Abstract:
A transmission includes a drive shaft ( 1 ), an output shaft ( 2 ), a housing (G), a first planetary gear set (PR 1 ), a second planetary gear set (PR 2 ) and a third planetary gear set (PR 3 ), as well as six shift elements, comprising a first brake (B 1 ), a second brake (B 2 ), a first clutch (K 1 ), a second clutch (K 2,  K 2′ ), a third clutch (K 3,  K 3′,  K 3″ ) and a fourth clutch (K 4,  K 4′ ). The shift elements are selectively actuated, by which nine forward gears and one reverse gear are realized through different transmission ratio relationships between the drive shaft ( 1 ) and the output shaft ( 2 ). Each planetary gear set (PR 1,  PR 2,  PR 3 ) features a sun gear (S 1,  S 2,  S 3 ), a planetary gear, a planetary carrier (PT 1,  PT 2,  PT 3 ) and a ring gear (H 1,  H 2,  H 3 ). The drive shaft ( 1 ) and the output shaft ( 2 ) are arranged in a manner axially offset to each other and the drive shaft ( 1 ) is connectable to the ring gear (H 3 ) of the third planetary gear set (PR 3 ) and the second brake (B 2 ) through the first clutch (K 1 ). The ring gear (H 3 ) of the third planetary gear set (PR 3 ) and the second brake (B 2 ) are also connected to each other. A third shaft ( 3 ) is arranged coaxially to the drive shaft ( 1 ).

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a transmission, in particular for use in motor vehicles. 
       BACKGROUND 
       [0002]    Here, a transmission in particular designates a multi-gear transmission, with which a predefined number of gears, thus fixed transmission ratio relationships between transmission input and transmission output, is automatically shiftable through shift elements. Here, the shift elements comprise, for example, clutches or brakes. 
         [0003]    DE 10 2008 032 015 discloses a powershift transmission with ten forward gears and one reverse gear. Thereby, the powershift transmission features three planetary gear sets, which are able to be shifted with each other in various combinations through six torque-transferring devices, two of which are fixed connections and four of which are clutches. A torque is initiated through a start-up element in the powershift transmission, and is transferred to an output element while taking into account the respective transmission ratio relationship. Thereby, the drive element and the output element are arranged coaxially to each other. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is subject to a task of proposing a transmission of the aforementioned type, which features small gear steps with a large gear spread, which at the same type optimizes installation space and/or features a high degree of efficiency. Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
         [0005]    A “gear spread” is understood to mean the quotient from the transmission ratio relationship of the lowest gear and the transmission ratio relationship of the highest gear, whereas the lowest gear features the largest transmission ratio relationship, and the highest gear features the smallest transmission ratio relationship. If there is a transmission ratio relationship of i&lt;1.0, a transmission ratio into fast mode takes place; that is, at the transmission output, a higher rotational speed than that at the transmission input is applied. 
         [0006]    In accordance with the invention, the tasks are solved with a transmission as described and claimed herein. 
         [0007]    The transmission comprises a drive shaft, an output shaft, a housing, a first planetary gear set, a second planetary gear set and a third planetary gear set, along with six shift elements. It is particularly preferable that, through the drive shaft, a torque or a rotational movement of a drive source, such as an internal combustion engine, is initiated in the transmission. In a preferred manner, a start-up element, such as a hydrodynamic torque converter or a fluid coupling, is located between the drive source and the drive shaft. 
         [0008]    In the following, a “shaft” is not solely understood as an exemplary cylindrical, rotatably mounted machine element for the transfer of torques, but is also understood as a general connection element, which connects individual components or elements to each other, in particular connection elements that connect several elements to each other in a torque-proof manner. 
         [0009]    In particular, two elements are described as connected to each other if there is a fixed (in particular, a torque-proof) connection between the elements. In particular, such connected elements rotate with the same rotational speed. 
         [0010]    Furthermore, two elements are described as connectable if there is a detachable connection between such elements. In particular, such elements rotate with the same rotational speed if the connection exists. 
         [0011]    The various components and elements of the specified invention may be connected to each other through a shaft or a connection element, or also directly, for example by means of a welded connection, crimping connection or another connection. 
         [0012]    It is particularly preferable that the six shift elements comprise a first brake, a second brake, a first clutch, a second clutch, a third clutch and a fourth clutch. 
         [0013]    Thereby, clutches describe shift elements that, depending on their operating state, allow for a relative movement between two components or represent a connection for the transfer of a torque. A “relative motion” is understood as, for example, a rotation of two components, where the rotational speed of the first component and the rotational speed of the second component differ from each other. In addition, the rotation of only one of the two rotatable components is conceivable, while the other component is at a standstill or rotates in the opposite direction. 
         [0014]    In the following, a “non-actuated clutch” is understood as an open clutch. This means that a relative motion between the two components is possible. With an actuated or locked clutch, the two components rotate accordingly with the same rotational speed and in the same direction. 
         [0015]    A “brake” is understood as a shift element that is connected on one side to a fixed element, such as a housing, and on another side to a rotating element. In the following, a “non-actuated brake” is understood as an open brake. This means that the rotating component is in free-running mode, which means that the brake preferably does not affect the rotational speed of the rotating component. With an actuated or locked brake, a reduction in the rotational speed of the rotating component up to a stop takes place, which means that a connection between the rotating element and the fixed element can be established. In this context, “element” and “component” are equated. 
