Abstract:
An electromagnetic fuel pump, including a pump, an electronic control circuit board assembly (PCB) and electromagnetic coil operatively arranged to operate the pump, and, a housing arranged to house the pump and the PCB/coil assembly, the housing including an integral inlet port and outlet port.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention broadly relates to fuel pumps, and more specifically, to electromagnetic fuel pumps and, even more specifically, to an electromagnetic fuel pump having a housing with integral inlet and outlet ports.  
       BACKGROUND OF THE INVENTION  
       [0002]     Electromagnetic fuel pumps are subject to demands that are not made on other types of pumps. In view of their intended use in association with motor vehicle, marine, generator, military, and agricultural applications, electromagnetic pumps must be capable of maintaining long-term, stable operational lives under extremely adverse working conditions. In addition, since millions of applications require fuel pumps, the number of electromagnetic pumps that are produced on an annual basis is high. Hence, cost considerations relating to pump manufacture dictates that a minimal number of parts be utilized. In addition, manufacturing processes must be accurate and reproducible such that identical pumps are produced. Finally, the manufacture of electromagnetic fuel pumps must be simple such that pumps can be quickly assembled using ordinarily skilled labor.  
         [0003]     Both internal and external variables impact a pump&#39;s performance. Fuel, which in most instances comprises gasoline, or diesel, are aggressive solvents that are capable of deteriorating internal components of a pump. As a result, pump components must be protected from contact with the solvents. Various configurations of O-rings and sealing collars have been disclosed in the prior art for preventing such contact.  
         [0004]     External factors, such as temperature, humidity, and fluid leaks, can also contribute to the problematic effects of pump instability and lead to shorter pump lifespan. Such factors can cause excitation timing circuits to behave irregularly, or they can accelerate the deterioration of the mechanical and electrical components of the pump. The incursion of salt water into pumps during the winter months in northern climates can also cause extensive damage to both the mechanical and electrical components of a pump. Such damage is usually attributed to the accelerated corrosion effects of the galvanic circuit created by salt water and dissimilar metals present within electronic circuits.  
         [0005]     The formation of pump housings has typically been one of the most difficult stages in the construction of an electromagnetic fuel pump. Known methods have generally included the bending of U-shaped yokes, assembly of multiple stamped sheet metal pieces, or foam filling completed assemblies for environmental compatibility. Unfortunately, these types of designs have been problematic in assembly and have been particularly unreliable in use. In known pump designs, such as that shown in  FIG. 1 , inlet and outlet ports have conventionally been components that are separate from the pump housing with which they communicate. Inlet and outlet ports have been traditionally detachably secured to housings by means of threaded nuts and the like. Assembly of the pump inlet and outlet ports has heretofore been very labor-intensive.  
         [0006]     Additionally, the location tolerances of moving parts of a pump have also presented challenges to the construction of electromagnetic pumps. Alignment of moving components, with respect to the inlet and outlet ports of a pump, requires highly accurate methods of assembly. Previous methods have utilized the pump housing to locate the surfaces to which the pump is built and aligned. Constraints created by the bending of U-shaped yokes and the stamping of individual metal housing pieces has limited the manufacturer&#39;s ability to coaxially align the inlet port, the outlet port, and the moving pump components. Such lack of coaxial alignment can reduce the pump efficiency and the stability of the pump performance.  
         [0007]     Furthermore, pumps known in the art typically comprise driving circuits that include a dual winding coil, i.e., one magnetic winding and one oscillator feedback winding. The coil together, with resistors, diodes, a transistor, and a power source, comprise the oscillator circuit, which drives the pumping mechanism. The dual winding coil requirement of most current pumps presents problems related to pump manufacture. For example, in order to manufacture a pump comprising two differently gauged coil wires, the manufacturer must stock and store the two differently gauged coil wires, which can be costly in terms of materials and space requirements. In addition, one winding is of a very small and fragile gauge wire.  
         [0008]     Known pumps have also suffered from the lack of on-board EM hardening and surge suppression circuitry.  
         [0009]     Thus, there has been a longfelt need for an electromagnetic fuel pump with inlet and outlet ports that are integral to the pump housing and have on-board surge suppression and EM hardening.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     The present invention broadly comprises an electromagnetic fuel pump comprising a pump, an electromagnetic coil operatively arranged to operate the pump, and a housing arranged to house the pump and coil, the housing comprising an integral inlet port and outlet port. In a preferred embodiment, the fuel pump includes on-board (e.g., within the housing) electromagnetic (EM) hardening and on-board surge suppression circuitry, in addition to a single-wire coil.  
         [0011]     A general object of the invention is to provide an electromagnetic fuel pump having inlet and outlet ports, which are integral with the pump housing, and a backwards-compatible configuration based on the same platform.  
         [0012]     Another object of the invention is to provide an electromagnetic fuel pump having on-board EM hardening, controlled pump speed, and on-board surge suppression circuitry with the use of a single-wire coil.  
         [0013]     These and other objects, features and advantages of the present invention will become readily apparent to those having ordinary skill in the art upon reading the following detailed description in view of the several drawing views and appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which:  
         [0015]      FIG. 1  is a perspective view of a known electromagnetic pump formed from a metal pump housing;  
         [0016]      FIG. 2   a  is a perspective view of the present invention comprising integral ports;  
         [0017]      FIG. 2   b  is a view of the present invention comprising removable threaded ports;  
         [0018]      FIG. 3  is an exploded view of the pump shown in  FIG. 2 ;  
         [0019]      FIG. 4  is a cross sectional view of the electromagnetic fuel pump of the present invention, taken generally along line  4 - 4  of  FIG. 2   a;    
         [0020]      FIG. 5  is a perspective view of the discharge plunger assembly of the electromagnetic fuel pump of the present invention;  
         [0021]      FIG. 5A  is a cross-sectional view of the discharge plunger assembly of  FIG. 5 , taken generally along line  5 A- 5 A of  FIG. 5 ;  
         [0022]      FIG. 6  is a perspective view of the clip for retaining the plunger valve within the discharge plunger assembly of  FIG. 5 ;  
         [0023]      FIG. 7  is a perspective view of the plunger valve shown in  FIG. 3 ;  
         [0024]      FIG. 8  is a perspective view of the inlet valve shown in  FIG. 3 ;  
         [0025]      FIG. 9  is a cross-sectional view of the inlet valve, taken generally along line  9 - 9  of  FIG. 8 ;  
         [0026]      FIG. 10  is a schematic diagram of the timing and switching circuit for the coil of the electromagnetic fuel pump;  
         [0027]      FIGS. 11A-11C  depict rest, filling, and dispensing stages, respectively, of the electromagnetic fuel pump of the present invention; and, 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]     At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred embodiments, it is to be understood that the invention as claimed is not limited to the disclosed embodiments.  
         [0029]     Adverting now to the Figures,  FIG. 1  illustrates a prior art electromagnetic pump described in U.S. Pat. No. 4,306,842, which patent is incorporated herein by reference. Patented pump  10  includes a housing that comprises U-shaped yoke member  12 , parallel leg  14 , and connecting plate  13 . A second parallel leg plate, arranged opposite leg  14 , is not shown in the figure. Inlet fixture  18  and outlet fixture  16  (the inlet and outlet ports) are operatively arranged to permit fuel pumping from a fuel source, for example, the fuel tank of an automobile. In this patented pump, the inlet and outlet ports are not integral with the housing. Rather, they are separately manufactured and then assembled/secured to the housing, a time-consuming assembly step.  
         [0030]     Referring now to  FIGS. 2   a  and  2   b , outer structures of electromagnetic pump  20  according to the present invention are broadly illustrated as comprising housing  22 , mounting flange  24 , integral inlet mount  27 , integral outlet mount  29 , end cap  30  and power leads  32 . Housing  22  generally comprises integral inlet mount  27  and integral mounting flange  24 .  
         [0031]     In a preferred embodiment housing  22  is constructed from molded plastic capable of withstanding the harsh environment of an engine compartment or chassis. Housing  22  is substantially cylindrical in shape such that a cavity is formed for accepting inner pump components. It should be appreciated, however, that the outer surface of the pump housing could comprise virtually any shape as may be desired and may be constructed from other moldable materials as may be appropriate. Integral inlet mount  27  is provided for connecting pump  20  to a fuel source via a fuel line (not shown) and further comprises inlet port  26  (See  FIG. 4 ). Integral mounting flange  24  is provided for securing the fuel pump to the surface of a fuel tank or as may be desired. End cap  30  generally comprises integral outlet mount  29  and is structured for complementary fit to the end of housing  22  and is sealably secured thereto by appropriate means, for example, sonic welding, etc. Integral outlet mount  29  is provided for connecting an outlet fuel line (not shown) for delivery of fuel to a fuel distribution means such as a carburetor, fuel injector, or the like via outlet port  29 . Power leads  32  provide the electrical energy required to operate the pumping mechanism and connects to printed circuit board  44  (See  FIG. 3 ).  
         [0032]     Alternatively,  FIG. 2   b  illustrates pump  90  configured to comprise threaded inlet  92  and threaded outlet ports  94  adapted for threadably inserting and removing threaded nipples  96  from housing  22  as may be desired, as for instance, to change the size of the nipples.  
         [0033]     Referring now to  FIG. 3 , as described supra, the inner structures of the pump of the present invention are operatively arranged to be secured within the cavity formed by housing  22  and end cap  30 . The inner structures of the pump broadly comprise end cap O-ring  34 , tube  36 , first EM end cap  38 , EM shield  40 , bobbin  42 , coil  43 , printed circuit board  44 , discharge valve retaining clip  46 , discharge valve  48 , discharge plunger  50 , helical spring  52 , second EM protective housing end cap  54 , housing O-ring  56  and inlet valve assembly  57 .  
         [0034]     With reference now to  FIGS. 3-9 , it is seen that sleeve  36  is operatively arranged for passing fluid therethrough and longitudinally traverses the pump from inlet port  26  to outlet port  28 . Tube  36  is adapted for slip fit into housing  22  and molded into the cover  30 . O-rings  34  and  56  are disposed within the tube and about the outer surface of the tube for dampening impact forces and preventing leakage of fluid therefrom, respectively. Tube  36  serves as the primary location wherein mechanical pumping operations are performed. Discharge valve retaining clip  46  secures discharge valve  48  into plunger  50 ; plunger and spring  52  are adapted for reciprocating movement within tube  36 . Valve  57  is retained in position between the force of spring  52  and housing  22 . Tube  36  is made from a non-magnetic material and spring  52  may vary according to pump type and the pressure output of the pump.  
         [0035]     Disposed within plunger  50  is the plunger valve  48  and retaining clip  46 . As illustrated more clearly in  FIGS. 5-7 , plunger valve  48  is operatively arranged for sealable fit within plunger  50  and comprises plunger valve sealing surface  60  for creating a seal between the plunger valve and the plunger. Plunger valve  48  is releasably retained within plunger  50  by means of plunger valve retaining spring clip  46 . As shown more clearly in  FIG. 7 , plunger valve retaining spring clip  46  secures plunger valve  48  to plunger  50 . Plunger valve  48  further comprises recess  72  capable of swelling for purposes of dampening pressure increases proximate the pump output as described in U.S. Pat. No. 3,797,522, which is incorporated herein by reference.  
         [0036]     As shown in  FIGS. 8 and 9 , suction valve assembly  57  generally comprises a one-way check valve for drawing fuel from a fuel source such as a fuel tank as described infra. Suction valve assembly  57  includes inlet valve  58 , inlet valve sealing surface  62 , inlet valve housing  64 , inlet valve spring  76  and inlet valve location post  78 .  
         [0037]     Operatively arranged about the outside of tube  36  is first EM cap  38 , shield  40 , bobbin  42 , coil  43 , second EM cap  54 , and circuit board  44 . Circuit board  44 , in combination with coil  43  and power leads  32  form drive circuit  80  (See  FIG. 10 ). Coil  43  comprises a single strand of wire wound about bobbin  42 . Coil  43  is operatively arranged to create an electromagnetic force when energized to attract plunger  50  against the force of spring  52  to its center of magnetic mass. First and second EM caps  38  and  54 , respectively, along with shield  40  are formed from metal and comprise an enclosure for providing a closed EM loop circuit. The metal enclosure is positioned between housing  22  and end cap  30 , and electrical circuit  80  (See  FIG. 10 ). By encapsulating the electrical components within a metal shield, the emission of EMI is prevented. In a preferred embodiment the metal enclosure is fabricated from sheet metal.  
         [0038]      FIG. 10  illustrates drive circuit  80  for the electromagnetic pump of the invention. In a preferred embodiment, the components of drive circuit  80  are surface mounted on printed circuit board  44 , which is mounted on the coil via conductive-pinned bobbin assembly within housing  22 . The circuit broadly comprises U 1 , a 555 timer or equivalent, operatively arranged to MOSFET SMT switch Q 1  which comprises a 15 A, 60V, N-Channel, (55 deg C./+175 Deg C.) DPAK. In a preferred embodiment, R 2  and R 3  are selected, as is well known in the art, such that the timer controls Q 1  to a 70 ms period with “On” time of approximately 25 ms, and an “Off” time of approximately 45 ms. When MOSFET Q 1  is turned “On” (25 ms), coil  43  is energized and attracts the plunger against spring  52 . When MOSFET Q 1  is turned “Off” (45 ms) coil  43  discharges through R 4 /D 3  and spring  52  returns plunger  50  to its point of origin. In a preferred embodiment, coil  43  is made of 21 gauge magnet wire and is a 2 mH inductor with a resistance of 1.4 ohms. Circuit  80  also includes surge suppression Zener diode D 2  which protects the circuit against voltage overloads. Diode D 1  functions as a polarity restrictor; D 2  as overload protection; and D 3  and R 4  functions to direct and suppress the discharge current of the coil.  
         [0039]      FIGS. 11A-11C  depict the operational aspects of the electromagnetic fuel pump of the present invention.  FIG. 11A  shows plunger  50 , plunger valve  48 , inlet valve  58 , and spring  52  in their rest positions. While coil  43  is not energized, spring  52  biases plunger  50  against O-ring  34 . If backpressure exists, i.e., pressure caused by fluid entering from outlet port  28 , plunger valve  48  forms a seal at surface  60  with plunger  50  to prevent fluid from flowing past plunger valve  48  into first chamber  59 . Inlet valve  58  is biased against plunger valve housing seal  62  by spring  76  (See  FIG. 9 ). This seal prevents fluid flowing from first chamber  59 , through plunger valve  58 , and continuing out inlet port  26 .  
         [0040]      FIG. 11B  illustrates coil  43  as being energized, which forms a magnetic field. The magnetic field created by the energized coil imparts a directional force upon plunger  50 . This force causes plunger  50  to move rightwardly toward inlet port  26 , thereby causing spring  52  to compress. As a result of the rightward movement and the configuration of valve  48 , fluid present in first chamber  59 , just prior to energizing coil  43 , is displaced around valve  48  and into second chamber  55 . During this stage, fluid is prevented from moving between first chamber  59  and inlet port  26  by the seal created between inlet valve  58  and inlet valve housing seal  62 .  
         [0041]     Referring now to  FIG. 11C , as coil  43  is de-energized, the magnetic field collapses. As a result, plunger  50  is no longer acted upon by a magnetic force and is returned to its rest location by the bias of spring  52 . Two simultaneous events occur during the movement of plunger  50 . First, fluid contained in second chamber  55  is forced out of outlet port  28 . The fluid is prevented from entering first chamber  59  by the seal created between surface  60  of discharge valve  48  and plunger  50 . Simultaneously, fluid is replenished in first chamber  59 . As plunger  50  moves, a negative pressure, or suction, is created in first chamber  59 . The negative pressure causes suction valve  58  to be displaced leftwardly to an open position, thus allowing fluid to be drawn from inlet port  26  into first chamber  59 . O-ring  34  provides force dampening for the impact between plunger  50  and end cap  30  as plunger  50  returns to its rest location.  
         [0042]     The operation described in the previous paragraphs, related to  FIGS. 1A-1C , is cyclically repeated during the use of the pump. As mentioned previously, the timing circuit controls Q 1  to switch “On” for approximately 25 ms, and switch “Off” for approximately 45 ms. This means that during each cycle of operation, the plunger is biased rightwardly by electromagnetic force for approximately 25 ms, and then biased leftwardly by the spring for approximately 45 ms. The reciprocal motion causes fluid to flow in inlet port  26 , through inlet valve  58 , first chamber  59 , second chamber  55 , and plunger valve  48 , and out outlet port  28 , thereby creating a continuous, low pressure flow of fluid.  
         [0043]     Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed.