JPH10252452A - Reducing method of hazardous substance in exhaust gas from internal combustion engine provided with exhaust catalyst and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce hazardous substances in exhaust gas effectively by providing at least one film (separation module) through which only oxygen molecules can permeate in a chamber and making oxygen rich to supply it to an internal combustion engine. SOLUTION: A secondary air pump 20 is provided as a reducing device of hazardous substances in exhaust gas in an internal combustion engine 10, and air 22 in which oxygen 22 is made rich is supplied to the secondary air pump 20. the air 22 in which oxygen is made rich is taken into from a pressure vessel and is mixed with ambient air in a mixer. An amount of air to be blown in is controlled by a secondary air blowing valve 30 which can be operated by an engine controller. The air 22 in which oxygen is made rich is supplied to this side of exhaust gas catalyst 52 in an exhaust pipe 50 of the internal combustion engine 10 through a pipe 40. The exothermic reaction occurs is the exhaust pipe 50 due to the supply of the air 22 in which oxygen is made rich, and the catalyst 52 is heated by the exothermic reaction to reduce hazardous substances in the exhaust gas effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an internal combustion engine provided with an exhaust gas catalyst, particularly an automobile, in which secondary air is supplied to the exhaust gas of the internal combustion engine by a secondary air pump as a function of the operating state of the internal combustion engine. The present invention relates to a method for reducing harmful substances in combustion exhaust gas from coal.

[0002]

2. Description of the Related Art Experience has shown that testing (eg, FTP7
In 5), approximately 80% of the total emissions of carbon monoxide (CO) and hydrocarbons (HC) are emitted during the first 120 seconds. This is due, on the one hand, to poor mixture formation in low-temperature engines and, on the other hand, to a lack of conversion of the catalyst which has not yet reached its operating temperature. Therefore, in order to solve this problem, the start-up time of the catalyst, that is, the elapsed time until the catalyst reaches its operating temperature, must be reduced. The reason is that this achieves a clear reduction of harmful substance emissions.

This can be achieved, for example, by supplying the exhaust gas with ambient air by means of a secondary air pump or a secondary air blower before the catalyst. A method for reducing harmful substances in the combustion exhaust gas of such an internal combustion engine and a device for carrying out the method are known, for example, from DE-A 41 41 946. In this case, secondary air is supplied to the exhaust gas of the internal combustion engine by a secondary air pump in order to increase the exhaust gas temperature as a function of the operating state of the internal combustion engine, before the catalyst. This is performed, for example, in a fuel-rich warm-up operation (excess fuel) by blowing air into the exhaust system in front of the catalyst for a short time after starting. This excess air oxidizes HC and CO in the exhaust system at sufficient temperature levels, thereby creating a more desirable high exhaust gas temperature. On the other hand, this hotter exhaust gas serves to quickly bring the catalyst to its operating temperature.

Furthermore, it is known to increase the exhaust gas temperature and thus reduce the catalyst start-up time by incorporating pure oxygen (O ₂ ) into the fresh air that is drawn in.

[0005] A method for reducing pollutants in the combustion exhaust gas from such internal combustion engines and a device for carrying out the method is known, for example, from DE 44 04 681 A1. In this case, it is designed such that the oxygen (O ₂ ) of the intake air is enriched by a membrane provided only in the room and permeable only to oxygen molecules (O ₂ ).

A problem with such a method is that the entire engine control must be determined by the O ₂ -rich intake air. For this reason, a significant increase in engine control engagement is required. Eventually, the overall engine management of the internal combustion engine must be changed.

[0007]

It is therefore possible to provide an exhaust gas catalyst of the type mentioned at the outset, which makes it possible to reduce the catalyst start-up time and thus reduce the harmful substances in the combustion exhaust gas in as simple a technical manner as possible. It is an object of the present invention to provide a method for reducing harmful substances in combustion exhaust gas from an internal combustion engine.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for reducing harmful substances in combustion exhaust gas from an internal combustion engine equipped with a catalyst of the type described at the outset, according to the invention. The problem is solved by increasing the (O ₂ ) content. By increasing the O ₂ content of the secondary air supplied, that is, by O ₂ enrichment of the exhaust gas in front of the catalyst, the oxidation conditions in front and in the catalyst of the catalyst is improved in a very advantageous manner, thereby catalyst The start-up time is reduced, so that a reduction in the pollutants in the combustion exhaust gas is achieved. Furthermore, it is advantageous that the volumetric flow rate of the air can be reduced as a whole when the oxygen content of the blown air is increased. Hereby, the cooling of the engine exhaust gas is reduced, which advantageously also serves to reduce the start-up time of the catalyst.

Purely in principle, various methods are conceivable for increasing the oxygen content in the secondary air.

[0010] For example, oxygen may be taken out of a gas cylinder mounted on an automobile and supplied to a secondary air pump.

In this case, the completely consumed oxygen compressed gas cylinder must be replaced or refilled, which requires very high technical and structural costs.