         [0016]    As a general rule, the use of shift elements that are locked in a non-actuated state and open in an actuated state is also possible. Accordingly, the allocations between function and shifting state of the shifting states described above are understood in reverse order. With the following embodiments, an arrangement in which an actuated shift element is closed and a non-actuated shift element is open is initially used as the basis. 
         [0017]    A planetary gear set comprises a sun gear, a planetary carrier and a ring gear. Planetary gears that mesh with the toothing of the ring gear and/or with the toothing of the sun gear are rotatably mounted on the planetary carrier. 
         [0018]    In the following, a negative planetary gear set describes a planetary gear set with a planetary carrier on which the planetary gears are rotatably mounted, with one sun gear and one ring gear, whereas the toothing of at least one of the planetary gears meshes with both the toothing of the sun gear and with the toothing of the ring gear, by which the ring gear and the sun gear rotate in opposite directions, if the sun gear rotates with a fixed planetary carrier. 
         [0019]    A positive planetary gear set differs from the negative planetary gear set just described in that the positive planetary gear set features inner and outer planetary gears, which are rotatably mounted on the planetary carrier. Thereby, the toothing of the inner planetary gears meshes, on the one hand, with the toothing of the sun gear and, on the other hand, with the toothing of the outer planetary gears. The toothing of the outer planetary gears also meshes with the toothing of the ring gear. This has the consequence that, with a fixed planetary carrier, the ring gear and the sun gear rotate in the same direction of rotation. 
         [0020]    A particularly compact transmission can be realized through the use of planetary gear sets, by which a high degree of freedom in the arrangement of the transmission in the vehicle is achieved. 
         [0021]    In particular, the sun gear, the ring gear, the planetary carrier and the planetary gears of the planetary gear set are understood as elements of a planetary gear set. 
         [0022]    It is particularly preferable that the shift elements are able to be actuated selectively, thus individually and in line with demand, by which nine forward gears and one reverse gear can be realized through different transmission ratio relationships between the drive shaft and the output shaft. Based on the numerous gears, it is possible to realize a fine gear shifting with a large gear spread, and thereby, for example, to operate the internal combustion engine in an optimal rotational speed range, and thus efficiently. At the same time, this contributes to increased driving comfort, since the internal combustion engine preferably can be operated at a low rotational speed level. Thus, for example, noise emissions that arise through the operation of the internal combustion engine are reduced. 
         [0023]    It is also preferable that the drive shaft and the output shaft are arranged in a manner axially offset to each other. This leads, for example, to a particularly low need for axial installation space for the transmission. Thereby, the transmission is suitable, in a particularly preferable manner, for use in a vehicle with a front-transverse arrangement of the drive train. 
         [0024]    “Front-transverse arrangement of the drive train” is understood to mean that the drive source, such as an internal combustion engine, is installed in the vehicle transverse to the direction of travel, and that, preferably, the wheels of the front axle are drivable by the drive source or the transmission. 
         [0025]    It is particularly preferable that all elements of the first planetary gear set, the second planetary gear set and the third planetary gear set are rotatable. This means that there is no permanent connection between the elements of the planetary gear sets and a fixed element, such as the housing; rather, a connection can be selectively established through the actuation of the shift elements. This also advantageously contributes to the fact that, by means of a low number of planetary gear sets, a high number of gears can be realized. Thereby, a blocking of the individual elements of the planetary gear sets can be produced only through the actuation of the respective shift elements. 
         [0026]    It is also preferable that the drive shaft is, through the first clutch, connectable to the ring gear of the third planetary gear set and the second brake. It is also preferable that the ring gear of the third planetary gear set and the second brake are also connected to each other. This achieves a multitude of degrees of freedom with respect to the planetary gear sets, such that a multitude of gears with the use of relatively few shift elements and planetary gear sets is feasible. It is also preferable that a third shaft is arranged coaxially to the drive shaft. 
         [0027]    The degree of efficiency of the transmission may be preferably increased by the fact that, for the shift elements, energy is necessary for the change to the shifting state, but not for maintaining the shifting state itself. Here, actuated shift elements in line with demand, such as electromechanical shift elements or electromagnetic shift elements, are suitable in a particular way. Particularly when compared to conventional hydraulically actuated shift elements, they are characterized by a particularly low and efficient energy demand, since they can be operated nearly loss-free. In addition, with the solution specified above, it is advantageous that permanently holding a control pressure for the actuation of the (for example) conventional hydraulic shift elements, and/or permanently applying the shift element in the shifted state with the required hydraulic pressure, can be avoided. Thereby, additional components such as a hydraulic pump (for example) may be omitted, to the extent that they are solely used for the control and supply of conventional hydraulically actuated shift elements. If the additional components are supplied with lubricant by the same hydraulic pump, and not by a separate lubrication pump, at least this can be dimensioned smaller. Moreover, any leaks at the oil transfer points of the hydraulic circuit that may arise, particularly with rotating components, are eliminated. It is particularly preferable that this also contributes to increased efficiency of the transmission in the form of a higher degree of efficiency. Upon the use of actuated shift elements in line with demand of the type specified above, it is particularly advantageous if they are accessible from the outside. Among other things, that has the advantage that the required shifting energy can be easily fed to the shift elements. Therefore, the shift elements are, particularly preferably, arranged so that they are easily accessible from the outside. Within the meaning of the shift elements, “easily accessible from the outside” means that no additional components are arranged between the housing and the shift element, and/or that the shift elements are, particularly preferably, arranged on the output shaft or on the drive shaft. 
