DK201670630A1

DK201670630A1 - Cylinder lubrication apparatus for a large two-stroke compression-ignited internal combustion engine

Info

Publication number: DK201670630A1
Application number: DKPA201670630A
Authority: DK
Inventors: Ahmad Abdul Hamid; Michael Holm Maina; Carsten Bredal Andersen
Original assignee: Man Diesel & Turbo Filial Af Man Diesel & Turbo Se Tyskland
Priority date: 2016-08-17
Filing date: 2016-08-17
Publication date: 2017-11-13
Also published as: JP6461251B2; DK179118B1; CN107762655B; KR20180020106A; KR101959852B1; JP2018028315A; CN107762655A

Abstract

A cylinder lubrication device (55) for supplying cylinder lubrication liquid to the inner surface (25) of a cylinder liner (1) of a large two-stroke uniflow compression-ignited internal combustion engine via a plurality of injectors (24) that are distributed around the circumference of the cylinder liner (1). The cylinder liner (1) defines a cylindrical interior in which a reciprocating piston (10) is slidably disposed. The cylinder lubrication device (55) comprises a plurality of piston pumps, each piston pump having a dosing plunger (70) slidably disposed in a dosing cylinder (71), each dosing cylinder (70) comprising a pump chamber (72) fluidically connected to a pump outlet (62) for fluidic connection to one of the injectors (24), a common drive (80) for driving all of the dosing plungers (70) simultaneously, a hydraulic linear actuator (83) operably connected to the common drive (80), and means for adjusting the length of the stroke of the common drive during operation of the cylinder lubrication device (55) to either of at least two predetermined discrete lengths (L1,L2) of stroke during operation of the cylinder lubrication device (55).

Description

CYLINDER LUBRICATION APPARATUS FOR A LARGE TWO-STROKE COMPRESSION-IGNITED INTERNAL COMBUSTION ENGINE

TECHNICAL FIELD

The disclosure relates to a cylinder lubrication apparatus for a large two-stroke uniflow compression-ignited internal combustion engine, in particular to an apparatus for supplying cylinder lubrication liquid to the inner surface of a cylinder liner of a large two-stroke uniflow compression-ignited internal combustion engines .

BACKGROUND

Large two-stroke uniflow turbocharged compression-ignited internal combustion crosshead engines are typically used as propulsion systems for large ships or as prime mover in power plants. The sheer size, weight and power output renders them quite different from common combustion engines and places large two-stroke turbocharged compression-ignited internal combustion engines in a class for themselves.

Large two-stroke compression-ignited internal combustion engines are conventionally operated with a liquid fuel such as e.g. fuel oil or in particular heavy fuel oil due to the low costs of latter type of fuel. Heavy fuel oil introduces large quantities of particles that are harmful to the engine into the cylinders, such as sulfur that forms sulfuric acid in the combustion process. This creates the need to protect the inner surface of the cylinder liners from attack by the sulfuric acid by applying cylinder lubrication liquid, typically an oil, with a low pH value to inner surface of the cylinder liner in order to compensate for the acid (high pH) combustion gas components. The cylinder lubrication liquid (oil) is relatively costly and the cylinder lubrication oil that is applied to the inner surface of the cylinder liner is consumed during engine operation, i.e. a continuous fresh supply of cylinder lubrication liquid is needed during engine operation. The consumption of cylinder lubrication liquid is significant factor in the operation of a large slow running two-stroke uniflow compression-ignited internal combustion engine with crossheads. Consequently, there is a need for efficient and accurate lubrication of the inner surface of the cylinder liners, ensuring proper protection of the latter and minimal consumption of the costly cylinder lubrication oil.

The injection of cylinder lubrication liquid is dosed according to engine load and engine status, as well as the fuel properties. Further, during running in of a new cylinder liner approximately double the amount of lubrication liquid needs to be applied to the inner surface of the cylinder liner .

The cylinder lubrication oil injections are usually timed, such that injections are made regularly relative to the revolutions of the engine. The injection of the lubrication liquid takes place either before or when the engine piston passes the injection quills (injectors) during the compression stroke. The injectors are distributed evenly around the circumference of the cylinder liner.

One type of apparatus for supplying cylinder lubrication liquid has a plurality of dosing plungers that are moved by a common drive by a linear actuator. When the linear actuator is activated the dosing plungers make a full stroke and each dosing plunger pumps out a fixed predetermined amount of cylinder lubrication oil to the respective injectors in a cylinder liner. Typically, the common drive that connects the dosing plungers to the linear actuator makes a return stroke by the action of the helical spring or other biasing means. In this type of cylinder lubrication apparatus the dosing plungers can only make the full stroke, and adjustment of the feed rate of cylinder lubrication liquid to the inner surface of the cylinder liner is achieved by changing the number of engine revolutions between cylinder lubrication injection events. The highest feed rate is obtained by activating the linear actuator for each engine revolution.

The feed rate needs to be approximately doubled when running in a new cylinder liner. Thus, a cylinder lubrication device to be able to handle a feed rate that ranges from the low feed rate required at low engine loads for a cylinder liner that has been run in to the doubled high feed rate at maximum engine load for a new cylinder liner.

Lower feed rates are obtained by skipping the injection event for one or more engine revolutions. Especially, for lower engine loads there can be a relatively high number of dry engine revolutions where no cylinder lubrication liquid injection event takes place. However, ideally, an injection event should take place for each engine revolution since experience has shown that dry engine revolutions between cylinder lubrication liquid injections are detrimental to the protection of the inner surface of the cylinder liner.

Another type of apparatus for supplying cylinder lubrication liquid is provided with a linear actuator that can make a part stroke of any desired and controllable length. With this cylinder lubrication device injection event will typically take place for each engine revolution with the amount delivered being exactly adjusted to the current needs of the engine by adjusting the length of the stroke of the linear actuator and thereby the length of the stroke of the dosing plungers. This type of apparatus for supplying cylinder lubrication liquid is capable of providing the exactly required rate of cylinder lubrication liquid under all engine operating conditions. However, this type of apparatus for supplying cylinder lubrication liquid is significantly more expensive than the above described cylinder lubrication device with a fixed length of the pump stroke.

Consequently, it is an object of the present invention to provide an apparatus for supplying cylinder lubrication liquid that is both inexpensive and capable of adjusting the feed rate with a reduced need for engine revolution events without a cylinder injection event.

SUMMARY

It is an object of the invention to provide a cylinder lubrication device that overcomes or at least reduces the problems indicated above.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures .

According to a first aspect there is provided a cylinder lubrication device for supplying cylinder lubrication liquid to the inner surface of a cylinder liner of a large two-stroke uniflow compression-ignited internal combustion engine via a plurality of injectors that are distributed around the circumference of the cylinder liner, the cylinder liner defining a cylindrical interior in which a reciprocating piston is slidably disposed, the cylinder lubrication device comprising: a plurality of piston pumps, each piston pump having a dosing plunger slidably disposed in a dosing cylinder, each dosing cylinder comprising a pump chamber fluidically connected to a pump outlet for fluidic connection to one of the injectors, a common drive for driving all of the dosing plungers simultaneously, a hydraulic linear actuator operably connected to the common drive, and means for adjusting the length of the stroke of the common drive during operation of the cylinder lubrication device to either of at least two predetermined discrete lengths of stroke during operation of the cylinder lubrication device.

By providing a cylinder lubrication device with means for adjusting the length of the stroke of the common drive it becomes possible to deliver an adjustable amount of cylinder lubrication liquid with a relatively simple and inexpensive apparatus .

According to a first possible implementation of the first aspect the cylinder lubrication device comprises a first fixed mechanical end stop determining a first extended position of the common drive.

According to a second possible implementation of the first aspect the device further comprises a second fixed mechanical end stop determining a retracted position of the common drive.

According to a third possible implementation of the first aspect the hydraulic linear actuator is a single acting hydraulic linear actuator and wherein the common drive is resiliently biased towards a retracted position.

According to a fourth possible implementation of the first aspect the hydraulic linear actuator is a double acting hydraulic linear actuator.

According to a fifth possible implementation of the first aspect the hydraulic linear actuator comprises a drive piston slidably disposed in a hydraulic cylinder, with an actuation chamber between the piston and the hydraulic cylinder, a first port disposed at or near a longitudinal end of the hydraulic cylinder, and a second port disposed at a position along the length of the cylinder at a distance from the longitudinal end of the hydraulic cylinder, the second port being connected to a first hydraulic valve.

By providing the second port at a position along the length of the cylinder at a distance from the longitudinal end of the cylinder where the first port is located in by controlling the opening of the second, port with a valve the maximum stroke of the common drive can be limited to the position where the drive piston passes the second port by opening the first hydraulic valve.

According to a sixth possible implementation of the first aspect the drive piston is provided with a conduit that opens to the actuation chamber and to the cylindrical outer surface of the drive piston.

According to a seventh possible implementation of the first aspect the first hydraulic valve is an electronically controlled valve, the first electronically controlled valve preferably being configured to connect to a source of hydraulic pressure or to tank, preferably in response to a control signal.

According to an eighth possible implementation of the first aspect the first port is selectively connected to a source of pressure or to tank.

According to a ninth possible implementation of the first aspect the apparatus further comprises a second hydraulic valve for selectively connecting the first port to a source of pressure or to tank.

According to a tenth possible implementation of the first aspect the second hydraulic valve is electronically controlled valve configured to connect the first port to the source of pressure or to tank in response to a control signal.

According to an eleventh possible implementation of the first aspect the distance between the end of the cylinder and the second port is less than the distance between the second fixed mechanical end stop and the first fixed mechanical end stop.

According to a twelfth possible implementation of the first aspect a pump stroke with a shorter one of the at least two discrete stroke lengths of the common drive is selected when the first hydraulic valve is open and wherein a pump stroke with a longer one of the at least two discrete stroke lengths of the common drive is selected when the first hydraulic valve is closed.

According to a thirteenth possible implementation of the first aspect the apparatus further comprises a controller configured to issue a control signal to the first hydraulic control valve to connect to a hydraulic source or to tank in response to instructions from a human operator or in response to an engine operating parameter.

According to a fourteenth possible implementation of the first aspect the apparatus further comprises a movable mechanical end stop, the movable mechanical end stop having at least two positions, a first position in which the movable mechanical end stop forms an end stop for the common drive at a first extended position of the common drive, and a second position in which the movable mechanical end stop forms an end stop for the common drive at a second extended position of the common drive that is different from the first extended position of the common drive.

According to a fifteenth possible and implementation of the first aspect the apparatus further comprises a second fixed mechanical end stop determines a retracted position of the common drive.

According to a sixteenth possible implementation of the first aspect the movable mechanical end stop is operably connected to an end stop actuator, the end stop actuator being configured to move the movable mechanical end stop between the first position and the second position.

According to a seventeenth possible implementation of the first aspect, the end stop actuator being in receipt of a control signal and the end stop actuator being configured to move the mechanical end stop from the first position to the second position or from the second position to the first position upon receipt of the control signal.

According to an eighteenth possible implementation of the first aspect the movable end stop comprises a rod slidably disposed in a bore, the movable end stop being configured to secure the rod in a first position or in a second position.

According to a nineteenth possible implementation of the first aspect the first longitudinal end of the rod forms an end stop abutment surface for abutting with a common drive abutment surface of the common drive.

According to a twentieth possible implementation of the first aspect the rod is secured in the first position by a third fixed mechanical end stop, and wherein the rod is secured in the second position by a movable bolt.

According to a twenty-first possible implementation of the first aspect the bolt is slidably disposed in a guide passage, the bolt being operably connected to an end stop actuator configured to move the bolt between a retracted position where the bolt does not protrude from the guide passage and an extended position where the bolt protrudes from the guide passage .

According to a twenty-second possible implementation of the first aspect the bolt is disposed between the third fixed mechanical end stop and the rod when the bolt is in its extended position.

According to a twenty-third possible implementation of the first aspect the guide passage is arranged substantially traverse to the axis of the rod.

According to a twenty-fourth possible implementation of the first aspect the bolt is provided with a slanting tip.

According to a twenty-fifth possible implementation of the first aspect a second longitudinal end of the rod opposite to the first longitudinal end is provided with a slanting portion .

According to a twenty-sixth possible implementation of the first aspect the rod is resiliently biased towards its first position.

According to a twenty-seventh possible implementation of the first aspect the end stop actuator is a linear actuator, preferably a single acting linear actuator but the bolt being resiliently biased towards its retracted position.

According to a twenty-eighth possible implementation the end stop actuator is a linear pneumatic actuator, a linear hydraulic actuator or a linear electric actuator.

According to a twenty-ninth possible implementation of the first aspect the maximum stroke of the common drive between the second fixed mechanical end stop and the movable end stop is larger when the movable end stop is in the first position than when the movable end stop is in the second position.

These and other aspects of the invention will be apparent from the embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, the invention will be explained in more detail with reference to the example embodiments shown in the drawings, in which:

Fig. 1 is an elevated front view of a large two-stroke diesel engine according to an example embodiment,

Fig. 2 is an elevated side view of the large two-stroke engine of Fig. 1,

Fig. 3 is a diagrammatic representation the large two-stroke engine according to Fig. 1,

Fig. 4 is a longitudinal-sectional view through a cylinder liner and cylinder frame of the engine of Figs. 1 to 3,

Fig. 5 is a side view of the cylinder liner of Fig. 4,

Fig. 6 is a cross-sectional view of the cylinder liner of Fig. 4,

Fig. 7 is an elevated view of an apparatus for providing cylinder lubrication liquid according to an example embodiment,

Fig. 8 is a top view of the apparatus of Fig. 7,

Fig. 9 is a longitudinal-sectional view of the apparatus of

Fig. 7,

Fig. 10 is another longitudinal-sectional view of the apparatus of Fig. 7,

Fig. 11 is an enlarged detail of a section of Fig. 9,

Fig. 12 is a longitudinal-sectional view of another example embodiment of an apparatus for providing cylinder lubrication liquid,

Fig. 13 is another longitudinal-sectional view of the apparatus of Fig. 12,

Fig. 14 is an enlarged elevated view of a bolt of the apparatus of Fig. 12,

Fig. 15 is a diagrammatic representation of the device of Fig. 12, and

Fig. 16 is a diagrammatic representation of yet another example embodiment of an apparatus for providing cylinder lubrication liquid.

DETAILED DESCRIPTION

In the following detailed description, an apparatus for providing cylinder lubrication liquid to the inner surface of the cylinder liners of an internal combustion engine will be described with reference to an cylinder lubrication apparatus and to a large two-stroke low-speed turbocharged compression-ignited internal combustion engine with crossheads in the example embodiments .

Figs. 1, 2 and 3 show a large low-speed turbocharged two-stroke diesel engine with a crankshaft 8 and crossheads 9. Fig. 3 shows a diagrammatic representation of a large low-speed turbocharged two-stroke diesel engine with its intake and exhaust systems. In this example embodiment the engine has six cylinders in line. Large low-speed turbocharged two-stroke diesel engines have typically between four and fourteen cylinders in line, carried by a cylinder frame 23 that is carried by an engine frame 11. The engine may e.g. be used as the main engine in a marine vessel or as a stationary engine for operating a generator in a power station. The total output of the engine may, for example, range from 1,000 to 110,000 kW.

The engine is in this example embodiment a compression-ignited engine of the two-stroke uniflow type with scavenge ports 18 at the lower region of the cylinder liners 1 and a central exhaust valve 4 at the top of the cylinder liners 1. The scavenge air is passed from the scavenge air receiver 2 to the scavenge ports 18 of the individual cylinders 1. A piston 10 in the cylinder liner 1 compresses the scavenge air, fuel is injected through fuel valves 50 in the cylinder cover 22, combustion follows and exhaust gas is generated.

