Abstract:
A first aspect of an oil distributing structure for an internal combustion engine includes a bearing support wall including a plurality of guide ribs which are radially mounted on a surface thereof. The guide ribs may be integrally formed, and extend around an upper half of the bearing, for collecting oil which is splashed onto, and flows down the wall surface. In a second aspect of an oil distributing structure for an internal combustion engine, a slanted edge portion, descending toward the bearing, is formed on the bearing support wall, and is disposed laterally of a lower portion of the bearing. The described structure is useful for collecting oil splashed onto a wall surface of a crankcase, and for supplying the collected oil to a bearing in an internal combustion engine of the type in which a crankshaft bearing is supplied with oil splashed from nearby gears.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims priority under 35 USC 119 based on Japanese patent application No. 2003-326554, filed Sep. 18, 2003.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to internal combustion engines. More particularly, the present invention relates to oil-guiding internal crankcase wall structure for an internal combustion engine, for promoting lubrication of a crankshaft support bearing via splash oil feed.  
         [0004]     2. Description of the Background Art  
         [0005]     A number of designs have been developed for internal combustion engines, of the type in which crankshaft support bearings are supplied with oil splashed from nearby gears. In order to properly lubricate the crankshaft support bearings, these engines must effectively collect oil splashed on an inner wall surface of the crankcase, and supply the collected oil to the bearings.  
         [0006]     In one of the known designs of this type, an oil splash receiving means is provided above the bearings, for collecting splashed oil, and for supplying the oil to the bearings through a communication hole defined in a lower portion of the oil splash receiving means (see, for example, Japanese Laid-Open Patent No. Sho 58-112799,  FIGS. 2 and 3 ).  
         [0007]     However, the structure of the design in this reference is complicated, because the separate oil splash receiving means needs to be separately manufactured, and mounted on the crankcase wall during engine assembly.  
         [0008]     Although the known devices have some utility for their intended purposes, a need still exists in the art a method and apparatus for effectively collecting oil splashed onto the wall surface of a crankcase, and supplying the collected oil to a bearing in an internal combustion engine of the type in which a support bearing of a crankshaft is supplied with oil splashed from nearby gears.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention has been provided in an effort to solve the above problem, and to simplify the manufacture of an engine in which a support bearing of a crankshaft is supplied with oil splashed from nearby gears.  
         [0010]     According to a first aspect of the present invention, a first lubricating structure is provided for supplying oil to a bearing with splash oil feed. In the lubricating structure according to the first aspect hereof, a plurality of divergent guide ribs are integrally formed on an interior surface of a crankcase bearing support wall. These guide ribs are situated in an area around an upper half of the bearing, and are provided for collecting oil which is splashed onto, and flows down the wall surface.  
         [0011]     According to a second aspect of the present invention, another lubricating structure is provided for a bearing with splash oil feed. In the lubricating structure according to the second aspect hereof, a slanted wall, descending toward the bearing, is integrally formed with a bearing support wall, and is disposed laterally of a lower portion of the bearing.  
         [0012]     According to a third aspect of the present invention, still another lubricating structure is provided for a bearing with splash oil feed. In the lubricating structure according to the third aspect hereof, guide ribs are integrally formed on a wall surface of a bearing support wall around an upper half of the bearing, for collecting oil which is splashed onto, and flows down the wall surface, and in addition, a slanted wall, descending toward the bearing, is formed integrally with a bearing support wall, and is disposed laterally of a lower portion of the bearing.  
         [0013]     According to the first aspect of the invention, oil which is splashed onto the wall surface of the crankcase can effectively be collected by a simple structure.  
         [0014]     According to the second aspect of the invention, the oil flowing from above can effectively be supplied to the bearing by a simple structure.  
         [0015]     According to the third aspect of the invention, the collection of the oil and the supply of the oil to the bearing can be combined for more effectively feeding the oil.  
