DK179051B1 - Large two-stroke engine, inlet valve and cylinder liner - Google Patents

Abstract

The invention is related to an inlet valve (1) for an large two-stroke uniflow engine, for locking and opening a gas flow passage leading through a ring (4) of inlet slits leading through a cylinder wall (3) of a cylinder of said engine. The inlet valve (1) consists of a valve body (5) retaining a number of movable valve elements (6, 7), said valve body (5) being mountable to said cylinder in order to place said movable valve elements (6, 7) in said gas flow passage, wherein said movable valve elements (6, 7) are arranged such that they can be moved from an open position, wherein the gas flow passage is open, into a closed position, wherein the gas flow passage is closed, and back. The inlet valve (1) is characterized in that it is designed for locking and opening a gas flow passage leading through one individual inlet slit (8) of said ring (4) of inlet slits, wherein said valve body (5) is mountable at said individual inlet slit (8) and is formed as a sealing for said individual inlet slit (8) being only penetrated by a number of gas passages (16), and wherein said number of movable valve elements (6, 7) are arranged and dimensioned to open and close said number of gas passages (16), and wherein said inlet valve (1) is dimensioned and said valve body (5) is mountable such that inlet slits (8) of said ring (4) of inlet slits neighboring said individual inlet slit (8) can also be provided with identical inlet valves (1). The invention is also related to above large two-stroke uniflow engine provided with said inlet valves and a cylinder liner for that engine.

Description

Reviewer: MAN Diesel & turbo

Branch of MAN Diesel & Turbo SE, Germany

2450 COPENHAGEN SV

DENMARK

Large two-stroke engine »inlet valve and cylinder liner

The invention is related to a large two-stroke uniflow engine, in particular a large two-stroke diesel engine of uniflow kind, according to (he preamble of claim 15, The invention is also related to an inlet valve according to the preamble of claim 1 and a cylinder liner according to tie preamble of claim 13 for such large two-stroke engine, in particular large two-stroke diesel engine.

Large two-stroke engine of the generic type having one cylinder with a cylinder wall, said cylinder wall is penetrated by at least one ring of inlet slits leading through said cylinder wall in order to connect a scavenging tract of said engine with a cylinder volume inside said cylinder above a piston of said engine.

In such unifiow engines, gas streams from said ring of inlet slits in the circumferential wall of the cylinder on one side of the combustion chamber to an outlet, usually provided with an outlet valve, on the end side of the cylinder on the opposite side of the combustion chamber, ie always in the same direction, therefore it is called unifiow engine.

With a ring of open inlet ports or slits in the cylinder liner connecting the combustion chamber with the scavenging tract of the engine, scavenging of the combustion chamber would begin when the pressure inside the combustion chamber fails during the expansion stroke of the piston below the value of the pressure in the scavenging tract after the piston has passed its way down the ring of inlet slits in the cylinder wall.

If the piston, or more specifically the piston ring set, passes the ring of open inlet slits in the expansion stroke and the pressure inside the combustion diamber is higher than in the scavenging tract, there will be a gas backflow into the scavenging tract and therefore and undesired loss of useable energy. Moreover, if the exhaust valve is opened in tie expansion stroke just before the piston passes and starts to expose the inlet slits, e.g. An opening time at 6-10 bar pressure inside the combustion chamber, gas outflow into the exhaust tract will reduce the overpressure, which could be used as work on the piston in the expansion stroke.

Therefore, it is desirable to delay the opening of the inlet ports and also the exhaust valve in the expansion stroke in order to prolong the work stroke of the piston before opening the inlet ports for scavenging the combustion chamber with scavenging gas, e.g. fresh air. However, if the ring of inlet slits is made lower in the cylinder liner in order to prevent such undesired loss of usable energy, the scavenging is aborted early during the compression stroke, when the piston, or more specifically the piston ring set, passes the ring or open inlet slits in the compression stroke, thereby cutting a gas passage through the inlet slits.

To this end, it is known in the art to use inlet valves to retard the opening during the expansion stroke, i.e. to create an asymmetric closure timing of the inlet slits during expansion stroke and compression stroke. That is, the closure timing of the inlet slits during the expansion stroke is prolonged beyond the time of piston passage, whereas the closure timing of the inlet slits during the compression stroke is not prolongated and ends with the piston passage.

An inlet valve of the generic type for a large two-stroke engine of uniflow type, for locking and opening a gas flow passage leading through a ring of inlet slits leading through a cylinder wall of a cylinder of said engine and connecting a scavenging tract of said engine with a cylinder volume inside said cylinder above a piston of said engine, locks the gas flow passage, if a pressure in said scavenging tract is below a pressure in said cylinder volume, and opens said gas flow passage, if said pressure in said scavenge tract is above said pressure in said cylinder volume. To this end, said inlet valve comprises a valve body carrying a number of movable valve elements. Said valve body is mountable to said cylinder in order to place said movable valve elements in said gas flow passage, said movable valve elements are arranged such that they can be moved from an open position, while the gas flow passage is open, into a closed position, when the gas flow passage is closed, and back. E.g. European Patent Application EP 1788218 AZ discloses an annular inlet valve mounted on the inside of the cylinder liner having valve portions which can open and close the inlet ports and which are driven by hydraulic pressure controlled by magnetic valves.

However, when the annular inlet valve is mounted Inside the combustion chamber, it is hard to change and the piston (Le. The piston rings) is scraping over the surface of the inlet vaive and a ring groove between the cylinder liner wail above the inlet valve and the inlet valve Itself.

