JP4181808B2 - Exhaust purification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust emission control device.
[0002]
[Prior art]
Conventionally, exhaust purification has been performed with an exhaust purification catalyst installed in the middle of an exhaust pipe. As this type of exhaust purification catalyst, when the exhaust air-fuel ratio is lean, NOx in the exhaust gas is oxidized and temporarily stored in the form of nitrate, and when the oxygen concentration in the exhaust gas decreases, unburned HC or There is known an NOx occlusion reduction catalyst having the property of decomposing and releasing NOx through CO or the like for reduction and purification.
[0003]
In this NOx occlusion reduction catalyst, when the occlusion amount of NOx increases and reaches the saturation amount, no more NOx can be occluded. Therefore, the oxygen concentration of the exhaust gas that periodically flows into the NOx occlusion reduction catalyst is reduced. It is necessary to reduce and release NOx by decomposition. For example, when used in a gasoline engine, the operating air-fuel ratio of the engine is reduced (the engine is operated at a rich air-fuel ratio), thereby reducing the oxygen concentration in the exhaust gas and unburned HC in the exhaust gas. Reduction components such as CO can be increased to promote decomposition and release of NOx.
[0004]
However, when the NOx storage reduction catalyst is used as an exhaust gas purification device for a diesel engine, it is difficult to operate the engine at a rich air-fuel ratio. For this reason, by adding fuel to the exhaust gas upstream of the NOx storage reduction catalyst, the added fuel is thermally decomposed in high-temperature exhaust gas to produce a large amount of hydrocarbon, and this hydrocarbon is reduced. It is necessary to reduce the oxygen concentration in the exhaust gas by reacting with oxygen on the NOx storage reduction catalyst as an agent.
[0005]
On the other hand, as a measure to reduce particulate matter (particulate matter) emitted from diesel engines, an exhaust purification catalyst such as an oxidation catalyst supported on a particulate filter or a flow-through oxidation catalyst is placed in the middle of the exhaust pipe. Has already been equipped. By using such an oxidation catalyst, it is possible to promote the oxidation reaction of the particulates collected in the particulate filter and the particulates in the exhaust gas, and to reduce the particulates by combustion removal.
[0006]
However, such an oxidation catalyst has an active temperature region, and if the operation state continues at an exhaust temperature that falls below the lower limit temperature of activation, the oxidation catalyst will not be activated and the particulates will not be burned and removed well. The malfunction that can happen. Therefore, if necessary, fuel is added to the exhaust gas on the upstream side, and the added fuel is pyrolyzed in high-temperature exhaust gas to produce a large amount of hydrocarbons, which are then oxidized on the oxidation catalyst. It has been proposed to react and positively raise the catalyst bed temperature by reaction heat.
[0007]
As described above with some examples, fuel is added to the upstream side of the exhaust purification catalyst (NOx storage reduction catalyst, oxidation catalyst, or particulate filter carrying these) installed in the middle of the exhaust pipe. The idea itself has been proposed in the past. For example, in Japanese Patent Laid-Open No. 2001-280125, a fuel addition injector is installed in an exhaust port of a cylinder head, fuel is added to exhaust gas by exhaust port injection by the injector, and the added fuel is stirred by a turbine. Means for supplying exhaust purification catalyst have been proposed above, and means for adding fuel to exhaust gas by such exhaust port injection has already been developed for practical use in some passenger cars and the like. It is made.
[0008]
However, in large vehicles equipped with diesel engines, it is possible to add fuel by installing an injector on the inlet side of the exhaust purification catalyst in the middle of the exhaust pipe from the viewpoint of ensuring the reliability of the EGR device and turbocharger. Japanese Patent Application Laid-Open No. 2000-240429 has already proposed means for adding fuel with an injector in the middle of an exhaust pipe.
[0009]
When an injector is provided in the middle of the exhaust pipe in this way, burnout due to exposure of the injector to high-temperature exhaust gas and seizure in the flow path of the added fuel can be reliably avoided. Therefore, it is necessary to take some heat countermeasures with respect to the injector.
[0010]
[Problems to be solved by the invention]
However, if a new cooling water system is installed that simply leads a part of the cooling water from the water pump, passes it around the injector and then returns it to the thermostat, the water pipe is routed. This complicates the process and increases the number of parts, leading to a significant increase in cost.
[0011]
The present invention has been made in view of the above-described circumstances, so that heat countermeasures for avoiding burnout of an injector installed in the middle of an exhaust pipe and seizure in the flow path of the added fuel can be realized at low cost. An object of the present invention is to provide an exhaust emission control device.
[0012]
[Means for Solving the Problems]
The present invention is provided with an exhaust purification catalyst in the middle of an exhaust pipe, an injector for injecting fuel into exhaust gas upstream of the exhaust purification catalyst in the exhaust pipe, and a water jacket around the injector. Forming and extracting a part of the cooling water from the water pump toward the cylinder block to the water jacket and introducing the cooling water from the water jacket through the center housing of the turbocharger and then guiding it to the thermostat. The present invention relates to an exhaust emission control device that is configured as described above.
[0013]
Thus, even if an injector is provided in the middle of the exhaust pipe, a part of the cooling water from the water pump to the cylinder block is introduced into the water jacket around the injector so that the injector Since it is cooled, burnout and seizure in the flow path of the added fuel due to exposure of the injector to high-temperature exhaust gas are reliably avoided.
[0014]
In addition, since the cooling water that has just cooled the injector does not rise to a very high temperature, the cooling water discharged from the water jacket around the injector is guided to the center housing of the turbocharger, which has a larger thermal load than the injector. Thus, it is possible to sufficiently contribute to cooling of the center housing.
[0015]
In this way, if the water jacket of the injector is returned to the thermostat as a cooling water system passing through the center housing of the turbocharger in series, the cooling water system necessary for cooling the center housing of the turbocharger can also be used. Therefore, it is possible to take measures against the heat of the injector, so that the complicated arrangement of the water pipe and the increase in the number of parts can be suppressed to the minimum necessary.
[0016]
Here, the cooling water system of the center housing of the turbocharger is selected as the other party. The turbocharger installed at the outlet of the exhaust manifold and the injector installed in the exhaust pipe on the downstream side are selected. Not only is the relationship convenient in terms of the size of the heat load, but the cooling water, which is relatively close to each other and has a temperature rise even from the height relationship, is positioned higher than the injector. This is also because it makes it possible to route water pipes that make sense to lead to a turbocharger, and this height relationship also increases the convenience in terms of draining and venting air. .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0018]
1 to 3 show an example of an embodiment for carrying out the present invention. Reference numeral 1 in FIG. 1 denotes a diesel engine equipped with a turbocharger 2, and an intake 4 led from an air cleaner 3 is connected to an intake pipe. 5 is introduced to the compressor 2a of the turbocharger 2 and pressurized, and the pressurized intake air 4 is distributed and introduced to each cylinder of the diesel engine 1 via the intercooler 6.
[0019]
Further, exhaust gas 8 discharged from each cylinder of the diesel engine 1 through the exhaust manifold 7 is sent to the turbine 2b of the turbocharger 2 through the exhaust pipe 9, and the exhaust gas 8 driving the turbine 2b is of a catalyst regeneration type. Particulates are collected through the particulate filter 10 (exhaust gas purification catalyst) and then discharged outside the vehicle.
[0020]
Furthermore, an appropriate position upstream of the particulate filter 10 in the exhaust pipe 9, that is, in the example shown here, the exhaust pipe 9 upstream of the bent portion with respect to the bent portion of the exhaust pipe 9 bent in an L shape. A fuel addition injector 11 is attached to the base end of the injector 11. A part of the fuel guided from a fuel tank (not shown) or the like is bent at the base end of the injector 11 from the front end of the injector 11. It is injected into the flow path in the exhaust pipe 9 through an injection space 12 formed in the direction along the exhaust pipe 9 downstream of the part.
[0021]
As shown in FIG. 2, a water jacket 14 having a cylindrical shape substantially concentric with the injector 11 is bored inside the boss portion 13 that holds the injector 11.
[0022]
Further, a water supply port 15 to the water jacket 14 is provided at the tip end side (lower end side) of the water jacket 14 of the boss portion 13 and the side away from the exhaust pipe 9, and the injector 11 in the water jacket 14 is provided. A drain port 16 to the water jacket 14 is provided on the base end side (upper end side) and on the side close to the exhaust pipe 9.
[0023]
As shown in FIG. 3, a part of the cooling water from the water pump 17 toward the cylinder block 18 is extracted and introduced into the water supply port 15 (see FIG. 2) of the water jacket 14 and the water jacket 14 is drained. The cooling water discharged from 16 (see FIG. 2) passes through the inside of the center housing 2c (see FIG. 1) of the turbocharger 2 and then led to the thermostat (temperature adjuster) 19.
[0024]
In the thermostat 19, the cooling water that has been heated through the water jacket 14 of the boss portion 13 and the center housing 2 c of the turbocharger 2 in sequence, and the cylinder block 18 and the cylinder head 20 of the diesel engine 1 are raised in sequence. The warm cooling water is merged and guided to the radiator 21.
[0025]
However, when the temperature of the cooling water is low immediately after starting the diesel engine 1 or the like, the water path returning from the radiator 21 is closed by the operation of the thermostat 19 and the cooling water from the center housing 2c and the cylinder head 20 of the turbocharger 2 is used as the water. By opening a water passage leading to the pump 17, the cooling water can be directly fed to the water pump 17 without passing through the radiator 21 to avoid overcooling of the diesel engine 1.
[0026]
Thus, if the exhaust gas purification device is configured in this way, even if the injector 11 is provided in the middle of the exhaust pipe 9, the water jacket 14 around the injector 11 is cooled to the cylinder block 18 from the water pump 17 to the cylinder block 18. Since a part of the water is introduced and the injector 11 is cooled, burnout and seizure in the flow path of the added fuel are surely avoided when the injector 11 is exposed to the high-temperature exhaust gas 8. Is done.
[0027]
Further, since the cooling water that has just cooled the injector 11 has not been raised to a very high temperature, the cooling water discharged from the water jacket 14 around the injector 11 is used as the turbocharger 2 having a larger heat load than the injector 11. By guiding to the center housing 2c, it is possible to sufficiently contribute to cooling of the center housing 2c.
[0028]
In this way, if the water jacket 14 of the injector 11 is returned to the thermostat 19 as a cooling water system passing through the center housing 2c of the turbocharger 2 in series, it is necessary for cooling the center housing 2c of the turbocharger 2. It becomes possible to take measures against heat of the injector 11 by also using the cooling water system.
[0029]
Here, the cooling water system of the center housing 2c of the turbocharger 2 is selected as the other party for the turbocharger 2 installed at the outlet of the exhaust manifold 7 and the exhaust pipe 9 downstream thereof. In addition to the fact that the relationship with the injector 11 is convenient from the viewpoint of the size of the heat load, the injector 11 is provided with cooling water that is relatively close to each other and whose temperature has increased even from the height relationship. This is also because it makes it possible to route the water pipe that makes sense to guide the turbocharger 2 to a relatively higher location. This is also because convenience increases (see FIG. 1).
[0030]
Therefore, according to the above embodiment, the cooling water system necessary for cooling the center housing 2c of the turbocharger 2 can also be used as a heat countermeasure for the injector 11, so that the complicated arrangement of water pipes is possible. And an increase in the number of parts can be suppressed to the minimum necessary, and heat measures for avoiding burnout of the injector 11 installed in the middle of the exhaust pipe 9 and seizure in the flow path of the added fuel can be made inexpensive. Can be realized.
[0031]
The exhaust purification apparatus of the present invention is not limited to the above-described embodiment. For exhaust purification catalysts that require the addition of hydrocarbons, in addition to catalyst regeneration type particulate filters, NOx reduction catalysts (selection) Reduction type catalyst), NOx occlusion reduction catalyst, particulate filter combined with NOx occlusion reduction catalyst, oxidation catalyst etc. may be adopted, and the fuel added by injector is a general diesel engine Of course, different fuels such as kerosene may be used in addition to the light oil used for the fuel, and various changes can be made without departing from the scope of the present invention.
[0032]
【The invention's effect】
According to the above-described exhaust gas purification apparatus of the present invention, the cooling water system necessary for cooling the center housing of the turbocharger can also be used to take measures against the heat of the injector. And the increase in the number of parts can be suppressed to the minimum necessary, and heat countermeasures for avoiding burnout of the injectors installed in the exhaust pipe and seizure in the flow path of the added fuel can be realized at low cost. It is possible to achieve an excellent effect of being able to.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an embodiment for carrying out the present invention.
FIG. 2 is an enlarged cross-sectional view showing details of an installation location of the injector of FIG.
FIG. 3 is a system diagram of cooling water supplied to and discharged from the water jacket of FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Turbocharger 2a Compressor 2b Turbine 2c Center housing 8 Exhaust gas 9 Exhaust pipe 10 Catalyst regeneration type particulate filter (exhaust purification catalyst)
11 Injector 14 Water jacket 17 Water pump 18 Cylinder block 19 Thermostat

Claims (2)

  An exhaust purification catalyst is provided in the middle of the exhaust pipe, an injector for injecting fuel into the exhaust gas is disposed upstream of the exhaust purification catalyst in the exhaust pipe, and a water jacket is formed around the injector, A part of the cooling water from the water pump to the cylinder block is extracted and introduced into the water jacket, and the cooling water discharged from the water jacket is guided through the center housing of the turbocharger and then guided to the thermostat. An exhaust purification device characterized by that. 2. The exhaust emission control device according to claim 1, wherein the turbocharger is provided at a relatively higher position than the injector.

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