Abstract:
A torque converter-mounted generator is provided that, along with power electronics, offers at least two types of electrical power output and may be attached to a transmission without impacting the axial length of a powertrain in comparison to a powertrain with an identical transmission and a torque converter not having a generator mounted thereto. Different torque-converter mounted generators and power electronics configurations providing different combinations of electrical power voltages may be offered for use with a given transmission type, thus allowing flexibility in meeting customer needs without unduly impacting assembly of the powertrains. A method of assembling transmissions is also provided.

Description:
TECHNICAL FIELD 
     The invention relates to a powertrain with a torque converter-mounted generator and to a method of assembling powertrains. 
     BACKGROUND OF THE INVENTION 
     Motor vehicles, especially those of the military or commercial type, often include power take-off units or add-on devices connected with the vehicle engine and transmission for providing electrical power for external or “offboard” uses such as powering industrial equipment or tools. Such power take-off units and add-on devices require a significantly time-consuming installation process. Additionally, the overall axial length of the transmission is typically increased significantly with the incorporation of these devices into the vehicle powertrain. The application of a specific type of transmission by different customers varies widely, as does onboard and offboard power needs. 
     SUMMARY OF THE INVENTION 
     A torque converter-mounted generator is provided that, along with power electronics, offers at least two electrical power output voltages and may be attached to a transmission without impacting the axial length of a powertrain in comparison to a powertrain with an identical transmission and a torque converter not having a generator mounted thereto. Different torque-converter mounted generators and power electronics configurations providing different combinations of power output voltages may be offered for use with a given transmission type, thus allowing flexibility in meeting customer needs without unduly impacting assembly of the powertrains. 
     Specifically, a powertrain within the scope of the invention includes a transmission housed within a transmission housing, and a torque converter operatively connected with the transmission and housed within a torque converter housing. The torque converter housing is secured to the transmission housing. A generator with a rotor is secured to the torque converter. The generator also has a stator that is secured to the torque converter housing. Power electronics are operatively connected with the generator. The generator and power electronics are configured to provide electrical power at multiple voltages. Voltage may be a relatively low voltage required for powering onboard vehicle accessories, while another voltage may be at a relatively high voltage for offboard power needs. As used herein, “onboard” refers to components normally connected with the vehicle at all times, including when the vehicle is in motion, while “offboard” components are those not integral with the vehicle and typically connected to the vehicle only when it is stationary. 
     In some embodiments, the generator may generate electrical power at two or more different voltages, such as if the stator includes first and second sets of stator segments adapted to provide the two different electrical voltages. Alternatively, the generator may generate electrical power at only one voltage that is then converted to different voltages for electrical power output by different components of the power electronics. 
     In one embodiment, the power electronics are configured to provide electrical power to the stator to drive the rotor, thereby operating the generator in a motoring mode for starting the engine and/or providing torque to the transmission in tandem with the engine. 
     Within the scope of the invention, the design of the torque converter-mounted generator may vary widely. For example, the stator and rotor may be configured with a radial gap or an axial gap, in which case there may be two rotors concentrically arranged with the stator and axially spaced on either side of the stator. The stator may have windings and multi-phase power outputs. The rotor may include different sets of magnets. 
     A method of assembling powertrains includes installing a first torque converter-mounted generator on a first transmission of a first type, and operatively connecting a first configuration of power electronics to the first torque converter-mounted generator. The first torque converter-mounted generator and the first configuration of power electronics provide electrical power at least two different voltages. The method further includes installing a second torque converter-mounted generator on a second transmission of the first type, wherein the first transmission and the second transmission are substantially identical. The method further includes operatively connecting a second configuration of power electronics to the second torque converter-mounted generator. The second torque converter-mounted generator and the second configuration of power electronics provide electrical power voltages different than the two voltages provided by the first torque converter-mounted generator and the first configuration of power electronics. Notably, only one of the voltages provided by each of the powertrain embodiments need be different in order for the two voltages provided by each to be considered different (e.g., the first torque converter-mounted generator and first configuration of power electronics may offer a low voltage power of 28 volts direct current, just as the second torque converter-mounted generator and second configuration of power electronics does, but different higher voltage power (e.g., 220 volts direct current versus 270 volts direct current) may be provided by the two embodiments. Preferably, the assembly of the transmissions with the different torque converters may occur on the same assembly line in a factory. Thus, customer needs for different types of electrical power may be addressed as the powertrains are assembled. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration in partial cross-sectional side view of a first powertrain including a transmission, and engine, a torque converter with a first type of generator mounted thereon, and power electronics, providing electrical power at two different voltages; 
         FIG. 2  is a schematic cross-sectional illustration of the torque converter-mounted generator of  FIG. 1 ; 
         FIG. 3  is a schematic illustration in partial cross-sectional side view of a second powertrain including a transmission of the same type of the transmission of  FIG. 1 , an engine of the same type as the ending of  FIG. 1 , and a torque converter with a second type of generator mounted thereon, and power electronics, providing electrical power at voltages different than the voltages provided by the generator of  FIGS. 1 and 2 ; and 
         FIG. 4  is a schematic illustration of a third powertrain including a transmission and an engine identical to those of  FIG. 3 , and a torque converter without a generator mounted thereon. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein like reference numbers refer to like components,  FIG. 1  shows a powertrain  10  that includes an engine  12 , such as an internal combustion engine or a diesel engine. The powertrain  10  further includes a torque converter  14  housed within a torque converter housing  16  and a transmission  18  housed within a transmission housing  20 . The engine crankshaft  22  is connected with an input shell  26  of the torque converter  14  via a flex plate  24  or other interface secured by bolts  28  or other fastening mechanisms to the torque converter input shell  26 . As is known, the torque converter  14  forms a fluid coupling between the engine  12  and the transmission  18 , providing torque multiplication via an impeller or pump portion rotating with the input shell  26  that forms a viscous coupling with a turbine portion rotating with an input member  30  of the transmission  18 . The internal components of the torque converter  14 , including the pump portion and turbine portion are well known and are not shown in  FIG. 1 . The torque converter  14  may be either stamped or machined steel or stamped aluminum. The transmission  18  utilizes intermeshing gears, such as planetary gear sets or gear planes in a countershaft arrangement, as well as selectively engagable torque-transmitting mechanisms, such as synchronizers, clutches and/or brakes, to establish torque transmission at various speed ratios to a transmission output member  31 . 
     A torque converter-mounted generator  34  is provided that establishes, along with multiple sets of power electronics (discussed below) multiple power outputs for onboard and/or offboard power needs. The torque converter-mounted generator  34  includes a rotor  36  secured to the torque converter  14 , specifically, to the torque converter input shell  26  for rotation therewith. The generator  34  further includes a stator  38  mounted to the torque converter housing  16  such that the stator  38  remains stationary with the torque converter housing  16 . The rotor  36  and stator  38  are concentrically arranged about an axis of rotation of the engine crankshaft  22  and the transmission input member  30  and define a circumferential radial air gap  32  therebetween. The engine  12  includes an engine block  40  secured by bolts  42  or other fasteners to the torque converter housing  16 . The torque converter housing  16  is also secured by bolts  44  or other fasteners to the transmission housing  20 . The engine block  40 , torque converter housing  16  and transmission housing  20  are stationary components. Preferably, the stator  38  is cooled by oil or water coolants in any known manner. 
     Referring to  FIG. 2 , the torque converter-mounted generator  34  is shown in cross-sectional view at the arrows indicated in  FIG. 1 . In this view, it is evident that the stator  38  is actually comprised of different stator segments, including a first set of stator segments  46  and a second set of stator segments  48 . The first set of stator segments  46  includes interpole slots  50  in which three-phase stator windings  52  are nested. The stator windings  52  form end turns  53  visible in  FIG. 1 . The number of segments in the first set of stator segments  46  and the number of windings  52  is exemplary only in  FIG. 2 , and is selected to achieve a desired first output voltage, as discussed below. The second set of stator segments  48  includes interpole slots  50 A in which three-phase stator windings  52 A are nested. The stator windings  52 A also form end turns, although these are not visible in the cross-section of the generator  34  taken in  FIG. 1 . The number of segments in the second set of stator segments  48  and the number of windings  52 A are also selected to achieve a second desired output voltage, different than the first output voltage, as discussed below. The stator segments  46 ,  48  are bolted or otherwise secured to the torque converter housing  16  with bolts  54  as indicated. 
     The rotor  36  of the torque converter-mounted generator  34  has magnets  56  circumferentially spaced therearound. The number of magnets  56  is selected to optimize the desired first and second output voltages. The rotor  36  is secured with bolts  58  or any other fastening method to the torque converter  14  so that it rotates with the torque converter  14 . The bolts  58  are shown in an exemplary arrangement only, and may be of a different number, spacing, or location than that shown. The radial air gap  32  is shown between the stator segments  46  and  48 , and the rotor  36 . 
     When the engine crankshaft  22  turns, the input shell  26  and rotor  36  are turned. The magnetic flux of the rotating magnets  56  generates current flow in the windings  52  and  52 A of stator  38 . 
     Referring again to  FIG. 1 , the powertrain  10  incorporates power electronics; specifically, a first set of power electronics  60  in electrical communication with the first set of stator segments  46  as well as a second set of power electronics  62  in electrical communication with the second set of stator segments  48 . Together, the first and second types of power electronics  60 ,  62  may be referred to as a first configuration of power electronics. The first set of stator segments  46  and the first set of power electronics  62  are configured to provide electrical power at a first voltage, such as a relatively low 28 volt direct current (VDC). The second set of stator segments  48  and the second set of power electronics  62  are configured to provide electrical power at a second voltage, such as a relatively high 270 volt direct current. The first set, or lower voltage, power electronics  60  includes a first power connection  64  connected with the first set of stator segments  52  which can function as a first power output, The first power connection  64  communicates power to a low voltage power module  66 , which includes an inverter and electronic controller. The low voltage power module  66  is operable to convert the three-phase alternating current provided by the first set of stator segments  52  into power in the form of 28 volt direct current to be stored in a low voltage battery  68 . The controller function of the power module  66  directs the battery  68  to provide energy to vehicle accessories  70  configured to function on power at the low voltage (e.g., 28 Volt) level. The vehicle accessories  70  may include air conditioning, audio systems, and any other onboard or offboard electrically-powered components designed to run on the low voltage power provided by the first set of power electronics. 
     The second set of power electronics  62  includes a second power connection  72  that connects to the second set of stator segments  48  and functions as a second power output for the second, higher voltage, type of electrical power. The second power connection  72  communicates power to a high voltage rectifier and controller module  74  which functions as an export power rectifier and controller. The high voltage rectifier and controller module  74  is operable to convert the three-phase alternating current provided by the three-phase stator windings  52 A into power in the form of  270  volt direct current that is provided to an external power load  76  under the control of the controller portion of the high voltage rectifier and controller module  74 . The external power load  76  may include, for example, offboard industrial and utility equipment or tools, or an onboard load, such as refrigeration for a trailer in transit. 
     Referring to  FIG. 3 , a second embodiment of a powertrain  10 A illustrates a second type of torque converter-mounted generator  34 A utilized with an engine  12 A and transmission  18 A interconnected in the same manner as the corresponding components of  FIG. 1 . In fact, the engine  12 A is an identical type engine as engine  12  and the transmission  18 A is an identical type transmission as the transmission  18 . In the powertrain  10 A however, the torque converter-mounted generator  34 A is of a different configuration, providing different voltage outputs, than the torque converter-mounted generator  34 . Thus, a transmission manufacturer can offer the transmission represented as  18  in  FIG. 1 and 18A  in  FIG. 3 , modified according to a customer&#39;s specific power output needs, by choosing one of the torque converter-mounted generators  34  or  34 A, designed with customized low and high voltage outputs. Additionally, the transmission  18 A may also be offered with a traditional torque converter  14 B, i.e., one without a generator mounted thereon, as illustrated in  FIG. 4 , as the traditional torque converter  14 B and the torque converters with generators mounted thereon  14 ,  14 A, occupy essentially the same axial packaging space, with only a different torque converter housing required for each different design. 
     The engine  12 A includes an engine block  40 A secured by bolts  42 A or other fasteners to the torque converter housing  16 A. The torque converter housing  16 A is also secured by bolts  44 A or other fasteners to the transmission housing  20 A. The engine block  40 A, torque converter housing  16 A and transmission housing  20 A are stationary components. 
     Referring in more detail to  FIG. 3 , the torque converter-mounted motor generator  34 A is an axial gap air core generator that includes a stator  38 A mounted to the torque converter housing  16 A such that the stator  38 A remains stationary with the torque converter housing  16 A. The stator  38 A includes multiple stator segments, circumferentially-spaced similar to those of  FIG. 3 , allowing multiple stator segments for multiple voltage outputs at the same time with separate output terminals, as discussed below. The torque converter-mounted generator  34 A also includes a first rotor  36 A and a second rotor  36 B secured to the torque converter  14 A, specifically, to the torque converter input shell  26 A for rotation therewith. The rotors  36 A,  36 B and stator  38 A are concentrically arranged about an axis of rotation of the engine crankshaft  22 A and the transmission input member  30 A, with the stator  38 A sandwiched between the rotors  36 A,  36 B such that axial air gaps  32 A,  32 B are defined between each of the rotors  36 A,  36 B and the stator  38 A, respectively. Each rotor has two sets of magnets  56 A and  56 B spaced circumferentially therearound, each set being characterized by different strengths, inducing different current flow in the axial core windings of the stator  38 A. Different voltage outputs associated with the magnets  56 A,  56 B are utilized to provide different types of power for onboard and/or offboard use, as described below. Those skilled in the art readily understand the construction of axial gap air core generators. 
     The powertrain  10 A incorporates a first set of power electronics  60 A in electrical communication with the stator  38 A via a first power connection  64 A. The first set of power electronics  60 A is configured for a first electrical power voltage, such as a lower voltage 24 volt direct current (VDC). The first set of power electronics  60 A includes a low voltage power module  66 A, including an inverter and an electronic controller, and a low voltage battery  68 A operatively connected to vehicle accessories  70 A. The components of the first set of power electronics  60 A are configured and function similar to those like components of the first set of power electronics  60  of the powertrain  10  of  FIG. 2 , except that the low voltage power module provides 24 volt direct current to the battery  68 A. 
     The powertrain  10 A also incorporates a second set of power electronics  62 A in electrical communication with the stator  38 A via a second power connection  72 A. Together the first and second sets of power electronics  60 A,  62 A, may be referred to as a second configuration of power electronics. The second set of power electronics  60 A is configured for a second electrical power voltage, such as a higher voltage 220 volt direct current. The second power connection  72 A communicates power to a high voltage rectifier and controller module  74 A which functions as an export power rectifier and controller. The high voltage rectifier and controller module  74 A is operable to convert three-phase 220 volt alternating current provided by the stator  38 A into power in the form of 220 volt direct current that is provided to an external power load  76 A under the control of the controller portion of the high voltage rectifier and controller module  74 A. The external power load  76 A may include, for example, offboard industrial and utility equipment of tools, or an onboard load, such as refrigeration for a trailer in transit. These components of the second set of power electronics  62 A are configured and function similar to those like components of the second set of power electronics  62  of the powertrain  10  of  FIG. 1 , except that the high voltage rectifier and controller module  74 A provides power at 220V to the external power load  76 A. 
     The second set of power electronics  62 A also includes componentry enabling the torque converter-mounted generator  34 A to function as a motor to start the engine  12 A or to provide power in tandem with the engine  12 A to the transmission  18 A, providing hybrid propulsion capability. Thus, the torque converter-mounted generator  34 A may be referred to as a motor/generator. Specifically, the second set of power electronics  62 A includes a high voltage alternating current to direct current power module  80 A that functions as a power inverter and as an electronic controller to invert power from a high voltage alternating current, such as 220 volts alternating current, to a high voltage direct current, such as 220 volts direct current. The high voltage direct current is then stored in a high voltage battery  82 A. A high voltage electronic controller  84 A is configured to direct stored energy from the battery  82 A to the stator  38 A when operating conditions warrant starting the engine  12 A, or when the engine  12 A is already powering the transmission  18 A and additional torque is required and may be provided by the motor/generator  34 A. It should be appreciated that the direct current power module  80 A, the battery  82 A and the high voltage electronic controller  84 A may also be employed on the powertrain  10  of  FIG. 2  such that the torque converter-mounted generator  34  could also function as a motor. 
     As indicated in  FIGS. 2 and 3 , different powertrains may be constructed with the same type of transmission and engine, but with different torque converter-mounted generators connected therebetween. The choice of torque converter-mounted generator in terms of the power outputs it is configured to provide may be driven by specific customer needs. Alternatively, if onboard or offboard power is not required for a specific powertrain implementation, a powertrain  10 B, configured as shown in  FIG. 4 , may be provided with an engine  12 B, a transmission  18 B and a torque converter  14 B, within a torque converter housing  16 B, that is not equipped with a generator. The engine  12 B may be of the same type as engines  12  and  12 A, and the transmission  18 B may be of the same type as transmissions  18  and  18 A. 
     Preferably, the power outputs of the various generators  34 ,  34 A are common and the power electronics  60 ,  62 ,  60 A,  62 A are common, so that the generators and power electronics can be used for various different types of transmissions as well. Various power electronic configurations, including those of the following electric power voltages, are preferably available for connection to the common power outputs of the generators  34 ,  34 A: 600 Volts DC, 12 Volts DC, 42 Volts DC, 110/220 Volts (60 Hz) alternating current “AC”, 220 Volts (50 Hz AC), 24 Volts DC and 270 Volts DC. 
     Accordingly, a method of assembling powertrains, described with respect to the powertrain embodiments of  FIGS. 1-4 , includes installing a first torque converter-mounted generator  34  on a first transmission  18  of a first type. This may include attaching a torque converter housing  16  to a transmission housing  20 . The method further includes operatively connecting a first configuration of power electronics  60 ,  62  to the first torque converter-mounted generator  34 . The first torque converter-mounted generator  34  and the first configuration of power electronics  60 ,  62  provide electric power at least two voltages (e.g., 28 VDC and 270 VDC). 
     The method also includes installing a second torque converter-mounted generator  34 A on a second transmission  18 A of the first type that is substantially identical to the first transmission  18 . This may include attaching a different torque converter housing  16 A to a transmission housing  20 A that is identical to the transmission housing  20 . The method then includes operatively connecting a second configuration of power electronics  60 A,  62 A, to the second torque converter-mounted generator  34 A. The second torque converter-mounted generator  34 A and the second configuration of power electronics  60 A,  62 A provide electric power at voltages different than the two voltages provided by the first torque converter-mounted generator  34  and the first configuration  60 ,  62  of power electronics. Within the scope of the method, a torque converter  14 B that does not have a generator mounted thereon may be connected with a transmission  18 B identical to the transmissions  18  and  18 A and with an engine  12 B identical to the engines  12  and  12 A. Thus, the method enables a given transmission and engine combination to be connected with different torque converters (with different types of generators, a motor/generator, or no generator mounted thereto) and different power electronic configurations (or no power electronics in the case of a torque converter without a generator) to meet a customer&#39;s specific electrical power needs. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.