Abstract:
An engine has a cylinder block mounted on a crankcase and a cylinder head mounted on the cylinder block. The cylinder head has one side forming an intake port and an intake valve and another side forming an exhaust port and an exhaust valve. A camshaft includes an intake cam assembly and an the exhaust cam assembly, which respectively drive an intake valve driving member and an exhaust valve driving member. The intake cam assembly includes a first intake cam and a second intake cam. The intake valve driving member includes a low lift driving member corresponding to the first intake cam and a high lift driving member corresponding to the second intake cam. The low lift driving member and the high lift driving member form a hydraulic cylinder, which receives therein hydraulically operable pistons.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to a variable valve lift mechanism for engine and an arrangement of oil control valve, and more particularly to a structure that prevent interference of the oil control valve with maintenance of other parts and realizes movement of valve driving member of engine for high and low lifts in order to miniaturize the oil pump and reduce engine power loss. 
       DESCRIPTION OF THE PRIOR ART 
       [0002]    Oil passage arrangement for a conventional variable valve lift mechanism of an engine  1  is shown in  FIG. 1 , wherein an electromagnet valve  2  is mounted on a cylinder head  11 . Oil received at hydraulic oil entrance is guided by a pipe  21  to supply external pressure to the electromagnetic valve  2 , and then the electromagnetic valve  2  introduces the lubrication oil into oil passages inside the cylinder head  11  to allow the hydraulic pressure to be applied to drive variable lift mechanism of each cylinder so as to realize switching of intake and exhaust valves in response to different rotational speeds of the engine  1 . 
         [0003]    The arrangement of the electromagnetic valve  2  and the oil pipe  21  of the conventional engine  1  are effective in realizing switching of intake and exhaust valves in response to different rotational speeds of the engine  1 . However, the electromagnetic valve  2  is mounted to the cylinder head  11  by bolts  22 . The assembling is complicated. Further, the oil pipe  21  connected to the electromagnetic valve  2  is susceptible to oil leakage and due to exposure outside the engine  1 , it is susceptible to damage due to high temperature of the engine  1 . Further, since the electromagnetic valve  2  is arranged above the cylinder head  11 , when the engine  1  swings, the electromagnetic valve  2  may easily get interfering with an upper side part, such as a storage box. 
         [0004]    In view of the above discussed problems of the conventional arrangement of oil passage for variable valve lift mechanism, the present invention aims to provide an oil control valve that simplifies the assembling of engine and allows of easy arrangement of lubrication oil passage and a structure to miniaturize the oil pump and reduce power loss of engine. 
       SUMMARY OF THE INVENTION 
       [0005]    The technical solution adopted in the present invention is to provide a variable valve lift mechanism and arrangement of control valve. The engine comprises a cylinder block mounted on a crankcase and a cylinder head mounted on the cylinder block. The cylinder head has one side forming an intake port and an intake valve and another side forming an exhaust port and an exhaust valve. A throttle valve communicates through an intake tube with the intake port. The intake valve and the exhaust valve are provided therebetween with a camshaft base. The camshaft base comprises a camshaft, and the camshaft comprises an intake cam assembly and an exhaust cam assembly, which respectively drive an intake valve driving member and an exhaust valve driving member. The intake cam assembly includes a first intake cam and a second intake cam. The intake valve driving member comprises a low lift driving member corresponding to the first intake cam and a high lift driving member corresponding to the second intake cam. The low lift driving member and the high lift driving member form a hydraulic cylinder, which receives therein hydraulically operable pistons. The oil control valve comprises a driving oil passage communicating the hydraulic cylinder. The high lift driving member of the intake valve driving member is closer to the oil control valve than the low lift driving member. The path of the driving oil passage of the oil control valve and the high lift driving member is shorter than the path of the driving oil passage that the oil control valve drives the low lift driving member. 
         [0006]    Another technical solution adopted in the present invention is to provide a variable valve lift mechanism for engine and arrangement of oil control valve, wherein the oil control valve seat is integrally formed on a surface of an intake port side of the cylinder head to be substantially perpendicular to an intake port and is located on an outer wall of a timing chain chamber. The oil control valve seat is set lower than the greatest height of the throttle valve. Further, the oil control valve seat is substantially in line with a timing chain tensioner and is located on the same side as the timing chain and is substantially parallel to the intake tube. The oil control valve seat forms an opening that is faces toward the cylinder block to receive the oil control valve to be mounted thereto. The oil control valve is mounted to the oil control valve seat in such a way to face from the cylinder block toward the cylinder head. In other words, a wire outlet joint end of the oil control valve faces toward the cylinder block in order to eliminate interference of the oil control valve with maintenance of other parts. 
