Abstract:
A two-mode, compound-split, electro-mechanical transmission utilizes an input member for receiving power from an engine, and an output member for delivering power from the transmission. First and second motor/generators are operatively connected to an energy storage device through a control for interchanging electrical power among the storage device, the first motor/generator and the second motor/generator. The transmission employs three planetary gear sets. Each planetary gear arrangement utilizes first, second and third gear members. The transmission also employs five torque-transmitting mechanisms. One of the five torque-transmitting mechanisms is contained within each of the first and second motor/generators.

Description:
TECHNICAL FIELD 
     The present invention relates to a clutch integrated into a motor in an electrically variable transmission, and more particularly to a hybrid electromechanical vehicular transmission that utilizes three interactive planetary gear arrangements that are operatively connected to an engine and two motor/generators, wherein clutches are positioned inside each of the motor/generators. 
     BACKGROUND OF THE INVENTION 
     The purpose of a vehicular transmission is to provide a neutral, at least one reverse and one or more forward driving ranges that impart power from an engine, and/or other power sources, to the drive members which deliver the tractive effort from the vehicle to the terrain over which the vehicle is being driven. As such, the drive members may be front wheels, rear wheels or a track, as required to provide the desired performance. 
     A series propulsion system is a system in which energy follows a path from an engine to an electric storage device and then to an electrical motor which applies power to rotate the drive members. There is no direct mechanical connection between the engine and the drive members in a series propulsion system. 
     Transmissions adapted to receive the output power from either an engine or an electric motor, or both, have heretofore relied largely on what has been designated as series, hybrid propulsion systems. Such systems are designed with auxiliary power units (APUs) of relatively low power for minimum emissions and best fuel economy. However, such combinations of small APUs and even large energy storage devices do not accommodate high-average power vehicles or address duty cycles that demand continuous, constant speed operation. Steep grades and sustained high-average cruising speeds at desired high efficiencies are not achievable with a typical, series, hybrid transmission configuration. 
     The challenge, therefore, is to provide a power system that will operate at high efficiencies over a wide variety of operating conditions. Desirable electric variable transmissions should leverage the benefits of a series, hybrid transmission for desirable low-average power duty cycles—i.e., low speed start/stop duty cycles—as well as the benefits of a parallel hybrid transmission for high-average output power, high speed duty cycles. In a parallel arrangement the power supplied by the engine and the power supplied by the source of electrical energy are independently connected to the drive members. 
     Moreover, perfecting a concept wherein two modes, or two integrated power split gear trains, with either mode available for synchronous selection by the on-board computer to transmit power from the engine and/or the motor/generator to the output shaft results in a hybrid transmission having an extremely wide range of applications. 
     The desired beneficial results may be accomplished by the use of a variable, two-mode, input and compound split, parallel hybrid electro-mechanical transmission. Such a transmission utilizes an input member to receive power from the vehicle engine and a power output member to deliver power to drive the vehicle. First and second motor/generator power controllers are connected to an energy storage device, such as a batter pack, so that the energy storage devices can accept power from, and supply power to, the first and second motor/generators. A control unit regulates power flow among the energy storage devices and the motor/generators as well as between the first and second motor/generators. 
     A variable, two-mode, input-split, parallel, hybrid electro-mechanical transmission also employs at least one planetary gear set. The planetary gear set has an inner gear member and an outer gear member, each of which meshingly engages a plurality of planet gear members. The input member is operatively connected to one of the gear members in the planetary gear set, and means are provided operatively to connect the power output member to another of the gear members in the planetary gear set. One of the motor/generators is connected to the remaining gear member in the planetary gear set, and means are provided operatively to connect the other motor/generator to the output shaft. 
     Operation in the first or second mode may be selectively achieved by using torque transfer devices. Heretofore, in one mode the output speed of the transmission is generally proportional to the speed of one motor/generator, and in the second mode the output speed of the transmission is generally proportional to the speed of the other motor/generator. 
     In some embodiments of the variable, two-mode, input-split, parallel, hybrid electromechanical transmission, a second planetary gear set is employed. In addition, some embodiments may utilize three torque transfer devices—two to select the operational mode desired of the transmission and the third selectively to disconnect the transmission from the engine. In other embodiments, all three torque transfers may be utilized to select the desired operational mode of the transmission. 
     With reference, again, to a simple planetary gear set, the planet gear members are normally supported for rotation on a carrier that is itself rotatable. When the sun gear is held stationary and power is applied to the ring gear, the planet gear members rotate in response to the power applied to the ring gear and thus “walk” circumferentially about the fixed sun gear to effect rotation of the carrier in the same direction as the direction in which the ring gear is being rotated. 
     When any two members of a simple planetary gear set rotate in the same direction and at the same speed, the third member is forced to turn at the same speed, and in the same direction. For example, when the sun gear and the ring gear rotate in the same direction, and at the same speed, the planet gears do not rotate about their own axes but rather act as wedges to lock the entire unit together to effect what is known as direct drive. That is, the carrier rotates with the sun and ring gears. 
     However, when the two gear members rotate in the same direction, but at different speeds, the direction in which the third gear member rotates may often be determined simply by visual analysis, but in many situations the direction will not be obvious and can only be determined by knowing the number of teeth present in the gear members of the planetary gear set. 
     Whenever the carrier is restrained from spinning freely, and power is applied to either the sun gear or the ring gear, the planet gear members act as idlers. In that way, the driven member is rotated in the opposite direction as the drive member. Thus, in many transmission arrangements when the reverse drive range is selected, a torque transfer device serving as a brake is actuated frictionally to engage the carrier and thereby restrain it against rotation so that power applied to the sun gear will turn the ring gear in the opposite direction. Thus, if the ring gear is operatively connected to the drive wheels of a vehicle, such an arrangement is capable of reversing the rotational direction of the drive wheels, and thereby reversing the direction of the vehicle itself. 
     As those skilled in the art will appreciate, a transmission system using a power split arrangement will receive power from two sources. Utilization of one or more planetary gear sets permits two or more gear trains, or modes, by which to deliver power from the input member of the transmission to the output member thereof. 
     U.S. Pat. No. 5,558,589 which issued on Sep. 24, 1996 to General Motors Corporation, as is hereby incorporated by reference, teaches a variable, two-mode, input-split, parallel, hybrid electromechanical transmission wherein a “mechanical point” exists in the first mode and two mechanical points exist in the second mode. U.S. Pat. No. 5,931,757 which issued on Aug. 3, 1999 to General Motors Corporation, and is hereby incorporated by reference, teaches a two-mode, compound-split, electromechanical transmission with one mechanical point in the first mode and two mechanical points in the second mode. 
     A mechanical point occurs when either of the motor/generators is stationary at any time during operation of the transmission in either the first or second mode. The lack of a mechanical point is a drawback inasmuch as the maximum mechanical efficiency in the transfer of power from the engine to the output occurs when one of the motor/generators is at a mechanical point, i.e., stationary. In variable, two-mode, input-split, parallel, hybrid electromechanical transmissions, however, there is typically one point in the second mode at which one of the motor/generators is not rotating such that all the engine power is transferred mechanically to the output. 
     If further clutches are added, more mechanical points may be achieved. However, the addition of clutches creates packaging challenges and the additional components add cost, which increases the difficulty of developing a commercially-feasible mass-produced electrically variable transmission. 
     SUMMARY OF THE INVENTION 
     The invention provides an electrically variable transmission including clutches integrated into the motor/generators to improve packaging efficiency and provide a low cost, compact module. 
     More specifically, the invention provides an electromechanical transmission including a plurality of planetary gear sets each having first, second and third gear members. A motor/generator is continuously connected with one of the gear members. A clutch is operative to selectively connect the motor/generator with another one of the gear members. The clutch is integrated into the motor/generator. Preferably, the clutch is located radially inside the motor/generator, and the motor/generator and clutch are both mounted to a common support structure. 
