US3068794A - Fuel-injection pumps for compressionignition internal combustion engines - Google Patents

Description

Dec. 18, 1962 J. N. MORRIS ETAL 3,068,794

FUEL-INJECTION PUMPS Foa coMpREssIoN-IGNITION INTERNAL coMBUsToN ENGINES Filed Aug. 7, 1959 .United States This invent-ion relates to fuel-injection pumps of the re- -ciprocatory plunger type for compression-ignition internal combustion engines, designed to meter liquid fuel and to deliver it at relatively high pressures, that -is to say, at

ypressures in the region of 5,000 p.s.i. or upwards. More specifically, it is concerned with certain improvements of the invention that forms the subject of co-pending application of John Neville Morris, Serial No. 757,731 tiled August 28, 1958.

According to the earlier invention referred to, a fuelinjection pump of the type shown herein is enabled to provide automatically a supply of unmetered fuel and, therefore,`in a limited sense, expendable fuel at a pres- .sure approximately equal to that of the metered fuel, this supply of expendable fuel remaining available for a variety of sealing purposes throughout the duration of the high pressure phase of the main metered fuel pumping action.

The object of the present invention is to enable a fuelinjection pump of the character set forth to provide automatically, in addition to its metered fuel output, a supply of auxiliary fluid, other than fuel, at a pressure approximately equal to that of the metered fuel, this supply of pressurized auxiliary fluid being rendered available for use throughout the duration of the high-pressure phase of the metered fuel pumping action.

According to this invention a fuel-injection pump of the reciprocatory plunger'type has a plunger which is associated with a pumping chamber for delivering metered quantities of fuel at high pressure. The Vmetering plunger is operable in conjunction with, and under the control exercised by, another plunger oflarger effective cross-sectional area working in an auxiliary pumping chamber. The auxiliary pumping chamber receives fluid other than fuel, which may conveniently be designated auxiliary fluid, the arrangement being such that at an early stage of the working stroke of the plungers, owing to their differential pumping action, the auxiliary fluid becomes pressurized at the moment at Which delivery of the metered fuel commences, and simultaneously therewith means become eifectiveto maintain the Vsupply of auxiliary fluid, rendered available in the auxiliary pumping chamber, at a pressure which varies instantaneously with, and remains approximately equal to, that of the metered fuel.

Although the pressurized auxiliary fluid may be used for other purposes, its primary function is to elfect highpressure sealing of ducts, ports and so forth in liquid-fuel supply systems. The auxiliary ud may, for example, be a lubricant such as ordinary engine lubricating oil. This possibility renders the invention especially useful for application to pumps which operate on fuels having exceptionally poor lubricating properties, such as gasoline. The invention is applicable to fuel-injection pumps of the non-distributing type as well as to those of the distributing type, namely,in which either a single reciprocating plunger or a system of such plungers meters and delivers fuel under high pressure to distributing means arranged to lsupply a multiplicity of engine cylinders.

Further objects and advantages of the invention will become apparent from the following description when conatent() 3,068,794 Patented Dec. 178, 1952 sidered in conjunction with the accompanying drawing wherein:

FIG. 1A is a diagrammatic elevational view, partly in section, depicting a fuel injection pump in accordance with the practice of the invention;

FIG. 1B is a fragmentary plan view, partly in section, and shows the practice of the invention in control means used in conjunction with the pumps of FIG. 1A;

FIG. 1C is a view similar to FIG. 1B and depicts the practice of the invention in distributor means used in conjunction with the pumps of FIG. 1A.

The invention Will now be described with reference to FIG. 1A. Liquid fuel is taken from a supply tank 1 by a feed pump 2, provided with the usual relief valve 3, and -is delivered to an inlet 4 of a casing 5 of a fuel-injection pump. An auxiliary fluid, which may conveniently be lubricating oil, is 4taken from a reservoir 6 by a feed pump 7, having the usual relief valve 8, and is delivered to an inlet 9' of the fuel-injection pump casing 5. The casing, which constitutes the main body of the fuel-injection pump, is formed with a pair of coaxial communicating bores 10 and 11 in which are mounted plungers 12 and 13 respectively. The bores 10 and 11 are of unequal diameter, and one end of the larger plunger 13 protrudes from the inner or as herein shown the lower end of itsl bore and is shaped at its lower end 14, to co-operate with a cam 15 mounted on a pump drive shaft 16.

