JP5155838B2 - Reducing agent injection control device, control method for reducing agent injection device, and exhaust purification device for internal combustion engine - Google Patents

Description

  The present invention relates to a reducing agent injection control device, a control method for a reducing agent injection device, and an exhaust purification device for an internal combustion engine. In particular, a reducing agent injection control device that controls a reducing agent injection device that supplies a reducing agent upstream of the reduction catalyst, a control method for the reducing agent injection device, and an exhaust gas from an internal combustion engine equipped with such a reducing agent injection control device The present invention relates to a purification device.

Conventionally, exhaust gas discharged from an internal combustion engine such as a diesel engine contains NO _x (nitrogen oxides such as NO and NO ₂ ) that may cause environmental pollution. This as an exhaust gas purifying device used for the NO _X is reduced to purify the exhaust gas, the exhaust gas purification apparatus using the liquid reducing agent from ammonia, such as urea aqueous solution has been known. The exhaust purification system injects aqueous urea solution or the like in the exhaust passage upstream of the reduction catalyst, the urea is adsorbed ammonia that is generated reduction catalyst by hydrolysis, come to flow into the reduction catalyst NO _X Is decomposed into nitrogen or water by ammonia and released.

In such an exhaust purification device, when the injection amount of the reducing agent is insufficient with respect to the NO _X amount contained in the exhaust gas, the NO _X reduction efficiency is reduced and NO _X flows out downstream of the reduction catalyst. There is a fear. On the other hand, if the injection amount of the reducing agent is excessive, ammonia generated by hydrolysis of urea may exceed the saturated adsorption amount of the reduction catalyst, and ammonia may flow out downstream of the reduction catalyst.

Therefore, when at least one of ammonia and urea is used as the reducing agent, the injection amount of ammonia or urea can be accurately corrected with a simple configuration, and the release of ammonia and NO _x can be minimized. A denitration system and a denitration method for suppressing the same have been proposed. More specifically, by reacting with ammonia a NO _X discharged through the pipe from the combustion device such as an internal combustion engine to provide energy to a load of the power generation or the like based on a predetermined combustion control by the combustion controller, and nitrogen in denitration system comprising a denitrator for the water, constituted by attaching the NO _X sensor downstream of the denitrator, an ammonia injection amount is disclosed denitration system for correction control based on the detection signal Si from the NO _X sensor (See Patent Document 1).

More specifically, Patent Document 1 describes that the ammonia injection amount is optimized as follows. First, when the injection amounts of ammonia and urea are increased, the NO _x discharged from the combustion device is reduced, and thereby the sensor value of the NO _x sensor becomes small. If the injection is further increased, ammonia is now discharged, which causes the NO _x sensor to be sensitive to ammonia and the sensor value to increase. When the sensor value of the NO _x sensor starts to increase, the injection amount of ammonia or urea starts to decrease. As the injection amount of ammonia or urea decreases, the sensor value of the NO _x sensor changes from increasing to decreasing. At this time, the injection amounts of ammonia and urea start to increase. By repeating these series of operations, the injection amount of ammonia or urea is repeatedly increased and decreased around the point where the total value of NO _x and ammonia is minimized (optimum point), and the injection amount of ammonia or urea is corrected. Is done.

Japanese Patent Laid-Open No. 10-33948 (full text, full diagram)

However, the denitration system of Patent Document 1 repeats the increase and decrease of the injection amount of ammonia and the like around the equivalent point (optimum amount) of injection, so that the injection amount of ammonia and the like does not occur as a whole so that excess or shortage of ammonia or the like does not occur. Is corrected. Therefore, since the injection amount is constantly increased and decreased during the injection of ammonia or the like, the operation control of the injection device is complicated.
Further, the denitration system in Patent Document 1, to prevent the NO _X concentration or amount of NO _X is determined from the relationship between operating conditions and concentration of NO _X internal combustion engine deviates from the actual emissions, it can not be efficiently denitration This system is not configured to inject ammonia or the like by obtaining an optimal amount in advance. Therefore, there is a possibility that it takes time until the optimum amount of injection is grasped and the injection amount is increased or decreased around the optimum amount.

On the other hand, there is also an apparatus in which the reducing agent is injected by obtaining the required injection amount of the reducing agent in advance and controlling the reducing agent injection device in accordance with the required injection amount. By calculating the required injection amount in advance and injecting the reducing agent, it is possible to avoid that the operation control of the reducing agent injection device becomes extremely complicated. For example, when a reduction catalyst having a function of adsorbing ammonia is used, the required injection amount of the reducing agent is discharged from the internal combustion engine while taking into account the design values and characteristics of the components constituting the reducing agent injection device. It is obtained by calculation based on a plurality of parameter values including the NO _x flow rate, the temperature of the reduction catalyst, the adsorption amount of ammonia adsorbed on the reduction catalyst, and the like.

However, when the required injection amount of the reducing agent is obtained in advance, the calculated required injection amount may be reduced due to deterioration of parts constituting the reducing agent injection device, a deviation in the calculated value that occurs based on the passage of time, or the like. There is a risk of excess or deficiency with the amount of reducing agent actually required. When excess or deficiency of the reducing agent occurs, either ammonia or NO _x will flow out downstream of the reduction catalyst, so a means for correcting the actual injection amount to be an appropriate amount is required. Become.

Accordingly, the inventor of the present invention has made diligent efforts to determine an abnormality in the actual injection amount of the reducing agent using a sensor that is sensitive to at least NO _x and ammonia in the reducing agent injection control device. The present invention has been completed by finding that such a problem can be solved by correcting the parameter value used for calculating the quantity. That is, the present invention relates to a reducing agent injection control device that performs correction so that the actual injection amount of the reducing agent is optimized when the actual injection amount injected according to the required injection amount of the reducing agent is excessive or insufficient. It is another object of the present invention to provide a control method for a reducing agent injection device, and an exhaust purification device for an internal combustion engine including such a reducing agent injection control device.

According to the present invention, a reducing agent capable of generating ammonia is injected upstream of a reduction catalyst that is connected to an exhaust system of an internal combustion engine and adsorbs ammonia and reduces NOx in exhaust gas flowing in using ammonia. In the reducing agent injection control device for controlling the reducing agent injection device, the request for the reducing agent is based on parameter values including at least the amount of NOx discharged from the internal combustion engine, the temperature of the reduction catalyst, and the adsorption amount of ammonia in the reduction catalyst. A required injection amount calculation unit for calculating the injection amount, a reducing agent injection control unit for injecting the reducing agent from the reducing agent injection device according to the required injection amount, and a specification sensitive to at least NOx and ammonia provided downstream of the reduction catalyst An injection amount abnormality determination unit that compares the sensor value of the gas concentration sensor with a predetermined threshold value to determine an abnormality in the actual injection amount of the reducing agent, and an abnormality in the actual injection amount occurs. When the, and the injection amount calculation parameter value correction unit for correcting the parameter values of the required injection amount calculation unit, when the abnormality of the actual injection quantity is observed even after a predetermined number of times the correction parameter value, the required injection amount An injection amount correction unit that corrects the required injection amount by multiplying the value of the required injection amount calculated by the calculation unit by a predetermined system correction coefficient, and the injection amount abnormality determination unit has a sensor value that is a threshold value. Is exceeded, the amount of adsorption of ammonia in the reduction catalyst is corrected to increase, and control is performed to reduce the injection amount of the reducing agent below the required injection amount, and the sensor value after a predetermined time is below the threshold value In this case, it is determined that the injection amount is excessive, and when the sensor value after a predetermined time has exceeded the threshold value, it is determined that the injection amount is insufficient. The injection amount correction unit is determined by the injection amount abnormality determination unit. The results When the system correction coefficient is set based on the history and the required injection amount is corrected by multiplying the predetermined system correction coefficient, the system correction coefficient is There is provided a reducing agent injection control device characterized by correcting , and the above-described problems can be solved.

