DE102019003004A1 - Transmission for the drive train of an electric or hybrid vehicle, drive train and method for operating such a drive train - Google Patents

Abstract

The present invention relates to a transmission (6) for the drive train (2) of an electric or hybrid vehicle with a first shaft (8), which can be rotationally connected to an electric machine (4), and a second shaft (10) (6) from a first gear (14), in which the first shaft (8) is rotationally connected or rotationally connectable to the second shaft (10) with a first transmission ratio, into a second gear (16) in which the first shaft (8) with a second transmission ratio which is smaller than the first transmission ratio, is rotationally driving-connected to the second shaft (10) or can be rotationally driving-connected. The first shaft (8) is rotationally driven or rotationally connected to the second shaft (10) in the first gear (14) via an overrunning clutch (30) and in the second gear (16) via a frictional coupling (32). The present invention also relates to a drive train (2) with such a transmission (6) and a method for operating such a drive train (2).

Description

The present invention relates to a transmission for the drive train of an electric or hybrid vehicle with a first shaft, which can be rotationally connected to an electric machine, and a second shaft, the transmission having a first gear in which the first shaft has a first gear ratio the second shaft is rotationally connected or rotationally connected, can be shifted into a second gear in which the first shaft is rotationally connected or rotationally connected to the second shaft with a second transmission ratio that is smaller than the first transmission ratio. The present invention also relates to a drive train for an electric or hybrid vehicle with an electric machine and such a transmission. The present invention also relates to a method for operating such a drive train for an electric or hybrid vehicle.

In practice, drive trains for electric or hybrid vehicles are known which have an electric machine, wherein the electric machine can be operated as a motor or generator within the drive train, which is why the electric machine can also be referred to as motor operation or generator operation. The electric machine or its output shaft, especially when the electric machine is arranged in parallel, is usually connected via a transmission to a further shaft which can be arranged, for example, in the torque transmission path of the drive train and, in the case of a hybrid vehicle, is also driven by an internal combustion engine can. Thus, in such a transmission, a first shaft, which can be rotationally connected to the electric machine, and a second shaft are provided, which are rotationally connected to one another via a gear stage. For shifting this gear step, a freewheel is known, for example, which enables the second shaft to be driven by the first shaft via a freewheel clutch, with the electric machine functioning here as a starter being able to be overtaken by the internal combustion engine within the hybrid vehicle after it has been started. Such overrunning clutches are highly efficient, but cannot meet the comfort requirements of modern drive trains. In addition, it is known to connect the output side of the electrical machine to the torque path via a frictional coupling, such as a wet-running multi-plate clutch, which enables particularly smooth switching that also meets high comfort requirements. The efficiency of such switching elements when connecting the electric machine within the drive train is, however, significantly reduced, which is due, for example, to the drag torques in wet-running frictional clutches.

It is therefore an object of the present invention to create a transmission for the drive train of an electric or hybrid vehicle which ensures a compact electric machine, can be adapted particularly flexibly to different driving situations and combines high efficiency with high driving comfort. The present invention is also based on the object of creating a drive train for an electric or hybrid vehicle with such an advantageous transmission. In addition, the present invention is based on the object of specifying an advantageous method for operating such a drive train.

This object is achieved by the features specified in claims 1, 8 and 9, respectively. Advantageous embodiments of the invention are the subject of the dependent claims.

The transmission according to the invention is designed for the drive train of an electric or hybrid vehicle and has a first shaft and a second shaft. The first shaft can be rotationally driven or connected to an electrical machine. In principle, the first shaft of the transmission can also be formed by the output shaft of the electrical machine. The transmission is designed as a two-speed transmission, it being preferred if the transmission has only two gears. Thus, the transmission can be shifted from a first gear in which the first shaft with a first gear ratio to the second shaft is rotationally driven or rotatably connected to a second gear in which the first shaft with a second gear ratio that is smaller than the first gear ratio is, rotatably connected to the second shaft or is rotatably connectable. In the case of the gear ratios mentioned here and below, it was assumed that the first shaft is the driving shaft and the second shaft is the driven shaft. In other words, when specifying the transmission ratios, it is assumed here and below that the electrical machine is operating as a motor, although the electrical machine can also be operated as a generator if the second shaft forms the driving shaft. While the first shaft in the first gear is rotationally driven or rotatably connected to the second shaft via an overrunning clutch, the first shaft in the second gear is rotationally driven or rotatably connected to the second shaft via a frictional coupling, for example a multi-plate clutch. The overrunning clutch can be, for example, a roller freewheel or a clamping body freewheel of the one pawl freewheel act, with an overrunning clutch also being referred to as a so-called overrunning clutch.

