US2984231A

US2984231A - Fuel injection system

Info

Publication number: US2984231A
Application number: US819798A
Authority: US
Inventors: Clessie L Cummins
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-07-29
Filing date: 1959-05-26
Publication date: 1961-05-16
Anticipated expiration: 1978-05-16

Description

May 16, 1961 Origmal Filed July 29, 1957 C. L. CUMMINS FUEL INJECTION SYSTEM 3 Sheets-Sheet 1 INVENTOR CLESSIE L.CUMM|N$ ATTORNEY Q FIG.- 3

United States Patent FUEL INJECTION SYSTEM Clessie L. Cummins, 80 Cloudvievv Road, Sausalito, Calif.

Original application July 29, 1957, Ser. No. 674,702. Divided and this application May 26, 1959, Ser. No. 819,798

8 Claims. (Cl. 123-140) My invention relates to improvements in the fuel injection systems of compression ignition internal combustion engines and injectors therefor. The invention also lends additional value and usefulness to the fuel supply apparatus shown in my Patent No. 2,670,725 and can be incorporated with the braking apparatus shown in my co-pending application S.N. 662,494 filed May 29, 1957, "now abandoned. This application is a division of application Serial No. 674,702, filed July 29, 1957.

For a long time, one of the serious problems facing the compression ignition engine industry has been to discover a fuel injection mechanism that would require an absolute minimum of servicing, that would have a long life, that would be simple, and that would require no special attention being paid, at the time of installation, to the fuel piping to and from the engine. This last requirement, as well as others enumerated, is met by the present invention.

The critical balance of pressures required by existing systems in controlling proper values of the several metering points in the fuel injection system in order to deliver the proper amount of fuel into the combustion chamber has been and continues a major problem. By means of my invention it is now possible for an engine manufacturer to ship an engine to a user, adjusted on a dynamometer at the factory to deliver the required horsepower, and for the installer to install the engine without further calibration, and without the necessity of periodically recalibrating the fuel system. Also by my invention the installer in connecting the engine to the fuel source, is no longer required to provide return line piping of special size, with each bend and restriction critical to the operation of the engines fuel system.

An illustration of how serious a problem this is can be seen in this: On an expensive yacht where an engine with the prior art balanced pressure fuel supply system was installed, two fuel tanks were used. In the process of changing from the empty tank to the full tank, the mechanic shut off the fuel return lines to both tanks. The engine immediately began to increase its speed, even though the throttle was not advanced. It did this because the extra fuel which normally passed to the tank via the return line was now being forced into the engine. Fortunately the mechanic realized what was happening and he succeeded in opening the valve in the return line before the engine disintegrated. This occurred because the balance in pressures provided by critically selected orifices in the fuel return line was disturbed. The foregoing is one of several like instances resulting from the same cause, namely, disturbing the balanced pressures in the fuel return line and in the fuel feed line.

It is, therefore, one object of my invention to make the installation and operation of compression ignition engines independent of a fuel return line; or of having to maintain balanced pressures if a return line is used; or of the hazards that at present are known to exist where a balance of pressures is relied on in regulating the fuel fed to the engine.

2,984,231 Patented May 16, 1961 Another serious problem facing the compression ignition engine industry today is to get better combustion in the cylinders. A symptom of the relatively poor combustion in the compression ignition engine of today is the cackle noise, an indication of delayed ignition. Delayed ignition, on an engine of the Cummins type, means that there has been a poor or inadequate preparation of the fuel and air so that when they are injected into the combustion chamber, the mixture does not immediately begin to burn, but instead, the burning begins after a substantial portion of the fuel is in the combustion chamber. Because of the delayed start in the burning, and the relatively large amount of fuel in the cylinder by that time, the combustion pressure rises momentarily to an excessive point to cause the cackle. Because the combustion is delayed, its force against the piston comes late in the stroke so that full advantage of the expansion of the burning mixture is: not obtained. This loss, multiplied three times for each revolution in a six cylinder engine turning 2100 r.p.m., means 6300 losses each minute from the maximum possible.

A homely illustration of delayed ignition is that of a housewife turning on the gas in an oven before she has a match in hand to light the burner. By the time she has lighted the match and applied it to the burner the amount of gas accumulated in the oven produces a noise as it explodes; whereas, if she has the lighted match at the burner when she turns on the gas, there is no explosion, or noise, and she can open the valve wide without producing an explosion.

7 An object of the present invention is, therefore, to provide a structure by which the fuel and air are so thoroughly mixed and heated that upon injection into the combustion chamber the burning of the fuel mixture will begin without delay.

Another problem having to do with the Cummins type injection engine arises from the physical wear and tear on the injection mechanism where some or all of the fuel remains in solid form at the time of injection. This is due to imperfect preparation and mixing of the air and fuel in the plunger chamber.

y An object of the present invention is therefore to provide a novel form of injector mechanism which 00- operates with the compressed air forced into the plunger chamber from the cylinder to produce two impinging streams which effect an even distribution and mixing of fuel and air throughout the plunger chamber.

