JP6241147B2 - Catalyst temperature estimation device for internal combustion engine - Google Patents

Catalyst temperature estimation device for internal combustion engine Download PDF

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JP6241147B2
JP6241147B2 JP2013181643A JP2013181643A JP6241147B2 JP 6241147 B2 JP6241147 B2 JP 6241147B2 JP 2013181643 A JP2013181643 A JP 2013181643A JP 2013181643 A JP2013181643 A JP 2013181643A JP 6241147 B2 JP6241147 B2 JP 6241147B2
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昌明 道下
昌明 道下
小林　俊介
俊介 小林
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Denso Corp
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Description

本発明は、内燃機関の排気浄化用の触媒の温度を推定する内燃機関の触媒温度推定装置に関する発明である。   The present invention relates to an internal combustion engine catalyst temperature estimation device for estimating the temperature of an exhaust gas purification catalyst for an internal combustion engine.

車両等に搭載される内燃機関においては、排気管に配置した三元触媒等の触媒で排出ガスを浄化するようにしている。この触媒の過熱による溶損や劣化を防止したり、触媒の冷却のための燃料増量を必要最小限にして燃費を向上させるには、触媒の温度を精度良く推定する必要がある。   In an internal combustion engine mounted on a vehicle or the like, exhaust gas is purified by a catalyst such as a three-way catalyst disposed in an exhaust pipe. In order to prevent the catalyst from being melted and deteriorated due to overheating, or to improve the fuel consumption by minimizing the fuel increase for cooling the catalyst, it is necessary to accurately estimate the temperature of the catalyst.

そこで、例えば、特許文献１（特許第４５１３４１６号公報）に記載されているように、内燃機関の運転状態に基づいてシリンダ部分のガス温度を推定し、このシリンダ部分のガス温度とシリンダ部分から触媒に至るまでのガス流路の熱伝達特性とに基づいて触媒入口のガス温度を推定し、この触媒入口のガス温度と触媒入口のガス温度に対する触媒の温度の応答特性とに基づいて触媒の温度を推定するようにしたものがある。   Therefore, for example, as described in Patent Document 1 (Japanese Patent No. 4513416), the gas temperature of the cylinder portion is estimated based on the operating state of the internal combustion engine, and the catalyst is calculated from the gas temperature of the cylinder portion and the cylinder portion. The gas temperature at the catalyst inlet is estimated based on the heat transfer characteristics of the gas flow path up to and the catalyst temperature based on the gas temperature at the catalyst inlet and the response characteristic of the catalyst temperature to the gas temperature at the catalyst inlet. There is something that was estimated.

特許第４５１３４１６号公報Japanese Patent No. 4513416

内燃機関の燃料カット中（燃料噴射停止中）は、触媒に供給される空気と触媒中の未燃燃料が反応し、その反応熱によって触媒の温度が上昇する。特に燃料増量領域から燃料カットを行った場合には触媒の温度が大きく上昇する傾向がある。しかし、上記特許文献１の技術では、このような触媒の反応熱による温度上昇を考慮していないため、触媒温度の推定精度を十分に高めることができないという欠点がある。   During the fuel cut of the internal combustion engine (when fuel injection is stopped), the air supplied to the catalyst reacts with the unburned fuel in the catalyst, and the temperature of the catalyst rises due to the reaction heat. In particular, when the fuel cut is performed from the fuel increase region, the temperature of the catalyst tends to increase greatly. However, the technique disclosed in Patent Document 1 does not consider such a temperature increase due to the reaction heat of the catalyst, and thus has a drawback that the accuracy of estimating the catalyst temperature cannot be sufficiently increased.

そこで、本発明が解決しようとする課題は、触媒温度の推定精度を向上させることができる内燃機関の触媒温度推定装置を提供することにある。   Therefore, an object of the present invention is to provide a catalyst temperature estimation device for an internal combustion engine that can improve the estimation accuracy of the catalyst temperature.

上記課題を解決するために、請求項１に係る発明は、内燃機関（１１）の排気浄化用の触媒（２５）の温度を推定する内燃機関の触媒温度推定装置において、触媒（２５）の反応熱による温度変化が無いと仮定した場合の触媒（２５）の温度（以下「無担持触媒温度」という）を演算する無担持触媒温度演算手段（３２）と、触媒（２５）の反応熱による温度上昇分（以下「触媒反応熱分」という）を演算する触媒反応熱分演算手段（３３）と、無担持触媒温度と触媒反応熱分とに基づいて触媒（２５）の温度の推定値を演算する推定触媒温度演算手段（３４）とを備え、触媒反応熱分演算手段（３３）は、内燃機関（１１）の燃焼中に触媒反応熱分を演算する場合には、内燃機関（１１）の排気流量と空燃比とに基づいて触媒反応熱分を演算し、内燃機関（１１）の燃料カット中に触媒反応熱分を演算する場合には、内燃機関（１１）の燃料カット前の空燃比に基づいて、燃料カット中に反応可能な未燃燃料量が変化する触媒反応熱分のピーク値を演算し、触媒反応熱分がピーク値に到達するまでは排気流量の積算値に基づいて触媒反応熱分を演算するとともに、触媒反応熱分がピーク値に到達した後は触媒反応熱分をピーク値から０に収束させるように一次なまし処理して触媒反応熱分を求めるようにしたものである。 In order to solve the above problems, the invention according to claim 1 is directed to a catalyst temperature estimation device for an internal combustion engine that estimates the temperature of an exhaust purification catalyst (25) of the internal combustion engine (11). Unsupported catalyst temperature calculating means (32) for calculating the temperature of the catalyst (25) (hereinafter referred to as “unsupported catalyst temperature”) assuming that there is no temperature change due to heat, and the temperature of the catalyst (25) due to the reaction heat Calculates an estimated value of the temperature of the catalyst (25) based on the catalyst reaction heat calculation means (33) for calculating the rise (hereinafter referred to as "catalyst reaction heat") and the unsupported catalyst temperature and the catalyst reaction heat. And an estimated catalyst temperature calculating means (34) for calculating the catalytic reaction heat during combustion of the internal combustion engine (11). Based on exhaust flow rate and air-fuel ratio When calculating the catalytic reaction heat during the fuel cut of the internal combustion engine (11), the amount of unburned fuel that can react during the fuel cut based on the air-fuel ratio before the fuel cut of the internal combustion engine (11). The peak value of the catalytic reaction heat is calculated, and the catalytic reaction heat is calculated based on the integrated value of the exhaust flow rate until the catalytic reaction heat reaches the peak value. After reaching the above, the first heat treatment is performed so that the heat of catalytic reaction converges to 0 from the peak value, and the heat of catalytic reaction is obtained.

本発明では、触媒の温度を、無担持触媒温度（触媒の反応熱による温度変化が無いと仮定した場合の触媒の温度つまり反応熱以外の要因で変化する温度）と、触媒反応熱分（触媒の反応熱による温度上昇分）とに分けて考え、それぞれを個別に演算することで、無担持触媒温度と触媒反応熱分を精度良く演算することができる。更に、内燃機関の燃焼中と燃料カット中とで触媒反応熱分の演算方法を切り換えることで、燃料カット中でも触媒反応熱分を精度良く演算することができる。そして、無担持触媒温度に触媒反応熱分を加算して推定触媒温度（触媒の温度の推定値）を求めることで、内燃機関の燃焼中と燃料カット中の両方で推定触媒温度を精度良く求めることができ、触媒温度の推定精度を向上させることができる。   In the present invention, the catalyst temperature includes the unsupported catalyst temperature (the temperature of the catalyst assuming that there is no temperature change due to the reaction heat of the catalyst, that is, the temperature that changes due to factors other than the reaction heat), and the catalyst reaction heat (catalyst). The temperature increase due to the reaction heat) is calculated separately, and each is calculated separately, whereby the unsupported catalyst temperature and the catalyst reaction heat can be calculated with high accuracy. Further, by switching the calculation method of the catalytic reaction heat during combustion of the internal combustion engine and during the fuel cut, the catalytic reaction heat can be accurately calculated even during the fuel cut. Then, the estimated catalyst temperature (estimated value of the catalyst temperature) is obtained by adding the catalytic reaction heat to the unsupported catalyst temperature, so that the estimated catalyst temperature is accurately obtained both during combustion of the internal combustion engine and during fuel cut. And the estimation accuracy of the catalyst temperature can be improved.

