JP5130378B2 - Valve operation system for large two-cycle diesel engines - Google Patents

Description

  The present specification relates to an electrohydraulic control type exhaust valve operating system for a large two-cycle diesel engine.

Background of the Invention

  Large two-cycle diesel engines are generally used as prime movers in large ocean-going vessels such as container ships or power plants.

  EP 1403473 relates to an engine valve actuation system comprising an actuation assembly having a body, a slidable piston, and first, second and third chambers defined between the piston and the body. Disclose. A low pressure fluid source and a high pressure fluid source are provided. The first fluid passage connects the low pressure fluid source to the second chamber. The second fluid passage connects the high pressure fluid source to the second chamber, and the third fluid passage connects the high pressure fluid source to the third chamber. The control valve connects to the low pressure fluid source, the high pressure fluid source, and the first chamber. The control valve is configured to move between a first position where the high pressure fluid source is connected to the first chamber and a second position where the low pressure fluid source is connected to the first chamber.

  The electro-hydraulic control type valve operating system in a large two-cycle diesel engine enables flexible control of exhaust valves and operation profile setting, and enables emission control and improvement of fuel efficiency.

  An enormous force is required to open the exhaust valve having a weight of up to 400 kg against the pressure in the combustion chamber and the gas spring that urges the exhaust valve in the closing direction. For this reason, in order to open the exhaust valve of a large two-cycle diesel engine, a high pressure and high output hydraulic system is required.

  A general electronically controlled (electrohydraulic) exhaust valve actuation system for a large two-cycle diesel engine uses hydraulic fluid (hydraulic oil or lubricating oil) to the upper plate or near the upper plate of the cylinder housing via a common rail. A high pressure pump is provided to feed the valve block located. The valve block has a hydraulic accumulator and a proportional electrohydraulic control valve that controls the flow of hydraulic fluid to operate the fuel injector and the exhaust valve.

  A pressure pipe connects each valve block to each exhaust valve. Since the valve block is typically mounted on the top of the cylinder housing, the pressure tube must bridge a considerable distance and height difference between the valve block and the top of the exhaust valve actuator. This height difference can extend to several meters.

  A pressure intensifier (basically a piston with a large or small pressure surface at either end) is installed at the top of the valve block. One end of the pressure pipe is connected to a pressure intensifier, and the other end of the pressure pipe is connected to the upper part of the exhaust valve. Thus, the pressure pipe extends from the valve block to the top of the exhaust valve.

  The height difference between the top of the exhaust valve and the valve block can be significantly increased due to the size of the engine. I.e. it can span several meters

  When the exhaust valve is in the closed position, the pressure in the pressure tube is close to zero.

  A pressure intensifier between the valve block and the lower end of the pressure tube prevents drainage of the hydraulic fluid in the pressure tube and prevents the pressure tube from being filled with air rather than hydraulic fluid.

  When it is time to close the exhaust valve, the electrohydraulic control valve connects the pressure pipe to the tank. At this time, bubbles may be generated in the pressure pipe due to the inertia of the exhaust valve. Since these bubbles can cause cavitation when the pressure increases again, it is necessary to install a pressure intensifier or pressure separator between the electrohydraulic control valve and the pressure pipe.

European Patent No. 1403473

  Against this background, the object of the present application is to provide a valve actuation system that avoids or at least mitigates the above-mentioned drawbacks.

  This object is achieved by providing the following exhaust valve actuation system for a crosshead large two-cycle diesel engine. The system includes a hydraulic actuator provided at an upper part of the exhaust valve and moving the exhaust valve in an opening direction; and the hydraulic actuator is connected to a hydraulic control valve provided at a position far below the upper part of the exhaust valve. The hydraulic control valve has a position for fluidly connecting the pressure pipe to a high pressure fluid source and moving the exhaust valve to an open position, and the hydraulic control The valve has another position for connecting the pressure pipe to the tank via the valve part and closing the exhaust valve to remain in its valve seat, the valve part restricting the backflow to the tank , Maintaining a minimum pressure upstream of the valve section.

  By providing a valve unit that controls the backflow to the tank, the generation of bubbles and cavitation are greatly reduced.

  In one embodiment, the valve unit includes a fixed flow restriction unit.

  Preferably, the valve portion includes a movable valve member in the bore on the downstream side of the fixed flow restricting portion.

  In one embodiment, the movable valve member has a first effective pressure surface at one end and a second effective pressure surface at the other end, and the first effective pressure surface is The first effective pressure surface faces a first pressure chamber provided between the first effective pressure surface and the flow restricting portion, and the second effective pressure surface is larger than the second effective pressure surface. The effective pressure surface faces the second pressure chamber

  Preferably, the second pressure chamber is maintained at a relatively low pressure. The pressure in the pressure pipe moves to this pressure.

  In one embodiment, the first pressure chamber is connected to the second pressure chamber via a bore in the movable valve member.

  In one embodiment, the valve portion has an outlet port connected to a tank, and the pressure of the first pressure chamber is adjusted toward the position where the first pressure chamber is connected to the outlet port. Energize the member.

  Preferably, the movable valve member defines a control edge together with an edge of a bore in which the movable valve member is accommodated.

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

In the following detailed description, the present invention will be described in more detail with reference to exemplary embodiments shown in the drawings.
2 is a partial schematic cross-sectional view of an exhaust valve actuation system using a valve structure in accordance with an exemplary embodiment. FIG. It is a figure which shows the hydraulic scheme of the valve operating system shown in FIG. It is a detailed sectional view of the valve structure in the exhaust valve operating system shown in FIG.

Detailed Description of the Preferred Embodiment

  FIG. 1 is a partial cross-sectional view of an exhaust valve actuation system according to an exemplary embodiment of the present disclosure. The exhaust valve operating system is a part of a large two-cycle diesel engine such as a crosshead large turbocharged uniflow diesel engine. The construction and operation of a large two-cycle diesel engine is well known and will not be described in detail herein.

  The valve block 3 is installed on an upper plate of a cylinder housing of a large two-cycle diesel engine. The valve block has an electronically controlled proportional hydraulic control valve 5. The electronically controlled proportional hydraulic control valve 5 is connected to an electronic control unit (not shown) of the engine. The valve block 3 includes one or more pressure accumulators 8 and a valve structure 20. One end of the pressure pipe 10 is connected to a port of the valve block 3. The difference in height between both ends of the pressure pipe 10 may reach several meters. If no measures are taken, if the pressure pipe 10 is depressurized to return the exhaust valve to its valve seat, the working fluid is removed from the pressure pipe 10 by gravity. May be discharged and air may enter.

  A bore 7 in the valve block 3 connects the pressure pipe 10 to the port of the proportional hydraulic control valve 5, a bore 11 connects the valve structure 20 to another port of the proportional hydraulic control valve 5, and another bore 9 The proportional hydraulic control valve 5 is connected to a high pressure source (common rail in this embodiment).

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

  FIG. 2 is a diagram showing a hydraulic scheme of the valve actuation system shown in FIG. The system includes a high pressure common rail 32 that is supplied with hydraulic pressure by one or more high pressure pump stations of the engine. The high-pressure common rail 32 is maintained at a pressure of several hundred bars. There is also a low pressure common rail 34 which is maintained at about 2.2 bar. The common rail 36 is connected to the tank at substantially atmospheric pressure.

  A conduit 9 (formed by a bore in the valve block 3) connects the proportional electrohydraulic control valve 5 to the high pressure common rail 32. The proportional electrohydraulic control valve 5 includes a pilot stage that uses the pressure from the conduit 9 to move the spool of the proportional electrohydraulic control valve 5 to a desired position. The conduit 9 as a branch connects to a hydraulic accumulator 8 which serves to maintain / stabilize the pressure when the flow rate (hydraulic fluid) suddenly increases.

  The conduit 13 connects the outlet port of the proportional electrohydraulic control valve 5 associated with the fuel injection system to the low pressure common rail 34. The conduit 11 connects the outlet port of the proportional electrohydraulic control valve 5 associated with the exhaust valve actuation system via the valve structure 20 to the low pressure common rail 34. The valve structure 20 has a flow restrictor, that is, a backflow prevention function, and maintains a minimum pressure in the conduit 11.

  Proportional electrohydraulic control valve 5 is connected to a fuel injection system 30 comprising its intensifier and injector 37, and proportional electrohydraulic control valve 5 is also connected to an exhaust valve actuator. Fuel injection systems are well known per se and will not be described in more detail here.

  The illustrated hydraulic system shows that the pressure pipe 10 is connected to an exhaust valve actuator housing 12 comprising a piston 18 and an exhaust valve spindle 14. A pressurized air source 19 is also connected to the exhaust valve housing 12 for supplying pressurized air to an air spring that biases the exhaust valve in the closing direction. In addition, a position sensor for determining the position of the exhaust valve is provided for the exhaust valve actuator.

  During engine operation, the proportional electrohydraulic control valve 5 receives commands from the engine's electronic control unit and connects either the exhaust valve actuation system or the fuel injection system to the high pressure common rail at the appropriate time during the engine cycle. Thus, when it is time to open the exhaust valve, the engine's electronic control unit sends a command to the proportional electrohydraulic control valve 5 to establish a connection between the pressure common rail 32 and the pressure pipe 10. Then, the exhaust valve opens against the pressure in the combustion chamber and the force of the air spring. When it is time to close the exhaust valve again, the electronic control unit sends a command to the proportional electrohydraulic control valve 5 to connect the pressure pipe 10 to the low pressure common rail 34 via the valve structure 20. Exhaust valves and associated exhaust valve actuators have great inertia. For this reason, if the pressure pipe 10 is directly connected to the tank when the proportional electrohydraulic control valve 5 establishes the connection, the closing of the exhaust valve is much slower than the pressure drop in the pressure pipe 10. The valve structure 20 includes a flow restriction that ensures that the pressure drop does not become too rapid and maintains a minimum pressure upstream of the valve structure 20. This prevents the pressure in the pressure tube 10 from dropping too quickly and excessively to a low pressure. Thereby, generation | occurrence | production of the bubble in the pressure pipe 10 is avoided, and it can prevent developing to cavitation.

  FIG. 3 shows the valve structure 20 in more detail. In the exemplary embodiment, the valve structure includes a housing with a through bore extending through the housing. The valve structure 20 includes a fixed flow restriction 21 disposed at or near the inlet port of the valve structure 20 at one end of the through bore. The inlet port of the valve structure 20 can be connected to the proportional electrohydraulic control valve 5 via the bore 11.

  A movable valve member 22 having a substantially cylindrical main body is slidably accommodated in the through-bore. The movable valve member 22 is provided with a pressure surface at each end. The first pressure surface is arranged on the end surface facing the inlet port and the flow restrictor 21. The first pressure chamber 23 is formed in the bore between the flow restricting portion 21 and the first pressure surface.

  The second pressure surface is disposed on the opposite side of the first pressure surface. The second pressure surface faces the second pressure chamber 25, which is also arranged in the through bore. The second pressure chamber is connected to a relatively low pressure source such as the low pressure common rail 34.

  The diameter of the through-bore is larger at the portion forming the first pressure chamber than at the portion forming the second pressure chamber. Therefore, the effective surface of the first pressure surface is larger than the effective surface of the second pressure surface. The movable valve member 22 is provided with a bore 26 that connects the first and second pressure chambers. Since the diameter of the bore 26 is relatively small, it has a function of restricting the flow between the two pressure chambers.

  The outlet port 27 is connected to the tank 36. The outlet port 27 is closed by the movable valve member 22 in a certain position range of the movable valve member 22 and opened in another position range of the movable valve member 22. In the position range where the movable valve member 22 opens the outlet port 27, the first pressure chamber 23 is connected to the outlet port 27.

  Referring to the state of the valve structure in FIG. 3, the movable valve member 22 cuts off the connection between the first pressure chamber 23 and the outlet port 27 when the movable valve member 22 is in its lower position range, When the movable valve member 22 is in the upper position range, the connection between the first pressure chamber 23 and the outlet port 27 is released.

  The larger first effective pressure surface urges the movable valve member 22 toward the position range where the outlet port 27 is connected to the first pressure chamber 23, and the smaller second effective pressure surface is the second effective pressure surface. 1 The movable valve member 22 is urged toward a position range where the connection between the pressure chamber 23 and the outlet port 27 is cut off.

  The movable valve member 22 is provided with a lateral bore 28 connected to the overflow port of the housing of the valve structure 20. When the movable valve member 22 moves greatly upward (see: upward in the direction of the valve structure in FIG. 3), the lateral bore 28 overlaps the overflow port 29. Therefore, the second pressure chamber 25 is connected to the tank 34, whereby the movable valve member 22 completely opens the outlet port 27, and the first pressure chamber 25 reaches the maximum pressure. The inside of the chamber 23 can be released.

  When there is no inflow into the first pressure chamber through the restricting portion 21, the pressure in the first pressure chamber is smaller than the pressure in the second pressure chamber in proportion to the effective pressure area of each of the first and second pressure chambers. Thus, for example, when the pressure in the second pressure chamber is 2.2 bar, the pressure in the first pressure chamber is 1.5 bar. When the proportional electrohydraulic control valve 5 connects the pressure pipe 10 to the valve structure 20, the inflow into the first pressure chamber through the restricting portion 21 increases and the pressure in the first pressure chamber increases. This pressure is sufficient to urge the movable valve member 22 and move the movable valve member 22 to a position where the first pressure chamber 21 and the outlet port 27 are connected and the hydraulic fluid is discharged to the tank. It becomes. The position of the movable valve member 22 is balanced by the pressures of the two pressure chambers.

  The position of the valve 22 is (second effective pressure area in the second pressure chamber 25) × (second effective pressure area in the first pressure chamber 23) × (pressure in the first pressure chamber 23) × (second Pressure in the pressure chamber 25). When the exhaust valve is closed, the pressure in the second pressure chamber 25 is about 2 bar. At this time, the pressure in the first pressure chamber 23 commensurate with it may be 1.5 bar. The pressure difference between the first pressure chamber 23 and the second pressure chamber 25 causes a fluid flow through the orifice 26 and into the first pressure chamber 23.

  Increasing the pressure in the first pressure chamber 23 moves the movable valve member 22 upward and gradually opens the outlet port 27. This again limits the pressure on the valve that balances the forces acting on the movable valve member 22.

  Therefore, the flow through the orifice 26 is the same as the flow from the pressure chamber 23 to the outlet port 27. The open area from the first pressure chamber 23 to the outlet port 27 is a flow through the orifice 26 at dP (pressure difference) between the first pressure chamber 23 and the second pressure chamber 25. Accordingly, the movable valve member 22 “floats” and adapts its position to operating conditions.

  This balance in combination with the flow restrictor 21 provides an adequate flow rate and maintains an overpressure condition upstream of the valve structure (ie, in the pressure tube when the valve structure is used in an exhaust valve actuation system). . These reliably control the flow rate and exhibit the effect of preventing air intrusion.

  The exhaust valve actuation system is described for one cylinder of a large two-cycle diesel engine. In a multi-cylinder engine, such an exhaust valve operation system must be provided for each cylinder (or at least for each exhaust valve) except for a common rail that can be shared by a plurality of cylinders.

  There are many advantages to what is taught from this specification. Different embodiments or implementations may provide one or more of the following advantages. It should be noted that this is not a comprehensive list and there may be other advantages not described herein. One advantage of the teachings herein is to provide an exhaust valve actuation system that can operate without a pressure intensifier or voltage divider below the pressure tube. Another advantage of the teachings herein is to avoid the generation of bubbles and cavitation by providing a valve structure that provides backflow to the tank in controlled conditions.

  Yet another advantage of the teachings herein is to provide an exhaust valve actuation system that allows a hydraulic exhaust valve actuator intensifier to be mounted on top of the exhaust valve. Yet another advantage of the teachings herein is a valve structure that can function as a check valve in harsh environments where a conventional check valve operated by a valve member that contacts the valve seat is not available. Is to provide.

  Although the teachings of the present application have been described in detail for purposes of illustration, such details are merely for that purpose and modifications may be made thereto by those skilled in the art without departing from the scope of the present teachings. It should be understood that additions may be made.

  The term “comprising”, when used in the claims, does not exclude other elements or steps. The singular terms in the claims do not exclude the plural. A single processor or other unit may fulfill the functions of several means recited in the claims.

Claims (8)

An exhaust valve actuation system for a crosshead large two-cycle diesel engine,
A hydraulic actuator provided at an upper portion of the exhaust valve and moving the exhaust valve in an opening direction;
A pressure pipe (10) for connecting the hydraulic actuator to a hydraulic control valve (5) provided at a position away from the upper part of the exhaust valve;
With
The hydraulic control valve (5) has a position for fluidly connecting the pressure pipe (10) directly to a high pressure fluid source (32) to move the exhaust valve to an open position;
The hydraulic control valve (5) is connected to the tank (36) said pressure tube (10) via a valve unit (20), another location for keep on its seat to close the exhaust valve Have
The valve portion includes a fixed flow restriction portion (21) and a movable valve member (22) on the downstream side of the fixed flow restriction portion (21) in the bore.
The movable valve member (22) has a first effective pressure surface at one end and a second effective pressure surface at the other end, and the first effective pressure surface is Facing the first pressure chamber (23) provided between the first effective pressure surface and the flow restricting portion (21), the second effective pressure surface facing the second pressure chamber (25),
The valve part (20) is characterized by restricting the backflow to the tank (36) and maintaining a minimum pressure upstream of the valve part (20),
Exhaust valve actuation system. Said first effective pressure surface, the second has magnitude than the effective pressure surface, the exhaust valve actuation system of claim 1. The exhaust valve actuation system according to claim 2 , wherein the second pressure chamber is maintained at a pressure lower than the pressure of the high pressure fluid source (32) . The exhaust valve operating system according to claim 3 , wherein the first pressure chamber (23) is connected to the second pressure chamber (25) via a bore (26) of the movable valve member (22). The valve portion has an outlet port (27) connected to a tank, and the pressure of the first pressure chamber (23) is such that the first pressure chamber (23) is connected to the outlet port (27). 5. The exhaust valve actuation system according to claim 4 , wherein the movable valve member (22) is biased towards a position. The exhaust valve operating system according to any one of claims 1 to 5, wherein the outlet port (27) is provided in a bore in which the movable valve member (22) is accommodated. The exhaust valve actuation system according to any one of claims 1 to 6 , wherein an air spring biases the exhaust valve in the closing direction. A crosshead type large two-cycle diesel engine comprising the exhaust valve operating system according to any one of claims 1 to 7.

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