Abstract:
A rocker box bottom for an internal combustion engine includes a body that defines an oil/air inlet, an oil outlet, a chamber therebetween and a valve seat between the chamber and the oil/air inlet. The body seals to a rocker box top and defines the inlet and outlets. The seat may accept a valve along a diagonally downward direction with the oil outlet below the seat. In the alternative, the path between the oil/air inlet and the air outlet may turn the air flowing therethrough approximately 180 degrees. In another preferred embodiment, the valve may be a reed valve that, in cooperation with the chamber walls, turns the oil/air mixture flowing therethrough approximately 180 degrees.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to rocker box assemblies for internal combustion engines. 
   BACKGROUND OF THE INVENTION 
   The moving components of a motorcycle engine require lubrication to preserve and extend their useful lives. Many of the moving components are located in the crankcase and rocker box of the engine. In operation, the oil used for lubricating the components in the crankcase (i.e. the connecting rod, crankshaft, and associated links) is atomized and sprayed thereon. As a result, a fine oil mist exists in the air in the crankcase. Some vaporized oil also exists within the crankcase because of the heat conducted from the combustion chamber. The air in the crankcase therefore holds a noticeable amount of atomized and vaporized oil. 
   The oil mixed in the air represents a problem because the crankcase must be vented for proper operation. If the crankcase were not vented, the trapped air would fluctuate in pressure as the pistons reciprocate. Since it is the pressure difference between the combustion chamber and the crankcase that drives the pistons down during the power stroke, the pressure of the trapped gas would oppose the power stroke and decrease the performance of the engine proportionally. 
   Venting the crankcase, though, creates other difficulties. Namely, as the piston moves toward the crankcase during the power stroke, the air being vented entrains the atomized and vaporized oil. If the oil is not separated from the air before being vented, the engine eventually runs dry and fails for lack of lubrication. For this reason, engine manufacturers typically include an oil/air separator, an air cleaner, or both in the crankcase vent subsystem. These devices minimize the amount of oil vented from the crankcase with the air. But they are not perfect. 
   Currently available oil/air separators and air cleaners tend to allow some oil to escape from the crankcase with the air. Once outside of the engine, the oil fouls the motorcycle and the rider thereon. The oil/air separators and cleaners of the prior art also add to the weight of the engine and tend to decrease the acceleration and handling characteristics of the bike according to the extra weight. Further, because a motorcycle engine must be small enough to fit within the frame of the motorcycle and to allow the rider to straddle the same, even small increases in the size of the engine are detrimental. Yet currently available oil/air separators and air cleaners increase the overall size of the engine. 
   A need therefore exists for improved oil/air separators. 
   SUMMARY OF THE INVENTION 
   It is in view of the above problems that the present invention was developed. The invention includes apparatus and methods for separating oil from the air being vented from motorcycle engines. 
   In a first preferred embodiment, the present invention provides a rocker box bottom for an internal combustion engine. The bottom has a surface that seals to a rocker box top and that lies in a first plane. The body defines an oil/air inlet, an air outlet, an oil outlet, a chamber therebetweeen, and a valve seat. The oil/air inlet accepts a mixture of oil and air from the crankcase of an internal combustion engine. The valve seat may accept a valve that lies in a second plane (at an acute angle relative to the first plane) between the oil/air inlet and the chamber. The oil outlet is located below the seat when the rocker box bottom is in an upright orientation. 
   A second preferred embodiment provides a rocker box bottom in which the path between the oil/air inlet and the air outlet turns the air through approximately 180 degrees. In still another preferred embodiment, the valve is a reed valve that, in cooperation with the walls of the chamber, turns the air through approximately 180 degrees around the valve. In yet other preferred embodiments, an air restrictor may be inserted in the airflow path near the air outlet. In other preferred embodiments, both the valve and valve seat are metallic. Metallic reed valves and seats enjoy improved performance and lengthened service lives over existing rubber components because the rubber becomes hard after repeated heat cycles. 
   Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention, and together with the description, serve to explain the principles of the invention. In the drawings: 
       FIG. 1  illustrates a motorcycle engine constructed in accordance with a preferred embodiment of the present invention; 
       FIG. 2  illustrates a cross sectional view of a motorcycle engine; 
       FIG. 3  illustrates an exploded view of a rocker box of  FIG. 2 ; 
       FIG. 4  illustrates a cross sectional view of the rocker box of  FIG. 2 ; and 
       FIG. 5  illustrates a side elevation view of a valve of the rocker box of FIG.  2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to the accompanying drawings in which like reference numbers indicate like elements,  FIG. 1  illustrates a motorcycle constructed in accordance with a preferred embodiment of the present invention. The motorcycle  10  includes a frame  12  on which the various components of the motorcycle are mounted. An internal combustion engine  14  is mounted near the bottom of the frame  12  in a position where the rider straddles it during operation. The engine  14  includes cylinder blocks  16  with pairs of pistons canted at an angle from each other. Beneath the cylinder blocks  16 , a crankcase  18  receives the reciprocal motion of the pistons and converts it to rotational motion for propelling the motorcycle  10 . 
   With reference now to  FIG. 2 , a simplified cross sectional view of the engine  14  is shown. The engine  14  includes the cylinder block  16 , the crankcase  18 , combustion chambers  20 , pistons  22 , connecting rods  24 , a crankshaft  26 , and links  27 . Near the top of the engine  14 ,  FIG. 2  also illustrates a push rod  30 , a rocker arm assembly  31 , a rocker arm  32 , a shaft  34 , a pair of valves  36  and  38 , a rocker box  40  and a cylinder head  42 . Also shown are coolant channels  46 , manifolds  48  and  50 , and a spark plug  52 . 
   In general, the engine  14  is constructed as follows. The cylinder head  42  contains many features of the engine  14  and is coupled to the top of the cylinder block  16 . First, the overall dimensions of the cylinder block  16  are determined primarily by performance requirements for the engine  14 . More particularly, the required stroke of the piston  22  largely determines the height of the cylinder block  16  and, therefore, of the engine  14 . The cylinder head must also accommodate, or guide, many moving components, such as the push rod  30 , that extends between the crankcase  18  and the rocker box  40 . Additionally, the cylinder block  16  includes passages within which the valves  36  and  38  move to control the entry and discharge of fluids (e.g. the air/fuel mixture and the exhaust gas) from the combustion chamber  20 . Therefore, the cylinder head  42  also includes lubrication channels (not shown) to provide oil for the moving components within its envelope. Like the valves  36  and  38 , the spark plug  52  extends into the combustion chamber  20  from the cylinder head  42 . The cylinder head  42 , as shown in  FIG. 2 , seals the valves  36  and  38  along with the spark plug  52  to prevent the escape of gases from the chamber  20 . Because the cylinder head  42  is in direct contact with the hot combustion gases, it must be designed to tolerate high temperatures and pressures. Thus, the cylinder head  42  also includes coolant channels (not shown) to maintain its temperature within a tolerable range during operation. The head  42  also defines the fuel/air and exhaust manifolds  48  and  50  respectively. Thus, the cylinder head  42  is relatively complex and requires expensive machining to fabricate. 
   With continued reference to  FIG. 2 , the rocker box  40  is also illustrated. It couples to the top of the cylinder head  42  and is therefore spaced apart from the hot gases in the combustion chamber  20 . Accordingly, the environment experienced by the rocker box  40  is comparatively mild. Within the rocker box  40 , the rocker assembly  31  is found. One end of the push rod  30  extends from the crankcase  18  (where a cam drives it) into the rocker box  40 . Therein the push rod  30  connects to the rocker arm  32  and causes it to pivot around the shaft  34 . Typically, one of the valves  36  or  38  connects to a particular rocker arm  32 . Though  FIG. 2  shows the rocker arm  32  connected to both valves  36  and  38  for illustrative purposes. Because the height of the cylinder block  16  largely determines the height of the engine, the height of the rocker box is preferably minimized. Otherwise, the rocker box  40  is of relatively simple construction. 
   The crankcase  18  contains the connecting rods  24 , the crankshaft  26 , and the links  27  and is shown with a reservoir of oil. The crank case  18  is coupled to the bottom of the cylinder block  16 , includes the coolant channels  46 , and allows the piston  22  to reciprocate within a cylinder defined by the cylinder block  16 . The connecting rod  24  couples the reciprocating piston  22  to the crankshaft  26  via a link  27 . Within the cylinder block  16 , and located above the piston  22 , the combustion chamber  20  is defined by the walls of the cylinder block  16 , the top of the piston  22 , and the cylinder head  42 . 
   In operation, fuel and air enter the combustion chamber  20  via the manifold  48  and valve  36 . The spark plug  52  ignites the fuel/air mixture and therefore causes the hot combustion gases to push the piston  22  down. Once the piston reaches the bottom of the cylinder, the exhaust valve  38  opens and allows the returning piston  22  to push the exhaust gases from the combustion chamber  20 . While the piston  22  is reciprocating in the cylinder it is turning crankshaft  26  via the connecting rod  24  and link  27 . For the valves  36  and  38  to actuate in timed relation with the reciprocating piston  22 , a cam driven by the crankshaft  26  is provided that causes the push rod  30  to reciprocate. In turn, the push rod  30  causes the rocker arm  32  to pivot about the shaft  34  thereby actuating the valves  36  and  38 . 
