Abstract:
A drive assembly for a supercharger for an internal combustion engine provides a continuously variable drive ratio between the engine and supercharger to provide a substantially, constant drive speed to the supercharger, thereby optimizing performance. The continuously variable drive may function in increments as well as allow the supercharger to free-wheel. The drive assembly includes a planetary gear drive assembly and a continuously variable hydrostatic transmission having a rotating, variably coupled master and slave pump and motor which, by adjusting its drive ratio, adjusts the ratio of the planetary gear assembly and thus the drive ratio between the engine and the supercharger.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates generally to drive assemblies for superchargers and more specifically to a continuously variable drive assembly for optimizing the speed of a supercharger driven by an internal combustion engine.  
         [0002]     Increasing the volume of air provided to the cylinders of an internal combustion engine during its intake cycle and thereby increasing the density of the air during the compression and ignition strokes has long been recognized as a means of increasing the horsepower output of an internal combustion engine. Two classes of equipment have been relied upon to achieve this goal: turbochargers and superchargers. Turbochargers are defined as devices of the class which are driven by a turbine exposed to the exhaust gasses of the engine to which the turbocharger is providing increased air pressure. Likely the most common and widely recognized issue with a turbocharger is what is referred to as turbo lag. Since the turbocharger depends upon an engine&#39;s exhaust gasses to drive it and increase its speed, when increased power output of the engine is desired, the turbocharger cannot increase its speed to increase engine performance until the flow of exhaust gasses increases to increase its rotational speed. Thus, inherent in the design is a delay from the feedback nature of the device. While there are design approaches which reduce turbo lag such as minimizing the rotating mass of the turbocharger, turbo lag remains a concomitant to turbocharger designs.  
         [0003]     Superchargers, on the other hand, achieve a similar goal, but rather than being driven by engine exhaust gasses, they are driven directly by a fan belt or belt which is driven by the crankshaft pulley. In this configuration, as the speed of the engine increases, the speed of the supercharger immediately and proportionally increases. Hence, the problem of turbo lag is essentially eliminated. However, due to the wide variation in engine speed, typically from 700-800 R.P.M. at idle to 6,000-8,000 R.P.M. or higher at red line, a supercharger is subjected to a wide variation in drive speeds. This wide variation interferes with optimum operation as many supercharger designs provide their best performance enhancing capabilities when driven at a constant or substantially constant speed.  
         [0004]     Attempts have been made to achieve this goal. For example, U.S. Pat. No. 5,462,035 teaches a supercharger which is driven through a continuously variable transmission (CVT) comprising a pair of variable diameter pulleys interconnected by a belt. The present invention is directed to a drive assembly for a supercharger which maintains a substantially constant supercharger drive speed notwithstanding variations in the speed of the associated internal combustion engine.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     A drive assembly for a supercharger for an internal combustion engine provides a continuously variable drive ratio between the engine and supercharger to provide a substantially, constant drive speed to the supercharger, thereby optimizing performance. The continuously variable drive may function in increments as well as allow the supercharger to free-wheel. The drive assembly includes a planetary gear drive assembly and a continuously variable hydrostatic transmission having a rotating, variably coupled master and slave pump and motor which, by adjusting its drive ratio, adjusts the ratio of the planetary gear assembly and thus the drive ratio between the engine and the supercharger.  
         [0006]     It is an object of the present invention to provide a substantially constant speed drive assembly for a supercharger for an internal combustion engine.  
         [0007]     It is a further object of the present invention to provide a variable speed drive assembly for a supercharger for an internal combustion engine having a planetary gear drive assembly and hydrostatic drive assembly.  
         [0008]     It is a still further object of the present invention to provide a constant speed drive assembly for a supercharger for an internal combustion engine having a planetary gear assembly controlled by a continuously variable hydrostatic drive assembly.  
         [0009]     Further objects and advantages to the present invention would become apparent by reference to the following description of the preferred embodiment and appended drawings wherein like reference numbers refer to the same component, element, or feature. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view of a supercharger assembly according to the present invention mounted upon an internal combustion engine;  
         [0011]      FIG. 2  is a diagrammatic view of a variable speed drive assembly for a supercharger according to the present invention;  
         [0012]      FIG. 3  is an enlarged, full sectional view of a hydrostatic continuously variable transmission assembly according to the present invention;  
         [0013]      FIG. 4  is a graph illustrating the various speeds of the components of the variable speed drive assembly for a supercharger according to the present invention operating in an active mode;  
         [0014]      FIG. 5  is a graph illustrating the various speeds of the components of the variable speed drive assembly for a supercharger according to the present invention operating in an open mode; and  
         [0015]      FIG. 6  is a graph illustrating the various speeds of the components of the variable speed drive assembly for a supercharger according to the present invention in a freewheeling mode. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     Referring now to  FIG. 1 , an internal combustion engine is illustrated and generally designated by the reference number  10 . The internal combustion engine  10  is essentially conventional, may be a gas or Diesel engine and includes an engine block  12  within which reside a plurality of pistons and a crankshaft (both not illustrated) which are coupled to a crankshaft pulley  14 . The crankshaft pulley  14  is engaged by a drive belt  16  which provides mechanical energy to various components of the engine  10  such as a water pump, an alternator, or steering pump and air conditioning compressor (all not illustrated). The internal combustion engine  10  also includes a supercharger assembly  20  which is driven by the belt  16  and increases the air pressure within the intake manifold of the internal combustion engine  10  in accordance with conventional practice.  
         [0017]     The supercharger assembly  20  includes a housing  22  which receives, supports and protects various components of the assembly  20 . The drive belt  16  is received upon a pulley  24  secured to an input shaft  26  which provides rotary energy to the supercharger assembly  20 . A first gear train  30  includes a pinion gear  32  which is secured to the input shaft  26 , rotates therewith and engages a larger diameter spur input gear  34 . The spur gear  34  drives a continuously variable hydrostatic transmission assembly  40 . Specifically, the spur gear  34  is secured to and drives an input shaft  42  of the continuously variable hydrostatic transmission assembly  40 . The hydrostatic transmission assembly  40  also includes an output shaft  44  which is coupled to and drives a spur output gear  46 .  
         [0018]     The input shaft  26  also drives a second gear train assembly  50 . Specifically, the input shaft  26  is directly coupled to and drives a carrier  52  which freely rotatably supports a plurality of planet gears  54  on associated stub shafts  56 . The planet gears  54  engage a circular ring gear  58  having both internal or female gear teeth  62  which engage the planet gears  54  and external or male gear teeth  64  which engage and are driven by the second spur gear  46  on the output shaft  44  of the continuously variable hydrostatic transmission assembly  40 . Disposed centrally within the carrier  52  and driven by the planet gears  54  is a sun gear  66  which is secured to and supported upon an input shaft  68  which drives the supercharger assembly  70 . The supercharger assembly  70  includes an impeller  72  which is secured to the input shaft  68 . The impeller  72  is disposed within a suitably shaped preferably involute housing  74  which channels the air compressed by the impeller  72  into an outlet duct  76  which leads to an intake manifold  78  on the internal combustion engine  10  (illustrated in  FIG. 1 ).  
         [0019]     Referring now to  FIG. 3 , the continuously variable hydrostatic transmission assembly  40  is seen to include a housing  82  which supports and encloses various components of the assembly  40  such as the input shaft  42  and the coaxially disposed output shaft  44 . Within the housing  82 , the input shaft  42  is connected to and drives a hydraulic motor assembly  84 . A hydraulic pump assembly  86  is also disposed within the housing  82  in axially opposed and aligned relationship with the motor assembly  84 . A wedge shaped swashplate assembly  88  is disposed between the motor assembly  84  and the pump assembly  86  and includes a plurality of through passageways  90  which provide fluid communication between the motor assembly  84  and the pump assembly  86 .  
         [0020]     The motor assembly  84  and the pump assembly  86  exert first and second components of torque on the swashplate assembly  88  in the rotational direction of the input shaft  42  and the hydraulic pressure in the passageways  90  of the swashplate assembly  88  exerts a third component of torque in the same direction on the swashplate assembly  88 . The third component of torque is a product of the hydraulic pressure and the differential area of the two ends of the higher pressure passageways  90  at the narrower and thicker portions of the wedge shaped swashplate assembly  88 . Thus, the swashplate assembly  88  rotates in the direction of the third torque component.  
         [0021]     The swashplate assembly  88  is drivingly connected to the output shaft  44  by drive pins  92 , one of which is illustrated in  FIG. 3 , which engage a bell shaped housing  94 . The bell shaped housing  94  is rotatably supported by an external anti-friction bearing such as a ball bearing assembly  96  and internal anti-friction bearings such as the ball bearing assemblies  98 . An actuator or controller  100  which may be a bi-directional, linear electric actuator, a double acting hydraulic actuator such as a spool valve, a spring biased hydraulic cylinder or a double acting or spring biased pneumatic cylinder, for example, is linked to the swashplate assembly  88  for the purpose of pivotally adjusting the angle of orientation of the swashplate assembly  88  relative to the axes of the input shaft  42  and the output shaft  44  thereby setting the ratio of the transmission assembly  40  between the input shaft  42  and its speed and the output shaft  44  and its speed.  
         [0022]     Further details of the continuously variable hydrostatic transmission assembly  40  may be found in U.S. Pat. No. 5,575,152 which is hereby incorporated by reference.  
         [0023]     Since a purpose of the present invention is to provide a supercharger drive assembly  20  which drives a supercharger assembly  70  at a substantially constant speed, notwithstanding variations in the speed of the associated internal combustion engine  10 , control componentry will now be briefly described. At the outset, it should be understood that since virtually every contemporary internal combustion engine  10  utilizes electronic engine management controls and one type of information generally always available from such electronic engine controls is engine speed, i.e., R.P.M., this information will be readily available. Once the engine R.P.M. is known, the speed of the input shaft  42  can be readily inferred or calculated by the use of a scaling factor corresponding to the relative sizes of the crankshaft pulley  14  and the pulley  24  on the input shaft  26 . If open loop control is satisfactory, this information can be provided to a microprocessor  102  having an output which drives the controller  100 . In this configuration, the controller  102  will include a read only memory or look up table relating engine (or pulley) speed to a required position of the controller  100  which will provide a desired output speed to the impeller  72 . If, however, closed loop control is desired, a speed sensor  104  such as a Hall effect, variable reluctance or optical sensor may by associated with a tone wheel on the input shaft  68  to the supercharger impeller  72 . Provided with the actual speed of the input shaft  68  and the impeller  72 , the microprocessor  102  provides an output signal to the controller  100  which appropriately positions the swashplate assembly  88 .  
         [0024]      FIG. 4  illustrates the relationship between the various speeds of the supercharger drive assembly  20  in the active mode as the continuously variable transmission assembly  40  is controlled to achieve a constant supercharger speed.  FIG. 4  illustrates the various component speeds as the speed of the internal combustion engine  10  is changed from 1200 R.P.M. through 6000 RPM and back to 1200 R.P.M. It should be noted that during this time, the speed of the supercharger impeller  72 , the uppermost line in  FIG. 4 , remains constant at 40,000 R.P.M.  FIG. 4  also illustrates the significant change of speed of the internal ring gear  58 . As the speed of the engine  10  moves from 1,200 R.P.M. to 6,000 R.P.M., the speed of the ring gear  58  which is initially approximately 26,000 R.P.M. changes to approximately 31,000 R.P.M. in the opposite direction. As the speed of the internal combustion engine  10  decreases, the speed change reverses.  
         [0025]      FIG. 5  illustrates the performance of the supercharger drive assembly  20  in what is referred to as the open mode. The open mode is that operating region wherein the continuously variable transmission assembly  40  operates where the speed of the pulley  24  and the ratio through the planetary drive which, is typically 4:1, cannot provide the minimum 40,000 rpm to the supercharger assembly  72 . Once again, it will be appreciated that the test protocol involves initial operation of the internal combustion engine  10  at 1,200 R.P.M. sweeping through 6,000 R.P.M. and back to 1,200 R.P.M.  
         [0026]     Referring now to  FIG. 6 , the graph therein illustrates operation in a free wheeling or uncoupled mode. Here, the continuously variable hydrostatic transmission assembly  40  operates until it is decided to open the planetary drive, uncouple the supercharger assembly  20  and allow the impeller  72  to free wheel. Once again, in the test illustrated, the speed of the internal combustion engine  10  is swept from 1,200 R.P.M. up to 6,000 R.P.M. and back to 1,200 R.P.M.  
         [0027]     It should be noted that the terms “variable speed”, “continuously variable” and “constant speed” used throughout this patent application refer generally to the input, drive assembly and output, respectively, of the supercharger drive assembly  20  for the supercharger assembly  72 . Specifically, the term “variable speed” refers generally to the input of the device and the fact that the speed of the input can vary over a significant range, as does the speed of the internal combustion engine  10  which drives it. The term “continuously variable” refers generally to the variable speed drive ratio achieved by the continuously variable hydrostatic transmission assembly  40  and the gear trains  30  and  50 . The term “constant speed” refers generally to the output of the device and its drive to the supercharger assembly  72  which is at a substantially constant speed, notwithstanding the variability of the speed of the input.  
         [0028]     The foregoing disclosure is the best mode devised by the inventor for practicing this invention. It is apparent however, that devices incorporating modifications and variations will be obvious to one skilled in the art of supercharger drive assemblies. Inasmuch as the foregoing disclosure presents the best mode contemplated by the inventor for carrying out the invention and is intended to enable any person skilled in the pertinent art to practice this invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.