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.
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.
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.
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'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
The housing cover 16 and gear case 14 cooperatively define an internal lubricant reservoir 46 (see
In an alternate embodiment of the cover 16 (see
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
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 80A 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, 48A preferably kidney-shaped, are provided in the side of the slinger disc 48 as shown in
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 74A or 76A 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
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.
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
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
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.
While the baffle assembly 72 discussed above and illustrated in
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.