JP5354214B2 - Catalyst deterioration judgment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst deterioration determining device capable of accurately determining deterioration of an exhaust emission control means, restricting costs. <P>SOLUTION: When deterioration determination allowing conditions are satisfied during execution of S-purge processing (S10, S12), besides addition of S-purge processing fuel, following additions are performed through a fuel addition valve: addition of desorption atmosphere generating fuel, addition of rich state generating fuel, and addition of catalyst deterioration determining fuel, which is formed of addition (a) of fuel for determination and addition (b) of fuel for determination (S14). A/F deviation is computed based on the A/F minimum values MinAFa and MinAFb of the A/F value corresponding to the fuel additions (a) and (b) for determination detected by an A/F sensor (S16). When the A/F deviation is a predetermined deviation or more, a determination that NOx storage reduction catalyst is deteriorated is done (S18, S20). <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a catalyst deterioration determination device that determines deterioration of exhaust purification means of an internal combustion engine.

The exhaust from the internal combustion engine contains harmful components such as nitrogen oxides (NOx), hydrocarbons (HC), carbon monoxide (CO), etc., and in order to detoxify them, NOx storage reduction catalysts, An exhaust purification catalyst (exhaust purification means), which is a post-treatment device such as an oxidation catalyst, is provided in the exhaust passage so that it is detoxified and discharged to nitrogen (N ₂ ), carbon dioxide (CO ₂ ), water (H ₂ O), etc. ing.
However, these exhaust purification catalysts are poisoned by the exhaust heat and sulfur contained in the fuel or oil, so that the catalyst performance gradually deteriorates and sufficiently detoxifies harmful components such as NOx, HC and CO. It becomes difficult.

For this reason, an O ₂ sensor for detecting the oxygen concentration in the exhaust and a catalyst temperature sensor for detecting the temperature of the exhaust purification catalyst are provided upstream and downstream of the exhaust purification catalyst, and fuel is supplied from the upstream of the upstream O ₂ sensor. An exhaust purification device for an engine that supplies (reducing agent) and determines the deterioration of the exhaust purification catalyst based on the detection value of each sensor has been developed (Patent Document 1).

JP 2003-83047 A

As described above, in the engine exhaust purification device of Patent Document 1, the oxygen concentration is detected by providing the O ₂ sensors upstream and downstream of the exhaust purification catalyst, and the temperature of the exhaust purification catalyst is further detected by providing the catalyst temperature sensor. Like to do.
However, it is not preferable to newly provide an O ₂ sensor and a catalyst temperature sensor in order to determine the deterioration of the exhaust purification catalyst because of increased costs.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a catalyst deterioration determination device that can accurately determine deterioration of exhaust purification means while suppressing cost. There is to do.

  In order to achieve the above object, a catalyst deterioration determination device according to claim 1 is provided in an exhaust passage of an internal combustion engine and oxidizes an oxidizable component in exhaust gas and oxygen in exhaust gas in an oxidizing atmosphere. Exhaust purification means having an oxygen storage function for desorbing the stored oxygen under a reducing atmosphere, a fuel supply means for supplying fuel into the exhaust flowing upstream of the exhaust purification means, and exhaust rich Supply control means for controlling the fuel supply means so as to perform rich state generation supply to be in a state and deterioration determination supply for determining deterioration of the exhaust purification means, and exhaust gas provided downstream of the exhaust purification means Oxygen concentration detecting means for detecting the oxygen concentration in the exhaust gas, and deterioration determining means for determining deterioration of the oxidation function of the exhaust gas purifying means, wherein the supply control means is the exhaust gas purifying means in the deterioration determining means. When the deterioration is determined, the rich state generation and supply of exhaust gas in a rich state are continuously performed, and a plurality of the deterioration determinations are performed in addition to the rich state generation and supply at predetermined intervals after a lapse of a predetermined time from the start of the rich state generation and supply. The fuel supply means is controlled to supply, and the deterioration determination means is based on a change in oxygen concentration in the exhaust gas corresponding to each of the plurality of deterioration determination supplies detected by the oxygen concentration detection means, The deterioration of the exhaust gas purification means is determined.

  According to a second aspect of the present invention, there is provided the catalyst deterioration determination device according to the first aspect, wherein the deterioration determination means is in the exhaust gas that changes corresponding to each of the plurality of deterioration determination supplies detected by the oxygen concentration detection means. Among the oxygen concentrations, the difference between the minimum oxygen concentrations corresponding to any two times of the deterioration determination supply is less than the minimum oxygen concentration that is the minimum value of the oxygen concentration corresponding to any two times of the deterioration determination supply. A certain concentration deviation is calculated, and if the concentration deviation is equal to or greater than a predetermined concentration deviation, it is determined that the exhaust gas purification means has deteriorated.

  According to a third aspect of the present invention, there is provided the catalyst deterioration determination device according to the first aspect, wherein the deterioration determination means is a portion of the exhaust gas that changes corresponding to each of the plurality of deterioration determination supplies detected by the oxygen concentration detection means. Of the oxygen concentrations, an oxygen concentration change rate that is a change rate of each oxygen concentration is calculated based on a change in oxygen concentration corresponding to any two times of the deterioration determination supply, and the oxygen concentration in each deterioration determination supply The difference between the change rate, which is the difference between the maximum value and the minimum value of the change rate, is calculated, and further, the change rate deviation, which is the deviation of the change rate difference between any two of the deterioration determination supplies, is calculated. If the rate deviation is greater than or equal to a predetermined change rate deviation, it is determined that the exhaust gas purification means has deteriorated.

According to a fourth aspect of the present invention, there is provided the catalyst deterioration determination device according to any one of the first to third aspects, wherein the supply control means performs the rich state generation supply at the start of the deterioration determination of the exhaust gas purification means by the deterioration determination means. In addition, the fuel supply means is controlled to perform desorption atmosphere generation supply for supplying the fuel in a larger amount than the supply amount of the fuel in the rich state generation supply.
Further, in the catalyst deterioration determination device according to claim 5, in any one of claims 1 to 4, the exhaust purification means occludes nitrogen oxide in exhaust under an oxidizing atmosphere, and occludes under a reducing atmosphere. It has a nitrogen oxide occlusion function for desorbing and reducing nitrogen oxides, and when the exhaust gas purification means is in a sulfur poisoning state, it performs a sulfur reduction treatment that reduces and removes the sulfur that has been occluded by making the exhaust gas rich at a high temperature. The apparatus further includes a sulfur removing unit, and the deterioration determining unit determines deterioration of the exhaust gas purifying unit at the time of the sulfur reduction process in the sulfur removing unit.

  Further, in the catalyst deterioration determination device according to claim 6, in any one of claims 1 to 4, the exhaust purification unit includes an oxidation catalyst and nitrogen oxidation in exhaust gas in an oxidizing atmosphere provided downstream of the oxidation catalyst. The exhaust gas is composed of a nitrogen oxide storage catalyst that desorbs and reduces the stored nitrogen oxides in a reducing atmosphere while the nitrogen oxide storage catalyst is in a sulfur poisoning state. It further comprises sulfur removal means for performing sulfur reduction treatment for reducing and removing sulfur stored in a rich state, and the deterioration determination means determines deterioration of the oxidation catalyst at the time of sulfur reduction treatment in the sulfur removal means. Features.

The catalyst deterioration determination apparatus according to a seventh aspect of the present invention is the apparatus according to the fifth or sixth aspect, further comprising a sulfur removal number detection means for detecting the number of times of the sulfur reduction treatment, wherein the deterioration determination means is the sulfur removal number detection means. The deterioration determination is performed when the number of times of the sulfur reduction treatment detected in step S is equal to or greater than a predetermined number of times.
Further, in the catalyst deterioration determination device according to claim 8, in any one of claims 1 to 7, a travel distance detection integration unit that further detects a travel distance of a vehicle on which the internal combustion engine is mounted, and integrates the travel distance; One or both of exhaust temperature detection integration means for detecting the exhaust temperature of the internal combustion engine and integrating the exhaust temperature are provided, and the deterioration determination means is an integration of the travel distance detected by the travel distance detection means The deterioration determination is performed when the value is equal to or greater than a predetermined integrated travel distance, or when the integrated value of the exhaust temperature detected by the exhaust temperature integrated value detecting means is equal to or greater than a predetermined integrated temperature.

  According to the first aspect of the present invention, the fuel supply means is controlled to continuously perform the rich state generation supply, and by enriching the exhaust gas, the oxygen stored in the exhaust gas purification means is released and further enriched. The exhaust gas purifying means is judged to be deteriorated based on the oxygen concentration change in the exhaust gas corresponding to the respective deterioration judgment supplies detected by the oxygen concentration detecting means. Like to do.

  In this way, the exhaust gas is always in a rich state at the time of deterioration determination, and the oxygen stored in the exhaust gas purification means is released during normal operation of the internal combustion engine. After the stored oxygen is released, the fuel for deterioration determination is used as the exhaust gas purification means. Since the gas is supplied, the oxidation of the exhaust gas purification means and the fuel decomposition reaction can be stably performed in the deterioration determination supply performed at the time of deterioration determination. Further, since the deterioration of the exhaust purification unit is determined based on the change in the oxygen concentration due to the plurality of deterioration determination supplies, the downstream of the exhaust purification unit regardless of the absolute detection accuracy of the fuel supply unit and the oxygen concentration detection unit. The deterioration determination can be performed based on the detection value of the oxygen concentration detection means provided in the above.

Therefore, oxidation and fuel decomposition reaction can be performed stably at the time of deterioration judgment, and furthermore, deterioration of the exhaust purification means can be judged without providing an oxygen concentration detection means upstream of the exhaust purification means, thereby reducing costs. In addition, the deterioration of the catalyst can be accurately determined.
According to the invention of claim 2, the oxygen concentration in the exhaust gas that changes corresponding to each deterioration determination supply detected by the oxygen concentration detecting means corresponds to any two deterioration determination supplies. From each minimum oxygen concentration that is the minimum value of oxygen concentration, a concentration deviation that is the difference between these minimum oxygen concentrations is calculated, and if the concentration deviation is equal to or greater than a predetermined concentration deviation, it is determined that the exhaust purification means has deteriorated Like to do.

  In this way, the oxygen concentration corresponding to each deterioration determination supply is determined from the change in the oxygen concentration corresponding to any two deterioration determination supplies detected by the oxygen concentration detection means provided downstream of the exhaust purification means. Since the minimum oxygen concentration, which is the minimum value, is detected and the deterioration of the exhaust gas purification means is determined from the deviation in the concentration, the exhaust purification means of the exhaust gas purification means does not depend on the absolute detection accuracy of the fuel supply means or the oxygen concentration detection means. Degradation can be accurately determined from the detection value of the oxygen concentration detection means provided downstream.

  According to the invention of claim 3, the oxygen concentration corresponding to each deterioration determination supply from the change in the oxygen concentration in the exhaust gas corresponding to any two times deterioration determination supply detected by the oxygen concentration detection means. The difference in change rate, which is the difference between the maximum value and the minimum value of the change rate of change, is calculated, and further, the change rate deviation, which is the deviation of the difference in change rate of each deterioration judgment supply, is calculated, and the change rate deviation is a predetermined change If it is more than the rate deviation, it is determined that the exhaust purification means has deteriorated.

