Abstract:
A lube-oil pump system for a diesel engine&#39;s fuel injection system has a first and second pump. Each pump is a multi-plunger swash-plate type pump. The first pump mounts to a neck portion of a front cover of the engine&#39;s crankcase and has a driven gear that meshes with and is driven by gear teeth formed on the engine&#39;s camshaft. The second pump mounts vertically stacked on top of the first pump and has its own driven gear that meshes with and is driven by the gear of the first pump. The second pump is configured to operate in the counter-rotational direction as the first pump.

Description:
CROSS-REFERENCE TO PROVISIONAL APPLICATION(S) 
   This application claims the benefit of U.S. Provisional Application No. 60/577,308, filed Jun. 5, 2004, which disclosure is incorporated by this reference thereto. 

   BACKGROUND AND SUMMARY OF THE INVENTION 
   The invention relates to fuel injection for diesel engines and, more particularly, to the high-pressure lube-oil supply system therefor. 
     FIGS. 1 and 2  show a conventional fuel injection system  20  for a diesel engine and high-pressure lube-oil supply system  30  as well, all in accordance with the prior art. For sake of an example,  FIG. 1  is a schematic based upon a model T444E diesel engine of the Navistar International Transportation Corporation (circa 1994). 
   In general, the fuel system  20  has a pump  22  drawing fuel from a tank  24  and pumping it through a filter  26 . Fuel pumped from this stage is divided through steel lines that lead into the back of each cylinder head. Each of these lines supplies a stream of fuel to a respective gallery drilled in each respective head, wherein these galleries intersect each injector bore to the cylinders. The fuel system  20  utilizes hydraulically-actuated injectors  28  to inject fuel into each cylinder. The hydraulic fluid utilized for this service is the engine&#39;s lube oil. Accordingly, to handle such a service, there is naturally some fashion of a pressurized lube-oil system (i.e., indicated as  30 ). Indeed, it is more conventionally referred to as a high-pressure lube-oil system  30  or the like. 
   The high-pressure lube-oil system  30  is able to produce operating pressures in a range between about 500 and 3000 psi (3,500 and 20,000 kPa) for service of hydraulic actuation of the fuel injectors  28 . The fuel injectors  28 , although driven by the actuation pressures noted just previously, are arranged to amplify/boost the delivered drive-pressures of the lube-oil such that the injected fuel (e.g., injected into the combustion chambers, but ejected from the injectors  28 ) is pressurized all the way up to about 18,000 psi (125,000 kPa). 
   As  FIG. 1  shows better, the high-pressure lube-oil system  30  draws lube oil from the oil pan  31  through a pickup tube by an engine oil (i.e., lube oil) pump. The engine oil pump can be a gerotor type pump mounted-axially on the front end of the crankshaft, which drives it. Lube oil is pumped through an oil cooler  33 , then oil filter  35 , and conducted through passages in the crankcase&#39;s front cover to the high-pressure lube-oil system  30 &#39;s reservoir that is mounted on top of the crankcase&#39;s front cover (the reservoir is not depicted in this drawing, but is indicated as  44  in  FIG. 2 ). 
   The reservoir  44  makes available a constant supply of lube oil to a high-pressure lube-oil pump  32 , which is mounted to a neck portion of the crankcase&#39;s front cover, and from there extends back into the engine block&#39;s “V.” Preferably the high-pressure lube-oil pump  32  is a nine (9) plunger swash-plate pump that has a drive gear that is driven by a camshaft gear. High pressure lube oil is divided between a left and right supply line for the LH (left cylinder head) and RH (right cylinder head) oil-galleries. Each oil gallery supplies the high pressure lube oil to a series of branching oil rails. The oil galleries and oil rails are all machined into the cylinder heads. 
   In operation, when an injector  28  is energized, a poppet valve thereof is opened by an attached solenoid valve (these are not shown). Pressurized lube oil is allowed to flow into the injector  28  and drive against an amplifier piston (not shown). When injection is ended, the lube oil pressure which was just previously applied to the amplifier piston is successively then vented by the poppet valve, and onward through oil spouts mounted on the top of the injector  28 , which not only releases the pressure applied to the amplifier piston but also returns the spouting lube oil to the sump  31 . 
   Control over the lube oil&#39;s service pressure is obtained by means of, in combination, data signals provided by an injection control pressure (ICP) sensor (not shown), and injector drive module (IDM)  37 , control instructions sent by electronic control module (ECM)  39 , which are acted upon by an injection pressure regulator (IPR) valve  34 . By way of background, the high-pressure lube-oil pump  32  is designed to deliver output at simply one design pressure. Regulated control over the lube oil&#39;s service pressure is henceforth obtained by the injection pressure regulator (IPR) valve  34 , which is mounted in a cavity for it in the body of the high-pressure lube-oil pump  32 . The IPR  34  regulates service pressure by dumping excess lube oil through a check valve into the crankcase&#39;s front cover, eventually to drain back down to the sump  31 . 
   There are various shortcomings with the prior art high-pressure lube-oil system  30 . As a matter of background, if a mechanic wishes to optimize a diesel engine for performance, one choice involves exchanging the original factory-equipment injectors for larger, custom or high-performance injectors. 
   Alternatively or in addition, the controller  39 &#39;s control over the injectors  28  might be changed to dwell longer. Either way, bigger injectors or longer dwell means a greater rate of fuel consumption. But the problem is this. That is, there isn&#39;t a sufficient supply of high-pressure lube oil to keep pace with such greater rate of fuel consumption. Typically, the original-equipment high-pressure lube-oil pump  32  is simply under-capacity to meet the increased capacity needs. 
   What is needed is a solution which overcomes the shortcomings of the prior art. 
   A number of additional features and objects will be apparent in connection with the following discussion of preferred embodiments and examples. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     There are shown in the drawings certain exemplary embodiments of the invention as presently preferred. It should be understood that the invention is not limited to the embodiments disclosed as examples, and is capable of variation within the scope of the appended claims. In the drawings, 
       FIG. 1  is a schematic diagram of both a fuel supply system as well as a companion high-pressure lube-oil system for a diesel engine, and both in accordance with the prior art; 
       FIG. 2  is a rear elevational view of a crankcase&#39;s front cover for a diesel engine and depicting other aspects of a representative, high-pressure lube-oil system in accordance with the prior art; 
       FIG. 3  is a rear elevational view comparable to  FIG. 2  except depicting aspects of a high-pressure lube-oil system in accordance with the invention; 
       FIG. 4  is an enlarged scale perspective view of the upper or supplemental high-pressure lube-oil pump and housing block therefor in accordance with the invention; 
       FIG. 5  is a partial section view taken along offset line V-V in  FIG. 4 ; and 
       FIG. 6  is a partial section view taken along offset line VI-VI in  FIG. 5 , with the supplementary pump unit removed from view. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 3  shows a dual-pump, high-pressure lube-oil system  50  in accordance with the invention. It combines an original-equipment high-pressure lube-oil pump  32  with an inventively-deployed supplementary pump  52 .  FIG. 2  contrastingly shows merely a representative single-pump system  30  in accordance with the prior art.  FIGS. 2 and 3  allow comparative study between each other for readily highlighting the distinctions between the invention and prior art. 
   It is an aspect of the invention that just even the possibility of inventively-deploying the supplementary pump (in the way that is here) is advantageously facilitated by an inventive housing block  60 . The housing block  60  will be more particularly described below, in part as developed through a series of three views of it in isolation (i.e.,  FIGS. 4 through 6 ). 
   Referring back to  FIG. 2 , it affords the opportunity to more particularly describe the state of the prior art. The crankcase&#39;s front cover  40  extends upwardly to culminate in a neck-portion  42  that terminates in a machined flange surface (not shown, but a substantial replication of it is shown by  FIG. 4 ). The flange surface serves in part to allow a gasket-sealed joint to be formed with a lidded reservoir  44 , which has a counterpart flange-surface bottom (not shown). The reservoir  44  is bolted to neck portion  42  of the front cover  40  by five bolt-connections  48   a/b  (or, i.e., five in this example) arranged in an array of two bolt-connections along each of the two longer sidewalls (i.e., the one plainly in view in  FIG. 2  is a rear sidewall  43 ) and one more  48   a  in the middle of the right sidewall. The front sidewall (not in view) and right sidewall (not in view) have their three bolted-connections formed by three elongated mounting bolts  48   a  extending through bore holes therefor that penetrate all the way down through the material of the of the reservoir  44  (i.e., spanning the full measure of the height of the reservoir  44 ) in order to allow the bolts  48   a  to poke out beyond the flange bottom of the reservoir  44  and thereafter screw into threaded holes for them formed in the neck portion  42  of the front cover  40  (i.e., and as apertured through the flange surface thereof). The rear sidewall  43  has its left, outer bolted-connection  48   a  formed the same way. 
   However, the rear sidewall  43  has another bolted-connection  48   b , more in the middle, that is formed differently. For this different bolted-connection, the neck portion  42  is formed to secure a threaded stud which extends up above the plane of the flange surface by just a small measure. The reservoir  44 &#39;s rear side wall  43  is formed with an apertured foot-pad along  48   b  its bottom, for allowing insertion and extension therethrough of the threaded stud of the neck portion  42  when the reservoir  44  is seated on the neck portion  42 . Tightening the four mounting bolts  48   a  and a nut on the threaded stud sticking through the apertured foot-pad  48   b  sufficiently mounts the reservoir  44  to the neck portion  42 . 
   The source of drive for the high-pressure lube-oil pump  32  can be reckoned as supplied by the camshaft and as, more particularly, taken off the camshaft&#39;s front gear  46 . The front cover  40 &#39;s neck portion  42  is formed with suitable cavities and apertures (none shown, but fair replications thereof are shown  FIGS. 4-6 ) to allow for the rotational operation of a pump-drive gear  36 . Both these gears  36  and  46  are helical gears, of opposite tooth-pitch angle (this is not shown, but see  FIG. 4 , wherein the tooth-pitch angle shown there corresponds to that of the camshaft gear  46 ). 
   The neck portion  42  of the crankcase&#39;s front cover  40  has a rear sidewall, as shown by  FIG. 2 . The rear side wall is (none of the following is shown until as noted below) bored all the way through to the front sidewall at least by a minor diameter. It is bored only about a third of the way through by a major diameter. A central region between the front and rear sidewalls is formed with an enlarged vertical slot that allows clearance for the pump-drive gear. The major diameter portion of the bore allows for a close-fitting insertion of the pump unit&#39;s cylindrical bearing block. The cylindrical bearing block has a relatively-short drive shaft extending out from it for insertion through and coupling with a center hole in the pump-drive gear. The drive shaft has a terminal end formed with external thread for accepting a tightening nut. The minor diameter through the neck portion is sized not only for rotational clearance of the nut but also for access by a socket wrench. The opening of the minor diameter through the front sidewall is covered by an O-ring sealed plate. Now, even though none of the foregoing is actually shown in the drawings, a fair replication of it all is shown by  FIG. 5 . 
   The neck portion  42  of the front cover  40  has a columnar or standpipe conduit formed in it (as before, not much of the following is shown until as noted below) which, during engine operation, is pumped full of lube oil by the engine oil (e.g., lube oil) pump described in connection with  FIG. 1  (i.e., the one typically mounted axially on the front end of the crankshaft, not camshaft, and which, e.g., is fairly typically of a gerotor type pump). Excess lube oil rising up the column of the standpipe conduit is conducted into the reservoir  44  for reserve storage. Excess overflow of lube oil in the reservoir  44  is allowed to spill out a vent or over a ledge but in any case, preferably directed to be discharged on top of the pump-drive and camshaft gears  36  and  46  in order to provide lubrication thereto. Now, even though not much of the foregoing is actually shown in the drawings, a fair replication of at least the standpipe passageway is shown by  FIGS. 4 and 5 . 
   In use, the pump unit  32  suctions in lube oil in from the standpipe conduit and discharges a pressurized flow of lube oil out a pair of dual discharge ports  38 . The discharge ports  38  are connected by flowlines  49  to supply the left cylinder head (LH) and right cylinder head (RH) as described above in the background section. It is presumed without it having been independently measured or verified that, the delivery outflows are substantially the same in both lines  49  (i.e., as in pressure and flowrate). 
   Now to turn more particularly to  FIG. 3 . There is an inventive advantage to be obtained as described above in the background section if the high-pressure lube-oil supply can be boosted somehow above the prior capacity of the state of the prior-art original equipment.  FIGS. 3 through 6  develop once such way of accomplishing such an inventive advantage. 
     FIG. 3  introduces the dual-pump, high-pressure lube-oil system  50  in accordance with the invention, in which the original-equipment high-pressure lube-oil pump  32  is combined with an inventively-deployed supplementary pump  52 . In general, the inventive supplementary pump  52  is inserted—sandwich-meat style—at the plane of the gasket-sealed joint between the front cover  40 &#39;s neck portion  42 &#39;s top flange and the original-equipment reservoir  44 . Various objects of the invention include the exercise of a high degree of effort (i) to retain all the original-equipment high-pressure lube-oil system  30 &#39;s equipment, (ii) as well as doing so without modifications to any of it either, and, aside from the reservoir  44 , (iii) to keep things in their original place, substantially unmoved. 
   Accordingly,  FIG. 3  shows that the original-equipment pump unit  32  is not simply just retained but kept in its original position, unmoved, and unmodified. The original-equipment reservoir  44  is, however, re-installed at an elevated position (relative its original-equipment elevation) by virtue of being installed on and attached to the inventive housing block  60 . 
   The inventive housing block  60  is shown better by  FIGS. 4 through 6 . It has a six-sided block shape, including front and rear sidewalls  61  and  62  spaced by spaced left and right sidewalls  63  and  64 , the four of which together extend between top and bottom flange surfaces  66  and  65 , respectively. The housing block  60 &#39;s bottom flange surface  65  is designed as a substantial duplication of the shape and arrangement of the original-equipment reservoir  44 &#39;s bottom flange surface (neither shown). That way, the housing block can be mated onto the front cover  40 &#39;s neck portion  42  just the same as the original-equipment reservoir  44  (e.g., including as by a gasket-sealed joint), without any modification to the front cover  40 &#39;s neck portion  42 . 
   Likewise, the housing block  60 &#39;s top flange  66  surface is designed as a substantial duplication of the shape and arrangement of the top flange surface of the front cover  40 &#39;s neck portion  42 . That way, the housing block  60  can accept the mating to it of the original-equipment reservoir  44  just the same as the top flange surface of the front cover  40 &#39;s neck portion  42  (and, e.g., as including a gasket-sealed joint), and likewise again without any modification to the original-equipment reservoir  44 . 
   To achieve this object in part, the housing block  60  includes four bore holes  67  that extend all the way through the housing block  60  for sliding passage of four mounting bolts  68 . Unlike the original-equipment mounting bolts  48   a  (the heads of which at least are shown in  FIG. 2 ), the inventive dual-pump system  50  as shown by  FIG. 3  will require replacement mounting bolts (e.g., as  68 ), ones which are about 4¾ inches (˜12 cm) longer (or, e.g., by about the measure of the chosen height for the housing block  60 ). Accordingly, the inventive dual-pump system  50  is removably installed by four elongated mounting bolts  68  that are arranged in the same pattern as for the original-equipment single-pump system  30 . 
   However, the original-equipment single-pump system&#39;s fifth-bolt connection—the one achieved by a threaded stud and nut tightened on an apertured footpad  48   b  provided by the original-equipment reservoir  44 —has to be matched by the inventive housing block by two features, not one. First,  FIG. 4  shows a stud-hole  69  bored shallowly into the top flange surface  66  for securing a threaded stud therein (not shown) and in a corresponding position of the threaded-stud projecting above the top flange surface of the front cover  40 &#39;s neck portion  42 . That way, the apertured foot-pad  48   b  along the bottom of the original-equipment reservoir  44 &#39;s rear side wall is readily accommodated by the threaded stud sticking up from the housing block  60 . 
   Second,  FIGS. 4 and 6  show (although partly obscured) that the housing block  60  has a recess  71  formed in its rear sidewall  62  and along the bottom. The recess  71  in part is formed with an apertured foot-pad to substantially correspond to the same (e.g.,  48   b ) in the original-equipment reservoir  44 . That way, the threaded stud of the front cover  40 &#39;s neck portion  42  is provided an aperture to insert and extend through when the housing block is seated on the neck portion. The rear sidewall  62 &#39;s recess  71  is sized and arranged in other part for rotational clearance of not only a nut but also for access by a box wrench or the like (not shown). 
   During installation, the inventive housing block  60  is preferably seated on the neck portion  42 &#39;s top flange surface of the unmodified front cover  40 . Of course, this step of “seating” furthermore includes (among other things still) preparations for and inclusion of a gasket. Then, the original-equipment reservoir  44  is preferably seated on the inventive housing block  60 &#39;s top flange surface  66  (including, among other things still, preparations for and inclusion of another gasket). Tightening the four mounting bolts  68  and a nut on the neck portion&#39;s threaded stud (e.g., as accessed through the recess  71 ) sufficiently mounts the inventive housing block  70  to the neck portion  42 . Finally, tightening a nut on the inventive housing block  70 &#39;s threaded stud (e.g., as extending through the apertured footpad  48   b ) sufficiently completes the mounting of the original-equipment reservoir  44  on the inventive housing block  70 . 
   As true for the single-pump system  30  of  FIG. 2 , the source of drive for the inventive dual-pump system  50  can be reckoned as supplied by the camshaft and as, to be more specific, taken off the camshaft&#39;s front gear  46 .  FIG. 3  shows that original-equipment pump-drive gear  36  is retained in place and without modification. As can be reckoned from either  FIG. 2  or  3 , the original-equipment pump-drive gear  36  is situated in a common lateral plane with and generally-above the camshaft gear  46 , wherein the two are enmeshed in direct, coupled contact therebetween. 
     FIG. 3  shows that the supplementary pump-unit  52  is likewise outfitted with a pump-drive gear  56 . As noted previously, the original-equipment pump-drive gear  36  is, customarily, a helical gear. In order to mesh with that, the inventive pump-drive gear  56  presents gear teeth of the same tooth pitch angle but of the opposite left-handedness or right-handedness to that of the original-equipment pump-drive gear  36 .  FIG. 4  depicts a preferred embodiment of the pump-drive gear  56  in accordance with the invention. 
   Other factors concerning the inventive pump-drive gear  56  is that it may be designed to have virtually the same diameter as that of the original-equipment pump-drive gear  36 . That way, the dual pump-units  32  and  52  will spin at virtually the same speed. However, in this preferred embodiment of the invention, the preferred intention is to obtain comparable pressures and output capacities between the two pump units  32  and  52 . It is a fortuitous circumstance that a given pump-unit such as  52  can be utilized which is fairly operationally comparable to the original-equipment pump unit  32  except operates counter-rotationally to the direction of rotation of the original-equipment pump unit  32 . Routine, alternative other design choices over matters of gearing ratios and pump capacities will readily be recognized by an ordinarily skilled designer as variables which can be readily varied in order to get performance as desired. 
     FIGS. 4 through 6  variously show that housing block  60 &#39;s rear sidewall  62  is bored all the way through to the front sidewall  61  by a bore having at least a minor diameter, in consequence there being a minor diameter portion  72  of the bore intersecting the front sidewall  61 . The rear sidewall  62  is bored only about a third of the way through by a portion  74  having a major diameter. A central region  73  between the front and rear sidewalls  61  and  62  is formed with an enlarged, open-ended rectangular column that allows clearance for the inventive pump-drive gear  56 . The major diameter portion  74  of the bore allows for a close-fitting insertion of the inventive pump unit  52 &#39;s cylindrical bearing block  76 . The cylindrical bearing block  76  has a relatively-short drive shaft  77  extending out from it for insertion through and coupling with a center hole in the inventive pump-drive gear  56 . The drive shaft  77  has a terminal end formed with external thread for accepting a tightening nut. The minor diameter portion  72  through the inventive housing block portion is sized not only for rotational clearance of the nut but also for access by a socket wrench (not shown). The opening of the minor diameter portion  72  through the housing block  60 &#39;s front sidewall  61  is covered by an O-ring sealed plate  79 . 
   The inventive housing block  60  has a standpipe passageway  78  formed in it which, during engine operation, is pumped full of lube oil by the engine oil (e.g., lube oil) pump described in connection with  FIG. 1 . Indeed, the housing block  60 &#39;s standpipe passageway is shaped and arranged simply to form a smooth continuation of its counterpart formed in the front cover  40 &#39;s neck portion  42 . Excess lube oil rising up the column of the standpipe passageway(s) (e.g.,  78  in part) is conducted into the original-equipment reservoir  44  for reserve storage. Excess overflow of lube oil in the original-equipment reservoir  44  is allowed to spill out or over the same vent or ledge described previously in connection with  FIG. 1 , but in any case, the spill is preferably directed to be cascade down over all three of the stack of the two pump-drive gears  56 / 36  and the camshaft gear  46  in order to provide lubrication thereto. 
   Indeed, even after engine operation is ended, the collective system of the standpipe passageways (e.g.,  78  in part) and the reserve storage in the original-equipment reservoir  44  will remain filled with lube-oil, at least to the level concurrent with the timing of shutting the engine off. That is, the lube oil filled in these passageways (e.g.,  78  in part) and the reservoir  44  is checked from below from draining out. That way, there is lube oil immediately on-hand for on-demand intake by the pump units  32  and  52  from the instance of restarting the engine. 
   It is preferred if the service of the supplementary pump unit  52  is fulfilled by a multiple (e.g., nine or 9) plunger swash-plate type high-pressure lube-oil pump. In other words, by something fairly comparable to the original-equipment pump unit  32  (except, as noted before, operative in the counter-rotational direction, and as indicated in  FIG. 3 ). As can be partly reckoned by  FIG. 6 , the inventive housing block  60  has an outflow passage  81  that opens out through an opening  82  in the rear sidewall  62 . At its other end, the outflow passage  81  has an origin in the standpipe passageway  78 &#39;s lateral wall. The supplementary pump unit  52  has a mounting flange  83  for making a sealed joint with the mounting block  60 &#39;s rear sidewall  62 . The mounting flange  83  has an intake opening (not shown) for communicating with and suctioning in an intake supply of lube oil. Accordingly, the housing block  60 &#39;s outflow opening  82  is located and arranged to align with the supplementary pump unit  52 &#39;s intake opening in order to achieve this object. 
   The supplementary pump unit  52  has dual discharge ports  58 , comparably as does the original-equipment pump unit  32 . As  FIG. 3  shows, it is an aspect of the invention that both discharge ports  58  of the supplementary pump unit  52  as well as both discharge ports  38  of the original-equipment pump  32  discharge into a common “balancing” line  84 . The balancing line  84  blends the total output of both pump units  32  and  52  in order to balance or level-out pressure and flowrate differences from the two pump units  32  and  52  despite that the pump units  32  and  52  are preferably fairly closely matched to provide fairly similar performance. In any event, the balancing line  84  smooths out any differences, if any. The balancing line  84  is then connected with the high-pressure lube-oil supply lines  49  which extend off separately to left cylinder head (LH) and right cylinder head (RH). 
   As can also be partly reckoned by  FIG. 6 , the inventive housing block  60  has an IPR dump passage  85  (e.g., the IPR is the “injection pressure regulator” valve  54 ) that originates in an opening in the rear sidewall  62 . At its other end, the IPR dump passage  85  terminates in an intersection with an IPR dump flowline  86 . The flow direction of lube oil dumped by or bled-off from the supplementary pump  52  unit within the IPR dump flowline  86  is ultimately conducted up to the original-equipment reservoir  44 . That is, lube oil dumped by the IPR  54  is sent back to re-join the lube oil in the collective reserve of the original-equipment reservoir  44  as well as the combined standpipe passageways (e.g.,  78  in part) of inventive housing block  60  and front cover  40 &#39;s neck portion  42 . Again, the combined function of both the IPR  34  on the original-equipment pump unit  32  and then the comparable IPR  54  on the supplementary pump unit  52  is to provide control over the service pressure and/or flowrate of pressurized lube oil that is fed to the fuel injection system  20 &#39;s injectors  28 . 
   As remarked upon in the background section, control over the original-equipment IPR  34  is handled by the ECM  39  (e.g., the “electronic control module” as indicated in  FIG. 1 ). It is an aspect of the invention to control the dual IPR valves  34  and  54  simultaneously by the one original-equipment ECM  39  without modification thereto. It has been inventively discovered that this can be expediently achieved by wiring the control-signal wire to the dual IPR valves  34  and  54  such that the dual IPR valves  34  and  54  are wired up not in parallel but, in contrast, in series. 
     FIG. 6  shows that the main IPR dump flowline  86  has a C-shaped continuation  86   c  downstream from the IPR dump passage  85 &#39;s intersection with it. The C-shaped continuation  86   c  is provided for the purpose of providing a flow passage for the IPR dump flow that is discharged by the original-equipment IPR  34  (not shown in  FIG. 6  but see, e.g.,  FIG. 3 ). The C-shaped continuation  86   c  is fabricated in the inventive housing block  60  by four bore holes as shown in  FIG. 6 . At least three openings of the C-shaped continuation  86   c  that are a necessary result of the chosen fabrication strategy are sealed off by hex-socketed cap screws  87 . Even if the C-shape is a designer&#39;s choice, the purpose behind the circuitous route of the continuation  86   c  is to route the original-equipment IPR  34 &#39;s dump flow around the housing block  60 &#39;s outflow passage and opening  81  and  82 . 
     FIG. 6  additionally shows that the housing block  60  includes a pump relief flow passage  89  that originates in an opening in the rear sidewall  62 , and terminates in an intersection with the enlarged, open-ended rectangular column  73  that accepts the inventive pump-drive gear  56  (the enlarged, open-ended rectangular column  73 &#39;s cavity is shown better by either of  FIG. 4  or  5 ). The supplementary pump unit  52 &#39;s mounting flange  83  is formed with a relief exhaust port (not shown). Accordingly, the opening for the housing block  60 &#39;s pump-relief flow passage  89  is located and arranged to align with the supplementary pump unit  52 &#39;s pump-relief exhaust port to achieve communication of a relief flow of lube oil therebetween. 
   It has been discovered that the original-equipment dimension tolerances for crankcase front cover  40 &#39;s are, while ordinarily quite tight, are relatively loose or lax in at least one significant respect. That is, the chosen elevation for the neck portion  42 &#39;s top flange surface can be routinely variable, and exceed the apparent tolerances that the majority other dimensions of the front cover are governed by. The consequence is the following. When the inventive housing block  60  is seated upon the top flange surface of one neck portion  42  after another of a random assortment of front covers  40  of the same model series, there in consequence can be an unacceptable amount of variation between the centers of (i) the original-equipment pump-drive gear  36  in any given front cover  40 &#39;s neck portion  42  and (ii) the at least minor diameter portion  72  of the inventive housing block  60 . “Unacceptable” as used here means that, because there can be variation in the distance between the two centers as described, in consequence there might be an unacceptable separation between the two centers the gears  36  and  56  for gear meshing purposes. By way of background, there is a high tolerance set for gear spacing for proper gear meshing. 
   It is an aspect of the invention to account for this matter by provision of an adjustable feature. More particularly, as  FIGS. 5 and 6  show, the major diameter portion  74  of the bore for accepting the cylindrical bearing block  76  of the supplementary pump unit  52  is more accurately formed not in the actual material of the housing block  60  proper but in a press-fitted sleeve  90 . The press-fitted sleeve  90  has a cylindrical outer wall. The housing block  60  has a super-sized bore  88  forming a major-diameter halo that has substantially the same inside diameter as the sleeve  90 &#39;s outside diameter (except a little over-sized for a close-fitting press fit). The super-sized halo-diameter bore  88  in the housing block  60 &#39;s rear sidewall  62  is aligned on the same central axis as the minor diameter portion  72  that extends through the front sidewall  61 . This common central axis is indicated in  FIG. 6  by reference numeral  91 . The sleeve  90 &#39;s inner bore  74 , while although cylindrical, is eccentric relative the common central axis  91 . The eccentric  74 &#39;s central axis is indicated in  FIG. 6  by reference numeral  92 . As can be inferred by re-use of the reference numeral  74 , the eccentric bore  74  is same the bore which defines what previously above has been referred to as the major diameter portion  74 . 
   Hence  FIG. 6  shows that the two central axes  91  and  92  might be spaced about as shown. Rotating the sleeve  90  to different positions on the clock dial causes the eccentric  74 &#39;s central axis  92  to orbit the stationary common axis  91  of the minor and super-sized halo diameter bores  72  and  88 . This can be reckoned in part as follows in  FIG. 6 . The rear sidewall  62  is inscribed with a reference mark  93  adjacent the super-sized halo diameter  88 &#39;s periphery, at about the 3 o&#39;clock position. The sleeve  90  has a comparable reference mark  94  inscribed in it, which appears at about the 2 o&#39;clock position. Accordingly, if a vector is imagined, having a tail in the stationary common axis  91  and a head pointing in the direction of the spaced away eccentric axis  92 , then this vector would point to the 2 o&#39;clock position. Correspondingly, if the sleeve  90  were twisted so that its reference mark  93  were at the 3 o&#39;clock position, the vector would point to 3 o&#39;clock, and so on, for 6 o&#39;clock, 9 o&#39;clock, 12 o&#39;clock, and all points in between. By this means, sleeve  90  can be twisted such the eccentric  74 &#39;s axis  92  orbits the stationary common axis  91 . It readily follows that the center of pump-drive gear  56  for the supplementary pump unit  52  will align with the eccentric  74 &#39;s center  92 . Accordingly, by twisting the sleeve  90 , this can thereby provide adjustability over the spacing between the centers of the two gears  36  and  56 , both that of the original-equipment pump unit  32  and that of the inventive supplementary pump unit  52 . 
     FIG. 5  shows the supplementary pump unit  52 &#39;s mounting flange  83  as secured tightly flush against the housing block  60 &#39;s rear sidewall  62 . Indeed, it is this tight mounting of the supplementary pump unit  52  against the housing block  60  which secures and holds fast the adjusted spacing between the centers of the two gears  36  and  56 . 
   The invention having been disclosed in connection with the foregoing variations and examples, additional variations will now be apparent to persons skilled in the art. The invention is not intended to be limited to the variations specifically mentioned, and accordingly reference should be made to the appended claims rather than the foregoing discussion of preferred examples, to assess the scope of the invention in which exclusive rights are claimed.