WO2019172357A1

WO2019172357A1 - Exhaust purification device, vehicle, and exhaust purification control device

Info

Publication number: WO2019172357A1
Application number: PCT/JP2019/009013
Authority: WO
Inventors: 洋阿野田
Original assignee: いすゞ自動車株式会社
Priority date: 2018-03-08
Filing date: 2019-03-07
Publication date: 2019-09-12
Also published as: CN111819349A; JP2019157667A

Abstract

This exhaust purification device is provided with: an exhaust pipe through which exhaust gas generated from an internal combustion engine flows; a NOx selective reduction-type catalyst which is disposed in the exhaust pipe and which purifies nitrogen oxides in the exhaust gas by adsorbing a reducing agent; a NOx storage reduction-type catalyst that is disposed upstream of the NOx selective reduction-type catalyst in the exhaust pipe in an exhaust direction in which the exhaust gas flows, and that stores nitrogen oxides in the exhaust gas; an adjustment unit which adjusts the flow rate of exhaust gas returned from the exhaust pipe to an intake pipe of the internal combustion engine; and a control unit which controls the adjustment unit such that the reduction reaction between the reducing agent and the nitrogen oxides contained in the exhaust gas is promoted according to the adsorption amount of the reducing agent of the NOx selective reduction-type catalyst.

Description

Exhaust purification device, vehicle, and exhaust purification control device

The present disclosure relates to an exhaust purification device, a vehicle, and an exhaust purification control device.

Conventionally, exhaust gas purification having a NOx occlusion reduction type catalyst for purifying nitrogen oxide (hereinafter referred to as “NOx”) contained in exhaust gas generated in an internal combustion engine and a NOx selective reduction type catalyst for reducing the NOx. An apparatus is known (see, for example, Patent Document 1). The NOx selective reduction catalyst adsorbs a reducing agent (for example, ammonia) generated from a precursor (for example, urea water) supplied into the exhaust pipe, and reduces the NOx contained in the exhaust gas by the adsorbed ammonia.

The NOx occlusion reduction type catalyst has a property of occluded NOx at a low temperature when the NOx selective reduction type catalyst is in an inactive region. Therefore, even when the temperature is low, NOx is occluded by the NOx occlusion reduction type catalyst and then reduced. Thus, when the NOx occlusion reduction type catalyst is used together with the NOx selective reduction type catalyst in the exhaust purification device, the exhaust purification processing in the exhaust purification device can be effectively performed.

Japanese Unexamined Patent Publication No. 2016-125390

By the way, the exhaust gas purification apparatus may be provided with a collection unit for collecting particulate matter. When the regeneration process for burning the particulate matter collected by raising the temperature of the exhaust gas flowing into the collection unit is performed, the temperature of the exhaust purification device rises. When the temperature in the exhaust purification device (exhaust pipe) rises, there arises a problem that ammonia is desorbed from the NOx selective reduction catalyst. Therefore, when the temperature in the exhaust purification device is raised, ammonia from the NOx selective reduction catalyst can be as much as possible. It is preferable to decrease.

However, when the NOx occlusion reduction amount of the NOx occlusion reduction catalyst is small, NOx contained in the exhaust gas is occluded in the NOx occlusion reduction catalyst, so the NOx selective reduction catalyst ammonia is absorbed by the NOx contained in the exhaust gas. It cannot be reduced. As a result, there arises a problem that ammonia still desorbs from the NOx selective reduction catalyst.

An object of the present disclosure is to provide an exhaust purification device, a vehicle, and an exhaust purification control device capable of suppressing a reducing agent from desorbing from a NOx selective reduction catalyst due to a temperature rise in an exhaust pipe. is there.

An exhaust emission control device according to the present disclosure includes:
An exhaust pipe through which exhaust gas generated from the internal combustion engine flows;
A NOx selective reduction catalyst that is disposed in the exhaust pipe and purifies nitrogen oxides in the exhaust gas by adsorbing a reducing agent;
An NOx occlusion reduction type catalyst which is disposed upstream of the NOx selective reduction type catalyst in the exhaust pipe in the exhaust direction in which the exhaust gas flows, and occludes nitrogen oxides in the exhaust gas;
A recirculation path section for connecting the exhaust pipe and the exhaust pipe of the internal combustion engine from the exhaust pipe, and recirculating the exhaust gas in the exhaust pipe to the intake pipe;
An adjustment unit for adjusting the flow rate of the exhaust gas recirculated in the recirculation path unit;
A control unit that controls the adjusting unit so that a reduction action of the reducing agent and nitrogen oxides contained in the exhaust gas is promoted according to the amount of adsorption of the reducing agent of the NOx selective reduction catalyst; ,
Is provided.