図１は本発明の一実施例におけるエンジン制御システムの概略構成を示す図である。FIG. 1 is a diagram showing a schematic configuration of an engine control system in one embodiment of the present invention. 図２は触媒温度推定の概要を説明する図である。FIG. 2 is a diagram for explaining the outline of catalyst temperature estimation. 図３はＥＣＵの触媒温度推定機能を概略的に示す機能ブロック図である。FIG. 3 is a functional block diagram schematically showing the catalyst temperature estimation function of the ECU. 図４は燃料カット中の触媒反応熱分の演算方法を説明する図である。FIG. 4 is a diagram for explaining a method of calculating the catalytic reaction heat during fuel cut. 図５は燃料カット中の触媒温度ピーク予測値の演算方法を説明する図である。FIG. 5 is a diagram for explaining a method of calculating a predicted catalyst temperature peak value during fuel cut. 図６は触媒温度推定ルーチンの処理の流れを示すフローチャートである。FIG. 6 is a flowchart showing the flow of processing of the catalyst temperature estimation routine.

以下、本発明を実施するための形態を具体化した一実施例を説明する。
まず、図１に基づいてエンジン制御システム全体の概略構成を説明する。
内燃機関であるエンジン１１の吸気管１２の最上流部には、エアクリーナ１３が設けられ、このエアクリーナ１３の下流側に、吸気流量（吸入空気量）を検出するエアフローメータ１４が設けられている。このエアフローメータ１４の下流側には、モータ１５によって開度調節されるスロットルバルブ１６と、このスロットルバルブ１６の開度（スロットル開度）を検出するスロットル開度センサ１７とが設けられている。 Hereinafter, an embodiment embodying a mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

更に、スロットルバルブ１６の下流側には、サージタンク１８が設けられ、このサージタンク１８に、吸気管圧力を検出する吸気管圧力センサ１９が設けられている。また、サージタンク１８には、エンジン１１の各気筒に空気を導入する吸気マニホールド２０が設けられ、各気筒の吸気マニホールド２０に接続された吸気ポート又はその近傍に、それぞれ吸気ポートに燃料を噴射する燃料噴射弁２１が取り付けられている。また、エンジン１１のシリンダヘッドには、各気筒毎に点火プラグ２２が取り付けられ、各気筒の点火プラグ２２の火花放電によって各気筒内の混合気に着火される。   Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. In addition, the surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and fuel is injected into the intake port at or near the intake port connected to the intake manifold 20 of each cylinder. A fuel injection valve 21 is attached. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in each cylinder is ignited by spark discharge of the ignition plug 22 of each cylinder.

一方、エンジン１１の排気管２３には、排出ガスの空燃比又はリッチ／リーン等を検出する排出ガスセンサ２４（空燃比センサ、酸素センサ等）が設けられ、この排出ガスセンサ２４の下流側に、排出ガスを浄化する三元触媒等の触媒２５が設けられている。   On the other hand, the exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying gas is provided.

また、エンジン１１のシリンダブロックには、冷却水温を検出する冷却水温センサ２６や、ノッキングを検出するノックセンサ２７が取り付けられている。また、クランク軸２８の外周側には、クランク軸２８が所定クランク角回転する毎にパルス信号を出力するクランク角センサ２９が取り付けられ、このクランク角センサ２９の出力信号に基づいてクランク角やエンジン回転速度が検出される。   A cooling water temperature sensor 26 that detects the cooling water temperature and a knock sensor 27 that detects knocking are attached to the cylinder block of the engine 11. A crank angle sensor 29 that outputs a pulse signal every time the crankshaft 28 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 28, and the crank angle and the engine are determined based on the output signal of the crank angle sensor 29. The rotation speed is detected.

これら各種センサの出力は、電子制御ユニット（以下「ＥＣＵ」と表記する）３０に入力される。このＥＣＵ３０は、マイクロコンピュータを主体として構成され、内蔵されたＲＯＭ（記憶媒体）に記憶された各種のエンジン制御用のプログラムを実行することで、エンジン運転状態に応じて、燃料噴射量、点火時期、スロットル開度（吸入空気量）等を制御する。   Outputs of these various sensors are input to an electronic control unit (hereinafter referred to as “ECU”) 30. The ECU 30 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount and the ignition timing are determined according to the engine operating state. The throttle opening (intake air amount) and the like are controlled.

ところで、触媒２５の過熱による溶損や劣化を防止したり、触媒２５の冷却のための燃料増量を必要最小限にして燃費を向上させるには、触媒温度（触媒２５の温度）を精度良く推定する必要がある。そこで、本実施例では、ＥＣＵ３０により後述する図６の触媒温度推定ルーチンを実行することで、触媒温度を次のようして推定する。   By the way, in order to prevent melting and deterioration due to overheating of the catalyst 25, or to improve fuel efficiency by minimizing the amount of fuel for cooling the catalyst 25, the catalyst temperature (the temperature of the catalyst 25) is accurately estimated. There is a need to. Therefore, in this embodiment, the catalyst temperature is estimated as follows by executing a catalyst temperature estimation routine of FIG.

図２に示すように、触媒２５の反応熱による温度変化が無いと仮定した場合の触媒温度（以下「無担持触媒温度」という）を演算すると共に、触媒２５の反応熱による温度上昇分（以下「触媒反応熱分」という）を演算し、無担持触媒温度に触媒反応熱分を加算して触媒温度の推定値（以下「推定触媒温度」という）を求める。その際、エンジン１１の燃焼中（燃料噴射中）と燃料カット中（燃料噴射停止中）とで触媒反応熱分の演算方法を切り換えるようにしている。   As shown in FIG. 2, the catalyst temperature (hereinafter referred to as “unsupported catalyst temperature”) when it is assumed that there is no temperature change due to the reaction heat of the catalyst 25 is calculated, and the temperature rise due to the reaction heat of the catalyst 25 (hereinafter referred to as “non-supported catalyst temperature”) "Catalytic reaction heat") is calculated, and the catalyst reaction heat is added to the unsupported catalyst temperature to obtain an estimated value of the catalyst temperature (hereinafter referred to as "estimated catalyst temperature"). At that time, the calculation method of the catalytic reaction heat is switched between the combustion of the engine 11 (during fuel injection) and the fuel cut (during fuel injection stop).

このように触媒温度を無担持触媒温度（触媒２５の反応熱による温度変化が無いと仮定した場合の触媒温度つまり反応熱以外の要因で変化する温度）と触媒反応熱分（触媒の反応熱による温度上昇分）とに分けて考え、それぞれを個別に演算することで、無担持触媒温度と触媒反応熱分を精度良く演算することができる。更に、エンジン１１の燃焼中と燃料カット中とで触媒反応熱分の演算方法を切り換えることで、燃料カット中でも触媒反応熱分を精度良く演算することができる。そして、無担持触媒温度に触媒反応熱分を加算して推定触媒温度を求めることで、エンジン１１の燃焼中と燃料カット中の両方で推定触媒温度を精度良く求めることができる。   Thus, the catalyst temperature is defined as the unsupported catalyst temperature (the temperature of the catalyst 25 assuming that there is no temperature change due to the reaction heat of the catalyst 25, that is, the temperature that changes due to factors other than the reaction heat) and the catalyst reaction heat (depending on the reaction heat of the catalyst). It is possible to calculate the unsupported catalyst temperature and the heat of catalytic reaction with high accuracy by calculating each of them separately and calculating each of them separately. Further, by switching the calculation method of the catalytic reaction heat during combustion of the engine 11 and during the fuel cut, the catalytic reaction heat can be accurately calculated even during the fuel cut. Then, by adding the catalytic reaction heat to the unsupported catalyst temperature to obtain the estimated catalyst temperature, the estimated catalyst temperature can be accurately obtained both during combustion of the engine 11 and during fuel cut.

