JP2016217228A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device which can stably and additionally supply a reductant for an exhaust state while having constitution in which two tanks of a main tank for storing the reductant and a sub-tank are arranged.SOLUTION: An exhaust emission control device comprises two tanks of a main tank in which a reductant is stored, and a sub-tank which is smaller than the main tank in a capacity, and used as an auxiliary tank. The exhaust emission control device reduces a nitrogen oxide in exhaust gas by adding the reductant thereto via an addition valve which is arranged in an exhaust passage of an internal combustion engine, and cleans the exhaust gas. The main tank is connected to the addition valve, and the addition valve can supply the reductant in the sub-tank to the main tank under a prescribed condition. When a temperature T1 of the reductant in the main tank, which is acquired by a first urea water temperature sensor is higher than a required determination temperature α1, an electronic control unit which controls supply of the reductant to the main tank from the sub-tank starts the supply of the reductant to the main tank from the sub-tank.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an exhaust purification device that purifies exhaust by reducing nitrogen oxides in exhaust by selective catalytic reduction.

  2. Description of the Related Art An exhaust emission control device is known that includes a catalyst that purifies nitrogen oxide (NOx) in exhaust gas using urea water that is a reducing agent added to the exhaust gas. In such an exhaust purification device, an addition valve (injection valve) for adding urea water is provided in the exhaust passage, and the urea water added (injected) from the addition valve is hydrolyzed by the heat of the exhaust gas and converted into ammonia. . This ammonia is adsorbed by a catalyst prepared for NOx purification, and NOx in the exhaust gas is reduced and purified by the ammonia adsorbed on the catalyst.

  On the other hand, an exhaust emission control device including a main tank for storing urea water and a sub tank to which urea water is supplied from the main tank and having the sub tank connected to an addition valve is also known (see, for example, Patent Document 1). ). In such an exhaust purification device, urea cannot be added when the urea water in the sub tank connected to the addition valve freezes. Therefore, the sub tank connected to the addition valve is disposed in the vicinity of the internal combustion engine. The thawing of urea water is promoted by the exhaust heat of the engine.

JP2013-2285A

  By the way, the main tank of the exhaust gas purification apparatus including the two tanks as described above has a larger capacity than the sub tank, and is often installed under the floor of the vehicle, which is a place where an installation space is easily secured. The underfloor of the vehicle is also a place where the temperature of the urea water is likely to rise due to heat propagated from a heat source such as an internal combustion engine or an exhaust pipe to the main tank. For this reason, it cannot be denied that the temperature of the urea water in the main tank rises excessively and it becomes difficult to stably supply the urea water through the addition valve.

In addition, even if the selective catalyst reduction system uses a reducing agent other than urea, such an actual situation as an exhaust purification device having two tanks is generally common.
The present invention has been made in view of the above circumstances, and an object of the present invention is to stably provide a reducing agent for exhaust purification while adopting a configuration including two tanks, a main tank and a sub tank for storing the reducing agent. An object of the present invention is to provide an exhaust emission control device that can be additionally supplied.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
An exhaust emission control device that solves the above problems includes two tanks, a main tank that stores a reducing agent, and a sub tank that has a smaller capacity than the main tank and is used as an auxiliary tank, and is provided in an exhaust passage of an internal combustion engine. An exhaust gas purification device that purifies exhaust gas by reducing nitrogen oxides in exhaust gas by adding the reducing agent through an addition valve, wherein the main tank is connected to the addition valve, and the sub tank The reducing agent is configured to be able to be supplied to the main tank under a predetermined condition, and a temperature acquisition unit that acquires the temperature of the reducing agent in the main tank, and the supply of the reducing agent from the sub tank to the main tank A control unit that controls the control unit, and when the temperature of the reducing agent in the main tank acquired by the temperature acquisition unit is higher than a predetermined temperature, the control unit And as its gist to start the supply of the reducing agent to said main tank from Butanku.

  In general, since the main tank has a larger capacity than the sub tank, it is often installed under the floor of a vehicle, which is a place where an installation space is easily secured. However, as described above, the under floor of the vehicle is also a place where the temperature of the reducing agent is likely to rise due to heat propagated from a heat source such as an internal combustion engine or an exhaust pipe. On the other hand, since the sub tank has a smaller capacity than the main tank, there is a high possibility that it will be installed in an empty space in the vehicle. Usually, heat from a heat source such as an internal combustion engine or an exhaust pipe is not easily propagated in the vehicle, so that the temperature of the reducing agent in the tank is hardly increased. In this regard, according to the above configuration, in such an installation environment of the main tank and the sub tank, even if the temperature of the reducing agent in the main tank may increase, the reducing agent in the sub tank is unlikely to increase in temperature. By supplying the agent to the main tank, the temperature of the reducing agent stored in the main tank is lowered, and the temperature increase of the reducing agent in the main tank can be suppressed. Thereby, the stable addition supply of a reducing agent can be maintained.

1 is a schematic diagram showing a configuration of an intake / exhaust system of an internal combustion engine to which an embodiment of an exhaust purification device is applied. The figure which shows the temperature characteristic of the reducing agent used for the exhaust gas purification apparatus of the embodiment. The flowchart which shows the cooling process of the reducing agent with respect to the main tank of the exhaust gas purification apparatus of the embodiment.

Hereinafter, an embodiment of an exhaust emission control device will be described with reference to FIGS. This exhaust purification device is provided in a diesel engine.
As shown in FIG. 1, an air cleaner 11, an air flow meter 12, a compressor 13, an intercooler 14, an I / C outlet gas temperature sensor 15, a throttle valve 16, an intake pressure are provided in the intake passage 10 of the diesel engine in order from the upstream side. A sensor 27 is provided. The air cleaner 11 filters impurities in the intake air. The air flow meter 12 detects the flow rate of intake air (intake air amount) flowing through the intake passage 10. The compressor 13 pressurizes intake air according to driving. The intercooler 14 cools the intake air after passing through the compressor 13. The I / C outlet gas temperature sensor 15 detects the temperature of the intake air after passing through the intercooler 14. The throttle valve 16 adjusts the intake air amount according to the change in the opening. The intake pressure sensor 27 detects the pressure of the intake air in the portion of the intake passage 10 on the downstream side of the throttle valve 16.

  The intake passage 10 is connected to each cylinder 17 of the diesel engine on the downstream side of the throttle valve 16. Each cylinder 17 of the diesel engine is provided with an injector 18 for injecting fuel. In each cylinder 17, a mixture of the intake air introduced through the intake passage 10 and the fuel injected from the injector 18 is combusted.

  Exhaust gas generated by combustion in each cylinder 17 is discharged to the outside air through the exhaust passage 19. A turbine 20 is installed in the exhaust passage 19. The turbine 20 constitutes an exhaust turbine supercharger together with the compressor 13 provided in the intake passage 10, and rotates by the flow of exhaust flowing through the exhaust passage 19 to drive the compressor 13. A variable nozzle 21 is provided in the exhaust passage 19 upstream of the turbine 20 so that the opening area of the exhaust outlet for the turbine 20 is variable. The opening of the variable nozzle 21 controls the opening of the turbine 20. The rotation speed is adjusted.

  Furthermore, the diesel engine is provided with an EGR (Exhaust Gas Recirculation) device that recirculates a part of the exhaust gas into the intake air. The EGR device is recirculated into the intake air through the EGR passage 22 that connects the upstream portion of the turbine 20 in the exhaust passage 19 and the downstream portion of the throttle valve 16 in the intake passage 10, and the EGR passage 22. An EGR cooler 23 that cools the exhaust gas (EGR gas) and an EGR valve 24 that adjusts the flow rate of the EGR gas are provided. The EGR device also includes a bypass passage 25 for bypassing the EGR cooler 23 and flowing EGR gas, and a bypass valve 26 for adjusting the flow rate of the EGR gas bypassing the EGR cooler 23 through the bypass passage 25. .