   Because of the relative motion of the moving components in the rocker box  40 , lubrication is required. The moving components include, but are not limited to, the push rod  30 , the rocker arm  32 , the shaft  34 , and the valves  36  and  38 . For convenience, the moving components  30 ,  32 ,  34 ,  36 , and  38  will hereinafter be referred to as the rocker assembly  31 . 
   With reference now to  FIGS. 3 and 4 , a rocker box  100  constructed in accordance with a preferred embodiment of the present invention is illustrated. The functions that the rocker box  100  serves include protecting the rocker assembly  31  from mechanical abuse, providing a source of lubrication for the rocker assembly  31 , and providing means for separating the oil/air mixture vented from the crankcase  18 . Preferentially, the separation of the oil from the air permits the oil to lubricate the rocker assembly  31 . 
   To serve these functions, the rocker box  100  includes several components and defines a number of chambers, voids, or cavities. First, the rocker box  100  includes a top  102  and bottom  104 , although, rocker boxes of generally one-piece construction are also within the spirit and scope of the present invention. The top  102  and bottom  104  are illustrated as sealing along a plane at a pair of surfaces  106  and  108  respectively. While the sealing surfaces  106  and  108  are illustrated as planar, they may be of any conventional configuration. A pair of cooperating cavities  10  and  112  in the top  102  and bottom  104 , respectively, provide space for the rocker assembly  31 . 
   As shown in cross section by  FIG. 4 , the bottom  104  includes an, oil/air separator  115 . The separator  115  includes an inlet plenum  114 , a valve  116 , a condensation chamber  118 , an oil outlet  120 , and an air outlet plenum  122 . In general these components are arranged and configured so as to cause pressure changes as the oil/air mixture flows through the oil separator  115 . As a result of these pressure changes the oil in the air tends to, condense. Various techniques may be used to create the condensation inducing pressure changes, such as restricting the flow of the mixture and creating large changes in the direction of the flow. Preferentially, the direction changes turn the air through about 180 degrees or more. 
   While the engine  14  is running, the oil/air mixture vented from the crankcase  18  enters the inlet plenum  114 . Preferentially, the mixture is generally flowing in a direction indicated by the arrow  124 . From the inlet plenum  114 , the mixture flows to the valve  116  and into the condensation chamber  118 . Therein, the oil condenses and drains to the oil outlet  120  as will be explained in more detail herein. From there, the oil outlet  120  may direct the oil to the chambers  110  and  112  to lubricate the rocker assembly  31 . In the meantime, the air continues flowing from the condensation chamber  118  to air outlet plenum  122  and may be further directed to an air cleaner thereafter. As shown by  FIG. 4 , the direction  126  of the air flow through the outlet plenum  122  is preferably 180 degrees from the direction  124  of the flow through the inlet plenum  114 . 
   In another preferred embodiment shown in  FIG. 4 , a rocker box  100  is provided in which the valve  116  is angled down (as viewed in  FIG. 4 ) relative to the sealing plane to aid in the separation of the oil from the air. More particularly, the bottom  104  is shown as including a valve seat  128  positioned at an acute angle  129  with respect to the plane along which the sealing surfaces  106  and  108  meet. The valve seat  128  is preferably coplanar with angled surface  130 . Herein, “down” refers to a direction generally parallel to the length of the cylinder block  16  and from the rocker box  40  to the crankcase  18 . 
   Thus, as the oil/air mixture flows through the restriction associated with the angled valve  116 , the associated pressure drop causes oil to condense from the mixture. Further, because of the angle  129 , the condensed oil flows along the seat  128  and continues across surface  130  toward the oil outlet  120 . The angle  129 , of course, would ordinarily cause an increase in the overall height of the engine by a distance d1. However, in a preferred embodiment, the vertical distance d1 between the outlet  120  and a proximal end  132  of the valve  116  is about equal to, or less, than the height d2 of the rocker assembly  31 . Additionally, the seat  128  and surface  130  are shown positioned relative to the rocker assembly  31  such that they reside within the height d2 required for the rocker assembly  31 . As a result, the present embodiment provides the angle  129  and accompanying improvement in oil/air separation without necessitating an increase in the overall height of the engine. 
   The oil outlet  120  is preferentially placed near the lowest point of the surface  130 . Additionally, it is preferred to provide an oil outlet  120  with a bore diameter that is about the diameter required to draw the oil into the outlet  120  by capillary action. Further, the rocker box  100  may be configured such that the oil outlet  120  points toward the rear of the motorcycle so that when the rider accelerates, oil flows through the outlet  120  because of the acceleration of the motorcycle. Such outlets  120  collect oil from the condensation chamber  118  even with the motorcycle  10  inclined in such a manner as to discourage oil drainage, as in a sharp turn. Moreover, the pressure in the condensation chamber  118  urges the oil in the oil outlet  120  toward the chambers  110  and  112 . While a preferred oil outlet  120  is circular in cross section, outlets  120  of various configurations are also provided with effective hydraulic diameters sufficient to wick the condensed oil into the outlet  120 . 
