Double clutch transmission having a layshaft design

A double clutch transmission of countershaft design having a central shaft and a concentric hollow transmission shaft, one countershaft, and two power-shift elements. Two hollow shafts are disposed on the countershaft coaxially to the countershaft, each of which can be fixed, via one shift device, to the countershaft, and to which at least two gearwheels are fixed. A further hollow shaft is coaxially provided on either the central or hollow transmission shafts and can be connected, via a shift device, to the central or hollow transmission shaft, and to which at least two further gearwheels of the gear stages are fixed. At least three transmission ratios are possible by engaging three of the gear stages on the shift-element side into the power flow, thereby enabling one transmission ratio to be at least partially implemented by a respective sole engagement on the shift-element side into the power flow.

This application is a National Stage completion of PCT/EP2011/063334 filed Aug. 3, 2011, which claims priority from German patent application serial no. 10 2010 040 660.0 filed Sep. 13, 2010.

FIELD OF THE INVENTION

The invention relates to a double clutch transmission having a countershaft design.

BACKGROUND OF THE INVENTION

A double clutch transmission having a countershaft design for implementing various transmission ratios for forward driving and travel in reverse, known from practical applications, is equipped with a central transmission shaft, a hollow transmission shaft disposed concentrically thereto, a countershaft, and two power-shift elements. Both of the power-shift elements are operatively connected on the input side to a drive assembly. One of the two power-shift elements is connected on the output side to the central transmission shaft, while the other of the two power-shift elements is connected on the output side to the hollow transmission shaft. The central transmission shaft and the hollow transmission shaft can be connected to the countershaft in order to implement a transmission ratio via gear stages that can be engaged into and disengaged from the power flow via shift devices. In addition, two gear stages are assigned to each of a plurality of shift devices.

A double clutch transmission comprising a double clutch, the input side of which can be driven by a drive shaft of a drive motor, and the output sides of which each have a drive connection to one of two coaxially disposed transmission input shafts, is known from DE 10 2005 005 163 A1. The double clutch transmission comprises an intermediate shaft, or exactly one countershaft, and has fixed gears and idler gears, which are fastened or rotatably supported on shafts, and shifting groups assigned to the idler gears. The idler gears can be connected to the particular dedicated shaft in a rotationally fixed manner via the shifting groups in order to implement transmission ratios or transmission ratio steps. The shifting groups are each assigned to two speeds, which are not in direct succession.

However, only seven transmission ratios for forward travel can be implemented using the two double clutch transmissions described above, thereby preventing drive motors, in particular internal combustion engines, that can be coupled to the double clutch transmissions, from being operated to the desired extent in the optimum operating range thereof in respect, in particular, to the available tractive force and low fuel consumption, across a large operating range of the drive motors.

Document DE 10 2007 049 271 A1 describes a double clutch transmission comprising at least two countershafts, in order to implement a plurality of transmission ratios for forward travel and travel in reverse.

Since the double clutch transmission is designed with two countershafts, a larger radial construction space is required therefore, as compared to double clutch transmissions comprising one countershaft; the larger radial construction space is not available to the necessary extent in various vehicle systems.

SUMMARY OF THE INVENTION

Therefore, the problem addressed by the present invention is that of providing a double clutch transmission having a countershaft design, which requires little construction space in the radial direction and in the axial direction, and by way of which more than seven transmission ratios for forward travel can be implemented.

The double clutch transmission having a countershaft design according to the invention is equipped with a central transmission shaft, a hollow transmission shaft disposed concentrically thereto, exactly one countershaft, and two power-shift elements. Both of the power-shift elements, as start-up elements of the double clutch transmission, can be operatively connected on the drive side to a drive assembly. One of the two power-shift elements is connected on the output side to the central transmission shaft, while the other of the two power-shift elements is connected on the output side to the hollow transmission shaft. Therefore, a speed of rotation of the drive assembly can be transferred either to the central transmission shaft or to the hollow transmission shaft via selective engagement of the two power-shift elements. The central transmission shaft and the hollow transmission shaft can be connected to the countershaft in order to implement a transmission ratio via gear stages that can be engaged into and disengaged from the power flow via shift devices. In addition, at least two gear stages are assigned to each of a plurality of shift devices.

