Abstract:
A powertrain for driving a motor vehicle includes an internal combustion engine including first and second rotors supported for rotation about an axis, a first epicyclic gear unit including a first component fixed against rotation, a first driving component, and a first driven component, a first power path alternately producing a first drive connection between the driven component and the first rotor, and opening said first drive connection, and a second power path producing a second drive connection between the driven component and the second rotor, and opening said second drive connection.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to a powertrain that includes a rotary internal combustion engine (ICE) and a planetary gear unit. More particularly the invention relates to such a powertrain for a motor vehicle, in which the engine is driven alternately by a second power source, such as stored pneumatic pressure for starting the engine and accelerating the vehicle from a stopped condition. 
         [0003]    2. Description of the Prior Art 
         [0004]    Most commercial engines for motor vehicles use internal combustion engines having cylinders and reciprocating pistons, the engines operating on a four stroke Otto cycle or Diesel cycle. The pistons reciprocate within the cylinders and change direction at the end of each piston stroke, twice per power stroke. Each piston must stop at each end of stroke and accelerate again from rest after having lost its momentum, repeating this stopping and starting four times per power stroke. Linear piston displacement is converted to rotation using a crankshaft, which transmits no power when the crank and connecting rod become aligned mutually during each rotation of the crankshaft. Such engines have inherently low operating efficiency. 
         [0005]    Rotary engines avoid these limitations and potentially have higher operating efficiency. But they too present problems that affect their cost, power output, engine wear, lubricant sealing, fuel consumption, etc. 
         [0006]    To overcome these difficulties, electric hybrid powertrains have been developed, in which an electric motor is located in a torque path between an ICE and a transmission. Power for driving the vehicle is provided by a gasoline or diesel internal combustion engine, or by an electric motor, or by both the engine and motor. But hybrid electric powertrains are expensive to manufacture and assemble. 
         [0007]    There is a need for a hybrid powertrain that incorporates the efficiency of a rotary IC engine, eliminates need for a torque converter, and is able to be packaged in a small space in the engine compartment adjacent a transmission. 
       SUMMARY OF THE INVENTION 
       [0008]    A powertrain for driving a motor vehicle includes an internal combustion engine including first and second rotors supported for rotation about an axis, a first epicyclic gear unit including a first component fixed against rotation, a first driving component, and a first driven component, a first power path alternately producing a first drive connection between the driven component and the first rotor, and opening said first drive connection, and a second power path producing a second drive connection between the driven component and the second rotor, and opening said second drive connection. 
         [0009]    The engine able to be packaged in a small space in the engine compartment adjacent a transmission, which requires no torque converter. The pneumatic system for starting the engine and accelerating the vehicle from rest is less expensive and has better efficiency in regenerative braking than the comparable features of an electric hybrid powertrain. Because the engine is located in the same case as the transmission, a common hydraulic pump can be used to lubricate the engine and transmission. The rotary pneumatic engine is less expensive and has better efficiency in regenerative braking than an electric machine, such as a starter/generator, inverter, and high voltage electric storage battery, which are required for brake regeneration in an electric hybrid powertrain. 
         [0010]    The rotary engine uses four one-way clutches and a planetary gear unit to synchronize the engine blades, which divide the engine into compression chambers within which the four stages or strokes of the Otto cycle are performed. 
         [0011]    The planetary transmission is driveably connected to the engine&#39;s output and to an air motor, supplied with a replenished charge of compressed air contained in an air tank onboard the vehicle. The transmission produces a continuously variable range of ratios of the speed of the transmission output to the speed of the engine output. The output of the engine and the carrier of the synchronizing gear unit are connected to the carrier of the transmission. The transmission&#39;s sun gear is driveably connected to an air pump/air compressor. The transmission&#39;s output is a ring gear, which drives the vehicle&#39;s wheels through a final drive gear set. The transmission&#39;s carrier is ground by four one-way clutches in the synchronizing transmission while the vehicle is being accelerated from rest using the air motor. The transmission output torque is more than two times the air motor torque and is amplified further by the final drive gear set, more than enough to launch the vehicle. 
         [0012]    The rotary engine can operate alternately on compressed air or gasoline. The motor can be started with air and thus power is delivered to the vehicle through the air motor and by air from the engine. Eventually the engine transitions from being air-driven to gasoline-driven by adding fuel to the inlet air, spark ignition, and turning off the grounded air motor. These actions place the transmission in an overdrive state. 
         [0013]    The engine has three spark plugs, but it can run with two active spark plugs or one active spark plug when variable engine displacement in response to operator demand is desired. 
