Abstract:
A spur-gear type fuel pump for vehicles is disclosed having a pair of interengaged gears contacting an interior surface of a pump body cavity for capturing fuel between teeth of the gears and the interior surface. The gears have a concentrically ground face that is flush against and slides over the interior surface to generally prevent or restrict fuel bleed or leakage across the interface and from between the teeth of the gears.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to a fuel pump for a vehicle and, in particular, to a spur gear pump for delivering fuel to an engine of a vehicle.  
       BACKGROUND  
       [0002]     It is currently known in the art to provide a fluid pump utilizing a pair of intermeshing gears. Often referred to as a spur gear pump, the gears cooperatively engage to rotate in the same plane, the direction of rotation determining an intake side and an output side. More specifically, the intake side is provided on a side of the gears where the teeth move out of engagement with the teeth of the other gear and generally rotate outward. The rotational movement of the gear teeth in this manner provides a vacuum or suction to draw fluid into interstices or spaces between the teeth and a pump body surrounding the gears. On the output side, the fuel is deposited as the teeth of the gears open to an output port and then intermesh, the accumulation of fuel creating a pressure to force the fluid into the output port.  
         [0003]     High-performance racing engines such as those used in sprint and drag racing cars commonly use spur gear pumps as a fuel pump. In this case, the fuel pump draws fuel from a fuel supply on the intake side and deposits the fuel under pressure on the output side for delivery downstream to the engine intake, such as an injection system.  
         [0004]     More specifically, many high-performance racing engines use spur gear fuel pumps to deliver alcohol or nitromethane fuel to fuel injectors for the engine. The passage of the pump surrounding the spur gears is defined by a body formed of aluminum, and the gears have a small flat face at the end of each tooth. In order to minimize damage due to contact with the aluminum body, the tooth faces are positioned a short distance or gap from the surface of the body. The size of the gap is further increased by accommodating for a range of operating temperatures. As a result, the interface between the gear teeth and the pump housing provides for fuel leakage at all operating temperatures and pressures. For a new fuel pump, this leakage or bleed is typically 3-5% of the fuel captured between adjacent teeth and up to 10% for a worn pump.  
         [0005]     This system results in a number of problems. Ideally, the provision of fuel is linear such that the volume of fuel is in direct and exact proportion to the engine speed, as measured in revolutions per minute (RPM), regardless of pressure. Generally this linearity is attempted by rotating the gears of the pump at a direct proportion to the RPM of the engine, such as by connecting the fuel pump to the engine via the serpentine belt or the cam shaft. However, the linearity is lost due to the leakage which is exacerbated as the leakage increases as pressure increases.  
         [0006]     In addition, the operation of the fuel pump may cause cavitation or vaporization of the fuel. The tooth faces are intentionally small to minimize the ability of the edges to contact the pump body. The vacuum at the intake created by the rotation of the gears may be sufficient to vaporize the fuel or mix air thereinto. In a vapor or gas form, it is easier for the fuel to pass between the tooth faces and the pump body, further contributing to the leakage. In any event, then the tooth face profile is combined with the narrow gap, the fuel leaking through the gap experiences a significant pressure drop. When the volatile fuel experiences this pressure drop, it often quickly vaporizes and/or cavitates.  
         [0007]     Cavitation of the fuel at the intake or within the fuel pump leads to a number of issues. In one instance, cavitation, either through vaporization or through mixing of air into the fuel, increases the volume of a molar amount of fuel. Though the pump can continue to deliver a volume of fuel between the teeth and the pump body, the molar quantity of fuel that is deliverable as a vapor or gas is significantly reduced from that which is deliverable as a liquid. Therefore, the quantity performance for the fuel pump is reduced when the volume is fully or partially vaporized fuel or air, perhaps to a point of failing to provide the requisite amount of fuel. This effect also results in the quantity of fuel delivered being unpredictable even for constant RPM conditions, the linearity of the fuel delivery with respect to the engine speed being again lost, and the fuel delivery varying with temperature (which causes expansion of the gas or vapor). As a result, the fuel delivery to the engine may be too high or too low. Beyond this, the high-pressure of the fuel over a small area on the gear teeth and pump body causes erosion on these surfaces, reducing the serviceable life of the pump and its components.  
         [0008]     Accordingly, there has been a need for an improved fuel pump for providing fuel to an engine in linear proportion to the engine speed and with a spur gear type fuel pump.  
       SUMMARY  
       [0009]     In accordance with one aspect, a spur-gear type fuel pump is disclosed. The fuel pump includes a pair of interengaged gears rotating in a common plane within a pump body, the gear teeth defining spaces for capturing and pumping fuel through the pump. The gear teeth rotate into contact with the interior surface to capture the fuel therebetween. The gears then rotate to pump the fuel from an intake side to an output side. The contact of the teeth with the interior surface prevents or minimizes leakage from the spaces. This allows the pump to operate at high pressure, and the high pressure aids in minimizing cavitation or vaporization of the fuel.  
         [0010]     In accordance with a further aspect, the gear teeth have a radially oriented terminal ends including an arcuate face concentrically formed with the center of rotation of the gear. The interior surface of the pump body which is contacted by the teeth is arcuate, and the interior surface is concentrically formed with the center of rotation of the gear. As the gear teeth rotate into contact with the interior surface, the arcuate faces are flush with the arcuate interior surface. This further serves to minimize leakage across the interface therebetween.  
         [0011]     In accordance with another aspect, the gear pair includes an idler gear positioned on a roller bearing on a fixed axle, and a driven gear. The roller bearing is provided with tolerances which allow the pressure of the driven gear to shift the idler gear relative to the fixed axle or shaft. In this manner, the idler gear can balance pressure from the driven gear, which pushes the idler gear away from the driven gear, with pressure from the pump body interior surface which pushes the idler gear towards the driven gear.  
         [0012]     In accordance with another aspect, the driven gear is secured with an axle or drive shaft for driving the driven gear. The drive shaft includes a pair of bearing assemblies on respective ends of the drive shaft. The bearing assemblies allow the drive shaft to self-align during operation.  
         [0013]     In an additional aspect, the fuel pump includes a casing. The pump body is secured within the casing so that a portion of the pump body extends to contact an inner surface of the casing. Preferably, the pump body contacts the inner surface of the casing in the directions in which internal pressure from the rotating gears may otherwise cause the pump body to flex outwardly. In this manner, the pump body is constrained from substantially flexing, which may otherwise lead to separation between the teeth arcuate faces and the interior surface of the pump body.  
         [0014]     A further aspect includes selecting materials to promote predictable and linear operation of the pump over a range of temperatures. In some forms, the interior surface of the pump body is formed of a hardened material with wear characteristics providing for a long life. In some forms, the gears are formed of a hardened material with similar long-life wear characteristics. In some forms, the gears and interior surface have different surface grain size to minimize gripping or locking between the gears and the interior surface. In some forms, the materials of the gears and of the interior surface may have similar or closely matched coefficients of thermal expansion so that, as the temperature of the pump increases, the gears and pump body expand in similar or closely matched amounts. In one example, the gears may be formed of hardened bearing-grade steel, and the interior surface may be formed of a hardened bronze alloy such as silicon bronze. In a further form, the pump body may be formed of a lightweight material such as aluminum or titanium, and the interior surface may be lined or covered with the hardened material such as the bronze alloy.  
         [0015]     In another aspect, the pump gears may be rotated in either direction for operation. In this manner, the pump may be mounted in a variety of configurations and locations in an engine compartment. The pump communicates with a fuel source to receive fuel and with the engine to deliver fuel thereto, such as via a fuel injection system, and passageways are provided for the respective fuel receipt and fuel delivery. The passageways are generally identical so that the direction of the rotation of the pump gears may be selected based on which passageway is output and intake, or vice versa. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     In the drawings,  FIG. 1  is a front elevation view of a portion of a fuel pump including a driven gear and an idler gear showing the gears engaging an interior surface of a pump body, the gears cooperating to draw fuel between ports of the pump body;  
         [0017]      FIG. 2  is a perspective view of a gear of a prior art spur gear pump;  
         [0018]      FIG. 3  is a front elevation view of the prior art gear of  FIG. 2 ;  
         [0019]      FIG. 4  is a perspective view of a gear of  FIG. 1  showing faces on the ends of teeth of the gear;  
         [0020]      FIG. 5  is a front elevation view of the gear of  FIG. 4  showing the faces arcuately shaped and concentric with a center of rotation of the gear;  
         [0021]      FIG. 6  is a front perspective view corresponding to  FIG. 1  showing the driven gear fixedly engaged with a driven axle for driving the driven and idler gear, and showing a bearing assembly between the idler gear and an axle around which the idler gear rotates;  
         [0022]      FIG. 7  is a rear perspective view of the portion of  FIG. 1  showing front and rear bearing assemblies for supporting the driven axle;  
         [0023]      FIG. 8  is a rear elevation view corresponding to  FIG. 7  showing the ports of the pump body;  
         [0024]      FIG. 9  is a front perspective view corresponding to  FIG. 6  showing a body cover on the pump body and an exploded thrust bearing assembly for the driven axle;  
         [0025]      FIG. 10  is a rear perspective view corresponding to  FIG. 9  showing a bearing housing for the rear bearing assembly and the exploded thrust bearing assembly;  
         [0026]      FIG. 11  is a front perspective view similar to  FIG. 9  showing a pump casing for housing the pump body and gears;  
         [0027]      FIG. 12  is a front perspective view corresponding to  FIG. 11  showing the fuel pump including a casing cover secured with the pump casing;  
         [0028]      FIG. 13  is a right side elevation view of the fuel pump showing the pump casing having a first pair of openings communicating with one of the ports of the pump body;  
         [0029]      FIG. 14  is a left side elevation view of the fuel pump similar to  FIG. 13  showing the pump casing having a second pair of openings for communicating with a second one of the ports of the pump body;  
         [0030]      FIG. 15  is a rear elevation view of the fuel pump showing a configuration of the pump casing for providing the first and second pairs of openings of  FIGS. 13 and 14 ;  
         [0031]      FIG. 16  is a cross-sectional view taken through the line  16 - 16  of  FIG. 14  showing passageways between the ports of the pump body and the pairs of openings of the pump casing; and  
         [0032]      FIG. 17  is a top plan view of the fuel pump along the line  17 - 17  of  FIG. 15  showing the passageways communicating between the pairs of openings of the pump casing. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]     Referring initially to  FIG. 1 , a body  20  having an interior surface  22  defining a cavity  24 , and a pair of gears  26  engaged with and contacting the interior surface  22  are shown for providing an operation portion of a fuel pump  10  (see  FIG. 12 ). A prior art fuel pump (not shown) utilizes gears  2  having teeth  4  radially extending therearound. The teeth  4  have a small face  6 , or are pointed, at the ends  8  of each, as can be seen in  FIGS. 2 and 3 . As discussed above, these prior art gears  2  are sized to provide a clearance or gap between the ends  8  and the interior surface  22  of the body  20 , allowing fuel to leak therebetween. As shown in  FIG. 1 , the present gears  26  contact with the interior surface  22  to minimize or generally prevent fuel crossing across the interface therebetween.  
         [0034]     More specifically, the gears  26  include a driven gear  28  and an idler gear  30 . Each of the gears  26  includes gear teeth  32  for cooperatively engaging with teeth  32  on the other of the gears  26  so that the engaged gears  26  rotate together in the same plane, though in opposite directions. As the driven gear  28  rotates in a first direction, the idler gear  30  rotates in the opposite direction to create a reduced-pressure suction or vacuum on one side  34  of the gears  28  at which the gears  28  dis-engage and rotate outward, and to create an increased pressure on an opposite side  36  of the gears  28  at which the gears  28  intermesh.  
         [0035]     Each of these sides  34 ,  36  is positioned adjacent a port  38  in the pump body  20 . One of the ports  38  is an intake port and the other is an output port, the selection of which is determined by the direction of driving the driven gear  28 . In other words, the fuel pump  10  may be used so that one of the ports  38  is an intake port  38   a  through which fuel is received into the body  20  from a fuel source, and the other of the ports  38  is an output port  38   b  through which fuel is delivered to the engine (not shown) such as through an injection system (not shown). Accordingly, the driven gear  28  rotates in a direction indicated by arrow D 1 , and the idler gear  30  cooperatively engaged with the driven gear  28  rotates in an opposite direction indicated by arrow D 2 . This produces the suction on a side  34  coincident with or adjacent the intake port  38   a  and an increased pressure on a side  36  coincident with or adjacent the output port  38   b , as shown in  FIG. 1 .  
         [0036]     The teeth  32  of the gears  26  capture fuel received on the intake side  34  between the teeth  32  and the body interior surface  22 . As the teeth on one gear rotate outward and away from the teeth of the opposite gear, a quantity of fuel is captured between consecutive teeth of each gear and the interior surface  22 . Representatively and with specific reference to  FIG. 1 , the driven gear  28  includes first and second teeth  32   a  and  32   b  with a space  40  therebetween that is exposed to the intake port  38   a  and fuel therefrom. With the first tooth  32   a  contacting the interior surface  22 , the driven gear  28  rotates in the direction D 1  so that the space  40  including fuel therein rotates so that the second tooth  32   b  is also in contact with the interior surface  22 . Once the teeth  32   a ,  32   b  rotate to the output side  36  adjacent the output port  38   b , the fuel may be released from the space  40 . In any event, as the teeth  32   a ,  32   b  cooperatively engage with a tooth of the idler gear  30 , the fuel is forced out of the space  40  so that it remains on the output side  36 . Thus, the fuel accumulates on the output side  36  to create a pressure which forces the fuel through the output port  38   b  and to the engine. As noted above, the rotation of the gears  26  may be reversed such that the intake port would be represented by port  38   b  and the output port would be represented by port  38   a . As can be seen in  FIG. 1 , the teeth  23  are in contact with the interior surface  22  for approximately two hundred twenty degrees of angular rotation.  
         [0037]     As shown, each of the gears  26  includes approximately ten teeth  32 , though this number may range up to fifteen or more in the preferred embodiments. As can also be seen in comparing  FIGS. 3 and 5 , each of the gears  26  is diametrally larger than the prior art gears  2  to provide a greater space between consecutive teeth  32  for capturing fuel.  
         [0038]     Each of the gear teeth  32  includes a terminal end  44  for contacting the interior surface  22 . As the gears  26  rotate, the teeth  32  will sequentially contact and slide against the interior surface  22  to prevent fuel bleed or leakage between the teeth  32  and the interior surface  22 . By doing so, the above-described problems associated with leakage are substantially reduced or eliminated.  
         [0039]     Additionally, this allows the fuel pump  10  to operate at a significantly greater pressure than those of the prior art. Under high pressure, a prior art pump will leak, vaporize a percentage of the fuel, and/or cavitate the fuel, thereby rendering the pump inadequate for its purpose. In a partial attempt to reduce these effects, the prior art pump is generally run at a maximum of 75-80 psi. The construction of the fuel pump  10  described herein allows for operation in the range of 400-500 psi, thus allowing for efficient fuel delivery across a wider range of pressures and temperatures and engine speeds without a loss of linearity between the speed and the volume of fuel delivered. The increased operating pressure for the fuel pump  10  also serves to minimize vaporization of the fuel on the intake side  34  due to the vacuum created. It is preferred for the fuel pump  10  to operate with a revolutions per minute speed that is approximately one-half the RPM speed of the engine. For high-performance engines, the engine RPM may be in the order of 4,000-12,000 RPM so that the pump  10  operates at 2,000-6,000 RPM. The pump  10  is also expected to operate properly at least through the temperature range of 30-200° F.  
         [0040]     The terminal ends  44  include a radially located face  46 . The face  46  is arcuately shaped with a center of curvature located with a center of rotation  48  of each gear  26 . Therefore, each point along the face  46  is generally positioned at a radius  50  for the gear  26 , as shown in  FIG. 5 . Preferably, the radius  50  is 0.5-1 inches. By having the full surface of the face  46  in contact with the interior surface  22 , the contact generally inhibits fuel entrapment therebetween. Again, this serves to inhibit fuel leakage from a high-pressure zone to a low-pressure zone which may otherwise result in vaporization. To ensure close mating between the faces  46  of the teeth  32  and the interior surfaces  22 , each is manufactured with a tolerance in the order of 0.00025 inches from the center of rotation  48 .  
         [0041]     Each of the gears  26  is positioned on a concentric shaft. For the driven gear  28 , a drive shaft  60  is provided having a socket  62  at one end for engagement with other drive components of the vehicle. For instance, the drive socket  62  may be coupled with the engine cam shaft, with the serpentine belt, or with another system for providing a speed ratio for the desired pump speed relative to the engine speed. The drive shaft  60  includes a pair of bearing assemblies  64   a ,  64   b  on respective front and rear portions  60   a ,  60   b  with the driven gear  28  positioned therebetween. The driven gear  28  includes a central opening  66  through which the drive shaft  60  is positioned, the drive shaft  60  and driven gear  28  being non-rotationally secured so that they co-rotate. The idler gear  30  includes a central opening  68  in which a bearing assembly  70  is positioned. The bearing assembly  70  is further positioned around an idler shaft  72 .  
         [0042]     As can be seen in  FIG. 9 , the cavity  24  of the pump body  20  may be enclosed by a body cover  76 , as well as the interior surface  22  of the body  20  and a body rear plate  78  including the ports  38 . Each of the cover  76  and rear plate  78  include aligned bores for receiving the shafts  60 ,  72  therethrough. Specifically, the cover  76  includes a throughbore  80  aligned with a throughbore  82  of the rear plate  78  for the drive shaft  60 , and the cover  76  and rear plate  78  have aligned throughbores  84  and  86  for receiving the idler shaft  72 . The drive shaft  60  is permitted to rotate within the throughbores  80 ,  82  and within the bearing assemblies  64 . The bearing assemblies  64  are preferably long roller bearings which provides a self-centering capability for the drive shaft  60 , which in turn facilitates a close-tolerance fit of the driven gear  28  the pump body  20 , the cover  76 , and the rear plate  78 , discussed in greater detail below.  
         [0043]     The idler shaft  72  is secured with the throughbores  84 ,  86  so that it generally remains stationary with respect to the body  20 . In prior art systems, the idler gear is fixed with its shaft or axle, which itself would have a bearing assembly at each axle end in the same manner as the drive shaft  60 . The prior art configuration is designed to preserve the gap size between the gear teeth and the body surface. In contrast, the present idler shaft  72  is held stationary and the idler gear  30  rotates around the single bearing assembly  70  so that the tolerances allow a small amount of shifting of the idler shaft  72 . In this manner, the idler shaft  72  can balance the pressure from its cooperative engagement with the driven gear  28  with pressure against the interior surface  22  of the body  20 . This allows the idler shaft  72  and idler gear  28  to self-align and to maintain contact with the interior surface  22 .  
         [0044]     During operation, the gears  26  contact the pump body  20 , rear plate  78 , and cover  76  to prevent fuel leakage. As discussed above, the faces  46  of the gears  26  contact the interior surface  22  to prevent leakage across their interface. Furthermore, the gears  26  each have a top surface  81  and a bottom surface  83  which respectively contact the cover  76  and the rear plate  78 . In this manner, fuel movement is generally restricted to being pumped through the spaces  40  between the teeth  32  and the interior surface  22  as the gears  26  rotate. Lubrication is provided by the fuel itself.  
         [0045]     In greater detail, the drive shaft  60  includes a thrust bearing assembly  87  so that forces exerted on the drive shaft  60  do not create excessive friction between the top and bottom surfaces  81 ,  83  of the driven gear  28 . The thrust bearing assembly  87  is secured to a terminal rear end  60   c  of the drive shaft by a bolt  88  and washer  89 . A thrust bearing  90  including a cage  91  having rollers is positioned between a pair of races  92   a ,  92   b , and one of the races  92   a  is positioned against the washer  89  while the other race  92   b  is positioned against a shoulder  93  on drive shaft terminal end  60   c  and around a threaded bore  94  therein for receiving the bolt  88 . A securing cap  95  is positioned with an annular portion  96  positioned around the bolt  88  and washer  89  so that a leading face  97  is positioned against the race  92   a . As can be seen in comparing  FIGS. 10 and 9  with  FIGS. 13 and 15 , the securing cap  95  is then secured on a rear side  100   a  of a casing  100 , discussed below.  
         [0046]     As such, the thrust bearing  90  prevents axial loads on the drive shaft  60  from forcing the driven gear  28  into either the body cover  76  or the rear plate  78 . When an axial load is directed in a push direction into the drive shaft  60 , that is, along the axis from the front portion  60   a  towards the rear portion  60   b , the drive shaft shoulder  93  presses against the thrust bearing  90  (specifically, the race  92   b ), which in turn presses against the securing cap  95  secured with the casing  100 . When an axial load is directed in a pull direction, opposite the push direction, the bolt  88  secured with the drive shaft  60  presses against the thrust bearing  90  (specifically, the race  92   a ), which in turn is secured within a step (not shown) formed within the casing  100 . Accordingly, the drive shaft  60  is assembled with the thrust bearing  90  through the casing rear side  100   a , and the securing cap  95  is then sealed and secured with the casing rear side  100   a.    
         [0047]     A number of considerations are presented with maintaining the contact between the tooth faces  46  and the interior surface  22 . In prior art fuel pumps, inadvertent contact between the gears  2  and an interior surface leads to galling or smearing of the material. That is, the gears  2  grab and lock with the interior surface, leading to rapid and excessive wear, if not failure. To minimize wear between the present gears  26  and the interior surface  22 , the gears  26  are formed of a high-strength steel such as a bearing-grade material. An example of this is AISI 8640 steel. In a preferred embodiment, the interior surface  22  is formed of an alloy such as a hardened bronze alloy, one example of which is silicon bronze. This provides wear resistant characteristics and a coefficient of friction that are generally similar to or matched with the same for the steel of the gears  26 .  
         [0048]     By utilizing different materials for the gears  26  and the interior surface  22 , these characteristics are also matched but have different surface structural granularity. That is, the microscopic grain size of the materials on the contact surface is mismatched. Accordingly, the materials have a lower tendency to grab and lock with each other. The faces  46  and the interior surface  22  are highly polished to further reduce any tendency to grab and lock.  
         [0049]     In a more preferred embodiment, the body  20  is made of a lightweight material such as aluminum or titanium that is lined with the bronze alloy on the interior surface  22 . It is noted that aluminum is corroded by nitromethane and alcohol fuels. Accordingly, the interior surface  22  formed of a hardened bronze alloy provides a longer life to the fuel pump  10 .  
         [0050]     The contact between the gears  26  and the interior surface  22  is maintained over a range of temperature. The described materials for the gears  26 , body  20 , and interior surface  22  generally provide for similar amount of expansion or contraction due to heat. Though not exactly matched, the thermal expansion coefficients combined with the bearing assemblies of the shafts  60 ,  72  allow differences in pressure to equilibriate so that contact between the gears  26  and the interior surface  22  is maintained.  
         [0051]     Referring now to  FIGS. 11 and 12 , the pump casing  100  is shown with the pump body  20  and cover  76  secured therein. In specific,  FIG. 12  shows a casing cover  102  secured on the casing  100  to enclose the pump body  20  with the drive shaft  60  extending therethrough so that the drive socket  62  is exposed for connection with other engine components. The casing cover  102  is secured with the casing  100  via bolts  104  around a perimeter portion. The casing cover  102  and casing  100  form a generally sealed compartment  106  therewithin so that a pressure can be maintained within the pump body  20 .  
         [0052]     It should also be noted that the pressure within the casing  100  and, in specific, the compartment  106  is maintained at the output pressure. The output side  36  of the pump body  20  is permitted to leak or is provided with a small port so that, within a brief time from pump start-up, the internal pressure within the compartment  106  is balanced with the output pressure. The pressure is thus generally balanced within the casing  100  and the pump body  20 . More precisely, the pressure inside and outside the pump body  20  is generally balanced so that the rear plate  78  and front cover  76  do not bulge during high-pressure operation. Otherwise, this bulging would cause the fuel in the pump to flow around the top and bottom surfaces  81 ,  83  of the gears  26  and between the gears  26  and the front cover  76  and rear plate  78 , leading to inefficiency and loss of performance.  
         [0053]     In greater detail, it should be recognized that the pump body  20  has a first pressure at the intake side  34  which is lower than a pressure at the output side  36 . In a prior art fuel pump, a seal such as an O-ring is located between the front cover  76  and body  20 . In forms of the present fuel pump  10 , the seal is omitted allowing the pressure from the intake and output sides  34 ,  36  to leak to the compartment  106  around the body  20  and within the casing  100 . The front cover  76  and body  20  are in direct contact, such as along an interface  78   a , that is not sealed such that the pressure is allowed to leak across the interface  78   a  ( FIG. 9 ). On initial start up, the pressure in the compartment rises to a pressure dependent on the combined pressures at the intake and output sides  34 ,  36 .  
         [0054]     However, the combined pressure in the compartment  106  is greater than the pressure at the intake side  34 . Therefore, this combined pressure tends to force the cover  76  and body  20  together proximate the intake side  34 . As this happens, the compartment combined pressure will rise as the pressure at the output side  36  imparts a greater contribution to the combined pressure, which further serves to close the intake pressure off from the compartment  106 . Eventually, the pressures equilibrate with the compartment pressure generally approximately, or equal to, the pressure at the output side  36 . In this manner, the pressure in the compartment  106  is substantially as high as pressure within the pump body  20 , thereby substantially eliminating problems due to bulging of portions of the body  20  or the front cover  76  or rear plate  78 . It should be noted that, though described for the front cover  76  and the body  20 , a seal may also or may alternatively be omitted between the body and the rear plate  78  such the interface  78   a  may be located therebetween.  
         [0055]     The casing cover  102  also serves to secure the drive shaft  60  and the idler shaft  72 . The drive shaft  60  is permitted to rotated within and extend through a throughbore  114  in the casing cover  102 . To maintain pressure within the casing compartment  106 , the drive shaft  60  is sealed with the casing cover  102 . A portion (not shown) of the casing cover  102  extends into the compartment  106  for receiving the bearing assembly  64   a  on the front portion  60   a  of the drive shaft  60 . The idler shaft  72 , which is stationary with the casing  100 , is secured in the casing cover  102  with a bolt  116 .  
         [0056]     Referring now to  FIGS. 13-17 , openings for communicating with the intake and output ports  38   a ,  38   b  are depicted. More specifically, the rear plate  78  is sealed with the casing  100 . The casing  100  includes an intake passageway  120  aligned with and sealed with the intake port  38   a  so that fuel can be delivered from the fuel source through the passageway  120  to the intake port  38   a . The casing  100  further includes an output passageway  122  generally identical to the intake passageway  120 , though aligned with and sealed with the output port  38   b  for receiving fuel therefrom and from the output side  36 .  
         [0057]     Each of the passageways  120 ,  122  communicates with a pair of openings for either receiving or delivering fuel therethrough. Each passageway  120 ,  122  includes a first portion  124 ,  126  that is generally axially aligned and parallel to the axis of rotation of the drive shafts  60 ,  72 . A first end of each first portion  124 ,  126  communicates with the respective intake and output ports  38   a ,  38   b , while a second end of each first portion  124 ,  126  communicates with a second portion  128 , 130  of the respective passageways  120 ,  122 . Each second portion  128 ,  130  is oriented generally transverse or orthogonal to the first portions  124 ,  126  and includes respective openings for fuel communication.  
         [0058]     In greater detail, the second portion  128  of the intake passageway  120  includes a pair of openings  132 ,  134 , while the second portion  130  of the output passageway  122  includes a pair of openings  136 ,  138 . This allows each of the passageways  120 ,  122  to be connected in fuel communication with the fuel source and with the engine, such as through the injection system, in a variety of locations within the engine compartment and with a variety of components, such as the cam shaft or serpentine belt. Additionally, it allows the operation of the pump  10  to be reversed, as noted above, depending on its mounting location and user preference.  
         [0059]     While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques that fall within the spirit and scope of the invention as set forth in the appended claims.