OIL SUPPLY SYSTEM

Abstract

An oil supply system for an internal combustion engine, comprising a lubricating oil circuit in which a first oil pressure generating device, a first device for oil temperature control, and a second device for oil temperature control are provided, wherein the two devices for oil temperature control are arranged in two arms of the lubricating oil circuit connected in parallel and wherein the first oil pressure generating device is arranged in the flow direction upstream of the branch to the two arms leading to the two devices for oil temperature control.

Claims

1-20. (canceled)

21. An oil supply system for an internal combustion engine, comprising a lubricating oil circuit in which a first oil pressure generating device, a first device for oil temperature control, and a second device for oil temperature control are provided, wherein the two devices for oil temperature control are arranged in two arms of the lubricating oil circuit connected in parallel and wherein the first oil pressure generating device is arranged in the flow direction upstream of the branch to the two arms leading to the two devices for oil temperature control.

22. An oil supply system according to claim 21, further comprising a second oil pressure generating device which is arranged in the flow direction downstream of the first device for oil temperature control and is arranged in the first arm of the first device for oil temperature control.

23. An oil supply system according to claim 21, further comprising an oil filter in the flow direction upstream of the first oil pressure generating device.

24. An oil supply system according to claim 21, further comprising an oil filter in the first arm of the lubricating oil circuit, wherein the oil filter in the first arm of the lubricating oil circuit is downstream of the second oil pressure generating device.

25. An oil supply system according claim 21, further comprising an oil filter in the second arm of the lubricating oil circuit.

26. An oil supply system according claim 22, wherein the first oil pressure generating device can be driven mechanically by the internal combustion engine via a transmission and is coupled to the rotational speed of the internal combustion engine, wherein the second oil pressure generating device is driven by a speed-controlled electric motor.

27. An oil supply system according claim 22, further comprising a control unit by way of which the pressure at the inlet into the oil lines of the lubricating oil circuit can be adapted to the operating conditions of the internal combustion engine, wherein the rotational speed of the second oil pressure generating device is regulated.

28. An oil supply system according to claim 23, wherein upstream of the first oil pressure generating device, an oil filter is arranged in the first arm and in the second arm, respectively, each oil filter having a different filter fineness or mesh size, wherein said mesh sizes differ from each other by, in each case, at least 100%, based on the mesh size of the other oil filter.

29. An oil supply system according to claim 21, wherein with the first oil pressure generating device is operable to generate an oil pressure of between 0.6 and 1.6 bar in the operating state.

30. An oil supply system according to claim 22, wherein at the second oil pressure generating device, the oil pressure at the inlet into the supply line for the lubrication points and into the cooling oil nozzles of the internal combustion engine can be regulated depending on the engine load, wherein the pressure at a maximum engine power is by at least 20% higher than at half load.

31. An oil supply system according to claim 21, wherein the temperature of the first device for oil temperature control is adaptable to the motor requirements.

32. An oil supply system according to claim 21, wherein the temperature of the first device for oil temperature control involves a multi-stage heat exchanger, which is incorporated into the cooling circuit for the engine cooling water or into a further cooling circuit and which comprises an electrical heating device.

33. An oil supply system according to claim 23, wherein the oil filter exhibits the smallest mesh size and the highest filter fineness of all oil filters in the first arm downstream of the first oil pressure generating device.

34. An oil supply system according to claim 21, wherein the second device for oil temperature control in the second arm is adjustable to a temperature between 70 and 80 C. during the operation of the engine.

35. An oil supply system according to claim 23, wherein in the second arm, an oil filter is provided the mesh size of which is larger by at least 100% or, respectively, the filter fineness of which is correspondingly lower than for the oil filter in the first arm.

36. An oil supply system according to claim 23, wherein viewed in the flow direction upstream of the first oil pressure generating device, an oil filter is arranged the mesh size of which is larger by at least 100% or, respectively, the filter fineness of which is lower to this extent than that of the oil filter in the second arm.

37. An internal combustion engine comprising an oil supply system according to claim 21.

38. An internal combustion engine according to claim 37, wherein the oil temperature in the pressure line of the internal combustion engine can be adjusted as a function of the engine load, wherein the oil temperature at a maximum engine power is by at least 10 C. lower than at half load.

39. An internal combustion engine according to claim 37, wherein the first arm supplies the oil lines of the internal combustion engine with finely filtered engine oil, whereas the second arm is responsible for the temperature control of the engine oil in the crankcase and, if present, in external oil reservoir containers, which, however, are incorporated into the engine oil circuit, as well as for the pre- or, respectively, side stream filtration of the engine oil.

40. A cogeneration plant comprising an internal combustion engine according to claim 39.

Description

[0042] FIG. 1 schematically shows the oil circuit of an oil supply system.

[0043] The engine oil is sucked from the oil sump (not illustrated) of the internal combustion engine 1 into the external lubricating oil circuit 2. From the internal combustion engine 1, the lubricating oil gets into the oil filter 3 designed as a pre-filter and, from there, into the first oil pressure generating device in the form of an oil pump 4. At the oil pump 4, a bypass line with a check valve is provided. Downstream of the oil pump 4, the lubricating oil circuit 2 is branched into two partial circuits with two arms 2a, 2b. Approximately one third of the engine oil delivered by the first oil pump 4 passes through the first arm 2a to the second oil pressure generating device 5 also in the form of an oil pump 5, wherein a bypass line with a check valve 6 is arranged, and, from there, to the device for oil temperature control 7 in the form of a preheating or cooling unit 7 and further to the oil filter 8 in the form of a fine filter. From the oil filter 8, the engine oil gets into the internal combustion engine 1 for supplying the lubrication points and the piston cooling nozzles.

[0044] However, the significantly larger part of the circulating engine oil flows through the second arm 2b in the second partial circuit, which branches off between the first and the second oil pumps 4, 5. In the scheme exemplified in FIG. 1, the branching is followed by a switch valve 9, an oil filter 10, a device for oil temperature control 11 in the form of a heat exchanger and an oil buffer volume 12, which may exhibit a bypass 13. Subsequently, the engine oil flows from the arm 2b back into the oil sump of the internal combustion engine 1. In the oil sump, the two arms 2a, 2b reunite.

[0045] The purpose of the 2-stage and separate design of the oil pressure generating devices 4, 5 is that the oil temperature and the oil pressure and thus the amount of the oil supply into the lubricating oil and cooling oil supply system of the internal combustion engine 1 can therewith be controlled and regulated independently of the cooling of the engine oil as a function of the operating requirements with minimum pump capacities. For this purpose, the second oil pump 5 is driven by a speed-controlled electric motor which is actuated and controlled, respectively, by the engine management.

[0046] The first oil pump 4 conveys the engine oil for the partial circuits with the two arms 2a, 2b and generates a pre-pressure for the second oil pump 5. In doing so, the first oil pump 4 is unregulated and can be driven, for example, directly and, respectively, mechanically by the internal combustion engine 1. Downstream of the second oil pump 5, the first device for oil temperature control 7 is arranged in the first partial circuit (arm 2a), which device serves the purpose that, when the cold internal combustion engine 1 is started, the oil temperature is raised to the ideal temperature for the bearing lubrication (e.g., 50-60 C.), but the oil temperature can be lowered under the cooling water temperature in the maximum load range. As soon as the internal combustion engine 1 reaches the nominal speed during the starting operation, the oil temperature is raised to about 95 C. In the high load range, the oil temperature is again lowered.

[0047] Therefore, the first device for oil temperature control 7 is preferably designed as a multi-stage and adjustable heat exchanger, which is in heat exchange, for example, with the engine cooling water circuit and/or with another cooling circuit, for example with a low-temperature cooling circuit, and/or, as a controllable electrical heating device (e.g., via an electrical resistance activated by the engine management), constitutes a system component independent of the cooling water circuit.

[0048] Downstream of the first device for temperature control 7, the oil filter 8 (designed as a fine filter) is arranged which makes sure that no abrasive solid-state particles larger than, for example, 8 m enter into the lubricating gaps of the bearing points.

[0049] In the second partial circuit (arm 2b), the cooling of the oil quantity in the oil sump of the internal combustion engine 1 is effected. For this purpose, about twice the amount of engine oil which gets into the internal combustion engine 1 via the arm 2a is branched off and conducted into the second device for oil temperature control 11 (a heat exchanger). The engine oil of this partial circuit is again conducted directly into the oil sump of the internal combustion engine 1, ideally at the other end of the internal combustion engine 1, from which the engine oil is removed. In this second partial circuit (arm 2b), further functional elements may be integrated, for example, a switch valve 9, a further oil filter 10 and an oil buffer volume 12 (e.g., in the form of a supplementary oil tank).

[0050] The first oil pump 4 produces an oil pressure of between 0.6 and 1.6 bar, which basically is sufficient for supplying the internal combustion engine 1 on short notice with lubricating oil in case the second oil pump 5 fails so that enough time remains for a proper shutdown of the internal combustion engine 1 without any bearing damage or corrosion of pistons. For this purpose, a bypass line around the second oil pump 5 may, for example, be provided, in which a check valve 6 is arranged so that the pressure downstream of the second oil pump 5 can never fall below the pressure downstream of the first oil pump 4. In the event that the second oil pump 5 fails, a switch valve 9 is arranged in the second partial circuit (arm 2b) which throttles or blocks the oil flow in said line correspondingly.

[0051] In the second partial circuit (arm 2b), the main cooling of the engine oil is effected during the operation of the engine. This is done by a heat exchanger 11 which is incorporated into the secondary circuit of the engine or, respectively, installation cooling, for example, into the hot-water return flow in applications with power-heat coupling.

[0052] The proposed division into two separate partial circuits also has the advantage that the entire engine oil in the oil sump can thus be brought to the operating temperature before the start-up of the internal combustion engine 1. Advantageously, a further oil filter 10 exhibiting a lower filter fineness than filter 8 is integrated into the second partial circuit (arm 2b). Overall, three oil filter 3, 8, 10 are therefore preferably provided which each have a different filter fineness: oil filter 3 is designed as a coarse filter having a relatively large mesh size (e.g., >50 m). Oil filter 10 acts as a cleaning filter with a mesh size of, e.g., >20 m, and oil filter 8 acts as a fine filter with a mesh size of approx. 10 m.

[0053] The best results are achieved with the proposed approach if, in addition to the oil temperature, also the oil pressure at the inlet into the lubricating oil supply lines of the internal combustion engine 1 is adapted to the operating requirements of the internal combustion engine 1 as precisely as possible.

[0054] In the high-load range and in particular in the overload range, a significantly higher oil pressure is required than under a partial load. According to the invention, the second oil pump 8 is, therefore, operated by the speed-controlled electric motor in such a way that the optimum oil pressure is always set. This occurs, for example, in that the engine management system controls and regulates the drive engine appropriately. The pressure increase is continuously adjustable from 0 to 3.5 bar via said second stage. In this way, unnecessary power losses are avoided, and a safe and efficiency-optimized engine operation is provided.

[0055] Overall, several improvements can thus be achieved simultaneously by the proposed solution as described: [0056] By dividing the oil production device into two structurally separate oil pumps, of which the first oil pump 4 provides a pre-pressure of between 0.6 and 1.6 bar, whereas the second oil pump 5, which is driven via a speed-controlled electric motor and is actuated by the engine management, builds up a supply pressure which is flexibly and optimally adapted to the motor requirements, a bearing lubrication and a piston cooling which are optimal for all operating conditions can be ensured with minimum energy input. [0057] By arranging the oil temperature control device 7 between the second oil pump 5 and the oil filter 8, the oil temperature can also be adapted optimally to the respective motor requirements, irrespective of the temperature downstream of the oil cooler. In this way, a safe and friction-optimized bearing lubrication as well as a piston cooling situationally adapted in an optimum way can be achieved under all operating conditions. [0058] By dividing the external oil circuit 2 into 2 partial circuits (arms 2a and 2b), the cooling of the stock oil in the crankcase and (if present) in the supplementary oil tank can be decoupled from the optimum temperature control of the engine oil at the inlet into the lubricating oil supply lines and the cooling nozzles. In this way, said stock oil can be kept at a temperature as low as possible, whereby thermal oil ageing can be minimized. [0059] By using a total amount of three separate oil filters 3, 8, 10 each having a different mesh size and filter grade, respectively, in the different partial circuits, namely upstream of the first oil pump 4, downstream of the oil temperature control device 7 as well as upstream of the oil cooler, the oil can be cleaned from abrasive floats and dirt particles in an efficient manner. The filters used can be optimized specially for the respective filter grade so that an optimally purified oil can be obtained therewith with the maximum possible filter lives.