JP2016160855A - Emission estimation device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an emission estimation device for an internal combustion engine that can highly accurately estimate emissions of soot or emissions of NOx while suppressing a calculation load.SOLUTION: By using an on-board emission estimation model, emissions of soot or emissions of NOx are estimated. When an operating region identified by using an intake O2 concentration belongs to an A region in which sensitivity of emissions relative to a change in the intake O2 concentration is large, intake O2 concentration correction for correcting a change in the emissions caused by a change in the intake O2 concentration according to absolute humidity is made. When a current operating region does not belong to the A region, specific heat correction for correcting a change of the emissions caused by a change in specific heat of gas sucked into the cylinder according to the absolute humidity is made.SELECTED DRAWING: Figure 8

Description

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

  The gas discharged from the cylinder of the internal combustion engine includes emissions such as soot (NO) and NOx (nitrogen oxide). In recent internal combustion engines, in order to suppress the emission of these emissions, the amount of emission generated from the cylinder of the internal combustion engine is estimated by a model, and catalyst regeneration and emission purification are performed using the estimated emission generation amount. Catalyst OBD control such as catalyst control, etc., and failure diagnosis diagnosis of the catalyst is performed. In this case, it is important to improve the estimation accuracy of the emission estimation model in order to accurately perform these controls.

  A technique for estimating an emission generation amount such as Soot and NOx is disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-249991. More specifically, with this technology, the injection period is divided equally into three periods, the air-fuel mixture based on the injection in each period is handled individually, and the emission generated due to the combustion of each air-fuel mixture The quantity is estimated individually. Thereby, since the nonuniformity of the emission generation degree is taken into consideration, the total generation amount of these emissions can be estimated accurately.

JP 2006-294991 A JP 2006-343136 A JP 2001-82233 A JP 2014-137004 A

  By the way, the amount of soot discharged from the cylinder varies depending on the humidity of the intake air. In the above-described conventional technique, since the consideration of the influence of humidity is not made, there is a possibility that the soot discharge amount cannot be estimated with high accuracy. However, there are a plurality of main causes of the change in the soot discharge amount due to humidity, and which of the main factors is dominant depends on the operating conditions. For this reason, in order to correct the change in the soot discharge amount due to humidity, it is necessary to specify which of these main factors is dominant and then correct the specified main factor. This is effective in improving the estimation accuracy while suppressing the calculation load. Note that the same problem applies to changes in the amount of NOx discharged from the cylinder due to humidity.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can estimate the soot discharge amount or the NOx discharge amount with high accuracy while suppressing the calculation load. And

In order to achieve the above object, a first invention is an emission estimation device,
Emission emission amount estimation means for estimating one of NOx and Soot discharged from the cylinder of the internal combustion engine based on the operating conditions of the internal combustion engine,
The emission emission estimating means includes:
Humidity detecting means for detecting the humidity of fresh air sucked into the internal combustion engine;
Intake air O2 concentration correction means for performing intake air O2 concentration correction for correcting a change in the emission amount due to a change in the intake air O2 concentration, which is the concentration of oxygen contained in the gas sucked into the cylinder, according to absolute humidity; ,
Specific heat correction means for performing specific heat correction for correcting a change in the emission amount due to a change in specific heat of the gas sucked into the cylinder according to absolute humidity,
In the operation region specified using the intake O2 concentration, when the current operation region belongs to the first operation region in which the amount of change in the emission emission amount relative to the change in the intake O2 concentration is relatively large, When the intake O2 concentration correction is performed and the specific heat correction is limited, and the current operation region belongs to the second operation region in which the amount of change in the emission emission amount relative to the change in the intake O2 concentration is relatively small, A specific heat correction is performed and the intake O2 concentration correction is limited.

According to a second invention, in the first invention,
The emission emission amount is a soot emission amount that is an amount of soot discharged from the cylinder of the internal combustion engine,
In the operation region specified by using the intake O2 concentration and the equivalence ratio, the first operation region is a region in which the change amount of the Soot discharge amount with respect to the change of the intake O2 concentration or the equivalence ratio is relatively large. The second operation region is a region in which a change amount of the soot discharge amount with respect to a change in the intake O2 concentration or the equivalence ratio is relatively small.

According to a third invention, in the second invention,
The emission emission estimating means includes:
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 the engine rotation speed of the internal combustion engine and a command fuel injection amount;
Basic air-fuel ratio calculating means for calculating a basic air-fuel ratio that is an air-fuel ratio in a steady state of the internal combustion engine based on the engine rotational speed of the internal combustion engine and the command fuel injection amount;
Basic intake O2 concentration calculating means for calculating a basic intake O2 concentration, which is an intake O2 concentration in a steady state of the internal combustion engine, based on the engine rotational speed of the internal combustion engine and a command fuel injection amount;
Estimated air-fuel ratio calculating means for calculating an estimated air-fuel ratio, which is an estimated value of the current air-fuel ratio, based on the intake air amount and the command fuel injection amount;
An estimated intake O2 concentration calculating means for calculating an estimated intake O2 concentration that is an estimated value of the current intake O2 concentration based on the intake air amount and the command fuel injection amount;
Transient correction means for correcting the basic soot discharge amount based on the ratio of the estimated air-fuel ratio to the basic air-fuel ratio and the ratio of the estimated intake O2 concentration to the basic intake O2 concentration;
The intake O2 concentration correction means calculates an intake O2 concentration correction value that is a correction value reflecting the degree of change in the intake O2 concentration due to absolute humidity, and uses the intake O2 concentration correction value to calculate the estimated intake O2 concentration. It is characterized by being comprised so that it may correct | amend.

4th invention is 2nd or 3rd invention,
The specific heat correction means calculates a specific heat correction coefficient, which is a correction coefficient for reflecting the increase or decrease in the specific heat in the soot discharge amount based on the absolute humidity, and uses the specific heat correction coefficient to calculate the soot discharge amount. It is characterized by being comprised so that it may correct | amend.

According to a fifth invention, in the first invention,
The emission amount is a NOx emission amount that is an amount of NOx discharged from the cylinder of the internal combustion engine,
In the operation region specified using the intake O2 concentration, the first operation region is a region where the intake O2 concentration is larger than a predetermined concentration, and in the second operation region, the intake O2 concentration is less than a predetermined concentration. It is an area.

According to a sixth invention, in the fifth invention,
The emission emission estimating means includes:
An estimated intake O2 concentration calculating means for calculating an estimated intake O2 concentration that is an estimated value of the current intake O2 concentration based on the intake air amount and the command fuel injection amount;
Basic NOx emission amount calculating means for calculating the NOx emission amount based on the engine speed of the internal combustion engine, the command fuel injection amount, the average injection timing, and the estimated intake O2 concentration,
The intake O2 concentration correction means calculates an intake O2 concentration correction value that is a correction value reflecting the degree of change in the intake O2 concentration due to absolute humidity, and uses the intake O2 concentration correction value to calculate the estimated intake O2 concentration. It is characterized by being comprised so that it may correct | amend.

