CA1047862A - Fuel injection system for internal combustion engines - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A high pressure gas-driven fuel pump is disclosed for use in a fuel injection system for an internal combustion engine. The upper end of the pump includes a chamber containing an annular seat spring-biased down-wardly against the top end of an annular piston fitted to a lower, coaxial chamber. A second piston fits into the annular piston and is itself spring-biased downwardly into the lower chamber. Below the lower chamber is a fuel chamber fitted with an upwardly biased plunger, engaging the bottom of the second piston. The pump is operated by the supply of gas to the lower chamber in a cyclic manner, or from the combustion chamber of an internal combustion engine. The application also discloses a system employing the pump.

Description

~047862 This application is a division of application 229,757, filed June 20, 1975.
This invention of the parent application relates to fuel injection systems for internal combustion engines, and more particularly to improve-ments therein.
According to the invention of the parent application there is provided in an internal combustion engine, a fuel injection system comprising first fuel pump means for providing a supply of fuel at a first pressure, second fuel pump means for providing a supply of fuel at a second pressure, said second pressure being higher than said first pressure, injection nozzle means for each cylinder for injecting fuel when open into a cylinder of said engine, means for measuring the amount of fuel to be injected into said `
cylinder, means for storing fuel to be injected into said cylinder by said injection nozzle means, means for transferring said measured amount of fuel ;
to said means for storing fuel for storage thereby at said first pressure, means for applying fuel from said means for storing fuel to said injection nozzle means at said first pressure to apply an opening bias, means for apply-ing fuel from said second pump means at said second pressure to said injection nozzle means to maintain said injection nozzle closed against the pressure of said fuel at said first pressure, timing means actuated responsive to opera-tion of said internal combustion engine for producing a signal when the time for fuel injection by said injection nozzle means occurs, and means responsive to said tim;ng means signal for increasing the pressure of said stored fuel until it exceeds said second pressure thereby opening said injection nozzle means whereby said stored fuel is injected into said cylinder. With this system, the fuel may be metered at low pressure, to satisfy operator demands within limitations of smoke, torque shaping, speed governing or emission requirements.
According to an exemplary embodiment, when the crankshaft reaches the angle desired for injection, an electroexpansive pump drives open an ~ .

injection control valve or successively drives open a pilot and then a main injection control valve whereby high pressure from a gas-driven high pressure pump can apply sufficient pressure to the stored fuel to open an injection nozzle which is maintained closed by fuel at high pressure from the gas pump. ~i This enables the fuel to be injected into the cylinder either for a single -main injection or for a successive pilot and then main injection. -The present invention is concerned with a gas-driven high pressure pump for such a system. ~
According to the present invention, there is provided a fuel pump ~ ~ -for operation responsive to gas pressure comprising: a first chamber, an annular disc extending into said first chamber, first biasing means for bias-ing said annular disc in one direction toward one end of said first chamber, a second chamber coaxial with said first chamber, a first piston extending into said second chamber, a fuel chamber, second biasing means for biasing said first piston in said one direction toward said second chamber, means ~ -for delivering fuel to said fuel chamber from a first fuel pump means, plunger means extending between said fuel chamber and said first piston for applying .~. . .... . .
pressure to the fuel in said fuel chamber in response to motion by said first piston in said one direction, third biasing means for biasing said plunger ~20 means in a direction so as not to apply pressure to the fuel in said fuel chamber, means coupling said first piston and said annular disc motion to-gether after said first piston has been moved a predetermined distance in a direetion opposite to said one direetion, and means for applying gas to said seeond ehamber to drive said first piston in said direction opposite to said one direction, as a funetion of the gas pressure in said seeond chamber.
In the accompanying drawings which illustrate an exemplary embodi-ment of the present invention and its environmental use:
Figure 1 is a schematic drawing illustrating a six-cylinder engine with an accompanying fuel injection system;

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Figure 2 is a view in section of a high pressure gas-driven fuel pump;
Figure 3 is a schematic view of a fuel metering and distribution ,, , ,, .. ,, , ,, , , ~ ~.

