JP2022003247A - Emission control device - Google Patents

Abstract

To provide an emission control device for accurately calculating a slip amount of ammonia from a NOX occlusion reduction type catalyst.SOLUTION: An emission control device 8 for applying emission control to NOX exhausted from an internal combustion engine 1 includes a correction part 14 for calculating a slip amount of ammonia from a NOX occlusion reduction type catalyst 6 on the basis of a temperature of the NOX occlusion reduction type catalyst 6 provided in an exhaust pipe 3 of a vehicle, calculating an occlusion amount of sulfur in the NOX occlusion reduction type catalyst 6 on the basis of a supply amount of fuel into the internal combustion engine 1, and correcting the slip amount of the ammonia on the basis of the occlusion amount of the sulfur in the NOX occlusion reduction type catalyst 6.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a purification control device.

Conventionally, in vehicles such as commercial vehicles, _{NO X} storage reduction catalysts (LNT catalysts, LNT: Lean NO _X Trap) and selective catalytic reduction catalysts (SCR _{) that purify NO X} (nitrogen oxides) contained in exhaust gas have been used. A purification device such as a catalyst (SCR: Selective Catalytic Reduction) is arranged in an exhaust pipe, and a purification control device for controlling this purification device has been put into practical use.

Here, ammonia (NH ₃ ) may be generated in the LNT catalyst, and if the ammonia slips from the LNT catalyst, it may have various effects on the SCR catalyst arranged on the downstream side of the LNT catalyst. For example, if ammonia slip from LNT catalyst is storage into the SCR catalyst, results in an excessive reducing agent to the SCR catalyst is supplied, the purification rate of increase and NO _X amount of slip of ammonia from the SCR catalyst May cause a decrease in the amount of water. Therefore, it is required to calculate the slip amount of ammonia from the LNT catalyst.

Therefore, as a technique for calculating the slip amount of ammonia from LNT catalyst, for example, Patent Document 1, while improving the purification rate of NO _X, suppress exhaust purification device slip of ammonia is disclosed. This exhaust gas purification device calculates the slip amount of ammonia based on the occluded amount _{of NO X in the LNT catalyst.}

JP-A-2015-151929

However, since the slip of ammonia from the LNT catalyst occurs due to various factors, it is difficult to accurately calculate the slip amount of ammonia with the apparatus of Patent Document 1.

The present disclosure aims to provide a purification controller to accurately calculate the amount of slip of ammonia from _the NO _X storage reduction catalyst.

Purification controller according to the present disclosure, there is provided a cleaning control unit for controlling the purification of the NO _X discharged from the internal combustion engine, NO _X based on the temperature of the NO _X storage reduction catalyst provided in an exhaust pipe of the vehicle It calculates the slip amount of the ammonia from the storage reduction catalyst, based on the supply amount of the fuel in an internal combustion engine calculates the storage amount of sulfur in _the NO _X storage reduction catalyst, occlusion of sulfur in _the NO _X storage reduction catalyst It is provided with a correction unit that corrects the slip amount of ammonia based on the amount.

According to the present disclosure, it is possible to accurately calculate the amount of slip of ammonia from _the NO _X storage reduction catalyst.

It is a figure which shows the structure of the vehicle provided with the purification control device which concerns on Embodiment 1 of this disclosure. It is a graph which shows the change of the air-fuel ratio and the slip amount of ammonia. It is a figure which shows the base map for calculating the slip amount of ammonia from an LNT catalyst. It is a graph which shows the change of the correction coefficient with respect to the occlusal amount of sulfur in an LNT catalyst. It is a graph which shows the change of the correction coefficient with respect to the air-fuel ratio of the exhaust gas flowing into the LNT catalyst in Embodiment 2. FIG. It is a graph which shows the change of the correction coefficient with respect to the air-fuel ratio of the exhaust gas flowing out from the LNT catalyst in Embodiment 3. FIG. It is a graph which shows the change of the correction coefficient with respect to the occlusion amount _{of NO X} in the LNT catalyst in Embodiment 4. FIG. It is a graph which shows the change of the correction coefficient with respect to the internal temperature of the LNT catalyst in Embodiment 5.

Hereinafter, embodiments according to the present disclosure will be described with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 shows a configuration of a vehicle provided with a purification control device according to the first embodiment of the present disclosure. The vehicle has an internal combustion engine 1, an intake pipe 2, an exhaust pipe 3, an internal combustion engine control unit 4, and a purification device 5. Examples of vehicles include commercial vehicles such as trucks.

The internal combustion engine 1 is for driving a vehicle, and is composed of, for example, a so-called four-stroke engine that repeats four strokes of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Examples of the internal combustion engine 1 include a diesel engine and the like.

The intake pipe 2 is a flow path whose tip end is connected to the intake port of the internal combustion engine 1 and supplies air sucked from the outside to the internal combustion engine 1.
The exhaust pipe 3 is arranged so as to extend outward from the exhaust port of the internal combustion engine 1, and is a flow path for discharging the exhaust gas discharged from the internal combustion engine 1 to the outside.

