JP2020051402A - Exhaust emission control system for internal combustion engine and exhaust emission control method for internal combustion engine - Google Patents

Abstract

To provide an exhaust emission control system for an internal combustion engine and an exhaust emission control method for an internal combustion engine capable of reducing a reducing agent storage amount in an SCR catalyst in a low-temperature side temperature region of exhaust gas and reducing frequency of rich air-fuel ratio control for an LNT in a high-temperature side temperature region by using a simple algorithm when NOx is eliminated by using both of the LNT and SCR catalyst so as to enable improvement of fuel economy and promote saving of an injected reducing agent amount and reduction of a reducing agent slip amount during a temperature rise and the like.SOLUTION: Either of regeneration control for controlling an NOx catalyst device 21, reducing agent supply control for controlling an injected reducing agent amount U1 to a selective reduction type catalyst device 23 or cooperative control for concurrently performing the regeneration control and the reducing agent supply control is selected by using a temperature Tg1 of exhaust gas G flowing into the NOx catalyst device 21 and a temperature Tg2 of exhaust gas G flowing into the selective reduction type catalyst device 23. When the cooperative control is selected, a parameter of the regeneration control and the injected reducing agent amount of the reducing agent supply control are changed by using the temperatures Tg1, Tg2 of the exhaust gas G.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine and a method for purifying exhaust gas of an internal combustion engine for reducing NOx emitted from the internal combustion engine.

  In an internal combustion engine such as a diesel engine or a lean burn gasoline engine, reduction of NOx (nitrogen oxide) in exhaust gas is required in a wide traveling state range from urban driving to high speed driving and low speed. As a conventional NOx reduction technology, Patent Literature 1 discloses an exhaust gas purification device combining an LNT (lean NOx trap catalyst) and an SCR catalyst (selective reduction catalyst).

International Publication No. WO 2013/190635

  In order to use the NOx purification functions of both the LNT and the SCR catalyst, it is necessary to perform rich air-fuel ratio control and urea water supply control, but if these controls are simply combined, they are unnecessary and have little effect. There is a problem that the rich air-fuel ratio control is performed at the timing, or the estimation of the storage amount of the reducing agent in the SCR catalyst is erroneous, and an excessive amount of the reducing agent is injected.

  The present invention has been made in view of the above, and an object of the present invention is to ensure the required exhaust gas purification performance in an exhaust gas purification system for an internal combustion engine having a NOx purification catalyst for an LNT and an SCR catalyst. An object of the present invention is to provide an exhaust gas purification system for an internal combustion engine and a method for purifying exhaust gas for an internal combustion engine, which can reduce the cost required for exhaust gas purification.

  An exhaust gas purification system for an internal combustion engine according to the present invention for achieving the above object includes a NOx catalyst device having a NOx adsorption function from an upstream side in an exhaust passage of the internal combustion engine, a reducing agent injection valve, and a selective reduction catalyst device. And a regeneration control device for performing regeneration control for supplying unburned fuel to exhaust gas in order to restore the NOx adsorption function of the NOx catalyst device, and for controlling NOx reduction in the selective reduction catalyst device. In an exhaust gas purification system for an internal combustion engine provided with a control device having a reducing agent supply control device, the control device exhausts an injection reducing agent amount of a reducing agent used for NOx purification in the selective reduction catalyst device. And a cooperative control unit that changes the temperature in accordance with the temperature of the gas.

  Further, an exhaust gas purifying method for an internal combustion engine according to the present invention for achieving the above object is provided with a NOx catalyst device having an NOx adsorption function, a NOx catalyst device having a NOx adsorption function, and a selective reduction catalyst device. In the exhaust gas purifying method for an internal combustion engine, the control of the NOx catalyst device is performed using a temperature of the exhaust gas flowing into the NOx catalyst device and a temperature of the exhaust gas flowing into the selective reduction catalyst device. Selecting one of regeneration control to be performed, reducing agent supply control for controlling the amount of injection of reducing agent to the selective reduction catalyst device, and cooperative control for performing the regeneration control and the reducing agent supply control in parallel. , When the cooperative control is selected, using the temperature of the exhaust gas, referring to a first weight coefficient database and a second weight coefficient database set in advance, Calculating a first weighting factor and a second weighting factor; using the first weighting factor to change a parameter used in the regeneration control of the NOx catalyst device; and using the second weighting factor to perform the selection. Changing the injection reductant amount of the reductant used for NOx purification in the reduction catalyst device.

  ADVANTAGE OF THE INVENTION According to the exhaust gas purification system for an internal combustion engine and the exhaust gas purification method for an internal combustion engine of the present invention, required exhaust gas purification performance is ensured in an exhaust gas purification system for an internal combustion engine having a NOx purification catalyst for an LNT and an SCR catalyst. In addition, the cost for purifying the exhaust gas can be reduced.

It is a figure showing typically composition of an exhaust gas purification system of an internal-combustion engine of an embodiment concerning the present invention. FIG. 2 is a diagram illustrating a functional configuration of a control device used in weighted NOx purification control in the exhaust gas purification system for an internal combustion engine according to the embodiment of the present invention. FIG. 2 is a diagram showing a functional configuration of a control device used for feedback control and transient control in the exhaust gas purification system for an internal combustion engine according to the embodiment of the present invention. It is a figure which shows typically the flow of the weighted NOx purification control in the exhaust gas purification system of the internal combustion engine of the embodiment according to the present invention. FIG. 2 is a diagram schematically illustrating a flow of feedback control in the exhaust gas purification system for an internal combustion engine according to the embodiment of the present invention. FIG. 4 is a diagram illustrating an example of a control flow for performing weighted NOx purification control in the exhaust gas purification method for an internal combustion engine according to the embodiment of the present invention. FIG. 3 is a diagram showing an example of a control flow for performing feedback control in the exhaust gas purifying method for an internal combustion engine according to the embodiment of the present invention. FIG. 3 is a diagram showing an example of a control flow for performing transient control in the exhaust gas purifying method for an internal combustion engine according to the embodiment of the present invention.

  Hereinafter, an exhaust gas purification system and an exhaust gas purification method according to an embodiment of the present invention will be described with reference to the drawings. Here, the urea selective reduction catalyst device will be described as an example of the selective reduction catalyst device, and ammonia generated from urea water will be described as an example of the reducing agent, but the present invention is not limited to this.

  First, an exhaust gas purification system for an internal combustion engine according to an embodiment of the present invention will be described. As shown in FIG. 1, the exhaust gas purification system 1 for an internal combustion engine has a NOx adsorption function having a NOx adsorption function from an upstream side in an exhaust passage 11 through which exhaust gas G discharged from an engine body (internal combustion engine body) 10 passes. The apparatus includes an apparatus (LNT catalyst apparatus) 21, a urea water injection valve (reducing agent injection valve) 22, and a urea selective reduction catalyst apparatus (urea SCR catalyst apparatus) 23.

