Patent Publication Number: US-8522743-B2

Title: Multi-cylinder internal combustion engine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2009-019223 filed on Jan. 30, 2009 the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a multi-cylinder internal combustion engine provided with a communicating passage for permitting a plurality of crank chambers communicate with each other. 
     2. Description of Background Art 
     A communicating passage for permitting adjacent cylinders to communicate outside a crankcase is provided to a skirt on the downside of a cylinder block. See, for example, JP-A No. 2006-70795 (FIGS. 1, 3). In such background art, it is a problem how oil splashed up by a crank weight should be discharged when the oil enters the communicating passage. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     According to an embodiment of the present invention, a means is provided for discharging oil that enters a communicating passage for making a plurality of crank chambers communicate and recovering the oil in an oil pan. 
     According to an embodiment of the present invention, a multi-cylinder internal combustion engine includes a communicating passage that permits internal spaces of a plurality of crank chambers corresponding to the plurality of cylinders to communicate. The communicating passage is provided relative to a crankcase wherein an opening of a drain for discharging oil inside the communicating passage is provided. The drain is provided and the oil is discharged via the drain from the opening of the drain. 
     According to an embodiment of the present invention, the drain is formed to discharge oil on the side of an oil pan provided to the crankcase. 
     According to an embodiment of the present invention, the communicating passage is configured by fixing a cover in the shape of a bowl that encloses a communicating hole provided to the crankcase so as to make the crank chamber and the communicating passage communicate to the crankcase. The bottom of the cover is inclined downwardly toward the opening of the drain. 
     According to an embodiment of the present invention, a return passage of oil that lubricates a cylinder head or a valve system is connected to the communicating passage. 
     According to an embodiment of the present invention, the multi-cylinder internal combustion engine is a parallel engine mounted in a motorcycle with its crankshaft located in a direction of vehicle width and the opening of the drain is arranged near to the outside in the direction of vehicle width. 
     According to an embodiment of the present invention, an inlet via which return oil via the oil return passage enters the communicating passage is set near to the inside in the direction of vehicle width off the opening of the drain in the direction of vehicle width. 
     According to an embodiment of the present invention, as the opening of the drain and the drain for discharging oil inside the communicating passage are provided, oil that enters the communicating passage can be discharged. 
     According to an embodiment of the present invention, as the drain is formed to discharge oil on the side of the oil pan provided to the crankcase, entering oil can be recovered in the oil pan. 
     According to an embodiment of the present invention, as the communicating passage is configured by fixing the cover in the shape of a bowl that encloses the communicating hole provided to the crankcase so as to make the crank chamber and the communicating passage communicate to the crankcase and the bottom of the cover is inclined downward toward the opening of the drain, oil splashed inside the cover can be gathered into the opening of the drain and the efficiency of recovery can be enhanced. 
     According to an embodiment of the present invention, as the return passage of oil that lubricates the cylinder head and the valve system is connected to the communicating passage, the oil can be recovered in the oil pan together. 
     According to an embodiment of the present invention, as the opening of the drain is arranged near to the outside in the direction of vehicle width, oil which is apt to accumulate outside in the direction of the vehicle width by centrifugal force as the motorcycle is laterally banked can be efficiently recovered. 
     According to an embodiment of the present invention, as the inlet for return oil is set near to the inside in the direction of the vehicle width off the opening of the drain in the direction of the vehicle width, oil taken in from the inside is made to flow toward the opening located outside of the drain by centrifugal force and therefore, the oil can be prevented from accumulating. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  is a side view showing a motorcycle provided with a four-cylinder internal combustion engine equivalent to one embodiment of the present invention; 
         FIG. 2  shows a longitudinal section of the internal combustion engine viewed from the left side; 
         FIG. 3  shows a cross section passing an intake valve of an upper part of the internal combustion engine viewed from the rear side; 
         FIG. 4  is a front view showing the appearance of the internal combustion engine; 
         FIG. 5  is a perspective view showing the internal combustion engine; 
         FIG. 6  is an enlarged view showing a longitudinal section of a communicating passage; and 
         FIG. 7  is a front view showing a crankcase and a cylinder block. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a side view showing a motorcycle  2  provided with an internal combustion engine  1  equivalent to one embodiment of the present invention. An arrow F in  FIG. 1  indicates a forward direction. A head pipe  3  is provided to a front end of a vehicle and a body frame  4  is provided with a pair of main frames  5  extending rearwardly with the main frames laterally separated from the head pipe  3  and inclined rearwardly and downwardly. A front fork  7  that supports a front wheel  6  is steerably supported by the head pipe  3  and a steering handlebar  8  is coupled to an upper part of the front fork  7 . A rear fork  10  that supports a rear wheel  9  is vertically swingably supported via suspending means by the body frame  4 . The internal combustion engine  1  mounted inside the body frame  4  is the four-cylinder internal combustion engine  1  where cylinders are arranged in a direction perpendicular to a traveling direction of the vehicle. A crankcase  11  of the internal combustion engine  1  is the crankcase  11  with which a transmission is integrated and includes a crankshaft  12 , a main shaft  13  and a countershaft  14  of the constant-mesh type transmission. An output shaft of the internal combustion engine  1  is the countershaft  14  of the transmission and power is transmitted to the rear wheel  9  via a driving sprocket (not shown) provided to a part protruding outside the crankcase  11  at a left end of the countershaft  14  and a chain for driving the rear wheel  15 . A fuel tank  16  is provided to an upper part of the body frame  4  and a tandem seat  17  is provided to the rear. 
       FIG. 2  shows a longitudinal section viewed from the left of the internal combustion engine  1 . The crankcase  11  is vertically divided in two and is configured by an upper crankcase  11 A and a lower crankcase  11 B. A cylinder block  21  provided with four cylinders  20  is integrated with the upper crankcase  11 A. A cylinder head  22  and a cylinder head cover  23  are connected to a top face of the cylinder block  21  in order. The crankshaft  12  and the countershaft  14  are held on a joined plane  76  of the upper crankcase  11 A and the lower crankcase  11 B in a direction of the vehicle width. The main shaft  13  is held in the direction of the vehicle width in the upper crankcase  11 A. 
     A piston  26  is connected to a crankpin  24  of the crankshaft  12  via a connecting rod  25  and is slid in the cylinder  20 . A combustion changer  27  is formed between each piston  26  and the cylinder head  22 . An intake port  28  and an exhaust port  29  respectively communicating with each combustion chamber  27  are provided in the cylinder head  22 , the intake port  28  connects with the combustion chamber  27  via a pair of its inside openings, and the exhaust port  29  also connects with the combustion chamber  27  via a pair of its inside openings. 
     An ignition plug  30  is provided in the center of the individual combustion chamber  27 . A pair of intake valves  31  and a pair of exhaust valves  32  are provided around the ignition plug  30 . These valves are driven by a valve gear  34 , and open and close the respective inside openings of the intake port and the respective inside openings of the exhaust port. The valve gear  34  is provided with an intake camshaft  37 , an exhaust camshaft  38 , an intake cam  39  and an exhaust cam  40 , presses an intake valve lifter  41  and an exhaust valve lifter  42  respectively provided to each valve, and opens and closes the intake valve  31  and the exhaust valve  32  at a predetermined time according to a rotational position of the crankshaft  12 . 
     An intake system is connected to an outside opening of the intake port  28 . The intake system includes a throttle valve  43 , a fuel injection system  44  and an air cleaner  45  (respectively shown in  FIG. 1 ). An exhaust pipe  46  is connected to each exhaust port  29 , each exhaust pipe is united in the rear through a lower part of a vehicle body, and the united exhaust pipe is connected to a muffler  47  in the rear of the vehicle ( FIG. 1 ). A radiator  52  is provided in front of the cylinder block  21  ( FIG. 1 ). 
     An oil pan  48  is provided to a lower part of the lower crankcase  11 B and an oil filter  49  is provided in front of the lower crankcase  11 B. An oil pump  50  and a main gallery  51  are provided in the lower crankcase  11 B. The oil pump  50  sucks oil reserved in the oil pan  48  and supplies it to lubricating locations via the oil filter  49 , the main gallery  51  and others. 
       FIG. 3  shows a cross section passing the intake camshaft  37  and viewed from the rear of an upper part of the internal combustion engine  1 . Arrows L, R in  FIG. 3  indicate a leftward direction and a rightward direction and correspond to the left and the right of the vehicle when the internal combustion engine  1  is mounted in the vehicle. The lower crankcase  11 B, the upper crankcase  11 A, the cylinder block  21 , the cylinder head  22  and the cylinder head cover  23  are connected in order from a lower part of the drawing. The four cylinders  20  are laterally arranged in parallel. 
     The intake camshaft  37  is supported between the cylinder head  22  and the cylinder head cover  23 . An intake camshaft driven sprocket  54  is provided at a right end of the intake camshaft  37  and is driven by the crankshaft  12  via a camshaft driving chain  55 . The two intake valves  31  are provided to one cylinder  20  and the intake valve lifter  41  is provided to an upper part of each intake valve  31 . The intake cam  39  provided to the intake camshaft  37  abuts on the top of the intake valve lifter  41 . Though the followings are not shown in  FIG. 3 , the exhaust camshaft  38 , the exhaust cam  40 , the exhaust valve  32 , the exhaust valve lifter  42 , an exhaust camshaft driven sprocket (not shown) and others are also similarly provided. 
     The four cylinders  20  of the internal combustion engine  1  are named the first cylinder C 1 , the second cylinder C 2 , the third cylinder C 3  and the fourth cylinder C 4  from the left side. The crankshaft  12  is in a shape shown in  FIG. 3  and an explosion stroke is repeated with phase difference at an equal interval of 180 degrees as a crank angle in the order of the first cylinder C 1 , the third cylinder C 3 , the fourth cylinder C 4 , the second cylinder C 2  and the first cylinder C 1 . 
     In the crankcase  11  around the crankshaft  12 , an upper bulkhead  56 A and a lower bulkhead  56 B extend from respective inside faces of the upper crankcase  11 A and the lower crankcase  11 B are provided between corresponding cylinders, a bearing  57  is formed on a joining surface of each bulkhead, and the crankshaft  12  is rotatably supported. The piston  26  is connected to the crankshaft  12  via the connecting rod  25 . The crankcase  11  is partitioned at every cylinder by the upper bulkhead  56 A and the lower bulkhead  56 B and plural crank chambers  58  are formed. The crank chambers  58  are named the first crank chamber R 1 , the second crank chamber R 2 , the third crank chamber R 3  and the fourth crank chamber R 4  from the left side. As each crank chamber  58  is located on the downside of the piston  26 , the volume of each crank chamber  58  increases or decreases according to the displacement of the piston  26 . 
       FIG. 4  is a front view showing the appearance of the internal combustion engine  1  and  FIG. 5  is a perspective view showing the appearance of the internal combustion engine  1 . As  FIGS. 4 and 5  show the internal combustion engine  1  viewed from its front side and the downside of the front side, the cylinders are arranged in the order of the first cylinder C 1 , the second cylinder C 2 , the third cylinder C 3  and the fourth cylinder C 4  from respective right sides in  FIGS. 4 and 5 . The crank chambers are similarly arranged in the order of the first crank chamber R 1 , the second crank chamber R 2 , the third crank chamber R 3  and the fourth crank chamber R 4  from the respective right sides in  FIGS. 4 and 5 . In these drawings, the cylinder head cover  23  is omitted. An ignition plug insertion hole  61  is provided to a top face of the cylinder head  22 .  FIG. 4  also shows a center line  37   c  of the intake camshaft  37  and a center line  38   c  of the exhaust camshaft  38 . An outside opening of the exhaust port  29  is provided to the front of the cylinder head  22 . The exhaust pipe  46  ( FIG. 2 ) is attached to this part. An oil filter attachment  62 A and an attachment  62 B of a water-cooled oil cooler (not shown) are provided to the front of the lower crankcase  11 B. The oil pan  48  is provided in a lower part of the lower crankcase  11 B. An alternator attachment  63  ( FIG. 5 ) is provided to a left projection of the crankshaft  12  between the upper and lower crankcases  11 A,  11 B. 
     Phase difference in a position of each piston between the first crank chamber R 1  and the second crank chamber R 2  is 180 degrees and when one crank chamber  58  is pressurized, the other crank chamber  58  is decompressed. The relation between the third crank chamber R 3  and the fourth crank chamber R 4  is also similar with the increase and the decrease of pressure function as resistance to the displacement of the piston  26  and power is lost. 
     As means for dissolving the resistance to the displacement of the piston caused by the increase and the decrease of pressure, a communicating passage  67  covered with a cover  66  is provided between the first crank chamber R 1  and the second crank chamber R 2  and between the third crank chamber R 3  and the fourth crank chamber R 4  as shown in  FIGS. 4 and 5 .  FIGS. 4 and 5  show the first communicating passage  67 A covered with the cover  66  on the respective fronts of the first cylinder C 1  and the second cylinder C 2  and the second communicating passage  67 B in a state in which the cover  66  is removed and the second communicating passage is exposed on the respective fronts of the third cylinder C 3  and the fourth cylinder C 4 . In the second communicating passage  67 B, a communicating hole  68  that communicates with the third crank chamber R 3  and a communicating hole  68  that communicates with the fourth crank chamber R 4  are shown. Though the followings are not shown in the drawings because they are covered with the cover  66 , the similar communicating holes  68  that communicate with the first communicating passage  67 A are also provided to the first crank chamber R 1  and the second crank chamber R 2 . The longitudinal sections of the cover  66 , the communicating passage  67  and the communicating hole  68  are shown in  FIG. 2 . 
     As owing to the communicating passage  67  and the communicating hole  68 , increased pressure in one crank chamber out of the first crank chamber R 1  and the second crank chamber R 2  is released into the other decompressed crank chamber and increased pressure in one crank chamber out of the third crank chamber R 3  and the fourth crank chamber R 4  is released into the other decompressed crank chamber, resistance to the displacement of the piston  26  caused by the increase and the decrease of pressure in the crank chamber, that is, power loss is dissolved. 
       FIG. 6  is an enlarged view showing the longitudinal section of the vicinity of the communicating passage  67 . The communicating passage  67  is provided across the joined plane  76  of the upper crankcase  11 A and the lower crankcase  11 B as shown in  FIG. 6 . The communicating hole  68  is provided to the upper crankcase  11 A, however, the communicating hole  68  may also be provided to the lower crankcase  11 B. As the communicating passage  67  can be laid with arrangement space shared by arranging the communicating passage across the upper and lower crankcases  11 A,  11 B, compared with a case that the communicating passage is arranged only on either side, the respective height of the upper and lower crankcases  11 A,  11 B can be reduced and the internal combustion engine can be miniaturized. 
     The first and second communicating passages  67 A,  67 B are both formed in the shape of a bowl to cover the communicating hole  68  in a front view, and space for the communicating passage  67  is configured by an inside face of the cover  66  and the front of the crankcase  11 . As the communicating passage  67  is configured utilizing a part of the crankcase  11  by attaching the cover  66  in the shape of a bowl covering the communicating hole  68  to the front of the crankcase  11 , the communicating passage can be configured by the simple member. 
     A concave portion  69  is made by hollowing the fronts of the upper and lower crankcases  11 A,  11 B respectively overlapped with the cover  66  in the front view ( FIG. 6 ). Thus, the space for the communicating passage  67  can be extended by only hollowing the side of the crankcase  11  without increasing the size and the depth of the cover  66  and the large-sizing of the outline of the communicating passage  67  can be inhibited. The concave portion  69  may be also provided to the front of either of the upper or lower crankcase  11 A,  11 B. 
     The cover  66  is fixed to the upper and lower crankcases  11 A,  11 B via a bolt  70  ( FIGS. 4 and 5 ) in upper and lower positions. The strength of the joining of the upper and lower crankcases  11 A,  11 B can be increased by fixing the cover  66  vertically across the crankcase  11 . 
     As shown in  FIG. 6 , to prevent oil from leaking from the communicating passage  67 , a groove  71  is formed on a face on which the cover  66  abuts on the crankcase  11 , a sealing member  72  is arranged there, and the above-mentioned face on the side of the upper and lower crankcases  11 A,  11 B is flatly formed. The groove  71  can be easily formed by forming the sealing groove  71  on the side of the cover  66 , compared with a case that the sealing groove is formed across the upper and lower crankcases on the side of the crankcase and the shape can be further easily adjusted. 
     Deposit is apt to accumulate in the communicating passage  67 . This means that the mixture cooled and liquidized of combusted gas that leaks from the cylinder  20  and misty lubricating oil and oil stirred up by a crank weight is entered into the communication passage. To discharge the deposit, an opening  73  of a drain for discharging oil accumulated inside the communicating passage  67  is provided as shown in  FIGS. 4 and 6  and the oil is discharged through a drain  74  (see  FIGS. 2 to 6 ) from the opening  73 . 
     The drain  74  is formed to discharge the oil into the oil pan  48  ( FIG. 2 ) provided to the lower crankcase  11 B. Thus, the oil accumulated in the communicating passage  67  is discharged and can be recovered in the oil pan  48 . 
     The communicating passage  67  is configured by fixing the cover  66  in the shape of a bowl surrounding the communicating hole  68  provided to the crankcase  11  to the crankcase  11  and as shown in  FIG. 6 , the bottom  66   a  of the cover  66  is inclined downward toward the opening  73  of the drain. Thus, oil splashed inside the cover  66  can be gathered to the opening  73  of the drain and the efficiency of recovery can be enhanced. The bottom  66   a  of the cover  66  is inclined rearwardly and downwardly at an angle of 20 degrees with a plane S parallel to the joined plane  76  of the upper and lower crankcases  11 A,  11 B. When the internal combustion engine  1  is mounted in the vehicle, the joined plane  76  is inclined forward and downward by 10 degrees. Accordingly, as the bottom of the cover  66  is kept inclined rearwardly and downward at the angle of 10 degrees with a horizontal plane, the oil can be gathered into the opening  73  of the drain. 
     As shown in  FIG. 4 , the opening  73  of the drain is arranged near to the outside in the direction of vehicle width of each communicating passage  67 . Thus, the deposit is apt to accumulate outside in the direction of vehicle width by centrifugal force as the motorcycle  2  is sometimes laterally banked and the oil can be efficiently recovered by providing the opening  73  of the drain near to the outside in the direction of vehicle width. 
     Oil that lubricates the cylinder head  22 , the valve gear  34  and others is returned into the communicating passage  67  via a valve system oil return passage  77  provided to the upper crankcase  11 A and a return oil inlet  78  provided to the communicating passage  67  as shown in  FIGS. 4 to 6 . The oil returned as described above is recovered in the oil pan  48  through the opening  73  of the drain and the drain  74  together with the above-mentioned deposit. 
     The return oil inlet  78  is set off the opening  73  inside in the direction of vehicle width ( FIGS. 4 and 5 ). Thus, oil taken from the inside is made to flow toward the outside opening  73  by centrifugal force and the oil can be prevented from accumulating, compared with a case wherein the return oil inlet  78  and the opening  73  are connected outside without setting the return oil inlet and the opening off. 
     As shown in  FIG. 2 , the internal combustion engine  1  is provided with the exhaust pipe  46  extending rearwardly of the vehicle after the exhaust pipe is curved from the cylinder head  22  in front and on the downside of the cylinder block  21 . The communicating passage  67  is arranged in an area enclosed by the front of the crankcase  11  and the exhaust pipes  46 . Accordingly, the communicating passage  67  is effectively arranged effectively utilizing vacant space, inhibiting interference with the exhaust pipe  46 . 
     A center line C of the cylinder  20  shown in  FIG. 2  is inclined forward at an angle of thirty degrees with a vertical line V perpendicular to the joined plane  76  of the upper and lower crankcases  11 A,  11 B. However, as the joined plane  76  of the crankcase  11  is inclined forward and downward by 10 degrees when the internal combustion engine  1  is mounted in the vehicle, the cylinder  20  is inclined forward at an angle of 40 degrees with a perpendicular line to the ground when the engine is mounted in the vehicle and the upside of the communicating passage  67  is fully covered. Thus, the upside of the communicating passage  67  is safely protected in the area enclosed by the cylinder block  21 , the front of the crankcase  11  and the exhaust pipes  46 , avoiding the interference with the exhaust pipes  46  ( FIG. 1 ). 
     As shown in  FIG. 2 , the oil filter  49  is arranged on the front of the lower crankcase  11 B located on the downside of the communicating passage  67 . The oil filter  49  is attached to the oil filter attachment  62 A shown in  FIGS. 4 and 5 . The water-cooled oil cooler (not shown) is attached to the water-cooled oil cooler attachment  62 B. The communicating passage  67  is arranged on the upside of the oil filter  49  and the oil cooler effectively utilizing the vacant space, preventing interference with the oil filter and the oil cooler. 
       FIG. 7  is a front view showing the crankcase  11  and the cylinder block  21 . The lower crankcase  11 B, the upper crankcase  11 A, the cylinder block  21  and the cylinder head  22  are connected by each stud bolt on both sides of the cylinders C 1  to C 4  arranged in a line. In  FIG. 7 , stud bolt insertion holes  79  are shown on the top face of the cylinder block  21 . Stud bolt insertion bosses  80  surrounding each insertion hole  79  are provided to the cylinder block  21  and the crankcase  11 . As shown in  FIG. 7 , the communicating hole  68  connected to the communicating passage  67  is arranged between adjacent stud bolt insertion bosses  80  on the front of the crankcase  11 . As the communicating hole  68  is arranged avoiding the stud bolt insertion boss  80 , the strength of the stud bolt insertion boss  80  can be prevented from being deteriorated by the communicating hole  68 . 
     The internal combustion engine  1  is a parallel four-cylinder internal combustion engine, the exhaust pipes  46  coupled to the individual exhaust port  29  extend rearwardly on the downside of the internal combustion engine as shown in  FIG. 1 , are afterward united, and the united exhaust pipe is connected to the muffler  47  in the rear of the vehicle. The communicating passages  67  ( FIG. 4 ) configured in a pair in a lateral direction of the internal combustion engine in the front view are provided at the back of the adjacent exhaust pipes  46 . As described above, as the communicating passage  67  is covered with the plural exhaust pipes  46  in the front view, the communicating passage is protected by the exhaust pipes and is hardly striking from the outside owing to the exhaust pipes  46 . 
     For a summary of the effects of the embodiment, the following effects are produced in this embodiment as described above in detail. 
     (1) As the opening of the drain for discharging oil into the drain is provided inside the communicating passage, the oil that enters the communicating passage can be discharged. 
     (2) As the drain is formed to discharge oil on the side of the oil pan provided to the crankcase, the entering oil can be recovered in the oil pan. 
     (3) As the communicating passage is configured by fixing the cover in the shape of a bowl that encloses the communicating hole provided to the crankcase so as to make the crank chamber and the communicating passage communicate to the crankcase and the bottom of the cover is inclined downward toward the opening of the drain, oil splashed inside the cover can be gathered into the opening of the drain and the efficiency of recovery can be enhanced. 
     (4) As the return passage of oil that lubricates the cylinder head and the valve system is connected to the communicating passage, the oil can be recovered in the oil pan together. 
     (6) As the opening of the drain is arranged near to the outside in the direction of vehicle width, oil which is apt to accumulate outside in the direction of vehicle width by centrifugal force can be efficiently recovered as the motorcycle is laterally banked. 
     (7) As the return oil inlet is set near to the inside in the direction of vehicle width off the opening of the drain in the direction of vehicle width, oil taken in from the inside is made to flow toward the opening of the drain outside the return oil inlet by centrifugal force and the oil can be prevented from accumulating. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.