また、従来は、燃料カット中の触媒温度を予測していないため、燃料カット中の触媒温度の上昇による触媒２５の過熱を防止するために、触媒温度が十分に低下するまで燃料カットを遅らせる必要があり、その分、無駄な燃料を消費していた。   Further, conventionally, since the catalyst temperature during the fuel cut is not predicted, in order to prevent the catalyst 25 from overheating due to an increase in the catalyst temperature during the fuel cut, it is necessary to delay the fuel cut until the catalyst temperature sufficiently decreases. There was a lot of wasted fuel.

そこで、本実施例では、エンジン１１の燃焼中に、次の燃料カット中における無担持触媒温度の予測値（以下「予測無担持触媒温度」という）を演算すると共に、次の燃料カット中における触媒反応熱分の予測値（以下「予測触媒反応熱分」という）を演算し、これらの予測無担持触媒温度と予測触媒反応熱分とに基づいて、次の燃料カット中における触媒２５の温度のピーク予測値（以下「触媒温度ピーク予測値」という）を演算する（図５参照）。この触媒温度ピーク予測値が所定の閾値よりも高い場合に燃料カットを禁止し、触媒温度ピーク予測値が閾値以下の場合に燃料カットを許可するようにしている。   Therefore, in this embodiment, during combustion of the engine 11, a predicted value of the unsupported catalyst temperature during the next fuel cut (hereinafter referred to as “predicted unsupported catalyst temperature”) is calculated, and the catalyst during the next fuel cut is calculated. A predicted value of reaction heat (hereinafter referred to as “predicted catalyst reaction heat”) is calculated, and the temperature of the catalyst 25 during the next fuel cut is calculated based on these predicted unsupported catalyst temperature and predicted catalyst reaction heat. A peak predicted value (hereinafter referred to as “catalyst temperature peak predicted value”) is calculated (see FIG. 5). The fuel cut is prohibited when the predicted catalyst temperature peak value is higher than a predetermined threshold value, and the fuel cut is permitted when the predicted catalyst temperature peak value is less than or equal to the threshold value.

次に図３を用いてＥＣＵ３０の触媒温度推定について詳しく説明する。
ＥＣＵ３０は、排気温度演算部３１（排気温度取得手段）で、エンジン運転状態に基づいてエンジン１１の排気温度を推定する。一般に、エンジン運転状態（例えば、運転モード、エンジン回転速度、負荷、空燃比、点火時期等）に応じて排気温度が変化するため、エンジン運転状態に基づいて排気温度を推定することで、排気温度を精度良く推定することができる。 Next, the catalyst temperature estimation of the ECU 30 will be described in detail with reference to FIG.
The ECU 30 estimates the exhaust temperature of the engine 11 based on the engine operating state by the exhaust temperature calculation unit 31 (exhaust temperature acquisition means). Generally, since the exhaust temperature changes according to the engine operating state (for example, the operation mode, engine speed, load, air-fuel ratio, ignition timing, etc.), the exhaust temperature is estimated by estimating the exhaust temperature based on the engine operating state. Can be estimated with high accuracy.

具体的には、予め運転モード毎にベース排気温度のマップ又は数式等を用意（例えばＥＣＵ３０のＲＯＭに記憶）しておき、現在の運転モードに応じたベース排気温度のマップ又は数式等を選択し、その選択したベース排気温度のマップ又は数式等を用いて、現在のエンジン回転速度と負荷とに応じたベース排気温度を算出する。この後、ベース排気温度を空燃比と点火時期とに応じて補正して排気温度を求めることで排気温度を推定する。   Specifically, a base exhaust temperature map or mathematical formula is prepared in advance for each operation mode (for example, stored in the ROM of the ECU 30), and a base exhaust temperature map or mathematical formula corresponding to the current operation mode is selected. Then, the base exhaust temperature corresponding to the current engine speed and load is calculated using the selected base exhaust temperature map or mathematical expression. Thereafter, the exhaust gas temperature is estimated by correcting the base exhaust gas temperature according to the air-fuel ratio and the ignition timing to obtain the exhaust gas temperature.

更に、無担持触媒温度演算部３２（無担持触媒温度演算手段）で、無担持触媒温度（触媒２５の反応熱による温度変化が無いと仮定した場合の触媒２５の温度）を演算する。触媒２５は、主に排気熱で暖められるため、排気温度に応じて無担持触媒温度が変化するが、排気温度の変化に対して無担持触媒温度の変化には触媒２５の熱容量による遅れが生じる。そこで、本実施例では、排気温度に対する無担持触媒温度の触媒２５の熱容量による遅れを考慮して排気温度に基づいて無担持触媒温度を演算する。   Further, the unsupported catalyst temperature calculation unit 32 (unsupported catalyst temperature calculation means) calculates the unsupported catalyst temperature (the temperature of the catalyst 25 when it is assumed that there is no temperature change due to the reaction heat of the catalyst 25). Since the catalyst 25 is mainly warmed by the exhaust heat, the unsupported catalyst temperature changes according to the exhaust temperature, but the change in the unsupported catalyst temperature is delayed by the heat capacity of the catalyst 25 with respect to the change in the exhaust temperature. . Therefore, in this embodiment, the unsupported catalyst temperature is calculated based on the exhaust temperature in consideration of the delay due to the heat capacity of the catalyst 25 of the unsupported catalyst temperature with respect to the exhaust temperature.

具体的には、排気温度を一次なまし処理（一次遅れ処理、一次フィルタ処理）して無担持触媒温度を求める。一次なまし処理の時定数は、予め試験データや設計データ等に基づいて、排気温度に対する無担持触媒温度の遅れ（触媒２５の熱容量による遅れ）を再現するように設定されている。   Specifically, the exhaust temperature is subjected to a primary smoothing process (primary delay process, primary filter process) to obtain the unsupported catalyst temperature. The time constant of the primary annealing process is set in advance so as to reproduce the delay of the unsupported catalyst temperature with respect to the exhaust temperature (the delay due to the heat capacity of the catalyst 25) based on test data, design data, and the like.

また、触媒反応熱分演算部３３（触媒反応熱分演算手段）で、触媒反応熱分（触媒２５の反応熱による温度上昇分）を演算する。
エンジン１１の燃焼中（燃料噴射中）に触媒反応熱分を演算する場合には、エンジン１１の排気流量（＝吸気流量）と空燃比とに基づいて触媒反応熱分をマップ又は数式等により演算する。エンジン１１の燃焼中は、主に排気流量と空燃比によって触媒反応熱分が変化するため、エンジン１１の排気流量と空燃比とに基づいて触媒反応熱分を演算することで、エンジン１１の燃焼中の触媒反応熱分を精度良く求めることができる。 In addition, the catalyst reaction heat calculation unit 33 (catalyst reaction heat calculation means) calculates the catalyst reaction heat (temperature increase due to the reaction heat of the catalyst 25).
When calculating the catalytic reaction heat during combustion of the engine 11 (during fuel injection), the catalytic reaction heat is calculated based on the exhaust flow rate (= intake flow rate) of the engine 11 and the air-fuel ratio using a map or a mathematical expression. To do. During combustion of the engine 11, the catalytic reaction heat changes mainly depending on the exhaust flow rate and the air-fuel ratio. Therefore, the combustion of the engine 11 is calculated by calculating the catalytic reaction heat based on the exhaust flow rate and the air-fuel ratio of the engine 11. The heat of catalytic reaction can be accurately determined.