According to a seventh invention, in the fifth or sixth invention,
The specific heat correction means calculates a specific heat correction coefficient that is a correction coefficient for reflecting an increase or decrease in the specific heat in the NOx emission amount based on absolute humidity, and uses the specific heat correction coefficient to calculate the NOx emission amount. It is characterized by being comprised so that it may correct | amend.

  According to the first aspect of the present invention, when the emission emission amount that is the amount of NOx or soot discharged from the cylinder is estimated, the operating region specified using the intake O2 concentration is an emission corresponding to the change in the intake O2 concentration. When the change amount of the exhaust amount belongs to the first region, the influence of the emission amount due to the change of the intake O2 concentration due to the absolute humidity is corrected, and the change amount of the emission amount with respect to the change of the intake O2 concentration Is in the second operating region with a relatively small value, the influence of the emission amount due to the change in specific heat due to the absolute humidity is corrected. For this reason, according to the present invention, it is possible to identify the main cause of the change in the emission emission amount due to humidity and perform correction for the main cause. Therefore, it is possible to improve the estimation accuracy of the emission emission amount while suppressing the calculation load. It becomes possible.

  According to the second aspect of the present invention, when estimating the amount of soot discharged from the cylinder, the current operating region specified using the intake O2 concentration and the equivalence ratio is a change in the intake O2 concentration or the equivalence ratio. When the amount of change in the emission emission amount belongs to the first operating region where the amount of change in the emission amount is relatively large, the influence of the emission emission amount due to the change in the intake O2 concentration due to the humidity is corrected, and the emission to the change in the intake O2 concentration or equivalent ratio When the change amount of the emission amount belongs to the second operation region that is relatively small, the influence of the emission emission amount due to the change of the specific heat due to the humidity is corrected. For this reason, according to the present invention, it is possible to identify the main cause of the change in the soot discharge amount due to humidity and perform correction for the main cause. Therefore, it is possible to improve the estimation accuracy of the soot discharge amount while suppressing the calculation load. It becomes possible.

  According to the third aspect of the invention, a correction for reflecting the degree of change in the intake O2 concentration due to the absolute humidity is applied to the current estimated value of the intake O2 concentration used when estimating the soot discharge amount. For this reason, according to the present invention, in the operation region where the change in the soot discharge amount due to the change in the intake O2 concentration is dominant, it is possible to correct the intake O2 concentration, so the soot discharge while suppressing the calculation load. It becomes possible to increase the estimation accuracy of the quantity.

  According to the fourth aspect of the invention, when the soot discharge amount is estimated, the correction for reflecting the increase / decrease in the specific heat due to the absolute humidity in the soot discharge amount is performed. For this reason, according to the present invention, the change in specific heat can be reflected in the soot discharge amount in the operation region where the change in the soot discharge amount due to the change in the specific heat of the intake air is dominant. It is possible to improve the estimation accuracy of the soot discharge amount.

  According to the fifth aspect of the present invention, when estimating the NOx emission amount discharged from the cylinder, the current operation region specified using the intake O2 concentration is the first operation in which the intake O2 concentration is greater than the predetermined concentration. When it belongs to the region, the influence of the emission emission amount due to the change of the intake O2 concentration due to the humidity is corrected, and when it belongs to the second operation region where the intake O2 concentration becomes a predetermined concentration or less, the specific heat changes due to the humidity. The effect of emissions due to is corrected. For this reason, according to the present invention, it is possible to identify the main cause of the change in the NOx emission amount due to humidity and perform correction for the main factor. Therefore, it is possible to improve the estimation accuracy of the NOx emission amount while suppressing the calculation load. It becomes possible.

  According to the sixth aspect of the invention, the current intake air O2 concentration estimated value used when estimating the NOx emission amount is corrected to reflect the degree of change in the intake air O2 concentration due to absolute humidity. For this reason, according to the present invention, in the operation region where the change in the NOx emission amount due to the change in the intake O2 concentration is dominant, the intake O2 concentration can be corrected, so that the NOx emission is suppressed while suppressing the calculation load. It becomes possible to increase the estimation accuracy of the quantity.

  According to the seventh aspect of the invention, when estimating the NOx emission amount, correction is performed to reflect the increase or decrease in specific heat due to absolute humidity in the NOx emission amount. Therefore, according to the present invention, the change in specific heat can be reflected in the NOx emission amount in the operation region where the change in the NOx emission amount due to the change in the specific heat of the intake air is dominant. It is possible to improve the estimation accuracy of the NOx emission amount.

It is a figure which shows the structure of the engine system to which the control apparatus of Embodiment 1 of this invention is applied. It is the control block diagram which extracted the functional block for estimating an emission discharge | emission amount, and the functional block for performing catalyst control among the control functions with which ECU is provided. It is the control block diagram which extracted the functional block for estimating the Soot discharge amount discharged | emitted from the cylinder among the estimation functions with which an emission estimation model is provided. It is a figure which shows an example of the map which prescribed | regulated the relationship of the target fresh air quantity with respect to an engine speed and command fuel injection quantity. It is a figure which shows an example of the map which prescribed | regulated the relationship of the target EGR rate with respect to an engine speed and command fuel injection quantity. It is a figure which shows an example of the map which specifies a transient correction coefficient from A / F ratio and intake air O2 concentration ratio. It is a figure which shows the amount of soot discharge | emission with respect to intake O2 density | concentration and an equivalence ratio. It is a flowchart which shows the routine of the humidity correction operation | movement performed in a humidity correction part. It is the control block diagram which extracted the functional block for calculating an inhalation O2 density | concentration correction value among the functions with which a humidity correction part is provided. It is the control block diagram which extracted the functional block for calculating a specific heat correction value among the functions with which a humidity correction part is provided. It is a figure which shows an example of the map which prescribed | regulated the relationship of the base intake gas specific heat with respect to an engine speed and command fuel injection quantity. It is a figure which shows an example of the specific heat correction value map which prescribed | regulated the relationship of the specific heat correction coefficient with respect to a specific heat correction value. It is a figure which shows the relationship of NOx discharge | emission amount with respect to intake O2 density | concentration. It is the control block diagram which extracted the functional block for estimating the NOx discharge | emission amount discharged | emitted from the cylinder among the estimation functions with which an emission estimation model is provided.

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

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram showing a configuration of an engine system to which a control device according to Embodiment 1 of the present invention is applied. The internal combustion engine according to the present embodiment is a diesel engine with a turbocharger (hereinafter simply referred to as “engine”). The engine body 2 is provided with four cylinders in series, and a fuel injection valve 8 is provided for each cylinder. An intake manifold 4 and an exhaust manifold 6 are attached to the engine body 2. An intake passage 10 through which fresh air taken in from the air cleaner 20 flows is connected to the intake manifold 4. A turbocharger compressor 14 is attached to the intake passage 10. A diesel throttle 24 is provided downstream of the compressor 14 in the intake passage 10. An intercooler 22 is provided between the compressor 14 and the diesel throttle 24 in the intake passage 10. The exhaust manifold 6 is connected to an exhaust passage 12 for releasing the exhaust gas emitted from the engine body 2 into the atmosphere. A turbocharger turbine 16 is attached to the exhaust passage 12. The turbocharger is a variable displacement type, and the turbine 16 is provided with a variable nozzle 18. In the exhaust passage 12, an oxidation catalyst 25 for purifying exhaust gas, a DPF (Diesel Particulate Filter) 26, and SCRs (Selective Catalytic Reduction) 27 and 28 are provided downstream of the turbine 16.

  The engine according to the present embodiment includes an EGR device that recirculates exhaust gas from the exhaust system to the intake system. In the EGR device, a position downstream of the diesel throttle 24 in the intake passage 10 and the exhaust manifold 6 are connected by an EGR passage 30. An EGR valve 32 is provided in the EGR passage 30. An EGR cooler 34 is provided on the exhaust side of the EGR valve 32 in the EGR passage 30. The EGR passage 30 is provided with a bypass passage 36 that bypasses the EGR cooler 34. A bypass valve 38 that switches the direction in which the exhaust gas flows is provided at a location where the bypass passage 36 branched from the EGR passage 30 joins the EGR passage 30 again.

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

  The ECU 50 captures and processes a sensor signal provided in the engine system. Sensors are installed in various parts of the engine system. An air flow meter 54 with a humidity sensor for detecting the intake air amount “Ga” and the absolute humidity “AH” of the intake air is attached to the intake passage 10 downstream of the air cleaner 20. Further, there are a rotational speed sensor 52 for detecting the rotational speed of the crankshaft, an accelerator opening sensor 56 for outputting a signal corresponding to the opening degree of the accelerator pedal, a differential pressure sensor 58 for detecting the differential pressure across the DPF 26, and the like. It is attached. Further, in the exhaust passage 12, an A / F sensor for detecting the air-fuel ratio is disposed between the DPF 26 and the SCR 27, and a NOx sensor 62 and a PM sensor are disposed downstream of the SCR 28, respectively. The ECU 50 processes the signals of the acquired sensors and operates the actuators according to a predetermined control program. The actuator operated by the ECU 50 includes the variable nozzle 18, the fuel injection valve 8, the EGR valve 32, the diesel throttle 24, and the like. There are many actuators and sensors connected to the ECU 50 other than those shown in the figure, but the description thereof is omitted in this specification.

[Operation of Embodiment 1]
In the engine control executed by the ECU 50, the emission emission amount estimation is performed by estimating the emission amount (NOx and Soot) emitted from each cylinder during operation using a virtually built on-board estimation model. Control and catalyst control for performing catalyst regeneration, emission purification, failure diagnosis, and the like using the estimated emission amount are included. FIG. 2 is a control block diagram in which a functional block for estimating an emission emission amount and a functional block for performing catalyst control are extracted from among the control functions provided in the ECU 50. The emission estimation model 100 shown in this figure is a functional block in which the emission emission amount estimation control of this embodiment is performed. In the emission estimation model 100, model calculations are performed in response to input of operating conditions such as engine speed, fuel injection amount, intake air O2 concentration, specific heat, and air-fuel ratio, and soot and NOx emissions are estimated. . Further, the catalyst control block 300 shown in this figure is a 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. In the catalyst control block 300, failure diagnosis and urea addition control of the SCRs 27 and 28 are performed using the NOx emission amount estimated by the emission emission amount estimation control. In addition, since the method is already proposed in many well-known literatures about these catalyst control, the detailed description is abbreviate | omitted in this specification.

(Soot emission estimation control)
The emission estimation model 100 of the present embodiment includes a function for estimating the soot discharge amount (mg / s) per unit time discharged from the cylinder during operation. FIG. 3 is a control block diagram in which function blocks for estimating the amount of soot discharged from the cylinder are extracted from the estimation functions provided in the emission estimation model 100. Hereinafter, the model configuration for estimating the soot discharge amount will be described in detail with reference to FIG.

  The emission estimation model 100 shown in FIG. 3 includes a base soot map 101, a base A / F calculation unit 102, a current A / F calculation unit 103, a base intake O2 concentration calculation unit 104, a current intake O2 concentration calculation unit 105, and a transient correction coefficient. A calculation unit 106, a specific heat correction coefficient calculation unit 107, an environment correction unit 108, and calculation units 111, 112, 113, 114, and 115 are provided.

  The base soot map 101 uses the engine rotational speed “Ne” detected by the rotational speed sensor 52 and the command fuel injection amount “Q” of the fuel injection valve 8 as arguments, and the current operation region (that is, the fuel injection amount “ The base soot discharge amount, which is the basic value of the amount of soot discharged from the cylinder (that is, the value in the steady state) in the operating range defined by Q ”and engine speed“ Ne ”, is calculated.

  In the target fresh air amount map 150 provided in another module, the engine speed “Ne” and the command fuel injection amount “Q” are used as arguments, and the current operation region (that is, the fuel injection amount “Q” and the engine speed “ The target fresh air volume is calculated in the operation range defined by “Ne”. FIG. 4 is a diagram showing an example of a map that defines the relationship between the target engine speed and the target fresh air amount with respect to the command fuel injection amount. For example, the map shown in FIG. 4 is stored in the target fresh air amount map 150, and the target fresh air amount for the input engine speed and command fuel injection amount is calculated using this map.

  The base A / F calculation unit 102 uses the following equation (1) with the target fresh air amount calculated in the target fresh air amount map 150 as an input value, thereby calculating the current (that is, the base soot discharge amount). (B) A base A / F (basic air-fuel ratio) serving as a reference in the operation region is calculated. Note that the base A / F calculation unit 102 is configured to calculate a base A / F that serves as a reference in the current operation region using the engine speed “Ne” and the command fuel injection amount “Q” as arguments. May be.

  The current A / F calculation unit 103 uses the intake air amount “Ga” and the command fuel injection amount “Q” measured by the air flow meter 54 as input values, and the current A / F (current A / F) (Estimated air-fuel ratio) is calculated using the following equation (2). If the engine body 2 has deteriorated over time, the current A / F may deviate from the actual A / F. Therefore, the current A / F calculation unit 103 reflects the A / F learning value for eliminating the difference between the actual A / F detected by the air-fuel ratio sensor and the current A / F to the current A / F. Let

  In the target EGR rate map 151 provided in another module, the engine speed “Ne” and the command fuel injection amount “Q” are used as arguments, and the current operation region (that is, the fuel injection amount “Q” and the engine speed “Ne”). The target EGR rate that is a target in the “operating region defined by“) is calculated. The EGR rate is a value defined as the ratio of the EGR gas amount to the in-cylinder gas amount (sum of the fresh air amount and the EGR gas amount) filled in the cylinder. FIG. 5 is a diagram illustrating an example of a map that defines the relationship of the target EGR rate with respect to the engine speed and the command fuel injection amount. For example, the map shown in FIG. 5 is stored in the target fresh air amount map 150, and the target EGR rate with respect to the input engine speed and command fuel injection amount is calculated using this map.

  The base intake O2 concentration calculation unit 104 uses the target EGR rate calculated in the target EGR rate map 151 and the base λ as input values, and uses the following equation (3) to obtain the current (that is, base soot discharge amount). The base intake air O2 concentration (wt%), which is the basic value of the oxygen concentration in the intake air in the operation region (when calculating the), is calculated. The base λ is calculated by dividing the base A / F calculated by the base A / F calculation unit 102 by the theoretical air-fuel ratio. The base intake O2 concentration calculation unit 104 may be configured to calculate the base intake O2 concentration in the current operation region using the engine speed “Ne” and the command fuel injection amount “Q” as arguments. .

  The EGR rate calculation unit 152 provided in another module uses the intake air amount “Ga” measured by the air flow meter 54 and the in-cylinder gas amount “Gcyl” obtained by any known method as input values, and The EGR rate is calculated by using Equation (4).

  The current intake O2 concentration calculation unit 105 uses the following equation (5) with the current A / F calculated by the current A / F calculation unit and the EGR rate calculated by the EGR rate calculation unit 152 as input values: Then, the current intake O2 concentration “D”, which is an estimated value of the current intake O2 concentration, is calculated. The current λ is calculated by dividing the current A / F calculated by the current A / F calculation unit 103 by the theoretical air-fuel ratio.

  Further, the calculation unit 111 calculates an A / F ratio used as an input to the transient correction coefficient calculation unit 106. The A / F ratio is calculated as a ratio of the current A / F calculated by the current A / F calculation unit 103 to the base A / F calculated by the base A / F calculation unit 102.

  The humidity correction unit 160 provided in another module calculates an intake O2 concentration correction value for correcting the intake O2 concentration according to the humidity and a specific heat correction value for correcting the specific heat according to the humidity. Details of the function of the humidity correction unit 160 will be described later.

  In addition, the calculation unit 112 calculates the corrected intake O2 concentration by multiplying the current intake O2 concentration calculated by the current intake O2 concentration calculation unit 105 by the intake O2 concentration correction value calculated by the humidity correction unit 160. . In addition, the calculation unit 113 calculates the intake O2 concentration ratio used as an input to the transient correction coefficient calculation unit 106. The intake O2 concentration ratio is calculated as a ratio of the corrected intake O2 concentration calculated by the calculation unit 112 to the base intake O2 concentration calculated by the base intake O2 concentration calculation unit 104.

  The transient correction coefficient calculation unit 106 uses the A / F ratio calculated by the calculation unit 111 and the intake O2 concentration ratio calculated by the calculation unit 113 as input values (base soot discharge). A transient correction coefficient for correcting the increase / decrease in the soot discharge amount during transition with respect to the amount) is calculated. FIG. 6 is a diagram showing an example of a map for specifying a transient correction coefficient from the A / F ratio and the intake O2 concentration ratio. Here, for example, the transient correction coefficient is calculated according to the map shown in FIG. Further, the specific heat correction coefficient calculation unit 107 receives the input of the specific heat correction value calculated by the humidity correction unit 160 and calculates the specific heat correction coefficient. The function of the specific heat correction coefficient calculation unit 107 will be described in detail later.

  The arithmetic unit 114 calculates the soot discharge amount after the transient correction by multiplying the base soot discharge amount calculated in the base soot map 101 by the transient correction coefficient calculated in the transient correction coefficient calculation unit 106. More specifically, by using a transient correction coefficient based on the A / F ratio and the intake O2 concentration ratio based on the base A / F and the base intake O2 concentration, respectively, it is possible to make the transition based on the base Soot emission amount. It is possible to calculate the soot discharge amount in consideration of the influence of a change in the air-fuel ratio and intake O2 concentration.

  In the calculation unit 115, the soot discharge amount after the transient correction calculated in the calculation unit 114 is multiplied by the specific heat correction coefficient calculated in the specific heat correction coefficient calculation unit 107. The environment correction unit 108 performs correction for reflecting environmental conditions such as the cooling water temperature and the atmospheric pressure on the soot discharge amount, and calculates the final soot discharge amount.

(About soot discharge humidity correction)
Next, the humidity correction function provided in the humidity correction unit 160 will be described in detail. The soot discharge amount discharged from the cylinder changes according to the humidity of the intake air sucked into the cylinder. There are two main causes of the change in the soot discharge amount due to humidity: a change in the intake O2 concentration, which is the oxygen concentration contained in the intake air sucked into the cylinder, and a change in the specific heat of the intake air. FIG. 7 is a diagram showing the soot discharge amount with respect to the intake O2 concentration and the equivalence ratio. As shown in this figure, the soot discharge amount (g / g) per 1 g of fuel has sensitivity to changes in the intake O2 concentration and the equivalence ratio. On the other hand, it is known that the soot discharge amount does not have a particular sensitivity to changes in specific heat. For this reason, in the region where the sensitivity of the soot discharge amount is large with respect to the change in the intake O2 concentration, the change in the intake O2 concentration is dominant with respect to the change in the soot discharge amount, and the influence of the change in specific heat is relatively small. It will be a thing. On the other hand, in the region where the sensitivity of the soot discharge amount is small with respect to the change in the intake O2 concentration, the soot discharge amount hardly changes even if the intake O2 concentration changes due to the humidity change. In such a region, the change in specific heat is dominant with respect to the change in the soot discharge amount, and the influence of the change in the intake oxygen concentration is relatively small.

  As a method for correcting the influence of humidity on soot emissions, for example, the relationship of changes in soot emissions with changes in operating conditions such as intake O2 concentration, specific heat, and equivalence ratio is calculated using a function or a multidimensional map It is possible to do. However, such sophisticated calculations increase the calculation load. Further, since the specific heat also changes when the intake O2 concentration changes, if the humidity correction of the intake O2 concentration and the humidity correction of the specific heat are performed at the same time, the influence of the humidity is corrected, resulting in erroneous correction. For this reason, if a parameter more dominant with respect to the sensitivity of the soot discharge amount can be selected and corrected, it is possible to improve the estimation accuracy of the soot discharge amount while reducing the calculation load.

  Therefore, in the soot discharge amount estimation control according to the present embodiment, the operation region shown in FIG. 7 specified by the intake O2 concentration and the specific heat is an A region where the sensitivity of the soot discharge amount to the change of the intake O2 concentration or specific heat is high. And the B region where the sensitivity of the soot discharge amount to the change of the intake O2 concentration or the specific heat is low. When the current operation region belongs to the A region, the humidity correction unit 160 corrects the influence of the humidity on the intake O2 concentration and restricts the correction on the specific heat. Further, when the current operation region belongs to the B region, the humidity correction unit 160 corrects the influence of the humidity on the specific heat and limits the correction on the intake O2 concentration. According to such control, since the target for correcting the influence of humidity is switched to a more dominant target with respect to the sensitivity of the soot discharge amount in the soot discharge amount estimation control, the calculation load is suppressed. In addition, the estimation accuracy of the soot discharge amount can be increased. Further, when the intake O2 concentration changes, the specific heat also changes. In the soot discharge amount estimation control according to the present embodiment, the target for correcting the influence of humidity is switched to a target more dominant with respect to the sensitivity of the soot discharge amount. Can be done.

