OPERATION OF AN INTERNAL COMBUSTION ENGINE HAVING AN ELECTRIC FRESH GAS COMPRESSOR AND HAVING AN EXHAUST TURBINE WITH A BYPASS LINE AND VTG

Abstract

A method for operating an internal combustion engine, which comprises a combustion engine, a fresh gas line into which a fresh gas compressor is integrated, wherein the fresh gas compressor can be driven by an electric motor, and an exhaust gas line, in which an exhaust turbine, which has a variable turbine geometry, a bypass line with a bypass valve for bypassing the exhaust turbine as required, and, downstream of the exhaust turbine and the bypass line, an exhaust gas aftertreatment component are integrated, wherein if, during operation of the combustion engine, an operating temperature of the exhaust gas aftertreatment component is below a set temperature, the bypass line is at least temporarily released, the fresh gas compressor is driven by the electric motor, and the VTG is set to a closed position of at least 50% or at least 80% or at least 90% or 100%.

Claims

1. A method for operating an internal combustion engine, the comprising: providing the internal combustion engine; providing a fresh gas line into which a fresh gas compressor is integrated, wherein the fresh gas compressor is adapted to driven by an electric motor; providing an exhaust gas line, in which an exhaust turbine, which has a variable turbine geometry, a bypass line with a bypass valve for bypassing the exhaust turbine as required, and, downstream of the exhaust turbine and the bypass line, an exhaust gas aftertreatment component are integrated; and determining if, during operation of the combustion engine, an operating temperature of the exhaust gas aftertreatment component is below a set temperature, then: the bypass line is at least temporarily released, the fresh gas compressor is driven by the electric motor, and the VTG is set to a closed position of at least 50% or at least 80% or at least 90% or 100%.

2. The method according to claim 1, wherein the set temperature is a light-off temperature of the exhaust gas aftertreatment component.

3. The method according to claim 1, wherein the set temperature is a regeneration temperature of the exhaust gas aftertreatment component.

4. The method according to claim 1, wherein immediately after a cold start of the internal combustion engine, the fresh gas compressor (11) is driven by the electric motor and the VTG is set to the closed position of at least 50% or at least 80% or at least 90% or 100%.

5. The method according to claim 1, wherein the fresh gas compressor and the exhaust turbine are mechanically coupled.

6. The method according to claim 5, wherein the VTG is set to the 100% closed position.

7. The method according to claim 1, wherein the fresh gas compressor and the exhaust turbine are mechanically decoupled.

8. The method according to claim 1, wherein the VTG is set to a position closed less than 100%.

9. The method according to claim 1, wherein, when the bypass line is released, the fresh gas compressor is driven by the electric motor and the VTG is set to the closed position of at least 50% or at least 80% or at least 90% or 100%, the exhaust gas is at least temporarily branched off from the exhaust gas line and introduced into the fresh gas line.

10. The method according to claim 9, wherein the exhaust gas is branched off from the exhaust gas line downstream of the exhaust turbine and introduced into the fresh gas line upstream of the fresh gas compressor.

11. A vehicle comprising: an internal combustion engine; a fresh gas line into which a fresh gas compressor is integrated, wherein the fresh gas compressor is adapted to driven by an electric motor; and an exhaust gas line, in which an exhaust turbine, which has a variable turbine geometry, a bypass line with a bypass valve for bypassing the exhaust turbine as required, and, downstream of the exhaust turbine and the bypass line, an exhaust gas aftertreatment component are integrated, wherein, during operation of the combustion engine, an operating temperature of the exhaust gas aftertreatment component is below a set temperature, then: the bypass line is at least temporarily released; the fresh gas compressor is driven by the electric motor; and the VTG is set to a closed position of at least 50% or at least 80% or at least 90% or 100%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0024] FIG. 1 shows an internal combustion engine that can be operated according to the invention in a simplified representation;

[0025] FIG. 2 shows the time curves of the exhaust gas temperature T.sub.3 upstream of an exhaust turbine for three differently operated internal combustion engines during the same operating cycle;

[0026] FIG. 3 shows corresponding curves of the mass flow rate {dot over (m)}.sub.AT of the exhaust gas through the respective exhaust turbine for the three internal combustion engines;

[0027] FIG. 4 shows corresponding curves of a temperature T.sub.AT of the respective exhaust turbine of the three internal combustion engines;

[0028] FIG. 5 shows corresponding curves of the operating temperature T.sub.PF of a particulate filter of the three internal combustion engines; and

[0029] FIG. 6 shows corresponding curves of the fuel consumption FC of a combustion engine of the three internal combustion engines.

DETAILED DESCRIPTION

[0030] FIG. 1 shows a motor vehicle internal combustion engine suitable for operation in accordance with the invention. It comprises a combustion engine 1, which by way of example is designed in the form of a reciprocating piston engine with four cylinder ports 2 arranged in series. Cylinder ports 2 each define a combustion chamber 4 with reciprocating pistons 3, movably guided therein, and with a cylinder head (not shown). Fresh gas is supplied to these combustion chambers 4 via a fresh gas line 5 during operation of combustion engine 1 and thus of the internal combustion engine, wherein the feeding of the fresh gas is controlled by means of inlet valves 6 associated with the individual combustion chambers 4. The fresh gas is exclusively or mainly air that has been drawn in from the environment. Exhaust gas arising during the combustion of mixture quantities, including the fresh gas as well as fuel injected directly into combustion chambers 4 via fuel injectors 7, is discharged via an exhaust gas line 8 of the internal combustion engine, wherein the removal of the exhaust gas is controlled by means of outlet valves 9 also associated with the individual combustion chambers 4. The exhaust gas here flows through an exhaust gas aftertreatment device 10, which is designed to remove exhaust gas components that are considered pollutants from the exhaust gas or to convert them into harmless components.

[0031] Ignition of the mixture quantities in combustion chambers 4 can take place by means of electrical ignition devices (not shown), which generate ignition sparks (spark plugs), for example, or by compression ignition.

[0032] The internal combustion engine is designed as supercharged, for which purpose a fresh gas compressor 11 is integrated into fresh gas line 5. Fresh gas compressor 11 is part of an exhaust turbocharger, which further comprises an exhaust turbine 12, integrated into exhaust gas line 8, with variable turbine geometry (VTG) 13. Exhaust gas flowing through exhaust turbine 12 leads to a rotating drive of a turbine wheel (not shown), which is connected to a compressor wheel (not shown) of fresh gas compressor 11 via a shaft 14 in a rotationally driven manner, so that as a result driving of fresh gas compressor 11 can occur by means of exhaust turbine 12. The exhaust turbocharger further comprises an electric motor 15, which is mechanically coupled to shaft 14 and by means of which shaft 14 and thus also the compressor wheel of fresh gas compressor 11 (as well as the turbine wheel of exhaust turbine 12) can be driven in a rotating manner as needed.

[0033] Exhaust gas line 8 further comprises a bypass line 16 with a bypass valve 17, which branches off immediately upstream of exhaust turbine 12 from a main line of exhaust gas line 8, said main line integrating exhaust turbine 12, and rejoins the main line of exhaust gas line 8 immediately downstream of exhaust turbine 12 and thus upstream of exhaust gas aftertreatment device 10. When bypass valve 17 is open, exhaust gas is routed via bypass line 16, whereby this exhaust gas bypasses exhaust turbine 12 or does not flow through it.

[0034] Exhaust gas aftertreatment device 10 can comprise, for example, an exhaust gas aftertreatment component in the form of an oxidation catalyst 18 and, downstream of oxidation catalyst 18, an exhaust gas aftertreatment component in the form of a particulate filter 19.

[0035] If, during the operation of combustion engine 1, at least one of these exhaust gas aftertreatment components has an operating temperature that is below a defined set temperature, the invention provides for at least temporarily releasing bypass line 16 by at least partially and preferably completely opening bypass valve 17 and for setting VTG 13 to a 100% closed position or a position closed as far as possible. It can be achieved thereby that, as far as possible, all the exhaust gas coming from combustion engine 1 is routed via bypass line 16 and thereby bypasses exhaust turbine 12. In this way, it can be avoided that the exhaust gas is largely cooled down as a result of a flow through exhaust turbine 12, which would be attributable, on the one hand, to an expansion by exhaust turbine 12 and, on the other hand, to a transfer of thermal energy for heating the also still relatively cold exhaust turbine 12, which has a relatively large thermal mass. In contrast, bypass line 16 has a relatively small thermal mass, so that flow through bypass line 16 results in only a relatively little cooling of the exhaust gas. Accordingly, the exhaust gas enters exhaust gas aftertreatment device 10 with a relatively high temperature and can thereby lead to a fastest possible heating of exhaust gas aftertreatment device 10 or the exhaust gas aftertreatment components comprised by it until at least the respective set temperature is reached.

[0036] Because due to the bypassing, exhaust turbine 12 generates no or hardly any drive power for fresh gas compressor 11 by means of the exhaust gas, during this operation of the internal combustion engine the fresh gas compressor (and due to the mechanical coupling with exhaust turbine 12, exhaust turbine 12 as well) is driven by means of electric motor 15 depending on the demand of combustion engine 1 for fresh gas. As a result, it can be avoided that the bypassing of exhaust turbine 12 leads to disadvantages in the operating behavior with regard to the exhaust gas flow and, in particular, also with regard to the power output of combustion engine 1.

[0037] FIGS. 2 to 6 illustrate this method of the invention and the advantages achievable thereby by means of time curves with respect to the temperature T.sub.3 of the exhaust gas upstream of exhaust turbine 12 (cf. FIG. 2), with respect to the mass flow rate {dot over (m)}.sub.AT of the exhaust gas through exhaust turbine 12 (cf. FIG. 3), with respect to a temperature T.sub.AT of exhaust turbine 12 (cf. FIG. 4), with respect to the operating temperature T.sub.PF of particulate filter 19 (cf. FIG. 5), and with respect to the fuel consumption FC of combustion engine 1 related to a mileage of a motor vehicle comprising the internal combustion engine (cf. FIG. 6), in each case during an operating cycle of the internal combustion engine in a warm-up operating phase immediately following a cold start of the internal combustion engine at t=0.

[0038] These curves are each shown with solid lines for an operation of the invention of an internal combustion engine according to, for example, FIG. 1; i.e., exhaust gas is routed continuously via bypass line 16 during operation. Furthermore, fresh gas compressor 11 is driven by means of electric motor 15 if and as required and VTG 13 is set to a 95% closed position.

[0039] The dashed lines, on the other hand, show the curves with respect to the operation of the same internal combustion engine in which the exhaust gas is also routed via bypass line 16 and fresh gas compressor 11 is driven by electric motor 15 if and as required, but in which VTG 13 is set to a fully open or 0% closed position.

[0040] And the dotted lines show the curves with respect to the operation of an internal combustion engine in which no electric motor 15 is associated with the exhaust turbocharger and in which the compression required for the operation of combustion engine 1 according to the operating cycle by means of the fresh gas compressor is carried out exclusively using drive power provided by means of exhaust turbine 12, wherein VTG 13 or exhaust turbine 12 is adjusted depending on the demand of fresh gas compressor 11 for drive power. The entire exhaust gas is always routed via exhaust turbine 12. Otherwise, this internal combustion engine corresponds to the other internal combustion engine.

[0041] The operating cycle extends over a period of 900 seconds and is characterized by a variable operation of combustion engine 1, which, according to FIG. 2, results in a highly fluctuating temperature T.sub.3 of the exhaust gas upstream of exhaust turbine 12. The curves of the exhaust gas temperature T.sub.3 for the different internal combustion engines or the different operating modes of the internal combustion engines are substantially congruent in this case.

[0042] However, according to FIG. 3, the different operating modes result in significantly different mass flow rates of the exhaust gas through exhaust turbine 12. It can be seen that the mass flow rate of the exhaust gas through the internal combustion engine operated according to the invention is again significantly reduced compared with that in which bypass line 16 is released but VTG 13 is also open at the same time. This has the result that exhaust turbine 12 of the internal combustion engine operated according to the invention heats up much more slowly and also to a lesser extent in the course of the operating cycle (cf. FIG. 4), whereas the operating temperature T.sub.PF of particulate filter 19 of this internal combustion engine rises much faster and also to higher values (cf. FIG. 5). Accordingly, a significantly faster heating of particulate filter 19 or of the entire exhaust gas aftertreatment device 10 can be realized by operating the internal combustion engine according to the invention. A disadvantage here may possibly be a slightly higher fuel consumption of combustion engine 1, which may be due to the fact that the electrical power required to operate electric motor 15 driving fresh gas compressor 11 must essentially be generated by means of a generator-driven electric machine (not shown in FIG. 1) mechanically coupled to combustion engine 1, which may result in a higher load during operation of combustion engine 1. In the case of the internal combustion engine, in which the exhaust gas is also (partially) routed via bypass line 16 but in which VTG 13 is kept open, in contrast, a higher proportion of the exhaust gas flows through the exhaust turbine (cf. FIG. 3), whereby, as a result of the mechanical coupling with fresh gas compressor 11, this covers part of the demand for drive power for fresh gas compressor 11, so that correspondingly less drive power has to be provided by electric motor 15.

[0043] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims