JP2021050714A - Exhaust emission control system - Google Patents

Abstract

To provide an exhaust emission control system for suppressing the release of exhaust gas where a lot of nitrogen oxide remains to the outside in the state that an internal combustion engine is driven.SOLUTION: An exhaust emission control system 10, in which a selective reduction catalyst device 12 are arranged at the halfway position of an exhaust passage 2 through which exhaust gas from an internal combustion engine 1 is distributed, for reducing and eliminating nitrogen oxide contained in the exhaust gas, includes a reservoir mechanism 20 for temporarily reserving the exhaust gas passing through the selective reduction catalyst device 12 in part of the state that the internal combustion engine 1 is driven without releasing it to the outside, to allow the reserved exhaust gas to pass through the selective reduction catalyst device 12 again.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exhaust gas purification system, and more particularly to an exhaust gas purification system provided with a selective reduction catalyst device in an exhaust passage.

An exhaust gas purification device in which a selective reduction catalyst device for reducing and purifying nitrogen oxides contained in exhaust gas is arranged in an exhaust passage has been proposed (see, for example, Patent Document 1). This exhaust gas purification device heats the ammonia storage unit located downstream of the selective reduction catalyst device when the diesel engine is stopped, collects the released ammonia and stores it in the tank, and stores it in the tank when the diesel engine is operating. Ammonia is supplied to the selective reduction catalyst device.

Japanese Unexamined Patent Publication No. 2014-047721

By the way, in some of the states in which the internal combustion engine is driven, the nitrogen oxides contained in the exhaust gas cannot be completely purified by the selective reduction catalyst device, and the exhaust gas containing a large amount of nitrogen oxides is released to the outside. There was a problem of being done. Some of the states in which such problems occur include a state in which the selective reduction catalyst device is inactive and the selective reduction catalyst device cannot reduce and purify nitrogen oxides, or nitrogen contained in the exhaust gas when the vehicle is accelerating. An example is a state in which a large amount of nitrogen oxides remain in the exhaust gas after passing even if the oxides temporarily increase rapidly and are reduced and purified by a selective reduction catalyst device.

In the apparatus described in Patent Document 1, even if a large amount of nitrogen oxides remain in the exhaust gas during the operation of the internal combustion engine, the exhaust gas is discharged to the outside. Therefore, even if the apparatus described in Patent Document 1 is simply used, it is not an effective solution to the problem that the exhaust gas in which a large amount of nitrogen oxides remains during the operation of the internal combustion engine is released to the outside.

An object of the present disclosure is to provide an exhaust gas purification system that suppresses the emission of exhaust gas containing a large amount of nitrogen oxides to the outside while the internal combustion engine is being driven.

The exhaust gas purification system of one aspect of the present invention that achieves the above object is a selective reduction catalyst device that reduces and purifies the nitrogen oxide contained in the exhaust gas at a position in the middle of the exhaust passage through which the exhaust gas discharged from the internal combustion engine flows. In the arranged exhaust gas purification system, the exhaust gas that has passed through the selective reduction catalyst device in a part of the states in which the internal combustion engine is driven is temporarily stored and stored without being released to the outside. It is characterized by including a storage mechanism for passing the exhaust gas through the selective reduction catalyst device again.

According to one aspect of the present invention, the exhaust gas that has passed through the selective reduction catalyst device is temporarily stored by the storage mechanism without being released to the outside, and the stored exhaust gas is passed through the selective reduction catalyst device again. Becomes possible. Therefore, it is possible to prevent the exhaust gas containing a large amount of nitrogen oxides from being released to the outside while the internal combustion engine is being driven.

It is a block diagram which illustrates the exhaust gas purification system of embodiment, and shows the state which the exhaust gas is temporarily stored by the storage mechanism. It is a block diagram which illustrates the exhaust gas purification system of embodiment, and shows the state which the exhaust gas stored by the storage mechanism is passed through again. It is a flow chart which illustrates the control method of the exhaust gas purification system of embodiment, and shows the method based on an activity parameter. It is a flow chart which illustrates the control method of the exhaust gas purification system of embodiment, and shows the method based on the inflow amount parameter.

