GB2506601A

GB2506601A - A four gear double clutch gearbox with electric motor synchronization

Info

Publication number: GB2506601A
Application number: GB1217597.2A
Authority: GB
Inventors: Christian Kunze; Olaf Heldmann; Mathias Remmler; Christian Rubsam; Christoph Hau
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2012-10-02
Filing date: 2012-10-02
Publication date: 2014-04-09
Also published as: GB201217597D0

Abstract

An automatically controlled four gear gearbox comprises a double clutch 15 with a solid input shaft 11 having fixed gear wheels 16, 17 and a coaxial hollow input shaft 12 having fixed gear wheels 18, 19. The fixed gear wheels 16-19 mesh with idler gear wheels 20-23 connected to an output shaft 13 by unsynchronized dog clutches 25, 26. A motor layshaft 14 is split into a first and second auxiliary/half shaft 27, 28 each having fixed output gears 29 and 30. Fixed output gears 29, 30 are connected to a motor 31 by motor dog clutches 32 and 33. Depending on which input shaft 11, 12 is engaged by clutch 15, the electric motor 31 drives via clutches 32, 33 and fixed gears 16-19 the idler gears 20-23 so as to match the idler gear 20-23 with the speed of output shaft 13 so the unsynchronized dog clutches 25, 26 may be engaged. Also claimed is a method, a computer program and an integrated circuit.

Description

Electrically supported double clutch transmission In the recent decades, fuel consumption requirements and driving comfort aspects have led to a replacement of four-gear gearboxes by gear boxes having five or more gears in passenger cars. Often, the highest gear has the function of a cruising gear. However1 four-gear gear boxes are generally easier to build and need less package space. Hybrid cars, on the other hand, may provide an economic fuel consumption even with fewer gears. In a hybrid car, a light weight combustion motor may be used which is assisted by an electric motor.

A further development is the use of double clutch transmissions instead of the less eco-nomic and less responsive automatic transmissions. Double clutch transmissions can be used in hybrid cars as well. In this case, an electrical motor of the hybrid transmission may be used to replace the function of gear synchronizers.

An example of a prior art in which an electrically assisted combustion motor is provided with a double clutch transmission is disclosed in the DE 19950679.

It is an object of the present application to provide an improved electrically assisted auto-mated four-gear gear box for a double clutch transmission.

The application discloses an automatically controlled four-gear gear box. Herein four-gear" refers to four forward gears. In particular, the gearbox according to the application may be built without a reverse shaft for a reverse gear or additional reverse gear gear wheels, or, in other words, the reverse gear may be provided by forward gear gear wheels.

The automatically controlled four-gear gearbox comprises a solid input shaft and a holiow input shaft and means for connecting a double clutch to the solid input shaft and to the hollow input shaft. Furthermore, the gearbox according to the application comprises an output shaft that is arranged in parallel to the solid input shaft, a first auxiliary shaft and a second auxiliary shaft, a first motor clutch and a second motor clutch.

According to the application, the first auxiliary shaft is connectable to an electric motor via the first motor clutch and the second auxiliary shaft is connectable to the electric motor via the second motor clutch. Thereby, the auxiliary shafts and the first and second motor clutches are provided to provide a power assistance from an electric motor which is used, among others, to synchronize idler gears of the gear box. The use of the electric motor to synchronize idler gears according to the application permits the use of simple unsynchro-nized dog clutches for the idler gears which are cheaper, have less weight and produce less friction.

A layout of the gear box according to the application is as follows. The output shaft com-prises a first gear idler wheel, a first unsynchronized dog clutch, a third gear idler wheel, a fourth gear idler wheel, a second unsynchronized dog clutch and a second gear idler wheel. The solid input shaft comprises a first gear fixed wheel and a third gear fixed wheel and the hollow input shaft compnses a fourth gearfixed wheel and a second gear fixed wheel. The first auxiliary shaft comprises a first output gear and the second auxiliary shaft comprises a second output gear.

