JP2019105170A - Diagnostic system and exhaust emission control device for internal combustion engine - Google Patents

Abstract

To provide a diagnostic system capable of improving detection accuracy of abnormalities such as missing and deterioration of an NOselective reduction catalyst provided in an exhaust passage downstream of an NOocclusion catalyst, and an exhaust emission control device for an internal combustion engine.SOLUTION: A diagnostic system for diagnosing an abnormality of an NOselective reduction catalyst in an exhaust emission control device having an NOocclusion catalyst and the NOselective reduction catalyst provided in an exhaust passage of an internal combustion engine from the upstream side in this order includes: a downstream side ammonia concentration estimation section for calculating a downstream side ammonia concentration estimation value that is an estimation value of an ammonia concentration in the exhaust passage downstream of the NOselective reduction catalyst; a downstream side ammonia concentration detection section for acquiring a downstream side ammonia concentration detection value that is a detection value of an ammonia concentration in the exhaust passage downstream of the NOselective reduction catalyst on the basis of a sensor signal of an ammonia concentration sensor provided in the exhaust passage downstream of the NOselective reduction catalyst; and a determination section for determining an abnormality of the NOselective reduction catalyst on the basis of the downstream side ammonia concentration estimation value and the downstream side ammonia concentration detection value.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a diagnostic device and an exhaust gas purification device for an internal combustion engine.

NO _x storage catalysts and NO _x selective reduction catalysts are known as members for reducing NO _x contained in exhaust gases of internal combustion engines such as diesel engines to purify the exhaust gases. _The NO _X storage catalyst occludes NO _X in the exhaust gas when the air-fuel mixture combusted in the internal combustion engine is fuel-lean (lean) state with respect to the stoichiometric air-fuel ratio (stoichiometric) air-fuel mixture over stoichiometric state or fuel concentrated by releasing NO _X when (rich) state, unburnt hydrocarbons in the exhaust gas (HC:: hydrocarbon) by reaction with, for reducing the NO _X to N _2. The NO _x selective reduction catalyst has a function of adsorbing ammonia (NH ₃ ) as a reducing component of NO _x , and reduces NO _x to N ₂ by reacting NO _x in the inflowing exhaust with NH _3. Do.

For example, Patent Document 1, as one embodiment of the exhaust gas purification apparatus for purifying an exhaust gas of the internal combustion engine, an exhaust gas purification apparatus having both _the NO _X storage catalyst and _the NO _X selective reducing catalyst. Specifically, in the exhaust purification system disclosed in Patent Document 1, the NO _X storage catalyst and the NO _X selective reduction catalyst are arranged in this order from the upstream side of the exhaust passage. In such an exhaust gas purification apparatus, when NH ₃ is generated by the reduction reaction between NO _x and HC in the NO _x storage catalyst, the NO _x selective reduction catalyst adsorbs the NH ₃ . When the NO _X flows out from the NO _X storing catalyst, NO _X selective reduction catalyst for reducing NO _X using NH _3.

Japanese Patent Application Publication No. 2006-522257

Here, in the exhaust purification apparatus disclosed in Patent Document 1, when _the NO _X selective reducing catalyst or when _the NO _X selective reducing catalyst advanced deterioration of missing (not installed), Ya NO _X into the atmosphere There is a possibility that the release amount of NH ₃ may increase. Therefore, it is meaningful if detectable diagnostics missing or deterioration of the NO _X selective reducing catalyst.

For example, _the NO _X selective reducing catalyst by utilizing the fact that with a heat capacity, the temperature sensor provided on the downstream side of _the NO _X selective reducing catalyst, _the NO _X selective reducing catalyst temperature model and a temperature sensor capacity created in consideration of the by comparing the temperature detected by, it is conceivable to determine the loss of _the NO _X selective reducing catalyst.

However, in the case of the method of comparing the temperature model and the detected temperature, in order to improve the accuracy of the diagnosis result, it is necessary to execute the diagnosis in an operating state in which the temperature change of the exhaust gas is relatively small. Is limited. Further, NO changes in _X selective reduction catalyst also deteriorates heat capacity since less, if the method of comparing the temperature model and the detected temperature, while it is possible to detect the missing of the NO _X selective reduction catalyst, NO _X It is difficult to detect the degradation of the selective reduction catalyst.

The present invention has been made in view of the above problems, and an object of the present invention is to eliminate or deteriorate the NO _X selective reduction catalyst provided in the exhaust passage downstream of the NO _X storage catalyst. An object of the present invention is to provide a diagnostic device and an exhaust gas purification device for an internal combustion engine capable of improving the detection accuracy of an abnormality.

In order to solve the above problems, according to an aspect of the present invention, _the NO _X selective reducing catalyst in the exhaust purification device provided in this order from the upstream side in an exhaust passage of an internal combustion engine and _the NO _X storage catalyst and _the NO _X selective reducing catalyst in the diagnostic apparatus for diagnosing an abnormality, and the downstream ammonia concentration estimating unit that calculates a downstream ammonia concentration estimated value is an estimated value of the ammonia concentration in the exhaust passage downstream of _the NO _X selective reducing catalyst, _the NO _X selective A downstream ammonia concentration detection value, which is a detection value of the ammonia concentration in the exhaust passage downstream of the NO _X selective reduction catalyst, based on the sensor signal of the ammonia concentration sensor provided in the exhaust passage downstream of the reduction catalyst be judged and the downstream ammonia concentration detection unit for acquiring, the abnormality of the NO _X selective reducing catalyst on the basis of the downstream ammonia concentration estimated value and a downstream ammonia concentration detection value Comprising a determining unit, a diagnostic device is provided.

Further, in order to solve the above-mentioned problems, according to another aspect of the present invention, an NO _X storage catalyst provided in an exhaust passage of an internal combustion engine and an exhaust passage downstream of the NO _X storage catalyst are provided. and _the NO _X selective reducing catalyst, _the NO _X selective reducing the ammonia concentration sensor provided in an exhaust passage downstream of the catalyst, the diagnostic device and the internal combustion engine exhaust purification provided with a diagnosing abnormality of the NO _X selective reducing catalyst in the device, the diagnostic device includes a downstream ammonia concentration estimating unit that calculates a downstream ammonia concentration estimated value is an estimated value of the ammonia concentration in the exhaust passage downstream of _the NO _X selective reducing catalyst, _the NO _X selective reducing catalyst The downstream ammonia concentration that is a detected value of the ammonia concentration in the exhaust passage downstream of the NO _X selective reduction catalyst based on the sensor signal of the ammonia concentration sensor provided in the exhaust passage further downstream than the NOx selective reduction catalyst An internal combustion engine comprising: a downstream ammonia concentration detection unit for acquiring a degree detection value; and a determination unit for determining an abnormality of the NO _X selective reduction catalyst based on the downstream ammonia concentration estimated value and the downstream ammonia concentration detection value. An exhaust purification device is provided.

As described above, according to the present invention, it is possible to improve the detection accuracy of abnormalities such as missing or deterioration of the NO _X selective reduction catalyst provided in the exhaust passage downstream of the NO _X storage catalyst.

It is a schematic diagram which shows the structural example of the exhaust gas purification device which concerns on this embodiment. It is a block diagram showing an example of composition of a diagnostic device (control device). It is an explanatory view showing change of an integrated value of downstream ammonia concentration detection value. It is a flowchart which shows the operation example of a diagnostic apparatus (control apparatus).

  The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In the present specification and the drawings, components having substantially the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

<1. Overall Configuration of Exhaust Purification System for Internal Combustion Engine>
A configuration example of an exhaust gas purification apparatus for an internal combustion engine according to the present embodiment will be described. FIG. 1 is a schematic view showing an example of the configuration of an exhaust purification system 10.

  The exhaust purification device 10 is provided in an exhaust system of an internal combustion engine 5 represented by a diesel engine or the like. In the present embodiment, an example in which the internal combustion engine 5 is a diesel engine will be described. The internal combustion engine 5 includes a fuel injection system that injects the fuel supplied to each cylinder. The fuel injection system may be, for example, a common rail system including a common rail holding high-pressure fuel and a plurality of fuel injection valves connected to the common rail. However, the internal combustion engine 5 is not limited to the above configuration example.

The operating state of the internal combustion engine 5 is controlled by the control device 100. In the internal combustion engine 5, the air-fuel ratio of the air-fuel mixture to be burned is switched to the stoichiometric state, the fuel lean state or the fuel rich state according to the operating condition. The exhaust gas of the internal combustion engine 5 contains NO _x , particulate matter (PM), carbon monoxide (CO), HC or the like.

The exhaust purification device 10 includes an oxidation catalyst 19 disposed in an exhaust pipe 11 of the internal combustion engine 5, an NO _X storage catalyst 15, a particulate filter 17, an NO _X selective reduction catalyst 13, and an ammonia concentration sensor 23. Prepare. The oxidation catalyst 19, the NO _x storage catalyst 15, the particulate filter 17 and the NO _x selective reduction catalyst 13 are disposed in the exhaust pipe 11 in this order from the upstream side of the flow of the exhaust.

The oxidation catalyst 19 oxidizes HC, CO or NO contained in the exhaust gas. For example, HC, CO or NO are oxidized to H ₂ O, CO ₂ or NO ₂ . The particulate filter 17 is a filter that collects PM in exhaust gas. The PM collected by the particulate filter 17 is burned at an appropriate time. For example, the amount of unburned HC contained in the exhaust gas of the internal combustion engine 5 is increased, and the exhaust heat temperature is raised by the oxidation heat generated when the HC is oxidized by the oxidation catalyst 19, and PM collected in the particulate filter 17 Burn the Note that the method of burning the PM collected by the particulate filter 17 is not limited to the above example.

The NO _x storage catalyst 15 reduces NO _x to N ₂ by reacting NO _x in the exhaust with HC. Specifically, NO _X storing catalyst 15 occludes NO _X in the exhaust gas when the internal combustion engine 5 is lean combustion state, releasing NO _X which the internal combustion engine 5 has been occluded during the rich combustion state, The HC and CO in the exhaust reduce NO _x to N ₂ . At the time of reduction of NO _x in the NO _x storage catalyst 15, NH ₃ is also generated.

The NO _X selective reduction catalyst 13 reduces NO _X to N ₂ by reacting NO _X in the exhaust gas with NH ₃ . Specifically, the NO _X selective reduction catalyst 13 adsorbs NH ₃ generated by the NO _X storage catalyst 15, and reduces NO _X in the inflowing exhaust gas to N ₂ by NH ₃ . The NO _X selective reduction catalyst 13 has a characteristic that the adsorption amount of NH ₃ decreases as the catalyst temperature increases. Further, NO _X selective reduction catalyst 13 has a reduction efficiency is high characteristic enough adsorbed NH ₃ amount is large NO _X.

Ammonia concentration sensor 23 is provided downstream of the exhaust pipe 11 than _the NO _X selective reducing catalyst 13, for detecting the concentration of ammonia in the exhaust gas flowing out of _the NO _X selective reducing catalyst 13. The sensor signal S_nh ₃ of the ammonia concentration sensor 23 is transmitted to the control device 100. The information on the ammonia concentration is used to diagnose an abnormality of the NO _X selective reduction catalyst 13.

Besides, one or more exhaust temperature sensors for detecting the exhaust temperature may be provided at appropriate positions of the exhaust pipe 11. The sensor signal S_tg of the exhaust temperature sensor is transmitted to the control device 100. The information on the exhaust temperature at the position where the exhaust temperature sensor is provided can be used to estimate the temperature of the NO _X storage catalyst 15 or the NO _X selective reduction catalyst 13.

<2. Diagnostic device (control device)>
Next, a configuration example of the control device 100 that functions as a diagnostic device according to the present embodiment will be described. FIG. 2 is a block diagram showing a configuration example of the control device 100. As shown in FIG. The illustrated control device 100 is a control device 100 that controls the operating state of the internal combustion engine 5. Control device 100 may be configured of one control device, or a plurality of control devices may be communicably connected to each other.

  The control device 100 is a device including a processor such as a central processing unit (CPU) or a micro processing unit (MPU) and an electric circuit, and the processor executes a computer program to realize various functions. You may Note that a part or all of the control device 100 may be configured by, for example, a microcomputer, a microprocessor unit, or the like, or may be configured by an updatable item such as firmware, or a CPU May be a program module or the like that is executed by a command from

  The control device 100 includes an upstream ammonia concentration acquisition unit 112, a downstream ammonia concentration estimation unit 114, a downstream ammonia concentration detection unit 116, and a determination unit 118. These units may be functions implemented by execution of a computer program by a processor. In addition, the control device 100 includes a storage unit including one or more storage elements such as a random access memory (RAM) or a read only memory (ROM). The storage unit stores a computer program executed by the processor, control parameters used for computations, computation results by the processor, acquired sensor values, and the like. The storage unit may include an HDD (Hard Disk Drive), a storage device, and the like.

(Upstream ammonia concentration acquisition unit)
The upstream ammonia concentration acquisition unit 112 is an estimated value of the ammonia concentration in the exhaust passage downstream of the NO _X storage catalyst 15 and upstream of the NO _X selective reduction catalyst 13 (upstream ammonia concentration estimated value) NH ₃ Calculate _us_mod. NH contained in the upstream side exhaust than _the NO _X selective reducing catalyst 13 ₃ is NH ₃ produced in the NO _X storing catalyst 15. In the NO _X storage catalyst 15, NH ₃ is generated according to the following reaction formula (1).
3.5 H ₂ + NO ₂ → NH ₃ + 2 H ₂ O (1)

For example, the upstream ammonia concentration acquisition unit 112 determines the temperature of the NO _X storage catalyst 15, the NO _X storage amount when the internal combustion engine 5 is switched to the rich combustion state, the rich degree in the rich combustion state of the internal combustion engine 5 The upstream ammonia concentration NH ₃ _us_mod is calculated based on the information such as the fuel ratio and the rich combustion time of the internal combustion engine 5. The temperature of the NO _X storage catalyst 15 can be estimated, for example, based on the exhaust temperature. The NO _X storage amount, the rich degree, and the rich combustion time in the rich combustion state of the internal combustion engine 5 can be estimated based on the operating conditions of the internal combustion engine 5, for example.

When the ammonia concentration sensor for detecting the ammonia concentration in the exhaust passage downstream of the NO _X storage catalyst 15 and upstream of the NO _X selective reduction catalyst 13 is provided, the upstream ammonia concentration acquisition unit 112 The upstream ammonia concentration NH ₃ _us_mod may be acquired based on the sensor signal of the ammonia concentration sensor.

(Downstream ammonia concentration estimation unit)
The downstream side ammonia concentration estimation unit 114 calculates an estimated value (downstream side ammonia concentration estimated value) NH ₃ _ds_mod of the ammonia concentration in the exhaust passage downstream of the NO _X selective reduction catalyst 13. NH ₃ contained in the exhaust downstream of _the NO _X selective reducing catalyst 13, of the NH ₃ flowing out is generated by the NO _X storing catalyst 15, except for the NH ₃ adsorbed in _the NO _X selective reducing catalyst 13 It is NH ₃ . As described above, the maximum amount of adsorption of NH ₃ in _the NO _X selective reducing catalyst 13 varies depending on the temperature of the NO _X selective reducing catalyst 13. Further, the amount of NH ₃ adsorbed to the NO _x selective reduction catalyst 13 is reduced by reacting with NO _x . In the NO _X selective reduction catalyst 13, the NO _X reduction reaction occurs according to the following reaction formula (2).
4NH ₃ + 3NO ₂ → 3.5N ₂ + 6H ₂ O (2)

For example, the downstream ammonia concentration estimating unit 114, for each predetermined processing cycle, upstream the ammonia concentration NH ₃ _us_mod, the temperature of _the NO _X selective reducing catalyst 13, and concentration of NO _X exhaust gas flowing to the NO _X selective reducing catalyst 13 The downstream ammonia concentration NH ₃ _ds_mod is calculated based on The downstream ammonia concentration estimated value NH ₃ _ds_mod can be determined, for example, according to the following equation (3).
NH ₃ _ds_mod = {Vn_in-(Vn_str_max-Vn_str_act)-Vn_red} / Vgas
... (3)
Vn_in: NH ₃ amount flowing into _the NO _X selective reducing catalyst
Vn_str_max: maximum amount of adsorption of NH ₃ in _the NO _X selective reducing catalyst
Vn_str_act: Current adsorbed NH ₃ amount in _the NO _X selective reducing catalyst
Vn_red: the amount of NH ₃ necessary for the reduction of NO _x flowing into the NO _x selective reduction catalyst
Vgas: displacement

The amount of NH ₃ Vn_in flowing into the NO _X selective reduction catalyst 13 is calculated by multiplying the upstream ammonia concentration NH ₃ _us_mod acquired by the upstream ammonia concentration acquisition unit 112 by the exhaust gas amount Vgas in the current processing cycle. be able to. Information on the operating conditions of the internal combustion engine 5 can be used as the displacement Vgas. Maximum adsorption amount Vn_str_max of NH ₃ in _the NO _X selective reducing catalyst 13 can be set according to the temperature of the NO _X selective reducing catalyst 13. The temperature of the NO _X selective reduction catalyst 13 can be estimated based on the exhaust gas temperature. The present NH ₃ adsorption amount Vn_str_act in the NO _X selective reduction catalyst 13 is a value obtained by subtracting the NH ₃ amount Vn_red necessary for reduction of NO _X from the inflowing NH ₃ amount Vn_in to the NH ₃ adsorption amount Vn_str_act in the previous processing cycle. It can be determined by adding.

(Downstream ammonia concentration detector)
The downstream ammonia concentration detection unit 116 detects the downstream ammonia concentration (downstream ammonia concentration detection value) NH ₃ _ds_det based on the sensor signal S_nh ₃ of the ammonia concentration sensor 23.

(Judgment unit)
The determination unit 118 determines the abnormality of the NO _X selective reduction catalyst 13 based on at least the downstream ammonia concentration estimated value NH ₃ _ds_mod and the downstream ammonia concentration detected value NH ₃ _ds_det. In the present embodiment, the determination unit 118 is configured to select the NO _X selective reduction catalyst 13 based on the upstream ammonia concentration estimated value NH ₃ _us_mod, the downstream ammonia concentration estimated value NH ₃ _ds_mod, and the downstream ammonia concentration detected value NH ₃ _ds_det. Determine lack and deterioration.

When the NO _X selective reduction catalyst 13 has no abnormality such as loss or deterioration, the downstream ammonia concentration detection value NH ₃ _ds_det obtained based on the sensor signal S_nh ₃ of the ammonia concentration sensor 23 is determined by the downstream ammonia concentration estimation unit 114 It approximates to the estimated downstream ammonia concentration estimated value NH ₃ _ds_mod. On the other hand, when an abnormality such as missing or degraded to the NO _X selective reducing catalyst 13 is generated, among the NH ₃ flowing into _the NO _X selective reducing catalyst 13, the amount of NH ₃ adsorbed in _the NO _X selective reducing catalyst 13 It also reduces the amount of NH ₃ used for the NO _x reduction reaction. Therefore, the downstream ammonia concentration detection value NH ₃ _ds_det is a value larger than the downstream ammonia concentration estimated value NH ₃ _ds_mod. Therefore, the determination unit 118 can determine the presence or absence of an abnormality in the NO _X selective reduction catalyst 13 by comparing the downstream ammonia concentration detection value NH ₃ _ds_det with the downstream ammonia concentration estimated value NH ₃ _ds_mod.

Furthermore, when the NO _X selective reduction catalyst 13 is missing, the amount of NH ₃ adsorbed to the NO _X selective reduction catalyst 13 and the amount of NH ₃ used for the reduction reaction with NO _X are almost zero. It becomes. Therefore, the downstream ammonia concentration detection value NH ₃ _ds_det approximates the upstream ammonia concentration estimated value NH ₃ _us_mod estimated by the upstream ammonia concentration acquisition unit 112. On the other hand, if _the NO _X selective reducing catalyst 13 is deteriorated, a part of the NH ₃ flowing into _the NO _X selective reducing catalyst 13, is adsorbed to _the NO _X selective reducing catalyst 13, or used in the reduction reaction of the NO _X Be Therefore, the downstream ammonia concentration detection value NH ₃ _ds_det is a value smaller than the upstream ammonia concentration estimated value NH ₃ _us_mod. Therefore, when the NO _x selective reduction catalyst 13 is abnormal, the determination unit 118 compares the upstream ammonia concentration estimated value NH ₃ _us _ mod with the downstream ammonia concentration detected value NH ₃ _ds _ det to obtain the NO _x selective reduction catalyst 13. Missing or degraded can be determined.

Further, the determination unit 118 calculates the integrated value of the downstream ammonia concentration detection value NH ₃ _ds_det in the predetermined period, the integrated value of the downstream ammonia concentration estimated value NH ₃ _ds_mod, or the integrated value of the upstream ammonia concentration estimated value NH ₃ _us_mod You may compare The difference between the downstream ammonia concentration detection value NH ₃ _ds_det and the downstream ammonia concentration estimated value NH ₃ _ds_mod or the upstream ammonia concentration estimated value NH ₃ _us_mod can be more easily determined by comparing the respective integrated values. Can.

FIG. 3 is an explanatory view showing the difference between the downstream side ammonia concentration detection value NH ₃ _ds_det when the NO _X selective reduction catalyst 13 is normal, missing, and deteriorated. Figure 3 shows the period from the time t1 to the time t2, the downstream ammonia concentration detection value NH ₃ _Ds_det, downstream ammonia concentration estimated value NH ₃ _Ds_mod, and an example of integrating the upstream ammonia concentration estimate NH ₃ _Us_mod ing.

If _the NO _X selective reducing catalyst 13 is functioning properly, the value of the downstream ammonia concentration estimated value NH ₃ _ds_mod is smaller than the upstream ammonia concentration estimate NH ₃ _us_mod. Therefore, the integrated value of the downstream ammonia concentration estimated value NH ₃ _ds_mod is to remain at a value smaller than the integrated value of the upstream ammonia concentration estimate NH ₃ _us_mod. Then, when the NO _X selective reduction catalyst 13 is normal, the integrated value of the downstream ammonia concentration detection value NH ₃ _ds_det changes almost in the same manner as the integrated value of the downstream ammonia concentration estimated value NH ₃ _ds_mod.

On the other hand, when the NO _X selective reduction catalyst 13 is missing, the downstream ammonia concentration detection value NH ₃ _ds_det changes almost in the same manner as the integrated value of the upstream ammonia concentration estimated value NH ₃ _us_mod. Further, when _the NO _X selective reducing catalyst 13 is deteriorated, the downstream ammonia concentration detection value NH ₃ _ds_det may transition between the upstream ammonia concentration estimate NH ₃ _us_mod and downstream ammonia concentration estimated value NH ₃ _ds_mod Do. In the example shown in FIG. 3, the downstream ammonia concentration detection value NH ₃ _ds_det shifts while taking an intermediate value between the upstream ammonia concentration estimated value NH ₃ _us_mod and the downstream ammonia concentration estimated value NH ₃ _ds_mod.

Therefore, if the difference between the integrated value of the downstream ammonia concentration detection value NH ₃ _ds_det and the integrated value of the downstream ammonia concentration estimated value NH ₃ _ds_mod at time t 2 is small, the determination unit 118 determines that the NO _X selective reduction catalyst 13 is Can be determined to be functioning properly. Further, when the difference between the integrated value and the downstream ammonia concentration estimated value integrated value of NH ₃ _ds_mod downstream ammonia concentration detection value NH ₃ _ds_det at time t2 is larger, the determination section 118, upstream the ammonia concentration estimated at time t2 If the difference between the integrated value of the value NH ₃ _us_mod and the integrated value of the downstream ammonia concentration detection value NH ₃ _ds_det is small, it can be determined that the NO _X selective reduction catalyst 13 is missing.

When the NO _X selective reduction catalyst 13 is missing, it is also considered that the NO _X selective reduction catalyst 13 is intentionally removed, so that the determination unit 118 takes a treatment to forcibly stop the internal combustion engine 5, for example. May be Further, at the time of deterioration of the NO _X selective reducing catalyst 13, the judgment unit 118, for example a warning lamp by sounding an alarm or turn it on, and also to urge the replacement of the NO _X selective reducing catalyst 13 to the driver or the like Good.

<3. Operation example of diagnostic device>
Next, an operation example of the control device 100 functioning as a diagnostic device will be described with reference to the flowchart of FIG. 4.

First, upstream the ammonia concentration acquisition unit 112 of the control apparatus 100, the downstream ammonia concentration estimating unit 114 and a downstream ammonia concentration detection unit 116, downstream ammonia concentration detection value NH ₃ _ds_det, downstream ammonia concentration estimated value NH ₃ _ds_mod And integration of the upstream ammonia concentration estimated value NH ₃ _us_mod is started (step S11). Next, the upstream ammonia concentration acquisition unit 112 and the downstream ammonia concentration estimation unit 114 calculate the upstream ammonia concentration estimated value NH ₃ _us_mod and the downstream ammonia concentration estimated value NH ₃ _ds_mod, respectively, and the downstream ammonia concentration detection unit 116 Detects the downstream ammonia concentration detection value NH ₃ _ds_det (step S13).

Next, the upstream ammonia concentration acquisition unit 112, the downstream ammonia concentration estimation unit 114, and the downstream ammonia concentration detection unit 116 respectively calculate the upstream ammonia concentration estimated value NH ₃ _us_mod and the downstream ammonia concentration estimated value obtained in step S13, respectively. NH ₃ for integrating the _ds_mod and downstream ammonia concentration detection value NH ₃ _Ds_det (step S15).

  Next, whether the upstream ammonia concentration acquisition unit 112, the downstream ammonia concentration estimation unit 114, and the downstream ammonia concentration detection unit 116 have elapsed a predetermined time set in advance has elapsed since the start of integration. Is determined (step S17). The predetermined time may be set to an appropriate time in consideration of the allowable range of the reliability of the diagnosis result and the like.

When the elapsed time has not passed the predetermined time (S17 / No), the upstream ammonia concentration acquisition unit 112, the downstream ammonia concentration estimation unit 114, and the downstream ammonia concentration detection unit 116 return to step S13, and the upstream side The calculation or detection and integration of the ammonia concentration estimated value NH ₃ _us_mod, the downstream ammonia concentration estimated value NH ₃ _ds_mod and the downstream ammonia concentration detected value NH ₃ _ds_det are repeated.

On the other hand, when the elapsed time has passed the predetermined time (S17 / Yes), the determination unit 118 of the control device 100 determines that the integrated value ∫NH ₃ _ds _mod of the downstream ammonia concentration estimated value NH ₃ _ds _ mod and the downstream ammonia concentration detection value NH ₃ the absolute value of the difference between the integrated value ∫NH ₃ _ds_det of _Ds_det it is determined whether it exceeds the threshold value alpha (step S19). The threshold value α can be set to an appropriate value in consideration of the error of the downstream ammonia concentration estimated value NH ₃ _ds_mod, the length of a predetermined time for integration, and the like.

If the absolute value | ∫NH ₃ _ds _mod-∫NH ₃ _ds det det is less than or equal to the threshold value α (S19 / No), the determination unit 118 determines that the NO _X selective reduction catalyst 23 is functioning normally (no abnormality). (Step S27), this routine ends. On the other hand, when the absolute value | ∫NH ₃ _ds _mod-∫NH ₃ _ds _det exceeds the threshold value α (S19 / Yes), the determination unit 118 determines that the integrated value ∫NH ₃ _us _mod of the upstream ammonia concentration estimated value NH ₃ _us _mod the absolute value of the difference between the integrated value ∫NH ₃ _ds_det side ammonia concentration detection value NH ₃ _ds_det it is determined whether or not less than the threshold value beta (step S21). The threshold value β can be set to an appropriate value in consideration of the error of the downstream ammonia concentration estimated value NH ₃ _ds_mod, the length of a predetermined time for integration, and the like. The threshold value β may be the same value as the threshold value α or may be a different value.

If the absolute value | ∫NH ₃ _us_mod-∫NH ₃ _ds_det | is less than the threshold value β (S21 / Yes), the determination unit 118 determines that the NO _X selective reduction catalyst 23 is missing (step S23). End the routine On the other hand, the absolute value _{| ∫NH 3 _us_mod-∫NH 3 _ds_det} | is equal to or greater than the threshold value β (S21 / No), the determination unit 118 determines that _the NO _X selective reducing catalyst 23 is deteriorated (step S25) , End this routine.

As described above, the exhaust gas purifying device 10 for an internal combustion engine 5 according to the present embodiment includes a the NO _X storing catalyst 15 and _the NO _X selective reducing catalyst 13 in order from the upstream side of the exhaust passage, _the NO _X selective reducing catalyst 13 An ammonia concentration sensor 23 is provided on the downstream side of the above. The control device 100 functioning as a diagnostic device that diagnoses the abnormality of the NO _X selective reduction catalyst 13 of the exhaust purification device 10 performs NO based on the downstream side ammonia concentration estimated value NH ₃ _ds_mod and the downstream side ammonia concentration detection value NH ₃ _ds_det. _It is determined whether there is an abnormality in the _X selective reduction catalyst 13 or not. Therefore, the control device 100 can detect an abnormal state in which the NO _X selective reduction catalyst 13 is not functioning properly.

Further, in the present embodiment, the control unit 100, when an abnormality of the NO _X selective reducing catalyst 13, further based on the upstream ammonia concentration estimate NH ₃ _us_mod and downstream ammonia concentration detection value NH ₃ _ds_det, NO _X selective reducing The absence or deterioration of the catalyst 13 is determined. Therefore, the control device 100 can execute the processing according to the state of abnormality of the NO _X selective reduction catalyst 13.

Further, in the present embodiment, the control device 100, the integrated value ∫NH ₃ _ds_mod and downstream ammonia concentration upstream integrated value of side ammonia concentration estimate NH ₃ _us_mod ∫NH ₃ _us_mod, downstream ammonia concentration estimated value NH ₃ _ds_mod determining an abnormality of the NO _X selective reducing catalyst 13 using the integrated value ∫NH ₃ _ds_det detection values NH _{3 _ds_det.} Thus, a downstream ammonia concentration detection value NH ₃ _ds_det, is the difference between the upstream ammonia concentration estimate NH ₃ _us_mod or downstream ammonia concentration estimated value NH ₃ _ds_mod easier to determine, in _the NO _X selective reducing catalyst 13 The reliability of the result of abnormality diagnosis can be improved.

  Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention belongs can conceive of various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also fall within the technical scope of the present invention.

Reference 5: Internal combustion engine, 10: Exhaust gas purification device, 11: Exhaust pipe, 13: NO _X selective reduction catalyst, 15: NO _X storage catalyst, 23: Ammonia concentration sensor, 100 ... Control device (diagnostic device), 112 ... upstream ammonia concentration acquisition unit 114 ... downstream ammonia concentration estimation unit 116 ... downstream ammonia concentration detection unit, 118 ... determination unit

Claims (7)

A diagnostic device for diagnosing an abnormality of the NO _x selective reduction catalyst in an exhaust gas purification apparatus provided with an NO _x storage catalyst and an NO _x selective reduction catalyst sequentially from the upstream side in an exhaust passage of an internal combustion engine,
A downstream ammonia concentration estimating unit that calculates a downstream ammonia concentration estimated value is an estimated value of the ammonia concentration in the exhaust passage downstream of the _the NO _X selective reducing catalyst,
Downstream is the detection value of the ammonia concentration downstream of the exhaust passage than the _the NO _X selective reducing catalyst on the basis of the sensor signals of the _the NO _X selective reducing ammonia concentration sensor provided in an exhaust passage downstream of the catalyst A downstream ammonia concentration detection unit that acquires an ammonia concentration detection value;
A determination unit that determines an abnormality of the NO _X selective reduction catalyst based on the downstream side ammonia concentration estimated value and the downstream side ammonia concentration detection value;
A diagnostic device comprising: The diagnostic device according to claim 1, wherein the determination unit determines the abnormality of the NO _X selective reduction catalyst using the integrated value of the downstream side ammonia concentration estimated value and the integrated value of the downstream side ammonia concentration detection value. . The determination unit determines abnormality of the _the NO _X selective reducing catalyst with the downstream ammonia concentration estimated value and the downstream ammonia concentration detection value in a period in which ammonia from the _the NO _X storage catalyst flows out, claim 1 Or the diagnostic apparatus as described in 2. Wherein _the NO _X storage downstream of the catalyst, and the _the NO _X selective reducing upstream the ammonia concentration acquisition unit for obtaining the upstream ammonia concentration is detected values or estimated value of the ammonia concentration in the exhaust passage upstream of the catalyst In addition,
The determination unit, the upstream ammonia concentration, on the basis of the downstream ammonia concentration estimated value and the downstream ammonia concentration detection value, determines missing and deterioration of the _the NO _X selective reducing catalyst, according to claim 1 Diagnostic device. The determination unit, the integrated value of the upstream ammonia concentration, using the integrated value of the integrated value and the downstream ammonia concentration detection value of the downstream ammonia concentration estimated value, the missing and deterioration of the _the NO _X selective reducing catalyst The diagnostic device according to claim 4, which determines. The determination unit, the NO _X the upstream ammonia concentration in the period ammonia storage catalyst flows out, missing the _the NO _X selective reducing catalyst with the downstream ammonia concentration estimated value and the downstream ammonia concentration detection value and The diagnostic device according to claim 4 or 5, wherein deterioration is determined. An NO _X storage catalyst provided in an exhaust passage of an internal combustion engine;
An NO _X selective reduction catalyst provided in an exhaust passage downstream of the NO _X storage catalyst;
And the ammonia concentration sensor provided in an exhaust passage on the downstream side of the _the NO _X selective reducing catalyst,
In the exhaust purification system of an internal combustion engine and a diagnostic apparatus for diagnosing an abnormality of the _the NO _X selective reducing catalyst,
The diagnostic device
A downstream ammonia concentration estimating unit that calculates a downstream ammonia concentration estimated value is an estimated value of the ammonia concentration in the exhaust passage downstream of the _the NO _X selective reducing catalyst,
Downstream is the detection value of the ammonia concentration downstream of the exhaust passage than the _the NO _X selective reducing catalyst on the basis of the sensor signals of the _the NO _X selective reducing ammonia concentration sensor provided in an exhaust passage downstream of the catalyst A downstream ammonia concentration detection unit that acquires an ammonia concentration detection value;
A determination unit that determines an abnormality of the NO _X selective reduction catalyst based on the downstream side ammonia concentration estimated value and the downstream side ammonia concentration detection value;
An exhaust purification system of an internal combustion engine, comprising: