JP2019190421A - Exhaust emission control device and vehicle - Google Patents

Abstract

To provide an exhaust emission control device and a vehicle capable of preventing NOx from being discharged to atmospheric air at a low temperature region of an exhaust gas.SOLUTION: An exhaust emission control device includes a NOx selective reduction type catalyst disposed at a downstream side in an exhausting direction with respect to a turbine in an exhaust pipe, an upstream-side bypass passage portion connecting a region at an upstream side in an exhausting direction with respect to the turbine and a region between the turbine and the NOx selective reduction type catalyst in the exhaust direction in the exhaust pipe, a downstream-side bypass passage portion connecting a region between the turbine and the NOx selective reduction type catalyst in the exhausting direction, and a downstream side in the exhausting direction with respect to the NOx selective reduction type catalyst in the exhaust pipe, a NOx adsorption catalyst disposed in the downstream-side bypass passage portion to adsorb nitrogen oxide in the exhaust gas and then reduce the same, and a control portion for controlling an upstream-side adjustment portion and a downstream-side adjustment portion so that the exhaust gas flows to the downstream-side bypass passage portion through the upstream-side bypass passage portion in a case when a temperature of the exhaust gas is a temperature to desorb NOx adsorbed to the NOx adsorption catalyst, or more.SELECTED DRAWING: Figure 1

Description

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

  2. Description of the Related Art Conventionally, there has been known an exhaust purification apparatus having a NOx selective reduction type catalyst that reduces nitrogen oxide (hereinafter referred to as “NOx”) in exhaust gas generated from an internal combustion engine in an exhaust system of the internal combustion engine.

  For example, Patent Document 1 discloses a turbine that constitutes a part of a supercharger that is disposed in an exhaust pipe of an internal combustion engine, and a NOx selective reduction catalyst that is disposed downstream of the turbine in the exhaust pipe in the exhaust direction. Is disclosed.

JP2013-124610A

  By the way, in a turbine, since thermal energy is recovered, the temperature of the exhaust gas decreases. When the temperature of the exhaust gas is lower than the lower limit activation temperature of the NOx selective reduction catalyst, the NOx selective reduction catalyst cannot appropriately reduce NOx. For example, during the period until the internal combustion engine is cold-started and the temperature of the exhaust gas sufficiently rises, NOx in the exhaust gas may be released from the exhaust system into the atmosphere without being reduced.

  An object of the present disclosure is to provide an exhaust purification device and a vehicle that can suppress release of NOx into the atmosphere in a low temperature range of exhaust gas.

An exhaust emission control device according to an aspect of the present disclosure includes:
An exhaust pipe in which an exhaust gas generated from the internal combustion engine flows and a turbine constituting a part of the supercharger is disposed;
A NOx selective reduction type catalyst that is disposed downstream of the turbine in the exhaust pipe in the exhaust direction and reduces nitrogen oxides in the exhaust gas;
An upstream bypass path connecting the upstream portion of the exhaust pipe in the exhaust direction with respect to the turbine and the portion between the turbine and the NOx selective reduction catalyst in the exhaust direction;
A downstream bypass path portion connecting a portion between the turbine and the NOx selective reduction catalyst in the exhaust direction in the exhaust pipe and a downstream side in the exhaust direction from the NOx selective reduction catalyst;
A NOx adsorption catalyst that is disposed in the downstream bypass passage, adsorbs nitrogen oxide in exhaust gas, and later reduces the NOx adsorption catalyst;
An upstream side adjustment unit that adjusts the flow rate of the exhaust gas between the exhaust pipe and the upstream side bypass path unit;
A downstream adjustment unit that adjusts the flow rate of the exhaust gas between the exhaust pipe and the downstream bypass path unit;
When the temperature of the exhaust gas is equal to or higher than the temperature at which the nitrogen oxides adsorbed on the NOx adsorption catalyst are desorbed, the exhaust gas is caused to flow to the downstream bypass route portion via the upstream bypass route portion. A control unit for controlling the upstream adjustment unit and the downstream adjustment unit;
Is provided.

A vehicle according to an aspect of the present disclosure is provided.
The exhaust purification apparatus is provided.

  According to the present disclosure, it is possible to suppress the release of NOx in the air at a low temperature range.

