DK179764B1

DK179764B1 - Large slow-running two-stroke engine and method of lubricating such engine, as well as an injector for such engine and method

Info

Publication number: DK179764B1
Application number: DKPA201770936A
Authority: DK
Inventors: Bak Peer
Original assignee: Hans Jensen Lubricators A/S
Priority date: 2017-12-13
Filing date: 2017-12-13
Publication date: 2019-05-13
Also published as: DK201770936A1

Abstract

A large slow-running two-stroke engine and a method of lubricating the engine with an injector (4) that comprises an electrically-driven inlet-valve system (13), for example in which an electrically-driven rigid push-rod (31) is used to push a ball (26) from its seat in a non-return valve (25) for lubricant injection. Optionally, the push rod (31) is accelerated prior to impact with the ball (26) in order to achieve a quick response time for the injection.

Description

Large slow-running two-stroke engine and method of lubricating such engine, as well as an injector for such engine and method

FIELD OF THE INVENTION

The present invention relates to a large slow-running two-stroke engine and a method of lubricating such engine, as well as an injector for such engine and method.

BACKGROUND OF THE INVENTION

Due to the focus on environmental protection, efforts are on-going with respect reduction of emissions from marine engines. This also involves the steady optimization of lubrication systems for such engines, especially due to increased competition. One of the economic aspects gaining increased attention is a reduction of oil consumption, not only because of environmental protection but also because this is a significant part of the operational costs of ships. A further concern is proper lubrication despite reduced lubricant volume because the longevity of engines should not be compromised by the reduction of oil consumption. Thus, there is a need for steady improvements with respect to lubrication.

For lubricating of large slow-running two-stroke marine diesel engines, several different systems exist, including injection of lubrication oil directly onto the cylinder liner or injection of oil quills to the piston rings.

An example of a lubricant injector for a marine engine is disclosed in EP1767751, in which a non-return valve is used to provide the lubricant access to the nozzle passage inside the cylinder liner. The non-return valve comprises a reciprocating springpressed ball in a valve seat just upstream of the nozzle passage, where the ball is displaced by pressurised lubricant. The ball valve is a traditional technical solution, based on a principle dating back to the start of the previous century, for example as disclosed in GB214922 from 1923.

An alternative and relatively new lubrication method, compared to traditional lubrication, is commercially called Swirl Injection Principle (SIP). It is based on injection of a spray of atomized droplets of lubricant into the scavenging air swirl inside the cylinder. The helically upwards directed swirl results in the lubricant being pulled towards the Top Dead Centre (TDC) of the cylinder and pressed outwards against the cylinder wall as a thin and even layer. This is explained in detail in international patent applications WO2010/149162 and WO2016/173601. The injectors comprise an injector housing inside which a reciprocating valve member is provided, typically a valve needle. The valve member, for example with a needle tip, closes and opens the lubricant’s access to a nozzle aperture according to a precise timing. In current SIP systems, a spray with atomized droplets is achieved at a pressure of, typically, 35-40 bars, which is substantially higher than the oil pressure of less than 10 bars that are used for systems working with compact oil jets that are introduced into the cylinder. In some types of SIP valves, the high pressure of the lubricant is also used to move a spring-loaded valve member against the spring force away from the nozzle aperture such that the highly pressurised oil is released therefrom as atomized droplets. The ejection of oil leads to a lowering of the pressure of the oil on the valve member, resulting in the valve member returning to its origin and remaining there until the next lubricant cycle where highly pressurized lubricant is supplied to the lubricant injector again.

In such large marine engines, a number of injectors are arranged in a circle around the cylinder, and each injector comprises one or more nozzle apertures at the tip for delivering lubricant jets or sprays into the cylinder from each injector. Examples of SIP lubricant injector systems in marine engines are disclosed in international patent applications WO2002/35068, WO2004/038189, WO2005/124112, WO2010/149162, WO2012/126480, WO2012/126473, WO2014/048438, and WO2016/173601.

The above mentioned WO2012/126473 and WO2016/173601, and also EP1426571 and EP1586751 disclose electromechanical outlet valves at the nozzle. An electrical coil exerts an electromagnetic force on the outlet valve member, which is equipped with a correspondingly electromagnetic responsive part. At excitation, the outlet valve member is withdrawn from its valve seat at the nozzle aperture and opens for flow of lubricant from a lubricant source and passing the valve member and out of the nozzle. In practice, the outlet valve member with the electromechanical responsive part is relatively long and has a mass that causes a slight delay in the action on the outlet valve member.

Whereas these systems use electromechanical actuation of the outlet valve member, it is also possible to use oil pressure to push back the outlet valve member from the valve seat. An example is disclosed in EP1426571 in which an electromechanical pilot valve is used for providing a pilot pressure behind the outlet valve member in order to open and close the outlet valve at the nozzle aperture by toggling the pilot pressure behind the outlet valve member. The toggling of the pilot pressure requires flow into and out of the volume behind the outlet valve, which delays a prompt movement of the outlet valve member. Compared to the electromechanical outlet valve, this pilottype valve also has the disadvantage of requiring a lubricant return line in order to empty the volume behind the valve member, which adds to costs and complexity of the system and increases the risk for leaks. Further, the pilot-type injection valve is sensitive against back pressure from the engine cylinder.

However, for SIP injection, a precisely controlled timing is essential in addition to the objective of minimizing oil consumption. For this reason, SIP systems should be optimized for quick reactive response during injection cycles. Accordingly, a steady motivation for improvements exists.

