KR100978035B1 - Exhaust valve actuator for a large two-stroke diesel engine - Google Patents

Abstract

The present invention relates to an exhaust valve actuator for a large two-stroke diesel engine. The actuator is movable in opposite directions between the closed position and the open position, and has a double acting piston having a hydraulic closed chamber and a hydraulic open chamber. The double acting spring assembly is operably connected to the double acting hydraulic piston to form a mass spring system with the mass of the exhaust valve actuator spindle and any other portions that move integrally with the exhaust valve actuator spindle. During the forward and backward reciprocating motion between the closed and open positions of the exhaust valve actuator, the double acting spring assembly stores energy for later propulsion in the opposite direction of the exhaust valve actuator. Hydraulic valves of the on-off type connect the hydraulic closing chamber to the high pressure source, the hydraulic opening chamber to the tank, and vice versa. The closing force of the double acting spring is in equilibrium with the opening force of the hydraulic opening chamber when the exhaust valve actuator is in the open position and the electronically controlled hydraulic valve connects the hydraulic opening chamber with the high pressure hydraulic liquid.

It is suggested to disclose Figure 1 with a summary.

Description

Exhaust valve actuator for a large two-stroke diesel engine

The present invention relates to an exhaust valve actuator for a large two-stroke diesel engine of the crosshead type, and more particularly to an exhaust valve actuator that is fluidly operated and electronically controlled.

Large two-stroke engines of the crosshead type, which are generally used in propulsion systems of large ships or as prime movers of power plants, have recently been developed from camshaft control engines to electronically controlled engines. Electronic control provides improved improvisational flexibility for the timing and formation of fuel injection and exhaust valves. Therefore, the combustion process is better controlled and lowered to allow more efficient combustion, smoke free operation at all operating speeds, reduced part-load fuel consumption, and low minimum running speeds. Get the emission value. Chinese Patent Publication No. CN1485530 (China Application), Japanese Patent Application Publication JP2004-084670 (Japanese Application), and Korean Patent Publication No. 2004-20003 (Korean Application) disclose an electronically controlled large two-stroke diesel engine. . In such engines the exhaust valves are driven by hydraulic actuators driven by high pressure hydraulic fluid. The actuator pressurizes the exhaust valve to open against the counter force of the air spring. Most of the energy delivered by the hydraulic actuator in the opening stroke of the exhaust valve is stored in the gas spring as potential energy. The stored energy is not reused in a closing stoke, unlike cam shaft driven engines, but instead is consumed because there is no means to reuse the energy. The unused energy is converted into heat and returned to the tank of the hydraulic system with the returning oil. The amount of hydraulic energy used to open the exhaust valves of large two-stroke diesel engines is quite substantial, and the fuel savings obtained by improved combustion control of electronically controlled engines are consumed in the exhaust valve drive.

Large two-stroke engines having substantially the same valve assemblies are disclosed in WO98 / 57048. In WO98 / 57048, however, a position sensor connected to the controller is provided in the exhaust valve. The signal from the position sensor is used to monitor the movement of the exhaust valve and is not used to control the movement of the exhaust valve (no position feedback, or other form of feedback control).

WO2006 / 108629 discloses an exhaust valve assembly for a large two-stroke diesel engine, having an exhaust valve movable in opposite directions between a closed position and an open position. A double acting spring assembly is operably connected to the exhaust valve to form a mass-spring system with the exhaust valve and the mass of other parts moving together integrally with the exhaust valve. The double acting spring assembly then stores energy during the forward and backward translation of the exhaust valve to propel the exhaust valve in the opposite direction. Hydraulic means maintains the exhaust valve in the closed or open position upon command from the controller. The system requires the electronic controller to generate a signal whenever the actual position of the exhaust valve is known and whenever the exhaust valve needs to be stopped at any of the maximum positions of the exhaust valve.

Against this background, the object of the present invention is to provide a double acting spring assembly which does not require the actual position of the exhaust valve to be known to the controller accurately and does not require the use of proportional valves. To provide an exhaust valve assembly for a large two-stroke diesel engine.

