Method for controlling the oil pressure of an oil pump in a combustion engine and an oil pressure arrangement

Abstract

The invention relates to a method for controlling the oil pressure of an oil pump (40, 140) in a combustion engine (100). The combustion engine (100) comprises a crankcase (11) and a separator (14, 114) for separating oil present in a blow-by gas from the crankcase (11). The method comprises the step (201) of providing oil pressure demand for a set of different engine operation conditions, the oil pressure demand defining the theoretical required oil pressure of the oil pump (40, 140); the step (203) of controlling the oil pressure of the oil pump (40, 140) based on the oil pressure demand for at least one engine operation condition in the set of different engine operation conditions; the step (205) of driving the separator (14, 114) using oil from the oil pump (40, 140), the oil being pressurized based on the oil pressure demand.

Claims

1. A method for controlling oil pressure of an oil pump in a combustion engine, the combustion engine comprising a crankcase and a separator for separating oil present in a blow-by gas from the crankcase, the method comprising providing an oil pressure demand for a set of different engine operation conditions, the oil pressure demand defining a theoretical required oil pressure of the oil pump, wherein the theoretical required oil pressure is determined based on at least an amount of blow-by gases in the crankcase; controlling the oil pressure of the oil pump based on the oil pressure demand for at least one engine operation condition in the set of different engine operation conditions; driving the separator using oil from the oil pump, the oil being pressurized based on the oil pressure demand.

2. The method according to claim 1, wherein the step of providing the oil pressure demand comprises determining the theoretical required oil pressure for the set of different engine operation conditions based on at least the engine load and/or engine speed.

3. The method according to claim 1, wherein the oil pressure demand for the set of different engine operation conditions is predetermined.

4. The method according to claim 1, wherein the step of providing the oil pressure demand comprises providing an oil pressure map, the oil pressure map determining the theoretical required oil pressure for the set of different engine operation conditions based on at least the engine load and the engine speed.

5. The method according to claim 1, wherein a further step of the method is detecting a first output signal of a pressure sensor arranged and configured to measure the oil pressure downstream of the oil pump, the first output signal being indicative of a first engine operation condition in the set of different engine operation conditions.

6. The method according to claim 5, wherein a further step of the method is controlling the oil pressure of the oil pump by comparing the first output signal of the pressure sensor with the oil pressure demand for an engine operation condition corresponding to the first engine operation condition.

7. The method according to claim 1, wherein the separator comprises an oil separation member rotatably arranged in the separator, the oil separation member being rotated by a rotating means, wherein a further step is driving the rotating means with oil from the oil pump, the oil being pressurized based on the oil pressure demand.

8. A control unit for controlling the oil pressure of the oil pump configured for driving at least the separator for separating oil present in blow-by gas from the crankcase, the control unit being configured to perform the method according to claim 1.

9. An oil pressure arrangement for a combustion engine comprising: an oil pump configured for driving at least a separator for separating oil present in blow-by gas from a crankcase, and a control unit configured to control the oil pressure of the oil pump wherein the control unit is configured to determine a theoretical required oil pressure for the oil pump, the theoretical required oil pressure being based on at least on an amount of blow-by gases in the crankcase; and control the oil pressure based on an oil pressure demand for at least one engine operation condition in a set of different engine operation conditions, wherein the oil pressure demand defines the theoretical required oil pressure of the oil pump.

10. The oil pressure arrangement according to claim 9, comprising a pressure sensor arranged and configured to measure the oil pressure downstream of the oil pump, the pressure sensor being configured to send a first output signal to the control unit, the first output signal being indicative of a first engine operation condition in the set of different engine operation conditions, wherein the control unit is configured to control the oil pressure of the oil pump by comparing the first output signal of the pressure sensor with the oil pressure demand for an engine operation condition corresponding to the first engine operation condition.

11. The oil pressure arrangement according to claim 9, wherein the control unit is configured to perform the method.

12. A vehicle comprising the oil pressure arrangement according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments of the present invention, wherein:

(2) FIG. 1 is a side view of a vehicle comprising a combustion engine according to an example embodiment of the present invention;

(3) FIG. 2 shows a schematic overview of a combustion engine of FIG. 1 equipped with a separator to separate oil from blow-by gases in a crankcase;

(4) FIG. 3 shows a cross section of a separator which is used according to one embodiment of the invention;

(5) FIG. 4 is a flow chart describing the steps of a method for controlling the oil pressure of an oil pump, according to one embodiment of the invention;

(6) FIG. 5 is a schematic overview of a separator and an oil pressure arrangement according to one embodiment of the invention;

(7) FIG. 6 is a graph showing an example of an oil pressure map according to one embodiment of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

(8) The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which an exemplary embodiment of the invention is shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein; rather, the embodiment is provided for thoroughness and completeness. Like reference character refer to like elements throughout the description.

(9) With particular reference to FIG. 1, there is provided a vehicle 800 with a combustion engine 100, such as an internal combustion engine 100, according to the present invention. The vehicle 800 depicted in FIG. 1 is a truck 800 for which the inventive concept which will be described in detail below, is particularly suitable for.

(10) FIG. 2 shows a schematic overview of parts of a combustion engine 100. In the non-limiting example of FIG. 2, the combustion engine 100 comprises an engine block 1 in a six-cylinder, four-stroke, diesel engine with a gear box 2 and a clutch that is connected to the engine's crankshaft. The crankshaft is at least partly comprised in the crankcase 11 of the combustion engine 100. In the example of FIG. 2, the combustion engine 100 is overloaded by means of a turbo compressor 3 of known type, which in turn comprises a turbine 4 connected to the engine's exhaust manifold 5 and a compressor 6 connected to the engine's induction (air intake) manifold 7 via an intercooler 8. By way of a suction pipe 9, the suction side of the compressor 6 is connected to an air filter 10. Moreover, the combustion engine 100 in FIG. 2 comprises a separator 14 for separating oil from blow-by gases in the crankcase 11, which will be further explained below.

(11) Crankcase blow-by gases are generated in the combustion engine 100 and will escape from the respective combustion chamber of the combustion engine 100 and into the crankcase 11, which contains oil or lubricating oil, also referred to as engine oil or main gallery engine oil. The blow-by gases are slipped into the crankcase 11 as a consequence of non-sealed piston rings between the combustion engine's pistons and the inner walls in the respective cylinders. The blow-by gases contain small particles in the form of oil drops, which are desirable to separate from the gases.

(12) The combustion engine 100 in FIG. 2 comprises a generally known screen separator 12 and a baffle separator 13 for guiding the blow-by gases in the crankcase 11. From the baffle separator 13, the crankcase gases are guided further into the separator 14 for separating the oil in the blow-by gases. Connected to the separator 14 is an oil sump via a drainage for draining the oil particles which have been separated by the separator 14, whereby the oil particles are enabled to be guided back to the oil sump. The oil may thereafter be guided back to the crankcase 11. A crankcase pressure sensor 50 is arranged to the crankcase 11 to detect the pressure inside the crankcase 11.

(13) For the purpose of describing the present invention, the separator 14 can be a conventional separator e.g. as described in the publication of EP 1,085,945 B1. The separator 14 comprises, in the described embodiment of the present invention, a plurality of rotating discs which during rotation separates the oil droplets from the blow-by gas by means of the imparted centrifugal force.

(14) As also shown in FIG. 2, the combustion engine 100 comprises an oil pump 40 configured for driving at least the separator 14. More specifically, the separator 14 is oil driven by means of circulating main gallery engine oil pressurized by means of the oil pump 40, to circulate throughout internal portions of the combustion engine 100 which is in need of lubricating oil.

(15) The separator 14, and its co-operation with the oil pump 40, will now be described in greater detail with reference to FIG. 3. FIG. 3 shows a cross section of the separator 14 which can be utilized according to the present invention. However, it should be noted that other separators than that described with reference to FIG. 3 can be used according to the invention. The separator 14 comprises a housing 20 in which a plurality of oil separation members 21, here embodied as rotating discs 21, are arranged, each rotating disc 21 rotates around a rotating axis 22. As the blow-by gas passes the rotating discs 21, the oil droplets are imparted with a centrifugal force which throws the oil droplets towards the inner surface of the housing 20, at which the oil droplets are free to flow along the inner surface of the housing 20 towards a drainage 23. The drainage 23 drains the housing 20 from the separated oil droplets to an oil sump 24 via a check valve 25. The drained and separated oil can thereafter be guided back to the crankcase 11 via a crankcase conducting line 26. The housing 20 is further provided with an inlet opening 29 through which the unclean blow-by gas enters the separator 14 and an outlet opening 30 through which the cleaned gas exists the separator 14. As also shown in FIG. 3, a pressure regulator 31 is comprised in the separator 14 for pressure control of the housing 20 and the exiting gas.

(16) In FIG. 3, the rotating discs 21 are rotated by means of a rotating means 27, here embodied as a drive turbine 27, which is fed with main galley engine oil via a turbine drive oil connection 28, which in this embodiment is in fluid communication with the crankcase 11. Moreover, as schematically shown in FIG. 3, a pressure sensor 50 is arranged downstream of the oil pump 40 in order to measure the oil pressure of the pressurized engine oil.

(17) The present invention also relates to a method for controlling the oil pressure of an oil pump, such as oil pump 40 in FIG. 2 and FIG. 3 and oil pump 140 in FIG. 5 (described below), in a combustion engine comprising a crankcase and a separator for separating oil present in a blow-by gas from the crankcase, such as separator 14 in FIG. 2 and FIG. 3 and separator 114 in FIG. 5 (described below). Thus, the present invention will hereafter be described with reference to the above described combustion engine 100, crankcase 11 and separator 14, in a non-limiting way, with reference to the flow-chart in FIG. 4 (hence, the reference numerals of FIG. 2 and FIG. 3 are used below when describing the steps of the method in the flow-chart in FIG. 4).

(18) In a first step 201, oil pressure demand for a set of different engine operation conditions is provided. The oil pressure demand defining the theoretical required oil pressure of the oil pump 40. That is, the combustion engine 100 may be operated in different engine operation conditions, for example dependent on the engine load and/or the engine speed. Thus, according to one embodiment, the first step 201 comprises determining the theoretical required oil pressure for the set of different engine operation conditions based on at least the engine load and/or engine speed.

(19) The required oil pressure in the combustion engine 100 typically varies with the different engine operation conditions. Hence, for at least some engine operation conditions, the required oil pressure is relatively low, and for at least some engine operation conditions, the required oil pressure is relatively high (as will be described later with reference to FIG. 6, the oil pressure demand can be described as an oil pressure map showing the required oil pressure as a function of engine load and engine speed). For at least a set of such different engine operation conditions, the oil pressure demand for the theoretical required oil pressure of the oil pump 40 is provided. According to one embodiment, the oil pressure demand for the set of different engine operation conditions is predetermined.

(20) In a second step 203, the oil pressure of said oil pump 40 is controlled based on the oil pressure demand for at least one engine operation condition in the set of different engine operation conditions. Hence, the oil pump 40 can be run more energy-efficient as the operation thereof corresponds to the oil pressure demand of the combustion engine. According to one embodiment, the oil pressure of said oil pump 40 is controlled based on the oil pressure demand for at least two different engine operation conditions in the set of different engine operation conditions.

(21) In a third step 205, the separator 14 is driven using oil from the oil pump 40. Thus, the oil is pressurized based on the oil pressure demand. Hereby, the separator 14 can be driven, at least partly, in accordance with the oil pressure demand. In other words, the separator 14 can be driven with oil pressurized (by the oil pump 40) in accordance with the oil pressure demand, and hence the combustion engine 100, and the corresponding crankcase ventilation system, and oil pump 40 can be made more energy-efficient.

(22) In a fourth, optional step 207, a first output signal O1 of a pressure sensor 50 arranged and configured to measure the oil pressure downstream of the oil pump 40 is detected. The first output signal O1 is indicative of a first engine operation condition in said set of different engine operation conditions.

(23) In a fifth, optional step 209 the oil pressure of the oil pump 40 is controlled by comparing the first output signal O1 of the pressure sensor 50 with the oil pressure demand for an engine operation condition corresponding to the first engine operation condition. In other words, the theoretical required oil pressure (comprised in the oil pressure demand) is compared with the measured oil pressure. The comparison is typically made for corresponding engine operation conditions, and at corresponding positions within the combustion engine 100 (i.e. the same conditions applies for the theoretical required oil pressure and for the measured oil pressure).

(24) As mentioned in relation to FIG. 3, the separator 14 may comprise at least one oil separation member 21 rotatably arranged in the separator 14. The at least one oil separation member 21 may be rotated by a rotating means 27. Thus, the third step 205 may comprise driving the rotating means 27 with oil from the oil pump 40, wherein the oil is pressurized based on the oil pressure demand.

(25) FIG. 5 shows an oil pressure arrangement 101 for a combustion engine, such as combustion engine 100 of FIG. 2. Thus, the oil pressure arrangement 101 of FIG. 5 may be comprised in the combustion engine 100 of FIG. 2. The oil pressure arrangement 101 comprises an oil pump 140, e.g. the same or similar to oil pump 40 of FIG. 2 and FIG. 3. The oil pump 140 may also be referred to as a controllable oil pump 140, configured for driving at least a separator 114 for separating oil present in blow-by gas from a crankcase. The separator 114 may be similar or the same as separator 14 of FIG. 2 and FIG. 3, but may as well be another type of separator, for example not comprising rotating discs 21, but instead e.g. a pressure drop driven separation device.

(26) The oil pressure arrangement 101 further comprises a control unit 160 configured to control the oil pressure of the controllable oil pump 140 and a pressure sensor 150 arranged and configured to measure the oil pressure downstream of the oil pump 140, e.g. in the crankcase and/or in close proximity to the separator 114.

(27) The function of the oil pressure arrangement 101 will now be described with reference to FIG. 5 and the method steps described in the flow-chart of FIG. 4. The control unit 160 in FIG. 5 is configured to control the oil pressure based on oil pressure demand for at least one engine operation condition in a set of different engine operation conditions. That is, the control unit 160 may be configured to perform at least some of the steps 201-209 (e.g. the first, second and third steps 201, 203, 205) of the method described with reference to the flow-chart in FIG. 4. The control unit 160 may comprise a computer program comprising program code means for performing at least some of the steps 201-209 (e.g. the first, second and third steps 201, 203, 205) of the method described with reference to the flow-chart in FIG. 4, when the program is run on the control unit. Moreover, the control unit 160 may comprise a computer readable medium carrying a computer program comprising program code means for performing at least some of the steps 201-209 (e.g. the first, second and third steps 201, 203, 205) described with reference to the flow-chart in FIG. 4, when said program product is run on the control unit 160. The control unit 160 may typically comprise a processor and a memory and may simply be referred to as a “computer”.

(28) Hence, control unit 160 may be configured to operate the oil pump 140 more energy-efficient as the operation of the oil pump 140 corresponds to the oil pressure demand of the combustion engine 100. Thus, at least indirectly, the control unit 160 may be configured to operate in such a way that the separator 114 can be driven, at least partly, in accordance with the oil pressure demand. In other words, the control unit 160 may be configured to operate such that the separator 114 can be driven with oil pressurized (by the oil pump 140) in accordance with the oil pressure demand, and hence, the combustion engine 100 and the oil pressure arrangement 101 can be made more energy-efficient.

(29) As mentioned above, the oil pressure arrangement 101 may comprise a pressure sensor 150. The pressure sensor 150 is configured to send a first output signal O1 to the control unit 160, the first output signal O1 is indicative of a first engine operation condition in the previously described set of different engine operation conditions. Moreover, a comparison between the first output signal O1 of the pressure sensor 150 and the oil pressure demand, or at least one of the reference values in the oil pressure demand, carried out in the control unit 160 may initiate a response action RA for the oil pump 140. Hereby, the control unit 160 may be configured to control the oil pressure of the controllable oil pump 140 by comparing the first output signal O1 of the pressure sensor 150 with the oil pressure demand for an engine operation condition corresponding to the first engine operation condition.

(30) FIG. 6 is a graph showing an example of oil pressure demand embodied as an oil pressure map 300 according to one embodiment of the invention. As seen in FIG. 6, the oil pressure map 300 corresponds to a 3D map 300, which can be described in an x, y, z-coordination system in which the x-axis represents the engine speed, the y-axis represents the engine load, and the z-axis represents the theoretical required oil pressure. Thus, it should be understood that in FIG. 6, the oil pressure demand, or oil pressure map 300, for the set of different engine operation conditions is predetermined. That is, the oil pressure demand, or oil pressure map 300, has been determined on beforehand, for example based on empirical studies and/or be based on theoretical calculations, i.e. to provide the theoretical required oil pressure for at least one, two, or more of engine operation condition(s) in the set of different engine operation conditions. For example, and as previously described, the combustion engine 100, or a typical engine of an engine type corresponding to the combustion engine 100, may be set up in an engine test-rig which is run for at least the engine operation conditions in the set of different engine operation conditions. For each different engine operation condition, here based on at least a specific engine speed and a specific engine load, the required oil pressure needed to be delivered from the oil pump 40, 140 is determined and saved as theoretical required oil pressures in the oil pressure demand or oil pressure map 300. As shown in FIG. 6, the theoretical required oil pressure may thus be mapped in relation to the engine operation conditions in the form of engine speed and engine load. By saving/storing the oil pressure map 300, or at least the values of the theoretical require oil pressure and its relation to the engine speed and engine load, in for example the control unit 160, the data (i.e. the oil pressure demand or oil pressure map 300) may subsequently be used to control the operation of the oil pump 40, 140, and the separator 14, 114 during normal operation of the combustion engine 100.

(31) Stated differently, by using an engine test-rig, and performing engine tests and calculations, the requirement of e.g. the separator 14, 114 (that is the oil pressure needed to fulfil the separation requirements, which may correspond to e.g. the rotational speed of the rotating means 27) in every engine operation condition in the set of different engine operation conditions, can be determined as the theoretical required oil pressure. In the control unit 160, these values are stored and thus the required oil pressure of the separator 14, 114 is known for each engine operation condition in the set of different engine operation conditions. By comparing the required oil pressure value with the measured oil pressure value, the control unit 160 can adjust the response action RA to the oil pump 40, 140 (or an oil pressure control valve regulating the oil pump 40, 140) until the measured oil pressure value correspond to the required oil pressure value.

(32) Thus, with reference to the method described in FIG. 4, the first step 201 may comprise providing an oil pressure map 300, wherein the oil pressure map 300 comprises the theoretical required oil pressure for the set of different engine operation conditions based on at least the engine load and the engine speed.

(33) It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims. For example, as already mentioned the separator may be of another structure than that described in herein.