GB2478298A

GB2478298A - Manual transmission for vehicle with overdrive

Info

Publication number: GB2478298A
Application number: GB1003440A
Authority: GB
Inventors: Eckhard Kirchner
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2010-03-02
Filing date: 2010-03-02
Publication date: 2011-09-07
Anticipated expiration: 2030-03-02
Also published as: GB2478298B; GB201003440D0; CN102192307A

Abstract

A transmission 10 that comprises an input shaft 17, a first and second layshafts 18, 21, first and second pinions 19, 22 and a plurality of gear groups. The gear groups are supported on the input shaft 17 on the first layshaft 18 and on the second layshaft 21 for providing gear ratios. The plurality of gear groups comprises a reverse gear group 27, 39, 52, and an overdrive forward gear group 28, 54. The overdrive forward gear group is used for providing an overdrive gear ratio, which is lower than the gear ratios of the other forward gear groups. The overdrive forward gear group and the reverse gear group are axially located next to each other. Pinions 19, 22 mesh with output gear 25 (Figure 24). Preferably the overdrive gear set comprises a planetary gear set (A, B, C, Figure 23).

Description

Manual transmission with a seventh high-ratio overdrive gear The present application relates to a manual transmission for a passenger car with a seventh forward gear speed.

A vehicle has an automotive power train that includes a foot-operated clutch unit interposed between a transmission and an output shaft of an automobile engine. The clutch unit is used for coupling the transmission to the engine for transmitting a torque of the engine to the transmission.

In general, before changing of gear, a driver of the autorrio-bile is required to depress a clutch pedal to separate the transmission from the engine. A gearshift lever that is mounted on a steering column or on a floorboard is then ma- nipulated to change gear. After this, the clutch pedal is re-leased to couple the engine to the transmission for allowing the engine drive to be transmitted to the transmission.

The vehicle is desired to be fuel-efficient. Cost of making a fuel-efficient vehicle can be expensive. A need thus exists for providing a transmission with high fuel efficiency at low cost.

It is an object of the application to provide a manual trans-mission or gearbox with seven forward gears. The forward gears allow a vehicle that is installed with the transmission to move in a forward direction of the vehicle.

One of the main thoughts of the application is that manual transmissions can be improved. The manual transmission can use conventional or other transmission technology, which is proven yet in branches or areas other than automotive.

A transmission with seven forward gears can be provided with a high gear ratio capability that does not use complex gear shifting mechanisms.

The application provides an engine transmission or gearbox.

The transmission includes an input driving shaft, a first layshaft, a second layshaft, a first pinion and a second pin-ion as well as a plurality of gear groups.

Structurally, a clutch disc is connected to the input shaft for selectively connecting the input shaft to an engine. The first layshaft and the second layshaft are spaced apart from the input shaft and are arranged or are provided in parallel to the input shaft.

The first pinion is provided on or is placed on the first layshaft whilst the second pinion is provided on the second layshaft. The first opinion and the second pinion are for meshing with a differential gearwheel for transmitting an en-gine torque to the differential gearwheel that is provided on an output shaft. The output gearwheel can be a differential gearwheel that is used for driving wheels of a vehicle.

The gear groups are supported on the input shaft, on the first layshaft, and on the second layshaft for providing dif-ferent gear ratios between the input shaft and one of the first layshaft or the second layshaft.

In particular, the gear groups include a reverse gear group and an overdrive forward gear group.

The reverse gear group includes a first reverse gearwheel, an idler gearwheel, and a second reverse gearwheel. The first reverse gearwheel is provided on or is placed on the input shaft. The idler gearwheel is provided on the first layshaft and it meshes with the first reverse gearwheel whilst the second reverse gearwheel is provided on the second layshaft.

The overdrive forward gear group is used for providing an overdrive gear ratio that is lower than the gear ratios of the other forward gear groups. The overdrive gear ratio can such that the output shaft rotates faster than the input shaft.

The overdrive forward gear group and the reverse gear group are axially located next to each other. This provides an ad-vantage of cost saving as the overdrive forward gear group and the reverse gear group can share the same coupling or shifting device. The coupling device is used for mechanically engaging a part of the forward gear group or the reverse gear group to the first layshaft or the second layshaft.

In practise, the overdrive forward gear ratio can provide a benefit of fuel saving for a vehicle that has this transmis-sion by enabling the vehicle to travel at high speed with low engine speed.

The overdrive forward gear group can include a forward gear-wheel group or a planetary gear group.

Referring to the planetary gear group, it includes a plural-ity of relatively rotatable elements and a brake mechanism for one of the elements engageable to hold the element sta-tionary.

In particular, the planetary gear group can include a sun gear, a ring or hollow gear, one or more pinion gears, and a rotary or planetary carrier.

The sun gear and the ring gear are separated by and are mesh-ing with the pinion gears. The rotary carrier supports the pinion gears and it is connected to one of the other forward gear groups, although a connection to a reverse gear group is also possible. The ring gear is connected to a brake mecha- nism, such a casing of the transmission for keeping it sta-tionary. The sun gear is used for coupling with the first layshaft or the second layshaft via the coupling device to selectively engage the sun gear. In this configuration, the rotary carrier and the sun wheel turn in the same direction and the gear ratio is such that it provides a low gear ratio between the input shaft and one of the first layshaft or the second layshaft.

Such a planetary gear group has an advantage of small size allows for easier design and installation.

In addition, the rotary carrier of the planetary gear group can be connected to one of the other forward or reverse gear groups via a One Way Clutch (OWC), such as a freewheeler, for reducing drag.

Referring to the overdrive forward gearwheel group, it in- cludes an overdrive fixed gearwheel, an overdrive idler gear-wheel, and an overdrive-coupling device. The overdrive fixed gearwheel is provided on the input shaft whilst the overdrive idler gearwheel meshes with the overdrive fixed gearwheel.

The overdrive-coupling device is used to selectively engage the overdrive idler gearwheel to the first layshaft. The overdrive idler gearwheel and an overdrive-coupling device are arranged together on the first layshaft.

The overdrive fixed gearwheel is often much larger than the overdrive idler gearwheel for providing a low gear ratio. The forward overdrive gearwheel group has a benefit of simpler design and implementation.

Referring to the forward gear groups, it can include a first gear group, a second gear group, a third gear group, a fourth gear group, and a sixth gear group.

In one possible configuration, the first gear group is pro-vided next to the second gear group. The third gear group is provided next to the fourth gear group. The fifth gear group is provided next to the sixth gear group.

The first gear group includes a first fixed gearwheel, a first idler gearwheel, and a first coupling device. The first fixed gearwheel is provided on the input shaft. The first idler gearwheel meshes or combs with the first fixed gear-wheel whilst the first coupling device selectively engages the first idler gearwheel. The first idler gearwheel and the first coupling device are arranged or are provided together on the first layshaft.

Similarly, the second gear group includes a second fixed gearwheel, a second idler gearwheel, and a second coupling device. The second fixed gearwheel is provided on the input shaft. The second idler gearwheel meshes with the second fixed gearwheel. The second coupling device selectively en-gages the second idler gearwheel, wherein the second idler gearwheel and the second coupling device are arranged to-gether on the first layshaft.

The third gear group includes a third fixed gearwheel, a third idler gearwheel, and a third coupling device. The third fixed gearwheel is provided on the input shaft. The third idler gearwheel meshes with the third fixed gearwheel. The third coupling device selectively engages the third idler gearwheel. The third idler gearwheel and the third coupling device are arranged together on the second layshaft.

The fourth gear group includes a fourth fixed gearwheel, a fourth idler gearwheel, and a fourth coupling device. The fourth fixed gearwheel is provided on the input shaft. The fourth idler gearwheel meshes with the fourth fixed gear-wheel. The fourth coupling device selectively engages the fourth idler gearwheel. The fourth idler gearwheel and the fourth coupling device are arranged together on the second layshaft.

The fifth gear group includes a fifth fixed gearwheel, a fifth idler gearwheel, and a fifth coupling device. The fifth fixed gearwheel is provided on the input shaft. The fifth idler gearwheel meshes with the fifth fixed gearwheel. The fifth coupling device selectively engages the fifth idler gearwheel. The fifth idler gearwheel and the fifth coupling device are arranged together on the first layshaft.

The sixth gear group includes a sixth fixed gearwheel, a sixth idler gearwheel, and a sixth coupling device. The sixth fixed gearwheel is provided on the input shaft. The sixth idler gearwheel meshes with the sixth fixed gearwheel. The sixth coupling device selectively engages the sixth idler gearwheel. The sixth idler gearwheel and the sixth coupling device are arranged together on the first layshaft.

In a general sense, one double-sided coupling device can re-place two one-sided coupling devices. In other words, one double-sided coupling device is equivalent to two one-sided coupling devices.

Practising this, the first coupling device and the second coupling device can be provided or be integrated as one dou-ble-sided coupling device, wherein the integrated coupling device thus serves as the first coupling device and as the second coupling device. Similarly, The third coupling device and the fourth coupling device can be provided as one double-sided coupling device whilst the fifth coupling device and the sixth coupling device can be provided as one double-sided coupling device.

Further, the third fixed gearwheel and the fifth fixed gear- wheel can be provided as one fixed gearwheel. Put differ-ently, the one fixed gearwheel serves as both the third fixed gearwheel and as the fifth fixed gearwheel. Likewise, the fourth fixed gearwheel and the sixth fixed gearwheel can be being provided as one fixed gearwheel.

The first layshaft can be situated above or be situated below the second layshaft. This allows for providing different op-tions of realizing the application.

The application also provides a powertrain and a vehicle. The powertrain includes an engine and the above transmission that is connected to the engine. The vehicle includes one or more wheels and the powertrain that is connected to the wheels.

In short, the application provides a high ratio gear or over- drive gear without using complex shift mechanisms. The over-drive gear can serve as an overdrive gear, wherein the gear ratio progression from the sixth gear ratio to the overdrive gear ratio is rather large.

In a generic sense, two single gear-coupling devices c.n re-place one double gear-coupling device. Two single meshing pinions or gearwheels can replace one double-meshing pinion.

In certain implementations, the fixed gearwheels are provided on the input shaft using spline connections. In other imple-mentations, the fixed gearwheels are provided on the input shaft as on-cut pinions or as pinions that are cut on the in-put shaft. These piriions form an integral part of the input shaft.

In the following description, details are provided to de- scribe the embodiments of the application. It shall be appar-ent to one skilled in the art, however, that the embodiments may be practised without such details.

Figs. 1 to 9 illustrate a an embodiment of an improved first transmission, Fig. 1 illustrates a stick diagram of the improved first transmission, Fig. 2 illustrates a torque path of a first gear transmis-sion ratio of the first transmission, Fig. 3 illustrates a torque path of a second gear trans-mission ratio of the first transmission, Fig. 4 illustrates a torque path of a third gear transmis-sion ratio of the first transmission, Fig. 5 illustrates a torque path of a fourth gear trans-mission ratio of the first transmission, Fig. 6 illustrates a torque path of a fifth gear transmis-sion ratio of the first transmission, Fig. 7 illustrates a torque path of a sixth gear transmis-sion ratio of the first transmission, Fig. 8 illustrates a torque path of a seventh gear trans-mission ratio of the first transmission, Fig. 9 illustrates a torque path of a reverse gear trans-mission ratio of the first transmission, Figs. 10 to 18 illustrate a an embodiment of an improved sec-ond transmission, Fig. 10 illustrates a stick diagram of the improved second transmission, Fig. 11 illustrates a torque path of a first gear transmis-sion ratio of the second transmission, Fig. 12 illustrates a torque path of a second gear trans-mission ratio of the second transmission, Fig. 13 illustrates a torque path of a third gear transmis-sion ratio of the second transmission, Fig. 14 illustrates a torque path of a fourth gear trans-mission ratio of the second transmission, Fig. 15 illustrates a torque path of a fifth gear transmis-sion ratio of the second transmission, Fig. 16 illustrates a torque path of a sixth gear transmis-sion ratio of the second transmission, Fig. 17 illustrates a torque path of a seventh gear trans-mission ratio of the second transmission, Fig. 18 illustrates a torque path of a reverse gear trans-mission ratio of the second transmission, Fig. 19 illustrates a gearshift pattern of a gear knob for use with the first transmission or with the second transmission, Fig. 20 illustrates an open view of a first embodiment of the second transmission, Fig. 21 illustrates an open view of a second embodiment of the second transmission Fig. 22 illustrates a stick diagram of the second embodi-ment of the second transmission of Fig. 21, Fig. 23 illustrates a torque path of an overdrive gear transmission ratio of the second transmission of Fig. 22, and Fig. 24 illustrates a meshing of upper and lower pinions with a differential gearwheel of the transmission of Fig. 1.

