JP2016169608A - Exhaust gas purification system for internal combustion engine, internal combustion engine, and exhaust gas purification method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine exhaust gas purification system, an internal combustion engine and an internal combustion engine exhaust gas purification method capable of substantially matching a necessary amount of a reducing agent corresponding to an amount of nitrogen oxide in exhaust gas and an available amount of the reducing agent in a selective reduction type catalyst device and thereby minimizing an injection amount of the reducing agent necessary to purify nitrogen oxide in the exhaust gas and reducing an amount of the reducing agent released from the internal combustion engine into the atmosphere while maintaining a high NOx purification rate by utilizing absorbed reducing agent.SOLUTION: An internal combustion engine exhaust gas purification system: detects an exhaust temperature Ta which is a temperature of exhaust gas G in an exhaust passage 12 at an upstream side of an exhaust gas purification device 21 and an inlet temperature Tb which is the temperature of the exhaust gas G when the same flows into a selective reduction type catalyst device 23; and controls an injection amount Uf of reducing agent generation solution U to be injected through a reducing agent injection device 24 on the basis of a temperature difference ΔT between the exhaust temperature Ta and the inlet temperature Tb.SELECTED DRAWING: Figure 2

Description

  The present invention includes an exhaust gas purification apparatus including a reducing agent injection device that injects a reducing agent such as urea water or ammonia and a selective reduction catalyst device in order from the upstream side in an exhaust passage of an internal combustion engine. 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.

Generally, an exhaust gas purification device provided in an exhaust passage of an internal combustion engine purifies nitrogen oxides (NOx) such as nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ) contained in the exhaust gas of the internal combustion engine. Therefore, a catalytic device such as a selective catalytic reduction device (SCR catalytic device) or a lean NOx trap catalytic device (LNT catalytic device) is provided.

In the exhaust gas purification system using this selective reduction catalyst device, ammonia (NH ₃ ) generated from urea water is often used as a reducing agent. In this case, the exhaust gas upstream of the selective reduction catalyst device is used. A urea water injection device is provided in the passage, and the urea water injected from the urea water injection device is hydrolyzed by the heat of exhaust gas, and ammonia is generated and supplied to the selective catalytic reduction catalyst device as a reducing agent. Nitrogen oxides contained in the exhaust gas are reduced and purified by the catalytic action of the reduction catalyst device.

  However, since the NOx reduction reaction rate in the selective catalytic reduction device is greatly influenced by the catalyst temperature, even if urea water is injected at a base injection amount determined based on the current engine operating state, this urea At the time when the water reaches the selective catalytic reduction device, the temperature of the selective catalytic reduction device changes between the injection time and the arrival time, and the injection amount of the urea water at the injection time is necessarily required at the time of arrival. There is a problem that it does not match the amount of ammonia.

  In this connection, for example, the injection amount of urea water may be controlled too early or too late due to the difference between the actual catalyst temperature and the temperature used to control the inlet temperature and outlet temperature of the selective catalytic reduction catalyst. In response to the problem that the NOx reduction performance cannot be sufficiently extracted, the exhaust temperature upstream of the selective catalytic reduction catalyst is detected, and the selective catalytic reduction catalyst is subdivided using a model of a first-order lag response to the detected temperature. The temperature is estimated for each cell unit, the cell volume is added for each of the plurality of humidity zones based on the estimated temperature for each cell unit, and the total cell volume is divided by the total catalyst volume for each temperature zone. The temperature distribution volume ratio is calculated, and the temperature distribution volume ratio is determined with respect to the reference injection amount of the reducing agent determined in light of the current engine operating condition on the assumption that the catalyst temperature is uniformly in the temperature range for each temperature range. Multiply by temperature range and By adding the values calculated for each temperature zone and using it as the command injection amount of the reducing agent to the reducing agent addition means, the outlet temperature and inlet temperature of the selective catalytic reduction catalyst can be used as substitute values for the catalyst temperature to meet the reaction rate. A control method for an exhaust gas purification device that maintains a high NOx reduction rate by appropriately controlling the injection amount of a reducing agent such as urea water without excess or deficiency has been proposed (see, for example, Patent Document 1). .

  On the other hand, many selective reduction catalysts supported on the selective reduction catalyst device have a function of adsorbing ammonia on the surface thereof. In a catalyst having this function, if a certain amount of ammonia is adsorbed on the catalyst, nitrogen oxides can be reduced by the adsorbed ammonia, so that the NOx purification rate tends to increase.

  As shown in FIG. 3, the maximum ammonia adsorption amount that can be adsorbed by the selective catalytic reduction apparatus is large at a low catalyst temperature and low at a high temperature. After the catalyst temperature of the catalyst device is low and the ammonia adsorption amount adsorbed on the catalyst surface reaches the maximum ammonia adsorption amount, the engine shifts to the operating state in the high load region, and the temperature of the selective catalytic reduction catalyst device In the case of a rapid increase, the maximum ammonia adsorption amount decreases rapidly, and a large amount of surplus ammonia that cannot be adsorbed is released.

  Therefore, the amount of ammonia released is larger than the amount of ammonia used for the purification of nitrogen oxides, and the remaining ammonia that has not been used for the reduction of nitrogen oxides is released directly into the atmosphere. In order to avoid the so-called ammonia slip, the conventional technology makes it possible to adsorb only a small amount of ammonia so that the ammonia adsorption amount adsorbed by the selective catalytic reduction device does not reach the maximum ammonia adsorption amount. ing.

  More specifically, at present, the relationship between the inlet temperature of the selective catalytic reduction catalyst device and the maximum ammonia adsorption amount is obtained by experiments, and the injection amount of urea water generating ammonia is converted into nitrogen flowing into the selective catalytic reduction catalyst. This is determined as an injection amount in which an amount of ammonia is generated by adding an ammonia adsorption amount adsorbed by the selective catalytic reduction catalyst to an ammonia amount necessary for purifying the oxide.

  Also, the amount of ammonia adsorbed on the selective reduction catalyst is integrated, and if the integrated ammonia amount exceeds the maximum ammonia adsorption amount of the catalyst at the catalyst temperature of the selective reduction catalyst during urea water injection, selective reduction is performed. Only the amount necessary to purify the nitrogen oxide flowing into the type catalyst device is injected. In order to prevent ammonia from being released into the atmosphere, control is performed so that the maximum ammonia adsorption amount is larger than the ammonia retention amount (ammonia adsorption amount integrated value).

  On the other hand, in the selective catalytic reduction catalyst device, when ammonia is adsorbed on the catalyst surface, the nitrogen oxide can be reduced and purified by the adsorbed ammonia even if the ammonia flowing into the selective catalytic reduction device is stopped. it can.

  In addition, after the catalyst temperature of the selective catalytic reduction apparatus is low and a certain amount of ammonia is adsorbed on the catalyst surface, it can be adsorbed when it is operated with a high engine load and the catalyst temperature rises rapidly. The lost ammonia is released from the catalyst surface. At this time, if the supplied ammonia is stopped, the released ammonia can be used to purify nitrogen oxides in the exhaust gas flowing from the engine. When the temperature of the selective catalytic reduction apparatus increases quickly, the amount of ammonia released from the catalyst surface is larger than the amount of ammonia used for purification, and this ammonia is released into the atmosphere. In order to cope with this, conventionally, in order to suppress the release of ammonia into the atmosphere, only an amount smaller than the amount of ammonia that can be adsorbed by the selective catalytic reduction catalyst device is adsorbed.

  However, there is a problem that the effect of improving the NOx purification rate by using adsorbed ammonia cannot be used.

JP 2006-46289 A

  The present invention has been made in view of the above, and an object of the present invention is to provide a reducing agent injection device and a selective reduction catalyst device for injecting urea water or the like in order from the upstream side into the exhaust passage of the internal combustion engine. In the exhaust gas purification system for an internal combustion engine, the required amount of the reducing agent corresponding to the amount of nitrogen oxide in the exhaust gas and the usable amount of the reducing agent in the selective catalytic reduction device can be made to substantially coincide. Thus, while maintaining a high NOx purification rate due to the use of the adsorbed reducing agent, it is possible to reduce the injection amount of the reducing agent necessary for purifying nitrogen oxides in the exhaust gas to a necessary minimum amount, and to improve the internal combustion engine. Another object of the present invention is 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 that can reduce the amount of reducing agent released from the atmosphere to the atmosphere.

  In order to achieve the above object, an exhaust gas purification system for an internal combustion engine of the present invention includes an exhaust gas purification device having a reducing agent injection device and a selective reduction catalyst device in order from the upstream side in the exhaust passage of the internal combustion engine. In the exhaust gas purification system for an internal combustion engine, a first temperature detection device that detects an exhaust temperature that is a temperature of exhaust gas discharged from a cylinder of the internal combustion engine in the exhaust passage upstream of the exhaust gas purification device. And a second temperature detection device for detecting an inlet temperature, which is a temperature of exhaust gas flowing into the selective reduction catalyst device, is provided on the inlet side of the selective reduction catalyst device, and the exhaust gas purification system is The control device for controlling is configured to control the injection amount of the reducing agent generating solution from the reducing agent injection device based on the temperature difference between the exhaust gas temperature and the inlet temperature.

