Abstract:
A four-stroke engine with intake air compression chamber. The intake air compression chamber has a pressure responsive displaceable member therein to compress inlet air passively in response to differential pressure between a sealed crankcase and air in the inlet side of the inlet air compression chamber. The displaceable member is substantially impervious to air, oil, and fuel. When the piston moves away from the intake air compression chamber, decreasing pressure draws the displaceable member toward the crankcase, and the movement of the displaceable member draws into the intake side of the inlet air compression chamber through a one way inlet valve. When the piston moves toward the inlet air compression chamber, fluidwise, compressed gas in the crankcase causes increased pressure on the displaceable member, compressing the inlet air, and directing compressed inlet air out through a one-way outlet valve. Power in a four-stroke engine is increased without the necessity to employ superchargers or turbochargers.

Description:
RELATED PATENT APPLICATIONS 
   This patent application is a continuation-in-part of an claims priority under 35 USC Section 120 from prior U.S. patent application Ser. No. 10/396,297 filed on Mar. 25, 2003, now abandoned which is a continuation-in-part of and claims priority under 35 USC Section 120 from U.S. patent application Ser. No. 09/557,455 filed on Apr. 24, 2000, entitled Two-Stroke Internal Combustion Engine with Isolated Crankcase, now U.S. Pat. No. 6,536,384 B1, issued Mar. 25, 2003, the disclosures of each of which are incorporated herein in their entirety by this reference. 

   TECHNICAL FIELD 
   This invention relates to a internal combustion engines with inlet air compression, and more particularly to four-stroke engines with inlet air compression. 
   BACKGROUND 
   In conventional four-stroke internal combustion engines, techniques such as turbocharging (exhaust driven blower) or supercharging (power driven blower) have been advanced for achieving compression of the inlet air, in order to obtain more power. Although such techniques have been used for many years, they remain relatively expensive. And, in the case of turbocharging, heat resistant materials are necessary for the exhaust side, and such materials are available only at significant capital expense. 
   Consequently, there remains a significant and as yet unmet need for a four-stroke engine which provides a significant boost in power, but without the complexity and expense of heretofore known turbocharging or supercharging techniques. 
   SUMMARY 
   I have found that utilization of the pressure and vacuum cycles created within the substantially sealed crankcase of a four-stroke internal combustion can be utilized to passively force compressed air into a combustion chamber. A pressure responsive displaceable member, such as a flexible diaphragm, may be utilized to isolate the air that travels to the combustion chamber from the air within the crankcase. In such a design, no oil ever enters the combustion chamber from the substantially sealed crankcase. Thus, such a design may be called an isolated crankcase design. 
   As a piston moves upward in a cylinder and thus away from a substantially sealed crankcase, a moderate vacuum is created within the crankcase. The pressure responsive displaceable member is drawn toward the vacuum, in turn drawing inlet air into the inlet air compression chamber. This allows air (in a fuel injected system) or a mixture of fuel and air (in a carbureted system) to be drawn through a one-way inlet valve and into an inlet air compression chamber. 
   When the piston moves downward in a cylinder, toward the substantially sealed crankcase, gas pressure within the substantially sealed crankcase is increased, pushing the pressure responsive displaceable member away from the substantially sealed crankcase. Because the air, or the mixture of fuel and air on the inlet air side of the pressure responsive flexible member cannot escape through the one-way inlet air valve, or through a timed induction vent valve, the air (or mixture of fuel and air, if applicable) or pure air is forced out of the inlet air compression chamber through a one-way outlet valve, into an intake air plenum, and thence through an intake valve and into a cylinder, for compression and subsequent ignition and combustion. 
   In the just described design, air (or a fuel/air mixture) is pumped into the combustion chamber without ever being exposed to oil that lubricates the crankcase. In a four-stroke engine, the inlet air compression chamber design taught herein precludes oil from reaching the combustion chamber, thereby allowing oil to be used in a conventional manner to lubricate the crankcase. 
