JP2011080397A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device effectively cooling a reducing agent adding valve regardless of the operating condition of an internal combustion engine or the travelling condition of a vehicle and preventing damage to the reducing agent adding valve caused by heat. <P>SOLUTION: This exhaust emission control device for the internal combustion engine purifies exhaust emissions from the internal combustion engine by the use of an exhaust emission control catalyst and a reducing agent. The device is equipped with: the exhaust emission control catalyst disposed in the exhaust passage of the internal combustion engine; a reducing agent tank storing the reducing agent; the reducing agent adding valve adding the reducing agent to the exhaust passage upstream of the exhaust emission control catalyst; a reducing agent pump pumping up the reducing agent from the reducing agent tank and forcibly feeding the pumped up reducing agent to the reducing agent adding valve; and a cooling system for cooling the reducing agent adding valve. The cooling system is provided with: a cooling means by a liquid refrigerant; and a radiation fin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust purification device, and more particularly to an exhaust purification device for an internal combustion engine that purifies NOx (nitrogen oxide) discharged from the internal combustion engine using a reducing agent and an exhaust purification catalyst.

  Conventionally, exhaust gas of an internal combustion engine mounted on an automobile or the like contains NOx (nitrogen oxide), PM (particulate matter), and the like. An SCR catalyst (NOx selective reduction catalyst), which is a kind of exhaust purification catalyst, is disposed in the exhaust passage of the internal combustion engine as one of the exhaust purification devices for the internal combustion engine for purifying NOx, and the upstream side of the SCR catalyst. There is a urea SCR system that purifies NOx by adding urea water (urea aqueous solution) as a reducing agent. There is also an NSC system in which an NSC catalyst (NOx occlusion reduction catalyst) is disposed in the exhaust passage and NOx is purified using fuel as a reducing agent.

  Further, as an exhaust purification device for purifying PM, there is an exhaust purification device in which a diesel particulate filter provided with an oxidation catalyst is disposed in an exhaust passage of an internal combustion engine. In this exhaust purification device, after PM is once captured by a diesel particulate filter, fuel is added to the oxidation catalyst, and the PM is burned and purified by oxidation heat generated in the oxidation catalyst. In addition, there is a type in which an oxidation catalyst is disposed in an exhaust passage upstream of a diesel particulate filter, and oxidation heat generated by the oxidation catalyst is used to purify PM captured by the diesel particulate filter. Even in this case, fuel is added to the oxidation catalyst.

  In each exhaust gas purification apparatus as described above, a reducing agent addition valve for adding a reducing agent such as urea water or fuel includes members such as an electromagnetic solenoid, a resin cover, and a nozzle plate. Since these members have lower heat resistance than other components, if a reducing agent addition valve is installed in the exhaust passage, there is a risk that the member is excessively heated by high-temperature exhaust gas and damaged.

  In addition, when the reducing agent addition valve is heated, a part of the reducing agent is crystallized or deposited around the reducing agent addition valve, and the spray formation of the reducing agent is hindered or uneven. There is a risk of Further, when the temperature of the reducing agent addition valve becomes high, a part of the reducing agent is vaporized, and there is a concern that accurate reducing agent spray formation is hindered. As a result, the desired exhaust purification performance may not be achieved.

  In view of this, a cooling means is provided to circulate the coolant by providing a cooling passage inside the jacket for placing the reducing agent addition valve (injection valve), and the heat of the reducing agent addition valve is provided through the jacket. Suppressing the heating by arranging the technology to cool by moving to the coolant (see Patent Document 1) and the reducing agent addition valve (reducing agent supply nozzle) at the position where the running wind of the vehicle is guided around it The technique (refer patent document 2) etc. to do are proposed.

JP 2009-174486 A (Full text, all figures) Japanese Patent Laid-Open No. 2003-083056 (full text, full diagram)

  In the above-described technology, the reducing agent addition valve is cooled by circulating the coolant through the cooling passage inside the jacket. However, the cooling is performed under the restriction of the operating state of the internal combustion engine and the remaining capacity of the on-vehicle battery. There is a possibility that the liquid is not sufficiently circulated and the reducing agent addition valve cannot be cooled sufficiently. In addition, the reducing agent addition valve is arranged at a position where the traveling wind of the vehicle is guided to suppress heating, but in addition to restricting the arrangement of the reducing agent addition valve, the vehicle is stopped, etc. There is a possibility that the effect is not sufficiently obtained.

