DK177676B1

DK177676B1 - Exhaust valve arrangement for a large slow-running two-stroke internal combustion engine with crossheads

Info

Publication number: DK177676B1
Application number: DK201300076A
Authority: DK
Inventors: Poul Cenker; Jens Noerby Hansen
Original assignee: Man Diesel & Turbo Deutschland
Priority date: 2013-02-08
Filing date: 2013-02-08
Publication date: 2014-02-17
Also published as: CN103742218A; KR101525218B1; CN103742218B; JP2014152774A; KR20140101289A; JP5543040B1

Abstract

An exhaust valve arrangement for a large slow-running two-stroke uniflow diesel engine with crossheads and a with an exhaust valve (l) that can open between a closed and an open position for scavenging of the combustion chamber a gas spring (123) operatively connected to said exhaust valve (1), a hydraulic actuator (109) being operatively connected the exhaust valve (1), the hydraulic actuator (109) comprising a plunger (10') received in a bore (6) and defining an actuation chamber ( 60) between said bore ( 6) and said plunger (l0' ) for carrying out said opening stroke when said actuation chamber (60) is pressurized and for allowing said exhaust valve (l) to carry out the return stoke when said actuation chamber (60) is connected to tank, a source of high-pressure hydraulic fluid, a tank, an electronically controlled hydraulic control valve (117, 120) operatively connected to an electronic control unit (115), the actuation chamber ( 60) being selectively connectable to said source of high-pressure hydraulic fluid or to said tank via said electronically-controlled hydraulic control valve (117, 120), a hydraulic passageway (80, 85) connecting said actuation chamber (60) to said electronically-controlled hydraulic control valve (117,120), said hydraulic passageway (80,85,280) including a flow restriction (19) that is active during the last part of the opening stroke and the first part of the return stroke of said exhaust valve (1), and a bypass arrangement (117,121,195,197) for bypassing said flow restriction (19) in said hydraulic passageway (80, 85) at least during the first part of said return stroke.

Description

1 DK 177676 B1 EXHAUST VALVE ARRANGEMENT FOR A LARGE SLOW-RUNNING TWO-STROKE INTERNAL COMBUSTION ENGINE WITH CROSSHEADS The present application relates to an exhaust valve 5 arrangement for a large slow running two-stroke internal combustion engine with crossheads. More specifically, the present invention relates to an exhaust valve arrangement that includes a source of high-pressure hydraulic fluid connected to a hydraulic exhaust valve actuator via 10 electronically-controlled hydraulic valve. The hydraulic actuator includes an actuation chamber that is defined between the end of a bore and a reciprocating plunger or piston that is connected to the exhaust valve.

15 BACKGROUND ART

Large slow-running two-stroke uniflow diesel engines of the cross-head type, such as prime movers in marine vessels, are becoming increasingly larger.

Correspondingly, exhaust valves for such engines are 20 becoming larger. For the larger of these engines, the exhaust valves may be 1 to 2 meters high. The valve spindles of such exhaust valves may weigh several hundred kilos. For each engine cycle the exhaust valve must open and close in order to evacuate the combustion chamber of 25 the engine cylinder. For a large two-stroke diesel engines of the cross-head type in normal operation that may be from 60-200 openings and closings per minute. In order to prevent damage from the large weight of the valve spindle abutting on any stop or end surfaces, the 30 opening travel of the valve spindle must be braked and be brought to a stop before contact to any such stop surfaces. Therefore, an end of opening stroke damping arrangement is usually provided on such exhaust valves.

Such an end of opening stroke damping arrangement may 2 DK 177676 B1 take the form of a conical surface formed on a part of the valve spindle, the conical surface cooperating with a sidewall of a portion of a spindle bore to close of a hydraulic fluid supply to an actuation chamber. An 5 example of such a mechanism is shown in JP2004084670.

Such a conical surface must have a quite an extension in the longitudinal direction of the valve spindle in order to work properly, and precision in braking is lost if the temperature of the valve spindle changes, which may cause 10 a substantial change in the length of the valve spindle.

The temperature of an engine and the exhaust valve parts changes due to e.g. differences in engine load conditions, and especially during startup, where the engine goes gradually from a cold condition towards 15 operating temperature. Due to such temperature differences in the engine, the exhaust valve spindle expands and contracts, and expands and contracts in a different rate than the housing, in which the spindle is mounted. The larger the engine, the larger the exhaust 20 valve, and the larger the valve spindle gets. Therefore, also the expansion and contraction of the valve spindle is large, and may have an impact on the operating conditions of the exhaust valve, as explained above. Therefore the longer the conical surface, the larger the 25 risk of influencing the precision of the braking of the valve spindle during the end of the opening phase. Further, the end of opening stroke damping arrangement is also active during the first part of the return stroke of the exhaust valve and this has a negative influence on 30 the precision and reproducibility of the closing movement of the exhaust valve.

WO 2006108438 discloses a large slow-running diesel engine according to the preamble of claim 1.

3 DK 177676 B1

DISCLOSURE OF THE INVENTION

On this background, it is an object of. the present invention to provide an exhaust valve arrangement with a 5 damping arrangement for slowing down and stopping the exhaust valve at the end of the valve opening stroke, which solves or at least reduces the problems associated with the prior art.

10 This object is achieved by providing exhaust valve (1) arrangement for a large slow-running two-stroke uniflow diesel engine with crossheads and a plurality of cylinders, the exhaust valve arrangement comprising an exhaust valve that can open between a closed position 15 where the disk of the exhaust valve rests on a valve seat in a cylinder cover of a cylinder of the engine and an open position where the disk of the exhaust valve does not rest on the valve seat for scavenging of the -combustion chamber in the cylinder, the exhaust valve 20 thereby moving in an opening stroke and a return stroke, a gas spring operatively connected to the exhaust valve and the exhaust valve being resiliently biased towards the closed position by the gas spring, a hydraulic actuator operatively connected to a spindle of the 25 exhaust valve, the hydraulic actuator comprising a plunger received in a bore and defining an actuation chamber between the bore and the plunger for carrying out the opening stroke when the actuation chamber is pressurized and for allowing the exhaust valve to carry 30 out the return stoke when the actuation chamber is connected to tank, a source of high-pressure hydraulic fluid, a tank for return of hydraulic fluid, an electronically-controlled hydraulic valve operatively connected to an electronic control unit, the actuation 4 DK 177676 B1 chamber being selectively connectable to the source of high-pressure hydraulic fluid or to the tank via the electronically-controlled hydraulic valve, a hydraulic passageway connecting the actuation chamber to the 5 electronically-controlled hydraulic valve, the hydraulic passageway including a flow restriction that is active during the last part of the opening stroke and the first part of the return stroke of the exhaust valve, and a bypass arrangement for selectively bypassing the variable 10 flow restriction in the hydraulic passageway at least during the first part of the return stroke.

By providing an arrangement to bypass the restriction in the hydraulic passageway during the first part of the 15 return stroke of the exhaust valve, a slow and lagging portion of the return stroke that causes variations and undermines precision of movement can be avoided and thereby the closing moment of the exhaust valve can be controlled more precisely. Because the closing moment of 20 the exhaust valve is decisive for determining the compression pressure for the next cycle it is absolutely crucial that the closing moment is accurate and reproducible.

25 In an embodiment the bypass arrangement includes a bypass passageway including an electronically-controlled valve.

In another embodiment the bypass arrangement includes a bypass passageway including non-return valve.

30

In an embodiment the variable restriction includes one or more of axially directed slits (19) in the plunger that cooperate with a control edge that is provided in the bore.

5 DK 177676 B1

In an embodiment the hydraulic passageway connects to the actuation chamber via a port at the top or end of the actuation chamber or to a port in the side wall of the 5 bore.

In an embodiment the exhaust valve arrangement further comprises an electronic control unit connected to the hydraulically-controlled valve and to the hydraulically-10 controlled bypass valve, and the control arrangement being configured to open the hydraulically-controlled bypass valve during the portion of the return stroke where the variable restriction is active.

15 In an embodiment the electronically-controlled bypass valve is an integral part of the ectronically-controlled hydraulic valve.

In an embodiment the electronically-controlled valve is a 20 proportional type spool valve, that has one port and one control edge assigned to the electronically-controlled bypass valve function.

In an embodiment the restriction is formed by a narrow 25 bore in the plunger.

Further objects, features, advantages and properties of the exhaust valve according to the invention will become apparent from the detailed description.

30

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present description, the invention will be explained in more 6 DK 177676 B1 detail with reference to the exemplary embodiments shown in the drawings, in which: - Fig. 1, in a sectional view, shows an upper part of a 5 large two-stroke uniflow diesel engine of the cross head type; -Fig. 2, in a sectional view, shows an exhaust valve according to an example embodiment; - Fig 3, in a sectional view, shows details of an upper 10 part of the exhaust valve in Fig. 2; -Fig. 4, in a sectional view, shows a spindle extender of the spindle of the exhaust valve according to an example embodiment invention formed in an upper part of the exhaust valve in Figs. 2 and 3; 15 - Fig. 5, in a perspective view, shows the upper part of a spindle according to an example embodiment; -Figs. 6A-G, in sectional views, illustrates flow of hydraulic fluid in the actuator part of the exhaust valve during different phases of the spindle's 20 travel during an opening and closing cycle of the exhaust valve, where Fig. 6A shows the spindle in a top position when the valve is closed and getting ready to open, Fig. 6B shows the spindle in a portion during its downward motion, Fig. 6C shows 25 the spindle in a position as it enters into a braking phase of its downwards motion, Fig. 6D shows the spindle in its most extended position, i.e. when the exhaust valve is fully open, Fig. 6E shows the flow of hydraulic fluid at the beginning of the 30 closing of the exhaust valve, Fig. 6F shows the spindle in a position where a flow out of a braking chamber begins; and 7 DK 177676 B1 - Fig. 7 is a graph illustrating the movement of the exhaust valve with and without an arrangement according to the present invention.

5 DETAILED' DESCRIPTION OF PREFERRED EMBODIMENTS

In the following, the exhaust valve arrangement according to the invention will be described in relation to a large slow-running two-stroke unit flow combustion engine that 10 is provided with crossheads. The exhaust valve arrangement according to the invention will be described by the preferred embodiments.

Fig. 1 shows a cylinder 100 of the uniflow type, used in 15 large slow-running two-stroke uniflow diesel engines with crossheads. Large slow-running two-stroke uniflow diesel engines with crossheads usually have 3 to 16 cylinders arranged in line. Each cylinder 100 has scavenge air ports 102 located in an air box 103, which from a 20 scavenge air receiver (not shown) is supplied with scavenge air pressurized by, for example, a turbocharger (not shown). The internal combustion engine may be a propulsion engine in a ship or a stationary prime mover in a power plant.

25

An exhaust valve 1 is mounted centrally in the top of each cylinder 100 in a cylinder cover 124. At the end of an expansion stroke of the engine, the exhaust valve 1 opens before an engine piston 105 that is received in a 30 cylinder concerned passes down past the scavenge air ports 102, whereby the combustion gases in a combustion chamber 106 above the piston 105 flow out through an exhaust passage 107 opening out into an exhaust gas receiver 108 and fresh scavenging air or gas enters the 8 DK 177676 B1 combustion chamber inside the cylinder 100. The exhaust valve 1 closes again during the upward movement of the piston 105 at an adjustable moment that may depend on e.g. the desired effective compression ratio/compression 5 pressure for the subsequent combustion. During the closing movement, the exhaust valve 1 is driven towards its seat in the cylinder cover by a pneumatic spring 123.

Thus, the exhaust valve 1 is resiliently biased towards its seat by the pneumatic spring 123.

