DK177481B1

DK177481B1 - Gas exchange valve for internal combustion engine

Info

Publication number: DK177481B1
Application number: DKPA201200208A
Authority: DK
Inventors: Paul Cenker
Original assignee: Man Diesel & Turbo Deutschland
Priority date: 2012-03-27
Filing date: 2012-03-27
Publication date: 2013-07-08
Also published as: CN103362585B; DE102013102660A1; DE102013102660B4; JP5536921B2; KR20130110036A; JP2013204586A; KR101423628B1; CN103362585A

Abstract

The invention relates to a gas exchange valve (1) for a combustion engine said gas exchange valve (1) comprising a spindle bore (5), a valve spindle (10) received in said spindle bore (5), a damping chamber (81), and a variable volume valve actuation chamber (60) arranged in the upper part of said spindle bore (5) said valve spindle (10) comprising an upper end (11) provided with damping means (32) adapted for cooperation with said damping chamber (81) for damping movement of the valve spindle (10) during closing of the exhaust valve, a longitudinal axis (A), and a compensation member (30) provided at said upper end (11), the compensation member (30) being slideable between a compressed position and an extended position along the longitudinal axis (A); and a spring (40) biasing said compensation member (30) towards said extended position; wherein a compensation chamber (50) is arranged in the upper part of said spindle, said compensation chamber (50) being in permanent fluid communication with the variable volume valve actuation chamber (60) arranged in the upper part of said spindle bore (5) through an orifice (70) formed through the an upper surface (31) of the compensation member (30)

Description

x DK 177481 B1

A GAS EXCHANGE VALVE FOR A COMBUSTION ENGINE

The present invention relates to a self-adjustable damper 5 for an exhaust valve top actuator for a large two stroke diesel engine.

BACKGROUND ART

In large two-stroke diesel engines of the cross-head 10 type, the exhaust valves are also correspondingly large, for some engines up the about 2 meters in height. In such large structures, the influence of material temperature has a measurable impact on the dimension of the structure that may influence the function of the structure.

15 Consequently, the temperature of the valve spindle and valve housing of an exhaust valve has an influence on the length of the valve spindle. The valve spindle length in turn has·an impact on the precision of the working of the valve. Exhaust valves are equipped with means for damping 20 the final travel of the valve spindle during the closing of the exhaust valve, such means often being provided at the top of the valve spindle. These damping means are provided in order to prevent or reduce wear and noise due to abutment of stop surfaces provided on the top of the 25 spindle and on the housing, and due to the abutment between the valve and the valve seat, as well. If the valve spindle, due to temperature dependent expansion, becomes too long there is a risk that the valve will not fit tightly with the valve seat, causing the combustion 30 chamber to leak. Further, the top of the valve stem may pound the top of the valve stem bore, causing increased wear and noise problems. If the valve is too short the damping of the closing of the valve will not function 2 DK 177481 B1 correctly, and the wear on the valve and valve seat will increase, and the hammering will cause a noise problem.

The temperature of an engine changes due to e.g.

5 differences in engine load conditions, and especially during startup, where the engine goes from a cold condition, and gradually towards operating temperature.

Due to such temperature differences in the engine, the 10 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 valve, and the larger the valve spindle gets. Therefore, also the expansion and 15 contraction of the valve spindle is large, and may have an impact on the operating conditions of the exhaust valve, as explained above. The length of the exhaust valve spindle is adapted to the main operating conditions of the' engine. In large engines, therefore you must 20 either accept that during certain engine operating conditions (temperatures), the exhaust valves operate in a less than optimal way, or certain measures may be taken in order to compensate for the spindle length difference.

Such measures are usually in the form of complicated 25 systems arranged in a joint of the valve stem or in connection with the valve closing damping (breaking) mechanism, which is often arranged at the top of the valve spindle. Such mechanisms are often complicated in construction using ball valves and bellows that may 30 easily break and require short interval maintenance and several pressure chambers with different pressure needing separate sources. Also known in the art are various spring mechanisms for adjusting the length of the stem.

Such mechanisms are not adjustable without active 3 DK 177481 B1 control. Examples are known from US 20060283411, FR 2674570, and DE 195 29 155 US 20060283411 discloses a gas exchange valve according to the preamble of claim 1.

5 DISCLOSURE OF THE INVENTION

On this background, it is an object of the present invention to provide an exhaust valve having a spindle the overall length of which is automatically and 10 passively adjustable. It is also an object of the invention to provide a simple, virtually maintenance-free, mechanism for automatically and passively adjusting the length of a valve stem.

15 This object is achieved by providing a gas exchange valve for a combustion engine said gas exchange valve comprising - a spindle bore, - a valve spindle received in said spindle bore, 20 - a damping chamber, and - a variable volume valve actuation chamber arranged in the upper part of said spindle bore said valve spindle comprising - an upper end provided with damping means adapted for 25 cooperation with said damping chamber for damping movement of the valve spindle during closing of the exhaust valve, - a longitudinal axis, and - a compensation member provided at said upper end, 30 the compensation member being slideable between a compressed position and an extended position along the longitudinal axis; and ( 4 DK 177481 B1 - a spring biasing said compensation member towards said extended position; wherein a compensation chamber is arranged in the upper part of said spindle, said compensation chamber being in 5 permanent fluid communication with the variable volume valve actuation chamber arranged in the upper part of said spindle bore through an orifice formed through the an upper surface of the compensation member.

10 Such a gas exchange valve may advantageously be an exhaust valve. Further such gas exchange valves may be particularly useful in slow running large two-stroke uniflow diesel engines of the cross-head type.

15 In an embodiment, said compensation chamber has a maximum volume, said orifice has dimension and shape, and said spring applies a predetermined upward force on the compensation member, and wherein the volume of said compensation chamber, the shape and dimension of the 20 orifice and the upward force of the spring is adapted to provide a close fit of the damping means adapted for cooperation with said damping chamber in response to temperature changes of the gas exchange valve.