The vehicle according to the present disclosure is
The above-described exhaust purification device is provided.

An exhaust purification control apparatus according to the present disclosure includes:
An exhaust pipe through which exhaust gas generated from an internal combustion engine flows, a NOx selective reduction catalyst that is disposed in the exhaust pipe and purifies nitrogen oxides in the exhaust gas by adsorbing a reducing agent, and the exhaust gas includes An NOx occlusion reduction type catalyst that is disposed upstream of the NOx selective reduction type catalyst in the exhaust pipe in the flowing exhaust direction and occludes nitrogen oxides in the exhaust gas, and an intake pipe of the internal combustion engine from the exhaust pipe An exhaust gas purification control device for an exhaust gas purification device, comprising: a recirculation path portion that connects the exhaust pipe and the exhaust pipe, and recirculates the exhaust gas in the exhaust pipe to the intake pipe,
An adjustment unit for adjusting the flow rate of the exhaust gas recirculated in the recirculation path unit;
A control unit that controls the adjusting unit so that a reduction action of the reducing agent and nitrogen oxides contained in the exhaust gas is promoted according to the amount of adsorption of the reducing agent of the NOx selective reduction catalyst; ,
Is provided.

According to the present disclosure, it is possible to prevent the reducing agent from desorbing from the NOx selective reduction catalyst due to the temperature rise in the exhaust pipe.

FIG. 1 is a schematic configuration diagram illustrating an exhaust system of an internal combustion engine to which an exhaust emission control device according to an embodiment of the present disclosure is applied. FIG. 2 is a graph showing the temperature change of NOx storage efficiency in the NOx storage reduction catalyst. FIG. 3 is a graph showing the temperature change of the NOx purification rate in the NOx selective reduction catalyst. FIG. 4 is a flowchart showing an operation example of the purification control in the exhaust purification device. FIG. 5 is a flowchart showing an operation example of the exhaust gas flow rate control in the recirculation path section.

Hereinafter, embodiments of the present disclosure will be described in detail based on the drawings. FIG. 1 is a schematic configuration diagram illustrating an exhaust system of an internal combustion engine 1 to which an exhaust purification device 100 according to an embodiment of the present disclosure is applied.

As shown in FIG. 1, the internal combustion engine 1 is, for example, a diesel engine mounted on a vehicle V, and is provided with an exhaust purification device 100 for guiding exhaust gas generated in the internal combustion engine 1 to the atmosphere. The exhaust purification device 100 includes an intake pipe 110, an exhaust pipe 120, a first temperature detection unit 130, a second temperature detection unit 140, a urea water injection unit 150, a recirculation path unit 160, and a control unit 300. It has.

The intake pipe 110 is provided with an intake valve (not shown), and the intake pipe 110 sucks outside air into the internal combustion engine 1 by opening the intake valve under the control of the control unit 300.

Exhaust gas generated from the internal combustion engine 1 flows through the exhaust pipe 120. In the exhaust pipe 120, a NOx occlusion reduction catalyst 210 and a DPF (capacitor) as an example of a collection unit are sequentially arranged from the upstream side in the direction in which the exhaust gas flows (the direction from the left to the right in the drawing, hereinafter referred to as “exhaust direction”). A diesel particulate filter) 220, a NOx selective reduction catalyst 230, and the like.

The NOx occlusion reduction type catalyst 210 is disposed upstream of the DPF 220 and the NOx selective reduction type catalyst 230 in the exhaust pipe 120 in the exhaust direction, and occludes nitrogen oxides (hereinafter referred to as NOx) in the exhaust gas.

Specifically, the NOx occlusion reduction type catalyst 210 occludes NOx in the exhaust gas when the exhaust temperature is the occlusion temperature and the exhaust air-fuel ratio is in a lean state. The range of the occlusion temperature includes a temperature at which the NOx selective reduction catalyst 230 is in a non-activated region.

The NOx occluded in the NOx occlusion reduction catalyst 210 is reduced by reacting with the hydrocarbons and carbon monoxide in the exhaust gas by setting the exhaust air-fuel ratio to a rich state under the control of the control unit 300. .