  Next, specific processing of the humidity correction operation executed in the humidity correction unit 160 will be described with reference to a flowchart. FIG. 8 is a flowchart showing a routine of humidity correction operation executed in the humidity correction unit 160. The humidity correction unit 160 includes a function for calculating the intake O2 concentration correction value and a function for calculating the specific heat correction value. FIG. 9 is a control block diagram in which functional blocks for calculating the intake air O2 concentration correction value are extracted from the functions provided in the humidity correction unit 160. FIG. 10 is a control block diagram in which functional blocks for calculating a specific heat correction value are extracted from the functions provided in the humidity correction unit 160. The details of the control executed in the routine shown in FIG. 8 will be described below with reference to FIGS. 9 and 10 as appropriate.

  In step S1 shown in FIG. 8, the intake air amount “Ga” and the absolute humidity “AH” measured by the air flow meter 54 with the humidity sensor, the current intake O2 concentration “D” calculated by the current intake O2 concentration calculation unit 105, The equivalent ratio “Φ” obtained from the current A / F calculated by the current A / F calculation unit 103 and the EGR rate “EGR” calculated by the EGR rate calculation unit 152 are input to the humidity correction unit 160. In the next step S2, it is determined whether or not the operating region specified from the intake O2 concentration and the equivalence ratio belongs to the A region shown in FIG. As a result, when it is determined that the current operating condition belongs to the A region, it is determined that humidity correction should be performed on the intake air O2 concentration, and the process proceeds to the next step S3. On the other hand, if it is determined that the current operating condition belongs to the B region, it is determined that humidity correction should be performed on the specific heat, and the process proceeds to the next step S4.

  In step S3, an intake air O2 concentration correction value is calculated. Here, more specifically, among the functions provided in the humidity correction unit 160, the calculation by the functional block shown in FIG. 9 is executed. The functional block shown in FIG. 9 includes a dry air amount calculation unit 121, a dry intake O2 concentration calculation unit 122, a base intake O2 concentration map 123, and an intake O2 concentration correction value calculation unit 124.

  The dry air amount calculation unit 121 receives the intake air amount “Ga” and the absolute humidity “AH” measured by the air flow meter 54 with a humidity sensor as input values, and uses the following equation (6) to obtain the dry air amount “ Calculate AirD ”[g / s].

  The dry intake O2 concentration calculation unit 122 is obtained from the dry air amount “AirD” calculated by the dry air amount calculation unit 121, the in-cylinder gas amount “Gcyl” acquired by any known method, and the current A / F. The dry air intake O2 concentration “O2inD” is calculated by using the following equation (7) with the excess air ratio “λ” as an input value.

  Further, the base intake O2 concentration map 123 uses the engine rotation speed “Ne” detected by the rotation speed sensor 52 and the command fuel injection amount “Q” of the fuel injection valve 8 as arguments, and the current operation region (that is, A base intake O2 concentration “O2inbse”, which is a basic value of the intake O2 concentration (that is, a value in a steady state) in an operation region defined by the fuel injection amount “Q” and the engine speed “Ne”) is calculated.

  The intake air O2 concentration correction value calculation unit 124 uses the dry air intake O2 concentration “O2inD” and the base air intake O2 concentration “O2inbse” as input values and uses the following equation (8) to obtain dry air intake for the base air intake O2 concentration “O2inbse”. An intake air O2 concentration correction value defined as a ratio of the O2 concentration “O2inD” is calculated.

  When it is determined in step S2 that the current operation region is the region A and the process of step S3 is executed, the process proceeds to step S5. In step S5, the intake O2 concentration correction value calculated in step S3 (O2inD / O2inbse) is reflected in the intake O2 concentration correction value input to the emission estimation model 100, and the specific heat input to the emission estimation model 100. The invalid value is reflected in the correction value. The calculation unit 112 of the emission estimation model 100 corrects the current intake O2 concentration using the input intake O2 concentration correction value (O2inD / O2inbse). On the other hand, the specific heat correction coefficient calculation unit 107 of the emission estimation model 100 receives an invalid value as a specific heat correction value and outputs a constant “1” as a proportional correction coefficient. In this case, the arithmetic unit 115 multiplies the soot discharge amount by the proportional correction coefficient “1”, so that the specific heat correction for the soot discharge amount is not performed.

  In step S4, a specific heat correction value is calculated. Here, in more detail, among the functions provided in the humidity correction unit 160, the calculation by the functional block shown in FIG. 10 is executed. The functional block shown in FIG. 10 includes an intake wet air molecular weight calculation unit 131, an intake wet air specific heat calculation unit 132, an intake gas molecular weight calculation unit 133, an intake gas specific heat calculation unit 134, a base specific heat map 135, and a specific heat correction value calculation unit 136. It is comprised by.

  The intake wet air molecular weight calculation unit 131 uses the following equation (9) with the intake air amount “Ga” and the absolute humidity “AH” measured by the air flow meter 54 with a humidity sensor as input values, and the intake wet air The molecular weight of “Mair_w” is calculated.

  The suction wet air specific heat calculation unit 132 uses the molecular weight “Mair_w”, the dry air specific heat “Cvair_d”, and the water specific heat “Cvw” calculated by the suction wet air molecular weight calculation unit 131 as input values, 10) is used to calculate the specific heat “Cvair_w” of the intake wet air.

  Further, the intake gas molecular weight calculation unit 133 uses the following equation (11) with the molecular weight “Mair_w” of the intake wet air and the molecular weight “Megr” of the EGR gas calculated by the intake wet air molecular weight calculation unit 131 as input values. Thus, the molecular weight “Mgas” of the intake gas, which is the sum of the intake humid air and the EGR gas, is calculated.

  The next intake gas specific heat calculating unit 134 uses the specific heat “Cvair_w” of the intake wet air, the molecular weight “Mair_w” of the intake wet air, the specific heat “Cvegr” of the EGR gas, and the molecular weight “Mgas” of the intake gas as input values. The specific heat “Cvgas” of the intake gas is calculated by using the equation (12).

  The base specific heat map 135 uses the engine rotational speed “Ne” detected by the rotational speed sensor 52 and the command fuel injection amount “Q” of the fuel injection valve 8 as arguments, and the current operation region (that is, the fuel injection amount “ The base intake gas specific heat “Cvgasbse”, which is the basic value of the specific heat of the intake gas (that is, the value in the steady state), is calculated in the operating range defined by “Q” and the engine speed “Ne”. FIG. 11 is a diagram illustrating an example of a map that defines the relationship between the engine intake speed and the base intake gas specific heat with respect to the command fuel injection amount. For example, the map shown in FIG. 11 is stored in the base specific heat map 135, and the base intake gas specific heat with respect to the input engine speed and command fuel injection amount is calculated using this map.

