Abstract:
An engine lubrication and speed control method is provided. The four-cycle engine has a engine block having a cylindrical bore and an enclosed oil reservoir formed therein. A vertical or horizontal crankshaft is rotatably mounted in the engine block for rotation about a crankshaft axis. An oil pump, which is driven by the camshaft connected with a cam gear or driven by the crank shaft connecting with the crank gear, inhales the oil from the oil reservoir to splash lubricate into the cylinder bore and valve chamber. A speed control governor is provided on the wall of the cylinder block. The engine is provided with a cylinder head assembly defining a compact combustion chamber having a pair of overhead intake and exhaust ports and cooperating intake and exhaust valves. A commonality of parts between the horizontal and the vertical engine is highly achieved.

Description:
FIELD 
       [0001]    This invention relates to an engine, and more particularly, a small four-cycle utility engine that is particularly suitable for typical power tools driven by a vertical or horizontal power shaft. 
       BACKGROUND 
       [0002]    Portable power tools such as line trimmers, blowers/vacuums, and chain saws must be able to run in a very wide range of orientations. However, in most power tools such as generators or tillers/cultivators, power shaft orientation is either substantially horizontal or vertical. Therefore, it is not necessary for these typical power tools to be able to run in a very wide range of orientations having complicated and economically ineffective constructions. 
         [0003]    For some tillers/cultivators powered by four-cycle engines with a vertical power shaft, lubrication also becomes a serious problem since it is difficult to use the same lubrication system as engines with a horizontal power shaft. 
         [0004]    U.S. Pat. No. 6,250,273 to Ryuu et al. discloses a prior art utility engine for horizontal and vertical shaft orientations, which is incorporated herein by reference. However, constructions are still complicated because special rotating parts having inclined shafts to a crankshaft or a camshaft are necessary for lubrication and speed control. 
         [0005]    Further, because the splashing blades  41  adjacent the driven gear  40  are immersed in an oil in the oil reservoir  17  and splash oil in the direction which is composed by the peripheral and centrifugal forces by rotation of rotary board  35 , splashed oil is concentrated in the corner of crankcase and does not direct to the center portion of the crankcase to lubricate moving parts effectively and it produces heating of oil by useless churning. 
         [0006]    Further, because the side cover has portions to support the intermediate shaft and the inclined governor shaft, size of the side cover is large and machining for the side cover is complicated and requires high level of accuracy. 
         [0007]    Therefore, it is an object of the present invention to provide a small four-cycle utility engine having an internal lubrication system, which is especially suitable for both vertical and horizontal power shaft engines having components that are easy to make. 
         [0008]    Although U.S. patent application Ser. No. 12/954,945 by Kurihara et al. and U.S. patent application Ser. No. 13/286,323 by Kurihara et al., which are incorporated herein by reference, disclose a useful prior art small four-cycle engine construction for portable power tools driven by a vertical or horizontal power shaft, to shorten the length of axial direction is required yet. 
         [0009]    It is a further object of the present invention to provide a small four-cycle utility engine having a short axial length and speed control system enabling the engine to be run at a desired speed at any load, which is especially suitable for both vertical and horizontal power shaft engines. 
         [0010]    It is yet a further object of the invention to provide a commonality of main parts between vertical and horizontal engines, which is especially suitable for both vertical and horizontal power shaft engines to reduce manufacturing cost. 
         [0011]    These and other objects, features, and advantages of the present invention will become apparent upon further review of the remainder of the specification and the accompanying drawings. 
       SUMMARY 
       [0012]    In order to achieve the above objects, a four-cycle, utility engine is provided which is suitable for both vertical and horizontal power shaft engines. 
         [0013]    The four-cycle, vertical shaft utility engine is provided with an engine block having at least one cylindrical bore oriented in a substantially horizontal orientation having an enclosed crankshaft chamber. A vertical crankshaft is pivotably mounted within the engine block. An enclosed oil reservoir is formed with the engine block and a crank shaft cover and is located below the crankshaft chamber. The enclosed oil reservoir when properly filled, enables the engine to rotate at least 30 degrees about the crankshaft axis in either direction without oil within the reservoir rising above the level of the crankshaft counter weight. A pump is connected drivably to a cam gear-cam assembly or to a speed governor assembly, said pump inhales lubrication oil from the oil reservoir through an inhale passage on a wall of the cylinder block to splash oil into the cylinder and valve train. Said inhale passage of the oil pump is extended to near the crank shaft cover, which is located below the cylindrical bore when the power shaft of said engine is oriented to be horizontal. 
