JP2005048710A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine for controlling a rich spiking timing corresponding to the exhaust property of NOx which is changed with a fuel nature. <P>SOLUTION: This exhaust emission control device comprises a specific gravity detecting means for detecting the specific gravity of fuel being used, a fuel nature detecting means S2 for detecting at least one fuel nature of a cetane number, an octane number, evaporating property, a heating value and the content of aromatic hydrocarbon in accordance with the detected specific gravity, and a total NOx trapped amount estimating means S3 for calculating and estimating the exhaust amount of NOx exhausted from an engine and the total trapped amount thereof in accordance with the amount of air in operating gas sucked into the engine and the fuel nature detected by the fuel nature detecting means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly to an exhaust gas purification device that purifies and controls NOx in exhaust gas.

Conventionally, an NOx trap catalyst that traps NOx when the air-fuel ratio of inflowing exhaust gas is lean and reduces the oxygen concentration in the inflowing exhaust gas (rich spike) to release trapped NOx is used as an engine exhaust passage. An exhaust purification device that estimates the rich spike timing of the NOx trap catalyst from the operation history of the engine has been proposed (see Patent Document 1). This is estimated from the cumulative value of the product of the intake air amount and the engine load or the cumulative value of the engine speed, for example, as the engine operating history.
Japanese Patent No. 2600492

  By the way, NOx emissions vary depending not only on the operation history but also on the fuel properties. At low cetane numbers, the ignitability is poor and the combustion of the main injected fuel becomes slow, so the NOx emissions per unit output unit time are compared. Therefore, as the cetane number increases, the ignitability of the fuel improves and the combustion of the main injected fuel becomes better, and the ignitability is better in the high cetane number region, so that the increase in the cylinder temperature can be suppressed. , NOx emission per unit output unit time decreases. That is, the NOx emission amount per unit output unit time is the highest at the median cetane number, and the NOx emission amount per unit output unit time decreases as the cetane number increases and decreases (FIG. 6 ( A)).

  However, in the above prior art, the NOx trap amount to the NOx trap catalyst is estimated from the operation history such as the rotational speed of the internal combustion engine and the fuel injection amount, and the rich spike timing of the NOx trap catalyst is controlled. Was not considered, and an error was caused in the estimation of the amount of NOx trapped in the NOx trap catalyst.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an exhaust purification device for an internal combustion engine that can control the rich spike timing in accordance with the NOx emission characteristics that change depending on the fuel properties.

  The present invention is arranged in an exhaust passage of an internal combustion engine, traps NOx in exhaust flowing when the exhaust air-fuel ratio is lean, and desorbs and purifies NOx trapped when the exhaust air-fuel ratio is rich, An air-fuel ratio control means that makes the exhaust air-fuel ratio rich according to the total amount of NOx trap of the NOx trap catalyst, cetane number, octane number, evaporability, calorific value, aromatic hydrocarbon content of the fuel used, The fuel property detection means for detecting at least one fuel property of the fuel, the amount of air in the working gas sucked into the engine and the total NOx trap amount according to the fuel property detected by the fuel property detection means NOx trap total amount estimation means.

  Therefore, in the present invention, fuel property detection means for detecting at least one fuel property among the cetane number, octane number, evaporability, calorific value, and aromatic hydrocarbon content of the fuel being used, and the intake to the engine And NOx trap total amount estimating means for estimating the total NOx trap amount according to the amount of air in the working gas and the fuel property detected by the fuel property detecting means. Accurate calculation can be performed according to the amount of air in the working gas to be sucked and the fuel property detected by the fuel property detecting means, and the total amount of NOx trap can be estimated with high accuracy even during transient operation. As a result, the timing for starting the NOx reduction process by the exhaust air-fuel ratio rich control according to the NOx emission characteristics that change depending on the fuel properties can be set appropriately, and the exhaust purification performance is improved.

  Hereinafter, an exhaust emission control device for an internal combustion engine of the present invention will be described based on an embodiment.

  FIG. 1 is a configuration diagram of an engine system to which an exhaust gas purification apparatus for an internal combustion engine to which the present invention is applied, and is configured by taking a diesel engine using light oil as fuel as an example.