         [0007]    The foregoing objectives and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention itself, all of which will become apparent to those skilled in the art, the following detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. Throughout the specification and drawings identical reference numerals refer to identical or similar parts. 
         [0008]    Many other advantages and features of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a conventional cylinder head. 
           [0010]      FIG. 2  is a cross-sectional view of an engine according to the present invention. 
           [0011]      FIG. 3  is a perspective view schematically showing oil route according to the present invention. 
           [0012]      FIG. 3A  is an enlarged sectional view illustrating the way how the throttle arrangement is mounted inside the crankshaft oil supply passage; 
           [0013]      FIG. 3B  is an enlarged sectional view illustrating the way how the throttle arrangement is mounted inside the valve driving member oil supply passage; 
           [0014]      FIG. 4  is a perspective view of an engine according to the present invention. 
           [0015]      FIG. 5  is a schematic view of a variable valve lift mechanism according to the present invention. 
           [0016]      FIGS. 6 and 7  are schematic views illustrating the operation of the variable valve lift mechanism according to the present invention. 
           [0017]      FIG. 8  is a perspective view illustrating an oil control valve according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    The following descriptions are exemplary embodiments only, and are not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention as set forth in the appended claims. 
         [0019]    The present invention provides an engine  3 , which is arranged, in a substantially horizontal manner, on a scooter as a rocker engine  3 . First of all, reference is made to  FIG. 2 . The engine  3  according to the present invention comprises a crankcase  31 , a cylinder block  32  mounted on the crankcase  31 , a cylinder head  33  mounted on the cylinder block  32 , and a cylinder head cover  34 . 
         [0020]    The crankcase  31  receives therein a crankshaft  310 . Referring to  FIGS. 3 ,  3 A and  3 B the crankcase  31  comprises therein an oil pump  311 . The oil pump  311  pumps oil into a primary oil supply passage  312 . The primary oil supply passage  312  extends from the crankcase  31  through the cylinder block  32  to the oil control valve  4  mounted to the cylinder head  33 . The primary oil supply passage  312  has an end forming a crankshaft oil supply passage  312   a  toward the crankcase  31 . The crankshaft oil supply passage  312   a  has an end forming a throttle arrangement  312   a ′ that supplies oil to a crankshaft bearing. The throttle arrangement  312   a ′ comprises a nozzle. The throttle arrangement  312   a ′ functions to regulate the internal pressure of the primary oil supply passage  312  and the ejected amount of oil and also functions to direct the oil to eject to a predetermined direction. 
         [0021]    The cylinder block  32  is coupled to the crankcase  31  and allows a timing chain  5  to extend therethrough. The cylinder block  32  comprises a timing chain tensioner  51  arranged at the intake port  331  side of the cylinder head  33 , as shown in  FIGS. 1 and 4 . Further, the timing chain tensioner  51  is arranged to be substantially in line with the oil control valve  4 . Since the timing chain chamber  330  provides a large amount of internal space, it is possible to prevent heat accumulation occurring at the location where an oil control valve seat  339  is mounted. 