   In one embodiment, to avoid having pressure generated within the crankcase by any piston blow-by impeding the pumping action of the inlet air compression chamber, a timed valve is utilized to open (i.e., vent) the crankcase to the surrounding atmosphere at the time when the piston is at about its closest point of approach to the crankcase, i.e., the bottom dead center position of the piston. 
   In yet another embodiment, an intake air plenum, which receives compressed air from the inlet air compression chamber, can be provided with a pre-selected volume sufficient that, taking into account the engine displacement, the pressure variation within the intake air plenum will be minimized as the engine operates. Note that in order to increase the power output of a given size engine, the compressed inlet air generated during the power stroke of a four-stroke engine must be stored in an intake air plenum of sufficient size so that, when the compressed inlet air generated during the power stroke is combined with the compressed inlet air generated during the intake stroke, maximum advantage is created with respect to pressurization of air (or a fuel/air mixture) that is ultimately charged to the cylinder for combustion. Thus, in one embodiment, storage of compressed inlet air is accomplished during crankshaft rotation from about 360 degrees to about 540 degrees. 
   In general, in order to prevent a vacuum from being created in the area between a throttle and an intake valve at the cylinder head, the throttle may be located near the intake valve. In one design, a fuel injection nozzle may be located in the vicinity of the throttle. 
   Thus, it can be appreciated that the addition of an inlet air compression chamber in a manner that isolates the crankcase from the inlet air supplied to the combustion chamber enables a four-stroke engine to function efficiently, and with enhanced power, compared to conventional four-stroke engines. Therefore, the apparatus and methods disclosed herein represents an important improvement in the design for, and operation of, four-cycle engines. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order to enable the reader to attain a more complete appreciation of the invention, and of the novel features and the advantages thereof, attention is directed to the following detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  illustrates a four-stroke engine with isolated crankcase during the intake stroke. 
       FIG. 2  illustrates a four-stroke engine with isolated crankcase during the compression stroke. 
       FIG. 3  illustrates a four-stroke engine with isolated crankcase during the power stroke. 
       FIG. 4  illustrates a four-stroke engine with isolated crankcase during the exhaust stroke. 
       FIG. 5  illustrates a four-stroke engine with isolated crankcase when the piston is at bottom dead center, showing the use of a timed crankcase valve to vent the crankcase before the exhaust stroke starts. 
       FIG. 6  provides a side perspective view of an embodiment for an air inlet compression chamber. 
       FIG. 7  provides a back perspective view of one embodiment for an air inlet compression chamber for isolation of an engine crankcase. 
       FIG. 8  illustrates a cross-sectional view of one embodiment for an inlet air compression chamber for isolation of a crankcase. 
   

   The foregoing figures, being merely exemplary, contain various elements that may be present or omitted from actual implementations depending upon the circumstances. An attempt has been made to draw the figures in a way that illustrates at least those elements that are significant for an understanding of the various embodiments and aspects of the invention. However, various other elements of the four-stroke engine are also shown and briefly described to enable the reader to understand how various features may be utilized in order to provide an efficient, reliable engine. 
   DETAILED DESCRIPTION 
   In  FIG. 1 , a diagrammatic view of one embodiment of an engine  10  with isolated and substantially sealed crankcase  12  is shown using an inlet air compression chamber  14 . Generally,  FIG. 1  illustrates the intake stroke of a four-cycle engine operating with a crankcase  12  isolated by an inlet air compression chamber  14 . An oil reservoir  16  having oil  18  therein is provided at the lower reaches of crankcase  12 . A cylinder  20  is provided, defined by a sidewall  22  extends outward or upward in this case from the crankcase  12  to an upper end portion  24 . The cylinder  20  further includes, adjacent the upper end portion  24 , a head  28 . The head  28  head further includes an inlet  30  defined by inlet aperture walls  32  and an outlet  34  defined by outlet aperture walls  36 . An intake valve  40  is schematically shown, operably disposed adjacent the inlet  30 . An exhaust valve  42  is schematically shown operably disposed adjacent the outlet  34 . 
