METHOD FOR CONTROLLING A PRESSURE IN A CRANKCASE

Abstract

A method for controlling a pressure in a crankcase of an internal combustion engine with a crankcase venting device. The crankcase venting device may include a suction line via which a blow-by gas is removable from the crankcase, a pumping device, and an oil mist separating device. The pumping device and the oil mist separating device may be arranged in the suction line. The method may include controlling a rotational speed of an electric drive in at least one of a closed-loop manner and an open-loop manner, the electric drive configured to drive the pumping device. The method may also include adjusting the pressure in the crankcase via manipulating the rotational speed of the electric drive. The method may further include inferring the pressure in the crankcase via evaluating at least one performance parameter of the electric drive.

Claims

1. A method for controlling a pressure in a crankcase of an internal combustion engine with a crankcase venting device, the crankcase venting device including a suction line via which a blow-by gas is removable from the crankcase, a pumping device, and an oil mist separating device, the pumping device and the oil mist separating device arranged in the suction line, the method comprising: controlling a rotational speed of an electric drive in at least one of a closed-loop manner and an open-loop manner, the electric drive configured to drive the pumping device; adjusting the pressure in the crankcase via manipulating the rotational speed of the electric drive; and inferring the pressure in the crankcase via evaluating at least one performance parameter of the electric drive.

2. The method according to claim 1, further comprising: comparing an actual current value corresponding to a current supplied to the electric drive with a current setpoint; and determining a rotational speed correction value for the rotational speed of the electric drive when there is a deviation between the actual current value and the current setpoint.

3. The method according to claim 2, wherein the current setpoint corresponds to a value for the current supplied to the electric drive which maintains the rotational speed of the electric drive at a given rotational speed, and wherein the pressure in the crankcase that corresponds to a target pressure.

4. The method according to claim 1, further comprising: determining a torque generated by the electric drive and acting on the pumping device; determining an actual rotational speed value of the electric drive, which corresponds to a rotational speed of the pumping device; and determining a pressure differential generated by the pumping device and a volume flow flowing through the pumping device from the torque acting on the pumping device and the actual rotational speed value of the electric drive.

5. The method according to claim 1, further comprising: determining a drop in a pressure at the oil mist separating device from a volume flow flowing through the pumping device; and inferring the pressure in the crankcase from the drop in the pressure at the oil mist separating device and a pressure differential generated by the pumping device.

6. The method according to claim 4 further comprising: determining a control deviation for the pressure in the crankcase; and determining a rotational speed correction value for the rotational speed of the electric drive based on the control deviation for the pressure in the crankcase.

7. The method according to claim 4, further comprising: determining a notional blow-by gas volume flow generated by the internal combustion engine from a rotational speed of the internal combustion engine and a torque generated by the internal combustion engine; and determining an estimated rotational speed value based on the notional blow-by gas volume flow generated by the combustion engine such that a notional volume flow displaced by the pumping device matches the notional blow-by gas volume flow generated by the combustion engine.

8. The method according to claim 1, further comprising supplying a rotational speed setpoint including a rotational speed correction value to a control device configured to control the rotational speed of the electric drive in the at least one of the open-loop manner and the closed-loop manner.

9. The method according to claim 7, further comprising: compiling a rotational speed setpoint from the estimated rotational speed value and a rotational speed correction value; and supplying the rotational speed setpoint including the rotational speed correction value to a control device configured to control the rotational speed of the electric drive in the at least one of the open-loop manner and the closed-loop manner.

10. The method according to claim 8, further comprising: detecting a switch of a pressure control valve of the crankcase venting device from a performance parameter of the electric drive, the pressure control valve arranged in the suction line; and determining the rotational speed correction value based at least partially on a switching behavior of the pressure control valve.

11. An internal combustion engine comprising: a crankcase having an internal pressure and including a crankcase venting device; the crankcase venting device including a suction line via which a blow-by gas is removable from the crankcase, a pumping device driven by an electric drive, and an oil mist separating device, the pumping device and the oil mist separating device arranged in the suction line; and a control device configured to control a rotational speed of the electric drive in at least one of an open-loop manner and a closed-loop manner; wherein the internal pressure of the crankcase is controllable via manipulating the rotational speed of the electric drive.

12. The method according to claim 3, further comprising supplying a rotational speed setpoint including the rotational speed correction value to a control device configured to control the rotational speed of the electric drive in the at least one of the open-loop manner and the closed-loop manner.

13. The method according to claim 4, wherein determining the pressure differential generated by the pumping device and the volume flow flowing through the pumping device includes using a characteristic curve of the pumping device.

14. The method according to claim 4, further comprising: determining a drop in a pressure at the oil mist separating device from a volume flow flowing through the pumping device; and inferring the pressure in the crankcase from the drop in the pressure at the oil mist separating device and the pressure differential generated by the pumping device.

15. The method according to claim 5, further comprising: determining a control deviation for the pressure in the crankcase; and determining a rotational speed correction value for the rotational speed of the electric drive based on the control deviation for the pressure in the crankcase.

16. The method according to claim 15, further comprising: determining a notional blow-by gas volume flow generated by the internal combustion engine from a rotational speed of the internal combustion engine and a torque generated by the internal combustion engine; and determining an estimated rotational speed value based on the notional blow-by gas volume flow generated by the combustion engine such that a notional volume flow displaced by the pumping device matches the notional blow-by gas volume flow generated by the combustion engine.

17. The method according to claim 9, further comprising: detecting a switch of a pressure control valve of the crankcase venting device from a performance parameter of the electric drive, the pressure control valve arranged in the suction line; and determining the rotational speed correction value based at least partially on a switching behavior of the pressure control valve.

18. A method for controlling a pressure in a crankcase of an internal combustion engine with a crankcase venting device, the crankcase venting device including a suction line via which a blow-by gas is removable from the crankcase, a pumping device, and an oil mist separating device, the pumping device and the oil mist separating device arranged in the suction line, the method comprising: controlling a rotational speed of an electric drive in at least one of a closed-loop manner and an open-loop manner, the electric drive configured to drive the pumping device; adjusting the pressure in the crankcase via manipulating the rotational speed of the electric drive; inferring the pressure in the crankcase via evaluating at least one performance parameter of the electric drive; comparing an actual current value corresponding to a current supplied to the electric drive with a current setpoint; determining a rotational speed correction value for the rotational speed of the electric drive when there is a deviation between the actual current value and the current setpoint; and supplying a rotational speed setpoint including the rotational speed correction value to a control device configured to control the rotational speed of the electric drive in the at least one of the closed-loop manner and the open-loop manner.

19. The method according to claim 18, further comprising: detecting a switch of a pressure control valve of the crankcase venting device from a performance parameter of the electric drive, the pressure control valve arranged in the suction line; and determining the rotational speed correction value based at least partially on a switching behavior of the pressure control valve.

20. The method according to claim 19, wherein the current setpoint corresponds to a value for the current supplied to the electric drive which maintains the rotational speed of the electric drive at a given rotational speed, and wherein the pressure in the crankcase corresponds to a target pressure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the schematic drawing

[0029] FIG. 1 is a schematic diagram of an internal combustion engine with a crankcase venting device,

[0030] FIG. 2 is a schematic diagram of a rotational speed control of an electric drive,

[0031] FIG. 3 is a schematic diagram of a control of a pressure in a crankcase of the internal combustion engine according to the first embodiment of the invention,

[0032] FIG. 4 is a schematic diagram of a determination of a pressure differential in the crankcase venting device on the basis of performance parameters of the electric drive,

[0033] FIG. 5 is a schematic diagram of the control of a pressure in the crankcase according to a second embodiment of the invention,

[0034] FIG. 6 is a schematic diagram of control of a pressure in the crankcase according to a third embodiment of the invention, wherein an operating point of the internal combustion is taken into account,

[0035] FIG. 7 is a schematic diagram of an internal combustion engine with a crankcase venting device according to a fourth embodiment of the invention,

[0036] FIG. 8 is a schematic diagram of a control of the driving power of an electric drive taking into account the operating point of the internal combustion engine according to the fourth embodiment of the invention,

[0037] FIG. 9 is a schematic diagram of a control of the pressure in the crankcase of the internal combustion engine according to a fifth embodiment of the invention, wherein switching operations of a pressure control valve are taken into account, and

[0038] FIG. 10 is a schematic diagram of a control of the pressure in the crankcase of the internal combustion engine according to a sixth embodiment of the invention, wherein switching operations of a pressure control valve and operating points of the internal combustion engine are taken into account.

DETAILED DESCRIPTION

[0039] An internal combustion engine 10 represented in FIG. 1 has a charging device 12, particularly a turbocharger. The internal combustion engine 10 further has a crankcase 14, in which blow-by gases 16 collect when the internal combustion engine 10 is in operation. In order to remove the blow-by gases 16 from the crankcase 14, the internal combustion engine 10 has a crankcase venting device 18.

[0040] The crankcase venting device 18 has a suction line 20, through which blow-by gases 16 may be removed from the crankcase 14. The crankcase venting device 18 further has a pumping device 22 and an oil mist separating device 24, which is embodied for example as an impactor. The pumping device 22 and the oil mist separating device 24 are arranged in the suction line 20, so that the oil mist may be extracted from the blow-by gases 16 before the gases are transported by the pumping device 22 through the suction line 20.

[0041] A pressure 26 in the crankcase 14 of the internal combustion engine 10 should be within a certain range. Malfunctions in the operation of the internal combustion engine 10 can occur if the pressure either exceeds or falls below this range. Therefore, a control 25 of the pressure 26 to a target pressure 27 is provided, hereinafter also referred to as pressure control 25. A first embodiment of the pressure control 25 is represented in FIGS. 1 to 3.

[0042] The pumping device 22 is preferably embodied as a side channel blower and driven by an electric drive 28. The electric drive 28 has a rotational speed control 30, such as is represented for example in FIG. 2. The rotational speed control 30 has a standard control schema 32, for example a proportional-integral (PI), or proportional-differential (PD) or proportional-integral-differential (PID) control schema 32. The rotational speed control 30 of the electric drive 28 is assured as follows. First, an actual rotational speed value 34 of the electric drive 28 corresponding to the rotational speed of the electric drive 28 is determined. The actual rotational speed value 34 is preferably measured. The actual rotational speed value 34 is compared with a rotational speed setpoint 36, which serves as an input value for the rotational speed control 30. A control deviation 38 is determined from the difference between the actual rotational speed value 34 and the rotational speed setpoint 36. A new value for a manipulated variable 40 is calculated from the control deviation 38 with the aid of control schema 32 and is supplied to an engine controller 42, which in turn actuates the electric drive 28. Pulse width modulation, an electrical voltage or similar for example may be used as manipulated variables 40.

[0043] The rotational speed setpoint 36 serves as the manipulated variable 41 for the actual pressure control 25 of the pressure 26 in the crankcase 14. The pressure control 25 according to the first embodiment is assured as follows. A current setpoint 44 is calculated on the basis of the existing rotational speed setpoint 36. The current setpoint 44 corresponds to a current value which must typically be supplied to the electric drive in order to maintain the rotational speed setpoint 36 under normal operating conditions of the internal combustion engine 10. This is based on the consideration that for a certain blow-by gas volume flow 46, which is to be removed, a rotational speed of the pumping device 22 is sufficient to the remove the given blow-by gas volume flow. As long as the pumping device 22 always has to overcome the same pressure differential to remove the blow-by gas volume flow 46, the current needed to drive the pumping device 22, that is to say the actual current value 48, may be constant. Therefore, when the desired target pressure 27 prevails in the crankcase 14, the current setpoint 44 should be adjusted automatically. If the pressure 26 in the crankcase 14 differs from the target pressure 27, the actual current value 48 should also differ from the current setpoint 44.

[0044] The current setpoint 44 may be determined either from theoretical characteristic curves 45 of the electric drive 28, the pumping device 22 and the oil mist separating device 24. Alternatively or in addition thereto, the relationship between the rotational speed setpoint 36 and the current setpoint 44 may also be determined experimentally.

[0045] Now for the pressure control 25 of pressure 26, the actual current value 48 is compared with the current setpoint 44, and a control deviation 50 is determined thereby. A rotational speed correction value 52 is determined 53 from the control deviation 50 and is added to the rotational speed setpoint 36 to calculate a new rotational speed setpoint 36, which is supplied to the rotational speed control 30 of the electric drive 28. In this way the control loop is closed and pressure control 25 is achieved.

[0046] A second embodiment of the method for pressure control 25 as represented in FIGS. 4 and 5 differs from the first embodiment of the method for pressure control 25 represented in FIGS. 1-3 in that a pressure differential 51 extending over the crankcase venting device 18 is estimated using performance parameters of the electric drive 28 to infer information about the pressure 26 in the crankcase 14 and thus determine a control deviation 64.

[0047] In the determination of the pressure differential 51 present at the crankcase venting device 18 represented for example in FIG. 4, first the actual current value 48 and the actual rotational speed value 34 of the electric drive 28 are evaluated. A torque 54 generated by the electric drive 28 may be determined from the actual current value 48. A pressure differential 56 generated by the pumping device 22 may be calculated together with the actual rotational speed value 34 of the electric drive 28, from which the rotational speed of the pumping device 22 can be inferred, with the aid of a characteristic curve 47 of the pumping device 22.