The first gear fixed wheel meshes with the first gear idler wheel and with the first output gear1 the third gear fixed wheel meshes with the third gear idler wheel, the fourth gear fixed wheel meshes with the fourthgear idlerwheel and the second gear fixed wheel meshes with the second gear idler wheel and with the second output gear. Furthermore, gear planes of the third and fourth gear are provided between gear planes of the first and the second gear.

According to this layout, a statically stable configuration is obtained in which the second and first gear gear wheels can be placed next to supporting bearings of a gear box casing.

Moreover, an assistance power from an electric motor can be directed over the second and first gear gear wheels, such that vibrations and forces can be balanced out effectively. A gearbox layout according to the application is especially advantageous in combination with smaller light weight passenger cars which do not require a high performance combustion motor.

In addition, the first motor clutch and the second motor clutch can also be provided by in-expensive unsynchronized dog clutches. For better synchronization of the motor gear wheels, rotation sensors may be placed near the auxiliry shafts.

In particular the first and second dog clutches may be provided as double sided dog clutches, wherein the first double sided dog clutch is arranged between the first gear idler wheel and the third gear idler wheel, and wherein the second dog clutch is arranged be-tween the fourth gear idler wheel and the second gear idler wheeL The use of a double sided dog clutch further reduces the package space as compared to two single sided dog clutches.

In a first embodiment, the first auxiliary shaft is provided by a first half shaft and the second auxiliary shaft is provided by a second half shaft. According to the application, an electric motor can be placed between the first and second half shafts. Thereby, an especially corn-pact arrangement is achieved.

In another embodiment, the first auxiliary shaft is a solid shaft and the second auxiliary shaft is a hollow shaft which is concentric to the solid shaft. With this arrangement, the electric motor can be placed at a side of the gear box, especially at a side of a launch clutch that connects the gear box with the motor. Thereby, the gears of the gearbox can be mounted and removed easily. Also, the motor clutches can be placed at a side of the gear box and encapsulation of the motor clutches is made easier. This is especially advanta- geous when electromagnetic clutches are used which may produce sparks during actua-tion.

In an arrangement with electromagnetic clutches, the first motor clutch and the second motor clutch are provided by electromagnetic clutches. Especially in comparison with hy-draulic clutches, electromagnetic clutches are easier to build and maintain but they may also provide advantages over electrical actuators, for example in terms of package space and cost. In another embodiment the motor clutches are provided by friction clutches, for example friction clutches with friction plates or with friction cones.

In an arrangement with an electric motor, an output shaft of the electric motor is connected to the first motor clutch and to the second motor clutch. The electric motor comprises means for controlling an output speed of the electric motor and means for operating the electric motor in a forward and a reverse operation mode. By providing the electric motor with a means of controlling its output speed, an engine control unit or.other control unit does not need to comprise data about the characteristics of the motor and the electric mo-tor can be exchanged without adapting the control unit.

A double clutch can be connected to the gear box by using a double clutch with a first fric-tion plate that is connectable to the solid input shaft and with a second friction plate that is.

connectable to the hollow input shaft. The use of a friction plate double clutch provides a particularly light weight and economic arrangement.

Alternatively, the double clutch may also be realized with dog clutches. This requires a more sophisticated synchronization but, on the other hand, provides a still more inexpen-sive and light weight double clutch. In this arrangement, the double clutch has a first dog clutch that is connectable to the solid input shaft and a second dog clutch that is connecta-ble to the hollow input shaft.

Moreover, the application provides a drivetrain with the abovementioned automatically con- trolled four-gear gear box, wherein a differential of the drivetrain is -directly or via interme-diate means -connected to an output gear on the output shaft. This layout can provide a compact arrangement for a front drive vehicle.

Furthermore, the application provides a car with the drivetrain wherein an output shaft of a combustion motor of the car is connected to a double clutch. The double clutch is connect- ed to the solid input shaft and to the hollow input shaft of the automatically controlled four-geargearbox.

