DE102013213294A1 - Combustion engine with cylinder deactivation and method for cylinder deactivation - Google Patents

Abstract

The invention relates to an internal combustion engine with a plurality of cylinders, which are grouped into a first and a second cylinder group, wherein the cylinders of the second cylinder group are switched off in a partial load operation of the internal combustion engine, and with a first (5, 6) and a second exhaust aftertreatment device (7, 8), which are arranged in parallel. According to the invention there is a common exhaust pipe (2) for the exhaust gases of both cylinder groups, which branches into a first line branch (3) to the first exhaust aftertreatment device (5, 6) and a second line branch (4) to the second exhaust aftertreatment device, and also a device (10) for closing the second line branch (4) is provided.

Description

The invention relates to an internal combustion engine with cylinder deactivation and a method for cylinder deactivation. In particular, the invention relates to an internal combustion engine having a plurality of cylinders grouped into a first and a second cylinder group, wherein the cylinders of the second cylinder group are switched off in a partial load operation of the internal combustion engine, and with a first and a second exhaust aftertreatment device, which are arranged in parallel, and a method for cylinder deactivation in such an internal combustion engine, according to the preambles of the independent claims.

A cylinder deactivation enables a reduction in the fuel consumption of multi-cylinder internal combustion engines. For this purpose, the fuel supply to a cylinder group is interrupted at low propulsion request, which may consist of one or more cylinders. The air supply can z. B. by deactivating the valves of the deactivated cylinders are interrupted to avoid gas exchange losses, but there are other solutions for this purpose.

In internal combustion engines with cylinder deactivation, there is usually a separate exhaust gas system with exhaust aftertreatment device for the deactivatable cylinders and the cylinders which are still fired in the cylinder deactivation operation. Such an internal combustion engine with cylinder deactivation according to the preamble of claim 1 is for example from the DE 103 22 509 B4 known. A first exhaust passage connects the outlets of the first cylinder group to the first exhaust aftertreatment device, and a second exhaust passage separated from the first exhaust passage connects the outlets of the first cylinder group to the second exhaust aftertreatment device. The exhaust paths behind the two exhaust aftertreatment devices can either stay separate or reunite.

The invention is based on the object to further reduce fuel consumption and pollutant emissions of multi-cylinder internal combustion engines with cylinder deactivation.

This object is achieved by a cylinder deactivation internal combustion engine and a cylinder deactivation method according to the independent claims.

In the invention, a common exhaust pipe for the exhaust gases of both cylinder groups from the internal combustion engine to the two exhaust aftertreatment devices and branches there into a first and a second line branch to the first and the second exhaust aftertreatment device, and the second line branch during a partial load operation of the internal combustion engine, in the cylinders of the second cylinder group are switched off, or be closed under other conditions.

This makes it possible to optimally adapt the two exhaust aftertreatment devices to the operating modes with or without cylinder deactivation and to ensure as fast as possible the light-off temperature of the catalyst of the exhaust gas aftertreatment device or its maintenance under all operating conditions.

In the known internal combustion engines with cylinder deactivation, this is not possible because the two parallel exhaust aftertreatment devices must be virtually identical when the two cylinder groups contain the same number of cylinders to meet full load conditions.

By contrast, it is possible with the invention to design the two exhaust aftertreatment devices differently, wherein the active during the cylinder deactivation first exhaust aftertreatment device can be optimally adapted to the prevailing in this mode exhaust gas quantity and exhaust gas composition and the switchable second exhaust aftertreatment device can be designed so that they in combination with the first exhaust aftertreatment device optimally meets the conditions prevailing in normal operation. In this way, the fuel consumption and pollutant emissions can be reduced.

In particular, the second exhaust gas aftertreatment device can have a greater exhaust gas purification capacity per cylinder than the first exhaust gas aftertreatment device, wherein the exhaust gas purification capability of an exhaust gas aftertreatment device is determined by its volume, flow cross sections or catalytically or filtering effective surfaces. In normal operation, in which all cylinders are fired, much more catalyst material per cylinder is required than in Zylinderabschaltbetrieb, because a cylinder shutdown tends to take place during lower engine loads.

During a transition from normal operation to cylinder deactivation operation while maintaining the load on the internal combustion engine, the exhaust gas temperature increases because the fired cylinders must generate more torque to maintain engine load, and accordingly more fuel must be received. However, the mass flow is almost halved. In total, this results in a lower energy flow through the exhaust aftertreatment device and in particular by the usually contained therein oxidation catalyst. If this is designed as in the prior art, to cope with the half full throttle exhaust gas, there is a possibility that in Zylinderabschaltbetrieb the working temperature or light-off temperature of the catalyst is exceeded or not or only slowly achieved, especially in cold combustion engine.

As a rule, a catalyst with a lower exhaust gas purification capacity also has a lower heat capacity and can therefore be heated up to its light-off temperature more quickly or kept at this temperature with less energy. Therefore, you can often reduce fuel consumption and pollutant emissions even more, if you use different sized parallel catalysts.

Parallel switched, partly also differently executed exhaust aftertreatment devices, which are each designed for different conditions, in particular different exhaust gas temperatures and can be shut off in adaptation to the straight prevailing conditions, switched or switched, are known in the art, for. B. from the EP 2 385 231 A2 , of the US 5 365 733 A , of the DE 100 11 612 A1 and the US 2010 0199 643 A1 but not in connection with a cylinder deactivation.

However, in conjunction with a cylinder deactivation and its particular problem as explained above, a dual exhaust aftertreatment device provides additional opportunities to achieve fuel economy and pollution reduction, both in cold and warm combustion engines.

In addition, the invention allows material savings and a reduction of the flow resistance of the exhaust pipe system of internal combustion engines with cylinder deactivation and thus further consumption reductions.

In an embodiment where both cylinder groups have the same number of cylinders, the second exhaust purification device has more than twice the total exhaust purification capability than the first exhaust after treatment device, and in some such engine configurations a ratio of the total exhaust purification capabilities of the two exhaust purification devices may be about 30 : 70 be particularly cheap.

The means for closing the second leg could be adapted to operate also on the first leg by selectively closing the first or second leg, intermediate positions also being possible, or opening both legs completely.

However, in a preferred embodiment, the means for closing the second leg is simply a flap located behind the branch in the second leg, which may close all or part of the second leg, and even more preferably is a butterfly, which either completely orbits the second leg opens or closes completely.

Each of the two exhaust after-treatment devices may include an oxidation catalyst and / or a particulate filter, and when the internal combustion engine is a diesel engine, each of the two exhaust after-treatment devices preferably consists of a diesel oxidation catalyst and a diesel particulate filter. For a diesel engine, it is particularly important to bring the catalyst as early as possible to its light-off temperature, so that carbon monoxide can be converted as early as possible. This is possible with the smaller designed second exhaust aftertreatment device also for diesel engines, which tend to produce less exhaust heat than gasoline engines. As soon as more exhaust gas purification capacity is required, this can be rapidly increased to the maximum value by switching on the larger exhaust gas aftertreatment device.

On the outlet side, the two exhaust aftertreatment devices can be connected to each other and open into a common muffler. The two exhaust aftertreatment devices then form a common assembly in which they may have thermal contact with each other, such that the second exhaust aftertreatment device is brought or maintained by the first exhaust aftertreatment device during a partial load operation of the internal combustion engine in which the cylinders of the second cylinder group are switched off , A good thermal contact can z. B. can be achieved by means of a tube-in-tube arrangement. In principle, however, the invention can also be implemented with two thermally separated exhaust aftertreatment devices.

In the inventive method for cylinder deactivation in a multi-cylinder internal combustion engine and having first and second exhaust aftertreatment devices, during a partial load operation of the internal combustion engine, some of the cylinders are shut down and the exhausted cylinder exhaust gas is caused to flow through the first exhaust after-treatment device as shown in FIG DE 10 359 693 B4 known, When all the cylinders are fired, all the exhaust gas is first flowed together to the two exhaust aftertreatment devices and then the exhaust gas flow is divided into two parts, part of which is flowed through the first exhaust aftertreatment device and the other part is flowed through the second exhaust aftertreatment device ,

When the exhaust stream is split in such a manner, more exhaust gas preferably flows through the second exhaust aftertreatment device than through the first exhaust aftertreatment device.

Preferably, in a cylinder deactivation operation, but also in a normal operation, when all cylinders are fired at break-up effective pressure (BMEP) in the cylinder up to about 3 bar for diesel and 6 bar for gasoline engine applications, exhaust gas is prevented from flowing through the cylinder second exhaust aftertreatment device flows. At higher pressures, when all cylinders are fired, exhaust gas aftertreatments are passed through both exhaust aftertreatment devices. At higher engine loads, which correspond to effective mean pressures in the cylinder of more than 3 bar (diesel) or 6 bar (Otto), the combustion engine runs with all cylinders fuel efficient, while at lower engine loads dilution effects occur, so the combustion stabilized by additional introduction of fuel must become.

The refinements of the internal combustion engine according to the invention specified in the dependent claims are also advantageous for the method according to the invention.

The following is a description of embodiments with reference to the drawings. Show:

1 a double exhaust aftertreatment device for a four-cylinder diesel engine, in which two cylinders are switched off; and

2a a schematic diagram illustrating a size ratio of the catalysts of 50:50; and

2 B a schematic diagram illustrating a size ratio of the catalysts of 30:70.

The double exhaust aftertreatment device 1 is to a common exhaust pipe 2 connected, which the exhaust gases of all cylinders of the internal combustion engine, not shown, to the double exhaust aftertreatment device 1 passes. Here the common exhaust pipe branches 2 in a first leg 3 and a second leg 4 , The first line branch 3 opens into a first exhaust aftertreatment device, which consists of a diesel oxidation catalyst 5 and a diesel particulate filter 6 exists, and the second leg 4 opens into a second exhaust aftertreatment device, which consists of a diesel oxidation catalyst 7 and a diesel particulate filter 8th consists. The first and the second exhaust aftertreatment device 5 . 6 respectively. 7 . 8th are arranged in parallel and open into a common exhaust pipe 9 , which leads to a silencer, not shown.

In the second leg 4 is a butterfly valve 10 arranged, located in 1 is in an open position, but by means of a not shown, for. B. electromagnetic actuator can be rotated in the dashed line position in which they the second leg 4 essentially closes, so that the exhaust gases only the diesel oxidation catalyst 5 and the diesel particulate filter 6 can flow through.

As in 2a illustrates the diesel oxidation catalysts 5 and 7 be the same size, in the sense that they have the same volume, flow cross sections or catalytically active surfaces. The same applies to the diesel particulate filter 6 . 8th and the flow cross sections of the line branches 4 . 3 ,

Alternatively, the diesel oxidation catalyst 7 and the diesel particulate filter 8th each larger than the diesel oxidation catalyst 5 and the diesel particulate filter 6 be like in 1 and 2 B illustrated. That is, they have larger volumes, flow cross sections or catalytically or filtering effective surfaces.

In a cylinder shut-down operation, or when the engine running on all cylinders measures effective center pressures in the cylinder up to approximately 3 bar (diesel) 6 bar (Otto), the damper will turn 4 brought into the closed position. At higher speeds or loads is the door 4 also open in cylinder deactivation mode. Alternatively or additionally, the flap 4 also be opened and closed depending on the currently measured exhaust gas temperature.

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

• DE 10322509 B4 [0003]
• EP 2385231 A2 [0013]
• US 5365733A [0013]
• DE 10011612 A1 [0013]
• US 20100199643 A1 [0013]
• DE 10359693 B4 [0021]

Claims (10)

Internal combustion engine with a plurality of cylinders, which are grouped into a first and a second cylinder group, wherein the cylinders of the second cylinder group are switched off in a partial load operation of the internal combustion engine, and with a first ( 5 . 6 ) and a second exhaust aftertreatment device ( 7 . 8th ), which are arranged in parallel, characterized in that a common exhaust pipe ( 2 ) is present for the exhaust gases of both cylinder groups, which are in a first line branch ( 3 ) to the first exhaust aftertreatment device ( 5 . 6 ) and a second line branch ( 4 ) branches to the second exhaust aftertreatment device, and that means ( 10 ) for closing the second line branch ( 4 ) is provided. Internal combustion engine according to claim 1, characterized in that the second exhaust gas aftertreatment device ( 7 . 8th ) a greater exhaust gas purification capacity per cylinder than the first exhaust gas aftertreatment device ( 5 . 6 ) and in particular has more than twice the total exhaust gas purification capacity if the two cylinder groups contain the same number of cylinders. Internal combustion engine according to claim 1 or 2, characterized in that the device ( 10 ) is a flap disposed behind the branch in the second line branch for closing the second leg and is in particular a butterfly valve. Internal combustion engine according to one of the preceding claims, characterized in that each of the two exhaust gas aftertreatment devices ( 5 . 6 ; 7 . 8th ) an oxidation catalyst ( 5 ; 7 ) and / or a particulate filter ( 6 ; 8th ) contains. Internal combustion engine according to one of the preceding claims, characterized in that the internal combustion engine is a diesel engine, wherein each of the two exhaust gas aftertreatment devices ( 5 . 6 ; 7 . 8th ) from a diesel oxidation catalyst ( 5 ; 7 ) and a diesel particulate filter ( 6 ; 8th ) consists. Internal combustion engine according to one of the preceding claims, characterized in that the two exhaust aftertreatment devices ( 5 . 6 ; 7 . 8th ) are connected to each other on the outlet side and in particular in a common exhaust pipe ( 9 ). Internal combustion engine according to claim 6, characterized in that the two exhaust aftertreatment devices an assembly ( 1 ), in which they have thermal contact with each other, such that the second exhaust aftertreatment device ( 7 ) during a partial load operation of the internal combustion engine in which the cylinders of the second cylinder group are switched off, from the first exhaust gas after treatment device ( 5 ) is brought to temperature or held. Method for cylinder deactivation in a multi-cylinder internal combustion engine and having first and second exhaust after-treatment devices ( 5 . 6 ; 7 . 8th ), wherein during a partial load operation of the internal combustion engine, some of the cylinders are switched off and the exhaust gas of the fired cylinders by the first exhaust gas aftertreatment device ( 5 . 6 ), characterized in that, when all the cylinders are fired, all of the exhaust gas is first communicated to the two exhaust aftertreatment devices ( 5 . 6 ; 7 . 8th ) and the exhaust stream is then divided into two parts, a part of which through the first exhaust aftertreatment device ( 5 . 6 ) and the other part through the second exhaust aftertreatment device ( 7 . 8th ) is allowed to flow. Method according to claim 8, characterized in that, when the exhaust gas flow is divided, more exhaust gas is passed through the second exhaust gas aftertreatment device (16). 7 . 8th ) than by the first exhaust aftertreatment device ( 5 . 6 ) is allowed to flow. A method according to claim 8 or 9, characterized in that in a Zylinderabschaltbetrieb, or at effective mean pressures in the cylinder up to about 3 bar (diesel) or 6 bar (Otto), prevents exhaust gas through the second exhaust aftertreatment device ( 7 . 8th ) flows.

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