EP3017212A1 - Twin-clutch transmission - Google Patents

Abstract

The invention relates to a twin-clutch transmission (14), comprising a twin-clutch assembly (16), which has a first and a second friction clutch (18, 20); a transmission assembly (22), which has a first and a second input shaft (30, 32) and a first and a second countershaft (34, 36); wherein the first friction clutch (18) is connected to the first input shaft (30) and the second friction clutch (20) is connected to the second input shaft (32), wherein the transmission assembly (22) has a plurality of gear sets for establishing gear stages (1-7, R), wherein a first gear set comprises a fixed gear (42; 46) on the first input shaft (30) and a free gear (44; 50) on the second countershaft (36), wherein a second gear set comprises a fixed gear (54) on the second input shaft (32) and a free gear (58) on the second countershaft (36), and wherein the transmission assembly (22) has an output gear set (70), which comprises a first output gear (72) rigidly connected to the first countershaft (34), and a second output gear (74), which is associated with the second countershaft (36), wherein the first and the second output gear (72, 74) mesh with a third output gear (76). The second output gear (74) is fixed on an output shaft (104), which is coaxial to the second countershaft (36) and is rotatably supported in relation to the second countershaft (36), wherein the output shaft (104) can be coupled to the second countershaft (36) by means of a coupling device (106) or can be decoupled from the second countershaft, in such a way that at least one winding path gear stage (WC, WO) can be established by means of the first and the second gear set while the coupling device (106) is open.

Description

 Double clutch

The present invention relates to a dual-clutch transmission having a dual clutch assembly having a first and a second friction clutch, with a transmission assembly having a first and a second input shaft and a first and a second countershaft, wherein the first friction clutch with the first input shaft and the second friction clutch is connected to the second input shaft, wherein the transmission assembly comprises a plurality of gear sets for establishing gear ratios, wherein a first gearset has a fixed gear on the first input shaft and a loose gear on the second countershaft, wherein a second gearset drives a fixed gear the second input shaft and a loose wheel on the second countershaft, and wherein the gear assembly comprises a driven gear, having a fixedly connected to the first countershaft first output gear and a second output gear, which is associated with the second countershaft, wherein the first and second output gears are engaged with a third output gear. Such a dual-clutch transmission is known for example from the document EP 1 815 162 B1.

In dual-clutch transmissions, the forward gears are generally divided into two partial transmissions. In this case, odd steps are generally associated with a sub-transmission, and even gear ratios are assigned to the other sub-transmission. Each partial transmission is connected by its own clutch to an output shaft of a drive motor. With such a dual-clutch transmission gear changes can be performed without interruption of traction by overlapping actuation of the two clutches.

In longitudinal design double clutch transmissions generally have a single countershaft, wherein an input shaft of the transmission and an output shaft are aligned coaxially with each other. Here, the axial construction is relatively long. In particular, for the front-transverse installation in motor vehicles, it is known to provide two countershafts in the gear assembly. It is known from the document EP 1 815 162 B1 mentioned at the beginning to set up a reverse gear stage by using both countershafts, so that a separate direction of rotation reversal shaft is not necessary. The gearbox shown there can therefore be realized with exactly three shaft axes. Furthermore, it is known from the document to use at least one, preferably a plurality of fixed wheels, which are connected to one of the input shafts, double use. A fixed gear is engaged both with a loose wheel on the first countershaft and with a loose wheel on the second countershaft, so that this fixed wheel is associated with two gear ratios. This also makes the axial design can be shortened.

From the document EP 1 815 162 B1 it is also known to realize a dual-clutch transmission with seven forward gears, so that a relatively large spread is feasible.

It is generally conceivable to set up at least one Windungsgangstufe to increase the spread. While at conventional grades of Power flow is generally passed from an input shaft to one of the countershafts, from where the power is then passed to an output, Windungsgangstufen generally include a power flow, which uses both countershafts in the aforementioned layout. In a Windungsgangstufe also generally at least two clutches are closed, whereas the insertion of a normal gear by closing only a single clutch is possible.

