JPH0914024A - Exhaust gas cleaning device for internal combustion engine - Google Patents
Exhaust gas cleaning device for internal combustion engineInfo
- Publication number
- JPH0914024A JPH0914024A JP7163835A JP16383595A JPH0914024A JP H0914024 A JPH0914024 A JP H0914024A JP 7163835 A JP7163835 A JP 7163835A JP 16383595 A JP16383595 A JP 16383595A JP H0914024 A JPH0914024 A JP H0914024A
- Authority
- JP
- Japan
- Prior art keywords
- oxygen sensor
- bypass valve
- switching
- catalyst
- fuel ratio
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Landscapes
- Exhaust Gas After Treatment (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、排気系に２つの触媒を
備える内燃機関の排気浄化装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification apparatus for an internal combustion engine having an exhaust system with two catalysts.
【０００２】[0002]
【従来の技術】従来の内燃機関の排気浄化装置として、
例えば特開昭６２−９９６１１号公報に示されるような
ものがある。これは、排気通路の上流側と下流側とにそ
れぞれフロント触媒及びリア触媒を配置し、また、フロ
ント触媒をバイパスしてリア触媒上流に合流するバイパ
ス通路と、排気の流れをフロント触媒側とバイパス通路
側とに切換えることのできるバイパス弁とを設けてあ
る。2. Description of the Related Art As a conventional exhaust gas purifying apparatus for an internal combustion engine,
For example, there is one disclosed in Japanese Patent Laid-Open No. 62-99611. This is because a front catalyst and a rear catalyst are arranged on the upstream side and the downstream side of the exhaust passage, respectively, and a bypass passage that bypasses the front catalyst and joins the rear catalyst upstream, and an exhaust flow to the front catalyst side. A bypass valve that can be switched to the passage side is provided.
【０００３】そして、機関運転状態、特には排気温度、
又は機関回転数及び負荷を検出し、これに応じてバイパ
ス弁を切換えている。具体的には、排気温度が低い時、
又は低回転・低負荷時には、バイパス弁をフロント触媒
側に切換えて、排気通路における機関になるべく近い位
置に設けたフロント触媒を用いて、排気浄化を図り、ま
たフロント触媒での燃焼熱によりリア触媒の活性化を促
進する。The engine operating condition, especially the exhaust temperature,
Alternatively, the engine speed and the load are detected, and the bypass valve is switched according to the detected value. Specifically, when the exhaust temperature is low,
Alternatively, when the engine speed is low and the load is low, the bypass valve is switched to the front catalyst side to purify the exhaust gas by using the front catalyst installed in the exhaust passage as close to the engine as possible, and the rear catalyst is generated by the combustion heat of the front catalyst. Promote the activation of.
【０００４】そして、排気温度が高い時、又は高回転・
高負荷時には、バイパス弁をバイパス通路側に切換え
て、フロント触媒の焼損を防止しつつ、リア触媒のみで
排気浄化を図る。また、空燃比をストイキに制御する空
燃比フィードバック制御のための酸素センサは、フロン
ト触媒の上流に配置し、この酸素センサからの信号に基
づいて空燃比フィードバック制御を行うが、バイパス通
路側への切換状態においても空燃比フィードバック制御
を可能とするために、バイパス通路側への切換状態に
て、排気がフロント触媒にわずかながら流入するよう
に、バイパス弁を少し開け、この少量の排気により酸素
センサで空燃比を検出している。When the exhaust temperature is high,
When the load is high, the bypass valve is switched to the bypass passage side to prevent burnout of the front catalyst and purify exhaust gas only with the rear catalyst. Further, an oxygen sensor for air-fuel ratio feedback control that controls the air-fuel ratio to stoichiometric is arranged upstream of the front catalyst, and air-fuel ratio feedback control is performed based on the signal from this oxygen sensor, but it does not affect the bypass passage side. In order to enable the air-fuel ratio feedback control even in the switching state, the bypass valve is opened slightly so that the exhaust gas slightly flows into the front catalyst in the switching state to the bypass passage side. The air-fuel ratio is detected at.
【０００５】[0005]
【発明が解決しようとする課題】しかしながら、前記公
報に記載の装置にあっては、バイパス弁のバイパス通路
側への切換状態においては、酸素センサにより少量の排
気から空燃比を検出するため、空燃比検出の精度及び応
答性に劣り、また、フロント触媒に高温の排気が常に流
入するため、触媒劣化を引き起こしやすいという問題点
がある。However, in the device described in the above publication, the air-fuel ratio is detected from a small amount of exhaust gas by the oxygen sensor when the bypass valve is switched to the bypass passage side. There are problems that the accuracy and responsiveness of the fuel ratio detection are poor, and that the high-temperature exhaust gas always flows into the front catalyst, which easily causes catalyst deterioration.
【０００６】そこで、フロント触媒及びリア触媒の各上
流にそれぞれフロント酸素センサ及びリア酸素センサを
設ける一方、バイパス弁の切換状態に応じ、フロント触
媒側への切換状態にてフロント酸素センサを選択し、バ
イパス通路側への切換状態にてリア酸素センサを選択し
て、選択された酸素センサからの信号に基づいて空燃比
フィードバック制御を行うことが検討されている。Therefore, while a front oxygen sensor and a rear oxygen sensor are provided upstream of the front catalyst and the rear catalyst, respectively, the front oxygen sensor is selected in the switching state to the front catalyst side according to the switching state of the bypass valve, It is considered that a rear oxygen sensor is selected in a switching state to the bypass passage side and air-fuel ratio feedback control is performed based on a signal from the selected oxygen sensor.
【０００７】これによれば、バイパス通路への切換状態
（高速・高負荷時）におけるフロント触媒への高温の排
気の流入を防止して、触媒劣化を抑制すると共に、いず
れの運転状態においても、それぞれ触媒の直上流の酸素
センサにより空燃比フィードバック制御ができるため、
空燃比はストイキに制御され、触媒の転換効率を高める
ことが可能となる。According to this, high temperature exhaust gas is prevented from flowing into the front catalyst when switching to the bypass passage (at high speed and high load), catalyst deterioration is suppressed, and in any operating state, Since the air-fuel ratio feedback control can be performed by the oxygen sensor directly upstream of each catalyst,
The air-fuel ratio is controlled stoichiometrically, which makes it possible to increase the conversion efficiency of the catalyst.
【０００８】ところが、バイパス弁により排気の流れを
切換えると同時に、空燃比フィードバック制御に使用す
る酸素センサを切換えるように制御すると、切換後に使
用する酸素センサが安定する前に（正しい空燃比を示す
前に）、その信号に基づいて空燃比フィードバック制御
を行ってしまうため、空燃比のリッチスパイク又はリー
ンスパイクが発生し、触媒の転換効率が大幅に悪化する
という問題点があった。However, when the exhaust valve is switched by the bypass valve and the oxygen sensor used for the air-fuel ratio feedback control is switched at the same time, the oxygen sensor used after the switching is stabilized (before the correct air-fuel ratio is shown). In addition, since the air-fuel ratio feedback control is performed based on the signal, there is a problem that a rich spike or a lean spike of the air-fuel ratio occurs and the conversion efficiency of the catalyst is significantly deteriorated.
【０００９】本発明は、このような従来の問題点に鑑
み、バイパス弁の切換時の空燃比制御を安定させること
を目的とする。SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems, and an object of the present invention is to stabilize the air-fuel ratio control when switching the bypass valve.