~047862 unit;
Figure 4 is a view in section of the wedge driving device for con-trolling the metering shuttle in the fuel metering unit;
Figure 5 is a schematic drawing of the fuel injection system for pilot and main injection;
Figure 6 is a view in section of a fuel injection structure which is schematically shown in Figure 5;
Figure 7 is a schematic diagram showing a fuel injection arrange- : ~
ment for main injection only, and is found on the same sheet as Figure 5; ~ :
Figure 8 is a block schematic diagram of the circuit used for con-trolling the piezoelectric valves used in the fuel injection system, and is found on the same sheet as Figure l;
Referring now to Figure 1, there may be seen a schematic arrange-ment for a fuel injection system, for an internal combustion engine 32.
Electrical controls for the fuel injection system, including the operator control, are contained in a control unit lO for which a power supply 12 is provided. A low pressure fuel pump 14, which is of conventional design, preferably of positive displacement gear pattern, draws fuel from the fuel storage tank, not shown, and raises it to a suitable pressure, such as about seven bars. The fuel at low pressure is then fed to a metering and distri-bution unit 16.
The metering is performed in a unit that partitions discrete in-jection volumes of fuel under the control of an interface control unit 18, and the metering and distribution unit 16 distributes the metered volume of fuel to the respective fuel injectors 20, 22, 24, 26, 28 and 30. There the fuel injectors store the metered quantity of fuel until the cranhshaft reaches an angle at which the fuel injectors are actuated to inject fuel into the respective cylinders of the engine 32.
The control unit 10 provides a signal to the interface control unit 18 in accordance with operator demand within limitations of smoke, torque ~ :

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shaping, speed governing and/or emission requirements. The interface control unit operates with a position transducer, not shown here, to insure that a proper quantity of fuel is metered in response to the signal received from the control unit. The control unit also provides triggering signals to the respective fuel injectors 20, through 30, in response to camshaft position.
A high pressure fuel pump respectively 34, 36, 38, is provided for each two fuel injectors. While conventional high pressure fuel pumps may be employed without any major effect upon the function of the remainder of the system, because of the high tolerance machining and heavy drives which would be required to provide pressures on the order of 320 bars, a novel gas operated high pressure pump in accordance with this invention, is proposed.
Each pump is directly connected to the combustion chamber of a different cylinder for obtaining the gas required for its operation. The high pressure fuel pumps receive fuel from the low pressure fuel pump, amplify the fuel pressure, and supply the fuel to the respective fuel injectors. The fuel injection nozzle valves are maintained closed by pressure applied by fuel from the high pressure pumps. The fuel under high pressure from the high pressure pumps is also used by each of the fuel injectors to boost the pressure of the fuel received from the metering and distribution un;t and ~ ~ -stored by the fuel injector so that the boosted fuel pressure overcomes the -high fuel pressure biasing the nozzle valve closed and opens the injection valve permitting the stored fuel to be injected into a cylinder at the boosted pressure.
Figure 2 is a view in section of a high pressure gas-driven fuel pump. The high pressure fuel pump comprises a housing 40 which, in its upper section~ comprises a chamber 42 within which there i9 a spring seating 44 centrally positioned by a spring 46, which urges the seating downward.
At the top of the chamber is a gas leakage valve 82, which is preset so that it will permit gas to leak out of the chamber when the pressure therein exceeds a predetermined value.