According to the present invention, a reducing agent capable of generating ammonia is injected upstream of a reduction catalyst that is connected to an exhaust system of an internal combustion engine and adsorbs ammonia and reduces NOx in exhaust gas flowing in using ammonia. In the reducing agent injection control device for controlling the reducing agent injection device, the request for the reducing agent is based on parameter values including at least the amount of NOx discharged from the internal combustion engine, the temperature of the reduction catalyst, and the adsorption amount of ammonia in the reduction catalyst. A required injection amount calculation unit for calculating the injection amount, a reducing agent injection control unit for injecting the reducing agent from the reducing agent injection device according to the required injection amount, and a specification sensitive to at least NOx and ammonia provided downstream of the reduction catalyst An injection amount abnormality determination unit that compares the sensor value of the gas concentration sensor with a predetermined threshold value to determine an abnormality in the actual injection amount of the reducing agent, and an abnormality in the actual injection amount occurs. The injection amount calculation parameter value correction unit that corrects the parameter value of the required injection amount calculation unit, and the required injection amount when an abnormality in the actual injection amount is observed after the parameter value is corrected a predetermined number of times. The injection amount correction unit that corrects the required injection amount by multiplying the value of the required injection amount calculated by the arithmetic unit by a predetermined system correction coefficient, and the self that performs abnormality diagnosis of each unit constituting the reducing agent injection device An injection amount abnormality determination unit that increases the amount of adsorption of ammonia in the reduction catalyst when the sensor value exceeds a threshold value, thereby correcting the injection amount of the reducing agent from the required injection amount. When the sensor value after a predetermined time elapses is less than or equal to the threshold, it is determined that the injection amount is excessive, and when the sensor value after the predetermined time elapses exceeds the threshold, it is determined that the injection amount is insufficient. Is a thing The injection amount correction unit sets a system correction coefficient based on the diagnosis result of the self-diagnosis unit, and after correcting the required injection amount by multiplying by a predetermined system correction coefficient, an abnormality in the actual injection amount is observed. A reducing agent injection control device is provided that corrects the system correction coefficient when possible, and can solve the above-described problems.

Further, another aspect of the present invention is capable of generating ammonia on the upstream side of a reduction catalyst that is connected to an exhaust system of an internal combustion engine and that adsorbs ammonia and reduces NOx in the inflowing exhaust gas using ammonia. In a control method for a reducing agent injection device for injecting a reducing agent, a required injection amount of the reducing agent based on parameter values including at least the amount of NOx discharged from the internal combustion engine, the temperature of the reduction catalyst, and the adsorption amount of ammonia in the reduction catalyst The sensor value of the specific gas concentration sensor that is sensitive to at least NOx and ammonia provided downstream of the reduction catalyst while injecting the reducing agent according to the required injection amount is compared with a predetermined threshold value. When the value exceeds the threshold, the amount of ammonia adsorbed on the reduction catalyst is corrected to increase, thereby reducing the injection amount of the reducing agent from the required injection amount. When the sensor value after a predetermined time elapses is less than or equal to the threshold, it is determined that the injection amount is excessive, and when the sensor value after the predetermined time elapses exceeds the threshold, it is determined that the injection amount is insufficient. After determining the abnormality of the actual injection amount of the reducing agent and correcting the parameter value used for calculating the required injection amount when the abnormality of the actual injection amount occurs, the parameter value is corrected a predetermined number of times. When the actual injection amount is abnormal, the required injection amount is corrected by multiplying the calculated required injection amount value by a predetermined system correction coefficient. Refer to the history of the determination result of the amount abnormality, set the system correction coefficient based on the history, and after correcting the required injection amount by multiplying by the predetermined system correction coefficient, the abnormality of the actual injection amount When seen A method of controlling the reducing agent injection apparatus characterized by correcting the Temu correction coefficient.

Further, another aspect of the present invention is capable of generating ammonia on the upstream side of a reduction catalyst that is connected to an exhaust system of an internal combustion engine and that adsorbs ammonia and reduces NOx in the inflowing exhaust gas using ammonia. In a control method for a reducing agent injection device for injecting a reducing agent, a required injection amount of the reducing agent based on parameter values including at least the amount of NOx discharged from the internal combustion engine, the temperature of the reduction catalyst, and the adsorption amount of ammonia in the reduction catalyst The sensor value of the specific gas concentration sensor that is sensitive to at least NOx and ammonia provided downstream of the reduction catalyst while injecting the reducing agent according to the required injection amount is compared with a predetermined threshold value. When the value exceeds the threshold, the amount of ammonia adsorbed on the reduction catalyst is corrected to increase, thereby reducing the injection amount of the reducing agent from the required injection amount. When the sensor value after a predetermined time elapses is less than or equal to the threshold, it is determined that the injection amount is excessive, and when the sensor value after the predetermined time elapses exceeds the threshold, it is determined that the injection amount is insufficient. After determining the abnormality of the actual injection amount of the reducing agent and correcting the parameter value used for calculating the required injection amount when the abnormality of the actual injection amount occurs, the parameter value is corrected a predetermined number of times. When the actual injection amount is abnormal, the required injection amount is corrected by multiplying the calculated required injection amount value by a predetermined system correction factor. The actual injection amount even after the required injection amount is corrected by setting the system correction coefficient based on the diagnosis result of the self-diagnosis that performs abnormality diagnosis of each part constituting the injection device and multiplying by the predetermined system correction coefficient Abnormalities A method of controlling the reducing agent injection apparatus characterized by correcting the system correction coefficient when seen.

Further, another aspect of the present invention is a reduction catalyst that is connected to an exhaust system of an internal combustion engine and that adsorbs ammonia and reduces NOx in exhaust gas flowing in using ammonia, and a reducing agent capable of generating ammonia. In an exhaust gas purification apparatus for an internal combustion engine comprising a reducing agent injection device for injecting the gas upstream of the reduction catalyst and a control device for controlling the reducing agent injection device, at least NOx and ammonia are provided downstream of the reduction catalyst. The control device is provided with a sensitive specific gas concentration sensor, and the control device is based on parameter values including at least the amount of NOx discharged from the internal combustion engine, the temperature of the reduction catalyst, and the amount of adsorption of ammonia in the reduction catalyst. A required injection amount calculation unit that calculates a reducing agent injection control unit that injects a reducing agent from the reducing agent injection device according to the required injection amount, and a specific gas concentration The sensor value of the sensor is compared with a predetermined threshold value to determine an abnormality in the actual injection amount of the reducing agent, and when an abnormality in the actual injection amount occurs, The injection amount calculation parameter value correction unit that performs correction, and the value of the required injection amount that is calculated by the required injection amount calculation unit when an abnormality in the actual injection amount is observed even after the parameter value is corrected a predetermined number of times. An injection amount correction unit that corrects the required injection amount by multiplying by a predetermined system correction coefficient, and the injection amount abnormality determination unit is configured to adsorb the amount of ammonia in the reduction catalyst when the sensor value exceeds a threshold value. Control to reduce the injection amount of the reducing agent below the required injection amount by correcting the value of the amount to increase, and if the sensor value after the predetermined time elapses below the threshold, it is determined that the injection amount is excessive, and the predetermined time has elapsed Later sensor value is threshold When exceeding, it is determined that the injection amount is insufficient, and the injection amount correction unit refers to the history of the determination result determined by the injection amount abnormality determination unit, sets the system correction coefficient based on the history, An exhaust purification device for an internal combustion engine , wherein the system correction coefficient is corrected when an abnormality in the actual injection amount is observed even after the required injection amount is corrected by multiplying by a predetermined system correction coefficient. .

Further, another aspect of the present invention is a reduction catalyst that is connected to an exhaust system of an internal combustion engine and that adsorbs ammonia and reduces NOx in exhaust gas flowing in using ammonia, and a reducing agent capable of generating ammonia. In an exhaust gas purification apparatus for an internal combustion engine comprising a reducing agent injection device for injecting the gas upstream of the reduction catalyst and a control device for controlling the reducing agent injection device, at least NOx and ammonia are provided downstream of the reduction catalyst. The control device is provided with a sensitive specific gas concentration sensor, and the control device is based on parameter values including at least the amount of NOx discharged from the internal combustion engine, the temperature of the reduction catalyst, and the amount of adsorption of ammonia in the reduction catalyst. A required injection amount calculation unit that calculates a reducing agent injection control unit that injects a reducing agent from the reducing agent injection device according to the required injection amount, and a specific gas concentration The sensor value of the sensor is compared with a predetermined threshold value to determine an abnormality in the actual injection amount of the reducing agent, and when an abnormality in the actual injection amount occurs, The injection amount calculation parameter value correction unit that performs correction, and the value of the required injection amount that is calculated by the required injection amount calculation unit when an abnormality in the actual injection amount is observed even after the parameter value is corrected a predetermined number of times. An injection amount correction unit that corrects the required injection amount by multiplying by a predetermined system correction coefficient, and a self-diagnosis unit that performs abnormality diagnosis of each part constituting the reducing agent injection device, the injection amount abnormality determination unit is When the sensor value exceeds the threshold value, the amount of ammonia adsorbed on the reduction catalyst is corrected to be increased to correct the reducing agent injection amount below the required injection amount. Is below threshold In this case, it is determined that the injection amount is excessive, and when the sensor value after a predetermined time has exceeded the threshold value, it is determined that the injection amount is insufficient. The injection amount correction unit is based on the diagnosis result of the self-diagnosis unit. The system correction coefficient is corrected when an abnormality is found in the actual injection quantity even after the required injection quantity is corrected by setting the system correction coefficient and multiplying by a predetermined system correction coefficient. An exhaust emission control device for an internal combustion engine.

