Abstract:
An internal combustion engine includes a cylinder structure in which a crankshaft assembly is journalled for rotation about a main axis of a main crankshaft segment having a main axis. A crank web is attached to the main crankshaft segment and projects from the main crankshaft segment, and a crank pin structure is attached to the crank web and has a central axis that is parallel to the main axis and is spaced from the main axis by a distance D. A first mechanism attaches the inner end of a connecting rod to the crank pin structure and permits substantially longitudinal movement of the connecting rod relative to the crank pin structure. A second mechanism permits selective adjustment of the distance D. The second mechanism is coupled to the first mechanism in a manner such that an increase in the distance D is associated with longitudinal movement of the connecting rod toward the central axis of the crank pin structure and a decrease in the distance D is associated with longitudinal movement of the connecting rod away from the central axis of the crank pin structure.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a variable displacement mechanism for an internal combustion engine. 
         [0002]      FIGS. 1 and 1A  illustrate in simplified form a conventional radial engine. The engine shown in  FIGS. 1 and 1A  comprises a main cylinder structure  2  defining five cylinders  4  and journaling a crankshaft  6 . Five pistons  8  are fitted in the cylinders respectively and are connected to the crankshaft by respective connecting rods  10 . As the pistons reciprocate in the cylinders in phased relationship, the crankshaft rotates relative to the main cylinder structure. 
         [0003]    The stroke of the piston depends on the eccentricity of the crankshaft. In the conventional radial engine, the eccentricity of the crankshaft, and hence the stroke of the piston, is fixed. 
         [0004]    The power output and fuel consumption of an internal combustion engine depends on the engine displacement, i.e. the volume that is swept by the pistons during one complete cycle. In order to minimize fuel consumption, it would be desirable to be able to adjust the displacement of an internal combustion engine depending on operating conditions. 
         [0005]    One approach to adjusting the engine displacement depending on operating conditions has been to interrupt fuel supply to one or more cylinders in low load conditions so that combustion takes place in fewer than all the cylinders of the engine. This and other approaches to varying engine displacement have not generally met commercial success. 
       SUMMARY OF THE INVENTION 
       [0006]    According to a first aspect of the present invention there is provided an internal combustion engine comprising a cylinder structure defining a combustion cylinder having a central axis, a piston fitted slidingly in the combustion cylinder for reciprocation therein, a crankshaft assembly including a main crankshaft segment having a main axis, a crank web that is attached to the main crankshaft segment and projects from the main crankshaft segment, and a crank pin structure that is attached to the crank web and has a central axis that is parallel to said main axis and is spaced from said main axis by a distance D, the crankshaft assembly being journalled in the cylinder structure for rotation about said main axis, an elongate connecting rod extending substantially radially of the crank pin structure and having an outer end attached to the piston and also having an inner end, a first mechanism attaching the inner end of the connecting rod to the crank pin structure, whereby reciprocation of the piston induces rotation of the crankshaft structure about said main axis, and a second mechanism for selectively adjusting the distance D, and wherein the first mechanism permits substantially longitudinal movement of the connecting rod relative to the crank pin structure, and wherein the second mechanism is coupled to the first mechanism in a manner such that an increase in the distance D is associated with longitudinal movement of the connecting rod toward the central axis of the crank pin structure and a decrease in the distance D is associated with longitudinal movement of the connecting rod away from the central axis of the crank pin structure. 
         [0007]    According to a second aspect of the present invention there is provided a radial-piston internal combustion engine comprising a cylinder structure defining a primary combustion cylinder and a plurality of secondary combustion cylinders, each combustion cylinder having a cylinder axis extending radially of a central axis and the cylinder axes being angularly spaced from each other about the central axis, a primary piston fitted slidingly in the primary combustion cylinder for reciprocation therein, a plurality of secondary pistons fitted slidingly in the secondary combustion cylinders respectively for reciprocation therein, a crankshaft assembly including a main crankshaft segment having a main axis that coincides with the central axis of the cylinder structure, a crank web that is attached to the main crankshaft segment and projects from the main crankshaft segment, and a primary rod journal that is attached to the crank web and has a central axis that is parallel to said main axis and is spaced from said main axis by a distance D, the crankshaft assembly being journalled in the cylinder structure for rotation about said central axis, a primary connecting rod extending substantially radially of the primary rod journal and having an outer end attached to the primary piston and also having an inner end, a first mechanism attaching the inner end of the connecting rod to the primary rod journal, whereby reciprocation of the primary piston induces rotation of the crankshaft assembly about said central axis, a plurality of secondary connecting rods connecting the secondary pistons respectively to the primary rod journal, and a second mechanism for selectively adjusting the distance D, and wherein the first mechanism permits movement of the primary connecting rod relative to the primary rod journal substantially radially of the primary rod journal, and wherein the second mechanism is coupled to the first mechanism in a manner such that an increase in the distance D is associated with movement of the primary connecting rod toward the central axis of the primary rod journal and a decrease in the distance D is associated with movement of the primary connecting rod away from the central axis of the primary rod journal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: 
           [0009]      FIG. 1  is a schematic view of a conventional radial engine, 
           [0010]      FIG. 1A  is a sectional view taken on the line A-A of  FIG. 1 , 
           [0011]      FIG. 2  is a sectional view of the crankshaft of an internal combustion engine embodying the present invention, 
           [0012]      FIG. 3  is a partial end view illustrating the spindle post and two connecting rods, and 
           [0013]      FIGS. 3A and 3B  are sectional views taken on the lines A-A and B-B of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 2  illustrates a crankshaft for use in a radial engine comprising a main cylinder structure (not shown) defining five cylinders containing respective pistons. The crankshaft  6  converts reciprocating movement of the pistons in the cylinders to rotation of the crankshaft. 
         [0015]    The crankshaft  6  is a composite assembly including a main crankshaft segment  8 , a crank web  10  and a pin  12 . The crankshaft is journalled for rotation in the main cylinder structure about the central axis of the main crankshaft segment  8 . The crankshaft  6  is provided with a means, such as a gear  14 , for coupling power to a consuming device (not shown). 
         [0016]    The crankshaft segment  8  is hollow and accommodates a ramp housing  18  that is slidable axially within the crankshaft segment  8  but is restrained against rotation relative to the segment  8 . 
         [0017]    The outer end of the crankshaft segment  8  (the right end as seen in  FIG. 2 ) is provided with a sleeve bearing  22 . The outer end of the ramp housing accommodates a ball thrust bearing  24 , which is aligned with the slide bearing  22 . A cylindrical operating shaft  28  is secured to the ball thrust bearing  24  by a bolt  26  and extends through the slide bearing  22  and is coupled to an adjustment mechanism (not shown) for displacing the operating shaft axially relative to the crankshaft segment  8 . The adjustment mechanism may be, for example, hydraulic or electromechanical. 
         [0018]    At its inner end (the left end seen in  FIG. 2 ), the crankshaft segment  8  is attached to the crank web  10  and contains a lever support insert  30 . The lever support insert  30  is stationary relative to the crankshaft  6  and includes two transverse mounting walls  32  (only one of which is shown) which are parallel and are spaced from each other and are located to opposite sides of the central axis of the crankshaft segment  8 . A lever  34  is disposed between the walls  32  and is pivotable relative to the insert  30  about a fulcrum pin  36  that is supported in the walls  32 . A pin  38  is attached to the outer (right) end of the lever and projects to opposite sides of the lever. 