【００１０】[0010]
【課題を解決するための手段】このため、請求項１に係
る発明では、図１に示すように、排気通路の上流側と下
流側とにそれぞれ配置されたフロント触媒及びリア触媒
と、フロント触媒をバイパスしてリア触媒上流に合流す
るバイパス通路と、排気の流れをフロント触媒側とバイ
パス通路側とに切換えることのできるバイパス弁と、機
関運転状態に応じてバイパス弁を切換えるバイパス弁切
換制御手段と、を備える内燃機関の排気浄化装置におい
て、フロント触媒及びリア触媒の各上流にそれぞれフロ
ント酸素センサ及びリア酸素センサを設ける一方、バイ
パス弁の切換状態に応じ、フロント触媒側への切換状態
にてフロント酸素センサを選択し、バイパス通路側への
切換状態にてリア酸素センサを選択する酸素センサ選択
手段と、選択された酸素センサからの信号に基づいて空
燃比フィードバック補正係数を演算する補正係数演算手
段と、バイパス弁の切換直後に、所定期間、前記補正係
数演算手段に優先して、空燃比フィードバック補正係数
を所定値に固定する補正係数固定手段と、機関への燃料
噴射量を前記空燃比フィードバック補正係数により補正
する燃料噴射量補正手段とを設けたことを特徴とする。For this reason, in the invention according to claim 1, as shown in FIG. 1, a front catalyst and a rear catalyst respectively arranged on the upstream side and the downstream side of the exhaust passage, and the front catalyst. Bypass passage that bypasses the engine and joins the rear catalyst upstream, a bypass valve that can switch the exhaust flow between the front catalyst side and the bypass passage side, and a bypass valve switching control means that switches the bypass valve according to the engine operating state. In an exhaust gas purification apparatus for an internal combustion engine, the front oxygen sensor and the rear oxygen sensor are provided upstream of the front catalyst and the rear catalyst, respectively, while switching to the front catalyst side according to the switching state of the bypass valve. Oxygen sensor selection means for selecting the front oxygen sensor and selecting the rear oxygen sensor when switching to the bypass passage side is selected. A correction coefficient calculation means for calculating an air-fuel ratio feedback correction coefficient based on a signal from an oxygen sensor, and immediately after switching the bypass valve, for a predetermined period, prior to the correction coefficient calculation means, the air-fuel ratio feedback correction coefficient is set to a predetermined value. A correction coefficient fixing means for fixing the fuel injection quantity to the engine and a fuel injection quantity correcting means for correcting the fuel injection quantity to the engine by the air-fuel ratio feedback correction coefficient are provided.
【００１１】請求項２に係る発明では、図２に示すよう
に、排気通路の上流側と下流側とにそれぞれ配置された
フロント触媒及びリア触媒と、フロント触媒をバイパス
してリア触媒上流に合流するバイパス通路と、排気の流
れをフロント触媒側とバイパス通路側とに切換えること
のできるバイパス弁と、機関運転状態に応じてバイパス
弁を切換えるバイパス弁切換制御手段と、を備える内燃
機関の排気浄化装置において、フロント触媒及びリア触
媒の各上流にそれぞれフロント酸素センサ及びリア酸素
センサを設ける一方、バイパス弁の切換状態に応じ、フ
ロント触媒側への切換状態にてフロント酸素センサを選
択し、バイパス通路側への切換状態にてリア酸素センサ
を選択する酸素センサ選択手段と、選択された酸素セン
サからの信号に基づいて空燃比フィードバック補正係数
を演算する補正係数演算手段と、フロント酸素センサ及
びリア酸素センサの各出力の反転周波数を検出する反転
周波数検出手段と、両酸素センサの反転周波数を比較す
る比較手段と、バイパス弁の切換時に、前記比較手段に
より、両酸素センサの反転周波数がほぼ同一と判断され
るまで、前記補正係数演算手段に優先して、切換前に選
択されていた酸素センサからの信号に基づいて空燃比フ
ィードバック補正係数を演算する切換時補正係数演算手
段と、機関への燃料噴射量を前記空燃比フィードバック
補正係数により補正する燃料噴射量補正手段とを設けた
ことを特徴とする。According to the second aspect of the present invention, as shown in FIG. 2, the front catalyst and the rear catalyst are respectively arranged on the upstream side and the downstream side of the exhaust passage, and the front catalyst is bypassed to join the upstream side of the rear catalyst. Exhaust gas purification for an internal combustion engine, which includes a bypass passage for switching the exhaust flow between the front catalyst side and the bypass passage side, and bypass valve switching control means for switching the bypass valve according to the engine operating state. In the device, a front oxygen sensor and a rear oxygen sensor are provided upstream of each of the front catalyst and the rear catalyst, while the front oxygen sensor is selected in the switching state to the front catalyst side according to the switching state of the bypass valve, and the bypass passage is selected. The oxygen sensor selection means for selecting the rear oxygen sensor in the switching state to the side and the signal from the selected oxygen sensor. A correction coefficient calculation means for calculating the air-fuel ratio feedback correction coefficient, an inversion frequency detection means for detecting the inversion frequency of each output of the front oxygen sensor and the rear oxygen sensor, and a comparison means for comparing the inversion frequencies of both oxygen sensors, At the time of switching the bypass valve, until the comparison means determines that the reversal frequencies of both oxygen sensors are substantially the same, priority is given to the correction coefficient calculation means, and based on the signal from the oxygen sensor selected before the switching. And a fuel injection amount correction means for correcting the fuel injection amount to the engine by the air-fuel ratio feedback correction coefficient.
【００１２】請求項３に係る発明では、請求項２に係る
発明に加え、更に、バイパス弁の切換時に、前記比較手
段により、両酸素センサの反転周波数がほぼ同一と判断
されるまで、前記バイパス弁切換制御手段に優先して、
バイパス弁の開度を排気をフロント触媒側とバイパス通
路側との両方へ流す中間開度に制御する中間開度制御手
段を設けたことを特徴とする。In the invention according to claim 3, in addition to the invention according to claim 2, further, at the time of switching the bypass valve, the bypass is continued until the comparison means determines that the reversal frequencies of both oxygen sensors are substantially the same. In preference to the valve switching control means,
An intermediate opening control means is provided for controlling the opening of the bypass valve to an intermediate opening that allows the exhaust to flow to both the front catalyst side and the bypass passage side.
【００１３】請求項４に係る発明では、請求項１〜請求
項３に係る発明において、前記バイパス弁切換制御手段
は、機関回転数及び負荷に基づいて、高回転・高負荷時
にバイパス弁をバイパス通路側に切換えるものであるこ
とを特徴とする。According to a fourth aspect of the invention, in the first to third aspects of the invention, the bypass valve switching control means bypasses the bypass valve during high rotation and high load based on the engine speed and load. The feature is that it is switched to the aisle side.
【００１４】[0014]
【作用】請求項１に係る発明では、バイパス弁の切換状
態に応じ、フロント触媒側への切換状態にてフロント酸
素センサを選択し、バイパス通路側への切換状態にてリ
ア酸素センサを選択して、選択された酸素センサからの
信号に基づいて空燃比フィードバック補正係数を演算し
て、空燃比フィードバック制御を行うが、バイパス弁の
切換直後は、所定期間、空燃比フィードバック補正係数
を所定値に固定する。In the invention according to claim 1, the front oxygen sensor is selected in the switching state to the front catalyst side and the rear oxygen sensor is selected in the switching state to the bypass passage side according to the switching state of the bypass valve. The air-fuel ratio feedback correction coefficient is calculated based on the signal from the selected oxygen sensor to perform air-fuel ratio feedback control.However, immediately after the bypass valve is switched, the air-fuel ratio feedback correction coefficient is set to a predetermined value for a predetermined period. Fix it.