The internal combustion engine control unit 4 controls the internal combustion engine 1 and is connected to the internal combustion engine 1 and the purification control unit 12 of the purification device 5, respectively. The internal combustion engine control unit 4 controls, for example, the flow rate of intake air, the flow rate of exhaust gas, the amount of fuel supplied, the engine speed, and the like. Examples of the fuel include light oil.

The purification device 5 includes a NO _X occlusion reduction catalyst (LNT catalyst) 6, a selective reduction catalyst (SCR catalyst) 7, and a purification control device 8.

The LNT catalyst 6 is arranged in the exhaust pipe 3 and occludes and reduces _{NO X contained in the exhaust gas to purify it.} For example, LNT catalyst 6 can be configured with a noble metal catalyst such as platinum, and _the NO _X storage material formed like an alkaline earth metal such as barium from molded body was supported on a carrier. As a result, when the exhaust gas has a lean air-fuel ratio, that is, an air-fuel ratio whose fuel ratio is lower than the stoichiometric air-fuel ratio (air excess ratio = 1), NO _X contained in the exhaust gas is occluded in the NO _{X storage material.} When the exhaust gas has a rich air-fuel ratio, that is, an air-fuel ratio having a higher fuel ratio than the stoichiometric air-fuel ratio, the oxygen concentration decreases and the amount of reducing agents such as carbon monoxide and hydrocarbons increases. the three-way function, NO _X occluded occluded NO _X in material is purified by reduction such as nitrogen reacts with the reducing agent.

The SCR catalyst 7 is arranged on the downstream side of the LNT catalyst 6 in the exhaust pipe 3, and NO _X contained in the exhaust gas is reduced and purified by supplying a reducing agent. For example, the SCR catalyst 7 can be composed of a zeolite catalyst such as iron ion exchange aluminosilicate and copper ion exchange aluminosilicate. As a result, for example, when urea water is supplied into the exhaust pipe 3 as a reducing agent, the urea water is thermally decomposed and hydrolyzed by the high temperature heat of the exhaust gas to generate ammonia, and the produced ammonia is SCR. It is stored in the catalyst 7. Then, the SCR catalyst 7 _{purifies the NO X} contained in the exhaust gas by reducing it to nitrogen or the like with the stored ammonia.

The purification control device 8 includes an inlet lambda sensor 9a, an outlet lambda sensor 9b, temperature sensors 10a to 10c, a supply unit 11, and a purification control unit 12. Further, the purification control unit 12 includes an air-fuel ratio control unit 13, a correction unit 14, and a supply control unit 15. The air-fuel ratio control unit 13 is connected to the supply control unit 15 via the correction unit 14. Further, the air-fuel ratio control unit 13 is connected to an inlet lambda sensor 9a, an outlet lambda sensor 9b, and temperature sensors 10a and 10b, respectively. Further, the supply control unit 15 is connected to the temperature sensor 10c and the supply unit 11, respectively. Further, the air-fuel ratio control unit 13, the correction unit 14, and the supply control unit 15 are each connected to the internal combustion engine control unit 4.

The inlet lambda sensor 9a is arranged on the upstream side of the LNT catalyst 6 in the exhaust pipe 3 and detects the air-fuel ratio of the exhaust gas flowing into the LNT catalyst 6. That is, the inlet lambda sensor 9a detects the air-fuel ratio before the _{LNT catalyst 6 reacts with NO X.}

The outlet lambda sensor 9b is arranged on the downstream side of the LNT catalyst 6 in the exhaust pipe 3 and detects the air-fuel ratio of the exhaust gas flowing out from the LNT catalyst 6. That is, the outlet lambda sensor 9b detects the air-fuel ratio after the _{LNT catalyst 6 reacts with NO X.}

The temperature sensor 10a is arranged on the upstream side of the LNT catalyst 6 in the exhaust pipe 3 and detects the temperature of the exhaust gas flowing into the LNT catalyst 6.
The temperature sensor 10b is arranged on the downstream side of the LNT catalyst 6 in the exhaust pipe 3 and detects the temperature of the exhaust gas flowing out of the LNT catalyst 6.

The temperature sensor 10c is arranged on the upstream side of the SCR catalyst 7 in the exhaust pipe 3 and detects the temperature of the exhaust gas flowing into the SCR catalyst 7.

The supply unit 11 is arranged on the upstream side of the SCR catalyst 7 in the exhaust pipe 3 and supplies the reducing agent to the SCR catalyst 7. The reducing agent includes _{not only a reducing agent that directly reduces NO X} such as ammonia, but also a precursor thereof, for example, urea water that is a precursor of ammonia.

