Abstract:
An automatic transmission of a motor vehicle driven by an internal combustion engine with a transmission oil circuit, a main oil pump, mechanically driven by a combustion engine, and an auxiliary oil pump ( 1 ) that can be electrically driven and is located inside an oil sump ( 4 ). It is proposed that the auxiliary oil pump ( 1 ) is arranged transversely with respect to the travel direction (x) of the motor vehicle.

Description:
[0001]    This application claims priority from German Application Serial No. 10 2008 000 019.1 filed Jan. 9, 2008. 
       FIELD OF THE INVENTION 
       [0002]    The invention concerns an automatic transmission of a motor vehicle driven by an internal combustion engine. 
       BACKGROUND OF THE INVENTION 
       [0003]    The automatic transmission disclosed in DE 10 2006 012 838 A1 by the present Applicant comprises a main oil pump that can be driven by the combustion engine of the motor vehicle and an auxiliary, electric oil pump, i.e., one that can be driven by an electric motor, for the transmission oil circuit of the automatic transmission. The mechanically driven main oil pump can be designed as a converter throat pump and can be arranged co-axially with the transmission input shaft. However, a non-co-axial arrangement and a mechanical drive, via an auxiliary shaft, are also possible. The auxiliary oil pump, which is used, in particular with an automatic start-stop system of the motor vehicle, is arranged in an oil sump located under the transmission and is connected to the transmission housing via a flange. The driving electric motor may be located either inside or outside the oil sump. 
         [0004]    The purpose of the present invention is to improve the fitting situation for an auxiliary oil pump still further and to utilize the available structural space in the transmission in an optimum manner. 
       SUMMARY OF THE INVENTION 
       [0005]    It is provided that the auxiliary oil pump is positioned transversely with respect to the travel direction of the motor vehicle within the transmission housing and/or the oil sump. In this way, structural space is gained particularly in the travel direction (x-axis) of the motor vehicle. 
         [0006]    The automatic transmission comprises a parking lock mechanism, i.e., a parking lock gear wheel, preferably arranged on the drive output shaft and a parking lock pawl which engages in the parking lock gear wheel. According to the invention, the auxiliary oil pump is arranged under the parking lock mechanism. In this way, the filling space in the transmission in this area is used to good advantage. The automatic transmission can be of any structure. For example, the automatic transmission can be designed as an automatic variable-speed transmission, an automated change-gear transmission, a dual-clutch transmission or even a continuously-variable transmission with or without power branching, without or even with an additional hybrid module or hybrid drive. 
         [0007]    The auxiliary oil pump can advantageously be combined with an electric motor to form a structural unit, a pump aggregate, which as an advantageous design feature, is attached to the transmission housing or the oil sump. 
         [0008]    In addition, the automatic transmission comprises a hydraulic shifting unit (HSU) under the transmission and a transmission oil filter, which is located in the oil sump. The auxiliary oil pump or the structural unit comprising it is arranged behind the hydraulic shifting unit relative to the direction of travel. 
         [0009]    As an advantageous design feature, the pressure connection of the auxiliary oil pump is connected to the hydraulic shifting unit and the suction connection to the oil filter. This ensures that the paths of the suction and pressure connections are short, resulting in a small pressure drop. 
         [0010]    Advantageously, the auxiliary electric oil pump or its structural unit is associated with a pump control unit, which is connected to the electric motor by connection leads. The pump control unit can either be outside the transmission housing or inside the oil sump and integrated with the electric motor. 
         [0011]    The automatic transmission also has an electronic transmission control unit (EGS) arranged inside the transmission housing, which is connected to the pump control unit by a signal lead. 
         [0012]    According to a further preferred embodiment, the spatial arrangement of the main oil pump and the auxiliary oil pump is such that the central axis of the auxiliary oil pump is below the central axis of the main oil pump. In this way, the suction height for the auxiliary oil pump is smaller, which increases its functional reliability. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
           [0014]      FIG. 1  is a first arrangement of an auxiliary electric oil pump in a transmission; 
           [0015]      FIG. 2  is a second arrangement of an auxiliary electric oil pump in a transmission; 
           [0016]      FIG. 3  is a third arrangement of an auxiliary electric oil pump in a transmission; 
           [0017]      FIG. 4  is a longitudinal section through an automatic transmission with an auxiliary electric oil pump, and 
           [0018]      FIG. 5  is a cross-section through the automatic transmission, with the parking lock and the auxiliary electric oil pump. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIG. 1  shows a first embodiment of the invention, with a structural unit  3  comprising an arrangement of an auxiliary oil pump  1  and an electric motor  2  in a transmission housing  4  of an automatic transmission for a motor vehicle. The travel direction of the motor vehicle is indicated by a co-ordinate arrow x and the transverse direction to the travel direction by a co-ordinate arrow y. The structural unit  3 , also called the pump aggregate, has a longitudinal axis a which extends in the y direction, i.e., transversely with respect to the travel direction of the motor vehicle. Inside the transmission housing, which also comprises an oil sump or is closed toward the outside by an oil sump, are arranged a hydraulic shifting unit (HSU)  5  and a transmission oil filter  6 . The auxiliary oil pump  1  has a pressure connection  7  which is connected to the hydraulic shifting unit  5 , and a suction connection  8  which is connected to the transmission oil filter  6 , from which it draws in oil. The pump aggregate  3  is fixed relative to the transmission housing  4  or the oil sump by three schematically represented struts  9 . Above the pump aggregate  3  (behind the plane of the drawing) a parking lock mechanism  10  is indicated schematically. The electric motor  2  of the pump aggregate  3  is controlled and supplied with current by a pump control unit  11  arranged outside the transmission housing  4 , via connection leads  12 . The connection leads  12 , between the pump control unit  11  and the electric motor  2 , pass into and through the transmission housing  4 , via an aperture  13 . For its part, the pump control unit  11  is supplied with current and signals from the vehicle via supply leads  14 . 
         [0020]      FIG. 2  shows another embodiment of the invention with the pump aggregate  3  arranged inside the transmission housing  4 —the same index numbers as before being used for the same components. In contrast to the previous embodiment, an electronic transmission control unit (EGS)  15  is arranged inside the transmission housing  4 , which is connected to the pump control unit  11  by an electric signal lead  16  (represented as a broken line) which passes through the aperture  13 . Thus, in this case, the EGS  15  also serves as a signal emitter for the pump aggregate  3 . 
         [0021]      FIG. 3  shows a third embodiment of the invention for the arrangement of a pump aggregate  17  in which a pump control unit  18  is integrated. The latter is therefore inside the transmission housing  4  or oil sump. The electronic transmission control unit  15  is connected to the pump control unit  18  by an electric signal lead  19  (represented as a broken line) running inside the transmission housing  4 . Current is supplied to the pump control unit  18  from the vehicle, via leads  20 , which pass through the aperture  13  through the wall of the housing  4 . 
         [0022]    Instead of the signal lead  19  that connects the EGS  15  to the pump control unit  18 , as shown in  FIG. 3 . In another embodiment of the invention it can also be provided that the pump aggregate  17  is controlled, via a separate signal lead from outside the transmission. Such a separate signal lead can be a data lead (CAN) which is connected electrically to the pump control unit  18 , via a transmission plug, through whose electric contacts the electric voltage supply is also provided. 
         [0023]      FIG. 4  shows a longitudinal section through an automatic transmission  21 , which comprises a transmission housing  22  to the lower part of which an oil sump  23  is connected, via a flange. The transmission  21  has an input shaft  24  and an output shaft  25 ; the latter formed as the carrier shaft of a planetary gearset and having a parking lock gear wheel  26  on its circumference. Under the drive output shaft  25 , a parking lock pawl  27  is arranged which, when the automatic transmission  21  is secured (selector lever in position P), engages in the parking lock gear wheel  26  and locks the transmission. The parking lock gear wheel  26  (parking lock teeth) and the parking lock pawl  27 , in essence, form a parking lock mechanism. Under the parking lock mechanism  26 ,  27  a pump aggregate  28  is arranged within the transmission housing  22  or within the oil sump  23 . The pump aggregate  28 , comprising a pump, an electric motor and, in some cases, also a pump control unit, is positioned transversely to the travel direction; the latter being indicated by a coordinate arrow x. Ahead of the pump aggregate  28  in the travel direction, there is a hydraulic shifting unit (HSU)  29  under the input shaft  24  and an oil filter  30  in the lowest area of the oil sump  23 . 
         [0024]      FIG. 5  shows a partial view of the automatic transmission  21  in the axial direction, looking at the carrier shaft  25  made as a parking disk with its parking lock gear wheel  26 . The parking lock pawl  27  is arranged under the parking disk  25 , which engages with a pawl tooth  27   a  in a tooth gap of the parking lock gear wheel  26  and so locks the drive output shaft  25 . The pump aggregate  28  is arranged under the parking lock pawl  27 , whose longitudinal (central) axis a runs transversely with respect to the travel direction of the motor vehicle. The pump aggregate  28  extends nearly over the full width of the transmission housing  22  and the oil sump  23 . Thus, the available space is used to good effect. 
       Indexes 
       [0000]    
       
           1  auxiliary oil pump 
           2  electric motor 
           3  structural unit (pump aggregate) 
           4  transmission housing 
           5  hydraulic shifting unit (HSU) 
           6  transmission oil filter 
           7  pressure connection 
           8  suction connection 
           9  fixing strut 
           10  parking lock mechanism 
           11  pump control unit 
           12  connection leads 
           13  aperture 
           14  supply leads 
           15  electronic transmission control unit (EGS) 
           16  signal lead 
           17  pump aggregate 
           18  pump control unit 
           19  signal control 
           20  current supply leads 
           21  automatic transmission 
           22  transmission housing 
           23  oil sump 
           24  input shaft 
           25  drive output shaft/carrier shaft/parking disk 
           26  parking lock gear wheel 
           27  parking lock pawl 
           27   a  pawl tooth 
           28  pump aggregate 
           29  hydraulic shifting unit (HSU) 
           30  oil filter 
         a longitudinal (central) axis 
         P selector lever in position 
         x travel direction coordinate arrow 
         y travel direction coordinate arrow