KR20090110216A - Large two-stroke diesel engine with outwardly moving exhaust valves - Google Patents

Abstract

A large two-stroke diesel engine with an exhaust valve actuating system that moves the exhaust valves in an outward direction in order to allow the exhaust gases to be evacuated from the combustion chambers. The exhaust valve is provided with a relief system that allows the exhaust valve to open automatically if excessive cylinder pressures occur.

Description

LARGE TWO-STROKE DIESEL ENGINE WITH OUTWARDLY MOVING EXHAUST VALVES}

The present invention relates to a large two-stroke diesel engine, and more particularly to an exhaust valve system of a large two-stroke diesel engine.

Large two-stroke diesel engines of the cross-head type are used, for example, for propulsion of large ocean-going vessels or as primary movers in power plants. As well as due to the sheer size, these two-stroke diesel engines are configured differently than other combustion engines. Their exhaust valves can weigh up to 400 kg, the pistons have a diameter of more than 1 meter, and the maximum working pressure in the combustion chamber generally reaches hundreds of bars. The forces acting at these high pressure levels and piston sizes are enormous.

Due to the enormous fuel injection timing or amount, excessive pressure can sometimes occur in one of the cylinders. In order to control this excessive pressure, the force that the cylinder cover presses on the top of the cylinder liner, the stay bolts that connect the cylinder cover and the bed plate and maintain the engine configuration together It is carefully controlled by the tension applied to it. Thus, when excessive pressure occurs, the cylinder cover is lifted between the top of the cylinder liner and the bottom of the cylinder cover and the excess pressure is stopped.

Such a system, which has conventionally been commonly used, is not without problems. First, if something like blow-off occurs, any bystanders can be seriously affected. Second, very hot and high pressure gases are precisely machined on the cylinder liner and the cylinder cover to severely corrode matched surfaces, so that the discharge event is machined to achieve the required fluid tightness. It needs to be. Therefore, the reparation cost after discharge is enormous. Third, the tension in the stay bolt varies with the temperature change of the engine and the environment, and thus cannot be adjusted very accurately. If discharge occurs when the tension in the stay bolts is relatively high, the forces on the piston and crankshaft cause damage to the big ends and other expensive engine parts. Such events are much more expensive than better controlled emissions.

Most engines also have safety valves that are adapted to open to empty the gas from the combustion chamber when excessive pressure occurs in the engine. However, because the maximum opening is insufficient to relieve the pressure quickly enough, the explosive nature of these events makes these valves relatively inefficient. Thus, these safety valves cannot efficiently provide the required opening area in a sufficiently short time.

Thus, there is a need for an improved blow-off control system for large two-stroke diesel engines.

Under this background, it is an object of the present invention to provide a large two-stroke diesel engine with an improved system for controlling excessive cylinder pressure generation.

This object comprises a plurality of cylinders each provided with at least one exhaust valve, and a plurality of cylinders acting as combustion chambers, and an exhaust valve actuation system synchronously opening and closing the exhaust valve in synchronism with the engine cycle, wherein the exhaust valve The operating system opens each exhaust valve outwardly with respect to the combustion chamber for controlled discharge of exhaust gases after combustion, and the exhaust valve actuation system opens each exhaust valve inwardly with respect to the combustion chamber before combustion. Closed, the exhaust valve actuating system allows the respective exhaust valve to open outwardly with respect to the combustion chamber when excessive pressure occurs in the associated cylinder, regardless of the current state of the engine cycle. By providing a stroke diesel engine.

Many advantages are obtained by arranging the exhaust valves away from the combustion chamber by automatically opening the exhaust valve for an opening when excessive pressure occurs in the cylinder:

One of the advantages is that the inertia of the exhaust valve spindle is smaller than the inertia of the cylinder cover. This provides fast response and reliability when excessive cylinder pressure events occur.

Another advantage is that the flow area in which the exhaust valves open under stable conditions is larger than the narrow gap between the cylinder cover and the cylinder liner. Thus, gases can be discharged faster and the pressure increase is lowered to reduce the risk of damage to engine parts such as the big end or the crankshaft.