The two plungers 12 and 13 contact each other at their adjacent ends through an abutment 17 formed uponvthe upper end face of the plunger 13. The area of contact 'of the abutment 17 is substantially less than the cross-sectional areaof the smaller plunger 12, and the larger plunger 13 is provided with a duct 18 which debouches at one end within the area of the contacting surface o-the abutment 17 and at its other end is in permanent open Vcommunicationl with a`region 19 for receiving spillage of the' auxiliary fluid. In the upper end of the small -bore 10 to 'the plunger 12 eects their inward motion and-insures that theplunger 13 at all times engages' and-followsthe cam.

' Formed in the large bore 11 is a circumferentialn groove 21 which, is in open communication with the auxiliary uid inletf9,.said groove being designated a filling groove.

The groove 21 is located in such a position that the end of the plunger 13 remote from the cam, overruns this groove shortly before the completion of the inward movement of theplungers. The small bore 10 is formed 'with a similar circumferential lling groove 22 in open communication with the tuel'inlet 4 and said groove is overrun by the small plunger 12 simultaneously with the overrunning action described above. The annular filling Vgroove 21 is in permanent communication with a moderately pressurized supply of the auxiliary iiud subsequently to be employed for lubricating and sealing purposes. The annular filling groove 22 communicates via an inwardly opening spring-biased-non-return valve 23 with a moderately pressurized source of fuel supply. The pump casing at its upper end is formed with a metered fuel outlet passage 24, controlled -by an outwardly open- 4ing spring-biased non-return valve 2S.

In open communication with an annular pumping space 26 which is constituted by the difference in areas between the two plungers 12 and 13 Withinthe outer end of large bore 11, there is provided an outlet passage 27 which is arranged to communicate with any regions of the-add- Y outlet 24 of the pump may lead.

tional units of the complete injection equipmentto which highly pressurized lubricating and sealing fluld 1s required to be applied. VThe region above the smallerY kplunge'rs, Vrotation of the camshaft k16 permits bothV plungers to move inwardly under `the action ofthe return spring 20, the two plungers being maintained in mechaniealfcontact by the intervening abutment 17. During this phase the non-return valve 25 leading from the main pumpingV chamber 28 remains closed, and thus a partial vacuum is formed, not only in the main pumping chamber 23 but also in the differential pumping chamber 26, it being assumed that no inward flow of fluid can occur via the outlet passage 27 leading from pumping chamber 26 by virtue of the check valve 27a mounted in the outlet passage 27. Shortly before the termination of the inward or downward stroke, the two plungers 12 and 13 overrun their- respective filling grooves 22 and 21, and thus theV main pumping chamber 28 is enabled to inspire and become replenished with fuel and the differential Vpumping chamber 26 is enabled to inspire and become replenished with lubricating and sealing fluid.

At an early stage of the ensuing outward or upward stroke of the plungers 12 and 13,V both filling grooves 21 and 22 become cut off simultaneously, The fuel previously inspired into the main pumping chamber 28 now becomes pressurized to the point where the non-return valve 25Y opens and fuel delivery commencesV notwithstanding any degree of back pressure which may be imposed, as, for instance, by the type of nozzle commonly employed for diesel engine in] Simultaneouslyk with action nextrhereinbefore recited, the auxiliary tiuid contained in the differential pump- Ying chamber 26 momentarily willhave no sufficiently rapid means of egressY since the outlet passage 27 fromV said differential pumping chamber 26 is capable of permitting a small'rate of ow only, as will subsequently be made apparent. The tiuid in said pumping chamber-26 V therefore rapidly attains a pressure which, acting upon the ditferential area existing between the cross-sectional area of the smaller plunger 12 and that of the'abutment 17 through which the two plungers contact, hydraulically ection, to which the fuel impels the smaller 'plunger 12 on its outward stroke. The

Ysnrlallerplunger thus tends to run away from the larger plungen but, in so doing, it exposes the upper end of the spillduc't 18 `in the larger plunger. 'I'he result ofV the foregoing action Vis that the auxiliary liuidrpressurized ,within the differential pumping chamber 26 is permitted to leak away, via thefduct'18,into the region 19 of the pump casing 5 fromvwhich it may be returned in any suit-Y Y Vable manner to the reservoirV 6. Consequently, aY controlled pressure isY automatically sustained within the differential pumping chamber 26 throughout the `remainder of the outward stroke ofthe plunger assembly, which Y pressurefvaries,instantaneouslywith any variation which Vmay occur within the main pumping chamber 28 and al- ;.waysrbeing somewhat higher than thepressureobtaining n .inthe main pumping chamber in accordance withthe rela- 1 tive crosssectional areas'of the smaller plunger 12-and ofthe abutmentY 17; For'example, if the cross-sectional area ofthe smaller plunger 12 were l sq; cm. andthe effective cross-sectional areaofthe abutment 17 were Y' approximately 0.1 sq. cm.; then the pressure generated,r iin the differential pumping chamber 26 during this phaseY wouldf be, at any instant, approximately. 10% greater than that obtaining in the main pumping chamber 28.

.Y During'the'rphas'e Aof operation just considered, leakagel of the'highly pressurized fuel in the main pumping chamber 28 into the annular fillingY groove 22 rapidly causes "the/pressure in thesertworegions kto become equalized the pump driveshaft since the inwardly opening non-return valve 23 provided in the fuel inlet passage 4 precludes any outward How.

One immediate consequence of this approximate equality tional construction, be a region at approximatelyvatmospherc pressure, is eliminated. The flow is, in fact, at a now much diminished rate, in the contrary direction. That is to say, some slight ow rof the lubricating Vand sealing fluid takes place into the fuel-filled annulargroove 22 and thence, intermixed with fuel therefrom, into the main pumping space 28. By this provision, it is clear that slight imperfections in plunger/ bore fit, due to manufacturing errors or to wear, can be tolerated without serious leakage of the highly rpressurized fuel in the main pumping chamber 28 and without serious intermixing of the fuel and the lubricating and sealing Huid. Y

It will also be clear that theV auxiliary fluid contained Y in the differential pumping space 26 can be led from it by a duct 29 to any further point in the injection system at which it can perform a lubricating'V and sealing function, analogous to that .which it has already been Vseen .Y

to perform in precluding leakage from the main ptunping space 28 ofthe pump.V The quantity of this auxiliaryl iiuidavailable per strokeV of the plungers, without disturbV`V ing the balance of hydraulic pressures as described above, depends upon the volume of the chamber 26, accommodate the'maximum uid. Y Y

. Examples of useful applications of the sealing and lubricating fluid fuel metering system, will now be described.

Provision for enabling the output per stroke of the pump to be varied, preferably by the abrupt spilling of the metered fuel at a variable Vpoint during the outward stroke of the main injection plunger, is a normal Vrequirement in diesel engine operation. v

Such a variable spill vkcontrol may convenientlybe afforded by a device Vshown in FIG. 1B comprising a fixed casing 30k having a cylindrical bore' 31 within which is mounted a continuously rotating control shaft 32 driven 5' by the pump drive shaft 16 thronghrdrive mechanism (not shown) arranged to permit the two shaftsV to Vbe phased or relatively rotated to a limited degree.

varying the output per stroke of the pump.

A connecting pipe 33, additional to that leading from the metered fuel outlet 24 of the pump to an injection nozzle 34, and arranged in parallel with an injection nozzle feed pipe 35, terminates in arduct 36 debouching1477 casingV 30, asf also does. a- `37 leading,Y via aipipeS, to a region into which fuel-may .conveniently be spilled,

in this case -fuel supply tank 1. Y. Thecontrol shaft Vv32isVVV n provided witha recess 39 capable of effecting temporary j Y In its simplest form the device comprises, onlyonefsuch recess, and` the control shaft'32 Vis driven at'the` Ysame speed asf;

16. '.Thefarrangement"issuch that rotation of the controlv shaft` 32. effects spillagerof the` metered fuel at Yany required interval'after the comrrrlencef.`V ment of the injection phase, in accordance with the vari- Q S rotational positions ofthe twoshafts'con-V upon bore 31 of the fixed further vadjacent relief duct Vcommunication between the two ducts 36,' 37.

able relative ce1-ned. Y v Y v Y. VWithin bore 31 of the fixed", casing 3G kand situated approximately diametrically opposite/,the nduct 36-which communicates with the metered yfuel outlet-24 from'the pump, a port 40 is' provided the cross-sectional'areat'rf which is somewhat'greater than Vlthat of the duct 36. This port 40 is ,placed in communication, by the .duct 29,

with the lubricating and sealing fluid 1in the,Ydifferential` differential pumping Y which. is therefore made of sufficient size to possible demand for suchv to other parts of a typical high-pressure This VphasingY or relative rotation of the shafts constitutes a means of p v:acusar/94 chamber 26 Ifrom which said fluid is thus able to perform the useful functions of lubrication and of hydrostatically forcing the control shaft 32, to the degree to which this shaft may be iitted with some small clearance in its bore, into intimate mechanical contact with the region at which the metered high-pressure fuel would otherwise tend to cause local separation of the shaft from its bore, and thus leak away. This hydrostatic sealing action automatically commences at the instant of pressure rise in the metered fuel and is automatically sustained throughout the high-pressure phase, namely until the recess 39 formed in the control shaft 32 causes spillage of the metered fuel.

Another example of a useful application for the highpressure auxiliary fluid is represented by a distributing device, which is employed when the output from a single pumping unit has to be distributed to a plurality of engine cylinders in sequence. This device as shown in FIG. 1C comprises a fixed casing 41 having a cylindrical bore 42 which contains a rotatable distributor Shaft 43. The shaft 43 is driven at some finite fraction of the pump shaft speed, in accordance with the number of engine cylinders to be served. Two circumferential grooves 44, 45 are provided in the bore 42 of the fixed casing 41. Bore 42 also has a fuel supply duct 46 spaced intermediately between grooves 44, 45. Communication, by way o-f the duct 29 and passages 47, is permanently established between the two grooves 44, 45 and the high-pressure auxiliary fluid in the differential pumping chamber 26. A further permanent communication, by the pipe 35, is established between the fuel supply duct 46 and the metered fuel outlet 24 from the pump.

VIn the normal application vof the distributing device, in which a variable spill control 30, such as that already shown in FIG. 1B is required system, two passages are provided from the metered fuel outlet 24 from the pump; one, represented by the branch pipe 33, leading to such variable `spill control 3i) and the other, represented by the continuation of the pipe 35, to the distributing device 41. Within the fixed casing 41 of the distributing device, in addition to the two grooves 44, 45 and the supply duct 46, there are also provided, in a plane longitudinally displaced therefrom, a plurality of equally spaced radial outlet ducts 4S debouching upon the bore of the casing, and each connected by a pipe 49 to the corresponding injection nozzle 34, their number being in accordance with the number of injection nozzles to be supplied.

The distributor shaft 43 has a circumferential groove 50 and a distributing port 51 spaced apart longitudinally and .interconnected by a duct. 52. Surrounding the distributing port 51 there is in the distributor shaft 43, a continuous or annular groove 53 such as can conveniently be formed by the operation of trepanning. A duct 54, which will be designated, the pressurizing duct, debouches at one end upon the surface of the distributor shaft 43 and at its other end communicates with the groove S3 surrounding the distributing port 51. The arrangement is such that, upon assembly, the circumferential groove i) in the distributor shaft 43 registers with the fuel supply duct 46 in the casing, the distributing port 51 in the shaft falls within the plane containing the radial outlet ducts 48 of the casing, and the pressurizing duct 54, where it debouches upon the surface of the shaft, registers with the circumferential groove 45 in the bore of the xed casing which communicates with the source l26 of high-pressure lubricating and sealing fluid.

The bores of the distributing port 51 and of the individual outlet ducts48, at their intersection with the surface of the distributor shaft 43 and the bore of the casing 41 respectively, are such that, whatever the timing of the pump and spill control in their effect upon the duration of the injection dwell, free communication is maintained between distributing port 51 and one of the outlet ducts 48 throughout the duration of each injection dwell. The

pumping to be incorporated in the land 55 provided between the distributing port 51 and the inner periphery of the annular groove 53 surrounding it is, moreover, of sufficient width to insure that this groove under no circumstances comes into communication with any of the outlet ducts 48 during the injection phase through that particular duct.

The metered fuel, at the commencement of the injection phase, passes by way of supply duct 46, into the associated circumferential groove 50 of the distributor shaft 43 and thence through the corresponding duct 52 in the shaft to the distributing ports 51, the relative rotational vposition of the distributor shaft 43 with respect to the main pump shaft 16 is such that the fuel then enters one of the outlet ducts 48 and passes to one ofthe injection nozzles 34. VSupply to .that particular nozzle then continues until such time as the injection phase is terminated, as by means of the spill device 30 previously described.

In the absence of a supply of high-pressure auxiliary uid coinciding in time with the injection dwell, or in the absence of a commercially impracticable closeness of fit between the distributor shaft 43 and its bore 42, serious leakage of metered fuel would occur in the vicinity of the supply duct 46 and its associated groove 50 in the shaft, and also in the vicinity of the distributing port 51. Such high-pressure auxiliary fluid is, however, rendered avail,- able .by the invention and is active from the moment of the commencement of the injection phase until the moment of its termination. The presence of expandable lfluid during this time, within the two circumferential grooves 44, 45 in the casing 41 and within the annular groove 53 surrounding the distributing ports 51, serves incidentally, to reverse the direction of such leakage since this uid is at somewhathigher pressure than the fuel, and, in particular, serves substantially to diminish the extent of such leakage.

Since many changes could be made in the above construction and many apparently entirely different embodiments of this invention could be made without departing from the scope thereof, it is to be understood that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What we claim is:

l. A fuel injection pump of the reciprocatory plunger type adapted for delivering metered quantities of liquid fuel at high pressure and rendering available simultaneously a supply of auxiliary liquid, other than fuel, at approximately the same pressure as the metered fuel, comprising a casing having a pair of coaxial communicat ing bores of different diameters, a pair of coaxial plungers of different diameters, movable in said respective bores and providing therewith pumping chambers for the fuel and the auxiliary liquidy respectively, means vfor charging fuel to one chamber and auxiliary liquid, other than fuel to the other chamber during the intake stroke of the pump, the plungers operating for cutting oif said chambers from said sources at an early stage of the working stroke, discharge ports leading from said respective chambers, the plunger of larger diameter working in the auxiliary liquid chamber and the plunger of smaller diameter working in the metered fuel chamber, means including a driving sha1-ft, a cam and a return spring reciprocating said plungers substantially in unison, said plungers at their adjacent ends being unconnected but normally held in liquid tight contact with each other within the auxiliary pumping chamber by said return spring and cam, an abutment provided upon an end face of one of said plungers in contact with the adjacent end face of the other plungers, the contact area of the abutment being substantially less than the cross-sectional area of the smaller plunger, the larger plunger having a spill duct which debouches at one end within the area of the contacting surface of the abutment and at its other end in permanent communication with a region for receiving spillage of auxiliary liquid; the end of the smaller plunger remote from the abutment contacting end constituting a movable boundary Wall of the metered fuel pumping chamber and the sup ply of auxiliary liquid being rendered available in the auxil-V iary pumping chamber in which it becomes pressurized by the diierential pumping action of the twoV plungers, the pressure of the auxiliary liquid being'limitedrby Vthe hy draulic separation of the contacting plungers in said auxiliary pumping'chamber and the consequent uncovering of the spill duct@ Y 2. A fuel injection pump accordingY to claim l Wherein each of the bores in the casing has an'annular groove in proximity to the respective inner ends of the pumping chambers, the groove in the smaller bore for receiving a quantity of liquid fuel and the groove in the larger bore for receiving a quantity of an auxiliary liquid, other than fuel. Y Y

3. A fuel-injection pump according to claim 1, in combination with means for distributing the metered fuel output of the pump to a plurality of'engine cylinders in sequenc'e, the said distributing means comprising aV xed casing having a cylindrical bore` containing a rotatable distributor shaft which is driven at some finite fraction of the speed of the pump driving shaft, said distributor casing having its bore formed with a pair of Yaxially spaced circumferential grooves in permanentY communication with the supply or auxiliary liquid available in the auxiliary pumping chamber, the distributor casing having a -supply duct leading to the bore of the casing in permanent communication with the metered fuel outlet of the pump and situated intermediate the. said axially spaced circumferential grooves, the distributor'shaft having a'circum- Vierential groove registering Vwith the metered fuel supply duct and in permanent communication with a Vdistribut-V ing port in the distributor shaft, thedistributor casing output of metered Vfuel per stroke ofthe pump, the said' i Y variable spill control means comprising affixed casing having a cylindrical bore containing a continuouslyrrotating control shaft driven invariable phase relationship to/,the driving yshaft associated with the'pump Yplungers,

said xed casing having a pair of axially spaced ducts leading to the control shaft'therein, one of Which ducts receives metered fuel and the other of which leads to a Y spill outlet, the control shaft having a recess disposed to Veffect transient communication with the axially spaced ducts in said xed casing which also has a port leadingV from the bore connected to the supply ofY auxiliary liquid available in the auxiliary pumpingfch'amber,V the said portV 'l being located approximately diametrically opposite the" casing duct which receives lthe metered fuel, and having f Va greater cross-sectional area than said casing duct.

References Cited in the file of this patent UNITED STATES PATENTS 1,563,328 Bradbury Dec. 1, 1925 FOREIGN PATENTS v Y Y s 520,995*V Germany Mar. 14, 1931Y 661,722

Great Britain' Nov. 28, 195i aan...

UNITED STATES PATENT oTTTCE CERHHCATE @F CRRECTMN Patent N0 3gO68794 December l8rl92 John Neville Morris et alo It s hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below e Column 6 line 63Y after webring insert me for =mg line ZO for plungers read plunger line v after 93end insert n is e- Signed and sealed this 24th day of September 1963o (SEAL) Attest:

ERNEST w. SWTDER DAVID Lu LADD Attesting @ficer Commissioner of Patents

Images