  According to this configuration, since the injection amount of the reducing agent generating solution from the reducing agent injection device is controlled based on the temperature difference between the exhaust temperature and the inlet temperature (SCR catalyst inlet temperature), based on this temperature difference, Predict the change in the catalyst temperature of the selective catalytic reduction device from the point of injection (injection time) of the reducing agent generating solution to the point of arrival when the reducing agent generated from the reducing agent generating solution reaches the selective catalytic reduction device Thus, the injection amount of the reducing agent generating solution can be controlled, and the reducing agent can be adsorbed at the predicted catalyst temperature (maximum reducing agent adsorption amount) and is currently adsorbed and held by the selective catalytic reduction catalyst device. The amount of reducing agent generating solution injected from the reducing agent injection device is estimated while predicting the amount of reducing agent released or adsorbed from the selective catalytic reduction catalyst device in consideration of the amount of reducing agent retained. Can be controlled So as to.

  That is, by predicting the catalyst temperature of the selective catalytic reduction device at the time when the reducing agent generating solution such as urea water from the reducing agent injection device reaches the selective catalytic reduction device, the reducing agent generating solution at the injection time is predicted. Since the injection amount can be controlled, even when the engine operating state is in a transient state, the reducing agent generating solution is injected with an appropriate injection amount so that the amount of nitrogen oxide in the exhaust gas is excessive or insufficient. A small amount of reducing agent such as ammonia can be supplied to the selective catalytic reduction apparatus.

  Therefore, the required amount of the reducing agent corresponding to the amount of nitrogen oxide in the exhaust gas in the selective catalytic reduction apparatus can be made substantially coincident with the usable amount of the reducing agent, and thereby the adsorbed reducing agent The amount of reducing agent generation solution required to purify the nitrogen oxides in the exhaust gas can be reduced to the minimum necessary amount while being released from the internal combustion engine to the atmosphere while maintaining a high NOx purification rate by using The amount of reducing agent can also be reduced.

  Further, in the exhaust gas purification system for an internal combustion engine, the control device has a preset amount of reducing agent necessary and sufficient for reducing the engine operating state and nitrogen oxides generated in the engine operating state. The relationship between the reference supply amount is stored, the reference supply amount is calculated from the engine operating state based on the relationship between the set engine operating state and the reference supply amount, and the temperature difference is equal to or greater than a preset steady-state temperature difference. When the reducing agent generating solution is determined to be less than the calculated reference supply amount, the reducing agent generating solution injection amount is set so that the reducing agent supply amount is less than the calculated reference supply amount. And when it is determined that the temperature difference is smaller than the steady-state temperature difference, the reducing agent generating solution is adjusted so that the supply amount of the reducing agent is larger than the calculated reference supply amount. Set the injection amount And a configured to inject from the reducing agent injection apparatus, the following effects can be exhibited.

  The steady-state temperature difference is a temperature difference between the exhaust temperature and the inlet temperature in the steady state with respect to the engine operating state. The relationship between the engine operating state and the steady-state temperature difference is stored in memory and controlled. Sometimes this is a value calculated from the engine operating condition.

  In other words, if the temperature difference is equal to or greater than the steady-state temperature difference, the catalyst temperature of the selective catalytic reduction device rises and the adsorbable amount decreases, so that the amount of injection of the reducing agent generating solution is less than the reference supply amount. Therefore, ammonia or the like adsorbed on the selective catalytic reduction apparatus by the nitrogen oxide in the exhaust gas flowing into the selective catalytic reduction apparatus until the catalyst temperature of the selective catalytic reduction apparatus rises. The amount of reducing agent can be reduced. Moreover, it can contribute to the reduction of the injection amount of the reducing agent generating solution such as urea water by reducing the necessary supply amount of the reducing agent in advance.

  Further, when the temperature difference is smaller than the steady-state temperature difference, the catalyst temperature of the selective catalytic reduction catalyst device decreases and the adsorbable amount increases, so that the injection amount of the reducing agent generating solution is made larger than the reference supply amount. As a result, the amount of reducing agent adsorbed on the selective catalytic reduction catalyst device can be increased, and the NOx purification rate can be increased with the use of the adsorbed reducing agent, thereby contributing to the improvement of the NOx purification rate.

  In the exhaust gas purification system for an internal combustion engine, the control device sets the temperature difference in a steady state as a steady-state temperature difference with respect to an engine operation state. A steady-state temperature difference storing means for storing the relationship, and a reference for setting the supply amount of the reducing agent in the steady state as a reference supply amount for the engine operating state and storing the relationship between the reference supply amount and the engine operating state From the supply amount storage means and the exhaust gas temperature and the inlet temperature measured at the present time, the reducing agent supplied by the injection of the reducing agent generating solution at the injection time after a preset control time is the selective reduction. Catalyst temperature predicting means for predicting the catalyst temperature of the selective catalytic reduction catalyst device at the time of reaching the catalyst type catalyst device, and the catalyst temperature predicted by the catalyst temperature predicting means Therefore, based on the catalyst temperature predicted by the catalyst temperature predicting means, a release amount calculating means for calculating a reducing agent release amount from the selective catalytic reduction catalyst device at the reaching time, and the selective reducing catalyst at the reaching time An adsorption amount calculating means for calculating a reducing agent adsorption amount of the apparatus; and a reducing agent calculated by the release amount calculating means while cumulatively adding the reducing agent adsorption amount calculated by the adsorption amount calculating means to the initial possessed amount Accumulated subtraction of the released amount, the retained amount calculating means for calculating the reducing agent retained amount currently adsorbed by the selective catalytic reduction catalyst device, and the steady-state temperature difference storage means are used to determine the current engine operating condition. A temperature difference is always introduced, and a current temperature difference is calculated from the exhaust temperature measured at the present time and the inlet temperature, and the current temperature difference is equal to or greater than the steady-state temperature difference. A temperature difference determining means for determining whether or not there is a reducing agent supply amount, and a reducing agent reduction amount from a reference supply amount obtained from the reference injection amount storage means by inputting an engine operating state at the present time or injection time The temperature increase supply amount setting means for setting the injection amount of the reducing agent generating solution at the injection time so that the required supply amount is subtracted, and the supply amount of the reducing agent is the engine operating state at the present time or injection time. Supply amount setting during cooling to set the injection amount of the reducing agent generating solution at the time of injection so that the required supply amount is obtained by adding the reducing agent increase amount to the reference supply amount introduced from the reference injection amount storage means And the temperature difference determination means determine that the current temperature difference is equal to or greater than the steady-state temperature difference at the time of injection by the temperature increase supply amount setting means. When the reducing agent generating device injects the reducing agent generating solution from the reducing agent injection device, and the temperature difference determining means determines that the current temperature difference is not greater than or equal to the steady-state temperature difference, And an injection executing means for injecting from the reducing agent injection device with the injection amount of the reducing agent generating solution set by the temperature drop supply amount setting means.

  At the same time, the release amount calculation means subtracts the adsorbable amount based on the catalyst temperature at the arrival time predicted by the catalyst temperature prediction means from the current reducing agent possession amount calculated by the retention amount calculation means, The reducing agent release amount at the time of injection is calculated, and the adsorption amount calculation unit calculates the current amount calculated by the possessed amount calculation unit from the adsorbable amount based on the catalyst temperature at the arrival time predicted by the catalyst temperature prediction unit. By subtracting the reducing agent possessed amount at the time of injection, the reducing agent adsorption amount at the time of injection is calculated, and the supply amount setting means at the time of temperature rise is calculated as the reducing agent release amount calculated by the releasing amount calculating means. The reducing agent adsorption amount calculated by the adsorption amount calculation unit is set to an amount that is greater than or equal to the amount and less than or equal to the retention amount of the reducing agent calculated by the retention amount calculation unit. Hereinafter, configured to greater than zero volume.

  Note that the time from the present time to the injection time is a time related to the calculation speed in the control device, and can be set to substantially the same time when the calculation for the control can be performed at high speed.

  On the other hand, from the injection time point to the arrival time point, from the injection time point when the reducing agent generating solution is injected, the reducing agent generated from the injected reducing agent generation solution actually reaches the selective catalytic reduction catalyst device and contributes to the reduction. And is related to the flow rate of the exhaust gas within that time.

  More precisely, this time relates to the gas flow rate of the exhaust gas, and is set in advance for the engine operating state based on the measurement result such as an experiment and stored in advance as map data. Alternatively, an exhaust gas amount (volume) that can be calculated from the intake air amount, fuel injection amount, EGR gas amount, exhaust gas temperature, etc. at the time of injection, the exhaust pipe diameter, and the selective reducing catalyst from the reducing agent injection device This is the time that can be calculated from the length of the exhaust pipe to the device.

