JPH0674023A - Exhaust gas purifying device of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve elimination efficiency of NOx in an engine in which fuel is injected to a cylinder head. CONSTITUTION:Fuel is directly injected to a cylinder by a fuel injection device 20 in an engine 10. Fuel utilized as a reductant is added to intake air flow by means of a first injector 110 mounted in an intake air pipe 50. Fuel is added to an exhaust gas by means of a second injector 120 mounted in an exhaust gas pipe 60. A catalyst 70 by which NOx is reduced is arranged, downstream from the exhaust gas pipe 60. The optimum quantity of HC is supplied by controlling two injectors in response to rotational speed of an engine and/or the condition of load by means of a controller 40.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a device for removing nitrogen oxides contained in the exhaust gas of an internal combustion engine (NO _X).

[0002]

2. Description of the Related Art Activated alumina (r-alumina), S ₁ O ₂ and Al are used as a means for removing NO _x in gases discharged from internal combustion engines such as gasoline engines and diesel engines.
Zeolite-based catalysts synthesized from ₂ O ₃ are known to be effective, and are disclosed, for example, in JP-A-63-283727 and JP-A-3-253713. Zeolite-based catalysts include, for example, mordenite and H-ZSM5.
However, this catalyst is effective as a NO _X reducing agent when hydrocarbon (HC) is present in an amount substantially equal to that of NO _X. Usually, the amount of HC contained in the exhaust gas is less than the amount of NO _X. In an engine that directly injects fuel into a cylinder of an engine, an injector for adding HC can be selectively disposed on the intake side or the exhaust side.
The applicant of the present application has proposed, as Japanese Patent Application No. 3-160088, a NO _X reduction device provided with an injector that injects fuel injected into the cylinder of the engine as a reducing agent to the intake side.

[0003]

FIG. 3 shows the engine speed N and torques T and HC of an engine having an injector on the intake side.
It is a graph which shows the relationship of injection quantity Q. When the engine is operating at a high speed (N ₁ ) and under high load, and trying to add a large amount of HC, the combustion noise becomes excessive, and in the case of a diesel engine, a large amount of smoke is generated and the required amount of HC is added. There was a problem that I could not do. FIG. 4 shows a case where an HC injection injector is provided on the exhaust side. In this configuration, there is a problem that the added HC is not sufficiently vaporized and cannot effectively function as a reducing agent when the exhaust temperature is low (N ₂ ) when the engine has a low load. The present invention provides an exhaust gas purifying apparatus for an internal combustion engine, which solves the above-mentioned conventional problems.

[0004]

SUMMARY OF THE INVENTION The present invention is an exhaust gas purifying apparatus for an internal combustion engine for injecting fuel into a cylinder head, the fuel being used as a reducing agent provided in an intake pipe connected to an intake port of the cylinder head. A first injector to add, a second injector provided in an exhaust pipe connected to an exhaust port of a cylinder head to add fuel as a reducing agent, and a reduction provided in an exhaust pipe downstream of the second injector. It is provided with a catalyst and a controller for controlling the first and second injectors according to the operating state of the internal combustion engine.

[0005]

The controller optimally controls the fuel injection amounts of the two injectors by using the engine speed and load as input information, and keeps the NO _X reduction efficiency at the maximum.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing the outline of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention. The engine main body 10 is a gasoline engine including a diesel engine and a fuel injection device, and includes an injector 22 that directly injects fuel into a fuel chamber inside a cylinder. The fuel in the fuel tank 30 is sent to the fuel injection pump 20 via the pipeline 32, pressurized by the fuel injection pump 20, and injected into the cylinder by the injector 22. Fuel injection pump 2
0 is a rotation sensor 42 and a controller lever sensor 44
The current engine speed and load condition are detected and sent to the controller 40 via lines 43 and 45.

The intake pipe 50 connected to the engine 10 is
The outside air is taken in through the cleaner 55 and the engine 10
Supply into the cylinder. The intake pipe 50 has a first portion for adding a reducing agent.
Injector 110 is provided. Hydrocarbon (HC) is used as the reducing agent, but in this device, the fuel of the engine 10 is diverted as the reducing agent. Fuel tank 30
The first pipe 34 that communicates with the fuel feeds the fuel to the first HC addition injector 110. The controller 40 outputs a control signal to the line 112 based on the engine speed and the load condition. With this control signal, the first injector 110 adds HC into the intake pipe 50.

The exhaust gas burned in the cylinder of the engine 10 is sent to the exhaust pipe 60. The exhaust pipe 60 has a catalytic converter 70, and NO _X in the exhaust gas is reduced and removed by a catalyst. The purified exhaust gas is discharged from the discharge port 62 to the atmosphere side. A second injector 120 for adding a reducing agent is attached to the exhaust pipe 60 that connects the exhaust port of the engine 10 and the catalytic converter 70. The second injector 120 is connected to the fuel tank 30 via the pipeline 36 and receives the supply of fuel as a reducing agent. The output of the controller 40 controls the second injector 120 via line 122 to add the required amount of HC into the exhaust pipe 60. Injectors for adding HC, which is a reducing agent, are provided in the intake pipe and the exhaust pipe, and the controller can operate each injector independently or simultaneously.

Therefore, as shown in FIG. 2, in the area A _{1 under} high load, only the second injector 120 is operated to add HC as a reducing agent to the exhaust side. Since the exhaust gas temperature is high at high load, H added to the exhaust side
C is fully vaporized. Further, no combustion noise due to addition of HC is generated. When the load is reduced from this state, the amount of HC to be added shifts to the region A ₃ . In this region, the exhaust gas temperature also tends to decrease, so the first injector 110 also operates and HC is also added to the intake side.
The HC added to the intake side is heated and vaporized in the cylinder, and the second
The injector 120 combines with HC added to the exhaust side to supply an optimal amount of reducing agent for reducing NO _X in the exhaust gas. Therefore, in this region, the first injector 110 and the second injector 1
20 is controlled synchronously by the controller 40. When the load is further reduced from this state and the region A ₂ is reached, the exhaust gas temperature is further lowered. Therefore, HC is added only to the intake side by the first injector 110 to heat and vaporize in the cylinder to improve the reduction efficiency.

[0010]

As described above, the present invention is an internal combustion engine that injects fuel into a cylinder, and uses HC as a reducing catalyst and a reducing agent.
In an apparatus for purifying exhaust gas, which is provided with an injector for adding, injectors are provided on an intake side and an exhaust side of an engine, and each injector is independently or simultaneously controlled by a controller. With this configuration, it is possible to achieve optimum addition of the reducing agent according to the operating state of the engine. Therefore, NO _x in the exhaust gas can be reduced and removed most effectively.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention.

FIG. 2 is an explanatory view showing the operation of the present invention.

FIG. 3 is an explanatory diagram showing an operation of a conventional technique.

FIG. 4 is an explanatory view showing the operation of the conventional technique.

[Explanation of symbols]

 10 Engine Body 20 Fuel Injection Pump 22 Injector 30 Fuel Tank 32 Pipeline 40 Controller 42 Rotation Sensor 44 Controller Lever Sensor 50 Intake Pipe 55 Cleaner 60 Exhaust Pipe 62 Discharge Port 70 Catalytic Converter 110 First Injector 120 Second Injector

Claims (2)

[Claims] 1. An apparatus for injecting fuel into a cylinder head of an internal combustion engine, a first injector provided in an intake pipe connected to an intake port of the cylinder head to add fuel as a reducing agent, and exhaust from the cylinder head. A second injector provided in an exhaust pipe connected to the port for adding fuel as a reducing agent, a reduction catalyst provided in an exhaust pipe downstream of the second injector, and a second injector depending on an operating state of the internal combustion engine. An exhaust gas purifying apparatus for an internal combustion engine, comprising a controller for controlling the first and second injectors. 2. The controller operates the second injector in the first region where the load is larger than a preset value, using the information from the sensor for detecting the engine speed and the load of the internal combustion engine as an input signal. A control signal is output, and if the load is in a second region smaller than a preset value, the first region is output.
Outputs a signal for controlling the operation of the injector, and when the load is in the third region between the first and second regions, the first
The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, which outputs a signal for simultaneously controlling the operation of the second injector.