US3627208A

US3627208A - Fuel injection apparatus for internal combustion engines of the liquid-fuelinjection compression-ignition type

Info

Publication number: US3627208A
Authority: US
Inventors: William M Scott; Brian W Millington; Royston Gordon Freese
Original assignee: Ricardo and Co Engineers 1927 Ltd
Current assignee: Ricardo PLC
Priority date: 1969-10-06
Filing date: 1969-10-06
Publication date: 1971-12-14
Anticipated expiration: 1988-12-14

Abstract

A fuel injection system for an internal combustion engine of the liquid-fuel-injection compression-ignition type, having a fuel pump arranged to deliver fuel under supply pressure via a pressure-reducing valve to a pressure chamber of an injection plug, the said plug having an injection valve arranged to open in response to the pressure in the pressure chamber and controlling the injection of fuel from the chamber through the nozzle into the associated combustion chamber. The pressure-reducing valve is of the spring-loaded-piston variable-orifice type and when operative controls the fuel pressure in the pressure chamber, and hence the injection pressure, to a predetermined reduced value for the purpose of reducing engine noise during periods of idling. Means is provided however for rendering the pressurereducing valve inoperative when full injection pressure is required, either by bypassing the pressure-reducing valve altogether so that the fuel pump delivery passes directly to the pressure chamber throughout the whole of each pump delivery stroke, or by bypassing the restricted orifice of the pressurereducing valve during the final stage only of each delivery stroke of the fuel pump. In either case the bypassing means may be operated by a running control member of the engine, for example a fuel or speed control member.

Description

Unite/1;;

[72] Inventors Wlillam M. Scott 3,456,884 7/1969 Knight et a1. 239/533 i w lvllllll t N rth L 1 FOREIGN PATENTS r an mg on, ant: lng; Royumn Gordon ewe, pp g, 8 6513359 4/1966 Netherlands 239/533 01 England Primary Examiner-M. Henson Wood, Jr. [21 App]. No. 864,123 Assistant Examiner-Edwin D. Grant [22] Filed Oct. 6, 1969 Atlurney-Watson, Cole, Grindle & Watson [45] Patented Dec. 114, 1971 [73] Assignee Ricardo & Cm, lEngineers(l927) Limited shommmmrswySussexlEmzhand ABSTRACT: A fuel in ection system for an internal combustion engine of the liquid-fuel-injection compression-ignition type, having a fuel pump arranged to deliver fuel under supply pressure via a pressure-reducing valve to a pressure I54] FUEL INJECTIUN APPARATUS FOR INTERNAL chamber of an injection plug. the said plug having an injection COMBUSTION ENGINES OF THE LHQUlmFUEL valve arranged to open in response to the pressure in the pres- ]NJEUHON (:OMPRESSHONJGNWHON TYPE sure chamber and controlling the injection of fuel from the Hanna, Drawing mt chamber through the nozzle into the associated combustion chamber. The pressure-reducing valve is of the spring-loaded- [52] 11.3. CI 239/533, piston variableoritice type and when operative Controls h I 123/32 137/ fuel pressure in the pressure chamber, and hence the injection [51] lint. C11 1805b 1/30 pressure to a predetermined reduced value f h Purpose f [50] FllEld 011 Search 239/533; reducing engine noise during periods f idling Means is 123/32 G; 137/] 10 vided however for rendering the pressure-reducing valve in- Reicmnces Cited operat ve when full in ection pressure '15 required, either by bypassing the pressure-reducing valve altogether so that the UNITED STATES PATENTS fuel pump delivery passes directly to the pressure chamber 2,173,814 9/1939 Bischof..... 239/533X throughout the whole of each pump delivery stroke, or by 2,813,752 1 1/1957 Pringham 123/32 G bypassing the restricted orifice of the pressure-reducing valve 3,104,817 9/1963 Vander Zee et a1. 239/533 X during the final stage only of each delivery stroke of the fuel 3,348,488 10/1967 Wolff 123/32 G pump. In either case the bypassing means may be operated by 3,387,597 6/1968 Wirsching 123/32 G a running control member of the engine for example a fuel or 3394,891 7/1968 Voit 239/533 speed control member.

/ i g a v if 755 18B 78 /-24 74A 76B k, v I t 7L u f K N t Annd v, '46 2/ 3] L 20 33 22 21 36 19 27 78A 32 23 II I 7 9 States te MENTEU HEB 1 A 19?"! SHEET 5 OF 5 fidw p /waif ATTORNEY This invention relates to fuel injection apparatus for internal combustion engines of the liquid-fuel-injection compressionignition type, of the hind comprising fuel delivery means, in the form of a reciprocating fuel pump or other fuel metering and delivery means, arranged to deliver fuel under pressure in predetermined quantities during delivery periods at appropriately timed intervals to at least one fuel injection device of the type which includes a nozzle and a valve (herein called the injection valve) controlling the flow of fuel through the nozzle and so arranged as to be opened automatically during each delivery period by the fuel pressure in a pressure chamber in the injection device, usually adjacent to the injection orifice or orifices, to which chamber the fuel delivery means delivers the fuel. Such fuel injection apparatus is referred to herein as being of the kind specified.

The injection apparatus to which the invention is applied may be of the usual type employing as the fuel delivery means a reciprocating fuel pump incorporating control means by which the quantity of fuel delivered during each injection period is controlled by varying the length of the effective part of the pump delivery stroke, although the invention may also be applied to fuel injection apparatus of the kind specified employing other forms of fuel delivery means in which a measured quantity of fuel is delivered to the injection device dur ing each injection period.

One of the disadvantages of reciprocating internal combustion engines of the liquid-fuel-injection compression-ignition type (and particularly those of relatively small capacity as are used in road vehicles) as compared with engines of the vaporized charge spark ignition type, is that they tend to be noisy, particularly when idling and at low speeds.

Research into the cause of the noisy operation has shown that a substantial proportion of the noise, including the well known diesel knock," appears to result from the high rate of injection inherent in existing injection systems, augmented in some cases by the fact that, at the delivery pressures employed, there is appreciable volumetric elasticity in the part of the system between the pump and the injection device which tends to delay the injection while pressure builds up in this part of the system until the injection valve opens, whereupon injection begins at a high volumetric rate. Moreover in existing systems there is a substantial delay between the beginning of injection and the initiation of burning, and the result, which is attributed to one or both of these causes, is that when burning begins, there is a rapid initial pressure rise in the engine cylinder and consequent noisy operation. It has also been found that if the rate of the initial pressure rise can be reduced, as by reducing the initial rate of injection and/or the delay between the beginning ofinjection and the beginning of burning, the noise is similarly reduced, and various proposals have, therefore, been made which aim at reducing the rapidity of the initial pressure rise. One such proposal is the injection into the air charge prior to the main injection (e.g. during the induction or compression period) of a small quantity of fuel which is insufficient in itself to cause an appreciable pressure rise but which ignites before the main injection begins so that burning of the fuel then injected tends to start with little delay. This proposal, which is usually called pilot injection, has not however, been entirely successful in its purpose.

it has been found, for example, that at the injection pressures required in practice it is difficult to provide for such pilot injection in advance of the main injection, whether there is a time interval between the pilot injection and the main injection or not, due to the volumetric elasticity referred to which causes the fuel line between the pump and the pressure chamber of the injector to act to some extent as a hydraulic accumulator so that when the injection valve opens the initial rate of injection is too high for quiet engine operation.

Vnrious other proposals huve also been made for the purpose ofrcducing noise. including those incorporated in the in jection system forming the subjects of the present applicants British Pat. Applications Ser. No. 43,576 of 1964 and 12,747 of 1965 and f at. l lo. l,0l4,l3l and the present invention has for its object to provide forms of fuel injection apparatus of the general kind referred to which will represent a still further improvement over existing systems.

According to the present invention, in fuel injection apparatus of the kind specified, there is included between the fuel delivery means and the pressure chamber a pressurereducing valve as defined hereinafter which when operative acts in each delivery period to reduce the pressure at which fuel is delivered to the pressure chamber to a determined constant reduced value substantially below the full supply pres sure at which the fuel delivery means supplies fuel to the pres sure-reducing valve, and there is also included means for rendering the pressure-reducing valve inoperative during periods when the delivery of fuel to the pressure chamber at substantially the full supply pressure is: required.

The term a pressure-reducing valve" as used herein is defined as a valve arranged to regulate a flow of fluid to a con stant output pressure less than the pressure at which the fluid is supplied to the valve, the valve having a variable orifice through which the fluid flows and whose cross-sectional area is controlled by and in accordance with the fluid pressure downstream of the said orifice in such a manner as to regulate the said downstream pressure to a constant value despite variations in the supply pressure. For example, the pressure downstream of the orifice may act on a piston against a stressed spring or other predetermined load, the resultant movement of the piston being used to vary the valve orifice area.

Preferably there is also included in the apparatus a restricted passage (hereinafter called for convenience a restrictor) arranged in series with the pressure-reducing valve and serving when the pressure-reducing valve is operative to control the rate at which fuel at the predetermined reduced pressure is delivered to the pressure chamber, this rate being determined by the rate at which fuel at the reduced pressure can flow through the restrictor.

in one type of arrangement according to the invention the said means for rendering the pressure-reducing valve inoperative is arranged to maintain the pressure-reducing valve opcrative during a predetermined initial part of each delivery period and to bypass the pressure-reducing valve during the remainder of that delivery period.

Thus there may be provided a piston valve device interposed between the pressure reducing valve and the pressure chamber, the piston valve device having a pressure face on which the output pressure of the pressure reducing valve acts to move it against a biasing force, and also having a working face which serves during the initial part of the total range of such movement to deliver fuel at the said constant reduced pressure to the pressure chamber of the injection device, and on further movement of the piston valve device serves to open a bypass passage which bypasses the pressure-reducing valve to permit the flow of fuel to the pressure chamber at substan tially the full supply pressure. in such an arrangement the restrictor is preferably interposed between the pressure chamber and the said working face of the piston valve device which applies pressure to the fuel to be delivered at reduced pressure to the pressure chamber, but the restrictor may alternatively be disposed between the pressure-reducing valve and the said pressure face of the piston valve device.

Three constructions according to the invention are shown by way of example in the accompanying; drawings, in which:

FllG. l is a diagrammatic view of a fuel injection system including a fuel pump, a fuel injection device, and one form of pressure-reducing valve assembly providing one form of fuel injection system according to the invention;

FIG. 2. is a cross section on an enlarged scale of the fuel injection device and pressurereducing valve assembly incorpornted in the system shown in FIG. ll;

FIG. 3 is a similar view to FIG. 2 showing an alternative form of apparatus which may be employed in conjunction with a fuel injection device and a fuel pump as shown in FIGS. 1 and 2 and with appropriate control apparatus to provide an alternative form of fuel injection system according to the invention;

FIG. 4 shows diagrammatically the manner in which the form of apparatus shown in FIG. 3 may be employed in con-' junction with fuel control apparatus embodying a speedresponsive governor; and

FIG. 4 shows diagrammatically the manner in which the form of apparatus shown in F l6. 3 may be employed in conjunction with fuel control apparatus embodying a speedresponsive governor; and

FIG. 5 is a diagrammatic view of a further form of apparatus which may be employed as part of the apparatus shown in FIG. 1 and embodying an alternative position for the metering orifice.

t The fuel injection system shown in FIG. 1 comprises the usual fuel pump 1 arranged to deliver fuel in measured quantities at appropriate timed intervals to the combustion chambers of an internal combustion engine of the liquid-fuel-injection compression-ignition type, which is assumed to be a fourcylinder engine, the quantity of fuel delivered during each delivery period being controlled in conventional manner by a pump control member 1A actuated by control mechanism 18. For simplicity, since the fuel injection apparatus associated with each of the cylinders would be the same, the fuel injection apparatus associated with one cylinder only is fully shown and will hereinafter be described. The apparatus comprises a fuel delivery passage 2 to which the appropriate pump piston delivers fuel in measured quantities in well-known manner, an assembly including a pressure-reducing valve shown generally at 3 to which the fuel delivery passage 2 is attached, and a fuel injection device generally indicated at 4 of conventional type to which the pressure-reducing valve assembly is attached.

The injection device and the associated pressure-reducing valve assembly providing a fuel injection system according to the invention is shown in cross section and will now be described with reference to FIG. 2. The fuel injection device comprises the usual casing 5 provided with a fuel inlet connection 6 to which the fuel delivery pipe from the pump would be directly coupled in a conventional system, but which in H6. 2 is connected in a manner more fully described hereinafter to the outlet end of the body part of the pressure-reducing valve assembly shown generally at 3 in FIG. 1. The inlet connection 6 communicates by way of a delivery passage 7, an annular chamber 8 formed by an annular recess in the upper end of a nozzle member 9, and a further delivery passage 10 in the nozzle member with a pressure chamber 11 from which opens an injection orifice which is normally closed by an injection valve 12. The valve 12 includes a part 13 forming a close sliding fit with a bore in the nozzle member 9 and an upper part 14 which is acted upon by the lower end of a push rod 15 the upper end of which is acted upon through a thrust member 15A by a compression spring 16 whereby the valve 12 is urged continuously towards its seating in the injection orifice. The construction and operation of the injection device above briefly described is of well-known conventional type providing for the lifting of the valve 12 by the pressure of fuel delivered to the pressure chamber 11 and acting on the lower end of the part 13 so that the ejection of the fuel from this chamber takes place through the injection orifice under a degree of control by the valve 12. In the construction shown in FIG. 2, the pres sure-reducing valve assembly 3 is interposed between the delivery passage 2 and the inlet connection 6 of the injection device and comprises a body part 14A partly housed within and projecting from a two-

part casing

15B, 16B of which the part 158 is provided with a connection 17 containing the end portion of the fuel delivery passage 2 communicates with an annular chamber 18 formed between the bore of the part 158 of the casing and the circumferential surface of the body part 14A.

The projecting end of the body part 14A is provided with a flange 18A and with a screw threaded part 188 which is screwed into the fuel inlet connection 6 of the fuel injection device.

The body part 14A contains a pressure-reducing valve and other parts by which the delivery of fuel from the fuel injection pump 1 to the pressure chamber 11 of the fuel injection device is regulated to a predetermined constant reduced value, as follows:

Formed in the body part 14A is a bore having a small diameter part 19 constituting a cylinder and a large diameter internally screw-threaded part 20 the open end of which opens into the fuel inlet connection 6 of the injection device. Communicating with the cylinder 19 are two

fuel inlet ports

21, 22 both leading from a passage 23 which is in open communication with the annular chamber 18, while two

parts

24, 25 open out of the cylinder 19. The

ports

24, 25 communicate with a common passage 26 extending parallel to the cylinder 19 and communicating with the end of the bore 20 and hence with the fuel inlet passage 6 of the injection device.

Arranged to reciprocate within the cylinder 19 is a pressurereducing valve 27 one end of which extends from the bore and is formed with a head 28 acted upon by one end of a compression spring 29 the other end of which acts on an abutment 30 resting against the end of the part 16B of the casing 4 formed integral with a guide 31 extending within the spring 29. Also arranged in the cylinder 19 is a piston valve member 32 acted upon by one end of a spring 33 the other end of which acts on a metering member 34 screwed into the bore 20 and having formed therein a restricted metering orifice 35, the spring 33 thus serving to urge the piston valve member 32 always towards the pressure-reducing valve 27 so that the parts normally occupy the position shown in FIG. 2.

Formed in the reducing valve 27 is a passage 36 which communicates with an annular recess in the circumferential wall of the reducing valve, which recess in turn communicates with the

ports

21 and 24. The arrangement is thus such that when fuel under pressure is initially delivered by the fuel pump the fuel pressure is transmitted through the passage 23, port 21 and passage 36 so as to move the pressure reducing valve 27 towards the right in H6. 2 against the action of its spring 29. Such movement reduces the effective cross section of the variable orifice constituted by the overlap between the port 21 and the annular recess 24 in the valve member 27, thereby reducing the fluid pressure in the passage 36 until it reaches a value which exactly balances the force of the spring 29. The pressure-reducing valve thus regulates the pressure in the passage 36 to this predetermined constant balancing value, determined by the setting of the spring 29, despite variation in the fuel pressure applied by the pump to the passage 23 and port 21. This movement of the pressure reducing valve into its operative" position closes the port 24 so that the reduced fuel pressure now acts to move the piston valve device 32 to the left in FIG. 2 against the action of its spring 33, so that it acts as a piston to deliver fuel, which was previously drawn into the chamber containing the spring 33 during the preceding injection cycle, through the restricted passage 35 to the fuel delivery passage 7 of the injection device and hence to the pressure chamber 11, at a pressure determined by the pressure reducing valve 27 and at a rate which is jointly a function of this pressure and the effective cross-sectional area of the restriction 35. It will be seen that when the piston valve device 32 reaches a certain point in its movement it brings the

ports

22 and 25 into communication so that thereafter fuel can be delivered at full pressure and at a volumetric rate determined solely by the pump delivery rate via the passages 26 and 7 to the pressure chamber 11 ofthe fuel injection device.

In operation, therefore, during each fuel delivery period there is delivered to the pressure chamber 11 of the fuel injection device first a quantity of fuel at a reduced pressure determined by the pressure-reducing valve 27 and at a rate which is controlled to a degree by the cross-sectional area of the restricted passage 35, after which fuel at full delivery pressure and without any substantial restriction will be delivered to the pressure chamber 11 ofthe fuel injection device.

memes At the end of each injection period the pressure-reducing valve 27 returns to the positions shown in H6. 1?. under the action of its spring 29 and port 2 3 is thus opened to act as a relief passage permitting the piston valve member 32 to move towards the right in FIG. 2 under the force of its spring 33 and to displace fluid into the passage M and through the orifice 3b into the chamber containing the spring 33, thus allowing the piston 32 to return to the position shown in readiness for the next injection.

In the arrangement shown in FIG. 3 the pump delivers fuel to the passage 37 to which the passage 2 in FIG. I may thus be assumed to be connected and the pressure-reducing valve assembly comprises a body part 38 similar to but shorter than the body part M in FIG. 2 and having a bore comprising a cylindrical part in which lies pressure-reducing valve 3%, and an internally screwthreaded part into which is screwed a metering member d containing a restricted orifice it. The passage 37 communicates with a port d2 similar to the port ml in FIG. 2 while a passage l3 similar to the passage 2h leads from a port at in the cylinder in which the pressure-reducing valve 39 operates into the delivery passage 7 of the injection device. A spring dd corresponding to the spring 29 in FIG. 2 acts on the pressure-reducing valve 3'9.

In the arrangement shown in FIG. 3 the pressure-reducing valve 3% in addition to being axially movable to perform its main function is arranged to be rotatable through an angle of about 90 by means of an actuating member do which permits the necessary axial movement of the pressure-reducing valve 39 against the action ofits spring 45 but has a sliding dog-type connection 47 with the thrust member dd through which the spring 45 acts so that the actuating member M can impart the required approximately 90 rotational movement to the valve 39. The pressure-reducing valve 39 has the usual annulus d9 which normally communicates with the passage 42, this annu lus communicating through two diametrically opposite slots 50 in the valve with the inlet end of the restriction dll and, in one rotational position of the valve, as shown in FIG. 3, being out of communication with the port Aid. In this rotational position of the valve 39 therefore all the fuel delivered is caused to pass through the restriction 4l1l to which it flows at a reduced pressure determined by the pressure-reducing valve. By rotating the valve 39 through 90, however by means of the control member t6 the slots 50 are brought into register respectively with the passage t2 and the port dd, thus rendering the pressure-reducing valve inoperative and permitting fuel to flow freely from the passage 37 through the passage dill, slots M annulus W and passage 33 to the passage ti at full pump delivery pressure.

The control member as in this construction may be connected either directly to the fuel control mechanism 11B of the fuel pump, indicated in FIG. l, or by appropriate mechanism to a manually or foot-operatedcontrol member, as shown in FIG. 4i. In FIG. 4! the fuel control member M of the fuel pump 52 is actuated by a speed-responsive governor d3 of conventional form the setting of the spring MA of which is under the control of foot-opcrated mechanism comprising an accelerator" pedal 54 connected by a link 55 to a lever t'iti one end of which acts on the movable abutment 57 of the spring 533A while during the last part of its travel towards the idling" position it acts on a lever 53 to move it from the position indicated by the chain line 59 into the position shown The lever b is connected by a link 6111), a bellcranlt lever er and a link 62 to a lever 63 secured to the control member as, and the arrangement is such that movement of the lever 58 from the position indicated by the chain line 59 into the posi' tion shown rocks the member 46 through an angle of approximately 90 from the position in which the pressure-reducing valve 39 is in the position in which the slots 5% register with the passage 42 and the port 44 into the position shown in FIG. 3. Thus, during the range of settings of the governor spring 53A corresponding to operation of the engine incorporating the fuel system at appreciable power and/or speed, fuel is delivered to the injection device substantially without restriction and substantially at full delivery pressure throughout the whole of each delivery period, through the passage d2, the lots 5ft, the annulus W. the passage ed and the delivery passage 7, whereas when the setting of the governor spring 53A is that corresponding to idling conditions or operation at low power, the fuel is delivered to the delivery passage 7 throughout the whole of each delivery period at a reduced pressure determined by the pressure-reducing valve 39 and at a rate which is a function jointly of the reduced pressure and the effective cross-sectional area of the restrictor M. In this arrangement therefore the injection characteristics under load-running conditions are similar to those in systems to which the invention is not applied but during idling conditions a lower rate of injection by reason of the reduced pressure will be in operation.

in the modification shown in FIG, 5, which may be regarded as a diagrammatic illustration of an arrangement of pressurereducing valve assembly generally similar to that shown in FIG. 2, the pressure-reducing valve, here identified by the reference numeral M, is similar to the pressure-reducing valve 237 in FIG. 2 except that, instead of the open passage 36 through which liquid pressure can be: applied directly to the piston member 31. in FIG. .2, the pressure-reducing valve 6d is provided with a passage 65 which opens into a chamber M5 which is separated by a restricted passage as from a chamber b7 in which liquid pressure acts on the piston member 32. The springs 6W and 7b shown diagrammatically in this construction correspond respectively to the

springs

29 and 33 in FIG. 2 while the passage 7ll communicates with the inlet 6 of the injection device. The chambers as and 67 are formed in a restrictor plug titlA fixed in the bore of the valve body.

in this construction, therefore, the operation is similar to that of the construction shown in FIG. 2 except that the rate of movement of the piston device 32 during the initial part of each delivery period, before it uncovers the

ports

22 and 25 to permit unrestricted flow of fuel from the passage 2 to the delivery passage 7, is a function of the reduced pressure determined by the pressure-reducing valve and at which fuel passes into the chamber as and of the effective cross-sectional area of the restrictor 6ft. In effect therefore the arrangement may be regarded as similar to that shown in FIG. 2 but with the restriction 35 moved from the position shown in FIG. 2. into a position between the pressure-reducing valve 27 and the piston valve member 32.