         [0014]    A sister engine, which is a horizontal shaft utility engine, is provided. Main parts of both vertical and horizontal engine are substantially common. The sister engine has an engine block having at least one cylindrical bore oriented in a substantially vertical orientation having an enclosed crankshaft chamber. A horizontal crankshaft is pivotably mounted within the engine block. An enclosed oil reservoir formed with the engine block and a crank shaft cover and is located below the crankshaft chamber. The enclosed oil reservoir when properly filled, enables the engine to rotate at least 30 degrees about the crankshaft axis in either direction without oil within the reservoir rising above the level of the crankshaft counter weight. A pump is connected drivably to a cam gear-cam assembly or to a speed governor assembly, and said pump inhales lubrication oil from the oil reservoir through an inhale passage on the cylinder block to splash oil into the cylinder and valve train. 
         [0015]    In both the vertical and horizontal engine, a breathing system is provided at a location in which an oil level within the reservoir is not above the breathing system. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is a cross-sectional side elevation view of the vertical shaft engine taken along the rotating axis of the crankshaft and axis of cylinder bore. 
           [0017]      FIG. 2  is a cross-sectional side elevation view of the horizontal shaft engine taken along the rotating axis of the crankshaft and axis of cylinder bore. 
           [0018]      FIG. 3  is a cross-sectional side elevation view of another embodiment of a vertical shaft engine taken along the rotating axis of the crankshaft and axis of cylinder bore. 
           [0019]      FIG. 4  is a cross-sectional side elevation view of another embodiment of a horizontal shaft engine taken along the rotating axis of the crankshaft and axis of cylinder bore. 
           [0020]      FIG. 5  is a cross-sectional side elevation view of the engine taken along line A-A in  FIG. 2  to show detail construction of breather system and speed governor. 
           [0021]      FIG. 6  is an enlarged schematic illustration of the camshaft and the follower mechanism. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0022]      FIG. 1  illustrates a cross-sectional side elevation view of a vertical shaft four-cycle engine. The four-cycle engine is made up of a lightweight aluminum housing including a cylinder block  1  having a cylindrical bore  2  formed therein. The cylinder block  1  is defined by a cylinder  90  and a lower case  91  mating each other in a plane which is perpendicular to the cylinder axis  16  and includes crankshaft axis  92 . 
         [0023]    The cylinder block  1  forms a crankshaft chamber  19 . 
         [0024]    The lower case  91  and the crankshaft cover  93  provide an enclosed oil reservoir  20  in a vertical shaft engine as illustrated in  FIG. 1 . 
         [0025]    A crankshaft  3  is a power shaft and is pivotably mounted within the engine block  1  in a conventional manner. A piston  4  slides within the cylinder bore  2  and is connected to the crankshaft  3  by a connecting rod  5 . A cylinder head  6  is affixed to the engine block  1  to define an enclosed combustion chamber  7 . 
         [0026]    In  FIG. 5 , the cylinder head  6  is provided with an intake port  8  coupled to an insulator  9  and carburetor  10  and selectively connected to the combustion chamber  7  via an intake valve  11 . A filter element  12  of an air cleaner is provided to eliminate dust from the intake air into the engine. The cylinder head  6  is also provided with an exhaust port  13  connected to a muffler  14  and selectively connected to the combustion chamber  7  by an exhaust valve  15 . 
         [0027]      FIG. 2  illustrates a cross-sectional side elevation view of a horizontal shaft four-cycle sister engine. Main parts of both vertical and horizontal engine are substantially common. The four cycle engine has an engine block  1  having at least one cylindrical bore oriented in a substantially vertical orientation having an enclosed crankshaft chamber  19 . The cylinder block  1  is defined by a cylinder  90  and a lower case  91  mating each other in a plane which is perpendicular to the cylinder axis  16  and includes crankshaft axis  92 . 
         [0028]    A horizontal crankshaft  3  is pivotably mounted within the engine block  1 . An enclosed oil reservoir  21  is formed within the engine block  1  and a crank shaft cover  93  and is located below the crankshaft chamber  19 . The enclosed oil reservoir  21  when properly filled, enables the engine to rotate at least 30 degrees about the crankshaft axis  92  in either direction without oil within the oil reservoir  21  rising above the level of the crankshaft counter weight. 
         [0029]    As illustrated in  FIGS. 1 and 2 , the cylinder axis  16  of a four-cycle engine is generally upright when in a horizontal power shaft engine and is generally horizontal when in a vertical power shaft engine. 