The transmission according to the invention for the drive train of an electric or hybrid vehicle has the advantage that, due to the switchable transmission, an electric machine that is as small as possible can be used. In addition, by appropriately shifting the transmission, flexible adaptation to extreme driving maneuvers, such as starting off the curb, accelerating or the like, can be achieved. In particular, the first gear, in which the rotary drive connection is made via an overrunning clutch, can be used for starting, in particular on the curb, and for maximum acceleration, with a particularly high efficiency of the transmission being achieved here. The second gear, on the other hand, can be used for most of the driving time, with a frictional clutch, in particular a wet multi-plate clutch, meeting the high comfort requirements that are placed on the drive train of a motor vehicle.

In a preferred embodiment of the transmission according to the invention, the overrunning clutch has several movable first clamping elements, which are arranged between a first raceway connected in a rotationally fixed manner to the first shaft and a second raceway connected in a rotationally fixed manner to the second shaft. As already indicated above, the overrunning clutch can be, for example, a roller freewheel, a clamping body freewheel or a pawl freewheel. The first race does not necessarily have to be connected directly to the first shaft in a rotationally fixed manner, while the second race also does not have to be directly connected to the second shaft in a rotationally fixed manner, as will be explained in more detail later.

In a further preferred embodiment of the transmission according to the invention, the first clamping elements of the overrunning clutch can be moved from an open position, in which the first raceway can be rotated in a first relative direction of rotation and a second relative rotation direction opposite to the first relative direction of rotation with respect to the second raceway, into a closed position which the first raceway is rotationally coupled to the second raceway in the first relative direction of rotation via the first clamping elements and can be rotated in the second relative rotation direction with respect to the second raceway.

In a further preferred embodiment of the transmission according to the invention, the first clamping elements can be moved or displaced into the open position by rotating the first race ring in the second relative direction of rotation with respect to the second running direction, so that they do not necessarily have to be actuated directly in order to be moved into the open position. rather, the movement or displacement into the open position inevitably occurs when the first raceway is rotated in the second relative direction of rotation with respect to the second raceway.

It can be seen from the preceding description that the aforementioned first clamping elements, in their closed position, only bring about a rotational driving coupling in the first relative direction of rotation between the first race and the second race. However, in order to create a transmission that can be used particularly flexibly and does justice to the different driving situations of a vehicle, the overrunning clutch in a particularly preferred embodiment of the transmission according to the invention also has several movable second clamping elements that are positioned between the first race on the one hand and the second On the other hand, the raceway are arranged, the second clamping elements from an open position in which the first raceway is rotatable in the first relative direction of rotation and the second relative direction of rotation with respect to the second raceway, into a closed position in which the first raceway in the first relative direction of rotation with respect to the the second raceway is rotatable and rotationally coupled to the second raceway in the second relative direction of rotation via the second clamping elements. Thus, by combining the first and second clamping elements, not only a rotational drive coupling of the races is also possible in the opposite relative direction of rotation, rather a simultaneous coupling or blocking can also take place in both opposite relative directions of rotation, whereby, among other things, a recuperation or introduction of a braking torque in first gear is possible by the electric machine. This also has the advantage that a torque-free downshift from first to second gear is also made possible, as a result of which the comfort and functional scope of the drive train with such a transmission is significantly increased.

In an advantageous embodiment of the transmission according to the invention, at least one first clamping element and at least one second clamping element can be moved into the respective closed position in the first and second relative direction of rotation, achieving a rotational drive coupling between the first and the second race.

In a particularly advantageous embodiment of the transmission according to the invention, the overrunning clutch is designed as a switchable overrunning clutch. Accordingly, in this embodiment, corresponding Actuating devices are provided for the targeted switching of the overrunning clutch into the various operating modes without the overrunning clutch reacting exclusively to the differences in speed between the races of the same.

In a further advantageous embodiment of the transmission according to the invention, the first clamping elements and / or the second clamping elements can be locked in the open position or closed position, it being moreover preferred in this embodiment if the first clamping elements and / or the second clamping elements are preloaded in the other position are.