25 In a further embodiment, said compensation chamber is arranged at least between said compensation member and the upper end of said spindle.

In a further embodiment said compensation member is 30 received in a first bore provided in the upper end, and open towards the upper end of the spindle.

In a further embodiment, said compensation chamber is at least partly arranged within said compensation member.

5 DK 177481 B1

In a further embodiment, said compensation chamber comprises a portion formed by a bore formed in said compensation member and a volume formed between said 5 compensation member and the bore in the spindle.

In a further embodiment, said portion of the compensation chamber in the compensation member comprises a first bore portion and a second bore portion, the first bore portion 10 having a larger cross-sectional area than the second bore portion.

In a further embodiment, the spring is arranged in the first bore portion.

15

In any of the above embodiments the compensation chamber may further comprise a second bore formed in the spindle, the second bore being in fluid communication with said first bore of the spindle.

20

In any of the above embodiments said damping means may further be provided at an uppermost portion of said compensation member.

25 In a further embodiment, at least one passage is provided to allow permanent fluid communication between the damping chamber and the uppermost portion of said spindle bore.

30 In any of the above embodiments said variable volume valve actuation chamber may have a portion defining a damping chamber, the damping chamber being formed in a top closure, and opening into uppermost part of said spindle bore.

, DK 177481 B1 b

In any of the above embodiments said damping chamber may communicate with a control valve for supplying the variable volume valve actuation chamber with pressurizes 5 hydraulic fluid.

In any of the above embodiments said gas exchange valve is an exhaust valve (1) for a large slow running two-stroke uniflow diesel engine of the crosshead type.

10

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

15 BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present description, the invention will be explained in more detail with reference to the exemplary embodiments shown 20 in the drawings, in which: -Fig. 1, in a sectional view, shows an upper part of a large two-stroke uniflow diesel engine of the crosshead type; 25 -Fig. 2, in a sectional view, shows an exhaust valve according to the invention; - Fig 3, in a sectional view, shows details of an upper part of the exhaust valve in Fig. 2; -Fig. 4, in a sectional view, shows a spindle 30 extending mechanism according to the invention , with a compensation member formed in an upper part of the exhaust valve in Figs. 2 and 3; 7 DK 177481 B1 -Figs. 5A-C, , in a sectional views, show the spindle extending mechanism of Fig. 4 in different positions relative to an upper end of a spindle, where Fig. 5A shows the compensation member in its most extended 5 position, Fig. 5C in its most compressed position, and Fig. 5B in a position in between; - Fig. 6, in a partly see-through perspective view, shows the upper part of a valve spindle with an compensation member according to the invention; 10 -Fig. 7, in a sectional view, shows an embodiment of an orifice in a compensation member; -Fig. 8, in a sectional view, shows another embodiment of an orifice in a compensation member; -Fig. 9, in a sectional view, shows another embodiment 15 of a spindle extending mechanism; - Fig. 10, in a graph, shows a simulation of the movement of a compensation member according to the invention; - Fig. 11, in a sectional view, shows an alternative 20 embodiment of an upper part of a spindle with a compensation member formed to fit over an upper end of a spindle; and - Fig. 12, shows details of an upper part of the exhaust valve, and illustrates a connection between 25 a damping chamber and an uppermost part of a spindle bore.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

30 In the following detailed description of the exhaust valve according to the invention will be described by the preferred embodiments.

8 DK 177481 B1

Fig. 1 shows a cylinder 100 of the uniflow type, used in large slow-running two-stroke uniflow diesel engines of the crosshead type. Large slow-running two-stroke uniflow diesel engines of the crosshead type usually have 3-14 of 5 such cylinders. The cylinder 100 has scavenge air ports 102 located in an airbox 103, which from a scavenge air receiver (not shown) is supplied with scavenge air pressurized by, for example, a turbocharger.

10 An exhaust valve 1 is mounted centrally in the top of the cylinder in a cylinder cover 124'. At the end of an expansion stroke the exhaust valve 1 opens before an engine piston 105 passes down past the scavenge air ports '102, whereby the combustion gases in a combustion chamber 15 10 6 above the piston 105 flow out through an exhaust passage 107 opening out into an exhaust receiver 108. The exhaust valve 1 closes again during the upward movement of the piston 105 at an adjustable moment that may e.g. depend on the desired effective compression ratio for the 20 subsequent combustion. During the closing movement, the exhaust valve 1 is driven upwards (away from the combustion chamber 106) by a pneumatic spring 123.

The exhaust valve 1 is opened by means of a hydraulically 25 driven actuator 109. Hydraulic fluid, e.g. a hydraulic oil, is supplied through a pressure conduit 110 connecting a port 80 (see Figs. 2-4) on the actuator 109 with a control port on the top surface of a distributor block 112 supported by a console 113. The distributor 30 block 112 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 range from 200 to 500 bar, preferably 300 bar. The common rail 9 DK 177481 B1 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 5 drive the valve actuator directly, or indirectly via pressure amplifiers/separators that separate the hydraulic fluid for the valve actuator 109 from the hydraulic fuel in the common rail, which may then be e.g. fuel oil. The pressure in the common rail fuel system 10 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.

15 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 standard hydraulic oil, but preferably, the lubricating 20 oil of the engine is used as hydraulic fluid, and the system is fed from the oil sump of the engine.

The internal combustion engine may be a medium speed four-stroke diesel or gas engine, or a low-speed two- 25 stroke crosshead diesel engine, which may be a propulsion engine in a ship or a stationary prime mover in a power plant.

Each cylinder 100 of the engine may be associated with an 30 electronic control unit 115 which receives general synchronizing and control signals through wires 116 (or wirelessly) and transmits electronic control signals to a control valve 117, among others, through a wire 118.