When an exhaust valve 4 is opened, the exhaust gas flows through an exhaust duct associated with the cylinder 1 into the exhaust gas receiver 3 and onwards through a first exhaust conduit 19 to a turbine 6 of the turbocharger 5, from which the exhaust gas flows away through a second exhaust conduit via an economizer 20 to an outlet 21 and into the atmosphere. Through a shaft, the turbine 6 drives a compressor 7 supplied with fresh air via an air inlet 12. The compressor 7 delivers pressurized scavenge air to a scavenge air conduit 13 leading to the scavenge air receiver 2. The scavenge air in the scavenge air conduit 13 passes an intercooler 14 for cooling the scavenge air.

The cooled scavenge air passes via an auxiliary blower 16 driven by an electric motor 17 that pressurizes the scavenge air flow when the compressor 7 of the turbocharger 5 does not deliver sufficient pressure for the scavenge air receiver 2, i.e. in low or partial load conditions of the engine. At higher engine loads the turbocharger compressor 7 delivers sufficient compressed scavenge air and then the auxiliary blower 16 is bypassed via a non-return valve 15.

Figs. 4,5 and 6 show a single cylinder liner 1 in longitudinal sectional, side and top view, respectively. A cylinder cover 22 is clamped down on the upper longitudinal end of the cylinder liner 1 by cylinder cover studs 43 that are tightened by hydraulically tightened nuts 44. The lower ends of the cylinder cover studs 43 are anchored in the cylinder frame 23.The cylinder cover 22 is provided with a central opening 46 for the exhaust valve. The cylinder liner 1 is provided near its lower longitudinal and with an array of scavenge ports 18. The cylinder liner 1 is carried by the cylinder frame 23, with a shoulder of the cylinder liner 1 resting on the upper surface of the cylinder frame 23.

The inner surface 25 of the cylinder liner 1 is generally smooth except for relatively small recesses in which the nozzles of the injectors 24 for injecting cylinder lubrication liquid are received. The injectors 24 are arranged at substantially identical height and equally distributed around the circumference of the cylinder liner 1.

The injectors 24 are inserted into the wall of the cylinder liner 1 and extend from the outer side of the cylinder liner 1 into the cylinder liner 1 with the nozzle at the tip of the injector 24 received in the aforementioned small recesses in the inner surface 25. The injectors 24 serve to inject the cylinder lubrication liquid onto the inner surface 25 of the cylinder liner 1. Various techniques are used to ensure that the injected cylinder lubrication liquid ends up on the inner surface 25. Some techniques spray the injected cylinder lubrication liquid directly from the nozzle holes onto the inner surface 25 before the piston 10 reaches the height at which the injectors 24 are arranged during the compression stroke. Another technique injects the cylinder lubrication liquid exactly at the moment where the piston 10 is at the height of the injectors 24 during the compression stroke so that the cylinder lubrication liquid is injected between the piston rings of the piston 10. Any type of technique that ensures that the cylinder lubrication liquid arrives at the inner surface of the cylinder liner 25 can be used with the present invention.

The injectors 24 are connected via respective supply conduits 41 to an apparatus for supplying cylinder lubrication liquid 55.

Figs. 7, 8, 9, 10, and 11 show a first example embodiment of an apparatus 55 for providing cylinder lubrication liquid to the inner surface 25, in elevated, top, longitudinal-sectional and enlarged views, respectively. The cylinder lubrication apparatus 55 comprises a housing 60 that is in the present embodiment assembled from several components, but could be formed from a single component.

The cylinder lubrication apparatus 55 includes a pump that comprises a plurality of positive displacement pumps that are formed by a plurality of dosing plungers 70 slidably disposed in corresponding dosing cylinders 72. The cylinder lubrication apparatus 55 also includes a linear actuator that is configured to move all dosing plungers 70 simultaneously during pump- and suction strokes. The linear actuator is operably connected to all of the dosing plungers 70 via a common drive 80.

The linear actuator is in the shown embodiment a linear hydraulic actuator 83 that comprises a drive piston 82 received in a matching cylinder disposed in the housing 60. The drive piston 82 defining a drive chamber 81 in the housing 60 together with the matching cylinder. However, it is understood that the hydraulic actuator 83 could also be a completely separate component with its own housing.

The drive piston 82 is operably connected to the common drive 80. In the present embodiment the drive piston and the common drive 80 are a single integral component. However, it is understood that the common drive 80 and the drive piston 82 merely needs to be operably connected and can therefore be separate components . A helical spring 75 is disposed in a spring chamber 73. The helical spring 75 serves to bias the common drive 80 resiliently towards the position where the dosing plungers 70 are fully retracted i.e. to make the suction stroke. The common drive 80 is partially disposed in the spring chamber 73.

