JPH11148342A - Internal combustion engine and its operation method for automobile in particular - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to operate an internal combustion engine for automobiles in particular and the internal combustion engine for automobiles in particular, which can completely oxidize hydro-carbon and/or carbon monoxide in any case. SOLUTION: An internal combustion engine 1 for automobiles in particular, which is provided with a means burning air-fuel mixture in a combustion chamber 4, and a catalyst 12 for disposing of the exhaust emission generated in combustion is defined. In this case, the catalyst 12 has a storage catalyst 13 and oxidation catalyst 14. An air supply means is provided on this side of the oxidation catalyst 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel / air mixture which is burned in a combustion chamber and the exhaust gas generated during the combustion is treated by a catalyst, wherein the catalyst reduces nitrogen oxides and produces hydrocarbons and hydrocarbons. In particular, it relates to a method for operating an internal combustion engine of a motor vehicle, which is suitable for oxidizing carbon monoxide. The invention further comprises means for combusting the fuel / air mixture in the combustion chamber and a catalyst for treating the exhaust gases generated during the combustion, wherein the catalyst comprises a storage catalyst and an oxidation catalyst, especially for automobiles. The present invention relates to an internal combustion engine.

[0002]

2. Description of the Related Art Such a method and such an internal combustion engine are known from DE 195 06 980.
In this German patent, the exhaust gas generated during the combustion is fed to a catalyst provided in particular for reducing nitrogen oxides. Such a catalyst acts on the one hand as an oxidation catalyst. This means that when the oxygen is insufficient, the catalyst extracts oxygen from the nitrogen oxides, and this oxygen oxidizes hydrocarbons generated during combustion and carbon monoxide generated simultaneously. Similarly, when oxygen is excessive, the oxidation catalyst itself can reduce nitrogen oxides. However, this reaction does not take place due to the excess oxygen,
The oxidation catalyst instead utilizes excess oxygen. On the other hand, the catalyst also serves as a storage catalyst. This means that when oxygen is in excess, the storage catalyst will accept the nitrogen oxides generated during combustion. When oxygen is deficient, the storage catalyst releases released nitrogen oxides again.

[0003] The use of an oxidation catalyst and a storage catalyst in the catalyst results in nitrogen oxides not being utilized by the oxidation catalyst when oxygen is in excess is received by the storage catalyst and stored intermediately. When oxygen is insufficient,
Nitrogen oxides released again from the storage catalyst will be reduced by the oxidation catalyst.

However, storage catalysts can only accept nitrogen oxides up to a certain limit. As a result, the storage catalyst must release nitrogen oxides again after a certain filling time to receive the nitrogen oxides. This release occurs when oxygen is scarce. The internal combustion engine may also be controlled (open loop and / or closed loop) to produce a rich fuel / air mixture. In these conditions, the storage catalyst releases nitrogen oxides again, which are used to oxidize hydrocarbons and / or carbon monoxide in the oxidation catalyst. At this time,
Nitrogen, water and carbon dioxide are generated as reaction products.

It has been found that excess hydrocarbons and carbon monoxide are often present upon release of such storage catalysts. This excess hydrocarbon and carbon monoxide cannot be oxidized by the oxygen released from the nitrogen oxides, and thus the hydrocarbons and / or carbon monoxide are released into the atmosphere as harmful substances.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method as described at the outset and an internal combustion engine which allow in each case the complete oxidation of hydrocarbons and / or carbon monoxide. .

[0007]

This object is achieved according to the invention in the manner described at the outset by supplying air to the catalyst. In an internal combustion engine as described at the outset, this problem is solved according to the invention by providing an air supply before the oxidation catalyst.

[0008] By supplying air, it is possible to oxidize hydrocarbons and carbon monoxide with oxygen released from nitrogen oxides and oxygen present in the supplied air. Therefore, even if hydrocarbons and carbon monoxide are present in excess, they can be decomposed by the supplied air. As a result, the entire hydrocarbon and carbon monoxide can be converted to water and carbon dioxide. Thus, noxious hydrocarbons and / or carbon monoxide are no longer released to the atmosphere.

The method according to the invention can be used, on the one hand, for internal combustion engines in which fuel is injected into the intake manifold and which is preferably driven by a lean fuel / air mixture.
On the other hand, the method according to the invention may be used for internal combustion engines in which fuel is injected directly into the combustion chamber.

It is particularly expedient for air to be supplied during the course of operation of the internal combustion engine which indicates a lack of oxygen. This corresponds to an operating process in which a large excess of hydrocarbons and / or carbon monoxide is generated. By supplying air during this operation, hydrocarbons and carbon monoxide can be completely oxidized.

In a preferred embodiment of the invention, a pump for supplying air is provided. In this way, air can be reliably supplied even when an overpressure exists in the catalyst due to the exhaust gas passing therethrough.
Furthermore, the pump can be controlled by a control device as a function of the respective operating process and can be switched on and off.

In a preferred embodiment of the invention, a valve which can be controlled, in particular by a control device, is arranged upstream of the oxidation catalyst. In this way, the supply of air to the oxidation catalyst can be very accurately (open and / or closed loop).
Can be controlled.

It is particularly expedient for the check valve to be arranged before the oxidation catalyst. In this way, it is ensured that the exhaust gas does not leak before being oxidized and / or that the exhaust gas enters the pump.

[0014] Other features, uses and advantages of the invention will be apparent from the following description of an embodiment of the invention which is illustrated in the drawings. In this case, all features described or illustrated form an object of the invention by itself or in a preferred combination, have nothing to do with their relationship in the claims or their citations, and Has nothing to do with their form or expression.

[0015]

FIG. 1 shows an internal combustion engine 1 in which a piston 2 can reciprocate within a cylinder 3. A combustion chamber 4 is provided in the cylinder 3, and an intake pipe 6 and an exhaust pipe 7 are connected to the combustion chamber 4 via a valve 5. Further, the injection valve 8 and the spark plug 9
Is attached.

In the first mode of operation of the internal combustion engine 1, namely stratified operation, fuel is injected from the injector 8 into the combustion chamber 4 during the compression stroke formed by the piston 2 and, moreover, the ignition plug is positioned. It is injected close to 9 and in time just before the top dead center of the piston 2. At this time, the fuel is ignited by the ignition plug 9 and, therefore, the piston 2 is driven by the expansion of the ignited fuel in the subsequent working stroke.

In the second mode of operation of the internal combustion engine 1, namely homogeneous operation, fuel is injected from the injector 8 into the combustion chamber 4 during the intake stroke formed by the piston 2.
At the same time, the fuel injected by the sucked air is swirled, whereby the fuel is distributed almost uniformly in the combustion chamber 4. Thereafter, the fuel / air mixture is compressed during the compression stroke, at which time it is ignited by the spark plug 9. The piston 2 is driven by the expansion of the ignited fuel.

In the stratified operation, similarly to the homogeneous operation, the crankshaft 10 is rotated by the driven piston, and finally the wheels of the automobile are driven through this rotation.

In stratified operation and homogeneous operation, the injection valve 8
The amount of fuel injected into the combustion chamber 4 is controlled by the control device 11 in particular so as to reduce fuel consumption and / or to reduce emissions (open loop and / or closed loop). For this purpose, the control device 11 is provided with a microprocessor, which stores in a storage medium, in particular a read-only memory (ROM), a program suitable for executing said (open-loop and / or closed-loop) control. ing.

The exhaust pipe 7 is connected to the catalyst 12, and the catalyst 12
Storage catalyst for storing nitrogen oxides (in other words,
A storage catalyst 13 and an oxidation catalyst 14 for oxidizing hydrocarbons and carbon monoxide in particular are provided. The storage catalyst 13 is disposed before the oxidation catalyst 14 in the flow direction of the exhaust pipe.

As a function of the fuel / air ratio of the fuel / air mixture set by the control unit 11, the stoichiometric ratio of oxygen-excess or lean mixture, oxygen-deficient or rich mixture or fuel-air in the combustion chamber 4 of the internal combustion engine 1. Is formed. The rich mixture is set, in particular, in homogeneous operation of the internal combustion engine 1, while the lean mixture is present, in particular, in stratified operation, in order to reduce fuel consumption.

Even when oxygen is in excess, the oxidation catalyst 14 itself can reduce the nitrogen oxides supplied to the catalyst 12 and thus extract oxygen from the nitrogen oxides. However, because of the excess oxygen, the oxidation catalyst 14 accepts the excess oxygen. Nitrogen oxides not utilized by the oxidation catalyst 14 are received and stored by the storage catalyst 13. This indicates a filling process of the storage catalyst 13, in which nitrogen oxides flow into the catalyst 12.

When oxygen is insufficient, the storage catalyst 13 releases the stored nitrogen oxides again. This is storage catalyst 1
3 shows a release process in which nitrogen oxides flow out of the catalyst 12. There is not enough oxygen due to lack of oxygen, and thus the oxidation catalyst 14 extracts oxygen from the nitrogen oxides, thereby oxidizing hydrocarbons and carbon monoxide generated during combustion.

The storage catalyst 13 cannot store nitrogen oxides without limitation. For this purpose, the filling process must be limited in time. Thereafter, the storage catalyst 13 must release nitrogen oxides again. This charging and discharging takes place by controlling (open loop and / or closed loop) the control device 11 and supplying the corresponding oxygen. The respective oxygen supply is effected by a corresponding operation of the internal combustion engine 1 in a homogeneous operation or a stratified operation. In particular, a throttle valve 15 present in the intake pipe 6 is used to regulate the supply of oxygen.

A means for supplying air to the catalyst is provided between the storage catalyst 13 and the oxidation catalyst 14.

In the embodiment shown in FIG. 1, this means comprises a pipe 16 which is connected to a pump 17 which can control the catalyst 12. A further controllable valve 18 is incorporated in the pipe 16. The pump 17 can be switched on and off, for example, by the control device 11. The valve 18 can likewise be opened and closed by the control device 11, for example. As an alternative, it is also possible to provide a check valve or the like instead of the controllable valve 18 as a means and / or to keep the pump 17 continuously switched on without controllably shutting off.

In the embodiment shown in FIG. 1, when the storage catalyst 13 is charged, that is, when the oxygen is insufficient, the pump 1
7 is turned on and valve 18 is opened. This provides air and thus additional oxygen to the oxidation catalyst 14. When oxygen is deficient, ie in a rich fuel / air mixture, the production of hydrocarbons and / or carbon monoxide is increased, the hydrocarbons and / or carbon monoxide being on the one hand released by the nitrogen oxides and On the other hand, it is oxidized by additional oxygen from the air.

When filling the storage catalyst 13, the valve 18 is closed. Pump 17 may be left on or shut off.

As an alternative, it is possible to open the valve 18 and leave the pump 17 switched on when the storage catalyst 13 is charged, ie when there is an excess of oxygen, and thus when a lean fuel / air mixture is present. In this case, valve 1
8 may be replaced by a check valve as described above, which in particular prevents exhaust gas from flowing into the pump.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an embodiment of an internal combustion engine of a motor vehicle according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Piston 3 Cylinder 4 Combustion chamber 5, 18 Valve 6 Intake pipe 7 Exhaust pipe 8 Injection valve 9 Ignition plug 10 Crankshaft 11 Control device 12 Catalyst 13 Storage catalyst 14 Oxidation catalyst 15 Throttle valve 16 Pipe 17 Pump

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F01N 3/32 F01N 3/32 EB

Claims (6)

[Claims] 1. A fuel / air mixture is burned in a combustion chamber (4), and exhaust gas generated during the combustion is supplied to a catalyst (1).
2) wherein the catalyst (12) is suitable for reducing nitrogen oxides and oxidizing hydrocarbons and / or carbon monoxide, in particular for internal combustion engines (1) of motor vehicles
The method according to claim 1, wherein air is supplied to the catalyst (12). 2. The method as claimed in claim 1, wherein the internal combustion engine is supplied with air during an operating phase indicating an oxygen deficiency. 3. Means for burning a fuel / air mixture in a combustion chamber (4), and a catalyst (12) for treating exhaust gas generated during the combustion, wherein the catalyst (12) is provided. In the internal combustion engine (1) for a vehicle, particularly having a storage catalyst (13) and an oxidation catalyst (14), air supply means is provided before the oxidation catalyst (14). ). 4. The internal combustion engine (1) according to claim 3, further comprising a pump (17) for supplying air. 5. The internal combustion engine (1) according to claim 3, wherein a valve (18) which can be controlled by a control device (11) is arranged in front of the oxidation catalyst (14). ). 6. The internal combustion engine (1) according to claim 3, wherein the check valve is arranged before the oxidation catalyst (14).