JP2019190417A - Exhaust emission control device and vehicle - Google Patents

Abstract

To provide an exhaust emission control device and a vehicle capable of surely desorbing NOx from a NOx adsorption catalyst of a bypass passage portion.SOLUTION: An exhaust emission control device includes an exhaust pipe, a turbine constituting a part of a supercharger, a NOx selective reduction type catalyst disposed at a downstream side with respect to the turbine in an exhausting direction of the exhaust gas and reducing nitrogen oxide in the exhaust gas in a case when a temperature of the exhaust gas is an active temperature, a bypass passage portion connecting a region at an upstream side in the exhausting direction with respect to the turbine, and a region between the turbine and the NOx selective reduction type catalyst in the exhaust pipe, a NOx adsorption catalyst disposed in the bypass passage portion and desorbing adsorbed nitrogen oxide in a case when the temperature of the exhaust gas is a desorption temperature higher than the active temperature, an adjustment portion for adjusting a flow rate of the exhaust gas flowing in the bypass passage portion, and a control portion for controlling the adjustment portion so that nitrogen oxide adsorbed to the NOx adsorption catalyst is desorbed according to a temperature of the exhaust gas.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, in an exhaust system of an internal combustion engine, an exhaust purification device having a turbine provided in an exhaust pipe and an exhaust purification catalyst provided downstream of the turbine is known. For example, Patent Document 1 discloses a configuration in which a bypass path portion connected to a portion between the turbine and the exhaust purification catalyst is provided from a portion upstream of the turbine of the exhaust pipe. The bypass passage is provided with a NOx adsorption catalyst that adsorbs nitrogen oxide (hereinafter referred to as “NOx”) contained in exhaust gas generated in the internal combustion engine.

  In this technology, the exhaust gas is allowed to flow through the bypass passage until the exhaust purification catalyst is heated to the activation temperature, NOx is adsorbed to the NOx adsorption catalyst, and after the exhaust purification catalyst is heated to the activation temperature, the NOx adsorption is performed. Control to desorb NOx from the catalyst is performed.

  As an exhaust purification catalyst, a NOx selective reduction type catalyst that performs a reduction treatment of nitrogen oxides (hereinafter referred to as “NOx”) contained in exhaust gas generated in an internal combustion engine is known. 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.

Table 2010/116541

  However, when the activation temperature of the NOx selective reduction catalyst is lower than the desorption temperature of the NOx adsorption catalyst, NOx can be desorbed from the NOx adsorption catalyst even if the NOx selective reduction catalyst is heated to the activation temperature. The problem that it is not possible arises.

  An object of the present disclosure is to provide an exhaust purification device and a vehicle that can reliably desorb NOx from a NOx adsorption catalyst in a bypass passage.

An exhaust emission control device according to the present disclosure includes:
An exhaust pipe through which exhaust gas generated in the internal combustion engine flows;
A turbine provided in the exhaust pipe and constituting a part of the supercharger;
A NOx selective reduction catalyst that is provided downstream of the turbine in the exhaust direction of the exhaust gas and promotes reduction of nitrogen oxides in the exhaust gas when the temperature of the exhaust gas is an active temperature;
In the exhaust pipe, a bypass path portion that connects a portion upstream of the turbine in the exhaust direction and a portion between the turbine and the NOx selective reduction catalyst;
A NOx adsorption catalyst that is provided in the bypass passage part and desorbs the adsorbed nitrogen oxide when the temperature of the exhaust gas is a desorption temperature higher than the activation temperature;
An adjusting unit that adjusts the flow rate of the exhaust gas flowing through the bypass path unit;
A control unit that controls the adjustment unit so that the nitrogen oxides adsorbed on the NOx adsorption catalyst are desorbed according to the temperature of the exhaust gas;
Is provided.

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

  According to the present disclosure, NOx can be reliably desorbed from the NOx adsorption catalyst in the bypass passage.

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. It is a flowchart which shows the operation example of adjustment control in an exhaust gas purification apparatus.

  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 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, a bypass path unit 130, an adjustment unit 140, a temperature detection unit 150, and a control unit 300.

  In the exhaust pipe 110, exhaust gas generated from the internal combustion engine 1 flows. 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 the 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 and is not used by the NOx selective reduction catalyst 220, but decomposes the slipped ammonia and discharges the ammonia out of the vehicle V. To be prevented. In the present embodiment, the ammonia slip catalyst 230 is accommodated in a case different from the NOx selective reduction catalyst 220 in the exhaust pipe 110, but the present disclosure is not limited to this, and the NOx selective reduction type. It may be accommodated in the same case as the catalyst 220.

  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 bypass passage portion 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 bypass passage unit 130 is provided with a NOx adsorption catalyst 240.