【００１５】このように、バイパス弁の切換時に、所定
期間、空燃比フィードバック補正係数を所定値に固定し
た後、空燃比フィードバック制御に使用する酸素センサ
を切換える制御としたため、バイパス弁の切換時に応答
性の低い酸素センサによる空燃比フィードバック制御を
停止することで、切換時に生じる空燃比のスパイクを防
止することができて、触媒の転換効率を高く保つことが
可能となり、エミッションの悪化を抑制できる。In this way, when the bypass valve is switched, the air-fuel ratio feedback correction coefficient is fixed to a predetermined value for a predetermined period, and then the oxygen sensor used for the air-fuel ratio feedback control is switched. By stopping the air-fuel ratio feedback control by the oxygen sensor having low property, it is possible to prevent the spike of the air-fuel ratio that occurs at the time of switching, it is possible to keep the conversion efficiency of the catalyst high, and it is possible to suppress the deterioration of emissions.
【００１６】請求項２に係る発明では、バイパス弁の切
換状態に応じ、フロント触媒側への切換状態にてフロン
ト酸素センサを選択し、バイパス通路側への切換状態に
てリア酸素センサを選択して、選択された酸素センサか
らの信号に基づいて空燃比フィードバック補正係数を演
算して、空燃比フィードバック制御を行うが、バイパス
弁の切換時は、フロント酸素センサ及びリア酸素センサ
の各出力の反転周波数を検出し、両酸素センサの反転周
波数を比較していて、両酸素センサの反転周波数がほぼ
同一と判断されるまで、切換前に選択されていた酸素セ
ンサからの信号に基づいて空燃比フィードバック補正係
数を演算して、空燃比フィードバック制御を行う。In the invention according to claim 2, the front oxygen sensor is selected in the switching state to the front catalyst side and the rear oxygen sensor is selected in the switching state to the bypass passage side according to the switching state of the bypass valve. The air-fuel ratio feedback correction coefficient is calculated based on the signal from the selected oxygen sensor to perform air-fuel ratio feedback control.However, when switching the bypass valve, the outputs of the front oxygen sensor and rear oxygen sensor are reversed. By detecting the frequency and comparing the reversal frequency of both oxygen sensors, until the reversal frequency of both oxygen sensors is judged to be almost the same, the air-fuel ratio feedback based on the signal from the oxygen sensor selected before switching The correction coefficient is calculated and the air-fuel ratio feedback control is performed.
【００１７】このように、バイパス弁の切換時は、両酸
素センサの信号をモニタし、略同一の反転周波数となっ
てから、空燃比フィードバック制御に使用する酸素セン
サを切換える制御としたため、バイパス弁の切換時に応
答性の高い酸素センサを用いることで、切換時に生じる
空燃比のスパイクを防止することができて、触媒の転換
効率を高く保つことが可能となり、エミッションの悪化
を抑制できる。As described above, when the bypass valve is switched, the signals of both oxygen sensors are monitored, and when the inversion frequency becomes substantially the same, the control of switching the oxygen sensor used for the air-fuel ratio feedback control is performed. By using a highly responsive oxygen sensor at the time of switching, it is possible to prevent the spike of the air-fuel ratio that occurs at the time of switching, it is possible to keep the conversion efficiency of the catalyst high, and suppress the deterioration of emissions.
【００１８】また、常に応答性の高い酸素センサを使用
して、空燃比フィードバック制御を行うため、切換直後
に運転条件が変化した場合でも、追従性良く制御でき、
空燃比の変動を抑制することができる。請求項３に係る
発明では、バイパス弁の切換時に、両酸素センサの反転
周波数がほぼ同一と判断されるまで、バイパス弁の開度
を排気をフロント触媒側とバイパス通路側との両方へ流
す中間開度に制御する。これにより、切換時に使用する
酸素センサの検出精度を高く維持できて、制御精度が大
幅に向上する。Further, since the oxygen sensor having a high responsiveness is always used to perform the air-fuel ratio feedback control, the followability can be controlled even if the operating condition changes immediately after the switching.
Fluctuations in the air-fuel ratio can be suppressed. In the invention according to claim 3, when switching the bypass valve, the opening degree of the bypass valve is set to an intermediate value in which the exhaust gas is flown to both the front catalyst side and the bypass passage side until it is determined that the reversal frequencies of both oxygen sensors are substantially the same. Control the opening. Thereby, the detection accuracy of the oxygen sensor used at the time of switching can be maintained high, and the control accuracy is significantly improved.
【００１９】請求項４に係る発明では、機関回転数及び
負荷に基づいて、高回転・高負荷時にバイパス弁をバイ
パス通路側に切換えるので、排気温度センサを用いるこ
となく、制御できる。In the invention according to claim 4, since the bypass valve is switched to the bypass passage side at the time of high rotation and high load based on the engine speed and load, control can be performed without using an exhaust gas temperature sensor.
【００２０】[0020]
【実施例】以下に本発明の実施例を説明する。先ず第１
の実施例を図３〜図５により説明する。図３はシステム
構成図である。内燃機関１の吸気通路２には、各気筒毎
に吸気ポートへ向けて燃料を噴射する燃料噴射弁３が設
けられている。Embodiments of the present invention will be described below. First,
The embodiment will be described with reference to FIGS. FIG. 3 is a system configuration diagram. The intake passage 2 of the internal combustion engine 1 is provided with a fuel injection valve 3 for injecting fuel toward an intake port for each cylinder.
【００２１】この燃料噴射弁３は、コントロールユニッ
ト10からの駆動パルス信号により通電されて開弁し、通
電停止されて閉弁する電磁式燃料噴射弁であって、駆動
パルス信号のパルス幅によって燃料噴射量が制御され、
この燃料噴射量の制御により空燃比が制御される。排気
通路４には、上流側にフロント触媒５が配置されると共
に、下流側にリア触媒６が配置されている。The fuel injection valve 3 is an electromagnetic fuel injection valve which is energized by a drive pulse signal from the control unit 10 to open the valve, and deenergized to close the valve. Injection quantity is controlled,
The air-fuel ratio is controlled by controlling the fuel injection amount. A front catalyst 5 is arranged on the upstream side and a rear catalyst 6 is arranged on the downstream side in the exhaust passage 4.
【００２２】また、フロント触媒５をバイパスしてリア
触媒６上流に合流するパイパス通路７が設けられ、フロ
ント触媒５側通路とバイパス通路７とを選択するバイパ
ス弁８が設けられている。このバイパス弁８は、電磁駆
動型であって、共通の弁軸に２つの弁体８ａ，８ｂが取
付けられており、非通電状態では、弁体８ａによりフロ
ント触媒５側通路を開いて弁体８ｂによりバイパス通路
７を閉止し、通電されると、弁体８ａによりフロント触
媒５側通路を閉止して弁体８ｂによりバイパス通路７を
開くように切換えられる。このバイパス弁８への通電も
コントロールユニット10により制御される。Further, a bypass passage 7 is provided which bypasses the front catalyst 5 and joins the rear catalyst 6 upstream, and a bypass valve 8 which selects the front catalyst 5 side passage or the bypass passage 7 is provided. This bypass valve 8 is of an electromagnetic drive type, and has two valve bodies 8a and 8b attached to a common valve shaft. In the non-energized state, the valve body 8a opens the passage on the front catalyst 5 side to open the valve body. When the bypass passage 7 is closed by 8b and is energized, the valve body 8a closes the passage on the front catalyst 5 side and the valve body 8b opens the bypass passage 7. The power supply to the bypass valve 8 is also controlled by the control unit 10.