  According to this configuration, by providing each of these means, when the temperature difference is greater than or equal to the steady-state temperature difference, the temperature of the selective catalytic reduction device increases at the time of arrival, and the selective catalytic reduction device Nitrogen oxidation in which the reducing agent desorbed at the time of arrival is estimated to be desorbed from the selective catalytic reduction catalytic converter as the reducing agent adsorbable amount (maximum reducing agent adsorption amount) decreases The injection amount of the reducing agent that is reduced by subtracting the reduction amount of the reducing agent from the reference injection amount can be injected at the time of injection so that it is used for purification of matter and is not released into the atmosphere.

  In addition, since the reduction amount of the reducing agent is set to an amount that is not less than the reducing agent release amount and not more than the reducing agent retention amount, nitrogen oxides can be reduced by using the reducing agent attached to the surface of the selective catalytic reduction catalyst device. Therefore, a high NOx purification rate can be obtained. In other words, if the reducing agent reduction amount is the reducing agent release amount, the reducing agent attached to the surface cannot be used or the reducing agent that cannot contribute to the reduction of nitrogen oxides is released into the atmosphere, and the reducing agent reduction amount is the reducing agent. If the amount is retained, the reducing agent adhering to the surface can be used, but the amount of reducing agent retained becomes zero, and after that, the reducing agent adhering to the surface can no longer be used. Is preferred. This reducing agent reduction amount is practically set to an appropriate amount within the range of the reducing agent release amount or more and the reducing agent holding amount or less by experiments or the like.

  Further, when the temperature difference is smaller than the steady-state temperature difference, at the time of arrival, the temperature of the selective catalytic reduction device decreases, and the amount of adsorbable reducing agent of the selective catalytic reduction device increases, so that the selective catalytic reduction type It is predicted that the reducing agent will be adsorbed on the catalyst device, and the reference injection is performed at the injection point so that the reducing agent is not shortaged at the point of arrival when the reducing agent is used to purify the nitrogen oxides contained in the exhaust gas. It is possible to inject the injection amount of the reducing agent increased by adding the reducing agent increase amount to the amount.

  In addition, since the reducing agent increase amount is less than the reducing agent adsorption amount and more than zero, a reducing agent that is not used in the reduction of nitrogen oxides can be adsorbed on the surface of the selective catalytic reduction catalyst device. In the subsequent reduction of nitrogen oxides, a high NOx purification rate can be obtained by using a reducing agent attached to the surface. In other words, if the amount of reducing agent increase is defined as the amount of reducing agent adsorption, the amount of reducing agent adhering to the surface can be saturated immediately, but thereafter the reducing agent that has not contributed to the reduction of nitrogen oxides can be released into the atmosphere. If the amount of reducing agent increase is zero, the amount of reducing agent attached to the surface cannot be increased, and the use of the reducing agent attached to the surface cannot be expanded thereafter. It is preferable to do this. This amount of increase of the reducing agent is practically set to an appropriate amount in the range of less than the reducing agent adsorption amount and more than zero by experiments.

  Therefore, in the selective catalytic reduction catalyst device, when reaching, the reference injection amount of the reducing agent corresponding to the amount of nitrogen oxide in the exhaust gas can be used for the reduction of nitrogen oxide. Maintenance, minimization of the required amount of reducing agent injection, and minimization of reducing agent slip can be achieved. In order to prevent control hunting, a dead zone is provided in the comparison between the temperature difference and the steady-state temperature difference.When the upper limit of the dead zone is exceeded, it is determined that the temperature difference is equal to or greater than the steady-state temperature difference. It may be configured to determine that the temperature difference has become smaller than the steady-state temperature difference when it falls below the lower limit of the dead zone.

  Further, in the exhaust gas purification system for an internal combustion engine, the emission amount calculating means is a catalyst at a reaching time predicted by the catalyst temperature predicting means from a current reducing agent held amount calculated by the held amount calculating means. Subtracting the adsorbable amount based on the temperature to calculate the reducing agent release amount at the time of injection, the adsorption amount calculating means from the adsorbable amount based on the catalyst temperature at the arrival time predicted by the catalyst temperature predicting means, When it is configured to calculate the reducing agent adsorption amount at the time of injection by subtracting the current reducing agent holding amount calculated by the holding amount calculation means, it is possible to control the grasp of the reducing agent holding amount at the present time. As a result, the reducing agent release amount and the reducing agent adsorption amount can be predicted more accurately.

  In addition to the cumulative calculation of the reducing agent adsorption amount and reducing agent release amount, a method of estimating the current reducing agent holding amount from the reducing agent slip amount and the amount of NOx that could not be reduced is also conceivable. In this method, the current reducing agent holding amount calculated by the holding amount calculating means may be corrected.

  In order to achieve the above object, an internal combustion engine of the present invention is configured to include the exhaust gas purification system of the internal combustion engine, and has the same effects as the exhaust gas purification system of the internal combustion engine. it can.

  And the exhaust-gas purification method of the internal combustion engine of this invention for achieving said objective WHEREIN: The exhaust-gas purification apparatus which has a reducing agent injection apparatus and a selective reduction type | mold catalyst apparatus in an exhaust passage of an internal combustion engine sequentially from an upstream. An exhaust gas purification method for an internal combustion engine comprising: an exhaust gas temperature that is an exhaust gas temperature in the exhaust passage upstream of the exhaust gas purification device; and an exhaust gas flowing into the selective catalytic reduction device. In this method, an inlet temperature, which is a temperature, is detected, and an injection amount of the reducing agent generating solution from the reducing agent injection device is controlled based on a temperature difference between the exhaust temperature and the inlet temperature.

  Further, in the exhaust gas purification method for an internal combustion engine described above, a relationship between a preset engine operating state and a reference supply amount that is an amount of a reducing agent necessary and sufficient to reduce nitrogen oxides generated in the engine operating state. The reference supply amount is calculated from the engine operating state based on the relationship between the set engine operating state and the reference supply amount, and it is determined that the temperature difference is equal to or greater than a preset steady-state temperature difference. The reducing agent generating solution is set so that the reducing agent supply amount is smaller than the calculated reference supply amount, and the reducing agent generating solution is injected from the reducing agent injection device. When it is determined that the difference is smaller than the steady-state temperature difference, the injection amount of the reducing agent generating solution is set so that the supply amount of the reducing agent is larger than the calculated reference supply amount. The reducing agent injection To put et al injection.

  Further, in the above exhaust gas purification method for an internal combustion engine, the temperature difference in the steady state is set as a steady-state temperature difference with respect to the engine operating state, and the supply of the reducing agent in the steady state with respect to the engine operating state. An amount is set as a reference supply amount, and the reducing agent supplied by the injection of the reducing agent generating solution at the injection point after a preset control time is determined from the exhaust gas temperature and the inlet temperature measured at the present time. Predicting the catalyst temperature of the selective catalytic reduction measure when reaching the selective catalytic reduction device, based on the catalyst temperature, reducing agent release amount and reduction from the selective catalytic reduction device at the arrival time The selective reducing catalyst device is calculated at the present time by calculating the amount of adsorbing agent, and performing cumulative addition of the reducing agent adsorption amount and cumulative subtraction of the reducing agent release amount with respect to the initial retained amount. The amount of reducing agent held is calculated, and the amount of reducing agent held above the amount of reducing agent released at the current time or injection time but less than the amount of reducing agent held is the reducing agent reduction amount, and the reducing agent at the current time or injection time If the amount below the adsorption amount and greater than zero is taken as the reducing agent increase amount, and it is determined that the current temperature difference is greater than or equal to the steady-state temperature difference, the reducing agent supply amount is the current or injection time point. Injection of the reducing agent generating solution at the time of injection so that the required supply amount is obtained by subtracting the reducing agent reduction amount from the reference supply amount obtained from the relationship between the engine operation state, the set engine operation state and the reference supply amount. When the amount of the reducing agent is injected from the reducing agent injection device and it is determined that the current temperature difference is smaller than the steady-state temperature difference, the amount of reducing agent supplied is the engine at the current time or the injection time. Injection amount of the reducing agent generating solution at the time of injection so that the required supply amount is obtained by adding the reducing agent increase amount to the reference supply amount obtained from the relationship between the operating state, the set engine operating state and the reference supply amount And is injected from the reducing agent injection device.

  In the exhaust gas purification method for an internal combustion engine, the reducing agent release amount at the injection time point is calculated by subtracting the adsorbable amount based on the catalyst temperature at the reaching time point from the reducing agent possession amount at the present time point, Then, the reducing agent adsorption amount is calculated by subtracting the present reducing agent holding amount from the adsorbable amount based on the catalyst temperature.

  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, a reducing agent injection device that injects urea water or the like sequentially into the exhaust passage of the internal combustion engine from the upstream side, selective reduction In an exhaust gas purification system for an internal combustion engine equipped with a catalytic converter, the temperature change of the selective catalytic converter is estimated, and the reducing agent release amount and the reducing agent adsorption by the selective catalytic converter based on the estimated temperature change The injection amount of the reducing agent generating solution from the reducing agent injection device is controlled while predicting the amount.

