Abstract:
A supercharger for an internal combustion engine having an internal reservoir adapted to receive a supply of lubricating oil. An oil slinger is mounted on the impeller shaft for rotation therewith that extends into the reservoir for collecting and slinging lubricating oil onto the supercharger bearings, shafts and the drive and impeller gears. A baffle assembly is carried by the interior of the supercharger housing for controlling the volume and flow of lubricating oil onto said gears and bearings and directing oil flow therefrom back into said reservoir to prevent excessive lubrication buildup on the gears and the deleterious effects that result therefrom.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to superchargers for internal combustion engines and more particularly, to an improved, low cost and compact self-lubricating centrifugal supercharger employing a rotary driven oil slinger that avoids excessive lubrication disposition onto and around the shafts, gears and associated bearings and excessive lubrication build-up on the rapidly rotating gears that cause power losses and an undesirable rise in temperature of the lubrication oil. 
         [0002]    The use of oil slingers as an economical means of lubricating intermeshing gears and associated bearings has been well known for many years. See, for example,  Gear Handbook,  published in 1962 by McGraw-Hill Book Company. A gear or disc is mounted on a rotating shaft, typically a drive shaft, so as to pass a lower portion of the gear or disc through an internal reservoir of lubrication oil. As the rotating gear or disc passes through the reservoir of lubrication oil, it lubricates the intermeshing gears and associated bearing assemblies by slinging a mist of oil from the reservoir onto the gears and bearings. Oil slingers have been used in a variety of high speed applications, including superchargers. See, for example, U.S. Pat. No. 1,974,974 (Puffer), U.S. Pat. No. 3,734,637 (Beck) and U.S. Pat. No. 4,090,588 (Willover). While such internal lubricating systems have several cost advantages over external systems, it has been found that during operation, these rapidly rotating oil slingers tend to throw an excessive volume of lubricating oil onto the gears and bearing assemblies inside the transmission case. Also, the rotating gears will collect lubricating oil on the perimeter of their toothed surfaces creating, in effect, rolling “doughnuts” of lubricant. Oil splashing onto the gears from the reservoir exacerbates the situation. The result of the entrained oil carried by the meshing gears in a supercharger is a significant power loss due to the shearing of the viscous lubricant film and resistance to rotation created by the large volume of lubricating oil engaging the mechanical components. Also, a significant rise in the temperature of the oil within the internal reservoir results which can ultimately lead to product failure. The supercharger of the present invention retains the simplified low cost solution for effecting lubrication of the gears and bearing assemblies provided by a rotating oil slinger, while effectively and efficiently controlling the volume and flow of lubricating oil so as to prevent the above-described power drain and associated temperature rise in the lubricating oil that was heretofore inherent in such lubricating systems. 
       SUMMARY OF THE PRESENT INVENTION 
       [0003]    Briefly, the present invention, in a preferred embodiment, comprises a supercharger having an internal lubrication reservoir, a drive gear mounted on a drive shaft above the reservoir, an impeller, an impeller gear mounted on an impeller shaft below the drive gear that engages the drive gear to effect stepped up rotation of said impeller in response to rotation of the drive shaft, bearing assemblies, an oil slinger mounted on the impeller shaft adjacent to the impeller gear for rotation therewith such that the oil slinger projects radially beyond the impeller gear and at least a lower portion thereof is submerged within the lubrication fluid in the reservoir and a baffle assembly proximate the gears and oil slinger for controlling the flow of lubricating oil. The baffle assembly limits the amount of oil directed by the slinger onto the gears and associated bearing assemblies, limits oil splash onto the gears from the oil reservoir, strips excess oil from the drive and impeller gears that is entrained on the perimeter thereof during rotation of the gears and directs oil back to the lubrication reservoir whereby the aforesaid power losses and temperature elevation of the lubricant are substantially reduced while maintaining adequate lubrication of the gears and associated bearings. A lightweight, foaming resistant oil is preferably employed in the preferred embodiment of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a perspective view of a preferred embodiment of a supercharger embodying the present invention. 
           [0005]      FIG. 2  is a sectional side view taken along the line  2 - 2  of  FIG. 1  with the teeth on the impeller gear being shown for clarification purposes. 
           [0006]      FIG. 3  is a frontal plan view of a portion of the supercharger of  FIG. 1  with a portion of the cover removed to reveal the interior components thereof. 
           [0007]      FIG. 4  is a sectional view of an alternate embodiment of the cover. 
           [0008]      FIG. 5  is a frontal plan view of a portion of the supercharger of  FIG. 1  illustrating preferred embodiments of the supercharger gear casing and oil slinger baffle assembly of the present invention. 
           [0009]      FIG. 6  is the frontal plan view of  FIG. 3  with the cover portion and slinger disc removed to illustrate the relative positioning of the gears with respect to the baffle assembly. 
           [0010]      FIG. 7  is a frontal plan view of a preferred embodiment of the interior of the supercharger housing cover. 
           [0011]      FIG. 8  is a perspective view of a gear casing illustrating an alternate embodiment of the oil slinger baffle assembly of the present invention. 
           [0012]      FIG. 9  is a perspective view of a gear casing illustrating a second alternate embodiment of the oil slinger baffle assembly of the present invention. 
           [0013]      FIG. 10A  is a frontal view of a preferred configuration of the slinger disc of the present invention. 
           [0014]      FIG. 10B  is a sectional view taken along the line  10 B- 10 B in  FIG. 10A . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    A preferred embodiment of the supercharger  10  of the present invention is a centrifugal supercharger of the type mechanically driven by an associated engine such as an internal combustion engine in an automobile. Such a supercharger is disclosed in Applicant&#39;s U.S. Pat. No. 5,224,459, the teachings of which are incorporated by reference as though fully set forth herein. In its preferred configuration, supercharger  10  of the present invention includes a housing  12  comprised of a gear case  14  and cover  16  and a volute  18 , all of which are preferably aluminum castings. The volute is mounted onto the back plate  20  of the gear casing and the cover  16  is bolted onto the gear case  14  through a plurality of aligned apertures  22  and  24  in the case and cover. The large drive gear  26  is mounted on a drive shaft  28  which is supported by ball bearing assemblies  30  and  32  mounted in the aligned cylindrical bearing bores  31  and  41  in the gear case and cover, respectively. The drive shaft projects outwardly from the supercharger housing  12  through an oil seal  34  in the housing cover  16  as seen in  FIG. 2 . A drive pulley  35  is mounted on the extended portion  28 A of the drive shaft for operable engagement with a drive belt (also not shown) driven by an external engine. A smaller driven impeller gear  36  is mounted on the impeller shaft  38  which is supported by ball bearing assemblies  40  and  42  mounted in the aligned cylindrical bearing bores  33  and  43  in the gear case and cover, respectively. The impeller gear  36  operatively meshes with the drive gear  26 . A high speed lip seal  44  or other suitable mechanical seal is concentrically positioned around the impeller shaft  38 . Other types of suitable seals, including a spring-biased carbon-ring face seal, also could be utilized. The impeller shaft carries the impeller  39  which turns in a chamber in the volute  18 . The drive and impeller gears  26  and  36  preferably feature helical teeth and, by way of example, form a gear ratio of 3.6:1. The relationship between the crankshaft pulley and the pulley on the drive shaft  28  also can be a gear ratio, such as about 2:1, providing an overall 7.2:1 step-up between the engine crankshaft and the supercharger impeller. These ratios are by way of example only and can be varied without affecting the scope of the present invention. 
         [0016]    The housing cover  16  and gear case  14  cooperatively define an internal lubricant reservoir  46  (see  FIG. 2 ) disposed below the impeller shaft  38  and gear  36 . An oil slinger  48 , preferably defined by an annular dished disc, is centrally mounted on the impeller shaft  38  adjacent the impeller gear  36 , as is also seen in  FIG. 2 . The oil slinger disc is sized so as to project radially beyond the impeller gear and into the internal lubricant reservoir  46  such that a lower portion of the oil slinger extends about 0.5 in. below the oil level  50  in the reservoir. The reservoir  46  is partially filled with oil lubricant, preferably a lightweight, non-foaming synthetic oil, through a fill channel  52  formed in the housing cover  16 . Channel  52  is generally closed by a dipstick assembly  54  threadably engaging the upper inlet end  60  thereof. The dipstick assembly  54  is comprised of a vented breather plug  56  and a dipstick rod  58  that depends from plug  56  and is preferably formed of a suitable plastic material but may be formed of metal as well (see  FIG. 3 ). 
         [0017]    In an alternate embodiment of the cover  16  (see  FIG. 4 ), the dipstick assembly  54  is replaced with a dipstick assembly  62  having a non-vented plug  64 . A second channel  66  communicating the reservoir  46  with the atmosphere is provided on the opposite side of the supercharger  10  from fill channel  52 . Channel  66  is provided with a threaded inlet  68  to threadably engage a vented breather plug  70 . The depending dipstick rod  72  in assembly  62 , like dipstick rod  58  in assembly  54 , is preferably formed of a plastic material for measuring the oil level within reservoir  46 . By separating the vented breather plug from the dipstick assembly, any oil leakage through a wicking effect of the oil up the dipstick rod is prevented. 
         [0018]    In use, the oil slinger disc  48  carried by the impeller shaft  38  is rotated through the lubricating oil in reservoir  46  at speeds of 12,960 rpm with an engine speed of 2000 rpm and over 43,000 rpm at an engine speed of 6000 rpm (using the gear ratio channels provided above). As the disc  48  passes through the lubricant oil in the reservoir  46 , it collects and “slings” a mist of lubricating oil onto the drive and impeller gears and associated bearing assemblies. To limit and control the “flow” of the lubricating oil, the interior of the gear case  14  is provided with a baffle assembly  72  (see  FIG. 5 ). The baffle assembly comprises a pair of oil impervious anti-windage or barrier walls  74  and  76  that extend at downward inclinations from the interior wall surface of the gear case and terminate in end portions  74 A and  76 A proximate upper lateral portions of a cylindrical bearing bore  33 . The baffle assembly  72  also includes a generally semi-circular, oil impervious, low barrier wall  80 , which preferably is disposed about the lower half of bore  33 . Barrier walls  74 ,  76  and  80  are preferably integrally cast with the gear case and are positioned relative to the diameters of the drive and impeller gears of supercharger  10  such that the inclined walls  74  and  76  are spaced approximately 1/16 in. from the perimeter surface of the drive gear  26  and the lower barrier wall  80  is spaced approximately ⅛ in. from the lower perimeter portion of the impeller gear  38  (see  FIG. 6 ). 