Therefore, in other examples known in the art, the inlet valve is mounted on the outside of the cylinder liner. E.g ,, Japanese Patent Application JP 59203820A shows an inlet valve arrangement, which ring segments are forming a ring around the cylinder liner such that slits in the ring segments are aligned with the Inlet slits in the cylinder liner. The inlet valve has movable valve elements, namely cylindrical valve pistons rotatably disposed in the ring segment silts, in the valve pistons there are two air channels, which can be selectively fed with pressurized air in order to rotate the valve piston from an open state into a closed state and back. It seems hard to synchronize the engine's piston movement and the valve piston movement. Therefore, in other examples, inlet valves with passively movable valve elements such as are already used.

Japanese Patent Application JP 59049316 A shows an engine with two rings of inlet slits through the cylinder liner wall. The upper ring of inlet slits is connected to a feed air pipe in which a check valve 11 is located,

Japanese Patent Application JP 62129518A discloses a ring shaped inlet valve body surrounding the cylinder liner around the inlet slits. There are flap valve doors hinged to the ring shaped valve body working as non-return valves, which dose the inlet slits when the pressure in the combustion chamber is higher than in the scavenging tract, and which opens against overpressure in the scavenging tract.

Japanese Patent Application JP 62129529A discloses a similar inlet valve arrangement, instead of hinged flaps, valve already fixed with one end fixed to the valve body, which can flexibly bend themselves, if impacted by an overpressure from inside the combustion chamber, so that they are pushed against valve body abutment faces and the inlet slits are closed.

Another inlet valve of the generic type is shown in Japanese Patent Application JP 56-081 223 A.

The above inlet valve arrangements are easier to mount on the cylinder liner than an inlet valve inside the cylinder liner. However, if one bears in mind the sheer dimensions of the generic type cylinder liner diameter, with inlet slits height in the magnitude of an adult man's forearm, the complex ring shaped parts are still hard to manufacture and mount on the cylinder liner.

It is therefore an object of the present invention to provide a large two stroke engine of the generic type, in particular a large two stroke diesel engine with a cylinder liner and an inlet valve, which allows an economical manufacture of the inlet valve and assembly of the engine on the one hand and good engine efficiency and small inlet valve space requirements on the other.

In view of the inlet valve, this object is solved by the features of claim 1. In view of the cylinder liner, this, object is solved by the features of claim 13. In view of the engine, this object is solved by the features or claim 15,

According to the invention, said inlet valve consists of a valve body and movable valve elements. Said valve body consists or substantially consists of an accommodated portion formed to be accommodated or substantially accommodated in said individual inlet slit, thereby lifting said individual inlet slit at least partially. That is, said valve body is as a whole or at least substantially accommodated or accommodatable within the respective inlet slit. The number of movable valve elements are retained at said accommodated portion. As also said movable valve elements are accommodated at least substantially in said individual inlet slit, said inlet valve as a whole is accommodated or substantially accommodated in said individual inlet slit. It is designed to lock and open a gas flow passage leading through one individual inlet slit of said ring of inlet silts. To this end, said valve body is mountable at said individual inlet slit and is formed as a seal for said individual inlet slit being penetrated solely by a number of gas passages. The inlet valves * movable valve elements are arranged and sized to open and close said number of gas passages.

Further, said inlet valve is sized and said inlet valve's valve body is mountable such that there is enough space that inlet slits of said ring of inlet slits neighboring said one individual inlet slit provided with said inlet valve can also be provided with identical inlet valves, such that all inlet slits or said ring of inlet slits can be provided with individual inlet valves.

It turned out that engine efficiency could be even more increased if said valve body formed an accommodated portion to be in assembled condition of said inlet valve on said engine's cylinder at least substantially accommodated in said individual inlet slit and said movable valve elements are an assembled condition of said inlet valve on said engine's cylinder accommodated at least substantially inside said individual inlet slit. In other words, said inlet valve is formed such that said accommodated portion and / or said movable valve elements are aceomodateable inside said individual inlet slit. This is because with closed inlet during the expansion stroke of piston, a volume inside said inlet slits between the inside of said combustion chamber and each of said closed inlet valves would be a dead volume reducing compression in the combustion chamber during the expansion stroke of the piston, as the gas in the combustion chamber could to some extent escape into said dead volume inside said inlet slits. It is therefore advantageous to reduce said dead volume inside said inlet slits or said ring of inlet slits. Furthermore, space requirements for said inlet valves around the cylinder's outer circumference are minimized if said inlet valves according to the invention are at least partially accommodated within said inlet slits. With. said accommodated portion accommodated in said individual inlet slit and / or said moveable valve elements accommodated in said individual inlet slit, said individual inlet slit is at least partially filled, thereby saying dead volume is reduced.

The large two-stroke uniflow engine of the present invention has at least one cylinder with a cylinder waif, which could be formed partially by a cylinder finer. Said cylinder wall is penetrated by at least one ring of inlet leads through said cylinder wall. Each individual inlet slit or said ring of inlet slits is provided with one separate inlet valve according to the invention.

Especially since said inlet valve's shape and shape is in dimension and shape determined by dimension and shape of the inlet sides, which have an elongated cross section approximately in the magnitude of an adult person's forearm, the inlet valve of the present invention is relatively easy to mount to the cylinder, respectively cylinder liner wall, as compared to the known annular type and therefore relatively large inlet valves. Moreover, it is also pretty easy to manufacture, e.g. with a cast valve body. It is also advantageous in terms of maintenance to have individual inlet valves for each inlet silt of said ring of inlet slits or said cylinder or cylinder liner, as it is not only easier to change the relatively small sized inlet valves, but it is also possible to change only that specific inlet valve, which is defective.

It is understood that it is also advantageous for the ease of mounting and maintanenee if the inlet valve is mountable from the outside of said cylinder. Moreover, for the present invention, the term "said valve body is penetrated by a number of gas passages" does not only mean that the valve body fully envelops all of said gas passages, it is also possible that said vaive body forms only a partial surrounding of one or more of said gas passages and the other part of the surrounding is formed by said inlet slit's Inner circumferential wall. Further, for the present invention, the term "said valve body retains said number of movable valve elements" is not limited to said movable valve elements being fixed to said valve body. Said movable valve elements can also be clamped between said valve body and in the advantageous further development, each of said inlet valves of said engine is formed and mountable such that in assembled condition inside said individual inlet slit, its inner surface forming in closed state foe border for the gas inside the combustion chamber towards the respective inlet slit and being exposed to foe gas inside the combustion chamber, ie the foe surface facing the inside of the combustion chamber, is inside the inlet slit. innermost surface of the closed inlet valve is formed at least partially by said movable vaive elements, such that there is no dead volume on foe combusti on chamber facing side of said moveable vaive elements. in this respect, said number of movable valve elements could advantageously be formed as a number of already or reed blades, respectively spring already being fiat and bendable, and could therefore easily form part of such inner surface forming in its closed state the border for foe gas inside the combustion chamber towards the respective inlet slit and being exposed to the gas inside the combustion chamber. Such a reed blade can be arranged fully or at least with its bendable part inside foe dedicated inlet slit and can form part of said innermost surface of foe dosed inlet valve. However, it is understood that the already need not bend into the foe volume of the combustion chamber. While it is preferred to use one or more movable valve elements of the reed blade type, it is also conceivable to use other kind of passively working elements as movable valve element, e.g., hinged flaps. In this connection, "passively working" means that the respective valve element is actuated solely by a pressure difference between the pressure in the combustion chamber and the pressure in the scavenging tract. Thereby, an external active control for said inlet valves, which is costly and hard to synchronize to engine's timing can be avoided.

The valve body needs to be mounted on the cylinder at the dedicated individual inlet slit Herefor, it is conceivable that the valve body is forced with its accommodated portion into said individual inlet slit and held there by clamping force. The valve body can consist of the accommodated portion only.

However, it is difficult to securely mount or change an inlet valve with such valve body. Therefore, the cylinder liner or cylinder according to the present invention may have at least one ring of inlet slits, each inlet slit of said ring of Inlet slits being formed for one separate inlet valve and at each inlet slit of said ring of Inlet slits are provided mounting means for said inlet valves.

However, land portions between said inlet slits in said ring of inlet slits should be as narrow as possible in order to maximize the size of the all together gas flow passage through the inlet slits, which on the other hand is already limited, as the inlet valves are accommodated inside the inlet slits, out of the above-mentioned reason of reducing the dead volume inside the inlet slits.

For the preferred mounting of such "accommodated only" valve body in an easily engaging and releasable fashion at the respective inlet slit, but also if the vaive body has an additional, non-accommodated portion, said mounting means of the cylinder or cylinder liner at each individual inlet slit might comprise preferably tapered engagement recesses at the edge of an outer surface of the cylinder circumferential wall and a lateral portion of said inner circumferential surface of the respective individual inlet slit, for engagement protrusions formed on each of said inlet valves * valve Each inlet valve in turn might comprise in the vicinity of an outermost cross section of its accommodated portion, on both lateral sides, laterally cantsievering engagement protrusions, to engage in said engagement recesses at said individual inlet slit, said engagement protrusions are preferably tapered to engage in the preferred tapered recesses.

The mounting means of the cylinder or cylinder liner might further comprise threaded bores in each interposed land portion between two neighboring inlet valves of said ring of inlet valves, because of narrowness requirement for the interposed land portions preferably arranged in a single row of threaded bores, each of which extends into the material of the cylinder wall. On each interposed land portion between two neighboring inlet valves or said ring of inlet valves, a mounting bar might then be fixed by screws screwed into said threaded bores in said interposed land portion. Said mounting bar might protrude over the lateral surfaces of said interposed land portion and might press the two neighboring inlet valves into the two neighboring inlet valves of said ring of inlet slits. Alternatively, the screw heads could cantilever over the lateral surfaces of said interposed land portion and might press the two neighboring inlet valves into the two neighboring inlet slits of said ring of inlet slits.

The shape and dimension of said accommodated portion of said valve body of the inlet valve according to the invention or, in the above preferred further development of its entire valve body, is predetermined by the shape and shape of said inlet slits if said ring of inlet slits of the cylinder or cylinder liner according to the invention. Such inlet slits generally have an elongated shape in the direction of the cylinder's axis and lead with constant cross section from the outside of the cylinder wall to the inside of the cylinder wail. That means that intermediate land portions between neighboring inlet slits are getting narrower from the outside to the inside. Further, said inlet slits usually have a plane arrangement parallel to a plane extending in radial direction of the cylinder. Preferably, the direction with which each of said inlet slits of said ring of inlet slits leads through said cylinder's wall has an angle to the radial direction of the cylinder, most preferably about 10 ° to 25 °, e.g., around 20 °, in order to produce a spin in the low of scavenging gas inside the combustion chamber to enhance gas mixing.

For the sake of clarity, in this application geometry of the inlet valve of the invention is defined by reference to the geometry of said inlet side provided with said inlet valve, assuming the cylinder has a vertical axis, with a crank shaft at the bottom, it is noted that the inlet valve should not be limited by those references to be used in such cylinders, only.

In order to form a seal for said inlet valve of the above form, said accommodated portion of said valve body may have, as viewed from the inside of the cylinder in assembled condition inside said individual inlet slit, an elongated form with a contour of said individual inlet slit, especially if sard inlet valve's body consists exclusively of said accommodated portion, in order to form a seal for the inlet slit only penetrated by said gas passages. No matter if said inlet valve's body consists exclusively of said accommodated portion or not, said accommodated portion may consist of a top contacting wail portion on its one narrow side being at the top in assembled condition inside the inlet slit, a bottom contacting wail portion on its other narrow side being at the bottom in assembled condition inside the inlet slit and a central portion interconnecting said top contacting wall portion and said bottom contacting wall portion and being penetrated by said gas passages.