  The NOx adsorption catalyst 240 adsorbs NOx in the exhaust gas when the temperature of the exhaust gas is the adsorption temperature. The range of the adsorption temperature is a range including the temperature below the activation temperature that is the lowest temperature among the above-described activation temperature ranges.

  The NOx adsorbed on the NOx adsorption catalyst 240 is desorbed from the NOx adsorption catalyst 240 when the temperature of the exhaust gas is equal to or higher than the desorption temperature. The desorption temperature is a temperature higher than the activation temperature that is the lowest temperature in the above-described range of the activation temperature.

  The adjustment unit 140 is a valve capable of adjusting the bypass flow rate of the exhaust gas flowing through the bypass path unit 130. As the adjustment unit 140 is controlled by the control unit 300, the exhaust gas in the exhaust pipe 110 flows into the bypass path unit 130.

  The temperature detection unit 150 is provided in a portion 112 between the turbine 120 of the exhaust pipe 110 and the NOx selective reduction catalyst 220, and detects the temperature of the exhaust gas upstream of the NOx selective reduction catalyst 220 in the exhaust direction. .

  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 adjustment unit 140 based on a preset program.

  The control unit 300 controls the adjustment unit 140 so that a part of the exhaust gas flows into the bypass path unit 130 according to the temperature of the exhaust gas and the NOx adsorption amount in the NOx adsorption catalyst 240.

  The temperature of the exhaust gas is the temperature detected by the temperature detection unit 150 described above. Further, the NOx adsorption amount in the NOx adsorption catalyst 240 is, for example, a known method such as a method calculated based on the flow rate of the exhaust gas flowing through the bypass passage 130, the NOx amount desorbed from the NOx adsorption catalyst 240, or the like. Is estimated by Further, the NOx adsorption amount may be estimated using a sensor for detecting NOx on the upstream side and the downstream side of the NOx adsorption catalyst 240, respectively, and using the difference value of the detection amount of each sensor.

  Specifically, when the temperature of the exhaust gas is lower than the activation temperature of the NOx selective reduction catalyst 220 and the NOx adsorption amount in the NOx adsorption catalyst 240 is less than the maximum amount, the control unit 300 determines that the bypass path unit The adjusting unit 140 is controlled so that a part of the exhaust gas flows through 130. At this time, the control unit 300 controls the adjustment unit 140 so that the flow rate of the exhaust gas flowing through the bypass path unit 130 is larger than the flow rate of the exhaust gas flowing toward the turbine 120 side.

  When the temperature of the exhaust gas is lower than the activation temperature, it is difficult for the NOx selective reduction catalyst 220 to perform the reduction process, so that NOx is easily discharged to the atmosphere. In particular, in the case of the configuration having the turbine 120, exhaust gas passes through the turbine 120, so that exhaust heat energy of the exhaust gas is converted into rotational energy of the turbine impeller, so that the temperature of the exhaust gas is likely to decrease.

  Therefore, in the present embodiment, when the temperature of the exhaust gas is lower than the activation temperature, NOx contained in the exhaust gas flowing through the bypass passage 130 is adsorbed by the NOx adsorption catalyst 240. As a result, when the temperature of the exhaust gas is a temperature at which the reduction process is difficult to be performed by the NOx selective reduction catalyst 220, NOx is adsorbed by the NOx adsorption catalyst 240, so that NOx is prevented from being discharged into the atmosphere. can do.

  The control unit 300 controls the adjustment unit 140 so that the exhaust gas does not flow through the bypass path unit 130 when the NOx adsorption amount in the NOx adsorption catalyst 240 reaches the maximum amount. When the NOx adsorption amount in the NOx adsorption catalyst 240 is the maximum amount, NOx in the exhaust gas is not adsorbed, so that it is not necessary to flow the exhaust gas through the bypass passage portion 130. Therefore, by controlling as described above, it is possible to prevent the exhaust gas from flowing unnecessarily through the bypass path portion 130. In addition, it is possible to suppress a decrease in the rotational driving force of the turbine 120 due to a part of the exhaust gas flowing through the bypass path portion 130.

  When the temperature of the exhaust gas is equal to or higher than the activation temperature of the NOx selective reduction catalyst 220, the control unit 300 controls the adjustment unit 140 so that the exhaust gas does not flow through the bypass path unit 130. When the NOx selective reduction catalyst 220 is at or above the activation temperature, NOx reduction processing is performed by the NOx selective reduction catalyst 220, so that it is not necessary for the NOx adsorption catalyst 240 to adsorb NOx. Therefore, by controlling as described above, it is possible to prevent the exhaust gas from flowing unnecessarily through the bypass path portion 130. In addition, it is possible to suppress a decrease in the rotational driving force of the turbine 120 due to a part of the exhaust gas flowing through the bypass path portion 130.

  Further, the control unit 300 controls the adjustment unit 140 so that NOx is desorbed (purged) from the NOx adsorption catalyst 240 according to the temperature of the exhaust gas and the NOx adsorption amount in the NOx adsorption catalyst 240.

  Specifically, the control unit 300 adjusts the exhaust gas so that the exhaust gas flows through the bypass passage unit 130 when the temperature of the exhaust gas is equal to or higher than the desorption temperature and NOx is adsorbed by the NOx adsorption catalyst 240. 140 is controlled. At this time, the control unit 300 controls the adjustment unit 140 so that the flow rate of the exhaust gas in the bypass passage unit 130 is smaller than the flow rate of the exhaust gas flowing to the turbine 120 side.

  In this way, NOx adsorbed on the NOx adsorption catalyst 240 can be desorbed from the NOx adsorption catalyst 240 as the exhaust gas temperature rises. Therefore, when the temperature of the exhaust gas decreases, NOx can be adsorbed again by the NOx adsorption catalyst 240. Further, NOx desorbed from the NOx adsorption catalyst 240 is reduced by the NOx selective reduction catalyst 220.

  Further, the control unit 300 determines that when NOx has been completely desorbed from the NOx adsorption catalyst 240, or when the exhaust gas temperature is equal to or higher than the desorption temperature and NOx is not adsorbed by the NOx adsorption catalyst 240, the bypass path The adjustment unit 140 is controlled so that the exhaust gas does not flow through the unit 130.

  In such a state, NOx is not adsorbed at all by the NOx adsorption catalyst 240, and even when exhaust gas flows through the bypass passage 130, the NOx adsorption catalyst 240 cannot adsorb NOx (desorption temperature). Therefore, there is no need to flow exhaust gas through the bypass path 130. Therefore, by controlling as described above, it is possible to prevent the exhaust gas from flowing unnecessarily through the bypass path portion 130. In addition, it is possible to suppress a decrease in the rotational driving force of the turbine 120 due to a part of the exhaust gas flowing through the bypass path portion 130.

  In addition, when the temperature of the exhaust gas is equal to or higher than the activation temperature and lower than the desorption temperature, the control unit 300 controls the adjustment unit 140 so that the exhaust gas does not flow through the bypass path unit 130. By doing in this way, the reduction process in the NOx selective reduction catalyst 220 can be promoted.

  An operation example of the adjustment control in the exhaust emission control device 100 configured as described above will be described. FIG. 2 is a flowchart showing an operation example of 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 activation temperature (step S101). As a result of the determination, when the temperature of the exhaust gas is equal to or higher than the activation temperature (step S101, NO), the process transitions to step S104. On the other hand, when the temperature of the exhaust gas is lower than the activation temperature (step S101, YES), the controller 300 determines whether or not the NOx adsorption amount in the NOx adsorption catalyst 240 is less than the maximum amount (step S102). .

  As a result of the determination, when the NOx adsorption amount in the NOx adsorption catalyst 240 is the maximum amount (step S102, NO), the process transitions to step S104. On the other hand, when the NOx adsorption amount in the NOx adsorption catalyst 240 is less than the maximum amount (step S102, YES), the control unit 300 controls the adjustment unit 140 so that a part of the exhaust gas flows through the bypass path unit 130. (Step S103). After step S103, the process returns to step S101.

  When it is determined NO in step S101 or step S102, the control unit 300 controls the adjustment unit 140 so that the exhaust gas does not flow through the bypass path unit 130 (step S104).

  Next, the controller 300 determines whether or not the temperature of the exhaust gas is equal to or higher than the desorption temperature (step S105). As a result of the determination, when the temperature of the exhaust gas is lower than the desorption temperature (step S105, NO), this control ends.

  On the other hand, when the temperature of the exhaust gas is equal to or higher than the desorption temperature (step S105, YES), the control unit 300 determines whether NOx is adsorbed on the NOx adsorption catalyst 240 (step S106).

  As a result of the determination, when NOx is not adsorbed on the NOx adsorption catalyst 240 (step S106, NO), this control is finished. On the other hand, when NOx is adsorbed on the NOx adsorption catalyst 240 (step S106, YES), the control unit 300 controls the adjustment unit 140 so that a part of the exhaust gas flows through the bypass path unit 130 (step S107). . After step S107, this control ends.

  According to the present embodiment configured as described above, when NOx is adsorbed on the NOx adsorption catalyst 240 and the temperature of the exhaust gas is equal to or higher than the desorption temperature, the exhaust gas is present in the bypass passage 130. Washed away. As a result, NOx is desorbed from the NOx adsorption catalyst 240 and is reduced by the NOx selective reduction catalyst 220 located in the subsequent stage.