  According to the present invention, in the exhaust gas purification apparatus as described above, the reducing agent addition valve can be effectively cooled regardless of the operating state of the internal combustion engine and the traveling state of the vehicle, and damage to the reducing agent addition valve due to heat is prevented. It is an object of the present invention to provide an exhaust emission control device that can perform such a process.

  According to the present invention, there is provided an exhaust purification device for an internal combustion engine that purifies exhaust gas of the internal combustion engine using an exhaust purification catalyst and a reducing agent, the exhaust purification catalyst disposed in an exhaust passage of the internal combustion engine, A reducing agent tank for storing the reducing agent; a reducing agent addition valve for adding the reducing agent to an exhaust passage upstream of the exhaust purification catalyst; and pumping the reducing agent from the reducing agent tank to the reducing agent addition valve An exhaust emission control device comprising a reducing agent pump for pumping and a cooling device for cooling the reducing agent addition valve, wherein the cooling device is provided with a cooling means by liquid refrigerant, and also has a radiation fin. An exhaust gas purification device for an internal combustion engine is provided to solve the above-described problem (claim 1).

  Further, in configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, the cooling device is attached to the exhaust passage below or on the side in the direction of gravity, and the heat dissipation is performed on the side opposite to the side facing the exhaust passage. It is preferable that fins are arranged (claim 2).

  Further, when configuring the exhaust gas purification device for an internal combustion engine of the present invention, the cooling device is configured to include at least a water jett shaped so as to cover the nozzle portion of the reducing agent addition valve, Preferably, the radiating fin is formed or attached (Claim 3).

  In configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, it is preferable that the liquid refrigerant is cooling water for cooling the internal combustion engine.

  According to the exhaust emission control device of the first aspect of the present invention, when the internal combustion engine is stopped and the cooling means using the liquid refrigerant hardly functions, or when the vehicle is stopped and the reducing agent addition valve is Even in the case where the cooling effect by forced cooling cannot be obtained without hitting the traveling wind, natural cooling is promoted by the radiation fins and the reducing agent addition valve is prevented from being damaged by heat.

  According to the exhaust purification device of the second aspect of the present invention, since the air around the radiation fins is reduced by the heat radiation from the exhaust passage, the heat radiation from the radiation fins is not hindered and is efficient. The reducing agent addition valve can be cooled. Further, it is possible to avoid the exhaust passage from being cooled by the influence of the heat radiation fin during the operation of the internal combustion engine, and to avoid the crystallization and deposit of the reducing agent in the exhaust passage.

  According to the exhaust emission control device of the third aspect of the present invention, the reducing agent addition valve can be efficiently cooled by forming or attaching the radiation fins to the water jet.

  In addition, according to the exhaust emission control device of the invention of claim 4, the reducing agent addition valve can be cooled with almost no additional equipment only for cooling the reducing agent addition valve.

It is a figure for demonstrating the structural example of the exhaust gas purification apparatus in embodiment. It is a figure for demonstrating the cooling device in embodiment. It is the figure which looked at the cooling device in embodiment from the X direction in FIG.

  Hereinafter, an embodiment for carrying out an exhaust emission control device according to the present invention will be described with reference to the drawings. In the drawings, the same reference numerals denote the same members, and the description thereof is omitted as appropriate. In addition, the state of embodiment shows one form of this invention, This invention is not limited, It can change arbitrarily in the scope of the present invention.

1. Exhaust gas purification device The exhaust gas purification device 10 is a device that purifies NOx in exhaust gas discharged from an internal combustion engine 5 such as a diesel engine mounted on a vehicle, and uses the SCR catalyst 13 and urea water to produce NOx. It is constructed as a urea SCR system that purifies water. An example of the overall configuration of the exhaust emission control device 10 is shown in FIG.

  The exhaust purification device 10 is constructed from various sensors and an SCR catalyst 13, a reducing agent addition device 20, a cooling device 30, a control device 40, and the like arranged in the exhaust system of the internal combustion engine 5. Various sensors, the reducing agent addition device 20, the control device 40, and the like are connected to a CAN (Controller Area Network) 44 so that information existing on the CAN 44 can be acquired and information can be output on the CAN 44. ing. The CAN 44 can communicate with a device for controlling the operating state of the internal combustion engine 5 (not shown; hereinafter referred to as “ECU: Engine Control Unit”), and the fuel injection amount and the injection. Information relating to the operating state of the internal combustion engine 5 such as timing and engine speed can be read.

  The internal combustion engine exhaust system is configured such that an exhaust passage 12 is connected to the internal combustion engine 5 and an SCR catalyst 13 is disposed in the exhaust passage 12. A reducing agent addition valve 21 for adding urea water as a reducing agent into the exhaust passage 12 is provided between the internal combustion engine 5 and the SCR catalyst 13.

  Further, a temperature sensor 41 is provided on the upstream side of the SCR catalyst 13, and a NOx sensor 42 is provided on the downstream side. These sensors detect temperature information and NOx concentration information inside the exhaust passage 12, and transmit them to the control device 40, the CAN 44, the ECU, or the like. Although a detailed description of the ECU is omitted here, a control device for a general internal combustion engine used in an automobile or the like may be used.

  The SCR catalyst 13 is made harmless by reducing NOx in the exhaust gas to N2 (nitrogen) or the like by contacting NOx in the exhaust gas together with ammonia (NH3) generated by the urea water added in the exhaust passage 12 NOx selective reduction catalyst to be used can be used as appropriate.

2. Reducing agent addition device The reducing agent addition device 20 is a device for adding and supplying urea water as a reducing agent stored in the reducing agent tank 27 to the SCR catalyst 13 via the reducing agent addition valve 21 and the like. A configuration example of the reducing agent addition apparatus 20 is shown in FIG. The reducing agent addition device 20 includes a reducing agent addition valve 21, a reducing agent pump 25, a reducing agent tank 27, an overflow valve 23, a cooling device 30, a control device 40, a pressure sensor 43, and the like.

  The reducing agent addition valve 21 has substantially the same configuration as an existing fuel injection valve (injector). Since a known configuration can be adopted as appropriate, the configuration will be briefly described here. The reducing agent addition valve 21 is configured as an electromagnetic on-off valve including a drive unit including an electromagnetic solenoid and a valve body unit having a needle for opening and closing the tip addition hole. The valve is opened or closed based on the signal. That is, when the electromagnetic solenoid is energized based on the drive signal, the needle moves in the valve opening direction along with the energization, and the tip addition hole is opened by the needle movement, and urea water is added.

  The reducing agent addition valve 21 is provided with an electromagnetic solenoid, a resin cover, a nozzle plate, and the like. However, these are less susceptible to heat than other components, and the heat-resistant temperature thereof is, for example, an electromagnetic solenoid or a nozzle plate. The temperature is about 160 ° C. and the resin cover is about 120 ° C. Therefore, the cooling device 30 is provided in the exhaust purification device 10 of the present embodiment.

  Next, the configuration of a reducing agent supply system for supplying urea water to the reducing agent addition valve 21 will be described. Urea water as a reducing agent is sequentially supplied from the reducing agent tank 27 to the reducing agent addition valve 21. The reducing agent tank 27 stores urea water having a predetermined concentration.

  A reducing agent pump 25 is connected to the reducing agent tank 27 via a reducing agent feeding passage 26. One end of a reducing agent supply passage 22 is connected to the reducing agent pump 25, and the other end of the reducing agent supply pipe 22 is connected to a reducing agent addition valve 21. The reducing agent pump 25 is an electric pump that is rotationally driven by a drive signal from the control device 40, and its output depends on the value of the pressure sensor 43 so that the pressure of the urea water in the reducing agent supply passage becomes a predetermined value. Feedback controlled.

  When the reducing agent pump 25 is driven to rotate with the start of the reducing agent addition device 20, urea water is pumped from the reducing agent tank 27 and supplied to the reducing agent addition valve 21 through the reducing agent supply passage 22. One end of a reducing agent discharge passage 24 is connected to the reducing agent supply passage 22 via an overflow valve 23, and the other end of the reducing agent discharge passage 24 is connected to a reducing agent tank 27. Thereby, when the pressure of the urea water in the reducing agent supply passage 22 increases excessively, a part of the urea water in the reducing agent supply passage 22 is returned to the reducing agent tank 27 through the overflow valve 23. It is.

  As described above, in the reducing agent addition device 20, during operation of the internal combustion engine 5, urea water in the reducing agent tank 27 is supplied to the reducing agent addition valve 21 through the reducing agent supply passage 22 by driving the reducing agent pump 25. Urea water is added into the exhaust passage 12 by the reducing agent addition valve 21. Then, urea water is hydrolyzed in the exhaust passage 12 to generate NH3, and is supplied to the SCR catalyst 13 together with the exhaust gas. In the SCR catalyst 13, a NOx reduction reaction is performed to purify the exhaust gas.

  Each actuator in the reducing agent supply device 20 is controlled by the control device 40. The control device 40 includes a known microcomputer (not shown), a storage device (not shown), and the like, and operates the reducing agent addition device 20 and the like in a desired manner based on detection values of various sensors. Thus, various controls relating to exhaust purification are performed. Specifically, an appropriate amount of urea water is added into the exhaust passage 12 at an appropriate time by controlling the energizing time of the reducing agent addition valve 21 and the driving amount and driving period of the reducing agent pump 25. Note that the control of the reducing agent addition device 20 and the like by the control device 40 can be appropriately performed by the ECU as a function of the ECU.

3. Cooling device The cooling device 30 is a device that uses part of the cooling water of the internal combustion engine 5 and cools the reducing agent addition valve 21 by the radiation fins 34. A configuration example of the cooling device is shown in FIGS. 2 is a side view of the cooling device, and FIG. 3 is a view of the cooling device as viewed from the X direction in FIG. The cooling device includes a water jacket 31, heat radiating fins 34, a flow rate adjusting valve 6, a cooling water supply passage 7, a cooling water circulation passage 8, and the like.

  The water jacket 31 is formed in a shape that covers the nozzle portion of the reducing agent addition valve 21, and the reducing agent addition valve 21 can be inserted into the center thereof. The water jacket 31 is provided with a refrigerant inlet 32 and a refrigerant outlet 33, and a refrigerant passage (not shown) for supplying and circulating the refrigerant liquid therein is formed. The refrigerant introduction port 32 and the refrigerant discharge port 33 are communicated with each other through a refrigerant passage. Relatively heat-sensitive members such as an electromagnetic solenoid, a resin cover, and a nozzle portion of the reducing agent addition valve 21 inserted in the water jacket 31 are cooled by the liquid refrigerant that has flowed through the refrigerant passage.

  The refrigerant inlet 32 and the refrigerant outlet 33 formed in the water jacket 31 are connected to the cooling water supply passage 7 and the cooling water circulation passage 8 respectively, and a part of the cooling water of the internal combustion engine 5 is connected to the cooling device 30 and the internal combustion engine. It is possible to circulate between 5 and 5. The cooling water is circulated by a circulation means provided in the internal combustion engine 5, for example, a pump (not shown) driven by the driving force of the internal combustion engine 5. In addition, an electric pump can be separately arranged in the middle of the cooling water supply passage 7 and the cooling water circulation passage 8 to circulate the cooling water. By separately arranging the electric pump, the reducing agent addition valve 21 can be cooled by circulating the coolant without depending on the operating state of the internal combustion engine 5 as much as possible.

  A flow rate adjustment valve 6 is installed in the cooling water supply passage 7, and the flow rate of the cooling water supplied to the cooling device depends on the operating state of the internal combustion engine 5, the temperature condition of the reducing agent addition valve 21, and the like. It is controlled appropriately. The control of the flow rate adjusting valve 6 and the electric pump can be performed by the control device 40 or the ECU.

  The heat radiating fins 34 are integrally formed or directly attached to the water jet 31. By directly attaching the radiating fins 34 to the water jet 31, it is possible to effectively cool the nozzle portion that is particularly exposed to high temperature in the addition valve injection valve 21. Further, the radiating fins 34 are arranged on the opposite side of the water jett 31 with the reducing agent addition valve 21 in between. When the cooling device 30 is attached to the exhaust passage 12, the radiating fins 34 and the exhaust passages are arranged. 12 and the cooling water supply passage 7 and the like are prevented from interfering with each other.

  As described above, the cooling device 30 for cooling the reducing agent addition valve 21 includes the cooling means using the liquid refrigerant, and includes the radiation fins 34, so that the internal combustion engine 5 is stopped and the cooling means using the liquid refrigerant is provided. Even in a case where the vehicle does not function substantially or a case where the vehicle is stopped and the reducing agent addition valve 21 does not hit the traveling wind and the cooling effect by forced cooling cannot be obtained, the radiating fin 27 Since natural cooling is promoted by this, it is possible to prevent the reducing agent addition valve 21 from being damaged by heat.

  The cooling device 30 is attached to the exhaust passage 12 via the exhaust passage attachment portion 37. As shown in FIG. 1, the reducing agent addition valve 21 and the cooling device 30 are attached to the exhaust passage 12 below or to the side of the gravity direction, and the radiating fins 34 are disposed on the opposite side of the exhaust passage 12. Since the installation reduces the air around the radiation fins 34 due to the heat radiation from the exhaust passage 12, the reducing agent addition valve 21 is efficiently prevented without inhibiting the heat radiation from the radiation fins 34. Can be cooled. In addition, the exhaust passage 12 is prevented from being cooled by the influence of the radiating fins 34 during the operation of the internal combustion engine 5, and crystallization and depositing of the reducing agent in the exhaust passage 12 can be avoided.

5: Internal combustion engine, 6: Flow rate adjusting valve, 7: Cooling water supply passage, 8: Cooling water circulation passage, 10: Exhaust purification device, 12: Exhaust passage, 13: SCR catalyst, 20: Reducing agent addition device, 21: Reduction Agent addition valve, 22: reducing agent supply passage, 23: overflow valve, 24: reducing agent discharge passage, 25: reducing agent pump, 26: reducing agent feeding passage, 27: reducing agent tank, 30: cooling device, 31: Water jacket, 32: Refrigerant introduction port, 33: Refrigerant discharge port, 34: Radiation fin, 35: Exhaust passage mounting bolt hole, 36: Reductant introduction passage, 37: Exhaust passage attachment portion, 40: Control device, 41: Temperature Sensor, 42: NOx sensor, 43: Pressure sensor, 44: CAN

Claims (4)

An exhaust purification device for an internal combustion engine that purifies exhaust gas of an internal combustion engine using an exhaust purification catalyst and a reducing agent, the exhaust purification catalyst disposed in an exhaust passage of the internal combustion engine, and a reduction that stores the reducing agent A reducing agent addition valve for adding the reducing agent to an exhaust passage upstream of the exhaust purification catalyst, a reducing agent pump for pumping the reducing agent from the reducing agent tank and pumping the reducing agent to the reducing agent addition valve; In the exhaust emission control device comprising a cooling device for cooling the reducing agent addition valve,
An exhaust gas purification apparatus for an internal combustion engine, characterized in that the cooling device includes a cooling means using liquid refrigerant and a heat radiating fin.   The said cooling device is attached to the gravity direction lower side or the side of the said exhaust passage, The said radiation fin is arrange | positioned on the opposite side to the side which faces the said exhaust passage. Exhaust gas purification device for internal combustion engine.   The cooling device is configured to include at least a water jacket formed in a shape covering a nozzle portion of the reducing agent addition valve, and the heat radiation fin is formed or attached to the water jacket. Item 3. An exhaust emission control device for an internal combustion engine according to Item 1 or 2.   4. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the liquid refrigerant is cooling water for cooling the internal combustion engine.

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