US 3927652 A
A fuel injection system for an internal combustion engine is described, which provides for independent, flexible control of timing as well as quantity of fuel injected. The system is programmable for torque shaping and adaptable to a wide range of engine sizes. It uses piezoelectric valves for controlling injection timing, a shuttle, fuel meter and a gas driven high pressure pump for injecting the fuel into the cylinders.
Claims available in
Description (OCR text may contain errors)
United States Patent ONeill Dec. 23, 1975 FUEL INJECTION SYSTEM FOR INTERNAL 3,625,192 12/1971- Dreisin 123/139 AT COMBUSTION ENGINES 3,752,136 8/1973 Knight l23/l39 AT 3,796,205 3/[974 Links l23/l39 E Inventor: Com ONeiII, Lafayette, Calif- 3,837,324 9/1974 Links 123/139 E  Assignee: Physics International Company, San
Leandro, C lif Primary Examiner-Charles J. Myhre Assistant Examiner-Ronald B. Cox [221 PM: June 1974 Attorney, Agent, or Firm-Lindenberg, Freilich, [21 App! 481,666 Wasserman, Rosen & Fernandez 52 us. 01... 123/139 AT; 123/139 13; 123/32 AB;  ABSTRACT 123 32 A A fuel injection system for an internal combustion en- 51 Int. F02M 39/00 a is described, which Provides for independent.  Field f S h 123/139 AT 139 R 139 flexible control of timing as well as quantity of fuel in- 23 32 AB, 32 EA jected. The system is programmable for torque shaping and adaptable to a wide range of engine sizes. It  References Ci d uses piezoelectric valves for controlling injection tim- UNITED STATES PATENTS ing, a shuttle, fuel meter and a gas driven high pressure pump for injecting the fuel into the cylinders. 3,500,799 3/l970 Benson 123/32 AE 3,587,547 6/1971 Hussey 123/139 E 10 Claims, 8 Drawing Figures |NDl /\DUAL CYLINDER lNJECTlON VALVES -1 FUEL FEED U.S. Patent Dec. 23, 1975 Sheet 1 of5 3,927,652
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v Luflflm FROM 245 mm: CONTROL 91H: CARCU \T AMP ow LATO R \82 24 v posmo CONSTANT jlllfljl Q AMPuTuDE PULSE GEN 4 FLVBACK 2 PULSE TRANSFORMER 2 5o AMP U.S. Patent Dec. 23, 1975 Sheet 2 of5 3,927,652
FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION This invention relates to fuel injection systems for internal combustion engines, and more paricularly to improvements therein.
In the operation of medium and high-speed compression-ignition engines, a compromise is always made between economy, smoke, peak cylinder pressure and more recently, emissions. The fuel injection system appears to be the factor which has the most significant influence on these variables, since limitations in its capabilities set practical boundaries to the choice of operational parameters.
It has been demonstrated that both speed and load influence ideal injection timing. Of the few conventional injection systems that provide timing adjustment, speed control advance is more commonly chosen. A few systems provide speed and load advance, but the mechanism required is heavy, complex and expensive. When unit pumplinjectors--driven by a cam, push rod and rocker from the engine camshaft--are employed, it is not practical to have controlled timing adjustment. Uncontrolled timing variations occur in some of these systems as the fueling is altered.
Control of the combustion by injection timing and/or rate is always attempted in engine development. For example, injection timing is adjusted to hold peak cylinder pressure within design limits. However, the employment of a programmed, non-uniform injection rate can be shown to reduce peak cylinder pressure without significantly influencing economy. A complete investigation of this mode of combustion control has been prevented because conventional injection systems lack the flexibility to achieve rapid changes in injection rate. Furthermore, since they derive injection energy directly from the crankshaft at the time injection is taking place, the entire energy transfer takes place over a small crankshaft angle and very high forces or torques are involved. Consequently, mechanical drives must be rugged and the requirement for variable timing becomes more difficult to satisfy. Torsional impulses are returned to the crankshaft, increasing engine roughness and placing greater demands upon the torsional vibration damper.
Fuels of varying cetane value and specific gravity generally require different injection timings for optimum combustion. The extent of the timing change requried for a range of fuels is greatly dependent upon the engine's design, but frequently the injection timing cannot be maintained at optimum by a single step adjustment. Existing injection systems can be provided with several alternative timing points. changes in fuel type can be accommodated by manually selecting the appropriate setting of the pump coupling to give a compromise timing curve. However, at some speeds and and loads, losses in combustion efficiency occur.
