# Patent

## Title
Transmission with a differential locking unit

## Abstract

A transmission with a differential locking unit which comprises an input shaft (10), first and second output shafts (11, 12), and first and second planetary gear sets (P1, P2). Torque introduced, via the input shaft (10), is converted and distributed to the two output shafts (11, 12) in a defined ratio, and development of a sum torque is prevented. The differential locking unit comprises an epicyclic gearing (P3) as well as a switching element (B 1). The epicyclic gearing (P3) has at least three connection shafts (3), a first connection shaft (WI) is rotationally fixed to a linking shaft (3), a second connection shaft (W2) is rotationally fixed to the second element (E21) of the first planetary gear set (PI), which is rotationally fixed to the first output shaft (11). A third connection shaft (W3) can be secured to a rotationally fixed component (GG) by the switching element (B 1).

## Background
This application is a national stage completion of International Application No. PCT/EP2020/055787 filed Mar. 5, 2020 which claims priority from German Patent Application Serial No. 10 2019 209 465.1 filed on Jun. 28, 20219.
FIELD OF THE INVENTION
The invention relates to a transmission with a differential locking unit. The invention also relates to a drivetrain and a vehicle.
BACKGROUND OF THE INVENTION
A conventional differential transmission makes cornering possible by allowing different rotational speeds of the two drive wheels. It transmits the drive torque equally to both wheels (open differential). It is disadvantageous that that wheel which has the better grip only has as much traction as that which is situated on slippery ground or which is lightly loaded during cornering. A differential lock can be used to increase traction and improve driving dynamics, which differential lock partially connects the two drive wheels to one another by way of friction. With adjustable differential locks, the cornering ability of an open differential can be combined with the improved traction of a locking differential. The differential transmission is also known as a differential or differential compensating transmission.
An integrated differential is known from DE 10 2018 112 880 A1.
Differential locking units are also known from the prior art. These are also referred to as locking differentials or self-locking differentials. A locking differential is a differential transmission which, by contrast to conventional differentials, has a certain degree of sluggishness in its movement. It brakes suddenly occurring increases in rotational speed at that driven wheel which, for example, has temporarily lost road grip as a result of wheel hop.
SUMMARY OF THE INVENTION
The object of the present invention is that of providing a transmission, in particular in the form of an integrated differential, which also has a differential locking unit.
The object is achieved by means of the features of claim 1. Preferred embodiments emerge from the subclaims.
The transmission comprises an input shaft, a first output shaft, a second output shaft, a first planetary gear set and a second planetary gear set which is connected to the first planetary gear set. The planetary gear sets each comprise multiple elements. The input shaft, the two output shafts, the planetary gear sets and elements thereof are arranged and configured such that a torque introduced via the input shaft is converted and divided between the two output shafts in a defined ratio, and the generation of a sum torque is prevented. Here, at least one element of the first planetary gear set is connected rotationally conjointly to another element of the second planetary gear set, and a further element of the second planetary gear set is fixed to a non-rotatable structural element.
The elements of the planetary gear sets are in particular in the form of sun gear, planet carrier and ring gear. If an element is fixed, it is prevented from rotating. The non-rotatable structural element of the transmission may preferably be a permanently static component, preferably a housing of the transmission, a part of such a housing or a structural element connected to said housing in a non-rotatable manner.
In the context of the invention, a “shaft” is to be understood to mean a rotatable structural part of the transmission, via which respectively associated components of the transmission are connected rotationally conjointly to one another or via which such a connection is established when a corresponding shift element is actuated. The respective shaft may in this case connect the components to one another axially or radially or both axially and radially. The respective shaft may thus also be present as an intermediate piece, via which a respective component is connected radially, for example. The term “shaft” does not preclude that the components to be connected may be formed in one piece.
In the context of the invention, “axial” means an orientation in the direction of a longitudinal central axis along which the planetary gear sets are arranged so as to lie coaxially with respect to one another. “Radial” is then to be understood to mean an orientation in the diameter direction of a shaft which lies on said longitudinal central axis.
A torque can be introduced into the transmission via the input shaft. The drive by means of which a torque can be introduced into the transmission may be realized by any drive source, for example by means of a drive machine in the form of an internal combustion engine or in the form of an electric machine.
The specification of the torque conversion is to be understood as follows:
The transmission has two output shafts, the torque sum of which, in relation to the input torque, describes the conversion of the transmission. The transmission has two output shafts, the respective speed ratio of which is initially not defined. It is the coupling of the two output shafts, for example via the wheels of the vehicle on a roadway, that first generates defined rotational speeds. If both output shafts rotate at the same rotational speed, for example during straight-ahead travel, then, as in the prior art, the speed ratio can be formed as a rotational speed ratio between the input rotational speed and one of the two identical output rotational speeds. In all other cases, it is not possible to use the common definition of torque conversion/speed ratio to specify a speed ratio of the transmission.
The two planetary gear sets of the transmission may be designed both as a minus or a plus planetary gear set. A combination of minus and plus planetary gear sets is also possible.
A minus planetary set is, in a manner known in principle to a person skilled in the art, made up of the elements sun gear, planet carrier and ring gear, wherein the planet carrier guides at least one but preferably multiple planet gears in rotatably mounted fashion, which planet gears specifically mesh in each case with both the sun gear and the surrounding ring gear.
In the case of a plus planetary set, it is likewise the case that the elements sun gear, ring gear and planet carrier are present, wherein the latter guides at least one planet gear pair, in the case of which one planet gear is in tooth meshing engagement with the inner sun gear and the other planet gear is in tooth meshing engagement with the surrounding ring gear, and the planet gears mesh with one another.
The first two planetary gear sets may be arranged axially adjacent to one another. The first planetary gear set may however also be arranged radially within the second planetary gear set. The latter embodiment is also referred to as a nested arrangement of the planetary gear sets.
The toothings of the two interconnected elements of the first and second planetary gear sets, that is to say of the third element of the first planetary set and of the first element of the second planetary set, may be formed on the same structural part. Furthermore, a pitch of the toothing on the third element of the first planetary set and on the first element of the second planetary set may be identical. The identical pitch allows the connecting structural part or the coupling shaft to be free from axial forces, such that an expensive axial bearing can be omitted.
The input shaft of the transmission may be connected to a drive machine, in particular an electric machine or an internal combustion engine, for the introduction of a torque into the transmission. According to an exemplary embodiment, the rotor of the electric machine is connected rotationally conjointly to the input shaft. As an alternative to this, in one possible embodiment of the transmission, the rotor is connected to the input shaft via at least one speed ratio stage. The electric machine may be arranged so as to lie either coaxially with respect to the planetary gear sets or axially parallel with respect thereto. In the first-mentioned case, the rotor of the electric machine may in this case either be directly connected rotationally conjointly to the input shaft or else coupled thereto via one or more interposed speed ratio stages, wherein the latter allows a more cost-effective design of the electric machine with higher rotational speed and lower torque. The at least one speed ratio stage may in this case be designed as a spur gear stage and/or as a planetary stage.
If, by contrast, the electric machine is provided so as to be axially offset with respect to the planetary gear sets, a coupling is thus realized via one or more interposed speed ratio stages and/or a traction mechanism drive. The one or more speed ratio stages may in this case also be implemented specifically either as a spur gear stage or as a planetary stage. A traction mechanism drive may be either a belt drive or a chain drive.
In the case of a coaxial arrangement of the electric machine, it is particularly preferred if the first output shaft is guided through the rotor of the electric machine. This makes the transmission with electric machine particularly compact.
The static transmission ratio of the second planetary gear set can be calculated at least approximately from the reciprocal of the static transmission ratio of the first planetary set minus 1.
Furthermore, a transmission is preferred in which the static transmission ratio of the second planetary set is calculated at least approximately from the reciprocal of the static transmission ratio of the first planetary set minus 1, that is to say:



 
  
   i
   
    0
    ⁢
    2
   
  
  =
  
   
    1
    
     i
     
      0
      ⁢
      1
     
    
   
   -
   
    1
    .
   
  
 



In the event that the two planetary sets are designed as minus planetary sets (for example as per FIG. 2 or 3), this calculation rule has the effect that, if transmission losses are neglected, the output torque is respectively divided equally between the two output shafts. This is particularly advantageous if the invention is used for distributing the torque between two wheels on the same axle.
If a different torque distribution is desired or if the planetary gear sets are designed differently (for example FIGS. 4 to 9), a calculation rule can thus be defined analogously (FIG. 19). The wording “at least approximately” is used because, during operation under real conditions, the asymmetrical transmission losses in the direction of the two output shafts can have the effect that a slight deviation from the calculation rule is advantageous in order to obtain the same output torques at both shafts. Furthermore, this wording is used because it is sometimes not possible to exactly adhere to the calculation rule while adhering to integer numbers of teeth and favorable combinations of numbers of teeth, for example with regard to acoustic requirements.
In FIG. 19, the calculation rules of the respective dependency of the static speed ratio of the second planetary set on the static speed ratio of the first planetary set are analogously specified for the gear set combinations with regard to FIGS. 4, 5, 6, 8 and 9. If transmission losses are disregarded, these each give rise to an output torque of equal magnitude and with the same sign at both output shafts.
The drive machine may be installed transversely with respect to a direction of travel. Furthermore, the two output shafts may be connected rotationally conjointly to the wheels of a vehicle.
It may furthermore be the case that the two output shafts distribute the introduced torque between different axles of a vehicle. An arrangement as a longitudinal transfer box (also called longitudinal transfer case) can thus be implemented, that is to say a transmission that distributes the introduced torque, for example, between multiple axles, in particular between a front axle and a rear axle of a vehicle.
The torque distribution of the transmission does not need to be uniform between the output shafts. In particular in the case of the embodiment as a longitudinal transfer box, a non-uniform distribution between one and the other axle may be realized. For example, the torque provided by the input shaft may be distributed such that 60% is directed to the rear axle and 40% to the front axle.
It has been found to be particularly advantageous if the first and second planetary gear sets are designed as minus planetary gear sets. These have good efficiency and can be arranged axially adjacent to one another and nested radially.
In the case of a combination of minus and plus planetary gear sets in a nested arrangement, the radially inner planetary gear set may be a minus planetary gear set and the radially outer planetary gear set may be a plus planetary gear set. Here, on the one hand, an easily implemented nesting capability is maintained. In addition, in this context, the fixed ring gear also offers the advantage that the (normally) relatively poor efficiency caused by the plus planetary gear set only affects one output shaft.
It is additionally possible for a transmission gearing or a multi-ratio transmission, preferably a 2-ratio transmission, to be connected upstream of the transmission. This transmission gearing or multi-ratio transmission may then also be a constituent part of the transmission and serves to configure an additional speed ratio by, for example, converting the rotational speed of the drive machine and driving the input shaft with this converted rotational speed. The multi-ratio transmission or transmission gearing may in particular be in the form of a planetary transmission.
The elements of the transmission may be designed as follows:

    
    
        a) Transmission with two minus planetary gear sets, wherein
        
            the first element of the first planetary gear set is a sun gear,
            the second element of the first planetary gear set is a planet carrier and
            the third element of the first planetary gear set is a ring gear, and wherein
            the first element of the second planetary gear set is a sun gear,
            the second element of the second planetary gear set is a planet carrier and
            the third element of the second planetary gear set is a ring gear.
        
        
    
    


This transmission could be referred to as a first concept with two minus planetary gear sets.

    
    
        b) Transmission with two minus planetary gear sets, wherein
        
            the first element of the first planetary gear set is a sun gear,
            the second element of the first planetary gear set is a ring gear and
            the third element of the first planetary gear set is a planet carrier, and wherein
            the first element of the second planetary gear set is a ring gear,
            the second element of the second planetary gear set is a planet carrier and
            the third element of the second planetary gear set is a sun gear.
        
        
    
    


This transmission could be referred to as a second concept with two minus planetary gear sets.

    
    
        c) Transmission with two minus planetary gear sets, wherein
        
            the first element of the first planetary gear set is a ring gear,
            the second element of the first planetary gear set is a planet carrier and
            the third element of the first planetary gear set is a sun gear, and wherein
            the first element of the second planetary gear set is a sun gear,
            the second element of the second planetary gear set is a planet carrier and
            the third element of the second planetary gear set is a ring gear.
        
        
    
    


This transmission could be referred to as a fifth concept with two minus planetary gear sets.

    
    
        d) Transmission with one plus and one minus planetary gear set, wherein the second planetary gear set is the minus planetary gear set, wherein
        
            the first element of the first planetary gear set is a sun gear,
            the second element of the first planetary gear set is a ring gear and
            the third element of the first planetary gear set is a planet carrier, and wherein
            the first element of the second planetary gear set is a sun gear,
            the second element of the second planetary gear set is a planet carrier and
            the third element of the second planetary gear set is a ring gear.
        
        
    
    


This transmission is, as it were, the first concept with one plus planetary gear set.

    
    
        e) Transmission with one plus and one minus planetary gear set, wherein the first planetary gear set is the minus planetary gear set, wherein
        
            the first element of the first planetary gear set is a sun gear,
            the second element of the first planetary gear set is a planet carrier and
            the third element of the first planetary gear set is a ring gear, and wherein
            the first element of the second planetary gear set is a sun gear,
            the second element of the second planetary gear set (P2) is a ring gear and
            the third element of the second planetary gear set is a planet carrier.
        
        
        f) Transmission with two plus planetary gear sets, wherein
        
            the first element of the first planetary gear set is a sun gear,
            the second element of the first planetary gear set is a ring gear and
            the third element of the first planetary gear set is a planet carrier, and wherein
            the first element of the second planetary gear set is a sun gear,
            the second element of the second planetary gear set is a ring gear and
            the third element of the second planetary gear set is a planet carrier.
        
        
    
    


This transmission is, as it were, the first concept with two plus planetary gear sets.
The differential locking unit comprises an epicyclic transmission, in particular in the form of a planetary gear set or a planetary stage, and a shift element.
The epicyclic transmission has at least three connection shafts. An at least first connection shaft is connected rotationally conjointly to the connecting shaft. An at least second connection shaft is connected rotationally conjointly to the second element of the first planetary gear set, which in turn is connected rotationally conjointly to the first output shaft. An at least third connection shaft can be fixed to a non-rotatable structural element by means of the shift element.
Through suitable selection of the static transmission ratio of the differential locking unit, the differential locking unit allows a rotational speed of zero or close to zero at the remaining third connection shaft during straight-ahead travel (both output shafts rotating at the same rotational speed). Synchronism of the output shafts can be enforced by fixing the third connection shaft, which can be achieved by closing the shift element, whereby the locking action is achieved.
An epicyclic transmission is to be understood to mean an arrangement of one or more planetary gear sets with three connection shafts. It applies equally to all design variants of the epicyclic transmission that the first of these three connection shafts is connected rotationally conjointly to the connecting shaft, the second connection shaft is connected rotationally conjointly to the first output shaft of the first planetary gear set, and the third connecting shaft can be fixed to a non-rotatable structural element by means of a shift element.
Such a transmission combines the two functions of torque conversion and torque distribution in a single assembly. The invention constitutes, so to speak, a combined transmission gearing and differential transmission, which on the one hand can implement a torque conversion with the aid of a housing support and on the other hand can implement the torque distribution to the output shafts. A locking action is also provided.
The shift element is preferably designed as a brake, in particular as a frictionally engaging or positively locking brake.
If the shift element is of frictionally engaging design, it can also be only partially closed if required. This makes it possible to set how much torque is to be transmitted from one wheel, for example a slipping wheel, to the other wheel. The advantage of a brake over a clutch is in particular that the brake can be of simpler design than a clutch. Furthermore, an electromechanical and therefore more economical actuator arrangement is made possible. Actuation bearings, which are disadvantageous in terms of losses and dimensioning, can thus be dispensed with. Furthermore, the invention makes a modular system possible in which either the preferred brake, or for example a torque vectoring unit, can be coupled to the same engagement point.
The shift element may also be designed as a positively locking shift element, for example as a claw-type brake. The advantage of a claw is that it can be engaged with little (or relatively little) actuation energy. This can for example be performed manually. Furthermore, a claw requires relatively little installation space.
In the context of the invention, the fact that two structural elements of the transmission or of the differential locking unit are rotationally conjointly “connected” or “coupled” or “are connected to one another” refers to a permanent coupling of these structural elements such that they cannot rotate independently of one another. In particular, no shift element is provided between these structural elements, which may be elements of the planetary gear sets and/or also shafts and/or a non-rotatable structural element of the transmission, but the corresponding structural elements are fixedly coupled to one another. A rotationally elastic connection between two structural parts is also understood to be conjoint or rotationally conjoint. In particular, a rotationally conjoint connection may also include joints, for example in order to allow a steering movement or a spring compression movement of a wheel.
The third planetary gear set of the differential locking unit may be arranged axially adjacent to the first planetary gear set or else radially outside the first planetary gear set of the transmission. The third planetary gear set may likewise be configured as a minus planetary gear set. In another embodiment, it may be configured as a plus planetary gear set. Furthermore, the third planetary gear set may be of stepped-planet design, in particular configured as a plus planetary gear set of stepped-planet design.
To increase the rotational speed of the third connection shaft, at least one further transmission, for example in the form of a planetary gear set or in the form of a spur gear stage, may be provided between the epicyclic transmission and the shift element. The speed ratio of the third connection shaft can thus be additionally increased.
A further transmission, preferably in the form of a planetary gear set or of countershaft design, may be provided for adapting the rotational speed of the input shaft. This further transmission is intended in particular to reduce the rotational speed.
If the drive machine is in the form of an electric machine, the electric machine is in particular arranged coaxially or axially parallel with respect to the input shaft.
If the drive machine is in the form of an electric machine and this is arranged coaxially with respect to the input shaft, then the epicyclic transmission either may be arranged at least partially radially within the rotor of the electric machine or is arranged axially spaced apart from the electric machine.
It is preferred if the input shaft is guided through the epicyclic transmission.
It is preferred if the first output shaft is guided through the epicyclic transmission.
If the input shaft and/or the first output shaft is guided through the epicyclic transmission, a particularly compact transmission with differential locking function can thus be realized.
The transmission can be used for example as an axle-differential lock. This is to be understood to mean the restriction of the differential function of two wheels of the same axle.
The transmission can however also be used for example as an interaxle-differential lock. This is understood to mean the restriction of the differential function between two driven axles.
The transmission with the differential locking unit is in particular part of a motor vehicle drivetrain for a hybrid or electric vehicle and is then arranged between a drive machine, configured as an internal combustion engine or electric machine, of the motor vehicle and further components of the drivetrain which follow in the direction of power flow to drive wheels of the motor vehicle. The transmission may also be part of a drivetrain for a conventional motor vehicle, that is to say a vehicle that is driven only by an internal combustion engine.
According to a further aspect, a drivetrain having an above-described transmission with a differential locking unit, and a vehicle having a transmission of said type or having a drivetrain of said type, are provided. The advantages of the transmission with differential locking unit likewise apply to the drivetrain and to the vehicle having such a transmission with a differential locking unit.
The invention is not restricted to the stated combination of the features of the main claim or of the claims dependent thereon. Possibilities additionally arise for combining individual features with one another, also insofar as they emerge from the claims, from the following description of preferred embodiments of the invention or directly from the drawings. The reference by the claims to the drawings through the use of reference designations is not intended to limit the scope of protection of the claims.



BRIEF DESCRIPTION OF THE DRAWINGS
Advantageous embodiments of the invention, which will be discussed below, are illustrated in the drawings. In the drawings:
FIGS. 1a-1e show a schematic view of a vehicle;
FIGS. 2-7 each show a schematic view of an exemplary transmission that can be used with a differential locking unit according to the invention in the vehicle from FIGS. 1a-1e; 
FIGS. 8-13 each show a schematic view of an exemplary drivetrain having a transmission with a differential locking unit, as can be used in the vehicle from FIGS. 1a to 1e; 
FIG. 14 shows the embodiment as per FIG. 3 in a sectional view;
FIGS. 15-18 show a schematic illustration of the functional principle of the invention;
FIG. 19 shows an overview of the static transmission ratios of the individual embodiments; and
FIGS. 20-34 show a schematic view of a respective drivetrain having a transmission with a differential locking unit in respectively preferred embodiments of the invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1a to 1e each show a schematic view of a transmission G, having a differential locking unit which is not illustrated in any more detail, of a motor vehicle drivetrain 100 of a vehicle 1000 in the form of a passenger motor vehicle.
The drivetrain 100 as per FIG. 1a shows an electric drive which drives the rear axle A of the vehicle 1000. The drivetrain comprises a transmission G, which divides the drive torque of the electric machine EM between two output shafts 11 and 12. The transmission G and the electric machine are arranged in a common housing. The forward direction of travel is illustrated by arrow 99. As can also be seen in FIG. 1a, the transmission G and the electric machine EM are oriented transversely with respect to the direction of travel of the vehicle.
The drivetrain 100 as per FIG. 1b shows an internal combustion engine drive which drives the rear axle A of the vehicle 1000. The drivetrain comprises a transmission G, which divides the drive torque of the internal combustion engine VM between two output shafts 11 and 12, wherein a further transmission, for example an automatic transmission of the vehicle, is arranged between the transmission G and the internal combustion engine VM. The forward direction of travel is illustrated by arrow 99. As can also be seen in FIG. 1a, the transmission G and the internal combustion engine VM are oriented longitudinally with respect to the direction of travel of the vehicle.
The drivetrain 100 as per FIG. 1c shows an internal combustion engine drive which drives the rear axle A and the front axle B of the vehicle 1000. The drivetrain comprises a transmission G, which divides the drive torque of the internal combustion engine VM between the axles A and B, wherein a further transmission, for example an automatic transmission of the vehicle, is arranged between the transmission G and the internal combustion engine VM. The transmission G may then be connected via an output shaft 11 to an axle differential of the rear wheel axle A and via an output shaft 12 to an axle differential of the front axle B. The forward direction of travel is illustrated by arrow 99. As can also be seen in FIG. 1c, the transmission G and the internal combustion engine VM are oriented longitudinally with respect to the direction of travel of the vehicle.
The drivetrain 100 as per FIG. 1d shows an electric drive which drives the front axle B of the vehicle 1000, that is to say an electric front transverse drive. The drivetrain comprises a transmission G, which divides the drive torque of the electric machine EM between two output shafts 11 and 12. The transmission G and the electric machine are arranged in a common housing. The forward direction of travel is illustrated by arrow 99. As can also be seen in FIG. 1d, the transmission G and the electric machine EM are oriented transversely with respect to the direction of travel of the vehicle.
The drivetrain 100 as per FIG. 1e shows an electric all-wheel drive which drives the rear axle A and the front axle B of the vehicle 1000. This involves a transmission designed as a longitudinal transfer case. The drivetrain comprises a transmission G, which divides the drive torque of the electric machine EM between two output shafts 11 and 12. The output shaft 11 transmits the torque to the front axle B, whereas the output shaft 12 transmits the torque to the rear axle A. The respective torques are then in turn introduced into respective axle differentials. The transmission G and the electric machine are arranged in a common housing. The forward direction of travel is illustrated by arrow 99. As can also be seen in FIG. 1e, the transmission G and the electric machine EM are oriented transversely with respect to the direction of travel of the vehicle.
FIG. 2 shows a transmission G in a first exemplary embodiment. The transmission G comprises an input shaft 10, a first output shaft 11, a second output shaft 12, a first planetary gear set P1 and a second planetary gear set P2 which is connected to the first planetary gear set P1. In the present case, the planetary gear sets P1 and P2 are each designed as a minus planetary gear set. The planetary gear sets P1, P2 each comprise multiple elements E11, E21, E31, E12, E22, E32, wherein the first element E11 is a sun gear SO1, the second element E21 is a planet carrier PT1 and the third element E31 of the first planetary gear set P1 is a ring gear HO1. In the case of the second planetary gear set P2, the first element E12 is a sun gear SO2, the second element E22 is a planet gear carrier PT2 and the third element E32 is a ring gear HO2. The planet gear carriers PT1, PT2 each support multiple planet gears, which are illustrated but not designated. The planet gears mesh both with the respective radially inner sun gear and with the respective surrounding ring gear. The input shaft 10, the first output shaft 11 and the second output shaft 12 are arranged coaxially with respect to one another. The two planetary gear sets P1, P2 are likewise arranged coaxially with respect to one another.
In the present case, the input shaft 10 is connected rotationally conjointly to the first element E11. The first output shaft 11 is connected rotationally conjointly to the second element E21 of the first planetary gear set. The second output shaft 12 is connected rotationally conjointly to the third element E32 of the second planetary gear set. The third element E31 of the first planetary gear set P1 is connected rotationally conjointly to the first element E12 of the second planetary gear set P2, whereas the second element E22 of the second planetary gear set P2 is fixed to a non-rotatable structural element GG. The non-rotatable structural element GG is a transmission housing of the transmission G.
The third element E31, that is to say the ring gear HO1 of the first planetary gear set P1, and the first element E12, that is to say the sun gear SO2 of the second planetary gear set, form a common structural part, which in the present case is in the form of a connecting shaft or shaft 3.
As can be seen in FIG. 2, the input shaft 10, the first output shaft 11 and the second output shaft 12 are arranged coaxially with respect to one another. The two planetary gear sets P1, P2 are likewise arranged coaxially with respect to one another. According to this embodiment, the two planetary gear sets P1, P2 are arranged so as to be axially spaced apart from one another.
The input shaft 10 may be connected to a drive machine and thus introduce an input torque into the transmission G. That is to say, the input shaft 10 and output shafts 11, 12 rotate in the same direction. Through the connection of the two planetary gear sets P1, P2 to one another and the support of the second element E22 on the housing GG, the introduced input torque can be distributed between the two output shafts 11, 12. In this case, the transmission performs not only the function of a transmission gearing but additionally that of a differential gear. That is to say, the introduced torque is not only subjected to a speed ratio but is also distributed between various output shafts. In this embodiment, no reversal of the direction of rotation occurs.
FIG. 3 shows a further exemplary embodiment of the transmission G. By contrast to the embodiment as per FIG. 2, the embodiment as per FIG. 3 shows a radially nested arrangement of the two planetary gear sets P1, P2. Whereas the embodiment as per FIG. 2 proposes an extremely radially compact solution, the embodiment as per FIG. 3 makes possible an extremely axially compact transmission G. The first planetary gear set P1 in this case forms the radially inner planetary gear set. The second planetary gear set P2 forms the radially outer planetary gear set. The first planetary gear set P1 is accordingly situated radially within the second planetary gear set P2. In this embodiment, too, the connection of the first ring gear HO1 of the first planetary gear set P1 to the sun gear SO2 of the second planetary gear set is configured as a single structural part, which in the present case is likewise in the form of a shaft 3. It is likewise the case in this embodiment that no reversal of the direction of rotation occurs.
FIG. 4 shows a transmission G in a further exemplary embodiment. By contrast to FIG. 2, the first planetary gear set P1 is now configured as a plus planetary gear set. That is to say, the third element E31 of the first planetary gear set is configured as a planet gear carrier, which is connected rotationally conjointly to the first element E12 of the second planetary gear set, that is to say the sun gear SO2. The second element E21 is now configured as a ring gear HO1 and is connected rotationally conjointly to the first output shaft 11. The third element E31 of the first planetary gear set and the first element E12 of the second planetary gear set are in turn formed on the same structural part, which in the present case is in the form of a shaft 3. Reference is otherwise made to the statements relating to FIG. 2.
FIG. 5 shows a further exemplary embodiment of the transmission G. By contrast to the embodiment as per FIG. 2, it is now the case that both planetary gear sets P1, P2 are configured as plus planetary gear sets. Thus, the second element E21 is configured as a ring gear HO1 and is connected rotationally conjointly to the first output shaft 11. The third element E31 is now configured as a planet carrier PT1 and is connected rotationally conjointly to the first element E12, that is to say the sun gear SO2 of the second planetary gear set P2. The second element E22 of the second planetary gear set P2 is now configured as the ring gear HO2 and is fixed to the non-rotatable structural element GG. By contrast, the third element E32 of the second planetary gear set P2 is configured as a planet carrier PT2 and is connected rotationally conjointly to the second output shaft 12.
Thus, in the case of the two planetary gear sets P1, P2, the planet carrier and ring gear connections have been interchanged. Reference is otherwise made to the statements relating to FIG. 2.
FIG. 6 shows a transmission in a further exemplary embodiment. By contrast to the embodiment as per FIG. 2, the second planetary gear set P2 is now configured as a plus planetary gear set, whereas the first planetary gear set P1 remains unchanged. Thus, the ring gear HO2 of the second planetary gear set P2 is fixed to the housing GG. In addition, the planet carrier PT2 is connected rotationally conjointly to the second output shaft 12. The planet carrier and ring gear connections of the second planetary gear set have thus been interchanged. Reference is otherwise made to the statements relating to FIG. 2.
FIG. 7 shows a further exemplary embodiment of the transmission G. By contrast to the embodiment as per FIG. 6, the embodiment as per FIG. 7 provides radially nested planetary gear sets P1, P2. The planetary gear set situated radially at the inside is the first planetary gear set P1. The planetary gear set situated radially at the outside is the second planetary gear set P2. Reference is otherwise made to the statements relating to FIGS. 6 and 2.
FIG. 8 shows the transmission G in a further exemplary embodiment. This embodiment has the following differences in relation to the embodiment as per FIG. 2. Firstly, a drive machine in the form of an electric machine EM is provided. The electric machine EM comprises a stator S, which is fixed to the housing, and a rotor R. The rotor R of the electric machine EM is connected rotationally conjointly to the first element E11, that is to say the sun gear SO1 of the first planetary gear set. A further difference is that the second element E21 of the first planetary gear set is configured as a ring gear HO1 and is connected rotationally conjointly to the first output shaft 11. Furthermore, the third element E31 of the first planetary gear set P1 is configured as a planet carrier PT1 and is connected rotationally conjointly to the first element E12 of the second planetary gear set P2, which in the present case is configured as a ring gear HO2. The second element E22 of the second planetary gear set is furthermore configured as a planet carrier PT2 and is fixed to the housing GG. Accordingly, the third element E32 is configured as a sun gear SO2 and is connected rotationally conjointly to the second output shaft. In this exemplary embodiment, a reversal of the direction of rotation of the input rotational speed occurs. Nesting of the planetary gear sets P1, P2 is not possible in this embodiment.
In other words, the torque continues to be introduced via the sun gear SO1 of the first planetary gear set P1, whereas the output is ensured via the ring gear HO1. By contrast to the situation in FIG. 2, the planet carrier of the first planetary gear set P1 is now connected rotationally conjointly to the ring gear HO2 of the second planetary gear set. By contrast to the embodiment as per FIG. 2, the output of the second planetary gear set accordingly takes place via the sun gear SO2.
FIG. 9 shows a further exemplary embodiment of the transmission G. The embodiment has the following differences in relation to the embodiment as per FIG. 2. Firstly, a drive machine in the form of an electric machine EM is provided, which has a stator S, which is fixed to the housing, and a rotor R. The rotor R is connected rotationally conjointly to the input shaft 10, which in turn is connected to the first element E11, which in the present case is configured as a ring gear HO1, of the first planetary gear set P1. The first output shaft 11 is in the present case connected to the second element E21, which in the present case is in the form of a planet carrier PT2, of the first planetary gear set P1. The third element E31 of the first planetary gear set P1, which in the present case is configured as a sun gear SO1, is connected rotationally conjointly to the first element E12, that is to say the sun gear SO2 of the second planetary gear set P2. The other elements of the second planetary gear set remain unchanged.
By contrast to the embodiment as per FIG. 2, it is the case in the embodiment as per FIG. 9 that the introduction of the torque takes place via the ring gear HO1 of the first planetary gear set P1, whereas the output of the first planetary gear set P1 continues to be realized via the planet carrier PT1. By contrast to FIG. 2, the two planetary gear sets P1, P2 are connected via a common sun gear, which in the present case is in the form of a shaft 3.
FIG. 9a shows a specific embodiment of the transmission G for the drivetrain from FIG. 1c. Output 12 transmits the torque to the rear axle A. Output 11 transmits the torque to the front axle B. As can be clearly seen, the output shafts 11, 12 are arranged axially parallel with respect to one another—and not coaxially with respect to one another. The second output shaft 12 of the second planetary gear set P2 meshes with an intermediate toothed gear ZZ, which in turn is connected to a shaft which in turn introduces the torque into a rear-axle differential (not illustrated).