         [0019]    As the lower portion of the rapidly rotating disc  48  passes through the lubricating oil in reservoir  46 , oil is entrained onto a perimeter portion of the disc, similar to the previously discussed oil entrainment on a toothed gear, but to a somewhat lesser extent, and, as described above with respect to a gear, tends to form an expanding “doughnut” of lubricant. Unrestrained, this entrained oil on the slinger disc  48  would be thrown or slung outwardly, predominantly upwardly, as a result of the centrifugal force acting thereon, significantly increasing the volumetric flow of oil onto the gears, shafts and bearings and giving rise to the power loss and temperature elevations noted earlier herein. With the present invention, however, the underside  80 A of the lower curvilinear barrier wall  80  functions as an anti-windage device, preventing a substantial amount of the airborne lubricant created by the rapidly rotating disc from reaching the impeller and drive gears and also substantially reducing the back-splashing from the lubricant reservoir  46  onto the gears. The lubricating oil that is slung upwardly by the slinger disc  48 , collects on the drive gear  26 , drive shaft  28  and associated bearing assemblies  30  and  32 . The oil then flows downwardly under the force of gravity onto and along the upper surfaces  74 ′ and  76 ′ of the inclined barrier walls  74  and  76  and onto the impeller gear  36  and shaft  38 . The rotating impeller gear will drive oil outwardly onto bearing assembly  42  in the gear case  14  and onto the bearing assembly  40  in the cover  16 . To enable the dispersed lubricating oil, to reach the bearing assembly  40  disposed about the impeller shaft in the housing cover, a pair of opposed apertures,  48 A preferably kidney-shaped, are provided in the side of the slinger disc  48  as shown in  FIG. 10B . Other aperture configurations in the disc could, of course, be employed. The lubricating oil will continue to flow downwardly and back into reservoir  46 , passing about the lower barrier wall  80  and through the gap  82  between the end surface  80 B of the lower barrier wall  80  and the opposed surface  84  on the interior of the supercharger cover  16 . Downwardly inclined flow channels  31 ′,  33 ′,  41 ′ and  43 ′ are provided in the bearing bores  31 ,  33 ,  41  and  43  respectively to facilitate oil drainage from the bores and prevent a build-up of lubrication oil behind the bearing assemblies. 
         [0020]    As lubricating oil builds up on the perimeter portion of the rotating drive gear, the upper surfaces  74 ′ and  76 ′ of the inclined barrier walls, located only about 1/16 of an inch from the perimeter of the toothed drive gear  26 , will strip entrained oil off the gear teeth and adjacent perimeter portions of the drive gear and direct the stripped oil, under the force of gravity, back into the reservoir  46 . The stripping of the oil from drive gear  26  occurs primarily at the extended end portion  74 A or  76 A of barrier wall  74  or  76 , depending on the rotational direction of the drive gear. If the drive gear is rotating in a clockwise direction, as seen from looking at  FIG. 6 , the striping would primarily occur at the end portion  76 A of barrier wall  76 . If the drive gear were rotating counter-clockwise, oil stripping would primarily occur at the extended end portion  74 A of barrier wall  74 . Similarly, the interior surface of the lower curvilinear barrier wall  80  will strip lubrication oil on the teeth and adjacent perimeter portion of the impeller gear  36  and the stripped oil will also flow back down into the lubrication reservoir  46 . 
         [0021]    By so limiting the “volumetric “flow” slinging of the lubricating oil onto the drive gear and surrounding area stripping excess entrained oil from the perimeter portions of the drive and impeller gears and directing the stripped oil back to the lubrication reservoir, the loss of power that typically results from the use of an oil slinger and the accompanying undesirable rise in temperature of the oil in reservoir  46  are prevented, enhancing the efficiency and durability of the supercharger, while continuing to provide adequate lubrication of the supercharger component. 
         [0022]    The gear case  14  of supercharger  10  is preferably provided with three spaced threaded ports  90 ,  92  and  94  in the underside thereof communicating with the oil reservoir  46 . Each of the three ports is generally initially sealed with a threaded closure plug  96 . Depending upon the particular orientation of the supercharger in the vehicle, the plug that is in the lowermost position of the three plugs is removed and replaced with a drain hose assembly for changing the oil in the reservoir  46  without having to remove the supercharger from the vehicle. In  FIG. 1 , hose  98  is connected to port  90  by means of a suitable threaded connector  100  and is provided with a valve assembly  102  or a removable plug at its extended end. When installed, the hose can be “snaked” down to a low point below the supercharger mounting location. The hose is then clamped or otherwise secured in place. Upon opening the valve assembly  102 , the oil can be easily drained from the supercharger, obviating the need to remove the supercharger from the vehicle in order to change the lubrication oil as is typically the case with existing superchargers having internal lubrication reservoirs. As the orientation of the supercharger  10  with respect to the vertical will vary in different vehicles and other applications, the use of a plurality of available spaced ports allows for the drain hose to be communicated with a port at or adjacent the lowest point of the reservoir regardless of the angular orientation of the supercharger within the vehicle. 
         [0023]    The threaded ports  90 ,  92  and  94  also can be used to accommodate an external oil lubrication system. In applications wherein the engine to which the supercharger is connected is operated at high load or full throttle over extended periods of time, as for example, in a watercraft, an external lubrication system may be necessary. Prolonged high load or full throttle operation can require a greater volumetric oil flow through the supercharger than can be readily provided by an internal system. In a preferred embodiment of the supercharger, two side ports  106  and  108  can be provided in the housing that communicate with the lubrication reservoir. Such ports are illustrated in  FIGS. 8 and 9 . The lubricating oil would flow to the reservoir through a hose (not shown) communicating with either port  106  or  108  and from the reservoir and back to the engine lubrication circuit or other external lubrication system through the lowermost of ports  90 ,  92  and  94 . The selection of ports  106  or  108  and  90 ,  92  or  94  again depends on the angular orientation of the supercharger in the vehicle or other application, and the rotational direction of the drive shaft  28 . Note that both side ports  106  and  108  are laterally aligned with the gap between the upper and lower barrier walls so that the lubricating oil can be directed at the interface of the intermeshing gear teeth on the drive and pinion gears. Port  106  or  108  is chosen such that the lubrication oil is introduced into the rotating direction of the intermeshing gear teeth and entrained thereon. Also note that in the embodiments of  FIGS. 8  and  9 , only one such gap exists as one of the upper baffle walls is removed, as will be described. However, in the previously discussed baffle assembly  72 , both of the side ports are aligned with the gaps between the upper and lower baffle walls. 
         [0024]    With an external lubrication system, the oil slinger would continue to operate as previously described as the lubrication oil was continuously replenished by the external system. However, in such applications, the baffle assembly will continue to control the oil flow through the supercharger. While heat build-up in the lubrication oil would not present as much of a problem in such applications as the oil is constantly “changed,” the oil entrainment phenomenon remains. The baffle assembly will continue to function as previously described, controlling the flow and preventing the power loss that would otherwise occur as a result of the entrainment phenomenon. In the majority of applications, however, where continuous high load or full throttle operation is not encountered, e.g. automobiles, the oil slinger  48  and baffle assembly  72  provide excellent lubrication of the supercharger components without the need for external oil. The addition of the extra ports for use with an external lubrication system enhances the flexibility of the supercharger  10 . 
         [0025]    While the baffle assembly  72  discussed above and illustrated in  FIG. 6  accommodates both clockwise and counter-clockwise rotation of the gears,  FIGS. 8 and 9  illustrate modified gear cases  114  and  214  particularly configured for a clockwise ( FIG. 8 ) or counter-clockwise ( FIG. 9 ) drive gear rotation as viewed from the front of the respective figures. As seen in  FIG. 8 , the upper portion of the upper barrier wall  174  has been removed such that the upper surface  174 ′ of the wall is coplanar with the flat casing surfaces  104  extending about the vertically aligned bearing bores  131  and  133  that house the bearing assemblies (not shown in  FIG. 8 ) that support the drive and impeller shafts in the gear case. Such a configuration better accommodates drainage of the lubrication oil back to the reservoir  146  and, with a clockwise rotation of the drive gear, the stripping of the oil therefrom primarily occurs at the extended end portion  176 A of barrier wall  176 .  FIG. 9  illustrates a corresponding modification of upper barrier wall  276  for a counter-clockwise rotation of the supercharger drive gear where stripping of the oil would primarily occur at the end portion  274 A of barrier wall  274 . In both the embodiments of  FIGS. 8 and 9 , the drive gear rotates in a direction so as to pass upwardly along the single inclined barrier wall  174  or  274  such that the end portion of the wall will more effectively strip oil from the drive gear. 
         [0026]    Although the present invention has been described by way of exemplary embodiments, it should be understood that various changes and modifications may be made in carrying out the present invention without departing from the spirit and scope thereof. Insofar as these changes and modifications are within the purview of the appended claims, they are to be considered as part of the present invention.