According to the invention, two hollow shafts are disposed on the countershaft coaxially thereto, each of which can be coupled in a rotationally fixed manner via one of the shift devices to the countershaft, and to which at least two gearwheels of the gear stages are connected in a rotationally fixed manner. A further hollow shaft is provided on the central transmission shaft or the hollow transmission shaft, being disposed coaxially thereto, the further hollow shaft being connectable via one of the shift devices to the central transmission shaft or the hollow transmission shaft, and to which at least two further gearwheels of the gear stages are connected in a rotationally fixed manner. At least three transmission ratios can be implemented by engaging three of the gear stages in each case on the shift-element side into the power flow, thereby enabling one transmission ratio to be at least partially implemented in each case by the respective sole engagement on the shift-element side into the power flow.

The embodiment of the double clutch transmission according to the invention comprising exactly one countershaft and a hollow shaft disposed on the central transmission shaft or the hollow transmission shaft, and the further hollow shafts provided on the countershaft, in combination with the provision of at least three transmission ratios as so-called winding path gears, makes it possible to implement a multiplicity of transmission ratios, preferably at least nine transmission ratio steps for forward travel, with a minimum requirement on radial and axial construction space and a low overall weight of the double clutch transmission, and makes it possible to operate a drive motor, preferably an internal combustion engine, to the desired extent in the optimum operating range thereof.

Moreover, due to the multiple uses of the shift devices, the transmission ratios can be implemented using a low number of actuators for actuating the shift devices, thereby also making it possible to produce the double clutch transmission at low cost.

In addition, due to the embodiment of the double clutch transmission according to the invention, the double clutch transmission is characterized by good power-shiftability and can be combined with an electric machine in a structurally simple manner.

In a further embodiment of the double clutch transmission according to the invention that is favorable in terms of construction space, the central transmission shaft or the hollow transmission shaft is designed in sections, and a first transmission subshaft of the central transmission shaft or the hollow transmission shaft can be coupled via one of the shift devices to a second transmission subshaft of the central transmission shaft or the hollow transmission shaft, and one of the transmission subshafts is connected to one of the two shift-element halves of the power-shift elements, wherein three of the gear stages can be coupled or are coupled to the other transmission subshaft via one of the shift devices, and an additional gear stage can be coupled to the other transmission subshaft via one of the shift devices.

In an alternative embodiment of the double clutch transmission according to the invention that is also favorable in terms of construction space, a further hollow shaft is disposed on the central transmission shaft or the hollow transmission shaft, which can be coupled to either one thereof by means of one of the shift devices, and to which three of the gear stages are connected, while a further gear stage can be connected or is connected to the central transmission shaft or the hollow transmission shaft via one of the shift devices, and an additional gear stage can be coupled to the central transmission shaft or the hollow transmission shaft via one of the shift devices.

In another alternative embodiment of the double clutch transmission having a countershaft design according to the invention, which comprises a central transmission shaft having a hollow transmission shaft disposed concentrically thereto, exactly one countershaft, and two power-shift elements, it is possible for both of the power-shift elements, as start-up elements of the double clutch transmission, to be operatively connected on the drive side to a drive assembly. One of the two power-shift elements is connected on the output side to the central transmission shaft, while the other of the two power-shift elements is connected on the output side to the hollow transmission shaft. Therefore, a speed of rotation of the drive assembly can be transferred either to the central transmission shaft or to the hollow transmission shaft via selective engagement of the power-shift elements. The central transmission shaft and the hollow transmission shaft can be connected to the countershaft in order to implement a transmission ratio via gear stages that can be engaged into and disengaged from the power flow via shift devices. In addition, at least two gear stages are assigned to each of a plurality of shift devices.

According to the invention, at least nine transmission ratios for forward travel can be implemented in a manner that is favorable in terms of construction space by means of engaging and disengaging the gear stages.

If at least three transmission ratios can be implemented by engaging three gear stages in each case on the shift-element side into the power flow, thereby enabling one transmission ratio to be at least partially implemented in each case by the respective sole engagement into the power flow on the shift-element side, then, in an advantageous embodiment of the double clutch transmission according to the invention, gear stages for implementing various transmission ratios are used multiple times, thereby resulting in a double clutch transmission that requires little construction space.

Further embodiments of the double clutch transmission according to the invention that are favorable in terms of construction space are designed with five shift devices, via each of which at least two gear stages can be engaged into the power flow, and/or comprise eight gear-set planes, each of which features spur-gear stages having discrete transmission ratios.

The features mentioned in the following example embodiments of the double clutch transmission according to the invention are suitable for developing the subject matter of the invention by themselves or in any combination with each other. The combinations of a given set of features do not limit the development of the subject matter of the invention and are merely substantially representative in nature.