The air-fuel ratio control unit 13 empty the exhaust gas flowing into the LNT catalyst 6 via the internal combustion engine control unit 4 based on the detection values detected by the inlet lambda sensor 9a, the outlet lambda sensor 9b, and the temperature sensors 10a and 10b. The fuel ratio is adjusted to control the occlusion and reduction _{of NO X in the LNT catalyst 6.}

The correction unit 14 calculates the slip amount of ammonia from the LNT catalyst 6 based on the inlet temperature of the LNT catalyst 6 detected by the temperature sensor 10a. Further, the correction unit 14 calculates the amount of sulfur stored in the LNT catalyst 6 based on the fuel supply amount in the internal combustion engine 1 obtained from the internal combustion engine control unit 4. Then, the correction unit 14 corrects the slip amount of ammonia from the LNT catalyst 6 based on the amount of sulfur stored in the LNT catalyst 6.

The supply control unit 15 controls the supply unit 11 so as to inject an amount of the reducing agent corresponding to the storage capacity of ammonia in the SCR catalyst 7 based on the temperature detected by the temperature sensor 10c. At this time, the supply control unit 15 controls the supply amount of the reducing agent from the supply unit 11 to the SCR catalyst 7 based on the slip amount of ammonia from the LNT catalyst 6 corrected by the correction unit 14.

The functions of the internal combustion engine control unit 4, the purification control unit 12, the air-fuel ratio control unit 13, the correction unit 14, and the supply control unit 15 can also be realized by a computer program. For example, the reading device of the computer records the program from the recording medium in which the program for realizing the functions of the internal combustion engine control unit 4, the purification control unit 12, the air-fuel ratio control unit 13, the correction unit 14, and the supply control unit 15 is recorded. Read and store in storage device. Then, the CPU copies the program stored in the storage device to the RAM, sequentially reads the instructions included in the program from the RAM, and executes the program, whereby the internal combustion engine control unit 4, the purification control unit 12, and the air-fuel ratio control unit are executed. The functions of 13, the correction unit 14, and the supply control unit 15 can be realized.

Next, the operation of this embodiment will be described.

First, as shown in FIG. 1, when the internal combustion engine control unit 4 controls the internal combustion engine 1 and the vehicle is driven, the exhaust gas generated by the internal combustion engine 1 flows through the exhaust pipe 3 and is discharged to the outside. .. For example, the internal combustion engine 1, the exhaust gas of a lean air-fuel ratio is generated by the exhaust gas flows through the LNT catalyst 6 arranged in the exhaust pipe 3, NO _X contained in the exhaust gas is sequentially at LNT catalyst 6 It is stored.

_{The occlusal amount of NO X} in the LNT catalyst 6 is calculated by the air-fuel ratio control unit 13. Air-fuel ratio control unit 13, for example, based on such a flow rate of intake air of the internal combustion engine 1 is sequentially input from the engine control unit 4 calculates the amount of the NO _X in the exhaust gas, the content of the NO _X Based on this, the _{amount of NO X} stored in the LNT catalyst 6 can be calculated. Further, the air-fuel ratio control unit 13 _{detects the NO X} amount of the exhaust gas flowing into the LNT catalyst 6 _{with a NO X} sensor (not shown), and calculates the occlusion amount _{of NO X} in the LNT catalyst 6 based on the _{NO X amount.} You can also do it.

_{When the calculated NO X} storage amount exceeds a predetermined value, the air-fuel ratio control unit 13 enriches the air-fuel ratio R1 of the exhaust gas flowing into the LNT catalyst 6 at time T1 as shown in FIG. The air-fuel ratio, for example, the excess air ratio is reduced to about 0.95.
The predetermined value in the storage amount of the NO _X, for example, can be set based on the capacity of absorbing possible NO _X in LNT catalyst 6. Further, the period from the time T1 to the time T3 in which the exhaust gas flowing into the LNT catalyst 6 is controlled by the rich air-fuel ratio is defined as the rich period.

In this way, the exhaust gas flowing into the LNT catalyst 6 has a rich air-fuel ratio, so that the oxygen concentration decreases and the reducing agents such as carbon monoxide and hydrocarbons increase as compared with the lean air-fuel ratio. become. _{As a result, NO X} occluded in the LNT catalyst 6 can be released and reduced to purify substances such as nitrogen, water and carbon dioxide.

In this case, oxygen is generated in response to release and reduction of the NO _X by the LNT catalyst 6. Therefore, the air-fuel ratio R2 detected by the outlet lambda sensor 9b arranged on the downstream side of the LNT catalyst 6 is higher than the air-fuel ratio R1 detected by the inlet lambda sensor 9a, for example, the excess air ratio is about 1.0. It will be maintained at the stoichiometric air-fuel ratio of. Then, when _{the purification of NO X} progresses and the latter half of the rich period is reached, the NO _X occluded in the LNT catalyst 6 decreases, and the reduction amount of the LNT catalyst 6 also decreases in time T2. Oxygen decreases from the surroundings of the LNT catalyst 6 due to this decrease in the amount of reduction, and NO _X released from the LNT catalyst 6, for example, NO ₂ reacts with H ₂ or the like to generate ammonia N, and ammonia is produced from the LNT catalyst 6. N will slip.