Certain terminology is used in the following description for convenience of reference only and should not be limiting. The words "upper" and "lower" refers to positions within most transmission. The words "left" and "right" refer respectively to left side and to right side of the figures.

Figs. 1 to 24 have similar parts. The similar parts have same names or same part numbers. The description of the similar parts is hereby incorporated by reference, where appropriate.

Figs. 1 to 9 show an embodiment of an improved first trans-mission 10.

Fig. 1 shows a stick diagram of the improved first transmis-sion 10. The first transmission 10 has seven forward gears and one reverse gear. The first transmission 10 is character-ised in that a seventh gear ratio and a reverse ratio share one double-side synchronizer. The seventh gear ratio is some-times referred to as an overdrive gear ratio.

The first transmission 10 includes an input shaft assembly 12, an upper layshaft assembly 13, and a lower layshaft as-sembly 14. The term layshaft is also called a secondary shaft.

In particular, the input shaft assembly 12 includes an input shaft 17. The upper layshaft assembly 13 includes an upper layshaft 18 and a relatively large driving or output upper pinion 19 that is fixed on the upper layshaft 18. The lower layshaft assembly 14 includes a lower layshaft 21 and a rela-tively large driving or output lower pinion 22 that is fixed on the lower layshaft 21.

The input shaft 17, the upper layshaft 18, and the lower lay-shaft 21 are provided parallel to each other at predetermined mutual distances within a casing 20 of the first transmission 10. The upper pinion 19 is fixed to a rotational axis of the upper layshaft 18 whilst the lower pinion 22 is fixed to a rotational axis of the lower layshaft shaft 21. The upper pinion 19 and the lower pinion 22 each meshes with a differ-ential gearwheel 25, as illustrated in Fig. 24 The upper and the lower pinions 19 and 22 relates to wheels with teeth-like parts around its edge. These parts are pro-vided here for engaging the differential gearwheel 25. The differential gearwheel 25 is intended for mounting onto an axle for allowing wheels of a vehicle to turn at different rates when going round a corner.

The input shaft assembly 12 includes the input shaft 17 and a plurality of components that is provided on the input shaft 17. The components includes, from a right end to a left end of the input shaft 17, a shaft bearing 26, a fixed first gearwheel 27, a fixed seventh gearwheel 28, a fixed second gearwheel 29, a fixed third gearwheel 31, a fixed fourth gearwheel 32, and a shaft bearing 34.

The fixed first gearwheel 27 also serves a fixed reverse gearwheel. The fixed third gearwheel 31 also serves a fixed fifth gearwheel. The fixed fourth gearwheel 32 also serves a fixed sixth gearwheel. The shaft bearings 26 and 34 support the input shaft 17. The fixed first gearwheel 27, the fixed seventh gearwheel 28, the fixed second gearwheel 29, the fixed third gearwheel 31, and the fixed fourth gearwheel 32 are fixed coaxially onto the input shaft 17.

The upper layshaft assembly 13 includes the upper layshaft 18 and a plurality of components that is provided on the upper layshaft 18. The components includes, from the right end to the left end, a layshaft bearing 37, the upper pinion 19, a idler first gearwheel 39, a double-side coupling device 40, a idler second gearwheel 42, a idler fifth gearwheel 43, a dou-ble-sided coupling device 45, a idler sixth gearwheel 46, and another layshaft bearing 47. The expression "coupling device" can be expressed alternatively as "shifting mechanism" or as "synchronizers". The layshaft bearing 47 is fixed to the cas-ing 23.

The layshaft bearings 37 and 47 support the upper layshaft 18. The idler first gearwheel 39, the idler second gearwheel 42, the idler fifth gearwheel 43, and the idler sixth gear- wheel 46, are mounted on the upper layshaft 18 by gear bear-ings separately. The mounting is done such that the idler first gearwheel 39, the idler second gearwheel 42, the idler fifth gearwheel 43, and the idler sixth gearwheel 46 act as idlers, being free to rotate around the upper layshaft 18.

The double-sided coupling device 40 is configured to move along the upper layshaft 18 to engage or disengage the idler first gearwheel 39 and the idler second gearwheel 42 to the upper layshaft 18. Similarly, the double-sided coupling de-vice 45 is configured to move along the upper layshaft 18 to engage or disengage the idler fifth gearwheel 43 and the idler sixth gearwheel 46 to the upper layshaft 18.

In relation with the input shaft 17, the idler first gear-wheel 39 meshes with the fixed first gearwheel 27. The idler second gearwheel 42 meshes with the fixed second gearwheel 29. The idler fifth gearwheel 43 meshes with the fixed third gearwheel 31. The idler sixth gearwheel 46 meshes with the fixed fourth gearwheel 32.

The lower layshaft assembly 14 comprises the lower layshaft 21 and a plurality of components that is provided on the lower layshaft 21. The components comprises, from the right end to the left end, a layshaft bearing 50, the lower pinion 22, a idler reverse gearwheel 52, a double-side coupling de- vice 53, a idler seventh gearwheel 54, a idler third gear-wheel 56, a double-sided coupling device 57, a idler fourth gearwheel 58, and another layshaft bearing 61. The layshaft bearing 61 is fixed to the casing 23.

The layshaft bearings 50 and 61 support the lower layshaft 21. The idler reverse gearwheel 52, the idler seventh gear-wheel 54, the idler third gearwheel 56, and the idler fourth gearwheel 58 are mounted on the upper layshaft 21 by gear bearings separately. The mounting is implemented such that the idler reverse gearwheel 52, the idler seventh gearwheel 54, the idler third gearwheel 56, and the idler fourth gear-wheel 58 act as idlers, being free to rotate around the lower layshaft 21. The double-sided coupling device 53 is config- ured to move along the lower layshaft 21 to engage or disen-gage the idler reverse gearwheel 52 and the idler seventh gearwheel 54 to the lower layshaft 21. The double-sided cou- pling device 57 is configured to move along the lower lay-shaft 21 to engage or disengage the idler third gearwheel 56 and the idler fourth gearwheel 58 to the lower layshaft 21.

In relation with the input shaft 17, the idler seventh gear-wheel 54 meshes with the fixed seventh gearwheel 28. The idler third gearwheel 56 meshes with the fixed third gear-wheel 31. The idler fourth gearwheel 58 meshes with the fixed fourth gearwheel 32.

In relation with the upper shaft 18, the idler reverse gear-wheel 52 meshes with the idler first gearwheel 39.

In summary, the transmission has three double-meshing fea-tures. The first double-meshing feature refers to the idler first gearwheel 39 meshing with the fixed first gearwheel 27 and with the idler reverse gearwheel 52. The second double- meshing feature refers to the fixed third gearwheel 31 mesh-ing with the idler third gearwheel 56 and with the idler fifth gearwheel 43. The third double-meshing feature refers to the fixed fourth gearwheel 32 meshing with the idler fourth gearwheel 58 and with the idler sixth gearwheel 46.

Six forward gears relate to the idler gearwheels 39, 42, 56, 58, 43, and 46 and share the three double-sided synchronizers 40, 45, and 57 whilst the seventh forward gear idler gear-wheel 54 and the reverse gear idler gearwheel 52 share one double-sided synchronizer 53.

In a generic sense, two single meshing features can replace one double meshing feature. Put differently, multi-meshing pinions or gearwheels can be replaced by multiple single meshing pinions. As an example, a first idler first gearwheel and second idler first gearwheel can replace the idler first gearwheel 39. The first idler first gearwheel meshes with the fixed first gearwheel 27 and the second idler first gearwheel meshes with the idler reverse gearwheel 52.

The seventh gear ratio can be provided as overdrive gear.

This is especially so in the case where gear ratio progres-sion from the sixth gear ratio to the seventh gear ratio is rather large. Two single-sided coupling devices can replace one double-sided coupling device to perform the same func-tion.

For efficient power transfer, the seventh gear ratio can also be provided using spur gear arrangement.

The fixed gearwheels 27, 28, 29, 31, and 32 can be fixed to the input shaft 17 using a spline mechanism. The fixed gear-wheels 27, 28, 29, 31, and 32 can also be provided as on-cut pinions or as pinions that are cut on the input shaft 17.

These pinions are thus an integral part of the input shaft 17.

The final drive or output drive ratios for the upper layshaft 18 and for the lower layshaft 21 do not necessarily need to be the same. This embodiment also applies to transmissions having separate driving pinions for all gears.

Furthermore, a power-take-off unit or a splined driveshaft may be added to a differential area of the transmission 10 to realize an all-wheel driven vehicle, which is another possi-ble embodiment of the present application.

The transmission 10 has an advantage of the seventh gear that can provide better fuel economy for vehicles with mid to high torque engines. The better fuel economy is especially impor-tant when fuel prices are high. This concept is tailored for primarily front-wheel driven passenger cars with transverse front installation of the engine but can also be used for other car types.

In addition, the transmission 10 also shows an advantage of upgrading transmissions with six forward gears and a reverse gear that uses one single-sided coupling device. The upgrade involves replacing the single-sided coupling device with a double-sided coupling device for the reverse gearwheel as well as to adding a gearwheel for the seventh gear that also uses the said double-sided coupling device. This upgrade pro-vides an advantage of high ratio capability without requiring complex shift mechanisms.

Fig. 2 shows a torque path of a first gear transmission ratio of the first transmission. The input shaft 17 receives an in-put torque. The torque is then transmitted via the fixed first gearwheel 27, via the idler first gearwheel 39, and via the double-sided coupling device 40. The double-sided cou-pling device 40 is engaged with or is connected to the idler first gearwheel 27. The torque is later transmitted via the upper layshaft 18, via the upper pinion 19, and via the dif-ferential gearwheel 25.

Fig. 3 shows a torque path of a second gear transmission ra-tio of the first transmission. The input shaft 17 receives an input torque. The torque is then transmitted via the fixed second gearwheel 29, via the idler second gearwheel 42, and via the double-sided coupling device 40. The double-sided coupling device 40 is engaged with the idler second gearwheel 42. The torque is later transmitted via the upper layshaft 18, via the upper pinion 19, and via the differential gear-wheel 25.

Fig. 4 shows a torque path of a third gear transmission ratio of the first transmission. The input shaft 17 receives an in-put torque. The torque is then transmitted via the fixed third gearwheel 31, via the idler third gearwheel 56, and via the double-sided coupling device 57. The double-sided cou-pling device 57 is engaged with the idler third gearwheel 56.

The torque is later transmitted via the upper layshaft 18, via the lower pinion 21, via the lower pinion 22, and via the differential gearwheel 25.

Fig. 5 shows a torque path of a fourth gear transmission ra-tio of the first transmission. The input shaft 17 receives an input torque. The torque is then transmitted via the fixed fourth gearwheel 32, via the idler fourth gearwheel 58, and via the double-sided coupling device 57. The double-sided coupling device 57 is engaged with the idler fourth gearwheel 58. The torque is later transmitted via the lower layshaft 21, via the lower pinion 22, and via the differential gear-wheel 25.

S

Fig. 6 shows a torque path of a fifth gear transmission ratio of the first transmission. The input shaft 17 receives an in-put torque. The torque is then transmitted via the fixed fifth gearwheel 31, via the idler fifth gearwheel 43, and via the double-sided coupling device 45. The double-sided cou-pling device 45 is engaged with the idler fifth gearwheel 43.

The torque is later transmitted via the upper layshaft 18, via the upper pinion 19, and via the differential gearwheel 25.

Fig. 7 shows a torque path of a sixth gear transmission ratio of the first transmission. The input shaft 17 receives an in-put torque. The torque is then transmitted via the fixed sixth gearwheel 32, via the idler sixth gearwheel 46, and via the double-sided coupling device 45. The double-sided cou-pling device 45 is engaged with the idler sixth gearwheel 46.

Fig. 8 shows a torque path of a seventh gear transmission ra-tio of the first transmission. The input shaft 17 receives an input torque. The torque is then transmitted via the fixed seventh gearwheel 28, via the idler seventh gearwheel 54, and via the double-sided coupling device 52. The double-sided coupling device 52 is engaged with the idler seventh gear- wheel 54. The torque is later transmitted via the lower lay-shaft 21, via the lower pinion 22, and via the differential gearwheel 25.

Fig. 9 shows a torque path of a reverse gear transmission ra-tb of the first transmission. The input shaft 17 receives an input torque. The torque is then transmitted via the fixed first gearwheel 27, via the idler first gearwheel 39, via the idler reverse gearwheel 52, and via the double-sided coupling device 21. The double-sided coupling device 21 is engaged with the idler reverse gearwheel 53. The torque is later transmitted via the lower layshaft 21, via the lower pinion 22, and via the differential gearwheel 25.

Figs. 10 to 18 show an embodiment of an improved second transmission 70.

