JPH05113144A - Nox reduction device - Google Patents

Abstract

PURPOSE:To effectively decrease a quantity of NOx by providing an intake air meter injector in the intake air system of an engine of a type for injecting fuel staying inside cylinders, and supplying a quantity of HC required for decreasing the quantity of NOx also to the intake air system through a process of injecting fuel. CONSTITUTION:In the case of a diesel engine 3 provided, in its cylinder, with injector 5 for injecting fuel in which a catalyst converter 7 is provided in its exhaust system, an injector 14 for fuel injection is installed in its intake air system 2 in the similar way, and also an NOx sensor 15 is installed on the outlet side from the catalyst converter 7. An engine load condition is detected at first from outputs of an engine rotational speed sensor 11 and a control lever sensor 12 in a controller 13, and an injection basic quantity from the intake air system injector 14 is found out by map retrieval by means of the detected result, and thereby a corrected injection quantity is found out from a detected value of NOx concentration and a quantity obtained by adding this corrected injection quantity to the injection basic quantity is injected from the injector 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle NOx reduction device.

[0002]

2. Description of the Related Art As a device for reducing NOx contained in exhaust gas of a diesel engine, a device for supplying and reducing a reducing agent (eg, ammonia) into the exhaust gas has been conventionally known. For example, in JP-A-64-83816,
The amount of NOx in the exhaust gas is detected by a NOx analyzer,
Ammonia is blown into the exhaust gas according to the detected NOx amount.

[0003]

However, the above-mentioned conventional technique has a problem in that ammonia is required, which is an odorous gas which must be handled severely. An object of the present invention is to solve such a problem.

[0004]

In order to solve the above-mentioned problems, in the NOx reduction device of the present invention, an intake system injector provided so as to inject fuel into the intake system of an engine of the type that injects fuel into the engine cylinder. And a NOx sensor provided at the exhaust pipe outlet behind the catalytic converter arranged in the exhaust pipe of the engine, and controlling the fuel injection amount from the intake system injector according to the engine load state and the NOx sensor detection value. I decided to have a controller that does.

[0005]

[Operation] In an engine of the type that injects fuel in the cylinder of an engine such as a diesel engine, the amount of HC generated is less than the amount required by the NOx reduction catalytic converter. Therefore, the amount of HC in the exhaust gas is increased by injecting fuel into the intake system. The injection amount is adjusted according to the engine load state and the detection value of the NOx sensor provided at the exhaust pipe outlet.

[0006]

EXAMPLES Recently, a zeolite-based catalyst has been known as a catalyst used for reducing NOx in a diesel engine, and a non-selective catalytic reduction method using the same is considered promising. This reduction method is a method of reducing in the presence of CO, HC, H ₂ and C, and HC (hydrocarbon) plays an important role among them.

The amount of HC required for the reduction is NO
The ratio of x to the amount of HC / NOx is 1 or more, but the ratio of the amount of HC naturally generated in the diesel engine to the amount of NOx is 1 or less. Therefore, although it is necessary to replenish the amount of HC by some method, the present invention replenishes it by injecting fuel into the intake system.

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the NO related to the embodiment of the present invention.
x reduction device. In FIG. 1, 1 is a filter, 2
Is an intake system, 3 is an engine, 4 is a fuel injection pump, 5 is an in-cylinder injector, 6 is an exhaust system, 7 is a catalytic converter,
Reference numeral 8 is an exhaust pipe outlet, 9 is a fuel tank, 10 is a fuel pipe, 11 is an engine rotation sensor, 12 is a control lever sensor, 13 is a controller, and 14 is an intake system injector.

The intake system 2 is a generic term for an intake pipe and an intake manifold, and the exhaust system 6 is a generic term for an exhaust pipe and an exhaust manifold. In the present invention,
The intake system 2 is provided with an intake system injector 14 for injecting the same fuel as that used for the engine 3. Further, the NOx sensor 15 is provided on the outlet side of the catalytic converter 7 provided in the middle of the exhaust pipe, that is, on the exhaust pipe outlet portion 8.

Intake system 2 by intake system injector 14
The fuel injected into the engine enters the engine cylinder in a state where it is slightly mixed with the intake air.
Unlike the fuel injected from, most of it comes out to the exhaust system 6 in an unburned state. As a result, a large amount of HC exists in the exhaust system 6 as compared with the case of a normal diesel engine in which fuel is not injected by the intake system injector 14. This is supplied to the catalytic converter 7 and is used for reduction.

FIG. 2 is a diagram showing the characteristics of the NOx sensor 15. The NOx sensor 15 has an electric resistance value,
The resistance value of the NOx sensor on the vertical axis of FIG. 2 indicates its electric resistance value. Since the NOx sensor resistance value increases as the NOx concentration increases, the NOx concentration (NOx amount) can be detected by monitoring the change in the resistance value.

FIG. 3 is a diagram showing the relationship between the ratio of HC amount / NOx amount and the NOx purification rate. The required amount of HC can be determined using the relationship in this figure. Next, it will be explained. As can be seen from FIG. 3, the amount of HC may be increased to increase the NOx purification rate. However, the degree of increase of the characteristic curve of FIG. 3 becomes gentler as it approaches the level of 100% indicated by the dotted line, so a large amount of HC is required to slightly increase the rate, which is not very efficient. Therefore, if the NOx is below the legal regulation,
x Determine the target value of the purification rate, and corresponding HC amount / NO
If the x amount is obtained, the required amount of HC can be obtained based on it.

FIG. 4 is a diagram showing the relationship between the intake system injection amount / engine in-cylinder injection amount ratio and the HC amount. Since the required HC amount is obtained in FIG. 3, by applying it to the relationship in this figure, the intake system injection amount /
The ratio of the in-cylinder injection amount of the engine is obtained. The in-cylinder injection amount is an amount that is injected in the engine 3 according to the engine load. The engine load state can be known from the engine speed from the engine speed sensor 11 and the control lever position from the control lever sensor 12.

FIG. 5 is a flow chart for explaining the control operation in the present invention. Step 1 ... Detects the engine load state. This is detected based on the engine speed detected by the engine speed sensor 11 and the control lever position detected by the control lever sensor 12.

Step 2 ... Corresponding relationship (map) is set in advance in which the basic injection amount as the base amount of the fuel injected by the intake system injector 14 is set to what value in what engine load state. .. Then, in accordance with the map, the injection basic amount according to the engine load state detected in step 1 is calculated in step 2.

Step 3 ... By the NOx sensor 15, the N at the exhaust pipe outlet 8 behind the catalytic converter 7
The Ox concentration (NOx amount) is detected (see FIG. 2). Step 4 ... Examine whether the detected NOx concentration is equal to a predetermined value. As this predetermined value, a value in a range that satisfies the legal regulation standard is appropriately set. The required HC amount changes according to the set value (see FIG. 3). If it is equal to the predetermined value, the process returns to step 1.

Step 5: If it is not equal to the predetermined value, the correction injection amount for correcting the injection amount in the intake system injector 14 is calculated. If the HC amount is insufficient, the correction injection amount is a positive value, and if the HC amount is excessive, the correction injection amount is a negative value. Step 6 ... An amount obtained by adding the corrected injection amount to the injection basic amount is injected from the intake system injector 14.

Although the engine 3 is a diesel engine in the above example, even if it is a gasoline engine,
Like the diesel engine, the present invention can be applied to any type that injects fuel in the engine cylinder (a normal gasoline engine injects fuel on the intake side).

[0019]

As described above, according to the NOx reduction device of the present invention, in an engine of a type such as a diesel engine that injects fuel in an engine cylinder, the amount of HC required for NOx reduction is intaken. It is also replenished by injecting fuel into the system. As described above, since the material used is a fuel that is used and is not an odorous gas such as ammonia, it is not necessary to handle the fuel strictly.

Further, by injecting fuel into the intake system, smoke is also reduced.

[Brief description of drawings]

FIG. 1 is a NOx reduction device according to an embodiment of the present invention.

FIG. 2 is a diagram showing characteristics of a NOx sensor.

FIG. 3 is a diagram showing the relationship between the ratio of HC amount / NOx amount and the NOx purification rate.

[FIG. 4] Ratio of intake system injection amount / engine in-cylinder injection amount and HC
Diagram showing the relationship with quantity

FIG. 5 is a flowchart illustrating a control operation according to the present invention.

[Explanation of symbols]

 1 Filter 2 Intake System 3 Engine 4 Fuel Injection Pump 5 Cylinder Injector 6 Exhaust System 7 Catalytic Converter 8 Exhaust Pipe Outlet 9 Fuel Tank 10 Fuel Pipe 11 Engine Rotation Sensor 12 Control Lever Sensor 13 Controller 14 Intake System Injector

Claims (1)

[Claims] 1. An intake system injector provided for injecting fuel into an intake system of an engine of a type that injects fuel in an engine cylinder, and an exhaust pipe rearward of a catalytic converter arranged in an exhaust pipe of the engine. N provided at the exit
An NOx reduction device comprising an Ox sensor and a controller that controls a fuel injection amount from an intake system injector according to an engine load state and a NOx sensor detection value.