Abstract: A chamfering portion provided at an inlet corner of a port of an inside way-out in a governor shaft is effective to decrease energy loss of fuel flowing into the inside way-out to less than one half in comparison with that of a conventional art. A flow amount characteristic of the fuel into the inside way-out improves so that a hysteresis between a pump chamber pressure decrease characteristic on increasing a load (a retarding characteristic) and a pump chamber pressure increase characteristic on decreasing the load (an advancing characteristic) is lowered, resulting in securing a highly accurate control of fuel injection timing.

Abstract: Systems and methods for reducing engine emissions in a locomotive are presented. In an embodiment, a fuel injector or a fuel injection pump of a fuel injection mechanism includes a plunger with an upper helix whose angle changes between points on the plunger that correspond to an idle throttle position and a full throttle position. As such, injection timing is optimized, and engine emissions are reduced.

Abstract: Although injection timing accuracy is sensitive to rail pressure, injection quantity of the fuel injection event is strongly a function of rail pressure. Thus, delivery accuracy of each injection event depends strongly upon the accuracy of a rail pressure estimate used in determining the injection control signal characteristics. These injection control signal characteristics include a calculated delay between a start of control current and start of injection, as well as the duration of the control signal. The present invention takes a rail pressure measurement substantially before an injection event, and then utilizes a rail pressure predictor model to predict what the rail pressure will be at each injection event in a succeeding injection sequence. This estimated rail pressure is then used as the means for determining the fuel injection control signal characteristics for that succeeding injection event.

Abstract: An actuator (1), in particular for operation of fuel injectors in fuel injection systems of internal combustion engines, has in this embodiment a plurality of layers (2) of a piezoelectric or magnetostrictive material arranged in a stack. The actuator (1) is prestressed by a tie rod (6) arranged in a central recess (5) by way of opposing threads (7 and 8). Securing the device and the transfer of force are accomplished by a cover plate (3) and a bottom plate (4). The prestress can also be created by a sheathing (9) surrounding the actuator (1), which transfers an axial force component onto the layers (2) via the cover plate (3) and the bottom plate (4) by flanging of projecting ends (10).

Abstract: In an engine equipped with a variable valve timing mechanism that variably controls the valve timing successively, when variably controlling the valve timing, a transient correction amount of fuel supplied to the engine is corrected based on the detection value of the valve overlap amount of the intake/exhaust valves.

Abstract: A combustion control system for a diesel engine provided with a fuel injection system and a sensor for detecting an ignition timing. The combustion control system comprises a control unit which is configured to control the ignition timing to be restored to a target value when the ignition timing shifts from the target value owing to circumferential factors such as cetane number of fuel. Preferably, the ignition timing is controlled to generally coincide with or be retarded relative to a fuel injection termination timing. This regulates an ignition delay period to be longer than a fuel injection period in a predetermined engine operating region, thereby effectively accomplishing so-called low temperature premix combustion.

Abstract: A chamfering portion provided at an inlet corner of a port of an inside way-out in a governor shaft is effective to decrease energy loss of fuel flowing into the inside way-out to less than one half in comparison with that of a conventional art. A flow amount characteristic of the fuel into the inside way-out improves so that a hysteresis between a pump chamber pressure decrease characteristic on increasing a load (a retarding characteristic) and a pump chamber pressure increase characteristic on decreasing the load (an advancing characteristic) is lowered, resulting in securing a highly accurate control of fuel injection timing.

Abstract: A technique is provided for enhancing fluid flow in an outwardly opening nozzle assembly. A flow enhancement assembly is provided adjacent an exit from an outwardly opening poppet to provide desired spray characteristics. The flow enhancement assembly includes converging and diverging passages and a plurality of ports to form a spray.

Abstract: In a method for operating a Diesel engine with a pump-line-nozzle injection system, which allows the pressure level to be raised in the lower and intermediate engine speed ranges in relation to a predetermined maximum permissible injection pressure without this maximum permissible injection pressure being exceeded in the upper engine speed range by providing an injection pump designed to deliver the desired fuel injection pressure at low and intermediate engine speeds and including a pressure relief valve in the fuel injection line permitting limiting of the fuel injection pressure at higher engine speeds.

Abstract: In an injection system for an internal combustion engine, having one fuel pump (10) per engine cylinder to be supplied of the engine, the pump being controlled electronically, having an injection nozzle (12) that is provided with a nozzle needle (34), and having a connecting line (14) between the fuel pump (10) and the injection nozzle (12), it is an object for the injection course to be freely selectable. To this end, the injection nozzle is provided with an electronically controlled valve (48, 50; 50, 52), which is capable of controlling the opening of the nozzle needle (34).