What we claim as our invention and desire to secure by Letters Patent is:

l. A fuel injection system for internal combustion engines of the liquid-fuel-injection compression-ignition type, and comprising a fuel injection device including a nozzle, a pressure chamber leading to the nozzle, and an injection valve controlling the flow of fuel from the pressure chamber to the nozzle, said injection system also comprising fuel delivery means arranged to deliver fuel under supply pressure in predetermined quantities at appropriately timed intervals to a pressure-reducing valve having an outlet connected to the said pressure chamber, said pressure-reducing valve having an orifree of variable cross-sectiona1 area through which passes the flow of fuel delivered by said fuel delivery means, the crosssectional area of said orifice being automatically controlled by and in accordance with the'fluid pressure downstream of said orifice to regulate said downstream fluid pressure to a constant reduced value substantially less than said supply pressure irrespective of variations in said supply pressure, said injection valve being opened automatically during each delivery period by the fuel pressure in said pressure chamber, and said pressure reducing valve when operative acting in each delivery period to reduce the fuel pressure at which fuel is delivered from the pressurereducing valve into said pressure chamber to said constant reduced value and a restricted metering passage of fixed cross section arranged in series with the pressure-reducing valve and serving when the pressure-reducing valve is operative to control the rate at which fuel is delivered to the pressure chamber at the said constant reduced pressure,

and means for rendering the pressure-reducing valve and the metering passage inoperative during periods when the delivery of fuel to the pressure chamber at substantially the full supply pressure is required.

2. A fuel injection system as claimed in claim 1 in which the said means for rendering the pressure reducing valve inoperative is arranged to maintain the pressure reducing valve operative during a predetermined initial part of each delivery period and to bypass the pressure reducing valve during the remainder of that delivery period.

3. A fuel injection system as claimed in claim 2, in which there is interposed between the pressure reducing valve and the pressure chamber a piston valve device which has a pressure face on which the output pressure of the pressure reducing valve acts to move the piston valve device against a biassing force, and a working face serving during the initial part of the said movement of the piston valve device to deliver fuel at the said constant reduced pressure to the pressure chamber and in which, after the said initial period of its movement, the further movement of piston valve device opens a passage which bypasses the pressure reducing valve to permit the flow of fuel to the pressure chamber at substantially the full supply pressure of the fuel delivery means.

4. A fuel injection system for internal combustion engines of the liquid-fuel-injection compression-ignition type, and comprising a fuel injection device including a nozzle, a pressure chamber leading to the nozzle, and an injection valve controlling the flow of fuel from the pressure chamber to the nozzle, said injection system also comprising fuel delivery means arranged to deliver fuel under supply pressure in predetermined quantities at appropriately timed intervals to a pressure-reducing valve having an outlet connected to the said pressure chamber, said injection valve being opened automatically during each delivery period by the fuel pressure in said pressure chamber, and said pressure-reducing valve when operative acting in each delivery period to reduce the fuel pressure at which fuel is delivered from the pressure-reducing valve into said pressure chamber to a determined constant reduced value substantially below the full supply pressure of the fuel delivery means, and means for rendering the pressurereduction valve inoperative during periods when the delivery of fuel to the pressure chamber at substantially the full supply pressure is required, said means for rendering the pressurereducing valve inoperative being arranged to maintain the pressure-reducing valve operative during a predetermined initial part of each delivery period and to bypass the pressurereducing valve during the remainder of that delivery period, there being a piston valve device interposed between the pressure-reducing valve and the pressure chamber, said piston valve device having a pressure face on which the output pressure of the pressure-reducing valve acts to move the piston valve device against a biasing force, and a working face serving during the initial part of the said movement of the piston valve device to deliver fuel at the said constant reduced pressure to the pressure chamber, said piston valve, after the said initial period of its movement, being operable upon further movement to open a passage which bypasses the pressurereducing valve to permit the flow of fuel to the pressure chamber at substantially the full supply pressure of the fuel delivery means, said pressure-reducing valve also controlling a relief port on the pressure face side of the fuel delivery means, said pressure-reducing valve also controlling a relief port on the pressure face side of the piston valve device, the pressurereducing valve being arranged to open the relief port between fuel delivery periods to permit the return movement of the piston valve device, and to close the relief port during its initial movement at the start of each delivery period.

5. A fuel injection system as claimed in claim 4, including a restricted passage arranged in series with the pressure-reducing valve and serving when the pressure-reducing valve is operative to control the rate at which fuel is delivered to the pressure chamber at the said constant reduced pressure.

6. A fuel injection system as claimed in claim 5, in which the restricted passage is disposed between the working face of the piston valve device and the pressure chamber.

7. A fuel injection system as claimed in claim 5, in which the restricted passage is disposed between the pressure-reducing valve and the pressure face of the piston valve device.

8. A fuel injection system for internal combustion engines of the liquid-fuel-injection compressiomignition type, and comprising a fuel injection device including a nozzle, a pressure chamber leading to the nozzle, and in injection valve controlling the flow of fuel from the pressure chamber to the nozzle, said injection system also comprising fuel delivery means arranged to deliver fuel under supply pressure in predetermined quantities at appropriately timed intervals to a pressure-reducing valve having an outlet connected to the said pressure chamber, said-injection valve being opened automatically during each delivery period by the fuel pressure in said pressure chamber, and said pressure-reducing valve when operative acting in each delivery period to reduce the fuel pressure at which fuel is delivered from the pressure-reducing valve into said pressure chamber to a determined constant reduced value substantially below the full supply pressure of the fuel delivery means, and means for rendering the pressurereducing valve inoperative during periodswhen the delivery of fuel to the pressure chamber at substantially the full supply pressure is required, said means for rendering the pressurereducing valve inoperative being arranged to be operated by a control member serving to control directly or indirectly the running of the engine to which the system is applied.

9. A fuel injection system as claimed in claim 8 in which the control member is arranged to control directly the quantity of fuel delivered by the fuel delivery means during each delivery period.

10. A fuel injection system as claimed in claim 8 in which the control member controls the setting of a speed-responsive governor driven by the engine and actuating a fuel-metering control by which the quantity of fuel delivered during each delivery period is varied.

11. A fuel injection system for internal combustion engines of the liquid-fuel-injection compression-ignition type, and comprising a fuel injection device including a nozzle, a pressure chamber leading to the nozzle, and an injection valve controlling the flow of fuel from the pressure chamber to the nozzle, said injection system also comprising fuel delivery means arranged to deliver fuel under supply pressure in predetermined quantities at appropriately timed intervals to a pressure-reducing valve having an outlet connected to the said pressure chamber, said injection valve being opened automatically during each delivery period by the fuel pressure in said pressure chamber, and said pressure-reducing valve when operative acting in each delivery period to reduce the fuel pressure at which fuel is delivered from the pressure-reducing valve into said pressure chamber to a determined constant reduced value substantially below the full supply pressure of the fuel delivery means, and means for rendering the pressurereducing valve inoperative during periods when the delivery of fuel to the pressure chamber at substantially the full supply pressure is required, said pressure-reducing valve comprising a valve housing containing a movable cylindrical valve shuttle which is rotatable in a surrounding cylindrical bore in the valve housing in addition to being axially movable therein, the shuttle when in a first orientation in the bore moving axially against an axial biasing force in response to variations in the delivery pressure of the valve to regulate the said delivery pressure, but when turned into a second orientation in the bore providing an unrestricted flow passage through which the full supply of pressure of the fuel delivered means is transmitted through the valve to the pressure chamber, and in which the means for bypassing or rendering the valve inoperative comprises means for rotating the valve shuttle into the second orientation.

12. A fuel injection system as claimed in claim 11 in which the valve shuttle is formed with a circumferential groove the said means for rendering the pressure-reducing valve inoperative is arranged to be operated by a control member serving to control directly or indirectly the running of an engine to which the system is applied, and in which the said control member is coupled to the valve shuttle by a transmission arranged to rotate the valve shuttle in response to control movements of the said control member.

Claims

1. A fuel injection system for internal combustion engines of the liquid-fuel-injection compression-ignition type, and comprising a fuel injection device including a nozzle, a pressure chamber leading to the nozzle, and an injection valve controlling the flow of fuel from the pressure chamber to the nozzle, said injection system also comprising fuel delivery means arranged to deliver fuel under supply pressure in predetermined quantities at appropriately timed intervals to a pressure-reducing valve having an outlet connected to the said pressure chamber, said pressurereducing valve having an orifice of variable cross-sectional area through which passes the flow of fuel delivered by said fuel delivery means, the cross-sectional area of said orifice being automatically controlled by and in accordance with the fluid pressure downstream of said orifice to regulate said downstream fluid pressure to a constant reduced value substantially less than said supply pressure irrespective of variations in said supply pressure, said injection valve being opened automatically during each delivery period by the fuel pressure in said pressure chamber, and said pressure reducing valve when operative acting in each delivery period to reduce the fuel pressure at which fuel is delivered from the pressure-reducing valve into said pressure chamber to said constant reduced value and a restricted metering passage of fixed cross section arranged in series with the pressure-reducing valve and serving when the pressure-reducing valve is operative to control the rate at which fuel is delivered to the pressure chamber at the said constant reduced pressure, and means for rendering the pressure-reducing valve and the metering passage inoperative during periods when the delivery of fuel to the pressuRe chamber at substantially the full supply pressure is required.

4. A fuel injection system for internal combustion engines of the liquid-fuel-injection compression-ignition type, and comprising a fuel injection device including a nozzle, a pressure chamber leading to the nozzle, and an injection valve controlling the flow of fuel from the pressure chamber to the nozzle, said injection system also comprising fuel delivery means arranged to deliver fuel under supply pressure in predetermined quantities at appropriately timed intervals to a pressure-reducing valve having an outlet connected to the said pressure chamber, said injection valve being opened automatically during each delivery period by the fuel pressure in said pressure chamber, and said pressure-reducing valve when operative acting in each delivery period to reduce the fuel pressure at which fuel is delivered from the pressure-reducing valve into said pressure chamber to a determined constant reduced value substantially below the full supply pressure of the fuel delivery means, and means for rendering the pressure reducing valve inoperative during periods when the delivery of fuel to the pressure chamber at substantially the full supply pressure is required, said means for rendering the pressure-reducing valve inoperative being arranged to maintain the pressure-reducing valve operative during a predetermined initial part of each delivery period and to bypass the pressure-reducing valve during the remainder of that delivery period, there being a piston valve device interposed between the pressure-reducing valve and the pressure chamber, said piston valve device having a pressure face on which the output pressure of the pressure-reducing valve acts to move the piston valve device against a biasing force, and a working face serving during the initial part of the said movement of the piston valve device to deliver fuel at the said constant reduced pressure to the pressure chamber, said piston valve, after the said initial period of its movement, being operable upon further movement to open a passage which bypasses the pressure-reducing valve to permit the flow of fuel to the pressure chamber at substantially the full supply pressure of the fuel delivery means, said pressure-reducing valve also controlling a relief port on the pressure face side of the piston valve device, the pressure-reducing valve being arranged to open the relief port between fuel delivery periods to permit the return movement of the piston valve device, and to close the relief port during its initial movement at the start of each delivery period.

8. A fuel injection system for internal combustion engines of the liquid-fuel-injection compression-ignition type, and comprising a fuel injection device including a nozzle, a pressure chamber leading to the nozzle, and in injection valve controlling the flow of fuel from the pressure chamber to the nozzle, said injection system also comprising fuel delivery means arranged to deliver fuel under supply pressure in predetermined quantities at appropriately timed intervals to a pressure-reducing valve having an outlet connected to the said pressure chamber, said injection valve being opened automatically during each delivery period by the fuel pressure in said pressure chamber, and said pressure-reducing valve when operative acting in each delivery period to reduce the fuel pressure at which fuel is delivered from the pressure-reducing valve into said pressure chamber to a determined constant reduced value substantially below the full supply pressure of the fuel delivery means, and means for rendering the pressure-reducing valve inoperative during periods when the delivery of fuel to the pressure chamber at substantially the full supply pressure is required, said means for rendering the pressure-reducing valve inoperative being arranged to be operated by a control member serving to control directly or indirectly the running of the engine to which the system is applied.

11. A fuel injection system for internal combustion engines of the liquid-fuel-injection compression-ignition type, and comprising a fuel injection device including a nozzle, a pressure chamber leading to the nozzle, and an injection valve controlling the flow of fuel from the pressure chamber to the nozzle, said injection system also comprising fuel delivery means arranged to deliver fuel under supply pressure in predetermined quantities at appropriately timed intervals to a pressure-reducing valve having an outlet connected to the said pressure chamber, said injection valve being opened automatically during each delivery period by the fuel pressure in said pressure chamber, and said pressure-reducing valve when operative acting in each delivery period to reduce the fuel pressure at which fuel is delivered from the pressure-reducing valve into said pressure chamber to a determined constant reduced value substantially below the full supply pressure of the fuel delivery means, and means for rendering the pressure-reducing valve inoperative during periods when the delivery of fuel to the pressure chamber at substantially the full supply pressure is required, said pressure-reducing valve comprising a valve housing containing a movable cylindrical valve shuttle which is rotatable in a surrounding cylindrical bore in the valve housing in addition to being axially movable therein, the shuttle when in a first orientation in the bore moving axially against an axial biasing force in response to variations in the delivery pressure of the valve to regulate the said delivery pressure, but when turned into a second orientation in the bore providing an unrestricted flow passage through which the full supply pressure of the fuel delivery means is transmitted through the valve to the pressure chamber, and in which the means for bypassiNg or rendering the valve inoperative comprises means for rotating the valve shuttle into the second orientation.

12. A fuel injection system as claimed in claim 11 in which the valve shuttle is formed with a circumferential groove which cooperates with a pressure port in the side of the bore to provide the variable-area valve orifice for regulating the delivery pressure, and is formed in its cylindrical surface with one or more longitudinal grooves leading into the said circumferential groove, one or more of the longitudinal grooves being arranged to overlap the pressure port and provide the unrestricted flow passage when the shuttle is turned into its second orientation.

13. A fuel injection system as claimed in claim 12 in which the said means for rendering the pressure-reducing valve inoperative is arranged to be operated by a control member serving to control directly or indirectly the running of an engine to which the system is applied, and in which the said control member is coupled to the valve shuttle by a transmission arranged to rotate the valve shuttle in response to control movements of the said control member.