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
  • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
  • F02M61/04—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00 having valves, e.g. having a plurality of valves in series
  • F02M61/08—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00 having valves, e.g. having a plurality of valves in series the valves opening in direction of fuel flow
• • 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
  • F02M51/00—Fuel-injection apparatus characterised by being operated electrically
  • F02M51/04—Pumps peculiar thereto
• • 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
  • F02M57/00—Fuel-injectors combined or associated with other devices
  • F02M57/02—Injectors structurally combined with fuel-injection pumps
• • 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
  • F02M57/00—Fuel-injectors combined or associated with other devices
  • F02M57/02—Injectors structurally combined with fuel-injection pumps
  • F02M57/022—Injectors structurally combined with fuel-injection pumps characterised by the pump drive
  • F02M57/027—Injectors structurally combined with fuel-injection pumps characterised by the pump drive electric
• • 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
  • F02M59/44—Details, components parts, or accessories not provided for in, or of interest apart from, the apparatus of groups F02M59/02 - F02M59/42; Pumps having transducers, e.g. to measure displacement of pump rack or piston
  • F02M59/46—Valves
  • F02M59/462—Delivery valves
• • 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
  • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
  • F02M2200/21—Fuel-injection apparatus with piezoelectric or magnetostrictive elements
• • 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
  • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
  • F02M63/0012—Valves
  • F02M63/0057—Means for avoiding fuel contact with valve actuator, e.g. isolating actuators by using bellows or diaphragms

Definitions

• the invention relates to a fuel injector with a piezoelectric or magnetostrictive actuator.
• a fuel injector with a piezoelectric actuator is e.g. B. from DE 195 00 706 AI known.
• the piezoelectric or magnetostrictive actuator actuates a working piston, which acts on a reciprocating piston via a hydraulic displacement transformer.
• the reciprocating piston is positively connected via a valve needle to a valve closing body provided at the spray opening.
• the piezoelectric or magnetostrictive actuator is therefore non-positively connected to the valve closing body via the hydraulic displacement transformer. If an appropriate electrical voltage is applied to the actuator, it expands and shifts the working piston accordingly.
• the known fuel injection valves have the disadvantage that the injection pressure is predetermined by the fuel pressure generated by the fuel pump in the fuel feed line and therefore the available injection pressure is limited. Furthermore, there is the disadvantage of a mass inertia of the reciprocating piston which should not be neglected Valve needle and the valve closing body. The response time of the fuel injector is determined by the inertia of these elements.
• the fuel injector according to the invention with the features of the main claim has the advantage that the fuel is injected with a relatively high injection pressure.
• the fuel is additionally compressed with a pump piston which can be driven by means of a piezoelectric or magnetostrictive actuator, so that the fuel pressure prevailing in a fuel pressure line between the pump piston and a spray nozzle is substantially greater than the fuel pressure prevailing in the fuel supply line.
• the spray nozzle is actuated hydraulically in that the spray nozzle opens when the fuel pressure in the fuel pressure line exceeds a predetermined threshold value.
• the piezoelectric or magnetostrictive actuator increases both the injection pressure and the hydraulic actuation of the spray nozzle. In this way, two functions are combined in an extremely compact unit.
• the compact design also results in relatively short suction paths for the fuel, so that cavitation problems are avoided.
• the fuel volume to be compressed by the pump piston is relatively small and is limited only to the volume of the relatively short fuel pressure line and the volume within the spray nozzle, which can also be implemented with very small dimensions.
• the damage space assigned to the pump piston is therefore relatively small, so that a relatively small stroke of the pump piston is sufficient.
• the thermal linear expansion compensation of the actuator required in the known fuel injection valves can be completely dispensed with, since the spray nozzle is actuated hydraulically rather than mechanically via a reciprocating piston and a valve needle. Slight temperature-dependent displacements of the pump piston due to a temperature-dependent linear expansion of the actuator connected to the pump piston are therefore harmless for the function of the fuel injector according to the invention.
• the modular structure of the fuel injector according to the invention enables an assembly-friendly plug-in solution which can also be assembled semi-automatically or fully automatically within a relatively short assembly time.
• the measures listed in the subclaims permit advantageous developments and improvements of the fuel injection valve specified in the main claim.
• the actuator can advantageously be non-positively connected to the pump piston via a coupling device comprising a part-spherical bearing element.
• the part-spherical bearing element ensures that radial forces exerted by the actuator in addition to the main translational force do not interfere with the translational movement of the pump piston.
• the pump piston can particularly advantageously be cup-shaped with a fuel pre-chamber surrounding a central mandrel.
• the central mandrel is used to introduce the force exerted by the actuator.
• the cup-shaped design of the pump piston has a particularly low mass inertia, which further reduces the response time of the fuel injection valve according to the invention.
• a fuel pre-chamber is integrated within the pump piston, which results in a particularly compact design.
• the fuel pre-chamber can furthermore advantageously be sealed off from the actuator or the components receiving the actuator by a flexible membrane. In this way there are no problematic sealing points that leak or wear, such. B. when using a sealing ring. There are no special requirements for the compressive strength of the membrane, since the membrane is only exposed to the fuel inlet pressure.
• a check valve preventing the backflow of fuel from the fuel pressure line into the fuel prechamber can advantageously be arranged directly at the inlet of the fuel pressure line.
• the check valve can have a valve piston which, together with a seat surface surrounding an outlet opening of the pump piston, forms a seat valve.
• a second check valve is advantageously provided at the outlet of the fuel pressure line or at the inlet of the spray nozzle, which ensures that the fuel pressure within the spray nozzle does not decrease during the suction stroke of the pump piston.
• FIG. 1 shows an axial section through a fuel injection valve according to the invention
• FIG. 2 shows an enlarged illustration of the end region on the injection-side side of the fuel injection valve according to the invention shown in FIG. 1.
• the piezoelectric actuator 2 is located within an actuator housing 3 and can be supplied with an electrical supply voltage via electrical supply cables 4.
• the piezoelectric actuator 2 can be designed in a known manner as a multilayer piezo stack. Instead of a piezoelectric actuator, a magnetostrictive actuator 2 can also be used in the same way.
• the piezoelectric actuator 2 is received at its free ends by two receiving elements 5, 6. At its end facing away from a pump piston 7 to be described in more detail, the piezoelectric actuator 2 is mounted via the receiving element 5 in a bearing block 8 which is fastened to the actuator housing 3 via a thread 9.
• the inner end face 11 of the cup-shaped bearing block 8 is spaced from the actuator housing 3 by a spacer ring 10.
• the receiving element 5 has in the region of the longitudinal axis 12 of the actuator 2 or the fuel injector 1, a projection 13 which bears on the inside end face 11 of the bearing block 8.
• the actuator 2 is mounted in a further receiving element 6, which has an annular recess 14 for receiving a plate spring 15.
• the plate spring 15 serves for the axial prestressing of the actuator 2 in order to clamp the actuator 2 with a predetermined compressive stress between the receiving elements 5 and 6.
• the annular space 16 formed between the actuator 2 and the actuator housing 3 can, if required, be flowed through by a liquid or gaseous coolant which flows in via a coolant supply opening 17 and flows out via a coolant discharge opening (not shown).
• the actuator housing 3 At its end adjacent to the pump piston 7, the actuator housing 3 has an external thread 18 which can be screwed into a corresponding internal thread 19 of a valve block 20.
• the valve block 20 can in turn be connected to a cup-shaped nozzle closure body 22 via a thread 21.
• the actuator housing 3, the valve block 20 and the nozzle closure body 22 can be preassembled as a unit before the fuel injector 1 is inserted as a unit into a stepped bore 23 of a cylinder head 24 of the internal combustion engine.
• the fuel injector 1 is in the Embodiment locked by means of a sleeve 25 on the cylinder head 24.
• the sleeve 25 can be screwed into a thread 26 of the stepped bore 23 of the cylinder head 24 and, for this purpose, engages an end face 27 of the valve block 20.
• the sleeve 25 has a tool engagement body 28, for. B. in the form of an external hexagon on which a suitable tool, for. B. can attack a wrench.
• a vent hole 29, which can be closed, is used for venting.
• the fuel is supplied via a fuel feed line 30 running at least partially within the cylinder head 24.
• suitable sealing means 31-33 which, for. B. can be designed as O-rings.
• FIG. 2 shows an enlarged representation of the spray-side end region of the fuel injector according to the invention shown in its entirety in FIG. 1. Elements already described are provided with the same reference numerals.
• the valve block 20 is provided with an axial stepped bore 40 which extends axially through the entire valve block 20.
• the pot-shaped and axially symmetrical pump piston 7 is inserted into a guide section 41 of the stepped bore 40.
• the pump piston 7 has a central mandrel 42 in the region of the longitudinal axis 12.
• the central mandrel 42 is surrounded by an annular fuel pre-chamber 43 which is connected to the fuel supply line 30 via radial bores 94 provided in the valve block 20.
• the fuel pre-chamber 43 is by means of a flexible membrane 44 which, for. B. can consist of a flexible plastic material, sealed from the actuator 2 or from the actuator housing 3, the receiving element 6 and in particular from the annular space 16 receiving the coolant.
• the membrane 44 can have at least one annular circumferential bead 45 to facilitate the deformation. Since the membrane 44 is only acted upon by the fuel inlet pressure prevailing in the fuel supply line 30, no special requirements have to be made of the compressive strength of the membrane 44.
• the fuel inlet pressure is, for example, only 3-4 bar.
• the sealing by means of the flexible membrane 44 has the advantage that leakage or wear is avoided, as it is e.g. B. can occur when using a sealing ring after a long period of operation of the fuel injector 1.
• the receiving element 6 adjacent to the pump piston 7 has a spherical recess 47 on an end face 46 opposite the pump piston 7, into which a part-spherical, for. B. semi-spherical bearing element 48 is inserted.
• the bearing element 48 lies opposite the central mandrel 42 of the pump piston 7 and is separated from it by the flexible membrane 44.
• a plate spring 51 Between a spray-side end face 49 of the pump piston 7 and a contact surface 50 of the stepped bore 23 of the valve block 20 there is a plate spring 51 which keeps the central mandrel 42 of the pump piston 7 in contact with the bearing element 48.
• the receiving element 6 can be tilted within certain limits relative to the position element 48 due to the spherical design of the interface. If the receiving element 6 tilts slightly with respect to the longitudinal axis 12 when the actuator 2 is actuated, the full-surface contact of the bearing element 48 on the membrane 44 and thus indirectly on the central mandrel 42 of the pump piston 7 is not impaired.
• the pump piston 7 has a hollow cylindrical wall section 52 which is guided in the guide section 41 of the stepped bore 40. At its spray-side end, the pump piston 7 has a central outlet opening 53, which is connected to the annular fuel pre-chamber 43 via transverse bores 54. The outlet opening 53 of the pump piston 7 opens into a fuel pressure line 60.
• the first check valve 61 consists of a cylindrical valve piston 62 which is connected by means of a spring element 93, for. B. a coil spring, is pressed against the end face 49 of the pump piston 7.
• valve piston 62 therefore interacts with the pump piston 7 to form a flat seat valve, the valve piston 62 sealingly abutting a seat surface 63 surrounding the outlet opening 53 of the pump piston 7 in a closed position of the check valve 61 and from the seat surface 63 when the check valve 61 is opened takes off.
• the end face 49 and the contact surface 50 delimit a pump chamber 90, the volume of which is determined by the axial position of the pump piston 7 and which preferably extends over several, e.g. B. three, the valve piston 62 surrounding connecting slots 64 is connected to the fuel pressure gluing 60.
• a second check valve 71 is located at the outlet of the fuel pressure line 60 or at the entrance to a spray nozzle 70 to be described in more detail.
• the second check valve 71 consists of a valve seat 72 which closes the fuel pressure line 60 and which can be closed by a spherical valve body 73 in the exemplary embodiment is.
• the valve body 73 is pressed against the valve seat 72 by means of a spring element 74.
• a nozzle body 75 Downstream of the second check valve 71 there is a nozzle body 75 with a spray opening 76.
• the spray opening 76 can be closed by means of a valve closing body 77 which is connected to a spring plate 80 by means of a valve needle 79 penetrating an axial longitudinal bore 78 of the nozzle body 75.
• a biased return spring 82 Between the spring plate 80 and a ruff 81 of the nozzle body 75 is a biased return spring 82, for. B. a coil spring is clamped, which biases the valve closing body 77 of the externally opening spray nozzle 70 in a closed position.
• the fuel flows to the nozzle body 75 via a section 83 of the stepped bore 40 of the valve block 20 which receives the check valve 71 and the nozzle body 75 and is guided through this by means of radial bores 84 to the axial longitudinal bore 78 surrounding the valve needle 79 and finally to the spray opening 76 .
• the fuel flows into the prechamber 43 via the fuel supply line 30.
• the supply voltage is applied to the piezoelectric actuator 2, it expands axially depending on the level of the supply voltage.
• the axial extension of the actuator 2 defines the axial position of the pump piston 7, which is held in contact by means of the plate spring 51 on the bearing element 48 and thus on the receiving element 6 connected to the free end of the actuator 2 on the pump piston side. If the supply voltage of the actuator 2 is reduced, its axial extent decreases, so that the pump piston 7 moves in the direction of the actuator 2 and consequently the volume of the pump chamber 90 formed between the end face 49 of the pump piston 7 and the contact surface 50 of the valve block 20 increases becomes.
• the increasing volume of the pump chamber 90 creates a reduced pressure in the fuel pressure line 60, which pressure drops below the fuel pressure prevailing in the fuel pre-chamber 43.
• the fuel pressure gluing 60 is closed by the second check valve 71 to the spray nozzle 70.
• the negative pressure which arises in the fuel pressure glue 60 with respect to the fuel pre-chamber 43 causes the first check valve 61 to open, in that the valve piston 62 lifts off from the seat surface 63 formed on the pump piston 7.
• the fuel therefore flows into the pump chamber 90 via the opening first check valve 61 during the suction stroke of the pump piston 7 described above, the volume of which increases with the increasing suction stroke of the pump piston 7. Fill around the pump chamber 90 to be able to. B. in the plate spring 51 axial bores or supply channels on the bearing surfaces of the plate spring 49, 50 are present.
• the pump piston 7 is therefore moved in the direction of the spray nozzle 70, so that the volume of the pump chamber 90 decreases increasingly. In this way, an overpressure arises in the pump chamber 90 and the fuel pressure glue 60 connected to it in relation to the fuel pre-chamber 43.
• the first check valve 61 therefore closes in that the valve piston 62 rests on the seat surface 63 formed on the pump piston 7.
• the second check valve 71 opens, so that the fuel under increased pressure flows from the fuel pressure glue into the inner volume 91 of the spray nozzle 70.
• the fuel pressure prevailing in the inner volume 91 of the spray nozzle 70 acts on the valve seat 77 with an adjusting force directed in the direction of the spray opening 76.
• the valve closing body 77 connected to the spring plate 80 via the valve needle 79 releases the spray opening 76 so that the fuel is injected into an upstream combustion chamber 92 of the internal combustion engine.
• the threshold value of the pressure at which the spray nozzle 70 opens depends on the restoring force exerted by the restoring spring 82 and can be predetermined via the spring constant and pretensioning of the restoring spring 82.
• the actuator 2 of the fuel injection valve 1 therefore fulfills two functions: on the one hand, a pressure increase of the fuel is achieved by means of the pump piston 7 driven by the actuator 2, so that the spray pressure of the fuel is substantially higher than the fuel supply pressure prevailing in the supply line 30. The increased injection pressure of the fuel results in very good injection properties.
• the actuator 2 serves for the indirect hydraulic actuation of the spray nozzle 70.
• the hydraulic actuation of the spray nozzle 70 or the valve closing body 77 has the advantage over a purely mechanical actuation of a low mass inertia of the overall system and thus a short response time.
• the suction paths on the fuel injection valve 1 according to the invention are relatively short, as a result of which cavitation problems are avoided.
• the clearance between the pump piston 7 and the spray opening 76 has a relatively small volume, which further reduces the response time of the fuel injector 1.
• a thermal linear expansion compensation of the actuator 2 is not necessary, since slight static displacements of the pump piston 7 have no influence on the dynamic function of the fuel injector 1.
• annular gap remaining between the wall section 52 of the pump piston 7 and the guide section 41 of the axial longitudinal bore 40 likewise has no critical influence on the dynamics of the fuel injector 1 according to the invention.
• the annular gap and thus the piston play of the pump piston 7 can easily be 3-4 ⁇ m without that the leakage occurring at the annular gap has a significant influence on the injection quantity. Since the actuating time of the actuator 2 is of the order of magnitude of 1 ms, no significant leaks occur at the annular gap between the wall section 52 and the guide section 41 during the actuating time of the pump piston 7.
• the manufacturing tolerances of the outer diameter of the pump piston 7 and the inner diameter of the guide section 41 are therefore not too great requirements, so that the manufacturing costs of the fuel injector 1 according to the invention are not significantly increased by fitting the pump piston 7 in the guide section 41 of the stepped bore 40.
• the amount of fuel injected can be influenced by the level of the supply voltage with which the piezoelectric actuator 2 is acted on, since the expansion of the actuator 2 is proportional to the supply voltage.
• the supply voltage is in the order of magnitude up to 1000 V. However, other piezo stacks with a lower voltage are also possible.
• pump pistons 7, check valves 61, 71 and spray nozzles 70 can also be used in another known configuration.

Applications Claiming Priority (3)

Publications (1)

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ID=7824816

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• 1997
  • 1997-03-27 DE DE19712921A patent/DE19712921A1/de not_active Withdrawn
• 1998
  • 1998-01-12 WO PCT/DE1998/000080 patent/WO1998044256A1/de not_active Application Discontinuation
  • 1998-01-12 US US09/180,850 patent/US6079636A/en not_active Expired - Fee Related
  • 1998-01-12 JP JP10541038A patent/JP2000511614A/ja active Pending
  • 1998-01-12 EP EP98905241A patent/EP0910740A1/de not_active Withdrawn
  • 1998-01-12 CZ CZ19983589A patent/CZ291253B6/cs not_active IP Right Cessation
  • 1998-01-12 KR KR1019980709449A patent/KR20000015898A/ko not_active Application Discontinuation

Non-Patent Citations (1)

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