         [0022]    The cylinder head  33  comprises an intake port  331  and an intake valve  332  arranged at the intake side and an exhaust port  333  and an exhaust valve  334  arranged at the exhaust side. A throttle valve  6  communicates through an intake tube  321  with the intake port  331  of the intake side. Referring to  FIGS. 3 ,  3 A,  3 B,  4 ,  5 , and  6 , the cylinder head  33  comprises an integrally formed cast camshaft base  335  between the intake valve  332  and the exhaust valve  334 . The camshaft base  335  supports a rotatable camshaft  336 . The camshaft  336  comprises an intake cam assembly  3361  and an exhaust cam assembly  3362  mounted thereon. The intake cam assembly  3361  includes a first intake cam  3361   a  (which is a low lift cam) and a second intake cam  3361   b  (which is a high lift cam). The intake cam assembly  3361  and the exhaust cam assembly  3362  function to push intake valve driving member  337  and exhaust valve driving member  337 ′ of the intake valve  332  and the exhaust valve  334  during the rotation of the camshaft  336 . The intake valve driving member  337  comprises a low lift driving member  3371  and a high lift driving member  3372  of variable valve lift mechanism. The low lift driving member  3371  and the high lift driving member  3372  are provided with a hydraulic cylinder  338 . The hydraulic cylinder  338  receives therein a first piston  3381  and a second piston that can be hydraulically moved. The oil control valve  4  comprises a driving oil passage  3383  communicating the hydraulic cylinder  338 . The driving oil passage  3383  includes a first driving oil passageway  3383   a  and a second driving oil passageway, which are respectively located at the ends of the low lift driving member  3371  and the high lift driving member  3372  close to the hydraulic cylinder  338 . The oil control valve  4  functions to set the low lift driving member  3371  and the high lift driving member  3372  to move together or to move individually. The driving oil passage  3383  extends from an oil control valve seat  339  outside the cylinder head  33  through the cylinder head  33  and the camshaft base  335  to the hydraulic cylinder  338  of the valve driving member  337 . Referring to  FIGS. 3 and 6 , the oil control valve seat  339  is integrally formed on a surface of the intake port  331  of the cylinder head  33  to be substantially parallel to the intake tube  321  and is located on an outer wall of the timing chain chamber  330 . The oil control valve seat  339  is set to be lower than the greatest height of the throttle valve  6 . Further, the oil control valve seat  339  is substantially in line with the timing chain tensioner  51  and is located at the same side of the timing chain  5 . The oil control valve seat  339  forms an opening  3391 , and opening  3391  is arranged to face the cylinder block  32  to receive the oil control valve  4  to be mounted thereto. The oil control valve  4  is mounted on the oil control valve seat  339  in such a way to face from the cylinder block  32  toward the cylinder head  33 . In other words, a wire outlet joint end  4   a  of the oil control valve  4  faces toward the cylinder block  32 . Further, the high lift driving member  3372  of the intake valve driving member  337  is arranged close to the oil control valve  4 . In other words, the high lift driving member  3372  of the intake valve driving member  337  is more close to the oil control valve  4  than the low lift driving member  3371 . Namely, the path of the driving oil passage  41 H of the oil control valve  4  and the high lift driving member  3372  is shorter than the driving oil passage  41 L that the oil control valve  4  drives the low lift driving member  3371 . The oil control valve  4  is arranged in a substantially horizontal on the cylinder head  33  in order to eliminate the influence caused by gravity and thereby reducing the consumption of electrical power. 
         [0023]    The cylinder head cover  34  is arranged on the cylinder head  33 . To practice the present invention, as shown in  FIGS. 3 ,  3 A and  3 B, the oil pump  311  arranged in the crankcase  31  pumps oil to the primary oil supply passage  312 , which extends from the crankcase  31  through the cylinder block  32  to communicate the oil control valve  4  arranged in the cylinder head  33 . 
         [0024]    The oil control valve  4  comprises a plurality of oil channels  41  inside the cylinder head  33 , and the oil control valve  4  forms a plurality of oil apertures  42 . The number of the oil apertures  42  of the oil control valve  4  determines the number of oil channels inside the cylinder head  33 . Further, the end of the primary oil supply passage  312  toward the crankcase  31  forms a crankshaft oil supply passage  41   a.  Referring to  FIGS. 3 ,  3 A,  3 B,  5 , and  6 , the primary oil supply passage  312  has an end toward the cylinder head cover  34  and the end forming a valve driving member oil supply passage  41   b.  The valve driving member oil supply passage  41   b  communicates the cylinder head  33 . Through the communication of the valve driving member oil supply passage  41   b  with the cylinder head  33 , oil is allowed to freely supply to the intake valve driving member  337 . The valve driving member oil supply passage  41   b  comprises a throttle arrangement  41   b ′ inside the cylinder head cover  34 . The throttle arrangement  41   b ′ comprises a nozzle. The throttle arrangement  41   b ′ regulates the internal pressure of the primary oil supply passage  312  and the amount of oil ejected, and to eject the oil in a predetermined direction in order to realize lubrication of the valve driving member  337 . 
         [0025]    Referring to  FIGS. 5 and 6 , the oil control valve  4  supplies oil into the first driving oil passageway  3383   a  of the driving oil passage  3383  of the cylinder head  33  to enter the hydraulic cylinder  338 . A control center ECU (not shown) of the engine  3  detects the moving condition of the vehicle and when it is determined that the valve needs to be opened in a low lift extent, the control center ECU of the engine  3  controls the oil control valve  4  to supply oil from the driving oil passage  3383  into the hydraulic cylinder  338 , as shown in  FIG. 6 , whereby hydraulic pressure causes the first piston  3381  and the second piston  3382  to move toward the high lift driving member  3372  to have the second piston  3382  located inside the high lift driving member  3372  and the first piston  3381  located inside the low lift driving member  3371 . Under this condition, the low lift driving member  3371  and the high lift driving member  3372  are allowed to individually rotate. Under this condition, due to engagement between the low lift driving member  3371  and the first intake cam  3361   a  (namely the low lift cam) of the camshaft  336 , the intake valve of the engine  3  is set in a low lift opening condition. As shown in  FIG. 7 , when the engine  3  is caused by a change of the moving condition of the vehicle to have the intake vale changed to a high lift opening coition, the control center ECU of the engine  3  controls the oil control valve  4  to supply oil from the second driving oil passageway  3383   b  of the driving oil passage  3383  into the hydraulic cylinder  338 . The hydraulic pressure causes the first piston  3381  and the second piston  3382  to move toward the low lift driving member  3371  to have the first piston  3381  located in the low lift driving member  3371  and the second piston  3382  located at a position between the low lift driving member  3371  and the high lift driving member  3372 . Under this condition, the low lift driving member  3371  and the high lift driving member  3372  are movable in unison with each other. Due to the engagement between the high lift driving member  3372  and the second intake cam  3361   b  (namely the high lift cam) of the camshaft  3361 , the low lift driving member  3371  is moved by the high lift driving member  3372  to set the intake valve  332  to a desired high lift opening condition by the lift of the second intake cam  3361   b  (namely the high lift cam). This realizes variation of valve lift of the engine  3 . 
         [0026]    Alternatively, in the practice of the oil control valve  4  according to the present invention, as shown in  FIG. 8 , the oil control valve seat  339  forms an opening  3391 , which faces toward the cylinder head  33  to receive the oil control valve  4  mounted thereto. The oil control valve  4  is mounted on the oil control valve seat  339  in such a way to face from the cylinder head  33  toward the cylinder block  32 . In other words, a wire outlet joint end  4   a  of the oil control valve  4  faces toward the cylinder head  33 . Similarly, the high lift driving member  3372  of the intake valve driving member  337  is arranged close to the oil control valve  4 . In other words, the high lift driving member  3372  of the intake valve driving member  337  is more close to the oil control valve  4  than the low lift driving member  3371 . 
         [0027]    The effectiveness of the present invention is that an oil control valve seat  339  is mounted to a surface on the intake port  331  side of the cylinder head  33  and located on an outer wall of the timing chain chamber  330 , the oil control valve seat  339  is mounted between the intake port  331  and not exceeding the greatest height of the throttle valve  6 ; the oil control valve  4  is mounted on the oil control valve seat  339  in such a way to face from the cylinder block  32  toward the cylinder head  33 , namely a wire outlet joint end of the oil control valve  4  facing toward the cylinder block  32 , whereby the oil control valve  4  is set away from high temperature of the engine  3  to prevent the oil control valve seat  339  from becoming a heat concentration object and to improve the durability of the oil control valve  4  and also to realize easy arrangement and eliminate interference of the oil control valve  4  with the maintenance of other parts. Further, the high lift driving member  3372  of the valve driving member  337  is arranged close to the oil control valve  4 , namely, the high lift driving member  3372  of the valve driving member  337  being more close to the oil control valve  4  than the low lift driving member  3371 , whereby the oil path that the oil control valve  4  supplies oil to the high lift driving member  3372  is shortened and the pressure loss is reduced thereby making the high lift driving member  3372  operating in a more reliable manner. Since the oil path that the oil control valve  4  supplies oil to the high lift driving member  3372  is shortened, the loss of oil pressure that the oil control valve  4  supplies to the high lift driving member  3372  is reduced, so that the oil pump  311  that supplies the oil can be miniaturized to thereby reduce the installation cost of the oil pump  311  and the consumption of power of the engine  3 , and allows internal arrangement of the engine  3  compact. 
         [0028]    It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. 
         [0029]    While certain novel features of this invention have been shown and described and are pointed out in the annexed claim, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention.