Title of Invention

"A RECIPROCATING FLUID PUMP ASSEMBLY"

Abstract

A reciprocating pump assembly includes a drive section and a pump section. The drive section has a reciprocating coil assembly to which alternating polarity control signals are applied during operation. A permanent magnet structure of the drive section creates a magnetic flux field which interacts with an electromagnetic field produced during application of the control signals to the coil. Depending upon the polarity of the control signals applied to the coil, the coil is driven in one of two directions of movement. A drive member transfers movement of the coil to a pump element which reciprocates with the coil to draw fluid into a pump chamber and expel the fluid during each pump cycle. The pump is particularly well suited to cyclic pumping applications, such as fuel injection and emissions control systems for internal combustion engines.

Full Text

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reciprocating fluid pump assembly. The present invention relates generally to the field of electrically-driven reciprocating pumps. More particularly, the invention relates to reciprocating fluid pump employing reversing polarity motor wherein a pump driven by a solenoid assembly employing a permanent magnet and a solenoid coil to produce pressure variations in a pump section and thereby to draw into and express a fluid from the pump section. The invention also relates to fuel injection systems, exhaust injection and emissions control systems employing such a pump. 2. Description Of The Related Art A wide range of pumps have been developed for displacing fluids under pressure produced by electrical drives. For example, in certain fuel injection systems, fuel is displaced via a reciprocating pump assembly which is driven by electric current supplied from a source, typically a vehicle electrical system. In one fuel pump design of this type, a reluctance gap coil is positioned in a solenoid housing, and an armature is mounted movably within the housing and secured to a guide tube. The solenoid coil may be energized to force displacement of the armature toward the reluctance gap in a magnetic circuit defined around the solenoid coil. The guide tube moves with the armature, entering and withdrawing from a pump section. By reciprocal movement of the guide tube into and out of the pump section, fluid is drawn into the pump section and expressed from the pump section during operation. In pumps of the type described above, the armature and guide tube are typically returned to their original position under the influence of one or more biasing springs. Where a fuel injection nozzle is connected to the pump, an additional biasing spring may be used to return the injection nozzle to its original position. Upon interruption of energizing current to the coil, the combination of biasing springs then forces the entire movable assembly to its original position. The cycle time of the resulting device is the sum of the time required for the pressurization stroke during energization of the solenoid coil, and the time required for returning the armature and guide to the original position for the next pressure stroke. The cycle times for these pumps can be extremely rapid where such pumps are employed in demanding applications, such as for supplying fuel to combustion chambers of an internal combustion engine or for injecting fluids into an exhaust stream to reduce emissions. Moreover, repeatability and precision in beginning and ending of pump stroke cycles can be important in optimizing the performance of the engine under varying operating conditions. While the cycle time may be reduced by providing stronger springs for returning the reciprocating assembly to the initial position, such springs have the adverse effect of opposing forces exerted on the reciprocating assembly by energization of the solenoid. Such forces must therefore be overcome by correspondingly increased forces created during energization of the solenoid. At some point, however, increased current levels required for such forces become undesirable due to the limits of the electrical components, and additional heating produced by electrical losses. There is a need, therefore, for an improved technique for pumping fluids in a linearly reciprocating fluid pump. There is a particular need for an improved technique for providing rapid cycle times in fluid pumps without substantially increasing the forces and current demands of electrical driving components. SUMMARY OF THE INVENTION The present invention provides a novel technique for pumping fluids in a reciprocating pump arrangement designed to respond to these needs. The technique is particularly well suited for delivering fuel to a combustion chambers such as with direct in-chamber fuel injection, and for injecting fluids into an exhaust stream for emissions control. However, the technique is in no way limited to such applications, and may be employed in a wide range of technical fields. The pumping drive system offers significant advantages over known arrangements, including a reduction in cycle times, controllability of initial positions of a reciprocating assembly, controllability of stroke of a reciprocating assembly, and thereby of displacement per cycle, and so forth. The technique is based upon a drive system employing at least one permanent magnet and at least one coil assembly. The coil assembly is energized cyclically to produce a Lorentz-force for reciprocally moving a drive member, which may be coupled directly to the coil. During movement of the drive member in either direction, the polarity ofthe coil assembly may be reversed to provide an opposite Lorentz-fbrce for dampening the movement as needed. The drive member may extend into a pumping section, and cause variations in fluid pressure by intrusion into and withdrawal from the pumping section during its reciprocal movement Valves, such as check valves, within the pumping section are actuated by the variations in pressure, permitting fluid to be drawn into the pumping section and expressed therefrom. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other advantages ofthe invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: Figure 1A is a diagrammatical representation of a series of fluid pump assemblies applied to inject fuel into an internal combustion engine; Figure IB is a diagrammatical representation of an emissions control system, which injects water-based fluid into the exhaust of the internal combustion engine; Figure 1C is a diagrammatical representation of an emissions control system, which injects a urea-based fluid into the exhaust of the internal combustion engine; Figure 2 is a partial sectional view of an exemplary pump in accordance with aspects of the present technique for use in displacing fluid under pressure, such as for fuel injection into a chamber of an internal combustion engine as shown in Figure 1A; Figure 3 is a partial sectional view of the pump illustrated in Figure 2 energized during a pumping phase of operation; Figure 4 is a partial sectional view of an alternative embodiment of a drive section of a fluid pump in accordance with aspects of the present technique; and Figure 5 is a partial sectional view of a further alternative embodiment of a pump drive section. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS Turning now to the drawings and referring first to Figure 1 A, a fuel injection system 10 is illustrated diagrammatically, including a series of pumps for displacing fuel under pressure in an internal combustion engine 12. While the fluid pumps of the present technique may be employed hi a wide variety of settings, they are particularly well suited to fuel injection systems in which relatively small quantities of fuel are pressurized cyclically to inject the fuel into combustion chambers of an engine as a function of the engine demands. The pumps may be employed with individual combustion chambers as in the illustrated embodiment, or may be associated in various ways to pressurize quantities of fuel, as in a fuel rail, feed manifold, and so forth. Even more generally, the present pumping technique may be employed in settings other than fuel injection, such as for displacing fluids under pressure in response to electrical control signals used to energize coils of a drive assembly, as described below. For example, the pumping technique may be employed in emissions control systems, such as illustrated in Figures IB and 1C.In the embodiment shown in Figure 1A, the fuel injection system 10 includes a fuel reservoir 14, such as a tank for containing a reserve of liquid fuel. A first pump 16 draws the fuel from the reservoir, and delivers the fuel to a separator 18. While the system may function adequately without a separator 18, in the illustrated embodiment, separator 18 serves to insure that the fuel injection system downstream receives liquid fuel, as opposed to mixed phase fuel. A second pump 20 draws the liquid fuel from separator 18 and delivers the fuel, through a cooler 22, to a feed or inlet manifold 24. Cooler 22 may be any suitable type of fluid cooler, including bom air and liquid heater exchangers, radiators, and so forth. Fuel from the feed manifold 24 is available for injection into combustion chambers of engine 12, as described more fully below. A return manifold 26 isprovided for recirculating fluid not injected into the combustion chambers of the engine. In the illustrated embodiment, a pressure regulating valve 28 is placed in series in the return manifold line 26 for maintaining a desired pressure within the retummanifbld. Fluid returned via the pressure regulating valve 28 is recirculated into the separator 18 where the fuel collects in liquid phase as illustrated at reference numeral 30. Gaseous phase components of the fuel, designated by referenced numeral 32 in Figure 1A, may rise from the fuel surface and, depending upon me level of liquid fuel within the separator, may be allowed to escape via a float valve 34. A vent 36 is provided for permitting the escape of gaseous components, such as forrepressurization, recirculation, and