         [0028]    In an additional preferred form of the arrangement, the sun gear of the third planetary gear set is connected to the first brake. 
         [0029]    In a particularly preferable form of the arrangement, the transmission features a first spur pinion and a second spur pinion. At least each one spur gear of the first spur pinion and one spur gear of the second spur pinion are arranged coaxially to the drive shaft. By means of the first spur pinion and/or the second spur pinion, a torque is transferable between the drive shaft and the output shaft, depending on the actuation of the shift elements. The use of spur pinions enables the transfer of torque or rotational movements between the axially offset drive shaft and the output shaft, by which a particularly low need for axial installation space of the transmission in the vehicle arise. This is of particular importance for vehicles with a front-transverse arrangement of the drive train, since the available installation space in the vehicle for the drive source and the transmission is, in a particular manner, limited by the width of the vehicle. However, other arrangements of the drive train (for example, for rear-wheel drive vehicles and/or for vehicles with a longitudinal arrangement of the drive train) are conceivable. 
         [0030]    For a vehicle with a longitudinal arrangement of the drive train, the drive source, such as an internal combustion engine, is preferably installed in the vehicle longitudinally to the direction of travel, and the wheels of the rear axle are preferably drivable by the drive source or the transmission. 
         [0031]    A spur pinion comprises a single-stage or multi-stage spur gearbox with at least two spur gears, which mesh with each other. Thereby, the respective shafts and/or rotation axes of the spur gears are arranged parallel to each other. 
         [0032]    In an additional preferred form of the arrangement, the two spur pinions are positioned in an axial alignment along the third shaft, particularly preferably between the first planetary gear set and the third planetary gear set. Thereby, they are arranged in the order of first planetary gear set, first spur pinion, second spur pinion, third planetary gear set. This arrangement ensures a particularly space-saving design, since the individual planetary gear sets and shift elements can be easily nested in one another, and the various shafts, for example with this arrangement, do not cross each other. To the extent that this allows for the binding ability of the elements, a geometric positioning of the individual gear sets, shift elements and spur pinions that deviates from the arrangement just described is conceivable, to the extent that the change to the geometric positioning of the components occurs along the third shaft. 
         [0033]    “Binding ability” is understood to mean that, with a different geometric positioning, thus an arrangement of components that deviates from the arrangement just described, the same binding or connection of the interfaces is ensured, without the individual connection elements or shafts crossing each other. 
         [0034]    Moreover, the use of a chain drive or a belt drive in place of the first spur pinion and/or the second spur pinion is conceivable. 
         [0035]    In an additional preferred embodiment, the first planetary gear set and the second planetary gear set are axially positioned with respect to the third shaft such that the second planetary gear set is arranged radially over the first planetary gear set. The arrangement of the second planetary gear set radially over the first planetary gear set is characterized, in a particular manner, by a particularly low need for axial installation space. It is particularly preferable that the sun gear of the second planetary gear set and the ring gear of the first planetary gear set are connected to each other. As an alternative to this, a one-piece or a single-part version of the sun gear of the second planetary gear set and the ring gear of the first planetary gear set is conceivable. In this case, for example, the ring gear of the first planetary gear set possesses, in addition to an inner toothing, which meshes with the toothing of the planetary gears of the first planetary gear set, an outer toothing, which preferably assumes the function of the toothing of the sun gear of the second planetary gear set. Thereby, the outer toothing of the ring gear of the first planetary gear set meshes with the toothing of the planetary gears of the second planetary gear set. 
         [0036]    In an additional preferred form of the arrangement, each of the first planetary gear set, the second planetary gear set and the third planetary gear set is designed as a negative planetary gear set. In a particular manner, this arrangement on the one hand proves to be a cost-effective option for realization of the gear set. On the other hand, this arrangement features a high degree of efficiency with respect to the gear set, since, compared to positive planetary gear sets, negative planetary gear sets have an improved degree of efficiency. 
         [0037]    To the extent allowed by the binding ability, as an alternative embodiment, at least one negative planetary gear set may be converted into a positive planetary gear set. However, at the same time, this requires that the planetary carrier connection and the ring gear connection are exchanged, and the amount of the stationary transmission ratio is increased by the value of 1. 
         [0038]    Thereby, the stationary transmission ratio indicates the transmission ratio relationship between the sun gear and the ring gear, if the planetary carrier is fixed. 