Hereinafter, embodiments of the exhaust gas purification system in the present disclosure will be described. In the figure, the white arrow indicates the flow of exhaust gas, and the alternate long and short dash line indicates the signal line.

As illustrated in FIGS. 1 and 2, the exhaust gas purification system 10 of the present embodiment is installed in the middle position of the exhaust passage 2 through which the exhaust gas generated by the combustion of fuel from the internal combustion engine 1 of the vehicle flows, and is contained in the exhaust gas. It purifies the nitrogen oxides produced. The exhaust gas purification system 10 of the present embodiment is arranged in the exhaust passage 2 downstream of the turbine of the turbocharger (not shown) with respect to the flow of exhaust gas, but the exhaust gas purification system 10 may be arranged in the exhaust passage 2 upstream of the turbine. Good. The exhaust gas purification system 10 can be applied to an internal combustion engine other than the internal combustion engine 1 mounted on the vehicle.

The exhaust gas purification system 10 includes a reducing agent injection device 11, a selective reduction catalyst device 12, and a reducing agent adsorption catalyst device 13 in the exhaust passage 2. The exhaust gas purification system 10 may include a fuel injection device for piping, an oxidation catalyst device, and a filter device (not shown) in the exhaust passage 2 upstream of those devices with respect to the flow of exhaust gas. The fuel injection device for piping is a device that is arranged on the upstream side of the oxidation catalyst device with respect to the flow of exhaust gas, injects fuel in advance, and supplies fuel to the oxidation catalyst device in advance. The oxidation catalyst device is a device that is arranged upstream of the filter device with respect to the flow of the exhaust gas and oxidizes hydrocarbons, carbon monoxide, and nitric oxide contained in the exhaust gas. The filter device is a device that collects particulate matter contained in exhaust gas.

The reducing agent injection device 11 is arranged on the upstream side of the selective reduction catalyst device 12 with respect to the flow of exhaust gas, and is a device that injects urea water to supply ammonia as a reducing agent to the selective reduction catalyst device 12. The selective reduction catalyst device 12 is a device that is arranged on the upstream side of the reducing agent adsorption catalyst device 13 with respect to the flow of exhaust gas, and reduces and purifies nitrogen oxides contained in the exhaust gas using ammonia as a reducing agent. The reducing agent adsorption catalyst device 13 is a device that adsorbs and removes the reducing agent contained in the exhaust gas after passing through the selective reduction catalyst device 12.

In addition to the above configuration, the exhaust gas purification system 10 includes a heating device 14 and a storage mechanism 20, and the selective reduction catalyst device 12 in a part of the states in which the internal combustion engine 1 is driven by the storage mechanism 20. The exhaust gas that has passed through the above is temporarily stored without being released to the outside, and the stored exhaust gas is passed through the selective reduction catalyst device 12 again. The storage mechanism 20 includes an exhaust switchgear 21, a storage passage 22, a suction pump 23, a check valve 24, a storage tank 25, and a storage switchgear 26. The suction pump 23, the check valve 24, the storage tank 25, and the storage switchgear 26 are arranged in the storage passage 22 in this order in the direction opposite to the flow of the exhaust gas in the exhaust passage 2. The direction opposite to the flow of the exhaust gas is the direction from the downstream to the upstream of the selective reduction catalyst device 12 as a reference.

