JP2017096138A - Exhaust emission control system for internal combustion engine, internal combustion engine and exhaust emission control method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control system for an internal combustion engine, the internal combustion engine and an exhaust emission control method for the internal combustion engine, which can highly accurately estimate ammonia amount stored in each of selective reduction type catalyst devices when an exhaust emission control device includes the plurality of selective reduction type catalyst devices, thus can make supply amount of urea water from an urea water supply device appropriate and can improve an NOx elimination ratio while suppressing ammonia slip from the selective reduction type catalyst devices.SOLUTION: An exhaust emission control device includes a selective reduction type catalyst device group 14 that comprises at least two or more selective reduction type catalyst devices. On the basis of a concentration of nitrogen oxide included in exhaust gas G flowing into the selective reduction type catalyst device group 14 and an ammonia concentration included in the exhaust gas G flowing out from each of the selective reduction type catalyst devices 141, 142, 143 constituting the selective reduction type catalyst device group 14, basic supply amount Qb of urea water U from an urea water supply device 22 is corrected.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine, an internal combustion engine, and an exhaust gas purification method for the internal combustion engine, which are provided with a urea water supply device and an exhaust gas purification treatment device in order from the upstream side in the exhaust passage of the internal combustion engine. About.

  An internal combustion engine such as a diesel engine mounted on a vehicle has an exhaust gas for purifying components to be purified contained in exhaust gas such as nitrogen oxide (NOx), particulate matter (PM), and hydrocarbon (HC). A gas purification treatment device is provided in the exhaust passage. This exhaust gas purification processing device is provided with devices such as an oxidation catalyst device (DOC), a particulate collection device (CSF), and a selective catalytic reduction device (SCR).

This selective catalytic reduction catalyst device generates ammonia (NH ₃ ) by hydrolyzing urea water, which is injected toward the exhaust gas from the urea water supply device provided in the preceding exhaust passage, by the heat of the exhaust gas, This is an apparatus for reducing and purifying NOx contained in exhaust gas by the generated ammonia (NH ₃ ). The catalyst supported on the selective catalytic reduction device can store ammonia, and NOx contained in the exhaust gas is mainly reduced and purified by the stored ammonia.

  However, there is an upper limit to the amount of ammonia that can be stored (storage amount), and ammonia that cannot be stored beyond this upper limit is released into the exhaust passage downstream of the selective catalytic reduction device. In particular, under certain conditions (for example, when the temperature of the selective catalytic reduction device suddenly rises due to a sudden rise in the temperature of exhaust gas due to a sudden change in the operating state of the internal combustion engine, etc.), Since the upper limit of the storage amount of ammonia that can be stored changes rapidly, the amount of ammonia released into the exhaust passage downstream of the selective catalytic reduction device (amount of ammonia slip) increases.

  Note that an ammonia slip catalyst device is usually disposed in the exhaust passage on the downstream side of the selective catalytic reduction device. By this ammonia slip catalyst device, most of the ammonia released from the selective catalytic reduction device is oxidized to NOx.

  By the way, laws and regulations on exhaust gas from internal combustion engines such as diesel engines are becoming stricter year by year, and in order to comply with these stricter laws and regulations, exhaust gas purification treatment devices are selectively reduced. It is necessary to take measures such as increasing the size by providing a plurality of catalyst devices.

  As an example provided with a plurality of selective reduction catalyst devices, an internal combustion engine provided with an urea water injection device, a first selective reduction catalyst, an NH3 sensor, and a second selective reduction catalyst in the exhaust passage of the engine in order from the upstream side. An exhaust gas purification apparatus has been proposed (see, for example, Patent Document 1).

  As described above, when the exhaust gas purification processing apparatus includes a plurality of selective reduction catalyst devices, it is necessary to estimate the amount of ammonia stored in each selective reduction catalyst device with high accuracy. In the purification process of NOx contained in the exhaust gas, ammonia stored in each selective reduction catalyst device is mainly used as a reducing agent. However, if the accuracy of estimating the storage amount of ammonia is not good, the urea water supply in the previous stage is supplied. This is because the urea water supply amount from the apparatus may be excessive or insufficient, and ammonia slip from the selective catalytic reduction apparatus may occur or the NOx purification rate may deteriorate.

  However, a means for estimating with high accuracy the amount of ammonia stored in each selective reduction catalyst device when a plurality of selective reduction catalyst devices are provided in the exhaust gas purification processing device has not yet been established.

JP 2011-163195 A

  The present invention has been made in view of the above, and an object of the present invention is to provide an internal combustion engine including a urea water supply device and an exhaust gas purification processing device in order from the upstream side in the exhaust passage of the internal combustion engine. The exhaust gas purification system, the internal combustion engine, and the exhaust gas purification method of the internal combustion engine, in particular, when the exhaust gas purification processing apparatus includes a plurality of selective reduction catalyst devices, the ammonia stored in each selective reduction catalyst device The amount can be estimated with high accuracy, and as a result, the amount of urea water supplied from the urea water supply device can be optimized, and the NOx purification rate can be reduced while suppressing ammonia slip from the selective catalytic reduction device. It is an object to provide an exhaust gas purification system for an internal combustion engine, an internal combustion engine, and an exhaust gas purification method for the internal combustion engine.

  In order to achieve the above object, an exhaust gas purification system for an internal combustion engine according to the present invention includes an urea water supply device and an exhaust gas purification treatment device in order from the upstream side in an exhaust passage of the internal combustion engine. In the exhaust gas purification system of the present invention, the exhaust gas purification processing device includes a selective reduction catalyst device group composed of at least two selective reduction catalyst devices, and an inlet of the selective reduction catalyst device group, Each of the selective reduction catalyst devices constituting the selective reduction catalyst device group includes a nitrogen oxide detection device that detects the concentration of nitrogen oxide contained in the exhaust gas flowing into the selective reduction catalyst device group. The rear stage is configured to include an ammonia concentration detection device that detects the concentration of ammonia contained in the exhaust gas flowing out from each selective reduction catalyst device.

  According to this configuration, the nitrogen oxide detection device provided at the inlet of the selective reduction catalyst device group with the amount (storage amount) of ammonia stored in each selective reduction catalyst device provided in the exhaust gas purification processing device. Therefore, the amount of ammonia stored in each selective catalytic reduction device can be estimated with high accuracy. As a result, the amount of urea water supplied from the urea water supply device can be optimized, and the NOx purification rate can be improved while suppressing ammonia slip from the selective catalytic reduction device. .

  In the exhaust gas purification system for an internal combustion engine, the control device for controlling the exhaust gas purification system is a selective reduction catalyst disposed on the upstream side of the exhaust passage in the selective reduction catalyst device group. The amount of ammonia stored in each selective reduction catalyst device is calculated in order from the device, and the calculated amount of ammonia is calculated for each selective reduction catalyst device based on the operating state of the internal combustion engine. The urea water that is preset based on the operating state of the internal combustion engine every time it is determined whether or not a preset threshold value is exceeded and the calculated value of the ammonia amount exceeds the preset threshold value It is configured to perform control for correcting the basic supply amount of urea water from the supply device.

