JP4924833B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine having a structure for injecting an additive supplied to a catalyst.

For purification of exhaust gas from diesel engine vehicles (vehicles), NOx trap catalyst or selection is used to prevent NOx (nitrogen oxide) and PM (particulate matter) contained in the exhaust gas of diesel engine from being released into the atmosphere. An exhaust gas purification device combined with a reduced NOx catalyst, a diesel particulate filter, or the like is used.
In such an exhaust gas purification device, a catalyst such as an oxidation catalyst, a NOx trap catalyst or a selective reduction type NOx catalyst, called a pre-stage catalyst, is provided in an exhaust pipe portion for exhausting exhaust gas exhausted from the engine to the outside. A structure in which a fuel addition valve (which adds a reducing agent) for injecting fuel required for the reaction of the catalyst is provided upstream, for example, upstream of the oxidation catalyst.

By the way, in order to always function the fuel addition valve normally, it is required to avoid the use exceeding the heat resistance temperature of the fuel addition valve.
For this purpose, it is effective to keep the fuel addition valve away from the exhaust gas flow so that the tip portion where the fuel is injected is not exposed to the high-temperature exhaust gas. Therefore, in the exhaust gas purification device, as in Patent Document 1, a fuel injection path that extends separately from the exhaust pipe section is provided in the exhaust pipe section, and a fuel addition valve is installed at the tip of the fuel injection path, A technique for injecting the fuel of the addition valve into the exhaust pipe part through a fuel injection path from a point away from the exhaust gas is being adopted.
JP 2004-44483 A

However, in this structure, since the fuel injection path is separated from the exhaust pipe part and exposed to the outside air, the temperature of the fuel injection path becomes lower than the temperature of the exhaust pipe part. For this reason, the fuel injected from the fuel addition valve is difficult to atomize and is difficult to mix with the exhaust gas. This becomes more prominent as the total length of the fuel injection path becomes longer.
Moreover, since the fuel injection path is retracted from the exhaust pipe part, the main flow of the exhaust gas flowing through the exhaust pipe part does not easily reach the inside of the fuel injection path, and a stagnated portion is likely to occur in the fuel injection path. For this reason, the evaporated fuel remaining in the fuel injection path becomes a binder, and the soot contained in the exhaust gas adheres to the wall surface of the fuel injection path, thereby generating a digipot.

Therefore, it is conceivable to introduce a part of the high-temperature and high-pressure exhaust gas in the exhaust manifold into the fuel injection path so as to promote the vaporization of the injected fuel and discharge the evaporated fuel and soot.
However, if the high-temperature and high-pressure exhaust gas is simply introduced into the fuel injection path, the fuel addition valve is always exposed to the high-temperature and high-pressure exhaust gas, so that the original problem is exposed again. That is, the fuel addition valve may not function normally due to thermal influence. For this reason, introduction of exhaust gas considering the fuel addition valve is required.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust gas purification device for an internal combustion engine that introduces high-temperature and high-pressure exhaust gas into an additive injection path while suppressing the thermal burden on the additive injection valve.

In order to achieve the above-mentioned object, the invention according to claim 1 is provided on the upstream side of the catalyst, an exhaust pipe part that guides exhaust gas from the exhaust manifold of the engine to the outside, a catalyst provided in the exhaust pipe part, The additive injection path that communicates with the exhaust pipe portion at the base end and extends in the direction away from the exhaust pipe portion, and the additive injection portion that the additive injects are disposed at the distal end portion of the additive injection path. An additive injection valve that supplies the additive injected from the additive injection section to the catalyst through the additive injection path, and a part of the exhaust gas from the exhaust manifold of the engine flows in from one end and the other end A swirl flow that opens at a point in the tangential direction on the inner peripheral surface of the additive injection path and swirls around the fuel injected from the additive propellant in the additive injection path by exhaust gas from the exhaust manifold. Exhaust gas forming And road, disposed in an exhaust gas passage, equipped with a gas introduction control valve for introducing the exhaust gas from the exhaust manifold to the exhaust gas passage when the additive injection valve injection.
With this configuration, high-temperature and high-pressure exhaust gas is introduced into the additive injection path as necessary, and a swirling flow of the exhaust gas is formed in the additive injection path .

The invention described in 請 Motomeko 2, as much as possible so that the heat of the high temperature and high pressure of the exhaust gas is avoided from being transferred to the additive injection valve, the exhaust gas passage, the exhaust gas is led toward the downstream side of the additive injection passage Adopted configuration.

According to the first aspect of the present invention, the high-temperature and high-pressure exhaust gas from the exhaust manifold is introduced into the additive injection path through the exhaust gas path as necessary. Exposure to the exhaust gas is minimized.
Therefore, while suppressing the thermal burden applied to the additive injection valve, the exhaust gas of high temperature and high pressure is fully utilized to effectively vaporize or stir the additive in the additive injection path, and further to the additive injection path. Additives and soot that stays inside can be discharged. As a result, even if high-temperature and high-pressure exhaust gas immediately after engine exhaust is used, the possibility that the additive injection valve will not function properly is avoided, and good exhaust gas purification performance can always be maintained, with high reliability. Is obtained.
In addition, the swirling flow of the exhaust gas generated in the additive injection path can promote the vaporization or stirring of the additive within a limited time such as when the additive is injected, and the negative flow generated at the center of the swirling flow. By using pressure, additives and soot can be effectively sucked out.

According to the invention of claim 2, it is possible to avoid the heat of the exhaust gas having a high temperature and high pressure as much as possible from being transmitted to the additive injection valve, and to effectively protect the additive injection valve from the heat of the exhaust gas .

Hereinafter, the present invention will be described based on an embodiment shown in FIGS.
FIG. 1 shows an exhaust system of an internal combustion engine, for example, a diesel engine. In the figure, reference numeral 1 denotes an engine body of a multi-cylinder diesel engine, 1a denotes an exhaust manifold of the engine body 1, and 2 denotes a turbocharger connected to an outlet of the exhaust manifold 1a.

An exhaust gas purification device 3 is provided at the exhaust outlet of the turbocharger 2. In this exhaust gas purification device 3, for example, NOx (nitrogen oxide) in exhaust gas is occluded, and NOx removal system 3a for reducing and removing NOx occluded regularly and PM (particulate matter) are collected. The structure which combined PM collection system 3b to be used is used.
For example, the NOx removal system 3a includes a catalytic converter 6 in which an oxidation catalyst 5 (corresponding to the catalyst of the present application), which is connected in a downward direction from an exhaust outlet of the turbocharger 1a, is incorporated. A catalytic converter 9 having a built-in NOx trap catalyst 8 connected laterally after the catalytic converter 6 and a fuel addition valve for supplying fuel for catalytic reaction as an additive described later (to the additive injection valve of the present application). Equivalent) 23 is used in combination. The collection system 3b employs a configuration in which a catalytic converter 12 having a particulate filter 11 incorporated therein is connected to the catalytic converter 9. An exhaust pipe portion 15 that guides the exhaust gas exhausted from the diesel engine (engine body 1) to the outside is constituted by the catalytic converters 6, 9, 12 and the connection portion 13 connecting the converters.

  Among these, the vertical cylindrical housing 17 accommodating the oxidation catalyst 5 of the catalytic converter 6 is formed, for example, in an L shape on the upper side, and an inlet portion 17a connected to the turbocharger 2 is disposed sideways. . The outlet portion 17b communicating with the catalytic converter 9 is disposed downward. The housing 17 forms a bent portion 15a bent in an L shape at a point immediately after the exhaust side of the diesel engine in the exhaust pipe portion 15. The oxidation catalyst 5 is housed at a point directly below the bent portion 15a.

  The fuel addition valve 23 is provided at a point immediately above the oxidation catalyst 5, for example, on the outer peripheral side of the bent portion 15 a in order to inject fuel into the oxidation catalyst 5. The fuel addition valve 23 has a fuel injection part for injecting fuel at the tip part. As shown in FIG. 2, a cylindrical portion 24 that extends away from the bent portion 15a, that is, outward is branched from the outer peripheral portion of the bent portion 15a on the outlet side. The fuel addition valve 23 is installed at the distal end portion of the cylindrical portion 24 separated from the bent portion 15a using the mounting flange 24a and the pedestal 25. As a result, the fuel injection part at the tip of the fuel addition valve 23 faces the fuel injection path (corresponding to the additive injection path of the present application) 24b (shown in FIG. 2) formed in the internal space of the cylindrical part 24. ing. The fuel injection path 24 b is inclined so that the entire fuel injection path faces the inlet end face of the oxidation catalyst 5. Thereby, the fuel required for the catalytic reaction is injected into the oxidation catalyst 5 from a point away from the exhaust gas flow. Thus, the fuel injection portion at the tip of the fuel addition valve 23 is not exposed to the high-temperature exhaust gas flow. A cooling water passage 26 is formed in the pedestal 24 to protect the fuel addition valve 23 from heat (water cooling).

  The fuel injected from the fuel addition valve 23 generates a reducing agent by the reaction of the oxidation catalyst 5, and the reducing agent removes NOx and SOx stored in the NOx trap catalyst 8. This is used to burn and remove the PM collected by the particulate filter 11 by the heat obtained by the above reaction. For this reason, the fuel addition valve 23 is injected with fuel by a control unit that controls the diesel engine, for example, the ECU 20, when a catalytic reaction such as NOx or SOx reduction removal or PM combustion removal is required during operation of the diesel engine. It is made to do.

The cylindrical part 24 is provided with an exhaust gas introduction part 29 for introducing a part of the exhaust gas into the fuel injection path 24. The detailed structure of the exhaust gas introducing portion 29 is shown in FIGS. The exhaust gas introduction portion 29 has a structure in which a long and narrow exhaust gas introduction pipe 30 and an exhaust gas introduction control valve 35 (corresponding to the gas introduction control valve of the present application) are combined.
Of these, the exhaust gas introduction pipe 30 has an inlet 31a (shown in FIG. 1) at one end and an outlet 31b (shown in FIGS. 1 and 2) at the other end. One end of the exhaust gas introduction pipe 30 is connected to a point immediately after the exhaust port of the engine body 1, specifically, to the exhaust manifold 1 a, and the inlet 31 a is communicated with the exhaust manifold 1. The other end portion of the exhaust gas introduction pipe 30 is connected to a wall portion of the cylindrical portion 24, for example, a middle wall portion, and the inlet 31 a communicates with the fuel injection path 24. An exhaust gas passage 32 that guides a part of the high-temperature and high-pressure exhaust gas in the exhaust manifold 1 a to the fuel injection passage 24 is configured by the exhaust gas introduction pipe 30 that bypasses between the exhaust manifold 1 a and the cylindrical portion 24. Yes.

  Further, as shown in FIG. 2, the other end portion of the exhaust gas introduction pipe 30 is inclined and connected to the cylindrical portion 24 so that the end approaches the downstream side of the fuel injection path 24, and the exhaust gas of high temperature and high pressure is connected. Is led out toward the downstream side of the fuel injection path 24. As shown in FIG. 3, the outlet 31a of the exhaust gas introduction pipe 30 is offset from the radial center of the fuel injection path 24b to the side, specifically, a tangential direction on the inner peripheral surface of the fuel injection path 24b. The exhaust gas is opened at a point, and exhaust gas derived from the outlet 31a is introduced into the fuel injection path 24b while turning along the inner peripheral surface. Due to the structure of each part, high-temperature and high-pressure exhaust gas flows out toward the downstream side of the fuel injection path 24b while being mixed with the fuel injected from the fuel addition valve 23.

  The exhaust gas introduction control valve 35 is interposed in the middle of the exhaust gas introduction pipe 30, for example, at the other end of the exhaust gas introduction pipe 30. The exhaust gas introduction control valve 35 is constituted by, for example, an on-off valve that can switch the exhaust gas introduction path 32 between “open” and “closed”. The code | symbol 35 in FIG. 1 has shown the valve body which opens and closes. This on-off valve is connected to a control unit, for example, an ECU 20 via a driver unit (not shown) for driving the valve so that high-temperature and high-pressure exhaust gas is introduced into the fuel injection path 24b as necessary. I have to. Specifically, the ECU 20 normally closes the exhaust gas control valve 35 when the fuel addition valve 23 injects fuel, that is, only when the fuel addition valve 23 is open. Settings to control “open” are made. With this valve opening control, the high-temperature and high-pressure exhaust gas in the exhaust manifold 1a is introduced into the fuel injection path 24b only when the fuel addition valve 35 is injecting fuel. By introducing the exhaust gas, the vaporization / mixing of the injected fuel and the prevention of the generation of the digipot are established while suppressing the thermal influence of the fuel addition valve 35.

That is, to explain the action, it is assumed that the diesel engine is now in operation.
At this time, the exhaust gas exhausted from the diesel engine is exhausted from the exhaust manifold 1a, the turbocharger 2, the bent portion 15a, the oxidation catalyst 5, the NOx trap catalyst 8, and the particulates as indicated by the arrow a in FIGS. The air is exhausted through the filter 11 to the outside air.

During this passage, NOx contained in the exhaust gas is occluded in the NOx trap catalyst 8, and PM is also collected by the particulate filter 11.
At this time, the fuel addition valve 23 is disposed at a point away from the main flow of the exhaust gas and is not exposed to the main flow of the exhaust gas. Therefore, even if the temperature of the fuel addition valve 23 rises, the heat resistance temperature is not exceeded.
It is time to remove the stored NOx and the collected PM, and fuel is injected from the fuel injection portion at the tip of the fuel addition valve 23 to remove them.

Then, the fuel is injected to the inlet end face of the oxidation catalyst 5 through the fuel injection path 24b as shown in FIGS. 1 and 2 indicates the fuel injection flow.
On the other hand, the exhaust gas introduction control valve 35 is opened in accordance with the fuel injection operation of the fuel addition valve 23.
As a result, the high-temperature and high-pressure exhaust gas in the exhaust manifold 1 a is forcibly introduced into the fuel injection path 24 b through the exhaust gas path 32.

At this time, the outlet 32b of the exhaust gas passage 32 is offset and tilted downstream, so that the fuel injection passage 24b moves downstream as indicated by the arrow b in FIGS. A swirling flow b of the exhaust gas is formed.
Thus, the high-temperature, high-pressure exhaust gas is mixed with the fuel of the injection flow α and goes downstream, and the fuel is vaporized and mixed. In particular, in the case of the swirl flow b, the vaporization and mixing of the fuel are effectively promoted by utilizing the heat and flow of the exhaust gas. At the same time, the evaporated fuel and soot are sucked out by the negative pressure generated at the center of the swirling flow b, and flow out of the fuel injection path 24b, thereby avoiding the generation of a digipot.

When the fuel injection from the fuel addition valve 23 is finished, the exhaust gas introduction control valve 35 is also switched to “closed”, the introduction of the exhaust gas is stopped, and the state where the exhaust gas is not exposed again is returned.
As described above, when the high-temperature and high-pressure exhaust gas is introduced into the fuel injection path 24b as necessary, the fuel addition valve 23 can be minimized from being exposed to the high-temperature and high-pressure exhaust gas. In particular, when high-temperature and high-pressure exhaust gas is introduced into the fuel injection path 24b each time fuel is injected, the time during which the fuel addition valve 23 is exposed to the exhaust gas can be kept to a minimum, such as a very short injection time.

  Therefore, while suppressing the thermal burden on the fuel addition valve 23, it is possible to promote the vaporization and mixing of the injected fuel by making full use of the high-temperature and high-pressure exhaust gas, and to generate a digipot due to evaporative fuel and soot retention. Can be prevented. As a result, even if high-temperature and high-pressure exhaust gas immediately after engine exhaust is used, the possibility that the fuel addition valve 23 will not function normally is avoided, so that exhaust gas purification performance can always be maintained satisfactorily and high reliability can be achieved. Can be secured.

  In particular, if the exhaust gas is led out toward the downstream side of the fuel injection path 24b, the heat of the exhaust gas having a high temperature and high pressure can be prevented from being transmitted to the fuel addition valve 23 as much as possible. It is effective to protect. In addition, when the swirl flow b is generated, mixing with the injected fuel is promoted, so that the injected fuel can be uniformly vaporized. In addition, the generation of a digipot can be suppressed by sucking out evaporative fuel and soot brought about by the negative pressure generated at the center of the swirling flow b, and the exhaust gas introduced for a limited time (fuel injection) can be effectively used. Thus, vaporization and mixing of the injected fuel can be promoted, and generation of a digipot can be avoided.

  In addition, this invention is not limited to any embodiment mentioned above, You may implement in various changes within the range which does not deviate from the main point of this invention. For example, in the above-described embodiment, an example in which the present invention is applied to an exhaust gas purification apparatus in which an oxidation catalyst is used as a pre-stage catalyst and a NOx trap catalyst and a particulate filter are provided downstream thereof is described. A purification-type exhaust gas purification device, for example, an exhaust gas purification device in which a NOx trap catalyst is used as a pre-stage catalyst, a particulate filter is provided downstream thereof, and an addition valve is provided upstream of the NOx trap catalyst, is also used as a pre-stage catalyst. NOx trap catalyst, oxidation catalyst, and particulate filter downstream of the exhaust gas purification device provided with an addition valve upstream of the NOx trap catalyst, or a selective reduction catalyst directly downstream of the additive injection valve, The present invention may be applied to an exhaust gas purification device provided with a particulate filter.

  Further, in the above-described embodiment, the fuel is used as the additive. However, any material may be used as long as it is supplied to the catalyst. For example, light oil, gasoline, ethanol, dimethyl ether, natural gas, propane gas, urea as a reducing agent. , Ammonia, hydrogen, carbon monoxide, etc. Further, a substance other than the reducing agent may be used. For example, air for cooling the catalyst, nitrogen, carbon dioxide, etc., air or ceria for promoting combustion removal of soot collected in the particulate filter, and the like may be used.

The perspective view which shows the exhaust-gas purification apparatus which concerns on one Embodiment of this invention. Sectional drawing which shows a state when exhaust gas is introduce | transduced into the additive injection path. Sectional drawing in alignment with the AA in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 1a Exhaust manifold 15 Exhaust pipe part 23 Fuel addition valve 24b Fuel injection path (additive injection path)
32 Exhaust gas passage 35 Exhaust gas introduction control valve (gas introduction control valve)

Claims (2)

An exhaust pipe section that guides exhaust gas from the exhaust manifold of the engine to the outside;
A catalyst provided in the exhaust pipe part;
An additive injection path provided on the upstream side of the catalyst, a base end communicating with the exhaust pipe portion, and a tip extending in a direction away from the exhaust pipe portion;
Addition in which an additive injection part for injecting an additive is disposed at the tip of the additive injection path and the additive injected from the additive injection path is supplied to the catalyst through the additive injection path An agent injection valve;
A part of the exhaust gas from the exhaust manifold of the engine flows in from one end, the other end is opened at a tangential point on the inner peripheral surface of the additive injection path, and the exhaust gas from the exhaust manifold An exhaust gas path that forms a swirl flow swirling around the fuel injected from the additive propellant in the additive injection path;
An exhaust gas purification system for an internal combustion engine, comprising: a gas introduction control valve that is provided in the exhaust gas passage and introduces exhaust gas from the exhaust manifold into the exhaust gas passage when the additive injection valve injects. apparatus. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas passage is configured such that exhaust gas is led out toward a downstream side of the additive injection passage.

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