In the present embodiment, the state in which the internal combustion engine 1 is driven means that the internal combustion engine 1 can output power to a drive shaft (not shown) by burning fuel, and the internal combustion engine 1 idles due to the rotating drive shaft. It shall include the state. That is, the state in which the internal combustion engine 1 is driven is a state in which the piston and the crankshaft (not shown) are driven, and the state in which the operation of the internal combustion engine 1 is stopped is a state in which the piston and the crankshaft are not driven. It is in a state. In addition, a part of the states is a state in which a large amount of nitrogen oxides remain in the exhaust gas that has passed through the selective reduction catalyst device 12. Specifically, some states include a state in which the selective reduction catalyst device 12 is inactive and the selective reduction catalyst device 12 cannot reduce and purify nitrogen oxides, or when the vehicle equipped with the exhaust gas purification system 10 is accelerated. An example is a state in which the nitrogen oxides contained in the exhaust gas temporarily increase rapidly and a large amount of nitrogen oxides remain in the exhaust gas after passing through the exhaust gas even if the selective reduction catalyst device 12 reduces and purifies the nitrogen oxides. The determination of this part of the state will be described later.

The heating device 14 is arranged in the exhaust passage 2 upstream of the selective reduction catalyst device 12 with respect to the flow of the exhaust gas, and heats the exhaust gas flowing through the exhaust passage 2 to indirectly raise the temperature of the selective reduction catalyst device 12. Is. The heating device 14 may have a configuration capable of raising the temperature of the selective reduction catalyst device 12, and is not limited to a configuration in which the temperature of the selective reduction catalyst device 12 is indirectly raised via exhaust gas. 12 may be directly heated to raise the temperature. An electric heater is exemplified as the heating device 14.

The exhaust opening / closing device 21 is arranged in the exhaust passage 2 downstream of the selective reduction catalyst device 12 with respect to the flow of the exhaust gas. The exhaust passage 2 is opened so that the exhaust gas can flow in the open state, and the exhaust passage 2 is closed. It is a device that blocks the exhaust gas so that it cannot flow. It is preferable that the exhaust opening / closing device 21 is arranged in the exhaust passage 2 downstream of the branch point of the recirculation passage 4 that branches from the exhaust passage 2 and joins the intake passage 3 through which the intake air flows.

The storage passage 22 is a passage that branches from the exhaust passage 2 between the outlet of the selective reduction catalyst device 12 and the exhaust switchgear 21 and joins the exhaust passage 2 upstream of the selective reduction catalyst device 12. The inlet of the storage passage 22 is preferably connected in the vicinity of the branch point between the exhaust passage 2 and the return passage 4, and the flow of exhaust gas is downstream from the branch point and upstream from the exhaust switchgear 21. It is more preferable to be arranged.

The suction pump 23 is arranged between the inlet of the storage passage 22 and the check valve 24, and the exhaust gas that passes through the selective reduction catalyst device 12 in a driven state and flows through the exhaust passage 2 is sent to the storage passage 22. It is a suction pump. The suction pump 23 has a function of increasing the pressure of the exhaust gas sucked from the exhaust passage 2 by pumping the exhaust gas to the storage tank 25 in a state of increasing the pressure of the exhaust gas.

The check valve 24 is arranged near the inlet of the storage tank 25. The check valve 24 allows the storage passage 22 to pass the exhaust gas from the downstream to the upstream of the selective reduction catalyst device 12, while blocking the flow of the exhaust gas from the upstream to the downstream of the selective reduction catalyst device 12. A switchgear having the same function as the check valve 24 may be used.

The storage tank 25 is a tank that is arranged between the check valve 24 and the storage switchgear 26 to temporarily store the exhaust gas. In the present embodiment, "temporary" indicates a period during which a part of the states in which the internal combustion engine 1 is being driven continues. The storage amount of the storage tank 25 is set in advance by experiments and tests. The amount of storage is preferably an amount capable of storing the exhaust gas discharged from the internal combustion engine 1 during a period in which some states continue, and further, a selective reduction catalyst device at the time of starting the internal combustion engine 1 in some states. It is more preferable that the amount of exhaust gas discharged from the internal combustion engine 1 can be stored in the period until the 12 becomes active.

