Abstract:
The invention relates to an electromechanically activated motor vehicle transmission ( 31, 14 ) such as an automated manual transmission ( 31 ) or a transfer case ( 14 ). This transmission comprises at least a transmission housing ( 11 ), an electromagnetic selecting or shifting device ( 1 ) and an electric motor ( 2, 8, 22 ) by means of which the selecting or shifting device ( 1 ) can be actuated. In the inventive motor vehicle transmission ( 31, 14 ), the electric motor ( 2, 8, 22 ) of the selecting or shifting mechanism ( 1 ) arranged within the transmission housing ( 11 ) and the motor housing ( 9, 12, 24 ) of the electric motor ( 2, 8, 22 ) is designed so that it corresponds to a portion of the transmission housing ( 11 ).

Description:
[0001]    This application is a national stage completion of PCT/EP2005/012875 filed Dec. 2, 2005 which claims priority from German Application Serial No. 10 2005 001 525.5 filed Jan. 13, 2005. 
       FIELD OF THE INVENTION 
       [0002]    The invention concerns an electromechanically actuated motor vehicle transmission, such as an automated manual transmission or a transfer case for example. Transmissions of this type usually have shifting devices that are actuated by means of an electric motor. 
       BACKGROUND OF THE INVENTION 
       [0003]    In automated or automatic manual transmissions, these electric motors are usually attached to the outside of the transmission housing. A transmission of this type is known from DE 103 44 106 A1, for example. That particular publication describes an electric motor that is screwed onto the outside of the transmission housing. The electric motor drives a gear that engages a shifting shaft through an opening in the wall of the transmission housing. In this type of arrangement, the engaging surface must naturally be painstakingly sealed. The sealing site is also the mechanical interface between the electric motor and the transmission housing, since the motor is attached to the transmission housing at this location by screw connections. When interfaces have multiple functions as described above, it is technically very difficult to ensure that all functions perform satisfactorily. Furthermore, it must be taken into consideration that the electric motor, attached to the outside of the transmission housing, constitutes a vibratable component that can be damaged by excessive resonance resulting from vibrational excitation generated by the transmission. Because of its exposed location, the electric motor is naturally subjected to strong temperature fluctuations. Through its own heat and the additional heat from the transmission, it can reach a temperature that considerably exceeds the temperature of the surrounding medium such as spray water, for example. Quenching with the surrounding medium causes pressure differences to appear at the sealing surface, which in turn increase the stress placed on the interface seal. 
         [0004]    DE 1 03 07 017 A 1 also discloses an electromechanically actuated transfer case in which an electric motor actuates a clutch device, via a drive converter device. 
         [0005]    In that system, a first output shaft is directly connected to a drive shaft. A second output shaft can be connected to the drive, via a clutch device. 
         [0006]    between the clutch device and the electric motor is a device via which a rotational movement of the electric motor is transformed into a translatory actuation movement for controlling the clutch device. 
         [0007]    The electric motor, in this example, is equipped with a motor housing and is installed in the transmission housing completely preassembled. The separate motor housing of the electric motor is nonrotatably attached to transmission housing. The installation of a separate motor housing also involves a mechanical interface that is technically difficult to realize. This results in a weak spot that can make the product more prone to defects. 
       SUMMARY OF THE INVENTION 
       [0008]    The object of the invention is to create an electromechanically shiftable motor vehicle transmission that is equipped with a shifting device actuated by an electric motor. At the same time, the interface between the electric motor and the transmission should be designed to be as economical, robust and unsusceptible to defects as possible. 
         [0009]    Accordingly, the invention proceeds from an electromechanically actuatable motor vehicle transmission, such as an automatic or automated manual transmission or a transfer case. The transmission features at least a transmission housing, an electromagnetic shifting device and an electric motor for driving the shifting device. According to the invention, the motor housing of the electric motor is designed so that it corresponds to a portion of the transmission housing and the electric motor is located inside the transmission housing. 
         [0010]    In an advantageous embodiment of the invention, the motor housing of at least one electric motor is designed so that it forms a portion of the transmission housing, which can be assembled separately. In this embodiment, the motor housing of the electric motor contains all individual components of the electric motor. The fully assembled electric motor is installed in the transmission housing in this way. At the same time, a portion of the motor housing serves as a transmission cover for closing the transmission housing. The transmission cover corresponds to a portion of the outerwall of the transmission housing. The electric motor is advantageously located inside the transmission housing. In this way, the electric motor can be supported by the transmission housing on an especially broad surface area, thereby reducing the mechanical stress on the interface, Because the motor does not protrude through the housing, excessive resonance does not result when the transmission generates vibrational excitations. Integrating the electric motor into the transmission housing results in improved heat dissipation for the electric motor. 
         [0011]    In another embodiment, the motor housing is designed as one piece with the transmission housing and is also arranged within the transmission housing. As a result, the electric motor does not require a separate motor housing. Instead, a portion of the transmission housing serves as motor housing and thus contains the individual components of the electric motor. The electric motor is therefore not assembled before being installed in the transmission. Rather, the individual components of the electric motor are assembled to form a functioning electric motor only during the process of being installed in the transmission housing. In another embodiment, a part of such an electric motor can be closed with a cover. 
         [0012]    A three-phase AC motor, for example an asynchronous motor, is preferably used as electric motor. Asynchronous motors can advantageously also be operated open in an oil-filled space. Having the electric motor rinsed with oil significantly improves cooling. The motor housing of the electric motor is therefore designed as partly open in another embodiment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]    The invention is explained in greater detail through an embodiment with a description of the drawings. Included in the drawings: 
           [0014]      FIG. 1  as a mechanical drawing of the invention; 
           [0015]      FIG. 2  as another mechanical drawing of the invention; and 
           [0016]      FIG. 3  as another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]      FIG. 1  is a mechanical drawing of an inventive transmission. An electromechanical shifting mechanism  1  is composed of an electric motor  2 , a motor shaft  3  and a transfer element  4 . The electric motor  2  is connected to the selector shaft  5 , via the motor shaft  3 , and the transfer element  4 . Connected to the selector shaft  5  are other transmission members, by means of which a previously selected gear ratio can be engaged on a transmission shaft  7 . The desired gear ratios are selected, via a selector motor  8 . 
         [0018]    The electric motor  2  features a first motor housing  9 , which is formed as one piece with a first transmission cover  10 . The first transmission cover  10  can be connected to a transmission housing  11 , illustrated in  FIG. 2 , and forms a portion of the outer wall of the transmission housing  11 . The individual components of the electric motor  2  are installed in the motor housing  9  before being installed in the transmission housing  11 . The motor shaft  3  of the electric motor  2  features a thread of a ball spindle, by means of which the transfer element  4  is directly displaced from the electric motor  2 , axially. The axial movement of the transfer element  4  causes the selector shaft  5  to move in the axial direction. Connected to the selector shaft  5  are other transfer elements  6 , by means of which previously selected gear ratios can be engaged on a transmission shaft  7 . The gear ratios are selected by a second electric motor, the selector motor  8 . 
         [0019]    The selector motor  8  features a second motor housing  12 , which also constitutes a portion of the transmission housing  11 , but which is formed as one piece with the transmission housing  11 . The individual components of the selector motor  8  are installed directly in the second motor housing  12 . The selector motor  8  becomes a functional drive only through the process of assembling the individual components in the second motor housing  12 . The transmission housing  11  is closed with a second transmission cover  13  following the assembly of the individual components. 
         [0020]      FIG. 2  illustrates a closed transmission housing  11 , where the first and second transmission cover  10 ,  13  are shown in assembled state. With the first transmission cover  10 , it is clear that extensive support is present. This is made possible by the one-piece construction of the motor housing  9  and the cover  10 . As a result of this feature, stress on the mechanical interface and the sealing surface between electric motor  2  and the transmission housing  11  is greatly reduced. The second transmission cover  13  primarily provides a sealing function. The demand on the second transmission cover  13  is thus related to providing a seal against the outside environment. 
         [0021]    Because of the decreased demands, the interfaces and sealing sites described above can be realized more simply and economically. Furthermore, the inventive incorporation of the motors  2 ,  8  into the transmission housing  11  increases the heat capacity of the surrounding environment of the electric motors  2 ,  8 . As a result, the temperature gradients drop when the transmission cover  10 ,  13  is sprayed with water. Altogether, incorporating the electric motor  2 ,  8  into the transmission housing allows the best possible dissipation of the heat of the motors  2 ,  8 . 
         [0022]      FIG. 3  represents another illustration of an inventive solution. It shows a partial sectional view of a transfer case  14  with a third transfer element  23 , a third electric motor  22  and a clutch device  18  for engaging a second output shaft. In this example, the third electric motor  22  and the third transfer element  23  combine to form a shifting mechanism  1 . 
         [0023]      FIG. 3  is a longitudinal section of a motor vehicle transfer case  14  designed as a longitudinal transfer case, by means of which drive torque generated, via a drive shaft  15 , can be routed to two output shafts, where the only parts of the two output shafts illustrated are the two connection flanges  16 ,  17  to which the output shafts are coupled. In the description of the mode of function of the transfer case  14 , the two connection flanges  16 ,  17  are equated with the output shafts, so the reference numbers of the two connection flanges are used for the two output shafts, which are not illustrated. 
         [0024]    The first output shaft  16  is directly connected to the first drive shaft  15 , so that the drive torque is directly transferred from the first drive shaft  15 , to the first output shaft  16 . The second output shaft  17  is connected to the drive shaft  15  via a clutch device  18 , a first gear  19  mounted on the drive shaft  15 , an intermediate gear  20  and a second gear  21 , when the clutch device  18  is in a state in which torque can be transmitted, via the clutch device  18 . 
         [0025]    The clutch device  18  can be actuated via the third electric motor  22 , while arranged between the clutch device  18  and the third electric motor  22  is a third transfer element  23  via which the rotational movement of the third electric motor  22  is converted into a translatory actuation movement for controlling the clutch device  18 . A third motor housing  24  of the third electric motor  22  is formed as one piece with the first part  25  of the transmission housing  11 . According to the invention, the individual components of the third electric motor  22 , such as the rotor  26  for example, are installed in the motor housing  24  before the two halves  25 ,  30  of the transmission housing  11  are put together. 
         [0026]    The third transfer element  23  features a gear ratio stage  27 , which in this example is designed as spur gear stage. The clutch device  18  is designed with a pressure disc  28 , which is attached in a rotationally fixed manner to the drive shaft  15  and is thus rotated at the same rotational speed as the drive shaft  15 , when the transfer case  14  is operated. A ball screw nut  29  of the transmission device  23  is moved in the direction of the pressure disc  28 , i.e. in the axial direction of the drive shaft  15 , when the clutch device  18  is engaged so that frictional forces between the pressure disc  28  and the ball screw nut  29  increased as the adjustment travel of the ball screw nut  29  increases, thereby allowing torque to be transmitted. 
         [0027]    In this example, the intermediate gear  20  is mounted in a rotationally fixed manner on the third motor housing  24  of the third electric motor  22 . The arrangement of the third electric motor  22  within the intermediate gear  20  represents an extremely compact and space-saving construction of the transfer case  14 , resulting in a considerably smaller space requirement in a motor vehicle compared to electric motors arranged outside the housing of the transfer case. 
         [0028]    If the electric motor  22  is advantageously configured as three-phase AC motor, it is possible to design the third electric motor  22  to be more compact than if the motor is as a DC-motor, since three-phase AC motors feature greater output than DC-motors of the same dimensions. Combining this feature with the previously described configuration in particular allows the electric motor  22  or the three-phase AC motor to be significantly more compact than a DC-motor of a known transfer case. 
         [0029]    Furthermore, it is also possible to design all three motor housings  9 ,  12 ,  24  as partially open. In this way, the motor housing  9 ,  12 ,  24  can be rinsed with oil, if an asynchronous motor is employed as electric motor  2 ,  8 ,  22 . This option facilitates optimal cooling of the electric motor. 
         [0030]    It is also conceivable to construct the first motor housing  9  of the first electric motor  2  as one piece with the transmission housing  11 , just as the second or third motor housing  12 ,  24  can also be constructed as one piece with a transmission cover  10 . 
       Reference Numbers 
       [0031]      1 . Shifting-/selecting device 
         [0032]      2 . First electric motor 
         [0033]      3 . Motor shaft 
         [0034]      4 . First transfer element 
         [0035]      5 . Shifting shaft 
         [0036]      6 . Second transfer element 
         [0037]      7 . Transmission shaft 
         [0038]      8 . Selector motor 
         [0039]      9 . First motor housing 
         [0040]      10 . First transmission cover 
         [0041]      11 . Transmission housing 
         [0042]      12 . Second motor housing 
         [0043]      13 . Second transmission cover 
         [0044]      14 . Transfer case 
         [0045]      15 . Drive shaft 
         [0046]      16 . First output shaft, connection flange 
         [0047]      17 . Second output shaft, connection flange 
         [0048]      18 . Clutch mechanism 
         [0049]      19 . First gear 
         [0050]      20 . Intermediate gear 
         [0051]      21 . Second gear 
         [0052]      22 . Third electric motor 
         [0053]      23 . Third transfer element 
         [0054]      24 . Third motor housing 
         [0055]      25 . First part of the transmission housing  11   
         [0056]      26 . Rotor 
         [0057]      27 . Gear ratio stage 
         [0058]      28 . Pressure disc 
         [0059]      29 . Ball screw nut 
         [0060]      30 . Second part of the transmission housing  11   
         [0061]      31 . Transmission