【００２３】前記燃料噴射弁３及びバイパス弁８の制御
のため、コントロールユニット10には、各種のセンサか
ら、吸入空気流量信号、回転数信号などが入力されてい
る。更に、排気通路４のフロント触媒５上流（入口部）
に、フロント酸素センサ11が設けられると共に、リア触
媒６上流（入口部）に、リア酸素センサ12が設けられて
いて、これらの信号もコントロールユニット10に入力さ
れている。In order to control the fuel injection valve 3 and the bypass valve 8, an intake air flow rate signal, a rotation speed signal, etc. are input to the control unit 10 from various sensors. Further, upstream of the front catalyst 5 in the exhaust passage 4 (inlet portion)
In addition to the front oxygen sensor 11, a rear oxygen sensor 12 is provided upstream (inlet) of the rear catalyst 6, and these signals are also input to the control unit 10.
【００２４】ここにおいて、コントロールユニット10
は、前記各種のセンサからの信号を入力しつつ、内蔵の
マイクロコンピュータにより、図４のフローチャートに
示す制御を行う。図４のフローチャートに従って説明す
る。尚、本ルーチンは所定時間（例えば10msec）毎に実
行される。Here, the control unit 10
Performs the control shown in the flowchart of FIG. 4 by the built-in microcomputer while inputting the signals from the various sensors. This will be described with reference to the flowchart of FIG. It should be noted that this routine is executed every predetermined time (for example, 10 msec).
【００２５】ステップ１（図にはＳ１と記してある。以
下同様）では、機関の運転状態として、機関回転数Ｎｅ
及び負荷（基本燃料噴射量）Ｔｐを読込む。ステップ２
では、バイパス弁８をバイパス通路７側に切換える条件
である高回転・高負荷状態か否かを判定する。高回転・
高負荷状態の場合は、ステップ３へ進み、バイパス弁８
をバイパス通路７側へ切換える。In step 1 (denoted as S1 in the figure, the same applies hereinafter), the engine speed Ne is set as the operating state of the engine.
And load (basic fuel injection amount) Tp. Step 2
Then, it is determined whether or not the condition is high rotation / high load, which is a condition for switching the bypass valve 8 to the bypass passage 7 side. High rotation
If the load is high, proceed to step 3 and bypass valve 8
To the bypass passage 7 side.
【００２６】次のステップ４では、バイパス弁８切換
後、所定時間（例えば２sec ）（又は所定回転）経過し
たか否かを判定する。所定時間経過する前は、ステップ
５へ進んで空燃比フィードバック補正係数αを１にクラ
ンプする。所定時間経過後は、ステップ６へ進んでリア
酸素センサ12を選択し、次のステップ６で選択されたリ
ア酸素センサ12からの信号に基づいて空燃比フィードバ
ック補正係数αを演算する。すなわち、リア酸素センサ
12により検出される空燃比がリッチのときは空燃比フィ
ードバック補正係数αを減少させ、空燃比がリーンのと
きは空燃比フィードバック補正係数αを増大させる。In the next step 4, it is determined whether or not a predetermined time (for example, 2 seconds) (or a predetermined rotation) has elapsed after switching the bypass valve 8. Before the predetermined time has elapsed, the routine proceeds to step 5, where the air-fuel ratio feedback correction coefficient α is clamped to 1. After the lapse of a predetermined time, the routine proceeds to step 6, the rear oxygen sensor 12 is selected, and the air-fuel ratio feedback correction coefficient α is calculated based on the signal from the rear oxygen sensor 12 selected at the next step 6. That is, the rear oxygen sensor
When the air-fuel ratio detected by 12 is rich, the air-fuel ratio feedback correction coefficient α is decreased, and when the air-fuel ratio is lean, the air-fuel ratio feedback correction coefficient α is increased.
【００２７】このようにして設定された空燃比フィード
バック補正係数αは、別ルーチンによる燃料噴射量Ｔｉ
の演算に際して用いられる。すなわち、吸入空気流量Ｑ
ａと回転数Ｎｅとから基本燃料噴射量Ｔｐ＝Ｋ・Ｑａ／
Ｎｅ（Ｋは定数）を演算し、これを空燃比フィードバッ
ク補正係数αにより補正して、最終的な燃料噴射量Ｔｉ
＝Ｔｐ・αを演算する。そして、このＴｉに相当するパ
ルス幅の駆動パルス信号を燃料噴射弁３に出力して燃料
噴射を行わせる。The air-fuel ratio feedback correction coefficient α set in this way is the fuel injection amount Ti in another routine.
Is used in the calculation of. That is, the intake air flow rate Q
Based on a and the rotation speed Ne, the basic fuel injection amount Tp = K · Qa /
Ne (K is a constant) is calculated, and is corrected by the air-fuel ratio feedback correction coefficient α to obtain the final fuel injection amount Ti.
= Tp · α is calculated. Then, a drive pulse signal having a pulse width corresponding to Ti is output to the fuel injection valve 3 to cause fuel injection.
【００２８】このように低回転・低負荷から高回転・高
負荷に運転状態が変化して、バイパス弁８がフロント触
媒５側からバイパス通路７側に切換わる場合に、本実施
例では、切換直後に、所定時間、空燃比フィードバック
補正係数α＝１にクランプするが、これによる効果を図
５により説明する。図５の従来例のように、バイパス弁
の切換えと同時に、フロント酸素センサからリア酸素セ
ンサに切換えた場合、リア酸素センサは切換前にフロン
ト触媒を通過した排気を検知していたため、応答性が悪
く、切換直後は正しい値を示さない場合がある。図で
は、切換時にリア酸素センサの出力が０Ｖなので、空燃
比はリーンと判断し、空燃比フィードバック補正係数α
は更にリッチ側に追いかける。結果として、リッチスパ
イクが生じ、リア触媒の転換効率が大幅に悪化し、Ｈ
Ｃ，ＣＯの排出が増大する。In this embodiment, when the operating state changes from low rotation / low load to high rotation / high load and the bypass valve 8 is switched from the front catalyst 5 side to the bypass passage 7 side, the switching is performed in this embodiment. Immediately after that, the air-fuel ratio feedback correction coefficient α = 1 is clamped for a predetermined time, and the effect of this will be described with reference to FIG. When the front oxygen sensor is switched to the rear oxygen sensor at the same time as the bypass valve is switched as in the conventional example of FIG. 5, the rear oxygen sensor detects the exhaust gas that has passed through the front catalyst before the switching, so that the responsiveness is low. In some cases, the correct value may not be shown immediately after switching. In the figure, since the output of the rear oxygen sensor is 0 V at the time of switching, the air-fuel ratio is judged to be lean, and the air-fuel ratio feedback correction coefficient α
Chases further to the rich side. As a result, a rich spike occurs, the conversion efficiency of the rear catalyst deteriorates significantly, and H
Emissions of C and CO increase.
【００２９】これに対し、図５の本発明では、バイパス
弁の切換直後は、空燃比フィードバック補正係数α＝１
にクランプし、リア酸素センサが排気中の酸素濃度を正
しく検知してから、リア酸素センサによる空燃比フィー
ドバック制御を開始するため、切換直後の更なるリッチ
化が行われず、リッチスパイクが生じない。従って、リ
ア触媒の転換効率は高く保たれ、ＨＣ，ＣＯの増加は防
止される。On the other hand, in the present invention of FIG. 5, the air-fuel ratio feedback correction coefficient α = 1 immediately after the switching of the bypass valve.