   In yet another preferred embodiment the valve  116  may be a reed valve. Reed valves typically include a body with the proximal end  132 , a distal end  134 , and a pair of side edges  136  (see FIGS.  3  and  5 ).  FIG. 4  shows the reed valve  116  as being affixed to the bottom  104  with conventional attachment means  138 . The body of the valve  116  is typically flexible enough to elastically deform when subjected to pressure from the seat side  141  of the body so as to open the valve  116 . In contrast, pressure from the downstream side  143  (facing the chamber  118 ) tends to urge the valve  116  against the seat  128 , thereby closing the valve  116 . Thus, the reed valve  116  may also serve as a check valve to prevent admittance of contaminants when the crankcase draws in air while also allowing venting of the oil/air mixture from the crankcase. 
   A closer inspection of the reed valve  116  reveals further advantages of the present embodiment. As the oil/air mixture flows from the inlet  114 , the mixture tends to impinge upon the seat side  141  of the valve  116 . Oil mist will therefore collect thereon and drain, or be urged by the flow of the mixture, toward the oil outlet  120 . A portion of the mixture also reaches a stagnation point, or low velocity area, adjacent the seat side  141  before turning to flow laterally (and distally) across the seat side  141  of the valve  116 . The pressure changes associated with the low velocity area also cause the oil mist and fumes to condense thereabout. 
   As the mixture flows from the stagnation region, the mixture changes direction by approximately 90 degrees (either by flowing around the side edges  136  or the distal end  134 ). After making its way around the body, the mixture then changes direction again (by approximately 90 degrees in the opposite direction). Thus, the body causes another condensation inducing 180 degree turn of the mixture. Meanwhile the mixture flowing around the edges  136  converges over the downstream side  143  of the valve  116  thereby creating an area of condensation inducing impingement of one stream against the other. 
   In still another preferred embodiment shown by  FIG. 5 , the flow around the valve  116  is channeled to further enhance oil separation. A pair of sidewalls  140  is shown partially enclosing the valve  116  adjacent to the side edges  136 . An end wall  142  (see  FIGS. 3 and 4 ) further encloses the valve  116  adjacent the distal end  134 . Thus, when the valve  116  opens, air flows preferentially around the distal end  134 . Little, if any, air flows around the side edges  136  because the clearance between the side edges  136  and sidewalls  140  is preferentially limited to an amount sufficient to avoid friction between the valve  116  and the walls  140 . In contrast, the distance between the distal end  134  and the end wall  142  is preselected such that the combination of the distal end  134  and end wall  142  restricts the flow as it rounds the distal end  134 . Thus, yet another condensation inducing pressure change is created in the flow by this restriction. Moreover, because the oil outlet  120  is positioned below, or adjacent to, the distal end  134 , oil condensing in this manner tends to drain immediately to the oil outlet  120 . 
   Referring to  FIG. 4  again, yet another preferred embodiment of the present invention is shown. In the current embodiment, a flow restrictor  144  is placed in the outlet plenum  122 . In particular, if the air outlet  122  presents a circular cross section to the airflow, the restrictor  144  is a cylindrical tube. It is understood, however, that other cross-sectional shapes could be used without departing from the scope of the invention. An orifice may also be included in the restrictor  144  to further restrict the flow. Furthermore, the restrictor  144  may have a length sized to create a restriction  145  in the flow between a proximal end  146  of the restrictor  144  and a bottom surface  148  of the top  102  adjacent the proximal end  146 . As the mixture flows from the condensation chamber  118 , a pressure drop develops across the restriction  145  and additional oil condensation occurs in the area of the restriction  145 . From there it drains to the oil outlet  120 . 
   With continuing reference to  FIG. 4 , another preferred embodiment is shown for use wherein the oil/air channel  148  of the cylinder block  16  is not aligned with the mixture inlet plenum  114 . According to a preferred embodiment, a channel  150  is provided in the rocker box bottom  104  to port the incoming mixture to the inlet plenum  114 . Likewise, a channel  152  is provided to port the air separated from the oil/air mixture to an air cleaner. Nonetheless, the directions of flow  124  and  126  in the inlet and outlet plenums remain approximately 180 degrees from each other. 
   In view of the foregoing, it will be seen that the several advantages of the invention are achieved and attained. First, a motorcycle oil/air separator with enhanced separation capabilities has been provided. Separators are also provided that maintain the envelope of pre-existing low-profile motorcycle engines. Notably, the height of the engine may be maintained while providing the enhanced oil separation of the present invention. 
   The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. 
   As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.