US3068793A - Fuel-injection pumps for compressionignition internal combustion engines - Google Patents

Description

- J. N. MORRIS 3,068,793 FUEL-INJECTION PUMPS FOR COMPRESSION-IGNITION Dec. 18, 1962 INTERNAL COMBUSTION ENGINES 2 Sheets-Sheet 1 Filed Aug. 28, 1958 a 5.1;, 1 I, 9m 5 5 P. 7 1 1 9 I I \I I I 3 I P INVENTOR JOHN NEVILLE MORRIS Y r 1 ATTORNEYS Ill/ Dec. 18, 1962 UEL-INJECTION PUMPS FOR INTERNAL COMBUST Filed Aug. 28, 1958 I J. N. MORRIS PRESS ION-IGNIT ENGINES 3,068,793 ION 2 Sheets-Sheet 2 lNVE R JOHN NEVI MORRIS BY W? Mkfifiwwf 644M ATTORNEYS.

States This invention relates to fuel-injection pumps of the reciprocatory 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 pressures in the region of 5,000 p.s.i. or upwards.

The invention is particularly applicable to fuel-injection pumps which are also of the distributing type, in which either a single reciprocating plunger or a set of plungers meter and deliver fuel under high pressure to distributing means arranged to supply a multiplicity of engine cylinders.

According to the 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 metering plunger is operable in conjunction with, and under the control exercised by, another plunger of larger effective crosssectional area working in an auxiliary pumping chamber. The auxiliary chamber receives and is adapted to deliver unmetered fuel, the arrangement being such that at an early stage of the working stroke of the plungers, owing to their differential pumping action, the unmetered fuel becomes pressurized at the moment at which delivery of the metered fuel commences, and simultaneously therewith means become effective to maintain the supply of unmetered fuel, rendered available in the auxiliary pumping chamber, at a pressure which varies instantaneously with, and remains approximately equal to, that of the metered fuel.

In one embodiment of the invention, a fuel-injection pump of the reciprocatory plunger type and arranged to deliver metered fuel at high pressure is, in addition, designed to render available simultaneously a separate supply of unmetered fuel at approximately the same pressure. The pump includes a casing provided with a fuel inlet and contains a pair of coaxial plungers of different diameter contacting each other endwise by means of an abutment provided upon an end face of one of the plungers. The contact area of the abutment is substantially less than the cross-sectional area of the other plunger. The first plunger has a spill duct which debouches at one end within the area of the contacting surface of the abutment and which at its other end is maintained in permanent communication with a region for receiving spillage of fuel. The second plunger constitutes a movable boundary of a pumping chamber for metering fuel; whereas, the supply of unmetered fuel is rendered available in the pumping chamber of the first plunger, which fuel becomes pressurized by the differential pumping action of the two plungers. The last-mentioned chamber is referred to herein as the auxiliary chamber. The pressure of the unmetered fuel is limited by the hydraulic Separation of the plungers and the consequent uncovering of the spill duct. The pressurized unmetered fuel may be ported or otherwise allowed to develop regions of high pressure in the pump in order to prevent leakage of the metered fuel, that is to say, the unmetered and pressurized fuel may be employed in numerous ways for hydraulically sealing the pump against undesirable leakage of the metered fuel.

The invention may advantageously be used in conjunction with provision for varying the output of metered fuel Bflihtiflfi Patented Dec. 18, 1962 per stroke of the pump. This is achieved by combining the pump with improved variable spill control means comprising a fixed casing having a cylindrical bore containing a continuously rotating control shaft driven in variable phase relationship to a driving shaft associated with the pump plungers. A recess in the control shaft is arranged to effect transient intercommunication of a pair of ducts in the fixing casing. One duct receives metered fuel and the other duct leads to a spill outlet. A port in the bore of the fixed casing is connected to the supply of unmetered fuel available in the auxiliary pumping chamber, which port is situated approximately diametrically opposite, and having a greater cross-sectional area than, that one of the casing ducts which receives the metered fuel. In this instance, the unmetered and pressurized fuel hydrostatically loads the control shaft to prevent leakage of the metered fuel from the vicinity of the aforesaid duets.

As already indicated, the invention is especially useful when employed in combination with means for distributing the high-pressure metered fuel output of the pump to a plurality of engine cylinders in sequence. The distributing means in question can be designed to take advantage of the supply of high-pressure unmetered fuel rendered available in the auxiliary pumping chamber. Consequently, the invention can be used to great advantage as follows. The fuel distributor is provided with a fixed 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. A pair of circumferential grooves are provided in the bore of the distributor casing in permanent communication with the supply of unmetered fuel available in the auxiliary pumping chamber. A supply duct in the distributor casing is provided in permanent communication with the metered fuel outlet of the pump and situated intermediate in said circumferential grooves. A circumferential groove is provided in the distributor shaft which groove is in register with the supply duct and in permanent communication with a distributor port in the distributor shaft. A plurality of radial outlet ducts in the distributor casing are each connected to individual injection nozzles for respective engine cylinders and cooperates individually with the distributor port. A continuous groove in the distributor shaft surrounds the distributor port and is in permanent communication with the supply of unmetered fuel available in the auxiliary pumping chamber. In this instance, the unmetered and pressurized fuel develops regions of high pressure surrounding the communicating conduits for the metered fuel in the distributor means and thus prevents leakage of such metered fuel at these vicinities.

The principal object of the invention is to enable a fuel-injection pump of the type shown herein to provide automatically a supply of unmetered and, therefore, is in a limited sense, expendable fuel at a pressure approximately equal to that of the metered fuel, wherein the supply of expendable fuel remains available for a variety of sealing purposes throughout the duration of the highpressure phase of the main metered fuel pumping action.

It is a further object and advantage of the invention to provide a supply of unmetered and pressurized fuel in a fuel-injection pump concurrently with the delivery of metered fuel by the pump wherein, the supply of unmetered fuel is expendable and available for sealing purposes in the pump. The unmetered fuel may be employed to develop regions of high pressure in the pump proper or elsewhere in the fuel system such as in control means or distributor means, and thus may serve in lieu of commercially impractical and relatively expen sive techniques of having close mechanical fittings be tween contiguous or cooperating elements in the vicinity of the fuel system where the metered fuel would otherwise leak away; the unmetered fuel creates high pressure regions in such vicinities whereby leakage of metered fuel is suppressed. 7

Further objects and advantages will become apparent from the following description of the invention taken in conjunction with the figures, in which:

FIG. 1A is a plan elevational view in section depicting a fuel-injection pump in accordance with the practice of the invention; FIG. 1B is a fragmentary plan elevational view in section and shows the practice of the invention in control means used in conjunction with the pump of FIG. 1A for varying output of metered fuel; FIG. 1C is a plan elevational view in section depicting the practice of the invention in distributor means used in conjunction with the pump of FIG. 1A;

FIG. 2 is a fragmentary and sectional view of the pump shown in FIG. 1A and illustrates the upper portion thereof and in particular the relative positions of the elements of the pump at the start of its downward stroke;

FIG. 3 depicts the apparatus shown in FIG. 2 wherein the coacting elements are in their respective positions just before the end of the downward stroke; and

FIG. 4 again shows the pump but in this instance the elements are in their respective positions depicting the delivery or working stroke at an instant of time just after that represented by the positions of the same elements as illustrated in FIG 1A.

The invention will now be described with reference to the accompanying FIG. 1A. Liquid fuel is taken from a supply tank 1 by a feed pump 2 and is delivered to an inlet 4 in the casing 5a of a fuel-injection pump 5. Pump 2 is provided with the usual relief valve 3. The main body of pump casing 5a is formed with a pair of coaxial bores 6 and 7 in which are mounted plungers 8 and 9 re- 'spectively. These plungers are of unequal diameter, and one end of the larger plunger 9 protrudes from its bore and is shaped, as at lower end 10, to co-operate with a cam 11 mounted on a pump drive shaft 12. A return spring 13 reacts upon the upper end of smaller plunger 8. Spring 13 urges the two plungers into contact over an area afforded by an abutment 14 on the plunger 9 and, additionally, maintains the protruding end 141 of plunger 9 in contact with cam 11. Rotation of drive shaft 12 and cam 11 against the action of spring 13 imparts the upward stroke, sometimes referred to as outward motion, to plungers 8, 9; whereas, return spring 13 effects the downward stroke, sometimes referred to herein as inward motion, to such plungers.

A circumferential groove 15 is formed in bore 7 containing larger plunger 9. Groove 15 as it is operationally associated with fuel inlet 4 will be referred to herein as the filling groove. Groove 15 is in such a position that the upper end of plunger 9, remote from cam 11, overruns groove 15 shortly before the completion of the inward or downward movement of plungers 8, 9. Ducts 16 and 17 are provided in smaller plunger 8. Simultaneously with that overrunning action of larger plunger 9, ducts 1'6, 17 establish communication between metering pumping chamber 18, of which the upper end of smaller plunger 8, remote from the cam 11, forms the movable boundary, and the annular space 19 which results from the difference in diameter between the two plungers 8, 9.

In the particular example illustrated, a circumferential groove 20 on larger plunger 9 is maintained in permanent communication with filling groove 15, the widths of these two grooves being so chosen as to ensure this.

Plunger 9 is provided with a spill duct 21 which debouches at one end within the face of abutment l4, and which communicates at its other end with groove 20. However, groove 20 is not an essential feature and it region for receiving spillage of fuel, instead of leading it into filling groove 15. An outwardly opening nonreturn valve 22 loaded by a spring 60 is situated at an outlet 23 leading from metering pumping chamber 18.

The operation of the-pump is as follows. Commencing at the outer or upper dead center position of plungers 8, 9, rotation of camshaft 12 permits the plungers to move downwardly under the action of return spring 13, as the plungersare maintained in mechanical contact by intervening abutment 14. During this phase, note FIG. 3, non-return valve 22 leading from the main or metering chamber 18 is closed, and thus a partial vacuum is formed, not only in chamber 18, but also in an auxiliary pumping chamber constituted by annular space Shortly before the termination of this inward or downward stroke of plungers 8, 9, the upper end of larger plunger 9 overruns filling groove 15 and, simultaneously, ducts 16 and 17 in smaller plunger 8 establish communication between pumping chamber 18 and auxiliary pumping chamber 19. Thereupon, both pumping chambers 18 and 19 are enabled to inspire fuel by cavitation from filling groove 15.

At an early stage of the ensuing outward or upward stroke of plungers 8 and 9, the top end of plunger 9 travels above groove 15; consequently, both means of communication leading from auxiliary pumping chamber 19, that is to say, to filling groove 15 and to pumping chamber 18, respectively, become cut off simultaneously as shown in FIG. lA. The fuel previously inspired into metering chamber '18 now becomes pressurized to the point where the non-return valve 22 opens against spring 60 and fuel delivery commences notwithstanding any degree of back pressure which may be imposed, as, for instance, by the type of nozzle commonly employed for diesel engine injection, to which pump outlet 23 may lead.

It Will be assumed for the moment that an outlet 61 leading from chamber 19 is plugged up and thus fuel cap-. tured in auxiliary chamber 19 momentarily will have no means of egress. Simultaneously with the aforesaid action wherein fuel in chamber 18 becomes pressurized to a point where valve 22 opens, the fuel contained in auxiliary chamber 19, rapidly rises to a pressure which could be dispensed with by simply increasing the radial depth of the filling groove 15. Moreover, the neighboring end of spill duct 21 could, if desired, be put into permanent communication with any other convenient action upon the differential area existing between the cross-sectional area of smaller plunger 8 and that of abutment 14 through which the two plungers make contact, hydraulically separates the plungers and impels smaller plunger 8 on its upward stroke. Smaller plunger 8 thus tends to run away from larger plunger 9, but, in so doing, it exposes spill duct 21 in larger plunger 9. The result is that the fuel pressurized within annular chamber 19 is permitted to leak away via the suitably dimensioned duct 21 into circumferential groove 20 along the side of plunger 9 and thence into filling groove 15. Consequently, a finite pressure is automatically sustained within auxiliary pumping chamber 19 throughout the remainder of the upward stroke of the plunger assembly; and this pressure is instantaneously somewhat but not much higher than the pressure obtaining in pumping chamber 18 in accordance with the elfective relative cross-sectional areas of smaller plunger 8 and of abutment 14. For example, if the cross-sectional area of smaller plunger '8 were 1 sq. cm. and the effective cross-sectional area of abutment 14 were approximately 0.1 sq. cm. then the pressure generated in auxiliary chamber 19 during this phase would at any instant be approximately 10% greater than that obtaining in pumping chamber 18.

One immediate consequence of this approximate equality of pressures between annular chamber 19 and metering chamber 18 is that the tendency for the metered fuel to leak away from chamber 18 into what would, in the case of a conventional construction, be a region of approximately atmospheric pressure, is greatly diminished and is, in fact, at this much diminished rate, in the contrary direction. 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 metered fuel. A further attribute of the invention is that the unmetered fuel contained in auxiliary chamber 19, that is to say, the fuel which has been referred as expendable, can be conveyed by a duct 24 (assuming now that outlet 61 is unplugged) leading from this chamber to any point in the injection system at which it can perform a sealing function or some other useful service.

Examples of useful applications for this expendable fuel to other parts of a typical high-pressure fuel metering and distributing 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 point during the upward stroke of metering injection plunger, is a normal requirement in diesel engine operation. Such a variable spill control may conveniently be afforded by a device shown in FIG. comprising a fixed casing 25 having a cylindrical bore 26 within which is mounted a continuously rotating control shaft 27 driven by main pump shaft 12 through a drive mechanism (not shown) arranged to permit the two shafts to be phased or relatively rotated to a limited degee. This phasing or relative rotation of the shafts constitutes a means of varying the output of metered fuel per stroke of the pump.

A connecting pipe 23, additional to that leading from metered fuel outlet 23 of the pump to the injection nozzle 29, is arranged in parallel with the injection nozzle feed pipe 3% Pipe 28 terminates in a duct 31 debouching upon bore 26 of fixed casing 25. A further and adjacent relief duct 32 leading to a region into which fuel may conveniently be spilled, in this case supply tank 1 also debouches upon bore surface 26. Control shaft 27 is provided with a recess 33 capable of effecting temporary communication between the two ducts 31, 32. In its simplest form, the device comprises only one such recess 33, and control shaft 27 is driven at the same speed as pump drive shaft 12. The arrangement is such that rotation of control shaft 27 effects spillage of the metered fuel at any required interval after the commencement of the injection phase, in accordance with the variable relative rotational positions of the two shafts concerned.

A port 34 is provided within bore 26 of fixed casing 25 and situated approximately diametrically opposite duct 31 which communicates with metered fuel outlet 23 from the pump. Port 34 has a cross-sectional area somewhat greater than that of the duct 31. Port 34 is placed in communication, by duct 24, with source 19 of the expendable unmetered high-pressure fuel. The flow of expendable fuel through port 34 is thus able to perform the useful function of hydrostatically forcing control shaft 27, to the degree to which this shaft may be fitted with some small clearance in its bore, into intimate mechanical contact with the region of bore 26 at which the metered highpressure fuel would otherwise tend to leak away by reason of local separation of the shaft from its bore. 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 recess 33 formed in the control shaft 27 causes spillage of the metered fuel.

Another example of a useful application for the expendable high-pressure fuel 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 35 having a cylindrical bore 36 which contains a rotatable distributor shaft 37. Shaft 37 is driven at some finite fraction of the pump shaft speed, in accordance with the number of engine cylinders to be served. The circumferential grooves 38, 39 are provided in bore 36 of fixed casing 35. Bore 36 also has a supply duct 40 spaced intermediately between grooves 38, 39. Communication, by way of a connecting pipe 41 and passages 42, is permanently 0 established between the two grooves 38, 39 and source 19 of expendable high-pressure fuel. A further permanent communication is established between supply duct 40 and the metered fuel outlet 23 from the pump.

In the normal application of the distributing device, in which a variable spill control 25, such as that already shown in FIG. 1B, is required to be incorporated in the fuel-injection system, two passages are provided from the metered fuel outlet 23 from the pump; one, represented by connecting pipe 28, leading to such Variable spill control 23 and the other, represented by a connecting pipe 43, to the distributing device 35. A plurality of equally spaced radial outlet ducts 44 debouch upon bore 36 of the casing. Ducts 44- are in a plane longitudinally displaced from grooves 38, 3? and duct 40. Each duct 44 is connected by a pipe 43 to a corresponding injection nozzle 29. The number of nozzles 29 are in accordance with the number of engine cylinders to be supplied.

The distributor shaft 37 has a circumferential groove 46 and a distributor port 47 spaced apart longitudinally and interconnected by a duct 43. A continuous groove 49 such as can conveniently be formed by the operation of trepanning surrounds the distributor port 47 in distributor shaft 37. A duct 5%, which will be designated as the pressurizing duct, debouches at one end upon the surface of distributor shaft 37 and at its other end com municates with continuous groove &9. The arrangement is such that, upon assembly, circumferential groove 46 in the distributor shaft registers with supply duct 40 in the casing. Distributor port 47 in shaft 37 falls within the plane containing the radial outlet ducts 44 of the casing; and pressurizing duct 5ft, where it debouches upon the surface of shaft 37, registers with circumferential groove 39 in the bore of the fixed casing which communicates with source 19 of expendable high-pressure fuel.

The bores of the distributor port 47 and of the individual outlet ducts 44, at their intersection with the surface of distributor shaft 37 and bore 36 of casing 35 respectively, are such that, whatever the timing of the pump and spill control in respect of the duration of the injection dwell, free communication is maintained between distributor port 47 and one of the outlet ducts 44 throughout the duration of each injection dwell. A land 51 provided between the bore of the distributor port 4-7 and the inner periphery of continuous groove 49 surrounding it, is, moreover, of sufficient width to ensure that groove 49 under no circumstances comes into communication with any of the outlet ducts 44 during the injection phase through that particular duct.

The metered fuel at the commencement of the injection phase, passes by way of supply duct 40, into the associated circumferential groove 46 of distributor shaft D 37 and thence through the corresponding duct 48 in the shaft to distributor port 47. The relative rotational position of distributor shaft 37 with respect to main pump shaft 12 is such that the fuel then enters one of the outlet ducts 44 and passes to one of the injection nozzles 29 associated with the engine cylinders. Supply to that partieular cylinder then continues until such time as the injection phase is terminated, as by means of the spill device 25 previously described.

In the absence of a supply of expendable high-pressure fuel coinciding in time with the injection dwell, or in the absence of a commercially impracticable closeness of fit between distributor shaft 37 and its bore 36, serious leakage of metered fuel would occur in the vicinity of supply duct 40 and its associated groove 46 in shaft 37, and also in the vicinity of distributor port 47. Such expendable high-pressure fuel is, however, rendered available 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 expendable fuel during this time, within the two circumferential grooves 38, 39 in casing 35 and within the annular groove 49 surrounding the distributor port 47, serves, incidentally, to reverse the direction of such leakage since the unmetered fuel is at somewhat higher pressure than the metered fuel, and, in particular, serves to diminish considerably the extent of such leakage.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended 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 is claimed is:

1. A fuel injection pump of the reciprocatory plunger type for delivering metered quantities of liquid fuel at high pressure, comprising a housing having two communicating co-axially disposed bores of different diam eters, the bore of smaller diameter having a substantially closed end, a first plunger reciprocable in said bore of smaller diameter, a second plunger co-axial with the first plunger reciprocable in the bore of larger diameter, means for reciprocating said plungers substantially in unison, the first plunger forming with said bore of smaller diameter and said closed end a metering chamber, said first plunger forming with said second plunger and said bore of larger diameter a second chamber, means for adnutting and delivering liquid fuel into and from the metering chamber, means for admitting sealing-liquid into said second chamber, said second plunger having a spill-duct one end of which has an outlet to said second chamber 'and at its other 'end is in permanent communication with a region for receiving spillage of sealing-liquid from the second chamber, the confronting ends of said plungers having different effective cross-sectional areas responsive to liquid under pressure in the second chamber and means on the confronting end of said first plunger constituting a valve for closing said spill-duct outlet during the non-working stroke of the plungers, movement of the second plunger during its working stroke operating to (1) pressurize sealing-liquid admitted to the second chamber, (2) pressurize fuel admitted to the metering chamber, (3) cause the first plunger to move to discharge the metered fuel, (4) diminish the tendency of the pressurized fuel to leak away from said metering chamber, and (5) cause the first plunger to move axially more rapidly than the second plunger to hydraulically open the valve and permit part of said pressurized sealing-liquid to discharge through the spillduct and thereby effectively to vary the pressure on the sealing-liquid in the second chamber instantaneously with, and maintain said pressure approximately equal to, the pressure on the metered fuel.

2. A fuel injection pump according to claim 1, Wherein the sealing-liquid is the liquid fuel, the casing and the r first plunger having ports controlled by the movement of the plungers for charging fuel from a source into said chambers during the intake stroke of the plungers and for cutting off said chambers from said source at an early stage of the working or discharge stroke, said metering chamber having a port controlled by a valve for discharge of fuel from the metering chamber and the confronting ends of said plungers being disposed in the second chamber and normally held in contact by the valve at the confronting end of the first plunger seating over the spill-duct outlet in the second plunger.

3. Apparatus as defined in claim 2, further including, variable spill control means for varying the output of metered fuel per working stroke of the pump, said spill control means comprising a casing having a cylindrical bore, a control shaft rotatable in said bore in variable phase relationship in respect to said driving shaft, a pair of ducts in said casing and debouching at the surface of said bore, a fluid passage extending from one of said ducts to the discharge port of said metering pumping chamber, a fluid passage extending from the other of said ducts to the fuel spill source, said control shaft having a spill recess arranged to effect, during rotation, transient intercommunication between said pair of ducts,

a port in said casing, communicating with said spill casing bore surface approximately diametrically opposite and having a cross-sectional area greater than the aforesaid duct communicating With said discharge port in the metering pumping chamber and a fluid passage extending from said last port to said second chamber in the pump housing. a

4. Apparatus as defined in claim 2 further including,

' distributor means for distributing metered fuel from said metering pumping chamber to a plurality of engine cylinders in desired sequence, said means for reciprocating said plungers including a driving shaft, said distributor means comprising, a casing having a cylindrical bore, a distributor shaft rotatable in said bore at some finite fractionof pump driving shaft speed, a pair of spaced circumferential grooves in the bore surface of said distributor casing, a fluid passage extending from said grooves to a discharge port in said second chamber in the pump housing for receiving fuel therefrom, said distributor shaft having a circumferential groove disposed between said pair of circumferential grooves, a fluid passage for maintaining the distributor shaft circumferential groove in fluid communication with the discharge port of said metering pumping chamber, said distributor shaft also having a duct therein in fluid communication with said lastmentioned circumferential groove, said distributor casing having a plurality of spaced radial outlet ducts therein for connection with respective ducts leading to the engine cylinders, said duct in the distributor shaft registering with individual ones of said radial outlet ducts upon rotation of said distributor shaft, and said annular groove in the peripheral surface of said distributor shaft surrounding said duct in the distributor shaft, said lastmentioned groove being in permanent fluid communication with said pair of circumferential grooves forreceiving fuel from said second chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,563,328 Bradbury Dec. 1, 1925 FOREIGN PATENTS 189,446 Austria ,May 15, 1956 661,722 Great Britain Nov. 28, 1951 922,415 France Feb. 3, 1947

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