The air-fuel ratio feedback control by the rear oxygen sensor is started after the rear oxygen sensor correctly detects the oxygen concentration in the exhaust gas, so that further enrichment immediately after the switching is not performed and a rich spike does not occur. Therefore, the conversion efficiency of the rear catalyst is kept high and the increase of HC and CO is prevented.
【００３０】ステップ２での判定で低回転・低負荷の場
合は、ステップ８へ進み、バイパス弁８をフロント触媒
５側へ切換える。次のステップ９では、バイパス弁８切
換後、所定時間（例えば２sec ）（又は所定回転）経過
したか否かを判定する。所定時間経過する前は、ステッ
プ10へ進んで空燃比フィードバック補正係数αを１にク
ランプする。If the engine speed is low and the load is low as determined in step 2, the process proceeds to step 8 and the bypass valve 8 is switched to the front catalyst 5 side. In the next step 9, it is determined whether or not a predetermined time (for example, 2 seconds) (or a predetermined rotation) has elapsed after switching the bypass valve 8. Before the predetermined time has elapsed, the routine proceeds to step 10, where the air-fuel ratio feedback correction coefficient α is clamped to 1.
【００３１】所定時間経過後は、ステップ11へ進んでフ
ロント酸素センサを選択し、次のステップ12で選択され
たフロント酸素センサからの信号に基づいて空燃比フィ
ードバック補正係数αを演算する。尚、本実施例におい
ては、ステップ１，２，３，８の部分がバイパス弁切換
制御手段に相当し、ステップ６，11の部分が酸素センサ
選択手段に相当し、ステップ７，12の部分が補正係数演
算手段に相当し、ステップ４，５，９，10の部分が補正
係数固定手段に相当する。また、別ルーチンにより燃料
噴射量Ｔｉを演算する部分が燃料噴射量補正手段に相当
する。After the lapse of a predetermined time, the routine proceeds to step 11, the front oxygen sensor is selected, and the air-fuel ratio feedback correction coefficient α is calculated based on the signal from the front oxygen sensor selected at the next step 12. In this embodiment, steps 1, 2, 3 and 8 correspond to bypass valve switching control means, steps 6 and 11 correspond to oxygen sensor selecting means, and steps 7 and 12 correspond. It corresponds to the correction coefficient calculation means, and the steps 4, 5, 9 and 10 correspond to the correction coefficient fixing means. Further, a portion for calculating the fuel injection amount Ti by another routine corresponds to the fuel injection amount correction means.
【００３２】次に本発明の第２の実施例を図６〜図７に
より説明する。システム構成は第１の実施例（図３）と
同じであり、図６のフローチャートに従って制御を行う
点が相違する。図６のフローチャートに従って説明す
る。ステップ21では、機関の運転状態として、機関回転
数Ｎｅ及び負荷（基本燃料噴射量）Ｔｐを読込む。Next, a second embodiment of the present invention will be described with reference to FIGS. The system configuration is the same as that of the first embodiment (FIG. 3), except that control is performed according to the flowchart of FIG. Description will be given according to the flowchart of FIG. In step 21, the engine speed Ne and the load (basic fuel injection amount) Tp are read as the operating state of the engine.
【００３３】ステップ22では、バイパス弁８をバイパス
通路７側に切換える条件である高回転・高負荷状態か否
かを判定する。高回転・高負荷状態の場合は、ステップ
23へ進み、バイパス弁８の状態を示すフラグＦの値を判
定する。高回転・高負荷状態に変化した直後は、これま
でバイパス弁８はフロント触媒５側であったため、Ｆ＝
０となっており、この場合、ステップ24へ進む。In step 22, it is judged whether or not the condition is high rotation / high load which is a condition for switching the bypass valve 8 to the bypass passage 7 side. For high rotation and high load, step
23, the value of the flag F indicating the state of the bypass valve 8 is determined. Immediately after changing to the high rotation / high load state, since the bypass valve 8 has been on the front catalyst 5 side so far, F =
It is 0, and in this case, the process proceeds to step 24.
【００３４】ステップ24では、フロント酸素センサ11及
びリア酸素センサ12の各出力の反転周波数ＨＺＦ，ＨＺ
Ｒを検出する。尚、反転周波数は反転周期の逆数として
算出できる。次のステップ15では、これらの反転周波数
ＨＺＦ，ＨＺＲを比較し、リア酸素センサ12側の反転周
波数ＨＺＲがフロント酸素センサ11側の反転周波数ＨＺ
Ｆに近い値となったか否かを判定する。具体的には、Ｈ
ＺＲ≧ＨＺＦ×0.9 となったか否かを判定する。In step 24, the inversion frequencies HZF and HZ of the outputs of the front oxygen sensor 11 and the rear oxygen sensor 12 are set.
Detect R. The inversion frequency can be calculated as the reciprocal of the inversion period. In the next step 15, these inversion frequencies HZF and HZR are compared and the inversion frequency HZR on the rear oxygen sensor 12 side is compared with the inversion frequency HZ on the front oxygen sensor 11 side.
It is determined whether or not the value is close to F. Specifically, H
It is determined whether or not ZR ≧ HZF × 0.9.
【００３５】切換条件成立直後は、リア酸素センサ12側
の反転周波数ＨＺＲは非常に小さいため、ステップ26へ
進む。ステップ26では、バイパス弁８を駆動し、中間開
度に制御する。この中間開度では、排気はフロント触媒
５側とバイパス通路７側との両方へ流れる。そして、ス
テップ27では、リア酸素センサ12の応答性が低いため、
フロント酸素センサ11を選択する。Immediately after the switching condition is satisfied, the reversal frequency HZR on the rear oxygen sensor 12 side is very small, so the routine proceeds to step 26. In step 26, the bypass valve 8 is driven to control the intermediate opening degree. At this intermediate opening, the exhaust gas flows to both the front catalyst 5 side and the bypass passage 7 side. Then, in step 27, since the responsiveness of the rear oxygen sensor 12 is low,
Select the front oxygen sensor 11.
【００３６】そして、ステップ28では、選択されたフロ
ント酸素センサ11からの信号に基づいて空燃比フィード
バック補正係数αを演算する。バイパス弁８が中間開度
に制御されて、フロント酸素センサ11及びリア酸素セン
サ12の両方に排気が流れると、リア酸素センサ12側の反
転周波数ＨＺＲは徐々に大きくなり、フロント酸素セン
サ11側の反転周波数ＨＺＦに近づく。Then, in step 28, the air-fuel ratio feedback correction coefficient α is calculated based on the signal from the selected front oxygen sensor 11. When the bypass valve 8 is controlled to an intermediate opening degree and exhaust gas flows to both the front oxygen sensor 11 and the rear oxygen sensor 12, the reversal frequency HZR on the rear oxygen sensor 12 side gradually increases and the front oxygen sensor 11 side It approaches the inversion frequency HZF.
【００３７】これにより、ＨＺＲ≧ＨＺＦ×0.9 となる
と、リア酸素センサ12の応答性は十分と判断されて、ス
テップ25からステップ29へ進む。ステップ29では、バイ
パス弁８を完全にバイパス通路７側に切換える。そし
て、ステップ30では、リア酸素センサ12を選択する。そ
して、ステップ31では、選択されたリア酸素センサ12か
らの信号に基づいて空燃比フィードバック補正係数αを
演算する。As a result, when HZR ≧ HZF × 0.9, it is judged that the responsiveness of the rear oxygen sensor 12 is sufficient, and the routine proceeds from step 25 to step 29. In step 29, the bypass valve 8 is completely switched to the bypass passage 7 side. Then, in step 30, the rear oxygen sensor 12 is selected. Then, in step 31, the air-fuel ratio feedback correction coefficient α is calculated based on the signal from the selected rear oxygen sensor 12.