         [0039]    In an additional preferred form of the arrangement, the drive shaft is connectable to the planetary carrier of the first planetary gear set through the first clutch. It is also preferable that the drive shaft is connectable to the sun gear of the first planetary gear set through the second clutch. It is also preferable that the drive shaft is connectable to the planetary carrier of the second planetary gear set through the third clutch. The ring gear of the second planetary gear set is preferably connected to a first spur pinion, and the first spur pinion is further connected to the output shaft. It is also preferable that the planetary carrier of the third planetary gear set is connected to a second spur pinion, the ring gear of the first planetary gear set and the sun gear of the second planetary gear set. In addition, it is also preferable that the second spur pinion is further connectable to the output shaft through the fourth clutch. In this preferred arrangement, the first clutch, the second clutch and the third clutch are positioned next to each and in a coaxial arrangement at the drive shaft, and in each case connected to the drive shaft on one side. Thereby, the first clutch, the second clutch and the third clutch are positioned between the transmission input and first planetary gear set along the third shaft, in the order of first clutch, second clutch, third clutch. Through this arrangement, the first clutch, the second clutch and the third clutch are particularly easily accessible from the outside. 
         [0040]    A transmission input thereby describes a location on a transmission at which, in driving mode, a torque is initiated by the drive source in the transmission. In contrast to this, a “transmission output” is understood to mean a location on the transmission at which the torque, taking into account the corresponding transmission ratio relationships (for example, in a transfer case) is initiated or transferred to the drive shafts of the vehicle. 
         [0041]    In an additional preferred variant of the transmission, the drive shaft of the first clutch and the second clutch is connectable to the planetary carrier of the first planetary gear set. It is also preferable that the drive shaft is connected to the sun gear of the first planetary gear set. The drive shaft is also preferably connected to the planetary carrier of the second planetary gear set through the third clutch. It is also preferable that the ring gear of the second planetary gear set is connected to a first spur pinion, and the first spur pinion is further connected to the output shaft. It is particularly preferable that the planetary carrier of the third planetary gear set is connected to a second spur pinion, the ring gear of the first planetary gear set and the sun gear of the second planetary gear set. It is also preferable that the second spur pinion is also connectable to the output shaft through the fourth clutch. 
         [0042]    In an additional preferred form of the arrangement, the drive shaft is connectable to the planetary carrier of the first planetary gear set through the first clutch. It is also preferable that the drive shaft is connectable to the sun gear of the first planetary gear set through the second clutch. The drive shaft is preferably connected to the planetary carrier of the second planetary gear set. Preferably, the ring gear of the second planetary gear set is connectable to a first spur pinion through the third clutch. The first spur pinion is preferably further connected to the output shaft. The planetary carrier of the third planetary gear set is preferably connected to a second spur pinion, the ring gear of the first planetary gear set and the sun gear of the second planetary gear set. It is also preferable that the second spur pinion is also connectable to the output shaft through the fourth clutch. 
         [0043]    In an additional preferred arrangement of the transmission, the drive shaft is connectable to the planetary carrier of the first planetary gear set through the first clutch. It is also preferable that the drive shaft is connectable to the sun gear of the first planetary gear set through the second clutch. The drive shaft is preferably connected to the planetary carrier of the second planetary gear set. It is also preferable that the ring gear of the second planetary gear set is connected to a first spur pinion, whereas the first spur pinion is preferably further connectable to the output shaft through the third clutch. The planetary carrier of the third planetary gear set is preferably connected to a second spur pinion, the ring gear of the first planetary gear set and the sun gear of the second planetary gear set. It is also preferable that the second spur pinion is connectable to the output shaft through the fourth clutch. 
         [0044]    In an additional preferred variant of the transmission, the drive shaft is connectable to the planetary carrier of the first planetary gear set through the first clutch and the second clutch. It is also preferable that the drive shaft is connected to the sun gear of the first planetary gear set. The drive shaft is preferably further connected to the planetary carrier of the second planetary gear set. It is particularly preferable that the ring gear of the second planetary gear set is connectable to a first spur pinion through the third clutch, whereas the first spur pinion is preferably further connected to the output shaft. It is also preferable that the planetary carrier of the third planetary gear set is connected to a second spur pinion, the ring gear of the first planetary gear set and the sun gear of the second planetary gear set. The second spur pinion is preferably further connectable to the output shaft through the fourth clutch. 
         [0045]    In an additional preferred form of the arrangement, the drive shaft is connectable to planetary carrier of the first planetary gear set through the first clutch and the second clutch. It is also preferable that the drive shaft is connected to the sun gear of the first planetary gear set. The drive shaft is preferably further connected to the planetary carrier of the second planetary gear set. Preferably, the ring gear of the second planetary gear set is connected to a first spur pinion, whereas the first spur pinion is preferably further connectable to the output shaft through the third clutch. It is also preferable that the planetary carrier of the third planetary gear set is connected to a second spur pinion, the ring gear of the first planetary gear set and the sun gear of the second planetary gear set. It is also preferable that the second spur pinion is connectable to the output shaft through the fourth clutch. 
         [0046]    In an additional preferred arrangement of the transmission, the drive shaft is connectable to the planetary carrier of the first planetary gear set through the first clutch. It is also preferable that the drive shaft is connectable to the sun gear of the first planetary gear set through the second clutch. The drive shaft is preferably connectable to the planetary carrier of the second planetary gear set through the third clutch. It is also preferable that the ring gear of the second planetary gear set is connected to a first spur pinion. It is also preferable that the first spur pinion is connected to the output shaft. The planetary carrier of the third planetary gear set is preferably connected to the ring gear of the first planetary gear set and the sun gear of the second planetary gear set, and is connectable to a second spur pinion through the fourth clutch. Preferably, the second spur pinion is further connected to the output shaft. 
         [0047]    In a particularly preferable form of the arrangement, the first forward gear can be represented by the locked first brake, the locked second clutch and the locked fourth clutch. The second forward gear preferably can be represented by the locked first brake, the locked first clutch and the locked fourth clutch. The third forward gear preferably can be represented by the locked first clutch, the locked second clutch and the locked fourth clutch. The fourth forward gear preferably can be represented by the locked second clutch, the locked third clutch and the locked fourth clutch or by the locked second brake, the locked third clutch and the locked fourth clutch or by the locked first brake, the locked third clutch and the locked fourth clutch or by the locked first clutch, the locked third clutch and the locked fourth clutch. The fifth forward gear preferably can be represented by the locked first clutch, the locked second clutch and the locked third clutch. The sixth forward gear preferably can be represented by the locked first brake, the locked first clutch and the locked third clutch. The seventh forward gear preferably can be represented by the locked first brake, the locked second clutch and the locked third clutch. The eighth forward gear preferably can be represented by the locked first brake, the locked second brake and the locked third clutch. The ninth forward gear preferably can be represented by the locked second brake, the locked second clutch and the locked third clutch. Particularly preferably, the reverse gear can be represented by the locked second brake, the locked second clutch and the locked fourth clutch. 
         [0048]    In accordance with an additional aspect of the present invention, a method for operating the transmission is proposed. Thereby, at least nine forward gears can be preferably selected in such a manner that, in each gear, three shift elements are simultaneously locked. The remaining shift elements are preferably open. A gear change to an adjacent higher gear or to an adjacent lower gear can be realized preferably by locking at least one previously open shift element and by opening at least one previously locked shift element. Regardless of whether they are able to be actuated hydraulically, electro-mechanically or in any other way, this leads to a lower need for energy of the shift elements, which ultimately has advantageous effects on consumption, for example the consumption of fuel if an internal combustion engine is the drive source of the vehicle. In addition, particularly low shifting times can be obtained in this manner, which is also advantageous. 
         [0049]    In principle, all shift elements can function in a frictional-locking or positive-locking manner. It is particularly preferable that the fourth clutch is designed as a positive-locking shift element, in particular as a claw coupling. This leads to a significantly improved degree of efficiency of the transmission, and thus significant consumption advantages with respect to fuel consumption, for example, for vehicles with internal combustion engines. 
         [0050]    In principle, on each shaft or each connection element, an electric motor or another power/drive source may also be arranged. 
         [0051]    In addition, at each shaft or each connection element, a freewheel may in principle be arranged at the housing or at another shaft. As a result, the corresponding shift element may be dimensioned smaller, since at least part of the torque is captured through the freewheel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0052]    The invention is described more specifically by example on the basis of the attached figures. The following is shown: 
           [0053]      FIG. 1  is a schematic view of a first preferred embodiment of a transmission in accordance with the invention; 
           [0054]      FIG. 2  is a schematic view of a second preferred embodiment of a transmission in accordance with the invention; 
           [0055]      FIG. 3  is a schematic view of a third preferred embodiment of a transmission in accordance with the invention; 
           [0056]      FIG. 4  is a schematic view of a fourth preferred embodiment of a transmission in accordance with the invention; 
           [0057]      FIG. 5  is a schematic view of a fifth preferred embodiment of a transmission in accordance with the invention; 
           [0058]      FIG. 6  is a schematic view of a sixth preferred embodiment of a transmission in accordance with the invention; 
           [0059]      FIG. 7  is a schematic view of a seventh preferred embodiment of a transmission in accordance with the invention; and 
           [0060]      FIG. 8  is an exemplary shift diagram for a transmission in accordance with  FIGS. 1 to 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0061]    Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein. 