  At the same time, a regeneration control device 71 for performing regeneration control for supplying a reducing agent into the exhaust gas G to restore the NOx adsorption function of the NOx catalyst device 21 and an injection amount of the urea water U injected from the urea water injection valve 22 ( The control device 70 includes a urea water supply control device (reducing agent supply device) 72 for controlling the injection reducing agent amount) U1. Although a filter for collecting exhaust particulates (PM) in the exhaust gas G is usually provided, it is omitted because it is not directly related to the present invention. The position of this filter is not particularly limited in the present invention.

  As the NOx catalyst device 21 having the NOx adsorption function, there is an LNT (lean NOx trap catalyst) such as a NOx storage reduction type catalyst. This NOx storage reduction type catalyst is composed of a molded body or the like in which a noble metal catalyst such as platinum and a NOx storage material formed of an alkaline earth metal such as barium are supported on a catalyst carrier. Then, when the NOx in the exhaust gas is in the lean air-fuel ratio state, the NOx storage material temporarily stores the NOx, and before the NOx storage amount is saturated, the exhaust gas is brought into the rich air-fuel ratio state, thereby storing the NOx in the NOx storage material. NOx is released and reduced by the three-way function of the noble metal catalyst.

  In other words, the NOx storage reduction catalyst adsorbs and stores NOx during normal operation and, when the amount of storage becomes full, sets a rich air-fuel ratio state to release NOx and release HC from CO and CO generated from unburned fuel. This is a catalyst for reduction treatment. The NOx adsorption capacity of this NOx storage reduction catalyst is excellent at low temperatures, but decreases at high temperatures (for example, about 250 ° C. or higher, depending on the type of catalyst). In addition, in the rich air-fuel ratio control of the regeneration control for restoring the NOx adsorption ability, unburned fuel (HC, CO) is required, so that the fuel efficiency is deteriorated by that amount.

  The urea water injection valve 22 is an injection device for supplying the urea water U supplied from the urea water tank 22a via the urea water supply pipe 22b to the urea selective reduction catalyst device 23. By 72, the presence or absence of the injection of the urea water U and the injection amount U1 thereof are adjusted and controlled.

  The urea selective reduction catalyst device (urea SCR device) 23 is configured to carry a selective reduction catalyst that reacts NOx in exhaust gas G with ammonia as a reducing agent to form nitrogen and water. Examples of the selective reduction catalyst include zeolite catalysts such as iron ion exchanged aluminosilicate and copper ion exchanged aluminosilicate, and have a function of adsorbing ammonia and reducing and purifying NOx with the adsorbed ammonia. By using this urea selective reduction catalyst device 23, instead of directly using ammonia, urea water is injected into the exhaust gas G to react ammonia and NOx generated from the urea water U by hydrolysis. This makes NOx harmless.

  In other words, this urea selective reduction catalyst is a catalyst for reducing NOx using ammonia obtained by hydrolysis of urea water U as a reducing agent. The NOx purification rate of the urea selective reduction catalyst is low at a low temperature (for example, about 170 ° C. or less, depending on the type of the catalyst), but becomes extremely high at a temperature higher than that. In addition, since ammonia is used as the reducing agent, urea water is required to generate the ammonia, and the cost increases accordingly.

  Further, a first exhaust gas temperature sensor 31 for detecting the temperature Tg1 of the exhaust gas G flowing into the NOx catalyst device 21 is provided upstream of the NOx catalyst device 21 with the exhaust gas G flowing into the urea selective reduction catalyst device 23. A second exhaust gas temperature sensor 32 for detecting the temperature Tg2 is provided upstream of the urea selective reduction catalyst device 23.

  Further, a first NOx concentration sensor 33 for detecting the NOx concentration of the exhaust gas G flowing into the NOx catalyst device 21 detects the NOx concentration of the exhaust gas G flowing out of the NOx catalyst device 21 upstream of the NOx catalyst device 21. The second NOx concentration sensor 34 is provided on the downstream side of the NOx catalyst device 21 and on the upstream side of the urea selective reduction catalyst device 23, and further, the NOx concentration of the exhaust gas G flowing out of the urea selective reduction catalyst device 23. Is provided on the downstream side of the urea selective reduction catalyst device 23, respectively.

  Further, a first air-fuel ratio sensor (λ sensor) 36 is provided in the exhaust passage 11 between the engine main body (internal combustion engine main body) 10 and the NOx catalyst device 21, and a second air-fuel ratio sensor (λ sensor) 37 is provided in the engine main body. An internal combustion engine body is provided in an exhaust passage 11 between the NOx catalyst device 21 and the NOx catalyst device 21. On the other hand, the intake passage 12 is provided with an intake air amount sensor (MAF sensor) 38 for measuring the flow rate of intake air (air) A.

  Further, the control device 70 receives the detection values of the various sensors 31 to 38 and performs a regeneration control for restoring the NOx storage capacity of the NOx catalyst device 21 by the regeneration control device 71, or performs a urea water supply control device 72. Thus, a control command is output to the urea water injection valve 22 to adjust and control the injection amount U1 of the urea water U injected from the urea water injection valve 22.

  The regeneration control device 71 and the urea water supply control device 72 are usually constituted by an engine control device called an ECU (engine control unit) for controlling the overall operation of the internal combustion engine, but are separate from the engine control device. , And control may be performed while cooperating with the engine control.

  With these configurations, the exhaust gas purification system 1 for the internal combustion engine includes the NOx catalyst device 21 having the NOx adsorption function, the urea water injection valve 22, and the urea selective reduction type catalyst device 23 in the exhaust passage 11 of the internal combustion engine from the upstream side. At the same time, a regeneration control device 71 for performing regeneration control for supplying unburned fuel to the exhaust gas G to recover the NOx adsorption function of the NOx catalyst device 21 and an injection amount U1 of the urea water U injected from the urea water injection valve 22 Urea water supply control device 72 for controlling the

  In this configuration, in the low temperature side temperature range Ra in which the temperature Tg2 of the exhaust gas G is lower than the first temperature (about 170 ° C.) T1 at which the purification rate of the urea selective reduction catalyst device 23 is improved, the NOx catalyst is mainly used. NOx is reduced by the NOx adsorption function of the device 21. In the high temperature range Rb where the temperature Tg1 of the exhaust gas G is higher than the second temperature (about 250 ° C.) T2 at which the purification rate of the NOx catalyst device 21 decreases, mainly the urea selective reduction catalyst device 23 NOx is reduced by the NOx reduction function by the above.

  In the intermediate temperature range Rc where the temperature Tg2 of the exhaust gas G is higher than the first temperature T1 and the temperature Tg1 of the exhaust gas G is lower than the second temperature T2, the NOx adsorption function of the NOx catalyst device 21 and the urea NOx is reduced by the NOx reduction function of the selective reduction catalyst device 23.

  Therefore, in the exhaust gas purifying system 1 for the internal combustion engine, in the low temperature range Ra in which the temperature Tg2 of the exhaust gas G is lower than the first temperature (for example, 170 ° C.) T1, the regeneration control device 71 controls the NOx catalyst device 21 in the NOx catalyst device 21. NOx regeneration control is performed, and in a high temperature range Rb in which the temperature Tg1 of the exhaust gas G is higher than a second temperature (for example, 250 ° C.) T2, the urea water supply control device 72 causes the urea in the urea selective reduction catalyst device 23 Water injection control (reducing agent injection control) is performed. As specific contents of the NOx regeneration control and the urea water injection control, control of a known technique can be adopted.

  In the present invention, in the intermediate temperature region Rc where the temperature Tg2 of the exhaust gas G is equal to or higher than the first temperature T1 and the temperature Tg1 of the exhaust gas G is equal to or lower than the second temperature T2, the regeneration control device 71 and the urea water supply control device 72 At this time, weighted control is performed to assign weights (contributions) W1 and W2 to the NOx regeneration control by the regeneration control device 71 and the urea water injection control by the urea water supply control device 72, respectively. I do. The weighted weight coefficients W1 and W2 are calculated from the temperatures Tg1 and Tg2 of the exhaust gas G with reference to a weighted database set in advance based on experimental results and the like.

  As an experiment for obtaining this weighted database, basically, in a steady operation state of the engine, the NOx purification rate of the entire system in which the weight coefficients W1 and W2 are fixed is measured, and the weight coefficients W1 and W2 are changed. Accordingly, the weighting factors W1 and W2 having the highest evaluation values in consideration of the NOx purification rate, fuel consumption, urea water consumption, and the like are adopted. This is performed for each engine operating state having different exhaust gas temperatures Tg1 and Tg2, and a database of weighting factors W1 and W2 for the exhaust gas temperatures Tg1 and Tg2 is set while observing the evaluation values.

  If the sum of the weighting factors W1 and W2 is set to be 1.0, the number of experiments can be reduced. However, it is not always necessary to stick to 1.0, and the sum of the weighting factors W1 and W2 depends on the combination. It may not be 1.0.

  In the intermediate temperature region Rc, parameters for rich air-fuel ratio control in NOx regeneration control (for example, regeneration frequency (regeneration control interval), rich degree in rich air-fuel ratio control, The first weighting factor W1 is multiplied by the rich air-fuel ratio control period and the like, and the amount of injection urea water U1 in the urea water supply control is multiplied by the second weighting factor W2 to control the NOx catalyst device 21 and the urea selective reduction. The control for the catalyst unit 23 is performed in parallel.

  This makes it possible to set the injection urea water amount U1 for NOx purification in the urea selective reduction catalyst device 23 in a state where the NOx purification amount by the NOx catalyst device 21 is subtracted from the NOx amount flowing out from the engine body 10. .

  Next, the configuration of the control device 70 used in the exhaust gas purification system 1 for an internal combustion engine according to the embodiment of the present invention will be described. As shown in FIG. 2, the control device 70 includes a regeneration control device 71 and a urea water supply control device (reducing agent supply control device) 72. The control device 70 includes a data acquisition unit 70A and a data calculation unit 70B. , A control selection unit 70C, a weight coefficient calculation unit 70D, and a cooperative control unit 70E. The regeneration control unit 71 includes a regeneration control unit 71A and a urea water supply control unit 72. Have a urea water supply control section (reducing agent supply control section) 72A.

  Each of these units may be constituted by a device having an analog circuit, but is usually combined with software such as a part of a program and hardware to which various data is input / output along with the execution of the program. It is composed of

  In the data acquisition unit 70A, the detection value of the first exhaust gas temperature sensor 31 is obtained, the temperature Tg1 of the exhaust gas G flowing into the NOx catalyst device 21 is obtained, and the detection value of the second exhaust gas temperature sensor 32 is obtained. To obtain the temperature Tg2 of the exhaust gas G flowing into the urea selective reduction catalyst device 23.

  Further, the detection value of the first NOx concentration sensor 33 is obtained, the NOx concentration Cn1 of the exhaust gas G flowing into the NOx catalyst device 21 is obtained, the detection value of the second NOx concentration sensor 34 is obtained, and the NOx concentration Then, the NOx concentration Cn2 of the exhaust gas G flowing into the urea selective reduction catalyst device 23 is obtained. Further, the detection value of the second NOx concentration sensor 35 is obtained, and the NOx concentration Cn3 of the exhaust gas G flowing out from the urea selective reduction catalyst device 23 is obtained.

  Then, the detection values of the first air-fuel ratio sensor (λ sensor) 36, the second air-fuel ratio sensor (λ sensor) 37, and the intake air amount sensor (MAF sensor) 38 are obtained, and the first air-fuel ratio λm and the second air-fuel ratio λs and the intake air amount Va are acquired. Further, data necessary for regeneration control and urea water supply control (reducing agent supply control) is obtained from the engine operation information.

  The data calculation unit 70B calculates data used by the control selection unit 70C, the coordination control unit 70D, the regeneration control unit 71A, and the urea water supply control unit 72A based on the data obtained by the data acquisition unit 70A.

  The control selection unit 70C uses the exhaust gas temperatures Tg1 and Tg2 acquired by the data acquisition unit 70A to change the current exhaust gas temperature state in the exhaust gas purification system 1 to the low temperature side temperature region Ra, the intermediate temperature region Rc, It is determined which of the high-temperature-side temperature ranges Rb is present, and one of the regeneration control, the urea water supply control, and the cooperative control of both is selected.

  In a simplified case, for example, if the average temperature Tm of the exhaust gas temperatures Tg1 and Tg2 is less than 170 ° C., the temperature is set to the low-temperature side temperature range Ra, and if the average temperature Tm is 170 ° C. or more and less than 250 ° C. If the average temperature Tm is equal to or higher than 250 ° C., the temperature is set to the high-temperature side temperature range Rb.

  In the weight coefficient calculation unit 70D, when the cooperative control is selected by the control selection unit 70C, the weight coefficient calculation unit 70D uses the exhaust gas temperatures Tg1 and Tg2 acquired by the data acquisition unit 70A, based on a preset weight coefficient database. A first weight coefficient W1 and a second weight coefficient W2 are calculated. More specifically, the first weighting factor W1 is based on the exhaust gas temperature Tg1, the second weighting factor W2 is based on the exhaust gas temperature Tg2, the first weighting factor map data, the second weighting factor map data, and the like. Or the first weighting coefficient W1 and the second weighting coefficient W2 for the average value of the exhaust gas temperature Tg1 and the exhaust gas temperature Tg2 using weighting coefficient map data and the like.

  In a simplified case, for example, the first weighting factor W1 is set smaller and the second weighting factor W2 is set larger as the average temperature Tm of the exhaust gas temperatures Tg1 and Tg2 increases. Then, at or near the boundary between the low temperature side temperature region Ra and the intermediate temperature region Rc, the first weighting coefficient W1 is 1.0, the second weighting coefficient W2 is zero, and the intermediate temperature region Rc and the high temperature side temperature are reduced. At or near the boundary with the region Rb, the first weighting factor W1 is zero and the second weighting factor W2 is 1.0. On the way, W1 + W2 = 1.0 or W1 + W2 ≠ 1.0. Further, the first weighting coefficient W1 and the second weighting coefficient W2 do not necessarily have to have a linear relationship with the average temperature Tm.

  In the cooperative control unit 70E, when the cooperative control is selected by the control selecting unit 70C, the reproduction control unit 71A uses the first weight coefficient W1 and the second weight coefficient W2 calculated by the weight coefficient calculating unit 70D. The calculated parameters used in the regeneration control and the injected urea water amount U1 calculated by the urea water supply control unit 72A are corrected.

  For simplicity, for example, the weight map (for the value obtained from the rich air-fuel ratio frequency map for the regeneration process of the NOx catalyst device 21 or the map of the injected urea water amount for the NOx reduction process in the urea selective reduction catalyst device 23) is used. The weighting coefficient obtained from the contribution degree map) is multiplied or divided by the weighting coefficient. For example, the frequency of the rich air-fuel ratio control of the NOx catalyst device 21 is reduced according to the first weight coefficient W1. Conversely, for the urea selective reduction catalyst device 23, the amount of NOx purification by the NOx catalyst device 21 is reduced from the NOx amount at the engine outlet to set the amount of injected urea water U1.

  More specifically, when the temperature state of the exhaust gas G is in the low temperature range Ra, the regeneration control device 71 controls the NOx regeneration in the NOx catalyst device 21. In this NOx regeneration control, for example, the engine speed and load (or the NOx concentration Cn1 detected by the first NOx concentration sensor 33 and the intake air amount Va detected by the intake air amount sensor (MAF sensor) 38) are used. The operating state is input, and a rich air-fuel ratio frequency map (a database indicating the regeneration control interval (period) Ta and the rich degree Dr corresponding to the engine operating state) set in advance for these engine operating states is referred to. Then, the regeneration control interval Ta and the rich degree Dr are calculated, and based on these, the NOx regeneration control by the NOx catalyst device 21 is performed. Note that the rich degree Dr is a function of the intake amount Va, the supply amount Mt of the unburned fuel supplied by the rich air-fuel ratio control, and the period Tb during which the reducing agent is supplied. As for Tb, the richness level Dr is set in advance as a fixed value, or a richness map (the supply amount Mt and the period Tb corresponding to the engine operating state, which are set in advance for the engine operating state, are shown). Database).

  Similarly, even when the engine temperature is in the intermediate temperature range Rc, the engine operation state is input, the regeneration control interval (period) Ta, the supply amount Mt, and the period Tb are referred to by referring to a rich air-fuel ratio frequency map or the like. Is calculated.

  When the temperature state of the exhaust gas G is in the high temperature side temperature range Rb, the regeneration control device 71 controls the supply of urea water in the urea selective reduction catalyst device 23. In this urea water supply control, for example, an engine operation state is input, and an injection urea water amount map (database indicating the injection urea water amount U1 corresponding to the engine operation state) set in advance for the engine operation state is referred to. To calculate the injection urea water amount U1 to control the urea water injection. Similarly, even when the engine temperature is in the intermediate temperature range Rc, the engine operating state is input, and the injection urea water amount U1 is calculated with reference to the injection urea water amount map.

  Further, in the intermediate temperature region Rc, with respect to the regeneration control for the NOx catalyst device 21, the regeneration control interval (period) Ta used in the regeneration control calculated by the regeneration control unit 71A, that is, the previous regeneration. The time from the end of the control to the start of the current reproduction control is divided by the first weighting coefficient W1, and the interval Tac (Ta / W1 => Tac) is changed until the reproduction control is performed. In this case, the rich degree Dr of the rich air-fuel ratio control is not changed.

  Alternatively, the rich degree Dr of the rich air-fuel ratio control is changed while the regeneration control interval Ta remains the same. This change in the rich degree Dr is obtained by multiplying the supply amount Mt of the unburned fuel supplied by the rich air-fuel ratio control by the first weighting coefficient W1 (Mt × W1⇒Mtc), and supplying the reducing agent. There is a case where the period Tb is changed by multiplying by the first weighting coefficient W1 (Tb × W1⇒Tbc).

  The supply amount Mt of the unburned fuel supplied by the rich air-fuel ratio control means that the NOx catalyst device (NOx storage reduction type catalyst) 21 adsorbs and stores NOx during normal operation, and the storage amount becomes full. When this happens, the amount of unburned fuel (HC, CO) supplied to make the rich air-fuel ratio state and release NOx in the regeneration control for the regeneration of the NOx catalyst device 21. Since the supply amount of the unburned fuel may be a value set based on a known regeneration method of the NOx storage reduction catalyst, a method of calculating the supply amount of the unburned fuel is, for example, as described above. Well-known technology shall be used.

  Alternatively, considering the total supply amount Mtt of unburned fuel supplied in one regeneration control, the total supply amount Mtt (= supply amount Mt × period Tb) is changed to a value obtained by multiplying the first weighting coefficient W1. The total unburned fuel supply amount Mttc (= supply amount Mt × period Tb × W1) is set.

  Further, regarding the urea water supply control to the urea selective reduction catalyst device 23, the injection urea water amount U1 calculated by the urea water supply control unit 72A is multiplied by the second weighting coefficient W2 to change the injection urea water amount U1. (U1 × W2⇒U1c).

  Then, the regeneration control device 71 performs the regeneration control in the low temperature side region Ra and the intermediate temperature region Rc. In this regeneration control, NOx concentration estimating means for calculating by referring to NOx emission concentration map data set in advance based on the engine operating state (engine speed Ne, load Q) may be used. As described above, the NOx concentration Cn1 may be detected by the first NOx concentration sensor 33.

  In other words, the NOx adsorption amount Na adsorbed by the NOx catalyst device 21 flows from the NOx concentration Cn1 flowing into the NOx catalyst device 21 obtained by the first NOx concentration sensor 33 to the NOx catalyst device 21 obtained by the second NOx concentration sensor 34. It is calculated by subtracting the NOx concentration Cn2 and multiplying by the exhaust gas amount Vg (Na = Vg × (Cn1-Cn2)).

  When the NOx adsorption amount Na exceeds a predetermined determination value Nj, the regeneration control is performed, or when the engine operation time or the running distance from the end of the previously set previous regeneration control exceeds a preset value. Or perform playback control. The determination value Nj is a value that changes according to the catalyst temperature Tc of the NOx catalyst device 21, and is a threshold value set in consideration of the maximum NOx storage amount at the catalyst temperature Tc. For example, the determination value Nj is set to about 90% of the maximum NOx storage amount.

  In general, in the regeneration control, a temperature increase control for increasing the catalyst temperature Tc of the NOx catalyst device 21 to the activation temperature or higher and a rich air-fuel ratio control for reduction purification (rich reduction event) are performed. Further, if necessary, the temperature Tg1 of the exhaust gas G is monitored to check the degree of operation stability and the purification rate, and to correct the prohibition conditions and parameters in the control.

  Further, in the rich air-fuel ratio control, when the catalyst temperature Tc of the NOx catalyst device 21 is increasing, the unburned fuel supply amount Mt is increased to decrease the first air-fuel ratio λm, and the latter half of the rich air-fuel ratio control is performed. Then, when the NOx release amount Nb decreases, it is preferable to decrease the unburned fuel supply amount Mt to increase the first air-fuel ratio λm. That is, in the rich air-fuel ratio control, when the temperature rises and the NOx adsorption amount Na of the NOx catalyst device 21 is still large, the NOx release amount Nb increases. Therefore, the unburned fuel supply amount Mt is increased to reduce the first air-fuel ratio λm. Make it smaller. In the latter half of the rich air-fuel ratio control, when the NOx release amount Nb decreases, the unburned fuel supply amount Mt is reduced to increase the first air-fuel ratio λm.

  Then, in the low temperature side temperature region Ra, the reproduction control is performed without correcting the parameters (Ta, Tb, Mt) calculated by the reproduction control unit 71A, and in the intermediate temperature region Rc, the calculation is performed by the reproduction control unit 71A. The reproduction control is performed by the parameters (Tac, Tbc, Mtc) in which the parameters (Ta, Tb, Mt) changed by the cooperative control unit 70E.

  In the urea water supply control device 72, urea water supply control is performed in the intermediate temperature region Rc and the high temperature side temperature region Rb. The urea water U is injected with the injected urea water amounts U1 and U1c up to the ammonia storage (reducing agent storage) amount threshold to store ammonia in the urea selective reduction catalyst device 23, and ammonia is consumed for NOx reduction. If the storage amount is smaller than the threshold, the urea water U is injected again. In addition, if necessary, the temperature Tg2 of the exhaust gas G is monitored, and the prohibition conditions and parameters in the control are corrected while checking the degree of operation stability and the purification rate.

  That is, it is known that, in practice, ammonia previously stored in the urea selective reduction catalyst device 23 contributes as ammonia (reducing agent) that contributes to reducing the NOx inflow amount Ns. The amount of ammonia storage (reducing agent storage) stored in advance in the urea selective reduction catalyst device 23 is grasped every moment, and this ammonia storage amount, the amount of ammonia generated from the injected urea water amounts U1, U1c, and The injection urea water amounts U1 and U1c are adjusted in consideration of the amount of ammonia consumed in the reduction of NOx. That is, the urea water supply control unit 72A calculates the injection urea water amounts U1 and U1c calculated in consideration of the ammonia storage amount. Here, a known technique is used for the urea water control in consideration of the ammonia storage amount.

  Furthermore, the relationship between the amount of ammonia and the second air-fuel ratio λs of the exhaust gas G flowing into the urea selective reduction catalyst device 23 is experimentally obtained, and is stored in a database. It is preferable to incorporate the calculated value in the ammonia storage control of the selective reduction catalyst device 23 to correct the urea injection control.

  Further, the urea water supply control device 72 performs the urea water supply control in the high temperature side temperature region Rb without changing the injection urea water amount U1 calculated by the urea water supply control unit 72A, and in the intermediate temperature region Rc. The urea water supply control is performed with the injected urea water amount U1c changed by the coordination control unit 70E from the injected urea water amount U1 calculated by the urea water supply control unit 72A.

With the configuration described above, the exhaust gas purification system 1 for an internal combustion engine according to this embodiment includes a NOx catalyst device 21 having a NOx adsorption function in an exhaust passage 11 of the internal combustion engine from an upstream side, a urea water injection valve 22, and a urea selective reduction type. A regeneration control device 71 for performing regeneration control for supplying unburned fuel to exhaust gas in order to restore the NOx adsorption function of the NOx catalyst device 21 and a urea selective reduction type catalyst device 23 The exhaust gas purification system 1 for an internal combustion engine includes a control device 70 having a urea water supply control device 72 for controlling NOx reduction in the internal combustion engine.
At the same time, the first exhaust gas temperature sensor 31 is provided upstream of the NOx catalyst device 21, and the second exhaust gas temperature sensor 32 is provided downstream of the NOx catalyst device 21 and upstream of the urea selective reduction catalyst device 23, respectively. Have been.

  The control device 70 controls the temperature Tg1 of the exhaust gas G flowing into the NOx catalyst device 21 by the first exhaust gas temperature sensor 31 and the exhaust gas flowing into the urea selective reduction catalyst device 23 by the second exhaust gas temperature sensor 32. A data acquisition unit 70A for acquiring the temperature Tg2 of G, a regeneration control for controlling the NOx catalyst device 21 using the temperatures Tg1 and Tg2 of the exhaust gas G acquired by the data acquisition unit 70A, a urea selective reduction type catalyst device. The control selection unit 70C that selects one of the urea water supply control that controls the supply amount of the urea water U to the control unit 23 and the cooperative control that performs the regeneration control and the urea water supply control in parallel, and the control selection unit 70C performs the cooperative control. When selected, the first weighting coefficient database and the predetermined weighting factor database are set using the temperatures Tg1 and Tg2 of the exhaust gas G acquired by the data acquiring unit 70A. Referring to the weight coefficient database, the weight coefficient calculation section 70D that calculates the first weight coefficient W1 and the second weight coefficient W2, and the weight coefficient calculation section 70D calculates when the cooperative control is selected by the control selection section 70C. The parameter used in the regeneration control of the NOx catalyst device 21 is changed using the obtained first weight coefficient W1, and the urea selective reduction catalyst is used using the second weight coefficient W2 calculated by the weight coefficient calculating unit 70D. A coordination control unit 70E for changing the injection urea water amount U1 of the urea water U used for NOx purification in the device 23 is provided.

  Further, with respect to the regeneration control for the NOx catalyst device 21, the cooperative control unit 70E divides the time from the end of the previous regeneration control to the start of the regeneration control by the first weighting coefficient W1 to increase the interval until the regeneration control is performed. A first change method for changing the amount of the reducing agent supplied by the rich air-fuel ratio control in the regeneration control by a first weighting coefficient W1, or a second change method for changing the rich amount in the regeneration control. Any one of the third changing methods of multiplying and reducing the period during which the reducing agent supplied by the air-fuel ratio control is supplied by the first weighting coefficient W1 is performed.

  Further, the cooperative control unit 70E sets the injected urea water amount U1 of the urea water U supplied to the urea selective reduction catalyst device 23 in consideration of the ammonia adsorption amount adsorbed by the urea selective reduction catalyst device 23, and The set urea water amount U1 of the urea water U is changed by multiplying by the second weight coefficient W2 calculated by the weight coefficient calculation unit 70D.

  Then, as shown in FIG. 3, the control device 70 further increases the next purification rate target value calculation unit 8OA, the purification rate actual value calculation unit 80B, and the feedback correction in order to enhance the robustness, which is the robustness against disturbance. It is preferable to include a feedback control unit 80 having a value calculation unit 80C and a control parameter correction unit 80D.

  That is, the control device 70 calculates the purification rate target value ηnt of the entire system of the exhaust gas purification system 1 of the internal combustion engine by the purification rate target value calculation unit 80A, and performs the purification of the entire system per a predetermined evaluation range. From the purification rate actual value calculation unit 80B that calculates the actual rate ηnm, and from the difference Δηn between the actual purification rate ηnm and the target purification rate ηnt, feedback correction values Fc1 and Fc2 for the regeneration control and the urea water supply control are determined. A feedback control unit 80 having a correction value calculation unit 80C to be calculated and a control parameter correction unit 80D that corrects a control parameter for regeneration control and a control parameter for urea water supply control using the feedback correction values Fc1 and Fc2, respectively. It is preferable that it is comprised.

  The purification rate target value calculation unit 8OA sets an overall purification rate target value map for the entire exhaust gas purification system 1 of the internal combustion engine, and calculates a target value of the NOx purification rate for the engine operating state. Further, in the actual purification rate calculation unit 80B, the purification rate target value ηnt calculated by the purification rate target value calculation unit 80A, the NOx concentration Cn3 detected by the third NOx concentration sensor 35 at the latter stage of the entire system, and the exhaust gas The amount Vg and the “evaluation range” calculated between preset evaluation ranges (for example, preset traveling distance, engine operating time, accumulated fuel consumption, etc.) after the regeneration control of the NOx catalyst device 21. The actual purification rate ηnm is calculated from “the amount of NOx discharged from the engine body per (for example, a predetermined traveling distance)” and “the amount of NOx discharged into the atmosphere per this evaluation range”.

  The correction value calculation unit 80C also calculates a difference Δηn (= ηnm−) between the actual purification rate ηnm calculated by the actual purification rate calculation unit 80B and the purification rate target value ηnt calculated by the purification rate target value calculation unit 80A. ηnt), and the feedback correction values Fc1 and Fc2 for the regeneration control and the urea water supply control are calculated. The control parameter correction unit 80D corrects the control parameters of the regeneration control and the urea water supply control using the feedback correction values Fc1 and Fc2 calculated by the correction value calculation unit 80C. Then, the feedback control unit 82 corrects the control parameter of the regeneration control and the control parameter of the urea water supply control using the feedback correction values Fc1 and Fc2 so as to maintain the purification rate target value ηnt of the entire system. Perform feedback control.

  For example, when the feedback control unit 80 detects that the NOx emission amount is higher than the exhaust gas regulation value in the RDE (real road driving test) or the actual driving, the regeneration control for the NOx catalyst device 21 is performed. Increases the frequency (frequency) of the rich air-fuel ratio control, or increases the value of the ammonia storage amount threshold (ammonia storage limit) by the urea water injection control for the urea selective reduction catalyst device 23. Even in this case, when the weighting coefficients W1 and W2 are used in the regeneration control and the urea water injection control in the cooperative control, the weighting is continued to further correct the feedback control. That is, in addition to the respective changes by the weighting coefficients W1 and W2, correction by the feedback correction values Fc1 and Fc2 is also added.

  In this feedback control, basically, in a state where the operating state of the engine is in a steady state, the fuel efficiency deterioration due to the rich air-fuel ratio control is minimized as far as the purification rate target value ηnt is satisfied, and the injection by the urea water injection control is performed. The feedback correction amounts Fc1 and Fc2 are calculated and set so that the urea water amount U1 may be as small as possible. The correction amount performed on the control parameter in the regeneration control for the NOx catalyst device 21 is referred to as a first feedback correction amount Fc1, and the correction performed on the control parameter in the urea water supply control performed on the urea selective reduction type catalyst device 23. The amount is defined as a second feedback correction amount Fc2.

  The priority of the feedback correction of this correction is, in other words, regarding the ratio between the first feedback correction amount Fc1 and the second feedback correction amount Fc2, both change at the same rate, or the first feedback correction amount When only the Fc1 is corrected and this correction is insufficient, the second feedback correction amount Fc2 is added and corrected. On the contrary, when only the second feedback correction amount Fc2 is corrected and the correction is insufficient. Then, the correction is performed by adding the first feedback correction amount Fc1, or the correction of only the first feedback correction amount Fc1 and the correction of only the second feedback correction amount Fc2 are alternately repeated. The order of these corrections and the magnitudes of the correction amounts Fc1 and Fc2 with respect to the difference Δηn (= ηnm−ηnt) between the actual purification rate ηnm and the target purification rate ηnt are to be set in advance through experiments. Become.

  Further, it is more preferable to include the transient control unit 90 so that a good response can be made to the transient state. That is, the control unit 70 calculates the transient state correction values Gc1 and Gc2 when the transient state determination unit 90A determines whether the state is the transient state and when the transient state determination unit 90A determines that the state is the transient state. A transient correction value calculating unit 90B, a control parameter correcting unit 90C for correcting the control parameters in the regeneration control and the urea water supply control with the transient correction values Gc1 and Gc2, and a transient state determining unit 90A. It is more preferable to include a transient control unit 90 having a transient correction reset unit 90D that cancels the correction of the control parameters by the transient correction values Gc1 and Gc2 when the determination is made.

  The transient control unit 90 performs transient control to evaluate fuel consumption and urea consumption while ensuring the total NOx purification rate of NOx purification in both the NOx purification catalyst 21 and the urea selective reduction catalyst device 23. Control is performed so that the value becomes a good value.

  For example, in the case of a transient condition such as rapid acceleration after traveling at a constant speed with a low load, the exhaust gas temperature rises immediately, but the catalyst temperature of the urea selective reduction catalyst device 23 is still low, and the activation of the catalyst is insufficient. In such a state, the reducing action on NOx in the urea selective reduction catalyst device 23 is insufficient, and it is conceivable that the amount of NOx discharged into the atmosphere may increase. In this case, until the catalyst temperature of the urea selective reduction catalyst device 23 rises, the addition of the urea water U is delayed without immediately supplying the urea water that cools the exhaust gas by the supply of the urea water. Response control, or rich control to supply rich air-fuel ratio to supply unburned fuel for raising the exhaust gas temperature until the catalyst temperature of the urea selective reduction catalyst device 23 rises. Extension control ”and other transient corrections.

  Next, an exhaust gas purifying method for an internal combustion engine according to an embodiment of the present invention will be described. This exhaust gas purification method for an internal combustion engine is an exhaust gas purification method for an internal combustion engine that purifies NOx in exhaust gas exhausted from the internal combustion engine with a NOx catalyst device having a NOx adsorption function and a urea selective reduction catalyst device. In this method, the control of the NOx catalyst device 21 is performed using the temperature Tg1 of the exhaust gas G flowing into the NOx catalyst device 21 and the temperature Tg2 of the exhaust gas G flowing into the urea selective reduction catalyst device 23. A step of selecting any of regeneration control, urea water supply control for controlling the amount of urea water U1 injected of the urea water U to the urea selective reduction catalyst device 23, and cooperative control for performing regeneration control and urea water supply control in parallel; When the cooperative control is selected, the first weight coefficient database and the second weight coefficient database preset using the temperatures Tg1 and Tg2 of the exhaust gas G are set. Referring to the step of calculating the first weighting coefficient W1 and the second weighting coefficient W2, using the first weighting coefficient W1 to change a parameter used in the regeneration control of the NOx catalyst device 21, Changing the injected urea water amount U1 of the urea water U used for purifying NOx in the urea selective reduction catalyst device 23 using the coefficient W2.

  The above control can be performed by an example control flow as shown in FIG. The control flow of FIG. 6 is called from a higher-level control flow when the internal combustion engine starts operating, and is executed in parallel with the operation control flow of the other exhaust gas purification system 1, and when the operation of the internal combustion engine ends. , An interrupt occurs, returns to the higher-level control flow, and ends with this higher-level control flow.

  When the control flow of FIG. 6 starts, in step S11, the exhaust gas temperatures Tg1 and Tg2 are obtained, and the target purification rate of NOx purification is calculated. This target purification rate of NOx purification is a purification rate of NOx in the entire exhaust gas purification system 1 of the internal combustion engine. The target purification rate of NOx is set in advance based on the engine operating state (engine speed Ne, load Q, etc.). It is calculated with reference to a map or the like.

  In the next step S12, the temperatures Tg1 and Tg2 of the exhaust gas G are compared with the first temperature T1 and the second temperature T2, and if the temperature Tg2 of the exhaust gas G is lower than the first temperature T1, the lower temperature Assuming that the region is the area Ra, in step S20, the regeneration control device 71 performs NOx regeneration control in the NOx catalyst device 21, and when the regeneration control in step S20 ends, the process returns to step S11. The first temperature T1 is, for example, 170 ° C., although it depends on the type of the SCR catalyst of the urea selective reduction catalyst device 23, and the second temperature T2 is the type of the catalyst (LNT catalyst) of the NOx catalyst device. For example, the temperature is 250 ° C.

  On the other hand, if the temperature Tg1 of the exhaust gas G is higher than the second temperature T2, it is determined that the temperature Tg1 is in the high temperature side temperature range Rb, and the urea water supply control device 72 injects urea water in the urea selective reduction catalyst device 23 in step S40. The control is performed, and after a predetermined time has elapsed in the urea water injection control in step S40, the process returns to step S11.

  If the temperature Tg2 of the exhaust gas G is equal to or higher than the first temperature T1 and the temperature Tg1 of the exhaust gas G is equal to or lower than the second temperature T2, the regeneration control device 71 is determined to be in the intermediate temperature region Rc by the cooperative control in step S30. And the urea water supply control device 72 performs cooperative control. In the cooperative control in step S30, weights (degrees of contribution) W1 and W2 are calculated from the temperatures Tg1 and Tg2 of the exhaust gas G with reference to a weighted database set in advance based on experimental results and the like in step S31. In the next step S32, weighted control for assigning weights (contributions) W1 and W2 to the NOx regeneration control by the regeneration control device 71 and the urea water injection control by the urea water supply control device 72 is performed. When the weighted reproduction control in step S32 ends, the process returns to step S11.

  Then, when the operation of the internal combustion engine is terminated, the control is returned to the higher-level control flow after performing the control ending operation of step S50 due to the interruption, and the process ends with the higher-level control flow.

  Further, control for enhancing robustness, which is robustness against disturbance, can be performed according to a control flow as shown in FIG. When the control flow of FIG. 7 starts, in step S81, a purification rate target value ηnt of the entire exhaust gas purification system 1 of the internal combustion engine is calculated. In the next step S10, the correction based on the feedback correction values Fc1 and Fc2 is applied to each control parameter of the NOx purification control including the regeneration control and the urea water supply control. When the feedback control is not performed, the feedback correction values Fc1 and Fc2 are each 1.0.

  After performing the NOx purification control in step S10, in step S82, the traveling distance (or the engine operating time, the engine operating time, the accumulated fuel consumption, and the like) in which the NOx purification control in step S10 is performed is set in advance. It is determined whether the evaluation range has been exceeded. If the determination in step S82 is within the evaluation range, the process returns to step S10, and the NOx purification control is continued without changing the feedback correction values Fc1 and Fc2.

  If the determination in step S82 is outside the evaluation range, the process proceeds to step S83, where the actual purification rate ηnm is calculated for the entire system. In the next step S84, the feedback correction values Fc1 and Fc2 are calculated. Update to Then, the process returns to step S81. If the operation of the internal combustion engine is terminated in the middle of the control, the process returns to the higher-level control flow due to an interruption, and ends with the higher-level control flow.

  The control for the transient state can be performed according to a control flow as shown in FIG. When the control flow of FIG. 8 starts, it is determined in a step S91 whether or not the engine operating state is in a transition state. If it is determined in step S91 that the state is not a transient state (NO), the process proceeds to step S92, resets the value of the transient correction value to a normal value (1.0), and returns to step S91.

  On the other hand, if it is determined in step S91 that the state is a transient state (YES), the process proceeds to step S93 to calculate a transient correction value for dealing with a transient state. This transient correction value is calculated with reference to a database set in advance through experiments or the like. For example, a correction value of the urine injection start timing for “response delay correction control of urea injection” and a correction value of the rich air-fuel ratio control time (unburned fuel supply time) for “extended control of rich air-fuel ratio control” And so on.

  In the next step S10, NOx purification control is performed with the correction based on the transient correction value, and the process returns to step S91. If the operation of the internal combustion engine is terminated in the middle of the control, the process returns to the higher-level control flow due to an interruption, and ends with the higher-level control flow.

  According to the exhaust gas purification system 1 for an internal combustion engine and the exhaust gas purification method for an internal combustion engine of this embodiment, the exhaust gas purification of the internal combustion engine includes the NOx purification catalyst of the NOx catalyst device 21 and the urea selective reduction catalyst device 23. In the system 1, in the low temperature side temperature range Ra, NOx flowing into the urea selective reduction type catalyst device 23 can be reduced, and the ammonia storage amount in the urea selective reduction type catalyst device 23 can be reduced. By reducing the frequency of the rich air-fuel ratio control for the NOx catalyst device 21, fuel efficiency can be improved, urea water consumption can be reduced, and the amount of ammonia slip at the time of temperature rise can be reduced.

  At the same time, in the intermediate temperature region Rc, the NOx purification rate is balanced by the simple algorithm of simple weighting control while the NOx purification of the NOx catalyst device 21 and the NOx purification of the urea selective reduction catalyst device 23 are balanced. NOx can be purified so that the evaluation value regarding fuel consumption and urea water consumption becomes a good value.

  Therefore, the fuel and urea water consumption required for rich air-fuel ratio control can be reduced, so that the cost for exhaust gas purification can be reduced while securing the required exhaust gas purification performance.

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification system for internal combustion engine 10 Engine main body 11 Exhaust passage 12 Intake passage 21 NOx catalyst device 22 Urea water injection valve 23 Urea selective reduction type catalyst device 30 Control device 31 First exhaust gas temperature sensor 32 Second exhaust gas temperature sensor 33 First NOx concentration sensor 34 Second NOx concentration sensor 35 Third NOx concentration sensor 36 First λ sensor (first air-fuel ratio sensor)
37 2nd λ sensor (2nd air-fuel ratio sensor)
38 MAF sensor (intake air amount sensor)
70 control device 70A data acquisition unit 70B data calculation unit 70C control selection unit 70D weight coefficient calculation unit 70E cooperative control unit 71 regeneration control unit 71A regeneration control unit 72 urea water supply control unit 72A urea water supply control unit 80 feedback control unit 80A Purification rate target value calculation unit 80B Purification rate actual value calculation unit 80C Feedback correction value calculation unit 80D Control parameter correction unit (FB correction)
90 Transient control section 90A Transient state determination section 90B Transient correction value calculation section 90C Control parameter correction section (transient correction)
90D Transient correction reset section A Intake G Exhaust gas U Urea water

Claims (5)

An NOx catalyst device having a NOx adsorption function, a reducing agent injection valve, and a selective reduction catalyst device are provided from the upstream side in the exhaust passage of the internal combustion engine. An exhaust gas purification system for an internal combustion engine, comprising: a regeneration control device for performing regeneration control for supplying fuel to exhaust gas; and a control device having a reducing agent supply control device for controlling NOx reduction in the selective catalytic reduction device. At
The control device,
A cooperative control unit that changes the injection reducing agent amount of the reducing agent used for NOx purification in the selective reduction catalyst device according to the temperature of exhaust gas. Exhaust gas purification system. The cooperative control unit includes:
Regarding regeneration control for the NOx catalyst device,
A first changing method of changing the time interval from the end of the previous reproduction control to the start of the reproduction control so as to be longer,
A second change method for changing the supply amount of the reducing agent supplied in the rich air-fuel ratio control in the regeneration control,
2. The exhaust gas of an internal combustion engine according to claim 1, wherein any one of a third change method for changing a period during which the reducing agent supplied in the rich air-fuel ratio control in the regeneration control is supplied is performed. 3. Gas purification system. The control device,
A purification rate target value calculation unit that calculates a purification rate target value for the entire exhaust gas purification system of the internal combustion engine,
A purification rate actual value calculation unit that calculates a purification rate actual value of the entire system per a predetermined evaluation range,
A correction value calculation unit that calculates a feedback correction value for the regeneration control and the reducing agent supply control from the difference between the purification rate actual value and the purification rate target value,
Using the feedback correction value, a control parameter correction unit that corrects the control parameter of the regeneration control and the control parameter of the reducing agent supply control, respectively.
The exhaust gas purification system for an internal combustion engine according to any one of claims 1 to 2, further comprising a feedback control unit having a feedback control unit for performing feedback control so as to maintain the purification rate target value. The control device,
A transient state determination unit that determines whether or not the state is a transient state;
When it is determined that the transient state is in the transient state by the transient state determination unit, a transient correction value calculation unit that calculates a transient correction value,
A control parameter correction unit that corrects a control parameter in the regeneration control and the reducing agent supply control with the transient correction value,
A transient control unit having a transient correction reset unit for canceling correction by the transient correction value for the control parameter when it is determined that the transient state determination unit has deviated from the transient state. An exhaust gas purification system for an internal combustion engine according to any one of claims 1 to 3. An exhaust gas purification method for an internal combustion engine that purifies NOx in exhaust gas discharged from an internal combustion engine with a NOx catalyst device having a NOx adsorption function and a selective reduction catalyst device,
Regeneration control for controlling the NOx catalyst device using the temperature of the exhaust gas flowing into the NOx catalyst device and the temperature of the exhaust gas flowing into the selective reduction catalyst device, and reducing the NOx catalyst device. Selecting one of cooperative control for controlling the regenerating control and the reducing agent supply control in parallel with the reducing agent supply control for controlling the injection reducing agent amount of the agent,
When the cooperative control is selected, the first weight coefficient and the second weight coefficient are calculated using the temperature of the exhaust gas and referring to a first weight coefficient database and a second weight coefficient database set in advance. Steps to
Using the first weighting factor, the parameter used in the regeneration control of the NOx catalyst device is changed, and the reducing agent used for NOx purification in the selective reduction catalyst device using the second weighting factor. Changing the injection reducing agent amount of the exhaust gas of the internal combustion engine.

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