In the present embodiment the linear actuator is a single acting linear hydraulic actuator 83 that is configured to power the pump stroke for the dosing plungers 7 0 via the common drive 80, whilst the return (suction) stroke of the dosing plungers 70 is powered by the helical wire spring 75. The helical wire spring 75 can be replaced by any other suitable resilient means for resiliently biasing the common drive 80 towards the retracted position of the dosing plungers 70. Alternatively, the linear actuator can be a double acting linear actuator that powers both the pump stroke and the suction stroke of the dosing plungers 70. A pump chamber is formed in each dosing cylinder 72. Each pump chamber is connected via a non-return valve 62 to a cylinder lubrication inlet chamber 65. The cylinder lubrication liquid in the chamber 65 is connected to a source of cylinder lubrication liquid (not shown) via a cylinder lubrication inlet port 61. When the dosing plungers 70 simultaneously retract during the suction stroke the pump chambers are refilled with cylinder lubrication liquid from the source of cylinder lubrication liquid via the cylinder lubrication liquid inlet port 61, the cylinder lubrication liquid inlet chamber 65 and the respective non-return valve 62. Each pump chamber is connected to an outlet port 62 via a passage 77. Each outlet port 62 is connected to an injector 24 via a supply conduit 41. The volume of the pump chambers is the smallest when the dosing plungers 70 are extended most into the dosing cylinders and the volume of the pump chambers is largest when the dosing plungers 70 are retracted most from the dosing cylinders.

When the dosing plungers 70 simultaneously move into the dosing cylinders during a pump stroke the cylinder lubrication liquid in the pump chambers is forced out of the pump chambers via respective passages 77, respective outlet ports 62, respective supply conduits 41 to respective injectors 24, i.e. each dosing plunger is in an embodiment connected to a single injector 24.

The hydraulic linear actuator 83 comprises a drive piston 82 slidably disposed in the matching cylinder, with the drive chamber 81 between the drive piston 82 and the matching cylinder. A first port 84 is disposed at or near a longitudinal end of the matching cylinder, and a second port 86 is disposed at a position along the length of the matching cylinder at a distance from the longitudinal end of the matching cylinder. The second port 86 is in an embodiment in the form of a ring chamber or annular groove.

As best shown in the enlarged section C, the longitudinal end of the drive piston 82 facing the actuation chamber 81 is provided with a conduit connecting the actuation chamber 81 to the circumferential outer surface of the drive piston 82. This conduit is formed in the present embodiment by a longitudinal channel 89 that opens to the drive chamber 81 and connects to one or more radial channels 88 that open to the cylindrical outer surface of the drive piston 82.

The first port 84 is connected via a passage 85 to a second hydraulic valve 59. The second hydraulic valve 59 selectively connects the first port 84 to a source of pressure or to tank. When the second hydraulic valve 59 connects the first port 84 to the source of pressure the actuation chamber 81 is pressurized and the drive piston 82 applies a force in the direction of the pump stroke to the common drive 80 and thereby to the dosing plungers 70 for making a pump stroke. The pump stroke is mechanically limited by a first mechanical end stop that is in this example embodiment formed by a first abutment surface 36 of the common drive abutting with a second abutment surface 37 of the housing 60. Thus, the first mechanical end stop determines the maximum extended position of the dosing plungers 70.

When the second hydraulic valve 59 connects the first port 84 to tank the drive piston 82 does not apply any significant force to the common drive 80 and thus the helical spring 70 urges the dosing plungers 70 back to their retracted position thereby making a suction stroke. The helical spring 7q will move the common drive 80 in the direction of the suction stroke until a third abutment surface 38 of the common drive 80 abuts with a fourth surface 35 of the housing 60, thereby forming an a second fixed mechanical end stop for the most retracted position of the dosing plungers 70.

The second port 86 is connected to tank via a bleed conduit 87 and a first hydraulic valve 58. When the first hydraulic valve 58 is in a first position it connects the second port 86 to tank via bleed conduit 87. When the fist hydraulic valve 58 is in a second position during the pump stroke it connects the drive chamber 81 to tank once the radial channels 88 in the actuation piston 82 have reached the second port 86, i.e. the radial channels 88 are facing the second port 86, thereby depressurizing the drive chamber 81 and terminating the pump stroke. Thus, the second port 86 forms part of an hydraulic end stop that limits the pump stroke to a short length LI by connecting the actuation chamber 81 to tank when the short stroke lengths LI has been achieved.

When the first hydraulic valve 58 is connected to the source of hydraulic pressure during the pump stroke the actuation piston 82 makes a full stroke with length L2, i.e. the pump stroke continues until the abutment surface 36 of the common drive abuts with the second abutment surface 37 of the housing 60 (first fixed mechanical end stop) .

The length of the full stroke L2 is larger than the length of the of the short stroke LI. The distance between the longitudinal end of the matching cylinder where the first port 84 is located, the position of the second port 86 determined together with the position of the radial channels 88 the length of the short stroke Ll. It is understood that the conduit formed by the axial passage 89 and the radial passages 88 is dispensable. However, without this conduit the second port 86 will need to be placed closer to the first port 84 to obtain the same short stroke length Ll. A pump stroke is initiated by moving the second hydraulic valve 59 to the position where it connects to the source of hydraulic pressure and the pump stroke is terminated by moving the second hydraulic valve 59 to the position where it connects to tank. The length of the pump stroke is determined by the position of the first hydraulic valve 58. The long pump stroke with the length L2 is obtained when the first hydraulic valve 58 is connected to the source of hydraulic pressure and the short pump stroke with the lengths Ll is obtained when the first hydraulic valve 58 is connected to tank. In an embodiment the first hydraulic valve 58 is an electronically controlled valve, such as a solenoid valve, that is in receipt of a control signal. In an embodiment the second hydraulic valve 59 is an electronically controlled valve, such as a solenoid valve, that is in receipt of a control signal.

In another embodiment (not shown) the first control valve 58 is a simple valve that can only be open or closed, with the valve in the open position connecting the second port 86 to tank. In this embodiment the short stroke lengths Ll is obtained by the first hydraulic valve 85 being open and the long stroke length L2 is obtained by the first hydraulic valve 85 being closed.

Figs. 12, 13, 14 and 15 show another example embodiment of the apparatus 55 for supplying cylinder lubrication liquid, in longitudinal sectional views, detailed view and diagrammatic view, respectively. The cylinder lubrication apparatus 55 of the embodiment of Figs. 12 to 15 is largely identical to the cylinder lubrication apparatus 55 the embodiment of Figs. 7 to 11, with identical reference numerals referring to identical features, however, with the following differences .

The linear actuator 83 is neither provided with a second port nor with a bleed channel. The drive piston 81 is not provided with a conduit connecting the actuation chamber 81 to the cylindrical outer surface of the drive piston 81 and there is no first hydraulic valve.

The second hydraulic valve 59 selectively connects the drive chamber 81 to the source of hydraulic pressure or to tank. Without the second bore 86, the length of the stroke of the dosing plungers 70 cannot be limited to a shorter length LI by depressurizing the actuation chamber 81. Instead, the length LI of the short stroke is in the present example embodiment limited by a movable mechanical end stop. The movable mechanical end stop has at least two positions. Fig. 12 shows the position of the movable mechanical end stop that results in a short stroke with length LI whilst Fig. 13 shows the position of the movable mechanical end stop that will result in the long stroke with length L2.

The movement of the dosing plungers 7 0 in the direction of the suction stroke is limited by the second fixed mechanical end stop formed by the third abutment surface 38 of the common drive 80 abutting with a fourth abutment surface 35 of the housing 60, thereby forming the second fixed mechanical end stop for the most retracted position of the dosing plungers 70. This retracted position of the dosing plungers 70 and the common drive 80 shown in Figs. 12 and 13.

The movable mechanical end stop comprises an end stop actuator operably connected to the movable mechanical end stop.

The end stop actuator is configured to move the movable mechanical end stop between a first position and a second position .

The end stop actuator is in receipt of a control signal from an electronic control unit 100 and the end stop actuator is configured to move the mechanical end stop from the first position to the second position or from the second position to the first position upon receipt of the control signal from the electronic control unit 100. Alternatively, the position of the mechanical end stop is simply controlled by the human operator using a control button that sends a signal to the end stop actuator.

The movable end stop comprises a rod 94 slidably disposed in a matching bore. The rod 94 can be retained in the first position or in the second position by the end stop actuator.

The first longitudinal end of the rod 94 forms the second abutment surface 37 for abutting with the first abutment surface 36 of the common drive 80.

The rod 94 is secured in its first position by a third fixed mechanical end stop, and the rod 94 is secured in its second position by a bolt 90.

The third fixed mechanical end stop is formed by plug 93. The plug 93 is secured in a bore in the housing 60. The plug 93 can be in the form of a screw in threaded engagement with a threaded bore in the housing 60 and the position of the plug 93 is in this case adjusted by rotation of the plug 93. The plug 93 is disposed on the same axis as the common drive 80 and provided with an axially facing fifth abutment surface 28. The rod 94 is provided on the longitudinal and that faces the plug 93 with an axially facing sixth abutment surface 29. When the bolt 90 is in the position shown in Fig. 13 the rod 94 can move all the way in the direction of the pump stroke until the sixth abutment surface 29 of the rod 94 abuts with the fifth abutment surface 28 of the plug 93. This is the first position of the mechanical end stop that allows the pump stroke with the longer length L2. In this position the bolt 90 is in its retracted position where it does not extend between the bolt 94 and the plug 93.

The bolt 90 is slidably disposed in a guide passage that is substantially at a right angle to the axis of the rod 94. The bolt 93 is operably connected to the end stop actuator that is configured to move the bolt 93 between a retracted position shown in Fig. 13 where the bolt 93 does not protrude from the guide passage and an extended position where the bolt protrudes from the guide passage between the rod 94 and the plug 93, thereby forcing the rod 94 in its second position.

This is the second position of the mechanical end stop that provides the pump stroke with the shorter length LI.

In the present embodiment the bolt 93 is provided with a slanting tip 97 and the second longitudinal end of the rod 94 opposite to the first longitudinal end is provided with a slanting portion 33. When the and stop actuator moves the bolt 93 from the retracted position to the extended position the slanting tip 97 engages the slanting portion 33 and thereby creates a force with an axial component on the rod 94, thereby forcing the rod 94 to its second position, shown in Fig. 15 by interrupted lines. In its second position the second abutment surface 37 is closer to the second fixed mechanical end stop and thus the pump stroke has the shorter length LI when the 90 is in its extended position where it forces the rod 94 in its second position.

In embodiment the rod 94 is resiliently biased towards its first position.

When the bolt 90 is in its retracted position the rod is in its first position and the pump stroke has the longer length L2 .

The end stop actuator is a linear actuator operably connected to the bolt 90. The end stop actuator is in an embodiment a single acting linear actuator with the bolt 90 resiliently biased to its retracted position. In the present embodiment end stop actuator is a linear pneumatic actuator, but it is understood that the end stop actuator could just as well be a linear hydraulic actuator, a linear electric actuator or a manual actuator.

The linear pneumatic actuator comprises a pneumatic cylinder 95 with the longitudinal end of the bolt 90 opposite to the slanting tip 97 being provided with a head 91 that acts as a piston that is slidably and sealingly disposed in the pneumatic cylinder 95. The pneumatic cylinder 95 is connected to a pneumatic valve 99 via a pneumatic conduit 96. The pneumatic valve 99 is in an embodiment a solenoid valve connected to an electronic control unit 100. The pneumatic valve 99 is configured to connect the pneumatic conduit 96 to a source of pneumatic pressure or to atmosphere.

When the electronic control unit 100 issues a signal to select the shorter stroke of the dosing plungers 70 with the length L2 the pneumatic valve 99 connects the pneumatic conduit 96 to the source of pneumatic pressure. The resulting pressure acting on the head 91 forces the bolt 90 to its extended position shown in Fig. 12, thereby forcing the rod 94 to its second position. When the electronic control unit 100 issues a signal to select the longer stroke of the dosing plungers 70 with the length LI the pneumatic valve 99 connects the pneumatic conduit 96 to atmosphere. The resulting lack of pressure acting combined with the resilient bias on the bolt 90 forces the bolt 90 to its retracted position shown in Fig. 13, thereby allowing the rod 94 to move to its first position.

Fig. 16 is a diagrammatic view of a third embodiment of the apparatus 55 for providing cylinder lubrication liguid to the inner surface 25 of the cylinder liner. The apparatus 55 according to this embodiment is essentially identical to the apparatus 55 of the embodiment of Figs. 12 to 15, except that the bolt 90 has been replaced by a hydraulic wedge, and the pneumatic valve has been replaced by a third hydraulic valve 99' . In this embodiment a portion of the rod 94 acts as a piston in the bore in which the rod 94 is received. Thus, a hydraulic pressure chamber 30 is formed between the rod 94 and the plug 93. The hydraulic pressure chamber 30 is connected to the third hydraulic valve 99' via a hydraulic conduit 96'. The third hydraulic valve 99 is in an embodiment an electronic control valve connected to an electronic control unit 100. The electronic control valve 99' is configured to connect the hydraulic conduit 96' to a source of hydraulic pressure or to tank upon receiving respective instructions from the electronic control unit 100. When the third hydraulic valve 99' connects the hydraulic conduit 96' to the source of hydraulic pressure the pressure in the hydraulic pressure chamber 30 increases and forces the rod 94 to move to its second position indicated by the interrupted lines, thereby selecting the pump stroke for the dosing plungers 70 with the shorter length. When the third hydraulic valve 99'connect the adult control unit 96' to tank the lack of pressure in the hydraulic pressure chamber 30 allows the rod 94 to move to its first position, thereby choosing the pump stroke for the dosing plungers 70 with the longer length.

The device 55 for supplying cylinder lubrication liquid to the inner surface 25 of the cylinder liner 1 with at least two different lengths for the pump stroke can be used in various ways. One way of using the device 55 is by using the long pump stroke with the length L2 for running in a new cylinder liner 1 with an injection for each engine revolution, and using the short pump stroke with the length LI to deliver the maximum feed rate for normal running conditions with an injection for each revolution when running at 100% engine load. The injections will skip engine revolutions when running low load, but still be significantly more frequent when compared to a prior art device with a single fixed lengths for the pump stroke.

Although the embodiments above have been described with reference to an automatic control of the stroke lengths using electronic control unit it is understood that the stroke length of the pump stroke of the plungers 70 can be controlled manually by controlling the respective hydraulic or pneumatic valve manually, e.g. by pressing a button.

The term "comprising" as used in the claims does not exclude other elements or steps. The term "a" or "an" as used in the claims does not exclude a plurality. The electronic control unit may fulfill the functions of several means recited in the claims. The reference signs used in the claims shall not be construed as limiting the scope. Although the present invention has been described in detail for purpose of illustration, it is understood that such detail is solely for that purpose, and variations can be made therein by those skilled in the art without departing from the scope of the invention .

Claims

1. A cylinder lubrication device (55) for supplying cylinder lubrication liquid to the inner surface (25) of a cylinder liner (1) of a large two-stroke uniflow compression-ignited internal combustion engine via a plurality of injectors (24) that are distributed around the circumference of said cylinder liner (1), said cylinder liner (1) defining a cylindrical interior in which a reciprocating piston (10) is slidably disposed, said cylinder lubrication device (55) comprising: a plurality of piston pumps, each piston pump having a dosing plunger (70) slidably disposed in a dosing cylinder (71) , each dosing cylinder (70) comprising a pump chamber (72) fluidically connected to a pump outlet (62) for fluidic connection to one of said injectors (24), a common drive (80) for driving all of the dosing plungers (70) simultaneously, a hydraulic linear actuator (83) operably connected to said common drive (80), and means for adjusting the length of the stroke of said common drive during operation of the cylinder lubrication device (55) to either of at least two predetermined discrete lengths (L1,L2) of stroke during operation of the cylinder lubrication device (55).

2. A cylinder lubrication device according to claim 1, comprising a first fixed mechanical end stop determining a first extended position of said common drive.

3. A cylinder lubrication device according to claim 1 or 2, further comprising a second fixed mechanical end stop determining a retracted position of said common drive.

4. A cylinder lubrication device according to any one of claims 1 to 3, wherein said hydraulic linear actuator is a single acting hydraulic linear actuator and wherein said common drive is resiliently biased towards a retracted position .

5. A cylinder lubrication device according to any one of claims 1 to 3, wherein said hydraulic linear actuator is a double acting hydraulic linear actuator.

6. A cylinder lubrication device according to any one of claims 2 to 5, wherein said hydraulic linear actuator comprises a drive piston (82) slidably disposed in a matching cylinder, with an actuation chamber (81) between said drive piston (82) and said matching cylinder, a first port (84) disposed at or near a longitudinal end of said matching cylinder, and a second port (86) disposed at a position along the length of said matching cylinder at a distance from said longitudinal end of said matching cylinder, said second port being connected to a first hydraulic valve (58).

7. A cylinder lubrication device according to claim 6, wherein said drive piston is provided with a conduit (88,89) that opens to said actuation chamber (81) and to the cylindrical outer surface of the drive piston (82).

8. A cylinder lubrication device according to claim 6, wherein said first hydraulic valve (58)is an electronically controlled valve, said first electronically controlled valve is preferably configured to assume an open position or a closed position in response to a control signal.

9. A cylinder lubrication device according to any one of claims 6 to 8, wherein said first port (84) is selectively connected to a source of pressure or to tank.

10. A cylinder lubrication device according to claim 9, comprising a second hydraulic valve (59) for selectively connecting said first port (84) to a source of pressure or tank.

11. A cylinder lubrication device according to claim 10, wherein said second hydraulic valve (59) is electronically controlled valve configured to connect said first port (84) to said source of pressure or to tank in response to a control signal.

12. A cylinder lubrication device according to any one of claims 6 to 11, wherein said distance between the end of said cylinder and said second port (86) is less than the distance between said second fixed mechanical end stop and said first fixed mechanical end stop.

13. A cylinder lubrication device according to any one of claims 11 or 12, wherein a pump stroke with a shorter one of said at least two discrete stroke lengths of said common drive (38) is selected when said first hydraulic valve (58) is in a first position and wherein a pump stroke with a longer one of said at least two discrete stroke lengths of said common drive is selected when said first hydraulic valve is another position .

14. A cylinder lubrication device according to claim 13, further comprising a controller configured to issue a control signal to said first hydraulic control valve (58) to change position in response to instructions from a human operator or in response to an engine operating parameter.

15. A cylinder lubrication device (55) according to claim 1, comprising a movable mechanical end stop, said movable mechanical end stop having at least two positions, a first position in which said movable mechanical end stop forms an end stop for said common drive (80) at a first extended position of said common drive, and a second position in which said movable mechanical end stop forms an end stop for said common drive (80) at a second extended position of said common drive (80) that is different from said first extended position of said common drive (80).

16. A cylinder lubrication device (55) according to claim 15, further comprising a second fixed mechanical end stop determines a retracted position of said common drive (80)

17. A cylinder lubrication device (55) according to claim 15 or 16, wherein said movable mechanical end stop is operably connected to an end stop actuator, said end stop actuator being configured to move said movable mechanical end stop between said first position and said second position.

18. A cylinder lubrication device (55) according to claim 17, said end stop actuator being in receipt of a control signal and said end stop actuator being configured to move said mechanical end stop from said first position to said second position or from said second position to said first position upon receipt of said control signal.

19. A cylinder lubrication device (55) according to any one of claims 15 to 18, wherein said movable end stop comprises a rod (94) slidably disposed in a bore, said movable end stop being configured to secure said rod (94) in a first position or in a second position.

20. A cylinder lubrication device (55) according to claim 20, wherein the first longitudinal end of said rod (94) forms an end stop abutment surface (37) for abutting with a common drive abutment surface (36) of said common drive (80).

21. A cylinder lubrication device (55) according to claim 19 or 20, wherein said rod (94) is secured in said first position by a third fixed mechanical end stop (93), and wherein said rod (94) is secured in said second position by a movable bolt (90) .

22. A cylinder lubrication device according to claim 21 wherein said bolt (90) is slidably disposed in a guide passage, said bolt (90) being operably connected to an end stop actuator configured to move said bolt (90) between a retracted position where said bolt (90) does not protrude from said guide passage and an extended position where said bolt (90) protrudes from said guide passage.

23. A cylinder lubrication device (55) according to claim 22, wherein said bolt (90) is disposed between said third fixed mechanical end stop (93) and said rod (94) when said bolt (90) is in its extended position.

24. A cylinder lubrication device (55) according to any one of claims 19 to 24, wherein said guide passage is arranged substantially traverse to the axis of said rod (90) .

25. A cylinder lubrication device (55) according to any one of claims 21 to 24, wherein said bolt (90) is provided with a slanting tip (97).

26. A cylinder lubrication device (55) according to claim 24, wherein a second longitudinal end of said rod (94) opposite to said first longitudinal end is provided with a slanting portion (33) .

27. A cylinder lubrication device (55) according to any one of claims 19 to 26, wherein said rod (94) is resiliently biased towards its first position.

28. A cylinder lubrication device (55) according to any one of claims 17 to 27, wherein said end stop actuator is a linear actuator, preferably a single acting linear actuator but the bolt (90) being resiliently biased towards its retracted position .

29. A cylinder lubrication device (55) according to claim 28, wherein said end stop actuator is a linear pneumatic actuator, a linear hydraulic actuator or a linear electric actuator.

30. A cylinder lubrication device (55) according to any one of claims 15 to 28, wherein the maximum stroke of said common drive between said second fixed mechanical end stop and said movable end stop is larger when said movable end stop is in said first position than when said movable end stop is in said second position.