  That is, in the present embodiment, NOx can be reliably desorbed from the NOx adsorption catalyst 240 of the bypass path portion 130. As a result, when the temperature of the exhaust gas becomes lower than the activation temperature next, NOx can be adsorbed by the NOx adsorption catalyst 240 of the bypass passage portion 130, so that NOx is prevented from being released to the atmosphere. Can do.

  Further, it becomes possible to guide the exhaust gas having a higher temperature to the NOx selective reduction catalyst 220 on the downstream side of the bypass passage 130, and the reduction efficiency in the NOx selective reduction catalyst 220 can be improved.

  Further, when the temperature of the exhaust gas is equal to or higher than the desorption temperature, the flow rate of the exhaust gas in the bypass passage 130 is smaller than the flow rate of the exhaust gas flowing to the turbine 120 side. By doing so, it is possible to reduce the amount of exhaust gas that carries NOx to the NOx selective reduction catalyst 220 while desorbing NOx from the NOx adsorption catalyst 240. Therefore, NOx can be efficiently desorbed from the NOx adsorption catalyst 240 while maintaining the reduction efficiency of the NOx selective reduction catalyst 220.

  In the above-described embodiment, the temperature of the exhaust gas is detected by the temperature detection unit 150. However, the present disclosure is not limited to this, and for example, the temperature is estimated based on a load applied to the internal combustion engine 1. May be.

  Further, in the above embodiment, a part of the exhaust gas is allowed to flow to the bypass passage portion 130. However, the present disclosure is not limited to this, and when necessary, for example, when supercharging in the supercharger is not necessary. Thus, all of the exhaust gas may be passed through the bypass path 130.

  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.

  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 construed 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.

  The exhaust purification device of the present disclosure is useful as an exhaust purification device and a vehicle that can reliably desorb NOx from the NOx adsorption catalyst in the bypass passage.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 100 Exhaust gas purification apparatus 110 Exhaust pipe 120 Turbine 130 Bypass path part 140 Adjustment part 150 Temperature detection part 210 Oxidation catalyst 220 NOx selective reduction type catalyst 230 Ammonia slip catalyst 240 NOx adsorption catalyst 300 Control part V Vehicle

Claims (7)

An exhaust pipe through which exhaust gas generated in the internal combustion engine flows;
A turbine provided in the exhaust pipe and constituting a part of the supercharger;
A NOx selective reduction catalyst that is provided downstream of the turbine in the exhaust direction of the exhaust gas and promotes reduction of nitrogen oxides in the exhaust gas when the temperature of the exhaust gas is an active temperature;
In the exhaust pipe, a bypass path portion that connects a portion upstream of the turbine in the exhaust direction and a portion between the turbine and the NOx selective reduction catalyst;
A NOx adsorption catalyst that is provided in the bypass passage part and desorbs the adsorbed nitrogen oxide when the temperature of the exhaust gas is a desorption temperature higher than the activation temperature;
An adjusting unit that adjusts the flow rate of the exhaust gas flowing through the bypass path unit;
A control unit that controls the adjustment unit so that the nitrogen oxides adsorbed on the NOx adsorption catalyst are desorbed according to the temperature of the exhaust gas;
An exhaust purification device comprising: When the temperature of the exhaust gas is equal to or higher than the desorption temperature and the nitrogen oxide is adsorbed on the NOx adsorption catalyst, the control unit is configured to cause the exhaust gas to flow through the bypass path. Control the adjuster,
The exhaust emission control device according to claim 1. The control unit controls the adjustment unit so that the exhaust gas does not flow through the bypass path when the nitrogen oxides adsorbed on the NOx adsorption catalyst are completely desorbed.
The exhaust emission control device according to claim 2. When the temperature of the exhaust gas is equal to or higher than the desorption temperature and the nitrogen oxide is not adsorbed on the NOx adsorption catalyst, the control unit prevents the exhaust gas from flowing into the bypass path portion. Controlling the adjusting unit;
The exhaust emission control device according to claim 1. The control unit controls the adjusting unit so that the exhaust gas does not flow to the bypass path when the temperature of the exhaust gas is equal to or higher than the activation temperature and lower than the desorption temperature;
The exhaust emission control device according to any one of claims 1 to 4. The control unit controls the adjustment unit so that a part of the exhaust gas flows through the bypass path and the remaining exhaust gas flows through the turbine.
The flow rate of the exhaust gas flowing through the bypass path is less than the flow rate of the exhaust gas flowing through the turbine.
The exhaust emission control device according to any one of claims 1 to 5. The exhaust emission control device according to any one of claims 1 to 6, comprising:
vehicle.

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