GB2547650A - A dual clutch transmission - Google Patents

Abstract

A dual clutch transmission 10, for a motor vehicle, comprises first and second input shafts 12, 14 that are selectively cooperable with a corresponding clutch C1, C2. One input shaft 12, 14 receives a drive input to become an active input shaft while the other input shaft 12, 14 is an inactive input shaft and the drive input is switchable between the input shafts 12, 14. The dual clutch transmission 10 also includes first and second output shafts 18, 20 which are selectively engageable with the first and second input shafts 12, 14 via four forward gearwheel sets 22, 24, 26, 28. Each forward gearwheel set 22, 24, 26, 28 includes a gearwheel mounted as a fixed wheel 30, 30 and at least one gearwheel mounted as a selectively engageable and disengageable loose wheel 32. The input shafts 12, 14 output shafts 18, 20 and the four forward gearwheel sets 22, 24, 26, 28 combine to sequentially provide first, second, third, fourth, fifth and sixth forward gear steps. The transmission 10 may comprise an electric motor (310, fig 12a) so it can be operated by a hybrid drive input.

Description

A DUAL CLUTCH TRANSMISSION

This invention relates to a dual clutch transmission for a motor vehicle.

It is known to provide an automatic transmission which uses two separate clutches to operate different gear sets of the transmission. Such transmissions are known as dual clutch transmissions but are sometimes referred to as twin clutch transmissions or double clutch transmissions.

According to an aspect of the invention there is provided a dual clutch transmission for a motor vehicle comprising: first and second input shafts selectively cooperable with a corresponding clutch whereby one input shaft receives a drive input to become an active input shaft while the other input shaft is an inactive input shaft and the drive input is switchable between the input shafts; and first and second output shafts selectively engageable with the first and second input shafts via four forward gearwheel sets, each forward gearwheel set including a gearwheel mounted as a fixed wheel and at least one gearwheel mounted as a selectively engageable and disengageable loose wheel, the input shafts, output shafts and the four forward gearwheel sets combining to sequentially provide first, second, third, fourth, fifth and sixth forward gear steps, the forward gearwheel sets establishing for each of the six forward gear steps an active torque path between the active input shaft and an output shaft to generate a corresponding current forward gear step output and an available torque path between the inactive input shaft and an output shaft to permit the generation of a corresponding next forward gear step output, and the output for each of the first, second, third, fourth, fifth and sixth forward gear steps shifting from the current forward gear step output to a next forward gear step output when the drive input switches from the active input shaft to the inactive input shaft.

The input shafts, output shafts and the four forward gearwheel sets combining to sequentially provide first, second, third, fourth, fifth and sixth forward gear steps means that the dual clutch transmission is able to produce six forward gear step outputs using only four forward gearwheel sets. Therefore the length of the dual clutch transmission is reduced due to a lower number of gearwheel sets being required to produce the desired six forward gear step outputs. Thus a compact dual clutch transmission is provided.

Meanwhile, the forward gearwheel sets establishing for each of the six forward gear steps and active torque path and an available torque path results in the corresponding next forward gear step output being immediately available when the drive input switches from the active input shaft to the inactive input shaft for the output of each of the first to sixth forward gear steps. Accordingly, the dual clutch transmission does not experience any interruption in power nor any delay when it is shifting sequentially either up or down through each of the first to sixth forward gear steps. As such, the dual clutch transmission can be operated as a “true seamless dual clutch transmission” for each of the first to sixth forward gear steps.

Preferably, the forward gearwheel sets simultaneously establish active and available torque paths for each of the first, second, third, fourth, fifth and sixth forward gear steps.

Such simultaneous establishment of the active and available torque paths means that the available torque path is pre-selected prior to the drive input being switched from the active input shaft to the inactive input shaft. Pre-selecting the available torque path provides an efficient way to ensure that the available torque path is immediately available when the drive input switches from the active input shaft to the inactive input shaft for the output of each of the first to sixth forward gear steps.

Optionally, a first forward gearwheel set includes first and second loose wheels.

The inclusion of first and second loose wheels in a first forward gearwheel set permits the establishment of a torque path between one input shaft and an output shaft via the other input shaft, and so provides flexibility in the combining of the input shafts, output shafts and the four forward gearwheel sets. Thus, a higher number of forward gear steps than the number of forward gearwheel sets can be provided.

The first loose wheel may mutually intermesh with the fixed wheel of the first gearwheel set.

The first loose wheel mutually intermeshing with the fixed wheel of the first gearwheel set provides the aforementioned flexibility in the combining of the input shafts, output shafts and the four forward gearwheel sets while at the same time reducing the length of the transmission.

In embodiments of the invention, the first loose wheel is selectively engageable with a corresponding input shaft or output shaft to establish a first direct forward gear step. Moreover, the first direct forward gear step may correspond to the third forward gear step.

Such an arrangement allows a forward gear step, e.g. the third forward gear step, to be provided efficiently.

Preferably the second loose wheel mutually intermeshes with a gearwheel of a second forward gearwheel set.

The second loose wheel mutually intermeshing with a gearwheel of a second forward gearwheel set means that an existing forward gearwheel set is utilised to permit the selective engagement of the output shaft corresponding to the second loose wheel and the input shaft corresponding to the second forward gearwheel set. Accordingly, such an arrangement permits the aforementioned establishment of a torque path between one input shaft and an output shaft via the other input shaft while at the same time reducing the number of parts and the length of dual clutch transmission. Therefore a compact design of the dual clutch transmission is obtained.

Optionally the second forward gearwheel set selectively establishes the fourth forward gear step.

Such an arrangement allows the fourth forward gear step to be provided efficiently.

The second loose wheel may be selectively engageable with the first loose wheel to modify a direct forward gear step and thereby provide an indirect forward gear step.

Such an arrangement means that existing wheels, i.e. the first and second loose wheels, are used to permit the aforementioned establishment of a torque path between one input shaft and an output shaft via the other input shaft which in turn modifies a direct forward gear step so as to provide an indirect forward gear step. Thus, a higher number of forward gear steps than the number of forward gearwheel sets can be provided by the dual clutch transmission.

In other embodiments of the invention, the second loose wheel when selectively engaged with the first loose wheel modifies the direct forward gear step selectively established by another forward gearwheel set to provide a first indirect forward gear step.

In further embodiments of the invention, the second loose wheel when selectively engaged with the first loose wheel modifies a direct forward gear step selectively established by a third forward gearwheel set to provide the first indirect forward gear step.

