GB2595874A

GB2595874A - A method for operating a lubricating and piston cooling system for an engine of a vehicle and a lubricating and piston cooling system

Info

Publication number: GB2595874A
Application number: GB2008693.0A
Authority: GB
Inventors: Dingle Philip
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2020-06-09
Filing date: 2020-06-09
Publication date: 2021-12-15
Also published as: GB202008693D0

Abstract

A method for operating a lubricating and piston cooling system 10 for a vehicle engine that has a first oil circuit 18 and associated first oil pump 20, and a second oil circuit 26 and associated second oil pump 28. In use, oil conveyed through the first oil circuit is directed to piston jet nozzles 12 which deliver oil jets 14 for cooling respective pistons of the engine, and oil conveyed through the second oil circuit is directed to consumers 16 other than the piston jet nozzles. The system further includes a valve device 44 that in a first mode of operation the first and second oil pumps are active and a) the valve connects the piston jet nozzles to the first oil circuit and disconnects from the second oil circuit, and b) disconnects at least one consumer from the first circuit. In a second mode of operation, the first pump is active and the second pump is de-active and a) the valve disconnects the piston jet nozzles from both the first and second oil circuits, and b) connects at least one consumer to the first oil circuit via the second oil circuit. The method of operation reduces parasitic oil pumping losses and improves fuel consumption and engine life.

Description

A METHOD FOR OPERATING A LUBRICATING AND PISTON COOLING SYSTEM

FOR AN ENGINE OF A VEHICLE AND A LUBRICATING AND PISTON COOLING

SYSTEM

FIELD OF THE INVENTION

[0001] The invention relates to a method for operating a lubricating and piston cooling system for an engine of a vehicle. The method also relates to a lubricating and piston cooling system for an engine of a vehicle.

BACKGROUND INFORMATION

[0002] US 6 655 342 B1 shows a pre-lubrication system that functions in combination with a vehicle engine. Furthermore, EP 3 150 811 Al shows a lubricating and cooling oil circuit of an internal combustion engine. EP 3 382 170 Al shows a lubricating and cooling system for an internal combustion engine. Moreover, EP 3 150 821 Al shows an internal combustion engine. From EP 3 536 918 Al, a management method of an internal combustion engine lubrication is known. Additionally, US 2015/0275713 Al shows a method for an engine. Furthermore, a lubrication system can be gathered as known from US 2019/0271241 Al.

SUMMARY OF THE INVENTION

[0003] It is an object of the present invention to provide a method for operating a lubricating and piston cooling system for an engine of a vehicle as well as a lubricating and piston cooling system for an engine of a vehicle such that the engine can be lubricated and cooled in a particularly advantageous way.

[0004] This object is solved by a method having the features of patent claim 1 and a lubricating and piston cooling system having the features of patent claim 7. Advantageous embodiments with expedient developments of the invention are indicated in the other patent claims.

[0005] A first aspect of the present invention relates to a method for operating a lubricating and piston cooling system for an engine of a vehicle. Preferably, the engine is an internal combustion engine. For example, the engine can be a reciprocating piston engine. The lubricating and piston cooling system comprises a first oil circuit having a first oil pump which is configured to convey oil through the first oil circuit thereby feeding the oil conveyed and flowing through the first oil circuit to piston jet nozzles which are configured to provide respective oil jets for cooling respective pistons of the engine. This means that the respective piston jet nozzle is configured to provide a respective oil jet which is formed from the oil fed to the respective piston jet nozzle. Thus, the respective piston jet nozzle provides the oil fed to the respective piston jet nozzle as an oil jet which is sprayed against the respective piston for the purpose of carrying away excessive heat. For example, the respective piston jet nozzle is also referred to as a piston cooling jet (PCJ).

[0006] The lubricating and piston cooling system further comprises a second oil circuit having a second oil pump configured to convey oil through the second oil circuit, thereby feeding the oil conveyed and flowing through the second oil circuit to consumers other than the piston jet nozzles. Moreover, for example, the consumers can comprise bearings and/or journals by which, for example, shafts and/or piston rods and/or other components of the engine are movably mounted. The first lubricating and piston cooling system further comprises a valve device. In the method according to the present invention, the first lubricating and piston cooling system is operated in a first operation mode and in a second operation mode. This means that the lubricating and piston cooling system may be successively operated in the first and second operation modes or vice versa. In or during the first operation mode the piston jet nozzles are fluidically connected to the first oil circuit by or via the valve device. Moreover, in the first operation mode, the piston jet nozzles are fluidically disconnected and/or isolated from the second oil circuit by the valve device. In the first operation mode, the consumers are fluidically disconnected and/or isolated from the first oil circuit by the valve device. Moreover, in the first operation mode, the second oil pump is activated (i.e. active). Preferably, in the first operation mode, the engine is active, (i.e. running). Additionally, in the first operation mode, the first oil pump is activated or active such that the first oil pump conveys oil. Thereby, the oil conveyed by the first pump through the first oil circuit is fed to the piston jet nozzles whilst a feeding of oil to the consumer via the first oil circuit is omitted. Since the second oil pump is active, the second pump conveys oil through the second oil circuit such that the consumer is supplied with oil via the second oil circuit. However, the consumer is not supplied with oil via the first circuit.

[0007] In the second operation mode, the piston jet nozzles are fluidically disconnected and/or isolated from the first oil circuit by the valve device and the piston jet nozzles are fluidically disconnected and/or isolated from the second oil circuit. Furthermore, in the second operation mode, the consumers are fluidically connected with the first oil circuit by the valve device. In the second operation mode, the second oil pump is deactivated (i.e. inactive or not active) and the first oil pump is activated (i.e. active) such that oil is conveyed by the first oil pump. Thereby, in the second operation mode, the oil conveyed by the first pump through at least a portion of the first oil circuit and at least a portion of the second oil circuit is fed to the consumers whilst a feeding of oil to the piston jet nozzles is omitted. This means, that, in the second operation mode, the piston jet nozzles are not supplied with oil. Thus, the second operation mode is a pre-lubricating mode or a pre-lubricating function by which the consumers can be supplied with oil and thus lubricated whilst the second oil pump, and for example the engine, are inactive and the feeding of oil to the piston jet nozzles is omitted.

[0008] A second aspect of the present invention relates to a lubricating and piston cooling system for an engine of a vehicle, wherein the lubricating and piston cooling system is configured to carry out a method according to the first aspect of the present invention. Advantages and advantageous embodiments of the first aspect of the present invention are to be regarded as advantages and advantageous embodiments of the second aspect of the present invention and vice versa. In the method according to the present invention, the lubricating and piston cooling system of the engine may be arranged with a lower parasitic drag on the engine in comparison with usual solutions, hence using less fuel but also capable of improving the health and longevity of the engine, resulting in lower overall cost to the operator. In the invention, the lubricating and piston cooling system is split into two discreet circuits. A first one of the two discreet circuits is the first oil circuit, and the second discreet circuit is the second oil circuit. By the second oil circuit and thus by the second oil pump the consumers such as bearings and journals can be supplied with oil in a usual way. The first oil circuit can supply the piston cooling jets, for example the engine is running under load, or when selected, the first oil circuit can provide said pre-lubricating function to the consumers, when, for example, the engine is stationary and about to be started. Thus, the lubricating and piston cooling system can be switched between the first and second operation modes such that the engine can be lubricated and cooled in a particular advantageous way and on a need-based manner. By lowering the parasitic drag on the engine relative to prior art systems that pump more oil than it is necessary, a reduction in fuel consumption is possible. Moreover, the whole life costs of the engine can be reduced.

[0009] Particularly, the invention is based on the following thoughts and findings. Currently, a majority of internal combustion engines have a lubrication system in which a crankshaft driven positive displacement pump, which typically may be selected from a gear, gerotor, or vane type, is sized to fulfill the complete demand for all of the consumers (i.e. bearings and other oil-using engine features such as the piston jet nozzles). The pump may be a fixed or a variable displacement pump. Engines that are capable of high specific power output, in particular expressed in terms of kW/liter displacement, will include oil flow for piston cooling.

[0010] Oil for piston cooling is drawn from the engine sump and sprayed onto the underneath of the engine pistons to carry away excess heat created by combustion that enters the piston through the crown and associated combustion bowl. Frequently, this oil is taken from the main oil gallery that also supplies the bearings such as crankshaft bearings, and sprays through crankcase-mounted jets into enclosed galleries formed in the piston behind the ring belt. The oil then returns to the sump. Thus, oil is being delivered to the pistons during the duration of time that the engine is running.

[0011] In a preferred scenario, the oil flow should be calibrated to be sufficient for the worst-case condition which will typically be when the engine is producing maximum power. However, for most engines used in transport applications, appreciable time is spent at part load conditions where either low PCJ flow or no flow is required. Hence, in the interests of parasitic energy loss reduction, there is an opportunity to control the PCJ flow to more nearly match the actual demand for heat removal from the piston. Thermal loading of the pistons is a function of injected fuel quantity and engine speed. As these increase, so does the piston thermal load.

[0012] Separate from the above, and in the interests of conserving fuel usage, modern vehicles are adopting strategies such as stop-start where the engine is stopped when the vehicle stops, at for instance, a road junction, or in another situation the engine may be stopped when the vehicle is able to roll downhill without the need for motive power. In these situations, the engine will be hot such that the lubricating oil will drain out of the bearings, leading to possible unwelcome wear when the engine is restarted, particularly since high power may be demanded immediately following the restart. What is required is a pre-lube facility where the main engine oil gallery is charged with oil under pressure such that the bearings (e.g. crankshaft, camshaft, valve train, turbocharger, etc.) may be lubricated immediately prior to restart, and thereby minimize the potential for undue wear. For example, said pre-lube facility can be realized by said pre-lubricating function.

[0013] It is more or less certain that future vehicles will incorporate both high specific power ratings thereby requiring piston cooling via oil jets, and they will employ stop-start strategies requiring a pre-lube facility. These features may be economically incorporated on the same engine. This is made possible by the present invention. For example, the pre-lube facility (i.e. the pre-lubricating function which is also referred to as a pre-lube function) can be advantageous when the engine is stopped while the PCJ function is used only when the engine is running under load. Therefore, a single auxiliary pump plus a switching control valve in conjunction with an appropriate control strategy is advantageous to supply both of these functions independently. For example, said single auxiliary pump can be said first oil pump, and said switching control valve can be said valve device. At the same time, an existing pump that supplies the main gallery and the bearings can now be re-specified to deliver a lower flow since it has been relieved of the PCJ function. For example, said existing pump can be said second oil pump. Moreover, for example, said main gallery can be one of said consumers. The lower flow may be achieved from a pump with a lower volumetric displacement (cc/revolution) or by running the existing pump at a lower speed. Such a reduced flow pump will be less costly and have a lower parasitic drag on the engine. This is an advantageous feature.

[0014] In one preferred embodiment, engine oil may be drawn from the sump through a coarse strainer intended to protect the pump, and is induced into the auxiliary pump by suction. Preferably, the auxiliary pump is driven by a variable speed electric motor under control of the engine management system (EMS). In an embodiment, said electric motor is a 48-volt machine. Pressurized oil is then delivered to a filter module to remove any damaging particles, and from there to the valve device. For example, the valve device can be a three-port valve module in which a two-position valve can be preferably actuated by a solenoid. Optionally, a heat exchanger may be placed in the circuit to control oil temperature.

[0015] In the deactivated state of the valve device, oil that enters the valve device via its inlet port is by default directed to one of two outlet ports of the valve device, which is also referred to as a valve. The outlet port to which, by default, the oil entering the valve is directed is also referred to as a first outlet port, while the second outlet port is isolated (i.e. closed). The first outlet port directs the oil to a piston cooling jet gallery or circuit (i.e. to the piston jet nozzles). This may be considered a first mode of operation. A pressure sensor in this circuit (i.e. in the first oil circuit) provides feedback to the controller allowing it to compare a measured pressure against the pressure value stored in a map. The measured pressure is measured by the pressure sensor. Knowledge of a possible deviation between the pressures may be used to adjust the speed and therefore flow of the auxiliary pump to achieve congruency in pressures. In place of a pressure sensor, a flow sensor may be used, however being typically more expensive, this is a less likely scenario.

[0016] When energized, the solenoid isolates the first outlet port and directs the oil to the second outlet port. The second outlet port directs the oil into the main engine oil gallery, for example via a non-return valve (NRV). The NRV permits oil from the auxiliary pump to enter the main oil gallery, but oil from the main gallery is occluded from flowing into the auxiliary circuit (i.e. into the first oil circuit). By this, oil from the auxiliary circuit is able to pressurize the main engine gallery system thereby providing the pre-lube functionality prior to engine start-up. A pressure sensor is not required in this branch of the circuit (i.e. in the second oil circuit) because such a sensor can already exist in the main gallery (i.e. the main oil gallery). This may be considered the second mode of operation during which, for example both the engine and vehicle are normally stationary.

[0017] In a third mode of operation, the pre-lube function is invoked immediately upon occasion of an engine hot shut-down while the vehicle is still rolling on a down gradient having just climbed a previous gradient. Thus, a strategy being used to conserve fuel can be realized. The objective here is to carry away excess heat that would otherwise carbonize the oil in the turbocharger bearings, for example, which degrades engine performance.

[0018] As the engine ages, wear will take place in the bearings and other journals which will increase the flow demand from the existing but downsized main engine oil pump (i.e. the second oil pump). In the event that the flow demand exceeds the capacity of the main oil pump (second oil pump), the oil pressure in the main oil gallery may no longer match the specified minimum value. In this case, and in a fourth mode of operation, the auxiliary pump (first oil pump) may be used in the pre-lube mode to provide make-up flow to the main gallery.

[0019] In a fifth mode of operation, the piston cooling jets (piston jet nozzles) may be energized periodically when the engine is operating under part load conditions where PCJ operation is not required for purposes of piston cooling. The feature that the piston cooling jets may be energized periodically means that the piston cooling jets may be supplied with oil periodically. In this mode, adequate lubrication of the power cylinder components, such as piston to liner interface, piston pin, etc., occurs. Since the objective is to minimize the use of energy, and because the duration of PCJ usage would normally be higher than that of the pre-lube function, electrical energy to activate the switching solenoid, in some embodiments, may only be required for the pre-lube function.

[0020] Other auxiliary oil circuit layouts are possible and fully contemplated in this disclosure. For example, in the preferred embodiment, the pre-lube connection to the main oil gallery is made after an oil cooler and oil filter. This may require that the auxiliary oil circuit (first oil circuit) should inconveniently have its own filter since supplying unfiltered oil to the bearings might not be advantageous. In an alternate embodiment, the pre-lube connection may be made prior to the main oil filter, such that a filter in the first oil circuit may be omitted.

