DE102004022414B4 - Double clutch - Google Patents

Abstract

Double-clutch transmission (11) having a double clutch (1), in which the output side of the first clutch (K1) is connected to an input shaft (4) designed as a hollow shaft, in which the output side of the second clutch (K2) is connected to one in the hollow input shaft (K1). 4) is arranged centrally arranged input shaft (3), wherein each of the two input shafts (3, 4) carries a fixed gear (5, 6), with two countershafts (7, 8), of which a countershaft (8) is designed as a hollow shaft in which a centric countershaft (7) is rotatably mounted, wherein each of the two countershafts (7, 8) carries a fixed wheel (9, 10), in which the fixed gear (6) of the hollow input shaft (4) with the fixed gear (9 ) on the centrally arranged countershaft (7) meshes, in which the fixed gear (5) of the coaxial input shaft (3) with the fixed gear (10) on the hollow countershaft (8) meshing, in which a transmission output shaft (17) centric to the two input shafts (3, 4) htet is where the two ...

Description

The The invention relates to a dual-clutch transmission with seven forward gears and a reverse gear according to the generic term of patent claim 1 or claim 7.

Double clutch transmissions of this type are for example from the publications EP 1 141 580 B1 . EP 1 342 934 A2 . EP 1 342 935 A2 . EP 0 061 845 A2 and DE 43 30 170 A1 known. In such an automatic transmission two axially juxtaposed clutches are driven by a motor shaft, wherein the input side first clutch sits on a central transmission input shaft, and the wheelsets of the transmission adjacent second clutch on a coaxial to said transmission shaft hollow shaft. The central transmission input shaft and the hollow transmission input shaft are each provided with fixed wheels, which are in meshing engagement with respective associated gears on two countershafts of the transmission.

insofar feature such automatic transmission over two so-called drive constants, ie wheelsets that drive the countershafts be driven directly by the two clutches. Of the two Countershafts is designed as a hollow shaft and rotatable the other countershaft stored. On both countershafts are for the realization of six forward gears and one reverse gear Loose and / or fixed wheels arranged with the loose or fixed wheels on a transmission output shaft comb, which concentrically aligned with the two transmission input shafts is.

Especially by the DE 43 30 170 A1 known six-speed dual-clutch transmission is additionally characterized in that the gears of said drive constants are designed as fixed wheels. In addition, it is known from this publication to create a rotationally rigid connection between the radially inner transmission input shaft and the transmission output shaft to realize one of the forward gears. In addition, it is provided that the formed as a hollow shaft countershaft carries another fixed wheel, which meshes with a rotatably mounted on the transmission output shaft idler gear. This idler gear is connectable by means of a shift sleeve with the transmission output shaft.

Of the DE 43 30 170 A1 is removable, that in modern transmission construction to improve the ride comfort strives to be able to choose the ratios for the individual forward gears of the transmission as freely as possible. Of interest is the value of the so-called increment, which is formed by the quotient of the transmission ratio between a higher and the adjacent lower gear. The increment is usually between 1.0 and 2.0. In order to achieve a high level of ride comfort, the aim is to set the incremental step from the lowest gear to the highest gear degressive, so that the gear ratios change from less than the lowest gear to the highest gear relative to each other less and less.

Finally, the reveals DE 103 10 471 A1 a dual-clutch transmission with a concentric output shaft, in which a rotatably mounted on a central countershaft idler gear is torsionally coupled with this countershaft.

moreover it is in the interests of the transmission manufacturer, such dual-clutch transmission short building as well as because of the manufacturing costs with as few gearbox components to be able to produce. However, it should be noted that conventionally for each gear at least a gear pairing or wheel plane in the transmission is necessary. These The number of wheel planes is increased by two more wheel planes, because for each the two partial transmissions of the dual-clutch transmission have a drive constant, So a direct drive for the respective countershaft is necessary. Finally is with regard to the manufacturing costs of a gearbox, note that the number of coupling devices for the rotationally fixed connection of idler gears with the respective associated transmission shaft also possible is to be kept low, as these are usually also still power-assisted Actuators must be assigned.