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A piston 48 is provided with a collar 47 at one end and carries a disc 50 on its upper extremity. An annular piston 54, surrounds the smaller piston 48. This annular piston 54 has a land 56 therein which can be engaged by the collar 47 on piston 48 when it is lifted to the position shown. The lower end of the annular piston 54 is exposed to gas pressure and forms a moveable boundary to a chamber 60. The lower end of piston 48 ~;
forms another moveable boundary to chamber 60. Gas is applied to the chamber 60 from a gas intake opening 61, which connects by a passage (not shown) to an engine cylinder. The upper end of the annular piston 54 engages the spring seating 44.
The housing walls 58 define the fixed walls of chamber 60. The housing 40 lower walls also form a fuel chamber 64. A fuel plunger 66 has a central hollow portion within which a spring 68 is inserted to bias the fuel plunger upwardly against the disc 47 and piston 48. Thus, when the -~
piston 48 moves upwardly, the fuel plunger will move upwardly therewith in response to the bias of its spring 68.
Formed within the housing walls is an inlet passage 70, leading to the fuel chamber 64, and an outlet passage 72 leading from the fuel chamber. The inlet passage is connected through suitable fittings 74 to the -~-low pressure fuel pump. The outlet pagsage 72 is connected through a suit-able fitting 76 to the two fuel injectors which it services.
Within the inlet passage is an inlet check valve 78. Within the outlet passage is an outlet check valve 80.
When the pump is not operating, the piston 48 is pushed by the inner spring 52 until it abuts the lower extremity of chamber 60, whereby it pushes the fuel plunger 66 downwardly. The inner spring 52 provides a pre-load on the piston 48, which is slightly lower than the gas load at starting compression ratio without firing. When the engine is running, gas pressure into the chamber 60 forces the piston 48 upwards compressing the inner spring 52 and also forces the annul~r piston 54 upwards compressing spring 46 and :

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enabling the fuel plunger 66 to rise, whereby fuel will be recived from the low pressure fuel pump 14, passing through the check valve 78 into the fuel chamber 64.
As engine gas pressure falls, the spring 52 exerts pressure on the piston 47 and spring 46 exerts pressure on piston 54 thereby pushing the fuel plunger 66 downwardly. This causes the check valve 78 to close and increases the pressure on the fuel in the fuel chamber, sufficiently to open the check valve 80. Fuel injection pressure to enable the engine to be started is achieved by fitting the smaller piston 48 within the annular piston 54. The pressure available for starting is lower than when the engine is firing but since cranking speed is low, the lower pressure more accurately matches requirements, effectively prolonging injection until the engine is close to top dead center. The spring 52 is designed to provide a 76-bar fuel pressure, for example, when lifted a distance of 12 mm. At this lift, the starting gas piston 48 reaches the position shown in the drawing, which is the limit of its travel, and can only lift further if the annular piston 54 is also lifted. As the engine fires, higher gas pressures are available and higher injection pressures are desired, the smaller piston 48 will cause the annular piston 54 to push the spring seating 44 until it moves upward, thus compressing the outer spring 46. When the gas pressure in the engine cylinder, due to the power stroke of the piston, reduces, a desirable higher pressure is provided by both springs for application to fuel in the fuel chamber 64.
The sizes of the inner and outer springs which are required to return the fuel plunger 66 are reduced by utilizing a "gas spring". This ~gas springl' is designed to contribute about 60% of the total load. The "gas spring" comprises using gas under pressure in the chamber 42 above the pigtong 54 and 48, which acts in the direction to assist the expansion of springs 52 and 46 There is compensation provided for temperature changes in the _ 6 - -. , . , : : ,. . .
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chamber 42, without which wide fuel injection pressure variations would re-sult, as for example from a temperature increase through a maximNm of 300F. ~
That is the purpose of the pressure relief valve 82, which is at the top of ~-the chamber 42. By way of example, the pressure relief valve is designed to lift at 29 bars, i.e., 10% higher than the nominal compressed maximum pressure.
This increase will produce a 6% increase in fuel injection pressure, or about 3% increase in the rate of fuel injection. When the engine is stopped, pressure on the chamber tends to fall due to leakage between piston 54 and housing 58. When the engine is cranked to restart, injection pressure is lower, a more desirable condition, to avoid over-penetration of the engine chamber at minimum swirl velocity, and to avoid excessive wall deposition. -However, as soon as the engine starts firing, gas pressure, in the chamber 42, due to seepage of gas past the grooves 84, for example, rises once again to the 29-bar figure, restoring the injection rate to normal.
A passageway 86 collects any fuel that leaks past the fuel plunger 66, and returns it to the inlet passageway 70. The high pressure pump is fitted with suitable lugs 88 whereby it may be mounted directly on the engine cylinder head.
Figure 3 is an isometric view of a fuel metering and distribution unit. Fuel is fed from the low pressure pump, at a pressure, for example, of 7 bars, through the tube 90, to the bore of a hollow cylinder 92, which is driven suitably from the engine crankshaft so that it rotates at half crank-~haft speed. A passageway 94, which is a right-angle passageway, is formed in the cylinder 92 so that any fuel delivered at the inlet 90 is transferred by the right-angle passageway to the periphery of the cylinder 92. The rotating cylinder then can deliver, alternately, fuel to opposite ends, -respectively, 96, 98, of a closed hollow cylinder 100, which contains an oscillating shuttle or plunger 102. The plunger is mounted on a shaft 104, which is attached to a shuttle control 106, which serves the function of con-troll;ng the length of the shuttle stroke.

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Tubing is provided for successively delivering fuel alternately, to the opposite ends of the metering shuttle-housing 100, and also for returning this fuel back to the cylinder 92 which thereafter, as it rotates, delivers the fuel to the individual injection valves of the engine. Such tubing com-prises a main tube 105 and a main tube 108, which extend from the respective ends 98, 96 of the metering shuttle to the cylinder 92. At the cylinder 92, tubing 105 has the respective tube stubs 110, 112, 114, 116, 118 and 120.
Tubing 108 has the following stubs, which extend from it to the periphery of the cylinder, respectively, 122, 124, 126, 128, 130 and 132.
Together with the main tubing 105, the stub tubing 110, 114 and 118 will be successively connected to the right-angle passageway 94 for delivering fuel to the side 98 of the metering shuttle as the cylinder 92 is rotated.
However, the connection of passageway 94 to the stubs of main tubing 105 occurs alternately with the connection to the stubs 122, 126 and 130, of the main tubing 108. In thedrawing, stub tubing 122 is shown connected to the passageway 94, and therefore fuel is being fed over the passageway 94 through stub 122 through main tubing 108, to the end 96 of the metering shuttle.
As the shuttle 102 is moved, in response to the pressure of the fuel being received on the side 96, toward the side 98, fuel is being returned from the metering shuttle over main tubing 105 and stub tubing 112, 116 and 120 to the cylinder 92.
~ When main tubing 108 ret w fuel to cylinder 92, it does so through tubing stubs 124, 128 and 132.
There is another passageway within the cylinder 92, which success-ively connects to the stub tubing returning fuel to the cylinder from the metering shuttle. This is a passageway comprising three parts. The first part 134 connects from the periphery of the cylinder 92 to the fuel delivery stubs, to the axis of the cylinder where there is a second passageway portion 136, which is connected thereto. A third passageway portion 138 connects from the central passageway 136 outward to the periphery of the cylinder ., ,. , , ,':: .

