DE112006001296B4 - Exhaust line for internal combustion engines - Google Patents

Abstract

An exhaust line (10) for an internal combustion engine comprising, between an inlet (12) for the exhaust gases and an outlet (14) a nitrogen oxide trap (28) located in a filter section (24) a bypass section (26) for diverting the exhaust gases outside the nitrogen oxide trap (28), means (32, 34) for switching the exhaust gases for passage through the filter section (24) or the bypass section (26), and a three way catalyst (18) disposed between the inlet (12) and a position upstream of the filter section (24) and the diverting section (26), characterized in that the exhaust line comprises means (36) for controlling the switching means (32), which control means (36) comprise means for detecting the outlet temperature of the gases from the Motors and that the means for switching (32) are adapted to the exhaust gases normally in the bypass section (26) to conduct when the temper nature of the gases is above 600 ° C; wherein the control means (36) comprises: - means (40) for determining whether the engine is operating on a rich mixture; - means (40) for determining whether the temperature measured by the temperature sensor (38) is above 600 ° C; - Means (36, 40) for arranging that the means (32, 34) for switching the exhaust gases, the gases in the bypass section (26) passes when the engine is working with rich mixture and when measured by the temperature sensor temperature above 600 ° C is located; and - means (36, 40) for arranging that the means (32, 34) for switching the exhaust gases to keep the gases to a passage through the filter section (24) when the engine is not working with a rich mixture or by the Temperature sensor measured temperature up to 600 ° C lies.

Description

The invention relates to an exhaust line for internal combustion engines according to the preamble of patent claim 1.

Today, certain automobiles have internal combustion engines that basically operate with a so-called lean mixture of fuel and combustion-promoting material. Such a mixture is characterized by an excess of the combustion-promoting material with respect to the fuel. The mixture that supplies the engine is referred to as sub-echiometric with respect to fuel. Conversely, an engine operating on super-stoichiometric fuel is so-called supplied by a richer mixture.

Such engines are used because of their reduced consumption of fuel. In any case, the engines operate under conditions where significant amounts of nitrogen oxides are produced. These nitrogen oxides, commonly referred to as NOx, are harmful to the environment and it is desirable to eliminate them.

For this purpose, the exhaust line of the vehicle is provided with catalytic means for purifying the gases and with a nitrogen oxide trap, commonly referred to by an English term as "NOx trap".

As is known per se, the nitrogen oxide capture device uses special catalytic elements to adsorb the nitrogen oxides during lean engine operation. When the limit of adsorption of the nitrogen oxide trap is reached, it is regenerated. For this purpose, the engine is controlled so that it runs for a few seconds with a rich mixture. A rich mixture is characterized by having overstoichiometric ratios in the fuel, the mixture containing an excess of fuel relative to the injected combustion-promoting material.

The trap for nitrogen oxides works so satisfactorily in a temperature range of 300 ° C to 600 ° C. This temperature is achieved by the exhaust gases themselves. In addition, the nitrogen oxide catcher along the length of the Auspufflinie is arranged as close to the engine.

However, this position in the exhaust line makes the nitrogen trap incompatible with the engine because the maximum temperature of the engine can reach 900 ° C during operation. In fact, at temperatures above 600 ° C, the catalytic material in the nitrogen oxide trap is destroyed.

It has been considered to develop catalytic materials which are stable at very high temperatures, but the results are not very satisfactory. It has also been considered to provide upstream of the nitrogen oxide trap a heat exchanger which allows the temperature of the exhaust gas to be lowered prior to passage through the nitrogen trap. However, the cost of this solution is very significant.

US 5,738,832 A relates to an exhaust gas purifying plant comprising a 3-way valve controlled by a controller to contain the exhaust gases optionally an adsorbent for hydrocarbons. To desorb the hydrocarbons, the adsorber is heated to 150 ° C.

DE 198 22 798 A1 relates to an engine exhaust purification system with an absorption element and a bypass channel parallel thereto. The absorption element serves to absorb hydrocarbonates. US 5 307 627 A also relates to an exhaust gas purification system with an HC trap.

US Pat. No. 6,233,927 B1 relates to an exhaust gas purification system with a NOx absorber. A bypass is used if the NOx absorber is to be regenerated.

DE 602 01 960 T2 relates to an exhaust gas purification system with a NOx absorber. NOX is absorbed by the NOx absorber at a lean mixture and the NOx absorber is regenerated at a rich mixture.

DE 103 35158 A1 also relates to an exhaust gas purification system with a NOx absorber.

The invention aims to propose an exhaust line for internal combustion engines, which has a nitrogen oxide capture device which is fully compatible with an internal combustion engine whose outlet temperature is above the temperature that tolerate the catalytic elements of the nitrogen oxide capture device.

To this effect, it is an object of the invention to provide a Auspufflinie for internal combustion engines of the above type with the features of the characterizing part of claim 1.

• - die Umschaltmittel umfassen Mittel zur Schließung des Filterabschnitts unmittelbar stromabwärts der Fangeinrichtung für Stickoxide;
• - die Mittel zur Umschaltung umfassen ein Dreiwege-Ventil, das den Umleitungsabschnitt und den Filterabschnitt mit dem Rest der Auspufflinie verbindet;
• - die Auspufflinie umfaßt eine Gabelung zwischen dem Einlaß einerseits und einer stromaufwärtigen Position des Filterabschnitts und einer stromaufwärtigen Position und des Umleitungsabschnitts, und das Dreiwege-Ventil liegt stromabwärts des Filterabschnitts und des Umleitungsabschnitts und ist vorgesehen zur Sicherung der wahlweisen Verbindung dieser Abschnitte mit dem gemeinsamen stromabwärtigen Abschnitt der Auspufflinie;
• - die Auspufflinie umfaßt einerseits wenigstens einen Fühler aus der Gruppe eines Fühlers in der Position wenigstens eines Ventils, eines Temperaturfühlers und eines Fühlers für die Zusammensetzung der Gase, und andererseits Mittel zur Diagnose des Funktionszustandes der Umschaltmittel von dem oder jedem Fühler; - die Auspufflinie umfaßt Mittel zur Steuerung der Umschaltmittel, welche Steuermittel Mittel zur Ermittlung der stoechiometrischen Bedingungen der Funktion des Motors aufweist, und die Umschaltmittel sind geeignet zum Ableiten der Auspuffgase in den Umleitungsabschnitt, wenn die Motorbedingungen über stoechiometrische Verhältnisse des Brennstoffs anzeigen;
• - die Steuermittel sind geeignet zur periodischen Steuerung der Umschaltmittel für eine temporäre Zirkulation der Auspuffgase durch den Filterabschnitt während der Phasen, in denen die Auspuffgase normalerweise durch den Umleitungsabschnitt strömen;
• - die Auspufflinie umfaßt Steuermittel für die Umschaltmittel, welche Steuermittel Mittel zur Ermittlung der künftigen Existenz einer Betriebsphase des Motors umfassen, in der dieser mit magerem Gemisch läuft, wenn er mit fettem Gemisch betrieben wird, und diese Mittel der Steuerung sind geeignet zur Steuerung der besagten Umschaltmittel zum Ableiten der Gase in den Filterabschnitt, wenn diese Phase der Funktion des Motors mit einem mageren Gemisch ermittelt wird.

According to certain embodiments, the exhaust line comprises one or more of the following features:

• - the switching means comprise means for closing the filter section immediately downstream of the nitrogen oxide catcher;
• the means for switching comprise a three-way valve which connects the bypass section and the filter section to the remainder of the exhaust line;
• the exhaust line comprises a bifurcation between the inlet on the one hand and an upstream position of the filter section and an upstream position and the bypass section, and the three-way valve is downstream of the filter section and the bypass section and is provided to ensure the selective connection of these sections to the common downstream Section of the exhaust line;
• - The exhaust line comprises on the one hand at least one sensor from the group of a sensor in the position of at least one valve, a temperature sensor and a sensor for the composition of the gases, and on the other hand means for diagnosing the functional state of the switching means of the or each sensor; the exhaust line comprises means for controlling the switching means, the control means comprising means for determining the stoichiometric conditions of operation of the engine, and the switching means being adapted to divert the exhaust gases to the bypass section when the engine conditions indicate stoichiometric ratios of the fuel;
• the control means are adapted to periodically control the switching means for temporary circulation of the exhaust gases through the filter section during the phases in which the exhaust gases normally flow through the bypass section;
• the exhaust line comprises control means for the switching means, said control means comprising means for determining the future existence of an operating phase of the engine in which it is running lean when operated with rich mixture, and these means of control are suitable for controlling said operation Switching means for diverting the gases into the filter section, if this phase of the function of the engine is determined with a lean mixture.

The invention is also directed to a drive group having an engine which normally runs with a lean mixture and an exhaust line as described above.

• 1 ist eine perspektivische Ansicht einer Auspufflinie gemäß der Erfindung;
• 2 ist eine schematische Darstellung der Auspufflinie gemäß der Erfindung mit einem Ventil in einer ersten Position, in der die Zirkulation durch die Fangeinrichtung aus Stikkoxiden gestattet;
• 3 ist ein Flußdiagramm und zeigt Einzelheiten der Regelung des Ventils in der Auspufflinie der 1 und 2; und
• 4A, 4B, 4C sind Flußdiagramme und zeigen Einzelheiten des Algorythmus der in der Auspufflinie gemäß der Erfindung eingesetzten Diagnose.

The invention will be better understood by reading the following description, given by way of example only and with reference to the accompanying drawings, in which:

• 1 Fig. 12 is a perspective view of an exhaust line according to the invention;
• 2 Figure 3 is a schematic representation of the exhaust line according to the invention with a valve in a first position, in which circulation through the trap of stikkoxiden allows;
• 3 is a flow chart showing details of the control of the valve in the exhaust line of 1 and 2 ; and
• 4A . 4B . 4C FIGURES are flowcharts showing details of the algorithm of the diagnosis used in the exhaust line according to the invention.

In the 1 and 2 illustrated exhaust line is intended for connection to the outlet of an internal combustion engine, which normally runs with a lean mixture.

The exhaust line includes an inlet 12 for connection to the outlet of the engine and an outlet 14 for the exhaust gases for delivery to the atmosphere.

The inlet 12 is formed by an exhaust manifold. It is connected to the inlet of a catalytic three-way purifier, which is known per se and is called in the following three-way catalyst.

Downstream of the catalyst 18 The exhaust line includes a tube 20 passing through a fork 22 is extended, which at the same time a filter section 24 and a divert section in parallel thereto 26 provided. The filter section 24 indicates the nitrogen oxide capture device 28 on.

The nitrogen oxide capture device 28 is mounted as close as possible to the outlet of the engine, according to the length of the exhaust line, to ensure rapid heating. In special cases, the portion of the exhaust line between the nitrogen oxide trap and the outlet of the engine is thermally insulated.

The detour section 26 has no treatment organs. The two sections 24 and 26 are connected downstream and open through an outlet pipe 30 via a three-way valve 32 using an actuator 34 is controlled. The outlet 14 is located at the end of the pipe 30 ,

As in 2 is shown, the three-way valve comprises a flap 33 that is adjustable between a first position in which the filter section 24 with the outlet section 30 is connected, wherein the diversion section 24 from the outlet section 30 is separated, and a second position in which the diversion section 24 with the outlet section 30 is connected and the filter section 24 from the outlet section 30 is disconnected.

The actuator 34 is with a control unit 36 connected, which control unit 36 appropriate information about the operation of the vehicle receives. In particular, a temperature sensor 38 immediately downstream of the exhaust manifold 16 intended. This temperature sensor is connected to the control unit 36 connected.

Otherwise, the control unit 36 connected to an engine operation control unit 40 , And especially phases of engine operation with rich mixture and lean mixture determined.

The units 36 and 40 can exchange information and commands. In particular, the unit 36 able to the unit 40 and cause it to reduce engine operation, which it changes from a supply of rich or lean mixture or triggers a phase of regeneration.

Conversely, the unit 40 the unit 36 inform you of the impending triggering of a regeneration phase or operation with a rich or lean mixture.

In addition, the control unit 36 an integrated diagnostic module 42 which diagnoses the function of the exhaust line.

According to a first embodiment is a sensor 44 to indicate the position of the valve 32 arranged in the exhaust line and with the module 42 connected.

In another embodiment, a temperature sensor 46 additionally or alternatively at the filter section downstream of the nitrogen oxide capture device 28 appropriate.

According to another variant is a feeler 48 for the composition of the gas, for example a sensor for the nitrogen oxide content, additionally or alternatively downstream of the valve 32 in the outlet section 30 arranged.

The control unit 36 is able to provide a control algorithm for the valve 32 and the engine operation control unit 40 to get going for the engine as it is in 3 is shown.

During the starting phase of the engine at the step 100 becomes the valve 32 set (step 102 ) to a position where the bypass section 26 closed and the filter section 24 is open.

Depending on what the supply of the engine looks like, with a rich mixture or with a lean mixture, the catching device heats up 28 achieved for nitrogen oxides under the influence of the circulation of the exhaust gases.

At step 104 it is determined whether the engine is working with a rich mixture. If this is not the case, will be at step 106 determines whether a regeneration of the capture device 28 is necessary for nitrogen oxides. If so, the control unit 36 controls the control unit 40 for temporarily controlling the engine with rich mixture at step 106 to allow desorption and reaction of the nitrogen oxides, as is known in the art.

If at step 106 a regeneration is not necessary or at the end of the regeneration, the steps become 104 and the following steps are done anew.

If at step 104 the engine is working with a rich mixture, is at step 110 determines if the temperature of the gas, measured by the temperature sensor 38 at the output of the engine, above 600 ° C. If not, the steps become 104 and the following steps are repeated.

If this temperature is above 600 ° C, the control unit arranges 36 at step 112 on that the valve 32 is switched, in such a way that the filter section 24 closed and the bypass section 26 in connection with the outlet section 30 manufactures.

At step 114 is determined by the computer 40 whether there is a short-term change to a lean mixture. If this is not the case, there will be a delay at step 116 triggered, and as long as this delay has not expired, the steps become 104 and the subsequent steps are repeated.

At the end of this delay will be the valve 32 temporarily switched, in such a way that during a short period, the exhaust gases through the nitrogen oxide capture device 28 to allow the temperature to rise again to keep it between a temperature of 300 ° C and 600 ° C.

At the end of this phase of temporary switching becomes the valve 32 at step 118 switched such that the gases through the bypass section 24 circulate, and the step 104 and the subsequent steps are repeated again.

If at step 114 the control unit 36 a need for a close change to a lean mixture for the control of the engine determines the valve 32 at step 120 switched so that the gases only by the nitrogen oxide capture device 28 to increase their temperature, awaiting the change to the lean mixture. At the end of a given period, the valve becomes 32 is held in one position, and the mixture that supplies the engine is changed and thus a lean mixture control is achieved (step 122 ).

With such an exhaust line, the nitrogen oxide trap never operates at a temperature above 600 ° C and constant at a temperature between 300 ° C and 600 ° C, so that a treatment of the exhaust gases is always possible while the engine is supplied with a lean mixture becomes.

The 4A . 4B and 4C illustrate phases of the diagnosis that are constantly made by the diagnostic unit 42 is carried out. It is understood that one or more of the phases shown in the figures can be performed together.

In 4A the test determines 140 using the feeler 44 whether the valve 32 is blocked. If this is the case, the control unit arranges 36 in step 142 to that the control unit 40 adjusts the control of the engine such that it does not produce nitrogen oxides and / or maintains the gas temperature at less than 600 ° C.

In the presence of a temperature sensor 46 becomes at step 150 according to 4B determines if the temperature upstream of the nitrogen oxide trap is above 600 ° C. If this is the case, at step 152 reduces the power of the engine.

If a feeler 48 is provided for the gas composition at the outlet is in step 160 checked whether the nitrogen oxide content is above a reference value Vref. If this is the case, the control unit controls 36 the unit 40 in that the engine is running in a rich mixture (step 162 ). After that the valve becomes 32 according to step 164 switched to the position where the exhaust gas only through the bypass section 24 flows.

Generally, in the case of a malfunction as in the embodiments according to 4A . 4B and 4C is mentioned, the control of the engine switched to a reduced operation, that is, a operation with rich mixture and / or limited outlet temperature of the gas. Incidentally, the driver is informed by a light signal in the dashboard.

Even if there is an error in the exhaust line, the nitrogen oxide trap is obtained and the exhaust gases that are released into the atmosphere have a low content of nitrogen oxides even if the performance of the engine is reduced in terms of consumption and performance.

In the case of a variant, the three-way valve 32 and the fork 22 exchanged, such that the three-way valve is disposed upstream of the filter section and the bypass section.

According to a variant of one of the embodiments, the three-way valve is replaced by two two-way valves. One of the valves is located in the bypass section and the other in the filter section.

Claims (10)

An exhaust line (10) for an internal combustion engine comprising, between an inlet (12) for the exhaust gases and an outlet (14) a nitrogen oxide trap (28) located in a filter section (24) a bypass section (26) for diverting the exhaust gases outside the nitrogen oxide trap (28), means (32, 34) for switching the exhaust gases for passage through the filter section (24) or the bypass section (26), and a three way catalyst (18) disposed between the inlet (12) and a position upstream of the filter section (24) and the diverting section (26), characterized in that the exhaust line comprises means (36) for controlling the switching means (32), which control means (36) comprise means for detecting the outlet temperature of the gases from the Engine and that the means for switching (32) are adapted to normally direct the exhaust gases in the bypass section (26) when the Tempe temperature of the gases is above 600 ° C; wherein the control means (36) comprises: - means (40) for determining whether the engine is operating on a rich mixture; - means (40) for determining whether the temperature measured by the temperature sensor (38) is above 600 ° C; - Means (36, 40) for arranging that the means (32, 34) for switching the exhaust gases, the gases in the bypass section (26) passes when the engine is working with rich mixture and when measured by the temperature sensor temperature above 600 ° C is located; and - means (36, 40) for arranging that the means (32, 34) for switching the exhaust gases to the gases to a passage through the filter section (24) to if the engine is not working with a rich mixture or if the temperature measured by the temperature sensor is up to 600 ° C. Exhaust line according to Claim 1 characterized in that the switching means (32) comprises means for closing the filter section (24) immediately downstream of the nitrogen oxide trap (28). Exhaust line according to one of the preceding claims, characterized in that the switching means comprise a three-way valve (32) connecting the diverting section (26) and the parallel filter section (24) to the remainder of the exhaust line (10). Exhaust line according to Claim 2 and 3 characterized in that the exhaust line comprises a bifurcation (22) disposed between the inlet (12) on the one hand and an upstream position above the filter section and above the bypass section (26), and the three-way valve (32) downstream Filter section (24) and the bypass section (26) is arranged and ensures that these sections are selectively connected to the common downstream portion (30) of the Auspufflinie. Exhaust line according to one of the preceding claims, characterized in that the Auspufflinie on the one hand at least one sensor from the group comprising a sensor (44) for the position of at least one valve, a sensor (46) for the temperature and a sensor (48) for the composition of the gases, and on the other hand means for diagnosing the functional state of the switching means (32, 34) of the or each sensor. Exhaust line according to one of the preceding claims, characterized in that the exhaust line means (36) for controlling the switching means (32) means (40) for detecting the future existence of an operating phase of the engine with lean mixture while it is operated with rich mixture, and that the control means (36) comprises means for arranging the switching means (32) to divert the gases into the filter section (24) when such an operating phase of the lean mixture engine is detected. Exhaust line according to Claim 6 characterized in that the control means (36) comprises means for causing deceleration when the means (40) for detecting the future existence of an operating phase of the lean-burn engine while operating in rich mixture does not detect such a phase, at the end of which the valve (32) is temporarily switched so that during a short period of time the exhaust gases circulate through the nitrogen oxide trap (28). Exhaust line according to one of the preceding claims, characterized in that the exhaust line comprises means (36) for controlling the switching means (32), which control means (36) comprises means (40) for detecting the stoichiometric conditions of the engine, and in that the switching means are suitable to direct the exhaust gases normally in the direction of the diversion section (26) when the engine is operating at super-stoichiometric conditions of the fuel. Exhaust line according to one of the preceding claims, characterized in that the control means are adapted to periodically control the switching means (32) for temporary circulation of the exhaust gases through the filter section (24) during the phases in which the exhaust gas is normally passed through the bypass section (26). circulated. Drive group with an engine, which normally runs with a lean mixture, and an exhaust line according to one of the preceding claims.

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