         [0014]    The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0015]    These and other advantages will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
           [0016]      FIG. 1  is a schematic diagram showing a motor vehicle powertrain; 
           [0017]      FIGS. 2A and 2B  are isometric views of alternate engine rotors with the engine block removed; and 
           [0018]      FIG. 3  is an end view of the engine shown in  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    Referring first to  FIG. 1 , a powertrain  10  includes a power source  12 , which can operate as a rotary internal combustion engine (ICE) using fuel as a power source, or as a motor driven by self-replenishing energy source, such stored pneumatic pressure. The powertrain  10  further includes a first planetary gear unit  14 , a tank  16  containing pressurized pneumatic fluid, an energy conversion and brake regeneration system  18 , and a second planetary gear unit  20  connected to an powertrain output  22 , such as the driven wheels of a motor vehicle. 
         [0020]    The engine  12  includes a first rotor  24  and two rotating blades  26 ,  28 , secured to the first rotor and spaced mutually diametrically opposite on the rotor about an engine axis  30 , a second rotor  32  and two rotating blades  34 ,  36 , secured to the second rotor and spaced mutually diametrically opposite on the second rotor  24  about axis  30 . The blades  34 ,  36  are arranged about axis  30  substantially  1800  offset, i.e., out of phase with respect to blades  26 ,  28 . 
         [0021]      FIGS. 2A and 2B  illustrate that the first engine rotor  24  is secured to a first shaft  38  and the second engine rotor  32  is secured to a second shaft  40 , each shaft being aligned with axis  30 . 
         [0022]      FIG. 3  shows that the engine  12  contains four combustion chambers  42 - 45  located angularly between the interleaved blades and enclosed by an engine block  46 , which conforms to the shape of the outer periphery the blades  26 ,  28 ,  34 ,  36 . Preferably as shown in  FIGS. 1 and 2B , the engine blades  26 ,  28 ,  34 ,  36  are circular and an internal surface of the engine block  42  adjacent the blades is toroidal. Alternately as shown in  FIG. 2B , the engine blades  26 ,  28 ,  34 ,  36  are rectangular and the internal surface of the engine block  42  adjacent the blades is cylindrical. Bearings fitted in the engine block  46  support the rotors  24 ,  32  for rotation about axis  30 . 
         [0023]    The engine block  42  is formed with an inlet  48 , through which air or a fuel/air mixture enters each combustion chamber  42 - 45  as it rotates to the inlet, and an outlet  50 , through which exhaust gas exits the each combustion chamber as it rotates to the outlet. A spark plug secured to the engine block  42  provides a timed source of engine ignition within each rotating combustion chamber  42 - 45 . When the engine  12  is powered by gasoline, it operates on the Otto cycle with four stages: intake, compression, power and exhaust, each stage occurring sequentially during each revolution of the rotors  24 ,  32  about axis  30 . The engine  12  has three spark plugs, but it can run with two active spark plugs or one active spark plug when variable engine displacement in response to operator demand is desired. 
         [0024]    The engine  12  first planetary gear unit  14  and related components are enclosed in a housing  50 , preferably located in an engine compartment of the motor vehicle and secure to the vehicle against rotation. The first gear unit  14  is a simple planetary gear unit, which includes a sun gear  52 , a ring gear  54  surrounding the sun gear and fixed against rotation on the housing  50 , a planet carrier  56 , and planet pinions  58  supported for rotation on carrier  56  and continually engaged with sun gear  52  and ring gear  54 . 
         [0025]    Sun gear  52  is driveably connected to the first rotor  24  through a one-way clutch  60 , which becomes locked, i.e., produces a drive connection when rotor  24  and sun gear rotate in the same direction and the speed of rotor  24  is equal to or greater than the speed of sun gear  52 ; otherwise, clutch  60  overruns and there is no drive connection between sun gear  52  and rotor  24 . Similarly, sun gear  52  and the second rotor  32  are driveably connected mutually through a one-way clutch  62 , which produces a drive connection when rotor  32  and sun gear  52  rotate in the same direction and the speed of rotor  32  is equal to or greater than the speed of sun gear  52 ; otherwise, clutch  62  overruns and there is no drive connection between sun gear  52  and rotor  32 . 
         [0026]    Carrier  56  is driveably connected to the first rotor  24  through a one-way clutch  64 , which produces a drive connection when rotor  24  and carrier  56  rotate in the same direction and the speed of rotor  24  is equal to or greater than the speed of carrier  56 ; otherwise, clutch  64  overruns and there is no drive connection between carrier  56  and rotor  24 . Similarly, carrier  56  and second rotor  32  are driveably connected mutually through a one-way clutch  66 , which produces a drive connection when rotor  32  and carrier  56  rotate in the same direction and the speed of rotor  32  is equal to or greater than the speed of carrier  56 ; otherwise, clutch  66  overruns and there is no drive connection between carrier  56  and rotor  32 . 
         [0027]    Preferably the pitch diameter of ring gear  54  is two times larger than the pitch diameter of sun gear  52 . Due to the ring gear being held against rotation and this 2:1 ratio of the pitch diameters, carrier  56  revolves about axis  30  at three times the speed of rotation of sun gear  52  and the magnitude of torque transmitted by carrier  56  is one-third the magnitude of torque transmitted by the engine rotors  24 ,  32  to the engine output  70 . As the rotors  24  and  32  rotate in the engine block  46 , rotor  24  may be assumed to lead rotor  32  through the four engine stages. 
         [0028]    The engine output  70  is driveably connected to the second planetary gear  2   0  unit  20 , which functions as a split torque transmission. Gear unit  20  includes a sun gear  72 , a ring gear  74  surrounding the sun gear and fixed to the powertrain output  22 , a planet carrier  76  driveably connected to engine output  70 , and planet pinions  78  supported for rotation on carrier  76  and continually engaged with sun gear  22  and ring gear  24 . 
         [0029]    An air motor  80 , secured to sun gear  72 , pneumatically communicates through line  82  with the air tank  16 . An air compressor  84 , continually, driveably connected to an electric motor  86  and connected through a one-way clutch  88  to the air motor and driven by the air motor  80  and/or electric motor  86 , supplies compressed air to tank  16  through line  90 . Kinetic energy of the vehicle can be recovered and stored in tank  16  during wheel braking conditions by having the wheels drive the air compressor  84 . Compressed air is supplied from tank  16  to the combustion chambers  42 - 45  of the engine rotors  28 ,  32  through inlet  48  and line  92  when starting the engine  12 . 
         [0030]    Therefore, during forward drive operation, when combustion of the air/fuel mixture occurs in a combustion chamber such that a blade  26 ,  28  of rotor  24  is driven by that combustion, sun gear  52  is driven through clutch  60 ; clutch  66  is locked to carrier  56 , thereby preventing reverse rotation of rotor  32 ; clutches  62  and  64  overrun; and carrier  56  drives the engine output  70  in the direction of rotor  24  and at one-third the speed of rotor  24 . Sun gear  72  may be driven by air motor  82  in the opposite direction from that of carrier  76 , or sun gear  72  held against rotation by air motor  80 . When sun gear  72  is driven by air motor  82  in the opposite direction from that of carrier  76 , gear unit  20  overdrives output  22  in a relatively low speed range. When sun gear  72  is held against rotation by air motor  80 , gear unit  20  overdrives output  22  a higher speed range. 
         [0031]    When combustion of the air/fuel mixture occurs in the next combustion chamber such that a blade  34 ,  36  of rotor  28  is driven by that combustion, sun gear  52  is driven through clutch  62 ; clutch  64 is locked to carrier  56 , thereby preventing reverse rotation of rotor  24 ; clutches  60  and  66  overrun; and carrier  56  drives the engine output  70  in the direction of rotor  32  and at one-third the speed of rotor  32 . Meanwhile, sun gear  72  is driven by air motor  82  at a speed that will produce a desired speed and torque at output  22  in response to the driver demanded torque and speed at powertrain output  22  and compatible with the speed and torque produced by the engine  12  at it output  70  and carrier  76 . 
         [0032]    The powertrain may include a selectable one-way clutch  100  for reverse drive operation. When the vehicle operator selects reverse drive operation by manually moving the gear selector to the reverse drive position, an electronic controller produce a command output signal, which closes a switch  102 , thereby producing a drive connection through clutch  100  between carrier  52  and housing  50 . This action holds carrier  56  against rotation, releases ring gear  54  from its connection to housing  50 , and connects ring gear  54  to the engine output  70 . Therefore, with sun gear  52  driven by the engine rotors  24 ,  32  and carrier  56  held against rotation, the ring gear  54  and output  70  are driven in a reverse direction. The speed of ring gear  54  and output  70  is one-half the speed of sun gear  52 , provided the pitch diameter of the ring gear is twice the pitch diameter of sun gear. 
         [0033]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.