In front In this background, the invention is based on the object Dual-clutch transmission with seven forward gears and one reverse gear to propose, which by small variations of the transmission components in a first transmission variant with comparatively few separate Coupling devices manages while according to another Transmission variant a short-building dual-clutch transmission with reduced Radebenenanzahl and slightly different coupling devices realized is.

The solution this task arises for the first transmission variant from the features of the main claim, while the characteristics of the independent Claim 7 characterize the second transmission variant. advantageous Further developments and refinements of the invention can be taken from the dependent claims.

Accordingly, the invention is initially based on a dual-clutch transmission with a double clutch, in which the output side of the first clutch K1 is connected to an input shaft designed as a hollow shaft, wherein the output side of the second clutch K2 with a in the hollow Input shaft coaxially or centrally arranged input shaft is connected, and in which each of the two input shafts carries a fixed gear. In addition, this dual-clutch transmission has two countershafts, of which a countershaft is designed as a hollow shaft in which a coaxial or concentric countershaft is rotatably mounted. Each of the two countershafts contributes to the direct drive of the same a fixed gear, the fixed gear of the hollow input shaft meshes with the fixed gear on the coaxially or centrally arranged countershaft, and in which the fixed gear of the coaxial or central input shaft with the fixed gear on the hollow countershaft is in meshing. In addition, a transmission output shaft is arranged in the transmission housing such that it is aligned concentrically with the two input shafts. Finally, it is provided in this transmission that the two countershafts wear loose and / or fixed wheels, which are in gear mesh with loose or fixed gears on the transmission output shaft, the idler gears are rotatably connected by means of coupling devices with the transmission output shaft or at least one countershaft.

to solution The object is in this first variant of a dual-clutch transmission according to the invention also provided that the two countershafts by pressing a coupling device C-D in an axial direction D rotatably connected to each other, and by operation in the other direction C a rotatable on the hollow countershaft stored idler gear torsionally coupled with this countershaft is, and that adjacent to the clutch distal end of the hollow countershaft two more loose wheels rotatably mounted axially one behind the other on the central countershaft arranged and by means of another coupling device E-F mutually rotatably connected with this countershaft.

In Development of this transmission with eight wheelsets for seven forward gears G1 to G7 and a reverse gear R is provided that in the region of the clutch remote end of the central countershaft two fixed wheels axially arranged one behind the other are. In addition, it is judged to be advantageous if said Idler gear in the area of the clutch distant end of the hollow countershaft is arranged.

to Realization of the seven forward gears is it is also useful if the hollow countershaft carries two fixed wheels and said idler gear.

Regarding the transmission output shaft, it is advantageous if this in one Swivel bearing is mounted, which at the free end of the central transmission input shaft is arranged.

One derived from the former gear in the sense of a modular system Dual-clutch transmission is therefore largely identical. It has a double clutch, in which the output side of the first Clutch K1 with a trained as a hollow shaft input shaft is connected, and at the output side of the second clutch K2 with one in the hollow input shaft coaxial or centric arranged input shaft is connected, wherein each of the two Input shafts carries a fixed wheel. In addition, this transmission includes two countershafts, one of which Countershaft is designed as a hollow shaft, in which a coaxial or Centric countershaft is rotatably mounted, each of these two countershafts bears a fixed wheel. The fixed gear meshes with the hollow input shaft with the fixed wheel on the centrally arranged countershaft, while the Fixed wheel of the centric input shaft with the fixed gear on the hollow Countershaft is in meshing engagement. Also belongs to the transmission a transmission output shaft concentrically aligned with the two input shafts is. In addition, the two countershafts wear loose and / or fixed wheels, the with loose or fixed wheels on the transmission output shaft meshing, wherein the loose wheels the transmission by means of coupling devices with the transmission output shaft or at least one countershaft rotatably connected.

to solution the task is with this Doppelkupplungstriebe than additional feature provided that a rotatable on the concentric countershaft stored idler gear on the one hand by means of a coupling device acting on one side D is rotatably connected to the hollow countershaft, and on the other hand by means of another coupling device E-F with the concentric countershaft rotatably coupled is.

This transmission has the advantage of having only seven wheel planes 01 . 02 . 03 . 05 . 06 . 07 . 08 For seven forward gears G1 to G7 and a reverse gear R manages, which over the former dual-clutch transmission, a wheel plane with two gears is saved. This has a positive effect on the manufacturing costs and on the axial length of the transmission.

moreover it is judged useful if the two countershafts by operation another one-way coupling device C rotatably with each other are connectable. This other single-sided coupling device C is preferably between the input side fixed wheel of the centric Countershaft and the input side fixed gear of the hollow countershaft arranged.

According to an advantageous development of this dual-clutch transmission is provided that the other coupling device E-F is formed axially effective two-sided gangbetätigungswirksam.

to Realization of seven forward gears and a reverse gear is also provided that the hollow countershaft two fixed wheels as well carrying said idler gear, and that at the axial ends coupling teeth are formed, which with the mentioned one-sided coupling devices C and D cooperate.

One Another common feature of both transmission variants is that the sixth gear G6 is designed as a direct gear, in which the central transmission input shaft without the interposition of gears directly is connected to the transmission output shaft.

Finally, point both transmission variants the same wheelsets for the gears G1, G2, G3, G6, G7 and R up. So is each for the first gear G1 and the reverse gear R in the region of the clutch remote end of the transmission output shaft a coupling device G-H arranged while for the second Gear G2 and the sixth gear G6 and the seventh gear G7 on the Transmission output shaft formed a coupling near coupling device A-B is.

With the coupling remote coupling device G-H is a loose wheel for the first Gear G1 or a loose wheel for the reverse gear R rotatably connected to the transmission output shaft.

to Clarification of the invention, the description is a drawing attached. Show:

1 a schematic representation of the transmission structure of a seven-speed dual-clutch transmission,

2 a table showing the operating states of two clutches and eight coupling means of the dual clutch transmission according to 1 .

3 a variant of the transmission structure according to 1 and

4 a table like in 2 , but for the dual-clutch transmission according to 3 ,

So shows 1 in the sense of a first variant of the invention, a dual-clutch transmission 11 whose double clutch 1 comprises two axially successively arranged clutches K1 and K2. The input side of the double clutch 1 stands with a motor shaft 2 For example, a motor vehicle drive technology in conjunction. The output side of the first clutch K1 is provided with a hollow input shaft 4 coupled, at the coupling remote end of a fixed gear 6 is attached. The output side of the second clutch K2, however, is through one in the hollow input shaft 4 mounted centric input shaft 3 formed, which at its free end a Festrad 5 as well as a shaft bearing 16 in which a transmission output shaft 17 is included.

In addition, this dual-clutch transmission has 11 over two countershafts 7 and 8th of which the one countershaft 8th is designed as a hollow shaft in the coaxial, the other countershaft 7 is rotatably mounted and this hollow shaft passes completely.

The dual-clutch transmission 11 has a number of wheel planes 01 to 08 on, in each of which two teeth meshing with each other are arranged. The first level of teeth 01 gets through that on the hollow input shaft 4 arranged fixed wheel 6 and a festival bike 9 formed, the latter on the centrally arranged countershaft 7 is attached. In the second wheel plane 02 combs that on the centric input shaft 3 fixed fixed wheel 5 with a fixed bike 10 , which is on the hollow countershaft 8th rotatably seated. These two wheel planes 01 and 02 form the so-called drive constants of this dual-clutch transmission 11 and serve as a direct drive for the two partial transmissions.

As 1 further shows, wearing the hollow countershaft 8th at her coupling remote end of a loose wheel 13 , which with a fixed wheel 15 output shaft on the gearbox 17 to mesh with the fourth gear G4. In addition, between the first fixed wheel 10 and said idler gear 13 in the wheel plane 03 another festival bike 12 on the hollow countershaft 8th attached, which is used to form the second gear G2 with a loose wheel 14 on the transmission output shaft 17 combs. This idler wheel 14 has a coupling toothing 27 for a coupling element of the coupling device (here A-B).

The fixed wheels 20 . 21 as well as the loose wheels 22 . 23 the centric countershaft 7 stand as gear wheels with assigned loose wheels 24 . 25 or fixed wheels 18 . 19 on the transmission output shaft 17 in the tooth mesh. The loose wheels 13 . 14 . 22 . 23 . 24 . 25 of the transmission are also by means of said coupling devices A-B, C-D, E-F, G-H rotatably connected to that transmission shaft, on which they are arranged rotatably mounted. These have loose wheels 13 . 14 . 22 . 23 . 24 . 25 Coupling on, of which for better drawing overview only some coupling teeth 27 . 29 . 30 . 31 . 32 are provided with reference numerals.

Before on the operation of this dual-clutch transmission 11 is discussed in more detail, it should be noted that the centric countershaft 7 a coupling toothing 26 through which this countershaft 7 with the help of coupling device CD with the hollow countershaft 8th drehstarr is connectable. For this purpose, a coupling element (for example, a sliding sleeve) of this coupling device is moved in the direction D. This coupling device CD is also provided in terms of a switching direction C to the idler gear 13 on the hollow countershaft 8th To connect drive technology with the latter so the fourth gear G4 in the wheel plane 04 to activate.

It is also between the wheel levels 02 and 03 arranged the further coupling device A-B, with the help of axial deflection in Rich direction A (ie in the direction of the double clutch 1 ) the centrally arranged input shaft 3 via a coupling toothing 28 for forming the sixth gear G6 directly with the transmission output shaft 17 is connected. Upon actuation of this coupling device in the direction B, however, the idler gear 14 to realize the second gear G2 rotationally fixed to the transmission output shaft 17 connected.

In addition, this dual-clutch transmission has 11 via the coupling device E-F between the two wheel planes 05 and 06 for switching the fifth gear G5 or the third gear G3, and via the coupling device G-H between the wheel planes 08 and 07 , By axial displacement of the coupling element of this coupling device G-H in the direction H, the idler gear 24 with the transmission output shaft 17 connected and so the reverse gear R inserted. A displacement of the coupling element of the coupling device G-H in the direction G, however, leads to the rotationally fixed connection of the idler gear 25 with the transmission output shaft 17 so that the first gear G1 is switched.

Like the in 1 illustrate gear positions G1, G2, G3, G4, G5, G6, G7, R indicated above the numbers for the individual wheel planes, each of the gear pairings of this transmission is used for the realization of at least one transmission gear. The sixth gear G6 is designed as a direct gear.

The operation of this seven-speed dual-clutch transmission is best through. a synopsis of the transmission structure according to 1 and the operation table according to 2 clarify. This actuation table shows which of the two clutches K1 and K2 of the dual clutch 1 with respect to which actuating positions A to H are to be operated in order to switch one of the possible transmission gears G1 to G7 or R together with said coupling devices. In addition, these tables show the transmission ratio "i" assigned to each gear, as well as the gear spread "phi" at the top right, and the respective gear jumps below.

According to 2 is marked with a black dot in the seven-speed dual-clutch transmission according to 1 shifted to insert the first gear G1, the coupling element of the coupling device G-H in the direction G, so that when the clutch K1 is a drive torque from the motor shaft 2 over the hollow transmission input shaft 4 , the fixed wheels 6 and 9 , the centric countershaft 7 , the fixed wheel 21 and the idler gear 25 on the transmission output shaft 17 is transferable.

When engaged first gear G1 can already the coupling teeth 27 at the idler wheel 14 to prepare the activation of the second gear G2 are connected to a coupling means of the coupling device A-B (position B), so that the shift from first to second gear can be done quickly and traction interruption free. This switch preparation is indicated by the white dot in the table 2 in line 1 , Column "b" marked.

To change from the first gear G1 to the second gear G2 then only the clutch K1 is opened and the clutch K2 is closed, so that of the motor shaft 2 offered torque over the centric input shaft 3 , the gears 5 and 10 , the hollow countershaft 8th , the gears 12 and 14 , as well as the coupling device A-B (position B) on the transmission output shaft 17 is transmitted.

The insertion and switching of the remaining gears results for the expert in the manner explained. Particular attention is drawn here only to the operating positions of the coupling device C-D, which also for comparison with the second transmission variant according to 3 is of particular interest.

To insert the fourth gear G4 a coupling means of the coupling device C-D is moved in the direction of actuation C. As a result, the coupling teeth 29 on the hollow countershaft 8th rotatably mounted idler wheel 13 with this hollow countershaft 8th rotatably connected, causing the fixed wheel 15 and thus also the transmission output shaft 17 is drivable.

In an axial displacement of the coupling means of the coupling device CD in the direction D, however, the hollow countershaft 8th with the centric countershaft 7 rotatably connected, which according to the operating table in 2 then the insertion of the seventh gear G7 result, even if the coupling device A-B is actuated in the direction A.

The just presented seven-speed dual-clutch transmission 11 according to 1 Compared to known dual-clutch transmissions is relatively compact, as it despite the two drive constants, the seven forward gears and the one reverse gear with only eight wheel planes 01 to 08 and therefore already saves two wheel planes compared to a conventional structure. In addition, a total of four axially double-acting coupling devices A-B, C-D, E-F, G-H are present, which also saves construction length and the production costs are reduced.

According to the problem posed by the invention, the basic structure of the in 1 shown transmission in terms of a gearbox for more than just a gearbox also be suitable for another dual-clutch transmission 40 according to 3 build, which is axially even shorter and in particular for further Redelining of manufacturing costs despite maintaining the number of gears with only seven wheel planes and therefore manages with a further reduced number of gear wheels.

Like a comparison of the two dual-clutch transmission 11 and 40 according to 1 and 3 shows, these differ only to a small extent, which can be produced at a transmission manufacturer very cost two gear with different numbers of coupling devices or wheel planes.

Accordingly, the gear pairings for the wheel planes 01 . 02 . 03 . 06 . 07 and 08 identical for both transmissions; also missing in the transmission 40 according to 3 the wheelset of the wheel plane 04 , To be able to realize the seven forward gears and the one reverse gear, it is provided that the rotatable on the central countershaft 7 stored idler gear 22 ' on the one hand by means of its coupling toothing 42 and one on the hollow countershaft 8th arranged unilaterally effective coupling device D with this countershaft 8th drehstarr is connectable, and on the other hand by means of its coupling teeth 43 and another coupling device E-F with the coaxial countershaft 7 rotatably coupled is.

In addition, this dual-clutch transmission is different 40 from the in 1 shown by the fact that the centric countershaft 7 in the region of the clutch remote side of the drive gear 9 a coupling toothing 41 has, in which a coupling toothing 44 a coupling element of an axially single-sided coupling device C on the hollow countershaft 8th can intervene.

Like the operation table in 4 shows, leads the structural design of the dual clutch transmission 40 to the fourth gear G4 is now engaged by pressing the coupling device D, while the seventh gear G7 is activated by pressing the coupling device C, although the coupling device A-B is actuated in direction A.

A comparison of the two actuation tables in the two right columns shows that the gear ratios "i", the gear spread phi = 5.00 and the gear ratio jumps have remained identical for both transmission variants. This depends, inter alia, on the multiplicity of identical transmission components, in particular the gearwheels. Overall, builds the dual-clutch transmission 40 in spite of the two coupling devices C and D acting axially only on one side because of the omission of the wheelset 04 axially much shorter than the dual-clutch transmission 11 according to 1 ,

One This gives the transmission manufacturer the opportunity to their gearshift and driving characteristics produce identical gear to be able to essentially only in terms of the number of wheel planes, their axial length and a part of the coupling devices differ.

1

Double coupling

2

motor shaft

3

centric input shaft

4

cave input shaft

5

Fixed wheel on input shaft 3

6

Fixed wheel on input shaft 4

7

centric Countershaft

8th

cave Countershaft

9

Fixed gear on countershaft 7

10

Fixed gear on countershaft 8th

11

Double clutch

12

fixed gear

13

Losrad on hollow countershaft

14

Losrad

15

fixed gear

16

Shaft bearing for transmission output shaft on input shaft 3

17

Gearbox output shaft

18

fixed gear

19

fixed gear

20

fixed gear

21

fixed gear

22

Idler gear at the transmission 11

22 '

Idler gear at the transmission 40

23

Losrad

24

Losrad

25

Losrad

26

coupling teeth

27

coupling teeth

28

coupling teeth

29

coupling teeth

30

coupling teeth

31

coupling teeth

32

coupling teeth

40

Double clutch

41

coupling teeth

42

coupling teeth

43

coupling teeth

44

coupling teeth

45

Coupling gear ratio

phi

spreading; ratio change

K1

First clutch

K2

Second clutch

FROM

coupling device

CD

coupling device

E-F

coupling device

G-H

coupling device

C

one-sided effective coupling device

D

one-sided effective coupling device

01

wheel plane

02

wheel plane

03

wheel plane

04

wheel plane

05

wheel plane

06

wheel plane

07

wheel plane

08

wheel plane

G1

first corridor

G2

second corridor

G3

third corridor

G4

fourth corridor

G5

fifth gear

G6

sixth corridor

G7

seventh corridor

R

reverse gear

Claims (13)

Double clutch ( 11 ) with a double clutch ( 1 ), in which the output side of the first clutch (K1) with an input shaft designed as a hollow shaft ( 4 ) is connected, in which the output side of the second clutch (K2) with one in the hollow input shaft ( 4 ) Centrally arranged input shaft ( 3 ), each of the two input shafts ( 3 . 4 ) a fixed wheel ( 5 . 6 ), with two countershafts ( 7 . 8th ), of which a countershaft ( 8th ) is designed as a hollow shaft, in which a central countershaft ( 7 ) is rotatably mounted, wherein each of the two countershafts ( 7 . 8th ) a fixed wheel ( 9 . 10 ), in which the fixed wheel ( 6 ) of the hollow input shaft ( 4 ) with the fixed wheel ( 9 ) on the centrally arranged countershaft ( 7 ) combs, in which the fixed wheel ( 5 ) of the coaxial input shaft ( 3 ) with the fixed wheel ( 10 ) on the hollow countershaft ( 8th ) is in meshing engagement, wherein a transmission output shaft ( 17 ) centric to the two input shafts ( 3 . 4 ), in which the two countershafts ( 7 . 8th ) Wear loose and / or fixed wheels, with loose or fixed wheels on the transmission output shaft ( 17 ) in meshing engagement, and in which the loose wheels of the transmission ( 11 ) by means of coupling devices (A-B, C-D, E-F, G-H) with the transmission output shaft ( 17 ) or at least one counter-wave ( 7 . 8th ) are rotatably connected, characterized in that the two countershafts ( 7 . 8th ) by operation of a coupling device (C-D) in an axial direction (D) rotatably connected to each other, and by actuation in the other direction (C) on the hollow countershaft ( 8th ) rotatably mounted loose wheel ( 13 ) torsionally rigid with this countershaft ( 8th ) and that adjacent to the coupling remote end of the hollow countershaft ( 8th ) two further loose wheels ( 22 . 23 ) axially one behind the other on the concentric countershaft ( 7 ) rotatably mounted and by means of a coupling device (E-F) mutually with this countershaft ( 7 ) are rotatably connected. Double-clutch transmission according to claim 1, characterized in that in the region of the coupling remote end of the central countershaft ( 7 ) two fixed wheels ( 21 . 20 ) are arranged axially one behind the other. Double-clutch transmission according to claim 1 or 2, characterized in that the idler gear ( 13 ) in the region of the coupling distal end of the hollow countershaft ( 8th ) is arranged. Double clutch transmission according to claim 3, characterized in that the hollow countershaft ( 8th ) two fixed wheels ( 10 . 12 ) as well as the loose wheel ( 13 ) wearing. Dual-clutch transmission according to at least one of claims 1 to 4, characterized in that the transmission output shaft ( 17 ) in a pivot bearing ( 16 ) at the free end of the central input shaft ( 3 ) is stored. Double clutch transmission according to at least one of claims 1 to 5, characterized in that this transmission ( 11 ) eight wheelsets ( 01 . 02 . 03 . 04 . 05 . 06 . 07 . 08 ) for seven forward gears (G1 to G7) and one reverse gear (R). Double clutch ( 40 ) with a double clutch ( 1 ), in which the output side of the first clutch (K1) with an input shaft designed as a hollow shaft ( 4 ) is connected, in which the output side of the second clutch (K2) with one in the hollow input shaft ( 4 ) Centrally arranged input shaft ( 3 ), each of the two input shafts ( 3 . 4 ) a fixed wheel ( 5 . 6 ), with two countershafts ( 7 . 8th ), of which a countershaft ( 8th ) is designed as a hollow shaft, in which a central countershaft ( 7 ) is rotatably mounted, wherein each of the two countershafts ( 7 . 8th ) a fixed wheel ( 9 . 10 ), in which the fixed wheel ( 6 ) of the hollow input shaft ( 4 ) with the fixed wheel ( 9 ) on the centrally arranged countershaft ( 7 ) combs, where the fixed wheel ( 5 ) of the central input shaft ( 3 ) with the fixed wheel ( 10 ) on the hollow countershaft ( 8th ) is in meshing engagement, wherein a transmission output shaft ( 17 ) coaxial with the two input shafts ( 3 . 4 ), in which the two countershafts ( 7 . 8th ) Wear loose and / or fixed wheels, with loose or fixed wheels on the transmission output shaft ( 17 ) in meshing engagement, and in which the loose wheels of the transmission ( 11 ) by means of coupling devices (A-B, C, D, E-F, G-H) with the transmission output shaft ( 17 ) or at least one counter-wave ( 7 . 8th ) are rotatably connected, characterized in that a rotatable on the central countershaft ( 7 ) stored loose wheel ( 22 ) on the one hand by means of a one-way coupling device (D) with the hollow countershaft ( 8th ) is torsionally rigid connectable, and on the other hand by means of another coupling device (E-F) with the central countershaft ( 7 ) is rotatably coupled, wherein the hollow countershaft ( 8th ) two fixed wheels ( 10 . 12 ), and that at its axial ends coupling teeth ( 44 . 45 ) are formed for engagement for the unilaterally acting coupling devices (C) or (D). Double clutch transmission according to claim 7, characterized characterized in that the other coupling device (E-F) axially two-sided gear actuation effect is trained. Double-clutch transmission according to claim 7 or 8, characterized in that the two countershafts ( 7 . 8th ) are rotatably connected to each other by pressing another one-way coupling device (C). Double-clutch transmission according to claim 9, characterized in that the other single-sided coupling device (C) between the input-side fixed gear ( 9 ) of the coaxial countershaft ( 7 ) and the input side fixed wheel ( 10 ) of the hollow countershaft ( 8th ) is arranged. Dual-clutch transmission according to at least one of claims 7 to 10, characterized in that this transmission ( 40 ) seven wheelsets ( 01 . 02 . 03 . 05 . 06 . 07 . 08 ) for seven forward gears (G1 to G7) and one reverse gear (R). Double clutch transmission according to at least one of previous claims, characterized in that the sixth gear (G6) as a direct gear is trained. Dual-clutch transmission according to at least one of the preceding claims, characterized in that in the region of the two axial ends of the transmission output shaft ( 17 ) Coupling devices (A-B, G-H) are arranged, wherein the coupling close coupling device (A-B) for the rotationally fixed connection of the central input shaft ( 3 ) with the transmission output shaft ( 17 ) is formed, while with the coupling remote coupling device (G-H) a loose wheel ( 25 ) for the first gear (G1) or a loose wheel ( 24 ) for the reverse gear (R) with the transmission output shaft ( 17 ) is rotatably connected.