[0048] A volume flow 58 displaced by the pumping device 22 and therewith the rotational speed of the pumping device 22 may be estimated from the pressure differential 56 and the actual rotational speed value 34 of the electric drive 28.

[0049] A drop in pressure 62 at the oil mist separating device 24 may be inferred from the volume flow 58 displaced by the pumping device 22 with the aid of characteristic curves 60 of the oil mist separating device 24.

[0050] Thus, the pressure differential 51 present at the crankcase venting device 18 may be inferred from the pressure differential 56 generated by the pumping device 22 and the drop in pressure 62 at the oil mist separating device 24. Since the suction line 20 typically opens in an area of an intake tract of the internal combustion engine 10 in which ambient pressure is present, this enables the pressure 26 in the crankcase 14 to be inferred. Thus, a determination 49 of the pressure 26 in the crankcase 14 may therefore be made with the aid of performance parameters of the electric drive 28.

[0051] In the pressure control 25 represented in FIG. 5, in order to determine the control deviation 64, the determination 49 of the pressure 26 is carried out on the basis of the performance parameters of the electric drive 28 by comparison with the desired target pressure 27. Alternatively, instead of specifying a target pressure 27, a setpoint pressure differential 66 may be specified, which is calculated from the target pressure 27 and compared with the pressure differential 51 present at the crankcase venting device 18, which was calculated with determination 49.

[0052] A standard control schema 68 operating for example according to a proportional-integral, proportional-differential or proportional-integral-differential method is applied to the control deviation 64 to calculate a correction value for the manipulated variable 41, in particular a rotational speed correction value 52, from which a new rotational speed setpoint 36 is calculated, which is supplied to the rotational speed control 30 of the electric drive 28. Changing the rotational speed setpoint 36 finally causes the actual rotational speed value 34 to change as well, thereby adjusting the volume flow 58 displaced by the pumping device 22, in order to modify the pressure 26 in the crankcase 14 particularly to shift it closer to the target pressure 27. This control section 70 thus sets a new pressure 26 in the crankcase 14.

[0053] In other respects, the second embodiment of the method for pressure control 25 represented in FIGS. 4 and 5 is the same as the first embodiment of the method for pressure control 25 represented in FIGS. 1-3 in terms of construction and function, and to this extent the preceding description thereof is referenced herewith.

[0054] A third embodiment of the method for pressure control 25 represented in FIG. 6 differs from the second embodiment of the method for pressure control 25 represented in FIGS. 4 and 5 in that a determination 72 of an estimated rotational speed value 74 is carried out to accelerate the pressure control 25. A determination 80 of a typical blow-by gas volume flow 46 may be made from a rotational speed 76 of the internal combustion engine 10 and a torque 78 of the internal combustion engine 10. The estimated rotational speed value 74 that would be necessary to displace the blow-by gas volume flow 46 may be calculated from the blow-by gas volume flow 46 with the aid of the characteristic curves 47 for the pumping device 22, the oil mist separating device 24 and the electric drive 28. The estimated rotational speed value 74 is supplied to the rotational speed control 30 of the electric drive 28. In this way, the rotational speed control 30 is able to respond very quickly to anticipated changes in the blow-by gas volume flow 46, so that fluctuations in the blow-by gas 16 volume and the associated pressure fluctuations in the crankcase 14 caused by changing loads in the internal combustion engine 10 are reduced.

[0055] However, since the estimated rotational speed value 74 is only based on theoretical assumptions, it may differ from the blow-by gas volume flow 46 that actually exists. Therefore, an additional control of the pressure 26 in the crankcase 14 is needed. The rotational speed correction value 52 is determined in similar manner to the pressure control 25, as described with reference to the second embodiment.

[0056] The rotational speed setpoint 36 supplied to rotational speed control 30 is thus compiled from a total of the estimated rotational speed value 74 and the rotational speed correction value 52.

[0057] In other respects, the third embodiment of the method for pressure control 25 represented in FIG. 6 is the same as the second embodiment of the method for pressure control 25 represented in FIGS. 4 and 5 in terms of construction and function, and to this extent the preceding description thereof is referenced herewith.

[0058] A fourth embodiment of the method for pressure control 25 represented in FIGS. 7 and 8 differs from the first embodiment of the method for pressure control 25 represented in FIGS. 1 to 3 in that a pressure control valve 82 is used for the pressure control 25 of pressure 26, which valve is arranged in the suction line 20 between the crankcase 14 and the pumping device 22. In addition, an estimated rotational speed value 74 is determined I similarly to the manner of the third from the operating point of the internal combustion engine 10, particularly from the rotational speed 76 of the internal combustion engine 10 and the torque 78 generated by the internal combustion engine 10. This estimated rotational speed value 74 is increased by an offset to absorb deviations from the expected blow-by gas volume flow 46. If the blow-by gas volume flow 46 is too small, the pressure 26 in the crankcase 14 falls, so that the pressure control valve 82 closes and thus temporarily interrupts the process of extracting blow-by gas 16 from the crankcase 14. This effectively prevents the pressure 26 in the crankcase 14 from falling too low.

[0059] The pressure is prevented from increasing above a permissible pressure 26 in the crankcase 14 by the addition of the offset to the estimated rotational speed value 74.

[0060] In other respects, the fourth embodiment of the method for pressure control 25 represented in FIGS. 7 and 8 is the same as the first embodiment of the method for pressure control 25 represented in FIGS. 1-3 in terms of construction and function, and to this extent the preceding description thereof is referenced herewith.

[0061] A fifth embodiment of the method for pressure control 25 represented in FIG. 9 differs from the fourth embodiment of the method for pressure control 25 represented in FIGS. 7 and 8 in that an algorithm 86 for detecting switching operations 84 of the pressure control valve 82 is used in the pressure control 25.

[0062] When the pressure control valve 82 opens or closes, the pressure conditions on the inlet side of the pumping device 22 change. This in turn changes the load on the pumping device 22, so that the power required to drive the pumping device 22 also changes. This is also reflected in the performance parameters of the electric drive 28.

[0063] For example, when the pressure control valve 82 closes, the volume flow stops and the pressure differential the pumping device 22 must overcome becomes greater, with the result that the load increases. Consequently, the actual rotational speed value 34 of the electric drive 28 would fall if no rotational speed control 30 were provided. If a rotational speed control 30 is provided, this causes the actual current value 48 to rise. When the pressure control valve 82 is opened, the effects are reversed, so that opening of the pressure control valve 82 can also be detected.

[0064] Control of the pressure 26 in the crankcase 14 is preferably carried out in such manner that the rotational speed of the electric drive 28 is used as a manipulated variable 41 by supplying a rotational speed setpoint 36 to the rotational speed control 30 of the electric drive 28. The desired rotational speed setpoint 36 is determined in such manner as to ensure that the pressure control valve 82 opens and closes regularly. In this way, it may be ensured that the pressure 26 in the crankcase 14 does not increase too much. It may further be guaranteed that the output of the electric drive 28 is not too high, and that energy is not wasted unnecessarily.

[0065] The rotational speed setpoint 36 is preferably adjusted in such manner that the pressure control valve 82 opens and/or closes least once every 10 seconds, preferably at least once every 5 seconds, particularly preferably at least once every second.

[0066] Moreover, when the rotational speed setpoint 36 is calculated, it is ensured that a ratio between opening times and closing times of the pressure control valve 82 is greater than 50%, particularly preferably greater than 80%, wherein the pressure control valve 82 would be permanently open at a ratio of 100%. In this context, however, it should be noted that there should be closing times. Consequently, the ratio between opening times and closing times of the pressure control valve 82 should be less than 100%. In this way, it may be guaranteed that the pressure 26 in the crankcase 14 does not exceed the permitted value.

[0067] In other respects, the fifth embodiment of the method for pressure control 25 represented in FIG. 9 is the same as the fourth embodiment of the method for pressure control 25 represented in FIGS. 7 and 8 in terms of construction and function, and to this extent the preceding description thereof is referenced herewith.

[0068] A sixth embodiment of the method for pressure control 25 represented in FIG. 10 differs from the fifth embodiment of the method for pressure control 25 represented in FIG. 9 in that the rotational speed setpoint 36 is compiled from an estimated rotational speed value 74 and a rotational speed correction value 52. The estimated rotational speed value 74 is determined in the same way as in embodiments three and four. The rotational speed correction value 52 is determined with the aid of the algorithm 86 for detecting switching operations 84 of the pressure control valve 82.

[0069] In other respects, the sixth embodiment of the method for pressure control 25 represented in FIG. 10 is the same as the fifth embodiment of the method for pressure control 25 represented in FIG. 9 in terms of construction and function, and to this extent the preceding description thereof is referenced herewith.