[0012] Therefore, a particularly advantageous embodiment is O
_{2 In} order to increase the content, the secondary air is designed to be supplied through a membrane provided only in the chamber, permeable only to oxygen molecules, a so-called separation module. In this manner, the O ₂ -rich secondary air may be continuously generated and supplied to the exhaust gas as needed by using the separation module mounted on the vehicle. Therefore, in this case, for example, an oxygen compressed gas cylinder or the like is not required at all.

Another very advantageous embodiment of the method is that the O ₂ -enriched secondary air is first generated in a separation module and then mixed with the exhaust gas of the internal combustion engine before being mixed in the pressure tank. And is designed to be supplied to the exhaust gas as a function of the operating conditions in a later operating cycle. As described above, the enrichment of the oxygen of the secondary air to be supplied to the exhaust gas later is performed in an operation state in which the secondary air is not required to be blown, for example, during a full load operation of the vehicle. In a later operating cycle, for example during a cold start or during a warm-up process, the secondary air enriched with O _2, which is then stored intermediately, can be supplied to the exhaust gas.

The membrane may, for example, be composed of a mixture-permeable ceramic which requires a driving force of O ₂ partial pressure drop through the membrane. Therefore, in an advantageous embodiment, the required partial pressure drop in the membrane is designed to be generated by a secondary air pump, so that no additional blowers need be used.

[0015] The present invention further relates to an exhaust gas comprising a secondary air pump in which the secondary air is supplied to the exhaust gas of the internal combustion engine by a secondary air pump as a function of the operating state of the internal combustion engine before the exhaust gas catalyst. The present invention relates to an internal combustion engine equipped with a catalyst, and more particularly to a device for reducing harmful substances in combustion exhaust gas from automobiles.

In this case, it is the object of the present invention to provide a device of the type mentioned at the outset, which makes possible a more effective reduction of pollutants from the combustion exhaust gas with as little technical expenditure as possible.

In order to solve this problem, an apparatus for reducing harmful substances in combustion exhaust gas from an internal combustion engine equipped with an exhaust gas catalyst of the type described above, thereby enriching the secondary air with oxygen (O ₂ ) Means according to the invention are provided which can be implemented.

In an advantageous embodiment, this means comprises:
It is designed to include at least one membrane (separation module) provided in the chamber and permeable only to oxygen molecules. This makes it possible to enrich oxygen on a vehicle.

Advantageously, the separation module is designed to be provided downstream of the secondary air pump. In this way, the pressure formed by the secondary air pump, for example a mixture permeability O ₂ in a membrane made of ceramics required to enrich, it may be used generated under partial pressure drop in the membrane.

[0020] For O ₂ in order to use the operating cycle after the internal combustion engine to store enriched air, O ₂ is the enrichment is secondary air temporarily storable pressure tank isolation It is provided downstream of the module.

Other features and advantages of the invention will be apparent from the following description of several embodiments, as well as from the drawings.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the apparatus for reducing harmful substances in the combustion exhaust gas of an internal combustion engine 10 according to the present invention includes a secondary air pump 20, and the secondary air pump 20 has a reference numeral 22. Ambient air enriched in oxygen, indicated by arrows, is supplied. In this case, oxygen or oxygen-enriched air is taken in, for example, from a pressure vessel (not shown) and is mixed in via an ambient air mixing device. Oxygen may be taken in, for example, from an oxygen container mounted on the vehicle (not shown), or oxygen may be generated on the vehicle in a manner described further below.

Control of the amount of air blown (not shown)
This is performed by the secondary air injection valve 30 operable from the engine control device, and is set by the engine control device according to the oxygen component of the blown air. In this case, one starts with a fixed mixing ratio.

The oxygen-enriched air is supplied to the exhaust pipe 50 of the internal combustion engine 10 via the pipe 40 before the catalyst 52.

The supply of oxygen-enriched air causes an exothermic reaction in the exhaust pipe 50 which heats the catalyst and thus reaches its operating temperature during the catalyst start-up time, for example, during a cold start. To reduce the elapsed time.

In the second embodiment shown in FIG. 2, the same elements as those of the first embodiment are denoted by the same reference numerals, and therefore, the description of the first embodiment will be omitted. It is referred to as it is. In contrast to the first embodiment, in the second embodiment shown in FIG.
Is provided. By means of this separation module 70 which is provided in the room and comprises a membrane which is permeable only to oxygen molecules, the oxygen-enriched air required for blowing can be supplied to the vehicle and the secondary air blower 20 Only fired during startup. In this way, whenever the secondary air blower is activated, the oxygen enrichment of the secondary air is also achieved at the same time.

The embodiment shown in FIG. 3 is different from the embodiment shown in FIG. 2 in that a pressure tank 80 is provided on the downstream side of the separation module 70. In a later operating cycle, the secondary air enriched in the secondary air generated by the separation module 70 is temporarily stored so that it can be supplied to the exhaust gas, for example, during the cold start of the internal combustion engine. In this case, it is advantageous for the secondary air pump to be started in an operating state in which no secondary air is required. The secondary air pump may be used in continuous operation.

[0028] The secondary air pump is advantageously started in a driving cycle with excess energy, for example in coasting operation or in the braking of a motor vehicle. This avoids, in particular, the large consumption of fuel for generating oxygen-enriched air. The secondary air injection may be performed while operating via the secondary air injection valve 30 without operating the secondary air pump. Various types of membranes can be used to generate oxygen-enriched blowing air in the separation module 70.

For example, zirconium dioxide (ZrO ₂ )
Ceramic membrane or perovski stone (Pero)
vskit) may be used.

In the case of zirconium dioxide, the acquisition of oxygen from the surrounding air is effected by the voltage difference across the membrane, which is obtained by the current flow between the two sides of the membrane via an external conductor connection. In this case, the enrichment of the oxygen (O ₂ ) thus obtained is achieved via the voltage, in particular without additional mechanical pumping work. In this case, no extra compressor is required to fill the pressure tank 80, since the voltage can set very high pressures (> 10 ²⁰ bar).

In a mixture permeable ceramic membrane, such as a Perovskiite membrane, the oxygen partial pressure drop to be generated through the membrane acts as a driving force. This driving force may be generated by the secondary air pump 20.

The heating of such zirconium dioxide membranes, as well as the mixture permeable membranes, only at high temperatures (> 400 ° C.) has meaningful transmission coefficients for economical use, so that heating such membranes is a simple process. The separation module is provided as close to or within the exhaust pipe 50 as possible.

Furthermore, enrichment of oxygen can be achieved by a plastic film, for example, a polymer film. With such a polymer membrane, an oxygen content of 40% by volume or less can be achieved. In order to operate the separation module 70 with a polymer membrane, mechanical separation power in the form of a pumping or compression work for generating a partial pressure drop is required. This pumping and compression work may be generated, for example, by using the kinetic energy to be reduced during braking by a suitable coupling of the pump / compressor and the brake. Further, a secondary air pump 20 may be used to create a pressure drop.

[Brief description of the drawings]

FIG. 1 is a partial cutaway view of a first embodiment of a device for reducing harmful substances in combustion exhaust gas from an internal combustion engine provided with an exhaust gas catalyst according to the present invention.

FIG. 2 is a partial cutaway view of a second embodiment of the apparatus for reducing harmful substances in combustion exhaust gas from an internal combustion engine provided with an exhaust gas catalyst according to the present invention.

FIG. 3 is a partial cutaway view of a third embodiment of the apparatus for reducing harmful substances in combustion exhaust gas from an internal combustion engine provided with an exhaust gas catalyst according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Internal combustion engine 20 Secondary air pump 22 Ambient air enriched with oxygen 30 Secondary air injection valve 40 Piping 50 Exhaust pipe 52 Exhaust gas catalyst 70 Membrane 80 Pressure tank

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI F01N 3/24 ZAB F01N 3/24 ZABF (72) Inventor Steffen Franke Germany 71701 Schwiebbe Rudingen, Danziger Straße 2 (72 ) Inventor Horst Harndorf, Germany 71701 Schwiebe Rudingen, Aoenweg 25

Claims (8)

[Claims] An exhaust gas of an internal combustion engine (10) is supplied to a secondary air pump (2) as a function of an operating state of the internal combustion engine (10).
0), secondary air is supplied by the exhaust gas catalyst (5
In the method for reducing harmful substances in combustion exhaust gas from an internal combustion engine (10), particularly from an automobile, the oxygen (O ₂ ) content of the supplied secondary air is increased. A method for reducing harmful substances in combustion exhaust gas from an internal combustion engine provided with a gas catalyst. _{2. In} order to increase the O ₂ content, secondary air is supplied through a membrane (separation module 70) provided only in the chamber and permeable only to oxygen molecules. The method of claim 1 wherein the method comprises: 3. The secondary air enriched in O ₂ is first intermediately stored in a pressure tank (80) before being mixed with exhaust gas of an internal combustion engine (10), and the operating state is determined in a subsequent operation cycle. 3. The method according to claim 1, wherein the exhaust gas is supplied as a function of the exhaust gas. 4. The method as claimed in claim 1, wherein the required partial pressure drop in the membrane is generated by a secondary air pump (20). 5. The exhaust gas of the internal combustion engine (10) is supplied with secondary air by a secondary air pump (20) as a function of the operating state of the internal combustion engine (10) before the exhaust gas catalyst (52). In an internal combustion engine (10) equipped with an exhaust gas catalyst (52) including a secondary air pump (20), particularly in a device for reducing harmful substances in combustion exhaust gas from automobiles, the oxygen (O ₂ ) A device for reducing harmful substances in combustion exhaust gas from an internal combustion engine equipped with an exhaust gas catalyst, wherein the device is provided with means for enabling the enrichment of ₂ ). 6. The apparatus according to claim 5, wherein said means comprises at least one membrane (separation module 70) provided in the chamber and permeable only to oxygen molecules. 7. Apparatus according to claim 5, wherein the separation module is provided downstream of the secondary air pump. 8. A pressure tank (80) capable of temporarily storing O ₂ -enriched secondary air is provided in a separation module (7).
The apparatus according to any one of claims 5 to 7, wherein the apparatus is provided downstream of (0).