  Therefore, the required amount of the reducing agent corresponding to the amount of nitrogen oxide in the exhaust gas in the selective catalytic reduction catalyst device can be made to substantially match the usable amount of the reducing agent. While maintaining a high NOx purification rate by use, the amount of reducing agent generation solution required to purify nitrogen oxides in exhaust gas can be reduced to the minimum required amount, and reduction released from the internal combustion engine to the atmosphere The amount of agent can also be reduced.

It is a figure showing typically composition of an internal-combustion engine provided with an exhaust-gas purification system of an internal-combustion engine of an embodiment concerning the present invention. It is a figure which shows the structure of the control apparatus of the exhaust gas purification system of an internal combustion engine. It is a figure which shows the relationship between the temperature of a selective reduction type | mold catalyst apparatus, and the ammonia adsorption | suction possible amount (maximum ammonia adsorption amount) which is the maximum amount of ammonia which can be adsorb | sucked to a selective reduction type | mold catalyst apparatus.

  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 of the internal combustion engine of the embodiment according to the present invention, and has the same effect as the exhaust gas purification system of the internal combustion engine described later. The effect of this can be achieved. In FIG. 1, the turbocharger system 13S is provided in the engine (internal combustion engine) 10, but the present invention can also be applied to an engine not provided with a supercharger system.

  Furthermore, here, a selective reduction catalyst device (SCR device) will be described by way of an example of a urea (or ammonia) selective reduction catalyst device using ammonia generated from urea water as a reducing agent, but other reducing agents may be used. A selective catalytic reduction catalyst that corresponds to the reducing agent, and that has a tendency to increase the reducing agent at a low temperature and decrease it at a high temperature. Any device may be used.

  First, an internal combustion engine (hereinafter referred to as an engine) 10 and an exhaust gas purification system 20 for an internal combustion engine according to an embodiment of the present invention will be described with reference to FIG. The engine 10 is provided with a fuel injection device (not shown), an intake valve (not shown), and an exhaust valve (not shown) facing the cylinder 10a, and further, an intake valve via an intake manifold 10b. An intake passage 11 communicating with the exhaust passage, an exhaust passage 12 communicating with the exhaust valve via the exhaust manifold 10c, and an EGR passage (not shown) are provided.

  An air cleaner (not shown), a turbocharger (turbocharger) 13 of a turbocharger (turbocharger) 13, an intercooler (not shown), an intake throttle valve ( The exhaust passage 12 is provided with a turbine 13a of the turbocharger 13 and an exhaust gas purification device 21 in order from the upstream side. The EGR passage is provided by connecting the intake passage 11 or the intake manifold 10b downstream from the compressor 13b and the exhaust passage 12 or the exhaust manifold 10c upstream from the turbine 13a. Although not shown, the EGR passage is provided with an EGR cooler and an EGR valve in this order from the upstream side.

  The fresh air A introduced from the atmosphere is sent to the cylinder (cylinder) 10a via the intake valve with exhaust gas (EGR gas) flowing into the intake passage 11 from the EGR passage as necessary. Further, the exhaust gas G generated in the cylinder 10a flows out to the exhaust manifold 10c via the exhaust valve, part of which flows as EGR gas in the EGR passage, and the remaining exhaust gas G is exhausted via the turbine 13a. After flowing into the gas purification device 21 and being purified, it is discharged into the atmosphere via a muffler (not shown) and a tail pipe (not shown).

  In the configuration of FIG. 1, the exhaust gas purification device 21 of the exhaust gas purification system 20 includes a particulate collection device (DPD) 22 and a selective catalytic reduction device (SCR catalyst device) 23. An oxidation catalyst device (DOC) is provided upstream of the particulate collection device (DPD) 22, and a catalyst device such as a post-stage oxidation catalyst device (DOC) is provided downstream of the selective reduction catalyst device (SCR catalyst device) 23. However, it is not shown here for simplification of the drawing.

Further, urea water (reducing agent generating solution) U for NOx reduction is injected into the exhaust passage 12 in the exhaust passage 12 downstream of the particulate collection device 22 and upstream of the selective catalytic reduction device 23. The urea water injection device (reducing agent injection device) 24 is disposed, and the injected urea water U is vaporized before reaching the selective catalytic reduction device 23, and ammonia (NH ₃ : reducing agent) is obtained by hydrolysis. ) R is generated. Using this ammonia R as a reducing agent, the selective reduction catalyst device 23 reduces nitrogen oxides (NOx) in the exhaust gas G to water and nitrogen to render them harmless. Instead of the urea water injection device 24, an ammonia injection device that directly injects ammonia into the exhaust passage 12 may be provided. However, it is necessary to pay attention to the harmfulness of ammonia.

  Further, a fuel injection device (not shown) for injecting unburned fuel into the exhaust passage 12 is disposed in the exhaust passage 12 upstream of the exhaust gas purification device 21, and the oxidation catalyst device and the selective reduction catalyst device 23. Although it is configured so that unburned fuel can be injected into the exhaust passage 12 during exhaust gas temperature rise control, such as sulfur purge (desulfurization) control for PM and PM regeneration control for the particulate collection device 22, Is not directly related, so the description is omitted.

  In the present invention, the first temperature sensor (first temperature) for detecting the exhaust temperature Ta, which is the temperature of the exhaust gas G on the outlet side of the engine 10, in the exhaust passage 12 upstream of the exhaust gas purification device 21. Detection device) 30 is provided. Although the first temperature sensor 30 is provided in the exhaust passage 12 upstream of the turbine 13 a in FIG. 1, it may be provided in the exhaust manifold 10 c of the engine 10. At the same time, a second temperature sensor (second temperature sensor) that detects an inlet temperature Tb that is the temperature of the exhaust gas Ga flowing into the selective reduction catalyst device 23 in the exhaust passage 12 on the inlet side of the selective reduction catalyst device 23. Temperature detecting device) 31 is provided.

  Moreover, the control apparatus 40 which controls the exhaust gas purification system 20 of an internal combustion engine is provided. The control device 40 is normally configured to be incorporated in an engine control unit (ECU) that controls the operation state of the engine 10 in general, but may be provided independently. It should be noted that the relationship between the catalyst temperature and the reducing agent (ammonia) adsorbable amount in the selective reduction catalyst device 23 as shown in FIG.

  In the exhaust gas purification system 20 for an internal combustion engine according to the embodiment of the present invention, the control device 40 that controls the exhaust gas purification system 20 has a temperature difference ΔT (= Ta−) between the exhaust temperature Ta and the inlet temperature Tb. The injection amount Uf of the urea water U from the urea water injection device 24 is controlled based on Tb).

  Then, the control device 40 stores a preset relationship between the engine operating state Ec and the reference supply amount Rsc that is an amount of reducing agent necessary and sufficient to reduce nitrogen oxides generated in the engine operating state Ec. The reference supply amount Rsc is calculated from the engine operation state Ec based on the relationship between the set engine operation state Ec and the reference supply amount Rsc.

  Further, when it is determined that the temperature difference ΔT is equal to or larger than the preset steady-state temperature difference ΔTc, the urea water is set so that the supply amount of ammonia R is smaller than the calculated reference supply amount Rsc. An injection amount Uf of U is set, and injection is performed from the reducing agent injection device 24. On the other hand, if it is determined that the temperature difference ΔT is smaller than the steady-state temperature difference ΔTc, the urea water U injection amount Uf is set so that the supply amount of ammonia R is larger than the calculated reference supply amount Rsc. And is configured to inject from the reducing agent injection device 24.

  This steady-state temperature difference ΔTc is a temperature difference ΔT (= Ta−Tb) in the steady state with respect to the engine operating state, and the relationship between the engine operating state Ec and the steady-state temperature difference ΔTc is stored in advance. It is a value calculated from the engine operating state Ec during control.

  As a result, when the temperature difference ΔT is equal to or greater than the steady-state temperature difference ΔTc, the catalyst temperature Tc of the selective catalytic reduction catalyst device 23 is increased, and the adsorbable amount Rsp is decreased. Since the injection amount Uf of U is reduced, the nitrogen oxides in the exhaust gas G flowing into the selective catalytic reduction device 23 until the catalyst temperature Tc of the selective catalytic reduction device 24 rises thereby. The reducing agent holding amount Rin of ammonia R adsorbed on the selective catalytic reduction device 23 can be reduced. Moreover, it can contribute to the reduction of the injection amount Uf of the urea water U by the amount of reducing the required supply amount Rsn of the ammonia R in advance.

  When the temperature difference ΔT is smaller than the steady-state temperature difference ΔTc, the catalyst temperature Tc of the selective catalytic reduction device 23 decreases and the adsorbable amount Rsp increases, so that the urea water U is more than the reference supply amount Rsc. Since the injection amount Uf is increased, it is possible to increase the amount of ammonia R adsorbed on the selective catalytic reduction device 23 and to improve the NOx purification rate with a high NOx purification rate by using the adsorbed ammonia R. Can contribute. In addition, the amount of ammonia R adsorbed on the selective catalytic reduction device 23 can be increased, and a high NOx purification rate due to the use of the adsorbed ammonia R can contribute to an improvement in the NOx purification rate.

