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
  • F01L1/02—Valve drive
  • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
  • F01L1/08—Shape of cams
• • 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
  • F01L1/12—Transmitting gear between valve drive and valve
  • F01L1/14—Tappets; Push rods
• • 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
  • F01L1/12—Transmitting gear between valve drive and valve
  • F01L1/14—Tappets; Push rods
  • F01L1/146—Push-rods
• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
  • F02N9/00—Starting of engines by supplying auxiliary pressure fluid to their working chambers
  • F02N9/04—Starting of engines by supplying auxiliary pressure fluid to their working chambers the pressure fluid being generated otherwise, e.g. by compressing air

Definitions

• the present invention relates to a multi-cylinder piston engine in accordance with the preamble of claim 1.
• the engine comprises a starting arrangement and at least one cam- operated valve lifting device for each cylinder of the engine, the valve lifting device being arranged to open a gas exchange valve.
• Patent application WO 2007/003693 Al discloses a starting system for a multi-cylinder piston engine.
• a pipe system connects a pressure medium source to each cylinder of the engine.
• Each cylinder is provided with a starting air valve for introducing pressure medium into the cylinders.
• Each starting valve is controlled by a control valve.
• the starting system is provided with timing equipment comprising a control part being in mechanical connection with a rotating part of the engine. This kind of starting arrangement guarantees accurate timing of the starting air injection, but a drawback is that control air has to be brought to each control valve in a separate control air pipe. Also, different timing equipment needs to be designed for engines with different number of cylinders.
• the object of the present invention is to provide an improved multi-cylinder piston engine with a starting arrangement.
• the engine according to the present invention is characterized by the characterizing part of claim 1.
• the multi-cylinder piston engine comprises at least one cam-operated valve lifting device for each cylinder of the engine, the valve lifting device being arranged to open a gas exchange valve.
• the starting arrangement comprises a pressure medium source, at least one starting valve for introducing pressure me- dium into a cylinder of the engine, means for connecting the pressure medium source to the starting valves, and a control valve for each cylinder of engine that is provided with a starting valve for controlling the operation of the starting valve.
• Each control valve is arranged to be operated by a gas exchange cam of the respective cylinder.
• starting valves are controlled by the gas exchange cams, a separate starting cam is not needed. Identical cams can be used regardless of the cylinder number of the engine and there is no need to design different starting cams for engines with different number of cylinders. Starting air can be distributed to the cylinders in a single starting air duct instead of separate ducts for each cy- linder. This saves both space and material.
• the invention also enables reliable and accurate control of starting air injection.
• each gas exchange cam that operates a control valve comprises a portion that is arranged below the base circle of the cam for operating the control valve.
• a simple and reliable control mechanism can be achieved.
• Identical cams can be used for engines with different number of cylinders and no separate adjustment is needed for the starting air injection timing.
• each control valve is in flow communication with the pressure medium source and the respective starting valve via a control air duct.
• control valve is arranged to allow pressure medium flow to the starting valve for opening the starting valve when the valve lifting device is engaged with the portion of the gas exchange cam that is below the base circle of the cam.
• each control valve comprises a valve member that is movable by the valve lifting device.
• the valve lifting device comprises a plunger pushing the valve member towards the gas exchange cam when the valve lifting device is engaged with the portion of the gas exchange cam that is below the base circle of the cam.
• the valve member is pushed towards the valve lifting device by the pressure of the pressure medium.
• the gas exchange cam is an intake cam. Starting air injection is started near top dead center and terminated close to the crank angle where the exhaust valve opens.
• the intake cam is used for controlling the starting valve, the portion of the cam that is below the base circle is far from the lobe of the cam. The shape of the portion below the base circle is thus not dependent on the shape of the lobe. If the portion below the base circle is close to the lobe of the cam, there might be some limitations to the shape of the portion below the base circle.
• each intake cam comprises a second portion that is arranged below the base circle of the cam for controlling the operation of variable intake valve closing, and the portion that is arranged below the base circle of the cam is arranged also below the said second portion.
• the gas exchange cam is an exhaust cam. When the control valves are operated by the exhaust cams, the invention can be used even in two-stroke engines with cam-operated exhaust valves.
• a two-stroke engine at least three cy- linders of the engine are provided with a starting valve and in a four-stroke engine at least five cylinders of the engine are provided with a starting valve.
• all the cylinders of the engine are provided with a starting valve. Since identical cam profiles and valve lifting devices can be used for all the cylinders of the engine, it is practical to provide all the cylinders with starting valves.
• each control valve comprises an inlet channel for introducing pressure medium into the control valve, an outlet channel for introducing the pressure medium to the starting valve for opening the starting valve, and a drain channel for releasing the pressure medium out of the control valve when the control valve is not actuated by the gas exchange cam.
• the starting arrangement comprises a main starting valve for initiating starting of the engine.
• Fig. 1 shows schematically a starting system of an internal combustion engine.
• Fig. 2 shows a simplified cross-sectional view of a part of a cylinder head with gas exchange valves and a starting valve.
• Figs. 3-6 show an intake cam of the engine and the control arrangement of a starting valve at different stages of operation according to an embodiment of the invention.
• Fig. 7 shows an intake cam of the engine and the control arrangement of a starting valve according to another embodiment of the invention.
• Fig. 8 shows schematically a starting system of an internal combustion engine according to another embodiment of the invention.
• Fig. 9 shows an exhaust cam of the engine and a control arrangement of an air injection valve.
• Figs. 10 shows the vertical position of the cam followers at different crank angles.
• Figs. 11 shows the vertical position of the cam followers at different crank angles in an engine with VIC. Detailed description of the invention
• Fig. 1 shows schematically a starting arrangement of a piston engine 20.
• the engine 20 comprises six cylinders 19, but the engine 20 could comprise any reasonable number of cylinders 19 arranged for instance inline or in a V- configuration.
• the engine 20 is a large internal combustion engine, such as those used for producing electricity and/or heat at a power plant or as main or auxiliary engines in ships.
• all the cylinders 19 are provided with means for introducing pressure medium, such as pressurized air, into the cylinders 19 for starting the engine 20.
• Pressurized air is stored in a starting air tank 18, from which it can be introduced into the cylinders 19 of the engine 20 in a starting air duct 26. Instead of air, also some other pressurized gas could be used.
• the starting air tank 18 can be filled by a compressor (not shown).
• Each cylinder 19 of the engine 20 that is used for starting is provided with a starting valve 10.
• a starting valve 10 in connection with a cylinder head 23.
• the cylinder head 23 is also provided with an intake duct 32 for introducing combustion air into the respective cylinder 19, and with an exhaust duct 33 for guiding exhaust gases out of the cylinder 19.
• One or more intake valves 24 and one or more ex- haust valves 25 are arranged in the cylinder head 23 for opening and closing the connection between the cylinder 19 and the intake and exhaust ducts 32, 33.
• the operation of each starting valve 10 is controlled by a respective control valve 12.
• Each cylinder 19 of the engine 20 can also be provided with more than one starting valves 10. If each cy- linder 19 is provided for instance with two starting valves 10, both valves 10 can be controlled by the same control valve 12.
• the control valves 12 are connected to the starting air duct 26.
• the starting air duct 26 is provided with a main starting valve 17 for controlling when the engine 20 is started.
• An example of the starting valve 10 and the control valve 12 is shown as a simplified illustration in Figs. 3-6.
• the starting arrangement comprises a valve lifting device 4 and a gas exchange cam 1.
• the gas exchange cam 1 is shown in the figures as being rotated 90 degrees around its vertical axis to better illu- strate the cam profile 2.
• the cam profile 2 of the gas exchange cam 1 comprises a base circle 2a, a lobe 2b and a portion 2c that is arranged below the base circle 2a.
• the expression "below the base circle” means that the radius of that portion of the cam profile
• the gas exchange cam 1 is an intake cam and the valve lifting device 4 is arranged to open an intake valve 24 of the engine 20.
• An identical cam lifting device 4 can be used for opening an exhaust valve 25 of the engine 20.
• the cam lifting device 4 comprises a body part 5 and a reciprocating plunger 6 that is arranged inside the body part 5.
• the plunger 6 is arranged to lift a push rod 8.
• a cam follower 3 is attached to the plunger 6 with a bearing.
• a coil spring 7 between the body part 5 and the plunger 6 pushes the cam follower 3 against the cam profile 2.
• the lifting arrangement works in a conventional manner. When the cam follower 3 is on the portion 2c of the cam profile 2 that is below the base circle 2a, the plunger 6 is at its lowest position.
• the body part 5 is provided with a stopper surface 9, against which the push rod 8 can rest so that the position of the push rod 8 and the intake valve 24 does not change when the cam follower 3 leaves the base circle 2a and enters the portion 2c below the base circle 2a, or vice versa.
• each valve 19 of the engine 20 is provided with a starting valve 10 comprising a valve member 22.
• the starting valve 10 is kept closed by a spring 11.
• each valve lifting device 4 is provided with a control valve 12.
• the main starting valve 17 is opened. This allows the starting air to flow in the starting air duct 26 to the control valves 12.
• the pressurized air enters the control valves 12 via inlet channels 14.
• the air pressure pushes the valve member 13 inside the control valve 12 upwards into the position shown in Fig. 4.
• the valve member 13 thus allows the pressurized air to flow out of the control valve 12 through a drain channel 16. The air is released from the drain channel 16 for instance into the engine room.
• FIG 7 is shown a slightly different embodiment of the invention.
• the push rod 8 is moved by a piston 30 that is arranged between the push rod 8 and the plunger 6.
• a second spring 29 for eliminating clearance between the push rod 8 and the piston 30 is arranged between the piston 30 and the plunger 6.
• the second spring 29 keeps the piston 30 against the end of the push rod 8 so that no gap is formed between the push rod 8 and the piston 30 or between the upper end of the push rod 8 and the rocker arm. This ensures smooth operation of the valve lifting device 4.
• figure 10 is shown as a graph the position of the cam follower 3.
• the broken line shows the position of the cam follower of the exhaust valve 25 and the solid line the position of the cam follower of the intake valve 24.
• the plungers 6 follow the same curves.
• the push rods 8 and the valve lifts also follow the same curves with the exception that because of the stopper surface 9 in the embodiment of figures 3-6 or the piston/spring arrangement 29, 30 in the embodiment of figure 7, the vertical position of the push rods 8 cannot be negative.
• the area below the horizontal axis indicates how the cam follower 3 of the intake valve lifting device 4 is engaged with the portion 2c below the base circle 2a.
• the starting air injection takes place during this phase, which starts in the embodiments shown in the figures just before top dead center (TDC) during the compression stroke and lasts until approximately 90 degrees of crank angle after top dead center during the power stroke.
• TDC top dead center
• VAC variable intake valve closing
• the intake cam profile comprises a portion that is arranged below the base circle for controlling the in- take valve closing timing. Another portion for controlling the starting valves is arranged below the portion that controls the intake valve closing timing.
• FIG 8 is shown another embodiment of the invention, where the starting air duct 26 and the starting air tank 18 are also used for introducing additional combustion air into the cylinders 19 of the engine 20.
• additional combustion air refers here to air that is introduced into the cylinders 19 of the engine 20 before ignition but after the normal air intake has ended. In a four-stroke engine this means that the additional combustion air is introduced into a cylinder 19 after closing of the intake valves of that cylinder 19. Additional combustion air can be introduced into the cylinders 19 of the en- gine 20 for reducing turbo lag in situations where the engine load suddenly increases.
• the engine 20 is provided with a control air duct 21 that connects the control valves 12 to the starting air tank 18.
• the main starting valve 17 is arranged in the control air duct 21.
• the starting air duct 26 is provided with a closing valve 34.
• Each cylinder 19 of the engine 20 is provided with a second control valve 12' for controlling the injection of the additional combustion air into the cylinders 19.
• the second control valves 12' are connected with a second control air duct 21 ' to the starting air tank 18.
• the second control air duct 21 ' is provided with an air injection control valve 17' for controlling when the injection of the additional combustion air is switched on.
• the starting valves 10 are used also for introducing the additional combustion air into the cylinders 19. However, also separate valves could be used.
• the control air duct 21 is provided with a check valve 32 downstream from each control valve 12 for preventing the additional combustion air from escaping through the respective control valve 12 when additional combustion air is introduced into the engine 20.
• the second control air duct 21 ' is provided with a second check valve 32' downstream from each second control valve 12' for preventing the starting air from escaping through the second control valve 12' during starting of the engine 20.
• the second control valves 12' are operated by the exhaust cams of the engine 20, as shown in figure 9.
• the valve lifting devices 4 that are used for opening the exhaust valves 25 can be identical with the valve lifting devices 4 that are used for opening the intake valves 24.
• the cam profile 2' of the exhaust cam 1 ' is different from the cam pro- file 2 of the intake cam 1, but otherwise the second control valves 12' are operated in the same manner as the first control valves 12. It is beneficial to use the exhaust cams 1 ' for operating the second control valves 12' since in the exhaust cams the portion 2c' below the base circle 2' can be arranged far from the lobe 2b' of the cam profile 2'. However, it would also be possible to use the intake cams 1 for operating the second control valves 12' and the exhaust cams 1 ' for operating the first control valves 12.
• the second control valves 12' are identical to the first control valves 12, comprising a valve member 13', an inlet channel 14', an outlet channel 15', and a drain channel 14'.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Valve Device For Special Equipments (AREA)
• Valve-Gear Or Valve Arrangements (AREA)
• Output Control And Ontrol Of Special Type Engine (AREA)
• Combustion Methods Of Internal-Combustion Engines (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (3)

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Citations (2)

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• 2011
  • 2011-05-17 FI FI20115471A patent/FI124085B/sv active IP Right Grant
• 2012
  • 2012-05-11 EP EP12726142.8A patent/EP2710253B1/en active Active
  • 2012-05-11 JP JP2014510841A patent/JP5926372B2/ja active Active
  • 2012-05-11 WO PCT/FI2012/050455 patent/WO2012156584A1/en active Application Filing
  • 2012-05-11 CN CN201280023438.0A patent/CN103534478B/zh active Active
  • 2012-05-11 KR KR1020137033252A patent/KR101729371B1/ko active IP Right Grant

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