According to the reducing agent injection control device and the control method of the reducing agent injection device of the present invention, when the sensor value of the predetermined specific gas concentration sensor exceeds a predetermined threshold, it is determined that the actual injection amount of the reducing agent is abnormal, By correcting the parameter value used for calculating the required injection amount of reducing agent, the parameter value caused by the deterioration of the parts that make up the reducing agent injection device or the deviation of the calculated value caused by the passage of time, etc. The error is reset. Therefore, the calculated required injection amount of the reducing agent is optimized, the excess or deficiency of the actual injection amount of the reducing agent injected according to the required injection amount is eliminated, and the ammonia or NO _x to the downstream side of the reduction catalyst is eliminated. Outflow is prevented.

  Further, in the reducing agent injection control device of the present invention, the injection amount abnormality determining unit increases or decreases the actual injection amount of the reducing agent from the required injection amount, and compares the sensor value after a predetermined time with a threshold value. By determining whether the actual injection amount is excessive or insufficient, it is accurately determined whether the actual injection amount is excessive or insufficient. Therefore, when the parameter value used for calculating the required injection amount of the reducing agent is corrected, it is accurately determined whether to increase or decrease, and the actual injection amount of the reducing agent can be quickly determined. It is optimized.

  Further, in the reducing agent injection control device of the present invention, the injection amount abnormality determination unit increases the value of the actual adsorption amount of ammonia in the reduction catalyst to reduce the actual injection amount of the reducing agent from the required injection amount. By determining whether the actual injection amount of the reducing agent is excessive or insufficient, it is possible to determine an abnormality in the actual injection amount of the reducing agent without increasing the amount of ammonia flowing out downstream of the reduction catalyst.

  Further, in the reducing agent injection control apparatus of the present invention, when the abnormality of the actual reducing agent injection amount is not resolved even after the parameter value is corrected a predetermined number of times, the calculated reducing agent required injection amount value By providing an injection amount correction unit that corrects the injection amount by multiplying by a predetermined system correction coefficient, the deviation of the calculated value of the required injection amount due to some malfunction of the reducing agent injection device, which is not an error in the parameter value, is eliminated Thus, excess / shortage of the actual injection amount of the reducing agent injected in accordance with the required injection amount is optimized.

  Further, in the reducing agent injection control device of the present invention, the injection amount correction unit is configured to operate the system when an abnormality in the actual injection amount of the reducing agent is observed even after correcting the injection amount by multiplying by a predetermined system correction coefficient. By correcting the correction coefficient, the required injection amount is optimized according to the degree of some malfunction that has occurred in the reducing agent injection device.

  Further, in the reducing agent injection control device of the present invention, the injection amount correction unit sets the system correction coefficient in consideration of the history of excess or shortage of the reducing agent injection amount so far, so that the actual reducing agent injection amount The required injection amount is appropriately increased or decreased in response to the excessive state or the insufficient state, and the actual injection amount of the reducing agent is quickly optimized.

  Further, in the reducing agent injection control device of the present invention, the injection amount correction unit sets a system correction coefficient based on an abnormality diagnosis result of each unit constituting the reducing agent injection device, so that each part of the reducing agent injection device The system correction coefficient is set according to the current state, and the actual injection amount of the reducing agent is optimized accurately.

Further, according to the exhaust gas purification apparatus for an internal combustion engine of the present invention, the abnormality of the actual injection amount of the reducing agent is determined using the predetermined specific gas concentration sensor and the sensor value of the specific gas concentration sensor, and the actual injection amount And a control device that corrects the parameter value used for calculating the required injection amount of the reducing agent in the case where the abnormality occurs, the error of the parameter value used for calculating the required injection amount of the reducing agent can be reduced. Reset is performed and the calculated required injection amount of the reducing agent is optimized. Accordingly, there is provided an exhaust emission control device for an internal combustion engine that eliminates the excess or deficiency of the actual injection amount of the reducing agent that is injected according to the required injection amount and prevents the outflow of ammonia or NO _x to the downstream side of the reduction catalyst.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments relating to a reducing agent injection control device, a reducing agent injection device control method, and an exhaust gas purification device for an internal combustion engine according to the present invention will be specifically described below with reference to the drawings as appropriate. However, this embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention. In addition, what attached | subjected the same code | symbol in each figure has shown the same member, and description is abbreviate | omitted suitably.

1. 1. Internal configuration of exhaust gas purification apparatus for internal combustion engine (1) Overall configuration of exhaust gas purification apparatus First, a configuration example of an exhaust gas purification apparatus for an internal combustion engine according to this embodiment provided with a reducing agent injection control device will be described with reference to FIG.
An exhaust purification device 10 shown in FIG. 1 is an exhaust purification device that uses an aqueous urea solution as a liquid reducing agent and selectively reduces NO _x in exhaust gas by a reduction catalyst 13. The exhaust purification device 10 includes a reduction catalyst 13 disposed in the exhaust passage 11 of the internal combustion engine 5, and a reducing agent injection device 40 for injecting a reducing agent into the exhaust passage 11 upstream of the reduction catalyst 13. It has. An upstream temperature sensor 26 is provided on the upstream side of the reduction catalyst 13, and a downstream temperature sensor 27 and a NO _X sensor 15 as a specific gas concentration sensor are provided on the downstream side of the reduction catalyst 13.

Further, the exhaust purification device 10 includes a control device (reducing agent injection control device) 30 for performing the reducing agent injection control by the reducing agent injection device 40. This control device 30 is not only the sensor values of all sensors provided in the exhaust purification device 10, but also the operating conditions of the internal combustion engine 5 including the fuel injection amount Qf, the injection timing TM, the rotational speed Ne, etc. of the internal combustion engine 5. Can also be read.
The control device may be configured to be separated into a control device for controlling the exhaust purification device 10 and a control device for controlling the operating conditions of the internal combustion engine.

The internal combustion engine 5 that discharges exhaust gas typically includes a diesel engine or a gasoline engine. However, the present invention is suitable for a diesel engine that is currently subject to NO _x purification. .

  The liquid reducing agent accommodated in the storage tank 41 is preferably used as long as ammonia is generated before reaching the reduction catalyst 13, and typical examples thereof include an aqueous urea solution and an aqueous ammonia solution.

As the reduction catalyst 13, a catalyst having a function of adsorbing ammonia generated from the reducing agent supplied by the reducing agent injection device 40 and selectively reducing NO _x in the inflowing exhaust gas is used. Such a reduction catalyst 13 is not particularly limited as long as it has a function of adsorbing ammonia. For example, a zeolite-based reduction catalyst is used.
The reduction catalyst 13 having such an ammonia adsorption function has a characteristic that the temperature of the reduction catalyst 13 and the saturated adsorption amount of ammonia are in inverse proportion, and the saturated adsorption amount of ammonia decreases as the catalyst temperature becomes higher. doing.

  The upstream temperature sensor 26 and the downstream temperature sensor 27 are used for measuring the temperature of the exhaust gas at each location. In addition, when estimating the temperature of the upstream and downstream of the reduction catalyst 13 by calculation, these temperature sensors may be omitted.

The NO _X sensor 15 is basically used for measuring the NO _X concentration in the exhaust gas, but the NO _X sensor 15 used in the exhaust purification device 10 of the present embodiment is also configured to be ammonia. It has sensitive characteristics. Therefore, when the injection amount of the reducing agent becomes excessive, ammonia flows out to the downstream side of the reduction catalyst 13 and is detected by the NO _X sensor 15, while when the injection amount of the reducing agent is insufficient, the NO _{X that} has not been reduced is It flows out downstream of the reduction catalyst 13 and is detected by the NO _x sensor 15. In the control device 30, the reducing agent injection amount is adjusted so that the sensor value of the NO _x sensor 15 does not exceed a predetermined threshold value.

FIG. 2 shows the relationship between the amount of ammonia in the reduction catalyst 13 and the sensor value of the NO _x sensor 15. As shown in FIG. 2, when the amount of ammonia in the reduction catalyst 13 is small, NO _X that is not reduced in the reduction catalyst 13 increases. Therefore, the NO _X concentration on the downstream side of the reduction catalyst 13 is in the reduction catalyst 13. The lower the amount of ammonia, the higher. On the other hand, when the amount of ammonia in the reduction catalyst 13 is large, the amount of ammonia that cannot be adsorbed on the reduction catalyst 13 increases. Therefore, the ammonia concentration on the downstream side of the reduction catalyst 13 increases as the amount of ammonia in the reduction catalyst 13 increases. .
Therefore, if the sensor value Snox of the NO _X sensor 15 is close to the lowest point P, there is no excess or deficiency in the actual injection amount Qudact of the reducing agent, so the sensor value Snox of the NO _X sensor 15 is The reducing agent injection amount is calculated so as to be less than the threshold value Sn0.

