JP5013101B2 - 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 that supplies an additive upstream of 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. Yes.

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 in an L shape is provided on the exhaust side of the engine, and the catalyst is installed in the exhaust pipe portion immediately below the bent portion. A possible 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, as shown in FIG. 1 of Patent Document 1, a fuel addition valve is installed on the outer peripheral side of the bent portion of the exhaust pipe portion to further secure the injection distance. In addition, the fuel required for the reaction of the pre-stage catalyst is injected from the outer peripheral side of the bent portion so as to cross the flow of the exhaust gas passing through the bent portion, and supplied to the catalyst.
JP 2005-127260 A

By the way, in order to cause the pre-stage catalyst to react most efficiently, the fuel injected from the fuel addition valve is required to be uniformly supplied to the inlet end face of the pre-stage catalyst.
However, the direction of the fuel injected from the fuel addition valve is likely to change depending on the behavior of the exhaust gas exhausted from the engine.
Specifically, the flow rate and flow rate of the exhaust gas exhausted from the engine changes according to the operating state of the engine. On the other hand, from the fuel addition valve, fuel is injected in a constant direction regardless of the operating state of the engine only when the reaction of the catalyst such as reduction is required.

In such a situation, the fuel is injected into the catalyst from the direction crossing the flow of the exhaust gas. Here, the initial fuel injection direction is adjusted in accordance with, for example, the medium load operation of the engine. Assume that the fuel from the valve is injected into the center of the inlet end face of the catalyst.
At this time, if the engine operation is not a medium load operation but a high load operation, the flow rate and flow rate of the exhaust gas are higher than those during the medium load operation, so the engine should be injected to the inlet end face of the catalyst. The fuel injection flow is pushed by the exhaust gas flow and biased toward the edge of the catalyst. On the other hand, during low-load operation, the flow rate and flow rate of exhaust gas are lower than during medium-load operation. It is biased toward the edge side.

For this reason, during the operation of the engine, the direction of fuel injection is not constant, and the fuel distribution of the catalyst tends to be biased.
Due to such behavior, there is a problem that the fuel for the reaction is not uniformly supplied to the pre-catalyst and the pre-catalyst cannot be sufficiently exhibited.
SUMMARY OF THE INVENTION An object of the present invention is to provide an engine exhaust gas purification apparatus that can uniformly supply an additive to a catalyst without being influenced by an exhaust gas flow.

In order to achieve the above object, the invention according to claim 1 is an exhaust pipe portion formed with a bent portion bent into an L shape for guiding the exhaust gas exhausted from the engine to the outside, and an exhaust pipe portion The catalyst is stored in the portion immediately downstream of the bent portion of the exhaust pipe, and the additive is provided on the outer peripheral side of the bent portion of the exhaust pipe portion, and is injected in a direction crossing the exhaust gas flow to supply the additive to a predetermined position of the catalyst The additive from the additive injection valve and the additive injection valve, which is provided in the exhaust pipe portion upstream from the additive injection valve and pushed by the flow of exhaust gas passing through the L-shaped bent portion, keeps the predetermined position of the catalyst. And an exhaust control valve for controlling the flow of the exhaust gas .
By this construction, regardless of the operating state of the engine, pushed by the flow of exhaust gas passing through the bent portion of the L-shaped injection direction additive injected from the additive injection valve may be kept in a predetermined. For this reason, the additive is supplied to a predetermined position of the catalyst .

Preferably, the injection hole of the additive injection valve is directed to the catalyst inlet end surface opposite to the side wall provided with the additive injection valve, and the additive is supplied to a predetermined position of the catalyst by the exhaust flow control valve.
The invention according to claim 2 is configured such that the exhaust flow control valve is provided on the side wall on the outer peripheral side of the bent portion along with the additive injection valve so that the digipot is not easily accumulated at the tip of the additive injection valve. .
According to a third aspect of the present invention, the exhaust flow control valve unit is configured so that the flow of exhaust gas in the vicinity of the injection hole of the additive injection valve becomes a predetermined flow so as to correspond to any engine operating state. It was supposed to be controlled.