  According to this configuration, the storage amount of ammonia in each selective reduction catalyst device is calculated in order from the selective reduction catalyst device disposed upstream of the exhaust passage, and the calculated storage amount of ammonia is set. It is determined whether or not the threshold value is exceeded, and in accordance with the determination result, the basic supply amount of urea water from the urea water supply device is corrected, so the storage amount of ammonia in each selective reduction catalyst device is determined. It can be reliably and accurately maintained at an appropriate amount, and the amount of urea water supplied from the urea water supply device can be optimized.

  Alternatively, in the exhaust gas purification system for an internal combustion engine, the control device that controls the exhaust gas purification system may reduce the amount of ammonia stored in each selective reduction catalyst device that constitutes the selective reduction catalyst device group. Calculating at the same time, determining whether the calculated value of each of these ammonia amounts exceeds a preset threshold value set in advance for each selective catalytic reduction device based on the operating state of the internal combustion engine, When there is a selective catalytic reduction device that determines that the calculated value of the amount of ammonia exceeds the set threshold value, the basic urea water from the urea water supply device that is preset based on the operating state of the internal combustion engine Based on the number of selective catalytic reduction catalytic devices that correct the supply amount and determine that the calculated value of the ammonia amount exceeds the set threshold value, the basic supply of the urea water Configured to perform control for increasing the correction amount to be added to.

  According to this configuration, the storage amount of ammonia in each selective reduction catalyst device provided in the exhaust gas purification processing device is calculated at the same time, and it is determined whether or not the calculated storage amount of ammonia exceeds a set threshold value. Since the correction amount added to the basic supply amount of urea water from the urea water supply device is changed according to the determination result, the storage amount of ammonia in each selective reduction catalyst device can be quickly adjusted to an appropriate amount. In addition, the amount of urea water supplied from the urea water supply device can be optimized.

  In the exhaust gas purification system for an internal combustion engine, the control device may be configured to control ammonia stored in a selective reduction catalyst device disposed in the uppermost stream of the exhaust passage in the selective reduction catalyst device group. The amount is calculated based on the detection value of the nitrogen oxide detection device and the detection value of the ammonia concentration detection device disposed downstream of the upstream selective reduction catalyst device, and the upstream selective reduction The amount of ammonia stored in the selective catalytic reduction device other than the catalytic catalytic device is detected by the ammonia concentration detection device disposed downstream of the selective catalytic reduction device adjacent to the upstream side of the selective catalytic reduction device. It is configured to perform control based on the value and the detection value of the ammonia concentration detection device disposed in the subsequent stage of the selective catalytic reduction device.

  According to this configuration, the calculation accuracy of the storage amount of ammonia of each selective reduction catalyst device can be increased.

  Alternatively, in the exhaust gas purification system for an internal combustion engine, the control device that controls the exhaust gas purification system may reduce the amount of ammonia stored in each selective reduction catalyst device that constitutes the selective reduction catalyst device group. The total amount of ammonia, which is the total amount, is calculated based on the detection value of the nitrogen oxide detection device and the detection value of the ammonia concentration detection device disposed at the subsequent stage of each selective reduction catalyst device, and When the calculated value of the total ammonia amount exceeds an ammonia total amount setting threshold that is preset based on the operating state of the internal combustion engine, the urea water supply device that is preset based on the operating state of the internal combustion engine It is comprised so that control which adds correction | amendment to the basic supply amount of the urea water from may be performed.

  According to this configuration, each selective reduction catalyst device provided in the exhaust gas purification processing device is regarded as one large selective reduction catalyst device, and the storage amount of ammonia of this large selective reduction catalyst device is calculated. Then, it is determined whether or not the calculated storage amount of ammonia exceeds the set threshold value, and the basic supply amount of urea water from the urea water supply device is corrected according to the determination result. It is possible to maintain an appropriate amount of ammonia storage in each selective catalytic reduction catalyst device while reducing the burden on the control device with optimized control, and optimize the amount of urea water supplied from the urea water supply device can do.

  An internal combustion engine equipped with the exhaust gas purification system for an internal combustion engine can achieve the same effects as the exhaust gas purification system for the internal combustion engine.

  In addition, an exhaust gas purification method for an internal combustion engine of the present invention for achieving the above object includes a urea water supply device and an exhaust gas purification treatment device in order from the upstream side in the exhaust passage of the internal combustion engine, In an exhaust gas purification method for an internal combustion engine comprising a selective reduction catalyst device group composed of at least two selective reduction catalyst devices in a gas purification treatment device, the exhaust gas flowing into the selective reduction catalyst device group Based on the concentration of the nitrogen oxide contained and the ammonia concentration contained in the exhaust gas flowing out from each selective reduction catalyst device constituting the selective reduction catalyst device group, based on the operating state of the internal combustion engine in advance. In this method, correction is made to the basic supply amount of urea water from the urea water supply device to be set.

  Further, in the above exhaust gas purification method for an internal combustion engine, each selective reduction catalyst device is arranged in order from the selective reduction catalyst device disposed upstream of the exhaust passage in the selective reduction catalyst device group. The amount of ammonia stored is calculated, and whether or not the calculated value of the amount of ammonia exceeds a preset threshold value set in advance for each selective catalytic reduction device based on the operating state of the internal combustion engine. Each time the determination is made and it is determined that the calculated value of the ammonia amount exceeds the set threshold value, the basic supply amount of the urea water is corrected.

  Alternatively, in the above exhaust gas purification method for an internal combustion engine, the amount of ammonia stored in each of the selective catalytic reduction devices constituting the selective catalytic reduction device group is calculated simultaneously, and the amount of each of these ammonia It is determined whether or not the calculated value exceeds a preset threshold value set in advance for each selective catalytic reduction device based on the operating state of the internal combustion engine, and the calculated value of the ammonia amount exceeds the set threshold value. When there is a selective catalytic reduction catalyst device that is determined to exceed, the number of selective catalytic reduction catalyst devices that corrects the basic supply amount of urea water and determines that the calculated value of the ammonia amount exceeds the set threshold value The correction amount to be added to the basic supply amount of the urea water is increased based on the above.

  Further, in the above exhaust gas purification method for an internal combustion engine, the amount of ammonia stored in the selective reduction catalyst device disposed in the uppermost stream of the exhaust passage in the selective reduction catalyst device group is selected. Calculation based on the concentration of nitrogen oxides contained in the exhaust gas flowing into the reduction-type catalyst device group and the ammonia concentration contained in the exhaust gas flowing out from this most selective reduction-type catalyst device, the selection of the most upstream The amount of ammonia stored in the selective catalytic reduction apparatus other than the catalytic reduction catalytic converter is determined based on the ammonia concentration contained in the exhaust gas flowing out from the adjacent selective catalytic reduction apparatus upstream of the selective catalytic reduction apparatus, The calculation is based on the ammonia concentration contained in the exhaust gas flowing out of the selective catalytic reduction device.