Examples of dual-clutch transmissions with the realization of Windungsgängen are known from the documents DE 10 2009 002 358 A1 and WO 2009/050078 A2. From the document DE 10 2009 002 358 A1 it is known to arrange on one of the countershafts a idler gear, which serves as a driven gear of a driven gear. As a result, at least one load-shiftable Windungsgang should be feasible if a coupling device associated with this idler gear is open.

Further, in these documents, in addition to the two countershafts, there is generally provided another shaft for rotatably supporting a reversing direction reversing gear for a reverse gear stage.

From the document EP 2 128 487 B1 another dual-clutch transmission is known, in which also a separate shaft is provided for reversing the direction of rotation to establish a reverse gear. It is also disclosed in this document to connect two primary waves by reducing the speed of the second primary shaft relative to the first primary shaft with each other, to form a sixth gear ratio, an additional translation is provided, the second primary shaft by two gears forming a gear directly with a Secondary shaft can be connected.

Against this background, it is an object of the invention to provide an improved dual-clutch transmission, which in particular has a large spread and preferably compact builds.

[0010] In the case of the dual-clutch transmission mentioned at the outset, this object is achieved in that the second driven gearwheel is fixed to an output shaft. is set, which is aligned coaxially with the second countershaft and rotatably supported relative to the second countershaft, wherein the output shaft with the second countershaft via a coupling device can be coupled or decoupled, such that at least over the first and the second set of wheels when the coupling device is open a Windungsgangstufe is set up.

With the dual-clutch transmission according to the invention, in addition to the primary gear ratios (for example, seven primary forward gear ratios) one or two or even more Windungsgangstufen be established. Preferably, a Windungsgangstufe is designed as a "crawler" -speed, with a translation that is shorter than the translation of the primary forward gear 1. Further, a Windungsgangstufe preferably be designed as an "overdrive" gear, with a translation that is greater than the translation of the highest primary forward gear. Overall, so the spread can be significantly increased. Furthermore, even more Windungsgangstufen can be set up between the individual primary gear ratios, if desired.

The dual-clutch transmission has two coaxial input shafts and two countershafts. Preferably, the means of a reverse gear stage, by a wheel of a countershaft is directly engaged with a wheel of the other countershaft. As a result, the dual-clutch transmission can be realized with exactly three shaft axes. A separate shaft or axle for supporting a direction of rotation reversing wheel is not required here.

A clutch for the reverse gear is preferably located on the second countershaft. Furthermore, it is preferable if the reverse gear and the first "primary" forward gear are on different partial transmissions.

Furthermore, it is generally advantageous if the lowest and the highest primary forward gear are on the same sub-transmission, in particular on a first partial transmission, which sets up the odd gear ratios. The coupling device can be realized as a dog clutch or as a synchronized clutch.

[0016] A transition from the "crawler" forward gear to the first "primary" forward gear can be done under load, ie with overlapping actuation of the two friction clutches. The same applies to the transition from the "overdrive" power stage to the highest "primary" gear stage.

The gear arrangement preferably has seven primary forward gear stages. A "crawler" speed step is preferably established by simultaneous switching of the idler gears of the forward gears 4, 5 and 1 and by closing the second friction clutch. The coupling device is opened here. The "overdrive" Windungsgangstufe is preferably realized by simultaneous switching of the primary forward gear stages 4, 3 and 7 and by closing the second friction clutch, wherein the coupling device is also open.

The dual-clutch transmission according to the invention makes it possible, starting from a wheelset for example, seven gears, the setting up of eight or nine forward gears. It is a large spread possible, which may for example be greater than 9. The realization of Windungsgangstufen can be done without affecting the basic functions of the dual clutch transmission. In other words, the primary gear stages are used in the same way as in a transmission which is constructed as shown by way of example in the document EP 1 815 162 B1. In addition, its disclosure content is fully referenced. Thus, high efficiency can be maintained in the primary gear stages. The double use of a fixed wheel is preferably at least twice possible, in particular for the forward gears 5 and 7 and for the forward gears 4 and 6.

If the forward gear 1 and the reverse gear are arranged on different partial transmissions of the dual-clutch transmission, a free-swing function after a collision of a motor vehicle is possible. An actuator assembly for clutches of the dual clutch transmission can be implemented hydraulically or electromechanically, or electromagnetically. In an electromechanical implementation, preferably two shift rollers are used, one of which switches the gear stages of one subtransmission and the other the gear stages of the other subtransmission.

It is preferred if the coupling device is also connected by means of one of the two shift rollers, preferably with that shift drum, which sets up the odd gear ratios. This would be particularly advantageous in terms of reliability, since when switching from an odd "lowest" primary "forward speed or an odd" primary "forward speed in one Windungsgangstufe can be ensured by turning the shift drum, that the coupling device is opened before the Torque is completely transferred to the Windungsgangstufe. As a result, a blockade of the wheelset can be prevented.

Overall, a dual clutch transmission can be created, which can constructively based on an existing wheelset build two additional gears, with no additional gears are necessary, only one-sided coupling device, in particular a synchronization.

The provision of the output shaft may also have advantages in the arrangement of a parking lock gear.

The object is thus completely solved.

According to a preferred embodiment, the second countershaft is formed at least adjacent to the driven gear as a hollow shaft.

As a result, the storage of the output shaft with respect to the countershaft can be simplified. In one embodiment, the output shaft may have a hollow shaft section into which the second countershaft extends.

As a result, a storage with a large diameter can be realized for the storage of the output shaft.

In an alternative variant, the output shaft may extend into the countershaft.

In this way, a radially more compact design can be achieved.

In a particularly preferred embodiment, the second countershaft is formed axially continuously as a hollow shaft.

In this way, in particular the supply of fluid to bearings, wheelsets, etc. can be simplified.

It is preferred if the output shaft extends through the second countershaft and is connected at its opposite end of the coupling device with a Parksperrenrad.

The coupling device is preferably arranged at the same axial end of the countershaft as the second output gear, but may also be formed at the opposite end.

A parking brake wheel of a parking brake assembly may for example be connected to the first countershaft, or with a member of a subsequent differential.

Of particular preference, it is when the output shaft is fixedly connected to a Parksperrenrad. As a result, the parking brake wheel can be spatially integrated in a favorable manner in the dual-clutch transmission.

Further, the parking lock gear may be disposed axially adjacent to the second output gear. This measure also contributes to an axially compact design.

According to a further preferred embodiment, the parking lock gear is arranged on the side facing away from the second countershaft side of the second output gear. In this case, the parking lock gear can be arranged directly adjacent to the second driven gear. Alternatively, it is possible to provide a bearing for supporting the output shaft between the parking brake wheel and the second output gear. In this case, the parking lock gear could thus be stored "flying". This "flying" storage of the parking lock wheel allows the simple attachment of a special housing cover or bearing cap, which is already equipped or pre-assembled with other components of a parking brake mechanism.

If such a bearing is arranged on the side facing away from the second countershaft side of the output gear, the parking brake can be arranged wheel between the output gear and this bearing. Arranging the parking lock gear between the bearing and the second output gear has the advantage of simpler static storage.

In an alternative embodiment, the parking lock gear is arranged on the second countershaft facing side of the second driven gear.

In general, it is possible to store the second countershaft and the output shaft independently of each other. Of particular preference, however, it is when the second countershaft and the output shaft are connected to each other via a pivot bearing. By this measure, at least one pivot bearing can be saved. The rotary bearing is preferably between an inner periphery of a hollow shaft arranged portion of the output shaft and an outer circumference of the second countershaft.

According to a further overall preferred embodiment, the output shaft is mounted on at least one shaft bearing on a housing of the dual clutch transmission.

This shaft bearing is preferably arranged axially adjacent to the second output gear in order to absorb the radial and / or axial forces occurring there well.

Furthermore, it is generally advantageous if the output gear is arranged in the region of one end of the second countershaft, which faces the first and the second friction clutch.

This also allows an axially compact design can be realized.

As mentioned above, the coupling device can be realized by a claw or a synchronous clutch. In a preferred variant, the coupling device on a guide sleeve which is fixedly connected to the output shaft and to which a sliding sleeve is axially displaceable, wherein the second countershaft is fixedly connected to a coupling body, wherein the sliding sleeve releases the coupling body in an axial position and in a second axial position produces a positive connection with the coupling body.

It is understood that the features mentioned above and those yet to be explained not only in the particular combination given, but also in other combinations or alone, without departing from the scope of the present invention.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. Show it: Fig. 1 is a schematic longitudinal sectional view through an embodiment of a drive train with a dual-clutch transmission according to the invention;

FIG. 2 shows a detailed view of a dual-clutch transmission of the type according to the invention in accordance with a further embodiment; FIG.

3 is a detailed view of a dual-clutch transmission of the type according to the invention according to a further embodiment;

4 shows a detailed view of a dual-clutch transmission of the type according to the invention in accordance with a further embodiment;

5 is a detailed view of a dual-clutch transmission of the type according to the invention according to a further embodiment; and

Fig. 6 is a schematic representation of an actuator assembly for a dual-clutch transmission according to the invention.

Fig. 1 shows in schematic form a drive train 10 for a motor vehicle. The powertrain 10 includes a drive motor 12 such as an internal combustion engine and a dual clutch transmission 14. The dual clutch transmission 14 includes a dual clutch assembly 16 having a first friction clutch 18 and a second friction clutch 20. Input members of the two friction clutches 18, 20 are connected to a drive shaft of the drive motor 12.

Further, the dual-clutch transmission 14 has a gear assembly 22 which is connected to the friction clutches 18 and 20. An output of the gear assembly 22 is coupled to a differential 24 by means of which drive power is distributed to driven wheels 26L, 26R. The gear arrangement 22 has a first input shaft 30 and a concentrically arranged second input shaft 32 in the form of a hollow shaft. The first input shaft 30 is connected to an output member of the first friction clutch 18. The second input shaft 32 is connected to an output member of the second friction clutch 20.

Furthermore, the gear assembly 22 includes a first countershaft 34 and a second countershaft 36.

The gear assembly comprises a plurality of gear sets for establishing gear stages, including primary forward gears 1 to 7 and a reverse gear R.

To set up the forward gear 1, a wheelset with a fixed gear 38 and a loose wheel 40 is provided. The fixed gear 38 is connected to the first input shaft 30. The idler gear 40 is rotatably mounted on the first countershaft 34. A wheel set for setting up the forward gear stage 3 includes a fixed gear 42 connected to the first input shaft 30 and a idler gear 44 rotatably mounted on the second countershaft 36.

To set up forward gears 5 and 7, a wheelset is provided, which is connected to the first input shaft 30 fixed gear 46 and a rotatably mounted on the first countershaft 34 idler gear 48 for the gear 7 and a rotatably mounted on the second countershaft 36 idler gear 50 for the forward gear stage 5 has.

The wheelsets to set up the forward gears 1, 3, 5, 7 form a first partial transmission 52 of the transmission assembly 22nd

To set up the forward gears 4 and 6, a wheelset is provided, which is connected to the second input shaft 32 fixed gear 54 and a rotatably mounted on the first countershaft 34 idler gear 56 for the forward gear stage. 6 and a rotatably mounted on the second countershaft 36 idler gear 58 for the forward gear stage 4 has. To set up the Vorwartsgangstufe 2, a wheelset is provided which has a fixed to the second input shaft 32 fixed gear 60 and a rotatably mounted on the first countershaft 34 idler gear 62.

To set up the reverse gear an idler 64 is rigidly connected to the idler gear 62, wherein the idler 64 is directly engaged with a idler gear 66 which is rotatably mounted on the second countershaft 36.

The wheelsets for establishing the forward gear stages 2, 4, 6, R form a second partial transmission 68 of the gear assembly 22nd

The transmission assembly 22 further includes an output gearset 70. The output gearset 70 includes a first output gear 72 rigidly connected to the first countershaft 34. Further, the output gearset 70 has a second output gear 74 associated with the second countershaft 36. The first output gear 72 and the second output gear 74 are engaged with a third output gear 76, which is shown schematically in FIG. 1 radially outwardly of the output gears 72, 74, for clarity. The third output gear 76 is preferably connected to an input member of the differential 24.

The transmission assembly 22 includes a first clutch pack 78 having a first clutch 80 for engaging the forward gear 1 and a second clutch 82 for engaging the forward gear 7. Further, the gear assembly 22 has a second clutch pack 84 with a clutch 86 for engaging the forward gear stage 3rd and a clutch 88 for engaging the forward gear stage 5. The transmission assembly 22 further includes a third clutch pack 90 with a clutch 92 for engaging the forward gear 6 and a clutch 94 for engaging the forward gear stage 2. Finally, the transmission assembly 22, a fourth clutch pack 96, which has a clutch 98 for engaging the forward gear 4 and a Clutch 100 for engaging the reverse gear R has. In the axial direction of the first countershaft 34, the idler gear 40, the clutch pack 78, the idler gear 48, the idler gear 56, the clutch pack 90 and the idler gear 62 with the idler 64, and finally the first output gear 72 is arranged, namely seen from one of the dual clutch assembly 16 opposite axial end of the gear assembly 22 from.

In the same direction, the idler gear 44, the clutch pack 84, the idler gear 50, the idler gear 58, the clutch pack 96 and the idler gear 66 are arranged on the second countershaft 36.

The gear assembly 22 further includes an output shaft 104 which is coaxially aligned with the second countershaft 36 and rotatably supported relative thereto. The output shaft 104 is coupled by means of a coupling device 106 with the second countershaft 36, that is preferably positively connected, or decoupled therefrom, so that the countershaft 36 can rotate without taking the output shaft 104.

The coupling device 106 may be designed in the manner of a claw or synchronous clutch, wherein a guide sleeve 108 is fixed to the output shaft 104. On the guide sleeve 108, a sliding sleeve 109 is mounted axially displaceable. The countershaft 36 is connected to a coupling body 1 10, wherein the sliding sleeve releases the coupling body 1 10 in an axial position (as shown) and in a second axial position a positive connection with the

Coupling body 1 10 produces.

When using the primary gear ratios 1 -7, R of the dual-clutch transmission 14 described above, the coupling device 106 is generally closed, so that the output shaft 104 is connected to the second countershaft 36. In this mode, load circuits between successive stages can be performed in a conventional manner by a gear stage is selected in a passive sub-transmission and the friction clutches 18, 20 are operated overlapping. Due to the decoupling of the countershaft 36 of the output shaft 104, it is also possible to establish Windungsgangstufen. These are designated in Fig. 1 with W. Thus, for example, a "crawler" -Windungsgangstufe WC set by the coupling device 106 is opened and by the clutch 98 for the forward gear 4, the clutch 88 for the forward gear 5 and the clutch 80 for the forward gear 1 are closed. In this case, the power flows from the second friction clutch 20 via the second input shaft 32, the fixed gear 54, the idler gear 58, the second countershaft 36, the idler gear 50, the fixed gear 46, the first input shaft 30, the fixed gear 38 and the idler gear 40 toward the first countershaft 34, from where, with a ratio smaller than the forward gear stage 1, drive power is applied via the first output gear 72 to the output.

Similarly, an "overdrive" Winstungsgangstufe can be set up in which the clutches 98, 86, 82 are closed. As a result, power flows from the second friction clutch 20 and the second input shaft 32 via the fixed gear 54, the idler gear 58, the second countershaft 36, the idler gear 44, the fixed gear 42, the first input shaft 30, the fixed gear 46 and the idler gear 48 toward the first countershaft 34, and from there via the first output gear 72 to the output, with a translation that is greater than that of the forward gear stage 7th

Consequently, with the crawler winding gear stage and the overdrive forward gear stage, it is possible to set up nine forward gear stages, with a total spread of preferably greater than 8.5, in particular greater than 9.0.

In general, it is also conceivable to realize further Windungsgangstufen in this embodiment, for example, a further reverse gear or intermediate gear stages between the gear stages 1 to 7.

On the output shaft 104, a parking lock gear 1 12 is further defined, which is part of a parking brake assembly for immobilizing a motor vehicle. In the illustration of Fig. 1, the parking lock gear 1 12 is axially adjacent to the second Output gear 74, wherein between (or axially adjacent) a shaft bearing can be arranged.

The countershaft 36 is presently shown as a hollow shaft, but can also be realized as a solid shaft. Between the countershaft 36 and the output shaft 104, a rotary bearing is preferably arranged, which is not shown in Fig. 1.

Variants of the drive train 10 of FIG. 1 are shown in FIGS. 2 to 5, which generally correspond to the drive train 10 of FIG. 1 in terms of structure and mode of operation. The same elements are therefore identified by the same reference numerals. The following section essentially explains the differences.

2 shows a section of a gear arrangement 22 ', with the second countershaft 36, to which the coupling body 1 10 is fixed. It is shown in Fig. 2 that the output shaft 104 has a hollow shaft portion 1 14 which engages around an end portion of the second countershaft 36. The second countershaft 36 and the output shaft 104 are mounted relative to each other via a pivot bearing 1 16 as a needle bearing or ball bearings together.

Further, it is shown in Fig. 2 that the output shaft 104 is rotatably supported by means of a shaft pivot bearing 1 18 with respect to a housing 120 of the gear assembly 22 '. The second output gear 74 is preferably disposed between the shaft journal 1 18 and the portion of the output shaft 104 which is rotatably supported with respect to the second countershaft 36. This measure is also preferred in all other embodiments.

In Fig. 2 it is shown that the parking lock gear 1 12 may be arranged instead of an arrangement between the second output gear 74 and the shaft bearing 1 18 between the second driven gear 74 and the coupling device 106, as shown at 1 12 ' , Furthermore, it is shown in Fig. 2 that the parking lock gear on the output gear 74 opposite axial side of the Shaft pivot bearing 1 18 may be arranged, as shown at 1 12 "in the manner of a flying bearing .. The parking lock gear 1 12" is thus on the output gear 74 opposite side of the bearing 1 18th

In the variant of Fig. 3, an end portion of the output shaft 104 '' is formed as a solid shaft portion which is inserted into the second countershaft 36 designed as a hollow shaft, wherein between a pivot bearing 1 16 "'is arranged. Further, it is shown that the parking lock gear 1 12 may be disposed on axially both sides of the second output gear 74, as shown at 1 12 'and 1 12 "'.

In the gear assembly 22 ^IV of FIG. 4, the output shaft 104 extends ^IV in the axial direction through the second countershaft 36 designed as a hollow shaft. The coupling device 106 can be arranged on the output gear 74 opposite end of the output shaft 104 ^IV (as indicated at 106A)

However, in FIG. 4, as in the previous embodiments, it is arranged on the axially same side. In the embodiment of FIG. 4, however, a parking lock gear 1 12 ^IV is fixedly connected to the output shaft 104 ^IV at the axially opposite end of the gear arrangement 22, ie adjacent to the idler gear 44 for the forward gear stage 3.

In the gear arrangement 22 ^v of FIG. 5, a driven gear 74 ^{v is} rotatably mounted as a loose wheel on a second countershaft 36 ^v , which is shown in this embodiment as a solid shaft, but may also be formed as a hollow shaft. In this variant, a coupling device 106 ^{V is} disposed on the second countershaft 36, with a guide sleeve 108 ^v and a sliding sleeve 109 ^v movable thereon, which are arranged between the output gear 74 ^v and the idler gear 66 for the reverse gear.

Fig. 6 shows in schematic form an actuator assembly 124 for the dual-clutch transmission illustrated above. The actuator assembly 124 includes a first shift drum 126, on which a shift groove 128 is formed, by means of which the clutch packs 90, 96 of the second sub-transmission are operated. The first shift drum 126 is driven by a first electric motor 130.

The actuator assembly 124 further includes a second shift drum 132 having two or, as shown, three shift grooves 134, 136, 138 herein. The shift groove 134 is associated with the clutch pack 80, the shift groove 136 is associated with the clutch pack 84. The switching grooves 134, 136 may also be integrated in a shift groove. The switching groove 138 is assigned to the coupling device 106. The second shift drum 132 is driven by a second electric motor 140. The motors 130, 140 are preferably independently controllable electric motors.

Claims

A dual clutch transmission (14) having a dual clutch assembly (16) having first and second friction clutches (18, 20), a transmission assembly (22) having first and second input shafts (30, 32) and first and second Countershaft (34, 36), wherein the first friction clutch (18) with the first input shaft (30) and the second friction clutch (20) with the second input shaft (32) is connected, wherein the gear assembly (22) a plurality of wheelsets for A gear set (1 -7, R), wherein a first gear set has a fixed gear (42, 46) on the first input shaft (30) and a loose wheel (44, 50) on the second countershaft (36), wherein a second A fixed gear (54) on the second input shaft (32) and a loose wheel (58) on the second countershaft (36), and wherein the gear assembly (22) has a driven gear (70) having a with the first countershaft (34 ) firmly connected first abbot driving gear (72) and a second driven gear (74) associated with the second countershaft (36), wherein the first and the second driven gear (72, 74) with a third output gear (76) are engaged, characterized in that the second output gear (74) is fixed to an output shaft (104) coaxially aligned with the second countershaft (36) and rotatably supported relative to the second countershaft (36), and wherein the output shaft (104) is connected to the output shaft second countershaft (36) via a coupling device (106) can be coupled or decoupled therefrom, such that at least one Windungsgangstufe (WC, WO) can be set via the first and the second wheelset with open coupling device (106). 2. dual-clutch transmission according to claim 1, characterized in that the second countershaft (36) at least adjacent to the driven gear (70) is designed as a hollow shaft. 3. dual-clutch transmission according to claim 1 or 2, characterized in that the output shaft (104) has a hollow shaft portion (1 14), in which the second countershaft (36) extends into it. 4. Dual-clutch transmission according to claim 2, characterized in that the output shaft (104 "', 104 ^IV ) extends into the countershaft (36) into it. 5. dual-clutch transmission according to one of claims 2-4, characterized in that the second countershaft (36) is formed axially continuous as a hollow shaft. 6. dual-clutch transmission according to claim 5, characterized in that the output shaft (104 ^IV ) through the second countershaft (36) extends therethrough and at its coupling means (106) opposite end with a Parksperrenrad (1 12 ^IV ) is connected. 7. dual-clutch transmission according to one of claims 1-5, characterized in that the output shaft (104) fixed to a parking brake wheel (1 12) is connected. A dual-clutch transmission according to claim 7, characterized in that the parking lock gear (1 12; 1 12 '; 1 12 "; 1 12"') is disposed axially adjacent to the second driven gear (74). 9. dual-clutch transmission according to claim 7 or 8, characterized in that the parking lock gear (1 12; 1 12 "; 1 12" ') on the second countershaft (36) facing away from the second driven gear (74) is arranged. 10. dual-clutch transmission according to claim 7 or 8, characterized in that the parking lock gear (1 12 ') on the second countershaft (36) facing side of the second output gear (74) is arranged. 1 1. Dual-clutch transmission according to one of claims 1 - 10, characterized in that the second countershaft (36) and the output shaft (104) via a pivot bearing (1 16) are interconnected. 12 dual-clutch transmission according to one of claims 1 - 1 1, characterized in that the output shaft (104) via at least one shaft bearing (1 18) on a housing (120) of the dual-clutch transmission (14) is mounted. 13. dual-clutch transmission according to one of claims 1-12, characterized in that the driven gear (70) in the region of one end of the second countershaft (36) is arranged, which faces the first and the second friction clutch (18, 20). 14 dual-clutch transmission according to one of claims 1-13, characterized in that the coupling device (106) has a guide sleeve (108) which is fixedly connected to the output shaft (104) and on which a sliding sleeve (109) is mounted axially displaceably, wherein the second countershaft (36) is fixedly connected to a coupling body (1 10), wherein the sliding sleeve (109) the coupling body (1 10) releases in an axial position and in a second axial position establishes a positive connection with the coupling body (1 10) ,