In further still embodiments of the invention, the first indirect forward gear step corresponds to the first forward gear step.

Such an arrangement allows a forward gear step, e.g. the first forward gear step, to be provided while reducing the number of gearwheel sets required to produce such a forward gear step. In other words, a gearwheel set for directly producing the first forward gear step is not required, thus reducing the length of the transmission.

The second loose wheel when selectively engaged with the first loose wheel may modify a direct forward gear step selectively established by another forward gearwheel set to provide a second indirect forward gear step.

Moreover, the second loose wheel when selectively engaged with the first loose wheel may modify a direct forward gear step selectively established by a fourth forward gearwheel set to provide the second indirect forward gear step.

In addition to the foregoing, the second indirect forward gear step may correspond to the sixth forward gear step.

Such an arrangement allows a forward gear step, e.g. the sixth forward gear step, to be provided while reducing the number of gearwheel sets required to produce such a forward gear step. In other words, a gearwheel set for directly producing the sixth forward gear step is not required, thus further reducing the length of the transmission.

Optionally gearwheels for the third and fifth forward gear steps are disposed on the first input shaft. The gearwheels disposed on the first input shaft may be fixed wheels.

Having the gearwheels for the third and fifth forward gear steps (i.e. the odd forward gear steps) disposed on the first input shaft helps to allow the dual clutch transmission to perform as a true seamless dual clutch transmission. Meanwhile, disposing the fixed wheels on the first input shaft provides ease of installation of the dual clutch transmission.

Preferably a gearwheel for the third forward gear step is disposed on the first output shaft.

The gearwheel disposed on the first output shaft may be a loose wheel.

Optionally gearwheels for the second and fourth forward gear steps are disposed on the second input shaft. The gearwheels disposed on the second input shaft may be fixed wheels.

Having the gearwheels for the second and fourth forward gear steps (i.e. the even forward gear steps) disposed on the second input shaft helps to allow the dual clutch transmission to perform as a true seamless dual clutch transmission. Meanwhile, disposing the fixed wheels on the second input shaft provides ease of installation of the dual clutch transmission.

Optionally gearwheels for the second, fourth and fifth forward gear steps are disposed on the second output shaft. The gearwheels disposed on the second output shaft may be loose wheels.

There now follows a brief description of preferred embodiments of the invention, by way of non-limiting examples, with reference being made to the following drawings in which:

Figure 1 schematically shows a dual clutch transmission according to a first embodiment of the invention;

Figure 2 shows an active torque path of the dual clutch transmission of Figure 1 when operating in a first forward gear step;

Figure 3 shows an active torque path of the dual clutch transmission of Figure 1 when operating in a second forward gear step;

Figure 4 shows an active torque path of the dual clutch transmission of Figure 1 when operating in a third forward gear step;

Figure 5 shows an active torque path of the dual clutch transmission of Figure 1 when operating in a fourth forward gear step;

Figure 6 shows an active torque path of the dual clutch transmission of Figure 1 when operating in a fifth forward gear step;

Figure 7 shows an active torque path of the dual clutch transmission of Figure 1 when operating in a sixth forward gear step;

Figure 8 shows an active torque path of the dual clutch transmission of Figure 1 when operating in a first auxiliary gear step;

Figure 9 shows an active torque path of the dual clutch transmission of Figure 1 when operating in a second auxiliary gear step;

Figure 10 schematically shows a dual clutch transmission according to a second embodiment of the invention;

Figure 11 schematically shows a dual clutch transmission according to a third embodiment of the invention;

Figures 12a, 12b and 12c schematically show a dual clutch transmission assembly according to a fourth embodiment of the invention; and

Figure 13 shows an active torque path of the dual clutch transmission assembly of Figure 12a when operating in a first forward gear step via an electric motor. A dual clutch transmission according to a first embodiment of the invention is designated generally by reference numeral 10 and is shown in Figure 1.

The first dual clutch transmission 10 includes first and second input shafts 12, 14 each of which is selectively cooperable with a corresponding first or second clutch C1, C2. The first and second clutches C1, C2 are housed within a rotating clutch housing 16. The rotating clutch housing 16 is rotated by an engine (not shown) to which the first dual clutch transmission 10 is operatively connected.

The first and second clutches C1, C2 are selectively engageable with the rotating clutch housing 16 via a pressure plate arrangement (not shown) which causes the first or second clutch C1, C2 to rotate with the clutch housing 16. Such rotation of the first or second clutch C1, C2 rotates the associated input shaft 12, 14, thus the input shaft 12, 14 receives a drive input to become an active input shaft while the other input shaft is an inactive input shaft. The drive input is switchable between the input shafts 12, 14 through the first and second clutches C1, C2 respectively.

In the embodiment shown, the first and second input shafts 12, 14 are concentrically arranged relative to one another. In particular, the second input shaft 14 is positioned inside the first input shaft 12. It will be understood that the input shafts 12, 14 can be arranged the other way around.

The first dual clutch transmission 10 also includes first and second output shafts 18, 20 which are selectively engageable with the first and second input shafts 12, 14 via four forward gearwheel sets 22, 24, 26, 28.

The first output shaft 18 is positioned above the concentrically arranged input shafts 12, 14 while the second output shaft 20 is positioned below the concentrically arranged input shafts 12, 14. In other embodiments the second output shaft 20 may be above while the first output shaft 18 may be below the concentrically arranged input shafts 12, 14.

Each of the first and second output shafts 18, 20 is connected to a differential 34 via respective final gearwheel pinions 36.

Each forward gearwheel set 22, 24, 26, 28 includes a gearwheel mounted as a fixed wheel 30, 30’ and at least one gearwheel mounted as a selectively engageable and disengageable loose wheel 32, 32’, 32a, 32b. In the embodiment shown, each forward gearwheel set 22, 24, 26, 28 includes a fixed wheel 30 disposed on a corresponding input shaft 12,14 and at least one loose wheel 32 disposed on a corresponding output shaft 18, 20.

It will be understood that in other embodiments of the invention (not shown) the fixed wheels 30 may instead be disposed on the output shafts 18, 20 and the loose wheels 32 may instead be disposed on the input shafts 12,14.

The first forward gearwheel set 22 includes a fixed wheel 30 disposed on the first input shaft 12. The first forward gearwheel set 22 further includes first and second loose wheels 32a, 32b which are selectively engageable with the first output shaft 18.

The fixed wheel 30 of the first forward gearwheel set 22 is intermeshed with the first loose wheel 32a. Moreover, the first loose wheel 32a is selectively engageable with the first output shaft 18 to establish a direct forward gear step which is the third forward gear step in this embodiment. As such, the first loose wheel 32a of the first forward gearwheel set 22 is a gear 3 wheel, i.e. as indicated by the number 3 in Figure 1.

In other embodiments of the invention (not shown) the direct forward gear step may instead correspond to another forward gear step.

The second loose wheel 32b mutually intermeshes with a gearwheel of a second forward gearwheel set 24.

The second forward gearwheel set 24 includes a fixed wheel 30 disposed on the second input shaft 14 and an intermeshed loose wheel 32 disposed on the second output shaft 20.

The loose wheel 32 of the second forward gearwheel set 24 is selectively engageable with the second output shaft 20 to establish a direct forward gear step which is the fourth forward gear step in this embodiment. As such, the loose wheel 32 of the second forward gearwheel set 24 is a gear 4 wheel, i.e. as indicated by the number 4 in Figure 1.

Returning to the first forward gearwheel set 22, the second loose wheel 32b is selectively engageable with the first loose wheel 32a to modify a direct forward gear step and thereby provide an indirect forward gear step.

More specifically the second loose wheel 32b when selectively engaged with the first loose wheel 32a modifies a direct forward gear step selectively established by another forward gearwheel set, i.e. the third forward gearwheel set 26 in this embodiment, to provide a first indirect forward gear step. The first indirect forward gear step corresponds to the first forward gear step, as shown in Figure 2 and described in more detail later on in this application.

In addition, the second loose wheel 32b when selectively engaged with the first loose wheel 32a modifies a direct forward gear step selectively established by another forward gearwheel set, i.e. the fourth forward gearwheel set 28 in this embodiment, to provide a second indirect forward gear step. The second indirect forward gear step corresponds to the sixth forward gear step, as shown in Figure 7 and described in more detail later on in this application.

It will be understood that the first and second indirect forward gear steps may instead correspond to different forward gear steps.

The third forward gearwheel set 26 includes a fixed wheel 30 disposed on the second input shaft 14 and an intermeshed loose wheel 32 disposed on the second output shaft 20. The loose wheel 32 of the third forward gearwheel set 26 is selectively engageable with the second output shaft 20 to establish a direct forward gear step which is the second forward gear step in this embodiment. As such, the loose wheel 32 of the third forward gearwheel set 26 is a gear 2 wheel, i.e. as indicated by the number 2 in Figure 1.

Meanwhile, the fourth forward gearwheel set 28 includes a fixed wheel 30 disposed on the first input shaft 12 and an intermeshed loose wheel 32 disposed on the second output shaft 20. The loose wheel 32 of the fourth forward gearwheel set 28 is selectively engageable with the second output shaft 20 to establish a direct forward gear step which is the fifth forward gear step in this embodiment. As such, the loose wheel 32 of the fourth forward gearwheel set 28 is a gear 5 wheel, i.e. as indicated by the number 5 in Figure 1.

The second loose wheel 32b of the first forward gearwheel set 22 does not on its own establish any direct forward gear step and is considered an idler wheel M1.

Moreover, the idler wheel M1 and the gear 3 wheel are both disposed on an idler shaft 38 which is concentrically mounted relative to the first output shaft 18. In particular, the gear 3 wheel is mounted as a fixed wheel 30’ relative to the idler shaft 38 while the idler wheel M1 is mounted as a loose wheel 32’ relative to the idler shaft 38. As such the gear 3 wheel is fixed to the idler shaft 38 while the idler wheel M1 is selectively engageable and disengageable with the idler shaft 38.

The idler shaft 38 is selectively engageable and disengageable with the first output shaft 18, thus permitting the gear 3 wheel and the idler wheel M1 to be mounted as loose wheels 32 relative to the first output shaft 18.

In other embodiments of the invention (not shown) the gear 3 wheel may be mounted as a loose wheel 32’ relative to the idler shaft 38 while the idler wheel M1 may be mounted as a fixed wheel 30’ relative to the idler shaft 38.

The first dual clutch transmission 10 also includes a reverse gear wheel R. The reverse gear wheel R is mounted as a loose wheel 32 relative to the first output shaft 18.

The outermost forward gearwheel sets on each side of the first dual clutch transmission 10 are the third forward gearwheel set 26 and the first forward gearwheel set 22.

In particular, the order of the forward gearwheel sets from left to right of the first dual clutch transmission 10 shown in Figure 1 is: the third forward gearwheel set 26 (which includes the gear 2 wheel), the second forward gearwheel set 24 (which includes the gear 4 wheel), the fourth forward gearwheel set 28 (which includes the gear 5 wheel) and the first forward gearwheel set 22 (which includes the gear 3 wheel and the idler wheel M1).

The first dual clutch transmission 10 further includes four synchronising devices 40a, 40b, 42a, 42b each of which is configured to selectively engage at least one loose wheel 32, 32’, 32a, 32b to a corresponding shaft 18, 20, 38.

More specifically, the first dual clutch transmission 10 includes two full synchronising devices 40a, 40b which are configured to selectively engage two loose wheels 32, 32a to a corresponding shaft 18, 20, 38, and two half synchronising devices 42a, 42b which are configured to selective engage only one loose wheel 32, 32’, 32b to a corresponding shaft 18, 20, 38. It will be understood that each synchronising device 40a, 40b, 42a, 42b can only selectively engage any one loose wheel 32, 32’, 32a, 32b at a given time.

The first output shaft 18 has a first full synchronising device 40a disposed thereon. The first full synchronising device 40a is configured to selectively engage the gear 3 wheel to the first output shaft 18. In this embodiment, the first full synchronising device 40a is therefore configured to selective engage the idler shaft 38 to the first output shaft 18 by virtue of the gear 3 wheel being fixed to the idler shaft 38.

The first full synchronising device 40a is also configured to selectively engage the reverse gear wheel R to the first output shaft 18.

The first output shaft 18 also has a first half synchronising device 42a disposed thereon. In particular, the first half synchronising device 42a is disposed on the idler shaft 38 and is configured to selectively engage the idler wheel M1 to the idler shaft 38.

Meanwhile, the second output shaft 20 has a second full synchronising device 40b disposed thereon. The second full synchronising device 40b is configured to alternatively selectively engage the gear 2 wheel and the gear 4 wheel to the second output shaft 20.

The second output shaft also has a second half synchronising device 42b disposed thereon. The second half synchronising device 42b is configured to selectively engage the gear 5 wheel to the second output shaft 20.

Each of the synchronising devices 40a, 40b, 42a, 42b is fixedly secured to a shaft 18, 20, 38 and is moved from a neutral position, wherein it is not engaged with any loose wheels 32, 32’, 32a, 32b, to an engaged position, wherein it is engaged with a loose wheel 32, 32’, 32a, 32b, so as to selectively engage a loose wheel 32, 32’, 32a, 32b to a corresponding shaft 18, 20, 38.

Each of the synchronising devices 40a, 40b, 42a, 42b is moved between the neutral and engaged positions by forks (not shown) that are controlled by fork actuators (not shown).

In the first embodiment shown, the first dual clutch transmission 10 requires only four fork actuators.

Moreover, the forks actuators are controlled by a transmission control unit (not shown) through an actuation device which is normally either electric or hydraulic. The transmission control unit obtains readings from the vehicle and engine in which the first dual clutch transmission 10 is operating to establish the most appropriate gear step that is required at that time. The transmission control unit controls the fork actuators so as to move the forks (and thus the synchronising devices 40a, 40b, 42a, 42b) in the correct sequence to enable the correct gearwheel selection to be made, thus producing the desired gear step output.

There now follows a description of the first dual clutch transmission 10 in use as it sequentially provides first, second, third, fourth, fifth and sixth forward gear steps (i.e. as it shifts up through the forward gear steps), as illustrated in Figures 2 to 7.

Starting with Figure 2, while the first and second clutches C1, C2 are disengaged (i.e. the first dual clutch transmission is in “Neutral”), the first half synchronising device 42a is engaged with the idler wheel M1 while the second full synchronising device 40b is engaged with the gear 2 wheel. As such, a soon to be active torque path Tact is established between a soon to be active input shaft ACT (i.e. the first input shaft 12) and the second output shaft 20. Such a torque path Tact is pre-selected prior to one of the clutches C1, C2 being engaged and thus prior to either input shaft 12, 14 receiving a drive input.

The first forward gear step is provided by the first clutch C1 engaging with the rotating clutch housing 16 so as to provide the first input shaft 12 with a drive input. The first input shaft 12 therefore becomes an active input shaft ACT while the second input shaft 14 is an inactive input shaft INACT.

Since the active torque path Tact between the active input shaft ACT (i.e. the first input shaft 12) and the second output shaft 20 has already been established, the first input shaft 12 receiving a drive input results in the generation of a first forward gear step output Oi.

At the same time, an available torque path between the inactive input shaft INACT and the second output shaft 20 is also established to permit the generation of a corresponding next forward gear step output, i.e. a second forward gear step output O2.

The respective available torque paths are not shown in Figures 2 to 7 for clarity purposes. However, the available torque paths can readily be seen in the subsequent (or previous) figure as it is shown as the active torque path Tact for the next (or previous) forward gear step output. For example, the available torque path that is established for the second forward gear step output O2 is shown as the active torque path Tact in Figure 3.

In particular, it can be seen that the torque path that permits generation of the second forward gear step output 02 need only the second clutch C2 to be engaged with the rotating clutch housing 16. In this way, the available torque path to permit generation of the second forward gear step output O2 is simultaneously established with the available torque path that permits the generation of the first forward gear step output O1.

Moving on to Figure 3, the first clutch C1 is disengaged from the rotating clutch housing 16 and at the same time the second clutch C2 is engaged with the rotating clutch housing 16. As such, the second input shaft 14 receives a drive input and so becomes the active input shaft ACT while the first input shaft 12 ceases to receive a drive input and so becomes the inactive input shaft INACT.

The second full synchronising device 40b is already engaged with the gear 2 wheel, and so an active torque path Tact is established between the active input shaft ACT (i.e. the second input shaft 14) and the second output shaft 20 which generates the second forward gear step output O2.

In this way, the output of the first dual clutch transmission 10 shifts from the first forward gear step output O1 to the second forward gear step output 02 when the drive input switches from the active input shaft ACT (which was the first input shaft 12 in Figure 2) to the inactive input shaft INACT (which was the second input shaft 14 in Figure 2).

The first half synchronising device 42a may be disengaged from the idler wheel M1 any time after the first clutch C1 is disengaged from the rotating clutch housing 16 so that the first half synchronising device 42a is in the neutral position ready for any subsequent engagement.

An available torque path for the generation of the third forward gear step output O3 (as shown as the active torque path Tact in Figure 4) is established by the first full synchronising device 40a engaging with the gear 3 wheel. Such engaging pre-selects the available torque path prior to the drive input being switched from the active input shaft ACT to the inactive input shaft INACT, i.e. prior to the first clutch C1 engaging with the rotating clutch housing 16.

Next, as shown in Figure 4, the second clutch C2 is disengaged from the rotating clutch housing 16 and at the same time the first clutch C1 is engaged with the rotating clutch housing 16 so as to provide a drive input to the first input shaft 12 which is now the active input shaft ACT.

Since the first full synchronising device 40a is already engaged with the gear 3 wheel, an active torque path Tact is established between the active input shaft ACT (i.e. the first input shaft 12) and the first output shaft 18 which generates the third forward gear step output 03.

In this way, the output of the first dual clutch transmission 10 shifts from the second forward gear step output O2 to the third forward gear step output 03 when the drive input switches from the active input shaft ACT (which was the second input shaft 14 in Figure 3) to the inactive input shaft INACT (which was the first input shaft 12 in Figure 4).

The second full synchronising device 40b may be disengaged from the gear 2 wheel any time after the second clutch C2 is disengaged from the rotating clutch housing 16 so that the second full synchronising device 40b is in the neutral position ready for any subsequent engagement.

Indeed, an available torque path for the generation of the fourth forward gear step output O4 (as shown as the active torque path Tact in Figure 5) is established by the second full synchronising device 40b engaging with the gear 4 wheel. Such engaging pre-selects the available torque path prior to the drive input being switched from the active input shaft ACT to the inactive input shaft INACT.

Moving onto Figure 5, the first clutch C1 is disengaged from the rotating clutch housing 16 and at the same time the second clutch C2 is engaged with the rotating clutch housing 16 so as to provide a drive input to the second input shaft 14 which is now the active input shaft ACT.

Since the second full synchronising device 40b is already engaged with the gear 4 wheel, an active torque path Tact is established between the active input shaft ACT (i.e. the second input shaft 14) and the second output shaft 20 which generates the fourth forward gear step output O4.

Again, this means that the output of the first dual clutch transmission 10 shifts from the third forward gear step output 03 to the fourth forward gear step output O4 when the drive input switches from the active input shaft ACT to the inactive input shaft INACT.

The first full synchronising device 40a may be disengaged from the gear 3 wheel any time after the first clutch C1 is disengaged from the rotating clutch housing 16 so that the first full synchronising device 40a is in the neutral position ready for any subsequent engagement.

An available torque path for generation of the fifth forward gear step output 05 (as shown as the active torque path Tact in Figure 6) is established by the second half synchronising device 42b engaging with the gear 5 wheel. Since the gear 5 wheel is mounted to the first input shaft 12 (via its fixed wheel 30) which is the inactive input shaft INACT at this time, the first input shaft 12 and associated first clutch C1 are able to rotate at a different speed to the drive input for the fourth forward gear step output 04.

Such engaging of the gear 5 wheel pre-selects the available torque path prior to the drive input being switched from the active input shaft ACT to the inactive input shaft INACT.

As shown in Figure 6, the second clutch C2 is disengaged from the rotating clutch housing 16 and at the same time the first clutch C1 is engaged with the rotating clutch housing 16 so as to provide a drive input to the first input shaft 12 which is now the active input shaft ACT.

Since the second half synchronising device 42b is already engaged with the gear 5 wheel, an active torque path Tact is established between the active input shaft ACT (i.e. the first input shaft 12) and the second output shaft 20 which generates the fifth forward gear step output O5.

As such, when the drive input switches from the active input shaft ACT (which was the second input shaft 14 in Figure 5) to the inactive input shaft (which was the first input shaft 12 in Figure 5), an active torque path Tact is established between the now active input shaft ACT (i.e. the first input shaft 12) and the second output shaft 20.

The second full synchronising device 40b may be disengaged from the gear 4 wheel any time after the second clutch C2 is disengaged from the rotating clutch housing 16 so that the second full synchronising device 40b is in the neutral position ready for any subsequent engagement.

An available torque path for the generation of the sixth forward gear step output Oe (as shown as the active torque path Tact in Figure 7) is established by the first half synchronising device 42a engaging with the idler wheel M1 and the second half synchronising device 42b already being engaged with the gear 5 wheel. Such engaging pre-selects the available torque path prior to the drive input being switched from the active input shaft ACT to the inactive input shaft INACT, i.e. prior to the second clutch C2 engaging with the rotating clutch housing 16.

Turning to Figure 7, the first clutch C1 is disengaged from the rotating clutch housing 16 and at the same time the second clutch C2 is engaged with the rotating clutch housing 16 so as to provide a drive input to the second input shaft which is now the active input shaft ACT.

Since the first half synchronising device 42a is already engaged with the idler wheel M1 and the second half synchronising device 42b is already engaged with the gear 5 wheel, an active torque path Tact is established between the active input shaft ACT (i.e. the second input shaft 14) and the second output shaft 20 which generates the sixth forward gear step output Oe.

As before, this means that the output of the first dual clutch transmission 10 shifts from the fifth forward gear step output Os to the sixth forward gear step output Oe when the drive input switches from the active input shaft ACT to the inactive input shaft INACT.

There now follows a description of the first dual clutch transmission 10 in use as it sequentially provides sixth, fifth, fourth, third, second and first forward gear steps (i.e. as it shifts down through the forward gear steps), as illustrated in Figures 7 to 2.

Starting from Figure 7, which shows the establishment of the sixth forward gear step output 06, an available torque path for the generation of the fifth forward gear step output O5 (as shown as the active torque path Tact in Figure 6) is already established. This is because generation of the fifth forward gear step output 05 needs only for the drive input to be shifted from the active input shaft ACT (i.e. the second input shaft 14 in Figure 7) to the inactive input shaft INACT (i.e. the first input shaft 12 in Figure 7).

Moving onto Figure 6, the second clutch C2 is disengaged from the rotating clutch housing 16 and at the same time the first clutch C1 is engaged with the rotating clutch housing 16 so that the first input shaft 12 is the active input shaft.

Since the second half synchronising device 42b is already engaged with the gear 5 wheel, an active torque path Tact is established between the active input shaft ACT (i.e. the first input shaft 12) and the second output shaft 20 so as to generate the fifth forward gear step output O5.

The first half synchronising device 42a may be disengaged from the idler wheel M1 at any time after the second clutch C2 is disengaged from the rotating clutch housing 16 so that the first half synchronising device 42a is in the neutral position ready for any subsequent engagement.

An available torque path for the generation of the fourth forward gear step output O4 (as shown as the active torque path Tact in Figure 5) is established by the second full synchronising device 40b engaging with the gear 4 wheel. Since the gear 4 wheel is mounted to the second input shaft 14, which is the inactive input shaft INACT at this time, the second input shaft 14 and associated second clutch C2 are able to rotate at a different speed to the drive input for the fifth forward gear step output O5.

Such engaging of the gear 4 wheel pre-selects the available torque path prior to the drive input being switched from the active input shaft ACT to the inactive input shaft INACT.

As shown in Figure 5, the first clutch C1 is disengaged from the rotating clutch housing 16 and at the same time the second clutch C2 is engaged with the rotating clutch housing 16 so as to provide a drive input to the second input shaft 14 which is now the active input shaft ACT.

Since the second full synchronising device 40b is already engaged with the gear 4 wheel, an active torque path Tact is established between the active input shaft ACT (i.e. the second input shaft 14) and the second output shaft 20 which generates the fourth forward gear step output O4.

As such, when the drive input switches from the active input shaft ACT (which was the first input shaft 12 in Figure 6) to the inactive input shaft (which was the second input shaft 14 in Figure 6), an active torque path Tact is established between the now active input shaft ACT (i.e. the second input shaft 14) and the second output shaft 20.

The second half synchronising device 42b may be disengaged from the gear 5 wheel any time after the first clutch C1 is disengaged from the rotating clutch housing 16 so that the second half synchronising device 42b is in the neutral position ready for any subsequent engagement.

An available torque path for generation of the third forward gear step output 03 (as shown as the active torque path Tact in Figure 4) is established by the first full synchronising device 40a engaging with the gear 3 wheel. Such engaging pre-selects the available torque path prior to the drive input being switched from the active input shaft ACT to the inactive input shaft INACT, i.e. prior to the first clutch C1 engaging with the rotating clutch housing 16.

Turning to Figure 4, the second clutch C2 is disengaged from the rotating clutch housing 16 and at the same time the first clutch C1 is engaged with the rotating clutch housing 16 such that the first input shaft 12 is the active input shaft ACT.

Since the first full synchronising device 40a is already engaged with the gear 3 wheel, an active torque path Tact is established between the active input shaft ACT (i.e. the first input shaft C1) and the first output shaft 18 so as to generate the third forward gear step output 03.

The second full synchronising device 40b may be disengaged from the gear 4 wheel at any time after the second clutch C2 is disengaged from the rotating clutch housing 16 so that the second full synchronising device 40b is in the neutral position ready for any subsequent engagement.

Indeed, an available torque path for generation of the second forward gear step output 02 (as shown as the active torque path Tact in Figure 3) is established by the second full synchronising device 40b engaging with the gear 2 wheel. Such engaging pre-selects the available torque path prior to the drive input being switched from the active input shaft ACT to the inactive input shaft INACT, i.e. prior to the second clutch C2 engaging with the rotating clutch housing 16.

Referring now to Figure 3, the first clutch C1 is disengaged from the rotating clutch housing 16 and at the same time the second clutch C2 is engaged with the rotating clutch housing 16 so that the second input shaft 14 is the active input shaft ACT.

Since the second full synchronising device 40b is already engaged with the gear 2 wheel, an active torque path Tact is established between the active input shaft ACT (i.e. the second input shaft 14) and the second output shaft 20 so as to generate the second forward gear step output O2.

The first full synchronising device 40a may be disengaged from the gear 3 wheel at any time after the first clutch C1 is disengaged from the rotating clutch housing 16 so that the first full synchronising device 40a is in the neutral position ready for any subsequent engagement.

An available torque path for generation of the first forward gear step output O1 (as shown as the active torque path Tact in Figure 2) is established by the first half synchronising device 42a engaging with the idler wheel M1 and by the second full synchronising device 40b already being engaged with the gear 2 wheel. Such engaging pre-selects the available torque path prior to the drive input being switched from the active input shaft ACT to the inactive input shaft INACT, i.e. prior to the first clutch C1 engaging with the rotating clutch housing 16.

Moving onto Figure 2, the second clutch C2 is disengaged from the rotating clutch housing 16 and at the same time the first clutch C1 engages with the rotating clutch housing 16 so that the first input shaft 12 is the active input shaft ACT.

Since the first half synchronising device 42a is already engaged with the idler wheel M1 and the second full synchronising device 40b is already engaged with the gear 2 wheel, an active torque path Tact is established between the active input shaft ACT (i.e. the first input shaft 12) and the second output shaft 20 so as to generate the first forward gear step output O1.

It can be seen that, for shifting down each gear step, the output of the first dual clutch transmission 10 shifts from each current forward gear step output to the subsequent forward gear step output when the drive input switches from the active input shaft ACT to the inactive input shaft INACT.

In other embodiments of the invention (not shown) the available torque path for each of the forward gear step outputs Οι, 02, O3, O4, O5, Oe may instead be established at the same time as the drive input switches from the active input shaft ACT to the inactive input shaft INACT.

Two reverse gear step outputs (not shown) are available for the first dual clutch transmission 10. Firstly, considering the first and second clutches C1, C2 are disengaged from the rotating clutch housing 16 (i.e. the first dual clutch transmission 10 is in “Neutral"), the first half synchronising device 42a engages with the idler wheel M1 and the first full synchronising device 40a engages with the reverse gear wheel R. Such engagement creates a first reverse torque path through the idler wheel M1, the second input shaft 14 and the third forward gearwheel set 26.

The first clutch C1 is then engaged with the rotating clutch housing 16 such that the first input shaft 12 receives a drive input and a first reverse gear step output is generated.

Secondly, considering the first and second clutches C1, C2 are disengaged from the rotating clutch housing 16 (i.e. the first dual clutch transmission 10 is in “Neutral”), the first full synchronising device 40a engages with the reverse gear wheel R, thus creating a second reverse torque path through the third forward gearwheel set 26 only.

The second clutch C2 is then engaged with the rotating clutch housing 16 such that the second input shaft 14 receives a drive input and a second reverse gear step output is generated.

The first dual clutch transmission 10 can be operated in first and second auxiliary gear steps so as to provide respective first and second auxiliary gear step outputs Oai, Oa2. Such outputs are described in more detail below and are shown in Figures 8 and 9.

The first and second auxiliary gear step outputs Oai, Oa2 are provided by establishing an active torque path Tact by utilising the idler wheel M1 and another gear wheel. The resulting auxiliary gear step outputs Oai, Oa2 have a ratio (and output speed) that lies between two consecutive forward gear step outputs Οι, O2, O3, O4, Os, CV

To provide the drive input to either the first or second clutch C1, C2 when operating in the first or second auxiliary gear steps, both of the first and second clutches C1, C2 are first disengaged from the rotating clutch housing 16. Then the appropriate wheels 2, 3, 4, 5, M1 are engaged via a corresponding synchronising device 40a, 40b, 42a, 42b while both clutches C1, C2 are disengaged. In this way, if the first dual clutch transmission 10 is operated in the first or second auxiliary gear steps it no longer (in that moment at least) operates as a true seamless dual clutch transmission.

In the embodiment shown, the first auxiliary gear step output Oai is provided by the first half synchronising device 42a engaging with the idler wheel M1 and the second full synchronising device 40b engaging with the gear 4 wheel. An active torque path Tact is therefore established between the first input shaft 12 and the second output shaft 20, as shown in Figure 8.

To provide a drive input to the first input shaft 12 so as to make that input shaft the active input shaft ACT, the first clutch C1 is engaged with the rotating clutch housing 16.

The first auxiliary gear step output Oai would be selected after the second forward gear step output 02 and before the third forward gear step output O3 if shifting consecutively up through the gear step outputs, or after the third forward gear step output O3 and before the second forward gear step output 02 if shifting consecutively down through the gear step outputs. Accordingly, the resulting ratio lies between that of the second and third forward gear step outputs 02, O3.

The second auxiliary gear step output Oa2 is provided by the first half synchronising device 42a engaging with the idler wheel M1 and the first full synchronising device 40a engaging with the gear 3 wheel. An active torque path Tact is therefore established between the second input shaft 14 and the first output shaft 18, as shown in Figure 9.

To provide a drive input to the second input shaft 14 so as to make that input shaft the active input shaft ACT, the second clutch C2 is engaged with the rotating clutch housing 16.

The second auxiliary gear step output Oa2 would be selected after the fourth forward gear step output 04 and before the fifth forward gear step output 05 if shifting consecutively up through the gear step outputs, or after the fifth forward gear step output 05 and before the fourth forward gear step output 04 if shifting consecutively down through the gear step outputs. Accordingly, the resulting ratio lies between that of the fourth and fifth forward gear step outputs O4, O5.

It will be understood that in other embodiments of the invention (not shown) the auxiliary gear step outputs Oai, Oa2 may be arranged such that the resulting ratio lies between gear step outputs other than the ones referenced above. A dual clutch transmission according to a second embodiment of the invention is designated generally by the reference numeral 100 and is shown in Figure 10.

The second dual clutch transmission 100 includes identical features to the first dual clutch transmission 10 and such like features share the same reference numerals.

The second dual clutch transmission 100 differs from the first dual clutch transmission 10 in that the fourth forward gearwheel set 28 is the outermost forward gearwheel set on one side of the second dual clutch transmission 100.

In particular, the second half synchronising device 42b is positioned between the gear 5 wheel and the gear 4 wheel. This is instead of the second half synchronising device 42b being positioned between the gear 5 wheel and the final gearwheel pinion 36 as it is in the first dual clutch transmission 10 arrangement.

As such, the order of the forward gearwheel sets from left to right of the second dual clutch transmission 100 shown in Figure 10 is: the third forward gearwheel set 26, the second forward gearwheel set 24, the first forward gearwheel set 22 and the fourth forward gearwheel set 28.

Operation of the second dual clutch transmission 100 is identical to that of the first dual clutch transmission 10. A dual clutch transmission according to a third embodiment of the invention is designated generally by the reference numeral 200 and is shown in Figure 11.

The third dual clutch transmission 200 includes identical features to the first dual clutch transmission 10 and such like features share the same reference numerals.

The third dual clutch transmission 200 differs from the first dual clutch transmission 10 in that the second half synchronising device 42b is positioned between the gear 5 wheel and the gear 4 wheel such that the fourth forward gearwheel set 28 is the outermost forward gearwheel set on one side of the third dual clutch transmission 200, i.e. in an identical manner to that of the second dual clutch transmission 100.

The third dual clutch transmission 200 further differs from the first dual clutch transmission 10 in that it requires only three fork actuators to move each of the synchronising devices 40a, 40b, 42a, 42b between the neutral position and the engaged position.

More specifically, two synchronising devices share a fork actuator. In the embodiment shown at Figure 11, the first and second half synchronising devices 42a, 42b share the same fork actuator since they are both configured to selectively engage only one loose wheel 32a, 32 to a corresponding shaft 18,20 in opposite directions to one another. Further details of the arrangement of the first half synchronising device 42a are outlined below.

In the third dual clutch transmission 200, the first half synchronising device 42a is disposed on the first output shaft 18 and is positioned between the gear 3 wheel and the final gearwheel pinion 36. The first half synchronising device 42a is configured to selectively engage the gear 3 wheel (instead of the idler wheel M1 in the first dual clutch transmission 10).

Moreover, the first full synchronising device 40a is disposed on the idler shaft 38 and is configured to alternatively selectively engage the reverse gearwheel R and the idler wheel M1.

As such, the first half synchronising device 42a is configured to selectively engage the idler shaft 38 to the first output shaft 18 by virtue of the gear 3 wheel being fixed to the idler shaft 38.

The benefit of the third dual clutch transmission 200 is that a reduced number of fork actuators are required to actuate the forks which in turn position the synchronising devices 40a, 40b, 42a, 42b to achieve the desired gear step output. Therefore the size, weight and cost of the third dual clutch transmission 200 is reduced.

The third dual clutch transmission 200 is operated to shift up through the forward gear steps in a similar manner to that described in relation to the first dual clutch transmission 10.

Operation of the third dual clutch transmission 200 to shift up through the forward gear steps differs from that of the first dual clutch transmission 10 in the following manner: • The available and active torque paths Tact for generation of the first forward gear step output Oi are provided by the first full synchronising device 40a engaging with the idler wheel M1 and the second full synchronising device 40b engaging with the gear 2 wheel; • The first full synchronising 40a is disengaged from the idler wheel M1 any time after the first clutch C1 is disengaged from the rotating clutch housing 16 when the second gear step output O2 is being produced; • The available and active torque paths Tact for generation of the third forward gear step output O3 are provided by the first half synchronising device 42a engaging with the gear 3 wheel; • The first half synchronising device 42a is disengaged from the gear 3 wheel any time after the first clutch C1 is disengaged from the rotating clutch housing 16 when the fourth gear step output O4 is being produced; • The same fork actuator that disengages the first half synchronising device 42a from the gear 3 wheel when the fourth gear step output O4 is being produced then actuates the engagement of the second half synchronising device 42b to the gear 5 wheel so as to provide the available torque path for generation of the fifth forward gear step output O5; and • The available and active torque paths Tact for generation of the sixth forward gear step output Oeare provided by the first full synchronising device 40a engaging with the idler wheel M1 and the second half synchronising device 42b engaging with the gear 5 wheel.

The third dual clutch transmission 200 is operated to shift down through the forward gear steps in a similar manner to that described in relation to the first dual clutch transmission 10.

Operation of the third dual clutch transmission 200 to shift down through the forward gear steps differs from that of the first dual clutch transmission 10 in the following manner: • As above, the active torque path Tact for generation of the sixth forward gear step output Oe is provided by the first full synchronising device 40a engaging with the idler wheel M1 and the second half synchronising device 42b engaging with the gear 5 wheel; • The first full synchronising device 40a is disengaged from the idler wheel M1 any time after the second clutch C2 is disengaged from the rotating clutch housing 16 when the fifth gear step output Os is being produced; • The available and active torque paths Tact for generation of the third forward gear step output 03 are provided by the first half synchronising device 42a engaging with the gear 3 wheel; • The first half synchronising device 42a is disengaged from the gear 3 wheel any time after the first clutch C1 is disengaged from the rotating clutch housing 16 when the second gear step output O2 is being produced; and • The available and active torque paths Tact for generation of the first forward gear step output O1 are provided by the first full synchronising device 40a engaging with the idler wheel M1 and the second full synchronising device 40b engaging with the gear 2 wheel.

Only one reverse gear step output (not shown) is available for the third dual clutch transmission 200. Considering the first and second clutches C1, C2 are disengaged from the rotating clutch housing 16 (i.e. the third dual clutch transmission 200 is in “Neutral”), the first full synchronising device 40a engages with the reverse gear wheel R and the first half synchronising device 42a engages with the gear 3 wheel. Such engagement creates a first reverse torque path through the third forward gearwheel set 26, through the reverse gear wheel R and through the idler shaft 38 and out to the first output shaft 18.

The second clutch C2 is then engaged with the rotating clutch housing 16 such that the second input shaft 14 receives a drive input and the reverse gear step output is generated. A dual clutch transmission assembly 300 according to a fourth embodiment of the invention is shown in Figures 12a, 12b and 12c. The dual clutch transmission assembly 300 includes either a first, second or third dual clutch transmission 10,100, 200 (only partially shown in Figures 12a, 12b and 12c) as described hereinabove and an electric motor 310 that is coupled to the dual clutch transmission 10,100, 200.

In the embodiment shown at Figure 12a, the electric motor 310 is coupled directly to the idler shaft 38 so as to provide an electric drive input to the dual clutch transmission 10, 100, 200 via the gear 3 wheel.

In other embodiments of the invention (not shown) the electric motor 310 may be coupled to the idler shaft 38 directly via another existing gear wheel, e.g. the idler wheel Ml. The electric motor 310 may instead be coupled to the idler shaft 38 via the gear 3 wheel (or the idler wheel M1) indirectly via a single intermediate gearwheel 312 (as shown in Figure 12b) or via an intermediate gearwheel pair 314 (as shown in Figure 12c).

In further embodiments of the invention (not shown) the electric motor 310 may instead be connected to either of the input shafts 12,14 and/or output shafts 18,20 via another means, for example via any other gear wheel, a synchronising device or a separate connection device.

The electric motor 310 provides an electric drive input which can be used to drive one or more forward gear step outputs Οι, O2, 03,04, O5, Oe.

An example of one such output is shown in Figure 13 wherein the electric motor 310 provides an electric drive input to produce the first forward gear step output O1 via an active torque path Tact.

The electric motor 310 can also be used in combination with the engine so that the fourth dual clutch transmission 300 can be operated by a hybrid drive input.

Claims (24)

CLAIMS:

1. A dual clutch transmission for a motor vehicle comprising: first and second input shafts selectively cooperable with a corresponding clutch whereby one input shaft receives a drive input to become an active input shaft while the other input shaft is an inactive input shaft and the drive input is switchable between the input shafts; and first and second output shafts selectively engageable with the first and second input shafts via four forward gearwheel sets, each forward gearwheel set including a gearwheel mounted as a fixed wheel and at least one gearwheel mounted as a selectively engageable and disengageable loose wheel, the input shafts, output shafts and the four forward gearwheel sets combining to sequentially provide first, second, third, fourth, fifth and sixth forward gear steps, the forward gearwheel sets establishing for each of the six forward gear steps an active torque path between the active input shaft and an output shaft to generate a corresponding current forward gear step output and an available torque path between the inactive input shaft and an output shaft to permit the generation of a corresponding next forward gear step output, and the output for each of the first, second, third, fourth, fifth and sixth forward gear steps shifting from the current forward gear step output to a next forward gear step output when the drive input switches from the active input shaft to the inactive input shaft.

2. A dual clutch transmission according to Claim 1 wherein the forward gearwheel sets simultaneously establish active and available torque paths for each of the first, second, third, fourth, fifth and sixth forward gear steps.

3. A dual clutch transmission according to Claim 1 or Claim 2 wherein a first forward gearwheel set includes first and second loose wheels.

4. A dual clutch transmission according to Claim 3 wherein the first loose wheel mutually intermeshes with the fixed wheel of the first gearwheel set.

5. A dual clutch transmission according to Claim 4 wherein the first loose wheel is selectively engageable with a corresponding input shaft or output shaft to establish a first direct forward gear step.

6. A dual clutch transmission according to Claim 5 wherein the first direct forward gear step corresponds to the third forward gear step.

7. A dual clutch transmission according to any of Claims 3 to 6 wherein the second loose wheel mutually intermeshes with a gearwheel of a second forward gearwheel set.

8. A dual clutch transmission according to Claim 7 wherein the second forward gearwheel set selectively establishes the fourth forward gear step.

9. A dual clutch transmission according to any of Claims 3 to 8 wherein the second loose wheel is selectively engageable with the first loose wheel to modify a direct forward gear step and thereby provide an indirect forward gear step.

10. A dual clutch transmission according to Claim 9 wherein the second loose wheel when selectively engaged with the first loose wheel modifies the direct forward gear step selectively established by another forward gearwheel set to provide a first indirect forward gear step.

11. A dual clutch transmission according to Claim 10 wherein the second loose wheel when selectively engaged with the first loose wheel modifies a direct forward gear step selectively established by a third forward gearwheel set to provide the first indirect forward gear step.

12. A dual clutch transmission according to Claim 10 or Claim 11 wherein the first indirect forward gear step corresponds to the first forward gear step.

13. A dual clutch transmission according to Claim 9 wherein the second loose wheel when selectively engaged with the first loose wheel modifies a direct forward gear step selectively established by another forward gearwheel set to provide a second indirect forward gear step.

14. A dual clutch transmission according to Claim 13 wherein the second loose wheel when selectively engaged with the first loose wheel modifies a direct forward gear step selectively established by a fourth forward gearwheel set to provide the second indirect forward gear step.

15. A dual clutch transmission according to Claim 14 wherein the second indirect forward gear step corresponds to the sixth forward gear step.

16. A dual clutch transmission according to any preceding claim wherein gearwheels for the third and fifth forward gear steps are disposed on the first input shaft.

17. A dual clutch transmission according to Claim 16 wherein the gearwheels disposed on the first input shaft are fixed wheels.

18. A dual clutch transmission according to any preceding claim wherein a gearwheel for the third forward gear step is disposed on the first output shaft.

19. A dual clutch transmission according to Claim 18 wherein the gearwheel disposed on the first output shaft is a loose wheel.

20. A dual clutch transmission according to any preceding claim wherein gearwheels for the second and fourth forward gear steps are disposed on the second input shaft.

21. A dual clutch transmission according to Claim 20 wherein the gearwheels disposed on the second input shaft are fixed wheels.

22. A dual clutch transmission according to any preceding claim wherein gearwheels for the second, fourth and fifth forward gear steps are disposed on the second output shaft.

23. A dual clutch transmission according to Claim 22 wherein the gearwheels disposed on the second output shaft are loose wheels.

24. A dual clutch transmission generally as described herein with reference to and/or as illustrated in the accompanying drawings.