Fig. 10 shows a stick diagram of the improved second trans-mission 70. The first transmission 70 has seven forward gears and one reverse gear, wherein a seventh gear ratio and a re-verse ratio share the same double-side synchronizer.

The first transmission 70 includes an input shaft assembly 71, an upper layshaft assembly 72, and a lower layshaft as-sembly 74.

Specifically, the input shaft assembly 71 includes an input shaft 76. The upper layshaft assembly 72 includes an upper layshaft 78 and a relatively large driving upper pinion 80 that is fixed on the upper layshaft 78. The lower layshaft assembly 74 includes a lower layshaft 81 and a relatively large driving lower pinion 82 that is fixed on the lower lay-shaft 81.

The input shaft 76, the upper layshaft 78, and the lower lay-shaft 81 are provided parallel to each other at predetermined mutual distances within a casing 84 of the second transmis-sion 70. The upper pinion 80 is fixed to a rotational axis of the upper layshaft 78 whilst the lower pinion 82 is fixed to a rotational axis of the lower layshaft shaft 81. The upper pinion 80 and the lower pinion 82 each meshes with a differ-ential gearwheel 85.

The input shaft assembly 76 comprises the input shaft 76 and a plurality of components that is provided on the input shaft 76. The components comprises, from a right end to a left end of the input shaft 76, a shaft bearing 87, a fixed first gearwheel 89, a fixed seventh gearwheel 90, a fixed second gearwheel 92, a fixed third gearwheel 93, a fixed fourth gearwheel 94, and a shaft bearing 95.

The fixed first gearwheel 89 also serves a fixed reverse gearwheel. The fixed third gearwheel 93 also serves a fixed fifth gearwheel. The fixed fourth gearwheel 94 also serves a fixed sixth gearwheel. The shaft bearings 87 and 95 support the input shaft 76. The fixed first gearwheel 89, the fixed seventh gearwheel 90, the fixed second gearwheel 92, the fixed third gearwheel 93, and the fixed fourth gearwheel 94 are fixed coaxially onto the input shaft 76.

The upper layshaft assembly 72 includes the upper layshaft 78 and a plurality of components that is provided on the upper layshaft 78. The components comprises, from the right end to the left end, a layshaft bearing 97, the upper pinion 80, a idler reverse gearwheel 99, a double-side coupling device 100, a idler seventh gearwheel 101, a idler third gearwheel 103, a double-sided coupling device 104, a idler fourth gear-wheel 105, and another layshaft bearing 106. The layshaft bearing 106 is fixed to the casing 84.

The layshaft bearings 97 and 106 support the upper layshaft 78. The idler reverse gearwheel 99, the idler seventh gear-wheel 101, the idler third gearwheel 103, and the idler fourth gearwheel 105, are mounted on the upper layshaft 78 by gear bearings separately. The mounted is implemented such that the idler reverse gearwheel 99, the idler seventh gear-wheel 101, the idler third gearwheel 103, and the idler fourth gearwheel 105 act as idlers, being free to rotate around the upper layshaft 78. The double-sided coupling de-vice 100 is configured to move along the upper layshaft 78 to engage or disengage the idler reverse gearwheel 99 and the idler seventh gearwheel 101 to the upper layshaft 78. Simi-larly, the double-sided coupling device 104 is configured to move along the upper layshaft 78 to engage or disengage the idler third gearwheel 103 and the idler fourth gearwheel 105 to the upper layshaft 78.

In relation with the input shaft 76, the idler seventh gear-wheel 101 meshes with the fixed seventh gearwheel 90. The idler third gearwheel 103 meshes with the fixed third gear-wheel 93. The idler fourth gearwheel 105 meshes with the fixed fourth gearwheel 94.

The lower layshaft assembly 74 includes the lower layshaft 81 and a plurality of components that is provided on the lower layshaft 81. The components includes, from the right end to the left end, a layshaft bearing 109, the lower pinion 85, a idler first gearwheel 111, a double-side coupling device 113, a idler second gearwheel 115, a idler fifth gearwheel 117, a double-sided coupling device 118, a idler sixth gearwheel 119, and a layshaft bearing 121. The layshaft bearing 121 is fixed to the casing 84.

The layshaft bearings 109 and 121 support the lower layshaft 81. The idler first gearwheel 111, the idler second gearwheel 115, the idler fifth gearwheel 117, and the idler sixth gear- wheel 119 are mounted on the lower layshaft 81 by gear bear-ings separately. The mounting is implemented such that the idler first gearwheel 111, the idler second gearwheel 115, the idler fifth gearwheel 117, and the idler sixth gearwheel 119 act as idlers, being free to rotate around the lower lay-shaft 81. The double-sided coupling device 113 is configured to move along the lower layshaft 81 to engage or disengage the idler first gearwheel 111 and the idler second gearwheel 115 to the lower layshaft 81. The double-sided coupling de-vice 118 is configured to move along the lower layshaft 81 to engage or disengage the idler fifth gearwheel 117 and the idler sixth gearwheel 119 to the lower layshaft 81.

In relation with the input shaft 78, the idler first gear-wheel 111 meshes with the fixed first gearwheel 89. The idler second gearwheel 115 meshes with the fixed second gearwheel 92. The idler fifth gearwheel 117 meshes with the fixed fifth gearwheel 93. The idler sixth gearwheel 119 meshes with the fixed sixth gearwheel 94.

In relation with the upper shaft 78, the idler reverse gear-wheel 99 meshes with the idler first gearwheel ill.

In short words, the transmission has three double-meshing features. The first double-meshing feature refers to the idler first gearwheel lii meshing with the fixed reverse gearwheel 89 and with the idler reverse gearwheel 99. The second double-meshing feature refers to the fixed third gear-wheel 93 meshing with the idler third gearwheel 103 and with the idler fifth gearwheel 117. The third double-meshing fea-ture refers to the fixed fourth gearwheel 94 meshing with the idler fourth gearwheel 105 and with the idler sixth gearwheel 119.

Six forward gears that relate to the idler gearwheels 103, 105, 111, 115, 117, and 119 share the three double-sided synchronizers 103, 113, and 118 whilst the seventh forward gear idler gearwheel 101 and the reverse gear idler gearwheel 99 share one double-sided synchronizer 100.

