DK177283B1

DK177283B1 - Valve arrangement

Info

Publication number: DK177283B1
Application number: DKPA201000153A
Authority: DK
Inventors: Poul Cenker
Original assignee: Man Diesel & Turbo Deutschland
Priority date: 2010-02-24
Filing date: 2010-02-24
Publication date: 2012-10-08
Also published as: KR101242611B1; CN102162384B; DK201000153A; JP2011174462A; CN102162384A; KR20110097673A; JP5372036B2

Abstract

A valve arrangement for a valve actuation system for a large two strolce diesel engine provides for controlled return flow from the pressure pipe (10) that connects the top of the exhaust valve actuator to the electro hydraulic control valve (5) placed on the top of the cylinder housing much below the top ot the exhaust valve. Thereby, formation of air pockets and subsequent cavitation can be avoided when the pressure pipe (10) is depressurized without the need of using a pressure booster or separator between the electro hydraulic control valve (5) and the pressure pipe (10) It is suggested that Fig. 3 is published with the abstract.

Description

i DK 177283 B1

VALVE ARRANGEMENT

5 The present disclosure relates to a valve arrangement, in particular a valve arrangement for controlled return flow and for maintaining a minimum pressure upstream of the valve arrangement.

10 BACKGROUND OF THE INVENTION

Conventional check valves that have a movable valve member that abuts with a seat cannot be used in harsh environments like in the exhaust valve actuation system 15 of a large two-stroke diesel engine.

Electro-hydraulically controlled valve actuation systems in large two-stroke diesel engines allow for flexible operation and profiling of the exhaust valve, allowing 20 improved emission control and fuel efficiency.

Enormous forces are required to open an exhaust valve weighing up to 400 kg against the pressure in the combustion chamber and in the gas spring that urges the 25 exhaust valve in the closing direction. Thus, a high pressure and high power hydraulic system is required for the opening of the exhaust valves of a large tow-stroke diesel engine.

30 A conventional electronically controlled (electro-hydraulic) exhaust valve actuation system for a large two-stroke diesel engine will include high-pressure pumps delivering a hydraulic fluid (hydraulic oil or lubrication oil) via a common rail to valve blocks DK 177283 B1 2 located near or on the top plate of the cylinder housing.

The valve blocks carry hydraulic accumulators and proportional electro-hydraulic control valves that control the flow of hydraulic fluid for operating the 5 fuel injectors and the exhaust valves.

A pressure pipe connects each of the valve blocks to their respective exhaust valve. The valve blocks are typically placed on the top of the cylinder housing, and !0 thus, the pressure pipes have to bridge a considerable distance and height difference between the valve blocks and the top of the exhaust valve actuator. This difference in height can be several meters.

15 A pressure booster (basically a piston with a large and a small active surface on either end) is mounted at the top of the valve block. One end of the pressure pipe connects · to the pressure booster whilst the other end of the pressure pipe connects to the top of the exhaust valve.

20 Thus, pressure pipe extends from the valve block to the top of the exhaust valve.

Due to the size of these engines the difference in height between the top of the exhaust valve and the valve block 25 can be significant, i.e. several meters.

When the exhaust valve is in the closed position the pressure in the pressure pipe should be close to zero.

30 The pressure booster between the valve block and the lower end of the pressure pipe prevents the hydraulic fluid in the pressure pipe from being drained and avoids that the pressure pipe is filled with air as opposed to hydraulic fluid.

s 3 DK 177283 B1

When it is time to close the exhaust valve, the electro-hydraulic control valve connects the pressure pipe to tank. Due to the inertia of the exhaust valve air 5 pockets may form in the pressure pipe. These air pockets may result in cavitation when pressure increases again and therefore it is necessary to place a pressure booster or pressure separator between the electro-hydraulic control valve and the pressure pipe. i 10 EP 1 403 473 which is considered the closest prior art discloses an engine valve actuation system including an actuation assembly having a piston, a housing, an inlet port, a fixed flow restriction at or downstream of the 15 inlet port, an actuation piston with two opposite effective pressure surfaces received in a bore in the housing, one of the effective pressure surfaces faces a first pressure chamber that is in fluid communication with said flow restriction, the other effective pressure 20 surfaces faces a second pressure chamber that is connected to a source of relatively low pressure, an outlet port that is closed off by said floating valve ! member in a range of positions of the floating valve member and open in another range of positions of the 25 floating valve member to thereby connect the first ; i pressure chamber to said outlet port, the one of said i effective pressure surfaces urging the floating valve j member towards the range of positions where the first ' pressure chamber is connected to the outlet port and the 30 other of said effective pressure surfaces urging the actuation piston towards the range of positions where the first pressure chamber is not connected to the outlet port.

4 DK 177283 B1

DISCLOSURE OF THE INVENTION

On this background, it is an object of the present application to provide a valve arrangement that avoids or 5 at least reduces the drawbacks mentioned above.

This object is achieved by providing a valve arrangement comprising a housing, an inlet port, a fixed flow restriction at or downstream of the inlet port, a 10 floating valve member with two opposite effective pressure surfaces received in a bore in said housing, the one of the effective pressure surfaces facing a first pressure chamber that is in fluid communication with said flow restriction, the other of the effective pressure ί 15 surfaces facing a second pressure chamber that is connected to a source of relatively low pressure, an outlet port that is closed off by said floating valve member in a range of positions of the floating valve member and open in another range of positions of the 20 floating valve member to thereby connect the first pressure chamber to said outlet port, the one of said effective pressure surfaces urging the floating valve member towards the range of positions where the first pressure chamber is connected to the outlet port and the 25 other of said effective pressure surfaces urging the floating valve member towards the range of positions where the first pressure chamber is not connected to the outlet port and a bore through said floating valve member that connects the first pressure chamber with the second 30 pressure chamber.

This valve arrangement that allows controlled flow back to tank and maintains a minimum pressure upstream of the a i 5 DK 177283 B1 valve. Thus, formation of air pockets and cavitation are i avoided or at least reduced.

Conventional check valves cannot be used in harsh 5 environments, such as in the exhaust valve actuation system of a large two stroke diesel engine, where large pressure gradients exist, since check valves that close by means of a seat will be destroyed after a relatively few cycles. io

Preferably, the bore through said floating valve member can be provided with a side bore that connects the second pressure chamber to an overflow port when said floating valve member is moved to a large extend in into the range 1 15 of positions where the floating valve member connects the first pressure chamber to the outlet port.

In an embodiment the one effective pressure surface is larger than the other effective pressure surface.

20

The floating valve member may define a control edge together with an edge of a bore in which the floating valve member is received.

25 Further objects, features, advantages and properties of the valve arrangement according to the present disclosure will become apparent from the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS 30

In the following detailed portion of the present description, the invention will be explained in more detail with reference to the exemplary embodiments shown in the drawings, in which: s i 6 DK 177283 B1

Fig. 1 is a diagrammatic and partially cross-sectional view of an exhaust valve actuation system using a valve '·.

arrangement according to an exemplary embodiment, 5 Fig. 2 is a diagram illustrating the hydraulic scheme of the valve actuation system shown in Fig. 1, and Fig. 3 is a detailed cross-sectional view of the valve in the exhaust valve actuation system shown in Fig. 1.

10 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 is a partially cross-sectional view of the exhaust valve actuation system according to an exemplary embodiment of the disclosure. The exhaust valve actuation 15 system is part of a large two stroke diesel engine, such as a large turbocharged uniflow diesel engine of the cross-head type. The construction and operation of large two stroke diesel engines is well known and therefore not described in detail here.

20 A valve block 3 is mounted on the top plate of the ; cylinder housing of a large two stroke diesel engine. The j i valve block carries an electronically controlled proportional hydraulic control valve 5. The 25 electronically controlled proportional hydraulic control valve 5 is connected to an electronic control unit (not ' shown) of the engine. The valve block 3 also carries one or more accumulators 8 and a valve arrangement 20. One end of a pressure pipe 10 is connected to a port in the ' 30 valve block 3. The difference in height covered by the pressure pipe 10 can be several meters, and without countermeasures gravity could cause the pressure pipe 10 to be drained and filled with air when the pressure pipe » 7 DK 177283 B1 10 is de-pressurized for allowing the exhaust valve to return to its seat.

A bore 7 in the valve block 3 connects the pressure pipe 5 10 to a port of the proportional hydraulic control valve 5, a bore 11 connects the a valve arrangement 20 to another port of the proportional hydraulic control valve 5 and another bore 9 connects the proportional hydraulic control valve 5 to a source of high pressure which is in 10 this case a common rail.

The other end of the pressure pipe 10 is connected to the top of the exhaust valve housing 12. Only the spindle 14 of the exhaust valve is shown in the figures. A hydraulic 15 actuator for opening of the exhaust valve is placed at the top of the spindle 14. The hydraulic actuator includes at least one pressure chamber 16 and one piston 18 and when the hydraulic actuator is pressurized it urges the exhaust valve in the opening direction. An air 20 spring (not shown) is used to urge the exhaust valve in the closing direction in a well-known manner.

Fig. 2 is a diagram illustrating the hydraulic scheme of the valve actuation system shown in Fig. 1. The system 25 includes a high-pressure common rail of 32 that is fed by one or more high pressure pumping stations of the engine.

The high-pressure common rail 32 is kept at a pressure of a couple of hundred bar. There is also a low-pressure common rail 34 that is kept at approximately 2,2 bar. A 30 common rail 36 connects to tank at substantially atmospheric pressure.

A conduit 9 (formed by bore 9 in valve block 3) connects the proportional electro-hydraulic control valve 5 to the 8 DK 177283 B1 high-pressure common rail 32. The proportional electro-hydraulic control valve 5 includes a pilot stage that uses pressure from conduit 9 to move the spool of the proportional electro-hydraulic control valve 5 in a 5 desired position. Conduit 9 as a branch that connects to several hydraulic accumulators 8 that serve to maintain/stabilize pressure when flow rates suddenly increase.

10 A conduit 13 connects an outlet port of the proportional electro-hydraulic control valve 5 that is associated with the fuel injection system to the low-pressure common rail 34. A conduit 11 connects an outlet port of the proportional electro-hydraulic control valve 5 that is 15 associated with the exhaust valve actuation system to the i low-pressure common rail 34 via a valve arrangement 20.

The valve arrangement 20 includes a flow restriction, a ! non-return function and maintains and minimum pressure in conduit 11.

20

The proportional electro-hydraulic control valve 5 is connected to the fuel injection system 30 with its pressure booster and injectors 37 and the proportional electro-hydraulic control valve 5 is also connected to 25 the exhaust valve actuator. The fuel injection system is as such well known and will not be described in greater detail here.

The hydraulic diagram shows the pressure pipe 10 30 connected to the exhaust valve actuator housing 12 with a piston 18 airs ping the exhaust valve spindle 14. A source of pressurized air 19 also connects to the exhaust valve housing 12 for supplying the pressurized air for the air spring that urges the exhaust valve in the 9 DK 177283 B1 closing direction. Further, a position sensor that determines the position of the exhaust valve is associated with the exhaust valve actuator.

5 During engine operation the proportional electro- hydraulic control valve 5 is commanded by the electronic control unit of the engine to connect either the exhaust valve actuation system or the fuel injection system to the high-pressure common rail at appropriate times in the 10 engine cycle. Thus, when it is time to open the exhaust valve the electronic control unit of the engine will command the proportional electro-hydraulic control valve 5 to establish a connection between the high pressure common rail 32 and the pressure pipe 10. Thereupon, the 15 exhaust valve will open against the pressure in the combustion chamber and against the force of the air spring. When it is time to close the exhaust valve again the electronic control unit will command the proportional electro-hydraulic control valve 5 to connect the pressure 20 pipe 10 to the low-pressure common rail 34 via valve arrangement 20. The exhaust valve and the exhaust valve actuator associated therewith have a considerable inertia and the closing of the exhaust valve will be much slower than the pressure drop in the pressure pipe 10 if the 25 pressure pipe 10 end was directly connected to tank when the proportional electro-hydraulic control valve 5 established the connection. The valve arrangement 20 includes a flow restriction that assures that the pressure drop is not too rapid and the valve arrangement 30 20 will maintain a minimum pressure on its upstream side.

Thereby, it is avoided that the pressure in the pressure pipe 10 will drop too rapid and too low. This will avoid the formation of air pockets in the pressure pipe 10 and will avoid subsequent cavitation.

10 DK 177283 B1

Fig. 3 shows the valve arrangement 20 in greater detail.

In this exemplary embodiment the valve arrangement includes a housing with a through going bore. The valve 5 arrangement 20 includes a fixed flow restriction 21 disposed at or near the inlet port of the valve arrangement 20 at one end of the through going bore. The inlet port of the valve arrangement 20 can be connected to the proportional electro-hydraulic control valve 5 via 10 a bore 11. i A floating valve member 22 with a substantially cylindrical body is slidably received in the through going bore. The floating valve member 22 is provided with 15 a pressure surface on each end. A first pressure surface is disposed on the side of the floating valve member 22 that faces the inlet port and the flow restriction 21. A first pressure chamber 23 is formed in the bore between the flow restriction 21 and the first pressure surface.

20

The second pressure surface is disposed on the opposite side of the floating valve member 22. The second pressure surface faces a second pressure chamber 25, also disposed in the through-going bore. The second pressure chamber is 25 connected to a source of relatively low pressure, such as the low pressure common rail 34.

The diameter of the through-going bore is larger in the section where it forms the first pressure chamber than in 30 the section where it forms the second pressure chamber.

Thus, the effective surface of the first pressure surface is larger than the effective surface of the second pressure surface. The floating valve member 22 is provided with a bore 26 that connects the first and DK 177283 B1 n second pressure chambers. The diameter of the bore 26 is relatively small so that throttles the flow between the two pressure chambers.

5 An outlet port 27 connects tank 36. The outlet port 27 is closed off by the floating valve member 22 in a range of positions of the floating valve member 22 and open in another range of positions of the floating valve member 22 to thereby connect the first pressure chamber to said 10 outlet port 27. In the range of open positions of the floating valve member 22 the first pressure chamber 23 is connected to outlet port 27.

With reference to the orientation of the valve 15 arrangement in Fig. 3, the floating valve member 22 closes off the connection between the first pressure chamber 23 and the outlet port 27 when the floating valve member 22 is in its lower range of positions and opens up for connection between the first pressure chamber 23 and 20 the outlet port 27 when the floating valve member 22 is in its upper range of positions.

The larger first effective pressure area urges the floating valve member 22 towards the range of positions 25 where the outlet port 27 is connected to the first pressure chamber 23 and the smaller second effective pressure area urges the floating valve member 22 towards the range of positions where the connection between the first pressure 23 chamber and the outlet port 27 is 30 closed.

The floating valve member 22 is provided with a side bore 28 that connects to an overflow port 29 in the housing of the valve arrangement 20 when said floating valve member 12 DK 177283 B1 22 is moved upwards (upwards with reference to the orientation of the valve arrangement in Fig. 3} to a large extent so that the side bore 28 overlaps with the overflow port 29. Thus, the second pressure chamber 25 is 5 connected to tank thereby allowing the floating valve member 22 to open up completely the output port 27 to relieve pressure in the first pressure chamber 23 during pressure peaks in the latter pressure chamber.

10 When there is no flow though the restriction 21 into the first pressure chamber the pressure in the latter chamber is lower than the pressure in the second pressure chamber by a factor that is equal to the ratio between the size of the effective pressure surfaces. Thus, when the 15 pressure is for example 2.2 bar in the second pressure chamber the pressure could be 1.5 bar in the first pressure chamber. When the proportional electro-hydraulic control valve 5 connects the pressure pipe 10 to the valve arrangement 20, there will be a substantial 20 flow through the restriction 21 and the pressure in the first pressure chamber will become high enough to urge the floating valve member 22 towards a position where a connection between the first pressure chamber 21 and the outlet port 27 is established so that hydraulic fluid can 25 be evacuated to tank. The position of the floating valve member 22 will be balanced between the pressure in the pressure chambers.

The position of the valve 22 is decided by the following 30 forces. The first effective pressure area at the first pressure chamber 23 x pressure in the first pressure chamber 23 against second effective valve area in the second pressure chamber 25 x pressure in the second pressure chamber 25. When exhaust valve is closed, the * 13 DK 177283 B1 pressure in the second pressure chamber 25 is about 2 bar. The force balancing pressure in the first pressure chamber 23 can be 1,5 bar. The pressure difference between the first pressure chamber 23 and the second 5 pressure chamber 25 will lead to a fluid flow through orifice 26, into the first pressure chamber 23.

A pressure increase in the first chamber 23 will move the valve member 22 upward and the increased opening to the 10 outlet port 27 will limit the pressure again to the value balancing the forces acting on the floating valve member 22.

Thus, the flow through orifice 26 will be the same as the 15 flow from chamber 23 to outlet port 27. The opening area from the first pressure chamber 23 to the outlet port 27 will be a flow through the orifice 26 at dP (the pressure difference) between the first pressure chamber 23 and the second pressure chamber 25. The moveable valve member 22 20 will thus "float" and adapt its position to the operating conditions .

This balance in combination with the flow restrictor 21 will provide for a suitable flow rate and maintain an 25 overpressure upstream of the valve arrangement (i.e. in the pressure pipe if the valve arrangement is used in an exhaust valve actuation system). These effects ensure that the flow rate is controlled and that there is no ingress of air.

30

The valve arraignment 20 has been described as part of an exhaust valve actuation system of a large two stroke diesel engine. However, it should be understood that the valve arrangement 20 can be used in other situations DK 177283 B1 14 where controlled return from and maintaining a minimum pressure is required in a harsh environment.

The exhaust valve actuation system has been described 5 with reference to a single cylinder of a large two-stroke diesel engine. In a multi-cylinder engine such an exhaust valve actuation system has to be provided for ! each cylinder (or at least for each exhaust valve), except for the common rails that can be used for a 10 plurality of cylinders.

The teaching of this disclosure has numerous advantages.

Different embodiments or implementations may yield one or more of the following advantages. It should be noted that 15 this is not an exhaustive list and there may be other advantages which are not described herein. One advantage of the teaching of this disclosure is that it provides for a valve arrangement that allows return to tank at controlled conditions thereby avoiding creation of air 20 pockets and cavitation.

It is another advantage of the present disclosure that it provides for a valve arrangement that can take the function of a check valve in harsh environments where conventional check valves that operate with a valve 25 member that abuts with a seat cannot be used.

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

a

Claims

A valve assembly comprising: a housing, an inlet opening, a fixed flow restriction (21) at or on the downstream side of the inlet opening, a float valve member (22) having two opposing effective pressure faces received in a bore in the housing, where one of the effective pressure faces faces a first pressure chamber (23) which is in fluid communication with the flow restriction, and the second effective pressure surface faces a second pressure chamber (25) connected to a source of relatively low pressure, an outlet opening (27) which is closed by means of of the float valve member (22) in a position area of the float valve member and opened in a second position area of the float valve member (22), thereby connecting the first pressure chamber (23) to the outlet opening (21), where one of the effective pressure faces forces the float valve member (22) into direction of the position area, where the first pressure chamber (23) is connected to the outflow opening (27) and the second of the effective pressure faces forces the float valve member (22) towards the position area where the first pressure chamber (23) is not connected to the outlet opening (27) and a bore (26) through the float valve member (22), connecting the first pressure chamber (23) to the second pressure chamber (25).

Valve assembly according to claim 1, wherein the bore (26) through the float valve member (22) is provided with a side bore (28) connecting the second pressure chamber (25) to an overflow opening (29) when the float valve member (22) is extensively moved. into the position area where the float valve member (22) connects the first pressure chamber (23) to the outlet opening (25).

Valve device according to claim 1, wherein the one effective pressure surface is larger than the other effective pressure surface.

Exhaust valve actuation system according to claim 1, wherein the float valve member (22) defines a guide edge together with an edge of a bore in which the float valve member (22) is received. x 1/3 (0) 10 DK 177283 B1 S 16 fif 18 —- I \ E i r i 12-7 j _, rice i i i] ^ i j J S! >, ....... Γ 20 f "Fig * 1 II! Π— uiii 2/3 DK 177283 B1 co Wrr— <m tj- 9 (999 Vid ffL___ n r + I! Ί ►,> | qqj ί CM! «-J /; T-; io ^ ..... 00 '· [yj! J rj i .......... J ............ .........; ay ~~ iis: ___ ”i! _! 'I ί yr J jsgfflfoyi. — 0 ----- \ Η Ϊ --------- ir-dJ x3> ι ^ ΡΤ-λη oo ^ - <3> 'lEr = rn V / Tpv, t TSlIza- viLT * 1 I s® η I å _jr; .________ i —-' O— · h- 00 © o © © © © 3/3 DK 177283 B1 CO cb ° σ> CM ^ CM LL. F ΐ i \ i \ c | \ ry —----------------.... ..............— i \ Vi ~~ c ϊ \ ii \ j I '! __ i! CM ΐ I V_po ~~ Γ ........... ....... Ί ff —- "A" kc fflff tO CM oo CO ^ CO V- CM CM CM CM CM CM CM CM