JP2009203865A - Variable valve timing for large-sized two cycle diesel engine equipped with camshaft - Google Patents

Abstract

An exhaust valve actuation system that provides the combustion efficiency of an electronically controlled variable timing exhaust valve actuation system for a large two-cycle diesel engine that itself consumes little energy.
A large two-cycle diesel engine having a camshaft driven exhaust valve actuation system of the type that uses a hydraulic push rod. The hydraulic push rod is connected to an oil amount control device 14, and the oil amount control device 14 can reduce the amount of hydraulic hydraulic oil from the hydraulic push rod based on a command from the electronic control device. The oil quantity control device 14 includes an elastically biased control piston 15 that defines an oil quantity control chamber 16. The 15 features of the control piston can be governed by an electronic controller via a hydraulic valve that selectively connects the control chamber 16 defined by the control piston 15 to the hydraulic accumulator 22.
[Selection] Figure 2

Description

  The present application relates to a large two-cycle diesel engine having an exhaust valve that operates on a camshaft, and more specifically to a large two-cycle diesel engine that has an exhaust valve that operates on a camshaft with variable timing.

  The aspects of high fuel efficiency and low emissions are very important in the design of large two-cycle diesel engines. Attempts have been made to improve the fuel usage efficiency of these engines by applying an exhaust valve actuation system with electronically controlled variable valve timing. In general, these known variable timing valve actuation systems operate with high pressure hydraulic fluid sources such as pump stations and hydraulic valve systems that control the flow of hydraulic pressure to the respective hydraulic exhaust valve actuators. The high pressure hydraulic fluid supplies power to an exhaust valve actuator that opens the exhaust valve against the pressure in the combustion chamber and an air spring that closes the exhaust again when the hydraulic pressure is removed.

  Although known electronically controlled variable valve timing systems certainly improve combustion efficiency, the hydraulic energy used to open the exhaust valve is dissipated when the exhaust valve is reclosed, thus reducing overall fuel efficiency. It cannot be improved significantly. In a conventional large two-cycle diesel engine having an exhaust valve system that operates on a camshaft, most of the energy required to open the exhaust valve is returned to the camshaft when the exhaust valve is closed. Thus, despite being slightly below optimal combustion efficiency, these conventional two-cycle diesel engines have an overall fuel usage efficiency that is substantially similar to the overall fuel usage efficiency of an electronically controlled variable valve timing engine.

  Under such circumstances, the present application aims to provide an exhaust valve actuation system that provides the combustion efficiency of an electronically controlled variable timing exhaust valve actuation system that itself consumes little energy.

  The object is to provide a plurality of cylinders each having at least one exhaust valve, at least one camshaft having a plurality of cams for operating the at least one exhaust valve of each of the plurality of cylinders, and the camshaft. A plurality of hydraulic piston pumps respectively driven by the respective cams; a hydraulic actuator provided in each of the exhaust valves for moving the exhaust valve in an opening direction; and provided in each of the exhaust valves, A crosshead type large two-cycle diesel engine comprising: a hydraulic pipe for connecting a hydraulic piston pump to the hydraulic actuator; and an elastic member provided in each of the exhaust valves for biasing the exhaust valve to a closed position. An engine, wherein the hydraulic pipe selectively sucks hydraulic fluid from the hydraulic pipe or Selectively back into serial hydraulic lines, it is connected to the oil amount control device including an oil amount adjusting unit of the hydraulic fluid is accomplished by providing a crosshead type large two-stroke diesel engines.

  By connecting an oil amount control device to the hydraulic pipe, it is possible to delay the opening of the exhaust valve and accelerate the closing of the exhaust with respect to the profile defined in the cam of the camshaft. Thus, the beneficial energy recovery effect of conventional camshaft actuation systems is retained, thus providing a variable valve timing system that itself uses little energy.

  Preferably, the hydraulic fluid is absorbed and returned based on commands from the engine's electronic control unit.

  The oil amount control device may include a control piston that defines an oil amount control chamber connected to the hydraulic pipe.

  The control piston can be elastically biased.

  The control piston may define a first control chamber opposite the oil quantity control chamber.