  Then, the structure of the exhaust gas purification apparatus applied to the diesel engine comprised as mentioned above is demonstrated. The exhaust emission control system is a DPF (Diesel Particulate Filter: Diesel Particulate Filter) system that collects PM (Particulate Matter) in exhaust gas, and NOx in exhaust gas by selective reduction using urea water as a reducing agent. And a urea SCR (Selective Catalytic Reduction) system to be purified.

  The DPF system includes a fuel addition valve 30, a pre-stage oxidation catalyst device 31, and a PM collection filter 32. The fuel addition valve 30 is installed in the upstream portion of the turbine 20 in the exhaust passage 19. Further, the front-stage oxidation catalyst device 31 is installed in the upstream side of the PM collection filter 32 on the downstream side of the turbine 20 in the exhaust passage 19. The fuel addition valve 30 adds fuel into the exhaust. The PM collection filter 32 captures PM in the exhaust. The front-stage oxidation catalyst device 31 oxidizes PM SOF (Soluable Organic Fraction) component and oxidizes nitrogen monoxide (NO) in the exhaust gas, which is necessary for continuous regeneration of the PM collection filter 32. Nitrogen dioxide (NO2) is produced. Further, when the PM collection filter 32 is forcibly regenerated, the pre-stage oxidation catalyst device 31 oxidizes hydrocarbons (HC) in the fuel added from the fuel addition valve 30 and raises the exhaust temperature by heat generated by the oxidation reaction. By doing so, it also plays a role of raising the temperature of the PM collection filter 32 to a temperature necessary for PM combustion.

  Further, the DPF system includes the following sensors for detecting the state of exhaust in each part of the system. An inlet gas temperature sensor 33 that detects the temperature of the exhaust gas flowing into the upstream oxidation catalyst device 31 is installed upstream of the upstream oxidation catalyst device 31 in the exhaust passage 19. An intermediate gas temperature sensor 34 that detects the temperature of the exhaust gas flowing into the PM collection filter 32 is installed in a portion of the exhaust passage 19 between the upstream oxidation catalyst device 31 and the PM collection filter 32. Further, an exhaust gas temperature sensor 35 that detects the temperature of the exhaust gas flowing out from the PM collection filter 32 is installed downstream of the PM collection filter 32 in the exhaust passage 19. In addition, a differential pressure sensor 36 that detects the pressure difference between the exhaust gas before and after the PM collection filter 32 is also installed in the installation portion of the PM collection filter 32 in the exhaust passage 19.

  On the other hand, the urea SCR system includes a urea addition valve 40, two front and rear SCR devices, that is, a front-stage SCR device 41 and a rear-stage SCR device 42, and an ASC (Ammonia Slip Catalyst) device 43. The urea addition valve 40 is installed in a portion of the exhaust passage 19 on the downstream side of the PM collection filter 32, and adds urea water, which is an aqueous solution of an ammonia precursor, to the exhaust gas. The front-stage SCR device 41 and the rear-stage SCR device 42 are selective reduction catalyst devices that reduce nitrogen oxides in exhaust gas using ammonia generated from urea by hydrolysis by exhaust heat as a reducing agent. The front-stage SCR device 41 is installed in the downstream portion of the urea addition valve 40 in the exhaust passage 19, and the rear-stage SCR device 42 is installed in a further downstream portion of the front-stage SCR device 41 in the exhaust passage 19. The ASC device 43 is an oxidation catalyst device that oxidizes the ammonia that has flowed through the front-stage SCR device 41 and the rear-stage SCR device 42, and is installed in a downstream portion of the rear-stage SCR device 42 in the exhaust passage 19. Incidentally, a dispersion plate 44 for diffusing urea water added by the urea addition valve 40 into the exhaust gas is installed in a portion of the exhaust passage 19 between the urea addition valve 40 and the pre-stage SCR device 41.