I have discovered that other problems heretofore existing in fuel injection systems are solved by making each injection device with the fuel supply port arranged in the wall of the injector housing bore so that the port is never uncovered upon the retraction stroke of the inector plunger, but instead is indexed with a cross port in the plunger. This location of the fuel supply port leads to another advantage in that it requires a fuel passageway from the cross port down through the inector plunger. This passageway may take the form of an axial bore extending from somewhere on the tip of the injector, upwardly to the cross port, the latter being adapted to index with the fuel supply port in the wall of the injector housing bore. This conducts relatively cool fuel down through the plunger body so the plunger is cooled evenly. This even cooling means less tendency for the plunger to warp or swell. Also it delivers the fuel at or near the center of the plunger chamber in the injector housing so that the hot compressed air coming into this chamber through the spray orifices will impinge with it and will mix more evenly. This has a Very beneficial elfectin preparing the fuel mixture, because it appears to release the more volatile fractions in the fuel as it is mixed with the hot air.

Another advantage of my fuel injection mechanism is that it places the working areas of the plunger cross port and of the fuel supply port up away from the working end of the plunger and in the area where more accuracy in dimensions can be maintained. It is a well known fact that a bore tends to bellmouth at its ends and a plunger tends to be slightly under-sized at its end.

Another problem with one current form of injector device, which has the fuel inlet port positioned in the plunger chamber, is that the hot gases coming up into the plunger chamber from the combustion chamber will leak past the end of the plunger into the fuel inlet port. There these hot gases will tend to dry out the fuel and to leave a carbon deposit on the walls of the fuel conduit. This affects engine performance so seriously that it is necessary periodically to clean out this carbon deposit. One object of the present invention is to eliminate this problem.

Another important advantages of my invention over prior devices is that the fuel supply port in the injector housing and the cross port in the injector plunger are both located where the housing can be of sutficient thickness so that it will not change shape during assembly or use.

A further advantage of my new fuel injector construction is that it lends itself to a fuel system in which the injector plunger can be immobilized when the vehicle in which the engine is installed is coasting, and during this coasting period fuel can be circulated around the plunger to cool it and to carry away any air bubbles which may be blown up from the combustion chamber through the plunger chamber.

Other objects and advantages of my invention will become apparent from the following description and the accompanying drawings in which:

Fig. 1 is a schematic diagrammatic view of one form of my improved fuel and injector system showing the piping and the control circuits;

Fig. 2 is a view in cross section of a modified form of injector mechanism having provision for the circulation of fuel when the engne is being motored, as when coast- 111g;

Fig. 3 is a view in cross section of the tip end of the injector of Fig. 2 showing a modified form of plunger tip and one having fewer lubrication channels;

Fig. 4 is like Fig. 3 with the extra lubrication channels omitted;

Fig. 5 is a view in cross section of the tip end of an injector with the plunger having a check valve in the fuel passageway;

Fig. 6 is an enlarged fragmental view of the check valve in Fig. 5;

Figs. 7 and 8 are views like Figs. 5 and 6 respectively showing another form of check valve;

Fig. 9 is a diagrammatic view showing a modified form of cam to achieve a two-stage operation of the plunger;

Fig. 10 is an enlarged diagrammatic view showing the impinging streams of hot gas and fuel in the plunger chamber;

Fig. 11 is an alternative form of switch actuator for the fuel system control.

Since portions of the fuel system shown diagrammatically in Fig. 1 are described and claimed in my Patent 2,670,725, only those parts will be referred to here which are necessary to an understanding of its application to the present invention. Where possible the same reference numerals are used as in my Patent No. 2,670,725. These parts are described under the section headed The Fuel Supply System, which section will follow the description now of my novel fuel injection mechanism. Subsequently I shall describe the Scavenging System shown in Figs. 1 and 2.

The fuel injection mechanism The injector mechanism shown in Fig. 1 is a preferred form of my invention but it is understood-that variations 4 of proportions and dimensions may be made while still retaining the essential features of the device. In Fig. I only one of the six injectors 96 needed in a six cylinder engine is shown. It is connected to the common rail 35, to which the fuel is fed from the fuel supply system, by a header branch 100. As shown in Fig. 2 the injector is secured in the top of the engine cylinder 101 so that its spray nozzles 102 project into the combustion chamber 103.

The injector body 104 has a cylindrical bore 105 tapered at its lower end to form a plunger chamber 106, which chamber has a perforation 107 connected to the radially directed holes 102 forming the orifices through which the fuel is sprayed into the combustion chamber. The injector plunger 98 has a tapered end 109 to fit the end of the bore 105 in which it is reciprocable. It is pushed downwardly therein in timed sequence by the camshaft 108 and rocker arm 110. It is retracted by the spring 111. t

The injector body 104 is bored to provide channels or

passages

112, 113, 114, for the feeding of fuel to and from the bore 105. The

channels

113 and 114 terminate in

ports

116 and 117 respectively in the wall of the bore 105 facing the plunger 98. I shall refer to port 116 as the fuel inlet port, and to port 117 as the scavenging port.