  The control piston may define a second control chamber opposite the oil quantity control chamber.

  The first control chamber can be connected to the second control chamber via a hydraulic valve.

  The second control chamber may be connected to a first hydraulic accumulator.

  The first hydraulic control chamber may be connected to a second hydraulic accumulator via a hydraulic valve.

  When the pressure of the hydraulic pipe exceeds a predetermined value that is lower than the pressure required to open the exhaust valve, and when the entire control device is in a state of delaying the opening of the exhaust valve, the amount of oil The control device can be configured to suck a predetermined amount of hydraulic fluid from the hydraulic pipe.

  When the pressure of the hydraulic pipe becomes equal to the pressure required to maintain the exhaust valve in the open position and the closing of the exhaust valve proceeds, the oil amount control device sets the predetermined amount of hydraulic hydraulic oil to the It can be configured to inhale from a hydraulic pipe.

  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 description, the invention will be described in more detail with reference to the illustrated exemplary embodiments.

  FIG. 1 is a cross-sectional view of one of the cylinders 1 of an engine according to a preferred embodiment of the present invention as viewed from the front of the engine. The engine is a uniflow low-speed two-cycle crosshead diesel engine with a turbocharge, and may be the driving force of a ship propulsion engine or a power plant. These engines typically have 3 to 14 cylinders in a row.

  The piston 2 is accommodated in the cylinder 1, and the two define a combustion chamber 3. The piston rod 4 connects the piston 2 to a crosshead (not shown). The cylinder 1 is a uniflow type, the scavenging hole 5 is provided at the lower end, and the exhaust valve 6 is provided at the upper end. The cylinder 1 receives air from a scavenging receiver (not shown) to which pressurized scavenging gas is supplied to a turbocharger (not shown).

  The camshaft 7 extends along the length of the engine. The camshaft 7 is one part that includes an exhaust cam, an indicator cam, a thrust disk, and a contraction chain wheel on the shaft. The exhaust cam is made of iron and has a curing roller groove.

  The exhaust valve 6 is attached to the center of the upper part of the cylinder in the cylinder cover. At the end of the expansion stroke, before the engine piston 2 passes through the scavenging hole 5, the exhaust valve 6 is opened, so that the combustion gas in the combustion chamber 3 on the piston 2 passes through the exhaust passage opening to the exhaust receiver 8. It flows out and the pressure in the combustion chamber is released. The exhaust valve 6 is closed again while the piston 2 moves upward. The exhaust valve 6 is driven upward by an air spring 9.

  The exhaust valve 6 is opened by a camshaft 7 that is disposed within a camshaft housing that extends along the length of the engine.

  The hydraulic exhaust valve actuator 10 of each exhaust valve 6 is connected to a piston pump 12 via a pressure pipe 11. In the present embodiment, one piston pump 12 and one exhaust valve 6 exist for each cylinder, but a plurality of piston pumps or a plurality of exhaust valves may exist for each cylinder (not shown).

  The piston pump 12 is mounted on the roller guide housing. The roller follows each cam on the camshaft 7. Accordingly, the piston pump 12 is operated by the camshaft 7.

  The piston pump 12, the pressure pipe 11, and the hydraulic actuator 10 integrally form a hydraulic push rod so that the exhaust valve 6 is driven by a cam on the cam shaft.

  The branch pipe 13 connects the pressure pipe 11 to the oil amount adaptation device 14. The oil amount adaptation device 14 can absorb the hydraulic fluid from the pressure pipe 11 and / or add / return the hydraulic fluid to the pressure pipe 11. The oil quantity adaptation device is connected to an electronic control unit of the engine.

  2 to 4 show the oil amount control device 14 in more detail.

  The oil amount control device 14 of FIG. 2 is in the first operating state, in which the device does not draw hydraulic fluid from the pressure pipe 11 and does not add hydraulic fluid to the pressure pipe 11.

  The oil quantity control device 14 includes a stepped control piston 15 that is housed in a stepped bore of the control device 14. The maximum diameter portion 17 of the piston 15 defines an oil amount control chamber 16 connected to the pressure pipe 11 via the branch pipe 13. The intermediate diameter portion 18 of the control piston 15 defines a first control chamber at 19 and the minimum diameter portion 20 defines a second control chamber 21.

  The first control chamber 19 is connected to the system pressure (high pressure hydraulic fluid source) via the flow rate restricting unit 23.

  The second control chamber 21 is connected to the first hydraulic accumulator 22 and is connected to the system pressure (high pressure hydraulic fluid source) via the flow rate limiting unit 24.

  Pipe 25 connects the first control chamber 19 to a hydraulic 4 / 3-way valve 26 having a solenoid operable by the engine controller. Another tube 27 connects the second control chamber 21 to the 4/3 way valve 26. The pipe 28 connects the 4/3 way valve 26 to a second hydraulic accumulator 29. In the present embodiment, the 4 / 3-way valve 26 is a proportional valve, but in the embodiment, the valve 26 may be an on / off type.

  When the 4 / 3-way valve 26 is in the position of FIG. 2, the piston is fixed at the intermediate position. In certain embodiments, the sum of the control volume 19 and the control volume 21 is substantially equal to the volume of the oil control chamber 16. The flow from the first control volume 19 and the second control volume 21 through the pipes 25 and 27 is blocked by the 4 / 3-way valve 26, so that the piston 15 cannot move (passes through the flow rate limiting unit 23). Since the flow is very small and only to compensate for hydraulic fluid leakage, the hydraulic fluid in the first control chamber 19 is confined, so the flow through the flow restrictor 23 is negligible).

  Therefore, when the 4 / 3-way valve 26 is in this position and the camshaft operates the piston pump 12, the control piston 15 does not move even if the pressure of the driven pressure pipe 11 increases significantly.

  When the engine control unit commands the 4 / 3-way valve 26 to move to the position of FIG. 3, the pipe 25 is connected to the pipe 27 and the hydraulic fluid in the first control chamber 19 is transferred to the second control chamber 21. It is possible to flow to the side and vice versa. The hydraulic fluid in the second control chamber 21 can flow into the first hydraulic accumulator 22 if the oil pressure is sufficiently high.

  When the pressure in the pressure pipe 11 exceeds a predetermined pressure, for example, 100 bar, the pressure in the oil amount control chamber 16 urges and moves the control piston 15 and hydraulically operates the first and second control chambers 19, 21. Oil is extruded into the first hydraulic accumulator 22. The pressure of the pressure pipe 11 when the control piston 15 moves and the oil amount control chamber 16 absorbs hydraulic fluid is selected to be lower than the pressure at which the exhaust valve 6 opens. Accordingly, the opening of the exhaust valve 6 is delayed until the control piston 15 reaches its end position and moves to a position where the hydraulic oil does not flow into the oil amount control chamber 16 any more. At this point, the pressure in the pressure pipe 11 begins to increase again and reaches a pressure at which the exhaust valve begins to open.

  The pressure in the pressure pipe 11 that keeps the exhaust valve in the open position is lower than the predetermined pressure (for example 100 bar), and the control piston 15 returns to the intermediate position at the end of the exhaust valve 6 opening stroke. Accordingly, the hydraulic fluid in the oil amount control chamber 16 returns to the pressure pipe 11 to ensure that the exhaust valve 6 is fully opened.

  When the engine controller commands the 4 / 3-way valve 26 to move to the position of FIG. 4, the pipe 25 is connected to the pipe 28, and the hydraulic fluid in the first control chamber 19 is the second hydraulic pressure. It becomes possible to flow into the accumulator 29. The hydraulic fluid in the second control chamber 21 can flow into the first hydraulic accumulator 22 and can flow in the opposite direction.

  When the 4 / 3-way valve 26 is in this position, the pressure in the pressure pipe 11 that keeps the exhaust valve 6 in the open position causes the piston 15 to move to the right and the hydraulic fluid in the first control chamber 19 to flow. Enough to energize the second hydraulic accumulator 29 and energize the hydraulic fluid in the second control chamber 21 to the first hydraulic accumulator 22. These features are obtained by selecting the size of the effective surface of each portion 17, 18, 20 of the control piston 15 and the features of the first hydraulic accumulator 22 and the second hydraulic accumulator 29.

  As shown in FIG. 5, the feature of the oil quantity adaptation device 14 allows the delay of the exhaust valve opening and the early closing of the exhaust valve under the control of the electronic control device. In the graph of FIG. 5, the line 30 represents the pressure of the pressure pipe 11, and the line 31 represents the actual position of the exhaust valve. When the pressure of the pressure pipe 11 exceeds the broken line 32 (representing the above-mentioned predetermined pressure), the control piston 15 moves to the right, and when the pressure of the pressure pipe 11 falls below the broken line 32, the 4/3 way valve is shown in FIG. When in the position shown, the control piston 15 moves to the left.

  In the lower part of the graph of FIG. 5, the standard opening profile of the exhaust valve 6 is indicated by a solid line, and possible opening delays and early closing are indicated by broken lines.

  The teachings of the present invention have many advantages. Various embodiments or implementations may provide one or more of the following advantages. It should be noted that this is not an exhaustive list and that there may be other advantages not listed here. One advantage of the teachings of the present application is to provide a large two-cycle diesel engine with a variable valve timing system that itself consumes little energy. Another advantage of the teachings of the present application is to provide a variable valve timing system based on conventional camshaft motion.

  Although the teachings of this application have been described in detail for purposes of illustration, it will be understood that this detail is not merely for that purpose and that the teachings can be modified by those skilled in the art without departing from the scope of the teachings of this application. I want.

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

It is sectional drawing of the cylinder of the engine which concerns on embodiment of this invention. It is a figure which shows the oil quantity control apparatus which concerns on embodiment of this invention in a 1st state. It is a figure which shows the oil quantity control apparatus of FIG. 2 in a 2nd state. It is a figure which shows the oil quantity control apparatus of FIG. 3 in a 3rd state. It is a graph which shows operation | movement of the engine and oil quantity control apparatus which concern on embodiment of this invention.

Claims (10)

A plurality of cylinders each having at least one exhaust valve;
At least one camshaft having a plurality of cams for operating the at least one exhaust valve of each of the plurality of cylinders;
A plurality of hydraulic piston pumps respectively driven by each cam on the camshaft;
A hydraulic actuator provided in each of the exhaust valves for moving the exhaust valve in an opening direction;
A hydraulic pipe provided in each of the exhaust valves for connecting the hydraulic piston pump to the hydraulic actuator;
An elastic member provided in each of the exhaust valves for biasing the exhaust valve to a closed position;
A crosshead type large two-cycle diesel engine comprising:
The hydraulic pipe is connected to an oil quantity control device including an oil quantity adjusting unit for the hydraulic hydraulic oil that selectively sucks hydraulic hydraulic oil from the hydraulic pipe or selectively returns the hydraulic hydraulic oil to the hydraulic pipe. ,
A crosshead large two-cycle diesel engine.   The apparatus of claim 1, wherein the oil quantity control device comprises a control piston that defines an oil quantity control chamber connected to the hydraulic pipe.   The apparatus of claim 2, wherein the control piston is resiliently biased.   The apparatus of claim 3, wherein the control piston defines a first control chamber opposite the oil quantity control chamber.   The apparatus of claim 4, wherein the control piston defines a second control chamber opposite the oil quantity control chamber.   The apparatus of claim 5, wherein the first control chamber is connectable to the second control chamber via a hydraulic valve.   The apparatus of claim 6, wherein the second control chamber is connected to a first hydraulic accumulator.   The apparatus of claim 7, wherein the first hydraulic control chamber is connectable to a second hydraulic accumulator via a hydraulic valve.   When the pressure of the hydraulic pipe exceeds a predetermined value that is lower than the pressure required to open the exhaust valve, and when the entire control device is in a state of delaying the opening of the exhaust valve, the amount of oil The apparatus according to claim 1, wherein the control device is configured to suck a predetermined amount of hydraulic fluid from the hydraulic pipe.   When the pressure of the hydraulic pipe becomes equal to the pressure required to maintain the exhaust valve in the open position and the closing of the exhaust valve proceeds, the oil amount control device sets the predetermined amount of hydraulic hydraulic oil to the 10. An apparatus according to any preceding claim, configured to inhale from a hydraulic pipe.

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