  The urea water added to the exhaust gas by the urea addition valve 40 is stored in the two urea water tanks 45 and 61. The urea water tank 45 is a main tank of the two urea water tanks, and is connected to the urea addition valve 40 through a pipe 46 with a heater. A feed pump 47 is installed in the urea water tank 45. The feed pump 47 pumps the urea water in the urea water tank 45 and sends the urea water to the urea addition valve 40 through the pipe 46. The urea water tank 45 is provided with a urea water level sensor 48 for detecting the remaining amount of urea water therein. The urea water tank 45 is provided with a first urea water temperature sensor 49 that detects the temperature of the urea water inside the urea water tank 45. The first urea water temperature sensor 49 corresponds to a temperature acquisition unit.

  As described above, this exhaust purification apparatus includes the urea water tank 45 as a main tank and the sub tank 61 having a smaller capacity than the urea water tank 45. The sub tank 61 stores the same urea water as the urea water tank 45 and is connected to the urea water tank 45. The sub tank 61 is an emergency tank when the urea water tank 45 cannot be used. The sub tank 61 is provided with a second urea water temperature sensor 62 that detects the temperature of the urea water therein. A feed pump 63 is installed in the sub tank 61. The feed pump 63 pumps up urea water in the sub tank 61 and sends the urea water to the urea water tank 45 through the pipe 64.

  Here, since the urea water tank 45 is a large-capacity tank used as a main tank, an installation space is required. Here, the urea water tank 45 is installed under the floor of a vehicle on which the diesel engine is mounted. Since the urea water tank 45 installed under the floor receives heat from a heat source such as a diesel engine or the exhaust passage 19, the temperature of the urea water stored in the urea water tank 45 may rise. And when the temperature rise of such urea water becomes excessive, the stable supply of urea water through the urea addition valve 40 may become difficult.

  On the other hand, since the sub tank 61 has a small capacity compared to the main tank, it is installed in a space in the vehicle, such as a trunk room, a fender, a rear seat, a spare tire storage space, and the like. Since the sub tank 61 installed in the vehicle is far from the heat source such as the diesel engine and the exhaust passage 19, the possibility that the temperature of the urea water stored in the sub tank 61 rises is low.

  In view of this, the exhaust gas purification apparatus according to the present embodiment has the urea in the sub tank 61 when the temperature of the urea water stored in the urea water tank 45 has risen and the temperature of the urea water stored in the sub tank 61 has not increased. Water is supplied to the urea water tank 45 to perform a cooling process that promotes cooling of the urea water in the urea water tank 45.

  Further, the urea SCR system includes the following sensors for detecting the state of exhaust in each part of the system. An input NOx sensor 50, an air-fuel ratio sensor 51, and an exhaust pressure sensor 52 are installed in the exhaust passage 19 between the PM collection filter 32 and the urea addition valve 40. The inflow NOx sensor 50 detects the flow rate of NOx in the exhaust gas flowing into the upstream SCR device 41 (hereinafter referred to as the inflowing NOx amount FrNOx). The air-fuel ratio sensor 51 generates an output corresponding to the difference in oxygen partial pressure between the exhaust gas and a reference gas (for example, the atmosphere), and the output is used to grasp the air-fuel ratio of the air-fuel mixture burned in the cylinder 17. It is done. Further, the exhaust pressure sensor 52 detects the pressure of the exhaust gas in the exhaust passage 19 at the installation portion. On the other hand, an exhaust NOx sensor 53, a post-ASC gas temperature sensor 54, and a PM sensor 55 are installed in the downstream portion of the ASC device 43 in the exhaust passage 19. The outgoing NOx sensor 53 detects the flow rate of NOx in the exhaust gas flowing out from the ASC device 43 (hereinafter referred to as the outflow NOx amount RrNOx). The post-ASC gas temperature sensor 54 detects the temperature of the exhaust gas flowing out from the ASC device 43 (hereinafter referred to as post-ASC gas temperature Tasc). Furthermore, the PM sensor 55 detects the amount of PM that flows out of the ASC device 43 and is released to the outside air.

  In such an exhaust purification device, the fuel addition by the fuel addition valve 30, the urea water addition by the urea addition valve 40, and the urea water supply from the sub tank 61 to the urea water tank 45 by the feed pump 63 are controlled by the electronic control unit 56. Has been. The electronic control unit 56 temporarily stores a central processing unit that performs arithmetic processing for control, a read-only memory in which control programs and data are stored, arithmetic results of the central processing unit and detection results of each sensor. A readable / writable memory for storing, an input port for receiving an external signal, and an output port for transmitting the signal to the outside are provided. Each sensor described above is connected to the input port of the electronic control unit 56. Further, the fuel addition valve 30, the urea addition valve 40 and the feed pump 63 are connected to the output port of the electronic control unit 56. The electronic control unit 56 controls the amount of fuel and ammonia added to the exhaust by drive control of the fuel addition valve 30 and the urea addition valve 40, and controls the temperature of urea water by drive control of the feed pump 63. Yes. In such an exhaust purification device, the electronic control unit 56 corresponds to a control unit.

Next, with reference to FIG.2 and FIG.3, the urea water cooling process of the urea water tank 45 which is a main tank is demonstrated concretely.
As shown in FIG. 2, the request determination temperature α <b> 1 is a limit value at which the urea addition valve 40 can perform stable supply of urea water by the urea water in the urea water tank 45. That is, the urea water in the urea water tank 45 needs to be cooled when the demand determination temperature α1 is exceeded. The cooling determination temperature α2 is a temperature for determining whether or not the urea water in the urea water tank 45 has been cooled. The cooling determination temperature α2 is a temperature lower than the request determination temperature α1 (α2 <α1). The supply determination temperature β is a temperature for determining whether or not the urea water in the urea water tank 45 can be cooled by supplying urea water from the sub tank 61 to the urea water tank 45. The supply determination temperature β is a temperature lower than the request determination temperature α1 (β <α1). Therefore, these determination temperatures α1, α2, and β are set as α1>α2> β.

  As shown in FIG. 3, the electronic control unit 56 checks whether or not the temperature of the urea water in the urea water tank 45 has risen during the operation of the diesel engine. If the temperature has risen, the electronic control unit 56 performs cooling. The cooling process to be performed is executed.

  First, the electronic control unit 56 acquires detection values from various sensors (step S1). That is, the electronic control unit 56 acquires the first urea water temperature T1 from the first urea water temperature sensor 49 provided in the urea water tank 45. Further, the electronic control unit 56 acquires the second urea water temperature T2 from the second urea water temperature sensor 62 provided in the sub tank 61. Further, the electronic control unit 56 acquires the urea water remaining amount V from the urea water level sensor 48.

  Subsequently, the electronic control unit 56 determines whether or not the urea water remaining amount V in the urea water tank 45 is smaller than the maximum value Vmax of the urea water remaining amount in the urea water tank 45 (step S2). That is, the electronic control unit 56 cannot supply urea water from the sub tank 61 when the urea water remaining amount maximum value Vmax of the urea water tank 45 has already been reached (V = Vmax), and is supplied from the sub tank 61. It is determined whether or not urea water can be stored. As a result, when the electronic control unit 56 determines that the urea water remaining amount V in the urea water tank 45 is not less than the maximum value Vmax of the urea water remaining amount in the urea water tank 45 (V ≧ Vmax) (step S2). : NO), the process proceeds to step S1.

  On the other hand, when the electronic control unit 56 determines that the urea water remaining amount V in the urea water tank 45 is smaller than the maximum value Vmax of the urea water remaining amount in the urea water tank 45 (V <Vmax) (step S2: YES), it is determined whether or not the first urea water temperature T1 is higher than the request determination temperature α1 (step S3). That is, the electronic control unit 56 determines that the temperature of the urea water in the urea water tank 45 is higher than the request determination temperature α1 at which the urea addition valve 40 can obtain a cooling effect. As a result, when the electronic control unit 56 determines that the first urea water temperature T1 is equal to or lower than the required determination temperature α1 (T1 ≦ α1) (step S3: NO), the electronic control unit 56 proceeds to step S1.