   A piston  44  is provided slidably mounted in the cylinder  20 . As best seen in  FIG. 2 , which depicts the compression stroke of a four-cycle engine, the piston  44  forms an upper compressible chamber  46  within the cylinder  20  between the piston  44  and the head  28 . A crankshaft  50  is rotatably mounted in the substantially sealed crankcase  12 . A connecting rod  52  is operatively mounted for translation of rotary motion of the crankshaft  50  into reciprocal motion of the piston  44 . 
   An air inlet line  54  is provided to supply inlet air to the engine  10 . The inlet air line  54  includes a one-way inlet only valve  56 . The one way inlet valve  56  is disposed adjacent the inlet air compression chamber  14 . The inlet air compression chamber  14  is fluidically disposed between the piston  44  and the inlet only valve  56 . The inlet compression chamber  14  includes, in one embodiment, opposing sidewalls, namely inlet air sidewall  60  and crankcase sidewall  62 , that define, in cooperation with flexible member  70  (further discussed below) an interior chamber  64  space for receiving inlet air  66  after it passes the inlet only valve  56 , or alternatively, an engine side chamber  65  for receiving compressed gas  68  from the substantially sealed crankcase  12 . Sealingly secured between the opposing inlet air sidewall  60  and the crankcase sidewall  62  is a displaceable member. In one embodiment, the displaceable member may be provided in the form of a flexible membrane  70 . As better seen in  FIG. 8 , the flexible membrane  70  and the opposing sidewalls  60  and  62  may be juxtaposed in a manner wherein most of the interior chamber  64  and  65  space within the intake air compression chamber  14  is utilized when the flexible membrane  70  moves from full deflection during a fill with inlet air  66  as shown in solid lines in  FIG. 8  (and reference arrows  67  in  FIGS. 2 and 4 ), and to full deflection during discharge of compressed inlet air  71  as shown in broken lines in  FIG. 8  (and reference arrows  69  in  FIGS. 1 and 3 ). This range of motion is more generally shown in  FIG. 8  by reference arrow  72 . 
   Returning now to  FIGS. 1 through 5 , an intake air outlet line  72  is provided for discharge of compressed inlet air. An outlet only valve  74  is provided in the intake air outlet line  72 . Upon discharge of the compressed air as shown by reference arrows  71  (in both  FIGS. 1 and 8 ), it travels into an intake air plenum  80 . The intake air plenum  80  has a plenum inlet  82  adjacent the outlet only valve  74 . The intake air plenum  80  also has a plenum outlet  84  adjacent the inlet  30  of the head  28 . 
   Overall, as shown in  FIG. 1 , movement of the piston  44  away from the head  28  in the direction of reference arrow  103  compresses gas  68  within the substantially sealed crankcase  12  against the displaceable member, shown as a flexible membrane  70 . The displaceable member, here flexible membrane  70 , responsively compresses inlet air  66  within the inlet air compression chamber until a threshold pressure is reached, whereupon the outlet only valve  74  opens, allowing compressed inlet air  71  to escape into the intake air plenum  80 . 
   In the  FIGS. 1 through 5 , a throttle valve  92  is provided. The throttle valve  92  is operatively disposed in the intake air plenum  80  for movement to increase or decrease air flow through the intake air plenum  80 . Further, a fuel injector  94 , having a fuel outlet  96  situated in the intake air plenum  80  downstream of the throttle valve  92 , is provided. The fuel injector  94  is operative to inject fuel  98  into compressed air in the intake air plenum  80 , to create a fuel/air mixture  100 . In one embodiment, the fuel injector  94  is located between the throttle  92  and the intake valve  40 . 
   As shown in  FIG. 1 , during the intake cycle, the intake valve  40  is operatively configured to open, wherein upon opening of the intake valve  40 , the fuel/air mixture  100  escapes into the upper compressible chamber  46 . Alternately, a carburetor may be provided upstream in inlet air line  54 , and as will known to those of ordinary skill in the art without further explanation, operatively configured to provide a fuel/air mixture (not shown) to the intake air plenum  80 , via said inlet air line  54  and the inlet air compression chamber  14 . 