  Alternatively, in the exhaust gas purification method for an internal combustion engine, the total ammonia amount, which is the sum of the amounts of ammonia stored in the selective reduction catalyst devices constituting the selective reduction catalyst device group, is selected. Calculation based on the concentration of nitrogen oxides contained in the exhaust gas flowing into the reduction catalyst device group and the ammonia concentration contained in the exhaust gas flowing out from each selective reduction catalyst device, and calculation of the total amount of ammonia When the value exceeds the ammonia total amount setting threshold set in advance based on the operating state of the internal combustion engine, the basic supply amount of urea water is corrected.

  According to these methods, the same operational effects as the exhaust gas purification system of the internal combustion engine can be obtained.

  According to the exhaust gas purification system for an internal combustion engine, the internal combustion engine, and the exhaust gas purification method for an internal combustion engine of the present invention, the amount of ammonia (storage) stored in each selective reduction catalyst device provided in the exhaust gas purification processing device. Amount) is estimated and calculated based on the detection value of the nitrogen oxide detection device provided at the inlet of the selective reduction catalyst device group and the detection value of the ammonia concentration detection device provided in the subsequent stage of each selective reduction catalyst device. Therefore, the amount of ammonia stored in each selective reduction catalyst device can be estimated with high accuracy, and as a result, the supply amount of urea water from the urea water supply device can be optimized, and the selective reduction type The NOx purification rate can be improved while suppressing ammonia slip from the catalyst device.

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. It is a figure which shows the 1st example of the control flow of the exhaust gas purification method of the internal combustion engine of embodiment which concerns on this invention. It is a figure which shows the 2nd example of the control flow of the exhaust gas purification method of the internal combustion engine of embodiment which concerns on this invention. It is a figure which shows the 3rd example of the control flow of the exhaust gas purification method of the internal combustion engine of embodiment which concerns on this invention. It is a figure which shows the structure of the exhaust-gas purification system of the internal combustion engine of an inventor's prior art. It is a figure which shows the control flow of the exhaust gas purification method of the internal combustion engine of an inventor's prior art.

  Hereinafter, an exhaust gas purification system for an internal combustion engine, an internal combustion engine, and an exhaust gas purification method for the internal combustion engine according to embodiments of the present invention will be described with reference to the drawings. The internal combustion engine of the embodiment according to the present invention is configured to include the exhaust gas purification system 1 of the internal combustion engine of the embodiment according to the present invention, and the effects obtained by the exhaust gas purification system 1 of the internal combustion engine described later are provided. The same operational effects can be achieved.

  As shown in FIG. 1, an exhaust gas purification system 1 for an internal combustion engine according to an embodiment of the present invention enters an oxidation catalyst device (in order from an upstream side (engine side)) into an exhaust passage 11 of an engine (internal combustion engine) 10. DOC) 12, particulate collection device (CSF) 13, urea water supply device 22, selective reduction catalyst device 14, and ammonia slip catalyst device (DOC) 15. By passing the exhaust gas G of the engine 10 through the devices 12 to 15 constituting the exhaust gas purification system 1, components to be purified such as nitrogen oxides (NOx) contained in the exhaust gas G are purified and purified. The exhaust gas Gc is released to the atmosphere through a muffler (not shown). In FIG. 1, the oxidation catalyst device 12 and the particulate collection device 13 constitute a first exhaust gas purification treatment device, and the selective reduction catalyst device 14 and the ammonia slip catalyst device 15 constitute a second exhaust gas purification treatment device. Is configured.

The oxidation catalyst device 12 is a device that oxidizes hydrocarbons (HC) and nitrogen monoxide (NO) contained in the exhaust gas G. In particular, when the exhaust gas G is at a low temperature, the closer the ratio of nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ) contained in the exhaust gas G becomes to 1: 1, the closer the downstream of the selective catalytic reduction device 14 is. Since the NOx purification rate increases, the oxidation catalyst device 12 oxidizes nitric oxide (NO) to increase the proportion of nitrogen dioxide (NO ₂ ).

  The particulate collection device 13 is a device that collects particulate matter (PM) contained in the exhaust gas G. There is an upper limit to the amount of PM (collected amount) that can be collected by the particulate collection device 13, and as the collected amount of PM approaches the upper limit, the differential pressure across the particulate collection device 13 increases and the particulate collection rate increases. In order to hinder the purification performance of the collecting device 13, the forced PM regeneration control of the particulate collecting device 13 is periodically performed to burn and remove the PM collected by the particulate collecting device 13.

The selective catalytic reduction device 14 hydrolyzes the urea water U injected toward the exhaust gas G from the urea water supply device 22 provided in the preceding exhaust passage 11 by the heat of the exhaust gas G, thereby producing ammonia (NH ₃ ) And NOx contained in the exhaust gas G is reduced and purified by the generated ammonia (NH ₃ ). This selective catalytic reduction device 14 can store ammonia in the supported catalyst, and mainly reduces and purifies NOx contained in the exhaust gas G by the stored ammonia, but the amount of ammonia that can be stored ( The storage amount) has an upper limit, and ammonia that cannot be stored beyond the upper limit is discharged into the exhaust passage 11 on the downstream side of the selective catalytic reduction device 14.

Note that the hydrolysis reaction from urea water U to ammonia in the selective catalytic reduction device 14 is “(NH ₂ ) ₂ CO + H ₂ O → NH ₃ + HNCO” (the temperature of the exhaust gas G is 135 ° C. or higher), “HNCO + H ₂ O → NH ₃ + CO ₂ "(temperature of the exhaust gas G is 160 ° C. or higher) is performed on the basis of the chemical formulas, such as. The oxidation-reduction reaction between ammonia and NOx in the selective catalytic reduction device 14 is “NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O”, “4NO + 4NH ₃ + O 2 → 4N ₂ + 6H ₂ O”, “4NO ₂ + 4NH ₃ → 4N”. It is performed based on a chemical formula such as “ ₂ + 6H ₂ O + O ₂ ”.

The ammonia slip catalyst device 15 is a device that oxidizes ammonia released from the selective catalytic reduction device 14 in the previous stage to nitrogen or NOx. This oxidation reaction is performed based on chemical formulas such as “4NH ₃ + 5O ₂ → 4NO + 6H ₂ O, 2NH ₃ + 2O ₂ → N ₂ O + 3H ₂ O”, “4NH ₃ + 3O ₂ → 2N ₂ + 6H ₂ O”, and the like. If the injection amount of the urea water U from the urea water supply device 22 is excessive, the amount of ammonia released from the selective reduction catalyst device 14 also increases, and is generated by oxidizing ammonia in the ammonia slip catalyst device 15. Since the amount of NOx to be increased also increases, the NOx purification rate of the exhaust gas purification system as a whole decreases.