Mechanically controlled injection introduces a programmed maximum fuel vs, speed characteristic by the complicated interaction of dynamic hydraulic effects. Adjustments of the fuel pipe unloading volume, pipe size, nozzle characteristics, pump element diameter, and pump cam are made during development to achieve the torque shaping desired for the particular vehicle or application. Subsequent change in the desired torque curve requires partial or complete rebuild of the fuel injection equipment. Similarly, with speedgoverning, changes in the governed speed, tolerable runout" or fall speed characteristics demand a mechanical rebuild.
This lack of flexibility in the control of mechanical systems requires a large inventory of spare parts or replacement fuel injection equipment sets and tends to prevent the adaptability of complete rebuild engines to a variety of vehicle installations.
OBJECTS AND SUMMARY OF THE INVENTION ,An object of this invention is to provide a fuel injection system which is adaptableto a wide range of engine sizes.
Another object of this invention is to provide a fuel injection system which has readily reprogrammable torque shaping and governing characteristics, and which requires only low torque drives from the engine.
Still a further object of this invention is the provision of a fuel injection system wherein injection timing is programmable with speed and load.
Yet another object of this invention is the provision of a fuel injection system which can be used for fueling engines with wide injection pressure requirements.
Yet another object of the invention is to provide extremely high injection pressure and to relieve pressure entirely on the nozzle valve in between injections to avoid critical dependence upon sealing and condition of nozzle valve.
These and other objects of the invention are achieved in a system wherein fuel is metered, from a central metering unit, to the appropriate cylinder, where it is stored by a structure in the injection valve until the crankshaft achieves the angle desired for injection. The fuel is metered at low pressure, to satisfy operation demands within limitations of smoke, torque shaping, speed governing or emission requirements.
When the crankshaft reaches the angle desired for injection, and 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. 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.
In US. Pat. No. 3,587,547 there is described a fuel injection system wherein the pressure of a metered quantity of fuel to be injected into a cylinder is raised when the time for fuel injection arises, until it can overcome the mechanical biasing force applied to an injection valve. The present invention also raises the pressure of a metered quantity of fuel at fuel injection time, but the force that must be overcome to open the injection valve is applied to the valve from the same high pressure pump whose output is being used to boost the metered fuel pressure. Thus, the effect of pressure variations on the quantity of fuel to he delivered is eliminated with the present invention since, if the pressure output from the high pressure pump vaires the pressure on the metered quantity of fuel and the pressure holding the injection nozzle closed vary correspondingly. This is not the case with a mechanically closed injection nozzle, asis found in the patent. Further, the present invention provides for pilot fuel injection, which is not found or provided for in the patented 3 fuel injection system.
The novel features'of the invention are' set forth with particularly in the appendedclaims. The inventionwill best be understood from the following description when read in conjunction with the accompanying drawlngs.
, BRIEF DESCRlPTlON OF THE DRAWINGS FIG. I is a schematic drawing illustrating a six-cylinderengine with the accompanying fuel injection system, in accordance with this invention.
FIG. 2 is a view in section" of a high pressure gasdriven fuel pump, in accordance with this invention.
FIG. 3 is a schematic view of a fuel metering and distribution 'unit'in accordance with this invention.
FIG. 4'is a view in section of the wedge driving device for controlling the metering shuttle in the fuel metering unit.
FIG. 5. is a schematic drawing of the fuel injection system for pilot and maininjection, in accordance with this invention.
'FIG. 6 is a view in section of a fuel injection structure which is schematically shown in FIG. 5.
HO. 7 is a schematic diagram showing a fuel injection' arrangement for main injection only, in accordance with this invention.
FIG. 8 is a block schematic diagram of the circuit used for controlling the piezoelectric valves used in the fuel injection system. i
DESCRIPTION OF THE EMBODIMENT OF THE INVENTION Referring now to FIG. I, there may be seen a schematic arrangement for a fuel injection system, for an internal combustion engine 32, in accordance with this invention. Electrical controls for the fuel injection system, including the operator control, are contained in a control unit 10 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, drawsfuel from the fuel storage tank, not shown, and raises it to a suitable pressure, such as about sevenbars. The fuel at low pressure is then fed to a metering anddistribution unit 16.
he metering isperformedin a' unit that partitions discrete injection volumes of fuel under the control of an interface control unit I8, and the metering and distribution unit 16 distributes the metal-ed volume of fuel to the respective fuel injectors 20, 22, 24, 26, 28 and 30. There the fuel injectors store in metered quantity of fuel until the crankshaft reaches an angle at which the fuel injectors are actuated to inject fuel into the respective cylinders of the engine 32.