The “current time” used below is the time when the control is performed, and the “injection time” is the time when the injection amount Uf of the urea water U from the urea water injection device 24 is controlled. The first time Δt1 (= t2−t1) from the current time t1 to the injection time point t2 is a time related to the calculation speed in the control device 40, and is substantially effective when the calculation for control can be performed at high speed. Can be the same time (same time).

  The “arrival time” means that ammonia R generated from the urea water U of the injection amount Uf injected at this injection time t2 actually reaches the selective catalytic reduction device 23 and reduces nitrogen oxides (NOx). The second time Δt2 (= t3−t2) from the injection time point t2 to the arrival time point t3 is an exhaust gas G within that time from the injection time point t2 when the urea water U having the injection amount Uf is injected. Related to the flow rate of

  More precisely, the time from the injection time t2 to the arrival time t3 is related to the gas flow rate Vg of the exhaust gas G, and is set in advance for the engine operating state Ec based on measurement results such as experiments. The exhaust gas amount (volume amount) and the exhaust gas distribution that can be stored in advance as map data or calculated from the intake air amount, the fuel injection amount, the EGR gas amount, the exhaust gas temperature, etc. at the injection time t2. This is the time that can be calculated from the pipe diameter and the length of the exhaust pipe from the reducing agent injection device to the selective catalytic reduction device.

  Therefore, the second time Δt2 from the injection time t2 to the arrival time t3 can be calculated from the engine operating state Ec. However, the second time Δt2 is set in advance for the engine operating state based on measurement results such as experiments. It can also be stored in the control device 40 as map data or the like.

  More specifically, as shown in FIG. 2, the control device 40 includes a steady-state temperature difference storage unit 41, a reference supply amount storage unit 42, a catalyst temperature prediction unit 43, a discharge amount calculation unit 44a, and an adsorption amount calculation unit. 44 b, possessed amount calculating means 45, temperature difference determining means 46, rising temperature supply amount setting means 47 a, decreasing temperature supply amount setting means 47 b, and injection execution means 48.

  The steady-state temperature difference storage means 41 sets the steady-state temperature difference ΔT (= Ta−Tb) as the steady-state temperature difference ΔTc with respect to the engine operation state, and the steady-state temperature difference ΔTc and the engine operation state Ec. This means is a means for storing the relationship, and is a means specific to the control device 40. This steady-state temperature difference ΔTc is obtained by measurement in an experiment in which the engine operating state (engine speed, load, etc.) Ec is changed, or by simulation calculation, and is stored in the control device 40 as map data or a function. Keep it.

  The reference supply amount storage means 42 sets the supply amount Rs of ammonia R in the steady state as the reference supply amount Rsc with respect to the engine operation state Ec, and stores the relationship between the reference supply amount Rsc and the engine operation state Ec. Means. This reference supply amount Rsc is also obtained by measurement in an experiment in which the engine operating state (engine speed, load, etc.) Ec is changed, or by simulation calculation, and is stored in the control device 40 as map data or a function. Keep it.

  Further, the catalyst temperature predicting means 43 is supplied by the injection of urea water U at the injection time t2 after the preset first time Δt1 has elapsed from the exhaust gas temperature Ta and the inlet temperature Tb measured at the current time t1. This is means for predicting the catalyst temperature Tc of the selective catalytic reduction device 23 at the time t3 (= t1 + Δt1 + Δt2) when the ammonia R to be reached reaches the selective catalytic reduction device 23.

  The release amount calculation means 44a is a means for calculating the reducing agent release amount Rs1 from the selective catalytic reduction device 23 at the arrival time t2 based on the catalyst temperature Tc predicted by the catalyst temperature prediction means 43. The amount of adsorbable Rsp based on the catalyst temperature Tc at the arrival time t3 predicted by the catalyst temperature prediction unit 43 is subtracted from the reducing agent possession amount Rin at the current time t1 calculated by the held amount calculation unit 45 of the catalyst at the injection time t2. The reducing agent release amount Rs1 is calculated. As a result, since it is possible to perform control after grasping the reducing agent holding amount Rin at the current time t1, the reducing agent release amount Rs1 can be predicted more accurately.

  Further, the change in the catalyst temperature Tc during the time (Δt1 + Δt2) from the current time t1 to the arrival time t3 and the reducing agent release amount Rs1 associated with the change are predicted, and the reduction agent release amount Rs1 at the arrival time t3 is predicted. Thus, it is preferable to perform correction to subtract the reducing agent release amount ΔRs1 from the current time t1 to the arrival time t3. As a result, the reducing agent release amount Rs1 at the arrival time t3 can be predicted more accurately.

  The adsorption amount calculating means 44b is a means for calculating the reducing agent adsorption amount Rs2 of the selective catalytic reduction device 23 at the arrival time t3 based on the catalyst temperature Tc predicted by the catalyst temperature predicting means 43. The reducing agent possessed amount Rin calculated at the current time t1 calculated by the retained amount calculating unit 47 is subtracted from the adsorbable amount Rsp based on the catalyst temperature Tc at the arrival time t3 predicted by the predicting unit 43, thereby reducing the reducing agent at the injection time t3. The adsorption amount Rs2 is calculated. As a result, since it is possible to perform control after grasping the reducing agent holding amount Rin at the current time t1, the reducing agent adsorption amount Rs2 can be predicted more accurately.

  Further, the change in the catalyst temperature Tc during the time from the current time t1 to the arrival time t3 (Δt1 + Δt2) and the reducing agent adsorption amount Rs2 accompanying the change are predicted, and the reducing agent adsorption amount Rs1 at the arrival time t3 is estimated. If the correction means is configured to correct the reducing agent adsorption amount ΔRs2 from the current time t1 to the arrival time t3, the reducing agent release amount Rs1 and the reducing agent adsorption amount Rs2 at the arrival time t3 can be more accurately determined. Be able to predict.

  Further, the retained amount calculating means 45 cumulatively adds the reducing agent adsorption amount Rs1 calculated by the adsorption amount calculating means 44b to the initial retained amount Ri, and also calculates the reducing agent release amount Rs2 calculated by the released amount calculating means 44a. This is a means for calculating the reducing agent holding amount Rin that is currently adsorbed by the selective catalytic reduction device 23 by cumulative subtraction.

  In addition to the cumulative calculation of the reducing agent adsorption amount Rs2 and the reducing agent release amount Rs1, a method of estimating the present reducing agent holding amount Rin from the slip amount of ammonia R and the NOx amount that could not be reduced is also conceivable. Furthermore, with this method, the accuracy can be further improved by correcting the reducing agent holding amount Rin at the current time t1 calculated by the holding amount calculating means 45 described above.

  Further, the temperature difference determination means 46 introduces the steady-state temperature difference ΔTc in the engine operating state Ec at the current time t1 from the steady-state temperature difference storage means 41, and the exhaust temperature Ta and the inlet temperature Tb measured at the current time t1. Is a means for calculating the temperature difference ΔT at the current time t1 and determining whether the temperature difference ΔT at the current time t1 is equal to or greater than the steady-state temperature difference ΔTc.

  The temperature increase supply amount setting means 47a receives the engine operating state Ec at the current time t1 or the injection time t2 as the supply amount Rs of the reducing agent R, and the reference supply amount Rsc obtained from the reference injection amount storage means 42. This is means for setting the injection amount Uf of the urea water U at the injection time point t2 so that the required supply amount Rsn is obtained by subtracting the reducing agent reduction amount Rs3 from the above. As for the engine operating state Ec, the engine operating state Ec at the current time t1 is determined because a control command is issued to the engine 10, but the engine operating state Ec at the injection time t2 is often estimated. When the value obtained by subtracting the reducing agent release amount Rs1 from the reference supply amount Rsc is negative, the required supply amount Rsn is set to zero and the urea water U injection amount Uf is set to zero.

  Further, the temperature drop supply amount setting means 47b reduces the supply amount Rs of the reducing agent R to the reference supply amount Rsc introduced from the reference injection amount storage means 42 by inputting the engine operating state Ec at the current time t1 or the control time t2. This is means for setting the injection amount Uf of the urea water U at the injection time point t2 so that the required supply amount Rsn obtained by adding the agent increase amount Rs4 is obtained.

  More precisely, regarding the calculation of the reference supply amount Rsc in the temperature increase supply amount setting means 47a and the temperature decrease supply amount setting means 47b, the exhaust gas G generated at the exhaust gas generation time point t0 is more strictly selected. When reaching the device 23, the ammonia R generated from the urea water U injected at the injection time point t2 reaches the selective reduction catalyst device 23, so that the engine operating state Ec at the exhaust gas generation time point t0 is reached. On the other hand, calculating the reference supply amount Rsc is more preferable in terms of accuracy improvement, although the control is complicated. The difference Δt0 = (Δt2−t0) between the exhaust gas generation time point t0 and the injection time point t1 is obtained by measurement in an experiment with changing the engine operating state (engine speed, load, etc.) Ec or simulation calculation. The data is stored in the control device 40 as map data or a function.

  When the temperature difference determination unit 46 determines that the temperature difference ΔT at the current time t1 is equal to or greater than the steady-state temperature difference ΔTc, the injection execution unit 48 determines the supply amount setting unit 47a during the temperature increase at the injection time t2. Is injected from the reducing agent injection device 23 with the injection amount Uf of the urea water U set in step S, and the temperature difference determination means 46 determines that the temperature difference ΔT at the current time t1 is not greater than or equal to the steady-state temperature difference ΔTc. These are means for injecting from the reducing agent injection device 23 with the injection amount Uf of the urea water U set by the cooling time supply amount setting means 47b at the injection time point t2.

  At the same time, the released amount calculating means 44a uses the reducing agent possessed amount Rsn calculated by the retained amount calculating means 45 at the present time to obtain the adsorbable amount Rsp based on the catalyst temperature Tc at the arrival time t3 predicted by the catalyst temperature predicting means 43. Is subtracted to calculate the reducing agent release amount Rs1 at the injection time point t2.

  In addition, the adsorption amount calculation unit 44b calculates the reducing agent holding amount Rsn at the current time t1 calculated by the holding amount calculation unit 45 from the adsorbable amount Rs2 based on the catalyst temperature Tc at the arrival time t3 predicted by the catalyst temperature prediction unit 43. Is subtracted to calculate the reducing agent adsorption amount Rs2 at the injection time point t2.

  Further, in the temperature increase supply amount setting means 47a, the reducing agent decrease amount Rs3 is equal to or greater than the reducing agent release amount Rs1 calculated by the release amount calculation means 44a and the reducing agent retention amount Rsn calculated by the retention amount calculation means 45. The following amount. Further, in the temperature drop supply amount setting means 47b, the reducing agent increase amount Rs4 is set to be less than the reducing agent adsorption amount Rs2 calculated by the adsorption amount calculating means 44 and greater than zero.

  Next, an exhaust gas purification method for the internal combustion engine in the exhaust gas purification system 20 for the internal combustion engine having the above-described configuration will be described. This method is an exhaust gas purification method for an internal combustion engine provided with an exhaust gas purification device 21 having a reducing agent injection device 24 and a selective reduction catalyst device 23 in the exhaust passage 12 of the engine 10 in order from the upstream side. The exhaust temperature Ta, which is the temperature of the exhaust gas G in the exhaust passage 12 upstream from the gas purification device 21, is detected, and the inlet temperature Tb, which is the temperature of the exhaust gas G flowing into the selective catalytic reduction device 23, is detected. This is a method of controlling the injection amount Uf of the urea water U from the reducing agent injection device 24 based on the temperature difference ΔT (= Ta−Tb) between the exhaust temperature Ta and the inlet temperature Tb.

  Further, the relationship between the preset engine operating state Ec and the reference supply amount Rsc that is the amount of ammonia R necessary and sufficient to reduce nitrogen oxides generated in the engine operating state Ec is stored, and the engine operating state is stored. From Ec, the reference supply amount Rsc is calculated based on the relationship between the set engine operating state Ec and the reference supply amount Rsc, and if it is determined that the temperature difference ΔT is equal to or greater than the steady-state temperature difference ΔTc, ammonia The injection amount Uf of the urea water U is set so that the supply amount of R is smaller than the calculated reference supply amount Rsc and is injected from the reducing agent injection device 24, and the temperature difference ΔT is always greater than the temperature difference ΔTc. If it is determined that the supply amount of ammonia R is smaller than the calculated reference supply amount Rsc, the injection amount Uf of the urea water U is set so that the supply amount of ammonia R is larger than the calculated reference supply amount Rsc. To injection.

  In order to prevent control hunting, a dead zone is provided in the comparison between the temperature difference ΔT and the steady-state temperature difference ΔTc, and when the upper limit of the dead zone is exceeded, the temperature difference ΔT is equal to or greater than the steady-state temperature difference ΔTc. It may be configured to determine that the temperature difference ΔT is smaller than the steady-state temperature difference ΔTc when it falls below the lower limit of the dead zone.

  Thus, until the catalyst temperature Tc of the selective catalytic reduction device 23 rises, the selective catalytic reduction device 23 is adsorbed by the nitrogen oxides in the exhaust gas G flowing into the selective catalytic reduction device 23. The amount of ammonia R can be reduced. Moreover, it can contribute to the reduction of the injection amount Uf of the urea water U by the amount of reducing the required supply amount Rsn of the ammonia R in advance.

  More specifically, in this exhaust gas purification method for an internal combustion engine, the temperature difference ΔT in the steady state is set as the steady state temperature difference ΔTc with respect to the steady state engine operating state Ec, and the engine operating state Ec The supply amount Rs of ammonia R in the steady state is set as the reference supply amount Rsc.

  Then, from the exhaust temperature Ta measured at the present time t1 and the inlet temperature Tb, the ammonia R generated from the urea water U injected at the injection time t2 after the preset first time Δt1 is converted into the selective catalytic reduction device 23. The catalyst temperature Tc of the selective catalytic reduction catalyst 23 at the arrival time t3 when reaching the value is predicted. This arrival time t3 is a time obtained by adding a preset second time Δt2 to the injection time t2.

  Further, based on the catalyst temperature Tc, the reducing agent release amount Rs1 and the reducing agent adsorption amount Rs2 from the selective catalytic reduction device 23 at the arrival time t3 are calculated, and the reducing agent adsorption amount Rs2 is set to the initial holding amount Ri. The cumulative addition and the cumulative subtraction of the reducing agent release amount Rs1 are performed to calculate the reducing agent holding amount Rsn that the selective catalytic reduction catalyst device 23 is adsorbing at the current time t1. That is, Rin = Ri + ΣRs2−ΣRs1.

  At the same time, the reducing agent release amount Rs1 at the current time t1 or the injection time t2 and the reductant retention amount Rsn or less is set as the reducing agent reduction amount Rs3, and zero at the current time t1 or the reductant adsorption amount Rs2 or less at the injection time t2. The larger amount is defined as a reducing agent increase amount Rs4.

  Further, when it is determined that the temperature difference ΔT at the current time t1 is equal to or larger than the steady-state temperature difference ΔTc, the supply amount Rs of ammonia R is equal to the engine operating state Ec at the injection time t2 or the arrival time t3. The injection amount Uf of the urea water U at the injection time t2 so that the required supply amount Rsn is obtained by subtracting the reducing agent reduction amount Rs3 from the reference supply amount Rsc obtained from the relationship between the set engine operating state Ec and the reference supply amount Rsc. Is injected from the reducing agent injection device 23. That is, the urea water U of the injection amount Uf of the amount that the ammonia R of the necessary supply amount Rsn is generated is injected at Rsn = Rsc−Rs3.

  That is, assuming that the catalyst temperature Tc of the reduction catalyst device 23 rises and the adsorbable amount Rsp decreases, the reducing agent release amount Rs1 is decreased from the reference supply amount Rsc. If the value obtained by subtracting the reducing agent release amount Rs1 from the reference supply amount Rsc is negative, the required supply amount Rsn is set to zero, and the injection amount Uf of the urea water U is set to zero.

  As a result, when the temperature difference ΔT is equal to or greater than the steady-state temperature difference ΔTc, the catalyst temperature Tc of the selective catalytic reduction device 23 rises at the arrival time t3, and the ammonia R of the selective catalytic reduction device 23 can be adsorbed. The amount (maximum reducing agent adsorption amount) Rsp becomes small, and it is predicted that ammonia R is desorbed from the selective catalytic reduction device 23, and the nitrogen oxide contained in the exhaust gas G is desorbed at the reaching time t3. The injection amount Uf of the urea water U, which is the amount of ammonia R that is reduced by subtracting the reducing agent reduction amount Rs3 from the reference injection amount Rsc at the injection time point t2, is used so that it is not discharged into the atmosphere. Can be injected.

  Further, since the reducing agent reduction amount Rs3 is set to an amount not less than the reducing agent release amount Rs1 and not more than the reducing agent holding amount Rsn, nitrogen oxidation is performed using ammonia R adhering to the surface of the selective catalytic reduction device 23. Since substances can be reduced, a high NOx purification rate can be obtained. That is, if the reducing agent reduction amount Rs3 is the reducing agent release amount Rs1, the ammonia R adhering to the surface cannot be used or ammonia R that cannot contribute to the reduction of nitrogen oxides is released into the atmosphere, and the reducing agent reduction amount Rs3. Is the reducing agent holding amount Rsn, the ammonia R adhering to the surface can be used, but the reducing agent holding amount Rsn becomes zero, and thereafter, the ammonia R adhering to the surface cannot be used. It is preferable to make it below this. The reducing agent reduction amount Rs3 is practically set to an appropriate amount within the range of the reducing agent release amount Rs1 or more and the reducing agent holding amount Rsn or less by experiments or the like.

  On the other hand, when it is determined that the temperature difference ΔT at the current time t1 is smaller than the steady-state temperature difference Tc, the supply amount Rs of ammonia R is set to the engine operating state Ec at the injection time t2 or the arrival time t3. The injection amount Uf of the urea water U at the injection time point t2 is set so that the required supply amount Rsn obtained by adding the reducing agent increase amount Rs4 to the reference supply amount Rsc obtained from the relationship between the engine operating state Ec and the reference supply amount Rsc. Then, it is injected from the reducing agent injection device 23. That is, the urea water U of the injection amount Uf of the amount that the ammonia R of the necessary supply amount Rsn is generated is injected at Rsn = Rsc + Rs4.

