JP4844758B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification device for an internal combustion engine that injects an additive supplied from an additive injection valve 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.
Recently, in order to increase the purification efficiency in the cold state of the engine, an oxidation catalyst, a NOx trap catalyst, a selective reduction type NOx, which is separately called a pre-stage catalyst, as close as possible to the engine, for example, near the outlet of the exhaust manifold of the engine. A catalyst such as a catalyst is provided, and a fuel addition valve (which adds a reducing agent) for injecting fuel required for the reaction of the catalyst is provided upstream of the catalyst to construct an exhaust gas purification device. ing.

By the way, the installation of the pre-stage catalyst near the exhaust outlet of such an engine requires a device that can be accommodated in the engine room of the automobile.
For this reason, as disclosed in Patent Document 1, in many cases, an exhaust pipe portion having a bent portion bent into an L shape, for example, is provided on the exhaust side of the engine, and the catalyst can be installed downstream from the bent portion. A place is secured, a pre-stage catalyst is provided in this portion, and a fuel addition valve is provided immediately upstream of the pre-stage catalyst.

Recently, in order to make the upstream catalyst as close as possible to the engine, a fuel addition valve is installed on the outer peripheral side of the bent portion of the exhaust pipe portion as shown in FIG. In addition, the fuel required for the reaction of the preceding catalyst tends to be injected from the outer peripheral side of the bent portion into the exhaust pipe portion and supplied to the catalyst.
By the way, in order to make the pre-stage catalyst react efficiently, the fuel injected from the fuel addition valve is preferably supplied over a wide range to the inlet end face of the pre-stage catalyst.

  However, the injection shape of the fuel injected into the catalyst is pushed by the exhaust gas flow and should expand into a predetermined shape, for example, a cone shape, but is a shape lacking expansion, specifically a flat shape at the tip of the injection flow, It will be changed to a fairly small spread. In particular, the fuel injection flow is more susceptible to the exhaust gas flow because the penetration force is smaller toward the tip. Moreover, the exhaust gas flow varies greatly depending on the operating state of the engine, such as during high load operation where the flow velocity and flow rate are large, and conversely during low load operation where the flow velocity and flow rate are small.

For this reason, it is difficult for the fuel for the reaction to be supplied to the catalyst in a wide range, and the function of the catalyst is not sufficiently exhibited.
Therefore, as disclosed in Patent Document 2, a guide pipe that guides the fuel injected from the fuel addition valve is formed only in the vicinity of the tip of the fuel addition valve among the exhaust pipe portions that form the bent portion, There has been proposed a structure for securing a distance for mixing the injected fuel and the exhaust gas immediately after the guide tube to the catalyst.
JP 2005-127260 A JP 2006-329019 A

  According to Japanese Patent Application Laid-Open No. 2004-260260, in an area where there is a guide pipe, interference between the injected fuel and the exhaust gas flow can be avoided. Therefore, the injection flow injected from the fuel addition valve is not affected by the exhaust gas flow. However, since there is a large distance between the tip of the guide tube and the catalyst, a mixture of a jet flow with a small penetrating force flowing out from the guide tube and a turbulent exhaust gas flow immediately after passing through the bend, The injection shape cannot be maintained, and fuel itself cannot be injected over a wide range. Moreover, the structure in which the guide pipe part is formed in the bent part of the exhaust pipe part is quite difficult.

  Accordingly, an object of the present invention is to provide an exhaust gas purifying apparatus for an internal combustion engine that has a simple structure and sufficiently expands fuel from an additive injection valve and injects it into a catalyst over a wide range.

In order to achieve the above object, the invention described in claim 1 divides the vicinity of the catalyst to the upstream bent portion into a bent portion outer peripheral side and an inner peripheral side along the exhaust gas flow direction by a partition wall. The inner peripheral side is an exhaust gas passage through which exhaust gas flows, and the outer peripheral side is divided as a pipe portion that does not interfere with the exhaust gas flowing through the exhaust gas passage, and the additive injection valve passes through the divided pipe portion, The additive is injected into the catalyst, and the partition wall is formed with an air supply hole that guides part of the exhaust gas to the tip of the additive injection valve .
With the same configuration, the additive from the additive injection valve is injected into the catalyst inlet while spreading to a predetermined extent without being influenced by the exhaust gas flow. Moreover, since the exhaust pipe is partitioned from the vicinity of the catalyst by the partition wall, a simple structure is sufficient. In addition, the digipot is less likely to accumulate in the injection portion of the additive injection valve.

In the invention according to claim 2 , the pipe portion through which the additive passes allows the injection shape of the additive injected from the additive injection valve so that the additive is injected to the catalyst without impairing the injection shape. The size.

According to the first aspect of the present invention, the additive injected from the additive injection valve can be expanded to a predetermined extent without being influenced by the exhaust gas flow, and can be led to the catalyst inlet as it is.
Therefore, with a simple structure, the additive from the additive injection valve can be sufficiently expanded and injected to the catalyst over a wide range.
Moreover, the catalyst was disposed immediately downstream of the bent portion, since the partitions in a bent portion outer peripheral side and inner peripheral side, with easy single structure to further, an additive from the additive injection valve, let fully expanded Thus, the catalyst can be injected over a wide range. In addition, since a very small amount of exhaust gas always flows through the injection portion of the additive injection valve, it is difficult for the digipot to accumulate in the injection portion.

According to invention of Claim 2, an additive can be injected to a catalyst, without impairing an injection shape .

Hereinafter, the present invention will be described based on an embodiment shown in FIGS. 1 and 2.
FIG. 1 shows an exhaust system of a diesel engine (internal combustion engine), in which 1 is an engine body of the diesel engine, 1a is an exhaust manifold (only a part of which is shown), and 2 is its exhaust manifold. 1 shows a turbocharger, for example a turbocharger, connected to the outlet of 1a.

  An exhaust gas purification device 3 is provided at the exhaust outlet of the turbocharger 1 a that forms the exhaust side of the diesel engine 1. 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 periodically occluded 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 (corresponding to the catalyst of the present application) 5 that is connected to face downward from the exhaust outlet of the turbocharger 1a is built. A combination with a catalytic converter 9 having a built-in NOx trap catalyst 8 connected laterally after the catalytic converter 6 is used. 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 exhaust gas exhausted from the diesel engine 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 upper turbocharger 2 is disposed sideways. ing. 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 catalyst installation space is directly below the bent portion 15a. The oxidation catalyst 5 is installed at a point directly downstream of the bent portion 15a in the secured catalyst installation space. Thereby, the oxidation catalyst 5 is installed at a point close to the engine main body 1 (in order to increase the temperature rise performance when the engine is cold).

  The upstream housing space (corresponding to the inside of the exhaust pipe) from the oxidation catalyst 5 is partitioned by a partition plate 19 (corresponding to the partition wall of the present application). The partition plate 19 is provided from the vicinity of the inlet end surface of the oxidation catalyst 5 to the upstream, and partitions the housing space along the flow direction of the exhaust gas. For example, a partition plate 19 partitions the vicinity of the inlet end surface of the oxidation catalyst 5 to the inside of the bent portion 15a along the exhaust gas flow direction. More specifically, for example, as shown in FIGS. 1 and 2, the inside of the housing 17 is partitioned by a partition plate 19 in the inner and outer directions such as the outer peripheral side and the inner peripheral side of the bent portion 15a. An upstream end of the partition plate 19 is attached to the inner surface of the housing 17 in the vicinity of the inlet of the bent portion 15a, and an exhaust gas passage 20 that communicates the upstream housing space from the oxidation catalyst 5 with the inlet 17a; It is divided into a pipe section 21 on the outer peripheral side whose upstream side is closed. That is, the exhaust gas passage 20 formed on the inner peripheral side is a passage through which the main flow of exhaust gas passes, and the pipe line portion 21 formed on the outer peripheral side is a space that does not interfere with the main flow of exhaust gas. The downstream end of the partition plate 19 is as close as possible to the inlet end surface of the oxidation catalyst 5 to reduce the gap δ (shown in FIG. 1) between the partition plate 10 and the oxidation catalyst 5. .

  A fuel addition valve 23 (corresponding to the additive injection valve of the present application) for injecting fuel such as light oil used in a diesel engine as an additive is provided on the outer peripheral wall portion of the bent portion 15a (upstream side of the conduit portion 21). Is provided. The fuel addition valve 23 has a fuel injection portion 23a at the tip. The fuel addition valve 23 is installed on a mounting seat 24 formed in the housing 17 by retracting the fuel injection part 23 a at the tip from the inner surface of the bent part 15 a. Specifically, as shown in FIG. 2, in the fuel addition valve 23, the fuel injection portion 23 a is disposed in the center of the pipe portion 21 with the injection direction directed toward the oxidation catalyst 5. The fuel injected from the fuel injection portion 23a is guided into the conduit portion 21 from a port 24a formed in the installation seat 24.

  As a result, the fuel α is injected from the fuel addition valve 23 toward the inlet end face of the oxidation catalyst 5 without interfering with the exhaust gas flow. That is, the fuel α is divided into the divided pipe portions 21. And is sprayed to the inlet end face of the oxidation catalyst 5 while expanding in a cone shape. In order to supply the fuel α to the oxidation catalyst 5 particularly effectively, the fuel injection section 23a is arranged at a predetermined injection distance L as shown in FIG. 1 so that the injected fuel spreads to the maximum and the momentum is increased. The break point at the leading end that disappears is arranged at a point that reaches the vicinity of the inlet end face of the oxidation catalyst 5. The length of the partition plate 19 also corresponds to this distance L.

The size of the pipe portion 21 not only allows the distance L, but also has a size that allows the injection diameter S when the injection shape is expanded to the maximum in a cone shape, thereby impairing the cone-shaped injection shape. Instead, it can be injected onto the inlet end face of the oxidation catalyst 5.
Further, in the partition plate 19, a position adjacent to the fuel injection portion 23a is provided with a small air supply hole 26 (corresponding to the air supply hole portion of the present application) that opens toward the fuel injection portion 23a. Yes. This small hole 26 allows a small amount of exhaust gas (a part of the exhaust gas) to be guided from the exhaust gas passage 20 toward the fuel injection unit 23 so that a digipot does not accumulate at the tip of the fuel injection unit 23 or the port 24a. ing.

  The fuel addition valve 23 uses the reaction (oxidation) of the oxidation catalyst 5 to generate a reducing agent, and this reducing agent reduces and removes NOx and SOx stored in the NOx trap catalyst 8. The PM collected by the particulate filter 11 is used for combustion removal by the temperature rise obtained by the reaction (oxidation) 5. For this reason, the fuel addition valve 23 is configured to inject fuel when a control unit that controls the diesel engine, for example, the ECU 27, requires a catalytic reaction such as NOx or SOx reduction removal or PM combustion removal during operation of the diesel engine. It is supposed to be done.

Next, the operation of the exhaust gas purification device configured as described above will be described.
During operation of the diesel engine, exhaust gas exhausted from the diesel engine is exhausted to the outside air through the exhaust manifold 1a, the turbocharger 2, the exhaust gas passage 20, the oxidation catalyst 5, the NOx trap catalyst 8, and the particulate filter 11.
At this time, NOx contained in the exhaust gas is occluded in the NOx trap catalyst 8, and similarly PM is collected by the particulate filter 11.

Here, it is time to remove the stored NOx or SOx and the collected PM, and the fuel addition valve 23 is operated, and the fuel α required for the removal from the fuel injection portion 23a enters the pipe portion 21. Suppose that it was injected.
At this time, since the duct portion 21 is separated from the exhaust gas passage 20 through which the exhaust gas flows, the injection flow of the fuel α injected from the fuel injection portion 23a affects the exhaust gas flow flowing through the bent portion 15a. Pass without.

As a result, the fuel α from the fuel addition valve 23 is guided to the inlet end face of the oxidation catalyst 5 while spreading into a predetermined cone shape without being influenced by the surroundings. In particular, since the downstream end of the partition plate 19 is disposed up to the vicinity of the oxidation catalyst 5, that is, the inlet end face of the catalyst, the influence of the exhaust gas flow is minimized.
Therefore, the fuel α is supplied to the inlet end face of the oxidation catalyst 5 while maintaining the circular injection shape that is expanded to the maximum.

Therefore, the fuel α of the fuel addition valve 23 can be sufficiently expanded and injected over a wide range to the oxidation catalyst 5, that is, the inlet end face of the catalyst. As a result, the functions of not only the oxidation catalyst 5 but also the downstream NOx trap catalyst 8 and the particulate filter 11 can be sufficiently exhibited, and the purification function of the exhaust gas purification device can be sufficiently exhibited.
In addition, the same effect is obtained by disposing the oxidation catalyst 5 (catalyst) immediately below the bent portion 15a and partitioning the upstream exhaust pipe portion from the vicinity of the oxidation catalyst 5 (catalyst) by the partition plate 19 so as not to interfere with the exhaust gas flow. Since it can be obtained by injecting the fuel α from the pipe section 21, a simple structure is sufficient.

In particular, the pipe section 21 has a size that allows the injection shape of the fuel injected from the fuel addition valve 23, so that the fuel can be properly injected to the oxidation catalyst 5, that is, the catalyst without impairing the expanding injection shape. Can do.
Moreover, since the partition plate 19 is provided with a small hole 26 for air supply, a very small amount of exhaust gas is always supplied to the tip of the fuel addition valve 23 during operation of the diesel engine. Digipots are unlikely to accumulate in the fuel injection section 23a and the port 24a of the fuel addition section 23, and fuel injection can always be performed satisfactorily.

  The present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the spirit of the present invention. For example, in one embodiment, the inside of the exhaust pipe portion is divided by the partition wall into the inner peripheral side and the outer peripheral side of the bent portion, but the present invention is not limited to this. A pipe line portion may be formed. Of course, the partition wall may be an integral structure instead of a separate structure. In one embodiment, an example is given in which the present invention is applied to an exhaust gas purification apparatus in which an oxidation catalyst is used as a catalyst immediately downstream of a bent portion, and a NOx trap catalyst and a particulate filter are provided downstream thereof. First, other purification type exhaust gas purification devices, for example, exhaust gas purification using a NOx trap catalyst as a catalyst immediately downstream of the bent portion, a particulate filter provided downstream thereof, and an addition valve provided upstream of the NOx trap catalyst Even in the system, an NOx trap catalyst is used as a catalyst immediately downstream of the bent portion, an NOx trap catalyst, an oxidation catalyst, and a particulate filter are provided downstream thereof, and an exhaust gas purification device and an addition provided with an addition valve upstream of the NOx trap catalyst An exhaust gas purifying device provided with a selective reduction catalyst or a particulate filter directly downstream of the agent injection valve may be used.

Further, in one embodiment, a bent portion is provided immediately upstream of the catalyst, and the partition wall extends from the bent portion, but the upstream portion of the catalyst is a straight exhaust pipe portion, for example, between the bent portion and the catalyst upstream end. You may provide a partition wall in the straight part formed.
Furthermore, in the above-described embodiment, the fuel is used as the additive. However, any fuel may be used as long as it is supplied to the catalyst, such as light oil, gasoline, ethanol, dimethyl ether, natural gas, propane gas, Urea, ammonia, hydrogen, carbon monoxide, etc. may be used. 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. In addition to the cone shape, the fuel addition valve 23 may be a flat or fan-shaped additive injection valve or an additive injection valve in which an additive is injected from a plurality of injection holes.

1 is a partial cross-sectional side view showing the structure of an exhaust gas purification apparatus according to an embodiment of the present invention. FIG. 2 is a plan sectional view taken along line AA in FIG. 1.

Explanation of symbols

1 Engine body 3 Exhaust gas purification device 5 Oxidation catalyst (catalyst)
15 Exhaust pipe portion 15a Bending portion 23 Fuel addition valve 26 Small hole (hole for air supply)

Claims (2)

An exhaust pipe for guiding exhaust gas exhausted from the engine to the outside;
A catalyst housed in the exhaust pipe section;
A bent portion bent into an L shape formed in a portion immediately upstream of the catalyst in the exhaust pipe;
The exhaust pipe is provided in the exhaust pipe portion and divides the bent portion upstream from the vicinity of the catalyst into the bent portion on the outer peripheral side and the inner peripheral side along the flow direction of the exhaust gas, and the exhaust gas flows on the inner peripheral side. A partition wall that divides the outer peripheral side as a duct portion that does not interfere with the exhaust gas flowing through the exhaust gas passage;
An additive injection valve for injecting an additive to be supplied to the catalyst through the pipe line portion to the catalyst ;
The partition wall is formed with an air supply hole that guides a part of the exhaust gas to the tip of the additive injection valve.
An exhaust gas purification apparatus for an internal combustion engine, characterized in that:   2. The exhaust gas purifying device for an internal combustion engine according to claim 1, wherein the pipe portion has a size that allows an injection shape of fuel injected from the additive injection valve. 3.

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