[0021] Further advantages, features, and details of the invention derive from the following description of preferred embodiments as well as from the drawings. The features and feature combinations previously mentioned in the description as well as the features and feature combinations mentioned in the following description of the figures and/or shown in the figures alone can be employed not only in the respectively indicated combination but also in any other combination or taken alone without leaving the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings show in: [0023] Fig. 1: a schematic view of an embodiment of a lubricating and piston cooling system for an engine of a vehicle according to the present invention; [0024] Fig. 2: a further schematic view of the lubricating and piston cooling system according to Fig. 1; [0025] Fig. 3: a further schematic view of the lubricating and piston cooling system according to Fig. 1; and [0026] Fig. 4: a schematic view of a further embodiment of the lubricating and piston cooling system.

[0027] In the figures the same elements or elements having the same function are indicated by the same reference signs.

DETAILED DESCRIPTION

[0028] Fig. 1 shows in a schematic view a first embodiment of a lubricating and piston cooling system 10 for an engine of a vehicle. For example, the engine is an internal combustion engine, wherein the engine is a reciprocating piston engine. Moreover, for example, the vehicle can be a commercial vehicle. The vehicle can be driven by the engine. The engine comprises cylinders in which pistons are arranged, wherein the pistons can translationally move in the respective cylinders. Per piston, the lubricating and piston cooling system 10 comprises at least one piston jet nozzle 12, which is also referred to as a piston cooling jet (PCJ). Oil that is fed to the respective piston jet nozzle 12 is provided by the respective piston jet nozzle 12 as a respective oil jet 14 which is sprayed against the respective piston the respective piston jet nozzle 12 is assigned to. By spraying the oil jet 14 against the respective piston, the respective piston can be cooled.

[0029] Furthermore, the engine comprises further consumers other than the piston jet nozzles 12. Said consumers are schematically shown in Fig. 1 and indicated by 16. For example, the consumers 16 comprise bearings and/or journals by which shafts and/or other components of the engine are movably mounted. For example, the engine comprises an output shaft which can be configured as a crankshaft. For example, the

S

crankshaft is rotatably mounted on a housing of the engine by the sump of said bearings and/or journals. For example, said housing is a crankcase. As further described in greater detail below, the pistons and the other consumers 16 can be supplied with oil by the lubricating and piston cooling system 10 such that the pistons and the consumers 16 can be lubricated and cooled. For this purpose, the lubricating and piston cooling system 10 comprises a first oil circuit 18, which is also referred to as an auxiliary circuit or an auxiliary oil circuit. The first oil circuit 18 comprises a first oil pump 20 which is also referred to as an auxiliary pump or an auxiliary oil pump. Preferably, the auxiliary pump (first oil pump 20) is configured as an electric pump. In other words, the auxiliary pump may be electrically operable such that the oil pump 20 can convey oil through the oil circuit 18 whilst the engine is deactivated (i.e. inactive) and the output shaft and the vehicle are stationary. The first oil pump 20 is configured to convey oil through the first oil circuit 18 thereby feeding the oil conveyed and flowing through the first oil circuit 18 to the piston jet nozzles 12 which are configured to provide the respective oil jets 14 for cooling the respective pistons of the engine. As can be seen from Fig. 1, the lubricating and piston cooling system 10 comprises an oil sump 22 which is also referred to as a sump. The oil pump 20 can convey the oil from the sump through the oil circuit 18. An oil pick-up in the sump 22 is indicated by 24, wherein, at the oil pick-up 24, the oil pump 20 can convey the oil from the sump 22 into and through the oil circuit 18.

[0030] The lubricating and piston cooling system 10 further comprises a second oil circuit 26 comprising a second oil pump 28 which is also referred to as a main pump or a main oil pump. The second oil pump 28 is an engine-driven oil pump. Moreover, the oil pump 28 can have an integrated regulator 29 which may be of the passive i.e. bias spring regulated type, or electronically regulated. For example, in comparison with conventional solutions, the second oil pump 28 can have a reduced size. The feature that the oil pump 28 can be an engine-driven oil pump means that the oil pump 28 is mechanically driven or drivable by the engine (i.e. by the output shaft). The second oil pump 28 is configured to convey oil through the second oil circuit 26 to the consumers 16. The second oil pump 28 is configured to convey the oil from the oil sump 22 into and through the second oil circuit 26. The second oil pump 28 can convey the oil to the consumers 16 via an anti-backflow valve 30 which is arranged in a line 32 of the oil circuit 26. The oil conveyed by the oil pump 28 can flow through the line 32 which is arranged downstream the oil pump 28 and upstream the consumers 16.

[0031] The oil circuit 18 may comprise a line 34 which is arranged downstream the oil pump 20 and upstream the piston jet nozzles 12. In this regard, the oil circuit 18 may comprise an optional auxiliary circuit filter 36 by which the oil flowing from the oil pump 20 to the piston jet nozzles 12 and thus through the line 34 can be filtered.

[0032] Moreover, a branch, circuit or gallery 38 can be assigned to the piston jet nozzles 12, wherein the piston jet nozzles 12 can be supplied with the oil via the gallery 38 from the line 34 and thus from the oil circuit 18. In this regard, the line 34 is arranged downstream the oil pump 20 and upstream the gallery 38. In the line 34 an optional oil cooler 40 may be arranged. For example, the oil cooler 40 may be arranged upstream the gallery 38 and thus upstream the piston jet nozzles 12 and downstream the oil pump 20, in particular downstream the auxiliary circuit filter 36.

[0033] For example, the second oil circuit 26 can comprise a main gallery which is also referred to as a main oil gallery or main engine oil gallery. The consumers 16 can be supplied with the oil from the line 32 or from the oil circuit 26 via said main gallery such that, for example, the main gallery is arranged downstream the line 32, in particular downstream the anti-backf low valve 30 and upstream the consumers 16. The lubricating and piston cooling system 10, in particular the second oil circuit may comprise a main oil conditioning module 42 configured to condition and filter the oil flowing through the second oil circuit 26. For example, the main oil conditioning module 42 comprises a cooler for cooling the oil flowing through the oil circuit 26 and a filter for filtering the oil flowing through the oil circuit 26.

[0034] The lubricating and piston cooling system 10 further comprises a valve device 44 which can be configured as a, or may comprise, at least one solenoid valve. The valve device 44 is also referred to as a valve. In the first embodiment shown in Fig. 1 to 3, the valve device 44 is configured as or comprises a three-port-two-way solenoid valve which might be arranged in a valve block. The valve device 44 has an inlet port 46 a first outlet port 48 and a second outlet port 50. As can be seen from Fig. 1, the outlet port 50 is fluidically connected to the oil circuit 26 by a line 52. In the line 52, a non-return valve 54 is arranged. For example, the line 52 is part of a pre-lube circuit which will be described in greater detail below. Moreover, the outlet port 48 is fluidically connected to the gallery 38. The lubricating and piston cooling system 10 comprises a pressure sensor 56 which is configured to measure a pressure in the gallery 38 which is also referred to as a PCJ circuit. For example, the pressure sensor 56 is arranged in the gallery 38 or in the line which is fluidically connected to the gallery 38 and preferably arranged downstream the outlet port 48.

[0035] The lubricating and piston cooling system 10 can be operated in a first operation mode shown in Fig. 2 and in a second operation mode shown in Fig. 3. Thus, the lubricating and piston cooling system 10 can be switched between the first and second operation mode. In the first operation mode, with respect to the pre-lube circuit and the gallery 38 the gallery 38 is active only. This means that, in the first operation mode, the gallery 38 and thus the piston jet nozzles 12 are fluidically connected to the first oil circuit 18 by or via the valve (valve device 44). Moreover, in the first operation mode, the gallery 38 and thus the piston jet nozzles 12 are fluidically disconnected and/or isolated from the second oil circuit 26 by the valve device 44. Moreover, in the first operation mode, the consumers 16 and the line 52 are fluidically disconnected and/or isolated from the first oil circuit 18 by the valve device 44 and the non-return valve 54. In particular, in the first operation mode, the line 52 and thus said pre-lube circuit are fluidically disconnected and/or isolated from the first oil circuit 18 by the valve device 44 and the non-return valve. Furthermore, in the first operation mode, the second oil pump 28 and the first oil pump 20 are active such that the oil pump 20 conveys oil through the first oil circuit 18 and the oil pump 28 conveys oil through the second oil circuit 26. Thereby, in the first operation mode, the oil conveyed by the first oil pump 20 through the first oil circuit 18 is fed to the gallery 38 and thus the piston jet nozzles 12 such that the piston jet nozzles 12 provide the oil jets 14. Hence, the pistons are cooled whilst a feeding of oil to the consumers 16 via the first oil circuit 18 is omitted. This means that the consumers 16 are not supplied with oil via the first oil circuit 18. However, the second pump 28 conveys oil through the second oil circuit 26. Thereby, the oil conveyed by the second oil pump 28 through the second oil circuit 26 is fed to consumers 16 thereby supplying the consumers 16 with oil. Moreover, in the first operation mode, no oil flows through the line 52. In the first operation mode, for example, the inlet port 46 is open, whilst the outlet port 48 is open and the outlet port 50 is closed (i.e. isolated). Thus, the oil conveyed by the oil pump 20 can flow through the inlet port 46 and thus into the valve. The oil flowing though the inlet port 46 and thus into the valve can flow through the outlet port 48 and thus into the gallery 38 and to the piston jet nozzles 12. Thus, the piston jet nozzles 12 are supplied with oil whilst the consumers 16 are not. In other words, the gallery 38 is active whilst the pre-lube circuit is inactive.

[0036] In the second operation mode shown in Fig. 3, the pre-lube circuit is active, whilst the gallery 38 and thus the piston jet nozzles 12 are inactive. For this purpose, in the second operation mode, the inlet port 46 and the outlet port 50 are open, whilst the outlet port 48 is closed (i.e. isolated). In the second operation mode, the gallery 38 and via the gallery 38 the piston jet nozzles 12 are fluidically disconnected and/or isolated from the first oil circuit 18 by the valve device 44, and the gallery 38 and thus the piston jet nozzles 12 are fluidically disconnected and/or isolated from the second oil circuit 26 by the valve device 44. In the second operation mode, the consumers 16 are fluidically connected with the first oil circuit 18 via or by the valve device 44. Moreover, in the second operation mode, the second oil pump 28 is deactivated or inactive, and the first oil pump 20 is activated or active. Thus, the oil pump 20 conveys oil through the first oil circuit 18, whilst oil is not conveyed by the oil pump 28. Thus, oil conveyed by the oil pump 20 through at least a portion of the first oil circuit 18 and at least a portion of the second oil circuit 26 is fed to the consumers 16 whilst a feeding of oil to the piston jet nozzles 12 is omitted. For example, said portion of the second oil circuit 26 can comprise said oil gallery such that, for example, the oil gallery, and via the oil gallery, the consumers 16 are supplied with oil conveyed by the oil pump 20 via at least a portion of the oil circuit 18. As can be seen from Fig. 3, in the second operation mode, the oil pump 20 conveys the oil from the oil sump 22 through the line 34, the inlet port 46, the valve device 44 and the outlet port 50 into and through the line 52 and thus the pre-lube circuit. Thus, a pre-lubricating function can be realized. By said pre-lubricating function, the consumers 16 can be lubricated whilst the engine and the output shaft are stationary and the piston jet nozzles 12 are not supplied with oil. This means that the piston jet nozzles 12 are inactive in the second operation mode. In other words, in the second operation mode, the valve device 44, which can be configured as a solenoid valve, directs the oil conveyed by the oil pump 20 back into at least said portion of the second oil circuit 26, which is also referred to as a main oil circuit such that the consumers 16, such as said bearings, can be pre-lubricated, in particular prior to a start of the engine. Moreover, in the second operation mode, the main pump is inactive.

[0037] Fig. 4 shows a second embodiment of the lubricating and piston cooling system 10. In other words, Fig. 4 shows one alternate circuit which is one of multiple possibilities. For example, the first oil circuit 18 can be also referred to as an auxiliary circuit or auxiliary oil circuit since the oil circuit 18 is used to realize said pre-lubricating function. In the first embodiment, the auxiliary circuit joins the main oil circuit after the main oil conditioning module 42. In the second embodiment, the auxiliary circuit joins the main oil circuit before the main oil conditioning module 42. Moreover, a non-return valve 58 is arranged in the line 34 which fluidically connects the main oil conditioning module 42 to the oil pump 20, wherein the non-return valve 58 is arranged downstream the oil pump 20 and upstream the main oil conditioning module 42 in the line 34. Moreover, the lubricating and piston cooling system 10 according to the second embodiment may comprise and optional divided oil rail 60 with two on-off solenoid valves 62 and 64.

[0038] The objectives of the lubricating and piston cooling system 10 are to provide the piston cooling jets 14 and the pre-lubricating function which is also referred to as pre-lube functionality or pre-lube facility. Thus, lube system parasitic loss can be reduced, and engine durability can be improved. In the lubricating and piston cooling system 10, the piston cooling jet (PCJ) flow is separated in conjunction with the reduced displacement engine driven oil pump, and the duty to supply the piston jet nozzles 12 with oil is assigned to a separate variable speed (e.g. 48V) electric pump that is under electronic control, wherein said electric pump is the oil pump 20. Moreover, by adding the valve device 44, which can be configured as a solenoid controlled three-way valve, it is possible to incorporate an engine pre-lube and make-up flow capability. With respect to the housing, the oil pump 20 may be an externally mounted oil pump. The externally mounted oil pump 20 draws oil from the oil sump 22, which is also referred to as an engine sump, directs it through the filter 36 and then, for example via the optional cooler 40, to the valve device 44. In the default de-energized state of the valve device 44, the oil is directed to the piston jet nozzles 12 only. In the energized state of the valve device 44, the oil is directed to the main oil gallery for pre-lube or make-up flow purposes only. For example, a pressure sensor such as the pressure sensor 56 can be mounted in the valve block of the valve device 44 to monitor all pressure in the PCJ circuit only (i.e. in the gallery 38). Preferably, an electronic control unit (ECU) has management responsibility for the auxiliary lubrication circuit and is in communication with the engine motor control module (MCM). For example, the auxiliary lubrication circuit is the first oil circuit 18 and/or the pre-lube circuit. In the following, a pre-lube control strategy will be described.

[0039] In a cold start, (e.g. an overnight cold soak situation), and upon key-on, the valve device 44 may be energized at a predetermined or pre-determinable voltage. Concurrently, the electric oil pump may be energized at a predetermined or pre-determinable voltage of, for example, 12, 24 or 48 Volt for a predetermined or pre-determinable duration of, for example, approximately 30 seconds or until the engine is cranked. When it is sensed that the engine is being cranked, both the valve device 44 and the oil pump (auxiliary pump) may be de-energized.

[0040] For example, in an urban driving start-stop-start scenario, the following steps of operation of the system 10 may be carried out: if the duration of an engine stop event is known, the valve and auxiliary pump may be energized for a pre-determinable or predetermined time of, for example, approximately 30 seconds prior to anticipated restart of the engine. If the duration of the engine stop event is not known, then upon engine stop the valve device 44 should be energized at a predetermined or pre-determinable voltage. Concurrently, the electric oil pump (auxiliary pump) may be energized at a predetermined or pre-determinable voltage. Upon sensing that the engine is being cranked, both the valve device 44 and the auxiliary pump may be de-energized. When a fuel economy driving operation mode (e.g. sailing or "Eco-Sail") is activated, the valve device 44 may be energized at a pre-determinable or predetermined voltage. Concurrently, the auxiliary pump may be energized at a pre-determinable or predetermined voltage for a pre-determinable or predetermined duration of, for example, approximately 60 seconds. For example, the auxiliary pump may be energized at a predetermined duration of approximately 60 seconds for the purposes of mitigating oil coking at the turbo charger or other locations within the engine. At a pre-determinable or predetermined time of, for example, approximately 30 seconds prior to an anticipated engine start, the valve device 44 may be energized at a predetermined or pre-determinable voltage. Concurrently, the auxiliary pump may be energized at a pre-determinable or predetermined voltage. When it is sensed that the engine is being cranked or has been bump-started, both the valve device 44 and the auxiliary pump may be de-energized.

[0041] In an embodiment of the present invention, the lubricating and cooling system 10 may operate by the following exemplary control strategy. Also described is a method for operating the lubricating and cooling system 10. In one embodiment, in an event that the range of authority of the electronically controlled oil pressure regulator 29 on the main oil pump is exceeded, resulting in a short-fall of main gallery oil pressure relative to a mapped value, demanded make-up oil flow will be provided by the auxiliary electric pump to satisfy the demand. In an embodiment, if the main gallery oil pressure as reported to the MCM by a main gallery oil pressure sensor falls below the mapped value start in the MCM for the current engine speed and loads, the valve device 44 may be energized at a predetermined or pre-determinable voltage. Concurrently, the auxiliary pump may be energized at a predetermined or pre-determinable voltage. Electrical energy to the auxiliary pump may be modulated, for example by pulse width modulation (PWM), local interconnect network (LIN), controller area network (CAN) methodologies to achieve an intended mapped pressure value for the current engine speed and load. When the main gallery oil pressure stabilizes within the main pump regulator range of authority, both the valve device 44 and the auxiliary pump may be de-energized.

[0042] Moreover, in the following, a piston cooling control strategy will be described. When the engine is running, the piston jet nozzles 12, which are also referred to as piston cooling jets, may be activated. In one embodiment, piston cooling oil flow may not be activated, for example, until the engine coolant outlet temperature has reached a predetermined or pre-determinable threshold temperature of, for example, approximately 80 degrees Celsius.

[0043] In an embodiment, when thermal loading at the piston, based on, for example fuel burn per cylinder per unit time, exceeds a predetermined or pre-determinable level, the auxiliary pump may be activated and piston cooling jet flow may be enabled. Electric oil pump delivery may be modulated by pump speed which may be controlled by a predetermined or pre-determinable input signal such as from a, for example, PWM signal, [IN or CAN. Above a predetermined or pre-determinable threshold, PCJ flow may be modulated according to the following exemplary formula: [0044] Pump delivery [Umin] = ((6000/785)*shaft power [kW])/60.

[0045] While operating in the piston cooling mode, the oil pressure in the valve block will be continuously monitored. If this oil pressure should fall below a predetermined or pre-determinable pressure such as, for example, approximately 1.0 bar, the engine power may be de-rated to a predetermined or pre-determinable level such as, for example, approximately 10 bar BMEP.

[0046] Moreover, in the following a cylinder lubrication control strategy is described. In an embodiment, the lubrication of the cylinder bore/piston and rings and the piston pin/connecting rod interface may depend, to an extent, on oil splash from the piston jet nozzles 12. Extended running at low load without PCJ activation may deprive the cylinder bore/piston and rings and the pin/connecting rod interface from adequate lubrication and/or cooling, leading to scuffing and engine failure. In order to obviate this failure, periodic activation of the PCJ may be advantageous. Therefore, in an embodiment of the invention, during periods where the engine is running at loads below the predefined threshold used during piston cooling, the auxiliary oil pump may be energized at a threshold count of engine revolutions (e.g. every 1000 revolutions), and operated at a threshold modulated pump speed for a pre-determined amount of time (e.g. 5 seconds). When the system 10 is operating under the cylinder lubrication control strategy, the oil pressure at the valve block may be continuously monitored. If this oil pressure should fall below a predetermined or pre-determinable pressure such as, for example, approximately 1.0 bar, the engine power may be de-rated to a predetermined or pre-determinable level such as, for example, approximately 10 bar BMEP.

Reference Signs lubrication and cooling system 12 piston jet nozzle 14 oil jet 16 consumers 18 first oil circuit first oil pump 22 oil sump 24 oil pick-up 26 second oil circuit 28 second oil pump anti-backf low valve 32 line 34 line 36 auxiliary circuit filter 38 gallery oil cooler 42 main oil conditioning module 44 valve device 46 inlet port 48 outlet port outlet port 52 line 54 none-return valve 56 pressure sensor 58 none-return valve divided oil rail 62 solenoid valve 64 solenoid valve

Claims

CLAIMS1. A method for operating a lubricating and piston cooling system (10) for an engine of a vehicle, the lubricating and cooling system (10) comprising: -a first oil circuit (18) comprising a first oil pump (20) configured to convey oil through the first oil circuit (18), wherein the first oil circuit (18) is configured to convey oil to piston jet nozzles (12),wherein the piston jet nozzles (12) are configured to provide oil to respective oil jets (14) for cooling respective pistons of the engine; -a second oil circuit (26) comprising a second oil pump (28) configured to convey oil through the second oil circuit (26), wherein the second oil circuit (26) is configured to convey the oil thereby feeding the oil conveyed through the second oil circuit (26) to at least one consumer (16) other than the piston jet nozzles (12); and -a valve device (44), wherein the lubricating and cooling system (10) is operated in: o a first operation mode in which: the piston jet nozzles (12) are, by the valve device (44), fluidically connected to the first oil circuit (18) and fluidically disconnected from the second oil circuit (26); * the at least one consumer (16) is, by the valve device (44), fluidically disconnected from the first oil circuit (18); * the second oil pump (28) is activated; and the first oil pump (20) is activated thereby feeding the oil conveyed by the first oil pump (20) through the first oil circuit (18) to the piston jet nozzles (12) whilst a feeding of oil to the at least one consumer (16) via the first oil circuit (18) is omitted; and o a second operation mode in which: the piston jet nozzles (12) are, by the valve device (44), fluidically disconnected from the first oil circuit (18) and fluidically disconnected from the second oil circuit (26); the at least one consumer (16) is, by the valve device (44), fluidically connected with the first oil circuit (18); the second oil pump (28) is deactivated; and the first oil pump (20) is activated thereby feeding the oil conveyed by the first oil pump (20) through at least a portion of the first oil circuit (18) and at least a portion of the second oil circuit (26) to the at least one consumer (16) whilst a feeding of oil to the piston jet nozzles (12) is omitted.
2. The method according to claim 1, wherein in the second operation mode, the vehicles stands still and the engine is deactivated such that an output shaft of the engine stands still.
3. The method according to claim 1 or 2, wherein the lubricating and cooling system (10) is operated in a third operation mode in which: -the piston jet nozzles (12) are, by the valve device (44), fluidically disconnected from the first oil circuit (18) and fluidically disconnected from the second oil circuit (26); -the at least one consumer (16) is, by the valve device (44), fluidically connected with the first oil circuit (18); -the second oil pump (28) is deactivated; and -the first oil pump (20) is activated thereby feeding the oil conveyed by the first pump (20) through at least a portion of the first oil circuit (18) and at least a portion of the second oil circuit (26) to the at least one consumer (16) whilst a feeding of oil to the piston jet nozzles (12) is omitted., wherein the third operation mode is carried out in response to a deactivation of the engine and whilst the vehicle is moving.
4. The method according to any one of the preceding claims, wherein the lubricating and cooling system (10) is operated in a fourth operation mode in which: -the at least one consumer (16) is, by the valve device (44), fluidically connected with the first oil circuit (18); -the second oil pump (28) is activated; and -the first oil pump (20) is activated thereby feeding the oil conveyed by the first pump (20) and the oil conveyed by the second oil pump (28) to the at least one consumer (16).
5. The method according to claim 4, wherein, in the fourth operation mode, the piston jet nozzles (12) are, by the valve device (44), fluidically disconnected from the first oil circuit (18) and from the second oil circuit (26) such that conveying oil to the piston jet nozzles (12) is omitted in the fourth operation mode.
6. The method according to any one of the preceding claims, wherein the lubricating and cooling system (10) is operated in a fifth operation mode in which the piston jet nozzles (12) are supplied with oil via the first oil circuit (18) periodically during part load operating conditions of the engine.
7. The method according to any one of the preceding claims, wherein at least one flow rate of the oil via the first oil circuit (18) to the piston jet nozzles (12) is modulated as a function of a thermal load of the engine and/or the pistons
8. A lubricating and cooling system (10) for an engine of a vehicle, the lubricating and cooling system (10) being configured to carry out a method according to any one of claims 1 to 7.