【００３８】そして、ステップ32では、フラグＦ＝１に
する。このように低回転・低負荷から高回転・高負荷に
運転状態が変化して、バイパス弁８をフロント触媒５側
からバイパス通路７側に切換える場合の空燃比フィード
バック制御の動きを図７により説明する。図７では、バ
イパス弁をフロント触媒側からバイパス通路側に切換え
る条件と判断されたら、リア酸素センサ側の反転周波数
ＨＺＲが未だ低いため、バイパス弁は中間開度に設定さ
れる。この時点では、まだフロント酸素センサにより空
燃比フィードバック制御を行っている。その後、徐々に
リア酸素センサの応答性が高くなり、その反転周波数Ｈ
ＺＲがフロント酸素センサ側の反転周波数ＨＺＦと同等
となったら、バイパス弁を切換えると同時に空燃比フィ
ードバック制御もリア酸素センサに切換える。その結
果、リア酸素センサの応答性が充分に高くなってから空
燃比フィードバック制御を切換えるため、空燃比のスパ
イクが生じず、従って触媒の転換効率を高く保つことが
可能となる。Then, in step 32, the flag F = 1 is set. The operation of the air-fuel ratio feedback control when the operating state changes from low rotation / low load to high rotation / high load and the bypass valve 8 is switched from the front catalyst 5 side to the bypass passage 7 side will be described with reference to FIG. 7. To do. In FIG. 7, if it is determined that the bypass valve is switched from the front catalyst side to the bypass passage side, the reversal frequency HZR on the rear oxygen sensor side is still low, so the bypass valve is set to the intermediate opening degree. At this point, the air-fuel ratio feedback control is still being performed by the front oxygen sensor. After that, the responsiveness of the rear oxygen sensor gradually increases, and its inversion frequency H
When ZR becomes equal to the inversion frequency HZF on the front oxygen sensor side, the bypass valve is switched and simultaneously the air-fuel ratio feedback control is switched to the rear oxygen sensor. As a result, the air-fuel ratio feedback control is switched after the responsiveness of the rear oxygen sensor has become sufficiently high, so that an air-fuel ratio spike does not occur, and therefore the conversion efficiency of the catalyst can be kept high.
【００３９】ステップ22での反転で低回転・低負荷状態
の場合は、ステップ33へ進む。ステップ33では、フラグ
Ｆの値を判定し、低回転・低負荷状態に変化した直後
は、これまでバイパス弁８はバイパス通路７側であった
ため、Ｆ＝１となっており、この場合、ステップ34へ進
む。ステップ34では、フロント酸素センサ11及びリア酸
素センサ12の各出力の反転周波数ＨＺＦ，ＨＺＲを検出
する。When the rotation is low and the load is low due to the reversal in step 22, the process proceeds to step 33. In step 33, the value of the flag F is determined, and immediately after the state is changed to the low rotation / low load state, since the bypass valve 8 has been on the bypass passage 7 side so far, F = 1, and in this case, step Proceed to 34. In step 34, the inversion frequencies HZF and HZR of the outputs of the front oxygen sensor 11 and the rear oxygen sensor 12 are detected.
【００４０】次のステップ35では、これらの反転周波数
ＨＺＦ，ＨＺＲを比較し、フロント酸素センサ11側の反
転周波数ＨＺＦがリア酸素センサ12側の反転周波数ＨＺ
Ｒに近い値となったか否かを判定する。具体的には、Ｈ
ＺＦ≧ＨＺＲ×0.9 となったか否かを判定する。切換条
件成立直後は、フロント酸素センサ11側の反転周波数Ｈ
ＺＲは非常に小さいため、ステップ36へ進む。In the next step 35, these inversion frequencies HZF and HZR are compared, and the inversion frequency HZF on the front oxygen sensor 11 side is the inversion frequency HZ on the rear oxygen sensor 12 side.
It is determined whether or not the value is close to R. Specifically, H
It is determined whether or not ZF ≧ HZR × 0.9. Immediately after the switching condition is satisfied, the inversion frequency H on the front oxygen sensor 11 side
Since ZR is very small, go to step 36.
【００４１】ステップ36では、バイパス弁８を駆動し、
中間開度に制御する。この中間開度では、排気はフロン
ト触媒５側とバイパス通路７側との両方へ流れる。そし
て、ステップ37では、フロント酸素センサ11の応答性が
低いため、リア酸素センサ12を選択する。そして、ステ
ップ38では、選択されたリア酸素センサ12からの信号に
基づいて空燃比フィードバック補正係数αを演算する。In step 36, the bypass valve 8 is driven,
Control to an intermediate opening. At this intermediate opening, the exhaust gas flows to both the front catalyst 5 side and the bypass passage 7 side. Then, in step 37, the rear oxygen sensor 12 is selected because the responsiveness of the front oxygen sensor 11 is low. Then, in step 38, the air-fuel ratio feedback correction coefficient α is calculated based on the signal from the selected rear oxygen sensor 12.
【００４２】バイパス弁８が中間開度に制御されて、フ
ロント酸素センサ11及びリア酸素センサ12の両方に排気
が流れると、フロント酸素センサ11側の反転周波数ＨＺ
Ｆは徐々に大きくなり、リア酸素センサ12側の反転周波
数ＨＺＲに近づく。これにより、ＨＺＦ≧ＨＺＲ×0.9
となると、フロント酸素センサ11の応答性は十分と判断
されて、ステップ35からステップ39へ進む。When the bypass valve 8 is controlled to the intermediate opening degree and the exhaust gas flows to both the front oxygen sensor 11 and the rear oxygen sensor 12, the reverse frequency HZ on the front oxygen sensor 11 side.
F gradually increases and approaches the inversion frequency HZR on the rear oxygen sensor 12 side. As a result, HZF ≧ HZR × 0.9
Then, it is determined that the responsiveness of the front oxygen sensor 11 is sufficient, and the process proceeds from step 35 to step 39.
【００４３】ステップ39では、バイパス弁８を完全にフ
ロント触媒５側に切換える。そして、ステップ40では、
フロント酸素センサ11を選択する。そして、ステップ41
では、選択されたフロント酸素センサ11からの信号に基
づいて空燃比フィードバック補正係数αを演算する。そ
して、ステップ42では、フラグＦ＝０にする。In step 39, the bypass valve 8 is completely switched to the front catalyst 5 side. And in step 40,
Select the front oxygen sensor 11. And step 41
Then, the air-fuel ratio feedback correction coefficient α is calculated based on the signal from the selected front oxygen sensor 11. Then, in step 42, the flag F = 0 is set.
【００４４】尚、本実施例においては、ステップ21，2
2，29，39の部分がバイパス弁切換制御手段に相当し、
ステップ30，40の部分が酸素センサ選択手段に相当し、
ステップ31，41の部分が補正係数演算手段に相当し、ス
テップ24，34の部分が反転周波数検出手段に相当し、ス
テップ25，35の部分が比較手段に相当し、ステップ26，
36の部分が中間開度制御手段に相当し、ステップ27，2
8，37，38の部分が切換時補正係数演算手段に相当す
る。また、別ルーチンにより燃料噴射量Ｔｉを演算する
部分が燃料噴射量補正手段に相当する。In this embodiment, steps 21, 2
The parts 2, 29, 39 correspond to the bypass valve switching control means,
The steps 30 and 40 correspond to the oxygen sensor selection means,
The steps 31 and 41 correspond to the correction coefficient calculating means, the steps 24 and 34 correspond to the inversion frequency detecting means, the steps 25 and 35 correspond to the comparing means, and the steps 26 and 26
The portion 36 corresponds to the intermediate opening control means, and steps 27, 2
The parts 8, 37, 38 correspond to the correction coefficient calculation means at the time of switching. Further, a portion for calculating the fuel injection amount Ti by another routine corresponds to the fuel injection amount correction means.
【００４５】[0045]
【発明の効果】以上説明したように、請求項１に係る発
明によれば、バイパス弁の切換時に、所定期間、空燃比
フィードバック補正係数を所定値に固定した後、空燃比
フィードバック制御に使用する酸素センサを切換える制
御としたため、バイパス弁の切換時に生じる空燃比のス
パイクを防止することができて、触媒の転換効率を高く
保つことが可能となり、エミッションの悪化を抑制でき
るという効果が得られる。As described above, according to the invention of claim 1, when the bypass valve is switched, the air-fuel ratio feedback correction coefficient is fixed to a predetermined value for a predetermined period and then used for the air-fuel ratio feedback control. Since the control is such that the oxygen sensor is switched, the spike of the air-fuel ratio that occurs when switching the bypass valve can be prevented, the conversion efficiency of the catalyst can be kept high, and the deterioration of emission can be suppressed.
【００４６】請求項２に係る発明によれば、バイパス弁
の切換時は、両酸素センサの信号をモニタし、略同一の
反転周波数となってから、空燃比フィードバック制御に
使用する酸素センサを切換える制御としたため、バイパ
ス弁の切換時に生じる空燃比のスパイクを防止すること
ができて、触媒の転換効率を高く保つことが可能とな
り、エミッションの悪化を抑制できるという効果が得ら
れる他、常に応答性の高い酸素センサを使用して、空燃
比フィードバック制御を行うため、切換直後に運転条件
が変化した場合でも、追従性良く制御でき、空燃比の変
動を抑制することができるという効果が得られる。According to the second aspect of the present invention, when the bypass valve is switched, the signals of both oxygen sensors are monitored and the oxygen sensor used for the air-fuel ratio feedback control is switched after the inversion frequency becomes substantially the same. Since the control is used, spikes in the air-fuel ratio that occur when switching the bypass valve can be prevented, the conversion efficiency of the catalyst can be kept high, and the effect of suppressing the deterioration of emissions can be obtained. Since the air-fuel ratio feedback control is performed using a high oxygen sensor, even if the operating conditions change immediately after the switching, control can be performed with good followability and fluctuations in the air-fuel ratio can be suppressed.
【００４７】請求項３に係る発明によれば、バイパス弁
の切換時に、バイパス弁の開度を中間開度に制御するこ
とで、切換時に使用する酸素センサの検出精度を高く維
持できて、制御精度が大幅に向上するという効果が得ら
れる。請求項４に係る発明によれば、機関回転数及び負
荷に基づいて制御することで、排気温度センサを用いる
ことなく制御できるという効果が得られる。According to the third aspect of the present invention, when the bypass valve is switched, the opening degree of the bypass valve is controlled to the intermediate opening degree, so that the detection accuracy of the oxygen sensor used at the time of switching can be maintained high and the control can be performed. The effect that the accuracy is significantly improved can be obtained. According to the invention of claim 4, since the control is performed based on the engine speed and the load, there is an effect that the control can be performed without using the exhaust gas temperature sensor.
【図１】 本発明の構成を示す機能ブロック図（その
１）FIG. 1 is a functional block diagram showing a configuration of the present invention (No. 1)
【図２】 本発明の構成を示す機能ブロック図（その
２）FIG. 2 is a functional block diagram showing the configuration of the present invention (part 2).
【図３】 本発明の第１の実施例を示すシステム構成図FIG. 3 is a system configuration diagram showing a first embodiment of the present invention.
【図４】 制御内容を示すフローチャートFIG. 4 is a flowchart showing control contents.
【図５】 効果を示す図FIG. 5 is a diagram showing an effect.
【図６】 本発明の第２の実施例のフローチャートFIG. 6 is a flowchart of the second embodiment of the present invention.
【図７】 同上第２の実施例の効果を示す図FIG. 7 is a diagram showing the effect of the second embodiment.
１ 内燃機関 ２ 吸気通路 ３ 燃料噴射弁 ４ 排気通路 ５ フロント触媒 ６ リア触媒 ７ バイパス通路 ８ バイパス弁 10 コントロールユニット 11 フロント酸素センサ 12 リア酸素センサ 1 internal combustion engine 2 intake passage 3 fuel injection valve 4 exhaust passage 5 front catalyst 6 rear catalyst 7 bypass passage 8 bypass valve 10 control unit 11 front oxygen sensor 12 rear oxygen sensor
Claims (4)
置されたフロント触媒及びリア触媒と、フロント触媒を
バイパスしてリア触媒上流に合流するバイパス通路と、
排気の流れをフロント触媒側とバイパス通路側とに切換
えることのできるバイパス弁と、機関運転状態に応じて
バイパス弁を切換えるバイパス弁切換制御手段と、を備
える内燃機関の排気浄化装置において、 フロント触媒及びリア触媒の各上流にそれぞれフロント
酸素センサ及びリア酸素センサを設ける一方、 バイパス弁の切換状態に応じ、フロント触媒側への切換
状態にてフロント酸素センサを選択し、バイパス通路側
への切換状態にてリア酸素センサを選択する酸素センサ
選択手段と、 選択された酸素センサからの信号に基づいて空燃比フィ
ードバック補正係数を演算する補正係数演算手段と、 バイパス弁の切換直後に、所定期間、前記補正係数演算
手段に優先して、空燃比フィードバック補正係数を所定
値に固定する補正係数固定手段と、 機関への燃料噴射量を前記空燃比フィードバック補正係
数により補正する燃料噴射量補正手段と、 を設けたことを特徴とする内燃機関の排気浄化装置。1. A front catalyst and a rear catalyst which are respectively arranged on an upstream side and a downstream side of an exhaust passage, and a bypass passage which bypasses the front catalyst and merges with the upstream of the rear catalyst.
An exhaust gas purification apparatus for an internal combustion engine, comprising: a bypass valve capable of switching an exhaust flow between a front catalyst side and a bypass passage side; and a bypass valve switching control means for switching the bypass valve according to an engine operating state. A front oxygen sensor and a rear oxygen sensor are provided upstream of the rear catalyst and the rear catalyst, respectively, while the front oxygen sensor is selected in the switching state to the front catalyst side according to the switching state of the bypass valve, and the switching state to the bypass passage side is selected. The oxygen sensor selection means for selecting the rear oxygen sensor, the correction coefficient calculation means for calculating the air-fuel ratio feedback correction coefficient based on the signal from the selected oxygen sensor, and immediately after switching the bypass valve for a predetermined period, Correction coefficient fixing means for fixing the air-fuel ratio feedback correction coefficient to a predetermined value in preference to the correction coefficient calculation means. An exhaust purification system for an internal combustion engine, comprising: a stage; and a fuel injection amount correction means for correcting the fuel injection amount to the engine by the air-fuel ratio feedback correction coefficient.