(2) Reducing agent injection device The reducing agent injection device 40 provided in the exhaust purification device 10 of this embodiment includes a reducing agent injection valve 43 fixed to the exhaust passage 11 upstream of the reduction catalyst 13 and a predetermined amount. A storage tank 41 in which a liquid reducing agent having a concentration is stored, and a pump 42 that pumps the reducing agent in the storage tank 41 to the reducing agent injection valve 43 are provided. A first supply passage 44 is connected between the storage tank 41 and the pump 42, and a second supply passage 45 is connected between the pump 42 and the reducing agent injection valve 43.

  Among these, as the pump 42, for example, an electric diaphragm pump is used. In the reducing agent injection device 40 provided in the exhaust purification device 10 of the present embodiment, the pump 42 is controlled so that the sensor value of the pressure sensor 47 provided in the second supply passage 45 is maintained at a predetermined value. Feedback control by the device 30 is performed.

  As the reducing agent injection valve 43, for example, an electromagnetic reducing agent injection valve whose opening and closing is controlled by ON / OFF of energization is used. In the reducing agent injection device 40 provided in the exhaust purification device 10 of the present embodiment, the pressure of the reducing agent in the second supply passage 45 is maintained at a predetermined value by feedback control of the pump 42, and the reducing agent injection valve 43 is When the valve is opened, the reducing agent is injected into the exhaust passage 11.

  Note that the reducing agent injection device 40 provided in the exhaust purification device 10 of the present embodiment sprays a liquid reducing agent by the reducing agent injection valve 43 to atomize, but in the present invention, the reducing agent injection. The configuration of the device 40 is not particularly limited. For example, the device 40 may be an air-assisted reductant injection device that supplies high-pressure air into the exhaust passage after forming a liquid reductant into a mist. it can.

(3) Control device (reducing agent injection control device)
FIG. 3 shows a configuration example in which a portion related to the injection control of the reducing agent is represented by a functional block in the control device 30 provided in the exhaust purification device 10 of the present embodiment.
The control device 30 includes a pump drive control unit (indicated as “pump control” in FIG. 3), a required injection amount calculation unit (indicated as “Qudtgt calculation” in FIG. 3), a reducing agent injection valve control unit ( In FIG. 3, it is expressed as “Udv control”, an injection amount abnormality determination unit (in FIG. 3, “abnormality determination”), and an injection amount calculation parameter value correction unit (in FIG. 3, “calculation pmt correction”). ), A self-diagnosis unit (indicated as “self-diagnosis” in FIG. 3), and an injection amount correction unit (indicated as “Qudtgt correction” in FIG. 3). Specifically, each of these units is realized by executing a program by a microcomputer (not shown).

(3) -1 Pump Drive Control Unit The pump drive control unit receives the sensor value Spu of the pressure sensor 47 indicating the pressure of the reducing agent in the second supply passage 45, and feedback of the pump 42 based on the sensor value Spu. Take control. The pressure in the second supply passage 45 is maintained at 0.5 MPa, for example.

(3) -2 Required Injection Amount Calculation Unit The required injection amount calculation unit calculates the required injection amount Qudtgt of the reducing agent to be injected from the reducing agent injection device 40 using a preset arithmetic expression. The calculated required injection amount Qudtgt is transmitted to the reducing agent injection valve control unit.

FIG. 4 is a diagram conceptually showing a calculation process of the required injection amount Qudtgt of the reducing agent by the required injection amount calculation unit of the control device 30 provided in the exhaust purification device 10 of the present embodiment.
As shown in FIG. 4, the required injection amount calculating unit, based on the operating conditions of the internal combustion engine 5, together with the estimated mass flow Fnox of the NO _X discharged from the internal combustion engine 5, a NO _X of the mass flow The mass flow rate Fnh3 of ammonia necessary for 100% reduction is calculated. Further, a reduction efficiency η determined based on the temperature Tcat of the catalyst 13 and the amount of ammonia currently adsorbed on the reduction catalyst 13 (hereinafter referred to as “actual adsorption amount”) Vact with respect to the mass flow rate Fnh3 of ammonia. And a correction obtained based on parameter values such as the temperature Tcat of the catalyst 13, the mass flow rate Fgas of the exhaust gas, the NO _x concentration Dnox in the exhaust gas, and the ratio Rno2 of NO _{2 in} the NO _x flowing into the reduction catalyst 13. By multiplying the coefficient, the required injection amount Qudtgt of the reducing agent to be injected from the reducing agent injection device 40 is calculated.

More specifically, the required injection amount calculation unit calculates the reduction efficiency by the reduction catalyst 13 estimated based on the temperature Tcat of the reduction catalyst 13 and the actual adsorption amount Vact of ammonia with respect to the calculated ammonia mass flow rate Fnh3. A second coefficient selected based on the temperature Tcat of the reduction catalyst 13 and the mass flow rate Fgas of the exhaust gas and the first coefficient fac1 selected based on the temperature Tcat of the reduction catalyst 13 and the NO _x concentration Dnox. Is multiplied by the temperature Tcat of the reduction catalyst 13 and the third coefficient fac3 selected based on the ratio Rno2 of NO _{2 in} NO _x to calculate the required injection amount Qudtgt of the reducing agent.

Among them, the mass flow rate Fnox mass flow Fgas and NO _X in the exhaust gas, NO _X concentration Dnox in the exhaust gas, the rotational speed Ne and the fuel injection amount Qf of the internal combustion engine 5, the fuel injection timing TM, the accelerator operation amount Ac such as It is estimated based on the operating conditions. Further, the mass flow rate Fnh3 of ammonia corresponding to the mass flow rate Fnox of NO _x is calculated on the assumption that a reduction reaction represented by NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O occurs in the reduction catalyst 13.

The temperature Tcat of the reduction catalyst 13 is estimated based on the sensor value Tu of the upstream temperature sensor 26 and the sensor value Tl of the downstream temperature sensor 27. Further, the ratio Rno2 of NO _{2 in} NO _X flowing into the reduction catalyst 13 is estimated using a sensor value of a NO _X sensor (not shown) provided on the upstream side of the reduction catalyst 13, or the internal combustion engine 5 It is possible to estimate it using the operating state, exhaust gas temperature, and the like.

Furthermore, the actual adsorption amount Vact of ammonia in the reduction catalyst 13, for example, from the amount of ammonia generated from the reducing agent injected actually into the exhaust passage 11, by subtracting the amount of ammonia used for the reduction of the NO _X value Is added to the amount of ammonia already adsorbed on the reduction catalyst 13. That is, the actual adsorption amount Vact of ammonia, the amount of ammonia generated from the reducing agent injected actually into the exhaust passage 11 so far, a value obtained by subtracting the amount of ammonia used for the reduction of the NO _X are integrated Value.

  The required injection amount calculation unit stores a map map1 in advance so that the reduction efficiency η of the reduction catalyst 13 is selected corresponding to the temperature Tcat of the reduction catalyst 13 and the actual adsorption amount Vact of ammonia. Maps map2 to map4 are stored in advance so that the first to third coefficients fac1 to fac3 are selected corresponding to the respective parameter values.

  The correction coefficient used when calculating the required injection amount Qudtgt of the reducing agent is not limited to the first to third coefficients fac1 to fac3 described above, but also, for example, the degree of deterioration of the reduction catalyst 13 and the carbonization in the reduction catalyst 13. You may multiply by the correction coefficient etc. which are determined based on the adsorption amount etc. of hydrogen (HC).

(3) -3 Reductant Injection Valve Control Unit The reductant injection valve control unit performs reductant injection so that the reductant of the required injection amount Qudtgt calculated by the required injection amount calculation unit is injected into the exhaust passage 11. Operation control of the reducing agent injection valve 43 of the apparatus 40 is performed. For example, the injection amount of the reducing agent is adjusted by adjusting the ON / OFF duty ratio of energization supplied to the reducing agent injection valve 43.

(3) -4 injection amount abnormality determination unit injection amount abnormality determination section detects the sensor value Snox of the NO _X sensor 15 provided downstream of the reduction catalyst 13, comparing the sensor value Snox with a predetermined threshold Sn0 Then, the abnormality of the actual injection amount Qudact of the reducing agent actually injected from the reducing agent injection device 40 is determined. As described above, when an excess or deficiency of the actual injection amount Qudact of the reducing agent with respect to the originally required reducing agent injection amount occurs, either excessive ammonia or unreduced NO _X is downstream of the reduction catalyst 13. To the side. Then, since the NO _X sensor 15 is sensitive to ammonia and NO _X , the sensor value Snox of the NO _X sensor 15 increases. Therefore, by setting the threshold value Sn0 sensor values allowed in accordance with the tolerance of ammonia or NO _X flowing downstream of the reduction catalyst 13, the coercive sensor value Snox below the threshold Sn0 of the NO _X sensor 15 By determining whether or not it is hit, it is determined whether the reducing agent injection amount is excessive or insufficient. The determination result by the injection amount abnormality determination unit is sent to the injection amount calculation parameter value correction unit and the injection amount correction unit.