Said top contact wall portion can have an outer surface formed to contact a top portion of said inner circumferential surface of said individual inlet slit over a full width of said individual inlet slit, e.g., with a convexly curved wall, protruding from an outermost end of said accommodated portion of said valve body into said individual not to an innermost end of said accommodated portion of said valve body, preferably in contact with said top portion, and said bottom contacting wail portion may have an outer surface formed to contact a bottom portion of said inner circumferential surface of said individual inlet slit over a whole width of said individual inlet slit, eg with a convexly curved wail, protruding from said outermost end into said individual inlet slit to said innermost end, preferably in contact with said bottom portion. Additionally, that portion of said accommodated portion, which does not retain or carry said number of movable valve elements and consists of full material, namely the wall of the above contacting wail portions, is protruding up to innermost end of said accommodated portion, such that a Major part of the volume inside the inlet slit, which cannot contribute to the overall size of the gas passages, either, is filled and thus pervented from being a dead volume. in a preferred further development, said central portion, in assembled condition inside said individual inlet slit, has a horizontal cross section having a substantially triangular envelope of contour and being constant in size and shape over its entire length between said top contacting waif portion and said bottom contacting wall portion and having lateral flanks tapered in inward direction. Both said lateral flanks contact over their entire length lateral portions of said inner circumferential surface of said individual inlet slit and at least one, preferably both of said lateral flanks is or are penetrated by said gas passages. With a central portion having said configuration, cover said gas passages in said closed position, said number of reed blades can be supported on said lateral flanks * surfaces and, in the open position, be bended against said lateral portions of said inner circumferential surface of said Inlet slit, with the outside end of each reed blade being fixed and the inside end of each reed blade being bended.

To this end, said central portion on its said lateral flanks preferably has a number of preferably plane support surfaces corresponding to said number of spring already, on which said number of spring is already supported in said closed position covering said gas passages.

Said lateral flanks are preferably extended from said outermost end to said innermost end in order to reduce dead volume. Not only if the inlet slit, for which the inlet valve is foreseen, leads with an angle to the radial direction of the cylinder angle to the inside of the cylinder, preferably also said lateral flanks have different lengths, so thai said triangular envelope is not isosceles, but inclined as to an isosceles triangle by an inclining angle of both flanks, preferably approximately 10 ° to 25 °, e.g. around 20 °, in order to assist or even produce the spin in the flow of scavenging gas inside the combustion chamber.

Especially for the above configuration of said central portion, it is preferable if each said number of spring is already formed rectangularly, and is, at least in said assembled condition, connected with a connecting portion on one of its sides to an outer section at that flanks of said central portion such that it extends inwardly into said individual inlet slit Each spring reed or reed blade might be fixedly connected to the central portion or just be clamped between an outer surface of the central portion, preferably at said tapered engagement protrusions, and said lateral portions of said inner circumferential surface of said inlet slit.

In order to support said central portion with its tapered flanks inside said inlet silt, on each lateral side of said tapered central portion at least one, preferably a plurality of mutually spaced support ribs are provided, protruding from said central portion at said lateral flanks in lateral, in said assembled condition preferably horizontal direction to contact a lateral portion of said inner circumferential surface of said individual inlet slit.

Preferably, said central portion comprises two lateral outermost land portions interconnecting laterally said top contacting wall portion and said bottom contacting wall portion, and an innermost end land portion connecting said top contacting wail portion and said bottom contacting wall portion, so that each said lateral flanks stretch from one lateral facing side of tee innermost end land portion to a lateral facing side of one of said lateral outermost land portions.

On the lateral facing side of each lateral outermost land portion, one of said engagement protrusions can be arranged. Preferably, engagement protrusions extend along the entire lateral outermost land portions. Preferably, said engagement protrusions protrude laterally over the lateral sides of said top contacting wail portion and said bottom contacting wail portion. Preferably, a lateral surface of each said engagement protrusions to be urged against a corresponding surface of the correspondent engagement recess forms a plane lateral surface of the correspondent lateral outermost land portion at least partially. That is, each said engagement protrusions could form an integral part with the correspondent lateral outermost land portion with a common plane lateral surface. Thus, the central portion and therewith the whole valve body gets a low-end geometry easy to manufacture, eg to cast. Consequently, in a preferred further development, said valve body is an integrally cast piece of cast iron, preferably gray Iran.

Said number of gas passages can then be formed on one, preferably on both flanks of said central portion between said top contacting wall portions, said bottom contacting wall portion, said innermost land portion and the respective one of said lateral outermost land portions.

For a reliable and inexpensive fixation of said number of spring reeds, said central portion could comprise a number of plane connection surfaces corresponding to said number of spring reeds and facing lateral portions of the inner circumferential surface of said individual inlet slit. In said assembled condition inside said individual inlet slit, said number of spring already can then be clamped between said corresponding number of connection surfaces and lateral portions of the inner circumferential surface of said individual inlet slit. Said number of planed connection surfaces could be formed on one, preferably both lateral outermost land portions integrally with the plane lateral surface of the one, preferably both lateral outermost land portions and preferably on such portion of the plane lateral surface of the one, preferably both lateral outermost land portions, which at the same time form the lateral surface of said engagement protrusions. Thus, said number of spring can already be clamped between said lateral surface of said engagement protrusion and said corresponding surface of the correspondent engagement recess.

As a matter of simplifying transport and mooting of said inlet valve, oniy, in the above preferred further development, said number of springs are already preconnected eg by bonding, soldering or spot welding to that number of connection surfaces.

Further, said inlet valve, on said innermost end portion on each of its lateral sides with gas passages, could comprise a number of plane surfaces forming part of the number of support surfaces for said correspondent number of spring already. Said number of plane surfaces can be one plane surface on the respective lateral side of said innermost end land portion.

Further, said number of support surfaces could be at least partially formed by lateral surfaces of interconnecting lands, which interconnect said inner land portion and at least one of said lateral outermost land portions on said flank of said central portion with gas passages. Said lateral surfaces of said interconnecting lands can be aligned with said number of plane surfaces on said innermost end land portion's flanks and said connection surfaces on said outermost land portions, such that flat springs are already supported in the closed state of the inlet valve with their full body.

With the support of the interconnecting lands, a buckling of the spring already in the closed state of the inlet valve can be reliably prevented, even if an overpressure of 8 to 10 bar exists in the combustion chamber as compared to the scavenging tract.

Further, said inlet valve having both outermost lateral land portions and said innermost land portion can comprise at least one, preferably a plurality of mutually spaced sectioning ribs interconnecting perpendicularly the both lateral land portions and the Inner land portion on the inside of said land portions . As a cross section of the inside of said land portions is approximately triangular, also the sect toning ribs are approximately triangular. 8y said sectioning ribs a further stiffening of the accommodated portion of the valve body is achieved.

An even more important effect is achievable, if said sectioning ribs are of full material and are therefore impermeable to gas, which means impermeably separating gas passages above each sectioning rib from gas passages below said sectioning rib. Then, a by-pass of gas inside the combustion chamber to a volume below the piston cannot be avoided then at least reduced to a position of the piston, where the piston ring package is passing said ring of inlet valves. This effect is enhanced if the sectioning ribs continue on the outside of said lateral flanks of said central portion of said vaive body, e.g., into said support ribs. ft is understood that in order to avoid the above short-cut effect, the distance between each two neighboring sectioning ribs, the distance between a sectioning rib neighboring the top contacting wall portion and the top contacting wall and the distance between a sectioning rib neighboring the bottom contact wall portion and bottom contact wall portion has to be smaller than the height of the piston ring package.

An engine's cylinder or cylinder liner provided with the advantageous inlet valves of the invention may have more than one ring of said inlet slits provided or stuffed with said inlet valves, in order to prolong opening time during the compression stroke of the piston. Alternatively, if the cylinder or cylinder liner comprises only one ring of said inlet slits, it is also possible to place the inlet silts at a higher position or make the inlet slits longer with the upper end thereof reaching a higher position Qian without the inlet vaives according to the invention, if the inlet valves according to the invention will keep the inlet slits closed during the expansion stroke, even if the overpressure inside the combustion chamber as compared to the scavenging tract is as high as 8 to 10 bar.

Moreover, in the large two-stroke uniflow engine having said inlet valves, the opening of the exhaust valve can be delayed until the piston in the expansion stroke is close to the BDC, bottom dead center, so as to utilize most of the pressure / energy inside the cylinder, as work on the top of the piston, eg, an opening time at 2 ~ 3 Bar pressure inside the combustion chamber during the expansion stroke.

In the following, the features and advantages of the invention are explained with the help of the accompanying drawings, which show in

FIG. a perspective view of a cylinder tiner according to an embodiment of the invention provided with inlet valves according to the embodiment of the invention;

FIG. 2 shows a partial sectional view taken along its INI in FIG. 1;

FIG. 3 is a perspective view of one of the inlet valves shown in FIG. 1 and 2;

Fig. 4 shows another perspective view of the inlet shown in Figs. 3 in an open state;

FIG. 5 a perspective view corresponding to FIG. 4 of the inlet valve in closed state;

FIG. 6 a perspective view of a valve body of the inlet valve shown in the preceding Figures;

FIG. 7 a sectional view taken along line VH ~ VH in FIG. 3 showing the inlet valve with open already;

FIG. 8 a sectional view corresponding to FIG. 7 showing the inlet vaive with closed already;

FIG. 9 in enlarged view of detail! X in FIG. 2; spirit

FIG. 10 a view of an area offset from the plane of sheet from region X in

FIG. 9th

Initially, reference is made to figures 1 and 2. A cylinder liner 2 is shown having a cylindrical circumferential wall 3 interspersed with identical inlet slits 8 being arranged as a ring 4 of said inlet slits 8. in said ring 4 of inlet slits, each pair of neighboring inlet slits 8 is mutually spaced and separated by an interposed land portion 9. Said inlet silts 8 of said ring 4 of inlet slits are stuffed with identical inlet valves 1 having a generally V-shaped cross section in the view of Fig. . 2 and, viewed from the outside of the cylinder, as being fully accommodated within the respective inlet slit 8, an outer contour following the contour of the respective inlet slit 4.

One of said inlet valves 1 is shown in overall views in Figs. 3, 4, and 5. The inlet valve generally consists of a valve body 5 having an elongated shape and dimension, predefined by the shape and dimension of said inlet slits 8, into which the inlet valve has fit. Said valve body 5 generally consists of a top contact wail portion 13a and a bottom contact wall portion 13b being interconnected by a central portion 10. Said central portion 10 carries on its one lateral sides reed blades 6 and on its opposite lateral side reed blades 7 .

Said top and bottom contacting wail portions 13a, 13b have wails being, as seen from the outside of said cylinder liner 3, convexly curved and protruding with constant cross section in the direction of the respective inlet slit 8. Said central portion 10 has on its both lateral sides two inwardly tapered flanks protruding from an outermost end of said top and bottom contacting wail portions 13a, 13b to an innermost end of said top and bottom contacting wall portions 13a, 13b, Said reed blades or spring already 6, 7 have a generally rectangular shape being fixedly connected to one side at an outer end portion of the respective lateral flank of said central portion 10, such that they may flap with their inwardly facing ends in order to open (Fig. 4) or close (Fig. 5 ) gas passages 16 (Fig. 6) through said centers! portion 10. In their closed position, they are supported on the respective flank of the central portion 10 (Fig. 9 "CLOSED") and they are supported in their open position on an inner circumferential surface of the respective inlet slit 8 (Fig. 9). 9, OPEN ").

Said valve body 5 is shown in detail in Fig. 6. Said valve body's central portion 10 comprises two lateral outermost land portions 11 at lateral outermost edges of the central portion 10 and an innermost land portion 17 at an innermost end of the tapering central portion. 10. Said outermost and innermost land portions 11,17 are interconnecting said top and bottom wall portions 13a, 13b. On the lateral flanks of said central portion 10, interconnecting webs or interconnecting lands 14 are extended perpendicularly to said outermost and innermost land portions 11, 17 between the respective lateral outermost land portion 11 and the innermost land portion 17. Said interconnecting lands 14 form together with plane surfaces 20 on the lateral Hanks of said innermost land portion 17 (Fig. 7) support surfaces 14, 20 for the spring already 6, 7 in said closed position (Fig. 9 '' CLOSED ').

On the lateral flanks of said lateral outermost land portions 11, there are provided plane surfaces 18 forming connection surfaces 18, where the spring already 6, 7 is connected to the valve body 5, eg by spot welding. Said gas passes 16 lead through the lateral Hanks of said centers! portion 10, between said interconnecting lands 14. Said gas passages 16 are closed, if said spring already 8, 7 are supported on said support surfaces 14, 20 (Fig. 8, Fig. 9, “CLOSED”) and are open, if said spring already 8, 7 are supported on said lateral portion of said inner circumferential wall of said inlet slit S (Fig. 7, Fig. 9, OPEN ”).

On each lateral side of said tapered central portion 10, two mutually spaced support ribs 12 are provided. Said support ribs 7 protrude laterally in order to support the valve body 5 in said inlet silt 8, that is, they protrude laterally as far as said top and bottom wall portions 13a, 13b, as the lateral portions of said inner circumferential surface 31 of said inlet slit 8 extend into parallel planes, see Figs, 9.10.

Further, both lateral outermost land portions 11 and said innermost land portion are mutually interconnected on the inside of the lateral flanks by generally triangular sectioning ribs 15, Said sectioning ribs 15 are uniformly distributed over the length of said central portion 10, with the uppermost and the lowermost sectioning rib 15 having a distance to the top contacting wall portion 13a, respectively, bottom contacting wail portion 13b, which corresponds to the distance between neighboring sectioning ribs 15. Said distance, on the other hand, is somewhat longer than the height of a piston ring package of a piston reciprocating in said cylinder. In addition, an undesired short-cut for the gas inside the combustion chamber during pass-by of the piston (exactly: the piston ring package) to a volume below the piston is at least substantially closed. The short-cut size is reduced by the cross section of space in front of the lateral flanks of the central portion 10. At least partially, this cross section could also be closed if said sectioning ribs 15 continue on the outside of the lateral flanks into support ribs 12. Therefore, the gas pressure in the combustion chamber does not drop suddenly at the moment of piston pass-by, as also the escape through the inlet slits 8 of said ring 4 of inlet slits is locked by over pressure In the scavenging tract, if at this moment the respective inlet slit 8 is open.

The inlet valve 1 is formed to be fully accommodated in the respective inlet slit 8, as can be seen best in FIG. 9. That means the valve body 5 consists of an accommodated portion, only, to be introduced together with the fixedly connected spring already 8, 7 from the outside of the cylinder into the respective inlet slit 8. in order to fix said inlet valve 1 in the respective inlet slit, said centers! portion 10 of said valve body 5 comprises, as can be seen best in Figs. 7 and 8, on both lateral outer edges, engagement protrusions 19 protruding or cantilevering laterally over the lateral edges of said top and bottom contacting wall portions 13a, 13b. Said engagement protrusions 19 are an integral portion of said lateral outermost land portions 11. Said engagement protrusions 19 are for engaging respective chamfers or tapered engagement recesses 32 at the outer edges of said interposed land portions 9 at an outer surface of said cylinder liner 2 and said lateral portion of said inner circumferential surface of the respective inlet sift 8 {designated with reference sign 31 in Figs. 9.10)

Turning now to said Figs. 9 and 10, the configuration and fixation of said inlet valves 1 inside said inlet slits 8 is explained. In FIG. 9, one inlet slit 8 is shown with a closed inlet valve 1, marked with the word "CLOSED" and the neighboring inlet slit 8 is shown with an opened inlet valve 8, marked as "OPEN". It is understood that this is for illustrative purpose only.

As mentioned above, each inlet valve 8 company said engagement protrusions 19 to engage respective chamfers 32 at outer lateral edges of each interposed land portion 9 of said cylinder wail 3 between the inlet slits 8 or said ring 4 of inlet slits. Between a laterally facing, common surface of each of said engagement protrusion 19 and the respective lateral outermost land portion 11, which is the support surface 18 shown in FIG. 6, and an opposite surface of the respective chamfer of engagement recess 32, the spring already-6, 7 are damped and thereby fixed in position.

By the form fit of said engagement protrusions 19 with said engagement recesses 32, also the entire inlet valve 1 is fixed against movement to the inside of the combustion chamber, In order to fix the inlet valve 1 against movement out of the respective inlet slit 8 in outward direction, mounting bars 34 are provided, each of which is fixed from the outside onto said interposed land portions 9 and canting over the lateral edges of said interposed land portion 9, i. E., Protruding over the engagement protrusions 19 of said inlet valves valve bodies 5 and urging the respective inlet valve 1 into position.