  In FIG. 1, 1 indicates a diesel engine (hereinafter simply referred to as an engine), and 3 indicates an exhaust passage of the engine 1.

  An exhaust outlet passage 3a constituting an upstream portion of the exhaust passage 3 of the engine 1 is connected to a turbine 3b of a supercharger, and downstream of the exhaust passage 3a is reduced and purified while trapping NOx in the exhaust as an exhaust aftertreatment device. Casing 20 which accommodates NOx trap catalyst 21 which carries out inside is arranged in series. An air-fuel ratio sensor 37 serving as an actual air-fuel ratio detection unit is provided at the inlet of the casing 20. The air-fuel ratio sensor 37 detects the oxygen concentration in the exhaust gas using, for example, an oxygen ion conductive solid electrolyte, and obtains the air-fuel ratio from the oxygen concentration.

  Between the intake collector 2c of the intake passage 2 and the exhaust outlet passage 3a, an EGR passage 4 for recirculating a part of the exhaust is provided, and the opening degree is continuously controlled by a stepping motor. A possible EGR valve 5 is interposed.

  The intake passage 2 is provided with an air cleaner 2a at an upstream position, and an airflower 7 serving as intake air amount detection means is provided on the outlet side thereof. A turbocharger compressor 2b is arranged downstream of the air flow overnight 7, and an intake throttle valve that is opened and closed by an actuator (for example, a stepping motor type) between the compressor 2b and the intake collector 2c. 6 is interposed.

  The fuel supply system of the engine 1 includes a fuel tank 60 that stores diesel oil as diesel fuel, a fuel supply passage 16 that supplies fuel to the fuel injection device 10 of the engine 1, and a fuel supply device 16 of the engine 1. And a fuel return passage 19 for returning the return fuel (spill fuel) to the fuel tank 60.

  The fuel injection device 10 of the engine 1 is a known common rail type fuel injection device, and generally includes a supply pump 11, a common rail (accumulation chamber) 14, and a fuel injection valve 15 provided for each cylinder. After the fuel pressurized by the supply pump 11 is temporarily stored in the common rail 14 via the fuel supply passage 12, the high-pressure fuel in the common rail 14 is distributed to the fuel injection valves 15 of each cylinder.

  The common rail 14 is provided with a pressure sensor 34 and a temperature sensor 35 in order to detect the pressure and temperature of the fuel in the common rail 14. Further, in order to control the fuel pressure in the common rail 14, the portion of the fuel discharged from the supply pump 11 is returned to the fuel supply passage 16 via the overflow passage 17 having a one-way valve 18. . Specifically, a pressure control valve 13 that changes the flow passage area of the overflow passage 17 is provided, and the pressure control valve 13 changes the flow passage area of the overflow passage 17 in accordance with a duty signal from the engine control unit 30. Thereby, the substantial fuel discharge amount from the supply pump 11 to the common rail 14 is adjusted, and the fuel pressure in the common rail 14 is controlled.

  The fuel injection valve 15 is an electronic injection valve that is opened and closed by an ON-OFF signal from the engine control unit 30, and injects fuel into the combustion chamber by the ON signal and stops injection by the OFF signal. The fuel injection amount increases as the period of the ON signal applied to the fuel injection valve 15 increases, and the fuel injection amount increases as the fuel pressure of the common rail 14 increases.

  The engine control unit 30 includes a signal (Qa) from the air flow meter 7 that detects the intake air amount Qas0, a signal from the water temperature sensor 31 (water temperature Tw), and a signal from the crank angle sensor 32 for crank angle detection (the basis of the engine speed Ne). Crank angle signal), a signal of the cylinder discrimination crank angle sensor 33 (cylinder discrimination signal Cy1), a signal of the pressure sensor 34 for detecting the fuel pressure of the common rail 14 (common rail pressure PCR), and a temperature sensor 35 for detecting the fuel temperature. Signal (fuel temperature TF), an accelerator opening sensor 36 signal (accelerator opening (load) L) for detecting an accelerator pedal depression amount corresponding to a load, an air-fuel ratio sensor 37 signal (O2), and the NOx trap The thermocouple 38 signals (catalyst carrier temperature Td) for detecting the catalyst carrier temperature of the catalyst 21 are respectively shown. It is a force.

  The engine control unit 30 obtains the target reference pressure PCRO of the common rail 14 by searching a predetermined map stored in advance in the ROM of the control unit 30 using the engine speed Ne and the load L as parameters. By executing feedback control of the pressure control valve 13 so as to obtain the pressure PCRO, common rail pressure control is performed.

  The control unit 30 performs drive control of the fuel injection valve 15 and opening control of the intake throttle valve 6 and the EGR valve 5 based on detection signals from the various sensors. In particular, as control according to the present invention, when the NOx trapped by the NOx trap catalyst 21 is reduced and purified by enriching the air-fuel ratio, the total amount of trapped NOx is accurately estimated.

  Next, the contents of the control of the exhaust emission control device of the present invention executed by the engine control unit 30 will be described based on the flowcharts of FIGS.

  FIG. 2 shows a basic control routine of the exhaust emission control device, which is periodically executed by the control unit 30.

  In this exhaust purification device basic control routine, in step S1, the water temperature Tw, the engine speed Ne, the cylinder discrimination signal Cyl, the common rail pressure PCR, the signal Qa of the air flow meter 7, the fuel temperature TF, the accelerator opening L, the air-fuel ratio sensor. 37 signals O2 are read, respectively, and the process proceeds to step S2.

  In step S2, the supplied fuel properties (cetane number, fuel specific gravity) are detected. For detecting the specific gravity of the fuel, for example, as shown in Japanese Utility Model Publication No. 3-45181, a pendulum that falls due to gravity acting on the weight is provided in the fuel tank, and the drop time of the pendulum that depends on the viscosity is measured. As shown in Japanese Patent Application Laid-Open No. 11-107820, a mechanism is provided to determine the viscosity from the drop time, add a correction based on the detected fuel temperature, and determine the cetane number. If the target ignition timing differs from the actual ignition timing due to variations in the cetane number of the fuel, etc., provided with means for detecting the ignition timing by the in-cylinder pressure sensor of the diesel engine, the target ignition timing of the actual ignition timing The fuel property such as the cetane number may be determined based on the difference with respect to.

  Here, focusing on the fact that fuel properties such as cetane number correlate with fuel density, that is, specific gravity, the cetane number is determined based on the specific gravity detected by the specific gravity detecting means for detecting the specific gravity of the fuel being used , Octane number, evaporability, calorific value, aromatic hydrocarbon content, at least one fuel property is detected. This fuel property detection method will be described based on a fuel property detection flowchart of FIG. 3 described later.

  In step S3, the total amount of NOx traps adsorbed and trapped on the NOx trap catalyst 21 is estimated. The method for estimating the total NOx trap amount will be described based on the NOx trap total amount estimation control flowchart of FIG.

  In step S4, it is determined whether or not the total amount of NOx traps adsorbed on the NOx trap catalyst 21 estimated in step S3 is less than a predetermined amount NOx1 that is the regeneration timing of the NOx trap catalyst 21. When it is determined that the total NOx trap amount exceeds the predetermined amount NOx1 indicating the regeneration timing of the NOx trap catalyst 21 (NOx trap total amount ≧ predetermined amount NOx1), the process proceeds to step S5, and the NOx trap catalyst 21 is regenerated. Rich spike control is executed. This rich spike control is executed by lowering the oxygen concentration in the exhaust gas flowing in. For example, the rich spike control is executed by reducing the intake throttle valve 6 and opening the EGR valve 5 to increase the EGR amount.

  Next, the details of the fuel property detection control routine in step S2 will be described based on the flowchart of FIG. By this control, the properties of the fuel being used are detected with high accuracy.

  The fuel property detection control routine will be described below. In step S11, based on the signal Qa of the air flow meter that detects the intake air amount, the table data of the predetermined intake air amount Qair stored in advance in the ROM of the control unit 30 is retrieved using the value of the signal Qa as a parameter. . Then, the process proceeds to step S12.

  In step S12, the main fuel injection amount (fuel supply amount) Qmain set with the engine speed Ne and the load L as parameters is obtained by searching a predetermined map stored in advance in the ROM of the control unit 30. Then, the process proceeds to step S13.

  Note that the main fuel injection amount (fuel supply amount) Qmain is not the above-described method, but the fuel injection period Mperiod of the fuel injection device set by using the engine speed Ne and the load L as parameters is set to the control unit 30. A search is made for a predetermined map stored in advance in the ROM, and a main fuel injection amount (fuel supply amount) Qmain set with the fuel injection period Mperiod and the common rail pressure PCR as parameters is stored in the ROM of the control unit 30. A predetermined map stored in advance may be searched for.

  In step S13, based on the signal O2 of the air-fuel ratio sensor 37, the table data of the actual air-fuel ratio AFrea1 stored in advance in the ROM of the control unit 30 is retrieved using the value of the signal O2 as a parameter. Then, the process proceeds to step S14.

  In step S14, it is determined whether or not the conditions are suitable for detecting the fuel property.

  For example, in general, an automobile engine is generally provided with an exhaust gas recirculation device including an EGR valve 12 or the like for reducing NOx. Since the fuel ratio shifts to the rich side, it is necessary to correct the exhaust gas recirculation in order to accurately obtain the actual air fuel ratio. Accordingly, since there is a concern that the detection accuracy of the actual air-fuel ratio deteriorates due to the correction, it is desirable to issue the actual air-fuel ratio detection command only in a region where exhaust gas recirculation is stopped. If it is not suitable for the detection condition in step S14, the process is terminated without detecting the fuel property. If it is suitable for the detection condition in step S14, the process proceeds to step S15.

  In step S15, the actual fuel supply weight Gmain is obtained based on the intake air flow rate Qair obtained in step S11 and the actual air-fuel ratio AFrea1 obtained in step S13. Specifically, the intake air flow rate Qair is divided by the actual air-fuel ratio AFreal to obtain the actual fuel supply weight Gmain (Gmain = Qair ÷ AFrea1). Then, the actual specific gravity Gfuel is determined based on the determined actual fuel supply weight Gmain and the main fuel injection amount (fuel supply amount) Qmain determined in step S12. Specifically, the actual fuel supply weight Gmain is divided by the main fuel injection amount (fuel supply amount) Qmain to obtain an actual specific gravity Gfue1 (Gfue1 = Gmain ÷ Qmain). Then, the process proceeds to step S16.

  In step S16, the standard specific gravity (reference temperature, for example, specific gravity at a standard temperature of 20 ° C.) Gstd is obtained from the actual specific gravity Gfue1 and the fuel temperature TF. Specifically, a map of the standard specific gravity Gstd stored in advance in the ROM of the control unit 30 is searched using the actual specific gravity Gfuel and the fuel temperature TF as parameters, and a corresponding value is obtained. Then, the process proceeds to step S17.

  In step S17, using the standard specific gravity Gstd as a parameter, the fuel property stored in advance in the ROM of the control unit 30, for example, table data of the cetane number Cnumber is searched.

  Through the above steps, the specific gravity is detected from the intake air amount, the fuel supply amount, and the actual air-fuel ratio, so that the fuel property can be accurately determined by a practical method, and the detected engine is used as the fuel supply amount detection means. By obtaining the fuel injection amount as map data from the rotation speed and the load, the function originally provided in the engine can be used, and the cost is not increased. Further, the actual fuel supply weight is obtained by dividing the intake air flow rate by the actual air-fuel ratio, and the actual specific gravity is obtained by dividing the actual fuel supply weight by the main fuel injection amount (fuel supply amount). The fuel property can be detected with high accuracy and without an increase in cost, and the fuel property is obtained with the standard specific gravity taken into consideration in consideration of the fuel temperature, so that the fuel property can be detected with higher accuracy.

  Next, a routine for estimating the total NOx trap amount will be described with reference to the flowchart of FIG.