     The clutch includes a piston, a return spring, a balance dam chamber, and a clutch pack, all positioned inside the motor/generator. 
     The motor/generator includes a rotor hub having internal contours, and the clutch includes reaction plates formed to engage the internal contours to prevent rotation of the reaction plates. An output hub is positioned radially inside the rotor hub, and friction plates are connected to the output hub and interposed between the reaction plates. 
     Another aspect of the invention provides a two-mode compound split hybrid electromechanical transmission, including first and second motor/generators, and three planetary gear arrangements. Each planetary gear arrangement includes first, second and third gear members. The first and second motor/generators are coaxially aligned with each other and with the three planetary gear arrangements. At least one of the gear members in the first or second planetary gear arrangement is connected to the first motor/generator, and at least one of the gear members in the third planetary gear arrangement is connected to the second motor/generator. 
     In this embodiment, a first torque-transmitting mechanism selectively connects one of the gear members associated with each of the first, second and third planetary gear arrangements to each other and to the output member. A second torque-transmitting mechanism selectively connects one of the gear members of the third planetary gear set with ground. A third torque-transmitting mechanism selectively connects one of the gear members of the second planetary gear set with ground. A fourth torque-transmitting mechanism selectively connects the first motor/generator with one of the gear members. The fourth torque-transmitting mechanism is positioned radially inside the first motor/generator. A fifth torque-transmitting mechanism selectively connects the second motor/generator with one of the gear members. The fifth torque-transmitting mechanism is positioned radially inside the second motor/generator. 
     A first interconnecting member continuously connects one of the members of the first planetary gear set with one of the members of the second planetary gear set. A second interconnecting member continuously connects another one of the members of the first planetary gear set with another one of the members of the second planetary gear set. 
     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 representation of a two-mode, electro-mechanical transmission embodying the concepts of the present invention; 
         FIG. 2  is a partial longitudinal cross-sectional view of a transmission corresponding with  FIG. 1 ; 
         FIG. 3  is partial cut-away perspective view of a clutch integrated into a motor, corresponding with  FIG. 2 ; and 
         FIG. 4  is a reverse partial cut-away perspective view of the assembly of  FIG. 3 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One representative form of a two-mode, compound-split, electromechanical transmission embodying the concepts of the present invention is depicted in  FIG. 1 , and is designated generally by the numeral  10 . The hybrid transmission  10  has an input member  12  that may be in the nature of a shaft which may be directly driven by an engine  14 . A transient torque damper may be incorporated between the output shaft  18  of the engine  14  and the input member  12  of the hybrid transmission  10 . An example of a transient torque damper of the type recommended for the present usage is disclosed in detail in U.S. Pat. No. 5,009,301 which issued on Apr. 23, 1991 to General Motors Corporation, which is hereby incorporated by reference in its entirety. The transient torque damper may incorporate, or be employed in conjunction with, a torque transfer device  20  to permit selective engagement of the engine  14  with the hybrid transmission  10 , but it must be understood that the torque transfer device  20  is not utilized to change, or control, the mode in which the hybrid transmission  10  operates. 
     In the embodiment depicted the engine  14  may be a fossil fuel engine, such as a diesel engine which is readily adapted to provide its available power output delivered at a constant number of revolutions per minute (RPM). In the exemplary embodiment, the engine  14  can—after start-up, and during the majority of its input—operate at a constant speed of approximately 6000 RPM. Although it must be understood that the speed and horsepower output of the engine  14  is not critical to the invention, for the purpose of effecting an absolutely clear understanding of the hybrid transmission  10 , an available output of about 305 horsepower from engine  14  will be assumed for the description of an exemplary installation. An input pump  15  is also provided. Irrespective of the means by which the engine  14  is connected to the input member  12  of the transmission  10 , the input member  12  is connected to a planetary gear set  24  in the transmission  10 . 
