JP2009002260A - Exhaust gas purification device - Google Patents

Abstract

An exhaust gas purification device and an exhaust gas purification device capable of reducing the vapor pressure of ammonia in a tank are obtained.
A urea SCR system 10 exhausts a urea water tank 22, a urea water supply pipe 30 for introducing urea water from the urea water tank 22 into an exhaust pipe 14, and urea water supplied from the urea water supply pipe 30. An openable / closable urea water injection valve 32 that injects into the pipe 14, a reducing agent supply operation that pumps urea water from the urea water tank 22 to the exhaust pipe 14, and urea water from the urea water injection valve 32 side to the urea water tank 22 A urea water pressure feed pump 34 that can switch between a reducing agent recovery operation for pressure feeding, and a urea water pressure feed pump 34 that opens the urea water injection valve 32 when there is a request to supply the urea water to the exhaust pipe 14. An ECU 42 that switches to the reducing agent supply operation and closes the urea water injection valve 32 and stops the urea water pressure feed pump 34 to the reducing agent recovery operation when the supply of urea water to the exhaust pipe 14 is stopped. There.
[Selection] Figure 1

Description

  The present invention relates to an exhaust gas purification device that purifies exhaust gas by supplying a reducing agent to an exhaust pipe.

In the reducing agent supply device that supplies urea water from the urea water tank to the exhaust pipe, as a measure to prevent freezing of the urea water remaining in the supply line, pressurized air from the air tank is placed at the most upstream part of the urea water supply line when the device is stopped. And supplying urea water in the supply line to the exhaust pipe is known (see, for example, Patent Document 1).
JP 2005-248823 A JP 2006-316684 A

  However, in the conventional technology as described above, the urea water discharged to the exhaust pipe does not contribute to the purification of the exhaust gas, and there is a problem that this urea water is wasted.

  An object of the present invention is to obtain an exhaust gas purification device capable of preventing the reducing agent from being frozen in a pipe while suppressing the waste of the reducing agent in consideration of the above facts.

  An exhaust gas purification apparatus according to claim 1 is a tank for storing a reducing agent, a supply pipe having one end side disposed in the tank and the other end side located outside the tank, Provided at the other end of the supply pipe, when the valve is open, the supplied reducing agent is injected into an exhaust pipe for exhausting exhaust gas from the internal combustion engine, and when the valve is closed, the supply pipe and the exhaust pipe communicate with each other. An injection valve for shutting off the fuel, a reducing agent supply operation for supplying the reducing agent from the tank to the exhaust pipe through the supply pipe, and a reducing agent recovery operation for returning the reducing agent in the supply pipe to the tank. When the pump and the supply of the reducing agent to the exhaust pipe are requested, the injection valve is opened, the reducing agent supply operation is performed by the pump, and the reducing agent is supplied to the exhaust pipe. When stopping supply to The injection valve as said reducing agent recovering operation by said pump while being closed is performed, and a, and control means for controlling the injection valve and the pump.

  In the exhaust gas purifying apparatus according to claim 1, when the control means determines that the supply of the reducing agent to the exhaust pipe is requested, such as when the internal combustion engine is operated, the control means The valve is opened and the pump is operated to supply a reducing agent. Thereby, urea water is introduced into the injection valve through the supply pipe, and is supplied from the injection valve to the exhaust pipe.

  On the other hand, when the control means determines that the supply of the reducing agent to the exhaust pipe has been stopped, for example, when the operation of the internal combustion engine is stopped, the control means closes the injection valve and turns on the pump. Let the reducing agent recover operation. Thereby, the reducing agent remaining in the supply pipe is collected in the tank.

  Thus, in the exhaust gas purification apparatus according to the first aspect, it is possible to prevent the reducing agent from being frozen in the piping while suppressing the waste of the reducing agent. In addition, since the reducing agent in the supply pipe is collected with the injection valve closed, foreign matter in the exhaust pipe is prevented from being collected in the supply pipe and the tank.

  The exhaust gas purifying apparatus according to claim 2 is the exhaust gas purifying apparatus according to claim 1, wherein the injection valve is closed at a portion of the supply pipe on the injection valve side and the pump. A gas inflow permissible portion that allows gas to flow into the supply pipe as the reducing agent recovery operation is performed is provided.

  In the exhaust gas purifying apparatus according to claim 2, the gas flows in from the vicinity of the end of the supply pipe on the injection valve side as the reducing agent is recovered from the supply pipe, so that the supply pipe has a negative pressure. Is suppressed or prevented.

  An exhaust gas purification apparatus according to a third aspect of the present invention is the exhaust gas purification apparatus according to the second aspect, wherein the exhaust gas purification apparatus is provided in the atmospheric open pipe connected to the tank, and is discharged from the tank. An adsorbing device for removably adsorbing at least a specific component of gas, the gas inflow permitting portion, a gas introducing pipe communicating the adsorbing device and the injection valve side portion of the supply pipe, and the gas introducing A valve device that is provided in a pipe and is closed when the reducing agent supply operation is performed by the pump, and is opened when the reducing agent recovery operation is performed by the pump. ing.

  In the exhaust gas purifying apparatus according to the third aspect, when the pressure (gas pressure) in the tank is higher than the atmospheric pressure (a predetermined value or more), the gas is released to the atmosphere from the atmosphere opening pipe. At this time, a specific component in the gas (for example, a vapor of the reducing agent) is adsorbed by the adsorption device. When the reducing agent in the supply pipe is recovered in the tank by the reducing agent recovery operation of the pump, the gas of the specific component separated from the adsorption device moves from the gas introduction pipe to the supply pipe and the tank. Thereby, the adsorption possible amount of the specific component of the gas by the adsorption device can be increased. Further, when the gas of the specific component is a component that can be used as a reducing agent, waste of the reducing agent is more effectively suppressed.

  According to a fourth aspect of the present invention, there is provided the exhaust gas purifying apparatus according to any one of the first to third aspects, wherein the control means supplies the reducing agent to the exhaust pipe. When stopping, the injection valve is closed and the pump is switched from the reducing agent supply operation to the reducing agent recovery operation, and after the first step, the injection valve is opened. And a second step of switching the pump from the reducing agent recovery operation to the reducing agent supply operation, and after the second step, closing the injection valve and switching the pump from the reducing agent supply operation to the reduction. The injection valve and the pump are controlled so that the third step of switching to the agent recovery operation is performed.

  In the exhaust gas purifying apparatus according to claim 4, when the control means determines that the supply of the reducing agent to the exhaust pipe has been stopped, such as when the operation of the internal combustion engine is stopped, the control means includes: First, in the first step, the reducing agent in the supply pipe is collected in the tank. Next, in the second step, the reducing valve remaining in the injection valve can be discharged to the exhaust pipe by opening the injection valve and causing the pump to perform the reducing agent supply operation. Thereafter, in the third step, the reducing valve that has flowed into the supply pipe in the second step can be recovered again in the tank by closing the injection valve again and causing the pump to perform the reducing agent recovery operation.

  As described above, the exhaust gas purification device and the exhaust gas purification device according to the present invention have an excellent effect of being able to prevent freezing of the reducing agent in the pipe while suppressing waste of the reducing agent. Have

  A urea SCR (Selective Catalytic Reduction) system 10 as an exhaust gas purifying apparatus according to an embodiment of the present invention will be described with reference to FIGS.

  In FIG. 1, a schematic overall configuration of the urea SCR system 10 is shown in a schematic system configuration diagram (flow sheet). As shown in this figure, the urea SCR system 10 has a urea water described later upstream of the selective reduction NOx catalyst 16 in the exhaust pipe 14 of the diesel engine 12 in order to reduce NOx in the exhaust gas of the diesel engine 12. It is configured to inject urea water as a reducing agent stored in the tank 22.

  Specifically, in the urea SCR system 10, the selective reduction NOx catalyst 16 is disposed downstream of the oxidation catalyst 18 in the exhaust pipe 14, and the urea water supply device 20 constituting the urea SCR system 10 exhausts the exhaust gas. Urea water is supplied between the oxidation catalyst 18 and the selective reduction NOx catalyst 16 in the pipe 14. In this embodiment, the oxidation catalyst 18 is integrally provided with a DPF (diesel particulate removing device).

  In the urea SCR system 10, when the urea supplied to the exhaust pipe 14 by the urea water supply device 20 is vaporized and flows into the selective reduction NOx catalyst 16 together with the exhaust gas as a reducing gas (ammonia gas), the reducing gas Selectively reduces or decomposes NOx in the exhaust gas. Thereby, in the vehicle to which the urea SCR system 10 is applied, the exhaust gas purified by the oxidation catalyst 18, the DPF, and the selective reduction NOx catalyst 16 of the urea SCR system 10 is released into the atmosphere.

  Hereinafter, the detailed configuration of the urea SCR system 10 will be described.

  As shown in FIG. 1, the urea water supply device 20 constituting the urea SCR system 10 includes a urea water tank 22 as a tank. The urea water tank 22 stores urea water injected from an inlet (not shown) in a gas-liquid two-phase state. An air release pipe 24 is connected to the urea water tank 22. One end 24 </ b> A communicates with the urea water tank 22 and the other end of the atmosphere release pipe 24 is an atmosphere release end 24 </ b> B to form an atmosphere release line.

  Further, a pressure regulating valve 25 is provided on the outside portion of the urea water tank 22 in the atmosphere opening pipe 24. The pressure regulating valve 25 is opened when the pressure (gas pressure) in the urea water tank 22 is higher than the first predetermined value with respect to the atmospheric pressure, and the pressure (gas pressure) in the urea water tank 22 is increased. The pressure regulating valve is a two-way valve that opens when the pressure becomes lower than the second predetermined value with respect to the atmospheric pressure. Thereby, the urea water tank 22 is protected against both positive pressure and negative pressure.

  On the other hand, an inflow prevention valve 26 disposed through the top wall 22 </ b> A of the urea water tank 22 is disposed at one end 24 </ b> A of the air release pipe 24. The inflow prevention valve 26 is configured to prevent urea water (liquid phase) from flowing into the atmosphere opening pipe 24. In this embodiment, the pressure regulating valve 25 is configured as a float valve that closes when a float that floats on urea water contacts a valve seat that is substantially downward in the direction of gravity.

  Further, a filter device 28 is disposed on the atmosphere opening end 24 </ b> B side with respect to the pressure regulating valve 25 in the atmosphere opening pipe 24. The filter device 28 is configured by incorporating a filter element made of, for example, a nonwoven fabric or the like and activated carbon as an adsorbent in a case 28A. The filter element prevents intrusion of foreign substances in the air flowing in from the air open end 24B into the urea water tank 22 and a gas introduction pipe 38 described later. The activated carbon is adapted to adsorb ammonia gas in the gas flowing in from the urea water tank 22 side. In this embodiment, the filter device 28 uses activated carbon that releases ammonia gas adsorbed by the introduction of air.

  As described above, the filter device 28 constituting the urea SCR system 10 functions as an air filter that purifies the air to be introduced and the ammonia gas discharged from the urea water tank 22 to temporarily adsorb the atmosphere of the ammonia gas. It is configured to serve as an ammonia adsorption device that suppresses the release. That is, in this embodiment, the filter device 28 corresponds to the adsorption device in the present invention.

  The urea water supply device 20 of the urea SCR system 10 includes a urea water supply pipe 30 as a supply pipe that forms a supply line for supplying urea water from the urea water tank 22 to the exhaust pipe 14. The urea water supply pipe 30 passes through the top wall 22A of the urea water tank 22 and has an inlet 30A having one end opened near the bottom wall 22B of the urea water tank 22, and the other end serving as an injection valve. The urea water injection valve 32 is connected so that urea water can be supplied.

  The urea water injection valve 32 is attached through the portion of the exhaust pipe 14 between the oxidation catalyst 18 and the selective reduction NOx catalyst 16 (upstream of the selective reduction NOx catalyst 16), and is introduced from the urea water supply pipe 30. The urea water thus produced is injected toward the selective reduction NOx catalyst 16 side in the exhaust pipe 14. In this embodiment, the urea water injection valve 32 is an electromagnetic valve that can be switched (controlled) by an ECU 42, which will be described later, and injects the urea water supplied from the urea water supply pipe 30 when opened. It is the structure to do.

  Further, a urea water pressure feed pump 34 as a pump for pressure-feeding urea water sucked from the suction port 30A side to the urea water injection valve 32 side is disposed at an intermediate portion of the urea water supply pipe 30. By the operation of the urea water pressure feed pump 34, a driving force toward the exhaust pipe 14 is applied to the urea water in the urea water tank 22. In this embodiment, the urea water pressure pump 34 is attached to the outside of the urea water tank 22.

  The urea water pressure pump 34 in this embodiment has a drive motor (not shown) capable of rotating in the forward and reverse directions, and when the drive motor is rotated forward, the urea water injection from the urea water tank 22 as described above. A flow of urea water toward the valve 32 is generated, and when the drive motor is reversed, a flow of urea water or the like toward the urea water tank 22 from the urea water injection valve 32 side is generated. That is, the urea water pressure pump 34 is configured to be capable of at least three states of normal rotation, reverse rotation, and stop, and these three states are switched by control of the ECU 42 described later.

  Further, a filter for preventing foreign matter from being introduced into the urea water pressure feed pump 34 and the urea water injection valve 32 (exhaust pipe 14) side at a portion of the urea water supply pipe 30 located in the urea water tank 22. 36 is provided. The filter 32 is a mesh filter made of a woven or non-woven fabric of resin fibers such as polyester.

  In the urea SCR system 10, a branch is made from a branch portion 30 </ b> B provided in a portion immediately upstream of the urea water injection valve 32 (in the immediate vicinity of the urea water injection valve 32) in the urea water supply pipe 30 constituting the urea water supply device 20. The gas introducing pipe 38 is provided. The end of the gas introduction pipe 38 is communicated with the inside of the filter device 28 (accommodated portion of activated carbon). The gas introduction pipe 38 is provided with a one-way valve 40 as a valve device. In this embodiment, the branch part 30B of the gas introduction pipe 38 in the urea water supply pipe 30 corresponds to a gas inflow permission part in the present invention.

  The one-way valve 40 is configured to operate so as to allow a gas flow from the filter device 28 side to the urea water supply pipe 30 side and prohibit a fluid flow from the urea water supply pipe 30 side to the filter device 28 side. Has been. As the one-way valve 40, for example, a spring type check valve (check valve) is used.

  Furthermore, the urea SCR system 10 includes an ECU 42 as control means. The ECU 42 is electrically connected to the urea water injection valve 32 and the urea water pressure feed pump 34, and controls opening / closing of the urea water injection valve 32 and normal rotation, reverse rotation, and stop of the urea water pressure feed pump 34. Yes. Further, vehicle information including the system ON and OFF of the urea SCR system 10 is input to the ECU 42. In this embodiment, the ignition (power) ON by the driver corresponds to the system ON of the urea SCR system 10 (when supply of urea water to the exhaust pipe 14 is required), and the ignition (power) OFF is the system OFF ( The configuration corresponds to a trigger for stopping supply of urea water to the exhaust pipe 14).

  The control by the ECU 42 will be described together with the explanation of the operation of the urea SCR system 10 according to the present embodiment.

  Next, the operation of this embodiment will be described with reference to the flowchart shown in FIG.

  In the urea SCR system 10 having the above configuration, when the ignition (IG) switch of the applied vehicle is turned on, the system is turned on and the ECU 42 is activated. Then, in step S10, the ECU 42 opens the urea water injection valve 32 and rotates the urea water pressure feed pump 34 in the normal direction. Thus, as shown in FIG. 2, in the urea SCR system 10, the urea water in the urea water tank 22 is pumped to the urea water injection valve 32 by the urea water pressure pump 34, and the exhaust pipe 14 is discharged from the urea water injection valve 32. The urea water is injected into the inside and supplied.

  The urea water injected into the exhaust pipe 14 is vaporized by exhaust heat to become a reducing gas (ammonia gas), and flows into the selective reduction NOx catalyst 16 together with the exhaust gas of the diesel engine 12. In the selective reduction NOx catalyst 16, the reducing gas selectively reduces or decomposes NOx in the exhaust gas. Thereby, the exhaust gas purified by the oxidation catalyst 18 and the selective reduction NOx catalyst 16 is released into the atmosphere.

  Next, the ECU 42 proceeds to step S12, and determines whether or not the system is turned off, that is, whether or not an ignition switch OFF signal is input. The ECU 42 that has determined that the system is not turned off maintains the urea water supply operation state to the exhaust pipe 14 by the urea water supply device 20 described above. At this time, for example, the urea water supply amount by the urea water pressure pump 34 may be controlled in accordance with the rotational speed (exhaust gas amount) of the diesel engine 12.

  On the other hand, the ECU 42 that has determined that the system has been turned off in step S12 proceeds to step S14, closes the urea water injection valve 32, and switches the urea water pressure pump 34 from normal rotation to reverse rotation. As a result, as shown in FIG. 3, in the urea SCR system 10, the urea water remaining in the urea water supply pipe 30 is pumped to the urea water tank 22 and collected by the urea water pumping pump 34. At this time, gas flows into the urea water supply pipe 30 from the branch portion 30B via the atmosphere opening end 24B of the atmosphere opening pipe 24, the filter device 28, and the gas introduction pipe 38 (one-way valve 40). This step S14 corresponds to the first step in the present invention.

  Next, the ECU 42 proceeds to step S16, and determines whether or not a first predetermined time has elapsed from the start of execution of step S14 (timer start). In this embodiment, the first predetermined time is set as a time sufficient to recover almost all of the urea water for the volume in the urea water supply pipe 30 under each environmental condition (temperature, atmospheric pressure, etc.). Yes. The ECU 42 that has determined in step S16 that the first predetermined time has not elapsed maintains the recovered state of the urea water. During this time, gas introduction to the urea water supply pipe 30 via the filter device 28 and the gas introduction pipe 38 is also maintained.

  On the other hand, the ECU 42 that has determined that the first predetermined time has passed in step S16 proceeds to step S18, opens the urea water injection valve 32, and switches the urea water pumping pump 34 from reverse rotation to normal rotation. As a result, the urea water is again pumped to the urea water injection valve 32 side after substantially the entire amount of urea water in the urea water supply pipe 30 is recovered. Then, the urea water remaining in the urea water injection valve 32 is discharged to the exhaust pipe 14 by the gas in the urea water supply pipe 30 pushed out by the urea water. This step S18 corresponds to the second step in the present invention.

  Next, the ECU 42 proceeds to step S20, and determines whether or not a second predetermined time has elapsed from the start of execution of step S18 (timer start). In this embodiment, the second predetermined time is a time sufficient for discharging almost all of the urea water for the volume in the urea water injection valve 32 under each environmental condition (temperature, atmospheric pressure, etc.) (first predetermined time). It is set as a sufficiently short time). The ECU 42 that has determined that the second predetermined time has not elapsed in step S20 maintains the discharge state of the urea water in the urea water injection valve 32.

  On the other hand, the ECU 42 that has determined that the second predetermined time has elapsed in step S20 proceeds to step S22, closes the urea water injection valve 32, and switches the urea water pressure pump 34 from normal rotation to reverse rotation. As a result, the urea water that has flowed into the urea water supply pipe 30 by the execution of step S18 is again collected in the urea water tank 22. This step S22 corresponds to the third step in the present invention.

  Next, the ECU 42 proceeds to step S24, and determines whether or not a third predetermined time has elapsed from the start of execution of step S22 (timer start). In this embodiment, the third predetermined time is sufficient to recover almost all of the urea water that has flowed into the urea water supply pipe 30 in the second predetermined time under each environmental condition (temperature, atmospheric pressure, etc.). Time (for example, a time slightly longer than the second predetermined time). The ECU 42 that has determined that the third predetermined time has not elapsed in step S24 maintains the urea water recovery state.

  On the other hand, the ECU 42 that has determined that the third predetermined time has elapsed in step S24 proceeds to step S26, stops the urea water pressure pump 34 while maintaining the closed state of the urea water injection valve 32, and ends the control. To do.

  Here, in the urea SCR system 10, when the system is turned off, the ECU 42 closes the urea water injection valve 32 and reversely rotates the urea water pressure feed pump 34 for the first predetermined time. It is possible to recover almost all of the urea water remaining in the urea water tank 22. This prevents the urea water remaining in the urea water supply pipe 30 from freezing.

  Supplementing the freezing of urea water, urea water has a relatively high freezing point of −11 ° C. and is accompanied by a volume expansion of about 12% during freezing. In order to prevent the urea water supply pipe 30 from being damaged due to freezing of the urea water, for example, measures such as installation of a heater are required. On the other hand, in the urea SCR system 10, the urea water in the urea water supply pipe 30 is collected in the urea water tank 22 as described above, so that the countermeasure for freezing urea water as described above becomes unnecessary.

  Thus, in the urea SCR system 10, it is possible to prevent freezing of the urea water in the urea water supply pipe 30 while suppressing waste of the urea water.

  In the urea SCR system 10, the urea water injection valve 32 is closed when the urea water is recovered from the urea water supply pipe 30, so that foreign matters such as soot and metal powder are discharged from the exhaust pipe 14 to the urea water supply pipe 30. Intrusion into the urea water tank 22 is prevented. Infiltration of soot or metal powder or the like causes clogging of the filter 36, for example, but the urea SCR system 10 prevents clogging of the filter 36 due to infiltration of soot or metal powder from the exhaust pipe 14.

  Further, in the urea SCR system 10, when recovering urea water in the urea water supply pipe 30, gas is introduced into the urea water supply pipe 30 from the branch portion 30 </ b> B of the urea water supply pipe 30 via the gas introduction pipe 38. Therefore, negative pressure in the urea water supply pipe 30 is prevented or suppressed. Moreover, the load of the urea water pressure pump 34 is also reduced.

  In particular, in the urea SCR system 10, with the recovery of the urea water in the urea water supply pipe 30, air is introduced from the atmospheric open end 24 </ b> B to the filter device 28 and the ammonia gas adsorbed on the filter device 28 is released. Therefore, the ammonia gas can be purged from the filter device 28 by the gas flow in the gas introduction pipe 38 from the filter device 28 toward the urea water supply pipe 30. Thereby, in the urea SCR system 10, the adsorption capability of the ammonia gas by the filter device 28 is recovered.

  Moreover, in the urea SCR system 10, ammonia gas (at least a part thereof) having high solubility in urea water (water) enters the urea water tank 22 from the suction port 30 </ b> A (part where the probability of being submerged in the urea water is high). Since it flows in, the ammonia gas is recovered in the urea water tank 22 as ammonia water. That is, the ammonia gas is recovered as it is, the gas pressure in the urea water tank 22 is increased, and it is suppressed from being adsorbed again by the filter device 28 via the air release pipe 24 and the pressure adjustment valve 25. Moreover, since ammonia water can be injected as it is into the exhaust pipe 14 as a reducing agent, in the urea SCR system 10, waste of the reducing agent is further effectively suppressed.

  Here, in the urea SCR system 10, after the urea water remaining in the urea water supply pipe 30 is recovered, the urea water slightly remaining in the urea water injection valve 32 is discharged to the exhaust pipe 14. The urea water is prevented from remaining in the urea water injection valve 32 (the amount of remaining urea water can be significantly reduced). Thereby, the countermeasure against freezing with respect to the urea water injection valve 32 can also be made unnecessary (simple).

  In addition, since the residual urea water of the urea water injection valve 32 is discharged to the exhaust pipe 14, soot and metal powder do not enter the urea water injection valve 32 from the exhaust pipe 14. Furthermore, in the urea SCR system 10, since the urea water recovery of the urea water supply pipe 30 is performed after the residual urea water is discharged from the urea water injection valve 32, the urea water flowing into the urea water supply pipe 30 is recovered and the urea water is recovered. Freezing of urea water in the supply pipe 30 does not become a problem.

  In the above-described embodiment, an example in which activated carbon capable of adsorbing and detaching ammonia gas is incorporated in the filter device 28 is shown, but the present invention is not limited to this, and for example, does not have activated carbon (ammonia adsorption function). A configuration may be adopted, and a configuration in which activated carbon that does not have a function of releasing the adsorbed ammonia may be built in the filter device 28 is also possible.

  Further, in the above-described embodiment, an example in which the one-way valve 40 which is a spring type check valve is provided in the gas introduction pipe 38 is shown, but the present invention is not limited to this, and for example, another type of one-way valve 40 A directional valve may be provided, and an electromagnetic valve whose opening / closing is controlled by the ECU 42 may be provided instead of the one-way valve 40. In this case, for example, this electromagnetic valve is controlled by the ECU 42 so as to be closed when the urea water injection valve 32 is opened and to be opened when the urea water injection valve 32 is closed. It should be done.

  Furthermore, in the above-described embodiment, an example in which the residual urea water in the urea water injection valve 32 is discharged after almost the entire amount of residual urea water in the urea water supply pipe 30 is recovered has been shown in the above-described embodiment. However, for example, the residual urea water in the urea water supply pipe 30 is collected, and the residual urea in the urea water injection valve 32 is collected in the urea water supply pipe 30 (between the urea water and the urea water injection valve 32). You may make it discharge the residual urea water of the urea water injection valve 32, after gas sufficient to discharge water is introduced.

  Furthermore, the present invention is not limited to the configuration in which the residual urea water of the urea water injection valve 32 is discharged to the exhaust pipe 14. In the urea SCR system 10, at least the urea water injection valve 32 is closed. It suffices to recover the residual urea water in the urea water supply pipe 30 in the urea water tank 22.

  Moreover, although the example which used urea water as a reducing agent was shown in above-described embodiment, this invention is not limited to this, It cannot be overemphasized that the structure Japanese invention using various reducing agents is applicable.

1 is a system configuration diagram showing a schematic overall configuration of a urea SCR system according to an embodiment of the present invention. It is a system block diagram which shows the urea water supply operation state in the urea SCR system which concerns on embodiment of this invention. It is a system block diagram which shows the urea water collection | recovery driving | running state in the urea SCR system which concerns on embodiment of this invention. It is a flowchart which shows the general | schematic control flow by ECU which comprises the urea SCR system which concerns on embodiment of this invention.

Explanation of symbols

10 SCR urea system (exhaust gas purification system)
12 Diesel engine (internal combustion engine)
14 Exhaust pipe 22 Urea water tank (tank)
24 Open air piping 28 Filter device (adsorption device)
30 Urea water supply pipe (supply pipe)
30B Branch (gas inflow permitting part)
32 Urea water injection valve (injection valve)
34 Urea water pressure pump (pump)
38 Gas introduction pipe (gas inflow permitting part)
40 One-way valve (valve device)
42 ECU (control means)

Claims (4)

A tank for storing the reducing agent;
A supply pipe having one end side disposed in the tank and the other end side positioned outside the tank;
Provided at the other end of the supply pipe, in the valve open state, the supplied reducing agent is injected into the exhaust pipe for exhausting the exhaust gas of the internal combustion engine, and in the valve closed state, the supply pipe and the exhaust pipe An injection valve that cuts off the communication;
A pump capable of switching between a reducing agent supply operation for supplying the reducing agent from the tank to the exhaust pipe through the supply pipe and a reducing agent recovery operation for returning the reducing agent in the supply pipe to the tank;
When the supply of the reducing agent to the exhaust pipe is requested, the injection valve is opened and the reducing agent supply operation is performed by the pump, and the supply of the reducing agent to the exhaust pipe is performed. Control means for controlling the injection valve and the pump so that the injection valve is closed and the reducing agent recovery operation is performed by the pump.
An exhaust gas purifying device.   A gas that allows the gas to flow into the supply pipe when the injection valve is closed and the reducing agent recovery operation is performed by the pump at a portion of the supply pipe on the injection valve side The exhaust gas purification device according to claim 1, further comprising an inflow permission portion. An open air pipe connected to the tank;
An adsorption device for removably adsorbing at least a specific component of the gas discharged from the tank, provided in the atmosphere open pipe;
Further comprising
The gas inflow permitting part is:
A gas introduction pipe communicating the adsorber and the injection valve side portion of the supply pipe;
A valve device that is provided in the gas introduction pipe, is closed when the reducing agent supply operation is performed by the pump, and is opened when the reducing agent recovery operation is performed by the pump;
The exhaust gas purifying device according to claim 2, comprising: The control means includes
When stopping the supply of the reducing agent to the exhaust pipe,
A first step of closing the injection valve and switching the pump from the reducing agent supply operation to the reducing agent recovery operation;
A second step that is performed after the first step, opens the injection valve, and switches the pump from the reducing agent recovery operation to the reducing agent supply operation;
A third step that is performed after the second step, closes the injection valve, and switches the pump from the reducing agent supply operation to the reducing agent recovery operation;
The exhaust gas purification device according to any one of claims 1 to 3, wherein the injection valve and the pump are controlled such that the injection is performed.

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