JP4566277B2 - Large two-cycle diesel engine with exhaust valves that move outward - Google Patents

Description

  The present invention relates to a large two-cycle diesel engine, and more specifically to an exhaust valve system for a large two-cycle diesel engine.

Background of the Invention

  A crosshead type large two-cycle diesel engine is used, for example, for propulsion of a large ocean-going vessel or as a generator of a power plant. These two-cycle diesel engines are built differently from any other combustion engine, not only because of their very large dimensions. The engine exhaust valve weighs up to 400 kg, the piston diameter exceeds 1 meter, and the maximum operating pressure in the combustion chamber is typically a few hundred bars. The forces and piston dimensions involved at such high pressure levels are just huge.

  Inadequate pressure may occur in one of the cylinders due to an incorrect fuel injection timing or fuel injection amount. In order to cope with such excessive pressure, the force with which the cylinder cover is pressed against the upper part of the cylinder liner is carefully determined by the tension applied to the retaining bolts that connect the cylinder cover to the base plate and keep the engine structure integrated. Be controlled. When overpressure occurs, the cylinder cover is lifted and overpressure is ejected between the top of the cylinder liner and the bottom of the cylinder cover.

  There are problems with this system commonly used in the art. First, when such a lateral ejection occurs, any person in the vicinity may be seriously ill. Secondly, the extremely hot high-pressure gas significantly erodes the contact surfaces of the precisely machined cylinder liner and cylinder cover, so that if there is a blowout, the required liquid-tightness is ensured. It becomes necessary to machine the surface. Therefore, the repair costs after the eruption are considerable. Third, the tension of the reserve bolt varies with changes in engine and environmental temperature, and cannot be controlled very precisely. When jetting occurs when the reserve bolt tension is relatively high, forces on the piston and crankshaft have traditionally caused damage to the large end and other expensive engine components. When this happens, it is more expensive than fully controlling the ejection.

  Most of the engine is also provided with a safety valve. This safety valve is supposed to release exhaust gas from the combustion chamber when excessive pressure is generated in the engine. However, since such an occurrence is explosive, the safety valve is relatively useless because there is not enough maximum opening to relieve pressure in a sufficiently short time. Accordingly, this safety valve cannot effectively provide the required open area in a sufficiently short time.

  Accordingly, there is a need for an improved jet control system for large two-cycle diesel engines.

  Against this background, it is an object of the present invention to provide a large two-cycle diesel engine with an improved system for dealing with excessive cylinder pressure events.

  The object is to provide a plurality of cylinders that serve as combustion chambers, each cylinder being provided with at least one exhaust valve, and an exhaust valve for opening and closing the exhaust valve in synchronism with the engine cycle. A cross-head type large two-cycle diesel engine having an operating system, wherein the exhaust valve operating system is directed outwardly with respect to the corresponding combustion chamber for exhaust gas exhaust control after combustion, respectively. The exhaust valve actuation system closes the exhaust valve inwardly with respect to the corresponding combustion chamber, respectively, before combustion, and the exhaust valve actuation system is free from any of the combustion chambers regardless of the current stage of the engine cycle. If excessive pressure is generated, the exhaust valve corresponding to the combustion chamber can be opened outward with respect to the combustion chamber. To be achieved by providing a crosshead type large two-stroke diesel engines.

  By disposing the exhaust valve away from the combustion chamber when opening, and by allowing the exhaust valve to automatically open when excessive pressure is generated in the corresponding cylinder, a number of Benefits are gained.

  One advantage is that the inertia of the exhaust valve spindle is small compared to the inertia of the cylinder cover. This will result in a quicker reaction and release when an over cylinder pressure event occurs.

  Another advantage is that the outflow area where the exhaust valve opens during a release situation is larger than the narrow gap between the cylinder cover and the cylinder liner. Accordingly, the gas can be exhausted more quickly, and the pressure increase is further suppressed, so that the risk to engine parts such as the large end or the crankshaft is reduced.