DESCRIPTION / SUMMARY OF THE INVENTION

It is therefore the objective of the invention to provide an improvement in the art. A particular objective is to provide a better speed and volume control of lubricant ejection by the injector. Especially, it is the objective to improve lubrication with SIP valves in a large slow-running two-stroke engine. These objectives are achieved by a large slow-running two-stroke engine with a plurality of injectors, a method for lubricating such an engine and with an injector for such engine and method as set forth in the following.

The large slow-running two-stroke engine comprises a cylinder with a reciprocal piston inside and with a plurality of injectors distributed along a perimeter of the cylinder for injection of lubricant into the cylinder at various positions on the perimeter during injection phases. For example, the large slow-running two-stroke engine is a marine engine or a large engine in power plants. Typically, the engine is burning diesel or gas fuel.

The engine further comprises a controller. The controller is configured for controlling the amount and timing of the lubricant injection by the injectors during an injection phase. Optionally, also the injection frequency is controlled by the controller. For precise injection, it is an advantage if the controller is electronically connected to a computer or comprises a computer, where the computer is monitoring parameters for the actual state and motion of the engine. Such parameters are useful for the control of optimized injection. Optionally, the controller is provided as an add-on system for upgrade of already existing engines. A further advantageous option is a connection of the controller to a Human Machine Interface (HMI) which comprises a display for surveillance and input panel for adjustment and/or programming of parameters for injection profiles and optionally the state of the engine. Electronic connections are optionally wired or wireless or a combination thereof.

The term “injector” is used for an injection valve system comprising a housing with a lubricant inlet and one single injection nozzle with a nozzle aperture as a lubricant outlet and with a movable member inside the housing, which opens and closes access for the lubricant to the nozzle aperture. Although, the injector has a single nozzle that extends into the cylinder through the cylinder wall, when the injector is properly mounted, the nozzle itself, optionally, has more than a single aperture. For example, nozzles with multiple apertures are disclosed in WO2012/126480.

The term “injection phase” is used for the time during which lubricant is injected into the cylinder by an injector. The term “idle phase” is used for the time between injection phases. The term “injection cycle” is used for the time it takes to start an injection sequence and until the next injection sequence starts. For example, the injection sequence comprises a single injection, in which case the injection cycle is measured from the start of the injection phase to the start of the next injection phase. The term “timing” of the injection is used for the adjustment of the start of the injection phase by the injector relatively to a specific position of the piston inside the cylinder. The term “frequency” of the injection is used for the number of repeated injections by an injector per revolution of the engine. If the frequency is unity, there is one injection per revolution. If the frequency is 1/2, there is one injection per every two revolutions. This terminology is in line with the above mentioned prior art.

In a practical embodiment, the housing of the injector comprises a base with a lubricant inlet port for receiving lubricant and comprises a flow chamber, typically a rigid cylindrical flow chamber, which rigidly connects the base with the nozzle. The flow chamber is hollow and, thus, allows lubricant to flow inside the flow chamber from the base to the nozzle. When the injector is mounted, the flow chamber extends through the cylinder wall of the engine so that the nozzle is held rigidly inside the cylinder by the flow chamber. Due to the base being provided at the opposite end of the flow chamber, it is typically located on or at the outer side of the cylinder wall. For example, the injector comprises a flange at the base for mounting onto the outer cylinder wall.

In order to fully understand the invention, it is pointed out that it has been discovered that lubricant conduits of a substantial length from a pumping system to the cylinder with the plurality of injectors introduce imprecision of the system. Long conduits tend to expand and retract slightly when being exposed to highly pressurised lubricant, which leads to slight uncertainties in timing and volume of injected lubricant. Furthermore, the lubricant is subject to minute compression and expansion during an injection cycle, which adds to the effect. Although, this effect is small, it introduces errors in the range of milliseconds for the injection, which is substantial in comparison to the short SIP injection time, which can be as little as 10 milliseconds or even below 1 millisecond. Such effect of imprecise timing has substantial influence on SIP lubrication systems due to the high lubricant pressure and the short injection periods. Also, it is noticed that the injection amount is typically regulated by the time length in which pressurised oil is supplied to the nozzle in an injection cycle, in which case, uncertainty factors that affect a precise timing should be minimised, if not eliminated.

Improvement with respect to the injection is achieved with a system and method as described in the following with various embodiments and details.

Each injector comprises a lubricant inlet port for receiving lubricant from a lubricant feed conduit. Typically, the lubricant feed conduit is connected to a common lubricant supply system including a potential lubricant pump that raises the pressure of the lubricant to an adequate level. For the described system, it suffices to provide a constant lubricant pressure at the lubricant inlet port of the injector.

Each of the injectors comprises an outlet-valve system at the nozzle configured for opening for flow of lubricant to the nozzle aperture during an injection phase upon pressure rise above a predetermined limit at the outlet-valve system and for closing the outlet-valve system after the injection phase. The outlet-valve system closes off for back-pressure from the cylinder and also prevents lubricant to enter the cylinder unless the inlet-valve is open. In addition, the outlet-valve system assists in a short closing time after injection, adding to precision in timing and volume of injected lubricant

For example, the outlet-valve system comprises an outlet non-return valve. In the outlet non-return valve, the outlet-valve member, for example a ball, ellipsoid, plate, or cylinder, is pre-stressed against an outlet-valve seat by an outlet-valve spring. Upon provision of pressurised lubricant in a flow chamber upstream of the outlet-valve system, the pre-stressed force of the spring is counteracted by the lubricant pressure, and if the pressure is higher than the spring force, the outlet-valve member is displaced from its outlet-valve seat, and the outlet non-return valve opens for injection of lubricant through the nozzle aperture into the cylinder. For example, the outlet-valve spring acts on the valve member in a direction away from the nozzle aperture, although, an opposite movement is also possible.

In order to solve the problem and achieve the objective of providing a better speed and volume control of lubricant ejection by the injector, each of the injectors comprises an electrically-driven inlet-valve system electrically connected to the controller and arranged between the lubricant inlet port and the nozzle for regulating the lubricant that is dispensed through the nozzle aperture by opening or closing for lubricant flow from the lubricant inlet port to the nozzle in dependence of an electrical control-signal received from the controller. The inlet-valve system is arranged upstream of and remotely from the nozzle, and it is also arranged upstream of and remotely from the outlet-valve system.

The inlet-valve system of the injector doses the amount of lubricant for injection by the time the inlet-valve system stays open for the injection phase. The time is determined by the controller.

For example, for lubricating the engine, the method comprises sending an electrical control signal from the controller to the electrically-driven inlet-valve system and by the control signal causing the inlet-valve system to open for flow of lubricant from the lubricant feed conduit through the lubricant inlet port, through the inlet-valve system, and into a conduit that flow-connects the inlet-valve system with the outlet-valve system. The lubricant flow into the conduit causes a pressure rise at the outlet-valve system, causing the outlet-valve system to open for flow of lubricant from the conduit to the nozzle aperture by which lubricant is injected into the cylinder through the nozzle aperture. At the end of the lubrication period, the electrical control signal from the controller is changed, causing the inlet-valve system to close again for lubricant supply from the lubricant inlet port to the nozzle aperture. The pressure in the conduit decreases again, and the outlet valve closes.

Thus, there are two valve systems in the injector. The inlet-valve system is regulated by electrical signals from the controller and the outlet-valve system is activated only by the elevated pressure of the lubricant at the outlet-valve system for example nonreturn valve, once the inlet-valve system has caused flow of lubricant to the outlet non-return valve. There is no mechanical connection that couples the movable parts of the inlet-valve system with the movable parts of the outlet-valve system. Coupling between the opening and closing of these two systems is done only by the lubricant that flows from the inlet-valve system to the outlet-valve system.

In practical embodiments, the inlet-valve system comprises an inlet non-return valve with an inlet-valve member, for example a ball, ellipsoid, plate, or cylinder, preDK 179764 B1 stressed against an inlet-valve seat by an inlet-valve spring and arranged for throughput of lubricant from the lubricant inlet port to the outlet-valve system upon displacement of the inlet-valve member from the inlet-valve seat against force from the inlet-valve spring.

In further embodiments, the inlet-valve system further comprises an electricallydriven rigid displacement-member, for example push-member, for displacing, for example pushing, the inlet-valve member from the inlet-valve seat during lubricant injection. For example, the displacement-member is connected to an arrangement of a solenoid-plunger and solenoid coil for upon electrical excitation of the solenoid coil to drive the displacement-member, for example push-member. Optionally, the displacement-member is connected to the solenoid-plunger, whereas the solenoid coil is stationary in the injector. Alternatively, the displacement-member is connected to the solenoid coil, which is movable together with the displacement-member. After the injection phase, the motion of the displacement-member is reversed and the inletvalve member is caused to return to the inlet-valve seat.

In principle, the displacement-member can be fastened to the inlet-valve member, for pushing or pulling the inlet-valve member from the inlet-valve seat. However, this need not be so, and the displacement-member is a push-member that is not fastened to the inlet-valve member.

Especially, in order to increase the opening speed of the inlet-valve system, the following embodiment has been found useful. In this case, the displacement-member is a push-member that is not fastened to the inlet-valve member. Further, while in an idle state, the push member is provided at a distance from the inlet-valve member, for example between 0.1 and 2 mm, optionally between 0.2 and 1 mm. By the control signal, the push-member is accelerated towards the inlet-valve member, obtains speed prior to impact with the inlet-valve member, and pushes the inlet-valve member from the inlet-valve seat by the impact. Because the push-member is accelerated over a distance prior to impact with the inlet-valve member, the displacement of the inletvalve member, for example ball, from the inlet-valve seat by the push is abrupt, and the results is a very short opening time of the inlet no-return valve with a consequently high degree of precision in timing.

In some embodiments, the push-member is a push-rod, optionally connected to the solenoid-plunger for displacement together with the solenoid-plunger upon excitation of the solenoid coil. For example, the push-rod has a first end for contact, for example impact, with the inlet-valve member for displacing the inlet-valve member by contact, for example impact, with the first end.

In some embodiment, the distance from the inlet-valve member to the push-member in the idle state is adjustable. For example, the travel distance for the push-member is adjustable by a movable end stop. For the event that the push-member is fastened to a solenoid-plunger in a solenoid plunger/coil arrangement, an adjustable end stop is optionally provided for the solenoid-plunger.

In practical embodiments, the lubricant inlet port and the inlet-valve system are provided in an inlet-valve housing. Optionally, the outlet-valve system is provided in the nozzle and a flow chamber is provided in the form of a hollow rigid tube connecting the inlet-valve housing with the nozzle.