Fig. 11 shows a torque path of a first gear transmission ra- tb of the second transmission 70. The input shaft 76 re-ceives an input torque. The torque is then transmitted via the fixed first gearwheel 89, via the idler first gearwheel 111, and via the double-sided coupling device 113. The dou-ble-sided coupling device 113 is engaged with or is connected to the idler first gearwheel ill. The torque is later trans-mitted via the lower layshaft 81, via the lower pinion 82, and via the differential gearwheel 85.

Fig. 12 shows a torque path of a second gear transmission ra- tio of the second transmission 70. The input shaft 76 re-ceives an input torque. The torque is then transmitted via the fixed second gearwheel 92, via the idler second gearwheel 115, and via the double-sided coupling device 113. The dou- ble-sided coupling device 113 is engaged with the idler sec-ond gearwheel 115. The torque is later transmitted via the lower layshaft 81, via the lower pinion 82, and via the dif-ferential gearwheel 85.

Fig. 13 shows a torque path of a third gear transmission ra- tio of the second transmission 70. The input shaft 76 re-ceives an input torque. The torque is then transmitted via the fixed third gearwheel 93, via the idler third gearwheel 103, and via the double-sided coupling device 104. The dou-ble-sided coupling device 104 is engaged with the idler third gearwheel 103. The torque is later transmitted via the upper layshaft 78, via the upper pinion 80, and via the differen-tial gearwheel 85.

Fig. 14 shows a torque path of a fourth gear transmission ra- tio of the second transmission 70. The input shaft 76 re-ceives an input torque. The torque is then transmitted via the fixed fourth gearwheel 94, via the idler fourth gearwheel 105, and via the double-sided coupling device 104. The dou-ble-sided coupling device 104 is engaged with the idler fourth gearwheel 105. The torque is later transmitted via the upper layshaft 78, via the upper pinion 80, and via the dif-ferential gearwheel 85.

Fig. 15 shows a torque path of a fifth gear transmission ra- tio of the second transmission 70. The input shaft 76 re-ceives an input torque. The torque is then transmitted via the fixed fifth gearwheel 93, via the idler fifth gearwheel 117, and via the double-sided coupling device 118. The dou-ble-sided coupling device 118 is engaged with the idler fifth gearwheel 117. The torque is later transmitted via the lower layshaft 81, via the lower pinion 82, and via the differen-tial gearwheel 85.

Fig. 16 shows a torque path of a sixth gear transmission ra- tio of the second transmission 70. The input shaft 76 re-ceives an input torque. The torque is then transmitted via the fixed sixth gearwheel 94, via the idler sixth gearwheel 119, and via the double-sided coupling device 118. The dou-ble-sided coupling device 118 is engaged with the idler sixth gearwheel 119. The torque is later transmitted via the lower layshaft 81, via the lower pinion 82, and via the differen-tial gearwheel 85.

Fig. 17 shows a torque path of a seventh gear transmission ratio of the second transmission 70. The input shaft 76 re-ceives an input torque. The torque is then transmitted via the fixed seventh gearwheel 90, via the idler seventh gear-wheel 101, and via the double-sided coupling device 100. The double-sided coupling device 100 is engaged with the idler seventh gearwheel 101. The torque is later transmitted via the upper layshaft 78, via the upper pinion 80, and via the differential gearwheel 85.

Fig. 18 shows a torque path of a reverse gear transmission ratio of the second transmission 70. The input shaft 76 re-ceives an input torque. The torque is then transmitted via the fixed reverse gearwheel 89, via the idler reverse gear-wheel 99, and via the double-sided coupling device 100. The double-sided coupling device 100 is engaged with the idler reverse gearwheel 99. The torque is later transmitted via the upper layshaft 78, via the upper pinion 80, and via the dif-ferential gearwheel 85.

Fig. 19 shows a gear-shifting pattern or arrangement 125 of a gear knob for use with the first transmission 10 of Fig. 1 or with the second transmission 70 of Fig. 10.

The shifting pattern 125 comprises multiple shifting tracks 127, 129, 131, 133, 134, and 137. The shift tracks 127, 129, 131, 133, and 134 are positioned parallel to each other. The shift track 127 separated from the shift track 129 by a unit of gear select travel whilst the shift track 129 is separated from the shift track 131 by also one unit of gear select travel. The shift track 133 is separated from the shift track 131 by one unit of gear select travel whilst the shift track 134 is separated from the shift track 133 by also one unit of gear select travel.

The shift tracks 127 and 134 have ideally or preferably but not necessarily the same length whilst the shift tracks 129, 131, and 133 have the same length. The length of the shift track 127 or 134 is about half the length of the shift track 129, 131, or 133.

The shift track 134 has a first side 139, a second side 140 and, a middle point 141.

The shift track 137 is jointed to middle points of the shift tracks 129, 131, and 133. The jointed is such that first ends 142, 143, and 144 of shift tracks 129, 131, and 133 respec-tively are positioned on the first side 139 whilst the second ends 147, 148, and 149 of the shift tracks 129, 131, and 133 respectively are positioned on the second side 140.

The shift track 127 is placed on the first side 139 such that a first end 151 of the shift track 127 is placed on the first side 139 whilst the second end 152 of the shift track 127 is connected to one end 153 of the shift track 134. Similarly, the shift track 134 is placed on the second side 140 such that a first end 157 of the shift track 134 is connected to another end 158 of the shift track 134 whilst a second end of the shift track 134 is placed on the second side 140.

In practise, the ends 142, 147, 143, 148, 14, 149, and 160 are intended to provide different gear change positions. In particular, the end 142 is intended to provide a first gear change position. The end 147 is intended to provide a second gear change position. The end 143 is intended to provide a third gear change position. The end 148 is intended to pro-vide a fourth gear change position. The end 144 is intended to provide a fifth gear change position. The end 149 is in-tended to provide a sixth gear change position. The end 160 is intended to provide a seventh gear change position or an overdrive gear change position. The end 151 is intended to provide a reverse gear change position. The middle point 141 is intended to provide a neutral gear change or shift posi-tion.

Referring to Fig. 19, the reverse gear change position 151 and the seventh gear change position 160 are spaced two units of gear select travel from the neutral gear change point 131.

The reverse gear change position and the seventh gear change position are placed on opposite sides of the shift track 137.

The reverse gear change position and the seventh gear change position are not on the same side of the shift track 137 be-cause the both gear change positions share the same coupling device.

In the example provided here, the seventh gear change posi-tion is provided on the second side 140 of the shift track 137 whereas according to gear change progression, the seventh gear change position should be on the first side 139 of the shift track 137. This is to indicate that change of gear ra-tio from the sixth to the seventh gear ratio is rather large.

The reverse gear change position is placed close to the first gear change position and to the second gear change position for safety reasons.

In a generic sense, the seventh gear ratio position can be placed on the first side 139 whilst the reverse gear ratio position is placed on the second side 140. The seventh gear ratio position can also be placed on the second side 140 of the shift track 137 whilst the reverse gear ratio position is placed on the first side 139.

Figs. 20 and 21 show embodiments of the second transmission 70. The embodiments add a seventh gear ratio to a six-speed transmission.

Fig. 20 shows an open view of a first embodiment of the sec-ond transmission 70. Fig. 20 that is not drawn to scale. A comparatively large driving gearwheel would used for mating or meshing with a small driven pinion or gearwheel.

Fig. 20 does not show an explicit driving gear for the sev- enth gear although the seventh gear driving wheel 90 is pref-erably placed between the fixed third gearwheel 93 and the fixed and cut-on-shaft pinion of the second gearwheel 92.

In this embodiment, the input shaft 76 carries 3 fixed splined driving gears that include the fixed third gearwheel 93 and the fixed fourth gearwheel 94. In addition, the input shaft 76 carries two on-cut pinions that include the fixed first gearwheel 89 and the fixed second gearwheel 92.

The lower shaft 81 carries a first driven gear, a second driven gear, a fifth driven gear, and a sixth driven gear that refer to the idler first gearwheel 111, the idler second gearwheel 115, the idler fifth gearwheel 117, and the idler sixth gearwheel 119 respectively. The lower shaft 81 and the said driven gears are not shown in Fig. 20.

The upper layshaft 78 carries a third driven gear, a fourth driven gear, a seventh driven gear, and a reverse driven gear that refer to the idler third gearwheel 103, the idler fourth gearwheel 105, the idler seventh gearwheel 101, and the idler reverse gearwheel 99 respectively.

The forward first to sixth idler gearwheels 111, 115, 103, 105, 117, and 119 share double-sided synchronizers 113, 104, and 118 whilst the idler reverse gearwheel 99 and the forward idler seventh gearwheel 101 share double-sided synchronizer 100.

Fig. 21 shows an open view of a second embodiment of the sec-ond transmission. The second embodiment uses a planetary gear set or assembly for implementing the seventh driving gear.

The planetary gear assembly includes one or two shafts. The shafts connect to other gearwheels, which is driven by a separate driving gearwheel of the input shaft 76. The driving gearwheel can drive the planetary gear assembly via, for ex-ample, the driven third gearwheel 103.

To achieve a high ratio overdrive for the seventh gear ratio, the planetary gear assembly operates in a sense preserving operational mode wherein an input rotational direction and an output rotational direction of the planetary gear assembly are the same.

Simple planetary gear sets translate motion of its carrier or planet carrier into a faster rotation of its sun gear when its hollow gear is kept fixed. Using the driven third gear-wheel 103 to drive the carrier has the benefit of saving package space and can provide an appropriate pre-ratlo for the planetary seventh gear.

As one example of the embodiment, the driven third gearwheel 103 is shown in Fig. 21 as a driver of the planetary seventh gear. The planetary seventh gear includes a carrier C, a sun-gear A, and a hollow gear B. The sun-gear A acts as an output shaft. The hollow gear B is fixed to a ground or to a trans-mission casing, which leads to the desired change of ratio and desired rotational sense.

To achieve, for example, an overdrive ratio of 0.5 requires a stand-ratio of the simple planetary gear of 2.2 assuming a third gear ratio of 1.6. The output sun-gear A is connected to a synchronizer S 100, which can be shared with the idler reverse gearwheel 99 to achieve the overdrive shift pattern of Fig. 10. In this case, the synchronizer S refers to the double-side coupling device 100 of Fig. 10.

To reduce any transmission drag in lower gears, a free wheeler that is marked as one-way clutch (OWC) in Fig. 21 may be added. However, this freewheeler arrangement then implies that engine braking and coast-mode fuel cut-off is probably unavailable in overdrive gear mode.

Fig. 22 shows a stick diagram of the second embodiment of the second transmission of Fig. 21 whilst Fig. 23 shows a torque path of an overdrive gear transmission ratio of the second transmission of Fig. 22.

The input shaft 76 receives an input torque. The torque is then transmitted via the fixed third gearwheel 93, via the idler third gearwheel 103, via the planetary gear set of Fig. 21 and via the double-side coupling device 100. The double-side coupling device 100 is engaged with or is connected to the planetary gear set. The torque is later transmitted via the upper layshaft 78, via the upper pinion 80, and via the differential gearwheel 85.

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 foresee-able 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 achieve-ments 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.

Reference number list first transmission 12 input shaft assembly 13 upper layshaft assembly 14 lower layshaft assembly 17 input shaft 18 upper layshaft 19 upper pinion 21 lower layshaft 22 lower pinion 23 casing differential gearwheel 26 shaft bearing 27 fixed first gearwheel 28 fixed seventh gearwheel 29 fixed second gearwheel 31 fixed third gearwheel 32 fixed fourth gearwheel 34 shaft bearing 37 layshaft bearing 39 idler first gearwheel double-side coupling device 42 idler second gearwheel 43 idler fifth gearwheel double-sided coupling device 46 idler sixth gearwheel 47 layshaft bearing layshaft bearing 52 idler reverse gearwheel 53 double-side coupling device 54 idler seventh gearwheel 56 idler third gearwheel 57 double-sided coupling device 58 idler fourth gearwheel 61 layshaft bearing second transmission 71 input shaft assembly 72 upper layshaft assembly 74 lower layshaft assembly 76 input shaft 78 upper layshaft 80 upper pinion 81 lower layshaft 82 lower pinion 84 casing differential gearwheel 87 shaft bearing 89 fixed first gearwheel fixed seventh gearwheel 92 fixed second gearwheel 93 fixed third gearwheel 94 fixed fourth gearwheel shaft bearing 97 layshaft bearing 99 idler reverse gearwheel double-side coupling device 101 idler seventh gearwheel 103 idler third gearwheel 104 double-sided coupling device idler fourth gearwheel 106 layshaft bearing 109 layshaft bearing 111 idler first gearwheel 113 double-side coupling device idler second gearwheel 117 idler fifth gearwheel 118 double-sided coupling device 119 idler sixth gearwheel 121 layshaft bearing 122 input fixed gearwheel pattern or arrangement 127 shifting track 129 shifting track 131 shifting track 133 shifting track 134 shifting track 137 shifting track 139 first side second side 142 first end 143 first end 144 first end 147 second end 148 second end 149 second end 151 end 152 end 153 end 157 end 158 end end

Claims

CLAIMS1. Transmission (10; 70) comprising: an input shaft (17; 76), a first layshaft (18; 78) and a second layshaft (21; 81) that are spaced apart from the input shaft (17; 76) and that are arranged in parallel to the input shaft (17; 76) a first pinion (19; 80) being provided on the first lay-shaft (18; 78), a second pinion (22; 82) being provided on the second layshaft (21; 81), the first opinion (19; 80) and the second pinion (22; 82) are for meshing with an out-put gearwheel (25; 85), and a plurality of gear groups being supported on the input shaft (17; 76), on the first layshaft (18; 78), and on the second layshaft (21; 81) for providing gear ratios between the input shaft (17) and one of the first lay-shaft or the second layshaft, the plurality of gear groups comprising -a reverse gear group (27, 39, 52), the reverse gear group comprising a first reverse gearwheel (27) be-ing provided on the input shaft (17), an idler gearwheel (39) being provided on the first layshaft (18), and a second reverse gearwheel (52) being provided on the second layshaft (21) and -an overdrive forward gear group for providing an overdrive gear ratio which is lower than the gear ratios of the other forward gear groups, wherein the overdrive forward gear group and the reverse gear group are axially located next to each other.
2. Transmission (70) of claim 1 characterized in that the overdrive forward gear group comprises a planetary gear group (A, B, C)
3. Transmission (70) of claim 2, characterized in that the planetary gear group comprises -a sun gear (A), -a ring gear (B), -at least one pinion gear, and -a rotary carrier (C) for supporting the at least one pinion gear, wherein -the rotary carrier (C) is connected to one of the other forward gear groups, -the ring gear (B) is connected to a brake mecha-nism, and -the sun gear (A) is for selectively coupling with the first layshaft.
4. Transmission (70) of claim 2 or 3 characterized in that the planetary gear group is connected to one of the other gear groups via a one way clutch (OWC)
5. Transmission (10) of claim 1 characterized in that the overdrive forward gear group comprises -an overdrive fixed gearwheel (28) that is provided on the input shaft (17), -an overdrive idler gearwheel (54) that is meshing with the overdrive fixed gearwheel (28), and -an overdrive-coupling device (53) to selectively engage the overdrive idler gearwheel (54), the overdrive idler gearwheel (54) and an overdrive-coupling device (53) being arranged on the first S layshaft (18)
6. Transmission (10; 70) of one claims 1 to 5 characterized in that the plurality of gear groups further comprising -a first gear group that comprises -a first fixed gearwheel (27; 89) that is pro-vided on the input shaft (17; 76), -a first idler gearwheel (39; 111) that is meshing with the first fixed gearwheel (27; 89), and -a first coupling device (40; 113) to selec-tively engage the first idler gearwheel (39; 111), the first idler gearwheel (39; 111) and the first coupling device (40; 113) being ar-ranged together on the first layshaft (18; 78), -a second gear group that comprises -a second fixed gearwheel (29; 92) that is pro-vided on the input shaft (17; 76), -a second idler gearwheel (42; 115) that is meshing with the second fixed gearwheel (29; 92), and -a second coupling device (40; 113) to selec-tively engage the second idler gearwheel (42; 115), the second idler gearwheel (42; 115) and the second coupling device (40; 113) being ar-ranged together on the first layshaft (18; 78), a third gear group that comprises -a third fixed gearwheel (31;93) that is pro-vided on the input shaft (17; 76), -a third idler gearwheel (56; 103) that is meshing with the third fixed gearwheel (31 93), and -a third coupling device (57; 104) to selec-tively engage the third idler gearwheel (56; 103), the third idler gearwheel (56; 103) and the third coupling device (57; 104) being ar-ranged together on the second layshaft (21; 81), a fourth gear group that comprises -a fourth fixed gearwheel (32; 94) that is pro-vided on the input shaft (17; 76), -a fourth idler gearwheel (58; 105) that is meshing with the fourth fixed gearwheel (32; 94), and -a fourth coupling device (57; 104) to selec-tively engage the fourth idler gearwheel (58; 105), the fourth idler gearwheel (58; 105) and the fourth coupling device (57; 104) being ar-ranged together on the second layshaft (21; 81), -a fifth gear group that comprises -a fifth fixed gearwheel (31; 93) that is pro-vided on the input shaft (17; 76), -a fifth idler gearwheel (43; 117) that is meshing with the fifth fixed gearwheel (31; 93), and -a fifth coupling device (45; 118) to selec-tively engage the fifth idler gearwheel (43; 117), the fifth idler gearwheel (43; 117) and the fifth coupling device (45; 118) being ar-ranged together on the first layshaft (18; 78), and -a sixth gear group that comprises -a sixth fixed gearwheel (32; 94) that is pro-vided on the input shaft (17; 76), -a sixth idler gearwheel (46; 119) that is meshing with the sixth fixed gearwheel (32; 94), and -a sixth coupling device (45; 118) to selec-tively engage the sixth idler gearwheel (46; 119), the sixth idler gearwheel (46; 119) and the sixth coupling device (45; 118) being ar-ranged together on the first layshaft (18; 78).
7. Transmission (10; 70) of claim 6 characterized in that the first coupling device and the second coupling device being provided as one coupling device.8 Transmission (10; 70) of claims 6 or 7 characterized in that the third coupling device and the fourth coupling device being provided as one coupling device.9. Transmission (10; 70) of one of claims 6 to 8 characterized in that the fifth coupling device and the sixth coupling device being provided as one coupling device.10. Transmission (10; 70) of one of claims 6 to 9 characterized in that the third fixed gearwheel and the fifth fixed gearwheel being provided as one fixed gearwheel.11. Transmission (10; 70) of one of claims 6 to 10 characterized in that the fourth fixed gearwheel and the sixth fixed gearwheel being provided as one fixed gearwheel.12. Transmission (10) of one of claims 6 to 11 characterized in that the first layshaft (18) being provided above the second layshaft (21) 13. Transmission (70) of one of claims 6 to 11 characterized in that the first shaft (81) being provided below the second shaft (78) 14. Powertrain comprising an engine and a transmission of one of claims 1 to 13 being connected to the engine.15. Vehicle comprising at least one wheel and a powertrain of claim 14 being connected to the at least one wheel.