so forth. Engine 12 includes a series of combustion chambers or cylinders 38 for driving an output shaft (not shown) in rotation. As will be appreciated by those skilled in the art, depending upon the engine design, pistons (not shown) are driven in a reciprocating fashion within each combustion chamber in response to ignition of fuel within the combustion chamber. The stroke of me piston within the chamber will permit fresh air for subsequent combustion cycles to be admitted into the chamber, while scavenging combustion products from the chamber. While the present embodiment employs a straightforward two-stroke engine design, the pumps in accordance with the present technique may be adapted for a wide variety of applications and engine designs, including other than two-stroke engines and cycles. In the illustrated embodiment, a reciprocating pump 40 is associated with each combustion chamber, drawing pressurized fuel from the feed manifold 24, and further pressurizing the fuel for injection into the respective combustion chamber. A nozzle 42 is provided for atomizing the pressurized fuel downstream of each reciprocating pump 40. While the present technique is not intended to be limited to any particular injection system or injection scheme, in the illustrated embodiment a pressure pulse created in the liquid fuel forces a fuel spray to be formed at the mouth or outlet of the nozzle, for direct, in-cylinder injection. The operation of reciprocating pumps 40 is controlled by an injection controller 44. Injection controller 44, which will typically include a programmed microprocessor or other digital processing circuitry, and memory for storing a routine employed in providing control signals to the pumps, applies energizing signals to the pumps to cause their reciprocation in any one of a wide variety of manners as described more fully below. Reciprocating pumps, such as described in detail below, can also be used in various other industrial, automotive, or marine applications. For example, a reciprocating pump can be used to inject a desired fluid into an exhaust stream from a combustion engine to control temperature and to facilitate other emissions control measures, such as by selective catalytic reduction (SCR) of nitrogen oxides (NOx) and catalytic oxidation (OXI) of hydrocarbons (HC) and carbon monoxide (CO). Accordingly, the particular fluid injected into the exhaust stream may effectively reduce emissions of nitrogen oxides, sulfur oxides, hydrocarbons, and various other particulate matter and undesirable pollutants. Figures IB and 1C illustrate exemplary emissions control systems 44, which treat exhaust 46 from a combustion engine 48. The combustion engine 48 may embody any sort of two-stroke or four-stroke engine for a particular application, such as automotive or marine applications. As illustrated, the combustion engine 48 has a piston 50 movably disposed in a cylinder 52 between a top dead center position 54 and a bottom dead center position 56, which form a variable combustion chamber 58 above the piston 50. The piston 50 is coupled to a crankshaft assembly 60 via a piston rod 62, which rotates the crankshaft assembly 60 following injection, ignition and combustion of a fuel-air mixture within the combustion chamber 58. The fuel-air mixture is provided via an air intake 64 and a fuel injection system 66, which draws a desired fuel mixture from a fuel source 68 (e.g., as illustrated in Figure 1 A). The desired fuel mixture may comprise gasoline, diesel fuel, a hydrogen based fuel, or any suitable fuel mixture. The fuel injection timing can be controlled by a dedicated control unit or by a master control unit, such as control unit 70, which also controls a spark ignition system 72 and a. fluid pump 74. Accordingly, the control unit 70 ensures that a suitable amount of fuel is injected into the combustion chamber 58 at me proper time to facilitate fuel-air mixing prior to ignition. The control unit 70 then commands the spark ignition system 72 to ignite the fuel-air mixture within the combustion chamber 58, causing the piston 50 to move downwardly within the cylinder 52. This downward motion of the piston 50 rotates the crankshaft to provide a desired mechanical motion, such as movement of a drive shaft for an automobile or marine propeller. Various combustion products (i.e., exhaust 46) are men expelled from the combustion chamber 58 via an exhaust passage 76, which may embody one or more exhaust ports, exhaust manifolds, exhaust headers, exhaust pipes, tune pipes, catalytic converters, mufflers, tail pipes, and other exhaust control devices. As illustrated in Figure IB, the fluid pump 74 draws water from a water source 78 and injects the water into the exhaust 46. This water injection advantageously reduces the temperature of the exhaust gases and reduces exhaust emissions from the engine 48. As illustrated in Figure 1C, the fluid pump 74 draws a urea-based fluid from a urea source 80 and injects the urea-based fluid into the exhaust 46. This urea-based fluid injection is particularly advantageous for emissions reduction in diesel engines. Although specific examples are provided in Figures IB and 1C, the fluid pump 74 may inject any suitable emissions control fluid into the exhaust 46. The control unit 70 also may time the fluid injections to the exhaust pulses exiting from the engine 48. As illustrated below with reference to Figures 2-5, the fluid pump 74 may embody a pump and nozzle assembly 100 that is configured to create an exhaust treatment spray comprising water, urea, ammonia, or any other desired treatment fluid. An exemplary reciprocating pump assembly, such as for use in a fuel injection system of the type illustrated in Figure 1A or an emissions control system 44 of the type illustrated in Figures IB and 1C, is shown in Figures 2 and 3. Specifically, Figure 2 illustrates the pump and nozzle assembly 100 which incorporates a pump driven in accordance with the present techniques. Assembly 100 essentially comprises a drive section 102 and a pump section 104. The drive section is designed to cause reciprocating pumping action within the pump section in response to application of reversing polarity control signals applied to an actuating coil of the drive section as described in greater detail below. The characteristics of the output of the pumping section may thus be manipulated by altering the waveform of the alternating polarity signal applied to the drive section. In the presently contemplated embodiment, the pump and nozzle assembly 100 illustrated in Figure 2 is particularly well suited to application in an internal combustion engine, as illustrated by pumps 40 and 74 in Figures 1A-1C. Moreover, hi the embodiment illustrated in Figure 2, a nozzle assembly is installed directly at an outlet of the pump section, such that the pump and the nozzle (e.g., pump 40 and nozzle 42 of Figure 1A) are incorporated into a single assembly or unit The pump 74 of Figures IB and 1C also may comprise a separate or integral nozzle assembly. As indicated above in Figure 1 A, in appropriate applications, the pump illustrated in Figure 2 may be separated from the nozzle, such as for application of fluid under pressure to an intake or exhaust manifold, a fuel rail, or any other downstream component. As illustrated in Figure 2, drive section 102 includes a housing 106 designed to sealingly receive the drive section components and support them during operation. The drive section further includes at least one permanent magnet 108, and in the preferred embodiment illustrated, a pair of permanent magnets 108 and 110. The permanent magnets are separated from one another and disposed adjacent to a central core 112 made of a material which is capable of conducting magnetic flux, such as a ferromagnetic material. A coil bobbin 114 is disposed about permanent magnets 108 and 110, and core 112. While magnets 108 and 110, and core 112 are fixedly supported within housing 106, bobbin 114 is free to slide longitudinally with respect to these components. That is, bottan 114 is centered around core 112, and may slide with respect to the core upwardly and downwardly in the orientation shown in Figure 2. A coil 116 is wound within bobbin 114 and free ends of the coil are coupled to leads L for receiving energizing control signals, such as from an injection controller 44, as illustrated in Figure 1A Bobbin 114 further includes an extension 118 which protrudes from the region of the bobbin in which the coil is installed for driving the pump section as described below. Although one such extension is illustrated in Figure 2, it should be understood that the bobbin may comprise a series of extensions, such as 2,3 or 4 extensions arranged circumferentially around the bobbin. Finally, drive section 102 includes a support or partition 120 which aids in supporting the permanent magnets and core, and in separating the drive section from the pump section. It should be noted, however, that in the illustrated embodiment, the inner volume of the drive section, including the volume hi which the coil is'disposed, may be flooded with fluid during operation, such as for cooling purposes. A drive member 122 is secured to bobbin 114 via extension 118. In the illustrated embodiment, drive member 122 forms a generally cup-shaped plate having a central aperture for the passage of fluid. The cup shape of the drive member aids in centering a plunger 124 which is disposed within a concave portion of the drive member. Plunger 124 preferably has a longitudinal central opening or aperture 126 extending from its base to a head region 128 designed to contact and bear against drive member 122. A biasing spring 130 is compressed between the head region 128 and a lower component of the pump section to maintain the plunger 124, me drive member 122, and bobbin and coil assembly in an upward or biased position. As will be appreciated by those skilled in the art, plunger 124, drive member 122, extension 118, bobbin 114, and coil 116 thus form a reciprocating assembly which is driven in an oscillating motion during operation of the device as described more fully below. The drive section 102 and pump section 104 are designed to interface with one another, preferably to permit separate manufacturing and installation of these components as subassemblies, and to permit their servicing as needed. In the illustrated embodiment, housing 106 of drive section 102 terminates in a skirt 132 which is secured about a peripheral wall 134 of pump section 104. The drive and pump sections are preferably sealed, such as via a soft seal 136. Alternatively, these housings may be interfaced via threaded engagement, or any other suitable technique. Pump section 104 forms a central aperture 138 designed to receive plunger 124. Aperture 138 also serves to guide the plunger in its reciprocating motion during operation of the device. An annular recess 140 surrounds aperture 138 and receives biasing spring 130, maintaining the biasing spring in a centralized position to further aid in guiding plunger 124. In the illustrated embodiment, head region 128 includes a peripheral groove or recess 142 which receives biasing spring 130 at an end thereof opposite recess 140. A valve member 144 is positioned in pump section 104 below plunger 124. In the illustrated embodiment, valve member 144 forms a separable extension of plunger 124 during operation, but is spaced from plunger 124 by a gap 146 when plunger 124 is retracted as illustrated in Figure 2. Gap 146 is formed by limiting the upward movement of valve member 144, such as by a restriction in the peripheral wall defining aperture 138. Grooves (not shown) may be provided at this location to allow for the flow of fluid around valve member 144 when the plunger is advanced to its retracted position. As described more fully below, gap 146 permits the entire reciprocating assembly, including plunger 124, to gain momentum during a pumping stroke before contacting valve member 144 to compress and expel fluid from the pump section. Valve member 144 is positioned within a pump chamber 148. Pump chamber 148 receives fluid from an inlet ISO. Inlet ISO thus includes a fluid passage 152 through which fluid, such as pressurized fuel, is introduced into the pump chamber. A check valve assembly, indicated generally at reference numeral 154, is provided between passage 152 and pump chamber 148, and is closed by the pressure created within pump chamber 148 during a pumping stroke of the device. In the illustrated embodiment, a fluid passage 156 is provided between inlet passage 152 and the volume within which the drive section components are disposed. Passage 156 may permit the free flow of fluid into the drive section, to maintain the drive section components bathed in fluid. A fluid outlet (not shown) may similarly be in fluid communication with the internal volume of the drive section, to permit the recirculation of fluid from the drive section. Valve 144 is maintained in a biased position toward gap 146 by a biasing spring 158. In me illustrated embodiment, biasing spring 158 is compressed between an upper portion of the valve member and a retaining ring 160. When the pump defined by the components described above is employed lor direct injection of a fuel or an emissions control fluid, a nozzle assembly 162 may be incorporated directly into a lower portion of the pump assembly. As shown in Figure 2, an exemplary nozzle includes a nozzle body 164 which is sealingly fitted to Hie pump section. A poppet 166 is positioned within a central aperture formed in the valve body, and is sealed against the valve body in a retracted position shown in Figure 2. At an upper end of poppet 166, a retaining member 168 is provided. Retaining member 168 contacts a biasing spring 170 which is compressed between the nozzle body and the retaining member to maintain the poppet in a biased, sealed position within the nozzle body. Fluid is free to pass from pump chamber 148 into the region surrounding the retaining member 168 and spring 170. This fluid is further permitted to enter into passages 172 formed in the nozzle body around poppet 166. An elongated annular flow path 174 extends from passages 172 to the sealed end of the poppet. As will be appreciated by those skilled in the art, other components may be incorporated into the pump, the nozzle, or the drive section. For example, where desired, an outlet check valve may be positioned at the exit of pump chamber 148 to isolate a downstream region from the pump chamber. Figure 3 illustrates the pump and nozzle assembly of Figure 2 in an actuated position. As shown in Figure 3, upon application of energizing current to the coil 116, the coil, bobbin 114, extension 118, and drive member 122 are displaced downwardly. This downward displacement is the result of interaction between the electromagnetic field surrounding coil 116 by application of the energizing current thereto, and the magnetic field present by virtue of permanent magnets 108 and 110. In the preferred embodiment, this magnetic field is reinforced and channeled by core 112. As drive member 122 is forced downwardly by interaction of these fields (i.e., the Lorentz-force), it contacts plunger 124 to force the plunger downwardly against the resistance of spring 130. During an initial phase of this displacement, plunger 142 is free to extend into pump chamber 148 without contact with valve member 144, by virtue of gap 146 (see Figure 2). Plunger 142 thus gams momentum, and eventually contacts the upper surface of valve member 144. The lower surface of plunger 124 seats against and seals with the upper surface of valve member 144, to prevent flow of fluid upwardly through passage 126 of the plunger, or between the plunger and aperture 138 of the pump section. Further downward movement of the plunger and valve member begin to compress fluid within pump chamber 148, closing inlet check valve 154. Still further movement of the plunger and valve member thus produces a pressure surge or spike which is transmitted downstream, such as to nozzle assembly 162. hi the illustrated embodiment, mis pressure surge forces poppet 166 to unseat from the nozzle body, moving downwardly with respect to the nozzle body by a compression of spring 170 between retainer 168 and the nozzle body. Fluid, such as fuel, is thus sprayed or released from the nozzle, such as directly into a combustion chamber of an internal combustion engine as described above with reference to Figure 1 A. As will be appreciated by those skilled in the art, upon reversal of the polarity of the drive or control signal applied to coil 116, an electromagnetic field surrounding the coil will reverse in orientation, causing an oppositely oriented force to be exerted on the coil by virtue of interaction between this field and the magnetic field produced by magnets 108 and 110 (i.e., a Lorentzrforce in a reversed direction). This force will thus drive the coil, and other components of the reciprocating assembly back toward their original position, hi the illustrated embodiment, as drive member 122 is driven upwardly back towards the position illustrated in Figure 1A, spring 130 urges plunger 128 upwardly towards its original position, and spring 158 similarly urges valve member 144 back towards its original position. Gap 126 is reestablished as illustrated in Figure 1 A, and a new pumping cycle may begin. Where a nozzle such as that shown in Figures 2 and 3 is provided, the nozzle is similarly closed by the force of spring 170. hi this case, as well as where no such nozzle is provided, or where an outlet check valve is provided at the exit of pump chamber 148, ressure is reduced within, pump chamber 148 to permit inlet check valve 154 to reopen for introduction of fluid for a subsequent pumping cycle. By appropriately configuring drive signals applied to coil 116, the device of the present invention may be driven in a wide variety of manners. For example, in a conventional pumping application, shaped alternating polarity signals may be applied to the coil to cause reciprocating movement at a frequency equal to the frequency of the control signals. Displacement of the pump, and the displacement per cycle, may thus be controlled by appropriately configuring the control signals (i.e. altering their frequency and duration). Pressure variations may also be accommodated in the device, such as to conform to output pressure needs. This may be accomplished by altering the amplitude of the control signals to provide greater or lesser force by virtue of the interaction of the resulting electromagnetic field and the magnetic field of the permanent magnets in the drive section. The Lorente-force, and corresponding motion of the foregoing devices, also may be modified by reversing polarity of the coil during motion. For example, the motion of the device can be dampened near the end of its path hi either direction of the cyclical movement to protect die device and to modify the fluid injection characteristics. The foregoing structure may be subject to a variety of adaptations and alterations, particularly hi the configuration of the coil, bobbin, permanent magnet structures, and drive components of the drive section. Two such alternative configurations of the drive section are illustrated in Figures 4 and 5. As shown in Figure 4, in a first alternative drive section 176, a bell-shaped housing 178 has a lower threaded region 180 designed to be fitted about a similar threaded region of a pump section. Moreover, in the embodiment of Figure 4, a central core portion 182 is formed in the housing to channel magnetic flux. An inner annular volume 184 surrounds core portion 182 and supports one or more permanent magnets 186 and 188. These annular magnets surround a bobbin 190 which is supported for reciprocal guided movement along oore portion 182. A coil 192 is wound on bobbin 90 and receives reversing polarity control signals via leads (not shown) as described above with reference to Figures 2 and 3. A lower portion of bobbin 190 may thus interface directly with a plunger (see plunger 124 of Figures 2 and 3) appropriately configured to remain centered with respect to the bobbin. During application of the reversing polarity control signals, an electromagnetic field is produced around coil 192 which interacts with the magnetic field created by magnets 186 and 188 to drive the coil and bobbh in reciprocating movement along core portion 182. This reciprocating movement is then translated into a pumping action through components such as those described above with reference to Figures 2 and 3. In the alternative embodiment of Figure 5, designated generally by reference numeral 194, a guide post or pin 198 is positioned within the pump section housing 196. The housing 196 may be made of a different material than post 198. Post 198 may preferably be formed of a magnetic material, such as a ferromagnetic material, such that the post forms a core for channeling flux at least within a central region 200. One or more permanent magnets 202 and 204 are provided for producing a magnetic flux field which is thus channeled by the core. A bobbin 206, similar to bobbin 190, as shown in Figure 4, is fitted and guided along central region 200. A coil 208 is wound on bobbin 206, and receives reversing polarity control signals during operation of the device. As before, the electromagnetic field resulting from application of the control signals interacts with the magnetic field produced by magnets 102 and 104, to drive the coil and bobbin in reciprocating motion which is translated to pumping action by pumping components such as those described above with reference to Figures 2 and 3. While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described hi detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope ot the invention as defined by the following appended claims. We claim: 1. A reciprocating fluid pump assembly, comprising: a drive section (102) having: a housing (106); a coil bobbin (114) disposed in the housing; a coil (116) wound on the bobbin, the coil having free ends for receiving energizing control signals; and a first biasing spring (130); a pump section (104) having a first end and a second end, the first end of the pump section being secured to the drive section, the pump section also having: a central aperture (138); a pump chamber (148) adjacent the central aperture for receiving fluid; and a first fluid passage (152) for introducing fluid into the pump chamber; and a nozzle assembly (162) having a nozzle body (164), the nozzle body having a central aperture; the fluid pump assembly being characterized in that: the drive section is also provided with: a pair of permanent magnets (108, 110) fixedly supported within the housing; and a plunger (124) operatively connected to the coil bobbin; one of the coil bobbin and the pair of permanent magnets surrounding the other of the coil bobbin and the pair of permanent magnets , the coil bobbin being slidable with respect to the pair of permanent magnets between a first position and a second position, the second position being closer to the pump section than the first position, movement of the coil bobbin in one direction causing movement of the plunger in the same direction, and the first biasing spring biasing the plunger and the coil bobbin towards the first position; the central aperture of the pump section receiving a portion of the plunger of the drive section, and the nozzle assembly also having: a poppet (166) positioned in the central aperture of the nozzle body, the poppet being movable between an open position and a sealed position; and a second biasing spring (170) for biasing the poppet towards the sealed position. the nozzle body being fitted to the second end of the pump section. 2. A reciprocating fluid pump assembly as claimed in claim 1, wherein a central core (112) made of a material that is capable of conducting magnetic flux, the central core is provided to separate the pair of permanent magnets and being disposed adjacent thereto. 3. A reciprocating fluid pump assembly as claimed in claim 1 or 2, wherein a partition (120) is provided separating the drive section from the pump section. 4. A reciprocating fluid pump assembly as claimed in any one of claims 1 to 3, wherein the housing has a skirt (132) secured about a peripheral wall (134) of the pump section. 5. A reciprocating fluid pump assembly as claimed in claim 4, wherein a seal (136) is provided located between the skirt and the peripheral wall. 6. A reciprocating fluid pump assembly as claimed in any one of claims 1 to 5, wherein a check valve (154) is disposed in the first fluid passage. 7. A reciprocating fluid pump assembly as claimed in any one of claims 1 to 6, wherein the pump chamber has a side wall, the first fluid passage introducing fluid in the pump chamber via an opening in the side wall of the pump chamber. 8. A reciprocating fluid pump assembly as claimed in any one of claims 1 to 7, wherein a second fluid passage (156) is provided extending from the first fluid passage to a volume defined by the housing of the drive section. 9. A reciprocating fluid pump assembly as claimed in any one of claims 1 to 8, wherein the fluid pump is a fuel injector for spraying fuel into a cylinder (38) of an internal combustion engine (12).

Documents:

1821-delnp-2004-abstract (18-06-2008).pdf

1821-DELNP-2004-Abstract-16-05-2008.pdf

1821-delnp-2004-abstract.pdf

1821-delnp-2004-assignment.pdf

1821-delnp-2004-claims(18-06-2008).pdf

1821-DELNP-2004-Claims-16-05-2008.pdf

1821-delnp-2004-claims.pdf

1821-delnp-2004-correspondence-others(18-06-2008).pdf

1821-DELNP-2004-Correspondence-Others-(11-06-2008).pdf

1821-DELNP-2004-Correspondence-Others-16-05-2008.pdf

1821-DELNP-2004-Correspondence-Others-21-06-2007.pdf

1821-DELNP-2004-Correspondence-Others-23-05-2007.pdf

1821-DELNP-2004-Correspondence-Others-31-12-2007.pdf

1821-delnp-2004-correspondence-others.pdf

1821-delnp-2004-description (complete)-16-05-2008.pdf

1821-delnp-2004-description (complete)-18-06-2008.pdf

1821-delnp-2004-description (complete).pdf

1821-delnp-2004-drawings.pdf

1821-delnp-2004-form-1-(18-06-2008).pdf

1821-DELNP-2004-Form-1-16-05-2008.pdf

1821-delnp-2004-form-1.pdf

1821-delnp-2004-form-13.pdf

1821-DELNP-2004-Form-18-16-05-2008.pdf

1821-delnp-2004-form-18.pdf

1821-delnp-2004-form-2(18-06-2008).pdf

1821-DELNP-2004-Form-2-16-05-2008.pdf

1821-delnp-2004-form-2.pdf

1821-delnp-2004-form-26.pdf

1821-DELNP-2004-Form-3-16-05-2008.pdf

1821-delnp-2004-form-3.pdf

1821-DELNP-2004-Form-5-16-05-2008.pdf

1821-delnp-2004-form-5.pdf

1821-delnp-2004-form-6.pdf

1821-DELNP-2004-GPA-(11-06-2008).pdf

1821-DELNP-2004-Others-Document-16-05-2008.pdf

1821-DELNP-2004-PCT-210-16-05-2008.pdf

1821-delnp-2004-pct-210.pdf

1821-delnp-2004-pct-306.pdf

1821-DELNP-2004-Petition-137-16-05-2008.pdf

1821-delnp-2004-petition-138.pdf

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