Additional advantages and advantageous embodiments of the double clutch transmission according to the invention are set forth in the example embodiments, the principle of which is described with reference to the drawings; for the sake of clarity, the same reference characters are used for components having the same design and function in the description of the different example embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows two alternative example embodiments of a double clutch transmission1having a countershaft design; the example embodiments basically have the same design, and so the design of the double clutch transmission1will be described first by reference to the first embodiment, and then the differences between the two embodiments will be discussed in greater detail.

The double clutch transmission1comprises17gearwheels, one central transmission shaft2and a hollow transmission shaft disposed concentrically thereto, exactly one countershaft4, and two power-shift elements K1, K2, which are embodied as friction-locking multi-disk clutches in the present case. The two power-shift elements K1and K2are the start-up elements of the double clutch transmission. In the installed state of the double clutch transmission, input elements, which are labeled “5”, of the power-shift elements K1, K2are connected or operatively connected to a drive assembly, which is not shown in greater detail in the drawing, of an internal combustion engine of a vehicle drive train, for example. An output element, which is labeled “6”, of the power-shift element K1is connected to the hollow transmission shaft3, while an output element, which is labeled “7”, of the power-shift element K2is coupled in a rotationally fixed manner to the central transmission shaft2. The structural embodiment of the two power-shift elements K1, K2depicted in the drawing is intended to be an example and is at the discretion of a person skilled in the art. Therefore, the two driven input elements5of the power-shift elements K1, K2are designed in this case, as an example, as a shared outer disk carrier for both power-shift elements K1, K2, and the two output elements6,7of the power-shift elements K1, K2are each correspondingly designed as inner disk carriers.

In the present case, the central transmission shaft2has a divided design, wherein a first transmission subshaft2A of the central transmission shaft2can be connected to a second transmission subshaft2B of the central transmission shaft via one shift device SE4of a total of five shift devices SE1to SE5of the double clutch transmission. The first transmission subshaft2A is connected to the second shift-element half6of the first power-shift element K1.

The central transmission shaft2or the transmission subshafts2A,2B thereof, and the hollow transmission shaft3, can be connected to the countershaft4in order to implement nine transmission ratios “1” to “9” for forward travel and one transmission ratio “R” for travel in reverse, the transmission ratios being described in greater detail with reference toFIG. 2, via exactly eight gear stages ZP2, ZP3, ZP4, ZP5, ZP6, ZP7, ZP9and ZPR, which can be engaged into and disengaged from the power flow of the double clutch transmission via exactly five shift devices SE1to SE5. The eight gear stages ZP2to ZPR form exactly eight gear stage planes, which are disposed next to one another in the axial direction. At least two gear stages ZP6and ZP2, ZP2and ZP4, ZP7and ZP5, ZP5and ZP9, as well as ZP3and ZPR are assigned to the five shift devices SE1to SE5, respectively.

In the present case, the shift devices SE1to SE5are embodied as so-called double synchronizations and comprise two shift elements S1and S2, S3and S4, S5and S6, S7and S8, S9and S10, respectively, via which at least one of the gear stages ZP2to ZPR can be coupled to the central transmission shaft2or the first transmission subshaft2A thereof, to the hollow transmission shaft3, or to the countershaft4, and in the region of which rotational speed differentials can be compensated for or reduced to a certain extent.

A hollow shaft8A is provided on the countershaft4, being disposed coaxially thereto, which can be connected in a rotationally fixed manner via the shift element S2of the shift device SE1to the countershaft4, and to which, in the present case, a gearwheel21of the gear stage ZP2and a gearwheel41of the gear stage ZP4, with which a gearwheel42disposed on the hollow transmission shaft3meshes, are connected in a rotationally fixed manner. Furthermore, in the present case, another hollow shaft9A is provided, which is disposed on the hollow transmission shaft3coaxially thereto, and which can be connected in a rotationally fixed manner via the shift element S3of the shift device SE2to the hollow transmission shaft3, and to which another gearwheel22of the gear stage ZP2and a gearwheel61of the gear stage ZP6, which is engaged with a gearwheel62designed as an idler gear and rotatably disposed on the countershaft4, are connected in a rotationally fixed manner.

Alternatively to the above-described embodiment of the double clutch transmission1comprising five shift devices SE1to SE5, each of which has two shift elements S1and S2, S3and S4, S5and S6, S7and S8, S9and S10, respectively, it is also possible to design one or more of the shift devices SE1to SE5as separate shift devices, in which case more than five actuators must be provided in order to actuate the individual shift elements S1to S10.

In addition, a second hollow shaft8B is provided on the countershaft4, being disposed coaxially thereto, which can be connected to the countershaft4in a rotationally fixed manner via the shift device SE3or the shift element S6thereof, and to which a gearwheel51of the gear stage ZP5and a gearwheel91of the gear stage ZP9are coupled in a rotationally fixed manner in the present case.

Moreover, another hollow shaft9B is rotatably disposed on the first transmission subshaft2A of the central transmission shaft2, wherein the hollow shaft can be coupled in a rotationally fixed manner to the first transmission subshaft2A via the shift element S7of the shift device SE4, and to which a gearwheel71of the gear stage ZP7, which is engaged with a gearwheel72that is designed as an idler gear and is rotatably disposed on the countershaft4, and another gearwheel52of the gear stage ZP5are connected in a rotationally fixed manner.

By means of the two power-shift elements K1and K2, a torque of a drive assembly present in the region of the input elements5can be selectively transferred to the first transmission subshaft2A of the central transmission shaft2or to the hollow transmission shaft3. In order to implement the various transmission ratios “1” to “R”, the gear stages ZP2to ZPR are engaged into or disengaged from the power flow of the double clutch transmission1via the shift devices SE1to SE5or the shift elements S1to S10thereof in the manner described in greater detail in the following.

In order to change a transmission ratio without interruption of tractive force in the region of the two power-shift elements K1and K2, the target transmission ratio to be implemented at the moment is preselected in the region of a subtransmission10or11, which is presently in the load-free operating state, by disengaging and engaging the applicable shift elements S1to S10accordingly and then transferring the currently engaged power-shift element K1or K2to a disengaged operating state, while the currently disengaged power-shift element K2or K1is transferred to the engaged operating state thereof during an overlapping shift.

The transmission ratios “2” to “7” and the transmission ratio “9” for forward travel can be implemented in the double clutch transmission1by the sole engagement, on the shift-element side, of the gear pairings ZP2, ZP3, ZP4, ZP5, ZP6, ZP7or ZP9, respectively

The first transmission ratio “1” for forward travel can be implemented by simultaneously engaging the three gear stages ZP5, ZP9and ZP3on the shift-element side into the power flow of the double clutch transmission1, and is therefore a so-called winding path gear. Furthermore, the eighth transmission ratio “8” for forward travel is implemented by simultaneously engaging the three shift stages ZP4, ZP2and ZP6on the shift-element side in the double clutch transmission1, while the transmission ratio “R” for travel in reverse is implemented by simultaneously engaging the three gear stages ZP5, ZP9and ZPR on the shift-element side in the double clutch transmission1. Therefore, the eighth transmission ratio “8” for forward travel and the transmission ratio “R” for travel in reverse are so-called winding path gears.

The two gear stages ZP5and ZP9are engaged into the power flow in order to implement the two transmission ratios “1” and “R”, respectively, while the gear stage ZP3or the gear stage ZPR are additionally engaged in order to implement the transmission ratios “1” and “R”, respectively.

The four gear stages ZP6, ZP7, ZP3and ZPR can be operatively connected to the countershaft4via the shift element S1, S5, S9or S10, respectively. In addition, the gear stages ZP6and ZP2, via which the sixth transmission ratio “6” or the second transmission ratio “2” for forward travel can be implemented, can be coupled to the hollow transmission shaft3via the shift element S3in the present case.

In addition to the two gearwheels61and22, which are connected in a rotationally fixed manner to the hollow shaft9A in the present case, the further gearwheel42of the gear stage ZP4can be operatively connected in a rotationally fixed manner to the hollow transmission shaft3via the shift element S4of the shift device SE2. In addition to the two gearwheels71and52of the gear stages ZP7and ZP5, which are connected in a rotationally fixed manner to the further hollow shaft9B, it is also possible to couple a gearwheel92of the gear stage ZP9, a gearwheel31of the gear stage ZP3, and a gearwheel12of the gear stage ZPR, each of which is connected in a rotationally fixed manner to the second transmission subshaft2B of the central transmission shaft2, to the first transmission subshaft2A in a rotationally fixed manner via the shift element S8of the shift device SE4. Another gearwheel13of the gear stage ZPR can be connected in a rotationally fixed manner to the countershaft4via the shift element S10of the shift device SE5, wherein the two gearwheels12and13of the gear stage ZPR are each engaged with an intermediate gear14, thereby making it possible to change the direction of rotation in the double clutch transmission1in the region of the gear stage ZPR, which is required in order to operate the vehicle in reverse.

In addition, a gearwheel32of the gear stage ZP3, which is designed as an idler gear, can be operatively connected in a rotationally fixed manner to the countershaft4via the shift element S9of the shift device SE5. The further gearwheel72of the gear stage ZP7is also connected in a rotationally fixed manner to the countershaft4in the engaged operating state of the shift element S7of the shift device SE3.

