Patent Application
20190145292
The invention relates to an oil supply system for an internal combustion engine, comprising an oil circuit in which an oil pressure generating device and a device for oil temperature control are provided. In addition, the invention relates to an internal combustion engine comprising such an oil supply system. Finally, the invention relates to a cogeneration plant comprising an internal combustion engine.
Internal combustion engines with reciprocating pistons comprise a lubricating oil circuit, wherein the engine oil, on the one hand, ensures the lubrication of the bearing points and of the piston assembly and, on the other hand, protects the surfaces exposed to the blow-by gases from corrosion, and finally cools the pistons. In modern high-performance engines, optimum oil supply is essential, as the component load reaches the limit of what is possible and minor disturbances in the lubricating oil circuit can already cause great damage.
The optimal temperature range for the engine oil in the internal combustion engine is between 70 and 95° C. At lower temperatures, the risk of condensate accumulation and acidification of the engine oil arises, at higher temperatures, thermal degradation and, respectively, thermal ageing increase progressively. Furthermore, the viscosity of the engine oil is highly dependent on the temperature, which, in turn, has a substantial influence on the thickness of the lubricating film. The temperature of the engine oil is, in turn, coupled to the cooling water temperature, since the engine oil is generally cooled by the engine cooling water, or the engine cooling water and the engine oil are incorporated into the same external cooling circuit (e.g., heating water system of the internal combustion engine system in cogeneration plants).
In addition to bearing lubrication and bearing cooling, the engine oil also serves for cooling the pistons. For this purpose, the engine oil is injected for example through nozzles into an opening at the underside of the piston, from where it gets to the annular cooling duct in the interior of the piston. During the operation of the engine, the engine oil is thereby supplied with thermal energy which must be dissipated via appropriate heat exchangers. At full load, the heat to be dissipated from the engine oil is about 4% of the energy supplied with fuel.
Overall, a relatively large amount of oil is required for feeding all functional elements appropriately, with the recirculated oil quantity of an internal combustion engine usually amounting to 0.5 litres/kW full engine load.
For the generation of oil pressure, oil pumps are usually used in the form of gear pumps which are driven mechanically by the internal combustion engine via a transmission and therefore are coupled to the rotational speed of the internal combustion engine. The delivery rate of the gear pumps essentially depends only on the rotational speed so that appropriate delivery reserves must be provided in order to maintain the necessary oil pressure in case of low oil viscosity (e.g., at a high oil temperature) or, respectively, enlarged lubrication gaps. The excess amount of oil has to be branched off via a shutoff valve downstream of the oil pump and must be returned to the oil sump. This entails major energy losses.
The efforts to render internal combustion engines ever more efficient and economical cause auxiliary drives and system functions such as the lubricating oil and cooling water circuit to be included increasingly in the overall optimization of internal combustion engines. This is especially about adapting also the peripheral systems in an optimal and precise fashion to the motor requirements, avoiding unnecessary losses.
For driving the cooling water and oil pumps for the cooling water and, respectively, oil circuit, powers must be applied which amount to several percent of the engine power and therefore cannot be neglected when it comes to further increasing the efficiency of internal combustion engines.
It is therefore the object of the present invention to improve the efficiency of an internal combustion engine with respect to the engine oil circuit. In particular, the engine oil supply of the internal combustion engine is to be optimized in such a way that energy losses are reduced to an absolute minimum.
This object is achieved by 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.
In addition, the object is achieved by an internal combustion engine comprising such an oil supply system.
The two arms of the lubricating oil circuit connected in parallel are recombined either in the oil sump or still upstream of the oil sump.
Furthermore, a second oil pressure generating device is preferably provided 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.
For example, the second oil pressure generating device may be arranged upstream of the first device for oil temperature control.
One embodiment is characterized by an oil filter (3) in the flow direction upstream of the first oil pressure generating device (5).
Preferably, the invention is further characterized by an oil filter in the first arm of the lubricating oil circuit, preferably downstream of the first oil pressure generating device.
Furthermore, the invention may be characterized by an oil filter in the second arm of the lubricating oil circuit.
Said oil filter may be arranged upstream of the second device for oil temperature control.
One embodiment is characterized in that 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.
Furthermore, in one embodiment of the invention, a control unit may be provided by means 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.
Furthermore, it may be provided that, 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 and mesh size, respectively, wherein said filter fineness and mesh size differ from each other by, in each case, at least 100%, based on the deposited particle diameter.
In addition, it is preferably provided that, with the first oil pressure generating device in the operating state, an oil pressure of between 0.6 and 1.6 bar can be generated.
Furthermore, it may be provided that, 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.
In a preferred embodiment variant, it is provided that the temperature of the first device for oil temperature control is adaptable to the motor requirements.
In addition, the invention may be characterized in that the first device for oil temperature control comprises a heat exchanger, which may preferably have a multi-stage design, with both a cooling and a heating function being provided.
In this connection, appropriate control means including control valves are provided.
It is preferably provided that the oil filter exhibits the smallest mesh size and the highest filter fineness of all oil filters in the first arm, preferably downstream of the first oil pressure generating device.
In a preferred embodiment variant, it is provided that the second device for oil temperature control in the second arm is adjustable to a temperature between 70 and 80° C., preferably to a temperature between 70 and 75° C., during the operation of the engine.
The adjustment is thereby independent of the temperature of the engine oil at the inlet into the pressure lines within the internal combustion engine. In this connection, the engine oil in the oil sump of the internal combustion engine and—if present—in an external oil reservoir, which, however, is incorporated into the engine oil circuit of the internal combustion engine, is adjusted to an optimum temperature level by means of a further device for oil temperature control.
Furthermore, it may be provided that, 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.
In one embodiment variant, it is provided that, 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.
Furthermore, it may be provided that, starting from the first oil pressure generating device, the oil circuit is branched into two partial circuits (with the two arms), wherein one partial circuit (first arm) supplies the oil pressure lines of the internal combustion engine with finely filtered oil, whereas the other partial circuit (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, and in which an oil filter can be used which causes a separation of dirt particles in a range greater than 20 μm.
One aspect of the invention relates to an internal combustion engine, comprising an oil supply system of the aforementioned type.
The internal combustion engine may be characterized in that 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.
The internal combustion engine may be characterized in that the first arm supplies the oil pressure lines of the internal combustion engine with finely filtered 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.
Furthermore, the invention relates to a cogeneration plant comprising an internal combustion engine of the aforementioned type.
The solution to the problem is aimed at a modified configuration of the engine oil circuit, whereby an optimization of the entire assembly of the oil supply of the internal combustion engine, including possible oil filters, is achieved. A special feature of modern high-performance engines is that they reach very high power densities via a (frequently 2-stage) high charging at full load. Ensuring operational reliability under the high mechanical and thermal component loads associated therewith requires specially designed and optimized cooling and lubrication systems. Especially for the high load range, for example, large volume flows of engine oil and cooling water must be conveyed through the internal combustion engine.
However, increasingly there are applications in which internal combustion engines are operated predominantly in the medium load range and only for a relatively short time at full load or overload, such as when consumption peaks must be covered. In contrast to the high load range, however, lower oil delivery rates and higher oil temperatures are more favourable for the medium or low load range.
However, engine oil circuits commonly designed according to the prior art do not make allowances for the different requirements between partial and full load.
The basic concept of the proposed invention forming the subject matter is, however, based precisely on the fact that, depending on the load and the operating conditions, the oil quantity, the oil supply pressure, the oil temperature and oil filtering can be optimally adapted to the respective requirements.
A central feature of the proposal is that, for oil production and pressure generation, two separate oil pressure generating devices (in particular oil pumps) connected in series are provided. Furthermore, the oil circuit is separated into two partial circuits, comprising the two arms, wherein one partial circuit may be provided for supplying the lubrication and cooling points of the internal combustion engine with oil and the other one may be provided for cooling and for the pre- or, respectively, side stream filtration of the engine oil.
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.
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
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.
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.
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.
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 μm enter into the lubricating gaps of the bearing points.
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).
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.
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.
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 μm). Oil filter 10 acts as a cleaning filter with a mesh size of, e.g., >20 μm, and oil filter 8 acts as a fine filter with a mesh size of approx. 10 μm.
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.
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.
Overall, several improvements can thus be achieved simultaneously by the proposed solution as described:
| Number | Date | Country | Kind |
|---|---|---|---|
| A 50232/2016 | Mar 2016 | AT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/056666 | 3/21/2017 | WO | 00 |