Abstract: In an engine equipped with a variable valve timing mechanism that variably controls the valve timing successively, when variably controlling the valve timing, a transient correction amount of fuel supplied to the engine is corrected based on the detection value of the valve overlap amount of the intake/exhaust valves.

Abstract: A fuel injection device for internal combustion engines, having a high-pressure collection chamber (common rail), which can be filled with fuel by a high-pressure pump and which communicates via injection lines with injection valves that protrude into the combustion chamber of the engine to be supplied, the opening and closing motions of the injection valves each being controlled by an electrically triggered control valve. The control valve is embodied as a 3/2-way valve which connects a high-pressure conduit, discharging at an injection port of the injection valve, with the injection line or a relief line. On the control valve member of the control valve, a hydraulic work chamber that can be filled with high fuel pressure is provided, which can be opened into a relief conduit in order to adjust the set position of the control valve member of the control valve.

Abstract: A fuel injection control system and method for determining a start angle for a fuel injection event based upon engine speed. A controller is coupled to a plurality of fuel injectors associated with the engine and is operable to convert a predetermined timing trim value associated with each fuel injector to an angle trim value.

Abstract: Fuel vapor is introduced into an intake passage of a direct fuel injection type engine by a fuel vapor purge apparatus. The intake passage is provided with an intake oxygen concentration sensor for detecting the amount of fuel vapor in intake air. An ECU corrects the amount of fuel injection from each direct fuel injection valve in accordance with the amount of fuel vapor detected, and changes the fuel injection starting timing and the fuel injection ending timing in accordance with the amount of fuel vapor.

Abstract: Fuel vapor is introduced into an intake passage of a direct fuel injection type engine by a fuel vapor purge apparatus. The intake passage is provided with an intake oxygen concentration sensor for detecting the amount of fuel vapor in intake air. An ECU corrects the amount of fuel injection from each direct fuel injection valve in accordance with the amount of fuel vapor detected, and changes the fuel injection starting timing and the fuel injection ending timing in accordance with the amount of fuel vapor.

Abstract: A fuel injection system for a diesel engine operating at retarded fuel injection timing includes a fuel cam configured to increase a fuel injection pressure and decrease a fuel injection duration, thereby improving fuel atomization and combustion in a plurality of engine cylinders and improving an indicated efficiency of the engine and reducing exhaust emissions. The fuel cam is oriented in a phase relationship with a compression stroke top-dead-center position to accommodate the retarded fuel injection timing and to optimize an engine brake efficiency and performance.

Abstract: An apparatus for reducing visible smoke in a railroad locomotive during throttle position changes. For key throttle position changes, the present invention introduces a temporary advance in injection timing and a delay in the application of additional current to the traction motors, thereby delaying the generation of additional horsepower requested by the new throttle position. These strategies of timing advance and load application delay are used together or separately to minimize transient visible smoke.

Abstract: An exemplary embodiment of the invention is a method of controlling fuel injection timing in a compression ignition engine including at least one cylinder. The method includes monitoring engine throttle position and change. One of an acceleration and a load ascending transient operating mode is detected in response to the monitoring of throttle position and change. Fuel injection timing for the at least one cylinder is controlled in accordance with a predetermined timing schedule in response to the detection of one of an acceleration and a load ascending transient operating mode. A system for implementing the method is also disclosed.

Abstract: A method of retarding injection timing of EMD-type unit injectors by a desired amount of crank degrees includes the steps of providing a modified pump plunger whose control helices differ, in their spacing from the top face of the associated tappet, from the spacing of the control helices of the pump plunger of the original injector from the top face of the associated tappet, such difference in spacing being by an amount equal to the amount of retardation, in linear units, that corresponds to the desired amount of retardation in crank degrees, and assembling the modified pump plunger into an injector assembly.

Abstract: The fuel pump control system includes an electronic control unit (ECU) for controlling the discharge capacity of a plunger type high pressure fuel pump driven by a driving cam connected to the camshaft of an engine. The engine is provided with a variable valve timing device for controlling valve timing of the engine by adjusting the rotation phase of the camshaft relative to the crankshaft. The pump is provided with a suction valve. When the open/close timing of the suction valve changes, the effective discharge stroke of the pump and, thereby the discharge capacity of the pump changes. The ECU estimates the change in the valve timing of the engine during the effective discharge stroke of the pump before the effective discharge stroke starts, and adjusts the open/close timing of the suction valve in accordance with the estimated change in the valve timing so that the discharge capacity of the pump becomes a target discharge capacity regardless of the change in the valve timing of the engine.

Abstract: A reprogrammable electronic step timing control system having a fuel pressure threshold that is discretely variable as a function of engine speed. The fuel pressure threshold is increased for engine speeds above rated speed by a predetermined amount. A programming key is provided in a wiring harness to allow fuel pressure and speed thresholds to be readily changed.

Abstract: The invention relates to a unit injector system for internal combustion engines, in particular diesel engines, having a pump element for subjecting fuel in a pump chamber to high pressure, having an injection element for injecting the pressurized fuel into the combustion chamber of the engine, and having a control valve, which opens and closes a connection between the pump chamber and a low-pressure chamber. To make a preinjection possible, a throttle device (13) is disposed in the connection between the pump chamber and the low-pressure chamber, and there is a flow through the throttle device as a function of the position of the control valve.

Abstract: A fuel injection timing control system for diesel engines operating at high altitude includes a barometric sensor coupled to an altitude timing controller, and a throttle position sensor coupled to the engine and the altitude timing controller. The altitude timing controller adjusts fuel injection timing in response to the sensed pressure and sensed throttle position by advancing or retarding fuel injection timing by predetermined values as barometric pressure and/or throttle position changes. The predetermined values are selected to reduce exhaust emissions and/or increase engine efficiency and performance under various barometric pressure conditions so that the engine may be operated continually and optimally under various barometric conditions.

Abstract: The present invention is a control device and a control method for a cam driving type electronic control unit injector, in which driving force transmitting parts do not separate from a cam even when a high injection pressure is used.

Abstract: A fuel injection pump for internal combustion engines, in particular one-cylinder diesel engines, has a pump piston (1) which can axially slide and rotate in a pump cylinder (13) with at least one fuel suction bore (14), a driving groove (6) arranged on the pump piston (1) parallel to the piston longitudinal axis, and geometrical connection between the front side (4) and the outer surface of the pump piston (1). In order to hydrodynamically regulate the optimum injection beginning during start, idle running and highest speed of rotation, a narrow slot (2,7) is provided as geometrical connection.

Abstract: A fuel injection device for a diesel engine adapted to perform a preliminary injection (1) and a main injection (2) to a combustion chamber (3), wherein the preliminary injection (1) is adjusted to begin within a valve overlap term (40).Within the valve overlap term (40), no intake air is introduced into the combustion chamber (3) or a little if any and the combustion chamber (3) contains a gas of high temperature. If the preliminary injection (1) is conducted into this gas of high temperature within the combustion chamber (3), a preliminary injection fuel vaporizes soon to thereby shorten the ignition lag of a main injection fuel with the result of improving the combustion.

Abstract: A plug-in pump is provided for an internal combustion engine having a receiving bore in the cylinder block to accommodate the plug-in pump. The plug-in pump includes a pump plunger and a spring-loaded roller tappet driven by a cam of a camshaft. The longitudinal axis of the plug-in pump lies transversely in relation to the camshaft axis and at a distance from it, so that the longitudinal axis of the plug-in pump, seen in the direction of turn of the camshaft, lies in front of the camshaft axis.

Abstract: An objective of the present invention is to provide a fuel injection pump wherewith, in addition to main injection, pre-injection is made possible in the vicinity of top dead center in the exhaust stroke, and wherewith, by regulating the pre-stroke, defined as the stroke from bottom dead center of a plunger 2 to the commencement of fuel line pressurization, it is possible to freely control both the pre-injection volume and the pre-injection timing relative to the main injection. Attention having been given to the combining of a pre-stroke varying mechanism together with a two-stage injection mechanism, the present invention is a fuel injection pump that is made so that a pre-stroke is regulated by changing the relative positions, in the axial direction, of a plunger 2 that sends fuel under pressure and a control sleeve 3 that fits around the outside of the plunger 2 so as to slide freely thereon.

Abstract: A rotary fuel pump and fuel injectors including a combination spark plug/fuel injector are described. The rotary fuel pump includes a camshaft carrying an eccentric cam. A plurality of rocker arms follow the cam and cause a plurality of plungers in fuel pumps to reciprocate pumping fluid with each plunger stroke. The rocker arms may include cooperating radially inner and outer rocker arms interposed between the eccentric cam and the plungers and having pivots which may be moved with respect to one another to varying the displacement of the plunger strokes. The fuel injector includes a housing having a plunger bore and a fuel inlet bore in fluid communication with one another. A plunger reciprocates within the plunger bore and has a valve seat is biased closed against a valve seat on the housing by elastomeric O-rings. The O-rings seal between the plunger and the plunger bore. Pressurized fluid pressing upon the plunger may overcome the bias allow fuel to sprayed from the plunger bore.

Abstract: A system is described for the control of an internal combustion engine, in particular a diesel gasoline engine, in the case of which at least one solenoid valve determines the beginning and the end of the fuel metering. First device (130) evaluate the signals of at least one first sensor (110) which generates a plurality of increment pulses. Second device (140) evaluate the signals of at least one second sensor. The second device transmits an angle size to the first device at specifiable points of time. The first device releases a signal starting out from this angle size and the signals of the first sensor (110).

Abstract: The fuel injection pump does not generate an excessively large drive torque at the end of the fuel injection under the condition of the most advanced injection timing, even if a geometric injection rate (GIR) is raised to shorten an injection period. The fuel injection pump includes a sleeve (4), a plunger (1) movably received in the sleeve (4), a cam (2') for moving the plunger up and down in the longitudinal direction of the sleeve. The sleeve is shiftable relative to the plunger in the longitudinal direction of the plunger to delay or advance an injection timing and to use different portions of the cam from start (22) to end (23) of fuel injection. The cam (2') has a unique configuration to insure that when the sleeve is shifted downward and the fuel. injection timing is most advanced, the GIR drops from the start of the injection to the end.

Abstract: Start of fuel delivery for a fuel-injected engine having separate unit injectors is adjusted by effecting a positional adjustment of camshaft lobes on a camshaft. The camshaft is used to operate the unit injectors, as well as control exhaust valve operations. By separately controlling the position of the cam lobes which operate the unit fuel injectors, a change it start of fuel delivery is effected. A change in relative position of the cam lobes is accomplished by shifting a guide rod within a hollow body of the camshaft. The change in position of the guide rod, in turn, effects a change in position of the cam lobes which are connected to the guide rod.

Abstract: A cam follower lever assembly is provided which permits variable control of the timing of the beginning of operation of an engine component, i.e. fuel injector or engine valve. The cam follower lever includes a timing control lever and a force transmitting lever mounted for pivotal movement on a common pivot shaft. The timing control lever is also mounted for nonpivotal movement, relative to the pivot shaft, by a hydraulic actuation device permitting selective nonpivotal movement of the timing control lever relative to a cam's outer surface so as to selectively advance or retard the timing of, for example, fuel injection. The actuation device includes actuator cavities formed in the levers and a control valve arrangement. In one embodiment, a control valve is mounted in a cavity formed in the timing control lever.

Abstract: In a fuel injection pump equipped with a plunger producing preflow effect, pressurized fuel is delivered at least in the low engine speed region by driving the plunger using a region of a cam on the decreasing velocity side of its maximum velocity point. As a result, the fuel delivery rate is reduced during low-speed engine operation and increased during high-speed engine operation, providing an ideal fuel delivery rate for an indirect-injection type engine equipped with swirl chambers or auxiliary chambers.

Abstract: The movement of a control sleeve in the circumferential direction is made to interlock with the movement of a timer piston to ensure that the control sleeve has a function of pre-stroke control. In order to interlock the movements of the timer piston and the control sleeve, they are linked with first through third link members and the control sleeve is caused to rotate in the circumferential direction at a specific ratio relative to the quantity of movement of the timer piston. In a fuel injection system provided with an actuator for adjusting the fuel force feed end by moving the control sleeve in the direction of the axis and an actuator for controlling the timing with which the cam lift begins, pre-stroke control can be achieved without requiring a separate actuator, with a simple mechanical structure.

Abstract: Inflow/outflow ports are provided in either one of a distribution member for distributing compressed fuel or a control sleeve which is externally fitted around the distribution member. Each of the ports includes a slit extending therefrom. At the other one of the distribution member and the control sleeve, an intake-cutoff hole that communicates sequentially with the inflow/outflow ports and a pilot port which communicates with the slits during part of the force feed period are provided. Since the fuel flows out through the slits during part of the force feed period, pilot injection can be more easily achieved prior to the main injection during low speed rotation and fuel is less likely to be diverted through the slits due to the constricting effect during high speed rotation so that only the main injection is performed.

Abstract: A fuel injection pump for internal combustion engines in which to control the fuel injection quantities with the internal combustion engine cold, a first control edge is provided. For controlling the start of fuel injection with the internal combustion engine hot, a second control edge and a third control edge are provided. Assigned to respective control edges are provided a first and second oblique control edge, by means of which an effective pump piston feed stroke is controlled according to the rotary position of the pump piston. To switch off the internal combustion engine, in the region of transition from the first control edge to the second control edge the assignment of this second control edge to the second oblique control edge is provided in such a way that injection ceases on account of an overlap with a control port.

Abstract: A prestroke controller 31 for an engine fuel injection pump 30 utilizes a magnetic coupling 26 and, by taking advantage of the fact that the secondary side (driven side internal magnet) of the magnetic coupling can be controlled to a desired position without being driven by force from a flyweight 11 on the primary side (driving side external magnet), not only secures speed timer characteristics but also provides a greater degree of freedom in determining the injection timing advance characteristic. The prestroke controller 31 includes the magnetic coupling 26 as a member of a displacement transfer section provided between the flyweight 11 and the timing control rod 6 and also includes an add-on device 36 for injection timing advance adjustment which can be engaged with or disengaged from the timing control rod 6 and is capable of controlling the prestroke independently of the magnetic coupling 26.

Abstract: A fuel-injection pump for internal combustion engines, particularly an in-line injection pump for diesel engine, with a control bore in the pump cylinder and with an upper control edge for determining the start of feed and an oblique spill edge for determining the end of feed. The pump piston is rotated about its longitudinal axis in order to set the desired feed quantity, for the purpose of achieving a better regulating behavior of the system as a whole, comprising the fuel-injection pump, feed-quantity regulator and internal-combustion engine. The spill edge is subdivided, along its run over a part of the circumference of the pump piston, into portions with different angles of inclination (.alpha..sub.1, .alpha..sub.2) to the axis of the pump piston. The control-edge portion having the large angle of inclination (.alpha..sub.

Abstract: In a method of injection fuel for Diesel engine comprising a high pressure injection pump with a fuel supply line for supplying high pressure fuel to fuel injection nozzles wherein a fuel control line extends between the pump and a low pressure fuel supply line for discharge in excess fuel thereto under the control of a magnetic valve which is closed to end the discharge of excess fuel and initiate pumping of fuel, the magnetic valve is opened at the end of fuel pumping at a point corresponding to a piston stroke length h after the upper dead center of the piston such that, when communication between the pump and the low pressure fuel line is established, pressure pulses in the low pressure fuel line are avoided.

Abstract: A multipiece fuel pump plunger assembly for controlling the fuel injection rate and delivery during the initial injection portion of a fuel injection cycle for an internal combustion engine. The injector includes a two piece plunger assembly including a plunger and a plunger sleeve. The plunger having a small predetermined diameter and being slidably positioned within a plunger sleeve having a diameter greater than the diameter of the plunger. The multipiece plunger is advantageous because it allows for shaping of the rate of fuel injected into the combustion process thereby reducing the excess fuel flow in the early portion of the injection cycle. Elimination of the excess fuel flow results in lower oxides of nitrogen and particulate exhaust emission levels and less engine noise.

Abstract: An apparatus and method for sampling the pressure of a hydraulic actuator fluid used in connection with an electronically controlled hydraulic actuator unit injector fuel system is disclosed. The apparatus and method eliminates aliasing and other sampling errors caused by oscillations in the hydraulic actuator fluid pressure. The apparatus and method senses an engine parameter to permit an electronic controller to calculate an injection time and duration for fuel to be delivered to a particular cylinder. The electronic controller issues a driver signal to a hydraulically actuated unit fuel injector. A hydraulic actuator fluid pressure sensor is associated with the pressurized hydraulic actuator fluid. The electronic controller samples the hydraulic actuator fluid pressure sensor in dependence on the issuance of the driver signal.

Abstract: An injection arrangement for injecting a pressure medium, especially fuel, into a cylinder of an internal combustion engine, specifically a large diesel engine with several cylinders, comprising at least two injection pump elements (1a,1b) arranged in a common pump body (1) and arranged to inject the pressure medium into the same cylinder during at least one continuous injection period, each pump element (1a,1b) including a pump cylinder (7a,7b), a piston member (8a,8b) reciprocatingly movable therein and a pressure chamber (13,13a,13b). The piston members (8a,8b) receive their control from a cam race (5a,5b) of at least one cam arranged in a camshaft (4) or the like of the engine and the pressure chambers (13,13a,13b,13c) in the pump cylinders (7a,7b) are continuously in connection with each other.

Abstract: An improved electronically-controlled fluid injector system comprises a fluid storage chamber and a direct-operated check. Pressurization of fluid in the storage chamber begins before the start of fluid injection. Fluid injection begins by hydraulically unbalancing the check. Fluid injection sharply ends by hydraulically balancing the check to allow a biasing device to close the check.The present invention provides improved control of several fluid injection parameters, including higher peak fluid injection capability and less fluid injection pressure drop at the end of injection, resulting in improved engine performance and lower emissions, noise, and wear.

Abstract: A fuel injection pump for internal combustion engines having a pump piston guided in a cylinder liner and defining in the cylinder liner a pump work chamber, which piston cooperates with a control opening in the wall of the cylinder liner to control the high pressure delivery. To control the supply onset, the pump piston has on its face end three control edges offset from each other along the length of the piston; a zero supply quantity region is provided between the first control edge, which controls a very early supply onset, and the remaining control edges.

Abstract: A solenoid valve unit is provided in the middle of fuel supply path that leads to a compression space in an injection pump main body, and the fuel injection quantity is adjusted through the open and close control of the solenoid valve unit. In this fuel injection system, the plug valve is moved until it is seated on the valve seat during the preliminary injection that is performed prior to the main injection. An arrangement for leaking the fuel from within the compression space is provided in the injection pump main body and the time period during which the fuel in the compression space is leaked via the arrangement for leaking and the time period during which the fuel supply path is restricted with the plug valve being seated on the valve seat are combined to stabilize the movement of the plug valve. Consequently, an optimal small quantity is achieved for the preliminary injection that is nearly constant regardless of the rate of rotation of the engine.

Abstract: A metering system is provided which controls the amount of fuel supplied to the combustion chambers of a multi-cylinder internal combustion engine comprising a fuel pump for supplying fuel at low pressure to a first and a second group of unit fuel injectors, a first solenoid-operated fuel control valve controlling the flow of fuel to the first set of injectors and a second solenoid-operated fuel control valve controlling the flow of fuel to the second set of injectors. The system may also include first and second solenoid-operated timing fluid control valves associated with the first and the second group of injectors, respectively. The injectors are capable of being in the fuel receiving mode, establishing a metering period, and the timing receiving mode, establishing a timing period, at the same time to increase the amount of time available for metering both timing fluid and fuel.

Abstract: A fuel injection pump for internal combustion engines, having a pump piston that moves in a cylinder liner and defines a pump work chamber with the cylinder. The piston has two control edges that cooperate with a control opening in the cylinder liner. One, control edge is oblique, disposed on the jacket face and communicates continuously with the pump work chamber which controls the end of supply. A first upper control edge formed by the face end of the pump piston, controls the supply onset upon overtaking the control opening. For a load- and temperature-dependent shift of the supply onset toward early, the face end of the pump piston has a first region (B), axially indented in the direction of the cam drive, forming a second control edge, which is separated from the flat region (A) on the face end by a longitudinal groove and in the first region a second region (C), indented via shoulders is disposed in turn in the direction of the cam drive, with a third control edge.

Abstract: A pump-line-nozzle fuel injection system in which a supply pump is coupled to a high pressure pump having a plurality of pumping cylinders, each of which has a cam-driven timing plunger and a floating metering plunger. During the retraction stroke, flow to a timing chamber formed between the pistons is blocked by a solenoid valve while the fuel passes into a metering chamber, at the discharge side of the pump, which is closed relative to the high pressure delivery line by a delivery valve. Once the proper quantity of fuel has been metered, the solenoid valve opens allowing fuel to flow into the metering chamber, balancing the pressure on opposite sides of the metering piston, so as to prevent the metering plunger from retracting further as the timing plunger continues to retract. During the compression stroke, at the appropriate time for commencement of injection, the solenoid valve recloses creating a hydraulic link between the metering and timing plungers, so that the fuel is pressurized.

Abstract: A unit fuel injector adapted to receive fuel from a fuel supply at relatively low pressure and adapted to inject fuel at relatively high pressure into the combustion chamber of an internal combustion engine is provided, comprising an injector body having a first internal bore and an injector orifice and a plunger mounted for reciprocating movement within the first internal bore to define a variable volume fuel pressurization chamber including a cam actuated upper plunger portion and a lower plunger portion mounted in the first internal bore between the variable volume fuel pressurization chamber and the upper plunger portion. While the upper plunger portion is in its retracted position, low pressure fuel from the fuel supply is supplied to the variable volume fuel pressurization chamber.