Abstract:
A power system for a motor vehicle having an internal combustion engine and an electric machine is disclosed. The electric machine has a stator, a permanent magnet rotor, an uncluttered rotor spaced from the permanent magnet rotor, and at least one secondary core assembly. The power system also has a gearing arrangement for coupling the internal combustion engine to wheels on the vehicle thereby providing a means for the electric machine to both power assist and brake in relation to the output of the internal combustion engine.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to U.S. Provisional Patent Application 60/543,069 filed Feb. 9, 2004, and is herein incorporated by reference. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
   This invention was made with Government support under Contract No. DE-AC05-00OR22725 awarded to UT-Battelle, LLC, by the U.S. Department of Energy. The Government has certain rights in this invention. 

   TECHNICAL FIELD 
   The field of the invention is electric machines for use in association with an internal combustion engine in a hybrid motor vehicle. 
   DESCRIPTION OF THE BACKGROUND ART 
   Hsu, U.S. Pat. No. 6,310,417, issued Oct. 30, 2001, disclosed an electric machine with uncluttered rotor magnetic coupling that has a significant potential to lower the cost of adjustable-speed drives. In addition to speed control below synchronous speed, this machine may also be operated above synchronous speed. 
   The term “uncluttered coupling” relates to a stator and rotor that couple slip energy. In an induction motor, the speed of the rotating stator field equals the sum of 1) the speed of the rotating rotor field plus 2) the mechanical rotation speed of the rotor. With the motor running at maximum torque and close to synchronous speed, rotor speed is high and slip (the difference between the speed of the rotating stator field and the rotational speed of the rotor) is small, about 3 to 10 per cent, and the slip frequency induced in the rotor is small, perhaps two to six cycles per second for a 60 Hz motor. 
   To couple only slip energy, the stator and rotor have coils that run circumferentially, sometimes referred to as “peripherally,” around the axis of rotor rotation. The peripheral coils of the rotor and stator are magnetically coupled. The rotor coil rotates and carries a slip-frequency current. Because the rotation does not change the total magnetic flux linking both the rotor and stator coils, no electromotive force (emf) is induced in the stator coil due to the rotation of the rotor coil. This “uncluttered coupling” allows only the slip energy power corresponding to the slip-frequency currents to be transferred between the rotor and stator coils of the transformer. 
   Hsu, U.S. Pat. Appl. Ser. No. 10/706,577, filed Nov. 12, 2003, disclosed an uncluttered machine with an additional PM rotor carrying permanent magnet material. This machine is capable of setting up torques and counter torques due to the reaction of the uncluttered rotor to the PM rotor. 
   It is desired to make such a machine that is applicable to the hybrid motor vehicle that uses both an electric machine and an internal combustion engine. 
   SUMMARY OF THE INVENTION 
   This invention provides a multiple-rotor permanent-magnet (PM) machine with a rotor that couples a slip flux to one or more secondary coils through a magnetic coupling rotor. 
   The invention further relates to an electric machine that is coupled to the internal combustion engine and the wheels of the vehicle through a gearing arrangement. 
   Various objects and advantages of the invention will be apparent to those of ordinary skill in the art from the description of the preferred embodiments which follow. In the description, reference is made to the accompanying drawings, which form a part hereof, and which illustrate examples of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of a hybrid vehicle that includes an internal combustion engine and an electric machine of the present invention; 
       FIG. 2  is a schematic view of a planetary gearing arrangement seen in  FIG. 1 ; 
       FIGS. 3   a - 3   d  are schematics of the planetary gearing in several modes of operation; 
       FIG. 4   a  is a sectional view taken in a plane indicated by line  4   a - 4   a  in  FIG. 4   b;    