  The urea water supply device 22 is connected to a urea water storage tank 20 that stores the urea water U via a urea water supply pump 21. And the urea water supply pump 21 is operated by a control signal from a urea water supply control unit (DCU) 41, which will be described later, so that a part of the urea water U stored in the urea water storage tank 20 is removed from the urea water supply pump. The urea water supply device 22 is supplied via 21. The urea water U supplied to the urea water supply device 22 passes through the exhaust passage 11 when the injection valve (not shown) of the urea water supply device 22 is opened by a control signal from the urea water supply control device 41. It is injected toward the exhaust gas G. When it is not necessary to inject the urea water U into the exhaust passage 11 when the engine 10 is stopped, the urea water supply pump 21 is operated by the operation of the urea water supply pump 21 according to a control signal from the urea water supply control device 41. 21 and the urea water U remaining in the urea water supply device 22 are returned to the urea water storage tank 20.

  The oxidation catalyst device 12 includes a first oxidation catalyst device temperature sensor 30 and a second oxidation catalyst device temperature sensor 31 on the inlet side (front stage) and the outlet side (rear stage), respectively, and a selective reduction type. A selective reduction catalyst device temperature sensor 32 that detects the temperature of the exhaust gas G flowing into the selective reduction catalyst device 14 is provided on the inlet side (front stage) of the catalyst device 14.

  Further, an engine control unit (ECU) 40 and a urea water supply control unit (DCU) 41 are provided. The engine control device 40 detects the detected values of the first temperature sensor 30 for the oxidation catalyst device 30 and the second temperature sensor 31 for the oxidation catalyst device, the temperature of the engine cooling water, the atmospheric pressure, the temperature and flow rate of the intake air flowing into the engine 10. This is a device that controls the operating state of the engine 10 based on data such as the flow rate of fuel injected into a cylinder (not shown) of the engine 10. The urea water supply control device 41 acquires the above-described data input to the engine control device 40 from the engine control device 40, and the acquired data or data directly input to the urea water supply control device 41 (for example, selection This is a device that controls the operating state of the urea water supply pump 21 and the urea water supply device 22 based on the detection value of the temperature sensor 32 for the reduction catalyst device).

  In the exhaust gas purification system 1 for an internal combustion engine of the present invention, the exhaust gas purification processing device includes the selective reduction catalyst device group 14 including at least two selective reduction catalyst devices. In FIG. 1, the selective catalytic reduction catalyst device group 14 is arranged in order of the first selective catalytic reduction device 141, the second selective catalytic reduction device 142, and the third selective catalytic reduction device 143 in order from the upstream side. It consists of two selective reduction type catalyst devices.

  Further, a nitrogen oxide detection sensor (nitrogen oxide) that detects the concentration of nitrogen oxide (NOx) contained in the exhaust gas G flowing into the selective reduction catalyst device group 14 at the inlet of the selective reduction catalyst device group 14. Detection device) 33 and exhaust gas flowing out from each selective reduction catalyst device 141, 142, 143 downstream of each selective reduction catalyst device 141, 142, 143 constituting the selective reduction catalyst device group 14. An ammonia concentration detection sensor (ammonia concentration detection device) 34, 36, 39 for detecting the concentration of ammonia contained in the gas G is provided. These ammonia concentration detection sensors 34, 36, and 39 are usually sensors having equivalent performance, and these detection values are input to the urea water supply control device 41.

  In FIG. 1, the ammonia concentration detection sensor 39 is provided downstream of the ammonia slip catalyst device 15, but may be provided between the third selective reduction catalyst device 143 and the ammonia slip catalyst device 15. However, if an ammonia concentration detection sensor is provided at the subsequent stage of the ammonia slip catalyst device 15, the urea water supply control device 41 is supplied from the urea water supply device 22 based on the concentration of ammonia contained in the exhaust gas Gc released to the atmosphere. This is preferable because the injection amount of the urea water U can be adjusted and controlled, and ammonia release to the atmosphere can be further suppressed.

  In FIG. 1, the NOx concentration detection sensors 35, 37, and 38 are provided at the subsequent stage of each selective reduction catalyst device 141, 142, and 143, but these NOx concentration detection sensors 35, 37, and 38 are provided. The present invention can be practiced without it. However, when the NOx concentration detection sensors 35, 37, and 38 are provided, and the urea water supply control device 41 adjusts and controls the injection amount of the urea water U from the urea water supply device 22 based on these detection values, the urea water This is preferable because the control accuracy of the U injection amount is improved.

  In the control, based on the configuration of the exhaust gas purification system 1 described above, the urea water supply control device 41 is selectively reduced in the upstream of the exhaust passage 11 in the selective reduction catalyst device group 14. The amount of ammonia stored in each of the selective catalytic reduction devices 141, 142, 143 is calculated in order from the type catalyst device, and calculated values (storage amounts) N 1, N 2, N 3 of the ammonia amount are stored in the engine 10. It is determined whether or not a preset threshold value N1c, N2c, or N3c preset for each of the selective catalytic reduction devices 141, 142, and 143 is exceeded based on the operating state. Then, every time it is determined that the calculated values N1, N2, and N3 of the amount of ammonia exceed the set threshold values N1c, N2c, and N3c, the urea water from the urea water supply device 22 set in advance based on the operating state of the engine 10 The control is performed to correct the basic supply amount Qb of U.

  In other words, first, the ammonia amount N1 stored in the first selective catalytic reduction device 141 is calculated, and it is determined whether or not the calculated value N1 exceeds the set threshold value N1c. When it is determined that the calculated value N1 of the ammonia amount exceeds the set threshold value N1c, a correction is made to the basic supply amount Qb of the urea water U from the urea water supply device 22, and it is determined that it is equal to or less than the set threshold value N1c. No correction is made to the basic supply amount Qb of the urea water U.

  Next, the amount N2 of ammonia stored in the second selective catalytic reduction device 142 is calculated, and it is determined whether or not the calculated value N2 exceeds the set threshold value N2c. When it is determined that the calculated value N2 of the amount of ammonia exceeds the set threshold value N2c, the basic supply amount Qb of the urea water U is corrected, and when it is determined that it is equal to or less than the set threshold value N2c, No correction is made to the basic supply amount Qb. When the basic supply amount Qb is corrected in accordance with the determination in the first selective catalytic reduction device 141, this correction amount is also taken into account.

  Finally, the amount N3 of ammonia stored in the third selective catalytic reduction device 143 is calculated, and it is determined whether or not the calculated value N3 exceeds the set threshold value N3c. When it is determined that the calculated value N3 of the amount of ammonia exceeds the set threshold value N3c, the basic supply amount Qb of the urea water U is corrected, and when it is determined that it is equal to or less than the set threshold value N3c, No correction is made to the basic supply amount Qb. When the basic supply amount Qb is corrected in accordance with the determination in the first selective reduction catalyst device 141 or the determination in the second selective reduction catalyst device 142, these correction amounts are also taken into account.

  According to this control, the storage amounts N1, N2, and N3 of ammonia in the selective reduction catalyst devices 141, 142, and 143 are calculated in order from the selective reduction catalyst device 14 disposed on the upstream side of the exhaust passage 11. Then, it is determined whether or not the calculated storage amounts N1, N2, and N3 of ammonia exceed the set threshold values N1c, N2c, and N3c, and the urea water U from the urea water supply device 22 is determined according to the determination result. Since the basic supply amount Qb is corrected, the ammonia storage amount of each selective catalytic reduction device 14 can be reliably maintained with an appropriate amount with high accuracy, and the urea water from the urea water supply device 22 can be maintained. The supply amount of U can be optimized.

  Alternatively, in the control, the urea water supply control device 41 is added to each of the selective reduction catalyst devices 141, 142, and 143 constituting the selective reduction catalyst device group 14 based on the configuration of the exhaust gas purification system 1. The amounts of stored ammonia N1, N2, and N3 are calculated at the same time, and the calculated values N1, N2, and N3 of each of these ammonia are calculated based on the operating state of the engine 10, and each of the selective catalytic reduction devices 141. , 142, and 143, it is determined whether or not the preset threshold values N1c, N2c, and N3c are exceeded, and the calculated ammonia amounts N1, N2, and N3 are determined to exceed the set threshold values N1c, N2c, and N3c. When there is a selective catalytic reduction catalyst device, a correction is made to the basic supply amount Qb of urea water U from the urea water supply device 22 set in advance based on the operating state of the engine 10. In addition, the correction amount to be added to the basic supply amount Qb of the urea water U based on the number of selective catalytic reduction devices that determine that the calculated values N1, N2, and N3 of the ammonia amount exceed the set threshold values N1c, N2c, and N3c. Control is performed to increase Qc.

  That is, if there are calculated values exceeding the set threshold values N1c, N2c, and N3c among the calculated values N1, N2, and N3 of the ammonia amount, the correction amount Qc is added to the basic supply amount Qb of the urea water U. Then, as the number of calculated values exceeding the set threshold increases, the value of the correction amount Qc is increased.

  According to this control, the ammonia storage amounts N1, N2, and N3 of the selective catalytic reduction devices 141, 142, and 143 provided in the exhaust gas purification processing device are simultaneously calculated, and the calculated ammonia storage amount N1 is calculated. , N2 and N3 determine whether or not the set threshold values N1c, N2c and N3c exceed, and the correction amount Qc added to the basic supply amount Qb of the urea water U from the urea water supply device 22 is changed according to the determination result. Therefore, the storage amount of ammonia in each of the selective catalytic reduction devices 141, 142, and 143 can be quickly adjusted to an appropriate amount, and the supply amount of urea water U from the urea water supply device 22 can be optimized. Can do.

  Further, in the exhaust gas purification system 1, the urea water supply control device 41 is controlled by the selective reduction catalyst device 141 disposed in the uppermost stream of the exhaust passage 11 in the selective reduction catalyst device group 14. The amount N1 of the stored ammonia is determined based on the detection value of the nitrogen oxide detection sensor 33, the detection value of the ammonia concentration detection sensor 34 disposed at the subsequent stage of the most upstream selective reduction catalyst device 141, and the first value. The detection value of the oxidation catalyst device temperature sensor 30, the detection value of the second oxidation catalyst device temperature sensor 31, the detection value of the selective reduction catalyst device temperature sensor 32, and the first selective reduction catalyst device. The calculation is made based on the flow rate of the inflowing exhaust gas G.

  For the ammonia amount N2 stored in the selective catalytic reduction device 142 other than the upstream selective catalytic reduction device 141, the urea water supply control device 41 is adjacent to the upstream side of the selective catalytic reduction device 142. This is calculated based on the detection value of the ammonia concentration detection sensor 34 disposed downstream of the selective reduction catalyst device 141 to be detected and the detection value of the ammonia concentration detection sensor 36 disposed downstream of the selective reduction catalyst device 142. It is configured to perform control. Regarding the relationship between the detected values of these sensors 34 and 36 and the ammonia amount N2, a control map is created in advance by experiments or the like and stored in the urea water supply control device 41.

  For the ammonia amount N3 stored in the selective catalytic reduction device 143 other than the upstream selective catalytic reduction device 141, the urea water supply control device 41 is adjacent to the upstream side of the selective catalytic reduction device 143. Calculation based on the detection value of the ammonia concentration detection sensor 36 disposed downstream of the selective catalytic reduction catalyst device 142 and the detection value of the ammonia concentration detection sensor 39 disposed downstream of the selective reduction catalytic device 143. It is configured to perform control. Regarding the relationship between the detected values of the sensors 36 and 39 and the ammonia amount N3, a control map is created in advance by experiments or the like and stored in the urea water supply control device 41.

  According to this control, the calculation accuracy of the storage amount of ammonia in each of the selective catalytic reduction devices 141, 142, 143 can be increased.

  Alternatively, in the control, the urea water supply control device 41 is added to each of the selective reduction catalyst devices 141, 142, and 143 constituting the selective reduction catalyst device group 14 based on the configuration of the exhaust gas purification system 1. The total ammonia amount Ns, which is the total amount of the stored ammonia, is used as the detected value of the nitrogen oxide detection sensor 33 and the ammonia concentration disposed in the subsequent stage of each selective reduction catalyst device 141, 142, 143. When the calculated value Ns of the total ammonia amount exceeds the ammonia total amount setting threshold value Nsc set in advance based on the operating state of the engine 10, while calculating based on the detection values of the detection sensors 34, 36, and 39, Control is performed to correct the basic supply amount Qb of urea water U from the urea water supply device 22 set in advance based on the operating state of the engine 10. It is configured.

  According to this control, each selective reduction catalyst device 141, 142, 143 provided in the exhaust gas purification processing device is regarded as one large selective reduction catalyst device, and ammonia of this large selective reduction catalyst device is obtained. Storage amount Ns is calculated, and it is determined whether or not the calculated ammonia storage amount Ns exceeds a set threshold value Nsc. Based on the determination result, the basic supply of urea water U from the urea water supply device 22 is determined. Since the amount Qb is corrected, the amount of ammonia stored in each of the selective catalytic reduction devices 141, 142, and 143 is set to an appropriate amount while reducing the burden on the urea water supply control device 41 with very simplified control. This can be maintained, and the supply amount of the urea water U from the urea water supply device 22 can be optimized.

  The control flow of the exhaust gas purification method for an internal combustion engine of the present invention based on the exhaust gas purification system 1 for the internal combustion engine is shown in FIG. 2, FIG. 3, and FIG. 2, 3, and 4 are independent control flows for controlling the supply amount of urea water U from the urea water supply device 22, respectively. This is shown as a control flow that is called and executed from the control flow and returns to the advanced control flow after execution.

  In the middle of the control based on the control flow shown in FIGS. 2, 3, and 4, when the engine 10 is shut down, an interrupt is generated and the return is made to return to the advanced control flow. End with the end of the control flow. 2, 3, and 4, when it is necessary to convert the unit of the amount of ammonia stored in the selective catalytic reduction device 14, for example, the unit is converted from ppm to g. Etc., as appropriate. In addition, in the middle of the control flow of FIGS. 2, 3, and 4, the amounts of ammonia N 1, N 2, and N 3 stored in the selective reduction catalyst devices 141, 142, and 143, and the selective reduction catalyst devices 141 are stored. , 142, and 143, the total ammonia amount Ns, which is the sum of the amounts of ammonia stored, is calculated. The calculation method of these amounts N1, N2, N3, and Ns is the same as the method described above. So it is omitted.

  The control flow of FIG. 2 will be described. When the control flow of FIG. 2 starts, the amount N1 of ammonia stored in the first selective catalytic reduction device 141 is calculated in step S10. After performing the control of step S10, the process proceeds to step S20.

  In step S20, it is determined whether the ammonia amount N1 calculated in step S10 exceeds a preset threshold value N1c based on the operating state of the engine 10. When it is determined that the ammonia amount N1 exceeds the set threshold value N1c (YES), the process proceeds to step S30, and urea from the urea water supply device 22 set in advance based on the operating state of the engine 10 in step S30. The basic supply amount Qb is corrected by adding a correction amount to the basic supply amount Qb of the water U. After performing the control of step S30, the process proceeds to step S40. On the other hand, when it is determined that the ammonia amount N1 is equal to or less than the set threshold value N1c (NO), the process proceeds to step S40 without passing through step S30.

  In step S40, the amount of ammonia N2 stored in the second selective catalytic reduction device 142 is calculated. After performing the control of step S40, the process proceeds to step S50.

  In step S50, it is determined whether or not the ammonia amount N2 calculated in step S40 exceeds a preset threshold value N2c based on the operating state of the engine 10. When it is determined that the ammonia amount N2 exceeds the set threshold value N2c (YES), the process proceeds to step S60, and urea from the urea water supply device 22 that is preset based on the operating state of the engine 10 in step S60. The basic supply amount Qb is corrected by adding a correction amount to the basic supply amount Qb of the water U. If correction is added to the basic supply amount Qb in step S30, the added correction amount is also taken into account. After performing the control in step S60, the process proceeds to step S70. On the other hand, when it is determined that the ammonia amount N2 is equal to or less than the set threshold value N2c (NO), the process proceeds to step S70 without passing through step S60.

  In step S70, an ammonia amount N3 stored in the third selective catalytic reduction device 143 is calculated. After performing the control in step S70, the process proceeds to step S80.

  In step S80, it is determined whether or not the ammonia amount N3 calculated in step S70 exceeds a preset threshold value N3c based on the operating state of the engine 10. When it is determined that the ammonia amount N3 exceeds the set threshold value N3c (YES), the process proceeds to step S90, and urea from the urea water supply device 22 set in advance based on the operating state of the engine 10 in step S90. The basic supply amount Qb is corrected by adding a correction amount to the basic supply amount Qb of the water U. When correction is added to the basic supply amount Qb in step S30 and step S60, the added correction amount is also taken into account. After executing the control of step S90, the process proceeds to return, ends the present control flow, and returns to the advanced control flow. On the other hand, when it is determined that the ammonia amount N3 is equal to or less than the set threshold value N3c (NO), the process proceeds to return without passing through step S90, ends the present control flow, and returns to the advanced control flow. .

  Next, the control flow of FIG. 3 will be described. When the control flow of FIG. 3 starts, the amounts of ammonia N1, N2, and N3 stored in the selective catalytic reduction devices 141, 142, and 143 are calculated simultaneously in step S10. After performing the control of step S10, the process proceeds to step S20.

  In step S20, the amount of ammonia Ni (i = 1, 2, 3) calculated in step S10 is changed to the respective selective catalytic reduction devices 14i (i = 1, 2, 3) based on the operating state of the engine 10. It is determined whether or not a preset threshold value Nic (i = 1, 2, 3) is exceeded every time. If there is a selective catalytic reduction device 14i that determines that the amount Ni of ammonia exceeds the set threshold value Nic (YES), the process proceeds to step S30, and urea that is preset based on the operating state of the engine 10 in step S30. The basic supply amount Qb is corrected by adding the correction amount Qc to the basic supply amount Qb of the urea water U from the water supply device 22. The correction amount Qc is increased as the number of selective catalytic reduction devices that determine that the ammonia amount Ni exceeds the set threshold value Nic increases. After executing the control of step S30, the process proceeds to return, ends the present control flow, and returns to the advanced control flow. On the other hand, when there is no selective catalytic reduction catalyst device 14i that determines that the ammonia amount Ni exceeds the set threshold value Nic (NO), the process proceeds to return without passing through step S30, and this control flow is terminated. Return to advanced control flow.

  Next, the control flow of FIG. 4 will be described. When the control flow of FIG. 4 is started, in step S10, ammonia that is the sum of the amounts of ammonia stored in the selective catalytic reduction devices 141, 142, 143 constituting the selective catalytic reduction device group 14 is obtained. The total amount Ns is calculated. After performing the control of step S10, the process proceeds to step S20.

  In step S20, it is determined whether or not the total ammonia amount Ns calculated in step S10 exceeds a preset threshold value Nsc based on the operating state of the engine 10. When it is determined that the total ammonia amount Ns exceeds the set threshold value Nsc (YES), the process proceeds to step S30, and urea from the urea water supply device 22 set in advance based on the operating state of the engine 10 in step S30. The basic supply amount Qb is corrected by adding a correction amount to the basic supply amount Qb of the water U. After executing the control of step S30, the process proceeds to return, ends the present control flow, and returns to the advanced control flow. On the other hand, when it is determined that the total ammonia amount Ns is equal to or less than the set threshold value Nsc (NO), the process proceeds to return without passing through step S30, ends this control flow, and returns to the advanced control flow. .

  From the above, the exhaust gas purification method for an internal combustion engine according to the present invention based on the exhaust gas purification system 1 for the internal combustion engine described above, in order from the upstream side to the exhaust passage 11 of the internal combustion engine 10, the urea water supply device 22, In the exhaust gas purification method for an internal combustion engine, which is provided with an exhaust gas purification processing device, and the exhaust gas purification processing device is provided with a selective reduction catalyst device group 14 composed of at least two selective reduction catalyst devices. The concentration of nitrogen oxides contained in the exhaust gas G flowing into the reduction catalyst device group 14 and the exhaust gas G flowing out from each of the selective reduction catalyst devices 141, 142, 143 constituting the selective reduction catalyst device group 14 The basic supply amount Qb of the urea water U from the urea water supply device 22 set in advance based on the operating state of the internal combustion engine 10 is corrected based on the ammonia concentration contained in The method characterized by performing the control.

  In the exhaust gas purification method for an internal combustion engine, the selective reduction catalyst devices 141 are sequentially arranged from the selective reduction catalyst device group 14 arranged upstream of the exhaust passage 11 in the selective reduction catalyst device group 14. , 142, and 143, the ammonia amounts N 1, N 2, and N 3 are calculated, and the calculated ammonia amounts N 1, N 2, and N 3 are calculated based on the operating state of the internal combustion engine 10. It is determined whether or not a preset threshold value N1c, N2c, or N3c preset for each of the devices 141, 142, and 143 is exceeded, and when the calculated ammonia amounts N1, N2, and N3 exceed the set threshold values N1c, N2c, and N3c This is a method characterized by performing control to correct the basic supply amount Qb of the urea water U every time it is determined.

  Alternatively, in the exhaust gas purification method for an internal combustion engine described above, the amounts of ammonia N1, N2, and N3 stored in the selective catalytic reduction devices 141, 142, and 143 that constitute the selective catalytic reduction device group 14 are simultaneously calculated. Then, whether or not the calculated values N1, N2, and N3 of the respective ammonia amounts exceed a preset threshold value set in advance for each selective catalytic reduction device based on the operating state of the internal combustion engine 10. When there is a selective catalytic reduction device that determines and determines that the calculated values N1, N2, and N3 of the ammonia amount exceed the set threshold values N1c, N2c, and N3c, the basic supply amount Qb of the urea water U is corrected The basic supply amount of urea water U based on the number of selective catalytic reduction devices that determine that the calculated amounts N1, N2, and N3 of the ammonia amount exceed the set threshold values N1c, N2c, and N3c It becomes method comprising performing control for increasing the correction amount Qc to be added to b.

  Further, in the exhaust gas purification method for an internal combustion engine, the amount N1 of ammonia stored in the selective reduction catalyst device 141 disposed in the uppermost stream of the exhaust passage 11 in the selective reduction catalyst device group 14 is expressed as follows: The calculation is based on the concentration of nitrogen oxides contained in the exhaust gas G flowing into the selective catalytic reduction device group 14 and the concentration of ammonia contained in the exhaust gas G flowing out from the upstream selective catalytic reduction device 141. Further, the amount of ammonia stored in the selective catalytic reduction device 142 other than the upstream selective catalytic reduction device 141 flows out from the adjacent selective catalytic reduction device 141 upstream of the selective catalytic reduction device 142. Calculation is based on the ammonia concentration contained in the exhaust gas G and the ammonia concentration contained in the exhaust gas G flowing out from the selective catalytic reduction device 142. Then, the amount of ammonia stored in the selective catalytic reduction device 143 other than the upstream selective catalytic reduction device 141 flows out from the adjacent selective catalytic reduction device 142 upstream of the selective catalytic reduction device 143. In this method, control is performed based on the ammonia concentration contained in the exhaust gas G and the ammonia concentration contained in the exhaust gas G flowing out from the selective catalytic reduction device 143.

  Alternatively, in the exhaust gas purification method for an internal combustion engine, the total ammonia amount that is the sum of the amounts of ammonia stored in the selective reduction catalyst devices 141, 142, and 143 constituting the selective reduction catalyst device group 14. The amount Ns is determined based on the concentration of nitrogen oxides contained in the exhaust gas G flowing into the selective catalytic reduction device group 14 and the concentration of ammonia contained in the exhaust gas G flowing out from the selective catalytic reduction devices 141, 142, 143. When the calculated value Ns of the total ammonia amount exceeds the ammonia total amount setting threshold value Nsc set in advance based on the operating state of the internal combustion engine 10, the basic supply amount Qb of the urea water U is set. This is a method characterized by performing control for adding correction.

  According to the exhaust gas purification system 1 for an internal combustion engine, the internal combustion engine, and the exhaust gas purification method for an internal combustion engine having the above-described configuration, the gas is stored in each of the selective catalytic reduction devices 141, 142, and 143 provided in the exhaust gas purification processing device. The amount (storage amount) of ammonia thus prepared is provided at the detection value of the nitrogen oxide detection device 33 provided at the inlet of the selective reduction catalyst device group 14 and the subsequent stage of each selective reduction catalyst device 141, 142, 143. Therefore, the amount of ammonia stored in each of the selective catalytic reduction devices 141, 142, 143 can be estimated with high accuracy, based on the detected values of the ammonia concentration detectors 34, 36, 39. As a result, the supply amount of urea water U from the urea water supply device 22 can be optimized, and NOx purification can be performed while suppressing ammonia slip from the selective catalytic reduction catalyst device 14. It is possible to improve the.

  As described above, the present invention is premised on a configuration in which the exhaust gas purification processing apparatus includes the selective reduction catalyst device group 14 including at least two selective reduction catalyst devices. As shown in FIG. 5, even in a configuration in which the exhaust gas purification processing apparatus includes one selective reduction catalyst device 14, the amount of ammonia stored in this selective reduction catalyst device 14 as shown in the control flow of FIG. The present inventor has created a control method that can estimate the above with high accuracy as the prior art. In FIG. 5, only the configuration around the selective catalytic reduction catalyst device 14 is illustrated, and other devices such as the engine 10 and control signal lines from the urea water supply control device 41 are omitted.

  The control flow in FIG. 6 will be described. When the control flow in FIG. 6 starts, the amount N1 of ammonia stored in the selective catalytic reduction catalyst group 14 is calculated in step S10. After performing the control of step S10, the process proceeds to step S20.

  In step S20, it is determined whether the ammonia amount N1 calculated in step S10 exceeds a preset threshold value N1c based on the operating state of the engine 10. When it is determined that the ammonia amount N1 exceeds the set threshold value N1c (YES), the process proceeds to step S30, and urea from the urea water supply device 22 set in advance based on the operating state of the engine 10 in step S30. The basic supply amount Qb is corrected by adding a correction amount to the basic supply amount Qb of the water U. After executing the control of step S30, the process proceeds to return, ends the present control flow, and returns to the advanced control flow. On the other hand, when it is determined that the ammonia amount N1 is equal to or less than the set threshold value N1c (NO), the process proceeds to return without passing through step S30, ends the present control flow, and returns to the advanced control flow. .