As can be seen best in Fig. 10, said interposed land portions 9 of the cylinder wall 3 are relatively narrow and provide space for a single row of threaded holes 33, only, in order to maximize the overall size of the gas flow passage through said inlet slits 8 of said ring 4 of inlet slits being stuffed with said inlet valves 1. Therefore, there would not be enough space for a mounting flange of the inlet valves. This problem is overcome by said mounting bar 34, which is fixed by screws 35 screwed into said single row of threaded holes 33 to said interposed land portion 9 of said cylinder wall 3,

FIG. 10 is taken with some offset to FIG. 9 in the direction out of the plane of the sheet, such that one can see one of said screws 34. Moreover, in Fig. 10, the inlet valves 1 are shown in a sectional view through one of their sectioning ribs 15.

Further, Figs. 9 and 10 show that the inlet slits 8 have a constant width, seen in a cylinder-axial plane. That means in turn, that said interposed land portions 9 are getting narrower from the outside to the inside of the cylinder 2. Moreover, it is shown that the symmetry axis of said inlet slits 8 is offset against a cylinder-radial axis, in the shown example approximately 20 °, in order to produce a spin in the inflowing scavenging gas. The valve body 5 follows the above offset of the inlet slit axis of symmetry against a cylinder-radial direction. That is, its envelope of contour in said cylinder-axial plane is not an iso-scene triangle, but has one longer tapered flank with already 6 and one shorter tapered flank with reed 7, such that the inflowing scavenging air, see large arrows in Fig. 9, still gets a spin, even though said inlet valves are positioned in said inlet slits. In fact, spring 6, 7 can be equal in dimension, in order to make common ports usable.

Modifications and variations of the above embodiment are possible without leaving the scope of the invention.

Claims (17)

An inlet valve (1) for a large uniflow type two stroke engine, for blocking and opening a gas flow passage passing through a ring (4) of inlet slots passing through a cylinder wall (3) of a cylinder of the engine and connecting a flushing channel of the engine with a cylinder volume inside the cylinder over a piston of the engine, the inlet valve (1) shutting off the gas flow channel if a pressure in the flushing channel is less than a pressure in the cylinder volume and opening the gas flow passage if the pressure in the flushing channel is above the pressure in the cylinder volume wherein the inlet valve (1) consists of a valve body (5) which holds a plurality of movable valve elements (6, 7), wherein the valve body (5) can be mounted to the cylinder to place the movable valve elements (6, 7) in the gas flow passage, wherein the movable valve members (6,7) are arranged so that they can be moved from an open position where the gas flow passage is open, to a closed position where the flow channel is closed and back where the inlet valve (1) is arranged to shut off and open a gas flow passage which passes through a single inlet slot (8) of the inlet slots of the ring (4) and where the valve body (5) can be mounted at the individual inlet slot ( 8), preferably from the outside of the cylinder, and is designed as a seal for the single inlet slot (8), which is penetrated only by a plurality of gas passages (16), and wherein the number of movable valve elements (6, 7) is arranged and sized for opening and closing the number of gas passages (16), and at least substantially the space of the individual inlet slot (8), and wherein the inlet valve (1) is dimensioned and the valve body (5) can be mounted such that the inlet slots (8) ) of the ring (4) of inlet slots which is adjacent to the individual inlet slot (8) can also be provided with similar inlet valves (1), characterized in that the valve body (5) consists of a space part which is designed to be re space or substantially the space of each inlet slot (8), thereby partially filling each inlet slot (8). An inlet valve (1) according to claim 1, characterized in that the accommodated part of the valve body (5) has an elongated shape with an outline of the individual inlet slot (8) seen from the inside of the cylinder in the assembled state within the individual inlet slot (8). ), and comprises a top abutting wall portion (13a) on its one narrow side with an outer surface designed to abut a top portion of an inner circumferential surface (31) of the individual inlet slot (8) over a full width of the individual inlet slot (8), e.g. having a convex curving wall extending from an outer end of the accommodated portion of the valve body (5) into the individual inlet slot (8) to an inner end of the accommodated portion of the valve body (5), preferably in contact with the top portion, a bottom abutment wall portion (13b) on its second narrow side with an outer surface designed to abut a bottom portion of the inner circumferential surface (31) of each inlet slot (8) over a full width of the individual inlet slot (8), e.g. . having a convex curving wall extending from the outer end to the inner end into the individual inlet slot (8), preferably in contact with the bottom portion, and a central portion (10) connecting the top adjacent wall portion (13a) and the bottom adjacent wall portion (13b), which is permeated by the gas passages (16). An inlet valve (1) according to claim 2, characterized in that the central part (10), as a combined state within the individual inlet slot (8), has a horizontal cross-section having a substantially triangular outline which is constant in size and shape over its entire length between the top-adjacent wall portion (13a) and the bottom-adjacent wall portion (13b), and having lateral flanks which are tapered inwardly and preferably extend from the outermost end to the innermost end, both of which lateral flanks abut lateral portions of the inner circumferential surface (31) of each inlet sound (8) over their entire length, and where at least one, preferably both lateral flanks, is penetrated by the gas passages (16), and in particular the lateral flanks have different lengths so that the triangular outline is not straight, but inclined to a straight triangle with an inclined angle of both flanks, preferably about 20 °. Inlet valve (1) according to claim 3, characterized in that at least one, preferably a plurality of spaced apart support ribs (12) projecting laterally from the lateral side of the tapered central portion (10) is provided. central portion (10) at the lateral flanks in the assembled state, preferably in the horizontal direction, to abut a lateral portion of the inner circumferential surface (31) of the individual inlet slot (8). An inlet valve (1) according to claim 2, 3 or 4, characterized in that the central part (10) comprises engagement projections (19) near the outer end of the accommodated part on both lateral sides, where the engagement projections (19) are laterally projecting over the top adjacent wall portion (13a) and bottom adjacent wall portion (13b) to engage in corresponding engagement recesses at the edge of an outer surface of the barrel and a lateral portion of the inner circumferential surface (31) of each inlet slot (8); wherein the engagement projections (19) are in particular tapered to engage in tapered recesses in particular, and wherein the projections (19) preferably form a portion which is aligned with the lateral flanks of the triangular outline of the horizontal cross-section on the outer surfaces of the projections (19). An inlet valve (1) according to any one of claims 3 to 5, characterized in that the central part (11,14,15,16,17) comprises two lateral outer surface parts (11) which laterally interconnect the top adjacent wall (13a) and the bottom adjoining wall portion (13b), preferably at the outermost end, and an inner surface portion (17) connecting the top adjacent wall portion (13a) and the bottom adjoining wall portion (13b), preferably at the innermost end, so that each of the lateral flanks extending from one lateral side of the innermost end surface portion (17) to a lateral facing side of one of the lateral outer surface portions (11), wherein the number of gas passages (16) is formed at least on one, preferably at both sides, between the top adjoining wall portion (13a), the bottom adjoining wall portion (13b), the inner surface portion (17) and the respective one of the lateral outer surface portions (11). Inlet valve (1) according to claim 6, characterized in that both the outer lateral surface portions (11) and the inner surface portion (17) are perpendicularly interconnected with at least one preferably a plurality of spaced apart section ribs (15) within both lateral surface portions. (11) and the inner surface portion (17) which impermeably separates gas passages (16) across each section rib (15) from gas passages (16) below the section rib (15). Inlet valve (1) according to any one of the preceding claims, characterized in that the number of movable valve elements (6, 7) is formed as a number of flat and flexible spring leaves (6, 7) · Inlet valve (1) according to claim 8, characterized in that each of the plurality of spring blades (6, 7) is rectangularly formed and, at least in its overall state, is connected to a connecting part (22) on one of its sides of the valve body (5), preferably to one of the lateral outer surface portions (11), so that it extends inwardly into the individual inlet slot (8), and wherein the valve body (5), preferably the central part (10) of its lateral flanks, has a plurality of preferably flat support faces (14, 20) corresponding to the number of spring blades (6, 7), and the number of spring blades (6, 7) being supported in the closed position covering the gas passages (16). An inlet valve (1) according to claim 8 or 9, characterized in that the central part (10), preferably on the lateral sides of the engagement projections (19), comprises a plurality of preferably flat connecting surfaces (18) corresponding to the number of spring blades (6,7) such that the number of spring blades (6, 7) is clamped between the number of connecting surfaces (18) and the lateral portions of the inner circumferential surface of each inlet slot (8) in the overall condition, wherein the number of spring blades (6, 7) are preferably connected e.g. by bonding, soldering or spot welding to the number of connecting surfaces (18). Inlet valve (1) according to claim 8, 9 or 10, characterized in that the innermost end surface portion (17), on each of its sides with gas passages (16), has a plurality of flat surfaces (20) for the number of spring blades ( 6, 7) on this side of the accommodated portion of the valve body (5), which flat surfaces (20) form at least a portion of the number of supporting faces (14, 20), and / or at least one of the outermost lateral surface portions. (11), which is on at least one side of the accommodated portion of the valve body (5) with gas passages (16), is coupled to the inner surface portion (17) by interconnecting surfaces (14) forming at least a portion of the number of support surfaces (14, 20), in the region between a connecting surface (18) and the inner surface portion (17). An inlet valve (1) according to any one of the preceding claims, characterized in that the valve body (5) is in one piece of cast iron, preferably gray iron. Cylinder liner (2) for a large uniflow type two-stroke engine, wherein the cylinder liner (2) has a cylindrical wall (3) to form part of a wall (3) of a cylinder of the motor, wherein the cylindrical wall (3) ) is penetrated by at least one ring (4) of inlet slots passing through the cylindrical wall (3) to connect a flushing channel of the engine with a cylinder volume within the cylinder over a piston of the engine, characterized in that each inlet slit (8) of the ring (4) of inlet slots is formed into one separate inlet valve (1) according to any one of the preceding claims, and by providing a mounting means (32, 33) for the inlet valves (1) at each inlet slot (8) of the ring (4) of inlet slots. Cylinder liner (2) according to claim 13, characterized in that the fastening means (32, 33) at each inlet slot (8) preferably comprises tapered engaging recesses (32) at the edge of an outer surface of the cylinder liner (2) and a lateral part of the the inner circumferential surface (31) of each inlet slot (8) for engagement projections (19) formed on each of the inlet valves, and / or wherein the mounting means (32, 33) preferably comprises a single row of bores with threads (33) at each inlet slot (8) in each intermediate surface portion (9) between each two adjacent inlet slots (8) of the ring (4) of inlet slots. A large uniflow type two-stroke engine, wherein the engine has at least one cylinder with a cylinder wall (3), the cylinder wall (3) being penetrated by at least one ring (4) of inlet slots passing through the cylinder wall (3) to connect a flushing channel of the motor with a cylinder volume within the cylinder over a piston of the motor, characterized in that each inlet slot of the ring (4) of inlet slots is provided with one separate inlet valve (1) according to any one of the preceding claims 1 to 12. Engine according to claim 15, characterized in that each individual inlet slot (8) is provided with preferably tapered engagement recesses at the edge of an outer surface of the cylinder liner (2) and a lateral part of the inner circumferential surface (31) of the individual inlet slot (31). 8), and each of the inlet valves (1) is provided with the spaced portion having the laterally projecting engagement projections (19) which engage the engagement recesses. Motor according to claim 15 or 16, characterized in that there is an intermediate surface part (9) of the cylinder wall (3) between the at least two adjacent inlet slots (8) of the ring (4) of inlet slots on which a mounting rod (34) is attached, e.g. by means of screws (35) screwed into a single row of bores with threads (33) in the intermediate surface portion (9), the mounting rod (34); protrude beyond the lateral surfaces of the intermediate surface portion (9) and press on the inlet valves (8) in the two adjacent inlet slots (8) of the ring (4) of the inlet slots.