  The specific heat correction value calculation unit 136 uses the following equation (13) with the specific heat “Cvgas” of the intake gas and the specific heat of the base intake gas “Cvbse” as input values, and the specific heat of the intake gas with respect to the base intake gas specific heat “Cvbse” Calculate the specific heat correction value defined as the ratio of “Cvgas”.

  When it is determined in step S2 that the current operation area is not the A area (that is, the B area) and the process of step S4 is executed, the process proceeds 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 input to the emission estimation model 100, and the intake O2 concentration correction value input to the emission estimation model 100 is reflected. The constant “1” is reflected. The specific heat correction coefficient calculation unit 107 of the emission estimation model 100 calculates a specific heat correction coefficient using the input specific heat correction value (Cvgas / Cvbse). FIG. 12 is a diagram illustrating an example of a specific heat correction value map that defines the relationship between the specific heat correction coefficient and the specific heat correction value. In the specific heat correction coefficient calculation unit 107, for example, a specific heat correction coefficient corresponding to the input specific heat correction value is calculated using a specific heat correction value map shown in FIG. The calculated specific heat correction coefficient is input to the calculation unit 115. The calculation unit 115 outputs a value obtained by multiplying the soot discharge amount after the transient correction by the specific heat correction coefficient as the soot discharge amount after the specific heat correction. On the other hand, a constant “1” is input to the calculation unit 112 as the intake O2 concentration correction value. In this case, since the current intake O2 concentration is multiplied by a constant “1”, the calculation unit 112 does not perform the intake O2 concentration correction on the current intake O2 concentration.

  As described above, according to the emission estimation model 100 of the present embodiment, in the estimation control of the soot discharge amount, the main cause of the change in the soot discharge amount due to the influence of humidity can be specified and the main cause can be corrected. Therefore, it is possible to improve the estimation accuracy of the soot discharge amount while suppressing the calculation load.

  By the way, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the first embodiment described above, the humidity and the intake air amount are detected using the air flow meter 54 with a humidity sensor. However, the humidity sensor may be provided independently from the air flow meter. In addition, the humidity sensor is not limited to a humidity sensor that detects absolute humidity, and a humidity sensor that detects relative humidity is used. This also applies to a second embodiment described later.

  In the first embodiment described above, the emission estimation model 100 corresponds to the “emission estimation device” of the first invention, the soot emission corresponds to the “emission emission” of the first invention, and the humidity The sensor-equipped air flow meter 54 corresponds to the “humidity detecting means” of the first invention, the region A corresponds to the “first operating region” of the first invention, and the region B corresponds to the “humidity detecting means” of the first invention. The humidity correction unit 160 and the calculation unit 112 correspond to the “second operation region”, and correspond to the “intake O2 concentration correction unit” of the first invention, and the humidity correction unit 160, the specific heat correction coefficient calculation unit 107, and the calculation unit 115. Corresponds to the “specific heat correcting means” of the first invention. Further, in the first embodiment described above, the “emission emission estimation means” in the first aspect of the present invention is realized when the ECU 50 executes the processes of steps S2, S3 and S5 or steps S2, S4 and S6. Yes.

  Further, in the first embodiment described above, the soot discharge amount corresponds to the “soot discharge amount” of the second invention.

  In the first embodiment described above, the base soot map 101 corresponds to the “basic soot discharge amount calculation means” of the third invention, and the base A / F calculation unit 102 is the “basic empty map” of the third invention. The base intake O2 concentration calculation unit 104 corresponds to the “basic intake O2 concentration calculation unit” of the third invention, and the current A / F calculation unit 103 corresponds to the “estimation” of the third invention. The transient correction coefficient calculation unit 106 and the calculation unit 114 correspond to “transient correction unit” of the third aspect of the invention.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described. In the first embodiment described above, the function of estimating the soot discharge amount with high accuracy by performing humidity correction among the functions of the emission estimation model 100 has been described. In the second embodiment, among the estimation functions provided in the emission estimation model 100, a function for accurately estimating the NOx emission amount discharged from the cylinder by performing humidity correction will be described. Note that the NOx emission amount used in the following description indicates the NOx amount (g / g) exhausted from the cylinder per gram of fuel.

(Regarding humidity correction of NOx emissions)
The amount of NOx discharged from the cylinder changes according to the humidity of the intake air drawn into the cylinder. This is the same as the soot discharge amount described above, and the main reason is the change in the intake O2 concentration, which is the oxygen concentration contained in the intake air sucked into the cylinder, and the change in the specific heat of the intake air. is there. However, while the soot discharge amount has a sensitivity distribution in the operation region represented by the intake O2 concentration and the equivalence ratio, the NOx discharge amount has a predetermined sensitivity distribution only by the magnitude of the intake O2 concentration.

  FIG. 13 is a diagram showing the relationship of the NOx emission amount with respect to the intake O2 concentration. As shown in this figure, the sensitivity of the NOx emission amount increases as the intake O2 concentration increases. On the other hand, it is known that the NOx emission amount changes with a change in specific heat, but does not have a significant sensitivity as much as a sensitivity to a change in intake O2 concentration. For this reason, in the region where the sensitivity of the NOx emission amount is large with respect to the change in the intake O2 concentration, the change in the intake O2 concentration is dominant with respect to the change in the NOx emission amount, and the influence of the change in specific heat is relatively small. It will be a thing. On the other hand, in the region where the sensitivity of the NOx emission amount is small with respect to the change in the intake O2 concentration, the NOx emission amount hardly changes even if the intake O2 concentration changes due to the humidity change. In such a region, the change in specific heat is dominant with respect to the change in NOx emission, and the influence of the change in intake O2 concentration is relatively small. For this reason, as in the case of the soot discharge amount, if the parameter more dominant with respect to the sensitivity of the NOx discharge amount can be selected and corrected, the estimation accuracy of the NOx discharge amount can be improved while reducing the calculation load. It becomes possible.

  Therefore, in the NOx emission amount estimation control of the present embodiment, the operation region shown in FIG. 13 specified by the intake O2 concentration is a region A in which the sensitivity of the NOx emission amount is high with respect to the change in the intake O2 concentration, and the intake O2 concentration. It is divided into the B region where the sensitivity of the NOx emission amount to the change is low. More specifically, a region where the intake O2 concentration is greater than a predetermined concentration is defined as an A region, and a region where the intake O2 concentration is equal to or less than a predetermined concentration is defined as a B region. For example, the predetermined concentration is set to a concentration at which a change amount of the NOx concentration with respect to the intake O2 concentration becomes a predetermined value indicating that the sensitivity is high. When the current operation region belongs to the A region, the humidity correction unit 160 corrects the influence of the humidity on the intake O2 concentration and restricts the correction on the specific heat. Further, when the current operation region belongs to the B region, the humidity correction unit 160 corrects the influence of the humidity on the specific heat and limits the correction on the intake O2 concentration. According to such control, in NOx emission amount estimation control, the target for correcting the influence of humidity is switched to a more dominant target with respect to the sensitivity of NOx emission amount. However, the estimation accuracy of the NOx emission amount can be increased. Further, when the intake O2 concentration changes, the specific heat also changes. In the NOx emission amount estimation control of the present embodiment, the target for correcting the influence of humidity is switched to a target more dominant with respect to the sensitivity of the NOx emission amount. Can be done. The specific process of the humidity correction operation executed in the humidity correction unit 160 is the same as the process in the first embodiment except that the map of FIG. 14 is used instead of the map of FIG. Description is omitted.

(NOx emission estimation control)
The emission estimation model 100 of the present embodiment includes a function for estimating the NOx emission amount discharged from the cylinder during operation. FIG. 15 is a control block diagram in which functional blocks for estimating the NOx emission amount discharged from the cylinder are extracted from the estimation functions provided in the emission estimation model 100. Hereinafter, a model configuration for estimating the NOx emission amount will be described in detail with reference to FIG.

  The emission estimation model 100 shown in FIG. 15 includes a pre-correction intake O2 concentration calculation unit 211, an average injection timing calculation unit 212, a NOx emission amount calculation unit 213, a specific heat correction coefficient calculation unit 214, and calculation units 221 and 222. .

  The pre-correction intake O2 concentration calculation unit 211 performs the same calculation as the current A / F calculation unit 103 and the current intake O2 concentration calculation unit 105 described above, and calculates the pre-correction intake O2 concentration that is the current intake O2 concentration before correction. To do. The calculation unit 221 calculates the corrected intake O2 concentration by multiplying the pre-correction intake O2 concentration calculated by the pre-correction intake O2 concentration calculation unit 211 by the intake O2 concentration correction value calculated by the humidity correction unit 160. . The average injection timing calculation unit 212 calculates an average injection timing reflecting the injection timings and injection amounts of all effective injections using a known method.

The corrected intake O2 concentration calculated by the calculation unit 221 and the average injection timing, injection amount, and engine speed calculated by the average injection timing calculation unit 212 are input to the NOx emission amount calculation unit 213. The NOx emission amount calculation unit 213 calculates the NOx emission amount based on the following equation (1) including a power of the corrected intake O2 concentration, a power of the average injection timing, a power of the injection amount, and a power of the engine rotation speed. . The exponents A, B, C, D, and E in the following equation (1) are set according to the engine model and characteristics.
NOx emissions = exp ^ A x (corrected intake O2 concentration) ^ B x (average injection timing) ^ C x (injection quantity) ^ D x (engine speed) ^ E (1)

  The specific heat correction coefficient calculation unit 214 calculates the specific heat correction coefficient by performing the same calculation as the specific heat correction coefficient calculation unit 107 described above. In the calculation unit 222, the NOx emission amount calculated by the NOx emission amount calculation unit 213 is multiplied by the specific heat correction coefficient calculated by the specific heat correction coefficient calculation unit 214. Thereby, the final NOx emission amount is calculated.

  Thus, according to the emission estimation model 100 of the present embodiment, in the estimation control of the NOx emission amount, the main cause of the change in the NOx emission amount due to the influence of humidity can be specified and the main factor can be corrected. Therefore, it is possible to improve the estimation accuracy of the NOx emission amount while suppressing the calculation load.

  In the second embodiment described above, the emission estimation model 100 corresponds to the “emission estimation device” of the first invention, the NOx emission amount corresponds to the “emission emission amount” of the first invention, and the humidity The sensor-equipped air flow meter 54 corresponds to the “absolute humidity detecting means” of the first invention, the region A corresponds to the “first operating region” of the first invention, and the region B corresponds to the first invention of the first invention. The humidity correction unit 160 and the calculation unit 221 correspond to the “second operating region”, and correspond to the “intake O2 concentration correction unit” of the first invention, and the humidity correction unit 160, the specific heat correction coefficient calculation unit 214, and the calculation unit. 222 corresponds to the “specific heat correcting means” of the first invention. In the second embodiment described above, the “emission emission estimation means” according to the first aspect of the present invention is realized when the ECU 50 executes the processes of steps S2, S3 and S5 or steps S2, S4 and S6. Yes.

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

  In the second embodiment described above, the pre-correction intake O2 concentration calculation unit 211 corresponds to the “estimated intake O2 concentration calculation unit” of the sixth invention, and the NOx emission amount calculation unit 213 of the sixth invention. This corresponds to “basic NOx emission calculation means”.

2 Engine body 4 Intake manifold 6 Exhaust manifold 8 Fuel injection valve 10 Intake passage 12 Exhaust passage 14 Compressor 16 Turbine 18 Variable nozzle 20 Air cleaner 22 Intercooler 24 Diesel throttle 25 Oxidation catalyst 30 EGR passage 32 EGR valve 34 EGR cooler 36 Bypass passage 38 Bypass valve 50 ECU (Electronic Control Unit)
52 Rotational speed sensor 54 Air flow meter 56 Accelerator opening sensor 58 Differential pressure sensor 62 NOx sensor 64 PM sensor 100 Emission estimation model 101 Base soot map 102 Base A / F calculation unit 103 Current A / F calculation unit 104 Base intake air O2 concentration calculation Unit 105 Current intake O2 concentration calculation unit 106 Transient correction coefficient calculation unit 107 Specific heat correction coefficient calculation unit 108 Environment correction unit 111, 112, 113, 114, 115 Calculation unit 121 Dry air amount calculation unit 122 Dry intake air O2 concentration calculation unit 123 Base Intake O2 concentration map 124 Intake O2 concentration correction value calculation unit 131 Intake wet air molecular weight calculation unit 132 Intake wet air specific heat calculation unit 133 Intake gas molecular weight calculation unit 134 Intake gas specific heat calculation unit 135 Base specific heat map 136 Specific heat correction value calculation unit 150 Target Fresh air 151 Target EGR rate map 152 EGR rate calculation unit 160 Humidity correction unit 211 Pre-correction intake O2 concentration calculation unit 212 Average injection timing calculation unit 213 NOx emission amount calculation unit 214 Specific heat correction coefficient calculation units 221 and 222 Calculation unit 300 Catalyst control block

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

The present invention has been made in view of the problems as described above, and provides an emission estimation device for an internal combustion engine capable of estimating the soot emission amount or the NOx emission amount with high accuracy while suppressing the calculation load. Objective.

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

Therefore, in the NOx emission amount estimation control of the present embodiment, the operation region shown in FIG. 13 specified by the intake O2 concentration is a region A in which the sensitivity of the NOx emission amount is high with respect to the change in the intake O2 concentration, and the intake O2 concentration. It is divided into the B region where the sensitivity of the NOx emission amount to change is low. More specifically, a region where the intake O2 concentration is greater than a predetermined concentration is defined as an A region, and a region where the intake O2 concentration is equal to or less than a predetermined concentration is defined as a B region. For example, the predetermined concentration is set to a concentration at which a change amount of the NOx concentration with respect to the intake O2 concentration becomes a predetermined value indicating that the sensitivity is high. Then, when the current operation region belongs to the A region, the humidity correction unit 160 corrects the influence of the humidity on the intake O2 concentration and restricts the correction on the specific heat. Further, when the current operation region belongs to the B region, the humidity correction unit 160 corrects the influence of the humidity on the specific heat and limits the correction on the intake O2 concentration. According to such control, in NOx emission amount estimation control, the target for correcting the influence of humidity is switched to a more dominant target with respect to the sensitivity of NOx emission amount. However, the estimation accuracy of the NOx emission amount can be increased. Further, when the intake O2 concentration changes, the specific heat also changes. In the NOx emission amount estimation control of the present embodiment, the target for correcting the influence of humidity is switched to a target more dominant with respect to the sensitivity of the NOx emission amount. Can be done. The specific process of the humidity correction operation executed in the humidity correction unit 160 is the same as the process in the first embodiment except that the map of FIG. 13 is used instead of the map of FIG. Description is omitted.

(NOx emission estimation control)
The emission estimation model 100 of the present embodiment includes a function for estimating the NOx emission amount discharged from the cylinder during operation. FIG. 14 is a control block diagram in which functional blocks for estimating the NOx emission amount discharged from the cylinder are extracted from the estimation functions provided in the emission estimation model 100. Referring to FIG. 14 will be described in detail for the model structure for estimating NOx emissions.

The emission estimation model 100 shown in FIG. 14 includes a pre-correction intake O2 concentration calculation unit 211, an average injection timing calculation unit 212, a NOx emission amount calculation unit 213, a specific heat correction coefficient calculation unit 214, and calculation units 221 and 222. .

The corrected intake O2 concentration calculated by the calculation unit 221 and the average injection timing, injection amount, and engine speed calculated by the average injection timing calculation unit 212 are input to the NOx emission amount calculation unit 213. The NOx emission amount calculation unit 213 calculates the NOx emission amount based on the following expression ( 14 ) including a power of the corrected intake O2 concentration, a power of the average injection timing, a power of the injection amount, and a power of the engine rotation speed. . The exponents A, B, C, D, and E in the following equation ( 14 ) are set according to the engine model and characteristics.
NOx emissions = exp ^ A x (corrected intake O2 concentration) ^ B x (average injection timing) ^ C x (injection amount) ^ D x (engine speed) ^ E ( 14 )

Claims (7)

Emission emission amount estimation means for estimating one of NOx and Soot discharged from the cylinder of the internal combustion engine based on the operating conditions of the internal combustion engine,
The emission emission estimating means includes:
Humidity detecting means for detecting the humidity of fresh air sucked into the internal combustion engine;
Intake air O2 concentration correction means for performing intake air O2 concentration correction for correcting a change in the emission amount due to a change in the intake air O2 concentration, which is the concentration of oxygen contained in the gas sucked into the cylinder, according to absolute humidity; ,
Specific heat correction means for performing specific heat correction for correcting a change in the emission amount due to a change in specific heat of the gas sucked into the cylinder according to absolute humidity,
In the operation region specified using the intake O2 concentration, when the current operation region belongs to the first operation region in which the amount of change in the emission emission amount relative to the change in the intake O2 concentration is relatively large, When the intake O2 concentration correction is performed and the specific heat correction is limited, and the current operation region belongs to the second operation region in which the amount of change in the emission emission amount relative to the change in the intake O2 concentration is relatively small, An emission estimation device for an internal combustion engine, which is configured to perform specific heat correction and limit the intake O2 concentration correction. The emission emission amount is a soot emission amount that is an amount of soot discharged from the cylinder of the internal combustion engine,
In the operation region specified by using the intake O2 concentration and the equivalence ratio, the first operation region is a region in which the change amount of the Soot discharge amount with respect to the change of the intake O2 concentration or the equivalence ratio is relatively large. 2. The internal combustion engine emission estimation device according to claim 1, wherein the second operation region is a region in which a change amount of the Soot emission amount with respect to a change in the intake O2 concentration or an equivalence ratio is relatively small. . The emission emission estimating means includes:
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 the engine rotation speed of the internal combustion engine and a command fuel injection amount;
Basic air-fuel ratio calculating means for calculating a basic air-fuel ratio that is an air-fuel ratio in a steady state of the internal combustion engine based on the engine rotational speed of the internal combustion engine and the command fuel injection amount;
Basic intake O2 concentration calculating means for calculating a basic intake O2 concentration, which is an intake O2 concentration in a steady state of the internal combustion engine, based on the engine rotational speed of the internal combustion engine and a command fuel injection amount;
Estimated air-fuel ratio calculating means for calculating an estimated air-fuel ratio, which is an estimated value of the current air-fuel ratio, based on the intake air amount and the command fuel injection amount;
An estimated intake O2 concentration calculating means for calculating an estimated intake O2 concentration that is an estimated value of the current intake O2 concentration based on the intake air amount and the command fuel injection amount;
Transient correction means for correcting the basic soot discharge amount based on the ratio of the estimated air-fuel ratio to the basic air-fuel ratio and the ratio of the estimated intake O2 concentration to the basic intake O2 concentration;
The intake O2 concentration correction means calculates an intake O2 concentration correction value that is a correction value reflecting the degree of change in the intake O2 concentration due to absolute humidity, and uses the intake O2 concentration correction value to calculate the estimated intake O2 concentration. The emission estimation device for an internal combustion engine according to claim 2, wherein the emission estimation device is configured to correct the above.   The specific heat correction means calculates a specific heat correction coefficient, which is a correction coefficient for reflecting the increase or decrease in the specific heat in the soot discharge amount based on the absolute humidity, and uses the specific heat correction coefficient to calculate the soot discharge amount. 4. The internal combustion engine emission estimation device according to claim 2, wherein the emission estimation device is configured to correct. The emission amount is a NOx emission amount that is an amount of NOx discharged from the cylinder of the internal combustion engine,
In the operation region specified using the intake O2 concentration, the first operation region is a region where the intake O2 concentration is larger than a predetermined concentration, and in the second operation region, the intake O2 concentration is less than a predetermined concentration. The emission estimation device for an internal combustion engine according to claim 1, wherein the emission estimation device is an area. The emission emission estimating means includes:
An estimated intake O2 concentration calculating means for calculating an estimated intake O2 concentration that is an estimated value of the current intake O2 concentration based on the intake air amount and the command fuel injection amount;
Basic NOx emission amount calculating means for calculating the NOx emission amount based on the engine speed of the internal combustion engine, the command fuel injection amount, the average injection timing, and the estimated intake O2 concentration,
The intake O2 concentration correction means calculates an intake O2 concentration correction value that is a correction value reflecting the degree of change in the intake O2 concentration due to absolute humidity, and uses the intake O2 concentration correction value to calculate the estimated intake O2 concentration. The emission estimation device for an internal combustion engine according to claim 5, wherein the emission estimation device is configured to correct the above.   The specific heat correction means calculates a specific heat correction coefficient that is a correction coefficient for reflecting an increase or decrease in the specific heat in the NOx emission amount based on absolute humidity, and uses the specific heat correction coefficient to calculate the NOx emission amount. The emission estimation device for an internal combustion engine according to claim 5 or 6, wherein the emission estimation device is configured to correct the above.

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