Abstract:
A noise reducing oil pan assembly for a motor vehicle engine, adapted for attachment to the engine block underside, includes outer and inner nested pan units supported in spaced relation defining an oil chamber between the units. An inflow gap between the upper opposed edge portions of the units upstanding walls is positioned subjacent the outflow of engine block return oil passages. With the engine running, the return oil flow fills the chamber and thereafter the overflow is received by the inner unit reservoir for re-circulation to the engine. The chamber oil provides a barrier that dampens engine noise radiating from the oil pan assembly.

Description:
FIELD OF THE INVENTION 
     The present invention relates to oil pans for internal combustion engines and, more specifically, to an engine noise dampening oil pan assembly. 
     BACKGROUND OF THE INVENTION 
     In the desire to reduce noise emitted from internal combustion engines oil pans, various sound dampening arrangements have been proposed. U.S. Pat. No. 4,851,271, discloses a laminated oil pan structure of a thin plastic damping material positioned between flat inner surfaces of the pan and stamped steel insert pan liners. 
     An engine sound deadening arrangement is disclosed in U.S. Pat. No. 3,991,735, which provides a liquid sound barrier in the form of an oil reservoir between a cylinder block walls and cowling cover. 
     The Society of Automotive Engineers, Inc. paper No. 1999-01-1759, entitled: “Development of a Technique for Using Oil Viscosity to Reduce Noise Radiated from the Oil Pan”, discloses a vibration dampening technique for engine oil pans to reduce radiation noise. Damping is obtained with a “squeeze” oil pan, formed with a thin oil film between the pan and an added inner plate, which reduces the pan vibration level to lower radiation noise. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention concerns an oil pan assembly for automotive internal combustion engine blocks formed with passages for returning oil to an oil pan reservoir. Applicant&#39;s pan assembly comprises a pair of corresponding inner and outer pan units, wherein the inner unit is supported in nested spaced relation within the outer unit. The space between unit walls provides a return oil chamber, with the upper opposed edge portions of its walls defining oil inflow gaps. The chamber substantially envelops the inner pan unit oil reservoir, allowing the chamber oil to dampen engine noise radiating from the reservoir. 
     Another feature of the invention set forth above is to provide an oil pan assembly wherein, with its outer pan unit being secured to the bottom of the engine block, the chamber inflow gaps are located subjacent the return oil flows exiting the block oil passages. Upon filling the chamber, the return oil overflows into the inner pan unit reservoir for re-circulation to the engine. 
     Still another feature is to provide a duel-walled oil pan assembly as set forth above, wherein the assembly is fabricated from thinner gauge sheet steel such that its weight is substantially the same as conventional oil pans formed from thicker gauge sheet steel. In the disclosed embodiment the inner and outer nested metal pan units are secured together in a spaced manner by a plurality of welded spacer members, defining a “honeycomb panel” type, dual wall structure. 
     It is yet another feature to terminate the inner wall upper edge portion in an upwardly facing convex curved lip for directing the return oil flow from the block passages into the chamber. After the chamber is filled with oil, the convex lip provides an overflow path for returning the oil to the pan unit reservoir. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages described herein will be more fully understood by reading an example of one embodiment in which the invention is used to advantage, referred to herein as the Description of the Preferred Embodiment, with reference to the drawings wherein: 
     FIG. 1 is a fragmentary, perspective view of a conventional V-configuration internal combustion engine provided with an oil pan assembly, according to the present invention; 
     FIG. 2 is an enlarged fragmentary cross sectional view, partly in elevation, taken substantially on line  2 — 2  of FIG. 1, showing a lower portion of the engine crankcase supporting the oil pan assembly of the present invention; 
     FIG. 3 is an enlarged elevation view, with parts broken away, of the forward end of the oil pan assembly, as viewed from line  3 — 3  of FIG. 1; 
     FIG. 4 is a cross sectional view, partly in elevation, taken on the line  4 — 4  of FIG. 3; 
     FIG. 4A is an enlarged fragmentary cross sectional view, partly in elevation, of the drain plug of the FIG. 4, of the area enclosed by circle “ 4 A”; 
     FIG. 4B is a view similar to FIG. 4A showing a modified drain plug arrangement; and 
     FIG. 5 is an enlarged elevation view, with parts broken away, of the aft end of the pan assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1 of the drawings, an embodiment of an oil pan assembly  10  is shown attached beneath a “V” configuration internal combustion engine, indicated generally at  12 . Engine cylinder block  14 , which supports right-hand and left-hand banks of cylinders,  16  and  17  respectively, are shown separated by block valley  18  in the form of a “V”. The block is formed with oil lubricating passages (not shown), and gravity flow oil return passages, exemplified by passage  19  in FIG.  2 . 
     As viewed in FIG. 2, right and left cylinders are partially shown at  20  and  21 , respectively. It should be noted that while a V type engine is shown other engines, such as an in-line four cylinder engine for example, could be equipped with the oil pan assembly  10 . The cylinder  20  has its piston  22  joined to engine crankshaft  24  by connecting rod  25 , while the cylinder  21  has a piston (not shown) joined by connecting rod  26  to the crankshaft. 
     The pan assembly  10  comprises an outer pan unit  27  and an inner substantially matching pan unit  28  of reduced size. As illustrated in FIGS. 2,  3  and  5 , the outer pan unit  27  is attached to the block underside by laterally extending side flanges  30 — 30  suitably secured, as by bolts  32 — 32 , to outboard lower extensions  34 — 34  of block walls  36 — 36 . A lubricant pick-up tube  40 , connected to lubricant pump  42 , terminates at its lower end in a-cone-shaped return-oil filter screen  44 . FIG. 4 shows the tube screen  44  located adjacent a threaded screw-in drain plug  47  for depressed sump areas  48  and  49 , of associated outer and inner pan units  27  and  28 , in a manner to be discussed. 
     With reference to FIGS. 3-5, the outer pan unit  27  is larger in size relative to its complementary-shaped inner pan unit  28 , enabling pan unit  28  to be supported in a nested, spaced manner within outer unit  27 . The outer and inner units define an oil chamber  29  there-between, which chamber substantially envelops the oil reservoir formed by the inner unit  28 . Although the oil pan units  27  and  28  are each formed with a generally rectangular box shape, other configurations, such as a cylindrical-shaped pan for example, are within the scope of the invention. The outer pan unit  27  includes front  50  and aft  50 ′ end walls, side walls  54 — 54 , and bottom wall  56  uniformly spaced apart from associated inner pan unit front  51  and aft  51 ′ end walls, side walls  55 — 55 , and bottom wall  57  by a predetermined dimension “D”. In the disclosed embodiment the dimension “D” is of the order of 5 mm. 
     The inner pan unit  28  is fixedly supported, in a rigid manner, relative to the outer unit  27  by suitable spacer segments secured, as by spot-welding, to the inner and outer sheet steel pan units  27  and  28 . In the disclosed form the spacer segments comprise a plurality of elongated hat-sectioned segments, shown at  58  in FIG.  4 . Relative to the weight factor, the dual walled oil pan assembly  10  allows the use of thinner gauge sheet steel for both units  27  and  28 . In the instant embodiment the pan assembly  10  replaces a prior art oil pan requiring a sheet steel gauge thickness of the order of 1.5 mm. The pan assembly outer unit  27  sheet steel has a reduced gauge thickness of about thirty percent (1.05 mm), while the inner unit  28  sheet steel has a reduced gauge thickness of about sixty percent (0.60 mm). Thus, applicant&#39;s pan assembly has a combined weight that is closely comparable to prior art oil pans of equal size. 
     It is understood that other spacer arrangements methods may be employed such as, for example, forming stamped dimples in the walls of one pan unit adapted for spot-welding to opposed walls of the other pan unit. Also, the pan units may be fabricated from other materials such as fiberglass, for example, without departing from the invention. 
     FIGS. 1 and 2 disclose portions of a conventional vehicle engine lubricating system. Thus, with the engine running, oil pump  42  pulls returned motor oil out of the inner unit reservoir  28 , via pickup tube  40 , after the oil has been passed through filter screen  44 . Pump pressure then pushes the oil through filter  55  and engine block passages (not shown), after which the filtered oil flows to the engine and lubricates its moving parts. The oil drains back through a plurality of block gravity return oil passages, such as the passage  19  in FIG. 2, and thereafter flows into a pan reservoir for re-circulation back to the engine. 
     In FIG. 1, with the engine running, the gravity flow of return oil exits block passage  19  for entry into an associated subjacent inflow gap  59 , defined by upper edge portions of the opposed side walls  54  and  55 , filling the pan-shaped chamber  29 . It will be noted in FIGS. 3-5 that the upper edge portions of the inner pan unit front  50  and aft end walls, together with its side walls  55 , terminate in associated upwardly extending convex or half-round lip portions  60 ,  60 ′, and  61 — 61 , respectively. The lip portions direct the return oil flow into the chamber  29  and, upon the chamber being filled, the lip portions provide a smooth path for the overflow oil into the inner pan unit reservoir  28 . 
     FIGS. 3 and 4 show the pan assembly outer front end wall  50  upper edge portion formed with a forward projecting front concave cradle portion  80  and its outer aft end wall  50 ′ formed with a rearward projecting, aft concave cradle portion  82 . The front  80  and aft  82  cradle portions are aligned on the longitudinal axis of the pan assembly  10  to receive, in juxtaposed conformity, engine crankshaft  24 . It will be seen in FIG. 5 that the aft cradle portion  82  has a greater depth below the side wall lip portions  61  than the front cradle portion  80  for accommodating an increased diameter portion of the crankshaft  24  adjacent the aft outer end wall  50 ′. 
     Referring to FIGS. 3 and 5, the inner unit front  51  and aft  51 ′ end walls are each provided with concave depressions formed in their associated lip portions  60  and  60 ′, and match front  80  and aft  82  concave cradles providing clearance for crankshaft  24 . As seen in FIG. 4, the inner end wall aft concave lip portion  60 ′ creates a lowermost point “Y” that is deeper than the front concave lip portion  60  point “X”. With the engine turned off, the chamber inner aft end wall  51 ′ attains a static oil level  70 ′ determined by the lowermost point “Y”. Upon turning the engine on, the chamber fills with return oil from the static oil level  70 ′ to dynamic overflow oil level  70  along the side walls  54 ,  55 . This fluctuation in the oil levels provides a re-circulation of the chamber oil thereby obviating a stagnation condition. 
     With reference to FIGS. 4 and 4A, the drain plug  47  is threaded into a drain hole  62  in outer sump area  48  and a drain hole  64  in inner sump area  49 , thus sealing pan-shaped oil chamber  29  and inner pan unit reservoir  28 . Removal of the drain plug  47  allows oil to flow out of chamber  29  and the inner pan unit reservoir  27 . 
     FIG. 4B shows a modified drain plug  47 ′ providing a threaded portion  65 , threaded in a drain hole  66  in outer sump area  48 , and an a cylindrical dowel stopper portion, aligned on free end of plug threaded portion  65 , received in smooth drain hole  68 . Upon removal of the drain plug  47 ′ both the inner pan unit reservoir  28  and the oil chamber  29  are drained. 
     While the best modes for carrying out the invention have been described in detail, those skilled in the art in which this invention relates will recognize various alternative designs and embodiments, including those mentioned above, in practicing the invention that has been defined by the following claims.