Lubrication structure for four-stroke engine

Abstract

A lubrication structure for a four-stroke engine to lubricate driving parts by supplying oil stored in an oil tank provided separately from a crank chamber, using pressure fluctuation in the crank chamber, includes: a first circulating route to supply the oil from the oil tank to the crank chamber and return oil mist generated in the crank chamber to the oil tank; a second circulating route to supply the oil mist from the oil tank to a valve operating mechanism and return to the oil tank; a discharge passageway to discharge blowby gas contained during circulation of the oil from the second circulating route to a combustion chamber; and a partition wall to separate between the crank chamber and the oil tank. A central part of the partition wall is located vertically above a surface of the oil stored in the oil tank even if an engine body is tilted.

1 . A lubrication structure for a four-stroke engine configured to lubricate driving parts by supplying oil stored in an oil tank provided separately from a crank chamber, using pressure fluctuation in the crank chamber, the lubrication structure comprising:
 a first circulating route configured to supply the oil from the oil tank to the crank chamber and return oil mist generated in the crank chamber to the oil tank;   a second circulating route configured to supply the oil mist from the oil tank to a valve operating mechanism and return to the oil tank;   a discharge passageway configured to discharge blowby gas contained during circulation of the oil from the second circulating route to a combustion chamber; and   a partition wall configured to separate between the crank chamber and the oil tank, wherein:   a central part of the partition wall is located vertically above a surface of the oil stored in the oil tank even if an engine body is tilted; and   an opening A 1  of the second circulating route is formed in the central part, the oil mist being supplied from the opening A 1 .   
     
     
         2 . The lubrication structure for a four-stroke engine according to  claim 1 , wherein an opening B 1  of the first circulating route is formed in the central part of the partition wall, the oil being returned from the opening  81  to the oil tank. 
     
     
         3 . The lubrication structure for a four-stroke engine according to  claim 2 , wherein the opening  81  of the first circulating route is configured to extend much farther in a direction in which the oil is discharged to the oil tank than the opening A 1  of the second circulating route. 
     
     
         4 . The lubrication structure for a four-stroke engine according to  claim 3 , wherein the opening B 1  of the first circulating route includes a reed valve. 
     
     
         5 . The lubrication structure for a four-stroke engine according to  claim 1 , wherein:
 part of the second circulating route is formed by an elastic tubular part; and   an end of the elastic tubular part forms the opening A 1  of the second circulating route.   
     
     
         6 . The lubrication structure for a four-stroke engine according to  claim 4 , wherein:
 part of the second circulating route is formed by an elastic tubular part; and   an end of the elastic tubular part forms the opening A 1  of the second circulating route.   
     
     
         7 . The lubricating structure for a four-stroke engine according to  claim 5 , wherein:
 a pair of upright walls facing one another is integrally formed with the central part of the partition wall, the elastic tubular part being provided between the pair of upright walls; and   a fixing part is placed on the pair of upright walls, the fixing part holding the elastic tubular part and a reed valve with one bolt, and fixing an end of the reed valve provided in the opening B 1 .   
     
     
         8 . The lubricating structure for a four-stroke engine according to  claim 6 , wherein:
 a pair of upright walls facing one another is integrally formed with the central part of the partition wall, the elastic tubular part being provided between the pair of upright walls; and   a fixing part is placed on the pair of upright walls, the fixing part holding the elastic tubular part and a reed valve with one bolt, and fixing an end of the reed valve provided in the opening B 1 .   
     
     
         9 . The lubrication structure for a four-stroke engine according to  claim 7 , wherein the pair of upright walls are configured to be connected by a plurality of connection walls. 
     
     
         10 . The lubrication structure for a four-stroke engine according to  claim 9 , wherein the elastic tubular part is fixed by the plurality of connection walls. 
     
     
         11 . The lubrication structure for a four-stroke engine according to  claim 3 , wherein the direction in which the oil is discharged, is configured to be parallel to a direction in which the oil mist is supplied from the opening A 1  of the second circulating route. 
     
     
         12 . The lubrication structure for a four-stroke engine according to  claim 11 , wherein the direction in which the oil mist is supplied, is configured to be opposite to the direction in which the oil is discharged. 
     
     
         13 . The lubricating structure for a four-stroke engine according to one of  claim 1 , wherein the partition wall is configured to be located near a rotating trajectory of a crank web rotating in the crank chamber.