The storage switchgear 26 is arranged near the outlet of the storage tank 25 to open the storage passage 22 so that the exhaust gas can flow in the open state, and makes the storage passage 22 unable to flow the exhaust gas in the closed state. It is a device that closes.

The exhaust gas purification system 10 includes a control device 30. The control device 30 controls the injection of the reducing agent injection device 11, temporarily stores the exhaust gas that has passed through the selective reduction catalyst device 12 by the storage mechanism 20, and re-passes the exhaust gas to the selective reduction catalyst device 12. The heating device 14 controls the temperature rise of the selective reduction catalyst device 12. The control device 30 is electrically connected to the reducing agent injection device 11, the heating device 14, the exhaust switchgear 21, the storage switchgear 26, and the suction pump 23 by a signal line. Further, the control device 30 is electrically connected to the inlet temperature sensor 31, the outlet temperature sensor 32, and the internal combustion engine control device 6. The internal combustion engine control device 6 is a device that controls the fuel injection of the internal combustion engine 1 and controls the opening and closing of the reflux opening / closing device 5 arranged in the reflux passage 4.

Each of the control device 30 and the control device 6 for an internal combustion engine is a central processing unit (CPU) that performs various information processing, an internal storage device that can read and write programs and information processing results used for performing various information processing, and various types. It is hardware that consists of interfaces and the like. The control device 30 may be a control device that integrates the functions of the internal combustion engine control device 6.

The control device 30 has a reducing agent control unit 33, a heating control unit 34, and a storage control unit 35 as functional elements. Each functional element is stored as a program in the internal storage device, and is executed by the central processing unit in a timely manner. In addition to the program, each functional element may be composed of a programmable controller (PLC) or an electric circuit in which each functions independently.

The reducing agent control unit 33 is a functional element that functions as an activity parameter acquisition device. The activity parameter acquisition device is a device that acquires activity parameters related to the active state of the selective reduction catalyst device 12. In the present embodiment, the active state of the selective reduction catalyst device 12 is a state in which the nitrogen oxide contained in the exhaust gas can be reduced and purified by using the reducing agent injected from the reducing agent injection device 11. The activity parameters are the inlet temperature Ty detected by the inlet temperature sensor 31 and the outlet temperature Tx detected by the outlet temperature sensor 32.

Specifically, the reducing agent control unit 33 is input with the temperature detected by the inlet temperature sensor 31 and the outlet temperature sensor 32 arranged before and after the selective reduction catalyst device 12, and the selective reduction catalyst device is based on the temperature. The active state of 12 is determined, and control is performed to inject the reducing agent from the reducing agent injection device 11 when the selective reduction catalyst device 12 is in the active state. Further, the reducing agent control unit 33 controls to adjust the injection amount of the reducing agent according to the content of nitrogen oxides detected by the NOx sensor (not shown).

In the reducing agent control unit 33, the outlet temperature Tx detected by the outlet temperature sensor 32 becomes equal to or higher than the preset active temperature Ta, and the temperature difference obtained by subtracting the outlet temperature Tx from the inlet temperature Ty detected by the inlet temperature sensor 31 is in advance. It is determined that the selective reduction catalyst device 12 is in the active state when the temperature becomes equal to or lower than the set soaking temperature Tb. The active temperature Ta is preferably set to a temperature at which hydrolysis of the urea water injected from the reducing agent injection device 11 is promoted. It is preferable that the soaking temperature Tb is set to a temperature at which the temperature difference between the front and rear of the selective reduction catalyst device 12 becomes small and it can be determined that the entire selective reduction catalyst device 12 is in the active state. As in the present embodiment, the selective reduction catalyst device 12 is surely in the active state by performing two determinations, that is, the comparative determination of the outlet temperature Tx and the active temperature Ta and the comparative determination of the temperature difference and the soaking temperature Tb. It becomes possible to determine that it has become.

The method for determining the active state of the selective reduction catalyst device 12 is not limited to the method using two sensors, the inlet temperature sensor 31 and the outlet temperature sensor 32, as in the present embodiment, and is not limited to, for example, selection. A method using a sensor that directly detects the temperature of the target reduction catalyst device 12 may also be used.

In the present embodiment, since the presence or absence of injection of the reducing agent determined by the reducing agent control unit 33 is based on the active state of the selective reduction catalyst device 12, the injection of the reducing agent causes the selective reduction catalyst device 12 to be active. It is synonymous with being in a state.

The heating control unit 34 receives a signal indicating the active state of the selective reduction catalyst device 12 from the reducing agent control unit 33 that functions as an activity parameter acquisition device, and controls the operation of the heating device 14 based on the signal. Is. The heating control unit 34 may directly input the detection values of the inlet temperature sensor 31 and the outlet temperature sensor 32 into the heating control unit 34, and the heating control unit 34 may determine the active state of the selective reduction catalyst device 12.

The storage control unit 35 is a functional element that controls the storage mechanism 20. Specifically, the storage control unit 35 receives a signal indicating the active state of the selective reduction catalyst device 12 from the reducing agent control unit 33 that functions as an activity parameter acquisition device, and based on the signal, the exhaust switchgear 21 and the storage Controls the drive of the switchgear 26 and the suction pump 23. The storage control unit 35 may be configured to directly input the detection values of the inlet temperature sensor 31 and the outlet temperature sensor 32 into the storage control unit 35 to determine the active state of the selective reduction catalyst device 12.

Further, the storage control unit 35 receives a signal from the internal combustion engine control device 6 functioning as an inflow parameter acquisition device indicating a state in which the content of nitrogen oxides contained in the exhaust gas rapidly increases, and based on the signal. It controls the drive of the exhaust opening / closing device 21, the storage opening / closing device 26, and the suction pump 23.

The internal combustion engine control device 6 is a device that functions as an inflow parameter acquisition device. The inflow amount parameter acquisition device is a device that acquires an inflow amount parameter regarding the inflow amount of nitrogen oxides flowing into the selective reduction catalyst device 12. In the present embodiment, the inflow of nitrogen oxides is the mass flow rate of nitrogen oxides flowing into the selective reduction catalyst device 12 per unit time. The inflow amount parameter is a parameter that can predict a rapid increase in the inflow amount, and more specifically, it is possible to predict a state in which the exhaust gas discharged from the internal combustion engine 1 suddenly increases due to the acceleration of the vehicle equipped with the internal combustion engine 1. Parameter. Examples of the inflow parameter include the fuel injection amount per unit time, the acceleration of the vehicle equipped with the internal combustion engine 1, and the depression amount of the accelerator pedal (not shown). The control device 6 for an internal combustion engine compares the inflow amount parameter with a preset threshold value and predicts a rapid increase in the inflow amount. It is desirable to predict a rapid increase in inflow using multiple inflow parameters. A function of acquiring an inflow parameter may be added to the storage control unit 35 so that the storage control unit 35 predicts a rapid increase in the inflow of nitrogen oxides.

In addition, the storage control unit 35 controls the internal combustion engine control device 6 to give an instruction to open the reflux switchgear 5 when the storage is controlled, and when the storage control is completed, the internal combustion engine control. The device 6 is controlled to give an instruction to close the reflux opening / closing device 5. Opening the reflux opening / closing device 5 means opening the opening / closing device 5 at a time when an instruction is given, and includes opening the reflux opening / closing device 5 fully open. Further, closing the reflux opening / closing device 5 means closing more than the portion opened by the storage control, and includes closing the reflux opening / closing device 5 fully closed. The storage control unit 35 is not limited to the configuration in which the reflux control device 5 is indirectly controlled via the internal combustion engine control device 6, and the storage control unit 35 directly controls the reflux switchgear 5. It may be configured.

As illustrated in FIGS. 3 and 4, the control method of the exhaust gas purification system 10 will be described as a function of the control device 30. This control method flow is repeated at predetermined intervals while the internal combustion engine is operating, and ends when the operation of the internal combustion engine is stopped. In the control flow, it is assumed that one cycle elapses when the return returns to the start.

As illustrated in FIG. 3, activity parameters are acquired at predetermined intervals (S110). Next, the reducing agent control unit 33 determines whether or not the outlet temperature Tx is smaller than the active temperature Ta (S120) and whether or not the temperature difference between the inlet temperature Ty and the outlet temperature Tx is larger than the soaking temperature Tb. Judgment (S130) is performed. The reducing agent control unit 33 determines that the selective reduction catalyst device 12 is in the active state when the outlet temperature Tx is equal to or higher than the active temperature Ta and the temperature difference is equal to or lower than the soaking temperature Tb, and the outlet temperature Tx is higher than the active temperature Ta. Is small, or the temperature difference is larger than the soaking temperature Tb, the selective reduction catalyst device 12 determines that the temperature is inactive. The reducing agent control unit 33 sends the two determination results to the heating control unit 34 and the storage control unit 35.

When the determination result that the selective reduction catalyst device 12 is in an inactive state is received (S110: YES or S120: YES), the heating control unit 34 operates the heating device 14 to raise the temperature of the selective reduction catalyst device 12. (S140). Then, the storage control unit 35 controls the storage by the storage mechanism 20 (S150), and returns to the start. Specifically, the storage control unit 35 completely closes the exhaust opening / closing device 21 to close the exhaust passage 2 downstream of the selective reduction catalyst device 12, and completely closes the storage opening / closing device 26 to the downstream of the storage tank 25. The storage passage 22 is closed, and the suction pump 23 is driven to suck the exhaust gas from the exhaust passage 2 into the storage passage 22. As a result, the exhaust gas that has passed through the selective reduction catalyst device 12 is stored in the storage tank 25. Further, the storage control unit 35 opens the reflux opening / closing device 5 via the internal combustion engine control device 6. As a result, a part of the exhaust gas that has passed through the selective reduction catalyst device 12 flows through the return passage 4 and joins the intake passage 3.

On the other hand, when the selective reduction catalyst device 12 receives the determination result that it is in the active state (S110: NO and S120: NO), the heating control unit 34 stops the operation of the heating device 14 (S160). Then, the storage control unit 35 controls the exhaust gas stored by the storage mechanism 20 to re-pass through the selective reduction catalyst device 12 (S170), and returns to the start. Specifically, the storage control unit 35 fully opens the exhaust opening / closing device 21 to open the exhaust passage 2 downstream of the selective reduction catalyst device 12, and fully opens the storage opening / closing device 26 to store the storage tank 25 downstream. The passage 22 is opened and the drive of the suction pump 23 is stopped. As a result, the exhaust gas stored in the storage tank 25 re-passes through the selective reduction catalyst device 12 and is reduced and purified by the selective reduction catalyst device 12. Further, the storage control unit 35 closes the reflux opening / closing device 5 via the internal combustion engine control device 6.

As illustrated in FIG. 4, the inflow amount parameter is acquired every predetermined cycle (S210). Next, the internal combustion engine control device 6 predicts whether or not the inflow amount is rapidly increasing (S220). The control device 6 for an internal combustion engine predicts that the inflow amount will suddenly increase when each of the fuel injection amount per unit time, the acceleration of the vehicle, and the depression amount of the accelerator pedal is equal to or higher than a preset threshold value. The internal combustion engine control device 6 sends this prediction result to the heating control unit 34 and the storage control unit 35.

Upon receiving the prediction result that the inflow amount will increase rapidly (S220: YES), the storage control unit 35 controls the storage by the storage mechanism 20 (S150), and returns to the start. On the other hand, upon receiving the prediction result that the inflow amount does not increase rapidly (S220: NO), the storage control unit 35 controls the exhaust gas stored by the storage mechanism 20 to re-pass through the selective reduction catalyst device 12 (S170). , Return to the start.

As described above, the exhaust gas purification system 10 of the present embodiment has a storage mechanism 20 when a large amount of nitrogen oxides remain in the exhaust gas that has passed through the selective reduction catalyst device 12 while the internal combustion engine 1 is being driven. The exhaust gas that has passed through the selective reduction catalyst device 12 is temporarily stored without being released to the outside. Then, when the selective reduction catalyst device 12 is in a state where reduction purification is possible, the stored exhaust gas can be passed through the selective reduction catalyst device 12 again. Therefore, it is possible to prevent the exhaust gas containing a large amount of nitrogen oxides from being released to the outside while the internal combustion engine 1 is being driven.

In the exhaust gas purification system 10, since the storage mechanism 20 has the suction pump 23, the exhaust gas can be sucked from the exhaust passage 2 into the storage passage 22 and guided to the storage tank 25 by driving the suction pump 23. That is, the exhaust gas that has passed through the selective reduction catalyst device 12 can be prevented from staying in the exhaust passage 2 and stored in the storage tank 25 only by closing the exhaust opening / closing device 21. Further, the pressure of the storage tank 25 can be increased by increasing the pressure of the exhaust gas sucked by the suction pump 23. As a result, when the storage switchgear 26 is opened, the exhaust gas with increased pressure can be merged from the storage tank 25 upstream of the selective reduction catalyst device 12.

It is desirable that the exhaust gas purification system 10 includes a heating device 14. By providing the heating device 14, when the selective reduction catalyst device 12 is in an inactive state, the selective reduction catalyst device 12 can be warmed up at an early stage by the operation of the heating device 14 to bring it into an active state. Further, since the selective reduction catalyst device 12 is activated at an early stage, it is possible to set a small capacity for storing the exhaust gas in the storage tank 25, and it is possible to suppress the increase in weight of the device.

In the exhaust gas purification system 10, it is desirable that the exhaust opening / closing device 21 is arranged in the exhaust passage 2 downstream of the branch port of the return passage 4 with respect to the flow of exhaust gas. That is, it is desirable that the exhaust gas can be diverted to the return passage 4 when the exhaust opening / closing device 21 is closed. By arranging the exhaust gas switchgear 21 in this way, when the exhaust gas is stored in the storage tank 25, the reflux switchgear 5 is opened and all the exhaust gas that has passed through the selective reduction catalyst device 12 is stored in the storage tank 25. A part of the exhaust gas can be returned from the return passage 4 to the intake passage 3 without being stored in the air. As a result, the capacity of the storage tank 25 for storing the exhaust gas can be set to be small, and it is possible to suppress the increase in weight and length of the device.

The exhaust gas purification system 10 includes a pressure sensor that detects the pressure inside the storage tank 25, and the control device 30 monitors the exhaust gas filling state of the storage tank 25 based on the value detected by the pressure sensor, and the storage tank 25 It is desirable to control the opening of the storage opening / closing device 26 when the storage opening / closing device 26 is full. This is advantageous in avoiding a situation in which the exhaust gas cannot be sucked from the exhaust passage 2 to the storage passage 22 when the storage tank 25 is full.

It is desirable that the exhaust gas purification system 10 empty the storage tank 25 when the internal combustion engine 1 is started to be driven. Specifically, when the control device 30 stops driving the internal combustion engine 1, the storage opening / closing device 26 is opened, and the exhaust gas remaining in the storage tank 25 is controlled to be discharged from the storage tank 25 to the exhaust passage 2. Is desirable. This is advantageous in avoiding a situation in which the exhaust gas cannot be stored in the storage tank 25 when the driving of the internal combustion engine 1 is started and the selective reduction catalyst device 15 is in an inactive state.

The storage mechanism 20 of the present embodiment includes an exhaust switchgear 21, a storage passage 22, a suction pump 23, a check valve 24, a storage tank 25, and a storage switchgear 26, and includes a selective reduction catalyst device 12. If it is possible to temporarily store the exhaust gas after passing and allow the stored exhaust gas to pass through the selective reduction catalyst device 12 again, it can be changed as appropriate.

1 Internal combustion engine 2 Exhaust gas passage 10 Exhaust gas purification system 12 Selective reduction catalyst device 20 Storage mechanism 21 Exhaust switchgear 22 Storage passage 23 Suction pump 24 Check valve 25 Storage tank 26 Storage switchgear

Claims (6)

In an exhaust gas purification system in which a selective reduction catalyst device for reducing and purifying nitrogen oxides contained in exhaust gas is arranged in the middle of an exhaust passage through which exhaust gas discharged from an internal combustion engine flows.
The exhaust gas that has passed through the selective reduction catalyst device is temporarily stored without being released to the outside in a part of the state in which the internal combustion engine is being driven, and the stored exhaust gas is again selectively stored. An exhaust gas purification system characterized by having a storage mechanism for passing through a reduction catalyst device. The storage mechanism is between an exhaust opening / closing device arranged in the exhaust passage downstream of the selective reduction catalyst device with respect to the flow of exhaust gas and an outlet of the selective reduction catalyst device to the exhaust opening / closing device. A storage passage that branches from the exhaust passage and joins the exhaust passage upstream of the selective reduction catalyst device, and a suction pump that is sequentially arranged in the storage passage in the direction opposite to the flow of exhaust gas in the exhaust passage. , A check valve, a storage tank, and an opening / closing device for storage,
When the exhaust switchgear and the storage switchgear are closed, the suction pump is driven, and the exhaust gas that has passed through the selective reduction catalyst device is sucked into the storage passage and stored in the storage tank.
The first aspect of claim 1, wherein the exhaust gas opening / closing device and the storage opening / closing device are opened, the drive of the suction pump is stopped, and the exhaust gas stored in the storage tank re-passes through the selective reduction catalyst device. Exhaust gas purification system. A control device connected to each of the exhaust switchgear, the storage switchgear, and the suction pump, and an activity parameter acquisition device for acquiring an activity parameter relating to the activity state of the selective reduction catalyst device are provided.
The control device monitors the active state of the selective reduction catalyst device based on the activity parameter acquired by the activity parameter acquisition device, and opens and closes the exhaust gas when the selective reduction catalyst device is in an inactive state. The device and the storage opening / closing device are closed and the suction pump is controlled to be driven, and when the selective reduction catalyst device is in the active state, the exhaust opening / closing device and the storage opening / closing device are opened and the storage opening / closing device is opened. The exhaust gas purification system according to claim 2, which is configured to control to stop the drive of the suction pump. A heating device for heating either the exhaust gas flowing through the exhaust passage upstream of the selective reduction catalyst device or the selective reduction catalyst device with respect to the flow of the exhaust gas is provided.
The control device controls to operate the heating device when the selective reduction catalyst device is in an inactive state, and stops the operation of the heating device when the selective reduction catalyst device is in an active state. The exhaust gas purification system according to claim 3, which is configured to perform control. A device for acquiring an inflow amount parameter for acquiring an inflow amount parameter relating to an inflow amount of nitrogen oxides flowing into the selective reduction catalyst device is provided.
The control device predicts an increase or decrease in the inflow amount based on the inflow amount parameter acquired by the inflow amount parameter acquisition device, and when it is predicted that the inflow amount will suddenly increase, the exhaust switchgear and the above. The exhaust gas purification system according to claim 3 or 4, wherein the storage opening / closing device is closed and the suction pump is controlled to be driven. Any of claims 2 to 5, wherein the exhaust opening / closing device is arranged in the exhaust passage downstream of the branch port of the return passage that branches from the exhaust passage and joins the intake passage through which the intake air flows. The exhaust gas purification system according to item 1.

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