         [0019]    The ramp housing  18  is pocketed at its inner (left) end and has two interior walls  40  formed with parallel ramp slots  42  in which the ends of the pin  38  are fitted and are able to slide. Thus, as the operating shaft  28  is moved axially relative to the crankshaft, the ramp housing moves axially of the crankshaft segment  8  and the pin  38  moves along the ramp slots. The lever  34  turns in the clockwise direction in the case of the operating shaft moving to the right relative to the crankshaft segment  8  and conversely if the operating shaft moves to the left, the lever turns in the counterclockwise direction. 
         [0020]    At its left end, as seen in  FIG. 2 , the lever  34  projects through an opening in the crankshaft web  10  and is provided at its projecting end with a ball or knob  44 . The crankshaft web  10  includes a base  46  that is attached to the crankshaft segment  8  and a dovetail tenon  48  projecting from the base and extending perpendicular to the axis of rotation of the crankshaft. A gear rack  50  is attached to the base  46  and extends parallel to the dovetail tenon  48 . 
         [0021]    The crank pin  12  includes a primary rod journal  52  formed with a dovetail groove in which the dovetail tenon  48  slides, whereby the primary rod journal  52  is movable linearly relative to the crankshaft segment  8  perpendicular to the axis of rotation of the crankshaft. The primary rod journal is also formed with a recess that receives the ball  44 . Engagement of the ball in the recess transmits pivotal movement of the lever  34  to the primary rod journal. When the lever turns in the clockwise direction due to movement of the operating shaft  28 , the primary rod journal  52  slides outward (relative to the central axis of the main crankshaft segment) along the dovetail tenon and conversely when the lever turns in the counterclockwise direction the primary rod journal slides inward along the dovetail slide. 
         [0022]    The primary rod journal  52  is formed with a pocket that is traversed by a pinion shaft  54  extending perpendicular to both the dovetail groove and the axis of rotation of the crankshaft. A pinion  56  mounted on the shaft  54  meshes with the gear rack  50 . When the primary rod journal  52  moves out (or in) along the dovetail slide, engagement of the gear rack  50  and pinion  56  causes clockwise (or counterclockwise) rotation of the pinion  56 . 
         [0023]    The primary rod journal  52  is formed with a bore that communicates with the pocket. A spindle post  60  is slidable in the bore parallel to the central axis of the crankshaft segment  8 . The spindle post is formed with a clearance slot for receiving the pinion  56  and is provided at the base of the slot with a gear rack  62  that meshes with the pinion  56 . When the primary rod journal  52  moves outward along the dovetail slide, the pinion  56  turns in the clockwise direction and consequently the spindle post  60  moves to the left of  FIG. 2 . Conversely, when the primary rod journal moves inward, the spindle post moves to the right. 
         [0024]    The left end of the spindle post is provided with ball thrust bearings  64 , which are secured to the spindle post by a bolt  66  and a washer and support a multifaced gear rack  68  having five faces, each provided with a gear rack segment. The bearings  64  allow relative rotation of the gear rack  68  and spindle post  60 . 
         [0025]    A primary rod assembly  70  is mounted on the primary rod journal  52  by a primary rod assembly journal bearing  71 , which allows relative rotation of the primary rod assembly  70  and primary rod journal  52 . The primary rod assembly  70  includes a hollow cylindrical pedestal support plate  72  and a 5-station (one primary and four secondary) base plate  74  attached to the pedestal support plate. 
         [0026]    The five stations of the base plate  74  are associated with the five cylinders respectively of the engine. Each piston is provided with a connecting rod  76 . One of the connecting rods is designated the primary connecting rod  76 P; the other four connecting rods are secondary connecting rods  76 S. The primary connecting rod is rigidly attached at its inner end to a primary connecting rod carriage  78 P. Each secondary connecting rod is attached at its inner end to a secondary connecting rod carriage  78 S by a bearing that allows pivotal movement of the connecting rod  76 S relative to the connecting rod carriage  78 S about an axis that is parallel to the axis of rotation of the crankshaft. The five stations of the base plate accommodate the five connecting rod carriages  78  respectively and each station permits sliding radial movement of the carriage relative to the base plate. The pedestal support plate  72  and the base plate  74  include formations  80  that guide movement of the connecting rod carriage relative to the base plate. 
         [0027]    Each connecting rod carriage  78  includes a gear rack  82 . At each station the pedestal support plate  72  includes sidewalls  80  that project to the left of the carriages and support a shaft  84  on which a two-sector gear  86  is mounted for rotation about an axis that is radially spaced from, and perpendicular to, the central axis of the spindle post  60 . The two-sector gear has one sector that engages the gear rack  82  and another sector that engages one face of the gear rack  68 . The two-sector gear  86  converts axial movement of the post  60  to radial movement of the connecting rod carriages  78 . Thus, in the event that the post  60  moves to the left of  FIG. 2 , the connecting rod carriages are displaced radially inward relative to the central axis of the post  60  and conversely if the post  60  moves to the right, the connecting rod carriages are displaced radially outward. 
         [0028]    In operation of the engine, the connecting rod carriages  78  remain stationary relative to the central axis of the post  60  as long as the operating shaft  28  remains stationary relative to the crankshaft segment  8 . 
         [0029]    Suppose the operating shaft is in the position shown in  FIG. 2  and accordingly the lever  34  is aligned with the crankshaft segment  8 . The primary piston is at top dead center of its range of reciprocation. The crown of the primary piston is at a distance T from the central axis of the shaft segment  8 . The eccentricity E 0  of the crankshaft is equal to the distance between the central axis of the post  60  and the central axis of the shaft segment  8 . When the crankshaft has turned through 180°, the primary piston is at bottom dead center and the crown of the piston is at a distance T−2E 0  from the central axis of the crankshaft segment  8 . The range of movement of the crown of the piston is thus equal to 2E 0 . Now suppose the operating shaft  1  is moved in the direction of the arrow and, through the action of the ramp slots  42  and lever  34 , the primary rod journal is moved radially outward by a distance e and consequently the eccentricity of the crankshaft changes to E 0 +e. Due to the interaction of the gear rack  50  and gear rack  62  through the pinion  56 , the spindle post  60  is displaced axially by a distance e and due to the interaction of the multifaced gear rack  68  and the gear rack  82  through the two-sector gear  86 , the primary connecting rod carriage  78 P is displaced radially inward by a distance e. At top dead center, the crown of the primary piston is at a distance T from the central axis of the crankshaft segment  8 , and the range of movement of the crown of the primary piston is from T to T−2*(E 0 +e). It will be appreciated that action at the four secondary stations is similar to that at the primary station. Thus, the mechanism shown in  FIG. 2  allows the stroke of the pistons to be selectively varied by axial movement of the operating shaft  28  without changing the top dead center position of the pistons. 
         [0030]    It will be appreciated that the invention is not restricted to the particular embodiment that has been described, and that variations may be made therein without departing from the scope of the invention as defined in the appended claims and equivalents thereof. For example, if the radius of the sector of the gear  86  that engages the rack  82  were different from the radius of the sector that engages the teeth of the multifaced gear rack  68 , the interaction of the multifaced gear rack  68  and racks  82  through the two-sector gear segments  86  would result in movement of the connecting rod carriages  78  by an amount that is not equal to the displacement of the primary rod journal  52  along the dovetail slide. In addition, the invention is not restricted to use of a ramp and lever mechanism for converting axial movement of the operating shaft  28  to radial movement of the crank pin  12 , since other mechanisms, such as a rack and pinion mechanism similar to that employed for converting radial movement of the primary rod journal to axial movement of the spindle post, may be used instead. Moreover, the invention is not restricted to use with a radial engine. Unless the context indicates otherwise, a reference in a claim to the number of instances of an element, be it a reference to one instance or more than one instance, requires at least the stated number of instances of the element but is not intended to exclude from the scope of the claim a structure or method having more instances of that element than stated.