一方、エンジン１１の燃料カット中に触媒反応熱分を演算する場合には、エンジン１１の排気流量（＝吸気流量）と燃料カット前の空燃比とに基づいて触媒反応熱分を演算する。具体的には、図４に示すように、(1) エンジン１１の燃料カット前の空燃比に基づいて触媒反応熱分のピーク値をマップ又は数式等により演算し、(2) 触媒反応熱分がピーク値に到達するまでは排気流量の積算値に基づいて触媒反応熱分をマップ又は数式等により演算し、(3) 触媒反応熱分がピーク値に到達した後は触媒反応熱分をピーク値から０に収束させるように一次なまし処理して触媒反応熱分を求める。   On the other hand, when calculating the catalytic reaction heat during the fuel cut of the engine 11, the catalytic reaction heat is calculated based on the exhaust flow rate (= intake flow rate) of the engine 11 and the air-fuel ratio before the fuel cut. Specifically, as shown in FIG. 4, (1) the peak value of the catalytic reaction heat is calculated based on the air-fuel ratio before the fuel cut of the engine 11 by a map or a mathematical formula, and (2) the catalytic reaction heat component. Until the peak value reaches the peak value, the catalytic reaction heat is calculated based on the integrated value of the exhaust flow rate using a map or numerical formula. (3) After the catalytic reaction heat reaches the peak value, the catalytic reaction heat is peaked. The first heat treatment is performed so that the value converges to 0, and the heat of catalytic reaction is obtained.

(1) 燃料カット前の空燃比によって燃料カット中に反応可能な未燃燃料量が変化して触媒反応熱分のピーク値が変化するため、燃料カット前の空燃比に基づいて触媒反応熱分のピーク値を演算することで、触媒反応熱分のピーク値を精度良く求めることができる。   (1) Since the amount of unburned fuel that can react during fuel cut changes due to the air-fuel ratio before the fuel cut and the peak value of the catalytic reaction heat changes, the amount of catalytic reaction heat is based on the air-fuel ratio before the fuel cut. By calculating the peak value, the peak value of the catalytic reaction heat can be obtained with high accuracy.

(2) 触媒反応熱分がピーク値に到達するまでは、排気流量の積算値に応じて空気と未燃燃料の反応によって発生する総熱量が増加し、それに伴って触媒反応熱分が増加するため、排気流量の積算値に基づいて触媒反応熱分（触媒２５の反応熱による温度上昇分）を演算することで、触媒反応熱分を精度良く求めることができる。   (2) Until the catalytic reaction heat reaches the peak value, the total heat generated by the reaction between air and unburned fuel increases according to the integrated value of the exhaust flow rate, and the catalytic reaction heat increases accordingly. Therefore, by calculating the catalytic reaction heat (temperature increase due to the reaction heat of the catalyst 25) based on the integrated value of the exhaust flow rate, the catalytic reaction heat can be obtained with high accuracy.

(3) 触媒反応熱分がピーク値に到達した後は、触媒反応熱分が低下していくため、触媒反応熱分をピーク値から０に収束させるように一次なまし処理して触媒反応熱分を求めることで、触媒反応熱分を精度良く求めることができる。   (3) After the heat of catalytic reaction reaches the peak value, the heat of catalytic reaction decreases, so the first heat treatment is performed so that the heat of catalytic reaction converges to 0 from the peak value. By calculating the amount, the heat of catalytic reaction can be determined with high accuracy.

この後、推定触媒温度演算部３４（推定触媒温度演算手段）で、無担持触媒温度に触媒反応熱分を加算して推定触媒温度（触媒２５の温度の推定値）を求める。
推定触媒温度＝無担持触媒温度＋触媒反応熱分 Thereafter, the estimated catalyst temperature calculation unit 34 (estimated catalyst temperature calculation means) calculates the estimated catalyst temperature (the estimated value of the temperature of the catalyst 25) by adding the catalytic reaction heat to the unsupported catalyst temperature.
Estimated catalyst temperature = unsupported catalyst temperature + catalytic reaction heat

このように触媒温度を無担持触媒温度と触媒反応熱分とに分けて考え、それぞれを個別に演算することで、無担持触媒温度と触媒反応熱分を精度良く演算することができる。そして、無担持触媒温度に触媒反応熱分を加算して推定触媒温度を求めることで、推定触媒温度を精度良く求めることができる。   As described above, the catalyst temperature is divided into the unsupported catalyst temperature and the catalytic reaction heat, and each is calculated separately, whereby the unsupported catalyst temperature and the catalytic reaction heat can be calculated with high accuracy. Then, the estimated catalyst temperature can be accurately obtained by adding the catalytic reaction heat to the unsupported catalyst temperature to obtain the estimated catalyst temperature.

また、ＥＣＵ３０は、エンジン１１の燃焼中に次の燃料カット中における触媒温度ピーク予測値を次のようにして演算する。
まず、予測吸気流量演算部３５（予測吸気流量演算手段）で、エンジン１１の燃焼中に次の燃料カット中における予測吸気流量を演算する（つまり次の燃料カット中における吸気流量を予測する）。 Further, the ECU 30 calculates the predicted catalyst temperature peak value during the next fuel cut during combustion of the engine 11 as follows.
First, the predicted intake flow rate calculation unit 35 (predicted intake flow rate calculation means) calculates the predicted intake flow rate during the next fuel cut during the combustion of the engine 11 (that is, predicts the intake flow rate during the next fuel cut).

具体的には、エンジン１１の燃料カット前の吸気流量（現在の吸気流量）からアイドル時の要求吸気流量に向かう吸気流量の挙動を求め、この吸気流量の挙動を予測吸気流量の挙動とする。この場合、燃料カット前の吸気流量からアイドル時の要求吸気流量に向かう吸気流量の挙動は、例えば、なまし処理や徐変によって求める。或は、トルク制御における要求トルク変化（燃料カット前の要求トルクからアイドル時の要求トルクまでの変化）を吸気流量の変化に変換して吸気流量の挙動を求めるようにしても良い。   Specifically, the behavior of the intake air flow from the intake air flow before the fuel cut of the engine 11 (current intake air flow) toward the required intake air flow during idling is obtained, and this behavior of the intake air flow is set as the behavior of the predicted intake air flow. In this case, the behavior of the intake air flow rate from the intake air flow rate before the fuel cut to the required intake air flow rate at the time of idling is obtained by, for example, a smoothing process or a gradual change. Alternatively, a change in required torque in torque control (change from a required torque before fuel cut to a required torque during idling) may be converted into a change in intake flow rate to determine the behavior of the intake flow rate.

更に、予測温度低下量演算部３６（予測温度低下量演算手段）で、エンジン１１の燃焼中に次の燃料カット中における無担持触媒温度の予測温度低下量を演算する（つまり次の燃料カット中における無担持触媒温度の低下量を予測する）。   Further, the predicted temperature decrease amount calculation unit 36 (predicted temperature decrease amount calculation means) calculates the predicted temperature decrease amount of the unsupported catalyst temperature during the next fuel cut during the combustion of the engine 11 (that is, during the next fuel cut). The amount of decrease in the temperature of the unsupported catalyst is predicted).

具体的には、予測吸気流量に基づいて無担持触媒温度の予測温度低下量をマップ又は数式等により演算する。燃料カット中の吸気流量（排気流量）に応じて触媒２５の放熱量が変化して無担持触媒温度の低下量が変化するため、予測吸気流量に基づいて無担持触媒温度の予測温度低下量を演算することで、無担持触媒温度の予測温度低下量を精度良く求めることができる。   Specifically, the predicted temperature decrease amount of the unsupported catalyst temperature is calculated based on the predicted intake flow rate using a map or a mathematical expression. Since the amount of heat released from the catalyst 25 changes in accordance with the intake flow rate (exhaust flow rate) during fuel cut, the amount of decrease in the unsupported catalyst temperature changes. By calculating, the predicted temperature decrease amount of the unsupported catalyst temperature can be obtained with high accuracy.

この後、予測無担持触媒温度演算部３７（予測無担持触媒温度演算手段）で、エンジン１１の燃焼中に次の燃料カット中における予測無担持触媒温度を演算する（つまり次の燃料カット中における無担持触媒温度を予測する）。具体的には、エンジン１１の燃料カット前の無担持触媒温度（現在の無担持触媒温度）から予測温度低下量を差し引いて予測無担持触媒温度を求める。
予測無担持触媒温度＝燃料カット前の無担持触媒温度−予測温度低下量 Thereafter, the predicted unsupported catalyst temperature calculation unit 37 (predicted unsupported catalyst temperature calculation means) calculates the predicted unsupported catalyst temperature during the next fuel cut during combustion of the engine 11 (that is, during the next fuel cut). Predict unsupported catalyst temperature). Specifically, the predicted unsupported catalyst temperature is obtained by subtracting the predicted temperature decrease from the unsupported catalyst temperature before the fuel cut of the engine 11 (current unsupported catalyst temperature).
Predicted unsupported catalyst temperature = Unsupported catalyst temperature before fuel cut-Predicted temperature drop

また、予測触媒反応熱分演算部３８（予測触媒反応熱分演算手段）で、エンジン１１の燃焼中に次の燃料カット中における予測触媒反応熱分を演算する（つまり次の燃料カット中における触媒反応熱分を予測する）。   Further, the predicted catalyst reaction heat calculation unit 38 (predicted catalyst reaction heat calculation means) calculates the predicted catalyst reaction heat during the next fuel cut during the combustion of the engine 11 (that is, the catalyst during the next fuel cut). Predict heat of reaction).

この場合、エンジン１１の燃料カット前の空燃比と予測吸気流量（予測排気流量）とに基づいて予測触媒反応熱分を演算する。具体的には、(1) エンジン１１の燃料カット前の空燃比（現在の空燃比）に基づいて予測触媒反応熱分のピーク値をマップ又は数式等により演算し、(2) 予測触媒反応熱分がピーク値に到達するまでの予測触媒反応熱分は予測吸気流量の積算値に基づいてマップ又は数式等により演算し、(3) 予測触媒反応熱分がピーク値に到達した後の予測触媒反応熱分は予測触媒反応熱分をピーク値から０に収束させるように一次なまし処理して求める。   In this case, the predicted catalytic reaction heat is calculated based on the air-fuel ratio before the fuel cut of the engine 11 and the predicted intake flow rate (predicted exhaust flow rate). Specifically, (1) the peak value of the predicted catalytic reaction heat is calculated based on the air-fuel ratio (current air-fuel ratio) before the fuel cut of the engine 11 by a map or a mathematical formula, and (2) the predicted catalytic reaction heat The predicted catalytic reaction heat until the minute reaches the peak value is calculated by a map or mathematical formula based on the integrated value of the predicted intake flow rate. (3) The predicted catalyst after the predicted catalytic reaction heat reaches the peak value The reaction heat is obtained by first-order annealing so that the predicted catalyst reaction heat is converged from the peak value to zero.

この後、触媒温度ピーク予測値演算部３９（触媒温度ピーク予測値演算手段）で、エンジン１１の燃焼中に次の燃料カット中における触媒温度ピーク予測値を演算する（つまり次の燃料カット中における触媒温度のピーク値を予測する）。   Thereafter, the catalyst temperature peak predicted value calculation unit 39 (catalyst temperature peak predicted value calculation means) calculates the catalyst temperature peak predicted value during the next fuel cut during the combustion of the engine 11 (that is, during the next fuel cut). Predict peak catalyst temperature).

この場合、次の燃料カット中における予測無担持触媒温度と予測触媒反応熱分とに基づいて触媒温度ピーク予測値を演算する。具体的には、図５に示すように、予測無担持触媒温度に予測触媒反応熱分を加算して予測触媒温度を求め、この予測触媒温度の最大値を触媒温度ピーク予測値とする。   In this case, the predicted catalyst temperature peak value is calculated based on the predicted unsupported catalyst temperature and the predicted catalytic reaction heat during the next fuel cut. Specifically, as shown in FIG. 5, the predicted catalyst temperature is obtained by adding the predicted catalyst reaction heat to the predicted unsupported catalyst temperature, and the maximum value of the predicted catalyst temperature is set as the predicted catalyst temperature peak value.

このように予測触媒温度を予測無担持触媒温度と予測触媒反応熱分とに分けて考え、それぞれを個別に演算することで、予測無担持触媒温度と予測触媒反応熱分を精度良く演算することができる。そして、予測無担持触媒温度に予測触媒反応熱分を加算して予測触媒温度を求め、この予測触媒温度の最大値を触媒温度ピーク予測値とすることで、触媒温度ピーク予測値を精度良く求めることができる。   In this way, the predicted catalyst temperature is divided into the predicted unsupported catalyst temperature and the predicted catalyst reaction heat, and the predicted unsupported catalyst temperature and the predicted catalyst reaction heat are calculated accurately by calculating each separately. Can do. Then, the predicted catalyst temperature is obtained by adding the predicted catalyst reaction heat to the predicted unsupported catalyst temperature, and the maximum value of the predicted catalyst temperature is used as the predicted catalyst temperature peak value, thereby accurately determining the predicted catalyst temperature peak value. be able to.

この後、燃料カット判定部４０（燃料カット判定手段）で、触媒温度ピーク予測値が所定の閾値よりも高いか否かを判定する。この閾値は、例えば、触媒温度の許容上限値又はそれよりも少し低い値に設定されている。触媒温度ピーク予測値が閾値よりも高い場合には、燃料カットを実行すると、燃料カット中に触媒温度が閾値を越える可能性が高いと判断して、燃料カットを禁止する。一方、触媒温度ピーク予測値が閾値以下の場合には、燃料カットを実行しても、燃料カット中に触媒温度が閾値を越えないと判断して、燃料カットを許可する。   Thereafter, the fuel cut determination unit 40 (fuel cut determination means) determines whether or not the predicted catalyst temperature peak value is higher than a predetermined threshold value. This threshold value is set to, for example, an allowable upper limit value of the catalyst temperature or a value slightly lower than that. When the predicted catalyst temperature peak value is higher than the threshold value, if the fuel cut is executed, it is determined that the catalyst temperature is likely to exceed the threshold value during the fuel cut, and the fuel cut is prohibited. On the other hand, when the predicted catalyst temperature peak value is equal to or lower than the threshold value, even if the fuel cut is executed, it is determined that the catalyst temperature does not exceed the threshold value during the fuel cut, and the fuel cut is permitted.

以上説明した本実施例の触媒温度推定は、ＥＣＵ３０によって図６の触媒温度推定ルーチンに従って実行される。以下、このルーチンの処理内容を説明する。
図６に示す触媒温度推定ルーチンは、ＥＣＵ３０の電源オン期間中（イグニッションスイッチのオン期間中）に所定周期で繰り返し実行される。本ルーチンが起動されると、まず、ステップ１０１で、エンジン運転状態（例えば、運転モード、エンジン回転速度、負荷、空燃比、点火時期等）に基づいて排気温度をマップ又は数式等により演算する。 The catalyst temperature estimation of the present embodiment described above is executed by the ECU 30 according to the catalyst temperature estimation routine of FIG. The processing contents of this routine will be described below.
The catalyst temperature estimation routine shown in FIG. 6 is repeatedly executed at a predetermined period during the power-on period of the ECU 30 (while the ignition switch is on). When this routine is started, first, in step 101, the exhaust temperature is calculated by a map or a mathematical formula based on the engine operation state (for example, operation mode, engine speed, load, air-fuel ratio, ignition timing, etc.).

この後、ステップ１０２に進み、排気温度を一次なまし処理して無担持触媒温度を求める。一次なまし処理の時定数は、予め試験データや設計データ等に基づいて、排気温度に対する無担持触媒温度の遅れ（触媒２５の熱容量による遅れ）を再現するように設定されている。
この後、ステップ１０３に進み、エンジン１１の燃焼中であるか否かを判定し、燃焼中ではない（燃料カット中である）と判定された場合には、ステップ１１４に進む。 Thereafter, the process proceeds to step 102, where the exhaust gas temperature is subjected to a primary smoothing process to obtain the unsupported catalyst temperature. The time constant of the primary annealing process is set in advance so as to reproduce the delay of the unsupported catalyst temperature with respect to the exhaust temperature (the delay due to the heat capacity of the catalyst 25) based on test data, design data, and the like.
Thereafter, the process proceeds to step 103, where it is determined whether or not the engine 11 is burning. If it is determined that the engine 11 is not burning (the fuel is being cut), the process proceeds to step 114.

一方、上記ステップ１０３で、エンジン１１の燃焼中であると判定された場合には、ステップ１０４に進み、エンジン１１の燃焼中に次の燃料カット中における予測吸気流量を演算する。具体的には、エンジン１１の燃料カット前の吸気流量（現在の吸気流量）からアイドル時の要求吸気流量に向かう吸気流量の挙動を求め、この吸気流量の挙動を予測吸気流量の挙動とする。   On the other hand, if it is determined in step 103 that the engine 11 is being burned, the routine proceeds to step 104 where the predicted intake air flow rate during the next fuel cut is calculated while the engine 11 is burning. Specifically, the behavior of the intake air flow from the intake air flow before the fuel cut of the engine 11 (current intake air flow) toward the required intake air flow during idling is obtained, and this behavior of the intake air flow is set as the behavior of the predicted intake air flow.

この後、ステップ１０５に進み、エンジン１１の燃焼中に次の燃料カット中における無担持触媒温度の予測温度低下量を演算する。具体的には、予測吸気流量に基づいて無担持触媒温度の予測温度低下量をマップ又は数式等により演算する。   Thereafter, the process proceeds to step 105, and the predicted temperature decrease amount of the unsupported catalyst temperature during the next fuel cut during the combustion of the engine 11 is calculated. Specifically, the predicted temperature decrease amount of the unsupported catalyst temperature is calculated based on the predicted intake flow rate using a map or a mathematical expression.

この後、ステップ１０６に進み、エンジン１１の燃焼中に次の燃料カット中における予測無担持触媒温度を演算する。具体的には、エンジン１１の燃料カット前の無担持触媒温度（現在の無担持触媒温度）から予測温度低下量を差し引いて予測無担持触媒温度を求める。
予測無担持触媒温度＝燃料カット前の無担持触媒温度−予測温度低下量 Thereafter, the routine proceeds to step 106, where the predicted unsupported catalyst temperature during the next fuel cut during the combustion of the engine 11 is calculated. Specifically, the predicted unsupported catalyst temperature is obtained by subtracting the predicted temperature decrease from the unsupported catalyst temperature before the fuel cut of the engine 11 (current unsupported catalyst temperature).
Predicted unsupported catalyst temperature = Unsupported catalyst temperature before fuel cut-Predicted temperature drop

この後、ステップ１０７に進み、エンジン１１の燃焼中に次の燃料カット中における予測触媒反応熱分を演算する。具体的には、(1) エンジン１１の燃料カット前の空燃比（現在の空燃比）に基づいて予測触媒反応熱分のピーク値をマップ又は数式等により演算し、(2) 予測触媒反応熱分がピーク値に到達するまでの予測触媒反応熱分は予測吸気流量の積算値に基づいてマップ又は数式等により演算し、(3) 予測触媒反応熱分がピーク値に到達した後の予測触媒反応熱分は予測触媒反応熱分をピーク値から０に収束させるように一次なまし処理して求める。   Thereafter, the process proceeds to step 107, and the predicted catalytic reaction heat during the next fuel cut is calculated during combustion of the engine 11. Specifically, (1) the peak value of the predicted catalytic reaction heat is calculated based on the air-fuel ratio (current air-fuel ratio) before the fuel cut of the engine 11 by a map or a mathematical formula, and (2) the predicted catalytic reaction heat The predicted catalytic reaction heat until the minute reaches the peak value is calculated by a map or mathematical formula based on the integrated value of the predicted intake flow rate. (3) The predicted catalyst after the predicted catalytic reaction heat reaches the peak value The reaction heat is obtained by first-order annealing so that the predicted catalyst reaction heat is converged from the peak value to zero.

この後、ステップ１０８に進み、エンジン１１の燃焼中に次の燃料カット中における触媒温度ピーク予測値を演算する。具体的には、予測無担持触媒温度に予測触媒反応熱分を加算して予測触媒温度を求め、この予測触媒温度の最大値を触媒温度ピーク予測値とする。   Thereafter, the routine proceeds to step 108, where a predicted catalyst temperature peak value during the next fuel cut during the combustion of the engine 11 is calculated. Specifically, the predicted catalyst reaction heat is added to the predicted unsupported catalyst temperature to obtain the predicted catalyst temperature, and the maximum value of the predicted catalyst temperature is set as the predicted catalyst temperature peak value.

この後、ステップ１０９に進み、触媒温度ピーク予測値が所定の閾値よりも高いか否かを判定する。このステップ１０９で、触媒温度ピーク予測値が閾値よりも高いと判定された場合には、燃料カットを実行すると、燃料カット中に触媒温度が閾値を越える可能性が高いと判断して、ステップ１１０に進み、燃料カットを禁止する。   Thereafter, the process proceeds to step 109, and it is determined whether or not the predicted catalyst temperature peak value is higher than a predetermined threshold value. If it is determined in step 109 that the predicted catalyst temperature peak value is higher than the threshold, it is determined that if the fuel cut is performed, the catalyst temperature is likely to exceed the threshold during the fuel cut. Proceed to ban fuel cut.

この後、ステップ１１１に進み、エンジン１１の燃焼中の演算方法で触媒反応熱分を演算する。具体的には、エンジン１１の排気流量（＝吸気流量）と空燃比とに基づいて触媒反応熱分をマップ又は数式等により演算する。   Thereafter, the process proceeds to step 111 where the heat of catalytic reaction is calculated by a calculation method during combustion of the engine 11. Specifically, based on the exhaust flow rate (= intake flow rate) of the engine 11 and the air-fuel ratio, the catalytic reaction heat is calculated by a map or a mathematical expression.

一方、上記ステップ１０９で、触媒温度ピーク予測値が閾値以下であると判定された場合には、燃料カットを実行しても、燃料カット中に触媒温度が閾値を越えないと判断して、ステップ１１２に進み、燃料カットを許可する。この場合、所定の燃料カット実行条件が成立したとき（例えばアクセルオフで且つエンジン回転速度が所定値以上のとき）に、燃料カットが実行される。   On the other hand, if it is determined in step 109 that the predicted catalyst temperature peak value is equal to or lower than the threshold, it is determined that the catalyst temperature does not exceed the threshold during the fuel cut even if the fuel cut is executed. Proceed to 112 to allow fuel cut. In this case, the fuel cut is executed when a predetermined fuel cut execution condition is satisfied (for example, when the accelerator is off and the engine speed is equal to or higher than a predetermined value).

この後、ステップ１１３に進み、燃料カット中であるか否かを判定し、燃料カット中ではない（まだ燃料カットが実行されていない）と判定されれば、ステップ１１１に進む。その後、上記ステップ１１３で、燃料カット中であると判定された場合には、ステップ１１４に進み、エンジン１１の燃料カット中の演算方法で触媒反応熱分を演算する。具体的には、(1) エンジン１１の燃料カット前の空燃比に基づいて触媒反応熱分のピーク値をマップ又は数式等により演算し、(2) 触媒反応熱分がピーク値に到達するまでは排気流量の積算値に基づいて触媒反応熱分をマップ又は数式等により演算し、(3) 触媒反応熱分がピーク値に到達した後は触媒反応熱分をピーク値から０に収束させるように一次なまし処理して触媒反応熱分を求める。   Thereafter, the process proceeds to step 113, where it is determined whether or not the fuel is being cut. If it is determined that the fuel is not being cut (the fuel cut has not been executed yet), the process proceeds to step 111. Thereafter, if it is determined in step 113 that the fuel is being cut, the routine proceeds to step 114 where the heat of catalytic reaction is calculated by the calculation method during the fuel cut of the engine 11. Specifically, (1) the peak value of the catalytic reaction heat is calculated based on the air-fuel ratio before the fuel cut of the engine 11 by a map or a mathematical formula, and (2) until the catalytic reaction heat reaches the peak value. Calculates the heat of catalytic reaction based on the integrated value of the exhaust flow rate using a map or numerical formula, etc. (3) After the heat of catalytic reaction reaches the peak value, the heat of catalytic reaction converges from the peak value to zero. First, heat treatment is performed to determine the heat of catalytic reaction.

上記ステップ１１１又は上記ステップ１１４で触媒反応熱分を演算した後、ステップ１１５に進み、無担持触媒温度に触媒反応熱分を加算して推定触媒温度を求める。
推定触媒温度＝無担持触媒温度＋触媒反応熱分
この推定触媒温度に基づいて、触媒２５の過熱防止用の制御（例えば燃料増量補正）、排出ガスセンサ２４のセンサ素子温度の推定、触媒早期暖機制御等を実行するようにしても良い。 After calculating the catalyst reaction heat in step 111 or step 114, the process proceeds to step 115, where the estimated catalyst temperature is obtained by adding the catalyst reaction heat to the unsupported catalyst temperature.
Estimated catalyst temperature = unsupported catalyst temperature + catalyst reaction heat content Based on the estimated catalyst temperature, control for preventing overheating of the catalyst 25 (for example, fuel increase correction), estimation of the sensor element temperature of the exhaust gas sensor 24, early catalyst warm-up Control or the like may be executed.

以上説明した本実施例では、触媒温度を無担持触媒温度（触媒２５の反応熱による温度変化が無いと仮定した場合の触媒温度）と触媒反応熱分（触媒２５の反応熱による温度上昇分）とに分けて考え、それぞれを個別に演算するようにしたので、無担持触媒温度と触媒反応熱分を精度良く演算することができる。更に、エンジン１１の燃焼中と燃料カット中とで触媒反応熱分の演算方法を切り換えるようにしたので、燃料カット中でも触媒反応熱分を精度良く演算することができる。そして、無担持触媒温度に触媒反応熱分を加算して推定触媒温度を求めることで、エンジン１１の燃焼中と燃料カット中の両方で推定触媒温度を精度良く求めることができ、触媒温度の推定精度を向上させることができる。   In the present embodiment described above, the catalyst temperature is the unsupported catalyst temperature (catalyst temperature when it is assumed that there is no temperature change due to the reaction heat of the catalyst 25) and the catalyst reaction heat (temperature increase due to the reaction heat of the catalyst 25). Since each is calculated separately, the unsupported catalyst temperature and the catalytic reaction heat can be calculated accurately. Furthermore, since the calculation method of the catalytic reaction heat is switched between the combustion of the engine 11 and the fuel cut, the catalytic reaction heat can be accurately calculated even during the fuel cut. Then, by adding the catalytic reaction heat to the unsupported catalyst temperature to obtain the estimated catalyst temperature, the estimated catalyst temperature can be accurately obtained both during combustion of the engine 11 and during fuel cut, and the catalyst temperature is estimated. Accuracy can be improved.

また、本実施例では、エンジン１１の燃焼中に次の燃料カット中における触媒温度ピーク予測値を演算し、この触媒温度ピーク予測値が所定の閾値よりも高いか否かを判定する。その結果、触媒温度ピーク予測値が閾値よりも高い場合には、燃料カットを実行すると、燃料カット中に触媒温度が閾値を越える可能性が高いと判断して、燃料カットを禁止する。これにより、燃料カット中の触媒温度の上昇による触媒２５の過熱を未然に防止することができる。一方、触媒温度ピーク予測値が閾値以下の場合には、燃料カットを実行しても、燃料カット中に触媒温度が閾値を越えないと判断して、燃料カットを許可する。これにより、燃料カットを必要以上に遅らせることを防止でき、燃費を向上させることができる。   Further, in this embodiment, a predicted catalyst temperature peak value during the next fuel cut during the combustion of the engine 11 is calculated, and it is determined whether or not this predicted catalyst temperature peak value is higher than a predetermined threshold value. As a result, when the predicted catalyst temperature peak value is higher than the threshold value, if the fuel cut is executed, it is determined that the catalyst temperature is likely to exceed the threshold value during the fuel cut, and the fuel cut is prohibited. Thereby, overheating of the catalyst 25 due to an increase in the catalyst temperature during fuel cut can be prevented in advance. On the other hand, when the predicted catalyst temperature peak value is equal to or lower than the threshold value, even if the fuel cut is executed, it is determined that the catalyst temperature does not exceed the threshold value during the fuel cut, and the fuel cut is permitted. Thereby, it can prevent delaying a fuel cut more than necessary, and can improve a fuel consumption.

尚、上記実施例では、エンジン運転状態に基づいて排気温度を推定するようにしたが、これに限定されず、例えば、排気温度を検出する排気温度センサを備えたシステムの場合には、この排気温度センサで排気温度を検出するようにしても良い。   In the above embodiment, the exhaust gas temperature is estimated based on the engine operating state. However, the present invention is not limited to this. For example, in the case of a system including an exhaust gas temperature sensor for detecting the exhaust gas temperature, the exhaust gas temperature is estimated. The exhaust temperature may be detected by a temperature sensor.

その他、本発明は、図１に示すような吸気ポート噴射式エンジンに限定されず、筒内噴射式エンジンや、吸気ポート噴射用の燃料噴射弁と筒内噴射用の燃料噴射弁の両方を備えたデュアル噴射式のエンジンにも適用して実施できる。   In addition, the present invention is not limited to the intake port injection type engine as shown in FIG. 1, but includes an in-cylinder injection type engine, and both an intake port injection fuel injection valve and an in-cylinder injection fuel injection valve. It can also be applied to dual-injection engines.

１１…エンジン（内燃機関）、２５…触媒、３０…ＥＣＵ、３２…無担持触媒温度演算部（無担持触媒温度演算手段）、３３…触媒反応熱分演算部（触媒反応熱分演算手段）、３４…推定触媒温度演算部（推定触媒温度演算手段）、３９…触媒温度ピーク予測値演算部（触媒温度ピーク予測値演算手段）、４０…燃料カット判定部（燃料カット判定手段）   DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 25 ... Catalyst, 30 ... ECU, 32 ... Unsupported catalyst temperature calculating part (unsupported catalyst temperature calculating means), 33 ... Catalytic reaction heat calculating part (catalyst reaction heat calculating means), 34 ... Estimated catalyst temperature calculator (estimated catalyst temperature calculator), 39 ... Catalyst temperature peak predicted value calculator (catalyst temperature peak predicted value calculator), 40 ... Fuel cut determiner (fuel cut determiner)

Claims (9)

内燃機関（１１）の排気浄化用の触媒（２５）の温度を推定する内燃機関の触媒温度推定装置において、
前記触媒（２５）の反応熱による温度変化が無いと仮定した場合の前記触媒（２５）の温度（以下「無担持触媒温度」という）を演算する無担持触媒温度演算手段（３２）と、
前記触媒（２５）の反応熱による温度上昇分（以下「触媒反応熱分」という）を演算する触媒反応熱分演算手段（３３）と、
前記無担持触媒温度と前記触媒反応熱分とに基づいて前記触媒（２５）の温度の推定値を演算する推定触媒温度演算手段（３４）とを備え、
前記触媒反応熱分演算手段（３３）は、
前記内燃機関（１１）の燃焼中に前記触媒反応熱分を演算する場合には、前記内燃機関（１１）の排気流量と空燃比とに基づいて前記触媒反応熱分を演算し、
前記内燃機関（１１）の燃料カット中に前記触媒反応熱分を演算する場合には、前記内燃機関（１１）の燃料カット前の空燃比に基づいて、燃料カット中に反応可能な未燃燃料量が変化する触媒反応熱分のピーク値を演算し、前記触媒反応熱分が前記ピーク値に到達するまでは前記排気流量の積算値に基づいて前記触媒反応熱分を演算するとともに、前記触媒反応熱分が前記ピーク値に到達した後は前記触媒反応熱分を前記ピーク値から０に収束させるように一次なまし処理して前記触媒反応熱分を求めることを特徴とする内燃機関の触媒温度推定装置。 In the internal combustion engine catalyst temperature estimation device for estimating the temperature of the exhaust purification catalyst (25) of the internal combustion engine (11),
Unsupported catalyst temperature calculation means (32) for calculating the temperature of the catalyst (25) (hereinafter referred to as "unsupported catalyst temperature") when it is assumed that there is no temperature change due to the reaction heat of the catalyst (25);
Catalyst reaction heat calculating means (33) for calculating a temperature rise due to reaction heat of the catalyst (25) (hereinafter referred to as “catalyst reaction heat”);
Estimated catalyst temperature calculation means (34) for calculating an estimated value of the temperature of the catalyst (25) based on the unsupported catalyst temperature and the heat of catalytic reaction;
The catalytic reaction heat component calculating means (33)
When calculating the catalytic reaction heat during combustion of the internal combustion engine (11), the catalytic reaction heat is calculated based on the exhaust flow rate and the air-fuel ratio of the internal combustion engine (11),
When calculating the heat of catalytic reaction during the fuel cut of the internal combustion engine (11), the unburned fuel that can react during the fuel cut based on the air-fuel ratio before the fuel cut of the internal combustion engine (11). Calculating a peak value of the catalytic reaction heat component whose amount changes, calculating the catalytic reaction heat component based on the integrated value of the exhaust flow rate until the catalytic reaction heat component reaches the peak value, and A catalyst for an internal combustion engine characterized in that after the reaction heat reaches the peak value, the catalyst reaction heat is obtained by performing a primary smoothing process so that the catalyst reaction heat converges to 0 from the peak value. Temperature estimation device. 前記内燃機関（１１）の排気温度を推定又は検出する排気温度取得手段（３１）を備え、
前記無担持触媒温度演算手段（３２）は、前記排気温度に対する前記無担持触媒温度の前記触媒（２５）の熱容量による遅れを考慮して前記排気温度に基づいて前記無担持触媒温度を演算することを特徴とする請求項１に記載の内燃機関の触媒温度推定装置。 Exhaust temperature acquisition means (31) for estimating or detecting the exhaust temperature of the internal combustion engine (11),
The unsupported catalyst temperature calculating means (32) calculates the unsupported catalyst temperature based on the exhaust temperature in consideration of a delay due to the heat capacity of the catalyst (25) of the unsupported catalyst temperature with respect to the exhaust temperature. The catalyst temperature estimation device for an internal combustion engine according to claim 1, wherein 前記排気温度取得手段（３１）は、前記内燃機関（１１）の運転状態に基づいて前記排気温度を推定することを特徴とする請求項２に記載の内燃機関の触媒温度推定装置。   The catalyst temperature estimation device for an internal combustion engine according to claim 2, wherein the exhaust temperature acquisition means (31) estimates the exhaust temperature based on an operating state of the internal combustion engine (11). 前記内燃機関（１１）の燃焼中に次の燃料カット中における前記触媒（２５）の温度のピーク予測値（以下「触媒温度ピーク予測値」という）を演算する触媒温度ピーク予測値演算手段（３９）と、
前記触媒温度ピーク予測値が所定の閾値よりも高い場合に前記燃料カットを禁止し、前記触媒温度ピーク予測値が前記閾値以下の場合に前記燃料カットを許可する燃料カット判定手段（４０）と
を備えていることを特徴とする請求項１乃至３のいずれか一項に記載の内燃機関の触媒温度推定装置。 Catalyst temperature peak predicted value calculation means (39) for calculating a peak predicted value of the temperature of the catalyst (25) during the next fuel cut during the combustion of the internal combustion engine (11) (hereinafter referred to as "catalyst temperature peak predicted value"). )When,
Fuel cut determination means (40) for prohibiting the fuel cut when the predicted catalyst temperature peak value is higher than a predetermined threshold value and permitting the fuel cut when the predicted catalyst temperature peak value is less than or equal to the threshold value; The catalyst temperature estimation device for an internal combustion engine according to any one of claims 1 to 3 , further comprising: 前記内燃機関（１１）の燃焼中に次の燃料カット中における前記無担持触媒温度の予測値（以下「予測無担持触媒温度」という）を演算する予測無担持触媒温度演算手段（３７）と、
前記内燃機関（１１）の燃焼中に次の燃料カット中における前記触媒反応熱分の予測値（以下「予測触媒反応熱分」という）を演算する予測触媒反応熱分演算手段（３８）とを備え、
前記触媒温度ピーク予測値演算手段（３９）は、前記予測無担持触媒温度と前記予測触媒反応熱分とに基づいて前記触媒温度ピーク予測値を演算することを特徴とする請求項４に記載の内燃機関の触媒温度推定装置。 Predicted unsupported catalyst temperature calculation means (37) for calculating a predicted value of the unsupported catalyst temperature during the next fuel cut during the combustion of the internal combustion engine (11) (hereinafter referred to as "predicted unsupported catalyst temperature");
Predictive catalytic reaction heat calculating means (38) for calculating a predicted value of the catalytic reaction heat during the next fuel cut (hereinafter referred to as “predicted catalytic reaction heat”) during combustion of the internal combustion engine (11). Prepared,
The said catalyst temperature peak predicted value calculating means (39) calculates the said catalyst temperature peak predicted value based on the said predicted unsupported catalyst temperature and the said predicted catalyst reaction heat component, The Claim 5 characterized by the above-mentioned. Catalyst temperature estimation device for internal combustion engine. 前記内燃機関（１１）の燃焼中に次の燃料カット中における前記無担持触媒温度の予測温度低下量を演算する予測温度低下量演算手段（３６）を備え、
前記予測無担持触媒温度演算手段（３７）は、前記内燃機関（１１）の燃料カット前の前記無担持触媒温度から前記予測温度低下量を差し引いて前記予測無担持触媒温度を求めることを特徴とする請求項５に記載の内燃機関の触媒温度推定装置。 A predicted temperature decrease amount calculating means (36) for calculating a predicted temperature decrease amount of the unsupported catalyst temperature during the next fuel cut during combustion of the internal combustion engine (11);
The predicted unsupported catalyst temperature calculating means (37) obtains the predicted unsupported catalyst temperature by subtracting the predicted temperature decrease from the unsupported catalyst temperature before the fuel cut of the internal combustion engine (11). The internal combustion engine catalyst temperature estimation device according to claim 5 . 前記内燃機関（１１）の燃焼中に次の燃料カット中における予測吸気流量を演算する予測吸気流量演算手段（３５）を備え、
前記予測温度低下量演算手段（３６）は、前記予測吸気流量に基づいて前記予測温度低下量を演算することを特徴とする請求項６に記載の内燃機関の触媒温度推定装置。 A predicted intake flow rate calculating means (35) for calculating a predicted intake flow rate during the next fuel cut during combustion of the internal combustion engine (11);
The catalyst temperature estimation device for an internal combustion engine according to claim 6 , wherein the predicted temperature decrease amount calculation means (36) calculates the predicted temperature decrease amount based on the predicted intake air flow rate. 前記内燃機関（１１）の燃焼中に次の燃料カット中における予測吸気流量を演算する予測吸気流量演算手段（３５）を備え、
前記予測触媒反応熱分演算手段（３８）は、前記内燃機関（１１）の燃料カット前の空燃比と前記予測吸気流量とに基づいて前記予測触媒反応熱分を演算することを特徴とする請求項５乃至７のいずれか一項に記載の内燃機関の触媒温度推定装置。 A predicted intake flow rate calculating means (35) for calculating a predicted intake flow rate during the next fuel cut during combustion of the internal combustion engine (11);
The predicted catalytic reaction heat calculating means (38) calculates the predicted catalytic reaction heat based on an air-fuel ratio before the fuel cut of the internal combustion engine (11) and the predicted intake flow rate. Item 8. The catalyst temperature estimation device for an internal combustion engine according to any one of Items 5 to 7 . 前記予測吸気流量演算手段（３５）は、前記内燃機関（１１）の燃料カット前の吸気流量からアイドル時の要求吸気流量に向かう吸気流量の挙動に基づいて前記予測吸気流量を演算することを特徴とする請求項７又は８に記載の内燃機関の触媒温度推定装置。 The predicted intake flow rate calculation means (35) calculates the predicted intake flow rate based on the behavior of the intake flow rate from the intake flow rate before the fuel cut of the internal combustion engine (11) toward the required intake flow rate during idling. The catalyst temperature estimation device for an internal combustion engine according to claim 7 or 8 .
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