         [0030]    The oil reservoir  20  or  21  is relatively deep so that there is ample clearance between the crankshaft  3  and the level of the oil within the oil reservoir during normal use (vertical or horizontal orientation of the crankshaft). 
         [0031]    The crankshaft  3  is provided with an axial shaft  22  coupled to an output end  23  adapted to be coupled to a counterweight web  24 . 
         [0032]    A crankpin  25  is affixed to counterweight web  24  and is parallel to and radially offset from the axial shaft  22 . The crankpin  25  pivotally cooperates with connecting rod  5 . 
         [0033]    The axial shaft  22  of crankshaft  3  is pivotably attached to the cylinder block  1  by a bearing  27 . 
         [0034]    Another axial shaft  28  of the crankshaft  3  is coupled to a counterweight web  26  and is pivotably attached to the cylinder block  1  by a bearing  29 . 
         [0035]    At the side of bearing  27  is a crank gear  30 . 
         [0036]    A camshaft drive and valve lifter mechanism is best illustrated in  FIGS. 1 and 6 . 
         [0037]    The crank gear  30  is mounted on the crankshaft  3 , which in turn drives a cam gear  31  with twice the number of teeth as the crank gear  30  resulting in the camshaft  32  rotating at one-half engine speed. The cam gear  31  is affixed to the camshaft  32  which includes a rotary cam lobe  33 . 
         [0038]    In the embodiment illustrated, a single cam lobe  33  is utilized for driving both the intake and exhaust valves  11 ,  15 . 
         [0039]    Followers  34  and  35  are pivotably connected to the cylinder block  1  by a pivot pin  36 . 
         [0040]    Push rods  37  and  38  extend between camshaft followers  34  and  35  and rocker arms  39  and  40  located within the cylinder head  6 . The cam lobe  33 , push rods  37 ,  38  and rocker arms  39 ,  40  are part of a valve train assembly. Affixed to the cylinder head  6  is a valve cover  41  which defines therebetween an enclosed valve chamber  42 . 
         [0041]    As illustrated in  FIG. 1  and  FIG. 2 , a cam chamber cover  50  is attached to the wall of the cylinder  90 . An end of the camshaft  32  is journaled to the wall of cylinder bore  2  of the cylinder  90 . The other end of said cam shaft  32  is journaled to a cam chamber cover  50 . An end of the pivot pin  36  is supported at the wall of cylinder bore  2  and the other end of said pivot pin is supported by the cam chamber cover  50 . Cylinder  90  and cam chamber cover defines a cam chamber  18 . 
         [0042]    In order to lubricate the engine, a trochoid pump  43  is placed at the cam chamber cover  50 . 
         [0043]    The pump  43  has an inner rotor  44  and outer rotor  45 . In other embodiments of the present application, a gear pump may be used. 
         [0044]    The camshaft  32  drives the inner rotor  44  and the outer rotor  45  is rotated following the rotation of the inner rotor  44 . 
         [0045]    Lubrication oil is inhaled from a passage  46 , which is extended to the crank shaft cover  93 . An oil seal  47  is installed on the cylinder block  1  to prevent leakage of oil from the crank shaft chamber  19 . 
         [0046]    An end of the passage  46  leads to the oil entrance of the pump. The other end of passage  46  is connected to an oil entrance at oil reservoir  20  or  21 . 
         [0047]    In the vertical shaft engine as illustrated in  FIG. 1 , the entrance of the oil passage  46  is dipped in the oil in the oil reservoir  20  within a certain inclination range of the power shaft from the normal position, because the oil passage  46  is substantially horizontal at the normal position. 
         [0048]    In the horizontal shaft engine as illustrated in  FIG. 2 , although oil passage  46  is substantially vertical at the normal position, the entrance of the oil passage  46  is dipped in the oil in the oil reservoir  21  within a certain inclination range of the power shaft from the normal position. 
         [0049]    The pump  43  and the cylinder  90  can be commonly used between the vertical shaft engine as in  FIG. 1  and the horizontal shaft engine as in FIG.  2 . 
         [0050]    The oil pushed out by the pump  43  is lead simultaneously to a hole  49  at the cylinder wall and to a hole  94  formed in the outer wall of the cam shaft  32  and a hole  95  in the cylinder  90  through an inner through hole  48  of the camshaft  32  and into the cylinder bore  2  as illustrated in  FIG. 1  and  FIG. 2 . 
         [0051]    Any other hole (not shown) at the wall of the camshaft  32  may lead oil to the valve actuating train. Accordingly, the engine parts inside the cylinder and crankcase are mist lubricated by the oil splashed by means of the rotation of and/or the centrifugal force generated by the rotating parts such as the web  24 ,  26  and the cam gear  31 . 
         [0052]    In the engine of  FIGS. 1 and 2 , a breather system is provided. The breather system is composed of a breather tube  57  and a check valve  58  as illustrated in  FIG. 5 . 
         [0053]    As shown in  FIG. 5 , in the valve chamber  42 , a breather tube  57  is opened through the valve cover  41  and is connected to an air cleaner case  59 . The breathing oil mist sent through a tube is inhaled to the carburetor through a filter element  12 . The check valve  58  is located at the position where it does not dip into oil in case of vertical or horizontal shaft engine. 
         [0054]    As illustrated in  FIGS. 2 and 5 , a governor shaft  51  parallel to the crank shaft axis  92 , is provided on the lower case  91  to compose a speed control system. A governor holder  52  is installed on the outer surface of said governor shaft  51  to be able to rotate. On the outer surface of said governor holder a governor gear  53  is provided to mate with the crank gear  30 . By the rotation of the crank shaft  3 , said governor gear  53  is rotated. 
         [0055]    On the governor holder  52 , a set of fly weights  68  for speed control of the engine is provided. The fly weights  68  are pivotably inserted by pin to the governor holder  52 . 
         [0056]    As shown in  FIG. 2 , the end of the fly weight  68  attaches to a slide piece  69 . The slide piece  69  is supported to slide on the governor shaft  51 . 
         [0057]    When engine runs, the fly weight  68  is spread outwardly by centrifugal force and pushes the slide piece  69  to slide. On the other end of the slide piece  69 , a contact face  72  is provided to contact the lever  73 , which is affixed by a rotatable shaft  74 . 
         [0058]    The shaft  74  is pivotably provided on the wall of cylinder  1 . Rotation of said shaft  74  controls engine speed with said carburetor  10 . 
         [0059]      FIGS. 3 and 4  show another embodiment of the present invention.  FIG. 3  corresponds to  FIG. 1  and  FIG. 3  corresponds to  FIG. 4 . The difference between  FIG. 1  and  FIG. 3  and between  FIG. 2  and  FIG. 4  is location and construction of pumps and speed governors. 
         [0060]    A cam chamber cover  55  is attached to the wall of the cylinder  90 . An end of the camshaft  32  is journaled to the wall of cylinder bore  2  of the cylinder  90 . The other end of said cam shaft  32  is journaled to a cam chamber cover  55 . An end of the pivot pin  36  is supported at the wall of cylinder bore  2  and the other end of said pivot pin is supported by the cam chamber cover  55 . Cylinder  90  and cam chamber cover define a cam chamber  18 . 
         [0061]    In  FIGS. 3 and 4 , a trochoid pump  43  is placed at the wall of lower case  91 . Said pump  43  has an inner rotor  44  and outer rotor  45 . A pump cover  54  is placed at the wall of the lower case  91  and covers the inner rotor  44  and the outer rotor  45 . As illustrated in FIGS.  3 , 4  and  5 , a governor shaft  51  parallel to the crank shaft axis  92 , is provided on said pump cover  54  to compose a speed control governor. 
         [0062]    A governor holder  52  is installed on said governor shaft  51  to be able to rotate. On the outer surface of said governor holder a governor gear  53  is provided to mate with the crank gear  30 . By the rotation of the crank shaft  3 , said governor gear  53  is rotated. 
         [0063]    On the governor holder  52 , a set of fly weights  68  for speed control of the engine is provided. The fly weights  68  are pivotably inserted by pin to the governor holder  52 . The governor holder  52  is connected to the inner rotor  44  of said pump and drives the inner rotor  44  and the outer rotor  45  is rotated following the rotation of the inner rotor  44 . 
         [0064]    Lubrication oil is inhaled from a passage  46 , which is extended to the crank shaft cover  93 . 
         [0065]    An end of the passage  46  leads to the oil entrance of the pump. The other end of passage  46  is connected to an oil entrance at oil reservoir  20  or  21 . 
         [0066]    In the vertical shaft engine as illustrated in  FIG. 3 , the entrance of the oil passage  46  is dipped in the oil in the oil reservoir  20  within a certain inclination range of the power shaft from the normal position, because the oil passage  46  is substantially horizontal at the normal position. 
         [0067]    In the horizontal shaft engine as illustrated in  FIG. 4 , although oil passage  46  is substantially vertical at the normal position, the entrance of the oil passage  46  is dipped in the oil in the oil reservoir  21  within a certain inclination range of the power shaft from the normal position. 
         [0068]    The pump  43  and the cylinder  90  can be commonly used between the vertical shaft engine as in  FIG. 3  and the horizontal shaft engine as in  FIG. 4 . 
         [0069]    The oil pushed out by the pump  43  is lead simultaneously to a hole  49  at the cylinder wall and to a hole  94  formed in the outer wall of the cam shaft  32  and a hole  95  in the cylinder  90  through an inner through hole  48  of the camshaft  32  and into the cylinder bore  2  as illustrated in  FIG. 3  and  FIG. 4 . 
         [0070]    In the embodiments of the present application illustrated in  FIG. 3  or  4 , a gear pump or a vortex pump may be used. 
         [0071]    It is believed that small light-weight four cycle engines made in accordance with the present invention will be particularly suitable for use with utility power tools having a horizontal or vertical power shaft and is sufficiently manufactured to use common parts between vertical and horizontal shaft engines. In the prior art, U.S. Pat. No. 6,250,273 to Ryuu et al. discloses a prior art utility engine for horizontal and vertical shaft orientations. However, constructions are complicated because a speed controlling system having inclined shaft to a crankshaft or a camshaft are necessary for lubrication and speed control. Further, the side cover which supports a cam shaft and a governor shaft is large sized and the mating plane to the cylinder block is inclined, so that machining procedure is complicated and manufacturing cost is expensive. 
         [0072]    On the other hand, present inventions as illustrated in  FIGS. 1 ,  2 ,  3  and  4 , any inclined speed governor shaft is not necessary. 
         [0073]    Further, in the embodiment illustrated in  FIGS. 1 and 2 , because the governor shaft is provided in the lower case, none of additional parts such as the side cover in the prior art, U.S. Pat. No. 6,250,273 to Ryuu et al., is necessary to support the governor shaft. 
         [0074]    Further, in the embodiment illustrated in  FIGS. 3 and 4 , the part to support the governor system is significantly smaller sized than the previous art, U.S. Pa. No. 6,250,273 to Ryuu et al. 
         [0075]    Further, in the embodiment illustrated in  FIGS. 3 and 4 , because the inhale passage of oil from oil reservoir to the pump in vertical shaft usage is short, no priming instrument for the pump as in used in the prior art such as U.S. patent application Ser. No. 12/954,945 by Kurihara et al. or U.S. patent application Ser. No. 13/286,323 by Kurihara et al., is necessary. 
         [0076]    Further, in the present invention, as illustrated in  FIGS. 1 ,  2 ,  3  and  4 , the governor holder  52  is not dipped in the lubrication oil, so that it does not agitate or heat the oil during normal operation. Lubrication is effectively done concentrating to adequate portion using a pump and the through hole in the cam shaft. 
         [0077]    While the present invention is discussed in relation to the engine to be used with a small utility engine for stationary power tools, a person having ordinary skill in the art will readily realize that it can be also used with hand-held power tools or larger power equipment. 
         [0078]    Other parts not specifically referenced to in the foregoing relate to conventional four-cycle engines. A spark plug  82  is installed in a spark plug hole formed in the cylinder head. A coil  83  is an ignition coil. A re-coil starter, not shown, having a re-winding rope is provided at a side of a flywheel  84 , which inhales cooling air for the engine generated by rotation of blade  85  on the flywheel  84 . 
         [0079]    In vertical shaft engines as shown in  FIG. 1  or  FIG. 3 , since oil entrance passage  46  is always dipped in the oil in the oil reservoir  20 , lubricating oil is immediately inhaled to the oil pump  43  by rotation of the rotors  44 ,  45  through oil passage  46 . The lubricating oil pressurized by the trochoid pump is sent into the cylinder or the valve train and lubricates moving parts of the engine. 
         [0080]    In horizontal shaft engines such as those of  FIG. 2  or  FIG. 4 , because oil entrance of the passage  46  is always dipped in the oil in the oil reservoir  21 , lubricating oil pressurized by the trochoid pump is sent into the cylinder or the valve train and lubricates moving parts of the engine. 
         [0081]    The breathing system works by the check valve  58  and pressure in the crankcase chamber  19  is kept normal during operation.