KR19980080272A - Method and apparatus for reducing harmful substances in combustion exhaust gas from an internal combustion engine having an exhaust gas catalyst - Google Patents

Abstract

A method and apparatus for reducing harmful substances in combustion exhaust gas from an internal combustion engine, in particular from an automobile, having an exhaust gas catalyst supplied with secondary air to the exhaust gas of the internal combustion engine which is a function of the operating state of the internal combustion engine by a secondary air pump. The present invention is characterized in that, in the simplest possible technical form, harmful substances in the combustion exhaust gas are surely reduced by shortening the catalyst start-up time, and the oxygen (O ₂ ) content of the supplied secondary air is increased.

Description

Method and apparatus for reducing harmful substances in combustion exhaust gas from an internal combustion engine with an exhaust gas catalyst

The present invention is directed to the reduction of harmful substances in an internal combustion engine, in particular combustion exhaust gas from an automobile, having an exhaust gas catalyst supplied with secondary air by a secondary air pump as a function of the operating state of the internal combustion engine to the exhaust gas of the internal combustion engine. It is about a method.

Experience has shown that about 80% of the total emissions of carbon monoxide (CO) and hydrocarbons (HC) from internal combustion engines are released during the first 120 seconds of the test (eg FTP75). This cause is, on the one hand, poor mixture formation in low temperature engines and, on the other hand, a lack of conversion of the catalyst which has not yet reached operating temperature. Therefore, in order to solve this problem, it is necessary to shorten the startup time of the catalyst, that is, the elapsed time until the catalyst reaches its operating temperature. The reason is that this achieves a definite reduction of the toxic substance emission gas.

This can be achieved, for example, by supplying ambient air to the exhaust gas directly in front of the catalyst by means of a secondary air pump or secondary air blowing. Such a method of reducing harmful substances in combustion exhaust gas of an internal combustion engine and an apparatus for carrying out the method are already known, for example, from German Patent Publication No. 4141946 A1. In this case, the secondary air is supplied to the exhaust gas of the internal combustion engine by the secondary air pump to raise the exhaust gas temperature as a function of the operating state of the internal combustion engine immediately before the catalyst. This is done, for example, by injecting air directly in front of the catalyst into the exhaust system for a short time after starting in fuel-rich warming operation (fuel excess). This excess of air oxidizes HC and CO in the exhaust system at a sufficient temperature level, thereby forming a more desirable high exhaust gas temperature. On the one hand, the hot exhaust gas thus acts to quickly reach the catalyst at its operating temperature.

In addition, a method has already been known in which the exhaust gas temperature is increased by incorporating pure oxygen (O ₂ ) in the inhaled fresh air, so that a shortening of the startup time of the catalyst is achieved.

A method for reducing harmful substances in combustion exhaust gas from such an internal combustion engine and an apparatus for carrying out the method are already known, for example, from German patent 44404681 C1. In this case, it is designed so that the enrichment of oxygen (O ₂ ) of the intake air can be achieved by a membrane that is permeable only to the oxygen molecules (O ₂ ) provided in the chamber.

In such a method, the problem is that the entire engine control must be determined by intake air rich in O ₂ . For this reason, institutional control is quite necessary. As a result, the entire institutional management of the internal combustion engine must be changed.

Therefore, in a technical form as simple as possible, reduction of the harmful substances in the combustion exhaust gas from the internal combustion engine provided with the exhaust gas catalyst of the type described in the beginning which can reliably reduce the harmful substances in the combustion exhaust gas by shortening the catalyst start-up time. It is an object of the present invention to provide a method.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partially cutaway view of a first embodiment of an apparatus for reducing harmful substances in combustion exhaust gas from an internal combustion engine equipped with an exhaust gas catalyst according to the present invention.

Fig. 2 is a partially cutaway view of a second embodiment of a noxious substance reduction device in combustion exhaust gas from an internal combustion engine equipped with an exhaust gas catalyst according to the present invention.

Fig. 3 is a partially cutaway view of a third embodiment of a noxious substance reduction device in combustion exhaust gas from an internal combustion engine equipped with an exhaust gas catalyst according to the present invention.

<Description of the code | symbol about the principal part of drawing>

10: internal combustion engine

20: secondary air pump

22: ambient air enriched with oxygen

30: secondary air blowing valve

40: piping

50: exhaust pipe

52: exhaust gas catalyst

70: the membrane

80: pressure tank

This problem is solved by being in the supply increases the oxygen (O ₂₎ content of the secondary air in the reduction method of the hazardous substances in the combustion exhaust gas from an internal combustion engine provided with a catalyst of the type described in the opening paragraph according to the invention. By increasing the O ₂ content of the supplied secondary air, that is, by enriching the O ₂ in the exhaust gas just in front of the catalyst, the oxidation conditions in front of and in the catalyst are improved in an extremely advantageous manner. This shortens the catalyst starting time and achieves the reduction of harmful substances in the combustion exhaust gas. And when raising the oxygen content of the blown air, it is advantageous that the volume flow volume of air can be reduced as a whole. Thereby, the cooling of the engine exhaust gas is reduced, and it is extremely advantageous that this also acts to shorten the startup time of the catalyst.

Purely in principle, various methods are contemplated for raising the oxygen content in the secondary air.

For example, oxygen may be taken out from the gas cylinder mounted on the vehicle and supplied to the secondary air pump.

In this case, a completely consumed oxygen compressed gas cylinder has to be replaced or recharged, and therefore technically and structurally extremely expensive.

Thus, a particularly advantageous embodiment is designed such that secondary air is supplied through a membrane, a so-called separation module, which is permeable only to oxygen molecules provided in the chamber in order to increase the O ₂ content. Thus, also by using a separate module that is mounted on the vehicle at the same time to generate a continuous O ₂ is rich secondary air supply to the exhaust gas, as needed. In this case, therefore, no oxygen compressed gas cylinder or the like is required at all.

Another extremely advantageous embodiment of this method is that the O ₂ enriched secondary air is first stored in the pressure tank first after it is generated in the separation module and before it is mixed with the exhaust gas of the internal combustion engine and operated in the next operating cycle. It is designed to be supplied to the exhaust gas as a function of state. In this way, the enrichment of oxygen of the secondary air supplied later to the exhaust gas is performed in the driving state which does not require blowing of the secondary air, for example, at the time of full load driving of the vehicle. In the next operation cycle, for example, at room temperature startup or in a warming process, secondary air enriched in O ₂ temporarily stored at this time can be supplied to the exhaust gas.

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

The present invention furthermore relates to an internal combustion engine comprising an exhaust gas catalyst comprising said secondary air pump supplied with secondary air by a secondary air pump as a function of the operating state of the internal combustion engine to the exhaust gas of the internal combustion engine immediately before the exhaust gas catalyst. In particular, it relates to a device for reducing harmful substances in combustion exhaust gases from automobiles.

In this case, it is a problem of the present invention to provide an apparatus of the kind described at the outset which enables a more effective reduction of harmful substances from combustion exhaust gases at a technical cost as low as possible.

In order to solve this problem, in the apparatus for reducing harmful substances in combustion exhaust gas from an internal combustion engine provided with an exhaust gas catalyst of the above aspect, the present invention enables enrichment of oxygen (O ₂ ) in secondary air. Means are provided.

In an advantageous embodiment, this means is designed to include at least one membrane (separation module) that is permeable only to oxygen molecules provided in the chamber. Thereby, it is possible to thicken oxygen on a motor vehicle.

It is advantageous that 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 may be used for generation of partial pressure drop in the film necessary for thickening O ₂ in a film made of a mixture-permeable ceramic, for example.

In order to store the air enriched in O ₂ for use in the next operation cycle of the internal combustion engine, a pressure tank capable of storing primary O ₂ enriched secondary air is provided downstream of the separation module.

Other features and advantages of the present invention will become apparent from the following description and drawings of some embodiments.

The first embodiment of the harmful substance reducing device in the combustion exhaust gas of the internal combustion engine 10 according to the present invention includes a secondary air pump 20, and is indicated by an arrow having a sign 22 at the secondary air pump 20. Ambient air enriched with oxygen is supplied. In this case, oxygen or oxygen-enriched air is blown out of a pressure vessel (for example, not shown) and mixed through the mixing device of ambient air. Oxygen may be blown in, for example (not shown) from an oxygen container mounted in an automobile, or may be generated on a vehicle by the method described below.

Control of the air intake amount (not shown) is performed by the secondary air blow valve 30 which can be operated 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, each starts from a fixed mixing ratio.

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

An exothermic reaction occurs in the exhaust pipe 50 by supplying air enriched with oxygen, and this exothermic reaction heats the catalyst until the catalyst reaches its operating temperature in the catalyst start-up time, i.e. at room temperature start-up. Shortens the elapsed time.

In the second embodiment shown in FIG. 2, the same reference numerals are given to the same elements as those of the first embodiment, and accordingly, the description of the first embodiment is referred to as these descriptions. Unlike the first embodiment, in the second embodiment shown in FIG. 2, the separation module 70 is provided downstream of the secondary air pump 20. By this separation module 70, which comprises a membrane permeable only to oxygen molecules provided in the chamber, the oxygen enriched air necessary for blowing is generated only on the vehicle and also while the secondary air blowing 20 is being activated. . In this way, when the secondary air blowing is activated, the enrichment of oxygen of the secondary air is also achieved at the same time.