(3) -5 Injection amount calculation parameter value correction unit When the injection amount abnormality determination unit determines that the actual injection amount Qudact of the reducing agent is excessive or insufficient, the injection amount calculation parameter value correction unit In particular, at least one of the parameters is corrected.
In the control device 30 of the present embodiment, among the parameters, the temperature Tcat of the reduction catalyst 13, the exhaust gas mass flow rate Fgas, the NO _x concentration Dnox in the exhaust gas, and the NO _{2 in} the NO _x flowing into the reduction catalyst 13. The ratio Rno2 is obtained by calculation based on the operating conditions of the internal combustion engine 5 each time, while the actual adsorption amount Vact of ammonia in the reduction catalyst 13 is an integrated value. For this reason, once the calculated value of the actual adsorption amount Vact of ammonia deviates from the actual value, the deviation of the calculated value thereafter is not eliminated, and the calculated required injection amount Qudtgt becomes excessive or insufficient. Therefore, the injection amount calculation parameter value correction unit of the control device 30 of the present embodiment corrects the value of the actual adsorption amount Vact of ammonia used for calculating the required injection amount Qudtgt, and the calculated required injection amount Qudtgt is optimized. It has become so.

Specifically, the injection amount calculation parameter value correction unit first performs a correction to increase the value of the actual adsorption amount Vact of ammonia in the reduction catalyst 13 when excess or deficiency of the actual injection amount Qudact of the reducing agent occurs. As a result, the calculated required injection amount Qudtgt is decreased. When the cause that the sensor value Snox of the NO _X sensor 15 is equal to or greater than the threshold value Sn0 is the excessive state of the actual injection amount Qudact of the reducing agent, the value of the actual adsorption amount Vact of ammonia used for calculating the required injection amount Qudtgt is set. performs increasing correction, by reducing the required injection amount Qudtgt calculated by the sensor value Snox of the NO _X sensor 15 drops below the threshold Sn0, a fair calculated value of the required injection amount Qudtgt subsequent reducing agent It becomes.

Meanwhile, due to sensor value Snox of the NO _X sensor 15 has become the threshold value Sn0 or, when in a shortage state of the actual injection quantity Qudact of reducing agent, when a correction to increase the value of the actual adsorption amount Vact ammonia Further, the sensor value Snox of the NO _X sensor 15 increases. In such a case, the injection amount calculation parameter value correction unit performs a correction to reduce the value of the actual adsorption amount Vact of ammonia used for calculation of the required injection amount Qudtgt, and increases the calculated required injection amount Qudtgt to obtain NO. The sensor value Snox of the _X sensor 15 falls below the threshold value Sn0, and the subsequent calculated value of the required injection amount Qudtgt of the reducing agent is optimized.

FIGS. 5A to 5B show a method for optimizing the required injection amount Qudtgt of the reducing agent performed by the injection amount calculation parameter value correcting unit of the control device 30 provided in the exhaust purification device 10 of the present embodiment. It is a time chart for demonstrating. 5A and 5B all show the sensor value Snox (ppm) of the NO _x sensor 15, the actual adsorption amount Vact (g) of ammonia in the reduction catalyst 13, and the actual injection amount Qudact (mg / s) of the reducing agent. , And the time-dependent change in the mass flow rate Flnox (mg / s) of NO _x on the downstream side of the reduction catalyst 13, and FIG. 5A shows the case where the actual injection amount Qudact of the reducing agent is excessive. FIG. 5B shows a case where the actual injection amount Qudact of the reducing agent is insufficient.

When the actual injection amount Qudact of the reducing agent is excessive, as shown in FIG. 5A, the NO _x mass flow rate Flnox on the downstream side of the reduction catalyst 13 is lower than the target value, and is adsorbed on the reduction catalyst 13. since completely not ammonia flows out to the downstream side of the reduction catalyst 13, the sensor value Snox of the NO _X sensor 15 gradually increases (the period of t0 to t1).
On the other hand, as shown in FIG. 5B, when the actual injection amount Qudact of the reducing agent is insufficient, NO _{X that} has not been reduced flows out downstream of the reduction catalyst 13, and downstream of the reduction catalyst 13. since the mass flow Flnox side of the NO _X exceeds the target value, also the sensor value Snox of the NO _X sensor 15 gradually increases (the period of t10 to t11).
At this time, it is not clear whether NO _x or ammonia is flowing out downstream of the reduction catalyst 13.

In either case of FIG. 5 (a) ~ (b) , the continued increase in the sensor values Snox of the NO _X sensor 15 exceeds a threshold value Sn0, the injection amount calculation parameter value correction unit, the required injection amount of the reducing agent Correction for increasing the actual adsorption amount Vact of ammonia used for the calculation of Qudtgt is performed (time t1 in FIG. 5A and time t11 in FIG. 5B). As a result, the required injection amount Qudtgt of the reducing agent calculated by the required injection amount calculation unit is reduced, and the actual injection amount Qudact of the reducing agent injected based on the calculated value decreases (t1 in FIG. 5A). ~ T2 period and t11 ~ t12 period of FIG. 5B).
Then, in the case of FIG. 5A in which the reducing agent actual injection amount Qudact is excessive, the increase rate of the sensor value Snox of the NO _X sensor 15 becomes smaller as the reducing agent actual injection amount Qudact decreases. Go. On the other hand, in the case of FIG. 5B in which the reducing agent actual injection amount Qudact is insufficient, the sensor value Snox of the NO _X sensor 15 continues to increase as the reducing agent actual injection amount Qudact decreases.

However, in any of the cases shown in FIGS. 5A to 5B, the sensor value Snox of the NO _X sensor 15 does not fall below the threshold value Sn0 just by reducing the actual injection amount Qudact of the reducing agent once. In the injection amount calculation parameter value correction unit, correction for increasing the actual adsorption amount Vact of ammonia in the reduction catalyst 13 is performed again (at time t2 in FIG. 5A and time t12 in FIG. 5B). . As a result, the required injection amount Qudtgt of the reducing agent calculated by the required injection amount calculation unit is continuously reduced, and the actual injection amount Qudact of the reducing agent injected based on the calculated value decreases (see FIG. 5A). the period from t2 to t3 and the period from t12 to t13 in FIG. 5B). At this time, in the example shown in FIGS. 5A to 5B, the second increase correction width a2 when correcting the actual adsorption amount Vact of ammonia is made larger than the first increase correction width a1. In addition, the actual injection amount Qudact of the reducing agent is decreasing step by step. The interval of the reducing agent injection start timing is, for example, about 20 seconds.

Thus, the injection amount calculation parameter value correcting unit, until the sensor value Snox of the NO _X sensor 15 is below a threshold Sn0, the actual adsorption amount of ammonia while gradually increasing the increasing correction width a1~an each inning Vact increase correction is repeated. In the optimization process of the reducing agent injection amount shown in FIGS. 5A to 5B, two determination thresholds n1 and n2 (n1 <n2) are set, and the number of corrections of the actual adsorption amount Vact of ammonia. There whereas it is determined that the actual injection quantity Qudact of the reducing agent when the sensor value Snox of the NO _X sensor 15 below n1 times has dropped below a threshold Sn0 is excessive, the number of corrections of the actual adsorption amount Vact of ammonia n2 is the actual injection quantity Qudact of reducing agent is determined to be insufficient when the sensor value Snox of the nO _X sensor 15 is not reduced to less than the threshold value Sn0 be. In the example of FIGS. 5A to 5B, n1 = 4 and n2 = 10 are set. However, the set values are the intervals of the reducing agent injection start timing and the correction widths a1 to an for each time. It can be arbitrarily set depending on the difference between the two or the determination accuracy.

In the case of FIG. 5A in which the reducing agent actual injection amount Qudact is excessive while the reducing agent actual injection amount Qudact is being reduced in this way, in the case of FIG. sensor values Snox of the NO _X sensor 15 corrects the two went time (t2) starts to decrease, when the correction was carried out four times the actual adsorption amount Vact ammonia (t4), the sensor value of the NO _X sensor 15 Snox falls below the threshold value Sn0. As a result, thereafter, the required injection amount Qudtgt of the reducing agent can be calculated appropriately without correcting the actual adsorption amount Vact of ammonia. In this case, it is recorded that the actual injection amount Qudact of the reducing agent is excessive.

On the other hand, when reducing agent actual injection amount Qudact is reduced while reducing agent actual injection amount Qudact is insufficient, in FIG. 5B, the actual ammonia adsorption amount Vact is corrected. The sensor value Snox of the NO _x sensor 15 exceeds the threshold value Sn0 even when it is performed 10 times (t20). In this case, it is recorded that the actual injection amount Qudact of the reducing agent is insufficient, and the actual adsorption amount Vact of ammonia is now corrected to decrease (at time t21 in FIG. 5B) and calculated. The required injection amount Qudtgt of the reducing agent is increased. As a result, the actual injection amount Qudact of the reducing agent increases and the amount of NO _X that flows out downstream of the reduction catalyst 13 without being reduced decreases, so the sensor value Snox of the NO _X sensor 15 falls below the threshold value Sn0. Therefore, thereafter, the required injection amount Qudtgt of the reducing agent can be calculated appropriately without correcting the actual adsorption amount Vact of ammonia.