  Preferably, the exhaust flow control valve is fully opened when the exhaust gas flow rate has the highest exhaust gas flow rate and flow rate when the engine is operating at a high load, and the exhaust gas flow rate and flow rate is the lowest when the engine is operated at a low load. If the exhaust gas flow is fully closed and the valve is controlled steplessly from fully open to fully closed according to the operating state of the engine, the additive injection valve will match the exhaust gas during high-load operation. By simply setting the direction, the optimum injection direction of the additive can be easily maintained.

According to the invention of claim 1, under operating conditions of the throat engines like, even if the additive is injected, additive pushed by the flow of exhaust gas passing through the bent portion of the L-shaped, the predetermined direction the continue to keep. Therefore, the additive can always be injected to a predetermined position of the catalyst .

Therefore, even if the flow of exhaust gas in the vicinity of the injection hole of the additive injection valve is greatly affected by the bent portion, the influence can be suppressed by the exhaust flow control valve.
According to the invention of claim 2, the exhaust flow control valve is disposed immediately upstream of the additive injection valve so that the exhaust flow control valve is fully opened. There is an effect that the digipot accumulated at the tip can be blown away with exhaust gas having a high flow velocity.

According to the invention of claim 3 , the exhaust flow control valve is further controlled so that the flow of the exhaust gas in the vicinity of the injection hole of the additive injection valve becomes a predetermined flow according to the operating state of the engine. There is an effect that it is possible to cope with any engine operating state.

Hereinafter, the present invention will be described based on an embodiment shown in FIGS.
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 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 (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 that houses the oxidation catalyst 5 of the catalytic converter 6 is formed in an L shape on the upper side, and an inlet portion 17a connected to the upper turbocharger 2 is disposed sideways. Yes. The outlet portion 17b communicating with the catalytic converter 9 is disposed downward. The housing 17 forms a bent portion 15 a bent in an L shape at a point immediately after the exhaust side of the diesel engine in the exhaust pipe portion 15. Further, a catalyst installation space is secured immediately below the bent portion 15a. The oxidation catalyst 5 is installed at a point immediately downstream of the secured bent portion 15a. Thereby, the oxidation catalyst 5 is installed as close to the engine main body 1 as possible (in order to increase the temperature rise characteristic when the engine is cold).

  A fuel addition valve 19 (additive injection valve) for injecting fuel (additive) such as light oil used in a diesel engine is provided at the center in the bending direction on the outer peripheral side of the bent portion 15a. The fuel addition valve 19 has a fuel injection part 19 a (injection hole) at the tip, and fuel is injected from the fuel injection part 19 a toward the inlet end face of the oxidation catalyst 5. The fuel addition valve 19 is installed on a mounting seat 20 provided in the housing 17 by retracting the fuel injection portion 19 a at the tip from the housing 17. That is, the fuel addition valve 19 is installed at an injection distance required for injection from the oxidation catalyst 5. Note that a port 21 for guiding the fuel injected from the fuel injection portion 19a into the housing 17 is formed in the installation seat 20. The fuel addition valve 19 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. It is used to burn and remove PM collected by the particulate filter 11 by the temperature rise obtained by the reaction (oxidation). The fuel addition valve 19 is injected with fuel by a control unit that controls the diesel engine, for example, the ECU 27, 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.

  Due to the injection operation of the fuel addition valve 19 performed at the bent portion 15a, the fuel required for the reaction of the catalyst is injected from the direction crossing the flow of the exhaust gas flowing through the bent portion 15a. It is made to be injected into. The direction of the fuel injection part 19a at this time is inclined in advance with reference to the time when exhaust gas during high-load operation of the diesel engine flows through the bent part 15a. Specifically, the fuel injected from the fuel injection unit 19a is injected toward a predetermined position, for example, the center of the end face of the inlet of the oxidation catalyst 5, while being pushed by the exhaust gas. For this reason, the direction of the fuel injection portion 19a is slightly inclined toward the inlet portion 17a in consideration of being pushed in advance by exhaust gas during high load operation.

On the other hand, an exhaust flow control valve 23 is provided in an exhaust pipe portion upstream from the fuel addition valve 19, for example, in a wall portion of a cylindrical mouth forming the inlet portion 17 a. More specifically, the exhaust flow control valve 23 is arranged at a point immediately upstream adjacent to the fuel addition valve 19.
The exhaust flow control valve 23 will be described. The reference numeral 24 denotes a damper type valve body 24 provided on the inner surface of the cylindrical mouth body so as to be opened and closed. The damper type valve body 24 is sized to open and close, for example, the upper half region of the cylindrical mouth body so as to control the flow of the exhaust gas flow toward the outer peripheral side of the bent portion 15a, and rotates toward the inlet portion 17a. The fulcrum 24a is arranged. More specifically, the valve body 24 is located between a fully open position indicated by a solid line in FIG. 1 in which the cylindrical mouth is fully opened and a fully closed position indicated by a two-dot chain line in which the cylindrical mouth is substantially halved. Is rotated and displaced.

The valve body 24 is connected to an actuator 25 for driving the valve portion such as an electric motor, which is installed outside the housing 17. Specifically, the valve body 24 and the actuator 25 are connected via a link mechanism 26. Thereby, the valve opening degree of the valve body 24 can be continuously displaced in the range from fully open to fully closed by driving the actuator 25.
The actuator 25 is connected to a control unit, for example, the ECU 27. The ECU 27 is set to control the flow rate of the exhaust gas flowing through the bent portion 15a regardless of the operating state of the diesel engine. In the control, for example, as shown in FIG. 2, when the exhaust gas flow rate is fast and the flow rate is high, the diesel engine is in a high load operation state (by detecting the engine speed and the accelerator opening), and the valve body 24 is fully opened. When the diesel engine is in a low load operation state where the flow rate of exhaust gas is low and the flow rate is low, the valve body 24 is fully closed, and a map is used in which there is no step in between.

  From the throttle control of the cylindrical mouth performed by the valve body 24 performed based on this map, the flow rate of the exhaust gas passing through the bent portion 15a toward the oxidation catalyst 5 is adjusted to be constant with reference to the exhaust gas flow during high load operation. The structure is made. Further, by controlling the exhaust gas flow toward the outer peripheral side of the bent portion 15a with the valve body 24, an exhaust gas flow having a constant flow velocity is always provided on the front end side of the fuel injection flow α injected from the fuel addition valve 19. It can be guided.

By controlling the exhaust gas flow, the fuel injected from the fuel addition valve 19 is uniformly supplied to the oxidation catalyst 5 as the preceding catalyst without being affected by the operating state of the diesel engine.
That is, the fuel injection will be described. Exhaust gas exhausted from the diesel engine during the operation of the automobile passes through the exhaust manifold 1a, the turbocharger 2, the oxidation catalyst 5, the NOx trap catalyst 8, and the particulate filter 11 to the outside air. Released.

During operation of such an automobile, regardless of high load operation, medium load operation, or low load operation, NOx contained in the exhaust gas is occluded in the NOx trap catalyst 8, and PM is also collected by the particulate filter 11. The
At this time, the valve opening degree of the valve body 24 of the exhaust flow control valve 23 is controlled based on the map shown in FIG. 2 performed by the ECU 27, and the exhaust gas flow rate toward the oxidation catalyst 5 is always set to the exhaust gas flow during the high load operation. The flow rate is adjusted to be the same.

Specifically, when the diesel engine is operating at a high load, the valve body 24 is positioned by the actuator 25 at the fully open position shown by the solid line in FIG. In this state, it is guided to the oxidation catalyst 5.
When the diesel engine is operating at a low load, the valve body 24 is fully closed and positioned as shown in FIG. 3 by the actuator 25, and the main flow of exhaust gas having a low flow velocity is caused by the restriction performed by the valve body 24. While the flow rate increases to the same level as during high-load operation, it passes through the course that is most biased toward the inner peripheral side of the bent portion 15a and travels toward the end face of the inlet of the oxidation catalyst 5.

  Further, when the diesel engine is operated at a medium load, the valve body 24 is positioned intermediately as shown in FIG. 4 by the actuator 25 according to the intermediate point determined by the map between fully open and fully closed, and the exhaust gas is exhausted. The main flow of the gas passes through a course biased toward the inner peripheral side of the bent portion 15a while being increased in flow rate to the same level as that during high-load operation due to the restriction performed by the valve body 24, and then toward the end face of the inlet of the oxidation catalyst 5.