Therefore, the air-fuel ratio control unit 13 detects the inlet temperature of the LNT catalyst 6, which affects the fluctuation of the slip amount of ammonia N from the LNT catalyst 6, with the temperature sensor 10a and outputs the temperature to the correction unit 14. At this time, it is preferable that the air-fuel ratio control unit 13 acquires the flow rate of the exhaust gas from the internal combustion engine control unit 4 and outputs the flow rate of the exhaust gas to the correction unit 14.
Further, the air-fuel ratio control unit 13 acquires the fuel supply amount in the internal combustion engine 1 from the internal combustion engine control unit 4, and outputs the fuel supply amount to the correction unit 14.

As shown in FIG. 3, the correction unit 14 stores in advance a base map showing changes in the amount of ammonia slip from the LNT catalyst 6 with respect to the inlet temperature of the LNT catalyst 6 and the flow rate of the exhaust gas. This basemap shows the slip of ammonia when the inlet temperature of the LNT catalyst 6 and the flow rate of the exhaust gas are changed based on experiments and simulations, for example, under the condition that the slip amount of ammonia from the LNT catalyst 6 is maximized. It can be created by calculating the amount. The conditions for the fluctuation of the slip amount of ammonia include, for example, the occluded amount of sulfur in the LNT catalyst 6, the air-fuel ratio R1 of the exhaust gas flowing into the LNT catalyst 6, and the air-fuel ratio R2 of the exhaust gas flowing out of the LNT catalyst 6. Examples include the amount of NO _X stored in the LNT catalyst 6 and the internal temperature of the LNT catalyst 6.

This base map shows a mountain-shaped distribution in which the slip amount of ammonia is maximized in the vicinity of the inlet temperature C2 between the inlet temperatures C1 and C3 of the LNT catalyst 6. In addition, the base map shows the distribution in which the slip amount of ammonia increases as the flow rate of exhaust gas increases.

The correction unit 14 calculates the slip amount of ammonia from the LNT catalyst 6 from the base map based on the inlet temperature of the LNT catalyst 6 and the flow rate of the exhaust gas in the rich period output from the air-fuel ratio control unit 13.

Further, the correction unit 14 calculates a storage amount of occlusion amount of sulfur in the LNT catalyst 6 based on the supply amount of the fuel in the internal combustion engine 1 outputted from the air-fuel ratio control unit 13, for example, SO X _(sulfur oxides) .. At this time, it is preferable that the correction unit 14 calculates the amount of sulfur stored in the LNT catalyst 6 based on the amount of fuel supplied during the lean air-fuel ratio period in _{which NO X is stored in the LNT catalyst 6.} The sulfur storage amount can be calculated by, for example, the following formula (1).

Sulfur occlusal amount = Sulfur weight concentration in fuel x Fuel supply amount in internal combustion engine 1 x Fuel specific gravity ... (1)
The weight concentration of sulfur in the fuel and the specific gravity of the fuel can be preset in the correction unit 14 according to the fuel specifications.

Here, when the slip amount of ammonia from the LNT catalyst 6 was actually measured with respect to the occluded amount of sulfur in the LNT catalyst 6, it was found that the slip amount of ammonia decreased as the occluded amount of sulfur increased. This is because, when occlusion amount of sulfur in LNT catalyst 6 is large, storage capacity of the NO _X is reduced in the LNT catalyst 6, by reduction amount of the NO _X is reduced along with this, ammonia in the LNT catalyst 6 It is probable that the amount of production of was reduced. Therefore, the correction unit 14 corrects the amount of ammonia slip calculated from the base map so that the larger the amount of sulfur stored in the calculated LNT catalyst 6, the lower the amount of ammonia slip from the LNT catalyst 6. ..

For example, as shown in FIG. 4, in the correction unit 14, the value of the correction coefficient with respect to the amount of sulfur stored in the LNT catalyst 6 is preset based on experiments, simulations, and the like. This correction coefficient is set so that the slip amount of ammonia from the LNT catalyst 6 decreases as the amount of sulfur stored in the LNT catalyst 6 increases.

The correction unit 14 obtains a correction coefficient corresponding to the sulfur storage amount calculated by the above formula (1), and multiplies the slip amount of ammonia from the LNT catalyst 6 calculated based on the base map by the correction coefficient. To correct the amount of ammonia slip.

Here, the change in the amount of ammonia slip according to the amount of occluded sulfur is due to a factor different from the change in the amount of ammonia slip according to the inlet temperature of the LNT catalyst 6 and the flow rate of the exhaust gas. Therefore, the correction unit 14 can accurately calculate the value by correcting the slip amount of ammonia from the LNT catalyst 6 based on the amount of sulfur stored in the LNT catalyst 6.
Further, since the correction unit 14 corrects by multiplying the ammonia slip amount calculated based on the base map by the correction coefficient, the ammonia slip amount can be easily calculated.

In this way, when the correction unit 14 corrects the slip amount of ammonia from the LNT catalyst 6, the slip amount of the ammonia is output to the supply control unit 15.