     The hybrid transmission  10  utilizes three planetary gear sets  24 ,  26  and  28 . The first planetary gear set  24  has an outer gear member  30  that may generally be designated as the ring gear, which circumscribes an inner gear member  32 , generally designated as the sun gear. A plurality of planet gear members  34  are rotatably mounted on a carrier  36  such that each planet gear member  34  meshingly engages both the outer gear member  30  and the inner gear member  32 . 
     The second planetary gear set  26  also has an outer gear member  38 , generally designated as the ring gear, which circumscribes an inner gear member  40 , generally designated as the sun gear. A plurality of planet gear members  42  are rotatably mounted on a carrier  44  such that each planet gear  42  meshingly engages both the outer gear member  38  and the inner gear member  40 . 
     The third planetary gear set  28  also has an outer gear member  46 , generally designated as the ring gear, which circumscribes an inner gear member  48 , generally designated as the sun gear. A plurality of planet gear members  50  are rotatably mounted on a carrier  52  such that each planet gear  50  meshingly engages both the outer gear member  46  and the inner gear member  48 . 
     In this embodiment, the ring gear/sun gear tooth ratio of the planetary gear set  24  is 66/34, the ring gear/sun gear tooth ratio of the planetary gear set  26  is 66/34, and the ring gear/sun gear tooth ratio of the planetary gear set  28  is 86/34. 
     The carrier  52  of the third planetary gear set  28  is connected directly to the transmission output member  64 . When the hybrid transmission  10  is used in a land vehicle, the output member  64  may be connected to the vehicular axles (not shown) that may, in turn, terminate in the drive members (also not shown). The drive members may be either front or rear wheels of the vehicle on which they are employed, or they may be the drive gear of a track vehicle. 
     The carrier  36  is continuously connected with the carrier  44  through the interconnecting member  90 . The sun gear  32  is continuously connected with the ring gear  38  through the interconnecting member  92 . The rotor of the first motor/generator  56  is continuously connected with the sun gear  32  through the interconnecting member  94 . The rotor of the second motor/generator  72  is continuously connected with the sun gear  48  through the interconnecting member  96 . 
     The first torque-transmitting mechanism (clutch)  62  selectively connects the carriers  36 ,  44  with the carrier  52 , and with the output member  64 . The first torque-transmitting mechanism  62  is engaged during the second mode of operation of the transmission. The second torque-transmitting mechanism (brake)  70  selectively connects the ring gear  46  with the transmission housing  60 . The second torque-transmitting mechanism  70  is engaged in the first mode of operation of the transmission  10 . 
     A third torque-transmitting mechanism (brake)  73  selectively connects the sun gear  40  with the transmission housing  60 . The fourth torque-transmitting mechanism (clutch)  75  selectively connects the rotor of the first motor/generator  56  with the sun gear  40 . The fifth torque-transmitting mechanism (clutch)  77  selectively connects the rotor of the second motor/generator  72  with the sun gear  40 . 
     It should be noted that both motor/generators  56  and  72  are of an annular configuration which permits them to circumscribe the three planetary gear sets  24 ,  26  and  28  such that the planetary gear sets  24 ,  26  and  28  are disposed radially inwardly of the motor/generators  56  and  72 . This configuration assures that the overall envelope, i.e., the circumferential dimension, of the transmission  10  is minimized. 
     As was previously herein explained in conjunction with the description of the engine  14 , it must similarly be understood that the rotational speed and horsepower output of the first and second motor/generators  56  and  72  are also not critical to the invention, but for the purpose of effecting an absolutely clear understanding of the hybrid transmission  10 , the motors/generators  56  and  72  have a continuous rating of 30 horsepower and a maximum speed of about 10200 RPM. The continuous power rating is approximately 1/10 that of the engine  14 , and the maximum speed is approximately 1.5× that of the engine  14 , although these depend on the type of engine, final gear schematic and duty cycle. 
     As should be apparent from the foregoing description, and with particular reference to  FIG. 1 , the transmission  10  selectively receives power from the engine  14 . As will now be explained, the hybrid transmission also receives power from an electric storage device  74 . The electric storage device  74  may be one or more batteries. Other electric storage devices that have the ability to store electric power and dispense electric power may be used in place of the batteries without altering the concepts of the present invention. As was explained in conjunction with the description of the engine  14  and the motor/generators  56  and  72 , it must similarly be understood that the horsepower output of the electrical storage device  74  is also not critical to the invention, but for the purpose of effecting an absolutely clear understanding of the hybrid transmission  10  an output of about 75 horsepower from the electrical storage device  74  will be assumed for description of an exemplary device. The battery pack is sized depending on regenerative requirements, regional issues such as grade and temperature, and propulsion requirements such as emissions, power assist and electric range. 
     The electric storage device  74  communicates with an electrical control unit (ECU)  76  by transfer conductors  78 A and  78 B. The ECU  76  communicates with the first motor/generator  56  by transfer conductors  78 C and  78 D, and the ECU  76  similarly communicates with the second motor/generator  72  by transfer conductors  78 E and  78 F. 
     As is apparent from the previous paragraph, a particular structural member, component or arrangement may be employed at more than one location. When referring generally to that type of structural member, component or arrangement, a common numerical designation will be employed. However, when one of the structural members, components or arrangements so identified is to be individually identified, it will be referenced by virtue of a letter suffix employed in combination with the numerical designation employed for general identification of that structural member, component or arrangement. Thus, there are at least six transfer conductors which are generally identified by the numeral  78 , but the specific, individual transfer conductors are, therefore, identified as  78 A,  78 B,  78 C,  78 D,  78 E and  78 F in the specification and on the drawings. This same suffix convention shall be employed throughout the specification. 
     A drive gear  80  may be presented from the input member  12 . As depicted, the drive gear  80  fixedly connects the input member  12  to the outer gear member  30  of the first planetary gear set  24 , and the drive gear  80 , therefore, receives power from the engine  14  and/or the motor/generators  56  and/or  72 . The drive gear  80  meshingly engages a transfer gear  84  that is secured to one end of a shaft  86 . The other end of the shaft  86  may be secured to a transmission fluid pump and/or auxiliary power take off unit. 
     The operator of the vehicle has three well-known, primary devices to control the transmission  10 . One of the primary control devices is a well-known drive range selector (not shown) that directs the ECU  76  to configure the transmission for either the park, reverse, neutral, or forward drive range. The second and third primary control devices constitute an accelerator pedal (not shown) and a brake pedal (also not shown). The information obtained by the ECU  76  from these three primary control sources will hereinafter be referred to as the “operator demand.” The ECU  76  also obtains information from both the first and second motor/generators  56  and  72 , respectively, the engine  14  and the electric storage device  74 . In response to an operator&#39;s action, the ECU  76  determines what is required and then manipulates the selectively operated components of the hybrid transmission  10  appropriately to respond to the operator demand. 
     For example, in the exemplary embodiment shown in  FIG. 1 , when the operator has selected a forward drive range and manipulates either the accelerator pedal or the brake pedal, the ECU  76  determines if the vehicle should accelerate or decelerate. The ECU  76  also monitors the state of the power sources, and determines the output of the transmission required to effect the desired rate of acceleration or deceleration. Under the direction of the ECU  76 , the transmission is capable of providing a range of output speeds from slow to fast in order to meet the operator demand. 
     To reiterate, the transmission  10  is a two-mode, compound-split, electromechanical, vehicular transmission. In other words, the output member  64  receives power through two distinct gear trains within the transmission  10 . A first mode, or gear train, is selected when the torque transfer device  70  is actuated in order to “ground” the outer gear member  46  of the third planetary gear set  28 . A second mode, or gear train, is selected when the torque transfer device  70  is released and the torque transfer device  62  is simultaneously actuated to connect the shaft  61  to the carrier  52  of the third planetary gear set  28 . 
     Those skilled in the art will appreciate that the ECU  76  serves to provide a range of output speeds from relatively slow to relatively fast within each mode of operation. This combination of two modes with a slow to fast output speed range in each mode allows the transmission  10  to propel a vehicle from a stationary condition to highway speeds while satisfying the other objects of the invention. Additionally, the ECU  76  coordinates operation of the transmission  10  so as to allow synchronized shifts between the modes. 
     A complete operating description of a transmission similar to that identified by the schematic of  FIG. 1  may be found in separately filed U.S. patent application Ser. No. 10/946,760, filed on Sep. 22, 2004, commonly assigned to General Motors Corporation, and hereby incorporated by reference in its entirety. 
     The invention is particularly characterized by the positioning of the fourth and fifth torque-transmitting mechanisms  75 ,  77  radially inside the first and second motor/generators  56 ,  72 , respectively, to provide a compact transmission design. 
     Turning to  FIG. 2 , a partial longitudinal cross-sectional view is shown of a transmission corresponding with the schematic of  FIG. 1 . Like numerals are used in  FIG. 2  to refer to like components from  FIG. 1 . Referring specifically to  FIG. 2 , the clutch  75  includes an outer hub  100  which is integral with the motor/generator  56 . The piston and bearing carrier  102  has an interference fit with the outer hub  100 , and carries the piston  104 , return spring  106 , and separator  108  which cooperates with the piston  104  to form the balance dam chamber  110 . 
     An inner hub  112  is supported by the bushing  114  and bearings  116 ,  118 . Friction plates  120  are splined to the inner hub  112 , and interposed between the reaction plates  122 , which are splined to the outer hub  100 , as described below. The outer hub  100  and piston and bearing carrier  102  are supported on the bearing assemblies  123 ,  125 . 
     The first motor/generator  56  is continuously connected with the ring gear  38  through the piston and bearing carrier  102 . The first motor/generator  56  is selectively connectable with the sun gear  32  via the clutch  75  and flanged shaft  124 . 
     The clutch  77  is configured similarly as a clutch  75 . The clutch  77  includes an outer hub  130  having an interference fit with a piston and bearing carrier  132 . The piston and bearing carrier  132  supports the piston  134 , the return spring  136  and separator  138 , which cooperates with the piston  134  to form the balance dam chamber  140 . An inner hub  142  is “floatable” along a spline engagement  143 , and supported by the bushing  144  and bearings  146 ,  148 . The inner hub  142  is externally splined to friction plates  150  which are interposed between reaction plates  152 , which are splined to the outer hub  130 . 
     The outer hub  130  and piston and bearing carrier  132  are supported between the bearing assemblies  154 ,  156 . 
     The second motor/generator  72  is continuously connected with the sun gear  48  (illustrated in  FIG. 1 ) via the piston and bearing carrier  132 , and selectively connectable with the sun gear  40  through the clutch  77 . 
     Turning to  FIGS. 3 and 4 , the clutch  77  is shown in greater detail. The bolts  160 ,  162  connect the piston and bearing carrier  132  to the outer hub  130 . Also, the snap ring  164  which retains the separator  138  is held within a retention ring  166 .  FIG. 3  also illustrates the inner hub  142  and the friction plates  150  engaged with the reaction plates  152 . The bushing  144  is also shown. 
       FIG. 4  illustrates that the reaction plates  152  include contours  170  to match the contours  172  of the outer hub  130  such that the reaction plates  152  are splined to the outer hub  130  to prevent rotation thereof. 
     The clutch  75  is configured nearly identically to the clutch  77 , so  FIGS. 3 and 4  are also representative of the clutch  75 . 
     While only a preferred embodiment of the present invention is disclosed, it is to be understood that the concepts of the present invention are susceptible to numerous changes apparent to one skilled in the art. Therefore, the scope of the present invention is not to be limited to the details shown and described but is intended to include all variations and modifications which come within the scope of the appended claims.