JPH0396612A - Method and apparatus for processing exhaust gas - Google Patents

Abstract

PURPOSE: To save expenses for covering a main converter with a catalyst by arranging the main converter and a front end converter in parallel to an exhaust duct so that exhaust gas can be guided to the main converter when the main converter is in catalyst conversion possible conditions. CONSTITUTION: A catalyst converter housing 60 is laid on the way of an exhaust gas duct 12 connected to an internal combustion engine and a catalyst front end converter 16 and a main catalyst converter 14 are arranged between an inlet room 62 and an outlet room 64 inside thereof. The inlet room 62 is divided into two areas 62a, 62b with partition 66 between both converters 16, 14 and the partition 66 is partially provided with a rotationally movable vane 68. During starting the cold engine, the vane 68 is closed to carry exhaust gas only through the front end converter 16. When the temperature of exhaust gas reaches a sufficiently high value to operate the main converter 14 and switching conditions are established, the vane 68 is rotationally moved to an opening position as shown by a dotted line to carry exhaust gas through both converters 16, 14.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an exhaust gas treatment method and an exhaust gas treatment device, and particularly relates to an exhaust gas treatment method and exhaust gas treatment method that performs a catalytic conversion process on exhaust gas in a catalytic conversion operation. It relates to a gas treatment device.

(Prior Art) When an internal combustion engine starts from a cold state, a large amount of pollutants are generated.It is possible to reduce the emission of pollutants in the exhaust gas by using a converter located downstream from the exhaust gas outlet of the engine. This is a known technology. The most common type of converter of this type used in gasoline engines is the catalytic converter.

This type of converter also reduces the amount of C in the exhaust gas, for example.
It is also used in diesel engines to reduce O and non-flammable hydrocarbons and soot or other solid particles.

Converters of this type require a certain minimum allowable temperature for the reactants fed to them in order to perform their function. If the exhaust gas is flowed through the converter before this minimum allowable temperature is reached, the pollutants in the exhaust gas will not be converted and will be released into the environment.

A typical three-use catalytic converter contains materials that oxidize CD and non-flammable hydrocarbons, and materials that reduce NOx. Due to the delay in activation of the catalytic converter before the operating temperature is reached under conversion operating conditions in which catalytic conversion is possible, pollutants such as CO and non-combustible hydrocarbons are released unconverted.

On the other hand, it is known that significant emissions of NOx occur only when normal operating temperatures are reached.

In order to reduce this delay at the start of the reaction in the catalytic converter, for example, it is possible to electrically heat the exhaust gas before it enters the catalytic converter, to heat the catalytic converter additionally, or to heat the catalytic converter overnight. Methods such as maintaining the temperature at high temperatures through insulation have been proposed, and these methods have shown at least theoretical possibility.

(Problem to be Solved by the Invention) When electrically heating the exhaust gas of a catalytic converter, the batteries or generators normally installed in automobiles cannot supply the necessary large current unless modified at an expensive cost. It is not possible. Keeping the catalytic converter hot with thermal insulation creates overheating problems, especially when operating at full load.

To reduce the response time of the catalytic converter, proposals have already been made to operate a small pre-converter designed to be cold-started, placed close to the engine on the inlet side of the main catalytic converter. In this system, the pre-converter is isolated using a bypass when the main catalytic converter reaches a temperature sufficient for operation. The exhaust gas then flows directly into the main catalytic converter for catalytic conversion, but these converters are located away from the engine to avoid overheating the front and main catalytic converters. There is a need to.

This device therefore has the disadvantage of a complex and expensive construction and the need for expensive catalyst-coated surfaces in the main catalytic converter and catalyst-coated surfaces in the pre-converter necessary for catalysis. For this reason, it has not been put into practical use, and in current systems, whenever a pre-converter is used, exhaust gas is routed through both the pre-converter and the main converter.

This catalytic pre-converter, which has a smaller capacity, heats up more quickly and takes care of removing pollutants even before the main catalytic converter is activated. However, this produces undesirable side effects, resulting in pressure losses that affect the engine, especially at full load.

The present invention has been made in view of the state of the art in the treatment of exhaust gases of this type, as described above, and one object of the invention is to provide a system for the treatment of such exhaust gases, which is designed to utilize the advantages of a pre-converter without producing undesirable side effects. The purpose of the present invention is to obtain a method and apparatus of the type. A further object of the invention is to provide a method and apparatus that takes into account the need for economical production.

A further object of the invention is to provide a method and apparatus that ensures reducing the cost of applying a catalytic coating to a main catalytic converter. A second object of the invention is to keep the space required for the installation of the device as small as possible.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method in which a main converter and a pre-converter that perform a catalytic conversion operation are arranged in parallel in an exhaust duct through which exhaust gas from an engine flows. established,
When the main converter reaches a conversion operation condition that allows catalytic conversion operation, the exhaust gas is guided to the main converter and the exhaust gas is subjected to catalytic conversion processing.

In order to achieve the above object, the present invention provides an apparatus including an engine and an exhaust gas having a first flow path and a second flow path arranged parallel to each other through which exhaust gas from the engine flows. a duct, a pre-converter provided in the first flow path, and a main converter provided in the second flow path;
The exhaust duct includes a setting device that forms at least one of the first flow path and the second flow path within the exhaust duct.

(Operation) In order to achieve the objects of the invention which are clear from the description, claims and drawings, the exhaust gas is introduced in parallel through the pre-converter and the main converter as soon as the conversion operating conditions are reached. Under operating conditions, the main converter has reached an operating temperature at which catalytic conversion is possible, at which temperature the main converter catalytically converts the exhaust gas.

According to a simple embodiment of the invention, outside conversion operating conditions, exhaust gas is routed through the pre-converter and the main converter is bypassed. Another advantageous embodiment of the invention provides that, outside conversion operating conditions, the exhaust gas is first sent via the pre-converter and then via the main converter, so that the main converter heats up to the required operating temperature at a particularly rapid rate. be done.

In a further possible embodiment according to the invention, a catalytic conversion takes place between the pre-converter and the main converter, this operation being made possible by adding catalytically active material to the exhaust gas flowing through the converter.

Normal gasoline and diesel engines start with excess fuel. There is therefore a risk of catalytic oxidation of the CO during the start-up phase, and the oxidation of non-flammable hydrocarbons is incomplete or does not occur at all due to the insufficient amount of air. Therefore, according to another possible embodiment of the invention, secondary air is added to the exhaust gas in a known manner before it enters the converter. According to a particularly advantageous embodiment of the invention, the preconverter is heated by waste heat from the engine.

Another aspect of the invention comprises an internal combustion engine and a main converter placed on its exhaust gas duct to cooperate with a pre-converter designed for cold start conditions, the exhaust gas duct comprising two parallel It has a flow path. The first flow path defines a flow path through the pre-converter and the second flow path defines a flow path through the main converter. The two flow paths are provided with setting devices that selectively switch the exhaust gas flow through the first flow path or the second flow path, and further through the first flow path and the second flow path. It will be done.

In another aspect of the invention, the exhaust gas duct has a first section located upstream from the converter and a second section located downstream from the converter, and wherein the first flow path is connected to the first section. Adjacent to the section and directing flow through the pre-converter, a second flow path directs flow through the main converter and is further provided with a setting device. This setting device is the first
in the position, the first and second passages are disposed in series between the first and second parts, while in the second position the first and second passages are disposed in series between the first and second parts. Arrange in parallel.

According to an advantageous aspect of the invention, first and second flow channels and a connecting duct are provided, which connect the inlet chamber connected to the first part and the outlet chamber connected to the second part. placed in a common housing between the two. In the first setting, the setting device separates the part of the inlet chamber coupled to the T-section from the part coupled to the second flow path and the coupling duct;
separating the portion of the outlet chamber coupled to the second flow path and the coupling duct from the portion of the outlet chamber coupled to the second flow path and the second portion. The second setting, on the other hand, negates the separation effect between the two parts of the inlet chamber and the two parts of the outlet chamber and blocks the coupling duct.

In yet another aspect of the invention, the setting device that is reconfigurable between two end positions is comprised of a first vane in the inlet chamber and a second vane in the outlet chamber. This setting device has a configuration in which in one position the chamber is separated into respective parts and in another position at least one vane covers the coupling duct and the two vanes are coupled together for combined movement. It has become.

In a next advantageous embodiment of the invention, the exhaust gas duct has a first part located upstream from the pre-converter, a second part located downstream from the main converter and between the pre-converter and the main converter. It consists of a placed connecting part. The coupling part can be shut off by a first valve arrangement and has a first bypass duct extending from the first part parallel to the preconverter and can be shut off by a second valve arrangement. This first bypass duct opens into the connection between the first valve arrangement and the main converter, and parallel to the main converter there is a second bypass duct, which is connected to the pre-converter and the first valve arrangement. Extending from the connecting part between the devices and opening into the second part, the two valve devices are combined for simultaneous operation.

In a further advantageous embodiment of the invention, the preconverter is equipped with a heat storage device, which is charged with waste heat from the engine without requiring additional expended energy. In another aspect, the converter is configured with a catalytic converter. In a further advantageous embodiment of the invention, the exhaust gas duct at a point upstream from the converter is provided with a connection capable of opening and closing the secondary air. Considering the normal mode of automobile operation, the heat storage device may be designed to be highly efficient at low engine speeds and low loads.

{Example} Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing the configuration of the main parts of the first embodiment;
The figure is an explanatory diagram showing the structure of the main part of the second embodiment, and FIG. 3 is an explanatory diagram showing the structure of the main part of the third embodiment.

In the preferred embodiment of the invention shown in FIG.
The portion 12a connected to the engine 10 is connected to a catalytic converter housing 60. Within the catalytic converter housing 60 there is an inlet chamber 62 and an outlet chamber 64 between which the catalytic converters (shown schematically) or catalytic pre-converter 16 and the main catalytic converter 14 are located. The catalytic preconverter 16 is located in an inlet chamber 62 adjacent to the inlet of the exhaust gas duct 12 . Between the catalytic pre-converter 16 and the main converter 14, the inlet chamber 62 is divided into two parts 62a, 62 by a partition 66.
b, the partition 66 has two parts 62 of the entrance chamber.
The pivot vane 68 is partially shaped so that a, 62b can be joined or split together.

When starting from cold, the vanes 68 are closed so that exhaust gas flows only through the preconverter 16. As soon as the switching condition is met, the vanes 68 are pivoted to the open position shown in dotted lines, and the exhaust gas can immediately flow through the preconverter 16 and the main converter 14. The pressure resistance caused by the upstream converter is therefore virtually non-existent here. Although in this embodiment the catalytic preconverter 16 is provided with a constant flow of exhaust gas, the catalytic preconverter 16 is additionally operated for conditions other than the conversion operating conditions obtained during cold start. The main catalytic converter should be designed to operate for conversion operating conditions found when the engine is producing high power and running at high speeds.

The switching of the blade 68 is performed when the temperature of the exhaust gas changes to the main converter 1.
4 operation is reached only when a sufficiently high value is reached to obtain conversion operating conditions and before the main converter is covered with hot exhaust gases from the outlet chamber 64. This allows the main catalytic converter 14 to slow down operation with virtually no delay when the vanes 68 are switched.

If the main converter 14 requires additional heat,
As shown in FIG. 2, exhaust gas leaving the preconverter 16 can be routed through the main converter 14 into a portion 12b of the exhaust gas duct 12 located downstream from the housing 60. For this purpose, a coupling duct 70 is placed in the housing 60 parallel to the pre-converter 16 and the main converter 14 to couple the inlet chamber 62 and the outlet chamber 64 therebetween, the outlet 72 of the duct 70 being To accomplish this action, another vane 74 (in combination with vane 68 for movement) is provided. In one configuration, when the vane 68 opens, it covers the outlet 72, and in the other configuration it closes a partition 76 located in the outlet chamber 64 between the coupling duct 70 and the main converter 14.

If the vanes 68 close, the partition 76 also closes and the coupling duct 70 becomes free, so that the exhaust gas first passes out of the part 62a of the inlet chamber 62 coupled to the exhaust gas duct 12 via the preconverter 16. , and then out of the part 64a of the outlet chamber 64 which is connected to the preconverter 16 and to the coupling duct 70 via the coupling duct 70. This exhaust gas is separated by vanes 68 and returns to the part 62b of the inlet chamber 62 connected to the main catalytic converter 14 and then via the main converter 14 to the other part 64b of the outlet chamber 64, i.e. the part of the exhaust gas duct 12. Return to 12b.

If feather 68. 74 are switched together, the exhaust gas flows from the inlet chamber 62 via the main converter 14 and the pre-converter 16 straight into the outlet chamber 64, while the passage through the coupling duct 70 is closed by the vane 74. ing. Apart from the device of FIG. 1, the vanes 68 can rotate together with the vanes 74 to cover the coupling duct 70.

If space is a constrained application, the accommodation of a housing enclosing the inlet chamber, outlet chamber, main catalytic converter, precatalytic converter and coupling duct presents an inconvenience. In such cases, the device according to FIG. 2 may be replaced by a device according to FIG. They can be placed in order in the direction. In FIG. 3, the first part 12a of the exhaust gas duct 12 coming from the engine 10 is connected to a pre-converter 16, which is connected by a connecting part 12c to the main converter 14, which is connected to the second part of the exhaust gas duct 12. part 12b
is connected to the downstream side. The coupling part 12c has a first valve arrangement 80, with which the coupling between the upstream converter 16 and the main converter 14 can be interrupted in the direction of exhaust gas flow.

A first bypass duct 82 is placed parallel to the preconverter 16 and extends from the first part 12a of the exhaust gas duct to the first
A connecting portion 12c between the valve device 80 and the main converter 14
and has a second valve arrangement 84 . A second bypass duct 86 branches off from the coupling part 12c between the pre-converter 16 and the first valve arrangement 80, short-circuits the main converter 14 and opens downstream thereof into the second part 12b of the exhaust gas duct. There is.

During the cold start phase the first valve arrangement 80 is open and the second valve arrangement 84 is open.
is closed, thus allowing exhaust gases exiting the preconverter 16 to flow via the main converter 14 and the second bypass duct 86 to the second part 12b of the exhaust gas duct. Since main converter 14 is disabled during this phase of operation, there is no need to flow all exhaust gas through main converter 14. The portion of the flow through main converter 14 is sufficient to heat main converter 14 to the temperature necessary for its operation.

As soon as the temperature required for operation of the main converter 14 is reached, the first valve arrangement 80 is closed and the second valve arrangement 84 is opened, so that the exhaust gas flows on the one hand via the pre-converter 16;
On the other hand, it is fed two parallel flow paths flowing through the main converter 14. These flow paths diverge from the first part 12a of the exhaust gas duct at the opening of the first bypass duct 82 and join again into the second part 12b at the opening of the second bypass duct 86.

Thus, according to the embodiment, exhaust gas is efficiently catalytically converted. For operating phases in which the exhaust gas temperature is insufficient for the main converter, a pre-converter designed for low mass flows is provided. This pre-converter does not impose a high resistance to the pressure of the exhaust gas flow when the internal combustion engine operates at high power or high rotational speeds, since the pre-converter has a small flow cross section. The reason is that in this case the flow cross section of the main converter and the pre-converter is used by the exhaust gas.

Moreover, the dimensions of the catalytically coated surface of the main converter are reduced by an amount equal to the working surface of the pre-converter coupled in parallel to the main converter. The absence of bypass ducts and the ability to house the preconverter and main converter in a common housing offers the advantage of a design that is extremely simple, compact and economical to manufacture.

(Effects of the Invention) As explained in detail above, according to the present invention, the pre-converter performs the catalytic conversion operation until the main converter reaches the conversion operation condition, and when the main converter reaches the conversion operation condition, the main converter Since the front converter performs the catalytic conversion operation, the exhaust gas from the engine is efficiently subjected to the catalytic conversion process. The device is smaller and occupies less space, and the cost of catalytic coating of the main converter is reduced, reducing manufacturing costs.

[Brief explanation of drawings]

FIGS. 1 to 3 are explanatory diagrams showing the configurations of essential parts of first to third embodiments of the present invention. DESCRIPTION OF SYMBOLS 10... Engine, 12... Duct, 14... Main converter, 16... Front converter, 60... Housing, 62... Inlet chamber, 64... Outlet chamber, 66
...Partition, 68...Blade, 70...Duct 72
...Exit, 74...Blade, 76...Partition, 80
... Valve device, 82... Duct, 84... Valve device,
86...Duct.

Claims (1)

[Claims] 1. In the exhaust duct through which exhaust gas from the engine flows,
A main converter and a pre-converter that perform a catalytic conversion operation are arranged in parallel, and when a conversion operating condition is reached in which the main converter can perform a catalytic conversion operation, the exhaust gas is guided to the main converter and the exhaust gas undergoes a catalytic conversion process. An exhaust gas treatment method characterized by: 2. In the method for treating exhaust gas according to claim 1, the exhaust gas is flowed to the pre-converter outside the conversion operating conditions;
A method for processing exhaust gas, characterized in that the main converter is set to a bypass state. 3. In the method for treating exhaust gas according to claim 1, outside the conversion operating conditions, the exhaust gas is flowed to the pre-converter;
A method for treating exhaust gas, characterized in that the exhaust gas is then passed to a main converter. 4. The method for treating exhaust gas according to any one of claims 1 to 3, characterized in that catalytic conversion is performed in a pre-converter and a main converter. 5. A method for treating exhaust gas according to claim 4, characterized in that a catalytically active material is added to the exhaust gas flowing through the pre-converter and the main converter. 6. The exhaust gas treatment method according to any one of claims 1 to 5, characterized in that secondary air is added to the exhaust gas before it flows into the front converter and the main converter. Method. 7. The exhaust gas treatment method according to any one of claims 1 to 6, characterized in that the pre-converter is heated with waste heat of the engine. 8. An engine, an exhaust duct through which exhaust gas from the engine flows and having a first flow path and a second flow path arranged parallel to each other, and a front exhaust duct provided in the first flow path. a main converter provided in the second flow path, and a setting device that forms at least one of the first flow path and the second flow path in the exhaust duct. Exhaust gas treatment equipment. 9. In the exhaust gas treatment device according to claim 8, under conversion operating conditions in which the main converter can perform catalytic conversion operation, the first
and the second flow path are arranged in parallel with each other in the exhaust duct by a setting device, and outside the conversion operating conditions, the first flow path
and the second flow path are arranged in series with each other in the exhaust duct by a setting device. 10. The exhaust gas treatment device according to claim 8, wherein a connecting duct is provided between the first flow path and the second flow path in parallel to each other, and the first flow path and the second flow path are connected to each other. The passageway and the coupling duct are housed in a common housing between the inlet and the outlet of the exhaust duct, and in converting operating conditions the coupling duct is blocked by a setting device and the first passageway and the second passageway are closed. are arranged in parallel with each other, and outside the conversion operating conditions, the second flow path and the coupling duct are separated from the inlet side of the exhaust duct by the setting device, and the first flow channel and the coupling duct are separated from each other by the setting device. An exhaust gas treatment device characterized in that the exhaust gas is separated from the outlet side of the exhaust duct. 11. The exhaust gas treatment device according to claim 10,
a first blade, the setting device being disposed on the inlet side of the exhaust duct and rotatable so as to separate the second flow path and the coupling duct from the inlet side or blocking one end side of the coupling duct; and a second blade arranged on the outlet side of the exhaust duct and rotatable so as to separate the first flow path and the coupling duct from the outlet side or to block the other end side of the coupling duct. An exhaust gas treatment device characterized by: 12. The exhaust gas treatment device according to claim 11, wherein the first blade and the first blade are configured to be integrally driven. 13. The exhaust gas treatment device according to claim 8, wherein the connecting portion is disposed between the upstream converter and the main converter and can be shut off by a first valve device, and a second valve is disposed in parallel with the upstream converter. a first bypass duct which can be shut off by a device and connects to the coupling part between the first valve device and the main converter; and a first bypass duct arranged parallel to the main converter and between the pre-converter and the first valve device. An exhaust gas treatment device comprising: a second bypass duct connected to the coupling portion. 14. The exhaust gas treatment device according to claim 13, wherein the first valve device and the second valve device are configured to be integrally driven. 15. The exhaust gas treatment device according to any one of claims 8 to 14, wherein the pre-converter is configured to operate as a heat storage device. 16. The exhaust gas treatment device according to any one of claims 8 to 15, wherein the converter is a catalytic converter. 17. The exhaust gas treatment device according to any one of claims 8 to 16, characterized in that a secondary air supply combination is provided on the upstream side of the exhaust gas duct. 18. The exhaust gas treatment device according to claim 15,
An exhaust gas treatment device characterized in that the heat storage device is configured to have high efficiency when the engine speed is low and the load is low.