  Yet another advantage is that the relief pressure setting for the exhaust valve can be adjusted relatively precisely, allowing it to be relatively close to the peak pressure during normal operation. Most engine component dimensions are based on the pressure at which the relief occurs. Therefore, the safety range of these parts can be designed to be smaller, and a lightweight engine structure with the same reliability is possible.

  A further advantage is that the hot gas at the time of ejection passes through parts designed to withstand the hot gas, so that these parts are not damaged when the ejection occurs. Therefore, normal engine operation can be continued even if these errors occur due to correction of excessive cylinder pressure. This is not possible with the prior art. This is because the contact surface between the cylinder cover and the cylinder liner must first be machined, so that normal operation could only be resumed after a relatively complex repair.

  Another advantage is that the gas at the time of the escape event is released to the exhaust system rather than the machine room.

  Another advantage is that the exhaust valve is assisted by the pressure of the combustion chamber to perform its opening movement. This is in contrast to the prior art where the exhaust valve must be opened against the pressure in the combustion chamber. This means that less force is required to open the exhaust valve and, consequently, the load on the valve actuation system is lower. Thus, the energy required for operation of the exhaust valve actuation system is reduced compared to prior art systems with exhaust valves that open to the inside.

  The exhaust valve may be biased outward in order to open the exhaust valve by a gas spring acting on the shaft of the exhaust valve.

  The hydraulic actuator may bias the exhaust valve inward to close the exhaust valve.

  The exhaust valve may comprise a valve head that interacts with a cylinder cover at the top of each cylinder to seal the combustion chamber when the exhaust valve is in its closed position.

  The valve head may be fitted to a sealing engagement portion in an annular opening of the cylinder cover. Accordingly, the closed position can have a width. Also, since the exhaust valve can be increased in speed before opening, there is a narrow opening gap and the resulting high-speed gas flow, resulting in a time zone during which the valve seat heat load and squeezing loss occur. Can be minimized.

  One or more sealing rings may be provided on the inner surface of the annular opening.

  One or more sealing rings may be provided on the peripheral surface of the valve head.

  The normal line of the sealing surface of the cylinder cover and the valve seat may have only a radial component.

  The exhaust valve may not have a seating position fixed, and may have a width at a position where the valve is closed.

  The valve head may contact the valve seat of the cylinder cover.

  The normal of the valve seat surface may have axial elements.

  The axial component may be directed outward with respect to the combustion chamber.

  The valve seat may be conical.

  The valve actuation system may include a camshaft and a cam driven actuator pump that is operatively coupled to a hydraulic actuator.

  The cam-driven pump may be connected to the actuator via a pressure conduit, and a timed shutoff valve may be disposed on the pressure conduit.

  When the shut-off valve is closed, the exhaust valve corresponding to the shut-off valve may be prevented from moving except when excessive pressure is generated in the combustion chamber corresponding to the exhaust valve.

  In order to protect the cam-driven pump and camshaft from the high pressure that the hydraulic actuator is exposed to during combustion, the shutoff valve opens only during exhaust valve lift.

  The valve actuation system may include a camshaft and a cam driven actuator pump that is operatively coupled to a hydraulic actuator.

  The cam-driven pump may be connected to the actuator via a pressure conduit, and a timed switching valve may be disposed on the pressure conduit.

  The switching valve may directly connect the pressure chamber in the hydraulic actuator to the cam driven pump during opening and closing of the valve in the first position, and while the exhaust valve is closed in the second position. In addition, the pressure chamber may be connected to a cam-driven pump via a pressure amplifier.

  The cam on the camshaft acting on the cam driven pump has a stepped profile that allows the cam driven pump to continuously supply at least a small amount of hydraulic fluid during the engine cycle when the exhaust valve is closed. You may have.

  The switching valve may be provided with a check valve element in the second position.

  In the first position, the switching valve may directly connect the pressure chamber in the hydraulic actuator to the cam-driven pump during opening and closing of the valve, and in the second position, another high-pressure hydraulic fluid source may be connected. You may connect with the pressure chamber in a hydraulic actuator.

  The another high-pressure hydraulic fluid source may be a hydraulic pump.

  The valve actuation system may comprise a high pressure hydraulic pump operatively coupled to the exhaust valve actuator via a pressure conduit and a control valve.

  A relief valve may be operably coupled to the hydraulic actuator, and the relief valve is configured to open when excessive pressure occurs in the combustion chamber.

  The relief valve may be configured to open when the pressure in the hydraulic actuator exceeds a predetermined threshold.

  The relief valve may be of the type that opens fully when a predetermined threshold is exceeded and remains open thereafter.

  Further objects, features, advantages, and characteristics of the large two-cycle diesel engine according to the present invention will become apparent from the detailed description.

Detailed Description of the Preferred Embodiment

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

  1 and 2 show an engine 1 according to a preferred embodiment of the present invention in a cross-sectional view and a longitudinal cross-sectional view (for one cylinder), respectively. The engine 1 is a cross-head type uniflow-type low-speed two-cycle diesel engine and can be a ship propulsion system or a power plant prime mover. Typically, such engines have 4 to a maximum of 14 cylinders in a row. The engine 1 is assembled from a base plate 2 having a main bearing for the crankshaft 3.

  The crankshaft 3 is a semi-assembled type. The semi-assembled mold is made from a cast steel throw or forged steel throw connected to the main journal shaft by a shrink fit connection.

  The base plate 2 can be partially manufactured, or can be divided into portions of an appropriate size according to the manufacturing facility. The base plate includes side walls and welded cross grinders having bearing supports. In the art, a cross beam is also referred to as a “transverse girder”. The oil receiver 58 is welded to the bottom of the base plate 2 and collects return oil from the forced lubricating oil and cooling oil system.

  The connecting rod 8 connects the crankshaft 3 to the crosshead bearing 22. The cross head bearing 22 is guided between the vertical guide surfaces 23.

  The welded A-type box frame 4 is mounted on the base plate 2. The box frame 4 is a welding design. The exhaust side box frame 4 is provided with a relief valve for each cylinder, while the camshaft side box frame 4 is provided with a large hinged door for each cylinder. The crosshead guide surface 23 is integral with the box frame 4.

  The cylinder frame 5 is mounted on the upper part of the box frame 4. The retaining bolt 27 connects the base plate 2, the box frame 4, and the cylinder frame 5, and maintains the structure in an integrated manner. The reserve bolt 27 is tightened with a hydraulic jack.

  The cylinder frame 5 is ultimately cast or welded into one or more parts having an integral camshaft housing 25. According to another embodiment (not shown), the camshaft 28 is housed in a separate camshaft housing that is attached to the cylinder frame.

  The cylinder frame 5 is provided with an access cover for cleaning the scavenging space and for checking the scavenging port and the piston ring on the camshaft side. The cylinder frame forms a scavenging space together with the cylinder liner 6. The scavenging receiver 9 is bolted to the cylinder frame 5 on its open side. At the bottom of the cylinder frame is a packing box for piston rods, which is equipped with a scavenging sealing ring and an oil ring that prevents exhaust products from entering the space between the box frame 4 and the base plate 2. In this way, all bearings existing in this space are protected.

  The piston 13 includes a piston crown and a piston skirt. The piston crown is made of heat-resistant steel, has four ring grooves, and hard chrome is plated on the upper and lower surfaces of the groove portions.

  The piston rod 14 is connected to the crosshead 22 by four screws. The piston rod 14 has two coaxial holes (not visible in the drawing) and is connected to a cooling oil pipe to form an inlet and an outlet for the cooling oil of the piston 13.

  The cylinder liner 6 is carried by the cylinder frame 5. The cylinder liner 6 is made of alloy cast iron and is suspended from the cylinder frame 5 by a flange at a low position. The top of the liner is surrounded by a cast iron cooling jacket. The cylinder liner 6 has a drill hole (not shown) for lubricating the cylinder.

  The cylinder is uniflow and has a scavenging port 7 positioned in the air box. The exhaust port is supplied with scavenging air pressurized by the turbocharger 10 (FIG. 1) from the scavenging receiver 9 (FIG. 1).

  The engine is equipped with one or more turbochargers 10. This turbocharger is arranged on the rear side of the engine in the case of 4 to 9 cylinder engines, and on the exhaust side in the case of 10 or more cylinder engines.

  The intake air to the turbocharger 10 is generated directly from the engine compartment via an intake silencer (not shown) of the turbocharger. Air is guided from the turbocharger 10 to the scavenging port 7 of the cylinder liner 6 through an air supply pipe (not shown), an air cooler (not shown), and a scavenging receiver 9.

  The engine is provided with an electric scavenging blower (not shown). The suction side of the blower is connected to the scavenging space after air cooling. A check valve (not shown) is provided between the air cooler and the scavenge receiver, and this check valve automatically closes when the auxiliary blower supplies air. The auxiliary blower assists the turbocharger compressor in low and medium load conditions.

  The fuel valve 40 is mounted concentrically on the cylinder cover 12. At the end of the compression stroke, the injection valve 40 injects the atomized fuel into the combustion chamber 15 at a high pressure through the injection nozzle. The fuel can be diesel oil, heavy oil, gas. When the engine is gas driven, the engine is usually provided with a fuel oil injection system and a gas injection system (not shown) so that the engine can operate with any type of fuel. To. The exhaust valve 11 is attached to the center of the cylinder cover 12 at the top of the cylinder. The exhaust valve 11 includes a valve head 11a and a valve rod 11b. At the end of the expansion stroke, before the engine piston 13 descends beyond the scavenging port 7, the exhaust valve 11 opens upward, so that the combustion gas in the combustion chamber 15 on the piston 13 is exhausted to the exhaust receiver 17 And the pressure in the combustion chamber 15 is released. The exhaust valve 11 is closed again by the downward movement of the cylinder 13 and the combustion chamber 15 during the upward movement of the piston 13. The exhaust valve 11 is hydraulically operated.

  FIG. 3 shows a first embodiment of an exhaust valve actuation system according to the present invention. The exhaust valve actuation system relates to all of the embodiments shown for a single cylinder. Even in a multi-cylinder engine, the same thing is provided for each cylinder. The exhaust valve actuation system includes a camshaft 28 having a cam 29 (only one is shown). The roller 30 follows the surface of the cam 29 and is connected to the piston of the cam-driven positive displacement pump 32. The positive displacement pump 32 is connected to the exhaust valve actuator 34 via a conduit 36. The exhaust valve actuator 34 includes a cylindrical pressure chamber and a piston accommodated so as to swing in the cylindrical pressure chamber, and acts on the rod 11b of the exhaust valve 11. The gas spring 38 is also connected to the exhaust valve rod 11b, and the gas pressure in the pressure chamber of the gas spring 38 urges the exhaust valve 11 in the opening direction away from the combustion chamber 15. When the valve actuator 34 is pressurized, the valve actuator 34 biases the exhaust valve in the closing direction toward the combustion chamber 15. In the present embodiment, the valve head 11a closes the cylinder by fitting together with the annular opening of the cylinder cover 12. The normal line of the peripheral surface of the valve head 11a faces the radial direction. The same applies to the inner surface of the annular opening, with its normal pointing in the radial direction.

  In an embodiment not shown, the position of the exhaust valve is measured by a sensor coupled to the engine's electronic control system.

  The shut-off valve 41 is disposed at a connecting portion between the cam-driven pump 32 and the pressure chamber of the hydraulic valve actuator 34. In this embodiment, the electronically controlled shutoff valve 41 has two positions. In the first position, the shut-off valve connects the pressure chamber of the hydraulic valve actuator 34 to the cam driven hydraulic pump 32 via the pressure conduit 36. In the second position (shown), the shutoff valve 41 closes the connection between the pressure chamber of the hydraulic exhaust valve actuator 34 and the cam driven hydraulic pump 32.

  A large hole in the wall of the pressure chamber of the hydraulic exhaust valve actuator 34 connects the pressure chamber to the pressure relief valve 43. The pressure relief valve 43 is configured to open to a tank (not shown) when the pressure in the pressure chamber exceeds a predetermined threshold. This threshold is set slightly above the maximum (peak) pressure generated in the pressure chamber of the hydraulic exhaust valve actuator 34 during normal engine operation. Typically, this peak pressure corresponds to the stage in the engine cycle where combustion occurs. The pressure relief valve 43 is of a type that fully opens when reaching a set pressure and continues to open thereafter. The primer pump 42 replenishes oil loss due to leakage.

  During operation, the camshaft 28 rotates in line with the crankshaft of the engine. The profile of the cam 29 determines the movement of the positive displacement pump 32. When the positive displacement pump 32 moves upward, hydraulic fluid is forced through the conduit 36 to the valve actuator 34. The actuator 34 closes the exhaust valve 11 against the pressure in the gas spring 38. During this time, the shutoff valve 41 is in the first position, allowing fluid from the cam driven positive displacement pump 32 to flow out into the pressure chamber of the hydraulic exhaust valve actuator 34. When the exhaust valve 11 reaches its closed position (shown as a solid line in FIG. 3), the shutoff valve 41 moves to the second position (shown), the pressure chamber of the hydraulic exhaust valve actuator 34 and the cam-driven volume. Any fluid communication with the mold pump 32 is not possible. Therefore, the exhaust valve 11 is locked at its closed position, and the peripheral end portion of the valve head 11a cooperates with the protruding portion 47 of the cylinder cover 12 to form a fluid seal. The protrusion 47 is the illustrated embodiment with a sealing ring 49. In other embodiments (not shown), one or more sealing rings 49 are provided on the peripheral surface of the valve head 11a.

  When the exhaust valve is opened (after combustion has occurred), the shutoff valve 41 returns to its first position and connects the pressure chamber of the hydraulic exhaust valve actuator 34 to the cam-driven positive displacement pump 32. The cam-driven positive displacement pump 32 moves downward, and the gas spring 38 urges the exhaust valve 11 and the exhaust valve actuator 34 to move upward by using the pressure of the fuel chamber acting on the valve head 11a together. Thereby, the fluid in the exhaust valve actuator 34 flows out back to the cam-driven positive displacement pump 32. Part of the energy transferred to the exhaust valve actuator 34 during the opening movement of the exhaust valve 11 returns to the camshaft 28 by the pressure generated by the positive displacement pump 32 during the return process of the exhaust valve actuator 34. Thus, only a small portion of the hydraulic energy is required to open the exhaust valve 11.

If excessive pressure is generated in the combustion chamber 15, the excessive pressure generates a high pressure that urges the exhaust valve 11 upward, resulting in a high pressure, that is, a pressure higher than that generated during normal engine operation. Occurs in the pressure chamber of the hydraulic exhaust valve actuator 34. Immediately thereafter, the pressure relief valve 43 is fully opened, allowing the fluid in the pressure chamber of the hydraulic exhaust valve actuator 34 to be immediately discharged . The excessively high pressure in the combustion chamber quickly opens the exhaust valve 11 in the direction away from the combustion chamber 15 by using the force of the gas spring 38 together. With the exhaust valve 11 open, the gas in the combustion chamber 15 can be exhausted through a normal channel designed to direct the exhaust gas from the combustion chamber 15 to the surroundings. This process normally does not cause any damage to the engine 1 because the threshold pressure at which the pressure relief valve 34 opens can be accurately set. Accordingly, the exhaust valve 11 is opened before the inadvertent pressure increased in the combustion chamber damages the engine parts. When the exhaust valve is opened, the gas is released to the surroundings through channels designed to handle such gas, dealing with this gas flow without causing any damage.

  In a variant not shown of the first embodiment, the shut-off valve is not electronically controlled but is instead controlled by a camshaft. This can be a camshaft 28 with an additional lobe for the control of the shutoff valve or it can be a separate camshaft just for the purpose of controlling the shutoff valve associated with the various cylinders Is possible.

  The enlarged portion of FIG. 3 shows details of a modification of the first embodiment. In this embodiment, the pressure with which the sealing ring 49 engages the valve head 11a is variable. The conduit 50 connects the outer periphery of the sealing ring 49 to the combustion chamber 15. When the pressure in the combustion chamber 15 increases, the sealing ring is biased toward the valve head 11a due to the increase in pressure. Therefore, if the pressure in the combustion chamber 15 is low and the valve head 11 repeats contact and non-contact with the sealing ring 49, there will be little or no pressure between these two elements, resulting in wear and tear. Decrease. When the pressure in the combustion chamber 15 is high, for example during combustion, the sealing ring 49 is biased toward the valve head 11a at a high pressure, so that the high-pressure gas in the combustion chamber 15 leaks over the sealing ring 49. Do not.

  FIG. 4 shows a modification of the embodiment shown in FIG. The embodiment shown in FIG. 4 is essentially the same as the embodiment described in connection with FIG. 3, except that the cylinder cover 12 includes a cylindrical portion with a port 60 and a ring channel 62 surrounding the port. It is. When the exhaust valve is in its upper position (indicated by the dashed line), exhaust gas can flow out of the combustion chamber 15 via the port 60 and the ring channel 62. The ring channel 62 is connected to the exhaust gas receiver. By providing the cylindrical portion having the port 60, the sealing ring on the valve head 11a continuously comes into contact with the wall surface, and the sealing ring is caused by repeating the contact state and the non-contact state with the wall surface. The possibility is avoided.

  FIG. 5 shows a third embodiment of an exhaust valve actuation system according to the present invention, which is essentially the same as the embodiment described in connection with FIG. 3 except that the shutoff valve 41 is replaced by a switching valve 42. Are the same. In this embodiment, the electronically controlled switching valve 42 has two positions. In the first position, the switching valve 42 connects the conduit 36 to the pressure chamber of the exhaust valve actuator 34. In the first position, the pressure amplifier 44 is coupled to the tank. In the second position shown, switching valve 42 connects conduit 36 to pressure amplifier 44. This arrangement prevents the cam driven positive displacement pump 32 from being exposed to the high pressure in the pressure chamber of the hydraulic exhaust valve actuator 34 during the combustion phase.

  In this embodiment, the exhaust valve 11 is provided with a conical exhaust valve seat 48 in the protruding portion 47. The conical valve seat is provided above the protruding portion 47 of the cylinder cover 12, and the normal of the valve seat surface has a component in the direction of the valve shaft 11b in the direction away from the combustion chamber 15. The valve head 11a has a corresponding conical end designed to sealing contact with the valve seat 48. In this embodiment, the profile of the cam 29 is gradual (indicated by the dashed line on the cam 29), and during the phase where the exhaust valve is in its closed position, the cam-driven positive displacement pump 32 is continuously reduced in volume. To supply the fluid. Therefore, even if the hydraulic fluid leaks, a considerable pressure acting on the hydraulic exhaust valve actuator 34 is ensured through the pressure amplifier 44.

  The pressure limiting valve 45 allows any excess hydraulic fluid supplied by the cam driven positive displacement pump 32 to flow into the tank.

  In operation, when the exhaust valve 11 is closed and present in its valve seat 48, the switching valve 42 is in the second position shown. During the opening and closing movement and while the exhaust valve 11 is open, the switching valve is in a first position (not shown).

  The operation of the exhaust valve actuation system according to the second embodiment is during normal engine operation and during an overpressure event in the combustion chamber 15 and is identical to the operation described in connection with the first embodiment.

  FIG. 6 shows a fourth embodiment of the present invention. In this embodiment, the hydraulic valve actuation system also uses a hydraulic push rod system that includes a positive displacement pump 32 that is connected to the hydraulic valve actuator 34 by a conduit 36. However, in this embodiment, the switching valve 42 alternatively connects the pressure chamber of the hydraulic exhaust valve actuator 34 to the cam driven positive displacement pump 32 via the conduit 36 and also to the hydraulic pump 54. In its first position (not shown), the electronically controlled switching valve 42 connects the pressure chamber of the hydraulic exhaust valve actuator 34 to the cam driven positive displacement pump 32. In its second position, the switching valve 42 connects the pressure chamber of the hydraulic exhaust valve actuator 34 to the hydraulic pump 54. The hydraulic pump 54 can be a positive displacement pump that is driven electrically or mechanically. Any unused capacity of the hydraulic pump 54 is led to the tank via the pressure adjustment valve 55.

  During normal engine operation and during the opening and closing movement of the exhaust valve 11, the switching valve 42 is in its first position (not shown). When the exhaust valve 11 is in its closed position, the switching valve 42 is in its second position shown, where the pressure chamber of the hydraulic exhaust valve actuator 34 is pressurized by the pump 54. This pressure causes the exhaust valve 11 to be pressed firmly against its valve seat 48 during its combustion phase of the engine cycle. This embodiment is also provided with a pressure relief valve 43 that operates in a manner similar to that described above in connection with the first and second embodiments.

  According to another embodiment (not shown), the exhaust valve actuation system operates without the use of a camshaft, and instead supplies hydraulic fluid to each hydraulic exhaust valve actuator at a desired time for opening and closing the exhaust valve. It may be of the type that operates with hydraulic pressure from a continuous high-pressure source controlled by a control valve that leads to (such as a common rail system). In this embodiment, the exhaust valve is kept closed by the pressure of the pressure chamber of the hydraulic exhaust valve actuator, and the pressure relief valve is connected to the pressure chamber of the hydraulic exhaust valve actuator and is combusted by the set pressure. The exhaust valve can be opened when excessive pressure is generated in the chamber.

  The term “comprising”, used in the claims, does not exclude other elements. The singular terms used in the claims do not exclude the plural.

  Although a detailed description has been given for the purpose of understanding the present invention, the detailed description is merely for this purpose, and various modifications can be made by those skilled in the art without departing from the scope of the present invention. I want you to understand.

1 is a cross-sectional view of an engine according to the present invention. FIG. 2 is a longitudinal sectional view of one cylinder portion of the engine shown in FIG. 1 is a diagrammatic representation of a first embodiment of an exhaust valve actuation system according to the present invention. 4 is a modification of the embodiment shown in FIG. 4 is a diagrammatic representation of a second embodiment of an exhaust valve actuation system according to the present invention. FIG. 6 is a diagrammatic representation of a third embodiment of an exhaust valve actuation system according to the present invention.

Claims (28)

A plurality of cylinders serving as combustion chambers, each cylinder provided with at least one exhaust valve;
An exhaust valve actuation system for opening and closing the exhaust valve in synchronization with the engine cycle;
A crosshead type large two-cycle diesel engine equipped with
The exhaust valve operating system opens the exhaust valves outwardly with respect to the corresponding combustion chambers, respectively, for exhaust gas exhaust control after combustion,
The exhaust valve actuation system closes the exhaust valve inwardly with respect to the corresponding combustion chamber before combustion,
The exhaust valve actuation system further includes means for limiting the force that prevents the exhaust valve from opening so that the pressure in the combustion chamber can be set to a predetermined threshold regardless of the current stage of the engine cycle. If it exceeds, releasably configured outward direction relative to the combustion chamber the exhaust valves corresponding to the combustion chamber,
A crosshead large two-cycle diesel engine.   The engine of claim 1, wherein the exhaust valve is biased outwardly to open the exhaust valve by a gas spring acting on a shaft of the exhaust valve. The engine according to claim 1 or 2, wherein a hydraulic actuator urges the exhaust valve in an inward direction to close the exhaust valve. The exhaust valve, in order to seal the combustion chamber when the exhaust valve is in its closed position, comprising a valve head which interacts with the cylinder cover of the top of the respective cylinder, according to claim 3 Engine.   The engine according to claim 4, wherein the valve head fits a sealing engagement portion in an annular opening of the cylinder cover.   The engine of claim 5, wherein one or more sealing rings are provided on an inner surface of the annular opening.   The engine according to claim 5 or 6, wherein one or more sealing rings are provided on a peripheral surface of the valve head.   The engine according to any one of claims 5 to 7, wherein a normal line of the cylinder cover and the sealing surface of the valve seat has only a radial component.   The engine according to any one of claims 5 to 8, wherein the exhaust valve is not fixed in a sitting position, and has a width at a position where the valve is closed.   The engine according to claim 4, wherein the valve head is in contact with a valve seat of the cylinder cover.   The engine according to claim 10, wherein a normal of a surface of the valve seat has an axial component.   The engine according to claim 11, wherein the axial component is directed outward with respect to the combustion chamber.   The engine according to any one of claims 10 to 12, wherein the valve seat is conical.   The engine according to any one of claims 5 to 9, wherein the valve actuation system includes a camshaft and a cam-driven actuator pump that is operatively connected to the hydraulic actuator. The engine of claim 14, wherein the cam driven actuator pump is connected to the hydraulic actuator via a pressure conduit, and a shutoff valve is provided on the pressure conduit.   16. The exhaust valve of claim 15, wherein when the shut-off valve is closed, the exhaust valve corresponding to the shut-off valve is prevented from moving except when excessive pressure is generated in the combustion chamber corresponding to the exhaust valve. engine.   17. The shut-off valve is only opened during exhaust valve lift to protect the cam driven pump and the camshaft from high pressures that the hydraulic actuator is exposed to during combustion. The listed engine.   The engine according to any one of claims 10 to 13, wherein the valve actuation system includes a camshaft and a cam-driven actuator pump that is operatively connected to the hydraulic actuator. The engine of claim 18, wherein the cam driven actuator pump is coupled to the hydraulic actuator via a pressure conduit, and a timed switching valve is disposed in the pressure conduit. The switching valve directly connects the pressure chamber in the hydraulic actuator to the cam-driven pump during opening and closing of the valve in the first position, and the exhaust valve is closed in the second position. The engine of claim 19, wherein the pressure chamber is coupled to the cam driven actuator pump via a pressure amplifier therebetween. The cam on the camshaft acting on the cam driven actuator pump continuously supplies at least a small amount of hydraulic fluid during the engine cycle when the exhaust valve is closed. 21. The engine of claim 20, wherein the engine has a stepped profile.   The engine according to claim 20 or 21, wherein the switching valve is provided with a check valve element in the second position. The switching valve directly connects the pressure chamber of the hydraulic actuator to the cam-driven actuator pump during opening and closing of the valve at the first position, and another high-pressure hydraulic fluid source at the second position. The engine according to claim 19, wherein the engine is connected to the pressure chamber of the hydraulic actuator.   24. The engine according to claim 23, wherein the other high-pressure hydraulic fluid source is a hydraulic pump. 14. An engine according to any of claims 3 to 13, wherein the valve actuation system comprises a high pressure hydraulic pump operatively coupled to the exhaust valve actuator via a pressure conduit and a control valve. Said means for limiting is a relief valve provided in the hydraulic actuator, said relief valve is configured to open when an overpressure is generated in the combustion chamber, to claim 3 25 The listed engine. The relief valve, wherein when the pressure in the hydraulic actuator exceeds the predetermined threshold value, configured to open, engine according to claim 26. The relief valve, the excess of a predetermined threshold and fully open, and of a type which remains then released, engine according to claim 27.

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