According to a further preferred embodiment of the transmission according to the invention, the transmission is designed as a spur gear in order to ensure a particularly safe and reliable transmission of the torque. The first and the second shaft are also preferably arranged offset parallel to one another.

According to a further preferred embodiment of the transmission according to the invention, the frictional coupling is arranged between a spur gear of the transmission and the first or second shaft. In this embodiment, it is preferred if the spur gear is also rotatably mounted on this first or second shaft, it being possible for this to take place, for example, via a roller bearing.

In a further advantageous embodiment of the transmission according to the invention, the overrunning clutch is arranged between a spur gear of the transmission and the first or second shaft. The said spur gear is preferably also rotatably mounted on this first or second shaft, this in turn preferably taking place via a roller bearing.

Both embodiments described above have the advantage of a particularly compact construction of the transmission. It is preferred if the frictional clutch and the overrunning clutch are arranged between the same shaft and the respective associated spur gear, the same shaft preferably being formed by the first shaft, which can be rotationally connected to the electrical machine or even forms its output shaft.

In order to achieve the above-mentioned demands on comfort and effectiveness to a particularly high degree, the first gear ratio in a further preferred embodiment of the transmission according to the invention is at least 1, the first gear ratio preferably being greater than 1.3, particularly preferably greater than 1.4 , while the second transmission ratio is less than 1, preferably less than 0.9, particularly preferably less than 0.8.

In a further advantageous embodiment of the transmission according to the invention, the frictional clutch is a multi-disc clutch, preferably a wet-running multi-disc clutch. With a wet multi-plate clutch, a lower efficiency than with a form-fit clutch - such as freewheeling - can be achieved due to drag torques that may occur, but such a friction-fit clutch ensures a high level of driving comfort.

In a further preferred embodiment of the transmission according to the invention, the frictional coupling is designed as a normally closed coupling.

The drive train according to the invention for an electric or hybrid vehicle has an electric machine and a transmission of the type according to the invention described above, the first shaft of the transmission being in rotary driving connection with the electric machine. As already explained above, the first shaft can equally be the output shaft of the electrical machine. With regard to the advantages of the drive train according to the invention, reference is made to the advantages of the transmission described above, which apply in a corresponding manner to the drive train.

In a preferred embodiment of the drive train according to the invention, the drive train also has an internal combustion engine, by means of which the second shaft of the transmission can be optionally driven. A drive train for a hybrid vehicle is thus created.

The method according to the invention for operating a drive train of the type according to the invention has the method steps described in more detail below.

First, the first shaft is driven by the electric machine in motor operation, the second shaft being driven by the first shaft in the first gear of the transmission via the overrunning clutch. Thus, the driving takes place here preferably via the first clamping elements of the overrunning clutch in their closed positions. While the first shaft and the second shaft are being driven in first gear, the frictional coupling is initially open. When a driving maneuver, such as starting off at the curb or the initial acceleration, is completed, shifting to second gear takes place by engaging the frictional clutch while overhauling the overrunning clutch, so that by overtaking the first race the second race of the overrunning clutch, the torque is transmitted in second gear via the frictional clutch. A smooth transition from the engaged overrunning clutch and therefore from the first gear to the higher second gear is achieved. The above-mentioned overhaul of the overrunning clutch takes place preferably with movement or displacement of the first clamping elements into the open position, as was already described above with reference to the transmission. In addition, it is preferred in this embodiment if the first clamping elements are locked in the same after their movement or displacement into the opening position in order to prevent unnecessary movement of the first clamping elements when driving in second gear.

In a preferred embodiment of the method according to the invention, after shifting into second gear, downshifting into first gear takes place by opening the frictional clutch and moving the first clamping elements from the open position to the closed position. The first clamping elements are moved from the open position into the closed position by releasing the previously described locking of the first clamping elements in their open position.

In a further preferred embodiment of the method according to the invention, the electric machine is driven in generator mode via the first shaft and the first shaft is driven by the second shaft in the first gear of the transmission via the overrunning clutch while the frictional clutch is open. The first shaft is driven by the second shaft in the first gear of the transmission via the overrunning clutch, preferably via the second clamping elements of the overrunning clutch in their closed position. In the next method step, the second shaft is braked, and this can preferably be done by existing motor vehicle brakes within a motor vehicle. The second gear is then shifted, this being done by releasing the overrunning clutch, preferably by moving the second clamping elements into their open position, the frictional clutch then being closed to complete the shifting process into second gear.

In a further advantageous embodiment of the method according to the invention, a downshift into first gear takes place by braking the second shaft, preferably by braking the vehicle, closing the overrunning clutch, preferably moving the second clamping elements into their closed position, and then opening the frictional clutch.

• 1 eine schematische Darstellung einer Ausführungsform eines Antriebsstrangs für ein Elektro- oder Hybridfahrzeug und
• 1 bis
• 5 eine teilweise Darstellung der schaltbaren Freilaufkupplung aus 1 in verschiedenen Positionen bzw. Schaltstellungen.

The invention is explained below using an exemplary embodiment with reference to the accompanying drawings.

• 1 a schematic representation of an embodiment of a drive train for an electric or hybrid vehicle and
• 1 to
• 5 a partial representation of the switchable overrunning clutch 1 in different positions or switch positions.

1 shows a schematic representation of a drive train 2 for an electric or hybrid vehicle. The drive train 2 has an electrical machine 4th which can be operated as a drive or motor in motor mode and as a generator in generator mode. On the electric machine 4th a transmission follows 6 , which is designed as a spur gear.

The gear 6 has a first wave 8th and one parallel to the first shaft 8th , but not coaxial with this arranged second shaft 10 on. Within a drive train for a hybrid vehicle, the second shaft 10 be rotationally driven for example with an internal combustion engine not shown. The first wave 8th of the transmission 6 is within the drive train 2 with the electric machine 4th connected to the rotation. More precisely, is the first wave 8th with an exit or entrance side 12 the electric machine 4th rotationally driven, the first shaft 8th equally from the exit and entry side 12 the electric machine 4th can be formed.

The transmission can be from a first gear 14th into a second gear 16 shifted and vice versa, with the realization of the operation in first gear 14th a first gear stage made up of two intermeshing gears 18th , 20th and for operation in second gear 16 a second gear stage with meshing gears 22nd , 24 is provided. In the case of the transmission shown here 6 in the form of a spur gear, the gears 18th to 24 can also be called spur gears accordingly. While the two gears 20th , 24 non-rotatably on the second shaft 10 are attached and supported are the two gears 18th , 22nd each rotatable on the first shaft 8th stored, this for example via the roller bearings indicated schematically 26th , 28 can be done.

Despite the rotatable bearing of the gears 18th , 22nd the first and the second gear on the first shaft is a torque transmission between the first shaft 8th and second wave 10 possible via the gear steps, namely by the first wave 8th in first gear via a one-way clutch 30th and in second gear 16 via a frictional coupling 32 with the second wave 10 is rotationally connected or rotationally connected. More precisely, is the switchable friction clutch 32 between the gear 22nd of the transmission 6 and the first wave 8th arranged, while the also switchable overrunning clutch 30th between the gear 18th of the transmission 6 and the first wave 8th is arranged.

Will the gear 18th assumed as the driving gear, so form the gear 18th and the gear 20th a first gear ratio. It is also assumed that the gear 22nd is the driving gear, so form the gear 22nd and the gear 24 a second gear ratio, wherein the second gear ratio is less than the first gear ratio. So is the transmission 6 from the first course 14th in which the first wave 8th with the first gear ratio with the second shaft via the gears 18th , 20th is rotationally driven or rotatable connected, into the second gear 16 switchable in which the first wave 8th with the second gear ratio via the gears 22nd , 24 is rotationally driven or rotatable connected to the second shaft. It has been found to be advantageous here if the first gear ratio is at least 1, the first gear ratio preferably being greater than 1.3, particularly preferably greater than 1.4, so that a gear ratio is achieved slowly. The second gear ratio, however, is advantageously less than 1, so that it is the second gear 16 is a quick translation. It is preferred here if the second transmission ratio is less than 0.9, particularly preferably less than 0.8.

The aforementioned friction clutch 32 is designed as a wet multi-plate clutch. This is how the wet multi-plate clutch 32 one with the first wave 8th Rotation-related first page 34 and one with the gear 22nd Second side connected to rotation 36 on that via a compressible plate pack 38 are rotatably coupled, with the representation of the corresponding actuating device for the disk pack 38 has been omitted for the sake of clarity. The frictional coupling 32 is also designed as a normally closed clutch, so that the disk pack 38 in the embodiment shown with coupling of the two sides 34 , 36 is compressed, provided the frictional coupling 32 is not specifically controlled and opened. The pretensioning in the closed position can be effected, for example, by a spring device not shown in detail.

The detailed and excerpts in the 2 - 5 One-way clutch shown has a first race 40 and a second race 42 on, which are in the circumferential directions 44 , 46 extend with the first race 40 rotatably with the first shaft 8th is connected while the second raceway 42 rotatably with the gear 18th and thus about the gears 18th and 20th rotatably with the second shaft 10 connected is. In the opposite radial directions 48 , 50 are recordings between the two races 40 , 42 formed in which a plurality of movable first clamping elements 52 and a plurality of movable second clamping members 54 are arranged. The clamping elements 52 , 54 the overrunning clutch 30th follow in the circumferential direction 44 , 46 alternately on each other.

The first clamping elements can be of an in 4th shown opening position in which the first race 40 in a first relative direction of rotation 56 and one of the first relative direction of rotation 56 opposite second relative direction of rotation 58 opposite the second race 42 can be rotated into an in 2 , 3 and 5 Shown closed position moved or pivoted, in which the first race 40 in the first relative direction of rotation 56 over the first clamping elements 52 with the second race 42 Coupled with rotation and in the second relative direction of rotation 58 opposite the second race 42 is rotatable. It is preferred here if the first clamping elements 52 by turning the first race 40 in the second relative direction of rotation 58 opposite the second race 42 moved into the open position or displaced, pivoted here. Also the second clamping elements 54 can move from an opening position that is in 2 and 3 shown and in which the first race 40 in the first relative direction of rotation 56 and the second relative direction of rotation 58 opposite the second race 42 is rotatable, moved into a closed position, which in 4th and 5 is shown and in which the first race 40 in the first relative direction of rotation 56 opposite the second race 42 rotatable and in the second relative direction of rotation 58 via the second clamping elements 54 with the second race 42 is rotationally coupled.

Thanks to the combination of first and second clamping elements shown here 52 , 54 are not just two switching positions of the overrunning clutch 30th possible. Rather, at least one first clamping element and at least one second clamping element can be achieved while achieving a rotational driving coupling between the first and second race 40 , 42 in the first and second relative direction of rotation 56 , 58 be moved into the respective closed position, as shown in 5 is shown.

As already indicated, the one-way clutch is 30th as a switchable overrunning clutch 30th formed, with the representation of a corresponding actuating device for actuating the Clamping elements 52 or. 54 was omitted for reasons of clarity. It is also preferred if the first clamping elements 52 or / and the second clamping elements 54 can be locked in the open position or closed position, preferably the open position, so that the mobility or pivotability of the clamping elements 52 or. 54 can be restricted or prevented by locking. It is also preferred if the clamping elements 52 or / and 54 are biased into the other position, this being able to be achieved, for example, by a spring element. Here, too, it is preferred if the first clamping elements and / or the second clamping elements 52 , 54 are biased into the closed position.

Below are other features of the powertrain 2 or the transmission 6 with reference to the 1 - 5 based on a method for operating the drive train 2 explained.

In a first process step, the electrical machine 4th operated as a motor, so that this is via the input or output side 12 the first wave 8th drives. The frictional coupling 32 is open while the second wave 10 through the first wave 8th in first gear 14th via the overrunning clutch 30th or their first clamping elements in the closed position and the gears 18th and 20th is driven. This shift position of the transmission 6 is suitable, for example, when driving off a curb, when the motor vehicle is accelerating rapidly, or the like. The corresponding switching position of the clamping elements 52 , 54 is in 2 shown. This is how the first clamping elements are located 52 in the closed position while the second clamping elements 54 are in the open position.

When you continue driving, you will then go into second gear 16 switched, this by closing the friction clutch 32 he follows. This creates the second wave 10 about the first wave 8th , the frictional clutch 32 , the gear 22nd and the gear 24 driven, so that as a result the overrunning clutch is overtaken. More specifically, the second race ring 42 about the gears 20th and 18th so by the second wave 10 driven that the second race 42 the first race 40 in the first relative direction of rotation 56 obsolete, as a result of which the first clamping elements 52 by the corresponding contour shown in the figures of the first race 40 moved or displaced to the open position as shown in 3 is indicated. As already mentioned above, the first clamping element 52 can then be locked in its open position.

Because the second wave 10 now about the frictional coupling 32 is driven, the transmission meets higher comfort requirements, even if the efficiency, for example due to drag torques occurring in the frictional clutch 32 , is reduced. The transition from first gear 14th into second gear 16 by overhauling the overrunning clutch described above 30th takes place very gently and without jerks. So there is a total of a transmission 6 created, which can be used particularly flexibly in various driving maneuvers and makes a small electrical machine possible due to the switchability.

In addition, it is also possible to shift back from second gear to first gear, this being done by simply opening the friction-locked clutch 32 and moving the first clamping elements 52 from the open position to the closed position 2 can be done. Are the clamping elements 52 locked in the open position and biased into the closed position, the return of the same into the closed position can be done simply by releasing the locking of the first clamping elements 52 respectively.

Even when operating the drive train 2 with the electric machine 4th as a generator has the drive train 2 or the transmission has the advantages described above. So can the electric machine 4th in generator mode via the first shaft 8th driven while driving the first shaft 8th through the second wave 10 in first gear 14th of the transmission via the overrunning clutch 30th he follows. In this case the second are clamping elements 54 pivoted in their closed position, while the first clamping elements 52 can be arranged and locked in the open position, as shown in FIG 4th is shown. The frictional coupling 32 however, is open. To get into second gear 16 Being able to switch becomes the second wave 10 first braked, which can be done, for example, by the motor vehicle brakes, by the first and second race 40 , 42 second clamping elements acted upon by force 54 to be released in the closed position from this clamping position and then the overrunning clutch 14th by moving the second clamping elements 54 open back to their open position, then the frictional clutch 32 is closed to complete the shift to second gear.

Even when the electrical machine is in generator mode 4th can the transmission 6 be shifted back from second gear to first gear, this is also preferably done initially by braking the second shaft, if necessary by the motor vehicle brakes, in order to prevent the race from hitting too hard 40 or. 42 on the second clamping elements 54 to prevent when they are pivoted into the closed position. The synchronization of the speed of the first and second race 40 , 42 by pivoting the first clamping elements 52 are supported in their closed position, as shown in 5 is shown. Is the second wave 10 has been braked in the manner described above, the overrunning clutch 30th by moving the second clamping elements 54 in their closed position 4th closed and the frictional clutch 32 can then be opened.

In the 5 Shown switching position of the overrunning clutch 30th , in which both the first clamping elements 52 as well as the second clamping elements 54 are arranged in their closed position, causes a complete blocking of the two races 40 , 42 to each other in the opposite relative directions of rotation 56 , 58 .

List of reference symbols

2

Powertrain

4th

electric machine

6th

transmission

8th

first wave

10

second wave

12

Output / input side

14th

first course

16

second gear

18th

gear

20th

gear

22nd

gear

24

gear

26th

roller bearing

28

roller bearing

30th

One-way clutch

32

frictional coupling

34

first page

36

second page

38

Disk pack

40

first race

42

second race

44

Circumferential direction

46

Circumferential direction

48

radial direction

50

radial direction

52

first clamping elements

54

second clamping elements

56

first relative direction of rotation

58

second relative direction of rotation

Claims (10)