The DPF 220 collects particulate matter contained in the exhaust gas that passes through the DPF 220. In the DPF 220, the particulate matter is removed by executing a regeneration process for burning the collected particulate matter under the control of the control unit 300. Specifically, under the control of the control unit 300, post injection into the cylinder of the internal combustion engine 1 and fuel supply into the exhaust pipe 120 are performed, for example, hydrocarbons are supplied to an oxidation catalyst (not shown) An oxidation reaction occurs in the oxidation catalyst, and the temperature of the exhaust gas in the exhaust pipe 120 rises. Then, the particulate matter is burned by the exhaust gas whose temperature has risen flowing into the DPF 220.

The NOx selective reduction catalyst 230 is disposed downstream of the DPF 220 in the exhaust pipe 120 and adsorbs ammonia as an example of a reducing agent generated based on the urea water injected by the urea water injection unit 150. The NOx selective reduction catalyst 230 reduces the NOx by reacting the adsorbed ammonia with NOx contained in the exhaust gas passing through the NOx selective reduction catalyst 230.

The first temperature detection unit 130 is arranged upstream of the NOx storage reduction catalyst 210 in the exhaust direction, and detects the temperature of the front portion of the NOx storage reduction catalyst 210 in the exhaust pipe 120.

The second temperature detection unit 140 is arranged upstream of the NOx selective reduction catalyst 230 in the exhaust direction, and detects the temperature of the front portion of the NOx selective reduction catalyst 230 in the exhaust pipe 120.

The urea water injection unit 150 is disposed upstream of the NOx selective reduction catalyst 230 in the exhaust pipe 120. When urea water is supplied into the exhaust pipe 120 by the urea water injection unit 150, the urea water is hydrolyzed by the temperature in the exhaust pipe 120, and ammonia is generated. Then, ammonia is adsorbed on the NOx selective reduction catalyst 230.

The recirculation path section 160 is a path that branches from the exhaust pipe 120 and recirculates the exhaust gas in the exhaust pipe 120 toward the intake pipe 110, and is connected to the intake pipe 110 and the exhaust pipe 120.

The recirculation path section 160 is provided with an adjustment section 161 that adjusts the flow rate of exhaust gas that is returned from the exhaust pipe 120 to the intake pipe 110 via the recirculation path section 160. The adjustment unit 161 adjusts the flow rate of the exhaust gas returned from the exhaust pipe 120 to the intake pipe 110 by changing the flow path of the exhaust gas from the open state to the closed state under the control of the control unit 300.

The controller 300 is, for example, an electronic control unit (ECU), and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input / output circuit (not shown). . The control unit 300 performs a regeneration process for burning the particulate matter collected in the DPF 220 based on a preset program, a rich process for making the exhaust air-fuel ratio in the exhaust pipe 120 rich, and a recirculation path unit 160. A process for adjusting the flow rate of the exhaust gas is executed. The control unit 300 corresponds to the “exhaust gas purification control device” of the present disclosure.

The control unit 300 estimates the ammonia adsorption amount of the NOx selective reduction catalyst 230 when executing the regeneration process of the DPF 220. Then, the control unit 300 adjusts the adjustment unit 161 so that the reduction action of ammonia adsorbed on the NOx selective reduction catalyst 230 and NOx contained in the exhaust gas is accelerated according to the estimated amount of adsorption of ammonia. To control. The control unit 300 corresponds to the “estimation unit” of the present disclosure.

More specifically, the control unit 300 estimates the NOx occlusion amount of the NOx occlusion reduction type catalyst 210. When the ammonia adsorption amount is larger than a predetermined target amount, the control unit 300 controls the adjustment unit 161 based on the estimated occlusion amount. It is determined whether or not to control. When the estimated storage amount is less than the predetermined storage amount of the NOx storage reduction catalyst 210, the control unit 300 controls the adjustment unit 161 so as to reduce the flow rate of the exhaust gas in the recirculation path unit 160. The predetermined target amount is, for example, the amount of ammonia that causes the ammonia slip concentration in the NOx selective reduction catalyst 230 to be equal to or less than the target value during the regeneration process.

The estimated adsorption amount of ammonia is estimated by the following equation (1).
Estimated adsorption amount of ammonia = previous adsorption amount of ammonia + supply ammonia amount-consumption ammonia amount-ammonia desorption amount (1)

The supplied ammonia amount is the amount of ammonia supplied to the NOx selective reduction catalyst 230, and is calculated based on the amount of urea water injected by the urea water injection unit 150.

The consumed ammonia amount is the amount of ammonia consumed in the NOx purification reaction, the amount of NOx that has passed through the NOx selective reduction catalyst 230, the temperature detection result of the second temperature detection unit 140, the flow rate of exhaust gas, Is calculated based on the ratio of NO ₂ and the amount of adsorbed ammonia.

The amount of NOx that has passed through the NOx selective reduction catalyst 230 is detected based on a sensor or the like (not shown). The ratio of NO ₂ in NOx is estimated by correcting the map based on the engine speed and the fuel injection amount based on the NOx storage amount and temperature of the NOx storage reduction catalyst 210. The previous adsorption amount of ammonia is the current adsorption amount of ammonia calculated last time by the equation (1).

The ammonia desorption amount is the amount of ammonia desorbed from the NOx selective reduction catalyst 230, and is calculated based on the ammonia adsorption amount, the temperature detection result of the second temperature detection unit 140, and the exhaust gas flow rate.

The estimated storage amount of NOx is estimated by the following equation (2).
NOx occlusion amount = A + B × CDE (2)
A: NOx stored amount B: NOx concentration upstream of the NOx storage reduction catalyst 210 C: NOx storage efficiency of the NOx storage reduction catalyst 210 D: NOx amount discharged from the NOx storage reduction catalyst 210 E: Amount of NOx reduced from the NOx occlusion reduction type catalyst 210

The stored amount of NOx is the amount of NOx already stored in the NOx storage-reduction catalyst 210. For example, the estimated value of the stored amount of NOx estimated last time is used.

The upstream NOx concentration of the NOx storage reduction catalyst 210 is the NOx concentration in the exhaust gas upstream of the NOx storage reduction catalyst 210 in the exhaust pipe 120. For example, the NOx concentration detected by a sensor (not shown). Is used.

The NOx occlusion efficiency of the NOx occlusion reduction catalyst 210 depends on the temperature detection result of the first temperature detector 130, the exhaust gas flow rate, the NOx concentration upstream of the NOx occlusion reduction catalyst 210, the NOx occlusion amount, and the like. Calculated based on The flow rate of the exhaust gas is the amount of exhaust gas flowing into the exhaust pipe 120 and is detected by a sensor or the like (not shown).

The amount of NOx discharged from the NOx storage reduction catalyst 210 is calculated based on the temperature detection result of the first temperature detection unit 130, the stored amount of NOx, and the like.

The amount of NOx reduced from the NOx storage reduction catalyst 210 is calculated based on the temperature detection result of the first temperature detection unit 130, the exhaust gas flow rate, the already stored storage amount of the NOx storage reduction catalyst 210, the exhaust air-fuel ratio, and the like. Is done. The exhaust air-fuel ratio is calculated based on the fuel injection amount in the exhaust pipe 120 and the like.

Here, when the temperature inside the exhaust pipe 120 rises due to regeneration processing or the like, there is a problem that ammonia is desorbed from the NOx selective reduction catalyst 230. Therefore, when the temperature inside the exhaust pipe 120 rises, NOx It is preferable to reduce ammonia from the selective catalytic reduction catalyst 230 as much as possible.

However, when the NOx occlusion amount of the NOx occlusion reduction type catalyst 210 is small, NOx contained in the exhaust gas is occluded in the NOx occlusion reduction type catalyst 210. Therefore, the NOx selective reduction type catalyst 230 is absorbed by the NOx contained in the exhaust gas. The ammonia can not be reduced. As a result, there arises a problem that ammonia is still desorbed from the NOx selective reduction catalyst 230.

Therefore, in this embodiment, in such a case, the adjustment unit 161 is controlled so as to reduce the flow rate of the exhaust gas in the recirculation path unit 160, so the exhaust gas returned to the intake pipe 110 by the recirculation path unit 160. Gas is reduced. Since the exhaust gas contains NOx, the concentration of NOx in the exhaust gas flowing through the exhaust pipe 120 is increased by controlling the adjustment unit 161.

Thereby, the NOx occlusion amount of the NOx occlusion reduction type catalyst 210 can be increased, and the ammonia adsorbed on the NOx selective reduction type catalyst 230 can be reduced by the purification reaction with NOx contained in the exhaust gas.

As a result, when the temperature in the exhaust pipe 120 rises due to regeneration processing or the like, ammonia in the NOx selective reduction catalyst 230 can be reduced by NOx contained in the exhaust gas, and as a result, the temperature rises. Desorption of ammonia can be suppressed.