  That is, assuming that the catalyst temperature Tc of the reduction catalyst device 23 is lowered and the adsorbable amount Rsp is increased, it is increased by an amount less than the reference supply amount Rsc by the reducing agent absorption amount Rs2.

  As a result, when the temperature difference ΔT is smaller than the steady-state temperature difference ΔTc, the catalyst temperature Tc of the selective catalytic reduction device 23 decreases at the reaching time t3, and the amount of ammonia R that can be adsorbed by the selective catalytic reduction device 23 is reduced. As Rsp increases and ammonia R is predicted to be adsorbed by the selective catalytic reduction device 23, the ammonia R to be used for purification of nitrogen oxides contained in the exhaust gas G due to the adsorption of ammonia R reaches the time t3. The injection amount Uf of urea water U, which is the amount of ammonia R increased by adding the reducing agent increase amount Rs4 to the reference injection amount Rsc, can be injected at the injection time point t2.

  In addition, since the reducing agent increase amount Rs4 is less than the reducing agent adsorption amount Rs2 and more than zero, ammonia R that is not used in the reduction of nitrogen oxides can be adsorbed on the surface of the selective catalytic reduction device 23. Therefore, a high NOx purification rate can be obtained by using ammonia R adhering to the surface in the subsequent reduction of nitrogen oxides. That is, if the reducing agent increase amount Rs4 is the reducing agent adsorption amount Rs2, the reducing agent holding amount Rsn adhering to the surface can be immediately saturated, but thereafter, ammonia R that has not contributed to the reduction of nitrogen oxides is released into the atmosphere. If the reducing agent increase amount Rs4 is made zero, the reducing agent holding amount Rsn adhering to the surface cannot be increased, and the use of ammonia R adhering to the surface after that cannot be expanded. Therefore, it is preferably zero or more. The reducing agent increase amount Rs4 is practically set to an appropriate amount within the range of less than the reducing agent adsorption amount Rs2 and more than zero by experiments.

  Further, the reductant release amount Rs1 at the injection time t2 is calculated by subtracting the adsorbable amount Rsp based on the catalyst temperature Tc at the arrival time t3 from the reducing agent holding amount Rin at the current time t1, and the catalyst temperature Tc at the arrival time t3. The reducing agent adsorption amount Rs is calculated by subtracting the reducing agent holding amount Rin at the current time t13 from the adsorbable amount Rsp based on the above. That is, Rs1 = Rin−Rsp and Rs = Rsp−Rin.

  Further, correction is performed by subtracting the reducing agent release amount ΔRs1 from the current time t1 to the reaching time point t3 with respect to the reducing agent release amount Rs1 at the reaching time point t3, while the reducing agent adsorption amount Rs2 at the reaching time point t3. On the other hand, the correction is performed by subtracting the reducing agent adsorption amount ΔRs2 from the current time t1 to the arrival time t3. That is, Rs1 is (Rs1-ΔRs1) and Rs2 is (Rs2-ΔRs2).

  According to the exhaust gas purification system 20 for an internal combustion engine, the internal combustion engine 10 and the exhaust gas purification method for an internal combustion engine having the above-described configuration, the following effects can be achieved.

  Since the injection amount Uf of the urea water U from the reducing agent injection device 24 is controlled based on the temperature difference ΔT between the exhaust temperature Ta and the inlet temperature Tb, based on this temperature difference ΔT, The change in the catalyst temperature Tc can be predicted, and the injection amount Uf of the urea water U can be controlled. The ammonia R adsorbable amount Rsp at the predicted catalyst temperature Tc and the selective reduction catalyst device 23 are currently held. The urea water U is injected from the reducing agent injection device 24 while predicting the amount of ammonia R released or adsorbed from the selective catalytic reduction device 23 in consideration of the reduction amount Rin during reduction. The amount Uf can be controlled.

  That is, the catalyst temperature Tc of the selective reduction catalyst device 23 at the arrival time t1 when the urea water U from the reducing agent injection device 24 reaches the selective reduction catalyst device 23 is predicted, and the urea water U at the injection time t2 is predicted. Since the injection amount Uf can be controlled, even when the engine operating state Ec is in a transient state, the urea water U can be injected with the appropriate injection amount Uf, and the ammonia R is selectively reduced with the appropriate supply amount Rs. 23.

  Therefore, the reducing agent required amount Rsn of ammonia R corresponding to the amount of nitrogen oxides in the exhaust gas G in the selective catalytic reduction device 23 can be made substantially equal to the usable amount Rss of ammonia R. Thus, while maintaining a high NOx purification rate, the injection amount Uf of the urea water U necessary for purifying the nitrogen oxides in the exhaust gas G can be reduced to the necessary minimum amount and also released from the engine 10 to the atmosphere. The amount of ammonia R can also be reduced.

  If the temperature difference ΔT is equal to or greater than the steady-state temperature difference ΔTc, the catalyst temperature Tc of the selective catalytic reduction device 23 increases and the adsorbable amount Rsp decreases, so that the urea water U is more than the reference supply amount Rsc. This reduces the injection amount Uf of the exhaust gas G so that it is selected by the nitrogen oxides in the exhaust gas G flowing into the selective catalytic reduction device 23 until the catalyst temperature Tc of the selective catalytic reduction device 23 rises. The amount of ammonia R adsorbed on the reduction catalyst device 23 can be reduced. Moreover, it can contribute to the reduction of the injection amount Uf of the urea water U by the amount of reducing the required supply amount Rsn of the ammonia R in advance.

  When the temperature difference ΔT is smaller than the steady-state temperature difference ΔTc, the catalyst temperature Tc of the selective catalytic reduction device 23 decreases and the adsorbable amount Rsp increases, so that the urea water U is more than the reference supply amount Rsc. Since the injection amount Uf is increased, it is possible to increase the amount of ammonia R adsorbed on the selective catalytic reduction device 23 and to improve the NOx purification rate with a high NOx purification rate by using the adsorbed ammonia R. Can contribute.

  In the selective catalytic reduction device 23, the ammonia R of the reference injection amount Rsc corresponding to the amount of nitrogen oxide in the exhaust gas G can be used for the reduction of nitrogen oxide at the arrival time t3. It is possible to maintain the NOx purification rate, minimize the required amount of urea water injection amount Uf, and minimize ammonia slip.

  Therefore, the temperature change of the selective catalytic reduction device 23 is estimated, and the reducing agent injection is performed while predicting the reducing agent release amount Rs1 and the reducing agent adsorption amount Rs2 by the selective catalytic reduction device 23 based on the estimated temperature change. Since the injection amount Uf of the urea water U from the device 23 is controlled, the required amount of ammonia R corresponding to the amount of nitrogen oxide in the exhaust gas G in the selective catalytic reduction device 23 and the usable amount Rss of ammonia R Thus, the injection amount of urea water U necessary to purify nitrogen oxides in the exhaust gas G while maintaining a high NOx purification rate due to the use of the adsorbed reducing agent. Uf can be reduced to the necessary minimum amount, and the amount of ammonia R released from the engine 10 to the atmosphere can also be reduced.

10 Engine (Internal combustion engine)
10a Cylinder 10b Intake manifold 10c Exhaust manifold 11 Intake passage 12 Exhaust passage 13S Turbo supercharging system 13 Turbocharger (turbo supercharger)
13a Turbine 13b Compressor 20 Exhaust gas purification system 21 for internal combustion engine Exhaust gas purification device 22 Particulate trap (DPD)
23 Selective reduction catalyst system (SCR)
24 Urea water injection device (reducing agent injection device)
30 1st temperature sensor (1st temperature detection apparatus)
31 2nd temperature sensor (2nd temperature detection apparatus)
40 Controller 41 Constant temperature difference storage means 42 Reference supply amount storage means 43 Catalyst temperature prediction means 44a Release amount calculation means 44b Adsorption amount calculation means 45 Retention amount calculation means 46 Temperature difference determination means 47a Temperature increase supply amount setting means 47b Supply amount setting means 48 when cooling down Injection means A Fresh air G Generated exhaust gas

Claims (9)

