METHOD OF OPERATING AN INTERNAL COMBUSTION ENGINE, AN INTERNAL COMBUSTION ENGINE AND A MOTOR VEHICLE

Abstract

A method of operating an internal combustion engine, wherein the internal combustion engine has at least one combustion engine, a fresh gas line, and a compressor integrated in the gas line, which is associated with a trim controller, via which an edge-side portion of the inlet cross section of a compressor impeller of the compressor is coverable to a variable extent. In this case, in a release position of the trim controller, the edge-side portion of the inlet cross section is covered relatively little, and in a covering position of the trim controller, is mostly covered. It is provided that in a transition from a traction mode of the combustion engine, in which the trim controller is in the release position, the trim controller is adjusted to an overrun mode of the combustion engine into the covering position. As a result, a so-called discharge hissing can be prevented or minimized.

Claims

1. A method for operating an internal combustion engine, the method comprising: providing a combustion engine and a fresh gas line, wherein a compressor is integrated in the fresh gas line and wherein the compressor is associated with a trim controller via which an edge-side portion of the inlet cross section of a compressor impeller of the compressor is adapted to be covered to a variable extent, wherein in a release position of the trim controller, the edge-side portion of the inlet cross section is covered relatively little and in a covering position of the trim controller, the edge-side portion is mostly covered; adjusting the trim controller to an overrun mode of the combustion engine into the covering position, in a transition from a traction mode of the combustion engine, in which the trim controller is in the release position.

2. The method according to claim 1, wherein, in the covering position, the trim controller covers the edge-side portion of the inlet cross section as much as possible.

3. The method according to claim 1, wherein the trim controller is again adjusted to the release position upon reaching a defined limit value.

4. The method according to claim 3, wherein the limit value defines a timing or a gas pressure in the fresh gas line.

5. An internal combustion engine comprising: a combustion engine; a fresh gas line; a compressor integrated in the fresh gas line, wherein the compressor is associated with a trim controller via which an edge-side portion of the inlet cross section of a compressor impeller of the compressor is covered to a varying extent, wherein in a release position of the trim controller, the edge-side portion of the inlet cross section is covered relatively little, and in a covering position of the trim controller, is mostly covered; and a control device which is adapted for an automated execution of the method according to claim 1.

6. The internal combustion engine according to claim 5, wherein the trim controller comprises an annular diaphragm (48).

7. The internal combustion engine according to claim 6, wherein the trim controller additionally comprises a flow guide device by means of which at least a portion of the fresh gas line is divided into a central flow region and a peripheral flow region, both transitioning into a flow space of the compressor in the area of the inlet plane of the compressor impeller, wherein the peripheral flow region is formed to be closeable via the diaphragm.

8. The internal combustion engine according to claim 7, wherein at least an end portion of the flow guide device located adjacent to the compressor impeller is formed to be longitudinally axially displaceable, wherein the peripheral flow region in the region of the inlet plane of the compressor impeller is closed in a closed position of the flow guide device via this end portion and is released in an open position.

9. The internal combustion engine according to claim 5, wherein, in an absence of activation by the control device, the trim controller is moved into a release position by means of a reset element in which the trim controller covers the edge-side portion of the inlet cross section as little as possible.

10. A motor vehicle comprising an internal combustion engine according to claim 5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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:

[0030] FIG. 1 illustrates an internal combustion engine according to the invention;

[0031] FIG. 2 illustrates a longitudinal section through a compressor for an internal combustion engine according to FIG. 1 with an associated trim controller in a position covering the inlet cross section of a compressor impeller as little as possible;

[0032] FIG. 3 illustrates the compressor according to FIG. 2 with the trim controller in a position covering the inlet cross section of the compressor impeller as much as possible; and

[0033] FIG. 4 illustrates in a total of four diagrams, the waveforms of various parameters during a portion of an operation of an inventive internal combustion engine, which comprises a transition from the traction mode to the overrun mode.

DETAILED DESCRIPTION

[0034] FIG. 1 shows a schematic representation of an inventive internal combustion engine with a combustion engine 10 embodied as a spark-ignited motor, comprising a plurality of cylinders 12. The cylinders 12, together with pistons guided up and down therein and a cylinder head, define combustion chambers in which fresh gas is combusted together with fuel. The fuel, controlled by a control device 14 (engine control), is injected directly into the combustion chambers by means of injectors 16. The combustion of the fuel fresh gas mixture amounts leads to cyclic up and down movements of the pistons, which in turn are transferred in a known manner via connecting rods to a crankshaft, whereby the crankshaft is driven in rotation.

[0035] The fresh gas is supplied to the engine 10 via a fresh gas line and is aspirated from the environment via an intake port 18, cleaned in an air filter 20 and then fed into a compressor 22, which is part of an exhaust gas turbocharger. The fresh gas is compressed by means of the compressor 22, then cooled in a charge-air cooler 24 and finally fed to the combustion chambers. The compressor 22 is driven by means of an exhaust gas turbine 26 of the exhaust gas turbocharger, which is integrated into an exhaust line of the internal combustion engine. Exhaust gas formed by the fuel fresh gas mixture amounts in the combustion chambers of the engine 10 is discharged through the exhaust line from the combustion engine 10 and thereby flows through the exhaust gas turbine 26. This leads in a known manner to a rotating drive of a turbine impeller, which is non-rotatably connected via a shaft 28 to a compressor impeller 30 (see FIGS. 2 and 3) of the compressor 22. The rotating drive of the turbine impeller is thus transferred to the compressor impeller 30.

[0036] In order to optimally implement the enthalpy of the exhaust gas for producing compression performance by means of the exhaust gas turbocharger during operation of the engine 10 at varying loads and speeds, the exhaust gas turbine 26 of the exhaust gas turbocharger may optionally comprise a device for variable turbine geometry (VTG) 32, which is controllable by means of the control device 14. This may comprise in a known manner a plurality of guide blades, which are arranged in an inlet channel of the exhaust gas turbine 26 and which are individually rotatable, wherein these may be adjusted together by means of an adjusting device. As a function of the rotational positions of the guide blades, these more or less narrow the free flow cross section in the inlet channel of the exhaust gas turbine 26 and also influence the portion of the primary flow of the turbine impeller and the orientation of this flow.

[0037] A throttle valve 34, likewise controllable by means of the control device 14, is integrated downstream of the compressor 22 in the charge-air duct, i.e. in the portion of the fresh gas line which is located between the compressor 22 and the engine 10.

[0038] The internal combustion engine may comprise an exhaust gas recirculation line 36 to recirculate (low pressure) exhaust gas, in which the exhaust gas is branched off from a portion of the exhaust gas line, which is located downstream of the exhaust gas turbine 26 and, in particular, also downstream of an exhaust gas aftertreatment device 38, such as a particulate filter, and is introduced into a section of the fresh gas line upstream of the compressor impeller 30. The amount of exhaust gas recirculated via the exhaust gas recirculation line 36 can in this case be controlled or regulated by means of a control valve 40 which is controllable by means of the control device 14. Further, an exhaust gas cooler 42 may be integrated in the exhaust gas recirculation line 36 for cooling the exhaust gas recirculated through it.

[0039] The compressor 22 is associated with a trim controller 44 by means of which the incident flow of the compressor impeller 30 can be influenced by the fresh gas. For this purpose, the trim controller 44 or an associated actuator can be controlled by means of the control device 14. The exhaust gas recirculation line 36 may end in the fresh gas line upstream or on the side of the trim controller 44 facing away from the compressor impeller 30. An orifice downstream or in the region of the trim controller 44 (and upstream of the compressor impeller 30) is also possible.

[0040] In a longitudinal section, FIGS. 2 and 3 each show a possible embodiment for an inventive compressor 22. This compressor 22 may be provided, for example, for an internal combustion engine according to FIG. 1, wherein the trim controller 44 and a connection channel 46 for the exhaust gas recirculation line 36 are integral parts of the compressor 22. This is indicated in FIG. 1 by a dashed border.

[0041] The compressor 22 according to FIGS. 2 and 3 includes a housing 50, which may constitute a partial housing of an overall housing of an exhaust gas turbocharger. The housing 50 of the compressor 22 forms a flow space 52 within which the compressor impeller 30 is rotatably mounted. On the inlet side, the flow space 52 has an inlet cross section located in an inlet plane 54. Via an inlet channel 56 likewise formed by the housing 50 of the compressor 22, fresh gas can be guided from a compressor inlet 58 to the compressor impeller 30. On the outlet side, the flow space 52 is limited by an outlet plane surrounding outlet edges of impeller blades 60 of the compressor impeller 30. There, it is adjoined by a diffuser space 62 also surrounding the outlet edges of the impeller blades 60, and adjoining that, which is in FIGS. 2 and 3, is a compressor volute. A compressor outlet branches off from the compressor volute.

[0042] Within the inlet channel 56, the trim controller 44 is arranged as closely as possible to the inlet cross section of the compressor impeller 30. The trim controller 44 includes an iris diaphragm 48 with a structure basically known from photo lenses. In a covering position according to FIG. 3, in a peripherally located annular area of the inlet cross section, the trim controller 44 mostly prevents an inflow of fresh gas flowing in the direction of the compressor impeller 30 to the compressor impeller 30. In this way, the trim controller 44 focuses this fresh gas flow on a hub-proximal portion of the compressor impeller 30. In a release position according to FIG. 2, however, the fresh gas can flow into the compressor impeller 30 over the entire inlet cross section. The diaphragm elements forming the iris diaphragm 48, which are each pivotably mounted about an axis within the housing 50 for opening or closing the iris diaphragm 48, in the release position are arranged completely in an annular recess 64 of the housing 50.

[0043] According to the invention, it is provided that during the operation of an internal combustion engine according to FIG. 1, when transitioning from the traction mode of the combustion engine 10 in which the trim controller 44 is in the release position according to FIG. 2, the trim controller 44 is always moved to an overrun mode to a covering position according to FIG. 3 in order to prevent or at least minimize discharge hissing. FIG. 4 clarifies this process based on four graphs, which show by way of example concurrent waveforms of different characteristics during a portion of the operation of the internal combustion engine involving such a transition from the traction mode to the overrun mode.

[0044] In each case, the top diagram of FIG. 4 shows the percentage open position S.sub.D of the throttle valve 34, wherein the throttle valve 34 is opened the farther, the higher the percentage open position. Accordingly, during a traction mode of the combustion engine 10, the throttle valve 34 is at least partially opened, whereas it is completely closed for an overrun mode of the combustion engine 10 (open position: 0%). The trajectory in the uppermost diagram of FIG. 4 thus shows a transition from a traction mode of the combustion engine 10 to an overrun mode, wherein this transition, characterized by a complete removal of the load with which the combustion engine 10 is operated, is marked by a vertically extending, dashed line. From this transition on, the throttle valve 34 is moved as quickly as possible to the fully closed position.

[0045] The complete load removal for the operation of the combustion engine 10, which characterizes the transition from a traction mode to an overrun mode, causes the drive power of the exhaust gas turbine 26 and thus the compression performance of the compressor 22 to drop relatively quickly. The relatively high pressure p.sub.2 in the charge-air duct of the fresh gas line, which was previously effected in the traction mode by the relatively high compression performance, does not decrease correspondingly faster since the possibility of outflow of the compressed fresh gas into the combustion engine 10 is not possible due to the closed throttle valve 34. Therefore, by a recirculation of compressed fresh gas, there is a reduction in the pressure difference between the high pressure side and the low pressure side of the compressor via the compressor impeller 30 rotating only at relatively low speed. The upper of the two middle diagrams of FIG. 4 illustrates this relatively slow pressure loss in the charge-air duct (until the ambient air pressure p.sub.u is almost reached) after a transition from the traction mode to the overrun mode.

[0046] The recirculation of compressed fresh gas from the high pressure side to the low pressure side of the compressor 22 causing this pressure loss in the charge-air duct can lead to discharge hissing since pressure oscillations can superimpose the average boost pressure shown in the upper middle graph of FIG. 4 and these pressure vibrations can lead to vibration excitations of components of the fresh gas line situated upstream of the compressor impeller.

[0047] The lowest graph in FIG. 4 illustrates this effect on the basis of progressions for the sound pressure level L.sub.P (in dB) measured at a location outside the fresh gas line near the compressor inlet 58. In this case, the course for the sound pressure level L.sub.P is shown on the one hand with dashed lines, which ensues when in a transition from the traction mode to the overrun mode according to FIG. 4, the trim controller 44, which was set to a release position (covering as little as possible) during the traction mode according to FIG. 2, is left in this release position. A significantly higher sound pressure level L.sub.P is apparent shortly after the transition from the traction mode to the overrun mode, as compared to an inventive process (compare the course in the lowest diagram of FIG. 4 with the continuous lines), in which according to the lower of the two middle diagrams of FIG. 4, the trim controller 44 previously set to the release position S.sub.T1 is adjusted simultaneously with the transition from the traction mode to the overrun mode in the covering position S.sub.T2 (covering as much as possible) according to FIG. 3.

[0048] 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.