again. This passageway section 138 successively connects with tubing respec-tively 140, 142, 144, 146, 148 and 150, as the cylinder rotates. These ~ubes are the ones which deliver the metered fuel to the individual injection valves for the cylinders of the engine, where the metered fuel will be stored.
In the drawing, main tubing 105 is delivering fuel from the meter-ing shuttle, over stub 120, to passageway 134, 136, 138 which is connected to tubing 140. Tubing 140 is connected to one of the injection valves.
When the passageway 138 ig not registering with the individual tubing 140 through 150, which delivers fuel to the individual cylinder injec-tion valves, a relief groove 152 is provided which connects each of these tubes to drain tubing 154.
The foregoing description is briefly directed to the metering of the fuel and the manner in which it is distributed to the respective injection cylinders from the metering apparatus. The description that follows is directed to the control of the metering shuttle. Reference should be had to Figures 3 and 4 in connection with this description.
One end of the shaft 104 which carries the shuttle 102 has been previously indicated as being connected to a shuttle stroke controlling device 106 This comprises for example, a pair of spaced forklike tines, respec-tively 160, 162, which are in the form of a tapered wedge. Fitted between the spaced tines of the tapered wedge is an H-shaped abutment unit 164, which, as shown in the cross-sectional view of Figure 4, has its inside edges at an angle parallel to the angle made by the tapered wedge sides and these are spaced from the tapered wedge so that as the wedge is moved down-wardly, the shaft 104, together with the abutment unit, can reciprocate a greater distance than when the wedge is moved upwardly. The wedge can be ved upwardly a sufficient distance to block motion by the shaft 104.
From the foregoing it should be appreciated that the position of the wedge tines 160, 162, oontrol the distance which the metering shuttle travels, thereby controlling the volume of fuel being metered to the engine 1~)4786Z
cylinders. The mOre ~he tapered wedge is withdrawn from the H-shaped abut-ment unit, the larger the quantity of fuel being delivered to each of the individual cylinders. The reverse is also true.
The position of the wedge is controlled by a piston 166, which is operated within a closed cylinder 168. A spring 171, urges the piston to return the wedge to the no shuttle travel position. A feed tube respectively 170, 172, is connected to each side of the piston 168 with a constriction being in the tube 172, which is connected to the spring side of the cylinder.
Also from that side of the cylinder, a tube 174 is connected to a vent to drain pressure tubing 176, through a valve 178. The valve includes, for example, a piezoelectric bimorph 180, which, in response to electrical signals from the control unit, can be made to assume a desired angle whereby the passageway between tubing 174 and 176 can range from fully open to fully closed.
A sensing unit 182 which may be electromagnetic Hall effect, a ~
linear variable differential transformer, or an inductive sensor, is positioned -at one end of an extension from the piston 166 whereby the position of the ;
piston and thereby the position of the wedge may be sensed. Effectively, the position of the~wedge determines the amplitude of travel of the metering shuttle and thus the amount of fuel being delivered to each cylinder. There-fore, the sensing unit 182 generates a signal indicative of the quantity of fuel being delivered. This signal is fed back to a circuit, shown in detail in Figure 8, which is within the control unit 10, to be compared with the signal being applied to the bimorph. Any signal disparity is either added to or subtracted from the bimorph controlling signal.
In operation, when a control signal is applied to the piezoelectric valve, the valve moves rapidly to almost fuIly open position. As the wedge adopts the position where the transducer output matches the control signal, the disparity falls to zero and the valve holds an opening that creates equilibrium between the hydraulic forces on opposite sides of the piston 166 ~ .

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and the spring 171. It should be noted, that when flow occurs through valve 178, because of the constriction in the tubing 172, the pressure of the fuel at the top of the piston is greater than the pressure of the fuel at the bottom, which tends to drive the piston downwardly against the pressure of the spring. Thus the bimorph 180, by controlling the size of the opening to the drain, can determine whether the hydraulic pressure applied to the bottom of the piston through the tubing 172 will be equal to the pressure at the top, whereby the spring 170 will drive the wedge to the fully closed position, or with the bimorph permitting a full opening, the fuel pressure at the top of the piston will drive it fully downwardly to permit maximum fuel delivery.
The positions in between maximum and minimum fuel delivery are thus determined by the bimorph position and consequently by its controlling signal.
Figure 5 is a schematic drawing of a fuel injection arrangement for injecting pilot and main fuel into the engine cylinder. Figure 6 is a cross-sectional view illustrating a suitable structure. They should both be considered together. Operation of the fuel injector is initiated by a valve 190, in response to control signals from the control unit 10. Effec-tively the valve, by way of example, comprises a stack of piezoelectric elements 192 which, in response to the signals from the control unit will ;~
cause a plunger 194, to move within a chamber 196.
Fuel under low pressure is supplied to the chamber 196 from the metering unit 16 which is described in Figure 3 of the drawings, over a passage 195 which includes a check valve 197.
High presgure fuel is delivered from a high pressure pump 198 of -~
the type shown in Figure 2, to an accumulator 200, to a main injection con-trol valve 202, shown in its inoperative position, and to a pilot injection control valve 204, shown in its operative position. The high pressure fuel is also applied to an injection nozzle valve 206, to maintain it in its closed position.
It will be recognized that the function of the accumulator 200 is . .

to maintain the high fuel pressure constant.
The pilot injection control valve 204 has two pressure balance plungers 203, 205 and valve seatings respectively 208 and 210. The main injection control valve also has two pressure balance plungers 207, 209 and has a single valve seating 212. The pilot injection control valve has a spring 214, which biases the plungers to their upward position. In the up-ward positions, the valves 208 and 212 block delivery of high pressure fuel to the remainder of the system. In order to effectuate pilot injection con-trol, a first signal is applied to the p~ valve 190 which causes it to move partially and not to its fullest extent. Since the spring 214 of the pilot injection control valve is made to have a lighter pressure than the spring 216 of the main injection control valve, the pilot injection control valve is moved first so that the valve seating 210 closes the lower passageway thereby closing the tubing 213 or passageway to the drain, and opening a passageway 215. The high pressure fuel then applied to this passageway actuates a pilot fuel quantity measuring device 218. This includes a chamber 220, wherein there is a plunger 222, which can be positioned by adjusting its axial clearance or by operation of an adjuster 241 so that the distance this plunger travels when it is actuated, determines the quantity of fuel which will be injected into the engine cylinder. ~-When the pilot plunger 222 is driven downwardly, in response to actuation of the pilot injection control valve, it applies pressure to the fluid that fills the tubing 219 connecting to the piston 224. Piston 224 is within a fuel injection preggure intensifier device 226. The piston 224 actuates a plunger 228 downwardly. Fuel was previously delivered from the fuel metering device shown in Figure 3 through a tube 230, through a check valve 232, to a storage passageway 234 which te~minates at the fuel injection nozzle 206. The plunger 228 is moved by the piston 224 downwardly on the fuel which is within the storage passageway 234. Since the surface area of the pist4n 224 is much greater than the area of the plunger 228 which is :,, . - . . ~- : :
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being brought to bear on the stored fuel, there is a multiplication of the pressure on the stored fuel which is determined, as is well known, by the ratios of the surface areas of the respective piston and plunger. By correct-ly determining these surface areas, the pressure applied to the stored fuel and therefore the pressure of the stored fuel is increased to a value where it exceeds the pressure being applied from the high pressure pump to the in-jection nozzle 206, whereby the injection nozzle is opened and the pilot fuel injection into the cylinder of the engine takes place.
After a suitable interval, which is determined by the control unit, a further signal is applied to the valve 190, in response to which piston 194 undergoes an additional displacement whereby the plunger of the main injection control valve 212 is caused to move downwardly. This opens the passageway 236 to receive high pressure fuel from the pump 198, which causes the plunger 224 to be moved still further downwardly causing the remainder of the fuel in the storage passageway 234 to b~ ~ 1ected into the cylinder. An injection nozzle of a type described in~Patent No. 3,738,576 may be modified for use with this invention. This constitutes the main fuel injection. The plunger : ~ -228 moves downwardly until the fuel injection cutoff passageway 238 lines up with a feedback passageway 240. At this time in the engine cycle the metered fuel feed ports (shown in Figure 3) will register with drain groove 152 allow-ing an unhibited passage to the relief of fuel spilled through the feedback passageway 240. This causes an immediate drop in the pressure being applied to the fuel in the storage passageway whereby the fuel injection is immediate-ly terminated.
The fuel injection arrangement on the succeeding cylinder in the engine~s firing order is then actuated in the manner described. The signal which actuated the pz valve 190 is removed whereby the springs 214, 216 can urge the plungers in the re~pective control valves, upwardly to their closed position. The next time that metered fuel is fed into the storage passageway 234, the pressure of the metered fuel cauges plunger 228 to be driven back - 13 - `~
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in the direction of its original position by a distance determined by the metered quantity of fuel. This also applies pressure to drive the pilot plunger back to its original position. A refill valve 242 within the pilot plunger will open at this time to permit fuel displaced by the fiIling action ~ -to be exhausted to drain.
When the timing signal is removed from the pz valve 190 the valve 210 is restored to its inoperative position by the spring 214. It then opens the passageway to the drain whereby pressure is removed from the top of the pilot plunger enabling it and the piston of the injection pressure intensifier to be easily restored in response to the pressure with which the metered fuel is delivered to the storage passageway 234.
Figure 7 is a schematic arrangement illustrating the fuel injector when no pilot injection is required. It will be seen that essentially the system is the same as the one shown in Figure 5, except that the pilot in-jection control valve and the pilot injection plunger are omitted and a double plunger respectively 212, 212A is provided for the main injection control ;~
valve instead of the single plunger as before. The purpose of the plunger 212A is to close the passageway to the drain when the injection control valve is operated. Otherwise, the system functions identically in the manner that has been described for the operation of the main injection control valve and therefore will not be redescribed. The components of the arrangement shown in Figure 7 are given the same reference numerals as are employed in Figure 5 since they perform the same functions. It will also be appreciated that when the piezoelectric valve 190 is actuated, it provides a full stroke for actuat-ing the main injection control valve rather than being operated in two steps as i~ required for pilot and then injection control valve operation.
The portion of the control unit which provides signals to the fuel injectors is described in detail in United States Patent No. 3,575,146, issued April 207 1971 to J.R. Creighton and C.G. OINeill, entitled Fuel Injection - 14 _ , 1~47862 System for Internal Combustion ~ngine. The system has operator inputs ~or : ;
load, fuel-type, and - 14a - :

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cold starting. It provides for sensor inputs for crank shaft position (which also act as a speed sensing input), engine temperature, ambient temperature and ambient pressure. It provides for plug-in programs for maximum fuel versus speed (torque-shaping) and speed governing.
The method by which these inputs are combined to give a predeterm-ined program of maximum fuel per injection, timing of pilot injection, timing of main injection against speed, and the means for achieving automatic fuel adjustment for ambient temperature, pressure, are completely shown and des-cribed.
In United States Patent No. 3,575,146, injection into the engine cylinders is determined by an arrangement such as an electroexpansive pump.
Two power supplies are provided for that pump, one known as the main in-jection power supply and the other is the pilot power supply. The pilot power supply output signal is determined at the factory since the quantity of pilot fuel to be injected iæ usually fixed. The main injection power supply signal is the variable signal, being determined in accordance with all previously indicated parameters. In the present system, the quantity of pilot fuel to be injected is determined by the setting of the pilot injection plunger in the pilot valve. The present system uses a metering shuttle device to measure the quantity of fuel to be supplied to each cylinder with the quantity of that fuel being determined in accordance with the position ;
of the wedge. The wedge position is determined in response to an electrical signal which is applied to a piezoelectric valve. Thus, in the present ~ -system, the electrical signal that in the Patent No. 3,575,146, would be ~ -applied to the main injection power supply to control the quantity of fuel ~ -which is to be injected, is applied to the piezoelectric valve which controls ~ -shuttle position.
The electrical circuit which receives the signal for controlling ~
the piezoelectric valve is shown in Figure 8, which is a schematic diagram of i` ~-the circuitry required. Again, it is to be understood that the electrical ~04786Z ~
signal which in the patent was applied to the main injection current supply to control the quantity of fuel to be delivered during the main injection, in this system is applied to the interface control device, shown in Figure 8, which determines the length of the stroke of the shuttle in the fuel meter-ing device.
Figure 8 is a schematic drawing of the electrical drive circuit for the control device. A differential amplifier, 243, receives as one input, a signal from the control circuit indicative of the quantity of fuel which is called for by the operator's control as modified by the various other parameters which are measured to de~ermine the correct quantity of fuel. The other input is from the position sensor 182, which is indicated in Figure 4 -as sensing the position of the shuttle travel determining wedge shaft 159.
The output of the differential amplifier is a signal propor*ional to the difference of the two inputs. This signal is applied to a modulator 245, which also receives as its input a pulse train, at a frequency, such as 25KHz, from a constant amplitude pulse generator 244, the modulator outpu* is a pulse train wherein the amplitude of the pulses is determined by the output from the differential amplifier 243. The output of the modulator 245 is then amplified by an amplifier 247 whose output is applied to a flyback pulse transformer 246. The output of the nyback pulse transformer is applied through a rectifying diode 248, to the bimorph piezoelectric device 180. A
resistor 250, is connected in parallel with the piezoelectric device. The piezoelectric device acts as a storage capacitor for the signals applied thereto by nyback transformer 246. The resistor 250 provides a continuous drain to reduce the voltage stored by the piezoelectric device as the electri-cal drive is remnved at some suitable removal rate.
The interface device driving circuit therefore applies pulse signals to the piezoelectric bimorph device, whose amplitude is determined by the difference in position between the voltage signal representing the desired quantity of fuel and the shuttle travel determining wedge position signal - 16 _ ,:
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indicative of the fuel quantity being delivered. The larger the fuel demand signal from the control circuit, the bigger the signal applied to the bimorph, the more wide open will be the passage control valve and therefore the lower the wedge position and therefore the greater the travel of the metering shuttle with an increased volume of fluid being delivered. The signal delivered across the piezoelectric bimorph element will thereafter oscillate slightly about this location. The interface driving circuit effectively per-forms a servo operation.

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A fuel pump for operation responsive to gas pressure comprising:
a first chamber, an annular disc extending into said first chamber, first biasing means for biasing said annular disc in one direction toward one end of said first chamber, a second chamber coaxial with said first chamber, a first piston extending into said second chamber, a fuel chamber, second bias-ing means for biasing said first piston in said one direction toward said second chamber, means for delivering fuel to said fuel chamber from a first fuel pump means, plunger means extending between said fuel chamber and said first piston for applying pressure to the fuel in said fuel chamber in re-sponse to motion by said first piston in said one direction, third biasing means for biasing said plunger means in a direction so as not to apply pres-sure to the fuel in said fuel chamber, means coupling said first piston and said annular disc for motion together after said first piston has been moved a predetermined distance in a direction opposite to said one direction, and means for applying gas to said second chamber to drive said first piston in said direction opposite to said one direction, as a function of the gas pres-sure in said second chamber.

2. A fuel pump as recited in Claim 1 wherein said means coupling said first piston and said annular disc comprises an annular piston surrounding said first piston, said annular piston having an internal abutment therein for being engaged by said first piston after said first piston has moved a predetermined distance in said direction opposite to said one direction, and said annular piston abutting said annular disc at one end for moving said annular disc in said direction opposite to said one direction with motion of said annular piston and having its other end extending into said second cham-ber.

3. A fuel pump as recited in Claim 1 wherein said first chamber con-tains gas and includes in the walls thereof a gas pressure relief valve means for venting gas above a predetermined pressure out of said first chamber.

4. A fuel pump as recited in Claim 2 wherein said annular piston moves in said direction opposite said one direction when the gas pressure in said second chamber reaches a level sufficient to overcome the bias applied by said first biasing means to said annular disc.

5. A fuel pump as recited in Claim 1 wherein said means for delivering includes means for admitting fuel into said fuel chamber when said plunger means moves in said direction opposite said one direction in response to the bias applied thereto by said third biasing means, with the fuel remaining in said fuel chamber until said plunger means moves in said one direction toward said fuel chamber.

6. A fuel pump as recited in Claim 1 wherein the gas pressure in said second chamber, required to overcome the bias applied to said annular disc by said first biasing means so as to move it in the direction opposite said one direction is greater than the gas pressure required to move said first piston in said direction opposite said one direction.

7. A fuel pump as recited in Claim 6 wherein said means for delivering includes means for admitting fuel into said fuel chamber when said plunger means moves in said direction opposite said one direction in response to the bias applied thereto by said third biasing means, with the fuel remaining in said fuel chamber until said plunger means moves in said one direction toward said fuel chamber.

8. A fuel pump as recited in Claim 4 wherein said means for delivering include means for admitting fuel into said fuel chamber when said plunger means moves in said direction opposite said one direction in response to the bias applied thereto by said third biasing means, with the fuel remaining in said fuel chamber until said plunger means moves in said one direction to-ward said fuel chamber.

9. A fuel pump as recited in Claim 4 wherein the gas pressure in said second chamber, required to overcome the bias applied to said annular disc by said first biasing means, so as to move it in the direction opposite said one direction is greater than the gas pressure required to move said first piston in said direction opposite said one direction.

10. A fuel pump as recited in Claim 9 wherein said first chamber con-tains gas and includes in the walls thereof a gas pressure relief valve means for venting gas above a predetermined pressure out of said first chamber.