JPH08200047A - Exhaust emission control device for engine - Google Patents

Abstract

PURPOSE: To simplify a structure and reduce a cost by utilizing a part of supercharging air, and spraying reducer of a catalyst for purifying exhaust gas. CONSTITUTION: A nozzle 7 for adding light oil as reducer is arranged in an exhaust pipe 5 arranged upstream from a catalyst 6 interposed on the exhaust pipe 5, and communicated with the intake passage arranged downstream from the intake compressor 3A of a turbo charger 3, for example, communicated with a position arranged in the vicinity of the connecting part of an intake pipe 2 and an intake manifold 4. An air leading-in pipe 11 for leading air for spraying reducer is arranged on the nozzle 7, a part of supercharging air is led to the nozzle 7, and light oil is sprayed toward the front surface of the catalyst 6. Therefore, atomization of light oil is promoted, and a part of supercharging air is utilized for atomization of light oil so as to simplify a structure and reduce a cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control system for an engine, and more particularly to a reducing agent for an exhaust emission control system for removing nitrogen oxides contained in exhaust gas of an engine with a catalyst interposed in an exhaust passage. Related to atomization supply technology.

[0002]

Background Art Exhaust gas recirculation (EGR) is well known as an effective means for reducing the concentration of nitrogen oxides (NOx) contained in the exhaust gas of an engine. A method of interposing and treating NOx with this catalyst is also conceivable. In this case, in order to efficiently reduce NOx, it has been proposed to provide a device for adding light oil as a reducing agent in the exhaust passage on the upstream side of the catalyst (see Japanese Utility Model Laid-Open No. 5-87218).

[0003]

By the way, in such an exhaust emission control device, since the light oil, which is the reducing agent of the catalyst, is evenly added to the front surface of the catalyst, the atomization of the light oil is promoted and its vaporization It is necessary to provide means for improving the mixing property. There is a method of spraying light oil using compressed air for atomization of this light oil, but an air compressor is newly required as an air source for supplying compressed air, and even if the air compressor is provided in advance, It is necessary to enhance the ability, which leads to a complicated structure and a high cost.

In view of the above-mentioned conventional problems, the present invention therefore eliminates nitrogen oxides contained in the exhaust gas of an engine.
An object of the present invention is to simplify the structure and reduce the cost of an exhaust gas purifying apparatus that removes with a catalyst provided in an exhaust passage by using a part of supercharged air to spray a reducing agent.

[0005]

Therefore, according to the invention of claim 1, the nitrogen oxide contained in the exhaust gas of the engine is
In an exhaust purification device that removes with a catalyst interposed in the exhaust passage, a nozzle for adding a reducing agent to the exhaust passage on the upstream side of the catalyst, and a communication with the intake passage on the downstream side of the intake compressor of the supercharger, An air introduction passage for introducing air for spraying the reducing agent to the nozzle, and an opening / closing valve interposed in the air introduction passage are included.

According to a second aspect of the present invention, an air storage buffer tank and a check valve located upstream of the buffer tank are provided upstream of the opening / closing valve in the air introduction passage.

[0007]

In the invention of claim 1, part of the supercharged air is guided to the nozzle, and the reducing agent such as light oil is sprayed on the front surface of the catalyst. Therefore, atomization of the reducing agent such as light oil is promoted, the vaporization and mixing properties thereof are improved, and the reducing agent such as light oil can be uniformly added to the front surface of the catalyst. Moreover, since a part of the supercharged air is used to atomize the reducing agent such as light oil, it is not necessary to newly add an air compressor or increase the capacity of the air compressor, and an air introduction pipe is added. Therefore, the structure can be simplified and the cost can be reduced.

According to the second aspect of the invention, when the reducing agent such as light oil is required to be added despite the low supercharging pressure by the supercharger, the air stored in the buffer tank is introduced into the nozzle, A reducing agent such as light oil can be added without any problem.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, an intake pipe 2 of a diesel engine 1
An intake compressor 3A of a supercharger (turbocharger) 3 is installed in the intake manifold, and the intake pipe 2 is connected to an intake manifold 4.

Further, the exhaust pipe 5 is provided with the turbocharger 3 described above.
Exhaust gas turbine 3B is installed in the exhaust pipe 5, and NOx
A purification catalyst 6 is provided. A nozzle 7 for adding light oil as a reducing agent is provided in the exhaust pipe 5 on the upstream side of the catalyst 6.
Is provided. A light oil supply pipe 8 is connected to the nozzle 7, and the light oil supply pipe 8 communicates with a light oil tank 9. Further, a light oil injection pump 10 is interposed in the light oil supply pipe 8.

On the other hand, the intake passage on the downstream side of the intake compressor 3A of the turbocharger 3, for example, a position near the connecting portion between the intake pipe 2 and the intake manifold 4, is communicated with, and air for reducing agent spraying is introduced into the nozzle 7. An air introducing pipe 11 is provided as an air introducing passage. An opening / closing valve 12 is interposed in the air introducing pipe 11. The light oil injection pump 10 and the opening / closing valve 12 are respectively controlled according to the engine operating state to properly adjust the addition timing and the addition amount of the light oil.

That is, a rotation speed sensor 13 for detecting an engine rotation speed and a load sensor 14 for detecting an engine load (for example, a control rack position of a fuel injection pump).
And a pump controller 15 for controlling the light oil injection pump 10, and the opening / closing valve 1.
A valve controller 16 for controlling the valve 2 is provided. Detection signals output from the rotation speed sensor 13 and the load sensor 14 are input to the controllers 15 and 16, respectively, and the controllers 15 and 16 are based on the engine rotation speed and the load, and the light oil injection pump, respectively. 10 and the on-off valve 12 are controlled respectively.

FIG. 2 is a flow chart for explaining the light oil addition control, which is executed by starting the engine, reads the engine speed and the load from the detection signals of the rotation speed sensor 13 and the load sensor 14, and adds the light oil corresponding thereto. The amount is obtained from the data map, and the pump 10 and the opening / closing valve 12 are operated by the pump driving voltage and the valve opening / closing operation corresponding to these, and high pressure injection of light oil from the nozzle 7 to the catalyst 6 is performed (S1 to S4). .

With such a configuration, light oil as a reducing agent for the catalyst 6 is added from the nozzle 7 to the front surface of the catalyst. still,
The optimum amount of light oil addition does not necessarily have to be increased proportionally according to the engine operating state, and may be decreased to prevent excessive temperature rise of the catalyst when the engine exhaust temperature exceeds a predetermined value. Will be needed.

According to this structure, a part of the supercharged air is guided to the nozzle 7 so that the light oil is sprayed on the front surface of the catalyst 6, so that the atomization of the light oil is promoted and the vaporization / mixability thereof is improved. Thus, the light oil can be uniformly added to the front surface of the catalyst 6. Further, since a part of the supercharged air is used for atomizing the light oil, it is not necessary to newly add an air compressor or increase the capacity of the air compressor, and only an air introduction pipe is added. Therefore, the structure can be simplified and the cost can be reduced.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, a buffer tank 17 for storing air and a check valve 18 located upstream of the buffer tank 17 are provided upstream of the opening / closing valve 12 of the air introducing pipe 11. In such a configuration, air is stored in the buffer tank 17 when the light oil is not added, that is, when the open / close valve 12 is closed.

Then, when the light oil addition is required despite the low supercharging pressure by the turbocharger 3, the air stored in the buffer tank 17 is introduced into the nozzle 7,
Light oil is added without any problem. If a buffer tank 17 with a pressure maintaining function as shown in FIG. 4 is provided, the air stored in the buffer tank 17 at a certain pressure or higher can be introduced into the nozzle 7.

That is, in this buffer tank 17, a pressing plate 19 is provided in the tank body 17A, one end of a cylindrical bellows 20 is attached to the peripheral edge of the pressing plate 19, and the other end of the bellows 20 is attached. The peripheral edge is fixed to the inner surface of the end wall of the tank body 17A. An air hole 21 is formed in a portion of the end wall of the tank body 17A surrounded by the bellows 20. Further, inside the bellows 20, both ends of the coil spring 22 are locked to the inner surface of the pressing plate 19 and the inner surface of the end wall of the tank body 17A.
Is provided, and the pressing plate 19 is always set to be biased by the coil spring 22 in the direction opposite to the end wall of the tank body 17A.

Reference numeral 23 is a stopper that regulates the position of the pressing plate 19 when the bellows 20 is expanded. Therefore, when air is introduced into the tank body 17A to reach a predetermined pressure,
The pressing plate 19 is pressed against the elastic force of the coil spring 22 by the air pressure, and air is released from the air hole 21, and the bellows 20 contracts to be in a state as shown in FIG. 4B. In this state, the air pressure in the tank body 17A is maintained at a predetermined pressure, the air maintained at this predetermined pressure is introduced into the nozzle 7, and the addition of light oil is performed without any problem.

[0020]

As described above, according to the invention of claim 1, since a part of the supercharged air is used for atomizing the reducing agent such as light oil, a new air compressor is required. In addition, it is not necessary to increase the capacity of the air compressor, the structure can be simplified, and the cost can be reduced.

According to the second aspect of the present invention, the air stored in the buffer tank is introduced into the nozzle when the reducing agent such as light oil needs to be added despite the low supercharging pressure by the supercharger. The reducing agent is added without any problem.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the invention described in claim 1.

FIG. 2 is a flowchart for explaining the operation of the above embodiment.

FIG. 3 is a system configuration diagram of an embodiment of the invention according to claim 2;

FIG. 4 is a sectional view illustrating a pressure maintaining function of the buffer tank according to the second aspect of the invention.

[Explanation of symbols]

 1 Diesel engine 3 Supercharger (turbocharger) 3A Intake compressor 6 Catalyst 7 Nozzle 8 Light oil supply pipe 9 Light oil tank 10 Light oil injection pump 11 Air introduction pipe 12 Open / close valve 17 Buffer tank 18 Check valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisashi Akagawa 1-chome, Ichome, Ageo City, Saitama Prefecture Nissan Diesel Industry Co., Ltd.

Claims (2)

[Claims] 1. An exhaust emission control device for removing nitrogen oxides contained in exhaust gas of an engine by a catalyst interposed in an exhaust passage, wherein a nozzle for adding a reducing agent to an exhaust passage upstream of the catalyst. An air introduction passage communicating with an intake passage on the downstream side of the intake compressor of the supercharger and introducing air for reducing agent spraying into the nozzle; and an opening / closing valve interposed in the air introduction passage. An exhaust purification system for an engine, which is characterized in that it is configured. 2. A buffer tank for storing air and a check valve located upstream of the buffer tank are provided upstream of the opening / closing valve in the air introducing passage. Exhaust gas purification device for the engine described.