Schematic configuration diagram showing 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 8 is a flowchart showing an operation example of exhaust gas flow rate adjustment control in the exhaust emission control device according to the embodiment of the present disclosure. The flowchart which shows the operation example of the flow volume adjustment control of the exhaust gas in the exhaust gas purification apparatus which concerns on the modification 2.

  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 to which an exhaust emission control device according to an embodiment of the present disclosure is applied.

  As shown in FIG. 1, the internal combustion engine 1 is a diesel engine, for example, 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 into the atmosphere. The exhaust emission control device 100 includes an exhaust pipe 110, a turbine 120, an upstream bypass path section 130, an upstream side adjustment section 140A, a downstream side adjustment section 140B, a temperature detection section 150, and a downstream side bypass path section 160. The control unit 300 is provided.

  Exhaust gas generated from the internal combustion engine 1 flows through the exhaust pipe 110. In the exhaust pipe 110, the turbine 120, the oxidation catalyst 210, the NOx selective reduction catalyst 220, the ammonia slip 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 catalyst 230 and the like are provided.

The oxidation catalyst 210 improves the purification performance of the NOX selective reduction catalyst 220 by oxidizing nitrogen monoxide (NO) or the like in the exhaust gas to generate nitrogen dioxide (NO ₂ ).

  The NOx selective reduction catalyst 220 is disposed downstream of the oxidation catalyst 210 in the exhaust pipe 110 and adsorbs ammonia generated based on urea water injected by a urea water injection unit (not shown). When the temperature of the exhaust gas is equal to or higher than the lower limit activation temperature, the NOx selective reduction catalyst 220 reduces the NOx by causing the adsorbed ammonia to react with NOx contained in the exhaust gas passing through the NOx selective reduction catalyst 220. The activation temperature is a temperature at which the NOx selective reduction catalyst 220 becomes an activation region.

  The ammonia slip catalyst 230 is located downstream of the NOx selective reduction catalyst 220 in the exhaust direction, decomposes ammonia that has not been used in the NOx selective reduction catalyst 220, and the ammonia is discharged out of the vehicle V. To prevent.

  The turbine 120 constitutes a part of the supercharger and is provided in the exhaust pipe 110. In the turbine 120, a turbine impeller (not shown) is rotated by exhaust gas discharged from the internal combustion engine 1. The turbine 120 is connected to a compressor (not shown) that constitutes the other part of the supercharger. When the compressor impeller and the turbine impeller of the compressor are integrally rotated by the shaft, the outside air sent from the intake pipe is supercharged by the rotation of the compressor impeller and sent to the internal combustion engine 1.

  The upstream bypass path 130 connects a portion 111 of the exhaust pipe 110 upstream of the turbine 120 in the exhaust direction and a portion 112 between the turbine 120 and the NOx selective reduction catalyst 220.

  The downstream bypass passage 160 connects the upstream portion 112 in the exhaust direction of the exhaust pipe 110 with respect to the NOx selective reduction catalyst 220 and the downstream portion 113 in the exhaust direction of the ammonia slip catalyst 230. The downstream bypass passage 160 is provided with a NOx adsorption catalyst 240.

  The NOx adsorption catalyst 240 can adsorb NOx in the exhaust gas even if the temperature of the exhaust gas is lower than the lower limit activation temperature of the NOx selective reduction catalyst 220.

  The upstream adjustment unit 140 </ b> A is a valve that can adjust the bypass flow rate of the exhaust gas flowing through the upstream bypass path unit 130. The control unit 300 controls the upstream adjustment unit 140 </ b> A, so that the exhaust gas in the exhaust pipe 110 flows into the upstream bypass path unit 130.

  The downstream adjustment unit 140 </ b> B is a valve that can adjust the bypass flow rate of the exhaust gas flowing through the downstream bypass path unit 160. The control unit 300 controls the downstream side adjustment unit 140 </ b> B, so that the exhaust gas in the exhaust pipe 110 flows into the downstream side bypass route unit 160.

  The temperature detection unit 150 is provided in a portion 112 between the downstream side adjustment unit 140B of the exhaust pipe 110 and the NOx selective reduction catalyst 220, and the temperature of the exhaust gas upstream of the NOx selective reduction catalyst 220 in the exhaust direction. Is detected.

  The control unit 300 is, for example, an electronic control unit, 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 is configured to control the exhaust gas bypass flow rate in the upstream adjustment unit 140A based on a preset program. Similarly, the control unit 300 is configured to control the exhaust gas bypass flow rate in the downstream side adjustment unit 140B based on a preset program.

  The control unit 300 controls the upstream adjustment unit 140A to flow the exhaust gas to the upstream bypass path unit 130 according to the temperature of the exhaust gas, and causes the exhaust gas to flow to the downstream side bypass path unit 160. The downstream adjustment unit 140B is controlled.

  Hereinafter, the control of the upstream adjustment unit 140A and the downstream adjustment unit 140B will be specifically described.

  First, the case where the temperature of exhaust gas is less than a predetermined first threshold value will be described. Here, the “first threshold value” will be described as the lower limit activation temperature of the NOx selective reduction catalyst 220.

  When the temperature of the exhaust gas is lower than the lower limit activation temperature of the NOx selective reduction catalyst 220, the control unit 300 controls the upstream adjustment unit 140A so that the exhaust gas flows through the upstream bypass passage unit 130, and the downstream side The downstream adjustment unit 140B is controlled so that the exhaust gas flows through the side bypass passage unit 160 (NOx adsorption catalyst 240). At this time, the upstream adjustment unit 140A is controlled so that the flow rate of the exhaust gas in the upstream bypass path 130 is larger than the flow rate of the exhaust gas flowing to the turbine 120 side. Further, at this time, the downstream adjustment unit 140B controls the flow rate of the exhaust gas in the downstream bypass passage 160 so as to be larger than the flow rate of the exhaust gas flowing to the exhaust pipe 110 (NOx selective reduction catalyst 220) side. Is done. Here, the flow rate of the exhaust gas flowing to the turbine 120 side is a flow rate that is necessary so that the rotational speed of the turbine 120 does not fall below the allowable lower limit value.

  If the temperature of the exhaust gas is lower than the lower limit activation temperature of the NOx selective reduction catalyst 220, the reduction process in the NOx selective reduction catalyst 220 is difficult to be performed, so that NOx in the exhaust gas is easily discharged to the atmosphere. For example, since the internal combustion engine 1 is cold-started and the temperature of the exhaust gas sufficiently rises, NOx is not easily reduced, so that NOx in the exhaust gas is easily discharged to the atmosphere. In particular, in the case of the configuration having the turbine 120, the exhaust gas passes through the turbine 120, whereby the exhaust energy of the exhaust gas is converted into the rotational energy of the turbine impeller, so that the temperature of the exhaust gas tends to decrease.

  Therefore, in the present embodiment, when the temperature of the exhaust gas is lower than the lower limit activation temperature, the exhaust gas is caused to flow through the upstream bypass path portion 130 to suppress the temperature decrease of the exhaust gas. Further, the NOx contained in the exhaust gas flowing through the downstream bypass passage 160 is adsorbed by the NOx adsorption catalyst 240. Thus, when the temperature of the exhaust gas is a temperature at which the NOx selective reduction catalyst 220 is difficult to reduce, NOx in the exhaust gas is adsorbed by the NOx adsorption catalyst 240 by flowing the exhaust gas to the NOx adsorption catalyst 240. Therefore, it can suppress that NOx is discharged | emitted by air | atmosphere.

  Next, the case where the temperature of the exhaust gas is equal to or higher than the lower limit activation temperature of the NOx selective reduction catalyst 220 and lower than the second threshold value will be described. Here, the “second threshold value” is a temperature at which the temperature of the exhaust gas flowing through the exhaust pipe 110 and reaching the NOx selective reduction catalyst 220 is equal to or higher than the lower limit activation temperature of the NOx selective reduction catalyst 220. Hereinafter, the “second threshold value” is referred to as a high load temperature of the internal combustion engine 1.

  When the temperature of the exhaust gas is equal to or higher than the lower limit activation temperature of the NOx selective reduction catalyst 220 and lower than the high load temperature, the control unit 300 controls the upstream adjustment unit 140A to flow the exhaust gas through the upstream bypass path unit 130. The downstream adjustment unit 140B is controlled so that the exhaust gas flows through the NOx selective reduction catalyst 220. At this time, the upstream adjustment unit 140A is controlled so that the flow rate of the exhaust gas in the upstream bypass path 130 is larger than the flow rate of the exhaust gas flowing to the turbine 120 side. Further, at this time, the downstream adjustment unit 140B controls the flow rate of the exhaust gas flowing to the exhaust pipe 110 (NOx selective reduction catalyst 220) side to be larger than the flow rate of the exhaust gas in the downstream bypass passage unit 160. Is done.