Another advantage is that the stable pressure setting of the exhaust valve can be made relatively precisely regular and thus can be placed relatively close to the peak pressure during normal operation. Multiple parts of the engine can be quantified based on the pressure when stabilization occurs. Thus, it becomes possible to design such parts with smaller safety margins that enable lighter engine configurations with the same degree of reliability.

A further advantage is that at blow out the hot gases pass through parts designed to transport hot gases and there is no damage to these parts when blow out occurs. Thus, once the error causing the excessive cylinder pressure is corrected, continuous normal engine operation is possible. In the prior art this was not possible. This is because the opposing surfaces of the cylinder cover and the cylinder liner must first be machined. Normal operation can, for example, only occur again after relatively complex repair work.

A further advantage is that in steady state the gases are vented into the exhaust system, not into the machine room.

A further advantage is that in the prior art the exhaust valve has to be opened against the pressure in the combustion chamber, while in contrast the exhaust valve is assisted by the pressure in the combustion chamber to make its opening operation. Is to receive. This means that the force required to open the exhaust valve is smaller and consequently the load on the valve drive system is lower. Thus, the energy required to operate the exhaust valve drive system is reduced compared to prior art systems of inward opening exhaust valves.

The exhaust valve may be forced outwardly to open the exhaust valve by a gas spring operating on a stem of the exhaust valve.

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

The exhaust valve may include 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 engaged with the sealing connection in the annular opening of the cylinder cover. Thus, a close range of positions can be obtained. In addition, the exhaust valve can improve the speed before opening, thus minimizing the time that there is a narrow opening gap, generating a high velocity gas flow with the resulting thermal load of the valve seat, and reducing losses. Adjust.

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

The circumferential surface of the valve head may be provided with one or more sealing rings.

The sealing surface and the valve seat on the cylinder cover can be normal to one radial element.

The exhaust valve does not have a fixed seating position but may have a range in which it is closed.

The valve head may abut the valve seat at the cylinder cover.

The valve seat may have a surface about normal with substantially axial elements.

The axial element may be oriented outward with respect to the combustion chamber.

The valve seat may be conical.

The valve actuation system may comprise a camshaft and a cam drive actuator pump connected to and operated by the hydraulic actuator.

The cam drive pump is connected to the actuator via a pressure conduit and a cutoff valve can be disposed in the pressure conduit.

Except when excessive pressure occurs in the associated combustion chamber, when the associated cutoff valve is closed, the associated exhaust valve may be shut off.

The cutoff valve may only be opened during a period in which the exhaust valve rise occurs to protect the cam drive pump and camshaft from the high pressure at which the hydraulic actuator is exposed during combustion.

The valve actuation system may include a cam shaft and a cam drive actuator pump operably connected to the hydraulic actuator.

The cam drive pump is connected to the actuator via a pressure conduit, and a timed changeover valve can be disposed in the pressure conduit.

In the first position, while opening and closing the valve, the changeover valve connects the pressure chamber of the hydraulic valve actuator directly to the cam drive pump, and in the second position, during the period in which the exhaust valve is closed, the A switching valve can connect the pressure chamber to the cam drive pump via a pressure amplifier.

The cam on the camshaft operating on the cam drive pump may have a progressive profile that allows the cam drive pump to continuously carry at least a small amount of hydraulic fluid during the period of the engine cycle in which the exhaust valve is closed. .

The diverter valve may be provided with a non-return valve element in the second position.

In a first position, while opening and closing the valve, the changeover valve connects the pressure chamber of the hydraulic actuator to the cam drive pump, and in the second position, the changeover valve is a high pressure in the pressure chamber of the hydraulic actuator. It can be connected from other pressure sources of hydraulic fluid.

Another pressure source of the high pressure hydraulic fluid may be a hydraulic pump.

The valve actuation system may include a high pressure hydraulic pump and a control valve operably connected to the exhaust valve actuator via a pressure conduit.

The hydraulic actuator is operatively connected to the relief valve, which can be opened when excessive high pressure occurs in the combustion chamber.

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

The relief valve may be of a type that remains fully open once the predetermined threshold is exceeded and then remains open.

Other objects, shapes, advantages and features of the large two-stroke diesel engine according to the present invention will be clearly described in the detailed description.

In the following detailed description of the specification, the invention will be described in more detail with respect to the preferred embodiment shown in the drawings.

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. FIG.

3 is a schematic view of a first embodiment of the exhaust valve drive system according to the present invention.

4 is a modified example of the embodiment shown in FIG.

Fig. 5 is a schematic diagram of a second embodiment of the exhaust valve drive system according to the present invention.

6 is a schematic view of a third embodiment of the exhaust valve drive system according to the present invention.

1 and 2 respectively show a cross-sectional view and a longitudinal cross-sectional view (one cylinder) of the engine 1 according to the preferred embodiment of the present invention. The engine 1 is a crosshead type uniflow low speed two-stroke crosshead diesel engine, which may be a propulsion system of a main actuator in a ship or power plant. These engines typically have four to fourteen cylinders in a line. The engine 1 consists of a bedplate 2 with the main bearings for the crankshaft 3.

The crankshaft 3 is a semi-built type. Semi-fabricated dies are manufactured from forged steel or cast steel throws and connected to the main journal by shrink fit connections.

The bed plate 2 may be manufactured in one piece, or may be divided into parts of appropriate size depending on the production equipment. The bed plate consists of welded cross girders with side walls and bearing supports. In the prior art cross girders are also called transverse girders. The oil pan 58 is welded to the bottom of the bed plate 2 to recover the return oil from the forced oil lubrication system and the oil cooling system.

Connecting rods 8 connect the crankshaft 3 to crosshead bearings 22. The cross head bearings 22 are guided between the vertical guide surfaces 23.

A shaped frame box 4 of the welded design is mounted on top of the bed plate 2. The frame box 4 is a welded design. The relief box for each cylinder is provided in the frame box 4 of the exhaust side, and the large hinge door for each cylinder is provided in the frame box 4 of the crankshaft side. The cross head guide surfaces 23 are integrated in the frame box 4.

The cylinder frame 5 is mounted on top of the frame box 4. Staybolts 27 connect the bed plate 2, the frame box 4 and the cylinder frame 5 to support the structure. The stay bolts 27 are tightened with hydraulic jacks.

The cylinder frame 5 is of a design welded or cast into one or more parts with the finally integrated crankshaft housing 25. The crankshaft 28 according to another embodiment (not shown) is housed in a separate crankshaft housing attached to the cylinder frame.

The cylinder frame 5 is provided with access covers for cleaning the scavenge air space and for inspecting the exhaust ports and piston rings from the crankshaft side. The access cover together with the cylinder liner 6 forms an exhaust space. A scavenge air receiver 9 is bolted to the cylinder frame 5 on the open side. At the bottom of the cylinder frame there are sealing rings for exhaust and scraper rings which prevent exhaust material from penetrating into the space of the frame box 4 and the bed plate 2, thereby protecting all bearings present in this space ( There is a piston rod stuffing box provided with scraper rings.

The piston 13 has a piston crown and a piston skirt. The piston crown is made of heat-resistant steel and has four ring grooves that are hard-chrome plated on both the top and bottom surfaces of the grooves.

The piston rod 14 is connected to the cross head 22 with four screws. The piston rod 14 has two coaxial holes (not shown) which are connected to the cooling oil pipe to form an inlet and an outlet for the cooling oil for the piston 13.

Cylinder liners 6 are formed in the cylinder frame 5. The cylinder liners 6 are made of alloyed cast iron and are arranged in the cylinder frame 5 by a flange located at the bottom. The uppermost part of the cylinder liner is surrounded by a cast iron cooling jacket. Cylinder liners 6 have perforated holes (not shown) for cylinder lubrication.

The cylinders are uniflow type and have an exhaust port located in an air box in which the exhaust receiving portion 9 (FIG. 1) is supplied with exhaust air pressurized by the turbocharger 10 (FIG. 1). Scavenge air ports 7.

The engine is equipped with one or more turbochargers 10, which are arranged on the rear of the engine for 4-9 cylinder engines and on the exhaust side for 10 or more cylinder engines.

Air intake towards the turbocharger 10 is generated directly from the engine room via an intake silencer (not shown) of the turbocharger. Air from the turbocharger 10 is directed to the exhaust ports 7 of the cylinder liners 6 through a supply air pipe (not shown), an air cooler (not shown), and an exhaust receiving portion 9. .

The engine is provided with electrically driven exhaust blowers (not shown). The suction side of the blowers is connected to the exhaust space after the air cooler. Between the air cooler and the exhaust accommodating portion is provided non-returning babs (not shown) which are automatically closed when the auxiliary blowers supply air. Auxiliary blowers assist the turbocharger compressor under low and medium load conditions.

The fuel valves 40 are mounted concentrically in the cylinder cover 12. The injection valves 40 inject fuel into the combustion chamber 15 at high pressure as fine spray through the injection nozzles at the end of the compression stroke. The fuel may be light oil, heavy fuel oil or gas. When the engine is gas driven, the engine is provided with a fuel injection system and a gas injection system (not shown) so that the engine can operate on all types of fuel. The exhaust valve 11 is mounted centrally in the upper side of the cylinder in the cylinder cover 12. The exhaust valve 11 has a valve head 11a and a valve stem 11b. At the end of the expansion stroke, the exhaust valve 11 opens upwards before the engine piston 13 passes down the exhaust ports 7 so that compressed gas above the piston 13 in the combustion chamber 15 is exhausted. It flows through the exhaust passage 16 which opens to the part 17, and the pressure in the combustion chamber 15 is reduced. The exhaust valve 11 is closed again in the downward movement toward the cylinder and the combustion chamber 15 during the upward movement of the piston 13. The exhaust valve 11 is hydraulically driven.

3 shows a first embodiment of an exhaust valve drive system according to the invention. The exhaust valve drive system is for all embodiments described with regard to a single cylinder. In a multi-cylinder engine there will be identical installations for each cylinder. The exhaust valve drive system includes a camshaft 28 with cams 29 (only one is shown). A roller 30 follows the surface of the cam 29 and is connected to a positive displacement pump 32 which is cam driven. The volumetric pump 32 is connected to the exhaust valve actuator 34 via a passage 36. The exhaust valve actuator 34 has a cylindrical pressure chamber and a piston slidably accommodated in the cylindrical pressure chamber and acting on the stem 11b of the exhaust valve 11. The gas spring 38 is also connected to the stem 11b of the exhaust valve, and the gas pressure in the gas chamber of the gas spring 38 presses the exhaust valve 11 toward the opening direction away from the combustion chamber 15. When the valve actuator 34 is pressurized, the exhaust valve actuator pressurizes the exhaust valve 11 in the direction of closing the exhaust valve 11 toward the combustion chamber 15. In this embodiment the valve head 11a is installed in a sealed manner on the inside of the annular opening in the cylinder cover 12. The circumferential surface of the valve head 11a has a normal having a radial direction. The same applies to the inner surface of the annular opening, and has a radial normal.

The position of the exhaust valve is measured by a sensor connected to the electrical control system of the engine in the embodiment not shown.

A cutoff valve 41 is arranged at the connection between the cam drive pump 32 and the pressure chamber of the hydraulic valve actuator 34. In this embodiment, the electronically controlled cutoff valve 41 has two positions. The cutoff valve connects the pressure chamber of the hydraulic valve actuator 34 to the cam driven hydraulic pump 32 via the pressure passage 36 in the first position. The cutoff valve 41 closes the connection between the hydraulic exhaust valve actuator 34 and the cam driven hydraulic pump 32 in the second position (position shown).

A large hole in the hydraulic exhaust valve actuator 34 connects the pressure chamber to the pressure relief valve 43. The pressure relief valve 43 is formed 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 that occurs in the pressure chamber of the hydraulic exhaust valve actuator 34 during normal engine operation. Typically this peak pressure will correspond to the phase in the engine cycle in which combustion occurs. The pressure relief valve 43 is of a type that opens once the set pressure has been reached and thereafter remains open. Primer pump 42 compensates for oil lost by leakage.

The crankshaft 28 rotates integrally with the crankshaft of the engine during operation. The shape of the cam 29 determines the motion of the volumetric pump 32. As the volumetric pump 32 moves upwards, hydraulic fluid is pressurized into the valve actuator 34 through the passage 36. The actuator 34 pressurizes the exhaust valve 11 such that the exhaust valve 11 closes against the pressure in the gas spring 38. During this period, the cutoff valve 41 is in the first position and allows fluid from the cam driven volumetric pump 32 to flow into the pressure chamber of the hydraulic exhaust valve actuator 34. When the exhaust valve 11 reaches the closed position shown by the solid line in FIG. 3, the cutoff valve 41 moves to the second position (shown) to drive the pressure chamber and cam drive volume in the hydraulic exhaust valve actuator 34. All fluid connections between the mold pumps 32 are disabled. The exhaust valve 11 is therefore locked in a closed position in which the circumferential edge of the valve head 11a cooperates with the protrusion 47 of the cylinder lid 12 to form a complete fluid seal. The protrusion 47 in the illustrated embodiment is provided with a sealing ring 49. In other embodiments (not shown), a sealing ring or sealing rings 49 are provided on the circumferential surface of the valve head 11a.

When it is time to open the exhaust valve (after combustion has been made), the cutoff valve 41 returns to the first position connecting the pressure chamber in the hydraulic exhaust valve actuator 34 to the cam drive volume pump 32. The cam driven displacement pump 32 moves downward, and the gas spring 38 presses the exhaust valve 11 and the exhaust valve actuator 34 to move upward in accordance with the pressure in the combustion chamber. Fluid in 34 flows back to cam drive volume pump 32. Part of the energy delivered to the exhaust valve actuator 34 during the opening movement of the exhaust valve 11 is returned to the camshaft 28 by the pressure formed in the drive volume pump 32 during the return stroke of the exhaust valve actuator 34. do. Therefore only a small fraction of the hydraulic energy required to open the exhaust valve 11 is lost.

If excess pressure occurs in the combustion chamber 15, this excess pressure causes pressure in the exhaust valve 11 upwards to cause a high pressure in the hydraulic exhaust valve actuator 34, i.e., a pressure greater than that which would occur during normal engine operation. will be. The pressure relief valve 43 is then fully open to allow the fluid in the pressure chamber of the hydraulic exhaust valve actuator 34 to be quickly discharged. The high pressure in the combustion chamber, in combination with the force of the gas spring 38, causes the exhaust valve 11 to open quickly in a direction away from the combustion chamber 15. When the exhaust valve 11 is open, gas in the combustion chamber 15 can be discharged through normal passages designed to direct the exhaust gas from the combustion chamber 15 to the outside air. This process generally does not cause any damage to the engine 1 since the threshold pressure at which the pressure relief valve 34 opens can be set accurately. Therefore, the exhaust valve 11 will open before the unintended pressure created in the combustion chamber damages the engine components. Once the exhaust valve is open, the gas is delivered to it through passageways that are designed to handle these gases and treat these gas flows without causing any damage.

In the not shown variation of the first embodiment, the cutoff valve is not controlled electronically, but instead is controlled by the camshaft. This camshaft may be a camshaft with additional lobes for control of the cutoff valve, or may be a separate camshaft with the sole purpose of controlling cutoff valves associated with various cylinders.

The enlarged part of FIG. 3 shows details of the variation of the first embodiment. In this embodiment, the pressure at which the sealing ring 49 engages the valve head 11a is varied. One passage 50 connects the outer circumferential surface of the sealing ring 49 to the combustion chamber 15. By increasing pressure in the combustion chamber 15, the sealing ring is pressurized with increasing pressure toward the valve head 11a. Therefore, when the valve head 11 is moved or separated to contact the sealing ring 49, there is little pressure or no pressure between these two elements due to the low pressure in the combustion chamber 15, Reduce breakage. For example, when the pressure in the combustion chamber 15 is high during combustion, the sealing ring 49 is pressurized toward the valve head 11a at high pressure so that the high pressure gas in the combustion chamber 15 passes through the sealing ring 49. No leakage

4 shows a variation of the embodiment shown in FIG. 3. The embodiment shown in FIG. 4 is described with reference to FIG. 3 except that the cylinder cover 12 has ports 60 and a cylindrical portion in which a ring channel 62 surrounding the ports is provided. It is substantially the same as the embodiments. When the exhaust valve is in the upper position (indicated by the dashed lines), the exhaust gas can exit the combustion chamber 15 through the ports 60 and the ring channel 62. The ring channel 62 is connected to the exhaust gas stream. The provision of the cylindrical portion with the ports 60 allows the sealing rings on the valve head 11a to be in continuous contact with the wall to avoid possible wear caused by the sealing ring coming into contact with the wall and detaching from the wall.

5 shows a third embodiment of an exhaust valve actuation system according to the invention which is essentially the same as the embodiment described in FIG. 3 except for the following differences. The cutoff valve 41 was replaced with a changeover valve 42. The electrically controlled switching valve 42 has two positions in the present embodiment. In the first position, the switching valve 42 connects the conduit 36 to the pressure chamber of the exhaust self actuator 34. In the first position, the pressure amplifier 44 is connected to the tank. In the second position shown, the switching valve 42 connects the conduit 36 to the pressure amplifier 44 towards the conduit 36. This arrangement prevents the cam driven displacement pump 32 from being exposed to high pressure in the pressure chamber of the hydraulic exhaust valve actuator 34 during the combustion state.

In this embodiment, the exhaust valve 11 is provided with a conical exhaust valve seat 48 of the projection 47. The conical valve seat is provided on the upper side of the protrusion 47 of the cylinder cover 12, the normal to the seat surface being substantially axially of the valve shift 11b in a direction away from the combustion chamber 15. With components. The valve head 11a has a corresponding conical edge which is moved to a seal in contact with the valve seat 48. In this embodiment, the profile of the cam 29 is progressive (as shown by the dashed line on the cam 29) such that the cam driven displacement pump 32 has a closed position where the exhaust valve is closed. It keeps carrying a small amount of fluid while in the. Thus, despite the leakage of the hydraulic fluid, it is ensured that substantial pressure is applied on the hydraulic exhaust valve actuator 34 via the pressure amplifier 44.

The pressure limiting valve 45 causes excess hydraulic fluid to be carried by the cam driven displacement pump 32 to flow into the tank.

In operation, when the exhaust valve 11 is in the closed position and seats on the seat 48, the diverting valve 42 is in the second position shown. During the opening and closing movements and during the period in which the exhaust valve 11 is opened, the changeover valve is in a first position (not shown).

The operation of the exhaust valve actuation system according to the second embodiment is effected at normal engine operation and at excessive pressure inflow in the combustion chamber 15 which is identical to the operation as described with reference to the first embodiment. .

6 shows a fourth embodiment of the present invention. In this embodiment, the hydraulic valve actuation system will use a hydraulic push rod system that includes a volumetric pump 32 connected to the hydraulic valve actuator 34 by conduit 36. However, in this embodiment, the switching valve 42 alternates the pressure chamber in the hydraulic exhaust valve actuator 34 through the conduit 36 to the cam driven displacement pump 32 and to the hydraulic pump 54. Connect. In a first position (not shown), an electrically controlled switching valve 42 connects the pressure chamber at the hydraulic exhaust valve actuator 34 to the cap drive volumetric pump 32. In the second position, the changeover valve 42 connects the pressure chamber at the hydraulic exhaust valve actuator 34 to the hydraulic pump 54. The hydraulic pump 54 may be a volumetric pump that is electrically or mechanically driven. Any unused performance of the hydraulic pump 54 is sent to the tank via the pressure regulating valve 55.

In normal engine operation, the changeover valve 42 is in a first position (not shown) during the opening and closing movement of the exhaust valve 11. When the exhaust valve 11 is in the closed position, the changeover valve 42 is in a second position where the pressure chamber of the hydraulic exhaust valve actuator 34 is pressurized by the pump 54. Due to this pressure, the exhaust valve 11 is firmly pressed against the seat 48 at the combustion of the engine cycle. This embodiment is provided with a pressure relief valve 43 which operates in the same manner as described above with reference to the first and second embodiments.

According to a further embodiment, the exhaust valve actuation system (not shown) is adapted for each of the desired times of closing (eg in the case of a common rail system) to open the exhaust valve instead of without a camshaft. It may be of the type operating with hydraulic pressure from a continuously high pressure source controlled by a control valve which directs hydraulic fluid to the fluid exhaust valve actuator.

The term "comprises" in the claims is used to exclude other components. The singular forms in the claims do not exclude a plurality of cases.

Although the present invention has been described in detail for the purpose of representing the drawings, these details are only for the surface of the drawings, and various modifications are possible to those skilled in the art without departing from the scope of the present invention.

It can be used in the technical field regarding the large diesel engine of the present invention.

Claims (28)

At least one exhaust valve, each provided with a plurality of cylinders acting as a combustion chamber; And An exhaust valve actuation system that opens and closes the exhaust valve synchronously with an engine cycle, The exhaust valve actuation system opens each exhaust valve in an outward direction with respect to the combustion chamber for controlled discharge of exhaust gas after combustion, The exhaust valve actuation system closes each exhaust valve inwardly with respect to the combustion chamber before combustion, The exhaust valve actuation system is a large cross-head type two-stroke diesel engine that allows each exhaust valve to open outwardly with respect to the combustion chamber when excessive pressure occurs in an associated cylinder, regardless of the current state of the engine cycle. . The method of claim 1, The exhaust valve is forced outwardly to open the exhaust valve by a gas spring operating on a stem of the exhaust valve. The method of claim 2, A hydraulic actuator forcing the exhaust valve inwardly to close the exhaust valve. The method according to any one of claims 1 to 3, And the exhaust valve includes a valve head interacting 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 method of claim 4, wherein And the valve head engages a sealing connection in an annular opening of the cylinder cover. The method of claim 5, wherein The inner surface of the annular opening is provided with at least one sealing ring. The method according to claim 5 or 6, At least one sealing ring is provided on the circumferential surface of the valve head. The method according to any one of claims 5 to 7, An engine, characterized in that the sealing surface on the cylinder cover and the valve seat are normal to one radial element. The method according to any one of claims 5 to 8, The exhaust valve does not have a fixed seating position but has a range in which it is closed. The method of claim 4, wherein And the valve head is in contact with the valve seat at the cylinder cover. The method of claim 10, And the valve seat has a surface against a normal having a substantially axial element. The method of claim 11, The axial element is oriented outward relative to the combustion chamber. The method according to any one of claims 10 to 12, And the valve seat is conical. The method according to any one of claims 5 to 9, The valve actuation system includes a camshaft and a cam drive actuator pump connected to and operated by the hydraulic actuator. The method of claim 14, The cam drive pump is connected to the actuator via a pressure conduit and a cutoff valve is disposed in the pressure conduit. The method of claim 15, Except when excessive pressure occurs in the associated combustion chamber, when the associated cutoff valve is closed, the associated exhaust valve is shut off. The method according to claim 15 or 16, The cutoff valve is opened only during a period in which the exhaust valve rise occurs to protect the cam drive pump and camshaft from the high pressure at which the hydraulic actuator is exposed during combustion. The method according to any one of claims 10 to 13, The valve actuation system includes a cam shaft and a cam drive actuator pump operably connected to the hydraulic actuator. The method of claim 18, The cam drive pump is connected to the actuator via a pressure conduit and a timed changeover valve is disposed in the pressure conduit. The method of claim 19, In the first position, while opening and closing the valve, the changeover valve connects the pressure chamber of the hydraulic valve actuator directly to the cam drive pump, and in the second position, during the period in which the exhaust valve is closed, the A switch valve connects the pressure chamber to the cam drive pump through a pressure amplifier. The method of claim 20, A cam on a camshaft operating on the cam drive pump has a progressive profile that allows the cam drive pump to continuously carry at least a small amount of hydraulic fluid during the period of the engine cycle in which the exhaust valve is closed. Engine made. The method of claim 20 or 21, The diverter valve is provided with a non-return valve element in a second position. The method of claim 19, In a first position, while opening and closing the valve, the changeover valve connects the pressure chamber of the hydraulic actuator to the cam drive pump, and in the second position, the changeover valve is a high pressure in the pressure chamber of the hydraulic actuator. An engine characterized by connecting at different pressure sources of hydraulic fluid. The method of claim 23, The other pressure source of the high pressure hydraulic fluid is a hydraulic pump. The method according to any one of claims 1 to 13, The valve actuation system includes a high pressure hydraulic pump and a control valve operably connected to the exhaust valve actuator via a pressure conduit. The method according to any one of claims 14 to 25, The hydraulic actuator is operatively connected to the hydraulic actuator, the relief valve being configured to open when excessive high pressure occurs in the combustion chamber. The method of claim 26, The relief valve is configured to open when the pressure in the hydraulic actuator exceeds a predetermined threshold. The method of claim 27, Wherein said relief valve is of a type that is fully opened once said predetermined threshold is exceeded and then remains open.

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