  In step S21, the fuel set by reference from a map or the like based on the engine speed Ne detected by the crank angle sensor 32, the accelerator opening degree L detected by the accelerator opening sensor 36, and the engine speed Ne. The injection amount Qf, the intake air amount Qac_mg_s per unit time calculated as described later based on the intake air amount Qas0 detected by the air flow meter 7, the catalyst carrier temperature Td of the NOx trap catalyst 21 detected by the thermocouple 38 Alternatively, the cooling water temperature Tw detected by the water temperature sensor 31 and the cetane number of the supplied fuel detected in step S2 are read.

  In step S22, for example, from the table corresponding to the cetane number of the supplied fuel detected in step S2 of the basic routine, the correlation between the intake air amount Qac_mg_s per unit time and the NOx amount as shown in FIG. A NOx emission amount per unit output unit time discharged from the engine 1 is calculated: NOx_g_kw_20 ms. The unit of the NOx emission amount is g / kW / 20 ms (in the case of 20 msec. Job). As shown in the figure, NOx_g_kw_20 ms is set to increase as the intake air amount Qac increases in accordance with the characteristics described above.

  The table is set for each cetane number from the fuel property of the supplied fuel, for example, for the fuel having a low cetane number to the fuel having a high cetane number. If the NOx emission amount per unit output unit time set in this table is shown continuously from the low cetane number region to the high cetane number region, as shown in FIG. The combustion of the main injected fuel becomes slow, so the amount of NOx emission per unit output unit time is relatively small, the ignitability of the fuel improves as the cetane number increases, and the combustion of the main injected fuel becomes better, Since the ignitability is good in the high cetane number region, the diffusion combustion ratio can be increased and the rise in the temperature in the cylinder can be suppressed even in those not accompanied by pilot injection as well as those accompanied by pilot injection. NOx emissions per hour are reduced. In other words, the standard median cetane number is the highest NOx emission amount per unit output unit time, and the NOx emission amount per unit output unit time decreases as the cetane number increases and decreases. Are reflected in each cetane number table.

  The table of NOx emissions per unit output unit time is set for each cetane number, but a reference table for a standard cetane number (for example, cetane number 50) and a supply fuel for a standard cetane number A cetane number correction coefficient map (FIG. 6B) in which cetane number correction coefficients are stored is set and stored in the reference table emission amount and the cetane number correction coefficient table when calculating the NOx emission amount per unit output unit time. The NOx emission amount per unit output unit time may be obtained by multiplying the coefficient corresponding to the cetane number.

In step S23, the NOx emission amount per unit time discharged from the engine 1 is calculated by the product of NOx_g_kw_20ms calculated in step 22 and the engine output Pe at that time, and this is the unit trapped by the NOx trap catalyst 21. NOx trap amount per hour: NOx_g_20 ms. Here, the fuel injection amount Qf detected in step 21 is regarded as the engine torque, and the following equation:
Pe = Ne × Qf
Thus, the output equivalent value Pe of the engine 1 may be calculated.

  In step S24, for example, a correction coefficient kNOx_eoe based on the NOx emission amount per unit time is calculated using a table as shown in FIG. As other methods, the relationship between the exhaust flow rate of the engine 1 and the NOx trap amount is taken into account, and kNOx_qexh calculated by a table as shown in FIG. 9 can be replaced with kNOx_ne_qf calculated by a map as shown in FIG.

  In step S25, considering that the NOx trap amount depends on the catalyst carrier temperature Td, the correction coefficient kNOx_td is calculated using a table as shown in FIG. As another method, as shown in FIG. 11, using the correlation between the catalyst carrier temperature and the engine coolant temperature Tw, kNOx_tw can be calculated and replaced with kNOx_td using a table as shown in FIG. .

  In step S26, the correction coefficient kNOx_trap is calculated from a table as shown in FIG. 13 considering that the NOx trap amount per unit time is affected by the total amount of NOx trapped in the catalyst 21 so far: NOx_trap.

In step S27, the correction coefficients calculated in steps 1 to 6 are as follows:
kNOx = kNOx_eoe (or kNOx_qexh, kNOx_ne_qf) × kNOx_bed (or kNOx_tw) × kNOx_trap
Multiply and calculate the final correction coefficient kNOx.

In step S28, the total amount of NOx traps up to the previous time (NOx_trap (n-1): n-1 indicates the previous calculation result in the figure) per unit time this time calculated in step S23 is calculated as in the following equation. The product of the NOx trap amount: NOx_g_20 ms and the final correction coefficient calculated in step S27: kNOx is as follows:
NOx_trap = NOx_trap (n−1) + NOx_g — 20 ms × kNOx
Addition and the current NOx trap total amount: NOxtrap are calculated.

  Next, a routine for calculating the intake air amount Qac_mg_s per unit time will be described with reference to the flowchart of FIG.

In step S31, the engine speed Ne and the intake air amount QasO detected by the air flow meter 7 are read. In step S32, based on these values,
QacO = (QasO / Ne) × KCON #
The intake air amount QacO per cylinder is calculated. However, KCON # is a constant determined according to the number of cylinders.

  As shown in FIG. 1, the air flow meter 7 is provided in the intake passage 2 upstream of the compressor 2b, and delay processing from the air flow meter 7 to the collector 2c downstream of the compressor 2b is performed. However, the value of QacO before the operation is obtained as the intake air amount Qacn per cylinder at the collector inlet.

In step S34, for this Qacn, the following equation (first-order lag equation):
Qac = Qac _n-1 × (1-KIN × KVOL) + Qacn × KIN × KVOL
An intake air amount Qac per cylinder at the intake throttle valve opening is calculated. However,
KIN: Volume efficiency equivalent value (value for correcting change in volume efficiency due to EGR)
KVOL: VE / NC / VM
VE: displacement NC: number of cylinders VM: intake system volume Qac _n-1 : previous Qac
This is to compensate for the dynamics from the collector inlet to the intake throttle valve 6.

Further, in step S35, the intake air amount Qac per cylinder is set as follows:
Qac_mg_s = QaC _n-1 × Kn # × {Ne / (60 × 2)}
The intake air amount per unit time is converted into Qac_mg_s. However, Kn # is a constant (4 for 4 cylinders, 6 for 6 cylinders).

  As described above, the NOx emission amount per unit time is obtained by multiplying the NOx emission amount per unit output unit time calculated based on the air amount (intake air amount) in the working gas by the engine output. By integrating the NOx trap amount per unit time calculated by performing various corrections on the NOx emission amount, the NOx trap total amount can be estimated and calculated with high accuracy even during transient operation.

  Based on the total amount of NOx traps estimated and calculated with high accuracy as described above, the regeneration timing of the NOx trap catalyst can be set appropriately to perform regeneration processing by enriching the air-fuel ratio, including NOx. Exhaust pollutants can be efficiently purified.

  In this embodiment, when calculating the NOx emission amount NOx_g_kw_20 ms per unit output unit time, in order to accurately grasp the delay in the intake air amount, the unit time calculated based on the detection value Qas0 of the air flow meter is used. The intake air amount Qac_mg_s is used, but the detection value Qas0 of the air flow meter may be used as it is.

  That is, as shown in FIG. 15, it is desirable that the intake air amount changes like tQa indicated by a one-dot chain line in accordance with changes in the fuel injection amount Qf and the engine speed Ne, but in reality, there is a delay. It changes like Qac_mg_s. Here, even when NOx_g_kw_20 ms is calculated using the detected value Qas0 of the air flow meter, the delay of the intake air amount can be grasped, and the delay of the intake air amount is detected compared with the case of calculating using Qac_mg_s. Although the accuracy is reduced by about 20%, the control logic can be simplified.

  In the present embodiment, the following effects can be achieved.

  (A) Specific gravity detection means (S11 to S16) for detecting the specific gravity of the fuel used, and based on the detected specific gravity, cetane number, octane number, evaporability, calorific value, aromatic hydrocarbon content, According to the fuel property detection means (S17) for detecting at least one fuel property, the amount of air in the working gas sucked into the engine 1 and the fuel property detected by the fuel property detection means (S17). The NOx trap total amount estimating means (S21 to S28) for estimating the total NOx trap amount is provided. Therefore, the NOx amount discharged from the engine 1 is the amount of air in the working gas sucked into the engine and the fuel property detecting means (S17). ) To accurately calculate the total amount of NOx traps even during transient operation. As a result, the timing for starting the NOx reduction process by the exhaust air-fuel ratio rich control according to the NOx emission characteristics that change depending on the fuel properties can be set appropriately, and the exhaust purification performance is improved.

  (A) As the NOx trap total amount estimation means (S21 to S28), the engine 1 discharges according to the amount of air in the working gas sucked into the engine 1 and the fuel property detected by the fuel property detection means (S17). Since the NOx emission amount NOx_g_kw_20 ms per unit output unit time is calculated, and the NOx trap total amount NOxtrap is estimated based on the NOx emission amount NOx_g_kw_20 ms per unit output unit time, the unit output unit for the intake air amount Qac_mg_s per unit time NOx per unit output unit time corresponding to the fuel property is set only by selecting the map to be used according to the fuel property to be set according to the fuel property by setting the map storing the NOx emission amount NOx_g_kw_20 ms per time and the fuel property to be supplied. Emission amount NOx_g_kw It is possible to calculate the 20ms.

  (C) As the NOx trap total amount estimating means (S21 to S28), the NOx emission amount NOx_g_kw_20ms per unit output unit time discharged by the engine according to the air amount in the working gas sucked into the engine 1 is calculated. The NOx emission amount NOx_g_kw_20 ms per output unit time is corrected according to the fuel property detected by the fuel property detecting means (S17), and the NOx trap total amount NOxtrap is based on the corrected NOx emission amount per unit output unit time. , A map storing NOx emissions per unit output unit time with respect to intake air amount per unit time for typical fuel properties, and a correction coefficient map storing correction factors for typical fuel properties, By adjusting the correction factor of the correction factor map according to the fuel properties to be supplied It is possible to calculate the NOx emission amount per unit output unit time corresponding to only the fuel property is calculated.

  (D) Intake air amount detection means (air flow meter 7) for detecting the intake air amount of the engine 1 and fuel supply amount detection means (crank angle sensor 32, accelerator opening sensor 36) for detecting the fuel supply amount to the engine 1 ) And an actual air / fuel ratio detecting means (air / fuel ratio sensor 37) for detecting the actual air / fuel ratio, the specific gravity detecting means (S11 to S16) are configured to detect the detected intake air amount Qair and the fuel supply amount Gmain. Since the specific gravity of the fuel is detected by the air-fuel ratio AFreal, the fuel property can be accurately determined by a practical method.

  (E) Engine output calculating means (S21) for calculating the engine output Pe based on the operating state (engine speed Ne and fuel injection amount Qf), and the NOx trap total amount estimating means (S21 to S28) By multiplying the NOx emission amount NOx_g_kw_20 ms per output unit time or the corrected NOx emission amount NOx_g_kw_20 ms per unit output unit time by the engine output Pe, the NOx emission amount NOx_g_20 ms per unit time can be easily converted. By integrating the NOx emission amount NOx_g_20 ms, the total NOx trap amount NOxtrap can be estimated.

  In the above-described embodiment, the NOx trap total amount estimating means is a unit output per unit output time discharged by the engine in accordance with the amount of air in the working gas sucked into the engine and the fuel property detected by the fuel property detecting means. In step S22 for calculating the NOx emission amount, or the NOx emission amount per unit output unit time discharged by the engine according to the air amount in the working gas sucked into the engine, the NOx per unit output unit time is calculated. A description has been given of correcting the discharge amount in accordance with the fuel property detected by the fuel property detecting means. However, although not shown, any of the correction coefficients in the subsequent steps S24 to S27 may be corrected in accordance with the fuel property detected by the fuel property detecting means.

