DE102017217712A1 - Method and arrangement for increasing the exhaust gas temperature of an internal combustion engine and vehicle - Google Patents

Abstract

A method of increasing the exhaust gas temperature of an internal combustion engine is provided, which comprises determining whether a combustion operation is performed in the internal combustion engine and closing a number of intake valves and / or a number of exhaust valves of the internal combustion engine if no combustion operation is performed An arrangement for increasing the exhaust gas temperature of an internal combustion engine and a vehicle are provided with such an arrangement.

Description

The present invention relates to a method and an arrangement for increasing the exhaust gas temperature of an internal combustion engine and to a vehicle having such an arrangement.

Modern exhaust aftertreatment devices for the aftertreatment of exhaust gases in the exhaust gas line of an internal combustion engine, in particular exhaust aftertreatment devices for diesel engines, are negatively influenced by low exhaust gas temperatures in their effectiveness. In particular, lean NOx trap (LNT) or selective catalytic reduction catalysts (SCR catalyst) require a certain minimum temperature in order to achieve the required efficiency in the exhaust aftertreatment.

Particularly critical with respect to the temperature are the warm-up phase of the internal combustion engine after the cold start and the operation of the engine at low load, for. B. during city driving a vehicle equipped with the engine, classify.

In order to achieve the minimum temperature for the exhaust aftertreatment device or to prevent the temperature from dropping to a temperature below the minimum temperature, it is possible to carry out additional fuel combustion in order to increase the exhaust gas temperature and thus also the temperature of the exhaust gas aftertreatment device. However, this has the disadvantage of increased fuel consumption and increased pollutant emissions due to the additional fuel required.

Other options for increasing the exhaust gas temperature include the use of bypasses to bypass the exhaust gas recirculation cooler or intercooler. These measures lead to an increase in the temperature of the intake air and thereby also to an increase in the exhaust gas temperature. However, cost-intensive structural changes are necessary. In addition, the available space is reduced by the bypasses.

Another possibility is the arrangement of an exhaust gas heating system in which fuel is injected directly into the exhaust line and ignited in order to increase the exhaust gas temperature. Such Abgasheizsysteme cause high costs and reduce the space. They also consume additional fuel.

In addition, from the GB 2536092 A It is known to influence the exhaust gas temperature by changing the air-to-fuel ratio during the combustion process by means of a variable valve timing (VTT). For example, the opening of an intake valve may be retarded to increase the exhaust gas temperature.

Object of the present invention is to provide a method and an arrangement for increasing the exhaust gas temperature of an internal combustion engine, so that the maintenance of a minimum temperature of an exhaust aftertreatment device can be ensured over a longer period and the disadvantages mentioned above can be reduced or eliminated. It would be desirable to have a cost-effective method which is designed such that no additional fuel is needed to increase the temperature of the exhaust gas. In addition, as little space as possible should be required to implement this method.

This object is achieved by the subject matters of the independent claims. The dependent claims contain embodiments of these inventive solutions.

The invention is based on the finding that even conditions in which the intake and exhaust valves of the internal combustion engine are at least partially opened, without resulting in fuel combustion, lead to a decrease in the exhaust gas temperature and thus the temperature of the exhaust gas aftertreatment device, as further air in enters the internal combustion engine and is discharged via the exhaust valves of the internal combustion engine in the exhaust line, where it acts cooling. Such conditions may occur, for example, under overrun fuel cutoff.

This effect can be enhanced by an additional influence of air currents. This may, for example, be the case if a vehicle operated by the internal combustion engine continues to roll without a combustion process taking place, eg. B. since the vehicle is operated temporarily by means of an electric motor.

The basic idea of the invention is therefore to close intake and / or exhaust valves of the internal combustion engine, if no combustion process takes place. As a result, no air gets into the exhaust system. A previously caused by the air flow cooling of an exhaust aftertreatment device can be avoided. The minimum temperature of the exhaust aftertreatment device may be reached at an earlier time and / or maintained for a longer period of time even after completion of the combustion process. When restarting the internal combustion engine, an exhaust aftertreatment can thus be effectively carried out from the beginning.

For activating (opening and closing) the intake or exhaust valves, a system for variable valve control can be used. Such a system for activating the intake valves may possibly already be present for influencing engine performance and fuel consumption. Additional components, which occupy the installation space and cause further costs, can be avoided.

An inventive method for increasing the exhaust gas temperature of an internal combustion engine comprises determining whether a combustion process is performed in the internal combustion engine and closing a number of intake valves and / or a number of exhaust valves of the internal combustion engine, if no combustion operation is performed. By means of the method according to the invention, the cooling of an exhaust gas aftertreatment device arranged in an exhaust line of the internal combustion engine can be reduced or prevented.

An internal combustion engine, also referred to as an internal combustion engine, is understood to mean an internal combustion engine for converting chemical energy contained in the fuel into mechanical work. The internal combustion engine can be designed, for example, as a self-igniting or externally ignited internal combustion engine.

In a first method step, it is determined whether a combustion process is performed in the internal combustion engine. This can be done directly, for. B. by the combustion chamber itself is monitored, or indirectly by z. B. is determined whether the combustion chamber fuel is supplied or whether an ignition takes place. If the fuel supply is interrupted, it can be determined that no combustion process is performed.

If no combustion process is performed, so z. B. the fuel supply is interrupted, a number of intake valves, ie z. B. some or all intake valves, and / or a number of exhaust valves, so z. B. some or all of the exhaust valves, the internal combustion engine closed, the closing is preferably complete. Thus, for example, all intake valves and all exhaust valves may be closed or only all intake valves or all exhaust valves. Any other combinations of inlet or outlet valves to be closed are possible. If the inlet and / or exhaust valves are closed, they remain in the closed position, d. H. they are kept closed.

Inlet valves are delivery devices for the supply of air or, depending on the type of engine, an air-fuel mixture to the combustion chamber to understand. Exhaust valves are to be understood as exhaust devices for removing exhaust gases from the combustion chamber into the exhaust gas line of the internal combustion engine. Each engine cylinder has at least one intake and one exhaust valve. However, there may also be several, for example three, four, five or eight intake valves per engine cylinder.

By closing the inlet and / or outlet valves, as already explained above, prevents air from passing through the combustion chamber into the exhaust gas line and thus also to the exhaust gas aftertreatment device during an interruption of the combustion operation of the internal combustion engine.

The method therefore reduces cooling of an exhaust aftertreatment device arranged in the exhaust line of the internal combustion engine. The exhaust aftertreatment device can be, for example, a catalyst, for. As a nitrogen oxide storage catalyst or a catalyst for selective catalytic reduction. It can also be several exhaust aftertreatment devices, eg. B. in parallel or serial arrangement, be provided in the exhaust system.

If the internal combustion engine is to be operated again in the combustion mode, a number of intake valves and / or a number of exhaust valves can be (re) opened.

According to various embodiments, the execution of the combustion process can be determined based on a fuel supply to the combustion chamber and / or an ignition process in the combustion chamber. For example, if the fuel supply is interrupted, closing of intake and / or exhaust valves may be provided at the same time.

Both the fueling and the ignition process are usually already monitored for other reasons, so this is a simple and inexpensive way to determine the performance of a combustion process.

According to further embodiment variants, a number of intake valves and / or a number of exhaust valves may be closed by means of a variable valve control system, for example a continuously variable valve control system. The continuously variable valve control system may be, for example, an electrohydraulic system for fully variable control of the intake valves.

Such variable valve timing systems are known for gasoline engines to increase the efficiency of fuel combustion.

By using these existing systems, the inventive method can be implemented inexpensively and without further affecting the space. For diesel engines such variable valve timing systems can also be used.

According to further embodiments, the method can be carried out under Schubabschaltungsbedingungen.

During fuel cut-off conditions, the fuel supply is interrupted. In addition, the combustion engine is coupled to the rest of the drive train. The internal combustion engine is not intended to deliver power, but is dragged by the rotating mass of a vehicle equipped with the internal combustion engine. Here, the crankshaft and thus usually also the camshaft continue to rotate, so that the inlet and exhaust valves are opened and air is pumped through the combustion chamber in the exhaust line. To reduce or eliminate the associated cooling of the exhaust aftertreatment device, a number of the intake and / or exhaust valves are closed.

According to further embodiments, the internal combustion engine may be a diesel engine. In particular, the exhaust aftertreatment systems used for exhaust aftertreatment of diesel engines require compliance with a narrow temperature window, so that the implementation of the method according to the invention has a particularly advantageous effect.

According to further embodiments, the internal combustion engine may be a vehicle engine. Vehicle engines have special regulations regarding the emission of air pollutants. In order to comply with these regulations, an exhaust aftertreatment is required, which can be carried out particularly effectively by means of the method according to the invention.

An arrangement for increasing the exhaust gas temperature of an internal combustion engine according to the invention comprises an internal combustion engine with intake valves and exhaust valves, an opening and closing device designed to open and close the intake and / or exhaust valves, a monitoring device for determining whether a combustion process is performed in the internal combustion engine and a control unit , which is adapted and arranged to receive and process a signal of the monitoring device and in response to the signal of the monitoring device, for. B. based on instructions or programmed in the control unit code according to one or more routines to output a control signal to the opening and closing device for opening or closing the intake and / or exhaust valves on. Of course, several exhaust aftertreatment devices can be arranged in the exhaust system.

The arrangement according to the invention is suitable, for example, for carrying out the method according to the invention explained above. Therefore, the above explanations serve to explain the method according to the invention also for the description of the arrangement according to the invention. The advantages of the device according to the invention correspond to those of the method according to the invention and its corresponding variants. The arrangement serves to reduce or prevent cooling of an exhaust gas aftertreatment device arranged in an exhaust line of the internal combustion engine.

The opening and closing means is arranged to open and close some or all of the intake valves, some or all of the exhaust valves, or to open and close intake valves and exhaust valves. The monitoring device can be designed for the direct or indirect monitoring of the combustion process as described above. The opening and closing device and the control unit can be designed as a common component.

According to various embodiments, the opening and closing device may be designed as a variable valve control system, for example as a continuously variable valve control system.

According to further embodiments, the control unit may further be designed to output a control signal to the opening and closing device for optimizing the combustion process. For this purpose, the timing of the intake valves and / or exhaust valves and the valve can be selectively changed. As a result, the engine power can advantageously be increased and / or the fuel consumption can be reduced.

According to further embodiments, the internal combustion engine may be a diesel engine. Reference is made to the above statements regarding the method.

According to further embodiments, the internal combustion engine may be a vehicle engine. Reference is made to the above statements regarding the method.

An inventive vehicle has an arrangement according to the above description. Under a vehicle is doing any mobile transport, ie both a land vehicle and a watercraft or aircraft, z. As a passenger car to understand. The vehicle may be designed, for example, as a hybrid electric vehicle. For vehicles special rules apply with regard to the emission of air pollutants, their compliance is facilitated by the vehicle according to the invention.

• 1 zeitlicher Verlauf der Fahrzeuggeschwindigkeit und der Abgastemperatur gemäß neuem Europäischen Fahrzyklus (Stand der Technik); und
• 2 zeitlicher Verlauf der Fahrzeuggeschwindigkeit und der Abgastemperatur nach dem Stand der Technik sowie bei Durchführung des erfindungsgemäßen Verfahrens gemäß neuem Europäischen Fahrzyklus.

The invention will be explained in more detail with reference to the figures and the accompanying description. Show it:

• 1 time course of the vehicle speed and the exhaust gas temperature according to new European driving cycle (prior art); and
• 2 Time course of the vehicle speed and the exhaust gas temperature according to the prior art and in carrying out the method according to the new European driving cycle.

In the 1 are the time course of the vehicle speed A and the associated time history of the exhaust gas temperature B according to the prior art, as obtained in a test of a vehicle equipped with an internal combustion engine according to the new European driving cycle.

Based on an exhaust gas temperature of about 25 ° C, as occurs in a cold start of the engine, the exhaust gas temperature increases with increasing operating time of the engine first. If the vehicle speed and thus the load to be applied by the internal combustion engine are increased for a short time, the exhaust gas temperature for this period also increases.

According to the invention, an increase in the exhaust gas temperature can be achieved, so that the minimum temperature of an exhaust gas aftertreatment device arranged in the exhaust gas line of the internal combustion engine is achieved or a cooling down is reduced.

This effect is in 2 it can be seen in which of the in 1 Dotted section shown in phantom is shown and achieved in carrying out the method according to the invention the course of the exhaust gas temperature C or the temperature in the exhaust system is additionally drawn. Selected areas with elevated exhaust gas temperature are in 2 gray background.

The curve C was achieved in carrying out the method according to the invention with a diesel engine as an internal combustion engine, wherein the diesel engine is a vehicle engine. First, it has been determined that no combustion is performed in the internal combustion engine by detecting an interruption of the fuel supply to the combustion chamber. The periods without combustion correspond approximately to the time periods with decreasing vehicle speed and time periods with a vehicle speed of zero.

Subsequently, all inlet valves were closed, so that an air flow through the combustion chamber is omitted. As a result, a decrease in the exhaust gas temperature or the temperature in the exhaust gas line, as can be observed in the prior art (curve B ), be reduced.

Significantly increased exhaust gas temperatures compared with the prior art can be observed after repeated interruption of the combustion process.

While the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

As used herein, the term "and / or" when used in a series of two or more elements means that each of the listed elements may be used alone, or any combination of two or more of the listed elements may be used. For example, if a composition is described as containing the components A . B and or C , contains, can the composition A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B , and C included in combination.

LIST OF REFERENCE NUMBERS

A

Course of the vehicle speed

B

Course of the exhaust gas temperature according to the prior art

C

Course of the exhaust gas temperature when carrying out the method according to the invention

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• GB 2536092 A [0007]

Claims (12)

Method for increasing the exhaust gas temperature of an internal combustion engine, comprising: - Determine whether a combustion process is performed in the internal combustion engine and - closing a number of intake valves and / or a number of exhaust valves of the internal combustion engine, if no combustion operation is performed. Method according to Claim 1 wherein the execution of the combustion process is determined based on a fuel supply to the combustion chamber and / or an ignition process in the combustion chamber. Method according to one of the preceding claims, wherein a number of the intake valves and / or a number of the exhaust valves by means of a variable valve timing system, for example, a continuously variable valve timing system, closed. A method according to any one of the preceding claims, wherein the method is performed under deceleration conditions. Method according to one of the preceding claims, wherein the internal combustion engine is a diesel engine. Method according to one of the preceding claims, wherein the internal combustion engine is a vehicle engine. Arrangement for increasing the exhaust gas temperature of an internal combustion engine comprising: an internal combustion engine with intake valves and exhaust valves, an opening and closing device designed to open and close the inlet and / or outlet valves, a monitoring device for determining whether a combustion process is carried out in the internal combustion engine and a control unit which is designed and arranged to receive and process a signal from the monitoring device and to output a control signal to the opening and closing device for opening or closing the inlet and / or outlet valves as a function of the signal from the monitoring device. Arrangement according to Claim 7 wherein the opening and closing device is designed as a variable valve control system, for example as a continuously variable valve control system. Arrangement according to Claim 7 or 8th wherein the control unit is further configured to output a control signal to the opening and closing means for optimizing the combustion process. Arrangement according to one of Claims 7 to 9 , wherein the internal combustion engine is a diesel engine. Arrangement according to one of Claims 7 to 10 , wherein the internal combustion engine is a vehicle engine. Vehicle with an arrangement according to one of the preceding claims.

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