10

The exhaust valve 1 is opened by means of a hydraulically driven actuator 109. Pressurized hydraulic fluid, e.g. hydraulic oil, is supplied at high pressure through a pressure conduit 110 connecting a port 80 on the actuator 15 109 with a control port on the top surface of a distributor block 112 supported by a console 113. The console 113 is connected to a high-pressure conduit 114 for hydraulic fluid supplied from a common rail (not shown) , at a pressure which may, for example, be in the 20 range from 200 to 500 bar, such as 300 bar. The common rail may also serve as a source of high-pressure fluid for the fuel injection system.

The hydraulic fluid in the common rail may be used to 25 drive the valve actuator 109 directly, or indirectly via pressure amplifiers/separators that separate the hydraulic fluid for the valve actuator 109 from the hydraulic fluid in the common rail, which may be e.g. fuel oil. The pressure in the common rail fuel system 30 varies in dependence of the operating state of the engine such as running speed and load condition. Typically the pressure in the common rail fuel system for a large two-stroke diesel engine varies between 800 bar and 2000 bar.

9 DK 177676 B1

If a dedicated common rail for the valve actuators 109 is used, the hydraulic fluid can be supplied through a pumping station (not shown) from a storage tank (not shown), and the hydraulic fluid may, for example, be a 5 standard hydraulic oil, but preferably, the lubricating oil of the engine is used as hydraulic fluid, and the system is fed from the oil sump of the engine.

Each cylinder 100 of the engine may be associated with an 10 electronic control unit 115 which receives general synchronizing and control signals through wires 116 and transmits electronic control signals to a control valve 117 etc., e.g. through a wire 118, and to the pneumatic spring 123, e.g. through a wire 173. There may be one 15 control unit 115 per cylinder, or several cylinders may be associated with the same electronic control unit 115.

The electronic control unit 115 may also receive signals from an overall control unit common to all the cylinders (not shown).

20

Alternatively (not shown), the pneumatic spring 123 and/or the hydraulic control valve 117 may be controlled by a cam, i.e. mechanical-hydraulic control.

25 The hydraulic control valve 117 may be of any usual type, preferably a proportional valve, such as a spool valve.

As shown in Fig 3, an electronically-controlled proportional 6/3 way spool valve would be suitable for use with the present invention. The control valve 117 is 30 in the present example embodiment a so-called FIVA (Fuel Injection & Valve Activation) valve in the form of an electronically-controlled solenoid-operated proportional valve 117. In the present embodiment the control valve 117 is a 6/3 way spool valve with three lands, two ports 10 DK 177676 B1 that are connected to tank, a port 191 connected via a supply and return conduit to port 80 and a port 193 connected with to channel 85 via a return conduit 195 and a port 197 that establishes the fluidic connection 5 between channel 85 and conduit 195. The control valve includes a housing in which a main spool 62 is disposed, an electrically-driven pilot valve (not shown), an electronic regulator (not shown) and a linear position transmitter (not shown). The regulator receives a command 10 signal from the electronic control unit 115 and a feedback spool position signal from the linear position transmitter. The regulator controls the position of the spool in a well-known closed loop manner.

15 When opening of the exhaust valve 1 is desired, a control signal from the control unit 115 actuates the control valve 117 so that the high-pressure hydraulic fluid has free access to the pressure conduit 110 and thus to the hydraulic fluid supply port 80. When the exhaust valve 1 20 is to be closed, the control valve 117 is actuated again so that the high pressure in the conduit 110 is drained off by connection to return line 122. With the hydraulic actuator depressurized, the pneumatic spring 123 will force the exhaust valve 1 towards its closed position.

25

Fig. 2 . shows in more detail a section through the upper part of a cylinder 100 and an exhaust valve 1. The exhaust valve 1 is of the type used for large two-stroke uniflow diesel engine of the crosshead type e.g. as in 30 Fig 1.

The exhaust valve 1 has a spindle (or stem) 10 projecting upright from the valve disc 3, with a bottom or lower end n DK 177676 B1 12, an upper end 11 and a central portion 13. The spindle 10 is elongate in shape and has a longitudinal axis A.

In Fig. 2, the open position of the exhaust valve is 5 indicated by a valve disc 3' being shown in dotted line a distance D below the position of the valve disc 3 in the closed position, and in contact with a valve seat 4 that is integral with the cylinder cover 124. The central portion 13 of the spindle 10 supports a spring piston 125 10 securely mounted on the spindle so as to be pressuresealing and longitudinally displaceable in a pneumatic cylinder 126. Below the spring piston 125 there is a spring chamber 127 connected to a pressurized-air supply (not shown) via suitable valves 156, which keeps the 15 spring chamber filled with pressurized air at a predetermined minimum pressure of, for example, an overpressure of 4.5 bar. Thereby, a pneumatic spring 123 is provided, the pneumatic spring 123 providing an upward bias on the spindle 10, and urging the valve disk 3 20 towards the valve seat 4. Other air pressures can also be used, such as from 3 to 10 bar. The minimum pressure is selected according to the desired spring characteristic of the pneumatic spring 123. It is possible to interconnect the spring chambers 127 on several different 25 cylinders, but preferably each spring chamber 127 is separately cut off by a non-return valve at the pressurized-air supply. The pressurized air in the spring chamber 127 creates a persistent upward force on the spring piston 125, and thereby on the spindle 10. Thus 30 the valve disk 3 is permanently urged towards the valve seat 4, i.e. in an upward direction. The upward force increases when the spring piston 125 is displaced downwards by the hydraulic valve actuator 109 (see below) and compresses the air in the spring chamber 127 that is 12 DK 177676 B1 prevented from flowing out by of the non-return valve 156.

A housing 128 defines a cavity 129 around and above the 5 pneumatic spring 123. The cavity is connected to a drain (not shown) so that the cavity has atmospheric pressure.

The hydraulic valve actuator 109 is constructed from an actuator cylinder 131 and an actuator part 10' of the 10 spindle 10. The actuator cylinder 131 may be supported by the top of the housing 128, or as shown, actuator cylinder 131 and housing 128 are formed in one integral piece.

15 Now referring to Fig. 3, the actuator part 10' of the spindle 10 is received in a central bore 6 in the actuator cylinder 131, the actuator cylinder forming a stationary housing for the valve actuator 109, the central bore 6 forming an upper part of the spindle bore 20 5. The central bore 6, is closed at the top of the actuator cylinder 131 by a top closure 132, and is open to the bottom of the actuator cylinder 131, such that the central bore 6 communicates with the remainder of the spindle bore 5. The central bore 6 is coaxially arranged 25 with the spindle bore 5 in the housing 128 and further in the lower parts of the exhaust valve 1. The actuator part 10' of the spindle forms a plunger in the central bore 6.

Now referring to Fig. 4, showing a close-up on the top of 30 the valve actuator 109 of the exhaust valve 1, the central bore 6 of the actuator cylinder 131 is divided into coaxial portions having different diameters (or cross sectional areas): An uppermost portion 6' has the largest diameter; a middle portion 6' ' has an 13 DK 177676 B1 intermediate diameter; and a lowest portion 6' '' has the narrowest diameter. Between the uppermost portion 6' and the middle portion 6' ' a first upward-facing ledge 7 is formed. Between the middle portion 6' ' and the lowest 5 portion 6''' a second upward-facing ledge 8 is formed. As shown in e.g. Figs. 3 and 6A, the lowest portion 6' ' ' of the central bore 6 extend to a bottom end of the valve actuator 109, where the valve actuator 109 is connected to the pneumatic spring 123. The lowest portion 6' ' ' of 10 the central bore 6 is closed by a bottom closure 133 (see Fig. 3). The bottom closure 133 has an aperture receiving a second reduced diameter section 16'' of a lower portion of an actuator part 10' of the spindle 10. Referring to Fig. 3, in the lowest portion 6' ' ' of the central bore 6 15 two chambers are formed. The chambers are in the form of a first widened portion 65' of the lowest portion 6'' ' of the central bore 6, and a second widened portion 65' ' of the lowest portion 6''' of the central bore 6. The first widened portion 65' is formed above the second widened 20 portion 65''. The first widened portion 65' communicates with a channel 85 through a port 83, the channel 85 being formed in the actuator cylinder 131. The second widened portion 65' ' communicates with the pressure conduit 110 through a port 80. Between the first widened portion 65' 25 and the second widened portion 65'', an intermediate portion 66 is formed, the intermediate portion 66 being a part of the lowest portion 6''' of the central bore 6 and having the same diameter or cross-sectional area. The intermediate portion 66 has an upper edge 66' (see Fig.

30 6A) , a wall 66' ' with a surface parallel to a surface of the lowest portion 6' ' ' of the central bore 6, and a lower edge 66'''.

14 DK 177676 B1

As may be appreciated from Fig. 5, the actuator part 10' of the spindle 10 has an upper portion 14. The upper portion 14 has a diameter, dl. The diameter, dl, is adapted to slide in the lowest portion 6' '' of the 5 central bore 6. The actuator part 10' further has a lower portion divided into three sections, a first reduced diameter section 16', a sealing section 16 having the same diameter, dl, as the upper portion 14, and a second reduced diameter section 16'' below sealing section 16.

10 The first reduced diameter section 16' and the second reduced diameter section 16'' may have the same diameter (or cross-sectional area if not cylindrical), or they may have different diameters, but they are both smaller than the diameter of the upper portion 14 and the sealing 15 section 16. The lowest located second section 16'' is connected to the central portion 13 of the spindle 10 in the pneumatic spring 123.

The sealing section 16 (together with the bottom closure 20 133) seals the central bore 6 from leaking hydraulic oil to the chamber or cavity 129 (where atmospheric pressure prevails).

An upper annular surface 15 is formed at an upper end 14' 25 of the upper portion 14 of the actuator part 10' of the spindle 10. A downward-facing ledge 18 is formed between a lower end 14'' of the upper portion 14 and the first reduced diameter section 16' . An upward-facing ledge .17 is formed between the first reduced diameter section 16' 30 and the section 16. A downward-facing ledge 17' is formed between the section 16 and the second reduced diameter section 16''.

15 DK 177676 B1

At least one slit 19 is formed in an outer surface at the lower end 14'' of upper portion 14. The slit or slits 19 are elongate with a longitudinal direction parallel to a longitudinal axis A of the spindle 10, and formed as 5 depressions or grooves in lower end 14' of upper portion 14. Each slit 19 has an upper end 19' and a lower end 19''. Each slit 19 has an increasing depth towards its lower end 19'' and the downward-facing ledge 18, into which the slit 19 opens. One slit may be provided, or 10 there may be a set of slits arranged around a periphery of the upper portion 14. Preferably, there are 3-20 slits 19. When there is more than one slit 19, the slits may all be of the same length (from upper end 19' to lower end 19' ' in the direction of axis A) . In an alternative 15 embodiment (not shown), the slits 19 have different lengths .

In another embodiment (not shown) , the slits 19 may alternatively be formed in a wall of the intermediate 20 portion 66 being a part of the lowest portion 6' '' of the central bore 6. The slit or slits 19 are elongate with a longitudinal direction parallel to a longitudinal axis A of the spindle 10, and formed as depressions or grooves in the intermediate portion 66. Each slit 19 has an upper 25 end 19' and a lower end 19'' . Each slit 19 has an increasing depth towards its upper end 19' and the upper edge 66' of the intermediate portion 66, and the first widened portion 65' into which the slit 19 opens. One slit may be provided, or there may be a set of slits 30 arranged around a periphery of the intermediate portion 66. Preferably, there are 3-20 slits 19. When there is more than one slit 19, the slits may all be of the same length (from upper end 19' to lower end 19'' in the DK 177676 B1 lo direction of axis A) . In alternative embodiment (not shown), the slits 19 have different lengths.

In a further embodiment (not shown), slits 19, as 5 described above are formed in the intermediate portion 66 and in the lower end 14'' of the upper portion 14 of the spindle 10.

In this application, by slit, groove and depression, is 10 understood, a formation with a bottom surface formed repressed with respect to another surface. Here the other surface is an outer surface of the cylindrical upper portion 14 of the spindle 10. In case the slits 19 are formed in the intermediate portion 66 of the lowest 15 portion 6' ' ' of the central bore 6, the other surface is the wall of the bore 6 at that location.

A piston 90 is arranged slideably in the central bore 6 (forming the upper part of the spindle bore 5). The 20 piston 90 has a cylindrical main part 91 and a collar 92 arranged above the main part 91. The piston 90 has a central bore 90' adapted for slidably receiving the upper portion 14 of the spindle 10 at an upper end 11 thereof.

The collar 92 has a larger diameter (or cross sectional 25 area) than the main part 91 of the piston 90. The diameter of the main part 91 is adapted with a minute clearance to be slideably arranged in the middle portion 6' ' (alternatively called intermediate portion 6' ' ) of the central bore 6. The diameter of the collar 92 is 30 adapted with a minute clearance to be slideably arranged in the uppermost portion 6' of the central bore 6. A downward-facing internal ledge 93 is formed between the collar 92 and the main part 91 in the central bore 90' of the piston 90. The internal ledge 93 is adapted for 17 DK 177676 B1 engagement with at least an outer part of an upper annular surface 15 of the spindle 10. The piston 90 further has an upward-facing upper surface 94 formed on the collar 92. This upper surface 94 on the collar 92 is 5 ring-shaped . like the upper annular surface 15 of the spindle 10. The surface area of the upper surface 94, however, is considerably larger that the area of the upper annular surface 15 of the spindle 10.

10 A downward-facing external ledge 95 is formed between the collar 92 and the main part 91 on an external surface of the piston 90. The main part 91 further has a lower surface 96. This lower surface 96 is ring-shaped or annular.

15 A damping chamber 81 is formed in the top closure 132, the damping chamber 81 opening into an uppermost portion 6' of the central bore 6. The damping chamber 81 provides . an entrance for hydraulic fluid during the opening phase 20 of the exhaust valve 1, an exit during the closing of the exhaust valve, and it brakes the upward movement of the spindle (see further below). The damping chamber 81 opens into the central bore 6 in actuator cylinder 131.

25 The piston 90, as mentioned, may slide with respect to the upper portion 14 at the upper end 11 of the spindle 10, and with respect to the portions 6', 6'' and 6''' of the central bore 6.

30 A variable volume valve actuation chamber 60 is defined between the upper portion 6' of the central bore 6, a downward-facing surface 132' of the top closure 132, the damping chamber 81, the upward-facing top surface of the piston 90, and the upper end 11 of the spindle 10. The 18 DK 177676 B1 variable volume valve actuation chamber 60 also includes the damping chamber 81. Preferably, the upper portion 6' of the central bore 6 and the damping chamber 81 is in permanent fluid communication via a minute clearance 5 between the lowest portion of conical surface 32 and the wall of damping chamber 81. Alternatively or additionally a set of slits 39 allow permanent fluid communication between the upper portion 6' of the central bore 6 and the damping chamber.

10

As mentioned, hydraulic fluid is supplied to and discharged from the valve actuator 109 via a port 80.

Port 80 is in connection with the pressure conduit 110, the end 110' of which can be seen in Fig. 6A. Via the 15 pressure conduit 110, port 80 is connected alternatingly with the high-pressure source and a return line 122, by the control valve 117.

The variable volume valve actuation chamber 60 is 20 connected via ports 82 in damping chamber 81 via conduits 85, see Fig. 6A, and ports 83 to a first pressure chamber 65. The first pressure chamber 65 is defined between - the lowest portion 6''' of the central bore 6, - a portion 14 of the upper part 10' of the spindle 10 25 - the first widened portion 65' of the central bore 6, - the second widened portion 65' ' of the central bore 6, and - a sealing section 16 of the spindle 10 formed between an upper 16' and a lower 16'' reduced 30 diameter section of the spindle 10.

The supply port 80 connects to second widened portion 65' ' . Second widened portion 65' ' connects to the first 19 DK 177676 B1 widened portion through the potion 6'''' (see Fig. 3) of the central bore 6. At least one port 83 connects first widened portion. 65' to channels 85 (one channel 85 per port 83) . Each channel 85 connects to damping chamber 81 5 through a port 82, between channels 85 and damping chamber 81.

Referring again to Fig 4, a slider 30 is formed in a bore 20 in the upper end 11 of the spindle, the slider being 10 biased in the upwards direction by a spring 40, and being slideable in a lengthwise direction of the bore 20 (parallel to axis A) . The slider 30 has an upward-facing surface 31, and a conical surface 32 (see Fig. 5) adapted for cooperation with the above-mentioned damping chamber 15 81 to brake the upwards travel of the spindle 10 during the closing of the exhaust valve. The slider 30 acts as a spindle length adjustment mechanism. In other embodiments, the upper end 11 of the spindle 10 may alternatively be formed without a spindle length 20 adjustment mechanism, such that spindle has as fixed length. In this case (not shown) the upward-facing surface 31 may be flush with the annular surface 15, a corresponding conical surface 32 being formed directly on an upper end on the upper portion 14 of the spindle 10.

25

With reference to Figs. 6A-H an opening and closing cycle of the exhaust valve will be described. In this embodiment the electro-hydraulic control valve is formed by two independent electro-hydraulic control valves 120 30 and 121. Electro-hydraulic control valve 120 is configured to selectively connect port 80 to the source of pressure or to tank under command from an electronic control unit and electro-hydraulic control valve 121 is configured selectively to connect port 197 to tank or to 20 DK 177676 B1 close connection of port 197 to tank under command from the electronic control unit.

When the exhaust valve 1 is to be opened to evacuate 5 combustion or exhaust gas from the combustion chamber 106, the pressure in the combustion chamber 106 is very high. Therefore, a large force is needed to open the exhaust valve 1 during the initial downward travel of the valve disc 3 and valve spindle 10. The piston 90 aids in 10 this initial phase by increasing the effective area of the pressure surface of the valve actuator 109 as will be described below.

To open the exhaust valve 1, the control valve 117 15 supplies high-pressure fluid to the port 80, and the hydraulic fluid pressurizes the first pressure chamber 65 and the variable volume valve actuation chamber 60 (via channel 85) . The flow is indicated by arrows in Fig. 6A.

In the first pressure chamber 65 the hydraulic fluid acts 20 on an upward-facing ledge 17 between the upper reduced diameter section 16' and the section 16 of the spindle 10. More details about the first pressure chamber 65 and its function are provided below.

25 The inflow of hydraulic fluid through the fluid connection provided by channel 85 will increase the pressure in the variable volume valve actuation chamber 60 comprising the damping chamber 81 and the uppermost portion 6' of the central bore 6. The pressure acts on 30 the surface 31 of the slider 30, the upper surface 15 of the spindle 10 and on the upper surface 94 of the piston 90 to move the spindle 10 together with the piston 90 in a downward direction.

21 DK 177676 B1

The arrow in Fig. 6B indicates that there is an inflow of hydraulic fluid into the first pressure chamber 65, increasing the pressure therein. The pressure acts on the upward-facing ledge 17 on the section 16 of the spindle 5 to force the spindle in the downwards direction to open the exhaust valve 1.

The hydraulic fluid increases the pressure in the variable volume valve actuation chamber 60, the pressure 10 acting on the upper surface 94 of the piston 90, the upper annular surface 15, and the upper surface 31 of the upper part 11 of the spindle 10 (as well as on the upward-facing ledge 17). The downward-facing internal ledge 93 abuts on a portion of the upper annular surface 15 15 of the spindle 10. This will force the spindle 10, and the piston 90 in a downwards direction (See Fig. 6B).

After traveling a distance in the downwards direction, the downward-facing external ledge 95 of the piston 90 20 will reach and stop before abutment on the upward-facing ledge 7 between the uppermost and middle portions 6', 6'' of the central bore 6, see Fig 6B.

A groove 99 (see Fig. 4) formed as an elongate 25 indentation in the bore uppermost portion 6'' of the central bore 6, and parallel to the elongate axis B allows passage of hydraulic fluid between a space above the piston 90 and a space below the piston 90. As the piston 90 is forced downward (the area of the lower 30 surface 95 being less than the area of the upward-facing surface 94), hydraulic fluid is passed from below to above the piston 90. The groove or grooves 99 ends a distance above the ledge 7 formed between the uppermost and middle portions 6', 6'' of the central bore 6. When 22 DK 177676 B1 the downward facing external ledge 95 of piston 90 passes the bottom of the groove or grooves 99, hydraulic fluid is prevented from passing from the space below the piston 90 to space above. This will cause a pressure increase in 5 the space below the piston 90 that will slow down and eventually stop the downward movement of the piston 90. Thereby, a small hydraulic fuel pressure chamber is formed, used to brake the downwards travel of the piston 90, this chamber acting somewhat like a hydraulic spring.

10

Thus the downward movement of the piston 90 is stopped while the spindle 10 continues its downward movement, see Fig. 6C. Further downwards travel of the piston is prevented. In Fig. 6C, the piston 90 still rests by the 15 upward-facing ledge 7, while the spindle 10 has continued its downwards motion. The upper portion 14 of the actuator part 10' has moved down relative to the piston 90.

20 Thus, the piston 90 has provided a larger area for the pressure in the variable volume valve actuation chamber 60 to act upon during the opening of the exhaust valve, thereby acting as an accelerating mechanism, and aiding in opening the exhaust valve against the high pressure of 25 the combustion chamber 106. Once the valve disc 3 has been moved away from the valve seat 4, the pressure in the combustion chamber 106 is reduced by the combustion gasses leaving the chamber 106 through the exhaust conduit 107. Therefore, in order to keep the exhaust 30 valve 1 moving in the downwards direction to open fully, a much smaller force is needed, than during the initial phase of opening. Thus, after the piston 90 has been stopped, the pressure in the variable volume valve actuation chamber 60 will only act on the upper annular 23 DK 177676 B1 surface 15 and the upper surface 31 of the upper part 11 of the spindle 10 (here the upper surface 31 is provided on slider 30).

5 Thereby, the spindle 10 will continue its downwards motion until the downward-facing ledge 18 on the upper portion 14 of the spindle 10 cuts off the hydraulic fluid flow to the variable volume valve actuation chamber 60, and the spindled 10 starts to slow down and stop. This 10 will be explained in further detail below.

During the downward travel of the spindle 10 during the opening phase of the exhaust valve 1, the downward-facing ledge 18 on the upper portion 14 of the spindle 10, 15 passes an upper edge 66' on an intermediate portion 66 of the central bore formed between the upper and lower widened portions 65' and 65''. The situation is illustrated in Fig. 16C. The passing of the upper edge 66' will start to cut off the flow to the channel 85 and 20 thereby to the variable volume valve actuation chamber 60. The slit or slits 19 formed in the lower end of upper portion 14 of the spindle 10 will allow a flow to the variable volume valve actuation chamber 60 until the upper end 19' of the slit 19 has passed the upper edge 25 66' on the intermediate portion 66 of the central bore.

From the lower end 19' ' to the upper end 19' of the slit 19, the slit 19 thus provides a gradually diminished flow area to the variable volume valve actuation chamber 60.

In Fig. 6C this is illustrated by the shortened arrows 30 303. The gradually reducing flow to the variable volume valve actuation chamber 60 will cause a braking of the downward movement of the spindle 10, as the pressure in the variable volume valve actuation chamber 60 is 24 DK 177676 B1 balanced by the pressure provided by the pneumatic spring 123 that acts in the upward direction.

In Fig. 6D it is shown how the upper end 19' of the slit 5 19 has passed the upper edge 66'. There is no flow to the variable volume valve actuation chamber 60. Further, the spindle 10 has traveled a short further distance downwards, such that the downward-facing ledge 17' on section 16 of the spindle 10 is close to abutment on the 10 bottom closure 133. The spindle 10 has been braked and brought to a stop. A pressure is still working on the ledge 17 (as indicated by arrow 304 in Fig. 6D) and in the variable volume valve actuation chamber 60 to balance the pressure provided by the pneumatic spring 123, and to 15 maintain the exhaust valve 1 open, until the combustion chamber 106 has been fully evacuated.

The slits 19 have been shown to provide a huge improvement over the prior art solutions for braking the 20 downward movement of the spindle during the opening of the exhaust valve 1. The application of slits 19 rather than a conical face has further reduced the vibration of the exhaust valve 1 when in the fully opened position.

25 Fig. 6E shows the situation in the instant where the pressure is discontinued and just before the spindle will start its upward movement due to the pressure provided by the pneumatic spring 123. The pressure on the ledge 17 is reduced. Flow between the variable volume valve actuation 30 chamber 60 and the port 80 is still prevented by the upper portion 14 of the spindle 10 still blocking the chamber 65'.

DK 177676 B1

Zd

In order to close the exhaust valve 1, when the combustion chamber 106 has been scavenged, as shown in Fig. 6F, the pressure of the hydraulic fluid supply is discontinued by the control valve 117 (or the control 5 valves 120 and 121) changing the position of the electro-hydraulic control valve 117 so that the port 80 and port 197 are connected to tank, and allowing the hydraulic fluid to flow back through the ports 197 and 80. The pneumatic spring 123 will force the spindle 10 upwards 10 thereby pressing out the hydraulic fluid in the secondary pressure chamber 65 and the variable volume valve actuation chamber 60. The flow back to tank meets relatively little resistance from the moment that the control valve 117 (or the control valves 120 and 121) 15 changes position since the return flow does not have to pass the flow restriction posed by the slits 19 (a small portion of the flow will still pass via the slits but the bulk of the flow back to tank will go via port 197 and conduit 195, especially at the first part of the return 20 stroke of the exhaust valve where the restriction posed by the slits is strongest).

In Fig. 6G, the ledge 18 has passed out of chamber 65' providing full access for a flow out of the variable 25 volume valve actuation chamber 60 via both ports 80 and 197, as indicated by the longer arrows 306 in the figure (Fig. 6G).

In the situation shown in Fig. 6F, only the spindle 10 30 itself is moving upwards, the piston 90 still rests by the upward-facing ledge 7. Thus only the upper surface 31 and annular surface 15 push the hydraulic fluid out of the variable volume valve actuation chamber 60.

26 DK 177676 B1

As the spindle 10 moves upwards, and as shown in Fig. 6G, the upper annular surface 15 of the spindle 10 will eventually abut against the downward-facing internal ledge 93 of the piston 90, and force the piston 90 in 5 unison with the spindle 10 to move from its lower, rest (where external ledge 95 of piston 90 rests by upward · facing ledge 7) in an upward direction.

Since the pistons upper surface 94 is larger than the 10 combined surfaces 15 and 31, a much larger surface area will now act on the hydraulic fluid in the variable volume valve actuation chamber 60. This will cause a braking of the upward travel of the spindle 10.

15 The upward motion of the spindle 10 will brake and eventually stop when the conical surface 32 at the top of the upper part 11 of the spindle 10 enters dampening chamber 81, and gradually closes the fluid connection between the upper portion 6' of the central bore 6 and 20 the damping chamber 81. When the conical surface 32 plunges into the dampening chamber most of the residual kinetic energy is absorbed by forcing the hydraulic liquid out of the dampening chamber through the port 80, and an upper surface 33 of the upper part 11 of the 25 spindle 10 abuts gently on the downward-facing surface 132' of the top closure 132. Fig. 6H shows the situation when the spindle 10 has reached its top position, and the exhaust valve 1 is closed and' ready for a new opening and closing cycle.

30 A set of vanes 214 on a portion of the valve spindle 10, which is located in the exhaust conduit 107 forces the spindle 10 to rotate when exhaust gas flows through the exhaust conduit 107, i.e. when the exhaust valve 1 is 27 DK 177676 B1 open. Thereby the spindle 10 will rotate at least a little for every opening of the exhaust valve. Thereby, a more even wear of the valve disc 3, the valve seat 4 and the abutment ledges of the spindle 10 and spindle bore 5 5 is secured.

Fig 7. Shows a graph illustrating the opening and closing movement of the exhaust valve 1. The movement of the exhaust valve is represented on the vertical axis and 10 time is represented on the horizontal axis.

The interrupted line represents the movement of the exhaust valve 1 without using the present invention, i.e. this is the curve where the hydraulic fluid that is to be 15 evacuated from the actuation chamber 60 needs to go through the restriction posed by the slits 19 during the first part of the closing movement of the exhaust valve.

This causes a delay during the start of the opening movement of the exhaust valve. At t=T0 the electronically-20 controlled hydraulic valve 117 initiates the valve opening phase by changing position under command from the electronic control unit 115 so as to connect the actuation chamber to the source of high-pressure fluid.

At t=Tc the electronically-controlled hydraulic control 25 valve 117 initiates the valve closing phase by changing position on the command from the electronic control unit 115 so as to connect the actuation chamber 60 to tank.

The restriction to the flow during the first part of the closing moment slows down the opening movement and also 30 negatively affects the reproducibility of the closing movement, which means that the actual closing moment of the exhaust valve cannot be accurately determined by controlling the moment in time where the electronically-controlled hydraulic control valve 117 initiates the 28 DK 177676 B1 closing phase. However, it is crucial to control the precise closing moment of the exhaust valve in order to accurately control the subsequent compression pressure.

5 The uninterrupted line represents the movement of the exhaust valve 1 with the use of the present invention, i . e. with an arrangement for bypassing the restriction in the hydraulic passageway that connects the actuation chamber to tank during the first part of the closing 10 stroke of the exhaust valve. As can be seen, there is substantially no delay in the opening movement of the exhaust valve directly after t=Tc. The closing movement of the exhaust valve has also turned out to be much more reproducible, and thus the accuracy of the closing moment 15 of the exhaust valve can be accurately controlled by controlling the moment where the closing movement of the exhaust valve starts.

In another example embodiment of the invention (not 20 shown) that is essentially identical to the embodiment described with reference to Figs. 1 to 6 the flow restriction that is active during the last part of the opening stroke and the first part of the return stroke is not formed by slits in the stem of the exhaust valve 1.

25 Instead, the restriction is formed by a narrow bore in the plunger. The plunger is arranged at the end of the valve spindle. The plunger is provided with a recess that opens towards the actuation chamber. An electronically-controlled hydraulic control valve 30 connects the actuation chamber selectively to tank or to a source of high pressure hydraulic fluid via a channel that cooperates with a radial bore 285 that is formed in the plunger and connects the radially outer surface of the plunger with the recess. The electronically- 29 DK 177676 B1 controlled hydraulic control valve is connected to an electronic control unit. A port connects to the actuation chamber and is not blocked by the plunger during the opening stroke of the exhaust valve. The port is 5 connected to an electronically-controlled bypass valve via a conduit. When the electronically-controlled bypass valve 221 is in its open position it connects the conduit to tank. Under command from the electronic control unit, the electronically-controlled bypass valve connects the 10 actuation chamber to tank during the first part of the return stroke of the exhaust valve. Thus, the first part of the return stroke of the exhaust valve is not hindered by the flow restriction posed by bore, and the first part of the return stroke is therefore reproducible and quick.

15

The pneumatic spring 123 described above may in an embodiment be replaced by a return stroke pressure chamber and a piston surface area that urges the first piston to the retracted position. This embodiment (not 20 shown) will require slightly modified control valve that is able to supply pressurized hydraulic fluid to the pressure return stroke chamber for urging the piston to the retracted position. The same principles as described above can be used to control the pressure in the return 25 stroke pressure chamber relative to the position of the first piston.

Although the teaching of this application has been described in detail for purpose of illustration, it is 30 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 teaching of this application.

( 30 DK 177676 B1

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 single processor or other unit may . fulfill the functions 5 of several means recited in the claims.

Claims

2. Udstødsventilanordning ifølge krav 1, hvor omløbsanordningen indbefatter en omløbspassage (195) indbefattende en elektronisk styret ventil (117, 121).Exhaust valve assembly according to claim 1, wherein the bypass means includes a bypass passage (195) including an electronically controlled valve (117, 121).

3. Udstødsventilanordnirig ifølge krav 1, hvor restriktionen er dannet ved en snæver boring i stemplet.Exhaust valve assembly according to claim 1, wherein the restriction is formed by a narrow bore in the piston.

4. Udstødsventil- (1) anordning ifølge krav 1 eller 2, hvor den variable restriktion indbefatter én eller flere aksialt orienterede spalter (19) i stemplet - 3 - DK 177676 B1 (10'), der samarbejder med en fremspring 66'', der er tilvejebragt i boringen (6).Exhaust valve (1) device according to claim 1 or 2, wherein the variable restriction includes one or more axially oriented slots (19) in the piston (3) cooperating with a projection 66 '', provided in the bore (6).

5. Udstødsventilanordning ifølge krav 1 eller 3, hvor den hydrauliske passage (80, 85) er forbundet med aktiveringskammeret (60) via en åbning (81) i det øvre eller enden af .aktiveringskammeret eller med en åbning (297) i aktiveringskammerets (60) sidevæg.Exhaust valve assembly according to claim 1 or 3, wherein the hydraulic passage (80, 85) is connected to the actuation chamber (60) via an opening (81) in the upper or end of the actuation chamber or to an opening (297) in the actuation chamber (60). ) sidewall.

6. Udstødsventilanordning ifølge krav 2, hvilken udstødsventilanordning endvidere omfatter en elektronisk styreenhed (115), der er forbundet med den elektronisk styrede hydrauliske ventil (117, 120) og med den hydraulisk styrede omløbsventil (121), og hvor den elektroniske styreenhed (115) er konfigureret til at åbne den hydraulisk styrede omløbsventil (121) under delen af returvandringen, hvor restriktionen er aktiv.Exhaust valve assembly according to claim 2, further comprising an electronic control unit (115) connected to the electronically controlled hydraulic valve (117, 120) and to the hydraulically controlled bypass valve (121), and wherein the electronic control unit (115) is configured to open the hydraulically controlled bypass valve (121) during the portion of the return trip where the restriction is active.

7. Udstødsventilanordning ifølge krav 2, hvor den elektronisk styrede omløbsventil (121) er en integrerende del af den elektronisk styrede hydrauliske ventil (117) .Exhaust valve assembly according to claim 2, wherein the electronically controlled bypass valve (121) is an integral part of the electronically controlled hydraulic valve (117).

8. Udstødsventilanordning ifølge krav 1, hvor den elektronisk styrede hydrauliske styreventil (117) er en stempelventil af den proportionelle type, der har én åbning og én styrekant til den elektronisk styrede omløbsventilfunktion.Exhaust valve assembly according to claim 1, wherein the electronically controlled hydraulic control valve (117) is a proportional type piston valve having one aperture and one control edge for the electronically controlled bypass valve function.

9. Udstødsventilanordhing ifølge krav 1., hvor restriktionen er dannet ved en radial passage, der forbinder den radiale ydre overflade af stemplet 10' med en aksial indskæring i stemplet 10', hvilken aksial indskæring er åben til aktiveringskammeret (60) .Exhaust valve assembly according to claim 1, wherein the restriction is formed by a radial passage connecting the radial outer surface of the piston 10 'to an axial cut in the piston 10', the axial cut open to the actuating chamber (60).