Incidentally, while the number of corrections of the actual adsorption amount Vact ammonia exceeds the threshold n1, when the sensor value Snox of the NO _X sensor 15 when less than the threshold n2 falls below the threshold value Sn0 is, as described above, since the reduction Although the required injection amount Qudtgt of the agent is properly calculated, it is not recognized that the reducing agent is excessive or insufficient, but is handled as an error range.

(3) -6 Self-diagnosis unit The self-diagnosis unit diagnoses whether any part of the reducing agent injection device 40 is abnormal. Such an abnormality diagnosis method for each part is not particularly limited, and various diagnosis methods can be employed. Specifically, the first supply passage 44, the second supply passage 45, or the reducing agent injection valve 43 constituting the reducing agent injection device 40 is diagnosed as to whether it is clogged, an error in each sensor value, or the like. . In the control device 30 provided in the exhaust purification device 10 of the present embodiment, the diagnosis result in the self-diagnosis unit is transmitted to the injection amount correction unit.

(3) -7 Injection amount correction unit The injection amount correction unit is configured to reduce the actual injection amount Qudact of the reducing agent even after the optimization of the required injection amount Qudtgt performed by the injection amount calculation parameter value correction unit. When excess or deficiency occurs, this time, the required injection amount Q _am udtgt after correction is calculated by multiplying the required injection amount Qudtgt calculated by the required injection amount calculation unit by a predetermined system correction coefficient α. To do. In this case, thereafter, the corrected required injection amount Q _am udtgt is transmitted to the reducing agent injection valve control unit, and the reducing agent injection control is performed based on the corrected required injection amount Q _am udtgt.

Here, in the control device 30 provided in the exhaust purification device 10 of the present embodiment, when the required injection amount Qudtgt is corrected by the injection amount correction unit, it is recorded in the injection amount calculation parameter value correction unit. The system correction coefficient α is set in consideration of the history of determination results of excess / deficiency of the actual reducing agent injection quantity Qudact. Specifically, when it is estimated that the actual reducing agent actual injection amount Qudact is in an excess state from the history of determination results of excess or insufficient actual reducing agent injection amount Qudact, The system correction coefficient α is set to a value of α <1 so that the required injection amount Q _am udtgt is reduced. On the other hand, when it is estimated that the actual injection amount Qudact of the reducing agent is in an insufficient state from the history of the determination result of the excess or shortage of the actual injection amount Qudact of the reducing agent so far, the calculated required injection after correction is calculated. The system correction factor α is set to a value of α> 1 so that the quantity Q _am udtgt increases.

  Further, the injection amount correction unit is based on not only the history of the determination result of excess / deficiency of the actual injection amount Qudact of the reducing agent, but also the result of abnormality diagnosis of each part constituting the reducing agent injection device 40 performed in the self-diagnosis unit. The system correction coefficient α can be set. Specifically, the reduction according to the diagnosis results such as clogging of the first supply passage 44, the second supply passage 45, or the reducing agent injection valve 43 constituting the reducing agent injection device 40, and error of each sensor value. The system correction coefficient α is set by estimating the excess or deficiency of the actual injection amount Qudact of the agent. For example, when the first or second supply passages 44 and 45 or the reducing agent injection valve 43 is clogged, the actual correction amount Qudact of the reducing agent is reduced, so that the system correction coefficient α is α> Set to a value of 1.

The injection amount correction unit corrects the required injection amount Qudtgt of the reducing agent once by the injection amount correction unit, and then the actual injection amount Qudact of the reducing agent injected based on the corrected actual injection amount Q _am udtgt. When the excess or deficiency occurs again, the system correction coefficient α used is corrected.
By calculating the required injection amount Q _am udtgt after correction by multiplying the required injection amount Qudtgt calculated by the required injection amount calculation unit in this way by a predetermined system correction coefficient α, it is not a deviation in calculation parameters, The influence of the temporal change that affects the entire system generated in the reducing agent injection device 40, such as clogging and deterioration of the reducing agent injection valve 43 and the first and second supply passages 44 and 45, is eliminated.

3. Control Method of Reducing Agent Injection Device Next, an example of a routine of the control method of the reducing agent injection device performed using the exhaust purification device 10 of FIG. 1 and the control device 30 of FIG. 3 described so far will be described with reference to FIGS. This will be described with reference to FIG. This routine is always executed in the operating state of the internal combustion engine.

First, after the first counter is reset in step S1 after the start, in step S2, the rotational speed Ne of the internal combustion engine 5, the fuel injection amount Qf, the fuel injection timing TM, the accelerator operation amount Ac, the upstream side of the reduction catalyst 13 Further, the exhaust temperature Tu, Tl, etc. on the downstream side are read. Next, in step S3, based on the values read in step S2, the NO _x flow rate Fnox, NO _x concentration Dnox discharged from the internal combustion engine 5, the ammonia flow rate Fnh3 required to reduce the NO _x by 100%, Calculation parameter values such as the temperature Tcat of the reduction catalyst 13 and the actual adsorption amount Vact of ammonia in the reduction catalyst 13 are calculated.

Next, in step S4, it is determined whether or not the first counter is zero. This first counter is advanced when the sensor value Snox of the NO _X sensor 15 exceeds the threshold value. In step S4, at least the previous sensor value Snox of the NO _X sensor 15 is equal to or greater than the threshold value Sn0. Is determined as YES, and the process proceeds to step S8.
On the other hand, when the first counter is 1 or more in step S4, the process proceeds to step S5, and it is determined whether or not the second counter value is zero. When the second counter is 0, since at least the actual injection amount Qudact of the reducing agent is not in a deficient state, the process proceeds to step S6, and correction is performed to increase the value of the actual adsorption amount Vact of ammonia calculated in step S3. Then, the process proceeds to step S8. The fact that the correction for increasing the actual adsorption amount Vact of ammonia is performed leads to a reduction in the required injection amount Qudtgt of the reducing agent calculated in the subsequent step S9.

  On the other hand, when the second counter is 1 or more, since the actual injection amount Qudact of the reducing agent is in a shortage state, the process proceeds to step S7, and correction is performed to reduce the value of the actual adsorption amount Vact of ammonia calculated in step S3. After being performed, the process proceeds to step S8. The correction that reduces the value of the actual adsorption amount Vact of ammonia leads to an increase in the required injection amount Qudtgt of the reducing agent calculated in the subsequent step S9.

In the example of this embodiment, it is determined in step S5 that the actual injection amount Qudact of the reducing agent is in an insufficient state based on the increase correction of the actual adsorption amount Vact of ammonia, that is, the reduction of the required injection amount Qudtgt of the reducing agent. Only when the actual adsorption amount Vact of ammonia is reduced, that is, the required injection amount Qudtgt of the reducing agent is increased. Therefore, the risk that ammonia that is relatively more toxic than NO _x flows out downstream of the reduction catalyst 13 is reduced.
These steps S6 and S7 are performed in order to optimize the actual reducing agent injection quantity Qudact.

Next, in step S8, the NO _x reduction efficiency η or the first value in the reduction catalyst 13 is calculated using the calculation parameter value calculated in step S3 or the value of the actual adsorption amount Vact of ammonia corrected in step S6 or step S7. To third coefficients fac1 to fac3 are obtained. In step S9, the required injection amount Qudtgt of the reducing agent is obtained by calculation based on the calculation parameter value obtained so far, the NO _x reduction efficiency η, and the first to third coefficients fac1 to fac3.

  When the required injection amount Qudtgt of the reducing agent is obtained, it is then determined in step S10 whether or not the system correction coefficient α is set. If the system correction coefficient α is not set, the process proceeds to step S12 as it is. If the system correction coefficient α has been set, the process proceeds to step S11, the required injection quantity Qudtgt is multiplied by the system correction coefficient α, and after the corrected required injection quantity Qudtgt ′ is calculated, the process proceeds to step S12. In this routine, if the excess or shortage of the actual reducing agent injection quantity Qudact has not occurred so far, the system correction coefficient α is not set, and the calculated required injection quantity Qudtgt is not corrected. Thereafter, in step S12, an operation signal is output to the reducing agent injection valve 43 according to the required injection amount Qudtgt of the reducing agent or the corrected required injection amount Qudtgt '.

The injection of reducing agent is performed, then step S13, NO _X sensor 15 sensor value Snox is read in a further, at step S14, whether the sensor value Snox is the threshold value Sn0 more is determined. A state where the sensor value Snox is equal to or greater than the threshold value Sn0 indicates that the reducing agent actual injection amount Qudact is excessive or insufficient, and at this time, the first counter value is advanced by one in step S15. Thereafter, in step S16, it is determined whether or not the first counter value has reached the determination threshold value n2. If the first counter value has not reached the determination threshold value n2, the process returns to step S2, and the previous steps are performed again. Done. On the other hand, when the first counter value has reached the determination threshold value n2, since the actual injection amount Qudact of the reducing agent is in an insufficient state (the state of FIG. 5B), in step S17 the amount of reducing agent is reduced. In addition to recognizing that the actual injection amount Qudact is insufficient, if the third counter value is not 0 in step S18, the third counter is reset and the second counter value is advanced by one, and then the process proceeds to step S22. move on.

Further, in the above-described step S14, the state where the sensor value Snox is less than the threshold value Sn0 indicates that the current reducing agent actual injection amount Qudact is optimized, and in this case, the first counter value is set in step S19. It is determined whether or not it is 1 or more and a determination threshold n1 or less. If the first counter value is 0, there since no sensor values Snox to date NO _X sensor 15 in this routine becomes the threshold value Sn0 above, performed well operation required injection amount Qudtgt of the reducing agent precision Therefore, it is determined as No and the process proceeds to step S22 as it is. Similarly, when the first counter value exceeds the determination threshold value n1 and is less than the determination threshold value n2 in step S19, there is a slight error in the calculated value of the required injection amount Qudtgt of the reducing agent. It is determined that the difference is not so large that it can be said that the actual injection amount Qudact is excessive or insufficient, and it is determined as No and the process proceeds to step S22 as it is.

  On the other hand, when the first counter value is not less than 1 and not more than the determination threshold value n1 in step S19, the actual injection amount Qudact of the reducing agent is in an excessive state (state in FIG. 5A), and therefore step S20. In step S21, when the second reducing counter value is not zero, the second counter is reset and the third counter value is advanced by one in step S21. The process proceeds to step S22.

  Next, in step S22, it is determined whether or not both the second counter value and the third counter value are less than the determination threshold value n3. In step S22, the actual injection amount of the reducing agent cannot be improved by the optimization process of the actual injection amount Qudact of the reducing agent by the increase correction of the actual adsorption amount Vact of ammonia in the reduction catalyst 13 performed in the above-described step S5. This is a step of determining whether or not an abnormality has occurred in the quadact. If both the second counter value and the third counter value are less than the determination threshold n3, it is determined that such an abnormality in the actual injection amount Qudact of the reducing agent has not occurred, and this routine is terminated and the process returns to the start.

  On the other hand, if either the second counter value or the third counter value is equal to or greater than the determination threshold value n3, the process proceeds to step S23, and it is determined whether or not the second counter value is equal to or greater than the determination threshold value n3. . In step S23, whether the set value of the system correction coefficient α should be set to α <1 or α> 1 by referring to the history of excess / deficiency in the actual injection amount Qudact of the reducing agent so far. This is done to determine If the second counter value is greater than or equal to the determination threshold n3, an abnormality in a state where the actual reducing agent injection amount Qudact is insufficient has occurred, and therefore, the required injection amount of reducing agent performed in step S11 in step S24. A system correction coefficient α used for correction of Qudtgt is set to a value of α> 1. On the other hand, when the second counter value is less than the determination threshold value n3, the third counter value is equal to or greater than the determination threshold value n3, and an abnormality occurs when the actual reducing agent injection quantity Qudact is excessive. In step S25, the system correction coefficient α is set to a value of α <1.

  The system correction coefficient α is determined according to the number of times the system correction coefficient α is set and the history of excess / deficiency of the actual reducing agent injection quantity Qudact so far, and the degree of deterioration of each part of the reducing agent injection device 40 is determined. Accordingly, the required injection amount Qudtgt of the reducing agent is corrected. When the system correction coefficient α is set in step S24 or S25, in the next routine, in step S11, the required injection amount Qudtgt ′ after correction by multiplying the required injection amount Qudtgt calculated in step S9 by the system correction coefficient α. Is calculated, and the reducing agent is injected according to the corrected required injection amount Qudtgt ′. As a result, in response to changes in the characteristics of the opening time and injection amount of the reducing agent injection valve caused by deterioration of each part of the reducing agent injection device, clogging of the reducing agent supply passage and the reducing agent injection valve, etc. The actual injection amount Qudact of the reducing agent is optimized.

It is a figure which shows the structural example of the exhaust gas purification apparatus of the internal combustion engine of this embodiment. And the amount of ammonia in the reduction catalyst is a diagram for explaining the relationship between the NO _X sensor values and ammonia or NO _X concentration. It is a block diagram which shows the structural example of the control apparatus (reducing agent injection control apparatus) of this embodiment. It is a figure for demonstrating the calculation method of the request | requirement injection amount of the reducing agent performed with a control apparatus. It is a time chart for demonstrating the method of the optimization process of the request | requirement injection quantity Qudtgt of a reducing agent. It is a flowchart for demonstrating an example of the control method of a reducing agent injection apparatus. It is a flowchart for demonstrating an example of the control method of a reducing agent injection apparatus.

Explanation of symbols

5: engine, 10: exhaust gas purification device, 11: exhaust passage, 13: reducing catalyst, 15: NO _X sensor 26: upstream temperature sensor, 27: downstream temperature sensor, 30: control device (reducing agent injection control Device), 40: reducing agent injection device, 41: storage tank, 42: pump, 43: reducing agent injection valve, 44: first supply passage, 45: second supply passage, 47: pressure sensor

Claims (6)

Reducing agent injection that is connected to an exhaust system of an internal combustion engine and injects a reducing agent capable of generating ammonia upstream of a reduction catalyst that adsorbs ammonia and reduces NOx in the inflowing exhaust gas using the ammonia. In the reducing agent injection control device for controlling the device,
A required injection amount calculation unit that calculates a required injection amount of the reducing agent based on at least a parameter value including an amount of NOx discharged from the internal combustion engine, a temperature of the reduction catalyst, and an adsorption amount of the ammonia in the reduction catalyst; ,
A reducing agent injection control unit that injects the reducing agent from the reducing agent injection device according to the required injection amount;
An injection amount abnormality determination unit for comparing the sensor value of a specific gas concentration sensor sensitive to at least NOx and ammonia provided on the downstream side of the reduction catalyst with a predetermined threshold to determine an abnormality in the actual injection amount of the reducing agent; ,
An injection amount calculation parameter value correction unit that corrects the parameter value of the required injection amount calculation unit when an abnormality occurs in the actual injection amount;
If the actual injection amount is abnormal after the parameter value is corrected a predetermined number of times, the required injection amount value calculated by the required injection amount calculation unit is multiplied by a predetermined system correction coefficient. An injection amount correction unit that corrects the required injection amount by
When the sensor value exceeds the threshold value, the injection amount abnormality determining unit corrects the ammonia adsorption amount in the reduction catalyst by increasing the amount, thereby reducing the injection amount of the reducing agent from the required injection amount. When the sensor value after a predetermined time elapses is less than or equal to the threshold value, it is determined that the injection amount is excessive, and when the sensor value after the predetermined time elapses exceeds the threshold value, the injection is performed. It is determined that the amount is insufficient,
The injection amount correction unit refers to a history of determination results determined by the injection amount abnormality determination unit, sets the system correction coefficient based on the history, and multiplies the predetermined system correction coefficient. A reducing agent injection control apparatus , wherein the system correction coefficient is corrected when an abnormality in the actual injection amount is observed even after the required injection amount is corrected . Reducing agent injection that is connected to an exhaust system of an internal combustion engine and injects a reducing agent capable of generating ammonia upstream of a reduction catalyst that adsorbs ammonia and reduces NOx in the inflowing exhaust gas using the ammonia. In the reducing agent injection control device for controlling the device,
  A required injection amount calculation unit that calculates a required injection amount of the reducing agent based on at least a parameter value including an amount of NOx discharged from the internal combustion engine, a temperature of the reduction catalyst, and an adsorption amount of the ammonia in the reduction catalyst; ,
  A reducing agent injection control unit that injects the reducing agent from the reducing agent injection device according to the required injection amount;
  An injection amount abnormality determination unit for comparing the sensor value of a specific gas concentration sensor sensitive to at least NOx and ammonia provided on the downstream side of the reduction catalyst with a predetermined threshold to determine an abnormality in the actual injection amount of the reducing agent; ,
  An injection amount calculation parameter value correction unit that corrects the parameter value of the required injection amount calculation unit when an abnormality occurs in the actual injection amount;
  If the actual injection amount is abnormal after the parameter value is corrected a predetermined number of times, the required injection amount value calculated by the required injection amount calculation unit is multiplied by a predetermined system correction coefficient. An injection amount correction unit for correcting the required injection amount,
  A self-diagnosis unit for performing an abnormality diagnosis of each part constituting the reducing agent injection device,
When the sensor value exceeds the threshold value, the injection amount abnormality determining unit corrects the ammonia adsorption amount in the reduction catalyst by increasing the amount, thereby reducing the injection amount of the reducing agent from the required injection amount. When the sensor value after a predetermined time elapses is less than or equal to the threshold value, it is determined that the injection amount is excessive, and when the sensor value after the predetermined time elapses exceeds the threshold value, the injection is performed. It is determined that the amount is insufficient,
  The injection amount correction unit sets the system correction coefficient based on the diagnosis result of the self-diagnosis unit, and also corrects the required injection amount by multiplying the predetermined system correction coefficient. A reducing agent injection control device, wherein the system correction coefficient is corrected when an abnormality in the injection amount is observed. Reducing agent injection that is connected to an exhaust system of an internal combustion engine and injects a reducing agent capable of generating ammonia upstream of a reduction catalyst that adsorbs ammonia and reduces NOx in the inflowing exhaust gas using the ammonia. In the device control method,
Calculating a required injection amount of the reducing agent based on at least a parameter value including an amount of NOx discharged from the internal combustion engine, a temperature of the reduction catalyst, and an adsorption amount of the ammonia in the reduction catalyst, and the required injection amount Injecting the reducing agent according to
The sensor value of a specific gas concentration sensor sensitive to at least NOx and ammonia provided on the downstream side of the reduction catalyst is compared with a predetermined threshold, and when the sensor value exceeds the threshold, the reduction catalyst in the reduction catalyst When the amount of ammonia adsorbed is corrected to be increased, the amount of the reducing agent injected is controlled to be less than the required injection amount, and when the sensor value is less than or equal to the threshold value after a predetermined time has elapsed, the injection amount When the sensor value after the predetermined time has passed is determined to be excessive, and when the sensor value exceeds the threshold, it is determined that the injection amount is insufficient, thereby determining an abnormality in the actual injection amount of the reducing agent,
When the abnormality in the actual injection amount occurs, the parameter value used for the calculation of the required injection amount is corrected,
When abnormality in the actual injection amount is observed even after the parameter value is corrected a predetermined number of times, the calculated value of the required injection amount is multiplied by a predetermined system correction coefficient to obtain the required injection amount. Make corrections
In the correction of the required injection amount, the system correction coefficient is set based on the history with reference to the history of the determination result of the abnormality of the actual injection quantity, and the predetermined system correction coefficient is multiplied to A control method for a reducing agent injection device , wherein the system correction coefficient is corrected when an abnormality in the actual injection amount is observed even after the required injection amount is corrected . Reducing agent injection that is connected to an exhaust system of an internal combustion engine and injects a reducing agent capable of generating ammonia upstream of a reduction catalyst that adsorbs ammonia and reduces NOx in the inflowing exhaust gas using the ammonia. In the device control method,
  Calculating a required injection amount of the reducing agent based on at least a parameter value including an amount of NOx discharged from the internal combustion engine, a temperature of the reduction catalyst, and an adsorption amount of the ammonia in the reduction catalyst, and the required injection amount Injecting the reducing agent according to
  The sensor value of a specific gas concentration sensor sensitive to at least NOx and ammonia provided on the downstream side of the reduction catalyst is compared with a predetermined threshold, and when the sensor value exceeds the threshold, the reduction catalyst in the reduction catalyst When the amount of ammonia adsorbed is corrected to be increased, the amount of the reducing agent injected is controlled to be less than the required injection amount, and when the sensor value is less than or equal to the threshold value after a predetermined time has elapsed, the injection amount When the sensor value after the predetermined time has passed is determined to be excessive, and when the sensor value exceeds the threshold, it is determined that the injection amount is insufficient, thereby determining an abnormality in the actual injection amount of the reducing agent,
When an abnormality in the actual injection amount occurs, the parameter value used for the calculation of the required injection amount
Make corrections
  When abnormality in the actual injection amount is observed even after the parameter value is corrected a predetermined number of times, the calculated value of the required injection amount is multiplied by a predetermined system correction coefficient to obtain the required injection amount. Make corrections
  In the correction of the required injection amount, the system correction coefficient is set based on a diagnosis result of self-diagnosis for performing an abnormality diagnosis of each part constituting the reducing agent injection device, and the predetermined system correction coefficient is multiplied. A control method for a reducing agent injection device, wherein the system correction coefficient is corrected when an abnormality in the actual injection amount is observed even after the required injection amount is corrected by the above. A reduction catalyst that is connected to the exhaust system of the internal combustion engine and that adsorbs ammonia and reduces NOx in the exhaust gas flowing in using the ammonia, and a reducing agent capable of generating ammonia is injected upstream of the reduction catalyst. In an exhaust gas purification apparatus for an internal combustion engine, comprising: a reducing agent injection device that performs control of the reducing agent injection device;
A specific gas concentration sensor sensitive to at least NOx and ammonia is provided on the downstream side of the reduction catalyst,
The control device is a request for calculating a required injection amount of the reducing agent based on at least a parameter value including an amount of NOx discharged from the internal combustion engine, a temperature of the reduction catalyst, and an adsorption amount of the ammonia in the reduction catalyst. An injection amount calculation unit, a reducing agent injection control unit for injecting the reducing agent from the reducing agent injection device in accordance with the required injection amount, and comparing a sensor value of the specific gas concentration sensor with a predetermined threshold value, An injection amount abnormality determination unit that determines abnormality of the actual injection amount; an injection amount calculation parameter value correction unit that corrects the parameter value of the required injection amount calculation unit when the abnormality of the actual injection amount occurs; If the actual injection amount is abnormal even after the parameter value has been corrected a predetermined number of times, a predetermined system is used for the required injection amount value calculated by the required injection amount calculation unit. An injection amount correction unit that corrects the required injection amount by multiplying by a fuel correction coefficient ,
When the sensor value exceeds the threshold value, the injection amount abnormality determining unit corrects the ammonia adsorption amount in the reduction catalyst by increasing the amount, thereby reducing the injection amount of the reducing agent from the required injection amount. When the sensor value after a predetermined time elapses is less than or equal to the threshold value, it is determined that the injection amount is excessive, and when the sensor value after the predetermined time elapses exceeds the threshold value, the injection is performed. It is determined that the amount is insufficient,
The injection amount correction unit refers to a history of determination results determined by the injection amount abnormality determination unit, sets the system correction coefficient based on the history, and multiplies the predetermined system correction coefficient. An exhaust emission control device for an internal combustion engine , wherein the system correction coefficient is corrected when an abnormality in the actual injection amount is observed even after the required injection amount is corrected . A reduction catalyst that is connected to the exhaust system of the internal combustion engine and that adsorbs ammonia and reduces NOx in the exhaust gas flowing in using the ammonia, and a reducing agent capable of generating ammonia is injected upstream of the reduction catalyst. In an exhaust gas purification apparatus for an internal combustion engine, comprising: a reducing agent injection device that performs control of the reducing agent injection device;
  A specific gas concentration sensor sensitive to at least NOx and ammonia is disposed downstream of the reduction catalyst.
As well as
  The control device is a request for calculating a required injection amount of the reducing agent based on at least a parameter value including an amount of NOx discharged from the internal combustion engine, a temperature of the reduction catalyst, and an adsorption amount of the ammonia in the reduction catalyst. An injection amount calculation unit, a reducing agent injection control unit for injecting the reducing agent from the reducing agent injection device in accordance with the required injection amount, and comparing a sensor value of the specific gas concentration sensor with a predetermined threshold value, An injection amount abnormality determination unit that determines abnormality of the actual injection amount; an injection amount calculation parameter value correction unit that corrects the parameter value of the required injection amount calculation unit when the abnormality of the actual injection amount occurs; If the actual injection amount is abnormal even after the parameter value has been corrected a predetermined number of times, a predetermined system is used for the required injection amount value calculated by the required injection amount calculation unit. An injection amount correction unit that corrects the required injection amount by multiplying by a correction coefficient, and a self-diagnosis unit that performs an abnormality diagnosis of each part constituting the reducing agent injection device,
  When the sensor value exceeds the threshold value, the injection amount abnormality determining unit corrects the ammonia adsorption amount in the reduction catalyst by increasing the amount, thereby reducing the injection amount of the reducing agent from the required injection amount. When the sensor value after a predetermined time elapses is less than or equal to the threshold value, it is determined that the injection amount is excessive, and when the sensor value after the predetermined time elapses exceeds the threshold value, the injection is performed. It is determined that the amount is insufficient,
  The injection amount correction unit sets the system correction coefficient based on the diagnosis result of the self-diagnosis unit, and also corrects the required injection amount by multiplying the predetermined system correction coefficient. An exhaust gas purification apparatus for an internal combustion engine, wherein the system correction coefficient is corrected when an abnormality in the injection amount is observed.

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