There may be one control unit 115 per cylinder, or 10 DK 177481 B1 several cylinders may be associated with the same control unit 115. The control unit 115 may also receive signals from an overall control unit common to all the cylinders.

5 Alternatively (not shown), the exhaust valve 1 and/or the control valve 117 may be controlled by a cam, i.e. mechanical-hydraulic control.

The control valve 117 may be of any usual type. The 10 construction and operation of the control valve 117 is as such well-known and should not require further explanation in the present context.

When the exhaust valve 1 is to be opened, a control 15 signal from the control unit 115 actuates the control valve 117 so that the high-pressure fluid has free access to the pressure conduit 110 and thus to the. fluid supply port 80 (Fig. 3) . When the exhaust valve 1 is to be closed, the control valve 117 is actuated so that the 20 high pressure in the conduit 110 is drained off to the return conduit 122. Thereby the pneumatic spring 123 will force the exhaust valve towards its closed position.

Fig. 2 shows an exhaust valve 1 according to the 25 invention. The exhaust valve 1 is of the type used for large slow running, two-stroke uniflow diesel engine of the crosshead type e.g. as in Fig 1.

The exhaust valve 1 has a spindle (or stem) 10 standing 30 upright from a valve disc 3, with a bottom or lower end or part 12, an upper end 11 and a central portion 13. The spindle 10 is elongate and has a longitudinal axis B. The spindle 10 is slideably received in a spindle bore 5.

n DK 177481 B1

The central portion 13 of the spindle 10 supports a spring piston 125 securely mounted on the spindle 10 so as to be pressure-sealing and longitudinally displaceable in a pneumatic cylinder 126. Below the spring piston 125 . 5 there is a spring chamber 127 connected to a pressurized-air supply (not shown) via suitable valves 156, which keeps the spring chamber 127 filled with pressurized air at a predetermined minimum pressure of, for example, an overpressure of 4.5 bar. Other air pressures can also be 10 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 cylinders, but preferably each spring chamber is 15 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 the valve disk 3 is permanently urged towards the valve 20 seat 4, i.e. in an upward direction. The upward force increases when the spring piston 125 is displaced downwards by the valve actuator 109 (see below) and compresses the air in the spring chamber 127 that is prevented from flowing out by of the non-return valve 25 156.

A housing 128 defines a cavity 129 around and above the spring piston 125 of the pneumatic spring 123. The cavity 129 is connected to a drain (not shown) so that the 30 cavity above the spring piston has atmospheric pressure, and so that leaking hydraulic oil from the hydraulic actuator 109 above the pneumatic spring can be drained of.

12 DK 177481 B1

The hydraulic actuator 109 is constructed from a cylinder 131 supported by the top of the housing 128, or as shown, cylinder 131 and housing 128 are formed in one integral piece.

5

In Fig. 2, a valve disc 3 is shown in a closed position, where the valve disc 3 abuts against a valve seat 4. In the figure, the valve disc is further shown in an opened position, where the valve disc has moved away from the 10 valve seat 4. The valve disc 3' in open position is indicated by the dotted outline.

An upper part 11 of the spindle 10 is received in a central bore 6 (see e.g. Fig. 3) in the cylinder 131, the 15 central bore 6 forming an upper part of the spindle bore 5. The central bore 6, is closed at the top of the cylinder 131 by a top closure 132, and is open to the bottom of the cylinder 131. The central bore 6 is coaxially arranged with the spindle bore 5 in the housing 20 128.

Turning now to Figs. 3 and 4, the central bore 6 is divided into coaxial portions having different diameters (or cross sectional areas): An uppermost portion 6' has 25 the largest diameter, a middle portion 6'' has an intermediate diameter, and a lowest portion 6''' has the narrowest diameter of the three. Between the uppermost portion 6' and the middle portion 6' ' a first upwardly facing ledge 7 is formed. Between the middle portion 6' ' 30 and the lowest portion 6' ' ' a second upwardly facing ledge 8 is formed.- A piston 90 is arranged slideably in the central bore 6 (forming the upper part of the spindle bore 5) . The 13 DK 177481 B1 piston 90 has a cylindrical main part 91 and a collar 92 arranged at the top of the main part 91. The piston 90 has a central bore 6 adapted for slidably receiving an upper part 11 of the spindle 10. The collar 92 has a 5 larger diameter (or cross sectional area) than the main part 91. The largest diameter of the main part 91 is adapted with a minute clearance to be slideably arranged in the middle portion 6'' of the central bore. The largest diameter of the collar 92 is adapted with a 10 minute clearance to be slideably arranged in the uppermost portion 6' . The collar is also cylindrical or ring shaped such that it has an opening through it communicating with the central bore 6 of the main part 91 of the piston 90. A downwardly facing internal ledge 93 15 is formed between the collar 92 and the main part 91 in the central bore 6 of the piston 90. The internal ledge 93 is adapted for engagement with an upper annular surface 15 of the spindle 10, or at least an outer part of the annular surface 15. The piston 90 further has an 20 upwardly facing upper surface 94 formed on the collar 92.

This upper surface 94 on the collar 92, is 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 25 surface 15 of the spindle 10. Thus, the surface area of the upper surface 94 may be from 2-10 times larger than the area of the upper annular surface 15 of the spindle 10. A downwardly facing external ledge 95 is formed between the collar 92 and the main part 91 on an external 30 surface of the piston 90. The main part 91 further has a lower surface 96. This lower surface 96 is ring shaped or annular.

14 DK 177481 B1 A damping chamber 81 is formed in the top closure 132.

The damping chamber opens into the uppermost portion 6' of the central bore 6, i.e. the uppermost part of the spindle bore 5.

5

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

10 A variable volume valve actuation chamber 60 is defined between the upper portion 6' of the central bore 6, a downwardly facing surface 132' of the top closure 132, the damping chamber 81, the upwardly facing top surface of the piston 90, and the upper part 11 of the spindle 15 10, and a compensation member 30 arranged in a first bore 20 arranged in said upper part 11 of the spindle 10 (see further below).

Hydraulic fluid is supplied to and discharged from the 20 variable volume valve actuation chamber of the valve actuator 109 via a port 80 (See Fig. 3) that is in fluid connection with the pressure conduit 110.The port 80 is in fluid connection with the variable volume valve actuation chamber through a chamber 65 formed as an 25 widened portion of the spindle bore 5, ports 83 formed in the chamber 65, conduits 85 communicating with the chamber 65 and port 82 forming inlets to the damping chamber 81. The pressure conduit 110 is not shown in Figs 2 and 3. Port 80 is thereby connected to the damping 30 chamber 81, which opens into the central bore 6 in cylinder 131.

Via the pressure conduit 110, port 80 is connected alternatingly with the high-pressure source (high 15 DK 177481 B1 pressure conduit 114) and a return conduit 122, see Fig.

1.

Thus the variable volume valve actuation chamber 60 is 5 connected via the ports 82 in the damper chamber 81 via the conduits 85 and ports 83 to the secondary pressure chamber 65, which is defined between the lowest portion 6' ' ' of the central bore 6, a portion of the upper part 11 of the spindle 10 and a first widened portion 65', and 10 a second widened portion 65'' of the central bore 6 and a widened portion 16 of the upper part 11 of the spindle 10.

When the exhaust valve is to be opened after a combustion 15 in the combustion chamber 106, the pressure in the combustion chamber 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 this initial phase by · increasing 20 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 supplies high-pressure fluid to the port 80. The 25 hydraulic fluid pressurizes the variable volume valve actuation chamber 60 and the secondary pressure chamber 65, where it acts on an upwardly facing ledge 16' on widened portion 16 of the spindle 10. One or more clearances or passages 39 allow the hydraulic fluid to 30 permanently pass between the damping chamber 81 and the uppermost portion 6' of the bore 6. Thereby, the variable volume valve actuation chamber 60 is initially constituted by damping chamber 81 and a part of the uppermost portion 6' of the bore 6. The inflowing _ DK 177481 B1 lo hydraulic fluid acts on the spindle 10, i.e. 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 (The upper surface 31 is situated on a slider 5 30, described in further detail below) . The downwardly facing internal ledge 93 abuts on a portion of the upper annular surface 15 of the spindle 10. This will force the spindle 10, and the piston 90 in a downwards direction.

10 A groove 99 formed as an elongate 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 15 95 is less than the area 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 the downward facing external ledge 95 of piston 20 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 the space below the piston 90 that will slow down and eventually stop the downward movement 25 of the piston 90.

Thus, after traveling a distance in the downwards direction, the downward facing external ledge 95 of the piston 90 will reach and stop before it abuts on the 30 upwardly facing ledge 7 between the uppermost and middle portions 6', 6' ' of the central bore 6. While the downward movement of the piston 90 is stopped, the spindle 10 continues it's downward movement, the pressure 17 DK 177481 B1 still acting on the upper annular surface 15, and the upper surface 31 of the upper part 11 of the spindle 10.

Thus, the piston 90 has provided a larger area for the 5 pressure in the variable volume valve actuation chamber 60 to act upon during the opening of the exhaust valve.

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 10 through the exhaust conduit 107. Therefore, in order to keep the exhaust valve moving in the downwards direction to open fully, a much smaller force is needed, than during the initial opening. Thus, after the piston 90 has been stopped, the pressure in the variable volume valve 15 actuation chamber 60 will only act on the upper annular surface 15, and the upper surface 31 of the upper part 11 of the spindle 10. Thereby, the spindle 10 will continue its downwards motion until a braking ledge (see Fig. 4) on the spindle 10 passes a lower rim of the second 20 widened portion 65' ' of the central bore 6. The spindle 10 starts slowing down to eventually stop because the upper portion 11 of the spindle 10 will cut of the connection to port 80 and the pressure will no longer increase in the variable volume chamber 60.

25

In order to commence the closing of the exhaust valve 1, when the combustion chamber 106 has been evacuated, the control valve 117 connects the pressure conduit 110 to the return conduit 122, and the hydraulic fluid is 30 allowed to flow back through the port 80. The pneumatic spring 123 will force the spindle 10 upwards thereby beginning to press out the hydraulic fluid in the variable volume valve actuation chamber 60 through the secondary pressure chamber 65.

18 DK 177481 B1

As the spindle 10 moves upwards, the upper annular surface 15 of the spindle 10 will eventually abut against the downwardly facing internal ledge 93 of the piston 90, 5 and force the piston 90 in unison with the spindle 10 to move from its lower rest (where external ledge 95 of piston 90 is close to the upward facing ledge 7 between upper and middle potions 6' , 6' ' of the central bore 6) in an upward direction.

10

The upward motion will brake and eventually stop when damping means in the form of a conical face 32 at the top of the upper part 11 (on compensation member 30) of the spindle 10 enters into the dampening chamber 81, 15 gradually decreasing the passageway between the damping chamber 81 and the uppermost part of the central bore 6' . Thereby, when the conical face 32 plunges into the dampening chamber 81, the pressure increases in the upmost part 6' of the central bore 6, i.e. in the 20 variable volume valve actuation chamber 60, and the upward motion of the spindle is thereby dampened until an upper annular surface 33 of the upper part 11 of the spindle 10 abuts gently on the downwardly facing surface 132' of the top closure 132. The upper annular surface 33 25 faces upward and is formed on the slider below the upper surface 31 and the conical surface 32.

A set of vanes 14 (Fig. 2) on a portion of the valve spindle 10, which is located in the exhaust conduit 107 30 forces the spindle 10 to rotate when exhaust gas flows through the exhaust conduit 107, i.e. when the exhaust valve 1 is 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 19 DK 177481 B1 seat 4 and the abutment ledges of the spindle 10 and spindle bore 5 is secured.

The pneumatic spring 123 described above may be replaced 5 by a return stroke pressure chamber and a piston surface area that urges the spindle 10 to the retracted position.

This embodiment (not shown) will require slightly modified control valve that is able to supply pressurized hydraulic fluid to the pressure return stroke chamber for 10 urging the piston to the retracted position. The same principles as described above can be used to control the pressure in the return stroke pressure chamber relative to the position of the first piston.

15 Turning now to Figs. 5A-C, the upper part 11 of the spindle 10 comprises a mechanism for adjusting the length of the spindle 10, also shown in the previous drawings.

This mechanism comprises a compensation member 30 arranged in a first bore 20 in said upper part 11 of the 20 spindle 10, said first bore 20 being open towards the upper end and the annular surface 15 of the spindle 10.

The first bore 20 has a longitudinal axis A, being coaxial with the longitudinal axis B of the spindle 10.

The compensation member 30 is slideably received in the 25 first bore 20, such that the compensation member may slide relative to the spindle 10 in a direction parallel to longitudinal axis A.

The compensation member 30 is preferably circular in 30 cross section and has an elongate cylindrical form. The compensation member 30 has an upwardly facing upper surface 31 and a downwardly facing lower surface 34. The compensation member 30 has length in its longitudinal direction that is longer than the length of the bore 20 20 DK 177481 B1 that the compensation member 30 is received in. Thus, a part of the compensation member 30 will always extend above the upper annular surface 15 of the spindle 10 and form an extension thereof.

5

The compensation member 30 has a bore 35. This bore 35 has an upper portion 35' and a lower portion 35''. The upper portion 35' has a diameter or cross sectional area, and the lower portion 35'' has a diameter or cross 10 sectional area. The diameter or cross sectional area of the upper portion 35' is smaller than that of the lower portion 35' ' . A downwardly facing ledge is formed between the upper portion 35' and the lower portion 35'' .

15 An upper portion 30' and lower portion 30''' of the compensation member 30 has a diameter or cross sectional area corresponding to the diameter or cross sectional area of the first bore 20 in the spindle 10. Thus, the compensation member 30 is received in the first bore 20, 20 with a minute clearance, and it is thus slideable between a compressed position as shown in Fig. 5C and an extended position as shown in Fig. 5A along the longitudinal axis A.

25 The compensation member 30 is biased towards an extended or upward position, i.e. towards the downwardly facing surface 132' of the top closure 132, by a spring 40. The spring 40 has and upper end 41 and a lower end 42. The spring 40 is arranged in, and guided by the lower portion 30 35'' of the bore 35 in the compensation member 30. The upper end 41 of the spring 40 abuts on the ledge and the lower end 42 on a bottom surface 22 of the first bore 20 in the spindle 10. As shown in Fig. 5A the lower end 41 21 DK 177481 B1 of the spring 40 may be fixed in a recess in the bottom surface 22 of the first bore 20 in the spindle 10.

The compensation member 30 further has a middle portion 5 30''. The middle portion 30'' has a diameter which is smaller than the diameter of the upper portion 30' and smaller than the lower portion 30''' of the compensation member 30. Thus the middle portion 30'' forms a recess with respect to the upper portion 30' and lower portion 10 30''' of the compensation member 30. A detent or screw 200 secures the compensation member 30 in the first bore 20, by interaction with the recess formed by the middle portion 30''. An upwardly facing ledge formed between middle portion 30'' and the lower portion 30''' of the 15 compensation member 30 will abut against detent or screw 200 to define an uppermost position of the compensation member 30 in bore 20. Thereby the compensation member 30 is prevented from being pushed out of the first bore 20 in the spindle 10 by the spring 40. The detent is 20 arranged in a bore 201 formed transverse to the elongate axis B of the exhaust valve 1, in the upper part 11 of the spindle 10 as shown in the see-through view in Fig.

6. Thus, the detent or screw 200 may be removed from the channel 201, allowing removal of the compensation member 25 30 from the bore 20 for repairs.

In the embodiment of the compensation member 30 shown in figs 5A-C, a second bore 25 is further formed in the spindle 10, the second bore 25 extending coaxially with 30 the first bore 20, and extending downwardly from the bottom 22 of the first bore 20, or from the recess.

The upper portion 30' of the compensation member preferably is provided with the above mentioned 22 DK 177481 B1 arrangement for damping movement of the valve spindle during closing of the exhaust valve in the form of a conical portion 32.

5 A compensation chamber 50 thereby is defined in the compensation member 30 and between the compensation member 30 and the bore 20 and the second bore 25 in the upper part 11 of the spindle 10. Thus, in the embodiment shown in Figs. 2-6, the compensation chamber 50 is formed 10 by the upper portion 35' and the lower portion 35'' of the bore 35 the space 21 in between the downwardly facing lower surface 34' of the compensation member 30 and the bottom 22 of the bore 20 in the spindle 10, and the second bore 25.

15

The compensation chamber 50 is in fluid communication with the variable volume valve actuation chamber 60 (see e.g. Fig 4) through an orifice 70 formed through the upper surface 31 of the compensation member 30.

20

Because the variable volume valve actuation chamber 60 and the compensation chamber 50 are in fluid connection through the orifice 70, there will be a flow of hydraulic fluid between the two chambers 50, 60 as long as there is 25 a pressure difference between the variable volume valve actuation chamber 60 and the compensation chamber 50. A pressure difference therefore will cause a longitudinal translation of the compensation member in the bore 20 in the spindle, and thereby cause an extension or a 30 reduction of the overall spindle length. The pressure in the variable volume valve actuation chamber 60 and the compensation chamber 50 is of course mainly determined by the pressure of the hydraulic fluid injected in the variable volume valve actuation chamber 60 through port 23 DK 177481 B1 80. However, the pressure is also dependent of the size of the chambers, which is again dependent on the temperature of the spindle 10 the compensation member 30, and the cylinder 131 (with top closure 132) . There is a 5 difference in temperature of the mentioned parts from a cold (inoperative) state of the engine to a state where the engine is running under normal operating conditions (due to friction between engine parts and the burning of fuel in the combustion chamber. The period before the 10 engine reaches its normal operating state temperature in large two-stroke engines used in marine vessels may well be in the order of 30 minutes to 1½ hours. There is also a (smaller) temperature difference between high and low load operation of the engine. These temperature 15 differences especially causes a difference in the length of the spindle 10 (that may be 0,5 to 2 m long in a large two stroke engine of the kind mentioned above).

A correct balancing of the compensation member extension 20 is made by balancing the spring force urging the compensation member upward, the size of the orifice 70 (determining the speed of hydraulic fluid flow) and the size of the compensation chamber 50.

25 In Fig. 5A the compensation member 30 is shown in a fully extended position. This position corresponds to a situation where the engine is cold, and the spindle 10 therefore is relatively short. Fig. 5C represents a situation, where the engine is running at full load and 30 where the spindle 10 has heated up and is at an expected maximum length. During normal operation the compensation member 30 will be located in a position in between the two extreme positions, as shown in Fig. 5B. However, as discussed below, the compensation member 30 will change DK 177481 B1 24 position for every stroke of the engine piston 105, why the positions discussed above should be understood as average positions for the individual temperature scenarios .

5

Simulations and experiments have shown suitable relations between the spring force, the orifice size, and the overall volume of the compensation chamber 50. Below an example is given for a 50 cm (internal bore) cylinder 10 engine, where the spindle bore 5 diameter is 52 mm (at portion 6''', see e.g. Fig. 4).

The pressure applied for actuating the exhaust valve is raised to approximately 300 bar in the variable volume 15 valve actuation chamber 60.

The spring 40 preferably provides an upward force on the compensation member 30 equivalent to 0.2-1.5 bar pressure difference between the variable volume valve actuation 20 chamber 60 and the compensation chamber 50. Preferably the spring 40 provides an upward force on the compensation member 30 equivalent to 0.5 bar.

The orifice preferably has a diameter in the range of 25 0.2-1 mm, preferably 0.5 mm.

The volume of the compensation chamber 50 is preferably 20.000-25000 mm3 (cubic millimeter), such as 22,453 mm3 when the compensation member is in fully extended 30 position.

Similar values may be calculated or found by experiments or simulation for other cylinder sizes, valve spindle bore diameters and exhaust valve actuation pressures.

25 DK 177481 B1

Thereby, the compensation member 30 automatically ensures that the position of the conical surface 32 and the upwardly facing ledge 33 forms a precise fit with the 5 damping chamber 81 and the surface 132' of the top closure 132 respectively, i.e. it is ensured that the overall length of the spindle 10 with the compensation member 30 is always adapted to ensure that the damping mechanism at the top of the spindle 10 is always at the 10 correct position in relation to the damping chamber 81, and that exhaust valve 1 valve disk 3 closes snugly onto the valve seat 4.

In the alternative embodiment shown in Fig. 9, the 15 compensation chamber 50 is formed in the compensation member 30 in a different way than in the embodiments shown above. The same reference numbers refer to the same parts as in Figs. 2-8. The compensation chamber 50 is formed by a single bore 35 in the compensation member 30, 20 and the space 21 between the compensation member 30 and the bottom 22 of the bore 20 in the spindle 10. The length of the bore 35 is greater than in the above mentioned embodiment, but the upper bore 35' and the second bore 25 of the above described embodiment has been 25 left out. The volume of the compensation chamber 50 may thus be selected to a desired magnitude and balanced with the spring force and the orifice diameter/size in order to adjust the overall length of the spindle 10 depending on the size of the engine and the speed of adjustment 30 desired. In other not shown embodiments, the volume of the compensation chamber 50 in the Fig. 9 embodiment may be adjusted with a second chamber 25 as shown in the Fig.

5 embodiment.

26 DK 177481 B1

In Fig. 10, an example of a simulation of the compensation member extension is shown during a single engine cycle. The simulation is done on a compensation member 30 according to the embodiment shown in Fig. 9, 5 and with the data of the above example. In the figure, the curve G1 shows the pressure applied in the variable volume valve actuation chamber 60. The pressure (in bar) is read on the scale to the right in the figure. The curve G2 shows the corresponding displacement of the 10 exhaust valve 1 (The distance traveled by the valve disc 3 away from the valve seat 4) . The distance (in mm) is read on the scale to the right in the figure. The curve G3 shows the displacement of the compensation member 30 relative to the bore 20 in the spindle 10. The distance 15 (in mm) is read on the scale to the left in the figure.

The scale on the abscissa is time in seconds. The situation illustrated is one where the compensation member 30 is in the process of adapting the overall spindle length to a low temperature of the spindle 10.

20 Thus the compensation member 10 position becomes increasingly extended over time. During the shown cycle the first (in time) third (until 0.15) the position of the compensation member increases gradually to approach the damper chamber 81. The pressure in the variable 25 volume valve actuation chamber 60 is at ambient, why the exhaust valve is closed. Then at 0.15 the exhaust valve must open to evacuate the combustion chamber 106.

Hydraulic fluid under pressure is conducted to the variable volume valve actuation chamber 60, and the 30 pressure rapidly increases forcing the spindle 10 to move to force the valve disc 3 from the valve seat 4, which initially gives pressure fluctuations. The variable volume valve actuation chamber 60 pressure eventually flattens out at about 300 bar and the displacement of the 27 DK 177481 B1 valve at about 200 mm. The position of the compensation member 30 is depressed into the bore 20 as a result of the quickly increased pressure in the variable volume valve actuation chamber 60. But when a pressure 5 equilibrium between the pressures in the compensation chamber 50 and the variable volume valve actuation chamber 60 has been reached, the position of the compensation member 30 resumes its travel towards a more extended position due to the spring force. When the 10 exhaust valve is to be closed again after evacuation of the combustion chamber 106, the pressure in the variable volume valve actuation chamber 60 is reduced, as can be seen by the almost momentary drop in the curve G1 (just before time t=0.3). When the pressure in the actuator 109 15 is thus discontinuated, the pressure of the air spring 123 will force the exhaust valve upwards towards its closed position. As soon as the pressure in the variable volume valve actuation chamber 60 is discontinued the compensation member 30 will move in a jump towards a more 20 extended position, until the pressure in the compensation chamber 50 and the variable volume valve actuation chamber 60 is again in equilibrium. Thus, a dynamic adjustment of the overall spindle length is achieved not only over various engine temperature conditions, but at 25 each cycle of the engine.

Figs. 7 and 8 show two different embodiments of the orifice 70. In the Fig. 7 embodiment the orifice has a conical portion opening into the upper surface 31 of the 30 compensation member 30, a first cylindrical portion 73 and a second conical portion opening into the hydraulic fluid receiving chamber 50, i.e. the bore 35 or the second bore portion 35'. The first cylindrical portion 73 has a diameter. The first cylindrical portion 73 forms 28 DK 177481 B1 the smallest area passage of the orifice, and thereby defines the diameter (or cross-sectional area) of the orifice. In the embodiment shown in Fig. 8, the orifice 70 has the orifice has a conical portion opening into the 5 upper surface 31 of the compensation member 30, a first cylindrical portion 73 and a second cylindrical portion 74. Said second cylindrical portion 74 is closer to said upper surface 31, and said cylindrical portion 73 is closer to said compensation chamber 50. In this 10 embodiment the first cylindrical portion opens into the hydraulic fluid receiving chamber 50, i.e. the bore 35 or the second bore portion 35' . The first cylindrical portion 73 has a diameter. The first cylindrical portion 73 forms the smallest area passage of the orifice, and 15 thereby defines the diameter (or cross-sectional area) of the orifice.

Fig. 6, in a partly see-through perspective view shows the upper part 11 of a spindle 10, with a compensation 20 member 30 arranged in a bore 20 open towards the upper surface 15 of the upper part 10 of the spindle 10. Fig. 6 illustrates how the compensation member 30 may easily be accessed from above for assembling and disassembling the spindle and compensation member 30, e.g. for repairs.

25 This . I made possible by the pin 200 arranged in bore 201 in the upper part 11 of a spindle 10, the bore having a longitudinal axis perpendicular to the longitudinal axis B of the spindle 10, a portion of the bore 201 opening into the bore 20 of the compensation member receiving 30 bore 20 open towards the upper surface 15. Thereby, a pin 200 inserted in the bore 201 may interact with the middle portion 30'' of the compensation member 30, allowing the compensation member 30 to slide along the axis A of the compensation member receiving bore 20, the ledge or' 29 DK 177481 B1 upwardly facing surface (between the middle portion 30'' and the lower portion 30''' of the compensation member 30) defining together with the pin a stop limiting the uppermost position of the compensation member 30 relative 5 to the spindle 10 as such.

Fig. 6 also clearly shows how the above mentioned passages 39 are formed in the upper portion 30' of the compensation member. A plurality of passages 39 are 10 distributed radially around a circumference of the compensation member 30, and formed as grooves in the an outer surface of the middle portion 30'' of the compensation member 30. The grooves allow hydraulic fluid to pass between the damping chamber 81 and the uppermost 15 part/portion 6' of the spindle bore 5 permanently, such that the damping chamber 81 and the uppermost part/portion 6' of the spindle bore 5 together forms a variable volume actuation chamber 60. The passages 39 may also be appreciated from Fig. 12, showing the upper part 20 of the actuator of hydraulic exhaust valve with a compensating member 30 provided at the uppermost portion of a spindle 10. Arrows in the figure indicate the flow of hydraulic fluid into the variable volume actuation chamber 60 formed by the damping chamber 81 and the 25 uppermost part 6' of the spindle bore 5. The hydraulic fluid enters from the conduits 85 via ports 82 into the damping chamber 81 and passes via the passages 39 (grooves) from the damping chamber 81 and into the uppermost portion/part 6' of the spindle bore 5 to 30 pressurize the variable volume actuation chamber 60. From Figs. 6 and 12 it will be appreciated that the conical surface 32 (forming damping means with the damping chamber 81) has a first diameter (or cross sectional area) at the top and a second diameter at a bottom part 30 DK 177481 B1 closest to the upwardly facing annular surface 33, and where the first diameter is smaller than the second diameter such that the conical surface 32 tapers in an upward direction. From Fig. 12 it will be appreciated, 5 that the second lower diameter is preferably smaller than a diameter of the damping chamber 81, such that hydraulic fluid is allowed to flow into and out from the upper part 6' of the spindle bore via the passages 39. The clearance between the conical surface 32 and the damping chamber 81 10 at the second, lower diameter of the conical surface 32 (when the upwardly facing annular surface 33 of the compensation member 30 abuts against the downwardly facing surface 132' of the top closure 132) is preferably minute. In Fig. 12 the upwardly facing annular surface 33 15 of the compensation member 30 abuts against the downwardly facing surface 132' of the top closure 132.

The section in Fig. 12 varies the section shown in Fig.

4, by the angle being slightly different. Thus in Fig. 4 20 the conduits 85 cannot be seen - only some of the ports 82 between the damping chamber 81 and the conduits 85. In Fig. 12 sections through two conduits 85 are shown. Thus the two figures illustrates that there may be more than one conduit 85 connecting to the damping chamber 81. In 25 Fig. 3 only one is shown.

Above, the embodiments of the spindle length adjusting mechanism has been described in connection with a spindle with a piston 90 for accelerating the spindle 10 movement 30 during the initial phase of the valve 1 opening, the piston 90 being arranged at an uppermost portion of the spindle. It will however be appreciated that similar accelerating piston may be arranged on another portion of 31 DK 177481 B1 the spindle, and where the above described embodiments of the spindle extension mechanism may still be functional.

Fig. 11 shows an alternative embodiment of the spindle 5 extension mechanism. The same reference numbers as used in connection with Figs 1-10 above are used in connection with similar features in connection with describing the embodiment shown in Fig. 11. In this embodiment a compensation member 30, instead of being arranged in a 10 bore in the spindle, is arranged slideably on the outside of the uppermost portion of the spindle. Thus, the compensation member 30 is a cup shaped structure arranged on and over an uppermost end portion 11 of the spindle 10. An orifice 70 is provided through the compensation 15 member to provide permanent fluid connection between a variable volume valve actuation chamber 60 and a compensation chamber 50. In this embodiment the variable volume valve actuation chamber 60 is defined by the damping chamber 81 and an upper portion 6' of a spindle 20 bore 5. Further, the compensation chamber 50 is defined by a space between the end 11 of the spindle and a downward facing internal wall of the compensation member, a main bore 20 and a secondary bore 25 provided in the spindle 10. Corresponding to the previously described 25 embodiments, the embodiment shown in Fig. 11 also has passages (not shown) similar to the passages 39 of the previous embodiments, which passages allows permanent fluid communication between a damping chamber 81 and an uppermost portion 6' of a spindle bore 5.

30

In all of the embodiments described above the damping means for damping the closure of the valve has been described as being in the from of a conical surface 32, provided on the compensation member 30, interacting with 32 DK 177481 B1 the damping chamber 81 wall. However, the conical surface may also be provided as a wall of the damping chamber 81, the top of the compensation member being formed as a straight cylindrical part. Likewise the passages 39 has 5 been described as being provided on the compensation member 30, however these passages may also be provided in the wall of the damping chamber 81.

The term "comprising" as used in the claims does not 10 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 of several means recited in the claims.

Claims

A gas exchange valve (1) for an internal combustion engine, comprising gas exchange valve (1) - a spindle bore (5), - a valve spindle (10) contained in the spindle bore (5), - a damping chamber (81) and - a valve actuation chamber ( 60) of variable volume arranged in the upper part of the spindle bore (5), comprising the valve spindle (10) - an upper end (11) provided with damping means (32) adapted to cooperate with the damping chamber ( 81) for attenuating the movement of the valve stem (10) while closing the gas changeover valve (1), - a longitudinal axis (A) and - a compensating element (30) provided at the upper end (11), which compensating element (30) can sliding between a compressed position and an extended position along the longitudinal axis (A); and - a spring (40) pushing the equalizing element (30) toward the extended position; characterized in that a compensating chamber (50) is located in the upper part of the spindle, which equalizing chamber (50) is in permanent fluid communication with the variable volume valve actuation chamber (60) arranged in the upper part of the spindle bore (5). an opening (70) formed through an upper surface (31) of the equalizer (30).

Gas exchange valve (1) according to claim 1, wherein the equalizing chamber (50) has a maximum volume, the opening (70) has dimension and shape and the spring is configured to apply a predetermined upward pressure to the equalizing element (30) and wherein the volume of the compensating chamber (50), the shape and dimension (70) of the opening (70) and the upward force of the spring (40) are adapted to provide a close adjustment of the damping member (32) adapted to cooperate with the damping chamber (81) in response to gas change valve temperature changes (1).

A gas changeover valve (1) according to claim 1 or 2, wherein the equalizing chamber (50) is located at least between the equalizing element (30) and the upper end of the spindle (10).

Gas exchange valve (1) according to any one of claims 1-3, wherein the equalizing element (30) is received in a first bore (20) provided at the upper end (11) and open towards (11) the spindle (10). ) upper end.

The gas exchange valve (1) according to claim 4, wherein the equalizing chamber (50) is located at least partially within the equalizing element (30).

The gas exchange valve (1) according to claim 5, wherein the equalizing chamber (50) comprises a portion formed by a bore (35) formed in the equalizing element (30) and a volume (21) formed between the equalizing element (30) and the bore (20) in the spindle (10). - 3 - DK 177481 B1

The gas exchange valve (1) of claim 6, wherein the portion of the equalizing chamber (50) of the equalizing element comprises a first bore portion (35 / ') and a second bore portion (35'), said first bore portion (35 ') having a larger cross-sectional area than the second bore part (35 ').

The gas changeover valve (1) according to claim 7, wherein the spring (40) is located in the first bore part (35 ')

A gas exchange valve (1) according to any one of claims 1-6, wherein the compensating chamber (50) further comprises a second bore (25) formed in the spindle (10), which second bore (25) is in fluid communication with (20) first bore of spindle (10).

The gas exchange valve (1) according to any one of claims 1-9, wherein the damping means (32) is provided in an upper part of the equalizing element (30).

The gas exchange valve (1) according to claim 10, wherein at least one passage (39) is provided to permit permanent fluid communication between the damping chamber (81) and the upper portion of the spindle bore (5).

A gas change valve (1) according to any one of claims 1-11, wherein the variable volume valve actuation chamber (60) has a portion defining a damping chamber (81), said damping chamber (81) formed in an upper closure (132). ) and which open into the upper part of the spindle bore (5).

The gas change valve (1) according to claim 12, wherein the damping chamber (81) communicates with a control valve (117) for supplying pressurized hydraulic fluid to the variable volume valve actuation chamber (60).

A gas change valve (1) according to any one of claims 1-13, wherein the gas change valve is an exhaust valve (1) for a large, slow-moving two-stroke diesel engine with cross-head longitudinal flushing.