JP6264553B2 - Exhaust purification system - Google Patents

Description

  The present invention relates to an exhaust purification system that reduces nitrogen oxides (NOx) in exhaust gas of an internal combustion engine.

  As a technique for reducing nitrogen oxide (NOx) contained in exhaust gas of an internal combustion engine (engine), an exhaust purification system using a urea SCR (Selective Catalytic Reduction) system is known. In an exhaust purification system using a urea SCR system, urea water is injected into an exhaust passage provided with a selective reduction catalyst (SCR catalyst), so that urea water is decomposed by the heat of exhaust gas and ammonia is generated. The generated ammonia reacts with NOx in the exhaust gas on the SCR catalyst, and NOx is reduced (purified) to nitrogen and water.

  That is, in the exhaust gas purification system using the urea SCR system, the urea water stored in the urea water tank is sent to the urea water injection valve through the urea water supply path, and the urea water is injected into the exhaust passage through the urea water injection valve. It is supposed to be configured. For this reason, when the engine is stopped (at the time of key-off), urea water remains from the urea water tank to the urea water supply path and the urea water injection valve.

  If urea water remains from the urea water supply path to the urea water injection valve, the urea water is thermally decomposed by the heat generated when the engine is started, and there is a possibility that a deposit derived from urea water may be generated. There is a problem that urea water remaining due to temperature deteriorates. In order to solve these problems, a technique has been proposed in which urea water is caused to flow backward from a urea water injection valve together with exhaust gas and recovered in a urea water tank when the engine is stopped (see Patent Document 1).

  By collecting the urea water in the reverse flow and collecting it in the urea water tank, even if the engine is stopped, the urea water does not remain on the urea water supply path and the urea water injection valve, and the generation of urea-derived deposits is suppressed. Is done.

  However, since exhaust gas components such as HC, NOx, and fine particles exist in the exhaust passage where the urea water injection valve faces, if the urea water is caused to flow backward, the exhaust gas components such as HC, NOx, and fine particles are urea. It will be collected in the water tank. For this reason, the urea water tank, the urea water supply path, and the urea water injection valve may be contaminated with exhaust gas components.

  It is conceivable that urea water is discharged into the exhaust passage using condensed water so that the urea water does not remain from the urea water supply path to the urea water injection valve. In this case, by using the condensed water in the intake system or the exhaust system of the engine as the condensed water, it is possible to use the condensed water that is reliably generated by the operation of the engine. However, at present, a technology for accurately collecting the condensed water in the intake system or exhaust system of the engine has not been established.

JP 2008-101564 A

  The present invention has been made in view of the above situation. In an exhaust purification system that supplies urea water for reducing nitrogen oxide (NOx) to an exhaust passage, the remaining urea water using condensed water is supplied to the exhaust passage. An object of the present invention is to provide an exhaust purification system capable of accurately collecting condensed water in an intake system or an exhaust system of an internal combustion engine when discharging.

  In order to achieve the above object, an exhaust purification system of the present invention according to claim 1 is directed to a urea water injection means for injecting urea water into exhaust gas in an exhaust passage facing an exhaust passage of an internal combustion engine, and urea water is stored. A urea water tank, a urea water supply line connecting the urea water injection means and the urea water tank, and an exhaust passage on the downstream side of a portion where the urea water injection means faces, and the urea water is supplied. A NOx purification catalyst that purifies NOx from the exhaust, a condensed water tank that stores condensed water containing exhaust components discharged from the internal combustion engine, and a condensed water recovery line that recovers the condensed water in the condensed water tank; , A condensed water supply line connecting the urea water supply line and the condensed water tank, an opening / closing means provided in the condensed water recovery line for opening and closing the condensed water recovery line, and a predetermined recovery condition is established. Characterized by comprising a control means for opening control of the switching means when the.

  In the exhaust purification system of the present invention according to claim 1, when urea water is supplied to the exhaust gas, the temperature is raised by the exhaust gas to generate ammonia, the ammonia is adsorbed by the NOx purification catalyst, and the ammonia is contained in the exhaust gas. It reacts with NOx and purifies NOx. The urea water remaining in the urea water supply line and the urea water injection means is discharged to the exhaust passage by the condensed water in the intake system or the exhaust system of the internal combustion engine including the exhaust component. For this reason, the urea water remaining in the urea water path (urea water supply line and urea water injection means) can be discharged to the exhaust path without causing the exhaust gas component in the exhaust path to flow.

  In the present invention according to claim 1, the condensate recovery line opening / closing means is opened when the condensate recovery condition is satisfied, and the condensed water is recovered in the condensed water tank. The condensed water can be recovered accurately.

  The exhaust purification system of the present invention according to claim 2 is the exhaust purification system according to claim 1, wherein the condensed water tank is provided with a condensed water amount detecting means for detecting a stored amount of condensed water, and the control The means closes the opening / closing means when the condensed water amount detecting means detects that a predetermined amount of the condensed water is stored.