In the exhaust gas purification system for an internal combustion engine, which is provided with an exhaust gas purification device having a reducing agent injection device and a selective reduction catalyst device in order from the upstream side in the exhaust passage of the internal combustion engine.
A first temperature detection device for detecting an exhaust temperature, which is a temperature of exhaust gas discharged from a cylinder of the internal combustion engine, is provided in the exhaust passage upstream of the exhaust gas purification device;
A second temperature detection device for detecting an inlet temperature, which is a temperature of exhaust gas flowing into the selective reduction catalyst device, is provided on the inlet side of the selective reduction catalyst device;
A control device for controlling the exhaust gas purification system,
An exhaust gas purification system for an internal combustion engine configured to control an injection amount of a reducing agent generating solution from the reducing agent injection device based on a temperature difference between the exhaust temperature and the inlet temperature. The control device stores a preset relationship between an engine operating state and a reference supply amount that is an amount of a reducing agent necessary and sufficient to reduce nitrogen oxides generated in the engine operating state;
Based on the relationship between the set engine operating state and the reference supply amount from the engine operation state, the reference supply amount is calculated,
When it is determined that the temperature difference is equal to or greater than a preset steady-state temperature difference, the reducing agent generating solution is set so that the supply amount of the reducing agent is smaller than the calculated reference supply amount. Set the injection amount of and inject from the reducing agent injection device,
When it is determined that the temperature difference is smaller than the steady-state temperature difference, the injection amount of the reducing agent generating solution is set so that the supply amount of the reducing agent is larger than the calculated reference supply amount. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the exhaust gas purification system is configured to be set and injected from the reducing agent injection device. The control device is
With respect to the engine operating state, the temperature difference in the steady state is set as a steady state temperature difference, and the steady state temperature difference storage means for storing the relationship between the steady state temperature difference and the engine operating state;
A reference supply amount storage means for setting a supply amount of the reducing agent in a steady state as a reference supply amount with respect to the engine operation state, and storing a relationship between the reference supply amount and the engine operation state;
From the exhaust gas temperature and the inlet temperature measured at the present time, the reducing agent supplied by the injection of the reducing agent generating solution at the injection time after a preset control time has reached the selective reduction catalyst device. Catalyst temperature prediction means for predicting the catalyst temperature of the selective catalytic reduction device at the time of arrival;
Based on the catalyst temperature predicted by the catalyst temperature predicting means, a release amount calculating means for calculating a reducing agent release amount from the selective catalytic reduction catalyst device at the time of arrival;
Based on the catalyst temperature predicted by the catalyst temperature prediction means, an adsorption amount calculation means for calculating the reducing agent adsorption amount of the selective reduction catalyst device at the time of arrival;
The selective reduction catalyst device adds the reducing agent adsorption amount calculated by the adsorption amount calculating means to the initial holding amount, and cumulatively subtracts the reducing agent release amount calculated by the release amount calculating means. Holding amount calculating means for calculating the reducing agent holding amount adsorbed at the present time;
A temperature difference at the present time is calculated from the exhaust gas temperature and the inlet temperature measured at the present time by introducing the temperature difference at the time of engine operation at the present time from the temperature difference storage means at the present time. Temperature difference determination means for determining whether the difference is equal to or greater than the steady-state temperature difference;
The injection time point is such that the supply amount of the reducing agent is the required supply amount obtained by subtracting the reducing agent reduction amount from the reference supply amount obtained from the reference injection amount storage means by inputting the engine operating state at the present time or injection time. A temperature increase supply amount setting means for setting the injection amount of the reducing agent generating solution in
The supply amount of the reducing agent is the required supply amount obtained by adding the reducing agent increase amount to the reference supply amount introduced from the reference injection amount storage means by inputting the engine operating state at the present time or the injection time point. A temperature drop supply amount setting means for setting the injection amount of the reducing agent generating solution;
When the temperature difference determination means determines that the current temperature difference is greater than or equal to the steady-state temperature difference, the reducing agent generating solution set by the temperature increase supply amount setting means at the time of injection When the temperature difference determining means determines that the current temperature difference is not equal to or greater than the steady-state temperature difference, the temperature drop supply is performed at the injection time point. Injection execution means for injecting from the reducing agent injection device at an injection amount of the reducing agent generating solution set by an amount setting means;
Configured with
The discharge amount calculation means subtracts the adsorbable amount based on the catalyst temperature at the arrival time predicted by the catalyst temperature prediction means from the current reducing agent possession amount calculated by the retention amount calculation means, and at the injection time point. Calculate the amount of reducing agent released
The adsorption amount calculating means subtracts the current reducing agent possessed amount calculated by the retained amount calculating means from the adsorbable amount based on the catalyst temperature at the arrival time predicted by the catalyst temperature predicting means, and at the injection time point. Calculate the reducing agent adsorption amount of
The temperature increase supply amount setting means sets the reducing agent decrease amount to an amount not less than the reducing agent release amount calculated by the release amount calculation means and not more than the reducing agent holding amount calculated by the holding amount calculation means. ,
The supply amount setting means at the time of lowering the temperature increases the reducing agent. The exhaust gas purification system for an internal combustion engine according to claim 1 or 2, wherein the amount is less than or equal to the reducing agent adsorption amount calculated by the adsorption amount calculation means and greater than zero. The discharge amount calculation means subtracts the adsorbable amount based on the catalyst temperature at the arrival time predicted by the catalyst temperature prediction means from the current reducing agent possession amount calculated by the retention amount calculation means, and at the injection time point. Is a means for calculating the reducing agent release amount of
The adsorption amount calculating means subtracts the current reducing agent possessed amount calculated by the retained amount calculating means from the adsorbable amount based on the catalyst temperature at the arrival time predicted by the catalyst temperature predicting means, and at the injection time point. The exhaust gas purification system for an internal combustion engine according to claim 3, which is means for calculating the reducing agent adsorption amount of the internal combustion engine.   An internal combustion engine comprising the exhaust gas purification system for an internal combustion engine according to any one of claims 1 to 4. In the exhaust gas purification method for an internal combustion engine provided with an exhaust gas purification device having a reducing agent injection device and a selective reduction catalyst device in order from the upstream side in the exhaust passage of the internal combustion engine,
Detecting an exhaust temperature that is the temperature of the exhaust gas in the exhaust passage upstream from the exhaust gas purification device, and detecting an inlet temperature that is a temperature of the exhaust gas flowing into the selective catalytic reduction device,
An exhaust gas purification method for an internal combustion engine, wherein an injection amount of a reducing agent generating solution from the reducing agent injection device is controlled based on a temperature difference between the exhaust temperature and the inlet temperature. Storing a relationship between a preset engine operating state and a reference supply amount that is an amount of a reducing agent necessary and sufficient to reduce nitrogen oxides generated in the engine operating state;
Based on the relationship between the set engine operating state and the reference supply amount from the engine operation state, the reference supply amount is calculated,
When it is determined that the temperature difference is equal to or greater than a preset steady-state temperature difference, the reducing agent generating solution is set so that the supply amount of the reducing agent is smaller than the calculated reference supply amount. Set the injection amount of and inject from the reducing agent injection device,
When it is determined that the temperature difference is smaller than the steady-state temperature difference, the injection amount of the reducing agent generating solution is set so that the supply amount of the reducing agent is larger than the calculated reference supply amount. The exhaust gas purification method for an internal combustion engine according to claim 6, wherein the exhaust gas purification method is set and injected from the reducing agent injection device. With respect to the engine operating state, the temperature difference in the steady state is set as a steady state temperature difference, and with respect to the engine operating state, the reducing agent supply amount in the steady state is set as a reference supply amount,
From the exhaust gas temperature and the inlet temperature measured at the present time, the reducing agent supplied by the injection of the reducing agent generating solution at the injection time after a preset control time has reached the selective reduction catalyst device. Predicting the catalyst temperature of the selective catalytic reduction at the time of arrival,
Based on the catalyst temperature, the reducing agent release amount and the reducing agent adsorption amount from the selective catalytic reduction catalyst device at the time of arrival are calculated, and the cumulative addition of the reducing agent adsorption amount with respect to the initial holding amount and the reducing agent are calculated. A cumulative subtraction of the released amount is performed to calculate the reducing agent possessed amount currently adsorbed by the selective catalytic reduction catalyst device,
The amount that is greater than or equal to the amount of reducing agent released at the current time or injection time but less than or equal to the retained amount of reducing agent is the reducing agent decrease amount, and the amount that is less than or equal to the reducing agent adsorption amount at the current time or injection time is greater than zero age,
When it is determined that the current temperature difference is equal to or greater than the steady-state temperature difference, the supply amount of the reducing agent is determined as follows: the engine operating state at the current time or the injection point, the set engine operating state, and the reference supply amount Injecting from the reducing agent injection device by setting the injection amount of the reducing agent generating solution at the time of injection so that the required supply amount is obtained by subtracting the reducing agent reduction amount from the reference supply amount obtained from the relationship of
If it is determined that the current temperature difference is smaller than the steady-state temperature difference, the supply amount of the reducing agent is the current engine operation state or the set engine operation state and the reference supply amount at the time of injection. The injection amount of the reducing agent generating solution at the time of injection is set and injected from the reducing agent injection device so that the required supply amount obtained by adding the reducing agent increase amount to the reference supply amount obtained from the relationship is set. 2. An exhaust gas purification method for an internal combustion engine according to 1. By subtracting the adsorbable amount based on the catalyst temperature at the time of arrival from the current amount of reducing agent possessed, the amount of reducing agent released at the time of injection is calculated,
The exhaust gas purification method for an internal combustion engine according to claim 8, wherein the reducing agent adsorption amount is calculated by subtracting the reducing agent possession amount at the present time from the adsorbable amount based on the catalyst temperature at the time of arrival.

Images