置されたフロント触媒及びリア触媒と、フロント触媒を
バイパスしてリア触媒上流に合流するバイパス通路と、
排気の流れをフロント触媒側とバイパス通路側とに切換
えることのできるバイパス弁と、機関運転状態に応じて
バイパス弁を切換えるバイパス弁切換制御手段と、を備
える内燃機関の排気浄化装置において、 フロント触媒及びリア触媒の各上流にそれぞれフロント
酸素センサ及びリア酸素センサを設ける一方、 バイパス弁の切換状態に応じ、フロント触媒側への切換
状態にてフロント酸素センサを選択し、バイパス通路側
への切換状態にてリア酸素センサを選択する酸素センサ
選択手段と、 選択された酸素センサからの信号に基づいて空燃比フィ
ードバック補正係数を演算する補正係数演算手段と、 フロント酸素センサ及びリア酸素センサの各出力の反転
周波数を検出する反転周波数検出手段と、 両酸素センサの反転周波数を比較する比較手段と、 バイパス弁の切換時に、前記比較手段により、両酸素セ
ンサの反転周波数がほぼ同一と判断されるまで、前記補
正係数演算手段に優先して、切換前に選択されていた酸
素センサからの信号に基づいて空燃比フィードバック補
正係数を演算する切換時補正係数演算手段と、 機関への燃料噴射量を前記空燃比フィードバック補正係
数により補正する燃料噴射量補正手段と、 を設けたことを特徴とする内燃機関の排気浄化装置。2. A front catalyst and a rear catalyst which are respectively arranged on an upstream side and a downstream side of an exhaust passage, and a bypass passage which bypasses the front catalyst and joins the rear catalyst upstream.
An exhaust gas purification apparatus for an internal combustion engine, comprising: a bypass valve capable of switching an exhaust flow between a front catalyst side and a bypass passage side; and a bypass valve switching control means for switching the bypass valve according to an engine operating state. A front oxygen sensor and a rear oxygen sensor are provided upstream of the rear catalyst and the rear catalyst, respectively, while the front oxygen sensor is selected in the switching state to the front catalyst side according to the switching state of the bypass valve, and the switching state to the bypass passage side is selected. At the rear oxygen sensor, an oxygen sensor selecting means for selecting the rear oxygen sensor, a correction coefficient calculating means for calculating an air-fuel ratio feedback correction coefficient based on a signal from the selected oxygen sensor, and an output for each of the front oxygen sensor and the rear oxygen sensor. A ratio that compares the reversal frequency of both oxygen sensors with the reversal frequency detection means that detects the reversal frequency. When the bypass valve is switched, until the comparison means determines that the reversal frequencies of both oxygen sensors are substantially the same, the correction coefficient computing means is given priority and the oxygen sensor selected before the switching is selected. A switching correction coefficient calculating means for calculating an air-fuel ratio feedback correction coefficient based on the signal; and a fuel injection amount correcting means for correcting the fuel injection amount to the engine by the air-fuel ratio feedback correction coefficient. Exhaust gas purification device for internal combustion engine.
り、両酸素センサの反転周波数がほぼ同一と判断される
まで、前記バイパス弁切換制御手段に優先して、バイパ
ス弁の開度を排気をフロント触媒側とバイパス通路側と
の両方へ流す中間開度に制御する中間開度制御手段を設
けたことを特徴とする請求項２記載の内燃機関の排気浄
化装置。3. When switching the bypass valve, the opening of the bypass valve is exhausted prior to the bypass valve switching control means until the comparing means determines that the reversal frequencies of both oxygen sensors are substantially the same. The exhaust emission control device for an internal combustion engine according to claim 2, further comprising an intermediate opening control means for controlling an intermediate opening for flowing to both the front catalyst side and the bypass passage side.
数及び負荷に基づいて、高回転・高負荷時にバイパス弁
をバイパス通路側に切換えるものであることを特徴とす
る請求項１〜請求項３のいずれか１つに記載の内燃機関
の排気浄化装置。4. The bypass valve switching control means switches the bypass valve to the bypass passage side at the time of high rotation and high load based on the engine speed and the load. The exhaust gas purification device for an internal combustion engine according to any one of 3 above.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16383595A JP3627296B2 (en) | 1995-06-29 | 1995-06-29 | Exhaust gas purification device for internal combustion engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16383595A JP3627296B2 (en) | 1995-06-29 | 1995-06-29 | Exhaust gas purification device for internal combustion engine |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0914024A true JPH0914024A (en) | 1997-01-14 |
| JP3627296B2 JP3627296B2 (en) | 2005-03-09 |
Family
ID=15781655
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16383595A Expired - Fee Related JP3627296B2 (en) | 1995-06-29 | 1995-06-29 | Exhaust gas purification device for internal combustion engine |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3627296B2 (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100405728B1 (en) * | 2001-09-11 | 2003-11-14 | 현대자동차주식회사 | Exhaust Gas Contorlling Method Of Vehicle |
| JP2007321652A (en) * | 2006-06-01 | 2007-12-13 | Nissan Motor Co Ltd | Internal combustion engine |
| JP2008057481A (en) * | 2006-09-01 | 2008-03-13 | Nissan Motor Co Ltd | Internal combustion engine |
| JP2008169772A (en) * | 2007-01-12 | 2008-07-24 | Nissan Motor Co Ltd | Air-fuel ratio control device |
| JP2009041464A (en) * | 2007-08-09 | 2009-02-26 | Nissan Motor Co Ltd | Air-fuel ratio control device |
| JP2009293414A (en) * | 2008-06-03 | 2009-12-17 | Nissan Motor Co Ltd | Air-fuel ratio control device and air-fuel ratio control method for engine |
| JP2010037976A (en) * | 2008-08-01 | 2010-02-18 | Nissan Motor Co Ltd | Changeover control device of air-fuel ratio sensor |
-
1995
- 1995-06-29 JP JP16383595A patent/JP3627296B2/en not_active Expired - Fee Related
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100405728B1 (en) * | 2001-09-11 | 2003-11-14 | 현대자동차주식회사 | Exhaust Gas Contorlling Method Of Vehicle |
| JP2007321652A (en) * | 2006-06-01 | 2007-12-13 | Nissan Motor Co Ltd | Internal combustion engine |
| JP2008057481A (en) * | 2006-09-01 | 2008-03-13 | Nissan Motor Co Ltd | Internal combustion engine |
| JP2008169772A (en) * | 2007-01-12 | 2008-07-24 | Nissan Motor Co Ltd | Air-fuel ratio control device |
| US8141343B2 (en) | 2007-01-12 | 2012-03-27 | Nissan Motor Co., Ltd. | Air-fuel ratio control apparatus |
| JP2009041464A (en) * | 2007-08-09 | 2009-02-26 | Nissan Motor Co Ltd | Air-fuel ratio control device |
| US8176728B2 (en) | 2007-08-09 | 2012-05-15 | Nissan Motor Co., Ltd. | Air-fuel ratio control device |
| US8607545B2 (en) | 2007-08-09 | 2013-12-17 | Nissan Motor Co., Ltd. | Air-fuel ratio control device |
| JP2009293414A (en) * | 2008-06-03 | 2009-12-17 | Nissan Motor Co Ltd | Air-fuel ratio control device and air-fuel ratio control method for engine |
| JP2010037976A (en) * | 2008-08-01 | 2010-02-18 | Nissan Motor Co Ltd | Changeover control device of air-fuel ratio sensor |
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| Publication number | Publication date |
|---|---|
| JP3627296B2 (en) | 2005-03-09 |
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