This object, according to claim 1, has a hydraulic opening chamber on one side of the double acting piston and a hydraulic closing chamber on the other side, and the double acting hydraulic piston is accommodated. Translation of an actuator housing provided with a bore hole and an exhaust valve actuator operably connected to the double acting hydraulic piston, and subsequently moving back and forth between the closed and open positions of the exhaust valve actuator to propel the exhaust valve in the opposite direction. It has a double acting gas spring, which stores energy during translation, and an electronically controlled hydraulic valve of the on / off type, wherein the electronically controlled hydraulic valve has a hydraulically closed chamber. To a source of high pressure hydraulic liquid and a hydraulic opening chamber to a low pressure outlet or tank, And a second position, wherein the electronically controlled hydraulic valve connects the hydraulic closing chamber to the low pressure outlet or the tank, and the hydraulic opening chamber to the source of the high pressure hydraulic liquid, the closing force of the double acting gas spring. Is a large crosshead type, in which the exhaust valve actuator is in the open position and the electronically controlled hydraulic valve balances the opening force of the hydraulic opening chamber when the hydraulic opening chamber is connected to a high pressure hydraulic liquid source. By providing a two-stroke diesel engine exhaust valve actuator.

By equilibrating the forces of the double acting hydraulic piston in the open position with the double acting air spring, the exhaust valve actuator can be configured without the end of the stroke buffering the chambers or other parts, and using the proportional valves It is not required and can be operated with a simple electronically controlled draw valve of the on-off type.

Preferably, the opening force of the gas spring is less than the closing force of the hydraulic closing chamber when the exhaust valve actuator is in the closed position and the electronically controlled hydraulic valve connects the hydraulic closing chamber to a source of high pressure hydraulic liquid.

The high pressure hydraulic fluid can only be supplied to the hydraulic opening chamber during the last part of the opening stroke and only to the hydraulic closing chamber during the last part of the closing stroke.

The flow of high pressure hydraulic fluid during the last part of the open or closed stroke can be controlled by ports in the valve housing that are closed by the double-acting hydraulic piston during the first part of the open or closed stroke.

The flow of hydraulic fluid from the source of high pressure hydraulic fluid towards the hydraulic opening chamber can be regulated during the last part of the opening stroke. Thus oscillations are avoided and the amount of acceleration force to slow down the exhaust valve actuator at the end of the open stroke is reduced.

The flow of hydraulic fluid from the source of high pressure hydraulic fluid towards the hydraulic closing chamber can be regulated during the last part of the closing stroke. Thus, vibrations are avoided, and the magnitude of the acceleration force to slow down the exhaust valve actuator at the end of the closing stroke and the landing speed on the seat are reduced.

The connection between the hydraulic opening chamber and the electronically controlled hydraulic valve may have a first passageway connected to the hydraulic opening chamber through a first port, and the first throttle valve connected to the hydraulic opening chamber through a second port. And a second passage provided therein, the position of the double acting hydraulic piston controls the opening and closing of the first port and the second port, the first port is opened during the first part of the opening stroke, and the end of the opening stroke. During the portion the second port may be open. A relatively simple hydraulic system is therefore provided for controlling the opening movement of the exhaust valve actuator.

The connection between the hydraulic closing chamber and the electronically controlled hydraulic valve may have a third passage having a second throttle valve connected to the hydraulic closing chamber via the third port, and the fourth port leading to the low pressure reservoir or tank may be provided. And a fourth passage connected to the hydraulic closing chamber through which the position of the double-acting hydraulic piston controls the opening and closing of the third and fourth ports, the fourth port being opened during the first portion of the closing stroke, The third port may be open during the last part of the closing stroke. A relatively simple hydraulic system is therefore provided for controlling the closing movement of the exhaust valve actuator.

The first throttle valve can be bypassed through the first check valve to empty the hydraulic opening chamber.

The second throttle valve can be bypassed through the second check valve to empty the hydraulic closing chamber.

Preferably, the hydraulic closure chamber is pressurized during at least a portion of the closing stroke to provide additional energy to compensate for energy dissipation in the exhaust valve actuator, and the hydraulic closing chamber is configured to maintain the exhaust valve actuator in the closed position. Pressurized while the actuator is in the closed position.

Preferably, the hydraulic opening chamber is pressurized during at least a portion of the opening stroke to provide additional energy to compensate for energy dissipation in the exhaust valve actuator, and the hydraulic opening chamber is configured to maintain the exhaust valve actuator in the open position. Pressurized while the actuator is in the open position.

