Abstract:
The subject invention is directed to a class of electric hybrid drives that can be retrofit easily to cars and trucks to reduce transportation costs. Certain embodiments include mechanisms for attachment to an existing powertrain, regenerative braking, on-the-road optimization of transportation costs depending on road and route conditions, or an operational mode in which motive power for a vehicle is solely derived from electric energy stored in a battery.

Description:
This application is a continuation of U.S. application Ser. No. 13/752,404, filed Jan. 29, 2013, which is entitled to the priority date of Oct. 3, 2012 for all material previously included in Provisional Application 61/709,302 for Crecelius et al., each of which is hereby incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present disclosure relates generally to the technical field of hybrid electric vehicle systems. More specifically, it relates to electric hybrid drives for retrofitting a rotary electric motor/generator with or without regenerative braking capability to an existing internal combustion automotive vehicle. Still more specifically, it relates to the mechanical interface of an electric rotary electric motor/generator to the existing driveline of an existing internal combustion automotive vehicle. 
     Rising global fuel prices have improved business prospects for manufacturers of fuel-saving systems. In particular, fleet operators often use their internal combustion automotive vehicles for purposes (e.g., urban delivery) which greatly reduce their average fuel efficiency. Existing vehicles waste substantial fuel when they decelerate using friction brakes, and when operating the engine under conditions which lead to low efficiency. Existing vehicles are also limited to gasoline or diesel operation, which prevents operators from choosing the best alternative between alternate power sources for particular driving conditions. There is thus a need for an efficient, inexpensive, and flexible electric hybrid drive which can be retrofit to internal combustion vehicles to improve fleet operational costs. 
     The subject invention was developed to reduce transportation costs primarily for fleet operators, and to do so in a manner in which initial costs can be quickly repaid through savings. Objectives in the invention were to simplify installation of the electric hybrid drive onto existing vehicles, to design as simple and robust an electric hybrid drive as possible, and to enable a vehicle equipped with the subject invention to have a regenerative braking capacity—to slow the vehicle using the motor/generator to charge an on-board battery. The invention further allows optimization of engine operating conditions that increases overall efficiency. Also, the invention in certain embodiments allows a vehicle to be propelled using solely the stored energy of its on-board battery. 
     SUMMARY OF INVENTION 
     The subject invention is directed to a class of electric hybrid drives that can be retrofit easily to cars and trucks to reduce transportation costs. Certain embodiments include mechanisms for attachment to an existing powertrain, regenerative braking, on-the-road optimization of transportation costs depending on road and route conditions, or an operational mode in which motive power for a vehicle is solely derived from electric energy stored in a battery. Combinations of these embodiments are included in the subject invention, as are embodiments which exclude certain of the above features. 
     Certain aspects of the subject invention are set forth below. It should be understood that the aspects shown and discussed are not intended to limit or exhaust the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  shows a side view of an automotive powertrain fitted with an embodiment of the instant invention. 
         FIG. 2  shows a schematic view of the operational system of an embodiment of the instant invention. 
         FIG. 3  shows an exploded view of an implementation of the electric hybrid drive. 
         FIG. 4 a    shows an end view of transfer shaft  301  according to an implementation of the instant invention. 
         FIG. 4 b    shows a side view of transfer shaft  301  according to an implementation of the instant invention. 
         FIG. 5  shows an internal lubrication channel directing cooling fluid to the slip yoke bearing. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows the powertrain of an automotive vehicle converted into a retrofit electric hybrid vehicle according to a particular implementation of the present invention. An electric hybrid drive  100  is shown substituted for the extension housing of transmission  102 . Slip yoke  101  engages output shaft  400  (of  FIG. 4 a   ) of transmission  102 . Motor/generator housing  103  comprises adapter element  104 , housing element  105 , and motor/generator housing cover  106 . Slip yoke seal  107  prevents leakage of transmission fluid around slip yoke  101 . 
     In preferred embodiments, any or all of slip yoke  101 , slip yoke seal  107 , universal joint  108 , and propeller shaft  110  can be those elements original with the automotive vehicle. They can be reused without modification or with modification. However, a different embodiment can comprise any or all of a new slip yoke, a new slip yoke seal, a new universal joint, and a new propeller shaft. 
     A cross-member mount  109  that in some embodiments will assist in anchoring motor/generator housing  103  to the existing drivetrain is also shown. In the embodiment shown, the electric hybrid drive and the existing transmission output shaft automatically rotate together at the same rotational velocity to provide power and torque to propeller shaft  110 . 
       FIG. 2  shows an electric hybrid drive schematic of a particular embodiment of the present invention  20  is an automotive vehicle in which the present invention has been installed. OEM elements of the original automotive vehicle kept in the installation comprise engine  200 , automatic transmission  201 , transmission control module  202 , engine control module  203  and front end accessory drive  204 . Add-on elements added to the original automotive vehicle comprise rotary electric motor/generator  210 , electric power converter  211 , drive controller  212 , and battery pack  220 . 
     In some embodiments of the electric hybrid drive, it will be beneficial to add an alternator onto the accessory drive of the engine, to provide alternator electric power output to aid in charging battery pack  220 . 
     Rotary electric motor/generator  210  is mounted coaxially to output shaft  400  (of  FIG. 4 a   ) of automatic transmission  201 . The rotary electric motor/generator is functionally connected to the output shaft of the automatic transmission by means of a transfer shaft  301  ( FIG. 4 a   ). In various implementations, this rotary electric motor/generator can be powered by DC electric power or by AC electric power. In various implementations, rotary electric motor/generator  210  can be a permanent magnet, induction, switched reluctance, brushed DC, wound field synchronous, synchronous motor/generator, or another type of motor/generator with similar characteristics. In a preferred embodiment, rotary electric motor/generator  210  comprises a position feedback sensor, which reports the position and/or rotational speed of the shaft of the rotary electric motor/generator to drive controller  212 . More preferably, the position feedback sensor is integrated into rotary electric motor/generator  210 . 
     In a preferred embodiment, rotary electric motor/generator  210  also is able to function as an electric generator. When the battery supplies electric power to the rotary electric motor/generator, it supplies battery electric power output and the rotary electric motor/generator receives motor electric power input converted from the battery electric power output by the electric power converter. When the rotary electric motor/generator acts as a generator charging the battery pack, it produces generator electric power output which is converted by the electric power converter into charging electrical power input used to charge the battery pack. 
     Particular embodiments of the operation of the electric power converter during the process of driving the rotary electric motor/generator as a motor include: i) the electric power converter acting to convert the DC battery electric power output into variable-frequency AC motor electric power input; ii) the electric power converter acting to convert the DC battery electric power output voltage into DC motor electric power input having a different voltage; iii) the electric power converter acting to convert the DC battery electric power output into pulse-width modulated motor electric power input; and iv) when the battery electric power output and the motor electric power input have substantially the same voltage. 
     In a preferred implementation, rotary electric motor/generator  210  can be used to convert electric power from battery pack  220  into additional torque at the nominal rotational speed of the output shaft of the automatic transmission, and to convert torque as supplied by engine  200  and automatic transmission  201  into electrical power to charge the battery pack. However, a system lacking the ability to charge the battery pack from power supplied by engine  200  and automatic transmission  201  is still considered within the scope of the instant invention. 
     Particular embodiments of the operation of the electric power converter during the process of charging the battery pack comprise: i) the electric power converter acting to convert variable-frequency AC generator electric power output into charging electric power input, and ii) the electric power converter acting to convert DC generator electric power output voltage into charging electric power input having a different voltage. 
     Drive controller  212  coordinates the operation of the electrical hybrid drive. The coordination comprises controlling rotary electric motor/generator  210  to supply additional torque to the output shaft of the automatic transmission when desired. In a preferred embodiment, additional torque is provided during acceleration of vehicle  20 . 
     The coordination can also comprise controlling rotary electric motor/generator  210  to remove torque from the transmission output shaft when desired, thereby slowing the vehicle. In a preferred embodiment, rotary electric motor/generator  210  charges battery pack  220  at least during braking of vehicle  20 , providing thereby the capacity of regenerative braking. Regenerative braking can be applied with various braking profiles, e.g., immediate full braking, a gentle initial application growing to a desired level, moderate braking at all speeds, and so on. In various implementations, the instant drive comprises at least one user control element allowing a user to control the braking profile of the drive. 
     The drive controller can also comprise at least one user control element controlling a drive characteristic, e.g., fast starts using the full torque of the rotary electric motor/generator, gentle starts followed by gradually increasing additions of torque from the rotary electrical motor/generator, and so on. 
     The drive controller comprises a communications network to communicate data and control instructions between the various components of an electric hybrid drive. The communications network can comprise the controller area network of the original automotive vehicle for communication of data and control instructions, a dedicated electrical hybrid drive communications network, or a combination of the two. The communications network can also comprise means for providing user commands and settings. 
     The drive controller comprises a digital, analog, or hybrid computer programmed so as to accept electric hybrid drive data and issue electric hybrid drive control instructions in such a manner to operate the electric hybrid drive. In a particular embodiment, the drive controller semi-automatically determines control instructions based at least on the current state of the electric hybrid drive and on operator inputs. In another embodiment, the drive controller automatically determines control instructions based at least on the current state of the electric hybrid drive and the conventional driving controls of vehicle  20 . 
     Rechargeable battery pack  220  comprises battery modules  221  and battery management system  222 . Battery modules  221  comprise rechargeable electric batteries suited to the desired performance of the electric hybrid drive. Additional considerations, such as the ratio of low-speed operation to high-speed operation, or city center versus suburban versus rural operations, may also inform the choice of the storage capacity of battery modules  221 . 
     Battery modules  221  can beneficially comprise more than one type of battery. For example, for some applications a combination of high-power batteries and high-capacity batteries may provide better system capabilities than modules built from only one type of battery. 
     Battery management system  222  provides a power conditioning interface between battery modules  221  and electrical inputs to and outputs from those modules. For example, some batteries have extended lifespan if charged using pulsed current rather than continuous current. Others charge best if the amount of charging current is above, below, or in the vicinity of a given set point. Similarly, most batteries charge most effectively if the charging voltage is maintained between a minimum and a maximum charging voltage. In many cases, the rate at which energy is drained from a battery must be limited to maintain, e.g., proper battery temperature. 
     Battery management system  222  can comprise any of these functions, as well as others that may be required to effectively use a particular type of batteries in the battery modules. Battery management system  222  can beneficially comprise sensors to monitor the condition (e.g., voltage, current, temperature, etc.) of the battery modules  221  and/or of the individual batteries contained by the battery modules. 
     The electric hybrid drive can also comprise a line battery charger  223 , thereby enabling charging of battery modules  221  from an external source of electricity. This converts vehicle  20  into a plug-in hybrid, with the capability of beginning a route with fully charged battery modules. This capability would be useful for improving mileage over a long-distance route comprising lots of highway driving, or a route that includes lots of uphill driving early on. 
     The electric hybrid drive can also comprise a site power inverter  224 , providing a source of AC power converted from energy stored in the battery pack at a work site without requiring that engine  200  be running. It is common for fleet vehicles to be driven to a work site and largely parked during a working period. In many remote locations, having a clean and silent source of electricity for tools is a desirable capability which can be served by site power inverter  224 . 
       FIG. 3  shows details of an electric hybrid drive  100  according to a preferred embodiment of the instant invention. Adapter element  104 , housing element  105 , and motor/generator housing element  106  of motor/generator housing  103  appear in an exploded view, but in the same relationship as in  FIG. 1 . Rotary electric motor/generator  210  in the implementation illustrated in  FIG. 3  is a coaxial rotary electric motor/generator having a driven rotating shaft  302  with a coaxial cylindrical aperture having splines disposed along the inner surface of said aperture. 
     The driven rotating shaft  302  of rotary electric motor/generator  210  is functionally coupled to the output shaft  400  of the automatic transmission by transfer shaft  301 . Shown in detail in  FIG. 4 , transfer shaft  301  in this implementation comprises a hollow cylinder comprising inner grooves disposed on the inside surface of the shaft so as to couple with a set of splines on the output shaft of the automatic transmission. Transfer shaft  301  further comprises outer grooves disposed on the external surface of the shaft so as to couple with the splines on the hollow output shaft  302  of rotary electric motor/generator  210 . The net effect is that, when assembled, the output shaft of the automatic transmission and the driven rotating shaft  302  are locked together in rotation. In another embodiment of the instant invention, the driven rotating shaft  302  of rotary electric motor/generator  210  meshes properly with the transmission output shaft  400  of the automatic transmission so that no transfer shaft is required. It will be clear to one skilled in the art that the means for transferring torque can include a coaxial speed matcher, such as a set of planetary gears. A variety of direct-drive couplings are also well suited for transferring torque between the driven rotating shaft and the transmission output shaft. 
     In a particular embodiment, rotary electric motor/generator  210  requires liquid cooling. For this purpose cooling fluid fittings  303  circulate automatic transmission fluid through the rotary electric motor/generator. The level of the cooling fluid can be monitored visually through cooling fluid viewport  307 . Coolant access port  304  provides access to the motor/generator coolant. 
     In a preferred embodiment, the original slip yoke  101  of the automotive vehicle  20  is used in the retrofit electric hybrid vehicle. The original bearing supporting the slip yoke, however, is typically removed along with the extension housing of the transmission  102 . The original bearing supporting the slip yoke is replaced by slip yoke bearing  305 , which is then sealed around the original slip yoke by slip yoke seal  306 . 
       FIGS. 4 a  and 4 b    show details of transfer shaft  301 . The transfer shaft  301  rotationally couples hollow output shaft  302  of rotary electric motor/generator  210  to output shaft  400  of the automatic transmission so that all three elements rotate together. In a particular embodiment, this is accomplished by providing transfer shaft  301  with internal splines  401  and external splines  402  that mesh, respectively, with transmission output shaft splines  403  and rotating shaft splines  404 . The shape of the internal splines  401  and the external splines  402  are chosen to function properly within a particular embodiment of the instant invention. 
     Lubrication for the slip yoke bearing  305  is originally provided from the internal structure of the automatic transmission  102  by any of a number of designs, e.g., a splash-lube system. In some embodiments of the instant invention, this source of lubrication may be blocked by rotary electric motor/generator  210  and its housing. In a particular embodiment of the instant invention, the automatic transmission fluid used for cooling rotary electric motor/generator  210  is also directed to slip yoke bearing  305  for purposes of lubrication. In a further embodiment as illustrated in  FIG. 5 , the automatic transmission fluid is routed from the cooling fluid fittings  303  through an internal lubrication channel  501  within housing element  105  and motor/generator housing cover  106  to slip yoke bearing  305 . 
     While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered to be the best mode thereof, those of ordinary skill will also understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention is therefore not intended to be limited by the above described embodiments, methods, and examples, but by all embodiments and methods within the scope and spirit of the invention as claimed below.