       FIG. 4   b  is a plan view of a magnetic coupling, two-phase uncluttered in the machine seen in  FIG. 1 ; 
       FIG. 4   c  is a detail view of the magnetic brushes included in the rotor of  FIGS. 4   a  and  4   b;    
       FIG. 5   a  is a sectional view taken in a plane indicated by line  5   a - 5   a  in  FIG. 5   b ; and 
       FIG. 5   b  is a plan view of a permanent magnet rotor in the two-phase machine seen in  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates power system for a hybrid electric vehicle including a vehicle engine  10  (an internal combustion engine), and an electric machine  12 , which are coupled and uncoupled to drive the wheels  14  of a vehicle. The vehicle engine  10  is coupled to the wheels  14  through a hollow shaft  16  and a main drive shaft  20 , which are coupled to each other through a planetary gearing assembly  22 . Both shafts  16 ,  20  are supported at various points by suitable bearings including bearings  18 . The main drive shaft  20  may also be coupled to the wheels  14  at the driving end through suitable gearing  24 . 
   The electric machine  12  is an uncluttered PM machine which has been previously disclosed in Hsu, U.S. Pat. Appl. No. 10/706,577, filed Nov. 12, 2003, the disclosure of which is incorporated herein by reference. This machine provides a housing  41 , an armature or stator  47 , and a secondary core assembly  43 . The stator  47  receives multi-phase electric power through lines  45  connecting to multi-turn windings. The secondary coil assembly  43  receives multi-phase electric power through lines  44  The toroidal secondary core assembly  43  has peripherally disposed windings which encircle the main drive shaft  20  and the hollow drive, shaft  16 . The machine  12  also includes a first, uncluttered rotor  46  coupled to a ring gear  23  (seen in  FIG. 2 ) in the planetary gear set  22  via the hollow shaft  19 . A second rotor  38  carrying permanent magnets  39  is positioned between a stator  47  and the first rotor  46 . The PM rotor  38  is mounted for rotation with the main drive shaft  20 . A first axial air gap  49  relative to the rotor shafts,  16 ,  19 ,  20  is located between the stator  47  and the PM rotor  38 . A second axial air gap  28  is provided between the PM rotor  38  and the uncluttered rotor  46 . And, a third axial air gap  48  is provided between the first rotor  46  and the secondary core and coil assembly  43 . The uncluttered rotor  46  rotates with the hollow shaft  19  and has non-contact magnetic brushes for conducting flux. 
   A battery  90  is connected to an inverter/rectifier  91  to supply power to, and to be charged from the secondary core assembly  43 . The battery  90  is also connected to an inverter/rectifier  92  to supply power to, and to be charged from, the stator  47 . The battery  90  can supply power to the assemblies  43 ,  47  on either side of the air gap region and can receive power from the assemblies  43 ,  47  on either side of the air gap region. 
   Speed sensors  15  and  17  are provided for sensing the speed of the internal combustion engine  10  and the wheels. A speed sensor is also provided in gear set  22  for sensing the speed of the uncluttered rotor  46 . These speed signals are sent to a controller  80 , which has the ability under certain conditions to move pin  26  into and out of engagement between a fixed member and the ring gear  23  so as to fix the position of the ring gear  23  or allow it to rotate. 
   As shown in  FIGS. 1 and 2 , the outside or ring gear  23  (denoted by the “r” subscript in the following equations) is coupled to the electric motor/generator of the present invention. The planetary gears  25  (denoted as a group by the “p” subscript and individually by the “1” subscript) are coupled to the internal combustion engine  10  through the hollow drive shaft  16 . The sun gear  27  (denoted by the “s” subscript) is coupled to the wheels  14  through the main drive shaft  20 . In  FIG. 2  and in the following equations, the radius of the these gears is denoted by “R” and the angular velocity is denoted by “ω”. 
   For point A on the outer circumference of sun gear  27  in  FIG. 2 , the following relationship applies:
 
ω s   ·R   s =ω 1   ·R   1 +ω p ·( R   p   −R   1 )  1)
 
   For point B on the inner circumference of ring gear  23  in  FIG. 2 , the following relationship applies:
 
ω r   ·R   r =ω 1   ·R   1 −ω p ·( R   p   +R   1 )  2)
 
   Solving for ω s  provides the following expressions: 
   
     
       
         
           
             
               
                 
                   ω 
                   s 
                 
                 = 
                 
                   
                     
                       2 
                       · 
                       
                         ω 
                         p 
                       
                       · 
                       
                         R 
                         p 
                       
                     
                     + 
                     
                       
                         ω 
                         r 
                       
                       · 
                       
                         R 
                         r 
                       
                     
                   
                   
                     R 
                     s 
                   
                 
               
             
             
               
                 3 
                 ) 
               
             
           
           
             
               
                 
                   ω 
                   r 
                 
                 = 
                 
                   
                     
                       
                         - 
                         2 
                       
                       · 
                       
                         ω 
                         p 
                       
                       · 
                       
                         R 
                         p 
                       
                     
                     + 
                     
                       
                         ω 
                         s 
                       
                       · 
                       
                         R 
                         s 
                       
                     
                   
                   
                     R 
                     r 
                   
                 
               
             
             
               
                 4 
                 ) 
               
             
           
         
       
     
   
   In the above equation 4) the minus sign signifies a direction opposite the positive direction. 
   The speed of the wheels, which corresponds to the rotational speed of the sun gear, ω s , can be controlled from both the stator  43  and secondary  47  of the machine of the present invention, with or without power to the wheels from the internal combustion engine. 
   The speed relationships are further expressed by the following equations. When the following expressions are true: 
                   ω   s     =         2   ·     ω   p     ·       R   p       R   s         ⁢           ⁢   or   ⁢           ⁢       ω   s       ω   p         =     2   ·       R   p       R   s                   5   )               
the speed of the wheels, ω s , is more than twice the speed of the engine speed, ω p , and when the ring gear speed, ω r , is zero, a locking pin  26  ( FIG. 1 ) can be inserted in the ring gear  23  to allow not supplying electric power to the electric motor/generator  12  at high vehicle speeds. The pin  26  can be disengaged by operating the motor/generator  12  so as to counter any forces on the pin  26  prior to disengagement.
 
   The object of the arrangement is to allow utilization the electric motor/generator at the entire speed range to be in motor, generator, and/or field weakening modes. 
   As seen in  FIG. 3   a , when the engine is being started, the ring gear is driven in a clockwise direction by the planetary gears  25  coupled to the engine via the hollow shaft  16 . The stationary sun gear  27  helps to make the engine start in a clockwise direction. 
   As seen in  FIG. 3   b , when the PM rotor  38  begins to rotate, it produces a torque on the sun gear  27  which aids the torque supplied to the wheels through the planetary gear set  25 . The rotation of the PM rotor sets up a counter torque (represented by the counterclockwise arrow in  FIG. 3   b ) in the uncluttered rotor which drives the ring gear  23 , but this torque aids the planetary gear set  25  in traveling around the sun gear  27 , which is also rotating in the direction of travel of the planetary gear set  25 . Thus, the torques from both the uncluttered rotor  46  and the PM rotor  38  combine to provide power to aid the drive provided by the internal combustion engine  10  to the wheels  14 . 
   As seen in  FIG. 3   c , when the vehicle reaches its middle speed range, the electric machine can be operated in a motoring mode, a regenerative braking mode or in a field weakening mode for operation above synchronous speed, as represented by the bi-directional arrow in the ring gear  23 . Field weakening can be provided to one or both sides. 
   As represented in  FIG. 3   d , the ring gear  23  can be de-coupled from moving by inserting a lock pin  26 . This effectively takes the PM rotor and the electric machine out of the power system, which may be desirable at very high speed, to conserve the energy that would otherwise be consumed to operate the electric machine. 
   Referring to  FIGS. 4   a - 4   c  and  5   a - 5   b , the details of the rotors  46 ,  38  in the PM machine  12  will now be described. The uncluttered rotor  46  is magnetically coupled to the PM rotor  38  instead of the armature  43 . The machine  12  sees the PM rotor  38  as the rotating field. The PM rotor  38  produces a flux wave that is either stationary or rotating. 
   An n-phase flux path for the rotating air-gap flux is formed on one side of the uncluttered rotor  46  facing the PM rotor  38 . On the other side of the uncluttered rotor  46 , the 2*n non-continuous rings are formed by the step-up portions  50  of the magnetic brushes A, B, C and D (seen in  FIGS. 4   a  and  4   b ). The n-phase secondary toroidal cores and coils  43  are coupled with the non-continuous rings for linking with the uncluttered fluxes that do not contain the rotation-frequency flux component. 
   The n-phase secondary toroidal coils can be connected to an inverter for speed controls in either a motor mode or a generator mode. Both modes can be with or without the field weakening mode. The uncluttered rotor  46  and the secondary toroidal cores and coils  43  are all parts of the secondary circuit. They are in the magnetic path of the permanent magnets  39  for controlling the air-gap flux density between the stator  43  and the PM rotor  38  for the field weakening and field enhancement modes, respectively. The PM rotor  38  can be operated in a motor mode or a generator mode depending on the control of the inverters connected to the stators  43  and  47 . 
   The PM rotor  38 , the uncluttered rotor  46 , and the secondary toroidal cores and coils  43  form an uncluttered slip energy machine except the PM rotor  38  is acting as an armature that produces either a rotating or a standstill flux wave between the PM rotor  38  and the uncluttered rotor  46 . For example, when the PM rotor  38  is standstill, the currents in the secondary toroidal coils  43  can produce a torque between the PM rotor  38  and the uncluttered rotor  46 . Under a relative rotation between the uncluttered rotor  46  and the PM rotor  38 , the secondary toroidal coils  43  can act as either a generator or a motor depending on the direction of current in the coils  43 . 
     FIGS. 4   a ,  4   b  and  4   c  show the details of the first rotor  46  with magnetic brushes A, B, C and D for a 2-phase, eighteen pole device rotor. Using symbol, n, as the number of phases of the uncluttered rotor  46 , each pole pair area (i.e., two times the pole-pitch  51 ) of the rotor consists of 2*n (i.e., 4) groups of magnetic brushes A, B, C and D. Two inner groups C, D of these four magnetic-brush groups A, B, C and D form one phase, and two outer groups A, B, form another phase. The detail views of these four groups of flux brushes, A, B, C, and D, are shown in  FIG. 4   c.    
   The magnetic brushes A, B, C and D can be made of stacked laminations, compressed powder cores, ferromagnetic wires or other equivalent soft magnetic materials that have good magnetic permeability, a high saturation level, and low core-loss properties. The magnetic brushes A, B, C and D are secured between the non-magnetic outer ring  54  and the non-magnetic rotor hub  55 . A two-phase flux path for the rotating air-gap flux is formed on one side of the rotor  46  facing the permanent magnet rotor  39 . On the other side of the rotor  46  are the step-up portions  50  ( FIGS. 4   a  and  4   b ) of the magnetic brushes A, B, C and D that form four non-continuous rings. The rings are separated in a radial direction by ring-shaped gaps  58  ( FIGS. 4   a  and  4   b ), which are made of material between each pair of magnetic brushes in each phase, each magnetic brush in the pair being separated on the secondary side from its counterpart magnetic brush by a ring-shaped air gap  59  ( FIGS. 4   a  and  4   b ). The rings of magnetic brushes are interrupted by radial gaps  56  ( FIG. 4   b ) between the magnetic-brush groups can be filled with non-magnetic materials. Because the summation of the opposite-polarity fluxes passing through the magnetic brushes per pole pair is zero, the boundary space of every pole pair can be made of electrically-conducting non-magnetic materials. This allows the rotor  46  to have sufficiently high mechanical strength required by certain designs. The outer ring  54  should be designed to withstand the centrifugal force of the rotor  46 . 
     FIGS. 5   a - 5   b  show the permanent magnet (PM) rotor  38  with alternating north (N) and south (S) pole permanent magnets  39 , one pair per pole pitch  73 . The magnets are also oriented N-S or the reverse through the thickness of the PM rotor  38  as seen in  FIG. 5   a . The rotor has an inner ring  70  and an outer ring  71  and radial gap portions  72  formed of non-magnetic material. 
   Although the invention has been described in an embodiment with the ring gear coupled to the uncluttered rotor  46 , in other embodiments the ring gear  23  can be coupled to the PM rotor  38  and the uncluttered rotor  46  can be coupled to the sun gear  27  and to the main drive shaft  20  driving the wheels  14 . 
   In still other embodiments, a three shaft differential gear set can be substituted for the planetary gear set  22 . 
   With the invention the electric machine can be operated as motor, as a generator or a field weakening region for speed above synchronous speed of the machine. 
   In the preferred embodiment, which is an axial gap machine, the primary air gap is disposed axially along an axis of rotation for the rotor and a second air gap is also disposed axially along an axis of rotation for the rotor. Radial gap embodiments can also be employed. 
   This has been a description of an example of the preferred embodiments of the invention. The present invention is intended to encompass additional embodiments including modifications to the details described above which would be apparent to one of ordinary skill in the art. To assist in defining the invention the following claims are provided.