         [0016]     For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a vertical cross-sectional view, as viewed from the right side, of an air-cooled internal combustion engine for a motorcycle, incorporating an oil-guiding crankcase wall structure according to a selected illustrative embodiment of the present invention;  
         [0018]      FIG. 2  is a cross-sectional view of the engine of  FIG. 1 , taken alone line II-II of  FIG. 1 ;  
         [0019]      FIG. 3  is a cross-sectional detail view of the engine of  FIG. 1 , taken along line III-III of  FIG. 1  and showing right half components in a crankcase;  
         [0020]      FIG. 4  is a view showing a region of a right crankcase wall as it is viewed from a vantage point inside the crankcase, according to the above embodiment;  
         [0021]      FIG. 5A  is a cross-sectional detail view of the crankcase wall of  FIG. 4 , taken along line V-V of  FIG. 4 , and showing a cross section of a crankshaft supporting section; and  
         [0022]      FIG. 5B  is an enlarged detail view of a portion of the crankcase wall of  FIG. 5A . 
     
    
     DETAILED DESCRIPTION  
       [0023]     It should be understood that only structures considered necessary for clarifying the present invention are described herein. Other conventional structures, and those of ancillary and auxiliary components of the engine are assumed to be known and understood by those skilled in the art.  
         [0024]      FIG. 1  is a vertical cross-sectional view, as viewed from the right side, of an air-cooled internal combustion engine for a motorcycle, incorporating an oil-guiding crankcase wall structure according to a selected illustrative embodiment of the present invention.  FIG. 1  shows the position of a rotational shaft projecting to the right of a right crankcase and the positions of some gears, with a right case cover of a transmission being omitted from the drawing for illustrative purposes.  FIG. 2  is a cross-sectional view of the engine of  FIG. 1 , taken along line II-II of  FIG. 1 .  
         [0025]     As shown in  FIGS. 1 and 2 , a crankcase assembly  60  includes a left case cover  1 , a left crankcase  2 , a right crankcase  3 , and a right case cover  4 . A cylinder block  5 , a cylinder head  6 , and a cylinder head cover  7  are connected to an upper portion of the crankcase assembly  60 .  
         [0026]     A crankshaft  10  is rotatably mounted in the crankcase assembly  60 , and is operatively connected to a main transmission shaft  11  via a clutch  30 , to be described later. The engine also includes a transmission countershaft  12 , and a starter shaft  13 .  
         [0027]     In the drawings, reference numeral  14  designates a central axis about which a shift drum is rotatable,  15  designates a foot-operated gearshift lever, and reference numeral  16  designates a balance shaft. Further in the drawings, reference numeral  17  designates an oil pump shaft,  18  designates a crankpin,  19  designates a connecting rod connected to the crankpin  18 , and  20  designates a piston connected to the connecting rod  19 . The piston  20  is vertically reciprocally movable in the cylinder block  5 .  
         [0028]     As shown in  FIG. 2 , the crankshaft  10  is rotatably supported in the left crankcase  2  by a ball bearing  21 , is supported in the right crankcase  3  by a roller bearing  22 . The main transmission shaft  11  and the transmission countershaft  12  are also supported on the left crankcase  2  and the right crankcase  3  by ball bearings. The kick starter shaft  13  is supported by the right crankcase  3  and the right case cover  4 .  
         [0029]     The countershaft  12  serves as the output shaft of the internal combustion engine, and has an outer end portion projecting out of the left crankcase  2  and supporting a drive sprocket  23 , which drives the rear wheel of the motorcycle through a chain  24 . An alternator  39  is coupled to the left end of the crankshaft  10 .  
         [0030]     A balancer drive gear  25  and a common drive gear  26  are fixed to a right portion of the crankshaft  10  by a key  27 . The balancer drive gear  25  is enmeshed with a balancer driven gear  37  ( FIG. 1 ). The common drive gear  26  is enmeshed with a main shaft driven gear  28  on the main transmission shaft  11 , and also with an oil pump driven gear  44  on the oil pump shaft  17  ( FIG. 1 ).  
         [0031]     As shown in  FIG. 2 , the main shaft driven gear  28 , which is constantly enmeshed with the common drive gear  26 , is fitted over a right portion of the main transmission shaft  11 , the main shaft driven gear  28  being selectively rotatable relatively to the main transmission shaft  11 .  
         [0032]     A multi-plate clutch  30 , which is normally engaged, but disengageable when an actuating mechanism  29  is operated, is mounted on the right end of the main transmission shaft  11 . The multi-plate clutch  30  has a clutch outer member  31  fixed to the main shaft driven gear  28 , and a clutch inner member  32  fixed to the main transmission shaft  11 . Rotary movement of the crankshaft  10  is transmitted through the common drive gear  26  to the main shaft driven gear  28  and then, through the multi-plate clutch  30 , to the main transmission shaft  11 .  
         [0033]     As shown in  FIG. 2 , a transmission gear train  33  is mounted on the main transmission shaft  11  and the countershaft  12 . The transmission gear train  33  includes five gears mounted on the main transmission shaft  11 , and five gears mounted on the countershaft  12 . The gears on the countershaft  12  are enmeshed with the five gears on the main transmission shaft  11  at nearly all times. These ten gears are classified into three types of different types as follows: (a) gears fixed to a shaft, (b) gears held on a shaft by a slide bearing, and circumferentially rotatable relatively to the shaft but axially immovable, and (c) gears held on a shaft by a spline, and axially movable, but rotationally fixed relative to the shaft.  
         [0034]     The axially movable gears (c) provide a dog clutch and are axially moved by a shift fork (not shown) engaging the dog clutch at all times, into engagement with the relatively rotatable gears (b) which are positioned adjacent thereto, thus securing the gears (b) to the shaft. Such a set of gears for transmitting power is selectively created by the above operation for providing gear positions ranging from first to fifth gear positions.  
         [0035]     A gear  34  on the kick starter shaft is capable of starting to rotate the crankshaft  10  through a gear  35  on the right end of the countershaft, a gear  36  on the right end of the main transmission shaft, the main shaft driven gear  28  on the main transmission shaft  11 , and the common drive gear  26  on the crankshaft.  
         [0036]      FIG. 3  is a cross-sectional detail view taken along line III-III of  FIG. 1 , showing components in the right side of the crankcase. The crankshaft  10  has a right end portion supported on the right crankcase  3  by the roller bearing  22 , with a bushing  38  interposed between the right crankcase  3  and the roller bearing  22 . As described above, the balancer drive gear  25  and the common drive gear  26  are mounted on the crankshaft  10  by the common key  27 .  
         [0037]     An oil pump  40  is disposed below the crankshaft  10 . The oil pump  40  has a pump case  41  fastened to the right crankcase  3  by a steel plate  42  and a bolt  43 . The oil pump shaft  17  is rotatably supported by the right crankcase  3  and a wall of the pump case  41 . The oil pump driven gear  44  is fixed to the oil pump shaft  17  by a tenon  17   a  formed at the end of the oil pump shaft and a set plate  45 . The oil pump driven gear  44  is enmeshed with the common drive gear  26 . An oil pump rotor  46  is fitted over the oil pump shaft  17 . When the crankshaft  10  is rotated, the oil pump rotor  46  is rotated by the common drive gear  26 , the oil pump driven gear  44 , the set plate  45 , the tenon  17   a,  and the oil pump shaft  17 .  
         [0038]      FIG. 4  is a detail view showing a region of the right crankcase  3  as it is viewed from the right. The right crankcase  3  has a central through hole  50  formed therein, and an end portion of the crankshaft  10  extends through this central through hole  50 . The solid line around the central through hole  50  represents a peripheral inner edge  51  of the right crankcase  3  surrounding the central through hole  50 . Although not shown in the illustration of  FIG. 4 , the roller bearing  22  is mounted in the right crankcase  3  on the other side of the peripheral edge  51 .  
         [0039]     An inwardly-facing wall surface  52  of the right crankcase  3 , in an area around an upper half of the bearing  22 , has four guide ribs  53  thereon, extending substantially radially outwardly from the central through hole  50 , for channeling and directing the flow of oil therepast. The guide ribs  53  are formed as an integral part of the right crankcase  3  when it is cast. The guide ribs are located above a horizontal dividing line  57  extending across the central through hole  50 , and each rib extends upwardly at an angle on the wall surface  52 , to direct oil towards the hole  50 . The guide ribs  53  serve to collect oil splashed onto and flowing down the crankcase wall surface, and to guide the collected oil to the peripheral edge  51  of the central through hole  50 .  
