Abstract:
A combination dynamic balancer and fuel pump for an internal combustion engine includes a common housing having at least one balancer shaft and a fuel pump, with the fuel pump having the pumping element mounted directly within a working chamber formed within the housing for the balancer shaft and fuel pump. A pumping element may include a reciprocating or a rotary pumping element.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is related to a mechanical fuel pump driven by, and incorporated within, a dynamic balancing mechanism in an internal combustion engine. 
         [0003]    2. Disclosure Information 
         [0004]    Automotive internal combustion engines once used carburetors for mixing air with fuel. Because carburetors utilize venturis to draw fuel into the air, carburetors were typically fed by low pressure fuel sources, such as mechanically or vacuum driven diaphragm pumps. 
         [0005]    With the advent of electronic fuel injection, the ubiquitous solution for fuel pumps became the in-tank mounted electric pump. Such pumps are typically capable of reliably producing fuel pressures in the sub-100 p.s.i. regime. 
         [0006]    Because of increasingly more stringent vehicle emission controls, engine developers have turned to direct injection of gasoline into the combustion chambers of the newest engines. Unfortunately, better mixture preparation requires that the desired injection pressures be much higher, and with these new fuel systems, electric pumps will likely be relegated to the role of a lift pump providing fuel to a higher pressure pump driven by the engine. Of course, it is desirable to provide such an added pump without unnecessary expense, and with a minimal requirement for additional space. Although it is known to mount pumps externally upon an engine, ever more crowded engine compartments do not readily lend themselves to this solution. 
         [0007]    It would be desirable to provide an engine-driven mechanical fuel pump which has a minimum number of additional parts, coupled with high pressure capability, and which causes no added expenditure of precious space within the underhood environment of the vehicle. 
       SUMMARY OF THE INVENTION 
       [0008]    A fuel pump for an internal combustion engine includes a housing containing both a balancer and a fuel pump, with the fuel pump including a working chamber contained within the housing. A fuel pump also includes at least one balance shaft mounted within the housing, with the balance shaft having at least one eccentric lobe for actuating a follower connected with a pump plunger mounted reciprocably within the working chamber. According to another aspect of the present invention, the balance shaft is driven rotationally by a crankshaft, preferably at twice the rotational speed of the crankshaft. 
         [0009]    According to another aspect of the present invention, the fuel pump further includes at least one pressure control valve operatively connected with the working chamber and mounted within the housing, as well as a pulsation damper operatively connected within the working chamber and also mounted within the housing. 
         [0010]    According to another aspect of the present invention, the housing of the fuel pump and balancer may be mounted adjacent a crankshaft of an engine. 
         [0011]    According to another aspect of the present invention, the pumping element driven by the balance shaft may comprise in the alternative, a reciprocating pump, or a rotary pumping element such as a gerotor element, or a set of intermeshing gears. 
         [0012]    It is an advantage of a combination dynamic balancer and fuel pump according to the present invention that the number of added parts needed to provide high pressure fuel pumping capability within an engine is reduced, as compared with prior art pumps, many of which are merely bolted to the outside of the engine in some fashion or another. 
         [0013]    It is another advantage according to the present invention that the present fuel pump and balancer combination requires little, if any, additional space within the engine compartment of the vehicle. 
         [0014]    It is another advantage of a combination balancer and high pressure fuel pump according to the present invention that very high fuel discharge pressures may be produced reliably due to the inherent strength of the integral working chamber and balancer housing. 
         [0015]    Other advantages, as well as features of the present invention, will become apparent to the reader of this specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is an exploded perspective view of a portion of an engine including a combination dynamic balancer and fuel pump according to an aspect of the present invention. 
           [0017]      FIG. 2  is a sectional view of a first embodiment of a pump portion according to an aspect of the present invention, taken along line  2 - 2  of  FIG. 1 . 
           [0018]      FIG. 3  is a perspective view of a portion of the balancer as shown in  FIG. 1 , but showing a rotary pump housing section,  76 , incorporated within balancer housing  12 . 
           [0019]      FIG. 4  illustrates a gerotor rotary pumping element according to an aspect of the present invention. 
           [0020]      FIG. 5  illustrates a two-gear pump according to an aspect of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    As shown in  FIG. 1 , engine  10  has a cylinder block,  14 , and a number of main bearing caps,  22 , securing crankshaft  18  within cylinder block  14 . A balancer assembly includes a housing,  12 , and two balancing shafts,  30  and  34 . The balancer is said to be “dynamic” because it uses weighted, counter-rotating shafts to achieve the desired balancing. Housing  12  is mounted to cylinder block  14  by means of mounting brackets  26 , and a number of fasteners,  28 . Balance shafts  30  and  34  are coupled to crankshaft  18  by a gear train (not shown). When engine  10  is operating, crankshaft  18  rotates balancing shafts  30  and  34  at a high speed, preferably twice the rotational speed of crankshaft  18 . In this manner, balance shafts  30  and  34  eliminate various imbalances associated with engine  12 , such as a rocking couple and secondary shaking forces. 
         [0022]      FIG. 1  also shows a pump section,  39 , which is incorporated within housing  12 . Pump section  39  is shown in detail in  FIG. 2 , and includes a cam follower,  42 , which is driven by a cam lobe,  32 , formed on balance shaft  30 . Cam follower  42  is spring loaded by return spring  46 , A piston,  44 , reciprocates in bore  45  to move fuel through pump section  39 . The pump housing,  38 , for pump section  39  is one piece with housing  12 . Pump section  39  further includes a parent bore,  50 , which allows various pump parts such as cam follower  42 , including piston  44 , as well as a sleeve,  54 , having a working chamber,  58 , formed therein, to be loaded into pump section  39  from the uppermost portion of pump section  39 . Because working chamber  58 , which includes pump bore  45 , is formed as an inner bore in sleeve  54 , the diameter of chamber  58  may be selected to deliver the desired capacity of the fuel pump. Those skilled in the art will appreciate in view of this disclosure that the number of cam lobes  32  and, indeed, the height of each lobe, may also be selected to deliver the desired pump capacity. 
         [0023]    The fuel pump of  FIG. 2  also includes a check valve,  62 , for maintaining line pressure at outlet  60  when the engine  10  is shut down, as well as a pressure control valve,  66 , and a pulsation damper,  70 . Because pump section  39  has housing  38  which is one piece with housing  12 , pump section  39  is very compact and structurally rigid. Structural integrity is important because it enables the capability for very high output pressures required with direct injection engines such as gasoline and diesel direct injection engines. 
         [0024]      FIG. 3  illustrates an embodiment in which a rotary pump housing section,  76 , is incorporated into an end portion of housing  12 . 
         [0025]      FIG. 4  illustrates a first type of rotary pumping element situated within working chamber  80  of rotary pump housing section  76 . In the arrangement of  FIG. 4 , outer gerotor  78  and inner gerotor  82  mesh to provide high pressure pumped fuel when rotated by balance shaft  30 . The coupling between the rotors and balance shaft  30  is not shown; those skilled in the art will appreciate in view of this disclosure, however, that a wide variety of common coupling devices could be employed, such as tang and slot or cross and yoke, or yet other devices known to those skilled in the art and suggested by this disclosure. 
         [0026]      FIG. 5  illustrates a second type of rotary pumping element, in this case a two gear pump in which gear housing  86  is mounted within working chamber  80  of rotary pump housing section  76 . Two meshed gears,  90 , provide the pumping action in a manner known to those skilled in the art and suggested by this disclosure. 
         [0027]    The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention. Accordingly the scope of legal protection afforded this invention can only be determined by studying the following claims.