         [0062]    In a schematic presentation,  FIG. 1  shows a first preferred embodiment of the transmission, whereas the transmission comprises a first planetary gear set PR 1 , a second planetary gear set PR 2 , a third planetary gear set PR 3 , a first spur pinion ST 1 , a second spur pinion ST 2  and six shift elements. All of the specified elements are arranged in a housing G. The six shift elements comprise a first brake B 1 , a second brake B 2 , a first clutch K 1 , a second clutch K 2 , a third clutch K 3  and a fourth clutch K 4 . The first brake B 1  and the second brake B 2  are firmly connected to the housing G on their one side.  FIG. 1  also shows a drive shaft  1  and an output shaft  2 , whereas the drive shaft  1  and the output shaft  2  are arranged parallel to each other. On a first side of the drive shaft  1 , the drive shaft  1  has a free end. On this first side of the drive shaft  1 , a rotational movement or a torque is initiated in the transmission. The drive shaft  1  is connectable to a third shaft through the first clutch K 1 . The third shaft  3  is further connected to the planetary carrier PT 1  of the first planetary gear set PR 1 , the ring gear H 3  of the third planetary gear set PR 3  and the second brake B 2 . In addition, the third shaft  3  connects the planetary carrier PT 1  of the first planetary gear set PR 1 , the ring gear H 3  of the third planetary gear set PR 3  and the second brake B 2 . The third shaft  3  runs coaxially to the drive shaft  1 . The first clutch K 1 , the second clutch K 2  and third clutch K 3  are arranged coaxially to the third shaft  3  in the order of first clutch K 1 , second clutch K 2 , third clutch K 3 , whereas the first clutch K 1  features a distance to the free end of the drive shaft  1  that is lower than that of the second clutch K 2  or the third clutch K 3 . The first planetary gear set PR 1 , the second planetary gear set PR 2 , the third planetary gear set PR 3 , the first brake B 1  and the second brake B 2  are also arranged coaxially to the third shaft  3 . The second planetary gear set PR 2  is arranged radially over the first planetary gear set PR 1 . The ring gear H 1  of the first planetary gear set PR 1  is connected to the sun gear S 2  of the second planetary gear set PR 2 . The first planetary gear set PR 1 , the third planetary gear set PR 3 , the first brake B 1  and the second brake B 2  are arranged along the third shaft  3 , beginning at the third clutch K 3 , in the order of first planetary gear set PR 1 , third planetary gear set PR 3 , first brake B 1 , second brake B 2 . The first spur pinion ST 1  and the second spur pinion ST 2  are located between the first planetary gear set PR 1  or the second planetary gear set PR 2  and the third planetary gear set PR 3 , in the order of first planetary gear set PR 1  or second planetary gear set PR 2 , first spur pinion ST 1 , second spur pinion ST 2 , third planetary gear set PR 3 . At least one spur gear of the first spur pinion ST 1  and the second spur pinion ST 2  are arranged coaxially to the third shaft  3 . Through the first spur pinion ST 1  and/or through the second spur pinion ST 2 , a transmission of torque or rotational movements takes place between the drive shaft  1  and the output shaft  2 . The output shaft  2  also has a free end. Thereby, the free end of the drive shaft  1  and the free end of the output shaft  2  point in the same direction. The fourth clutch K 4  is arranged coaxially to the output shaft  2  at the free end of the drive shaft  2 , beginning at the fourth clutch K 4 . Thereby, the first spur pinion ST 1 , the second spur pinion ST 2  and the fourth clutch K 4  are arranged along the output shaft  2 , in the order just specified. At least each one spur gear of the first spur pinion ST 1  and one spur gear of the second spur pinion ST 2  are arranged coaxially to the output shaft  2 . The drive shaft  1  is further connectable to a fourth shaft  4  through the second clutch K 2 , whereas the fourth shaft  4  is further connected to the sun gear S 1  of the first planetary gear set PR 1 . The drive shaft  1  is connectable to a fifth shaft  5  through the third clutch K 3 , whereas the fifth shaft  5  is further connected to the planetary carrier PT 2  of the second planetary gear set PR 2 . The ring gear H 2  of the second planetary gear set PR 2  is connected to the first spur pinion ST 1  through a sixth shaft  6 . The first spur pinion ST 1  is further connected to the output shaft  2 . The sun gear S 3  of the third planetary gear set PR 3  is connected to the first brake B 1  through a seventh shaft  7 . The planetary carrier PT 3  of the third planetary gear set PR 3  is connected to an eighth shaft  8 , whereas the eighth shaft  8  is further connected to the second spur pinion ST 2 , the ring gear H 1  of the first planetary gear set PR 1  and the sun gear S 2  of the second planetary gear set PR 2 . In addition, the eighth shaft  8  connects the elements just specified among each other. The second spur pinion ST 2  is further connected to a ninth shaft  9 , whereas the ninth shaft  9  is connectable to the output shaft  2  through the fourth clutch K 4 . 
         [0063]    Each of the first planetary gear set PR 1 , the second planetary gear set PR 2  and the third planetary gear set PR 3  is designed as a negative planetary gear set. This means that planetary gears of the planetary carrier PT 1  mesh with the sun gear S 1  and the ring gear H 1  of the first planetary gear set PR 1 . The same applies for the second planetary gear set PR 2  or the sun gear S 2 , the planetary carrier PT 2  and the ring gear H 2  of the second planetary gear set PR 2 , and for the third planetary gear set PR 3  or the sun gear S 3 , the planetary carrier PT 3  and the ring gear H 3  of the third planetary gear set PR 3 . 
         [0064]    Each of the first spur pinion ST 1  and the second spur pinion ST 2  is designed as a single-stage spur gearbox. 
         [0065]      FIG. 2  shows an additional embodiment of the transmission described in  FIG. 1 , which differs from the embodiment described in  FIG. 1  primarily by a deviating positioning of the second clutch K 2 ′. In the present embodiment, the second clutch K 2 ′ is positioned, in terms of space, in a coaxial arrangement to the third shaft  3  between the first planetary gear set PR 1  and the first spur pinion ST 1 . This results in the following changes with respect to the interfaces and connections in the transmission. The drive shaft  1  is connectable to the third shaft  3  through the first clutch K 1 . The third shaft  3  is also connected to the ring gear H 3  of the third planetary gear set PR 3  and the second brake B 2 . By way of derogation from the arrangement described in  FIG. 1 , the third clutch  3  is also connectable to the fourth shaft  4  through the second clutch K 2 ′, whereas the fourth shaft  4  is further connected to the planetary carrier PT 1  of the first planetary gear set PR 1 . An additional difference of the connection of the individual elements of the planetary gear sets PR 1 , PR 2 , PR 3  consists of the fact that the drive shaft  1  is now directly connected to the sun gear S 1  of the first planetary gear set PR 1 . All additional interfaces and arrangements of the components correspond to the arrangement described in  FIG. 1 . 
         [0066]      FIG. 3  shows a third variant of the transmission described in  FIG. 1 . A significant difference with the arrangement described in  FIG. 1  consists of the positioning of the third clutch K 3 ′. Thereby, the third clutch K 3 ′ is arranged coaxially to the third shaft  3  between the first planetary gear set PR 1  or the second planetary gear set PR 2  and the first spur pinion ST 1 . This has the consequence that the drive shaft  1  is now directly connected to the planetary carrier PT 2  of the second planetary gear set PR 2 . The ring gear H 2  of the second planetary gear set PR 2  is connected to the sixth shaft  6 , whereas the sixth shaft  6  is now connectable to the fifth shaft  5  through the third clutch K 3 ′. The fifth shaft  5  is further connected to the first spur pinion ST 1 , and the first spur pinion ST 1  is further connected to the output shaft  2 . All additional connections and interfaces, along with the arrangement of the respective components, correspond to the arrangement described in  FIG. 1 . 
         [0067]      FIG. 4  shows a fourth variant of the transmission described in  FIG. 1 . Thereby, the transmission corresponds to large extent to the embodiment described in  FIG. 1 . A significant difference with the transmission described in  FIG. 1  is reflected in the geometric position of the third clutch K 3 ″. Thereby, the third clutch K 3 ″ is arranged coaxially to the output shaft  2 . Along the output shaft  2 , the third clutch K 3 ″, the first spur pinion ST 1 , the second spur pinion ST 2  and the fourth clutch K 4  are arranged in the specified order, beginning on the free end of the output shaft  2 . Thereby, the third clutch K 3 ″ and the fourth clutch K 4  are arranged coaxially to the output shaft  2 . Thereby, at least one spur gear of the spur pinion ST 1  and at least one spur gear of the second spur pinion ST 2  are also arranged coaxially to the output shaft  2 . Here, in contrast to the embodiment described in  FIG. 1 , the planetary carrier PT 2  of the second planetary gear set PR 2  is directly connected to the drive shaft  1 . The ring gear H 2  of the second planetary gear set PR 2  is connected to the sixth shaft  6 , whereas the sixth shaft  6  is further connected to the first spur pinion ST 1 . The first spur pinion ST 1  is further connected to the fifth shaft  5 , which is connectable to the output shaft  2  through the third clutch K 3 ″. All additional connections and interfaces, along with the arrangement of the respective components, correspond to the arrangement described in  FIG. 1 . 
         [0068]      FIG. 5  shows a fifth variant of the transmission described in  FIG. 1 . This differs from the variant described in  FIG. 1  in that the second clutch K 2 ′ and the third clutch K 3 ′ are arranged, in terms of space, coaxially to the third shaft  3  between the first planetary gear set PR 1  or the second planetary gear set PR 2  and the first spur pinion ST 1 , in the order of first planetary gear set PR 1  or second planetary gear set PR 2 , second clutch K 2 ′, third clutch K 3 ′, first spur pinion ST 1 . This results in changes with respect to interfaces or connections, as described below. The drive shaft  1  is connectable to the third shaft  3  through the first clutch K 1 . The third shaft  3  is further connectable to the fourth shaft  4  through the second clutch K 2 ′, whereas the fourth shaft  4  is further connected to the planetary carrier PT 1  of the first planetary gear set PR 1 . Further, the drive shaft  1  is connected to the sun gear S 1  of the first planetary gear set PR 1  and the planetary carrier PT 2  of the second planetary gear set PR 2 . The ring gear H 2  of the second planetary gear set PR 2  is connected to the sixth shaft  6 , whereas the sixth shaft  6  is connectable to the fifth shaft  5  through the third clutch K 3 ′. The fifth shaft  5  is also connected to the first spur pinion ST 1 , and the first spur pinion ST 1  is further connected to the output shaft  2 . The embodiment shown in  FIG. 5  arises from a combination of the embodiments of the alternative embodiments of the second clutch K 2 ′ and the third clutch K 3 ′ described in  FIG. 2  and  FIG. 3 . 
         [0069]      FIG. 6  shows an additional embodiment of the transmission described in  FIG. 1 . By way of derogation from the arrangement described in  FIG. 1 , in the present embodiment, the second clutch K 2 ′ is positioned, in terms of space, in a coaxial arrangement to the third shaft  3  between the first planetary gear set PR 1  or the second planetary gear set PR 2  and the first spur pinion ST 1 . In addition, the third clutch K 3 ″ is arranged coaxially to the output shaft  2 , whereas the following elements are arranged along the output shaft  2 , beginning at the free end of the output shaft  2 , in the order of third clutch”, first spur pinion ST 1 , second spur pinion ST 2 , fourth clutch K 4 . The differences described below with respect to the interfaces or connections of the individual elements arise from the specified changes to the positioning of the second clutch K 2 ′ and the third clutch K 3 ″. The drive shaft  1  is connectable to the third shaft  3  through the first clutch K 1 , whereas the third shaft  3  is further connectable to the fourth shaft  4  through the second clutch K 2 ′, and the fourth shaft  4  is further connected to the planetary carrier PT 1  of the first planetary gear set PR 1 . The drive shaft  1  is further connected to the sun gear S 1  of the first planetary gear set PR 1  and the planetary carrier PT 2  of the second planetary gear set PR 2 . The ring gear H 2  of the second planetary gear set PR 2  is connected to the sixth shaft  6 , whereas the sixth shaft  6  is further connected to the first spur pinion ST 1 . The first spur pinion ST 1  is further connected to the fifth shaft  5 , whereas the fifth shaft  5  is connectable to the output shaft  2  through the third clutch K 3 ″. All additional connections and interfaces, along with the arrangement of the respective components, correspond to the arrangement described in  FIG. 1 . The embodiment of the transmission shown in  FIG. 6  arises from a combination of the embodiments of the second clutch K 2 ′ and the third clutch K 3 ″ described in  FIG. 2  and  FIG. 4 . 
         [0070]      FIG. 7  shows an additional embodiment of the transmission described in  FIG. 1 . This differs from the arrangement described in  FIG. 1  in that the fourth clutch K 4 ′ is positioned, in terms of space, in a coaxial arrangement to the third shaft  3  between the second spur pinion ST 2  and the third planetary gear set PR 3 .Among other things, this leads to the fact that the output shaft  2  is free of shift elements. Differences with respect to the interfaces, which are described below, arise from the positioning of the fourth clutch K 4 ′. The planetary carrier PT 3  of the third planetary gear set PR 3  is connected to the ring gear H 1  of the first planetary gear set PR 1  and the sun gear S 2  of the second planetary gear set PR 2  through the eighth shaft  8 . In addition, the eighth shaft  8  is connectable to the ninth shaft  9  through the fourth clutch K 4 ′. The ninth shaft  9  is further connected to the second spur pinion ST 2 , and the second spur pinion ST 2  is further connected to the output shaft  2 . All additional connections and interfaces, along with the arrangement of the respective components, correspond to the arrangement described in  FIG. 1 . 
         [0071]    In a table,  FIG. 8  shows a shift matrix of the transmission in accordance with the invention. By means of an X in the corresponding box of the table, the shift element that is locked for the realization of the first to ninth forward gear and the reverse gear is made clear. In addition, three shifting alternatives for the fourth forward gear are indicated with the numbers  4 -I,  4 -II and  4 -III. 
         [0072]    The shifting states of the alternative embodiment of the second clutch K 2 ′ are identical to the shifting states of the second clutch K 2 . The same applies to the shifting states of the alternative embodiment of the third clutch K 3 ′, K 3 ″ and the shifting states of the third clutch K 3 , and/or the shifting states of the alternative embodiment of the fourth clutch K 4 ′ and the shifting states of the fourth clutch K 4 . This means that, for example, the shifting states of the alternative embodiments of the third clutch K 3 ′, K 3 ″ are defined in the table, for example, through the shifting states of the third clutch K 3 . 
         [0073]    Furthermore, the transmission ratio of the respective gear is specified, whereas the first forward gear features a transmission ratio relationship of i=4.476, the second forward gear features a transmission ratio relationship of i=2.599, the third forward gear features a transmission ratio relationship of i=1.667, the fourth forward gear features a transmission ratio relationship of i=1.267, the fifth forward gear features a transmission ratio relationship of i=1.000, the sixth forward gear features a transmission ratio relationship of i=0.807, the seventh forward gear features a transmission ratio relationship of i=0.705, the eighth forward gear features a transmission ratio relationship of i=0.600 and the ninth forward gear features a transmission ratio relationship of i=0.501. Given the reversal of direction of the rotary movement, the reverse gear features a negative transmission ratio relationship of i=−3.357. Here, “transmission ratio” and “transmission ratio relationship” are synonymous. 
         [0074]    The corresponding gear jumps of the forward gears can also be derived from the table. Under “gear jump,” the quotient of the transmission ratios of the lower forward gear and the adjacent higher forward gear is understood. Thereby, the gear jump from the first forward gear to the second forward gear features a value of φ=1.722, the gear jump from the second forward gear to the third forward gear features a value of φ=1.559, the gear jump from the third forward gear to the fourth forward gear features a value of φ=1.316, the gear jump from the fourth forward gear to the fifth forward gear features a value of φ=1.267, the gear jump from the fifth forward gear to the sixth forward gear features a value of φ=1.239, the gear jump from the sixth forward gear to the seventh forward gear features a value of φ=1.145, the gear jump from the seventh forward gear to the eighth forward gear features a value of φ=1.175 and the gear jump from the eighth forward gear to the ninth forward gear features a value of φ=1.199. 
         [0075]    The gear spread, as a quotient of the transmission ratio relationship of the lowest forward gear and the transmission ratio relationship of the highest forward gear, is 8.942. 
         [0076]    Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims.