Patent Publication Number: US-11384711-B2

Title: Engine

Description:
CROSS REFERENCE TO PRIOR APPLICATION 
     This application is a National Stage Patent Application of PCT International Patent Application No. PCT/JP2018/013847 (filed on Mar. 30, 2018) under 35 U.S.C. § 371, which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to an engine which can be mounted on a working machine such as a lawn mower or a high pressure washer. 
     BACKGROUND ART 
     Generally, an engine includes a crankcase having first and second bearing portions which support both ends of a crankshaft and a cylinder into which a piston is fitted. For example, Patent Literature 1 discloses an engine in which a crankcase is formed of first and second case half bodies which are joined to each other at a dividing surface which diagonally intersects axes of first and second bearing portions and a cylinder and the first bearing portion are integrally formed on the first case half body, and further the second bearing portion is integrally formed on the second case half body. 
     Related Art Literature Patent Literature 
     Patent Literature 1: JP-A 2017-160833 
     SUMMARY OF THE INVENTION 
     Problem that the Invention is to Solve 
     However, in the engine structure of Patent Literature 1, the second case half body is to be removed at the time of maintenance of the engine, and when removing the second case half body, a case opening faces downward, so it is necessary to lower the engine from the frame and disassemble the engine with the case opening facing upward. As a result, there is a problem that the number of man-hours is increased. 
     The invention provides an engine which can reduce the number of man-hours required for maintenance. 
     Means for Solving the Problem 
     The invention is an engine which includes: 
     a crankcase body including a bottom portion including a first crankshaft insertion hole and a tubular portion including the bottom portion integrally formed at one end in a first direction and including a case opening portion at the other end in the first direction: 
     a crankcase cover including a second crankshaft insertion hole and covering the case opening portion of the crankcase body; 
     a crankshaft inserted through the first crankshaft insertion hole and the second crankshaft insertion hole; 
     a cylinder base portion located inside the crankcase body, and 
     a cylinder block located outside the crankcase body, where 
     the first direction is an up-down direction of the engine, and 
     the crankcase cover is detachably attached to an upper portion of the crankcase body. 
     Advantages of the Invention 
     According to the invention, the crankcase cover is detachably attached to the upper portion of the crankcase body. Therefore, by removing the crankcase cover during maintenance of the engine, it is possible to access the inside of the crankcase body from the top. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of an engine according to an embodiment of the invention. 
         FIG. 2  is a perspective view of the engine with a top cover removed, as viewed from diagonally above and front. 
         FIG. 3  is an exploded perspective view of the engine as seen from diagonally above and front. 
         FIG. 4  is an exploded perspective view of an engine body as viewed from diagonally above and front. 
         FIG. 5  is a plan view of the engine with a crankcase cover removed. 
         FIG. 6  is a cross-sectional view taken along the line A-A of  FIG. 5 . 
         FIG. 7  is a perspective view of a valve mechanism of the engine as viewed from diagonally above and front. 
         FIG. 8  is an exploded perspective view of the valve mechanism of the engine as viewed from diagonally above and front. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the invention will be described with reference to  FIGS. 1 to 8 . An engine E of the embodiment is a small general-purpose engine mounted on a walk-type lawnmower or the like and constitutes an OHV engine. In the present specification and the like, in order to simplify and clarify the explanation, an axial direction of a crankshaft  2  is defined as an up-down direction (first direction), a direction which is perpendicular to the up-down direction and in which a cylinder portion  1   b  extends is defined as a front-back direction (second direction), and a direction perpendicular to the up-down direction and the front-back direction is defined as a left-right direction. In the drawing, the front of the engine E is shown as Fr, the rear as Rr, the left as L, the right as R the upper as U, and the lower as D. 
     As illustrated in  FIGS. 1 to 3 . the engine E of the embodiment includes an engine body  1  including a crankcase portion  1   a  and the cylinder portion  1   b , the crankshaft  2  which is rotatably supported by the crankcase portion  1   a  in the up-down direction, a piston  4  slidably fitted in the cylinder portion  1   b  and connected to the crankshaft  2  via a connecting rod  3 , an intake valve  5 , an exhaust valve  6 , and a spark plug  7  provided in a head portion  1   c  of the cylinder portion  1   b , a head cover  8  for covering the head portion  1   c  of the cylinder portion  1   b , a valve mechanism  9  which operates the intake valve  5  and the exhaust valve  6  according to the rotation of the crankshaft  2 , a flywheel  10  connected to an upper end of the crankshaft  2 , a recoil starter  11  which is placed above the flywheel  10  and starts the engine E, a top cover  12  which covers the top of engine E, a fuel tank  13  for storing fuel, an air cleaner  14  which purifies the air, a carburetor  15  which produces and supplies a mixture of fuel and air to the cylinder portion  1   b , a muffler  16  which exhausts the exhaust gas from the cylinder portion  1   b  while muffling the gas, a governor mechanism  17  (see  FIGS. 5 and 6 ) which automatically opens and closes a throttle valve (not illustrated) of the carburetor  15  according to the rotation speed of the crankshaft  2 , and an auto choke mechanism  18  which automatically opens and closes the throttle valve of the carburetor  15  according to the temperature of the engine body  1 . 
     [Engine Body] 
     As illustrated in  FIG. 4 , the engine body  1  includes a crankcase body  19 , a crankcase cover  20 , and a cylinder unit  21 . 
     As illustrated in  FIGS. 4 to 6 , the crankcase body  19  includes a bottom portion  19   a  and a tubular portion  19   c  including the bottom portion  19   a  integrally formed at a lower end portion and a case opening portion  19   b  at an upper end portion. A first crankshaft insertion hole  19   d  into which the lower end side of the crankshaft  2  is inserted is formed in the center of the bottom portion  19   a  and a cylinder insertion hole  19   e  through which the cylinder base portion  21   a  of the cylinder unit  21  is inserted is formed on the front surface of the tubular portion  19   c . In  FIG. 4 , reference numerals and letter  19   i  indicate a drain opening for discharging the oil accumulated inside the crankcase portion  1   a.    
     As illustrated in  FIG. 4 , the crankcase cover  20  covers the case opening portion  19   b  of the crankcase main body  19  and forms the crankcase portion  1   a  of the engine body  1  together with the crankcase main body  19 . A second crankshaft insertion hole  20   a  into which the upper end of the crankshaft  2  is inserted is formed in the center of the crankcase cover  20 . Returning to  FIG. 1 , the crankshaft  2  is rotatably supported between a second bearing  22  provided adjacent to the second crankshaft insertion hole  20   a  of the crankcase cover  20  and a first bearing  23  provided adjacent to the first crankshaft insertion hole  19   d  of the crankcase body  19 . 
     The crankcase cover  20  is detachably attached to the upper end of the crankcase body  19  via a plurality of bolts B 1 . Specifically, a plurality of bolt insertion holes  20   b , through which the bolts B 1  are inserted from above, are formed in the peripheral portion of the crankcase cover  20  and a plurality of bolt fastening holes  19   f  into which the bolts B are fastened from above are formed in the upper end of the crankcase body  19 . The crankcase cover  20  is attached to the crankcase body  19  by fastening the bolts B 1  to the bolt fastening holes  19   f  through the bolt insertion holes  20   b . Conversely, the crankcase cover  20  can be removed from the crankcase body  19  by releasing the fastening of the bolts B 1  from the bolt fastening holes  19   f.    
     According to the crankcase body  19  and the crankcase cover  20  as described above, by removing the crankcase cover  20  during maintenance of the engine E, it is possible to access the inside of the crankcase body  19  from above. In particular, when replacing the crankshaft  2 , it is possible to easily replace the crankshaft  2  by removing the crankcase cover  20  and pulling out the crankshaft  2 . 
     As illustrated in  FIGS. 4 to 6 , the cylinder unit  21  includes the cylinder base portion  21   a  which is inserted into the cylinder insertion hole  19   e  of the crankcase body  19  from the front and is located inside the crankcase body  19  and a cylinder block  21   b  which extends forward from the cylinder base portion  21   a  and is located outside the crankcase body  19 . The cylinder unit  21  alone forms the cylinder portion  1   b  of the engine body  1  and the front end of the cylinder block  21   b  forms the head portion  1   c . The cylinder base portion  21   a  and an inner peripheral surface of a cylindrical portion of the cylinder block  21   b  form a cylinder bore  21   c  which is a sliding surface with the piston  4  and a large number of cooling fins  21   d  are provided on the outer peripheral portion of the cylinder block  21   b.    
     According to such cylinder unit  21 , by preparing a plurality of types of cylinder unit  21  having different bore diameters, it becomes possible to provide an engine body  1  having a different displacement simply by replacing the cylinder unit  21  while making the crankcase body  19  and the crankcase cover  20  common. 
     The cylinder unit  21  is detachably attached to the crankcase body  19  via a plurality of bolts B 2  and B 3 . For example, when a plurality of bolt insertion holes (not illustrated) through which the bolts B 2  are inserted from the front are formed at the rear end of the cylinder block  21   b  and a plurality of bolt fastening holes  19   g  for fastening the bolts B 2  from the front are formed at the front end of the crankcase body  19 , by fastening the bolts B 2  to the bolt fastening holes  19   g  through the bolt insertion holes of the cylinder block  21   b , the cylinder unit  21  can be attached to the crankcase body  19 . Conversely by releasing the fastening of the bolts B 2  to the bolt fastening holes  19   g , the cylinder unit  21  can be removed from the crankcase body  19 . 
     However, in the engine body  1  of the embodiment, when the cylinder unit  21  is detachably attached to the crankcase body  19  via the plurality of bolts B 2  and B 3 , the bolts B 3  on the upper end side is fastened to the cylinder unit  21  from the inside of the crankcase body  19 . Specifically, a plurality of bolt insertion holes  19   h  through which the bolts B 3  are inserted from the inside of the crankcase body  19  toward the front are formed in the front end of the crankcase body  19  and a plurality of bolt fastening holes (not illustrated) for fastening the bolts B 3  from the rear are formed at the rear end of the cylinder block  21   b , and further the bolts B 3  is fastened to the bolt fastening holes of the cylinder block  21   b  through the bolt insertion holes  19   h  of the crankcase body  19 . 
     According to such a mounting structure of the cylinder unit  21 , since it is not necessary to form a space for fastening the bolts B 3  from the front side at least on the upper end side of the cylinder block  21   b , the cylinder unit  21  can be attached to the crankcase body  19  without disturbing the external structure (for example, the cooling fin  21   d ) of the cylinder block  21   b , and thus the cooling performance of the engine E can be improved. 
     [Valve Mechanism] 
     As illustrated in  FIGS. 6 to 8 , the valve mechanism  9  includes a timing gear  24  fixed to the crankshaft  2 , a camshaft  25  rotatably supported on the bottom portion  19   a  of the crankcase body  19 , a pair of lifters  27  supported to be swingable on the bottom portion  19   a  of the crankcase body  19  via stepped bolts  26 , a pair of rocker arms  29  which are supported to be swingable at the front end of the cylinder block  21   b  via rocker arm shafts  28  and one end of which abuts the front end of the intake valve  5  or the exhaust valve  6 , a pair of push rods  30  which are accommodated in a push rod accommodation portion  21   e  formed in the lower part of the cylinder unit  21  and which respectively connect the lifters  27  to the other end portions of the pair of rocker arms  29 , and a pair of valve springs  31  for urging the intake valve  5  and the exhaust valve  6  in a closing direction. 
     A camshaft  25  includes a gear portion  25   a  which meshes with the timing gear  24  and is rotationally driven by the timing gear  24  at a speed reduction ratio of 1/2 and a cam portion  25   b  which alternately pushes the pair of lifters  27  according to the rotational drive of the gear portion  25   a . When the cam portion  25   b  pushes the lifter  27 , the other end of the corresponding rocker arm  29  is pushed through the push rod  30  and the intake valve  5  or the exhaust valve  6  connected to one end of the rocker arm  29  is opened. Conversely, when the pushing of the lifter  27  by the cam portion  25   b  is released, the intake valve  5  or the exhaust valve  6  is closed by the urging force of the valve spring  31 . 
     The camshaft  25  of the embodiment is arranged below the cylinder base portion  21   a  of the cylinder unit  21 . When the camshaft  25  is arranged as such, it is possible to access the inside of the crankcase body  19  from the top without removing the camshaft  25  by simply removing the crankcase cover  20  when maintaining the engine E. 
     In  FIG. 6 , reference numerals and letter  21   g  indicate a communication hole provided in a rear wall  21   f  of the push rod accommodation portion  21   e . The communication hole  21   g  is provided at the lowest position when the oil accumulated inside the crankcase portion  1   a  is drained from a drain opening  19   i  of the crankcase body  19  to the outside. The communication hole  21   g  guides the oil accumulated in the head portion  1   c  and the push rod accommodation portion  21   e  to the crankcase portion  1   a . Therefore, it is possible to more reliably prevent the accumulation of oil in the push rod accommodation portion  21   e  when the oil is discharged. 
     The embodiment described above can be appropriately modified, improved, and the like. For example, in the embodiment described above, the front-back direction is described as the second direction, but the second direction may be the left-right direction. 
     Although the cylinder unit  21  is detachable from the crankcase body  19  in the embodiment described above, the cylinder unit  21  may be formed integrally with the crankcase body  19 . 
     SUMMARY 
     At least the following matters are described in the specification. Although the constituent elements and the like corresponding to those of the embodiment described above are shown in parentheses, the invention is not limited to this. 
     (1) An engine which includes: 
     a crankcase body (crankcase body  19 ) including a bottom portion (bottom portion  19   a ) including a first crankshaft insertion hole (first crankshaft insertion hole  19   d ) and a tubular portion (tubular portion  19   c ) including the bottom portion integrally formed at one end in a first direction and including a case opening portion (case opening portion  19   b ) at the other end in the first direction: 
     a crankcase cover (crankcase cover  20 ) including a second crankshaft insertion hole (second crankshaft insertion hole  20   a ) and covering the case opening portion of the crankcase body; 
     a crankshaft (crankshaft  2 ) inserted through the first crankshaft insertion hole and the second crankshaft insertion hole: 
     a cylinder base portion (cylinder base portion  21   a ) located inside the crankcase body; and 
     a cylinder block (cylinder block  21   b ) located outside the crankcase body, where 
     the first direction is an up-down direction of the engine (engine E), and 
     the crankcase cover is detachably attached to an upper portion of the crankcase body. 
     According to (1), the crankcase cover is detachably attached to the upper portion of the crankcase body. Therefore, by removing the crankcase cover during maintenance of the engine, it is possible to access the inside of the crankcase body from the top. In particular, when replacing the crankshaft, it is possible to easily replace the crankshaft by removing the crankcase cover and pulling out the crankshaft. 
     (2) The engine according to (1), where 
     a camshaft (camshaft  25 ) is installed inside the crankcase body, and 
     the camshaft is arranged further on a lower side than the cylinder base portion. 
     According to (2), the camshaft is located below the cylinder base portion. Therefore, by simply removing the crankcase cover during engine maintenance, it is possible to access the inside of the crankcase body from the top without removing the camshaft. 
     (3) The engine according to (1) or (2), where 
     the engine includes a valve mechanism (valve mechanism  9 ), 
     the valve mechanism includes, 
     a timing gear (timing gear  24 ) fixed to the crankshaft, 
     a camshaft (camshaft  25 ) rotatably supported by the bottom portion of the crankcase body, 
     a pair of lifters (lifters  27 ) supported to be swingable on the bottom portion of the crankcase body, 
     a pair of rocker arms (rocker arms  29 ) which are supported to be swingable via rocker arm shafts (rocker arm shafts  28 ) and one end of which abuts against an intake valve (intake valve  5 ) or an exhaust valve (exhaust valve  6 ), 
     a pair of push rods (push rods  30 ) for connecting the pair of lifters to the other ends of the pair of rocker arms, and 
     a pair of valve springs (valve springs  31 ) for urging the intake valve and the exhaust valve in a closing direction, and 
     the pair of push rods are accommodated in a push rod accommodation portion (push rod accommodation portion  21   e ) formed in a lower portion of the cylinder block. 
     According to (3), the pair of push rods of the valve mechanism are accommodated in the push rod accommodation portion formed in the lower portion of the cylinder block. Therefore, by simply removing the crankcase cover during engine maintenance, it is possible to access the inside of the crankcase body from the top without removing the push rod. Since the push rod accommodation portion is integrally formed in the lower portion of the cylinder block, the number of parts can be reduced. As a result, the manufacturing cost can be reduced. 
     (4) The engine according to (3), where 
     the push rod accommodation portion is provided with a communication hole (communication hole  21   g ) communicating with the inside of the crankcase body. 
     According to (4), the oil accumulated in the push rod accommodation portion flows into the crankcase body through the communication hole, so that the accumulation of oil in the push rod accommodation portion can be prevented. 
     (5) The engine according to (4), where 
     the communication hole is provided at the lowest position when oil accumulated inside the crankcase body is discharged to the outside from a drain opening (drain opening  19   i ) of the crankcase body. 
     According to (5), since the communication hole is provided at the lowest position when the oil accumulated inside the crankcase body is discharged to the outside from the drain opening of the crankcase body. Therefore, it is possible to more reliably prevent oil from accumulating in the push rod accommodation portion during oil discharge. 
     DESCRIPTION OF REFERENCE NUMERALS AND CHARACTERS 
     
         
         
           
             E: engine 
               2 : crankshaft 
               5 : intake valve 
               6 : exhaust valve 
               9 : valve mechanism 
               19 : crankcase body 
               19   a : bottom portion 
               19   b : case opening portion 
               19   c : tubular portion 
               19   d : first crankshaft insertion hole 
               19   e : cylinder insertion hole 
               19   i : drain opening 
               20 : crankcase cover 
               20   a : second crankshaft insertion hole 
               21 : cylinder unit 
               21   a : cylinder base portion 
               21   b : cylinder block 
               21   g : communication hole 
               21   e : push rod accommodation portion 
               24 : timing gear 
               25 : camshaft 
               27 : lifter 
               28 : rocker arm shaft 
               29 : rocker arm 
               30 : push rod 
               31 : valve spring