Subsequently, the supply control unit 15 calculates the storage amount of ammonia in the SCR catalyst 7 based on the slip amount of ammonia from the LNT catalyst 6 calculated by the correction unit 14, and urea based on the slip amount of ammonia. Calculate the amount of water supplied. For example, the supply control unit 15 calculates the converted amount of the amount of ammonia slipped from the LNT catalyst 6 converted into urea water, that is, the amount of urea water for producing the slipped ammonia amount. Then, the supply control unit 15 reduces the supply amount of urea water as the converted amount of urea water increases.

Then, for example, when the temperature detected by the temperature sensor 10c is within a range suitable for the reduction reaction of the SCR catalyst 7, the supply control unit 15 transfers the calculated supply amount of urea water from the supply unit 11 to the SCR catalyst 7. Supply. The urea water supplied from the supply unit 11 is thermally decomposed and hydrolyzed by the heat of the exhaust gas to generate ammonia, and the ammonia is stored in the SCR catalyst 7 together with the ammonia slipped from the LNT catalyst 6. _{Then, NO X} contained in the exhaust gas is reduced to nitrogen or the like by the ammonia stored in the SCR catalyst 7 to be purified.

In this way, the supply control unit 15 calculates the supply amount of urea water to the SCR catalyst 7 based on the slip amount of ammonia from the LNT catalyst 6 corrected by the correction unit 14. As a result, an appropriate amount of ammonia can be stored in the SCR catalyst 7, _{the purification rate of NO X} can be improved, and the slip of ammonia from the SCR catalyst 7 can be suppressed.

According to the present embodiment, since the correction unit 14 corrects the slip amount of ammonia based on the amount of sulfur stored in the LNT catalyst 6, the slip amount of ammonia from the LNT catalyst 6 can be accurately calculated. ..

(Embodiment 2)
Hereinafter, Embodiment 2 of the present disclosure will be described. Here, the differences from the first embodiment will be mainly described, and the common reference numerals will be used for the common points with the first embodiment, and detailed description thereof will be omitted.

In the first embodiment described above, the correction unit 14 corrects the amount of ammonia slipped from the LNT catalyst 6 based only on the amount of sulfur stored in the LNT catalyst 6, but flows into the amount of sulfur stored and the LNT catalyst 6. It is also possible to correct the amount of ammonia slip from the LNT catalyst 6 based on the air-fuel ratio R1 of the exhaust gas.

For example, the correction unit 14 acquires the air-fuel ratio R1 of the exhaust gas flowing into the LNT catalyst 6, and the larger the air-fuel ratio R1 of the exhaust gas flowing into the LNT catalyst 6, the lower the slip amount of ammonia from the LNT catalyst 6. Can be corrected as follows.

Here, when the slip amount of ammonia from the LNT catalyst 6 was actually measured with respect to the air-fuel ratio R1 of the exhaust gas flowing into the LNT catalyst 6, the larger the air-fuel ratio R1 of the exhaust gas flowing into the LNT catalyst 6, the more ammonia. It was found that the amount of slip was reduced. This is because when the air-fuel ratio R1 of an exhaust gas flowing into the LNT catalyst 6 is increased, and the oxygen concentration in the exhaust gas increases, occluded NO _X is prevented from reacting with such hydrogen LNT catalyst 6, LNT It is considered that the amount of ammonia produced in the catalyst 6 decreased. Therefore, the correction unit 14 calculated the slip of ammonia from the base map so that the larger the air-fuel ratio R1 of the exhaust gas flowing into the acquired LNT catalyst 6, the lower the slip amount of ammonia from the LNT catalyst 6. Correct the amount.

For example, as shown in FIG. 5, in the correction unit 14, the value of the correction coefficient with respect to the air-fuel ratio R1 of the inlet lambda sensor 9a, that is, the air-fuel ratio R1 of the exhaust gas flowing into the LNT catalyst 6 is based on experiments and simulations. It is preset. This correction coefficient is set so that the larger the air-fuel ratio R1 of the exhaust gas flowing into the LNT catalyst 6, the lower the slip amount of ammonia.

The correction unit 14 acquires the air-fuel ratio R1 detected by the inlet lambda sensor 9a during the rich period, and obtains a correction coefficient corresponding to the air-fuel ratio R1. At this time, the correction unit 14 obtains the air-fuel ratio R1 between the time T2 and the time T3 in which the reduction amount decreases according to the decrease of _{NO X} occluded in the LNT catalyst 6 during the rich period, and obtains the correction coefficient. Is preferable. Then, the correction unit 14 sets the correction coefficient corresponding to the air-fuel ratio R1 of the inlet lambda sensor 9a in addition to the correction coefficient corresponding to the occlusal amount of sulfur with respect to the slip amount of ammonia calculated based on the base map. Further multiplication is performed to correct the slip amount of ammonia.

Here, the change in the amount of ammonia slip according to the air-fuel ratio R1 is due to a factor different from the change in the amount of ammonia slip according to the amount of sulfur stored in the LNT catalyst 6. Therefore, the correction unit 14 can more accurately calculate the slip amount of ammonia from the LNT catalyst 6 by further correcting the slip amount of ammonia from the LNT catalyst 6 based on the air-fuel ratio R1.

