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
• • 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
  • F02M59/24—Varying fuel delivery in quantity or timing with constant-length-stroke pistons having variable effective portion of stroke
  • F02M59/243—Varying fuel delivery in quantity or timing with constant-length-stroke pistons having variable effective portion of stroke caused by movement of cylinders relative to their pistons

Definitions

• This invention relates to a fuel pump for Diesel engines of the type in which each engine cylinder is associated with a pump, the pump plunger of which has leading and trailing cut-off edges cooperating with apertures in the wall of the pump cylinder for determin ⁇ ing the effective stroke volume of the pump, and includ- ing means for changing the stroke volume by a relative rotation of the pump cylinder and plunger.
• leading and trailing refer to the location of the cut-off edges relative to the direction in which the pump plunger moves during the pump stroke.
• each fuel pump delivers the fuel to the injector or injec ⁇ tors through an accumulator having a spring-loaded plunger. It is then possible, irrespective of the
• OMPI engine load and rp to maintain the maximum injection pressure at a predetermined value which is determined solely by the accumulator spring, and thus ensure optimum atomization of the fuel at any operating conditions.
• a fuel pump of the last mentioned kind is characterized in that in an ' inlet duct leading from the pump chamber to the accumulator there is a first valve which is biased to ⁇ wards open position by the pressure in the pump chamber and towards closed position by the accumulator pressure, and in that in an outlet duct from the accumulator there is a second valve which is biased towards open position by the 'accumulator pressure and biased towards closed position by the pressure in the pump chamber, and in that the leading cut-off edge of the pump plunger extends exactly or substantially along a helix.
• each fuel pump of a reversible engine can be actuated by the same cam at either direction of rotation without the necessity of rotating the cam relative to the engine crankshaft preparatory to the reversal.
• a duct may extend from the outlet duct downstream of the second valve * and open into an aperture in the sidewall of the accumulator cylinder, while -in the accumulator plunger there is a relief duct which in the bottom position of that plunger provides a communication between said aperture and the suction side of the pump- through a chamber surrounding the accumulator cylinder.
• the relief duct may comprise an annular groove in the accumulator plunger.
• the connection to the suction side of the pump may then comprise a transverse bore through the.-wall of the accumulator cylinder.
• That area of the second valve which is sub ⁇ jected to the pressure in the pump chamber, is preferably larger than..the area subjected to the accumulator pressure.
• the second valve will then, without a built-in closing spring, be moved to its closed position at the moment when the accumulator pressure is relieved to the same low value as the pressure in the pump chamber so that the valve has closed in advance when next time the pump plunger starts delivering fuel to the accumulator.
• the trailing edge of the pump plunger is, at least on a part of its length, slightly inclined relative to a plane normal to the centre line of the plunger.
• the pump cylinder may be axially adjustable from the exterior by means of a nut rotatably supported in the pump housing and engaging with a thread on the pump cylinder.
• a pump known from Danish patent specification No. 114 873 such adjustment is effected by means of an adjusting spindle protruding through the end face of the pump housing.
• this arrangement is not possible because the pressure accumulator is built together with the pump housing, and instead one may provide a worm or helical gearing externally on the nut and meshing with an adjustment spindle extending transversely of the cylinder axis.
• Fig. 1 is a longitudinal, section through a fuel pump embodying the invention
• Fig. 2 is ' a developed -view, on a substantial ⁇ ly larger scale, of the active portion of the pump plunger with the leading and trailing cut-off edges when the pump is set to minimum delivery, the so- called zero delivery
• Fig. 3 is a developed view, corresponding to Fig. 2, but with the pump set to maximum delivery
• Fig. 4 is ' a section through the pump cylinder along line IV-IV in Fig. 1, and o ' .the same scale as that figure
• Fig. 5 is a section along line V-V in Fig. 1.
• the fuel pump illustrated in the drawings comprises a pump housing 1, which on one end face ' thereof is secured to a valve block 2 to the opposed end face, of which an accumulator housing 3 is secured.
• a pump cylinder 4 which is axially displaceable within housing 1? is centred in the housing at its lowermost end and is spring-biased downwardly by means of a set of Belleville springs 5 between the end face of the cylinder and the valve block 2. The upper end of .the pump cylinder is guided on a central
• valve block 2 O PI hub 6 extending downwardly from valve block 2.
• Suction chamber 8 communicates with pump chamber 9 defined within cylinder 4 by means of two sets of axially staggered apertures 10 and 11 in the cylinder wall. Apertures 10 serve for the inflow of fuel to chamber 9 , while the substantial- ly smaller apertures 11 serve " , for relieving the pressure in chamber 9 , as described in more detail below.
• a central bore 12 through hub 6 of the valve block opens at its lower end in pump chamber 9 and at its upper end in a transverse bore 13 which at either end opens into an enlargement in which a valve insert 14 and 15, respectively, has been screw ⁇ ed in.
• Insert 14 contains a hollow slide valve 16, the interior of which communicates, through transverse bores in the slide valve proper and in the insert 14, with a duct 17 in valve block 2, which duct opens at the bottom of an accumulator chamber defined between a cylinder liner 18 secured in an upwardly extending boss 19 on valve block 2 ; and an accumulator plunger 20.
• the pressure in the accumulator chamber acts on the slide valve to effect engagement between a conical sealing surface on the forward, right-hand end of the slide valve and an opposed • conical seat surface in insert 14.
• the accumulator plunger is integral with a substantially larger piston 21, which is axially displaceable within a cylinder chamber 22 formed within accumulator housing 3.
• a source of pressurized air (not shown) which e.g. may be a reservoir common to all fuel pumps of an engine, which reservoir may be supplied from the starting air system of the engine.
• a slide valve 25 is axially displaceable with- in valve insert 15 and at its ends it is formed with conical sealing surfaces cooperating with opposed seats in insert 15.
• the left-hand valve seat as shown in Fig. 1, surrounds the opening of transverse bore 13 while the right-hand valve seat surrounds a bore 26 in the valve insert " through which fuel is delivered to the enq ⁇ ne cylinder through a high pressure duct (not shown) , which is connected to insert 15.
• a transverse bore 27 in cylinder liner ' 18 closely adjacent the bottom of the accumulator chamber communicates, through a duct 28 in the valve block and transverse bores- through insert 15, with an annular chamber 29 in the insert intermediate the valve seat surroundinq bore 26 and the annular end face of slide valve 25 at the left of the associated sealing surface.
• bore 26 communicates permanently with a transverse bore 31 extending through cylinder liner 18.
• bore 31 there is a second bore extending through the cylinder liner and through a
• chamber 33 communicates with the suction chamber 8 of the pump housing.
• one or more further transverse bores extend through cylinder liner 18 and continue in transverse bores 35 through boss 19 to the annular chamber 33.
• pump plunger 7 has two separate sealing surfaces 36 in sealing againstment against the inner wall of pump cylinder 4 and each surface 36 is defined above and . below by a leading and trailing cut-off edge 37 and 38, respectively, which edges -cooperate with aper ⁇ tures 10 and 11 in the cylinder wall.
• a leading and trailing cut-off edge 37 and 38 respectively, which edges -cooperate with aper ⁇ tures 10 and 11 in the cylinder wall.
• a milled recess 39 above each edge 37, and this recess continues in a groove 40 extending parallel to the plunger axis between the two sealing surfaces and opening into the annular space which is formed below the trailing cut-off edge 38 between the cylinder wall and a reduced por ⁇ tion of the pump plunger.
• edges 38 uncover apertures II'., a communication is established between pump chamber 9 and suction chamber 8 whereby the pressure in the pump chamber is relieved, and slide valve 16 closes.
• the amount of fuel delivered to accumulator chamber is sub-
• Slide valve 25 slide valve has dropped. Slide valve 25 is, there ⁇ fore, displaced towards the left to the position shown in Fig. -l.in which bore 26 communicates with the accumulator chamber whereby the pneumatic pressure in cylinder 22 presses accumulator plunger 30 20 downward to deliver the. measured amount of pressurized- fuel through the outlet duct (not shown) to the injectors of the engine cylinder.
• plunger 20 Shortly before plunger 20 assumes its bottom position, it obturates bore 27 in cylinder liner '
• cut-off edges 38 extend perpendicular to the axis of the pump plunger. -25 By slightly inclining these edges, either as shown in Figs. 2 and 3 or in the opposite direction, it ". is possible to ⁇ cause the fuel injection to start, with increasing motor load, at an earlier or later ..- point, respectively, of the movement of the engine 30 piston towards top dead centre.
• This mechanism comprises a worm wheel 43 located at the bottom of suction chamber 8 and having an internal thread engaging with an external thread on cylinder 4, and a-transverse adjustment spindle 44 having a worm gear 45 meashing with worm wheel 43.
• the Belleville springs 5 mentioned above provide an axial preload on the threaded connection between the pump cylinder and worm wheel 43, whereby the latter is always maintained in abutment against the bottom of chamber 8, and because cylinder 4 is prevented from rotating relative to pump housing 1 by means of a guide pin 46 engaging in a groove in cylinder 4 parallel to the cylinder axis, a rotation of spindle 44 and, . hence, of worm wheel 43 results in the stated, pure- ly axial displacement of pump cylinder 4.
• bores - ' 35 safeguard against overload of the component parts of the pump in case the outflow of fuel is hindered in any way because in that case the pump only provides an internal circf ⁇ lation flow of fuel to the accumulator chamber and through bores 35 back to - suction chamber 8 as soon as accumulator plunger 20 has been lifted sufficiently to uncover the bores. If the fuel is delivered at a certain pressure to suction chamber 8 by means of a primary pump, a circulating flow through the pump and through the fuel injector or injectors connected thereto can be maintained during standstill of the pump in that from chamber 8 oil then flows through ducts 34, chamber 33, bore 32, groove 42, and duct 30 to bore 26 from which the fuel can flow to the injectors.

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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)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8103562

Family Applications (1)

Country Status (4)

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Family Cites Families (3)

• 1980
  • 1980-03-27 DK DK132280A patent/DK145088C/da active
• 1981
  • 1981-03-25 WO PCT/DK1981/000031 patent/WO1981002765A1/en not_active Ceased
  • 1981-03-25 EP EP19810900820 patent/EP0048256A1/de not_active Withdrawn
  • 1981-03-25 JP JP56501115A patent/JPS57500990A/ja active Pending

Non-Patent Citations (1)

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