The control unit [0 provides a signal to the interface control'unit I8 is accordance with operator demand within limitations of smoke torque 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 injections 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, in accordance with this invention, a' novel high pressure pump is proposed which is gas operated. 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 unit 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.
FIG. 2 is a view in section of the high pressure gasdriven fuel pump. The high pressure fuel pump comprises a housing 40 which, in its upper section, comprises a chamber 42 within which there is a spring seating 44 centrally positioned bya spring 46, which urges the seating downward. At the top of the chamber is a gas leakage valve 82, which is present so that it will permit gas to leak out of the chamber when the pressure thereinexceeds a predetermined value.
A piston 48 is provided with a c ollar 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 bountlary to chamber60. 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. I L
The housing walls 58 define the fixed walls of chamber 60. The housing 40 lower walls also form a fuel chamber 64, Afu'el 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 leadingfrorn the fuel chamber. The inlet passage is connected through suitable fittings74 to thelow pressure fuel pump. The outlet passage 72 is connected through a suitable fitting 76 to the two fuel injectors which it services. I
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 5; provides a preload 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 annular piston 54 upwards compressing spring 46 and enabling the fuel plunger 66 torise, whereby fuel will be received 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 [2 mm. At this lift, the starting gas piston 48 reaches the position shown in the drawing, which is the limit ofits 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 of 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 spring is designed to contribute about 60% of the total load. The gas spring" comprises using gas under pressure in the chamber 42 above the pistons 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 chamber 42, without which wide fuel injection pressure variations would result, as for example from a temperature increase through a maximum of 300 F. 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., l% 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.
FIG. 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 crankshaft 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 pe riphery of the cylinder 92. The rotating cylinder then can deliver, alternately, fuel to opposite ends, respectively, 96, 98, of a closed hollow cylinder I00, which contains an oscillating shuttle or plunger 102. The plunger is mounted on a shaft I04, which is attached to a shuttle control I06, which serves the function of controlling the length of the shuttle stroke.
Tubing is provided for successively delivering fuel alternately, to the opposite ends of the metering shuttIe-housing I00, 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 comprises a main tube I05 and a main tube 108, which extend from the the respective ends 98, 96 of the metering shuttle to the cylinder 92. At the cylinder 92, tubing I05 has the respective tube studs I10, I12, I14, I16, I18 and I20. Tubing 108 has the following stubs, which extend from it to the periphery of the cylinder, respectively, I22, I24, I26, I28, 130 and 132.
Together with the main tubing 105, the stub tubing I10, I14 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 I05 occurs alternately with the connection to the stubs 122, I26 and 130, of the main tubing I08. In the drawing, stub tubing I22 is shown connected to the passageway 94, and therefore fuel is being fed over the passageway 94 through stub I22 through main tubing I08, to the end 96 of the metering shuttle.
As the shuttle I02 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 I05 and stub tubing II2, 116 and I20 to the cylinder 92.
When main tubing I08 returns fuel to cylinder 92, it does so through tubing stubs I24, I28 and I32.
There is another passageway within the cylinder 92, which successively connects to the stub tubing returning fuel to the cylinder from the metering shuttle. This is a passageway comprising three parts. The first part I34 connects from the periphery of the cylinder 92 to a the fuel delivery stubs, to the axis of the cylinder where there is a second passageway portion I36, which is connected thereto. A third passageway portion I38 connects from the central passageway I36 outward to the periphery of the cylinder again. This passageway section I38 successively connects with tubing respectively I40, I42, I44, 146, I48 and 150, as the cylinder rotates. These tubes 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 I05 is delivering fuel from the metering shuttle, over stub 120, to passageway I34, I36, I38 which is connected to tubing I40. Tubing I40 is connected to one of the injection valves.
When the passageway I38 is not registering with the individual tubing I40 through 150, which delivers fuel to the individual cylinder injection valves, a relief groove 152 is provided which connects each of these tubes to drain tubing I54.
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. Refer ence should be had to FIGS. 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 I06. This comprises for example, a pair of spaced forklike tines, respectively 160, 162, which are in the form of a tapered wedge. Fitted between the space tines of the tapered wedge is an H-shaped abutment unit I64, which, as shown in the cross-sectional view of FIG. 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 downwardly, the shaft 104, together with the abutment unit, can reciprocate a greater distance then when the wedge is moved upwardly. The wedge can be moved upwardly a sufficient distance to block motion by the shaft 104.
From theforegoing it should be appreciated that the position of the wedge tines I60, 162, control the distance which the metering shuttle travels, thereby controlling the volume of fuel being metered to the engine cylinders. The more the tapered wedge is withdrawn from theH-s'haped abutment 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 clos'ed cylinder 168. A spring 171, urges the piston to return the wedge to the no shuttle travel position. A feed tube respectively 170, I72, is connected to each side of the piston 168 with a constriction being in the tube I72, 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 value includes, for example, a piezoelectric bimorph I80, which, in response to electrical signals from the control unit, can be madeto assume a desired angle whereby the passageway beteen tubing 174 and 176 can range from fully open to fully closed.
, A sensing unit 182 which may be electromagnetic Fiall effect, a linear variable differential transformer, or an inductive sensor, is positioned at one end of the extension from the piston 166 whereb the position of thetpiston and thereby the position 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. Therefore, the sensing unit 182 generates a signal indicative of the quantity of fuel being delivered. The signal is fed back to a circuit, shown in detail in FIG. 8, which is within the control unit I0, 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 fully open position. As the wedge adopts the position where the transducer output matches the controlsignal, the disparity falls to zero and the valve holds an opening that creates equalibrium between the hydraulic forces on opposite sides of the piston I66 and the spring I71. 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 I80, by controlling the size of the opening of 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 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 pistonwill 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.
FIG. 5 is a schematic drawing of a fuel injection arrangement for injecting pilot and main fuel into the engine cylinder. FIG. 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 I90, in response to control signals from the control unit 10. Effectively the valve,by way of example, comprises a stack of piezoelecric elements 192 which, in response to the signals from the control unit will cause a plunger 194, to move within a chamber I96. 7
Fuel under low pressure is supplied to the chamber 196 from-the metering unit 16 which is described in FIG. 3 of the drawings, over a-passage which includes a check valve I97. I
High pressure fuel is delivered from a high pressure pump 198 which may be of the type shown in FIG. 2, to
anaccumulator 200, to a main injection control valve 202, shown in its inoperative position, and to a pilot injection control valve 204, shown in its operativeposition. 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 upward positions,
the valves 208 and 212 block delivery of high pressure fuel to the remainder of the system. In order to effectuate pilot injection control, a first signal is applied to the pz valve I90 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 axialcleatance or by operating of an adjuster 241 so that thei'distance' this plunger travels which it is actuated, determines the quantity of fuel which will be injected into the engine cylinder. t
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 pressure intensifier device 226. The piston 224 actuates a plunger 228 downwardly. Fuel was previously delivered from the fuel metering device shown in FIG. 3 through a tube 230, through a check valve 232, to a storage passageway 234 which terminates 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 piston 224 is much greater than the area of the plunger 228 which is 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 correctly 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 injection 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 be injected 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 FIG. 3) will register with drain groove 152 allowing 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 passagway whereby the fuel injection is immediately terminated.
The fuel injection arrangement on the succeeding cylinder in the engines 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 respective control valves, upwardly to their closed position. The next time that I metered fuel is fed into the storage passageway 234, the
pressure of the metered fuel causes plunger 228 to be driven back 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 filling 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.
FIG. 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 FIG. 5, except that the pilot injection 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 2124 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 FIG. 7 are given the same reference numerals as are employed in FIG. 5 since they perform the same functions. it will also be appreciated that when the piezoelectric valve is actuated, it provides a full stroke for actuating the main injection control valve rather than being operated in two steps as is 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 U.S. Pat. No. 3,575,146, entitled Fuel injection System for Interval Combustion Engine. The system has operator inputs for load, fuel-type, and 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 predetermined 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 described.
In the U.S. Pat. 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 injection 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 is usually fixed. The main injection power supply signal is the variable signal, being determined in accordance with all previously indicated parameters. 1n the present application, the quantity of pilot fuel to be injected is determined by the setting of the pilot injection plunger in the pilot valve. The present invention 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 invention, the electrical signal that in the U.S. Pat. No. 3,575,146, would be applied to the main injection power supply to control the quantity of fuel which is to be injected, in the present invention 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 FIG. 8, which is a schematic diagram of the circuitry required. Again, it is to be understood that the electrical 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 invention is gf jtrom the differential applied to the interface control device, shown in FIG. 8, which determines the length of the stroke of the shuttle in the fuel metering device.
FIG. 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 iscalled for by the operator's control as modified by the various other parameters which are measured to determine the correct quantity of fuel: The other inputis from the position sensor I82, which isindicated in FIG. 4 as sensing the position of the shuttle travel determining wedge shaft 159. The output-of the differential ampli-' fier is a signal proportional 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 25KH2, from a constant amplitude pulse generator 244, the modulator outputis a pulse train wherein the amplitude of the pulses is determined by the output amplifier 243. The output of the inodulator 245 ,is then amplified by an amplifier 247 whose output is applied to a flyback pulse transformer 246. The output of the flyback pulse transformer is applied through a rectifying diode piezoelectric device 180. A resistor 250, is connected in parallel with the piezoelectric device-The piezoelec tric device acts as a storage capacitor for the signals applied thereto by flyback transformer 246. The resistor 250 provides a continuous drain to reduce the voltage stored by the piezoelectric device as the electrical drive is removed at'some suitable rempvalrate.
The interface device driving circuit therefore applies pulse signals to the piezoelectric bimorph device, whose amplitude is determined by the difference in positionbetween the voltage signal representing the desired quantity of fuel and the shuttle travel determining wedge position signal 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 performs a servo operation.
There has accordingly been described and shown hereinabove a novel fuel injection system which permits independent control of the timing of fuel delivery and of the quantity of fuel delivered, using novel structural arrangements for accomplishing these, which permit full advantage to be taken of all of the parameters that should be considered for controlling timing and fuel injection to obtain the maximum operation of an internal combustion engine. While a specific embodiment of thisinvention has been shown and described, it will be understood that this is by way of illustration and not by way of limitation, since the scope of spirit of the claim is set forth in the claims appended hereto.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. In an internal combustion engine, a fuel injection system comprising first fuel pump means for providing a supply of fuel at a first pressure,
248, to the bimorph second fuel pump means for providing a supply of fuelat a'second pressure, said second pressure beinghigher than said first pressure,
injectionnozzle 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, a
means for applying fuel from said means for storing fuel to said injection nozzle meanstat said first pressure to apply an opening bias,
means for applying 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 totoperation 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 timing 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.
2. In an internal combustion engine as recited in claim 1 wherein said timing means signal generated by said timing means includes a first signal signifying the time for a pilot fuel injection followed by a second signal signifying the time for a, main injection,
said means responsive to said timing means signal includes means responsive to said first timingsignal for enabling said means for increasing the pressure of said stored fuel to increase said stored fuel pressure until a predetermined amount of said fuel is injected into said cylinder by said injection nozzle means, and v V r g means responsive to said second signal for enabling said means responsive to said timing signal to increase the pressure of said stored fuel until the balance of said stored fuel is injected into said cylinder.
3. In an internal combustion engine as recited in claim] wherein said means responsive to said timing means signal for increasing the pressure of said stored fuel includes a piston having a first surface area,
a plunger moveable responsive to motion of said piston and having a second surface area which is smaller than said first surface area, said plunger surface area being in contact with the fuel stored in said means for storing fuel,
means for applying fuel from'said second fuel pump means to said piston first surface area including a valve means having a closed position wherein it prevents application of fuel from said first fuel pump means to said piston and an open position wherein it enables application of fuel from said second pump means to said piston,
yieldable means biasing said valve means to its closed position, and
means for applying said timing means signal to said valve means to move it'to its open position whereby said piston moves said plunger against said stored 13 fuel to increase its pressure.
4. In an internal combustion engine as recited in claim I wherein said timing means signal generated by said timing means includes a first signal signifying the time for a pilot fuel injection followed by a second signal signifying the time for a main fuel injection,
wherein said means responsive to said timing means signal for increasing the pressure of said stored fuel includes,
a piston having a first surface area,
a plunger moveable responsive to motion of said piston and having a second surface area which is smaller than said first surface area, said plunger surface area being in contact with the fuel stored in said means for storing fuel,
means for applying fuel from said first fuel pump means to said piston first surface area including a pilot valve means and a main valve means, both said valve means having a closed position wherein they each prevent the application of fuel from said second pump means to said piston and an open position wherein fuel from said second pump means is applied to said piston,
means biasing said pilot valve means and said main valve means to their closed positions,
means for applying said first signal to said pilot valve means to move it to its open position whereby said piston is moved responsive to the application of fuel from said second pump means increasing pres sure on said stored fuel sufficiently to open said injection nozzle means to inject stored fuel into said cylinder,
means for limiting the amount of fuel applied to said piston through said pilot valve means to a predete rmined amount to thereby limit the amount of stored fuel injected into said cylinder to a predetermined amount, and
means for applying said second signal to said main valve means to move it to its open position whereby said piston is moved to increase pressure on said remaining stored fuel until it is injected into said cylinder.
5. 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 which is higher than said first pressure,
injection nozzle means for injecting fuel into a cylinder of said engine, when open,
means for applying fuel from said second fuel pump means to said injection nozzle means to bias said injection nozzle means closed,
means for measuring the amount of fuel to be injected into said cylinder,
means for applying fuel from said first fuel pump means at said first pressure to said means for measuring,
means for storing at said first pressure fuel measured by said means for measuring and applying said stored fuel to said injection nozzle means to apply an opening bias at said first pressure,
pressure intensifier means responsive to the application of fuel from said second fuel pump means for increasing the pressure of said stored fuel when operative,
injection control means for enabling the application of fuel from said second pump means to said pressure intensifier means when enabled,
means for generating fuel injection timing signals,
piezoelectric valve means responsive to a fuel injection timing signal for enabling said injection control valve means, whereby said pressure intensifier means increases the pressure of said stored fuel until it exceeds said second pressure and is injected into said cylinder.
6. In an internal combustion engine as recited in claim 5 wherein said injection control valve means includes a pilot injection control valve means for enabling a limited application of fuel from said second pump means to said pressure intensifier to enable injection of a predetermined amount of stored fuel into said cylinder,
a main injection control valve means for enabling further application of fuel from said second pump means to said pressure intensifier to enable injection of the remainder of stored fuel into said cylinder;
wherein said means for generating fuel injection timing signals includes means for generating a pilot timing signal followed by a main timing signal,
said pilot injection control valve means includes biasing means for enabling response to said piezoelectric valve means when activated in response to a pilot timing signal, and
said main injection control valve means includes biasing means for enabling response to said piezoelectric valve means only when activated in response to a main timing signal.
7. In an internal combustion engine as recited in claim 5, wherein said second fuel pump means comprises a first chamber,
an annular disc in said chamber,
first spring means biasing said annular disc toward one end of said chamber,
a second chamber coaxial with said first chamber,
a piston in said second chamber,
a fuel chamber means for delivering fuel to said fuel chamber from said first fuel pump means,
plunger means extending between said fuel chamber and said piston for applying pressure to the fuel in said fuel chamber in response to motion by said piston in one direction,
means for biasing said plunger means in a direction so as not to apply pressure to the fuel in said fuel chamber,
means within said first chamber for biasing said piston toward said one direction,
means coupling said piston and said annular disc motion together after said piston has been moved a predetermined distance in a direction opposite to said one direction, and
means for applying gas from a cylinder of said internal combustion engine to said second chamber to drive said first piston in a direction opposite to said one direction.
8. In an internal combustion engine, as recited in claim 7 wherein said means coupling said first piston and said annular disc comprises an annular piston surrounding said piston, said annular piston having an internal abutment therein for being engaged by said piston after said piston has moved a predetermined distance in a direction opposite to said one direction. and
said annular piston abutting said annular disc at one end for moving said annular disc in a direction opposite to said one direction with motion of said annular piston and having its other end extending into said chamber.
9. In an internal engine as recited in claim 7, wherein said first chamber includes in the walls thereof a gas pressure relief valve means for venting gas above a predetermined pressure out of.said first chamber.
10. In an internal combustion engine as recited in claim 5 wherein said means for measuring the amount of fuel to be injected into said cylinder includes a hollow chamber,
a moveable shuttle within said chamber,
means for alternately directing fuel from said first fuel pump means into opposite ends of said chamher while removing fuel from the end of said chamher opposite to the one into which fuel is being directed, said shuttle being moved by the pressure of fuel being directed into one end of said chamber to force fuel out of the other end of said chamber, and
means for controlling thetravel of said shuttle in response to fuel pressure including wedge means positionable to control the travel of said'shuttle,
valve means actuable for determining the position of said wedge means,
means for generating a fuel signal representative of the quantity of fuel desired,
means for generating a position signal representative of the position of said wedge means,
means for comparing said fuel signal and said position signal to generate a difference signal, and
means for applying said difference signal to said valve means to actuate it responsive thereto.