DE102008055750B4 - Exhaust gas purification device for an internal combustion engine - Google Patents

Abstract

When the amount of sulfur components left in a NOx catalyst is large, high-temperature sulfur poisoning recovery control is performed in which the catalyst bed temperature is raised more than the regular sulfur poisoning recovery control, thereby more effectively removing sulfur components from the NOx catalyst and thereby reducing the amount of sulfur components remaining in the NOx catalyst is reduced. Thus, performing the high temperature sulfur poisoning recovery control reduces the amount of sulfur components remaining in the NOx catalyst while avoiding excessively increasing the catalyst bed temperature, thereby increasing the NOx emissions from the engine caused by the sulfur components present in the NOx catalyst remain, is caused, is suppressed.

Description

The invention relates to an exhaust gas purification device for an internal combustion engine.

As an exhaust gas purifying apparatus, there is often provided a catalytic converter having adsorption-reduction NOx catalysis for removing nitrogen oxides (NOx) from an exhaust gas in the exhaust system of an internal combustion engine mounted in, for example, a motor vehicle.

In such an exhaust gas purifier, the NOx storage capacity of the NOx catalyst decreases as the amount of sulfur components (for example, sulfur oxides) adsorbed in the NOx catalyst increases. Therefore, when such an exhaust gas purification device is used, a sulfur poisoning amount S representing the amount of sulfur components adsorbed (stored) in the NOx catalyst is typically determined, and when the determined sulfur poisoning amount S is equal to or greater than a threshold value, sulfur poisoning recovery control for removing sulfur components from the NOx catalyst is performed to restore the NOx storage capacity of the NOx catalyst, which has decreased due to the sulfur components adsorbed therein, as described in paragraphs [0003], [0033] and [ 0037] of Japanese Patent Laid-Open Publication JP-A-2005-90253 is described. During the sulfur poisoning recovery control described above, by supplying unburned fuel components to the catalytic converter in the exhaust system, the NOx catalyst is heated to approximately 600 to 700 ° C, while the atmosphere surrounding the NOx catalyst is fuel-enriched using the heat is (hereinafter referred to as "fuel-rich combustion atmosphere"), whereby the sulfur components which are adsorbed in the NOx catalyst, are removed and then reduced therefrom to restore the NOx storage capacity of the NOx catalyst. The sulfur poisoning recovery control is terminated when the sulfur poisoning amount S in the NOx catalyst decreases due to execution of the sulfur poisoning recovery control to a predetermined value (for example, 0) smaller than the threshold value.

According to the above-described exhaust gas purification device, the sulfur poisoning amount is estimated on the basis of the operating state of the internal combustion engine, etc. Specifically, when the sulfur poisoning recovery control is not performed, the sulfur poisoning amount is calculated on the basis of the amount of fuel consumed since the end of the last sulfur poisoning recovery control, and so on. On the other hand, when the sulfur poisoning recovery control is performed, the sulfur poisoning amount is calculated by estimating the amount of sulfur components removed from the NOx catalyst by the sulfur poisoning recovery control.

As mentioned above, during the sulfur poisoning recovery control, the sulfur poisoning amount of the NOx catalyst is calculated by estimating the amount of sulfur components removed from the NOx catalyst during the sulfur poisoning recovery control. However, the estimated amount of the removed sulfur components may differ from the actual amount in some cases because some sulfur components are not removed from the NOx catalyst and remain therein.

If a theoretical value is used for the removed amount of sulfur components, i. that is, if the amount is estimated rather than actually detected, it deviates from the amount of sulfur components actually removed from the NOx catalyst by the amount of sulfur components remaining in the NOx catalyst. The reason why some sulfur components remain in the NOx catalyst is that the catalyst bed temperature increases at some portions of the catalytic converter, such as the catalytic converter. B. the upstream end is not greatly increased. Ie. it is believed that the sulfur components adsorbed in the NOx catalyst are difficult to remove at such portions of the catalytic converter, even when the NOx catalyst is heated and a fuel-rich combustion atmosphere around the NOx catalyst in sulfur poisoning recovery control is generated.

As such, some sulfur components can not be removed from the NOx catalyst by the sulfur poisoning recovery process, and therefore they remain in the NOx catalyst, i. H. residual sulfur components are present in the NOx catalyst. For this reason, in a case where the sulfur poisoning amount is estimated without considering the amount of sulfur components not removed from the NOx catalyst, the estimated sulfur poisoning amount becomes smaller than the actual sulfur poisoning amount.

As a result, when the sulfur poisoning recovery control is terminated in response to the estimated sulfur poisoning amount reaches 0, the actual sulfur poisoning amount has not yet been reduced to zero, that is, some sulfur components are still present in the NOx catalyst. Further, when the NOx catalyst is used, the amount of sulfur components remaining in the NOx catalyst increases, and therefore, the deviation of the estimated sulfur poisoning amount S from its actual value, that is, the amount of sulfur components contained in the NOx catalyst increases. Catalyst remain at the end of the sulfur poisoning recovery control increases.

• (1) Wenn ein Fahrer ein Kraftfahrzeug nur während einer kurzen Zeitdauer fährt, erhöht sich die Temperatur des Abgases von der Brennkraftmaschine nicht stark, und daher besteht die Tendenz, dass die Katalysatorbetttemperatur des NOx-Katalysators niedrig bleibt. Daher ist die Wahrscheinlichkeit, dass die Schwefelvergiftungswiederherstellungssteuerung ausgeführt wird, relativ gering, und sogar wenn sie ausgeführt wird, kann sich die Katalysatorbetttemperatur in der Schwefelvergiftungswiederherstellungssteuerung nicht stark erhöhen. Als Ergebnis verringert sich die Rate der Entfernung der Schwefelkomponenten von dem NOx-Katalysator, und es verbleibt eine größere Menge an Schwefelkomponenten in dem NOx-Katalysator.
• (2) Wenn ein Fahrer die Gewohnheit hat, das Kraftfahrzeug derart zu fahren, dass eine große Menge an Kraftstoff verbraucht wird, wie z. B. ein schnelles Beschleunigen des Kraftfahrzeugs, ist die Menge an Schwefelkomponenten, die in den NOx-Katalysator eintreten, wenn Kraftstoff verbraucht wird, groß, und daher ist die Menge an Schwefelkomponenten, die in dem NOx-Katalysator verbleibt, groß.
• (3) Wenn die Schwefelkonzentration des verwendeten Kraftstoffes größer als ein Standardwert ist, besteht die Tendenz, dass eine große Menge an Schwefelkomponenten in den NOx-Katalysator im Vergleich dazu eindringt, wenn Kraftstoff verwendet wird, der eine Standardkraftstoffkonzentration aufweist. Es wird eine größere Menge an Schwefelkomponenten in dem NOx-Katalysator adsorbiert, und daher verbleibt eine größere Menge an Schwefelkomponenten in dem NOx-Katalysator.

Specifically, in the following cases (1) to (3), the deviation of the estimated sulfur poisoning amount from its actual value is significantly large, that is, the estimated sulfur poisoning amount is significantly larger than its actual value.

• (1) When a driver drives a motor vehicle only for a short period of time, the temperature of the exhaust gas from the internal combustion engine does not increase greatly, and therefore, the catalyst bed temperature of the NOx catalyst tends to be low. Therefore, the probability that the sulfur poisoning recovery control is carried out is relatively small, and even when it is carried out, the catalyst bed temperature in the sulfur poisoning recovery control can not increase much. As a result, the rate of removal of the sulfur components from the NOx catalyst decreases, and a larger amount of sulfur components remain in the NOx catalyst.
• (2) When a driver has a habit of driving the vehicle so that a large amount of fuel is consumed, such as fuel. For example, a quick acceleration of the motor vehicle, the amount of sulfur components entering the NOx catalyst when fuel is consumed is large, and therefore, the amount of sulfur components remaining in the NOx catalyst is large.
• (3) When the sulfur concentration of the fuel used is larger than a standard value, a large amount of sulfur components tend to enter into the NOx catalyst as compared with using fuel having a standard fuel concentration. A larger amount of sulfur components are adsorbed in the NOx catalyst, and therefore, a larger amount of sulfur components remain in the NOx catalyst.

As described above, in a state where a larger amount of sulfur components remain in the NOx catalyst than in a normal state, that is, in a normal state, that is. H. in which the actual sulfur poisoning amount becomes larger than the estimated amount, the NOx storage capacity of the NOx catalyst becomes low due to the sulfur components remaining in the NOx catalyst even after the end of the sulfur poisoning recovery control, resulting in an increase in NOx emissions from the NOx catalyst Internal combustion engine leads. However, this problem can be solved by enabling more effective removal of sulfur components from the NOx catalyst by further increasing the catalyst bed temperature for sulfur poisoning recovery control. Thus, the amount of sulfur components remaining in the NOx catalyst can be made to be smaller, in other words, the estimated amount of sulfur poisoning amount can be made to be closer to the actual sulfur poisoning amount. However, if the catalyst bed temperature for sulfur poisoning recovery control is further increased, the temperature may become too high to cause heat damage, which often results in an increase in NOx emissions from the engine.

The DE 10 2006 034 805 A1 describes a method for the regeneration of a particulate filter and for the desulfurization of a NOx storage catalyst in an exhaust aftertreatment system of an internal combustion engine, wherein the regeneration of the particulate filter with respect to a normal operation, the temperature of the particulate filter is raised in at least one mode "DPF heating" and wherein for the desulfurization of the NOx Storage catalytic converter in at least one operating mode "NOx storage heat" (λ ≥ 1) of the NOx storage catalyst heated and in a subsequent operating mode "NOx storage desulfurization" a lambda value in the exhaust gas of λ <1 is set, wherein in a regeneration request for the Particle filter or a desulphurisation for the NOx storage catalyst, a combined complete or partial regeneration of both the particulate filter and a desulfurization of the NOx storage catalyst is triggered.

It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine which reduces the amount of sulfur components remaining in the NOx catalyst while avoiding excessively increasing the catalyst bed temperature of the NOx catalyst, thereby increasing NOx Emissions from the internal combustion engine, which can be caused by the sulfur components that remain in the NOx catalyst, is suppressed.

The object is achieved with the features of the independent claims. The dependent claims are directed to preferred embodiments of the invention.

The first aspect of the invention relates to an exhaust gas purifying apparatus for an internal combustion engine, which includes an adsorption-reduction NOx catalyst provided in an exhaust system of the internal combustion engine and an estimator for estimating a sulfur poisoning amount representing the amount of sulfur components contained in the NOx When the sulfur poisoning amount is equal to or greater than a threshold value, sulfur components are removed from the NOx catalyst by performing sulfur poisoning recovery control in which a catalyst bed temperature is increased by supplying unburned fuel components to the NOx catalyst Target catalyst bed temperature is increased while an atmosphere around the NOx catalyst is brought into a state of fuel-rich combustion, and the sulfur poisoning recovery control is terminated when the sulfur vac amount of seizure becomes smaller than a predetermined value which is smaller than the threshold value. This exhaust gas purification apparatus includes: a cumulative value calculation means for calculating a high-temperature time cumulative value as a value indicative of the degree of heat deterioration of the NOx catalyst and which is a cumulative length of time during which the temperature of the NOx catalyst is larger is a predetermined temperature; default value calculating means for calculating a standard value of the high-temperature time cumulative value corresponding to a current total operating time of the internal combustion engine on the basis of a total engine operating time indicating the current total operating time of the internal combustion engine; and a controller for executing a high-temperature poisoning recovery control in which the catalyst bed temperature is raised to a target catalyst bed temperature that is above the target catalyst bed temperature according to the sulfur poisoning recovery control when the high-temperature time cumulative value calculated by the cumulative value calculator is equal to or smaller than the standard value determined by Default value calculation device is calculated.

In the case where a driver drives a motor vehicle only for a short period of time, the temperature of the exhaust gas from the internal combustion engine does not increase greatly, and therefore, the catalyst bed temperature of the NOx catalyst tends to be low. Therefore, in such a case, the probability that the sulfur poisoning recovery control is carried out is relatively low, and even if it is carried out, it is relatively difficult to increase the catalyst bed temperature during the sulfur poisoning recovery control. As a result, the rate of removal of sulfur components removed from the NOx catalyst decreases, leaving a larger amount of sulfur components in the NOx catalyst. In particular, in a case where fuel having a sulfur concentration larger than a standard sulfur concentration is used, the amount of sulfur components entering the NOx catalyst is larger than when fuel having the standard sulfur concentration is used, and therefore For example, a larger amount of sulfur components is adsorbed in the NOx catalyst, and thus a larger amount of sulfur components is left in the NOx catalyst.

As such, in a case where the motor vehicle is often run only for a short period of time, there is a tendency that the increase in the high-temperature time cumulative value, which is a cumulative value of the time during which the catalyst bed temperature of the NOx catalyst is high, is low; and therefore, the probability that the high-temperature time cumulative value becomes equal to or smaller than the standard value is relatively high. As such, by carrying out the high-temperature sulfur poisoning recovery control, when the high-temperature time cumulative value becomes equal to or lower than the standard value, sulfur components can be efficiently removed from the NOx catalyst, and thus the amount of sulfur components left in the NOx catalyst can be reduced efficiently become. As such, the exhaust gas purifying apparatus according to the first aspect of the invention is capable of reducing the amount of sulfur components left in the NOx catalyst while avoiding excessively increasing the catalyst bed temperature of the NOx catalyst, thereby increasing the NOx Emissions from the internal combustion engine, which can be caused by the sulfur components, which are left in the NOx catalyst, is suppressed.

The exhaust gas purifying apparatus according to the first aspect of the invention may be such that the smaller the high-temperature time cumulative value is, the larger the target catalyst bed temperature used in the high-temperature sulfur poisoning recovery control is set by the controller.

When the high-temperature time cumulative value is smaller than the standard value, the greater the deviation of the high-temperature time cumulative value from the standard value, the more sulfur components are left in the NOx catalyst. In this state, even if the sulfur poisoning recovery control is carried out, the catalyst bed temperature does not increase greatly, and therefore the sulfur components are not effectively removed from the NOx catalyst. In other words, this condition may be regarded as a condition in which the catalyst bed temperature is likely not excessively increased as the catalyst bed temperature is raised by the high-temperature sulfur poisoning recovery control. According to the above-described exhaust gas purifying apparatus, since the maximum temperature of the target catalyst bed temperature when the high-temperature time cumulative value is smaller than the standard value is set larger, the larger the deviation of the high-temperature time cumulative value from the standard value, preventing excessive increase of the catalyst bed temperature of the NOx catalyst and effective removal of sulfur components from the NOx catalyst can be achieved as desired.

In addition, the exhaust gas purifying apparatus according to the first aspect of the invention may be such that the controller increases the target catalyst bed temperature used in the high temperature sulfur poisoning recovery control to a predetermined optimum amount.

In addition, the exhaust gas purifying apparatus according to the first aspect of the invention may be such that the standard value of the high-temperature time cumulative value increases, the larger the total engine running time display value becomes.

The second aspect of the invention relates to an exhaust gas purification device for an internal combustion engine, which includes an adsorption-reduction NOx catalyst provided in an exhaust system of the internal combustion engine and an estimator for estimating a sulfur poisoning amount representing the amount of sulfur components present in the NOx When the sulfur poisoning amount is equal to or greater than a threshold value, sulfur components are removed from the NOx catalyst by performing sulfur poisoning recovery control in which a catalyst bed temperature is increased by supplying unburned fuel components to the NOx catalyst Target catalyst bed temperature is increased while an atmosphere around the NOx catalyst is brought into a state of fuel-rich combustion, and the sulfur poisoning recovery control is terminated when the Sch is less than a predetermined value, which is smaller than the threshold value. This exhaust gas purification apparatus comprises: introduction sulfur amount calculating means for calculating a total introduction sulfur amount indicating the total amount of sulfur components flowing into the NOx catalyst; default value calculating means for calculating a standard value of the total introduction sulfur amount that corresponds to a current total operating time of the internal combustion engine on the basis of a total engine operating time indicating the current total operating time of the internal combustion engine; and a controller for executing a high-temperature sulfur poisoning recovery control in which the catalyst bed temperature is raised to a target catalyst bed temperature that is above the target catalyst bed temperature according to the sulfur poisoning recovery control when the total introduction sulfur amount calculated by the introduction sulfur amount calculating means is equal to or greater than the standard value derived from Default value calculation device is calculated.

In a case where the driver has a habit of driving a vehicle so that a large amount of fuel is consumed, such. As a rapid acceleration of the motor vehicle, the amount of sulfur components entering the NOx catalyst when fuel is consumed, relatively large, and therefore a relatively large amount of sulfur components is left in the NOx catalyst. In particular, in a case where the sulfur concentration in the fuel used is greater than the standard sulfur concentration, there is a tendency that a large amount of sulfur components enters the NOx catalyst as compared with when the fuel used has the standard sulfur concentration. In such a case, therefore, a larger amount of sulfur components are adsorbed in the NOx catalyst, resulting in a significant increase in the amount of sulfur components remaining in the NOx catalyst.

As such, in a case where the motor vehicle is frequently driven in such a fuel-consuming manner, the total introduction sulfur amount indicating value indicating the total amount of sulfur components entering the NOx catalyst increases at a relatively large rate, and therefore the possibility that the Total introduction sulfur amount display value equal to or larger than the standard value becomes relatively high. As such, by performing the high-temperature sulfur poisoning recovery control, when the total introduction sulfur amount display value exceeds the standard value, sulfur components can be efficiently removed from the NOx catalyst, and thus the amount of sulfur components left in the NOx catalyst can be efficiently reduced. As such, the exhaust gas purifying apparatus according to the second aspect of the invention is capable of reducing the amount of sulfur components left in the NOx catalyst while avoiding excessively increasing the catalyst bed temperature of the NOx catalyst, thereby increasing the NOx Emissions from the internal combustion engine, which can be caused by the sulfur components, which are left in the NOx catalyst, is suppressed.

The exhaust gas purification device according to the second aspect of the invention may be such that the larger the total introduction sulfur amount display value than the standard value, the larger the target catalyst bed temperature used in the high temperature sulfur poisoning recovery control is set by the controller.

When the total introduction sulfur amount display value is larger than the standard value, the larger the deviation of the high temperature time cumulative value from the standard value, the more sulfur components are left in the NOx catalyst. In this state, even if the sulfur poisoning recovery control is carried out, the catalyst bed temperature does not increase greatly, and therefore the sulfur components are not effectively removed from the NOx catalyst. In other words, this condition may be regarded as a condition where the catalyst bed temperature is unlikely to excessively increase as the catalyst bed temperature is raised by the high-temperature sulfur poisoning recovery process. According to the above-described exhaust gas purifying apparatus, since the maximum temperature of the target catalyst bed temperature is set larger when the total introduction sulfur amount display value is larger than the standard value, the greater the deviation of the total introduction sulfur amount display value from the standard value, prevention of excessive increase of the catalyst bed temperature of the NOx catalyst and effective removal of sulfur components from the NOx catalyst can be achieved as desired.

In addition, the exhaust gas purifying apparatus according to the second aspect of the invention may be such that the controller increases the target catalyst bed temperature used in the high temperature sulfur poisoning recovery control to a predetermined optimum temperature.

Furthermore, the exhaust gas purification device according to the second aspect of the invention may be such that the larger the total engine operation time indication value becomes, the larger the standard value of the total introduction sulfur amount.

In addition, the exhaust gas purifying apparatus according to the second aspect of the invention may include correcting means for correcting the total introduction sulfur amount corresponding to the total engine operating time toward the standard value when the high-temperature sulfur poisoning recovery control is executed.

Since carrying out the high-temperature sulfur poisoning recovery control further reduces the amount of sulfur components remaining in the NOx catalyst, it is preferable to reduce the frequency of executing the high-temperature sulfur poisoning recovery control so as to prevent an excessive increase in the catalyst bed temperature of the NOx catalyst. According to the above-described exhaust gas purifying apparatus, the total introduction sulfur amount corresponding to the total engine operation time indication value changes toward the standard value because the total introduction sulfur amount is corrected toward the standard value when the high temperature sulfur poisoning recovery control is executed, thereby reducing the likelihood that the total introduction sulfur amount is equal to or greater than Standard value, and thus the likelihood of excessive increase in the catalyst bed temperature is reduced.

In addition, the above-described exhaust gas purifying apparatus may be such that the smaller the amount of sulfur components remaining in the NOx catalyst, the lower the frequency of executing the high temperature sulfur poisoning recovery control by the correcting means.

The exhaust gas purification apparatuses according to the first and second aspects of the invention may be such that the control means determines whether the degree of cooling is determined on the basis of the catalyst bed temperature when the catalyst bed temperature is increased Deterioration of the NOx catalyst due to heat and sulfur components remaining in the NOx catalyst is large. The controller may execute the high-temperature sulfur poisoning recovery control when the degree of deterioration of the NOx catalyst is determined to be large.

In addition, the exhaust gas purification devices according to the first and second aspects of the invention may be such that the total engine operation time display value is calculated based on a total travel distance of a vehicle including the internal combustion engine or based on an accumulation value of a rotational speed of the internal combustion engine.

Further, the exhaust gas purification devices of the first and second aspects of the invention may be such that increasing the catalyst bed temperature to the desired catalyst bed temperature includes increasing the average catalyst bed temperature to the desired catalyst bed temperature.

When the degree of deterioration of the NOx catalyst due to heat and sulfur components remaining in the NOx catalyst is large, the catalyst bed temperature does not greatly increase even when sulfur poisoning recovery control is performed. Therefore, by executing the high-temperature sulfur poisoning recovery control only when the degree of deterioration of the NOx catalyst due to heat and sulfur components remaining in the NOx catalyst is large, an excessive increase in the temperature of the NOx catalyst in a reliable manner during the high-temperature sulfur poisoning recovery control be avoided.

The foregoing and other objects, features and advantages of the invention will become more apparent from the following description of preferred embodiments with reference to the accompanying drawings, in which like reference characters refer to like elements. Show it:

1 a view illustrating the overall structure of an internal combustion engine, which includes an exhaust gas purification device according to the first exemplary embodiment of the invention;

2A Fig. 10 is a timing chart showing how the fuel adding pulses for driving the fuel adding valve are controlled during the sulfur poisoning recovery control;

2 B Fig. 10 is a timing chart showing how the atmosphere around the NOx catalyst is changed during the sulfur poisoning recovery control;

2C Fig. 10 is a time chart showing how the catalyst bed temperature T of the NOx catalyst changes during sulfur poisoning recovery control;

2D Fig. 9 is a timing chart showing how the cumulative values ΣQr, ΣQ change during sulfur poisoning recovery control;

2E Fig. 10 is a timing chart showing how the fuel adding permission flag F is set during the sulfur poisoning recovery control;

3 5 is a flowchart illustrating the procedure for selectively executing the regular sulfur poisoning recovery control or the high-temperature sulfur poisoning recovery control in the exhaust gas purification apparatus of the first exemplary embodiment;

4 a graph illustrating how the high-temperature time accumulation value Σt and the standard value Bh increase as the travel distance of the motor vehicle increases;

5 a graph illustrating how the total introduction sulfur amount ΣSU and the standard value Bsu increase as the traveling distance of the motor vehicle increases;

6 5 is a flowchart illustrating the procedure for selectively executing the regular sulfur poisoning recovery control or the high-temperature sulfur poisoning recovery control in an exhaust gas purification device of the second exemplary embodiment;

7 5 is a flowchart illustrating a correction routine for correcting the total introduction sulfur amount ΣSU after the end of the high-temperature sulfur poisoning recovery control; and

8th FIG. 12 is a graph illustrating the catalyst bed temperatures at respective positions of the catalytic NOx converter between its upstream and downstream ends. FIG.

Hereinafter, the first exemplary embodiment of the invention will be described with reference to FIGS 1 to 4 described. In the first Exemplary embodiment, an exhaust gas purification device according to the invention is provided in an internal combustion engine for motor vehicles.

1 represents the construction of an internal combustion engine 10 , which contains the exhaust gas purification device of the first exemplary embodiment of the invention. The internal combustion engine 10 is a diesel engine having a common rail fuel injection system.

A suction passage 12 in the intake system of the internal combustion engine 10 is provided, and an exhaust passage 14 in an exhaust system of the internal combustion engine 10 is provided, both are with combustion chambers 13 connected in the respective engine cylinders. An air flow meter 16 is in the intake passage 12 provided, and a catalytic NOx converter 25 , a particle filter (PM filter) 26 and a catalytic oxidation converter 27 are in the exhaust passage 14 provided in this order from the upstream side.

The catalytic NOx converter 25 performs adsorption-reduction NOx catalysis. The NOx catalyst adsorbs (stores) the NOx contained in the exhaust gas when the oxygen concentration in the exhaust gas is high, and releases the adsorbed NOx when the concentration is low. When a sufficient amount of unburned fuel components serving as a reducing agent is present around the NOx catalyst, the NOx removed from the NOx catalyst is reduced and thus removed from the exhaust gas.

The particle filter 26 It is made of a porous material and is used to trap particles mainly composed of the soot contained in the exhaust gas. Similar to the catalytic NOx converter 25 leads the particle filter 26 also performs adsorption-reduction-NOx catalysis and removes the NOx contained in the exhaust gas as described above. In addition, the particles that are in the particle filter 26 be captured, burnt (oxidized) and thus by means of reactions caused by the NOx catalysis by the particle filter 26 is performed, removed.

The catalytic oxidation converter 27 performs oxidation catalysis. The oxidation catalysis removes the hydrocarbons and carbon monoxides contained in the exhaust gas by oxidizing them. In the exhaust passage 14 is a suction gas temperature sensor 28 on the upstream side of the particle filter 26 provided to the temperature of the exhaust gas, which is in the particle filter 26 flows to capture. On the other hand, an outlet gas temperature sensor 29 at the downstream side of the particle filter 26 in the exhaust passage 14 provided to the temperature of the exhaust gas coming out of the particle filter 26 flows to capture. A differential pressure sensor 30 is in the exhaust passage 14 provided, which is the differential pressure between the upstream side and the downstream side of the particulate filter 26 detected. Furthermore, there is eleven air-fuel ratio sensor 31 upstream of the catalytic NOx converter 25 in the exhaust passage 14 provided, and an air-fuel ratio sensor 32 is between the particle filter 26 and the catalytic oxidation converter 27 in the exhaust passage 14 intended.

An injector 40 for injecting fuel is in the combustion chamber 13 a respective cylinder of the internal combustion engine 10 intended. The injectors 40 in the respective cylinders are each via high pressure fuel supply lines 41 with a common line 42 connected. Fuel at high pressure becomes the common conduit 42 via a fuel pump 43 fed. The high pressure of the fuel in the common pipe 42 is through a line pressure sensor 44 who is on the common line 42 is envisaged. In addition, the fuel pump sends 43 Low pressure fuel to a fuel addition valve 46 via a supply line 45 for low pressure fuel.

An electronic control unit 50 executes various controls to the operation of the internal combustion engine 10 to control. The electronic control unit 50 consists of a CPU (central processing unit), the various calculation processes for controlling the internal combustion engine 10 executing; a ROM (read only memory) containing various programs and data for controlling the internal combustion engine 10 stores; a RAM (Random Access Memory) used to temporarily store the results of calculations from the CPU, etc.; an input port for inputting various external signals; an output port for outputting various signals to the outside; etc.

The input port of the electronic control unit 50 is as with the above-described sensors with various sensors such as an engine speed sensor 51 (NE sensor) for detecting the engine speed, an acceleration sensor 52 for detecting the accelerator operation amount, an intake temperature sensor 54 for detecting the temperature of the sucked air entering the internal combustion engine 10 is introduced, and a coolant temperature sensor 55 for detecting the temperature of the coolant of the internal combustion engine 10 connected. On the other hand, the output port of the electronic control unit 50 with drive circuits for the injectors 40 , the fuel pump 43 , the fuel addition valve 46 etc. connected.

The electronic control unit 50 provides drive signals to the drive circuits for the respective components connected to the output port of the electronic control unit 50 as described above, based on the operating state of the internal combustion engine 10 which is detected on the basis of the signals obtained from the above-described sensors. Ie. the electronic control unit 50 performs various controls such. For example, the fuel injection control for controlling the fuel injection amount, the fuel injection timing and the fuel injection pressure and the fuel adding control for adding fuel from the fuel adding valve 46 out.

In the exhaust gas purification device constructed as described above, the electronic control unit performs 50 a sulfur poisoning recovery control for restoring the NOx storage capacity of the NOx catalyst when it has decreased due to sulfur components (for example, sulfur oxides (SOx)) adsorbed in the NOx catalyst. The sulfur poisoning recovery control is started when the amount of sulfur components adsorbed in the NOx catalyst is based on the recording of the operating state of the internal combustion engine 10 calculated (estimated) reaches a threshold. The amount of sulfur components adsorbed in the NOx catalyst is hereinafter referred to as "sulfur poisoning amount S".

For example, during the sulfur poisoning recovery control, the NOx catalyst is heated to approximately 600 to 700 ° C by supplying unburned fuel components to the NOx catalyst while enriching the atmosphere around the NOx catalyst using the heat (hereinafter, referred to as "Fuel-rich combustion atmosphere"), whereby the sulfur components adsorbed in the NOx catalyst are removed, and thus the NOx storage capacity of the NOx catalyst is restored. Note that in the sulfur poisoning recovery control, unburned fuel components in the NOx catalyst are added by adding fuel from the fuel adding valve 46 can be supplied to the exhaust gas.

The sulfur poisoning recovery control is suspended when the sulfur poisoning amount S has dropped to a target value (for example, 0) smaller than the threshold value by execution of the sulfur poisoning recovery control. In the following, the calculations performed to start and stop the sulfur poisoning recovery control will be described in more detail.

The sulfur poisoning amount S is calculated using the following formula (1) every time fuel from the fuel injectors 40 is injected; Si = Si - 1 + SU - SD (1) where "Si" represents the current sulfur poisoning amount S, "Si - 1" represents the last sulfur poisoning amount S, "SU" the amount of sulfur components newly adsorbed in the NOx catalyst since the last fuel injection until the current fuel injection (hereinafter as "the newly adsorbed sulfur component amount SU"), and "SD" represents the amount of sulfur components newly removed from the NOx catalyst since the last fuel injection up to the current fuel injection (hereinafter referred to as "the newly removed sulfur component amount SD ").

The newly adsorbed sulfur component amount SU is calculated by using a fuel injection command value Qfin, which is a command value representing the amount of fuel delivered by injection from a respective injector 40 inject is identified. Note that the fuel injection command value Qfin is calculated before fuel from the injectors 40 is injected. More specifically, the amount of sulfur components that are included in the fuel is that produced by injection from a respective injector 40 is calculated by multiplying the fuel injection command value Qfin by the value obtained by dividing a sulfur concentration N, which is the standard sulfur concentration of the fuel, by 100 (N / 100). The value Qfin * (N / 100) obtained by the above-described multiplication is then converted to a parameter conversion factor K for converting the amount of sulfur components contained in the injected fuel into the amount of sulfur components injected therefrom Fuel in the NOx catalyst are re-adsorbed, multiplied, whereby the newly adsorbed sulfur component amount SU is calculated. The parameter conversion factor K is determined by applying the air-fuel ratio provided by the air-fuel ratio sensors 31 . 32 is detected, and the catalyst bed temperature is set to a table or map or function. According to this table, map, the parameter conversion factor K is set to 0 when the air-fuel ratio is that of air-fuel ratio sensors 31 . 32 is detected, equal to or smaller (richer) than the stoichiometric air Fuel ratio is (14.5 in this example). Also, when the air-fuel ratio is that of the air-fuel ratio sensors 31 . 32 is larger (poorer) than the stoichiometric air-fuel ratio, the larger (poorer) the air-fuel ratio obtained by the air-fuel ratio sensors, the larger the parameter conversion factor K becomes 31 . 32 is detected, and the larger the catalyst bed temperature is.

The amount of sulfur components theoretically derived from the NOx catalyst at the current catalyst bed temperature and air-to-fuel ratio from that of the air-fuel ratio sensors 31 . 32 is detected as the newly removed sulfur component amount SD in the formula (1). When the air-fuel ratio, that of the air-fuel ratio sensors 31 . 32 is detected, lower (richer) than the stoichiometric air-fuel ratio, the estimated newly removed sulfur component amount SD is greater than 0, and is greater, the larger the catalyst bed temperature and the smaller (richer) the air-fuel ratio is that of the air-fuel ratio sensors 31 . 32 is detected. The newly removed sulfur component amount SD is maintained at 0 when the air-fuel ratio obtained by the air-fuel ratio sensors 31 . 32 is greater (poorer) than the stoichiometric air-fuel ratio is.

The sulfur poisoning amount S (the current sulfur poisoning amount Si) calculated using the above-described formula (1) gradually increases by the newly adsorbed sulfur component amount SU when fuel during normal operation of the internal combustion engine 10 is consumed while gradually decreasing by the newly removed sulfur component amount SD during sulfur poisoning recovery control. As such, during normal operation of the engine increases 10 the sulfur poisoning amount S, when sulfur components are newly adsorbed by the NOx catalyst by fuel consumption, and during the sulfur poisoning recovery control, the sulfur poisoning amount S decreases as sulfur components are removed from the NOx catalyst by the controller.

The following will be described with reference to the timing charts shown in FIGS 2A to 2E in more detail, how the sulfur poisoning recovery control is started and stopped according to the sulfur poisoning amount S. In the sulfur poisoning recovery control, the average bed temperature T of the NOx catalyst is increased up to a target catalyst bed temperature Tt in steps to, for example, approximately 700 ° C by supplying unburned fuel components to the NOx catalyst by fuel addition from the fuel addition valve 46 is increased while the fuel-rich combustion atmosphere is generated around the NOx catalyst using the heat.

In the example that is in the 2A to 2E is shown, the fuel addition from the fuel addition valve 46 in response to a fuel addition permission flag F (in 2E shown), which is set to 1 (allowed), that is, in this case, for example, at a time T1. The fuel addition permission flag F is reset to 0 after setting to 1. After the start of the addition of fuel from the fuel addition valve 46 Fuel is intermittent from the fuel addition valve 46 according to the fuel adding pulse, which in 2A shown is added in a concentrated way.

During such a concentrated intermittent Addition of fuel from the fuel addition valve 46 For example, each fuel addition execution duration a, each fuel addition suspension duration b and the number of additions of the fuel from the fuel addition valve become 46 set such that the air-fuel ratio, that of the air-fuel ratio sensors 31 . 32 is detected, approaches a target air-fuel ratio AFt, which is set to smaller (richer) than the stoichiometric air-fuel ratio. More specifically, the fuel addition suspension period b (fuel addition interval) is set to be shorter, the larger (poorer) the air-fuel ratio, that of the air-fuel ratio sensors 31 . 32 is detected, as compared with the target air-fuel ratio AFt, and the fuel addition execution duration a is set to be larger, the larger (poorer) the air-fuel ratio, that of the air-fuel ratio sensors 31 . 32 is detected, compared to the target air-fuel ratio AFt. The number of additions of fuel is increased, the larger (poorer) the air-fuel ratio, that of air-fuel ratio sensors 31 . 32 is detected, compared to the target air-fuel ratio AFt.

The concentrated intermittent addition of fuel from the fuel addition valve 46 , which is started as described above, is continued until the fuel has been added a certain number of times, which has been determined on the basis of the above-described target air-fuel ratio AFt. In the example that is in the 2A and 2 B is shown, the addition of fuel from the fuel addition valve 46 ended at the time T2.

After the start of the addition of fuel from the fuel addition valve 46 For example, a heat generation fuel amount Q is repeated based on the driving state of the fuel adding valve 46 calculated in predetermined control cycles. The heat generation fuel amount Q is the amount of fuel supplied from the fuel addition valve 46 is added within a respective control cycle. In the example that is in the 2A to 2E is the length of this control cycle 16 Milliseconds. The calculated heat generation fuel amount Q is accumulated or accumulated each time in accordance with the following formula (2): ΣQ + Q (2) where "ΣQ" represents the cumulative value of the heat generation fuel amounts Q accumulated until the last 16 millisecond control cycle, and "Q" represents the heat generation fuel amount Q calculated in the current 16 milliseconds. As such, the heat generation fuel quantity accumulation value ΣQ, which is the total amount of fuel added from the fuel addition valve 46 since the start of the addition of fuel (T1), in other words, the total amount of fuel used since the start of the fuel addition (T1) for the oxidation that generates heat has been calculated. According to the solid line in 2D The heat generation fuel quantity cumulative value ΣQ calculated as described above greatly increases in a fuel addition execution period A that is the time duration while the fuel from the fuel addition valve increases 46 is added (T1 to T2), but does not increase during a fuel adding suspension period B following the fuel adding execution period A.

On the other hand, during the addition of fuel from the fuel adding valve 46 Each time the next 16 millisecond control cycle begins, the required amount of fuel Qr, which is the amount of fuel that is from the fuel addition valve 46 in the next 16 millisecond control cycle, which is the amount of fuel needed to bring the catalyst bed temperature T of the NOx catalyst to the target catalyst bed temperature Tt. The required amount of fuel Qr is calculated based on a difference ΔT between the catalyst bed temperature T of the NOx catalyst and the target catalyst bed temperature Tt and a flow rate Ga of the exhaust gas from the internal combustion engine 10 calculated. More specifically, the required amount of fuel Qr is calculated so that the lower the catalyst bed temperature T of the NOx catalyst compared to the target catalyst bed temperature Tt, the larger the required fuel amount Qr and calculated so that the required fuel amount Qr is smaller, depending is greater than the catalyst bed temperature of the NOx catalyst compared to the target catalyst bed temperature Tt. The calculated required amount of fuel Qr is accumulated according to the following formula (3): ΣQr + Qr (3) where "ΣQr" represents the cumulative value of the values of the required fuel amount Qr accumulated up to the last control cycle, and "Qr" is the value of the required fuel amount Qr calculated in the current control cycle. By this accumulation, the cumulative value of the required amount of fuel ΣQr, which represents the total amount of fuel, since the start of fuel addition by the fuel adding valve 46 (T1) is required to bring the average catalyst bed temperature T of the NOx catalyst to the target catalyst bed temperature Tt. Since the cumulative value of the required amount of fuel ΣQr is calculated (renewed) as described above, the increase of the cumulative value of the required amount of fuel ΣQr represented by the broken line in FIG 2D in comparison with the increase of the heat generation fuel quantity cumulative value ΣQ indicated by the solid line in FIG 2D is stated, gentle.

When the required fuel amount cumulative value ΣQr exceeds the heat generation fuel amount cumulative value ΣQ at time T3, the fuel addition permission flag is set to 1 (allowed), and the concentrated intermittent addition of fuel from the fuel adding valve 46 is started. At this time, the heat generation fuel amount cumulative value ΣQ is subtracted from the cumulative value of the required fuel amount ΣQr, and the heat generation fuel amount cumulative value ΣQ is cleared (set to 0), since fuel of the heat generation fuel amount cumulative value ΣQ accumulated from the time point T1 is already from the fuel addition valve 46 was added. Then, the concentrated intermittent addition of fuel of the fuel adding valve becomes 46 restarted, that is, the next fuel addition execution period A starts followed by the fuel addition suspension period B as mentioned above. As such, the fuel addition execution period A and the Fuel adding suspension period B during the sulfur poisoning recovery control.

During the sulfur poisoning recovery control, the smaller the catalyst bed temperature T of the NOx catalyst compared to the target catalyst bed temperature Tt, the larger the required fuel amount Qr, which is the amount of fuel supplied from the fuel addition valve 46 in each 16 millisecond control cycle, and therefore the more the cumulative value of the required amount of fuel ΣQr increases. This reduces the time necessary for the cumulative value of the required fuel amount ΣQr to reach the heat generation fuel amount cumulative value ΣQ, and thus shortens the fuel addition suspension period B. As a result, the average amount of fuel added from the fuel adding valve increases 46 per unit time (corresponding to the ratio between the length of the fuel addition execution period A and the length of the fuel addition execution period A + the fuel addition suspension period B), thereby accelerating the increase of the catalyst bed temperature T lower than the target catalyst bed temperature Tt to the target catalyst bed temperature Tt.

As the catalyst bed temperature T of the NOx catalyst approaches the target catalyst bed temperature Tt, the required fuel amount Qr is decreased for each 16 millisecond control cycle, thereby softening the increase of the required fuel amount accumulation value ΣQr. As such, the time required for the cumulative value of the required fuel amount ΣQr to reach the heat generation fuel amount cumulative value ΣQ becomes longer, whereby the fuel addition suspension period B becomes longer. As a result, the average amount of fuel flowing from the fuel adding valve decreases 46 is added per unit of time. Ie. By decreasing the average fuel supply amount, it is possible to prevent the catalyst bed temperature T of the NOx catalyst from increasing excessively beyond the target catalyst bed temperature Tt.

As described above, when the length of the fuel addition exposure period B changes according to the difference between the catalyst bed temperature T of the NOx catalyst and the target catalyst bed temperature Tt in the manner described above, the catalyst bed temperature T of the NOx catalyst varies, for example, as shown by the solid line Line in 2C is specified so that the center of the fluctuation of the catalyst bed temperature T of the NOx catalyst (the average catalyst bed temperature T) coincides with the target catalyst bed temperature Tt. As such, during the sulfur poisoning recovery control, unburned fuel components are supplied to the NOx catalyst to bring the catalyst temperature T to the target catalyst bed temperature Tt, which is increased in increments up to 700 ° C, thereby increasing the catalyst bed temperature T of the NOx catalyst to approximately 700 ° C C increased.

When the concentrated intermittent addition of fuel from the fuel addition valve 46 in the fuel addition execution period A is performed in a state where the temperature of the NOx catalyst is already high after the average catalyst bed temperature T of the NOx catalyst is increased up to the target catalyst bed temperature Tt as described above, the fuel generates that of the fuel addition valve 46 is added, a fuel-rich combustion atmosphere around the NOx catalyst having an air-fuel ratio that is equal to the target air-fuel ratio AFt, which is lower (richer) than the stoichiometric air-fuel ratio. The fuel-rich combustion atmosphere thus generated around the NOx catalyst facilitates the removal of sulfur components from the NOx catalyst and their reduction. Thus, when the fuel addition execution period A and the fuel addition exposure period B are repeated, sulfur components (for example, SOx) are removed from the NOx catalyst and then reduced, thereby reducing the amount of sulfur components adsorbed in the NOx catalyst, thereby reducing the NOx Storage capacity of the NOx is restored. The sulfur poisoning recovery control is terminated when the sulfur poisoning amount S representing the amount of sulfur components adsorbed in the NOx catalyst has decreased to the aforementioned target value ("0" in this example).

According to the formula (1), the sulfur poisoning amount S is calculated (estimated) in consideration of the newly removed sulfur component amount SD representing the amount of sulfur components removed from the NOx catalyst during the sulfur poisoning recovery control. However, the newly removed sulfur component amount SD may differ from the amount of sulfur components actually removed from the NOx catalyst. Ie. the newly removed sulfur component amount SD is calculated as an amount of sulfur components theoretically removed from the NOx catalyst during sulfur poisoning recovery control were. In fact, however, some sulfur components are not removed by the sulfur poisoning recovery process and remain in the NOx catalyst. More specifically, even when the NOx catalyst has been heated and the atmosphere around the NOx catalyst has been made fuel rich, sulfur components may be present at some portions of the NOx catalytic converter 25 not be removed, where the catalyst bed temperature is not greatly increased, such. At the upstream end portion of the catalytic NOx converter 25 ,

As such, the newly removed sulfur component amount SD used to calculate the sulfur poisoning amount S may be determined from the amount of sulfur components actually removed from the NOx catalyst by the amount of sulfur components left in the NOx catalyst , as described above, differ. More specifically, the newly removed sulfur component amount SD may be smaller than the amount of sulfur components actually removed from the NOx catalyst during the sulfur poisoning recovery control, and such deviation of the newly removed sulfur component amount SD from the amount of actually removed sulfur components causes a deviation of the sulfur poisoning amount S, which is calculated from the newly removed sulfur component amount SD.

Therefore, in a case where the calculated (estimated) sulfur poisoning amount S is smaller than the actual sulfur poisoning amount S when the sulfur poisoning recovery control is terminated in response to the calculated (estimated) sulfur poisoning amount S 0 being reached, the actual sulfur poisoning amount S is still larger as 0, leaving some sulfur components still in the NOx catalyst. Further, when the NOx catalyst is used, the amount of sulfur components left in the NOx catalyst increases, and therefore the deviation of the calculated sulfur poisoning amount S from the actual sulfur poisoning amount S becomes larger, thereby increasing the amount of sulfur components contained in NOx catalyst at the end of the sulfur poisoning recovery control increases. The cases (1) to (3) described above in the description of the prior art are typical cases where a relatively large amount of sulfur components are left in the NOx catalyst for the reason mentioned above. As such, in a state in which the amount of sulfur components left in the NOx catalyst is large, even if the sulfur poisoning recovery control has been completed, the NOx storage capacity of the NOx catalyst continues to be high due to the sulfur components, which in As described above, the NOx catalyst can be left low, and therefore, the NOx emissions from the internal combustion engine 10 increase.

However, this problem can be solved by allowing a more effective removal of sulfur components from the NOx catalyst by further increasing the average temperature of the catalyst bed temperature T of the NOx catalyst during the sulfur poisoning recovery control, and this can be achieved by setting the target catalyst bed temperature Tt to greater than 700 ° C become. Ie. by allowing a more effective removal of sulfur components from the NOx catalyst, the amount of sulfur components left in the NOx catalyst can be made smaller than in a normal state, in other words, the calculated sulfur poisoning amount S can be closer to the actual sulfur poisoning amount S lie. However, if the target catalyst bed temperature Tt for the sulfur poisoning recovery control is set high as described above, the catalyst bed temperature T of the NOx catalyst may become excessively high, and this may cause heat damage to the NOx catalyst, which may reduce the NOx emissions from the engine 10 elevated.

Hereinafter, a sulfur poisoning recovery control execution routine executed to prevent the above-described problem will be more specifically described with reference to the flowchart of FIG 3 described. This sulfur poisoning recovery control execution routine is repeated by the electronic control unit 50 at given time intervals as an interrupt.

In this routine, it is determined whether or not the amount of sulfur components left in the NOx catalyst is likely to be large, and if so, high-temperature sulfur poisoning recovery control is performed. In the high temperature sulfur poisoning recovery control, the catalyst bed temperature is increased more than that in the above-described sulfur poisoning recovery control (hereinafter referred to as "regular sulfur poisoning recovery control" as distinguished from the high temperature sulfur poisoning recovery control). Ie. By performing the high-temperature sulfur poisoning recovery control, it is possible to reduce the amount of sulfur components left in the NOx catalyst and thus increase the NOx emissions from the internal combustion engine 10 to be caused by the sulfur components, which are left in the NOx catalyst, without causing an excessive increase in the temperature of the NOx catalyst.

First, in the sulfur poisoning recovery control execution routine, a high temperature time cumulative value Σt and its standard value Bh are calculated (S101, S102). This high temperature time accumulation value Σt and the default value Bh are used in determining whether the amount of sulfur components left in the NOx catalyst is likely to be large.

More specifically, in step S101, the high temperature time cumulative value Σt is calculated by, for example, accumulating the time during which the catalyst bed temperature T of the NOx catalyst is above 600 ° C. Since the high-temperature time cumulative value Σt corresponds to the degree of heat deterioration of the NOx catalyst, the high-temperature time cumulative value Σt is small when the degree is low, and increases as the degree increases.

In step S102, the standard value Bh corresponding to the current travel distance of the motor vehicle is calculated. The travel distance of the motor vehicle corresponds to the total operating time of the internal combustion engine 10 (hereinafter referred to as "total engine operating time equivalent value"), and the travel distance of the motor vehicle increases as the total operating time of the internal combustion engine increases 10 elevated. For example, the default Bh is calculated using a function, table, or map. More specifically, a relationship between the travel distance of the motor vehicle and the standard value Bh is determined empirically, and a map which determines the predetermined relationship is formulated and stored in the ROM of the electronic control unit 50 saved. In this case, the default value Bh is calculated by applying the current travel distance of the motor vehicle to the map. The calculated standard value Bh increases as the travel distance of the motor vehicle increases, as for example in the dashed line in FIG 4 is specified.

After the high temperature time accumulation value Σt and the standard value Bh have been calculated as described above, a request to execute the sulfur poisoning recovery control is issued (S103). This request is issued when the sulfur poisoning amount S calculated by the formula (1) is equal to or greater than a threshold, while predetermined conditions for executing the sulfur poisoning recovery control are all satisfied. If the result in step S103 is "YES", it is determined whether or not the high temperature time cumulative value Σt is equal to or smaller than the standard value Bh (S104). This determination determines whether the amount of sulfur components left in the NOx catalyst is likely to be large.

In the case where a driver drives a motor vehicle only for a short period of time, the temperature of the exhaust gas from the internal combustion engine increases 10 not strong, and therefore, the catalyst bed temperature T of the NOx catalyst tends to be low. In such a case, the probability that the sulfur poisoning recovery control is carried out is relatively low, and even if it is carried out, it is relatively difficult to increase the catalyst bed temperature T of the NOx catalyst during the sulfur poisoning recovery control. As a result, the rate of removing the sulfur components removed from the NOx catalyst decreases, leaving a large amount of sulfur components in the NOx catalyst. Specifically, in a case where fuel having a sulfur concentration larger than a standard sulfur concentration (sulfur concentration N in this example) is used, the amount of sulfur components that enter the NOx catalyst is larger than that when fuel, having the standard sulfur concentration is used, and therefore, a larger amount of sulfur components are adsorbed in the NOx catalyst, and thus a larger amount of sulfur components is left in the NOx catalyst.

As such, in a case where the automobile is often run only for a short period of time, the increase of the high temperature time cumulative value Σt is sluggish, and therefore the high temperature time cumulative value Σt increases as indicated by the solid line in FIG 4 is indicated when the driving distance of the motor vehicle increases. In this case, the probability that the high-temperature time accumulation value Σt in step S104 in the routine that is in 3 is determined to be equal to or lower than the standard value Bh, relatively high. If it is determined in step S104 that the high-temperature time cumulative value Σt is larger than the standard value Bh, it indicates that the Amount of sulfur components left in the NOx catalyst is not likely to be large, and therefore the regular sulfur poisoning recovery control is executed (S106). On the other hand, when it is determined in step S104 that the high temperature time cumulative value Σt is equal to or smaller than the standard value Bh, it indicates that the amount of sulfur components left in the NOx catalyst is likely to be large, and therefore the high temperature sulfur poisoning recovery control (FIG. S105) instead of the regular sulfur poisoning recovery control.

In the high temperature sulfur poisoning recovery control, the maximum temperature of the target catalyst bed temperature Tt is caused to be greater than 800 ° C, that is, greater than the maximum temperature of the target catalyst bed temperature Tt used in the regular sulfur poisoning recovery control. During the high temperature sulfur poisoning recovery control, the target catalyst bed temperature Tt is increased in steps in the same manner as in the regular sulfur poisoning recovery control. Then, even when the target catalyst bed temperature Tt reaches 700 ° C (the maximum temperature of the target catalyst bed temperature Tt in the regular sulfur poisoning recovery control), the target catalyst bed temperature Tt is further increased beyond 700 ° C under the condition that the mean catalyst bed temperature T of the NOx catalyst is not increased greater than 700 ° C. The amount by which the target catalyst bed temperature Tt is increased beyond 700 ° C during the high-temperature sulfur poisoning recovery control is set small enough to cause thermal damage (heat damage) to the catalytic NOx converter 25 and the larger the deviation KA of the high-temperature time cumulative value Σt from the standard value Bh (see FIG 4 ). Therefore, when the target catalyst bed temperature Tt is increased in the high-temperature sulfur poisoning recovery control, the average catalyst bed temperature T of the NOx catalyst becomes greater than in the regular sulfur poisoning recovery control, enabling more effective removal of sulfur components from the NOx catalyst, and as a result, the amount of sulfur components decreases. which are left in the NOx catalyst.

The high temperature sulfur poisoning recovery control and the regular sulfur poisoning recovery control are terminated when the sulfur poisoning amount S has decreased to the target value (0 in this example). Since carrying out the high temperature sulfur poisoning recovery control facilitates the increase of the high temperature time cumulative value Σt, the high temperature time cumulative value Σt corresponding to the current travel distance of the motor vehicle is close to the standard value Bh (indicated by the broken line in FIG 4 specified).

• (1) Die Hochtemperaturschwefelvergiftungswiederherstellungssteuerung wird ausgeführt, um ein effektiveres Entfernen von Schwefelkomponenten von dem NOx-Katalysator nur dann, wenn der Hochtemperaturzeitkumulationswert Σt gleich oder kleiner als der Standardwert Bh ist, mit anderen Worten nur in einem Fall, in dem die Entfernungsrate von Schwefelkomponenten, die von dem NOx-Katalysator entfernt werden, durch die Schwefelvergiftungswiederherstellungssteuerung aufgrund der Fahrweise des Fahrers niedrig ist und somit die Menge an Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, wahrscheinlich groß ist, zu ermöglichen. Somit kann die Menge an Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, durch die Hochtemperaturschwefelvergiftungswiederherstellungssteuerung verringert werden. Als solches wird durch die Hochtemperaturschwefelvergiftungswiederherstellungssteuerung die Menge an Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, verringert, während eine übermäßige Erhöhung der Katalysatorbetttemperatur T des NOx-Katalysators vermieden wird, und somit ist es möglich, eine Erhöhung der NOx-Emissionen von der Brennkraftmaschine 10, die durch die Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, verursacht wird, zu unterdrücken.
• (2) Wenn der Hochtemperaturzeitkumulationswert Σt kleiner als der Standardwert Bh wird, was die Abweichung KA des Hochtemperaturzeitkumulationswerts Σt von dem Standardwert Bh vergrößert, erhöhen sich die Schwefelkomponenten, die in dem NOx-Katalysator belassen werden. In diesem Zustand könnten sogar dann, wenn die Katalysatorbetttemperatur T des NOx-Katalysators durch Zuführen von unverbrannten Kraftstoffkomponenten zu dem NOx-Katalysator in dem Schwefelvergiftungswiederherstellungsverfahren erhöht wird, die Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, nicht entfernt werden. Mit anderen Worten kann dieser Zustand als ein Zustand betrachtet werden, bei dem sich die Katalysatorbetttemperatur T des NOx-Katalysators wahrscheinlich nicht übermäßig erhöht, wenn die Katalysatorbetttemperatur T des NOx-Katalysators durch die Hochtemperaturschwefelvergiftungswiederherstellungssteuerung erhöht wird. Im Hinblick dessen wird während der Hochtemperaturschwefelvergiftungswiederherstellungssteuerung, wenn der Hochtemperaturzeitkumulationswert Σt kleiner als der Standardwert Bh wird, die maximale Temperatur der Sollkatalysatorbetttemperatur Tt umso größer, je größer die Abweichung KA des Hochtemperaturzeitkumulationswerts Σt von dem Standardwert Bh ist, und je mehr die Katalysatorbetttemperatur T des NOx-Katalysators erhöht wird. Als solches können in der Hochtemperaturschwefefvergiftungswiederherstellungssteuerung eine Verhinderung einer übermäßigen Erhöhung der Katalysatorbetttemperatur T des NOx-Katalysators und eine effektive Entfernung von Schwefelkomponenten von dem NOx-Katalysator auf gewünschte Weise erzielt werden.
• (3) In einem Fall, in dem die Schwefelkonzentration in dem verwendeten Kraftstoff größer als der Standardwert (Schwefelkonzentration N) ist, besteht die Tendenz, dass eine relativ große Menge an Schwefelkomponenten in dem NOx-Katalysator belassen wird. Sogar in einem derartigen Fall entfernt die Hochtemperaturschwefelvergiftungswiederherstellungssteuerung effektiv die Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, während eine übermäßige Erhöhung der Katalysatorbetttemperatur T vermieden wird.

According to the exemplary embodiment described above, the following advantages are achieved.

• (1) The high-temperature sulfur poisoning recovery control is carried out to more effectively remove sulfur components from the NOx catalyst only when the high-temperature time cumulative value Σt is equal to or smaller than the standard value Bh, in other words, only in a case where the removal rate of sulfur components, which are removed from the NOx catalyst, by the sulfur poisoning recovery control due to the driving style of the driver is low, and thus the amount of sulfur components, which are likely to be left in the NOx catalyst, is likely to be large. Thus, the amount of sulfur components left in the NOx catalyst can be reduced by the high temperature sulfur poisoning recovery control. As such, by the high-temperature sulfur poisoning recovery control, the amount of sulfur components left in the NOx catalyst is reduced while avoiding excessively increasing the catalyst bed temperature T of the NOx catalyst, and thus it is possible to increase the NOx emissions of the NOx catalyst internal combustion engine 10 to be suppressed by the sulfur components left in the NOx catalyst.
• (2) When the high temperature time accumulation value Σt becomes smaller than the standard value Bh, which is the deviation KA of the High temperature time accumulation value Σt increases from the standard value Bh, increase the sulfur components, which are left in the NOx catalyst. In this state, even if the catalyst bed temperature T of the NOx catalyst is increased by supplying unburned fuel components to the NOx catalyst in the sulfur poisoning recovery process, the sulfur components left in the NOx catalyst could not be removed. In other words, this condition can be regarded as a condition where the catalyst bed temperature T of the NOx catalyst is likely not excessively increased as the catalyst bed temperature T of the NOx catalyst is increased by the high temperature sulfur poisoning recovery control. In view of this, during the high temperature sulfur poisoning recovery control, when the high temperature time accumulation value Σt becomes smaller than the standard value Bh, the larger the deviation KA of the high temperature time accumulation value Σt from the standard value Bh, and the more the catalyst bed temperature T of the NOx, the greater the maximum temperature of the target catalyst bed temperature Tt becomes Catalyst is increased. As such, in the high-temperature sulfur poisoning recovery control, prevention of excessive increase in the catalyst bed temperature T of the NOx catalyst and effective removal of sulfur components from the NOx catalyst can be achieved as desired.
• (3) In a case where the sulfur concentration in the used fuel is larger than the standard value (sulfur concentration N), there is a tendency that a relatively large amount of sulfur components is left in the NOx catalyst. Even in such a case, the high-temperature sulfur poisoning recovery control effectively removes the sulfur components left in the NOx catalyst while avoiding excessively increasing the catalyst bed temperature T.

In the following, the second exemplary embodiment of the invention will be described with reference to FIGS 5 to 7 explained. The second exemplary embodiment differs from the first exemplary embodiment in the manner of determining whether the amount of sulfur components left in the NOx catalyst is likely to be large. More specifically, in the second exemplary embodiment, based on a total introduction sulfur amount ΣSU, the total amount of sulfur components added to the NOx catalyst from the start of the operation of the internal combustion engine 10 and, whose default value Bsu corresponding to the current travel distance of the motor vehicle determines whether the amount of sulfur components left in the NOx catalyst is likely to be large.

The graphic in 5 represents the relationship between the travel distance of the motor vehicle, the default value Bsu, and the total introduction sulfur amount ΣSU. The default value Bsu increases as the travel distance of the motor vehicle increases, as indicated by the solid line in FIG 5 is specified, and the total introduction sulfur amount ΣSU also increases as the traveling distance of the motor vehicle increases. However, in a case where the driver has a habit of driving a motor vehicle such that a large amount of fuel is consumed, such as fuel. For example, in order to accelerate the vehicle quickly, the amount of sulfur components entering the NOx catalyst when fuel is consumed (introduced sulfur amount SU) is relatively large, and therefore, a relatively large amount of sulfur components is left in the NOx catalyst , In particular, in a case where the sulfur concentration in the fuel used (sulfur concentration N) is greater than the standard sulfur concentration, there is a tendency that a large amount of sulfur components enters the NOx catalyst as compared with when the fuel used has the standard sulfur concentration , In such a case, hitherto, a larger amount of sulfur components have been adsorbed in the NOx catalyst, resulting in a significant increase in the amount of sulfur components left in the NOx catalyst. When the vehicle is driven in such a fuel-consuming manner, the total introduction sulfur amount ΣSU increases at a relatively high rate as the travel distance of the motor vehicle increases, as indicated by the solid line in FIG 5 is specified.

So such is when the total introduction sulfur amount ΣSU (represented by the solid line in 5 indicated) is equal to or greater than the standard value Bsu corresponding to the current travel distance of the motor vehicle (indicated by the broken line in FIG 5 given), the amount of sulfur components left in the NOx catalyst is likely to be large, and therefore, the high-temperature sulfur poisoning recovery control is executed under the condition that the request for execution in the controller has been issued.

The flowchart of 6 FIG. 12 illustrates the sulfur poisoning recovery control execution routine of the second exemplary embodiment. This routine is also repeated by the electronic control unit 50 as an interruption, for example at given crank angles.

In this routine, first, the newly adsorbed sulfur component amount SU is accumulated each time it is calculated (each time fuel is injected), thereby calculating the total introduction sulfur amount ΣSU representing the cumulative value of the newly adsorbed sulfur component amount SU (S201). Then, the default value Bsu corresponding to the current travel distance of the motor vehicle is calculated. The calculated default Bsu increases, as indicated by the dashed line in 5 is indicated when the driving distance of the motor vehicle increases. After the total introduction sulfur amount ΣSU and the standard value Bsu have thus been calculated, it is determined whether the request for executing the sulfur poisoning recovery control has been issued (S203). When the result in step S203 is "YES", it is determined whether or not the total introduction sulfur amount ΣSU is equal to or greater than the standard value Bsu is (S204). This determination is made to determine if the amount of sulfur components left in the NOx catalyst is likely to be large.

If it is determined in step S204 that the total introduction sulfur amount ΣSU is smaller than the standard value Bsu, it indicates that the amount of sulfur components left in the NOx catalyst is unlikely to be large. In this case, therefore, the regular sulfur poisoning recovery control is executed (S206). On the other hand, when it is determined in step S204 that the total introduction sulfur amount ΣSU is equal to or larger than the standard value Bsu, the amount of sulfur components remaining in the NOx catalyst is likely to be large. In this case, therefore, the high-temperature sulfur poisoning recovery control is executed (S205).

During the high-temperature sulfur poisoning recovery control, the target catalyst bed temperature Tt is increased to a temperature greater than 700 ° C, ie, greater than the maximum temperature of the target catalyst bed temperature Tt in the regular sulfur poisoning recovery control. The amount by which the target catalyst bed temperature Tt is increased beyond 700 ° C. during the high-temperature sulfur poisoning recovery control is set small enough to cause thermal damage (heat damage) to the catalytic NOx converter 25 and the larger the deviation KA of the total introduction sulfur amount ΣSU from the standard value Bsu, the greater the amount 5 ). Accordingly, when the target catalyst bed temperature Tt is increased, the average catalyst bed temperature T of the NOx catalyst increases, allowing for more efficient removal of sulfur components from the NOx catalyst and thus reducing the amount of sulfur components left in the NOx catalyst.

The high temperature sulfur poisoning recovery control and the regular sulfur poisoning recovery control are terminated when the sulfur poisoning amount S has decreased to the target value (0 in this example). Since carrying out the high temperature sulfur poisoning recovery control reduces the amount of sulfur components left in the NOx catalyst, the frequency of executing the high temperature sulfur poisoning recovery control is preferably reduced to prevent an excessive increase in the catalyst bed temperature T of the NOx catalyst. For this reason, in a total introduction sulfur quantity correction routine, which is described in US Pat 7 That is, when the high-temperature sulfur poisoning recovery control has been completed (S301: YES), the total introduction sulfur amount ΣSU is corrected toward the standard value Bsu (S302). At this time, the total introduction sulfur amount ΣSU is corrected by an optimum amount empirically determined in advance. By this correction, the total introduction sulfur amount ΣSU corresponding to the current running distance of the motor vehicle changes toward the standard value Bsu, which reduces the likelihood that the total introduction sulfur amount ΣSU becomes equal to or larger than the standard value Bsu, and thus increases the likelihood of excessively increasing the catalyst bed temperature T of the NOx Catalyst, as described above, reduced.

• (4) Die Hochtemperaturschwefelvergiftungswiederherstellungssteuerung wird ausgeführt, um ein effektiveres Entfernen von Schwefelkomponenten von dem NOx-Katalysator nur dann, wenn die Gesameinleitungsschwefelmenge ΣSU gleich oder größer als der Standardwert Bsu ist, mit anderen Worten wenn der Kraftstoffverbrauch der Brennkraftmaschine 10 (die eingeleitete Schwefelmenge SU) aufgrund beispielsweise der Fahrweise des Fahrers groß ist und daher die Menge an Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, groß ist, zu ermöglichen. Somit kann die Menge an Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, durch das Hochtemperaturschwefelvergiftungswiederherstellungsverfahren verringert werden. Als solches wird durch das Hochtemperaturschwefelvergiftungswiederherstellungsverfahren die Menge an Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, verringert, während eine übermäßige Erhöhung der Katalysatorbetttemperatur T des NOx-Katalysators vermieden wird, und somit ist es möglich, eine Erhöhung der NOx-Emissionen der Brennkraftmaschine 10, die durch die Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, verursacht wird, zu unterdrücken.
• (5) Wenn die Gesamteinleitungsschwefelmenge ΣSU größer als der Standardwert Bsu ist, ist, je größer die Abweichung KA der Gesamteinleitungsschwefelmenge ΣSU von dem Standardwert Bsu ist, die Menge an Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, umso größer. In diesem Zustand könnten sogar dann, wenn die Katalysatorbetttemperatur T des NOx-Katalysators durch Zuführen von unverbrannten Kraftstoffkomponenten zu dem NOx-Katalysator in der Schwefelvergiftungswiederherstellungssteuerung erhöht wird, die Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, nicht entfernt werden. Mit anderen Worten kann dieser Zustand als ein Zustand betrachtet werden, in dem sich die Katalysatorbetttemperatur des NOx-Katalysators wahrscheinlich nicht übermäßig erhöht, wenn die Katalysatorbetttemperatur T des NOx-Katalysators durch die Hochtemperaturschwefelvergiftungswiederherstellungssteuerung erhöht wird. Im Hinblick dessen wird während der Hochtemperaturschwefelvergiftungswiederherstellungssteuerung, wenn die Gesamteinleitungsschwefelmenge ΣSU größer als der Standardwert Bsu wird, die maximale Temperatur der Sollkatalysatorbetttemperatur Tt umso größer, je größer die Abweichung KA der Gesamteinleitungsschwefelmenge ΣSU von dem Standardwert Bsu ist, und je mehr die Katalysatorbetttemperatur T des NOx-Katalysators erhöht wird. Als solches können in der Hochtemperaturschwefelvergiftungswiederherstellungssteuerung eine Verhinderung einer übermäßigen Erhöhung der Katalysatorbetttemperatur des NOx-Katalysators und ein effektives Entfernen von Schwefelkomponenten von dem NOx-Katalysator auf gewünschte Weise erzielt werden.
• (6) Da das Ausführen der Hochtemperaturschwefelvergiftungswiederherstellungssteuerung außerdem die Menge an Schwefelkomponenten, die in dem NOx-Katalysator belassen werden, verringert, wird vorzugsweise die Häufigkeit der Ausführung der Hochtemperaturschwefelvergiftungswiederherstellungssteuerung verringert, um eine übermäßige Erhöhung der Katalysatorbetttemperatur T des NOx-Katalysators zu verhindern. Im Hinblick dessen wird die Gesamteinleitungsschwefelmenge ΣSU am Ende der Hochtemperaturschwefelvergiftungswiederherstellungssteuerung in Richtung des Standardwerts korrigiert. Durch diese Korrektur ändert sich die Gesamteinleitungsschwefelmenge ΣSU, die der derzeitigen Fahrtstrecke des Kraftfahrzeugs entspricht, in Richtung des Standardwerts Bsu, was die Wahrscheinlichkeit verringert, dass die Gesamteinleitungsschwefelmenge ΣSU gleich oder größer als der Standardwert Bsu wird, womit die Wahrscheinlichkeit verringert wird, dass sich die Katalysatorbetttemperatur T des NOx-Katalysators wie oben beschrieben übermäßig erhöht.

According to the second exemplary embodiment of the invention, the following advantages can be achieved in addition to the advantages (1) to (3) of the first exemplary embodiment.

• (4) The high-temperature sulfur poisoning recovery control is carried out to more effectively remove sulfur components from the NOx catalyst only when the total introduction sulfur amount ΣSU is equal to or larger than the standard value Bsu, in other words, when the fuel consumption of the internal combustion engine 10 (the introduced sulfur amount SU) is large due to, for example, the driving style of the driver and therefore the amount of sulfur components left in the NOx catalyst is large. Thus, the amount of sulfur components left in the NOx catalyst can be reduced by the high temperature sulfur poisoning recovery process. As such, by the high-temperature sulfur poisoning recovery process, the amount of sulfur components left in the NOx catalyst is reduced while avoiding excessively increasing the catalyst bed temperature T of the NOx catalyst, and thus it is possible to increase the NOx emissions of the internal combustion engine 10 to be suppressed by the sulfur components left in the NOx catalyst.
• (5) When the total introduction sulfur amount ΣSU is larger than the standard value Bsu, the larger the deviation KA of the total introduction sulfur amount ΣSU from the standard value Bsu, the larger the amount of sulfur components left in the NOx catalyst. In this state, even if the catalyst bed temperature T of the NOx catalyst could be increased by supplying unburned fuel components to the NOx catalyst in the Sulfur poisoning recovery control is increased, the sulfur components, which are left in the NOx catalyst, are not removed. In other words, this condition can be regarded as a condition in which the catalyst bed temperature of the NOx catalyst is likely not excessively increased as the catalyst bed temperature T of the NOx catalyst is increased by the high-temperature sulfur poisoning recovery control. In view of this, during the high temperature sulfur poisoning recovery control, when the total introduction sulfur amount ΣSU becomes larger than the standard value Bsu, the larger the deviation KA of the total introduction sulfur amount ΣSU from the standard value Bsu, and the more the catalyst bed temperature T of the NOx, the larger the maximum temperature of the target catalyst bed temperature Tt becomes Catalyst is increased. As such, in the high-temperature sulfur poisoning recovery control, prevention of excessive increase of the catalyst bed temperature of the NOx catalyst and effective removal of sulfur components from the NOx catalyst can be achieved as desired.
• (6) Since carrying out the high-temperature sulfur poisoning recovery control also reduces the amount of sulfur components left in the NOx catalyst, it is preferable to reduce the frequency of executing the high-temperature sulfur poisoning recovery control to prevent excessive increase in the catalyst bed temperature T of the NOx catalyst. In view of this, the total introduction sulfur amount ΣSU is corrected toward the standard value at the end of the high temperature sulfur poisoning recovery control. By this correction, the total introduction sulfur amount ΣSU corresponding to the current travel distance of the motor vehicle changes toward the standard value Bsu, which reduces the likelihood that the total introduction sulfur amount ΣSU becomes equal to or larger than the standard value Bsu, thus reducing the likelihood that the total introduction sulfur amount .SIGMA Catalyst bed temperature T of the NOx catalyst excessively increased as described above.

• (a) In der ersten und zweiten beispielhaften Ausführungsform kann die Hochtemperaturschwefelvergiftungswiederherstellungssteuerung ausgeführt werden, wenn sich der NOx-Katalysator aufgrund von Wärme und Restschwefelkomponenten verschlechtert hat. In diesem Fall kann auf der Grundlage der mittleren Katalysatorbetttemperatur des NOx-Katalysators, während die Katalysatorbetttemperatur T erhöht wird, beispielsweise während die reguläre Schwefelvergiftungswiederherstellungssteuerung ausgeführt wird, bestimmt werden, ob sich der NOx-Katalysator aufgrund von Wärme und Restschwefelkomponenten verschlechtert hat.

The foregoing exemplary embodiments of the invention may be modified as follows.

• (a) In the first and second exemplary embodiments, the high temperature sulfur poisoning recovery control may be performed when the NOx catalyst has deteriorated due to heat and residual sulfur components. In this case, based on the average catalyst bed temperature of the NOx catalyst while increasing the catalyst bed temperature T, for example, while the regular sulfur poisoning recovery control is being executed, it may be determined whether the NOx catalyst has deteriorated due to heat and residual sulfur components.

The graphic of the 8th Sets the catalyst bed temperature between the upstream end and the downstream end of the catalytic NOx converter 25 in comparison between the case where the aforementioned deterioration of the NOx catalyst has occurred (indicated by the solid line) and the case where the deterioration has not occurred (indicated by the broken line). As it is from the graph of 8th is apparent, in a case where the deterioration of the NOx catalyst has occurred, even when it is attempted to increase the catalyst bed temperature T of the NOx catalyst, for example, by executing the regular sulfur poisoning recovery control, the catalyst bed temperature T of the NOx catalyst increases at the respective positions of the catalytic NOx converter 25 between the upstream end and the downstream end is not strong. Therefore, the degree of deterioration of the NOx catalyst due to heat and residual sulfur components can be determined to be large if the average catalyst bed temperature of the NOx catalyst is lower than the target catalyst bed temperature Tt by a predetermined reference amount while the catalyst bed temperature T of the NOx catalyst is, for example, the sulfur poisoning recovery control is increased.

• (b) In der zweiten beispielhaften Ausführungsform kann die Fahrtstrecke des Kraftfahrzeugs an dem Ende der Hochtemperaturschwefelvergiftungswiederherstellungssteuerung auf größer korrigiert werden. Dadurch kann die Gesamteinleitungsschwefelmenge ΣSU, die der Fahrtstrecke des Kraftfahrzeugs entspricht, in Richtung des Standardwerts Bsu korrigiert werden. In diesem Fall können dieselben Wirkungen wie der Vorteil (6) der zweiten beispielhaften Ausführungsform erzielt werden.
• (c) In der zweiten beispielhaften Ausführungsform kann der Kumulationswert des Kraftstoffeinspritzbefehlswerts Qfin, der von dem Start des Betriebs der Brennkraftmaschine 10 an akkumuliert wird (Kraftstoffeinspritzmengenkumulationswert), anstelle der Gesamteinleitungsschwefelmenge ΣSU verwendet werden. In diesem Fall kann der Kumulationswert als ein Beispiel eines ”Gesamteinleitungsschwefelmengenentsprechungswerts” betrachtet werden. Außerdem kann die Anzahl der Male, die die Schwefelvergiftungswiederherstellungssteuerung seit dem Start des Betriebs der Brennkraftmaschine 10 ausgeführt wurde, anstelle der Gesamteinleitungsschwefelmenge ΣSU verwendet werden. In diesem Fall kann die Anzahl als ein Beispiel eines ”Gesamteinleitungsschwefelmengenanzeigewerts” betrachtet werden.
• (d) In der ersten und zweiten beispielhaften Ausführungsform muss der Betrag, um den die Sollkatalysatorbetttemperatur Tt in der Hochtemperaturschwefelvergiftungswiederherstellungssteuerung jenseits der maximalen Temperatur der Sollkatalysatorbetttemperatur Tt in der regulären Schwefelvergiftungswiederherstellungssteuerung erhöht wird, nicht notwendigerweise größer werden, wenn sich die Abweichung KA erhöht. Dieser Betrag kann beispielsweise auf einen optimalen Wert (konstanten Wert) eingestellt werden, der im Voraus empirisch bestimmt wurde.
• (e) In der ersten und zweiten beispielhaften Ausführungsform kann die Gesamtbetriebszeit seit dem Start des Betriebs der Brennkraftmaschine 10 anstelle der Fahrtstrecke des Kraftfahrzeugs verwendet werden. Außerdem kann der Kumulationswert der Drehzahl der Brennkraftmaschine 10 seit dem Start des Betriebs der Brennkraftmaschine 10 anstelle der Fahrtstrecke des Kraftfahrzeugs verwendet werden. In diesem Fall kann der Kumulationswert als ein Beispiel eines ”Gesamtmaschinenbetriebszeitanzeigewerts' betrachtet werden, der der Gesamtbetriebszeit der Brennkraftmaschine 10 seit dem Start ihres Betriebs entspricht.
• (f) Unverbrannte Kraftstoffkomponenten können dem NOx-Katalysator durch Einspritzen von Kraftstoff von Einspritzern 40 in einem Abgastakt zugeführt werden.

Thus, by carrying out the high-temperature sulfur poisoning recovery control only when the degree of deterioration of the NOx catalyst due to heat and residual sulfur components is determined to be large, an excessive increase in the temperature of the NOx catalyst can be more reliably prevented.

• (b) In the second exemplary embodiment, the travel distance of the motor vehicle at the end of the high temperature sulfur poisoning recovery control can be corrected to larger. Thereby, the total introduction sulfur amount ΣSU corresponding to the traveling distance of the motor vehicle can be corrected toward the standard value Bsu. In this case, the same effects as the advantage (6) of the second exemplary embodiment can be obtained.
• (c) In the second exemplary embodiment, the cumulative value of the fuel injection command value Qfin obtained from the start of the operation of the internal combustion engine 10 is accumulated (fuel injection amount accumulation value) instead of the total introduction sulfur amount ΣSU. In this case, the accumulation value may be considered as an example of a "total introduction sulfur amount correspondence value". In addition, the number of times the sulfur poisoning recovery control has started since the start of the operation of the internal combustion engine 10 has been executed instead of the total introduction sulfur amount ΣSU. In this case, the number may be considered as an example of a "total introduction sulfur amount display value".
• (d) In the first and second exemplary embodiments, the amount by which the target catalyst bed temperature Tt in the high temperature sulfur poisoning recovery control is increased beyond the maximum temperature of the target catalyst bed temperature Tt in the regular sulfur poisoning recovery control need not necessarily increase as the deviation KA increases. For example, this amount may be set to an optimum value (constant value) that has been empirically determined in advance.
• (e) In the first and second exemplary embodiments, the total operation time may be from the start of the operation of the internal combustion engine 10 be used instead of the route of the motor vehicle. In addition, the cumulative value of the rotational speed of the internal combustion engine 10 since the start of the operation of the internal combustion engine 10 be used instead of the route of the motor vehicle. In this case, the cumulative value may be regarded as an example of a "total engine operating time display value", that of the total operating time of the internal combustion engine 10 since the start of their operation.
• (f) Unburned fuel components may be added to the NOx catalyst by injecting fuel from injectors 40 be supplied in an exhaust stroke.

While the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the described embodiments or configurations. On the contrary, the invention covers various modifications and equivalent arrangements. Additionally, while the various elements of the described invention are shown in various example combinations and configurations, other combinations and configurations, including more, less, or only a single element, are contemplated within the scope of the appended claims.

Claims (13)

Exhaust gas purification device for an internal combustion engine ( 10 ), which is an adsorption-reduction-NOx-catalyst, which in an exhaust system of the internal combustion engine ( 10 ) and an estimating device ( 50 ) for estimating a sulfur poisoning amount (S) representing the amount of sulfur components adsorbed in the NOx catalyst, wherein when the sulfur poisoning amount (S) is equal to or greater than a threshold value, sulfur components pass from the NOx catalyst Carrying out a sulfur poisoning recovery control in which a catalyst bed temperature (T) is increased by supplying unburned fuel components to the NOx catalyst up to a target catalyst bed temperature (Tt) while bringing an atmosphere around the NOx catalyst into a high-fuel combustion state and wherein the sulfur poisoning recovery control is terminated when the sulfur poisoning amount (S) becomes smaller than a predetermined value smaller than the threshold value, the exhaust gas purification device comprising: a cumulative value calculation device ( 50 ) for calculating a high-temperature time cumulative value (Σt) as a value indicative of the degree of heat deterioration of the NOx catalyst and which is a cumulative time length during which the temperature of the NOx catalyst is higher than a predetermined temperature; a default value calculator ( 50 ) for calculating a standard value (Bh) of the high-temperature time cumulative value (Σt) corresponding to a current total operating time of the internal combustion engine ( 10 ), based on a total engine operating time, the current total operating time of the internal combustion engine ( 10 ) indicates; and a control device ( 50 ) for carrying out a high-temperature sulfur poisoning recovery control in which the catalyst bed temperature (T) is increased to a target catalyst bed temperature (Tt) greater than the target catalyst bed temperature (Tt) according to the sulfur poisoning recovery process when the high-temperature time cumulative value (Σt) generated by the cumulative value calculator (T) 50 ) is equal to or less than the standard value (Bh) determined by the standard value calculator ( 50 ) is calculated. An exhaust purification device according to claim 1, wherein the smaller the high-temperature time cumulative value (Σt) as compared with the standard value (Bh), the larger the target catalyst bed temperature becomes (Tt) used in the high-temperature sulfur poisoning recovery control by the controller (FIG. 50 ). An exhaust purification device according to claim 1, wherein said control means ( 50 ) increases the target catalyst bed temperature (Tt) used in the high temperature sulfur poisoning recovery control to a predetermined optimum temperature. An exhaust purification device according to any one of claims 1 to 3, wherein the standard value (Bh) of the high-temperature time cumulative value (Σt) is set the larger the larger the engine operation time display value becomes. Exhaust gas purification device for an internal combustion engine ( 10 ), which is an adsorption-reduction-NOx-catalyst, which in an exhaust system of the internal combustion engine ( 10 ) and an estimating device ( 50 ) for estimating a sulfur poisoning amount (S) representing the amount of sulfur components adsorbed in the NOx catalyst, wherein when the sulfur poisoning amount (S) is equal to or greater than a threshold value, sulfur components pass from the NOx catalyst Carrying out a sulfur poisoning recovery control in which a catalyst bed temperature (T) is increased by supplying unburned fuel components to the NOx catalyst up to a target catalyst bed temperature (Tt) while bringing an atmosphere around the NOx catalyst into a high-fuel combustion state and wherein the sulfur poisoning recovery control is terminated when the sulfur poisoning amount (S) becomes smaller than a predetermined value smaller than the threshold value, the exhaust gas purification device comprising: an introduction sulfur amount calculating device ( 50 ) for calculating a total introduction sulfur amount (ΣSU) indicating the total amount of sulfur components flowing into the NOx catalyst; a default value calculator ( 50 ) for calculating a standard value (Bsu) of the total introduction sulfur amount (ΣSU) corresponding to a current total operating time of the internal combustion engine ( 10 ), based on a total engine operating time, the current total operating time of the internal combustion engine ( 10 ) indicates; and a control device ( 50 ) for performing a high-temperature sulfur poisoning recovery control in which the catalyst bed temperature (T) is increased to a target catalyst bed temperature (Tt) greater than the target catalyst bed temperature (Tt) according to the sulfur poisoning recovery process, if the total introduction sulfur amount (ΣSU) provided by the initial sulfur amount calculator (T) 50 ) is equal to or greater than the standard value (Bsu) calculated by the default value calculator (Bsu) 50 ) is calculated. The exhaust gas purifying apparatus according to claim 5, wherein the larger the total introduction sulfur amount display value as compared with the standard value (Bsu), the larger the target catalyst bed temperature (Tt) used in the high-temperature sulfur poisoning recovery control by the control means (Bsu). 50 ). Exhaust gas purification device according to claim 5, wherein the control device ( 50 ) increases the target catalyst bed temperature (Tt) used in the high temperature sulfur poisoning recovery control to a predetermined optimum temperature. An exhaust purification device according to any one of claims 5 to 7, wherein the larger the total engine operation time display value, the larger the standard introduction value (Bsu) of the total introduction sulfur amount (ΣSU) becomes. An exhaust gas purification device according to any one of claims 5 to 8, further comprising a correction device ( 50 ) for correcting the total introduction sulfur amount (ΣSU) corresponding to the total engine operating time toward the standard value (Bsu) when the high temperature sulfur poisoning recovery control has been executed. The exhaust gas purification device according to claim 9, wherein the smaller the amount of sulfur components left in the NOx catalyst is, the lower is the amount to be corrected by the correction means (FIG. 50 ) frequency of execution of the high-temperature sulfur poisoning recovery control. Exhaust gas purification device according to one of claims 1 to 10, wherein the control device ( 50 ) based on the catalyst bed temperature (T), when the catalyst bed temperature (T) is increased, it is determined whether the degree of deterioration of the NOx catalyst due to heat and sulfur components left in the NOx catalyst is large; and the control device ( 50 ) performs the high-temperature sulfur poisoning recovery control when the degree of deterioration of the NOx catalyst is determined to be large. An exhaust purification device according to any one of claims 1 to 11, wherein the Total engine running time display value based on a total travel distance of a vehicle that drives the engine ( 10 ) or on the basis of a cumulative value of the engine speed ( 10 ) is calculated. An exhaust gas purifying apparatus according to any one of claims 1 to 12, wherein increasing the catalyst bed temperature (T) to the target catalyst bed temperature (Tt) includes increasing the average catalyst bed temperature (T) to the target catalyst bed temperature (Tt).

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