According to the present embodiment, the correction unit 14 further corrects the slip amount of ammonia from the LNT catalyst 6 so that the larger the air-fuel ratio R1 of the exhaust gas flowing into the LNT catalyst 6 is, the more the LNT catalyst is corrected. The amount of ammonia slip from 6 can be calculated more accurately.

(Embodiment 3)
Hereinafter, the third embodiment of the present disclosure will be described. Here, the differences from the above embodiments 1 and 2 will be mainly described, and the common points with the above embodiments 1 and 2 will be described in detail by using a common reference code. Omit.

In the above-described first and second embodiments, the correction unit 14 can further correct the slip amount of ammonia from the LNT catalyst 6 based on the air-fuel ratio R2 of the exhaust gas flowing out from the LNT catalyst 6.

For example, the correction unit 14 acquires the air-fuel ratio R2 of the exhaust gas flowing out from the LNT catalyst 6, and the air-fuel ratio R2 of the exhaust gas flowing out from the LNT catalyst 6 decreases from the stoichiometric air-fuel ratio so that the ammonia from the LNT catalyst 6 is reduced. It can be corrected so that the slip amount increases.

Here, when the amount of ammonia slip from the LNT catalyst 6 was actually measured with respect to the air-fuel ratio R2 of the exhaust gas flowing out from the LNT catalyst 6, the amount of ammonia slip increased as the air-fuel ratio R2 decreased from the stoichiometric air-fuel ratio. I found out that I would do it. This is because when the air-fuel ratio R2 becomes smaller than the stoichiometric air-fuel ratio, the oxygen concentration in the LNT catalyst 6 is greatly reduced, NO _X occluded in the LNT catalyst 6 is reacted with such as hydrogen, ammonia in LNT catalyst 6 It is probable that the amount produced increased. Therefore, the correction unit 14 corrects the amount of ammonia slip calculated from the base map so that the amount of ammonia slip from the LNT catalyst 6 increases as the acquired air-fuel ratio R2 decreases from the stoichiometric air-fuel ratio. ..

For example, as shown in FIG. 6, in the correction unit 14, the value of the correction coefficient with respect to the air-fuel ratio R2 of the outlet lambda sensor 9b, that is, the air-fuel ratio R2 of the exhaust gas flowing out from the LNT catalyst 6, is based on experiments and simulations. It is preset. This correction coefficient is set so that the slip amount of ammonia increases as the air-fuel ratio R2 of the exhaust gas flowing out from the LNT catalyst 6 decreases from the stoichiometric air-fuel ratio.

The correction unit 14 acquires the air-fuel ratio R2 of the exhaust gas detected by the outlet lambda sensor 9b during the rich period, and obtains a correction coefficient corresponding to the air-fuel ratio R2. At this time, the correction unit 14 acquires the air-fuel ratio R2 between the time T2 and the time T3 in which the reduction amount decreases according to the decrease of _{NO X} occluded in the LNT catalyst 6 in the rich period, and obtains the correction coefficient. Is preferable. Then, the correction unit 14 adds the correction coefficient corresponding to the occluded amount of sulfur and the correction coefficient corresponding to the air-fuel ratio R1 to the slip amount of ammonia calculated based on the base map, and the outlet lambda sensor. The slip amount of ammonia is corrected by further multiplying by the correction coefficient corresponding to the air-fuel ratio R2 of 9b.

Here, the change in the amount of ammonia slip according to the air-fuel ratio R2 is due to a factor different from the change in the amount of ammonia slip according to the amount of sulfur stored in the LNT catalyst 6. Therefore, the correction unit 14 can more accurately calculate the slip amount of ammonia by correcting the slip amount of ammonia from the LNT catalyst 6 based on the air-fuel ratio R2.

According to the present embodiment, the correction unit 14 corrects so that the slip amount of ammonia from the LNT catalyst 6 increases as the air-fuel ratio R2 of the exhaust gas flowing out from the LNT catalyst 6 decreases from the stoichiometric air-fuel ratio. Therefore, the slip amount of ammonia from the LNT catalyst 6 can be calculated more accurately.

(Embodiment 4)
Hereinafter, the fourth embodiment of the present disclosure will be described. Here, the differences from the above-described embodiments 1 to 3 will be mainly described, and the common points with the above-described embodiments 1 to 3 will be described in detail by using a common reference code. Omit.

In the above-described first to third embodiments, the correction unit 14 can further correct the amount of ammonia slip from the LNT catalyst 6 based on the amount _{of NO X stored in the LNT catalyst 6.}

For example, the correction unit 14 can acquire the storage amount _{of NO X in} the LNT catalyst 6 and correct so that the slip amount of ammonia from the LNT catalyst 6 increases as the storage amount of _{NO X increases.}

Here, when the slip amount of ammonia from the LNT catalyst 6 was actually _{measured with respect to the occluded amount of NO X in} the LNT catalyst 6, it was found that the slip amount of ammonia increased as the occluded amount increased. It is considered that this is because the larger the occluded amount _{of NO X} in the LNT catalyst 6, the _{more the reduced amount of NO X} increased, and the more the amount of ammonia produced in the LNT catalyst 6 increased accordingly. Therefore, the correction unit 14 corrects the amount of ammonia slip calculated from the base map so that the amount of ammonia slip from the LNT catalyst 6 increases as the amount of _{acquired NO X stored increases.}

For example, the correction unit 14, as shown in FIG. 7, the value of the correction coefficient for storage amount of the NO _X in the LNT catalyst 6 are set in advance based on an experiment and simulation. This correction coefficient is set so that the slip amount of ammonia increases as the occluded amount _{of NO X} in the LNT catalyst 6 increases.

The correction unit 14 acquires the storage amount _{of NO X} in the LNT catalyst 6 and obtains a correction coefficient corresponding to the storage amount of _{NO X.} The correction unit 14 can calculate the occlusion amount of _{NO X based on, for example, the NO X} concentration of the exhaust gas flowing into the LNT catalyst 6 and the flow rate of the intake air in the internal combustion engine 1. At this time, _{it is preferable that the correction unit 14 obtains the NO X} concentration of the exhaust gas and the flow rate of the intake air during the lean air-fuel ratio period in _{which the NO X is occluded in the LNT catalyst 6 to obtain the correction coefficient.}
The NO _X concentration of the exhaust gas can be calculated based on the amount of fuel supplied in the internal combustion engine 1, or can be obtained by arranging a _{NO X sensor on the upstream side of the LNT catalyst 6.} Further, the flow rate of the intake air can be acquired from the internal combustion engine control unit 4.

Then, the correction unit 14 corresponds to the correction coefficient corresponding to the occluded amount of sulfur, the correction coefficient corresponding to the air-fuel ratio R1, and the air-fuel ratio R2 with respect to the slip amount of ammonia calculated based on the base map. In addition to the correction coefficient, the slip amount of ammonia is corrected by further multiplying the correction coefficient corresponding to the occluded amount _{of NO X} in the LNT catalyst 6.

Here, the slip amount of ammonia from the LNT catalyst 6 changes greatly depending on the occluded amount of _{NO X.} Therefore, the correction unit 14 _{further corrects the slip amount of ammonia from the LNT catalyst 6 based on the occluded amount of NO X} in the LNT catalyst 6, thereby making the slip amount of ammonia from the LNT catalyst 6 more accurate. Can be calculated.

According to the present embodiment, the correction unit 14 further corrects the slip amount of ammonia from the LNT catalyst 6 so that the larger the occluded amount of _{NO X is, the more the slip amount of ammonia from the LNT catalyst 6 is increased.} It can be calculated more accurately.

(Embodiment 5)
Hereinafter, the fifth embodiment of the present disclosure will be described. Here, the differences from the above-described embodiments 1 to 4 will be mainly described, and the common points with the above-described embodiments 1 to 4 will be described in detail by using common reference numerals. Omit.

In the above-described first to fourth embodiments, the correction unit 14 can further correct the slip amount of ammonia from the LNT catalyst 6 based on the internal temperature of the LNT catalyst 6.

For example, the correction unit 14 can acquire the internal temperature of the LNT catalyst 6 and correct the slip amount of ammonia from the LNT catalyst 6 so that the higher the internal temperature of the LNT catalyst 6 is.

Here, when the amount of ammonia slip from the LNT catalyst 6 was actually measured with respect to the internal temperature of the LNT catalyst 6, it was found that the higher the internal temperature of the LNT catalyst 6, the greater the amount of ammonia slip. This is because the internal temperature of the LNT catalyst 6 affects the reaction with _{NO X, and due to the relationship between the release rate of NO X} and the reduction rate, the higher the internal temperature of the LNT catalyst 6, the higher the amount of ammonia produced. Conceivable. Therefore, the correction unit 14 further corrects the slip amount of ammonia calculated from the base map so that the higher the internal temperature of the acquired LNT catalyst 6 is, the more the slip amount of ammonia from the LNT catalyst 6 increases.

For example, as shown in FIG. 8, in the correction unit 14, the value of the correction coefficient with respect to the internal temperature of the LNT catalyst 6 is preset based on experiments, simulations, and the like. This correction coefficient is set so that the slip amount of ammonia increases as the internal temperature of the LNT catalyst 6 increases.

The correction unit 14 acquires the internal temperature of the LNT catalyst 6 during the rich period, and obtains a correction coefficient corresponding to the internal temperature. The internal temperature of the LNT catalyst 6 is calculated, for example, by multiplying the difference in temperature detected by the temperature sensor 10a and the temperature sensor 10b by the response delays of the temperature sensors 10a and 10b according to the flow rate of the exhaust gas. Can be done. At this time, the correction unit 14 acquires and corrects the internal temperature of the LNT catalyst 6 between the time T2 and the time T3 in which the reduction amount decreases according to the decrease of _{NO X} occluded in the LNT catalyst 6 during the rich period. It is preferable to obtain the coefficient.

Then, the correction unit 14 corresponds to the correction coefficient corresponding to the occluded amount of sulfur, the correction coefficient corresponding to the air-fuel ratio R1, and the air-fuel ratio R2 with respect to the slip amount of ammonia calculated based on the base map. In _{addition to the correction coefficient and the correction coefficient corresponding to the occlusion amount of NO X} , the slip amount of ammonia is corrected by further multiplying by the correction coefficient corresponding to the internal temperature of the LNT catalyst 6.

Here, the change in the amount of ammonia slip according to the internal temperature of the LNT catalyst 6 is due to a factor different from the change in the amount of ammonia slip according to the amount of sulfur stored in the LNT catalyst 6. Therefore, the correction unit 14 further corrects the slip amount of ammonia from the LNT catalyst 6 based on the internal temperature of the LNT catalyst 6 to more accurately calculate the slip amount of ammonia from the LNT catalyst 6. Can be done.

According to the present embodiment, the correction unit 14 corrects the slip amount of ammonia from the LNT catalyst 6 so that the higher the internal temperature of the LNT catalyst 6 is, the more the slip amount of ammonia from the LNT catalyst 6 is. It can be calculated more accurately.

Moreover, in Embodiment 1-5 of the above embodiment, the supply control section 15 has been controlling the supply amount of the reducing agent to the SCR catalyst 7 based on the slip amount of ammonia that has been corrected by the correction unit 14, purification of the NO _X It is only necessary to be able to control, and it is not limited to this.
For example, the purification control unit 12 controls the purification _{of NO X} in the SCR catalyst 7 by controlling the amount of _{NO X} discharged from the internal combustion engine 1 based on the slip amount of ammonia corrected by the correction unit 14. You can also do it.

Further, in the above-described embodiments 1 to 5, the purification control unit 12 controls _{the purification of NO X} in the SCR catalyst 7 based on the amount of ammonia slip corrected by the correction unit 14, but the correction unit 14 corrects it. It suffices if the slip amount of the generated ammonia can be used, and the present invention is not limited to the SCR catalyst 7.

In addition, the above embodiments are merely examples of embodiment of the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. be. That is, the present invention can be implemented in various forms without departing from its gist or its main features. For example, the disclosure of the shape, number, and the like of each part described in the above embodiment is merely an example, and can be appropriately modified and carried out.

The purification control device according to the present disclosure can be used as a device for controlling the purification of _{NO X.}

1 Internal combustion engine 2 Intake pipe 3 Exhaust pipe 4 Internal combustion engine control unit 5 Purification device 6 NO _X Occlusion reduction type catalyst 7 Selective reduction type catalyst 8 Purification control device 9a Inlet lambda sensor 9b Outlet lambda sensor 10a to 10c Temperature sensor 11 Supply unit 12 Purification control unit 13 Air-fuel ratio control unit 14 Correction unit 15 Supply control unit N Ammonia R1, R2 Air-fuel ratio T1 to T3 Hours C1 to C3 Temperature

Claims (7)

A cleaning control apparatus for controlling the purification of the discharged NO _X from an internal combustion engine,
Calculates the slip amount of ammonia from the _the NO _X storage reduction catalyst based on the temperature of the NO _X storage reduction catalyst provided in an exhaust pipe of a vehicle, the NO _X based on the supply amount of the fuel in the internal combustion engine A purification control device including a correction unit that calculates the amount of sulfur stored in the storage-reducing catalyst and corrects the slip amount of ammonia based on the amount of sulfur stored in the _{NO-X storage-reducing catalyst.} The purification control device according to claim 1, wherein the correction unit corrects so that the slip amount of ammonia decreases as the amount of sulfur stored in the _{NO X storage-reducing catalyst increases.} Wherein the correction unit is configured to acquire the air-fuel ratio of the exhaust gas flowing into the NO _X occluding and reducing catalyst, the slip amount of the ammonia larger the air-fuel ratio of the exhaust gas flowing into the _the NO _X storage reduction catalyst is reduced The purification control device according to claim 1 or 2, which is further amended as described above. Wherein the correction unit is configured to acquire the air-fuel ratio of the exhaust gas flowing out from _the NO _X storage reduction catalyst, the air-fuel ratio of the exhaust gas flowing out of the _the NO _X storage catalytic reduction catalyst of the ammonia as lower than the stoichiometric air-fuel ratio The purification control device according to any one of claims 1 to 3, further correcting so that the slip amount increases. The correction unit obtains the occluded amount _{of NO X in the NO X} occluded reduction catalyst, and further corrects so that the slip amount of the ammonia increases as the occluded amount of _{NO X increases.} The purification control device according to any one item. Wherein the correction unit is configured _the NO _X storage reduction type internal temperature to get the catalyst, the _the NO _X storage reduction claims 1 to 5, the slip amount of the ammonia as the internal temperature is higher catalyst further corrected so as to increase The purification control device according to any one of the above. A claim further comprising a supply control unit that controls the supply amount of the reducing agent to the selective reduction catalyst arranged on the downstream side of the _{NO X} occlusion reduction catalyst based on the slip amount of the ammonia corrected by the correction unit. Item 5. The purification control device according to any one of Items 1 to 6.

Images