Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
  • F01L1/46—Component parts, details, or accessories, not provided for in preceding subgroups
  • F01L1/462—Valve return spring arrangements
  • F01L1/465—Pneumatic arrangements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L9/00—Valve-gear or valve arrangements actuated non-mechanically
  • F01L9/10—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C5/00—Crossheads; Constructions of connecting-rod heads or piston-rod connections rigid with crossheads
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
  • F01L1/34—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift
  • F01L1/344—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear
  • F01L1/3442—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear using hydraulic chambers with variable volume to transmit the rotating force
  • F01L2001/34423—Details relating to the hydraulic feeding circuit
  • F01L2001/34446—Fluid accumulators for the feeding circuit
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B75/00—Other engines
  • F02B75/02—Engines characterised by their cycles, e.g. six-stroke
  • F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
  • F02B2075/025—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle two
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C2360/00—Engines or pumps
  • F16C2360/22—Internal combustion engines

Definitions

• the present invention relates to a large two-stroke diesel engine of the crosshead type with an electronically controlled exhaust valve actuation system, in particularly to a large two-stroke diesel engine of the crosshead type with an electronically controlled exhaust valve actuation system that is energy efficient.
• JP 2004-084670 discloses a large electronically controlled two-stroke diesel engine.
• the exhaust valves are actuated by a hydraulic actuator that is powered with high pressure hydraulic fluid.
• the actuator urges the exhaust valve to open against the counter force of the gas forces in the combustion chamber and the air spring.
• a significant part of the energy delivered by the hydraulic actuator during the opening stroke of the exhaust valve is stored in the gas spring as potential energy.
• the energy stored in the gas spring is, unlike in camshaft driven engines, not reused in the closing stroke, but instead, wasted (dissipated) because there are no means to reuse the stored energy.
• the stored energy is transformed to heat going with the return oil to the tank of the hydraulic system.
• the amount of hydraulic energy that is used to open the exhaust valve on a large two-stroke diesel energy is quite significant, and a substantial part of the fuel savings obtained by the increased combustion control of the electronically controlled engine are lost in the exhaust valve actuation.
• DK 148664B discloses a large two-stroke diesel engine with an electro-hydraulic valve actuation system in which two different hydraulic pressures are applied to open the exhaust valve with an hydraulic actuator.
• the high pressure level is used during the initial phase of the opening stroke and the lower pressure is used during the remaining part of the opening stroke of the exhaust valve.
• WO2006108629 discloses an exhaust valve assembly for a large two-stroke diesel engine that includes an exhaust valve that is movable in opposite directions between a closed position and an open position.
• a double acting spring assembly is operably connected to the exhaust valve and forms a mass-spring system together with the exhaust valve and the mass of any other parts moving in unison with the exhaust valve.
• the double acting spring assembly stores energy during translation of the exhaust valve back and forth between the closed and open position for subsequent propulsion of the exhaust valve in an opposite direction.
• Hydraulic means hold the exhaust valve on command from a controller in the closed or in the open position.
• This system requires that the actual position of the exhaust valve is known and that the electronic controller issues a signal every time that the valve needs to be stopped at one of its extreme positions.
• the hydraulic system is relatively complicated and the construction of the air spring and the hydraulic activator at the top of the valve stem is significantly different from the corresponding construction in a conventional camshaft engine. Thus, this prior art construction is relatively expensive and complicated.
• a large multicylinder two-stroke diesel engine of the crosshead type with an exhaust valve actuating system comprising for each cylinder an exhaust valve with a valve stem and a valve disc, the exhaust valve being movable in opposite directions between a closed position in which the valve disk rests on a valve seat and an open position, an air spring with a spring piston received in an air spring cylinder, the air spring being operably connected to the valve stem and urges the exhaust valve towards the closed position, a hydraulic actuator with a pressure chamber, the hydraulic actuator being operably connected to the stem of the exhaust valve and the hydraulic actuator urges the exhaust valve in the opening direction when the pressure chamber is pressurized, an electronically controlled hydraulic system that selectively connects the pressure chamber of the hydraulic actuator to a source of high pressure hydraulic fluid for a first short period at the start of the opening stroke of the exhaust valve, an intermediate pressure hydraulic accumulator for a period immediately following the first short period until the exhaust valve has reached its open position, the intermediate pressure hydraulic accumulator from the start of the closing
• the exhaust valve actuating system has the flexibility of an electronically controlled exhaust valve actuating system without the high energy consumption that is normally associated with an electronically controlled exhaust valve actuating system.
• the hydraulic system may comprise a first electronically controlled valve configured to connect the pressure chamber of the hydraulic actuator to the source of high pressure hydraulic fluid for a short period at the start of the opening stroke of the exhaust valve.
• the hydraulic system may comprise a second electronically controlled valve configured to connect the pressure chamber of the hydraulic actuator to the intermediate pressure hydraulic accumulator for a period following the short period of opening of the first electronically controlled valve until the exhaust valve has reached its open position.
• the hydraulic system may comprise a third electronically controlled valve configured to connect the pressure chamber of the hydraulic actuator to the intermediate pressure hydraulic accumulator from the start of the closing stroke of the exhaust valve until the start of a last short period at the end of the closing stroke of the exhaust valve.
• the hydraulic system may comprise a fourth electronically controlled valve configured to connect the pressure chamber of the hydraulic actuator to tank during the last short period of the closing stroke of the exhaust valve.
• Check valves can be used to ensure a smooth transition between the respective phases of the cycle since they are controlled by the hydraulic flow.
• the first electronically controlled valve and the fourth electronically controlled valve can be formed by a single two-way valve.
• the second electronically controlled valve and the third electronically controlled valve can be formed by a single two-way valve.
• the large two-stroke diesel engine can be provided with a first check valve allowing flow only towards the intermediate pressure hydraulic accumulator that is associated with the second electronically controlled valve and with a second check valve allowing flow only away from the intermediate pressure hydraulic accumulator that is associated with the third electronically controlled valve.
• first and second check valve allows a substantial overlap for the opening of the first electronically controlled valve, the second electronically controlled valve, the third electronically controlled valve and the fourth electronically controlled valve .
• the large two-stroke diesel engine may further comprise an electronic control unit configured to control the hydraulic connection between the pressure chamber and the source of high pressure hydraulic fluid, the intermediate pressure hydraulic accumulator and tank.
• figure 1 is a cross-sectional view of an engine according to the present invention
• figure 2 is a longitudinal-sectional view of one cylinder section of the engine shown in figure.
• figure 3 is a symbolic representation of a first embodiment of the exhaust valve actuating system according to the present invention
• figure 4 is a sequence diagram illustrating the timing of the opening and closing of the electronically controlled valves of the exhaust valve actuating system of figure 3
• figure 5 is the sequence diagram of figure 4 illustrating alternative opening times of the electronically controlled valves in which the effect of the check valves is exploited
• figure 6 is a symbolic representation of a second embodiment of the exhaust valve actuating system according to the present invention.
• Figures 1 and 2 show an engine 1 according to a preferred embodiment of the invention in cross-sectional view and longitudinal-sectional view (for one cylinder) respectively.
• the engine 1 is a uniflow low-speed two- stroke crosshead diesel engine of the crosshead type, which may be a propulsion system in a ship or a prime mover in a power plant. These engines have typically from 4 up to 14 cylinders in line.
• the engine 1 is built up from a bedplate 2 with the main bearings for the crankshaft 3.
• the crankshaft 3 is of the semi-built type.
• the semi- built type is made from forged or cast steel throws that are connected with the main journals by shrink fit connections .
• the bedplate 2 can be made in one part or be divided into sections of suitable size in accordance with production facilities.
• the bedplate consists of side walls and welded cross girders with bearing supports.
• the cross girders are in the art also referred to as "transverse girders”.
• the oil pan 58 is welded to the bottom of the bedplate 2 and collects the return oil from the forced lubricating and cooling oil system.
• the connecting rods 8 connect the crankshaft 3 to the crosshead 22.
• the crossheads 22 are guided between vertical guide planes 23.
• a welded design A-shaped frame box 4 is mounted on the bedplate 2.
• the frame box 4 is a welded design.
• On the exhaust side the frame box 4 is provided with relief valves for each cylinder, while on the opposite side the frame box 4 is provided with a large hinged door for each cylinder.
• the crosshead guide planes 23 are integrated in the frame box 4.
• a cylinder frame 5 is mounted on top of the frame box 4.
• Staybolts 27 connect the bedplate 2, the frame box 4 and the cylinder frame 5 and keep the structure together.
• the staybolts 27 are tightened with hydraulic jacks.
• the cylinder frame 5 is cast in one or more pieces or it is a welded design.
• the cylinder frame 5 is provided with access covers for cleaning the scavenge air space and for inspection of scavenge ports and piston rings. Together with the cylinder liner 6 it forms the scavenge air space.
• the scavenge air receiver 9, is bolted with its open side to the cylinder frame 5.
• a piston rod stuffing box which is provided with sealing rings for scavenge air, and with oil scraper rings which prevent exhaust products to penetrate into the space of the frame box 4 and the bedplate 2 and in this way protects all the bearings which are present in this space.
• the piston 13 includes a piston crown and piston skirt.
• the piston crown is made of heat-resistant steel and has four ring grooves which are hard-chrome plated on both the upper and the lower surfaces of the grooves.
• the piston rod 14 is connected to the crosshead 22 with four screws.
• the piston rod 14 has two coaxial bores (not visible in the drawings) which, in conjunction with a cooling oil pipe, forms the inlet and outlet for cooling oil for the piston 13.
• the cylinder liners 6 are carried by the cylinder frame 5.
• the cylinder liners 6 are made of alloyed cast iron and are suspended in the cylinder frame 5 by means of a low situated flange. The uppermost part of the liner is surrounded by cast iron cooling jacket.
• the cylinder liners 6 have drilled holes (not shown) for cylinder lubrication.
• the cylinders are of the uniflow type and have scavenge air ports 7 located in an airbox, which forms a scavenge air receiver 9 (Fig. 1), that is supplied with scavenge air pressurized by a turbocharger 10 (Fig. 1).
• the engine is fitted with one or more turbochargers 10 arranged on the aft end of the engine for 4-9 cylinder engines and on the exhaust side for 10 or more cylinder engines .
• the air intake to the turbocharger 10 takes place directly from the engine room through an intake silencer (not shown) of the turbocharger. From the turbocharger 10, the air is led via a charging air pipe (not shown) , air cooler (not shown) and scavenge air receiver 9 to the scavenge ports 7 of the cylinder liners 6.
• the engine is provided with electrically-driven scavenge air blowers (not shown) .
• the suction side of the blowers is connected to the scavenge air space after the air cooler.
• non-return valves (not shown) are fitted which automatically close when the auxiliary blowers supply the air.
• the auxiliary blowers assist the turbocharger compressor at low and medium load conditions.
• Fuel valves 40 are mounted concentrically in a cylinder cover 12. At the end of the compression stroke the injection valves 40 inject fuel at high pressure through their injection nozzles as a fine mist into the combustion chamber 15.
• An exhaust valve 11 is mounted centrally in the top of the cylinder in the cylinder cover 12. At the end of the expansion stroke the exhaust valve 11 opens before the engine piston 13 passes down past the scavenge air ports 7, whereby the combustion gases in the combustion chamber 15 above the piston 13 flow out through an exhaust passage 16 opening into an exhaust receiver 17 and the pressure in the combustion chamber 15 is relieved. The exhaust valve 11 closes again during the upward movement of the piston 13.
• the exhaust valve 11 is hydraulically activated.
• Figure 3 shows a first embodiment of the exhaust valve actuating system according to the present invention.
• the exhaust valve actuating system is for all of the embodiments illustrated with respect for a single cylinder. In a multi-cylinder engine there will be the same provisions for each cylinder.
• the exhaust valve actuating system includes the exhaust valve 11 with a valve stem 31 and a valve disc 32. In the closed position shown in figure 3 the valve disc 32 rests on the valve seat that is arranged in the top of the cylinder 6. The open position of the exhaust valve 11 is illustrated in figure 6.
• An air spring 34 urges the exhaust valve 11 towards its closed position.
• the air spring 34 is provided with a air piston 35 that is connected to the valve stem 31, so that the air spring 34 is operably connected to the exhaust valve 11.
• a position sensor 33 measures the position of the exhaust valve 11 either in an analog or digital fashion.
• the signal of the position sensor 33 is communicated to the engine control unit (e.g. a computer) 42 via a signal cable.
• the engine control unit 42 also receives a crankshaft position signal from a crankshaft sensor (not shown) .
• An exhaust valve actuator 37 is placed on the top of the valve stem 31 and includes a cylindrical valve housing with a hydraulic piston 38 received inside the cylindrical housing and the hydraulic piston 38 connected to the valve stem 31 so that the hydraulic actuator 37 is operably connected to the exhaust valve 11.
• a pressure chamber 39 is defined above the hydraulic piston 38.
• a pressure conduit 40 connects the pressure chamber 39 of the hydraulic actuator 38 to the hydraulic system of the exhaust valve actuating system.
• the hydraulic system of the exhaust valve actuating system includes a source of high-pressure hydraulic fluid, such as a pumping station (not shown) which may be a dedicated pumping station for the exhaust valve actuating system or may be a pumping station that is also used for other purposes (system pressure) , such as providing pressure for the fuel injection system or for cylinder lubrication system.
• system pressure typically, the system pressure will be a few hundred bar.
• the hydraulic system and the hydraulic actuator 37 will often be separated by a pressure booster or similar device to avoid contamination between the systems.
• a first electronically controlled valve 44 such as a hydraulic on/off valve, allows the pressure conduit 40 to be selectively connected to the source of high-pressure hydraulic fluid.
• the pressure conduit 40 is also connected to a branch conduit 41.
• the branch conduit 41 connects to an intermediate pressure hydraulic accumulator 43 via a first check valve 45 and a second electronically controlled valve 46 (e.g. a hydraulic on/off valve) .
• a first check valve 45 connects to an intermediate pressure hydraulic accumulator 43 via a first check valve 45 and a second electronically controlled valve 46 (e.g. a hydraulic on/off valve) .
• the intermediate pressure hydraulic accumulator 43 is preferably of the type that is provided with an elastic membrane dividing the accumulator into a part that is filled with pressurized hydraulic fluid and a part that is filled with pressurized gas.
• the branch conduit 41 also connects to the hydraulic accumulator 43 via a second check valve 47 and a third electronically controlled valve 48 (e.g. a hydraulic on/off valve) .
• a third electronically controlled valve 48 e.g. a hydraulic on/off valve
• the branch conduit 41 further connects to tank via a fourth electronically controlled valve 50 (e.g. a hydraulic on/off valve) .
• a fourth electronically controlled valve 50 e.g. a hydraulic on/off valve
• the first check valve 45 and the second check valve 47 have opposite flow directions.
• the first electrically controlled valve 44, the second electronically controlled valve 46, the third electronically controlled valve 48 and the fourth electrically controlled valve 50 are coupled to the engine control unit 42 via signal cables and these valves open and close on command of the engine control unit 42.
• the electronic control unit 42 determines the end of period "1" based on time, but use the signal from sensor 33 to determine the valve lift and correct the length of "1" in next cycle to obtain the requested valve lift.
• the operation of the exhaust valve 11 is divided into six sequential periods. In the first period "0" the exhaust valve 11 is closed and so are the first to fourth electronically controlled valves 44, 46, 48, 50.
• the electronic control unit 42 When the electronic control unit 42 has determined, on the basis of the crankshaft signal and possible also on the basis of other operating conditions of the engine that it is time to open the exhaust valve 11 period "0" ends and period "1" commences.
• the first electronically controlled valve 44 opens and allows high-pressure hydraulic fluid to flow into the pressure chamber 39.
• the high pressure hydraulic fluid in the pressure chamber 39 enables the exhaust valve 11 to open against the pressure of the combustion gases in the combustion chamber 15.
• the hydraulic actuator 37 is required to provide a high opening force at the very start of the opening stroke of the exhaust valve 11 because the high pressure of the gases in the combustion chamber presses the exhaust valve 11 into its seat.
• the electronic control unit 42 commands the first electronically controlled valve 44 to close and commands the second electronically controlled valve 46 to open.
• the electronic control unit 42 determines the end of period "1" using the signal from the position sensor 33 and corrects the timing on the basis of the result of the last cycle.
• period 2 The remaining period of the opening stroke of the exhaust valve 11 is referred to as period "2" in the sequence diagram of figure 4.
• the hydraulic accumulator 43 contains hydraulic fluid at an intermediate pressure, e.g. 10 to 30 bar.
• hydraulic fluid at an intermediate pressure flows towards the pressure chamber 39 and allows the exhaust valve 11 to complete its opening stroke.
• an intermediate pressure for a major part of the opening stroke the amount of energy that is used to open the exhaust valve 11 is relatively low, and due to the lower forces the opening movement is more controlled and smooth.
• the inertia of the moving valve and actuator in combination with the force acting is reduced to zero and the force of the air in the spring chamber of the air spring 34 acting on the air piston 35 starts to urge the exhaust valve 11 to move back.
• the return movement is prevented by check valve 45 and the exhaust valve 11 is stopped in its open position.
• the electronic control unit 42 can determine the end of period "2" on the basis of the signal from the position sensor 33.
• Period "4" includes the start and a major portion of the closing stroke of the exhaust valve 11.
• the electronic control unit 42 commands the third electronically controlled valve 48 to open.
• the hydraulic pressure chamber 39 is again connected to the hydraulic accumulator 43.
• the air spring 34 urges the exhaust valve 11 in the closing direction and the hydraulic fluid evacuating from the hydraulic pressure chamber 39 causes the hydraulic accumulator 43 to fill and thereby store the energy that was before stored in the gas spring 34.
• the energy now stored in the hydraulic accumulator 43 can be used for the next opening stroke of the exhaust valve 11.
• the electronic control unit 42 commands the third electronically controlled valve 48 to close and commands the fourth electronically controlled valve 50 to open.
• Period “5" includes the last short period of the closing stroke of the exhaust valve 11, and during this period the pressure chamber 39 is connected to tank thus allowing the exhaust valve 11 to be pressed on to its seat by the remaining pressure in the air spring 34.
• the start of period “5" is determined by the electronic control unit 42 on the basis of the signal from the position sensor 33 and on the basis of the pressure in the accumulator 43.
• the signal of a pressure sensor connected to the accumulator 43 is fed to the engine control unit 42.
• the control is such that the timing of the start of period "5" is adapted on the bases of the result in the previous cycle in a way to maintain a predetermined pressure in the accumulator 43.
• the pressure in the cumulative 43 is increasing the start of period "5" is advanced and if the pressure in the accumulator 43 is decreasing the start of period "5" is delayed.
• Figure 5 illustrates the sequence diagram of figure 4 with added hatched areas that indicate further possible opening periods of the respective electronically controlled valve's 46, 48 and 50. These overlaps are possible due to the provision of the first check valve 45 and the second check valve 47. The overlaps make it easier to ensure that respective electronically controlled valve 46,48 or 50 is opened at the moment that a preceding valve is not yet closed.
• the second electronically controlled valve 46 can be opened during period "1" and does thereby not need to be opened exactly at the transition from period "1" to period "2".
• the hatched areas in the diagram indicate periods in which the valve concerned can be either open or closed.
• Figure 6 illustrates another embodiment of the electro- mechanical valve actuation system in which the first electronically controlled valve 44 and the fourth electronically controlled valve 50 are merged into a single three-way valve.
• the the second electronically controlled valve 46, and the third electronically controlled valve 48 are merged into a single 2-way valve (cartridge valve) .
• the first check valve 45, the second electronically controlled valve 46, the second check valve 47 and the third electronically controlled valve 48 are merged into a single 3-way valve that has a middle position in which the connection between the conduit 41 and the hydraulic accumulator 43 is cut.
• This embodiment requires fewer control signals since the switchover between the first and fourth valve can be realized with one signal from the electronic control unit and the switchover between the second and third valve can be realized with one signal from the electronic control unit .
• one hydraulic accumulator 43 could be shared by several or all cylinders of the engine.
• the teaching of this invention has numerous advantages. Different embodiments or implementations may yield one or more of the following advantages. It should be noted that this is not an exhaustive list and there may be other advantages which are not described herein.
• One advantage of the teaching of this application is that it provides for an electro-hydraulic valve actuation system for a large two-stroke diesel engine that uses relatively little energy.
• Another advantage of the teaching of this application is that it provides for an electro-hydraulic valve actuation system that can be fitted to a large two- stroke diesel engine with a completely conventional exhaust valve arrangement that uses a simple (non- stepped) hydraulic actuator acting on the valve stem and using a conventional air spring to urge the exhaust valve in the closing direction.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Valve Device For Special Equipments (AREA)

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• 2008
  • 2008-11-11 CN CN2008801105554A patent/CN101970812B/zh not_active Expired - Fee Related
  • 2008-11-11 WO PCT/DK2008/000397 patent/WO2010054653A1/en active Application Filing
  • 2008-11-11 JP JP2010537255A patent/JP4657386B2/ja not_active Expired - Fee Related
  • 2008-11-11 KR KR1020107008592A patent/KR101210870B1/ko active IP Right Grant

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