
WO2008093616A1 (en) | 2007-02-02 | 2008-08-07 | Bosch Corporation | Breakdown diagnosing device for exhaust cleaning system, and breakdown diagnosing method for exhaust cleaning system |
US8171723B2 (en) | 2007-12-06 | 2012-05-08 | Toyota Jidosha Kabushiki Kaisha | Abnormality detection system and abnormality detection method for internal combustion engine |
Also Published As
Publication number | Publication date |
---|---|
JP3082523B2 (en) | 2000-08-28 |
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