METHOD FOR OPERATING AN ACTIVE OIL SEPARATOR AND DEVICE FOR SEPARATING OIL

Abstract

A method for operating an active oil separator for separating oil from exhaust air of a crankcase of a motor vehicle with an internal combustion engine. An engine operating state of the internal combustion engine is detected. A first SET rotational speed of the oil separator is determined as a function of the detected engine operating state and a first characteristic map. A maximum SET rotational speed of the oil separator is determined as a function of the first SET rotational speed by the determination device. A preferred SET rotational speed is determined on the basis of the maximum SET rotational speed by a determination device. An electric motor is controlled to drive the oil separator at the preferred SET rotational speed by a control device. A device is also provided for separating oil from exhaust air of a crankcase of a motor vehicle with an internal combustion engine.

Claims

1. A method for operating an active oil separator for separating oil from exhaust air of a crankcase of a motor vehicle with an internal combustion engine, the method comprising: detecting an engine operating state of the internal combustion engine via a detection device, the engine operating state being determined by an engine load and/or an engine speed of the internal combustion engine; determining, via a determination device, a first SET rotational speed of the oil separator as a function of the detected engine operating state and a first characteristic map, wherein the first characteristic map specifies the first SET rotational speed of the oil separator as a function of the engine operating state; determining a maximum SET rotational speed of the oil separator as a function of the first SET rotational speed by means of the determination device in such a manner that the maximum SET rotational speed is at least as high as the first SET rotational speed; determining a preferred SET rotational speed on the basis of the maximum SET rotational speed via the determination device such that the preferred SET rotational speed is, at most, as large as the maximum SET rotational speed; and controlling an electric motor to drive the oil separator at the preferred SET rotational speed via a control device.

2. The method according to claim 1, wherein the engine operating state is detected via the detection device from an engine control unit for controlling the internal combustion engine.

3. The method according to claim 1, wherein an oil temperature of the internal combustion engine is detected via the detection device, wherein a second SET rotational speed of the oil separator is determined via the determination device as a function of the detected oil temperature and a second characteristic map, wherein the second characteristic map specifies the second SET rotational speed of the oil separator as a function of the oil temperature, wherein the determination of the maximum SET rotational speed of the oil separator via the determination device additionally takes place as a function of the second SET rotational speed such that the maximum SET rotational speed is at least as high as the second SET rotational speed.

4. The method according to claim 1, wherein an oil pressure of the internal combustion engine is detected via the detection device, wherein a third SET rotational speed of the oil separator is determined via the determination device as a function of the detected oil pressure and a third characteristic map, wherein the third characteristic map specifies the third SET rotational speed of the oil separator as a function of the oil pressure, wherein the determination of the maximum SET rotational speed of the oil separator via the determination device additionally takes place as a function of the third SET rotational speed such that the maximum SET rotational speed is at least as high as the third SET rotational speed.

5. The method according to claim 1, wherein a vehicle system voltage of a vehicle electrical system for operating the electric motor is detected via the detection device, wherein a fourth SET rotational speed of the oil separator is determined via the determination device as a function of the detected vehicle system voltage and a fourth characteristic map, wherein the fourth characteristic map specifies the fourth SET rotational speed of the oil separator as a function of the vehicle system voltage, wherein a minimum SET rotational speed is determined via the determination device as a function of the fourth SET rotational speed such that the minimum SET rotational speed is at most as large as the fourth SET rotational speed, wherein the determination of the preferred SET rotational speed of the oil separator via the determination device additionally takes place as a function of the minimum SET rotational speed such that the preferred SET rotational speed is at most as high as the minimum SET rotational speed.

6. The method according to claim 5, wherein a water content in the oil is detected via the detection device, wherein a fifth SET rotational speed of the oil separator is determined via the determination device as a function of the detected water content and a fifth characteristic map, wherein the fifth characteristic map specifies the fifth SET rotational speed of the oil separator as a function of the water content, wherein the minimum SET rotational speed is additionally determined via the determination device as a function of the fifth SET rotational speed such that the minimum SET rotational speed is at most as large as the fifth SET rotational speed.

7. The method according to claim 5, wherein a fuel content in the oil is detected via the detection device, wherein a sixth SET rotational speed of the oil separator is determined via the determination device as a function of the detected fuel content and a sixth characteristic map, wherein the sixth characteristic map specifies the sixth SET rotational speed of the oil separator as a function of the fuel content, wherein the minimum SET rotational speed is additionally determined via the determination device as a function of the sixth SET rotational speed such that the minimum SET rotational speed is at most as large as the sixth SET rotational speed.

8. The method according to claim 1, wherein the method is performed repeatedly, and wherein the preferred SET rotational speed is changed via a hysteresis only when the change exceeds a minimum change specified by the hysteresis.

9. The method according to claim 8, wherein the control of the electric motor for driving the oil separator at the preferred SET rotational speed via the control device takes place with a limited gradient such that a current for operating the electric motor does not exceed a predefined current limit value.

10. A separator for separating oil from exhaust air of a crankcase of a motor vehicle with an internal combustion engine, the separator comprising: an active oil separator; an electric motor for driving the oil separator; a detection device to detect operating parameters of the motor vehicle; a determination device to determine SET rotational speeds of the electric motor as a function of at least one operating parameter and at least one characteristic map; and a control device to control the electric motor as a function of a preferred SET rotational speed, wherein the separator is adapted to perform the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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:

[0036] FIG. 1 shows an example of a device according to the invention in a schematic representation,

[0037] FIG. 2 shows an example of an oil separator in a sectional representation and side view,

[0038] FIG. 3 shows a detail of the oil separator from FIG. 2,

[0039] FIG. 4 shows the oil separator from FIG. 2 in a sectional representation and top view,

[0040] FIG. 5 shows example aspects of the method according to the invention in a schematic representation, and

[0041] FIG. 6 shows the method according to the invention in a flow chart.

DETAILED DESCRIPTION

[0042] In FIG. 1, an example of a device 8 according to the invention is shown schematically. The device 8 has an oil separator 1 with an air inlet 16 for uptake of exhaust air A from a crankcase 2 of an internal combustion engine 3, an oil outlet 18 for returning an oil flow B of oil separated from the exhaust air A to the crankcase 2, as well as an air outlet 17 for removing cleaned air C. The air outlet 17 is coupled in a fluid-communicating manner to, e.g., an exhaust turbocharger 9 and/or an intake manifold 10 of an intake tract of the internal combustion engine 3. Furthermore, the device 8 has an electric motor 6 for driving the oil separator 1. In addition, the device 8 has a detection device 4, in particular for detecting an engine operating state of the internal combustion engine 3, a determination device, in particular for determining a preferred SET rotational speed SB, and a control device 7 for controlling the electric motor 6.

[0043] FIG. 2 schematically shows an oil separator 1 of the device 8 according to the invention in a sectional representation and side view. In FIG. 3, a detail of the oil separator 1 from FIG. 2 is shown schematically in a side view. The oil separator 1 has a central shaft 11 with a shaft longitudinal axis L, on which is arranged a disk stack with a multiplicity of disks 12. The shaft 11 can be set into rotation about the shaft longitudinal axis L by means of the electric motor 6. The disks 12 are spaced apart from one another along the shaft longitudinal axis L. The shaft longitudinal axis L runs through the centers of mass of the disks 12 in order to ensure smooth operation of the oil separator 1. Edge regions 13 of the disks 12 are bent downward in order to improve a separation of the oil droplets O from the exhaust air A. To collect the oil droplets O, the oil separator 1 has a baffle 14. The cleaned air C can be conducted out of the oil separator 1 through the air outlet 17. An oil flow B can be conducted out of the oil separator 1 through the oil outlet 18.

[0044] FIG. 4 schematically shows the oil separator 1 from FIG. 2 in a sectional representation and top view. Multiple exhaust air passages 19 that are formed in the disks 12 and that are designed to allow a portion of the exhaust air A to pass can be seen in this view. In this way, the exhaust air A can be distributed better among the individual disks 12 of the disk stack.

[0045] In FIG. 5, preferred aspects of the method according to the invention are shown schematically. As is evident from the illustration, a first SET rotational speed S1 can be detected from an engine load ML and/or an engine speed MD in conjunction with a first characteristic map K1. A second SET rotational speed S2 can be detected from an oil temperature OT and a second characteristic map K2. A third SET rotational speed S3 can be detected from an oil pressure OD and a third characteristic map K3. A maximum SET rotational speed S.sub.max can be detected from the first SET rotational speed S1, the second SET rotational speed S2, and the third SET rotational speed S3. A fourth SET rotational speed S4 can be detected from a vehicle system voltage U and a fourth characteristic map K4. A fifth SET rotational speed S5 can be detected from a water content W of the oil and a fifth characteristic map K5. A sixth SET rotational speed S6 can be detected from a fuel content K of the oil and a sixth characteristic map K6. A minimum SET rotational speed S.sub.min can be detected from the fourth SET rotational speed S4, the fifth SET rotational speed S5, and the sixth SET rotational speed S6. A preferred SET rotational speed SB for controlling the electric motor 6 can be detected from the maximum SET rotational speed S.sub.max and the minimum SET rotational speed S.sub.min by means of a hysteresis H and a gradient limiting G.

[0046] FIG. 6 schematically shows a preferred embodiment of the method according to the invention in a flow chart. In a first method step 100, an engine operating state of the internal combustion engine 3 is detected by means of the detection device 4. The engine operating state is determined by an engine load ML and/or an engine speed MD of the internal combustion engine 3. In a second method step 200, the first SET rotational speed S1 of the oil separator 1 is determined by means of the determination device 5 as a function of the detected engine operating state and the first characteristic map K1. The first characteristic map K1 specifies the first SET rotational speed S1 of the oil separator 1 as a function of the engine operating state. In a third method step 300, a maximum SET rotational speed S.sub.max of the oil separator 1 is determined by means of the determination device 5 as a function of the first SET rotational speed in such a manner that the maximum SET rotational speed S.sub.max is at least as high as the first SET rotational speed S1. In a fourth method step 400, the preferred SET rotational speed SB is determined by means of the determination device 5 on the basis of the maximum SET rotational speed S.sub.max in such a manner that the preferred SET rotational speed SB is, at most, as large as the maximum SET rotational speed S.sub.max. In a fifth method step 500, the electric motor 6 is controlled at the preferred SET rotational speed SB by means of the control device 7 in order to drive the oil separator 1.

[0047] 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.