FIG. 10 shows a drivetrain 100 of a vehicle with a transmission in an exemplary embodiment, wherein a transmission gearing in the form of a planetary gear P33 is additionally connected upstream of the transmission G.
The transmission G is the embodiment as per FIG. 3, to which reference is hereby made. The planetary gear set P33 is configured as a minus planetary gear set and has a first element E133, which is configured as a sun gear, a second element E233, which is configured as a planet carrier, and a third element E333, which in the present case is configured as a ring gear HO33. The second element E233 of the additional planetary gear set P33 is connected rotationally conjointly to the input shaft 10 of the transmission G.
Furthermore, a shift element SE is assigned to the planetary transmission P33. The shift element SE is configured to fix the third element E333 to the non-rotatable structural element GG. Furthermore, the shift element SE is configured to, in a second shift position, connect the third element E333 to the first element E133 of the planetary gear set P33, that is to say to place these in a block state. If a planetary gear set is in a block state, the speed ratio is always 1, regardless of the number of teeth. In other words, the planetary gear set revolves as a block. In a third shift position, the third element E333 is not fixed to the housing, nor is the planetary gear set P33 in a block state. The shift element SE is in this case present in a neutral shift position. The first shift position of the shift element SE is denoted by the reference designation G1, which at the same time represents a first gear ratio stage. The second shift position is denoted by the reference designation G2, which at the same time represents a second gear ratio stage. The first element E13 of the planetary gear set P3 is connected via an input shaft 14 to a drive machine (not illustrated). If the shift element SE is in its neutral position, the drive torque introduced into the transmission gearing P33 is not transmitted to the input shaft 10 of the transmission G.
As can also be clearly seen from FIG. 10, the transmission gearing P33 is arranged coaxially with respect to the input shaft 10 and with respect to the output shafts 11, 12. In addition, it can be clearly seen how the first output shaft 11 is guided through the input shaft 10 designed as a hollow shaft and, over the further course, through the further shaft 14 designed as a hollow shaft. The two output shafts 11, 12 are each connected to a drive wheel 20. Vibration dampers 15 are provided in order to absorb the vibrations of the vehicle.
FIG. 11 shows a drivetrain of a vehicle having a transmission in a further exemplary embodiment. The transmission G is the preferred embodiment as per FIG. 2, to which reference is made. By contrast to FIG. 10, no transmission gearing is connected upstream in the embodiment as per FIG. 11. The drive machine is configured as an electric machine EM. The electric machine EM has a stator S, which is fixed to the housing, and a rotor R. The rotor R is connected rotationally conjointly to the input shaft 10. As can be clearly seen, the electric machine EM is arranged coaxially with respect to the input shaft 10 and with respect to the output shafts 11, 12. In addition, said electric machine is thus arranged coaxially with respect to the planetary gear sets P1, P2. The input shaft 10 is configured as a hollow shaft through which the first output shaft 11 is guided. Reference is otherwise made to the statements relating to FIG. 10.
FIG. 12 shows a further drivetrain 100 with a transmission G in an exemplary embodiment. By contrast to the embodiment as per FIG. 11, the planetary gear sets P1, P2 are arranged not axially adjacent to one another but radially one above the other, that is to say in nested fashion. The transmission G is thus the preferred embodiment from FIG. 3. Reference is otherwise made to the statements relating to FIG. 11 and FIG. 3.
FIG. 13 shows a drivetrain 100 in a further exemplary embodiment. This embodiment is similar to the embodiment as per FIG. 11, wherein, by contrast thereto, the electric machine EM is arranged not coaxially but axially parallel with respect to the transmission G. A connection is realized here via a spur gear stage SRS, which is composed of a first spur gear SR1 and a second spur gear SR2. The first spur gear SR1 is in this case connected rotationally conjointly to the input shaft 10. The spur gear SR1 is then in tooth meshing engagement with the spur gear SR2, which is located rotationally conjointly on an input shaft EW of the electric machine EM, which input shaft, within the electric machine EM, produces the connection to the rotor (not illustrated in any more detail here) of the electric machine EM. Otherwise, the embodiment as per FIG. 13 corresponds to the embodiment as per FIG. 11, such that reference is made to the description given with regard thereto.
FIG. 14 shows the embodiment of the transmission Gas per FIG. 3 in a sectional view. The shaft situated in the center is the output shaft 11. In this drawing, the input shaft 10 coincides with the sun gear of P1, that is to say, in other words, the input shaft 10 is connected to a sun gear of the first planetary gear set P1. The sun gear of the first planetary gear set P1 is in turn in tooth meshing engagement with planet gears of the first planetary gear set P1. The planet gears of the first planetary gear set P1 in turn mesh with the surrounding ring gear of the first planetary gear set P1, wherein the ring gear simultaneously forms the sun gear of the second planetary gear set P2. The sun gear of the second planetary gear set P2 is in turn in tooth meshing engagement with planet gears of the second planetary gear set P2. The planet gears of the second planetary gear set P2 are in turn in tooth meshing engagement with the ring gear, which surrounds the planet gears, of the second planetary gear set P2.
The following FIGS. 15 to 17 show the introduction of force and force support configurations of the transmission according to this invention in relation to the prior art, such as DE 10 2011 079 975 A1. The prior art is compared with the preferred embodiment with two minus planetary transmissions, as have been described inter alia in FIGS. 2 and 3. However, this consideration also applies analogously to the other embodiments.
The following generally applies to FIGS. 15 to 17:
At the first planetary gear set P1, the torque of the input shaft 10 is converted into the output torque for the first output 11. The third element E31 of the first planetary gear set P1 (which is at the same time the first element E12 of the second planetary gear set P2) is driven backward by its reaction moment. The backward movement of the third element E31 is permitted, such that a proportion of the mechanical drive power (preferably 50% in the case of the transverse differential and straight-ahead travel) is conducted through the first planetary set P1 into the second planetary set.
Furthermore, the backward rotation causes the speed ratio with respect to the first output (11) to be increased (static transmission ratio i0=−3 would allow only a speed ratio of i=4 in the case of a fixed ring gear).
In the second planetary set P2, the direction of rotation (backward) introduced at the first element (E12) is, with the aid of a housing support (E22), reversed (forward) into the output movement of the second output (12). Here, the torque introduced into the second planetary set P2 and the torque conducted out to the second output (12) are summed to give the housing support torque. Here, the second planetary set P2 transmits only that proportion of the mechanical power that is conducted to the second output (12) (typically 50%). Only a proportion of the power is applied to the second planetary set P2, such that the overall efficiency is positively influenced.
In the prior art, a torque conversion usually takes place with the aid of a housing support. The reaction moment of the transmission gearing is in this case conducted directly into the housing and does not serve to generate the second output torque. The result is that a transmission must firstly be configured for the sum torque of the two output shafts (generally double the torque). A separate differential transmission is then required to divide this sum torque, which is not required in this form at any location, into two output torques again.
The individual FIGS. 15 to 18 specifically show the following:
FIG. 15 schematically shows the first planetary gear set P1 of the transmission G (right) and a first stage of the spur gear differential from the prior art (left). The introduction of force from the planet gears to the sun gear takes place in parallel via 3 static, that is to say fixed, tooth meshing engagement points. The output to the first output shaft takes place via the sun gear.
By contrast to this, the introduction of force according to the preferred embodiment takes place in parallel via eight moving, that is to say rotating, tooth meshing engagement points. There are four tooth meshing engagement points between sun gear SO1 and four planet gears. Four further tooth meshing engagement points act between a respective planet gear and the ring gear HO1 (not illustrated). The output to the first output shaft 11 takes place via the planet gear carrier PT1. The technical effect lies in the significantly lower tooth forces that act on the first planetary gear set.
FIG. 16 schematically shows the second planetary gear set P2 of the transmission G (right) and a second stage of the stepped planet from the prior art (left). The introduction of force from the planet gears to the sun gear takes place in parallel via 3 static, that is to say fixed, tooth meshing engagement points. The output to the second output shaft takes place via the sun gear.
By contrast to this, the introduction of force into the second planetary gear set P2 according to the preferred embodiment takes place in parallel via 6 moving, that is to say rotating, tooth meshing engagement points. The six tooth meshing engagement points act in each case between one of the six planet gears and the ring gear HO2. The fixed planet carrier PT2, which carries the six planet gears and the sun gear SO2, are not illustrated. The output to the second output shaft 12 takes place via the ring gear HO2. The technical effect lies in the significantly lower tooth forces that act on the second planetary gear set owing to the larger effective diameter and owing to the larger possible number of planets.
FIG. 17 schematically shows the introduction of the supporting torque into the housing. The introduction of force in the case of the stepped planet according to the prior art (left) takes place into a fixed ring gear via 3 parallel tooth meshing engagement points.
The introduction of force according to the preferred embodiment takes place into the fixed planet carrier PT2 via 12 parallel tooth meshing engagement points. Six tooth meshing engagement points act between the sun gear SO2 and the six planet gears of the second planetary gear set. The six other tooth meshing engagement points act between each planet gear of the second planetary gear set and the ring gear HO2. The technical effect lies in the significantly lower tooth forces that act on the second planet carrier PT2.
FIG. 18 shows the principle illustrated in more detail in FIGS. 15 to 17 in a further view. The figure symbolically illustrates the torques in terms of magnitude on their path through the transmission. Directions of rotation are not apparent from this.
The stepped planetary set according to the prior art (left) generates the full output torque, that is to say the sum torque of both wheels, from one input torque Man. The differential divides this high moment into two half wheel moments Man1 and Man2.
The greatest torque in the gear set according to the invention (right) corresponds to the output torque of a single gear. Only the housing support has a high torque factor in accordance with physical principles.
FIG. 19 gives an overview of the calculation rule for the static transmission ratio of the individual embodiments. These each give rise, if transmission losses are neglected, to an output torque of equal magnitude and with the same sign at both output shafts (11, 12). i01 denotes the static transmission ratio of the second planetary gear set P1. i02 denotes the static transmission ratio of the second planetary gear set P2. One of the planetary gear set configurations with corresponding static transmission ratio may be selected depending on the use of the transmission.
FIG. 20 shows a drivetrain 100 of a vehicle having a transmission G with a differential locking unit in a preferred embodiment. The drivetrain 100 is based on the drivetrain known from FIG. 10, wherein, by contrast thereto, no additional planetary transmission P33 is provided in order to increase the rotational speed of the drive machine. The planetary gear sets P1, P2 accordingly constitute the radially stacked arrangement of two minus planetary gear sets, which is likewise known from FIG. 3. This arrangement is particularly highly suitable for the provision of a differential locking unit, because the radially stacked arrangement saves axial installation space, which can be used for the differential locking unit.
The differential locking unit comprises an epicyclic transmission (P3) with at least three connection shafts. The epicyclic transmission P3 is in the form of a third planetary gear set, wherein the third planetary gear set is designed as a minus planetary transmission with multiple elements.
A first connection shaft W1 forms a first element E13 of the third planetary gear set, which in the present case is configured as a sun gear SO3. A second connection shaft W2 forms a third element E33 of the third planetary gear set P3, which in the present case is configured as a ring gear HO3. A third connection shaft W3 forms a second element E23 of the third planetary gear set, which in the present case is configured as a planet carrier PT3.
The sun gear SO3 of the third planetary gear set P3 is connected rotationally conjointly to the connecting shaft 3. The ring gear HO3 of the third planetary gear set P3 is connected rotationally conjointly to an element of the first planetary gear set P1, in the present case configured as a planet carrier PT1. The first planet carrier PT1 is in turn connected rotationally conjointly to the first output shaft 11. The planet carrier PT3 of the third planetary gear set P3 is connectable by means of a shift element designed as a brake B1 to a non-rotatable structural part GG.
In other words, the epicyclic transmission P3 is configured as a 3-shaft transmission, wherein the planet carrier PT3 is fixable to the housing GG by means of the brake B1, the ring gear HO3 is connected rotationally conjointly to the output 11 of the first planetary gear set P1, and the sun gear SO3 is connected rotationally conjointly to the connecting shaft 3, that is to say that shaft 3 which connects the two planetary gear sets P1 and P2 to one another. The connecting shaft 3 is formed by the ring gear HO1 of the first planetary gear set P1 and the sun gear SO2 of the second planetary gear set P2. The locking action is achieved when the brake B1 is actuated, that is to say the third connection shaft W3 is fixed to the housing.
The third planetary gear set P3 and the electric machine EM are arranged coaxially with respect to the two output shafts 11, 12 and the input shaft 10 of the transmission G. As can be clearly seen, the third planetary gear set P3 is arranged axially spaced apart from the radially stacked planetary gear sets P1, P2.
The static transmission ratio may for example be configured as follows:

i0_P1=−3.00

i0_P2=−1.33

i0_P3=−1.33

During straight-ahead travel, the third connection shaft W3 has the rotational speed zero. When the brake B1 is closed, synchronism of the two output shafts is enforced, which results in the locking action.
FIG. 21 shows a drivetrain 100 of a vehicle having a transmission G with a differential locking unit in a further preferred embodiment. By contrast to FIG. 20, the third planetary gear set P3 is designed as a plus planetary gear set, wherein the planet carrier and ring gear connections have been interchanged and the magnitude of the static transmission ratio has been increased by one. A functionally identical transmission is thus realized.
The sun gear SO3 and thus the first connection shaft W1 remain connected to the connecting shaft 3. The second connection shaft W2 is still connected to the output of the first planetary gear set P1, wherein the shaft W2 is now formed by the planet carrier PT3. The third connection shaft W3 can still be fixed by means of the brake B1, wherein the shaft W3 now forms the ring gear HO3.
The locking action is achieved when the ring gear HO3 is fixed to the housing GG. The static transmission ratio may for example be configured as follows:

i0_P1=−3.00

i0_P2=−1.33

i0_P3=+2.33

During straight-ahead travel, the third connection shaft W3 has the rotational speed zero. When the brake B1 is closed, synchronism of the two output shafts is enforced, which results in the locking action.
Otherwise, the embodiment as per FIG. 21 corresponds to the embodiment as per FIG. 20, such that reference is made to the description given with regard thereto.
FIG. 22 shows a drivetrain 100 of a vehicle having a transmission G with a differential locking unit in a preferred embodiment. By contrast to FIG. 20, the third planetary gear set P3 is designed as a plus planetary gear set, wherein the connections of the elements and the required static transmission ratio have been adapted.
The second connection shaft W2 of the third planetary gear set P3 is accordingly configured as a sun gear SO3 and is connected to the output 11. The first connection shaft of the third planetary gear set P3 is configured as a planet carrier PT3 and is connected rotationally conjointly to the connecting shaft 3. The third connection shaft of the third planetary gear set P3 is in the form of a ring gear and is connectable to the housing GG by means of the brake B1. The static transmission ratio may for example be configured as follows:

i0_P1=−3.00

i0_P2=−1.33

i0_P3=+1.75

During straight-ahead travel, the third connection shaft W3 has the rotational speed zero. When the brake B1 is closed, synchronism of the two output shafts is enforced, which results in the locking action.
Otherwise, the embodiment as per FIG. 22 corresponds to the embodiment as per FIG. 21 or 20, such that reference is made to the description given with regard thereto.
FIG. 23 shows a drivetrain 100 of a vehicle having a transmission G with a differential locking unit in a preferred embodiment. By contrast to FIG. 22, the epicyclic transmission is in the present case designed as a stepped planet with multiple sun gear connections. For this purpose, two fixed gears of different sizes and mounted on the planet carrier PT3 are in tooth meshing engagement with a respective sun gear. This thus constitutes a planetary stage with two sun gear connections. A relatively large first fixed gear Z1 meshes with a first sun gear SO3-1. A relatively small second fixed gear Z2 meshes with a second sun gear SO3-2.
The first connection shaft W1 is configured as a planet carrier PT3 and is connected rotationally conjointly to the connecting shaft 3.
The second connection shaft W2 is configured as the first sun gear SO3-1 and is connected rotationally conjointly to the planet carrier PT1 and thus to the output 11. The third connection shaft W3 is now not in the form of the ring gear HO3 but is configured as the second sun gear SO3-2 and is fixable to the housing GG by means of the brake B1.
The static transmission ratio may for example be configured as follows:

i0_P1=−3.00

i0_P2=−1.33

i0_P3=+1.75

During straight-ahead travel, the third connection shaft W3 has the rotational speed zero. When the brake B1 is closed, synchronism of the two output shafts is enforced, which results in the locking action.
Otherwise, the embodiment as per FIG. 23 corresponds to the embodiment as per FIG. 22, such that reference is made to the description given with regard thereto.
FIG. 24 shows a drivetrain 100 of a vehicle having a transmission G with a differential locking unit in a preferred embodiment. By contrast to FIG. 23, the connections of the third planetary gear set are implemented not by means of two sun gears but by means of two ring gears HO3-1 and HO3-2. The smaller of the two fixed gears of the planetary stage is in tooth meshing engagement with the ring gear HO3-1, while the larger of the two fixed gears is in tooth meshing engagement with the ring gear HO3-2. This is also referred to as a planetary stage with two ring gear connections. The first connection shaft of the third planetary gear set P3 is still configured as a planet carrier PT3 and connected rotationally conjointly to the connecting shaft 3.
The second connection shaft W2 of the third planetary gear set P3 is in the form of the ring gear HO3-2 and is connected rotationally conjointly to the planet carrier PT1 and thus to the output 11. The third connection shaft W3 of the third planetary gear set P3 is accordingly configured as a ring gear HO3-1 and is fixable to the housing GG by means of the brake B1. The static transmission ratio may for example be configured as follows:

i0_P1=−3.00

i0_P2=−1.33

i0_P3=1.75

During straight-ahead travel, the third connection shaft W3 has the rotational speed zero. When the brake B1 is closed, synchronism of the two output shafts is enforced, which results in the locking action.
Otherwise, the embodiment as per FIG. 24 corresponds to the embodiment as per FIG. 23, such that reference is made to the description given with regard thereto.
FIG. 25 shows a drivetrain 100 of a vehicle having a transmission G with a differential locking unit in a preferred embodiment. By contrast to FIG. 21, the epicyclic transmission unit P3 is designed as a plus planetary gear set with a stepped planet design.
Here, two fixed gears of different sizes and mounted on the planet carrier PT3 are in tooth meshing engagement with a respective sun gear. This thus constitutes a planetary stage with two sun gear connections. A relatively small first fixed gear meshes with a first sun gear SO3-1. A relatively large second fixed gear meshes with a second sun gear SO3-2.
The second connection shaft W2 of the third planetary gear set P3 is configured as the planet carrier PT3 and is connected to the output 11. The first connection shaft W1 of the third planetary gear set P3 is configured as a sun gear SO3-2 and is connected rotationally conjointly to the connecting shaft 3. The third connection shaft W3 of the third planetary gear set P3 is in the form of sun gear SO3-1 and is fixable to the housing GG by means of the brake B1. The static transmission ratio may for example be configured as follows:

i0_P1=−3.00

i0_P2=−1.33

i0_P3=+2.33

During straight-ahead travel, the third connection shaft W3 has the rotational speed zero. When the brake B1 is closed, synchronism of the two output shafts is enforced, which results in the locking action.
Otherwise, the embodiment as per FIG. 25 corresponds to the embodiment as per FIG. 21, such that reference is made to the description given with regard thereto.
FIG. 26 shows a drivetrain 100 of a vehicle having a transmission G with a differential locking unit in a preferred embodiment. By contrast to FIG. 25, the connection of the third planetary gear set P3 is implemented not by means of sun gears but by means of two ring gears HO3-1 and HO3-2. Here, two fixed gears of different sizes and mounted on the planet carrier PT3 are in tooth meshing engagement with a respective ring gear. This thus constitutes a planetary stage with two ring gear connections. A relatively large first fixed gear meshes with a first ring gear HO3-1. A relatively small second fixed gear meshes with a second ring gear HO3-2.
The second connection shaft of the third planetary gear set P3 is configured as the planet carrier PT3 and is connected to the output 11. The first connection shaft W1 of the third planetary gear set P3 is configured as a ring gear HO3-1 and is connected rotationally conjointly to the connecting shaft 3. The third connection shaft W3 of the third planetary gear set P3 is in the form of ring gear HO3-2 and is fixable to the housing GG by means of the brake B1. The static transmission ratio may for example be configured as follows:

i0_P1=−3.00

i0_P2=−1.33

i0_P3=+2.33

During straight-ahead travel, the third connection shaft W3 has the rotational speed zero. When the brake B1 is closed, synchronism of the two output shafts is enforced, which results in the locking action.
Otherwise, the embodiment as per FIG. 26 corresponds to the embodiment as per FIG. 25, such that reference is made to the description given with regard thereto.
The advantages of the differential locking unit or the transmission G with the differential locking unit according to the embodiments of FIGS. 20 to 26 lie in a compact design and good efficiency. The differential locking unit is of technically low complexity in terms of construction and is thus inexpensive. Furthermore, the potential can be fully exploited by way of the connection of the planetary transmission P3 to the connecting shaft 3.
The potential of the application of force to the connecting shaft 3 lies in the fact that the planetary gear set P3 can be of simpler design owing to the different directions of rotation. If this were to act between two shafts running in synchronism, as in the prior art, the outlay complexity would be greater. Furthermore, in a conventional differential, the left-hand and right-hand side shafts are generally difficult to bind owing to the drive action on the differential cage.
FIGS. 27 and 28 show further preferred variants based on the embodiment according to FIG. 20. In these variants, the second and third planetary gear sets P2, P3 are arranged radially outside the first planetary gear set P1. The third planetary gear set P3 is arranged axially spaced from the second planetary gear set P2. The connections are maintained here. The third connection shaft W3 is fixable to the housing GG by means of the brake B1. The embodiments of FIGS. 27 to 29 are more complex in terms of construction than the embodiments of FIGS. 20 to 26.
The variant according to FIG. 27 shows an axial sequence as follows: second planetary gear set P2, third planetary gear set P3, electric machine EM.
The variant according to FIG. 28 shows an axial sequence in which the two planetary gear sets P2, P3 have been interchanged. The third connection shaft W3 is connectable by means of the brake B1 to the planet carrier PT2, which is permanently fixed to the housing GG, of the second planetary gear set P2.
Based on the embodiment according to FIG. 20, FIG. 29 shows the shift element B1 as a positively locking shift element in the form of a claw-type brake or claw. The design of the brake as a claw is possible in all of the differential locking units described above. The advantage of a claw is that it can be engaged with little actuation energy. This can for example be performed manually. Furthermore, a claw requires little installation space.
It is conceivable for an additional speed ratio to be applied both to the rotational speed of the third connection shaft W3 and/or to that of the input shaft 10, that is to say for the speed ratio imparted by the differential locking unit to be additionally increased. Irrespective of the specific design as a minus planetary gear set, plus planetary gear set or planetary stage, the third connection shaft W3 may have a speed ratio applied thereto by means of a further planetary transmission or by means of a spur gear stage.
Based on the embodiment according to FIG. 20, FIG. 30 shows an application of a speed ratio to the third connection shaft W3 by means of a further transmission VÜ1 in the form of a fourth planetary gear set P4. The fourth planetary gear set P4 has three elements, namely a first element E14, a second element E24 and a third element E34.
The first element E14 is designed as a sun gear SO4. The second element E24 is designed as a planet carrier PT4. The third element is designed as a ring gear HO4.
The ring gear HO4 is permanently fixed. The planet carrier PT4 is connected rotationally conjointly to the third connection shaft W3. The sun gear SO4 is fixable to the housing by means of the brake B1.
By contrast to the embodiment according to FIG. 30, FIG. 31 shows a spur gear stage SRS as a further transmission VÜ1. The spur gear stage SRS comprises a first spur gear SR1 and a second spur gear SR2, wherein the two spur gears are in tooth meshing engagement with one another. The smaller of the two spur gears SR1 is fixable to the housing GG by means of the brake B1. The larger of the two spur gears SR2 is connected rotationally conjointly to the third connection shaft W3.
FIG. 32 shows the embodiment according to FIG. 22 with a fourth planetary gear set P4 for applying a speed ratio to the third connection shaft W3.
The fourth planetary gear set P4 has three elements, namely a first element E14, a second element E24 and a third element E34.
The first element E14 is designed as a sun gear SO4. The second element E24 is designed as a planet carrier PT4. The third element is designed as a ring gear HO4.
The ring gear HO4 is permanently fixed. The planet carrier PT4 is connected rotationally conjointly to the third connection shaft W3. The sun gear SO4 is fixable to the housing by means of the brake B1.
The application of a speed ratio to the third shaft is also possible in the same way in the case of the differential locking unit according to FIG. 21.
FIG. 33 shows the embodiment according to FIG. 23 with a fourth planetary gear set P4 for applying a speed ratio to the third connection shaft W3.
The fourth planetary gear set P4 has three elements, namely a first element E14, a second element E24 and a third element E34.
The first element E14 is designed as a sun gear SO4. The second element E24 is designed as a planet carrier PT4. The third element is designed as a ring gear HO4.
The ring gear HO4 is permanently fixed. The planet carrier PT4 is connected rotationally conjointly to the third connection shaft W3. The sun gear SO4 is fixable to the housing by means of the brake B1.
The application of a speed ratio to the third shaft is also possible in the case of the other differential locking units of stepped-planet design, that is to say in particular in the case of the designs according to FIGS. 25 and 26. The third connection shaft W3 in the embodiment according to FIG. 24 is possible but cumbersome.
FIG. 34 shows, by way of example, the application of a speed ratio to the input shaft 10 based on the embodiment known from FIG. 20. The embodiment comprises a further transmission VÜ2 in the form of a fifth planetary gear set P5. The fifth planetary gear set P5 has three elements, namely a first element E15, a second element E25 and a third element E35.
The first element E15 is designed as a sun gear SO5. The second element E25 is designed as a planet carrier PT5. The third element E35 is designed as a ring gear HO5.
The ring gear HO5 is permanently fixed. The planet carrier PT5 is connected rotationally conjointly to the input shaft 10. The sun gear SO5 is permanently connected to the drive machine. According to this embodiment, the sun gear SO5 is connected to the rotor R of the electric machine EM.
In the illustrated FIGS. 20 to 34, the transmission gearings P4, P5, SRS are illustrated as being integrated into the rotor R. However, it is equally preferred to arrange the elements axially adjacent to one another. Axially parallel arrangements of the electric machines are additionally conceivable. All of the solutions in FIGS. 20 to 34 have in common the fact that the epicyclic transmission P3 engages firstly on the output 11 of the first planetary gear set P1 and secondly on the connecting shaft 3 between the two planetary gear sets P1 and P2.
The invention has been described and explained comprehensively with reference to the drawings and the description. The description and explanation are to be understood as examples and not as being limiting. The invention is not limited to the disclosed embodiments. Other embodiments or variations will become apparent to a person skilled in the art from the use of the present invention and from a close analysis of the drawings, the disclosure and the following claims.
In the patent claims, the words “comprising” and “having” do not exclude the presence of further elements or steps. The indefinite article “a” or “an” does not exclude the presence of a multiplicity. A single element or a single unit may perform the functions of several of the units mentioned in the patent claims. The mere mention of certain measures in several different dependent patent claims should not be understood to mean that a combination of these measures cannot likewise be advantageously used.
REFERENCE DESIGNATIONS


    G Transmission
    GG Non-rotatable structural element, housing
    P1 First planetary gear set
    P2 Second planetary gear set
    P33 Additional planetary gear set
    P3 Third planetary gear set
    P4 Fourth planetary gear set
    P5 Fifth planetary gear set
    E1(x) First element of x-th planetary gear set
    E2(x) Second element of x-th planetary gear set
    E3(x) Third element of x-th planetary gear set
    SO(x) Sun gear of x-th planetary gear set
    PT(x) Planet carrier of x-th planetary gear set
    HO(x) Ring gear of x-th planetary gear set
    E133 First element of the additional planetary transmission P33
    E233 Second element of the additional planetary transmission P33
    E333 Third element of the additional planetary transmission P33
    EM Electric machine
    S Stator
    R Rotor
    EW Input shaft, electric machine
    VÜ1 Further transmission
    VÜ2 Further transmission
    SRS Spur gear stage
    SR1 First spur gear
    SR2 Second spur gear
    SE Shift element
    G1 First shift position, first gear ratio stage
    G2 Second shift position, second gear ratio stage
    N Neutral position
    VM Internal combustion engine
    A Axle of the vehicle, rear
    B Axle of the vehicle, front
    T Transmission, automatic transmission
    3 Shaft, connecting shaft
    10 Input shaft
    11 First output shaft
    12 Second output shaft
    15 Dampers
    20 Wheels
    99 Direction of travel, forward
    100 Drivetrain
    1000 Vehicle

## Claims

1. A transmission with a differential locking unit, the transmission comprising:
an input shaft,
a first output shaft,
a second output shaft,
a first planetary gear set, and
a second planetary gear set connected to the first planetary gear set,
wherein the first and the second planetary gear sets each comprise multiple elements,
the input shaft, the first and the second output shafts, the first and the second planetary gear sets and elements thereof are arranged and are configured such that:
a torque introduced via the input shaft is converted and divided between the first and the second output shafts in a defined ratio, and the generation of a sum torque is prevented,
at least one element of the first planetary gear set is rotationally conjointly connected to another element of the second planetary gear set via a connecting shaft, and
a further element of the second planetary gear set is fixed to a non-rotatable structural element;

the differential locking unit comprising an epicyclic transmission in a form of a planetary gear set or a planetary stage, and a shift element,
the epicyclic transmission has at least three connection shafts,
an at least first connection shaft is rotationally conjointly connected to the connecting shaft,
an at least second connection shaft is rotationally conjointly connected to a second element of the first planetary gear set, and
an at least third connection shaft is fixable to the non-rotatable structural element by the shift element.

2. The transmission according to claim 1, wherein the shift element is designed as one of:
a frictionally engaging brake, or
a positively locking brake.

3. The transmission according to claim 1, wherein at least one further transmission, for increasing a rotational speed of the third connection shaft, is provided between the epicyclic transmission and the shift element.

4. The transmission according to claim 3, wherein the at least one further transmission is one of:
in a form of a planetary gear set, or
in a form of a spur gear stage.

5. The transmission according to claim 1, wherein a further transmission, in a form of a planetary gear set or a countershaft design, is provided for adapting a rotational speed of the input shaf.

6. The transmission according to claim 1, wherein a drive machine, in a form of an internal combustion engine or an electric machine, is provided for driving the input shaft.

7. The transmission according to claim 6, wherein the drive machine is in a form of an electric machine, and the electric machine is arranged coaxially or axially parallel with the input shaft.

8. The transmission according to claim 7, wherein the electric machine is arranged coaxially with the input shaft and the epicyclic transmission is either:
arranged at least partially radially within a rotor of the electric machine, or
arranged so as to be axially spaced apart from the electric machine.

9. The transmission according to claim 1, wherein the first output shaft is guided through the epicyclic transmission.

10. The transmission according to claim 1, wherein the input shaft is guided through the epicyclic transmission.

11. The transmission according to claim 1, wherein the epicyclic transmission is arranged axially adjacent to the first planetary gear set.

12. The transmission according to claim 1, wherein the epicyclic transmission is arranged radially outside the first planetary gear set.

13. A drivetrain having the transmission according to claim 1.

14. A vehicle having the drivetrain according to claim 13.

15. A vehicle having the transmission according to claim 1.