         [0040]      FIG. 5A  is a cross-sectional view taken along line V-V of  FIG. 4 , showing at an enlarged scale a cross section of the crankshaft supporting section shown in  FIG. 3 .  FIG. 5B  is a detail view of the circled section of  FIG. 5A .  
         [0041]      FIG. 5A  shows a region of the right crankcase  3 , the roller bearing  22 , and the bushing  38 . The crankshaft  10  is omitted from the drawing in  FIGS. 5A-5B  for purposes of illustration. The dot-and-dash line C-C represents the center line of the crankshaft.  
         [0042]     In the right crankcase  3 , the peripheral edge  51  around the central through hole is positioned laterally of the roller bearing  22 .  
         [0043]     The cross-sectional shape of the peripheral edge  51 , surrounding the central through hole, is different in its upper and lower sides. Specifically, the tip portion of the peripheral edge  51  has a normal-type cross-sectional shape A. The normal-type cross-sectional shape A has an inner peripheral surface parallel to the crankshaft axis, and is beveled normally.  
         [0044]     In contrast, the bottom portion of the peripheral edge  51  has an oil-collecting-type cross-sectional shape B, with a raised lower lip  55  formed thereon. The raised lower lip  55  is formed with an upper surface  56  which is inclined inwardly and downwardly towards the bearing  22 , as shown in  FIG. 5B , and the ramped upper surface  56  defines a slanted surface descending toward the roller bearing.  
         [0045]     As shown in  FIG. 4 , the normal-type cross-sectional shape A is applied to the peripheral edge  51  on the upper side and the left and right sides of the central through hole  50 . The oil-collecting-type cross-sectional shape B is applied to the peripheral edge  51  on the lower side of the central through hole only. The peripheral edge  51  of the oil-collecting-type cross-sectional shape B is capable of guiding oil toward the roller bearing  22 .  
         [0046]     In order to achieve adequate lubrication, internal combustion engines, of the type in which the crankshaft bearing is supplied with oil splashed from nearby gears, need to effectively collect oil splashed onto the wall surface of the crankcase, and supply an adequate lubricating amount of the collected oil to the bearing. In the engine depicted in the drawings, oil is splashed on the crankcase wall  52  from, e.g., the balancer drive gear  25 , the balancer driven gear  37 , the common drive gear  26 , the main shaft driven gear  28 , and the oil pump driven gear  44 , among other engine components.  
         [0047]     According to the present embodiment, a significant amount of the oil splashed onto and flowing down the crankcase wall surface  52 , around the upper half of the roller bearing  22 , is collected by the guide ribs  53  ( FIG. 4 ), and is directed down the guide ribs toward the peripheral edge  51 . The oil is then allowed to flow along the peripheral edge  51 , and then received by the bottom portion of the peripheral edge  51 , having the oil-collecting-type cross-sectional shape B thereon. The oil is then guided to the roller bearing  22  along the slanted surface  56  of the raised lower lip  55 , and supplied to the roller bearing  22 .  
         [0048]     Since the rollers of the roller bearing  22  move along the peripheral edge  51  of the central through hole  50 , the supplied oil is distributed to all the rollers of the roller bearing  22 . The smaller arrows  54  shown in  FIGS. 4 and 5  represent the flow of the oil as it flows downwardly.  
         [0049]     In the above embodiment, the present invention has been described with respect to the bearing on the right crankcase. However, the present invention is also applicable to the bearing on the left crankcase. In the above embodiment, oil on the outer wall surface of the crankcase is collected and supplied to the bearing. However, it is possible, with the same means as described above, to collect oil on the inner wall surface of the crankcase and supply the collected oil to the bearing. While the peripheral edge  51  has both the guide ribs  53  and the oil-collecting-type cross-sectional shape B in the above embodiment, the peripheral edge  51  may have either the guide ribs  53  or the oil-collecting-type cross-sectional shape B.  
         [0050]     Although the present invention has been described herein with respect to a number of specific illustrative embodiments, the foregoing description is intended to illustrate, rather than to limit the invention. Those skilled in the art will realize that many modifications of the preferred embodiment could be made which would be operable. All such modifications, which are within the scope of the claims, are intended to be within the scope and spirit of the present invention.