  In this way, from the change in oxygen concentration due to any two times of deterioration determination supply detected by the oxygen concentration detection means provided downstream of the exhaust purification means, each change rate corresponding to each deterioration determination supply is different from each other. Since the difference in the change rate is calculated, the change rate deviation is calculated from the difference between the change rates, and the deterioration of the exhaust purification means is determined from the change rate deviation, the absolute value of the fuel supply means and the oxygen concentration detection means is determined. Regardless of the detection accuracy, the deterioration determination can be accurately performed based on the detection value of the oxygen concentration detection means provided downstream of the exhaust purification means.

According to the invention of claim 4, when starting the deterioration determination of the exhaust gas purification means, in addition to the rich state generation supply, the desorption atmosphere generation supply larger than the fuel supply amount of the rich state generation supply is performed.
As described above, since the desorption atmosphere generation and supply are performed at the start of the deterioration determination of the exhaust purification unit, the oxygen stored in the exhaust purification unit can be reliably released in a short time.

Accordingly, the oxygen stored in the exhaust purification means can be reliably released in a short period of time, and the oxidation and fuel decomposition reaction in the exhaust purification means can be stably performed in the deterioration judgment supply performed at the time of deterioration judgment. The deterioration of the catalyst can be judged well.
According to the invention of claim 5, since the deterioration of the exhaust purification means is determined together with the sulfur reduction process for reducing and removing the sulfur content stored in the exhaust purification means, the exhaust purification process is performed during the sulfur reduction process. Deterioration determination of the exhaust gas purification means is performed using the state where the means is warmed up, so that consumption of fuel for warming up the exhaust gas purification means can be suppressed, and deterioration of fuel consumption can be prevented.

  Further, according to the invention of claim 6, since the exhaust purification means is configured to be divided into the oxidation catalyst and the nitrogen oxide storage catalyst, a highly efficient catalyst specialized in the function of fuel oxidation is provided. As a result, the exhaust purification efficiency can be improved, and the heat generated due to oxidation can be dispersed to the plurality of catalysts, so that the deterioration of the system that can improve the durability of the exhaust purification means can be determined.

According to the invention of claim 7, since the deterioration of the exhaust purification means is determined when the number of times of the sulfur reduction treatment is equal to or greater than the predetermined number of times, the initial exhaust purification means in which the catalyst has not deteriorated. The number of executions of deterioration determination can be reduced and unnecessary deterioration determination can be suppressed, so that further deterioration of fuel consumption can be prevented.
According to the invention of claim 8, when the integrated value of the travel distance detected and integrated by the travel distance detection integration means is equal to or greater than the predetermined integration travel distance, or detected and integrated by the exhaust temperature detection integration means. When the integrated value of the exhaust gas temperature is equal to or higher than the predetermined integrated temperature, the deterioration of the exhaust gas purification means is determined. Therefore, the deterioration determination of the exhaust gas purification means can be performed according to the traveling state of the vehicle, and the catalyst is deteriorated. Since it is possible to suppress the initial unnecessary deterioration determination, the fuel consumption can be further prevented from deteriorating.

It is a schematic block diagram of the catalyst deterioration determination apparatus which concerns on this invention. It is a block diagram which shows the internal structure of ECU in the catalyst degradation determination apparatus which concerns on this invention. It is a flowchart which shows the control routine of the catalyst degradation determination control which concerns on 1st Example of this invention. It is a characteristic view which shows the fuel addition amount at the time of catalyst degradation determination in S purge which concerns on 1st Example of this invention. It is a graph which shows the change of the fuel addition amount at the time of the normal catalyst based on 1st Example of this invention, and the output value of an A / F sensor. It is a graph which shows the change of the fuel addition amount at the time of catalyst deterioration which concerns on 1st Example of this invention, and the output value of an A / F sensor. It is a flowchart which shows the control routine of the catalyst deterioration determination control which concerns on 2nd Example of this invention. It is a characteristic view which shows the fuel addition amount at the time of catalyst deterioration determination in S purge which concerns on 2nd Example of this invention. It is a graph which shows the change of the fuel addition amount at the time of the normal catalyst based on 2nd Example of this invention, and the change rate of A / F. It is a graph which shows the change of the fuel addition amount at the time of catalyst deterioration which concerns on 2nd Example of this invention, and the change rate of A / F.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration diagram of a catalyst deterioration determination apparatus according to the present invention, and FIG. 2 shows a block diagram showing an internal configuration of an ECU in the catalyst deterioration determination apparatus according to the present invention.
Hereinafter, the configuration of the catalyst deterioration determination device of the present invention will be described.
As shown in FIG. 1, an engine (internal combustion engine) 1 is a multi-cylinder in-cylinder direct injection internal combustion engine (for example, a common rail diesel engine). Specifically, high pressure fuel accumulated in the common rail is injected into each cylinder as fuel injection. The fuel is supplied to the nozzle 20 and can be injected from the fuel injection nozzle 20 into the combustion chamber 11 of each cylinder at an arbitrary injection timing and injection amount.

  Each cylinder of the engine 1 is provided with a piston 2 that can slide up and down. The piston 2 is connected to a crankshaft (not shown) via a connecting rod 3. Further, a flywheel (not shown) is provided at one end of the crankshaft, and a crank angle sensor 22 for detecting the rotational speed of the crankshaft is provided on the flywheel.

An intake port 9 and an exhaust port 13 are communicated with the combustion chamber 11.
The intake port 9 is provided with an intake valve 10 for communicating and blocking the combustion chamber 11 and the intake port 9. The exhaust port 13 performs communication and blocking between the combustion chamber 11 and the exhaust port 13. An exhaust valve 12 is provided.

  Further, upstream of the intake port 9, an intake duct 4 for sucking in fresh air, an air cleaner 5 for removing dust in the sucked fresh air, and a turbocharger 6 for compressing the sucked fresh air using exhaust energy. , A compressor housing (not shown), an intercooler 7 that cools the compressed and heated fresh air, and an intake manifold 8 that distributes the intake air to each cylinder are provided in communication with each other.

  An air flow sensor 23 for detecting the amount of fresh air sucked into the combustion chamber 11 is provided downstream of the air cleaner 5 and upstream of the compressor housing of the turbocharger 6 so as to protrude into the passage. A boost sensor 24 for detecting the pressure of intake air sucked into the combustion chamber 11 and an intake air temperature sensor 25 for detecting the temperature of the intake air are provided so as to protrude into the intake manifold 8.

Further, downstream of the exhaust port 13, an exhaust manifold 14 that collects exhaust discharged from each cylinder, and a turbine housing (not shown) that introduces exhaust into the turbocharger 6 and an exhaust pipe 18 are provided so as to communicate with each other.
The exhaust pipe 18 includes an oxidation catalyst (exhaust purification means) 15 that oxidizes components to be oxidized in order from upstream, an NOx storage reduction catalyst (exhaust purification means) 16 that occludes and reduces NOx in the exhaust, and exhaust. A diesel particulate filter (DPF) 17 that collects and burns particulate matter mainly composed of graphite is communicably provided.

Further, a fuel addition valve (fuel supply means) 26 for adding a reducing agent (fuel) to the exhaust gas is provided downstream of the turbocharger 6 of the exhaust pipe 18 and upstream of the oxidation catalyst 15, and an exhaust gas temperature sensor for detecting the temperature of the exhaust gas. (Exhaust temperature detection integrating means) 27 is provided so as to protrude into the passage.
Further, an A / F sensor (oxygen concentration detection means) 28 for detecting an A / F value (oxygen concentration) that is an oxygen ratio in the exhaust gas is located downstream of the NOx storage reduction catalyst 16 in the exhaust pipe 18 and upstream of the DPF 17. Is provided so as to protrude into the passage.

The intake manifold 8 and the exhaust manifold 14 are provided with an EGR passage 21 for returning a part of the exhaust gas to the intake air so as to communicate with each other. The EGR passage 21 adjusts an EGR amount (exhaust gas flow rate). A valve 19 is provided.
The EGR valve 19, fuel injection nozzle 20, crank angle sensor 22, air flow sensor 23, boost sensor 24, intake air temperature sensor 25, fuel addition valve 26, exhaust gas temperature sensor 27, A / F sensor 28, and engine 1 Various devices and various sensors such as a vehicle speed sensor (traveling distance detection integrating means) 29 for detecting the vehicle speed of a vehicle (not shown) on which the vehicle is mounted are control devices for performing overall control of the engine 1 and are input / output. It is electrically connected to an electronic control unit (ECU) 30 including a device, a storage device (ROM, RAM, nonvolatile RAM, etc.), a timer, a central processing unit (CPU), etc. Various devices are operated and controlled based on information from various sensors.

Specifically, referring to FIG. 2, a block diagram showing the internal configuration of the ECU 30 in the catalyst deterioration determination device according to the present invention is shown, and the input / output relationship of the ECU 30 will be described below with reference to FIG.
Sensors such as a crank angle sensor 22, an air flow sensor 23, a boost sensor 24, an intake air temperature sensor 25, an exhaust gas temperature sensor 27, an A / F sensor 28, and a vehicle speed sensor 29 are electrically connected to the input side of the ECU 30. Detection information from these various devices and various sensors is input.

On the other hand, the EGR valve 19, the fuel injection nozzle 20, and the fuel addition valve 26 are electrically connected to the output side of the ECU 30.
Thus, the ECU 30 generates a control signal so that the fuel injection amount control unit 31 can inject an optimal fuel amount into the combustion chamber 11 based on a detection value of an accelerator position sensor (not shown) that detects the driver's accelerator operation. The fuel injection nozzle 20 is supplied and controlled.

Further, based on a control signal to the fuel injection nozzle 20 of the fuel injection control unit 31, the fuel injection amount integration unit 32 integrates the injection amount of fuel injected from the fuel injection nozzle 20.
Further, based on the time measured by the timer 33 built in the ECU 30, the operation time of the engine 1 is integrated by the operation time integration unit 34.
Further, based on the integrated value of the fuel injection amount in the fuel injection amount integrating unit 32 and the integrated value of the operating time of the engine 1 in the operating time integrating unit 34, the S purge control unit (sulfur removal means) 35 stores NOx. The amount of sulfur stored in the reduction catalyst 16 is calculated, and if it is determined that the NOx storage reduction catalyst 16 has been poisoned with sulfur based on the calculated amount of sulfur, S purge processing (sulfur reduction processing) for reducing and removing sulfur. A control signal is supplied to the fuel addition control unit (supply control means) 41 so as to perform the above.

Further, based on a control signal from the S purge control unit 35 to the fuel addition control unit 41, the S purge number detection unit (sulfur removal number detection means) 36 detects the number of S purge processes.
Further, based on the vehicle speed detected by the vehicle speed sensor 29 and the time measured by the timer 33, the travel distance of the vehicle is calculated by a travel distance calculation unit (travel distance detection integration means) 37.
Further, the travel distance of the vehicle calculated by the travel distance calculation section 37 is integrated by a travel distance integration section (travel distance detection integration means) 38.

The exhaust temperature detected by the exhaust temperature sensor 27 is integrated by an exhaust temperature integration unit (exhaust temperature detection integration means) 39.
Also, the number of S purges detected by the S purge number detection unit 36, the integrated value of the vehicle travel distance integrated by the travel distance integration unit 38, and the integration of the exhaust temperature integrated by the exhaust temperature integration unit 39. Based on the value, the exhaust catalyst deterioration determination unit (deterioration determination means) 40 determines whether or not the catalyst deterioration of the oxidation catalyst 15 is to be determined. ) Is supplied to the fuel addition control unit 41 so as to perform the addition of Further, the exhaust catalyst deterioration determination unit 40 determines the catalyst deterioration of the oxidation catalyst 15 based on the detection value of the A / F sensor 28 during addition of the fuel for catalyst deterioration determination.

Further, based on the control signal of the S purge control unit 35 and the control signal of the exhaust catalyst deterioration determination unit 40, the fuel addition control unit 41 adds the reducing agent (fuel) for performing the S purge process and the catalyst deterioration determination. The fuel addition valve 26 is controlled to be performed from the fuel addition valve 26.
[First embodiment]
Next, a determination procedure for determining catalyst deterioration in the first embodiment will be described.

FIG. 3 is a flowchart showing a control routine of catalyst deterioration determination control according to the first embodiment of the present invention, and FIG. 4 is a characteristic diagram showing a fuel addition amount at the time of catalyst deterioration determination during S purge. 5 is a graph showing changes in the fuel addition amount and the output value of the A / F sensor when the catalyst is normal, and FIG. 6 is a graph showing changes in the fuel addition amount and the output value of the A / F sensor when the catalyst is deteriorated. It is.
As shown in FIG. 3, first, in step S10, it is determined whether or not an S purge process (sulfur reduction process) is being performed. If the determination result is true (Yes) and the S purge process is being performed, the process proceeds to step S12. If the determination result is false (No) and the S purge process is not being performed, the process of step S10 is performed again.

  In step S12, the number of S purge processes detected by the S purge number detection unit 36 is greater than or equal to a predetermined number of processes, or the accumulated travel distance of the vehicle accumulated by the travel distance accumulation unit 37 is greater than or equal to a predetermined accumulated travel distance, or It is determined whether or not any of the deterioration determination permission conditions in which the integrated value of the exhaust temperature integrated by the exhaust temperature integrating unit 39 is equal to or higher than a predetermined integrated temperature is satisfied. If the determination result is true (Yes) and any of the deterioration determination permission conditions is satisfied, the process proceeds to step S14. If the determination result is false (No) and neither of the deterioration determination permission conditions is satisfied, step S10 is performed. Return to. The predetermined number of treatments, the predetermined integrated travel distance, and the predetermined integrated temperature are determined based on the degree of thermal damage of the oxidation catalyst 15 that has been determined in advance through experiments or the like.

  In step S14, as shown in FIG. 4, the fuel addition valve 26 is controlled so that the catalyst deterioration determination fuel addition is performed during the S purge processing fuel addition performed every predetermined time. The catalyst deterioration determination fuel addition is performed in addition to the rich state generation fuel addition (rich state generation supply) in order to desorb the oxygen stored in the oxidation catalyst 15 and the NOx storage reduction catalyst 16 in a short time. Only the rich state generated fuel addition that performs the desorption atmosphere generation fuel addition (desorption atmosphere generation supply) and then reliably desorbs the oxygen stored in the oxidation catalyst 15 and the NOx occlusion reduction catalyst 16 and keeps the exhaust in a rich state only. And a determination fuel addition a and a determination fuel which are two determination fuel additions (determination determination supply) for determining deterioration of the oxidation catalyst 15 after a predetermined time has elapsed since the start of the addition of the rich state generation fuel. It is performed by adding the addition b at a predetermined interval. Then, the process proceeds to step S16.

In step S16, as shown in FIGS. 5 and 6, it is the minimum value in the change of the respective A / F values (oxygen concentrations) corresponding to the determination fuel additions a and b detected by the A / F sensor 28. The A / F deviation (concentration deviation) is calculated from the A / F minimum value (minimum oxygen concentration) MinAFa and MinAFb. Then, the process proceeds to step S18.
In step S18, it is determined whether or not the A / F deviation calculated in step S16 is greater than or equal to a predetermined density deviation. If the determination result is true (Yes) and the A / F deviation is equal to or greater than the predetermined concentration deviation, the process proceeds to step S20. If the determination result is false (No) and the A / F deviation is not equal to or greater than the predetermined concentration deviation, the process proceeds to step S22. move on.

In step S20, it is determined that the oxidation catalyst 15 has deteriorated. Then, this routine is exited.
In step S22, it is determined that the oxidation catalyst 15 has not deteriorated, and the process returns to step S10.
Thus, according to the catalyst deterioration determination device of the present invention, when the S purge process is being performed and the deterioration determination permission condition is satisfied, that is, the number of S purge processes is equal to or greater than the predetermined number of processes, or the vehicle integration Deterioration determination is performed when either the travel distance is equal to or greater than the predetermined cumulative travel distance or the deterioration determination permission condition that the exhaust gas temperature integrated value is equal to or greater than the predetermined cumulative temperature is satisfied.

  At the time of deterioration determination, desorption atmosphere generation fuel addition and rich state generation fuel addition are performed. Oxygen stored in the NOx occlusion reduction catalyst 16 is desorbed by the addition of the desorption atmosphere generation fuel, and the exhaust gas is always made rich by the subsequent addition of the rich state generation fuel, so that the oxidation catalyst 15 and the NOx occlusion reduction catalyst. 16 is prevented from adsorbing oxygen. In this state, the determination fuel is added twice to determine the deterioration of the oxidation catalyst 15, and each determination fuel is burned by the oxidation catalyst 15, and the A / F of the exhaust gas after combustion is burned. The deterioration of the oxidation catalyst 15 is determined based on the change. Specifically, in the determination fuel addition twice, the minimum A / F values MinAFa and MinAFb of the exhaust after combustion are detected, and the A / F deviation is calculated from the deviation of the A / F minimum values MinAFa and MinAFb. If the A / F deviation is equal to or greater than the predetermined concentration deviation, it is determined that the oxidation catalyst 15 has deteriorated.

  Here, if the oxidation catalyst 15 is deteriorated, the ability of the oxidation catalyst 15 to process the fuel for determination (combustion or decomposition of the fuel) decreases. Accordingly, the processing capacity of the determination fuel addition b that is continuously added at a predetermined interval with respect to the determination fuel addition a is insufficient, and a part of the determination fuel addition b is discharged as unburned fuel. Since oxygen is not consumed, the A / F value of the determination fuel addition b is lean with respect to the A / F value of the determination fuel addition a. Therefore, the minimum value A / F MinAFa for the determination fuel addition a is compared with the minimum A / F value MinAFb for the second determination fuel addition b, and the oxidation catalyst 15 increases as the deviation increases. Can be determined to have deteriorated. As described above, the deterioration of the oxidation catalyst 15 is determined based on the difference in A / F after the NOx storage reduction catalyst 16 when the plurality of determination fuel additions are continuously added. It is possible to determine the deterioration of the oxidation catalyst 15 without requiring / F, and an A / F sensor is not required upstream of the NOx occlusion reduction catalyst 16, and the cost can be suppressed.

  In addition, since the oxidation catalyst 15 and the NOx storage reduction catalyst 16 have an oxygen storage function, if oxygen is released or absorbed from the oxidation catalyst 15 and the NOx storage reduction catalyst 16 at the time of deterioration determination, the A / F may fluctuate and it may be difficult to accurately determine deterioration. In contrast, in the present embodiment, as described above, the exhaust gas is always made rich by the addition of the desorption atmosphere generation fuel and the rich state generation fuel, so that the oxygen storage function of the oxidation catalyst 15 and the NOx occlusion reduction catalyst 16 is increased. It is possible to accurately determine deterioration without acting. In particular, by first adding the desorption atmosphere generating fuel with a large amount of fuel added, the oxygen stored in the oxidation catalyst 15 and the NOx storage reduction catalyst 16 can be released in a short period of time, and the deterioration determination can be performed quickly. Can be performed. In addition, by performing the deterioration determination together with the S purge, the deterioration determination is performed by utilizing the fact that the catalyst temperature is maintained at a high temperature by intermittently repeating the rich state, thereby suppressing fuel consumption during the deterioration determination. can do.

In this embodiment, since the deterioration determination is performed only when the deterioration determination permission condition is satisfied, the initial deterioration determination in which the oxidation catalyst 15 has not deteriorated can be eliminated. Thereby, the frequency | count of deterioration determination can be suppressed and fuel consumption can be suppressed.
Therefore, according to the catalyst deterioration determination apparatus according to the first embodiment of the present invention,
(1) Desorption atmosphere generation fuel addition and rich state generation fuel addition are performed at the time of deterioration determination, and oxygen stored in the oxidation catalyst 15 and the NOx storage reduction catalyst 16 is released in a short period of time, and then two times for deterioration determination Since the determination fuel addition is performed, the catalytic reaction of the determination fuel addition can be stably performed by the oxidation catalyst 15, and the deterioration of the catalyst can be accurately determined.
(2) The A / F sensor 28 provided downstream of the NOx occlusion reduction catalyst 16 detects the A / F value in the exhaust gas corresponding to the determination fuel addition, and the A / F is based on the detected A / F value. Since the deviation is calculated and the deterioration of the oxidation catalyst 15 is determined, the number of detection sensors can be reduced and the cost can be reduced.
(3) Since the deterioration determination of the oxidation catalyst 15 is performed when the deterioration determination permission condition is satisfied during the S purge process, the initial deterioration determination in which the oxidation catalyst 15 has not deteriorated can be eliminated. Furthermore, since the deterioration is determined during the S purge process, it is not necessary to perform the deterioration determination of the exhaust gas purification means independently, so that unnecessary fuel consumption can be suppressed and deterioration of fuel consumption can be prevented. be able to.
[Second Embodiment]
Next, a determination procedure for determining catalyst deterioration in the second embodiment will be described.

FIG. 7 is a flowchart showing a control routine of catalyst deterioration determination control according to the second embodiment of the present invention, and FIG. 8 is a characteristic diagram showing a fuel addition amount at the time of catalyst deterioration determination during S purge. 9 is a graph showing a change in fuel addition amount and A / F change rate when the catalyst is normal, and FIG. 10 is a graph showing a change in fuel addition amount and A / F change rate when the catalyst is deteriorated. .
As shown in FIG. 7, in the second embodiment, the deterioration of the catalyst is determined based on the A / F change rate with respect to the first embodiment, and the following points are different from the first embodiment. I will explain.

As shown in FIG. 7, in step S10 to step S14, it is determined whether the S purge process is being performed as in the first embodiment, and whether the deterioration determination permission condition is satisfied, and if each is satisfied, The fuel for deterioration determination shown in FIG. 8 is added, and the process proceeds to step S15 ′.
In step S15 ′, the A / F change rate (oxygen) is determined based on the change in the A / F value corresponding to the determination fuel additions a and b detected by the A / F sensor 28 as shown in FIGS. (Concentration change rate) is calculated, and the difference in A / F change rate (difference in change rate) ΔAFa and ΔAFb, which is the difference between the maximum and minimum values of the respective A / F change rates corresponding to the determination fuel additions a and b Is calculated. Then, the process proceeds to step S16 ′.

In step S16 ′, the difference ΔAFa in the A / F change rate of the determination fuel addition a is calculated from the differences ΔAFa and ΔAFb in the respective A / F change rates corresponding to the determination fuel additions a and b calculated in step S15 ′. A change rate deviation, which is a deviation of the difference ΔAFb in the A / F change rate of the determination fuel addition b, is calculated. Then, the process proceeds to step S18 ′.
In step S18 ′, it is determined whether or not the change rate deviation calculated in step S16 ′ is greater than or equal to a predetermined change rate deviation. If the determination result is true (Yes) and the change rate deviation is equal to or greater than the predetermined change rate deviation, the process proceeds to step S20. If the determination result is false (No) and the change rate deviation is not equal to or greater than the predetermined change rate deviation, the process proceeds to step S22. move on.

  As described above, according to the catalyst deterioration determination device according to the present invention, as in the first embodiment, the deterioration determination is performed when the deterioration determination permission condition is satisfied, and the desorption atmosphere generation fuel addition and the rich state generation fuel are performed. In addition to the addition, the fuel for determination is added twice. Then, each A / F value in the exhaust gas after combustion is detected by the A / F sensor 28 to calculate the A / F change rate, and the determination is made based on the difference between the maximum value and the minimum value of each A / F change rate. The difference ΔAFa and ΔAFb of the A / F change rate corresponding to the fuel addition is calculated, and further the change rate deviation is calculated from the deviation of the A / F change rate difference ΔAFa and ΔAFb. If so, it is determined that the oxidation catalyst 15 has deteriorated.

  The present embodiment is different from the first embodiment in that the deterioration determination is performed based on the deviation of the change rate of the A / F value corresponding to the determination fuel addition. If the oxidation catalyst 15 is deteriorated, the combustion capacity is lowered. Therefore, the A / F value of the determination fuel addition b continuously added at a predetermined interval with respect to the determination fuel addition a becomes lean, and A The rate of change of / F value also decreases. Therefore, the difference ΔAFa of the A / F change rate that is the difference between the maximum value and the minimum value of the change rate of A / F at the time of determination fuel addition a, and the A / F at the time of the second determination fuel addition b. The change rate difference ΔAFb is compared, and it can be determined that the oxidation catalyst 15 is deteriorated as the deviation is larger.

Therefore, according to the catalyst deterioration determination device according to the present invention,
(1) As in the first embodiment, desorption atmosphere generation fuel addition and rich state generation fuel addition were performed at the time of deterioration judgment, and oxygen stored in the oxidation catalyst 15 and the NOx occlusion reduction catalyst 16 was released in a short period of time. Since the determination fuel addition is performed twice for deterioration determination later, the NOx occlusion reduction catalyst 16 can stably perform the catalytic reaction of the determination fuel addition and accurately determine the deterioration of the catalyst. Can do.
(2) The A / F sensor 28 provided downstream of the NOx storage reduction catalyst 16 detects the A / F value in the exhaust gas corresponding to the determination fuel addition, and the change rate deviation is calculated based on the detected A / F value. Since the calculation and the deterioration of the oxidation catalyst 15 are determined, the number of sensors for detection can be reduced and the cost can be reduced.
(3) As in the first embodiment, since the deterioration determination of the oxidation catalyst 15 is performed when the S purge process is being performed and the deterioration determination permission condition is satisfied, the oxidation catalyst 15 is not deteriorated in the initial stage. In addition, since the deterioration is determined during the S purge process, it is not necessary to perform the deterioration determination of the exhaust gas purification means independently, so that unnecessary fuel consumption can be suppressed. It is possible to prevent deterioration of fuel consumption.

Although the description of the embodiment of the invention is finished as above, the embodiment of the present invention is not limited to the above embodiment.
For example, in the above embodiment, the fuel addition valve 26 is provided upstream of the oxidation catalyst 15 to perform the desorption atmosphere generation fuel addition, the rich state generation fuel addition, and the determination fuel addition. However, the present invention is not limited to this. Instead, the fuel injection nozzle 20 into the cylinder is used to enrich the air-fuel ratio of the in-cylinder combustion gas, or so-called post-injection in which fuel is injected at a timing such that unburned fuel is discharged to the oxidation catalyst 15. Even in this case, the same effect as described above can be obtained. Furthermore, since the fuel addition valve 26 can be reduced, the cost can be reduced.

  Further, in the above embodiment, the catalyst deterioration determination fuel addition is performed during the S purge process fuel addition performed every predetermined time (intermittently) during the S purge process, but the deterioration determination is performed. The deterioration determination may be performed by adding the determination fuel simultaneously with the addition of the fuel for the S purge process. In this case, the amount of fuel added for determination fuel is increased and the exhaust temperature rises, so that the oxidation catalyst 15 may be overheated. However, even if the determination fuel addition is performed simultaneously with the addition of the fuel for the S purge process. Since the state in which oxygen is released from the oxidation catalyst 15 is maintained during the S purge, the detection accuracy of the A / F value can be ensured.

In the above embodiment, the deterioration determination is performed during the execution of the S purge process. However, the present invention is not limited to this, and the deterioration determination may not be performed during the execution of the S purge process.
In the above embodiment, the desorption atmosphere generation fuel addition, the rich state generation fuel addition, and the determination fuel addition are performed. However, the present invention is not limited to this, and the oxidation catalyst 15 and the NOx occlusion reduction catalyst 16 It is sufficient that the stored oxygen is released, and only the rich state generation fuel addition and the determination fuel addition may be performed.

In the above embodiment, the determination fuel addition is performed twice. However, the present invention is not limited to this, and it may be performed three or more times, and the rich state generation fuel addition and the determination fuel addition may be performed. It may be only.
Moreover, in the said embodiment, although it is set as the common rail type diesel engine, it is not limited to this, A gasoline engine may be sufficient and the same effect as the above can be acquired even in this case.

  Further, in the above embodiment, the exhaust purification means is composed of the oxidation catalyst 15 that oxidizes the components to be oxidized in the exhaust and the NOx storage reduction catalyst 16 that occludes and reduces NOx in the exhaust. However, the present invention is not limited to this. Instead, it may be composed of only three or more catalysts, or a NOx occlusion reduction catalyst having both an oxidation function and an oxygen storage function. In the case where the effect of suppressing fuel consumption due to the deterioration determination during the S purge process is not expected, the exhaust purification means does not need to include a NOx storage reduction catalyst, and the ternary having both an oxidation function and an oxygen storage function. You may comprise only a catalyst.

1 engine (internal combustion engine)
15 Oxidation catalyst (exhaust purification means)
16 NOx storage reduction catalyst (exhaust gas purification means)
26 Fuel addition valve (fuel supply means)
27 Exhaust temperature sensor (exhaust temperature detection integration means)
28 A / F sensor (oxygen concentration detection means)
29 Vehicle speed sensor (travel distance detection integration means)
30 ECU
35 S purge control unit (sulfur removal means)
36 S purge number detection part (sulfur removal number detection means)
37 Travel distance calculation unit (travel distance detection integration means)
38 Travel distance integration unit (travel distance detection integration means)
39 Exhaust temperature integration unit (exhaust temperature detection integration means)
40 Exhaust catalyst deterioration determination unit (deterioration determination means)
41 Fuel addition control unit (supply control means)

Claims (8)

An oxidation function that is provided in the exhaust passage of an internal combustion engine and that oxidizes oxidizable components in the exhaust, and an oxygen storage function that stores oxygen in the exhaust under an oxidizing atmosphere while desorbing the stored oxygen in a reducing atmosphere An exhaust purification means having
Fuel supply means for supplying fuel into the exhaust flowing upstream of the exhaust purification means;
Supply control means for controlling the fuel supply means so as to perform rich state generation supply for making exhaust rich, and deterioration determination supply for determining deterioration of the exhaust purification means;
An oxygen concentration detection means provided downstream of the exhaust purification means for detecting the oxygen concentration in the exhaust;
Deterioration determining means for determining deterioration of the oxidation function of the exhaust purification means,
The supply control means continuously performs the rich state generation supply for making the exhaust gas rich when the deterioration determination means determines the deterioration of the exhaust purification means, and after a lapse of a predetermined time from the start of the rich state generation supply. Controlling the fuel supply means to perform a plurality of the deterioration determination supply in addition to the rich state generation supply at a predetermined interval;
The deterioration determining means determines deterioration of the exhaust purification means based on a change in oxygen concentration in the exhaust gas corresponding to each of the plurality of deterioration determination supplies detected by the oxygen concentration detecting means. Catalyst deterioration determination device.   The deterioration determination means corresponds to any two of the deterioration determination supplies among the oxygen concentration in the exhaust gas that changes corresponding to each of the plurality of deterioration determination supplies detected by the oxygen concentration detection means. From each minimum oxygen concentration that is the minimum value of oxygen concentration, a concentration deviation that is the difference between the minimum oxygen concentrations corresponding to any two times of the deterioration determination supply is calculated, and if the concentration deviation is not less than a predetermined concentration deviation 2. The catalyst deterioration determination device according to claim 1, wherein the exhaust gas purification unit is determined to be deteriorated.   The deterioration determination means corresponds to any two of the deterioration determination supplies among the oxygen concentration in the exhaust gas that changes corresponding to each of the plurality of deterioration determination supplies detected by the oxygen concentration detection means. Based on the change in oxygen concentration, the oxygen concentration change rate that is the change rate of each oxygen concentration is calculated, and the difference between the change rate that is the difference between the maximum value and the minimum value of the oxygen concentration change rate in each deterioration determination supply is calculated. And further calculating a change rate deviation that is a difference between the change rates of the two times the deterioration judgment supply, and if the change rate deviation is equal to or greater than a predetermined change rate deviation, the exhaust purification means The catalyst deterioration determination device according to claim 1, wherein it is determined that the catalyst has deteriorated.   The supply control means, at the start of the deterioration determination of the exhaust gas purification means by the deterioration determination means, in addition to the rich state generation supply, desorption that supplies more fuel than the supply amount of the fuel of the rich state generation supply 4. The catalyst deterioration determination device according to claim 1, wherein the fuel supply means is controlled to perform atmosphere generation and supply. The exhaust purification means has a nitrogen oxide storage function for storing nitrogen oxides in exhaust under an oxidizing atmosphere and desorbing and reducing the stored nitrogen oxides under a reducing atmosphere. Further comprising sulfur removal means for performing sulfur reduction treatment for reducing and removing sulfur stored in a rich state at a high temperature when the exhaust gas is in a sulfur poisoning state,
The catalyst deterioration determination device according to any one of claims 1 to 4, wherein the deterioration determination means determines deterioration of the exhaust purification means in conjunction with sulfur reduction processing in the sulfur removal means. The exhaust purification unit is provided on the downstream side of the oxidation catalyst and stores nitrogen oxides in the exhaust under an oxidizing atmosphere, and desorbs and reduces the stored nitrogen oxides under a reducing atmosphere. Consists of nitrogen oxide storage catalyst,
When the nitrogen oxide storage catalyst is in a sulfur poisoning state, the exhaust gas further comprises sulfur removal means for performing sulfur reduction treatment for reducing and removing the stored sulfur in a rich state at a high temperature,
5. The catalyst deterioration determination device according to claim 1, wherein the deterioration determination unit determines deterioration of the oxidation catalyst at the time of sulfur reduction treatment by the sulfur removal unit. Furthermore, a sulfur removal number detection means for detecting the number of times of the sulfur reduction treatment is provided,
7. The deterioration determination unit according to claim 5, wherein the deterioration determination unit performs the deterioration determination when the number of times of the sulfur reduction treatment detected by the sulfur removal number detection unit is equal to or greater than a predetermined number of times. Catalyst deterioration judgment device. Further, a travel distance detection integration means for detecting the travel distance of the vehicle on which the internal combustion engine is mounted and integrating the travel distance;
Either or both of exhaust temperature detection integration means for detecting the exhaust temperature of the internal combustion engine and integrating the exhaust temperature,
The deterioration determining means is the integrated value of the exhaust temperature detected by the exhaust temperature integrated value detecting means when the integrated value of the travel distance detected by the travel distance detecting means is equal to or greater than a predetermined integrated travel distance. The catalyst deterioration determination device according to any one of claims 1 to 7, wherein the deterioration determination is executed when the temperature is equal to or higher than a predetermined integrated temperature.

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