An electronically controlled hydraulic valve can connect the hydraulic closing chamber to a source of high pressure hydraulic liquid when in an inactive position and connect the hydraulic opening chamber to a low pressure reservoir or tank.

The exhaust valve actuator is a second electronically controlled hydraulic valve for supplying a high pressure hydraulic liquid to the hydraulic chamber to achieve an open stroke for the first time when the engine is started without pressure applied to the gas spring before the engine is started. It may be further provided.

A gas spring chamber that presses the double acting pneumatic piston in the closing direction can always be connected to a high pressure air source. Therefore, when no hydraulic pressure is applied, the exhaust valve actuator will take the closed position.

The gas spring chamber which presses the double acting pneumatic piston in the open direction can be connected to a source of high pressure air via an electronic control pneumatic valve. Therefore, the first pressurization of the gas spring chamber which presses the actuator in the open direction can be controlled electronically.

The gas spring chamber which presses the double acting pneumatic piston in the closing direction can be connected to atmospheric pressure via an electronically controlled pneumatic valve. Therefore, the gas spring chamber which presses the double acting pneumatic piston in the closing direction can be emptied if it is filled with leaking oil.

The gas spring chamber, which presses the double acting pneumatic piston in the open direction, is connected to atmospheric pressure through a pressure limiting valve or a pressure control valve. Therefore, if the leaking oil accumulates on the double acting pneumatic piston, the leaking oil can be emptied by the pressure limiting valve.

Other objects, configurations, effects, and characteristics of the exhaust valve actuator according to the present invention will become apparent from the detailed description.

The disclosure of the present invention has various advantages. Other embodiments and implementations can yield one or more of the following advantages. These advantages are not an exhaustive list and there may be other advantages not described herein. One advantage of the disclosure of this application is to provide an exhaust valve actuator of the type that operates with a reciprocating mass spring system that does not require a feedback signal based on the position of the actuator. Another advantage of the disclosure of this application is to provide an exhaust valve actuator of the type operating with a reciprocating mass spring system that does not require proportional hydraulic valves. Another advantage of the disclosure of this application is to provide an exhaust valve actuator of the type that operates with a reciprocating mass spring system that does not require chambers or the like that cushion the end of the stroke. Another advantage of the present invention is that the present invention reduces energy loss. Another advantage of the present invention is to provide small hydraulic opening surfaces that allow for further energy savings. Another advantage of the present invention is to provide an exhaust valve actuator that can be controlled with hydraulic valves of the on-off type. Another advantage of the present invention is to provide a more reliable exhaust valve actuator.

Although the disclosure of the present application has been described in detail for purposes of illustration, it will be understood that such details are for the purpose of illustration only and are to be understood by those of ordinary skill in the art. It is to be understood that variations can be made without departing from the scope of the disclosure of the application.

It should also be understood that there are many alternative ways of implementing the devices of the present disclosure.

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. A single processor or other apparatus may implement the functions of the various means described in the claims.

In the following detailed description of the present description, the invention will be described in more detail with reference to exemplary embodiments shown in the drawings.

Exhaust valve actuators according to the invention can be used to drive exhaust valves of low speed two-stroke crosshead diesel engines (not shown), which may be prime movers of ships or power plants. Can be. Such engines generally have six to sixteen cylinders with cylinder bore of 1 m or more in diameter. The exhaust valves are correspondingly large and weigh more than 400 kg. The engine power of these turbocharged engines ranges from 100,000 kw (largest type) to 1,600 kw (smallest type).

The operation of the exhaust valve according to the invention is controlled electronically, ie the electronic signal from the electronic control unit determines when the exhaust valve is opened and when the exhaust valve is closed. The electronic control unit receives a signal from a sensor that determines the angular position of the crankshaft. The engine therefore does not require a camshaft for the operation of the exhaust valves.

The exhaust valve is opened and closed by the exhaust valve actuator, and the spindle of the exhaust valve is firmly connected to the exhaust valve actuator.

1 is a schematic cross-sectional view when an engine of an exhaust valve actuator according to an embodiment of the present invention is in a first state in a standby state.

The exhaust valve actuator has a valve housing 1 provided with a hole for accommodating a double acting hydraulic piston 2 and a hole for accommodating a double acting air spring piston 3. . The double acting hydraulic piston 2 is connected via the shaft to the double acting air spring piston 3, but also extends downwardly towards the exhaust valve spindle (not shown) and is firmly connected to the exhaust valve spindle.

Since large two-stroke diesel engines typically have an exhaust valve in a vertical position on the top of the cylinders and are operated only by cylinders in a vertical position, we assume that the exhaust valve actuator is always in the vertical position shown in the drawings. It will be referred to as up and down, up and down as mounted. Of course, the exhaust valve actuator may be mounted in other positions if necessary.

The hydraulic closing chamber is formed under the double-acting hydraulic piston 2, and the effective pressure region 7 is provided on the inner surface of the double-acting hydraulic piston 2. The hydraulic opening chamber is formed on the double-acting hydraulic piston 2, and the effective pressure region 8 is provided above the double-acting hydraulic piston 2. The effective pressure region 7 is determined larger than the effective pressure region 8 for the reasons described below.

A stub counduit 17 connects the hydraulic opening chamber in the first part of the opening stroke of the double acting hydraulic piston 2 to a port 16 formed in the actuator housing. The stub passage 17 connects the hydraulic opening chamber to a port 18 formed in the actuator housing during the last part of the opening stroke of the double acting hydraulic piston 2.

Port 22 may optionally be connected to a tank and a source of high pressure hydraulic fluid (HP). The connection to either the tank or the source of high pressure hydraulic fluid is electronically controlled by the on / off valve 4.

In the passage connecting the port 22 to the electronically controlled on-off valves 4, a non-return valve and a throttle valve 14 are provided. This arrangement allows the flow of fluid to be substantially unrestricted towards the tank, but the flow from the high pressure source towards the port 22 is controlled by the throttle valve 14. In one embodiment, the throttle valve has a variable restriction that can be adjusted by the operator.

The position sensor 12 connected to the electronic control unit measures the position of the actuator spindle by sensing the distance to the conical part on the upper side of the actuator spindle.

The first spring chamber is formed above the double acting air spring piston 3 and the second spring chamber is formed below the double acting air spring piston 3. The double acting air spring piston 3 is provided with an effective pressure region 9 facing the second spring chamber and an effective pressure region 10 facing the first spring chamber. Effective area regions 9 and 10 are substantially the same in size.

The first spring chamber is connected to a passage leading to an electronically controlled two-way valve 6 via a port 24 in the valve housing 1. The two-way valve optionally selects to disconnect or make a connection to the source of pressurized air in response to a command from the electronic control unit. In one embodiment, the air pressure is approximately 7 bar.

The first spring chamber is connected to a passage leading to the pressure control valve 15, or pressure limiting valve, via a port 25 in the valve housing 1.

The second spring chamber is connected to a passage that leads to a source of pressurized air through a port 27 in the valve housing 1. This passage is provided with a non-return valve that allows only flow towards the second spring chamber. The second spring chamber is connected via a port 28 to a passage leading to the electronically controlled two-way valve 13. The two-way valve 13 optionally selects to disconnect or make a connection to the tank upon command from the electronic control unit.

The first spring chamber is compressed when the exhaust valve moves towards the closed position during operation and the second spring chamber is compressed when the exhaust valve moves towards the open position. The first and second spring chambers function as potential energy accumulators.

When the first spring chamber is compressed, the potential energy accumulated in the first spring chamber may drive the exhaust valve in the open direction. When the second spring chamber is compressed, the energy accumulated in the second spring chamber can drive the exhaust valve in the closing direction.

The air spring forms a combination with the mass of the exhaust valve actuator spindle, the mass of the exhaust valve, and the mass of certain parts moving integrally with the exhaust valve, which, when set to move, is stored in the spring chamber of the double acting gas spring or The energy released is mainly used to reciprocate between the closed and open positions. The kinetic energy of the exhaust valve and any other parts moving integrally with the exhaust valve are converted into potential energy in the spring chamber of the gas spring and vice versa. Only the energy lost due to friction and viscous dissipation needs to be replenished in order to allow the exhaust valve to reciprocate between the closed and open positions, i.e. to avoid gradual reduction in reciprocating motion.

1 to 5 show exhaust valve actuators in various operating states, and FIG. 6 shows the opening and closing of valves 4, 5 and 6, including two engine cycles from starting the engine. A sequence diagram showing the timing of. 6 also shows the resulting exhaust valve motion contour for two exhaust valve openings (two engine cycles).

In the standby mode (FIG. 1), the hydraulic valves 4, 5 are in a default position connecting the ports 16, 18 to the tank and the port 22 to a source of high pressure hydraulic fluid. . In this state, the pneumatic two-way valve 6 and the pneumatic two-way valve 13 are also in the basic position. In this position of the pneumatic two-way valve 6, the first spring chamber is emptied through the port 24. The second spring chamber is pressurized to approximately 7 bar through the port 27. The air pressure in the second spring chamber acting on the effective pressure region 9 of the double acting piston 3 and the hydraulic pressure in the closed chamber acting on the effective pressure region 7 cause the actuator spindle to assume a closed position. At the same time the open chamber above the double acting hydraulic piston 2 is connected to the tank via the port 16 and therefore is not pressurized.

In Fig. 2, an engine start signal will be issued and the pneumatic two-way valve 6 will be activated to supply about 7 bar of air to the first spring chamber during the first opening of the exhaust valve after engine atmosphere. The pneumatic two-way valve 6 remains in operation while the engine is running, ie until an engine stop signal is generated.

When the exhaust valve is opened for the first time after the engine is started, the hydraulic two-way valves 4 and 5 are actuated by a signal from the electronic control unit. The electronic control unit determines the timing of valve opening based on the information available to the electronic control unit with respect to the crankshaft angle and the operating conditions of the engine. Since no compressed air acting on the effective pressure surface area 10 yet, a full opening stroke must be performed by the hydraulic fluid (oil). Therefore, the hydraulic two-way valve 5 is also driven. The operating position of the hydraulic two-way valves 4, 5 is shown in FIG. 3. When the hydraulic two-way valves 4 and 5 move to the operating position, the high pressure fluid first flows into the hydraulic open chamber through the port 16 at a relatively high flow rate, and the double acting hydraulic piston 2 approaches the open position. , Flows through the port 18 at a low flow rate caused by the throttle effect of the throttle valve 11. The force generated by the pressure in the hydraulic opening chamber with respect to the effective pressure region 8 of the double acting hydraulic piston 2 causes the spindle of the exhaust valve actuator to move to the open position. The oil in the hydraulic closing chamber is emptied into the tank through the ports 21, 20 during the opening movement. When the actuator is fully open as shown in FIG. 3, the force of the pressure on the effective pressure region 8 of the double-acting hydraulic piston 2 and the pressurized pressure on the effective pressure region 9 of the double-acting gas spring piston 3 There is an equilibrium between the air. The last part of the hydraulic oil supplied to the hydraulic opening chamber passes through the throttle valve 11 to reduce the reciprocation and reduce the acceleration force when slowing down the exhaust valve.

If hydraulic oil accumulates under the double-acting air piston 3, an equilibrium will occur when the spindle of the exhaust valve actuator has only partially moved towards the fully open position. This condition will be recorded by the position sensor 12, and as a response the electronic control unit will generate a very short opening signal to the relief valve 13, through which excess hydraulic oil will flow through the port 28 to the second air. It will be emptied from the spring chamber.

The signal for closing the exhaust valve causes the hydraulic two-way valves 4, 5 to return to the idle position shown in FIG. 4. The effective pressure region 8 of the double acting hydraulic piston 2 is first quickly discharged through the port 18 and the non-return valve 11 (throttling contra-valve), and secondly the port. Ejected through 16. The force of the pressure on the effective pressure region 9 of the double acting air spring piston 3 in the second air spring chamber causes the actuator's spindle to move in the closing direction. During the first part of the closing motion, low pressure hydraulic oil is fed through the port 21 to the hydraulic closing chamber below the double acting hydraulic piston 2. During the last part of the closing motion (FIG. 4), the high pressure hydraulic oil is supplied to the hydraulic closing chamber below the double acting hydraulic piston 2 via the throttle valve 14 and the port 22. Hydraulic assistance ensures that the exhaust valve actuator is fully closed in a slowly controlled fashion, and the air above the effective pressure surface area 10 is strongly compressed. The nature of the throttle valve 14 determines the settling velocity with respect to the seat of the exhaust valve.

Since the effective pressure region 7 is larger than the effective pressure region 8, a high pressure can be achieved above the double acting air spring piston 3 of the first spring chamber rather than in the second spring chamber. This high pressure can overcome the gas pressure in the combustion chamber in the continued opening of the exhaust valve. If leakage oil accumulates on the double acting air spring piston 3, the air pressure will increase beyond the set point when the exhaust valve actuator is in the closed position. As a result, the pressure control valve 15 is opened, and the leaked oil is discharged until the steady state is restored.

During the subsequent opening of the exhaust valve (FIG. 5), only the hydraulic two-way valve 4 is driven. The high pressure oil under the double acting hydraulic piston 2 is discharged into the tank via the port 22. Pressurized air above the effective pressure surface area 10 moves the exhaust valve. Fluid (oil) in the hydraulic closing chamber is pressurized and discharged into the tank through the ports 21, 22. High pressure hydraulic fluid is supplied through the port 16 during the first part of the opening stroke in the hydraulic opening chamber. During the last part of the open stroke, high pressure hydraulic fluid is supplied through the port 18 to hold the exhaust valve actuator in the open position. At the same time the air under the effective pressure region 9 in the second spring chamber is compressed for subsequent closing operation.

When the exhaust valve actuator is in the open position, the force on the effective pressure region 8 of the double acting hydraulic piston 2 is in equilibrium with the force on the effective pressure region 9 of the double acting air spring piston 3. The magnitude of the closing force for the effective pressure region 9 is sized to ensure that the exhaust valve actuator is closed within a predetermined time interval. The size of the effective pressure region 8 is determined based on the hydraulic pressure and the closing force. The compression ratio is determined by the length of the stroke required.

When the exhaust valve actuator is in the closed position, the compression ratio in the spring chamber above the effective pressure region 10 is such that the opening force is greater than the force of the combustion chamber gas acting on the exhaust valve. The size of the effective pressure region 7 is such that the pressure of the hydraulic pressure acting on the effective pressure region 7 is greater than that of the pneumatic pressure acting on the effective pressure region 10 so that the exhaust valve is closed to ensure proper closing of the exhaust valve. It is adapted to pressurize against the seat of the exhaust valve. The various aspects described above can be used alone or in various combinations.

1 is a schematic cross-sectional view of a main configuration in a first state of an exhaust valve actuator according to an embodiment of the present invention.

2 shows the actuator of FIG. 1 in a second state.

3 shows the actuator of FIG. 1 in a third state.

4 shows the actuator of FIG. 1 in a fourth state.

5 shows the actuator of FIG. 1 in a fifth state.

6 is a sequence diagram showing the timing of opening and closing of the valves of the exhaust valve actuator of FIGS. 1 to 5.

DESCRIPTION OF THE REFERENCE NUMERALS

1: valve housing 11: throttle valve

2: double acting hydraulic piston 12: position sensor

3: double acting air spring piston 13: pneumatic two-way valve

4, 5, 6: Valve 14: Throttle Valve

7: effective pressure range 15: pressure control valve

8: effective pressure area 16: port

9: effective pressure zone 17: stub passage

18, 20, 21, 22, 24, 25, 27, 28: port 10: effective pressure range

Claims (19)

Exhaust valve actuator for large two-stroke diesel engines of the crosshead type, An actuator housing having a hydraulic opening chamber on one side of the double acting piston and a hydraulic closing chamber on the other side thereof, the actuator housing having a hole for accommodating the double acting hydraulic piston; Operatively connected to the double acting hydraulic piston and thereafter storing energy during translation of the exhaust valve actuator back and forth between the closed and open positions of the exhaust valve actuator to propel the exhaust valve in the opposite direction. Double acting gas spring; And Equipped with an on / off type of electronically controlled hydraulic valve, On-off type electronically controlled hydraulic valve, An on-off type electronically controlled hydraulic valve connecting the hydraulic closing chamber to a source of high pressure hydraulic liquid and the hydraulic opening chamber to a low pressure outlet or tank; An on-off type electronically controlled hydraulic valve having a second position, connecting the hydraulic closing chamber to a low pressure outlet or a tank, and connecting the hydraulic opening chamber to a source of high pressure hydraulic liquid, The exhaust valve actuator has a closing force of the double acting gas spring when the exhaust valve actuator is in the open position and the on-off type electronically controlled hydraulic valve connects the hydraulic opening chamber of the double acting hydraulic piston to the high pressure hydraulic liquid source. Is formed in equilibrium with the opening force of the opening chamber, High pressure hydraulic fluid is supplied only to the hydraulic opening chamber during the last part of the opening stroke, only to the hydraulic closing chamber during the last part of the closing stroke, The flow of high pressure hydraulic fluid during the last part of the open or closed stroke is controlled by ports in the valve housing which are closed by the double acting hydraulic piston during the first part of the open or closed stroke. Actuator. The method of claim 1, The opening force of the gas spring is the closing of the hydraulic closing chamber of the double acting hydraulic piston when the exhaust valve actuator is in the closed position and the on-off type electronically controlled hydraulic valve connects the hydraulic closing chamber of the double acting hydraulic piston to the source of the high pressure hydraulic liquid. Exhaust valve actuator, smaller than force. delete delete The method of claim 1, The flow of hydraulic fluid from the source of high pressure hydraulic fluid towards the hydraulic opening chamber is throttled during the last part of the opening stroke. The method of claim 1, The flow of hydraulic fluid from the source of high pressure hydraulic fluid towards the hydraulic closing chamber is throttled during the last part of the closing stroke. The method of claim 1, The connection between the hydraulic opening chamber and the electronically controlled hydraulic valve includes a first passage connected to the hydraulic opening chamber through a first port and a first throttle valve connected to the hydraulic opening chamber through a second port. Having a second passage, the position of the double acting hydraulic piston controls the opening and closing of the first port and the second port, the first port is opened during the first part of the open stroke, and the second during the last part of the open stroke. Exhaust valve actuator, in which the port is opened. The method of claim 7, wherein The connection between the hydraulic closing chamber and the electronically controlled hydraulic valve has a third passage having a second throttle valve connected to the hydraulic closing chamber via the third port, and the hydraulic pressure through the fourth port leading to the low pressure reservoir or the tank. A fourth passage connected to the closing chamber, wherein the position of the double-acting hydraulic piston controls the opening and closing of the third port and the fourth port, the fourth port is opened during the first portion of the closing stroke, The exhaust valve actuator of the third part is opened during the last part. The method of claim 8, An exhaust valve actuator, wherein the first throttle valve is bypassed through the first check valve to empty the hydraulic opening chamber. The method of claim 8, The second throttle valve is bypassed through the second check valve to empty the hydraulic closing chamber. The method of claim 1, The hydraulic closing chamber is pressurized during at least a portion of the closing stroke to provide additional energy to compensate for energy dissipation in the exhaust valve actuator, and the hydraulic closing chamber is closed with the exhaust valve actuator in order to maintain the exhaust valve actuator in the closed position. Exhaust valve actuator, which is pressurized while in the chamber. The method of claim 1, The hydraulic opening chamber is pressurized during at least a portion of the opening stroke to provide additional energy to compensate for energy dissipation in the exhaust valve actuator, and the hydraulic opening chamber has the exhaust valve actuator in the open position to maintain the exhaust valve actuator in the open position. Exhaust valve actuator, which is pressurized while in the chamber. The method of claim 1, An electronically controlled hydraulic valve connects the hydraulic closing chamber to a source of high pressure hydraulic liquid when in an inactive position and connects the hydraulic opening chamber to a low pressure reservoir or tank. The method of claim 13, When starting a large two-stroke diesel engine with no pressure applied to the gas spring before the large two-stroke diesel engine is started, a second electronic for supplying a high pressure hydraulic liquid to the hydraulic open chamber to achieve the open stroke for the first time. An exhaust valve actuator, further comprising a control hydraulic valve. The method of claim 1, A gas spring chamber for pressurizing the double acting pneumatic piston in the closing direction is always connected to a high pressure air source. The method of claim 15, A gas spring chamber for pressurizing the double acting pneumatic piston in the open direction is connected to a source of high pressure air via an electronic control pneumatic valve. The method of claim 16, A gas spring chamber for pressurizing a double acting pneumatic piston in the closed direction is connected to atmospheric pressure through the electronically controlled pneumatic valve. The method of claim 17, A gas spring chamber for pressurizing the double acting pneumatic piston in the open direction is connected to atmospheric pressure through a pressure limiting valve or a pressure control valve. The method of claim 1 An exhaust valve actuator further comprising an electronically controlled pneumatic valve configured to connect a gas spring chamber that pressurizes the exhaust valve actuator in the open direction to the atmosphere when the large two-stroke diesel engine is in standby mode.

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