In a further aspect, the application discloses a method far automatically controlling a four-gear gear box with a double clutch. Therein, a first idler wheel is engaged to an output shaft, a second idler wheel is connected to an electric motor by engaging a motor clutch. A revolution speed of the output shaft is derived or measured and a revolution speed of an output shaft of the electric motor is derived, for example using an input power, or meas-ured. A revolution speed of the second idler wheel is derived from the revolution speed of the electric motor, The revolution speed of the electric motor is adjusted until the derived revolution speed of the second idler wheel matches the derived revolution speed of the output shaft within a predetermined limit. Taking into account a slowing down before an engagement, the de-rived speed of the second idler wheel can also be slightly higher than that of the shaft. The second idler wheel is engaged the first idler wheel is disengaged. Connecting the second idler wheel to the electric motor comprises connecting the second idler wheel via a first gear fixed wheel or via a second gear fixed wheel.

With a method according to the application, expensive synchronizers can be avoided. The assistant power of the electric motor is directed over the lower gear gear wheels which produces a statically stable arrangement.

In particular, the step of disengaging the first idler wheel may be carried out after the step of engaging the second idler wheel. At this time, the clutch of the double clutch which drives the first idler wheel is already disconnected. Therefore there is no blocking of the gear box and fast shifting between gears is possible.

The application furthermore provides a method for providing an additional gear ratio to an automatically controlled four-gear gear box of a passenger car. An output shaft of an elec-tric motor is connected to a first fixed gear wheel of a gearbox via a first motor clutch and the output shaft of the electric motor is connected to a second fixed gear wheel via a se-cond motor clutch. Especially, the first fixed gear wheel may be a first gear fixed wheel and the second fixed gear wheel a second gear fixed wheel. Thereby, the low gear range is provided with additional gear ratios for an effective use of the combustion motor. Therein, the electric motor can be used for assistance power, for example to smoothen out torque irregularities of the combustion motor, or for generating electricity.

Furthermore, the application discloses a method for providing a reverse gear to an auto-matically controlled four-gear gear box. An electric motor is driven in a reverse operating mode. A motor clutch is engaged to an auxiliary shaft, wherein an output gear of the auxil- iary shaft meshes with a first gear fixed wheel on a solid input shalt of the four-gear gear-box and wherein the first gear fixed wheel on the solid input shaft meshes with a first gear idler wheel on an output shaft of the four-gear gearbox. The first gear idler wheel is en- gaged to the output shaft. According to the application a reverse gear is provided by elec-tronically controlling an electric motor and dog clutches. Thereby, package space, cost and weight can be saved.

Furthermore, the application discloses a computer program product for executing the steps of one of the aforementioned methods as well as an integrated circuit, such as a microcon-trollerorembedded computer, forexecuting forexecuting the steps of the aforementioned method.

The subject of the application will now be explained in further detail with reference to the following Figures in which Figure 1 shows a four-gear gearbox according to the application, Figure 2 shows a torque flow of the flrst gear, Figure 3 shows a torque flow for synchronizing the second gear withthe electric mo-tor, Figure 4 shows a torque flow for the second gear, Figure 5 shows a torque flow for synchronizing the third gear, Figure 6 shows a torque flow with a pre-engaged third gear, Figure 7 shows a torque flow for the third gear, Figure 8 shows a launch support configuration, Figure 9 shows a first gear boost configuration of the four-gear gear box, Figure 10 shows an engine starting mode of the four-gear gear box, Figure 11 shows a charging mode of the four-gear gear box, Figure 12 shows a recuperative breaking mode of the four-gear gear box, Figure 13 shows an additional gear mode of the four-gear gear box, Figure 14 shows an electric creeping mode of the four-gear gear box, Figure 15 shows an electrically driven reverse gear mode of the four-gear gear box, and Figure 16 shows a second embodiment of a four-gear gear box with an electromagnetic double clutch.

In the following description, details are provided to describe the embodiments of the appli-cation. It shall be apparent to one skilled in the art, however, that the embodiments may be practised without such details.

Figure 1 shows a four-gear gearbox 10 according to the application. The gearbox 10 com- prises a solid input shaft 11, a hollow input shaft 12, an output shaft 13 and a motorlay- shaft 14. The solid input shaft 11 and the hollow input shaft 12 can be coupled to a com-bustion motor 14 via a double clutch 15. From left to right, a first gear fixed wheel 16 and a third gear fixed wheel 17 are provided on the solid input shaft 11 and a fourth gear fixed wheel 18 and a second gear fixed wheel 19 are provided on the hollow input shaft 12.

From left to right, a first gear idler wheel 20, a third gear idler wheel 21, a fourth gear idler wheel 22, a second gear idler wheel and an output wheel 23 are arranged on the output shaft 13.

A first double sided dog clutch 25 is provided on the output shaft 1 3between the first gear idler wheel 20 and the third gear idler wheel 21. A second double sided dog clutch 26 is provided on the output shaft 13 between the fourth gear idler wheel 22 and the third gear idler wheel 23. Advantageously, the dog clutches 25, 26 are provided with arrow shaped teeth for guiding the alignment of the dog clutches.

The motor layshaft 14 is split into a first half shaft 27 and a second half shaft 28 which are arranged in line with each other. A first output gear 29 is provided on the first half shaft 27 and a second output gear 30 is provided on the second half shaft 28. An electric motor 31 is provided between the first half shaft 27 and the second half shaft 28. Furthermore, a first electromagnetic motor clutch 32 is provided between the first haft shaft 27 and the electric motor 31. Between the second shaft 28 and the electric motor 31 a second electromagnetic motor clutch 33 is provided. The dimensions of Fig. 1 are not drawn to scale. For example, the output gears 29, 30 may be smaller as shown.

The first gear fixed wheel 16 meshes with the first gear idler wheel 20 and with the first output gear 29. The third gear fixed wheel 17 meshes with the third gear idler wheel 21, the fourth gear fixed wheel 18 meshes with the fourth gear idler wheel 22, the second gear fixed wheel 19 meshes with the second gear idler wheel 23 and with the second gear input wheel 28 and the output gear wheel 24 meshes with a differential case gear wheel 34 of a differential 35. A right half shaft 36 is connected to the differential 35 and to a right wheel 37 and a left half shaft 38 is connected to the differential 35 and to a left wheel which is not shown in Fig. 1.

The motor layshaft 14 is supported on bearings 38 and 39, the input shaft ills supported on bearings 40 and 41 and the output shaft 14 is supported on bearings 42 and 43.

According to the application, the shaft bearings are placed close to the gearwheels of the low gears 1 and 2 with the highest torque load. Furthermore, the output gears of the elec- tric motor are provided in the gear planes of first and second gear, respectively, which pro-vides a robust arrangement as well as an effective transmission of power from the electric motor to the first and second gears. The gear actuation is electronically controlled which makes it easily feasible to place the dog clutches between gear planes of the first and third and between the second and fourth gear, respectively: A first rotation sensor 44 is provided at the output shaft 13 and a second rotation sensor 45 is provided at the electric motor 31. The sensors are connected to a control unit which can be provided by an integrated circuit of the electric motor 31, for example. For simplicity, the rotation sensors 44, 45 are not shown in the other Figures. The electric motor 31 is con-trolled via a feedback control loop, for example a PID loop, that uses the difference of the idler wheel revolution speed and the output shaft revolution speed as input. The idler wheel revolution speed is be deduced from the motor output speed from the rotation sensor 44 times an idler wheel gear ratio, while the output shaft revolution speed is provided by the rotation sensor 45 at the output shaft 13.

Figure 2 shows a torque flow of the first gear which passes via the solid input shaft 11, the first gear fixed wheel 16 the first gear idler wheel 20, the double sided dog clutch 25 and the output shaft 13 to the output gear wheel 24.

Figure 3 shows a torque flow for an engaged first gear in which the second gear idler wheel 23 is synchronized with the output shaft 13 via the output gear 30 and the second gear fixed wheel 19. During the synchronization, a controller of the control loop adjusts a power supply to the electric motor such that the revolution speed of the second gear idler wheel 23 approaches the revolution speed of the output shaft 13.

For a first gear gear ratio i_i = 4 from the output shaft of the combustion motor 14 to the output shaft 13 and for an output shaft revolution speed N_input2 of 2000 rpm, an output shaft speed N_output of 500 rpm results. If, by way of example, the gear ratio i_motorl from the output gear 30 of the electric motor 3lto the solid input shaft 11 is 0.3 and the second gear gear ratio i_2 from the solid input shaft 11 to the output shaft 13 is 2, the mo-tor controller regulates the output speed N_inputl of the electric motor, which is measured by the sensor 44, to 500 rpm * (2 * 0.3) = 300 rpm to achieve a revolution speed of 1000 rpm of the third gear idler wheel 21.

Figure 4 shows a torque flow for an engaged second gear. To engage the second gear, the dog clutch 25 is released and the dog clutch 26 is engaged to the second gear idler wheel.

Figure 5 shows a torque flow for an engaged second gear in which the third gear idler wheel 23 is synchronized with the output shaft 13 via the output gear 29, the first gear fixed wheel 16 and the second gear fixed wheel 17. During the synchronization a controller of the control loop adjusts a power supply to the electric motor such that the revolution speed of the third gear idler wheel 23 approaches the revolutiOn speed of the output shaft 13.

For a second gear gear ratio i_2 = 2 from the output shaft of the combustion motor 14 to the output shaft 13 and for an output shaft revolution speed N_input2 of 2000 rpm, an out-put shaft speed N_output of 1000 rpm results. If, by way of example, the gear ratio i_motor2 from the output gear 29 of the electric motor 3lto the solid input shaft 11 is 0.2 and the third gear gear ratio i_3 from the solid input shaft 11 to the output shaft 13 is 1.51 the motor controller regulates the output speed N_inputl of the electric motor, which is measured by the sensor 44, to 1000 rpm * (3/2 * 1/5) = 300 rpm to achieve a revolution speed of 1000 rpm of the third gear idler wheel 21.

Figure 6 shows a torque flow for a pre-engaged third gear. In Figure 6, the torque flow to the second gear idler wheel 23 is similar to the torque flow of Figure 5. For pre-engagirig the third gear, the electric motor 31 is decoupled from the output gear 29 and the double-sided dog clutch 25 is moved quickly towardsthe third gear idler wheel 21. Thereby, the dog clutch teeth engage with corresponding teeth on the third gear idler wheel 21 and out-put shaft 13 drives the third gear idler wheel 21, the third gear fixed wheel 17 and the solid input shaft 11.

Figure 7 shows a torque flow for an engaged third gear. To engage the third gear, an elec-tronic control unit for the double clutch 15 gives a command signal to release the clutch for the hollow input shaft and the dog clutch 26 and to engage the clutch for the solid input shaft.

Figure 8 shows a torque flow for a launch support for starting the vehicle in the first gear.

By providing a launch support according to the invention, a vehicle may be built with a smaller and economic combustion motor while still providing enough power to start the fully loaded vehicle on a hill slope. During launch support, the double clutch is engaged to the solid input shaft 11, which drives the output shaft 13 via the first gear fixed wheel 16 and the first gear idler wheel 20. Simultaneously1 the electric motor 31, which is coupled to the output gear 30, drives the output shaft 13 via the second gear fixed wheel 19 and the se-cond gear idler wheel 23. The output speed of the electric motor 31 increases from 0rpm to a speed in which the combustion motor takes over the propulsion. The electric motor 31 may be specially adapted for slow output speeds to provide a good efficiency at low output speeds.

A synchronization of the fourth gear idler wheel 22, which is not shown in the Figures is provided in a similar way as the synchronization of the second gear idler wheel 23.

Figure 9 shows a torque flow for starting the engine. In the start mode, the electric motor 31 is coupled to the solid input shaft 11 via the output gear 29 and the first gear fixed wheel 16 and the solid input shaft 11 is coupled to the output shaft of the combustion motor 14 via the double clutch 15. The combustion motor 14 may also be started via the output wheel 30, but in the embodiment of Fig. 9, the output wheel 29 and the first gear fixed wheel pro-vide a higher output torque. Using the output torque of the electric motor 31, the pistons of the combustion motor 14 are moved and the ignition is started. The required motor torque of the electric motor 31 varies depending on whether the combustion motor is a Diesel en-gine or a petrol engine. In addition to the electric motor 31 or as backup, a conventional starter motor may be provided as well.

Figure 10 shows a torque flow for a charging of a battery that is connected to the electric motor 31, which is used in a generator function. In the charge mode, the electric motor 31 is engaged to the output gear 30 and is driven from the output shaft 13. In the example of Figure 10, the output shaft 13 is driven via the solid input shaft 11, the first gear fixed wheel 16 and the first gear idler wheel 20. In the chargig configuration of Fig. 10, a battery of a car is charged while the car is driving.

Other charging configurations are also possible. All in all, there are four charging configura-tions in which either the first or the third gear is driven and the electric motor 31 is charged via the output gear 30 or in which either the second or the fourth gear is driven and the electric motor 31 is charged via the output gear 29. Alternatively, the electric motor 31 may also be charged when the car is not driven and none of the dug clutches 23, 25 is en-gaged. In this case, there are two possible charging configurations, via the output shaft 29 or via the output shaft 30.

Figure 11 shows a torque flow in a recuperative breaking mode via the second gear. Dur- ing recuperative breaking, the solid input shaft 11 and the hollow input shaft 12 are discon- nected from the motor. The electric motor 31 is coupled to the output shaft 30 via the elec-tromagnetic motor clutch 33 and is driven from the ouput shaft 13 via the second gear idler wheel 23 and the second gear fixed wheel 19. In a similar way, recuperative braking is also possible via the other three forward gears. In particular, when the car is driving in a first gear, recuperative braking via the second gear can be achieved by engaging the second gear idler wheel 23, disengaging the combustion motor 14 and the first gear idler wheel 20 and engaging the electromagnetic motor clutch 33 between the output gear 30 and the electricmotor3l.

Figure 12 shows a torque flow for an additional gear. The additional gear is provided by using coupling the first half shaft 27 to a shaft of the electric motor 31 and coupling the second half shaft 28 to the electric motor 31. Thereby, the first half shaft 27 and the second half shaft 28 provide a layshaft 14. In the additional gears, the electric motor 31 runs idle or it can be using as an electric generator or as assisting motor. In the example of Fig. 12, the electromagnetic motor clutch 32 and the dog clutch 26 are engaged. The first half shaft 27 receives input torque via the first gear fixed wheel 20 and the output gear 29 and transmits the received input torque via the second half shaft 28, the output gear 30, the second gear fixed wheel 19, the second gear idler wheel 23 and the dog clutch 26.

The torque path over the layshaft 14 provides an additional factor of i_addl = i_motor2 * 1/i_motorl in a first direction and i_add2 = i_motorl * 1/i motor2 in a second direction.

For i_motorl = 0.3 and i_motor2 = 0.2 this results in i_add = i_addl = 3/2 and i_add2 = 2/3. For an engaged second gear idler wheel 23, a gear ratio Ladd = 3/2 * 2 = 3 results, while for an engaged fourth gear idler wheel 22, a gear ratio i_add = 3/2* 0.8 = 1.2 results.

Alternatively, the solid input shaft 11 or the hollow input shaft 12 may also remain coupled to the combustion motor 14 to use the braking force of the combustion motor 14. For ex- ample, an engine control unit may decide on whether to engage the double clutch in addi-tion based on measuring an inclination of the car and a throttle opening.

Figure 13 shows a torque flow of an electrical creeping mode in which the output shaft 13 is driven only by the electric motor 31 in a forward direction and in which the first gear is driven from the electric motor via the electromagnetic motor clutch 32, the output gear 29, the first gear fixed wheel 16 and the first gear idler wheel 20.

Figure 14 shows a torque flow of an electrical reverse drive mode. According to the appli-S cation, the reverse gear is provided by the electric motor 31 in a reverse mode. Thereby, the package space, the weight and the production cost of the gear box 10 is reduced.

Moreover, additional reverse gears can be provided by engaging, for example, the second gear fixed wheel 23 via the dog clutch 26.

The output shaft 13 is driven via the electric motor 31, the electromagnetic motor clutch 32, the output gear 29, the first gear fixed wheel 16, the first gear idler wheel 20 and the dog clutch 25.

In an alternative embodiment, a separate reverse gear may be provided, for example via one or two gear wheels on an additional reverse gear layshaft.

Figure 16 shows a second embodiment of a four-gear gear box 10' with an electromagnetic double clutch 47. Different from the embodiment of Fig. 1, the electric motor 31 is arranged on the same side of the gear planes than the double clutch 15'. The electromagnetic dou-ble clutch 47 is connected to a hollow shaft 28' and to a solid shaft 27'. The output gear 30 is arranged on the hollow shaft 28' and the output gear 29 is arranged on the solid shaft 27'.

In one embodiment, the motor shaft 46 of the electric motor 31 is movable along its axis such that the solid shaft 27' and the hollow shaft can be engaged alternatively by moving the motor shaft 46 back and forth. In another embodiment, a clutch box of the electromag-netic double clutch comprises a coupling element, such as a shift collar or a friction plate, which is movable by an electromagnet into a first engaged position in which the solid shaft 27' is engaged and into a second engaged position in which the hollow shaft 28' is en-gaged.

Furthermore, the double clutch 15, which is connected to the combustion motor 14, is pro-vided by a wet multi-plate double clutch 15', different from the embodiment of Fig. 1. As a further alternative, which is not shown in the Figures, the launch clutch 15 may also be provided by a double clutch with two unsynchronized dog clutches.

Although the above description contains much specificity, these should not be construed as limiting the scope of the embodiments but merely providing illustration of the foreseeable embodiments. Especially the above stated advantages of the embodiments should not be construed as limiting the scope of the embodiments but merely to explain possible achievements if the described embodiments are put into practise. Thus, the scope of the embodiments should be determined by the claims and their equivalents, rather than by the

examples given.

Claims

CLAIMS1. Automatically controlled four-gear gear box (10; 10'), the automatically controlled four-gear gearbox (10; 10') comprising -a solid input shaft (11)and a hollow input shaft (12), -means for connecting a double clutch (15) to the solid input shaft (11) and to the hollow input shaft (12), -an output shaft (13), the output shaft (13) being arranged in parallel to the solid input shaft (11), -a first auxiliary shaft (27, 27') and a second auxiliary shaft (28, 28'), -a first motor clutch (32) and a second motor clutch (33), wherein the output shaft (13) comprises a first gear idlerwheel (20), a first unsyn-chronized dog clutch (25), a third gear idler wheel (21), a fourth gear idler wheel (22), a second unsynchronized dog clutch (26) and a second gear idler wheel (24), wherein the solid input shaft (11) comprises a first gear fixed wheel (16) and a third gear fixed wheel (21), wherein the hollow input shaft (12) comprises a fourth gear fixed wheel (18) and a second gear fixed wheel (19), wherein the first auxiliary shaft (27; 27') comprises a first output gear (29) and the second auxiliary shaft (28; 28') comprises a second output gear (30), wherein the first gear fixed wheel (16) meshes with the first gear idler wheel (20) and with the first output gear (29), the third gear fixed wheel (17) meshes with the third gear idler wheel (21), the fourth gear fixed wheel (18) meshes with the fourth gear idler wheel (22), and the second gear fixed wheel (19) meshes with the se-cond gear idler wheel (23) and with the second output gear (30), wherein gear planes of the third and fourth gear are provided between gear planes of the first and the second gear, and wherein the first auxiliary shaft (27, 27') is connectable to an electric motor (31) via the first motor clutch (32) and wherein the second auxiliary shaft (28, 28') is connectable to the electric motor (31) via the second motor clutch (33).
2. Automatically controlled four-gear gear box (10) according to claim 1, wherein the first motor clutch (32) and the second motor clutch (33) are provided by dog clutch-es, respectively.
3. Automatically controlled four-gear gear box (10) according to claim I or claim 2, wherein the first dog clutch (25) and the second dog clutch (26) are double sided dog clutches (25,26), wherein the first dog clutch (25)is arranged between the first gear idler wheel (20) and the third gear idler wheel (21), and wherein the second S dog clutch (26) is arranged between the fourth gear idler wheel (22) and the second gear idler wheel (23).
4. Automatically controlled four-gear gear box (10) according to one of the preceding claims, wherein the first auxiliary shaft (27) is provided by a half shaft and wherein the second auxiliary shaft (28) is provided by a half shaft.
5. Automatically controlled four-gear gear box (10: 10') according to one of the pre-ceding claims, wherein the first auxiliary shaft (27') is provided by a solid shaft (27') and wherein the second auxiliary shaft (28') is provided by a hollow shaft (28') which is concentric to the solid shaft (27').
6. Automatically controlled four-gear gear box (10:10') according to one of the pre-ceding claims, wherein the first motor clutch (32) is provided by an electromagnetic clutch (32) and wherein the second motor clutch (33) is provided by an electromag-netic clutch.
7. Automatically controlled four-gear gear box (10) according to one of the preceding claims! the automatically controlled four-gear gear box (10) further comprising an electric motor (31), an output shaft of the electric motor being connected to the first motor clutch (32) and to the second motor clutch (33), wherein the electric motor (31) comprises means for controlling an output speed of the electric motor (31) and means for operating the electric motor (31) in a forward and a reverse operation mode.
8. Automatically controlled four-gear gear box (10) according to one of the preceding claims, the automatically controlled four-gear gearbox (10) further comprising a double clutch (15) with a first friction plate that is connectable to the solid input shaft (11) and with a second friction plate that is connectable to the hollow input shaft (12).
9. Automatically controlled four-gear gear box (10) according to one of the preceding claims, the automatically controlled four-gear gearbox (10) further comprising a double clutch with a first dog clutch that is connectable to the solid input shaft (11) and with a second dog clutch that is connectable to the hollow input shaft (12).
10. Drivetrain with an automatically controlled four-gear gear box (10) according to one of the preceding claims wherein a differential (35) of the drivetrain is (directly or via intermediate means) connected to an output gear (24) on the output shaft (13).
11. Car with a drivetrain according to claim 10, wherein an output shaft of a combustion motor (14) of the car is connected to a double clutch (15) and wherein the double clutch (15) is connected to the solid input shaft (11) and to the hollow input shaft (12) of the automatically controlled four-gear gear box (10).
12. Method for automatically controlling a four-gear gear box (10, 10') the four-gear gear box comprising a double clutch (15), the method comprising -engaging a first idler wheel (20, 21, 22, 23) to an output shaft (13), -connecting a second idler wheel (20, 21, 22, 23)to an electric motor by engaging a motor clutch (32, 33), -deriving a revolution speed of the output shaft (13), -deriving a revolution speed of the electric motor (31), -deriving a revolution speed of the second idler wheel (20, 21, 22, 23) from the revolution speed of the electric motor (31), -adjusting the revolution speed of the electric motor (31) until the derived revolution speed of the second idler wheel (20, 21, 22, 23) matches the derived revolution speed of the output shaft (13) -engaging the second idler wheel (20, 21, 22, 23), and -disengaging the first idler wheel (20, 21, 22, 23), wherein connecting the second idler wheel (20, 21, 22, 23) to the electric motor (31) comprises connecting the so-cond idler wheel (20, 21, 22, 23) via a first gear fixed wheel (16) or via a second gear fixed wheel (19).
13. Method for providing an additional gear ratio to an automatically controlled four-gear gear box (10, 10'), comprising -connecting an output shaft of an electric motor (31) to a first fixed gear wheel (16, 19) via a first motor clutch (32, 33), -connecting the output shaft of the electric motor (31) to a second fixed gearwheel (16, 19) via a second motor clutch (32, 33).
14. Computer program product for executing the steps of a method according to one of the claims 12 to 13.
15. Integrated circuit for executing for executing the steps of a method according to one of the claims 11 to 13.