Further, the control unit 300 may determine whether to control the adjustment unit 161 based on the detection result of the first temperature detection unit 130. FIG. 2 is a graph showing a change in the NOx storage efficiency with temperature in the NOx storage reduction catalyst 210.

As shown in FIG. 2, the NOx occlusion efficiency of the NOx occlusion reduction type catalyst 210 is relatively high occlusion efficiency, for example, in the range of temperature T1 to temperature T2. For this reason, the control unit 300 determines to control the adjustment unit 161 in such a temperature range that the occlusion efficiency is higher than the predetermined efficiency. The predetermined efficiency can be appropriately determined according to the storage amount of the NOx storage reduction catalyst 210 or the like. Thereby, the storage efficiency of the NOx storage reduction catalyst 210 can be improved, and ammonia in the NOx selective reduction catalyst 230 can be reduced by the NOx contained in the exhaust gas.

Further, the control unit 300 may determine whether to control the adjustment unit 161 based on the detection result of the second temperature detection unit 140. FIG. 3 is a graph showing the temperature change of the NOx purification rate in the NOx selective reduction catalyst 230. As shown in FIG.

As shown in FIG. 3, it can be confirmed that the NOx purification rate becomes a relatively high purification rate when the NOx selective reduction catalyst 230 reaches or exceeds the activation temperature T3 that becomes the active region. Therefore, the control part 300 determines with controlling the adjustment part 161, when it is more than the activation temperature T3. As a result, the ammonia reduction efficiency of the NOx selective reduction catalyst 230 can be improved, and as a result, the ammonia of the NOx selective reduction catalyst 230 can be easily reduced.

Further, the control unit 300 may control the adjustment unit 161 based on the temperature of the NOx storage reduction catalyst 210 and the temperature of the NOx selective reduction catalyst 230. Table 1 is a graph showing the relationship between the estimated storage amount of NOx, the temperature of the NOx storage reduction catalyst 210, the temperature of the NOx selective reduction catalyst 230, and the exhaust gas flow rate in the recirculation path section 160.

“Estimated storage amount” in Table 1 indicates the estimated storage amount of the NOx storage reduction catalyst 210. The “first temperature” in Table 1 indicates the temperature of the NOx storage reduction catalyst 210 (temperature detection result of the first temperature detection unit 130). “Second temperature” in Table 1 indicates the temperature of the NOx selective reduction catalyst 230 (temperature detection result of the second temperature detection unit 140). “Flow rate” in Table 1 indicates the exhaust gas flow rate of the recirculation path section 160.

Further, “large” in the “estimated storage amount” in Table 1 indicates a case where the estimated storage amount of the NOx storage reduction catalyst 210 is larger than the predetermined storage amount, and “small” indicates that the NOx storage reduction catalyst 210. The case where the estimated occlusion amount is smaller than the predetermined occlusion amount is shown.

For example, the control unit 300 controls the adjustment unit 161 by reading the relationship shown in Table 1 from a storage unit (not shown) or the like according to conditions. By doing in this way, control of the adjustment part 161 can be simplified.

Specifically, when the estimated amount of occlusion is large and the temperature of the NOx selective reduction catalyst 230 is equal to or lower than the activation temperature (the first line of Table 1), the flow rate of the exhaust gas flows through the recirculation path unit 160. The amount is “normal” in a fully open state.

When the temperature of the NOx selective reduction catalyst 230 is equal to or lower than the activation temperature, NOx and ammonia are not easily reduced, and NOx is easily discharged to the outside. Therefore, the necessity of reducing the amount of NOx contained in the exhaust gas by using the recirculation path unit 160 is increased, so that the control as in the first row of Table 1 is effective.

When the estimated amount of occlusion is large and the temperature of the NOx selective reduction catalyst 230 is equal to or higher than the activation temperature (the second row in Table 1), the flow rate of the exhaust gas is a flow rate that is “reduced” from the “normal” flow rate. The The degree to which the amount is reduced is determined according to the estimated storage amount, the estimated adsorption amount of ammonia, and the like.

When the flow rate of the exhaust gas in the recirculation path section 160 is reduced, NOx contained in the exhaust gas flowing through the exhaust pipe 120 increases. However, when the temperature of the NOx selective reduction catalyst 230 is equal to or higher than the activation temperature, NOx and ammonia are easily reduced, so that ammonia can be efficiently reduced. As a result, the control as shown in the second row of Table 1 is effective.

Further, when the estimated storage amount is small, the temperature of the NOx storage reduction catalyst 210 is outside the storage temperature range, and the temperature of the NOx selective reduction catalyst 230 is equal to or higher than the activation temperature (third line in Table 1), The flow rate of the exhaust gas is “decreased”. The storage temperature range is, for example, a range from the temperature T1 to the temperature T2 in FIG.

When the temperature of the NOx storage reduction catalyst 210 is outside the storage temperature range and the estimated storage amount is small, the NOx storage reduction catalyst 210 cannot store NOx and is exhausted from the NOx storage reduction catalyst 210. This is a situation where NOx cannot be used. Therefore, in such a case, the exhaust gas in the recirculation path unit 160 can be reduced, the concentration of NOx contained in the exhaust gas in the exhaust pipe 120 can be increased, and ammonia can be reduced by using the NOx. As a result, the control as shown in the third row of Table 1 is effective.

Further, when the estimated storage amount is small, the temperature of the NOx storage reduction catalyst 210 is outside the storage temperature range, and the temperature of the NOx selective reduction catalyst 230 is equal to or lower than the activation temperature (the fourth row of Table 1), The flow rate of the exhaust gas is set to “normal”.

In this case, it is difficult to reduce ammonia in the NOx selective reduction catalyst 230 and it is difficult to store NOx in the NOx storage reduction catalyst 210. Therefore, it is desirable to reduce NOx in the exhaust pipe 120 as much as possible. Therefore, by performing the control as shown in the fourth row of Table 1, NOx contained in the exhaust gas flowing in the exhaust pipe 120 can be reduced using the recirculation path section 160. As a result, the control as shown in the fourth row of Table 1 is effective.

Further, when the estimated storage amount is small and the temperature of the NOx storage reduction catalyst 210 is within the storage temperature range (line 5 in Table 1), the flow rate of the exhaust gas is set to “decrease”. In such a case, it is possible to promote the reduction action of NOx and ammonia contained in the exhaust gas while actively storing NOx in the NOx storage reduction catalyst 210. As a result, the control as shown in the fifth line of Table 1 is effective.

Further, the control unit 300 prohibits the rich process when the reproduction process is executed.

By prohibiting the rich process, the NOx occlusion amount in the NOx occlusion reduction type catalyst 210 can be easily increased. That is, since the ammonia in the NOx selective reduction catalyst 230 can be easily reduced by NOx contained in the exhaust gas, the regeneration process can be executed quickly.

An operation example of the purification control in the exhaust purification apparatus 100 configured as described above will be described. FIG. 4 is a flowchart showing an operation example of the purification control in the exhaust purification device 100. The process in FIG. 4 is appropriately executed while the vehicle V is traveling, for example.

As shown in FIG. 4, the control unit 300 determines whether or not it is necessary to execute the reproduction process (step S101). The determination as to whether the regeneration process in step S101 needs to be executed is based on, for example, the collected amount of particulate matter in the DPF 220. Specifically, when the trapped amount of the particulate matter in the DPF 220 reaches the amount to be burned, the control unit 300 determines that the regeneration process needs to be executed.

As a result of the determination, if it is not necessary to execute the reproduction process (step S101, NO), this control ends. On the other hand, when it is necessary to execute the reproduction process (step S101, YES), the control unit 300 prohibits the rich process (step S102).

Next, the controller 300 estimates the ammonia adsorption amount of the NOx selective reduction catalyst 230 (step S103). Next, the control unit 300 determines whether or not the ammonia adsorption amount is larger than a predetermined target amount (step S104).

As a result of the determination, if the ammonia adsorption amount is larger than the predetermined target amount (step S104, YES), the control unit 300 performs exhaust gas flow rate control in the recirculation path unit 160 described later (step S105). After step S105, the process returns to step S103.

On the other hand, when the ammonia adsorption amount is equal to or smaller than the predetermined target amount (step S104, NO), the control unit 300 determines whether or not the regeneration processing condition is satisfied (step S106). The regeneration process condition includes, for example, the temperature condition of the NOx storage reduction catalyst 210 and the like.

As a result of the determination, if the reproduction processing condition is not satisfied (step S106, NO), the process returns to step S103. Here, in the case of NO in step S106, and the reason why the process returns to step S103 after step S105, the exhaust gas passes through the exhaust pipe 120 during the process from step S103 to step S106. This is because the NOx storage amount and the ammonia adsorption amount vary due to the flow.

On the other hand, when the reproduction process condition is satisfied (step S106, YES), the control unit 300 executes the reproduction process (step S107). After the reproduction process is finished, this control is finished. This control is repeatedly executed while the vehicle V is traveling.

Next, an operation example of the exhaust gas flow rate control in step S105 in FIG. 4 will be described. FIG. 5 is a flowchart showing an operation example of the exhaust gas flow rate control in the recirculation path section 160. The process in FIG. 5 is executed when YES is determined in step S104 in FIG.

As shown in FIG. 5, the control unit 300 estimates the NOx occlusion amount of the NOx occlusion reduction type catalyst 210 (step S201). Next, the controller 300 determines whether or not the estimated storage amount of NOx is less than the predetermined storage amount (step S202).

As a result of the determination, if the estimated occlusion amount is equal to or greater than the predetermined occlusion amount (step S202, NO), the process transitions to step S204. On the other hand, when the estimated storage amount is less than the predetermined storage amount (step S202, YES), the control unit 300 determines whether or not the first temperature of the NOx storage reduction catalyst 210 is within a predetermined range (step S203). ). The first temperature is, for example, a detection result of the first temperature detection unit 130. Further, the predetermined range is, for example, within the range of T1 and T2 in FIG.

As a result of the determination, if the first temperature is within the predetermined range (step S203, YES), the process transitions to step S205. On the other hand, when the first temperature is not within the predetermined range (step S203, NO), the controller 300 determines whether or not the second temperature of the NOx selective reduction catalyst 230 is equal to or higher than the activation temperature (step S204). . The second temperature is, for example, a detection result of the second temperature detection unit 140.

As a result of the determination, when the second temperature is lower than the activation temperature (step S204, NO), this control ends. On the other hand, when the second temperature is equal to or higher than the activation temperature (step S204, YES), the control unit 300 controls the adjustment unit 161 to decrease the exhaust gas flow rate in the recirculation path unit 160 (step S205). Thereafter, this control ends. In addition, after this control is complete | finished, a process returns to step S103 in FIG.

According to the present embodiment configured as described above, the control unit 300 promotes the reduction action of ammonia and NOx contained in the exhaust gas according to the estimated ammonia adsorption amount of the NOx selective reduction catalyst 230. Thus, the adjustment unit 161 is controlled.

That is, ammonia in the NOx selective reduction catalyst 230 is reduced using NOx contained in the exhaust gas. As a result, it is possible to suppress the desorption of ammonia from the NOx selective reduction catalyst 230 due to the temperature rise in the exhaust pipe 120 during the regeneration process.

Further, when the ammonia adsorption amount is larger than the predetermined target amount and the estimated storage amount is less than the predetermined storage amount of the NOx storage reduction catalyst 210, the control unit 300 adjusts the adjustment unit 161 so as to decrease the flow rate of the exhaust gas. To control. As a result, the concentration of NOx contained in the exhaust gas is increased so that NOx is stored in the NOx storage reduction catalyst 210, and the ammonia in the NOx selective reduction catalyst 230 is reduced by the NOx by the NOx contained in the exhaust gas. Can do.

In the above embodiment, the NOx occlusion amount is estimated using the above-described equation (2). However, the present disclosure is not limited to this, and the NOx occlusion amount may be estimated by other methods. good. For example, sensors for detecting NOx may be provided on the upstream side and the downstream side of the NOx storage reduction catalyst 210, respectively, and the NOx storage amount may be estimated using the difference value of the detection amount of each sensor.

In the above embodiment, the adjustment unit 161 is controlled when the regeneration process is executed. However, the present disclosure is not limited to this, and the temperature inside the exhaust pipe 120 is increased due to a factor other than the regeneration process. At this time, the adjustment unit 161 may be controlled.

In the above embodiment, the estimation unit is exemplified as the control unit 300. However, the present disclosure is not limited to this, and the estimation unit may be provided separately from the control unit 300.

Moreover, although the exhaust emission control device 100 in the above embodiment is mounted on the vehicle V equipped with a diesel engine, the present disclosure is not limited to this, and may be mounted on a vehicle equipped with a gasoline engine, for example. good.

Moreover, in the said embodiment, although DPF220 was illustrated as an example of a collection part, this indication is not limited to this, What kind of thing may be used if it is a filter which can collect a particulate matter. . Further, when the exhaust gas purification device 100 is mounted on a vehicle equipped with a gasoline engine, a GPF (gasoline particulate filter) may be the collection unit.

In addition, each of the above-described embodiments is merely an example of implementation in carrying out the present disclosure, and the technical scope of the present disclosure should not be interpreted in a limited manner. That is, the present disclosure can be implemented in various forms without departing from the gist or the main features thereof.

This application is based on a Japanese patent application filed on March 8, 2018 (Japanese Patent Application No. 2018-041868), the contents of which are incorporated herein by reference.

The exhaust purification device of the present disclosure is useful as an exhaust purification device, a vehicle, and an exhaust purification control device capable of suppressing the reduction agent from desorbing from the NOx selective reduction catalyst due to the temperature rise in the exhaust pipe. is there.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 100 Exhaust gas purification device 110 Intake pipe 120 Exhaust pipe 130 1st temperature detection part 140 2nd temperature detection part 150 Urea water injection part 160 Recirculation path | route part 161 Adjustment part 210 NOx storage reduction type catalyst 220 DPF
230 NOx selective reduction type catalyst 300 control unit V vehicle

Claims

An exhaust pipe through which exhaust gas generated from the internal combustion engine flows;
A NOx selective reduction catalyst that is disposed in the exhaust pipe and purifies nitrogen oxides in the exhaust gas by adsorbing a reducing agent;
An NOx occlusion reduction type catalyst which is disposed upstream of the NOx selective reduction type catalyst in the exhaust pipe in the exhaust direction in which the exhaust gas flows, and occludes nitrogen oxides in the exhaust gas;
A recirculation path section for connecting the exhaust pipe and the exhaust pipe of the internal combustion engine from the exhaust pipe, and recirculating the exhaust gas in the exhaust pipe to the intake pipe;
An adjustment unit for adjusting the flow rate of the exhaust gas recirculated in the recirculation path unit;
A control unit that controls the adjusting unit so that a reduction action of the reducing agent and nitrogen oxides contained in the exhaust gas is promoted according to the amount of adsorption of the reducing agent of the NOx selective reduction catalyst; ,
An exhaust purification device comprising:
An estimation unit for estimating the amount of adsorption of the reducing agent of the NOx selective reduction catalyst;
The exhaust emission control device according to claim 1.
The estimation unit estimates a storage amount of nitrogen oxides of the NOx storage reduction catalyst,
The control unit determines whether or not to adjust the adjustment unit based on the estimated storage amount of the nitrogen oxide estimated by the estimation unit when the reducing agent adsorption amount is greater than a predetermined target amount. ,
The exhaust emission control device according to claim 2.
The controller reduces the flow rate of the exhaust gas returned to the intake pipe when the estimated storage amount is less than a predetermined storage amount of the NOx storage reduction catalyst;
The exhaust emission control device according to claim 3.
A collection unit for collecting particulate matter contained in the exhaust gas;
The control unit controls the adjustment unit when a regeneration process for burning the particulate matter is performed.
The exhaust emission control device according to claim 1.
The control unit prohibits a rich process to bring the exhaust air-fuel ratio in the exhaust pipe into a rich state when the regeneration process is executed;
The exhaust emission control device according to claim 5.
The control unit determines whether to control the adjustment unit based on the temperature of the NOx storage reduction catalyst.
The exhaust emission control device according to claim 1.
The control unit determines whether to control the adjustment unit based on the temperature of the NOx selective reduction catalyst.
The exhaust emission control device according to claim 1.
The exhaust emission control device according to claim 1 is provided.
vehicle.
An exhaust pipe through which exhaust gas generated from an internal combustion engine flows, a NOx selective reduction catalyst that is disposed in the exhaust pipe and purifies nitrogen oxides in the exhaust gas by adsorbing a reducing agent, and the exhaust gas includes An NOx occlusion reduction type catalyst that is disposed upstream of the NOx selective reduction type catalyst in the exhaust pipe in the flowing exhaust direction and occludes nitrogen oxides in the exhaust gas, and an intake pipe of the internal combustion engine from the exhaust pipe An exhaust gas purification control device for an exhaust gas purification device, comprising: a recirculation path portion that connects the exhaust pipe and the exhaust pipe, and recirculates the exhaust gas in the exhaust pipe to the intake pipe,
An adjustment unit for adjusting the flow rate of the exhaust gas recirculated in the recirculation path unit;
A control unit that controls the adjusting unit so that a reduction action of the reducing agent and nitrogen oxides contained in the exhaust gas is promoted according to the amount of adsorption of the reducing agent of the NOx selective reduction catalyst; ,
An exhaust purification control apparatus comprising: