Abstract:
An apparatus for providing two features that improve fuel economy of four stroke internal combustion engines. The first is the provision of a compression ratio which is higher than normal when the engine is operating at light load; and which varies from very high at idling, down to normal at full power. This is effected by a movable piston associated with the inlet valve and connected to the throttle. The second is the provision of variable timing as well as a variable amount of opening of the inlet valve, such that at idle, the valve opens at top center of the main piston, opens only a fraction of its full lift, and closes about 70° crankshaft past top center. As the throttle is opened, the inlet valve opens farther at each open excursion to create as little flow resistance as possible to the inlet draw. At the middle of its open excursion during each valve actuation it moves in the same direction as the crankshaft enough that as the open duration becomes greater, the valve always begins to open as the main piston starts its inlet stroke, but closes later. Finally, at full power, the inlet valve begins to open slightly before the main piston comes to top center, opens fully, and closes somewhat after the main piston has reached bottom center and has started the compression stroke.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the filing date priority of Provisional Patent Application No. 61/002,212, filed Nov. 6, 2007. 
     
    
     FEDERALLY SPONSORED RESEARCH 
       [0002]    Not applicable. 
       SEQUENCE LISTING, ETC ON CD 
       [0003]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    This invention relates to internal combustion engines which have one or more power pistons that reciprocate in one or more cylinders. In particular, the invention relates to engines of this type that operate on a four-stroke cycle in which the power pistons cyclically undergo fuel inlet strokes, compression strokes, expansion strokes and exhaust strokes. More particularly, the invention relates to inlet valves and valve operating components which admit a fuel and air mixture into the cylinders of engines of this type. This invention may be considered an improvement over my prior patent U.S. Pat. No. 6,672,270, issued Jan. 6, 2004, which is incorporated herein by reference in its entirety. 
         [0006]    2. Description of Related Art 
         [0007]    Fuel efficiency may be defined as pounds of fuel consumed per horsepower hour of work delivered. The fuel efficiency of most engines of the above identified type varies greatly as a function of power output or engine speed. Efficiency is highest when the engine is operating at or near its full power output and at a steady speed. Efficiency decreases when the engine is operated at reduced power outputs. Many uses of such engines require that power output be reduced much of the time. This is most notably the case with automobile engines. Automobile engines are designed to provide for occasional periods of high power output. This is needed, for example, to accelerate the vehicle on freeway on-ramps or while passing other vehicles or to maintain speed on an upgrade. Power output is reduced when the vehicle is cruising at a steady speed on a freeway or highway or is slowed by traffic conditions. Power output ceases when the vehicle is temporarily stopped with the engine idling. 
         [0008]    The practical result of these factors is that most conventional automobile engines operate with reduced fuel efficiency much of the time. This increases operating cost, unproductively consumes fuel resources and has adverse effects on efforts to reduce emission of pollutants into the environment. 
         [0009]    This problem arises in part as the typical automobile engine is designed to have a low compression ratio that provides for optimum performance when the engine operates at or near full power output. A higher compression ratio would provide greater efficiency during the periods when the engine is being operated at reduced power output but, in the conventional engine, the high ratio causes overly rapid fuel burning resulting in detonation or “knocking” at times when the engine must be operated at or near maximum power output. Fuel detonation severely strains engine components, creates unacceptable noise and drastically reduces engine efficiency. 
         [0010]    It has heretofore been recognized that more efficient overall operation can be realized by designing the engine to have a compression ratio which varies as a function of engine load. Compression ratio can be high when the load is light as detonation is not a problem under that condition. In engines which operate on the Atkinson cycle, a mechanism is provided which varies the length of travel of the power pistons in the cylinders so that the inlet stroke is much shorter than the power or expansion stroke. Some prior engines have auxiliary pistons which reciprocate in chambers that are communicated with the power piston cylinders. Auxiliary piston movement varies the compression ratio in response to changes of engine load. The auxiliary pistons take up a substantial amount of space in the combustion chambers. This requires that the inlet and exhaust valves be smaller than would be desirable for optimum breathing capacity. Engines of these prior kinds require bulky additional components which substantially complicate the engine and which are very prone to rapid wearing. 
         [0011]    Although Miller cycle internal combustion engines vary the compression ratio as a function of power output and do not suffer from the drawbacks described above, However, the mode of operation of prior Miller cycle engines requires the effective size of the combustion chamber to be relatively small, resulting in low power output per liter of piston displacement. 
         [0012]    The fuel inlet valves and valve operating mechanism of prior Miller cycle engines are not designed to resolve other problems which also adversely affect fuel efficiency. For example, the operator controls the speed and power output of a conventional engine with a throttle valve which is situated in the flow path of the air and fuel. The engine must expend power in order to draw the mixture through the flow path constriction formed by the throttle valve. This throttling loss is a function of the product of the flow rate through the throttle valve and the pressure difference between the upstream and downstream side of the valve. Throttling loss is minimal when the engine operates at maximum power as the pressure difference across the fully open valve is minimal. The throttling loss is also minimal when the engine is operating at or near idling speed as the flow rate through the valve is minimal at that time. Throttle loss rises substantially and may consume as much as 30% of the engine power at the intermediate region of the engines output power range. As has been pointed out above, automobile engines operate within this intermediate power region much of the time. Elimination of the throttle and its attendant losses would substantially increase fuel efficiency of the engine. 
         [0013]    A further factor is the increasing use of ethanol as an additive (or significant constituent) to the gasoline fuel. It has been observed that spontaneous detonation of the fuel charge in the combustion chamber, otherwise known as knocking, can result in power loss and even damage to the engine. Although ethanol additives are known to reduce spontaneous detonation, the alcohol has less energy density than gasoline, resulting in reduced power and fuel efficiency. It is very desirable to derive the maximum efficiency from this fuel mixture in order to realize the economy of ethanol-based fuels. 
       BRIEF SUMMARY OF THE INVENTION 
       [0014]    The present invention comprises method and apparatus for providing three features aimed at improving fuel economy of four stroke internal combustion engines. The first of these features is the provision of a compression ratio which is higher than normal when the engine is operating at light load; and which varies from very high at idling, down to normal at full power. This is effected by a movable piston in the combustion chamber connected to the throttle. 
         [0015]    The second of these features is the provision of variable timing as well as a variable amount of opening of the inlet valve, such that at idle, the valve opens at top center of the main piston, opens only a fraction of its full lift, and closes about 70° crankshaft past top center. As the throttle is opened, the inlet valve opens farther at each open excursion to create as little flow resistance as possible to the inlet draw. The middle of its open excursion during each valve actuation moves in the same direction as the crankshaft enough that as the open duration becomes greater, the valve always begins to open as the main piston starts its inlet stroke, but closes later. Finally, at full power, the inlet valve begins to open slightly before the main piston comes to top center, opens fully, and closes somewhat after the main piston has reached bottom center and has started the compression stroke. 
         [0016]    A third feature of the invention is the provision of a mechanism that separates the function of variable timing of the inlet valve from the variable compression ratio function, thereby providing greater control and efficiency. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0017]      FIG. 1  is a cross-sectional elevation of a cylinder and cylinder head of an internal combustion engine, showing the variable compression and variable inlet valve timing mechanism of the present invention. 
           [0018]      FIG. 2  is a cross-sectional elevation as in  FIG. 1 , showing additional portions of the variable compression and variable inlet valve timing mechanism. 
           [0019]      FIG. 3  is a cross-sectional elevation of a cylinder and cylinder head of an internal combustion engine, showing another embodiment of the variable compression and variable inlet valve timing mechanism of the present invention. 
           [0020]      FIGS. 4 and 5  are both side elevations of the cam and cam follower of the embodiment of  FIG. 3 , showing the extreme positions of the cam. 
           [0021]      FIG. 6  is a plan view showing the shape of the constant diameter cam, symmetrical about a vertical centerline. 
           [0022]      FIG. 7  is plan view showing the same 80° lift portion as in  FIG. 6 , but as it would appear on a conventional cam. 
           [0023]      FIG. 8  is a graphic depiction of the variable inlet valve operation and a comparison operating arc and opening arc for different engine load conditions, and 
           [0024]      FIG. 9  is a plan elevation depicting the geometric features of the rocker cam of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The present invention generally comprises an improvement for internal combustion engines. With regard to  FIG. 1 , a typical internal combustion reciprocating engine  12  has one or more cylinders  13  in which power pistons  17  reciprocate and which operate on a four stroke cycle in which the pistons repetitively undergo fuel inlet strokes, compression strokes, expansion strokes and exhaust strokes. Engines  12  of this type have one or more fuel inlet valves  14  and one or more exhaust valves  16  at the head end  18  of each cylinder  13 . This initial example of the invention has a single inlet valve  14  and a single exhaust valve  16  at each cylinder  13 . 
         [0026]    The inlet and exhaust valves  14  and  16  extend within a cylinder head member  19  which is secured to the engine block  11 , a head gasket  21  being disposed between the head member and engine block. Head member  19  and engine block  11  have internal passages  22  through which fluid coolant is circulated in the known manner. 
         [0027]    The exhaust valve  16  may be of the conventional poppet type having a circular head  23  from which a stem  24  extends upward into a recess  26  in cylinder head member  19 . The circular head  23  seats in a conforming circular valve seat  27  at the underside of head member  19  at the end of an exhaust flow passage  28  in the head member. A compression spring  29  seated in recess  26  biases the exhaust valve  16  to the closed position of the valve. The valve actuator mechanism, which will be described in detail below, temporarily opens the exhaust valve  16  during exhaust strokes of the power piston  17 . 
         [0028]    Unlike a typical fuel inlet valve, which is typically a poppet valve type, the invention provides an inlet valve mechanism  14  that is designed to fulfill the objectives of the invention: to vary the compression ratio of the power cylinder in response to load demand, and to vary the timing as well as the open dwell of the inlet valve. With continued reference to  FIG. 1 , the inlet valve mechanism  14  includes a reciprocable piston  33  slidably received in a sleeve  34  that lines the valve bore in the cylinder head and provides a durable wearing surface. A power control shaft (throttle shaft)  31  is supported to extend along the cylinder head, and an eccentric  32  is mounted on the shaft  31  for each cylinder of the engine. The upper end of piston  33  is joined by pin  36  to the eccentric  32  so that the piston  33  is driven to translate in the sleeve  34  toward and away from the combustion chamber. Note that the throttle shaft may be the output of a direct mechanical connection to the driver&#39;s throttle control (e.g., accelerator pedal), but in modern vehicles the shaft  31  typically may be the output of a servo motor that is driven by throttle input sensors, pressure and temperature sensors, and the like. 
         [0029]    As the inner end of the piston moves toward the combustion chamber in response to angular excursions of the power control shaft  31 , the effective volume of the chamber is reduced and the compression ratio is increased accordingly. 
         [0030]    In addition, the inlet valve includes a valve stem  44  which extends through a central opening in the piston  33 , and a circular head  43  is supported at the inner end of the stem  44 . The head  43  is dimensioned to seat in conforming circular valve seat  47  in the underside of head member  19  at the end of inlet flow passage  48  in the head member. A compression spring  49  is seated in piston  33  to bias the valve stem outwardly and maintain the valve head seated and closed. 
         [0031]    The upper end of piston  33  is provided with a transverse slot  50  extending generally diametrically into the outer end thereof, in which the lower end of eccentric strap  32  is secured by pin  36 . In addition, the inlet valve mechanism includes a rocker cam  51  joined in pivoting fashion to the piston  33  by axle  52 . Rocker cam  51  impinges on the flat confronting surface  54  of cam follower  53 , which impinges on the valve stem. Drive pin  56  is located on an eccentric lobe of rocker cam  51  to rock the cam back and forth on its engagement with the flat surface  54 , under the direction of a mechanism described below. The rocker cam  51  has a unique profile which begins at the left edge (in  FIGS. 1 and 9 ) with a portion  57  having a constant radius R 1 , that provides zero lift (opening motion) to the valve stem. It transitions smoothly into an increasing radius portion  58  that provides increasing lift with rocker displacement through an angle of about 60°. At the opposed end of the portion  58  is a cam surface portion  59  having a constant radius R 2 . 
         [0032]    The rocker cam  51  provides functionality that is not known to be achievable with a rotating cam. This is due in part to the conformation of the camming surface portions  57 - 59 , and in part to the fact that the cam  51  is designed to rock back and forth rather than rotate, and the rocking action can be controlled as described below. Moreover, the reversal of direction that is inherent in the rocking motion may occur at differing valve timing positions, leading to a more flexible and controllable inlet valve action. The cam portion  57  provides no valve lift through a substantial arc, and transitions smoothly into portion  58 , which provides increasing lift as the cam rotates clockwise. The cam surface  59  at the maximum lift end of portion  58  is also a constant radius, so that the valve may remain fully open even when the cam travels past the point of maximum lift. 
         [0033]    With regard to  FIG. 2 , the inlet valve mechanism further includes a bell crank  61  that rotates about a fixed pivot  62 . The triangular bell crank  61  is tied at one vertex to link  63  that is in turn connected to eccentric  32 . Thus as eccentric  32  is rotated counterclockwise about shaft  31 . link  63  pulls upward on bell crank  61  and rotates the bell crank clockwise about pivot  62 . The third vertex of crank  61  is rotatably pinned to link  64  extending laterally to join a roller lever yoke  66 , that is rotatably secured on spinning camshaft  67 . Consequently, as link  64  is pulled leftward by the crank  61 , the roller lever yoke  66  is rotated clockwise about camshaft  67 . Roller lever  68  is pivotably pinned on its yoke  66 , and supports a cam following roller  71  that is engaged by a single lobe cam  72  mounted on camshaft  67 . Roller lever  68  includes a cam surface  73  disposed to impinge on lever  74  that is pivotally secured by axle  76 . The free end of lever  74  is secured by an adjustable threaded connection  77  to link  78 , which in turn is pivotally pinned at its opposite end to the pin  56  of the lobe of rocker cam  51  (see also  FIGS. 1 and 9 ). Spring  79  bears continuously on lever  74  to keep the roller in lever  68  against the cam  72  and prevents play from developing in the system. 
         [0034]    As noted above, link  64  is pulled leftward by bell crank  61  when the throttle shaft  31  is rotated counterclockwise, and roller lever yoke  66  is rotated clockwise about camshaft  67  (in the same direction as the rotation of camshaft  67 ). This causes roller lever  68  to be drawn clockwise about the center of camshaft  67 , in the direction of decreasing phase angle, and cam surface  73  to move closer to fixed pivot  76  along the surface of lever  74 . Thus, as cam lobe  72  engages the roller and pushes cam surface  73  rightward, lever  74  moves further, pulling further on link  78  and causing rocker cam  51  to turn further on axle  52  in a clockwise direction, pushing down further on cam follower  53  and opening the inlet valve further. Thus the inlet valve is opened slightly earlier and is closed significantly later (than it would be in a position of lower power output). This means that the opening time of the inlet valve retards (occurs later in time). With reference to  FIG. 8 , the net effect on the valve timing is depicted graphically. Note that the inlet valve actuation is shown for idle, intermediate, and wide open (full throttle) engine operation. Also, the opening arc and operating arc for each engine setting are depicted. The difference in opening and operating arcs is found in the “overtravel” of the rocker cam  51 ; that is, the rocker cam always starts within the closed, zero lift zone  57 , and can travel a variable distance to the lift portion  58  and then reverse, or travel all the way to the fully lifted portion  59  before reversal. The overtravel may occur in the zero lift areas  57  and  59  when the valve is fully open or fully closed. The opening arc is thus always narrower than the operating arc, due to the dwell time on the zero lift portions 
         [0035]    Thus, with reference to  FIG. 8 , the idle opening arc (as the rocker cam moves from portion  57  to  58 ) is much narrower than the idle operating arc, which includes all of the zero lift portion  57  as well. Both are relatively narrow compared to the other engine settings. Likewise, the intermediate operating arc begins in a slightly retarded timing, and is much wider that the idle operating arc, due to the fact that the rocker cam moves much farther onto the lifting surface  58  during intermediate engine speed. Similarly, the wide open operating arc is even more retarded in time, and extends through a much wider angle. The threaded connection  77  enables adjustment to obtain optimum valve motion at the time of assembly. The working surface of lever  74  may be contoured to obtain optimum combinations of valve timing and open duration throughout the power range. 
         [0036]    To summarize the operation of the invention, As the throttle is opened by moving eccentric  32  counterclockwise, three things occur together: 
         [0037]    1) Piston  33  rises, increasing the volume of the combustion chamber, thereby lowering the compression ratio; 
         [0038]    2) The inlet valve opens further according to the action of rocker cam  51  operated by the mechanism described with particular reference to  FIG. 2 ; 
         [0039]    3) The inlet valve opens slightly earlier and closes substantially later, relative to other events in the engine, so that the period of an open duration retards. 
         [0040]    Note that the exhaust valve is driven by the camshaft  67  in any manner known in the prior art, and that operation is not affected by the presence and operation of the present invention. 
         [0041]    It may be appreciated that in the mechanism of  FIGS. 1 and 2  the variation in compression ratio is linked (literally and figuratively) with the variation of inlet valve timing, through the use of the bell crank  61  connected to the eccentric  32  that also operates the piston  33 . With regard to  FIG. 3 , a further embodiment of the invention is designed to achieve the same results as the previous embodiment, while also providing independent control of the compression ratio variation and the inlet valve timing and dwell. In doing so it also eliminates the closing bias spring  49  of the inlet valve mechanism. The advantage of this configuration is not only that the timing and magnitude of the variation in compression ratio is independent of the timing of the inlet valve opening and duration, but also that the friction between rocker cam  51  and follower  53  as well as the friction between follower  63  in its bore in piston  33  is very much reduced, requiring less work to be done by cam  72 . 
         [0042]    The embodiment of  FIG. 3  employs many of the components described in the previous embodiment, which are labeled with corresponding reference numerals having a prime (′) suffix. In this embodiment the throttle shaft  31 ′ is actuated by a servomotor that is driven by a computer. The computer calculates a desired compression ratio based on inputs such as pressure, temperature, engine speed, load, accelerator position, and the like, and rotates the shaft  31 ′ accordingly. In addition, the inlet valve timing and lift control mechanism is driven by another servomotor that is driven by a different computer signal, based on a calculation of optimum inlet valve timing and duration. The second servomotor is connected to rotate shaft  80 , which supports an eccentric  85  that is linked to roller lever yoke  66 ′. As a result, rotation of the shaft  80  rotates the roller lever yoke  66 ′ in the same manner as did bell crank  61  in the previous embodiment, except that the servomotor actuation of shaft  80  is independent of the servomotor actuation of shaft  31 ′. 
         [0043]    Furthermore, the previous rocker cam and its cam follower and the spring  49  are eliminated. The inner end of inlet valve stem  44 ′ is secured to box-type cam follower  81  that is operatively engaged with a cam  82  that is secured to piston  33 ′ by axle  83 . Cam follower  81  includes a coffer-like recess  84  that opens upwardly and receives the cam  82  therein, and a cam seat  86  is pivotally connected to the left vertical side of cam follower  81  and disposed to span the opening of the coffer recess  84 . A cap screw  95  extends through the free end of cam seat  86  to the right side of the cam follower  81  and secures a helical spring  96  that bears on the seat  86 . Link  78 ′ is fashioned as a pair of parallel rods that are connected to lever  74 ′ at one end by an eccentric bushing  90  that enables length adjustment of the distance between the lever  74 ′ and the cam  82 . At the other end the links  78 ′ join eccentrically to opposite sides of the cam  82  and cam follower  81  to maintain the cam and follower aligned in the recess  33 ′ in which they are located. It may be appreciated that as the cam  82  reciprocates within the follower  81 , it drives the follower  81  to reciprocate up and down in a direction coaxial with the valve stem  44 ′, opening and closing the inlet valve in response to the mechanism described above with reference to the previous embodiment. The spring  96  pushing down on the seat  86  maintains constant contact with the cam  82  and creates a constant force urging the valve stem upwardly to the closed valve position. 
         [0044]    With regard to  FIG. 4 , the cam  82  is shown rotated counterclockwise about axle  83  to the point of maximum upper travel of the follower  81 , which necessarily drives the valve stem upwardly to the same extent to close the inlet valve. The follower  81  rests on cylindrical portions of the cam  82  and thus is held still, even if the cam should overtravel by some small amount. In  FIG. 5 , the links  78 ′ have pulled the cam  82  approximately 80° clockwise. The follower, which has been driven downwardly to the maximum extent, again rests on cylindrical portions of the cam. Thus  FIGS. 4 and 5  depict the limits of travel of the follower  81 . (Note that the 80° excursion is not mandatory, but may be set empirically or by design to suit an engine layout.) 
         [0045]    The requirements for the shape of cam  82  are simple, and achievable using simple design rules. As shown in  FIG. 6 , the cam has a unique symmetrical profile wherein there is a large radius cylindrical portion  91  and a small radius cylindrical portion  92 . The difference in these two radii is the amount of motion the cam will impart to the box follower (similar to the rocker cam of the previous embodiment). The curved flanks  93  and  94  that connect the large and small radii together area a mirror image of each other about the vertical centerline. Each flank is like one flank of an ordinary valve actuating cam. It has a gentle accelerating portion blending into a maximum velocity part at midpoint, then blending into a gentle deceleration portion, which again joins a cylindrical portion. In all cases the angular separation between the end of one cylindrical portion and the beginning of the next cylindrical portion is approximately 80°. In this way the cam remains in contact with bother upper and lower flat surfaces of the box follower at all times. 
         [0046]    The exact cam flank curvature is not critical as it has only three criteria to meet: 
         [0047]    a) The profile of the rise to its midpoint, where the follower is accelerated to its maximum velocity, must be equal to but opposite in sense from the second half of the rise, which decelerates the follower and brings the follower&#39;s velocity from maximum to zero. 
         [0048]    b) The profile of the follower return flank on the opposite side of the cam must be a mirror image of the follower lift flank on the first side. 
         [0049]    c) The identical but opposite rise and fall flanks are angled apart from each other to the point where the cam&#39;s diameter is constant. 
         [0000]    In this way the cam remains in contact with both upper and lower flat surfaces of the box follower at all times. 
         [0050]      FIG. 7  depicts another possible shape design for cam  82 , showing how the same flanks  93  and  94  would appear on a conventionally configured, single lobe cam, for purposes of illustration only. 
         [0051]    Returning to  FIG. 3 , the threaded end of valve stem  44 ′ screws into the bottom of cam follower  81 . Spring  87  surrounds stop screw  95  which is screwed into the right vertical leg of follower  81 . For reasons familiar to those in engine design, valve  43 ′ must remain firmly against valve seat  47 ′ at all times that cam  82  is not pushing it open. To ensure this condition, at the time of assembly cam  82  is turned so that its small radius cylindrical portion or heel is resting in the bottom of follower  81 . Then valve stem  44 ′ is screwed into follower  81  to the point where a gap  88  opens up to a clearance of approx. 0.012″. Then thread clamp locking screw  89  is accessed through a hole in the side of piston  33 ′ and tightened, locking the assembly in the preferred arrangement. 
         [0052]    The operation of most portions of the embodiment of  FIG. 3  is the same as described with reference to  FIGS. 1 and 2 . That is, the roller lever yoke  68 ′ and roller  71 ′ are driven by the cam  72 ′, and lever  74 ′ and links  78 ′ transfer reciprocal motion to reciprocate the cam  82 . However, the servo shaft  80  rotates to rotate the roller lever yoke about the camshaft  67 ′ to modify the inlet valve timing as described previously. A major difference is that the cam follower  81  drives the inlet valve to open and close due to the rotation of cam  82 , obviating the inlet valve spring  49  and the rocker cam  51 . And, the operation of piston  33 ′ to alter the compression ratio of the power cylinder is entirely separate from the operation of roller lever yoke  68 ′ and its control of the inlet valve timing and duration of opening. 
         [0053]    The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teaching without deviating from the spirit and the scope of the invention. The embodiment described is selected to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as suited to the particular purpose contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.