DE102016203333B4 - EMISSION ESTIMATION DEVICE FOR INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

Emission estimating apparatus for an internal combustion engine, comprising:an emission discharge amount estimating means for estimating an emission discharge amount of either NOx or soot discharged from a cylinder of the internal combustion engine based on operating conditions of the internal combustion engine,wherein the estimating means for the An emission discharge amount comprising: humidity detection means (50) for detecting a humidity of fresh air drawn into the internal combustion engine, intake air O2 concentration correcting means (160, 112; 160, 221) for correcting the to perform an intake air O2 concentration that corrects a change in the emission discharge amount due to a change in an intake air O2 concentration that changes in accordance with an absolute humidity, the intake air O2 concentration having a concentration v one is oxygen contained in a gas introduced into the cylinder, andmeans (107, 115; 214, 222) to perform a specific heat correction which corrects a change in the emission discharge amount due to the change in the specific heat of the gas sucked into the cylinder which changes in accordance with an absolute humidity, and the emission discharge amount estimating means is constructed thereto is to perform the correction of the O2 concentration in the intake air and to limit the correction of the specific heat when a current operation area belongs to a first operation area in which an amount of change in the emission output amount in an operation area calculated using the O2 concentration in the intake air is fixed is comparatively large, and performs the correction based on the specific heat and restricts the correction based on the O2 concentration in the intake air when the current operating area belongs to a second operating area in which the amount of change in the emission output amount vs is comparatively small over the change in the O2 concentration in the intake air in an operating range determined using the O2 concentration in the intake air.

Description

background

field of invention

The present invention relates to an emission estimating device that estimates an amount of soot or NOx discharged from a cylinder of an internal combustion engine.

State of the art

The gas discharged from the cylinder of an internal combustion engine contains emissions such as soot or NOx. Recently, in order to restrict the discharge of these emissions, internal combustion engines estimate the generated amounts of emissions discharged from the cylinders of the internal combustion engine based on a model, and perform catalyst control such as catalyst regeneration and exhaust gas purification and catalyst on-board diagnosis (OBD ) control such as a diagnosis of catalyst failure using the estimated emission generation amount. In this case, it is important to improve the accuracy of estimation of the emission output model in performing this kind of control with high precision.

• [Patentschrift 1]: JP 2006 - 274 991 A
• [Patentschrift 2]: JP 2006 - 343 136 A
• [Patentschrift 3]: JP 2001 - 82 233 A
• [Patentschrift 4]: JP 2014 - 137 004 A

For example, a technique for estimating the generation amount of emissions such as soot or NOx is in the JP 2006-274 991 A described. More specifically, in this prior art, the injection period is equally divided into three periods, the mixed gases based on injections in the respective periods are treated individually, and the emission generation amounts generated due to the combustion of the respective mixed gases are individually estimated. Therefore, non-uniformity of emission generation rates is considered, and hence the total generation amounts of these emissions can be estimated with high precision.

• [Patent Document 1]: JP 2006 - 274 991 A
• [Patent Document 2]: JP 2006 - 343 136 A
• [Patent Document 3]: JP 2001 - 82 233 A
• [Patent Document 4]: JP 2014 - 137 004 A

Also the JP 2008 286 019 A and the post-released US 2015/0 252 699 A1 show various emission estimation devices from the technical field of the invention. However, none of these references discloses a means to perform specific heat correction which corrects a change in the emission discharge amount due to the change in specific heat of gas sucked into the cylinder changing in accordance with an absolute humidity, and wherein the estimating means for the emission output amount is configured to perform the correction of the O2 concentration in the intake air and restrict the correction of the specific heat when a current operation area belongs to a first operation area in which an amount of change in the emission output amount in an operation area calculated using the O2 - concentration in the intake air is fixed, is comparatively large,

Brief explanation of the invention

It should be noted that the discharge amount of soot discharged from a cylinder changes depending on the humidity of intake air. In the prior art described above, the influence of humidity is not taken into account, and therefore there is a fear that it is not possible to estimate the discharge amount of soot with high precision. However, there are a number of major causes of change in soot discharge rate due to humidity, and it depends on different operating conditions which of these major causes is dominant. Therefore, in order to correct the change in the soot discharge amount depending on humidity, it is effective to determine which of the main causes is dominant to improve the estimation precision while restricting a calculation load in the determination, and thereafter perform correction for the predetermined main cause. A similar problem occurs in the change in the amount of discharge of NOx from the cylinder due to humidity.

The present invention is performed in view of the problem as described above, and has an object to provide an emission estimating device for an internal combustion engine capable of estimating a soot discharge amount or a NOx discharge amount with high precision while restraining a calculation load.

• eine Emissionsabgabemengenabschätzungseinrichtung, um auf der Grundlage der Betriebsbedingungen der Brennkraftmaschine eine Emissionsabgabemenge entweder von NOx oder Ruß abzuschätzen, die von einem Zylinder der Brennkraftmaschine abgegeben wird,
• wobei die Emissionsabgabemengenabschätzungseinrichtung Folgendes umfasst:
  • eine Feuchtigkeitserfassungseinrichtung zum Erfassen einer Feuchtigkeit von Frischluft, die in die Brennkraftmaschine eingesaugt wird,
  • eine Korrektureinrichtung für die O₂-Konzentration in der Ansaugluft, um eine Korrektur der O₂-Konzentration in der Ansaugluft durchzuführen, die eine Änderung der Emissionsabgabemenge aufgrund einer Änderung der O₂-Konzentration in der Ansaugluft entsprechend einer absoluten Feuchtigkeit korrigiert, wobei die O₂-Konzentration in der Ansaugluft eine Konzentration von Sauerstoff ist, der in einem Gas enthalten ist, das in den Zylinder eingesaugt wird, und
  • eine Einrichtung zur Korrektur der spezifischen Wärme, um eine Korrektur der spezifischen Wärme durchzuführen, die eine Änderung der Emissionsabgabemenge aufgrund der spezifischen Wärme des in den Zylinder eingesaugten Gases passend zu einer absoluten Feuchtigkeit korrigiert, und
  • wobei die Emissionsabgabemengenabschätzungseinrichtung dazu aufgebaut ist, die Korrektur der O₂-Konzentration in der Ansaugluft durchzuführen und die Korrektur der spezifischen Wärme zu beschränken, wenn ein derzeitiger Betriebsbereich zu einem ersten Betriebsbereich gehört, in dem eine Änderungsgröße der Emissionsabgabemenge mit Bezug auf eine Änderung der O₂-Konzentration in der Ansaugluft in einem unter Verwendung der O₂-Konzentration in der Ansaugluft festgelegten Betriebsbereich vergleichsweise groß ist, und die spezifische Wärmekorrektur durchzuführen und die Korrektur der O₂-Konzentration in der Ansaugluft zu beschränken, wenn der derzeitige Betriebsbereich zu einem zweiten Betriebsbereich gehört, in dem die Änderungsgröße der Emissionsabgabemenge bezüglich der Änderung der Konzentration von O₂ in der Ansaugluft in einem Betriebsbereich vergleichsweise klein ist, der unter Verwendung der O₂-Konzentration in der Ansaugluft festgelegt ist.

In order to achieve the above object, according to a first aspect of the present invention, there is provided an emission estimating device for an internal combustion engine, comprising:

• an emission discharge amount estimating means for estimating an emission discharge amount of either NOx or soot discharged from a cylinder of the internal combustion engine based on the operating conditions of the internal combustion engine,
• wherein the emission charge amount estimating means comprises:
  • a humidity detection device for detecting a humidity of fresh air that is sucked into the internal combustion engine,
  • intake air O _{2 concentration correction means for performing intake air O 2 concentration} correction which corrects a change in the emission discharge amount due to a change in intake air O ₂ concentration according to an absolute humidity, wherein the O ₂ -concentration in intake air is a concentration of oxygen contained in a gas sucked into the cylinder, and
  • specific heat correction means for performing a specific heat correction that corrects a change in the emission discharge amount due to the specific heat of the gas sucked into the cylinder in accordance with an absolute humidity, and
  • wherein the emission output amount estimating means is configured to perform the correction of the O ₂ concentration in the intake air and to limit the correction of the specific heat when a current operating area belongs to a first operating area in which an amount of change in the emission output amount with respect to a change in the O ₂ concentration in the intake air is comparatively large in an operation range set using the O ₂ concentration in the intake air, and perform the specific heat correction and limit the correction of the O ₂ concentration in the intake air when the current operation range becomes a second An operating range in which the amount of change in the emission discharge amount with respect to the change in the concentration of O ₂ in the intake air is comparatively small in an operating range set using the O ₂ concentration in the intake air.

According to a second aspect of the present invention, there is provided an emission estimating device for an internal combustion engine as described in the first aspect, wherein the emission discharge amount is a soot discharge amount, which is an amount of soot discharged from the cylinder, and
in an operation area set using the O ₂ concentration in intake air and an equivalence ratio, the first operation area is an area in which a magnitude of change in the soot discharge amount with respect to a change in O ₂ concentration in intake air or the equivalence ratio is comparatively large, and the second operating region is a region in which the amount of change in the discharge amount of soot with respect to the change in the O ₂ concentration in the intake air or the equivalence ratio is relatively small.

• eine Basis-Rußabgabemengenberechnungseinrichtung, um auf der Grundlage einer Maschinendrehzahl der Brennkraftmaschine und einer befohlenen Kraftstoffeinspritzmenge eine Basis-Rußabgabemenge zu berechnen, die eine Rußabgabemenge in einem stabilen Zustand der Brennkraftmaschine ist,
• eine Basis-Luft/Kraftstoff-Verhältnisberechnungseinrichtung, um auf der Grundlage der Maschinendrehzahl und der befohlenen Kraftstoffeinspritzmenge ein Basis-Luft/Kraftstoff-Verhältnis zu berechnen, das ein Luft/Kraftstoff-Verhältnis im stabilen Zustand ist,
• eine Basis-Berechnungseinrichtung für die O₂-Konzentration in der Ansaugluft, um eine Basis-O₂-Konzentration in der Ansaugluft auf der Grundlage der Maschinendrehzahl und der befohlenen Kraftstoffeinspritzmenge zu berechnen, die eine O₂-Konzentration in der Ansaugluft im stabilen Zustand ist,
• eine Einrichtung zur Berechnung eines abgeschätzten Luft/Kraftstoff-Verhältnisses, um auf der Grundlage einer Ansaugluft und der befohlenen Kraftstoffeinspritzmenge ein abgeschätztes Luft/Kraftstoff-Verhältnis zu berechnen, das ein abgeschätzter Wert eines derzeitigen Luft/Kraftstoff-Verhältnisses ist,
• eine Einrichtung zur Berechnung einer abgeschätzten O₂-Konzentration in der Ansaugluft, um eine abgeschätzte O₂-Konzentration in der Ansaugluft auf der Grundlage der Ansaugluftmenge und der befohlenen Kraftstoffeinspritzmenge zu berechnen, die ein abgeschätzter Wert einer derzeitigen O₂-Konzentration in der Ansaugluft ist, und
• einer Übergangskorrektureinrichtung, um die Basis-Rußabgabemenge auf der Grundlage eines Verhältnisses des abgeschätzten Luft/Kraftstoff-Verhältnisses zum Basis-Luft/Kraftstoff-Verhältnis und eines Verhältnisses der abgeschätzten O₂-Konzentration in der Ansaugluft zur Basis-O₂-Konzentration in der Ansaugluft zu korrigieren, und
• wobei die Korrektureinrichtung für die O₂-Konzentration in der Ansaugluft dazu aufgebaut ist, einen Korrekturwert für die O₂-Konzentration in der Ansaugluft zu berechnen, der ein Korrekturwert ist, in dem ein Änderungsgrad der O₂-Konzentration in der Ansaugluft durch die absolute Feuchtigkeit wiedergegeben wird, und die abgeschätzte O₂-Konzentration in der Ansaugluft unter Verwendung des Korrekturwerts für die O₂-Konzentration in der Ansaugluft zu korrigieren.

According to a third aspect of the present invention, there is provided the emission estimating device for an internal combustion engine as described in the second aspect, wherein the emission discharge amount estimating means comprises:

• a basic soot discharge amount calculating means for calculating a basic soot discharge amount, which is a soot discharge amount in a steady state of the internal combustion engine, based on an engine speed of the internal combustion engine and a commanded fuel injection amount,
• basic air-fuel ratio calculation means for calculating a basic air-fuel ratio, which is a steady-state air-fuel ratio, based on the engine speed and the commanded fuel injection amount,
• basic intake air O ₂ concentration calculation means for calculating a basic intake air O ₂ concentration based on the engine speed and the commanded fuel injection amount, which is a steady state intake air O ₂ concentration ,
• estimated air-fuel ratio calculation means for calculating an estimated air-fuel ratio, which is an estimated value of a current air-fuel ratio, based on intake air and the commanded fuel injection amount,
• estimated intake air O _{2 concentration calculation means for calculating an estimated intake air O 2 concentration} based on the intake air amount and the commanded fuel injection amount, which is an estimated value of a current intake air O ₂ concentration , and
• transition correction means for correcting the base soot discharge amount based on a ratio of the estimated air/fuel ratio to the base air/fuel ratio and a ratio of the estimated O ₂ concentration in intake air to the base O ₂ concentration in intake air to correct, and
• wherein the intake air O ₂ concentration correcting means is configured to calculate an intake air O ₂ concentration correction value, which is a correction value in which a degree of change of the intake air O ₂ concentration by the absolute humidity is reflected, and to correct the estimated intake air O ₂ concentration using the correction value for the intake air O ₂ concentration.

According to a fourth aspect of the present invention, there is provided an emission estimating apparatus for an internal combustion engine as described in the second or third aspect, wherein the specific heat correction means is configured to calculate a specific heat correction coefficient which is a correction coefficient is to reflect the increase or decrease of the specific heat in the discharge amount of soot on the basis of the absolute humidity, and correct the discharge amount of soot using the specific heat correction coefficient.

According to a fifth aspect of the present invention, there is provided the emission estimating device for an internal combustion engine described in the first aspect, wherein the emission discharge amount is a NOx discharge amount, which is an amount of NOx discharged from the cylinder and
in an operating range set using the O ₂ concentration in intake air, the first operating range is a range in which the O ₂ concentration in intake air is greater than a predetermined concentration, and the second operating range is a range , in which the O ₂ concentration in the intake air is equal to or lower than the predetermined concentration.

• eine Berechnungseinrichtung für die abgeschätzte O₂-Konzentration in der Ansaugluft, um eine abgeschätzte O₂-Konzentration in der Ansaugluft zu berechnen, die ein abgeschätzter Wert einer derzeitigen O₂-Konzentration in der Ansaugluft ist, und zwar auf der Grundlage einer Ansaugluftmenge und einer befohlenen Kraftstoffeinspritzmenge, und
• einer Berechnungseinrichtung einer Basis-NOx-Abgabemenge, um die NOx-Abgabemenge auf der Grundlage einer Maschinendrehzahl der Maschine mit interner Verbrennung, der befohlenen Kraftstoffeinspritzmenge, eines mittleren Einspritzzeitpunkts und der abgeschätzten O₂-Konzentration in der Ansaugluft zu berechnen, und
• wobei die Korrektureinrichtung für die O₂-Konzentration in der Ansaugluft dazu aufgebaut ist, einen Korrekturwert für die O₂-Konzentration in der Ansaugluft zu berechnen, der ein Korrekturwert ist, in dem ein Änderungsgrad der O₂-Konzentration in der Ansaugluft durch die absolute Feuchtigkeit wiedergegeben wird, und dazu, die abgeschätzte O₂-Konzentration in der Ansaugluft unter Verwendung des Korrekturwerts für die O₂-Konzentration in der Ansaugluft zu korrigieren.

According to a sixth aspect of the present invention, there is provided the emission estimating apparatus for an internal combustion engine described in the fifth aspect, wherein the emission discharge amount estimating means comprises:

• estimated intake air O _{2 concentration calculating means for calculating an estimated intake air O 2 concentration} , which is an estimated value of a current intake air O ₂ concentration, on the basis of an intake air amount and a commanded fuel injection amount, and
• basic NOx discharge amount calculating means for calculating the NOx discharge amount based on an engine speed of the internal combustion engine, the commanded fuel injection amount, an average injection timing and the estimated O ₂ concentration in intake air, and
• wherein the intake air O ₂ concentration correcting means is configured to calculate an intake air O ₂ concentration correction value, which is a correction value in which a degree of change of the intake air O ₂ concentration by the absolute humidity is reflected, and correcting the estimated intake air O ₂ concentration using the intake air O ₂ concentration correction value.

According to a seventh aspect of the present invention, there is provided an emission estimating apparatus for an internal combustion engine as described in the fifth or sixth aspect, wherein the specific heat correction means is configured to calculate a specific heat correction coefficient which is a correction coefficient for reflecting an increase or reducing the specific heat in the NOx discharge amount based on the absolute humidity, and correcting the NOx discharge amount using the specific heat correction coefficient.

According to the first invention, when estimating the emission discharge amount, which is the amount of _NOx or soot discharged from the cylinder when the the operating range specified using the O ₂ concentration in the intake air belongs to the first range in which the amount of change in the emission output amount with respect to the change in the O ₂ concentration in the intake air is relatively large, and the influence of the emission output amount due to the specific heat, that changes by the absolute humidity is corrected when the operating range belongs to the second operating range in which the amount of change in the emission discharge amount is relatively small with respect to the change in the O ₂ concentration in the intake air.

Accordingly, according to the present invention, the main cause of the change in the emission discharge amount is determined by the humidity, and correction for the main cause can be performed. Therefore, the estimation precision of the emission discharge amount can be improved while the calculation load is restricted.

According to the second invention, the influence of the emission discharge amount due to the change in the O ₂ concentration in the intake air by the humidity is corrected when estimating the discharge amount of soot discharged from the cylinder when the present operating range using the O ₂ concentration is specified in the intake air and the equivalence ratio belongs to the first operating region in which the amount of change in the emission discharge amount with respect to the change in the O ₂ concentration in the intake air or the equivalence ratio is comparatively large, and the influence of the emission discharge amount due to the specific heat that develops changes by the humidity is corrected when the present operating range belongs to the second operating range in which the amount of change in the emission discharge amount relative to the change in the O ₂ concentration in the intake air or the equivalence ratio is comparatively small. Accordingly, according to the present invention, the main cause of the change in the discharge amount of soot is determined by the humidity, and correction for the main cause can be performed. Therefore, the estimation precision of the soot discharge amount can be improved while the calculation load is restricted.

According to the third invention, a correction for reflecting the degree of change of the intake air O ₂ concentration by the absolute humidity is applied to the estimated value of the current intake air O ₂ concentration used at the time of estimating the soot discharge amount. Consequently, according to the present invention, a correction for the O ₂ concentration in the intake air can be performed in the operating range in which the change in the soot discharge amount due to the change in the O ₂ concentration in the intake air is dominant, and therefore the precision of the estimation of the The amount of soot discharged can be improved while the computational load is reduced.

According to the fourth invention, a correction for reflecting the increase or decrease in specific heat by absolute humidity in the discharge amount of soot is applied at the time of estimating the discharge amount of soot. Consequently, according to the present invention, the change in specific heat can be reflected in the soot discharge amount in the operating range in which the change in soot discharge amount dominates due to the change in specific heat of intake air, and therefore the estimation precision of the soot discharge amount can be improved while reducing the computational load will.

According to the fifth invention, the influence of the emission discharge amount due to the O ₂ concentration in the intake air changing by the humidity is corrected when estimating the amount of NOx discharged from the cylinder when the current operation range using the O ₂ concentration in the intake air belongs to the first operation region in which the O ₂ concentration in the intake air is greater than the predetermined concentration, and the influence of the emission discharge amount due to the specific heat that changes with humidity is corrected when the current operating range belongs to the second operating range in which the O ₂ concentration in the intake air is equal to or lower than the predetermined concentration. Accordingly, according to the present invention, the main cause of the change in the NOx discharge amount is determined by the humidity, and correction for the main cause can be performed. Therefore, the accuracy of the NOx discharge amount estimation can be improved while the calculation load is restrained.

According to the sixth invention, a correction for reflecting the degree of change of the O ₂ concentration in the intake air by the absolute humidity is applied to the estimated value of the present O ₂ concentration in the intake air calculated at the time of estimating the NOx discharge amount ver is turned. Consequently, according to the present invention, a correction for the O ₂ concentration in the intake air can be performed in the operating range in which the change in the NOx discharge amount due to the change in the O ₂ concentration in the intake air is dominant, and therefore the estimation precision of the NOx -Delivery rate can be improved while the computational load is limited.

According to the seventh invention, a correction for reflecting the increase or decrease in specific heat by absolute humidity in the NOx discharge amount is applied at the time of NOx discharge amount estimation. Consequently, according to the present invention, the specific heat change in the NOx discharge amount can be reflected in the operation region in which the change in the NOx discharge amount due to the change in the specific heat of the intake air is dominant, and therefore the precision of the NOx discharge amount can be improved. while the computational load is limited.

character list

• 1 14 is a diagram showing a configuration of an engine system to which a control device of Embodiment 1 of the present invention is applied.
• 2 14 is a control block diagram separately illustrating a functional block for estimating an emission discharge amount and a functional block for performing catalyst control from control functions executed by an ECU.
• 3 14 is a control block diagram separately illustrating functional blocks for estimating a cylinder-discharged particulate matter amount from estimating functions included in an emission estimation model.
• 4 14 is a diagram showing an example of a map defining a relationship of a target fresh air amount to an engine speed and a commanded fuel injection amount.
• 5 14 is a diagram showing an example of a map defining a relationship of a target EGR rate to the engine speed and the commanded fuel injection amount.
• 6 14 is a graph showing an example of a map that sets a transient correction coefficient based on an A/F ratio and an O ₂ concentration ratio in intake air.
• 7 14 is a graph showing a soot discharge amount with respect to an O ₂ concentration ratio in intake air and an equivalence ratio.
• 8th Fig. 12 is a flowchart showing a routine of a humidity correction operation executed in a humidity correction section.
• 9 14 is a control block diagram that extracts functional blocks for calculating a correction value for the O ₂ concentration in intake air from functions included in the humidity correction section.
• 10 14 is a control block diagram that extracts functional blocks for calculating a specific heat correction value from the functions included in the humidity correction section.
• 11 14 is a graph showing an example of a map defining a relationship of a specific heat of a basic intake gas versus the engine speed and the commanded fuel injection amount.
• 12 14 is a diagram showing an example of a heat specific correction value map defining a relationship of a heat specific correction coefficient with respect to the heat specific correction value.
• 13 14 is a graph showing a relationship of a NOx discharge amount with respect to the O ₂ concentration in intake air.
• 14 14 is a control block diagram that highlights functional blocks for estimating an in-cylinder discharge amount of NOx from the estimation functions included in the emission estimation model.

Detailed explanation of the preferred embodiment

Embodiments of the present invention will be described with reference to the figures.

First embodiment

[Structure of the First Embodiment]

1 14 is a diagram showing a structure of an engine system in which a control device of a first embodiment of the present invention is used. An internal combustion engine according to the present embodiment is a diesel engine equipped with a turbocharger (hereinafter referred to simply as “an engine”). In a main body 2 of the engine, four cylinders are included in series, and a fuel injection valve 8 is provided in each of the cylinders. On the engine main body 2, an intake manifold 4 and an exhaust pipe 6 are mounted. An intake passage 10 into which fresh air drawn in through an air cleaner 20 flows is connected to the intake manifold 4 . A turbocharger compressor 14 is mounted on the intake passage 10 . A diesel throttle 24 is provided in the intake passage 10 downstream of the compressor 14 . An intercooler 22 is included in the intake passage 10 between the compressor 14 and the diesel throttle 24 . An exhaust gas passage 12 for releasing an exhaust gas escaping from the engine main body 2 or the engine block 2 to the atmosphere is connected to the exhaust manifold 6 . A turbine 16 of the turbocharger is mounted in the exhaust passage 12 . The turbocharger is of the variable vane type and the turbine 16 is equipped with a variable nozzle 18 . In the exhaust passage 12, an oxidation catalyst 25, a DPF (Diesel Particulate Filter) 26, and an SCR (Selective Catalytic Reduction) 27 and 28 for purifying the exhaust gas downstream of the turbine 16 are provided.

The engine according to the present embodiment includes an EGR device that recirculates exhaust gas from an exhaust system to an intake system. The EGR device connects a position downstream of the diesel throttle 24 in the intake passage 10 to the exhaust manifold 6 through an EGR passage 30. The EGR passage 30 is provided with an EGR valve 32. As shown in FIG. An EGR cooler 34 is provided on an exhaust gas side of the EGR valve 32 in the EGR passage 30 . A bypass passage 36 bypassing the EGR cooler 34 is provided in the EGR passage 30 . At a point where the bypass passage 36 branching from the EGR passage 30 meets the EGR passage 30 again, a bypass valve 38 that switches a direction in which the exhaust gas flows is provided.

The engine system according to the present embodiment includes an ECU (electronic control unit, Electronic Control Unit) 50. The ECU 50 is a control device that integrally controls the entire engine system, and the control device according to the present invention is used as a function of the ECU 50 embodied.

The ECU 50 receives and processes signals from sensors included in the engine system. The sensors are attached to respective locations of the machine system. An air flow meter 54 equipped with a humidity sensor for detecting an intake air amount “Ga” and an intake air absolute humidity “AH” is attached to the intake passage 10 downstream of the air cleaner 20 . In addition, a rotation speed sensor 52 that detects a rotation speed of a crankshaft, an accelerator opening sensor 56 that outputs a signal corresponding to a position of an accelerator pedal, a differential pressure sensor 58 for detecting a pressure difference before and after the DPF 26, and the like are attached . Also, in the exhaust passage 12, an A/F sensor for detecting an air/fuel ratio is arranged between the DPF 26 and the SCR 27, and a NOx sensor 62 and a PM sensor are each at one downstream side of the SCR 28 arranged. The ECU 50 processes the read signals from the respective sensors and actuates the respective actuators in accordance with a predetermined control program. The actuators operated by the ECU 50 include the variable nozzle 18, the fuel injection valve 8, the EGR valve 32, the diesel throttle 24 and the like. Note that there are other actuators and sensors connected to the ECU 50 besides those illustrated in the figure, but the explanation thereof is omitted in the present description.

[Operation of the First Embodiment]

An engine control executed by the ECU 50 includes an emission discharge amount estimation control that estimates a discharge amount of emissions (NOx and soot) discharged from the respective cylinders during operation using a virtually constructed onboard estimation model, and a catalyst control that performs catalyst regeneration , emission purification, performs a failure diagnosis and the like using estimated emission discharge amounts. 2 Fig. 12 is a control block diagram showing a functional block for estimating the emission discharge amount and a functional block for performing catalyst control out of control functions included in the ECU 50 . a in 2 The emission estimation model 100 shown is the functional block in which the estimation control of the emission discharge amount of the present embodiment is performed. In the emission estimation model 100, model calculation is performed by taking inputs of operating conditions such as an engine speed, a fuel injection amount, an O ₂ concentration in intake air, specific heat and an air-fuel ratio, and estimating the exhaust amounts of soot or NOx . In addition, a catalytic converter control block 300, which is 2 shown is the functional block for performing the catalyst control of the present embodiment. In the catalyst control block 300, regeneration control and failure diagnosis of the DPF 26 are performed using the soot discharge amount estimated by the emission discharge amount estimation control. Also, in the catalyst control block 300, failure diagnosis and urea supply control of the SCRs 27 and 28 are performed using the NOx discharge amount estimated by the emission discharge amount estimation control. Because the methods of these types of catalyst control are already proposed in a number of known documents, the detailed explanation thereof is omitted in the present specification.

(Soot Discharge Amount Estimation Control)

The emission estimation model 100 of the present embodiment includes a function of estimating an exhaust amount per unit time (mg/s) of soot exhausted from the cylinder during operation. 3 14 is a control block diagram that extracts a functional block for estimating the discharge amount of in-cylinder soot discharged from estimation functions included in the emission estimation model 100. FIG. With reference to 3 a model structure for estimating the soot emission quantity is described in detail.

This in 3 The emission estimation model 100 shown includes a basic soot map 101, a basic A/F calculation section 102, a current A/F calculation section 103, a basic O ₂ concentration in intake air calculation section 104, a current calculation section 105 O ₂ concentration in intake air, a transient correction coefficient calculation section 106, a specific heat correction coefficient calculation section 107, an environmental correction section 108, and arithmetic sections 111, 112, 113, 114, and 115.

The base soot map 101 calculates a base soot discharge amount, which is a base value (i.e., a value in a steady state) of an amount of soot discharged from the cylinder in a current operating range (that is, an operating range defined by a fuel injection amount “Q”). and an engine speed “Ne” is defined) with the engine speed “Ne” detected using the speed sensor 52 and the commanded fuel injection amount “Q” of the fuel injection valve 8 as arguments.

A target fresh air amount map 150, which is included in another module, calculates a fresh air amount that is a target in the current operating range (that is, the operating range defined by the fuel injection amount "Q" and the engine speed "Ne"), where the engine speed “Ne” and the commanded fuel injection amount “Q” serve as the arguments. 4 14 is a diagram showing an example of a map defining a relationship between a target fresh air amount in terms of engine speed and the commanded fuel injection amount. This in 4 The map shown in FIG. 1 is stored, for example, in the target fresh air amount map 150, and the target fresh air amount for the engine speed and the commanded fuel injection amount that are input is calculated using this map.

The base A/F calculation section 102 calculates a base A/F (a base air/fuel ratio) as a current reference in the operating range (that is, at a time of calculating the base soot discharge amount) using the equation below (1) where the target fresh air amount calculated in the target fresh air amount map 150 is used as an input value. Note that the basic A/F calculation section 102 can be configured to calculate the basic A/F as the reference in the current operating range, with the engine speed “Ne” and the commanded fuel injection amount “Q” serving as the arguments .
[Equation 1] $$Basis-A/f=\frac{SOll-f\mathrm{right}iscHl\mathrm{and}ftmenGe}{K\mathrm{right}aftstOffeinsp\mathrm{right}it\mathrm{e.g}menGe}$$

The current A/F calculation section 103 calculates a current A/F (estimated air/fuel ratio), which is an estimated value of a current air/fuel ratio, with an intake air amount “Ga” measured by the air flow meter 54 and the commanded fuel injection amount “Q” as input values. Note that in a case where deterioration occurs in the engine main body or the engine block 2 or the like, the actual A/F may deviate from an actual A/F. The current A/F calculation section 103 outputs an A/F learning value for eliminating a difference between the actual A/F detected by the air/fuel ratio sensor and the current A/F in the current A/F. F again.
[Equation 2] $$De\mathrm{right}\mathrm{e.g}eitiGe\mathrm{right}A/f=\frac{Ga}{Q}$$

In the target EGR rate map 151 included in another module, a target EGR rate that is a target in a current operating range (that is, an operating range defined by the fuel injection amount "Q" and the engine speed “Ne” is defined), taking the engine speed “Ne” and the commanded fuel injection amount “Q” as arguments. Note that the EGR rate refers to a value defined as a ratio of an EGR gas amount to a cylinder gas amount (a sum of the fresh air amount and the EGR gas amount) charged into the cylinder. 5 14 is a diagram showing an example of a map defining a relationship of the target EGR rate to the engine speed and the commanded fuel injection amount. In target fresh air quantity characteristics map 150, for example, in 5 is stored in the map shown, and the target EGR rate with respect to the engine speed and the commanded fuel injection amount that are read in is calculated using this map.

The basic intake air O ₂ concentration calculation section 104 calculates a basic intake air O ₂ concentration (wt %) which is a basic value of an intake air oxygen concentration in an operation region at the current time (that is, at a time of calculation of the base soot discharge amount) by using the following equation (3) with the target EGR rate calculated in the target EGR rate map 151 and a base λ being used as input values. The base λ is calculated by dividing the base A/F calculated in the base A/F calculation section 102 by a theoretical air-fuel ratio. Note that the basic intake air O _{2 concentration calculation section 104 may be configured to calculate the basic intake air O 2 concentration} in the operating range at the current time with the engine speed “Ne” and the commanded fuel injection amount “Q ' as arguments to calculate.
[Equation 3] $$Basis-{\mathrm{<figure-callout\; id="2"\; label="O"\; filenames="DE102016203333B4\_0016.png,DE102016203333B4\_0021.png"\; state="\{\{state\}\}">O</figure-callout>}}_2-KOn\mathrm{e.g}ent\mathrm{right}atiOnin\mathrm{i.e}e\mathrm{right}Ansa\mathrm{and}Gl\mathrm{and}ft=23.2\left(1-\frac{SOll-EGR-Rate}{Basis-\lambda }\right)$$

An EGR rate calculation section 152, which another module includes, calculates an EGR rate using Equation (4) below with the intake air “Ga” measured by the air flow meter 54 and a cylinder gas amount “Gcyl” represented by a any known method is included as input values.
[Equation 4] $$EGR-Rate=\frac{Gcyl-Ga}{Gcyl}$$

The current intake air O ₂ concentration calculation section 105 calculates a current intake air O ₂ concentration “D”, which is an estimated value of a current intake air O ₂ concentration, using an equation (5) below. , where the current A/F calculated in the current A/F calculation section and the EGR rate calculated in the EGR rate calculation section 152 are used as input values. A current λ is obtained by dividing the current A/F calculated in the current A/F calculation section 103 by calculates the theoretical air/fuel ratio.
[Equation 5] $$D=23.2\left(1-\frac{EGR-Rate}{\lambda }\right)$$

Also, in the arithmetic section 111, an A/F ratio used as an input of the transient correction coefficient calculation section 106 is calculated. The A/F ratio is calculated as a ratio of the current A/F ratio that the current A/F calculation section 103 calculates to the base A/F that the base A/F calculation section 102 calculates.

A humidity correction section 160 included in another module calculates a specific heat correction value for correcting a specific heat to match a correction value for the O ₂ concentration in intake air to match the O ₂ concentration in intake air Humidity and correcting the humidity. Note that a function of the humidity correction section 160 will be detailed later.

In addition, the arithmetic section 112 calculates a corrected intake air O ₂ concentration by multiplying the current intake air O ₂ concentration calculated in the current intake air O ₂ concentration calculation section 105 by the correction value for the O ₂ - Concentration in the intake air calculated in the humidity correction section 160. Also, in the arithmetic section 113 , an O ₂ concentration ratio in the intake air, which is used as an input of the transient correction coefficient calculation section 106 , is calculated. The O ₂ concentration in the intake air is calculated as a ratio of the corrected O ₂ concentration in the intake air calculated in the arithmetic section 112 to the basic O ₂ concentration in the intake air calculated in the basic O calculation section 104 ₂ concentration in the intake air is calculated.

The transient correction coefficient calculation section 106 calculates a transient correction coefficient for correcting the increase or decrease in the soot discharge amount at a time of transient with respect to the value (the basic soot discharge amount) at a time when the engine is in a steady state with which A/F ratio calculated in the arithmetic section 111 and the O ₂ concentration in intake air calculated in the arithmetic section 113 as input values. 6 14 is a graph showing an example of a map that sets a transient correction coefficient based on the A/F ratio and the O ₂ concentration in intake air. Here, for example, the transition correction coefficient is matched to the in 6 map shown is calculated. In addition, the specific heat correction coefficient calculation section 107 calculates a specific heat correction coefficient by receiving the input of the specific heat correction value calculated in the humidity correction section 160 . Note that a function of the specific heat correction coefficient calculating section 107 will be described later in detail.

In the arithmetic section 114, a soot discharge amount after transient correction is calculated by multiplying the base soot discharge amount calculated in the basic soot map 101 by the transient correction coefficient calculated in the transient correction coefficient calculating section 106. More specifically, by using the transient correction coefficient based on the A/F ratio and the O ₂ concentration ratio in the intake air with the base A/F and the base O ₂ concentration in the intake air serving as references, respectively, the A soot discharge amount is calculated taking into account influences of the transient air-fuel ratio and the change in the O ₂ concentration in the intake air, using the basic soot discharge amount as a basis.

In the arithmetic section 115, the discharge amount of soot after transient correction calculated in the arithmetic section 114 is multiplied by the specific heat correction coefficient calculated in the specific heat correction coefficient calculation section 107. In the environmental calculation section 108, correction for reflecting environmental conditions such as a cooling water temperature and an atmospheric pressure in the discharge amount of soot is performed, and the final discharge amount of soot is calculated.

(moisture correction for soot discharge amount)

Next, a humidity correction function included by the humidity correction section 160 will be described in detail. The exhaust amount of soot discharged from the cylinder changes according to the humidity of the intake air drawn into the cylinder. Two causes are cited as the main causes of the change in the amount of PM discharge due to humidity, namely, a change in the concentration of O ₂ in intake air, which is a concentration of oxygen contained in the intake air sucked into the cylinder, and a change in the specific heat of the intake air intake air. 7 14 is a graph showing the soot discharge amount with respect to the O ₂ concentration in intake air and the equivalent ratio. As in 7 As shown, a soot discharge amount (g/g) per gram of fuel has a sensitivity to changes in the O ₂ concentration in the intake air and the equivalence ratio. Meanwhile, it is known that the discharge amount of soot has no particular sensitivity to a change in specific heat. Therefore, in a range where the sensitivity of the soot discharge amount to the change in the O ₂ concentration in the intake air is large, the change in the O ₂ concentration in the intake air is dominant with respect to the change in the soot discharge amount, and the influence of the change the relative heat is comparatively low. In relation to this, the discharge amount of soot hardly changes in a range where the sensitivity of the discharge amount of soot to the change in the O ₂ concentration in intake air is low even if the O ₂ concentration in intake air changes due to a change in humidity. In such a range, the change in specific heat with respect to the change in the discharge amount of soot is dominant, and the influence of the change in O ₂ concentration in the intake air is comparatively small.

As a method for correcting the influence of humidity on the soot discharge amount, it is conceivable to calculate the change in the soot discharge amount with respect to the change in operating conditions such as the O ₂ concentration in intake air, the specific heat and the equivalence ratio using a function, for example , a multi-dimensional map or the like. However, such high-precision calculation increases a calculation load. In addition, the influence of humidity is redundantly corrected when the humidity correction of the O ₂ concentration in the intake air and the humidity correction of the specific heat are performed at the same time, because the specific heat also changes when the O ₂ concentration in the intake air changes, and erroneous correction is likely to be performed as a result. Consequently, an estimation accuracy of the soot discharge amount can be improved while the calculation load is reduced if correction can be made by selecting a parameter that is more dominant in the sensitivity of the soot discharge amount.

Therefore, in the soot discharge amount estimation control of the present embodiment, the FIG 7 the operating range shown, which is determined by the O ₂ concentration in the intake air and the specific heat, is divided into a range A in which the sensitivity of the soot discharge amount to the change in the O ₂ concentration in the intake air or the specific heat is high, and a region B in which the sensitivity of the discharge amount of soot to the change in the O ₂ concentration in the intake air or the specific heat is low. In a case where the current operation area belongs to the area A, the humidity correction section 160 corrects the influence of humidity on the O ₂ concentration in the intake air and restricts the specific heat correction. In addition, the humidity correction section 160 corrects the influence of humidity on the specific heat when the current operating range belongs to the range B, and restricts the correction of the O ₂ concentration in the intake air. After such control, in the soot discharge amount estimation control, an object for which the influence of humidity is corrected can be switched to the object that is more dominant with respect to the sensitivity of the soot discharge amount, and therefore the estimation accuracy of the soot discharge amount can be improved while reducing the computational load is restricted. In addition, the specific heat also changes when the O ₂ concentration in the intake air changes. In the soot discharge amount estimation control of the present embodiment, the object for which the influence of humidity is corrected can be switched to the object that is more dominant with respect to the sensitivity of the soot discharge amount, and therefore the influence of humidity can be redundantly corrected.

Next, a specific flow of the humidity correction process executed in the humidity correction section 160 will be described with reference to a flowchart. 8th FIG. 14 is a flowchart showing a routine of the humidity correction process executed in the humidity correction section 160. FIG. The humidity correction section 160 includes a function of calculating the O ₂ concentration value in the intake air and a function of calculating the specific heat correction value. 9 Fig. 12 is a control block diagram showing functional blocks for calculating the correction value for the O ₂ concentration in the intake air is extracted from functions included in the humidity correction section 160 . In addition 10 FIG. 14 is a control block diagram that extracts functional blocks for calculating the specific heat correction value from the functions included in the humidity correction section 160. FIG. Below are details of the controls included in an in 8th program shown is executed, also with reference to 9 and 10 suitably described.

In step S1 as in 8th Shown are the intake air amount “Ga” and the absolute humidity “AH” measured by the air flow meter 54 equipped with the humidity sensor, the actual O ₂ concentration “D” in the intake air calculated in the actual O ₂ concentration in the intake air, an equivalence ratio “φ” obtained from the current A/F calculated in the current A/F calculation section 103, and the EGR rate “EGR” calculated in the EGR rate calculation section 152 is read into the humidity correction section 160 . In the next step S2, it is determined whether the operating range, which is set based on the O ₂ concentration in the intake air and the equivalence ratio from the current operating conditions, at in 7 shown area A belongs. When it is determined as a result that the current operating conditions belong to the area A, it is determined that the humidity correction for the O ₂ concentration in the intake air should be performed, and the flow advances to the next step S3. When it is determined that the current operating conditions belong to the region B, it is determined that humidity correction for specific heat should be performed, and the flow advances to the next step S4.

In step S3, the O ₂ concentration value for the intake air is calculated. More precisely, a calculation is performed here by the in 9 functional blocks shown are executed from the functions included in the humidity correction section 160 . In the 9 The functional _blocks shown in _FIG O ₂ concentration built up in the intake air.

The dry air amount calculation section 121 calculates a dry air amount “AirD” [g/s] using Equation (6) below, where the intake air amount “Ga” and the absolute humidity “AH” measured by the air flow meter 54 associated with the humidity sensor is used as input values.
[Equation 6] $$Ai\mathrm{right}D=\frac{Ga}{\left(1+AH\right)}$$

The dry intake air O ₂ concentration calculation section 122 calculates a dry intake air O ₂ concentration “O2inD” using equation (7) below, where the dry air amount “AirD” calculated in the dry air amount calculation section 121 is calculated, the cylinder gas amount “Gcyl” taken in by any known method and the excess air rate “λ” obtained from the actual A/F are used as input values.
[Equation 7] $$\begin{array}{l}O2inD=23.2\left(1-\frac{Ai\mathrm{right}DBasis-EGR-Rate}{\lambda }\right)\\ \text{AirD base}-\text{EGR}-\text{rate}=\frac{\left(Gcyl-Ai\mathrm{right}D\right)}{Gcyl}\end{array}$$

In addition, the basic intake air O ₂ concentration map 123 calculates a basic intake air O ₂ concentration “O2inbse”, which is a basic value (that is, a value in a steady state) of the O ₂ concentration in of the intake air is in the current operating range (that is, the operating range defined by the fuel injection amount “Q” and the engine speed “Ne”, the engine speed “Ne” detected using the speed sensor 52 and the commanded fuel injection amount “ Q” of the fuel injection valve 8 can be used as arguments.

The intake air O _{2 concentration correction value calculation section 124 calculates the correction value of the intake air O 2 concentration} , which is the ratio of the O ₂ concentration ration in the dry intake air "O2inD" to the base O ₂ concentration in the intake air "O2inbse" is defined by using equation (8) below, where the O ₂ concentration in the dry intake air "O2inD" and the base O ₂ concentration in the intake air "O2inbse" can be used as input values.
[Equation 8] $$KO\mathrm{right}\mathrm{right}ekt\mathrm{and}\mathrm{right}we\mathrm{right}t\mathrm{i.e}e\mathrm{<figure-callout\; id="2"\; label="right\; O"\; filenames="DE102016203333B4\_0016.png,DE102016203333B4\_0021.png"\; state="\{\{state\}\}">right</figure-callout>}{O}_{}{}_2-KOn\mathrm{e.g}ent\mathrm{right}atiOnin\mathrm{i.e}e\mathrm{right}Ansa\mathrm{and}Gl\mathrm{and}ft=\frac{O2inD}{O2inbse}$$

When it is determined in step S2 described above that the current operation area is the area A and the process in step S3 described above is executed, the flow advances to step S5 thereafter. In step S5, the intake air O _{2 concentration correction value (O2inD/O2inbse) calculated in step S3 is reflected in the intake air O 2 concentration} correction value read in the exhaust gas estimation model, and an invalid value is set in the The specific heat correction value that is input to the emission estimation model 100 is shown. In the arithmetic section 112 of the emission estimation model 100, the current O ₂ concentration in the intake air is corrected using the read-in correction quantity for the O ₂ concentration in the intake air (O2inD/O2inbse). Meanwhile, in the specific heat correction coefficient calculation section 107 of the emission estimation model 100, a constant “1” is output as a proportion correction coefficient when the input of the invalid value is received as the specific heat correction value. In this case, the discharge amount of soot is multiplied by the proportion correction coefficient “1” in the arithmetic section 115, and therefore no specific heat correction is performed for the discharge amount of soot.

In addition, the specific heat correction value is calculated in step S4. Here, more specifically, a calculation by the in 10 functional blocks shown are executed from the functions included in the humidity correction section 160 . In the 10 The functional blocks shown in FIG specific heat and a specific heat correction value calculation section 136 .

The wet intake air molecular weight calculation section 131 calculates a wet intake air molecular weight “Mair_w” using Equation (9) below, where the intake air “Ga” and the absolute humidity “AH” measured by the air flow meter 54 associated with equipped with the humidity sensor can be used as input values.
[Equation 9] $$\begin{array}{l}Mai\mathrm{right}\_w=\frac{Ai\mathrm{right}D}{28.8}+\frac{Wasse\mathrm{right}}{18}\\ Ai\mathrm{right}D=\frac{Ga}{\left(1+AH\right)}\\ Wasse\mathrm{right}=\frac{Ai\mathrm{right}D}{1000\times AH}\end{array}$$

The wet intake air specific heat calculation section 132 calculates the wet intake air specific heat “Cvair_w” using Equation (10) below, where the wet intake air molecular weight “Mair_w” is calculated in the wet intake air molecular weight calculation section 131 the specific heat "Cvair_d" of the dry air and the specific heat "Cvw" are used as input values.
[Equation 10] $$Cvai\mathrm{right}\_w=\frac{\raisebox{1ex}{$Ai\mathrm{right}D$}\!\left/ \!\raisebox{-1ex}{$28.8$}\right.}{Mai\mathrm{right}\_w}\times Cvai\mathrm{right}\_\mathrm{i.e}+\frac{\raisebox{1ex}{$Wasse\mathrm{right}$}\!\left/ \!\raisebox{-1ex}{$18$}\right.}{Mai\mathrm{right}\_w}\times Cvw$$

$$Megr=\frac{\left(Gcyl-Ga\right)}{44}$$

In addition, the intake gas molecular weight calculation section 133 calculates a molecular weight “Mgas” of an intake gas, which is a sum of the wet intake air and the EGR gas, using Equation (11) below, where the molecular weight “Mair_w” is the wet intake air calculated in the wet intake air molecular weight calculation section 131 and a molecular weight “Megr” of the EGR gas are used as input values.
[Equation 11] $$MGas=Mai\mathrm{right}\_w+MeG\mathrm{right}$$

$$MeG\mathrm{right}=\frac{\left(Gcyl-Ga\right)}{44}$$

The next intake gas specific heat calculation section 134 calculates the intake gas specific heat “Cvgas” using Equation (12) below with the wet intake air specific heat “Cvair_w”, the wet intake air molecular weight “Mair_w”, the specific heat “Cvegr” of EGR gas and molecular weight “Mgas” of intake gas as input values.
[Equation 12] $$CvGas=\frac{Mai\mathrm{right}\_w}{MGas}\times Cvai\mathrm{right}\_\mathrm{i.e}+\frac{MeG\mathrm{right}}{MGas}\times CveG\mathrm{right}$$

The base specific heat map 135 calculates the base specific heat of intake gas “Cvgasbse”, which is a base value (a steady-state value) of the specific heat of intake gas in the present operating range (that is, the operating range defined by the fuel injection amount “Q”). and the engine speed “Ne” is defined) with the engine speed “Ne” detected using the speed sensor 52 and the commanded fuel injection amount “Q” of the fuel injection valve 8 as arguments. 11 14 is a graph showing an example of a map that sets a relationship of the specific heat of the basic intake gas with respect to the engine speed and the commanded fuel injection amount. In the basic map 135 for the specific heat, for example, the in 11 is stored, and the specific heat of the basic intake gas with respect to the engine speed and the commanded fuel injection amount that are read in is calculated using this map.

The specific heat correction value calculation section 136 calculates a specific heat correction value defined as a ratio of the intake gas specific heat “Cvgas” to the intake gas base specific heat “Cvbse”, using the following equation (13), where the specific heat "Cvgas" of the intake gas and the specific heat "Cvgasbse" of the intake gas are used as input values.
[Equation 13] $$Spe\mathrm{e.g}ifiscHe\mathrm{right}W\ddot{a}\mathrm{right}mekO\mathrm{right}\mathrm{right}ekt\mathrm{and}\mathrm{right}we\mathrm{right}t=\frac{CvGas}{CvGasbse}$$

When it is determined in step S2 described above that the current operation area is not the A area (that is, it is the B area) and the flow of step S4 is executed as described above, the flow then advances to step S6. In step S6, the specific heat correction value (Cvgas/Cvbse) calculated in step S4 is reflected in the specific heat correction value read into the emission estimation model 100, and the constant "1" is set in the correction value for the O ₂ concentration in the Intake air that is fed into the emissions estimation model 100 is represented. In the specific heat correction coefficient calculation section 107 of the emission estimation model 100, the specific heat correction coefficient is calculated using the read specific heat correction value (Cvgas/Cvbse). 12 14 is a diagram showing an example of a heat specific correction value map defining a relationship of heat specific correction coefficient to heat specific correction value. In the specific heat correction coefficient calculation section 107, for example, the specific heat correction coefficient appropriate to the read specific heat correction value is calculated using the in 12 calculated from the map shown for the specific heat correction value. The calculated specific heat correction coefficient is read into the arithmetic section 115 . In the arithmetic section 115, the value obtained by multiplying the discharge amount of soot after transient correction by the specific heat correction coefficient is output as the discharge amount of soot after being subjected to specific heat correction. Meanwhile, the arithmetic section 112 the constant "1" is read as the correction value of the O ₂ concentration in the intake air. In this case, in the arithmetic section 112, the current O ₂ concentration value in intake air is multiplied by the constant “1”, and therefore no O ₂ concentration correction in intake air is performed for the current O ₂ concentration in intake air.

As discussed above, according to the emission estimation model 100 of the present embodiment, the main cause of the change in the soot discharge amount is determined by the influence of humidity and correction can be made for the main thing in the estimation control of the soot discharge amount, and therefore the estimation accuracy of the soot discharge amount can be improved while the computing load is limited.

Incidentally, the present invention is not limited to the embodiment explained above, and can be carried out while being modified in various ways within the range without departing from the gist of the present invention. For example, the present invention can be carried out by being modified as follows.

In the first embodiment explained above, the absolute humidity and the intake air amount are detected using the airflow meter 54 equipped with the humidity sensor, but a structure may be used in which the humidity sensor is provided independently of the airflow meter. In addition, the humidity meter is not limited to the humidity meter that detects absolute humidity, but a humidity sensor that detects relative humidity can be used. This also applies to a second embodiment described later.

In the first embodiment explained above, the emission estimation model 100 corresponds to an “emission estimation device” of the first invention described above. The soot discharge amount corresponds to an “emission discharge amount” of the first invention described above. The air flow meter 54 equipped with the humidity sensor corresponds to the “humidity detector” of the first invention described above. The area A corresponds to a “first operation area” of the first invention described above. The area B corresponds to a “second operation area” of the first invention described above. The humidity correction section 160 and the arithmetic section 112 correspond to “correction means for O ₂ concentration in intake air” of the first invention described above. The humidity correcting section 160, the specific heat correction coefficient calculating section 107, and the arithmetic section 115 correspond to the “specific heat correcting means” of the first invention described above. Also, in the first embodiment explained above, the ECU 50 executes the processes in steps S2, S3 and S5 or steps S2, S4 and S6 as described above, thereby realizing “emission discharge amount estimating means” in the first invention described above.

In addition, the discharge amount of soot corresponds to “amount of discharge of soot” in the second invention described above.

In addition, the basic soot map 101 corresponds to the above-described first embodiment of the “basic soot discharge amount calculation means” in the third invention described above. The basic A/F calculation section 102 corresponds to “basic air/fuel ratio calculation means” of the third invention described above. The basic intake air O _{2 concentration calculation section 104 corresponds to the “basic intake air O 2 concentration} calculation means” of the third invention described above. The current A/F calculation section 103 corresponds to “estimated air-fuel ratio calculation means” of the third invention described above. The transition correction coefficient calculation section 106 and the arithmetic section 114 correspond to the “transition correction means” of the third invention described above.

Second embodiment

[Feature of the second embodiment]

Next, the second embodiment of the present invention will be described. In the first embodiment explained above, the function is described among the functions included in the emission estimation model 100, which estimates the emission amount of soot with high precision, by performing moisture correction. In the present second embodiment, one of the estimation functions included in the emission estimation model 100 that estimates a discharge amount of NOx discharged from the cylinder by performing humidity correction with high precision will be described. Note that the NOx discharge amount used in the explanation below indicates a NOx amount (g/g) discharged from the cylinder per gram of fuel.

(humidity correction for NOx discharge amount)

The amount of NOx discharged from the cylinder changes according to the humidity in the intake air drawn into the cylinder. This is similar to the soot discharge amount explained above, and it is similar to the soot discharge amount explained above that the main causes thereof are the change in the O ₂ concentration in intake air, which is an oxygen concentration contained in the intake air sucked into the cylinder. and the change in specific heat of intake air. However, the discharge amount of soot has the sensitivity distribution in the operating range expressed by the O ₂ concentration in intake air and the equivalence ratio, while the discharge amount of NOx has a predetermined sensitivity distribution only by the degree of O ₂ concentration in intake air.

13 14 is a graph showing a relationship of the NOx discharge amount with respect to the O ₂ concentration in intake air. As in 13 1, a sensitivity of the NOx discharge amount becomes larger as the O ₂ concentration in the intake air becomes higher. On the other hand, it is known that the NOx discharge amount changes with respect to the change in specific heat, but does not have such a marked sensitivity as the sensitivity to the change in intake air concentration. Consequently, in a region where the sensitivity of the NOx discharge amount with respect to the change in O ₂ concentration in intake air is large, the change in O ₂ concentration in intake air dominates over the change in NOx discharge amount, and the The influence of the change in specific heat is comparatively small. In this regard, even if the O ₂ concentration in intake air changes by a change in humidity, the NOx discharge amount hardly changes in a range where the sensitivity of the NOx discharge amount with respect to the change in O ₂ concentration in the intake air is small. In such a range, the change in specific heat is dominant to the change in NOx discharge amount, and the influence of the change in O ₂ concentration in intake air is comparatively small. Consequently, an estimation precision of the NOx discharge amount can be improved while reducing a calculation load similarly to the case of the soot discharge amount if correction can be made by selecting a parameter that is more dominant to the sensitivity of the NOx discharge amount.

Therefore, in the NOx discharge amount estimation control of the present embodiment, an operation range as shown in FIG 13 shown, which is determined by the O ₂ concentration in the intake air, is divided into an area A in which the sensitivity of the NOx discharge amount to the change in the O ₂ concentration in the intake air is high, and an area B in which the sensitivity of the NOx discharge amount to the change in the O ₂ concentration in the intake air is low. More specifically, the range where the O ₂ concentration in the intake air is greater than a predetermined concentration is referred to as the range A, and the range where the O ₂ concentration in the intake air is equal to or less than is the predetermined concentration is referred to as the B region. Note that the predetermined concentration is set as a concentration at which the amount of change in the NOx concentration with respect to the O ₂ concentration in the intake air becomes a predetermined value indicating high sensitivity, for example. When the current operation area belongs to the area A, the humidity correction section 160 corrects the influence of humidity on the O ₂ concentration in the intake air and restricts the correction for the specific heat. In addition, the humidity correction section 160 corrects the influence of humidity on the specific heat and limits the correction for the O ₂ concentration in the intake air when the current operating range belongs to the B range. After such control, in the NOx discharge amount estimation control, the object for which the influence of humidity is corrected changes to an object that is more dominant for the sensitivity of the NOx discharge amount, and therefore the estimation precision of the NOx discharge amount can be improved while the computing load is reduced. In addition, the specific heat also changes when the O ₂ concentration in the intake air changes. In the NOx discharge amount estimation control of the present embodiment, the object for which the influence of humidity is corrected changes to the object that is more dominant in the sensitivity of the NOx discharge amount, and therefore the influence of humidity can be redundantly corrected. Notice that specific flows of the humidity correction process executed in the humidity correction section 160, except that the map in FIG 13 instead of the map in 7 is used are similar to the operations in the first embodiment explained above, and therefore an explanation thereof is omitted.

(NOx discharge amount estimation control)

The emission estimation model 100 of the present embodiment includes a function of estimating the discharge amount of NOx discharged from the cylinder during operation. 14 14 is a control block diagram that extracts functional blocks for estimating the discharge amount of in-cylinder NOx from estimation functions included in the emission estimation model 100. FIG. A model structure for estimating the NOx discharge amount will be explained below with reference to FIG 14 precisely described.

This in 14 The emission estimation model 100 shown in _FIG and arithmetic sections 221 and 222.

The intake air O ₂ concentration calculation section 211 before correction performs a calculation similar to those of the current A/F calculation section 103 and the current intake air O ₂ concentration calculation section 105 described above. and calculates the O ₂ concentration in intake air before correction, which is the current O ₂ concentration in intake air before correction. The arithmetic section 221 calculates the corrected intake air O ₂ concentration by multiplying the intake air O ₂ concentration before correction, which is calculated in the intake air O ₂ concentration calculation section 211, by the correction value for the O ₂ - Concentration in the intake air calculated in the humidity correction section 160. The average injection timing calculation section 212 calculates an average injection timing in which injection timings and injection amounts of all effective injections are reflected using a known method.

The corrected O ₂ concentration in the intake air calculated in the arithmetic section 221 and the average injection timing calculated in the average injection timing calculation section 212, the injection amount and the engine speed are read in the NOx discharge amount calculation section 213. The NOx discharge amount calculating section 213 calculates the NOx discharge amount based on Equation (14) below, which is exponentiated by corrected O ₂ concentration in intake air exponentiated, average injection time exponentiated, average injection timing exponentiated the injection quantity and a potentiation of the engine speed. Note that the exponents A, B, C, D, and E in Equation (14) below are set to match the model and characteristics of the machine.
[Equation 14] $$\begin{array}{l}NOx-AbGabemenGe=expA\times \left(kO\mathrm{right}\mathrm{right}iGie\mathrm{right}\mathrm{<figure-callout\; id="2"\; label="t\; e\; O"\; filenames="DE102016203333B4\_0016.png,DE102016203333B4\_0021.png"\; state="\{\{state\}\}">t</figure-callout>}e{O}_{}{}_2-KOn\mathrm{e.g}ent\mathrm{right}atiOnin\mathrm{i.e}e\mathrm{right}Ansa\mathrm{and}Gl\mathrm{and}ft\right)B\times (mitt-\\ le\mathrm{right}eEinsp\mathrm{right}it\mathrm{e.g}\mathrm{i.e}a\mathrm{and}e\mathrm{right})C\times \left(Einsp\mathrm{right}it\mathrm{e.g}menGe\right)D\times \left(MascHinen\mathrm{i.e}\mathrm{right}eH\mathrm{e.g}aHl\right)E\end{array}$$

The specific heat correction coefficient calculation section 214 calculates the specific heat correction coefficient by performing a calculation similar to that of the specific heat correction coefficient calculation section 107 explained above. In the arithmetic section 222 , the NOx discharge amount calculated in the NOx discharge amount calculation section 213 is multiplied by the specific heat correction coefficient calculated in the specific heat correction coefficient calculation section 214 . This calculates the final NOx discharge amount.

As explained above, according to the emission estimation model 100 of the present embodiment, the main cause of the change in the NOx discharge amount is determined by the influence of humidity, and correction of the main cause can be employed in the NOx discharge amount estimation control. Thereby, the estimation accuracy of the NOx discharge amount can be improved while the calculation load is restrained.

In the second embodiment explained above, the emission estimation model 100 corresponds to the “emission estimation device” of the first invention explained above. The NOx discharge amount corresponds to the “emission discharge amount” of the first invention described above. The air flow meter 54 equipped with the humidity sensor corresponds to the “absolute humidity detection means” of the first invention described above. The area A corresponds to the “first operation area” of the first invention described above. The area B corresponds to the “second operation area” of the first invention described above. The humidity correction section 160 and the arithmetic section 221 correspond to the “means for correcting the O ₂ concentration in intake air” of the first invention described above. The humidity correction section 160, the specific heat correction coefficient calculation section 214, and the arithmetic section 222 correspond to the “specific correction means” of the first invention described above. Also, in the second embodiment explained above, the ECU 50 performs the processes in steps S2, S3 and S5 or steps S2, S4 and S6 as described above, thereby realizing the “emission discharge amount estimating means” in the first invention described above is.

In addition, the NOx discharge amount in the above second embodiment corresponds to the “NOx discharge amount” of the fifth invention described above.

In addition, the intake air O ₂ concentration before correction calculation section 211 corresponds to “intake air O ₂ concentration estimated calculation means” of the sixth invention described above, and the NOx discharge amount calculation section 213 corresponds to “calculation means for the basic NOx discharge amount” of the sixth invention described above.

Claims (7)

Emission estimating apparatus for an internal combustion engine, comprising: an emission discharge amount estimating means for estimating an emission discharge amount of either NOx or soot discharged from a cylinder of the internal combustion engine based on operating conditions of the internal combustion engine, the estimating means for the An emission discharge amount comprising: humidity detecting means (50) for detecting a humidity of fresh air drawn into the internal combustion engine, correcting means (160, 112; 160, 221) for O ₂ concentration in intake air to make a correction of the O ₂ concentration in the intake air correcting a change in the emission discharge amount due to a change in an O ₂ concentration in the intake air changing in accordance with an absolute humidity, the O ₂ concentration in the intake air having a con concentration of oxygen contained in a gas introduced into the cylinder and means (107, 115; 214, 222) to perform a specific heat correction which corrects a change in the emission discharge amount due to the change in the specific heat of the gas sucked into the cylinder which changes in accordance with an absolute humidity, and the emission discharge amount estimating means thereto is constructed to perform the correction of the O ₂ concentration in the intake air and to limit the correction of the specific heat when a current operating area belongs to a first operating area in which an amount of change in the emission output amount in an operating area calculated using the O ₂ - concentration in the intake air is comparatively large, and performs the correction due to the specific heat and restricts the correction due to the O ₂ concentration in the intake air when the current operating range belongs to a second operating range in which the amount of change in the emission output me is relatively small against the change in the O ₂ concentration in the intake air in an operating range set using the O ₂ concentration in the intake air. Emission estimating apparatus for an internal combustion engine claim 1 , wherein the emission discharge amount is a soot discharge amount that is an amount of soot discharged from the cylinder, and in an operating range set using the O ₂ concentration in intake air and an equivalence ratio, the first operating range is a range in which a change amount of the soot discharge amount is comparatively large with respect to a change in the O ₂ concentration in the intake air or the equivalence ratio, and the second operational region is a region in which the changes The magnitude of the soot discharge amount relative to the change in the O ₂ concentration in the intake air or the equivalence ratio is comparatively small. Emission estimating apparatus for an internal combustion engine claim 2 wherein the emission discharge amount estimating means comprises: base soot discharge amount calculating means (101) for calculating a base soot discharge amount, which is a soot discharge amount in a steady state, based on an engine speed of the internal combustion engine and a commanded fuel injection amount of the internal combustion engine, basic air/fuel ratio calculating means (102) for calculating a basic air/fuel ratio based on the engine speed and the commanded fuel injection amount, the air/fuel ratio is in the steady state, basic intake air O ₂ concentration calculating means (104) for calculating a basic intake air O ₂ concentration having an O ₂ - concentration in the intake air is in the steady state, a B estimated air/fuel ratio calculating means (103) for calculating an estimated air/fuel ratio, which is an estimated value of a current air/fuel ratio, based on an intake air amount and the commanded fuel injection amount, a calculating means (105) for an estimated intake air O ₂ concentration to calculate an estimated intake air O ₂ concentration, which is an estimated value of a current intake air O ₂ concentration, based on the intake air amount and the commanded fuel injection amount, and transition correction means (114) for calculating the basic soot discharge amount based on a ratio of the estimated air/fuel ratio and a ratio of the estimated O ₂ concentration in intake air to the base O ₂ concentration in intake air, and wherein the correction device (160, 112) for the O ₂ -K concentration in intake air is constructed to calculate an intake air O ₂ concentration correction value, which is a correction value in which a degree of change of the Oz concentration in intake air by absolute humidity is reflected, and the estimated O ₂ - Correct the intake air concentration using the correction value for the intake air O ₂ concentration. Emission estimating apparatus for an internal combustion engine claim 2 or 3 wherein the specific heat correction means (107, 115) is configured to calculate a specific heat correction coefficient which is a correction coefficient for reflecting an increase or decrease in specific heat in the soot discharge amount based on the absolute humidity, and correct the soot discharge amount using the specific heat correction coefficient. Emission estimating apparatus for an internal combustion engine claim 1 , wherein the emission discharge amount is a NOx discharge amount, which is an amount of NOx discharged from the cylinder, and in an operating range set using the O ₂ concentration in the intake air, the first operating range is a range in which the O ₂ concentration in the intake air is greater than a predetermined concentration, and the second operating range is a range in which the O ₂ concentration in the intake air is equal to or lower than the predetermined concentration. Emission estimating apparatus for an internal combustion engine claim 5 , wherein said emission discharge amount calculating means comprises: estimated intake air O ₂ concentration calculating means (211) for calculating an estimated intake air O ₂ concentration based on an intake air amount and a commanded fuel injection amount which is a is an estimated value of a current O ₂ concentration in intake air, and basic NOx discharge amount calculating means (213) for calculating the NOx discharge amount based on an engine speed of the internal combustion engine, the commanded fuel injection amount, an average injection timing and the estimated intake air O ₂ concentration, and wherein the intake air O ₂ concentration correcting means (160, 221) is configured to calculate an intake air O ₂ concentration correction value which is is a correction value in which a degree of change in the O ₂ -Ko ncentration in the intake air due to the absolute humidity such as and correct the estimated intake air O ₂ concentration using the intake air O ₂ concentration correction value. Emission estimating apparatus for an internal combustion engine claim 5 or 6 wherein the specific heat correcting means (214, 222) is configured to calculate a specific heat correction coefficient which is a correction coefficient for reflecting the increase or decrease of the specific heat in the NOx discharge amount on the basis of the absolute humidity , and correct the NOx discharge amount using the specific heat correction coefficient.

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