The figure which shows the system configuration | structure of the exhaust gas purification apparatus of the internal combustion engine which concerns on this invention. The flowchart which shows control of one Embodiment of this invention. The flowchart which shows the control routine for the fuel property detection of this invention. The flowchart which shows the control routine for estimating the NOx trap total amount to the NOx trap catalyst of this invention. The map which shows the relationship between the amount of intake air for every fuel property, and NOx discharge | emission amount per unit time. The figure (A) which shows the relationship between a fuel property and NOx discharge | emission amount, and the map (B) which memorize | stored the correction coefficient of the NOx adsorption amount with respect to a typical cetane number. A map for obtaining a correction coefficient based on the NOx emission amount per unit time. A map for obtaining the correction coefficient based on the exhaust flow rate. A map for obtaining a correction coefficient based on the engine speed and the fuel injection amount. The figure which shows the relationship between the catalyst carrier temperature after engine starting, and engine cooling water temperature. A map for obtaining a correction coefficient based on the catalyst carrier temperature. A map for determining the correction coefficient based on the engine coolant temperature. A map for obtaining a correction coefficient based on the total amount of NOx traps. The flowchart for calculating | requiring the intake air amount per unit time. The figure which shows the change of the fuel-injection amount at the time of a transient operation, an engine speed, intake air amount, and NOx discharge | emission amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diesel engine 7 Air flow meter 10 Fuel injection apparatus 21 NOx trap catalyst 30 Engine control unit 34 Pressure sensor 36 Accelerator opening sensor 37 Air-fuel ratio sensor 38 Thermocouple

Claims (6)

A NOx trap catalyst disposed in an exhaust passage of the internal combustion engine for trapping NOx in exhaust flowing when the exhaust air-fuel ratio is lean, and desorbing and purifying the trapped NOx when the exhaust air-fuel ratio is rich; and the NOx trap catalyst An exhaust gas purification apparatus for an internal combustion engine, comprising: air-fuel ratio control means for enriching the exhaust air-fuel ratio in accordance with the total amount of NOx traps of
Fuel property detection means for detecting at least one fuel property among cetane number, octane number, evaporability, calorific value, and aromatic hydrocarbon content;
An internal combustion engine comprising: NOx trap total amount estimation means for estimating the total NOx trap amount in accordance with the amount of air in the working gas sucked into the engine and the fuel property detected by the fuel property detection means Exhaust purification equipment. The fuel property detection means includes specific gravity detection means for detecting the specific gravity of the fuel being used,
2. The fuel property of at least one of cetane number, octane number, evaporability, calorific value, and aromatic hydrocarbon content is detected based on the specific gravity detected by the specific gravity detecting means. 2. An exhaust gas purification apparatus for an internal combustion engine according to 1.   The NOx trap total amount estimation means calculates the NOx emission amount per unit output unit time discharged by the engine according to the amount of air in the working gas sucked into the engine and the fuel property detected by the fuel property detection means. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the total NOx trap amount is estimated based on the NOx emission amount per unit output unit time.   The NOx trap total amount estimating means calculates the NOx emission amount per unit output unit time discharged by the engine according to the air amount in the working gas sucked into the engine, and calculates the NOx emission amount per unit output unit time. The correction according to the fuel property detected by the fuel property detection means, and the NOx trap total amount is estimated based on the corrected NOx emission amount per unit output unit time. An exhaust purification device for an internal combustion engine. The exhaust gas purification device for the internal combustion engine includes:
Intake air amount detection means for detecting the intake air amount of the engine;
Fuel supply amount detection means for detecting the fuel supply amount to the engine;
An actual air-fuel ratio detecting means for detecting the actual air-fuel ratio,
5. The internal combustion engine according to claim 1, wherein the specific gravity detecting means detects the specific gravity of the fuel based on the detected intake air amount, fuel supply amount, and actual air-fuel ratio. Exhaust purification equipment. Engine output calculation means for calculating the engine output based on the operating state,
The NOx trap total amount estimation means calculates the NOx emission amount per unit time by multiplying the NOx emission amount per unit output unit time or the corrected NOx emission amount per unit time by the engine output. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the total amount of NOx traps is estimated by integrating NOx emission amounts per hour.

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