The shift elements S1to S10of the shift devices SE1to SE5are actuated according to the shift logic, which is depicted in greater detail inFIG. 2, in order to implement the transmission ratios “1” to “9” for forward travel, and to implement the transmission ratio “R” for travel in reverse, wherein each of the shift elements51to S10is engaged or held in the engaged operating state in order to implement one of the transmission ratios “1” to “R”, the cells of which are filled with the letter “X”, while the other shift elements S1to S10, the cells of which are blank, are transferred to the disengaged operating state thereof or are retained in the disengaged operating state. At the same time, the power-shift element K1or K2, which is marked by the letter “X”, is transferred to the engaged operating state, while the other power-shift element K2or K1, the cell of which is blank, is disengaged.

In the aforementioned second embodiment of the double clutch transmission1according toFIG. 1, the two gear stages ZP2and ZP6are reversed in the axial extension of the central transmission shaft2relative to the above-described configuration in which the gear stage ZP6is disposed between the gear stage ZP2and the two power-shift elements K1, K2, and so the gear stage ZP2is positioned between the gear stage ZP6and the power-shift elements K1and K2.

In the second embodiment of the double clutch transmission1according toFIG. 1, the shift elements S1to S10are actuated in a manner analogous to the shift logic depicted in greater detail inFIG. 3in order to implement the transmission ratios “1” to “9” for forward travel and to implement the transmission ratio “R” for travel in reverse. Due to the reversed configuration of the gear stages ZP2and ZP6, instead of the transmission ratio step “8”, the transmission ratio step “4”, in addition to the two other transmission ratios “1” and “R”, is embodied as a winding path gear, and the transmission ratio step ZP4of the first embodiment is replaced by the transmission ratio step ZP8, which is then engaged solely into the power flow of the double clutch transmission1in order to implement the eighth transmission ratio “8”.

The two gear set variants of the double clutch transmission1depicted inFIG. 1can be changed while retaining the same function via a different positioning of the gear stages ZP2to ZPR with respect to one another, and of the shift devices SE1to SE5and the shift elements S1to S10thereof, as described in greater detail in the following, wherein the shift elements S1to S10, which are preferably designed as synchronizations, are fixedly assigned to the gear stages ZP2to ZPR according to the tables shown inFIG. 4, which relates to the first embodiment of the double clutch transmission1according toFIG. 1, and inFIG. 5, which relates to the second embodiment of the double clutch transmission1according toFIG. 1. Due to this fixed assignment, the particular shift matrix shown inFIG. 2andFIG. 3does not change if the gear stages ZP2to ZPR, which are designed as spur-gear stages in the present case, are positioned in a manner that differs from the configuration of gear stages ZP2to ZPR depicted inFIG. 1.

According to the assignment shown inFIG. 4, the shift element S1is assigned to gear stage ZP6, the shift element S2is assigned to gear stage ZP2, the shift element S3is assigned to gear stage ZP2, the shift element S4is assigned to gear stage ZP4, the shift element S5is assigned to gear stage ZP7, the shift element S6is assigned to gear stage ZP5, the shift element S7is assigned to gear stage ZP5, the shift element S8is assigned to gear stage ZP9, the shift element S9is assigned to gear stage ZP3and the shift element S10is assigned to gear stage ZPR.

In deviating therefrom, in the second gear set variant of the double clutch transmission1according toFIG. 1, in which the gear stages ZP2and ZP6are disposed in a reversed configuration compared to the first gear set variant, the shift elements S1to S10are assigned to the gear stages ZP2to ZPR as follows. The shift element S1is assigned to the gear stage ZP2, the shift element S2is assigned to the gear stage ZP6, the shift element S3is assigned to the gear stage ZP6, the shift element S4is assigned to the gear stage ZP8, the shift element S5is assigned to the gear stage ZP7, the shift element S6is assigned to the gear stage ZP5, the shift element S7is assigned to the gear stage ZP5, the shift element S8is assigned to the gear stage ZP9, the shift element S9is assigned to the gear stage ZP3, and the shift element S10is assigned to the gear stage ZPR.

In the first gear set variant and in the second gear set variant of the double clutch transmission1according toFIG. 1, the gear stages ZP2and ZP6, and the gear stage ZP4or the gear stage ZP8are assigned to the first subtransmission10and are disposed between the power-shift elements K1and K2and the gear stages ZP7, ZP5, ZP9, ZP3and ZPR, which are assigned to the second subtransmission11. In an embodiment of the double clutch transmission1that deviates therefrom, the gear stages ZP7, ZP5, ZP9, ZP3and ZPR of the second subtransmission11are disposed between the power-shift elements K1and K2and the gear stages ZP2, ZP6and ZP4or ZP8of the first subtransmission, wherein, in the variant embodiment that deviates fromFIG. 1, the two subtransmissions10and11are reversed by reflecting the double clutch transmission1along a line L1shown in greater detail inFIG. 1.

Alternatively to the latter-described variant embodiment of the gear stages ZP2to ZPR or, cumulatively therewith, the gear stages ZP2, ZP3, ZP4or ZP8, ZP5, ZP6, ZP7and ZPR can exchange positions with one another or can be disposed at various axial positions in the double clutch transmission1in the axial extension of the main central transmission shaft2of the double clutch transmission1in the manner described in greater detail by reference toFIG. 1andFIG. 6andFIG. 7, without changing the functionality of the double clutch transmission1, which is described in greater detail by reference toFIG. 1. In addition, in deviating from the variant embodiment shown inFIG. 1, the gear stages ZP3and ZPR can be disposed in a manner reflected along a line L2shown in greater detail inFIG. 7, thereby making it possible to engage the gear stages ZP3and ZPR by coupling the gear stages ZP3and ZPR to the countershaft4, the central transmission shaft2, or the hollow transmission shaft3, depending on the particular variant embodiment.

The gear stages ZP3and ZPR can be engaged into the power flow via the shared shift device SE5, wherein the gear stage ZP3is disposed, in the axial extension of the central transmission shaft2and relative to the assigned shift device SE5, on a side of the shift device SE5facing the power-shift elements K1and K2, and the gear stage ZPR is disposed on a side of the shift device SE5facing away from the power-shift elements K1and K2.

Alternatively, the gear stage ZPR can be disposed on the side of the shift device SE5facing the power-shift elements K1and K2, and the gear stage ZP3can be disposed on the side of the shift device SE5facing away from the power-shift elements K1and K2.

In deviating from the embodiment of the double clutch transmission1depicted in the drawing, in which the hollow shaft9B is disposed on the central transmission shaft2or the first transmission subshaft2A, it is also possible to design the double clutch transmission1without the hollow shaft9B, in which case the gearwheel71of gear stage ZP7is designed as a fixed gear and is connected in a rotationally fixed manner to the central transmission shaft2or the first transmission subshaft2A. The gearwheel52of the gear stage ZP5is furthermore disposed as an idler gear on the central transmission shaft2or the first transmission subshaft2A and can be coupled in a rotationally fixed manner to the first transmission subshaft2A via the shift element S7.

The gear stage ZP7is provided between the gear stage ZP5and the power-shift elements K1and K2in the manner depicted inFIG. 1,FIG. 6, andFIG. 7, wherein the gear stage ZP5is positioned in the axial extension of the central transmission shaft2on the side of the shift device SE4facing the power-shift elements K1and K2.

If the gearwheel71of the gear stage ZP7is designed as a fixed gear and the double clutch transmission1is designed without the hollow shaft9B, it is possible to dispose the gear stage ZP3, which is disposed in the middle between the gear stages ZP9and ZPR relative to the axial extension of the central transmission shaft2, at the position of the gear stage ZP5, in which case the gear stage ZP5is disposed at the position of the central gear stage ZP3.

In turn, as an alternative or cumulatively therewith, the outer gear stage ZPR, which is disposed on the side of the central gear stage ZP3facing away from the power-shift elements K1and K2relative to the axial extension of the central transmission shaft2, can be disposed at the position of the gear stage ZP7, while the gear stage ZP7is then provided at the position of the outer gear stage ZPR. The latter-described reversal of the gear stages ZP7and ZPR can only be implemented when the gearwheel71of the gear stage ZP7is disposed as a fixed gear on the central transmission shaft2or the first transmission subshaft2A and the double clutch transmission1is designed without the hollow shaft9B.

In turn, as an alternative to the above-described positioning of the gear stages ZP2to ZPR of the double clutch transmission1, or cumulatively therewith, it is also possible to dispose the gear stage ZP7between the central gear stage ZP3and the outer gear stage ZP9, which is disposed on the side of the gear stage ZP3facing the power-shift elements K1and K2in the axial extension of the central transmission shaft2, wherein this configuration substantially corresponds to a mirror image of the region B1, which is shown in greater detail inFIG. 7, along a line L3, which is shown in greater detail inFIG. 7. By reflecting the region B1about the line L3, the shift device SE3is also moved from the position between the gear stages ZP9and ZP7depicted inFIG. 7and is then disposed on the side of the gear stage ZP9facing away from the power-shift elements K1and K2.

In turn, as an alternative to or cumulatively with respect to the above-described variant embodiments of the gear stages ZP2to ZPR of the double clutch transmission1, it is also possible to reflect the subtransmission2A at another line L4shown inFIG. 6, in which case the gear stage ZP4or ZP8is disposed between the power-shift elements K1and K2and the gear stages ZP2and ZP6, while the shift device SE2is provided on the side of the gear stage ZP2or ZP6facing the power-shift elements K1and K2, and the shift device SE1is disposed in the axial extension of the central transmission shaft2on the side of the power-shift elements K1and K2facing away from the gear stage ZP2or ZP6.

Combining the various above-described variant embodiments of the gear stages ZP2to ZPR with one another results in128functionally identical variants of the double clutch transmission1.

Depending on the variant embodiment of the gear stages ZP2to ZPR of the double clutch transmission1that is implemented, the hollow shaft9A is disposed either directly on the central transmission shaft2or on the hollow transmission shaft3, as shown in the drawing. Furthermore, the hollow shaft9B is provided either on the central transmission shaft2or on the hollow transmission shaft6, depending on the variant embodiment of the gear stages ZP2to ZPR that is implemented.

The gear stages ZP6, ZP2and ZP4or ZP8can be coupled to the central transmission shaft2or the hollow transmission shaft3, and to the countershaft4via the shift elements S1to S4of the shift devices SE1and SE2, depending on which variant embodiment of the gear stages ZP2to ZPR of the double clutch transmission1is selected.

Furthermore, depending on which variant embodiment of the gear stages ZP2to ZPR is selected, the gear stages ZP7, ZP5, ZP9, ZP3and ZPR are assigned either to the central transmission shaft2, to the two transmission subshafts2A and2B, or to the hollow transmission shaft3.

If the two subtransmissions10and11are reversed with respect to the configuration shown inFIG. 1, i.e. if the subtransmission11is located between the power-shift elements K1and K2and the subtransmission10, the hollow transmission shaft has a sectional design and a first transmission subshaft of the hollow transmission shaft can be coupled to a second transmission subshaft of the hollow transmission shaft via the shift device SE4, and one of the transmission subshafts is connected to one of the output sides of the power-shift elements. In addition, the three gear stages ZP9, ZP3and ZPR are then coupled in a rotationally fixed manner to one transmission subshaft of the hollow transmission shaft, and the gear stage ZP7can be coupled together with the gear stage ZP5via the shift device SE4to the other transmission subshaft, or the gear stage ZP7is connected in a rotationally fixed manner in the region of the gearwheel71thereof, which is designed as a fixed gear, to the transmission subshaft of the hollow transmission shaft.

Alternatively to the sectional design of the central transmission shaft2or the hollow transmission shaft3, it is also possible to design the central transmission shaft or the hollow transmission shaft to be continuous and to dispose another hollow shaft on the central transmission shaft or the hollow transmission shaft such that the hollow shaft can be coupled to the central transmission shaft or the hollow transmission shaft via the shift device SE4, wherein the three gear stages ZP9, ZP3and ZPR are connected in a rotationally fixed manner to the hollow shaft, while the gear stage ZP7can be connected to the central transmission shaft2or the hollow transmission shaft3via the shift element S7of the shift device SE4. In an embodiment of the double clutch transmission1without the hollow shaft9B, the gear stage ZP7is connected in a rotationally fixed manner via the fixed gear71to the central transmission shaft2or the hollow transmission shaft3, while the gear stage ZP5can be coupled via the shift device SE4or the shift element S7thereof to the central transmission shaft2or the hollow transmission shaft3.

In turn, depending on the variant embodiment of the gear stages ZP2to ZPR that is implemented, the gear stage ZP6or the gear stage ZP2can be coupled via the shift element S3of the shift device SE2to the central transmission shaft2or the hollow transmission shaft3, and via the shift device SE1, to the countershaft4.

In the example embodiment of the double clutch transmission1depicted inFIG. 1, an output drive15of the double clutch transmission1is provided coaxially to the countershaft4, and the double clutch transmission1is designed with only one transmission output. The output drive15of the double clutch transmission can be coupled to at least one drivable vehicle axis via appropriate devices.

If the double clutch transmission1according toFIG. 1is part of an all-wheel vehicle drive train, a power divider device should be connected downstream of the double clutch transmission1, via which the torque transmitted from the double clutch transmission1in the region of the gear stage ZPR via the output element15can be distributed between a plurality of drivable vehicle axes.

Alternatively thereto, it is also possible to transfer the torque present at the countershaft4from the double clutch transmission1, according to the manner depicted inFIG. 6andFIG. 7, via the output drive15in the region of the gear stage ZPR and, additionally, via another output drive16in the region of the gear stage ZP6or ZP2, wherein the output drive15and the further output drive16are disposed coaxially to the countershaft4.

Alternatively to the coaxial arrangement of the output drives15and16with respect to the countershaft4, it is also possible to route the output drive15and/or the further output drive16out of the double clutch transmission1in the manner shown in addition inFIG. 6andFIG. 7with axle offset with respect to the countershaft4and/or to the central transmission shaft2, wherein the axle-offset variant of the output drive or the further output drive is indicated in greater detail by reference character151or161, respectively.

The axle offset is implemented in a structurally simple manner via an additional output drive constant gear pairing17, wherein a gearwheel18of the output drive-constant gear pairing17, which is designed as a fixed gear, is connected in a rotationally fixed manner to the countershaft4in the manner depicted inFIG. 6andFIG. 7. The gearwheel18meshes with a gearwheel19of the output drive constant gear pairing17, which is connected to the output drive151and/or the output drive161.

In an example embodiment of the double clutch transmission1shown inFIG. 6, the output drive-constant gear pairing17is provided on the side of the gear stage ZPR facing away from the gear stage ZP3in axial extension of the central transmission shaft2, wherein the gearwheel19is disposed coaxially with respect to the main transmission shaft2and is rotatably supported thereon.

In an example embodiment of the double clutch transmission1shown inFIG. 7, the gearwheel18of the output drive-constant gear pairing17is disposed, from a spatial perspective, axially between the gear stage ZP4or ZP8and the gear stage ZP7.

If one of the gearwheels of the gear stages ZP2to ZPR assigned to the countershaft4is designed as a fixed gear, it is also possible to bring the gearwheel19of the output drive-constant gear pairing into gear engagement with this fixed gear and to implement the axle offset between the output drive151and the further output drive161in a manner that is favorable in terms of structural space.

The double clutch transmission1is also designed with at least one electric machine20in the manner depicted inFIG. 1andFIG. 7. The electric machine20can be mechanically engaged into the power flow of the double clutch transmission. To this end, the electric machine20should be connected to one of the shafts of the gear set of the double clutch transmission1. It is thereby possible to provide an operative connection between the electric machine20and the double clutch transmission1in the region of the fixed gear or an idler gear of the gear set of the double clutch transmission1, or to connect the electric machine20in the region of an additional fixed gear to the gear set.

An advantageous operative connection between the electric machine20and the power flow of the double clutch transmission1is present when the operative connection between the electric machine20and the power-shift elements K1and K2and between the electric machine20and the output drive15or16, or151or161can be shifted depending on the particular current operating state of the vehicle drive train and the electric machine, since it is then possible to implement various hybrid functions, such as a charging procedure of an electric accumulator assigned to the electric machine20while the vehicle is at a standstill, or a purely electric driving mode, which is implemented while the electric machine20is operated as a motor.

The double clutch transmission1according to the invention is designed, in the present case, with five coupling devices disposed in a group, and five shift devices SE1to SE5, which can be actuated using only five actuators. Furthermore, the double clutch transmission1is designed in a manner that is favorable in terms of construction space having only eight gear planes for implementing at least nine transmission ratios “1” to “9” for forward travel and one transmission ratio “R” for travel in reverse.

Advantageously, one transmission ratio change proceeding from the first transmission ratio “1” for forward travel, which is currently selected in the double clutch transmission1, can be carried out in the direction of all even transmission ratios “2”, “4”, “6” and “8” without interruption of tractive force or in a power-shiftable manner. Furthermore, transmission ratio changes in the double clutch transmission1proceeding from all even transmission ratios “2”, “4”, “6” and “8” can be carried out in the direction of all uneven transmission ratios “1”, “3”, “5”, “7” and “9”, and in the reverse direction, also in a power-shiftable manner or without interruption of tractive force. This also applies for transmission ratio changes across a plurality of transmission ratio steps.

Any impairment of the overall efficiency of the double clutch transmission1during the implementation of the winding path gears “1” and “R” due to the simultaneous engagement of three gear stages ZP5, ZP9and ZP3and ZP5, ZP9and ZPR, respectively, into the power flow is negligible since these transmission ratios make up substantially smaller portions of driving in the course of the service life and the entire usage cycle compared to the other transmission ratios of the double clutch transmission1. This also applies if the output drive15and/or16is connected to the countershaft4via the additional output drive-constant gear pairing17.

REFERENCE CHARACTERS