JPH08246851A - Secondary air supply device for internal combustion engine - Google Patents

Secondary air supply device for internal combustion engine

Info

Publication number
JPH08246851A
JPH08246851A JP7046010A JP4601095A JPH08246851A JP H08246851 A JPH08246851 A JP H08246851A JP 7046010 A JP7046010 A JP 7046010A JP 4601095 A JP4601095 A JP 4601095A JP H08246851 A JPH08246851 A JP H08246851A
Authority
JP
Japan
Prior art keywords
air
secondary air
state
fuel ratio
supply
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.)
Pending
Application number
JP7046010A
Other languages
Japanese (ja)
Inventor
Yoichi Kishimoto
洋一 岸本
Toshio Takahata
敏夫 高畑
Atsushi Shoji
淳 庄司
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nissan Motor Co Ltd
Original Assignee
Nissan Motor Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Nissan Motor Co Ltd filed Critical Nissan Motor Co Ltd
Priority to JP7046010A priority Critical patent/JPH08246851A/en
Publication of JPH08246851A publication Critical patent/JPH08246851A/en
Pending legal-status Critical Current

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
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F01N2550/14—Systems for adding secondary air into exhaust

Landscapes

  • Testing Of Engines (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Abstract

PURPOSE: To accurately diagnose leakage of a secondary air introducing passage by detecting the existence of secondary air in exhaust air on the basis of a detecting signal from an air-fuel ratio detecting means when a cutoff condition and a supply condition overlap with each other for a prescribed time, and judging it as leakage of an opening-closing means when the secondary air is detected. CONSTITUTION: An overlap of a cutoff condition by an air cut valve 22 generated at supply stopping time of secondary air and a supply condition by an air pump 21 is detected by a judging part 32b. A cutoff condition where the air cut valve 22 cuts off a secondary air introducing passage 20 by a condition overlapping part 32a and a supply condition where the air pump 21 delivers and supplies secondary air in the secondary air introducing passage 20, are overlapped with each other for only a prescribed short time. The existence of the secondary air is detected in this overlapped condition on the basis of the air-fuel ratio in exhaust gas detected by a first air-fuel ratio sensor 16 by a judging part 32b. Therefore, when the secondary air is detected, since it is judged as leakage of the air cut valve 22, valve opening failure can be accurately diagnosed.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、所定の運転条件下で２
次空気導入路を介して排気通路内に２次空気を導入し、
触媒コンバータの転化効率を維持、向上させる内燃機関
の２次空気供給装置に関し、特に、２次空気導入路内に
２次空気を吐出供給する２次空気供給手段と、２次空気
導入路を連通，遮断する開閉手段を備えた内燃機関の２
次空気供給装置に関する。BACKGROUND OF THE INVENTION The present invention is designed for use under certain operating conditions.
Secondary air is introduced into the exhaust passage through the secondary air introduction passage,
The present invention relates to a secondary air supply device for an internal combustion engine that maintains and improves the conversion efficiency of a catalytic converter, and in particular, connects a secondary air supply means for discharging secondary air into a secondary air introduction passage and a secondary air introduction passage. , 2 of internal combustion engine equipped with opening / closing means for shutting off
Regarding the secondary air supply device.

【０００２】[0002]

【従来の技術】機関本体から排出される排気中のＨＣ、
ＣＯ、ＮＯX等を除去すべく、排気通路の途中には、三
元触媒等からなる触媒コンバータが介装されている。そ
して、この触媒コンバータは、理論空燃比近傍の環境で
転化性能（酸化反応）を発揮するため、２次空気導入路
を介して排気通路内に２次空気を供給する２次空気供給
装置を設けている。2. Description of the Related Art HC in exhaust gas discharged from an engine body,
In order to remove CO, NO X, etc., a catalytic converter including a three-way catalyst or the like is provided in the middle of the exhaust passage. Since this catalytic converter exhibits conversion performance (oxidation reaction) in an environment near the stoichiometric air-fuel ratio, it is provided with a secondary air supply device that supplies secondary air into the exhaust passage via the secondary air introduction passage. ing.

【０００３】つまり、排気通路に接続して設けられた２
次空気導入路と、２次空気導入路の途中に設けられ、２
次空気を吐出供給する２次空気供給手段としてのエアポ
ンプと、エアポンプよりも下流側に位置して２次空気導
入路に設けられ、２次空気導入路を連通，遮断する開閉
手段としてのエアカット弁とを備えて２次空気供給装置
を構成し、例えば空燃比がリッチ側にクランプされた場
合等の如く、排気中の酸素が不足する運転条件下で２次
空気を供給することにより、触媒コンバータの転化性能
（酸化反応）を維持している。That is, 2 provided connected to the exhaust passage
It is provided in the middle of the secondary air introduction path and the secondary air introduction path,
An air pump as a secondary air supply means for discharging and supplying the secondary air, and an air cut as an opening / closing means which is provided on the secondary air introduction path located on the downstream side of the air pump and which connects and disconnects the secondary air introduction path. And a valve to form a secondary air supply device, and by supplying the secondary air under operating conditions in which oxygen in exhaust gas is insufficient, such as when the air-fuel ratio is clamped to the rich side, The conversion performance (oxidation reaction) of the converter is maintained.

【０００４】従って、例えば２次空気導入路が閉塞等し
て、２次空気が十分に供給できない場合には、十分な酸
化が行われないため、排気中のＨＣ等が増大する上に、
触媒コンバータ自体の温度も活性化温度より低下して一
層転化効率が悪化する。そこで、例えば特開平５−３０
２５１１号公報、特開平５−２９６０３３号公報、特開
平４−１４４３号公報、特開平４−３０８３１２号公報
等では、空燃比センサ（酸素センサ）により２次空気導
入後における排気中の空燃比を検出して、この検出され
た空燃比がリーン側である場合には２次空気の供給が正
常に行われていると判定し、検出された空燃比がリッチ
側である場合には異常であると判定する自己診断機能を
備えている。Therefore, for example, when the secondary air cannot be supplied sufficiently due to the obstruction of the secondary air introduction passage, sufficient oxidation is not performed, so that HC and the like in the exhaust gas increase and
The temperature of the catalytic converter itself also falls below the activation temperature, further degrading the conversion efficiency. Therefore, for example, Japanese Patent Laid-Open No. 5-30
In Japanese Patent No. 2511, Japanese Unexamined Patent Publication No. 5-296033, Japanese Unexamined Patent Publication No. 4-1443, Japanese Unexamined Patent Publication No. 4-308312, the air-fuel ratio in the exhaust gas after the introduction of secondary air is measured by an air-fuel ratio sensor (oxygen sensor). When the detected air-fuel ratio is on the lean side, it is determined that the secondary air is normally supplied, and when the detected air-fuel ratio is on the rich side, it is abnormal. It is equipped with a self-diagnosis function.

【０００５】[0005]

【発明が解決しようとする課題】上述した自己診断機能
を有する２次空気供給装置では、２次空気導入後の排気
中の空燃比を監視し、この空燃比がリッチ側であれば、
２次空気の供給に異常ありと判定するため、２次空気導
入路の閉塞や、エアカット弁の開弁不良（エアカット弁
が開かない状態）等の如き「供給異常」を検出できる
が、かかる自己診断では、２次空気導入時に空燃比がリ
ーン側であれば正常であると判定するため、その現象が
リーン側の空燃比として現れるエアカット弁の閉弁不良
（エアカット弁が閉じない状態）を検出できない。In the secondary air supply device having the self-diagnosis function described above, the air-fuel ratio in the exhaust gas after the introduction of the secondary air is monitored, and if this air-fuel ratio is on the rich side,
Since it is determined that there is an abnormality in the supply of the secondary air, it is possible to detect a "supply abnormality" such as a blockage of the secondary air introduction passage or a defective opening of the air cut valve (a state where the air cut valve is not open). In such self-diagnosis, if the air-fuel ratio is lean when the secondary air is introduced, it is determined to be normal. Therefore, the phenomenon appears as an air-fuel ratio on the lean side. Poor closing of the air cut valve (air cut valve does not close. Status) cannot be detected.

【０００６】もちろん、エアカット弁に閉弁不良が生じ
ても、エアポンプ自体が作動しなければ、原則として２
次空気が排気通路内に導入されることはないため、この
エアカット弁の閉弁不良によって、直ちに触媒コンバー
タの転化性能が著しく低下する等の不具合は生じない。
しかし、エアカット弁が開いたままになる異常状態を放
置すれば、排気通路内の排気が２次空気導入路を介して
エアカット弁やエアポンプにまで逆流し、排気中の成分
（例えばカーボン等）が徐々にこれら各機器に付着等し
て、他の故障を誘発する可能性がある。Of course, as a general rule, if the air cut valve fails to close, but the air pump itself does not operate,
Since the secondary air is not introduced into the exhaust passage, the incomplete closing of the air cut valve does not cause a problem such that the conversion performance of the catalytic converter is remarkably deteriorated immediately.
However, if the abnormal state in which the air cut valve remains open is left, the exhaust gas in the exhaust passage flows back to the air cut valve and the air pump through the secondary air introduction passage, and the components in the exhaust gas (for example, carbon etc.) ) May gradually adhere to each of these devices and cause other failures.

【０００７】本発明は、かかる従来技術の問題点に鑑み
てなされたもので、その目的は、開閉手段による２次空
気導入路の遮断が正常に行われているか否かの診断を行
うことができるようにした内燃機関の２次空気供給装置
を提供することにある。The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to make a diagnosis as to whether or not the secondary air introducing passage is normally shut off by the opening / closing means. It is an object of the present invention to provide a secondary air supply device for an internal combustion engine that is made possible.

【０００８】[0008]

【課題を解決するための手段】そこで、本発明は、開閉
手段が２次空気導入路を遮断している状態で、２次空気
供給手段から２次空気を吐出せしめ、この２次空気が排
気通路内に現れるか否かを空燃比検出手段を介して監視
することにより、開閉手段の遮断が正常に行われている
か否かを診断するようにした。即ち、本発明に係る内燃
機関の２次空気供給装置が採用する構成は、触媒コンバ
ータの上流側に位置して排気通路の途中に接続された２
次空気導入路と、この２次空気導入路内に２次空気を吐
出供給する２次空気供給手段と、この２次空気供給手段
よりも下流側に位置して前記２次空気導入路の途中に設
けられ、該２次空気導入路を連通，遮断する開閉手段
と、前記２次空気導入路の排気通路接続部よりも下流側
に位置して前記排気通路の途中に設けられ、空燃比を検
出する空燃比検出手段とを備えた内燃機関の２次空気供
給装置であって、前記開閉手段が前記２次空気導入路を
遮断している遮断状態と前記２次空気供給手段が前記２
次空気導入路内に２次空気を吐出供給している供給状態
とを所定の短時間だけ重複させる状態重複手段と、前記
遮断状態と前記供給状態とが重複しているときに、前記
空燃比検出手段からの検出信号に基づいて排気中におけ
る２次空気の有無を検出し、２次空気が検出された場合
は前記開閉手段の漏洩であると判定する判定手段とを設
けたことを特徴としている。Therefore, according to the present invention, the secondary air is discharged from the secondary air supply means in a state where the opening / closing means blocks the secondary air introduction path, and the secondary air is exhausted. By monitoring whether or not it appears in the passage through the air-fuel ratio detecting means, it is possible to diagnose whether or not the opening / closing means is normally shut off. That is, the configuration adopted by the secondary air supply system for an internal combustion engine according to the present invention is located upstream of the catalytic converter and connected in the middle of the exhaust passage.
A secondary air introduction path, a secondary air supply means for discharging secondary air into the secondary air introduction path, and a downstream side of the secondary air supply means, which is in the middle of the secondary air introduction path. And an opening / closing means for connecting and disconnecting the secondary air introducing passage and a part of the secondary air introducing passage which is located downstream of the exhaust passage connecting portion and which is provided in the middle of the exhaust passage. A secondary air supply device for an internal combustion engine, comprising: an air-fuel ratio detection means for detecting; a shut-off state in which the opening / closing means shuts off the secondary air introduction path, and the secondary air supply means
When the supply state in which the secondary air is discharged and supplied into the secondary air introduction path overlaps for a predetermined short time, and the cut-off state and the supply state overlap, the air-fuel ratio The presence of secondary air in the exhaust gas is detected based on the detection signal from the detection means, and when the secondary air is detected, a determination means for determining the leakage of the opening / closing means is provided. There is.

【０００９】また、前記状態重複手段は、前記２次空気
供給手段の供給停止時期を前記開閉手段の閉時期よりも
所定の短時間だけ遅らせることにより、前記遮断状態と
前記供給状態とを所定の短時間だけ重複させるようにし
てもよい。Further, the state overlapping means delays the supply stop timing of the secondary air supply means by a predetermined short time from the closing timing of the opening / closing means, so that the shut-off state and the supply state are predetermined. You may make it overlap only for a short time.

【００１０】さらに、前記状態重複手段は、前記開閉手
段が前記２次空気導入路を遮断している期間中に、所定
の短時間だけ前記２次空気供給手段から２次空気を吐出
させることにより、前記遮断状態と前記供給状態とを所
定の短時間だけ重複させるようにしてもよい。Further, the state overlapping means discharges the secondary air from the secondary air supply means for a predetermined short time while the opening / closing means is blocking the secondary air introducing passage. The shut-off state and the supply state may be overlapped for a predetermined short time.

【００１１】また、前記状態重複手段は、前記２次空気
供給手段が前記２次空気導入路内に２次空気を吐出供給
している期間中に、所定の短時間だけ前記開閉手段によ
って前記２次空気導入路を遮断させることにより、前記
遮断状態と前記供給状態とを所定の短時間だけ重複させ
るようにしてもよい。Further, the state overlapping means is configured to operate the opening / closing means for a predetermined short time while the secondary air supply means is discharging and supplying the secondary air into the secondary air introducing passage. The cutoff state and the supply state may be overlapped for a predetermined short time period by blocking the next air introduction path.

【００１２】[0012]

【作用】状態重複手段によって、開閉手段が２次空気導
入路を遮断する遮断状態と２次空気供給手段が２次空気
導入路内に２次空気を吐出供給する供給状態とが所定の
短時間だけ重複した場合、開閉手段による２次空気導入
路の遮断が正常に行われているならば、排気通路内に２
次空気が流入せず、逆に、開閉手段による遮断に異常が
あるならば、排気通路内に２次空気が流入する。従っ
て、空燃比検出手段を介して排気中の２次空気の有無を
検出することにより、開閉手段の漏洩を判定することが
できる。With the state overlapping means, the shut-off state in which the opening / closing means shuts off the secondary air introduction path and the supply state in which the secondary air supply means discharges the secondary air into the secondary air introduction path for a predetermined time. If the secondary air introduction path is normally shut off by the opening / closing means in the case of overlap, only 2 in the exhaust passage.
If the secondary air does not flow in, and conversely there is an abnormality in the shutoff by the opening / closing means, secondary air will flow into the exhaust passage. Therefore, the leakage of the opening / closing means can be determined by detecting the presence or absence of the secondary air in the exhaust gas via the air-fuel ratio detecting means.

【００１３】また、２次空気供給手段の供給停止時期を
開閉手段の閉時期よりも所定の短時間だけ遅らせること
により、遮断状態と供給状態とを所定の短時間だけ重複
させる構成とすれば、通常処理による２次空気の供給停
止時に、開閉手段の漏洩を簡易に診断することができ
る。Further, if the supply stop timing of the secondary air supply means is delayed by a predetermined short time after the closing timing of the opening / closing means, the shut-off state and the supply state are overlapped by a predetermined short time. The leakage of the opening / closing means can be easily diagnosed when the supply of the secondary air is stopped by the normal processing.

【００１４】さらに、開閉手段が２次空気導入路を遮断
している期間中に、所定の短時間だけ２次空気供給手段
から２次空気を吐出させることにより、遮断状態と供給
状態とを所定の短時間だけ重複させる構成とすれば、例
えば機関暖機後の如く、通常２次空気を供給しない運転
条件下で、開閉手段の漏洩を積極的に診断することがで
きる。Further, while the opening / closing means is shutting off the secondary air introduction passage, the secondary air is discharged from the secondary air supply means for a predetermined short time so that the shut-off state and the supply state are predetermined. If it is configured to be overlapped for a short period of time, leakage of the opening / closing means can be positively diagnosed under operating conditions in which secondary air is not normally supplied, such as after engine warm-up.

【００１５】また、２次空気供給手段が２次空気を吐出
供給している期間中に、所定の短時間だけ開閉手段によ
って２次空気導入路を遮断させることにより、遮断状態
と供給状態とを所定の短時間だけ重複させる構成とすれ
ば、例えば低水温時等の如く、２次空気を供給する運転
条件下で、積極的に開閉手段の漏洩を診断することがで
きる。Further, while the secondary air supply means is discharging and supplying the secondary air, the opening / closing means shuts off the secondary air introduction path for a predetermined short time so that the shut-off state and the supply state are changed. If the structure is made to overlap for a predetermined short time, the leakage of the opening / closing means can be positively diagnosed under operating conditions in which the secondary air is supplied, such as when the water temperature is low.

【００１６】[0016]

【実施例】以下、本発明の実施例を図１〜図１１に基づ
いて詳細に説明する。Embodiments of the present invention will now be described in detail with reference to FIGS.

【００１７】まず、図１〜図３は、本発明の第１の実施
例に係り、図１は、本実施例による内燃機関の２次空気
供給装置の全体構成を示す構成説明図であって、シリン
ダブロック１に列設された複数のシリンダ２内にはピス
トン３が設けられ、このピストン３は、シリンダ２の上
側を気液密に施蓋して設けられたシリンダヘッド４との
間に燃焼室５を画成している。このシリンダヘッド４に
は、吸気通路６，排気通路７が互いに対向して、各シリ
ンダ２毎に接続されていると共に、その頂部には、後述
するコントロールユニット３２からの信号によって燃焼
室５内の混合気を着火燃焼させる点火栓８が設けられて
いる。First, FIGS. 1 to 3 relate to a first embodiment of the present invention, and FIG. 1 is a structural explanatory view showing the overall structure of a secondary air supply system for an internal combustion engine according to this embodiment. A piston 3 is provided in each of the plurality of cylinders 2 arranged in line in the cylinder block 1, and the piston 3 is provided between the cylinder head 4 and the cylinder head 4, which is provided by covering the upper side of the cylinder 2 in a gas-liquid tight manner. It defines the combustion chamber 5. An intake passage 6 and an exhaust passage 7 are connected to the cylinder head 4 so as to oppose each other for each cylinder 2, and the top of the cylinder head 4 is provided with a signal from a control unit 32, which will be described later, inside the combustion chamber 5. An ignition plug 8 for igniting and burning the air-fuel mixture is provided.

【００１８】吸気通路６は、その下流側がシリンダヘッ
ド４内で二股に分岐する一対の吸気ポート６Ａとなり、
その上流側は吸気集合通路９に接続されている。排気通
路７は、その上流側がシリンダヘッド４内で二股に分岐
する一対の排気ポート７Ａとなり、その下流側は図外の
マフラに接続されている。そして、これら吸気通路６，
排気通路７は、図示せぬ動弁機構により駆動される吸気
弁１０，排気弁１１を介して燃焼室５内と連通するよう
になっている。また、吸気通路６の途中には、コントロ
ールユニット３２からの燃料噴射パルスに応じて開弁す
ることにより吸気ポート６Ａ内に燃料を噴射する燃料噴
射弁１２が設けられ、吸気集合通路９には、その上流側
から順に、空気中の塵埃を除去するエアフィルタ１３，
吸入空気量を検出するエアフローメータ１４，吸入空気
量を調整するスロットル弁１５が設けられている。The intake passage 6 has a pair of intake ports 6A on the downstream side thereof, which branch into two branches in the cylinder head 4.
The upstream side is connected to the intake collecting passage 9. The exhaust passage 7 has a pair of exhaust ports 7A whose upstream side branches into two in the cylinder head 4 and whose downstream side is connected to a muffler (not shown). Then, these intake passages 6,
The exhaust passage 7 communicates with the inside of the combustion chamber 5 via an intake valve 10 and an exhaust valve 11 driven by a valve mechanism (not shown). Further, in the middle of the intake passage 6, a fuel injection valve 12 for injecting fuel into the intake port 6A by opening the valve in response to a fuel injection pulse from the control unit 32 is provided. An air filter 13 for removing dust in the air in order from the upstream side,
An air flow meter 14 for detecting the intake air amount and a throttle valve 15 for adjusting the intake air amount are provided.

【００１９】一方、排気通路７の途中には、その上流側
から順に、排気中の空燃比（酸素濃度）を検出する「空
燃比検出手段」としての第１の空燃比センサ１６，排気
中のＨＣ，ＣＯ，ＮＯX等を酸化還元反応によって除去
する触媒コンバータ１７，排気の温度を検出する排気温
度センサ１８，触媒コンバータ１７通過後の排気中の空
燃比を検出する第２の空燃比センサ１９が設けられてい
る。これら各空燃比センサ１６，１９は、排気中の残存
酸素濃度に応じた起電力を検出信号としてコントロール
ユニット３２に出力するもので、例えばジルコニア管式
の酸素センサが使用される。そして、これら各空燃比セ
ンサ１６，１９は、理論空燃比を境に、その起電力がス
テップ状に急変すると共に、常温程度で例えば２８０ｍ
Ｖ程度の基準電圧を発生するものである。On the other hand, in the middle of the exhaust passage 7, the first air-fuel ratio sensor 16 as "air-fuel ratio detecting means" for detecting the air-fuel ratio (oxygen concentration) in the exhaust gas in order from the upstream side, Catalytic converter 17 that removes HC, CO, NO x, etc. by redox reaction, exhaust temperature sensor 18 that detects the temperature of exhaust gas, second air-fuel ratio sensor 19 that detects the air-fuel ratio in the exhaust gas after passing through catalytic converter 17. Is provided. Each of the air-fuel ratio sensors 16 and 19 outputs an electromotive force corresponding to the residual oxygen concentration in the exhaust gas as a detection signal to the control unit 32. For example, a zirconia tube type oxygen sensor is used. The electromotive force of each of the air-fuel ratio sensors 16 and 19 suddenly changes in steps at the stoichiometric air-fuel ratio, and at room temperature, for example, 280 m.
A reference voltage of about V is generated.

【００２０】吸気集合通路９と排気通路７との間には２
次空気を流通させるための２次空気導入路２０が設けら
れ、この２次空気導入路２０は、その流入口２０Ａがエ
アフローメータ１４とエアフィルタ１３との間に位置し
て吸気集合通路９の途中に開口し、「排気通路接続部」
としての流出口２０Ｂが第１の空燃比センサ１６の上流
側近傍に位置して排気通路７の途中に開口している。ま
た、２次空気導入路２０の途中には、「２次空気供給手
段」としてのエアポンプ２１と、「開閉手段」としての
エアカット弁２２とが設けられている。2 are provided between the intake collecting passage 9 and the exhaust passage 7.
A secondary air introducing passage 20 for circulating the secondary air is provided, and the secondary air introducing passage 20 has an inflow port 20A located between the air flow meter 14 and the air filter 13 and is provided in the intake collecting passage 9. Open in the middle, "Exhaust passage connection part"
Is located near the upstream side of the first air-fuel ratio sensor 16 and opens in the middle of the exhaust passage 7. An air pump 21 as a “secondary air supply means” and an air cut valve 22 as an “opening / closing means” are provided in the middle of the secondary air introducing passage 20.

【００２１】このエアポンプ２１は、吸気集合通路９か
ら吸引した空気を加圧して２次空気導入路２０内に吐出
供給するもので、その流入口，吐出口には図示せぬサイ
レンサが設けられており、コントロールユニット３２か
らの駆動信号によってモータが回転することにより作動
するものである。このエアポンプ２１によって、排気通
路７内の圧力に抗しつつ、２次空気導入路２０内に２次
空気を略安定的に吐出供給することができる。なお、エ
アポンプ２１としては、例えばタービンベーンやスクロ
ール、スクリュー、ピストン、ロータリピストン等の各
種ポンプを利用できる。また、エアポンプ２１の吐出側
にエアタンクを設け、このエアタンクを介して２次空気
を供給する構成としてもよい。この場合は、部品点数が
増大し、全体寸法も大型化するが、吐出圧を速やかに立
ち上げることができる。The air pump 21 pressurizes the air sucked from the intake collecting passage 9 and discharges it into the secondary air introducing passage 20, and a silencer (not shown) is provided at its inlet and outlet. The motor is operated by rotating the motor in response to a drive signal from the control unit 32. By this air pump 21, it is possible to discharge and supply the secondary air into the secondary air introducing passage 20 substantially stably while resisting the pressure in the exhaust passage 7. As the air pump 21, various pumps such as a turbine vane, a scroll, a screw, a piston, and a rotary piston can be used. Further, an air tank may be provided on the discharge side of the air pump 21 and the secondary air may be supplied via this air tank. In this case, the number of parts increases and the overall size increases, but the discharge pressure can be raised quickly.

【００２２】一方、エアカット弁２２は、２次空気の流
通を強制的に遮断するためのものであり、ケーシング２
２Ａと、このケーシング２２Ａ内を上側に位置する制御
圧室２２Ｂと下側に位置する２次空気室２２Ｃとに画成
するダイヤフラム２２Ｄと、２次空気室２２Ｃ内に位置
してダイヤフラム２２Ｄに設けられ、２次空気導入路２
０の途中に位置して形成された弁座２２Ｅに離着座する
弁体２２Ｆと、この弁体２２Ｆをダイヤフラム２２Ｄを
介して閉弁方向に付勢する弁ばね２２Ｇとから大略構成
されている。そして、このエアカット弁２２は、後述す
る負圧制御用の電磁弁２３からのパイロット圧によって
弁体２２Ｆを開弁，閉弁させることにより、２次空気導
入路２０の途中を連通，遮断するようになっている。On the other hand, the air cut valve 22 is for forcibly shutting off the flow of the secondary air, and the casing 2
2A, a diaphragm 22D defining a control pressure chamber 22B located on the upper side and a secondary air chamber 22C located on the lower side in the casing 22A, and a diaphragm 22D located in the secondary air chamber 22C. The secondary air introduction path 2
The valve body 22F is formed of a valve seat 22E that is formed in the middle of 0, and a valve spring 22G that biases the valve body 22F in a valve closing direction via a diaphragm 22D. Then, the air cut valve 22 opens and closes the valve body 22F by a pilot pressure from a solenoid valve 23 for negative pressure control, which will be described later, thereby connecting and blocking the middle of the secondary air introduction passage 20. It is like this.

【００２３】電磁弁２３は、径方向に開口する流出ポー
ト２３Ａ，軸方向に互いに対向して開口する第１の流入
ポート２３Ｂ及び第２の流入ポート２３Ｃが形成された
ケーシング２３Ｄと、第１の流入ポート２３Ｂ側寄りに
位置してケーシング２３Ｄ内に配設されたソレノイド２
３Ｅと、このソレノイド２３Ｅ内に軸方向に移動可能に
設けられた弁体２３Ｆとを備えた３ポート２位置の電磁
ソレノイド弁として構成され、エアカット弁２１の駆動
源としての役割を果たすものである。また、流出ポート
２３Ａはパイロット管路２４を介してエアカット弁２２
の制御圧室２２Ｂに接続され、第１の流入ポート２３Ｂ
は第１の導圧管路２５を介してエアフローメータ１４と
エアフィルタ１３との間で吸気集合通路９に接続され、
第２の流入ポート２３Ｃは第２の導圧管路２６を介して
スロットル弁１５の下流側で吸気集合通路９に接続され
ている。そして、電磁弁２３は、常時（非通電時）は、
流出ポート２３Ａと第１の流入ポート２３Ｂとを連通さ
せて制御圧室２２Ｂ内に大気圧を導入することによりエ
アカット弁２２を閉弁せしめ、一方、コントロールユニ
ット３２からの制御信号によって切り換わると、流出ポ
ート２３Ａと第２の流入ポート２３Ｃとを連通させて制
御圧室２２Ｂ内に吸入負圧を導入することによりエアカ
ット弁２２を開弁させるものである。The solenoid valve 23 has a casing 23D having an outflow port 23A opening in the radial direction, a first inflow port 23B and a second inflow port 23C opening opposite to each other in the axial direction, and a first casing 23D. Solenoid 2 disposed in casing 23D, located near the inflow port 23B
It is configured as a 3-port 2-position electromagnetic solenoid valve provided with 3E and a valve body 23F that is movably provided in the solenoid 23E in the axial direction, and serves as a drive source of the air cut valve 21. is there. Further, the outflow port 23A is connected to the air cut valve 22 via the pilot line 24.
Connected to the control pressure chamber 22B of the first inflow port 23B
Is connected to the intake collecting passage 9 between the air flow meter 14 and the air filter 13 via the first pressure guiding line 25,
The second inflow port 23C is connected to the intake collecting passage 9 on the downstream side of the throttle valve 15 via the second pressure guiding line 26. The solenoid valve 23 is normally (when not energized)
By connecting the outflow port 23A and the first inflow port 23B to introduce the atmospheric pressure into the control pressure chamber 22B, the air cut valve 22 is closed, and when the control signal from the control unit 32 switches the air cut valve 22. The air cut valve 22 is opened by connecting the outflow port 23A and the second inflow port 23C to introduce a suction negative pressure into the control pressure chamber 22B.

【００２４】また、２次空気導入路２０には、排気通路
７からの逆流を防止するための第１のチェック弁２７が
エアカット弁２２の下流側に位置して設けられ、第２の
導圧管路２６の途中には第２のチェック弁２８が設けら
れている。In the secondary air introduction passage 20, a first check valve 27 for preventing backflow from the exhaust passage 7 is provided at the downstream side of the air cut valve 22, and the second check valve 27 is provided. A second check valve 28 is provided in the pressure line 26.

【００２５】一方、２９は冷却水温を検出するための水
温センサ、３０はスロットル弁１５の弁開度を検出する
ためのスロットルセンサ、３１は機関回転数を検出する
ためのクランク角センサをそれぞれ示し、これら各セン
サ２９，３０，３１は、上述した各空燃比センサ１６，
１９等と共に、コントロールユニット３２に接続されて
いる。On the other hand, 29 is a water temperature sensor for detecting the cooling water temperature, 30 is a throttle sensor for detecting the valve opening of the throttle valve 15, and 31 is a crank angle sensor for detecting the engine speed. , These respective sensors 29, 30, 31 are the above-mentioned respective air-fuel ratio sensors 16,
19 and the like are connected to the control unit 32.

【００２６】機関を電気的に集中制御するコントロール
ユニット３２は、ＣＰＵ等の演算回路、ＲＯＭ，ＲＡＭ
等の記憶回路、入出力回路等を備えたマイクロコンピュ
ータシステムとして構成され、その内部機能として、エ
アカット弁２２による２次空気導入路２０の遮断状態と
エアポンプ２１による２次空気の供給状態とを所定の短
時間だけ重複させる状態重複部３２Ａと、遮断状態と供
給状態とが重複したときの第１の空燃比センサ１６から
の検出信号に基づいて排気中の２次空気の有無を検出
し、２次空気が検出された場合はエアカット弁２２の閉
弁不良であると判定する判定部３２Ｂとを含んでいる。
そして、このコントロールユニット３２は、各空燃比セ
ンサ１６，１９等からの検出信号に基づいて燃料噴射量
をフィードバック制御すると共に、触媒劣化診断や、後
述する自己診断を行うようになっている。The control unit 32 for electrically centrally controlling the engine includes an arithmetic circuit such as a CPU, ROM, RAM.
It is configured as a microcomputer system including a memory circuit such as the above, an input / output circuit, and the like, and as its internal functions, a cutoff state of the secondary air introduction passage 20 by the air cut valve 22 and a supply state of the secondary air by the air pump 21 are provided. The presence or absence of secondary air in the exhaust gas is detected based on a detection signal from the state overlapping portion 32A that overlaps for a predetermined short time and the first air-fuel ratio sensor 16 when the cut-off state and the supply state overlap. When the secondary air is detected, the determination unit 32B that determines that the air cut valve 22 is defectively closed is included.
The control unit 32 feedback-controls the fuel injection amount based on the detection signals from the air-fuel ratio sensors 16 and 19 and also performs catalyst deterioration diagnosis and self-diagnosis described later.

【００２７】即ち、このコントロールユニット３２は、
エアフローメータ１４が検出した吸入空気量Ｑとクラン
ク角センサ３１が検出した機関回転数Ｎとに基づいて基
本噴射量ＴPを算出し（ＴP＝Ｑ／Ｎ）、この基本噴射量
ＴPを水温増量補正等の各種増量補正（Ｃoef）、空燃比
フィードバック補正（α）、電圧補正分（ＴS）等で修
正することにより、機関の運転条件に最適な燃料噴射量
Ｔiを決定するものである（Ｔi＝ＴP×Ｃoef×α）。That is, the control unit 32 is
The basic injection amount T P is calculated based on the intake air amount Q detected by the air flow meter 14 and the engine speed N detected by the crank angle sensor 31 (T P = Q / N), and this basic injection amount T P is calculated. The optimum fuel injection amount T i for the operating condition of the engine is determined by making corrections by various corrections such as water temperature increase correction (C oef ), air-fuel ratio feedback correction (α), and voltage correction amount (T S ). (T i = T P × C oef × α).

【００２８】また、コントロールユニット３２は、触媒
コンバータ１７の上流側に位置する第１の空燃比センサ
１６の検出信号と触媒コンバータ１７の下流側に位置す
る第２の空燃比センサ１９の検出信号との比に基づい
て、触媒コンバータ１７の劣化を診断する機能も備えて
いる。即ち、触媒コンバータ１７が劣化していない場合
は、触媒の酸素ストレージ能力によって、下流側の空燃
比センサ１９の検出信号は、リッチ，リーンの反転を長
い周期で繰り返す。一方、触媒コンバータ１７が劣化す
るにつれて、酸素ストレージ能力も低下するため、下流
側の空燃比センサ１９は、第１の空燃比センサ１６に近
似した周期で反転するようになる。従って、両センサ１
６，１９の反転周期の比によって、触媒の劣化診断を行
うことができる。Further, the control unit 32 receives a detection signal of the first air-fuel ratio sensor 16 located upstream of the catalytic converter 17 and a detection signal of the second air-fuel ratio sensor 19 located downstream of the catalytic converter 17. It also has a function of diagnosing the deterioration of the catalytic converter 17 based on the ratio. That is, when the catalytic converter 17 is not deteriorated, the oxygen storage capacity of the catalyst causes the detection signal of the air-fuel ratio sensor 19 on the downstream side to repeat inversion of rich and lean in a long cycle. On the other hand, as the catalytic converter 17 deteriorates, the oxygen storage capacity also decreases, so that the air-fuel ratio sensor 19 on the downstream side inverts at a cycle similar to that of the first air-fuel ratio sensor 16. Therefore, both sensors 1
Deterioration diagnosis of the catalyst can be performed by the ratio of the inversion periods of 6 and 19.

【００２９】次に、図２の状態説明図に基づいて、状態
重複部３２Ａの構成を説明すると、この状態重複部３２
Ａは、２次空気の供給を停止する時に、エアポンプ２１
の供給停止時期ＴPofをエアカット弁２２の閉時期ＴVof
よりも所定の短時間たるｔ1だけ遅らせることにより、
エアカット弁２２による２次空気導入路２０の遮断状態
と、エアポンプ２１による２次空気の供給状態とを時間
ｔ1だけ重複させるものである。具体的には、例えば低
水温時等の所定の運転条件が成立すると、触媒コンバー
タ１７の転化性能を維持すべく、２次空気が排気通路７
内に供給されるが、この２次空気の供給を停止する際
に、状態重複部３２Ａは、エアポンプ２１の方をエアカ
ット弁２２よりも例えば１〜２秒程度の短い時間ｔ1だ
け遅らせて停止させることにより、遮断状態と供給状態
との重複した状態を生成するようになっている。Next, the structure of the state overlapping section 32A will be described with reference to the state explanatory view of FIG.
When A stops the supply of secondary air, the air pump 21
Supply stop timing T Pof is set to the air cut valve 22 closing timing T Vof
By a predetermined short time t 1
The cutoff state of the secondary air introduction passage 20 by the air cut valve 22 and the supply state of the secondary air by the air pump 21 are overlapped by time t 1 . Specifically, when a predetermined operating condition such as when the water temperature is low is established, the secondary air is discharged from the exhaust passage 7 in order to maintain the conversion performance of the catalytic converter 17.
When the supply of the secondary air is stopped, the state overlapping portion 32A delays the air pump 21 from the air cut valve 22 by a short time t 1 of, for example, about 1 to 2 seconds. By stopping the operation, an overlapping state of the cutoff state and the supply state is generated.

【００３０】従って、例えば、エアポンプ２１の駆動回
路中にオフディレータイマを設けることにより、ハード
ウエア上で状態重複部３２Ａの機能を実現してもよい
し、２次空気供給プログラムのポンプ停止処理ステップ
を遅延させることにより、ソフトウェア上で実現しても
よい。なお、ソフトウェア上で状態重複部３２Ａを実現
した場合は、時間ｔ1の変更等が容易となるため、種々
の機関に速やかに対応することができる点で有利であ
る。なお、図中では、エアポンプ２１を「ポンプ」と、
エアカット弁２２を「カット弁」と、空燃比を「Ａ／
Ｆ」と、それぞれ略記する。Therefore, for example, an off-delay timer may be provided in the drive circuit of the air pump 21 to realize the function of the state overlapping section 32A in hardware, or the pump stop processing step of the secondary air supply program. May be implemented on software by delaying. It should be noted that when the state overlapping unit 32A is realized by software, it is easy to change the time t 1 and the like, which is advantageous in that it can promptly deal with various engines. In the figure, the air pump 21 is referred to as "pump".
The air cut valve 22 is "cut valve" and the air-fuel ratio is "A /
And "F".

【００３１】次に、遮断状態と供給状態の重複による排
気中の空燃比変化を考察すると、まず、２次空気の供給
中（図２中の閉時期ＴVof以前）は、この供給された２
次空気によって、排気中の酸素濃度が高まるため、第１
の空燃比センサ１６の検出する空燃比はリーン側になっ
ている。そして、エアカット弁２２が正常に閉じ、２次
空気導入路２０を遮断すると、排気通路７内への２次空
気の供給が停止するため、第１の空燃比センサ１６が検
出する空燃比は、時間ｔ1中に、リッチ側に向けて移行
していく。Next, considering the change in the air-fuel ratio in the exhaust due to the overlap of the cutoff state and the supply state, first, during the supply of the secondary air (before the closing timing T Vof in FIG. 2), this supplied 2 is supplied.
Because the secondary air increases the oxygen concentration in the exhaust gas,
The air-fuel ratio detected by the air-fuel ratio sensor 16 is lean. When the air cut valve 22 is normally closed and the secondary air introduction passage 20 is shut off, the supply of secondary air into the exhaust passage 7 is stopped, so that the air-fuel ratio detected by the first air-fuel ratio sensor 16 is , During time t 1 , the transition is made to the rich side.

【００３２】一方、エアカット弁２２に閉弁不良が発生
し、２次空気導入路２０を遮断できない場合は、図２中
の最下段に示す如く、エアカット弁２２に閉弁信号が印
加されても（正確には、電磁弁２３に閉弁信号が印加さ
れても）、エアポンプ２１が作動している限り、エアカ
ット弁２２を介して２次空気が排気通路７内に流れ込む
ため、第１の空燃比センサ１６が検出する空燃比はリー
ン側になったままで、変化は生じず、エアポンプ２１の
停止後に（停止時期ＴPof以降）、リッチ側に移行す
る。On the other hand, when the air cut valve 22 has a valve closing failure and the secondary air introducing passage 20 cannot be shut off, a valve closing signal is applied to the air cut valve 22 as shown in the lowermost stage of FIG. Even (correctly, even if the closing signal is applied to the solenoid valve 23), as long as the air pump 21 is operating, the secondary air flows into the exhaust passage 7 through the air cut valve 22, so The air-fuel ratio detected by the No. 1 air-fuel ratio sensor 16 remains lean and does not change. After the air pump 21 is stopped (after the stop timing T Pof ), the air-fuel ratio shifts to the rich side.

【００３３】従って、時間ｔ1中における排気中の空燃
比変化を第１の空燃比センサ１６を介して検出すること
により、エアカット弁２２が正常に閉弁動作している
か、即ち、閉弁不良が発生しているか否かを判定するこ
とができる。なお、第２の空燃比センサ１９を用いて時
間ｔ1中の空燃比を検出すると、触媒コンバータ１７の
酸素ストレージ能力によって、正確な空燃比変化を速や
かに検出できないため、２次空気導入路２０の流出口２
０Ｂと触媒コンバータ１７との間に設けた第１の空燃比
センサ１６を使用している。Therefore, by detecting the change in the air-fuel ratio in the exhaust gas during the time t 1 through the first air-fuel ratio sensor 16, whether the air cut valve 22 is normally closed, that is, the valve is closed. It is possible to determine whether a defect has occurred. If the second air-fuel ratio sensor 19 is used to detect the air-fuel ratio during the time t 1 , an accurate air-fuel ratio change cannot be swiftly detected due to the oxygen storage capacity of the catalytic converter 17, so the secondary air introduction passage 20 Outlet 2
The first air-fuel ratio sensor 16 provided between 0B and the catalytic converter 17 is used.

【００３４】次に、図３に基づいて、コントロールユニ
ット３２の判定部３２Ｂの処理を説明する。即ち、図３
は、判定処理のフローチャートを示し、ステップ１（図
中ではステップを「Ｓ」と略記する）では、空燃比フィ
ードバック補正係数αの状態を読み出し、ステップ２で
は、この空燃比フィードバック補正係数αの状態に基づ
いて、空燃比がリッチ側に設定されているか否かを判定
する。つまり、空燃比がリッチ側に設定されていれば、
エアカット弁２２の閉弁不良を正確に発見できるため
（正常に閉じていればリッチ側となり、閉弁不良があれ
ばリーン側に移行するため）、ステップ２では、空燃比
フィードバック補正係数αがクランプされて空燃比がリ
ッチ側となる条件（例えば低水温時等の所定の運転条件
下で２次空気を供給する場合やアイドリング時等）を検
出している。Next, with reference to FIG. 3, the processing of the determination section 32B of the control unit 32 will be described. That is, FIG.
Shows a flow chart of the determination process. In step 1 (step is abbreviated as “S” in the figure), the state of the air-fuel ratio feedback correction coefficient α is read, and in step 2, the state of this air-fuel ratio feedback correction coefficient α is read. It is determined whether or not the air-fuel ratio is set to the rich side based on. That is, if the air-fuel ratio is set to the rich side,
Since it is possible to accurately detect a valve closing failure of the air cut valve 22 (if the valve is normally closed, it becomes the rich side, and if there is a valve closing failure, it shifts to the lean side). Therefore, in step 2, the air-fuel ratio feedback correction coefficient α is The condition where the air-fuel ratio is clamped to the rich side (for example, when secondary air is supplied under a predetermined operating condition such as low water temperature or during idling) is detected.

【００３５】そして、前記ステップ２で「ＹＥＳ」と判
定したときは、空燃比フィードバック補正係数αをクラ
ンプして２次空気の供給を行っている場合等であるた
め、ステップ３ではエアカット弁２２が閉弁しているか
否かを監視し、ステップ４ではエアポンプ２１が作動し
ているか否かを監視する。即ち、これらステップ３，４
では、エアカット弁２２による遮断状態とエアポンプ２
１による供給状態とが重複しているか否かを判定する。If "YES" is determined in step 2, it means that the air-fuel ratio feedback correction coefficient α is clamped to supply the secondary air. Is monitored, and in step 4, it is monitored whether the air pump 21 is operating. That is, these steps 3 and 4
Then, the shutoff state by the air cut valve 22 and the air pump 2
It is determined whether or not the supply state according to 1 overlaps.

【００３６】前記各ステップ３，４で共に「ＹＥＳ」と
判定したときは、状態重複部３２Ａによって、２次空気
供給停止の際に、遮断状態と供給状態との重複が形成さ
れた場合のため、ステップ５では、第１の空燃比センサ
１６の検出信号を読込み、ステップ６では、この読み込
んだ検出信号に基づいて、排気中の空燃比がリッチ側と
なったか否かを判定する。このステップ６で「ＹＥＳ」
と判定したときは、エアカット弁２２の閉弁によって２
次空気の供給が正常に遮断され、排気中の空燃比がリッ
チ側に移行した場合のため、ステップ７に移って、エア
カット弁２２の閉弁動作は正常であると判定する。When it is determined to be "YES" in each of the steps 3 and 4, it is because the state overlapping portion 32A forms an overlap between the cutoff state and the supply state when the secondary air supply is stopped. In step 5, the detection signal of the first air-fuel ratio sensor 16 is read, and in step 6, it is determined whether or not the air-fuel ratio in the exhaust gas is on the rich side based on the read detection signal. "YES" in this step 6
If it is determined that the air cut valve 22 is closed,
Since the supply of the next air is normally shut off and the air-fuel ratio in the exhaust gas has shifted to the rich side, the process proceeds to step 7 and it is determined that the closing operation of the air cut valve 22 is normal.

【００３７】一方、このステップ６で「ＮＯ」と判定し
たときは、エアカット弁２２を閉弁させたはずであるに
も拘わらず、第１の空燃比センサ１６が検出した排気中
の空燃比がリッチ側とならない場合のため、ステップ８
に移って所定の短時間ｔ1が経過するのを待つ。即ち、
前記ステップ３，４で遮断状態と供給状態の重複が検出
されたとしても、２次空気導入路２０内に残存した２次
空気等により、排気中の空燃比が瞬時にリッチ側に移行
する訳ではないため、時間ｔ1が経過するのを待って判
定している。従って、この所定の短時間ｔ1は、エアカ
ット弁２２によって遮断された２次空気導入路２０内に
２次空気を吐出しても、エアポンプ２１が損傷しない程
度の短い時間であって、かつ、エアカット弁２２の応答
遅れや２次空気流入の時間遅れよりも長い時間（エアカ
ット弁２２の閉弁による空燃比変化を確認できるだけの
時間）として、例えば１〜２秒程度に設定される。On the other hand, when "NO" is determined in this step 6, although the air cut valve 22 should have been closed, the air-fuel ratio in the exhaust gas detected by the first air-fuel ratio sensor 16 is detected. Is not on the rich side, step 8
And waits for a predetermined short time t 1 to elapse. That is,
Even if it is detected in Steps 3 and 4 that the shutoff state and the supply state are overlapped, the air-fuel ratio in the exhaust gas instantaneously shifts to the rich side due to the secondary air remaining in the secondary air introduction passage 20. Therefore, the determination is made by waiting for the time t 1 to elapse. Therefore, this predetermined short time t 1 is a short time such that the air pump 21 is not damaged even if the secondary air is discharged into the secondary air introduction passage 20 which is blocked by the air cut valve 22, and The time longer than the response delay of the air cut valve 22 or the time delay of the secondary air inflow (the time required to check the air-fuel ratio change due to the closing of the air cut valve 22) is set to, for example, about 1 to 2 seconds. .

【００３８】所定の短時間ｔ1が経過する間に、排気中
の空燃比がリッチ側に移行した場合は、前記ステップ６
が「ＹＥＳ」と判定し、前記ステップ７で閉弁動作が正
常であると診断される。一方、前記ステップ８で「ＹＥ
Ｓ」と判定したときは、所定の短時間ｔ1が経過して
も、空燃比がリッチ側にならない場合、即ち、エアカッ
ト弁２２の閉弁不良によって２次空気の漏洩が生じてい
る場合のため、ステップ９に移って、エアカット弁２２
の閉弁動作が異常であると診断し、例えば警告ランプを
点灯させたり、故障フラグを立てる等の必要な処理を行
う。When the air-fuel ratio in the exhaust gas shifts to the rich side during the elapse of the predetermined short time t 1 , the above step 6
Is determined to be “YES”, and it is diagnosed in step 7 that the valve closing operation is normal. On the other hand, in step 8 above, "YE
When it is determined to be “S”, when the air-fuel ratio does not become rich even after the lapse of a predetermined short time t 1 , that is, when the air cut valve 22 has a valve closing failure and leakage of secondary air occurs. Therefore, move to step 9 and cut the air cut valve 22
It is diagnosed that the valve closing operation is abnormal, and necessary processing such as turning on a warning lamp and setting a failure flag is performed.

【００３９】ここで、エアカット弁２２が正常に閉弁動
作を行わない閉弁不良の形態としては、例えば弁座２２
Ｅに付着した異物等によって弁体２２Ｆとの間に隙間が
形成されている場合、電磁弁２３自体が故障している場
合等が挙げられる。Here, as a form of valve closing failure in which the air cut valve 22 does not normally close, for example, the valve seat 22
There are a case where a gap is formed between the valve body 22F and a foreign substance attached to E, a case where the electromagnetic valve 23 itself is out of order, and the like.

【００４０】次に、本実施例による２次空気供給装置の
作用について説明すると、図示せぬ２次空気供給プログ
ラムによって、機関の運転条件が例えば低水温時等の所
定の運転条件に達すると、エアポンプ２１が作動して２
次空気の吐出を開始すると共に、電磁弁２３からの吸入
負圧によってエアカット弁２２が開弁する。これによ
り、エアポンプ２１から吐出された２次空気は、２次空
気導入路２０を介してエアカット弁２２の２次空気室２
２Ｃ内に流入し、この２次空気室２２Ｃから弁座２２Ｅ
内を介して２次空気導入路２０内に流れ込み、第１のチ
ェック弁２７を開弁させて排気通路７内に流入する。そ
して、この結果、第１の空燃比センサ１６が検出する空
燃比はリーン側となる。Next, the operation of the secondary air supply apparatus according to this embodiment will be described. When the operating condition of the engine reaches a predetermined operating condition such as low water temperature by a secondary air supply program (not shown), 2 when the air pump 21 operates
At the same time when the next air is discharged, the air cut valve 22 opens due to the suction negative pressure from the solenoid valve 23. As a result, the secondary air discharged from the air pump 21 passes through the secondary air introduction passage 20 and the secondary air chamber 2 of the air cut valve 22.
2C and flows into the secondary air chamber 22C from the valve seat 22E.
It flows into the secondary air introduction passage 20 through the inside, opens the first check valve 27, and flows into the exhaust passage 7. As a result, the air-fuel ratio detected by the first air-fuel ratio sensor 16 becomes lean.

【００４１】そして、機関の運転条件に基づいてコント
ロールユニット３２が２次空気の供給を停止すべきと判
断すると、状態重複部３２Ａのオフディレー処理によ
り、まず、エアカット弁２２が電磁弁２３からの大気圧
によって閉弁し、所定の短時間ｔ1経過後にエアポンプ
２１の作動が停止する。これにより、２次空気の供給が
停止して、第１の空燃比センサ１６が検出する空燃比は
リッチ側に移行する。また、この供給停止時に生じたエ
アカット弁２２による遮断状態とエアポンプ２１による
供給状態との重複は、判定部３２Ｂによって検出され、
これにより、図３と共に上述した判定処理が行われる。When the control unit 32 determines that the supply of the secondary air should be stopped based on the operating conditions of the engine, the air cut valve 22 is first operated from the solenoid valve 23 by the off-delay processing of the state overlapping portion 32A. The valve is closed by the atmospheric pressure of 1 and the operation of the air pump 21 is stopped after a predetermined short time t 1 . As a result, the supply of the secondary air is stopped, and the air-fuel ratio detected by the first air-fuel ratio sensor 16 shifts to the rich side. Further, the overlap between the shutoff state by the air cut valve 22 and the supply state by the air pump 21 that occurs when the supply is stopped is detected by the determination unit 32B,
As a result, the determination process described above with reference to FIG. 3 is performed.

【００４２】このように構成される本実施例によれば、
以下の効果を奏する。According to the present embodiment configured as described above,
The following effects are obtained.

【００４３】第１に、状態重複部３２Ａによって、エア
カット弁２２が２次空気導入路２０を遮断している遮断
状態とエアポンプ２１が２次空気導入路２０内に２次空
気を吐出供給している供給状態とを所定の短時間ｔ1だ
け重複させ、判定部３２Ｂにより、この重複状態で第１
の空燃比センサ１６が検出した排気中の空燃比に基づい
て２次空気の有無を検出し、２次空気が検出されたとき
にはエアカット弁２２の漏洩であると診断する構成のた
め、エアカット弁２２の閉弁不良を簡易かつ正確に診断
することができ、排気の逆流に起因する他の故障の発生
を未然に防止することができる。即ち、例えば、リミッ
トスイッチ、近接スイッチ、リードスイッチ等のセンサ
によって、エアカット弁２２の作動を直接的に検出する
ことも可能であるが、これでは、部品点数、組立工数、
製造コスト等が増大する。これに対し、本実施例では、
空燃比制御のために既に装着されている第１の空燃比セ
ンサ１６を利用して、エアカット弁２２の閉弁不良を間
接的に判定する構成のため、簡易かつ正確に、エアカッ
ト弁２２の漏洩を診断できる。First, due to the state overlapping portion 32A, the air cut valve 22 shuts off the secondary air introducing passage 20 and the air pump 21 discharges and supplies the secondary air into the secondary air introducing passage 20. The supplied state is overlapped by a predetermined short time t 1 , and the determination unit 32B determines that the first state
The presence or absence of secondary air is detected based on the air-fuel ratio in the exhaust gas detected by the air-fuel ratio sensor 16 and the air cut valve 22 is diagnosed as leaking when the secondary air is detected. The valve closing failure of the valve 22 can be easily and accurately diagnosed, and the occurrence of other failures due to the backflow of exhaust gas can be prevented. That is, for example, it is possible to directly detect the operation of the air cut valve 22 with a sensor such as a limit switch, a proximity switch, or a reed switch. However, in this case, the number of parts, the number of assembling steps,
Manufacturing costs and the like increase. On the other hand, in this embodiment,
Since the first air-fuel ratio sensor 16 already mounted for air-fuel ratio control is used to indirectly determine the valve closing failure of the air cut valve 22, the air cut valve 22 can be simply and accurately configured. Can be diagnosed.

【００４４】第２に、状態重複部３２Ａは、エアポンプ
２１の供給停止時期ＴPofをエアカット弁２２の閉時期
ＴVofよりも所定の短時間ｔ1だけ遅らせることにより、
遮断状態と供給状態とを重複させる構成のため、所定の
短時間ｔ1を短く設定することができ、速やかに診断を
終了することができる。即ち、エアカット弁２２の応答
速度は比較的速いため、実質的には、エアカット弁２２
の弁座２２Ｅ近傍の２次空気が第１の空燃比センサ１６
を通過するのに要する時間遅れ要素だけ考慮すれば足
り、この結果、後述する第２の実施例に比較して、時間
ｔ1を短く設定することができる。[0044] Second, the state overlapped portion 32A, by delaying the supply stop timing T Pof the air pump 21 for a short time t 1 of a given than closing timing T Vof the air cut valve 22,
Since the cutoff state and the supply state are overlapped with each other, the predetermined short time t 1 can be set to be short, and the diagnosis can be finished promptly. That is, since the response speed of the air cut valve 22 is relatively high, the air cut valve 22 is substantially
Secondary air near the valve seat 22E of the first air-fuel ratio sensor 16
It suffices to consider only the time delay element required to pass through, and as a result, the time t 1 can be set shorter than in the second embodiment described later.

【００４５】第３に、本実施例では、状態重複部３２Ａ
により生成する遮断状態と供給状態との重複と、判定部
３２Ｂによる閉弁不良の診断とを別個独立に形成する構
成のため、各処理内容を簡素化することができ、仕様の
変更にも速やかに対応することができる。即ち、判定部
３２Ｂは、状態重複部３２Ａによって遮断状態と供給状
態の重複が形成されたときに、これを検出して判定処理
を行う構成であり、両者は別ユニットとなっているた
め、アルゴリズムの改良等にも容易に対応することがで
きる。Thirdly, in this embodiment, the state overlapping part 32A is used.
Since the configuration in which the shutoff state and the supply state that are generated by the above and the diagnosis of the valve closing failure by the determination unit 32B are formed separately and independently, each processing content can be simplified and the specification can be promptly changed. Can correspond to. That is, the determination unit 32B is configured to detect the overlapping state of the cutoff state and the supply state when the state overlapping unit 32A forms the state and perform the determination process. Can be easily dealt with.

【００４６】第４に、本実施例では、２次空気の供給停
止時に遮断状態と供給状態とを重複させる結果、所定の
短時間ｔ1中に、排気中の空燃比が変化した場合に、エ
アカット弁２２の閉弁動作が正常であると判定する構成
となるため（供給停止前は、空燃比がリーン側となって
おり、正常であれば、エアカット弁２２の閉弁によっ
て、空燃比はリッチ側に変化するため）、フェイルセー
フ機能を持たせることができ、後述する第２の実施例に
比較して、一層信頼性を向上できる。即ち、万が一、第
１の空燃比センサ１６に故障が生じ、その検出信号がリ
ーン側に張り付いたままで変化しない場合でも、この状
態は、少なくともエアカット弁２２の閉弁不良として認
識されるため、信頼性が向上する。Fourthly, in the present embodiment, when the cutoff state and the supply state are overlapped when the supply of the secondary air is stopped, the air-fuel ratio in the exhaust gas changes during a predetermined short time t 1 , Since the configuration is such that it is determined that the closing operation of the air cut valve 22 is normal (before the supply is stopped, the air-fuel ratio is on the lean side, and if it is normal, the air cut valve 22 is closed to close the air-fuel ratio. Since the fuel ratio changes to the rich side), a fail-safe function can be provided, and reliability can be further improved as compared with the second embodiment described later. That is, even if a failure occurs in the first air-fuel ratio sensor 16 and the detection signal is stuck to the lean side and does not change, this state is recognized as at least a valve closing failure of the air cut valve 22. , Reliability is improved.

【００４７】次に、図４に基づいて、本発明の第２の実
施例を説明する。なお、以下の各実施例では、上述した
第１の実施例と同一の構成要素に同一の符号を付し、そ
の説明を省略するものとする。本実施例の特徴は、２次
空気の供給開始時に、オンディレーをかけて、エアカッ
ト弁２２による遮断状態とエアポンプ２１による供給状
態とを重複せしめ、エアカット弁２２の閉弁不良を診断
する点にある。Next, a second embodiment of the present invention will be described with reference to FIG. In each of the following embodiments, the same components as those in the above-described first embodiment are designated by the same reference numerals, and the description thereof will be omitted. The feature of this embodiment is that when the supply of the secondary air is started, an on-delay is applied to make the shut-off state by the air cut valve 22 and the supply state by the air pump 21 overlap with each other to diagnose a valve closing failure of the air cut valve 22. In point.

【００４８】即ち、図４は、本実施例による遮断状態と
供給状態との重複の生成を示す状態説明図であって、状
態重複部３２Ａは、２次空気の供給を開始する際に、エ
アカット弁２２による遮断状態とエアポンプ２１による
供給状態とを、所定の短時間ｔ2だけ重複させている。
具体的には、図４中に示す如く、状態重複部３２Ａは、
２次空気の供給開始時に、まず、エアポンプ２１を供給
開始時期ＴPonにおいて作動せしめ、所定の短時間ｔ2後
に、エアカット弁２２を開時期ＴVonで開弁させること
により、この短時間ｔ2中に、エアカット弁２２による
遮断状態とエアポンプ２１による供給状態とを重複させ
るようになっている。That is, FIG. 4 is a state explanatory view showing the generation of the overlap between the shut-off state and the supply state according to the present embodiment, and the state overlapping section 32A makes the air supply when the supply of the secondary air is started. The cutoff state by the cut valve 22 and the supply state by the air pump 21 are overlapped by a predetermined short time t 2 .
Specifically, as shown in FIG. 4, the state overlapping part 32A is
At the start of the supply of the secondary air, first, the air pump 21 is operated at the supply start timing T Pon , and after the predetermined short time t 2 , the air cut valve 22 is opened at the open timing T Von. During the period 2 , the shut-off state by the air cut valve 22 and the supply state by the air pump 21 are made to overlap.

【００４９】ここで、エアポンプ２１の吐出圧が安定化
するまでには多少の時間を要するため、本実施例による
所定の短時間ｔ2は、遮断状態の２次空気導入路２０内
に２次空気を吐出してもエアポンプ２１が損傷しない時
間内であって、かつ、吐出圧が安定化するのに十分な時
間として、例えば３秒程度に設定される。なお、その他
の構成は、第１の実施例と同一のため、重複説明を省略
する。Since it takes some time for the discharge pressure of the air pump 21 to stabilize, the secondary air is introduced into the secondary air introducing passage 20 in the shut-off state for a predetermined short time t 2 according to this embodiment. For example, about 3 seconds is set as the time within which the air pump 21 is not damaged even if the air is discharged and the discharge pressure is stabilized. The rest of the configuration is the same as that of the first embodiment, so duplicate description will be omitted.

【００５０】本実施例によれば、エアカット弁２２が正
常に閉弁動作を行える場合は、図４中に示す如く、供給
開始時期ＴPonで、エアポンプ２１が作動し、２次空気
導入路２０内に２次空気が吐出されても、エアカット弁
２２が開時期ＴVonで開弁しない限り、この２次空気が
排気通路７内に流入しないため、排気中の空燃比は、所
定の短時間ｔ2中にリッチ側になったままで変化せず、
エアカット弁２２が開時期ＴVonで開弁した後に、リー
ン側に移行する。一方、エアカット弁２２に閉弁不良が
生じている場合は、図４中の最下段に示す如く、エアポ
ンプ２１の作動だけで、排気通路７内に２次空気が供給
されるため、排気中の空燃比は、所定の短時間ｔ2中に
リーン側に移行する。According to the present embodiment, when the air cut valve 22 can normally perform the closing operation, the air pump 21 is operated at the supply start timing T Pon as shown in FIG. Even if the secondary air is discharged into the inside 20, the secondary air does not flow into the exhaust passage 7 unless the air cut valve 22 is opened at the opening timing T Von . Therefore, the air-fuel ratio in the exhaust is a predetermined value. It remains on the rich side during a short time t 2 and does not change,
After the air cut valve 22 opens at the opening timing T Von , it shifts to the lean side. On the other hand, when the air cut valve 22 is defectively closed, the secondary air is supplied into the exhaust passage 7 only by operating the air pump 21 as shown in the lowermost stage of FIG. The air-fuel ratio of is shifted to the lean side during a predetermined short time t 2 .

【００５１】従って、このように構成される本実施例で
も、エアカット弁２２による遮断状態とエアポンプ２１
による供給状態とを所定の短時間ｔ2だけ重複させるこ
とができ、図３に示す判定処理により、上述した第１の
実施例と同様の効果を得ることができる。Therefore, also in this embodiment having such a configuration, the shutoff state by the air cut valve 22 and the air pump 21 are prevented.
It is possible to overlap with the supply state by the predetermined time t 2 and the determination processing shown in FIG. 3 can obtain the same effect as that of the first embodiment described above.

【００５２】次に、図５に基づき、本発明の第３の実施
例を説明する。本実施例の特徴は、２次空気の供給中
に、エアカット弁２２を所定の短時間ｔ3だけ一時的に
閉弁させることにより、エアカット弁２２による遮断状
態とエアポンプ２１による供給状態とを重複させた点に
ある。なお、他の構成は、第１の実施例と同一であるか
ら、その重複説明を省略する。Next, a third embodiment of the present invention will be described with reference to FIG. The feature of the present embodiment is that the air cut valve 22 is temporarily closed for a predetermined short time t 3 during the supply of the secondary air so that the air cut valve 22 shuts off and the air pump 21 supplies the air. Is the point that was duplicated. Since the other structure is the same as that of the first embodiment, the duplicated description will be omitted.

【００５３】即ち、図５は、本実施例による遮断状態と
供給状態との重複の生成を示す状態説明図であって、本
実施例では、２次空気の供給中に、エアカット弁２２に
よる遮断状態とエアポンプ２１による供給状態とを、所
定の短時間ｔ3だけ重複させている。具体的には、図５
中に示す如く、状態重複部３２Ａは、２次空気の供給中
において、ある時刻ＴVof1でエアカット弁２２を閉弁さ
せ、それから所定の短時間ｔ3経過後に、再びエアカッ
ト弁２２を開弁させることにより、エアカット弁２２に
よる遮断状態とエアポンプ２１による供給状態とを重複
させるようになっている。ここで、例えば２次空気の供
給開始時（図４中の開時期ＴVon）から所定の時間が経
過した後の時刻ＴVof1で、エアカット弁２２が一時的に
閉弁するように設定されている。That is, FIG. 5 is a state explanatory view showing the generation of the overlap between the shutoff state and the supply state according to this embodiment. In this embodiment, the air cut valve 22 is used during the supply of the secondary air. The cutoff state and the supply state by the air pump 21 are overlapped for a predetermined short time t 3 . Specifically, FIG.
As shown in the figure , the state overlapping portion 32A closes the air cut valve 22 at a certain time T Vof1 during the supply of the secondary air, and after a predetermined short time t 3 , the air cut valve 22 is opened again. By opening the valve, the shutoff state by the air cut valve 22 and the supply state by the air pump 21 are made to overlap. Here, for example, the air cut valve 22 is set to be temporarily closed at a time T Vof1 after a predetermined time has elapsed from the start of the supply of the secondary air (the opening timing T Von in FIG. 4). ing.

【００５４】また、本実施例では、エアカット弁２２の
開閉によって所定の短時間ｔ3を形成するため、第１の
実施例と同様に、２次空気導入路２０内に残留した２次
空気が第１の空燃比センサ１６を通過するまでの時間遅
れを考慮して、短時間ｔ3を第１の実施例における所定
の短時間ｔ1と略同様に、例えば１〜２秒程度に設定し
ている。Further, in this embodiment, since the predetermined short time t 3 is formed by opening / closing the air cut valve 22, the secondary air remaining in the secondary air introducing passage 20 is similarly to the first embodiment. In consideration of the time delay until the vehicle passes the first air-fuel ratio sensor 16, the short time t 3 is set to about 1 to 2 seconds, for example, substantially the same as the predetermined short time t 1 in the first embodiment. are doing.

【００５５】このように構成される本実施例によれば、
時刻ＴVof1よりも前の期間中では、２次空気が供給され
ているため、排気中の空燃比はリーン側になっている。
そして、閉弁不良が生じていない場合は、時刻ＴVof1で
エアカット弁２２が閉弁すると、これにより２次空気の
供給が遮断されるため、排気中の空燃比はリッチ側に移
行し、所定の短時間ｔ3経過後にエアカット弁２２が再
び開弁すると、リーン側に向かう。一方、エアカット弁
２２に閉弁不良が生じている場合は、エアカット弁２２
を一時的に閉じたつもりでも、２次空気の供給が停止し
ないため、排気中の空燃比はリーン側になったままで変
化しない。従って、本実施例でも、第１の実施例と同様
の効果を得ることができる。According to the present embodiment configured as described above,
During the period before time T Vof1 , secondary air is being supplied, so the air-fuel ratio in the exhaust gas is on the lean side.
Then, when the valve closing failure does not occur, when the air cut valve 22 is closed at the time T Vof1 , the supply of the secondary air is cut off by this, so that the air-fuel ratio in the exhaust gas shifts to the rich side, When air cut valve 22 is opened again after a predetermined short time t 3 has elapsed, toward the lean side. On the other hand, if the air cut valve 22 is defectively closed, the air cut valve 22
Even if you intend to temporarily close the valve, the secondary air supply does not stop, so the air-fuel ratio in the exhaust remains lean and does not change. Therefore, also in this embodiment, the same effect as that of the first embodiment can be obtained.

【００５６】次に、図６に基づき、本発明の第４の実施
例を説明する。本実施例の特徴は、２次空気の供給を行
わない運転条件下で、エアポンプ２１を所定の短時間ｔ
4だけ一時的に作動させることにより、エアカット弁２
２による遮断状態とエアポンプ２１による供給状態とを
重複させた点にある。なお、他の構成は、第１の実施例
と同一ゆえ、その説明を省略する。Next, a fourth embodiment of the present invention will be described with reference to FIG. The feature of this embodiment is that the air pump 21 is operated for a predetermined short time t under the operating condition that the secondary air is not supplied.
Air cut valve 2 by temporarily operating only 4
This is because the shutoff state by 2 and the supply state by the air pump 21 overlap. Since the other structure is the same as that of the first embodiment, the description thereof is omitted.

【００５７】即ち、図６は、本実施例による遮断状態と
供給状態との重複の生成を示す状態説明図であって、本
実施例では、例えばアイドリング時等の如く、２次空気
の供給を行わない運転条件下であって、かつ、空燃比が
リッチ側に設定されている場合に、エアポンプ２１を一
時的に作動させることにより、エアカット弁２２による
遮断状態とエアポンプ２１による供給状態とを、所定の
短時間ｔ4だけ重複させている。具体的には、図６中に
示す如く、状態重複部３２Ａは、空燃比がリッチ側に設
定されていて２次空気の供給を行わない運転条件下にお
いて、ある時刻ＴPon1で、エアポンプ２１を作動させ、
所定の短時間ｔ4経過後に、再びエアポンプ２１を停止
させることにより、遮断状態と供給状態とを重複させる
ようになっている。ここで、本実施例では、エアポンプ
２１の一時的作動によって遮断状態と供給状態との重複
を生成するため、エアポンプ２１の吐出圧が安定化する
までの時間を考慮して、所定の短時間ｔ4を、前記第２
の実施例と略同様に、例えば３秒程度に設定している。That is, FIG. 6 is a state explanatory view showing the generation of the overlap between the shutoff state and the supply state according to this embodiment. In this embodiment, the supply of the secondary air is performed, for example, at the time of idling. When the air-fuel ratio is set to the rich side under the operating condition not performed, the air pump 21 is temporarily operated to switch between the shutoff state by the air cut valve 22 and the supply state by the air pump 21. , And overlap for a predetermined short time t 4 . Specifically, as shown in FIG. 6, the state overlapping portion 32A turns on the air pump 21 at a certain time T Pon1 under operating conditions in which the air-fuel ratio is set to the rich side and secondary air is not supplied. Activate
By stopping the air pump 21 again after the elapse of a predetermined short time t 4 , the cutoff state and the supply state are made to overlap. Here, in the present embodiment, since the shutoff state and the supply state are overlapped by the temporary operation of the air pump 21, a predetermined short time t is taken into consideration in consideration of the time until the discharge pressure of the air pump 21 is stabilized. 4 , the second
The time is set to, for example, about 3 seconds, similar to the embodiment described above.

【００５８】このように構成される本実施例では、エア
カット弁２２に閉弁不良がなければ、エアポンプ２１の
みが時刻ＴPon1で作動しても、排気通路７内に２次空気
は供給されないため、排気中の空燃比に変化は生じな
い。一方、エアカット弁２２に閉弁不良が生じていれ
ば、エアポンプ２１の作動によって、排気通路７内に２
次空気が供給されてしまうため、所定の短時間ｔ4中
に、排気中の空燃比はリーン側に移行し、再びエアポン
プ２１の作動が停止した後に、リッチ側に向けて変化す
る。従って、本実施例でも、上述した第２の実施例と同
様の効果を得ることができる。In this embodiment having such a configuration, if the air cut valve 22 has no valve closing defect, the secondary air is not supplied into the exhaust passage 7 even if only the air pump 21 operates at time T Pon1. Therefore, the air-fuel ratio in the exhaust does not change. On the other hand, if the air cut valve 22 has a valve closing failure, the operation of the air pump 21 causes the exhaust passage 7 to be closed.
Since the next air is supplied, the air-fuel ratio in the exhaust gas shifts to the lean side during the predetermined short time t 4 , and after the operation of the air pump 21 is stopped again, it changes toward the rich side. Therefore, also in this embodiment, the same effect as that of the above-described second embodiment can be obtained.

【００５９】次に、図７，図８に基づき、本発明の第５
の実施例を説明する。本実施例の特徴は、空燃比フィー
ドバックを行う運転条件下で、エアポンプ２１を一時的
に作動させることにより、遮断状態と供給状態とを重複
せしめ、排気通路７内の２次空気の有無を空燃比フィー
ドバック補正係数αに基づいて検出する点にある。Next, based on FIGS. 7 and 8, the fifth embodiment of the present invention will be described.
An example will be described. The feature of this embodiment is that by temporarily operating the air pump 21 under the operating condition of performing the air-fuel ratio feedback, the cutoff state and the supply state are made to overlap, and the presence or absence of secondary air in the exhaust passage 7 is emptied. The point is that detection is performed based on the fuel ratio feedback correction coefficient α.

【００６０】即ち、図７は、本実施例による遮断状態と
供給状態との重複の生成を示す状態説明図であって、本
実施例では、例えば空燃比フィードバックを行うアイド
リング時（アイドルλ制御）等の如く、空燃比フィード
バック補正係数αがクランプされていない運転条件下
で、エアポンプ２１を一時的に作動させることにより、
エアカット弁２２による遮断状態とエアポンプ２１によ
る供給状態とを所定の短時間ｔ5だけ重複させている。
具体的には、図７中に示す如く、状態重複部３２Ａは、
空燃比フィードバックを行うアイドルλ制御中における
ある時刻ＴPon2で、エアポンプ２１を作動させ、所定の
短時間ｔ5経過後に、再びエアポンプ２１を停止させる
ことにより、遮断状態と供給状態とを重複させるもので
ある。ここで、本実施例では、エアポンプ２１の一時的
作動によって遮断状態と供給状態との重複を生成するた
め、エアポンプ２１の吐出圧が安定化するまでの時間を
考慮して、所定の短時間ｔ5を、前記第２の実施例と略
同様に、例えば３秒程度に設定している。That is, FIG. 7 is a state explanatory view showing the generation of the overlap between the cutoff state and the supply state according to the present embodiment. In the present embodiment, for example, during idling (idle λ control) for performing air-fuel ratio feedback. As described above, by temporarily operating the air pump 21 under operating conditions in which the air-fuel ratio feedback correction coefficient α is not clamped,
The shutoff state by the air cut valve 22 and the supply state by the air pump 21 are overlapped for a predetermined short time t 5 .
Specifically, as shown in FIG. 7, the state overlapping part 32A is
At a certain time T Pon2 during the idle λ control for performing air-fuel ratio feedback, the air pump 21 is operated, and after a predetermined short time t 5 , the air pump 21 is stopped again to make the cutoff state and the supply state overlap. Is. Here, in the present embodiment, since the shutoff state and the supply state are overlapped by the temporary operation of the air pump 21, a predetermined short time t is taken into consideration in consideration of the time until the discharge pressure of the air pump 21 is stabilized. 5 is set to about 3 seconds, for example, as in the second embodiment.

【００６１】このように構成される本実施例では、エア
カット弁２２に閉弁不良がなければ、エアポンプ２１の
みが時刻ＴPon2で作動しても、排気通路７内に２次空気
は供給されないため、空燃比フィードバック補正係数α
は変化せず、リッチ側で一定である。一方、エアカット
弁２２に閉弁不良が生じていれば、エアポンプ２１の作
動によって、排気通路７内に２次空気が供給されるた
め、所定の短時間ｔ5中に、排気中の空燃比はリーン側
に移行し、これにより、空燃比フィードバック補正係数
αは、目標空燃比に修正すべく、その積分制御分ＩLが
長くなってリッチ側に変化し（αが大きくなる方向）、
再びエアポンプ２１の作動が停止すると、リーン側に向
けて変化（αが小さくなる方向）する。なお、図７中の
ＩL，ＩRは積分制御分、ＰL，ＰRは比例制御分である。In this embodiment having such a configuration, if the air cut valve 22 has no valve closing defect, the secondary air is not supplied into the exhaust passage 7 even if only the air pump 21 operates at time T Pon2. Therefore, the air-fuel ratio feedback correction coefficient α
Does not change and is constant on the rich side. On the other hand, if the air cut valve 22 has a valve closing defect, the secondary air is supplied into the exhaust passage 7 by the operation of the air pump 21, so that the air-fuel ratio in the exhaust gas is reduced within a predetermined short time t 5. Shifts to the lean side, whereby the air-fuel ratio feedback correction coefficient α changes to the rich side with the increase of the integral control amount I L in order to correct the target air-fuel ratio (direction in which α increases).
When the operation of the air pump 21 is stopped again, the air pump 21 changes toward the lean side (the direction in which α decreases). Note that I L and I R in FIG. 7 are integral control components, and P L and P R are proportional control components.

【００６２】次に、図８に示すフローチャートに基づい
て、本実施例による判定処理を説明すると、まず、ステ
ップ１１では、燃料噴射量の制御状態を読込み、ステッ
プ１２では、現在の制御状態が、アイドリング時に空燃
比フィードバックをかけるアイドルλ制御であるか否か
を判定する。そして、アイドルλ制御に入った場合は、
ステップ１３でエアカット弁２２が閉弁しているか否か
を確認すると共に、ステップ１４でエアポンプ２１が作
動しているか否かを確認し、これら各ステップ１３，１
４で共に「ＹＥＳ」と判定したときは、エアカット弁２
２による遮断状態とエアポンプ２１による供給状態とが
重複した場合のため、ステップ１５で空燃比フィードバ
ック補正係数αを読込み、ステップ１６では、この読み
込んだ空燃比フィードバック補正係数αが所定の目標値
であるか否かを判定する（より詳しくは、αの移動平均
に基づいて判定する）。Next, the determination process according to the present embodiment will be described with reference to the flow chart shown in FIG. 8. First, in step 11, the control state of the fuel injection amount is read, and in step 12, the current control state is It is determined whether or not the idle λ control is performed in which the air-fuel ratio feedback is performed during idling. And when entering the idle λ control,
In step 13, it is confirmed whether the air cut valve 22 is closed, and in step 14, it is confirmed whether the air pump 21 is operating.
If both are judged to be "YES" in 4, the air cut valve 2
Since the shut-off state by 2 and the supply state by the air pump 21 overlap, the air-fuel ratio feedback correction coefficient α is read in step 15, and the read air-fuel ratio feedback correction coefficient α is a predetermined target value in step 16. It is determined whether or not (more specifically, it is determined based on the moving average of α).

【００６３】このステップ１６で「ＹＥＳ」と判定した
ときは、２次空気が排気通路７内に供給されず、空燃比
がリーン側に変化しないため、空燃比フィードバック補
正係数αも変化する必要がない場合であるから、ステッ
プ１７に移って、エアカット弁２２の閉弁動作は正常で
あると判定する。一方、ステップ１６で「ＮＯ」と判定
したときは、空燃比フィードバック補正係数αが変化し
た場合のため、ステップ１８に移って、所定時間ｔ5が
経過するのを待ち、この所定時間ｔ5が経過しても空燃
比フィードバック補正係数αが目標値から変化している
場合には、エアカット弁２２の漏洩によって排気中の空
燃比がリーン側に変化し、これに応じて空燃比フィード
バック補正係数αが増大する方向に変化している場合の
ため、ステップ１９に移って、エアカット弁２２の閉弁
動作が異常、故障であると判定し、警告ランプを点灯さ
せる等の処理を行ってプログラムを終了する。If "YES" is determined in this step 16, since the secondary air is not supplied into the exhaust passage 7 and the air-fuel ratio does not change to the lean side, the air-fuel ratio feedback correction coefficient α also needs to change. Since there is no such a case, the process proceeds to step 17 and it is determined that the closing operation of the air cut valve 22 is normal. On the other hand, if it is determined to be “NO” in step 16, it means that the air-fuel ratio feedback correction coefficient α has changed, so the process moves to step 18 and waits for the predetermined time t 5 to elapse, and the predetermined time t 5 If the air-fuel ratio feedback correction coefficient α has changed from the target value even after the lapse of time, the air-fuel ratio in the exhaust changes to the lean side due to the leakage of the air cut valve 22, and the air-fuel ratio feedback correction coefficient is changed accordingly. Since α is changing in the increasing direction, the process proceeds to step 19, where it is determined that the closing operation of the air cut valve 22 is abnormal or a failure, and the warning lamp is turned on to perform the processing. To finish.

【００６４】このように構成される本実施例でも、エア
カット弁２２による遮断状態とエアポンプ２１による供
給状態とが重複しているときに、空燃比フィードバック
補正係数αの変化に基づいて、エアカット弁２２の閉弁
不良を診断することができ、上述した第４の実施例と同
様の効果を得ることができる。Also in this embodiment having such a configuration, when the shut-off state by the air cut valve 22 and the supply state by the air pump 21 overlap, the air cut is performed based on the change of the air-fuel ratio feedback correction coefficient α. The valve closing failure of the valve 22 can be diagnosed, and the same effect as that of the above-described fourth embodiment can be obtained.

【００６５】次に、図９に基づき、本発明の第６の実施
例を説明する。本実施例の特徴は、一つの診断処理プロ
グラム内で、２次空気の供給診断の終了後に２次空気の
供給停止診断を行う点にあり、第１の実施例の変形例に
相当する。Next, a sixth embodiment of the present invention will be described with reference to FIG. A feature of the present embodiment is that the secondary air supply stop diagnosis is performed after the secondary air supply diagnosis is completed in one diagnostic processing program, and corresponds to a modification of the first embodiment.

【００６６】即ち、図９は、本実施例による判定処理の
フローチャートを示し、本判定処理では、その前半で、
２次空気の供給が正常であるか否かを診断し、その後半
では、第１の実施例で述べた如く、２次空気の供給停止
の際に、エアカット弁２２の閉弁動作が正常か否かを診
断する。まず、ステップ２１では、機関の運転条件を求
めるべく、エアフローメータ１４，クランク角センサ３
１等からの検出信号を読込んで、例えば所定回転数以
下、所定の機関負荷以下、所定の目標空燃比範囲かつ空
燃比センサ１６の出力が所定値である場合等を検知し、
次のステップ２２では、これら各検出信号に基づいて、
２次空気の供給が可能な運転領域であるか否か、例えば
中負荷域よりも下の運転領域に達しか否かを監視する。
そして、このステップ２２で「ＮＯ」と判定したとき
は、２次空気を導入する運転条件が成立していない場合
のため、ステップ２１に戻る。一方、前記ステップ２２
で「ＹＥＳ」と判定したときは、所定の運転条件に達し
た場合のため、ステップ２３に移ってエアカット弁２２
を開弁させ、ステップ２４では、エアポンプ２１を作動
させる。次に、ステップ２５では、第１の空燃比センサ
１６から排気中の空燃比を読込み、ステップ２６では、
この読み込んだ排気中の空燃比がリーン側であるか否か
を判定する。That is, FIG. 9 shows a flow chart of the judgment processing according to the present embodiment. In this judgment processing, in the first half,
It is diagnosed whether or not the supply of the secondary air is normal, and in the latter half, as described in the first embodiment, the closing operation of the air cut valve 22 is normal when the supply of the secondary air is stopped. Diagnose whether or not. First, in step 21, in order to obtain the operating conditions of the engine, the air flow meter 14, the crank angle sensor 3
The detection signal from 1 or the like is read to detect, for example, a predetermined rotation speed or lower, a predetermined engine load or lower, a predetermined target air-fuel ratio range, and a case where the output of the air-fuel ratio sensor 16 is a predetermined value,
In the next step 22, based on each of these detection signals,
It is monitored whether or not the operating range is such that secondary air can be supplied, for example, whether or not the operating range below the medium load range is reached.
Then, when it is determined to be "NO" in this step 22, it means that the operating condition for introducing the secondary air is not satisfied, and therefore the process returns to step 21. On the other hand, the step 22
If it is determined to be “YES”, it means that the predetermined operating condition is reached, and therefore the process proceeds to step 23 and the air cut valve 22
Is opened, and in step 24, the air pump 21 is operated. Next, in step 25, the air-fuel ratio in the exhaust gas is read from the first air-fuel ratio sensor 16, and in step 26,
It is determined whether or not the read air-fuel ratio in the exhaust gas is on the lean side.

【００６７】このステップ２６で「ＹＥＳ」と判定した
ときは、エアカット弁２２を開弁させ、エアポンプ２１
を作動させた結果、２次空気が排気通路７内に正常に流
入し、排気中の空燃比がリーン側に変化した場合のた
め、ステップ２７で、２次空気の供給は正常であると判
定する。一方、前記ステップ２６で「ＮＯ」と判定した
ときは、エアポンプ２１の作動不良、エアカット弁２２
の開弁不良、２次空気導入路２０の閉塞等によって、排
気通路７内に２次空気が供給されず、排気中の空燃比が
リーン側に変化していない場合のため、ステップ２８に
移って、２次空気の供給に異常ありと判定する。If "YES" is determined in this step 26, the air cut valve 22 is opened and the air pump 21 is opened.
As a result of the operation, the secondary air normally flows into the exhaust passage 7 and the air-fuel ratio in the exhaust changes to the lean side. Therefore, in step 27, it is determined that the supply of the secondary air is normal. To do. On the other hand, when it is determined to be “NO” in step 26, the air pump 21 does not operate properly and the air cut valve 22
Since the secondary air is not supplied into the exhaust passage 7 and the air-fuel ratio in the exhaust has not changed to the lean side due to the poor valve opening of the secondary air, the obstruction of the secondary air introduction passage 20, or the like, the process proceeds to step 28. It is determined that there is an abnormality in the supply of secondary air.

【００６８】このように、２次空気の供給の正常，異常
を診断した後、ステップ２９では、エアポンプ２１を作
動させたまま、先に、エアカット弁２２を閉弁し、これ
により、エアカット弁２２による遮断状態とエアポンプ
２１による供給状態との重複状態を形成する。そして、
ステップ３０では、この重複状態における排気中の空燃
比を第１の空燃比センサ１６から読込み、ステップ３１
では、この空燃比がリッチ側であるか否かを判定する。
このステップ３１で「ＹＥＳ」と判定したときは、エア
カット弁２２の正常な閉弁動作によって排気通路７内へ
の２次空気の供給が遮断された結果、排気中の空燃比が
リッチ側に変化した場合のため、ステップ３２に移っ
て、エアカット弁２２の閉弁動作は正常であると判定す
る。一方、ステップ３１で「ＮＯ」と判定したときは、
ステップ３３に移って、図２に示す所定の短時間ｔ1が
経過するのを待つ。この短時間ｔ1中に空燃比がリッチ
側に変化しなければ、エアカット弁２２の閉弁不良によ
って、排気通路７内に２次空気が流入している場合のた
め、前記ステップ３３は「ＹＥＳ」と判定し、これによ
り、ステップ３４で、エアカット弁２２の閉弁動作が異
常であると判定して、必要な処理を行う。最後に、ステ
ップ３５では、エアポンプ２１の作動を停止してプログ
ラムを終了する。After diagnosing whether the supply of the secondary air is normal or abnormal as described above, in step 29, the air cut valve 22 is first closed while the air pump 21 is still operating, whereby the air cut is performed. An overlapping state of the shut-off state by the valve 22 and the supply state by the air pump 21 is formed. And
In step 30, the air-fuel ratio in the exhaust gas in this overlapping state is read from the first air-fuel ratio sensor 16, and step 31
Then, it is determined whether or not this air-fuel ratio is on the rich side.
If “YES” is determined in this step 31, the normal closing operation of the air cut valve 22 cuts off the supply of the secondary air into the exhaust passage 7, and as a result, the air-fuel ratio in the exhaust gas becomes rich. Since it has changed, the routine proceeds to step 32, where it is judged that the valve closing operation of the air cut valve 22 is normal. On the other hand, when it is determined to be “NO” in step 31,
The process moves to step 33, and waits for the predetermined short time t 1 shown in FIG. 2 to elapse. If the air-fuel ratio does not change to the rich side during this short time t 1 , secondary air is flowing into the exhaust passage 7 due to a valve closing failure of the air cut valve 22, and thus the step 33 is “ It is determined to be “YES”, and accordingly, in step 34, it is determined that the valve closing operation of the air cut valve 22 is abnormal, and necessary processing is performed. Finally, in step 35, the operation of the air pump 21 is stopped and the program ends.

【００６９】このように構成される本実施例によれば、
一つの診断処理内で、２次空気の供給診断と、２次空気
の供給停止診断との２つを実行することができる。According to the present embodiment configured as described above,
Within one diagnostic process, it is possible to execute two diagnostics, a secondary air supply diagnosis and a secondary air supply stop diagnosis.

【００７０】次に、図１０に基づいて、本発明の第７の
実施例を説明する。本実施例の特徴は、一つの診断処理
プログラム内で、２次空気の供給停止診断の終了後に、
２次空気の供給診断を行う点にあり、第２の実施例の変
形例に相当する。Next, a seventh embodiment of the present invention will be described with reference to FIG. The feature of the present embodiment is that, in one diagnostic processing program, after completion of the secondary air supply stop diagnostic,
The secondary air supply diagnosis is performed and corresponds to a modification of the second embodiment.

【００７１】図１０は、本実施例による判定処理のフロ
ーチャートを示し、本判定処理は、その前半で、第２の
実施例で述べた如く、２次空気の供給停止が正常である
か否かを２次空気供給時に診断し、その後半では、２次
空気の供給が正常か否かを診断する。即ち、ステップ４
１では、エアフローメータ１４，クランク角センサ３１
等からの検出信号を読込んで、所定回転数以下、所定の
機関負荷以下、所定の目標空燃比範囲かつ空燃比センサ
１６の出力が所定値である場合等を検知し、ステップ４
２では、各検出信号に基づいて、２次空気の供給が可能
な運転領域であるか否かを判定する。そして、このステ
ップ４２で「ＹＥＳ」と判定したときは、ステップ４３
でエアポンプ２１を先に作動させることにより、図４に
示すエアカット弁２２による遮断状態とエアポンプ２１
による供給状態とを重複させ、ステップ４４では、第１
の空燃比センサ１６から排気中の空燃比を読込み、ステ
ップ４５では、空燃比がリッチ側であるか否かを判定す
る。FIG. 10 shows a flow chart of the judgment processing according to the present embodiment. In the first half of the judgment processing, as described in the second embodiment, whether or not the supply of secondary air is stopped is normal. Is diagnosed when the secondary air is supplied, and in the latter half, it is diagnosed whether the supply of the secondary air is normal. That is, step 4
1, the air flow meter 14, the crank angle sensor 31
And the like, and detects a case where the engine speed is lower than a predetermined number of revolutions, a predetermined engine load is lower than a predetermined target air-fuel ratio range, and the output of the air-fuel ratio sensor 16 is a predetermined value.
At 2, it is determined based on each detection signal whether or not it is in the operation region where the secondary air can be supplied. When it is determined “YES” in step 42, step 43
By operating the air pump 21 first, the shutoff state by the air cut valve 22 shown in FIG.
And the supply state by
The air-fuel ratio in the exhaust gas is read from the air-fuel ratio sensor 16 of No. 1, and in step 45, it is determined whether the air-fuel ratio is on the rich side.

【００７２】そして、このステップ４５で「ＹＥＳ」と
判定したときは、エアカット弁２２が正常に閉弁してい
る結果、エアポンプ２１が作動しただけでは、排気通路
７内に２次空気が流入せず、排気中の空燃比が変化しな
い場合のため、ステップ４６で、エアカット弁２２の閉
弁動作は正常であると判定する。前記ステップ４５で
「ＮＯ」と判定したときは、空燃比がリッチ側ではない
場合のため、ステップ４７に移って、図４中に示す所定
の短時間ｔ2が経過するのを待ち、短時間ｔ2が経過して
も空燃比が変化しているときは、エアカット弁２２の漏
洩によって排気通路７内に２次空気が流入している場合
のため、ステップ４８で、エアカット弁２２の閉弁動作
が異常であると判定する。If "YES" is determined in this step 45, the air cut valve 22 is normally closed, so that the secondary air flows into the exhaust passage 7 only by operating the air pump 21. If not, the air-fuel ratio in the exhaust does not change. Therefore, in step 46, it is determined that the closing operation of the air cut valve 22 is normal. If the determination in step 45 is "NO", it means that the air-fuel ratio is not on the rich side, so the process moves to step 47 and waits for a predetermined short time t 2 shown in FIG. If the air-fuel ratio is changing even after t 2 elapses, secondary air is flowing into the exhaust passage 7 due to leakage of the air cut valve 22. It is determined that the valve closing operation is abnormal.

【００７３】一方、前記ステップ４６で、エアカット弁
２２の正常な閉弁動作を確認した後は、ステップ４９に
移って、エアカット弁２２を開弁させることにより、排
気通路７内に２次空気を導入する。そして、ステップ５
０では、２次空気導入時の空燃比を第１の空燃比センサ
１６から読込み、ステップ５１では、この空燃比がリー
ン側か否かを判定する。このステップ５１で「ＹＥＳ」
と判定したときは、エアカット弁２２の開弁によって、
エアポンプ２１からの２次空気が排気通路７内に流入
し、空燃比がリーン側に移行した場合のため、ステップ
５２で、２次空気の供給は正常であると判定する。一
方、ステップ５１で「ＮＯ」と判定したときは、エアカ
ット弁２２を開弁しても、２次空気が排気通路７内に流
入せず、空燃比がリーン側に移行しない場合のため、ス
テップ５３で、２次空気の供給に異常ありと判定する。
最後に、ステップ５４では、エアポンプ２１の作動を停
止すると共に、エアカット弁２２を閉弁し、診断処理を
終了する。On the other hand, after confirming the normal valve closing operation of the air cut valve 22 in step 46, the process proceeds to step 49 to open the air cut valve 22 so that the secondary air is discharged into the exhaust passage 7. Introduce air. And step 5
At 0, the air-fuel ratio at the time of introducing the secondary air is read from the first air-fuel ratio sensor 16, and at step 51, it is judged if this air-fuel ratio is on the lean side. "YES" in this step 51
When it is determined that the air cut valve 22 is opened,
Since the secondary air from the air pump 21 flows into the exhaust passage 7 and the air-fuel ratio shifts to the lean side, it is determined in step 52 that the supply of the secondary air is normal. On the other hand, when it is determined to be “NO” in step 51, even if the air cut valve 22 is opened, the secondary air does not flow into the exhaust passage 7 and the air-fuel ratio does not shift to the lean side. In step 53, it is determined that the secondary air supply is abnormal.
Finally, in step 54, the operation of the air pump 21 is stopped, the air cut valve 22 is closed, and the diagnosis process is ended.

【００７４】かくして、このように構成される本実施例
によれば、一つの診断処理において、最初にエアカット
弁２２の閉弁動作を診断し、次に、２次空気の供給を診
断することができる。Thus, according to the present embodiment having such a configuration, in one diagnosis process, first, the closing operation of the air cut valve 22 is diagnosed, and then the supply of secondary air is diagnosed. You can

【００７５】なお、前記各実施例では、状態重複部３２
Ａが「状態重複手段」の具体例であり、判定部３２Ｂが
「判定手段」の具体例である。In each of the above embodiments, the state duplication unit 32 is used.
A is a specific example of "state overlapping means", and the determination unit 32B is a specific example of "determination means".

【００７６】また、前記各実施例では、電磁弁２３から
の吸入負圧によって作動するエアカット弁２２を用いた
場合を例に挙げて説明したが、本発明はこれに限らず、
例えば図１１に示す如く、エアカット弁４１を電磁ソレ
ノイド弁から構成し、コントロールユニット３２の制御
信号により直接作動させてもよい。Further, in each of the above-described embodiments, the case where the air cut valve 22 which operates by the suction negative pressure from the solenoid valve 23 is used is described as an example, but the present invention is not limited to this.
For example, as shown in FIG. 11, the air cut valve 41 may be composed of an electromagnetic solenoid valve and directly operated by a control signal of the control unit 32.

【００７７】さらに、前記各実施例では、空燃比がリッ
チ側か否か、空燃比フィードバック補正係数が目標値か
否かのように、ある基準値を境に正常、異常を診断する
ものとして述べたが、本発明はこれに限らず、空燃比、
空燃比フィードバック補正係数の「変化の割合」に基づ
いて、漏洩の程度を複数段階で診断してもよい。例え
ば、空燃比のリーン側への変化が小さい場合は小異常、
リーン側への変化が大きい場合は大異常、の如くであ
る。この場合、変化の割合は、基準値と実測値との差分
でもよいし、変化の微分値であってもよい。Further, in each of the above-described embodiments, normality / abnormality is diagnosed at a certain reference value such as whether the air-fuel ratio is on the rich side or whether the air-fuel ratio feedback correction coefficient is the target value. However, the present invention is not limited to this, the air-fuel ratio,
The degree of leakage may be diagnosed in multiple stages based on the “rate of change” of the air-fuel ratio feedback correction coefficient. For example, when the change in the air-fuel ratio to the lean side is small, it is a small abnormality,
If the change to the lean side is large, it is like a big abnormality. In this case, the rate of change may be the difference between the reference value and the actual measurement value, or may be the differential value of the change.

【００７８】また、各実施例中の数値（所定の短時間）
は例示であって、本発明は、これに限定されない。Numerical values in each embodiment (predetermined short time)
Is an example, and the present invention is not limited thereto.

【００７９】なお、当業者であれば、前記各実施例を適
宜組み合わせて実施したり、処理ステップ等の追加や削
除等を行うことも可能である。従って、本発明は、前記
各実施例に拘束されず、専ら特許請求の範囲によって定
まる。Those skilled in the art can appropriately combine the above-described embodiments and add or delete processing steps and the like. Therefore, the present invention is not limited to the above-described embodiments, but is defined only by the claims.

【００８０】[0080]

【発明の効果】以上詳述した通り、本発明に係る内燃機
関の２次空気供給装置によれば、開閉手段が２次空気導
入路を遮断する遮断状態と２次空気供給手段が２次空気
導入路内に２次空気を吐出供給する供給状態とを所定の
短時間だけ重複させ、排気中の２次空気の有無で開閉手
段の漏洩を診断するため、開閉手段の漏洩を簡易かつ正
確に診断することができ、排気の逆流による他の故障の
発生を未然に防止することができる。As described in detail above, according to the secondary air supply system for an internal combustion engine according to the present invention, the shut-off means shuts off the secondary air introduction passage and the secondary air supply means operates the secondary air. Since the leakage of the opening / closing means is diagnosed depending on the presence / absence of the secondary air in the exhaust gas by overlapping the supply state in which the secondary air is discharged and supplied into the introduction passage for a predetermined short time, the leakage of the opening / closing means can be easily and accurately performed. It is possible to make a diagnosis and prevent the occurrence of other failures due to the backflow of exhaust gas.

【００８１】また、２次空気供給手段の供給停止時期を
開閉手段の閉時期よりも所定の短時間だけ遅らせること
により、遮断状態と供給状態とを所定の短時間だけ重複
させる構成としたため、通常処理による２次空気の供給
停止時に、開閉手段の漏洩を簡易に診断することができ
る。Further, since the supply stop timing of the secondary air supply means is delayed from the closing timing of the opening / closing means by a predetermined time, the shut-off state and the supply state are overlapped by a predetermined short time. When the supply of the secondary air due to the processing is stopped, the leakage of the opening / closing means can be easily diagnosed.

【００８２】さらに、開閉手段が２次空気導入路を遮断
している期間中に、所定の短時間だけ２次空気供給手段
から２次空気を吐出させることにより、遮断状態と供給
状態とを所定の短時間だけ重複させる構成としたため、
例えばアイドリング時等の如く、通常２次空気を供給し
ない運転条件下で、開閉手段の漏洩を積極的に診断する
ことができる。Further, while the opening / closing means is shutting off the secondary air introducing passage, the secondary air is discharged from the secondary air supply means for a predetermined short time so that the shut-off state and the supply state are predetermined. Since it was configured to overlap for a short time of,
For example, the leakage of the opening / closing means can be positively diagnosed under operating conditions in which secondary air is not normally supplied, such as during idling.

【００８３】また、２次空気供給手段が２次空気を吐出
供給している期間中に、所定の短時間だけ開閉手段によ
って２次空気導入路を遮断させることにより、遮断状態
と供給状態とを所定の短時間だけ重複させる構成とした
ため、例えば低水温時等の如く、２次空気を供給する運
転条件下で、積極的に開閉手段の漏洩を診断することが
できる。Further, while the secondary air supply means is discharging and supplying the secondary air, the opening / closing means shuts off the secondary air introducing passage for a predetermined short time so that the shut-off state and the supply state are changed. Since the structure is made to overlap for a predetermined short time, it is possible to positively diagnose the leakage of the opening / closing means under an operating condition in which the secondary air is supplied such as when the water temperature is low.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明の第１の実施例に係る内燃機関の２次空
気供給装置の全体構成を示す構成説明図である。FIG. 1 is a configuration explanatory view showing an overall configuration of a secondary air supply system for an internal combustion engine according to a first embodiment of the present invention.

【図２】遮断状態と供給状態との重複、空燃比の変化を
示す状態説明図である。FIG. 2 is a state explanatory view showing an overlap between a shutoff state and a supply state and a change in an air-fuel ratio.

【図３】判定処理を示すフローチャートである。FIG. 3 is a flowchart showing a determination process.

【図４】本発明の第２の実施例に係る内燃機関の２次空
気供給装置の遮断状態と供給状態との重複、空燃比の変
化を示す状態説明図である。FIG. 4 is a state explanatory view showing an overlap between a shutoff state and a supply state of a secondary air supply apparatus for an internal combustion engine according to a second embodiment of the present invention, and a change in an air-fuel ratio.

【図５】本発明の第３の実施例に係る内燃機関の２次空
気供給装置の遮断状態と供給状態との重複、空燃比の変
化を示す状態説明図である。FIG. 5 is a state explanatory view showing an overlap between a shutoff state and a supply state of a secondary air supply device for an internal combustion engine according to a third embodiment of the present invention, and a change in an air-fuel ratio.

【図６】本発明の第４の実施例に係る内燃機関の２次空
気供給装置の遮断状態と供給状態との重複、空燃比の変
化を示す状態説明図である。FIG. 6 is a state explanatory view showing an overlap between a shutoff state and a supply state of a secondary air supply system for an internal combustion engine according to a fourth embodiment of the present invention, and a change in an air-fuel ratio.

【図７】本発明の第５の実施例に係る内燃機関の２次空
気供給装置の遮断状態と供給状態との重複、空燃比フィ
ードバック補正係数の変化を示す状態説明図である。FIG. 7 is a state explanatory view showing an overlap between a shutoff state and a supply state of a secondary air supply system for an internal combustion engine according to a fifth embodiment of the present invention, and a change in an air-fuel ratio feedback correction coefficient.

【図８】判定処理を示すフローチャートである。FIG. 8 is a flowchart showing a determination process.

【図９】供給診断後に供給停止診断を行う判定処理のフ
ローチャートである。FIG. 9 is a flowchart of a determination process of performing supply stop diagnosis after supply diagnosis.

【図１０】供給停止診断後に供給診断を行う判定処理の
フローチャートである。FIG. 10 is a flowchart of a determination process of performing supply diagnosis after supply stop diagnosis.

【図１１】電磁ソレノイド弁をエアカット弁に用いた場
合の構成説明図である。FIG. 11 is a structural explanatory view when an electromagnetic solenoid valve is used as an air cut valve.

【符号の説明】[Explanation of symbols]

７…排気通路 １６…第１の空燃比センサ（空燃比検出手段） １７…触媒コンバータ ２０…２次空気導入路 ２１…エアポンプ（２次空気供給手段） ２２…エアカット弁（開閉手段） ２３…電磁弁（開閉手段） ３２…コントロールユニット ３２Ａ…状態重複部（状態重複手段） ３２Ｂ…判定部（判定手段） 7 ... Exhaust passage 16 ... First air-fuel ratio sensor (air-fuel ratio detecting means) 17 ... Catalytic converter 20 ... Secondary air introduction passage 21 ... Air pump (secondary air supply means) 22 ... Air cut valve (opening / closing means) 23 ... Solenoid valve (opening / closing means) 32 ... Control unit 32A ... State overlapping part (state overlapping means) 32B ... Judgment part (judgment means)

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｆ０２Ｂ 77/08 Ｆ０２Ｂ 77/08 Ｌ ＺＡＢ ＺＡＢＭ Ｆ０２Ｄ 41/14 ＺＡＢ Ｆ０２Ｄ 41/14 ＺＡＢ ３１０ ３１０Ｋ Ｇ０１Ｍ 15/00 ＺＡＢ Ｇ０１Ｍ 15/00 ＺＡＢＺ ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI Technical display location F02B 77/08 F02B 77/08 L ZAB ZABM F02D 41/14 ZAB F02D 41/14 ZAB 310 310K G01M 15 / 00 ZAB G01M 15/00 ZABZ

Claims (4)

【特許請求の範囲】[Claims] 【請求項１】 触媒コンバータの上流側に位置して排気
通路の途中に接続された２次空気導入路と、この２次空
気導入路内に２次空気を吐出供給する２次空気供給手段
と、この２次空気供給手段よりも下流側に位置して前記
２次空気導入路の途中に設けられ、該２次空気導入路を
連通，遮断する開閉手段と、前記２次空気導入路の排気
通路接続部よりも下流側に位置して前記排気通路の途中
に設けられ、空燃比を検出する空燃比検出手段とを備え
た内燃機関の２次空気供給装置であって、 前記開閉手段が前記２次空気導入路を遮断している遮断
状態と前記２次空気供給手段が前記２次空気導入路内に
２次空気を吐出供給している供給状態とを所定の短時間
だけ重複させる状態重複手段と、 前記遮断状態と前記供給状態とが重複しているときに、
前記空燃比検出手段からの検出信号に基づいて排気中に
おける２次空気の有無を検出し、２次空気が検出された
場合は前記開閉手段の漏洩であると判定する判定手段と
を設けたことを特徴とする内燃機関の２次空気供給装
置。1. A secondary air introducing passage located upstream of the catalytic converter and connected in the middle of an exhaust passage, and secondary air supplying means for discharging and supplying secondary air into the secondary air introducing passage. An opening / closing means which is located on the downstream side of the secondary air supply means and which is provided in the middle of the secondary air introduction path, and which connects and disconnects the secondary air introduction path, and exhaust of the secondary air introduction path. A secondary air supply device for an internal combustion engine, comprising: an air-fuel ratio detecting means for detecting an air-fuel ratio, the air-fuel ratio detecting means being provided on a downstream side of a passage connecting portion, in the middle of the exhaust passage. A state overlap in which the shut-off state in which the secondary air introducing passage is shut off and the supply state in which the secondary air supplying means discharges and supplies the secondary air into the secondary air introducing passage overlaps each other for a predetermined short time. Means and when the cutoff state and the supply state overlap
The determination means is provided for detecting the presence or absence of secondary air in the exhaust gas based on the detection signal from the air-fuel ratio detection means, and determining the leakage of the opening / closing means when the secondary air is detected. A secondary air supply device for an internal combustion engine, comprising: 【請求項２】 前記状態重複手段は、前記２次空気供給
手段の供給停止時期を前記開閉手段の閉時期よりも所定
の短時間だけ遅らせることにより、前記遮断状態と前記
供給状態とを所定の短時間だけ重複させることを特徴と
する請求項１に記載の内燃機関の２次空気供給装置。2. The state overlapping means delays the supply stop timing of the secondary air supply means by a predetermined short time from the closing timing of the opening / closing means, so that the shut-off state and the supply state are predetermined. The secondary air supply device for an internal combustion engine according to claim 1, wherein the secondary air supply devices are overlapped for a short time. 【請求項３】 前記状態重複手段は、前記開閉手段が前
記２次空気導入路を遮断している期間中に、所定の短時
間だけ前記２次空気供給手段から２次空気を吐出させる
ことにより、前記遮断状態と前記供給状態とを所定の短
時間だけ重複させることを特徴とする請求項１に記載の
内燃機関の２次空気供給装置。3. The state overlapping means discharges secondary air from the secondary air supply means only for a predetermined short time while the opening / closing means is blocking the secondary air introduction passage. The secondary air supply device for an internal combustion engine according to claim 1, wherein the cutoff state and the supply state are overlapped for a predetermined short time. 【請求項４】 前記状態重複手段は、前記２次空気供給
手段が前記２次空気導入路内に２次空気を吐出供給して
いる期間中に、所定の短時間だけ前記開閉手段によって
前記２次空気導入路を遮断させることにより、前記遮断
状態と前記供給状態とを所定の短時間だけ重複させるこ
とを特徴とする請求項１に記載の内燃機関の２次空気供
給装置。4. The state overlapping means is configured to operate the opening / closing means by the opening / closing means for a predetermined short time during a period in which the secondary air supply means discharges and supplies secondary air into the secondary air introduction passage. The secondary air supply device for an internal combustion engine according to claim 1, wherein the cutoff state and the supply state are overlapped for a predetermined short time period by blocking the secondary air introduction path.
JP7046010A 1995-03-07 1995-03-07 Secondary air supply device for internal combustion engine Pending JPH08246851A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP7046010A JPH08246851A (en) 1995-03-07 1995-03-07 Secondary air supply device for internal combustion engine

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP7046010A JPH08246851A (en) 1995-03-07 1995-03-07 Secondary air supply device for internal combustion engine

Publications (1)

Publication Number Publication Date
JPH08246851A true JPH08246851A (en) 1996-09-24

Family

ID=12735102

Family Applications (1)

Application Number Title Priority Date Filing Date
JP7046010A Pending JPH08246851A (en) 1995-03-07 1995-03-07 Secondary air supply device for internal combustion engine

Country Status (1)

Country Link
JP (1) JPH08246851A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6393833B2 (en) 2000-02-15 2002-05-28 Toyota Jidosha Kabushiki Kaisha Abnormality test method and apparatus for secondary air supply system of a vehicle
JP2014010104A (en) * 2012-07-02 2014-01-20 Ngk Spark Plug Co Ltd Particle detection system
US11746687B2 (en) 2021-12-27 2023-09-05 Hyundai Motor Company EHC line leakage diagnosis method and vehicle exhaust system thereof

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6393833B2 (en) 2000-02-15 2002-05-28 Toyota Jidosha Kabushiki Kaisha Abnormality test method and apparatus for secondary air supply system of a vehicle
JP2014010104A (en) * 2012-07-02 2014-01-20 Ngk Spark Plug Co Ltd Particle detection system
US11746687B2 (en) 2021-12-27 2023-09-05 Hyundai Motor Company EHC line leakage diagnosis method and vehicle exhaust system thereof

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