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification system of internal combustion engine 10 Engine (internal combustion engine)
11 exhaust passage 14 selective reduction catalyst device, selective reduction catalyst device group 141 first selective reduction catalyst device 142 second selective reduction catalyst device 143 third selective reduction catalyst device 22 urea water supply device 32 selection Reduction type catalyst device temperature sensors 33, 35, 37, 38 NOx concentration detection sensor (NOx concentration detection device)
32, 34, 36, 39 Ammonia concentration detection sensor (ammonia concentration detection device)
41 Urea water supply control device U Urea water Qb Basic supply amount of urea water Qc Corrected supply amount of urea water G Engine exhaust gas Gc Purified exhaust gas

Claims (11)

In the exhaust gas purification system of the internal combustion engine configured to include the urea water supply device and the exhaust gas purification processing device in order from the upstream side in the exhaust passage of the internal combustion engine,
The exhaust gas purification processing apparatus includes a selective reduction catalyst device group including at least two selective reduction catalyst devices,
A nitrogen oxide detection device that detects the concentration of nitrogen oxide contained in the exhaust gas flowing into the selective reduction catalyst device group at the inlet of the selective reduction catalyst device group,
An ammonia concentration detection device for detecting the concentration of ammonia contained in the exhaust gas flowing out from each selective reduction catalyst device is provided at the subsequent stage of each selective reduction catalyst device constituting the selective reduction catalyst device group. An exhaust gas purification system for an internal combustion engine. A control device for controlling the exhaust gas purification system,
The amount of ammonia stored in each selective reduction catalyst device is calculated in order from the selective reduction catalyst device disposed upstream of the exhaust passage in the selective reduction catalyst device group. Determining whether or not the calculated value of the amount exceeds a set threshold set in advance for each selective catalytic reduction device based on the operating state of the internal combustion engine,
Control for correcting the basic supply amount of urea water from the urea water supply device that is set in advance based on the operating state of the internal combustion engine every time it is determined that the calculated value of the ammonia amount exceeds the set threshold value The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the exhaust gas purification system is configured to perform. A control device for controlling the exhaust gas purification system,
The amount of ammonia stored in each selective reduction catalyst device constituting the selective reduction catalyst device group is calculated simultaneously, and the calculated value of each of these ammonia amounts is based on the operating state of the internal combustion engine. To determine whether or not a preset threshold value is preset for each selective catalytic reduction device,
When there is a selective catalytic reduction device that determines that the calculated value of the amount of ammonia exceeds the set threshold value, the basic urea water from the urea water supply device that is preset based on the operating state of the internal combustion engine While correcting the supply amount,
The control unit is configured to perform control to increase a correction amount to be added to the basic supply amount of the urea water based on the number of selective catalytic reduction apparatuses that determine that the calculated value of the ammonia amount exceeds the set threshold value. Item 6. An exhaust gas purification system for an internal combustion engine according to Item 1. The control device is
Of the selective catalytic reduction catalyst group, the amount of ammonia stored in the selective catalytic reduction device disposed in the uppermost stream of the exhaust passage is determined by the detected value of the nitrogen oxide detection device and Calculated based on the detection value of the ammonia concentration detection device disposed downstream of the selective catalytic reduction catalyst device,
The amount of ammonia stored in the selective catalytic reduction device other than the upstream selective catalytic reduction device is arranged at the subsequent stage of the adjacent selective catalytic reduction device upstream of the selective catalytic reduction device. 4. The control device according to claim 2, wherein the control is performed based on a detection value of the ammonia concentration detection device and a detection value of the ammonia concentration detection device disposed in a subsequent stage of the selective reduction catalyst device. 5. Exhaust gas purification system for internal combustion engines. A control device for controlling the exhaust gas purification system,
The total ammonia amount, which is the sum of the amounts of ammonia stored in the selective reduction catalyst devices constituting the selective reduction catalyst device group, is detected by the detected value of the nitrogen oxide detection device and each selective reduction. While calculating based on the detected value of the ammonia concentration detector disposed in the latter stage of the type catalyst device,
When the calculated value of the total ammonia amount exceeds an ammonia total amount setting threshold that is preset based on the operating state of the internal combustion engine, the urea water supply device that is preset based on the operating state of the internal combustion engine The exhaust gas purification system for an internal combustion engine according to claim 1, configured to perform a control for correcting a basic supply amount of urea water from the engine.   An internal combustion engine comprising the exhaust gas purification system for an internal combustion engine according to any one of claims 1 to 5. A selective reduction type comprising an urea water supply device and an exhaust gas purification treatment device in order from the upstream side in the exhaust passage of the internal combustion engine, and comprising at least two selective reduction catalyst devices in the exhaust gas purification treatment device In an exhaust gas purification method for an internal combustion engine provided with a catalyst device group,
The concentration of nitrogen oxides contained in the exhaust gas flowing into the selective reduction catalyst device group and the ammonia concentration contained in the exhaust gas flowing out from each selective reduction catalyst device constituting the selective reduction catalyst device group An exhaust gas purification method for an internal combustion engine, wherein control is performed to correct a basic supply amount of urea water from the urea water supply device preset based on an operating state of the internal combustion engine. The amount of ammonia stored in each selective reduction catalyst device is calculated in order from the selective reduction catalyst device disposed upstream of the exhaust passage in the selective reduction catalyst device group. Determining whether or not the calculated value of the amount exceeds a set threshold set in advance for each selective catalytic reduction device based on the operating state of the internal combustion engine,
The exhaust gas purification of an internal combustion engine according to claim 7, wherein control is performed to correct the basic supply amount of the urea water every time it is determined that the calculated value of the ammonia amount exceeds the set threshold value. Method. The amount of ammonia stored in each selective reduction catalyst device constituting the selective reduction catalyst device group is calculated simultaneously, and the calculated value of each of these ammonia amounts is based on the operating state of the internal combustion engine. To determine whether or not a preset threshold value is preset for each selective catalytic reduction device,
When there is a selective catalytic reduction device that determines that the calculated value of the ammonia amount exceeds the set threshold value, the basic supply amount of the urea water is corrected, and
The control for increasing the correction amount to be added to the basic supply amount of the urea water is performed based on the number of selective catalytic reduction devices that are determined that the calculated value of the ammonia amount exceeds the set threshold value. Item 8. An exhaust gas purification method for an internal combustion engine according to Item 7. The amount of ammonia stored in the selective catalytic reduction device disposed in the uppermost stream of the exhaust passage in the selective catalytic reduction device group is included in the exhaust gas flowing into the selective catalytic reduction device group. Calculated based on the concentration of nitrogen oxides and the ammonia concentration contained in the exhaust gas flowing out from this upstream selective reduction catalyst device,
The amount of ammonia stored in the selective catalytic reduction device other than the upstream selective catalytic reduction device is included in the exhaust gas flowing out from the adjacent selective catalytic reduction device upstream of the selective catalytic reduction device. 10. The exhaust gas purification method for an internal combustion engine according to claim 8, wherein control is performed based on the ammonia concentration and the ammonia concentration contained in the exhaust gas flowing out from the selective catalytic reduction device. The total ammonia amount, which is the sum of the amounts of ammonia stored in the selective reduction catalyst devices constituting the selective reduction catalyst device group, is included in the exhaust gas flowing into the selective reduction catalyst device group. While calculating based on the concentration of nitrogen oxides and the ammonia concentration contained in the exhaust gas flowing out from each selective catalytic reduction device,
When the calculated value of the total ammonia amount exceeds an ammonia total amount setting threshold set in advance based on the operating state of the internal combustion engine, control is performed to correct the basic supply amount of the urea water. An exhaust gas purification method for an internal combustion engine according to claim 7.

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