The embodiment shown in FIG. 3 differs from the embodiment shown in FIG. 2 in that the pressure tank 80 is provided downstream of the separation module 70, and the next operation cycle in the pressure tank 80 is different. Thus, for example, secondary air enriched in the air generated by the separation module 70 may be temporarily stored so that the exhaust gas may be supplied to the exhaust gas during the normal temperature startup of the internal combustion engine. In this case, the secondary air pump is advantageously started in an operating state that does not require any blowing of secondary air. The secondary air pump may be used in continuous operation.

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

For example, a ceramic film made of zirconium dioxide (ZrO ₂ ) or a ceramic film made of perovskite stone may be used.

In the case of zirconium dioxide, the acquisition of oxygen from the ambient air is performed by a voltage difference secured by a current flow between both sides of the film via an external conductor connection and applied to the film. In this case, the concentration of oxygen (O ₂ ) obtained in this way is achieved without mechanical pump work being added in particular via a voltage. In this case, an extremely high pressure (10 ₂₀ bar) can be set by the voltage, so no addition of a compressor for filling the pressure tank 80 is necessary at all.

In a mixture-permeable ceramic membrane, for example, a perovskite membrane, the oxygen partial pressure drop that must occur across the membrane acts as the driving force. This driving force may be generated by the secondary air pump 20.

Since not only zirconium dioxide membranes but also mixture permeable membranes also exhibit meaningful permeability coefficients for economic use for the first time at high temperatures (400 ° C.), in order to enable such heating of the membranes in a simple way, the separation module is capable of It is provided in the vicinity of the exhaust pipe 50 or in the exhaust pipe 50.

And the enrichment of oxygen can be achieved with plastic membranes, for example polymer membranes. With such a polymer film, an oxygen content of 40% by volume or less can be achieved. In order to operate the separation module 70 with the polymer membrane, mechanical separation power in the form of a pump operation or a compression operation is required to generate partial pressure drop. This pumping and compressing operation may be generated using kinetic energy that must be lowered during brake operation, for example by proper coupling of the pump / compressor and brake. The secondary air pump 20 may be used to generate a pressure drop.

The present invention can more effectively reduce the harmful substances from the combustion exhaust gases at the lowest possible technical cost.

Claims (8)

Internal combustion engine 10, in particular a motor vehicle, having an exhaust gas catalyst 52 in which secondary air is supplied by secondary air pump 20 as a function of the operating state of internal combustion engine 10 to the exhaust gas of internal combustion engine 10. In the method for reducing harmful substances in combustion exhaust gas from A method of reducing harmful substances in combustion exhaust gas from an internal combustion engine with an exhaust gas catalyst, characterized by an increase in oxygen (O ₂ ) content of the supplied secondary air. The internal combustion engine with an exhaust gas catalyst according to claim 1, wherein secondary air is supplied through a membrane (separation module 70) which is permeable only to oxygen molecules provided in the chamber in order to increase the O ₂ content. Method for reducing harmful substances in combustion exhaust gas from petroleum gas. The method of claim 1 or claim 2, O, and ₂ is first temporarily stored in the pressure tank 80, before the enriching the secondary air is mixed into the exhaust gas of the internal combustion engine 10, the operation state in the next operation cycle of the A method of reducing harmful substances in combustion exhaust gas from an internal combustion engine with an exhaust gas catalyst, characterized in that it is supplied to the exhaust gas as a function. The combustion exhaust gas from the internal combustion engine with an exhaust gas catalyst according to any one of claims 1 to 3, characterized in that the partial pressure drop necessary for the membrane is generated by the secondary air pump 20. How to reduce harmful substances. The secondary air pump 20 is supplied with secondary air by the secondary air pump 20 as a function of the operating state of the internal combustion engine 10 to the exhaust gas of the internal combustion engine 10 directly in front of the exhaust gas catalyst 52. In an apparatus for reducing harmful substances in combustion exhaust gas from an internal combustion engine 10 having an exhaust gas catalyst 52, in particular from an automobile, A device for reducing harmful substances in combustion exhaust gas from an internal combustion engine with an exhaust gas catalyst, characterized in that a means for enriching oxygen (O ₂ ) of the supplied secondary air is provided. 6. Combustion exhaust gas from an internal combustion engine with an exhaust gas catalyst according to claim 5, characterized in that said means comprises at least one membrane (separation module 70) permeable only to oxygen molecules provided in the chamber. Harmful abatement device. 7. Hazardous substances in combustion exhaust gas from an internal combustion engine with an exhaust gas catalyst according to claim 5 or 6, characterized in that the separation module (70) is provided downstream of the secondary air pump (20). Reduction device. The exhaust gas according to any one of claims 5 to 7, wherein a pressure tank (80) capable of temporarily storing secondary air enriched in O ₂ is provided downstream of the separation module (70). A device for reducing harmful substances in combustion exhaust gas from an internal combustion engine having a catalyst.