Abstract:
Bearing caps and methods for manufacturing bearing cap are disclosed. Bearing cap includes a body that comprises an abutment surface, a bearing surface, an exterior surface, and a recess portion. The abutment surface provides for the bearing cap to be coupled to an engine along a flat and even surface. The bearing surface provides for the bearing cap to at least partially capture the bearing shaft to secure the bearing shaft when the bearing cap is abutted to the engine. The recess portion extends into the body of the bearing cap from the exterior surface to reduce the weight of the bearing cap. The recess portion can be located anywhere along the exterior surface and be any shape and dimension that retains sufficient structural integrity of the bearing cap to secure the balance shaft to the engine.

Description:
RELATED APPLICATIONS  
       [0001]     This non-provisional application claims the benefit of U.S. Provisional Patent Application No. 60/716,774, entitled “BEARING CAP WITH WEIGHT RESUCTION FEATURE,” filed Sep. 13, 2005, which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates generally to engine components and their manufacture, and relates particularly to a bearing cap with features that reduce the weight of the bearing cap.  
       BACKGROUND  
       [0003]     In reciprocating piston engines, vibrational forces are produced due to the movement and mass of reciprocating parts. To offset such vibrational forces, engines are often equipped with balance shafts, which include balancing weights. Such balancing weights act to counterbalance and offset vibrational forces produced by reciprocal parts during the operation of the engine. Typical reciprocal engines often utilize pairs of balance shafts. Such pairs of balance shafts are supported on casings disposed in an oil pan below the engine cylinder block. The balance shafts are linked to each other and a to an engine crankshaft to transfer the rotational forces from the crankshaft to the balance shafts. Balance shafts are typically linked to the crankshaft via a chain, belt, or the like, such that the balance shafts rotate at twice the rotational speed and in the opposite direction of the crankshaft. The resultant vibrational forces of the balance shafts counterbalance and offset the vibrational forces of the engine.  
         [0004]     In general, such balance shafts are supported at a plurality of positions to secure the balance shafts to the engine. Since a substantial amount of balancing torque is produced when the balance shafts rotate, the shafts must be supported by a sufficiently rigid bearing structure to remain secured to the engine during operation of the engine. Typically, balance shafts are supported and secured by bearing caps having journal portions designed to capture a portion of the balance shaft. Bearing caps known in the art are generally solid bodies fabricated from cast iron and split into upper and lower halves, as disclosed in U.S. Pat. No. 5,535,643.  
         [0005]     As is known in the art, one method of increasing the strength of the journal portion is to manufacture bearing caps from billet steel or other such rigid material through a casting or machining process. Secondary operations often accompany such processes, such as the drilling of journal portions through the cast or machined bearing cap. The journal portions are drilled to accommodate the insertion of the balance shafts into the journal portions.  
         [0006]     There is a constant need in the art to reduce the weight of automotive components, increase the strength and machinability of such components, and reduce costs. Any such improvements are constantly sought in the automotive industry.  
       SUMMARY OF INVENTION  
       [0007]     These needs and others are addressed by the invention disclosed herein. An apparatus and methods are provided for reducing the weight of a bearing cap. Such bearing caps are utilized for securing a balance shaft to an engine. Methods and features for reducing the weight of a bearing cap retain the structural integrity of the bearing cap. The apparatus and methods further provide for cost reductions by limiting the amount of post-forming machining needed to finish a bearing cap.  
         [0008]     As such, an apparatus for a bearing cap is disclosed herein. The bearing cap includes a body that comprises an abutment surface, a bearing surface, an exterior surface, and a recess portion. The abutment surface provides for the bearing cap to be coupled to an engine along a flat and even surface. The bearing surface provides for the bearing cap to at least partially capture the bearing shaft to secure the bearing shaft when the bearing cap is abutted to the engine. The recess portion extends into the body of the bearing cap from the exterior surface to reduce the weight of the bearing cap. The recess portion can be located anywhere along the exterior surface and be any shape and dimension that provides sufficient structural integrity to the bearing cap for securing the balance shaft to the engine.  
         [0009]     Furthermore, a method for forming a bearing cap is disclosed herein. The bearing cap is formed in a mold. The mold includes a cavity into which material is place. A die is used to compress the material in the cavity to form the bearing cap. A protrusion in the cavity produces a recess in a portion of the bearing cap. Such recess reduces the weight of the bearing cap. In addition, a contact surface of the die may form an abutment surface of the bearing cap. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0010]     In the accompanying drawings, which are incorporated in and constitute a part of this specification, embodiments of the invention are illustrated, which, together with a general description of the invention given above, and the detailed description given below serve to illustrate the principles of this invention. The drawings and detailed description are not intended to and do not limit the scope of the invention or the claims in any way. Instead, the drawings and detailed description only describe embodiments of the invention and other embodiments of the invention not described are encompassed by the claims.  
         [0011]      FIG. 1  is a perspective view of a bearing cap arranged in accordance with an embodiment of the present invention;  
         [0012]      FIG. 2  is a front elevational view of the bearing cap of  FIG. 1 ;  
         [0013]      FIG. 3  is a top plan view of the bearing cap of  FIG. 1 ;  
         [0014]      FIG. 4  is a bottom plan view of the bearing cap of  FIG. 1 ;  
         [0015]      FIG. 5  is a cross-sectional view of the bearing cap of  FIG. 1  taken along the line  5 - 5  of  FIG. 2 ; and  
         [0016]      FIG. 6  is a perspective view of a bearing cap arranged in accordance with another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     This invention and disclosure are directed to apparatus and methods for providing a bearing cap for securing a balance shaft to an engine. Such bearing caps include features that reduce the weight of bearing caps. Such features include recesses extending into the bearing cap from exterior surfaces of bearing caps. Such features are arranged such that the structural integrity of the bearing cap is not compromised with regard to securing the balance shaft to the engine.  
         [0018]     An exemplary bearing cap  10  in accordance with an embodiment of the invention is illustrated in FIGS.  1  though  5 . The bearing cap  10  includes a body  12  formed from metal or other such rigid material. The body  10  includes abutment surfaces  14 A and  14 B (best seen in  FIG. 4 ), a bearing surface  16 , and a plurality of exterior surfaces. As illustrated in the figures, the exemplary embodiment includes a pair of side surfaces  18  and  20  and a top surface  22 .  
         [0019]     Additionally, the bearing cap  10  includes four apertures  24 ,  26 ,  28 , and  30 . The apertures  24 ,  26 ,  28 , and  30  pass though the body  10  from the top surface  22  to the abutment surfaces  14 A and  14 B. The apertures  24 ,  26 ,  28 , and  30  are arranged to accommodate bolts or other such fasteners. The body  12  also includes a number of weight reducing features. For example, a weight reducing recess  32  extending into the body  12  from the top surface  22 , and a plurality of weight reducing recesses  34 ,  36 ,  38 , and  40  extending into the body  12  from the side surfaces  18  and  20 . As illustrated, the recesses  32 ,  34 ,  36 ,  38 , and  40  are areas that are lower than the surrounding surfaces  18 ,  20 , and  22  due to the elimination of material that would normally be present to complete an even exterior surface. The elimination of material from exterior surfaces of the bearing cap  10  allows for a multitude of embodiments for the reduction of overall weight of the bearing cap  10  without compromising the structural integrity of the bearing cap  10 .  
         [0020]     The bearing cap  10  is designed to be coupled to the engine, either directly or indirectly. Bolts or other such fasteners are passed through the apertures  24 ,  26 ,  28 , and  30  and fastened in threaded holes (not shown) in an engine. Alternatively, the bolts may be fastened to an intermediate component, which is secured to the engine, to couple the bearing cap  10  to the engine. When the bearing cap  10  is coupled to the engine, the bearing cap  10  abuts or otherwise contacts the engine or intermediate component along the abutment surfaces  14 A and  14 B. The abutment surfaces  14 A and  14 B are flat and coplanar, such that the surfaces  14 A and  14 B may effectively contact opposing surfaces on the engine or intermediate component. The bearing surface  16  is arranged to capture a balance shaft (not shown) when the bearing cap  10  is coupled to the engine. The bearing surface  16  cooperates with a similar bearing surface on the engine or other intermediate component to form a bearing to contain a journal portion of the balance shaft and secure the balance shaft to the engine. Coupled as used herein is defined as connected, either directly or indirectly. Two components that are coupled, may have one or more intermediate components that are used to connect the components together.  
         [0021]     As previously described, the body  12  includes a number of recesses  32 ,  34 ,  36 ,  38 , and  40  to reduce the weight of the bearing cap  10 . Preferably, the recesses  32 ,  34 ,  36 ,  38 , and  40  are arranged to offer the maximum reduction of weight without affecting the structural integrity of the bearing cap  10 , which is needed to secure balance shafts to the engine. Although the preference is to achieve a maximum reduction of bearing cap weight, any reduction of weight through the weight reduction features as described herein is included in the present invention.  
         [0022]     The exemplary embodiment as illustrated includes a recess  32  in the top surface  22 . The recess  32  is a groove or channel located along an end  42  of the top surface  22 . Although the recess  32  in the top surface  22  is illustrated and described as a groove or channel along an end  42  of the top surface  22 , it will be understood by those skilled in the art that a recess of any size or shape that extends into the body  12  from the top surface  22  is included in the present invention. Indeed, the invention is not limited to one recess or weight reduction feature on the top surface  22 , any number of recesses or other weight reduction features may be incorporated into the top surface  22 , provided the structural integrity of the bearing cap  10  is not compromised.  
         [0023]     The exemplary embodiment as illustrated, includes four recesses  34 ,  36 ,  38 , and  40  in the side surfaces  18  and  20 . Each recess  34 ,  36 ,  38 , and  40  is an elongated channel extending from the intersections of the top surface  22  and the side surfaces  18  and  20  towards the abutment surfaces  14 A and  14 B and terminating a short distance from the abutment surfaces  14 A and  14 B. Each recess  34 ,  36 ,  38 , and  40  in the side surfaces  18  and  20 , includes a ledge  44  at the end of the channel  34 ,  36 ,  38 , and  40  that terminates proximate to the abutment surfaces  14 A and  14 B. Each ledge  44  is generally perpendicular to the side surfaces  18  and  20 . The purpose for terminating the channels  34 ,  36 ,  38 , and  40  a short distance from the abutment surfaces  14 A and  14 B is to maintain a maximum footprint or profile for the abutment surfaces  14 A and  14 B. If a channel  34 ,  36 ,  38 , and  40  were to extend to the intersection between the side surfaces  18  and  20  and an abutment surface  14 A and  14 B, the surface area of the abutment surface  14 A and  14 B would be reduced. Such reduction in surface area may enhance contact fatigue between the abutment surface  14 A and  14 B and a mating surface on the engine, which may lead to premature failure of the bearing cap  10 .  
         [0024]     As best seen in  FIGS. 1 and 3 , each elongated channel  34 ,  36 ,  38 , and  40  in a side surface  18 ,  20  is located between a pair of apertures  24 ,  26  and  28 ,  30 . When a recess in a side surface  18  and  20  is an elongated channel  34 ,  36 ,  38 , and  40 , locating the channel  34 ,  36 ,  38 , and  40  between a pair of apertures  24 ,  26  and  28 ,  30  is preferred. Such a location does not affect the structural integrity of the bearing cap  10 . Each channel  34 ,  36 ,  38 , and  40  is arranged such that the amount of material surrounding the perimeter of each aperture  24 ,  26 ,  28 , and  30  is as large or larger than the amount of material surrounding the perimeter of each aperture  24 ,  26 ,  28 , and  30  when a weight reducing feature is not located near an aperture. Therefore, whether a weight reducing feature is located near an aperture or not, the structural integrity of the bearing cap  10 , specifically the area surrounding apertures, is unaffected.  
         [0025]     Although the recesses  34 ,  36 ,  38 , and  40  in the side surfaces  18  and  20  are illustrated and described as channels extending from the top surface  22  to a short distance from the abutment surfaces  14 A and  14 B, it will be understood by those skilled in the art that a recess or other weight reduction feature of any shape or size that extends from a side surfaces  18  and  20  into the body is included in the present invention. Indeed, the invention is not limited to the four recesses  34 ,  36 ,  38 , and  40  shown on the side surfaces  18 ,  20 , any number of recesses or other weight reduction features may be positioned on the side surfaces  18 ,  20 , provided the structural integrity of the bearing cap  10  is not compromised.  
         [0026]     Bearing caps as described herein may be formed or manufactured through a molding process that utilizes a mold and a die. The mold typically includes a cavity that generally defines the shape of the bearing cap. Material is placed into the cavity through an open end of the cavity. The die, which includes a contact surface that defines one exterior surface of the bearing cap, enters the cavity though the open end and compresses the material in the cavity to form the bearing cap. A common material used to mold bearing caps is a powder metal material. Such powder metal can be placed into the cavity, the die can enter the cavity to compress the powder metal, and the powder metal can be sintered upon compression of the material to form a solid bearing cap. Such a process may produce a near-net-shape part, i.e., a part that needs little or no machining to achieve a final form.  
         [0027]     Typically, a bearing cap is molded with the cavity forming the abutment surfaces  14 A and  14 B, the bearing surface  16 , and the side surfaces  16  and  18 . The contact surface of the die forms the top surface  22 . That is to say, bearing caps are normally molded in the upright position, with reference to  FIG. 1 . However, with the embodiment shown in the figures, the bearing cap would not be able to be removed from the cavity of a standard mold. Each channel  34 ,  36 ,  38 , and  40  includes a ledge  44  formed just above the abutment surfaces  14 A and  14 B. The outer dimensions of the abutment surfaces  14 A and  14 B are larger than the outer dimensions of the channels  34 ,  36 ,  38 , and  40 . Thus, the exemplary bearing cap  10 , as illustrated in the figures, cannot be manufactured in the upright position. As such, the exemplary bearing cap  10  may be manufactured in a reversed, or upside down position, with reference to  FIG. 1 . In this arrangement the cavity forms the side surfaces  18  and  20 , any weight reduction features in the side surfaces  18  and  20 , the top surface  22 , and any weight reduction features in the top surface  22 . The contact surface of the die forms the abutment surfaces  14 A and  14 B and the bearing surface  16 . The arrangement of the contact surface of the die, along with the alignment of the die is such that the abutment surfaces  14 A and  14 B are coplanar and generally flat upon the forming of the bearing cap  10 .  
         [0028]     Molding the bearing cap in a reversed position provides flexibility in designing and molding weight reduction features into bearing caps. As most designs that include weight reducing features will seek to maintain the largest possible footprint or profile for the abutment surfaces, the outer dimensions of the side surfaces and top surface will typically be less than the outer dimensions of the abutment surfaces footprint. Therefore, molding the bearing cap in the reversed position may reduce concerns over removal of the bearing cap from the cavity once the bearing cap is formed. Weight reduction features, such as channels and groove, can be formed by including protrusions on an inner wall of the cavity. Such protrusions reduce the amount of material needed to mold a bearing cap, and thus, reduce the overall weight of the bearing cap.  
         [0029]     An alternative to molding a bearing cap in a reversed position is to utilize a split mold, which includes two halves. In such an arrangement, the bearing cap can be molded in either the upright or reversed positioned. Once the bearing cap is formed, the two halves of the mold can be separated to remove the formed bearing cap.  
         [0030]     Referring to  FIG. 6 , another exemplary bearing cap  100  in accordance with an embodiment of the invention is illustrated. The bearing cap  100  includes a rigid frame  102  coupled to a sintered bearing cap body  104 . The bearing cap body  104  includes weight reduction features  106 . For example, the bearing cap body  104  may include channels or grooves as described herein.