Transmission (6) for the drive train (2) of an electric or hybrid vehicle with a first shaft (8), which can be rotationally connected to an electric machine (4), and a second shaft (10), the transmission (6) being driven by a first gear (14), in which the first shaft (8) with a first gear ratio with the second shaft (10) is rotationally driven or rotatable, can be shifted into a second gear (16) in which the first shaft (8) with a second gear ratio, which is smaller than the first gear ratio, is rotationally driven or rotationally driven connected to the second shaft (10), characterized in that the first shaft (8) in the first gear (14) via an overrunning clutch (30) and in the second gear (16) is rotationally driven or rotatably connected to the second shaft (10) via a frictional coupling (32). Gear (6) Claim 1 , characterized in that the overrunning clutch (30) has a plurality of movable first clamping elements (52) between a first race (40) connected non-rotatably to the first shaft (8) and a second race connected non-rotatably to the second shaft (10) (42) are arranged on the other hand, the first clamping elements (52) preferably from an open position in which the first race (40) in a first relative direction of rotation (56) and a second relative direction of rotation (58) opposite to the first relative direction of rotation (56) second race (42) is rotatable into a Closing position can be moved in which the first race (40) is rotationally coupled to the second race (42) in the first relative direction of rotation (56) via the first clamping elements (52) and can be rotated in the second relative direction (58) with respect to the second race (42) is, wherein the first clamping elements (52) are particularly preferably movable or displaced into the open position by rotating the first race (40) in the second relative direction of rotation (58) with respect to the second race (42). Gear (6) Claim 2 , characterized in that the overrunning clutch (30) has several movable second clamping elements (54) which are arranged between the first race (40) on the one hand and the second race (42) on the other hand, the second clamping elements (54) from an open position, in which the first race (40) can be rotated in the first relative direction of rotation (56) and the second relative direction of rotation (58) with respect to the second race (42), can be moved into a closed position in which the first race (40) in the first relative direction of rotation (56) rotatable with respect to the second race (42) and rotatably coupled in the second relative direction of rotation (58) via the second clamping elements (54) to the second race (42), preferably at least one first clamping element (52) and at least one second clamping element (54) while achieving a rotational driving coupling between the first and second race (40, 42) in the first and second relative direction of rotation (56, 58) in di e respective closed position are movable. Gearbox (6) according to one of the preceding claims, characterized in that the overrunning clutch (30) is designed as a switchable overrunning clutch (30), the first clamping elements (52) and / or second clamping elements (54) preferably being lockable in the open position or closed position and are particularly preferably biased into the other position. Gear (6) according to one of the preceding claims, characterized in that the gear (6) is designed as a spur gear, the frictional coupling (32) preferably between a spur gear of the gear (6) and the first or second shaft (8; 10 ) is arranged, on which the spur gear (22) is particularly preferably rotatably mounted, possibly via a roller bearing (28), and / or the overrunning clutch (30) preferably between a spur gear (18) of the transmission (6) and the first or second Shaft (8; 10) is arranged, on which the spur gear (18) is particularly preferably rotatably mounted, optionally via a roller bearing (26). Transmission (6) according to one of the preceding claims, characterized in that the first gear ratio is at least 1, preferably greater than 1.3, particularly preferably greater than 1.4, while the second gear ratio is less than 1, preferably less than 0.9, particularly preferably less than 0.8. Transmission (6) according to one of the preceding claims, characterized in that the frictional coupling (32) is a multi-disc clutch, preferably a wet-running multi-disc clutch, and / or a normally closed clutch. Drive train (2) for an electric or hybrid vehicle with an electric machine (4) and a transmission (6) according to one of the preceding claims, the first shaft of which is in rotary drive connection with the electric machine (4), an internal combustion engine preferably also being provided , by means of which the second shaft (10) can be optionally driven. Method for operating a drive train (2) according to Claim 8 with the process steps of driving the first shaft (8) by the electric machine (4) in motor operation and driving the second shaft (10) by the first shaft (8) in the first gear (14) of the transmission (6) via the overrunning clutch (30 ), preferably via the first clamping elements (52) in the closed position while the frictional clutch (32) is open, and switching to second gear (16) by closing the frictional clutch (32) while overhauling the overrunning clutch (30), preferably moving or displacing the first clamping elements (52) into the open position and particularly preferably locking the first clamping elements (52) in the open position and particularly preferably shifting down to first gear (14) by opening the frictional coupling (32) and moving the first clamping elements (52) from the open position to the closed position, preferably by releasing the locking of the first clamping elements (52) in the open position. Method for operating a drive train (2) according to Claim 8 with the process steps of driving the electric machine (4) in generator mode via the first shaft (8) and driving the first shaft (8) by the second shaft (10) in the first gear (14) of the transmission via the overrunning clutch (30), preferably Via the second clamping elements (54) in the closed position while the frictional clutch (32) is open, braking the second shaft (10), preferably by braking the motor vehicle, shifting into second gear (16) by releasing the overrunning clutch (30), preferably Moving the second clamping elements (54) into their open position, and then closing the frictional clutch (32), particularly preferably downshifting to first gear (14) by braking the second shaft (10), preferably by braking the vehicle, closing the overrunning clutch (30) , preferably moving the second clamping elements (54) into their closed position, and then opening the frictional coupling (32).

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