EP0289467A1 - Fuel injection system for internal combustion engines, particularly for compression ignition engines for commercial motor vehicles - Google Patents

Fuel injection system for internal combustion engines, particularly for compression ignition engines for commercial motor vehicles Download PDF

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Publication number
EP0289467A1
EP0289467A1 EP88830155A EP88830155A EP0289467A1 EP 0289467 A1 EP0289467 A1 EP 0289467A1 EP 88830155 A EP88830155 A EP 88830155A EP 88830155 A EP88830155 A EP 88830155A EP 0289467 A1 EP0289467 A1 EP 0289467A1
Authority
EP
European Patent Office
Prior art keywords
line
pumping
fuel
metering
space
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP88830155A
Other languages
German (de)
English (en)
French (fr)
Inventor
Mario Montuschi
Mario Incardona
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Iveco SpA
Original Assignee
Iveco Fiat SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Iveco Fiat SpA filed Critical Iveco Fiat SpA
Publication of EP0289467A1 publication Critical patent/EP0289467A1/en
Ceased legal-status Critical Current

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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
    • F02M59/02—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type
    • F02M59/10—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type characterised by the piston-drive
    • F02M59/105—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type characterised by the piston-drive hydraulic drive

Definitions

  • the present invention relates to fuel injection systems for internal combustion engines and particularly concerns an injection system including: - pumping means for generating a fuel pressure, - at least one injector unit comprising a metering and injection space and a pumping space which can receive respective masses of fuel, with a piston for compressing the mass of fuel present in the metering and injection space to effect its injection due to the pressure of the mass of fuel introduced into the pumping space, - a metering line which can connect the metering space with the pumping means, - a pumping line which can connect the pumping space with the pumping means, - a line for controlled discharge of the fuel pressure, and - valve means acting on the metering and injection line, the pumping line and the controlled-fuel-­pressure discharge line alternately to cause controlled filling of the metering and injection space and filling of the pumping space, with consequent injection of the fuel.
  • a reservoir for fuel to be supplied to the cylinders of a compression ignition internal combustion engine (not illustrated as a whole) through respective injector units, one of which is indicated 2 here.
  • the fuel taken from the reservoir 1 is fed to the injectors 2 through a first pump 3, usually constituted by an electric pump, and a subsequent pump 4 with a greater head, operated by the internal combustion engine through a drive shaft 5.
  • a first pump 3 usually constituted by an electric pump
  • a subsequent pump 4 with a greater head, operated by the internal combustion engine through a drive shaft 5.
  • Branching from the pumps 3 and 4 are a fuel supply line 8 including a main line or pumping line 9, in which an accumulator 10 is connected for collecting fuel under pressure, and a secondary line or metering line 11, which are connected fluid-dynamically in series with each other and are provided with respective pressure regulators 6, 7.
  • the injector unit 2 can generally be seen: - a metering and injection chamber 12 communicating with the fuel injection nozzles 13, - a pumping chamber 14, and - a piston (intensifier piston) 15 having respective end surfaces 15a and 15b facing the pumping chamber 14 and the metering chamber 12 respectively.
  • intensifier piston derives from the fact that the surface 15a which faces the pumping chamber 14 has a much greater area (as much as eight-ten times) than the area of the surface 15b facing the metering chamber.
  • valve means Interposed in the hydraulic path between the metering chamber 12 and the nozzles 13 are further valve means, such as an obturator 18, which can be struck by the piston 15 at the bottom of its pumping stroke, so as to cause a rapid and accurate cut-off of the injection operation due to the closure of the nozzle 13.
  • valve means usually constituted by a slide-valve distributor 19 whose movement is driven by a solenoid valve 20 which uses the same fuel taken from the supply line 8 as the means (servo means) for operating the slide valve 19.
  • the slide valve 19 also communicates with a controlled fuel discharge line 21 (usually leading to a point between the pumps 3 and 4) in which the choke element 22 of calibrated section is inserted.
  • the slide valve 19 is generally arranged, in accordance with a predetermined sequence and in dependence on a control signal sent to the control lines 20a of the solenoid valve 20, to enable the following operational stages to be carried out: - a metering stage in which the pressurised fuel is supplied to the chamber 12 through the metering line 11 while the pumping chamber 14 is in communication with the controlled discharge line 21, and - a stage in which the pumping chamber 14 is directly connected to the pumping line 9.
  • the pressurised fuel which flows into the chamber 14 causes a consequent displacement of the intensifier piston 15, which in turn causes the compression and consequent injection into the cylinder of the mass of fuel supplied to the chamber 12.
  • the solenoid valve 20 governed by the accelerator pedal (remembering that the example relates to a compression ignition engine), the duration of the stage in which the mass of fuel present in the pumping chamber 14 is partially discharged through the controlled discharge line 21, 22, one can regulate with equal precision the quantity of fuel which is supplied to the metering chamber 12 and therefore the quantity of fuel which is subsequently injected into the cylinder.
  • the quantity of fuel injected is essentially determined by the quantity of fuel discharged from the pumping chamber 14 through the controlled discharge line 21. Since this line, and particularly the calibrated choke 22, may even be located physically in positions remote from the cylinders of the engine, it is quite unlikely that their physical parameters (and therefore their behaviour) will alter with time. Furthermore, a single controlled discharge line 21 and a single choke 22 may be used to control the carrying out of the injection operation in all the cylinders of the engine, ensuring that the cylinders operate uniformly. Further advantages are derived from the possibility of having precise control over the speed of closure of the injectors (end of injection).
  • the present invention aims to provide a fuel injection system for internal combustion engines of the type specified above, which retains the advantages set out above but eliminates the disadvantages mentioned.
  • this object is achieved by virtue of a fuel injection system for internal combustion engines of the type specified above, characterised in that: - pressure reduction means are interposed between the metering line and the pumping line so that the fuel pressure in the metering line is less than the fuel pressure in the pumping line, - a duct with one-way valve means is interposed between the metering line and the controlled discharge line for preventing the discharge of fuel under pressure from the metering line to the controlled discharge line, and - the valve means comprise a distributor element connected to the pumping line and to the controlled discharge line and having an obturator which can be driven selectively between: - a first position in which the pumping space is put into communication with the controlled discharge line, and a first stage in which the pumping space also communicates with the metering line through the one-way valve means to discharge the fuel pressure, and at least one second stage in which the pumping space is reduced in a controlled manner due to communication with the controlled discharge line, while the metering chamber is gradually filled, and
  • a first characteristic of the system according to the invention is the fact that a pressure regulator 23, whose structure is illustrated in greater detail in Figure 3, is inserted between the pumping line 9 and the metering line 11.
  • the purpose of the regulator 23 is to reduce the fuel pressure (approximately 500 bars) in the pumping line 9 to a lower level (for example, of the order of 150 bars) which is used for the supply of the metering line 11.
  • a further accumulator 24 is associated with this line and is intended to contain a reserve mass of fuel at the pressure used in the metering line 11.
  • the pressure regulator 23 is of a conventional type similar to those used, for example, in liquid gas distribution systems or in underwater breathing systems.
  • the regulator 23 has an inlet chamber 25a connected to the pumping line 9, an outlet chamber 25b connected to the metering line 11, and an obturator 26.
  • the obturator 26 moves between an end-of-travel position, which is that shown in Figure 3, and a position removed from this position, so as to enable the fuel under pressure to pass selectively from the inlet chamber 25a to the outlet chamber 25b with a consequent reduction in pressure.
  • the magnitude of this pressure reduction is determined by the elastic constant of a spring 27 which opposes the movement of the obturator 26 away from the end-of-travel position described above.
  • An overpressure discharge valve 32 is preferably connected to the duct 29 and set at a threshold level of the order, for example, of 200 bars.
  • the purpose of the valve 32 is to discharge any fuel pressure levels higher than the threshold level to the outside through a duct 33. Such pressure levels, if they were propagated through the metering line 11 to the injectors 13, could cause an unwanted injection of fuel.
  • a sensor 34 is associated with the pumping pressure accumulator 10 and can provide feedback, through a line 35, to the regulator 7 of the pump 5 so as to achieve precise regulation of the fuel pressure in the pumping line 9 to the required value.
  • a one-way valve 36 for by-passing the pump 4 when it is not operating (head almost nil), as well as an auxiliary blow-by duct 37 connected fluid-dynamically in parallel within the valve 36 and enabling the accumulator 10 to be discharged gradually through the regulator 7 when the system is not operating, are also connected in the pumping line 9. This is to avoid any injector 13 from dripping, introducing fuel into the cylinders, due to defects in the sealing of the closure elements.
  • a distributor element replaces the slide-valve distributor 19 (of very complex structure) of the system of Figure 1.
  • the distributor 38 includes: - a connector 39 for connection to the pumping line 9, - a connector 40 for connection to the pumping chamber 14, and - a connector 41 for connection to the controlled discharge line 21.
  • the latter line is further connected to the pumping line 11 through a non-return valve 142 oriented so as to prevent discharge of the fuel in the line 11 through the line 21 when the pressure in the latter line (detected upstream of the choke 22) is lower than the fuel pressure in the line 11.
  • connection between the connectors 39, 40 and 41 is controlled by an obturator 42 which is movable along the body of the distributor 38 between: - a first operating position, shown in Figure 4, in which the connector 39 is isolated while the connectors 40 and 41 are in communication with each other, and - a second position, schematically indicated by the broken line indicated B on the left-hand side of Figure 4, in which the connector 41 is isolated and the connector 40 is put into communication with the connector 39.
  • the movement of the obturator 42 is also driven hydraulically in this case, with fuel being taken from the pumping line 9 for use as the operating fluid.
  • a branch 43 of the pumping line 9 extends towards an operating chamber 44 which communicates through a duct 45 in the body of the distributor 39 with a chamber towards which one of the ends 42a of the obturator 42 faces.
  • the chamber 44 also communicates with a further duct 46 through which the fuel may be discharged from the chamber 44 to the reservoir 1 through a return line, not illustrated.
  • Two obturators 47 and 48 act in the operating chamber 44 with a transmission element acting between them, illustrated here in the form of a rod 49.
  • the transmission element 49 enables the obturators 47 and 48 to be driven in a simultaneous and complementary manner by means of the control shaft of a solenoid valve 50 to which the injection signals derived from the operating position of the accelerator are sent through a line 50a.
  • the valve 50 therefore carries out the control function performed by the solenoid valve 20 in the diagram of Figure 1.
  • the obturator 47 can put the chamber 44 and hence the duct 45 into communication with the branch 43 of the pumping line, while the obturator 48 isolates the same chamber and the duct 45 from the discharge duct 46.
  • a movement of the obturator 48 away from its seat puts the chamber 44 and the duct 45 into communication with the duct 46, while the obturator 47 simultaneously isolates the chamber 44 and the duct 45 from the branch 43 of the pumping line 9.
  • the obturator 42 has a tubular structure housing a piston 51.
  • the piston 51 is generally mushroom-shaped with an enlarged head end 52a which acts against the end of the cavity, acting as a seat for movement of the obturator 42, opposite the end 42a, and a narrower shank end whose end face 52b faces into the chamber of the distributor 38 which communicates with the connector 39.
  • the surface of the ace 52b which is exposed to the fuel coming from the line 9 is smaller than the surface of the end face 42a facing the duct 45.
  • the whole structure of the distributor 38 is therefore much that: - when the solenoid valve 50 causes closure of the obturator 47 and opening of the obturator 48, the obturator 42 is forced, by the same fuel pressure coming through the connector 39, to move into the first operating position illustrated in Figure 4, - when the solenoid valve 50 causes opening of the obturator 47 and closure of the obturator 48, however, the operating chamber 44 and the duct 45 are filled with fuel coming from the branch 43 of the pumping line 9; the fuel pressure which is thus exerted on the surface of the face 42a is such as to overcome the reaction force which the same fuel pressure, coming from the connector 39, exerts on the smaller end face 53 and the obturator 42 is therefore brought into its second operating position.
  • Any leakage of fluid fuel towards the end chamber in which the mushroom-shaped end 52 of the piston 51 is situated may be discharged to the reservoir 1 through a discharge duct 53.
  • Movement of the obturator 42 between the first and second positions causes operation of the system of Figure 2, according to the following criteria.
  • the fuel under pressure in the chamber 14 (typically at a pressure of the order of the pumping pressure of 500 bars) is able to overcome the reaction of the one-way valve 142, enabling rapid discharge of the fuel pressure towards the metering line 11: at this stage, the discharge through the calibrated choke 22 is negligible.
  • the pressure in the chamber 14 may thus fall rapidly to a pressure equal to the pressure (for example, 150 bars) present in the metering line 11.
  • the one-way valve 142 closes so that further discharge of fuel from the chamber 14 can only take place through the calibrated choke 22. This further discharge of fuel is caused by the fuel pressure which is gradually supplied to the metering chamber 12 by the line 11 through the one-way valve 16 and the choke 17.
  • the switching signal for the solenoid valve 50 is sent on the line 50a.
  • the obturator 42 is made to move into its second operating position. In this second position, the chamber 14 is put into communication with the pumping line 9 so that the fuel under pressure (for example, 500 bars) flows rapidly into the chamber 14, causing the injection of the fuel in the chamber 12.
  • the solenoid valve 50 Upon completion of the injection operation, the solenoid valve 50 is switched once again to re-establish (particularly rapidly due to the thrust exerted by the piston 51) the initial operating condition.

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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)
EP88830155A 1987-04-28 1988-04-12 Fuel injection system for internal combustion engines, particularly for compression ignition engines for commercial motor vehicles Ceased EP0289467A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT6736287 1987-04-28
IT8767362A IT1208413B (it) 1987-04-28 1987-04-28 Sistema di iniezione del combustibile per motori a combustione interna particolarmente per motori ad accensione per compressione di autoveicoli industriali

Publications (1)

Publication Number Publication Date
EP0289467A1 true EP0289467A1 (en) 1988-11-02

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ID=11301768

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88830155A Ceased EP0289467A1 (en) 1987-04-28 1988-04-12 Fuel injection system for internal combustion engines, particularly for compression ignition engines for commercial motor vehicles

Country Status (3)

Country Link
EP (1) EP0289467A1 (it)
JP (1) JPS63280849A (it)
IT (1) IT1208413B (it)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102014210779A1 (de) * 2014-06-05 2015-12-17 Volkswagen Aktiengesellschaft Kraftstoffeinspritzvorrichtung

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2140020A1 (it) * 1971-05-28 1973-01-12 Bosch
DE2602280A1 (de) * 1975-01-24 1976-07-29 Diesel Kiki Co Hochdruck-kraftstoffeinspritzeinrichtung fuer dieselmotoren
EP0077716A1 (fr) * 1981-10-15 1983-04-27 Regie Nationale Des Usines Renault Dispositif d'injection pression-temps à prédosage

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2140020A1 (it) * 1971-05-28 1973-01-12 Bosch
DE2602280A1 (de) * 1975-01-24 1976-07-29 Diesel Kiki Co Hochdruck-kraftstoffeinspritzeinrichtung fuer dieselmotoren
EP0077716A1 (fr) * 1981-10-15 1983-04-27 Regie Nationale Des Usines Renault Dispositif d'injection pression-temps à prédosage

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102014210779A1 (de) * 2014-06-05 2015-12-17 Volkswagen Aktiengesellschaft Kraftstoffeinspritzvorrichtung

Also Published As

Publication number Publication date
JPS63280849A (ja) 1988-11-17
IT8767362A0 (it) 1987-04-28
IT1208413B (it) 1989-06-12

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