The

ports

116 and 117 are located up the bore 105 far enough from the plunger chamber 106 so that when the plunger 98 is at the top of its upward stroke its edge 118, where the taper 109 starts, will not have uncovered the ports. In other words, when the plunger 98 is at the end of its upward stroke away from the nozzles 102 the inlet port 116 remains covered by the plunger. This means that for fuel to get out of the inlet port 116 down into the plunger chamber 106, it must go through a passageway in the plunger because there is too close a fit of the plunger in the bore to have the fuel leak down the bore wall past the plunger. If this close fit did not exist, the plunger would fail to function properly in forcing the fuel out of the plunger chamber 106 through the nozzles 102 and into the combustion chamber 103 because the pressure at the time of fuel injection is in the range of 800 pounds p.s.i. to several thousand pounds p.s.i. I have found that in an injector with a plunger in diameter, the distance from X to Y can be from %1" to one inch. (See Figs. 1 and 5.)

It is important to keep the fuel inlet port 116 far enough up on the bore wall so that it is where the injector body is thick and is not subject to distortion. Another factor to bear in mind in locating the fuel inlet port 116 is the facility with which a passageway 124 may be drilled up the injector plunger 98. The point to have in mind always is that the inlet port 116 must be high enough so that it is not uncovered by the edge 118 of the plunger when the latter is at the top of its stroke.

Another point to have in mind is that the cross channel 120 in the plunger 98 should have its

ends

121 and 122 so they align or index with the fuel inlet port 116 when the plunger is at the top of its stroke (see Figs. 4, 5, 7). The plunger preferably is grooved annularly ,at 123 to connect

ports

121 and 122 and to make indexing with the port 116 a certainty. The distance from the lower edge of the annular groove 123 to the edge 118 is equal to the distance from X to Y minus the stroke of the plunger (see Fig. 5).

The passageway down through the plunger 98 from the cross channel 120 may take the form of a straight drilled hole 124 as shown in the drawings. Since reliance is placed on the pressure of the fuel supply mechanism to get the correct amount of fuel into each fuel injector, no particular metering or orifice size is necessary in the plunger 98 inasmuch as all conduits in all injectors will be of substantially equal size. If it were practical with production tools, the hole 124 would be made the size of hole 125, and no insert bushing would be needed, but'since it is not practical to drill so small a hole for sucha distance, I employ inserts 126 as in Figs. 3 and 4'; The small size hole has the advantageoftend ing to atomize the fuel entering the plunger chamber 106 as part of, the fuel preparation before injection, and is as large a hole as is needed.

With my improved fuel injection system it is optional whether a return line from the injectors is provided, and where it is used I arrange for it to be effective only when the engine is being motored, as when an engine in a vehicle is coasting with the throttle closed. Under this operating condition some air may find its way up into the plunger chamber 106 in each injector and require disposal so it will not delay production of power when the coasting ends.

The injector plunger 98 as shown in Figs. 5 to 8 has an added feature to which attention should be called, namely, a check valve 127 secured to the end of a hollow shank 129 slidable in the channel 124. The check valve can close the channel 124 so that pressure from the combustion chamber cannot force the fuel back up the inlet channel 112. In Fig. 5 the check valve seats on the beveled rim 1 28 and in Fig. 7 it seats on the beveled end 130 of the plunger. In Figs. 7 and 8, the clearance on the pin 129a determines the stroke of the shank 129, whereas in Figs. 5 and 6, the shoulder 129 determines the stroke. In neither case is a spring used to keep the valve seated, as any difference in spring rates could affect the amount of fuel delivered to the several injectors. The valve in each case is caused to seat by the inertia force resulting from sudden downward movement of the plunger 98 and it is held seated by the pressure rise in the plunger chamber 106 during injection. Likewise on the upward stroke of the plunger 98 the inertia causes the check valve 127 to open so that by the time the fuel port 116 is aligned with the cross bore 120, there is an open passage down through the plunger into the plunger chamber, through which the fuel flows without restriction from the header 35. This assures equal feeding of fuel to each cylinder and is distinguished from earlier constructions where a spring loaded check valve had to be opened and held open by the pressure of the fuel. Under these latter conditions, any unequal spring loading or difference in area of the seating of the valve (where spring pressed) would cause an unequal feeding of fuel resulting in loss of horsepower and a rough running engine.

The two-stage injector In Fig. 9 is shown a further modification of my fuel injection system which might be characterized as a twostage system. A special cam 108a is employed to actuate each plunger. The cam is flattened at 108b so the spring 111 retracts the plunger 98 earlier than normal and an additional amount above that required for normal injection. When so retracted, it is indexed with the fuel supply port 116 and receives the fuel charge. Then as the cam moves from the surface 10% to the surface 'M to N, it holds the plunger with the fuel inlet port 116 closed. The beneficial effects this has on the system are (a) that the injector receives its charge of fuel early and the inlet port 116 is sealed off before there is any appreciable pressure in the plunger chamber 106; (b) that the cam 108a moves the plunger 98 far enough to seal off the port 116 and to prevent the fuel or air from escaping back into the supply line 112; (c) that the plunger, after sealing off the port 116, still has its full stroke for building up its required pressure for proper injection and has not used up part of its effective stroke for the charging interval; and (d) that the additional stroke gives that much more sealing area along the surface of the plunger 98 and the wall of the bore 105.

Summary of the fuel injection mechanism Summarized, what my invention provides is a fuel injection system for an internal combustion engine including a' combustion chamber '103, an injector body 96 secured therein havinga bore closed at its lower end to form a plunger chamber 106, said chamber'ha'ving at least one orifice 107 therein to distribute thezfuel into the combustion chamber; an injector plunger 98 reciprocablein the bore 105; cam means 108 for reciprocating the plunger in the bore in predetermined timed sequence; a fuel feeding mechanism 20 for supplying fuel to an inlet port 116 in the injector body, the injector body being characterized by having the fuel inlet port 116 in the wall of the bore 105, facing the plunger 98, and spaced along the wall so that when the plunger is at the end of its retraction stroke, the inlet port 116 remains covered by the plunger; the plunger 98 being characterized by having passage means 120, 121, 122, 124, therein which open at 125 into the plunger chamber 106 and open at 123 adjacent the inlet port 116 in the bore wall, the latter opening 123 being spaced on the plunger 98 so that indexing with the inlet port 116 occurs only when the plunger 98 is at the end of its retraction stroke. In this way the fuel feeding means 20 will cause fuel to enter the passage means 123, '120, 124, 125 when the plunger is at the end of its retraction stroke thereby feeding a predetermined amount of fuel into the plunger chamber 106, which fuel will be forced through the

orifice

107, 102 into the combustion chamher 103 when the plunger 98 is moved on its injection stroke.

Reference was made earlier to one of the advantages of my system being that the injector plunger 98 is working on a homogeneous compressible gaseous mixture, rather than on partially solid fuel. Fig. 10 assists in understanding what occurs where the introduction of the fuel into the plunger chamber 106 is done at or near the center. As the hot compressed air is forced into the plunger chamber 106 through the

openings

102, 107, it impinges on the fuel entering from directly above it. This mixes the two and the air fuel mixture is evenly distributed in the plunger chamber 106. In Fig. 10 the direction arrows a indicate the stream of hot air from the combustion chamber and the arrows f indicate the fuel leaving the central passage 124 in the injector plunger 98. The impinging of these oppositely moving columns produces a desirable mixing and distribution of the fuel and air.

In the prior art devices where the fuel is introduced into the chamber through a hole on the side of the plunger chamber, a thorough mixing does not occur, therefore, in seating, the plunger will engage solid fuel on one side and air on the other side, resulting in undue strain on the injector parts. Also, in prior art engines, because the fuel is not completely mixed as it is injected into the combustion chamber, the fuel will be delayed in igniting and the engine will cackle.

The fuel supply system While the injector mechanism set forth herein is adapted for use with various forms of fuel feeding devices, it is particularly suited to use with the fuel supply system of my Patent No. 2,670,725, which I have incorporated in Fig. 1 of the drawings of this present case.

The fuel apparatus may include, as a means to conduct fuel to the engine, either a distributor by which flow to the respective injectors 96 is determined or may omit the distributor and have the fuel injectors for the respective cylinders connected to a common rail which in turn is connected to the fuel supply or conduit. In the case where a distributor is utilized, the period of overlap between asupply passage in the distributor and each of the passages leading to the respective injectors determines the time factor. In the case where the distributor is eliminated, each of the fuel injectors is provided with a cam operated plunger 98 which opens and closes a supply port 116 in the injector in timed relation'to the operation of the engine and thus determines the time of opening.

In a fuel supply apparatus of the character herein contemplated where the fuel is maintained under constant pressure, a constant area of opening for the metering orifice would result in a greater fuel delivery to the engine as its speed decreases. This fact becomes evident in considering a distributor since the time during which the supply passage and each of the passages leading to the cylinders are overlapping increases with a decrease in engine speed. Similarly, the time that the supply port 116 in an injector is opened by the plunger is increased as the speed of the engine decreases. As a result, when the engine speed is pulled down by an increased load for a given throttle sett ing, the engine torque curve would rise above acceptable limits under such conditions, and thus overload the engine.

The invention of my Patent 2,670,725 overcomes this difficulty by providing a variable orifice in the line between a source of fuel under constant pressure and the distributor or fuel injectors, as the case may be, with the effective area of the variable orifice regulated by a governor to so control the fuel flow to the engine that .any desired torque at maximum throttle opening may be obtained throughout the speed range of the engine. Such variable orifice may be provided by a needle or other type valve operable by the governor and connected with another variable orifice provided by a second needle or other type valve, also under control of the governor but acting oppositely to the first mentioned valve and operable to determine the maximum speed of the engine. In series with these two valves is a manually operable throttle which may also have the form of a needle valve.

The apparatus is also so arranged that an idling speed control is provided, which is connected to the governor for automatic operation.

While my present fuel injection mechanism is illustrated in an embodiment like Patent No. 2,670,725 in which the fuel is maintained under substantially con stant pressure throughout the speed range of the engine, the invention is equally applicable to a fuel pressure which may be varied with the engine speed but is constant for any given speed, and in that case the shape of the first mentioned needle valve is varied to compensate for such variation in pressure. The term constant pressure as used is therefore in the broader sense and is not limited to the idea of a constant pressure throughout the speed range of the engine.

The fuel supply system shown diagrammatically in Fig. 1 is of such form that it may be mounted at any convenient location on the engine and may comprise a main casing or housing 20, a pump casing 21 with the governor mounted on the housing 20. Fuel for the engine is adapted to be drawn from a fuel supply tank (not shown) through piping adapted to be connected to a fitting 22 carried by the pump casing and leading to the intake passage 23 of a pump 24 which may be of the gear type or other suitable form. The gear pump 24 discharges fuel into a passage 25 adapted to drain into a float tank 26. The float tank 26 is provided with a float controlled valve 27 to shut off the flow of fuel supplied by the pump 24 when the fuel in the float chamber reaches a predetermined level. When the valve 27 closes the discharge passage 25, a relief passage 30 controlled by a pressure relief valve 31 permits the fuel delivered by the pump 24 to be returned to the intake side thereof.

The source of fuel under constant pressure in the present instance comprises a second pump 32 herein illustrated as a gear pump having a passage 33 for returning "the fuel, in excess of that used by the engine, to the intake side of the pump 32 with a pressure regulator 34 mounted in the passage 33. The pressure regulator'34 is of the type which maintains the pressure of the fuel at the delivery side of the pump 32 at a constant value so that there will be little, if any, variation in pressure to affect the flow of fuel through the remainder of the apparatus.

From the pump 32, fuel flows through conduit means provided by passages formed chiefly in the main housing 20, to the respective injectors 96, and the flow is controlled by valve means mounted in such passages. The main conduit or passage 36 extends from-the second gear pump 32 and is connected to the common rail 35 through a series of valves. Thus the main conduit 36 has a manually operable valve in the form of a needle valve 37 which constitutes the throttle for the engine. Beyond the throttle 37, the main passage is extended, as at 4%, to open into a valve chamber 39. In the latter is a governor-controlled valve 41, also in the form of a needle valve, cooperating with the opening of the passage 40 into the chamber 39 to provide a variable orifice. From the needle valve 41 the main passage is still further extended, as at 42, to open into a valve chamber 47 having a third needle valve 43 mounted therein, which is also governor-controlled. The needle valve 43 cooperates with the opening of the passage 42 into the chamber 41 to provide another variable orifice. From the latter, the main passage continues, as at 44, to the common rail 35 with a shut-off valve 45 placed in the continuation 44.

As mentioned above, both the valve 41 and the valve 43 are under the control of the governor, which is here indicated at 46. The governor 46 is illustrated as comprising a pair of centrifugal weights 50 pivotally carried by a rotating head 51 mounted on and driven by a main shaft 52. The drive shaft 52 is journaled in the governor casing to the left of casing 20 and is there provided with means (not shown) adapted to be connected to and driven by the engine.

The governor weights 50 are provided with inwardly turned fingers 55 adapted to engage a collar 56 mounted on a stub shaft near its end. The governor weights 50 are so positioned that as the speed of the engine increases and the weights tend to move outward, the collar 56 will be moved to the left. Resisting such movement of the collar is a spring means, indicated generally at 57, and interposed between the collar 56 and the driving head 51. The collar 56 includes a sleeve 60 on which are provided a pair of spaced flanges 61 and 62. Mounted above the flanges 61 and 62 in the casing 20 and extending transversely to the drive shaft 52 is a rock shaft 63, journaled at its ends in the casing 20. Secured on the rock shaft 63, intermediate its end, is a rock lever or yoke having a pair of spaced arms 65 embracing the drive shaft and having rollers 66 mounted on their ends and engaging in the groove formed by the flanges 61 and 62.

Thus, as the governor weights 50 move inwardly or outwardly in response to variations in the speed of the engine, the rock shaft 63 will be actuated in opposite directions, depending upon the changes in engine speed.

Secured to therock shaft 63, adjacent the ends thereof and on opposite sides of the main drive shaft 52, are a pair of levers 70 and 71, the lever 70 extending upwardly and engaging the end of the needle valve 43, while the lever 71 extends downwardly from the rock shaft and engages the end of the needle valve 41. Thus, the levers 70 and 7-71, as they are rocked by the rock shaft 63, will move the needle valves 43 and 41 toward their closed positions, depending upon the direction of rotation of the rock shaft. To move the needle valves 43 and 41 in an opening direction, springs 72 are mounted about the adjacent ends of the needle valves and bear at one end against the main housing 20 and at their other ends against collars 73 provided on the ends of the valves.

It will be evident from the foregoing, and by an inspection of Fig. 1, that when the speed of the engine increases i i 9 arm 70 will move the needle valve 43 toward its closed position against the resistance of its spring 72, while the rocker arm 71 will move in a direction permitting the spring 72 on the needle valve 41 to move the latter toward an open position. Thus, the two needle valves 41 and 43 are moved oppositely in response to changes in engine speed. Since the needle valve 43 is moved toward a closed position as the engine speed increases, such valve is utilized to determine the maximum speed of the engine. Thus, the needle valve 43 will close sufliciently to decrease the flow of fuel to the engine through the main conduit when the engine speed closely approaches its maximum and will eventually completely close the main conduit to prevent all flow of fuel to the engine and thus limit its speed. It is obvious, of course, that as soon as the speed falls below its maximum, the needle valve 43 will open to again permit flow through the main conduit.

For a given setting of the various valves in the system, the amount of fuel delivered to the engine would increase with a decrease in engine speed. This would obviously cause the torque curve of the engine to rise on decreasing engine speed and if the engine were operating at full throttle, it would cause an excessive overloading of the engine. By means of the valve 41, such a condition is compensated for to a predetermined extent so that the resultant torque curve of the engine may be of a predetermined character and preferably is substantially a flat curve with only a slight increase in torque as the engine speed decreases. While the valve 41 may be so constructed as to give any desired shape to such curve, the foregoing shape is preferred, although in some instances it may be more desirable to cause the torque to fall oif at lower engine speeds.

In the present construction, the needle valve 41 moves toward its closed position as the engine speed decreases. Consequently, the flow of fuel through the main conduit may thereby be decreased, upon decrease in engine speed, to compensate for the tendency toward increased flow due tothe longer period of opening in the injectors. The extent of compensation thereby obtained may be predetermined by so shaping the valve 41 as to provide a given area of flow about the needle valve for any given engine speed. The valve 41 may also be shaped to compensate for variations in pressure of the fuel.

The throttle valve 37 may be opened to any desired extent to control the speed of the engine, but when fully opened to its full throttle position, the valves 41 and 43 will exercise the necessary control over the flow of fuel. Thus, with the hand throttle 37 fully opened, if the load on the engine is light and the speed thereof tends to exceed the desired maximum, the governor 46 in response opened, the engine speed will tend to decrease, but any tendency. for increased flow of fuel due to the increased time of indexing of the ports 116 in the injectors will be compensated for by the needle valve 41, which decreases the flow offuel with a decrease in engine speed.

The common rail 35, as heretofore mentioned, is connected to the respective engine cylinders through injectors, one of which is indicated at 96 in Fig. 1. The fuel is delivered to each injector through an inlet port 116, the opening of which is controlled by a plunger 98 operated by the engine camshaft 108.

Each injector cam 108 is so designed that the period of time during which the port 116 is opened by the plunger 98 determines the time in which fuel is supplied to the cylinder. Since the plunger 98 is thus operated in timed relation to the speed of the engine, the period of time during which the port 116 is open increases with a decrease in engine speed. The needle valve 41, however,

, 10 in thisinstance, under the control of the governor, cornpensates for the variation in time caused by changes in engine speed. The several plungers 98 in their respective injectors 96 are, of course, opened and closed sequentially and the opening of two or more injectors may overlap if desired.

The fuel control apparatus also includes means for providing a governed idling speed control for the engine.

To this end, a by-pass 91 extends from the main conduit 36 around the throttle 37 to the needle valve 41 so that fuel may flow through the passage 91, when the throttle 37 is closed, to operate the engine at idle speed. The by-pass passage 91 opens into the bore in which the needle valve 41 is mounted at a point spaced from the tapered end of the needle valve, and a groove 92 is formed in the needle valve 41 at a point which registers vnth the opening of the passage 91 when the engine is operating at idle speed. Extending from the groove 92 is a diagonal passage 93 formed in the needle valve 41 and opening into the valve chamber 39 in which the needle valve 41 is located. At this time, since the engine speed is low, the needle valve 43 is in its fully opened position. Thus, suflicient fuel may flow from the pump 32 through the by-pass passage 91 to the groove 92 and the passage 93 in the needle valve to operate the engine at idle speed. Should the engine speed tend to increase slightly above the desired idle speed, the needle valve 41 will be moved by the governor to the left, and flow through the passage 93 in the needle valve will be decreased and eventually cut off by the movement of the needle valve to shift the passage 93 out of communication with the valve chamber 39. When the speed of the engine has decreased sufliciently, the needle valve 41 will be moved to the right to again permit flow through the passage 93. The engine will thus be maintained at idle speed under the control of the governor 46.

The scavenging by-pass Certain portions of Fig. 1 now to be described can be utilized with the braking and fuel shut-off mechanism disclosed in my co-pending application Serial Number 662,494 filed May 29, 1957, wherein provision is made for holding down the injector plungers 98 to stop the flow of fuel into the injectors, whenever the throttle 37 is closed and the engine is being rotated above idling speed as it is in a truck when coasting.

In the present case, I provide a piston 130 (on the injector plunger 98) fitted in a cylinder 131 formed in the top of the injector body 96. The underside of the cylinder 131 is vented to atmosphere at 132. The upper working side of the cylinder 131 is connected to a hydraulic pressure line 133 adapted to receive fluid under pressure from the line 134 through the solenoid actuated control valve 135 and the line 136. In Fig. 1 the solenoid 137 is shown in its energized position. When the solenoid 137 on valve 135 is de-energized, the valve *135 is lifted by the spring 138 and the fluid in the lines I133 and 136 flows back to the sump through line 140. This allows the spring 111 to lift the injector plunger 98, returning the plunger to normal action. The parts described function to hold the. plunger 98 seated in the bore with an annular communication groove 141 aligned with the fuel inlet port 116 and with the outlet port 117. The purpose of this is to permit fuel to flow through the

injector housing ducts

112, 113, 114 and for the purposes (a) of cooling the parts; (b) of maintaining a lubricant around the plunger 98 and in the bore 105; and (c) of scavenging any air bubbles that might have worked up into the fuel line. As shown in Fig. 2, additional

annular lubricating passages

142 and 143 may be provided along the bore 105 to reach aligned annular lubricating grooves in the plunger 98.

The fuel that flows through the injector body .under the conditions mentioned above is carried back to a 15 float chamber 26 through the line 144, the common col- 11 lecting header 145, the valve 146, and

lines

147,, 148 and 150. The solenoid 151 which opens the valve 146 is in series with the solenoid 138 so the hydraulic fluid which actuates the piston 130 to hold down the plunger 98 is introduced simultaneously with the opening of the

fuel return lines

114, 115, 144, 145, 147, 148, 150.

In Fig. 2, I show an alternative for the single valve 146 in the

fuel return lines

144, 145, 147 of Fig. 1. In Fig. 2, each injector housing 96 is provided with its own cut-01f valve 146a reciprocable in the bore 139. The valve is shown in Fig. 2 in its open position, in which position it is held by the same hydraulic pressure medium that is acting in the cylinder 131 on piston 130 to hold down the injector plunger 98. A passage 131a conducts the fluid into the bore 139 so it acts on the piston at the end .of the valve 146a. A spring 149 will push the valve 146a downwardly the instant the valve 135 (Fig. 1) closes oif the hydraulic pressure medium and connects the

conduits

133, 136 to the return 140.

As already explained, when the throttle 37 is closed and the engine r.p.m. is above idling speed (as when coasting), the idling ports in passage 93 will be closed so no fuel will be reaching the chamber 47. Under these conditions only, my system shown in Figs. 1 and 2 calls for the circulation of fuel through and out the injector housing 96 and back to the float chamber 26 for the reasons given just above. This fuel circulation I provide in the by-

pass conduits

152, 153, 154, 155, which connect the fuel pressure pump 32 directly to the conduit 44 without going through the throttle 37 or the governor controlled valves 41 and 43. The manually adjusted valve 156 regulates the quantity of fuel that can flow in this by-pass line to lubricate and scavenge the fuel passages in the injector 96. The shut-off valve 157, shown open in Fig. 1, controls the admission of fuel to the bypass line and has the hydraulic ram 158 resisted by a spring 160. The hydraulic fluid conduit 161 is connected to the conduit 136, which means that the valve 157 is moved to open position whenever the injector plunger 98 is held down by the piston 130. A solenoid may be used instead to actuate the valve 157, just as a mechanical or other hold down arrangement may be used to hold the plunger 98 closed.

One Way of actuating these various valves is to use the battery charging circuit in the electrical system of the vehicle, which includes a battery 162, a generator 163,

and a cut-off relay switch 164 having contacts 165 which open when the engine r.p.m. drops to idling speed but close and stay closed when the rpm. is above idling speed. I couple this circuit from ground to the leads 166, 1-67 to solenoid 151, then to the leads 168, '170 to solenoid 138, then to the

leads

171, 172, 173, 174 to the switch 175, then to the lead 176 and to ground at 177. The switch 175 is closed only when the throttle 37 is closed.

There are alternatives to the use of the battery charging cut out relay 165 to control the electrical circuit. For example, in Fig. 11, I show a switch 169 to replace the switch 165 in Fig. l. The switch 169 is actuated by the governor controlled arm 70, so that it opens when the engine slows down to a predetermined speed, above idling speed. An advantage of this arrangement is that the switch 169 can be mounted for adjustment to and from the lever 70 and in this way allow for any desired time for the contacts in the switch to close or to open.

Another alternative to the electrical control system for my invention is to have a mechanically operated valve means responsive to the governor 46, and to the foot throttle 29. At a predetermined speed, the valves would open and admit fluid under pressure to actuate the piston 130, the piston 158 and the valve 146 in the fuel return line.

It will thus be seen that I have provided a fuel system in which fuel is circulated through the injector and back to the supply source, only when the engine is being rotated above idling speed (this closes switch with the throttle closed (this closes switch and that as soon as. the throttle is opened, or the engine r.p.m. drops below battery charging (idling) speed, the fuel return line is closed (by deenergization of the solenoid 151) and the, only outlet for the fuel is through the

plunger chamber outlet

107, 102. Thus it will be seen that there is no possible route for the fuel to get into the combustion chamber when the engine is being rotated above idling speed with the throttle closed.

Summarized very briefly, it will be seen that When the throttle 37 is open, the governor controlled valves 41 and 43 regulate the quantity of fuel reaching the feeder header 35 and the fuel injectors 98; and that the valve 146 shuts off the fuel return line during all conditions of the engine when firing. Also, when the throttle is closed and the engine is idling, the above condition exists. However, when the throttle is closed and the engine is rotating above idling speed, as when coasting (with the engine in gear and being motored by the momentum of the vehicle) the by-pass linevalve 157 opens to admit fuel to by-pass the closed throttle 37 and the closed valve 41, and to reach the injector chamber inlet 116, where the fuel is barred from entry into the plunger chamber 106 by the closed down injector plunger 98, but is admitted to the

return line conduits

141, 115, 144, 145, 147, 148 and 150. As the engine speed drops below charging speed the relay switch 165 opens and the engine returns instantly to a normal operating condition with fuel ready at the port 116 to enter the plunger 98 and cleared of any air bubbles which, if they came up into the injector during coasting, were carried away in the fuel returned to the sump 26.

It will thus be seen that the device (a) wastes no fuel when coasting; (b) lubricates and cools the plunger mechanism by circulating fuel therein when coasting; (c) scavenges any air bubbles reaching the plunger by entraining them in the fuel being returned to the sump 26 when coasting; (d) avoids any dependence on resistance pressures in a fuel return line which could influence the rate of feed of fuel to the injectors, by closing off the fuel return line whenever the engine is firing; (e) and simplifies the supply of fuel for scavenging air bubbles and lubricating the injector Plungers by by-passing the governor and throttle control means; and (f) separates the functions of lubrication and scavenging from the fuel feeding operation.

It will also be seen from the above that in my system when the engine is producing power, only the amount of fuel is fed to the injectors that will be injected into the engine cylinders. In other Words, in my system, I do not feed an excess of fuel, use part of it to power the engine and return the unused portion to the fuel source. It will now be clear that where this latter system is used, if anything occurs to block or restrict the surplus or unused portion of the fuel in its return to the fuel source, the surplus fuel will be backed up and will be injected into the engine, causing it to run wild. This is what occurred in the example given earlier where the mechanic made the mistake of closing 01f the return lines to the two tanks. Not only can this not happen in the present system, but by keeping the fuel return line closed when injection is occurring, I relieve the installer of the engine from having to take into account or pay any attention to the size of the fuel return piping, the size of the vent in the fuel tank, or whether there are any restrictions in this piping.

It will also be seen from the above that with the plungers 98 held down, the problem of having them stick or wear during coasting is eliminated, and that they are kept freshly lubricated and cooled when the engine is being motored during coasting.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. In a fuel injection system for a multi-cylinder internal combustion engine connected to drive a vehicle, the combination of: a source of fuel under pressure; fuel feeding means connected to said source; a throttle for said engine acting on said fuel feeding means; speed responsive means for regulating the flow of fuel to the engine through said fuel feeding means; injector mechanisms connected to said fuel feeding means, each having a plunger reciprocable therein for injecting a measured amount of fuel into the combustion chamber of the cylinder to which it is attached; a fuel return line leading from each injector to the fuel source; each injector being characterized by having means for holding its injector plunger inactive when the engine is rotating above a predetermined minimum r.p.m. with the throttle closed; means connecting the fuel feeding means to said fuel return line when said plungers are inactive, whereby fuel flows to and through said injectors into said return line under the aforesaid condition; and means for closing said fuel return line when said plungers resume their reciprocatory movement.

2. The system of claim 1 in which there is a by-pass around said speed-responsive means for the fuel feeding means, and means for opening said by-pass whenever the throttle is closed and the engine is rotating above a predetermined minimum r.p.m.

3. A fuel control system for a multi-cylinder internal combustion engine powering a vehicle, including a source of fuel under pressure; fuel feeding means connected to said source; an injector for each cylinder connected to said fuel source by said fuel feeding means; a valve controlled fuel return line also connected to each injector and said fuel source; cam means with plunger and valve actuating means moved thereby; a piston reciprocable in each cylinder, by a shaft adapted to be connected to the drive wheels of said vehicle; throttle means for regulating the flow of fuel to said engine; a speed responsive electrical circuit adapted to be controlled by said engine, having a switch to open said circuit when said engine speed is below a predetermined rpm, and to close said circuit when it is above said r.p.m.; said fuel control system including means for holding closed the fuel injector plungers and for Opening the valve in the fuel return line, when said electrical circuit is closed and said throttle means is closed; whereby when said electrical circuit is closed and said throttle means is closed, said fuel is shut off to each cylinder but is flowing through each injector and back to said supply source.

4. The fuel system of claim 3 in which there is a bypass around said throttle means connected between said source of fuel under pressure and said injectors, and means for opening said by-pass when said throttle means is closed.

5. The device of claim 3 in which each injector has a by-pass around its plunger to connect the source of fuel under pressure to the fuel return line when said plunger is in its closed position.

6. A fuel control system for a multi-cylinder internal combustion engine powering a vehicle, including a source of fuel under pressure; fuel feeding means connected to said source; an injector for each cylinder connected to said fuel source by said fuel feeding means; a valve controlled fuel return line also connected to each injector and said fuel source; cam means with plunger and valve actuating means moved thereby; a piston reciprocable in each cylinder, by a shaft adapted to be connected to the drive wheels of said vehicle; throttle means on said fuel feeding means for regulating the flow of fuel to said engine; control means responsive to engine speed and to throttle position for closing the valve in the fuel return line when the engine speed is above a predetermined r.p.m. and for opening the valve in the fuel return line when the engine speed is below a predetermined rpm. and the throttle is closed; said fuel control system also including means for holding closed the fuel injector plungers when the valve in the fuel return line is held open; whereby when said valve in the fuel return line is open, said fuel is shut off to each cylinder but is flowing through each injector and back to said supply source; and when said valve is closed and said injectors are released, said fuel immediately resumes feeding into said cylinders and the fuel return line is closed, thereby causing to flow in the fuel lines to the injectors only the amount of fuel that will be injected to power the engine.

7. The fuel system of claim 6 in which there is a bypass around said throttle means connected between said source of fuel under pressure and said injectors, and means for opening said by-pass when said throttle means is closed.

8. The device of claim 6 in which each injector has a by-pass around its plunger to connect the source of fuel under pressure to the fuel return line when said plunger is in its closed position.

No references cited.