  In this invention which concerns on Claim 2, the reverse flow of the condensed water from a condensed water tank to a collection | recovery line can be prevented by managing the storage amount of condensed water below predetermined. The predetermined amount may be set as appropriate. However, it is preferable to set the predetermined amount or more to an amount necessary for discharging all the urea water remaining in the urea water supply line when the engine is stopped.

  The exhaust purification system of the present invention according to claim 3 is the exhaust purification system according to claim 1 or 2, wherein the condensed water tank is provided with suction means, and the control means is the opening / closing means. The suction means is actuated when opening is controlled.

  In the present invention according to claim 3, since the suction means is operated when the opening / closing means is controlled to open, the condensed water can be more reliably collected in the condensed water tank.

The exhaust purification system of the present invention according to claim 4 provides:
The exhaust gas purification system according to any one of claims 1 to 3,
The condensed water recovery line connects the exhaust passage and the condensed water tank.

  In the present invention according to claim 4, the condensed water in the exhaust system can be recovered.

  The exhaust purification system of the present invention according to claim 5 is the exhaust purification system according to claim 4, wherein the recovery condition includes that the exhaust gas temperature is lower than a predetermined temperature.

  In the present invention according to claim 5, the condensed water is recovered when the exhaust gas temperature is lower than the predetermined temperature, that is, the dew point temperature, which is the temperature at which condensation starts, and the condensed water is surely present. For this reason, condensed water can be collected more reliably.

  The exhaust purification system of the present invention according to claim 6 is the exhaust purification system according to claim 4 or claim 5, wherein the fuel injection to the internal combustion engine is stopped under the recovery condition. It is included.

  In the present invention according to claim 6, when the fuel injection is stopped, that is, during the deceleration fuel cut or after the engine is stopped, the opening / closing means is controlled to open, so that polluted components such as HC and NOx in the exhaust gas are condensed water. Inflow into the tank can be suppressed.

  An exhaust gas purification system of the present invention according to claim 7 is the exhaust gas purification system according to any one of claims 1 to 3, wherein the turbine provided in the exhaust passage and driven by exhaust gas, A turbocharger provided in an intake passage of an internal combustion engine and driven by the turbine; and exhaust in the exhaust passage on the downstream side in the exhaust flow direction from the turbine. Low-pressure EGR means that recirculates to the intake passage, and an intercooler that is provided in the intake passage downstream of the compressor in the intake flow direction and cools the intake air, and the condensed water recovery line includes the intercooler or the The intake passage downstream of the intercooler in the intake flow direction is connected to the condensed water tank.

  In the present invention according to claim 7, the exhaust gas component is sent to the intake air by the low pressure EGR means, the exhaust gas component is contained in the intake air, the exhaust gas component is contained, and the condensed water generated in the intake passage downstream of the supercharging means ( It is possible to recover the condensed water generated in the intercooler or downstream of the intercooler (condensed water in the intake system). Further, the condensed water discharged from the intercooler flows into the cylinder, and adverse effects on the internal combustion engine such as misfire and water hammer can be suppressed.

  The exhaust purification system of the present invention according to claim 8 is the exhaust purification system according to claim 7, wherein the recovery condition includes that the load of the internal combustion engine is a predetermined value or less. And

  When collecting condensed water from the intake system, part of the intake air to be supplied to the internal combustion engine may be sent to the condensed water collection line together with the condensed water, which may deteriorate drivability (the occupant feels uncomfortable with the driving situation). There is. In particular, deterioration of drivability in a high-load operation state such as during acceleration is not preferable. In the present invention according to claim 8, it is possible to more appropriately collect condensed water from the intake system while suppressing deterioration of drivability due to collection of condensed water from the intake system.

  The exhaust purification system of the present invention is an exhaust purification system for supplying urea water for reducing nitrogen oxides (NOx) to an exhaust passage. When exhausting residual urea water using condensed water to an exhaust passage, It becomes possible to accurately collect the condensed water in the intake system or exhaust system of the engine.

It is a schematic block diagram showing the system | strain of the exhaust gas purification system which concerns on 1st Example of this invention. It is a flowchart of a condensed water collection | recovery process. It is a schematic block diagram showing the system | strain of the exhaust gas purification system which concerns on 2nd Example of this invention. It is a flowchart of a condensed water collection | recovery process.

  The exhaust purification system of the present embodiment is an exhaust purification system using a urea SCR (Selective Catalytic Reduction) system. That is, in order to reduce nitrogen oxide (NOx) contained in the exhaust gas, a NOx purification catalyst (selective reduction catalyst: SCR catalyst) is provided, and urea water is injected from the urea water injection valve into the exhaust passage. In this system, urea water is decomposed by the heat of exhaust gas to generate ammonia, and the generated ammonia reacts with NOx in the exhaust gas on the SCR catalyst, and NOx is reduced (purified) to nitrogen and water. .

  When the internal combustion engine (engine) is stopped, the urea water remaining in the urea water supply line (including the urea water injection valve) is discharged into the exhaust passage using the condensed water in the engine system. I am doing so. Thus, urea water does not remain in the urea water supply path and the urea water injection valve without causing exhaust gas components to flow into the exhaust passage, and deposits due to the urea water remaining can be suppressed.

  Further, since the condensed water contains acidic exhaust gas components such as NOx, the alkaline urea water is neutralized. By neutralizing the urea water, the urea water can be discharged as water, and no deposit or the like derived from the urea water (ammonia) is generated in the exhaust passage.

  In this embodiment, in the above-described exhaust purification system, the condensed water used for discharging the urea water remaining in the urea water supply line (including the urea water injection valve) to the exhaust passage is supplied from the engine system. It is trying to collect accurately.

  A first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a schematic configuration representing a system of an exhaust purification system according to a first embodiment of the present invention, and FIG. 2 shows a processing flow in the case of collecting condensed water.

  The exhaust purification system will be described with reference to FIG.

  As shown in the drawing, an exhaust purification device 3 is provided in an exhaust pipe 2 as an exhaust path of a multi-cylinder diesel engine (engine) 1 as an internal combustion engine mounted on a vehicle. A piston 5 is provided in the bore of the cylinder block 4 of the engine 1 so as to be able to reciprocate. A combustion chamber 7 is formed between the piston 5 and the cylinder head 6. The piston 5 is connected to the crankshaft 9 via a connecting rod 8, and the crankshaft 9 is driven by the reciprocating motion of the piston 5.

  An intake pipe 12 including an intake manifold 11 is connected to the cylinder head 6 via an intake port. The intake port is opened and closed by an intake valve. Further, an exhaust pipe (exhaust passage) 2 including an exhaust manifold 13 is connected to the cylinder head 6 through an exhaust port. The exhaust port is opened and closed by an exhaust valve.

  The cylinder head 6 is provided with an electronically controlled fuel injection valve 10 that directly injects fuel into the combustion chamber 7 of each cylinder. The fuel injection valve 10 is supplied with fuel from a common rail (not shown). In the common rail, the fuel is adjusted to a predetermined fuel pressure, and high pressure fuel controlled to the predetermined fuel pressure is supplied to the fuel injection valve 10.

  A turbocharger 15 is provided in the middle of the intake pipe 12 and the exhaust pipe 2 as a turbocharger. The turbocharger 15 is provided with a turbine on the exhaust pipe 2 side, and a compressor connected to the turbine is provided on the intake pipe 12 side. It has been. When the exhaust gas of the engine 1 is sent from the exhaust pipe 2 to the turbocharger 15, the turbine rotates by the flow of the exhaust gas, and the compressor rotates with the rotation of the turbine to supercharge the intake air in the intake pipe 12. .

  An intercooler 16 is disposed in the intake pipe 12 on the downstream side of the turbocharger 15, and the supercharged intake air is cooled by the intercooler 16 and sent to the combustion chamber 7. A throttle valve 17 for opening and closing the intake pipe 12 is provided in the intake pipe 12 on the downstream side of the intercooler 16. Although not shown, the intake pipe 12 on the downstream side of the throttle valve 17 is provided with an intake air temperature sensor for detecting the intake air temperature and an intake manifold pressure sensor for detecting the pressure in the intake manifold 11.

  One end of a high-pressure EGR pipe 31 is connected to the exhaust pipe 2 upstream of the turbocharger 15, and the other end of the high-pressure EGR pipe 31 communicates with the intake pipe 12 downstream of the throttle valve 17 (downstream of the turbocharger 15). doing. A high pressure EGR cooler 32 is provided in the high pressure EGR pipe 31, and a high pressure EGR valve 33 is provided in a connection portion of the high pressure EGR pipe 31 with the intake pipe 12.

  By opening the high pressure EGR valve 33, a part of the exhaust gas flowing through the exhaust pipe 2 upstream of the turbocharger 15 is introduced into the high pressure EGR pipe 31, and the exhaust gas introduced into the high pressure EGR pipe 31 is introduced into the high pressure EGR cooler 32. And is supplied to the intake pipe 12 on the downstream side of the turbocharger 15. By recirculating a part of the exhaust gas to the intake air, the combustion temperature in the combustion chamber 7 of the engine 1 can be lowered and the amount of NOx emission can be reduced.

The exhaust pipe 2 on the downstream side of the turbocharger 15 is provided with a purification device 23 having a diesel oxidation catalyst (oxidation catalyst) 21 and a diesel particulate collection filter 22 for exhaust purification. When exhaust gas flows into the oxidation catalyst 21, nitrogen monoxide (NO) in the exhaust gas is oxidized to generate nitrogen dioxide (NO ₂ ). Further, particulate matter (PM) in the exhaust gas is collected by the diesel particulate collection filter 22.

The PM collected by the diesel particulate filter 22 is oxidized (combusted) by NO ₂ in the exhaust gas and discharged as CO ₂ , and the NO ₂ remaining in the diesel particulate filter 22 is decomposed into N _2. Discharged. That is, in the purification device 23, the exhaust gas is purified and the exhaust amount of PM and NOx can be greatly reduced.

  A urea SCR (Selective Catalytic Reduction) system is provided as an exhaust gas purification device 3 on the downstream side of the purification device 23. That is, a selective reduction catalyst (SCR catalyst) 24 is provided as a NOx purification catalyst in the exhaust pipe 2 on the downstream side of the purification device 23, and urea as urea water injection means is provided in the exhaust pipe 2 on the upstream side of the SCR catalyst 24. A water injection valve 28 is provided.

  A urea water tank 27 for storing urea water injected from the urea water injection valve 28 is provided, and the urea water injection valve 28 is connected to the urea water tank 27 by a urea water supply line 25. A urea water pump 26 is provided in the urea water tank 27, and urea water is injected (supplied) from the urea water injection valve 28 into the exhaust pipe 2 by driving the urea water pump 26.

  The exhaust pipe 2 on the front side of the SCR catalyst 24 is provided with a mixer 29, and urea water injected from the urea water injection valve 28 is diffused by the mixer 29 and contacts the SCR catalyst 24 evenly.

  By urea water being injected into the exhaust pipe 2 from the urea water injection valve 28, the urea water is decomposed by the heat of the exhaust gas to generate ammonia, and the generated ammonia is contained in the exhaust gas on the SCR catalyst 24. It reacts with NOx, and NOx is reduced (purified) to nitrogen and water.

  The urea water remaining in the urea water supply line 25 (urea water injection valve 28) is discharged to the exhaust pipe 2 when condensed water in the system (exhaust system) of the engine 1 is supplied to the urea water supply line 25. Is done.

  That is, the exhaust manifold 13 as an exhaust system is provided with a condensed water outlet 13a, and one end of a condensed water recovery line 35 is connected to the condensed water outlet 13a. The other end of the condensed water recovery line 35 is connected to a condensed water tank 36. One end of a condensed water supply line 37 is connected to the condensed water tank 36, and the other end of the condensed water supply line 37 is connected to the urea water supply line 25 in the vicinity of the outlet of the urea water tank 27.

  The condensed water recovery line 35 is provided with an adjustment valve 41 as an opening / closing means, and the adjustment valve 41 is controlled to open when a condensed water recovery condition is satisfied. The condensed water tank 36 is provided with a suction pump 42 as a suction means, and the inside of the condensed water tank 36 is made negative pressure by the suction pump 42.

  The condensed water tank 36 is provided with a level sensor 43 as a condensed water amount detecting means. The condensed water tank 36 is provided with an oil separator 45, and the condensed water from which the oil has been separated is sent to the condensed water supply line 37. A flow rate adjusting valve 44 that adjusts the flow rate of the condensed water and prevents a reverse flow from the urea water supply line 25 side is provided in the vicinity of the connection portion of the condensed water supply line 37 with the urea water supply line 25.

  Instead of the flow rate adjustment valve 44, a check valve that allows only the flow of condensed water to the urea water supply line 25 side may be provided.

  The condensed water tank 36 is located at a position lower than the condensed water outlet 13a of the exhaust manifold 13 and is connected to the urea water pump 26 (the other end of the condensed water supply line 37 to the urea water supply line 25) of the urea water tank 27. ) Mounted higher. By defining the mounting position (height) of the condensed water tank 36, the condensed water can be reliably sent to the urea water supply line 25.

  Further, the connection portion of the other end of the condensed water supply line 37 to the urea water supply line 25 is set in the vicinity of the outlet portion of the urea water tank 27 (near the outlet of the urea water pump 26). The urea water remaining in the entire area can be discharged to the exhaust pipe 2. Further, since the condensed water outlet 13a of the exhaust manifold 13 is on the upstream side of the urea water injection valve 28, urea water is not mixed into the condensed water to be recovered.

  Condensed water generated in the exhaust manifold 13 and containing exhaust gas components is sent to the condensed water recovery line 35 from the condensed water outlet 13a by opening the regulating valve 41 when the condensed water recovery condition is satisfied. And stored in the condensed water tank 36. And after conditions, such as the stop state of the engine 1, are satisfied, the flow regulating valve 44 is controlled to be opened and sent to the urea water supply line 25.

  For this reason, when the engine 1 is stopped, the urea water remaining from the urea water supply line 25 to the urea water injection valve 28 is pushed out to the exhaust pipe 2 by the condensed water from the exhaust manifold 13 of the engine 1 and discharged. .

  Since the condensed water tank 36 is provided to temporarily accumulate the condensed water, the condensed water can be immediately sent from the condensed water supply line 37 to the urea water supply line 25 when the engine 1 is stopped.

  By supplying condensed water to the urea water supply line 25 and discharging the urea water to the exhaust pipe 2, exhaust gas components inside the exhaust pipe 2 are transferred to the urea water injection valve 28, the urea water supply line 25, and the urea water tank 27. Without flowing in, urea water does not remain from the urea water supply line 25 to the urea water injection valve 28, and the occurrence of deposits due to the urea water remaining can be suppressed.

  The vehicle is provided with an electronic control unit (ECU) 40 as a control means, and the ECU 40 is provided with an input / output device, a storage device for storing a control program, a control map, and the like, a central processing unit, timers and counters. Yes. Information from sensors is input to the ECU 40, and comprehensive control of the engine 1 including the exhaust purification device 3 and the high pressure EGR means is performed by the ECU based on the information of the sensors.

  In the engine 1 having the above-described exhaust purification system, urea water is sent to the urea water injection valve 28 by driving the urea water pump 26, and urea water is injected into the exhaust pipe 2 from the urea water injection valve 28. Water is decomposed by the heat of the exhaust gas to produce ammonia. The produced ammonia reacts with NOx in the exhaust gas on the SCR catalyst 24, and NOx is reduced (purified) to nitrogen and water.

  When the engine 1 is stopped, the urea water remaining from the urea water supply line 25 to the urea water injection valve 28 is pushed out by the condensed water from the exhaust manifold 13 of the engine 1 and discharged. . As a result, the urea water does not remain in the urea water supply line 25 and the urea water injection valve 28 without causing the exhaust gas component in the exhaust path to flow (without returning the urea water to the urea water tank 27). Moreover, generation | occurrence | production of the deposit by urea water remaining can be suppressed.

  Since the condensed water contains an acidic exhaust gas component such as NOx, the urea water is neutralized and discharged as water when discharging the alkaline urea water. No deposit or the like derived from is generated.

  In the exhaust purification system described above, the regulating valve 41 is controlled to open when the condensate recovery condition is satisfied. That is, the exhaust gas temperature information is input to the ECU 40 and the information of the level sensor 43 is input to the ECU 40 in order to determine whether the recovery condition is satisfied. The ECU 40 outputs an opening / closing command to the adjustment valve 41 and a driving command to the suction pump 42.

  For example, when the exhaust gas temperature is lower than a predetermined temperature (the dew point temperature at which condensation starts) and the condensed water is reliably present, the suction pump 42 is driven and the regulating valve 41 is controlled to be opened to condense. Condensed water is collected in the water tank 36. Further, when the level sensor 43 detects that a predetermined amount of condensed water is stored, the regulating valve 41 is controlled to be closed, thereby preventing a predetermined amount or more of condensed water from being collected.

  For this reason, while being able to collect | recover condensed water reliably to the condensed water tank 36, the condensed water more than predetermined amount is not collect | recovered.

  One end of the condensed water recovery line 35 is connected to the exhaust pipe 2 on the upstream side of the portion where the urea water injection valve 28 is provided downstream of the purification device 23, and the condensed water in the exhaust pipe 2 downstream of the purification device 23. It is also possible to adopt a configuration for collecting the.

  In the present embodiment, the collection condition when collecting condensed water is set when the exhaust gas temperature is lower than a predetermined temperature, the condensed water generation condition is satisfied, and the fuel injection is stopped. .

  That is, since the exhaust gas temperature is high during the start of the engine 1, the percentage of water vapor in the exhaust gas is high. For example, when the fuel is cut during idling or deceleration, or after key-off, the dew point temperature is the temperature at which condensation starts. The exhaust gas temperature becomes lower than that. When the exhaust gas temperature is lowered, the water vapor contained in the exhaust gas is condensed in the exhaust manifold 13 to become condensed water, so that the condensed water exists reliably (condensed water generation conditions are established).

  For this reason, the conditions are set so that the condensed water is recovered when the exhaust gas temperature is lower than the predetermined temperature, which is a situation where the condensed water exists reliably. Even when the exhaust gas temperature is low, when the fuel is injected, since the pollutant component is contained in the exhaust gas, the recovery of the condensed water is stopped.

  The flow of processing for collecting condensed water will be described with reference to FIG.

  In step S1, the level sensor 43 is read, and in step S2, it is determined whether the condensed water is less than a predetermined amount. That is, it is determined whether or not the condensed water has accumulated a predetermined amount or more. If it is determined in step S2 that the condensed water satisfies the predetermined amount, that is, if it is determined that the condensed water is equal to or larger than the predetermined amount, the process ends because the condensed water is not required to be collected.

  If it is determined in step S2 that the condensed water is less than the predetermined amount, the temperature of the exhaust gas is read in step S3, and it is determined whether or not the condensate recovery condition is satisfied in step S4. That is, it is determined whether or not the fuel injection valve is stopped and the exhaust gas temperature is lower than a predetermined temperature (for example, dew point temperature).

  If it is determined in step S4 that the condensate recovery condition is satisfied, that is, if it is determined that the fuel injection valve is stopped and the condensed water is present, step S5 is performed. Then, the suction pump 42 is driven to make the inside of the condensed water tank 36 have a negative pressure. After the inside of the condensed water tank 36 is set to a negative pressure, the control valve 41 is controlled to be in an open state in step S6, the condensed water recovery line 35 is opened, and the condensed water is recovered in the condensed water tank 36.

  That is, when the condensate recovery condition is satisfied, the regulating valve 41 is opened with the inside of the condensate tank 36 at a negative pressure, and the condensate is recovered in the condensate tank 36 with improved recoverability. .

  If it is determined in step S4 that the condensate recovery condition is not satisfied, that is, if it is determined that fuel injection is being performed or that the condensate does not exist reliably, processing is performed. End.

  After the condensed water is collected in the condensed water tank 36, the detection information of the level sensor 43 is read in step S7, and it is determined whether or not the condensed water has accumulated a predetermined amount or more in step S8. The predetermined amount of the condensed water is preferably set to a minimum amount capable of discharging all of the urea water remaining in the urea water supply line 25, that is, the volume of the urea water supply line 25 or more. In this embodiment, the predetermined amount is set as a value larger than the minimum amount and smaller than the maximum capacity of the condensed water tank.

  When it is determined in step S8 that the condensed water is not accumulated more than the predetermined amount, the process proceeds to step S3, and the condensed water collecting process is repeated until the condensed water is accumulated more than the predetermined amount.

  If it is determined in step S8 that the condensed water has accumulated a predetermined amount or more, the control valve 41 is controlled to be closed in step S9, the condensed water recovery line 35 is closed, and the condensed water recovery is terminated. In step S10, the suction pump 42 is stopped and the process is terminated.

  In other words, when the condensed water is accumulated more than a predetermined amount, the collection of the condensed water is finished, and even if the condensed water collecting condition is satisfied, the condensed water is not collected more than the predetermined amount.

  The exhaust purification system described above makes it possible to accurately collect the condensed water in the exhaust manifold 13 of the engine 1 when the remaining urea water is discharged to the exhaust path using the condensed water.

  A second embodiment of the present invention will be described with reference to FIG.

  FIG. 3 shows a schematic configuration representing a system of an exhaust purification system according to the second embodiment of the present invention, and FIG. 4 shows a processing flow in the case of collecting condensed water. In addition, the same code | symbol is attached | subjected to the same component as the exhaust gas purification system of 1st Example shown in FIG. 1, and the overlapping description is abbreviate | omitted.

  The exhaust gas purification system of the second embodiment includes low pressure EGR means for returning exhaust gas taken from the downstream of the turbine of the turbocharger 15 (downstream of the purification device 23) to the front side of the compressor, and is supercharged cooled by the intercooler 16 It is configured to collect the condensed water in the intake air.

  As shown in the drawing, one end of a low-pressure EGR pipe 51 is connected to the exhaust pipe 2 downstream of the purification device 23 and upstream of the SCR catalyst 24 (downstream of the turbocharger 15), and the other end of the low-pressure EGR pipe 51. Is in communication with the intake pipe 12 upstream of the turbocharger 15. The low pressure EGR pipe 51 is provided with a low pressure EGR cooler 52, and a low pressure EGR valve 53 is provided in the vicinity of the connection portion of the low pressure EGR pipe 51 with the exhaust pipe 2.

  By opening the low pressure EGR valve 53, a part of the exhaust gas flowing through the exhaust pipe 2 on the downstream side of the turbocharger 15 is introduced into the low pressure EGR pipe 51, and the exhaust gas introduced into the low pressure EGR pipe 51 is the low pressure EGR cooler 52. And is supplied to the intake pipe 12 upstream of the turbocharger 15. That is, the exhaust gas containing the exhaust component is mixed with the intake air of the intake pipe 12.

  By recirculating a part of the exhaust gas to the intake air by the low pressure EGR means, the combustion temperature in the combustion chamber 7 of the engine 1 can be lowered, and the amount of NOx emission can be reduced. Even in the operation state where the turbocharger 15 needs to be supercharged sufficiently (the operation state where it is necessary to secure the air amount), the low-pressure EGR means can be used to reduce the NOx emission amount.

  The intake pipe 12 downstream of the intercooler 16 is provided with a condensed water outlet 12a, and one end of a condensed water recovery line 35 is connected to the condensed water outlet 13a. The other end of the condensed water recovery line 35 is connected to a condensed water tank 36. One end of a condensed water supply line 37 is connected to the condensed water tank 36, and the other end of the condensed water supply line 37 is connected to the urea water supply line 25 in the vicinity of the outlet of the urea water tank 27.

  The condensed water outlet 12a may be provided in the intercooler 16. In this case, the position of the condensed water outlet 12a is preferably provided near the intake outlet at the bottom of the intercooler 16.

  The condensed water recovery line 35 is provided with an adjustment valve 41 as an opening / closing means, and the adjustment valve 41 is controlled to open when a condensed water recovery condition is satisfied. The condensed water tank 36 is provided with a suction pump 42 as a suction means, and the inside of the condensed water tank 36 is made negative pressure by the suction pump 42.

  The condensed water tank 36 is provided with a level sensor 43 as a condensed water amount detecting means. The condensed water tank 36 is provided with an oil separator 45, and the condensed water from which the oil has been separated is sent to the condensed water supply line 37. A flow rate adjusting valve 44 that adjusts the flow rate of the condensed water and prevents a reverse flow from the urea water supply line 25 side is provided in the vicinity of the connection portion of the condensed water supply line 37 with the urea water supply line 25.

  Condensate water generated in the intake pipe 12 inside the intercooler 16 or downstream of the intercooler 16 and containing exhaust gas components is controlled to open the regulating valve 41 when the condensate recovery condition is satisfied. Thus, the condensed water is sent from the condensed water outlet 12 a to the condensed water recovery line 35 and stored in the condensed water tank 36. And after conditions, such as the stop state of the engine 1, are satisfied, the flow regulating valve 44 is controlled to be opened and sent to the urea water supply line 25.

  For this reason, when the engine 1 stops, the urea water remaining from the urea water supply line 25 to the urea water injection valve 28 is pushed out to the exhaust pipe 2 by the condensed water from the intake pipe 12 downstream of the intercooler 16. Discharged.

  In the condensed water supply means described above, the exhaust gas containing a large amount of moisture is sent to the intake pipe 12 by the low pressure EGR means, pressurized by the compressor of the turbocharger 15, passes through the intercooler 16, and exhaust gas components in the exhaust gas The water containing is recovered as condensed water. Since condensed water is not sent to the combustion chamber 7 as it is, it is possible to suppress torque fluctuation, misfire, and generation of water hammer.

  In the exhaust purification system described above, the regulating valve 41 is controlled to open when the condensate recovery condition is satisfied. That is, in order to determine whether the recovery condition is satisfied, the operation information of the throttle valve 17 and the information of the level sensor 43 are input to the ECU 40. The ECU 40 outputs an opening / closing command to the adjustment valve 41 and a driving command to the suction pump 42.

  For example, when the load (output torque) of the engine 1 is less than a predetermined value, that is, when the operating state of the engine 1 is not a high load operating state such as acceleration, the suction pump 42 is driven and the adjustment valve 41 is opened. Controlled, the condensed water is recovered in the condensed water tank 36.

  When the level sensor 43 detects that a predetermined amount of condensed water is stored, the regulating valve 41 is controlled to be closed so as to prevent a predetermined amount or more of condensed water from being collected.

  For this reason, when there is little possibility that the occupant feels uncomfortable in the driving situation, the condensed water can be collected in the condensed water tank 36, and a predetermined amount or more of condensed water is not collected.

  In the present embodiment, the recovery condition when recovering the condensed water is set when the load of the engine 1 is a predetermined value or less (when the intake air amount is a predetermined value or less).

  That is, when the operation state of the engine 1 is a high load operation state such as acceleration, if the intake pipe 12 and the condensed water recovery line 35 are brought into communication (when the adjustment valve 41 is opened), the intake air necessary for the engine 1 is increased. There is a possibility that drivability is deteriorated by being sent to the condensed water recovery line 35 together with the condensed water. For this reason, when the load of the engine 1 is equal to or less than a predetermined value, the condensed water recovery condition is satisfied, and the condensed water is sent from the intake passage to the condensed water recovery line.

  The flow of processing for collecting condensed water will be described with reference to FIG.

  In step S11, detection information of the level sensor 43 is read. In step S12, it is determined whether or not the condensed water is less than a predetermined amount. That is, it is determined whether or not the condensed water has accumulated a predetermined amount or more. When it is determined in step S12 that the condensed water satisfies the predetermined amount, that is, when it is determined that the condensed water is equal to or larger than the predetermined amount, the process is terminated because the condensed water is not required to be collected.

  The predetermined amount of condensed water is set in the same manner as in the first embodiment.

  If it is determined in step S12 that the condensed water is less than the predetermined amount, the load on the engine 1 is calculated based on the intake air amount in step S13, and whether or not the load on the engine 1 is equal to or less than the predetermined value in step S14. Is judged. That is, it is determined whether the operating state of the engine 1 is not a high-load operating state such as during acceleration.

  If it is determined in step S14 that the load of the engine 1 is equal to or less than the predetermined value, it is determined that the collection condition is satisfied. If it is determined in step S14 that the load of the engine 1 is equal to or less than the predetermined value, the suction pump 42 is driven in step S15 to make the inside of the condensed water tank 36 have a negative pressure. After the inside of the condensed water tank 36 is set to a negative pressure, in step S16, the regulating valve 41 is controlled to be in an open state, the condensed water recovery line 35 is opened, and the condensed water is recovered in the condensed water tank 36.

  That is, when the condensed water stored in the condensed water tank 36 is less than a predetermined amount and the recovery condition is satisfied, the adjustment valve 41 is opened with the inside of the condensed water tank 36 at a negative pressure, The condensed water is collected in the condensed water tank 36 in a state where the recoverability is improved.

  If it is determined in step S14 that the load on the engine 1 exceeds the predetermined value, the recovery condition is not satisfied, and the process ends without collecting the condensed water.

  After the condensed water is collected in the condensed water tank 36, the detection information of the level sensor 43 is read in step S17, and it is determined whether or not the condensed water is accumulated in a predetermined amount or more in step S18. If it is determined in step S18 that the condensed water has not accumulated more than a predetermined amount, the process proceeds to step S13, and it is determined whether or not the recovery condition is satisfied. As long as the recovery conditions are satisfied, the condensed water recovery process is repeated until a predetermined amount or more of condensed water accumulates.

  If it is determined in step S18 that condensate has accumulated a predetermined amount or more, the control valve 41 is controlled to be closed in step S19, the condensate recovery line 35 is closed, and the condensate recovery is terminated, in step S20. The suction pump 42 is stopped and the process is terminated.

  That is, when the condensed water is accumulated more than a predetermined amount, the collection of the condensed water is finished, and even if the collection condition is satisfied, the collection of the condensed water more than the predetermined amount is not performed.

  When the remaining urea water is discharged to the exhaust path using the condensed water by the exhaust purification system described above, the condensed water in the intake pipe 12 downstream of the intercooler 16 is not given to the occupant. Can be collected accurately.

  In the second embodiment described above, the recovery condition is that the load of the engine 1 is equal to or less than a predetermined value. However, a value correlated with the intake air amount (the value of the throttle valve 17 or the valve lift amount) is used as the recovery condition. It may be used. Further, the recovery condition may be that the accelerator opening, that is, the driver's required output is not more than a predetermined value. In either case, the same effects as in the second embodiment can be obtained.

  The present invention can be used in the industrial field of exhaust purification systems that reduce nitrogen oxides (NOx) in exhaust gases of internal combustion engines.

1 Multi-cylinder diesel engine (engine)
2 Exhaust pipe 3 Exhaust gas purification device 4 Cylinder block 5 Piston 6 Cylinder head 7 Combustion chamber 8 Connecting rod 9 Crankshaft 10 Fuel injection valve 11 Intake manifold 12 Intake pipe 13 Exhaust manifold 15 Turbocharger 16 Intercooler 17 Throttle valve 21 Diesel oxidation catalyst ( Oxidation catalyst)
22 Diesel particulate filter 23 Purification device 24 Selective reduction catalyst (SCR catalyst)
25 Urea water supply line 26 Urea water pump 27 Urea water tank 28 Urea water injection valve 29 Mixer 31 High pressure EGR pipe 32 High pressure EGR cooler 33 High pressure EGR valve 35 Condensed water recovery line 36 Condensed water tank 37 Condensed water supply line 40 Electronic control unit (ECU)
41 Adjustment valve 42 Suction pump 43 Level sensor 44 Flow rate adjustment valve 45 Oil separator 51 Low pressure EGR pipe 52 Low pressure EGR cooler 53 Low pressure EGR valve

Claims (8)

Urea water injection means for injecting urea water into the exhaust in the exhaust passage facing the exhaust passage of the internal combustion engine;
A urea water tank in which urea water is stored;
A urea water supply line connecting the urea water injection means and the urea water tank;
A NOx purification catalyst that is provided in an exhaust passage on the downstream side of a portion where the urea water injection means faces, and purifies NOx from the exhaust gas supplied with the urea water;
A condensed water tank in which condensed water containing exhaust components discharged from the internal combustion engine is stored;
A condensed water recovery line for recovering the condensed water in the condensed water tank;
A condensed water supply line connecting the urea water supply line and the condensed water tank;
An opening / closing means provided in the condensed water recovery line, for opening and closing the condensed water recovery line;
An exhaust purification system comprising: control means for controlling the opening and closing means to open when a predetermined recovery condition is satisfied. The exhaust purification system according to claim 1,
The condensed water tank is provided with a condensed water amount detecting means for detecting the amount of condensed water stored,
The control means includes
The exhaust gas purification system characterized in that when the condensed water amount detecting means detects that a predetermined amount of the condensed water is stored, the opening / closing means is closed. The exhaust gas purification system according to claim 1 or 2,
The condensed water tank is provided with suction means,
The control means includes
The exhaust purification system, wherein the suction means is operated when the opening / closing means is controlled to be opened. The exhaust gas purification system according to any one of claims 1 to 3,
The exhaust purification system, wherein the condensed water recovery line connects the exhaust passage and the condensed water tank. The exhaust purification system according to claim 4,
The recovery condition includes that the exhaust gas temperature is lower than a predetermined temperature. The exhaust gas purification system according to claim 4 or 5,
The recovery condition includes that fuel injection to the internal combustion engine is stopped. The exhaust gas purification system according to any one of claims 1 to 3,
A turbocharger comprising a turbine provided in the exhaust passage and driven by exhaust; and a compressor provided in an intake passage of the internal combustion engine and driven by the turbine;
Low pressure EGR means for recirculating exhaust gas in the exhaust passage downstream of the turbine in the exhaust flow direction to the intake passage upstream of the compressor in the intake flow direction;
An intercooler that is provided in the intake passage downstream of the compressor in the intake flow direction and cools the intake air,
The exhaust purification system, wherein the condensed water recovery line connects the intercooler or the intake passage downstream of the intercooler in the intake flow direction and the condensed water tank. The exhaust purification system according to claim 7,
The recovery conditions include
It is included that the load of the said internal combustion engine is below a predetermined value. The exhaust gas purification system characterized by the above-mentioned.

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