   A spark plug  102  may be provided for each cylinder  20 . The spark plug  102 , operatively connected to an ignition electrical system, provides ignition energy for igniting the fuel air mixture  100  in the upper compressible chamber  46 . A depicted in  FIGS. 1 through 4 , conventional four-cycle engine operation is feasible when using the inlet air compression chamber  14  as taught herein.  FIG. 1  depicts the engine  10  when in the intake cycle, with the intake valve  40  open, so the fuel/air mixture  100  can be moved into the upper compressible chamber  46 . The piston  44  is moving in the direction of reference arrow  103 .  FIG. 2  depicts the engine  10  in the compression cycle, with both the intake valve  40  and the exhaust valve  42  closed. In this cycle, the piston  44  is moving towards head  28  in the direction of reference arrow  104 . 
   In  FIG. 3 , a power stroke is illustrated. Here, after combustion of the fuel/air mixture in upper compression chamber  46 , the piston  44  moves in the direction of reference arrow  106 . Compressed inlet air is moved, as shown by reference arrow  71 , from inlet compression chamber  14  and into the intake air plenum  80 , for temporary storage. Finally, in  FIG. 4 , an exhaust stroke is illustrated. Here, the piston  44  moves in the direction of reference arrow  108 . The exhaust valve  42  is open, allowing combustion gases  110  to escape from the cylinder  20 . 
   Turning now to a comparison of  FIGS. 1 and 5 , in an embodiment, it may be advantageous to provide, on the substantially sealed crankcase side of the displaceable member (flexible membrane  70 ), a vent  112 . The vent  112  is operatively configured to provide fluid communication between the substantially sealed crankcase side  68  of the inlet air compression chamber  14  and the surrounding environment  114 . As shown in  FIG. 5 , the vent  112  may include a vent valve  116  and a vent exit line  118 . It is useful to provide a vent exit line  118  (and vent line  112 , before the vent valve  116 ) in the form of a fluid conductor having a cross-sectional area sufficiently large so that when gas  68  within the substantially sealed crankcase  12  is discharged, that the vent valve  116  is closeable sufficiently quickly so that air from the surrounding environment  114  is not permitted to substantially enter the substantially sealed crankcase  12  through the vent line  118 . In one embodiment, a timed crankcase valve may be utilized for vent valve  116 . As depicted in  FIG. 5 , the timed crankcase valve may be operably configured to open the substantially sealed crankcase  12  to the surrounding environment  114  when the piston  44  is approximately at a bottom dead center position. At other times, as shown in  FIGS. 1-4 , the vent valve  115  is normally closed. 
   As more clearly seen in  FIGS. 6 and 8 , the inlet air compression chamber  14  may be affixed to the substantially sealed crankcase  12  via an activation passageway  120 . And, although noted above, it is more clearly evident in  FIGS. 6 and 8  that in one embodiment, the inlet air compression chamber  14  may be provided with opposing concave sidewalls  60  and  62  arranged to define an interior space therebetween. Generally, in one embodiment, the inlet air compression chamber  14  may be provided with a generally hollow chamber interior space having inner surfaces, defined by the sidewalls  60  and  62 . In one embodiment, the flexible membrane  70  may be a flexible diaphragm that is provided in a material substantially impervious to oil Also, in one embodiment, the flexible membrane  70  may be a flexible diaphragm that is provided in a material that is substantially impervious to air. 
   For further clarity, one way to visualize certain components of the apparatus described herein for compression of inlet air is to note that the piston  44  includes, in some fashion, a lower sealing wall  124 . The cylinder  20  sidewalls  22 , below a then operable location of the lower sealing wall  124 , cooperate with the substantially sealed crankcase  12 , (c) the crankcase side of the inlet air compression chamber  14 , and (d) the displaceable member such as a flexible membrane  70  within the inlet air compression chamber  12 , to form a lower compressible chamber  126 . Thus, the lower compressible chamber  126  contains the compressed gas  68  during movement of the piston  44  toward the substantially sealed crankcase  12 . In one embodiment, the inlet air compression chamber  14  may be considered to be fluidically disposed between the substantially sealed crankcase  12  and the inlet only valve  56 . In such an embodiment, the inlet air compression chamber  14  includes (a) a crankcase side interior sidewall  62  and an inlet air side interior sidewall  60 , and (b) a flexible membrane  70  sealingly affixed between the crankcase side interior sidewall and the inlet air side interior sidewall for motion cyclically toward and away from each of the crankcase side interior sidewall  62  and the inlet air side interior sidewall  60 . 
   Overall, use of the inlet air compression chamber will provide power improvements over an equivalent four-stroke engine without addition of an inlet air compression chamber  12 . The precise power advantage will depend upon a variety of factors. 
   Having described the various components for an advantageous apparatus for compression of inlet air in a four stroke internal combustion engine, the process of operation will be further explained. An inlet air compression chamber  14  is provided, located between an air inlet  54  and a sealed crankcase  12 . The air inlet  54  includes an inlet only valve  56  adjacent the inlet air compression chamber  14 . The inlet air compression chamber  14  comprises an inlet air side and a crankcase side with a displaceable member  70  secured therebetween. The displaceable member  70  is passively responsive to differential pressure between said sealed crankcase  12  and said inlet air side  64  of said inlet air compression chamber  14 . Air  66  in the inlet side  64  of the inlet air compression chamber  14  is compressed during an intake stroke of a piston  44 . The compressed air is discharged from the inlet air compression chamber  14  through an outlet only valve  74 . When fuel injection is utilized, fuel is added to the compressed inlet air to form a compressed air/fuel mixture  100 . The compressed fuel/air mixture is injected into upper compressible chamber  46  within cylinder  20 . The fuel/air mixture  100  is further compressed in response to upward movement of the piston  44  during a compression stroke, to provide a compressed combustible fuel/air mixture. Then, the compressed combustible fuel/air mixture is ignited by a spark plug. The engine is timed for four cycle engine operation. In one embodiment, the process comprises storing, in the intake air plenum, the inlet air compressed in the inlet air compression chamber during a downward stroke of a piston, when the down stroke occurs during a power stroke of the four stroke combustion engine. Further optimization can be achieved by providing an inlet air plenum shaped and sized to for optimum operation by minimizing pressure variation in the inlet air plenum  80  while maximizing the pressure of compressed air provided for injection into the upper compression chamber  46 . 
   It should also be noted, and those of ordinary skill in the art and to whom this specification is addressed will appreciate that an engine utilizing a carburetor may, instead of providing a fuel/air mixture to the inlet air line  54 , may leave the inlet air line  54  free of fuel, and provide a fuel/air mixture in the vicinity of the outlet  84  of the intake air plenum  80 , or upstream therefrom to the vicinity of the throttle  92 . Also, such persons will appreciate that the “one-way” valves  56  and  74  have been depicted as reed type valves, other valves types or designs may provide the necessary unidirectional flow, such as timed rotary valves, or other actuated valves which operatively block fluid backflow. 
   It is to be appreciated that various aspects and embodiments of the engine designs described herein are an important improvement in the state of the art of four-cycle engines. Although only a few exemplary embodiments have been described in detail, various details are sufficiently set forth in the drawings and in the specification provided herein to enable one of ordinary skill in the art to make and use the invention(s), which need not be further described by additional writing in this detailed description. Importantly, the aspects and embodiments described and claimed herein may be modified from those shown without materially departing from the novel teachings and advantages provided by this invention, and may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Therefore, the embodiments presented herein are to be considered in all respects as illustrative and not restrictive. As such, this disclosure is intended to cover the structures described herein and not only structural equivalents thereof, but also equivalent structures. Numerous modifications and variations are possible in light of the above teachings. Thus, the scope of the invention(s), as set forth in the appended claims, and as indicated by the drawing and by the foregoing description, is intended to include variations from the embodiments provided which are nevertheless described by the broad interpretation and range properly afforded to the plain meaning of the claims set forth below.