Patent Publication Number: US-2018034356-A1

Title: Constantly variable transmission device

Description:
FIELD OF THE INVENTION 
     The present invention relates to a constantly variable, power transmission device with energy storage for harnessing the kinetic energy from a decelerating vehicle, storing it and supplying this energy to power the vehicle, at a high capacity, as it accelerates. 
     The invention has been primarily developed for automobile transmissions and gearboxes used in cars. However, it is envisaged that the invention also has other applications such as motor bikes, buses, trucks, trains, and in the generation of electricity in wind turbines and other renewable energy systems. 
     BACKGROUND 
     The price of energy, in particular oil based fuels such as petroleum and diesel that powers most of the vehicles on the road, ocean or air is continually increasing over time. Large sectors of the economy are affected by the rising cost of transportation and governments are continually introducing more rigid environmental standards for emissions control. 
     As a result, considerable effort and investment has gone into developing hybrid vehicles. These vehicles use the internal combustion engine as a main source of power with power augmented by an electric motor. Other recent developments include electric cars, the performance of which is now comparable to petrol and diesel vehicles. However, the electrical energy used to power the vehicles is stored in batteries which are heavy, expensive and have a limited storage capacity. The operating range of an electric vehicle is accordingly limited and this has constrained the mainstream uptake of these vehicles. 
     A majority of vehicles, including hybrid and electric, operate in a city environment with large amounts of traffic causing regular stopping and starting of the vehicle. The traditional method to slow down a vehicle is the use of disc or drum brakes that use friction pads to slow the vehicle. A large amount of energy is dissipated as heat during the deceleration process and is effectively wasted. Hybrid vehicles have the ability to operate their electric motors as generators when the vehicle is slowing and often use regenerative braking to reclaim a proportion of the energy normally wasted in braking, store it and then use it to propel the vehicle when it accelerates. However, the electrical storage capacity of such vehicles is limited by the instantaneous capacity of the batteries and at low speeds the changing magnetic flux in the generator reduces to ineffective levels meaning that only small proportions of the overall kinetic energy can be harnessed upon braking. 
     A recent development in the drive to improve vehicle efficiency has focused on the vehicle transmission or gearbox. Traditional automatic transmissions lose some energy in the torque converter so their efficiency drops. While manual transmissions have more efficient mechanical systems, the driver controlled gear changes usually reduce any gains. Two of the main most recent competing technologies in this field are the double-clutch transmission (DCT) and the constantly variable transmission (CVT). The DCTs are preferred on high performance cars and have very quick gear changes but can be unstable at low speeds. The area of CVT development has evolved from a traditional mechanical gearbox to an electrical gearbox and more recently a magnetic gearbox to fulfil different needs. Current CVTs are typically less efficient than DCTs and are typically limited to small cars so there exists a big opportunity to develop efficient and powerful CVTs for larger applications. 
     With batteries being the limiting factor, there is no effective method to store large amounts of kinetic energy and release it on demand. CVTs scaled up for higher capacities with integrated mechanical storage would be very attractive to energy-conscious drivers and businesses. 
     In the wind industry, gearboxes are one of the biggest issues for operating a wind farm. They represent about 15% of all wind turbine failures and changing a gearbox typically takes 3 weeks and approximately US$300,000 for a 3 MW wind turbine. One of the methods to overcome this is to use a direct drive wind turbine. However, due to the slower speeds, generator efficiency is reduced. The generator is also complex and expensive to maintain. 
     It is the variable speed of the rotor that creates complexity in wind turbines. If power could be supplied to the generator at a fixed speed, then a synchronous generator could be used. This could also alleviate the need for a power converter which currently represents the largest proportion of wind turbine failures at about 27%. Using a CVT gearbox could provide this functionality and has the potential to alleviate most gearbox and power converter failures, amounting to about 42% of all wind turbine failures. A mechanical CVT could not operate under such high loads and, without energy storage, there is no load levelling or effective technique to dampen the wind power spikes or low power levels that are inherent to the operation of a wind turbine. There exists a real opportunity to use a more advanced gearbox and to potentially solve some large and costly issues in the wind industry and other renewable industries. 
     OBJECT OF THE INVENTION 
     It is the object of the present invention to substantially meet one or more of the above needs at least to an extent. 
     SUMMARY OF INVENTION 
     There is disclosed herein a variable ratio transmission device, comprising: 
     at least one first rotor having an axis of rotation and including at least one first set of coils; 
     at least one second rotor having an axis of rotation and including at least one first set of iron segments; 
     at least one third rotor having an axis of rotation and including at least one second set of coils and at least one third set of coils; 
     at least one fourth rotor having an axis of rotation and including at least one second set of iron segments; 
     at least one fifth rotor having an axis of rotation and including at least one fourth set of coils; 
     wherein the at least one first set of coils is arranged in magnetic communication with the at least one first set of iron segments and the at least one first set of iron segments is arranged in magnetic communication with the at least one second set of coils on the same rotor as the at least one third set of coils; the at least one first rotor, at least one second rotor and at least one third rotor being configured to form a first set of magnetic gears; and 
     wherein the at least one third set of coils on the at least one third rotor is arranged in magnetic communication with the at least one second set of iron segments on the at least one fourth rotor and the at least one second set of iron segments is arranged in magnetic communication with the at least one fourth set of coils, the third rotor, fourth rotor and fifth rotor being configured to form a second set of magnetic gears coupled to the first set of magnetic gears. 
     Such a device forms a set of two integrated magnetic gears made up of the first, second and third rotors in the first set of magnetic gears and the third, fourth and fifth rotors in the second set of magnetic gears, with the third rotor being common to both. Each of the five rotors is magnetically coupled to its adjacent rotor, whereby the first set of magnetic gears includes an input shaft and an output shaft and is typically used to transmit power with a variable gear ratio to the output shaft, which may be either of the second or third rotors depending on the transmission configuration, as will be described in further detail herein. 
     Preferably, the second set of magnetic gears includes a flywheel for the mechanical storage of kinetic energy harnessed during braking (in a vehicle application) or at times of excess power (in a wind turbine application). This stored energy can then be supplied back into the transmission device for acceleration of the output shaft or to provide additional power to a generator, depending on the use, at a later time. 
     Preferably, each of the first and second sets of magnetic gears have at least one chosen rotor that includes an integrated motor/generator having magnets or induction coils and windings for control of the rotor speed via an associated gearbox controller). The gearbox controller ultimately controls the gear ratio of each of the first and second set of magnetic gears. A battery is preferably provided in electrical communication with the gearbox controller. For approximately 50% of the operation of the transmission device, the battery associated with the motor/generator will feed electrical power into the motor/generators to speed up the rotors and for about 50% of the operation it will need to slow them down. During the latter phase of operation, the motor/generator generates power back to the gearbox controller and battery to be stored and used to speed up the rotors later. This arrangement somewhat reduces the power requirements of and increases the efficiency of the transmission device. 
     The first and second sets of magnetic gears are designed so that if the first set of coils (such as permanent magnets) on the first rotor has N 1  pole pairs and the second set of coils (such as permanent magnets) on the third rotor has N 2  pole pairs then the number of iron segments on the second rotor will have N 3  segments whereby: 
     
       
      
       N 
       3 
       =N 
       L 
       +N 
       2  
      
     
     This same rule applies to both the first and second sets of magnetic gears if maximum efficiency with minimal noise is desired. This sets the intrinsic gear ratio (the gear ratio when the iron segment rotor of the particular magnetic gear is at rest) to be: 
     
       
      
       G 
       r 
       =N 
       1 
       /N 
       2  
      
     
     When the second rotor is selected as being the rotor that comprises an integrated motor/generator and which thereby has it speed controlled, the speed of the second rotor can be controlled to adjust the operating gear ratio of the magnetic gear according to the following relationship between the speed of the first rotor ω 1 , second rotor ω 2  and third rotor ω 3 : 
       ω 1   +G   r ·ω 2 −(1+ G   r )ω 3 =0
 
     The negative sign in front of the last term of the equation signifies that the third rotor rotates in the opposite direction to the first rotor. To control the operating gear ratio of the magnetic gear, it can be shown that by measuring the speed of the first rotor (assigned as an input shaft) ω 1  and third rotor ω 3  (assigned as an output shaft), and knowing the intrinsic gear ratio G r , then the speed of the second rotor can be used to control the speed of the third rotor with a variable gear ratio using power input from the first rotor. Similarly, any of the three rotors can be selected as the speed control rotor to control the speed of whichever rotor is assigned as the output rotor with a variable gear ratio achieved via the power input at the input rotor. 
     When the first set of magnetic gears is combined with the second set of magnetic gears via the third rotor, the transmission device works as a single set of coupled gears such that the operating gear ratio of the first set is controlled by the speed of one of the first or second rotors and the gear ratio of the second set is controlled by the speed of the fourth or fifth rotors. Using a configuration in which the first set of magnetic gears is arranged to transmit power from an engine to a vehicle drive shaft and the second set being arranged to transmit power from the drive shaft to a flywheel power transfer, then the first or second rotor controls the operating gear ratio and ultimately the speed at the drive shaft while the fourth or fifth rotor controls the amount of power added to or taken from the flywheel that is used in regenerative braking vehicle acceleration or load leveling in the application of a wind turbine. 
     In a preferred embodiment, the first set of magnetic gears is used to transmit power at a variable gear ratio to the assigned output shaft and is coupled with the second set of magnetic gears which are coupled to a flywheel to mechanically store kinetic energy harnessed during braking or power spikes for the supply of this energy back for acceleration or in times of low power. In this parallel arrangement, power mixing, splitting and storage can be achieved in a single device. 
     In another preferred embodiment, the first set of magnetic gears is a first stage gear set that is used to transmit power at a variable gear ratio to the input to a second stage (or third) set of magnetic gears that is located between the first stage set of magnetic gears and the second set of magnetic gears. The second stage set of magnetic gears transmits power at a variable gear ratio to the output shaft of the second stage set of magnetic gears. In this series arrangement, very high, variable gear ratios can be achieved in a single device such as those required for a wind turbine. 
     In a preferred embodiment, the axes of rotation of the five rotors of the first and second set of magnetic gears are preferably on the same axis so as to provide concentrically and preferably coaxially configured magnetic gear sets. 
     In another embodiment, the axes of rotation of twin fifth rotors are arranged perpendicularly to the axes of the other four rotors. The magnetic gears are very forgiving of misalignment and the magnetic flux can be transmitted over a diverse range of rotating styles of gears mimicking and sometimes exceeding the performance of their mechanical counterparts. The rotor axes may accordingly be aligned with the other rotor axes in various configurations such as series, parallel, perpendicular, offset, transverse, split, mixed and at an arbitrary angle for flexible magnetic gearbox designs. 
     In a preferred embodiment, the first set of magnetic gears is arranged in a configuration having a radial magnetic flux between the first, second and third rotors. The second set of magnetic gears is arranged in an axial flux configuration between the third, fourth and fifth rotors. In this embodiment, the power flow in the first set of magnetic gears is well balanced and transmitted in the radial flux configuration while the axial flux from the flywheel couples to the output shaft in minimal space, highlighting how mixing the configurations within the transmission device can be highly advantageous. 
     In another embodiment, the second set of magnetic gears includes a pair of fifth flywheel rotors that rotate on a vertical axis perpendicular to the third and fourth rotors. This configuration is advantageous to cancel any large precession forces in the flywheels which is optimal for use in racing cars and other vehicles. The fourth sets of coils on the fifth rotors and iron segments on the fourth rotor can be geometrically designed in stretched and skewed magnetic pole shapes to optimise the magnetic flux transfer on the fourth and fifth rotors. 
     Each of the sets of coils may be composed of a series of permanent magnets or induction coils excited by their corresponding stator coils. 
     In a preferred embodiment the coils are composed of permanent magnets installed using a Hallbach Array configuration whereby the magnetic poles may span two, three, four or more magnets. This configuration has the advantage of reducing the number of poles installed on a rotor so that higher gear ratios can be achieved and the majority of the magnetic field is sinusoidal in the air gap for reduced noise and is exerted on a single side which increases magnetic utilisation. 
     In another embodiment, the coils are composed of permanent magnets installed with the magnet poles being arranged in a traditional north/south configuration. A number of options exist for the number of pole pairs of each of the first, third and fifth rotors as long as the total number of poles follows the rule N 3 =N 1 +N 2  as described above. 
     Each of the five or more rotors is rotatably mountable and supported by at least one bearing for hold the rotor substantially fixed in space while allowing free rotation about its axis. The transmission device provides for a range of input shaft and output shaft options. That is, either of the first, second or third rotor could be configured as an input shaft and correspondingly one of the other two rotors as the output shaft. This is advantageous to configure the transmission device for a range of product designs. 
     In a preferred embodiment, the first rotor is configured as the input shaft, the second rotor is configured as the output shaft and the third rotor is configured as the speed controlled rotor. In this configuration, the input and output shafts rotate in the same direction, which is advantageously compatible with current automobile gearbox configurations. 
     In another embodiment, the first rotor is configured as the input shaft, the second rotor is configured as the speed controlled rotor and the third rotor is configured as the output shaft. In this configuration the gear ratio is typically a much higher ratio, such as are required for those gearboxes used in wind turbines. 
     In a preferred embodiment, there is a single input shaft and single output shaft. In another embodiment, there are multiple input shafts all feeding into the magnetic gearbox. This is useful to augment power into a single source. 
     In another embodiment, there are multiple output shafts all fed from the transmission device. This is useful to supply multiple streams of power from a single source. 
     In another embodiment, there are multiple input and output shafts all fed into and from the magnetic gearbox. This is useful to supply multiple streams of power from multiple sources. 
     In a preferred embodiment, the input and output shafts each have rotational speed sensors and preferably torque sensors associated therewith and in electronic communication with the gearbox controller. 
     The two speed and/or torque sensors are used as feedback into the gearbox controller so that based on the speed requirements accepted from the engine control unit (ECU) and/or driver demands on the accelerator and brake pedals, the gearbox controller can adequately control the speed of the first or second and fourth or fifth rotors to achieve the required gear ratios. The driver sends demands for power and braking and this is used by the gearbox controller to control and ensure that the regenerative braking and acceleration are smooth. The gearbox controller sends and receives power from the battery. It connects to motor/generators on the first or second and fourth or fifth rotors typically by a three-phase connection and is connected to the rotational speed sensors, which may be rotary encoders or Hall sensors. Additional control measures utilise speed and/or torque sensors so that the gearbox controller can accurately predict and set the speeds for the two control rotors. In the case of a wind turbine, the speed of the output shaft is set as a constant and the gearbox controller sets the speeds of the control rotors to ensure that this constant speed is achieved. The controller may also be capable of remote monitoring and control, including the remote tuning of control parameters and output requirements. 
     In a preferred embodiment, the third rotor and the fifth rotor have their speed controlled to adjust the gear ratios in the transmission device. This configuration is advantageous since the motor/generator coils or permanent magnets on the first and fifth rotors are setup at the extents of the magnetic gearbox and allow easy access to their corresponding stator coils. 
     In another embodiment, the second rotor and the fourth rotor have their speed controlled to adjust the gear ratios in the magnetic gearbox. 
     Preferably, an enclosure or casing is arranged to substantially surround or encapsulate the transmission device so as to secure the device to a stable mounting and contain the energy contained therein in the event of a flywheel failure, while allowing at least the input and output shafts to protrude from the enclosure. The input and output shafts may employ seals to close off the transmission device to the environment. However, in normal usage, the various transmission device parts never touch and are lubricant free, therefore seals are typically not required unless a full or partial vacuum is desired in the enclosure. 
     In an embodiment, the enclosure further includes a non-return valve and a vacuum pump adapted for placing the enclosure and transmission device under a full or partial vacuum. The vacuum reduces any fluid friction on the flywheel as it spins and thereby increases the efficiency of its energy storage. Preferably, the apparatus includes a water jacket arranged outside the transmission device and enclosure. The water jacket absorbs any heat generated inside the transmission device. Alternatively the enclosure may be hermetically sealed, vacuumed to a low internal pressure and a coupling such as a magnetic coupling is provided to transmit power between the inside of the enclosure and an external shaft, thereby eliminating mechanical seals. 
     In an embodiment, the drive shaft is a drive shaft of a vehicle. In another embodiment, the drive shaft is adapted for driving a compressor. In yet another embodiment, the drive shaft is connected for driving an electrical generator inside a wind turbine. 
     Preferably, the gearbox controller is a digitally controlled switched brushless motor controller capable of controlling at least two motors and accepting a range of inputs such as driver demands, speed and torque sensor inputs according to a controller program and specific design requirements. 
     Preferably, the gearbox controller and motor/generators each include a rotor position and speed sensor. More preferably, the gearbox controller includes at least one rotary encoder and/or magnetic hall sensor. 
     Preferably, the gearbox controller is sufficiently powerful and capable to control the first or second and fourth or fifth rotors in a controlled manner with an appropriate response time to control the gear ratios and meet the transmission power and response time requirements. 
     Preferably, the energy storage comprises an external electrical power storage device such as a battery or a super capacitor. 
     Preferably, the coils are permanent magnets. Alternatively, the coils are induction coils, switched reluctance coils or coils capable of generating a magnetic flux. 
     Preferably, the first, second, third and fourth sets of coils are arranged in a radial flux configuration. 
     Alternatively, the first, second, third and fourth sets of coils are arranged in an axial, transverse or hybrid flux configuration, or a mixture thereof. 
     Preferably, the iron segments are composed of laminated electrical steel or soft magnetic composites to lower hysteresis losses and increase efficiency. 
     Alternatively, the iron segments are solid iron or ferrite bars. 
     Preferably, external clutches are provided at the input and output shafts to fully decouple the magnetic gearbox from the engine and output shafts. 
     Alternatively, the speed of the first or second and fourth or fifth rotors in the magnetic gearbox can be controlled at a certain speed to perform a clutching operation so that the output shaft can be at rest while the input shaft is rotating. 
     Alternatively, a vehicle clutch can be used or other conventional clutching device can be used to decouple the magnetic gearbox from the engine and output shaft. 
     Alternatively, a magnetic clutch can be installed inside the transmission device to decouple the desired rotors, for example decoupling the transmission device from the flywheel and/or input shaft. The magnetic clutch may typically consist of a thin steel or metal screen that dissipates any magnetic flux as Eddy currents between the rotors in the steel screen and will decouple that rotor from the rotor on the other side of the steel screen. Alternatively, moving the rotors apart so that their air gaps become very large is another form of mechanically actuated magnetic clutch. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings wherein: 
         FIG. 1 a    is a half sectional schematic plan view of a first embodiment of a constantly variable transmission device configured in a radial and axial magnetic flux configuration; 
         FIG. 1 b    is a schematic side sectional view of a first set of magnetic gears of  FIG. 1   a;    
         FIG. 2  is a half sectional schematic plan view of a second embodiment of the transmission device, in which the output shaft is configured to rotate in the same direction as the input shaft; 
         FIG. 3  is a half sectional schematic plan view of a third embodiment in which the transmission device is advantageously configured so that the motor/generators are at the device extents: 
         FIG. 4  is a half sectional schematic plan view of a fourth embodiment, in which the transmission device is set up with hybrid flux coils with increased flux density; 
         FIG. 5  is a half sectional schematic plan view of a fifth embodiment, in which the transmission device is set up with hybrid flux coils with increased flux density and the motor/generators at the device extents; 
         FIG. 6  is a half sectional schematic plan view of a sixth embodiment, in which the transmission device is set up with twin flywheels rotating in opposite directions; and 
         FIG. 7  is a half sectional schematic plan view of a seventh embodiment, in which the transmission device includes a first set of magnetic gears and a further (third) set of magnetic gears arranged in series and then coupled to the second set of magnetic gears 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1 a    shows a first embodiment of a constantly variable transmission device  100  with energy storage in half sectional view. The transmission device  100  includes an input shaft  1  as the first rotor, iron segment rotor  2  as the second rotor, output shaft  3  as the third rotor, iron segment rotor  4  as the fourth rotor, and the flywheel  5  as the fifth rotor. The rotors  1 ,  2 ,  3 ,  4  and  5  are all housed inside an enclosure  6  that can be used to secure the device to a stable mounting and minimise damage in the event of failure of the flywheel  5 . 
     In this first embodiment, all five rotors  1 ,  2 ,  3 ,  4 ,  5  share the same axis of rotation as depicted by the dashed line  47 . The first rotor  1  is generally ‘Y’ shaped in section and comprises an input shaft at the input end of the transmission device and a distal annular section. A set of coils  7  is installed on a peripheral surface of the annular section. The first rotor  1  is supported by a set of bearings  21 , suitably mounted to allow free rotation of the input shaft  1 . The second rotor  2  is supported by a set of bearings  23 . The second rotor  2  is also annular, having an internal diameter that is slightly larger than the outer diameter of the annular section of the first rotor  1 , such that when the first rotor  1  and the second rotor  2  are mounted concentrically on the same axis of rotation  47 , an air gap is present between the two rotors. The third rotor  3  is also ‘Y’ shaped in cross section and its annular section is slightly larger in internal diameter than an external diameter of the second rotor  2 , such that an air gap exists between the second rotor  2  and the third rotor  3 . The annular section of the rotor  3  terminates in an end face, the output shaft  3  of the transmission device extending distally therefrom. The output shaft  3  is supported by a set of bearings  26 . 
     The third rotor  3  includes a set of coils  11  installed on the end face of the annular section. The fourth rotor  4  is annular in cross section and is mounted on the axis  47  adjacent the end face of the third rotor  3 , such that an air gap is present between the two rotors. The fifth rotor is also annular in cross section and is mounted on the axis  47  adjacent the fourth rotor  4 , such that an air gap is present between the two rotors. The fourth rotor  4  is supported by a set of bearings  24  and the flywheel  5  is supported by a set of bearings  25 . 
     The input shaft  1  has coils  7  installed on its rotor that are typically powerful rare-earth permanent magnets, preferably arranged in a Hallbach Array to maximise their power. Alternatively, the coils may be induction coils or a mixture thereof. The third rotor/output shaft  3  has similar coils  9  installed on the external surface of the annular section. The number of coils installed on the third rotor  3  is different to the number of coils installed on the annular section of the input shaft  1 , in accordance with the design criteria N 3 =N 1 +N 2  described in the Summary section above. The second shaft  2  has iron segments  8  installed on the rotor so that the magnetic flux as depicted by the arrow  10 , can transmit magnetic and ultimately mechanical torque through the magnetic gear at a variable gear ratio. The first set of magnetic gears  101  is shown in side view in  FIG. 1 b    with four pole pairs on the input shaft  1 , seven pole pairs (N 2 ) on the output shaft  3 , and using the relationship N 3 =N 1 +N 2 , eleven iron segments on the second rotor  2 . This sets the intrinsic gear ratio (Gr) at 1:1.75. 
     As seen in  FIG. 1 b   , the pole pairs of the rotors  1 ,  2  and  3  are typically divided into a north pole  32  and a south pole  33  on the first rotor  1 , divided into a north pole  28  and a south pole  29  on the third rotor  3 , and divided into iron segments  30  and air or non-ferrite segments  31  on the second rotor  2  such that the magnetic flux couples the input shaft  1  with the output shaft  3  in a fixed intrinsic gear ratio (Gr) when the second rotor  2  is stationary, or a variable operating gear ratio according to the speed of the second rotor  2 . Hallbach Arrays that have their magnetic poles extending over multiple magnets can be employed to adjust the intrinsic gear ratio (Gr) to higher levels. 
     In the first set of magnetic gears  101 , the set of coils  7  comprises of permanent magnets installed on the input shaft  1  and transmits a magnetic flux  10  into, and out of, the set of iron segments  8  installed on the second rotor  2 . The set of iron segments transmits this magnetic flux  10  into, and out of the set of permanent magnets  9  that are installed the third rotor  3 . When mechanical torque is applied to the input shaft  1 , it is converted into the magnetic flux  10  that produces magnetic torque in the air gaps present between the first set of coils  7  and iron segments  8 , and between the iron segments  8  and second set of coils  9 . This magnetic torque is converted back into mechanical torque at the output shaft  3 . The magnetic flux  10  of the first set of magnetic gears is arranged in a radial flux configuration as shown in  FIGS. 1 a    and  1   b.    
     The second set of magnetic gears comprises of the third rotor  3 , the fourth rotor  4  and the fifth rotor  5 . The set of coils  11  comprises a set of permanent magnets that is installed on the output shaft  3  and which transmits a magnetic flux  14  into and out of the set of iron segments  12  installed on the fourth rotor  4 . The set of iron segments  12  transmits this magnetic flux  14  into and out of the set of permanent magnets  13  that are installed the flywheel  5 . When mechanical torque is applied to the output shaft  3 , it is converted into the magnetic flux  14  that produces magnetic torque in the air gaps present between the coils  11  and iron segments  12 , and between the iron segments  12  and coils  13 . This magnetic torque is converted back into mechanical torque at the flywheel  5  for charging the flywheel by speeding it up when in regenerative braking mode, or when power spikes require load leveling, depending on the application. Under acceleration or at times of low power, the flywheel  5  discharges and slows down to transmit power in reverse and supply mechanical torque to the output shaft  3 . The magnetic flux  14  of the second set of magnetic gears is in an axial flux configuration as shown in  FIG. 1 a   . Combining a radial flux configuration for the first set of magnetic gears and an axial flux configuration for the second set of magnetic gears allows for greater utilisation of space and infrastructure, making the gearbox more compact and lightweight. 
     A rotational speed sensor  22  is installed near the input shaft  1  at the input end of the transmission device  100 . The speed sensor  22  is coupled to a torque sensor  22   a  so that speed and torque can be measured. A rotational speed sensor  27  is installed near the output shaft  3 . This speed sensor  27  is coupled to a torque sensor  27   a  so that speed and torque can be measured. Alternatively, if torque sensors are not fitted then the speed sensor  22  monitors the speed of the second rotor  2 , and the speed sensor  27  monitors the speed of the fourth rotor  4 . The sensors  22 ,  27  are in electrical communication with a gearbox controller  34 . Additional and more accurate control is provided when further speed sensors  27   b ,  27   c  installed inside two control motor stators  16  and  19  installed on the enclosure  6  and a further speed sensor  27   d  installed near the flywheel  5 , are also in electrical communication with the gearbox controller  34 . Accordingly, the gearbox controller  34  can be configured to ascertain the speed of all five rotors, providing the potential for maximum control for the transmission device  100 . 
     A set of small coils  15  composed of permanent magnets is installed on the second rotor  2 . A motor stator or motor generator  16  includes a corresponding set of stator coils  16  mounted on the enclosure  6 , adjacent the second rotor  2 . The motor generator  16  uses electrical power supplied from the gearbox controller  34  to generate a magnetic flux  17  in a controlled manner to cause rotation of the second rotor  2 . The gearbox controller  34  uses the feedback from the speed sensors  27   b  located inside or near the stator coils  16  to measure the speed of the second rotor  2 , following which it employs closed loop control algorithms to send an appropriate amount of power to the stator coils  16 , which in turn accurately controls the speed of the second rotor  2 . The speed of the second rotor  2  sets the operating gear ratio of the first set of magnetic gears  101  as the ratio between the speed of rotation of the input shaft  1  and the speed of rotation of the output shaft  3 . 
     A set of small coils  18  comprising of permanent magnets is installed on a periphery of the fourth rotor  4 . The motor stator or motor generator  19  includes a corresponding set of stator coils mounted on the enclosure  6 , adjacent the fourth rotor  4 . The motor generator  19  uses electrical power supplied from the gearbox controller  34  to generate a magnetic flux  20  in a controlled manner to cause rotation of the fourth rotor  4 . The gearbox controller  34  uses the feedback from the speed sensors  27   c  located inside or near the stator coils  19  to measure the speed of the fourth rotor  4 , following which it employs closed loop control algorithms to send appropriate power to the stator coils  19 , which in turn accurately controls the speed of the fourth rotor  4 . The speed of the fourth rotor  4  sets the operating gear ratio of the second set of magnetic gears as the ratio between the speed of rotation of the output shaft  3  and the speed of rotation of the flywheel  5 . This operating gear ratio is used to charge the flywheel  5  using regenerative braking or during large power spikes and to discharge the flywheel  5  under acceleration or at times of low power by setting the appropriate gear ratio corresponding to the required direction of power transfer. 
     The gearbox controller  34  is connected to a battery  35  so that power can travel in either direction; that is from the gearbox controller  34  to the battery  35  or vice versa. The gearbox controller  34  is also connected to an engine control unit  36  so that any commands from a vehicle driver, engine and other systems can be communicated to the gearbox controller  34  via the engine control unit  36  and/or directly from a source such as a brake pedal or accelerator pedal of a vehicle. The gearbox controller  34  is connected to the rotational speed sensor  27  using the cables  37 , connected to the set of coils of the motor generator  19  using the cables  38 , connected to the set of coils of the motor generator  16  using the cables  39 , and connected to the rotational speed sensor  22  using the cables  40 . Using the large amount of data available from the speed and torque sensors, the gearbox controller  34  is able to process this data and provide the correct power profiles to accurately control the speed of the second rotor  2  and fourth rotor  4  to enable smooth power transfer from the input shaft  1  to the output shaft  3  and smooth power transfer between the output shaft  3  and flywheel  5 . 
       FIG. 2  shows a second embodiment of a constantly variable transmission device  200  in half sectional plan view. The device  200  has many similarities with the device  100  and like components are numbered accordingly. The transmission device  200  is connected to a gearbox controller  234 , shown schematically in  FIG. 2 . In this embodiment, the second rotor  202  and third rotor  203  have been swapped around compared to the embodiment of  FIG. 1 a   . The second rotor  202  having the iron segments  208  installed on it is now configured as the output shaft and is ‘Y’-shaped in section in the same manner as the third rotor  3  of the embodiment of  FIG. 1 . The third rotor  203  having the permanent magnets  209  installed on it is now configured as the speed controlled rotor and is simply annular in section. The third rotor  203  has its speed controlled via the magnetic flux  217  from a corresponding motor/generator  216 . As in the first embodiment, a battery  235  and an engine control unit  236  are connected in two-way electric communication with the gearbox controller  234 . The configuration of  FIG. 2  advantageously changes the direction of rotation of the output shaft  202  to match the direction of rotation of the input shaft  201 , which is the current standard for automobile gearboxes. 
       FIG. 3  shows a third and preferred embodiment of a constantly variable transmission device  300  in half sectional plan view. The transmission device  300  is connected to a gearbox controller shown only schematically in the Figure. The rotor configuration of this embodiment is the same as that of  FIG. 2  in many respects and like numbers are used for similar components as numbered in  FIG. 2 . However, the third rotor  303  now accommodates a much larger set of permanent magnets  315  installed in the middle of the outer peripheral face of the third rotor  303 . The fourth rotor  304  is now configured as the flywheel with a set of iron segments  312  installed on it. The fifth rotor  305  is now a speed controlled rotor with a set of permanent magnets  318  installed its peripheral outer face. A motor generator is arranged to control the speed of the fifth rotor  305  and comprises of the set of permanent magnets  318  and the stator coils  319 , the magnetic flux  320  existing between the coils  319  and magnets  318 . A motor/generator is used to control the speed of the third rotor  303  and comprises of the set of permanent magnets  315  and the stator coils  316 . A magnetic flux  317  exists between the coils  316  and magnets  315 . In this configuration, the third rotor  303  and fifth rotor  305  are used as the speed controlled rotors for the first and second set of magnetic gears respectively. As in the first embodiment, a battery  335  and an engine control unit  336  are connected in two-way communication with the gearbox controller  334 . The configuration of  FIG. 3  provides significantly more space to install the motor/generators at the transmission device extents which potentially reduces cost and/or increases performance. 
       FIG. 4  shows a fourth embodiment of a constantly variable transmission device  400  in a half sectional plan view, shown schematically connected to a gearbox controller  434 . Like numbers are used for similar components as numbered in  FIG. 1 a   , however in this embodiment the rotor and coil configuration differs from the previous embodiments. The embodiment includes a first rotor  401  that is configured as the output shaft and is ‘T’ shaped in cross section. The input shaft at a proximal end of the first rotor expands into a short cylindrical section at a distal end of the first rotor  401  and terminates in an end face  401   a . The second rotor  402  comprises an annular shaped rotor that has a peripheral wall with an internal diameter that is slightly larger than the external diameter of the short cylindrical section of the first rotor  401 . The second rotor  402  is mounted for rotation about the axis  47  such that an air gap exists between the peripheral walls of the two rotors  401 ,  402 . The peripheral wall of the second rotor  402  extends beyond the end face  401   a  of the first rotor  401 . It also includes an inwardly facing annular flange  402   a  that extends from an internal face of the peripheral wall approximately halfway along the peripheral wall. The flange  402   a  is positioned adjacent the end face  401   a  of the first rotor  401  such that an air gap is present between the end face  401   a  and the flange  402   a.    
     The third rotor  403  is configured as an elongate output shaft having a ‘T’-shaped cross section. The third rotor  403  is mounted on the axis  47  such that a proximal end thereof is positioned adjacent the flange  402   a  with an air gap present therebetween and such that an outer peripheral wall thereof fits inside the peripheral wall of the second rotor  402  with an air gap therebetween. The second rotor  402  terminates part way along the peripheral wall of the third rotor  403 . The third rotor  403  has a cylindrical section that terminates at a distal face, the output shaft extending distally thereform. 
     The fourth rotor  404  is the same shape and dimensions as the second rotor  402  and is mounted for rotation on the axis  47  so that it fits adjacent the outer peripheral wall of the third rotor  403  with an air gap between the two rotors  403 ,  404  and so that an inwardly facing annular flange  404   a  of the fourth rotor  404  fits adjacent the distal face of the third rotor  403  so that an air gap exists between the two rotors  403 ,  404  also in this orientation. 
     The fifth rotor  405  is annular and is mounted on the shaft  47  concentrically with the output shaft portion of the rotor  403  and adjacent the annular flange  404   a  of the fourth rotor  404 , such that an air gap is present between the rotors  403  and  404  and  404  and  405  respectively. 
     The first rotor  401  has a first set of permanent magnets  407  installed on both the end face  401   a  and at the peripheral face thereof. The second rotor  402  includes a first set of iron segments  408  installed on both the peripheral wall and the annular flange  402   a . The third rotor includes a second set of permanent magnets  409  installed at the proximal end thereof adjacent the iron segments  408 , and also a third set of permanent magnets  411  installed at the distal face and the distal end of the outer peripheral wall thereof. The fourth rotor  404  includes a second set of iron segments  412  installed along its peripheral wall and annular flange  404   a . The fifth rotor  405  includes a fourth set of permanent magnets  413  installed at a proximal end thereof and at the periphery thereof, adjacent the iron segments  412 . All four sets of permanent magnets  407 ,  409 ,  411  and  413  are setup in a hybrid configuration whereby they can supply magnetic field into the iron segments  408  and  412  in both a radial and an axial direction. The first set of permanent magnets  407  supplies magnetic flux  410  into the iron segments  408  that supply magnetic flux  410  into the second set of permanent magnets  409 . The third set of permanent magnets  411  supplies magnetic flux  414  into the iron segments  412  that supply magnetic flux  414  into the fourth set of permanent magnets  413 . As in the first embodiment, a battery  435  and an engine control unit  436  are connected in two-way electrical communication with the gearbox controller  434 . The hybrid flux configuration of this embodiment can significantly increase the magnetic flux density in the air gap, torque density and capacity of the transmission device. 
       FIG. 5  shows a fifth embodiment of a constantly variable transmission device  500  in half sectional plan view. The transmission device  500  is connected to a gearbox controller  535 . The rotor configuration is similar to that of the embodiment of  FIG. 4  and like numbers are used for similar components as numbered in  FIG. 4 , with the exception of the second rotor  502 , fourth rotor  504 , a set of permanent magnets  515 , a set of stator coils  516 , magnetic flux  517 , a set of permanent magnets  518 , a set of stator coils  519  and magnetic flux  520 . In this embodiment, the second rotor  502  and fourth rotor  504  each have motor/generators  516 ,  519  installed on them on the outer face of the rotors  504 ,  502  respectively. The set of permanent magnets  515  are installed on the second rotor  502  in close proximity to the stator coils  516  that create a magnetic flux  517 . Another set of permanent magnets  518  are installed on the fourth rotor  504  in close proximity to the stator coils  519  that create a magnetic flux  520 . In this configuration, the motor/generators  516 ,  519  can utilise a significantly larger space than in previously described embodiments, allowing them to be bigger and more powerful. This is very effective for controlling a hybrid flux magnetic gearbox that is typically very powerful. 
       FIG. 6  shows a sixth embodiment of a constantly variable transmission device  600  in half sectional plan view. The transmission device  600  is connected to a gearbox controller  634 , shown only schematically. The rotor configuration of the first, second and third rotors is similar to that of the embodiment of  FIG. 1 a    and like numbers are used for similar components as numbered in  FIG. 1 . However, the third rotor  603 , now has an additional second set of permanent magnets  611   a  installed on it. The fourth rotor  604  is mounted adjacent the third rotor  603  for rotation about the axis  47 , that is the same axis as the third rotor  603 . The fifth rotor is now divided into a pair of flywheels comprising a first flywheel  641  and a second flywheel  642 . The flywheels  641 ,  642  are each located adjacent the fourth rotor  404  but are now mounted for rotation about an axis of rotation  648  that is perpendicular to the axis  47  about which the third rotor  603  and fourth rotor  604  are mounted. The flywheels  641 ,  642  each span the length of the transmission device  600 . The first flywheel  641  has a first set of permanent magnets  645  installed thereon and the second flywheel  642  has a second set of permanent magnets  643  installed thereon adjacent a set of iron segments  612  installed on the fourth rotor  604 . 
     The set of permanent magnets  611   a  is installed on a periphery of the third rotor  603  adjacent the set of iron segments  612  installed on the fourth rotor  604 . The corresponding magnetic flux is now divided into two areas of the first magnetic flux  646  and second magnetic flux  644 , first set of permanent magnets  645  installed on the rotor  641 , second set of permanent magnets  643  installed on the rotor  642 . The first flywheel  641  and second flywheel  642  rotate about the axis  648  with their corresponding top set of permanent magnets  645  and bottom set of permanent magnets  643  both in magnetic communication with the second set of iron segments  612  so that both flywheels are coupled to the single fourth rotor  604 . The set of permanent magnets  611   a  is magnetically coupled to the set of iron segments  612  which is coupled to both the first set of permanent magnets  645  and the second set of permanent magnets  643  to produce a corresponding first magnetic flux  646  and second magnetic flux  644 . The first magnetic flux  646  and second magnetic flux  644  are usually equivalent in magnitude but operate in opposite directions. These magnetic fluxes cause rotation of the first flywheel  641  and second flywheel  642  to be in opposite directions. In normal operation, the speed of the flywheels will be similar so that any precession forces that the flywheels may apply to the enclosure  606  and its mounts can be substantially cancelled out by each flywheel applying a substantially equal but opposite force to their shaft and enclosure  606 . This significant reduction or cancellation of precession forces can be highly advantageous in moving vehicles and in particular performance and racing vehicles to reduce any adverse effects to vehicle handling. 
       FIG. 7  shows a seventh embodiment of a constantly variable transmission device  700  in half sectional plan view. The transmission device  700  is connected to a gearbox controller  734 . Like numbers are used for similar components as numbered in  FIG. 3 . However, a second set (second stage) of magnetic gears is installed in between the first set of magnetic gears and the flywheel  704 . This second stage set of magnetic gears comprises of an input shaft  702  as the first rotor, iron segment rotor  750  as the second rotor and output shaft, third rotor  751  as the controlled rotor i.e. the rotor that is controlled by the gearbox controller  734 . This second stage set of magnetic gears then integrates with the energy storage system comprising the flywheel and iron segment rotor  704  as the fourth rotor, and the controlled rotor  705  of the second set of magnetic gears as the fifth rotor. All seven rotors of this embodiment are housed inside an enclosure  706 . 
     In this configuration, the 2-stage gearbox is typically used for gearing up wind turbines from low speeds such as 20 RPM up to about 1,500 RPM. Such a speed up requires a 1:75 gearbox ratio achievable from gear ratios such as 1:8 and 1:9 in the first and second stages of the gearbox respectively. In this configuration, it is advantageous to couple the flywheel  704  with the second stage set of magnetic gears as it is spinning much faster than the first stage set of magnetic gears so that gear ratio between the second stage set of gears and flywheel is significantly reduced which increases efficiency. If a gearbox is required to significantly step down from a high speed such as 1,500 RPM to 20 RPM then the gearbox can be used in reverse by adding torque to the current output shaft  750  which will gear down the speed and supply torque to the current input shaft  1 . It will be appreciated by the skilled person that this embodiment can be expanded to incorporate a mixture of two or more stages combined with multiple input and output shafts to achieve very high gear ratios, flexibility and transmitted torque without departing from the basic principle of the embodiment described herein. 
     All five rotors  702 ,  750 ,  751 ,  704 ,  705  of the second stage set of magnetic gears and the second set of magnetic gears share the same axis of rotation as depicted by the dashed line  747 . The input shaft  702  is supported by a set of bearings  23 , suitably mounted to allow free rotation of the input shaft  702 . Similarly, the second rotor and output shaft  750  is supported by the set of bearings  760 , the control rotor  751  is supported by the set of bearings  59 , the fourth flywheel rotor  704  is supported by the set of bearings  24  and the control rotor  705  is supported by the set of bearings  725 . 
     In the second set of magnetic gears, the input shaft  702  has coils  752  installed on its rotor. The controlled rotor  751  has similar coils  765  but a different number from the number of coils installed on the shaft  702  according to the gearbox design. The second rotor  750  also the output shaft from the gearbox, has iron segments  753  installed thereon so that the magnetic flux as depicted by the arrow  755  can transmit magnetic and ultimately mechanical torque through the magnetic gear at a variable gear ratio. 
     In the second set of magnetic gears, a set of small coils  754  are installed on the third rotor  751 , composed of permanent magnets. A corresponding set of stator coils  757  installed an inner wall of enclosure  706  uses electrical power supplied from the gearbox controller (not shown) to generate a magnetic flux  756  in a controlled manner to cause rotation of the third rotor  751 . This controlled rotation sets the variable gear ratio for the second set of magnetic gears and second stage of the magnetic gearbox. 
     In the second set of magnetic gears, a second set of coils  758  are installed on the second rotor for interaction with the fourth rotor and flywheel  704  using the magnetic flux  714  that enters the fourth set of coils  704  or iron segments  712  that transmits the magnetic flux and torque to the fifth set of coils  713  installed on the fifth control rotor  705 . The fifth control rotor  705  is speed controlled (as previously described in  FIG. 1 ) to control the operative gear ratio and ultimately the direction and magnitude of power transfer between the flywheel  704  and the output shaft  750 . 
     When used for wind power generation, the magnetic gearbox  700  typically utilises the flywheel  704  as a load leveling device that is able to smooth out the large wind gusts and power spikes while providing additional power when the wind is weak or not blowing at all. If a wind power spike is experienced then the flywheel gear ratio is increased to speed up the flywheel  704  and draw energy from the input shaft  701 . When the wind is slow, the flywheel  704  is slowed down to provide power to the output shaft  750 . When the wind stops for a long period, then the flywheel  704  can also stop. When the wind starts again, then it is preferable to charge up the flywheel  704  first by accelerating it to near full speed ready to absorb or supply energy depending on the wind speeds and power requirements. 
     The total operatively gear ratio for this embodiment is carefully controlled by setting an appropriate gear ratio for the first and second set of magnetic gears using their associated control rotors  703  and  759  respectively. 
     When a flywheel  704  is employed, it is more efficient to operate it in a partial or full vacuum to reduce fluid friction on the flywheel  704  which can cause failure if the rotor speeds are too high. One method is to fully vacuum the air inside the enclosure  706 . This can work effectively although small leaks may appear and additional maintenance may be required. A more effective method may be to install mechanical seals  761  and  762  at the juncture between the enclosure  706  and the input  701  and the enclosure  6  and the output shaft  750  respectively. These mechanical seals  761  and  762  and typical low speeds of the shafts  1  and  50  will provide adequate sealing of the enclosure  706 . Once the seals  761  and  762  leak then the air pressure sensor (not shown) will detect this and operate the vacuum pump  764  and pull a partial or full vacuum on the enclosure  706  via the suction pipe  763 . This will improve the efficiency of the magnetic gearbox  700  and the power used by the vacuum pump  764  should be significantly lower than the power normally lost when not operating in a partial or full vacuum. 
     In an alternative to the battery  35 ,  235 ,  335 ,  435 ,  535 ,  635 ,  735 , the transmission devices  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700  may employ a super capacitor as a means of providing external electrical power storage capacity for the gearbox controller  34 ,  234 ,  334 ,  434 ,  534 ,  634 ,  734 . 
     The iron segments are composed of laminated electrical steel or soft magnetic composites. Alternatively they are solid iron or ferrite bars. 
     External clutches can be provided at the input and output shafts to decouple the transmission device from the engine and output shafts. Alternatively, the rotor speeds can be controlled by the gearbox controller to perform a clutching operation so that the output shaft can be at rest whilst the input shaft rotates. 
     A magnetic clutch can be installed inside the transmission device to decouple the desired rotors, for example decoupling the transmission device from the flywheel and/or input shaft. The magnetic clutch may typically consist of a thin steel or metal screen that dissipates any magnetic flux as Eddy currents between the rotors in the steel screen and will decouple that rotor from the rotor on the other side of the steel screen. Alternatively, moving the rotors apart so that their air gaps become very large is another form of mechanically actuated magnetic clutch. 
     Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.