In order to mount the injector in the cylinder wall, the injector optionally comprises a flange provided around the flow chamber. For example, the flange is bolted against the inlet-valve housing, thereby clamping the flow chamber to the inlet-valve housing. The separation of inlet-valve system and outlet-valve system reduced the total mass that has to be moved during operation. This accounts in particular for the non-return vales with small valve members, such as balls, that are spring-pressed against valve seats. The reduced mass reduces reaction time of the movable objects, why the system implies an increased reaction speed and corresponding precision with respect to timing and amount. The electrically controlled inlet-valve system with the push member, for example push-rod, implies a sudden impact on the inlet-valve member, for example ball, such that the onset of injection is very abrupt and, therefore, precise.

In case that the outlet-valve system comprises a non-return valve in the nozzle, and the non-return valve comprises a valve member, for example ball, which is spring pressed against a valve seat, a high degree of robustness against failure has been observed. These systems are simple, and the risk for clogging is minimal. Also, the valve seats tend to be self-cleaning and subject to little uneven wear, especially for valve members being balls, why a high and long-term reliability is provided. Accordingly, the injector is simple and reliable, quick and precise, and easy to construct from standard components with low production costs.

The invention also has distinct advantages over systems in which an outlet-valve system is provided in the injector and a valve system for feeding the injector is provided remote from the injector, for example as disclosed in the above-mentioned EP1767751. As the injector as described above only has a short and rigid flow chamber from the inlet-valve system to the outlet-valve system, uncertainties and imprecisions of the injection amount and the timing are minimized in that minutes compression and expansion of the oil in the relatively long conduits are avoided as well as expansion of the conduits themselves.

For example, the injectors comprise a nozzle with a nozzle aperture of between 0.1 and 1 mm, for example between 0.2 and 0.5mm, and are configured for ejecting a spray of atomized droplets, which is also called a mist of oil.

A spray of atomized droplets is important in SIP lubrication, where the sprays of lubricant are repeatedly injected by the injectors into the scavenging air inside the cylinder prior to the piston passing the injectors in its movement towards the TDC. In the scavenging air, the atomized droplets are diffused and distributed onto the cylinder wall, as they are transported in a direction towards the TDC due to a swirling motion of the scavenging air towards the TDC. The atomization of the spray is due to highly pressurized lubricant in the lubricant injector at the nozzle. The pressure is higher than 10 bars, typically between 25 bar and 100 bar for this high pressure injection. An example is an interval of between 30 and 80 bars, optionally between 35 and 60 bars. The injection time is short, typically in the order of 5-30 milliseconds (msec). However, the injection time can be adjusted to 1 msec or even less than 1 msec, for example down to 0.1 msec. Therefore imprecisions of only a few msec may alter the injection profile detrimentally, why high precision is required, as already mentioned above, for example a precision of 0.1 msec.

Also, the viscosity influences the atomization. Lubricants used in marine engines, typically, have a typical kinematic viscosity of about 220 cSt at 40°C and 20 cSt at 100°C, which translates into a dynamic viscosity of between 202 and 37 mPa-s. An example of a useful lubricant is the high performance, marine diesel engine cylinder oil ExxonMobil® Mobilgard™ 560VS. Other lubricants useful for marine engines are other Mobilgard™ oils as well as Castrol® Cyltech oils. Commonly used lubricants for marine engines have largely identical viscosity profiles in the range of 40-100°C and are all useful for atomization, for example when having a nozzle aperture diameter of 0.1-0.8 mm, and the lubricant has a pressure of 30-80 bars at the aperture and a temperature in the region of 30-100°C or 40-100°C. See also, the published article on this subject by Rathesan Ravendran, Peter Jensen, Jesper de Claville Christiansen, Benny Endelt, Erik Appel Jensen, (2017) Rheological behaviour of lubrication oils used in two-stroke marine engines, Industrial Lubrication and Tribology, Vol. 69 Issue: 5, pp.750-753, https://doi.org/10.1108/ILT-03-2016-0075.

The term “a solenoid coil” should be understood as “at least one solenoid coil”, as it is possible and in some cases advantageous to use more than one coil, for example two or three coils.

SHORT DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail with reference to the drawing, where

FIG. 1 is a sketch of part of a cylinder in an engine;

FIG. 2 is a drawing of the injector with a) an overview sketch, b) an enlarged section of the inlet-valve housing;

FIG. 3 illustrates an example of a nozzle;

FIG. 4 illustrates an alternative example of a nozzle;

FIG. 5 illustrates an alternative embodiment.

DETAILED DESCRIPTION / PREFERRED EMBODIMENT

FIG. 1 illustrates one half of a cylinder 1 of a large slow-running two-stroke engine, for example marine diesel engine. The cylinder 1 comprises a cylinder liner 2 on the inner side of the cylinder wall 3. Inside the cylinder wall 3, there are provided a plurality of injectors 4 for injection of lubricant into the cylinder 1. As illustrated, the injectors 4 are distributed along a circle with the same angular distance between adjacent injectors 4, although this is not strictly necessary. Also, the arrangement along a circle is not necessary, seeing that an arrangement with axially shifted injectors is also possible, for example every second injector shifted towards the piston's top dead centre (TDC) relatively to a neighbouring injector.

Each of the injectors 4 has a nozzle 5 with a nozzle aperture 5' from which a fine atomized spray 8 with miniature droplets 7 is ejected under high pressure into the cylinder 1.

For example, the nozzle aperture 5' has a diameter of between 0.1 and 0.8 mm, such as between 0.2 and 0.5 mm, which at a pressure of 10-100 bars, for example 25 to 100 bars, optionally 30 to 80 bars or even 50 to 80 bars, atomizes the lubricant into a fine spray 8, which is in contrast to a compact jet of lubricant. The swirl 14 of the scavenging air in the cylinder 1 transports and presses the spray 8 against the cylinder liner 2 such that an even distribution of lubrication oil on the cylinder liner 2 is achieved. This lubrication system is known in the field as Swirl Injection Principle, SIP.

However, also other principles are envisaged in connection with the improved lubrication system, for example injectors that have jets directed towards the cylinder liner.

Optionally, the cylinder liner 2 is provided with free outs 6 for providing adequate space for the spray 8 or jet from the injector 4.

The injectors 4 receive lubrication oil through a feed conduit 9, typically through a common feed conduit 9, from a lubricant supply 9', for example oil circuit, of the engine including a potential lubricant pump that raises the pressure of the lubricant to an adequate level. For example, the pressure in the feed conduit 9 is in the range of 25 to 100 bars, optionally 30 to 80 bars, which is a typical range of pressure for SIP valves.

The injectors 4 are provided with electrical connectors 10' that are electrically communicating with a controller 11 through electrical cables 10. The controller 11 sends electrical control signals to the injectors 4 for controlling injection of lubricant by the injector 4 through the nozzle 5. As it is illustrated, one cable 10 is provided for each injector 4, which allows individual control of injection by the respective injector. However, it is also possible to provide one electrical cable 10 from the controller 11 to all injectors 4 such that all injectors 4 are injecting simultaneously upon receiving an electrical control signal through one single electrical cable. Alternatively, it is also possible to provide one electrical cable 10 from the controller 11 to a subgroup of injectors, for example a subgroup of 2, 3, 4, 5 or 6 injectors, such that a first subgroup is controlled by the controller through a first cable 10 and a second subgroup is controlled through a second cable 10. The number of cables and subgroups are selective dependent on preferred configurations.

The electrical control signals from the controller 11 to the injectors 4 are provided in precisely timed pulses, synchronised with the piston motion in the cylinder 1 of the engine. For example, for the synchronisation, the controller system 11 comprises a computer 11' or is electronically connected a computer 11', by wires or wireless, where the computer 11' monitors parameters for the actual state and motion of the engine, for example speed, load, and position of the crankshaft, where the latter reveals the position of the pistons in the cylinders.

FIG. 2 illustrates principle sketches of an injector 4. FIG. 2a is an overview sketch with three different views of the exemplified injector, top view, end view and crosssectional side view. FIG. 2b is an enlarged portion of the inlet-valve system. The injector 4 comprises a lubricant inlet port 12 for receiving lubricant from the lubricant feed conduit 9. The inlet port 12 is provided in an inlet-valve housing 21 comprising an inlet-valve system 13 communicating with the inlet port 12 for regulating the amount of lubricant received from the lubricant feed conduit 9 during a lubrication phase. The injector 4 also comprising an outlet-valve system 15 for regulating the lubricant that is dispensed through the nozzle aperture 5'. A rigid flow chamber 16 connects the inlet-valve system 13 with the outlet-valve system 15 for flow of lubricant to the nozzle 5. In the shown embodiment, the flow chamber 16 is provided as a hollow rigid rod. The flow chamber 16 is sealed against the inlet-valve housing 21 of the inlet-valve system 13 by an O-ring 22 and held tightly against the inlet-valve housing 21 by a flange 23 that is bolted by bolts 24 against the inlet-valve housing 21.

An example of an outlet-valve system 15 is shown in greater detail in FIG. 3, the outlet-valve system 15 comprises an outlet non-return outlet-valve 17. In the outlet nonreturn outlet-valve 17, an outlet-valve member 18, exemplified as a ball, is prestressed against an outlet-valve seat 19 by an outlet-valve spring 20. Upon provision of pressurised lubricant in the flow chamber 16, the pre-stressed forced of the outletvalve spring 20 is counteracted by the lubricant pressure, and when the pressure gets higher than the spring force, the outlet-valve member 18 is displaced from its outletvalve seat 19, and the outlet non-return outlet-valve 17 opens for injection of lubricant through the nozzle aperture 5' into the cylinder 1. As exemplified, the outlet-valve spring 20 acts on the outlet-valve member 18 in a direction away from the nozzle aperture 5'. However, the configuration could be different with respect to the direction of the force of the outlet-valve spring 20 on the outlet-valve member 18 relatively to the nozzle aperture 5', as long as the outlet non-return valve 17 is closing for the supply of lubricant to the nozzle aperture 5' when in an idle state. The closing of the nonreturn outlet-valve 17 in an idle state prevents unintended flow of lubricant from the flow chamber 16 through the nozzle aperture 5' into the cylinder 1 between injection phases.

FIG. 2b illustrates the inlet-valve system 13 in greater detail. Inside the inlet-valve housing 21, a non-return inlet-valve 25 is provided with an inlet-valve member 26 that is pre-stressed against an inlet-valve seat 27 by an inlet-valve spring 28. The inletvalve member 26 is exemplified as a ball, however, a different shape, for example oval, conical, plane, or cylindrical, would also work. When the inlet-valve member 26 is displaced from the inlet-valve seat 27 against the force of the inlet-valve spring 28, lubricant flows from the inlet port 12 along the inlet-valve spring 28, passes the inletvalve member 26 and the inlet-valve seat 27, and enters a channel 29 on an opposite side of the inlet-valve member 26. From the channel 29, the lubricant flows through passage 30 and enters the hollow part 16' of the flow chamber 16, for flow to the outlet-valve system 17, which is shown on FIG. 3.

In order to displace the inlet-valve member 26 (ball), a push-member 31, exemplified as a push-rod, is provided reciprocal in the channel 29. The push-member 31 is not fastened to the inlet-valve member 26 but is fastened to a reciprocal solenoid-plunger 33 that is driven by a solenoid coil 32. The solenoid-plunger 33 is retracted by a plunger spring 34 when in idle condition. When the solenoid coil 32 is excited by electrical current, the solenoid-plunger 33 is moved forward against the force of the plunger spring 34 until it comes to a halt against a plunger stop 35. Due to the movement of the solenoid-plunger 33, the push-member (push-rod) 31 pushes the inletvalve member (ball) 26 away from the inlet-valve seat 27, allowing lubricant to flow through the inlet non-return valve 25 and into the flow chamber 16.

In advantageous embodiments, the push-member (push-rod) 31 is withdrawn a distance from the inlet-valve member (ball) 26 when in idle state, such that there is a free range distance in between the push-member 31 and the inlet-valve member 26. When the solenoid coil 32 is excited, the push-member 31 is accelerated by the solenoid coil 32 over the free range distance before it impacts the inlet-valve member 26 after initial acceleration. This results in the inlet-valve member 26 being displaced abruptly from the inlet-valve seat 27, as compared to a situation where the inlet-valve member 26 moves together with push-member 31 during the first part of the acceleration. The quick displacement of the inlet-valve member 26, in turn, is advantageous for a precise timing of the start of the lubricant injection into the cylinder 1. Optionally, the free range distance is adjustable by an adjustment screw 36 at the end of the solenoidplunger 33

After the injection phase, the lubricant supply from the inlet port 12 to the nozzle 5 is stopped by cutting the current to the solenoid coil 32, which results in the solenoidplunger 33 being pushed back by the plunger spring 34, and the inlet-valve member 26 returns to the tight inlet-valve seat 27 for an idle phase in the injection cycle.

FIG. 4 illustrates a second, alternative embodiment of an outlet-valve system 15. The generalised principle of the outlet-valve system 15 is similar to the one disclosed in WO2014/048438. This reference also provides additional technical details as well as explanations to the functioning of the injector presented here, which are not repeated here, for convenience. A nozzle aperture 5' is provided in the nozzle 5 tip for ejection of lubrication oil. Inside a cavity 40 of the nozzle 5, an outlet-valve member 18 is provided, the outlet-valve member 18 comprising a stem 41 and a cylindrical sealing head 42 which is arranged slidingly in a cylindrical cavity part 43 at the nozzle tip 44. The position of the valve member 18 is pre-stressed backwards away from the nozzle tip 44 by a spring 45 and is offset forwards by oil pressure acting through a channel 46 upon the back part 47 of the stem 41, the oil pressure acting against the spring force. The nozzle aperture 5' is sealingly covered by the sealing head 42 which abuts the cylindrical cavity part 43 at the nozzle tip 44, unless the valve member 18 is pushed forward such that the sealing head 43 slides pass and away from the nozzle aperture 5' to allow lubricant oil to flow from the inner cavity 46 through the nozzle aperture 5' for ejection.

FIG. 5 illustrates an alternative inlet-valve system 13, where the push-member 31 and the solenoid-plunger 33 are combined into a single rod. The direction of movement of the push member 31 and the solenoid-plunger 33 in the solenoid coil 32 is parallel to the flow chamber 16. As compared to the embodiment in FIG. 2b, the direction of the movement of the push member 31 is rotated 90 degrees. This results in an even more compact configuration than in FIG. 2b, despite an analogous principle for the functioning. Accordingly, the explanation given in connection with FIG. 2b applies equally well in the inlet-valve system 13 of FIG. 4 with respect to the motion of the pushmember 31 and the inlet-valve member and the flow of the lubricant from the inlet port 12 to and along the push member 31 in the channel 29 and through the passage 30 to the hollow part 16' of the flow chamber 16.

Numbering cylinder cylinder liner cylinder wall oil injector nozzle

5' nozzle aperture free cut in liner atomised spray from a single injector 4 swirling spray lubricant feed conduit

9' lubricant supply electrical signal cable

10' electrical connection between electrical signal cable 10 and solenoid in injector 4 controller

11' computer lubricant inlet port of injector 4 inlet-valve system of injector 4 swirl in cylinder outlet-valve system of injector 4 flow chamber connecting inlet-valve system 13 with outlet-valve system 15

16' to hollow part of flow chamber 16 outlet non-return valve, exemplified as outlet ball valve outlet-valve member outlet-valve seat outlet-valve spring inlet-valve housing of inlet-valve system 15

O-ring at end of flow chamber 16 flange for holding flow chamber bolts for holding flange 23 and flow chamber 16 against inlet-valve housing 21 inlet non-return valve, exemplified as inlet ball valve inlet-valve member, exemplified as ball inlet-valve seat inlet-valve spring channel in inlet-valve system passage from channel 29 to hollow part 16' of flow chamber 16 push-member fastened to solenoid-plunger 33, push-member exemplified as rod solenoid coil solenoid-plunger in solenoid coil 31 plunger spring plunger stop

36 adjustment screw for adjustment of the free range distance cavity stem cylindrical sealing head cylindrical cavity part

44 nozzle tip spring channel back part 47 of the stem 41

Claims

A large slow-running two-stroke engine comprising a cylinder (1) with a reciprocating piston inside and with a plurality of injectors (4) distributed along a circumference of the cylinder (1) for injecting lubricant into the cylinder (1) at different positions on the perimeter; wherein the motor further comprises a controller (11) for controlling the amount and timing of the lubricant injection by means of at least one of the injectors (4), each injector (4) comprising

- a lubricant inlet port (12) for receiving lubricant from a lubricant supply line (9);

a nozzle (5) with a nozzle opening (5 ') extending into the cylinder (1) for injecting lubricant from the inlet port (12) into the cylinder (1);

- an outlet valve system (15) at the nozzle (5) for opening and closing the flow of lubricant to the nozzle opening (5 ') during an injection cycle; wherein the outlet valve system (15) is configured to open for flow of lubricant to the nozzle opening (5 ') in an injection phase by pressure rise above a predetermined limit at the outlet valve system (15) and to close the outlet valve system (15) after the injection phase;

characterized in that each injector comprises an electrically driven inlet valve system (13) electrically connected to the controller (11) and arranged between the lubricant inlet port (12) and the nozzle (5) for regulating the lubricant supplied through the nozzle opening (5 ') at opening or closing for lubricant flow from the lubricant inlet port (12) to the nozzle (5) depending on an electrical control signal received from the controller (11); wherein the inlet valve system (13) is arranged upstream and at a distance from the nozzle (5) and upstream and at a distance from the outlet valve system (15).

An engine according to claim 1, wherein the inlet valve system (13) comprises a one-way inlet valve (25) with an inlet valve element (26) biased against an inlet valve seat (27) by means of an inlet valve spring (28) and arranged for passage of lubricant from the lubricant inlet port (12) to the outlet valve system (15) by displacing the inlet valve member (26) from the inlet valve seat (27) against force from the inlet valve spring (28); wherein the inlet valve system (13) further comprises an electrically driven rigid displacement member (31) for displacing the inlet valve member (26) from the inlet valve seat (27) during lubricant injection.

The motor of claim 2, wherein the displacement member is a pushing member (31) for pushing the inlet valve member (26) away from the inlet valve seat (27) against the force of the inlet valve spring (28) during lubricant injection.

An engine according to claim 3, wherein the pushing element (31) is not attached to the inlet valve element (26); wherein the push member (31) in the rest position is provided at a distance from the inlet valve member (26) and arranged to accelerate against the inlet valve member (26) to achieve velocity prior to impact on the inlet valve member (26) to displace the inlet valve member (26) from the inlet valve seat (26). 27) using the shock.

An engine according to claim 3 or 4, wherein an additional spring (34) is provided for retracting the pushing element (31) to a rest position after a lubricant injection phase.

A motor according to any one of claims 2 to 5, wherein the displacement element (31) is connected to a device of a solenoid piston (33) and a solenoid coil (32) for driving the displacement element (31) by electrically igniting the solenoid coil (32). ).

A motor according to claim 6, wherein the displacement element (31) is a push rod connected to the solenoid piston (33) or a part of the solenoid piston (33) for displacement together with the solenoid piston (33) by igniting the solenoid coil (32); and wherein the push rod has a first end for contact with the inlet valve member (26) for displacing the inlet valve member (26).

A method of lubricating a large slow-running two-stroke engine comprising a cylinder (1) having a reciprocating piston inside and having a plurality of injectors (4) distributed along a circumference of the cylinder (1) for injecting lubricant into the cylinder (1). ) at different positions on the perimeter; wherein the engine further comprises a controller (11) for controlling the amount and timing of the lubricant injection by means of at least one of the injectors (4), each injector (4) comprising

characterized in that each injector (4) comprises an electrically driven inlet valve system (13) electrically connected to the controller (11) and arranged between the lubricant inlet port (12) and the nozzle (5) for regulating the lubricant supplied through the nozzle opening (5). ') by opening or closing lubricant flow from the lubricant inlet port (12) to the nozzle (5) depending on an electrical control signal received from the controller (11); wherein the inlet valve system (13) is arranged upstream and at a distance from the nozzle (5) and upstream and at a distance from the outlet valve system (15);

wherein the method comprises:

sending an electrical control signal from the controller (11) to the electrically driven inlet valve system (13) to start an injection phase and consequently cause flow of lubricant from the lubricant supply line (9) through the lubricant inlet port (12), through the inlet valve system (13) and into a conduit (16 ') flowing connecting the inlet valve system (13) to the outlet valve system (15);

increasing the pressure in the line (16 ') and at the outlet valve system (15) by means of lubricant flow into the line (16');

causing the outlet valve system (15) to open for flow of lubricant from the line (16 ') to the nozzle opening (5') due to the increased pressure and to inject lubricant into the cylinder (1) through the nozzle opening (5 ');

changing the electrical control signal from the controller (11) to the inlet valve system (13) at the end of the injection phase and causing the inlet valve system (13) to close the lubricant supply from the lubricant inlet port (12) to the line (16 ') ·

A method according to claim 8, wherein the inlet valve system (13) comprises a one-way inlet valve (25) with an inlet valve element (26) biased towards an inlet valve seat (27) by means of an inlet valve (28) and arranged for passage of lubricant from the lubricant inlet port (12) to the outlet valve system (15) by displacing the inlet valve member (26) from the inlet valve seat (27) against force from the inlet valve spring (28); wherein the inlet valve system (13) further comprises an electrically driven rigid displacement member (31) for displacing the inlet valve member (26) from the inlet valve seat (27) during lubricant injection;

which method comprises causing the displacement element (31) to move the inlet valve element (26) by means of the control signal and causing lubricant flow from the lubricant supply line (9) through the lubricant inlet port (12) during the injection phase and to retract the displacement element (31) to obtain the inlet valve member to return to the inlet valve seat (27) to close the lubricant supply from the lubricant inlet port (12) to the conduit (16 ') after the injection phase.

The method of claim 9, wherein the displacing member is a pushing member (31) and the method comprises pushing the inlet valve member (26) away from the inlet of the swivel seat (27) by the pushing member (31) against the force of the inlet valve spring (28). during the lubricant injection.

The method of claim 10, wherein the pushing member (31) is not attached to the inlet valve member (26); wherein the pushing element (31) in the rest position is provided at a distance from the inlet valve element (26); and wherein the method comprises causing acceleration of the pushing element (31) towards the inlet valve element (26) by means of the control signal, achieving velocity prior to the impact against the inlet valve element (26) and displacing the inlet valve element (26) from the inlet valve seat (27) by by means of the shock, keeping the inlet valve element offset from the inlet valve seat for a predetermined period of time and subsequently reversing the movement of the pushing element (31) and causing the inlet valve element (26) to return to the inlet valve seat (27).

A method according to any one of claims 8-11, wherein the displacement element (31) is connected to a device of a solenoid piston (33) and a solenoid coil (32), and the method comprises driving the displacement element (31) by means of of the device by electrically igniting the solenoid coil (32).

The method of claim 12, wherein the displacement member (31) is a push rod connected to the solenoid piston (33) or a portion of the solenoid piston (33), and wherein the push rod has a first end for contact with the inlet valve member (26) for displacing the inlet valve member (26). ), the method comprising displacing the push rod together with the solenoid piston (33) by igniting the solenoid coil (32) and pushing the inlet valve member (26) away from the inlet valve seat (27) with the push rod.

An injector for a motor according to any one of claims 1-7 or for a method according to any one of claims 8-13, wherein the injector (4) comprises

- a lubricant inlet port (12) for receiving lubricant from a lubricant outlet line (9);

- a nozzle (5) with a nozzle opening (5 ') for injecting lubricant from the inlet port (12) into a cylinder (1) of an engine;

- an outlet valve system (15) at the nozzle (5) for opening and closing lubricant flow to the nozzle opening (5 ') during an injection cycle; wherein the outlet valve system (15) is configured to open for flow of lubricant to the nozzle opening (5 ') during an injection phase by pressure rise above a predetermined limit at the outlet valve system (15) and for closing the outlet valve system valve system (15) after the injection phase;

an electrically driven inlet valve system (13) disposed between the lubricant inlet port (12) and the nozzle (5) for regulating the lubricant supplied through the nozzle opening (5 ') by opening or closing lubricant flow from the lubricant inlet port (12) to the nozzle (5) depending on an electrical control signal received from a controller (11); wherein the inlet valve system (13) is arranged upstream and at a distance from the nozzle (5) and upstream and at a distance from the outlet valve system (15).

An injector according to claim 14, wherein the inlet valve system (13) comprises a one-way inlet valve (25) with an inlet valve element (26) biased against an inlet valve seat (27) by means of an inlet valve spring (28) and arranged to pass lubricant from the lubricant inlet port (12) to the outlet valve system (15) by displacing the inlet valve member (26) from the inlet valve seat (27) against force from the inlet valve spring (28); wherein the inlet valve system (13) further comprises an electrically driven rigid displacement member (31) for displacing the inlet valve member (26) from the inlet valve seat (27) during lubricant injection.

The motor of claim 15, wherein the displacement member is a push member (31) adapted to push the inlet valve member (26) away from the inlet valve seat (27) against the force of the inlet valve valve spring (28) during lubricant injection.

An injector according to claim 16, wherein the pushing element (31) is not attached to the inlet valve element (26); wherein the resting member (31) in the rest position is provided at a distance from the inlet valve member (26) and adapted to accelerate toward the inlet valve member (26) to achieve velocity prior to impact on the inlet valve member (26) to displace the inlet valve member (26) from the inlet valve seat (26). 27) using the shock.

An injector according to claim 17, wherein the distance from the inlet valve element (26) to the pushing element (31) in the rest position is adjustable.

An injector according to any one of claims 10-14, wherein an additional spring (34) is provided for retracting the pushing element (31) into a rest position after a lubricant injection phase.

An injector according to any one of claims 14-19, wherein the displacement element (31) is connected to a device of a solenoid piston (33) and a solenoid coil (32) for electrically igniting the solenoid coil (32) to drive the displacement element (31). ).

An injector according to claim 20, wherein the displacement element (31) is a push rod connected to the solenoid piston (33) or a part of the solenoid piston (33) for displacement together with the solenoid piston (33) by igniting the solenoid coil (32); and wherein the push rod has a first end for contact with the inlet valve member (26) for displacing the inlet valve member (26).

An injector according to any one of claims 14-21, wherein the lubricant inlet port (12) and the inlet valve system (13) are provided in an inlet valve housing (21) and wherein the outlet valve system (15) is provided in the nozzle (5) and wherein a flow chamber ( 16) is provided in the form of a hollow rigid pipe connecting the inlet valve housing 5 (21) to the nozzle (5); and wherein the injector (4) further comprises a flange (23) for attaching the injector (4) to a wall (2) of the cylinder (1) when the flow chamber extends through the cylinder wall (2) with the nozzle (5) into the cylinder (1) of the engine for injecting lubricant from the inlet port (12) through the flow chamber (16) and the nozzle (5) into the cylinder (1).