Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
  • F02M59/20—Varying fuel delivery in quantity or timing
  • F02M59/36—Varying fuel delivery in quantity or timing by variably-timed valves controlling fuel passages to pumping elements or overflow passages
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M55/00—Fuel-injection apparatus characterised by their fuel conduits or their venting means; Arrangements of conduits between fuel tank and pump F02M37/00
  • F02M55/02—Conduits between injection pumps and injectors, e.g. conduits between pump and common-rail or conduits between common-rail and injectors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
  • F02M59/38—Pumps characterised by adaptations to special uses or conditions

Definitions

• the invention relates to a fuel injection system with variable adjustment of the injection timing in a diesel engine with high-pressure injection in order to change the maximum pressure in a cylinder during combustion, which engine has several cylinders, each having at least one fuel injector connected with a fuel pump via a high-pressure conduit, a drain valve arranged on the high-pressure side of the fuel pump being capable of being closed for initiation of an injection sequence, and fuel from the pump being capable of influencing the drain valve in the closing direction.
• the liquid fuel is injected at a high pressure, such as from 500 to 800 bar, and is ignited by the compression heat in the cylinder, where ⁇ upon the cylinder pressure increases to the maximum pressure as the combustion progresses.
• the efficiency of the engine increases with increasing maximum pres ⁇ sure, but so do also the mechanical influences on the engine members.
• the combustion process in modern engines is usually controlled in such a manner that the largest possible maximum pressure is achieved in the lower load area of the engine, while the maximum pressure in the upper load area, such as from 80 to 105 per cent of the nominal full load point of the engine is limited to a substantially constant value determined with due regard to the mechanical strength of the structural members.
• the maximum pressure is affected by the compression pressure which, in turbocharged engines, depends on the engine load, and is affected by the injection timing, i.e. the moment of initiation of the fuel injection seen in relation to the point in the engine cycle where the piston is in its top dead centre position (TDC) and the working stroke is to be initiated.
• the injection timing is normally stated as the relative angular position of the crank at which the injection starts.
• the maximum pressure can be restricted by delaying the moment of injection so that the maximum cylinder pressure is achieved later in the cycle, where the gas in the combustion chamber has expanded to some extent because the piston has moved some distance downwards.
• the injection timing can be changed by changing the moment for initiation of the pressure increase in the high-pressure conduit, to be specific, by changing the closing time of a controlled drain valve arranged in the high-pressure conduit .
• This known system has certain disadvantages in connection with large diesel engines of high outputs where it is desired to delay the injection moment at high loads. If the electric system fails, the ignition timing is advanced and the maximum pressure rises, thus causing a risk of mechanical failure in the heavily loaded engine components.
• GB-A-2 273 319 describes an injection system where the high-pressure side of the fuel pump is connected with a drain valve for controlling the start and stop of the fuel supply to the fuel injector in an injection sequence.
• the fuel from the fuel pump is used for closing the drain valve.
• Some of the fuel flows through a restricted flow passage in the drain valve slider and into a pressure chamber in which the pressure build-up results in closure of the drain valve.
• This injection system seems to relate to injection rate control.
• the object of the invention is to provide an injection system of a more simple design for the delivery of large amounts of fuel per injection and having a drain valve which can be actuated electroni ⁇ cally by means of suitably small adjustment forces in such a manner that the risk of overloading the engine is minimized.
• the injection system according to the invention is characterised in that the fuel from the fuel pump used for closure of the drain valve passes through a restricted flow passage, that the injection timing is advanced by actuation of an electrically actuated control valve for increasing the flow area in the restricted flow passage, and that at failure in the electric control system the control valve is adapted to be in the position without increased flow area.
• the first amount of fuel delivered from the fuel pump is drained away through the drain valve, and at the same time a small amount of fuel flows through the passage and builds up a pressure which begins closing the drain valve when its actuating pressure is exceeded.
• the pressure in the high-pressure conduit rises to a level where the fuel injector opens.
• control valve must be actuated to advance the injection timing to achieve a larger maximum pressure at combustion.
• the restricted flow passage does not achieve an increased area, and the drain valve closes slowly so that the maximum pressure at combustion is not increased. Mechanical overloading of the engine owing to power failure in the control of the injection system is thus avoided.
• the flow volume in the restricted flow passage required for closure of the drain valve is substantially smaller than the delivery volume of the pump per injection, which renders it possible to manufacture the control valve with small dimensions and associated small mass so that the actuating force can be supplied, for example, by a solenoid.
• the use of the fuel pressure for closure of the drain valve combined with the small control valve provides an injection system of a very simple design, requiring only electrical actuation of the control valves. Control of the injection timing for the whole engine can thus be provided with a simple controller, like an ignition distributor, instead of the heavy and slow-acting mechanical control systems formerly used in large engines .
• a secondary control valve can open the drain valve by passing the pressure from the high-pressure side of the fuel pump on to a piston surface acting in the opening direction of the drain valve, which interrupts the injection.
• Fig. 1 shows a diagram of the pressure sequences in the high-pressure conduit during an injection period for two different injection timings
• Fig. 2 shows the corresponding pressure sequences in the cylinder during combustion
• Fig. 3 is an outline of an injection system according to the invention.
• Figs. 4 and 5 are outlines of two different embodi ⁇ ments of the drain valve with associated control valve.
• cam-actuated piston pumps of the Bosch type are conventionally used to generate the required injection pressure in the fuel oil.
• the engines can yield outputs of between 4,000 and 70,000 kW, and a typical cylinder output may be in the interval from 1,000 to 5,000 kW, which means that a considerable volume of fuel must be injected during each engine cycle.
• the injection into each cylinder may be in the order of about 200 g of fuel per engine cycle, which may, for example be distributed on three injectors per cylinder.
• Engines of this type typically have maximum speeds in the interval of 60-190 r.p.m.
• Fig. 3 shows an example of a well-known fuel pump 1 of the make MAN B&W Diesel.
• a cam 2 on a camshaft 3 can, via a cam roller 4, move a pump piston 5 upwards so that the pump performs a delivery stroke, whereby the fuel in a pump chamber 6 delimited by the piston and a surrounding pump cylinder 7 is pressed out of the discharge opening of the pump and over into a high- pressure conduit 9.
• a compression spring 10 presses the cam roller 4 against the cam 2, so that the pump piston is returned to its starting position after the delivery stroke with simultaneous suction of a new portion of fuel into the pump chamber via an inlet conduit 11 and an annular chamber 12 around the pump cylinder.
• the high-pressure conduit 9 leads to a fuel injector 13 having a central through-going fuel passage with a spring-biassed valve, the spring force determin ⁇ ing the opening pressure of the injector.
• the fuel passage opens out downwards in an atomizer 14 with atomizer nozzles from where the fuel can be atomized into the combustion chamber of the cylinder.
• Fig. 1 shows in a solid line the pressure sequence on the high-pressure side of the pump, measured in the pump chamber 6, during an injection period with advanced moment of injection.
• the pressure is indicated in bar as a function of the crank angle, where 180° indicates the crank position with the piston in the top dead centre position.
• Figs. 1 and 2 indicate in broken lines the pressure sequences appearing when the moment of injection of the fuel is delayed.
• the time difference between the two injection sequences corresponds to a crank turn of 3.5° so that the points 0' and M' are located this angle later in the cycle.
• the delayed injection of the fuel has the effect that the compression pressure has time to fall by about 2 bar from the point P to the point P' r/ « before the combus ⁇ tion makes the cylinder pressure rise, and that the maximum pressure P' max of about 140 bar appears at a crank angle of 196°.
• the pressures and angles of rotation are merely one concrete example out of many possibilities, but it shows that a delay of the start of the injection sequence reduces the maximum pressure in the cylinder.
• the fuel injection timing can be varied by means of a drain valve 15 which can be set in the first extreme position shown in Fig. 3, where the fuel discharge of the pump is connected with a low-pressure source or a drain 16 preventing the pressure in the conduit 9 from reaching the opening pressure of the injector.
• the drain valve 15 connects the fuel discharge of the pump with the injector, and the connection to the drain is inter ⁇ rupted.
• the drain valve is spring-biassed in the opening direction, i.e., for movement towards the first extreme position shown in Fig. 3, where the pump pressure is drained away.
• the drain valve may be moved to its first extreme position by a hydrau ⁇ lic or pneumatic influence or by some other returning force which is temporarily active in the period between two pump strokes.
• a small amount of fuel flows into a restricted flow passage 17 branching off from the high-pressure conduit on the upstream side of the valve 15.
• the branched-off amount of fuel is via the flow passage 17 made to act on the drain valve in the closing direction.
• Fig. 3 illustrates both options by means of a control valve 18 in a parallel flow passage.
• the control valve 18 can be activated electroni ⁇ cally and may, for example, be a solenoid valve.
• control valve is spring-biassed for movement in the direction of a starting position without increased flow ares, a spring influence from a mechan ⁇ ical spring being completely independent of failures in the electronic system.
• the spring bias may also be provided in any other manner, for example by a permanent magnet.
• control valve With only two fixed extreme positions, but the control valve can also be designed so that the activated extreme position with the increased area is adjustable, and that the size of the increased area depends on this adjustment.
• the control valve becomes adjustable in a number of inter ⁇ mediate positions with a gradual increase of the flow area in the restricted flow passage.
• a solenoid valve which creates a magnetic field by the electrical actuation, which field pulls the valve body to an extreme position determined by the valve body encountering a mechanical stop, which is adjustable in the direction of movement of the valve body.
• the valve body may comprise a rod extending transversely in through the flow passage and constituting a restriction of the flow area.
• the rod may, for example, have a number of wedge-shaped depressions of increasing depth towards one end of the rod so that a longitudinal displacement away from the starting position moves still larger depressions into the flow passage, which renders possible a step-wise increase of the flow area without the fuel pressure in the passage influencing the rod with a resulting force.
• a first embodiment of the control valve 18 is shown in Fig. 4 where the flow passage 17 extends from the high-pressure conduit 9 to a pressure chamber 19.
• the movable body 20 of the drain valve comprises a seat 21 which, through a connecting portion 22 in the high- pressure conduit, is supported by a cylindrical guide section 23 passing in a pressure-sealing manner through a guiding bore 24 into the pressure chamber where the guide section is joined with a cylindrical piston 25 of a larger diameter than the guide section and consti ⁇ tuting a movable end wall in the pressure chamber.
• annular piston surface 26 on the piston 25 is influenced by a force acting in the closing direction of the valve body, i.e., upwards in Fig. 4, which moves the valve body to the closed position where the seat 21 contacts a corresponding stationary seat and cuts off the drain port 27.
• the piston 25 has a larger diameter than the drain port, which ensures that the valve body is kept in a closed position as long as the fuel pump maintains a high pressure in the conduit 9.
• the flow area in the restricted flow passage is adjustable by means of the control valve 18, which in a first embodiment comprises a slider 30, which is longitudinally displaceable in a transverse direction in relation to the passage 17 between the starting position shown in Fig. 4, where a first, relatively small flow opening 31 is arranged in the passage and restricts the fuel flow, and an activated extreme position, where a second, relatively larger flow opening
• the flow openings in the slider 30 are designed as sections with a smaller diameter, where the section with the opening 32 is longer than the section with the opening 31.
• the slider 30 is moved between the extreme posi ⁇ tions by means of an electrically/magnetically acting drive comprising two coils 33, 34, each with associated magnetisable core material, and a circular disc 35 acting as a fitting, fastened at the end of the slider and movable from one to the other extreme position by a magnetic field created by passing current through one of the coils 33, 34 through associated wires 36, 37.
• an electrically/magnetically acting drive comprising two coils 33, 34, each with associated magnetisable core material, and a circular disc 35 acting as a fitting, fastened at the end of the slider and movable from one to the other extreme position by a magnetic field created by passing current through one of the coils 33, 34 through associated wires 36, 37.
• the magnetising current pulls the disc 35 over to the magnet and leaves a certain residual magnetism in the core material. The residual magnetism is sufficient to retain the disc after interruption of the current.
• the coil 33 may be connected to a capacitor which is discharged through the coil at power failures, whereby the disc is fixed in the starting position until the electric control system is operating again.
• the control valve is seen to be a digital valve.
• a usual solenoid can be used, i.e., a single coil which, when magnetising current is applied, can pull the disc from the starting position to the actuated position with simultaneous compression of a compression spring which returns the slider to the starting position when the magnetising current of the solenoid is interrupted.
• the drain valve is in principle designed in the same manner as described above, and the same reference numerals are therefore used.
• the flow passage 17 is divided into a primary passage 40 permanently interconnecting the high-pressure conduit 9 and the pressure chamber 19.
• the flow area of the primary passage has been chosen to achieve the same fuel flow through the passage as through the passage in Fig. 4 when the slider 30 is in its starting position.
• the pressure chamber 19 can further be connected with the conduit 9 through a secondary passage 41 which, like the passage 40, is arranged on the upstream side of the drain port 27.
• the control valve 18 is designed as a solenoid valve having a valve needle 42 which is pressed by a compression spring 43 towards a starting position, in which the needle is in contact with a stationary seat at the inlet opening to the secondary passage and bars access to it.
• a solenoid 44 is magnetised by current passing through the wires 45, the valve needle is retracted from the stationary seat so that fuel can also flow through the secondary passage into the pressure chamber 19.
• the chamber 50 may have a drain passage, not shown, with an orifice to prevent sustained substantial pressure build ⁇ up on the spring side of the piston 25.
• the second pressure chamber could have a large volume and the lifting height of the drain valve 15 could be small .
• a passage 51 may interconnect the second pressure chamber and the high-pressure conduit 9 on the down ⁇ stream side of the drain port 27, when a secondary control valve 52 is actuated to open for access to the passage 51.
• the secondary control valve 52 may be constructed in the same manner as the control valve 18. In the embodiment shown in Fig.
• the secondary control valve comprises a valve needle 53, which can be moved away from the inlet opening of the passage by means of a solenoid.
• the valve body 20 is influenced by a resulting force in the opening direction, because the piston 25 has an effective area acting in the opening direction and corresponding to the cross-sectional area of the connecting portion 22.
• Actuation of the secondary control valve 52 results in opening of the drain valve, which interrupts injection.
• the secondary control valve 52 can be used to adjust or meter the amount of fuel injected.
• the drain valve with associated control valve is shown in connection with the high- pressure conduit 9.
• the valves may be designed in a valve unit which can be connected to the high-pressure conduit 9.
• the valve unit may, for example, be mounted on top of the housing of the fuel pump. It is possible to retrofit the valve unit on engines already existing to enable adjustment of the injection timing in a simple manner. It is also possible to build in the valve unit as an integral part of the fuel pump.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fuel-Injection Apparatus (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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ID=8091458

Family Applications (1)

Country Status (5)

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Citations (3)

• 1995
  • 1995-03-14 DK DK25395A patent/DK174139B1/da not_active IP Right Cessation
• 1996
  • 1996-03-07 WO PCT/DK1996/000096 patent/WO1996028655A1/en active IP Right Grant
  • 1996-03-07 JP JP52718596A patent/JP3396483B2/ja not_active Expired - Fee Related
  • 1996-03-07 EP EP96905757A patent/EP0815357B1/en not_active Expired - Lifetime
  • 1996-03-07 DE DE69605900T patent/DE69605900T2/de not_active Expired - Fee Related

Patent Citations (3)

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