The flow rate of the exhaust gas flowing through the bent portion 15a is kept constant by the valve opening degree of the valve body 24 corresponding to the operating state of the diesel engine.
Here, it is time to remove the stored NOx and the collected PM, and it is assumed that the fuel required for the removal is injected from the fuel addition valve 19. Then, the fuel is injected so as to cross the flow of the exhaust gas flowing through the bent portion 15 a and is injected to the end face of the inlet of the oxidation catalyst 5.

This fuel injection is performed when the diesel engine is in a high load operation as shown in FIG.
At this time, considering that the fuel addition valve 10 is already pushed by the exhaust gas, the fuel addition valve 10 is attached with an inclined injection direction so as to avoid the influence of the exhaust gas from the beginning, and as shown in FIG. In addition, the tip of the fuel injection flow from the fuel addition valve 19 is injected to a predetermined position at the inlet of the oxidation catalyst 5, that is, the center of the end face of the oxidation catalyst 5 while being pushed by the exhaust gas.

Further, the time when fuel injection is performed is the time of low load operation of the diesel engine as shown in FIG.
At this time, the main flow of the exhaust gas whose flow velocity is increased by the valve body 24 to the same level as the exhaust gas at the time of high load operation is the fuel injection flow from the fuel addition valve 19 as shown in FIG. In the same manner as during high-load operation, it is pushed from the lateral direction toward the inlet of the oxidation catalyst 5. Thereby, as shown in FIG. 3, the tip of the fuel injection flow from the fuel addition valve 19 has a behavior of being pushed by the exhaust gas as in the case of high load operation.

That is, the fuel is injected to a predetermined position at the inlet of the oxidation catalyst 5, that is, to the center of the end surface of the oxidation catalyst 5 even during low load operation where the flow rate and flow rate of the exhaust gas are small.
Further, the time when fuel injection is performed is during the middle load operation of the diesel engine as shown in FIG.
At this time, the main flow of the exhaust gas whose flow velocity is increased by the valve body 24 to the same level as the exhaust gas at the time of high load operation is the fuel injection flow from the fuel addition valve 19 as shown in FIG. In the same manner as during high-load operation, it is pushed from the lateral direction toward the inlet of the oxidation catalyst 5. As a result, as shown in FIG. 4, the tip of the fuel injection flow from the fuel addition valve 19 has a behavior of being pushed by the exhaust gas as in the high load operation.

In other words, the fuel is injected to a predetermined position at the inlet of the oxidation catalyst 5, that is, to the center of the end face of the oxidation catalyst 5 even during medium load operation where the flow rate and flow rate of the exhaust gas are small.
Of course, since the valve body 24 is controlled steplessly according to the operating state of the diesel engine, the tip of the fuel injection flow from the fuel addition valve 19 is the inlet of the oxidation catalyst 5 in any operating state. Is injected to the predetermined position, that is, the center of the end face of the oxidation catalyst 5.

Therefore, no matter what engine operating state the fuel is injected from the fuel addition valve 19, the injection direction of the injected fuel is kept constant, so that the fuel is always injected into a predetermined position of the oxidation catalyst 5. be able to.
As a result, the uneven distribution of fuel in the oxidation catalyst 5 is suppressed, and fuel can be supplied uniformly from the bent portion 15a to the oxidation catalyst 5, so that not only the oxidation catalyst 5 but also the downstream NOx trap catalyst 8 and particulates. The function of the filter 11 can be exhibited sufficiently. For this reason, the purification function of the exhaust gas purification device can be sufficiently exhibited. This is particularly effective when the flow of exhaust gas in the vicinity of the injection hole of the fuel addition valve 19 is easily affected by the bent portion 15a.

Moreover, the valve part 24 can respond | correspond rapidly to the driving | running state of any engine by being controlled continuously according to the driving | running state of a diesel engine.
Moreover, the structure in which the exhaust gas flow having a constant flow velocity is guided to the front end side of the injection flow from the fuel addition valve 19 by the valve body 24, the injection direction on the front end side where the penetrating force of the injected fuel is weakened. Since it is controlled, the optimum injection direction can be easily maintained.

  In addition, the valve body 24 is fully opened when the exhaust gas flow has the highest exhaust gas flow rate and flow rate during the high load operation of the diesel engine, and has the highest exhaust gas flow rate and flow rate during the low load operation of the diesel engine. The direction of the fuel addition valve 19 is set to a high load by using a control in which the exhaust valve flow is fully closed when the exhaust gas flow is small and the valve unit 24 is continuously opened to fully closed according to the operation state of the diesel engine. By simply setting according to the exhaust gas during operation, the optimal fuel injection direction can be easily maintained.

In addition, since the valve body 24 is arranged immediately upstream of the fuel addition valve 19, even when a digipot is accumulated at the tip of the fuel addition valve 19, the valve body 24 is fully utilized by utilizing the time when the valve portion 24 is fully opened. There is an advantage that it can be blown away with exhaust gas at a flow velocity, and it is difficult to deposit a digipot at the tip of the fuel addition valve 19.
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, an example is given in which the present invention is applied to an exhaust gas purification apparatus in which an oxidation catalyst is provided as a catalyst immediately downstream of a bent portion, and a NOx trap catalyst and a particulate filter are provided downstream thereof. First, an exhaust gas purification apparatus of another purification system, for example, an exhaust gas purification system in which a NOx trap catalyst is provided as a catalyst immediately downstream of the bent portion, a particulate filter is provided downstream thereof, and an addition valve is provided upstream of the NOx trap catalyst. The exhaust gas purification device may also be an exhaust gas purification device in which a NOx trap catalyst is provided as a catalyst immediately downstream of the bent portion, a NOx trap catalyst, an oxidation catalyst, and a particulate filter are provided downstream thereof, and an addition valve is provided upstream of the NOx trap catalyst. In short, an exhaust gas purification device in which a catalyst is disposed immediately downstream of the bent portion and a fuel addition valve is disposed upstream of the catalyst, or If the exhaust gas purification device provided with a selective reduction catalyst and the particulate filter immediately downstream of the additive injection valve may be applied to the present invention.

In one embodiment, the additive injection valve is provided at the bent portion. However, the additive injection valve may be provided at a straight exhaust pipe portion immediately upstream of the catalyst, for example, a straight portion formed between the bent portion and the catalyst upstream end. good.
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 one embodiment, a structure using a damper-type valve body as an exhaust flow control valve has been described as an example. However, the present invention is not limited to this, and an exhaust flow control valve having another valve structure may be used.

The side view which carried out the partial cross section which shows the structure of the exhaust-gas purification apparatus which concerns on one Embodiment of this invention with the state in which fuel is injected from a fuel addition valve at the time of high load driving | operation. The diagram which shows the operation | movement characteristic of the exhaust-flow control valve of the same exhaust gas purification apparatus. The side view which carried out the partial cross section which shows when fuel is injected from a fuel addition valve at the time of low load operation. The side view which carried out the partial cross section which shows when fuel is injected from a fuel addition valve at the time of a medium load driving | operation.

Explanation of symbols

1 Engine body 5 Oxidation catalyst (catalyst)
15 Exhaust pipe portion 15a Bending portion 19 Fuel addition valve (additive injection valve)
19a Fuel injection part (nozzle hole)
23 Exhaust flow control valve

Claims (3)

Directing exhaust gas exhausted from the engine to the external, and the exhaust pipe portion which is formed with a bent portion that is bent in an L shape,
A catalyst housed in a portion immediately downstream of the bent portion of the exhaust pipe portion ;
An additive injection valve that is provided on the outer peripheral side of the bent portion of the exhaust pipe portion, and injects the exhaust gas in a direction across the flow of the exhaust gas to supply the additive to a predetermined position of the catalyst;
The additive from the additive injection valve, which is provided in the exhaust pipe portion upstream from the additive injection valve and is pushed by the flow of exhaust gas passing through the L-shaped bent portion, keeps the predetermined position of the catalyst. exhaust gas purification system of an internal combustion engine, characterized by comprising an exhaust control valve for controlling the flow of pre-Symbol exhaust gas. 2. The exhaust gas purification device for an internal combustion engine according to claim 1 , wherein the exhaust flow control valve is provided on the exhaust pipe side wall on the outer peripheral side of the bent portion along with the additive injection valve. 2. The exhaust flow control valve is controlled so that a flow of exhaust gas in the vicinity of an injection hole of the additive injection valve becomes a predetermined flow according to an operating state of an engine. Or the exhaust-gas purification apparatus of the internal combustion engine of Claim 2 .

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