  By doing so, the reduction process in the NOx selective reduction catalyst 220 can be promoted while suppressing the temperature drop of the exhaust gas.

  Next, the case where the exhaust gas temperature is equal to or higher than the high load temperature will be described.

  When the temperature of the exhaust gas is equal to or higher than the high load temperature, the control unit 300 controls the upstream adjustment unit 140A so that the exhaust gas flows through the exhaust pipe 110, and the exhaust gas is supplied to the NOx selective reduction catalyst 220. The downstream adjustment unit 140B is controlled to flow. At this time, the upstream adjustment unit 140 </ b> A is controlled so that the flow rate of the exhaust gas flowing to the turbine 120 side is larger than the flow rate of the exhaust gas in the upstream bypass path unit 130. Further, at this time, the downstream adjustment unit 140B controls the flow rate of the exhaust gas flowing to the exhaust pipe 110 (NOx selective reduction catalyst 220) side to be larger than the flow rate of the exhaust gas in the downstream bypass passage unit 160. Is done.

  When the temperature of the exhaust gas is equal to or higher than the temperature at the time of high load, even if the exhaust gas flows through the exhaust pipe 110 provided with the turbine 120 or the like and the temperature of the exhaust gas decreases, the temperature of the exhaust gas that has decreased is It is equal to or higher than the lower limit active temperature of the selective catalytic reduction catalyst 220. For this reason, the reduction process in the NOx selective reduction catalyst 220 can be promoted.

  An operation example of the exhaust gas flow rate adjustment control in the exhaust purification apparatus 100 configured as described above will be described. FIG. 2 is a flowchart showing an operation example of the exhaust gas flow rate adjustment control in the exhaust purification apparatus 100. The process of FIG. 2 is appropriately executed while the vehicle V is traveling, for example.

  As shown in FIG. 2, the controller 300 determines whether or not the temperature of the exhaust gas is lower than the lower limit activation temperature of the NOx selective reduction catalyst 220 (step S100). As a result of the determination, when the temperature of the exhaust gas is equal to or higher than the lower limit activation temperature (step S100: NO), the process transitions to step S120. On the other hand, when the temperature of the exhaust gas is lower than the lower limit activation temperature (step S100: YES), the control unit 300 causes the exhaust gas to flow to the downstream bypass path unit 160 via the upstream bypass path unit 130. The upstream adjustment unit 140A and the downstream adjustment unit 140B are controlled (step S110). After step S110, the process ends.

  When it determines with NO by step S100, the control part 300 determines whether the temperature of exhaust gas is less than the temperature at the time of high load (step S120). As a result of the determination, when the temperature of the exhaust gas is lower than the temperature at the time of high load (step S120: YES), the control unit 300 causes the exhaust gas to flow to the exhaust pipe 110 via the upstream bypass path unit 130. The upstream adjustment unit 140A and the downstream adjustment unit 140B are controlled (step S130). After step S130, the process ends.

  As a result of the determination, when the temperature of the exhaust gas is equal to or higher than the temperature at the time of high load (step S120: NO), the control unit 300 does not pass the exhaust gas through the upstream bypass path unit 130 and the downstream bypass path unit 160. Then, the upstream adjustment unit 140A and the downstream adjustment unit 140B are controlled so as to flow through the exhaust pipe 110 (step S140). After step S140, the process ends.

  As described above, according to the exhaust gas purification apparatus 100 according to the above embodiment, when the temperature of the exhaust gas is lower than the lower limit activation temperature of the NOx selective reduction catalyst 220, the exhaust gas is routed through the upstream bypass passage 130. Then, the control unit 300 is provided to control the upstream adjustment unit 140A and the downstream adjustment unit 140B so as to flow to the downstream bypass path unit 160.

  By causing the exhaust gas to flow through the upstream bypass passage portion 130, it is possible to suppress the temperature drop of the exhaust gas. Further, even if the temperature of the exhaust gas is lower than the lower limit activation temperature of the NOx selective reduction catalyst 220, NOx can be adsorbed by the NOx adsorption catalyst 240 by flowing the exhaust gas to the downstream bypass path portion 160. As a result, it is possible to suppress the release of NOx in the atmosphere at a low temperature range of the exhaust gas.

  Further, according to the exhaust purification apparatus 100 according to the above embodiment, when the temperature of the exhaust gas is equal to or higher than the lower limit activation temperature of the NOx selective reduction catalyst 220 and lower than the high load temperature of the internal combustion engine 1, the exhaust gas is A control unit 300 that controls the upstream adjustment unit 140A and the downstream adjustment unit 140B is provided so as to flow to the exhaust pipe 110 via the upstream bypass path unit 130.

  By causing the exhaust gas to flow through the upstream bypass passage 130, the temperature of the exhaust gas can be maintained above the lower limit activation temperature. Further, NOx can be purified in the NOx selective reduction catalyst 220 by flowing exhaust gas having a temperature equal to or higher than the lower limit activation temperature to the exhaust pipe 110. As a result, it is possible to suppress the release of NOx into the atmosphere in the middle temperature range of the exhaust gas.

  Further, according to the exhaust gas purification apparatus 100 according to the above-described embodiment, when the temperature of the exhaust gas is equal to or higher than the high load temperature of the internal combustion engine 1, the exhaust gas is separated from the upstream bypass path portion 130 and the downstream bypass path portion. A control unit 300 that controls the upstream side adjustment unit 140A and the downstream side adjustment unit 140B is provided so as to flow through the exhaust pipe 110 without passing through the 160.

  Thereby, since the temperature of the exhaust gas that has passed through the exhaust pipe 110 (the turbine 120) is a high load temperature that is equal to or higher than the lower limit activation temperature, the exhaust gas passes through the upstream bypass route portion 130 and the downstream bypass route portion 160. Even if the NOx is selectively supplied to the exhaust pipe 110, the NOx selective reduction catalyst 220 can purify NOx in the exhaust gas. As a result, it is possible to suppress the release of NOx in the atmosphere of the exhaust gas at a high temperature.

  That is, according to the exhaust purification apparatus 100 according to the present embodiment, NOx release into the atmosphere can be suppressed in a wide temperature range including a low temperature range.

<Modification 1>
In the above embodiment, when the downstream bypass path 160 and the NOx adsorption catalyst 240 disposed in the downstream bypass path 160 are provided, and the temperature of the exhaust gas is less than the lower limit active temperature (low temperature range), Exhaust gas is allowed to flow through the downstream bypass passage 160, NOx is adsorbed by the NOx adsorption catalyst 240, and NOx is reduced later.

  Incidentally, since the NOx adsorption amount of the NOx adsorption catalyst 240 is limited, it is necessary to appropriately desorb NOx adsorbed on the NOx adsorption catalyst 240. However, when the temperature of the exhaust gas is lower than the lower limit activation temperature (low temperature range), it is difficult to desorb NOx. In other words, in order to desorb NOx, the temperature of the exhaust gas needs to be higher than the lower limit activation temperature (specifically, higher than the NOx desorption temperature).

  In view of this, the exhaust purification apparatus 100 according to Modification 1 includes means for desorbing NOx adsorbed on the NOx adsorption catalyst 240. Note that the configuration of the exhaust purification apparatus 100 in the first modification is the same as the configuration of the exhaust purification apparatus 100 in the above embodiment.

  When the temperature of the exhaust gas is equal to or higher than the NOx desorption temperature, the control unit 300 allows the exhaust gas to flow to the downstream bypass path 160 (NOx adsorption catalyst 240) via the upstream bypass path 130. The side adjustment unit 140A and the downstream side adjustment unit 140B are controlled. Here, the “NOx desorption temperature” is a temperature at which NOx adsorbed on the NOx adsorption catalyst 240 can be desorbed.

  NOx adsorbed on the NOx adsorption catalyst 240 is desorbed by flowing exhaust gas having a temperature equal to or higher than the NOx desorption temperature to the downstream bypass path portion 160 (NOx adsorption catalyst 240) via the upstream bypass passage portion 130. The NOx purge is performed. At this time, the upstream adjustment unit 140A is controlled so that the flow rate of the exhaust gas in the upstream bypass path 130 is larger than the flow rate of the exhaust gas flowing to the turbine 120 side. Further, at this time, the downstream adjustment unit 140B controls the flow rate of the exhaust gas in the downstream bypass passage 160 so as to be larger than the flow rate of the exhaust gas flowing to the exhaust pipe 110 (NOx selective reduction catalyst 220) side. Is done.

  According to the exhaust gas purification apparatus 100 according to the first modification, when the temperature of the exhaust gas is equal to or higher than the NOx desorption temperature, the exhaust gas is caused to flow to the downstream bypass route portion 160 via the upstream bypass route portion 130. As a result, even in the NOx adsorption catalyst 240 disposed in the downstream bypass passage 160, it is possible to appropriately perform the purge of NOx.

  When the temperature of the exhaust gas is lower than the NOx desorption temperature, the control unit 300 allows the exhaust gas to flow to the exhaust pipe 110 (NOx selective reduction catalyst 220) via the upstream bypass path unit 130. The adjustment unit 140A and the downstream adjustment unit 140B may be controlled. Thereby, for example, it becomes possible to purify NOx in the middle temperature range of the exhaust gas.

  When the temperature of the exhaust gas is equal to or higher than the degree of SOx desorption higher than the NOx desorption temperature, the control unit 300 transmits the exhaust gas to the exhaust pipe 110 (NOx selective reduction catalyst 220 via the upstream bypass path unit 130). ), The upstream side adjustment unit 140A and the downstream side adjustment unit 140B may be controlled. By flowing the exhaust gas through the NOx selective reduction catalyst 220, the SOx purge of the NOx selective reduction catalyst 220 is executed. As a result, the NOx selective reduction catalyst 220 can be recovered from SOx poisoning.

<Modification 2>
In the first modification, when the temperature of the exhaust gas is equal to or higher than the NOx desorption temperature, the NOx purge is executed by flowing the exhaust gas through the NOx adsorption catalyst 240. However, depending on the temperature condition of the exhaust gas (for example, the temperature of the exhaust gas does not rise above the NOx desorption temperature), the NOx purge may not be executed for a long time.

  Therefore, the exhaust emission control device 100 according to the modified example 2 includes means for forcibly purging NOx.

  Next, the exhaust emission control device 100 according to Modification 2 will be described. The configuration of the exhaust purification device 100 in the second modification is also the same as the configuration of the exhaust purification device 100 in the above embodiment.

  In the second modification, the control unit 300 determines whether or not it is necessary to desorb NOx based on the NOx adsorption amount adsorbed on the NOx adsorption catalyst 240. When the control unit 300 determines that it is necessary to desorb NOx, the control unit 300 causes the exhaust gas to flow to the downstream side bypass route unit 160 (NOx adsorption catalyst 240) via the upstream side bypass route unit 130 so as to flow upstream. The side adjustment unit 140A and the downstream side adjustment unit 140B are controlled. Here, “when it is necessary to desorb NOx” is, for example, a case where the NOx adsorption amount in the NOx adsorption catalyst 240 reaches the maximum adsorption amount. When the adsorption amount of NOx reaches the maximum adsorption amount, the NOx adsorption capacity decreases. In order to recover the NOx adsorption capacity, it is necessary to desorb NOx adsorbed on the NOx adsorption catalyst 240.

  The amount of NOx adsorbed on the NOx adsorption catalyst 240 is determined from the NOx emission amount calculated based on the operating state of the internal combustion engine 1, the flow rate (circulation time) of exhaust gas to the downstream bypass passage 160, and the like. Presumed.

  The exhaust gas is passed through the upstream bypass passage portion 130 to the downstream bypass passage portion 160 (NOx adsorption catalyst 240), whereby NOx purge is executed. At this time, the upstream adjustment unit 140A is controlled so that the flow rate of the exhaust gas in the upstream bypass path 130 is larger than the flow rate of the exhaust gas flowing to the turbine 120 side. Further, at this time, the downstream adjustment unit 140B controls the flow rate of the exhaust gas in the downstream bypass passage 160 so as to be larger than the flow rate of the exhaust gas flowing to the exhaust pipe 110 (NOx selective reduction catalyst 220) side. Is done.

  By the way, even if the exhaust gas flows through the downstream bypass passage 160 (NOx adsorption catalyst 240), it is difficult to desorb NOx if the temperature of the exhaust gas is lower than the NOx desorption temperature.

  Thus, in the second modification, when the temperature of the exhaust gas is lower than the NOx desorption temperature, the control unit 300 controls the temperature raising unit so as to raise the temperature of the exhaust gas to be higher than the NOx desorption temperature. Specifically, the control unit 300 causes the oxidation catalyst 210 disposed upstream of the NOx adsorption catalyst 240 in the exhaust direction to supply fuel from a fuel supply device (not shown), and the exhaust gas is generated by the oxidation action at this time. Is raised above the NOx desorption temperature. The temperature raising unit is not limited to the oxidation catalyst 210 and the fuel supply device described above, and may be a known means such as a heater for raising the temperature of the exhaust gas.

  Next, an operation example of the exhaust gas flow rate adjustment control in the exhaust purification apparatus 100 will be described with reference to FIG. FIG. 3 is a flowchart showing an operation example of the exhaust gas flow rate adjustment control in the exhaust purification apparatus 100 according to the second modification. The process in FIG. 3 is appropriately executed while the vehicle V is traveling, for example.

  As shown in FIG. 3, the controller 300 determines whether or not the NOx adsorption amount of the NOx adsorption catalyst 240 has reached the maximum adsorption amount (step S200). As a result of the determination, when the NOx adsorption amount has reached the maximum adsorption amount (step S200: YES), the control unit 300 determines whether or not the temperature of the exhaust gas is equal to or higher than the NOx desorption temperature (step S210). . On the other hand, when the NOx adsorption amount does not reach the maximum adsorption amount (step S200: NO), the process ends.

  When it is determined YES in step S210, the control unit 300 causes the upstream adjustment unit 140A and the downstream adjustment unit to flow the exhaust gas to the downstream bypass route unit 160 via the upstream bypass route unit 130. 140B is controlled (step S220).

  When it is determined NO in step S210, the control unit 300 performs control to increase the temperature of the exhaust gas to be equal to or higher than the NOx desorption temperature (step S230). After step S230, the process transitions before step S210.

  According to the exhaust gas purification apparatus 100 according to the modified example 2, when the adsorption amount of the NOx adsorption catalyst 240 reaches the maximum adsorption amount, the exhaust gas is passed through the upstream bypass passage portion 130 and the downstream bypass passage portion 160 ( The NOx adsorption catalyst 240). Thereby, the purge of NOx is forcibly executed, so that the NOx adsorption capacity can be recovered.

  The exhaust emission control device of the present disclosure is useful for a vehicle equipped with an internal combustion engine that is required to suppress NOx emission in the atmosphere in a low temperature range.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 100 Exhaust gas purification device 110 Exhaust pipe 120 Turbine 130 Upstream bypass path part 140A Upstream side adjustment part 140B Downstream side adjustment part 150 Temperature detection part 160 Downstream side bypass path part 210 Oxidation catalyst 220 NOx selective reduction type catalyst 230 Ammonia slip Catalyst 240 NOx adsorption catalyst 300 Control unit V Vehicle

Claims (3)

An exhaust pipe in which an exhaust gas generated from the internal combustion engine flows and a turbine constituting a part of the supercharger is disposed;
A NOx selective reduction type catalyst that is disposed downstream of the turbine in the exhaust pipe in the exhaust direction and reduces nitrogen oxides in the exhaust gas;
An upstream bypass path connecting the upstream portion of the exhaust pipe in the exhaust direction with respect to the turbine and the portion between the turbine and the NOx selective reduction catalyst in the exhaust direction;
A downstream bypass path portion connecting a portion between the turbine and the NOx selective reduction catalyst in the exhaust direction in the exhaust pipe and a downstream side in the exhaust direction from the NOx selective reduction catalyst;
A NOx adsorption catalyst that is disposed in the downstream bypass passage, adsorbs nitrogen oxide in exhaust gas, and later reduces the NOx adsorption catalyst;
An upstream side adjustment unit that adjusts the flow rate of the exhaust gas between the exhaust pipe and the upstream side bypass path unit;
A downstream adjustment unit that adjusts the flow rate of the exhaust gas between the exhaust pipe and the downstream bypass path unit;
When the temperature of the exhaust gas is equal to or higher than the temperature at which the nitrogen oxides adsorbed on the NOx adsorption catalyst are desorbed, the exhaust gas is caused to flow to the downstream bypass route portion via the upstream bypass route portion. A control unit for controlling the upstream adjustment unit and the downstream adjustment unit;
Comprising
Exhaust purification device. When the temperature of the exhaust gas is equal to or higher than the temperature at which the SOx adsorbed on the NOx selective reduction catalyst is desorbed, the control unit sends the exhaust gas to the exhaust pipe via the upstream bypass path. Controlling the upstream adjustment unit and the downstream adjustment unit to flow,
The exhaust emission control device according to claim 1. The exhaust emission control device according to claim 1 or 2 is provided.
vehicle.

Images