  On the other hand, when the electronic control unit 56 determines that the first urea water temperature T1 is higher than the request determination temperature α1 (T1> α1) (step S3: YES), the second urea water temperature T2 is the supply determination temperature. It is determined whether it is lower than β (step S4). That is, the electronic control unit 56 determines whether the urea water in the urea water tank 45 can be cooled to a temperature at which a cooling effect can be obtained by the urea water in the sub tank 61. As a result, when the electronic control unit 56 determines that the second urea water temperature T2 is equal to or higher than the supply determination temperature β (T2 ≧ β) (step S4: NO), the electronic control unit 56 proceeds to step S1.

  On the other hand, when it is determined that the second urea water temperature T2 is lower than the supply determination temperature β (T2 <β) (step S4: YES), the electronic control unit 56 turns on the second pump operation flag F2. (Step S5). That is, the electronic control unit 56 determines that the urea water in the urea water tank 45 can be cooled by the urea water in the sub tank 61. At this time, the electronic control unit 56 operates the feed pump 63 of the sub tank 61 to supply the urea water from the sub tank 61 to the urea water tank 45 to promote cooling. Thus, the urea water in the sub tank 61 is supplied into the urea water tank 45, so that the temperature of the urea water in the urea water tank 45 decreases.

  Subsequently, the electronic control unit 56 determines whether or not the first urea water temperature T1 is lower than the cooling determination temperature α2 (step S6). That is, the electronic control unit 56 determines whether or not the temperature of the urea water in the urea water tank 45 has dropped below the cooling determination temperature α2 at which a cooling effect is obtained. As a result, when the electronic control unit 56 determines that the first urea water temperature T1 is lower than the cooling determination temperature α2 (T1 <α2) (step S6: YES), the electronic control unit 56 turns off the second pump operation flag F2. (Step S7). That is, the electronic control unit 56 determines that the temperature of the urea water in the urea water tank 45 has decreased below the cooling determination temperature α2, and it is not necessary to supply the urea water from the sub tank 61 to the urea water tank 45. Then, the operation of the feed pump 63 of the sub tank 61 is stopped, and the processing is ended.

  On the other hand, when the electronic control unit 56 determines that the first urea water temperature T1 is equal to or higher than the cooling determination temperature α2 (T1 ≧ α2) (step S6: NO), the urea water remaining amount V in the urea water tank 45 is determined. Is greater than or equal to the maximum value Vmax of the remaining amount of urea water in the urea water tank 45 (step S8). That is, the electronic control unit 56 cannot store the urea water supplied from the sub tank 61 because the urea water cannot be supplied from the sub tank 61 when the urea water remaining amount maximum value Vmax of the urea water tank 45 has already been reached. It is determined whether or not it can be performed. As a result, when the electronic control unit 56 determines that the urea water remaining amount V in the urea water tank 45 is smaller than the maximum value Vmax of the urea water remaining amount in the urea water tank 45 (V <Vmax) (step S8). : NO), the replenishment warning flag F3 is turned on (step S9). That is, urea water is supplied from the sub tank 61 to the urea water tank 45, but the urea water remaining amount in the urea water tank 45 does not reach the maximum value Vmax, so the urea water remaining amount V in the urea water tank 45 is abnormally reduced. The user is informed of a urea water replenishment warning for prompting replenishment. The notification of urea water replenishment warning is displayed on, for example, an instrument panel.

  On the other hand, when the electronic control unit 56 determines that the urea water remaining amount V in the urea water tank 45 is not less than the maximum value Vmax of the urea water remaining amount in the urea water tank 45 (V ≧ Vmax) (step S8: YES), the second pump operation flag F2 is turned off (step S7). That is, the electronic control unit 56 determines that the urea water in the urea water tank 45 has reached the maximum value Vmax of the urea water remaining amount due to the urea water being supplied from the sub tank 61 and cannot store the urea water. Then, the operation of the feed pump 63 of the sub tank 61 is stopped, and the process ends.

  As described above, the exhaust gas purification apparatus of the present embodiment includes the sub tank 61 in addition to the urea water tank 45 that is the main tank, and when the temperature of the urea water in the urea water tank 45 rises above the required determination temperature α1. The urea water is supplied from the sub tank 61 to the urea water tank 45. As a result, the temperature of the urea water in the urea water tank 45 is lowered, and the temperature increase of the urea water is suppressed. And it becomes possible to maintain the stable supply of urea water, and to ensure NOx purification performance by the urea SCR system.

As described above, according to this embodiment, the following effects can be obtained.
(1) Even if the temperature of the urea water in the urea water tank 45 installed under the floor of the vehicle rises, the urea water in the sub tank 61 that does not easily rise in temperature is supplied to the urea water tank 45. The temperature rise of the urea water stored in the urea water tank 45 is suppressed. Thereby, the stable addition supply of urea water can be maintained.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
In the above embodiment, the first urea water temperature sensor 49 directly detects the temperature of the urea water, but the temperature of the urea water tank 45 is measured to estimate the temperature of the urea water stored in the tank. Thus, the temperature value may be acquired.

  In the above embodiment, the determination process of whether or not the second urea water temperature T2 in step S4 shown in FIG. 3 is lower than the supply determination temperature β may be omitted. That is, since the temperature of the urea water in the sub tank 61 is likely to be lower than the temperature of the urea water in the urea water tank 45, urea is transferred from the sub tank 61 to the urea water tank 45 regardless of the temperature of the urea water in the sub tank 61. Water may be supplied.

  The exhaust purification device of the above embodiment has a DPF system in addition to the urea SCR system, but the urea water addition amount control in the above embodiment has a urea SCR system and does not have a DPF system. The present invention can be similarly applied to an exhaust purification device.

  An aqueous solution other than urea water may be used as the aqueous solution of the ammonia precursor added to the exhaust gas, that is, as the reducing agent.

  DESCRIPTION OF SYMBOLS 10 ... Intake passage, 11 ... Air cleaner, 12 ... Air flow meter, 13 ... Compressor, 14 ... Intercooler, 15 ... I / C outgas temperature sensor, 16 ... Throttle valve, 17 ... Cylinder, 18 ... Injector, 19 ... Exhaust passage , 20 ... Turbine, 21 ... Variable nozzle, 22 ... EGR passage, 23 ... EGR cooler, 24 ... EGR valve, 25 ... Bypass passage, 26 ... Bypass valve, 27 ... Intake pressure sensor, 30 ... Fuel addition valve, 31 ... Previous stage Oxidation catalyst device, 32 ... PM collection filter, 33 ... Inlet gas temperature sensor, 34 ... Medium gas temperature sensor, 35 ... Outlet gas temperature sensor, 36 ... Differential pressure sensor, 40 ... Urea addition valve, 41 ... Pre-stage SCR device, 42 ... latter stage SCR device, 43 ... ASC device, 44 ... dispersion plate, 45 ... urea water tank (main tank) , 46 ... piping, 47 ... feed pump, 48 ... urea water level sensor, 49 ... first urea water temperature sensor (temperature acquisition unit), 50 ... input NOx sensor, 51 ... air-fuel ratio sensor, 52 ... exhaust pressure sensor, 53 ... exit NOx sensor, 54 ... gas temperature sensor after ASC, 55 ... PM sensor, 56 ... electronic control unit (control unit), 60 ... filling pressure sensor, 61 ... sub tank (urea water tank), 62 ... second urea water temperature Sensor, 63 ... feed pump, 64 ... pipe.

Claims (1)

The reducing agent is provided via an addition valve provided in an exhaust passage of an internal combustion engine, which includes two tanks, a main tank in which the reducing agent is stored and a sub-tank having a smaller capacity than the main tank and used as an auxiliary tank. An exhaust gas purification device that purifies exhaust gas by reducing nitrogen oxides in the exhaust gas by adding
The main tank is connected to the addition valve, and the reducing agent of the sub tank is configured to be supplied to the main tank under a predetermined condition.
A temperature acquisition unit that acquires the temperature of the reducing agent in the main tank; and a control unit that controls supply of the reducing agent from the sub tank to the main tank,
The control unit starts supplying the reducing agent from the sub-tank to the main tank when the temperature of the reducing agent in the main tank acquired by the temperature acquisition unit is higher than a predetermined temperature. Purification equipment.

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